Comparing Polymers: Material and Ceramics

Ceramics are inorganic and nonmetallic materials formed from metallic and nonmetallic elements whose interatomic bonds are either ionic or largely ionic. Many of the ceramics suitable properties are obtained usually by a high temperature heat therapy. Ceramics are made up of two or more elements. Inside a crystalline structure is more technical than that of metals. If the bonding is mostly ionic the crystal structure comprises of positively costed metallic ions, cations, negatively recharged nonmetallic ions and anions. If the ions are bonded along the overall charge must be natural. To have a stable system the anions in the composition that surround a cation must be in contact with that one ion. There has to be a proportion of the cation radius to the anion radius for the coordination and knowledge of the buildings geometry. If for example there is a insufficient coordination, the cation would be incorrectly incased by the anions thus creating a collapse in its expected structural stability. There are many different types of structures can be found for ceramics. One crystal structure is the AX type where there are an equal variety of cations and anions. Another crystal composition that exists for ceramics has some other variety of cations and anions but nonetheless has a neutral fee because the ions have different magnitudes of charge is called an AmXp structure. An AmBnXp composition has several type of cation, represented by way of a and B but only 1 kind of anion. This sort of framework is also seen in close packaging of ions in metals. Flaws arise in the crystal composition of ceramics nearly the same as metal structural flaws. Defects may appear in each one of the two ions of the composition. At any time there can be cation, anion interstitials, cation or anion vacancies. Most flaws or imperfections occur in pairs to maintain the electroneutrality. A Frenkel defect is a cation vacancy and cation interstitial pair. Whenever a cation and anion vacancy pair occurs they can be called a Schottky defect. Ceramics can also have pollutants in the crystal composition like metals. Figure 12. 21 provides schematic diagram of the Frenkel and a Schotkey problems (pg 435). In many cases ceramics have a tendency to be very brittle which can result in catastrophic inability with hardly any signs of exhaustion. This is due to the fact that ceramics absorb very little energy before they fracture. When ceramics are subjected to a tensile stress, they more often than not fracture before any vinyl deformation takes place. Fracture occurs as a result of development and propagation of breaks perpendicular to the applied weight. Ceramics have a greater ability to withstand compression than pressure. The modulus of elasticity diminishes with more pores in the ceramic materials. Whenever there are many pores in the materials they become stress concentrators which expose the material to weak section. However, ceramics are incredibly hard and are good for applications where abrasive or grinding action is necessary.

Most polymers are organic and are comprised of hydrocarbons with interatomic pushes that are displayed as covalent bonds. Most polymers chains are very long and incredibly complex. These long substances are made of repeat models that happen to be repeated over the chain. The smaller repeating unit is called a monomer. Polymers can consist of a single repeat unit, called a homopolymer, or two or more different repeating products called copolymers.

Polymers generally have a very large molecular weight. These molecular chains tend to have many kinking, bending, and coiling along with entanglement with neighboring chains might occur. This causes the results material to be very stretchy. Polymer chains can have side groupings which cause different configurations based on which part and using what regularity they relationship. They are able to present an even of crystallinity similar to the packaging of the molecular chains to generate an requested atomic array. This crystal composition can be more complicated than metallic crystal structures. Flaws in polymers also differ from those within metals and ceramics. Defects in polymers are linked to the chain ends because they are slightly different than the string itself and emerge from the sections of the crystal. Polymers are incredibly sensitive to pressure rate, temperatures, and chemical dynamics of the surroundings. Different polymers can display different stress pressure behavior depending on complexity of the molecular chain. Certain polymers display a level of is brittle where fracture occurs before elastic deformation which is very similar regarding ceramics. Another type of polymers is very similar to metals where flexible deformation takes place first accompanied by yielding and clear plastic deformation. Another type is exhibited by elastomers that have totally elastic and recoverable deformation. Polymers generally have a lower modulus of elasticity and tensile durability then metals. Some Polymers can be stretched up to ten times much longer than its original talk about where metals and ceramics cannot easily accomplish. Polymers show viscoelasticity at temperature ranges between where elastic and liquid like habits are prevalent. Very much like metals and ceramics, polymers can experience creep. Creep is a period dependent factor due to deformation under stress or elevated heat. In both ceramics and polymers, creep is determined by time and temperature. Polymers may be ductile or brittle depending on heat, strain rate, specimen geometry, and way of loading which is very similar to the properties of metals. Polymers are brittle at low temps and have somewhat low impact strengths. Polymers can experience exhaustion under a repetitive loading. They are usually softer than metals and ceramics and unlike metals and ceramics, polymer melting occur over a range of temperatures instead at a particular temperature.

Metals are a material made up of metallic elements that are bonded metallically like common alloys. The electrons aren't bound to any particular atom developing a matrix of ion cores bounded by many electrons. They are incredibly good conductors of heat and electricity while ceramics and polymers lack. Polymers and metals are both ductile and aren't that brittle though metals also show an even of malleability. Ceramics are incredibly brittle, they have a tendency to fracture under a load which means they lack in ductility. Polymers will be the softest material because of the complex framework, while ceramics will be the hardest but are not very hard because they fracture before clear plastic deformation occurs. Polymers plastically deform quickly and have the tiniest Young's modulus. Ceramics have the highest value for their brittleness and never reach the point of clear plastic deformation because they might fracture first. The ideals of Young's modulus for metals street to redemption between those for polymers and ceramics. These three materials have diverse buildings and display different levels of defects.

"Alloying, " using the term in the broadest sense.

Simply an alloy is a metal compound that consists of 2 or even more material or nonmetallic elements. These combinations of metallic and non metallic elements finally create new ingredients that in final result screen superior structural properties as compared to the elements by themselves. The type of alloy mixtures is highly dependent on the desired mechanical property of the materials. Alloying can be applied to metals, ceramics and polymers where in each specific properties are desired.

One of the very most desired properties of steel alloys is the hardenability. A material with a higher level of hardness will resist deformation brought on by surface indentation or abrasion while a materials with a minimal hardness level will deform easier under similar conditions. The primary factor in a material's hardenability is its martensite (the rate which austenitized iron carbon alloys are created when cooled) also content and is related to the amount of carbon in a material. With this request of alloying on metals, the material can exhibit increased strain and stress resistances as well as elasticity. These properties are favorable when dealing with development and manufacturing techniques.

A ceramic alloy is actually a fusion of the ceramic with of 2 or even more metals. As seen in metallic alloys, ceramic alloys can contain impurity atoms in a solid status. In ceramic alloys an interstitial and substitutional states are possible. In an interstitial type, the anion needs to be bigger than the impurity of the ionic radius. The substitutional impurity is applicable where in fact the impurity atom usually forms a cation in the ceramic materials thus the variety cation will be substituted. Figure 12. 23 offers a great visible representation of interstitial and substitutional types in a ceramic alloy (pg 437). Significantly, to properly achieve a good point out of solubility for substituting impurity atoms, the demand and the ionic size must be as the same as the variety ion. If they were different it there would need to be various other way for the electroneutrality to be taken care of within the sturdy. A good way to do this is to create a formation of lattice problems of vacancies or interstitial of both ion types. Cobalt chromium is a perfect example of a ceramic alloy in which was designed to be utilized for coronary interventions thus since it will not degrade once positioned in the human body.

Polymer alloys contain several different kinds of polymers in a way blended together. There are a number of additives that can be blended or merged in with the polymer to create the desired result for the materials. Polymer additives that support the adjustment of its physical properties are fillers, plasticizers, stabilizers and of course fire retardants. Fillers are usually released to a polymer, when a greater comprehensive durability and thermal stability is desired. Creating these kinds of alloys are extremely beneficial because they're generally super easy to create and utilization in their desired form. Plasticizers help increase the versatility and toughness of polymers by minimizing the hardness and stiffness of the materials. They are often launched to polymers that are generally brittle at room temp. These additives are especially useful because they often lower the glass transition temp thus allowing the polymer to have a extent of pliability. Due to the fact that one polymers aren't resilient to environmental conditions, stabilizers are launched. They provide balance and integrity against deterioration resistant to the mechanical properties. Both most common types of environmental deterioration are UV exposure and oxidation. A major concern with many polymers is that they are highly flammable. Fire retardants are introduced to such polymers to reduce the combustibility of the materials by interfering with its ability to combust via a gas stage or initiating a different combustion response that produces less heat. This process will certainly reduce the temperature that could eventually cease the using up process.

Kirill Shkolnik


ESG 332 - R01

Exam #2 (Question #2)

Describe with reference to period diagrams and dislocation theory, how precipitation time hardening can be achieved in light weight aluminum alloys.

Generally aluminium is a metal with a low level of denseness compared to other metals. Due to this low level of density, it conducts electricity and high temperature better than copper. Aluminums just over 1200 diplomas Fahrenheit which is comparably low to other metals. Because of these simple facts, it appears ideal to bond elements such as titanium, silicon, copper, zinc and other materials to magnify aluminums positive characteristics. The process precipitation time hardening can amplify the alloying of aluminium. This process requires supersaturating a good solution precipitating consistently dispersed contaminants on the light weight aluminum. This can help stop the activity of dislocations within the material structure. The essential idea of dislocation is the atomic misalignment of atoms in a linear plane. These atomic misalignments impact a whole series of atoms on the plane. The series of misalign atoms form a line called a dislocation series. You will discover two known types of dislocation called the screw and border dislocation. Screw dislocation and edge dislocation will be the most important types of dislocations but require a certain amount of the other person that occurs. By reducing the quantity of dislocations can radically boost the power in the material. The process of alloying usually makes a natural material harder. The process of alloying is having one metallic connection with impurity atoms from other materials to change its mechanised properties. An alloying process called sturdy solution alloying uses a solution to replace bonds inside the metallic. The limiting of dislocation motion is a significant factor for alloying because it may be used to reinforce metals. Alloying metals with the precipitation hardening makes the effectiveness of the new material better as the improvement of the process is delayed. The explanation for precipitation hardening is sought after is due to its abilities in making metals better.

Aluminum alloys can have precipitation in an exceedingly specific way. Heat treatment occurs when one materials is warmed a supersaturated mixture at a particular phase and so two different stages can be present collectively. A precipitate varieties in small portions throughout the whole material. When the mixture is at its equilibrium, the forming process comes to an end. The small bits of precipitate then diffuse alongside one another to create one large precipitate. This level of the precipitate will weaken the materials important structure. The tiny bits of precipitate in the material make it harder for dislocations to move. When durability of the materials diminishes because of the activity of the precipitate it is called overaging.

There are two things need for heating treatments to be employed. Figure 11. 21 offers a graphical representation the partnership between temp and structure for lightweight aluminum and copper (pg 402). The copper stage displayed at a shows a supersaturated stable solution in lightweight aluminum while the chemical substance that between your two elements is symbolized as ?. Oddly enough the idea M signifies the potential solubility point at certain temperature and structure in the material. Point N symbolizes the solubility limit of an and (a + ?) L symbolizes the temperatures needed for the perfect solution to become a liquid. If a major amount of solute is manufactured available in the solution, we'd have a precipitation solidified alloy. The limit of the solubility curve significantly decreases in concentration as the heat decreases.

There are two different ways precipitation can occur. One process is the utilization heat treatment where in fact the solute can be dissolved to create a solid solo phase solution. This method can be done by heat an alloy to a very temperature. Figure 11. 24 demonstrates the ? stage is combined into a period (pg 404). Then the alloy is cooled where all that is remaining is a supersaturated a phase. Precipitation heat therapy the (a + ?) stage is warmed to a specific temperature to permit the ? phase to precipitate. The alloy is cooled and the hardness of the alloy is determined by time. A logarithmic function a comparison with power and time proves the dependence of temperature and durability.

Kirill Shkolnik


ESG 332 - R01

Exam #2 (Question #3)

Describe what is meant by the word "glass transition temperatures" and illustrate your answer from polymer and ceramic point of view.

Typically a cup transition temperature is in which a noncrystalline form of a polymer or a ceramic is cooled and transforms from a brilliant cooled water into a goblet. A ceramic or a glassy material is a noncrystalline material that becomes a lot more viscous when it is cooled. Due to the fact that glassy materials are noncrystalline there is no definite temperature when the water will change into a solid. Though, additionally it is important to notice that in noncrystalline materials the specific volume is dependent on temperature and can lower with the temperatures. The glass transition temperature displays a decrease in the rate at which the specific size decreases with temps. When the temps is below this value, the materials is a ceramic from and straight above this aspect the material is considered a supercooled liquid. The glass changeover heat occurs in both glassy and semicrystalline polymers, however, not in crystalline materials. As certain molecular chains in noncrystalline materials temp drop anticipated to lack of motion the goblet temperature change occurs. Basically wine glass transition is the time in which a steady transformation occurs from the liquid express to a just a bit rubbery status and then to the final more rigid sound material. The goblet transition temperatures is the state in which the material will go from its rubbery to rigid express.

This transition can take place in both directions. As the polymer for example is cooled to a rigid sturdy, it can be heated and undergo the same transition in reverse. As the material undergoes many of these changes its properties change from state to convey. Some materials can experience greater change are the stiffness, heating capacity, and the coefficient of thermal expansion for the material during this changeover. The glass move temperature also functions as a limit boundary for applications of polymers and polymer matrix like components. If this temp is beyond the materials threshold, it'll no longer fit the required properties the duty had needed and the application would be useless. The molecules that were frozen set up below the will both rotate and translate at the temperature above. Molecular characteristics impact on the chain's stiffness and will in turn affect the glass transition heat for the materials.

Some molecular characteristics that can cause the chain's versatility to be reduced and the glass transition heat range to increase that include bulky side categories on the molecular string. Also these characteristics can affect polar atoms or groups of polar atoms privately of the molecular chain, double bonds, and aromatic organizations. The glass move temperature will can also increase as the molecular weight of the materials increases. Branching also affects the of your material, many branches will decrease the chains mobility and increase, a lower density of branches may cause the to diminish as the molecular chains will have a freer range of motion.

Crosslinks may appear in glassy polymers and make a difference, they cause the reduced amount of motion and for that reason increase. If there are way too many crosslinks arise in the material, the molecular motion would be so limited that cup transition may not occur. It could be understood that many of the same molecular characteristics which have an effect on the glass change temperature also have an effect on the melting change temperature. The two are affected in such a similar manner that is usually somewhere between 0. 5 to 0. 8 times the melting change heat range. Figure 15. 19 shows this mathematic marriage (pg 548). Both ceramic and polymers have a glass transition temps. A goblet can be described by a number of different labels; such as vitreous sturdy, an amorphous sturdy or glassy sound. An amorphous solid has the mechanised properties of a good, but does not have long range molecular order where they are really in movement at an extremely slow rate which it be considered rigid for regular purposes. When glassy materials have been supercooled below the wine glass transition temperature they will undertake characteristics a lot like those of a crystalline solid. This solid can be rigid with an elevated hardness and will be more brittle. However, if a glassy materials is heated up to above its a glass transition temperature it'll become softer and many of the intermolecular bonds will break allowing the materials to stream at an increasing fluid viscosity. A polymer below the a glass transition temperatures is more rigid, but as it gets into its glass change phase, the material becomes more rubbery as its viscosity increases. The polymer can get into its glass transition at a lesser temperatures when critical factors that always affect the action of the substances in the materials aren't all present.

When molecular weight of a polymer rises, the glass changeover temperature will can also increase. Many factors that improve the the rubber gasket wouldn't normally do its job properly.

Polymers can display the following structures: amorphous, semi-crystalline and crystalline. Describe these buildings and explain how the mechanised properties may be inspired by these structural forms for a polymer of the same chemical type formula.

Polymers can develop amorphous, semi-crystalline and crystalline buildings of the same chemical substance method. Polymers can can be found as fluids, semi solids, or solids related to the crystal constructions respectively. However each one of these structures exhibit a number of different mechanical properties. The crystallinity of the polymer will depend on the intermolecular supplementary bonding that will heavily affect the level of any mechanical property of the polymer.

The tensile durability, stretchy modulus and compression durability of any crystalline composition will be more powerful than a semicrystalline framework and significantly more powerful than amorphous type composition.

For a crystalline framework the molecular chains of the polymer are securely packed together within an sorted out atomic group which take up space and can affect the polymers mechanical properties. These crystalline structures are heavily influenced by the wine glass transition heat. Also the isomer and chemical substance solution lays out important factors that will be very important in the formation of the bulk materials structure.

From certain large large functional groupings there becomes an impending hindrance that will inhibit the activity capability of a molecule. This process will improve the energy requirement of any stage change. The outcome of this process is a greater transition temperature. This new temp transition will improve the chances for the formation of a crystalline structure. The reason behind this is and span of time before the material becomes a disorganized water and requires a longer time for the substances to arrange themselves properly. When polymers have many branches the weaker the material will be, even though crystalline buildings are stronger than less ordered materials. Figure 15. 18 shows the change in these structural says when specific size and heat range are compared (pg 546). Pure polymers employ a small melting point varies and bond strength. Doped polymers and polymer alloys will generally have wider melting point runs. The process of branching will decrease the strength of a polymer, which would continuously reduce the melting point temperatures. Though, the take action of branching on closely thick branches will lower molecule range of motion. Also within this technique the molecular weight is influenced as well.

Kirill Shkolnik


ESG 332 - R01

Exam #2 (Question #4)

How are T-T-T and C-C-T diagrams used to design heat treatment schedules for basic carbon steels.

Time-Temperature-Transformation or T-T-T and ongoing cooling transformation or

C-C-T are being used for heat treatment schedules for basic carbon steel. T-T-T are commonly called an isothermal change diagrams can show the change of different stages at certain temperature ranges. C-C-T may be used to calculate percent change from the logarithm function through time.

The use the isothermal change and ongoing cooling transformation diagrams may be used to develop a heat therapy for basic carbon steels. These diagrams will support the knowledge of carbon steels through period diagrams. When a structure is heat treated, its cooling process helps keep its structure. This process can be analyzed through T-T-T. Figure 10. 13 shows a graphical representation of temperature against time with a third dimension with the percent of the metal alloy changed to pearlite (pg 326). The knowledge of an instant cooling alloy sully depends on the understanding and program of heat therapy. It is grasped that isothermal transformations do not change in temperature but continuous cooling transformation diagrams do. C-C-T and T-T-T display the same measurements but over a more substantial spectrum of time and heat. Figure 10. 28 shows different varieties of metallic alloys (pg 338). A material that has been cooled to a temperatures just a little below its eutectoid temperature, and isothermal transformation is maintained for a long period of time, interestingly it cannot be depicted on T-T-T diagrams in spheroid varieties.

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