Heating and melting mechanism of stainless steelmaking dust pellet in liquid slag

The heating and melting mechanisms of the pellets immersed in liquid slag were investigated, and the effect of the pellet heating and the melting conditions were studied. The results show that the dust component in the pellet is melted from the surface and no metallic elements are melted before the dust component, the time for the pellet completely melted is reduced as the iron powder content increases since the metallic iron has high thermal conductivity. These are four stages of heating and melting of pellet in liquid slag, they are the growth and melt of solid slag shell, penetration of liquid slag, dissolving of dust component and melting of reduced metals. The lifetime of the solid slag shell is in the range of 7-16 s and increasing the pre-heating temperature of the pellet and the slag temperature can shorten the slag shell lifetime. The time for the dust component in the pellet to be melted completely is in the range of 20-45 s and increasing the pre-heating temperature, especially in the range of 600-800 ℃, can obviously reduce the melting time. A higher slag temperature can also improve the pellet melting and the melting time is reduced by 10-15 s when the slag temperature is increased from 1 450 to 1 550 ℃. The pellet with higher content of iron powder is beneficial to the melting by improving the heat conductivity.     

不锈钢电弧炉粉尘加热过程的TGA及FTIR分析

本研究采用热重分析仪(TGA)和傅里叶变换远红外气体分析仪(FTIR)检测了不锈钢电弧炉粉尘的加热过程,确定了加热过程中粉尘热性质变化的3个阶段.第1阶段表现为失重,它是由水分的蒸发以及粉尘中的游离碳与金属氧化物作用所致.第2阶段表现为增重,粉尘中的金属与空气中的氧发生氧化反应.第3阶段为缓慢失重过程,粉尘中部分金属挥发进入气相.研究结果可为不锈钢电弧炉粉尘的直接回收及固化处理提供数据.     

Synthesis of Poly（aryl amide imide） s Derived from o—diphenyltrimellitic Anhydride

The synthesis and characterization of a series of novel poly(aryl amide imide)s based on o-diphenyltrimellitic anhydride are described.The poly(aryl amide-imide) s having inherent viscosities of 0.39-1.43dL/g in N-methyl-2-pyrrolidinone at 30℃ ,were prepared by polymerization with aromatic diamines in N,N-dimethylacetamide and subsequent chemical imidization,All the polymers were amorphous,readily soluble in aprotic polar solvents such as DMAC,NMP,DMF,DMSO,and m-cresol,and could be cast to form flexible and tough films,The solvents such as DMAC,NMP,DMF,DMSO,and m-cresol,and could be cast to form flexble and tough films,The glass trsanition temperatures were in the range of 284-336℃,and the temperatures for 5% weight loss in nitrogen were above 468℃。     

Fabrication of Ti2AlC by Spark Plasma Sintcring from Elemental Powders and Thermodynamics Analysis of Ti-M-C System

A ternary-layered carbide Ti2AlC material could be synthesized by spark plasma sintering（SPS） technology using elemental powder mixture of Ti, Al and active carbon. By means of XRD and SEM, phases were identified and microscopically evaluated. The experimental results show that the main phase in the product was fully crystallized Ti2AlC with small particle size when sintered at 1200℃. The synthesis temperature of SPS was 200-400℃ lower than that of hot pressing （HP） or hot isostatic pressing （HIP）. Through thermodynamics calculations, the mechanism of Ti2AlC was studied by calculating changes of Gibbs free energy of reactions.     

Fabrication, Structures and Properties of Quasi One-dimensional ZnO Toothed- nanostructures

Uniform ZnO toothed-nanobelts and nanocombs were fabricated respectively through pure zinc powder evaporation without catalyst at temperature of 600-650℃. Scanning electron microscopy （SEM） and high-resolution transmission electron microscopy （HRTEM） observations show that such ZnO nanostructures have several types in morphology, and all of them are single crystalline. The experimental results reveal that the growth of the ZnO nanostructures was controlled by vapor-solid mechanism. Room temperature photoluminescence spectra of the toothed-nanobelts show a UV emission at - 390 nm and a broad green emission with 4 subordinate peaks at 455-495 nm.     

The Properties of YSZ Electrolyte Sintering at 1300 ℃

The properties of yttria stabilized zirconia（YSZ） related to the sintering process were discussed.YSZ nano-powders about 40-100 nm as raw material,the sub-micrometer grain sizes such as 0.4-3 μm in YSZ were gotten by sintering process at 1300 ℃,which was performed at 1000 ℃ for 2 h,then raised the temperature at the rate of 50 ℃ / h to 1400 ℃,then decreased directly to 1300 ℃ in 30 minutes,finally at 1300 ℃ for 5-20 hours.The ratio of bigger grain size becomes larger as the holding time increasing at 1300 ℃.The grains less than 1 μm are about 50%,eg,43.2%,52.2% and 51.1% related to 1300 ℃ holding 5 hours,8 hours and 10 hours,respectively.As YSZ grain size became small,the electrical conductivities did not decrease,even increased,about 0.20 s/cm at 1000 ℃.The reduced sintering temperature and time were benefited to co-fire with the electrodes in electrode-supported SOFCs.     

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.     

Thermal deformation behavior and microstructure of nuclear austenitic stainless steel

Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate...     

The Antioxidation Properties of the In-situ Ceramic from Pyrolyzing Polysilicone Preceramic

A systematic research on the pyrolysis process of polymethysilicone ( SAR- 2) and the thermostability of the pyrolysis residue was made by the thermogravimetric analysis, DTA and infrared spectroscopy. The experimental results indicate that the pyrolysis residue of SAR- 2 converted into the amorphous SiCxO4-x phase above 900 ℃ , the residue at 1200 ℃ is the most thermostable and antioxidant . It is suitable to be used as polysilicone preceramic .     

Effect of tin on the reaction synthesis of ternary carbide Ti3AlC2

The effect of tin on synthesis of Ti₃AlC₂ by spark plasma sintering (SPS) from TiC/Ti/Al powders was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for phase identification and microstructure evaluation. The experimental results show that addition of tin can considerably accelerate the synthesis reaction of Ti₃AlC₂ and fully dense, essentially single-phase polycrystalline Ti₃AlC₂ could be successfully obtained by sintering 2TiC/1Ti/1Al/0.2Sn powders at 1200–1250 °C under a pressure of 30 MPa. SEM images show that Ti₃AlC₂ samples in about 2–5 μm thick and 10–25 μm long platelets can be obtained. The fracture toughness and flexural strength of Ti₃AlC₂ were 6.5±0.2 MPa·m^1/2 and 560±10 MPa, respectively. Funded by the National Natural Science Foundation of China (No.20771088, No.50572080) and Doctoral Foundation of Wuhan University of Technology (No.471-38650142)     

Microstructural Characteristic of Montmorillonite and Its Thermal Treatment Products

The montmorillonite was studied by different methods, such as chemical analysis, DAT, TG, XRD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octahedra sheets beans dehydrating when the thermal treatment temperature reaches 659℃, but the layer structure remavins the same, and the corresponding Al ( Ⅳ ) is turned into Al ( Ⅳ ) in octahedra sheets. When the temperature reaches 900℃ , the layer structure of montmorillontite is destrtoyed, and the new mineral phase μ-cordierite is found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase. Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅳ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃ , the cristobalite and mullite phases reduce sligluly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.     

Synthesis and Performance of Transparent Casting Polyurethane Resin

A series of transparent casting polyurethane resins (TCPU) were synthesized from cycloaliphatic diisocyaruae ( 1PDI or H12 MDI) , polyol, chain extender, crosslinking agents, catalyst and special aids (T),which were characterized by FTIR. The thermal stabilities of the obtained TCPU were examined by DSC and TGA , the glass transition temperature ( Tg ) was in the range of 95- 110 ℃ , the initial decomposition temperature (5% weight loss) was 250-265 ℃, and 10% weight loss at the temperature was in the range of 260-286℃ in nitrogen atmosphere. The morphologies of the fractured surfaces of TCPU were revealed by a scanning electron microscope (SEM). The crystalline-amorphous characters of TCPU were studied by WAXD, the result shows that TCPU possesses amorphous glassy characters. The optical properties of TCPU were studied by a UV7500 visible light absorbance measurement. All the samples exhibited excellent optical properties and possessed light transmittarwe in the range of 91%-93% .     

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.     

Electrical resistivity of TiB2/C composite cathode coating for aluminum electrolysis

1INTRODUCTIONThere are many disadvantages in the presentHall-Heroult electrolytic process[1],such as highenergy consumption,low unit productivity and se-rious environmental pollution and so on,especiallythe high energy consumption of per ton alumin-ium,which ranges from13MW·h to15MW·h,and the energy efficiency is less than50%[2].Therefore,low-energy consumption aluminumre-duction cell has been a research focus for interna-tional aluminum companies and institutes.Thedrained cathode cel…     

Synthesis of Cordierite by Decomposition of Metal Nitrates on the Surface of Carbon Black Powder

Cordierite precursor was obtained through a process, which inwolved the decomposition of metal nitrates on the surface of ultrafine carbon black pouder between 100-300℃ and the gasification of the carbon black at higher temperature in air ,the average size of the particles,which were heat-treated at 700℃ for 10h is about 1020nm,and the specific surface area is about 129m^2/g,the experimental restults show that the ultrafine particles of cordierite precursor can be produced by this process.the precursor potcder was cacined at different temperatures.X-ray diffraction examination indicates the β-quartz is crystallized from the amorphous matrixaround 850℃ firstly and then MgO-Al2O3 spinel and α-cordierite appears.Above 1000℃.MgO-Al2O3spinel and cristobalite disappear gradnally and form an intermediate phase(sapphirine)At aronmd 1300℃.the main phase is α-cordierite,and no other phase is detected.     

Anti-Crack Performance of Low-Heat Portland Cement Concrete

The properties of low-heat Portland cement concrete（LHC） were studied in detail. The experimental results show that the LHC concrete has characteristics of a higher physical mechanical behavior, deformation and durability. Compared with moderate-heat Portland cement（MHC）, the average hydration heat of LHC concrete is reduced by about 17.5%. Under same mixing proportion, the adiabatic temperature rise of LHC concrete was reduced by 2 ℃-3 ℃,and the limits tension of LHC concrete was increased by 10× 10^-6-15×10^-6 than that of MHC. Moreover, it is indicated that LHC concrete has a better anti-crack behavior than MHC concrete.     

Purification and characterization of extracellular chitinase from a novel strain Aspergillus fumigatus CS-01

Twelve samples derived from different locations in south central area of China are treated by enrichment and spread-plate technique for initial screening. Seven chitinase-producing strains are isolated. The chitinase present in the culture supernatant of strain CS-01 possesses the maximum activity of 0.118 U/mL. Analysis of the morphological feature and the ITS rDNA sequence reveals that strain CS-01 belongs to Aspergillus fumigatus. Production of the chitinase is regulated by a inducible way and the maximum activity appears at 36 h in colloidal chitin culture. Purification of the chitinase is carried out by salting out, gel filtrate chromatography and anion exchange chromatography sequentially. Native-PAGE and SDS-PAGE indicate that the chitinase from A. fumigatus CS-01 is a monomer with the relative molecular mass estimated to be 4.50×10⁴. Its maximum activity appears at pH 5 and 55 °C. The chitinase is stable at pH 4.0–7.5 and below 45 °C. Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China     

Deformation behavior of Cu-12wt%Al alloy wires with continuous columnar crystals in dieless drawing process

The microstructure and mechanical properties of Cu-12wt%Al alloy wires which are composed of continuous columnar crystals after dieless drawing forming at drawing speed of 1.0―1.4 mm/s and deformation temperature of 600―900℃ were analyzed, and deformation behavior of the alloy during dieless drawing forming was experimentally investigated. The results showed that in the abovemen-tioned conditions, recrystallization phenomenon was not found during dieless drawing forming. When a drawing speed of 1.0 mm/s was...     

Thermodynamic calculation on the smelting slag of direct recycling of electric arc furnace stainless steelmaking dust

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Manufacture of high-dispersed W-Cu composite powder by mechano-thermal process

In order to improve the process of co-reduction of oxide powder, a new mechano-thermal process was designed to produce high-dispersed W-Cu composite powder by high temperature oxidation, short time high-energy milling and reduction at lower temperature. The particle size, oxygen content and their sintering abilities of W-Cu composite powder in different conditions were analyzed. The results show that after a quick milling of the oxide powder for about 3-10 h, the reduction temperature of the W-Cu oxide powder can be lowered to about 650 ℃ from 700-750 ℃ owning to the lowering of particle size of the oxide powder. The average particle size of W-Cu powder after reduction at 650 ℃ is about 0. 5μm smaller than that reduced at 750 ℃. After sintering at 1 200℃ for 1 h in hydrogen atmosphere, the relative density and thermal conductivity of final products (W-20Cu) can attain 99. 5% and 210 W ·m-1· K-1 respectively.