High-purity Powder Research Articles

Glycine/sucrose-based solution combustion synthesis of high-purity LiMn2O4 with improved yield as cathode materials for lithium-ion batteries

Single-phase, high-purity nanosized LiMn2O4 powders, which are employed as cathode materials for lithium-ion batteries, were produced by solution combustion synthesis using glycine, sucrose, and nitrate, followed by calcination. Phase structure and morphology of the powders were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performance was measured by galvanostatic charge–discharge cycling in a voltage range of 3.2–4.4V. The analysis of yield, morphology, and electrochemical performance mainly focused on the influence of different glycine/sucrose ratios. Compared to the sample obtained using 100% glycine, the yields of powders obtained by adding sucrose to the fuel were remarkably improved, from around 50% to over 90%. The highest discharge capacity at 1C was obtained for the sample with 2% added sucrose, which retained a capacity of 116.6mAh/g after 80 cycles.

Study on Preparation Technology of Nickel Powder with Liquid Phase Reduction Method

Ultrafine nickel powder was prepared without dispersant by liquid phase reduction method. The hydrazine hydrate was used as the reductant, the nickel sulfate as the raw material and NaOH was the pH regulator. The influences of the reaction temperature, pH, concentration of Ni2+ ions, mole ratio of N2H4·H2O/Ni2+ on the particle size, the morphology and the dispersion of nickel powder were studied. The samples were characterized by the scanning electron microscope (SEM), X-ray diffraction (XRD), laser particle size analysis etc. The results show that the high purity and spherical nickel powder with face-centered cubic structure can be prepared when the temperature is 80 C, pH is 11, the concentration of Ni2+ ions is 0.5 mol/L, the mole ratio of N2H4·H2O/Ni2+is 4. The average particle size of nickel powder is about 400 nm.

Combustion synthesis process for the rapid preparation of high-purity SrO powders

Abstract A rapid, safe and simple technique for the production of high purity strontium oxide powders via a chemical combustion process is reported. The combustion reactions were performed to optimize the fuel to oxidizer ratios in the reaction mixtures required to obtain pure SrO powders by varying the molar ratio of chemical precursors and the temperature. The synthesized powders were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and N2-physisorption measurements. The results indicate that crystalline SrO was obtained using a 1:1 strontium nitrate: urea molar ratio at 1000 °C after 5 minutes. In addition, high-purity, homogeneous and crystalline SrO powders were easily produced in a short time via a chemical combustion process.

Nanocrystalline Ti–Ni–Cu shape memory alloys: Metallurgical, mechanical and thermal properties

In this paper, the metallurgical properties, microhardness and thermal behavior of NiTiCu12 shape memory alloy were studied by means of X-ray diffractometry, scanning electron microscopy, microhardness measurements and differential scanning calorimetry. For this purpose, the nanocrystalline samples were prepared via mechanical alloying of high-purity elemental powders followed by heat treatment. Milling of powders was performed in a planetary high-energy ball mill in different milling condition. Annealing of milled samples was executed in a quartz tubes under high-vacuum. The experimental results indicated that during milling, the B2 phase with nanocrystalline uniform structure, grain size of 23 nm, and high microhardness of 861 HV can be obtained. Martensitic transformation during annealing occurred in a single-stage manner and thermal hysteresis was found to decrease. Annealing also resulted in larger crystallite size and decreased microhardness. • The mean crystallite size was found to be about 23 nm. • The microhardness of the powders increased with milling time. • Cu addition resulted in enhances the shape memory effect. • Martensitic transformation occurred in single manner.

Study of the formation of the apatite-type phases La9.33+x(SiO4)6O2+3x/2 synthesized from a lanthanum oxycarbonate La2O2CO3

Lanthanum silicated apatites with nominal composition La9.33+x(SiO4)6O2+3x/2 (−0.2 < x < 0.27) have been successfully synthesized by solid state reaction using a new reagent La2O2CO3 and amorphous SiO2 precursors. The formation mechanism of La2O2CO3 reagent, which cannot be purchased, has been followed by in-situ temperature depend XRD of La2O3 under CO2 atmosphere. The stability of this reagent during the synthesis step allowed to limit the formation of secondary phase La2Si2O7 and made the weighting of the reagent easier. High purity powders could be synthesized at the temperature of 1400 °C. Dense pellets (more than 98.5%) were obtained by isostatic pressing of powders calcined at 1200 °C and then sintered at 1550 °C. Traces of La2SiO5 secondary phase present in synthesized powder disappeared after densification and pure oxyapatite materials were obtained for all the compositions. Electrical measurements confirmed that conductivity behaviors of the sintered pellets were dependent to the oxygen over-stoichiometry. Indeed, a relatively high conductivity of 1 × 10−2 S cm−1 was exhibited at 800 °C for the nominal composition La9.60(SiO4)6O2.405 with low activation energy around 0.79 eV. The ionic conductivity properties were comparable with that of the earlier obtained materials.

Phase equilibria studies of the “MnO”–Al2O3–SiO2 system in equilibrium with metallic alloy. Part 1: Development of the technique and determination of liquidus isotherms between 1 423 K and 1 523 K

Abstract Phase equilibria in the “MnO”–Al2O3–SiO2 pseudo-ternary system in equilibrium with metallic alloy have been experimentally investigated in the temperature range from 1 423 K to 1 523 K. This study is a part of a broader research program on the phase equilibria in the Al2O3–CaO–Li2O–“MnO”–SiO2 system, which is of importance to the slags used in a novel pyrometallurgical process for recycling of electric car batteries. The experimental procedures involve equilibration of high purity powder mixtures at high temperatures, rapid quenching, and accurate measurement of phase compositions using electron probe X-ray microanalysis, which allow the slag liquidus temperatures to be determined. This paper is part 1 of a series of two papers and focuses on the improvement of the experimental methodology. A number of elementary reactions taking place in the samples have been identified, including the formation of a tridymite ring around the alloy particles, manganese oxidation and manganese vaporization. This enabled relevant modifications to the experimental methodology to be introduced. The liquidus at 1 423 K, 1 473 K and 1 523 K in the high silica area and the solid solubility data in the tridymite and rhodonite phases have been reported.

Study on manufacturing of recycled SiC powder from solar wafering sludge and its application

Slurry containing SiC powder and oil is used to cut ingots with a wire in a solar cell wafering process. The slurry, which is generally recycled due to its high price, produces a residue known as sludge during the recycling process. The sludge is mainly composed of SiC, Si, and oil. This study proposed a method to remove Si and oil from sludge to obtain a high-purity SiC powder of approximately 98.5% in an economically feasible manner. Additionally, this study utilized the recycled SiC powder to develop a porous SiC ceramic heat sink with thermal conductivity of about 10W/mK and showed that the heat sink can be used as an efficient apparatus to release heat of electronics.

Consolidation of different hydroxyapatite powders by SPS: Optimization of the sintering conditions and characterization of the obtained bulk products

The difference in purity, particle size, microstructure, and thermo-chemical stability of three commercially available hydroxyapatite powders are found to play an important role during their consolidation using spark plasma sintering (SPS) as well as strongly affect the characteristics of the resulting sintered bodies. A fully dense material without secondary phases was obtained by SPS at 900°C, when using the relatively small sized, with refined grains and high purity powders. The sintered product, consisting of sub-micrometer sized hydroxyapatite grains, displayed optical transparency and good mechanical properties.In contrast, the higher temperature levels (up to 1200°C) needed to sinter powders with larger particles, or finer ones which contain additional phases, lead to products with coarser microstructures and/or significant amount of β-TCP as a result of HAp decomposition. Optical characteristics, hardness and elastic modulus of the resulting sintered samples are correspondingly worsened.

NCM(Li[Ni,Co,Mn]O2)계 폐 리튬이차전지로부터 NiSO4의 회수와 이를 이용한 LiNiO2제조 및 전기화학적 특성

The electrochemical properties of cells assembled with the <TEX>$LiNiO_2$</TEX> (LNO) recycled from cathode materials of waste lithium secondary batteries (<TEX>$Li[Ni,Co,Mn]O_2$</TEX>), were evaluated in this study. The leaching, neutralization and solvent extraction process were applied to produce high-purity <TEX>$NiSO_4$</TEX> solution from waste lithium secondary batteries. High-purity NiO powder was then fabricated by the heat-treatment and mixing of the <TEX>$NiSO_4$</TEX> solution and <TEX>$H_2C_2O_4$</TEX>. Finally, <TEX>$LiNiO_2$</TEX> as a cathode material for lithium ion secondary batteries was synthesized by heat treatment and mixing of the NiO and <TEX>$Li_2CO_3$</TEX> powders. We assembled the cells using the <TEX>$LiNiO_2$</TEX> powders and evaluated the electrochemical properties. Subsequently, we evaluated the recycling possibility of the cathode materials for waste lithium secondary battery using the processes applied in this work.

Synthesis of compositionally different multicomponent metal-oxide films (SnO2) x (ZnO)1 − x (x = 1–0.5)

The study is concerned with high-purity SnO2 and ZnO powders produced from salt solutions of corresponding metals by low-temperature hydrothermal synthesis. Fragments of SnO2 and ZnO ceramic targets formed as 1 × 8 cm bars are fabricated by dry pressing. The bars are used to form composite targets for ion-beam sputtering and the fabrication of compositionally different (SnO2)x(ZnO)1 − x (x = 1–0.5) films appropriate for the production of gas sensors or transparent electronic devices. The optical and electrical parameters of the films with different compositions are studied.

Preparation of high-purity tellurium powder by hydrometallurgical method

This hydrometallurgical method consists of oxidation leaching, sulfide impurities removing, and sulfur dioxide reduction. The crude tellurium powder was treated by H2O2 oxidation for 2.0 h at pH 2.5 when adding 50 ml H2O2 (30 %) per 100 g raw material, a tellurium recover rate around 91 % is achieved. The tellurium leaching ratio can reach 98.9 % under 3.75 mol·L−1 NaOH concentration in liquid–solid ratio of 5:1 at 80 °C for 1.5 h. The overall separation of tellurium and other heavy metals is optimum at sulfide dosages of about 1.1 times of the theoretical values. The removal rates of Ag, Ni, Pb, and Cu from the solution are greater than 99.8 %, and As and Se removal rates are 98.6 % and 97.2 %, respectively. Over 99.5 % tellurium can be recovered by SO2 reaction when the operation is conducted at 85 °C in 6 mol·L−1 HCl solution. The tellurium powder with size of 99.999 % is obtained.

A two-stage reduction process for the production of high-purity ultrafine Ni particles in a micro-fluidized bed reactor

A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work. The raw ultrafine NiO particles are first pre-reduced using hydrogen at lower temperatures (340–400°C), followed by further reduction at higher temperatures (500–600°C). The self-agglomeration of Ni particles formed during low-temperature reduction decreases the sintering activity of the newly formed ultrafine Ni particles, leading to good fluidization quality, even for the subsequent high-temperature reduction process. The agglomerated Ni particles have a high Ni content (above 99wt%), a low density (0.78g/cm3) and a uniform particle size (approximately 100μm). A concept design for a novel two-stage fluidized bed reactor process used to produce high-purity Ni powder was also proposed. This approach may be extended to the synthesis of other ultrafine/nanosized metals or metal oxides through a fluidization method.

Experimental observation and theoretical calculation of magnetic properties in Fe-doped cubic SiC nanowires

Abstract Fe-doped SiC nanowires samples were fabricated using high-purity carbon nanotubes, SiO and Fe powders as starting materials. The surface morphology, microstructure and chemical composition of the samples were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results reveal that the samples crystallize with cubic structure and grow along the [1 1 1] direction. Results of magnetic measurement show the samples exhibit room temperature ferromagnetism without the formation of magnetic clusters. The saturation magnetization of the samples decreases with the increase of Fe concentration. From the first-principles calculations, it is strongly proposed that the magnetic state are depend on the distance between Fe dopant atoms. Combined the theoretical calculations with the experimental results, it is suggested that C vacancies play a vital role in determining the magnetic properties in Fe-doped SiC nanowires.

Phase-field simulation of platelike grain growth during sintering of alumina

Abstract The toughness of alumina can be improved by utilizing the in situ formation of platelike anisotropic grains during sintering, that is, abnormal grain growth (AGG). Computer simulations of AGG may be effective to realize the conditions for obtaining the desired self-composite microstructure. In the first part of this study, sintering experiments of high-purity alumina powders were conducted to confirm the effects of powder size distribution as well as the amounts of additives. In the second part, a phase-field method for simulating the platelike grain growth was proposed. The large platelike grains were reproduced when the critical driving force of coarsening was set up. The incubation time of AGG was also observed in the case of the narrow size distribution. Although the morphology of the platelike grains did not exactly agree with the experimental observations, a possibility of the present method as a computational tool for simulating platelike AGG was verified.

Advances in High-Purity Alumina and Resource Distribution

High-purity alumina has excellent performance and wide application in high-tech industries and areas of modern materials, so industrialized, low-cost, non-polluting and sustainable development preparation process has become one of the priorities of present high-purity alumina powder research. The use of high purity alumina and its major domestic craft preparation methods are described in the paper.

In vitro hemocompatibility and corrosion behavior of new Zr-binary alloys in whole human blood

Abstract The aim of this study is to evaluate the accuracy of three binary alloys’ composition, and their biocompatibility. Depending on the intended use of the medical devices made from these materials, dynamic or static tests should be performed. We have chosen static tests as we thought they may be used as knee or hip replacement, and not as cardiac valves. Three binary alloys ( Zr10Nb, Zr2.5Nb and Zr12Ta) were obtained from high purity powders (&gt;99.9%), using an induction furnace first, and an electric arc furnace for a perfect homogenization. Their final composition was verified with a XRF analyzer-INNOV-X. Hemolysis tests can determine the degree of red blood cells lysis and the release of hemoglobin. The released hemoglobin quantity was extremely small, under 2%, in all cases, and the coagulation tests showed no risk for thrombosis. The electrochemical behavior was also studied in biological fluid, human female serum, and showed a low corrosion rate. The obtained alloys do not cause hemolysis, so they are hemocompatible with all blood types.

Synthesis of Pure Dicalcium Silicate Powder by the Pechini Method and Characterization of Hydrated Cement

Calcium silicate (CS) is a main component of Portland cement and is responsible for the strength development. Recent research has shown that dicalcium silicate cement (CSC) is bioactive and is a potential candidate for bone replacement. Traditionally, dicalcium silicate powder is synthesized by a solid state reaction or a sol-gel method. The solid-state reaction, however, usually needs a higher temperature and a longer calcination time. Furthermore, the dicalcium silicate powder made by the sol-gel method is not pure, and contains a significant quantity of CaO which is harmful to the strength and biological properties of the CSC. The Pechini technique is an alternative, low temperature polymeric precursor route for synthesis of high purity powders. In this study, purer CS powder was synthesized via the Pechini method by calcination at 800°C for 3h. DSC-TGA, XRD, SEM were used for characterization of CS powder and the hydrated cement. The DSC-TGA curves showed that the main exothermic peak was at 479°C and the total mass loss was 79.2%. The XRD patterns of CSC after hydration for 7, 14, and 35 days illustrated that dicalcium silicate hydrate (Ca1.5SiO3.5·xH2O, C-S-H) was formed in the hardened CS paste. The XRD peaks on the diffraction pattern of the C-S-H of the day 35 sample were of greater intensity than those at day 7 and day 14. This demonstrates that the hydration speed was slow and complete hydration could take more than one month. Flake-like crystals were observed on scanning electron micrographs following hardening. The degradation study result showed that there was no mass loss of CSC after the samples were soaked into phosphate buffered saline (PBS) for 40 days. The silicon assay revealed that orthosilicic acid could be released from CSC after the samples were soaked in simulated body fluid (SBF). Silicon is known to be critical to skeletal mineralization. The existence of silicon may stimulate the proliferation of bone and activate cells to produce bone. Investigation of cell attachment confirmed that the MC-3T3 cells attached well to the surfaces of CSC after seeding.

Synthesis of Commercial Products from Copper Wire-Drawing Waste

Copper powder and copper sulfate pentahydrate were obtained from copper wire-drawing scale. The hydrometallurgical recycling process proposed in this article yields a high-purity copper powder and analytical grade copper sulfate pentahydrate. In the first stage of this process, the copper is dissolved in sulfuric acid media via dismutation of the scale. In the second stage, copper sulfate pentahydrate is precipitated using ethanol. Effects such as pH, reaction times, stirring speed, initial copper concentration, and ethanol/solution volume ratio were studied during the precipitation from solution reaction. The proposed method is technically straightforward and provides efficient recovery of Cu from wire-drawing scale.

Thermal Characteristics of Fused Silica Ceramic Waste and its Application in Casting Jewelry

Cristobalite SiO2 can be obtained from fused silica ceramic wastes formed at factories that make polycrystalline silicon, where fused silica is converted to cristobalite during the production of polycrystalline ingots. High-purity cristobalite powder is obtained by grinding these wastes. A study was made of the coefficient of linear thermal expansion of molds which are composed of cristobalite with a gypsum binder and are used to make jewelry. It was established that the thermal expansion which takes place during the transition to the cristobalite phase can effectively compensate for the shrinkage which the gypsum undergoes in the temperature range from 200 to 400°C. Experiments involving the casting of a copper alloy showed that the use of cristobalite can improve the thermal performance of molds employed in the production of jewelry.

유도결합 열 플라즈마를 이용한 고순도 질화알루미늄 나노 분말 합성

질화알루미늄(AlN)은 뛰어난 열적, 전기절연성 특성을 갖고 있어 반도체 기판용 재료나 전자 패키징 재료로 주목받고 있다. 질화알루미늄은 소결온도가 높고 불순물로 인한 물성저하 때문에 고순도화 및 나노원료화가 필수적이다. 본 연구에서는 RF 유도결합 열플라즈마를 이용하여 알루미늄 분말로부터 고순도의 질화알루미늄 나노분말을 합성하였다. Sheath gas로 사용된 암모니아의 유량 제어를 통해 고순도의 질화알루미늄 나노분말이 합성되는 조건을 확립하고자 하였으며 합성된 분말은 XRD, SEM, TEM, BET, FTIR, N-O분석을 통해 특성분석을 진행하였다. Aluminum nitride, which has outstanding properties such as high thermal conductivity and electrical resistivity, has been received a great attention as a substrate and packaging material of semiconductor devices. Since aluminum nitride has a high sintering temperature of 2173 K and its properties depends on the impurity level, it is necessary to synthesize high-purity and nano-sized aluminum nitride powders for the applications. In this research, we synthesized high purity aluminum nitride nanopowders from aluminum using RF induction thermal plasma system. Sheath gas (NH3) flow was controlled to establish the synthesis condition of high purity aluminum nitride nanopowders. The obtained aluminum nitride nanopowders were evaluated by XRD, SEM, TEM, BET, FTIR and N-O analysis.