首页 › 答案 › 题库 › 慕课

未分类

195321Thermosetting polymers have the distinct advantage of being chemically and thermally resistant materials used in many high-performance applications.

195322Thermoset polymers are generally harder and stronger than thermoplastics and have better dimensional stability.

195323Thermoplastics are mainly prepared by addition polymerization.

195324Examples of common thermoplastic polymers include（）.

195325Poly(1,4-cis-butadiene) has a higher Tg than Poly(1,4-trans-butadiene) because the cis -form reduces the energy barrier for rotation of adjacent bonds.

195326PVC and PAN have a lower Tg than amorphous polypropylene.

195327Polycarbonate has a lower Tg than polyethylene.

195328Semicrystalline polymer is formed in a temperature range from Tg to Tm

195329Totally elastic deformation occurs very quickly, and the strain is independent of time.

195330Viscosity refers to the ability of a material to return to its original, initial size　shape once an external load or force is removed.

195331Which one (s) of the following is or are correct?

195332Which ones of the following are correct?

195333Materials in solid state may be（）.

195334When the methyl group and H atom are located on opposite sides of the double bond, the polymer is a cis-isomer.

195335The formation of cross-linked structures in synthetic rubbers is usually called vulcanization.

195336Common polymers, such as PE, PP, PVC, PSt, nylon, and PET have linear structures.

195337Through controlled/living free-radical polymerization (CRP), molecular weight distribution could be narrowed greatly, and PDI could be near to 1.

195338In condensation polymerization, two monomers, dimers, trimers, tetramers, or oligomers, can react with each other at any time.

195339The activity of a growing radical can be destroyed by reaction with（）.

195340The molecular weight distribution, PDI, could be a value near to 1, when polymers are produced by living or controlled polymerizations.

195341The length or size of a polymer molecule can be quantified by（）.

195342Number average molecular weights provide us some information related to（）.

195343Saturated molecules-containing more than two functional groups cannot be used to produce polymers.

195344Nowadays, all of the polymers are synthesized artificially.

195345Slower cooling permits some crystallization in the process, we call it（）

195346（）is considered as glass former.

195347In cold step, the ceramic part is formed or shaped into a preform, which called .

195348Some flaws can occur at any of sintering stages, which consist of.

195349The main driving force in sintering process is

195350（）refers to the network of pores that a liquid such as water can penetrate.

195351Following material is not sorted to silicates.

195352Ceramics can be produced at than that of competing metal-alloy components.

195353Following processing technique is not suitable for the biomicmickry or biomimetics.

195354Amorphous materials do not have clearly defined freezing or melting points as do crystalline materials.

195355The most expensive glass is.

195356The firing consolidates the particles and bonds the ceramic particles together permanently.

195357Traditional processing for fabricating ceramic is .

195358A major problem in ceramic processing is achieving the same properties every time when a process is repeated.

195359Sintering furnaces usually heat ceramic compacts externally by following thermal transfer.

195360Grinding is accomplished by confining the ceramic powder, this process can be called a　.

195361The bulk density of complex geometric parts as well as their various porosities can be determined based on Archimedes' principle.

195362There are two factors influence the density of material.

195363The term describing the density of ceramics that includes its porosity and both crystalline and noncrystalline phase is（）.

195364Sand consists of fine particles of quartz.

195365Clay is a complex mixture of .

195366Ceramics can be produced at　 than that of competing metal-alloy components.

195367The crystalline structure of Silicon carbide is　 with alternating Si and C atoms covalently bonded together

195368The main source of quartz is.

195369Advanced materials include　 , exhibit specialized properties.

195370Ceramics based primarily on the natural raw materials of clay and silicates are（）

195371In corrosion process, the total rate of oxidation must equal the total rate of reduction.

195372Annealing and normalizing present a significant difference on the ductility of low carbon steels.

195373The phase diagram contained only two components is known as binary diagrams.

195374Compared with ferrous alloys, nonferrous metals are much lighter, and have lower conductivity.

195375Some general corrosion protection techniques include material selection,（）,（）, and（）

195376uses cooling in still air？

195377Stainless steels are divided into three classes on the basis of the predominant phase constituent of the microstructure:（）,（）, or（）

195378According to the composition, metal alloys are grouped into two classes:（）, and（）metals

195379（）is believed “the most glamorous metal in the world”

195380Metals are good conductors of both（）

195381（）is one of the principal alloying elements in stainless steels, and one major constituent in superalloys.

195382The predominant alloying element in stainless steel is（）, which concentration should be higher than 11 wt%.

195383Most cast irons have a chemical composition of（）percent carbon.

195384Cast iron can be classified into four categories: gray cast iron, white cast iron, nodular cast iron and（）cast iron.

195385Which of the following do not belong to non-ferrous metal?

195386All alloys that are not（）based, are called nonferrous metals

195387Amorphous metals are non-crystalline, and have a glass-like structure. Like common glasses, amorphous metals are electrical insulators.

195388The magnetic shape memory effect results due to martensitic phase change to austenite phase at higher temperature

195389Magnetostrictive materials can convert　energy into kinetic energy, or the reverse

195390Stress corrosion cracking (SCC) results from the combined action of an applied tensile stress and a corrosive environment

195391Cathodic protection involves supplying electrons to the metal to be protected from an external source. The external source maybe be an external（）or by（）

195392For some stainless steels, when heated to a certain temperature range (（）) for a sufficiently long time, these alloys become sensitized to intergranular attack

195393Refractory metals are those metals which have extremely low melting temperatures

195394For brasses, tin is the predominant alloying elements as substitutional impurity.

195395Refractory metals include niobium (Nb),（）,（）, and（）

195396Cast iron is the most widely used engineering material, and also the most recycled of all materials

195397According to carbon content, the steels are classified into low-carbon, medium-carbon, and high-carbon types.

195398A thermal process to toughen the high carbon steel by providing more ductility is（）

195399（）is usually performed after quenching

195400The eutectic concentration of carbon is 0.76%

‹1…195319541955…2612 ›