Charge-discharge process of MnO2 supercapacitor

Mechanochemical synthesis of α-MnO2 was carried out with KMnO4 and Mn（CH3COO）2 in 1：1 mole ratio. The electrochemical performance of MnO2 electrode was investigated by cyclic voltammograms and alternating current impedance. The charge-discharge process of MnO2 supercapacitor in 6 mol/L KOH was studied within 1.2 V at 200 mA/g, suggesting that it displays double-layer capacibility in low potential scope and pseudo-capacitance properties in high potential scope. It is found that Mn3O4, an electrochemical inert, mainly forms in the initial 40 charge-discharge cycles. During cycling, the pseudo-capacitance properties disappear and the discharge curves are close to ideal ones, indicating double-layer capability. The maximum capacitance of MnO2 electrode is as high as 416 F/g, and retains 240 F/g after 200 cycles. The equivalent series resistance increases from 17 to 41Ω.     

铸造Al-7Si-2.5Cu-0.5Mg合金的固溶处理温度研究

通过相图计算、示差热(DSC)分析,结合显微组织观察方法对Al-7Si-2.5Cu-0.5Mg合金的固溶处理温度进行了研究。结果表明:非平衡凝固Al-7Si-2.5Cu-0.5Mg合金在505℃左右发生共晶组织转变,而平衡凝固合金在520℃附近发生共晶转变;500℃、3h的初始固溶处理可使铸态合金中的低熔点共晶物完全溶入铝基体,此时合金的熔点为540℃。     

软开关逆变电阻点焊机主电路参数的优化及实验分析

设计了软开关逆变式电阻点焊主电路,采用带有饱和电感的全桥逆变主电路结构,利用饱和电感的特殊作用,在退出饱和时,呈现出很大的感抗,阻止了电流的进一步流动,使电流保持在零状态,为滞后臂开关管的导通与关断创造了零电流开关的条件.分析了逆变频率在软开关逆变点焊机中的作用.通过理论计算和Pspice电路仿真波形分析等方法,对主电路的主要参数进行了优化.经实验测试分析,设计的主电路参数合理,焊机性能达到设计要求.     

凝固模拟热物性参数数据库系统的研究与开发

针对凝固模拟中热物性参数数据量大、种类多,数据查找困难、更新不便的问题,研究开发了一套热物性参数数据库系统.系统包括参数录入、数据更新、数据查询和液固相线温度计算模块,实现了对参数数据的集中有效管理.     

Mg-Cu-Y块体金属玻璃的塑性变形特性

通过对Mg-Cu-Y块体金属玻璃在深过冷液体区间塑性变形特性的研究，探讨了影响其塑性变形的因素及其影响规律。结果表明，加载温度和时间均对其塑性变形有明显的影响，在深过冷液体区间，要达到合适的变形量，加载温度和时间必须适中；Mg-Cu-Y块体金属玻璃在压缩条件下能够发生流变，较好地复制模具表面的显微形貌。同时，在加载条件下，Mg-Cu-Y块体金属玻璃更容易发生晶化。     

高速电弧喷涂FeAlCr/Ni包Cr3C2涂层高温性能

用高速电弧喷涂技术制备了FeAlCr/Ni包Cr3C2涂层,并对涂层的耐高温冲蚀性能、高温腐蚀性能和高温磨损性能进行了研究.结果表明,与基体比较涂层具有良好的耐高温冲蚀性能,并随温度的升高和冲击角度增大,耐冲蚀性能提高;良好的高温抗腐蚀性能,随温度升高,腐蚀率略有上升;优异的常温耐磨损性能,超过550℃的耐磨损性能高.     

铸造Al-Si-Cu-Mg合金分级热处理工艺及对力学性能的影响

通过示差热分析及对Al-7.0Si-2.5Cu-0.5Mg合金热处理工艺参数的研究发现为了防止合金中低熔点共晶物在固溶处理过程中熔化,同时提高Q、Al2Cu等相在合金中的溶解度,应选择分级固溶的方式进行.一级固溶在500 ℃固溶3 h后,可使合金中低熔点共晶物完全溶解,此时合金的熔点为540 ℃;综合各因素,该合金较好的热处理工艺为500 ℃×3 h、530 ℃×14 h;175 ℃×6 h,此时,合金的力学性能可以达到σb≥385 MPa,δ5≥5.0%.     

热浸镀铝钢扩散层的AlFe3C0.5相

采用740℃热浸镀铝方法,在20碳钢表面制备热浸镀铝层。镀铝层经850℃扩散处理4 h后,采用SEM和XRD确定扩散层的相组成,采用TEM研究组成相的晶体学取向关系。分析AlFe3C0.5相的形成原因。结果表明：扩散层与基体之间存在Fe3Al、FeAl和点阵常数为0.377 nm的针叶状AlFe3C0.5相;针状AlFe3C0.5与Fe3Al相之间存在的晶体学取向关系是（220）Fe3Al//（1^-11）AlFe 3C0.5、[11^-0]Fe3Al//[1^-23^-]AlFe 3 C0.5。     

Mg-Cu-(Al-Si)-Y大块非晶合金的制备及晶化研究

采用Al-Si合金部分替代Mg65Cu25Y10大块非晶合金中的Cu元素,形成Mg-Cu-(Al-Si)-Y非晶合金。通过铜模浇注法制备Mg-Cu-(Al-Si)-Y大块非晶合金,发现Al-Si合金的添加对非晶合金的玻璃形成能力没有明显改善,但改善了非晶合金的室温塑性。在晶化温度附近低于晶化温度的条件下对铜辊旋淬法制备的Mg-Cu-(Al-Si)-Y非晶条带进行了处理。结果表明,Mg-Cu-(Al-Si)-Y非晶合金随加热温度的提高和处理的时间的延长晶化程度也随之提高,同时加热晶化增大了合金的室温脆性。     

Performance of positive and negative electrodes in amorphous manganese oxide supercapacitor

Using potassium permanganate and acetic manganese as the reactants, amorphous manganese oxide was prepared with mechanochemical method. XRD was used for microstructure characterization, while cyclic voltammetry and constant current charge-discharge were used for electrochemical performance testing. The positive electrode （PE） and negative electrode （NE） were investigated respectively in amorphous manganese oxide supercapacitor, aiming to find their different performances in charging-discharging. The results show that the crystalline structure is destroyed in both the PE and NE material during charge-discharge process. Thereinto, the NE suffers a bit more seriously. When cycling, the PE potential scope diminishes while the NE potential scope enlarges. The increased inner resistance makes the NE curves almost bended to be a right angle, but not the PE curves. The cell＇s equivalent series resistance （ESR） is more dependent on the NE, and the capacitance is mainly determined by the rapid descent of the NE potential range. The capacitances of the NE are highly rate-dependent, decreasing from 121.3 to 53.1 F/g, by 56.2%, over the range of 5-25 mV/s. However, the PE appears to be weakly dependent and its capacitance is only dropped by 22.1%.