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Investigation on the dissolution of η phase in a cast Ni-based superalloy

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International Journal of Minerals,Metallurgy and materials 2013年第1期20卷 42-48页

作者： M.R. Jahangiri H. Arabi S.M.A. Boutorabi School of Metallurgy and materials Engineering Iran University of Science and Technology Metallurgy Department Niroo Research Institute center of excellence for Advanced materials & processing Iran University of Science and Technology

The dissolution behavior of rI phase has been investigated in a cast Ni-based superalloy. The results showed that the platelets and blocks of η phase were formed within the interdendritic regions of the microstructure. Applying standard solution annealing at 1150-1160℃ for a period of 4 h did not result in the complete dissolution of η phase. For the complete dissolution of η phase without residual incipient melting, a 2-step solution annealing has been recommended. After dissolution at high tem- peratures, the TI phase transforms to two MC-type carbides： one is enriched in Ti, Nb, and Ta, and the other is of （Zr,Ti）C type.

关键词： superalloys nickel alloys phase transitions dissolution heat treatment carbides

Tempering Behavior of 4.5Cr-2W-0.25V Steel

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Journal of Iron and Steel Research International 2010年第10期17卷 57-62页

作者： Mohsen Asadi Asadabad Shahram Kheirandish Abdul Javad Novinrooz Department of materials Science and Metallurgical Engineering Iran University of Science and Technology Advanced materials Group Materials Research School center of excellence for Advanced materials and processing

The tempering behavior of a Cr-W-V steel was investigated in this research. This new alloy with the com- position of Fe-4.5Cr-2W-0. 25V-0. 1C was austenitized at 1 000 ℃ for 30 rain and tempered at 600 and 700 ℃ for dif- ferent time up to 100 h. An OM analysis of the microstructure of air cooled and water quenched specimens before tempering showed that although under both conditions fully martensitic matrix formed, finer structure had formed in the water quenched specimens. The XRD and TEM results showed that the most stable carbides formed during tempering of the steel were M23C6 and M7C3, respectively. Other carbides such as M3C and M2C, formed in the first stages of tempering, and stable MC were also observed. The results showed that when the tempering time, tempera- ture and cooling rate were increased, mass percent of extracted precipitates was increased. In addition, the formation rate of the stable carbides such as M23 Cs and dissolution rate of the metastable carbides such as M3C and M2C were increased.

关键词： Cr-W-V steel carbide tempering TEM XRD

Synthesis of mesoporous tin dioxide via sol-gel process assisted by resorcinol-formaldehyde gel

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Particuology 2018年第2期16卷 26-32页

作者： Kornkamol Banjerdteerakul Paravee Vas-Umnuay Varong Pavarajarn center of excellence in particle technology Department of Chemical Engineering Faculty of Engineering Chulalongkorn University Thailand

Tin dioxide is a useful n-type oxide semiconductor used in a variety of applications owing to its superior optical, electrical, and multifunctional properties. Here, we used a network of resorcinol-formaldehyde （RF） gel to synthesize mesoporous tin dioxide via a sol-gel process. The effects of various synthesis parameters on the morphology and mesoporosity of the obtained product were investigated, including aging time of the RF gel, tin-to-formaldehyde molar ratio, resorcinol-to-carbonate molar ratio, and the aging time of the tin/RF mixed gel. Our experimental results showed that the interaction between the network of the RF gel and tin-containing sol is a key factor that affected the structural strength of the porous network and the porosity of the final product. Through control of the interactions in the tin/RF mixed gel we obtained porous tin dioxide materials that could be effectively used to form large-surface area films with desirable mesoporous properties.

关键词： Tin dioxide Mesoporous Resorcinol- formaldehyde gel Synthesis

Dispersion of multi-walled carbon nanotubes in poly(p-phenylene) thin films and their electrical characteristics

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Particuology 2009年第5期7卷 403-407页

作者： Adi Ilcham Amornwong Srisurichan Apinan Soottitantawat Tawatchai Charinpanitkul center of excellence in particle technology Department of Chemical EngineeringFaculty of EngineeringChulalongkorn UniversityBangkokThailand

Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） composite exposed to toluene was experimentally investigated. 3 mg of multi-walled carbon nanotubes with nominal size of 20 nm was compounded with 30 mg of poly（p-phenylene） with the presence of terpineol as binding initiator. To investigate an optimal condition for homogenizing all constituents, ultrasonication with an output power of 750W was employed with compounding time of 3, 10, 20 and 30 min. With FTIR analyses, it could be confirmed that homogeneous composite of multi-walled carbon nanotubes and poly（p-phenylene） could be prepared. SEM analyses were also conducted to examine the dispersion of multi-walled carbon nanotubes in the polymer matrix. Then intrinsic electrical resistance of the composites after being exposed to toluene was also investigated. It was found that the composite film prepared with ultrasonication for 20 min could provide sufficiently sensitive response with respect to varied concentration of toluene.

关键词： Dispersion Carbon nanotube Poly(p-phenylene) Composite Electrical resistance

Kinetics and mechanism of titanium hydride powder and aluminum melt reaction

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International Journal of Minerals,Metallurgy and materials 2012年第2期19卷 165-172页

作者： Ali Rasooli Mehdi Divandari Hamid Reza Shahverdi Mohammad Ali Boutorabi School of Metallurgy and materials Engineering Member of Center of Excellence for Advanced Material and Processing (CEAMP) Iran University of Science and Technology Tehran 16844 Iran Department of materials Faculty of Engineering Tarbiat Modaress University Tehran 14115-143 Iran

Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of TiH2 powder and aluminum melt was studied. The results show that the-time curves have three regions; in the first and second regions, the rate of reaction conforms zero and one order, respectively; in the third region, the hydrogen gas pressure remains constant and the rate of reaction reaches zero. The main factors that control the rate of reaction in the first and second regions are the penetration of hydrogen atoms in the titanium lattice and the chemical reaction between molten aluminum and titanium, respectively. According to the main factors that control the rate of reaction, three temperature ranges are considered for the reaction mechanism：（a） 700-750°C, （b） 750-800°C, and （c） 800-1000°C. In the first temperature range, the reaction is mostly under the control of chemical reaction; at the temperature range of 750 to 800°C, the reaction is controlled by the diffusion and chemical reaction; at the third temperature range （800-1000°C）, the dominant controlling mechanism is diffusion.

关键词： titanium hydride aluminum reaction kinetics reaction rate constants

Kinetics of Silver Dissolution in Nitric Acid from Ag-Au_(0.04)-Cu_(0.10) and Ag-Cu_(0.23) Scraps

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Journal of materials Science & technology 2006年第5期22卷 696-700页

作者： S.K.Sadrnezhaad E.Ahmadi M.Mozammel center of excellence for Advanced Processes of Production of materials Department of materials Science and Engineering Sharif University of TechnologyTehranIran

Kinetics of dissolution of silver present in precious metal 26～85℃. Dissolution rate of silver was much faster than scraps in HNO3 was studied in temperature range of that of copper at all temperatures. Effects of particle size, stirring speed, acid concentration and temperature on the rate of dissolving of silver were evaluated. Dissolution rate decreases with particle size and increases with temperature. Dissolving was accelerated with acid concentrations less than 10 mol/L. Concentrations greater than 10 mol/L resulted in slowing down of the dissolution rate. Shrinking core model with internal diffusion equation t/τ=1-3（1-x）^2/3＋2（1-x） could be used to explain the mechanism of the reaction. Silver extraction resulted in activation energies of 33.95 kJ/mol for Ag-Au0.04-Cu0.10 and 68.87 kJ/mol for Ag-Cu0.23 particles. Inter-diffusion of silver and nitrate ions through the porous region of the insoluble alloying layer was the main resistance to the dissolving process. Results were tangible for applications in recycling of the material from electronic silver-bearing scraps, dental alloys, jewelry, silverware and anodic slime precious metal recovery.

关键词： Silver Copper Kinetics, Dissolution Shrinking core model Internal diffusion

Evaluation of the Electroslag Remelting Process in Medical Grade of 316LC Stainless Steel

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Journal of materials Science & technology 2009年第5期25卷 592-596页

作者： S.Ahmadi H.Arabi A.Shokuhfar A.Rezaei Institute of Advanced Technologies for Metallic materials Tarbiat Modares University center of excellence of Advanced materials and processing(CEAMP) Department of Metallurgy and Materials Science and EngineeringIran University of Science&Technology(IUST) Department of Material Science Faculty of Mechanical EngineeringK.N.Toosi University of Technology

This study is focused on the effects of electroslag remelting by prefused slag （CaO, Al2O3, and CaF2） on macrostructure and reduction of inclusions in the medical grade of 316LC （316LVM） stainless steel. Analysis of the obtained results indicated that for production of a uniform ingot structure during electroslag remelting, shape and depth of the molten pool should be carefully controlled. High melting rates led to deeper pool depth and interior radial solidification characteristics, while decrease in the melting rates caused more reduction of nonmetallic inclusions. Large shrinkage cavities formed during the conventional casting process in the primary ingots were found to be the cause of the fluctuation in the melting rate, pool depth and extension of equiaxed crystals zone.

关键词： Ultra clean steel Electroslag Radial solidification remelting Prefused slag Vertical solidification

Ultraviolet Photodetector based on Sr_(2)Nb_(3)O_(10) Perovskite Nanosheets

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Journal of Wuhan University of technology(materials Science) 2024年第2期39卷 282-287页

作者：张斌斌 JIA Mengmeng LIANG Qi WU Jinsong ZHAI Junyi 李宝文 School of materials Science and Engineering Wuhan University of TechnologyWuhan 430070China CAS center for excellence in Nanoscience Beijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijin 100083China State Key Laboratory of Advanced technology for materials Synthesis and processing Wuhan University of TechnologyWuhan 430070China

Liquid-phase exfoliation was employed to synthesize Sr_(2)Nb_(3)O_(10) perovskite nanosheets with thicknesses down to 1.76 *** electron microscopy(TEM),atomic force microscope(AFM),X-ray photoelectron spectrometer(XPS),and other characterization techniques were used to evaluate the atomic structure and chemical composition of the exfoliated nanosheets.A UV photodetector based on individual Sr_(2)Nb_(3)O_(10) nanosheets was prepared to demonstrate the application of an ultraviolet(UV) *** UV photodetector exhibited outstanding photocurrent and responsivity with a responsivity of 3×10^(5) A·W^(-1) at 5 V bias under 280 nm illumination,a photocurrent of 60 nA,and an on/off ratio of 3×10^(2).

关键词： perovskite nanosheets liquid-phase exfoliation ultraviolet photodetector

Effect of Ablation Casting on Microstructure and Casting Properties of A356 Aluminium Casting Alloy

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Acta Metallurgica Sinica(English Letters) 2013年第1期26卷 85-91页

作者： V. Bohlooli M. Shabani Mahalli S. M. A. Boutorabi Casting Research center School of Metallurgy and Materials Engineering Iran University of Science and Technology (IUST) center of excellence for High Strength Alloys technology (CEHSAT) School of Metallurgy and Materials Engineering Iran University of Science and Technology (IUST)

Recently the Ablation Casting technology was invented as a new casting process to improve foundry products quality. In this study, the effects of processing variables on the porosity content, rnicrostructure and feedability of A356 casting alloy were investigated. Secondary dendrite arm spacing （SDAS） and eutectic silicon mor-phologies were studied to evaluate the influence of Ablation Casting on the rnicrostructure. Casting density was measured in order to identify porosity content and feedability of ablated and non-ablated specimens. In addition, solidification behavior of the samples was investigated by using thermal analysis technique. The cooling curves and the first derivative curves were plotted and compared with each other. Results showed the ablation process could increase solidification rate significantly. In addition, the microstructural evidences revealed that Ablation Casting process results in more fine and homogeneous structure compared to the non-ablated casting. The feedability improved, SDAS reduced to 35% and porosity content decreased to 3.84 vol.% by implementing this process. It concluded the Ablation Casting is an effective process to gain higher quality in aluminum foundry.

关键词： Ablation Casting A356 aluminium alloy Microstructure Porosity Cooling curve