Experimental study on new method and automatic system for fast evaluating Al-Si alloy modification effect in front of furnace

A new method based on the surface tension measurement for fast evaluating modification effect of Al-Si alloy in front of furnace and an automatic system for fast measuring surface tension of molten Al-Si alloy are introduced. By theoretical analysis the relation between surface tension σe of molten Al-Si alloy and information parameters △P , N , φx and T has been established, namely, σ e = a △P b . N c . (φ x- φ0) d . T e . By ex- periments the relationship between surface tension and modification level of Al-Si alloy has been also got that σ e > 530 mN/m, 400 ≤σe ≤530 mN/m and σ e < 400 mN/m are corresponding with AFS 1-2, AFS 3-4 and AFS 5-6 of Al-Si modification effect. Depending on the conclusions, modification effect can be recognized in a few seconds, which is of practical significance for real-time evaluating modification effect of Al-Si alloy in front of furnace.     

Use of double edge-cracked Brazilian disk geometry for compression-shear fracture investigation of rock

A new specimen geometry-the double edge-cracked Brazilian disk and a relevant fracture analysis by weight function method are proposed for the investigation of rock fracture caused by compression-shear loading. Not only can the mixed mode fracture with any ratio of KI /KII be achieved, but also the pure mode n crack extension can be obtained. The combined mode fracture analysis for this geometry shows that diametral compression in the far-field can induce a compression-shear stress state in the singular stress field ahead of crack tips. Experimental investigations conducted on marble specimens show that the pure mode [I crack extension can be obtained when the dimen-sionless crack length a>0. 7 and the inclined crack angle 5°≤ψ≤40°. Normalized mode I and mode II stress intensity factors decrease from -0. 45 and 2. 47 at ψ= 5° to - 1. 65 and 1. 52 at ψ=40°, respectively. The strains at three points of specimen are also measured in order to investigate the influence of stress singularity on initi     

Microstructure and mechanical properties of ultrafine grained Mg15Al alloy processed by equal-channel angular pressing

An as-cast magnesium alloy with high Al content Mg15Al was subjected to equal-channel angular pressing (ECAP) through a die with an angle of ϕ=90° at 553 K following route B_c. It is found that the network β-Mg₁₇Al₁₂ phases in the as-cast Mg15Al alloy are broken into small blocks and dispersed uniformly with increasing numbers of pressing passes. Moreover, many nano-sized Mg₁₇Al₁₂ particles precipitate in the ultra-fine α-Mg matrix. The grains are obviously refined. However, the grain structure is inhomogeneous in different areas of the alloy. The average size of the primary phase α-Mg is reduced to about 1 μm while grains of around 0.1–0.2 μm are obtained in some two-phase areas. With additional ECAP passes (up to 8), coarsening of the grains occurs by dynamic recovery. Room temperature tensile tests show that the mechanical properties of Mg15Al alloys are markedly improved after 4 ECAP passes. The ultimate tensile strength and elongation to failure increase from 150 MPa to 269.3 MPa and from 0.05% to 7.4%, respectively. Compared with that after 4 passes, the elongation to failure of the alloy increases but the strength of the alloy slightly decreases after 8 ECAP passes. Fracture morphology of the ECAP-processed alloy exhibits dimple-like fracture characteristics while the as-cast alloy shows quasi-cleavage fractures.     

Effects of heat treatment on microstructure and mechanical properties of Fe-Co-Ni-Cr-Mo-C alloy

A kind of Fe-Co-Ni-Cr-Mo-C alloy was designed for valve seat use. The effects of the quenching temperature, tempering time and tempering temperature on the mechanical properties and microstructure of the alloy were investigated. The results show that the hardness decreases, while tensile strength (σb), transverse rupture strength (σbb) and impact toughness(Kit) increase after the alloy is quenched and tempered. The best complex property (σb, 446 MPa; σbb ,793 MPa; Kic, 2.96 J/cm2 ) can be obtained when the alloy is quenched at 1 100 ℃ and tempered at 650 ℃. The results of X-ray diffraction and energy dispersive X-ray analysis (EDX) show that the major strengthening phases are carbides such as (Fe, Cr)7 C3 and Fe2 MoC. The obvious secondary hardening appears when the alloy is tempered at 550 ℃, which results from the precipitated carbides of Cr and Mo in the alloy from the matrix and the heat-resistant retained austenite .     

Preparation and characterization of continuous high-temperature resistant Si-Al-C fibers by one-step method

Using polymer-derived technology, continuous high-temperature resistant Si-Al-C fibers were prepared by one step method, which included melt-spinning of polyaluminocarbosilane (PACS), curing of continuous PACS fibers, and sintering of the cured products. The results show that the average diameter and tensile strength of continuous Si-Al-C fibers are 11 to 12 μm and 1.8 to 2.0 GPa, respectively. The chemical formula of Si-Al-C fibers is SiC_1.01O_0.0400Al_0.024, which is nearly stoichometric. The fibers are mainly composed of β-SiC crystalline, small amount of α-SiC, and amorphous SiC. Continuous Si-Al-C fibers exhibit excellent thermal stability. When the fibers were exposed in argon for 1 h, the tensile strength did not decrease until 1500°C. After heat treatment at 1800°C in argon for 1 h, the fibers maintained about 80% of the initial strength. It was higher than that of Nicalon and Hi-Nicalon fibers. Supported by the National Natural Science Foundation of China (Grant No. 59972042)     

Preparation of High Performance Foamed Concrete from Cement, Sand and Mineral Admixtures

The titled high performance foamed concrete was developed from Portland cement, ultra fine granulated blast-furnace slag, pulverized fly ash and condensed silica fume by means of pre-foaming process. The resultant foamed concrete presents its thermal conductivity of about 0.16-0.75 W/（m·℃） and 28 d compressive strength of about 1.1-23.7 MPa when its mix proportion varies in the range of cement content 280 kg-650 kg/m^3, fly ash 42-97 kg/m^3, slag 64-146 kg/m^3, silica fume 34-78 kg/m^3, and sand 0-920 kg/m^3. The compressive strength of the foamed concrete with oven dried bulk density of 1500 kg/m^3 in appropriate mix proportion and with small amount of superplasticizer reached as high as 44.1 MPa. Meanwhile, the flesh foamed concrete behaves like an excellent flow-ability, therefore, is especially suitable for the application in case of massive foamed concrete casting in situ and in the case of filling casting into large volume underground irregular voids, except for pre-casting of building components like blocks, bricks, and wall panels.     

Hot deformation behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy with acicular microstructure

The characteristics of hot deformation of an α+β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s-1 at 860-1 100 °C. The true stress-true strain curves of alloy hot-compressed in the α+β region exhibit a peak stress followed by continuous flow softening; whereas in the β region,the flow stress attains a steady-state regime. At a strain rate of 10 s-1 and in a wide temperature range,the alloy exhibit...     

Physical simulation of hot deformation of TiAI based alloy

In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti-49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1 100 ℃ with strain rates of 10^-3-10^-1 s^-1. Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n, has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ = K1 drex^-0.56. The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lgdrex= -0.281 1gZ 3.908 1.     

Preparation of ITO nano-powders by hydrothermal-calcining process

1 INTRODUCTIONSn-doped In2O3(ITO) is one kind of n-typesemiconductor material[1].It has excellent electro-optical properties , such as electrical conductivityand high transparency under visible light[2],andiswidely used in electronic , transparent electrode ,solar cells and electro-irradiance , especially inscreen display[3 ,4].Recently nearly half of the met-al indium has been used to prepare ITO materialsin the developed countries[5], such as Japan, A-merica ,France and so on.So the…     

<Emphasis Type="Italic">In-situ</Emphasis> growth and photoluminescence of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> cone-like nanowires on the surface of Ga substrates

β-Ga₂O₃ cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750–1000°C for 2 h in air. The controllable synthesis of β-Ga₂O₃ nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesized products were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the β-Ga₂O₃ nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30–100 nm and 0.5–1.5 μm, respectively. A possible mechanism was also proposed to account for the formation of β-Ga₂O₃ cone-like nanowires. Photoluminescence spectra of the β-Ga₂O₃ nanowires obtained at different temperatures were measured at room temperature, and a strong blue photoluminescence with peaks at 430 and 460 nm and a weak red photoluminescence with peak at 713 nm were observed. The blue light emission intensity decreases with increasing the reaction temperature, however, the red light emission intensity hardly changes. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants, etc., respectively. Supported by the National Natural Science Foundation of China (Grant No. 20573072) and Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060718010)     

Rock fracture under anti-plane shear (Mode III) loading

Anti-plane punch-through shear test and anti-plane four-point bending test are used to study the crack initiation and propagation under anti-plane shear (Mode III) loading. The tensile and shear stresses at the crack tip are calcualted by finite element method. The results show that under Mode III loading the maximum principal stress σ₁ at crack tip is smaller or a little larger than the maximum shear stress τ_max. Since the tensile strength of brittle rock is much lower than its shear strength, σ₁ is easy to reach its critical value before τ_max reaches its critical value and thus results in Mode I fracture. The fracture trajectory is helicoid and the normal direction of tangential plane with the fractured helicoid is along the predicted direction of the maximum principal stress at the notch tip. It is further proved that Mode I instead of Mode III fracture occurs in brittle rock under Mode III loading. The fracture mode depending on the fracture mechanism must be distinguished from the loading form. Foundation item: Project (50374073) supported by the National Natural Science Foundation of China; project (2002032256) supported by the Postdoctor Science Foundation of China     

Microstructural evolution during aging of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

The evolution of microstructure on aging of an (α+β) titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe) in the β and (α+β) solution-treated and quenched conditions was investigated. The presence of very fine ω phase was detected by electron diffraction for samples aged below 400 °C. The fine α aggregates are uniformly formed within β grains by nucleating at the ω particles or β/ω interfaces. At higher temperature, the formation of ω phase is avoided and the α lamellae are precipitated at the preferred site of grain boundary and then within the matrix. The highest hardness values are found when the alloys are aged at 450 °C for β condition and 350 °C for (α+β) condition. Foundation item: Project (50634030) supported by the National Natural Science Foundation of China; Project (2007DS04014) supported by the Program of Science and Technology of Shandong Province, China; Project supported by the Open Research Fund from the State Key Laboratory of Rolling and Automation, Northeastern University, China     

Preparation and properties of ceramic facing brick from East-lake sediment

In order to utilize solid wastes, ceramic facing brick was made form East-lake sediment and some additives. The strength and freeze-thaw resistance of the samples were tested, and the crystal phases and microstructures were studied by XRD and SEM. The results indicate that the samples have a wide firing temperature range. The main crystal phases are CaAl2Si2O8, α-Al2O3, Fe2O3, which distribute uniformly in the samples. The sample have the best properties in the series ’Ca-Al-Si’, and water absorption (Wa) , porosity (Pa), bulk density (D), bending strength and compressive strength are 7.24%, 15.82%, 2.19 g.cm-3, 45.57 MPa and 56.81 MPa respectively, when the addition amount of East-lake sediment is 80% and the firing temperature is 1 100 ℃. In the series ’K-Al-Si’, the sample with the best properties was obtained when addition amount of East-lake sediment was 70% and firing temperature was 1 060 ℃. The water absorption, porosity, bulk density, bending strength and compressive strength are 7.62%, 16.37%, 2.15 g～cm-3, 39.26 MPa, and 50.81 MPa respectively. They all come up to the national standardization, and meet the needs of manufacturing production.     

Quality evaluation of layerlike backfilling and flow pattern of backfill slurry in stope

Stability condition and quality evaluation formula of layerlike backfilling roof,Q≥C,where Q denotes is quality index depending on allowable compressive or tensile strength and integrity of backfilling,and C is the technical index depending on mining method and backfilling technology,were inferred according to simply supported beam theorem.Technical treatment measures for instable backfilling roof,including optimum of appropriate filling materials and dosage for excellent flow property and reduction of backfill cost.It is proved that slope equation of backfill slurry in a stope to be filled is y=hexp[x2/(2σ)2)],where h is height of cone and σ2 is mean square,and that optimum drainage point of backfill slurry can be determined by the equation and sizes of stope.Case study indicates that the results can give a theoretical support for quality evaluation and control of layerlike backfilling.     

Effect of carbon fibre on properties of TiB2/C composite cathode coating for aluminum electrolysis

The tensile strength, compressive strength and electrical resistivity of TiB₂/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30–200 °C) is more obvious than that at high temperature (960 °C). Foundation item: Project(2005CB623703) supported by the Major State Basic Research Development Program of China     

Magnetic Properties of NiCuZn Ferrite Thin Films Prepared by the Sol-gel Method

Ni0.4Cu0.2Zn0.4Fe2O4 thin films were fabricated on Si substrates by using the sol-gel method and rapid thermal annealing （RTA）, and their magnetic properties and crystalline structures were investigated. The samples calcined at and above 600 ℃ have a single-phase spinel structure and the average grain size of the sample calcined at 600 ℃ is about 20 nm. The initial permeability μi, saturation magnetization M and coercivity H of the samples increase with the increasing calcination temperature. The sample calcined at 600 ℃ exhibits an excellent soft magnetic performance, which has μi=33.97 （10 MHz）, Hc=15.62 Oe and Ms=228.877 emu/cm^3. Low-temperature annealing can enhance the magnetic properties of the samples. The work shows that using the sol-gel method in conjunction with RTA is a promising way to fabricate integrated thin-film devices.     

Asymmetric synthesis of 3β-acetoxy-17,17-ethylendioxy-15β, 16β-methylene-5-androsten-7β-ol

3β-acetoxy-17, 17-ethylendioxy-15β, 16β-methylene-5-androsten-7β-ol(I) was prepared by 3 steps from 3β-acetoxy-15β, 16β-methylene-5-androsten-17-one (II) with overall yield of 52.7%. Thus, interaction of ethylene glycol and material (II) gave 3β-acetoxy- 17, 17-ethylendioxy-15β, 16β-methylene-5-androsten (III) which was subsequently oxidated and stereoselectively reduced to produce compound(I). The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO₃-C₅H₅N (1:1, mole fraction)>CrO₃-C₅H₅N(1:2)>(C₅H₅NH)₂Cr₂O₇ in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 °C, and n(III)/n(CrO₃-C₅H₅N(1:2))=1:20. The yield of the −7β alcohol order with Li[Al(OC(CH₃)₃)₃H] (e. g. 78.6%) is more than that with NaBH₄ (e. g. 14.5%) in terms of the reductive agent and the reduction rate decreases in the course of reaction. The compound (I) is characterized by IR and MS. Foundation item: Project (1357) supported by the Excellent Young Teachers Program of the Ministry of Education of China     

Fabrication and its characteristics of low-temperature polycrystalline silicon thin films

In order to reduce the cost of solar cells or flat-panel display, it is very important to synthesis poly-crystalline silicon films on low cost substrate such as glass at low temperature. In this work, electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) system was successfully applied to synthesize poly-Si thin-film on common glass substrate using H2 as the plasma source and SiH4 (Ar:SiH4=19:1) as the precursor gas at low temperature. Since the multicusp cav- ity-coupling ECR plasma source was adopted to provide active precursors, the growth temperature decreased to lower than 200℃. In the plasma, the electron temperatures kTe are ~2―3 eV and the ion temperatures kTi≤1 eV. This leads to non-remarkable ion impacts during the film deposition. The characteristic of poly-Si films was investigated. It was shown that the crystalline fraction Xc of the films can be up to 90% even deposit at room temperature, and the film was (220) preferably oriented. The growth behaviors of the film between the interface of glass and Si films were also discussed in detail.     

Chemieal Synthesis and Magnetie Properties of Nanocrystalline （La0.67-XGdx）Sr0.33MnO3 Using Amorphous Molecular Alloy as Precursors

A new route to synthesize nanosized crystalline of （La0.67-xGdx）Sr0.33MnO3 （X=0.05, 0.10, 0.15, 0.20） perovskite-type complex oxides at calcination temperature of 600-1000℃ using the amorphous molecular alloy as precursors was reported. The precursor could be completely decomposed into complex oxide at temperature below 500℃ according to the TGA and DTA results. XRD demonstrates that the decomposed species is composed of perovskite-type structure at calcination temperature of 600℃ for 2 h. The particle size that depends on the calcination temperature of the precursor is in a range of 30-120 nm as determined by transmission electron microscopy （TEM）. This method is effective and can be easily quantitatively controlled to synthesize nanosized perovskite-type complex oxides. The magnetic properties of （La0.67 xGdx）Sr0.33MnO3 nanocrystalline were preliminary studied.     

Isolation and characterization of YNTC-1, a novel Alicyclobacillus sendaiensis strain

A heterotrophic acidothermophilic bacterial strain, YNTC-1, was isolated from an acidic hot spring in Tengchong, Yunan, China. YNTC-1 grows at pH value of 1.5-8.0 and temperature of 40-70 ℃, with optimal pH and temperature at 3.0 and 55 ℃, respectively. The cells of the strain are in shape of short rod, with 1.0-1.2 μm in length and 0.7-0.8 μm in diameter, and with distinct spores at both poles of each cell. The predominant fatty acids in cellular membrane of the strain are C18：1 ω7c. 16s rRNA gene analysis reveals that this strain is closely related to Alicyclobacillus sendaiensis, with over 99% sequence similarity. Based on phenotypic and genotypic analyses, YNTC-1 is identified as a member ofA. sendaiensis. Considering some important morphological and biochemical differences between strain YNTC-1 and A. sendaiensis ATCC 27009T, YNTC-1 may be proposed to be a novel subspecies of A. sendaiensis. However, this viewpoint has to be confirmed by further studies. Co-bioleaching of pyrite and chalcopyrite with strain YN22, Sulfobacillus thermosulfidooxidans, shows that strain YNTC-1 has no evident influence on bioleaching rates of these two sulphide minerals.