淀粉固结成型工艺制备多孔陶瓷

探索了以淀粉作为粘结剂和造孔剂来制备多孔陶瓷的淀粉固结工艺,制成的多孔陶瓷的密度为0.804~1.032g/cm3,孔隙率为65.6%~73.2%。研究表明,陶瓷浆料具有剪切变稀的特性,且随淀粉含量的增加,浆料的粘度上升;另外,淀粉含量、烧成温度、保温时间等对材料孔隙率、体积密度等有很大影响。     

超微细粉末材料的发展

超微细粉末材料因具有独特的结构和物理、力学性质而受到人们的关注。本文综合评述了超微细粉末制备技术的发展和超微细粉末材料物理、力学性质方面的研究成果，展望了这种材料在舰船及其它工业技术领域的应用前景。     

多孔陶瓷材料的研究进展

多孔陶瓷是一种新型功能材料,由于其具有气孔率高、耐高温、抗化学腐蚀、热稳定性好等优良性能,而被广泛应用于众多领域。本文总结了多孔陶瓷材料的分类方法和性能指标,介绍了多孔陶瓷的制备工艺和特点;并列举了多孔陶瓷在过滤器、催化剂载体、节能隔热材料、吸声材料和生物材料等方面的应用;最后展望了多孔陶瓷材料的发展前景。     

陶瓷空心球/镁合金复合多孔材料制备及压缩性能

本文选用两种不同的陶瓷空心球(商购氧化铝空心球和自制含硅复合氧化物陶瓷空心球)作为增强体,采用粉末烧结的方式在烧结温度600℃、保温时间3 h 20 min的烧结条件下,成功制备出两种轻质、含孔的镁合金复合多孔材料。通过扫描电子显微镜观察烧结样品的微观结构,发现含硅陶瓷空心球与镁合金的界面处发生了界面反应,生成了含有MgO、Mg₂Si等成分的合金相。研究了采用不同种类陶瓷空心球对样品表观密度、压缩强度和比强度的影响。结果表明,采用商购氧化铝空心球制备的复合样品的体密度最低,与镁合金致密体的密度相比,平均表观密度下降了33.3%,为1.20 g·cm^-3;选用自制含硅陶瓷空心球制备的复合样品的平均表观密度下降了16.1%,为1.51 g·cm^-3;在压缩过程中两种样品都表现出了弹性阶段、屈服平台和致密化阶段的多孔材料典型的压缩特征;自制含硅陶瓷空心球所制样品的压缩强度明显高于氧化铝空心球所制样品,自制含硅陶瓷空心球所制复合样品的比强度也高于商购氧化铝空心球所制复合样品。     

陶瓷粉末靶与陶瓷块状靶溅射制备PZT薄膜的性能比较

介绍了RF溅射冷压法制备的PZT陶瓷粉末靶和块状靶制取PZT薄膜的过程.二种方法避开了热压法制作PZT陶瓷块状靶的复杂工艺及昂贵设备,均能获得化学成分稳定的钙钛矿结构PZT铁电薄膜;用粉末靶制取的薄膜的热处理温度比块状靶低200℃;用块状靶制取的薄膜具有清晰的晶粒,较好的化学配比、电性能及高的密度;用粉末靶未见有明显的晶粒,存在玻璃质,其化学配比与源材料相比有较大差异,电性能也略为逊色.     

液相共沉淀制备镍铁尖晶石前躯体工艺研究

本文对于溶液均相共沉淀法制备镍铁尖晶石前躯粉体的工艺进行了探索研究。论文以Fe（N02）3和Ni（N02）2的混合溶液为反应物,滴加沉淀剂,进行共沉淀反应。对得到的沉淀产物进行洗涤、过滤、干燥、研磨、压制、烧结制备NiFe2O3尖晶石陶瓷粉体。通过正交试验确定了在共沉淀过程中影响共沉淀颗粒粒度的影响因素的主次顺序依次为：反应温度、搅拌速度、沉淀剂浓度、金属离子浓度;并通过反应温度和沉淀荆浓度对产率的影响试验,最终得到共沉淀反应沉淀的最佳条件。对于所制得的镍铁尖晶石陶瓷粉体检测结果表明：溶液均相共沉淀法得到的镍铁尖晶石前躯体粉末具有纯度高、粒度细的特点,并且制备出的镍铁尖晶石惰性阳极基体材料的强度显著提高。     

Aligned Porous Structures by Directional Freezing

Materials with aligned porous structures have broad potential in applications such as organic electronics, microfluidics, and tissue engineering. Materials of this type can be fabricated using techniques such as microfabrication, soft lithography, and photolithography. Directional freezing is a cheap, simple, and novel route to prepare aligned porous materials in the form of 2D surface patterns or 3D monolithic structures. A solvent—typically water but also organic solvents or carbon dioxide—is frozen unidirectionally and the pore structure is templated from the aligned solvent crystals that are formed. These methods can produce complex composite materials with a range of aligned pore architectures.     

Powder Metallurgical Fabrication and Characterization of Nanostructured Porous NiTi Shape-Memory Alloy

Production of NiTi alloy from elemental powders was conducted by mechanical alloying (MA) and sintering of the raw materials. Effects of milling time and milling speed (RPM) on crystallite size, lattice strain, and XRD peak intensities were investigated by X-ray analysis of the alloy. Powder compaction and sintering time and temperature effects on pore percentage of the as-mixed and the mechanically alloyed samples were empirically evaluated. The crystallite size of the mechanically alloyed Ni₅₀Ti₅₀ samples decreased with MA duration and with the milling speed. Depending on the crystal structure of the raw materials, the lattice strain increases with the milling duration. Metallographic studies proved the existence of martensitic B19' after sintering of both the as-mixed and the mechanically alloyed samples. Its amount was, however, greater for the former. Sintering lowered the porosity of the samples; no matter what powder (as-mixed or mechanically alloyed) was used. The porosity was greater, however, for the MA powders. This difference seemed to be due to the sharper liquid phase sintering effect of the as-mixed samples.     

通孔型多孔陶瓷材料制备技术新进展

简要介绍了通孔型多孔陶瓷材料的性能及其应用领域,综合论述了通孔型多孔陶瓷材料的制备技术及研究进展,分析了各种制备方法的优缺点,预测了通孔型多孔陶瓷制备技术的发展方向。     

超声波-共沉淀法制备ZrO_2-MgO超细粉

以ZrOCl2·8H2O为原料,用乙醇和聚乙二醇两种有机溶液处理,在化学共沉淀阶段使用超声波辐照制备MgO稳定ZrO2超细粉,通过X射线衍射(XRD)、激光粒度分析、扫描电子显微镜(SEM)和差热分析(DSC)等手段对试样的微观结构进行表征。试验结果表明,用超声波辐照制备合成MgO稳定ZrO2超细粉,其结晶温度低,粉料的分散性好,不易团聚。     

Porous epoxy microparticles prepared by an advanced aqueous method

This paper reports the synthesis of emulsions of epoxy compounds with various ratios of epoxy, polyamide and calcium carbonate by homogenization in water at room temperature. The emulsion is cured at 80 °C, and during curing the small epoxy droplets in the emulsion coalesce. The cured coalesced epoxy droplets contain holes formed due to water trapped inside them and also due to the difference in curing rates between epoxy molecules on the outside versus inside of the coalesced droplets. The porous epoxy particles are obtained when the cured coalesced epoxy droplets are treated with hydrochloric acid to remove the calcium carbonate. The size of the porous epoxy particles and the number of holes formed depends on the curing rate of the epoxy compound.     

Production of Metallic Foams Having Open Porosity Using a Powder Metallurgy Approach

A technique has been recently developed to produce foamed metallic structures from dry powder blends containing a metallic powder, a polymeric binder, and a foaming agent. The blend is molded and heat-treated to foam and consolidate the material. The final properties may be tailored by varying the sintering temperature. Microstructure, chemical composition, and properties of nickel (Ni) foams sintered at different temperature are presented and discussed. The resulting material has an open cell microstructure with three levels of porosity. This structure leads to materials having low density (∼ 90% porosity) and high specific surface area. The specific surface area is reduced and the mechanical strength is increased when the sintering temperature increases.     

采用定向SiC纳米线烧结制备高强多孔 SiC陶瓷

利用直接墨水打印方法制备了由定向SiC纳米线交错叠层组成的具备网络状孔隙结构的高强SiC多孔陶瓷.制备的碳化硅多孔陶瓷具有高的通孔结构和完全由定向SiC纳米线组装而成的结构特征.研究了烧结温度对定向SiC纳米线多孔陶瓷的微观结构、相组成演变及力学性能的影响.研究结果表明:烧结温度低于1900℃时,SiC纳米线能保持高长...     

多孔陶瓷材料的制备技术

本文评述了近年来多孔陶瓷材料制备技术的研究现状，对目前研究比较活跃，应用比较成功的几种制备技术进行了分析，并讨论了今后的发展趋势。     

Porous Metal Sheets of NiTi made by Wet Powder Spraying

As a promising method to produce thin porous NiTi sheets, Wet Powder Spraying (WPS) is applied for NiTi powders. Layers with a thickness of 150 μm are obtained from pre‐alloyed NiTi powders with a particle size of < 12 μm. Optimized process control for spraying and sintering was used. Microstructure and phase formation is characterized. The sheets with a porosity of 15 % show a high pseudoelastic flexibility at room temperature. Phase transformation temperatures are determined by Differential scanning calorimetry (DSC). The one way effect could be demonstrated.     

Heat Dissipation Performance of Porous Copper with Elongated Cylindrical Pores

The purpose of this paper is to investigate heat dissipation performance of porous copper with long cylindrical pores fabricated by a unidirectional solidification method. Three samples with porosity of 29.87%, 34.47% and 50.98% were chosen and cut into size of 60 mm （length） × 26 mm （width） × 2 mm （thickness） along the vertical direction of pore axis. Their heat dissipation performance was evaluated by a nonsteady method in air and compared to those of not only bulk copper but also bored coppers with porosity of 30.61% and 32.20%. It is found that the porous copper dissipated heat faster by a forced air convection than that by natural convection from 80 ℃ to room temperature and both porosity and pore size play an important role in the performance for the porous copper. Furthermore, the heat dissipation rate is higher when the forced air was circulated along the specimens than that perpendicular to the specimens for the porous copper. It is revealed that porous copper with bigger porosity and a proper pore size possesses a higher heat dissipation rate. It is concluded that the porous copper with elongated cylindrical pores has larger heat dissipation performance than both the bulk copper and the bored copper, which is attributed to its higher specific surface area. Application of the porous copper for heat dissipation is promising.     

LiAITiO_4系多孔湿敏陶瓷导电机理的研究

通过对 LiAlTiO_4材料直流、交流特性、敏感特性及显微结构的测量与分析,讨论了材料的湿敏导电机理,建立了相应的物理模型。对材料的表面态、表面吸附过程、参与导电的载流子类型和各种可能的极化机制做了一定的阐述,给出了理论分析结果,与实验结果相一致。     

车用氧传感器多孔保护层的制备及性能研究

为了延长汽车氧传感器的寿命,通常在氧传感器敏感元件的铂电极表面涂覆多孔陶瓷保护层。本文以尖晶石、氧化铝、氧化锌等为原料,通过控制各组分的配比和烧结工艺参数,制得了性能良好的多孔陶瓷保护层。     

Processing of Ceramic Rifled Gun Barrel

Ceramic gun barrels have the potential to provide a significant increase in barrel life as well as reduction in weight for small caliber systems. The potential use of ceramic tubes as gun barrels may be severely limited due to the difficulty in introducing the rifling on the inner diameter. The processing of ceramic gun barrels with internal rifling pattern poses a tremendous processing challenge to the materials community. The rifling lands and grooves and desired twist rate, coupled with the difficulty of machining ceramics, makes the economic manufacturing of such gun barrels extremely difficult. The current paper describes the preliminary efforts of fabricating an alumina gun barrel tube that was around 100-mm long with a 25-mm inner diameter (ID), a 33-mm outer diameter, and eight lands and eight grooves. Over and above the lands and grooves in the ID, the barrel had to have a 10:1 twist (one complete twist in 250-mm) incorporated into it. The paper will describes our preliminary attempts at processing such a rifled gun barrel tube made of alumina.