Metal

Element Arrangement The elements show a periodic recurrence of chemical and physical properties when they are arranged in order of increasing atomic number. Elements in the same vertical column are known as groups and the horizontal rows of elements are called periods. All elements in a specific group have equivalent outermost, or valence electron, configurations which accounts for the similarity in the number and type of chemical bonds these elements form. In moving from element to element across a period or down a group, chemical and physical properties change gradually.

Most of the elements are metals that chemically tend to lose electrons and form positive ions. The relatively few nonmetals appear in the upper right-hand section of the chart except for hydrogen. The nonmetals have a tendency to react chemically with metals and gain electrons to form negative ions. Nonmetals often bond to each other by forming covalent bonds. Alkali Metals: Highly reactive elements that combine with many nonmetals to form ionic solids (salts).

They also form compounds with oxygen that dissolve in water to create solutions that are strongly basic (alkaline). Alkaline Earth Metals: Very reactive elements that form ionic compounds with nonmetals. Many of their oxygen compounds are found in deposits in the ground. Transition Metals: Generally less reactive than the alkali and alkaline earth metals, these elements vary in physical and chemical properties. Many form important alloys with one another and other metals. Several of the transition elements can form more than one positive ion.

For example, iron can form more than one compound with a given nonmetal since it exists as two different ions, Fe 2+ and Fe 3+. Lanthanides: Series of transition elements between lanthanum (La) and hafnium (Hf). These elements are found together in nature and they are similar chemically. Actinides: Series of transition elements between actinium (Ac) and rutherfordium (Rf). Many can be prepared in minute quantities only. They tend to form insoluble compounds. Noble Gases: Elements exhibit limited chemical reactivity though the heavier noble gases show degrees of reactivity.

These elements have generally complete electron shells. Halogens: Reactive elements that form compounds known as halides. Several halogens including chlorine, fluorine and iodine, have important applications in everyday life. Other Metals: Also referred to as post transition metals. Aluminum is the most abundant metal on earth. Lead, tin and mercury have industrial uses. Other Nonmetals: Includes chemically reactive elements important for life on the planet, such as carbon, oxygen, nitrogen and phosphorous.

Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film. [ The camera is the image-forming device, and photographic film or a silicon electronic image sensor is the sensing medium. The respective recording medium can be the film itself, or a digital electronic or magnetic memory. [4]

Photographers control the camera and lens to “expose” the light recording material (such as film) to the required amount of light to form a “latent image” (on film) or “raw file” (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras use an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on paper or film.

SAFETY IN WELDING A Safe Journey with UNITOR Norwegian Training Center – Manila A SAFE JOURNEY WITH UNITOR Welding and Flame Cutting elsewhere than in workshop should be the subject of a “HOT WORK PERMIT” A Safe Journey with UNITOR 2 Norwegian Training Center – Manila Production welding is done under optimum conditions. The appropriate equipment is provided for and the specification are set. A Safe Journey with UNITOR 3 Norwegian Training Center – Manila Maintenance and repair welding onboard involves a host of unknowns.

Problems relate to chemical composition of the base metals, weldability, pre and post heat, choice of electrode, and the handicaps of field welding. A Safe Journey with UNITOR 4 Norwegian Training Center – Manila PROTECT THE EYES Never expose bare eyes to the glare and rays from the ARC! This will cause arc-eye (very painful) and damage to the ayes. Use filter glass of correct grade. Amperage Below 20 A 20 – 40 A 40 – 80 A 80 – 175 A 175 – 300 A 300 – 500 A A Safe Journey with UNITOR Grade 8 9 10 11 12 13 5 Norwegian Training Center – Manila A Safe Journey with UNITOR 6

Norwegian Training Center – Manila Train the crew to do the repair welding work themselves instead of subcontracting it away. A Safe Journey with UNITOR 7 Norwegian Training Center – Manila What about your welding technique? Could you need a bit of time at the welding school? A Safe Journey with UNITOR 8 Norwegian Training Center – Manila Both welding cable and return cable should be stretched to the welding site Remember that if you connect the return cable in the ships structure you are actually standing on the return current A Safe Journey with UNITOR 9 Norwegian Training Center – Manila

Place the return clamp as near to where the welding takes place as possible. If you don’t, the return current might travel through ball bearings and other critical machine parts and destroy them. A Safe Journey with UNITOR 10 Norwegian Training Center – Manila If you are a smoker remember that disposable plastic cigarette lighters kept in pockets may cost you your life on a welding job. Should a spark fall into your pocket the lighter may explode, resulting in extensive, even fatal burns. Always leave your lighter behind when you shall weld. A Safe Journey with UNITOR 11

Norwegian Training Center – Manila Prevent sparks dropping down hatchways or hold ventilators. Keep fire extinguishers ready. A Safe Journey with UNITOR 12 Norwegian Training Center – Manila Before hot work is begun, check that there are no combustible solids, liquids or gases, at below or adjacent to welding area. A Safe Journey with UNITOR 13 Norwegian Training Center – Manila Remember that protective clothing is not only meant to protect you from burns spatter and arc radiation but also serves as an insulator so you don’t become part of the electric circuit A Safe Journey with UNITOR 14

Norwegian Training Center – Manila Hoses and cables should be kept clear of passage ways. A Safe Journey with UNITOR 15 Norwegian Training Center – Manila To work with worn or damaged welding cables is extremely dangerous. Inspect the condition of the cables regularly. Worn cables should be replaced, not “Repaired” with insulation tape. If the damage is local the damaged part should be cut away and the cable joined with a cable connector. A Safe Journey with UNITOR 16 Norwegian Training Center – Manila Be sure you never get any electric shock when using electric equipment.

A Safe Journey with UNITOR 17 Norwegian Training Center – Manila DO NOT lean directly on to the structure if the return current runs through it, but make sure to insulate yourself using either a RUBBER MAT or WOOD. A Safe Journey with UNITOR 18 Norwegian Training Center – Manila In no circumstances should a welder work while standing in water. Water and electricity do not mix. A Safe Journey with UNITOR 19 Norwegian Training Center – Manila DO NOT weld on drums or tanks before they are cleaned and made absolutely gas free. A Safe Journey with UNITOR 20 Norwegian Training Center – Manila

Poisonous gas might develop during welding caused by elements in the base materials or due to paints and metal coatings on the surface. A Safe Journey with UNITOR 21 Norwegian Training Center – Manila HAVE ELECTRODES BEEN PROPERLY STORED? If electrodes are left in the open air they start to attract moisture. When the electrode is used the moisture in the coating goes over as Hydrogen Porosity in the weld. This will in time develop into Hydrogen Cracking. A Safe Journey with UNITOR 22 Norwegian Training Center – Manila WHY IS IT THAT THE WELD I DID ONE WEEK AGO HAVE CRACKED. A Safe Journey with UNITOR 23

 The humble kettle people use for heating water will serve, for the purposes of this essay, as an example in the life cycle assessment (LCA) of a product. Concerns regarding the environmental impact of products from its manufacturing, use, and up to its disposal (“cradle to grave”), have been given close scrutiny by ecologically conscientious groups.

One strategy that has seen wide use in major businesses concerned with sustainability issues is LCA. Briefly, LCA is a methodology for evaluating the environmental impact involved in the manufacture, distribution, use, and disposal of a product of interest in an organized manner. Its importance was recognized by ISO, and standards regarding its implementation have been set.

In drawing up the phases of the kettle’s life cycle, the processes involved in its manufacture can include the molding of the plastic handle (which can be made from polymers like high-density polyethylene, polystyrene, or some other appropriate polymer), the casting of the metal to be used for the kettle body, cover, and spout (which can be any of steel, cast iron, aluminum, and maybe copper, copper being one of the best heat conducting metals with only its cost relative to the other metals mentioned precluding its use), the addition of other functionalities (a whistle that sounds off when the water in the kettle has started boiling is traditional, but fancier additions such as a thermometer have been seen), and the final assembly of all the kettle’s essential parts.

The manufacturing and/or processing of the materials used in making the kettle (e.g. whether the metal used was recycled or mined) and the transport of these to the manufacturing facility can be given less focus on the analysis and thus be relegated to background status and parameters related to such can be set to appropriate values that may already have been cataloged or given reasonable estimates. Distribution-wise, packaging and transportation are main concerns. With packaging, the production of the usual packaging materials such as cardboard or plastic would be of concern.

How the kettle will be transported (truck or van if distribution will be local; international distribution will add some further complications) will also come into play. For the usage phase of the kettle, the primary concern is in how the consumer will use the kettle. A usual concern is that the kettle is left for too long a time on the stove (or whatever other heating utility is in use), more than sufficient to heat the water to a boil, and thus wasting energy that could have been used more productively. Apart from this, heat loss due to possible imperfections or flaws in the kettle may also have to be taken into account. Read about Product Life Cycle of BMW

If the user of the kettle resides in a region where the water is hard (water containing calcium, magnesium, and other ions that form a nonconductive coating on the inside of the kettle and reduce the kettle’s heating efficiency), this can also be an additional factor. With regards to the disposal of the kettle, the kettle may have already been used for many years before it might be considered for disposal due to wear and tear related damage.

Should the kettle have to undergo disposal, however, it can either be sent to a landfill or have its plastic and metal components recycled for other uses. For any other factors where there is uncertainty, one would do well to do an analysis with both the best and worst possible scenarios for the assurance of having been able to cover the entire spectrum.

Having set up the phases and boundaries of the kettle’s life cycle, the needed data can then be gathered from the appropriate sources. Databases might be available that can be used to obtain cost data for materials and/or labor required in manufacture. In the case of the SimaPro 7 software commonly used for LCA by industries, databases such as the ecoinvent database that facilitate the construction of LCA models.

However, if data required is not available in such databases, one must fall back on traditional methods of data gathering such as the use of questionnaires and surveys. Once the data has been gathered, though, it is a simple task to perform the needed analysis. In this respect, if ballpark estimates can be obtained when data is not readily available, it is wise to utilize the estimates to have a feel for what may be involved.

For the scenario of the kettle, data on cost of material production/procurement and processing (dependent on metal and plastic used), the amount and cost of energy required in casting the metal and molding the plastic parts of the kettle, as well as the cost of processing any waste or emissions produced in the manufacture can be taken into consideration.

In distribution, the cost of local or international shipping and handling are for consideration, as well as the production or procurement of packaging material and handling of any waste produced. This sort of data is most probably easily obtained from statistics gathered by manufacturers and distributors, and can be had through surveying if otherwise.

Slightly more complicated is the analysis of how a consumer might use the kettle. The kettle’s capacity for heating is dependent on the material used to make it. Different methods of heating are in use in different parts of the world. The hardness of water in different areas might also have to be considered in evaluating the heating efficiency of a kettle when in use, for lime scale that accumulates after a kettle has long been used to heat hard water impedes efficient heat transfer.

Since the inefficient usage of heat sources is known to be a contributor to waste and pollution, it will be of utility to take these into account when looking into the environmental impact of the kettle during use. Also, it is usually the case that consumers heat far more water in the kettle than what will be used, and that contributes to wastage as well. With this, one can set a period of time for which the kettle will be used (frequency taken into account) and estimate the amount of energy that will be spent for heating in the whole lifetime of the kettle. Typically, kettles are built durably enough to last years. Data on this can be done by an appropriate statistical sampling method. The cost of recycling or disposal in a landfill completes the accounting for data needed.

As a ballpark estimate, a kilogram of the appropriate metal might be needed to construct the metal parts of the kettle, and about 40 grams for the plastic handles. Depending on the temperatures needed and the heat capacity of the metal to be used, around 10-50 kJ/kg of heat might be needed for processing the metal parts, which may take up to an hour. Much less than that can be used to shape the plastic. A typical production of kettles might net around 1000 kettles made per day.

For usage, depending on the capacity of the kettle and the efficiency of the heating, approximately 5 kJ/kg might be needed and about 30 minutes to heat the water to an agreeable temperature. Any of the other needed quantities can be obtained from databases provided on LCA software such as the ecoinvent database built into SimaPro 7 or be obtained from industrial reports or handbooks.

Possible changes in the life cycle may include the use of recycled metal and plastic as raw material, the use of an efficient and nonpolluting heat source for processing the raw materials used in producing the kettle in the manufacturing portion of the life cycle. With regards to consumer usage, the use of softened water and efficient heat sources are possible changes that can be made. Also, modifications that would prevent the consumer from having to use more heat than necessary to heat the water (a whistle, for instance) would also prove useful.

An LCA analysis is only as good as the data put into it, so the gathering of useful data is an absolute must. Uncertainties in data gathering such as how the data was aggregated or whether the data used is applicable to local conditions can affect the analysis considerably. Rigorous bounding of uncertainties involved is of utility in this aspect. The assignment of values to such things as the cost of environmental impact is subjective, and can be considered a both a flaw and a necessary assumption to simplify the analysis.

Of course, automated analyses should also be subjected to human scrutiny to assess whether the results are applicable in an industry’s scenario. An LCA analysis performed at a certain point in time may be either confirmed or refuted by future LCA analyses, and that too is a confounding factor. LCAs may also hinder the adoption of technological innovations that might be even better solutions than that considered in the analysis.

References

AYRES, R.U. and A.V. KNEESE, 1969. Production, consumption and externalities, American Economic Review, 69, p.282.
BRITISH STANDARDS INSTITUTE, n.d. International Standard for ISO 14041 – Environmental Management – Life Cycle Inventory, BSI, Chiswick
CIAMBRONE, D.F., 1997. Environmental Life Cycle Analysis, CRC Press LLC, Boca Raton, Florida

CURRAN, M. A., 1996. Environmental Life Cycle Assessment, McGraw-Hill, London.

DEPARTMENT OF THE ENVIRONMENT, 1990. Protection and Water Statistics no. 13, HMSO, London.
DEFRA, 2005. Securing the Future: Delivering UK Sustainable Development Strategy [online] Available from <http://www.sustainable-development.gov.uk/publications.htm> Accessed November 2005.
DETR, 2000. Waste Strategy 2000, HMSO, London.
DEPARTMENT OF TRADE AND INDUSTRY, 2001. Digest of United Kingdom Statistics, HMSO, London.
ECOBILAN, 1998. Life Cycle Inventory Analysis and Impact Assessment – ‘Disposal’ Options for Used Newspapers and Magazines, Aylesford Newsprint Limited, Aylesford, Kent
GRAEDEL,T.E., B.R. ALLENBY and P. COMRIE, 1995. Matrix approaches to abridged life cycle assessment, Environmental Science and Technology, 29(3), p.134.
HEIJUNGS, R. et al., 1996. Life Cycle Assessment: What It Is and How to Do It, United Nations Environment Programme, Paris, France.
INTERNATIONAL STANDARDS ASSOCIATION, 1995. Life Cycle Assessment Principles and Guidelines, CD 14040. 3

INTERNATIONAL STANDARDS ORGANISATION, 1997. ISOs 14040/1/2/3, Environmental management – Life Cycle Assessment Series.
NISSEN, U., 1995. A methodology for the development of cleaner products: The ideal eco–product approach, Journal of Cleaner Production, 3(1-2), p.83.

PRÉ CONSULTANTS, 2000. Eco-indicator 99: Manual for Designers, Ministry of Housing, Spatial Planning and the Environment Communications Directorate, The Netherlands [online] <http://www.pre.nl/eco-indicator99/ei99-reports.htm> Accessed November 2005.

RUSSELL, A., EKVALL, T. and BAUMANN H., 2005. Editorial: Life cycle assessment – An introduction and overview, Journal of Cleaner Production, 13(13-14), p.1207.
SOCIETY OF ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, 1991. A Technical Framework for Life-Cycle Impact Assessment; Workshop report, SETAC Foundation for Environmental Education, Washington.
SOCIETY OF ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, 1993. Guidelines for Life-Cycle Impact Assessment: A Code of Practice, SETAC Foundation for Environmental Education, Brussels
SOCIETY OF ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY, 1993. A Conceptual Framework for Life-Cycle Impact Assessment; Workshop Report, SETAC Foundation for Environmental Education, Washington.
SIMON, M., 1997. The politics of ecodesign, EcoDesign 5(1), p.12.
SWEATMAN, A. AND SIMON, M., 1996. Design for environment tools and product innovation, In CIRP Seminar on Design for Life-Cycle, ETH Zurich, 1996, Zurich. SWEATMAN, A., SIMON, M., AND BLOMBERG, S., 1997. Integrating design for environment within an environmental management system, In International Conference on Engineering Design (ICED’97), WDK.
UNEP, 2004. LCA Tools [online] ;http://www.uneptie.org/pc/pc/tools/lca.htm; Accessed November 2005.

WELFORD, R. AND STARKEY, R. (eds.), 1996. The Earthscan Reader in Business and the Environment, Earthscan. London.

Galvanic corrosion (also called ” dissimilar metal corrosion ” or wrongly “electrolysis”) refers to corrosion damage induced when two dissimilar matter l’s are coupled with a corrosive electrolyte. Galvanic corrosion is an electrochemical process In which one metal corrodes onto another when both metals are in electrical co intact, in the presence Of an electrolyte. When a galvanic couple forms, one Of the metals I n the couple becomes the anode and corrodes faster than it would all by itself, while e the other becomes the cathode and corrodes slower than it would by itself.

So basically the anode metal is breaking down onto the cathode metal. For galvanic corrosion to occur, three things must be present: Electrochemically dissimilar metals must be pre.NET, these metals must be in electrical contact, and the metals must be exposed to an electrolyte. Galvanic Corrosion was discovered in the late part of the eighteenth century b Lugging Galvanic in a series of experiments with the exposed muscles and nerves of a frog that contracted when connected to a conductor.

Its humorous to think Galvan ICC corrosion was found on accident when experimenting on frogs. The concept was also e engineered into the useful protection of metallic structures by Sir Humphrey Davys and Mice hall Faraday in the early part of the nineteenth century. The sacrificial corrosion of en metal such as zinc, magnesium or aluminum is a widespread method of protecting metallic Structures. While galvanic corrosion is potentially problematic to civil engineers, they can use it to their benefit.

For example buried or submerged structures, in HTH s case, sacrificial anodes work as part of a galvanic couple, promoting corrosion of the e anode, in order to protect the cathode metal. To dumb it down one metals life is been g drastically reduce so the other metals life will last longer. On another note if you do not want galvanic corrosion taking place corrosion inhibitors such as sodium nitrite or sodium moldboard can be injected into the systems to reduce the galvanic potential.

However, the application Of these co erosion inhibitors must be monitored closely. If the application of corrosion inhibitors increases the conductivity of the water within the system, the galvanic corrosion potent al can be greatly increased. A different means of avoiding galvanic corrosion is to coins deer the 2 electrical potential of the metals you are selecting. A galvanic series list the el citric potentials of metals, the relative position of two metals on such a series gives good indication of which metal is more likely to corrode more quickly.

Looking back at my opening statement, you can now understand why galvanic corrosion can be so hostile. If you select the wrong metals in a system, and the e load bearing metal of the system corrodes, you systems is bound to fail. On the to her end of the spectrum, galvanic corrosion can possibly be helpful, if indeed you want t o sacrifice one metal in order to protect another. With an indented knowledge of galvanic corrosion civil engineers can predict and act upon potentially hazardous situations.

Metals are electropositive chemical elements that are characterised by the following qualities: ductility, malleability, luster, opacity, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals.

Density is defined as a material’s mass divided by its volume. Metals typically have relatively high densities, particularly when compared to polymers. Often, materials with high densities contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities. These metals are useful in applications requiring other metallic properties but in which low weight is also beneficial.

Fracture Toughness can be described as a material’s ability to avoid fracture, especially when a flaw is introduced. Glass, for example, has low fracture toughness (although it exhibits high strength in the absence of flaws). Metals typically have high fracture toughness. Metals can generally contain nicks and dents without weakening very much. They are also impact resistant. A football player relies on this fact to ensure that his facemask won’t shatter. The roll cage on a racecar, for example, is created from steel. This steel should remain intact in a crash, protecting the driver.

The ability of a material to bend or deform before breaking is known as plastic deformation. Some materials are designed so that they don’t deform under normal conditions. You don’t want your car to lean to the east after a strong west wind, for example. However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break.

Stress takes place when forces pull (this is known as tension), push (compression) or act in combination on a material. Once the force is applied, the material responds by distorting, counterbalancing the force. With a larger force, there will be a correspondingly greater distortion until the item breaks.

Stress is the force applied per unit of cross-sectional area square to the force. This can be expressed mathematically as::

• Stress (s) = Force / unit of area
• The metric system units for stress are Newton per square meter (N/m2) and imperial system units are pounds per square inch (psi).

Strain is the amount the material deforms from the unloaded state when the force is applied. Its formula is:

• Strain (x) = Change in length / original length
• Since strain is a ratio of length divided by a length, it has no units. By the formula, we can see that it represents a proportional change in size.

Deformation occurs when a force is applied to a metal. The metal is therefore strained. The greater the force – the more the deformation (strain). This relationship is recognised in Hooke’s Law.

Hooke’s Law describes an elastic region where stress and strain are proportional (a straight line on a graph). In this region the metal acts like a spring and when the load is removed the deformation (strain) reduces and it returns to its original shape. If instead the load increases, the strain (deformation) rises and the metal undergoes uniform plastic deformation.

The stress-strain graph is curved in this region. Eventually, a maximum stress is reached when the metal when the material reaches its limit of necking. Necking is localized thinning that occurs during sheet metal forming prior to fracture. The onset of localized necking is dependent upon the stress state which is affected by geometric factors. Finally, past the maximum stress point, a point is reached where the metal can no longer sustain the load and it yields.

The behavior of metals under load is a result of their atomic arrangement. When a material is loaded it deforms minutely in reaction to the load. The atoms in the material move closer together in compression and further apart in tension. The amount an atom moves from its neighbor is its strain. As a force is applied the atoms change a proportionate distance.

This model however, does not explain why there is sudden yielding. With most modern metals yielding usually occurs at about 1% of the theoretic strength of the atomic bonds. Many materials yield at about 0.1% of the theoretic strength.

Rather, metals exhibit such low strengths because of imperfect atomic structures in the crystal lattices which comprise them. A row of atoms will often stop mid crystal, creating a gap in the atomic structure. These gaps act as dislocations, which are huge stress raising points in the metal.

These dislocations move when the metal is stressed. A dislocation is defined as allowing atoms to slip one at a time, making it easier to deform metals. Dislocation interactions within a metal are a primary means by which metals are deformed and strengthened. When metals deform by dislocation motion, the more barriers the dislocations meet, the stronger the metal. The presence of dislocations in metal allows deformation at low levels of stress. However, eventually so many dislocations accumulate that insufficient atoms are left to take the load. This causes the metal to yield.

Plastic deformation causes the formation of more dislocations in the metal lattice. This has the potential to create a decrease in the mobility of these dislocations due to their tendency to become tangled or pinned. When plastic deformation occurs at temperatures low enough that atoms cannot rearrange, the metal can be strengthened as a result of this effect. Unfortunately, this also causes the metal to become more brittle. As a metal is used, it tends to form and grow cracks, which eventually cause it to break or fracture.

Atoms of melted metal pack together to form a crystal lattice at the freezing point. As this occurs, groups of these atoms form tiny crystals. These crystals have their size increased by progressively adding atoms. The resulting solid, instead of being a single crystal, is actually many smaller crystals, called grains. These grains will then grow until they impose upon neighbouring growing crystals. The interface between the grains is called a grain boundary. Dislocations cannot easily cross grain boundaries. If a metal is heated, the grains can grow larger and the material becomes softer. Heating a metal and cooling it quickly (quenching), followed by gentle heating (tempering), results in a harder material due to the formation of many small Fe3C precipitates which block dislocations.

The atomic bonding of metals also affects their properties. Metal atoms are attached to each other by strong, delocalized bonds. These bonds are formed by a cloud of valence electrons that are shared between positive metal ions (cations) in a crystal lattice. These outer valence electrons are also very mobile. This explains why electrons can conduct heat and electricity – the free electrons are easily able to transfer energy through the material. As a result, metals make good cooking pans and electrical wires. In the crystal lattice, metal atoms are packed closely together to maximize the strength of the bonds. It is also impossible to see through metals, since the valence electrons absorb any photons of light hitting the metal. Thus, no photons pass through.

Alloys are compounds consisting of more than one metal. Creating alloys of metals can affect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. As an example, adding a small amount of iron to aluminum will make it stronger. Alternatively, adding some chromium to steel will slow the rusting process, but will make it more brittle. Some alloys have a higher resistance to corrosion.

Corrosion, by the way, is a major problem with most metals. It occurs due to an oxidation-reduction reaction in which metal atoms form ions causing the metal to weaken. The following technique that has been developed to combat corrosion in structural applications: sacrificial anode made of a metal with a higher oxidation potential is attached to the metal. Using this procedure, the sacrificial anode corrodes, leaving the structural part, the cathode, undamaged. Corrosion can also be resisted by the formation of a protective coating on the outside of a metal. For example, steels that contain chromium metal form a protective coating of chromium oxide. Aluminum is also exhibits corrosion resistant properties because of the formation of a strong oxide coating. The familiar green patina formed by copper is created through a reaction with sulfur and oxygen in the air.

In nature, only a few pure metals are found. Most metals in nature exist as ores, which are compounds of the metal with oxygen or sulfur. The separation of the pure metal from the ore typically requires large amounts of energy as heat and/or electricity. Because of this large expenditure of energy, recycling metals is very important.

Many metals have high strength, high stiffness, and have good ductility. Some metals, such as iron, cobalt and nickel are magnetic. Finally, at extremely low temperatures, some metals and intermetallic compounds become superconductors.

Ceramic

Ceramic materials are inorganic, nonmetallic materials, typically oxides, nitrides, or carbides. Most ceramics are compounds between metallic and nonmetallic elements in which the interatomic bonds are either totally ionic, or predominantly ionic but having some covalent character. While many adopt crystalline structures, some form glasses. The properties of the ceramics are due to their bonding and structure.

The term ceramic comes from the Greek word keramikos, which means burnt stuff! This signifies that the desirable properties of these materials are typically achieved through a high-temperature heat treatment process. This process is called firing.

Ceramics are often defined to simply be any inorganic nonmetallic material. By this definition, glasses are also ceramic materials. However, some materials scientists state that a true ceramic must also be crystalline, which excludes glasses.

The term “ceramic” once referred only to clay-based materials. However, new generations of ceramic materials have tremendously expanded the scope and number of possible applications, broadening the definition significantly. Many of these new materials have a major impact on our daily lives and on our society.

Ceramics and glasses possess the following useful properties: high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance. Additionally, ceramics are often good electrical and thermal insulators.

Since they are good thermal insulators, ceramics can withstand high temperatures and do not expand greatly when heated. This makes them excellent thermal barriers. The applications of this property range from lining industrial furnaces, to covering the space shuttle, shielding it from high reentry temperatures.

The aforementioned glasses are transparent, amorphous ceramics which are extensively used in windows and lenses, as well as many other familiar applications. Light can induce an electrical response in some ceramics. This response is called photoconductivity. An example of photoconductivity occurs in fiber optic cable. Fiber optic cable is speedily replacing copper for communications – optical fibers can transmit more information for longer distances, and have less interference and signal loss than traditional copper wires.

Ceramics are also typically strong, hard, and durable materials. As a result, they are attractive structural materials. One significant drawback to their use is their brittleness. However, this problem is being addressed by the creation of new materials such as composites.

While ceramics are typically good insulators, some ceramics can actually act as superconductors. Thus, they are used in a wide range of applications. Some (the good insulators) are capacitors, others semiconductors in electronic devices. Some ceramics are piezoelectric materials, which convert mechanical pressure into an electrical signal. These are extremely useful for sensors. For superconducting ceramics, there is a strong research effort to discover new high Tc superconductors and to then develop possible applications.

Processing of crystalline ceramics is based on the basic steps which have been used for ages to make clay products. The materials are first selected, then prepared, formed into a required shape, and finally sintered at high temperatures. Glasses, on the other hand, are typically processed by pouring while in a molten state. They are then worked into shape while hot, and finally cooled. There are also new methods, such as chemical vapor deposition and sol-gel processing, currently being developed. Ceramics have a wide range of applications. For example, ceramic tiles cover the space shuttle as well as our kitchen floors. Ceramic electronic devices make possible high-tech instruments for everything from medicine to entertainment.

There are also some special properties which a few ceramics possess. For example, some ceramics are magnetic materials and, as mentioned above, some have piezoelectric properties.

The one major drawback of ceramics and glasses is that they are brittle.

As mentioned above, certain types of ceramics possess superconducting properties at extremely low temperatures. For example, there are high-temperature superconducting ceramic materials that have recently been discovered. These materials exhibit virtually no electrical resistance below 100 degrees Kelvin. Also, these materials exhibit what is known as the Meissner effect. This means that they repel magnetic flux lines, allowing a magnet to hang in the space above the superconductor.

An example of special group of crystalline ceramics is the group called Perovskites. They have captured the interest of geologists due to the information they can yield about Earth’s history. The most intensely studied Perovskites at the present time are those that superconduct at liquid nitrogen temperatures.

Ceramics were historically used for creating pottery and artwork, largely because the brittleness and difficulty of manufacturing ceramics restricted them from other uses until recently. However, the market requirement for microelectronics and structural composite components has risen, causing the demand for ceramic materials to likewise increase.

Fiber-reinforced composites, an example of a modern ceramic application, are being created from ceramic fibers with extremely high stiffness, such as graphite and aluminum oxide.

Polymers

Polymers are substances which contain a large number of structural units joined by the same type of linkage. They are any of many natural and synthetic compounds, usually of high molecular weight. They typically consist of up to millions of repeated linked units, each a relatively light and simple molecule. These substances often form into a chain-like structure. Some polymers have been around since the beginning of time in the natural world. For example, starch, cellulose, and rubber all possess polymeric properties. Man-made polymers, a relatively recent development, have been studied since 1832. However, the polymer industry today has is larger than the aluminum, copper and steel industries combined.

Polymers have a huge range of applications that greatly surpasses that of any other class of material available to man. Current applications include adhesives, coatings, foams, packaging materials, textile and industrial fibers, elastomers, and structural plastics. Polymers are also widely used for many composites, electronic devices, biomedical devices, optical devices, and precursors for many newly developed high-tech ceramics (such as the fiber-reinforced composite mentioned at the end of the ceramic section).

The word polymer literally has the meaning “many parts.” A polymeric solid material can be considered to be one containing many chemically bonded parts or units, themselves which are bonded together to form a solid. Polymers are typically good insulators. While a large variety of polymer applications were described above, two of the most industrially important polymeric materials are plastics and elastomers. Plastics are a large and varied group of synthetic materials. They are processed by forming or molding into shape. There are many types of plastics such as polyethylene and nylon.

Polymers can be separated into two different groups depending on their behaviour when heated. Polymers with linear molecules are often thermoplastic. Thermoplastic substances soften upon heating and can be remolded and recycled. They can be semi-crystalline or amorphous. The other group of polymers is the thermosets. In contast to thermoplastics, these substances do not soften under heat and pressure and cannot be remolded or recycled. Instead, they must be remachined, used as fillers, or incinerated to remove them from the environment.

Thermoplastics are typically carbon-containing polymers which are synthesized by addition or condensation polymerization. This procedure forms strong covalent bonds within the chains and weaker secondary Van der Waals bonds between the chains. Normally, the secondary forces can be easily overcome by thermal energy, which makes thermoplastics moldable at high temperatures. After cooling, thermoplastics will also retain their newly reformed shape. Common applications of thermoplastics include parts for common household appliances, bottles, cable insulators, tape, blender and mixer bowls, medical syringes, mugs, textiles, packaging, and insulation.

Thermosets exhibit the same Van der Waals bonds that thermoplastics do. They also have a stronger linkage to other chains. Different chains together in a thermoset material are chemically held together by strong covalent bonds. The chains may be directly bonded to each other, or alternatively may be bonded through other molecules. This “cross-linking” between the chains is what allows the material to resist softening upon heating. Thus, thermosets must be machined into a new shape if they are to be reused or they can serve as powdered fillers.

However, while thermosets are difficult to reform, they have many distinct advantages in engineering design applications. These include high thermal stability and insulating properties, high rigidity and dimensional stability, resistance to creep and deformation under load, and low weight. A few common applications for thermosets include epoxies (glues), automobile body parts, adhesives for plywood and particle board, and as a matrix for composites in boat hulls and tanks.

The polymer molecule, a long chain of covalent-bonded atoms, is the basic building block of a plastic. Polymers are typically carbon based and have relatively low melting points. Polymers have a very wide range of properties that enable them to be extensively used in society. Some uses include car parts, food storage, electronic packaging, optical components, and adhesives.

Synthetic fabrics are essentially man-made copies of natural fabrics. Synthetic fibers do not occur in nature as themselves. They are usually derivatives of petroleum products. Examples of common synthetic fabrics are polyester, pdex, rayon, and velcro.

Recent technological developments have lead to electrically conductive polymers. The behaviour of semiconductors can now be achieved with polymeric systems. For example, there are semiconducting polymers which, when sandwiched between two electrodes, can generate light of any color. This technology has the potential of leading to OLED (organic light-emitting diode) flat panel displays. This display would be light in weight, have low power consumption, and perhaps be flexible.

Liquid crystals are another example of polymeric materials. As the name suggests, a liquid crystal is a state of matter intermediate between a standard liquid and a solid. Liquid crystal phases are formed from geometrically anisotropic molecules. This typically means they are cigar shaped, although other shapes are possible. The polymer molecules have a certain degree of order in a liquid crystal phase. Take the simplest case, the Nematic phase, in which the molecules generally point in the same direction but still move around with respect to one another as would be expected in a liquid. However, under the influence of an applied electric field, the alignment of the polymer molecules gives rise to light absorption.

Composites

Composites are materials, usually man-made, that are a three-dimensional combination of at least two chemically distinct materials, with a distinct interface separating the components. They are created to obtain properties that cannot be achieved by any of the components acting alone.

In composites, one of the materials, called the reinforcing phase, is in the form of fibers, sheets, or particles. This material is embedded in the other materials, called the matrix phase. The reinforcing material and the matrix material can be metal, ceramic, or polymer. Typically, reinforcing materials are strong with low densities while the matrix is usually a ductile, or tough, material.

The purpose of the composite, when it is designed and fabricated correctly, is to combine the strength of the reinforcement with the toughness of the matrix to achieve a combination of desirable properties not available in any single conventional material. The downside is that such composites are often more expensive than conventional materials. Some examples of current applications of composites include the diesel piston, brake-shoes and pads, tires and the Beechcraft aircraft in which 100% of the structural components are composites.

A structural composite often begins with lay-up of prepreg. At this point, the choice of fiber will influence the basic tensile and compressive strength and stiffness, electrical and thermal conductivity, and thermal expansion of the final pre-preg material. The cost of the composite can also be strongly influenced by the fiber selected.

The resin/fiber composite’s strength depends primarily on the amount, arrangement and type of fiber (or particle) reinforcement in the resin. Typically, the higher the reinforcement content, the greater the strength. There are also some cases in which glass fibers are combined with other fibers, such as carbon or aramid, to create a hybrid composite that combines the properties of more than one reinforcing material. Additionally, the composite is typically formulated with fillers and additives that change processing or performance parameters.

Integrating the ceramic, metallic, plastic and semiconductor materials is a necessary requirement to the fabrication of the micro-electronics package. This is an example of a composite system whose function is to provide interface between the central IC (Integrated Chip) and the other items on, for example, a PCB (printed circuit board).

Semiconductors

There is a relatively small group of elements and compounds that has an important electrical property, semi-conduction, which makes them neither good electrical conductors nor good electrical insulators. Instead, their ability to conduct electricity is intermediate. These materials are called semiconductors, and in general, they do not fit into any of the structural materials categories based on atomic bonding. For example, metals are inherently good electrical conductors. Ceramics and polymers (non-metals) are generally poor conductors but good insulators. The semiconducting elements (Si, Ge, and Sn) from column IV of the periodic table serve as a kind of boundary between metallic and nonmetallic elements.

Silicon (Si) and germanium (Ge), widely used elemental semiconductors, are outstanding examples of this class of materials. These elemental semiconductors are also known as Mono Semiconductors. Binary semiconductors are formed by a compound of two elements, normally an element from group III combined with an element from group V (such as CdS), or a element from group II combined with an element from group VI (such as GaAs). Tertiary semiconductors are formed by a compound of three elements. These semiconductors are typically compounds of elements from groups I, III and VI (such as AgInS) or elements from groups II, IV and V (such as ZnGeAs).

All materials have energy bands in which their electrons can exist. In metals, as stated above, the valence band is partially-filled, and the electrons can move through the material. In semiconductors, on the other hand, there is a band gap that exists, and electrons cannot jump the gap easily at low temperatures. At higher temperatures, more of the semiconductor`s electrons can jump the gap. This causes its conductivity to go up accordingly. Electrical properties can also be changed by doping This too, is one of their great assets.

Putting impurities in a semiconductor material can result in two different types of electrical behaviour. These are the so-called n (negative) and p (positive) type materials. Group V elements like arsenic added to a group IV element, such as silicon or germanium, to produce n-type materials. This occurs due to the extra valence electron in group V materials. On the other hand, group III materials like boron produce the p-type because they have only three valence electrons. When n-type material is connected to a p-type material, the device then exhibits diode behaviour. In other words, current can flow in one direction across the interface but not in the other.

Diodes can act as rectifiers, but they have also led to the development of the transistor. A bipolar junction transistor (BJT) is a diode with an added third material which creates a second interface. While both npn or pnp types exist, their basic operation is essentially the same as two diodes connected to each other. With proper biasing of the voltages across each diode of the device, large current amplification can be produced. Today, metal oxide semiconductor field effect transistors (MOSFETS) have become widely used and have replaced the BJT in many applications. As a result, millions of transistors can be placed on a single silicon chip or integrated circuit. These IC chips have better reliability and consume less power than the large vacuum tube circuits of the past.

The fabrication of electronic devices from the raw materials requires two major steps. The semiconductor is first melted, and a seed crystal is used to draw a large crystal of pure, solid semiconductor from the liquid. Wafers of the semiconductor are sliced and polished. Second, the circuit pattern is etched or deposited using a photolithographic process. The individual chips are finally sectioned from the initial wafer.

Semiconductors experience covalent bonding. Their electrons are more tightly bound than the electrons in metals, but much more loosely bound than the electrons in insulators. The atoms in semiconductors are typically arranged in a crystal structure: a diamond-like tetrahedral (in which each atom is bonded to 4 others). Semiconductors are also typically semi-shiny.

The intermediate ability of semiconductors to conduct electricity at room temperature makes them very useful for electronic applications. For example, the modern computing industry was made possible by the capability of silicon transistors to act as fast on/off switches.

Electronic computing speed has greatly increased with the integrated circuit. For example, the cycle times of today’s computers are now measured in nanoseconds. Opto-electronic (laser diode) research is extending the already huge rate at which information can be transmitted.

Biomaterials

A biomaterial is any nondrug material that can be used to treat, enhance, or replace any tissue, organ, or function in an organism. The term biomaterial refers to a biologically derived material that is used for its structural rather than its biological properties. It also refers to any material, natural or man-made, that comprises whole or part of a living structure, or biomedical device which performs, augments, or replaces a natural function. A biomaterial can be a metal, ceramic, polymer or composite.

They may be distinguished from other materials because they possess a combination of properties, including chemical, mechanical physical and biological properties, which allow them to be suitable for safe, effective and reliable use within a physiological environment. For example, collagen, the protein found in bone and connective tissues, can be used as a cosmetic ingredient. A second example is carbohydrates modified with biotechnological processes that have been used as lubricants for biomedical applications or as bulking agents in food manufacture.

The performance of biomaterials depends on material properties, design, biocompatibility, surgical technique, and the health of patient. In particular, biocompatibility relies on the acceptance of the device by the body. Ideally, there should be no irritation, inflammation, or allergic response

Both biomaterials and biomechanical expertise are needed to perform in vitro testing of spinal implants.

Endo-vascular stents provide structural support vessels following angioplasty and other major medical procedures. After an angioplasty procedure, vessels can experience re-stenosis and eventually return to their original pre-operative diameter. In as many as 10% of the procedures, the vessels may even collapse immediately. To prevent the vessels from shrinking, endo-vascular prosthesis or stents are used. These stents are examples of biomaterials. Stents are tubular structures consisting of a spring, wire mesh or slotted tubes that are deployed inside the vessel. Depending on the design and intended use (coronary/ peripheral), they can range in diameter from several millimeters to many times that size.

A biomaterial must be typically have the following properties: it must be inert or specifically interactive, biocompatible, mechanically and chemically stable (or biodegradable), processable (for manufacturability), have good shelf life, be nonthrombogenic (does not cause clot formation) if it is blood-contacting, and be sterilizable.

There are examples of biomaterials and compatibility problems which arise from the materials not having the above properties. These include dialysis tubing made of cellulose acetate, a “commodity plastic”, which is known to activate platelets and blood complement. Additionally, Dacron, a polymer widely used in textiles, has been used in vascular grafts, but only gives occlusion-free service for diameters larger than 6 mm. Finally, commercial grade polyurethanes, initially used in artificial hearts, can be thrombogenic (they cause clot formation).

There are many prominent applications of biomaterials used in the medical profession today. Biomaterials are used in orthopedics for joint replacements (hip, knee), bone cements, bone defect fillers, fracture fixation plates, and artificial tendons and ligaments. They are also used for cardiovascular vascular grafts, heart valves, pacemakers, artificial heart and ventricular assist device components, stents, balloons, and blood substitutes. Another application is in ophthalmics, for contact lenses, corneal implants and artificial corneas, and intraocular lenses. They can also have cosmetic applications, such as in augmentation mammoplasty. Finally, other applications include dental implants, cochlear implants, tissue screws and tacks, burn and wound dressings and artificial skin, tissue adhesives and sealants, drug-delivery systems, matrices for cell encapsulation and tissue engineering, and sutures.

The following paragraphs will provide an analysis of the modern pop can and the considerations taken by the manufacturer in its design. The overall design of the can has several advantages over another popular beverage container, the glass bottle. The pop can is inherently light weight and cheap due to the aluminum or steel alloys that are used in its creation. The cost of a can accounts for only about 4 cents of the price of a canned beverage. About 10 cents goes for advertising. The 12 ounces of beverage in the container typically costs less than a penny to produce. It is also not easily breakable, unlike glass.

The shape of the can is easy to hold in the hand, making it much easier for a customer to use. The aluminum or steel alloys of the can also have the ability to undergo expansion without breaking the container. Thus, if a pop can is frozen, it will not explode, it will simply deform. Glass, on the other hand, would not as easily deform and would likely break in this situation.

Pop cans are also allow cheaper packaging methods than bottles to be used. This is because the cans can come into contact with each other without breaking, unlike bottles. This allows many cans to be transported without the need for extensive protective barriers between the individual cans. An additional feature that allows the cans to be more easily transported and organised is the shape of the bottom and top of the can. Both the bottom and top have a lip. This lip protrudes upward from the top and downwards from the bottom. In other words, there is a indentation in both the top and bottom of the can, as shown in the following figure:

The radii of the top and bottom lips are matched so that one can is able to be stacked on top of another can. In other words, the top lip of one can fits neatly into the bottom lip of the second can. This is shown in the following diagram. This stacking feature is not possible with bottles, since the bottom base of a bottle does not resemble its top spout.

The pop-top soda, with their attached tab, can provide an excellent example of inherently safer design from everyday life. When soda in cans was first introduced, a separate device was required to open these cans, and the first “pop-tops” represented a major advance in convenience (and environmentalism). The initial pop-tops were scored tear strips in the can top with attached rings or levers to grasp and tear the metal tab from the can. The top was completely removed from the can once the tab was opened, and this top was then discarded. These tabs were therefore environmental hazards when discarded. Alternatively, some people would dispose of the tab by placing it into the can

before drinking the soda. This caused the tab to occasionally be swallowed when drinking from the can, so it sometimes had to be surgically removed. The current design of the pop-top soda can, where the tab remains an integral part of the can after opening, represents an inherently safer design. While the tab can be detached by flexing it back and forth until the metal fails, this requires some additional effort to do.

It is therefore easier to use the can safely. The procedure involved in creating pop cans will now be outlined. This procedure demonstrates some of the major components of the cans.

Modern pop cans are made from either steel or aluminium using advanced engineering and sophisticated technology.

There is a special grade of low-carbon steel is used for steel drink cans, which is coated on each side with a very thin layer of tin. This tin allows the surface to be protected against corrosion. It also acts as a lubricant while the can is being formed.

In aluminium cans, the aluminium is alloyed with magnese and magnesium, providing greater strength and ductility. Aluminium alloys of different strengths and thickness are used for making the can body and the end. The reason that the alloy used from the end must be stronger than that used for the body will be described shortly.

The steps involved in manufacturing cans are illustrated in a simplified way below:

1. The aluminium or steel strip arrives at the can manufacturing plant in huge coils.
2. A thin film of oil is then used to lubricate the strip. The strip is then fed continuously through a cupping press that blanks and draws thousands of shallow cups every minute.
3. Each cup is pressed through a set of tungsten carbide rings. This ironing process redraws and literally thins and raises the walls of the cans into their final can shape.
4. Trimmers are then used to remove the surplus irregular edge and cut each can to a precise, specific height. The excess can material is recycled.
5. These trimmed can bodies are passed through highly efficient washers. They are then dried. As a result, all traces of oil are removed in preparation for coating internally and externally.
6. The clean cans are coated externally with a clear or pigment base coat. This coat provides a good surface for the printing inks.
7. The cans are then passed through a hot air oven to dry the lacquer onto the surface.
8. Next, a highly sophisticated printer/decorator applies the printed design in up to six colours. A varnish is also applied.
9. A coat of varnish is also applied to the base of each can by a rim-coater.
10. The cans pass through a second oven which dries the inks and varnish.
11. The inside of each can is sprayed with lacquer. This special layer is to protect the can itself from corrosion and its contents from any possibility of interaction with the metal.
12. Once again, lacquered internal and external surfaces are dried in an oven.
13. The cans are passed through a necker/flanger. Here the diameter of the wall is reduced or ‘necked-in’. The top of the can is flanged outwards to accept the end once the can has been filled.
14. Every can is tested at each stage of manufacture. At the final stage it passes through a light tester which automatically rejects any cans with pinholes or fractures.
15. The finished can bodies are then transferred to the warehouse to be automatically palletised before dispatch to filling plant.

The Can End

1. Can end manufacture begins with a coil of special alloy aluminum sheet.
2. The sheet is fed through a press which stamps out thousands of ends every minute.
3. At the same stage the edges are curled.
4. The newly formed ends are passed through a lining machine which applies a very precise bead of compound sealant around the inside of the curl.
5. A video inspection system checks the ends to ensure they are perfect. The pull tabs are made from a narrow width coil of aluminum. The strip is first pierced and cut and the tab is formed in two further stages before being joined to the can end.
6. The ends pass through a series of dies which score them and attach the tabs, which are fed in from a separate source.
7. The final product is the retained ring pull end.
8. The finished ends, ready for capping the filled cans, are packaged in paper sleeves and palletised for shipment to the can filler.

As mentioned above, a printer/decorator is used in the manufacturing of cans to apply a printed design in up to six colours to the can body. A varnish is then applied. A varnish is a viscid liquid, consisting of a solution of resinous matter in an oil, or a volatile liquid, typically laid on work with a brush. Once it is applied, the varnish soon dries, either by evaporation or chemical action, and the resinous part forms thus a smooth, hard surface, with a beautiful gloss, capable of resisting, to a greater or less degree, the influences of air and moisture. The varnish therefore improves the appearance of the printed design on the can. It also increases the durability of the design by ensuring that it is more resistant to the wearing effects of the elements. This can be readily observed through common experience.

Even old, used pop cans retain their printed designs very well, despite being subjected to the elements such as moisture or air. Bottles, on the other hand, typically have paper labels attached with glue. This requires glue and paper. These bottle labels also do not possess the glossy sheen of the pop can design. Finally, they are more easily susceptible to the influences of the elements, particularly air and moisture. For example, placing a glass bottle and its label in water will cause the label to saturate with water. This degrades the legibility and appearance of the label, and greatly increases the chance that it will tear or fall off the bottle. In contrast, placing a pop can in water has no effect on the legibility, appearance, or durability of the printed design.

• The base-coater gives the can an exterior coat to enable the printing colours to fix properly
• The of the pop can is a separate piece to allow filling by the beverage maker prior to the top being installed.
• It can now be revealed why bottled beer and beer from a tap tastes different from beer in a can.
• Be forewarned: if you’re a six-pack enthusiast, you’re not going to like the explanation.

When you sip a can of your favorite brew, you are savoring not only fermented grain and hops but just a hint of the same preservative that kept the frog you dissected in 10th-grade biology class lily-pad fresh: formaldehyde.

• What is formaldehyde doing in beer? The same thing it’s doing in pop and other food and drink packaged in steel and aluminum cans: killing bacteria. But not the bacteria in the drink, the bacteria that attacks a lubricant used in the manufacture of the can.

Notre Dame’s Steven R. Schmid, associate professor of aerospace and mechanical engineering, is an expert in tribology – the study of friction, wear and the lubrication – applied to manufacturing and machine design. The co-author of two textbooks, Fundamentals of Machine Elements and Manufacturing Engineering and Technology (considered the bible of manufacturing engineering), Schmid has conducted extensive research on the manufacturing processes used in the production of beverage and other kinds of cans.

Schmid explains that back in the 1940s, when brewers and other beverage makers began putting drinks in steel (and, later, aluminum) cans, the can makers added formaldehyde to a milk-like mixture of 95 percent water and 5 percent oil that’s employed in the can manufacturing process. The mixture, called an emulsion, bathes the can material and the can-shaping tooling, cooling and lubricating both.

Additives in the oil part are certain bacteria’s favorite food. But if the bacteria eat the emulsion, it won’t work as a lubricant anymore. So can makers add a biocide to the emulsion to kill the bacteria.

Before a can is filled and the top attached, this emulsion is rinsed off, but a small residue of the oil-water mixture is inevitably left behind, including trace amounts of the biocide. The amounts remaining are not enough to be a health hazard, but they are enough to taste, and the first biocide used back in the 1940s was formaldehyde.

In the decades since, can makers have devised new formulas for emulsions, always with an eye toward making them more effective, more environmentally friendly and less costly. But because formaldehyde was in the original recipe, people got used to their canned Budweiser or whatever having a hint of the famous preservative’s flavor. For this reason, Schmid says, every new emulsion formula since then has had to be made to taste like formaldehyde, “or else people aren’t going to accept it.” Extensive tests are run to make sure the lubricant and additives taste like formaldehyde.

The formaldehyde flavor legacy is one little-known aspect of can-making. Another involves the smooth coating applied to the inside of cans. The rinse cycle that attempts to wash off the emulsion also aims to remove particulate metal debris that forms on the metal’s surface during the bending and shaping of a can. Like the emulsion, some of the microscopic debris always remains after rinsing. Unlike the emulsion, it can be dangerous to swallow.

To keep powdered metal out of a can’s contents, Schmid says, manufacturers spray-coat the inside with a polymer dissolved in a solvent. When the can is heated, the solvent boils away, leaving only the protective polymer coating.

The coating not only plasters any microscopic debris to the can wall and away from the food, it keeps the food from interacting with can material, an especially important consideration with steel cans.

“Say you’ve got tomato soup in this steel can. You don’t want that acidic soup corroding your can. It would kill your can, and the can would adulterate your food,” Schmid says. “It’s also why you’re advised that when you go camping and you have Spaghettios you don’t cook them in the can, because the polymer will degrade and you’re going to be eating polymer.” (Industry sources tell Schmid that the typical consequences of such a culinary blunder are headaches and constipation.)

Schmid says can manufacturers are forever searching for ways to improve efficiency in their struggle to stay price competitive with plastic and glass bottles. A single can-tooling machine can form 400 cans a minute. In a typical process, all but the top is shaped during a single stroke through a disk of aluminum or steel. The top, seamed on after filling, is made of a more expensive aluminum alloy, rich in magnesium. The added ductile strength of the magnesium is necessary so another machine can mash down a pillar of the metal to form the rivet that attaches the pop top. Today’s beverage cans are “necked” near the top for a reason. The narrower-diameter means less of the expensive lid alloy is needed. It saves a minuscule fraction of a cent per can, but it adds up, Schmid says.

“In this country alone we use about a can per person per day, so you have to make 250 million cans per day. It’s an amazing thing to watch these machines kick out these cans.” Rivet is likely a separate part from the tab. It should be strong enough to attach the tab to the can and to ensure that it does not break when the can is opened. Lip on top of can prevents liquid from flowing down the side of the can. Bottom is indented to enable stacking even when the tab has been opened. The indent provides the necessary room for the open tab. For recycling purposes, pop cans can be neatly compacted flat, and are easy to transport using a wide range of containers. Rivet is a separate piece which connects the tab to the can top. Top of the pop can is stamped with words such as “recyclable” and “return for refund”. Thus, the alloy of the top must be soft enough to allow this stamping to occur.

Aluminum costs more than steel, and the price has been rising. Steel “minimills” now have continuous casting processes that make sheet steel thin enough to form seamless cans. And there is competition from other materials as well. “We h ave to find ways to make cans lighter and lighter to keep fending off polymers, steel and glass. Lighter cans means lower prices to the consumer, who’s then more likely to buy cans off the grocery shelf instead of two-liter bottles or glass.”

ALCOA’s answer is lightweighting, designing cans to use the thinnest aluminum possible within the constraints of strength and appearance.

In 1993, Americans recycled 59.5 billion aluminum cans, 3 billion more than in 1991, and raised the national aluminum can recycling rate to 2 out of every 3 cans. Aluminum can recycling saves 95% of the energy needed to make aluminum from bauxite ore. Energy savings in 1993 alone were enough to light a city the size of Pittsburgh for 6 years.

Special pallets and stacking techniques are used to protect can bodies from crushing stresses and to enable quick and efficient loading into the filling machine line.

The first beverage can, filled by a brewer in Newark, New Jersey in 1935, weighed three ounces. Today, an aluminum beverage can weighs one half ounce – 600% less than the original beverage can. Can manufacturers strive to do even better through a process called “light weighting”-the use of lighter can ends and thinner body walls. Using less material at the beginning of the manufacturing process results in a more effective means of creating safe, reliable, performance-driven packaging. This results in less waste once the packages’ contents have been consumed. It also saves manufacturers money – an added incentive.

The diameter of the bar is 12.7 mm. Its radius is half the diameter. Therefore, its radius can be calculated to be (12.7 mm)/ 2 = 6.35 mm. By applying the conversion factor that 1000 mm = 1 m, this radius can also be expressed as (6.35 mm) * (1 m / 1000 mm) = 6.35 x 10-3 m. The bar has a cross-sectional area given by the following formula:

• Cross-sectional area = r2
• where r is the radius of the steel bar. Using this formula, the cross-sectional area of the bar can be calculated to be:
• Cross-sectional area = (6.35 x 10-3 m)2
• Cross-sectional area = 1.266768698 x 10-4 m2
• (Cross-sectional area = 1.27 x 10-4 m2 when significant figures are applied).
• Gravity applies a force to the bar proportional to the bar’s mass. This force is given by the formula:
• Force due to Gravity = (Mass of object) * (Acceleration of Gravity)

If we assume that the steel bar is located at the surface of the earth, the acceleration of gravity is approximately 9.8 m/s2 at this elevation. Therefore, the force applied to the bar by gravity can be calculated to be:

• Force due to Gravity = (7000 kg) * (9.8 m/s2)
• Force due to Gravity = 68600 kg*m/s2
• (Force due to Gravity = 70000 kg*m/s2 when significant figures are applied)
• The stress placed on the bar is given by the following formula:
• Stress = (force) / (unit area)
• Therefore, the stress placed on the bar can be calculated to be:
• Stress = (68600 kg*m/s2) / (1.266768698 x 10-4 m2)
• Stress = 541535326.2 kg/(m*s2)
• (Stress = 500000000 kg/(m*s2) when significant figures are applied)

The steel bar has a modulus of elasticity of 205,000 Mpa. 1 Pa is defined to be equal to 1 kg/(m*s2). Using the conversion factor that 1 x 106 Pa = 1 Mpa, 1 Mpa is defined to be equal to 1 x 106 kg/(m*s2). We can therefore express the modulus of elasticity of the steel bar in Pa as (205,000 Mpa) * (1 x 106 Pa / 1 Mpa) = 2.05 x 1012 Pa. The strain experienced by the steel bar is the fractional deformation it undergoes when a stress is applied. This strain can be represented mathematically by the following formula: where l represents the length of bar, and l represents the change in length of the bar due to the applied stress.

The elastic region of the stress-strain curve refers to the portion of the curve in which an increase in stress will cause a linearly proportional increase in strain. Within this elastic region, removal of the stress will cause the strain to be reduced to zero as well. In other words, the material is not permanently deformed, and removal of the stress causes the material to return to its original dimensions. The strain is therefore reversible, or elastic. In the elastic region, therefore, stress and strain can be related by a proportionality coefficient. This proportionality coefficient relating the reversible strain to stress in the elastic region of the stress-strain curve is known as the modulus of elasticity. This modulus of elasticity can be represented mathematically as:

• Modulus of Elasticity = (Elastic Stress) / (Unit Strain)

This equation can be rearranged to solve for the unit strain. This rearranged equation is expressed as:

• Unit Strain = (Elastic Stress) / (Modulus of Elasticity)

Assuming the stress applied to the bar is small enough to ensure that the bar is still operating in the elastic region of the stress-strain curve, we can use the above equation to determine how much the bar will be strained by the load. Mathematically, this solution takes the following form:

• Unit Strain = (541535326.2 kg/(m*s2)) / (2.05 x 1012 Pa)
• Unit Strain = (541535326.2 kg/(m*s2)) / (2.05 x 1012 kg/(m*s2))
• Unit Strain = 2.641635738 x 10-4
• (Unit Strain = 3 x 10-4 when significant figures are applied)

This strain is unitless because it represents the fractional deformation of the bar when the stress is applied.

The wall switches come in various shapes and designs, but they generally consist of a metal conducting plate and Insulating plates to cover It. wall switches are constructed of metal faceplates that is to be made out of ferrous metals not less than 0. 76 mm in thickness or non ferrous metals not less than 1. 2 mm In thickness, and the insulating tace plates are made out ot an insulating non combustible material not less than 2. 54 mm in thickness (NFPA 2011 The light fixtures of the place usually etermines the location of the switch to help get the most efficient lighting for the place. For residential places, all the rooms light fixtures must be on a 15-amp circuit. A wall switch has to be placed near every room entry door and a receptacle has to be found every 12 feet to help operate non permanent light fixtures that cannot be operated by a switch.

Closets shall have one globe covered fixture operated by a wall switch. Bathrooms require special moisture resistant light fixtures due to its damp environment also the fixtures should be covered with lenses or globes and one 20- mp circuit for bathroom outlets only (thiele, 2010). In the presence of a laundry room, the washer and dryer should have their individual 20 circuit and in case of electric dryer an Independent 240-volt circuit shall be used.

The kitchen Is commonly the place with the highest number of appliances all over the home. thus it requires Its own 15-amp circuit for the lighting. Stairways needs proper lighting fixtures, a switch, mostly three-way switch, Is to be placed at the top and bottom of the stair and at every turn if necessary Hallways requires three-way switches at the two ends of the ay and four-way switches near every door throughout the hallway, hallways over 10 feet long requires a mlnlmum ot one outlet for general purposes (NFPA, 2011).

Basements and garages is recommended to have three-way switches between doors and a minimum of 1 outlet is required. Outdoor lighting fixtures of a building have to be protected trom weather tactors and any other exterior tactors by sealing the wires and having underground cables. Outdoor lighting shall has to be highly effcient and controlled by a switch In addition to a sensor to turn off the lights during daytime for energy saving purposes

Newey and Weaver described nucleation as a process that must occur in a system, undergoing a phase transition, before the formation of another phase (Royce). This process is called homogeneous nucleation if it occurs away from any boundaries. On the other hand, heterogeneous nucleation takes place on a surface, interface, dislocation or other defect in the material. In addition, the latter type is favored because it requires a lower free energy change to form the initial stable nucleus where others can adhere resulting an increase in size (cited in Royce).

During nucleation, the atoms are forming nano-sized solid clusters. In homogeneous nucleation, clustering occurs above the melting of the metal (Tm) turns back into the liquid state due to its stability on that phase while clustering below Tm can lead to crystallization-nuclei formation if its size reaches stability against melting (Iqbal 3). High solid-liquid interface surface energy is a thermodynamic hindrance in nucleation. Due to this energy barrier, foreign materials are added to serve as nucleation sites. These nucleation sites have lower surface energy, thus, increases the nucleation rate.

The stable nuclei then grow into an equiaxed and finer grain structure (Iqbal 3). Moreover, nucleation is a kinetic process wherein atoms of the melted metal form into clusters within the liquid medium at solidification temperature (Iqbal 9). These clusters act as crystallization nuclei where other atoms adhere and solidify. The rate of nucleation process is directly affected by the difference between the equilibrium melting temperature (Tm) and the freezing temperature (Tf) or undercooling. As a rule of thumb, a higher undercooling yields higher nucleation rate. Nucleation Mechanism

Ben Best discussed that mixtures of some metals, like copper and nickel, both in liquid and solid states are highly soluble in all given concentration. Since both copper and nickel have similar crystal structures and atomic radii, in the cooling process the particles formed have properties imparted by both of these metals. This metal mixture type is called isomorphous. In contrast to this, the mixture of lead and tin is eutectic because of partial solubility of these metals in the solid state. Unlike copper and nickel, lead and tin have different crystal structures and atomic radii.

This is the reason why the solid lead-tin alloy can only consist of 2. 5% lead and 19. 2% tin their maximum composition by weight. In addition, a eutectic mixture has composition that completely liquefies at eutectic temperature. For lead-tin mixture, the eutectic composition is 61. 9% that has a eutectic temperature of 183ºC. This property makes lead-tin mixture as a good soldering agent. Metals typically solidify as crystals at a temperature lower than its melting temperature (Best). The difference in melting and solidification temperatures is called as the maximum undercooling.

This undercooling is the effect of pure metal crystallization. During the crystallization process, the nucleation of small particles or crystallization nuclei occurs first then the adherence of other particles on these nuclei follows. As such, other surrounding particles tend to dissolve it back into the liquid phase. Successful fusion into the crystal releases heat which causes other adjacent atoms to dissolve. This means that the high fusion of a metal reflects its tendency for a high solidification temperature and maximum undercooling (Best).

The energy affects the dissolution process with respect to the surface area of the nucleus while energy variation favoring nucleus growth is a factor of volume proportion (Best). Surface area varies with the square of the radius, whereas volume varies with the cube of the radius. Thus, a large crystal is not susceptible to surface dissolution. In addition, a metal at a specific temperature has a critical radius size. Radius bigger than the critical radius tend to increase in size while smaller radius is susceptible to dissolution.

Nonetheless, lower temperature facilitates the attainment of the critical radius (Best). Further, crystallization may occur in less undercooling if a higher melting point metal with similar crystal structure to and insoluble at the melting temperature of the original metal is added (Best). The crystal growth around these insoluble nuclei is referred to as heterogeneous nucleation. In heterogeneous nucleation, specific sites in a material catalyze the nucleation process through the reduction of the critical free energy of nucleation (?Gc) (Balluffi, Allen, and Carter 477).

It is always in kinetic competition with homogeneous nucleation wherein the faster rate mechanism prevails. The lower value of ?Gc supports heterogeneous nucleation while the greater number of potential nucleation sites favors homogeneous nucleation. Moreover, by means of the nucleation rate expressed as J = Z ßc N exp[-?Gc /(kT )], regimes of temperature, supersaturation, relative interfacial energies, and microstructure in which one nucleation mechanism occurs can be predicted.

When a small particle deposits on the grain boundaries, edges or corners of a polycrystalline microstructures such as grain boundaries, edges or corners, these crystal imperfections will be eliminated with an associated free-energy decrease lowering ?Gc (Balluffi, Allen, and Carter 477). Solidification in Metals The solidification of metals and their alloys starts when a welded small portion of metal melts and resolidifies (“Phase Transformation”). Homogeneous nucleation occurs when there are no other chemical species involved in a nucleation process.

For instance when a pure liquid metal is slowly cooled below its equilibrium m freezing temperature to a sufficient degree numerous homogeneous nuclei are created by slow-moving atoms bonding together in a crystalline form. While the involvement of other chemical species to favor nucleation results to heterogeneous nucleation. Solidification is a crucial stage in metallurgical processes such as in ingot casting, continuous casting, squeeze casting, pressure casting, atomization (Phanikumar and Chattopadhyay 25).

This is also an important stage in secondary manufacturing processes such as welding, soldering, brazing, cladding and sintering. For the properties of the product largely depend on the mechanical properties and the microstructure of the different phases. The microstructure of the products on the other hand, is affected by thermal and solutal processing conditions and thermodynamic and kinetics factors of the materials (Phanikumar and Chattopadhyay 25). Solidification involves heat extraction through diffusion and convection processes, and solid-liquid interface movement.

In addition, the microstructure solidification is a complex process affected by the rate of solidification (v), temperature gradient (G), composition (C) and kinetics factors such as phase equilibrium reactions, nucleation and growth, and crystallographic constraints (Phanikumar and Chattopadhyay 25). Solidification and Mechanical Properties Industrial treatments such as rolling or forging, alloying and thermal treatment are done to metals to strengthen their mechanical properties.

For instance, pure aluminum has a tensile strength of around 13,000 pounds per square inch (psi), however, by cold-working its strength is approximately doubled. This can also be done by adding alloying metals such as manganese, silicon, copper, magnesium and zinc. Similarly, heat treatment makes the tensile strength of aluminum over 100, 000 psi (“Property Modification” n. p. ). Plastic or permanent deformation of crystalline materials is largely affected by the tendency of dislocation within the material. Thus, restraining the dislocation movement improves its strength.

This is done by controlling the grain size, strain hardening, and alloying (“Strengthening/Hardening Mechanisms”). In the material science engineering, a grain is a crystal with unsmooth faces due to the deferred growth in contact with a boundary (“Solidification”). The grain boundary is the interface between grains. Atoms in this region are disordered, hence, no crystalline structure. The different orientation of adjacent grains within the material, the boundary between grains hinders the dislocation movement and the resulting slip.

The solidification rate controls the size and number of grains. Smaller grains denote shorter distances between atoms that can move in a slip plane, thus, improving the strength of the material (“Strengthening/Hardening Mechanisms”). The improvement of metallic strength is done through strain or work hardening or cold-working. In plastic deformation of metals, the movement of dislocations produces additional dislocations (“Strengthening/Hardening Mechanisms”). These dislocations interact, pin or tangle resulting to decline in dislocations movement and causes material strengthening.

This strengthening is called as cold-working for the occurrence of plastic deformation is at low temperature which impedes atom movements. However, cold-working process reduces the ductility of metals. On the other hand, when the process is done at higher temperature, the atoms rearrange to improve material strength (“Strengthening/Hardening Mechanisms”). Since cold-working process reduces ductility, thermal or heat treatment is used to remove its effect. The strengthening gained through the cold-working will be lost if the strain hardened materials are exposed at higher temperatures.

Recovery, re-crystallization, and grain growth may occur during the heat treatment (“Strengthening/Hardening Mechanisms”). Nucleation and Mechanical Properties The number of nucleation sites for the freezing metal affects the grain structure of the solid metal product. Few number of nucleation sites means smaller number of crystallization nuclei, hence, large-grain or coarse structure results. An increase in nucleation site numbers, on the other hand, yields fine-grain structure because a lot of crystallization nuclei are available for the dissolve phase attach and solidify.

Fine grain structure is the most desired product for strength and uniformity in metal production (Poster and Easterling 125). An ideal crystal has a perfect crystalline structure and characterized by a regular repetitive lattice in any space direction. However, crystalline materials have crystallographic defects. Minor crystal defect may impart significant metallic properties. The conductivity of silicon, for instance, is doubled when it is contaminated with 10-8 percent mass of boron (Tisza 107).

There are several properties that can be identified based on the ideal lattice structure such as thermal and electrical conductivities, and specific heat. These are called as structure-insensitive properties. However, there are structure-sensitive properties such as mechanical properties that are hardly predicted on the basis of ideal crystal structure. The discrepancy between the ideal and real crystal structures result to the large differences in theoretical and experimental computation of properties (Tisza 107).