Reducing the self-healing temperature of Ti2AlC MAX phase coating by substituting Al with Sn

In an effort to overcome the property degradation of Ti₂AlC MAX phase coating used in harsh environments, we fabricated a solid solution Ti₂(Al_0.6Sn_0.4)C coating with amount of Ti₅Sn₃ (20 wt.%) by a combined technique composing of magnetron sputtering and post-heat treatment. The cracks induced by Vickers indentation on coating surface were self-healed at 700 ℃, which is the lowest self-healing temperature among the Al-based MAX phase coatings till now. The structural evolution and kinetic diffusion revealed that the formation of SnO₂ is the key factor to achieve the crack self-healing at such a low temperature for Al-based MAX phase coatings. Additionally, the self-healed Ti₂(Al_0.6Sn_0.4)C coating exhibited better oxidation resistance compared to the unhealed one at 800 ℃. The results provide a novel and facile strategy to develop the protective MAX phase coatings with high performance at high temperature by partially substituting Al with Sn.     

基于Fuzzy-AHP农村变电站选址新的方法

针对农村变电站选址涉及的因素多,决策难的问题,提出应用模糊层次分析法对变电站选址进行科学评价,同时可以避免层次分析法的判断矩阵不一致性的问题。通过建立递阶层次结构图,构建模糊一致性矩阵,对被选的各个方案进行综合考虑得到最佳的变电站选址。通过对110kV某农村变电站的选址进行科学评价,选出了最优的地址,证明了此方法的有效性和正确性。     

Solar energy absorption efficiency of an ellipsoidal receiver-reactor with specularly reflecting walls

An ellipsoidal cavity-receiver with specularly reflecting inner walls, in which the reactor component is positioned at one focal point and the aperture at the other, may be useful in solar applications. Most of the incident radiation from a solar concentrator should reach the reactor directly or after one reflection from the cavity walls. Because the source (aperture) and sink (reactor) have finite areas, the ellipsoidal reflector no longer conveys all of the entering radiation into the reactor; some radiation entering the cavity does not reach the target after one reflection and is eventually absorbed by the cavity walls after multiple reflections or escapes through the aperture. We have examined the conditions for which this radiation loss becomes significant and have estimated the effects on the energy-collection efficiency of the system.     

Hyperpolarization of gas evolving electrodes—I. Aqueous electrolysis

Electrodes evolving oxygen and hydrogen in aqueous media were rotated at up to several thousand rpm in order to shear away gas bubbles and allow measurement of a voltage component, called hyperpolarization, due to masking of the electrode by gas bubbles. The difference in overpotential between rotated and non-rotated electrodes increased as a function of rotation rate at low rpm and then reached a plateau between one and three thousand rpm. Upon further rotation, the voltage difference increased again. The plateau was the hyperpolarization in the measurement, less then five mV at 0.1 A cm⁻², that corresponds to an effective surface coverage of less than 10%. The increase beyond the plateau marked the relief of the supersaturation of the electrolyte with product gas near the electrode.     

既有建筑节能改造障碍识别及对策研究

分析既有建筑改造过程中在技术、管理和政策方面存在的问题,为我国开展既有建筑节能改造提供了完善的技术标准体系,建立节能运行管理制度,制定可行的供热体制改革方案和探索多渠道的融资模式。     

黑龙江省清洁发展机制项目潜力分析

能源与环境问题已成为当今世界发展中遇到的一个十分重要的问题。本文将清洁发展机制（Clean Development Mechanism,简称CDM）与黑龙江省的各类资源特点相结合,从新能源和可再生能源,节能及能效提高,燃料替代以及甲烷回收利用等几个方面分析了该省可开发CDM项目的潜力,并得到如下结论：黑龙江省在新能源和可再生能源领域拥有巨大潜力,节能及能效提高领域应得到重视,做好燃料替代领域的相关研究和积极做好甲烷的回收和利用。     

Tribological behaviour of duplex treated Ti–6Al–4V: combining nitrogen PSII with a DLC coating

The chemical structure and tribological behaviour of Ti–6Al–4V plasma source ion implanted with nitrogen then DLC-coated in an acetylene plus hydrogen-glow discharge (bias voltage −10 to −30 kV) were investigated. The as-modified samples have a TiN/H:DLC multilayer architecture (coating resistivity 1.6×10⁹ to 2.4×10¹¹ Ω/cm) and exhibit higher hardness, especially at low loads or plastic penetrations in the order of deposition bias voltage −10, −20 and −30 kV. At a lower contact load (1 N) and higher sliding speed (0.05 m/s), frictional properties in most cases improved, as did wear properties. At a higher contact load (5 N) and lower sliding speed (0.04 m/s), friction showed almost no improvement, and wear properties deteriorated. When the material of the counterbody was then changed from AISI 52100 to Ti–6Al–4V modified as the disc (contact load 5 N unchanged, sliding speed decreased), the friction coefficient decreased (but showed no improvement compared with the unmodified sample), while wear properties deteriorated further, and wear was changed from just the disc to both disc and ball, abrasive and adhesive dominated. Transfer films, mainly made up of wear debris transferred from the disc wear surfaces, were formed on the wear scars of the counterbodies. The deterioration of wear properties of the modified samples at the higher contact load is considered to be caused by the “thin ice” effect.     

一种改进的亚像素算法

传统的灰度重心法是一种用于对称目标的亚像素定位技术,但其抗噪声性能较差。针对这一问题,本文提出一种改进算法,通过将目标区域划分成内部像素区域和边缘像素区域两部分,并对内部像素灰度进行均值化,从而有效抑制内部像素噪声。同时,利用误差理论对改进算法的不确定性进行分析。最后,通过仿真实验验证了改进算法的正确性,并表明改进算法有更好的噪声抑制性能。     

2.79μm Cr,Er:YSGG固体激光器发展现状

2.79 μm激光器在医疗、非线性光学、军事等方面具有重要的应用价值,介绍了Cr,Er:YSGG晶体的物理、化学及激光特性,重点分析了2.79 μm Cr,Er:YSGG固体激光器的发展现状,以及存在的主要问题,阐述了其可能的发展前景。Cr,Er:YSGG激光器可以使用脉冲闪光灯或激光二极管泵浦,并使用电光、声光、被动调Q等方法调Q输出高峰值功率2.79 μm激光,二极管泵浦时激光器可以连续输出。Cr,Er:YSGG晶体的热导率低,泵浦过程中热透镜效应严重,因此,激光器不适合高重复频率工作,输出功率受到一定的限制。实现稳定可靠的2.79 μm调Q巨脉冲激光输出需要解决的关键技术是获得对2.79 μm激光吸收系数小,破坏阈值高的Q开关材料。