Mechanical performance of ITO/Ag/ITO multilayer films deposited on glass substrate by RF and DC magnetron sputtering

ITO/Ag/ITO multilayer thin films have been a potential substitute of the conventional single-layer transparent conducting film. Nevertheless, the mechanical stability under preparation and in-service conditions still limits their applications and developments. In this paper, the influences of different structural properties as well as layer structure on both surface morphological properties and mechanical properties of the ITO/Ag/ITO multilayer thin films in comparison with commercial single-layer ITO thin film were systematically investigated. The results demonstrate that, i) the tri-layer composite has large impacts on the preferential orientation, and exhibits the decreased values of surface roughness, net lattice distortion and residual stress; ii) the increased hardness (H) and decreased Young's modulus (E) for full annealed ITO/Ag/ITO multilayer films indicate that it is possible to tailor mechanical properties of the materials by manufacturing multilayer composite; iii) the ITO/Ag/ITO multilayer thin film exhibits remarkable improvements in wear resistance with the increase of annealing temperature, which is mainly attributed to the increased ratios of H/E and H³/E².     

[可靠性建模及试验技术]重型机床液压元件油液污染退化量分布剖面可靠性建模

针对重型机床液压系统故障频繁且多与油液中的固态颗粒污染物相关的问题，进行了油液污染趋势变化试验。通过时域分析获得了油样颗粒数的有量纲和量纲一参数，通过Q-Q图和K-S检验分析有量纲参数，污染颗粒数是退化量服从正态分布的退化数据。进行了油液污染与环境相关性分析试验，采用相关系数法分析得到，颗粒数变化量与一定范围内的温度、流量、压力的相关性小；将液压元件分为管路、阀、过滤器三类，用直径5 μm左右的颗粒和直径大于15 μm的颗粒分别研究管路及阀件的堵塞和磨损情况，以过滤器过滤精度大小的颗粒研究过滤器的堵塞情况，设定ISO4406标准20/17级对应的颗粒数为阈值，利用退化量分布建立了液压元件单一故障模式的可靠性模型；利用竞争失效模型将上述模型融合为多故障模式下的可靠性模型。     

Developing high-performance laminated Cu/TiC composites through melt infiltration of Ni-doped freeze-cast preforms

Nacre-inspired laminated composites have been proven to possess a unique combination of strength and toughness. In this study, we fabricated nacre-mimetic Cu/TiC composites via unidirectional freezing of aqueous TiC slurries containing different amounts of NiO additives, followed by ice sublimation, carbothermal reduction of NiO to Ni during sintering and then gas-pressure infiltration of the Cu melt. The introduction of Ni greatly facilitated the densification of ceramic lamellae and enhanced the interfacial bonding between Cu and TiC. The resultant composites displayed outstanding damage tolerance and anisotropic electrical conductivities. Specifically, for an ～31?vol% TiC–Cu composite containing 24?wt% Ni in the ceramic lamellae (based on the TiC content), a fracture toughness (K_Jc) of 72.5?±?1.0?MPa·m^1/2, work of fracture of 53.4?±?3.5?kJ/m², bending strength of 725?±?11?MPa and longitudinal electrical conductivity of 22.7?MS/m (～60% of the Cu matrix) were achieved, which were approx. 81%, 536%, 122% and 97% higher than those of the Ni-free composite, respectively. Noticeable toughening was demonstrated to be a consequence of multiple cracking, plastic deformation and uncracked-ligament bridging of the metal layers, as well as crack deflection and blunting. On the other hand, significant strengthening resulted from tailoring the microstructures in the ceramic layers and at the Cu/TiC interface as a result of Ni doping. We believe that the facile strategy adopted herein provides an effective way to solve the problems of wetting and bonding related to metal infiltration and can be readily extended to the preparation of other nacre-inspired metal?ceramic composites.     

A review on spindle thermal error compensation in machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.     

Pressureless ultrafast sintering of near-net-shaped superhard isotropic B4C/rGO composites with Ti-Al additives

Superhard composites of B₄C reinforced with randomly-oriented reduced graphene oxide (rGO) nanoplatelets are manufactured by a near-net-shape fabrication route based on three successive steps. Firstly, aqueous colloidal processing is used for the environmentally-friendly preparation of a semi-concentrated multi-component slurry (B₄C as main component, Ti-Al as sintering additive, and rGO as toughening reinforcement), whose suitability for wet shaping is demonstrated by rheological measurements. Secondly, slip casting is used to produce robust green parts with shapes on demand and microstructures free of macro- and micro-defects. And thirdly, pressureless spark-plasma sintering (PSPS) is used for the ultrafast and energy-efficient densification of the green parts with shape retention. Measurements of shrinkage and hardness, as well as the microstructural observations, are used to identify suitable PSPS temperatures leading to obtaining isotropic B₄C/rGO composites that are superhard and almost twice as tough as the monolithic B₄C ceramics.     

One-step synthesis of CuCo2O4-Sm0.2Ce0.8O1.9 nanofibers as high performance composite cathodes of intermediate-temperature solid oxide fuel cells

One-dimensional nanostructured CuCo₂O₄-Sm_0.2Ce_0.8O_1.9 (SDC) nanofibers are prepared by the electrospinning method and one step sintering as a cathode with low polarization resistance for intermediate temperature solid oxide fuel cells (IT-SOFC). The CuCo₂O₄-SDC nanofibers cathodes form a porous network structure and have large triple-phase boundaries. Correspondingly, the electrochemical performance of the CuCo₂O₄-SDC nanofibers composite cathodes shows significantly improve, achieving the polarization resistance of 0.061 Ω cm² and the maximum power densities of 976 mW·cm⁻² at 750 °C. Thus, these results suggest that CuCo₂O₄-SDC nanofiber could be a highly active cathode material for IT-SOFCs.     

Thermal performance analysis of fin-and-tube heat exchanger circuit in supercritical hydrogen refrigeration cycle system

A circuit arrangement model for air-to-refrigerant fin-and-tube heat exchanger with supercritical hydrogen as the refrigerant is developed. The mass, momentum and energy balance equations in the circuit arrangement model are solved by the effectiveness-NTC method. The effects of gravity force, flow state and inhibit heat conduction on the heat transfer in the supercritical hydrogen refrigerant heat exchanger are investigated. Results show that the flow arrangement placed at a location where the fluid flows from the high place to the low one can achieve a better heat heat transfer performance. The form of counter-flow has a better heat transfer performance compared to that of parallel-flow. The heat transfer performance in the six-in-three-out arrangement is the better compared to that of three-in-three-out arrangement. Thus, the structure of the six-in-three-out with counter-flow from high to low one is recommend to achieve a better heat transfer performance in the supercritical hydrogen refrigerant heat exchanger.     

Experimental study on heat and exergy balance of a dual-fuel combined injection engine with hydrogen and gasoline

In this paper, a dual-fuel engine test rig with gasoline injected in the intake port and gasoline (or hydrogen) injected directly into the cylinder is built up; therefore, two injection models are realized. One is port fuel injection + gasoline direct injection (PFI + GDI), the other is port fuel injection + hydrogen direct injection (PFI + HDI). And the effects of two injection models on heat and exergy balance are investigated experimentally. The results show that, from the perspective of the first law of thermodynamics (heat balance), no matter what the injection mode is, the heat proportion of cooling water is the largest, the exhaust heat ratio and brake power are the second, which two are roughly equivalent, and the uncounted loss is the least. In PFI + GDI mode, the local mixture is too dense due to the increase of mixing ratio, which leads to insufficient combustion and a slight decrease of brake power ratio. However, due to the special characteristics of hydrogen, the increase of direct injection ratio improves the brake power ratio in PFI + HDI mode. Moreover, because of the short quenching distance of hydrogen, the cooling loss rises up with the increase of hydrogen ratio. The engine speed and load also have great impacts on heat distribution, but on account of the different physical and chemical properties between gasoline and hydrogen, resulting in varying degrees of impact and trends. On the basis of the second law of thermodynamics (exergy balance), it is found that no matter what injection mode is, the ratio of exergy destruction is always the highest, accounting for half of the total fuel energy, and the exhaust exergy ratio is lower than the brake power ratio. However, the proportion of exergy contained in cooling water is the smallest, which is quite different from the result of the first law of thermodynamics. The influences of several factors on engine energy balance are analyzed, and the differences and similarities between heat balance and exergy balance are compared. The two analytical methods are interrelated and complementary, and the purpose is to find a reasonable and comprehensive energy balance analysis method for internal combustion engine.     

Development of a two-component structural adhesive for bonding of metals and polymeric composites

To minimize the structure distortion and potential de-bonding in adhesive bonding of dissimilar materials (e.g., metals and polymeric composites), a two-component (2 K) low temperature cure modified adhesive consisting of 93.5 wt% commercial Henkel 5089 adhesive, 2.5 wt% N-(2-Hydroxyethyl) ethylenediamine (AEEA) and 4.0 wt% 2-ethyl-4-methylimidazole (2,4-EMI) was formulated. Experimental results showed that the use of the modified adhesive lowered the curing temperature from recommended 177 °C (for 20 min) for Henkel 5089 to 100 °C (for 20 min) or 120 °C (for 10 min) for AA6061-AA6061 joint, and 120 °C (for 20 min) or 130 °C (for 10 min) for AA6061-C_f/PA6 (Nylon 6) and C_f/PA6-C_f/PA6 joints, respectively, due to the faster curing reaction caused by the combined addition of AEEA and 2,4-EMI. It took 5, 3, and 2 days to cure the adhesive-bonded AA6061-AA6061, AA6061-C_f/PA6, and C_f/PA6-C_f/PA6 joints made with the modified adhesive and cured at ambient temperature, respectively. In addition, the modified adhesive had sound working life (5 h) at ambient temperature. The static strengths of all adhesive-bonded AA6061-AA6061, AA6061-C_f/PA6, and C_f/PA6-C_f/PA6 joints with the modified adhesive were hardly affected by thermal exposure cycle (i.e., exposure to 82 °C for 30 min). These results indicated that the modified adhesive possesses the promising characteristics for joining of similar and dissimilar materials.