催化剂中铁和镍的测定

研究了用微波等离子体炬原子发射光谱法(MPT-AES)测定催化剂中铁、镍质量分数的方法,样品用超声物化法引入。详细考察了测定铁和镍的实验条件,进行了系统优化,并考察了共存离子的干扰情况。催化剂使用压力容弹处理。测定时,使用标准加入法来消除基体影响,效果较好。测定铁和镍质量浓度检出限分别为28.78μg/L和47.15μg/L,方法的精密度(RSD)均≤2.5%,线性范围分别为0.1～100g/L和1～100g/L,加标回收率在95.1%～105.8%之间。实验结果表明,使用MPT-AES法测定催化剂中的铁、镍含量,快速、准确,操作简便,自动化程度高,具有广泛的应用前景。     

GTA焊枪套筒直径对保护效果影响的数值分析

GTA（Gas Tungsten Arc）焊接时保护气流流场的数值分析对于焊枪的设计提供了新的思路。针对不同直径的套筒建立了三维稳态的对称模型,研究了套筒的保护气体的流体流动,计算了速度场的分布情况,控制方程的求解采用以SAMPLE算法为基础编写的通用热流计算软件——PHOENICS。通过计算得到不同直径套筒下的流体速度轮廓、速度矢量和保护气在试板表面速度分布的分析,得出了套筒直径设计最佳取值范围并和通常的实践结果吻合良好。     

Effects of inter-electrode insertion on the performance and thermal flow fields of a hollow-electrode plasma torch

The effects of inter-electrode insertion on the performance of a hollow-electrode plasma torch have been investigated by numerical analysis. Simulation results revealed that when inter-electrodes are inserted, the arc voltages and plasma powers increase due to the increase in the arc length. In addition,it was predicted that thermal efficiency can be improved with the increase in plasma power by injecting plasma gases through the gaps between inter-electrodes. These unique effects of inter-electrode insertion are a result of the plasma temperatures adjusting themselves to increase arc voltages when the arc column is contracted radially by increasing gas-flow rate or decreasing inter-electrode diameter.     

Wear behaviour at 600°C of surface engineered low-alloy steel containing TiC particles

The work aimed to develop surfaces that could resist wear at high temperatures, thus achieving a prolonged component life. Surface modification of a low-alloy steel by incorporating TiC particles has been undertaken by melting the surface using a tungsten inert gas torch. The dry sliding wear behaviour at 600°C of the original and modified surfaces was compared. Microscopic examination of both surfaces showed glazed layers across the wear tracks, with differing amounts of oxide and homogeneity. Extensive wear occurred on the steel surface, which showed deformation of the wear scar tracks and a steadily increased friction coefficient. The TiC addition reduced the wear loss, coinciding with a glazed layer 33% thinner than that on the low-alloy steel sample.     

喷射清洗设备中喷管的设计与研究

首先介绍了干冰清洗和高压水射流两种工业物理清洗的原理及机理;其次,论述了喷枪的核心喷管的设计理论;接着,编制了喷管型线设计计算程序,并用该程序给出了一个算例结果;再次,用FLUENT软件对上述算例进行了数值模拟;最后,对程序计算和数值模拟这两种结果进行了比较分析.     

Deposition of graded SiO2/SiC coatings using high-velocity solution plasma spray

Carbon/carbon (C/C) composites are widely used in structural components, particularly in the aerospace and aeronautics sectors. However, the application of C/C composites is limited by low oxidation resistance at high temperatures. In order to overcome this problem, graded SiO₂/SiC coatings were deposited on C/C composites by a high-velocity solution plasma spray (HVSPS) process. Graded coatings were formed by reactions between the Si(OH)₄ sprayed liquid precursor and the C/C substrate; these reactions were promoted by the high temperature of the plasma torch. The morphologies, microstructures, and chemical compositions of the coatings were investigated by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. By altering the deposition time, the coating thickness was controlled, therefore demonstrating SiC formation and realizing graded SiO₂/SiC coatings.     

自粘卷材防水层渗漏水处理实例

某住宅倒置式屋面防水层，用自粘防水卷材铺贴完成后，在试水过程中检查发现有多处渗漏水。分析渗漏原因，研究处理方案，采用SBS防水卷材热熔法施工，解决了屋面渗漏。     

Effects of arc current and electrode size on electrode erosion in ac plasma torches

Heavy erosion of the electrode is a problem in using ac plasma torches. In a series of our studies, the effects of electrode stem size (diameter and length) and tip shape on the electrode erosion were clarified at a low current of 200 A. In this paper, on the basis of the 200-A data, in order to reduce the electrode erosion with the current increased, the effects of current and electrode size on electrode erosion were clarified experimentally and analytically between 100 and 550 A. The electrode used was of solid type and the material was tungsten containing 2 wt% of lanthanum oxide. The plasma gas was argon. Main results are as follows. (1) As the current increased, the electrode erosion increased linearly. In the case of thin electrodes (8 mm ø), between 450 and 550 A, the electrode tip was molten partially and the electrode erosion increased rapidly over 5 mg/h. However, for thick electrodes (13 mm ø), the electrode erosion did not increase rapidly. (2) The temperature distribution along the electrode axis was calculated. As a result, a good correlation was obtained between the calculated temperature of electrode tip and the measured electrode erosion. As the tip temperature decreased to 3000 K (cf. tungsten melting point: 3660 K), the electrode erosion decreased below 5 mg/h of the linearly increasing range.     

基于多传感器的焊枪定位系统的设计

针对焊接模拟器中焊枪的定位,设计了一种新型的焊枪定位系统.该定位系统在焊件上布置有感应线圈膜,基于电磁感应得以确定焊枪在工作平面上的投影坐标x和y值,应用光纤传感器测量焊枪与焊件的距离,并通过空间几何转换从而间接确定焊枪的z坐标,应用焊枪内置的三轴陀螺仪和三轴加速度传感器模块获得焊枪的姿态,最后根据空间位置关系推导出了熔池的位置和操作者的动作,从而完成了焊枪定位系统的设计.结果表明,该设计能够较好地满足了虚拟焊接模拟器焊枪定位精度和实时性的要求.