一种新型氮化铝陶瓷凝胶注模成型体系

为了解决凝胶注模成型中常见的氧阻聚和毒性问题,本文尝试了用操作性较强的低毒不饱和聚酯树脂作为凝胶体系,凝胶注模成型氮化铝陶瓷.研究了该体系的固化过程及机理,成型后的坯体具有较高的强度,可以进一步机械加工成预期的形状.无压烧结该体系浇注的异形AlN陶瓷密度为3.26 g/cm3,热导率为182 W/(m·K).     

凝胶注模成型制备BaNd2Ti5O14介电陶瓷的电学性能

讨论了用凝胶注模成型制备BaNd2Ti5O14介电陶瓷的过程。本实验以化学式为BaNd2Ti5O14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);采用正交实验设计法,优化出生坯密度最大的配方。分析了凝胶注模成型与干压成型制备的BaNd2Ti5O14介电陶瓷的体积密度、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BaNd2Ti5O14介电陶瓷具有体积密度高、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、降低介质损耗。     

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。     

凝胶注模成型制备Sialon陶瓷的研究进展

本文系统阐述了凝胶注模成型制备Sialon陶瓷的研究与进展,根据凝胶来源分成非水基凝胶注模体系和水基凝胶注模体系,介绍它们的工艺过程和原理。最后提出了凝胶注模成型制备Sialon陶瓷目前应当注意的问题,并展望了它的前景。     

陶瓷凝胶注模成型技术及其应用研究

凝胶注模成型技术是一种近净尺寸陶瓷成型技术，它为解决陶瓷材料的加工成型问题提供了一条十分有效的的工艺途径。介绍了陶瓷凝胶注模成型技术的基本原理和工艺过程，着重介绍了目前凝胶注模成型技术的应用研究。     

陶瓷凝胶注模成型技术及其应用研究

凝胶注模成型技术是一种近净尺寸陶瓷成型技术，它为解决陶瓷材料的加工成型问题提供了一条十分有效的工艺途径。介绍了陶瓷凝胶注模成型技术的基本原理和工艺过程，着重介绍了目前凝胶注模成型技术的应用研究。     

凝胶注模制备多孔陶瓷的研究进展

凝胶注模是将传统的陶瓷粉体成型与有机物原位聚合相结合的一种新型成型工艺,为制备高性能、复杂结构的多孔陶瓷提供了一条新途径.在阐述凝胶注模工艺原理的基础上,综述了凝胶注模结合不同成孔方法制备多孔陶瓷的成孔机制以及最新研究进展,并展望了凝胶注模制备多孔陶瓷的发展趋势.     

琼脂糖凝胶注模成型制备氧化铝陶瓷的研究

本文利用琼脂糖做凝胶剂,对凝胶注模成型所需的水性无毒氧化铝陶瓷浆料进行了正交实验,分析了各因素对凝胶注模成型浆料制备的影响,经实验确定了形成较好琼脂糖凝胶注模成型的技术条件,所得陶瓷坯体具有较高的强度和较好的表面质量。     

凝胶注模成型法制备多孔陶瓷的研究进展

凝胶注模成型法因可生产准净近尺寸、形状复杂的大尺寸陶瓷制品,且成型后的生坯具有整体均匀性好、缺陷少、强度高等优点被广泛应用于多孔陶瓷的制备.本文在阐述凝胶注模成型技术基本原理和工艺过程的基础上,重点综述了凝胶注模成型法制备多孔陶瓷的研究进展,最后就多孔陶瓷的制备及研究现状,分析凝胶注模成型法制备多孔陶瓷所存在的问题及其...     

高压陶瓷电容器凝胶注模成型研究

凝胶注模成型是九十年代初发明的一种新型成型技术.它是传统陶瓷工艺和高分子化学结合的产物.这种方法具有素坯密度高、密度均匀、强度大,可成型复杂形状近净尺寸的大型陶瓷制品等特点,应用前景十分广阔.本文报告了高压陶瓷电容器凝胶注模成型研究结果.     

Aqueous alkaline suitable gel system and related mechanism for highly transparent La0.4Gd1.6Zr2O7 ceramic preparation

In this work, a fabrication route combined optimized ISOBAM-104/TAC gel-casting (where TAC refers to triammonium citrate) and one-step sintering technology was developed to prepare highly transparent La_xGd_2-xZr₂O₇ (LGZO) ceramics. The gelling behavior in an alkaline environment was investigated, and the corresponding mechanism was systematically proposed for the advanced spontaneous gel system. The starting materials after ball milling were directly shaped into green bodies without any treatment, and high-quality LGZO ceramics were obtained by three-stage debinding and one-step sintering. The in-line transmittance of these ceramics reaches 74% at 1100 nm, which is about 95% of the theoretical value. This work not only establishes an efficient method to fabricate LGZO ceramics in large and complex shapes but also elucidates the gelling mechanism in alkaline, which expands the application of gel-casting technology in transparent ceramics.     

Fabrication and properties of dense silicon carbide ceramic via gel-casting and gas silicon infiltration

The dense Silicon Carbide (SiC) ceramics are fabricated by means of gel-casting and gas silicon infiltration (GSI) using carbon black and α-SiC as raw materials. We have successfully introduced a new initiator AIBA which is very suitable to aqueous gel-casting system containing carbon black, overcoming the problems posed by the conventionally used initiator. We have investigated the influences of the monomer acrylamide (AM) content, the ratio of the monomer to crosslinking agent AM/MBAM content, the particle size distribution and the solid content on the mechanical and structural properties of samples. The result show that, the linear shrinkage of the green body can be reduced to 1.0% and its bending strength can reach 59.2 MPa at the optimized gel-casting process that has an AM content of 25 wt%, an AM to MBAM ratio of 12, a SiC particle distribution of 3/2 and a solid content of 60 vol%. After the GSI process, the bending strength and elastic modulus of the final products from such green bodies can reach 245 MPa and 220 GPa respectively. The study highlights that the combined application of the gel-casting and the GSI processes can produce high-quality silicon carbide ceramics that are suitable in the space optical applications.     

Gel-casting of fused silica based core packing for investment casting using silica sol as a binder

A novel approach for the fabrication of core packing via silica sol gel-casting is described. Concentrated slurry dispersed in silica sol with high solid loading but low viscosity is successfully prepared at about pH 10.2. In situ consolidation of the slurry is realized through adjustment of NH₄Cl concentration to control the gelation time of the slurry. High compaction and uniform green body is obtained by gel-casting technology without de-airing process. The results from flexural strength tests show that wet gel bodies with 0.5 wt.% calcium aluminate obtained by silica sol gel-casting have exceptionally high strength, which are responsible for the integrity of core packing during autoclaving.     

高温抗蠕变氧化铝陶瓷成型工艺的研究

分别采用注凝成型和干压成型工艺进行了样品的制备,对两种成型工艺进行了比较,对试样的烧成制度、烧成制品致密性、高温抗蠕变等性能方面进行了比较。结果表明:注凝成型虽然生产周期较长,但制备的试样致密性、高温抗形变能力均优于干法成型制备的样品。     

Effects of fiber length and solid loading on the properties of lightweight elastic mullite fibrous ceramics

Mullite fibrous ceramics were successfully prepared by a TBA-based gel-casting with mullite fibers as the main matrix. The effects of the fiber length and the gel-casting solid loading on the composite properties and microstructure were investigated. The 3D structure of the composite was constructed by the randomly arranged mullite fibers with the fixed crossing point, and therefore the fiber length was the most important factor influencing the microstructure of the composition. Further analyses indicate that long fibers were more suitable for the fabrication of high porosity composite. Compared with controlling the fiber length, adjusting the gel-casting solid loading was an easy method of tailoring the properties of the composite. The composite fabricated with the low solid loading and long fibers exhibited a high porosity, a low thermal conductivity, and an excellent elastic property, and can be regarded as a potential high-temperature thermal insulator applied in the industrial or aerospace thermal protection system.     

固含量对凝胶注模成型碳化硅陶瓷性能的影响

碳化硅陶瓷具有优良的性能,广泛应用于各个领域。凝胶注模成型是通过有机单体的聚合反应实现原位固化的成型方法。成型的坯体具有结构均匀、致密度高、强度大等特点。本文采用凝胶注模成型工艺和无压烧结制备了碳化硅陶瓷材料,研究了固含量对无压烧结碳化硅陶瓷微观结构和性能的影响。研究结果表明:随着固含量的增加,碳化硅料浆的粘度值逐渐增加,流动性变差,而制得的碳化硅陶瓷弯曲强度和断裂韧性随固含量的增加而增加。     

A novel gel-cast SiC with potential application in turbine hot section: Investigation of the rheological behavior and mechanical properties

Using a gel-cast technique, SiC bodies were fabricated and their mechanical properties were thoroughly studied. The main goal of this study is improvement of SiC green body features by the adjustment of slurry composition or processing parameters. The influences of gel-casting parameters such as the monomer acrylamide (AM) content, tetramethyl ammonium hydroxide (TMAH) content as a dispersant, the ratio of the monomer to crosslinking agent AM/MBAM content and the ammonium persulfate (APS) as an initiator on the properties of the samples were investigated. Based on the viscosity measurement and sedimentation tests, TMAH exhibited great electro-sterically stability at the pH of 10–11. After the gel-cast process, the relative density of sintered body can be enhanced to 93% and its flexural strength can reach 293 MPa at the optimized gel-casting process that has an AM content 15%, a TMAH content of 0.4 wt%, an AM:MBAM ratio of 17.5:1, an APS 10% and a solid content of 50 vol%, comparable to the best results reported in the other works for SiC bodies.     

Gel-casted porous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ceramics by use of natural fibres as pore developers

An approach using ceramic shaping by gel-casting and addition of natural tropical fibres as burnable pore developers has been explored for development of porous alumina materials with predetermined pore structures. The fibres used have been characterized in terms of size, shape, water uptake and surface charge. The degree of fibres loading in slurry has been varied. It has been shown that the amount of added fibres correlates well with the measured porosity, the shape of the developed pores however deviating slightly with that of the introduced fibres. The ceramic bodies have been characterised in terms of porosity, shrinkage and flexural strength. It could be assumed that at fibres amount in slurry above 30% V, an open porosity appears which is accompanied by a sharp drop in strength. In order to explore the benefits of the gel-casting method for complex bodies development, two key issues need to be addressed: air evacuation prior to casting and lowering slurry viscosity at fibre loadings higher than the tested ones. For reaching the latter objective, surface modification of fibres has been undertaken.     

Lanthanum Strontium Manganite Powders Synthesized by Gel-Casting for Solid Oxide Fuel Cell Cathode Materials

Lanthanum strontium manganite ((La_0.8Sr_0.2)_0.9MnO₃; LSM) powder was successfully synthesized by an aqueous gel-casting technique, using carbonaceous precursors. Both thermal and X-ray diffraction analysis confirmed that the gel-casting LSM powder formed a single perovskite phase at 850°C, which is 100°–150°C lower than that of the LSM powder prepared by the conventional solid-state reaction route. The significantly reduced phase formation temperature of the gel-casting LSM powder is most likely due to the homogeneously distributed and immobilized precursor particles in a polymeric network, promoting the sintering and crystallization process. The LSM electrode prepared by the gel-cast LSM powder showed good electrocatalytic activity for the O₂ reduction reaction for solid oxide fuel cells.     

注凝成型纳米防火玻璃

采用分散剂对纳米硅溶胶进行分散,和丙烯酰胺衍生聚合物结合,应用注凝成型（gelcasting）工艺制成具有高防火性能的纳米防火玻璃。其组成为硅溶胶、分散剂、丙烯酰胺、N-羟甲基丙烯酰胺。