盐酸浸出机械活化和碳热还原钛铁矿制备纳米二氧化钛(英文)

采用一个新工艺来处理天然钛铁矿并制备高品位的人造金红石纳米颗粒。该工艺主要包括球磨、碳热还原和盐酸浸出步骤。天然钛铁矿通过球磨处理后,颗粒尺寸会大幅度减小;后续的碳热还原会导致高钛渣的形成。在盐酸浸出工序中,重点考察了酸浸时间、温度和酸的浓度对浸出过程的影响。通过优化工艺条件,最后所得到的产品为纯度超过98.0%、颗粒尺寸为10～200nm的TiO2纳米颗粒。     

机械活化和氧化-还原处理对攀西钛铁矿精矿盐酸浸出的影响(英文)

研究机械活化和氧化-还原处理对攀西钛铁矿精矿盐酸浸出过程的影响。结果表明:机械活化和氧化-还原处理均可明显提高钛铁矿精矿中铁、钙和镁的浸出;氧化-还原处理的钛铁矿经盐酸浸出后得到的人造金红石,其钙镁含量过高,不能满足沸腾氯化法的要求;经机械活化处理的氧化-还原钛铁矿,能进一步降低盐酸浸出渣的钙镁含量,所得到的人造金红石含TiO290.50%、全铁1.37%、钙镁总量1.00%,完全满足沸腾氯化法的生产要求。最佳的氧化还原处理条件为:在900℃氧气气氛中氧化15min,在750℃氢气气氛中还原30min。     

机械激活工艺对TiO2碳热还原合成纳米TiC的影响

以纳米TiO2/碳黑为原料,通过机械激活-碳热还原法合成纳米TiC粉末,研究了机械激活工艺对TiO2碳热还原反应的影响.产物经XRD分析表明,激活时间延长、球料比增大、球磨机转速加快都有利于促进纳米TiO2碳热还原反应进行得更完全,但最终TiC产物中(Fe,C)杂质含量也随之上升.综合考虑,球磨时间4～8h,球料比10:1,转速250r/min对后续碳热还原合成纳米TiC是较合适的工艺选择.     

机械力活化合成机制研究

用两种球磨方式活化氧化铝,用化学分析法测量氧化铝碳热还原反应后生成氮化铝的转化率,考察了球磨活化对氧化铝碳热还原反应合成氮化铝的作用,研究了机械力活化合成的机制。结果表明,氧化铝与碳粉混合球磨时对碳热还原反应的作用远小于氧化铝单元单独球磨时对反应的作用,经球磨活化后,氧化铝碳热还原的反应温度降低,两相复合结构机制不能合理地解释这一实验结果。本研究认为,球磨过程中晶粒尺寸细化至纳米级以及显微应变的存在是球磨化活化促进化学反应的主要原因。     

低温机械化学法制备Mo-Cu纳米复合粉末

以CuMoO4-MoO3粉末为前驱体,采用机械化学-氢气共还原的方法制备出Mo-Cu纳米复合粉末。通过DSC对前躯体的制备温度进行研究,通过XRD、SEM及TEM分别对粉末的相组成、形貌和粒度进行表征,从热力学的角度对粉末的还原过程进行分析。结果表明,机械球磨可以有效地降低粉末的颗粒尺寸,增大反应面积,提高粉末还原活性,从而在低温下制备出Mo-Cu复合粉末。通过优化工艺参数,对机械球磨15h的CuMoO4-MoO3混合粉末在680℃下还原,可以得到颗粒尺寸为50～100nm的Mo-25%Cu(质量分数)纳米复合粉末。     

机械活化-盐酸常压浸出钛铁矿的影响

采用机械活化-盐酸常压浸出法对钛铁矿进行了选择性浸出,研究机械活化对钛铁矿的结构、形貌、粒度及浸出效果的影响。结果表明,机械活化可以细化钛铁矿的粒径,增加颗粒表面的粗糙度,从而增大其比表面积;机械活化可以破坏钛铁矿晶粒的完整性,并产生大量晶格缺陷,使晶格膨胀,上述作用均能强化钛铁矿浸出。最优浸出条件为:盐酸质量分数20%,反应温度100℃,酸矿比1.2,钛铁矿活化时间2 h。最优条件下Ti和Fe的浸出率分别为1.07%和95.5%,最终Ti和Si富集在渣中,其他元素进入浸出液。将上述得到的富钛渣煅烧获得了品位高于90%的人造金红石。     

醇热还原法制备纳米金属钌颗粒

报道了利用溶剂热工艺在乙醇溶液中制备胶态纳米金属钌颗粒的方法. 在120.℃热处理不同时间后, 观测到溶剂热还原反应形成不同颜色的中间体. 通过添加醋酸根稳定剂, 在乙醇溶剂中形成晶粒尺寸为3～6纳米的单分散金属钌颗粒. 通过该方法还合成了溴化十六烷基三甲铵(HTAB)包敷的晶粒尺寸为1～5纳米的金属钌粉体.     

预处理方式对盐酸浸出钛铁矿制备人造金红石的影响

本文以钛铁矿精矿为原料,采用盐酸浸出制备人造金红石,首先采用Factsage 6.0热力学软件绘制了相关组分的φ-pH图,研究了盐酸浸出制备人造金红石的热力学基础;而后研究了还原焙烧和弱氧化焙烧两种预处理方式对人造金红石品位、粉化率等的影响。结果表明:在盐酸加压浸出体系中,钛铁矿中的FeO、Fe_2O_3、CaO和MgO均能溶解在溶液中,而SiO_2和TiO_2则留在固相中;还原焙烧和弱氧化焙烧预处理有利于提高产品TiO_2的品位,其中弱氧化焙烧还可降低产品的粉化率。     

球磨转速对碳热还原钛铁矿合成Ti(C,N)复合粉末性能的影响

在碳热还原钛铁矿合成Ti(C,N)复合粉末前的高能球磨预处理过程中,采用不同的球磨转速,研究了合成的Ti(C,N)复合粉末的粒径、形貌、物相组成、烧结性能和耐腐蚀性能。结果表明,随球磨转速从250 r/min增至750 r/min,Ti(C,N)复合粉末的粒径先减小后增大,烧结性能和耐腐蚀性能先提高后降低;与250 r/min相比,600 r/min时碳热还原钛铁矿合成Ti(C,N)复合粉末的烧结体抗折强度增加18.3%,断裂韧度增加48.7%,腐蚀电位正移253 m V。球磨转速优选为500~600 r/min。     

采用混合Nb_2O_5,B_2O_3和Mg粉末冶金法合成硼化铌（英文）

在强还原剂条件下,以相关的金属氧化物为原材料,采用粉末冶金法成功合成具有不同含量NbB、NbB_2和Nb_3B_4相的硼化铌粉末和单相NbB粉末。在室温下使用高能球磨机球磨Nb_2O_5、B_2O_3和Mg混合粉末。随后,利用HCl浸出除去球磨粉末中无用的MgO相,合成最终产物NbB-NbB_2-Nb_3B_4,产物在1500℃下退火4 h,以便观察硼化物之间的转换。采用XRD、DSC、PSA、SEM/EDX、TEM和VSM表征该产物。研究球磨时间(达9h)对产物形成、显微组织和热行为的影响。化学计量混合粉末经2 h球磨后,发生了还原反应。在不存在任何二次相和杂质时,通过机械化学法,球磨5 h并采用4 mol/L HCl浸出,得到高纯纳米尺寸NbB-NbB_2-Nb_3B_4粉末。经退火处理后,纯的纳米尺寸NbB-NbB_2-Nb_3B_4粉末转变为单相NbB,不存在NbB_2和Nb_3B_4相。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.