低温烧结等静压成型陶瓷柱塞的研制

阐述了采用等静压成型工艺和低温烧结技术生产大型高铝陶瓷柱塞的过程。通过精心配方设计和对主要工艺参数的优化，含氧化铝85％的陶瓷柱塞烧结温度从1400℃到1550℃，机械强度高，烧成变形小，合格率高，生产成本低，使用寿命较注浆产品显著延长。     

精细陶瓷热压烧结工艺中的模具问题

精细陶瓷热压烧结工艺中的模具问题段曦东姚吉升唐三川（湖南长沙矿冶研究院·４１００８２）１引言现代陶瓷科学的发展中,烧结始终是个重要内容,从根本上说,烧结是促使微细颗粒之间的化学反应和界面结合等,从而得到具有一定的组分分布,微细观结构和具有宏观稳定形状...     

ZTA陶瓷刀具材料制造工艺的研究

本实验采用冷压法、热压法和热等静压法三种不同工艺制得ＺＴＡ陶瓷刀具材料并研究它们对刀具材料性能的影响。实验结果表明：采用加压烧结工艺（热压或热等静压）可增加ＺＴＡ材料内部易相变四方相氧化锆含量,同时提高材料的抗弯强度和断裂韧性,从而增强了材料的耐磨性。热等静压工艺可望得到更大的发展和应用。     

氧化铝陶瓷低温烧结的研究现状和发展前景

本文综述了氧化铝陶瓷低温烧结的研究现状,包括粉体的制备,处理,成型及烧结工艺,并对此领域做了相应的设想和展望。     

柱塞气举排水采气工艺运行优化探究

柱塞气举排水采气工艺是进行低产气井排水采气的主要工艺技术之一,在气井采气生产中具有十分显著的应用优势。将结合柱塞气举排水采气工艺的实践应用情况,从柱塞气举排水采气的选井/气井管理以及工艺装置等方面,对其工艺运行优化的具体措施进行研究,以供参考。     

超低温烧结微波介质陶瓷制备工艺的研究进展

传统方法制备微波介质陶瓷通常需要1 000℃以上高温,不仅工艺周期长、能量消耗高,而且难以实现多种材料体系的集成共烧。如今,无线通讯技术的不断革新和蓬勃发展对微波器件小型化、集成化提出了更高要求,低温共烧陶瓷/超低温共烧陶瓷技术被开发和广泛应用。研究烧结温度更低、烧结效率更高,且微波介电性能优异的节能环保型绿色制备工艺,已经成为全球范围内研究热点之一。液相烧结、热压烧结、微波烧结、放电等离子体烧结、闪烧等烧结工艺的提出促进了低温烧结微波介质陶瓷的发展。最近,又出现了一种新的超低温烧结工艺—冷烧结技术。冷烧结具有极低的烧结温度(一般≤300℃)、可在短时间内实现陶瓷高致密化,且在物相稳定性、复合共烧以及晶界控制等方面有着优势,为超低温烧结工艺以及微波介质材料体系的开发提供了新的契机。     

高压大流量陶瓷柱塞泥浆泵密封系统的研究

高压大流量陶瓷柱塞泥浆泵集成隔膜泵与喷水式柱塞泵的结构特征,用水或其他介质将输送介质与密封接触面分开,避免了固体颗粒对泵造成严重磨损。其核心技术是使用高低压水阀的切换使密封面的环境保持干净,并使进入介质的水量最小化。     

浅析液压陶瓷柱塞泥浆泵的密封

主要介绍了液压陶瓷柱塞泥浆泵矩形密封的分类,对其进行了受力及密封效果的分析,并总结了密封的改进方式。     

Freeform fabrication of ceramics

Abstract

Fabrication of ceramic objects by solid freeform fabrication (SFF) techniques is reviewed, with emphasis on ceramic versions of commercial rapid prototyping (RP) methods. A wide range of ceramics have been demonstrated, including aluminium oxide, silica, hydroxyapatite, silicon nitride, and lead zirconate titanate, with techniques based on extrusion, ink jet deposition, green tape lamination, and photopolymerisation. The quality of SFF ceramics compares well with conventionally processed ceramics.     

先进陶瓷快速无模成型方法研究的进展

介绍了快速无模成型的发展历史和特点,重点介绍了激光选区烧结成型（Selective Laser Sintering,SLS)、三维打印成型（3Dimensional Printing,3DP)、熔融沉积成型（Fused Deposition of Ceramics,FDC)、分层制造成型（Laminated Object Manufacturing,LOM)、立体光刻成型9Stereilithography,SL)、喷墨打印成型（Ink-jet Printing,I-JP）、选区凝胶成型（Selective Gelation,SG)和激光选区气相沉积成型（Selective Area Laser Deposition,SALD)等8种先进陶瓷的成型方法,并分析了目前该技术产业化所面临的一些问题。     

Innovative fabrication of PZT pillar arrays by a colloidal approach

An innovative approach for fabricating pillar arrays for ultrasonic transducer applications is disclosed. It involves the preparation of concentrated piezoelectric lead zirconate titanate (PZT) suspensions in aqueous solutions of epoxy resin and its polymerization upon adding a polyamine based hardener. Zeta potential and rheological measurements revealed that 1 wt.% dispersant, 20 wt.% of epoxy resin and a hardener/epoxy resin ratio of 0.275 mL g⁻¹, were the optimized contents to obtain strong PZT samples with high green strength (35.21 ± 0.39 MPa). Excellent ellipsoidal and semi-circle shaped pillar arrays presenting lateral dimensions lower than 10 μm and 100 μm height were successfully achieved. The organics burning off was conducted at 500 °C for 2 h at a heating rate of 1 °C min⁻¹. Sintering was then carried out in the same heating cycle at 1200 °C for 1 h. The microstructures of the green and sintered ceramics were homogeneous and no large defects could be detected.     

Bend strength variation of ceramics in serial fabrication

We have performed a statistical evaluation of more than 10 000 experimental strength values of test pieces from a serial production of alumina products where in each production series 12 samples were broken. The Weibull parameters were obtained by three different methods: linear regression, maximum-likelihood and moments’ method. The methods give different values of parameters even for this large number of data, but all the correlation coefficients are high and similar. Evaluating Weibull parameters for each testing group gives expected systematically different values of particular Weibull modulus as compared to the whole population of collected data. However, when the order of experimental data is mixed, the average Weibull modulus is lower than that corresponding to time ordered data. This difference can be served as an indication for variation of products’ quality from series to series.     

Low-temperature fabrication of steatite ceramics with boron oxide addition

Steatite ceramics have been fabricated by using coarse starting materials such as talc, clay, and barium carbonate with addition of boron oxide (B₂O₃). B₂O₃ has been found to be a useful flux to densify MgO–Al₂O₃–SiO₂–BaO (MASB) powders. The steatite ceramic with a relative density of 97% was obtained at a sintering temperature of 1200 °C. The temperatures needed to densify MASB powders decrease with increase of B₂O₃ addition. For the same sintering temperature, as the amount of B₂O₃ addition increases, the crystallization rate of protoenstatite increase. Large pores and visible cracks were seen in B₂O₃-free samples, while pore elimination and enhancement of densification for B₂O₃-added steatites were promoted by the viscous flow due to B₂O₃. Hence, nearly dense ceramics were obtained for use in high temperature electrical applications.     

Pressureless fabrication of dense monolithic SiC ceramics from a polycarbosilane

This paper presents the pressureless preparation of dense and crack-free near stoichiometric SiC monoliths via cross-linking and pyrolysis of a polycarbosilane, followed by polymer-infiltration-pyrolysis cycles. The composition and the porosity of the samples strongly depend on the processing temperature. Thus, at 1050–1100 °C, the SiC monoliths are X-ray amorphous and exhibit low amounts of oxygen and excess carbon; their porosity was rather high (>10%). Higher processing temperatures induced the crystallization of β-SiC. The removal of oxygen and excess carbon due to CO release allowed for obtaining near-stoichiometric compositions at 1700 °C. However, the residual porosity of the samples increased. The use of the PIP technique led already after six cycles to dense monoliths (residual porosity ca. 0.5%).The present study emphasizes the potential of the polymer processing technique for the fabrication of near stoichiometric and dense SiC monoliths, which might be used for structural applications in harsh conditions.     

Fused deposition fabrication of high-quality zirconia ceramics using granular feedstock

Benefiting from the mature technology of ceramic injection molding, Fused deposition modeling based on highly-filled ceramic-polymer granular feedstocks has been showing great potential and advantage for fabricating 3D ceramics. Herein, 3D zirconia ceramics using granular feedstock were fabricated, and typical morphology, surface quality, and effect of the thermal accumulation on 3D structure were clarified. Typical morphology of printing steps on the surface were quantitatively characterized, and determined by the surface curvature and layer height of the printed structure. Aligned triangular pores were confirmed at the junction of the deposited filaments with elliptical cross-section morphology. Simple square plates with different size were used to illustrate the influence of thermal accumulation on the morphology of 3D structure. Small printing size increased the thermal accumulation during deposition, resulting in decreased printing quality caused by the secondary over-melting of former deposited layers. Except for the pores at the junctions, dense zirconia ceramics with uniform structure and smooth surface could be achieved. A low-cost and high-quality route for the preparation of 3D ceramics was demonstrated via FDM of highly-filled granular feedstocks.     

Pressure filtration assisted gel casting in translucent alumina ceramics fabrication

High density and homogeneous green body is important for fabricating transparent ceramics. Inspired by the improved samples’ homogeneity in slip casting, we introduced low pressure filtration to gel casting to further increase the relative density and homogeneity of the green body and to shorten the drying time. The effect of pressure filtration on drying characteristics, bulk density and porosity of the pre-sintered bodies, and the microstructure and optical transmittance of the resultant ceramics were intensively investigated. The results showed that pressure filtration can reduce the drying time by 27.3%, improve the density of the pre-sintered bodies and reduce the residual pores of the sintered ceramics. The in-line transmittance of the translucent alumina prepared by the pressure filtration assisted gel casting was 32.7% at 600?nm with a thickness of 1?mm, which is about 6% higher than that without pressure filtration. In principle, this process can be applied to fabricate any other high-performance ceramic.     

The fabrication of porous mullite ceramics based on the different sizes of aluminum hydroxide

In this research, for studying the influence of size and heat treatment temperature of initial Al(OH)₃ on the physical properties of porous mullite ceramics, porous mullite ceramics were prepared by in situ reaction sintering of amorphous silica and treated Al(OH)₃. The transition phases χ-Al₂O₃, к-Al₂O₃, and stable phase α-Al₂O₃ can be obtained in turn when the treatment temperature of raw Al(OH)₃ is 500, 1000, and 1500°C, respectively. The coarser the raw Al(OH)₃, the higher the strength of porous mullite ceramics. When the sintering temperature is 1500°C, the bending strengths of PS500-C, PS1000-C, and PS1500-C (PSx-C represents that the specimen was prepared by the coarse grade Al(OH)_3, which was previously treated at x°C) are 40.3 ± 2.1, 54.9 ± 5.2, and 64.8 ± 4.8 MPa, respectively. In addition, although the activated Al₂O₃ can decrease the formation temperature (∼100°C) of porous mullite ceramics, the strength and density of porous mullite ceramics prepared by activated Al₂O₃ will decrease at the same sintering temperature. It is believed that the increase of defects and pores during the phase transformation should be responsible for this phenomenon.