Synthesis and characterization of proton conducting Sr(Ce1−xZrx)0.95Yb0.05O3−δ by the citrate method

The citrate method was used to synthesize Sr(Ce_1−xZr_x)_0.95Yb_0.05O_3−δ (x = 0.1, 0.2, 0.3, 0.4) and to avoid the drawbacks of the conventional solid state reaction method. The products were characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe X-ray microanalyzer (EPMA). The results indicate that the citrate method is an advantageous route in producing Sr(Ce_1−xZr_x)_0.95Yb_0.05O_3−δ materials. Sr(Ce_0.9Zr_0.1)_0.95Yb_0.05O_3−δ powders are composed of nanoscaled crystallites with the average grain size in the range of 60–70 nm. Single phase is confirmed over the whole x range. In addition, chemical stability against CO₂ and electrical conduction behavior of the sintered Sr(Ce_1−xZr_x)_0.95Yb_0.05O_3−δ ceramics were investigated. The chemical stability of the ceramics against CO₂ is certified to increase with the increase in zirconium content. Impedance spectroscopy was used to study the electrical conduction behavior of Sr(Ce_0.9Zr_0.1)_0.95Yb_0.05O_3−δ ceramic.     

Ambient to high-temperature fracture toughness and cyclic fatigue behavior in Al-containing silicon carbide ceramics

A series of in situ toughened, Al, B and C containing, silicon carbide ceramics (ABC-SiC) has been examined with Al contents varying from 3 to 7 wt.%. With increasing Al additions, the grain morphology in the as-processed microstructures varied from elongated to bimodal to equiaxed, with a change in the nature of the grain-boundary film from amorphous to partially crystalline to fully crystalline. Fracture toughness and cyclic fatigue tests on these microstructures revealed that although the 7 wt.% Al containing material (7ABC) was extremely brittle, the 3 and particularly 5 wt.% Al materials (3ABC and 5ABC, respectively) displayed excellent crack-growth resistance at both ambient (25 °C) and elevated (1300 °C) temperatures. Indeed, no evidence of creep damage, in the form of grain-boundary cavitation, was seen at temperatures at 1300 °C or below. The enhanced toughness of the higher Al-containing materials was associated with extensive crack bridging from both interlocking grains (in 3ABC) and uncracked ligaments (in 5ABC); in contrast, the 7ABC SiC showed no such bridging, concomitant with a marked reduction in the volume fraction of elongated grains. Mechanistically, cyclic fatigue-crack growth in 3ABC and 5ABC SiC involved the progressive degradation of such bridging ligaments in the crack wake, with the difference in the degree of elastic vs. frictional bridging affecting the slope, i.e. Paris law exponent, of the crack-growth curve.     

铸造金属颗粒用定量器滴嘴的研究与应用

研究了一种铸造金属颗粒用定量器滴嘴的结构及其制造工艺。结果表明,由烧结陶瓷加工而成的滴嘴本体及与滴嘴本体配合的塞子两部分构成的组合式定量器滴嘴,强度高,韧性、耐磨性和耐蚀性好,使用寿命长,更换时不断裂,可提高铸造金属颗粒生产线的作业率,降低金属颗粒加工成本。金属液流经定量器滴嘴后,能够实现平稳、断续流动,加工的金属颗粒尺寸均匀、稳定性好。     

Effect of vanadium doping on fabrication and property of Bi4Ti3O12 ceramics

Vanadium-doped bismuth titanate ceramics of composition Bi₄Ti_3−xV_xO_12+x/2 (BTV, x = 0.02, 0.03, 0.04, 0.06, 0.08) were prepared using the conventional solid-state reaction method. The sintering activity was significantly improved by the addition of even a small amount of vanadium. The effects of the incorporation of vanadium in the Bi₄Ti₃O₁₂ lattice on the microstructure, Raman characteristics, dielectric and ferroelectric properties of the samples were investigated.     

微弧氧化铝、镁等合金材料表面陶瓷化处理

在碱性电解液中，如在电极上施加较高的电压，作为电极的铝、镁等合金材料表面就会产生微区弧光放电现象；利用这一现象可在材料表面生成具有一定厚度，致密的陶瓷氧化层，可用来改善材料自身的防腐、耐磨和电绝缘等特性。     

Crystallization of magnesium niobate from mechanochemically derived amorphous phase

The effect of high-energy ball milling and subsequent annealing on the mixture of MgO and Nb₂O₅ has been investigated. X-ray diffraction (XRD) measurement indicates that an amorphous phase is produced after milling for 5 h, while traces of MgNb₂O₆ crystallized from the amorphous phase during prolonged milling. Significant crystallization of MgNb₂O₆ from the amorphous state is observed after annealing at 500 °C, while the reaction of the remaining MgO and Nb₂O₅ does not take place at this temperature. Single phase MgNb₂O₆ can be achieved for all the milled samples at 700 °C. No significant grain growth is observed when the milled powders were annealed at temperature below 900 °C. Almost fully dense MgNb₂O₆ ceramics are obtained after annealing at 1100 °C from the as-milled powders.     

微装配中微靶球的三维移动

设计了一种用于惯性聚变的微靶球三维移动装置。采用CCD显微镜检测实现闭环装配以保证精度;由电控平移台作为粗动环节,压电陶瓷作为微动环节而形成的两级微动机构可以实现最小分辨力为0.1μm的微位移;直线 旋转执行器的旋转/线性移动实现了微靶球的三维移动;专用真空吸取器的设计解决了微靶球的取放问题。     

耐磨工程陶瓷在引风机和排粉风机上的应用

简要分析了引风机和排粉风机的磨损机理。介绍了耐磨工程陶瓷的特性，及其采用机械卡接、粘接工艺和在防磨风机中的应用。     

The relationship between microstructure and wear of mica-containing glass-ceramics

A series of mica-containing glass-ceramics with three different mica platelet sizes were tested for wear against a harder alumina counterface in a pin-on-disk tribometer under distilled water lubrication. Under all test conditions (i.e, different loads and number of passes), the wear rate increased with the increase in mica platelet diameter. Examination of the wear scars on the glass-ceramic samples using a scanning electron microscope indicated that the wear process was dominated by a microfracture mechanism either along the mica cleavage planes or along the weak mica-glass interfaces. Three wear modes were observed. (1) At low loads and small number of passes, wear occurred by formation of isolated fracture sites on the wear track. No measurable wear took place during this 'localized fracture' wear mode. (2) The number of fracture sites increased and covered the entire contact width as the load or number of passes increased. This 'contact fracture' mode resulted in wear factors on the order of 10⁻⁴ mm³ Nm⁻¹. (3) At higher loads or after a large number of passes, accumulation of subsurface microfracture damage led to 'spallation' wear mode which resulted in wear factors on the order of 10⁻² mm³ Nm⁻¹. The mica platelet diameter was found to be an important factor in controlling the wear modes and wear transitions. The transitions from 'localized fracture' to 'contact fracture' and to 'spallation' occurred at lower loads and smaller number of passes as the mica plate diameter was increased.     

Ceramic Response to High Speed Grinding

Material response was investigated with respect to normal grinding forces, surface roughness, and removal mechanisms in grinding of alumina, silicon carbide, silicon nitride, and zircona with a resin-bond 160 μm grit diamond wheel at the grinding speeds of upto 160 m/s. The results reveal that the normal grinding forces decreased significantly with an increase in grinding speed; they also increased substantially with an increase in a complex relation of the ceramic hardness and toughness. High speed grinding produced a reduction in surface roughness for silicon carbide and alumina but gave no improvement for zirconia and silicon nitride. Also the surface roughness in high speed grinding was found to be material-dependent that the ground silicon nitride exhibited much smoother than the other ground ceramics. The influence of grinding speed on material removal mechanisms was analyzed in terms of grinding geometry and ceramic material properties.