Colloidal processing of Al2O3-doped zirconia ceramics with CaO–P2O5–SiO2 glass as additive

Well-dispersed concentrated aqueous suspensions of Al₂O₃-doped Y-TZP (AY-TZP), AY-TZP with 5.4 vol% of CaO–P₂O₅–SiO₂ (CaPSi) glass (AY-TZP5) and 10.5 vol% CaPSi glass (AY-TZP10), with ammonium polyacrylate (NH₄PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300°C-1500°C. The optimum NH₄PA concentration of 35 vol% AY-TZP5 and AY-TZP10 slips at pH ~9 was found to be about 43% and 67% greater than that of AY-TZP slips; this behavior was related to the greater amounts of Ca²⁺ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH₄PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY-TZP5 can be sintered at a lower temperature (1300°C) compared to that of AY-TZP. AY-TZP5 exhibited a fine microstructure of tetragonal ZrO₂ (grain sizes below 0.3 µm), and ZrSiO₄–Ca₂P₂O₇ particles homogeneously distributed within the zirconia matrix. It presented similar fracture toughness and a slightly lower hardness compared to those of AY-TZP.     

Preparation and characterization of multilayer Gd2O2S:Tb phosphor screen for X-ray detection application

Gd2O2S:Tb (GOS) phosphor screen, generally with a multilayer structure, has been widely used in digital X-ray imaging. GOS phosphor screen is fabricated via a slip casting route, which is an effective method to obtain multilayer composites with good strength. The GOS slurry was prepared using the menhaden oil, polyvinyl butyral and PEG-400 as dispersant, binder and plasticizer, respectively, and slip casted on a support layer. After the GOS scintillation layer is formed, a transparent polyethylene terephthalate film is covered on it as a protective layer. The X-ray excited emission spectra of the obtained GOS phosphor screen is well match to the spectral response of a-Si:H photodiode, and the spatial resolution was close to 3.7 LP/mm, which could meet the request of the commercial application.     

Making reusable reaction-bonded silicon nitride crucibles for silicon casting from kerf-loss silicon waste

Silicon kerf loss during wafer slicing and the broken quartz crucibles after silicon casting are two major solid wastes from photovoltaic (PV) industry. Especially, the recycle of kerf-loss silicon has become an urgent issue because near 100 000 t of solid wastes are generated every year. One of the most meaningful recycle routes of the kerf-loss silicon is to make silicon nitride crucibles to replace the quartz crucibles. In this study, we demonstrated how this is feasible through acid leaching refining, slip casting, and nitridation. The reaction-bonded silicon nitride (RBSN) crucibles after oxidation were found pure enough for silicon ingot growth. More importantly, they could be reused after ingot growth. With the present examples, the potential of using the kerf-loss silicon for fine ceramics is prominent.     

水力冲孔作用下煤层底抽巷围岩损伤机理及位置优化方法研究

底抽巷作为瓦斯抽采的辅助巷道,有时还要兼顾煤层回采期间的通风等作用,服务期间需经历2次掘进扰动和煤层采动等影响,因此底抽巷合理布置对瓦斯抽采效果、岩巷支护稳定性具有极其重要的作用。基于理论分析、现场工程类似、数值模拟等方法对梁北煤矿大埋深底抽巷布置方案展开研究。在综合考虑应力环境、瓦斯抽采与底板突水等综合因素的影响后,最终确定梁北煤矿21071底抽巷层位选择为沿L8灰岩进行掘进,割灰岩厚度1~1.5m,距煤层实际距离约21m。     

基于MATLAB乘用车门玻璃密封压装机动态特性研究

建立了东风轻型乘用车EQ6472前门玻璃密封条气动压装机系统的数学模型,采用MATLAB对其进行了动态特性分析,得到了压装机的时域响应和频域响应特性曲线.分析结果表明:系统调整时间满足生产要求;系统是稳定的.     

船用柴油机选择性催化还原系统设计及试验验证

结合船用中速柴油机开展选择性催化还原(selective catalytic reduction,SCR)系统的设计和性能试验验证,着重关注还原剂均匀分布、排气均匀度、系统稳定可靠控制及催化剂布置等方面,形成适用于船用环境的SCR系统设计方案.基于6L21/31中速柴油机D2以及E3循环工况开展SCR系统配机试验,结果...     

纳米ZrO_2－Al_2O_3复合粉末注浆成型与烧结行为研究

平均粒径为２０ｎｍ的ＺｒＯ_２添加５～１５ｖｏｌ％的粒径为２００ｎｍ的Ａｌ_２Ｏ_３粉末注浆成型与烧结特性表现出与普通微米及亚微米级粉末不同的特性：浆料具有较低的含固量，粘度为５厘泊时为５５ｗｔ％；浆料呈微弱触变性：生坯具有较低相对密度，仅为理论值的３５．５％；少量Ａｌ_２Ｏ_３（５～１０ｖｏｌ％）促进复合材料的烧结，但也伴随着Ａｌ_２Ｏ_３晶粒异常长大。上述现象归因于纳米粉末具有非常高的比表面，粉末表面吸附大量紧吸附水不能被石膏模所排除，而粉末巨大的表面能促进了烧结过程中的质点扩散。     

Effect of nanoparticle shapes on irreversibility analysis of nanofluid in a microchannel with individual effects of radiative heat flux,velocity slip and convective heating

In this study, the flow of a nanoliquid in a microchannel is examined. Two distinct metallic nanoparticles, titanium and silver, are used in this study. The slip regime and convective boundary are considered to compute the momentum and energy balance equation. The mathematical expressions are made dimensionless by using nondimensional quantities. A numerical approach called Runge‐Kutta‐Fehlberg scheme is employed to obtain the solution. Effects of the internal heat source and radiative flux on fluid model are examined. The upshots of the pertinent flow parameter and the physical features are visualized through graphical elucidations. The effect of flow constraints on the second law analysis for the described physical phenomenon is predicted. Conclusion indicates that lowering of temperature of the nanofluid is obtained by higher values of nanoparticle volume fraction. The causes of irreversibility in a thermal system is explored in this investigation. The results indicate that nonspherical nanoparticles has higher thermal conductivity ratio as compared with spherical nanoparticles. Minimization of entropy can be attained through increasing volume fraction of titanium and silver nanoparticles. Besides, it is emphasized that entropy generation is high in case of disc‐shaped nanoparticles, followed by needle and sphere shapes.     

高温期滑模快速施工条件下的重力坝表孔长闸墩温控防裂

针对滑模快速施工条件下混凝土闸墩温控防裂问题,以官地水电站表孔闸墩为例,采用仿真计算方法预测并优化了该闸墩施工期温度和应力发展过程。结果表明,在混凝土所处环境温度较高、混凝土结构体积较大、约束大时,二级配混凝土、门槽、溢流面顶部附近的闸墩混凝土、间歇面四个区域易开裂,需加强水管冷却和表面保温措施。