Crystal structure and hydrogen storage behaviors of Mg/MoS<Subscript>2</Subscript> composites from ball milling

The Mg/MoS₂ composites were prepared by ball milling under argon atmosphere, and the effect of MoS₂ on the crystal structure and hydrogen storage properties of Mg was investigated. It is found that 10 wt% of MoS₂ is sufficient to prevent particle aggregation and cold welding during the milling process. The crystallite size of Mg will remain constant at slightly less than 38.8 nm with the milling process due to the size confinement effect of MoS₂. The dehydrogenation temperature of MgH₂ is reduced to 390.4-429.4 °C due to the crystallite size reduction. Through fitting by Johnson-Mehl-Avrami model, it is found that Mg crystal grows by three dimension controlled by interface transformation during the process of MgH₂ decomposition. MoS₂ has a weak catalyst effect on the decomposition of MgH₂ and activation energy of 148.9 kJ/mol is needed for the dehydrogenation process calculated by the Arrhenius equation.     

球磨镁和石墨混合粉末的相结构及其氢化行为

研究了机械球磨对镁和石墨混合粉末相结构和吸氢性能的影响。结果发现：随着球磨时间的增加,石墨由晶态转变为非晶,而镁的颗粒尺寸则逐渐减小。在温度为573 K,H2压力为1MPa的条件下,样品的吸氢量随着球磨时间的增加而减少。这主要是由于在吸氢的过程中,部分非晶碳与镁形成了MgaC3,消耗了可与氢反应的镁,阻碍了镁与氢的反应,导致样品吸氢量下降。     

Effect of Mg/Al ratios on hydration mechanism of tabular alumina carbon composites reinforced by Al<Subscript>4</Subscript>C<Subscript>3</Subscript> in situ reaction

Hydration mechanism of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 °C to 85 °C. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 °C-84 °C in H₂O(g). The hydration was controlled by diffusion from 24.7 °C to 33 °C. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al₄C₃ crystals at high temperature. Besides, the matrix changes into the Al₄C₃ with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction was immersed in the wax at suitable temperature or storing them below 33 °C in a dry place or storing them with paraffin-coating.     

MgO掺杂Ba0.6Sr0.4TiO3铁电材料的结构研究

采用固相反应法制备了掺杂不同量氧化镁（MgO）的钛酸锶钡（BST）微波铁电材料。采用SEM、EPMA、XRD等测试手段，分析研究了烧结产物的微观形貌特征、相组成、微区成分等特点，结果表明：MgO总是以单独相存在，Mg^2＋没有取代Ba^2＋（Sr^2＋）或Ti^4＋离子而进入BST晶格。     

Low-temperature Rapid Synthesis of Ultrafine Hafnium Carbide Ceramic Powders

Nano hafnium carbide(HfC) powders were synthesized by sol-gel combining hightemperature rapid heat treatment process using citric acid and hafnium tetrachloride as the raw materials. The effects of ball milling treatment on the phase and morphology of pyrolysis products(HfO_2-C) and final HfC product were investigated and the influences of heat treatment temperature and holding time on the structure and properties of the synthesized hafnium carbide powders were also studied. The experimental results showed that the HfO_2-C powders with good uniformity and small particle size were prepared by controlling the milling time. Pure HfC powders with an average particle size of 500 nm were obtained at 1 700 ℃ with a holding time of 3 min, and the oxygen content was about 0.69 wt%, lower than that of the hafnium carbide powders prepared by SPS(0.97%).     

Effects of EVA Latex on the Properties of Glass-fiber/Magnesium-oxychloride Cement Composites

1 IntroductionMagnesiumOxychloride Cement (MOC) or Sorel Ce-ment ,discovered by Sorel in1867 ,is a kind of air-curi-ng colloid material and has many advantages over othercements,including excellent fire retardance ,a lowheatconductivity coefficient , good abradability and corrosionresistance against organic solvents and sulphides . Fur-thermore ,it requires no maintenance under wet condi-tions . For many years , GF/MOC composites have beensuccessfully applied in many fields . However , G…     

Composites of sodium manganese oxides with enhanced electrochemical performance for sodium-ion batteries: Tailoring properties via controlling microstructure

Composites of Na_0.44MnO₂, Na_0.7MnO_2.05, and Na_0.91MnO₂ were synthesized by facile solid-state reaction, ball milling, and annealing methods. Two different composites of identical overall composition but drastically different morphologies and microstructures were synthesized. A composite of a hierarchical porous microstructure with primary and secondary particles (i.e., a “meatball-like” microstructure) achieved an excellent stable capacity of 126 mA h g^-1 after 100 cycles. The rate capability of the composite could be dramatically enhanced by another round of high-energy ball milling and reannealing; subsequently, a composite that was made up of irregular rods was obtained, for which the capacity was improved by more than 230% to achieve ~53 mA h g^-1 at a particularly high discharge rate of 50C. This study demonstrated the feasibility of tailoring the electrochemical performance of electrode materials by simply changing their microstructures via facile ball milling and heat treatments, which can be particularly useful for optimizing composite electrodes for sodium-ion batteries.     

球磨参数及Ni比例对Mg2Ni合金储氢性能影响研究

采用中频感应炉熔炼出铸态Mg2 Ni合金,将Mg2Ni合金与一定量的Ni粉进行混合球磨处理.系统研究在不同Ni粉添加量及球磨时间等条件下所得合金样品的结构及储氢性能.研究表明,随着Ni含量的增大及球磨时间的延长,合金的非晶纳米晶结构逐渐增多;合金的最大放电容量及循环稳定性得到明显提升;合金的表面催化活性及合金体相内的H传输能力都有了显著提高.Ni粉的作用主要在于可促进合金非晶化,同时对合金的放氢过程起到了催化的作用.     

机械合金化制备Mg-Cu非晶合金粉末的机理研究

采用XRD和TEM研究了MgCu2和Mg58Cu42混合粉末在机械合金化过程中的结构变化。结果表明:Mg、Cu粉末在机械合金化过程中是互溶的,机械合金化可以大大提高它们之间的固溶度;球磨过程中,Mg原子逐步溶入Cu基体中,形成Mg在Cu中的过饱和固溶体;固溶体的变形能量积聚到很大时,发生固溶体晶体结构的失稳,最后形成非晶态合金。在相同的球料比的条件下,提高球磨转速,可以大大促进非晶化的形成过程,缩短非晶形成的时间。     

Effect of High-energy Ball Milling on Synthetic Reaction in Al-TiO2-C System

High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of reactants.Reaction temperature characters（reaction ignition time,ignition temperature time.the maximum temperature and temperature rising rate）were changed by different milling time.The longer the milling time.the earlier the reaction.the quicker the temperature rise and the higher the maximum temperature.When the milling time exceeded 10 hours,the reactivity of reactants was so high that the synthetic reaction could take place at 850℃ directly without a long time pretreatment at 670℃.The microstructure of synthetic composites became uniform and the reinforced particles（TiC and α-Al2O3）became fine with milling time increasing.     

Preparation of Fe-Al Intermetallie /TiC-Al2O3 Ceramie Composites from llmenite by SHS

Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by selfpropagating high-temperature synthesis （SHS） from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed. It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis; Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave are improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 ℃.     

Eleetrodeposition and Characterization of CulnSe2 Thin Films for Solar Cells

CulnSe2 （CIS） thin films were prepared by electrodeposition from the de-ionized water solution consisting of CuCl2, InCl3, H2SeO3 and Na-citrate onto Mo/soda-lime glass （SLG） substrates. A thermal processing in Se atmosphere at 450℃ was carried out for the electrodepositied films to improve the stoichiometry. The composition and morphology of selenized CIS thin films were studied using energy dispersive spectroscopy （EDS） and scanning electron microscopy （SEM）, respectively. X-ray diffraction （XRD） studies show that the annealing in Se atmosphere at 450℃ promotes the structural formation of CIS chalcopyrite structure.     

Microstructure characterization of 3D C/SiC composites in combustion gas environments

C/SiC composites prepared by chemical vapor infiltration(CVI) were subjected to a stationary loading of 160 MPa in a combustion gas environment with flame temperature of 1300 ℃.Lifetime of C/SiC composites in such environment was measured.Microstructures of the composites after the testing were also characterized by SEM.The experimental results indicate the lifetime of C/SiC composites is average 2.3 hours in combustion gas environments.The combustion gas flow accelerates the damage of carbon fibers and the failure of the composites by speeding up the diffusion of gas reactants and products,destroying the layer of SiO2 on the surface of SiC coating and bringing fused SiO2 inside the composites.The fracture face of C/SiC is uneven,i e,a flat area close to the windward side and a pulling-out of long fibers near the leeward side,which results from the directionality effect of the combustion gas flow.     

机械化学法制备碳化硼及其晶体结构的研究

以氧化硼、镁粉和石墨粉为原料,通过机械合金化与镁热法相结合,制备了碳化硼材料:在氧化硼、镁、石墨的质量比为10:11:1、行星式球磨机转速为200 rpm、研磨时间为72 h、研磨罐温度略高于室温的条件下,诱导了化学反应,合成制备了碳化硼颗粒材料。由酸洗和水洗产物后粉末的XRD谱图,证明粉末的主要成分为碳化硼。用三线法和最小二乘法,对所制备的碳化硼粉末的晶体结构及晶格常数进行了分析计算,结果表明碳化硼的晶系为六方晶系,晶胞的晶格常数a=0.562 8 nm,c=1.218 6 nm,与文献报道的结果相一致。     

Enhanced photoelectric property of Mo-C codoped TiO<Subscript>2</Subscript> films deposited by RF magnetron cosputtering

Mo-C codoped TiO₂ films were prepared by RF magnetron cosputtering. Ultraviolet-visible spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray Analysis and X-Ray Diffraction were used to study the influences of codoping on energy gap, surface morphology, valence states of elements, ions content and crystal structure, respectively. The concentration of photogenerated carriers was measured by studying photocurrent density, while catalytic property was evaluated by observing degradation rate of methylene blue under visible light. A Mo-doped TiO₂ film, whose content of Mo had been optimized in advance, was prepared and later used for subsequent comparisons with codoped samples. The result indicates that Mo-C codoping could curtail the energy gap and shift the absorption edge toward visible range. Under the illumination of visible light, codoped TiO₂ films give rise to stronger photocurrent due to smaller band gaps. It is also found that Mo, C codoping results in a porous surface, whose area declines gradually with increasing carbon content. Carbon and Molybdenum doses were delicately optimized. Under the illumination of visible light, sample doped with 9.78at% carbon and 0.36at% Mo presents the strongest photocurrent which is about 8 times larger than undoped TiO₂ films, and about 6 times larger than samples doped with Mo only.     

Influence of annealing time on the microstructure and properties of Pb(Zr0.53Ti0.47)O3 thin films

The PZT thin films were prepared on (111)- Pt/Ti/SiO2/Si substrates by sol-gel method, and lead acetate [Pb(CH3COO)2], zirconium nitrate [Zr(NO3)4] were used as raw materials. The X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were used to characterize the phase structure and surface morphology of the films annealed at 650 ℃ but with different holding time. Ferroelectric and dielectric properties of the films were measured by the ferroelectric tester and the precision impedance analyzer, respectively. The PZT thin films were constructed with epoxy resin as a composite structure, and the damping properties of the composite were tested by dynamic mechanical analyzer (DMA). The results show that the films annealed for 90 minutes present a dense and compact crystal arrangement on the surface; moreover, the films also achieve their best electric quality. At the same time, the largest damping loss factor of the composite constructed with the 90 mins-annealed film shows peak value of 0.9, higher than the pure epoxy resin.     

Effect of application rates of assistant agents on properties of nano SiO2/NR composites

Nano SiO₂/NR composites were prepared through blending nano SiO₂ emulsion with natural rubber latex and then concreting with acetic acid. The emulsion nano SiO₂ was prepared with Na₂SiO₃·9H₂O and hydrochloric acid under the reaction of the assistant agents. The was analyzed effect of the application rates of assistant agents such as silane coupling agent, surfactant, nucleating agent and dispersant on the properties and interface structure of the nano SiO₂/NR composites with IR, TEM, SEM, DMA was analyzed. An orthogonal test was arranged to select optimum condition. The results show that the best combination for preparing nano SiO₂/NR composites is as follows: the rate of the silane coupling agent (TESPT), the surfactant(dodecyl benzene sulfonate natrium), nucleating agent(AlCl₃) and dispersant(ethylene diamine tetraacetie acid) in the course of preparing nano SiO₂ are 15%, 2.0%, 2.5% and 0.4%, respectively. Several replications in the experiment had produced desirable nano SiO₂ products and nano SiO₂/NR composites with better properties. Funded by the Special Fund of Basic Scientific Research of Rubber Research Institute of CATAS and Key Laboratory of Ministry of Agriculture for Natural Rubber Processing (No. xjszx-13 and No. xjsbywfzx2009-19, 706057)     

Photocatalytic activity of porous magnesium oxychloride cement combined with AC/TiO<Subscript>2</Subscript> composites

As a decorative material, magnesium oxychloride cement was used as a photocatalyst supporter to purify the pollutants indoors. Due to excellent adsorption properties of activated carbon (AC), the photocatalytic composties, TiO₂/AC, were prepared and introduced into the porous magnesium oxychloride cement (PMOC) substrate to composite a sort of photocatalytic cementitious material (PCM). The optimal composite processes were assessed by gas chromatograph, using toluene as the target. By comparing the perspective of toluene purification and thorough decomposition, it can be found that the optimal mass ratio for TiO₂/AC composites is 4/25, and the heat treatment to TiO₂/AC sample at 350 °C can play the optimal synergetic role of adsorbents in photocatalytic process. The synergistic effect of TiO₂, AC and magnesium oxychloride cement (MOC) was also evaluated by gas chromatograph. One-take molding process was adopted to introduce the TiO₂/AC into PMOC substrate, and its optimal mass fraction was 4 wt%, while the appropriate density of substrate was 0.35 g/cm3. Toluene degradation showed that the prepared PCM can degrade pollutants efficiently. The appropriate treatment process of TiO₂/AC, mass of TiO₂/AC, substrate density, and stable pore structure should be coordinated to maximize the adsorption-photodegradation performance. The combination of photocatalytic materials, adsorbents, and building materials provided a new idea for the application of photocatalysis.     

Preparation and Performance of Hollow Spherical Li_4Ti_5O_(12) Doped by Mg~(2+)

The microstructure and performance of Li_4Ti_5O_(12) doped by Mg prepared by hydrothermal method and solid phase method were investigated. Lithium dihydrate, magnesium acetate and tetrabutyl titanate were used as the main raw materials. This study reveals that Mg~(2+) has influences on the spherical structure, crystal development of Li_4Ti_5O_(12) and the electrochemical performances. The hollow spherical structure is composed of nano-sheet structure and the nano-sheet structure can be affected by the Mg~(2+) content. For Li4-xMgxTi5 O12, the sheet structure can be refined with the increment of Mg~(2+) content when x value is 0-0.1 and coarsen with the increment of Mg~(2+) content when x value is 0.1-0.2. The hollow spherical Li_4Ti_5O_(12) powders prepared by hydrothermal method have better performance. The optimal Mgdoped amount of hydrothermal method is 0.1. At 0.1 C, the first discharge capacity of Li_(3.9)Mg_(0.1)Ti_5O_(12) prepared through hydrothermal method at 0.1 C and 10 cycles is 182 and 178 m A h g~(-1), respectively.     

Effects of oxidation treatment on properties of SiO2f/SiO2-BN composites

The silica fiber reinforced silica and boron nitride-based composites (SiO_2f/SiO₂-BN) were prepared firstly via the sol-gel method and then the urea route, and the effects of oxidation treatment on the component, structure, mechanical and dielectric properties of the composites were investigated. The results show that the oxidation treatment at 450 °C will not impair the structure of boron nitride, and carbon is the main impurity with the excessive urea. The density of SiO_2f/SiO₂-BN composites is 1.81 g/cm³, and the flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, respectively. After oxidation treatment, the density varies to 1.80 g/cm³, and the flexural strength and elastic modulus are decreased to 58.9 MPa and 9.4 GPa, respectively. The mechanical properties of the composites are severely damaged, but they still exhibit a good toughness. The composites show excellent dielectric properties with the dielectric constant and loss tangent being 3.22 and 0.003 9, respectively, which indicates that the oxidation treatment is ineffective to improve the dielectric properties of SiO_2f/SiO₂-BN composites.