基于铁矿粉液相流动性的塞拉利昂高铝铁矿配矿研究

以塞拉利昂高铝铁矿粉及其他5种烧结常用铁矿粉为原料,通过添加CaO、SiO2、Al2O3纯试剂改变铁矿粉中三种组分的含量,并分析了其对铁矿粉液相流动性的影响,比较了6类铁矿粉液相流动性对SiO2、Al2O3含量的敏感性差异,研究了混合矿粉液相流动性随塞拉利昂高铝铁矿粉配比的变化并进行了烧结试验。结果表明,随着CaO配比的增加,铁矿粉的液相流动性变好,其中塞拉利昂高铝铁矿粉变化的幅度最大;SiO2含量对塞拉利昂高铝铁矿粉液相流动性的影响较Al2O3含量更为明显;随着塞拉利昂高铝铁矿粉配比增加,混合矿粉的液相液动性指数降低,烧结矿的强度和成品率下降。     

Modes of occurrence of arsenic in high-arsenic coal by extended X-ray absorption fine structure spectroscopy

The concentration ranges of As and Sb in six Late Permian high-arsenic coals collected from Xingren and Xingyi, Guizhou Province are 94.1 μg·g -1-3 2 and 8 1 μg·g -1-120 μg·g -1, respectively. Based on the mineralogical analysis, no arsenic and arsenic-bearing minerals are detected in these samples and arsenic occurs in coal macerals. By extended X-ray absorption fine structure(EXAFS) spectroscopy, we have found that arsenic in these high-arsenic coal samples coordinates with oxygen; the coordination number of As with oxygen for these samples is 4 except one sample(H-9) for which the coordination number of As is 3. Therefore, arsenic in these high-arsenic coals does not occur in sulfide minerals, but occurs in arsenate or arsenite phase, and the preponderance of As is in arsenate of As 5+.     

Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (?T) and the softening start temperature (T_10%) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI_+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO·SiO₂ and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.     

Acting mechanism of F,K, and Na in the solid phase sintering reaction of the Baiyunebo iron ore

The effect of F, K, and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis (DTA) and X-ray diffraction (XRD). It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na₂SiO₃ and Na₂O·Fe₂O₃ and the generation of molten state in the solid phase sintering. Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO₂·CaF₂ in the solid phase reaction. The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point. In the sintering process, CaF₂ and SiO₂ react with CaO first and form 3CaO·2SiO₂·CaF₂ and 3CaO·2SiO₂, so the formation of ferrites, Na₂O·Fe₂O₃, and 2CaO·Fe₂O₃ is inhibited.     

In situ reaction mechanism of MgAlON in Al-Al2O3-MgO composites at 1700℃ under flowing N2

The Al-Al₂O₃-MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M₁, M₂, and M₃, respectively, were prepared at 1700℃ for 5 h under a flowing N₂ atmosphere using the reaction sintering method. After sintering, the Al-Al₂O₃-MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M₁ was composed of MgO and MgAl₂O₄. Compared with specimen M₁, specimens M₂ and M₃ possessed MgAlON, and its production increased with increasing aluminum addition. Under an N₂ atmosphere, MgO, Al₂O₃, and Al in the matrix of specimens M₂ and M₃ reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al₂O₃-MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N₂ atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al₂O₃-MgO composites were soaked at 580℃ for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al₂O₃ diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al₂O₃ to form MgAl₂O₄. When the temperature was greater than (1640 ±10)℃, AlN diffused into Al₂O₃ and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl₂O₄ at high temperatures because of their similar spinel structures.     

Syntheses and lyotropic liquid crystal properties of a series of sandwich-type tungstoarsenates heteropoly compounds with As/W ratio of 4/30

A series of sandwich-type tungstoarsenates heteropoly compounds with As/W ratio of 4/30, Na16[As4W30M4(H2O)2O112]·XH2O (M = Zn,Cu,Co,Ni,Mn and Cd), have been synthesized for the first time and structurally characterized by elemental analysis, IR and 183W NMR spectra. The crystal structure of Na16[As4W30Cu4(H2O)2O112]·63H2O was determined to be a triclinic system, of P1 symmetry, a = 1.2721(3) nm, b = 2.451 6(5) nm, c = 2.6450(5) nm, α= 89.90(3)°,β= 77.32(3)°, γ= 89.96(3)°, 2=2. Using tetrahepty lammonium bromide as a phase transfer reagent, [As4W30Cu4(H2O)2O112]16- was transferred from aqueous solution to organic phase (benzene), and the heteropolyanion lost the coordination water molecules to form the coordination-unsaturated ion. After lactic acid was added to the benzene solution, the coordination-saturation was recovered. By esterification reaction between lactic acid and cholesterin, the latter was attached to the heteropolyanion indirectly. Therefore, a new type of lyotropic liquid crystal was obtained, which was characterized by a polarimicroscope, DSC and variable temperature wide-angle X-ray diffraction.     

铁酸钙熔体对赤铁矿的渗透行为及对烧结强度的影响

考察了铁酸钙熔体添加SiO2或Al2O3对赤铁矿渗透行为的影响.采用以铁酸钙为粘结相的烧结赤铁矿试样,考察在铁酸钙中添加SiO2或Al2O3对烧结试样抗折和抗压强度的影响.试验结果表明,添加SiO2和Al2O3抑制了铁酸钙熔体对赤铁矿的渗透行为.在1300℃,恒温20min条件下,在铁酸钙中添加质量分数为2%的SiO2的烧结赤铁矿有最大的抗折和抗压强度,这是由于添加了SiO2的铁酸钙具有较短的熔化时间和较好的渗透性,在烧结过程中充分形成流动性好的液相,提高了粘结相固结铁矿石颗粒的作用.     

Investigation of novel zirconium based perovskite-type mixed conducting membranes for oxygen separation

A series of BaZr_0.2Co_0.8-xFe_xO_3-δ materials for oxygen separation were synthesized through a citric and EDTA acid combined complexing method, and their crystal structures, oxygen permeabilities, sintering and sealing abilities were investigated. The results showed that the cubic perovskite structure was formed for materials in the composition range investigated. Oxygen permeation flux and stability, as well as sintering and sealing abilities of the synthesized materials were increased or improved apparently due to the introduction of zirconium. For example, the oxygen permeation flux reached 0.8 mL/min·cm² when x = 0.2 or 0.3 at 950℃, and a stable time-related oxygen permeation flux was found for the BaZr_0.2Co_0.3Fe_0.5O_3-δ membrane at 800℃.     

Burn-resistant behavior and mechanism of Ti14 alloy

The direct-current simulation burning method was used to investigate the burn-resistant behavior of Ti14 titanium alloy. The results show that Ti14 alloy exhibits a better burn resistance than TC4 alloy (Ti–6Al–4V). Cu is observed to preferentially migrate to the surface of Ti14 alloy during the burning reaction, and the burned product contains Cu, Cu₂O, and TiO₂. An oxide layer mainly comprising loose TiO₂ is observed beneath the burned product. Meanwhile, Ti₂Cu precipitates at grain boundaries near the interface of the oxide layer, preventing the contact between O₂ and Ti and forming a rapid diffusion layer near the matrix interface. Consequently, a multiple-layer structure with a Cu-enriched layer (burned product)/Cu-lean layer (oxide layer)/Cu-enriched layer (rapid diffusion layer) configuration is formed in the burn heat-affected zone of Ti14 alloy; this multiple-layer structure is beneficial for preventing O₂ diffusion. Furthermore, although Al can migrate to form Al₂O₃ on the surface of TC4 alloy, the burn-resistant ability of TC4 is unimproved because the Al₂O₃ is discontinuous and not present in sufficient quantity.     

First-principles studies of the adsorption of O2 on Al （001）

Oxidationisaubiquitousphenomenonofnature.Theeconomiclossduetooxidationisverylargeeveryyear.Theinvestigationoftheadsorptionofoxygenonthesur-facesofmetalsisofgreatimportanceforbetterunder-standingoftheoxidationmechanismbecauseitistheverybeginningstageofoxidationofmetals.Itisgenerallybe-lievedthattheprocessofO2adsorptiononmetalsisinanorderofO2?O?O-?O2-,andthefollowingstagesareoxidenucleation,growthandtheoxidefilmformation.Astheprocessofadsorptionistooquicktobeobservedbyexperiments,atheoreticals…     

支撑板对烧结过程的影响

烧结料层上部荷重是造成烧结过程中燃烧熔融带透气性差的重要因素,而烧结料层透气性是制约我国厚料层烧结技术进一步发展的限制性环节. 从减轻烧结料层燃烧熔融带荷重以及改善烧结过程料层透气性的角度出发,通过在烧结料层中安装支架研究不同荷重条件下对铁矿粉烧结行为的影响. 烧结杯实验研究表明:安装支撑板后,烧结料层透气性明显改善,烧结矿转鼓强度大于65%;垂直烧结速度显著提高,最高可达28. 4 mm·min-1;成品率波动幅度不大,利用系数从1. 89 t· m-2·h-1增加到2. 31 t·m-2 ·h-1;燃耗有所降低,最大降幅达1. 32%. 理论分析和实验表明,支撑板对减轻烧结熔融带上部荷重,提高料层透气性,以及改善燃耗和烧结矿质量具有重要意义.     

Optimum sintering conditions for optical properties of translucent aluminum nitride ceramics

High translucency is one of the excellent properties of AlN ceramics because of its wide optical band gap energy of 6.2 eV. We have achieved success in producing AlN ceramic tube of 98% total visible light transmittance at 0.6 mm thick tube wall by applying an improved sintering technique. This AlN ceramic was produced by sintering at 1880℃ using Ca3Al2O6 as a sintering additive and in reduction atmosphere to remove the sintering additive from the final sintered material. After the sintering, the annealing ...     

Effect of sintering temperature on the physical properties and electrical contact properties of doped AgSnO<Subscript>2</Subscript> contact materials

AgSnO₂ electrical contact materials doped with Bi₂O₃, La₂O₃, and TiO₂ were successfully fabricated by the powder metallurgy method under different initial sintering temperatures. The electrical conductivity, density, hardness, and contact resistance of the AgSnO₂/Bi₂O₃, AgSnO₂/La₂O₃, and AgSnO₂/TiO₂ contact materials were measured and analyzed. The arc-eroded surface morphologies of the doped AgSnO₂ contact materials were investigated by scanning electron microscopy (SEM). The effects of the initial sintering temperature on the physical properties and electrical contact properties of the doped AgSnO₂ contact materials were discussed. The results indicate that the physical properties can be improved and the contact resistance of the AgSnO₂ contact materials can be substantially reduced when the materials are sintered under their optimal initial sintering temperatures.     

Arsenic removal from water by iron-sulphide minerals

In bench-scaled experiments, iron-sulphide minerals, pyrite and pyrrhotite are used as adsorbents for arsenic removal from As-spiked water of As⁵⁺ and As³⁺ species. The adsorption rate, efficiency, As-adsorption stability and the associated pH conditions have been examined. Observations indicate that these iron-sulphide minerals are very efficient to adsorb arsenic from water for both As⁵⁺ and As³⁺ species. Similar to other studies, As³⁺-adsorption shows a slower rate than As³⁺. The stability of the adsorbed arsenic seems closety retated to the pH values of the solution. A lower pH levet commonly less than 4.0 is required to protect the adsorbed arsenic from serious oxidation and backward retease. Fining of the mineral powders and shaking of the solution during adsorption enhance the adsorption efficiency and adsorption rate. For practical use of the method presented in this study, the waste produced should be managed with great care to keep it from redistribution over water system. A further study of the protection for the waste from oxidation on real water systems will greatly enhance the application of the strong ability of arsenic adsorption by these minerals, which is observed from this study.     

Synthesis and performance of Ca-α/β-SiAlON composites from tailings

Ca-α/β-SiAlON composites were prepared using Ca-α/β-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520℃ for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-α-SiAlON):I(β-SiAlON):I(Fe₃Si) = 23:74:3, where I_i stands for the diffraction peak intensity of phase i.     

Active compounds-based discoveries about the differentiation and apoptosis of leukemic cells

Acute myeloid leukemia （AML） is a heterogeneous group of hematopoietic malignancies which are characterized by the blockage of hematopoietic cell differentiation with uncontrolled proliferation and/or impaired apoptosis. Over the past 20 years, there has been tremendous progress in the biological, molecular, and cytogenetic aspects of the disease, accompanied by significant advancements in the treatment of AML patients. For example, all-trans retinoic acid （ATRA） and arsenic trioxide （As2O3） have been used clinically for effective treatments of patients with acute promyelocytic leukemia （APL, a unique subtype of AML） through differentiation and/or apoptosis induction. More intriguingly, these active compounds-based chemical biological studies greatly accelerated our understanding on leukemogenesis and targeted therapy of AML patients. Based on some recent findings mainly from our group, this review attempts to summarize the related advances from Chinese researchers.     

铁矿石粉矿成分对烧结强度的影响

在铁矿石烧结过程中,熔体性质决定了烧结矿粘结相的结构.采用小型试验来考察铁矿石粉矿的化学成分(SiO2,Al2O3,MgO和碱度)对烧结强度的影响.并通过化学成分对熔体的黏度和表面张力的影响来对烧结强度的变化加以解释.试验结果表明,随着粉矿中配加CaO与矿石的质量比的变化(0.08~0.15),在CaO与矿石质量比为0.12时获得最大烧结强度;而碱度R=2时获得最大的烧结强度;随着MgO含量的增加其烧结强度逐渐降低;而烧结原料中Al2O3质量分数不宜超过2.5%.     

高温水热法合成系列介孔氧化铝负载铂催化

采用高温水热法制备稳定、 高度晶化的介孔氧化铝材料(M-Al₂O₃-n), 通过异丙醇铝前驱体与聚四乙烯基吡啶(P4VP)模板间的酸碱自组装实现材料介孔结构的构筑, 再经高温水热处理（180 ℃）实现孔壁的晶化, 并通过担载少量的铂活性组分研究其在催化完全燃烧苯中的性能. 结果表明: M-Al₂O₃-n具有高度晶化的孔壁结构和典型的γ-Al₂O₃晶型; M-Al₂O₃-n具有较大的比表面积（335 m²/g）、 孔容(1.36 cm³/g)和均一的孔径分布（16.1 nm）; M-Al₂O₃-n具有粗糙的表面结构及丰富的纳米多孔结构; 该材料负载少量的铂（质量分数为03%）活性组分得到的新型催化材料在较温和的条件下即可将苯类VOCs完全催化燃烧.     

Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

In this paper, the diffusion behavior between MgO and Fe₂O₃ (the main iron oxide in pellets) is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe₂O₃ in the form of solid solution; the diffusion rate considered here is 13.64 μm·min-1. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {(Mg_1-x Fe_x)O·Fe₂O₃, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {(Mg_0.35-0.77·Fe_0.65-0.23) O·Fe₂O₃} and in the inner layer is {(Mg_0.13-0.45·Fe_0.87-0.55) O·Fe₂O₃}.     

Alternative beneficiation of tantalite and removal of radioactive oxides from Ethiopian Kenticha pegmatite-spodumene ores

The beneficiation methods for Ethiopian Kenticha pegmatite-spodumene ores were assessed through mineralogical and quantitative analyses with X-ray diffraction (XRD) and energy-dispersive X-ray fluorescence (EDXRF). The tantalite in the upper zone of the Kenticha pegmatite-spodumene deposit is 58.7wt% higher than that in the inner zone. XRD analysis revealed that the upper zone is dominated by manganocolumbite, whereas the inner zone is predominantly tantalite-Mn. Repeated cleaning and beneficiation of the upper-zone ore resulted in concentrate compositions of 57.34wt% of Ta₂O₅ and 5.41wt% of Nb₂O₅. Washing the tantalite concentrates using 1vol% KOH and 1 M H₂SO₄ led to the removal of thorium and uranium radioactive oxides from the concentrate. The findings of this study suggest that the beneficiation and alkaline washing of Kenticha pegmatite-spodumene ores produce a high-grade export-quality tantalite concentrate with negligible radioactive oxides.