陶瓷注射成型工艺及进展

综述了陶瓷注射成型目前的发展状况，重点介绍了陶瓷注射成型技术的基本工艺过程，讨论了陶瓷注射成型技术的发展趋势。     

Influence of the Compacts Homogeneity on the Incidence of Cracks during Thermal Debinding in Ceramic Injection Molding

During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions,typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.     

Sintering Characteristics of a Powder Injection Molded Ceria-Stabilized Zirconia–Mullite Composite

Powder injection molding (PIM) technology has the potential for economically manufacturing several complex-shaped zirconia–mullite components in mass production. The sintering behavior of a zirconia–mullite composite fabricated by injection molding was analyzed in this paper. The focus of this study is to assess the dependence on properties and microstructure on PIM processing conditions. The sintered density of the samples displayed a strong dependence on sintering temperature. The hardness of the samples followed a similar trend as sintered density. A maximum fracture toughness of 4.1 ± 0.3 MPa · m^1/2 and strength around 450 ± 60 MPa was observed for samples sintered at 1500°C for 4 h. The properties from this study are significantly higher than the values reported in majority of the prior studies where other technologies like uniaxial and cold isostatic pressing were used to fabricate zirconia–mullite composites. The above results support the suitability of PIM as a manufacturing process for complex-shaped zirconia–mullite components with good mechanical properties.     

炮管材料的发展现状与趋势

简述了炮管材料的发展历程,并根据炮管的工作条件总结出其基本性能要求。对传统炮管材料——炮钢的化学成分、力学性能进行了论述,重点归纳了现阶段炮钢发展思路和研究重点。对国外新型炮管材料技术——复合材料炮管技术及新型绿色炮管抗烧蚀涂层技术动态进行了跟踪介绍。     

Hybrid Ceramic Matrix/Metal Matrix Composite Gun Barrels

Future Army gun systems will require lighter weight and significantly more erosion-resistant materials. One route to achieve this goal is via the development of ceramic matrix composite barrel liners with lightweight metal matrix composite jackets. Such materials systems are hybrids of a ceramic matrix composite/metal matrix composite (CMC/MMC), which can provide functionally graded properties. This paper will describe the materials system development, fabrication, and property validation testing of such a hybrid CMC/MMC for a 25-mm-bore, 915-mm-long, rifled barrel.     

Sintering of 17-4PH stainless steel feedstock for metal injection molding

The sintering behavior of 17-4PH stainless steel feedstock for metal injection molding was investigated in the temperature range of 650-1050 °C. Effects of sintering conditions, such as sintering temperature and sintering atmosphere, were examined. Results showed that when sintered in the hydrogen/nitrogen atmosphere, the 17-4PH feedstock was oxidized over the temperature range of investigation. The degree of oxidization increased with the sintering temperature. The main oxidization product was Cr₂O₃ as revealed by X-ray diffraction and composition analysis. The oxidation can be avoided by sintering in vacuum or argon atmosphere.     

Effects of Injection Molding Parameters on the Production of Microstructures by Micropowder Injection Molding

Micropowder injection molding (μPIM) is a potential low-cost process for the mass production of metal or ceramic microstructures. In order to obtain good molded microstructures and to avoid molding defects, it is important to select suitable injection molding parameters. In this paper, the selection of injection molding conditions for the production of 316L stainless steel microstructures by μPIM is presented. Silicon mold inserts with 24 × 24 microcavities were injection molded on a conventional injection molding machine. The dimensions of each microcavity were Φ 100 μ m × depth 200 μm, giving an aspect ratio of 2. The distance between each microcavity was 200 μm. Five sets of experiments were conducted by varying one injection molding parameter at a time. The parameters included injection pressure, holding pressure, holding time, mold temperature, and melt temperature. Higher injection pressure and holding pressure were required during the injection molding process due to the small dimensions of the microcavities and the large number of microcavities (576 microcavities). High mold temperature was required for complete filling of the microcavities. Molded microstructures without visual defects were obtained using appropriate injection molding parameters. Catalytic debinding and sintering of the 316L stainless steel microstructures were successfully conducted.     

Processing of alumina and zirconia nano-powders and compacts

Magnesia–doped alumina and yttria–doped zirconia nano-powders were synthesized using sucrose as a chelating agent and template material from the aqueous solutions of aluminium nitrate, magnesium nitrate, ytrrium nitrate and zirconyl nitrate, respectively. Synthesis parameters were optimized with varying sucrose to metal ion ratio, calcinations time, and temperature to produce these nano-powders. As-synthesized powders were characterized by room temperature X-ray diffraction, BET surface area analyzer and transmission electron microscopy. Y₂O₃–ZrO₂ nano-powders had particle size in the range of 80–200 nm with specific average surface area of 119 m²/g and for MgO–Al₂O₃ powders, particle sizes were 30–200 nm with the specific average surface area of 250 m²/g. Our results indicate that this synthesis method is a versatile one and can be applied to a variety of oxide-based materials to form nano-powders. Nano-powders were compacted uniaxially and densified in a muffle furnace. Sintered discs were used for hardness testing and density measurements, as well as for microstructural characterization.     

Effects of thermal debinding on surface roughness in micro powder injection molding

Micro metal injection molding (μMIM) is a promising process for the replication of metallic microstructures. In the micrometer regime, surface roughness is important in view of the dimensional tolerance and the applications of microstructured parts. In this paper, the effects of debinding on the surface roughness of 316 L stainless steel microstructured parts were investigated. Experimental results showed that using higher heating rates during debinding increased the weight loss of debound parts. The debound parts of higher weight loss gave better surface finish after sintering. Comparing the increase of sintering time and temperature, the surface finish improvement was more significant for increasing temperature.     

氧化铝陶瓷膜的组成与热膨胀

利用微等离子体氧化技术在LY1 2铝合金表面制备了氧化铝陶瓷膜。通过X射线衍射法研究了陶瓷膜的相组成 ,发现陶瓷膜由α Al2 O3和γ Al2 O3两相组成 ,α Al2 O3在陶瓷膜的外层含量高 ,γ Al2 O3在陶瓷膜的内层含量高。陶瓷膜的热膨胀系数为 7.3798×1 0 - 6 /K ,与α Al2 O3大块固体的热膨胀系数相近     

Processing of Composite Gun Tubes with GLEEM and Hammer Forging

Refractory metal liners have been shown to extend the service life of gun tubes a considerable amount. The major technical hurdle to date has been keeping the liners in place during firing. To address this problem, composite gun tubes made of steel and pure niobium have been fabricated through a combination of the GLEEM (gun liner emplacement with an elastomeric material) and the hammer forging. The three barrels made by this approach were test fired in single-shot and burst-fire mode. One of the barrels whose liner had been cold-sprayed with tungsten carbide particles before the GLEEM process showed no liner movement in any of the tests. The success of this new liner processing technology to prevent liner movement offers the potential for further investigations of refractory metals that are more suitable as liner materials.     

Characterization of Gradual Porous Ceramic Structures Obtained by Powder Sedimentation

Asymmetric membranes present better separation and service characteristics than the symmetric ones. In our preliminary studies the possibility of obtaining sintered porous materials with gradual structure by sedimentation of metallic and ceramic powders was demonstrated. Zirconium silicate (ZrSiO4) particles were used for the manufacturing of the porous supports, and mullite powder was deposited by sedimentation in order to achieve the active layer with pores size gradient. The used powders and the obtained structures were characterized by laser scattering particle size analyzer, scanning electron microscopy and mercury porosimetry. The permeability and the filtration fineness of the structures were also determined. By using a thin active layer made of small particles deposited onto a macro-porous support, one can achieve membranes with high flow rates and filtration fineness in the microfiltration area.     

铜合金粉末注射成形缺陷分析

针对所用铜合金粉末的特点，探讨了CuSn6Zn6Pb3舍金注射成形过程中各步工序所可能产生的缺陷及产生机理，并详细分析了实验过程中出现的几种典型缺陷。     

Microstructural evolution of injection molded gas- and water-atomized 316L stainless steel powder during sintering

The present study investigates the microstructural evolution and densification behavior of water- and gas-atomized 316L stainless steel powder. Dilatometry and quenching studies were conducted to determine the extent of densification and corresponding microstructural changes. Results indicate that water-atomized powder could be sintered to 97% of theoretical density, while gas-atomized powders could be sintered to near-full density. The difference in the densification behavior is examined in terms of the particle morphology, initial green density and the particle chemistry.     

陶瓷注射成形中脱脂工艺及其新进展

陶瓷注射成形是先进的陶瓷近净成形技术,可高效成形形状复杂的陶瓷部件.而脱脂是陶瓷注射成形中最复杂和重要的环节.详细介绍了陶瓷注射成形各种脱脂工艺的脱脂原理,并对各种脱脂工艺的优缺点进行了比较.     

Processing of Net‐shaped Nanocrystalline Fe‐Ni Material

Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. This paper provides an overview on our recent investigations on the processing of net‐shaped nanocrystalline Fe‐Ni powder and related material property such as mechanical property. The key‐processing concept is the synthesis of nanopowders and subsequent consolidation with controlled microstructure by using powder injection molding (PIM) process. Especially, the pressureless sintering process is inevitable for consolidation of the PIMed nanopowder. The present review focuses on the densification process and related mechanical property of the PIMed Fe‐Ni nanopowder in association with microstructural evolution and diffusion process.     

大尺寸ZrO2注射成型坯体热脱脂缺陷成因探究

采用蜡基ZrO2粉末喂料注射成型获得大尺寸ZrO2陶瓷粉末注射产品（坯体）,并根据喂料热分析曲线的变化特点,系统研究了大尺寸ZrO2坯体的热脱脂过程及规律。通过对热脱脂前后坯体的重量损失、尺寸收缩、外观缺陷和微观组织形貌的分析评估,着重探讨了大尺寸ZrO2坯体热脱脂过程中存在的主要缺陷和成因。研究表明,流蜡、鼓泡和开裂等热脱脂缺陷主要发生在低温脱脂阶段,其主要原因是液态石蜡扩散及分解过程的失衡。为此,结合“失重率控制”的思路和喂料的热失重规律,对热脱脂工艺进行了优化,在不延长总脱脂时间的前提下,显著提高了大尺寸ZrO2坯体的脱脂合格率。     

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.     

硅藻土基轻质陶瓷素坯配方及烧结工艺的研究

本实验以轻质、多孔的硅藻土为主要基料，通过引入叶腊石、石英、锂辉石、硅灰石及粘土等原料，研制出了吸水率及强度均达到了国标要求，而体积密度仅为1.4～1.5g／cm^3的轻质多孔的内墙釉面砖用素坯。还借助了XRD、SEM等现代化手段对坯体在烧成过程中的物相变化以及低温烧结机理进行了分析。