低品位菱镁矿与硅石制备镁橄榄石的研究

以低品位菱镁矿与天然硅石为原料制备镁橄榄石材料。研究了低品位菱镁矿轻烧氧化镁粉引入量对制备的镁橄榄石材料中镁橄榄石的晶胞常数、微观结构及常温性能的影响。用X射线衍射（XRD）和扫描电镜（SEM）对试样的相组成和显微结构进行了研究。利用X′ pert plus软件对试样中镁橄榄石相的晶胞常数进行分析。结构与性能分析结果表明：低品位菱镁矿中氧化镁与天然硅石中二氧化硅在高温条件下通过固相反应可以制备出以镁橄榄石为主晶相的镁橄榄石材料。随着低品位菱镁矿轻烧氧化镁粉引入量的增加,镁橄榄石材料中镁橄榄石相的晶胞常数和晶胞体积有增加趋势。同时,随着方镁石相在镁橄榄石材料中的脱溶作用,镁橄榄石材料的体积密度和强度逐渐降低,显气孔率和吸水率逐渐增加。     

Thermal Conductivity of Refractory Brick

Thermal conductivity measurements were made on many types of refractory brick including high-alumina, fireclay, silica, chrome, magnesia, forsterite, zircon, silicon carbide, and insulating brick. These measurements, made with a modified ASTM C 201–47 apparatus, covered mean specimen temperatures of 200° to 2000°F. The results are compared with other published data.     

Ceramic Electrical Insulating Materials

During the past 30 years, the principal ceramic insulating materials have been the electrical porcelains, the steatites, and the high alumina bodies. The compositions, the structures, and the properties of these materials are discussed. Other porcelains and insulating compositions, containing as their principal crystalline phases mullite, zircon, forsterite, cordierite, wollastonite, or β-spodumene, have unusual properties and are useful for specialty items. Predictions of future trends in ceramic insulating materials are made.     

玻璃窑用轻质镁橄榄石砖的研制

为了开发玻璃窑用碱性耐火隔热产品,以镁橄榄石砂和镁砂为主原料制备了轻质镁橄榄石砖,并研究了结合剂种类(分别为MgCl2.6H2O、亚硫酸盐纸浆和QH)及其加入量(质量分数分别为5%、7.5%和10%)、添加剂加入量(质量分数分别为2%、3%、4%和5%)、造孔剂菱镁矿加入量(质量分数分别为10%、15%、20%、28%和36%)以及烧成温度(分别为1 300、1 350、1 400、1 450和1 500℃)对轻质镁橄榄石砖的影响。结果表明:以镁橄榄石砂为主要原料,添加36%(w)的造孔剂和4%(w)的添加剂,同时外加7.5%(w)的QH作结合剂,干燥后于1 400℃保温2 h煅烧,可以生产出体积密度为1.84 g.cm-3,显气孔率为43%,耐压强度为10 MPa,热导率(800℃)为0.63 W.m-1.K-1的玻璃窑用轻质镁橄榄石砖。     

Forsterite products from calcined Solov'evogor dunite

Conclusions The porosity of Solov'evogor dunite, calcined in a rotary kiln, is less than 17%. Forsterite products based on calcined dunite have good properties, except for thermal shock resistance.Use of calcined dunite for preparation of forsterite products promotes an increase in their heat conductivity.The possibility of using part of the dunite dust collected in the gas purification system of a rotary kiln as an additive to the charge for preparation of forsterite products has been established. Forsterite products made of calcined dunite are used successfully in the brickwork of the regenerators of open-hearth furnaces; however, a relatively low thermal shock resistance limits their use in brickwork which is washed with water.Translated from Ogneupory, No. 4, pp. 4–8, April, 1968.     

中间包绝热板的损毁机理

研究了三种用后中间包绝热板的显微结构。其损毁机理为：硅质绝热板原石英颗粒向α－方石英转变，与渣反应生成大量玻璃相，属溶蚀型损毁；镁质绝热板与渣反应生成ＭＡ、Ｃ３ＭＳ２及黄长石类矿物．属溶蚀及剥落型损毁；镁橄榄石质绝热板与渣反应，原镁铁橄榄石固溶体中的［Ｆｅ］被渣相中的［Ｍｎ］置换反应生成镁锰铁橄榄石固溶体，析出［Ｆｅ］，属剥落及溶蚀型损毁。并讨论了绝热板对钢液质量的影响。     

Effect of Attritor Milling on Synthesis and Sintering of Forsterite Ceramics

Forsterite (Mg₂SiO₄) was chosen as a new candidate for bone implant application because of its superior fracture toughness and good bioactivity. However, synthesizing pure forsterite has been a challenge to many researchers because of its inability to eliminate secondary phases that have similar chemical compounds as forsterite. Attritor mill was introduced to form pure forsterite via solid‐state method through the reaction between magnesium carbonate (MgCO₃) and talc (Mg₃Si₄(OH)₂). Attritor‐milled samples showed superior mechanical properties compared with ball‐milled samples because of the smaller particle size of the former which in turn eliminated the secondary phases at low sintering temperature.     

Densification and properties of magnesia-rich magnesium-aluminate spinel derived from natural and synthetic raw materials

Magnesia rich magnesium aluminate spinel (MgO: Al₂O₃=2:1) was developed by reaction sintering of Indian natural magnesite of Salem region as well as from synthetic caustic magnesia with calcined alumina. Dilatometric study of the green compacts was carried out to evaluate the spinelisation and sintering behaviour of both the samples. Green samples were heat treated between 1400 to 1600 °C and characterised in terms of densification behaviour, high temperature flexural strength, microstructure and phase development. Spinel and periclase are the major phases in both the samples, where as forsterite is found only in the sample developed from Indian magnesite due to presence of silica as impurities.     

(1-x)NBT-xBaTiO3系陶瓷材料制备过程中预烧温度的研究

根据(1-x)NBT-xBaTiO3的配方,分别选取不同组成点,采取不同的预合成温度,根据样品的体积密度和压电性能,确定最佳的预烧温度。     

氟、硼共掺杂对纳米TiO_2能带结构与可见光光催化性能的影响

以钛酸四丁酯、氟化铵、硼酸为原料,采取改进的溶胶-凝胶法制备了氟、硼共掺杂的纳米二氧化钛粉体.XRD结果显示氟、硼共掺杂不仅可以抑制晶粒生长,还可以阻止锐钛矿相向金红石相的转变.当氟、硼物质的量比为5∶ 20时,其表现出更好的可见光响应.XPS 结果表明:氟和硼分别和钛形成了F-Ti键和B-Ti键,它们的形成可提高价带中光生空穴的氧化能力和拉窄二氧化钛的带隙,从而提高了其可见光照射下的光催化活性.可见光照射下降解4-氯苯酚,结果表明:经600 ℃煅烧2 h的样品,氟、硼物质的量比为5∶ 20,其降解率分别是单掺杂和纯二氧化钛的1.5到3倍.总有机碳(TOC)分析结果表明4-氯苯酚在可见光照射下被光催化剂有效地矿化.     

Sr-doped forsterite nanopowder: Synthesis and biological properties

Nanoscale forsterite (Mg₂SiO₄) has recently been proposed for bone tissue engineering application. Due to the special role of strontium (Sr) in bone remodeling, the stimulation of bone formation and reduction in bone resorption, the modification of forsterite by doping with Sr is expected to increase bioactivity and biocompatibility. The aim of this study was to incorporate Sr (0, 0.05, 0.1, 0.2 and 0.4 at%) into forsterite using sol-gel method and to investigate the effect of Sr content on the phase composition, in vitro apatite-formation ability as well as osteoblast-like MG63 viability. Results demonstrated that while forsterite was the main phase of all Sr-doped forsterite nanopowders, Sr₂MgSi₂O₇, MgO and MgSiO₃ were present as the minor phases depending on the Sr content. Moreover, the presence of Sr atom influenced the crystallite and particle size as well as lattice parameters of the forsterite powder, while did not significantly change the morphology of particles. Noticeably, the incorporation of Sr up to 0.2 at% enhanced the average crystallite size (from 25.3 nm to 45.9 nm) and particle size (31.0 ± 3.9 nm to 62.9 ± 11.8 nm) of pure forsterite powder. Additionally, according to the Rietveld refinement, the incorporation of Sr up to 0.2 at% increased the lattice parameters of forsterite more than 0.1%, depending on the Sr content. In vitro bioactivity assessment in simulated body fluid (SBF) revealed while all Sr-forsterite samples possessed greater bioactivity than pure forsterite nanopowder, the incorporation of 0.1 at% Sr revealed improved bioactivity compared to other Sr-forsterite samples. However, according to MTT assay, while all forsterite-based ceramics significantly improved the cell proliferation compared to tissue culture plate (TCP) and forsterite nanopowder, Sr-forsterite nanopowders consisting of 0.05–0.1 at% Sr revealed a considerably promoted cell proliferation. In conclusion, Sr-forsterite nanopowder could be a promising candidate for bone tissue engineering and reconstruction of bone defects such as osteoporosis.     

High performance multi-layer varistor (MLV) from doped ZnO nanopowders by water based tape casting: Rheology,sintering, microstructure and properties

In this work, we report the fabrication of a high performance multi-layer varistor (MLV) via water based tape casting method using novel compositions of nanomaterials. Bi₂O₃, CaO and Co₃O₄ doped ZnO nanopowders were prepared by solution combustion synthesis (SCS) route, calcined at different temperatures (550, 650, 750 and 850?°C) and characterized by TEM, XRD, SEM and AFM. The nanopowder (crystallite size ~30?nm) calcined at 650?°C for 1?h was used as the starting material for MLV fabrication. Compositions of the slurry containing doped ZnO nanopowders, binder and plasticizer in water solvent were optimized for the fabrication of thick film. The rheological properties of the slurries having different solid loadings were analysed and thick films of various thicknesses (50–500?µm) were prepared by varying the feeding rate of tape casting. The film roughness of 38.3?nm for the thick film made from 40?wt% solid slurry was found to be superior compared to other samples due to the presence of reduced crack and shrinkage. MLV fired at 950?°C for 1.5?h exhibited a coefficient of nonlinearity of 18 and breakdown voltage of 291.5?V that yields superior properties compared to commercial MLVs.     

Forsterite refractory brick produced by talc and magnesite from Thailand

This research focuses on refractory material synthesized from precursors of talc and magnesite in Thailand. They were mixed at a molar ratio of 1:5 with mechanical activation at 5 h and calcined at 1300 °C for 1 h to create forsterite. The resulting forsterite crystals were round with less than 1-μm particle size. Synthetic forsterite refractory was formed into refractory bricks and studied at various sintering temperatures of 1200, 1300, and 1400 °C with a dwell time of 2 h. The characteristics and properties of refractory samples were tested in physical properties, cold crushing strength, thermal conductivity, thermal shock, and corrosion resistance from various substances. The results showed that increasing the sintering temperature increases the physical properties and cold crushing strength values. Also, the sintering temperature increases will increase thermal conductivity. The best condition of forsterite refractory brick sintering was 1400 °C for 2 h (FB-14), which showed the following desirable properties: firing shrinkage of 18%, bulk density of 3.03 g/cm³, the apparent density of 3.26 g/cm³, both apparent porous and water absorption values of zero, and cold crushing strength of 72.18 MPa. The FB-14 brick has excellent resistance to corrosion and penetration from lead silicate frit and copper slag. There was minor weight loss from the corrosion of the chemical solutions used in sodium hexametaphosphate production, whereby weight loss will begin on the 18^th cycle. Consequently, the FB-14 brick can be used for blast furnace walls to slow down corrosion, which will allow the blast furnace to have a longer life cycle.     

改性煅烧剥片高岭土对PVC塑料的改性作用

采用PVC树脂为主原料,以4种改性高岭土为改性剂和其他助剂相混合填充PVC塑料制成改性塑料,研究了4种改性高岭土对改性塑料的力学性能和电学性能影响。改性煅烧剥片高岭土的性能最优,其最佳添加量为10～20份。     

Synthesis of fluorine-graphite intercalation compounds by elemental fluorine and high oxidation-state transition-metal fluorides

Fluorine-graphite intercalation compounds have been synthesized using high purity fluorine gas and high oxidation-state transition-metal fluorides, AgF₃ and NiF₃, at room temperature and at −78 °C. At room temperature, a mixture of stage 1 + 2 − 4 compounds with compositions, C_4.2F to C_14.6F were obtained. On the other hand, stage 2–4 compounds with compositions C_5.6F to C_14.2F were synthesized at −78 °C. The fluorinating ability of AgF₃ and NiF₃ has been shown more clearly at room temperature because a small amount of fluorine was intercalated/absorbed into graphite at −78 °C without catalysts. XPS spectra show that ionic, nearly ionic, semi-covalent and covalent fluorines coexist in the C_xF samples, and that the covalency of CF bonding increases with decreasing stage number.     

Formation and Morphology of Zn(2)Ti(3)O(8) Powders Using Hydrothermal Process without Dispersant Agent or Mineralizer

Synthesis of Zn(2)Ti(3)O(8) powders for attenuating UVA using TiCl(4), Zn(NO(3))(2)·6H(2)O and NH(4)OH as precursor materials by hydrothermal process has been investigated. The X-ray diffractometry (XRD) results show the phases of ZnO, anatase TiO(2) and Zn(2)Ti(3)O(8) coexisted when the zinc titanate powders were calcined at 600 °C for 1 h. When calcined at 900 °C for 1 h, the XRD results reveal the existence of ZnO, Zn(2)TiO(4), rutile TiO(2) and ZnTiO(3). Scanning electron microscope (SEM) observations show extensive large agglomeration in the samples. Transmission electron microscope (TEM) and electron diffraction (ED) examination results indicate that ZnTiO(3) crystallites formed with a size of about 5 nm on the matrix of plate-like ZnO when calcined at 700 °C for 1 h. The calcination samples have acceptable absorbance at a wavelength of 400 nm, indicating that the zinc titanate precursor powders calcined at 700 °C for 1 h can be used as an UVA-attenuating agent.     

Synthesis and characterization of nanocrystalline forsterite through citrate–nitrate route

Nanocrystalline forsterite, Mg₂SiO₄, powder was synthesized according to the citrate–nitrate technique using an aqueous solution of magnesium nitrate, colloidal silica, citric acid, and ammonia. The dried precursor and the powders calcined at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The initial crystallization temperature of forsterite was around 770 °C while fully crystallized forsterite was obtained at 860 °C with a crystallite size of about 30 nm.     

Occurrence of Dielectric 1:1:4 Compound in the Ternary System BaO—Ln2O3—TiO2 (Ln = La, Nd, and Sm): II, Reexamination of Formation of Isostructural Ternary Compounds in Identical Systems

To establish the correct composition of a ternary compound having higher TiO₂ content in the BaO—Nd₂O₃—TiO₂ system, the phase change of samples with variable controlled compositions, which were prepared by a modified coprecipitation method, was examined by X-ray diffractometry and Raman spectroscopy. Identification of the phases present in the calcined samples and microstructural evidence for the fired product from electron microprobe analysis clearly indicated that the ternary compound having the composition 1:1:4 occurs in the present system. X-ray powder diffraction data of the isostructural 1:1:4 and 1:1:3 compounds in each identical ternary system (Ln = La, Nd, and Sm) were refined and indexed. Partial subsolidus phase relations consisting of different composition triangles were also proposed for the present ternary systems.     

High-throughput preparation and testing of MoNbSbV mixed oxide catalysts for direct oxidation of propane to acrylic and acetic acids

An automated robotic method using a solution at pH=2 containing four precursor salts dissolved has been developed and validated for high-throughput preparation of Mo, Nb, Sb and V mixed metal oxide solids, which are known to be selective for propane oxidation to acrylic (AA) and acetic (AcA) acids. Spherical shaped silica beads of exceptionally narrow size distribution were synthesised using oil drop technique from a Brace™ instrument. Automated impregnation of the beads by the previous solution has been developed and validated. Catalytic studies were performed using a conventional micro-reactor system with an Ultra-Fast™ GC analysis (<2 min against >30 min). After calcination of the samples under either N₂ or air at 873 K, a mixture of phases was obtained, such as VSbO₄, Mo_xM_1−xO_2.8 (M=V and/or Nb), Sb₄₍₂₎Mo₁₀O₃₁, and other minor phases, such as MoO₃ if activated in air. Mixed oxide samples calcined under N₂ gave better catalytic activity and selectivity to AA/AcA compared to those calcined under air. Measures of catalytic performance of 16 supposedly identical materials fell within a ±5% range of the median values, showing that our experimental set-up is relevant to combinatorial studies. By preparing 15 samples of different chemical composition, optimum catalytic performance was found to correspond to Mo_0.55 Nb_0.09 Sb_0.18V_0.18 mixed oxide calcined at 773 K under N₂, containing a mixture of phases, in particular Mo_xM_1−xO_2.8 and Sb₂Mo₁₀O₃₁, similarly to the M1 and M2 phases observed for MoNbTeV mixed oxide catalysts.     

ELECTRIC FURNACE STUDY OF THE MgO-SiO2 SYSTEM*

Fusions of compositions spaced at intervals throughout the magnesia-silica system were prepared in an electric arc furnace. Potter's flint and precipitated magnesium carbonate were used as starting materials for one series of samples, and olivine, quartz sand, and magnesite were used as lower purity raw materials in a second series to simulate commercial conditions. Chemical, spectrographic, microscopic-petrographic, density, and pyrometric cone equivalent (P.C.E.) determinations were made on typical specimens selected from each melt. Periclase, forsterite, and clinoenstatite crystallized in strict agreement with the phase diagram, and the phenomenon of immiscible silicate phases was observed in high silica compositions. No new compounds, however, were seen. The possibility of beneficiating olivine for refractory service by electric furnacing was also investigated.