Papers by Keyword: Precursor

Abstract: In the preparation of hydrogen, the bio-oil from pyrolysis of biomass must be further upgraded (catalytic steam reforming)SO as to improve its quality．However the catalyst used in the steam reforming reaction is easy to lose its activity due to being coked' SO that it is important to study the coke formation and its efects on the catalyst activity in the steam reforming process．Fourier Transform Infrared Spectroscopy were used to analyze the precursor of coke on the catalyst Ni/MgO-La₂O₃-Al₂O₃ used in steam reforming reaction and the mechanism of coking Was also discussed based on it．The results indicate that precursors of coke deposited inside the pore of the molecular sieve are mainly paraffin, alcohols, aldehydes and ketones, and aromatic compounds.

Abstract: Vanadiunm carbide (V8C7) nanopowders were prepared by the solution-derived precursor method, ammonium vanadate (NH4VO3) and glucose (C6H12O6) were used as raw materials. The samples were characterized by TG-DTA, XRD and SEM. The results show that the weight of the sample reduces rapidly before 600°C (about 25 wt.%), but it changes very slowly (about 1.0 wt.%) after 600°C. The DTA curve mainly includes 5 endothermic peaks and an exothermic peak which are corresponding to the peaks of 110°C, 300°C, 348°C, 677°C, 1000°C and 509°C, respectively. When the carbon content between 24 wt.% and 30 wt.%, the samples mainly consist of V2O3 and VC1−X (1−X = 0.66–0.88). When the carbon content is 32 wt.%, the sample includes a main phase (V8C7) and a second phase (V2O3). When the carbon content reaches to 36 wt.%, the single-phase V8C7 powder can be obtained. The SEM results show that major powders exhibit good dispersion and are mainly composed of particles with a mean diameter of ~200 nm.

Abstract: The precursor of LiNi_0.5 Mn_{Subscript text}1.5O₄ cathode material with high density was synthesized by two-dryness co-precipitation method. The optimized parameters were found out by studying the relationship between the density of precursor and the concentration of reactants, the manner of adding agglomerating agent, the remaining water in filter cake and the manner of dryness. The highest density (1.74 g/cm3) of precursor can be achieved under optimized condition: NiSO₄ 0.375 mol/L, coagulation agent added with little amount but many times, 28% of water in filter cake and two-step dryness, which is much better than that made by other methods. Our experiment provides a significant reference for the synthesis of excellent-performance cathode materials of lithium-ion battery. LiNi_0.5 Mn_{Subscript text}1.5O₄has a good cycle performance, a higher discharge capacity and a discharge platform of 4.7v, so it has become a research focus of 5-voltage cathode materials in the field of lithium ion battery recently.[1-4] However, LiNi0.5Mn1.5O4 prepared by common methods usually has a lower tap volume capacity.[5-9] HiroyuKi Ito[6] reported a continuous fabricated high-density cobalt-manganese-doped nickel hydroxide method with which the density of product was between 1.5-1.91g/cm3, however the used ammonia as a complexation agent in the preparation process not only increased the cost of the preparation, but also led to environmental pollution. Research results show that the cathode material synthesized using high-density precursor has a higher tap density, a larger volume capacity and a good electrochemical performance.[10] In this paper, we find out the optimized parameters of preparation of precursor of LiNi_0.5 Mn_{Subscript text}1.5O₄ by studying the relationship between the density of precursor and concentration of reactants, the manner of adding agglomerating agent, the remaining water in filter cake and the manner of dryness.

Abstract: The sucrose was used as a carbonaceous precursor to fabricate composite alloy powder of Fe-Cr-C-TiFe by the precursor carbonization-composition process using the powder matirial of chromium, iron, tungsten, nickel and ferrotitanium. And the powder of Fe-Cr-C-TiFe was used to form a high-chromium iron-base composite coating on substrate of Q235 steel by plasma cladding process. The microstructure and hardness of the coating were investigated by scanning electron microscope (SEM), energy disperse spectroscopy (EDS), microhardness tester. Wear resistance of the coating was tested on wear tester at room temperature and high temperature 600°C compared with the base material Q235 steel and bearing steel. Results show that the coating consists of TiC, (Cr,Fe)₇C₃ and austenite and the hardness of the coating is 3.4 times as high as the base body Q235 steel. The wear resistance of the coating at room temperature is 11-15 times as high as the base body Q235 steel. The wear resistance of the coating at high temperature 600°C is 2.45 times as high as Q235 steel and is 1.5 times as high as bearing steel. The composite coating has excellent wear resistance because the reinforce phase TiC and (Cr,Fe) ₇C₃ in the coating have high hardness and good wear resistance. They can play key roles in process of friction and wear.

Abstract: We prepared nanometer-sized nickel oxide by hydrothermal decomposition. In this work, NiSO₄•6H₂O and Na₂CO₃ were used as raw materials to prepare the precursors. Nanometer-sized nickel oxide was obtained after calcining the precursors. The temperature of the calcination process affects the morphology and size of the nanometer-sized nickel oxide. The precursors and products were analyzed by TG, XRD and SEM. Sheet nanometer-sized nickel oxide was obtained and characterized by its high purity, smooth surface, regular hexagon shape, average size of 500 nm and 30-60 nm thickness. The results indicate that the NiO particles become open pore structures at a calcination temperature above 500 °C

Abstract: Dissolved organic matter (DOM) from different biological treated wastewater in secondary effluent of different municipal wastewater treated plants are isolated and fractionated using resin adsorption into five different fractions: hydrophobic bases (HOB), hydrophobic acids (HOA), hydrophilic bases (HIB), hydrophilic acids (HIA) and hydrophilic neutrals (HIN). The characteristics of three dimensional excitation emission matrix fluorescence spectroscopy (3DEEM) and disinfection by-products formation potential (THMFP) of each fraction are investigated. The objective of this study is to investigate the influence of different biological processes on THMs generation and transformation. The results show that for each municipal wastewater treated plant, HIA and HOA fractions content more fulvic-like acid and humic-like acid, which are the important matter to result the higher THMFP. THMFP of HIA rang from 736μg/L to 359μg/L in the secondary effluent. It shows that acidic organic matters are important THMs precursors, especially fulvic-like acids and humic-like acids. The Orbal oxidation ditch process can lead to the highest THMFP, and secondly is the Convert A²/O process.

Abstract: Abstract: An epoxy based nano-SiO₂/TiO₂/polyimide hybrid enhanced sizing for carbon fiber was prepared by modified SiO₂/TiO₂ precursor in PAA collosol with silane couple agent(WD-50) and eligibility surfactant via sol-gel reaction, and both ultrasonic cavitation and multi-complex technology were used during the process. The properties of PAA-SiO₂-TiO₂ hybrid sizing and micro-morphology of carbon fiber surface were analyzed by FTIR, DSC, Particle Size Analyzer and STM. The results indicated that nanoscale SiO₂•TiO₂ particles dispersed in the hybrid sizing film homogeneously, and a layer with nano particles was formed on carbon fiber surface after treated by the hybrid enhanceing sizing. The roughness was increased and interface properties of carbon fiber would be improved. At the same time both tensile strength and the interlaminar shear strength were increased obviously.

Abstract: Petaliform magnesium oxide nanomaterials were prepared by which the basic magnesium carbonate made from light burning powder of low grade magnesite were used as precursor. The XRD results indicated that aqueous magnesium carbonate changed to basic magnesium carbonate (4MgCO₃•Mg(OH)₂ •4H₂O) when heating temperature reached 95°C, the SEM confirmed that the morpholo_Zgy of basic magnesium carbonate (4MgCO₃•Mg(OH)₂•4H₂O) were petaliform, after calcinations the magnesium oxide with the same morphologies as precursors’ were obtained, simultaneously , the products with high activity (iodine value of 197mgI₂/g).

Abstract: Fe-Cr-Ti-C composite powder was prepared by precursor carbonization-composition process using the mixture of ferrotitanium, chromium, iron powders and precursor sucrose as raw materials. In situ synthesized TiC particle reinforced composite coating was fabricated on substrate of Q235 steel by reactive plasma cladding process using Fe-Cr-Ti-C composite powder. Microstructure of the coating was observed by scanning electron microscope (SEM), the phases in the coating were determined by X-ray diffraction (XRD), and the wear resistance of the composite coating was evaluated under dry sliding wear test conditions at room temperature. Results indicate that the composite coating consists of in-situ the reinforcing TiC carbide, (Cr,Fe)₇C₃ eutectics and austenitic, and is metallurgically bonded to the Q235 steel substrate. TiC carbide in the composite coating showed the gradient distribution. TiC particles present granular in the fusion zone and central zone, and present dendritic in the surface of the composite coating. Hardness of the coating from surface to fusion zone is little difference, the average hardness of the coating is about HV_0.2750, is as 3.2 times as the base. The wear mass loss of Q235 base material is 12 times as that of the composite coating.

Abstract: W-Cu precursor was prepared by chemical precipitation. Then the superfine W-Cu composite powder was prepared by roasting and hydrogen reduction process. The composite powder sample were characterized by SEM and XRD. The experimental results show that component uniform and stabilising ratio W-Cu precursor can be prepared by controlling pH of solution, then W-20%Cu uhrafine composite powder was prepared by hydrogen reduction proces ,The sizes of three compositions in the powder(Cu_0.4W_0.6, W and Cu)was to nanometer, in which the size of Cu_0.4W_0.6 and W was 40nm while the size of Cu was 70nm.