问题 问答题

什么是陶瓷材料?陶瓷材料有哪此特点?

答案

参考答案:

陶瓷是无机非金属材料,是用粉状氧化物,碳化物等,通过成型和高温烧结而制成。陶瓷材料是多相多晶材料,结构中同进存在着晶体相、玻璃相和气相,各组成相的结构、数量、形态、大小和颁均对陶瓷性能有显著影响。陶瓷材料具有高硬度(>1500HV)、耐高温(溶点>2000℃)、抗氧化(在1000℃高温下不氧化)、耐腐蚀(对酸、碱、盐有良好的耐蚀性)以主其他优良的物理、化学性能(优于金属的高温强度和高温蠕变能力,热膨胀系数小。热导率低,电阻率高,是良好的绝缘体,化学稳定性高等)。陶瓷材料是脆性材料,故其抗冲击韧度和断裂韧度都很低。陶瓷材料的抗压强度比其抗拉强度大得多(约为抗拉强度的10~40倍),大多数工序陶瓷材料的弹性模量都比金属高。由于工程陶瓷材料硬度高,常采用洛式硬度HRA、HT45N、小负荷维氏硬度或洛氏硬度表示。

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Children have gentle minds. To find the best way to teach children to share and care is easy. Kids are naturally attracted to animals.   71   Also we can show them the cow eating grass on a farm.

Making them have a look at the animals that are dying out and rare pictures from newspapers is another exciting way to make them love animals. The effects of pollution are difficult for them to understand.     72   There are great pictures of animals like cute rabbits and gorillas.

73    Tell them they are our friends, so we can’t hurt them.Take them to the conservation park and show them a monkey or a rare bird. Show them the types of penguins. Teach your children that animals can feel pain but cannot express themselves like us.    74    If you have pets at home, let them accompany your children deal with them well.

One could call an ambulance for injured dogs or nurse a sick animal back to health. Taking a nature walk is liked by kids and also the best way to get along with the family. Kids love to see some newborn dogs and the mother nursing them.     75     .

A.otions are well understood by children and they may have the same feeling.

B.ildren all like small animals, but they don’t consider them as their friends.

C.ach them never to throw stones to hit animals.

D.is can make children know how to care others.E.e could teach them to be kind to ants and show them how they carry food to save for the rainy day.

F.rents should protect the environment first.

G.erefore one could tell them that the environment should be(kept ) clean.

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