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陶瓷新型胶态成型工艺(修订版) Novel Colloidal Forming of Ceramics(2nd Ed.)

以注射成型工艺为主线,介绍陶瓷胶态注射成型的理论基础和应用技术。

作者:杨金龙 黄勇 Jinlong Yang, Yong Huang
定价:198
印次:2-1
ISBN:9787302575917
出版日期:2021.03.01
印刷日期:2021.03.03

本书介绍了清华大学在高性能陶瓷成型工艺领域取得的研究成果和其他国家学者在该领域所取得的进展,内容包括:基于凝胶体系的陶瓷胶态注射成型新工艺;陶瓷基片的凝胶流延工艺;无毒或低毒体系凝胶成型工艺;陶瓷制备过程中缺陷产生、演化、遗传和控制;非氧化物陶瓷凝胶注模成型新工艺;胶态成型工艺的应用;悬浮体成型技术;胶态成型工艺新方法和新技术。

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Introduction In ancient times, ceramic vessels or crafts were usually manufactured using clay-based natural raw materials. It is well known that the mud mixed clay with water has good plasticity and can be easily processed into products of various shapes. However, the forming techniques used earlier were mainly manual proce-dures. Therefore, to a large extent, the forming of ceramic wares was just a kind of skill or workmanship. By the 1960s, new ceramic materials had already developed into an independent scienti.c system. At the same time, raw materials that were used to manufacture ceramics began to transition from the clay-based system to one with accurate chemistry composition. In particular, for preparing high-performance ceramics, synthetic chemical raw materials, such as Al2O3,ZrO2,Si3N4, and SiC, were mainly used. These ceramics had excellent properties because of their struc-tural characteristics of covalent bond and ionic bond, and were widely considered as candidate materials in many .elds requiring high-temperature resistant, wear-resistant, and corrosion resistant substances. It had been predicted that such materials would be developed rapidly, and various new types of materials with excellent properties would be explored. By the late 1970s, the emergence of the worldwide oil crisis caused many developed countries led by America and Japan to draft national development plans for high temperature structural ceramic materials used in the .eld of internal combustion engines, especially automobile engines. With excellent properties such as resistance to high temperature, wear, and corrosion, high-performance ceramics were considered the optional material for non-water cooling and adiabatic ceramic engine parts. The forming technique of ceramics was also among the top-ranking research topics. During the period of the ‘7th Five-Year Plan’ and ‘8th Five-Year Plan’ in China, around the key components of ceramic insulation engines, an in-depth research on ceramic injection molding, extrusion molding, slip casting, and pressure .ltration was done. Moreover, a few engine parts samples with high performance were prepared. However, because of the high cost, poor performance repeatability, and low yield, the process of industrialization of high-performance ceramics was greatly restricted. After years of research and exploration, there was a growing recognition as the key technology for forming high-performance ceramic materials and parts. The forming technique is not only the precondition for materials design and for-mula, but also the important factor in reducing manufacturing costs and improving the yield and the performance repeatability of products. Simultaneously, several research booms were set off around the new forming technique of ceramics at home and abroad. During the period of the ‘9th Five-Year Plan’ in China, in order to achieve high-tech ceramic industrialization at the earliest, the ceramic forming technique with high performance and low cost was granted special funds from the 863 Program. Along with the research upsurge in the .eld of ceramic engines, there was also considerable interest in the .eld of injection molding of ceramics. On the basis of the theory of plastic injection molding, thermoplastic, thermosetting, and water-soluble organic compounds were used as binders, and then mixed with ceramic powder to prepare a suspension with high volume loading. In addition, ceramic parts with high size precision and complex shape can be prepared by injection molding. It is suitable for automotive and large-scale production. After several decades, owing to in-depth studies on ceramic injection molding, it developed into an integrated science and technology involving rheology, the dynamic molding process of injection suspen-sion and thermal degradation of organic compounds as well as other interdisciplinary technology. However, some problems caused by organic enrichment or particle rearrangement were exposed during the time and energy consuming process of debindering, such as poor uniformity and easy cracking. Therefore, debindering was considered the key issue to be solved, and the solution to lower the organic content gradually became an important research topic. In order to simplify the process of debindering, low-pressure injection molding with some small molecular organics was paid more attention. After the 1990s, quickset injection molding was invented by B. E. Novich of the U.S. The pore .uid was used as a carrier in the process, the volume of which did not change with temperature. After the suspension was injected into the container, the carrier was sublimated, and then the green body was solidi.ed by controlling the temperature and pressure. Because of avoiding the polymer organic carrier with large molecule, the problem of organic debindering was solved ingeniously. Due to sig-ni.cant advantages such as high automation and good size precision, injection molding continues to be highly used and is considered a highly competitive forming process. In the mid-1980s, in order to avoid the dif.culty of debindering in injection molding, which was caused by the large number of organic binders, traditional slip casting was again paid more attention, as it involved less organics and low cost. Moreover, the operation and control were easy in this method. However, because of the green body with low green density and poor strength, it was not suitable for the preparation of high-performance ceramics. On the basis of traditional slip casting, the pressure .ltration and centrifugal casting techniques were developed thereafter. The green body’s density and strength were improved by applied pressure and centrifugal force, and at the same time the complicated debindering process was avoided. However, such processes were also unable to meet the green bodies with high reliability and high performance due to poor uniformity of the green bodies. After the 1990s, in order to improve the uniformity and reliability of ceramic bodies, forming in situ techniques such as gelcasting, temperature-induced .oc-culation, colloidal vibration casting, and direct coagulation casting were developed. The in situ solidi.cation process is highly regarded because it is the precondition to ensure uniformity and is an important way to improve the reliability of ceramics. Gelcasting, a novel colloidal forming technology of ceramics, was .rst invented by Oak Ridge National Laboratory (ORNL), USA, in 1990. In the gelcasting process, about 2–4 wt.% acrylamide monomer is added into the ceramic suspen-sion, and then it polymerizes in situ by the interaction of catalysts and initiators. Furthermore, the drying process should take place at room temperature and high humidity for a long time; otherwise, the green bodies would easily crack. In addition, the degree of automation and industrialization of the gelcasting process is poor when compared to injection molding. The ceramic bodies prepared by gel-casting have the obvious advantages of high strength and excellent machinability. Thus, some ceramic parts with complex shape or that are dif.cult to be demolded, just like inside thread, can be passed through green body machining after drying to achieve the required shape and precision. As a kind of brittle and dif.cult-to-machine material, it is very important, even necessary for the bodies to be machined partly, which also provides people a very good idea. Temperature-induced .occulation was developed by L. Bergstrom, a professor at the Institute of Surface Chemistry of Stockholm University, Sweden, in 1993. A special amphoteric polyester surfactant or dispersant changing with temperature is introduced into the concentrated suspension to make particles disperse. One end of the dispersant is adsorbed on the particle surface, and the other end goes inside the solvent. As the temperature is reduced, the solubility of the dispersant declines, the function of dispersion fails, and then the suspension is .occulated in situ. The outstanding advantage of this method is the recycling of the unquali.ed green bodies, but it is restricted to use such dispersant for the different ceramic system. Colloidal vibration casting molding was .rst developed by F. F. Lange, a pro-fessor at the University of California, Santa Barbara, USA, in 1993. In this method, the prepared dilute suspension (20–30% by volume) with high ionic concentration is pressure-.ltered or centrifuged to obtain a green body with high solid loading, which is in the solid state under static conditions but is in the .uid state if certain external forces (such as vibration) are applied. Then, the suspension will solidify in situ under static conditions, after be poured. The outstanding advantage is the use of the thixotropic property when the concentrated suspension has a high ionic strength. Moreover, the concentrated suspension need not be prepared with high solids loading. However, the green bodies have poor strength and are prone to cracking and deformation. Direct coagulation casting was invented by the research team under Prof. Gauckler from the Swiss Federal Institute of Technology in Zurich, Switzerland in 1994. In this method, .rst, a biological enzyme and a substrate are introduced into the ceramic concentrated suspensions at low temperature. At this time, the enzyme is in the inactivated state and does not almost react with the substrate. Then, the temperature of the suspension rises to 20–40 °C, and the enzyme is activated and reacts with the substrate. By adjusting the pH value to the isoelectric point or by increasing the internal ionic strength, the suspension is coagulated in situ. This method results in wet bodies with enough strength to be demolded. In the process, it is necessary that the solid loading of the suspension is more than 50% by volume, but the strength of the green body is low. However, the body is extremely uniform and does not contain any organic substance. Thus, it is suitable for preparing high-reliability ceramics, for which the Weibull modulus can reach 40. Thus, after the 1990s, research on the in situ forming technique had become a new hot spot in the .eld of high-performance ceramics. People gradually realized that the forming technique is very important in the whole study of ceramic mate-rials, and that the industrialization process of high-performance ceramics would be promoted greatly through in-depth study on the forming technique and its basic theory. In the mid-1980s, studies were conducted on injection molding and pressure .ltration in the Tsinghua University in China. After the 1990s, the study of gel-casting and direct coagulation casting had progressed signi.cantly, especially with the invention of the novel injection molding technique for water-based nonplastic slurry of ceramics, also called colloidal injection molding. A colloidal injection molding machine was also developed. The development of the gel tape casting process and gelcasting with low toxicity system was studied in detail in the nearly .ve years. Recently, techniques such as freeze-gelcasting and colloidal forming for ultralight and high-strength porous ceramics have been invented, which further enrich the theory and technique of ceramic forming. The industrialization process of high-performance ceramics is also being promoted greatly. In China, other uni-versities and institutes such as Shanghai Institute of Ceramics, Chinese Academy of Sciences, and Tianjin University are conducting similar research. The key tech-nology and development trends regarding the colloidal forming of ceramics include the following aspects. (1) The preparation of a concentrated suspension with low viscosity and high solids loading is the precondition to guarantee the density, uniformity, and strength of the green bodies. With high density, the shrinkage of the green bodies can be decreased in drying, and deformation and cracking can be avoided in the sintering process. Therefore, the foundation of colloidal forming is to prepare the suspension with high solids loading. (2) The in situ consolidation technique: In a sense, a new consolidation technique of suspension means a new forming process. It is very important for colloidal forming to look for a new solidi.cation method of suspension. For forming in situ, the relative position of particles does not change during the solidi.-cation of suspension. It is a necessary condition to guarantee body uniformity, which is also a key factor in improving the reliability of ceramic materials. Currently, the development of an in situ consolidation technique requires the suspension to contain a few or no any organic substances. By varying the charged and dispersant characteristic between colloidal particles, the viscosity of the suspension is increased and this leads to in situ solidi.cation of the green bodies. At the same time, with enough strength to be demolded, the ceramic green bodies can be easily transported during large-scale production. (3) It is very important to avoid residual stress in green bodies by using colloidal forming. Normally, there is no shrinkage in the green body when the sus-pension is formed, and no residual stress also. Thus, we believe that colloidal forming without shrinkage will become an important trend in the next 10 or 20 years. (4) Near net-size forming: Ceramic substances are hard-machined materials with high hardness and brittleness. The sintered bodies should be close to the actual size of the .nal parts in order to decrease machining of ceramics. The preparation process of high-performance ceramic materials and parts is the sticking point of development and application of ceramics. It involves the prepa-ration of high-performance ceramic powders, and the forming and sintering pro-cesses. The quality of the green and sintered body is directly impacted by the quality of the powder, because the rheological behaviors and solids loading of concentrated suspension are directly determined by the properties of the powder during colloidal forming. Moreover, the quality of green bodies guarantees the quality of the sintered body. The preparation of powders, and the forming and sintering of ceramics are mutual constraints and complementary. However, according to the current devel-opment of ceramic forming, the forming process, which plays an important role in the preparation process of ceramic materials and is related with the industrialization and scale of production, is the critical step to guarantee performance reliability and repeatability as well as yield of ceramics. Hence, research on forming techniques for ceramics involving low cost and having high reliability is of great signi.cance. This will promote the industrialization of high-performance ceramics in China and abroad. This is not only the requirement of governments around the world and of industries, but also the urgent need of ceramic scientists. To sum up, the green bodies prepared by an ideal forming process should have a good uniformity, a high green density, enough strength to be demolded, and no residual internal stress. It can obtain ceramic material with high performance, guarantee the homogeneous of shrinkage, and avoid deformation during the sin-tering process. In order to meet the above requirements, the forming process from a technical perspective should have the following characteristics: (1) Adding no or as few as possible polymers (0.1–4 wt.%). (2) Solids loading of suspension more than 55 vol.%. (3) The solidi.cation of suspension is a rapid, in situ technology. (4) The suspension has no shrinkage and internal stress during the transformation from liquid to solid state. (5) A kind of near-net-size forming process. The .rst point is to avoid the problem of debindering. The second point is to improve the density and the strength of the green bodies. The third point is to guarantee the uniformity and the dimensional accuracy of the green bodies. The fourth point is to avoid deformation and cracking of the green bodies during burn-out and sintering, in order to improve the reliability. The .fth point is to guarantee the dimensional accuracy of the sintered products, so that there is no or less machining. There are eight chapters in this book. The main contents involve our research achievements and developments in more than a decade. Recent international research results in the .eld of ceramic forming are also introduced. To summarize, the basic problems and the future development trends of the forming process are proposed and discussed in detail.

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  • 杨金龙教授,1966年5月出生于山西省太原市;1987年,毕业于北京理工大学金属材料及热处理专业,获得学士学位;1990年,毕业于中北大学金属材料及热处理专业,获得硕士学位;1996年,毕业于清华大学材料系无机非金属专业,获得博士学位。1999年5月-2000年8月在瑞士联邦理工大学做博士后研究工作,师从国际著名陶瓷科学家Gauckler教授。1996年8月至今,分别担任清华大学材料系讲师、副教授、教授、博导。2006年7月,被中北大学聘为特聘教授,并担任先进陶瓷实验室主任。2010年5月,被聘为大连交通大学兼职教授。2014年5月,被聘为河北工程大学兼职教授。同时,杨金龙教授担任硅酸盐学报编委,中国硅酸盐学会溶胶凝胶分会理事,材料导报编委,IJMPT(International Journal of Materials Product and Technology)Guest Editor。曾获多项荣誉,包括国家技术发明二等奖1项,河北省科技进步二等奖1项,山西省自然科学二等奖1项,其他省部级科技奖项3项,德国纽伦堡国际发明博览会金奖1项,国际发明展览会金奖1项。截至2017年12月31日,通过技术成果鉴定
  • 本书是有关陶瓷成型技术的学术专著,反映了中国学者在胶态成型方面的基础理论研究进展和工艺发展情况,对无机非金属材料的技术进步和学科发展有良好的参考价值。
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  • Contents 

    1  Aqueous Colloidal Injection Molding of Ceramics (CIMC) Based on Gelation ....................................... 1 

    1.1  WhatisColloidalInjectionMolding? ..................... 3 

    1.1.1  Colloidal Injection Molding of Ceramics (CIMC) .. .. .. . 3 

    1.1.2  TheFlowchartofCIMC .......................... 4 

    1.1.3  The Machine of Colloidal Injection Molding ofCeramics ................................... 5 

    1.2  Pressure-InducedForming .............................. 6 

    1.2.1  Effect of Hydrostatic Pressure on Solidi.cation ......... 6 

    1.2.2  HomogeneityoftheGreenBodies .................. 7 

    1.2.3  Controlling the Inner Stress in the Green Body .. .. .. .. . 7 

    1.3  Stor...

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