Nicalon SiC/Al复合材料中的界面反应

从热力学和动力学方面对Nicalon SiC纤维与Al的化学反应进行了研究,探讨了反应机理及合金元素的影响.实验表明,从953K开始就发生SiC纤维和Al之间的反应.其反应符合抛物线规律;在1013K和1033K反应速率常数分别为3.30×10~(-8)m·s~(-1/2)和3.85×10~(-8)m·s~(-1/2).Mg,Cu和Mn等合金元素的共同作用会加剧其反应.     

THE KINETICS OF REACTION OF MOLTEN CUPROUS SULPHIDE WITH HYDROGEN

本文研究了在1150℃,1200℃和1250℃下熔锍Cu_2S与氢反应的动力学。动力学方程式为: 单相熔体 u_(S％)=d(S％)/dτ=k_S(S％-a)~2P_(H_2)~(1/2) 分层区 u_S％=d(S％)/dτ=AP_(H_2)~(1/2) 通过测定反应速度与硫浓度状态曲线的转折点,验证了Cu-S系相图分层的数据,此数据含硫成分为: ℃ 1150 1200 1250 ％ 19.805 19.73 19.61 研究了温度对反应速度的影响,测得反应活化能E和反应速率常数k: E=11000卡/克分子Cu_2S k_(1150℃)=3.27×10~(-2)/分·S％·大气压1/2 k_(1200℃)=3.76×10~(-2)/分·S％·大气压1/2 k_(1250℃)=4.12×10~(-2)/分·S％·大气压1/2 实验数据表明,反应速度受温度的影响是不大的。 还讨论了Cu-S系相图与反应速度的关系。     

熔锍Cu_2S与氢反应的动力学

本文研究了在1150℃,1200℃和1250℃下熔锍Cu_2S与氢反应的动力学。动力学方程式为: 单相熔体 u_(S％)=d(S％)/dτ=k_S(S％-a)~2P_(H_2)~(1/2) 分层区 u_S％=d(S％)/dτ=AP_(H_2)~(1/2) 通过测定反应速度与硫浓度状态曲线的转折点,验证了Cu-S系相图分层的数据,此数据含硫成分为: ℃ 1150 1200 1250 ％ 19.805 19.73 19.61 研究了温度对反应速度的影响,测得反应活化能E和反应速率常数k: E=11000卡/克分子Cu_2S k_(1150℃)=3.27×10~(-2)/分·S％·大气压1/2 k_(1200℃)=3.76×10~(-2)/分·S％·大气压1/2 k_(1250℃)=4.12×10~(-2)/分·S％·大气压1/2 实验数据表明,反应速度受温度的影响是不大的。还讨论了Cu-S系相图与反应速度的关系。     

马氏体相变动力学的深入描述

在论述变温马氏体相变动力学时 ,人们相当习惯的会提出Koistinen和Marburger公式来 ,其公式如下 :　　　　　　　　　　Xm=1-exp[α(Ms-Tq) ]( 1)实际上 ,这公式并不完全符合相当多的实验事实。G .Murry在《TraitmentThermique》上载文提出深入描述马氏体相变的动力学公式为 :　　　　　　　　　　Mxm=Ms- [K( 6 5 0 -Ms) ]( 2 )式中Mxm 为马氏体分数为Xm时对应的温度 ;K为马氏体分数Xm的函数 ,即K =f(Xm) ,经研究 ,　　　　　　　　　　K =1.6 7× 10 -2 ·Xm0 .55+ 3.18× 10 -18·Xm8.7 ( 3)系数K反映了马氏体发生过程中随马氏…     

Rh(Ⅲ)—5-Br-PADAP配合物吸附波研究

Rh(Ⅲ)在0.1mol/L HAc-0.1mol/L NaAc、1.60×10~(-5)mol/L5-Br-PADAP和0.0025％OP溶液(pH≈4.7)中,有良好的极谱波,峰电位Ep=-0.64V(vs.SCE)。Rh(Ⅲ)浓度在3.90×10~(-9)～6.80×10~(-7)mol/L(即0.40～70ppb)与峰电流成线性关系,检出下限为1.9×10~(-9)mol/L。用直线法测定配合比为:Rh(Ⅲ):5-Br-PADAP=1:2。用多种电化学方法研究极谱波的性质和电极反应机理,实验证明,-0.64V极谱波是Rh(Ⅲ)与5-Br-PADAP的配合物吸附波。     

焊工考试试题(四十一)的解答

41-2 设所求板厚为t(mm) (1)因接头效率是100％故10.3×t×500×1=103000 t=103000/10.3×500=20 (2)因接头效率是70％故10.3×t×500×0.7=103000 t=103000/10.3×500×0.7=28.57≈28.6因此,(1)20mm(2)28.6mm(或29mm)。 41-4(1)(○) 一有余高,就会在焊缝边缘处产生应力集中,从而将使疲劳强度降低。 (2)(○) 因为高强钢由缺口而导致的疲劳强度的下降率高,所以,当承受重复载荷时,即使     

碳热法生产稀土硅化物合金的物料性质(Ⅰ)——热物性参数与电阻率

用非稳态热线法测定了碳热法生产稀土硅化物合金原料的导热系数 ,用激光脉冲法测定了稀土硅化物合金的导热系数、热扩散系数和比热容。在 2 88～ 1 573K内 ,原料的导热系数与温度的关系可表示为 :λ =2 .56×1 0 - 2 7.8× 1 0 - 4 T(W·m- 1 ·K- 1 ) ;在 2 88～ 1 2 73K内 ,稀土合金的导热系数与温度的关系可表示为 :λ =1 4.30- 7.4× 1 0 - 3 T(W·m- 1 ·K- 1 )。还测定了原料中两种稀土配碳团块在 773K和 1 2 73K焙烧后的电阻率。     

C411树脂吸附与解吸金的动力学

对大孔交联哌啶树脂吸附与解吸金的动力学研究结果表明,吸附和解吸均符合Boyd液膜扩散方程,吸附金的速率是随着HCl浓度的增加而下降。实验测得的吸附扩散系数K=4.75×10~(-4)s~(-1),吸附表观热效应△H=12.43kJ/mol。当温度升高时,吸附金的分配比上升,表明该树脂吸附金是吸热反应。还研究了硫脲解吸金的特性。     

预热温度和真空度对自蔓延法制备MgB2超导块材的影响

用自蔓延(SHS)法成功制备了MgB2超导块材.B,Mg合成MgB2是放热反应,预热温度和真空度是影响MgB2性能的主要因素,当预热温度太低时不能用电弧引导反应,理论计算和实验结果表明预热温度应该大于484 K,但预热温度太高会使部分MgB2分解为MgB4和MgB7,当预热温度为520K,真空度为2.4×10-3Pa时,试样的临界温度Tc=38.45K,温度转变宽度小于0.4 K,临界电流密度Jc=1.60×106A/cm2(10 K,0.5 T),1.65×106A/cm2(20 K,0 T).试样的致密度较低时,结构为层状,层与层之间有空洞,每层由颗粒状晶粒组成,颗粒尺寸为2 μm～5 μm.SHS法制备MgB2超导块材工艺简单、反应时间短(3 s～5 s).     

THE KINETICS OF SULPHURIC ACID LEACHING OF SYNTHETIC γ-NiS UNDER OXYGEN PRESSURE

研究了110—160℃及po_2<4900 kPa条件下,硫酸溶液中γ-NiS(针镍矿)氧化浸取动力学。浸取速率过程可用表面无固体生成物沉积的核心收缩模型描述,如 1-(1-α)~(1/3)=(k/ρr_0)t=Kt浸取速率在pH<2.5时,与H~+浓度无关;pH>2.5时,为pH值的一个函数。浸取反应对氧分压来说为0.5级。反应的表观活化能为97.5kJ·mol~(-1),pH<2.5时,上式中的速率常数可表示为 K=1.45×10~5(4.55+1/(?)_0)P_(O_2)~(1/2)[H~+]~(?)e~(-11720/T)溶液中少量Cu~(2+),Ag~+的存在,降低了对γ-NiS的浸取速率。     

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pressure leaching was 0.899. The kinetic equation was ob-tained and the mathematical model of iron removal from metallurgical grade silicon (MG-Si) was given as follows: 1-2/3x-(1-x)2/3=exp(5.1654-4811.4591/T+1.287lnp+1.046ln[C])·t/r02· The values calculated from the equation were consistent with the experimental results.     

Leaching process of germanium oxide dust

A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid concentration, leaching time and stirring speed on the leaching rate of germanium were investigated. Based on the characteristic of the dust, the kinetics and reactive mechanism of acid leaching were stud- ied. The results show that the leaching of the dust by acid belonged to "the unreacted core shrinking model" of producing solid outgrowth layer. The chemical reaction was controlled by inner diffusion process. The apparent activation energy of leaching process was 12.60 kJ/mol. The leaching reaction of germanium was determined to be mainly second order reaction. The optimum conditions were the reaction tem- perature of 363 K, the leaching time of 2.5 h, the stirring speed of 120 r/min, the solid-to-liquid ratio of 1/8 and the acid concentration of 120 g/L. Under these conditions, the leaching rate of germanium can come up to more than 87%.     

Leaching kinetics of antimony-bearing complex sulfides ore in hydrochloric acid solution with ozone

The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation–leaching with ozone. The effects of temperature, HCl concentration, stirring speed and particle size on the process were explored. It is found that the recoveries of Sb and Fe reach 86.1% and 28.8%, respectively, when the reaction conditions are 4.0 mol/L HCl, 900 r/min stirring speed at 85 °C with <0.074 mm particle size after 50 min leaching. XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model. The leaching of Sb corresponds to diffusion-controlled model at low temperature (15–45 °C) and mixed-controlled model at high temperature (45–85 °C), and the apparent activation energies are 6.91 and 17.93 kJ/mol, respectively. The leaching of Fe corresponds to diffusion-controlled model, and the apparent activation energy is 1.99 kJ/mol. Three semi-empirical rate equations are obtained to describe the leaching process.     

以废茶叶为还原剂在硫酸溶液中还原浸出氧化锰矿（英文）

采用废茶叶在硫酸溶液中还原浸出加蓬和湘西氧化锰矿石,探索废茶叶用量、硫酸浓度、固液比、浸出温度和反应时间对浸出过程的影响。对加蓬氧化锰矿,优化的浸出条件为:氧化锰矿与废茶叶的质量比10:4、硫酸浓度2.5 mol/L、固液比7.5:1、浸出温度368 K、浸出时间8 h;在此条件下,加蓬氧化锰矿的浸出率几乎达100%。对于湘西氧化锰矿,优化浸出条件为:氧化锰矿与废茶叶的质量比10:1、硫酸浓度1.7 mol/L、液固比7.5:1、温度368 K、浸出时间8 h;在此条件下,锰的浸出率达到99.8%。氧化锰矿的还原浸出过程符合内扩散控制模型,加蓬和湘西氧化锰矿石的还原浸出反应表观活化能分别为38.2 kJ/mol和20.4 kJ/mol。采用X-射线衍射(XRD)和扫描电子显微镜(SEM)对浸出前、后的锰渣进行表征。     

Kinetics of indium dissolution from marmatite with high indium content in pressure acid leaching

The kinetics of oxygen pressure acid leaching marmatite with high indium content was studied. The effects of particle size, agitation rate, temperature, H_2SO_4 concentration, and oxygen partial pressure on leaching rate of indium were investigated. The results show that when the agitation rate is above 600 r-min~(-1), its influence on indium leaching rate is insignificant. It is determined that the leaching rates increase with the increase in sulfuric acid concentration, temperature, partial oxygen pressure, and the decrease in particle size. Moreover, the results demonstrate that the process of indium leaching is controlled by interface chemical reaction, with apparent activation energy of 65.7 k J-mol~(-1). The apparent reaction orders of sulfuric acid and oxygen partial pressure are determined to be 0.749 and 1.260, respectively. The leaching reaction process follows shrinking unreacted core model. And finally, the kinetics model equation is established for indium.     

采用Na2SO3溶液从硒渣中选择性浸出Se及其动力学

采用SO2还原沉金后液制得硒渣,再用Na2SO3选择性浸出硒渣,使Se得到有效分离;通过研究浸出过程中Se浸出率随时间的变化,建立该反应的动力学方程,确定Na2SO3溶液浓度、液固比、搅拌速度及反应温度对Se浸出率的影响,并计算相应的表观活化能。结果表明:增加Na2SO3溶液浓度和升高反应温度可以较大幅度提高Se的浸出率,液固比和搅拌速度对浸出Se的影响较小;Na2SO3浸出Se过程为Avrami模型混合控制,其特征参数n和表观活化能E分别为0.235和20.847 kJ/mol,Se的浸出率受反应温度的影响较大。     

Leaching performance of Al-bearing spent LiFePO4 cathode powder in H2SO4 aqueous solution

The leaching performance and leaching kinetics of LiFePO₄ (LFP) and Al in Al-bearing spent LFP cathode powder were systematically studied. The effects of temperature (273?368 K), stirring speed (200?950 r/min), reaction time (0?240 min), acid-to-material ratio (0.1:1?1:1 mL/g) and liquid-to-solid ratio (3:1?9:1 mL/g) on the leaching process were investigated. The results show that the concentration of reactants and the temperature have a greater impact on the leaching of Al. Under the optimal conditions, leaching efficiencies of LFP and Al are 91.53% and 15.98%, respectively. The kinetic study shows that the leaching of LFP is kinetically controlled by mixed surface reaction and diffusion, with an activation energy of 22.990 kJ/mol; whereas the leaching of Al is only controlled by surface chemical reaction, with an activation energy of 46.581 kJ/mol. A low leaching temperature can effectively suppress the dissolving of Al during the acid leaching of the spent LFP cathode material.     

银离子在氧化浸出黄铜矿中的动力学研究

研究了银离子在氧化剂A氧化浸出黄铜矿中的动力学,讨论了Ag^ 添加、Ag^ 浓度、氧化剂A浓度、黄铜矿粒度等因素对浸出过程的影响。研究结果表明,扩散控制模型可以很好地描述氧化剂A氧化浸出黄铜矿液-固反应过程;在实验范围内,确定了反应的比速率常数、反应级数及表观活化能,并根据实验数据,导出动力学方程为：1-2/3a-(1-a)^2/3=0.0685r。^-1[Ag^ ]^0.27exp(-25096/RT)t     

低钒转炉钢渣提钒湿法工艺的动力学研究

为了提高湿法浸出低钒钢渣中钒的浸出效率,并对湿法浸出低钒钢渣中钒提供理论依据,从动力学角度分析整个浸出过程。考察温度、液固比、硫酸质量分数和搅拌速率对浸出过程的影响。研究结果表明:在90℃、液固比为10?1以及硫酸浓度6.0mol/L时,浸取9h,低钒钢渣中钒的浸出率可达到95.3%。通过正交实验和动力学推导,得到描述浸出过程的经验方程,低钒钢渣湿法浸出钒的动力学模型为收缩核动力学模型,浸出过程的表观活化能为12.794kJ/mol,该模型表明浸出过程中的控制步骤取决于固膜扩散速率。提高温度、液固比和硫酸质量分数,均可加速钒的浸出速度,提高钒的浸出率。     

Leaching of natural stibnite using sodium hydroxide solution

This paper presents the results of a laboratory investigation of alkaline leaching of stibnite sample, which originated from Pezinok (Slovakia) mine. The leaching media used was aqueous solution containing sodium hydroxide. This research focused on establishing the effect of the following parameters on alkaline leaching: NaOH concentration, temperature of leaching, and grain size of solid phase. The apparent activation energy and apparent order of stibnite reaction with the solution that contained NaOH were determined from experiments as E_a ≈ 50.7 kJ mol⁻¹ and n ≈ 1, respectively. The rate-determining step is the reaction at the solid/liquid interface. A simple mathematical model equation was applied to describe the dissolution of antimony during leaching and to summarize the kinetic data.