Synthesis of bis(indolyl) methanes using aluminiumoxide(acidic) in dry media

Heterogeneous catalyst aluminium oxide(acidic) is found to be an effective catalyst for the solvent-free condensation reaction of indole with aldehydes in microwave irradiation with shorter reaction time and higher yields.

Corrosion resistance of waterborne epoxy coating pigmented by nano-sized aluminium powder on steel

A novel kind of waterborne epoxy coating pigmented by nano-sized aluminium powders on high strength steel was formulated. Several coatings with different pigment volume content (PVC) were prepared. The coating morphology was observed using scanning electron microscopy (SEM), and the electrochemical properties were investigated by electrochemical impedance spectroscopy (EIS). Immersion test and neutral salt spray test were also conducted to investigate the corrosion resistance of the coating. It is demonstrated that the critical pigment volume content (CPVC) value is between 30% and 40%. The coating with PVC of 30% exhibits good corrosion resistance in 3.5% (mass fraction) NaCl solution.

Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.

Mechanical and Abrasive Wear Properties of Anodic Oxide Layers Formed on Aluminium

Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications. The rickets microhardness, D （HV0.2）, and the abrasion weight loss, Wa （mg） were measured. Influence of oxalic acid concentration （Cox）, bath temperature （T） and anodic current density （J） on D and Wa has been examined, and the sulphuric acid concentration （Csul） was maintained at 100 g.L-1. It was found that high microhardness and abrasive wear resistance of oxide layers were produced under low temperatures and high current densities with the addition of oxalic acid. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy （SEM）, atomic force microscopy （AFM）, optical microscopy and glow-discharge optical emission spectroscopy （GDOES）. It was found that the chemistry of the anodizing electrolyte, temperature, and current density are the controlling factors of the mechanical properties of the anodic oxide layer.

Deposition of Aluminium Oxide Films by Pulsed Reactive Sputtering

Pulsed reactive sputtering is a novel process used to deposit some compound films, which are not deposited by traditional D.C. reactive sputtering easily. In this paper some experimental results about the deposition of Al oxide films by pulsed reactive sputtering are presented. The hysteresis phenomenon of the sputtering voltage and deposition rate with the change of oxygen flow during sputtering process are discussed.

Electrospark Coatings Based on WC-Co Alloys with Aluminium Oxide and Carbon Additives

The structure and properties of coatings based on WC-Co alloys containing additives of 1% - 5% aluminium oxide and 2.5% - 4.5% carbon were investigated. The coatings had a nanocrystalline structure. Depending on the duration and frequency of the discharge pulses, the ratio between WC and W2C in the coatings was different. The additives in the hard alloy allowed us increase the microhardness and wear resistance of the coatings by a factor of 2 - 3 in comparison to coatings created using a conventional WC-10%Co alloy.

Characteristics of Magnesium-iron-aluminium Composite Oxides and Their Influence on Properties of Magnesia-based Bricks

The composition,structure and micro-morphology of magnesium- iron- aluminum composite oxides were investigated using various methods such as XRF,SEM,EDS,XRD and KMn O4-titration. Compared to hercynite,the composite oxides have completely different phases including solid solution（ Mg O）0. 77（ Fe O）0. 23,composite spinel Mg Fe0. 2Al1. 8O4 and a small amount of Mg Fe2O4. The composite oxides exhibit excellent corrosion resistance to cement clinker and potassium salts.The products produced by magnesite and the composite oxides show better performance than magnesia- hercynite bricks,especially the corrosion resistance and thermal shock resistance.

Microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy by micro-arc oxidation

The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.

Optimizing the micro-arc oxidation (MAO) parameters to attain coatings with minimum porosity and maximum hardness on the friction stir welded AA6061 aluminium alloy welds

Micro-arc oxidation(MAO) technique is capable of producing dense oxide films on the aluminium alloy surface. This oxide film protects the aluminium alloy from the corrosion attack for longer duration.Empirical relationships were derived to evaluate the MAO coating properties(porosity and hardness) by incorporating very important MAO parameters(current density, inter-electrode distance and oxidation time). MAO parameters were also optimized to achieve coatings with minimum porosity and maximum hardness. Further, the effect of MAO parameters on coating characteristics was analysed. From the results, it is found that the current density has greater influence on the responses than the other two parameters.

Effect of nano-size nickel particles on wear resistance and high temperature oxidation resistance of ultrafine ceramic coating

In order to improve the wear resistance and high temperature oxidation resistance of titanium and titanium alloy, the high temperature ultra fine ceramic coating containing nano-size nickel particles was prepared by flow coat method on the surface of industrially pure titanium TB1-0. The effects of nano-size nickel particles on the wear resistance and high temperature oxidation resistance of coating substrate system were investigated through oxidation kinetics experiment and wear resistance test. The morphologies of the specimens were examined by means of optical microscopy, scanning electron microscopy and X-ray diffraction. The results show that the high temperature ultra fine ceramic coating has notable protection effect on industrially pure titanium TB1-0 from oxidation. The oxidation and wear resistance properties of the coating can be effectively improved by adding nano-size nickel particles. The oxidative mass gain of the specimen decreases from 11.33 mg·cm-2 to 5.25 mg·cm-2 and the friction coefficient decreases from 1.1 to 0.6 by adding nano-size nickel particles, and the coating containing 10% （mass fraction） nano-size nickel shows the optimum properties.

Research on the Impact of CeO2 -based Solid Solution Metal Oxide on Combustion Performance of Diesel Engine and Emissions

This paper mainly studies on the performance of high-speed diesel engines and emission reduction when the engine uses heavy oil mixed with nanometer-sized additives Ce0.9 Cu0.1 O2 and Ce0.9 Zr0.1 O2.During the test,Indiset 620 combustion analyzer made by AVL,was used to make a real-time survey on the cylinder pressure,the fuel ignition moment,and establish a relation between the change trend of temperature in cylinder and the crank angle.For the engine burning heavy oil and heavy oil mixed with additives,combustion analysis software Indicom and Concerto were used to analyze its combustion process and emission conditions.Experimental investigation shows that nano-sized complex oxide can improve the performance of diesel engine fueled with heavy oil,and reduce the emission of pollutants like NOx and CO,comparing it with the pure heavy oil.According to the consequences of this experiment,the additives improve the overall performance in the use of heavy oil.

Electrochemical anodic oxidation assisted fabrication of memristors

Owing to the advantages of simple structure,low power consumption and high-density integration,memristors or memristive devices are attracting increasing attention in the fields such as next generation non-volatile memories,neuromorphic computation and data encryption.However,the deposition of memristive films often requires expensive equipment,strict vacuum conditions,high energy consumption,and extended processing times.In contrast,electrochemical anodizing can produce metal oxide films quickly(e.g.10 s) under ambient conditions.By means of the anodizing technique,oxide films,oxide nanotubes,nanowires and nanodots can be fabricated to prepare memristors.Oxide film thickness,nanostructures,defect concentrations,etc,can be varied to regulate device performances by adjusting oxidation parameters such as voltage,current and time.Thus memristors fabricated by the anodic oxidation technique can achieve high device consistency,low variation,and ultrahigh yield rate.This article provides a comprehensive review of the research progress in the field of anodic oxidation assisted fabrication of memristors.Firstly,the principle of anodic oxidation is introduced;then,different types of memristors produced by anodic oxidation and their applications are presented;finally,features and challenges of anodic oxidation for memristor production are elaborated.

Structure and tensile/wear properties of microarc oxidation ceramic coatings on aluminium alloy

Thick and hard ceramic coatings were prepared on the Al-Cu-Mg alloy by microarc oxidation in alkali-silicate electrolytic solution. The thickness and microhardness of the oxide coatings were measured. The influence of current density on the growth rate of the coating was examined. The microstructure and phase composition of the coatings were investigated by means of scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Moreover, the tensile strength of the Al alloy before and after microarc oxidation treatment were tested, and the fractography and morphology of the oxide coatings were observed using scanning electron microscope. It is found that the current density considerably influences the growth rate of the microarc oxidation coatings. The oxide coating is mainly composed of α-Al2O3 and γ-Al2O3, while high content of Si is observed in the superficial layer of the coating. The cross-section microhardness of 120 μm thick coating reaches the maximum at distance of 35 μm from the substrate/coating interface. The tensile strength and elongation of the coated Al alloy significantly decrease with increasing coating thickness. The microarc oxidation coatings greatly improve the wear resistance of Al alloy, but have high friction coefficient which changes in the range of 0.70.8. Under grease lubricating, friction coefficient is only 0.15 and wear loss is less than 1/10 of the loss under dry friction.

Design and Analysis of MEMS Based Aluminum Nitride (AlN), Lithium Niobate (LiNbO₃) and Zinc Oxide (ZnO) Cantilever with Different Substrate Materials for Piezoelectric Vibration Energy Harvesters Using COMSOL Multiphysics Software

Interest in energy harvesters has grown rapidly over the last decade. The cantilever shaped piezoelectric energy harvesting beam is one of the most employed designs, due to its simplicity and flexibility for further performance enhancement. The research effort in the MEMS Piezoelectric vibration energy harvester designed using three types of cantilever materials, Lithium Niobate (LiNbO3), Aluminum Nitride (AlN) and Zinc Oxide (ZnO) with different substrate materials: aluminum, steel and silicon using COMSOL Multiphysics package were designed and analyzed. Voltage, mechanical power and electrical power versus frequency for different cantilever materials and substrates were modeled and simulated using Finite element method (FEM). The resonant frequencies of the LiNbO3/Al, AlN/Al and ZnO/Al systems were found to be 187.5 Hz, 279.5 Hz and 173.5 Hz, respectively. We found that ZnO/Al system yields optimum voltage and electrical power values of 8.2 V and 2.8 mW, respectively. For ZnO cantilever on aluminum, steel and silicon substrates, we found the resonant frequencies to be 173.5 Hz, 170 Hz and 175 Hz, respectively. Interestingly, ZnO/steel yields optimal voltage and electrical power values of 9.83 V and 4.02 mW, respectively. Furthermore, all systems were studied at different differentiate frequencies. We found that voltage and electrical power have increased as the acceleration has increased.

Influence of nano-SiC on microstructure and property of MAO coating formed on AZ91D magnesium alloy

Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy（SEM）, film thickness meter, X-ray diffraction （XRD）, energy disperse spectroscopy（EDS） and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy （EIS）. The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.

Wear and corrosion resistant coatings on surface of cast A356 aluminum alloy by plasma electrolytic oxidation in moderately concentrated aluminate electrolytes

Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte （for comparison） were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC （tungsten carbide） ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of -4.5×10^-7 mm3/（N· m）. A low corrosion current density of -8.81×10^-9 A/cm2 was also recorded. Despite low α-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.

Preparation and structure of microarc oxidation ceramic coatings containing ZrO2 grown on LY12 Al alloy

Ceramic coatings containing ZrO2 were prepared in situ on LY12 aluminum alloy by microarc oxidation（MAO） in the mixed solution of zirconate and phosphate solution.The phase composition and morphology of the coatings were studied by XRD and SEM,respectively.The growing mechanism of ceramic coatings was discussed in a preliminary manner.The results show that with an increase in MAO time,the compactness of the coating improved and the thickness increased.From the inner layer to the coating surface,the content of Zr increased,while the content of Al decreased.In addition,the coating was composed of m-ZrO2,t-ZrO2,and a little amount of γ-Al2O3.With an increase in reaction time,the relative content of t-ZrO2 within the coating sharply decreased while the relative content of m-ZrO2 sharply increased,and then both generally kept at a constant level after 60 min.

Recent advances in energy efficient PEO processing of aluminium alloys

Plasma electrolytic oxidation(PEO)coatings developed under voltage-controlled mode on various commercial wrought,gravity cast and rheocast aluminium alloys were discussed with respect to enhancement of their tribological and corrosionperformance and minimization of the PEO energy consumption.It is demonstrated that use of conventional porous anodic filmprecursors reduces the PEO energy consumption by up to50%.The wear of6082alloy with PEO coatings with addedα-Al2O3particles is two times lower compared with electrolytic hard chrome.The long-term corrosion resistance of the PEO-coatedA356rheocast alloy is enhanced via use of a precursor and hydrophobic post-treatment.

Improving the wear resistance of plasma electrolytic oxidation(PEO)coatings applied on Mg and its alloys under the addition of nano-and micro-sized additives into the electrolytes:A review

As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating.In this procedure,more efficient protection can be acquired via adding additives(in the form of particle,powder,sheet,etc.)into solutions and producing composite coatings.These additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness,hardness,and diminishing the porosity size and content.The efficiency of each additive can be changed owing to its intrinsic properties like melting point,size,participation type(reactive,partly reactive,or inert)and potential of zeta.In this review,the effects of distinct additives in nano-and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.

Corrosion resistance of micro-arc oxidized ceramic coating on cast hypereutectic alloy

The corrosion resistance of the micro-arc oxidation(MAO) ceramic coating on a cast Al-13Si-5Cu alloy was investigated using various electrochemical methods including electrochemical impedance spectroscopy(EIS) and polarization curves.Microstructures of MAO ceramic coating were studied by SEM,and the influence of microscopic patterns on corrosion resistance was analyzed.The corrosion resistance of the aluminum alloy can be improved significantly by MAO process owing to increasing impedance and corrosion potential and decreasing corrosion current,and the ceramic coatings are composed of loose layer,compact layer and transition layer,which improve the corrosion resistance.The corrosin resistance is determined by the thickness of the compact layer and is not proportional to the total thickness of MAO,though the latter is one of the important factors influencing the corrosin resistance.