Pulsed Nd：YAG laser cladding of high silicon content coating on low silicon steel

A pulsed Nd:YAG (yttrium aluminum garnet) laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), with associated energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The microhardness was also measured along the depth direction of the specimens. A crack-and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized sin-gle-track and multi-track laser cladding. The phases of the coating are α-Fe, γ-Fe, and FeSi. The high microhardness of the la-ser-cladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt/ in the single-track cladding and 6.5wt/ in the multi-track cladding, respectively.     

Erythrocyte-Like Mg(OH)2 Microspheres Self-Assembled by Nanocrystallites

The erythrocyte-like magnesium hydroxide microspheres were synthesized in large scale through a simple solution phase route. The structures and morphologies of the products were analyzed by the X-ray diffractometer (XRD),scanning electron microscope (SEM),transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM). The possible growth mechanism of the nanostructure was discussed briefly and the potential application was proposed.     

Microstructure and properties of high emissivity coatings

A new coating on lining in industrial furnace for energy saving has been developed. Properties and microstructure of the coatings were revealed by emissivity instrument,X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The result indicates that the emissivity of coatings is higher than 0.90 and the thickness of coatings is about 200 μm. ZrO2,Cr2O3 and SiC in the coating benefit practical applications of coatings at high temperature with du-ra...     

Characteristics and properties of SiO2-Al2O3/EP-PU composite

SiO 2-Al2O3/EP-PU nanocomposites, which contained polyurethane(PU) flexible chain, were prepared via epoxy resin, PU and modified silica and alumina particles. Silica and alumina particles were modified by coupling agents KH-560 and KH550, respectively. EP-PU was used as matrix, PU as toughening agent, Si O2-Al2O3 as filled and MTHPA as curing agent. The mass ratio of PU was 30% in this system. The chemical structure of the products was confirmed by FT-IR measurements, the morphological structure of fracture surface and the surface of the hybrid materials were observed by scanning electron microscope(SEM) and transmission electron microscope(TEM), and shearing strength and breakdown field were measured, respectively. When the mass fraction of inorganic component was 10% and the mass ratio of Si O2 to Al2O3 was 4.5:5.5, shearing strength of Si O2-Al2O3/EP-PU was 28.5 MPa and breakdown field was 15 k V/mm, the data could meet the property requirement of insulating material.     

Corrosion mechanism of HVOF silicate glass coating in 5% NaCl solution

On the basis of good anticorrosion capability of silicate glass,silicate glass coating was sprayed by high velocity oxygen fuel (HVOF) and the corrosion mechanism in 5% NaCl solution was studied. Scanning electron microscope (SEM) ,energy dispersive X-ray analysis (EDX) ,X-ray diffraction (XRD) and potentiom- eter were used to study the coating composition and corrosion process. The result shows that silicate glass coating is entirely noncrystallizable. Silicate glass coating has very low incidence of hole with compact structure. Electric double-layer can form at coating/solution interface and corrosive solution performs as a lead connecting the coating surface and substrate after permeating through glass coating. The corrosion mechanism of silicate glass coating is similar to that of glass and the entire corrosion process can be divided into some states. The whole corrosion process happens in glass coating without substrate basically. The fluctuation of the self-corrosion potential about glass coating in corrosion solution can help to research the corrosion process.     

Effects of Annealing Processes on Cu_xSi_(1-x) Thin Films

The Cu_xSi_(1-x) thin films have been grown by pulsed laser deposition(PLD) with in situ annealing on Si(001) and Si(111),respectively.The transformation of phase was detected by X-ray diffraction(XRD).The results showed that the as-deposited films were composed of Cu on both Si(001) and Si(111).The annealed thin films consisted of Cu +η "-Cu_3Si on Si(001) while Cu +η'-Cu_3Si on Si(111),respectively,at annealed temperature(T_a)= 300-600℃.With the further increasing of T_a,at T_a= 700℃,there was only one main phase,η"-Cu_3Si on Si(001) while η'-Cu_3Si on Si(111),respectively.The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing T_a detected by field emission scanning electron microscope(FESEM).It was also showed that the grain size would enlarge with increasing annealing time(t_a).     

Microstructure and Properties of A IN Coating/Graphite Fabricated via In-situ Reaction

A novel method was used to fabricate AIN coating on graphite substrate.This approach included two steps:firstly,the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate;secondly,AIN coating was formed through the in-situ reaction of Al with the sprayed BN.The reaction was investigated by thermogravimetric-differential thermal analysis(TG-DTA),and the phase composition in the synthetic process was characterized by X-ray diffraction(XRD).Scanning electronic microscopy(SEM)was used to observe the morphology,and electron probe microanalysis(EPMA)was used to observe the distribution of the elements.The experimental results show that the AIN coating is dense and bonded with graphite tightly.     

Behavior of NiCrAIY coating on the TC6 titanium alloy

A NiCrAlY coating was deposited on the TC6 titanium substrate by arc ion plating (AIP). The structure and morphologies of the NiCrAlY coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the influence of vacuum heat treatment on the element diffusion behavior was studied. The results showed that the γ'-Ni3Al phase was precipitated on the NiCrAlY coating after heat treatment. The Ni3(Al,Ti), TiNi, and Ti2Ni intermetallic layers appeared at the interface from the outside to the inside at 700°C, and the thickness of the intermetallic layers increased with the increase in temperature. At 700°C Ti and Ni were the major diffusion elements, and the diffusion of Cr was observed when the heat treatment temperature increased up to 870°C. The violent inward diffusion of Ni at 950°C resulted in the degradation of the NiCrAlY coating.     

Hexagonal hematite platelets synthesized from pyrite cinders by hydrothermal process

Well-crystallized hexagonal hematite (α-Fe2O3) platelets were synthesized by hydrothermal process,using a highly concentrated ferric hydroxide as precursor.The precursor was prepared by adding ammonia to the ferric sulfate solution which was obtained by leaching pyrite cinders with sulfuric acid.Structure and morphology of the synthesized products were investigated by X-ray diffraction,scanning electron microscope,transmission electron microscope and selected area electron diffraction.The results reveal tha...     

Hydroxyapatite bioceramic coatings prepared by hydrothermal-electrochemical deposition method

The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6Al4V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystallinity and morphologies of deposits were influenced by depositing temperature(100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃ and 200 ℃, respectively). The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6Al4V surface when the depositing temperature is 100 ℃. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.     

时效处理对铝硅系合金超细粉末微观组织的影响

采用双级雾化水冷快凝工艺制备了Ａ１－２０Ｓｉ和（２０２４Ａ１）－２０Ｓｉ－５Ｆｅ合金粉末,对其中的细粉进行了时效热处理,并在透射电镜下观察了其微现组织,分析了时效引起粉末组织细化的机理．结果表明：时效热处理使合金粉末中的第二相发生显著细化和均匀化．     

Effect of electromagnetic stirring on the microstructure and wear behavior of iron-based composite coatings

The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental re- sults showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe)7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe)7C3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe)7C3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.     

Direct hydrothermal synthesis and magnetic property of titanate nanotubes doped magnetic metal ions

Pure titanate nanotubes and titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions were synthesized by the hydrothermal method. In this process, titanate nanotubes were first prepared synchronously with doping Fe3 /Ni2 /Mn2 ions. The morphology,structure, thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions are paramagnetic behaviors.     

Surface Modfication of Fe3O4 Nanoparticles

Nanometer particles are important portion of magnetic fluid. Fe3O4 magnetic nanoparticles were studied in this paper and the surface modification of Fe3O4 nanoparticles was investigated by a series of experiments. Fe3O4 magnetic nanoparticles were synthesized with pH value, temperature, and the dosage of surfactant. The phase, structure, size and magnetism of nanoparticles were tested by X-ray diffration （XRD）, transmission electron microscopy （TEM） and magnetic balance. On the basis of the surface modification coating mechanism, the experimental phenomena and the effects on the variation of size, magnetism and stability of Fe3O4 nanoparticles were theoretically analyzed. X-Ray diffraction spectrum and TEM photograph show that 1） the nanoparticles structure is perfect, 2） the diameter of narnoparticles is small and have good deliquescence, and 3） Sodium oleate is the anion surfactant. Therefore 1） the good condition of surface modification is in an acidic solution, 2） the best temperature of surface modification is at 80 ℃, and 3） the dosage of surfactant should be about 0.6 times of that of Fe^2＋.     

真空熔覆原位自生WC/Ni基复合涂层的组织及耐磨性能x

为了提高煤油泵的使用寿命,利用真空熔覆技术在316L不锈钢表面原位合成了W_{C/Ni基复合涂层.采用扫描电子显微镜、能谱仪、X射线衍射仪研究了复合涂层的显微组织和相组成,并对其进行了硬度测量和摩擦性能试验.结果表明,复合涂层组织细密且与基材呈冶金结合.复合涂层主要由γ-Ni固溶体、原位生成的WC、(Cr,Fe)7C3和Cr7C3相组成,且WC相弥散分布在γ-Ni固溶体中.复合涂层的硬度约为316L不锈钢基材的4倍,相对耐磨性约为基材的37倍.xx}x     

激光熔覆纳米La2O3/Ni基合金涂层

采用横流5kWCO2激光在低碳钢基体表面制备纳米La2O3/Ni基激光熔覆涂层。采用光学显微镜（OP）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）分别对熔覆涂层进行显微组织和相组成的观察。用显微硬度计和滑动磨损试验机对熔覆涂层的硬度和耐磨性进行测试。试验结果表明：熔覆层主要由γ-（Ni,Fe）,Cr23C6,LaNi10.5Si2.5等相组成,随离结合面距离增大,熔覆层的组织逐渐变细。随着纳米La2O3加入量及扫描速度增加,熔覆层组织变细。加入纳米La2O3后,平均硬度由未加时500HV0.5提高到约700HV0.5,耐磨性也得到不同程度的提高。在本试验条件下,添加质量分数为1.0%纳米La2O3熔覆层的耐磨性明显高于质量分数为1.5%纳米La2O3熔覆层的耐磨性。扫描速率采用250mm/min的熔覆层,其综合性能最佳。     

SiC粉体在硫酸铝-硫酸钠复合熔盐中的反应转化

对碳化硅粉体在硫酸铝-硫酸钠复合熔盐反应转化成莫来石晶须的过程进行了研究。借助X射线粉末衍射仪(XRD)、红外光谱仪(IR)、高分辨透射电镜(TEM)、扫描电镜(SEM)和能谱仪(EDS),研究碳化硅与熔盐反应后的物相和微观形貌的变化。XRD和IR的结果表明,碳化硅在高温熔盐体系中可完全转化成莫来石晶须;SEM分析结果表明,莫来石沿[111]晶面优先生长形成晶须。并提出了循环的氧化-溶解机理,对碳化硅陶瓷粉体在复合熔盐中的反应过程进行了解释。     

40NiCrMo7钢表面锰系磷化膜的制备及耐蚀性

为了满足紧固件在工业中的实际应用,采用不同磷化工艺于40NiCrMo7钢表面制备了锰系磷化膜,并作为紧固件的表面腐蚀防护层.运用扫描电子显微镜、能谱仪、X射线衍射仪、盐雾腐蚀试验机与电化学测试系统对磷化膜的结晶组织、相结构及耐蚀性进行了研究.结果表明,磷化膜的主要相结构为MnHPO_4·2.25H_2O;在工艺Ⅱ条件下,锰系磷化膜组织均匀致密,且覆盖完整;磷化膜的腐蚀速率为0.018 mm/a,同时腐蚀防护率高达97.20%;经240h盐雾腐蚀试验后,磷化膜在工艺Ⅱ条件下的腐蚀面积仅为1%.     

原材料对原位合成强化相结晶状态的影响

钛合金表面耐磨性能差限制了电厂重要成品部件的寿命。采用激光熔覆方法,研究了不同原料状态和稀土添加对原位合成复合TiB/TiN钛基涂层强化相粒度以及分布均匀性的影响。采用X射线衍射分析(XRD)、扫描电子显微分析(SEM)和高分辨投射分析(TEM)技术等方法研究了强化相组织形貌,得出以下结论:分别采用h-BN和纯硼酸、尿素为原料形成的Core-shell结构为原料,涂层中均原位合成TiB/TiN强化颗粒,采用非晶态BN有利于获得细小强化相组织,但强化相含量相对较少;添加CeO2有利于强化相晶粒细化以及均匀分布。