This research work was carried out with the aim of continuing to expand knowledge on the behaviour of AISI 304 stainless steel against solid particle erosion. In this particular case, the steel was subjected to the im...This research work was carried out with the aim of continuing to expand knowledge on the behaviour of AISI 304 stainless steel against solid particle erosion. In this particular case, the steel was subjected to the impact of alumina particles, which are hard abrasives with irregular and angular shapes. Different characterization techniques were applied to gain a better understanding of alumina. For instance, particle size distribution was obtained using the Analysette 28 Image Sizer and the particle size was between 300 - 400 µm. SEM and EDS analysis were used to know the morphology and chemical composition of both the abrasive particles and AISI 304 stainless steel. Additionally, mechanical properties values such as the hardness and Young’s modulus of AISI 304 steel were attained using a Berkovich indenter (model TTX-NHT, CSM Instruments). On the other hand, two tests were carried out for each impact angle used, 30˚, 45˚, 60˚ and 90˚, with a particle velocity of 24 ± 2 m/s and an abrasive flow rate of 63 ± 0.5 g/min, employing a test rig based on ASTM G76-95 standard. SEM images using two detectors, Backscattered Electron Detector (BED) and Low Electron Detector (LED), were employed to identify the wear mechanisms on the AISI 304 eroded surfaces at 30˚ and 90˚. Finally, the erosion rates of AISI 304 compared to those results reached by AISI 1018 steel and AISI 420 stainless steel tested under identical conditions in previous works.展开更多
A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was use...A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was used to calculate the size dissolution rate, dissolution time and mass of alumina dissolved employing commercial software and custom algorithm based on the shrinking sphere assumption. The effects of some convection and thermal condition parameters on the dissolution process were studied. The calculated results show that the decrease of alumina content or the increase of alumina diffusion coefficient is beneficial for the increase of size dissolution rate and the decrease of dissolution time of non-agglomerated particles. The increase of bath superheat or alumina preheating temperature results in the increase of size dissolution rate and the decrease of dissolution time of agglomerated particles. The calculated dissolution curve of alumina（mass fraction of alumina dissolved） for a 300 k A aluminum reduction cell is in well accordance with the experimental results. The analysis shows that the dissolution process of alumina can be divided into two distinct stages： the fast dissolution stage of non-agglomerated particles and the slow dissolution stage of agglomerated particles, with the dissolution time in the order of 10 and 100 s, respectively. The agglomerated particles were identified to be the most important factor limiting the dissolution process.展开更多
The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables（ LCC）. Three different combinations of alumina have been included in the matrix formulat...The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables（ LCC）. Three different combinations of alumina have been included in the matrix formulation of the castables. All the three combinations are composed of a bimodal reactive alumina and a fine ground monomodal reactive alumina. The first A1 and second A2 combinations are respectively composed of bimodal and monomodal aluminas from Alteo,with a different fine /coarse particles ratio for the bimodal alumina. The two Alteo combinations have been compared with a third combination C composed of a bimodal commercially available grade and a monomodal commercially available grade. Optimization of particle size packing has been performed for the three different formulations using the Dinger and Funk model. With this optimization,the two formulations based on Alteo material（ PFR,PBR and PFR40） achieve the same level of performance in applicative tests（ flowability,cold physical properties,mechanical resistance,crystalline phases,thermal shocks and corrosion） as reference solutions on the market.展开更多
The impact-abrasive wear behavior of ZTA(zirconia toughened alumina)particle(ZTAp)and NbC particle(NbCp)reinforced Fe60 matrix composites(ZTAp-NbCp/Fe60)were investigated.Specimens of pure Fe60 matrix material,NbCp re...The impact-abrasive wear behavior of ZTA(zirconia toughened alumina)particle(ZTAp)and NbC particle(NbCp)reinforced Fe60 matrix composites(ZTAp-NbCp/Fe60)were investigated.Specimens of pure Fe60 matrix material,NbCp reinforced Fe60 composite(NbCp/Fe60)and ZTAp-NbCp/Fe60 with different contents of ZTAp were prepared through vacuum sintering and tested on an MLD-10B Impact Wear Rig.As revealed by the results,NbCp could strengthen Fe60 matrix,and had fine grain strengthening effect on Fe60matrix.When the mass fraction of ZTAp was 5%-15%,the impact-abrasive wear performance of ZTAp-NbCp/Fe60 composites was better than that of Fe60 and NbCp/Fe60.When the mass fraction was 15%,the ZTApNbCp/Fe60 had the best performance.ZTAp could weaken the impact and wear effect of abrasive particles on the composite and protect the matrix.Cracks occured at the interface and at defects in the ZTAp.The former leaded to ZTAp shedding,while the latter leaded to ZTAp fracturing.In both cases,the performance of the composite material would decrease.展开更多
Al2O3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet（Lu...Al2O3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet（Lu3Al5O（12）：Ce^3＋）green phosphors were synthesized by high temperature solidstate method using commercial lutetium（III）oxide,cerium（III）oxide,and as-prepared Al2O3 powders with different morphologies.The phases,morphologies,and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and photoluminescence spectroscopy（PL）.Moreover,the influences of the morphologies ofα-Al2O3 on the types of crystal structure,morphologies,and photoluminescent properties of LuAG：Ce^3＋green phosphors were investigated.The results indicated that the morphologies and particle sizes of theα-Al2O3 powders could be controlled by the additives and parameters.Notably,the sphericalα-Al2O3 powders with good dispersibility were found to be the excellent base materials of LuAG：Ce^3＋green phosphors for white light emitting diodes.展开更多
Electromagnetic separation of non-metallic inclusions from Al-Si melt is studied by theoretical analysis and experiments on self-designed electromagnetic separation apparatus. Metallographs and LECO Image Analysis Sy...Electromagnetic separation of non-metallic inclusions from Al-Si melt is studied by theoretical analysis and experiments on self-designed electromagnetic separation apparatus. Metallographs and LECO Image Analysis System were used to analyze the content of alumina in aluminum alloy before and after electromagnetic separation. It is seen that removal effciency increases with the increase of electromagnetic force (EMF) and diameter of inclusion particles while decreases with the increase of melt velocity and height of separator. All alumina particles with diamete of 14μm have been removed successfully from the melt.展开更多
In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates,morphology(spherical and irregular)and content on the deposition behavior of the coatings(including sur...In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates,morphology(spherical and irregular)and content on the deposition behavior of the coatings(including surface roughness,surface residual stress,cross-sectional microstructure and microhardness)was investigated.Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition,which result in remarkable low surface roughness and porosity of the coatings.In addition,very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved.For irregular alumina particles,the embedding of ceramic particulates in the coating was dominant during deposition process,resulting in high retention in the final deposit.However,it showed limited influence on porosity,surface roughness and interfacial bonding of the deposit.The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.展开更多
To contribute to the understanding of Eu(Ⅲ)interaction properties on hydrous alumina particles in the absence and presence of fulvic acid(FA),the complexation properties of Eu(Ⅲ)with hydrous alumina,FA and FA-alumin...To contribute to the understanding of Eu(Ⅲ)interaction properties on hydrous alumina particles in the absence and presence of fulvic acid(FA),the complexation properties of Eu(Ⅲ)with hydrous alumina,FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy(TRLFS)techniques.The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(Ⅲ).Eu(Ⅲ)is adsorbed onto alumina particles as outer-sphere surface complexes of≡(Al-O)-Eu·(OH)·7H_2O and≡(Al-O)-Eu·6H_2O at low pH values,and as inner-sphere surface complexes as≡(Al-O)_2-Eu^+·4H_2O at high pH.In FA solution,Eu(Ⅲ)forms complexes with FA as(COO)_2Eu^+(H_2O)_x and the hydration water number in the first coordination sphere decreases with pH increasing.The formation of≡COO-Eu-(O-Al≡)·4H_2O is observed on FA-alumina hybrids,suggesting the formation of strong inner-sphere surface complexes in the presence of FA.The surface complexes are also characterized by their emission spectra[the ratio of emission intensities of^5D_0→~7F_1(λ=594nm)and^5D_0→~7F_2(λ=619nm)transitions]and their fluorescence lifetime.The findings is important to understand the contribution of FA in the complexation properties of Eu(Ⅲ)on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(Ⅲ),or its analogue trivalent lanthanide and actinide ions in natural environment.展开更多
This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investig...This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).展开更多
文摘This research work was carried out with the aim of continuing to expand knowledge on the behaviour of AISI 304 stainless steel against solid particle erosion. In this particular case, the steel was subjected to the impact of alumina particles, which are hard abrasives with irregular and angular shapes. Different characterization techniques were applied to gain a better understanding of alumina. For instance, particle size distribution was obtained using the Analysette 28 Image Sizer and the particle size was between 300 - 400 µm. SEM and EDS analysis were used to know the morphology and chemical composition of both the abrasive particles and AISI 304 stainless steel. Additionally, mechanical properties values such as the hardness and Young’s modulus of AISI 304 steel were attained using a Berkovich indenter (model TTX-NHT, CSM Instruments). On the other hand, two tests were carried out for each impact angle used, 30˚, 45˚, 60˚ and 90˚, with a particle velocity of 24 ± 2 m/s and an abrasive flow rate of 63 ± 0.5 g/min, employing a test rig based on ASTM G76-95 standard. SEM images using two detectors, Backscattered Electron Detector (BED) and Low Electron Detector (LED), were employed to identify the wear mechanisms on the AISI 304 eroded surfaces at 30˚ and 90˚. Finally, the erosion rates of AISI 304 compared to those results reached by AISI 1018 steel and AISI 420 stainless steel tested under identical conditions in previous works.
基金Project(2010AA065201)supported by the High-tech Research and Development Program of ChinaProject(2013zzts038)supported by the Fundamental Research Funds for the Central Universities of Central South University,ChinaProject(ZB2011CBBCe1)supported by the Major Program for Aluminum Corporation of China Limited
文摘A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was used to calculate the size dissolution rate, dissolution time and mass of alumina dissolved employing commercial software and custom algorithm based on the shrinking sphere assumption. The effects of some convection and thermal condition parameters on the dissolution process were studied. The calculated results show that the decrease of alumina content or the increase of alumina diffusion coefficient is beneficial for the increase of size dissolution rate and the decrease of dissolution time of non-agglomerated particles. The increase of bath superheat or alumina preheating temperature results in the increase of size dissolution rate and the decrease of dissolution time of agglomerated particles. The calculated dissolution curve of alumina（mass fraction of alumina dissolved） for a 300 k A aluminum reduction cell is in well accordance with the experimental results. The analysis shows that the dissolution process of alumina can be divided into two distinct stages： the fast dissolution stage of non-agglomerated particles and the slow dissolution stage of agglomerated particles, with the dissolution time in the order of 10 and 100 s, respectively. The agglomerated particles were identified to be the most important factor limiting the dissolution process.
文摘The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables（ LCC）. Three different combinations of alumina have been included in the matrix formulation of the castables. All the three combinations are composed of a bimodal reactive alumina and a fine ground monomodal reactive alumina. The first A1 and second A2 combinations are respectively composed of bimodal and monomodal aluminas from Alteo,with a different fine /coarse particles ratio for the bimodal alumina. The two Alteo combinations have been compared with a third combination C composed of a bimodal commercially available grade and a monomodal commercially available grade. Optimization of particle size packing has been performed for the three different formulations using the Dinger and Funk model. With this optimization,the two formulations based on Alteo material（ PFR,PBR and PFR40） achieve the same level of performance in applicative tests（ flowability,cold physical properties,mechanical resistance,crystalline phases,thermal shocks and corrosion） as reference solutions on the market.
基金Funded by the National Key Research and Development Program(No.2017YFB0305105)the National Natural Science Foundation of China(No.51571210)。
文摘The impact-abrasive wear behavior of ZTA(zirconia toughened alumina)particle(ZTAp)and NbC particle(NbCp)reinforced Fe60 matrix composites(ZTAp-NbCp/Fe60)were investigated.Specimens of pure Fe60 matrix material,NbCp reinforced Fe60 composite(NbCp/Fe60)and ZTAp-NbCp/Fe60 with different contents of ZTAp were prepared through vacuum sintering and tested on an MLD-10B Impact Wear Rig.As revealed by the results,NbCp could strengthen Fe60 matrix,and had fine grain strengthening effect on Fe60matrix.When the mass fraction of ZTAp was 5%-15%,the impact-abrasive wear performance of ZTAp-NbCp/Fe60 composites was better than that of Fe60 and NbCp/Fe60.When the mass fraction was 15%,the ZTApNbCp/Fe60 had the best performance.ZTAp could weaken the impact and wear effect of abrasive particles on the composite and protect the matrix.Cracks occured at the interface and at defects in the ZTAp.The former leaded to ZTAp shedding,while the latter leaded to ZTAp fracturing.In both cases,the performance of the composite material would decrease.
基金Funded by Shan’xi Educational Committee(No.17JK0395)
文摘Al2O3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet（Lu3Al5O（12）：Ce^3＋）green phosphors were synthesized by high temperature solidstate method using commercial lutetium（III）oxide,cerium（III）oxide,and as-prepared Al2O3 powders with different morphologies.The phases,morphologies,and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and photoluminescence spectroscopy（PL）.Moreover,the influences of the morphologies ofα-Al2O3 on the types of crystal structure,morphologies,and photoluminescent properties of LuAG：Ce^3＋green phosphors were investigated.The results indicated that the morphologies and particle sizes of theα-Al2O3 powders could be controlled by the additives and parameters.Notably,the sphericalα-Al2O3 powders with good dispersibility were found to be the excellent base materials of LuAG：Ce^3＋green phosphors for white light emitting diodes.
基金This work supported by the National Natural Science Foundation of China(Grant,No.59871029)the National Key Fundamental Research Project(973)(No.G1999064900)
文摘Electromagnetic separation of non-metallic inclusions from Al-Si melt is studied by theoretical analysis and experiments on self-designed electromagnetic separation apparatus. Metallographs and LECO Image Analysis System were used to analyze the content of alumina in aluminum alloy before and after electromagnetic separation. It is seen that removal effciency increases with the increase of electromagnetic force (EMF) and diameter of inclusion particles while decreases with the increase of melt velocity and height of separator. All alumina particles with diamete of 14μm have been removed successfully from the melt.
基金financially supported by the National Natural Science Foundation of China (Nos.51671205 and 51801217)
文摘In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates,morphology(spherical and irregular)and content on the deposition behavior of the coatings(including surface roughness,surface residual stress,cross-sectional microstructure and microhardness)was investigated.Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition,which result in remarkable low surface roughness and porosity of the coatings.In addition,very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved.For irregular alumina particles,the embedding of ceramic particulates in the coating was dominant during deposition process,resulting in high retention in the final deposit.However,it showed limited influence on porosity,surface roughness and interfacial bonding of the deposit.The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.
基金Financial supports from the National Natural Science Foundation of China(21225730,91326202 and 21577032)the Fundamental Research Funds for the Central Universities(JB2015001)+1 种基金Kunlun scholarship of Qinghai province,the priority Academic program development of Jiangsu Higher Education Institutionsthe Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions are acknowledged
文摘To contribute to the understanding of Eu(Ⅲ)interaction properties on hydrous alumina particles in the absence and presence of fulvic acid(FA),the complexation properties of Eu(Ⅲ)with hydrous alumina,FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy(TRLFS)techniques.The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(Ⅲ).Eu(Ⅲ)is adsorbed onto alumina particles as outer-sphere surface complexes of≡(Al-O)-Eu·(OH)·7H_2O and≡(Al-O)-Eu·6H_2O at low pH values,and as inner-sphere surface complexes as≡(Al-O)_2-Eu^+·4H_2O at high pH.In FA solution,Eu(Ⅲ)forms complexes with FA as(COO)_2Eu^+(H_2O)_x and the hydration water number in the first coordination sphere decreases with pH increasing.The formation of≡COO-Eu-(O-Al≡)·4H_2O is observed on FA-alumina hybrids,suggesting the formation of strong inner-sphere surface complexes in the presence of FA.The surface complexes are also characterized by their emission spectra[the ratio of emission intensities of^5D_0→~7F_1(λ=594nm)and^5D_0→~7F_2(λ=619nm)transitions]and their fluorescence lifetime.The findings is important to understand the contribution of FA in the complexation properties of Eu(Ⅲ)on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(Ⅲ),or its analogue trivalent lanthanide and actinide ions in natural environment.
基金financially supported by the authors would like to acknowledge the National Key Research and Development Program of China(No.2016YFB1100104)the National Natural Science Foundation of China(No.51875470)+1 种基金the State Key Laboratory of Solidification Processing(NPU,China)(No.2019-QZ-01)the financial support from the fund of SAST(No.SAST2016043)。
文摘This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).
