基因及凝固注模成型Si3N4及SiC陶瓷：基本原理及工艺过程

直接凝固注模成型（ｄｉｒｅｃｔ ｃｏａｇｕｌａｔｉｏｎ ｃａｓｔｉｎｇ，ＤＣＣ）是一种崭新的（准）净尺寸陶瓷成型方法。本文了采用此法成ｉ３Ｎ４及ＳｉＣ陶瓷的基本原理和工艺过程，ＤＣＣ成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中，事先加入到浆料中的生物酶及化学物质通过改变浆料的ＰＨ或电解质浓度醚改变浆料的胶体化学行为，从而使浆料原位凝固，得到有足够脱模强陶瓷坯体。ＤＣＣ成型的特点为坯体     

陶瓷直接凝固注模（DCC）成型

直接凝固注模式型（ＤＣＣ）是一种陶瓷净尺寸胶态成型方法，ＤＣＣ成型的坯体具有成型密度高，密度及组分分布均匀，不含或只含少量有机物等特点，本文了ＤＣＣ成型的原理、成型过程及特点。     

直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程

直接凝固注模成型（ｄｉｒｅｃｔｃｏａｇｕｌａｔｉｏｎｃａｓｔｉｎｇ，ＤＣＣ）是一种崭新的（准）净尺寸陶瓷成型方法。本文报道了采用此法成型Ｓｉ_３Ｎ_４及ＳｉＣ陶瓷的基本原理和工艺过程。ＤＣＣ成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中，事先加入到浆料中的生物酶及化学物质通过改变浆料的ｐＨ或电解质浓度来改变浆料的胶体化学行为，从而使浆料原位凝固，得到有足够脱模强度的陶瓷坯体。ＤＣＣ成型的特点为坯体密度高（理论密度的５５％～７０％），坯体均匀，不用或只需少量的有机添加剂（少于１％），可成型大尺寸、复杂形状、高可靠性的陶瓷部件。     

酶催化明胶原位凝固成型陶瓷坯体的研究

采用天然高分子凝胶进行陶瓷原位凝固成型具有机物加入量少，无毒等优点。本文讨论了一种新的凝胶化工艺用以成型陶瓷坯体，其原理是利用尿素作为氢键阻断剂，阻止热明胶溶胶溶胶冷却时的凝胶化转变。待球磨，真空除泡等工艺操作完成后，再加入尿酶使尿素分解，明胶大分子重新获得氢键结合能力，在室温下完成凝胶化转变，形成网络结构，实现原位凝固成型。该成型方法可获得表面光洁，内部均匀的陶瓷坯体。     

陶瓷成型新方法及其应用的研究

介绍和讨论了作为一种借助酶催化化学反应实现原位凝固的崭新近净尺寸陶瓷成型概念的直接凝固注浆成型方法与技术，以及通过与陶瓷粉料混合形成浓悬浮胶体的有机单体在加人偶联剂、催化剂和引发剂后的聚合反应促成原位聚合凝固的注疑成型方法与技术。利用这两种成型技术可以获得均匀、无密度梯度的近净尺寸坯体和致密陶瓷制品。这里也简单介绍和讨论了喷墨打印成型技术。它是一种利用计算机控制实现多层打印、逐层叠加制出三维陶瓷坯体的计算机辅助制造(CAM)陶瓷的成型新技术。     

琼脂糖凝胶大分子在陶瓷原位凝固成型中的应用

研究了一种新的陶瓷原位凝固成型方法,其原理是依据琼脂糖凝胶大分子在水溶液中加热时溶解,冷却时凝固这一物理变化。对于固相体积分数大于50％陶瓷悬浮体中引入约1％（质量分数）琼脂糖大分子,即可凝胶注模进行各种形状复杂的陶瓷部件成型,获得表面光洁、内部孔隙尺寸和密度分布均匀的陶瓷坯体,并烧结出均匀致密内部无明显缺陷的涡轮转子等异型部件。     

东盟成为广东潮州陶瓷主要进出口市场

清华大学材料系黄勇教授课题组承担的九五期间863课题“低成本、高性能陶瓷胶态注射原位快速凝固成型新工艺的研究”（简称为“陶瓷胶态注射成型新工艺”）取得重大成果,使陶瓷的制造成本降低一半,可靠性提高一倍以上,使各种复杂形状陶瓷零部件的近净尺寸制造技术获得突破性的进展。制备的陶瓷材料与制品的性能达到;坯体密度均匀（密度分布差小于0．5％）、坯体强度高（抗弯强度在20～30MPa）、易于加工：烧结后产品性能优异;     

精密陶瓷原位凝固制备技术的研究

七十年代末，世界范围内伴随着陶瓷热机部件的热潮，精密陶瓷受到了各国政府、研究部门及产业界的充分重视。进入九十年代后，精密陶瓷的发展遇到了许多问题，其中形状复杂结构部件的成型工艺是制造高性能陶瓷材料最为关键的环节之一。本文综合分析了近年来精密陶瓷成型工艺的研究进展，着重强调指出砂位凝固成型技术是保证坯体均匀性和解决高性能陶瓷可靠性的重要环节，同时，指出成型工艺今后需要加强和解决的几个关键技术。     

PCRBSC材料的原位凝固成型制备

依据淀粉颗粒的水中润胀吸水，在加热时产生糊化的特性，实现了一种新的陶瓷原位凝固成型方法。在固相含量接近50％(体积分数)的SiC陶瓷料浆中引入约3％(质量分数)的淀粉，用水溶加热的方法可以原位凝固成型各种形态的SiC陶瓷部件，获得致密、均匀的PCRBSC和RBSC坯体。经真空渗硅，制备出微现结构均匀，性能良好的SiC材料。     

凝胶注模成型制备大尺寸臭氧发生器陶瓷基板

讨论了用凝胶注模成型制备大尺寸臭氧发生器陶瓷基板的过程。本实验以化学式为Ba（Sm，Nd）2Ti5O14的介电陶瓷为固相粉末．以丙烯酰胺（MBAM）为凝胶有机单体，用传统球磨的方法制备出了高固相、低粘度的陶瓷浆料（浓悬浮体）。分析了凝胶注模成型与干压成型制备的Ba（Sm，Nd）2Ti5O14陶瓷基板的体积密度、结构均匀性以及电学性能不同的原因。结果表明：凝胶注模成型制备的Ba（Sm，Nd）2Ti5O14陶瓷基板具有体积密度商、结构均匀的特点。合理使用凝胶注模成型工艺可以提高陶瓷介电常数、抗电强度和降低介质损耗。     

水溶性高分子聚丙烯酰胺对氧化铝注凝成型的影响

为了解决坯体表面起皮现象，避免氧阻聚，陶瓷注凝成型必须在氮气保护下进行。研究表明：通过添加适量的水溶性高分子聚丙烯酰胺（PAM0到陶瓷悬浮体中，可以消除在空气中注凝成因的坯体的表面起皮现象，并且可提高坯体的抗弯强度。在PAM存在下，研究分析了Al2O3粉末在水中的分散特性，Al2O3悬浮体的流变特性和固化特性。同时对坯体的抗弯强度和显微结构进行了测试和观察。     

Freeform Fabrication of Ceramics via Stereolithography

Ceramic green bodies can be created using stereolithography methods where a ceramic suspension consisting of 0.40–0.55 volume fraction ceramic powder is dispersed within an ultraviolet-curable solution. Three ceramic materials were investigated: silica for investment casting purposes, and alumina and silicon nitride for structural parts. After mixing the powders in the curable solution, the ceramic suspension is photocured, layer by layer, fabricating a three-dimensional ceramic green body. Subsequent binder removal results in a sintered ceramic part. Three-dimensional objects have been fabricated from a 0.50 volume fraction silica suspension.     

Direct coagulation casting of silicon carbide suspension via polyelectrolyte dispersant crosslink reaction

A direct coagulation casting method for silicon carbide ceramic suspension using dispersant crosslink reaction is reported. Polymer electrolyte (polyethyleneimine, PEI) was used as dispersant to prepare silicon carbide suspension. Common food additives (carboxymethyl cellulose, CMC) were used to coagulate the electrosteric stabilized silicon carbide suspension. There was a well disperse silicon carbide suspension with 0.2 wt% PEI at pH = 5-6. Influence of coagulant on viscosity and zeta potential of the silicon carbide suspension was investigated. It indicates that the high solid loading silicon carbide suspension can be destabilized and coagulated at elevated temperature. It can be attribute to the gradual decrease of electrosteric force due to the crosslink reaction between PEI and CMC. Silicon carbide wet green body with compressive strength of 1.99 MPa could be demolded at 70°C which is higher than that prepared by traditional DCC and dispersant reaction method for nonoxide ceramics. Dense silicon carbide ceramics with relative density above 98.8% and 99.3% had been prepared by liquid phase pressureless and hot pressed sintering, respectively.     

α-Al2O3悬浮体的流变性及凝胶注模成型工艺的研究

陶瓷凝胶注模型工艺是一种新颖的成型工艺,具有很好的应用前景。它将高分子化学单体聚合的思路引入到陶瓷的成型工艺中,可制备高强度、高均匀性的陶瓷坯体。     

Hierarchically Structured Materials by Anodic Coagulation Casting of Fibrinogenic Alumina Suspensions

Anodic coagulation casting of fibrinogenic ceramic suspensions is a novel processing technology, which is based on the electrically induced transformation of the water soluble fibrinogen into the insoluble fibrin. Contrary to the direct coagulation casting (DCC) technology, green formation does not depend on a pH‐shift and as the fibrin coagulate forms on an anode, it can be combined with the electrophoretic deposition (EPD) technology. In this study, the conversion of fibrinogen into fibrin is activated via electron transfer processes at an electrode material and is combined with the green formation of alumina by embedding the ceramic particles in the protein matrix. The focus of this work was to establish a technology to shape thin hierarchically structured ceramic films and thick porous materials with a distinct pore structure. Film thickness and porosity were controlled by the applied voltage and the processing‐time. The range of the established green bodies included two‐dimensional and simple three‐dimensional shapes including multilayered deposition and fiber coatings. Overall the process of anodic coagulation casting can be reported to be successful for all established ceramic shapes except multilayers, where delamination was observed. The deposited alumina ceramics were characterized using light microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and synchrotron micro computed tomography (μCT), while the coagulation mechanism was studied using high‐performance liquid chromatography (HPLC).     

3D printing of CaO-based ceramic core using nanozirconia suspension as a binder

The 3D printing of a ceramic core with nanoceramic suspension as a binder was performed to investigate a novel method for the fabrication of a complex-shaped ceramic core. Green bodies were printed using CaO powder as a precursor material and nanozirconia-absolute ethyl alcohol solution suspension as a binder. The green bodies were sintered at 1300–1500 °C for 2 h. The effects of binder saturation level on the properties of the sintered bodies were investigated. Increasing the binder saturation level caused decreases in the linear shrinkage of the sintered bodies, but increases in hydration resistance and bending strength. The nanozirconia particles were deposited on the surfaces of the CaO particles and filled the pores of green bodies, and then formed a high melting temperature CaZrO₃ layer with the CaO at the surfaces of the CaO grains, which improved the hydration resistance of the CaO-based ceramic core parts.