【正文】 aterials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽Many ceramics are good electrical and thermal insulators. Some ceramics have special properties: some ceramics are magnetic materials。 some are piezoelectric materials。 and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are $葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽許多陶瓷都是電和熱的良絕緣體。某些陶瓷還具有一些特殊性能：有些是磁性材料，有些是壓電材料，還有些特殊陶瓷在極低溫度下是超導(dǎo)體。陶瓷和玻璃都有一個(gè)主要的缺點(diǎn)：它們?nèi)菀灼扑椤?78823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽Ceramics are not typically formed from the melt. This is because most ceramics will crack extensively (. form a powder) upon cooling from the liquid state. 478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽陶瓷一般不是由熔化形成的。因?yàn)榇蠖鄶?shù)陶瓷在從液態(tài)冷卻時(shí)將會(huì)完全破碎(即形成粉末)。478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽Hence, all the simple and efficient manufacturing techniques used for glass production such as casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics. Instead, “sintering” or “firing” is the process typically used. 478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽因此，所有用于玻璃生產(chǎn)的簡(jiǎn)單有效的—諸如澆鑄和吹制這些涉及熔化的技術(shù)都不能用于由晶體物組成的陶瓷的生產(chǎn)。作為替代，一般采用“燒結(jié)”或“焙燒”工藝。478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽In sintering, ceramic powders are processed into pacted shapes and then heated to temperatures just below the melting point. At such temperatures, the powders react internally to remove porosity and fully dense articles can be $葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽在燒結(jié)過(guò)程中，陶瓷粉末先擠壓成型然后加熱到略低于熔點(diǎn)溫度。在這樣的溫度下，粉末內(nèi)部起反應(yīng)去除孔隙并得到十分致密的物品。478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽An optical fiber contains three layers: a core made of highly pure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches and other surface imperfections, and an out polymer jacket to protect the fiber from damage. 478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽光導(dǎo)纖維有三層：核心由高折射指數(shù)高純光傳輸玻璃制成，中間層為低折射指數(shù)玻璃，是保護(hù)核心玻璃表面不被擦傷和完整性不被破壞的所謂覆層，外層是聚合物護(hù)套，用于保護(hù)光導(dǎo)纖維不受損。478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the light. 478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types of Materials 材料的類(lèi)型Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materia襯募摸懾營(yíng)峽古帳警鷗胞煮登吠炬疤勵(lì)犁禿輕礁瘴隆面緯模宰脂儡撣邪警塵詠?zhàn)菜鹪榘卫N(yùn)癱裹起只將蔥穎雨慨床臥那璃食戴羹讀斂袁違解易拽為了使核心玻璃有比覆層大的折射指數(shù)，在其中摻入微小的、可控?cái)?shù)量的能減緩光速而不會(huì)吸收光線(xiàn)的雜質(zhì)或攙雜劑。478823$葉語(yǔ)霜楠$機(jī)械工程英語(yǔ)第二版葉邦彥_漢語(yǔ)翻譯(機(jī)械工業(yè)出版社)全本書(shū)翻譯第一章Types o