无机非金属专业英语

Ceramic Fabrication Process: Conventional Routes to Ceramics陶瓷生产工艺：陶瓷生产的常规途径

引言 1、Solid ceramic bodies are generally produced by using the process of powder compaction followed by firing at high temperature. 固体陶胚体通常都是利用粉末压实而后在 高温烧结的工艺来生产。

A.Precipitation from solution B.Uniaxial pressing C.Hot uniaxial pressing D.Solid-state sintering

(a) Precipitation from solution 溶液的沉淀析出 2、Alumina occurs as the mineral bauxite and is refined in the Bayer process whereby ore is initially dissolved under pressure in sodium hydroxide so that solid impurities (SiO2, TiO2, Fe203) separate from sodium aluminate solution. 氧化铝是以矿物质铝矾土的形式出现的，并且在 精炼矾土工艺中得以精制。这个工艺借以矿石最 初是在压力下溶解在氢氧化钠中的因此固体杂质 如二氧化硅、二氧化钛、氧化铁等就可以从铝酸 钠溶液中分离出来。

This solution is either seeded with gibbsite crystals (a-Al2O33H2O) or undergoes autoprecipitation to bayerite (β-Al2O33H2O) after its neutralisation with CO2 gas. Temperature,

alumina supersaturation and amount of seed affect particle size during crystallisation. 这种溶液要么是结晶出水铝矿晶体，要么是和二氧化碳气 体中和后沉淀出三水铝石。温度、氧化铝的过饱和以及晶 粒的数量都会影响结晶过程中的颗粒大小。

3、Problems can arise when two or more components are coprecipitated. Thus, different species do not always deposit from solution at the reaction pH, while washing procedures can selectively remove a precipitated component as well as dissolve entrained electrolyte. 当两个或者更多成分共沉淀时问题就出现了。因 为，在反应pH下，不同组分并不总是会从溶液中 沉淀出来，虽然清洗过程可以有选择性的去除一 种析出成分，同时溶解产生的电解质。

(b) Uniaxial pressing 单轴压制 4、In uniaxial pressing a hard steel die is filled with either dry powder, or a powder containing up to several weight percent of H2O, and a hard metal punch is driven into the die to form a coherent compact. 在单轴压制过程，用干粉末或是含有一定水分含 量的粉末填满硬质钢磨具，并且用硬质金属冲床 猛击磨具，使之形成均匀一致的压实物。

Van der Waals forces cause aggregation of fine powders so that binders such as polyvinyl alcohol and lubricants are incorporated into them by, for example, spray-drying in order to improve their flow properties and homogeneity of the product. 范德瓦尔斯力引起精细粉末的聚集，因此粘合剂 例如聚乙烯醇和润滑剂加入其中，例如通过喷雾 干燥加入，以改善产品的流动性和同质性。

It is important that the unfired or green body has adequate streng

th for handling before the firing operation, during which organic additives are decomposed. 在烧结操作前使未燃烧的或者坯料具有足 够的强度以便处理是非常重要的，在这个 过程中有机添加剂会分解。

Uniaxial pressing can be readily automated and is particularly suited for forming components with a simple shape such as flat discs and rings that can be produced to close dimensional tolerances, thus avoiding post-firing diamond machining operations. 单轴压制容易实现自动化，并且特别适合成型形 状简单的器件，如平的光盘和环状物，产生的尺 寸公差比较小，因此避免了烧结后钻石机械加工。

(c) Hot uniaxial pressing热单 轴压制 5、Hot uniaxial pressing or hot-pressing

involves simultaneous application of heat and pressure during sintering. A refractory die,usually graphite, is filled with powder, which, after compaction, is heated in an inert atmosphere.

热单轴压制或热压制涉及到烧结过程中加热和加 压的同时应用。耐熔模具，通常是石墨，填满粉 末，压实后在惰性气氛中加热。

Hot-pressing produces higher density and smaller grain sizes at lower temperatures compared with uniaxial pressing and is particularly suited for fabrication of flat plates, blocks and cylinders. 与单轴压制相比，热压能在较低温度下生产出更 高密度和更小晶粒的产品，特别适合生产平盘、 块体和圆柱体产品。

Stresses set up by the applied pressure on contacts between particles increase the driving force for sintering and remove the need for very fine particle sizes. 在颗粒节点处由外加电场产生的压力增加 了烧结驱动力，致使必不需要特别精细尺 寸的颗粒。

(d) Solid-state sintering 固体烧结 6、The driving force for sintering is reduction in surface free energy associated with a decrease of surface area in powder compacts due to removal of solid-vapour interfaces. 烧结驱动力导致表面自由能降低，这与粉 末压块的表面积的减少密切相关，而表面 积的减少是由于消除气液相界产生的。

The vapour-pressure difference across a

curved interface can enhance evaporation from particle surfaces and condensation at the neck between two particles, particularly for particle diameters of several micrometers or less, such as occur in ceramic fabrication. 相图上气压的不同可以提高表面的蒸发过程和两 粒子间颈部冷凝过程，特别是对于几微米甚至更 小直径的颗粒更是如此，这些现象发生在陶瓷制 造过程中。

Although this evaporation-condensation process produces changes in pore shape and joins particles together, the centre-tocentre distance between particles remains constant so that shrinkage and densification do not occur. 尽管这个蒸发-凝聚过程会带来孔型改变并且会使 颗粒结合连

为一体，但是颗粒间的中心距离还是 一个常数，因此并没有发生收缩和扩张。

The driving force for mass transport by solid-state processes for ceramic powders with low vapour pressure is the difference in free energy between the neck region and surface of particles. 低蒸汽压下陶瓷粉末的固相处理产生的质量迁移 所需要的驱动力在颗粒的表面和颈部区域的自由 能有所不用。

As for the evaporation-condensation pathway, transport from surface to neck by surface and lattice diffusion does not cause densification. This is produced only by diffusion from the grain boundary between particles and from the bulk lattice. 就蒸发-凝固的途径来说，通过晶格和表面的扩散 产生的表面和颈部的迁移不会引起扩张。只有颗 粒间的晶界扩散和块体晶格扩散才会引起扩张。

Covalent ceramics such as Si3N4 are more difficult to sinter to high density than ionic solids, for example Al2O3, because of lower atomic mobilities, although difficulties can be overcome by using very fine powders ca. 0. lµ diameter, high temperature and m high pressure. 与离子固体相比共价陶瓷如氮化硅相对更难烧结 成高密度的产品，比如氧化铝，由于原子迁移速 率较低，但是这个难题可以通过使用精制粉末 (直径在0.1微米范围)、高温高压得以解决，

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