The paper describes process details for extraction of rare earths from an intermediate grade concentrate of Madhya Pradesh region in India and a South African slag. The xenodme concentrate obtained from the former pla...The paper describes process details for extraction of rare earths from an intermediate grade concentrate of Madhya Pradesh region in India and a South African slag. The xenodme concentrate obtained from the former place was an intermediate grade （47%） rare earth phosphate containing both monazite and xenotime. The South African slag was a low-grade waste product typically containing only 4% of rare earths. The rare earth resource concentrates have been treated individually by different methods such as alkali fusion and alkali leaching to convert them into their mixed oxides. Both types of materials have been processed and greater than 98% solubilization of metal values has been achieved in the intermediate grade xenotime and 80% from the South African slag. The residue of xenotime hydroxide has been washed thoroughly to collect the sodium phosphate, as by-product and the slurry pH have been adjusted to separate rare earths from thorium effectively. Other impurities such as uranium and iron have been removed by precipitation of rare earths by oxalic acid. It has been possible to recover 〉95% yttrium along with other rare earth oxides.展开更多
Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In...Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In this study,a comprehensive and systematic investigation was conducted,by encompassing the analysis of hot deformation mechanisms,along with the microstructure evolution and magnetoc aloric properties of hot-rolled La-Fe-Co-Si alloy.The La_(1.05)Fe_(11.2)Co_(0.7)Si_(1.38)alloy was examined using multiscale mechanical analysis to assess the effects of temperature.A series of macroscale hot compression and microscale nanoindentation tests were performed to access global and local mechanical properties,including variations in hardness and indentation modulus of the primaryα-Fe and secondary 1:1:1 phases up to 800℃.A significant decrease in hardness and elastic recovery of the secondary phase was observed between 600and 800℃,above half of its melting point(1113℃),suggesting pronounced flow softening in both theα-Fe and 1:1:1 phases.Additionally,a novel multi-step annealing process was introduced for hot-rolled La-Fe-Co-Si alloys,involving partial transient liquid-phase diffusion in the 1:1:1 phase to address deformation-induced defects,such as residualα-Fe and lattice distortions in the 1:13 phase,which have not been previously reported.As a result,a primary La(Fe,Co,Si)13phase with a volume fraction of97.5%was achieved after multi-step annealing,compared to 87.5%using conventional annealing.Correspondingly,the magnetocaloric properties were restored,with the Curie temperature(TC)recovering from 276 to 268 K and the maximum magnetic entropy change(ΔSM)increasing from 7.56 to 8.67 J kg^(-1)K^(-1)under a 2 T magnetic field.展开更多
The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants.A hex bolt sample was prepared in the following steps...The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants.A hex bolt sample was prepared in the following steps:1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area;2) nickel(Ni) film coating as a glue layer on the surface of the bolt;and 3) Ag-Pd alloy coating on the Ni film.The films were deposited by using a direct current(DC) magnetron sputtering system.The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient,which was determined using axial force measurement.A 500 nm-thick Ag-Pd(80-20,molar ratio) alloy film has the lowest friction coefficient of 0.109.A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd(80-20) alloy film or N-5000 oil.In a cycle,the bolts were inserted into a block using a torque wrench,which was followed by heating and disassembling.After only one cycle,it was not possible to remove the bolts coated with the N-5000 oil from the block.However,the bolts coated with the Ag-Pd(80-20) alloy could be easily removed up until 15 cycles.展开更多
The influence of low energy laser peening on fatigue lives of Ti-6Al-4V was investigated. Laser peening was carried out on Ti-6Al-4V samples. Laser peened samples were characterized by residual stress analysis, surfac...The influence of low energy laser peening on fatigue lives of Ti-6Al-4V was investigated. Laser peening was carried out on Ti-6Al-4V samples. Laser peened samples were characterized by residual stress analysis, surface roughness measurements, X-ray diffraction, optical microscopy, nanoindentation hardness tests, scanning and transmission electron microscopy and fatigue testing. Laser peening resulted in the formation of nanocrystallites on the surface and near surface regions with associated increase in hardness and introduction of compressive residual stress. Owing to positive influence of nanostructured surface and compressive residual stress, fatigue lives of the laser peened samples were significantly increased compared to the unpeened samples.展开更多
The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） wa...The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） was lowered from 2 mg/L to below 0.01 mg/L in the optimum pH range 4.0-7.0 using a 5 g/L CRB within 3 h contact time. The adsorption data fits well with Langmuir isotherm and yielded Langmuir monolayer capacity of 1.78 mg As（Ⅴ）/g of CRB at pH 7.0. Presence of anions such as silicate and phosphate decreased As（Ⅴ） adsorption efficiency. An increase temperature resulted a decrease in the amount of As（Ⅴ） adsorbed by 6%. The continuous fixed bed column study showed that at the adsorbent bed depth of 30 cm and residence time of 168 min, the CRB was capable of treating 340 bed volumes of As（V） spiked water （C0 = 2 mg/L） before breakthrough （Ce = 0.01 mg/L）. This solid adsorbent, although not reusable, can be considered for design of adsorption columns as an efficiency arsenic adsorption media.展开更多
As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and th...As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.展开更多
Raw scrap powders containing 10 wt.% In were recovered by sand-blasting chamber shields of sputter coaters and used as a sole source of indium components for both sieving and air-classification. Sieving was performed ...Raw scrap powders containing 10 wt.% In were recovered by sand-blasting chamber shields of sputter coaters and used as a sole source of indium components for both sieving and air-classification. Sieving was performed first as a feasibility test, and enrichment of indium component was possible up to 19 wt.% with a mesh size of 635. With this experimental basis, the raw scrap powders were air-classified into 12 lots according to the revolution per minute （r/min） of a single horizontally arranged classifying wheel： 4000, 6000, 8000, 10000, 12000, and 14000 r/rain. The particle cut size varied from 56 to 5 μm with turbo wheel speeds corresponding to 4000 to 14000 r/min, respectively, and enrichment of indium component was possible in fine overflow fractions at all turbo wheel speeds while the indium components were not concentrated in all of the coarse underflow fractions. The grade of the indium components became higher with decreasing particle size of the air-classified scrap powders, with the highest grade obtained in the fine overflow fraction with a turbo wheel speed of 14000 r/min. The amount of indium in the fine overflow fractions varied between 15.9 wt.% and 31.5 wt.%. All in all, the grade or purity of the indium component improved rather significantly from 15.9 wt.% to 31.5 wt.% by air-classification, but this also resulted in overall decrease in recovery rate from 99.33% to 49.64%. Therefore, enrichment and separation of indium should be optimized for maximum recovery and grade of the indium components, which can be used as raw materials in the subsequent electro-refining processes.展开更多
Chemical composition, Raman microspectrometry, and Fourier transform infrared(FT-IR)and SEM-CL (Cathodluminescence)analyses are carried out for Tanzania and Madagascar garnets for locality identification. Inclusion st...Chemical composition, Raman microspectrometry, and Fourier transform infrared(FT-IR)and SEM-CL (Cathodluminescence)analyses are carried out for Tanzania and Madagascar garnets for locality identification. Inclusion study was sustained after electron probe microanalysis(EPMA). Needle-like illmenites, apatites and zircons were the most common solid inclusions in Tanzania garnets. Madagascar garnets revealed rutile needles and apatites were also observed, but differences in size, shape and distribution patterns were noticed compared to Tanzania garnets. Tanzania garnets exhibited all types of observable fluid inclusions such as"fingerprint"pattern, called Type I-A, liquid-only(L) single phase fluid inclusion, called Type I-B and Type II-A(L+S), Type II-B(L+V)and Type III-A(L+Sylvite+S), Type III-B(L+S+V), while no more than two phase fluid inclusions found in both Madagascar and Korea garnets even if all examined garnets from three localities retained"fingerprint"features, so called, partially healed fractures, in common. Chemical composition, Raman microspectrometry and Fourier transform infrared(FT-IR)analysis taken turned out to be useful methods for the purpose of this study. Using consequences of SEM-CL and inclusion study, accordingly, the locality identification of gem-quality garnets is capable of being available in further application for other kinds of gemstones.展开更多
文摘The paper describes process details for extraction of rare earths from an intermediate grade concentrate of Madhya Pradesh region in India and a South African slag. The xenodme concentrate obtained from the former place was an intermediate grade （47%） rare earth phosphate containing both monazite and xenotime. The South African slag was a low-grade waste product typically containing only 4% of rare earths. The rare earth resource concentrates have been treated individually by different methods such as alkali fusion and alkali leaching to convert them into their mixed oxides. Both types of materials have been processed and greater than 98% solubilization of metal values has been achieved in the intermediate grade xenotime and 80% from the South African slag. The residue of xenotime hydroxide has been washed thoroughly to collect the sodium phosphate, as by-product and the slurry pH have been adjusted to separate rare earths from thorium effectively. Other impurities such as uranium and iron have been removed by precipitation of rare earths by oxalic acid. It has been possible to recover 〉95% yttrium along with other rare earth oxides.
基金financially supported by the Fundamental Research Program of the Korea Institute of Materials Science(No.PNKA330)
文摘Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In this study,a comprehensive and systematic investigation was conducted,by encompassing the analysis of hot deformation mechanisms,along with the microstructure evolution and magnetoc aloric properties of hot-rolled La-Fe-Co-Si alloy.The La_(1.05)Fe_(11.2)Co_(0.7)Si_(1.38)alloy was examined using multiscale mechanical analysis to assess the effects of temperature.A series of macroscale hot compression and microscale nanoindentation tests were performed to access global and local mechanical properties,including variations in hardness and indentation modulus of the primaryα-Fe and secondary 1:1:1 phases up to 800℃.A significant decrease in hardness and elastic recovery of the secondary phase was observed between 600and 800℃,above half of its melting point(1113℃),suggesting pronounced flow softening in both theα-Fe and 1:1:1 phases.Additionally,a novel multi-step annealing process was introduced for hot-rolled La-Fe-Co-Si alloys,involving partial transient liquid-phase diffusion in the 1:1:1 phase to address deformation-induced defects,such as residualα-Fe and lattice distortions in the 1:13 phase,which have not been previously reported.As a result,a primary La(Fe,Co,Si)13phase with a volume fraction of97.5%was achieved after multi-step annealing,compared to 87.5%using conventional annealing.Correspondingly,the magnetocaloric properties were restored,with the Curie temperature(TC)recovering from 276 to 268 K and the maximum magnetic entropy change(ΔSM)increasing from 7.56 to 8.67 J kg^(-1)K^(-1)under a 2 T magnetic field.
基金Project supported by Power Research and Development Program funded by Ministry of Knowledge Economy and Korea Institute of Materials Science,a subsidiary branch of Korea Institute of Machinery and Materials
文摘The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants.A hex bolt sample was prepared in the following steps:1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area;2) nickel(Ni) film coating as a glue layer on the surface of the bolt;and 3) Ag-Pd alloy coating on the Ni film.The films were deposited by using a direct current(DC) magnetron sputtering system.The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient,which was determined using axial force measurement.A 500 nm-thick Ag-Pd(80-20,molar ratio) alloy film has the lowest friction coefficient of 0.109.A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd(80-20) alloy film or N-5000 oil.In a cycle,the bolts were inserted into a block using a torque wrench,which was followed by heating and disassembling.After only one cycle,it was not possible to remove the bolts coated with the N-5000 oil from the block.However,the bolts coated with the Ag-Pd(80-20) alloy could be easily removed up until 15 cycles.
文摘The influence of low energy laser peening on fatigue lives of Ti-6Al-4V was investigated. Laser peening was carried out on Ti-6Al-4V samples. Laser peened samples were characterized by residual stress analysis, surface roughness measurements, X-ray diffraction, optical microscopy, nanoindentation hardness tests, scanning and transmission electron microscopy and fatigue testing. Laser peening resulted in the formation of nanocrystallites on the surface and near surface regions with associated increase in hardness and introduction of compressive residual stress. Owing to positive influence of nanostructured surface and compressive residual stress, fatigue lives of the laser peened samples were significantly increased compared to the unpeened samples.
文摘The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） was lowered from 2 mg/L to below 0.01 mg/L in the optimum pH range 4.0-7.0 using a 5 g/L CRB within 3 h contact time. The adsorption data fits well with Langmuir isotherm and yielded Langmuir monolayer capacity of 1.78 mg As（Ⅴ）/g of CRB at pH 7.0. Presence of anions such as silicate and phosphate decreased As（Ⅴ） adsorption efficiency. An increase temperature resulted a decrease in the amount of As（Ⅴ） adsorbed by 6%. The continuous fixed bed column study showed that at the adsorbent bed depth of 30 cm and residence time of 168 min, the CRB was capable of treating 340 bed volumes of As（V） spiked water （C0 = 2 mg/L） before breakthrough （Ce = 0.01 mg/L）. This solid adsorbent, although not reusable, can be considered for design of adsorption columns as an efficiency arsenic adsorption media.
基金the research fund of the Korea Institute of Materials Science, a subsidiary branch of the Korea Institute of Machinery and Materialssupported by a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea
文摘As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.
文摘Raw scrap powders containing 10 wt.% In were recovered by sand-blasting chamber shields of sputter coaters and used as a sole source of indium components for both sieving and air-classification. Sieving was performed first as a feasibility test, and enrichment of indium component was possible up to 19 wt.% with a mesh size of 635. With this experimental basis, the raw scrap powders were air-classified into 12 lots according to the revolution per minute （r/min） of a single horizontally arranged classifying wheel： 4000, 6000, 8000, 10000, 12000, and 14000 r/rain. The particle cut size varied from 56 to 5 μm with turbo wheel speeds corresponding to 4000 to 14000 r/min, respectively, and enrichment of indium component was possible in fine overflow fractions at all turbo wheel speeds while the indium components were not concentrated in all of the coarse underflow fractions. The grade of the indium components became higher with decreasing particle size of the air-classified scrap powders, with the highest grade obtained in the fine overflow fraction with a turbo wheel speed of 14000 r/min. The amount of indium in the fine overflow fractions varied between 15.9 wt.% and 31.5 wt.%. All in all, the grade or purity of the indium component improved rather significantly from 15.9 wt.% to 31.5 wt.% by air-classification, but this also resulted in overall decrease in recovery rate from 99.33% to 49.64%. Therefore, enrichment and separation of indium should be optimized for maximum recovery and grade of the indium components, which can be used as raw materials in the subsequent electro-refining processes.
文摘Chemical composition, Raman microspectrometry, and Fourier transform infrared(FT-IR)and SEM-CL (Cathodluminescence)analyses are carried out for Tanzania and Madagascar garnets for locality identification. Inclusion study was sustained after electron probe microanalysis(EPMA). Needle-like illmenites, apatites and zircons were the most common solid inclusions in Tanzania garnets. Madagascar garnets revealed rutile needles and apatites were also observed, but differences in size, shape and distribution patterns were noticed compared to Tanzania garnets. Tanzania garnets exhibited all types of observable fluid inclusions such as"fingerprint"pattern, called Type I-A, liquid-only(L) single phase fluid inclusion, called Type I-B and Type II-A(L+S), Type II-B(L+V)and Type III-A(L+Sylvite+S), Type III-B(L+S+V), while no more than two phase fluid inclusions found in both Madagascar and Korea garnets even if all examined garnets from three localities retained"fingerprint"features, so called, partially healed fractures, in common. Chemical composition, Raman microspectrometry and Fourier transform infrared(FT-IR)analysis taken turned out to be useful methods for the purpose of this study. Using consequences of SEM-CL and inclusion study, accordingly, the locality identification of gem-quality garnets is capable of being available in further application for other kinds of gemstones.
