Synthesis of photocatalytic TiO2 nanoparticles at low cost

Anatase TiO2 nanoparticles were synthesized by using HTiO3 as raw material and adopting TiOSO4 solution neutralizing process. The results show that the hydrolytic reaction temperature and time, molar ratio of urea to Ti precursors （R）, volume ratio of distilled water to the TiOSO4 solution （F） determine the yield of TiO2; the average crystalline size of TiO2 nanoparticles can be controlled through the sintering temperature and the optimum temperature is about 600 ℃; the TiO2 particles have good photocatalytic activity for decolorization of methyl orange.     

Preparation of doping titania antibacterial powder by ultrasonic spray pyrolysis

Doping titania powders were synthesized by ultrasonic spray pyrolysis method from an aqueous solution containing H2TiF6 and AgNO3. The effects of the processing parameters on particle size distribution, structure, and morphology of doping particles were investigated. The results show that aggregation-free spherical particles with average diameter of 200-600 nm are obtained and the particle size of the powder can be controlled by adjusting the concentration of solution. The experimental approach indicates that the size and the value of standard deviation of particle size increase from 210 nm to 450 nm and from 0.46 to 0.73 respectively with the increase of the titanic ion concentration from 0.05 to 0.4 mol/L. Composite TiOF2 is obtained when the pyrolysis temperature is set to be 400 ℃. With increasing pyrolysis temperature from 400 ℃ to 800 ℃, the crystal size of titania powders increases from 14.1 to 26.5 nm and TiOF2 content of powder decreases dramatically. The property of ion released from powder is affected significantly by the pyrolysis temperature, and the amount of fluorine ion and silver ion released from powder decrease with increasing pyrolysis temperature. The optical property of doping titania powders is not affected by pyrolysis temperature. Antibacterial test results show that composite powders containing more fluorine ions exhibit stronger antibacterial activity against E.coli.     

Effect of surfactants on preparation of nanometer TiO2 by pyrohydrolysis

The nanometer TiO2 was prepared by pyrohydrolysis with titanic solution.The effects of species and content of the surfactants on the particle size,morphology and phase of TiO2 were studied by using LPA,XRD and TEM respectively.The results show that it is beneficial to reducing the aggregation of TiO2 particles with adding surfactants to the solution.Nanometer TiO2 powders with the size of 40-55 nm are obtained by adding the anion surfactants in the optimal content of 1.5%(mass fraction).The effect of cationic surfactant for reducing particle aggregation is not as good as that of anion.The crystal phase constitutent of TiO2 is dependent on the temperature of thermal treatment and complete anatase can be achieved after calcining in the temperature range of 350-750℃.     

PREPARATION OF NANOMETER ZINC OXIDE BY EVAPORATION METHOD

Nanometer ZnO particles were synthesized by evaporating of zinc powders of averageparticle size of 370μm studied by XRD, TEM and electron diffraction. The particleswere formed by the oxidation of evaporated zinc vapor in the air. It was found that the particles range from 70 to 100nmin average particle size. The effect of experimental parameters was investigated, the increase of the air flow-rates reduced the average particle size, while increasing the evaporation temperature and the amount of metal charged increased the average particle size. TEM of the particles collected showed that the crystal habits of particles have a tetrapod-like of wurtzite structure consists of four needle crystals. It was found by electron diffraction that all particles were single crystal.     

Synthesis and electrochemical behavior of LiCoO2 recycled from incisors bound of Li-ion batteries

LiCoO2 was separated from AI foil with dimethyl acetamide（DMAC）, and then polyvinylidene fluoride（PVDF） and carbon powders in active material were eliminated by high temperature calcining. The content of the elements in the recovered powders were analyzed. Then the Li2CO3 was added in recycled powders to adjust molar ratio of Li to Co to 1.00, 1.03 and 1.05, respectively. The new LiCoO2 was obtained by calcining the mixture at 850 ℃ for 12 h in air. Structure and morphology of the recycled powders and resulted sample were observed by XRD and SEM technique, respectively. The layered structure of the LiCoO2 is improved with the decrease of molar ratio of Li to Co. The charge/discharge performance, and cyclic voltammograms performance were studied. The recycle-synthesized LiCoO2 powders, whose molar ratio of Li to Co is 1.0, is found to have the best characteristics as cathode material in terms of charge--discharge capacity and cycling performance. And the cyclic voltammograms（CV） curve shows the lithium extraction/insertion characteristics of the LiCoO2 well.     

STUDY ON NANOMETER ZINC PARTICLES FABRICATED BY GAS EVAPORATION METHOD

Nanometer Zn particles with mean diameters 12-100nm made by evaporating its powders in argon gas were studied mainly by X-ray diffraction and electron microscopy. They are collected at various distances and those factors influencing the mean particle size were studied. The optimal synthetic conditions were obtained, i.e., evaporation temperature is 1200℃; argon flow rate is 0.4m3/h; amount of powder charged is 3g; distance from evaporation source is 10cm. It was found that the size of particles was governed by argon flow rate, evaporation temperature, amount of metal charged and distance from the source. The size increases remarkably with distance in the space where no metal vapor exists. This implies that the crystallites grow by coalescence. Electron micrographs and diffraction patterns are reproduced to show the size, shape and state of oxidations. Nanoparticles with definite crystal habits were sometimes observed among those with irregular ones.     

Aging behavior of A1Np/2024A1 composites fabricated by squeeze casting

2024 aluminum matrix composites reinforced with different size AIN particles （0.5, 4 and 10 μm） were fabricated by the squeeze-casting technology. The aging behavior and microstructure of AINp/2024AI composites were investigated by Brinell hardness measurement and transmission electron microscopy （TEM）. The results show that the precipitation sequence of AINJ2024AI composites is similar to that of the matrix alloy aged at 160 and 190 ℃, but the age hardening rate of composites is improved, and the AIN particles with large size promote the precipitation process more obviously, in comparison with smaller AIN particles. With increasing temperature, the precipitation processes are accelerated, and the time to reach the peak hardness is shortened. The acceleration of the formation of GP region and phase S＇ in the composites is attributed to the interfaces （between particles and the matrix） and the high density of dislocations introduced by addition of AIN particles.     

Preparation of nickel nanoparticles in emulsion

The nickel nanoparticles with different sizes and spherical shape were prepared by the reduction of nickel sulfate with sodium borohydride in the water-in-oil emulsions of water/SDBS（sodium dodecylbenzene sulfonate）/n-pentanol/n-heptane. The effects of aging time, molar ratio of water to SDBS（R） and the concentration of nickel sulfate on the size of particles were studied. The samples were characterized by transmission electron microscopy（TEM） and inductively coupled plasma spectrometry（ICP）. The results show that the average particle size changes from 20 to 40 nm by adjusting aging time （15-30 min） and R （9-11.5）. The concentration of nickel sulfate of 1.0 mol/L is the favorite condition.     

Synthesis and characterization of tantalum nitride nanopowder prepared through homogeneous reaction

Tantalum nitride powders with particle size of 20--50 nm were prepared by the homogeneous reduction in liquid ammonia, and were treated at the temperature range from 500℃ to 1 170℃. The results of XRD analysis indicate that the powders heated up to 500℃ are in the form of amorphous. The powder heated at 600℃ tends to transform into crystal, the powder heated to temperatures higher than 700℃ is clearly of crystal. The results of surface area analysis by BET show that the surface area of the powder increases as the heating temperature increases, and reaches a maximum value of 21.8 m^2/g at the heating temperature around 700℃.     

Preparation of ZrO2 spherical nanometer powders by emulsion processing route

ZrO2 precursor powders containing 3% Y2O3 were prepared via a single emulsion processing route and a double emulsion processing route. In both routes xylol was used as the oil phase, span-80 as the surfactant, and an aqueous solution containing zirconium or ammonia as the water phase. The calcination of the precursor powders was performed at 600 ℃ for 2 h, leading to tetragonal phase ZrO2 nanometer powders. The ZrO2 powders and the precursor powders were analyzed and characterized by means of TGA-DTA, XRD, TEM, BET and laser particle size analyser. The results indicate that xylol-span-80-water phase system contain more water phase, which to a certain extent overcomes the disadvantages of low output by emulsion route in preparing powders. The best volume ratio Vxylol ： Vspan-80 ： Vwater= 95 ： 5 ： 25 leads to the attaining of powders. The special tetragonal phase powders with less agglomeration were prepared via either the single emulsion processing route or the double emulsion processing route according with the ratio. But compared to the single emulsion processing route, the powders prepared via the double emulsion processing route display smaller particles with more even size distribution, the average size of around 15 nm.     

Synthesis and characterization of aluminum particles coated with uniform silica shell

The silica coated aluminum composite particles were prepared by hydrolysis-condensation polymerization of tetraethylorthosilicate（TEOS） on the surface of aluminum particle. The structure, morphology, and properties of the silica coated aluminum were studied. The peaks of Si-O-Si are presented in the Fourier transform infrared （FT-IR） spectrum of the composite particles. The thickness of the silica shell is about 80 nm according to the results of transmission electron microscopy（TEM） and laser particle size analysis, while the mean diameter of the aluminum particle is 7.13 μm. The mass fraction of silica in the sample was determined by fluorescent X-ray spectrometry（XRF）. Result of the thermogravimetric analysis（TGA） indicates that thermal stability of silica coated aluminum particles is better than that of pure aluminum particles at low temperature while more reactive at high temperature.     

Preparation of antimony-doped nanoparticles by hydrothermal method

Antimony-doped tin oxide (ATO) nanoparticles were prepared by the mild hydrothermal method at 200℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3%and 5.1%(molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.     

Fabrication of micro-fine high Nb-containing TiAl alloyed powders by fluidized bed jet milling

A fluidized bed jet milling process was used to make micro-fine high Nb-containing TiAl alloyed powders from the chippings obtained by crushing the Ti-45Al-8.5Nb-(W,B,Y) ingot.The influences of classifier frequency on powder characteristics were investigated.The results show that the powders with controlled average particle size can be prepared on a large scale.The powders with different sizes are all dominated by γ with a minor amount of α2-Ti3Al.The particle size significantly decreases with the classifier frequency increasing.At a classifier frequency higher than 38 Hz,the average particle size of the ground powders is lower than 25 μm.The powders are composed of two different sizes of particles:shaped particles and some clastic particles,and both particle sizes meet the log-normal distribution.With the classifier frequency increasing,the both sizes decrease; meanwhile,the proportion of the clastic particles gradually increases,and the size distribution span value of the ground powders increases correspondingly.     

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.     

Synthesis and sintering of indium tin oxide nanoparticles by citrate-nitrate combustion method

Spherical indium tin oxide(ITO) nanoparticles were synthesized by combustion method using citric acid as fuel and nitrates as oxidizer.The obtained ITO nanoparticles were characterized by TG-DSC,FT-IR,XRD,BET,TEM,and SEM.The ITO nanoparticles grew steadily with the increase of heat treatment temperature,and the 700℃ calcined particles had a crystallite size of 25.3 nm and a specific surface area of 26.1 m2·g-1.The avoidance of chlorine ions in the synthesis process decreases particle agglomeration and promotes powder densification.The 900℃ sintered pellet had a density of 67.6% of theoretical density(TD) and increased steadily to 97.3% for the 1400℃ sintered ceramics,respectively.     

Manufacturing of cast A356 matrix composite reinforced with nano- to micrometer-sized SiC particles

In this study, large micron-sized Si C particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–Si C and Ni–Si C. Continuous fracturing of brittle Si C powders leads to the formation of multi-modalsized Si C powders with size of from 50 nm to slightly higher than 10 lm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine Si C particles by using iron and nickel as their carrier agents.The final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the36-h milled Ni–Si C mixture compared to that of Fe–Si C powders, leading to incorporation of Si C particles into the melt with a lower size and suitable distribution for the Ni–Si C mixture. It is found that lower-sized composite particles could release the fine Si C particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength(UTS) and yield strength(YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.     

Preparation of YAG：Ce^3＋ phosphor by sol-gel low temperature combustion method and its luminescent properties

YAG：Ce^3＋ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 ℃ by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG：Ce^3＋ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.     

Particle melting behavior during high-velocity oxygen fuel thermal spraying

Particle melting behavior during high-velocity oxygen fuel (HVOF) thermal spraying was investigated using Inconel 625 powders. The powder characteristics and coating properties were investigated using scanning electron microscopy (SEM), x-ray, and microhardness studies. Results indicated that the volume fraction of unmelted particles in the coatings was dependent on the proportion of powder within a specified size range, in these experiments, 30 to 50 μm. This particle size range was primarily determined by the particle temperature, which was measured during spraying. Particle temperature significantly decreased as particle size increased. The microhardness values for the coatings containing unmelted particles were predicted by a simple rule-of-mixtures equation for the case of a low volume fraction of unmelted particles. However, for the condition of high volume fraction of unmelted particles, the measured microhardness values did not compare favorably with the calculated values, probably due to the presence of porosity, which occurred in the form of voids found among unmelted particles. The microstructure and characteristics of the feedstock powder were retained in the corresponding coating under certain spray conditions.     

Synthesis of vanadium and chromium carbides(V_8C_7–Cr_3C_2) nanocomposite via an in situ precursor method

In situ synthesis method was used to prepare V8C7–Cr3C2nanocomposite.Ammonium vanadate, ammonium dichromate and nanometer carbon black were used as raw materials.The products were characterized by X-ray diffractometry(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), thermogravimetric and differential scanning calorimetry(TGDSC) and X-ray photoelectron spectroscopy(XPS) techniques.The results show that V8C7–Cr3C2nanocomposite with an average crystallite size of 25.4 nm can be synthesized at 1200 °C for 1 h.The synthesis temperature required by the method is at least 200 °C lower than that required by the conventional approaches for preparing vanadium and chromium carbides.The powders show good dispersion and are mainly composed of spherical or nearly spherical particles with a mean diameter of about 30 nm.The weight loss ratio of the precursor throughout the reaction process reaches 58 wt%.Three exothermic peaks and four endothermic peaks occur during the reaction.The surface of the specimen is mainly composed of V, Cr, C and O elements.     

Preparation of colloidal Sb2O5 from arsenic-alkali residue

The stable colloidal antimony pentoxide was prepared by oxidation of the mixture of Sb2O3 and Sb2O5 obtained from arsenic-alkali residue by hydrometallurgical process, with hydrogen peroxide as oxidant and phosphoric acid as stabilizer. Effects of main factors were investigated. The theories on thermodynamics, kinetics and electrical double layer（EDL） were used to analyze the experimental phenomena and results. The results show that no＇aging time is the most beneficial to forming colloid, when molar ratio of phosphoric acid to antimony is in the range from 0.8 to 1.0 and 1.0 to 1.3, the particle sizes of sol with the concentration of 10% and 15% antimony pentoxide by mass are both smaller. With increasing concentration of the mixture of antimony oxide from 10% to 20%, the reaction time decreases from 90 to about 30 min, but the optimized range of molar ratio of H3PO4 to antimony increases. The reaction temperature is not the main factor on particle size with the existence of H3PO4 in the temperaturd range from 60 to 90℃.