Magnetoelectric CoFe2O4/Pb(Zr0.53Ti0.47)O3 composite thin films of 2-2 type structure derived by a sol-gel process

CoFe₂O₄/Pb(Zr_0.53Ti_0.47)O₃ (CFO/PZT) magnetoelectric composite thin films of 2-2 type structure have been prepared onto Pt/Ti/SiO₂/Si substrate by a sol-gel process and spin coating technique. The optimal annealing process of composite thin films was determined by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It is found that the amount of the citric acid and concentration of CFO starting precursor solution have great impact on morphologies of composite thin films. Subsequent scanning electron microscopy (SEM) investigations show that the prepared thin films exhibit good morphologies and compact structure, and cross-sectional micrographs clearly display a multilayered nanostructure of multilayered thin films. The purpose of this work is to determine the optimal annealing processes of composite thin films and to prepare magnetoelectric composite thin films with good microstructure. It is shown that the films exhibit both good magnetic and ferroelectric properties, as well as a magnetoelectric effect.     

Microstructure Characterization of the FeAl<Subscript>2</Subscript>O<Subscript>4</Subscript>-Based Nanostructured Composite Coating Synthesized by Plasma Spraying Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al Powders

The microstructure of the coating prepared by reactive plasma spraying Fe₂O₃/Al composite powders was characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicated that the coating exhibited nanostructured microstructure which consisted of FeAl₂O₄, Fe or Fe solid solution, Al₂O₃ and a little FeAl. In the composite coating, spherical Fe particles (tens of nanometers to hundreds of nanometers) were distributed uniformly within the equiaxed and columnar nanograins FeAl₂O₄ matrix. There were two kinds of Al₂O₃ phases present in the composite coating. One kind was nano-sized Al₂O₃ particles uniformly dispersed within the matrix, forming eutectic structure of (FeAl₂O₄ + γ-Al₂O₃); the other was 1-1.5 μm Al₂O₃ particles embedded individually within the matrix. The composite coating had higher toughness than the conventional microstructured Al₂O₃ coating.     

反应等离子喷涂 Al2O3-TiB2-Al 复相涂层的反应机理

目的在铝合金表面制备Al2O3-TiB2-Al复合涂层,研究Al,TiO2,B2O3在等离子喷涂中的反应机理。方法采用反应等离子喷涂技术在铝合金表面制备复合涂层,应用扫描电镜与X射线衍射技术测试复合涂层的物相组成和显微组织,并通过燃烧波淬熄试验分析等离子喷涂产物。结果机械球磨可以有效降低粉末发生反应的活化能,等离子喷涂最佳飞行距离范围为150~200 mm。结论喷涂粉末在飞行过程中发生反应,经历了预热、熔化、分解、团聚等过程,验证了最终引燃发生燃烧化学反应的机理。     

Performance evaluation of laser surface alloyed hard nanostructured Al2O3-TiB2-TiN composite coatings with in-situ and ex-situ reinforcements

Hard and wear resistant Al₂O₃-TiB₂-TiN composite coatings have been developed on low carbon steel (AISI 1025) substrate by following two different routes involving laser surface treatment. In the first (termed ‘in-situ’ process), reinforcing phases TiB₂ and TiN, as well as the matrix Al₂O₃ of the composite are synthesized in-situ by laser-triggered self-propagating high temperature synthesis (SHS) from a mixture of Al, TiO₂ and h-BN and coated onto the substrate surface by laser surface alloying (LSA). In the second (termed ‘ex-situ’ process), the constituents Al₂O₃, TiB₂ and TiN of the coating are provided directly as a pre-placed precursor powder mix and laser surface alloyed onto the substrate. Of these two laser assisted manufacturing procedures, it is of interest to determine the one that is more appropriate for the development of a hard, wear resistant coating. In the present work, investigation of the comparative merits and demerits of Al₂O₃-TiB₂-TiN coatings produced by in-situ and ex-situ processes is attempted through analysis of microstructure and evaluation of mechanical and tribological properties.     

A study on mechanochemical behavior of B2O3–Al system to produce alumina-based nanocomposite

One possible route for producing the fine and homogenous distribution of hard particles in composite microstructure is the mechanochemical processing in which high-energy ball milling promotes the reaction in a mixture of reactive powders. In this study mechanochemical reaction of B₂O₃ and Al powder during ball milling was studied. The phase transformation and microstructure of powder particles during ball milling were investigated by X-ray diffractometry and scanning electron microscopy. The results showed that during ball milling the B₂O₃–Al reacted with a combustion mode producing Al₂O₃–AlB₁₂ nanocomposite. The crystallite size of Al₂O₃ and AlB₁₂ was 40 and 25 nm, respectively. This structure appeared to be stable upon annealing.     

Y2O3对原位自生TiC增强Ni基涂层组织和性能影响

采用氩弧熔覆的方法,以Ni60A自熔性合金粉末为粘结相,添加Ti粉、C粉和不同含量的稀土氧化物Y₂O₃,在16Mn钢基体上制备出TiC陶瓷颗粒增强金属基熔覆涂层. 运用XRD, SEM等手段对复合涂层的显微组织进行表征和分析,并对熔覆涂层的硬度及耐磨性进行了测试. 结果表明,适量添加Y₂O₃可以使涂层组织中枝晶的方向性减弱、同时细化涂层组织,使涂层组织更加均匀,涂层的硬度和耐磨性有显著提高. 添加2% Y₂O₃熔覆涂层的组织为最细,涂层具有较高的显微硬度和良好的耐磨性能.     

Preparation of nanostructured Ni/Al2O3 composite coatings in high magnetic field

Ni/Al₂O₃ composite coatings were prepared by a novel method from a modified Watt's type electrolyte containing nano-Al₂O₃ particles, where a high magnetic field was imposed in the direction parallel to an electrolytic current instead of mechanical agitation. Effects of magnetic field on the content of particles, surface morphology, microhardness and wear resistance of plating layer were investigated. It was found that the high magnetic field played an important role in the formation of composite coatings. The amounts of nano-Al₂O₃ particles in the composite coating increased with increasing of magnetic flux density and reached a maximum value at 8 T, then reduced slightly. The microhardness and wear resistance of the nanocomposite coatings also enhanced with increasing of magnetic flux density as compared to that of pure Ni coating fabricated in the absence of magnetic field. That was because the co-deposited nano-Al₂O₃ particles were uniformly distributed in the Ni matrix and contributed to greatly increase the microhardness and wear resistance of the composite coatings. Moreover, the mechanism of action of high magnetic field was discussed preliminarily.     

Effect of applied current on the electrodeposited Ni-Al2O3 composite coatings

Nano-sized Al₂O₃ ceramic particles (50 nm) were co-deposited with nickel using electrodeposition technique to develop composite coatings. The coatings were produced in an aqueous nickel bath at different current densities and the research investigated the effect of applied current on microstructure and thickness of the coatings. The variation in some mechanical properties such as hardness, wear resistance, and the adhesive strength of the composite coatings is influenced by the applied current and this was also studied. The morphology of the coatings was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The hardness, wear resistance, and bond strength of the coatings were evaluated by Vickers micro-hardness test, pin-on-disc test, and tensile test, respectively. Results showed that the Al₂O₃ particles were uniformly distributed in the coatings, and the coatings deposited at a current density of 0.01 A/cm² was most favorable in achieving a maximum current efficiency which causes the co-deposition of a maximum amount of Al₂O₃ particles (4.3 wt.%) in the coatings. The increase in Al₂O₃ particles in the coatings increased the mechanical properties of the Ni-Al₂O₃ composite coatings by grain refining and dispersion strengthening mechanisms.     

等离子喷涂制备ZrB2/SiC/Ta2O5涂层抗烧蚀性能研究

为了提高C/C复合材料的抗烧蚀性能,通过等离子喷涂法在C/C表面制备了SiC/Al₂O₃内层和ZrB₂/SiC/Ta₂O₅外层的双层涂层,通过XRD,SEM和EDS分析了涂层烧蚀前后的物相组成、微观结构和成分分布。烧蚀前涂层表面没有裂纹并且内层与基体、内层与外层之间结合良好。元素Zr、Si、Ta在涂层表面的分布相近,涂层表面成分分布均匀性良好。通过氧乙炔火焰在1800 ℃下对涂层的抗烧蚀性能进行考核。烧蚀过程中形成的镶嵌结构有利于阻挡氧气的渗入,Ta-Si-O玻璃层的形成封填了涂层孔隙,对基体有良好的保护效果,涂层表现出了较好的抗烧蚀性能。     

Al2O3-nanodiamond composite coatings with high durability and hydrophobicity prepared by aerosol deposition

We attempted the room-temperature fabrication of Al₂O₃-based nanodiamond (ND) composite coating films on glass substrates by an aerosol deposition (AD) process to improve the anti-scratch and anti-smudge properties of the films. Submicron Al₂O₃ powder capable of fabricating transparent hard coating films was used as a base material for the starting powders, and ND treated by 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) was added to the Al₂O₃ to increase the hydrophobicity and anti-wear properties. The ND powder treated by PFOTES was mixed with the Al₂O₃ powder by ball milling to ratios of 0.01 wt.%, 0.03 wt.%, and 0.05 wt.% ND. The water contact angle (CA) of the Al₂O₃-ND composite coating films was increased as the ND ratio increased, and the maximum water CA among all the films was 110°. In contrast to the water CA, the Al₂O₃-ND composite coating films showed low transmittance values of below 50% at a wavelength of 550 nm due to the strong agglomeration of ND. To prevent the agglomeration of ND, the starting powders were mixed by attrition milling. As a result, Al₂O₃-ND composite coating films were produced that showed high transmittance values of close to 80%, even though the starting powder included 1.0 wt.% ND. In addition, the Al₂O₃-ND composite coating films had a high water CA of 109° and superior anti-wear properties compared to those of glass substrates.     

Hot corrosion of a novel NiO/NiFe2O4 composite coating thermally converted from the electroplated Ni–Fe alloy

A novel NiO/NiFe₂O₄ composite coating thermally converted from an electroplated Ni–Fe alloy was successfully fabricated. The composite coating consisted of a NiO matrix and homogeneously distributed criss-cross intragranular and intergranular NiFe₂O₄ precipitates, with a very dense and flat structure. The composite, compared to bare Ni metal, exhibited increased hot corrosion resistance under an atmosphere of Na₃AlF₆–AlF₃–CaF molten salts and air at 960 °C, mainly because of the dense structure and well-adhered, homogeneously dispersed intragranular and intergranular NiFe₂O₄ precipitates.     

Phase constituents and microstructure of laser cladding Al2O3/Ti3Al reinforced ceramic layer on titanium alloy

Laser cladding of the Fe₃Al + TiB₂/Al₂O₃ pre-placed alloy powder on Ti-6Al-4V alloy can form the Ti₃Al/Fe₃Al + TiB₂/Al₂O₃ ceramic layer, which can greatly increase wear resistance of titanium alloy. In this study, the Ti₃Al/Fe₃Al + TiB₂/Al₂O₃ ceramic layer has been researched by means of electron probe, X-ray diffraction, scanning electron microscope and micro-analyzer. In cladding process, Al₂O₃ can react with TiB₂ leading to formation of amount of Ti₃Al and B. This principle can be used to improve the Fe₃Al + TiB₂ laser cladded coating, it was found that with addition of Al₂O₃, the microstructure performance and micro-hardness of the coating was obviously improved due to the action of the Al-Ti-B system and hard phases.     

Microwave-assisted synthesis and characterization of Nd1.5Mg17Ni0.5-Fe3O4 hydrogen storage composite

This work reports the preparation of Nd_1.5Mg₁₇Ni_0.5-Fe₃O₄ hydrogen storage composite in a single mode 2.45 GHz microwave cavity. The physicochemical properties (thermodynamic and kinetic characteristics, hydrogen absorption/desorption properties, thermal behavior, phase composition and morphology) were characterized by pressure-composition isotherms, differential scanning calorimetry, X-ray diffraction, scanning electron microscope with an energy dispersive X-ray spectrometer, transmission electron microscopy, and laser granulometry. The proposed microwave synthesis, in contrast with conventional sintering method, offers rapid heating, makes homogenous composition and hence improves the hydrogen storage properties of the composite.     

Al2O3-ZrO2 mixed oxide composite incorporated aluminium rich zinc coatings for high wear resistance

Corrosion resistance and wear resistance are the two important parameters for high performance of zinc galvanic coating. In the present work, the improvement of these two characteristics was achieved by the incorporation of Al₂O₃-ZrO₂ mixed oxide composite in the coating. Al₂O₃-ZrO₂ mixed oxide composite was synthesized from ZrOCl₂·8H₂O. Aluminium rich zinc coatings with high sliding wear resistance was developed from a galvanic bath containing the mixed oxide. Based on the performance of the coating during physicochemical and electrochemical characterization, the concentration of mixed oxide composite in the bath was optimized as 0.50 wt% Al₂O₃-0.50 wt% ZrO₂. While rich in Al-metal content in the coating caused high corrosion resistance, the incorporation of the mixed oxide improved structural characteristics of the coating resulting in high wear resistance also. The coating was nonporous in nature and even the interior layers had high stability. The coatings have potential scope for high industrial utility.     

Characteristic of AlON-Al2O3 coatings on Al6061 alloy by electrolytic plasma processing in aluminate and nitride electrolytes

In this work, 6061 series aluminum alloy is used as the matrix material for its wide application in engineering to make AlON coating layers by the electrolytic plasma processing (EPP) method. The experimental electrolytes include: 10 g/L NaAlO₂ as alumina formative agent, 2 g/L NaOH as the electrolytic conductive agent, 0.4 g/L NaNO₃ as a nitride supply agent. A combined composition and structure analysis of the coating layer was carried out by X-ray diffractometer (XRD) and scanning electron microscopy (SEM) for the specimens EPP-treated at 25 °C in 5 to 30 min under a hybrid voltage of 260 V DC plus AC 50 Hz power supplies (200 V). In addition, microhardness values were measured to correlate the evolution of microstructure and resulting mechanical properties. A composite of AlON-Al₂O₃ coating was formed as a result of a reactive process between Al in the alloy itself and O-N supplied by the electrolyte, which presents high hardness and anti-abrasion behaviors.     

Improvement in the properties of nickel by nano-Cr2O3 incorporation

Nano-ceramic composite coatings were prepared by the electrodeposition method using sulphamate electrolyte. Nickel was chosen as the metal matrix and nano-Cr₂O₃ particles were chosen as the reinforcement. The surface morphology and the particle distribution in the coating were analysed using field emission scanning electron microscope (FESEM). The particle content was obtained using energy dispersive X-ray analysis (EDAX). A change in the surface morphology of Ni was seen on the incorporation of Cr₂O₃ particles. The coatings were characterized for their structure and no change in the diffraction pattern was seen between plain Ni and Ni-Cr₂O₃ composite. The mechanical property like microhardness and tribological behaviour of the nano-composite coatings was studied and it was observed that the incorporation of Cr₂O₃ particles enhanced the mechanical properties of Ni matrix. The nano-composites were analysed for their thermal stability and corrosion resistance. An improvement in thermal stability was observed but no change in the corrosion behaviour of Ni was seen on the incorporation of nano chromium oxide particles.     

钛合金表面氩弧熔覆原位合成TiB2-TiN涂层组织及耐磨性能

以BN和Ni60A合金粉末为熔覆材料,采用氩弧熔覆技术在TCA合金表面原位合成TiB2-TiN增强颗粒耐磨涂层．利用x射线衍射仪、扫描电子显微镜和摩擦磨损试验机对熔覆层的组织和性能进行分析测试．结果表明,复合涂层的显微组织沿层深方向分为熔覆区、结合区和热影响区;熔覆层与基体呈良好冶金结合,TiB2-TiN颗粒弥散分布,...     

Formation of Al2O3-Bi4Ti3O12 nanocomposite oxide films on low-voltage etched aluminum foil by sol-gel processing

A water-based bismuth titanate Bi₄Ti₃O₁₂ (BTO) sol was synthesized by mixing bismuth nitrate, tetra-n-butyl titanate, lactic acid, acetic acid and distilled water. The sol was applied to low-voltage etched aluminum foil by dip-coating. The crystallization process of Bi₄Ti₃O₁₂ on low-voltage etched aluminum foil was measured by thermal gravimetry-differential scanning calorimetry (TG-DSC) and high-temperature X-ray diffraction (HT-XRD). It was found that Bi₄Ti₃O₁₂ sol first converted into intermediate phase Bi_1.74Ti₂O_6.624, then transformed into perovskite phase Bi₄Ti₃O₁₂. After annealed at 600 °C for 30 min in air, the low-voltage etched aluminum foil covered with Bi₄Ti₃O₁₂ sol was anodized galvanostatically in 15 wt.% ammonium adipate solution. The voltage-time variation during anodizing was monitored and recorded. The structure and composition of samples were investigated by field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDAX). Results showed that the anodic composite oxide film was composed of an inner Al₂O₃ layer and an outer Bi₄Ti₃O₁₂ layer. The specific capacitance and the product of specific capacitance and withstanding voltage of samples with a BTO coating were about 56.64% and 43.77% larger than that without a BTO coating.     

氩弧熔敷原位合成TiC-TiB2/Ti基复合涂层组织及性能分析

利用氩弧熔敷技术,在TC4合金表面原位合成了TiC-TiB₂增强镍基复合材料涂层,利用SEM和XRD等方法分析了涂层的显微组织并测试了涂层的显微硬度.结果表明,熔敷组织主要由TiC,TiB₂和Ti(Ni,Cr)组成,TiB₂主要以棒状形式存在;在所形成的TiC-TiB₂/Ti复合材料层中,TiC和TiB₂颗粒分布均匀且尺寸细小;熔敷涂层由表及里组织不同;熔敷层与基体呈冶金结合,无气孔、裂纹等缺陷;涂层的显微硬度达到13.8 GPa,较基体提高了4.5倍.