Effects of Admixtures on the Anti—oxidation Property of MgO／Si3N4 Composite Refractory

The effect of the admixtures of Al and Si metals and B4C and MgAlON compounds on the oxideation of MgO/Si3N4 composite refractory has been studied,which is a promising carbon free refractory for steel-making applicatlon.The four kinds of admixtures can be used as anti-oxidants for Si3N4,ut the mixture of Al and Si achieved the best result .The mixture can not only play the role as antioxidant,but also assist the sintering process and help form dense sintering layer,improving the property of the composite.     

Thermodynamic Properties of Non-Oxide Composite Refractories

For initiative application of non-oxides in refractories, it is essential to study thermodynamic properties of non-oxides. The stability and stable order of non-ox- ides under oxidized atmosphere are analyzed firstly and then a new process, “converse reaction sintering”, is proposed. The results of study on oxidation mechanism of silicon and aluminum nitrides indicate that the gaseous suboxides can be produced observably when the oxygen partial pressure is lower than “conversion oxygen partial pressure”. The suboxides can be deposited near the surface of composite to become a compact layer. This causes the material possessing a performance of “self-impedient oxidation”. Metal Si and Al are the better additives for increasing the density and width of compact layer and increasing the ability of anti-oxidation and anti-corrosion. The study on Si3 N4-Al2O3, Si3N4-MgO, Si3 N4-SiC systems is also enumerated as examples in the paper. The experimental results show that the converse reaction sintering is able to make high performance composites and metal Si and Al not only can promote the sintering but also increase the density and width of compact layer.     

Phase Composition Analysis of TiN-AI2O3Synthesized from Aluminum-containing Dross and Rutile by Aluminothermic Reductionnitridation Method

TiN- Al2O3 composite powder was prepared by aluminothermic reduction- nitridation method with starting materials of aluminum-containing dross and rutile,and metallic aluminum in the aluminum-containing dross as reducer. The influences of synthesis temperature(600-1 400 ℃) and aluminum-containing dross addition(20% lower than theoretical value,theoretical value,20% higher than theoretical value,and 50% higher than theoretical value) on phase compositions and microstructure of the composites were investigated,and the reaction mechanism was analyzed. The results show that(1) TiN- Al2O3 composite powder can be synthesized under the experimental conditions; the main phases are TiN,α-Al2O3,a little bytownite,and MgAl2O4;(2)enhancing synthesis temperature or increasing aluminumcontaining dross addition favors the reaction of aluminothermic reduction- nitridation;(3) in the synthesized products,α-Al2O3 is platy or columnar; TiN is sub-micron granular,which reinforces and toughens the composite.     

Effect of Zircon Addition on Properties of Low Carbon Al2O3-C Refractories

Using tabular alumina as aggregate,tabular alumina fines, reactive alumina ultra-fines, aluminum powders,silicon powders,carbon black,flake graphite,B4C and zircon fines as matrix,low carbon Al2O3- C refractories were prepared. Influences of zircon powders additions( 0,3%,5% and 7%,in mass,the same hereinafter) on properties,phase composition and microstructure were investigated. The results show that the ZrO2- nitride can be in-situ formed through carbothermal reduction and nitridation in Al2O3- C refractories.With the increase of zircon powder,the oxidation resistance of the Al2O3- C refractories improves obviously,the oxidized layer thickness decreases from 7. 94 mm without zircon to 2. 71 mm with 5% zircon. HMOR at 1 400 ℃of the Al2O3- C refractories reaches the maximum 14. 9MPa when zircon addition is 5%. With the increase of zircon powder,the apparent porosity and bulk density change a little,CMOR and CCS increase.     

LIQUID AXIAL BACKMIXING IN MULTISTAGE BUBBLE COLUMN

The characteristics of a staged bubble column can be described by a multi-stage backmixing model,provided: (1) Each stage can be considered as a perfect mixing reactor,and (2) The backmixing coeffi-cients do not vary with time and reactant concentrations.Experimental results indicate that the first conditionis approached under certain conditions,while the second assumption is correct.Studies were made using steady state chemical tracer method to determine the backmixing coefficientsof each plate between stages.The fluid flow through the holes of perforatcd plates is a stochastic process.From the statistical point,the experimental data could be correlated by semicmpirical equation developed.This equation can also be used to correlate the data reported by Nishiwaki for bubble column with plateshaving high percentage of opening area and large size holes between stages.Continuous oxidation of unsaturated sulfur compounds (mainly in the form of thiosulfatc and also somein polythionate form) in nickel ammonium carbonate solution were carried out in bubble columns with heightof 3400mm and diameters of 36 mm and 100mm respectively.The oxidation has to be taken in a multistagebubble column for high degree of oxidation.The axial concentration of unsaturated sulfur compoundsalong a multi-stage bubble column can be calculated from the backmixing model and the kinetic equationof oxidation.Results of calculation agree with the data taken along the column height.Equation was alsodeveloped to calculate the optimum temperatures of oxidation which agree favorably with the experimentalresults.     

A CFD model for gas uniform distribution in turbulent flow for the production of titanium pigment in chloride process☆

The fluid dynamic behavior of feeding gas (TiCl4) in an annular channel affects the combination of O2 and TiCl4 in an oxidation reactor, a key piece of equipment in titanium pigment production. The numerical procedure was validated by a 3-dimensional gas flow in the annular channel. Applying the validated model, the flow character-istics of TiCl4 in the oxidation reactor with a tangential inlet were simulated and characterized. The flow distribu-tion with five rectifying rings of different structure was simulated and analyzed. The results showed that the rectifying ring improved the distribution uniformity of the pressure and outlet velocity. Compared to the original case without a rectifying ring, the non-uniformity of the pressure and outlet velocity could be reduced by up to 91%and 69%respectively. The rectifying ring #5, which can be instal ed and adjusted easily, is more effective in realizing even distribution. In addition, instal ation of the rectifying ring effectively reduced the circulating flow in an annular channel as well as the total energy loss.     

高Al_(13)含量聚合氯化铝制备γ-Al_2O_3及表征(英文)

In this paper a polyaluminum chloride solution with high Al13 content was prepared and used as raw material for preparation ofγ-Al2O3.The texture and crystalline phase of the prepared alumina samples were characterized by energy dispersive X-ray spectroscopy(EDX) ,X-ray diffraction,transmission electron microscope(TEM) and nuclear magnetic resonance(NMR) analyses.The effects of alkaline solution and calcination temperature were investigated.The results showed that alkaline solution including NH3·H2O and NaOH had little effect on the alumina sample formation.The impurities of NH4Cl and NaCl in solution can be removed through repeated washing by EDX analysis.Calcination temperature had a significant effect on alumina crystal phase.The alumina sample can transform completely toγ-Al2O3 in the subsequent heating from 600°C to 800°C.It is very interesting that Al13 can be existed inγ-Al2O3 phase even after calcinations.The results indicate that polyaluminum chloride with high Al13 content is an effective material to prepareγ-Al2O3.     

Effect of Al on Al_4SiC_4-Al_4O_4C Composite Synthesized from Kaolinite Grog

The Al4SiC4-Al4O4C composites were synthesized using 1∶6.5∶2.6 of molar ratio of kaolinite grog powder, carbon black, and aluminum powder as basic formulation, fixing the additions of kaolinite grog powder and carbon black, varying aluminum powder addition to make its proportion from 2.6 to 3.9, 5.5, 7.0, 8.6, and 10.4, respectively, adding phenolic resin as binder and absolute alcohol as dispersant, mixing well, pressing, drying, and firing at 1 700 ℃ for 2 h in a corundum tubular furnace in flowing argon. The effect of Al addition on phase composition and microstructure of Al4SiC4-Al4O4C composites was investigated by DTA-TG, XRD, and SEM. The results show that:(1) in a certain degree, more Al4SiC4 forms with Al powder addition increasing; (2) the formed Al4SiC4 has two morphologies, namely, sheet and block, and their particle sizes are 5-15 μm and 10-20 μm, respectively; (3) the Al powder addition increase has little effect on the grain shape and size of Al4SiC4; (4) the formed Al4O4C mainly distributes on the surface of the Al4SiC4 grains with irregular shape and particle size below 1 μm, and some of them bond together.     

Fe2O3对天然原料合成Al4SiC4/Al4O4C复合耐火材料的影响（英文）

以焦宝石、活性炭和铝粉为原料并添加Fe2O3后制备了Al4SiC4/Al4O4C复合耐火材料。利用化学分析、X射线衍射和扫描电镜研究了Fe2O3对所制备复合材料的物相组成和显微结构的影响。结果表明：在烧结过程中,从1400℃开始,Fe2O3转变为低熔点物相Fe3Si,产生液相促进Al4SiC4成核、细化晶粒,同时包裹Al4SiC4。此外,未添加Fe2O3的样品中生成的Al4O4C短纤维,Fe2O3的加入使得Al4O4C相变为细小的晶粒。

Abstract：

Al4SiC4/Al4O4C composite refractory was synthesized by using flint clay,activated carbon and aluminum powders as the raw materials and Fe2O3 as the additive. The effects of Fe2O3 on the phase composition and microstructure of Al4SiC4/Al4O4C composite refractory were investigated by chemical analysis,X-ray diffraction and scanning electron microscopy. The results show that Fe2O3 transforms into a low melting point phase of Fe3Si above 1 400 ℃,which leads to generate liquid phase and promote the nu-cleation and grain refinement of Al4SiC4 phase. Fe3Si also could coat Al4SiC4 grains. Moreover,the morphology of Al4O4C in Al4SiC4/Al4O4C composite refractory without addition of Fe2O3 is short fibrous-like structure,but changes into fine granules structure after adding Fe2O3.     

The Formation of γ—AlON Spinel in the Reaction of Al2O3—AlN—MgO System

The stabilization of γ-aluminium oxyni-tride spinel(γ-AlON) has been investigated by addition of MgO,MgAl2O4,etc.,in reaction process.The results indicated that there are wider solid solution areas near ,Al2O3-rich side in AlN-Al2O3-MgO ternary systems,The content of stabilized AlON phase in samples is related to heating temperatures,additives,etc.The lattice parameters of their AlON phases could be well describedby the equation: a0=0.7900 0.0375[MgO] 0.015[AlN](nm)     

Effect of Metal Additives on Performance of Low-Carbon Magnesia-Carbon Materials

In this paper,both oxidation and corrosion resistance of low-carbon magnesia-carbon materials containing 4.0wt% graphite with metallic Al and Mg-Al alloy powders as antioxidants were investigated.Meanwhile,the microstructures of samples corroded by slag were observed with optical microscope as well.The test results revealed the properties of oxidation and corrosion resistance of low-carbon magnesia-carbon materials could be improved obviously by adding metal Al powder and Mg-Al alloy powder.The rule of improving oxidation resistance was illegibility when metal Al powder and Mg-Al alloy powder were added together.It was harmful to corrosion resistance by mixed adding metal Al powder and Mg-Al alloy powder into the materials,at the same time,the corrosion resistance would decreased with the increasing of Mg-Al alloy content.The corrosion resistance of samples with 0.5wt% or 3.0wt% Mg-Al alloy was better. The oxidation resistance and corrosion resistance of materials with metal Al or Mg-Al alloy respectively were better than that with mixed metal Al and Mg-Al alloy. As a result, Mg-Al alloy was more suitable for low-carbon composite materials than metal Al as additives.     

Synthesis and adsorption property of zeolite FAU/LTA from lithium slag with utilization of mother liquid☆

Co-crystalline zeolite FAU/LTA-0 was synthesized by hydrothermal method from lithium slag. To make the most of excess silicon and alkali sources in mother liquid derived from FAU/LTA-0, zeolite FAU/LTA-1b was synthesized in the same method with the use of mother liquid by adding a certain amount of aluminum source. Influences of different adding ways of aluminum source and recycling dosages of mother liquid on synthesis of zeolites FAU/LTA with mother liquid were investigated. The phase, microstructure and thermostability of FAU/LTA-0 and FAU/LTA-1b were characterized by XRD, SEM and TG-DTA. The calcium and magnesium cation exchange capacities (CECs) of the zeolites were determined. The results have shown that co-crystalline zeolite can be synthesized with the use of mother liquid by adding aluminum source after 2 h of reaction. Compared with FAU/LTA-0, the crystal twinning structure of FAU/LTA-1b became weaker, the grain size was smaller, and the thermostability was better. With a lower dosage of mother liquid, the content of P-type impurity in product decreased significantly, and the content of LTA phase increased. The reuse rate of mother liquid can reach 48%. The CECs of FAU/LTA-1b-150 can reach 343 mg CaCO3·g?1 and 180 mg MgCO3·g?1, showing more excellent adsorption capacities than FAU/LTA-0 and commercial zeolite 4A. The full recycling use of mother liquid to synthesize zeolite FAU/LTA which can be applied for detergent not only improves resource utilization but also reduces production cost.     

Degradation analysis of A2/O combined with AgNO3+K2FeO4 on coking wastewater

In this work, a coking wastewater was selected and a biochemical A~2/O treatment device for fractional degradation was designed and employed. After each stage of the treatment, the products were analyzed through gas chromatography–mass spectroscopy(GC–MS) to determine their composition. Finally, AgNO_3+ K_2 FeO_4 was used as an advanced deep catalytic oxidation treatment. It was concluded from the analysis that cyclic organics could be degraded and the chemical oxygen demand(COD) was controlled within 50 mg·L~(-1), in line with the target value. Meanwhile, the spectra obtained from the GC–MS were in accordance with the conclusions reached based on the COD. The research results showed that all hard-degradable organics in coking wastewater could be eliminated through the A~2/O bio-membrane treatment and the advanced treatment of making use of K_2FeO_4 as an oxidant and Ag+as a catalyst, the catalytic efficiency with Ag+as a catalyst of K+2FeO_4 was very high. Agcould evidently improve the oxidation capacity of K_2FeO_4 to wastewater in its short stability time, and this is an important innovation.     

Preparation of ZrN （ZrON）-SiAlON Composite Ceramics via a Pressureless Sintering Process

ZrN-SiAlON composite materials were synthesized at 1 550 ℃ for 6 h via a carbothermal reduction nitridation route using fly ash （≤74 μm）,zircon （≤ 44 μm） and active carbon as starting materials.The processed ZrN-SiAlON composite micropowders were mixed with polyvinyl alcohol as binder to prepare ZrN （ZrON）-SiAlON composite ceramics by carbon-embedded pressureless firing at 1 450,1 500 and 1 550 ℃ for 1 h,respectively.Influences of firing temperature on the phase compositions,microstructure and sintering properties of the ceramics were investigated.The results show that：（1） β-SiAlON based composite ceramics with different compositions can be prepared by controlling firing temperature,and the main crystalline phases of the specimen fired at 1 550 ℃ for 1 h involve ZrN,ZrON and β-SiAlON （z =2,Si4Al2O2N6）; （2） ZrN （ZrON）,β-SiAlON and a Fe-Si based compound can be observed in the microstructures of the specimens fired at different temperatures.ZrN （ZrON） particles distribute homogeneously in the β-SiAlON matrix; （3） raising firing temperature can increase the shrinkage ratio of the ceramics,and the volume shrinkage ratio increases from 19.4％ to 40.3％ when the firing temperature rises from 1 450 to 1 550 ℃.     

Phase Evolution and Microstructure of C-AI System in Carbon-embedded Atmosphere

In order to investigate the phase evolution and microstructure of aluminum containing carbon composites,- 195 graphite flake and ≤0. 074 mm aluminum powders( Al 99%,in mass,the same hereinafter) were used as main starting materials. The mixture with 1 ∶ 1of graphite and aluminum was well mixed with additional 15% phenolic resin and then shaped in a hydraulic machine. The specimens were first dried at 250 ℃ for12 h,and then graphite-embedded fired at 800,1 000,1 200,1 400,and 1 600 ℃ for 3 h,respectively. XRD and SEM were used to characterize the phase compositions and section microstructure. The results show that at800 ℃ aluminum powder melts and reacts with carbon in resin forming granular Al4C3 at the edge of graphite;at 1 000 ℃,Al4C3 increases in amount and grows in volume,and AlN commences to form; at 1 200 ℃,some Al4C3 grows to tabular shape,and other Al4C3 nitridizes forming fibrous AlN; at 1 400 ℃,Al4C3 decreases because it is nitridized or oxidized forming fibrous AlN or Al2O3; at 1 600 ℃,Al4C3 disappears,AlN or Al2O3 gets big and coarse.     

苯胺在超临界水中氧化反应路径

An aqueous solution of aniline was oxidized in supercritical water with a flow reactor under the conditions of 25 MPa, 300％ excess oxygen, 2.351×10-4 mol*L-1 aniline .GC-MS analysis of the oxidation products extracted from the aqueous reactor effluent permitted identification of compounds such as azobenzene, phenazine and acetic acid. The products could be classified as dimers,single-ring or ring-opening produces,carboxylic acids and ultimate products.The contents of dimers (such as azobenzene and phenazine) were greater than other products.A reaction network consistent with the experimental observations was developed. The study revealed that aniline might be oxidized to ultimate products through two parallel pathways. The formation of dimers such as azobenzene, phenazine and the further oxidation of these dimers were the main pathways. It was indicated experimentally that the rate controlling step of aniline oxidation was the further oxidation of azobenzene and phenazine, but not the further oxidation of organic acid such as acetic acid, formic acid and so on.     

Application of Semi—rebonded Magnesite—Chrome Bricks of LRF at RH Lower Vessl of NKK Keihin Wroks

The application results of semi-rebonded magnesite-chrome bricks at RH lowe vessel of NKK Corporation Keihin Works have been analysed,The results indicate that the main reasons that cause the damage of the refactory brcks include:chemical attack of slage to the semi-rebonded magnesite-chrome bricks;pene-tration of molten stel,slag into the bricks;and therma spalling due to temperature fluctua-tion during steel making operation.The results of multiple effection of these factors lead to alternative action of erosion(chemical attack and penetration)and spalling(thermal spalling and structure peeling) resulting in the damage of the brik ,In order to improve the performance of the bricks ,it is necessary to promote the resistance to erosion and thermal shock resistance as well as to keep the accurate dimensions of the brick,The measures of improvement of resistance to erosion of magne-site-chrome bricks taken by the researches mainly include:lowering the contents of impu-rities in the bricks(mainly including SiO2,CaO,and next Fe2O3 and Al2O3);promoting the extent of direct bond of the brick;forming a large amount of magnesia-chrome composite spinel well-distributed in the bricks through adding a large amount of synthesized materi-als;enhancing the resistance to erosion by adding a little amount of high-effective additives,Improvement of thermal shock resistance of the bricks is mainly through introducing some additive to make a certain amount of mi-cro-cracks occur in the brick so as to obtain an effect of increasing toughnes or through for-mation of second high temperature solid phase in the brick by adopting additive,In addition,it is needed to improve the quality of the brick appearance and ensure accurate dimensions of the brick,The purpose of this paper is to further iprove the service life of the refractory bricks by making use of the improvement mea-sures taken on the basis of the analysis results of the used bricks.     

在VPO催化剂上丁烷选择氧化的质谱研究

The selective oxidation of n-butane to maleic anhydride(MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique.The reaction intermediates,butene and furan,were found in the reaction effuent under near industrial feed condition (3% butane 15% O2),while dihydrofuran was detected at high butane concentration (12% butane,5%O2).Some intermediates of MA decomposition were also identified.Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene,and butene further to form MA.Based on these observations,a modified scheme of reaction network is proposed.The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice,without a proceeding adsorption step.Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation.Adsorbed oxygen leads to deep oxidation,while lattice oxygen leads to selective oxidation.     

Flux mechanism of compound flux on ash and slag of coal with high ash melting temperature

The melting temperature of Z coal ash was reduced by adding calcium–magnesium compound flux(W_(CaO)/W_(MgO)=1). In the process of simulated coal gasification, the coal ash and slag were prepared. The transformation of minerals in coal ash and slag upon the change of temperature was studied by using X-ray diffraction(XRD). With the increase of temperatures, forsterite in the ash disappears, while the diffraction peak strength of magnesium spinel increases,and the content of the calcium feldspar increases, then the content of the amorphous phase in the ash increases obviously. The species and evolution process of oxygen, silicon, aluminum, calcium, magnesium at different temperatures were analyzed by X-ray photoelectron spectroscopy(XPS). The decrease of the ash melting point mainly affects the structural changes of silicon, aluminum and oxygen. The coordination of aluminum and oxygen in the aluminum element structure, e.g., tetracoordinated aluminum oxide, was changed. Tetrahedral [AlO_4] and hexacoordinated aluminoxy octahedral [AlO_6] change with the temperature changing. The addition of Ca~(2+) and Mg~(2+) destroys silica chain, making bridge oxide silicon change into non-bridge oxysilicon; and bridge oxygen bond was broken and non-bridge oxygen bond was produced in the oxygen element structure. The addition of calcium and magnesium compound flux reacts with aluminum oxide tetrahedron, aluminum oxide octahedron and silicon tetrahedron to promote the breakage of the bridge oxygen bond. Ca~(2+) and Mg~(2+) are easily combined with silicon oxide and aluminum oxide tetrahedron and aluminum. Oxygen octahedrons combine with non-oxygen bonds to generate low-melting temperature feldspars and magnesite minerals, thereby reducing the coal ash melting temperatures. The structure of kaolinite and mullite was simulated by quantum chemistry calculation, and kaolinite molecule has a stable structure.     

Control of Microstructural Development in Reaction—Bonded Silicon Nitride（RBSN） by Seeding With β—Si3N4 Single Crystals

The addition of β－Si3N4 seed grains to a ceramic powder is an effective means of controlling the microstructural evolution,In this work addition of β－Si3N4 seed grains gave rise to a bi-modal microstructure made up of large rod-lkike grains that grew from the added seed during the liquid phase sintering process and the usua elongated grains which are developed from the α→β transformation process in silicon nitride,The morphology of te grains that were grown epitaxially from the seed was influenced by the size and shape of the seed crystals;the relatively large and elongated seed grains gave rise to large rod-like grains whilst those with equiaxed-like shape gave rise to large grains similar in shape to the seed from which they were grown.The evolution of the large rod-like grains and the resultant bi-modal microstructure led to a considerable improvement in the mechanical properties.