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1.
Niobium carbide coating was produced by thermal-reactive diffusion technique on AISI 52100 steel in salt bath at 1 123 K, 1 173 K, and 1 223 K for 1, 2, 4, and 6 hours. The salt consisted of borax, sodium fl uoride, boron carbide, and niobium pentoxide. The presence of NbC phase on the steel surface was confi rmed by X-ray diffraction analysis. Microscopic observation showed that niobium carbide coating formed on the substrate was smooth and compact. There was a distinct and fl at interface between the coating and substrate. The micro-hardness of niobium carbide coating was 2892±145HV. The thickness of coating ranged from 1.6 μm to 14μm. The forming kinetics of niobium carbide coating was revealed. Moreover, a contour diagram derived from experimental data was graphed for correct selection of process parameters. Some mathematical equations were built for predicting the coating thickness with predetermined processing temperature and time. The results showed that these mathematical equations are very practical as well as the kinetics equation. 相似文献
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Xianchun Peng Jie Sun Huan Liu Liang Li Qikun Wang Liang Wu Wei Guo Fanping Meng Li Chen Feng Huang Jichun Ye 《半导体学报》2022,43(2):79-85
AIN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing (HTTA) on the structural,optical properties as well as surface stoichiometry were comprehensively investigated.The significant narrowing of the (0002) diffraction peak to as low as 68 arcsec of AIN after HTTA implies a reduction of tilt component inside the AIN thin films,and consequently much-reduced dislocation densities.This is also supported by the appearance of E2(high) Raman peak and better Al-N stoichiometry after HTTA.Furthermore,the in-creased absorption edge after HTTA suggests a reduction of point defects acting as the absorption centers.It is concluded that HTTA is a universal post-treatment technique in improving the crystalline quality of sputtered AIN regardless of sapphire orienta-tion. 相似文献
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利用大型有限元分析软件ANSYS,结合井塔的实际框筒结构工程进行建模分析,通过矿井井塔在水平荷载作用下的具体性能表现,得出梁柱刚度比对剪力滞后效应有较大的影响。再对梁柱刚度比对剪力滞后效应的现象进行分析,将计算结果与仿真分析的结果进行比较,提出改进方法。 相似文献
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近几年,国家计委和国家旅游局为支持中西部地区旅游业发展进行专项投资,重点支持旅游基础设施建设和旅游开发中的自然生态环境保护.由于中西部生态旅游资源位于我国江河上游、旅游城市幅射区、少数民族地区和经济贫困区,具有旅游资源丰富、地理环境封闭、生态保护极为重要和社会经济急待发展等特点.如何积极稳妥开发,真正达到既发展经济又改善生态、保护环境之目的,需要做大量调查研究工作. 相似文献
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声光调QCO_2激光器的理论计算和实验研究 总被引:3,自引:0,他引:3
采用谐振腔内插入声光调制器的方法进行了小型CO2激光器的调Q实验,并根据影响激光器输出的诸多因素,利用调Q脉冲激光器速率方程对该激光器输出的主要技术参数进行了理论计算,据此提出了声光调QCO2激光器优化设计的途径和方法。设计制成的声光调QCO2激光器获得峰值功率超过4000 W,激光脉冲宽度为180 ns,与理论计算基本一致。激光器脉冲重复频率调节范围1 Hz~100 kHz。理论分析和实验结果均证明,调Q晶体中超声场的渡越时间并不会影响输出激光的脉冲宽度,因此无需在腔内插入光学透镜进行光束直径的压缩变换;渡越时间的影响只是体现在延长了激光脉冲的建立时间上;激光器的最佳工作频率在1 kHz左右,这与CO2分子0001能级大约1 ms的辐射寿命相匹配,当频率超过1 kHz时,激光的脉冲宽度随着频率的增加而开始加宽。激光器通过光栅选线的设计方式实现了9.2~10.8μm的全波段波长调谐,测得激光输出谱线超过60条。 相似文献
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复合微合金化对SiMn3型贝氏体钢力学性能的影响 总被引:1,自引:1,他引:0
研究了用少量Mo,微量V,B,Re进行复合微合金化,对低碳SiMn3型贝氏体高强钢力学性能的影响。结果表明,复合微合金化可显著提高其空冷状态的韧性,明显改善低温韧性,并可显著提高回火抗力和高温回火后的强度。 相似文献
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In this paper, we describe the facile and effective preparation of a series of cobalt-doped Fe3O4 nanocatalysts via chemical coprecipitation in an aqueous solution. The catalyst allowed the hydrogenation of chloronitrobenzenes to chloroanilines (CAs) to proceed at low temperatures in absolute water and at atmospheric pressure, resulting in approximately 100% yield and selectivity. Several factors that influence the yield of CAs were investigated. The results showed that the suitable dosage of the catalyst was ~10 mol.% of the substrate, and the optimal reaction time, reaction temperature, and reaction pressure were 20 min, 80 °C, and atmospheric pressure, respectively. Under the optimal reaction conditions, the CA yield was as high as 98.4%, and the nitro reduction rate reached 100%, which indicates the excellent selectivity of the homemade catalyst. This process also overcomes the environmental pollution harms associated with the traditional process. 相似文献
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The spherulitic structure and morphology of poly(3‐hydroxybutyrate) (PHB) thin films crystallized from the melt were observed with a polarizing optical microscope. Depending on the thickness of the PHB thin film and crystallization temperature, banded and nonbanded spherulites could form. Reducing the thin‐film thickness and crystallization temperature was favorable for the formation of the banded structure. The morphology transition from banded spherulites to nonbanded spherulites was related to the ratio of the crystallization rate to the diffusion rate. The formation mechanism of the banded structure was examined with the discontinuity growth theory. A depletion zone was considered to appear periodically at the crystal growth front because of the slow diffusion rate, and this may have resulted in the banded spherulites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献