稀土应用开发的新趋向

本文对有可能实现商品化的稀土应用开发新领域：稀土硫化物颜料、柴油发动机用催化剂、铝电解用非自耗涂层阳极、固体氧化物燃料电池、含钪Ａｌ－Ｌｉ合金等的现状和前景做了扼要介绍。小批量、多品种、高效益是稀土作为独立行业的成功之路。     

膨润土在涂料中的应用性能研究

膨润土在涂料工业中有非常广泛的应用,如可作为涂料的增稠剂、悬浮防沉降剂、辅助粘结剂等。本文对膨润土在其中的应用机理以及对涂料性能的影响作了探讨,并在此基础上分析了膨润土在涂料中应用的优缺点。     

土层锚杆-土钉复合支护的作用机理及影响因素

土层锚杆和土钉联合使用的支护措施在边坡工程中的应用越来越广，而在实际工程中，往往混淆土钉和土层锚杆的概念，对其作用机理的认识也不十分清楚。在明确土钉和土层锚杆概念的基础上，分析了其作用机理，讨论了影响土层锚杆和土钉复合支护边坡稳定的重要因素。     

液中脉冲放电沉积ZrC陶瓷涂层的强化工艺及涂层性能的研究

采用特殊设计的专用脉冲电源液中放电表面强化设备,以硬质金属Zr为电极、45号钢为基体,进行了放电沉积ZrC陶瓷涂层的强化试验.研究了电参数、放电时间与涂层性能之间的关系,同时还研究了强化层形貌、物相结构及强化层的耐磨损性能.试验结果表明：强化层主要成分是ZrC;单个脉冲能量越大,形成的强化层就越厚;当放电时间超过25min时,强化层厚度基本不再增加;强化层具有良好的抗磨损性能.     

特长活塞杆镀铬层不均匀问题分析及改进措施

活塞杆镀层不均严重影响活塞杆的使用寿命 ,镀层不均问题在特长活塞杆中表现尤为突出 ,通过对特长活塞杆镀铬分析 ,指出镀层不均的原因 ,并提出改进措施。介绍了特长活塞杆的井式槽电镀与卧式槽电镀方法 ,给出其工艺参数     

Slot die coating window for a uniform fuel cell ink dispersion

The continuous roll-to-roll slot die coating technique has shown great potential for fuel cell electrode fabrication. It is essential to determine the particulate coating window to obtain a defect-free film of uniform thickness and uniform particle dispersion. For this dual-purpose, an additional upper operating limit has been proposed via a “flow field analysis scheme” that combines analysis and simulation. In this analysis, the fundamentals of flow pattern transition (Poiseuille–Couette–bubbly flow) behind coating limits are clarified. The Couette flow is advantageous for uniform shear rate and dispersion. Furthermore, phase-field simulations systematically investigate the effect of fluid and geometrical parameters and quantitatively present the flow limit with explicit expression. Results reveal that the slope of the upper limit is inversely correlated with shear-thinning index n while proportional to the coating gap H. Combining the bubble entrainment boundary, lower n and H are favorable for a larger particulate coating window.     

Fabrication of highly bioactive zirconia ceramics via grain-boundary activation for dental implants

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics with outstanding mechanical properties and aesthetic origins are expected to be used in dental implant applications. However, tetragonal zirconia ceramics are not bioactive, which affect the osseointegration and reliability as dental implant materials. Herein, in this study, Y-TZP ceramics were modified by grain-boundary activation via coating a bioactive glass (BG) sol with different content on the crystal surfaces of zirconia powder and followed by being gelled, dried, granulated, low-temperature treated, molded and sintered at 1450°C for 3 h in air. The effects of BG content on the morphology, phase compositions, mechanical properties, in vitro mineralization ability and cell biological properties of the bioactivity modified Y-TZP ceramics were evaluated. The BG additive did not affect the tetragonal–monoclinic phase transformation of ZrO₂. However, the addition of BG decreased the flexural strength of the modified Y-TZP ceramics compared to that of Y-TZP. The in vitro mineralization results showed that a homogeneous apatite layer was produced on the surface of the Y-TZP ceramics when they were immersed in the simulated body fluid for 21 days. The cell response results indicated that the bioactive surface modification of Y-TZP ceramics could promote cell adhesion, propagation and osteogenic differentiation performance. Thus, our research results suggest that the highly bioactive Y-TZP ceramics could be a potential candidate for dental implant material.     

Recycling MoSi2 heating elements for preparing oxidation resistant multilayered coatings

Spent MoSi₂ heating elements were used to fabricate MoSi₂, ZrB₂/MoSi₂ and MoSi₂-ZrB₂/MoSi₂ oxidation resistant coatings via a two-step process of slurry painting and spark plasma sintering. Cracks appeared in simple MoSi₂ and ZrB₂/MoSi₂ coatings, whilst MoSi₂-ZrB₂/MoSi₂ coating was crack-free as CTE mismatch was reduced. Mo₅Si₃ and MoB diffusion layers formed under MoSi₂-ZrB₂ transition layer in MoSi₂-ZrB₂/MoSi₂ coating, revealing good metallurgical combination between the substrate and coating. On one side the silica layers covering MoSi₂ and ZrB₂/MoSi₂ coatings displayed diffused cracks after oxidation at 1773 K for 100 h, on the other side it was dense and continuous for MoSi₂-ZrB₂/MoSi₂ coating, showing low oxidation rate constant at 1773 K. Furthermore, MoSi₂-ZrB₂ transition layer in MoSi₂-ZrB₂/MoSi₂ coating possessed good short-term oxidation protective properties at 1873 and 1973 K since the formation of ZrSiO₄ improved the stability of Si-O-Zr composite oxide scale and diminished the oxygen permeability, therefore demonstrating good high-temperature oxidation resistance.     

Influences of SiC infiltration and coating on compressive mechanical behaviours of 2D C/SiC composites up to 1600 °C at wide-ranging strain rates

The influences of the SiC infiltration and coating on the compressive mechanical behaviours of 2D C/SiC composites were determined up to 1600 °C at 0.001 and 1000/s strain rates in argon and air. In addition, the failure mechanisms responsible for the compressive mechanical behaviours were elucidated through in-situ observation and micro-analysis-based methods. The 2D C/SiC composite compressive strength was highly sensitive to temperature, loading rate, and oxidation, and was enhanced by the change in the thermal residual stress and decreased by oxidation. In argon, because of the extra infiltrated SiC matrix, SiC treated 2D C/SiC specimens exhibited higher compressive strengths and lower strain rate sensitivity factors than SiC untreated 2D C/SiC specimens. The SiC coating effectively improved the oxidation resistance of the 2D C/SiC composites in air, regardless of the temperature, strain rate, and oxidative damage-which depends on SiC coating, strain rate, and temperature.     

Fabrication and investigation of Ca/Tb co-doped HfO2 infrared coatings

In this study, Ca/Tb co-doped HfO₂ coatings were prepared by atmosphere plasma spraying. The chemical composition, morphology and infrared property of the coatings were characterized. The coatings possessed a layer-stacked morphology. When the Ca/Tb doping atomic ratio was 1:1, the phase of the coatings gradually changed from monoclinic to cubic with increasing the doping mass. The CTH2 coating had the highest emissivity which was 0.820 in 0.75–6.5 µm and 0.902 in 6.5–15 µm respectively. The enhancement in short band was mainly due to the introduction of Ca²⁺ and Tb³⁺ ions that generated oxygen vacancies in the lattice forming impurity levels within the forbidden band, moreover, the transfer of Tb³⁺ to Tb⁴⁺ increased the concentration of free electrons, which promoted the absorption of free carriers. The increase in long band attributed to the lattice distortion that reduced the lattice symmetry and strengthened the absorption of lattice polar vibration.