多孔陶瓷过滤件的试制

本文详细地叙述了制造多孔陶瓷所需要的各种原料的选择及工艺控制，给出了多孔陶瓷坯体的原料组成，化学组成和坯式及产品的各项性能指标，指出了坯料的制备，坯体的成形，干燥、烧成及冷却的方法和工艺。     

多孔陶瓷过滤件的试制

本文详细地叙述了制造多孔陶瓷所需要的各种原料的选择及工艺控制，给出了多孔陶瓷坯体的原料组成、化学组成和坯式及产品的各项性能指标，指出了坯料的制备，坯体的成形、干燥、烧成及冷却的具体方法和工艺。     

高纯度羟基磷灰石纳米功能材料的制备工艺

本文利用碳酸钙高温分解得到的氧化钙和磷酸为原料，通过湿式法制备医用生物活性陶瓷羟基磷灰石(HAP)。用X射线衍射(XRD)、傅立叶变换红外光谱(FTIR)等技术对陶瓷材料的组织结构和化学组成进行分析。结果表明在适当工艺条件下。得到的钙磷陶瓷产物为高纯度的羟基磷灰石纳米材料。该方法容易操作，重复性好，适于大批量工业生产，是制备高纯度羟基磷灰石纳米功能材料的理想方法。     

羟基磷灰石多孔陶瓷的制备和性能

本工作采用造孔剂（ＰＦＡ）干压工艺制备羟基磷灰石多孔陶瓷。通过两种造孔剂制得的多孔羟基磷灰石陶瓷性能的对比,发现两种造孔剂可制得多孔羟基磷灰石陶瓷。并借助ＳＥＭ、压汞仪等仪器和设备,对多孔体的性能进行了测试,讨论了造孔剂粒径、添加量及形状对多孔体性能的影响,结果表明：采用碳粉作造孔剂制得的多孔体具有较高的强度,而采用聚甲基丙烯酸甲酯（ＰＭＭＡ）作造孔剂制得的多孔体孔径的可控性高。     

羟基磷灰石生物陶瓷及固定化载酶初探

本文以为Ca（OH）2,（NH4）2HPO4为原料,利用酵母细胞作为模板合成羟基磷灰石粉体,并以羧甲基纤维素为粘结剂来制备羟基磷灰石陶瓷,利用X射线衍射（XRD）测试手段对样品化学组成进行表征,并用其固定α-淀粉酶,来初步测定羟基磷灰石陶瓷载体的固定化性能。     

炭粉作造孔剂制备多孔羟基磷灰石陶瓷的研究

以炭粉作追孔剂，制备了孔径在50nm-1mm的多孔羟基磷灰石陶瓷。运用TG—DTA、SEM等测试手段对产品的微观形貌、力学性能进行了测试分析，并对烧结温度、炭粉加入量、玻璃粉加入量这些影响陶瓷体性能的工艺参数进行了研究。     

电沉积法制备磷酸钙生物活性陶瓷涂层

综述了用电沉积法在金属生物材料表面涂敷磷酸钙生物活性陶瓷的工艺，分析了电沉积工艺的特点，并介绍了制备金属－羟基磷灰石复合涂层的复合电沉积工艺。     

高纯超细羟基磷灰石粉末的合成

研究了湿式法配合适当的热处理工艺制备高纯超细羟基磷灰石的过程，考察了溶液ｐＨ值，溶液Ｃａ／Ｐ摩尔比，反应时间，热处理温度的影响，合成的羟基磷灰石粒子纯强度高，颗粒细小而均匀，晶型完整，可以用作制备生物陶瓷的原料。     

羟基磷灰石陶瓷微球的制备研究

羟基磷灰石陶瓷微球的流动性好、容易填充,近年来在骨修复,尤其是口腔手术中得到较多应用。以HA-(NaPO3)6-Mg(H2PO4)2-明胶为陶瓷浆料,应用液滴-冷凝法对羟基磷灰石陶瓷微球的制备工艺进行了探索研究,获得了球形度好、粒径均一的陶瓷微球。     

多孔羟基磷灰石生物陶瓷的制备及应用

多孔羟基磷灰石生物陶瓷具有良好的生物相容性、生物活性、骨传导性、可降解及非免疫原性等优点,在骨修复和药物载体等方面极具应用潜力。然而,制备具有相互贯通且孔径可控的多孔羟基磷灰石陶瓷一直是其应用的热点和难点。文章从多孔羟基磷灰石的特性和制备工艺入手,分析了多孔羟基磷灰石制备方法的优缺点,重点评述了近年来为提高材料特性、拓宽应用领域而开发的新型制备工艺技术;并对多孔羟基磷灰石的应用进行了介绍;在此基础上,提出了今后值得关注的热点和研究的方向。     

Experimental Analysis of Fine–Particle Migration during Ceramic Filtration Processes

Slip casting and filter pressing are ceramic forming processes which can be affected by the migration of fine particles during filtration. Fine particles can be carried along with the filtrate and deposited within the ceramic compact and /or filter medium, thereby clogging and reducing the permeabilities of the porous media. This in turn affects the growth rate as well as the porosity of the compact. Evidence of clogging of the ceramic compact and filter medium was obtained by (1) SEM analysis of the compact and filter media, (2) surface area measurements of cross sections of compacts, and (3) measurements of the thickness of compacts as a function of casting time.     

Cleaner production of porcelain tile powders. Granule and green compact characterization

A new ceramic powder preparation process, the droplet-powder granulation process (DPGP), was recently proposed in pursuit of energy/water conservation and environment protection for sustainable development of the ceramic industry.This study characterizes the DPGP granules and resulting pressed green compacts and compares them with those obtained using traditional spray-drying (hereafter SD) and granulation (hereafter G) processes. Powder and granule properties (granule size distribution, flowability, microstructure, yield pressure, etc.), powder pressing behaviour, and green compact properties (microstructure, bending strength, etc.) were determined. The properties of the DPGP powder and the resulting compacts displayed an intermediate performance between those of the powders and compacts obtained by the SD and G processes, demonstrating the feasibility of the DPGP process in the pre-firing stage of porcelain tile manufacture. The study also shows that, in addition to the key spray-mixing step, the subsequent rolling treatment also plays a major role in DPGP granule formation.     

Overall shape of sintered alumina compacts

The extent of the thermally induced shrinkage during sintering of nominally homogeneous ceramic compacts depends upon the green density; compacts with a low green density shrink more than those with a higher density. Therefore, shape distortions of compacts with variable density during their sintering is inevitable. The overall shapes of various sintered alumina compacts, prepared using different types of alumina agglomerates, is described. The agglomerates were prepared using organic polymer [poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG)] binders and the influence of the particle agglomerates size and the water content in the agglomerates is considered. The extent of the shape distortions in the cylindrical sintered compacts were reduced with the application of lubricants to the die walls. The agglomerate properties are shown to affect the overall shape of the sintered compacts significantly. The compacts, produced using the wet (plastisized) agglomerates, have the smallest shape distortions. A prediction of the sintered shape evolution is obtained using a first order model. The model predicts that the shape distortions in the sintered compacts increase with the increasing of the sintered density and a good agreement between the predicted and measured data is demonstrated.     

Fracture properties of spray-dried powder compacts: Effect of granule size

Inappropriate mechanical properties of spray-dried powder compacts lead to significant green product losses, entailing considerable costs in ceramic tile manufacture as well as serious environmental problems. In addition, green strength can be indicative of how well a ceramic processing system is working.In this study, granules were prepared by spray drying a red clay slurry used in floor tile manufacture. The resulting granules were characterised and their porosity, morphology, and mechanical behaviour were determined.The study analyses the fracture properties of green ceramic materials using Linear Elastic Fracture Mechanics (LEFM), which has been widely used for fired materials, but whose application to green compacts has drawn much less attention. Two types of tests for determining fracture parameters (fracture toughness, fracture energy, and crack size) in green materials are also critically examined. Finally, the fracture parameters have been correlated to the microstructural characteristics of the compacts, in particular to granule size and the topography of the fracture.     

Cleaner production of porcelain tile powders. Fired compact properties

A new ceramic powder preparation process, the droplet-powder granulation process (DPGP), was recently proposed for the cleaner production of ceramic tiles. The DPGP granules and resulting pressed compacts were characterized and compared with the granules and compacts obtained by spray-drying (SD) and dry granulation (G) processes in a previous paper. The results showed the feasibility of using the DPGP in the pre-firing stage of porcelain tile manufacture.This study compares the firing behaviour and fired properties of compacts pressed from three different types of granulated powders: DPGP, SD, and G and from a non-granulated powder (NG) obtained by dry milling. The evolution of compact microstructure (porosity and pore size distribution) with firing temperature was monitored and the fired compact properties (bulk density, water absorption, and stain resistance) were determined.The study shows that the DPGP improved the sintering behaviour and final properties of the resulting porcelain tiles with respect to those obtained by the G process. However, the fired compacts prepared from the DPGP powder exhibited a higher porosity and pore size compared with those of the compacts obtained from the SD granules at the same pressing pressure. The results obtained open up the possibility of manufacturing glazed porcelain tiles with a more eco-friendly process. However, the results also indicate that polished porcelain tile manufacture by the DPGP requires further research in order to improve granule characteristics, in particular green granule deformability, which is the critical factor in porcelain tile densification and vitrification during firing.     

Densification of Sol-Gel-Derived Mullite Ceramics after Cold Isostatic Pressing up to 1 GPa

Molecular-designed ultrafine mullite precursor powders with a stoichiometric composition were prepared by copolymerization of alkoxides. The precursor powders were calcined in the range from 800° to 1200°C and consolidated by ultra-high-pressure cold isostatic pressing up to 1 GPa. Ultrahigh isostatic pressure of 1 GPa led to a closed packing structure in the green compacts. Interaggregate pores in the green compacts were collapsed by the ultrahigh cold isostatic pressure to reduce the pore size below 6 nm. As a result, the maximum density of the green compacts reached 70% of theoretical. These closely packed green compacts of precursor powders with a stoichiometric composition and calcined at relatively low temperatures could be sintered to >95% of theoretical at 1500°C. Relatively low-temperature sintering below the liquid formation temperature resulted in fine microstructure of the resultant mullite ceramic with a grain size below 300 nm.     

Densification behavior of nanocrystalline titania powder under cold compaction

Densification behavior of nanocrystalline titania powder was investigated under cold compaction. Experimental data were obtained from triaxial compression with various loading conditions. Lee and Kim proposed the Cap model by employing the parameters involved in the yield function of sintered metal powder and volumetric strain evolution under cold isostatic pressing. The parameters in the Drucker/Prager Cap model and the proposed Cap model were obtained from experimental data under triaxial compression. Finite element results from the models were compared with experimental data for densification behavior of nanocrystalline ceramic powder under cold isostatic pressing and die compaction. The proposed model and the Drucker/Prager Cap model agreed well with experimental data under cold compaction. Finite element results and experimental data also, show that relative density distribution of nanocrystalline ceramic powder compacts is nonuniform compared to the conventional micron powder compacts at the same averaged relative density.     

Validity of Using Mercury Porosimetry to Characterize the Pore Structures of Ceramic Green Compacts

The ability of mercury porosimetry in characterizing particle packing and pore structures of dense ceramic green compacts is evaluated. Differences in intrusion spectra between the dry-pressed and slip-cast compacts demonstrate the utility of mercury porosimetry for particle-packing analysis. Of the voids embedded in the matrix, only those at or extending to the matrix surface are detectable. Intrusion—extrusion spectra show hysteresis, but otherwise do not provide added insight into bulk defect structure.     

Synthesis and microstructure of Ti2AlN ceramic by thermal explosion

Ti₂AlN ceramic with a small amount of TiN was rapidly synthesized by the thermal explosion (TE) technique using Ti, Al and TiN as starting materials. The effects of the starting composition, the particle size of TiN and the compacts’ height on the phase composition and microstructure of obtained Ti₂AlN ceramic were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that high purity Ti₂AlN ceramic containing 4% TiN could be fabricated at 700 °C for 2 min with a molar ratio of 1.1:1.1:1(Ti: Al: TiN). It was further found that small particle size of TiN and compacts’ height of 2–8 mm were beneficial to obtain high purity Ti₂AlN. Finally, the formation mechanism of Ti₂AlN ceramic via thermal explosion was proposed.     

Electron-beam sintering of an Al2O3 / Ti composite using a forevacuum plasma-cathode electron source

We present the results of electron-beam sintering of composite ceramic compacts based on alumina and titanium powders. The electron beam was generated by a plasma-cathode electron source at elevated pressure values of the fore-vacuum range. We have studied the effect of the pressed compact thickness on the sintered sample parameters. It has been established that the pressed thickness significantly affects the uniformity of parameters. The samples with the most uniform parameters were obtained for thickness values below 4 mm. At a greater thickness, the parameter non-uniformity increases considerably due to outgassing from the surface of the sintered compacts.