Ni/ZrO2梯度镀层的制备和性能

采用Watt型镀镍溶液，恒电流电沉积方法制备Ni／ZrO2梯度镀层．扫描电镜(SEM)测试和X-射线衍射分析表明，沿镀层的生长方向，ZrO2的含量由0逐渐增加到21％(体积分数，下同)，呈梯度分布；Ni和ZrO2各自在特定的角度分别出现其衍射特征峰，互不干扰，镀层中ZrO2的含量增高，衍射强度变强．断口分析表明，在梯度镀层的内部，材料的塑性变形能力大，韧性最好；沿镀层生长的方向，断口中的韧窝特征逐渐减小，镀层的韧性下降；在表层的断口中ZrO2微粒明显增多，呈团聚状态，基本上没有韧窝特征，镀层的韧性最差．Ni／ZrO2梯度镀层的韧性由外至内逐渐增加，呈梯度分布，其延展性为复合镀层的2．5倍．     

Ni/ZrO_2复合镀层电沉积行为与耐高温氧化性能的研究

通过电化学试验、高温氧化试验、扫描电镜及X 射线衍射 ,研究了电沉积Ni/ZrO2 复合镀层的电化学行为和添加微粒对镍镀层高温抗氧化性能和组织结构的影响。研究结果表明 ,在瓦特 (Watts)镀液中加入ZrO2 微粒使电镀时阴极电流密度明显降低 ,阴极电位与时间 (E t)、阴极电流对时间 (I t)的关系曲线变化趋势不大 ,但I t曲线抖动加快 ;高温氧化试验结果表明 ,ZrO2 微粒可以使复合镀层的高温抗氧化能力明显提高 ;Ni/ZrO2 复合镀层与瓦特镍镀层的高温氧化规律基本满足W =ktn;扫描电镜能谱分析则证实 :在 80 0℃高温氧化过程中 ,明显存在铜向镍镀层中的扩散 ,这可能有利于增强镀层与基底之间的粘合。X 射线衍射表明 ,在高温氧化时 ,镀层表面主要生成NiO产物。     

Ni/ZrO2纳米复合刷镀层的抗高温氧化性

采用电刷镀技术制备了Ni/ZrO2纳米复合镀层。利用扫描电子显微镜、X射线衍射等手段,研究了Ni/ZrO2纳米复合刷镀层的组织和抗高温氧化性能,并与快速镍镀层进行对比分析。结果表明,与快速镍镀层相比,Ni/ZrO2纳米复合镀层的表面形貌更为平整致密,晶粒尺寸明显减小;在800℃氧化后复合镀层晶粒依然较快速镍镀层细小、均匀,氧化增重速率明显低于快速镍镀层;X射线衍射分析表明,Ni/ZrO2复合镀层的氧化程度较轻,镀层中仍然存在大量的Ni相。     

Cu-Zr合金基体上的复合镀层的性能研究

利用复合电沉积的方法在Cu-Zr合金基体上沉积出含ZrO2微粒的Ni-ZrO2复合镀层,研究了镀层中的ZrO2微粒含量与镀液中ZrO2微粒含量的关系以及Ni-ZrO2合度层在高温条件下的抗高温氧化笥能和耐腐蚀性能,结果表明：Cu-Zr合金基体上镀覆的Ni-ZrO2复合镀层的抗高温气化性能和耐腐蚀性能得到了很大的提高。     

电沉积Ni-W非晶态合金复合镀层研究

研究了在Ni－W非晶态合金镀液中加入ZrO2纳米微粒后的电沉积工艺,得到工艺参数与非晶态复合镀层的成分、结构和镀层在面形貌的关系。加入ZrO2纳米微粒后,提高了Ni-W非晶态复合镀层的高温抗氧化性能和硬度。     

基于组分磁性差异制备ZrO2/Ni功能梯度材料研究

根据不同组分的磁性差异，提出一种在梯度磁场中，采用粉浆浇注法制备铁磁性／非磁性功能梯度材料的方法，并用此方法制备出成分连续变化的ZrO2／Ni功能梯度材料．采用能谱分析仪、光学显微镜和X射线衍射仪对ZrO2／Ni功能梯度材料的成分分布、微观结构和相组成进行了研究．结果表明，在0．5T／m的磁场梯度作用下，浆料中Ni和ZrO2颗粒由于所受磁场作用不同而发生重新排列，形成沿样品厚度方向成分的梯度分布．此外，建立了功能梯度材料成分与颗粒粒度、饱和磁化强度以及磁场梯度之间的定量关系．     

0Cr18Ni10Ti不锈钢热浸镀铝及高温扩散后的高温氧化行为

为提高0Cr18Ni10Ti不锈钢的抗高温氧化能力,采用熔剂法在0Cr18Ni10Ti不锈钢表面制备热浸镀铝层,并经950℃、2 h高温扩散。采用SEM、EDS对热浸镀铝高温扩散试样及不锈钢试样900℃氧化不同时间的表面、截面进行了形貌观察及成分分析。结果表明:镀铝高温扩散试样的氧化动力学曲线较平缓且氧化增重较小;0Cr18Ni10Ti不锈钢经900℃、100 h氧化后表面主要由Fe2O3组成,氧沿晶界向内扩散产生内氧化;镀铝高温扩散试样900℃氧化期间,表面主要由Al2O3氧化膜组成,有效地阻止了合金元素与氧的互扩散,Ni元素在Fe Al层与Al固溶层富集阻碍了Fe Al合金层Al向基体扩散,使镀铝高温扩散试样Fe Al合金层经900℃、100 h氧化后Al元素贫化量较少。镀铝高温扩散试样900℃、100 h下的抗氧化性能优于0Cr18Ni10Ti不锈钢。     

机器臂缸套表面电沉积Ni-P-xZrO2纳米复合镀层性能表征

为了提高机器臂缸套表面电沉积Ni-P复合镀层的综合性能,通过电沉积工艺使ZrO2掺入Ni-P镀层内,研究了Ni-P-xZrO2纳米复合镀层的组织结构、润湿性、硬度以及电化学腐蚀性能.结果 表明:逐渐提高电沉积液内的ZrO2含量后,位于8.94°处的ZrO2衍射峰强度不断提高.镀层进行煅烧后析出了Ni与Ni3P 2种物相成分,ZrO2已经掺杂到Ni-P镀层内.当在电沉积液内加入更高含量的ZrO2后,镀层形成了更粗糙的表面,产生了更多树枝晶,镀层表面从最初的亲水性变为疏水性.在一定范围内提高ZrO2含量后可获得硬度更高的Ni-P-ZrO2复合镀层,在ZrO2浓度为5 g/L时复合镀层的硬度最大,接近1110 kg/mm2.析出硬质相Ni3P的过程中形成了大量的晶界,从而引起大量位错堆积在晶界区域,导致发生应变硬化现象.腐蚀电流密度随着ZrO2含量的增大先降低后增加,最小值发生在ZrO2浓度为5g/L时;腐蚀电压表现出的规律与之相反.     

钛合金表面梯度Al2O3陶瓷涂层的高温抗氧化性能

钛合金应用广泛,但在高温环境中极易被氧化,降低其力学性能及寿命。利用溶胶-凝胶法在TC11钛合金上制备梯度层(ZrO_2+Al_2O_3)+表层(Al_2O_3)的复合梯度涂层,提高其高温抗氧化能力。将复合梯度涂层、单层氧化铝涂层以及基体在700℃进行100h的高温氧化,利用氧化增重数据拟合得到梯度涂层的氧化速率为0.015mg~2/(cm4·h),氧化指数为2.137,并结合氧化后EDS成分分布,发现复合梯度涂层可以提高基体的高温抗氧化性能。同时利用700℃热震实验比较了复合梯度氧化铝涂层试样和单层氧化铝陶瓷试样的热震次数,梯度层(ZrO2+Al_2O_3)的存在缓解了基体与氧化铝陶瓷涂层之间热膨胀系数不匹配而导致的易剥落的问题,延长了涂层寿命,进一步提高了基体的高温抗氧化能力。     

先驱体转化制备ZrO2改性SiC陶瓷的氧化行为研究

采用先驱体转化法,以聚碳硅烷、二乙烯基苯和正丁醇锆为原料高温裂解制备了ZrO2改性的SiC陶瓷材料,结合XRD,SEM和EDS能谱等测试方法,研究ZrO2的添加对材料氧化行为的影响。结果表明:ZrO2引入后,SiC陶瓷材料在1600℃开始氧化,表面生成了SiO2阻氧层阻止气体逸出,宏观上形成气泡,到1700℃材料氧化较严重,表面变得凹凸不平,出现较多空洞,并且存在一定程度的失重;1700℃氧化后,含ZrO2的材料表面和内部均有一定程度的氧化,表面的主要成分为SiO2,内部有部分SiC发生了氧化,两种材料氧化层呈梯度分布;在高温氧化过程中,ZrO2会发生由四方相向单斜相的相变,SiC对ZrO2的相变具有抑制作用,而材料氧化后生成的SiO2则无法抑制ZrO2的相变。     

High-throughput screening of critical size of grain growth in gradient structured nickel

Nanocrystalline metals with high Gibbs free energy have a strong tendency towards thermally driven grain growth,thus understanding the critical size or temperature of grain growth is vital for their applications.The investigations of thermal stability were usually conducted on the materials with a homo-geneous structure;however,these methods are time-consuming and expensive.In the present work,we reveal a high-throughput experimental strategy to characterize the size-dependent thermal stability via annealing the gradient structured Ni.Employing this method,the critical size of grain growth(dc)at a given annealing temperature was rapidly determined.The critical size of grain growth was～95 nm when annealed at 503 K for 3 h,which is consistent with the value reported in the homogeneous structured Ni.Furthermore,this critical size was found to be identical in three types of gradient structured Ni,i.e.,independent on the gradient structure.Our present work demonstrates a high-throughput strategy for exploring the critical size of grain growth and size-dependent thermal stability of metals.     

离心成型技术制备孔梯度分布的氧化锆多孔陶瓷

以2种粒径分布不同的ZrO_2微粉为原料,利用离心成型技术制备孔梯度分布的ZrO_2多孔陶瓷.测量了ZrO_2颗粒在不同pH值下的Zeta电位,研究了离心加速度和浆料固相含量对ZrO_2颗粒分离现象的影响,观察了烧结产物的微观形貌、孔隙度以及孔径分布.研究结果表明,在pH=10时,ZrO_2颗粒的Zeta电位最高,浆料具有良好的分散性.在较低的固相含量和较高的离心加速度下,ZrO_2颗粒的分离现象明显,孔隙呈梯度分布.40%(体积分数)固含量ZrO_2浆料离心所得样品在1400℃烧结3h后,孔隙呈现良好的梯度分布,其底部孔隙度为24.6%,气孔尺寸在1～3μm之间;顶部孔隙度为15.2%,气孔尺寸大多在0.3μm以下.     

Effect of pressure on the electrodeposition of nanocrystalline Ni-C in supercritical CO2 fluid

Electrodeposition of Ni in a Watt's bath at different applied pressure, and in the presence of CO₂ fluid was investigated. The reduction of carbon and its alloying into the Ni deposit was focused. The current efficiency of electrodeposition and the carbon content in the Ni deposit were found to vary with the applied pressure. The crystal structure of the resulting Ni-C film was characterized by performing X-ray diffraction. The composition of the deposit was analyzed using X-ray photoelectron spectroscopy. Transmission electron microscopy was employed for microstructure analysis. The results showed that nanocrystalline Ni-C deposit could be obtained. The grain size of the Ni-C film varied from 14 to 43 nm, depending on the deposition pressure and carbon content. A significant increase in microhardness from 450 to 720 Hv could be obtained for the Ni film electrodeposited from a bath of 15 MPa supercritical CO₂ fluid. In 1 M HCl solution, a higher open circuit potential and a lower anodic current density were found when the carbon content in the Ni deposit was increased.     

Use of different sensing materials and deposition techniques for thin-film sensors to increase sensitivity and selectivity

The performances of metal oxide semiconducting materials used as gas-sensing detectors depend strongly on their structural and morphological properties. The average grain size has been proved to play a prominent role and better sensor performances were found in polycrystalline films where the grain size is few tens of nm or smaller. On the other hand, thermal treatments during thin-film deposition and/or sample postprocessing could lead to a grain coalescence, thus decreasing the conductivity of the sensing film. Avoiding such a phenomenon, still keeping optimized processing conditions, will increase the sensor performances, maintaining the resistivity at acceptable values. In this work, new gas-sensing materials and new thin-film deposition procedures have been investigated. Aiming to preserve the sensitivity, to enhance selectivity and to reduce the drift, thin films of WO/sub 3/ and CrTiO/sub 3/ deposited by pulsed-laser ablation (PLA) and of SnO/sub 2/ deposited by rheotaxial growth and thermal oxidation techniques were comparatively characterized. Three issues were mainly addressed: the variation of the conductivity as a function of RH, the sensitivity toward benzene, CO, acetone, and NO/sub 2/, and the selectivity.     

Fabrication of a nanocrystalline Ni-Co/CoO functionally graded layer with excellent electrochemical corrosion and tribological performance

Nanocrystalline (NC) Ni-Co/CoO functionally graded materials with excellent lubricating, high anti-corrosion and anti-wear performance were fabricated by electrodeposition and subsequent cyclic thermal oxidation and quenching. Transmission electron microscopy and energy dispersive x-ray spectroscopy investigations show that bulk Ni-Co gradient deposits with an average grain size in the range of 13-40?nm demonstrated a graded structure transition from face-centred cubic to hexagonal close packed and graded composition changes from Ni-rich to Co-rich regions with the increase in deposit thickness. X-ray diffraction and x-ray photoelectron spectroscopy analysis indicated the surface layer of NC Ni-Co graded materials to be mainly composed of dense and ultrafine CoO with a (111) preferred orientation. The NC Ni-Co/CoO functionally graded materials exhibited significantly enhanced corrosion resistance in both NaOH and NaCl solutions and remarkably improved wear resistance and dry self-lubricating performance when compared with the NC Ni and Ni-Co graded deposits under dry sliding wear conditions. The higher corrosion and tribological performance of NC Ni-Co/CoO graded materials can be attributed to the graded microstructure within the deposits, the anti-corrosion barrier of a dense oxide layer and the solid lubrication effect of CoO-rich tribo-surface films.     

钕铁硼器件表面电沉积铜层及性能

针对钕铁硼器件现有Ni/Cu/Ni镀层防护体系存在的磁性能衰减问题,用碱性HEDP络合剂镀液在钕铁硼磁体表面直接电沉积铜层,并在其上电镀镍,构成Cu/Ni镀层防护体系代替通常的Ni/Cu/Ni镀层体系。通过电化学测试研究镀铜液中HEDP络合剂浓度对铜沉积过程的影响;应用SEM,XRD,TEM对铜层微观形貌进行了表征;分别用热震实验和热减磁实验对铜层结合力和钕铁硼器件的热减磁性能进行测试。结果表明:镀铜溶液中HEDP对铜离子沉积过电位影响较大,铜晶粒在钕铁硼晶界处优先沉积,并以(111)晶面取向为主;钕铁硼磁体上镀铜层结构致密,与钕铁硼的结合力良好,满足SJ 1282—1977的要求;Cu/Ni镀层体系的钕铁硼热减磁衰减率相比于Ni/Cu/Ni镀层显著减小。     

Temperature effect on the structure of ZnSe layers grown by chemical vapor deposition

The heat exchange between the substrate, growing layer, and gas flow in a CVD reactor is analyzed theoretically. The results indicate that the temperature of the gas mixture in the reactor influences the surface temperature of the polycrystalline zinc selenide deposit. Experimental data are presented on the variation of the average grain size across the ZnSe deposit. The thermal conditions of CVD and secondary crystallization during long-term deposition are shown to have a significant effect on the depth distribution of the grain size.     

Structure of Plasma-sprayed ZrO_2/(Ni/AI)Interface

The structures of plasma-sprayed ZrO_2/(Ni/AI) interface before and after hot isostatic pressing(HIP) treatment were studied by TEM,ED and X-ray diffraction analysis.Plasma-sprayedZrO_2/(Ni/AI) interfacial region is of definite thickness and consists of multi-phase structures.Amorphous ZrO_2 sublayer,amorphous plus microcrystalline ZrO_2 sublayer and NiO were found inthe interface.NiO phase formed by the reaction between ceramic coating and metallic substrate inlocal regions.However.the thickness and amount of NiO trended to increase and the distribution ofNiO particles trended continuously when the coating was subjected to HIP treatment.HIP treatmentcan accelerate the diffusion of atoms in the interfacial region.     

Microstructure Formation of HVOF Sprayed WC-Ni Coatings Deposited on Low Alloy Steel

A low alloy steel was coated with WC-Ni by the High Velocity Oxy-Fuel process, in order to increase the wear resistance and corrosion resistance of the material. The microstructure of the coating was determined using various techniques, such as SEM, TEM, EDAX, EPMA and X-ray diffraction methods

During spraying, the WC-Ni powder granules were heated to above the melting point of Ni, before arriving at the substrate surface. The molten Ni dissolves WC rapidly, forming Ni-W-C liquid alloys. Some C and some W are removed from the WC particles by oxidation. When each droplet strikes the steel substrate, a pancake-shaped splat forms, and solidifies with a rapid cooling rate. The structure is built up by the progressive deposition of the splats to produce a continuous coating. The Ni-W-C metallic matrix of the coatings consists of two basic structural types, Ni-rich material with a grain size of 10 - 100 nm, and a FCC crystal structure with a lattice parameter larger than that of Ni indicating the presence of dissolved W and C. The other metallic phase is W-rich, with a grain size less than 10 nm, and in some regions it appears to be amorphous. Dispersed within this material there were sometimes small crystals of W and W₂C. In the initial powder the volume fraction of WC was about 75%, but in the sprayed coating the volume fraction of the WC was reduced to about 20%. This is partly due to loss of W by oxidation, but chiefly due to dissolution of W into the metallic phase.