Effect of coaxial laser cladding parameters on bead formation

We investigated the shape and morphology of nickel-based powder particles (Sulzer Metco) and coatings produced by laser gas-powder deposition onto steel substrates. Laser deposition was performed using an LC-10 IPG-Photonics laser complex equipped with a 10-kW fiber laser. The shape and microstructure of the samples were studied using optical and electronic microscopy and X-ray diffraction analysis. The results showed that the deposition speed and laser power significantly influenced the shape and size of the beads. The depth of diffusion of nickel into the steel substrate after deposition was less than 20 μm; the microstructure of the resulting coating was fcc Fe₃Ni. As a result, detailed information about the form and shape of the filler powder, modes of its deposition, and the resulting coating structure was obtained; this information is important for the production of high-quality products by additive technologies.     

城市再生水中大肠杆菌在浮选过程中迁移规律

通过再生水模拟浮选试验和吸附、解吸附试验分析研究了城市再生水中大肠杆菌在浮选过程中的迁移规律.研究结果表明:再生水中大肠杆菌能够快速被矿物颗粒吸附,尾矿废水继续回用于浮选流程是安全的,但精矿、中矿、尾矿中吸附了大量的大肠杆菌,在特定暴露水平下会对从业人员构成健康风险;矿物颗粒对大肠杆菌的吸附是影响再生水中大肠杆菌在浮选过程迁移的主要因素;随着大肠杆菌浓度的升高,大肠杆菌衰减率、吸附速率随之下降;矿物颗粒对大肠杆菌的吸附对pH变化敏感,随着pH升高,矿物颗粒对大肠杆菌的吸附呈下降趋势,捕收剂煤油、Pj053和调整剂CaO的加入会明显提高矿物颗粒对大肠杆菌的吸附.     

Au(Cu、Ag)／SiO_2纳米薄膜的制备及其微观结构表征

用多靶磁控溅射技术制备了不同形貌的Au(Ag、Cu)纳米颗粒分散SiO2薄膜。利用透射电镜对Au／SiO2薄膜的微观结构、表面形貌进行了表征。结果表明通过调控金属颗粒的沉积时间和靶材的溅射频率可以制备不同形貌金属颗粒ISi02单层薄膜。单层Au／SiO2薄膜中Au沉积时问为5s时,Au颗粒为圆形,当沉积时间为10s时,Au颗粒连接成网络状结构;单层AgiSi02薄膜中,Ag靶的射频功率为150W时,颗粒形状接近圆形,Ag靶的射频功率为100W时,Ag颗粒几乎密集在一起,形成膜状结构:单层Cudsi02薄膜中Cu的沉积时间为10s时,Cu颗粒形成网络状结构,Cu的沉积时问为20s时,形成的是Cu膜。     

钢表面化学气相沉积碳化钛

采用化学气相沉积（CVD）法，以TiCl4-CH4-H2为原料气体，在不锈钢表面获得了致密的碳化钛(TiC)膜，研究了TiC的成膜速度、表面形貌和日本择优取向与沉积条件的关系。结果表明，沉积温度Taep、碳钛比CH4／TiCl4强烈的影响TiC的成膜速度、表面形貌和晶体择优取向。CH4／TiCl4低时，TiC晶体的择优取向为（220）；CH4／TiCl4高时，TiC晶体的择优取向为（200）。气氛中活性碳的平衡浓度是决定碳化钛的表达形貌、晶体择优取向的主要因素。     

Deposition behavior of multi-particle impact in cold spraying process

In the practical cold-spraying process, a number of particles impact onto a substrate and then form a coating. To study the deformation behavior and multi-particle interactions, single-particle, two-particle, and three-particle impacts were simulated using the AN-SYS/LS-DYNA version 970. A copper coating was prepared and scanning electron microscopy (SEM) was employed to analyze the microstructures of the powders and the coating. Numerical results reveal that the critical deposition velocity is 600 m/s for a copper particle/copper substrate. The particles deform more fully due to multi-particle interactions, such as tamping, interlocking, and extrusion effects. The compression ratio increases from 40% to 70% as a result of the tamping effect. This is beneficial for achieving the cold-sprayed coating. The multi-particle morphology and compression ratio in the experiment are consistent with those of simulation results. Based on these results, the coating of high performance can be prepared through selecting appropriate parameters and suitable pre-treatment processes.     

镁合金表面热喷涂WC-10Co-4Cr粒子沉积及分布特性

为了探究高速空气燃料热喷涂（AC-HVAF）过程中喷涂粒子撞击基材后的沉积特性。采用AC-HVAF热喷涂技术在AZ80镁合金基体上沉积WC-10Co-4Cr硬质涂层。通过离散沉积实验获得薄层沉积粒子,探讨各种沉积形貌的种类、形成原因、结合机制及射流中粒子的径向和轴向分布。结果表明：在AC-HVAF粒子沉积过程中,嵌入型沉积为主要的沉积形貌,同时包含少量的破碎型与空腔型沉积粒子。在涂层的形成过程中,嵌入型沉积对涂层/基体结合性能起重要作用;空腔型沉积的小颗粒及破碎型沉积的大颗粒是造成沉积效率下降的主要原因。喷涂粒子主要集中在射流中心,越靠近射流边缘,空腔型沉积粒子越多,最终导致AC-HVAF粒子射流呈现出空间分布特征。     

氧化亚铁硫杆菌抑制黄铁矿可浮性作用机理

通过对氧化亚铁硫杆菌吸附前后黄铁矿Zeta电位和表面接触角的测定,研究了其表面电性和润湿性变化,探讨了氧化亚铁硫杆菌抑制黄铁矿可浮性的作用机理.结果表明,氧化亚铁硫杆菌作用后,黄铁矿的表面电性发生明显变化,等电点pH值降低,表面润湿性变化不明显;氧化亚铁硫杆菌吸附对黄铁矿可浮性的抑制作用不是来源于增强黄铁矿表面的亲水性,而是由于减少了浮选捕收剂在黄铁矿表面的吸附,静电作用和空间位阻效应是导致黄铁矿可浮性受到抑制的重要原因.     

溅射沉积温度对薄膜生长影响的计算机模拟

利用Monte Carlo方法对薄膜生长过程进行计算机模拟.模型针对粒子的沉积、吸附及粒子的扩散等过程,研究了粒子允许行走的最大步数对薄膜生长形貌的影响.结果表明:随温度升高,粒子行走步数增加,薄膜的生长经历了从分散到分形团聚的过程;在粒子行走步数越小的情况下,薄膜越易趋向于分散生长.     

Diffusion mechanism in molten salt baths during the production of carbide coatings via thermal reactive diffusion

The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investigated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ±0.5, 5.2 ±0.5, or 5.7 ±0.5 μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the substrate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure (Na₂O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.     

直流磁控反应溅射制备Al2O3薄膜的工艺研究

应用直流磁控反应溅射技术在不锈钢基体上制备Al2O3薄膜,研究了溅射气压、氧气流量和基体温度对Al2O3薄膜的沉积速率和膜基结合力的影响规律。结果表明,随着压力的增大,沉积速率和膜基结合力先增大后减小,在压力为1.0 Pa时最大;随着氧气流量的增加,沉积速率和膜基结合力也随之不断减小;随着温度的升高,沉积速率和膜基结合力略有下降。利用扫描电子显微镜观察了薄膜与基体界面及薄膜的表面微观形貌,薄膜与基体的结合性好,薄膜表面晶粒大小均匀,组织致密。     

PB-g-SAN弹性体的合成及其对SAN树脂的增韧

采用种子乳液聚合技术在聚丁二烯(PB)乳胶粒子上接枝共聚苯乙烯(St)和丙烯腈(AN)合成了一系列PB质量分数为40%的PB g SAN弹性体·研究了共聚单体中叔 十二烷基硫醇(TDDM)质量分数对SAN共聚物接枝行为、弹性体粒子结构及其动态力学性能的影响·结果发现,随着单体中TDDM质量分数的增加,SAN在PB上的接枝率和接枝效率降低,弹性体粒子中SAN包容结构的尺寸增大,在低温区的动态剪切模量下降·将其与SAN树脂共混后发现在共聚单体中引入TDDM后提高了弹性体粒子的增韧效率·     

银纳米粒子在聚苯乙烯球表面的异相成核与生长

采用原位化学还原法,将银纳米颗粒直接沉积到没有进行任何活化处理的聚苯乙烯（Polysty-rene,PS）亚微米球的表面.运用X射线衍射（XRD）、透射电子显微观察（TEM）和X射线能谱（EDS）等分析手段对产物的成分、形态、尺寸、以及分布等特征进行了详细表征.结果表明,产物为大量均匀的PS-Ag复合粒子,银纳米粒子以带状为主,并沿着球形基体的弧形表面不连续分布.高分辨电子显微分析（HRTEM）表明,银粒子均为结晶度较高的单晶,它们与非晶PS球形基体之间结合的很好,这应归因于银在基体表面的异相成核及沿着与球面切向方向的生长.此外,研究了反应物浓度、温度等因素对银纳米粒子在PS球表面沉积的影响.根据实验结果,详细探讨了原位化学还原过程中银纳米粒子在非晶PS球表面的异相成核与生长的机理.     

pH值对β-MnO2颗粒光催化去除银离子的影响

The presence of silver ions (Ag(I)) in wastewater has a detrimental effect on living organisms. Removal of soluble silver, especially at low concentrations, is challenging. This paper presents the use of β-MnO₂ particles as a photocatalyst to remove Ag(I) ions selectively from aqueous solution at various pH levels. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), field emission electron microscope (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron microscopy (XPS) were employed to determine the removal efficiency and to characterize the deposition of silver onto the surface of β-MnO₂ particles. The optimum pH for the removal of Ag(I) ions was at pH 4 with 99% removal efficiency under 1 h of visible light irradiation. This phenomenon can be attributed to the electrostatic attraction between β-MnO₂ particles and Ag(I) ions as well as the suppression of electron–hole recombination in the presence of H+ ions.     

空间电场对单根纳米纤维沉积的影响分析

基于近场静电纺丝,分别讨论单根纳米纤维在平面硅片、图案化硅片基底上的沉积规律.当收集板运动速度大于纳米纤维喷射速度时,将获得直线状纳米纤维;而当收集板运动速度小于纳米纤维喷射速度,纳米纤维易受电场力和电荷排斥力的影响而产生弯曲鞭动,并缠绕成纳米纤维带或螺旋状结构.采用图案化硅基作为收集板时,电场分布发生变化,微结构表面电场强度大于其他区域.纳米纤维在微结构表面产生聚集,且微结构表面电场的增强也加快纳米纤维喷射速度.     

油酸钠与微细粒黑钨矿的作用机理

通过浮选实验、溶液化学计算、吸附量测试、动电位和红外光谱分析等方法,系统研究了油酸钠对微细粒黑钨矿的浮选捕收机理.结果表明:黑钨矿可浮性与油酸钠吸附量正相关,微细粒黑钨矿可浮性较好的pH区间为7.0～9.0,溶液中油酸离子和离子-分子缔合物组分对黑钨矿浮选过程起主要作用.溶液化学计算表明:油酸钠的吸附量和黑钨矿的可浮性与金属阳离子形成的油酸盐组分浓度有直接关系;油酸钠的添加使荷负电的黑钨矿动电位负移.红外光谱分析表明油酸钠在黑钨矿表面发生化学吸附,生成金属油酸盐,进而增强了黑钨矿的可浮性.     

金属Au纳米膜的电子输运及非线性效应

使用Matlab软件对N方势垒在偏压下电流随电压的变化关系进行了模拟计算，计算结果表明N方势垒的伏安特性（I-V）曲线上显现出非线性效应和震荡效应。利用溅射方法将Au颗粒沉积在经过电化学腐蚀处理的硅基片上，得到具有纳米结构的Au膜。采用SEM对基片表面上的金膜进行观察，发现了纳米颗粒的聚集体，样品的I-V曲线测试结果表明：常温下，测得电流在0至1.5×10^-6A范围内，样品电阻率呈非线性电阻效应和振荡效应；N方势垒模型的模拟计算结果与实验测量结果很好的吻合。     

无规扩散类反应表面生长动力学行为

研究了无规扩散类表面生长的动力学和标度行为，研究了两种粒子（Ａ、Ｃ）在二维衬底上的聚集．当Ｃ粒子的几率ｑ＝０时，系统表现出泊松生长．当ｑ≠０时，表面表现出粗化的形貌特性，存在着粗化转变．对Ｃ粒子扩散步长以及扩散几率对粗化转变的影响也进行了研究     

旋涂辅助连续离子反应法制备CdS纳米晶及其光电性能

为了解决CdS传统制备工艺中连续离子吸附反应(SILAR)法存在的产物颗粒小、敏化层厚度不易提高的问题,将传统SILAR法中的浸泡吸附工艺改为旋涂工艺,采用全新的旋涂辅助连续离子反应法(S-SILR)制备CdS纳米晶颗粒,同时将新旧两种方法制备的CdS纳米晶分别沉积到ZnO纳米棒有序阵列中进行对比研究,利用扫描电子显微镜(SEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-vis)、瞬态光电流等分析手段对产品形貌、结构、光吸收性能和光电转换性能进行了表征和测试。结果表明,利用S-SILR法制备CdS纳米晶光敏层更容易形成对ZnO纳米有序阵列的完全包覆;与传统的浸泡吸附法相比,改进后的旋涂法所得ZnO/CdS复合薄膜在可见光区的光吸收和光电转换性能更加优异。CdS沉积方法的改进对提高太阳电池制备工艺的可操作性及其光电转换性能有一定的指导意义。     

多分散悬浮体沉积的动力学特征

采用拉格期日方法,通过描述微粒的运动轨迹,研究了多分散愚浮固休很拉向孔道表面沉积的徽观动力学特征,给出了五种不同沉积方式的判定条件,通过对流场的修正,得到了微粒液度的宏观变化与局部沉积特性之间的关系。     

气流控制的碳纳米管的定向生长研究

通过严格控制气流的方向和催化剂颗粒的密度,加以利用材料自身的重力作用,用热化学气相沉积（T-CVD）的方法在硅衬底上制备了长度可控且与衬底平行的碳纳米管（CNTs）。并研究了催化剂的厚度,生长时间和重力等因素对碳纳米管定向生长的影响。利用扫描电镜对制备的碳纳米管进行了表征。