酶催化明胶原位凝固成型陶瓷坯体的研究上

采用天然高分子凝胶进行陶瓷原位凝固成型具有有机物加入量少、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,阻止热明胶溶液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.     

高分子多糖凝胶在高性能陶瓷原位凝固成型中的应用

简要介绍了高性能陶瓷原位凝固成型技术的发展,重点介绍了琼脂糖、明胶、果胶和淀粉等高分子多糖的凝胶特性以及这些多糖凝胶应用于高性能陶瓷原位凝固成型时,对悬浮浆料的流变性能和成型坯体性能的影响.     

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     

直接凝胶凝固成型SiC(M,Y)-Al2O3复合陶瓷材料的研究(Ⅱ)基本原理及工艺过程研究

本文研究了一种新的陶瓷原位凝固成型技术 (直接凝胶凝固成型 )的基本原理和工艺过程 ,找出了影响成型工艺的基本因素 ,并且利用该成型技术制备出强度和密度较高 ,且密度均匀性好的坯体。     

陶瓷直接凝固注模成型（DCC）原理及应用

直接凝固注模成型是一种崭新的净尺寸陶瓷成型概念，其基本过程是通过酶催化底物的化学反应改变，ｐＨ值至等电点（ＩＥＰ）或增加盐离子浓度，使双电层稳定的陶瓷浓悬浮体实现原位凝固，得到均匀，无密度梯度的坯体，然后干燥（无需脱脂）烧结致密化，本文详细讨论了这种成型工艺的原理和应用研究成果。     

淀粉原位凝固成型纯碳反应烧结碳化硅坯体的研究

研究了一种新的陶瓷原位凝固成型方法，其原理是依据淀粉颗粒在水中润胀吸水，在加热时产生糊化的特性。在固相体积分数接近50％的碳粉料浆中引入约3％质量分数的淀粉，用水浴加热期化的方法即可原位凝固成型各种形状的陶瓷部件，获得致密、均匀的坯体。研究了淀粉-碳粉料浆的流变学特性，单纯淀粉呈现膨胀型流动，含淀粉的碳粉料浆悬浮液的表观粘度随淀粉的加入量的增加而提高。料浆中淀粉的加入量应控制在原料干基质量的1％-5％范围内，料浆分散条件为中性。研究了淀粉原位凝固成型的机理以及对素坯结构的影响。     

用改性淀粉原位凝固成型制备Al2O3陶瓷

陶瓷凝胶注模成型工艺是一种新颖的成型工艺,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.本文用改性淀粉原位凝胶注模成型技术制备了具有较高强度和均匀性良好的氧化铝陶瓷坯体.研究了氧化铝陶瓷的凝胶注模成型工艺中低粘度高固相体积分数浓悬浮体的制备、浓悬浮体的固化、成型坯体的显微结构及性能.     

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。     

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。     

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。     

A novel casting forming for ceramics by gelatine and enzyme catalysis

A new kind of gelation process for forming a ceramic green body is discussed. The forming method is based on a process in which gelatine, enzyme (urease) and urea are used. Urea is employed to prevent attraction between gelatine molecules when the dissolved hot gelatine solution cools down for preparing a well-dispersed suspension by ball milling and degassing at ambient conditions. After urease is added into the suspension, gelatine molecules attract each other and form three-dimensional network through hydrogen bonding due to urea decomposition by urease. Slurry containing alumina and gelatin could be consolidated in situ by the above gelation process at room temperature. A green body with homogeneous microstructure and smooth surface was obtained.     

Gelation forming of ceramic compacts using agarose

Abstract

The development of a cast forming process for ceramics based on agarose gelation is described and the properties of green and sintered bodies are presented. For this process, a warm alumina slurry containing more than 50 vol.-% solids loading and ～1 wt-% agarose binder (Al₂O₃ basis) is cast into a relatively cold, non-porous mould, resulting in a tough green body formed by gelation (37°C) of the agarose molecules. The green compacts show uniform density distribution, with precise dimensions and very smooth surfaces. After drying, they can be sintered directly without special binder burn out procedures. Complex ceramic parts with thick and thin cross-sections can be formed. The process is illustrated for the preparation of a turbine rotor component.     

水基明胶-氧化铝浆料的流变及注凝特性

研究了以氧化铝为原料,以明胶为胶凝剂的注模成型工艺中固含量、分散剂、pH值等对浆料流变特性及素坯性能的影响。结果表明,明胶具有良好的胶凝效果,成功制备出了固相含量高达56vol%,体积密度为2.2g/cm3,抗弯强度达到7.64MPa,内部均匀的陶瓷素坯。     

日用陶瓷铅溶出量超标的原因及对策

氧化铅（PbO）是日用陶瓷釉料中常用的助熔剂，是陶瓷行业制釉的优质原料，最早应用于陶瓷装饰。但铅是重要的生物毒性元素，严重威胁着人们的身体健康。笔者从我国目前的日用陶瓷生产条件出发，分析了日用陶瓷中铅溶出量超标的原因，提出了一些降低铅溶出量的方法。     

明胶体系凝胶注模成形氧化铝素坯

采用明胶—尿素体系进行凝胶注模成形,制备了固相体积分数为53%的氧化铝陶瓷料浆悬浮体,利用尿酶将尿素分解,使明胶重新获得氢键形成能力,在尿酶用量为20单位时,室温下制备了抗弯强度为8.26 MPa的氧化铝陶瓷材料。     

Temperature induced gelation of non–aqueous alumina suspension using oleic acid as dispersant

A novel temperature induced gelation method for alumina suspension using oleic acid as dispersant is reported. Non–aqueous suspension with high solid loading and low viscosity is prepared using normal octane as solvent. Influence of oleic acid on the dispersion of suspension was investigated. There was a well disperse alumina suspension with 1.3 wt% oleic acid. Influence of gelation temperature on the coagulation process and properties of green body was investigated. The sufficiently high viscosity to coagulate the suspension was achieved at −20 °C. The gelation temperature was controlled between the melting point of dispersant and solvent. The gelation mechanism is proposed that alumina suspension is destabilized by dispersant separating out from the solvent and removing from the alumina particles surface. The alumina green body with wet compressive strength of 1.07 MPa can be demolded without deformation by treating 53 vol% alumina suspension at −20 °C for 12 h. After being sintered at 1550 °C for 3 h, dense alumina ceramics with relative density of 98.62% and flexural strength of 371±25 MPa have been obtained by this method.     

Direct Coagulation Casting of Silicon Carbide Components

Direct coagulation casting is a novel near-net-shape method for forming ceramic green bodies from homogenous high-solids-loaded particle suspensions. It is based on the principle of the in situ coagulation of a powder suspension via a reaction-rate-controlled internal-enzyme(urease)-catalyzed reaction after casting. Low-viscosity (<3 Pas) suspensions with a high solids loading (>62 vol%) of SiC, boron, and carbon powder mixtures with a high surface area (>7-10 m²/g) have been prepared at pH = 10. Salt ions (up to 1-2 mol/L) are created by the urease-catalyzed decomposition of urea, to destabilize the suspensions. The coagulation kinetics and the strength of the wet green bodies have been investigated. The reaction rate is strongly dependent on the temperature (in the range of 5°-30°C) and the enzyme concentration (for the range of 4-16 units/g SiC) and is independent of the substrate (urea) concentration for urea concentrations of <2 wt%, based on the powder content. The resulting green bodies show no shrinkage during coagulation and 1%-2% linear shrinkage during drying. The compressive strengths of the wet green bodies are as high as 60 kPa and increase as the coagulation time increases. The wet green strength of the coagulated suspensions scales with the solids content, according to a power law with an exponent of 11, in the range of 56-61 vol% solids content. The possibilities of fabricating high-solids-containing complex SiC green and sintered components with homogenous microstructures and high sintered densities are demonstrated.     

Heterogene Ultrafiltrationsmembranen zur Fixierung von Enzymen

Cellulose acetate as well as polysulphon are well established polymers for the production of ultrafiltration membranes. Contrary to the former polysulphon is not suitable for enzyme immobilization. These difficulties can be eliminated by introduction of distinct substituents, but by this process the film forming tendency is lost. By mixing the original polymer with the substituted material a casting solution can be obtained to producing heterogeneous membranes. The enzymes dextranase and urease were fixed and the activated membranes were tested using dextrane and urea as substrates.