肯尼亚天然金红石矿沸腾氯化热力学和动力学

以焦炭作还原剂,利用天然金红石和氯气制备四氯化钛。在1173到1273 K的温度范围内,对肯尼亚天然金红石颗粒在间歇式流化床中的氯化反应热力学和动力学进行研究。体系的热力学分析显示：生成CO的反应在高温下占主导地位;若生成CO反应的比率η越大,且随着体系反应受温度的影响加剧,高温下反应的吉布斯自由能越负;同时,η增大,产物中TiCl4分压对反应的吉布斯自由能的影响趋于减小。应用气-固多相反应理论和流化床两相模型建立反应的数学模型,计算了气泡相和乳相中模型的各种参数,床层高度范围内氯气的平均浓度为0.3 mol/m^3。结果表明：天然金红石氯化反应主要在乳相中进行,反应速率主要由界面反应控制。     

Prediction of the global volatilization rate of gas-metal-alloy reaction systems—Method of calculation

The methods and equations used to predict the global volatilization rate of high temperature gas-solid reactions have been presented. The procedure includes the formulation of Bartlett's model, determining the equilibrium constant, and the estimation of the nonequilibrium properties of gases at high temperatures. For the alloy system forming the protective Cr₂O₃ layer, the global volatilization rate can be estimated with a modified Tedmon's model using a nonlinear regression technique.Prepared for the U.S. Department of Energy under contract No. W-7405-ENG-82.     

肯尼亚天然金红石矿流化床氯化率的研究

对肯尼亚金红石矿加碳氯化体系的热力学和动力学进行了研究,分析表明,C在固相中过量,体系处于平衡态时,TiCl4和CO是仅有的2个稳定的产物,增加C/TiO2比对产物组成影响不大;高温时,TiO2与C和Cl2生成CO的方程是占主导地位的。本实验提出了一个反应速率模型,得到金红石氯化率的公式,与实验数据吻合较好。反应速率与颗粒初始半径和天然金红石密度有关,在900℃到1000℃温度范围内,表观活化能为10.569 kJ/mol,扩散是反应的主要控制步骤。得到了C-Cl2体系中氯气反应率表达式,氯气反应率取决于反应程度、氯气浓度和焦炭粒径。     

Redox abilities of rutile TiO2 ultrafine powder in aqueous solutions

Redox abilities of rutile TiO₂ powder with an acicular primary particle, having about a 200 m²/g BET surface area obtained by a homogeneous precipitation process in aqueous TiOCl₂ solution at 50°C for 4 hrs, were investigated using a photocatalytic reaction in aqueous 4-chlorophenol, Cu- and Pb-EDTA solutions. Its abilities were then compared with those of commercial P-25 powder, together with investigating those of anatase TiO₂ powder obtained from the aqueous TiOCl₂ solution, having a similar surface area and primary particle shape as those of the rutile powder. The powder was more effective than the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest decomposition rate and the smallest amount in the same experiments in spite of similar particle shapes and surface area. From the results, it is found that the excellent photo redox abilities of the powder is likely to be caused by the specific powder preparation method regardless of crystalline structures even when having similar particle shapes and values in the surface area. Also, many OH⁻ attached to the surface of the TiO₂ particle appeared to interfere with the adsorption of decomposing target materials to the TiO₂ surface in the solution during the photocatalytic reaction, resulting in a delay in the reaction.     

粒径可控金红石型纳米二氧化钛的制备及表征

以成本低廉的偏钛酸为起始反应物,含羧基或羟基的有机化合物为修饰剂,采用水热合成法进行了纳米金红石型二氧化钛的合成研究,利用XRD和TEM等对制得的纳米二氧化钛进行表征。结果表明:含羧基或羟基的有机化合物在修饰剂条件下都制得了纳米金红石型二氧化钛,且修饰剂的加入抑制了棒状纳米二氧化钛的颗粒大小,其中修饰剂的空间位阻效应在控制合成小尺寸二氧化钛纳米棒中起主要作用,且修饰剂的羟基和羧基的络合作用对颗粒的生长也起到抑制作用。     

Parameters affecting reaction rate and conversion of TiO2 chlorination in a fluidized bed reactor: Experimental and modeling approach

Pilot scale chlorination of TiO₂ was carried out with CO as reducing agent. The experimental analysis and modeling of chlorination process of TiO₂ in the presence of CO and Cl₂ in a semi-continuous fluidized bed reactor were aimed. Chlorination process was continuously monitored by measuring the amount of produced TiCl₄ with time. The effects of different operating parameters including chlorination temperature, feedstock particle size and size distribution, amount of feedstock and Cl₂ and CO flow rates on the conversion were systematically investigated. A gradual increase in chlorination temperature led to monotonous increase of conversion rate. Conversion decreased with increased particle size of feedstock. An increase in loaded feedstock led to a decrease in reaction conversion. A model was proposed to predict conversion, particle size distribution and mole fraction of components in gas phase as reaction proceeds. A good agreement between conversions predicted by the model and experimental data under various operating conditions was observed.     

Mechanism of non isothermal reaction between elemental powders Ti and Al

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氧化铝碳热还原氯化法制低价氯化铝反应的热力学研究

对氧化铝碳热还原氯化法制低价氯化铝的反应进行了热力学研究,经过热力学计算得到:在常压下,该反应发生的起点温度为2121.21K,而当系统压力下降时,该反应的起点温度也会下降;经过计算得到了该反应起点温度与系统压力间的关系,也得到了不同系统压力下反应吉布斯自由能与系统温度间的关系。     

降低热法再生设备天然气能耗的方法

通过研究热法再生设备的使用特性,分析影响热法再生设备能耗的关键因素,根据关键因素做出相应的降低天然气能耗的方案措施。提高助燃空气温度及燃烧介质的温度;降低除尘负压系统的风量;沸腾燃烧充分,燃烧反应控制在流化床内部;增加炉体保温性能及增加再生砂的保温时间;选择比热容较低的介质材料以及增加可燃烧的有机物助燃等措施均可有效的降低天然气能耗。     

Geometrical approach to reaction schemes of multicomponent phase diagrams

A unique method for describing and establishing the reaction scheme of a multicomponent phase diagram is proposed in terms of graph theory. A geometrical representation of the connections between invariant reactions is considered as the basis to introduce the matrix formula of a graph that models a reaction scheme; then the number of all possible reaction schemes is enumerated. With a matrix operation, the most probable (full or partial) reaction scheme(s) can be selected within available experimental data. A ternary phase diagram was chosen as an example to show how to relate with experimental data. It is also shown that the number of invariant reactions in a ternary phase diagram can be expressed as a function of the numbers of binary and ternary phases. This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference and Exposition. Columbus. Ohio, 18–20 October, 2004.     

Effect of antimony on vigorous interfacial reaction of Sn-Sb/Te couples

A vigorous reaction between molten Sn-Sb solder and Te substrate leads to a thick SnTe-Sn mixture layer at the soldered junction. The effect of Sb addition in Sn on the kinetics of Sn-Sb/Te interfacial reaction and formation of SnTe-Sn reaction layer is reported. Sb element was found to expedite the growth of SnTe-Sn reaction layer in the Sn-Sb/Te couples dramatically. With increasing Sb content in Sn-Sb solder, the growth rate of SnTe-Sn reaction layer increases while both the size of SnTe grains and the fraction of Sn in SnTe-Sn decrease. The thickness of SnTe-Sn layer follows a parabolic law with reaction time for Sn-Sb/Te couples, unlike the linear dependence with time for Sn/Te couples. An apparent diffusivity of 2 × 10⁻⁷ cm²/s was determined for Sn transport through the SnTe-Sn layer in the Sn-Sb/Te couples reacting at 250 °C.     

固态置换反应的界面稳定性

通过建立界面扰动模型,推导了三元固态置换反应系界面稳定性的化学势梯度判据.结果表明如果扰动微区前沿速率控制元素的化学势梯度升高小于20.7%,平面界面稳定长大,将形成层状结构;若大于20.7%,平面界面不稳定长大,将形成束集型结构.计算了某一常见假设下棒状束集型结构的束集密度.     

高能激光束引燃Fe-Al系合金的制备与性能研究

采用激光引燃自蔓延高温合成技术制备Fe-Al合金,利用扫描电镜、X射线衍射仪、显微硬度计、磨粒磨损试验机等对合成试样进行显微组织观察和性能测试.结果表明:合金是由富Al相和过渡相构成的多相结构;合金的显微组织比较细小,晶粒随着Al含量增加而增大;Al含量为70 at%时,孔隙率达到最小,此时试样硬度值最大;在50 at%Al时试样耐磨性最好,磨损量为0.0011 g.     

高温堆芯熔融物池瞬态反应机理研究

为模拟核电厂高温堆芯熔融物堆内滞留的瞬态现象,采用冷坩埚电磁感应加热熔炼50kg级ZrO₂-Fe-Zr体系的混合物,通过XRD、SEM、EDS等检测手段分析了凝固后的熔融物铸锭的氧化层、金属层和氧化结壳的物相和元素分布情况。结果表明：50kg级初始熔池形成过程中,高温熔融物由于重力作用和不相容性分离成金属层和氧化层的两层结构,在熔池顶部及周围形成氧化结壳。之后,由于二次加料形成顶部液态金属三层熔池,顶部金属熔池可穿过氧化物硬壳以液滴状逐渐沉降到熔池底部。     

High temperature DSC study on interfacial reaction of aluminum borate whisker reinforced aluminum alloys

1lNTR0DUCTIONRecently,theceramicwhiskerreinfOrcedmetalshavebeenpaidmoreattentionbecausethesecompositesp0ssessexcellentbehaviorssuchaslowdensity,goodstrength,highspecificstiffnessandspecificmodulus,exce1lentfatigue-resistanceandwear-resistance,andthenwhisker/metalcompositesbecomeanimportantbranchofmetalmatrixcomposites.TheearlydevelopedwhiskerreinforcedmetalaremainlyexpensiveSiCandSi3N4seriescomp0sites,sothatthewideapplicationsofthiskindofcompos-itesarelimited.Atpresent,astateofartwhisker…     

复合层对Al接触反应钎焊过程及接头性能的影响

研究了Cu ,Zn复合层对Al接触反应钎焊过程和接头质量的影响规律。Cu和Al形成共晶液相破坏了Al表面氧化膜 ,促使Cu Zn包晶液相和Al Zn Cu共晶液相在Al表面润湿。结果表明 ,采用复合层进行Al接触共晶反应钎焊时 ,Cu和Zn厚度比例合适 ,可提高钎焊接头的抗电化学腐蚀性能和接头强度     

电沉积非晶/纳米晶Ni-Mo-La合金电极的析氢性能

在非晶/纳米晶Ni-Mo合金镀液中添加适量的LaCl3溶液,获得了非晶/纳米晶混合结构的Ni-Mo-La合金电极。结果表明:稀土La元素的加入,有利于镀层Mo含量的提高,形成非晶态Ni-Mo合金,细化镀层晶粒,减小镀层微应变,并使镀层表面积增加。在25℃、7 mol/L的NaOH溶液中的电化学实验表明:Ni-Mo-La合金电极比Ni-Mo合金电极具有更高的析氢催化活性,在电流密度为150 mA/cm2条件下,Ni-Mo-La合金电极的析氢过电位比Ni-Mo合金电极的降低了约80 mV。Ni-Mo-La合金具有储氢材料的特性,其析氢过程含有吸氢—储氢—脱附的过程。     

Molecular simulation of interfacial reaction between TiAl alloy melts and different coatings

The effect of coatings (Y2O3, ZrO2 and Al2O3) on the interfacial reaction of TiAl alloys was studied with molecular dynamics. The binding energy of coatings and the diffusion process of oxygen in the melt were simulated, and then the simulation results were compared with the experimental results. The simulation results indicate that for each of the three simulated coatings, inordinate interfacial reactions have occurred between the coating and the melt. The binding energy results show that Y2O3 has the best stability and is the most difficult to break down. ZrO2 has the greatest decomposition energy and is the easiest to break down in the melt. Besides,the molecular dynamics indicate that the diffusion coefficient of the oxygen atom in Al2O3 is larger than that in the other two coatings, indicating that oxygen diffusion in Al2O3 is the fastest at a given temperature. The experimental results show that the oxygen concentration of the melt with Al2O3 coating is the highest, and the oxygen diffusion is of similar magnitude to the simulation values, from which the conclusion can be obtained that the oxygen concentration is significantly influenced by the coating materials.     

铝-钢连接液固界面反应研究进展

详细综述了铝钢异种材料连接过程中液态铝与固态钢界面反应的研究进展,重点分析了钢的热浸镀铝、铝钢异种金属钎焊以及熔钎焊的界面反应产物的种类、生成顺序及生长机制,并对熔钎焊短时非平衡态固液界面反应的特点进行了分析和讨论。