Abstracts from Naihuo Cailiao(Refractories)——A Chinese-Language Bimonthly

Development and properties of β-Sialon-Al_2O_3-SiCcomposite materials(1～4). -β-Sialon, Al_2O_3, SiC,Composite material, Advanced refractories. -The nitri-dation sintering technique of β-Sialon-Al_2O_3-SiC compos-ites was studied by using Si powder, Al powder, Al_2O_3 finepowder, corundum and SiC particles as raw materials at1500℃ under flowing nitrogen. SEM and XRD analysisconfirm that the microstructure of β-Sialon as bondingphase changes from fiber-like to hexagonal prism-like de-pending on the increasing amount of corundum. The hotMOR of the composites at 800～1400℃ is higher than     

Effects of Pore-forming Agents on Properties of Silicon Carbide Porous Ceramics Prepared from Crystalline Silicon Cutting Waste

SiC powder was rapidly synthesized in an induction furnace with crystalline silicon cutting waste and active carbon as raw materials, and then SiC porous ceramics were prepared at 1 600 ℃ for 4 h with carbon embedded using the powder as raw material, the starch and the graphite as pore-forming agents. Effects of additions of different pore-forming agents on the phase composition, microstructures, physical properties, and cold crushing strength of the porous ceramics were investigated. The results show that the main crystalline phases of the synthetic powder are α-SiC(6 H-SiC) and β-SiC(3 C-SiC). The phase composition of the porous ceramics includes α-SiC(6 H-SiC), β-SiC(3 C-SiC), Fe Si, quartz and Si_2N_2O. The apparent porosity and closed porosity of the porous ceramics prepared by adding starch are higher, and the cold compressive strength of the porous ceramics added with graphite is higher. As increasing the additions of the starch, the apparent porosity, closed porosity and linear shrinkage ratio of the porous ceramics increase, and the bulk density decreases correspondingly. When 20 mass% starch is added, the apparent porosity, closed porosity, linear shrinkage ratio and cold compressive strength are 57.05%, 2.03%, 5.10% and 10.20 MPa, respectively.     

Nickel-catalyzed Construction of Heat Conductive Network in Electrically Calcined Anthracite (ECA) Based Carbon Blocks

Nickel nitrate was introduced into carbon blocks by using ECA aggregates as catalyst-carrier.The Ni-containing anthracite aggregates were firstly prepared by mixing anthracite aggregates in nickel nitrate ethanol solution and then incorporated into carbon blocks after pre-treating.The phase composition,microstructure and properties of all carbon blocks fired at 1 000℃or 1 400℃in a coke bed were studied with the aid of an X-ray diffractomer,a field emission scanning electron microscope,a mercury porosimetry and a laser thermal conductivity meter.The results showed that the addition of Ni-containing anthracite aggregates promoted the formation of one-dimensional nanocarbon andβ-SiC whiskers at 1 000℃and the growth ofβ-Sialon at 1 400℃,respectively.Moreover,the cold compressive strength and microporosity characteristics of the carbon blocks with the addition of Ni-containing anthracite aggregates were enhanced and the thermal conductivity was remarkably improved attributing to the high heat conductive network formed by the ceramic phases.     

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.     

酮麝香-二甲苯麝香双液相萃取结晶

To evaluate the effect of two liquid phase on the separation of musks mixture, the phase equilibria of musk ketone musk xylene dimethyl sulfoxide heptane system were studied for the first time. The whole and every part of the phase equilibrium for the quaternary system were shown by three-dimensional phase diagrams, the liquid-liquid equilibria, solid-liquid equilibria and solid-liquid-liquid equilibria of the quaternary system were also shown. As a result, the compositions of musks in the equilibrium liquid phases were different from those in the feed, that is, musk ketone was enriched in dimethyl sulfoxide phase while musk xylene was enriched in heptane phase. So these equilibrium liquid phases were useful in separating musk ketone and musk xylene. On the basis of these results, a new process “two liquid phase extractive crystallization” was proposed to separate the eutectics of musk ketone and musk xylene.     

Texture and anisotropy of hot-pressed h-BN matrix composite ceramics with in situ formed YAG

Textured hexagonal boron nitride(h-BN)matrix composite ceramics were prepared by hotpressing using different contents of 3Y₂O₃–5Al₂O₃(molar ratio of 3:5)as the sintering additive.During hot-pressing,the liquid Y₃Al₅O₁₂(YAG)phase showing good wettability to h-BN grains was in situ formed through the reaction between Y₂O₃ and Al₂O₃,and a coherent relationship between h-BN and YAG was observed with[010]_h-BN//[111]_YAG and(002)_h-BN//(321)_YAG.In the YAG liquid phase environment formed during hot-pressing,plate-like h-BN grains were rotated under the uniaxial sintering pressure and preferentially oriented with their basal surfaces perpendicular to the sintering pressure direction,forming textured microstructures with the c-axis of h-BN grains oriented parallel to the sintering pressure direction,which give these composite ceramics anisotropy in their mechanical and thermal properties.The highest texture degree was found in the specimen with 30 wt%YAG,which also possesses the highest anisotropy degree in thermal conductivity.The aggregation of YAG phase was observed in the specimen with 40 wt%YAG,which resulted in the buckling of h-BN plates and significantly reduced the texture degree.     

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 ℃.     

La(III) Transport in Dispersion Supported Liquid Membrane Including PC-88A as the Carrier and HCl Solution as the Stripping Solution

The transport of La(III) through a dispersion supported liquid membrane with polyvinylidene fluoride membrane as the liquid membrane support and dispersion solution including HCl solution as the stripping solution and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in kerosene as the membrane solution, was studied. As a result, the optimum transport conditions of La(III) were obtained as that concentration of HCl solution was 4.0 mol/L, concentration of PC-88A 0.16 mol/L, and volume ratio of membrane to stripping solution 30:30 in the dispersion phase, and pH value 4.0 in the feed phase. Ionic strength had no obvious effect on the transport of La(III). Under the optimum conditions, when initial concentration of La(III) was 0.8′10-4 mol/L, the transport rate was up to 96.3% during the transport time of 125 min. The kinetic equation was developed based on the law of mass diffusion and theory of interface chemistry. The diffusion coefficient of La(III) in the membrane and the thickness of diffusion layer between feed and membrane phases were obtained as 3.20′10-7 m2/s and 3.22′10-5 m, respectively. The calculated results were in good agreement with experimental results.     

Effect of Sintering Additives on the Nitridation and Densification Behavior of Si—SiC Composite

Most of the thermo-mechanical properties of reaction bonded silicon nitride,including a second phase such as SiC depend on the final denstiy and the grain boundary glass phase of the sintered material .Thus it is necessary to know the sintering aid system most effective for the Si0-SiC compostie system ,Sintering experiments carried out using different combinations of sintering aids has indicated that two combinations,i.e.,(a) yttria with alumina and (b) yttia with aluminium nitride are effective sintering aid systems for the reation bonded Si-SiC composites.Adensity of 98.5% theoretical was obtained with yttria and aluminium nitride system.     

Properties and Microstructure Evolution of Al_2O_3-Si Material Fired in Different Atmospheres

Al2O3- Si composite specimens were prepared using fused corundum,ultra-fine α-Al2O3and Si powder as starting materials and resin as binder. Effects of sintering atmospheres on properties,phase composition and microstructure of specimens after firing at 1 500 ℃ were investigated. The results show that:( 1) after firing in oxidizing or weak oxidizing atmosphere,there is some Si in the specimens and some glass phases containing mullite form on specimen surface,the density and strength at room temperature are relatively high,but hot modulus of rupture and thermal shock resistance are relatively poor;( 2) after firing in weak reducing or reducing atmosphere,Si reacts completely with CO or N2forming whisker-like SiC,granular Si2N2O or O'-SiAlON,and the thermo-mechanical properties of specimens are enhanced;( 3) after firing in nitrogen atmosphere,Si reacts completely with N2,CO or C forming whisker-like SiC and columnar β-SiAlON crystals,the hot modulus of rupture and thermal shock resistance of specimens are enhanced noticeably.     

Relationship Between Electric Properties and Temperature of ZrB,-SiC Composite Ceramic Heating Element

ZrB2 -SiC composite ceramic has been successfully introduced as heating element in super high temperature .field. This paper further investigated the microstructure of ZrB2 - SiC composite ceramic heating element and the relationship between electric properties and temperature. SEM photos show that the heating element consists of SiC grains and ZrBz grains smaller than 10 μm. The voltage and current gradually increase and the furnace tempera- ture rises lineally with heating time prolonging. The electric resistance increases linearly with the temperature rising. The service temperatltre of the heating element can reach 1 800 ℃ and 2 150 ℃ in air and argon at- mosphere, respectively.     

筛板塔气-液-液系统内相含率和传质特性研究

The gas and dispersed phase holdups and mass transfer coefficients of liquid-iquid were determined for gas-liquid-liquid three phase system in a screen plate column. The flow pattern of gas-liquid-liquid three phase system was studied under different gas velocities. The shape factors showed the geometric properties of screen plates and the corrected drop chaxacteristic velocities were introduced. The phase holdup in two phases was correlated.The research results indicated that mass transfer coefficient for liquid-liquid system in a column with screen plates and gas agitation was found to increase apparently.     

伴随传质的液液体系微分散流型图的实验研究(英文)

This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MIBK) + PA + water,30% kerosene in tri-n-butylphosphate(TBP) + PA + water.The direction and intensity of mass transfer were adjusted by adding PA in one of two phases mutual saturated in advance.When PA transferred from the organic phase to the aqueous phase,tiny aqueous droplets may generate inside the organic phase by mass transfer inducement to form a new W/O/W flow pattern directly on some special cases.Once the PA concentration was very high,violent Marangoni effect could be observed to throw part of organic phase out of droplets as tail.The interphase transfer of PA could expand the jetting flow region,in particular for systems with low or medium inter-facial tension and when the mass transfer direction was from the aqueous phase to the organic phase.     

Phase Formation and Process Analysis of SiC-Al_2O_3-Al_6Si_2O_(13) Composite Powder via Carbothermal Reduction of Fly Ash at 1 550 ℃

Silicon carbide(SiC)-alumina(Al_2O_3)-mullite(Al_6Si_2O_(13)) composite powder was successfully synthesized at 1 550 ℃ for 5 h via carbothermal reduction reaction,and the effects of various mass ratios of active carbon to fly ash(0.38,0.44 and 0.58) on the phase composition and microstructure of products were investigated,and the formation process of the powder was also analyzed in detail.The products mainly consist ofβ-SiC,α-Al_2O_3,Al_6Si_2O_(13) and FeSi.Increasing carbon content favors the decomposition of Al_6Si_2O_(13) and formation of SiC.The average particle size of β-SiC andα-Al_2O_3 is about 1 μm and that of Al_6Si_2O_(13) is 5-10μm.The formation process of SiC-Al_2O_3-Al_6Si_2O_(13)powder includes the decomposition of mullite in fly ash and formation of SiC.     

段塞流的流量瞬变特性试验研究

An investigation of the characteristics of flowrate transients within slug flow was conducted in a largescale outdoor testing facility.The test section consisted of a 378m long,7.62cm diameter stainless steel pipe. Air and water were used as the test fluids.The response to a change of flowrate o either phase or two phases was measured using a series of pressure transducers and differential pressure transducers.An increase or decrease in gas flowrate caused a pressure overshoot above the value at new steady state or led to a pressure undershoot to form a temporary stratified flow.Pressure waves existed in the pipeline,spreading from the entrance to the exit.The magnitude of pressure overshoot in “up-gas”transient or of pressure undershoot and period of the temporary stratified flow in “Down-gas” transient are related to the change of gas flowrate and the distance away from the entrance.In contrast,the change in liquid flowrate was accommodated by smooth transitions between the corresponding steady states,and only one obvious change was found in the slug frequency.According to experimental results,the pressure overshoot,pressure undershoot and the pressure wave propagation were analyzed,and the phenomena were explained reasonably.Some correlations for the calculation of the pressure overshoot and undershoot were proposed.     

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.     

Synthesis of SiC Whiskers from Silicon Nitride in Argon Atmosphere

SiC whiskers were synthesized by carbothermal reduction of silicon nitride. α-Si3N4 and β-Si3N4 powders were used as silicon sources, and graphite, active carbon and black carbon as carbon sources, as well as boron oxide as catalyst. The synthesized SiC whiskers were characterized by XRD and SEM. The results showed that the synthesizing temperature should be above 1 716 K; the decomposition of Si3N4 was the limited step in the synthesis of SiC whiskers; and catalyst not only offered the liquid condition, bu...     

Improvement of FeO Corrosion Resistance by Addition of β－Sialion in Matrix of Corundum Castable

Silicon aluminum oxynitride (β-Si4Al2O2N6) powder was added into corundum castable and its FeO corrosion resistance was tested in crucible method.It was found that FeO corrosion resistance of sialon containing corundum castables was better than that of no sialon powder added ,The optimum content of the sialon powder in castables was higher than mass of the sialon powder in castables was higher than mass 15%.Moreover,O‘-sialon phase,together with β-sialon phase occurred in corundum castables heated in coke bed at 1500℃,although β-sialon powder was initially admixed into the matrix of castables.The EPMA results showed these nitrogen-containing phases located in the matrix of castables were favorable to hinder the penetration of FeO melt at high temperature in comparison with pure corundum castable.However,the flowability of corundum castable became worse originated from the sialon powder added.     

Properties and Microstructure Evolution of Al203-Si Material Fired in Different Atmospheres

A1203-Si composite specimens were prepared using fused corundum, ultra-fine α-A1203 and Si powder as starting materials and resin as binder. Effects of sintering atmospheres on properties, phase composition and microstructure of specimens after firing at 1 500 ℃ were investigated. The results show that： （ 1 ） after .firing in oxidizing or weak oxidizing atmosphere, there is some Si in the specimens and some glass phases containing mullite form on specimen surface, the density and strength at room temperature are relatively high, but hot modulus of rupture and thermal shock resistance are relatively poor; （2） after firing in, weak reducing or reducing atmosphere, Si reacts completely with CO or N2forming whisk-phere, Si reacts completely with CO or N2forming whisk-er-like SiC, granular Si2N20 or 0＇-SiAION, and the er-like SiC, granular Si2N20 or O＇-SiMON, and the thermo-mechanical properties of specimens are enhanced;（3） after firing in nitrogen atmosphere, Si reacts completely with N2, CO or G forming wbisker-like SiC and columnar β-SiA10N crystals, the hot modulus of rupture and thermal shock resistance of specimens are enhanced noticeably.     

Effect of ZnO on Oxidation Resistance of Low Carbon MgO-C Refractories

Al-containing low carbon MgO- C refractories were prepared using 70%( in mass,the same hereinafter)fused magnesia( ≤3 mm),24% fused magnesia powder( 0. 074 mm),3% flake graphite,3% Al powder and 4% phenolic resin( extra-added) as the basic formulation. Influence of ZnO addition on oxidation resistance of the materials was investigated by adding 1%ZnO to substitute fused magnesia powder. The relationship between in-situ formed spinel and ZnO in the matrix was discussed by comparing apparent porosity, cold crushing strength,and phase evolution of the materials matrix. The oxidation resistances of the two materials were compared by observing the formed dense MgO layer between the decarburized layer and the original layer.The result shows that adding ZnO in MgO- C refractories accelerates the in-situ formation of ZnAl2O4spinel and the formation of dense MgO layer,thus improves the oxidation resistance of the low carbon MgO- C refractories.