Ch.2-2 Structures of CERAMIC Materials

Ceramic crystal structures (16)
Calculation of the density of NaCl
n’ = 4 (4 Na+ ions and 4 Cl- ions in each unit cell)
VC = a3 where a = 2rNa+ + 2rCl-
rCs+=0.170nm; rCl-=0.181nm
rCs+/ rCl-=0.939 BBB2
Ceramic crystal structures (10) (3) Zinc blende structure (ZnS)
The base: FCC formed by S 4 of the tetrahedral interstices occupied by Zn There are 8 atoms (4 Zn and 4 S) in a unit cell CN: 4 Some common ceramic materials: ZnS, ZnTe (zinc telluride), and SiC Atomic bonding: highly covalent BBB
Ceramic crystal structures (12) AmBnXp-type crystal structures
Features: The number of charges on the cations is different from that on the anions , and it is composed of two kinds of cation (A and B) Example 1: Perovskite structure – ABX3 (BaTiO3, SrZrO3, and SrSnO3) Cube corners occupied by barium ions – equivalent to 1 Cube center occupied by a titanium ion Six face centers occupied by oxygen ions equivalent to 3 The formula: BaTiO3

硅酸盐学报· 1590 ·2007年二硼化锆基超高温陶瓷的制备及性能王海龙1,2，汪长安2，张锐1，黄勇2，方岱宁3(1. 郑州大学材料科学与工程学院，郑州 450000；2. 清华大学，新型陶瓷与精细工艺国家重点实验室，北京 100084；3. 清华大学航空航天学院，北京 100084)摘要：用碳化硅(SiC)颗粒增韧二硼化锆(ZrB2)陶瓷，在氩气流中热压烧结温度为1950℃、保温1h，20MPa压力下成功制备出了致密的ZrB2/SiC p 复合材料。

ZrB2/SiC p复合材料的致密度随着SiC颗粒添加量的增加而增加。

当SiC颗粒的体积分数(下同)为15%时，相对致密度达到100%。

ZrB2/SiC p 复合材料的抗弯强度和断裂韧性都随着SiC添加量的增加成上升趋势，当SiC颗粒的添加量在15%时同时达得最大值，分别为646MPa和8.52MPa·m1/2。

SiC p的添加还提高了ZrB2/SiC p复合材料的耐氧化烧蚀性能。

关键词：超高温陶瓷；二硼化锆；热压烧结；性能中图分类号：TB333 文献标识码：A 文章编号：0454–5648(2007)12–1590–05PREPARATION AND PROPERTIES OF ZIRCONIUM DIBORIDE-BASEDULTRA-HIGH TEMPERATURE CERAMICSWANG Hailong1,2，WANG Chang'an2，ZHANG Rui1，HUANG Yong2，F ANG Daining3(1. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450000; 2. State Key Laboratory of New Ceramicsand Fine Processing, Tsinghua University, Beijing 100084; 3. School of Aerospace, Tsinghua University, Beijing 100084, China)Abstract: Zirconium diboride (ZrB2)-based ultra-high temperature ceramics (UHTC) reinforced by silicon carbide (SiC) particles were prepared by hot press sintering at 1950 for 1℃h under 20MPa pressure in an argon flow. The relative density of ZrB2/SiC p composites increased with the content of SiC addition, and reached 100% when 15% (in volume) SiC particles were added. The bending strength and toughness of the composites also increased with increasing SiC amount, and reached values of 646MPa and 8.52MPa·m1/2, respectively, at 15% SiC addition. Furthermore, the addition of SiC particles improved the resistance to oxida-tion/ablation of ZrB2/SiC p composites.Key words: ultra-high temperature ceramics; zirconium diborde; hot press sintering; propertyUltra-high temperature ceramics (UHTCs) are usua- lly defined as ceramic materials that can be used at tem-peratures in excess of 2000.℃[1] The characteristics of UHTCs, such as their strength and oxidation resistance at high temperature, allow them to be used in extreme en-vironments including those associated with hypersonic flight, atmospheric re-entry, and rocket propulsion.[2] One UHTC, zirconium diboride (ZrB2), is an important mate-rial because it has a high melting point (3245), high℃strength, high thermal conductivity and good thermal shock resistance.[3–4] However, there are two main issues restricting the development and application of ZrB2-based ceramics. One drawback is that ZrB2-based ceramics ex-hibit poor sinterability, which originates mainly from their strong covalent bonding characteristics. The other problems of ZrB2-based ceramics are their poor me-chanical properties and low resistance to oxidation at high temperatures. Therefore, much attention has been focused on the preparation process, mechanical proper-ties and resistance to oxidation of ZrB2-based cera- mics.[5–7] In order to improve the mechanical proper-ties and resistance to ablation/oxidation of ZrB2-based ceramics at high temperatures, some carbides and nitrides have been introduced in previous researches.[8–10]收稿日期：2007–04–21。

Unit 2 Classification of MaterialsSolid materials have been conveniently grouped into three basic classifications: metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are some intermediates. In addition, there are three other groups of important engineering materials —composites, semiconductors, and biomaterials.译文：译文：固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

这个分类是首先基于这个分类是首先基于化学组成和原子结构来分的，化学组成和原子结构来分的，大多数材料落在明显的一个类别里面，大多数材料落在明显的一个类别里面，大多数材料落在明显的一个类别里面，尽管有许多中间品。

尽管有许多中间品。

除此之外，此之外， 有三类其他重要的工程材料－复合材料，半导体材料和生物材料。

有三类其他重要的工程材料－复合材料，半导体材料和生物材料。

Composites consist of combinations of two or more different materials, whereas semiconductors are utilized because of their unusual electrical characteristics; biomaterials are implanted into the human body. A brief explanation of the material types and representative characteristics is offered next.译文：复合材料由两种或者两种以上不同的材料组成，然而半导体由于它们非同寻常的电学性质而得到使用；生物材料被移植进入人类的身体中。

Advanced Ceramic Materials: Innovations and Applications**Introduction:**Advanced ceramic materials represent a fascinating frontier in materials science and engineering. These materials, known for their exceptional properties, have found applications in a wide range of industries, from electronics and energy to aerospace and healthcare. This article explores the unique characteristics of advanced ceramics, their manufacturing processes, and their diverse applications across various sectors.**I. Characteristics of Advanced Ceramic Materials:**1. **High Hardness and Strength:**Advanced ceramics exhibit remarkable hardness and strength properties, making them suitable for applications where traditional materials may fail. Materials like silicon carbide and boron nitride are known for their exceptional hardness.2. **Low Thermal Conductivity:**Many advanced ceramics possess low thermal conductivity, making them useful for applications requiring thermal insulation. This property is vital in fields such as aerospace, where ceramic tiles are used to protect spacecraft from the intense heat during re-entry.3. **Electrical Insulation:**Ceramics are excellent electrical insulators, making them essential in electronics and telecommunications. Components like ceramic capacitors and insulating substrates play a crucial role in modern electronic devices.4. **Chemical Inertness:**Advanced ceramics often demonstrate high chemical inertness, resisting corrosion and degradation in harsh environments. This property makes them ideal for applications in chemical processing and biomedical devices.5. **Biocompatibility:**Some ceramics, such as alumina and zirconia, exhibit biocompatibility, making them suitable for use in medical implants. Their inert nature reduces the risk of adverse reactions within the human body.**II. Manufacturing Processes for Advanced Ceramics:**1. **Powder Processing:**The majority of advanced ceramics are produced through powder processing techniques. This involves the synthesis of ceramic powders, followed by shaping and sintering to achieve the desired final product.2. **Chemical Vapor Deposition (CVD):**CVD is a technique where ceramic materials are deposited onto a substrate from gaseous precursors. This process allows for the precise control of thin-film coatings and the production of intricate shapes.3. **Additive Manufacturing:**Recent advancements in additive manufacturing, or 3D printing, have extended to ceramics. This method enables the fabrication of complex ceramic structures with enhanced design flexibility.4. **Hot Isostatic Pressing (HIP):**HIP is a technique used to improve the density and mechanical properties of ceramics by subjecting them to high pressures and temperatures. This process reduces porosity and enhances material performance.**III. Applications of Advanced Ceramic Materials:**1. **Electronics and Semiconductors:**Ceramics such as alumina and silicon nitride are widely used in electronic components, including insulating substrates, capacitors, and semiconductor packages.2. **Aerospace Industry:**The aerospace sector utilizes ceramics for applications such as thermal protection systems on spacecraft, turbine blades in jet engines, and lightweight structural components.3. **Medical Implants:**Biocompatible ceramics like zirconia and alumina are employed in medical implants such as dental prosthetics and artificial joints, owing to their durability and compatibility with the human body.4. **Energy Sector:**Ceramics play a critical role in the energy industry, particularly in high-temperature environments. They are used in components for gas turbines, nuclear reactors, and solid oxide fuel cells.5. **Automotive Applications:**Advanced ceramics find use in the automotive sector for components that require high wear resistance and thermal stability, including brake components and engine components.**IV. Challenges and Future Prospects:**1. **Brittleness:**Despite their exceptional properties, ceramics are inherently brittle, limiting their use in certain applications. Ongoing research focuses on developing strategies to enhance the toughness of ceramics.2. **Cost and Manufacturing Complexity:**The production of advanced ceramics can be cost-intensive, and certain manufacturing processes involve complex procedures. Advancements in cost-effective manufacturing techniques are essential for widespread adoption.3. **Innovations in Composite Materials:**Researchers are exploring the incorporation of ceramics into composite materials to harness their unique properties while addressing limitations such as brittleness.4. **Nanotechnology Integration:**The integration of nanotechnology into ceramic materials is an area of active research. Nanoceramics exhibit enhanced properties, and their precise control at the nanoscale opens new possibilities for applications.**Conclusion:**Advanced ceramic materials stand at the forefront of materials innovation, offering a diverse range of properties that make them indispensable across various industries. As research continues to push the boundaries of ceramic science, addressing challenges and unlocking new potentials, these materials will likely play an increasingly pivotal role in shaping the technologies of the future. The versatility, durability, and unique characteristics of advanced ceramics position them as key contributors to advancements in electronics, healthcare, aerospace, and beyond.。