Fabrication of Ni-, Co- and NiCo-coated graphite microspheres by heterogeneous precipitation

The precursors with NiCO₃·2Ni(OH)₂·2H₂O, Co₂(OH)₂CO₃, or both NiCO₃·2Ni(OH)₂·2H₂O and Co₂(OH)₂CO₃ coated graphite microspheres were prepared respectively by the aqueous heterogeneous precipitation using nickel sulfate, cobalt nitrate, sodium carbonate, ammonium bicarbonate and graphite microspheres as the main starting materials. Subsequently, Ni-, Co- and NiCo-coated graphite microspheres were successfully obtained by thermal reduction of the as-prepared precursors at 500 °C for 2 h, respectively. These metal-coated graphite microspheres were characterized with a smooth, cohesive surface consisting of fine metallic particles. Optimized precipitation processing parameters of the concentration of graphite microspheres (10 g/L), the rate of adding reactants (3 mL/min) and pH value (8.0) were determined by a trial and error method. The thermal analysis of the precursors was investigated by TG. Powders of the precursors and the resultant metal-(Ni, Co and NiCo alloy) coated graphite microspheres were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Funded by the Post-graduate Innovation foundation of Jiangsu Province of China (No. CX07B_085z)     

Preparation and Characterization of Nanosized Hydroxyapatite Particles in AOT Inverse Microemulsion

1　IntroductionSynthetichydroxyapatite (HAP) ,whichisthemajorconstitutionofnaturalboneandteeth ,iswell knownasbiocompatibleandbioactivematerialthathasbeenwidelyusedinmanyclinicalapplications[1 3] .Forexample ,po roushydroxyapatitehasbeenusedinbone ingrow…     

Preparation of mullite whiskers and their enhancement effect on ceramic matrix composites

Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF3·3H2O. The as-prepared whiskers have been characterized systematically in terms of phase composition, morphology, and structure. Results showed that the morphology and size of mullite whiskers were strongly depended on the content of AlF3·3H2O and sintering temperature. At temperatures in the range of 1 100 to 1 500 ℃ with 4 wt% addition of AlF3·3H2O, the well-shaped mullite whiskers were obtained. For an instance, the mullite whiskers with 5-10 μm in length and 0.1-0.2 μm in cross-section could be formed at 1 400 ℃, with 4 wt% addition of AlF3·3H2O. Moreover, results showed that the addition of mullite whiskers into ceramic matrix enhanced its fracture toughness significantly.     

Modeling and estimation of the kinetics of seeded solvent-mediated phase transformation in a batch crystallizer

Modeling the kinetics of the preparing process is necessary to produce a product with the appropriate particle properties and minimum production cost.Owing to the lackness of crystal size distributor (CSD) information,however,solvent-mediated phase transformation encounters difficulty in modeling the kinetics as compared to solution crystallization.Consequently,a model was established by making the product CSD to move along by horizontal translation to obtain the CSDs of the stable phase in the process of transformation.Then the moment method was used to solve the popular balance equation,and the least square nonlinear regression method was applied to estimate the kinetics parameters.The model has been successfully used to simulate the transformation of CaSO4?2H2O to α-CaSO4?1/2H2O in an isothermal seeded batch crystallizer with different stirring speeds,and it is beneficial to producing high performance α-CaSO4?1/2H2O crystals which have the right particle characteristics.     

Study on Graphene Oxide Modified Inorganic Phase Change Materials and Their Packaging Behavior

We prepared the nano-inorganic phase-change "alloy" materials through the modification of Na_2SO_4·10H_2O using Na_2HPO_4·12H_2O and GO nano-nucleating agent, and further investigated their thermophysical properties such as melting/solidification temperatures and enthalpies via differential scanning calorimetry. When the weight ratio of Na_2SO_4·10H_2O and Na_2HPO_4·12H_2O was 8:2 and the weight ratio of graphene oxide was 0.5% of phase change material, the phase change "alloy" material showed excellent performances, specifically, the melting temperature and latent heat were found to be 22 ℃ and 190 J/g with a degree of subcooling decreased from 8.6℃ to 2.1℃. In order to extend the application of the phase change "alloy" material to building energy saving field, it was adsorbed on expanded glass beads under vacuum and further covered with diatomite. When the adsorption rate of EGB(volume) and PCAM(weight) was 2.5:1, the particle size of diatomaceous earth was found to be 3.6μm, while the best packaging result was obtained with the melting temperature and latent heat being 21℃ and 135 J/g, and no leakage was observed.     

Controlled preparation of monodisperse CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles by a facile method

CoFe2O4 nanoparticles (NPs) were synthesized by coprecipitation method using FeCl3·6H2O and CoCl2·6H2O as precursors.The synthesized conditions were optimized,such as added means of precipitator,quantity of precipitator,the mol ratio of Fe 3+ to Co2+,reaction temperature and pH value.The synthesized material was characterized by XRD,TEM,FTIR,EDS,Raman and its magnetic properties were studied by VSM.The experimental results confirm that the sample is cubic spinel structure CoFe2O4 with a narrow size distribution and a good dispersion feature.CoFe2O4 NPs with well-controlled shape and size was obtained at 70℃.The magnetic properties indicate superparamagnetic behavior and good saturated magnetization.     

Synthesis of γ-Al2O3 nanoparticles by chemical precipitation method

Highly pure active γ-Al₂O₃ nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al₂O₃ nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)₃ sols are produced by using 0.1 mol/L Al(NO₃)₃ · 9H₂O and 0.16 mol/L (NH₄)₂CO₃ · H₂O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 °C, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80°C for 8 h, final calcined at 800 °C for 1 h in the air, and high purity active γ-Al₂O₃ nanoparticles can be prepared with cubic in crystal system, O _H ⁷ -FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131. 35 m²/g in BET specific surface area, 7 – 11 nm in pore diameter, and not lower than 99.93% in purity. Foundation item: Project(03JJY3015) supported by the Natural Science Foundation of Hunan Province     

Synthesis of mesoporous chromium aluminophosphate (CrAlPO) via solid state reaction at low temperature

Mesoporous chromium aluminophosphate（CrAlPO）was successfully synthesized via solid state reaction（SSR）route at low temperature in the presence of a cationic surfactant cetyltrimethyl ammonium bromide（CTAB）and inorganic sources such as AlCl₃·6H₂O,CrCl₃·6H₂O and NaH₂PO₄·2H₂O.Characterizations by means of powder X-ray diffraction（XRD）,N₂ adsorption-desorption,high resolution transmission electron microscopy（HR-TEM）,scanning electron micrography（SEM）,energy dispersion spectroscopy（EDS）,thermo-gravimetry（TG）,Fourier transform infrared spectroscopy（FT-IR）,and ultraviolet visible light spectroscopy（UV-Vis）were carried out to understand both the pore characteristics and electron transition route of these obtained materials.The experimental results show that the meso-CrAlPO materials with various Cr/Al molar ratios possess a mesostructure and a specific surface area of 193 to 310 m² /g corresponding to an average pore size of 5.5 to 2.2 nm,respectively.The maxium content of Cr in meso-CrAlPO materials synthesized via SSR route can achieve 16.7wt%,being significantly higher than that of the meso-CrAlPO prepared via a conventional sol-gel route.Meanwhile,the formation mechanism of the meso-CrAlPO was also proposed.     

Synthesis and characterization of CePO4 nanorods via solvothermal process

One-dimensional cerium phosphate(CePO4) nanorods were successfully synthesized by a facile and simple solvothermal method at 150 ℃ for 12 h, using Ce(NO3)3·6H2O and NaH2PO4·2H2O as the starting materials. Phase and morphologie of the as-synthesized CePO4 products, characterized by XRD, FESEM, and TEM, were proved to be perfect and uniform hexagonal CePO4 nanorods with aspect ratio of more than 100. The photoluminescence(PL) spectrometer was used to investigate the optical properties of the assynthesized hexagonal CePO4 nanorods.     

Effect of CaCO3 on hydration characteristics of C3A

Hydration products and morphology characteristics of C₃A (tricalcium aluminate)-CaCO₃-H₂O system were studied by means of XRD, DSC, FTIR spectrum analysis and SEM. The results indicate that, the new phases, i.e., C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O and C₃A·CaCO₃·11H₂O are found in this system due to the activity of CaCO₃; the formation of C₄AH₁₃ and C₂AH₈ is prohibited and the generation of C₃AH₆ is delayed in the early hydration process. C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O is not stable and will be totally transferred within 24 h; C₃A·CaCO₃·11H₂O exists stably once formation, and its flake-like crystalline phases in the early hydration transform to long rod shape, and to finally fine-needle at 28 d.     

Mg<Subscript>2</Subscript>(OH)<Subscript>2</Subscript>CO<Subscript>3</Subscript>·3H<Subscript>2</Subscript>O whiskers growth mechanism

From the perspective of growth units, the growth mechanism of Mg₂(OH)₂CO₃·3H₂O whisker is investigated in this paper. Results show that the growth morphology of Mg₂(OH)₂CO₃·3H₂O whisker is consistent with the model of anion coordination polyhedron growth units. The growth solution Raman shift of Mg₂(OH)₂CO₃·3H₂O was monitored using Raman spectroscopy. The growth units are [Mg-(OH)₄]^2- and H₂CO₃. The growth process of Mg₂(OH)₂CO₃·3H₂O whisker is as follows: growth unit [Mg-(OH)₄]^2- first incorporates into the larger dimension [Mg-(OH)₄] _n ^2- , then the [Mg-(OH)₄] _n ^2- combines with H₂CO₃ into a linear skeleton Mg₂(OH)₂CO₃ in the same line. Mg₂(OH)₂CO₃ combines with H₂O by hydrogen bonds and ultimately transforms into Mg₂(OH)₂CO₃·3H₂O whisker. Magnesium carbonate whiskers have a layered structure, each of which is made of magnesium, carbon, oxygen, with H₂O in between each layer. When skeletons are superimposed within the same plane as a parallelepiped one, they grow into solid cuboid-shaped whiskers. When the parallelepiped skeletons planes combine with each other through the cascading links, they grow into hollow cylindrical whiskers.     

Spherical and radiate Ni particles prepared by the tartrate precipitation and thermal decomposition method

Nickel tartrate precursor particles were synthesized by the liquid phase precipitation method in an ethanol-water-ammonia mixed solution, with tartaric acid and using nickel chlorate as raw materials, with the pH value controlled at 4.0, and the temperature controlled at 50 °C. Nickel particles with complicated morphology were prepared by the decomposition of nickel taratrate precursor particles at temperatures of 360, 380 and 400 °C, respectively. The study of infrared spectroscopy (IR) indicated that the product was pure nickel tartrate. The studies of the atomic absorption spectrometry (AAS) and organic elemental analysis (OEA) indicated that the molar ratio of Ni²⁺ to (C₄H₄O₆)^2? is close to 1:1. The studies of the differential scanning calorimeter and thermo-gravimetric analysis (DSC-TG) indicated that the chemical formula Ni₂(C₄H₄O₆)₂·5H₂O was confirmed. The studies of X-ray diffractions (XRD) indicated that the silvery white metal powders were pure Ni, with a face-centered cubic crystal structure. The images of scanning electron microscopy (SEM) showed that the morphology of metal Ni particles was obvious spherical and radiate. The diameter of nickel tartrate particles was about 60 μm, which consisted of many nanolathes; and the diameter of metal Ni particles was about 30 μm, which consisted of many lathes about 0.5 μm in thickness.     

Electrochemical performance of LiFePO4/（C＋Fe2P） composite cathode material synthesized by sol-gel method

A LiFePO4/(C+Fe2P) composite cathode material was prepared by a sol-gel method using Fe(NO3)3·9H2O,LiAc·H2O,NH4H2PO4 and citric acid as raw materials,and the physical properties and electrochemical performance of the composite cathode material were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and electrochemical tests.The Fe2P content,morphology and electrochemical performance of LiFePO4/(C+Fe2P) composite depend on the calcination tempera...     

Electroless copper plating process of N, N, N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine system with high plating rate

Electroless copper plating process of N, N, N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine (THPED) chelating agent was researched comprehensively. The results indicate that plating rate decreases with the increase of concentration for THPED, CuSO₄ · 5H₂O and HCHO, pH value and bath temperature. The additive of K₄[Fe(CN)₆] · 3H₂O, 2, 2′-dipyridyl and polyethylene glycol(PEG) decrease plating rate and K₄[Fe(CN)₆] · 3H₂O has a bad effect on deposits quality, but 2, 2′-dipyridyl and PEG make deposits quality improve greatly. Low concentration of 2-mercaptobenzothiozole (2-MBT) increases plating rate and improves deposits quality, but decreases plating rate and worsens deposits quality when 2-MBT reaches 5 mg/L. The optimal conditions of this electroless copper plating process are that the concentration of THPED, HCHO, CuSO₄ · 5H₂O, PEG, 2, 2′-dipyridyl and 2-MBT are 16.8 g/L, 16.0 mL/L, 13.3 g/L, 0.5 g/L, 5.0 mg/L and 2.0 mg/L, respectively, pH value is 12.75, bath temperature is 30 °C. Plating rate reaches 9.54 μm/h plating for 30 min in the bath. The SEM images demonstrate that the surface of copper film is smooth and the crystal is fine. Foundation item: Project supported by Hubei Daye Nonferrous Metal Corporation of China     

Preparation of calcium phosphate coating on pure titanium substrate by electrodeposition method

The influences of pH value, electrolyte temperature and loading time on depositing calcium phosphate coating on pure titanium substrate by electrodeposition process were investigated. The process was carried out with an electrochemical work-station supplying a direct current power at potential of -0.8V (vs SCE). The electrolyte consists of 7 mmol·L-1 CaCl2·2H2O, 3 mmol·L-1 Ca(H2PO4)2·H2O and 2.5% H2O2. NaOH and HCl solutions were used to adjust pH value. The deposited samples were characterized by X-ray diffraction and scanning electron microscope. The comparison of the deposits obtained at lower and higher pH values demonstrates that the crystallization process at the interface is favoured by high pH value. With temperature increasing, the deposited hydroxyapatite is occasionally of plate-like shape, and the width and the length of the deposited calcium phosphates at 65 ℃ are larger than those at 55 ℃. Therefore, it is confirmed that the morphology and microstructure of electrochemically deposited calcium phosphates can be regulated. Additionally, the coating formed in electrolyte with H2O2 additive is homogeneous and the evolution of H2 bubble can be eliminated.     

Thermal Behavior Study of Carbonate Inorganic Materials

The thermal decomposition processes of(MgCO_3)_4·Mg(OH)_2·5H_2O(MCH),5ZnO·2CO_3·4H_2O(ZCH),NiCO_3·2Ni(OH)_2·4H_2O(NCH),PbCO_3(LC)and [Cr(OH)_5]_2·CO_3·8H_2O(CC)were studied via TG-DSC.The results of research imply that MCH has the largest capacity of heat absorption and ZCH is second to MCH among the studied materials.The non-isothermal kinetic parameters of MCH and ZCH were calculated by Kissinger and Ozawa methods.Furthermore,thermal decomposition mechanisms of MCH and ZCH were investigated by Coats-Redfern method.Due to the large specific heat capacity,MCH and ZCH are promising to be used as a coolant in extinguishant formulations.     

Preparation of microsized single-crystalline Co_3O_4 by high-temperature hydrolysis

Microsized single-crystalline Co3O4 has been synthesized by high-temperature hydrolysis of CoCl2·2H2O at 600 °C.The samples were characterized by powder X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results reveal that the as-prepared powders are microsized single-crystalline Co3O4 with cubic spinel structure.An increase in the high-temperature hydrolysis time results in the evolution of particle shapes from cube to quasi-sphere,and then to octahedron...     

Coating of Fe, Ni on α-alumina microspheres by heterogeneous precipitation

1INTRODUCTION Themagneticmetal coatedceramicoxides,core shellstructuralcompositematerials,inwhichthinmetallicfilmsarecoatedonaceramicoxide matrixwithmicrometerparticlesizes,areattrac tiveduetothecombinationofthefunctionalchar acteristicsofmetalsandmechanicalpropertiesoftheceramicmatrix.Theceramic basedtransition metal coated,core shellcompositessuchasNi coatedAl2O3[1],Fe coatedAl2O3[2],FeNi coated Al2O3[3]orCoFe coatedSiO2[4],havebeenfoundtoexhibitinterestingfunctionalperformancesdue…     

Influence of La-dopant on the material characteristics and supercapacitive performance of MnO<Subscript>2</Subscript> electrodes

Manganese dioxide was synthesized by electrodeposition method with Mn (CH3COO)2?4H2O as a raw material. La(NO3)3?6H2O was doped in electroyte during the preparing process to improve the performance of MnO2 electrodes. The micrographs, crystal structure and element content of electrodes were analyzed by SEM, XRD and atomic absorption spectroscopy, respectively. It is found that the La content ratio in the dioxide can be easily controlled by adjusting the composition of the plating solution. Appropriate amoun...     

Preparation and microstructure of spinel zinc ferrite ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> by Co-precipitation method

Spinel zinc ferrites ZnFe₂O₄, prepared by co-precipitation method using the zinc nitrate Zn(NO₃)₂·6H₂O and ferric nitrate Fe(NO₃)₃·2H₂O as the raw materials, were characterized by the thermo gravimetric analysis (TG) and differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The influence of synthesis conditions, such as Zn/Fe molar ratio, pH value, the sintering temperature and time, on the microstructures was detailedly investigated. The relationships between the microstructures and the synthesis conditions were discussed. The results show that the pure spinel zinc ferrites ZnFe₂O₄ are formed when the Zn/Fe molar ratio is 1.05:2 at pH=8.5 or Zn/Fe molar ratio is 1:2 at Ph=9-10, and the precursors are sintered at 1100 °C for 4 h. Especially no other phases are observed when the Zn/Fe molar ratio is 1:2 at pH=10 and the precursor is sintered above 700 for 4 °C h. The higher sintering temperature and longer sintering time contribute to grain growth.