Effect of Co,Pd and Pt ultra-thin films on the Ni-silicide formation: investigating the sandwich configuration

The effect of Co, Pd and Pt ultrathin films on the kinetics of the formation of Ni-silicide by reactive diffusion is investigated. 50 nm Ni/1 nm X/ 50 nm Ni (X?=?Co, Pd, Pt) deposited on Si(100) substrates are studied using in-situ and ex-situ measurements by X-ray diffraction (XRD). The presence of Co, Pd or Pt thin films in between the Ni layers delays the formation of the metal rich phase compared to the pure Ni/Si system and thus these films act as diffusion barriers. A simultaneous silicide formation (δ-Ni₂Si and NiSi phases) different from the classic sequential formation is found during the consumption of the top Ni layer for which Ni has to diffuse through the barrier. A model for the simultaneous growth in the presence of a barrier is developed, and simulation of the kinetics measured by XRD is used to determine the permeability of the different barriers. Atom probe tomography (APT) of the Ni/Pd/Ni system shows that the Pd layer is located between the Ni top layer and δ-Ni₂Si during the silicide growth, in accordance with a silicide formation controlled by Ni diffusion through the Pd layer. The effect of the barrier on the silicide formation and properties is discussed.

     

High strain rate compressive response of the Cf/SiC composite

Carbon fiber reinforced ceramic owns the properties of lightweight, high fracture toughness, excellent shock resistance, and thus overcomes ceramic's brittleness. The researches on the advanced structure of astronautics, marine have exclusively evaluated the quasi-static mechanical response of carbon fiber reinforced ceramics, while few investigations are available in the open literature regarding elastodynamics. This paper reports the dynamic compressive responses of a carbon fiber reinforced silicon carbide (C_f/SiC) composite (CFCMC) tested by the material test system 801 machine (MTS) and the split Hopkinson pressure bar (SHPB). These tests were to determine the rate dependent compression response and high strain rate failure mechanism of the C_f/SiC composite in in-plane and out-plane directions. The in-plane compressive strain rates are from 0.001 to 2200?s^?1, and that of the out-plane direction are from 0.001 to 2400?s^?1. The compressive stress-strain curves show the C_f/SiC composite has a property of strain rate sensitivity in both directions while under high strain rate loadings. Its compressive stiffness, compressive stress, and corresponding strain are also strain rate sensitive. The compressive damage morphologies after high strain rate impacting show different failure modes for each loading direction. This study provides knowledge about elastodynamics of fiber-reinforced ceramics and extends their design criterion with a reliable evaluation while applying in the scenario of loading high strain rate.     

新景矿3号煤层渗透率对有效应力敏感性实验分析

利用KDZS-Ⅱ型煤体瓦斯瞬时解吸及渗流特性测试仪在0.31、0.61 MPa气体压力条件下,开展了新景矿3号煤层渗透率对有效应力敏感性实验分析。结果表明:新景矿3号煤层渗透率对有效应力具有极强的敏感性,煤层渗透率随有效应力增加而降低,二者之间具有良好的负指数幂函数关系;相同气体压力和有效应力下各煤样试件的渗透率变化不同且分异现象显著;煤样试件的渗透率大小与孔隙度、裂隙方向密切相关,煤样试件裂隙方向平行于轴线方向、孔隙度大时,煤样试件的渗透率相对较大;煤样试件的裂隙方向垂直于轴线方向、孔隙度较小时,煤样试件的渗透率相对较小。     

架空-海缆混合高压输电线路自适应重合闸方案的研究

提出了利用比率制动差动原理判别架空-海缆混合高压输电线路的故障区段判别方法,以应用于自适应重合闸。在架空线路和海缆连接处增设电流互感器,并通过通信通道将二次电流传输至混合线路两端的保护。当混合线路发生故障,保护动作后,利用线路两端电流互感器和增设的电流互感器二次电流分别构成比率制动差动判据,进行故障区段判别。若故障发生在架空线段,开放重合闸;若故障发生在电缆段,则闭锁重合闸。PSCAD/EMTDC仿真结果表明,该故障区段识别方法能够准确可靠地判别故障区段,无死区、不受故障位置和过渡电阻的影响,可提高自动重合闸的重合成功率。     

广元市江口小学滑坡稳定性研究

“江口小学滑坡”在“5．12”地震期间发生变形,影响了学校综合楼的稳定性,给学校的正常教学秩序造成了安全隐患。文章通过野外调研和搜集现有资料,系统分析了该滑坡的地质环境和坡体特征。根据坡体的机构及形态特征研究了滑坡的形成机制,判定滑坡为牵引式土质滑坡,破坏模式为蠕滑拉裂。通过室内土工试验及反演分析合理确定滑带土的抗剪强度指标,并运用瑞典条分法、传递系数法进行滑坡各工况的稳定性验算,得出稳定性计算成果,最后通过各影响因子的敏感性分析,综合确定滑坡的稳定性,为后期工程治理提供设计依据。     

稀乙烯制乙苯在节能环保领域的技术及发展方向

介绍了稀乙烯制乙苯工艺中四种现有的节能环保技术,针对其技术现状,进行了技术分析,提出了八项在节能环保领域今后可以探索的课题,使稀乙烯制乙苯工艺具有更好的发展前景。     

大底盘多塔楼结构抗震性能研究

大底盘多塔楼结构是底部相连上部分开的一种复杂结构形式。本工程由于立面收进要求采用竖向搭接转换块,目前对竖向搭接转换的结构研究不够充分全面。针对竖向搭接转换的结构形式,进行模拟地震整体结构振动台试验,并利用MIDAS软件进行整体结构分析。结果表明,采取搭接块的结构竖向刚度均匀,没有形成软弱层;大底盘与塔楼交界处的剪力突变,应采取适当的加强;裙房底部柱子应采取适当加强措施。     

一种应用于RFID标签的新型功率放大器设计

A novel matching method between the power amplifier (PA) and antenna of an active or semi-active RFID tag is presented. A PCB dipole antenna is used as the resonance inductor of a differential power amplifier. The total PA chip area is reduced greatly to only 240 × 70 μm² in a 0.18 μm CMOS process due to saving two on-chip integrated inductors. Operating in class AB with a 1.8 V supply voltage and 2.45 GHz input signal, the PA shows a measured output power of 8 dBm at the 1 dB compression point.     

椰壳纤维的热解动力学分析

将椰壳纤维在NaOH、KOH、ZnCl2和(NH4)2HPO4溶液中进行处理,并采用耐驰STA449C-Jupiter同步热分析仪研究了椰壳纤维在不同升温速率时的热分解反应.通过积分法对椰壳纤维的热解失重曲线进行动力学分析发现,升温速率为5K/min时热解的主反应阶段的活化能最低,低温段和高温段的分别为30.52kJ/mol、56.44kJ/mol,对椰壳纤维的热解反应最有利.采用5%的碱溶液浸泡处理可以有效除去椰壳纤维中的半纤维素、果胶等易降解的成分,改变热解反应过程,从而更有利于制备活性炭纤维.     

Effects of different potassium salts on the formation of mullite as the only crystal phase in kaolinite

The phase transition in kaolinite from 1050 °C to 1600 °C without and with different potassium salts (KF, KNO₃ and K₂SO₄) as mineralizers and the changes of the composition and morphologies of mullite formed in kaolinite have been investigated. The adding of enough potassium has been found to inhibit the formation of cristobalite in kaolinite. The fluorine is found to be beneficial to increase the reaction activity of aluminium from metakaolinite and so the potassium fluoride has promoted more pseudotetragonal mullite formed at 1100 °C than the other two mineralizers. The influence of potassium salts on the composition and microstructure of mullite formed from kaolinite with increasing the heating temperature has been scrutinized in detail. The formation condition for the only crystal phase of mullite from kaolinite has been shown.