Investigation of ZrO2 nanoparticles concentration and processing time effect on the localized PEO coatings formed on AZ91 alloy

AZ91 Mg alloy was treated through a new localized PEO(Plasma Electrolytic Oxidation)coating approach,using electrolyte solutions with varying ZrO2 nanoparticles concentration(2-8 g/L)and processing times.With increase in the ZrO2 concentration,several microstructural changes were observed including;formation of cluster-type structure,damage to the inner layers(∼30 min)and sealing of defects.Corrosion analysis of the final coatings was carried out using potentiodynamic polarization,electrochemical impedance spectroscopy and post-corrosion analysis.It was explored that highest corrosion resistance(Rp∼81.17 kΩcm^2)of the coatings was obtained for ZrO2∼2 g/L.However,higher concentration of the ZrO2 nanoparticles caused weak crystalline coating structure,due to unstable and lower intensity discharges,thus failed to offer high corrosion resistance performance.

Effects of ZrO_2 Nanoparticles on the Microstructure and Thermal-protective Properties of PEO Coating on Al-12.5%Si Alloy

PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO_2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO_2 and high temperature steady phases such as a-Al_2O_3 and c-ZrO_2. Both the content of c-ZrO_2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO_2 nanoparticles possess excellent heat insulation performance and thermal shock resistance.

Microstructure and Thermal-protective Property of CPED Coating with ZrO2 Nanoparticles Addition on Al-12Si Alloy

A novel thermal-protective coating has been successfully prepared by CPED process on a cast Al-12%Si alloy with the addition of ZrO2 nano-particles in the electrolyte. The microstructures and phase composition of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. With ZrO2 nanoparticles addition, the cathode plasma discharge on the coating surface is more obvious than that without ZrO2 nanoparticles addition, the coating is more uniform and compact, and the thickness of the coating increases. Furthermore, the content of Zr and Y elements increases and the degree of crystallization of the coating is more complete. The formation of the solid solution of yttrium stabilized zirconia is promoted by cathode plasma discharge. In addition, the thermal insulation temperature increases as ZrO2 nano-particles are added to the electrolyte. After 1 000 cycles of thermal shock, there was no cracking in the coating surface layer, which indicated that the CPED coating with ZrO2 nanoparticles addition possessed a good thermal shock resistance.

Preparation and Characterization of ZrO_2 Nanoparticles Capped by Trioctylphosphine Oxide (TOPO)

Monodisperse ZrO2 nanoparticles capped by trioctylphosphine oxide （TOPO） were prepared in non-aqueous solvent using in-situ synthesis method. Transmission electron microscopy（TEM）, X-ray diffraction（XRD）, X-ray photoelectron spectrometer（XPS）, Fourier transformation infrared spectroscopy （FTIR）, and thermogravimetric analysis（TGA） were adopted to characterize and investigate the size, structure, composition, and the binding manners between organic capping agent TOPO and inorganic ZrO2 nanocores of the as-prepared nanoparticles. In addition, the nanoparticles were also studied to determine their solubility and relative stability. The experimental results show that the prepared nanoparticles contain about 25% organic capping shell TOPO, 75% inorganic ZrO2 nanocores, and can be easily dissolved and be stably disersed in non-polar organic solvents.

Influence of the Ratio of Ethanol to Water on the Agglomeration of Al_2O_3/Y_2O_3-ZrO_2 Nanoparticles

A method of heating ethanol-aqueous salt solution combined with co-precipitation was used to synthesize Al2O3/ZrO2 nanoparticles. The analysis of DSC and XRD revealed that the transformation temperature from amorphous to crystal phase was about 850 ℃. The grain size was increased with the raising of calcine temperature. The alcohol-water ratio did not affect the formation of main crystal phases, but affected the agglomeration of nanoparticles based on the results of TEM. When alcohol-water ratio was 5∶1, the dispersion of nanoparticles was good. When there was not alcohol, the dispersion of nanoparticles was poor because there was only pure co-precipitation reaction and the speed of co-precipitation reaction was too high to have enough time of PEG. dispersing particles.

Synthesis, Characterization and Thermal Stability of CeO_2 Stabilized ZrO_2 Ultra Fine Nanoparticles Via a Sol-gel Route

CeO_2 stabilized ZrO_2 ultra fine nanoparticles were successfully synthesized via a simple and effective sol-gel synthetic approach by using zirconylchloride octahydrate, cerium nitrate hexahydrate, and citric acid as starting materials. A series of techniques, including X-ray diffraction（XRD）, thermogravimetry（TG）, differential scanning calorimetry（DSC）, Fourier transform infrared spectroscopy（FTIR）, transmission electron microscopy（TEM）, and N_2-sorption analysis, were used to characterize the structure and morphology of the asprepared samples. XRD studies indicate that the as-synthesized sample is of well crystallized tetragonal phase of CeO_2 stabilized ZrO_2 with high purity. TEM images show that the as-synthesized sample is composed of a large number of fine dispersive nanoparticles with an average size about 10 nm. The as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample was heated at different temperatures in order to evaluate its thermal stability. The exprimental results reveal that the as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample exhibits excellent stability without the occurrence of phase transformation.

Antiferroelectricity in ZrO₂and Ferroelectricity in Zr, Al, La Doped HfO₂Nanoparticles

The dependence of the polarization P in Hf1-xZrxO2 nanoparticles on electric field, dopant concentration x, size and temperature are studied using the transverse Ising model and the Green’s function method. Pure ZrO2 shows at high electric fields an antiferroelectric behavior. Pure HfO2 is a linear dielectric in the monoclinic phase. With increasing ZrO2 content the of HZO shows a ferroelectric behavior. The composition dependence x of the remanent polarization Pr(x)?has a maximum for x = 0.5. For x = 0, pure HfO2, and x = 1, pure ZrO2, Pr=0.?P increases with decreasing HZO nanoparticle size. The influence of Al and La doping on Pr?in HfO2 nanoparticles is also studied. The exhibiting of the ferroelectricity in ion doped HfO2 is due to a phase transformation and to an internal strain effect. The observed results are in good qualitative agreement with the experimental data.

ZrO_2-CuO复合纳米粒子薄膜阻变特性研究

利用水热法在180℃下制备ZrO_2-CuO复合纳米粒子(ZrCu),XRD测试表明随CuO含量增加,样品的结晶性变好。在ITO基片上旋涂制膜,通过GaIn微滴技术测试伏安特性,研究了复合比对ZrCu薄膜电学特性的影响。结果发现,ZrCu有良好可重复的双极阻变特性,随CuO含量增加,阈值电压降低,开关比降低。ZrCu低阻态符合欧姆特性,高阻态为空间电荷限制导电机制,阻变机理为氧空位细丝的形成与断裂。第一性原理计算结果与实验观察一致。

表面修饰ZrO_2纳米微粒的结构表征及摩擦学行为研究(英文)

采用XPS,FTIR,DSC,TGA等多种现代分析手段表征了硬脂酸修饰ZrO2 纳米微粒的结构.在四球摩擦磨损试验机上,首次评价了表面修饰ZrO2 纳米微粒用作润滑油添加剂的摩擦学性能,结果表明ZrO2

碱液回流老化ZrO(OH)_2制备纳米晶ZrO_2的影响因素

通过考察回流老化所用的碱液 (NH4OH ,NaOH和KOH)介质和容器材质 (玻璃和Teflon)对ZrO(OH) 2 凝胶及其焙烧产物ZrO2 的织构 /结构和热稳定性的影响 ,研究了杂质元素掺杂和凝胶溶解 -再沉淀等因素在形成高表面积纳米晶ZrO(OH) 2 /ZrO2 过程中的作用 .在Teflon容器中 ,以NH4OH为介质 (pH =11.5 )的回流老化对ZrO(OH) 2 /ZrO2 的性质无明显影响 .而使用玻璃容器则可显著提高ZrO(OH) 2 /ZrO2 的表面积、孔容和抗烧结性质 ,并在 80 0℃获得小晶粒 (5～ 7nm)四方晶相ZrO2 纳米晶材料 ;在DTA曲线上ZrO(OH) 2 转变成ZrO2 晶体的温度由回流老化前的 463℃提高到 810～ 840℃ .在以KOH和NaOH为介质 (pH =13 )的实验中 ,使用玻璃容器得到与以NH4OH为介质时相类似的结果 ;但在Teflon容器中只形成低表面积和较大尺寸 (约 2 0nm)以单斜相为主的混合晶相ZrO(OH) 2 ,其在 80 0℃焙烧后形成大晶粒 (3 5nm)单斜相ZrO2 .样品的元素分析结果清楚地揭示出使用玻璃容器时有SiO2 从器壁溶解掺杂进入ZrO(OH) 2 凝胶 .样品的表面积和孔容与杂质Si4+ 含量之间有顺变关系 ,表明Si4+ 掺杂是形成高表面积和大孔容ZrO(OH) 2 /ZrO2 、提高ZrO2 晶化温度以及稳定小晶粒四方晶相ZrO2 的最主要因素 .在不发生Si4+ 掺杂前提下 ,K+ 和Na+ 的?

表面修饰ZrO_2纳米微粒的合成及结构表征(英文)

在溶液中化学合成了硬脂酸修饰ZrO2 纳米微粒 ,采用XRD、TEM和EA表征了ZrO2 纳米微粒的结构 ,结果表明成功合成了表面包覆硬脂酸分子的ZrO2 纳米微粒。

Au/ZrO_2催化剂中ZrO_2的尺寸效应:1,3-丁二烯加氢反应

在不同温度 (673～ 1 0 73 K)下 ,于流动 N2 气中焙烧 Zr O(OH) 2 醇 (乙醇 )凝胶 ,制备了不同尺寸的Zr O2 -AN纳米晶 (6～ 3 0 nm) .采用沉积 -沉淀方法制备了相应的质量分数为 0 .7%的 Au/Zr O2 -AN催化剂 .用 XRD,XRF,TEM/HRTEM,EDS,N2 吸附和 1 ,3 -丁二烯加氢反应对 Zr O2 -AN和 Au/Zr O2 -AN催化剂进行了表征 .结果表明 ,在所有的 Au/Zr O2 -AN样品中 ,Au粒子的平均尺寸为 4～ 5 nm,Zr O2 -AN的颗粒大小没有因为负载 Au粒子而发生改变 . 1 ,3 -丁二烯在 Au/Zr O2 -AN催化剂催化下能以 1 0 0 %的选择性进行加氢反应生成单烯烃 .随着 Au/Zr O2 -AN催化剂中 Zr O2 -AN纳米晶尺寸的增加或“载体”焙烧温度的升高 ,1 ,3 -丁二烯的转化率明显降低 ;1 -丁烯的选择性先增加后减小 ,2 -丁烯中反 /顺异构体的摩尔比在 0 .5～ 1 .0的范围内逐渐增大 ,TEM/HRTEM表征结果清楚地表明 ,Au/Zr O2 -AN催化剂中 Au粒子与 Zr O2 -AN颗粒接触界面 /周边随 Zr O2 -AN颗粒尺寸的减小而明显增加 ,这很可能是含有更小尺寸 Zr O2 -AN纳米粒子的Au/Zr O2 -AN催化剂具有更高的催化活性的重要原因 .

用不同表面活性剂制备纳米ZrO_2粉体的TEM分析

本文借助于透射电镜 (TEM)等分析手段 ,研究了表面活性剂PEG、PMAA、P1 2 3在化学沉淀法制备纳米ZrO2 粉体中的作用。结果表明 :在沉淀反应初期 ,表面活性剂可有效抑制沉淀的长大 ;随反应的进行 ,沉淀产物形成网络状结构 ,结构的形态与表面活性剂的种类有关 ;水洗后 ,吸附在颗粒表面的表面活性剂有助于抑制干燥引起的团聚 ;P1 2

微波合成非晶形ZrO_2纳米粒子

在Zr(NO3) 4·5H2 O、聚乙二醇 (PEG)和脲的水溶液中 ,通过微波加热合成了约 8nm的非晶形ZrO2 纳米粒子 ,并用XRD、TEM进行了表征。

介孔Au/ZrO2复合薄膜的制备及其三阶非线性光学性能(英文)

以尿素为沉淀剂,通过沉积沉淀的方法,制备了高分散的金纳米颗粒负载的介孔氧化锆薄膜;以1064 nm激光为入射光束,通过Z扫描实验测试了复合薄膜的非线性光学折射和吸收,并计算了复合薄膜的非共振三阶非线性光学极化率（~10-10esu）,金纳米颗粒的高分散性和氧化锆薄膜衬底的高线性折射率使复合薄膜显示了增强的三阶非线性极化率.

纳米ZrO_2的性能及其气敏性的研究

本文用沉淀法制备出平均晶粒尺寸在 18nm的单斜相ZrO2 纳米粉末。并对其的形状和大小进行了透射电镜及激光散射分析 ,确认ZrO2 粒子为球形 ,分散性较好 ,平均粒径约 70～ 80nm。本文着重研究了纳米级ZrO2 细粉对乙醇的气敏性能 ,结果表明 ,用纳米级ZrO2 粒子制备的气敏元件对乙醇气体有好的敏感性 ,并且随着纳米粒子尺寸降低 。

Crystalline texture evolution, control of the tribocorrosion behavior, and significant enhancement of the abrasion properties of a Ni-P nanocomposite coating enhanced by zirconia nanoparticles

This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties,crystalline texture developments,and tribocorrosion behavior of Ni-P nanostructured coatings.In the investigation,Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),cyclic-static polarization tests in 3.5wt%NaCl solution,the tribocorrosion test(by back-and-forth wear in electrochemical cell),and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings.The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance,the change of the wear mechanism from sheet to adhesive mode,the reduction of pitting corrosion resistance,significant reduction in the tribocorrosion protective properties,change in the preferred orientation of the crystalline texture coating from(111)to(200),increase in the sedimentation rate during the deposit process,and a sharp increase in the thickness of the Ni-P nanostructured coatings.

ZrO2/PMMA Nanocomposites： Preparation and Its Dispersion in Polymer Matrix

ZrO2/PMMA nanocomposite particles are synthesized through an in-situ free radical emulsion polymerization based on the silane coupling agent （Z-6030） modified ZrO2 nanoparticles, and the morphology, size and its distribution of nanocomposite particles are investigated. Scanning electron microscopy （SEM） images demonstrate that the methyl methacrylate （MMA） feeding rate has a significant effect on the particle size and morphology. When the MMA feeding rate decreases from 0.42 ml-min-1 to 0.08 ml. min-1, large particles （about 200-550.nm） will not form, and the size distribution become narrow （36-54 nm）. The average nanocomposite particles size increases from 34 nm to 55 nm, as the MMA/ZrO2 nanoparticles mass ratio increased from 4 ： 1 to 16 ： 1. Regular spherical ZrO2/PMMA nanocomposite particles are synthesized when the emulsifier OP-10 concentration is 2 mg.m1-1. The nanocomposite particles could be mixed with VAc-VeoVa10 polymer matrix just by magnetic stirring to prepare the ZrOE/PMMA/VAc-VeoVal0 hybrid coatings. SEM and atomic force microscopy （AFM） photos reveal that the distribution of the ZrO2/PMMA nanocomposite particles in the VAc-VeoVal0 polymer matrix is homogenous and stable. Here, the grafted-PMMA polymer on ZrO2 nanoparticles plays as a bridge which effectively connects the ZrO2 nanoparticles and the VAc-VeoVal0 polymer matrix with improved comparability. In consequence, the hybrid coating with good dispersion stability is obtained.

Zr（Ⅳ） surface sites determine CH3OH formation rate on Cu/ZrO2/SiO2-CO2 hydrogenation catalysts

Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.

Fabrication and Studying the Mechanical Properties of A356 Alloy Reinforced with Al₂O₃-10% Vol. ZrO₂Nano-particles through Stir Casting

Al2O3-ZrO2 with a high level of hardness and toughness is known as ceramic steel. Due to its unique properties it can be used as a reinforcement in fabrication of metal matrix composites. In this study, nanoparticles of Al2O3-10% ZrO2 with an average size of 80 nm were used to fabricate Al matrix composites containing 0.5, 1, 1.5 and 2 wt.% of the reinforcement. The fabrication route was stir casting at 850?C. There is no report about usage of this reinforcement in fabrication of composites in the literature. The microstructures of the as-cast composites were studied by scanning electron microscope (SEM). Density measurement, hardness and tensile properties were carried out to identify the mechanical properties of the composites. The results revealed that with increasing the reinforcement content, density decreased while yield, ultimate tensile strength and compressive strength increased. Also, hardness increased by increasing the reinforcement content up to 1 wt.% Al2O3-10% ZrO2 but it decreased in the samples containing higher amounts of reinforcement.