硫化矿氧化自热性质测试的新方法

介绍一种新的测试硫化矿样氧化自热性质的方法。该套实验装置由程序控温箱、金属网篮、热电偶以及温度自动记录仪等构成。通过设置不同的恒温条件,运用该套实验系统首次测试3种不同硫化矿样的氧化自热性质,得出各矿样在不同恒温条件下的自热规律;利用交叉点温度法解算出3种矿样(硫铁精矿、高硫精矿、原矿)的表观活化能分别为13.7366、21.3817、36.2350kJ/mol,比较3种矿样的自燃倾向性。结果表明:随着恒温温度的升高,矿样的自热幅度变大,温度交叉的速度变快;硫铁精矿的表观活化能最小,原矿的表观活化能最大,这与硫精矿更容易发生自燃的现象一致。与传统的研究硫化矿石氧化自热性质的实验方法相比,该方法的测试成本低、操作简便、可重复性强,用于判定硫化矿石的自燃倾向性有一定的适用性。     

机械力活化诱导硫化矿石自燃的热分析动力学

为揭示硫化矿石在经历机械力活化后的氧化自燃特性,运用热分析技术表征矿样在不同功率(100~450r/min)、不同料球比(1:3~1:12)条件下活化后的热分解动力学参数;采用X射线衍射技术对活化矿样进行线形分析,比较矿样活化前后的晶格畸变率和晶块尺寸。结果表明:硫化矿石在530~640℃温度区间的氧化热解过程符合一维扩散反应动力学机制;其表观活化能随着球磨功率、料球比的增加而降低,呈现出较好的一致性;矿样在未活化、200 r/min、350 r/min活化条件下的表观活化能依次为258.93、181.34、150.97 k J/mol,对应的指前因子分别为2.35×10~(18)、1.45×10~(13)和1.60×10~(11);矿样在料球比为1:3、1:8活化条件下的表观活化能依次为240.57、150.97 k J/mol,指前因子分别为1.58×10~(17)、1.60×10~(11);硫化矿石的表观活化能的降低与活化矿样晶格畸变率的增大及晶块尺寸减小存在一定的相关性,进而容易引发自燃。     

碳热还原法制取铝硅合金的反应机理及其动力学

利用XRD、TG/DTA技术分别分析真空碳管炉内不同反应温度下的物相组成和碳热共还原Al2O3、SiO2的反应过程,并在此基础上探讨碳热还原法制取铝硅合金的反应机理.分别采用10、15、20和25 K/min升温速率的差热分析,研究动态氩气气氛中碳热法制取铝硅合金的反应动力学.结果表明:碳热还原反应过程可分为4个阶段,其中,以碳化物的生成与分解阶段为主.碳热还原反应的4种还原机理中,碳化物的生成与分解理论能较好地解释反应过程中出现的反应现象.各个吸热峰的表观活化能分别为848.9、945.4、569.7、325.7、431.9和723.1 kJ/mol,给出了各个吸热峰的动力学方程.同时,利用XRF和红外定硫定碳仪对碳管炉和电炉所得产物组成的定量分析,验证了动力学分析结果的可行性.     

碳热还原法合成TiB_2的反应动力学研究

采用TG-DSC热分析仪,对碳热还原法合成TiB2的反应混合物进行了热重分析,采用全程等温热重法,对碳热还原法合成TiB2的反应过程进行了动力学研究,并对反应产物进行了XRD分析。研究结果表明,碳热还原法合成TiB2的反应过程分为三个阶段:第一个阶段试样单位面积的失重与反应时间成抛物线关系,反应速率由碳的扩散过程所控制,反应的表观活化能为168.36kJ/mol;第二阶段试样单位面积的反应失重与时间成线性关系,反应速率由化学反应速率所控制,反应的表观活化能为165.28kJ/mol;第三阶段试样单位面积的失重与反应时间成抛物线关系,这一阶段的反应速率由碳的扩散过程所控制,反应的表观活化能为218.47kJ/mol。     

H_2SO_4分解富钛精矿的反应动力学

攀钢含钛高炉渣是一种尚待开发利用的钛资源。选用攀钢含钛高炉渣经选择性分离后的富钛精矿为原料 ,以液固异相反应的收缩未反应芯模型研究了硫酸法制取钛白的反应动力学过程。根据搅拌强度和温度对反应的影响判别反应过程为膜扩散控制过程 ;分析了反应速度的温度因素和粒度因素 ,导出了硫酸分解富钛精矿的动力学方程式 ,并按该方程计算得到反应温度在 6 0～ 80℃的活化能为 34.5 9kJ/mol。     

硫化矿自燃的机械活化机理

为了揭示硫化矿发生自燃的本质原因,从典型金属矿山采集了具有代表性的矿样,在室内开展了硫化矿的机械活化实验.采用扫描电镜(SEM)、X射线衍射技术(XRD)、综合热分析技术(STA)表征了矿样在经历不同时间的机械活化作用后的表观形貌、微观结构和热行为等物理化学性质的差异.结果发现:硫化矿石经历机械活化作用后,比表面积增大,出现团聚效应,产生晶格畸变与晶格缺陷,初始放热点及最大反应速率所对应的温度值均有所下降.由此提出了一种新的解释硫化矿自燃的机械活化理论,认为在金属矿山开采中施加于矿体上的各种机械力使得硫化矿产生了机械活化效应,从而使化学反应活性得到相应提高,在一定的环境条件下更加容易产生氧化自热,最终引发自燃火灾.     

用热分析技术研究氟碳铈精矿碳酸钠焙烧反应动力学

利用山东微山氟碳铈精矿添加２０％Ｎａ２ＣＯ３的ＴＧＤＴＡ曲线,采用ＦｒｅｅｍａｎＣａｒｏｌ法和差减微分法热分析技术,研究其焙烧反应动力学,取得了令人满意的结果。利用ＴＧ曲线计算得到的反应表观活化能Ｅ＝１８８．６ｋＪ／ｍｏｌ,反应级数ｎ＝０．８９;利用ＤＴＡ曲线计算得到的反应表观活化能Ｅ＝１８１．４ｋＪ／ｍｏｌ,反应级数ｎ＝０．７３。两种方法计算的结果吻合较好。同单纯氟碳铈精矿的焙烧反应动力学计算结果相比较,加入Ｎａ２ＣＯ３使氟碳铈精矿的焙烧分解反应变得复杂,但可以使反应的活化能降低,有利于精矿的分解。     

金精矿碘化浸出过程动力学

采用碘-碘化物体系对金精矿进行浸出,通过实际矿石的浸出试验考察搅拌速度、浸出温度、碘浓度及碘离子浓度对金精矿碘化浸出反应动力学的影响。结果表明:提高搅拌速度对金的浸出有不利影响;通过对影响该体系动力学参数的考察,发现其符合核收缩模型,反应过程总体由界面化学反应控制,其表观活化能为31.674kJ/mol,碘浓度和碘离子浓度的反应级数分别为1和0.5,建立了金精矿碘化浸出过程的反应速率方程。     

硫化锌精矿直接浸出动力学及其半经验模型（英文）

在中试规模管式反应器中直接浸出贫铁硫化锌精矿,研究其浸出动力学。为满足静压浸出条件,将含硫酸亚铁和硫酸的矿浆注入到垂直放置的直径8 m的管式反应器中,空气从反应器的底部吹入。考察了初始硫酸浓度、反应温度、矿粒直径、初始硫酸锌浓度、矿浆浓度和铁含量对反应动力学的影响。结果表明,硫化锌精矿的直接浸出遵循收缩核模型,过程受化学反应控制,其表观活化能为49.7 k J/mol。采用半经验模型描述该过程,得到铁含量、硫酸浓度、硫化锌精矿浓度和矿粒直径的反应级数分别为0.982、0.189、-0.097和-0.992。采用SEM-EDS对硫化锌精矿浸出反应前后的矿粒进行分析,发现当锌的浸出率低于60%时,由于反应器搅拌的问题,颗粒表面硫产物层脱落,会影响浸出溶液与颗粒表面的接触。     

低粘度环氧树脂体系的固化动力学及其热稳定性

采用一种新型奇士增韧剂对环氧树脂进行增韧改性,获得一种热熔预浸料用环氧树脂体系,采用NDJ-8S型旋转粘度仪对环氧树脂体系的粘度进行测定,应用差示扫描量热法(DSC)对环氧树脂体系的固化反应过程进行分析,并确定其固化反应动力学参数,利用热失重分析法(TGA)对其热稳定性进行研究。结果表明:环氧树脂体系的粘度较低,50℃时仅为3.5Pa.s。采用外推法得出环氧树脂体系的凝胶温度为58.82℃,固化温度为139.08℃,后固化温度为265.92℃,通过计算得出表观活化能E为53.1kJ/mol,反应能级为0.88。室温下固化反应速率较低,约为3.28×10-3 s-1,有利于存储,同时树脂体系起始分解温度达271.23℃,具有良好的热稳定性。     

Influence of metal ions on the formation of artificial zinc rusts

The artificial rust particles were prepared from ZnCl₂ solutions dissolving Al(III), Fe(III), Fe(II), Ni(II), Co(II) and Mg(II) at different atomic ratios from 0 to 0.3 in metal/Zn. With increasing metal/Zn the crystal phases of the products turned following as ZnO → a mixture of ZnO and Zn₅(OH)₈Cl₂ · H₂O (ZHC) → ZHC. Al(III) most facilitated the formation of ZHC but Mg(II) and Fe(III) produced no ZHC. The morphology of the formed particles varied following as agglomerate → fine → rod → sheet → irregular with the increase of metal/Zn. The sheet and irregularly shaped particles were identified as ZHC and the other particles as ZnO.     

NiAl－Fe金属间化合物合金的正电子寿命谱

测量了塑性金属间化合物合金Ｎｉ（５０）Ａｌ（３０）Ｆｅ（２０），Ｎｉ（５０）Ａｌ（２０）Ｆｅ（３０）和Ｎｉ（６０）Ａｌ（２０）Ｆｅ（２０）单晶和多晶的正电子寿命谱．基于正电子寿命谱的特征参数引入了正电子双区域捕获模型，并讨论了这些合金微观结构与力学性能之间的关系．     

NiAl—Fe金属间化合物合金的正电子寿命谱

测量了塑性金属间化合物合金Ｎｉ５０Ａｌ３０Ｆｅ２０，Ｎｉ５０Ａｌ２０Ｆｅ３０，Ｎｉ６０Ａｌ２０Ｆｅ２０单晶和多晶的正电子寿命谱。基于正电子寿命谱的特征参数引入了正电子双区域捕获模型，并讨论了这些合金微观结构与力学性能之间的关系。     

Effect of dislocation density on the low temperature aging behavior of an ultra low carbon bake hardening steel

Strain aging was studied in an ultra low carbon (ULC) steel with a total carbon content of 20 ppm (wt.%) in order to identify the process stages and mechanism of bake hardening in this type of steel. The effects of dislocation density, varied by means of uniaxial tensile prestraining (1–10%) on the aging kinetics were investigated within an aging temperature range of 50–170°C. The aging was evaluated by means of strength measurements and the determination of interstitial carbon content after aging using a piezoelectric composite oscillator operating at 40 kHz. The interaction between interstitial carbon and dislocations was examined through amplitude dependent internal friction measurements. The influence of dislocation density on the aging behavior have been discussed with reference to the kinetics and mechanism of the aging process.     

Effect of solution heat treatment on galvanic coupling between intermetallics and matrix in AA7075-T6

Susceptibility to localised corrosion is strongly affected by heat treatments performed on Al-Zn-Cu-Mg alloys. In order to study how galvanic coupling between intermetallics and matrix is affected by solution heat treatment, AA7075-T6 and solution heat treated AA7075 have been characterised by means of scanning electron microscopy and scanning Kelvin probe force microscopy. Solution heat treatment strongly increased the Volta potential difference between the intermetallics and the surrounding matrix showing a strong increase in galvanic coupling. This is explained by Zn and Mg enrichment of the matrix caused by dissolution of strengthening particles during solution heat treatment.     

Characterizing corrosion behavior under atmospheric conditions using electrochemical techniques

AC and DC electrochemical experiments were performed as a function of humidity and contaminant concentration in an effort to identify the range of atmospheric environments where corrosion processes could be detected and possibly quantified. AC measurements exhibited two time constants at 25% relative humidity (RH), possibly indicating the ability to resolve both electrolyte resistance and interfacial impedance. Galvanic current measurements were sensitive to the presence of Cl_2(g) at 30% RH and electrochemical transients were detected at both 30% and 50% RH levels, also indicating sensitivity to interfacial processes. Higher humidity levels allowed better quantification due to decreasing electrolyte and interfacial impedances.     

A study on the deactivation of an IrO2–Ta2O5 coated titanium anode

The deactivation of an IrO₂–Ta₂O₅ coated titanium anode was studied during an accelerated life test at 2 A cm⁻² in 1 mol dm⁻³ H₂SO₄ solution using CV, EIS, SEM and EDX. The changes of voltammetric charge, double layer capacitance, oxide film resistance and charge transfer resistance of oxygen evolution with time during the electrolysis were monitored. The morphology and surface composition of the oxide anode before and after electrolysis test were analysed. A comprehensive process of deactivation of the oxide anode was proposed based on the test results and analysis.     

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr-Pd and Zr-Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr₇₀Pd₃₀ and Zr₈₀Pt₂₀ alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H₂SO₄ and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H₂SO₄, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.     

Corrosion behaviour of powder metallurgical and cast Al-Zn-Mg base alloys

The behaviour of Al-Zn-Mg base alloys produced by powder metallurgy and casting has been studied using potentiodynamic polarisation in 0.3% and 3% NaCl solutions. The influence of alloy production route on microstructure has been examined by scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectrometry. An improvement in performance of powder metallurgy (PM) materials, compared with the cast alloy, was evident in solutions of low chloride concentration; less striking differences were revealed in high chloride concentration. Both powder metallurgy and cast alloys show two main types of precipitates, which were identified as Zn-Mg and Zr-Sc base intermetallic phases. The microstructure of the PM alloys is refined compared with the cast material, which assists understanding of the corrosion performance. The corrosion process commences with dissolution of the Zn-Mg base phases, with the relatively coarse phases present in the cast alloy showing ready development of corrosion.     

Inhibitors performance in CO2 corrosion: EIS studies on the interaction between their molecular structure and steel microstructure

The performance of three imidazoline-like inhibitors in CO₂ corrosion was studied by means of electrochemical measurements employing a.c. and d.c. techniques. Carbon steel with two different microstructures (annealed, and quenched and tempered (Q&T)) was used in a deoxygenated 5% wt. NaCl solution, saturated with CO₂ at 40 °C and pH 6. Aminopropylimidazol (API) and two commercial imidazoline-based products (PC and QB) were used as inhibitors. Electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LRP) studies showed that the annealed samples have a better corrosion resistance than the Q&T samples when API and PC were added. On the other hand, the presence of QB yielded the opposite results. From the Bode phase angle plots it can be concluded that in the first case and for both microstructural conditions, there is no indication of formation of an inhibitor film, whereas in the presence of QB its formation is clearly evident. Based on these experimental findings, a mechanism of action for each inhibitor is proposed.