Economic, Environmental, and Societal Issues in Materials Science PDF

Economic, Environmental, and Societal Issues in Materials Science Overview In addi on to fundamental materials proper es, selec ng which material to use in an applica on can be limited by a number of factors. Some of these factors include the cost of produc on, availability of star ng materials (nat...

Economic, Environmental, and Societal Issues in Materials Science Overview In addi on to fundamental materials proper es, selec ng which material to use in an applica on can be limited by a number of factors. Some of these factors include the cost of produc on, availability of star ng materials (natural resources), level of pollu on resul ng from the manufacturing process, and amount of waste produced at the end of the lifecycle of the applica on. In this lesson, I will present rela vely brief overviews of economic, environmental, and societal considera ons that are important in the materials selec on process. Introduc on In this lesson, we're going to look at the economic, environmental, and societal issues of materials science. The textbook reading for this week will introduce these topics, while the addi onal text on this website will supplement the reading material and explore further the topics of green design and social jus ce with regard to materials. The video for this lesson, Making Stuff: Cleaner, explores the science and technology of making energy produc on and usage cleaner and more efficient. Materials development in genera ng, storing, and distribu ng energy towards crea ng a more sustainable future are highlighted in the video. Economic Considera ons First and foremost, a product must make economic sense. The price of a product must be a&rac ve to customers, and it must return a sustainable profit to the company. To minimize product costs, materials engineers should consider three factors: component design, material selec on, and manufacturing technique. Also, there could be other significant costs including labor and fringe benefits, insurance, profit, and costs associated with regulatory compliance. As the world has become more populated and that popula on is increasing its usage of the earth's natural resources, engineers are increasingly being asked to consider sustainable prac ces when developing new products. Also, since it is es mated that approximately half the energy consumed by the U.S. manufacturing industry is used to produce and manufacture materials, the efficient use of energy for manufacturing processes and u liza on of sustainable energy sources when available is highly desirable. Sustainability represents the ability to maintain an acceptable lifestyle at the current level and into the future while preserving the exis ng environment. Your textbook discusses one approach to achieving sustainability: green product design. In the next sec on, we will look at some green design principles and examples of their applica on. Before moving on to that sec on, please watch the following short video. This (1:53) video on using renewable feedstock to replace nonrenewable star ng raw materials highlights a green design principle used to make processes more sustainable. The term renewable feedstock refers to raw material that can be grown or produced by humans. The usage of renewable feedstock is a&rac ve because it reduces the amount of harmful waste produced from the crude oil refinery and dis lla on processes. Most print inks are made from crude oil derived pigments. If you think about the amount of prin ng that is done on a global scale, this can be a problem in the long term. Currently in development are soy-based inks which are derived from the oil of the soybean plum. As a plum, soybeans are a renewable resource. The produc on process of these inks is overall more environmentally friendly then their petroleum-based counterparts. Also, these soy-based inks are much brighter than the petroleum-based inks. The recycling process of paper products printed with soy-based inks is also considerably more environmentally friendly. When paper products are recycled, the ink needs to be removed. Petroleum inks can be difficult to remove, but soy-based inks can be removed with rela ve ease. Components of Green Design There are three primary components of green design: reduce, reuse, and recycle. The reduce concept means to redesign a product to use less material. The reuse concept means to fabricate a product using material that can be used again. Recycling refers to the concept of reprocessing a product at the end of its lifecycle into new raw material that can be process sed into new products. One green design principle is that if there is less waste produced, then there is less to clean up. Please watch the following short (2:23) video that highlights this principle. Recycling Recycling of used products rather than disposing of them as waste is a desirable approach for several reasons. Recycled material replaces the need to extract raw materials from the earth. The energy requirements to process recycled materials are normally less, and in the case of aluminum much less, than the energy required to process extracted raw materials from the earth. In addi on, recycling conserves natural resources and eliminates the ecological impact from the extrac on of raw materials from the earth. Proper product design facilitates recycling, which reduces pollu on emissions and landfill deposits. Some issues surrounding recycling include that products must be disassembled or shredded to recover materials, and collec on and transporta on costs are significant factors in the economics surrounding recycling. Recycling of Metals As men oned in the e-book, aluminum is the most commonly recycled nonferrous metal. (Ferrous is La n for iron, so a nonferrous metal is a metal which does not contain iron.) Aluminum is recycled because it takes a lot less energy to recycle aluminum than it takes to extract aluminum from bauxite ore, which requires hea ng and electrolysis. In addi on, aluminum readily forms an oxide that forms a protec ve surface. This protec ve surface protects the bulk of the aluminum from oxidizing further. This results in most of the aluminum being recovered every me it goes to the recycling phase, in contrast to iron. In the case of iron, oxida on, i.e., rust, does not protect iron from oxygen and water, and significant amounts of iron are not recyclable because the iron has been converted to rust. Recycling of Glass Glasses are the most common commercial ceramics, however, there is li&le economic incen ve to recycle glass. The raw materials for producing glass are inexpensive and readily available. Glass is rela vely dense, which makes it expensive to transport which adds to the costs of recycling. Glass must be sorted before being processed during recycling, usually done manually which adds to costs. Not all glass is recyclable, and the glass comes in many different forms. Recycling Polymers One way of classifying polymers is to break them up into two classes. The two classes of polymers are thermoplas c polymers and thermose"ng polymers. The basic property that separates a thermoplas c polymer from a thermose=ng polymer is the polymer’s response to being heated. When the thermoplas c polymer is heated, it melts, so?ens, and can be reformed when cooled. When the thermose=ng polymer is heated, it hardens and cannot be reformed and stays hard when cooled. We will learn much more about each of these two classes of polymers and the reasons for their defining proper es later in our lesson on polymer structures. Since thermoplas c polymers can be melted and reformed, they are easily recycled. However, their proper es do degrade with each reuse. Thermose=ng polymers are much more difficult to recycle. Some of them can be ground up and used as filler for other processes, and, on a case-by-case basis, some can be processed to be broken down into their underlying base units which can be reused. Another approach to reducing the amount of plas c that ends up in our landfills is the development of biodegradable plas c. The idea here is that plas c can be made to breakdown (be compostable). In addi on, bioplas cs o?en come from renewable raw materials. But this leads to an ethical issue: do you use the available arable land for plas c or food produc on? Incinera on leads to a huge volume reduc on of waste, which results in less waste ending up in the landfill. Waste in the landfill is the least environmentally friendly op on. However, incinera on typically results in less recycling, which would be a more efficient use of recyclable material than incinera ng it. This reduc on of recycling due to incinera on is considered the major disadvantage of incinera on. Although an important concern with incinera on is the produc on of toxins, with proper technology these toxins can be managed. A segment of the video for this week, Making Stuff: Cleaner, discusses burning waste to create electricity. Please watch the following short video (4:40) which discusses burning waste to create electricity as well as the issues regarding incinera on discussed above. Limits of Recycling Recycling has a number of advantages. Properly done, it reduces the usage of raw materials, energy usage, air pollu on, water pollu on, and greenhouse gas emissions. There are, however, a number of limits to the effec ve implementa on of recycling. Recycling can involve energy usage, hazards, labor costs, and prac ces by individuals and countries, which can hamper the efficient implementa on of recycling plans. The biggest limit to recycling is that not all materials can be recycled and so materials can only be recycled a limited number of mes due to degrada on each me through the process. This degrada on is referred to as downcycling. In addi on, recycling poses a number of societal and ethical issues. As highlighted in the e-book, e- waste recycling has led to electronic waste from developed countries being shipped to undeveloped countries for recycling. In many cases, this leads to low wages and terrible condi ons for workers involved in the recycling process and the release of toxins which are environmental and health risks for the individuals and their surrounding communi es Summary Producing a sustainable society is one of the greatest challenges facing our society. The supply of natural resources, the crea on of pollu on during the manufacture of materials, recycling issues, and materials waste all issues of concern towards crea ng a sustainable society. By considering a material's total life cycle, u lizing materials life cycle analysis, and implemen ng a ‘green design’ philosophy, engineers can work towards allevia ng some of these issues. STAINLESS STEEL - A steel that has been mixed with chromium which makes it corrosion resistant.  Strong and resist wear and tear.  Stainless steel is NOT completely corrosion proof.  Ideal for pan exteriors.  It does not react to acidic or alkaline foods and won't pit or scratch easily.  It has one drawback: it's a poor conductor of heat and doesn't react to temperature changes very quickly. ALUMINUM - Second to copper  Transmits heat rapidly.  Pure aluminum is quite so?, so it is o?en alloyed, or mized with other metals such as magnesium, copper or bronze for added strength.  Lightweight  Fairly inexpensive  According to whfoods.org, cookware made of aluminum should be avoided. COPPER - Best heat conductor.  Conducts heat well, making it easy to control cooking temperature.  Not magne c.  Coa ng of copper cookware can be dissolved by food especially the acidic foods. CAST-IRON - Extremely durable and resists warping, den ng and chipping.  Heats slowly but has an equal distribu on heat that extremely retains.  Ideal for browning meats or poultry and frying all types of food.  Extremely heavy and unless it has an enamel lining, it requires seasoning to protect it from rus ng. CARBON STEEL - A metal alloy formed by combining Iron and carbon.  Extremely hard and durable.  Ideal material for woks, omelet pans and crepe pans.  Unlike stainless steel, it is more suscep ble to rust.  Should not be washed unless absolutely necessary. NONSTICK PANS Popular because they release food easily and clean up with a li&le effort.  Requires li&le or no oil for cooking.  The non-s ck coa ng industry started out with Teflon in l 946. ENAMEL - Thin, durable layer of colored glass used to coat the Interior and exterior of other cookware.  It prevents corrosion.  It doesn’t transmit heat well, but it does hold heat efficiently.  Provides rapid changes in food's color TIN -Used as lining for copper pans.  Protects copper from acidic foods with which the copper may react.  Tends to be a be&er transmi&er of copper's renowned heat conduc vity.  Should be used only over low heat. Fa gue failure is a type of structural damage that occurs when a material is repeatedly or cyclically loaded, causing cracks to form and spread. This process can weaken the material over me, eventually leading to a catastrophic failure. Fa gue failure is a cumula ve process that can happen without warning. It's responsible for about 80%of failures in metallic structures and machinery parts. When selec ng a material for a par cular applica on, it's important to consider the service condi ons it will be subjected to. The material's ul mate tensile strength, which is the maximum load it can withstand before failure, is one of the most important proper es to consider. THREE STAGES OF FATIGUE IN MATERIALS 1. CRACK INITIATION. Microcracks form when a material cycles between stress levels. These cracks are usually less than 0.5mminsizeand are not visible to the naked eye. They typically start at a free surface or near a stress riser. 2. CRACK GROWTH. The microcracks grow into larger cracks. The cracks grow with each stress cycle, and the stress on the uncracked material increases 3. FRACTURE. When a cri cal amount of the material has cracked, the remaining uncracked material can't support the load and fractures. FORMS OF FATIGUE 1. MECHANICAL FATIGUE is a type of structural damage that occurs when a material is repeatedly subjected to cyclic loads, or fluctua ng stresses and strains. 2. VIBRATION FATIGUE is a type of mechanical fa gue that occurs when equipment vibrates during opera on, causing the material to undergo dynamic stress. This stress can weaken components over me and lead to cracks and eventual failure. 3. LOW CYCLE FATIGUE Occurs when a material is subjected to high stresses over a small number of cycles, which can cause structural failure in hundreds or thousands of cycles. 4. HIGH CYCLE FATIGUE Occurs when a material is subjected to low stresses over a large number of cycles, which can cause failure a?er millions of cycles. This type of fa gue is common in rota ng parts like sha?s, gears, and turbine blades 5. THERMAL FATIGUE Occurs when a material is subjected to cyclic thermal loads, which causes the material to expand and contract, leading to stress build-up and cracking. This type of fa gue is common in materials that experience hot-cold cycles, like engine parts. 6. ACOUSTIC FATIGUE Occurs when a material is subjected to cyclic stress loading from acous c (noise) waves.