用注凝成型技术制备莫来石陶瓷坯体

用注凝成型技术，通过控制合成莫来石粉料的细度，调节好pH值在单体和交联剂的比例，制备出稳定性好的料浆和强度高的生坯。     

Thermoreversible Gelcasting: A Novel Ceramic Processing Technique

A new ceramic processing method, thermoreversible gelcasting (TRG), has been developed. The method uses a gelation process that can be reversed multiple times. Two Al₂O₃ systems have been explored with the use of a specific triblock copolymer to form a binding gel network. The mixture becomes a free-flowing liquid on heating above 60°C. However, on cooling below 60°C, the slurry instantaneously transforms to a physical gel. This process can be reversed easily (essentially with an infinite processing time window) while the solvent is present in the system, which is advantageous when trying to produce high-quality dense pieces if initial casting irregularities occur. Near-theoretically dense specimens have been produced with properties consistent with reported values of high-density Al₂O₃.     

高填充Al2O3-聚丙烯酰胺复合材料的摩擦学特性

利用凝胶注模方法可以制备出高填充含量的Al2O3-聚丙烯酰胺复合材料。考察了PTFE对高填充聚合物复合材料摩擦学性能的影响，并对复合材料的磨损机理进行了探讨。研究表明．在适当高的填充条件下．复合材料的力学性能和摩擦磨损性能可以得到一定的改善，PTFE的填充将降低Al2O3-聚丙烯酰胺复合材料的力学性能，并使材料的摩擦系数有所增大；但是复合材料的耐磨特性可以得到显著改善。高填充含量的PTFE-Al2O3聚丙烯酰胺复合材料表现出了摩阻材料特性。Al2O3-聚丙烯酰胺复合材料的磨损主要表现为磨粒磨损特征。     

中间相炭微球(MCMB)水基浆料的流变性

研究了固相含量、混合方式、分散剂种类及加入量、粉料加入方式及除气处理方式等因素对中间相炭微球(MCMB)水基浆料黏度和稳定性的影响.结果表明:浆料黏度随固相含量的增加而增加;球磨比搅拌有利于降低浆料黏度并提高稳定性;Darvan-821A分散剂的分散效果比Tween80好;球磨浆料的最大固相含量为60.06%,而搅拌浆料为53.00%;循环水真空泵比旋片式真空泵有利于浆料的低黏度和稳定.     

Effect of Porosity on Structure,Young's Modulus,and Thermal Conductivity of SiC Foams by Direct Foaming and Gelcasting

The study demonstrates the aqueous processing of solid‐state‐sintered SiC foams by gelcasting technique. Aside from increasing strength of green bodies, gelcasting monomers were the source of carbon additive which helped in sintering of SiC foams. Sintered foams with the relative density (RD) between 0.44 and 0.11 were processed by direct foaming of SiC slurries followed by gelcasting and sintering. Structural analysis by X‐ray tomography showed the presence of spherical pores with bimodal pore size distribution and the proportion of large size cell and their interconnectivity increased in low RD foams. SEM study revealed that decreased RD resulted in gradual changes in the strut microstructure from the grains with faceted interface to smooth interfaced grains. The analysis of changes in Young's modulus and thermal conductivity with RD were in agreement with the Ashby model for open cell foams.     

凝胶注模成形Ti6Al4V钛合金的组织和性能研究

目的 为了实现低成本、低能耗、高效率制备大尺寸复杂形状钛合金的问题,以凝胶注模技术为成形手段,制备近净成形Ti6Al4V合金,并研究其组织及性能.方法 通过溶液包覆法,在Ti6Al4V钛合金球形粉末表面包覆石蜡(PW),分析有机包覆层在凝胶注模过程中的作用机制及流变行为的影响,测定包覆前后不同粉末进行凝胶注模烧结后的组...     

Water-Based Gelcasting of Surface-Coated Silicon Nitride Powder

A layer of Y₂O₃–Al₂O₃, used as a sintering aid, was coated onto the surface of Si₃N₄ particles by the precipitation of inorganic salts from a water-based solution containing Al(NO₃)₃, Y(NO₃)₃, and urea. The electrokinetic and colloidal characteristics of the Si₃N₄ powder were changed significantly by the coating layer. As a result, dispersion of the Y₂O₃–Al₂O₃-coated Si₃N₄ powder was significantly greater than that of the original powder. Furthermore, the Y₂O₃–Al₂O₃ coating layer prevented the hydrogen-gas-discharging problem that occurred during gelcasting of the original Si₃N₄ powder because of reaction between the uncoated powder and the basic aqueous solution in suspension. Surface coating, as well as the gelcasting process, significantly improved the microstructure, room-temperature bending strength, and Weibull modulus of the resulting ceramic bodies.     

TiO_2对堇青石多孔陶瓷微观结构和性能的影响

以叔丁醇为成形介质和造孔剂,二氧化钛为烧结助剂,采用凝胶注模成形和无压烧结工艺制备堇青石多孔陶瓷.研究了添加5%(体积分数,下同)二氧化钛对堇青石多孔陶瓷的气孔率、微观结构、力学性能和气孔结构的影响,并对样品的断口形貌进行观察.结果表明,在1175 ℃烧结温度条件下,与不添加二氧化钛相比,当二氧化钛含量为5%时,所得堇青石多孔陶瓷的气孔率和开口气孔率分别由76.9%和96.4%下降为72.4%和95.1%,线性收缩率从20.7%提高到22.1%,而抗压强度则由3.23 MPa提高到5.83 MPa,气孔尺寸均呈单峰分布,中位孔径由2.29 μm下降到1.62 μm.二氧化钛的加入提高了堇青石粉末的低温烧结性能,在未明显降低堇青石多孔陶瓷气孔率以及未改变其气孔结构、孔径尺寸分布的前提下,材料的力学性能得到了显著改善.     

低毒的丙烯酸羟乙酯聚合体系凝胶注模成型Al2O3陶瓷

凝胶注模成型技术由于使用了具有神经毒性的单体-丙烯酰胺在一定程度上限制了其在工业上应用。本实验利用低毒的甲基丙烯酸羟乙酯凝胶注模成型Al2O3，研究了在该体系下低粘度高固相体积分数浓悬浮体的流变性及其固化过程。对比研究了JN281和柠檬酸铵两种分散剂对Al2O3浆料流变特性的影响，结果表明：对于该新体系JN281比常用的柠檬酸铵更有效。加入适量JN281可得到低粘度的高固相含量（≥50%）的陶瓷浆料。由新体系凝胶注模得到的素坯表面光滑，强度可达18MPa，SEM照片显示素坯具有均匀的显微结构，最终可烧结出均匀致密内部无明显缺陷的陶瓷部件。     

Synthesis of silver nanoparticles by gelcasting using a low toxic monomer and optimization of gelation time using the Taguchi method

Silver nanoparticles were synthesized using a gelcasting process, which includes using in situ polymerization for forming the samples followed by calcination. Methacrylamide (MAM) was used as a monomer and N,N′-methylene-bis-acrylamide (MBAM) was used as a cross-linker to form a cross-linked polymer network. The effects of monomer content, cross-linker to monomer ratio, and silver salt to monomer ratio on gelation time were investigated using the Taguchi experimental design method. A set of 16 experiments was conducted at a constant temperature and agitation speed. The results from the Minitab design of experiments (DOE) analysis indicate that the cross-linker to monomer ratio had the greatest effect on gelation time. Finally, silver nanoparticles were synthesized by burning out a gel sample in a furnace. Scanning electron microscopy (SEM) analysis showed that the average size of the silver nanoparticles was approximately 42 nm.