Effect of atmosphere on the synthesis of potassium titanate

Potassium titanate (K4Ti3O8) was synthesized by the reaction between ilmenite and concentrated KOH solution in the atmosphere of nitrogen,still air, and oxygen, respectively. The obtained samples were systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), and scanning electron microscopy (SEM). XRD results indicate that K4Ti3O8 have been synthesized in different atmospheres. The oxidizing atmosphere could enhance the conversion rate of Ti from ilmenite to K4Ti3O8, and Fe(Ⅱ) is easily oxidized to trivalent iron Fe(Ⅲ) during the reaction. Furthermore, SEM images show that the different atmospheres have significant effect on K4Ti3O8 crystal morphology and particle size. Well shaped K4Ti3O8 crystals are obtained in nonoxidizing atmosphere.     

电渣精炼去除铝中杂质铁(英文)

采用添加Na2B4O7的KCl-NaCl-Na3AlF6渣剂对浇注的工业纯铝自耗电极棒进行电渣精炼,以去除纯铝中的杂质铁,并改善其力学性能。结果表明:电渣精炼后纯铝中的铁含量随着Na2B4O7添加量和电渣重熔时间的增加而减少,在Na2B4O7添加量为9%和重熔时间为30min的情况下,铁含量从0.400%降低到0.184%。电渣精炼后,纯铝的弹性模量、屈服强度和抗拉强度得到改善,尤其是其延伸率提高了43%。铁含量降低的主要原因是电渣重熔过程中熔渣和铝液滴反应生成富铁相Fe2B。渣-液体系的反应热力学计算从理论上解释了Fe2B的生成。     

预氧化钒钛磁铁精矿的固态还原动力学及其机理

研究预氧化钒钛磁铁精矿固态还原反应的动力学,采用XRD、SEM和EDS等手段研究还原产物的显微结构和物相变化,在此基础上,对其固态还原机理进行研究。结果表明：以煤为还原剂,在还原温度为950~1100°C时,预氧化钒钛磁铁精矿的固态还原受界面化学反应控制,反应的表观活化能为67.719 k J/mol;预氧化钒钛磁铁精矿的还原历程可描述为：预氧化钒钛磁铁精矿→钛铁晶石→钛铁矿→亚铁板钛矿（Fe Ti2O5）→（FenTi1-n）Ti2O5。预氧化钒钛磁铁精矿在1050°C还原60 min后,还原产物中会形成M3O5型（M为Fe、Ti、Mg、Mn等）固溶体,存在于M3O5固溶体中铁的难还原性是限制预氧化钒钛磁铁矿还原的主要原因。     

铝热自蔓延法制备低氧高钛铁合金及表征

以金红石、钛精矿、Al为原料采用铝热自蔓延法制备出低氧高钛铁。研究相关反应体系的热力学及动力学问题,考察配料比、熔渣类型、发热剂等对铝热自蔓延过程的影响,采用XRD,SEM以及化学分析等技术对高钛铁合金进行表征。结果表明:反应体系的绝热温度大于1800K,反应能自我维持进行;Al还原TiO2反应的表观活化能为93.676kJ.mol-1,反应级数为0.01,Al还原TiO2和Fe2O3的表观活化能为300.740kJ.mol-1,反应级数为1.20;合金主要由TiFe2、TiFe以及Fe2TiO0.13等钛铁低氧固溶体相组成,夹杂相存在是导致合金中氧含量高及微观缺陷存在的直接原因;合金中钛、铝、铁、硅含量分别为:60.0%～62%、7.0%～11.0%、21.0%～25.0%以及3.0%左右;合金中的氧被有效去除,最低为1.85%。     

氧气底吹铜熔池熔炼过程的机理及产物的微观分析

对氧气底吹熔炼过程气体喷吹行为、造锍熔炼化学反应机理及熔炼炉内热工作状态进行理论分析及水模型实验和取样分析验证。结果表明,氧气底吹气流能使熔体形成均匀的扩散区,实现熔体的搅拌,在气体连续相区和液体连续相区,气液、液液之间的相互作用强烈,为炉内化学反应及传热传质提供了良好的动力学条件;氧气底吹熔炼过程在零配煤的情况下能达到自热熔炼,在节能减排方面,该工艺具有很强的优势;获得了铜渣、冰铜和蘑菇头中各组分的形貌,确定了铜渣、冰铜和蘑菇头的物相组成,渣样主要由冰铜相、磁铁矿相、铁橄榄石相和玻璃体相组成,熔炼内的氧势和硫势分布有利于反应的进行,能有效抑制Fe3O4的形成以及降低渣含铜。     

KINETICS OF REDUCTION IRON OXIDE IN CaO-SiO_2-Al_2O_3-Fe_tO SLAGS WITH CARBON SATURATED IN MOLTEN IRON

1.IntroductionItisimportanttoinvestigatethekineticsofreductionofironoxideinslagswithcarbonsaturatedinmoltenironforunderstandingboththeslag-metalreactioninthehearthofblastfurnaceandthefinalreductionbehavioursofprereductionironorepelletscontainingcarboninironbathreactor.Theprevious.......h..sll--7]focusedtheirattentionsmainlyonthereductionrateofpureironoxideortheredlltionrateofironoxideinsimpleslags.Thoseresultsarenotconsistentwiththatoftilerealsituation.Throughanalyzinggascompositionattheoutlet…     

涡流贫化法回收铜渣中的金、银、铜

采用熔融铜渣为原料,经过涡流贫化过程,回收铜渣中的金、银、铜,贫化渣进一步升温还原得到含铜铁水,最终可制备成耐磨铸铁。结果表明,通过涡流贫化,铜渣中的Fe_3O_4被还原为FeO,然后FeO与SiO_2结合,生成Fe_2SiO_4。经过涡流贫化后,金、银、铜的回收率分别达到了99.44%、93.97%和93.14%。贫化渣中Fe_3O_4和铜的含量分别为1.53%和0.61%(质量分数)。贫化渣涡流还原后得到的含铜铁水制备的耐磨铸铁成分满足高铬耐磨铸铁国标要求。     

在有机添加剂存在的情况下共沉淀制备纳米Fe3O4及其性能

在有机添加剂甲基丙烯酸乙酯存在的情况下,采用共沉淀方法从Fe2 与Fe3 的水溶液中制备了Fe3O4纳米粒子.分别通过X射线衍射、透射电镜研究了其结构与形貌.结果表明:当溶液中甲基丙烯酸乙酯浓度为0.015 mol/L时,所制备的纳米粒子为单一的Fe3O4相;粒子呈球形,半径大约为15～30 nm.同时,采用振动样品磁强计对Fe3O4纳米粒子的磁性能进行了表征.结果显示,在不同温度下测得的M-H/T曲线与温度无关,表明该粒子具有典型的超顺磁性.     

氟磷灰石还原的影响因素和等温动力学

为深入了解高磷铁矿煤基还原过程中氟磷灰石还原行为的影响因素和等温动力学参数,试验采用纯矿物配比的方式研究了二氧化硅含量、氧化铁含量、碳用量、还原时间和还原温度对磷灰石还原度的影响,并在此基础上,探明Ca10(PO4)6F2-SiO2-Fe2O3-C体系下氟磷灰石还原的等温动力学机理函数和动力学方程。结果表明:在一定的条件下,增加二氧化硅、氧化铁、碳用量、还原时间或还原温度均能够促进氟磷灰石的还原反应。在Ca10(PO4)6F2-SiO2-Fe2O3-C体系中,二氧化硅和氧化铁与氟磷灰石的最佳含量比分别为1.8和2.2,最佳C/O摩尔比为2.0。在最佳反应物用量条件下,氟磷灰石深度还原的最佳动力学机理函数为A1/3:1/3(1?α)[?ln(1?α)]?2;最佳动力学方程为:k(T)=3.89033×10^7exp(?282.748×10^3/RT),其中,指前因子为3.89033×10^7 min^?1,活化能为282.748 kJ/mol。还原反应的限制环节为固态扩散。     

Anodic reaction kinetics of electrowinning zinc in system of Zn(Ⅱ)-NH3-NH4Cl-H2O

The anodic reaction kinetics of zinc electrowinning was investigated on the titanium base RuO2 anode in the system of Zn(Ⅱ)-NH3-NH4Cl-H2O. The effects of stirring speed, ammonium chloride concentration and temperature on anodic reaction rate were studied through the curve measurement of potentiostatic polarization. The results reveal that the electrochemically controlled anodic reaction obeys Tafel equation and the anodic reaction order for ammonium chloride is 1. 056, with the apparent activation energy of 40.17 kJ/mol. The general equation of anodic reaction kinetics was obtained.     

采用草酸和紫外光催化法处理赤泥(英文)

利用草酸作为浸出剂以除去拜耳法残渣赤泥中的氧化铁,从而提高赤泥的工业应用价值,同时对草酸浸出液进行紫外光照射,将草酸铁还原成草酸亚铁沉淀,实现草酸溶液循环再利用。实验结果表明,在75°C下,赤泥在1mol/L草酸溶液中浸出2h,氧化铁的浸出率可达到96%,浸出后赤泥中氧化铁的含量由17.6%降低至小于1%。在紫外光照催化作用下,1h内浸出液中90%以上的草酸铁转变成草酸亚铁沉淀,剩余草酸可循环再利用。该草酸亚铁为β-FeC2O4.2H2O。对UV催化沉淀的机理进行讨论分析。     

微波加热碳热还原铁酸锌的动力学及热力学

研究550-950°C下微波加热配碳还原焙烧分解铁酸锌生成ZnO和Fe3O4/FeO的工艺及机理。利用HSC热力学软件对铁酸锌分解的热力学温度进行计算,并利用碳气化控制、化学控制及扩散控制模型研究样品中铁酸锌分解的动力学行为。分析微波功率、反应温度、配碳比和时间对铁酸锌分解率的影响。结果表明：在微波加热温度750°C,C/ZnFe2O4质量比为1：3,粒径74~89μm,微波功率1.2 kW的条件下,被还原的铁酸锌样品经过浸出后,Zn的回收率可以高达97.93%。通过采用不同的动力学模型对分解动力学进行测试。结果表明：碳气化控制机制是良好的机制。碳气化反应的活化能为38.21 kJ/mol。     

Thermal decomposition kinetics of antimony oxychloride in air

The DTA and XRD techniques were employed to study thermal decomposition mechanism of antimony oxychloride SbOCl in the air. The thermal decomposition reaction occurs in four steps, and the former three steps as: SbOCl (s)→Sb4O5Cl2(s) SbCl3(g)→Sb8O11Cl2(s) SbCl3 (g)→Sb2O3 (s) SbCl3(g). The forth step is the oxidation of Sb2O3 by air, Sb2O3(s) O2→Sb2O4(s). The activation energy and the order of the thermal decomposition reaction of antimony oxychloride in three steps presented in DTA curves were calculated according to Kinssinger methods from DTA curves The values of activation energy and the order are respectively 91.97kJ/mol, 0.73 in the first step,131.14 kJ/mol, 0.63 in the second step and 146.94 kJ/mol, 1.58 in the third steP.     

Kinetics of Oxidation of Fe–6Si

Surface oxidation of Fe–6Si during annealing in low-pressure air (～10⁴ Pa) in the temperature range 500–550 °C was investigated using resistivity measurements, Mössbauer spectroscopy, X-ray diffraction and scanning-electron microscopy (SEM). The time dependence of the resistivity exhibits an increase in two steps, which indicates changes in the structure and/or phase composition of the alloy. Structure and phase investigations show that the first step can be explained as formation of hematite (α-Fe₂O₃) and the second step is due to transformation of the hematite to magnetite (Fe₃O₄). The kinetics of the transformations were derived from the resistivity data. The activation energies (estimated from Arrhenius plots) of 194 kJ/mol and 165 kJ/mol were obtained for the formation of hematite and transformation of hematite to magnetite, respectively.     

Modification of the Surface of Magnetic Iron Oxides with Phosphonic Complexones

Protection of Metals and Physical Chemistry of Surfaces - The conditions of chemical modification of the surface of synthetic magnetic iron oxides (magnetite Fe3O4, maghemite γ-Fe2O3) by...     

长庆油田某采油厂集输管道内腐蚀原因及腐蚀机理

采用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等对长庆油田6个典型区块管道腐蚀失效的原因进行了分析,并对腐蚀机理进行了探讨。结果表明:6个典型区失效管道的组织为铁素体和少量的珠光体,元素分布均匀,化学成分符合20#钢的标准规定。1号、3号、4号、5号、6号典型区块腐蚀穿孔管节腐蚀产物的主要成分为铁的氧化物(Fe2O3、Fe3O4)。2号典型区块腐蚀穿孔管节腐蚀产物的主要成分为铁的氧化物(Fe2O3、Fe3O4)和铁的硫化物(FeS)。1号、4号、5号、6号典型区块管道主要发生了二氧化碳腐蚀。2号典型区块管道发生了二氧化碳和硫化氢腐蚀。3号典型区块管道发生了二氧化碳和氧腐蚀。     

Plasma post oxidation of nitrocarburized AISI 4140 steel

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel.Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase.It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ'-Fe4(N,C) phase.The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively.Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h.The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation.It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer.     

Investigation on Preparation of Tb2Fe17 by Direct Electrochemical Reduction of Tb4O7-Fe2O3 Pellet in Molten Calcium Chloride

在CaCl2熔盐中直接电化学还原固态Tb4O7与Fe2O3(Tb∶Fe=2∶17)的混合 粉末, 一步制得了金属间化合物Tb2Fe17. 结合混合氧化物烧结片在850 ℃的CaCl2 熔盐中3.1 V电解不同时间段产物的成分分析探讨了还原机理：Fe2O3优先还原 成金属Fe, 随后Tb4O7粉末在Fe上还原逐渐生成Tb2Fe17. 采用不锈钢筛网电极 循环伏安法证明了Tb4O7在Fe上的欠电位还原.     

Effect of temperature,oxygen partial pressure and calcium lignosulphonate on chalcopyrite dissolution in sulfuric acid solution

The pressure leaching mechanism of chalcopyrite was studied by both leaching tests and in-situ electrochemical measurements. The effects of leaching temperature, oxygen partial pressure, and calcium lignosulphonate, on copper extraction and iron extraction of chalcopyrite pressure leaching were investigated. The leaching rate is accelerated by increasing the leaching temperature from 120 to 150 °C and increasing oxygen partial pressure to 0.7 MPa. The release of iron is faster than that of copper due to the formation of iron-depleted sulfides. Under the optimal leaching conditions without calcium lignosulphonate, the copper and iron extraction rates are 79% and 81%, respectively. The leaching process is mixedly controlled by surface reaction and product layer diffusion with an activation energy of 36.61 kJ/mol. Calcium lignosulphonate can effectively remove the sulfur passive layer, and the activation energy is 45.59 kJ/mol, suggesting that the leaching process with calcium lignosulphonate is controlled by surface chemical reactions. Elemental sulfur is the main leaching product, which is mixed with iron-depleted sulfides and leads to the passivation of chalcopyrite. Electrochemical studies suggest that increasing the oxygen partial pressure leads to increasing the cathodic reaction rate and weakening the passivation of chalcopyrite.     

还原扩散法制备DyFe2反应机理的探讨

从化学反应动力学角度出发。探讨了还原扩散法制备DyFe2过程中Ca的迁移形态。Ca还原Dy2O3的速度，还原出的Dy迁移到Fe粉表面的方式以及DyFe2的形成过程。相应表观活化能的计算值为45kJ/mol。