The grain density,Nv,in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling,ΔT,of a liquid alloy.This type of function depends on the characteristics of heterogeneous nucl...The grain density,Nv,in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling,ΔT,of a liquid alloy.This type of function depends on the characteristics of heterogeneous nucleation sites and number of SiC present in the alloy.The aim of this paper was selection of parameters for the model describing the relationship between the grain density of primary phase and undercooling.This model in connection with model of crystallisation,which is based on chemical elements diffusion and grain interface kinetics,can be used to predict casting quality and its microstructure.Nucleation models have parameters,which exact values are usually not known and sometimes even their physical meaning is under discussion.Those parameters can be obtained after mathematical analysis of the experimental data.The composites with 0,1,2,3 and 4wt.% of SiC particles were prepared.The AZ91 alloy was a matrix of the composite reinforcement SiC particles.This composite was cast to prepare four different thickness plates.They were taken from the region near to the thermocouple,to analyze the undercooling for different composites and thickness plates and its influence on the grain size.The microstructure and thermal analysis gave set of values that connect mass fraction of SiC particles,and undercooling with grain size.These values were used to approximate nucleation model adjustment parameters.Obtained model can be very useful in modelling composites microstructure.展开更多
Exploring the structure-activity relationship between the performance of gas sensors and the structure of semiconductor metal oxide(SMO)nanomaterials is crucial for understanding and designing gas-sensing materials an...Exploring the structure-activity relationship between the performance of gas sensors and the structure of semiconductor metal oxide(SMO)nanomaterials is crucial for understanding and designing gas-sensing materials and overcoming the application limitations of SMO-based gas sensors.Regulation of a single SMO microstructure provides a promising solution to address this scientific problem due to its controllable composition.In this study,we control the grain boundary(GB)density of Fe_(2)O_(3)nanomaterials using a simple solvothermal method.They have similar chemical compositions and crystal phases,providing an ideal platform for studying the influence of the GB density on the gas-sensing performance.Gas-sensing tests showed that the Fe_(2)O_(3)-1 sensor with medium GB density and the Fe_(2)O_(3)-2 sensor with high GB density had higher sensitivity and selectivity than the Fe_(2)O_(3)-0 sensors with low GB density before reaching the optimal operating temperature.However,when the GB density increased,the response to acetone decreased slightly,whereas the optimal operating temperature decreased.This work highlights the unique performance of the GB density in enhancing the gas sensitivity of a single SMO.展开更多
Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is...Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is coupled with the process of heat flow in the macroscopic scale,resulting from the heat emission during the nucleation and the growth of grains.Taking into account both of these phenomena,the proposed model is distinguished by a good reflection of reality.Moreover,the presented model assumes that the function of grain density depends on the maximal supercooling and the mass volume of the reinforcement phase particles.The knowledge of the equations,describing the function of grain density depending on the degree of supercooling,is necessary in the,more and more often used,numerical modelling of the casting structure.展开更多
The influences of cupric ion concentration （5-35 g/L）,current density （500-2000 A/m2）,circulation rate of the electrolyte solution （15-120 mL/min）,and temperature （25-60℃） on the physical and chemical propert...The influences of cupric ion concentration （5-35 g/L）,current density （500-2000 A/m2）,circulation rate of the electrolyte solution （15-120 mL/min）,and temperature （25-60℃） on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated.Two industrial processes,electrorefining （ER） cells with a synthetic electrolyte and electrowinning （EW） cells with an original solution of coppermineral leaching,were utilized to produce copper powders.Finally,the statistical full factorial method of design of experiments （DOE） was employed to investigate the interaction or the main effects of processes.The results show that increasing the copper concentration and temperature can increase the grain size,apparent density,and electrical energy consumption.On the other hand,increasing the current density and circulation rate of the electrolyte can decrease them.This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.展开更多
Barium titanate[BaTiO_(3)(BT)]-based ceramics are typical ferroelectric materials.Here,the discontinuous grain growth(DGG)and relevant grain size effect are deeply studied.An obvious DGG phenomenon is observed in a pa...Barium titanate[BaTiO_(3)(BT)]-based ceramics are typical ferroelectric materials.Here,the discontinuous grain growth(DGG)and relevant grain size effect are deeply studied.An obvious DGG phenomenon is observed in a paradigmatic Zr^(4+)-doped BT-based ceramic,with grains growing from∼2.2–6.6 to∼121.8–198.4μm discontinuously near 1320℃.It is found that fine grains can get together and grow into large ones with liquid phase surrounding them above eutectic temperature.Then the grain boundary density(D g)is quantitatively studied and shows a first-order reciprocal relationship with grain size,and the grain size effect is dependent on D g.Fine grains lead to high D g,and then cause fine domains and pseudocubic-like phase structure because of the interrupted long-range ferroelectric orders by grain boundary.High D g also causes the diffusion phase transition and low Curie dielectric peak due to the distribution of phase transition temperature induced by internal stress.Local domain switching experiments reveal that the polarization orientation is more difficult near the grain boundary,implying that the grain boundary inhibition dominates the process of polarization orientation in fine-grain ceramics,which leads to low polarization but a high coercive field.However,large-grain ceramics exhibit easy domain switching and high&similar ferroelectricity.This work reveals that the grain boundary effect dominates the grain size effect in fine-grain ceramics,and expands current knowledge on DGG and grain size effect in polycrystalline materials.展开更多
Mechanical shear resistance of wheat grain is a significant concern for the designers and researchers related to the design of threshing,handling and processing machinery of the field crops.The grain mechanical proper...Mechanical shear resistance of wheat grain is a significant concern for the designers and researchers related to the design of threshing,handling and processing machinery of the field crops.The grain mechanical properties directly affect the machine geometry and its operational parameters.The present study was carried out to determine the shear resistance of five wheat varieties(Locally names;TD-02,Sindhu-1105,Benazir,China and SKD-118)influenced by moisture content(16.7%,18.7%and 19.5%)and loading rate(3 mm/s,6 mm/s and 9 mm/s).However,some physio-dimensional properties(length,width,thickness,slenderness ratio,surface area and sphericity)were obtained at different moisture contents.The results showed that the shear resistance reduced by increasing the moisture content and loading rate.The average shear resistance decreased from 10.45 N to 3.74 N for 3-9 mm/s loading rate at moisture content of 16.7%to 19.5%.Thus,the maximum correlation(r=0.905)of shear resistance obtained at 16.7%,whereas minimum correlation(r=0.692)obtained at 19.5%.The shear resistance of wheat grain was highly significant(p<0.05)at 9 mm/s for 19.5%.Shear resistance decreased with an increase in the moisture content in the grain whereas deformation is increasing with the increase of moisture content.However,the maximum bulk density of wheat grain obtained at 19.5%for SKD-118,while the minimum obtained at 16.7%for TD-02.It is recommended that the design and modification of wheat grain processing equipment should be executed on the physio-mechanical properties of grain varieties.展开更多
基金supported financially by the European Community under Marie Curie Transfer of Knowledge grant No. MTKD-CT-2006-042468 (AGH No.27.27.170.304)Polish Ministry of Science and Higher Education for financial support under grant No. N507-44-66-34 (AGH No.18.18.170.325)
文摘The grain density,Nv,in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling,ΔT,of a liquid alloy.This type of function depends on the characteristics of heterogeneous nucleation sites and number of SiC present in the alloy.The aim of this paper was selection of parameters for the model describing the relationship between the grain density of primary phase and undercooling.This model in connection with model of crystallisation,which is based on chemical elements diffusion and grain interface kinetics,can be used to predict casting quality and its microstructure.Nucleation models have parameters,which exact values are usually not known and sometimes even their physical meaning is under discussion.Those parameters can be obtained after mathematical analysis of the experimental data.The composites with 0,1,2,3 and 4wt.% of SiC particles were prepared.The AZ91 alloy was a matrix of the composite reinforcement SiC particles.This composite was cast to prepare four different thickness plates.They were taken from the region near to the thermocouple,to analyze the undercooling for different composites and thickness plates and its influence on the grain size.The microstructure and thermal analysis gave set of values that connect mass fraction of SiC particles,and undercooling with grain size.These values were used to approximate nucleation model adjustment parameters.Obtained model can be very useful in modelling composites microstructure.
基金financially supported by the National Natural Science Foundation of China(Nos.21571119 and 22209102)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-12-1035)+2 种基金the Natural Science Foundation of Shanxi Province(Nos.202203021211253 and 20210302124473)the Postgraduate Innovation Project of Shanxi Normal University(No.2022XSY022)China Postdoctoral Science Foundation(No.2021M691366)。
文摘Exploring the structure-activity relationship between the performance of gas sensors and the structure of semiconductor metal oxide(SMO)nanomaterials is crucial for understanding and designing gas-sensing materials and overcoming the application limitations of SMO-based gas sensors.Regulation of a single SMO microstructure provides a promising solution to address this scientific problem due to its controllable composition.In this study,we control the grain boundary(GB)density of Fe_(2)O_(3)nanomaterials using a simple solvothermal method.They have similar chemical compositions and crystal phases,providing an ideal platform for studying the influence of the GB density on the gas-sensing performance.Gas-sensing tests showed that the Fe_(2)O_(3)-1 sensor with medium GB density and the Fe_(2)O_(3)-2 sensor with high GB density had higher sensitivity and selectivity than the Fe_(2)O_(3)-0 sensors with low GB density before reaching the optimal operating temperature.However,when the GB density increased,the response to acetone decreased slightly,whereas the optimal operating temperature decreased.This work highlights the unique performance of the GB density in enhancing the gas sensitivity of a single SMO.
基金supported by the Polish Ministry of Science and Higher Education within the frames of independent studies AGH(Nos:11.11.170.318 and 15.11.170.424)
文摘Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is coupled with the process of heat flow in the macroscopic scale,resulting from the heat emission during the nucleation and the growth of grains.Taking into account both of these phenomena,the proposed model is distinguished by a good reflection of reality.Moreover,the presented model assumes that the function of grain density depends on the maximal supercooling and the mass volume of the reinforcement phase particles.The knowledge of the equations,describing the function of grain density depending on the degree of supercooling,is necessary in the,more and more often used,numerical modelling of the casting structure.
文摘The influences of cupric ion concentration （5-35 g/L）,current density （500-2000 A/m2）,circulation rate of the electrolyte solution （15-120 mL/min）,and temperature （25-60℃） on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated.Two industrial processes,electrorefining （ER） cells with a synthetic electrolyte and electrowinning （EW） cells with an original solution of coppermineral leaching,were utilized to produce copper powders.Finally,the statistical full factorial method of design of experiments （DOE） was employed to investigate the interaction or the main effects of processes.The results show that increasing the copper concentration and temperature can increase the grain size,apparent density,and electrical energy consumption.On the other hand,increasing the current density and circulation rate of the electrolyte can decrease them.This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.12104093,52072075,and 52102126)the Natural Science Foundation of Fujian Province(Nos.2021J05122,2021J05123,2022J01087,and 2022J01552)+2 种基金the Sichuan Province Science and Technology Support Program(No.2021YJ0560,22ZDYF3306,2022NSFSC1970,and 2022YFG0099)the Qishan Scholar Financial Support from Fuzhou University(No.GXRC-20099)the Fundamental Research Funds for the Central Universities,Southwest Minzu University(No.2020NTD03).
文摘Barium titanate[BaTiO_(3)(BT)]-based ceramics are typical ferroelectric materials.Here,the discontinuous grain growth(DGG)and relevant grain size effect are deeply studied.An obvious DGG phenomenon is observed in a paradigmatic Zr^(4+)-doped BT-based ceramic,with grains growing from∼2.2–6.6 to∼121.8–198.4μm discontinuously near 1320℃.It is found that fine grains can get together and grow into large ones with liquid phase surrounding them above eutectic temperature.Then the grain boundary density(D g)is quantitatively studied and shows a first-order reciprocal relationship with grain size,and the grain size effect is dependent on D g.Fine grains lead to high D g,and then cause fine domains and pseudocubic-like phase structure because of the interrupted long-range ferroelectric orders by grain boundary.High D g also causes the diffusion phase transition and low Curie dielectric peak due to the distribution of phase transition temperature induced by internal stress.Local domain switching experiments reveal that the polarization orientation is more difficult near the grain boundary,implying that the grain boundary inhibition dominates the process of polarization orientation in fine-grain ceramics,which leads to low polarization but a high coercive field.However,large-grain ceramics exhibit easy domain switching and high&similar ferroelectricity.This work reveals that the grain boundary effect dominates the grain size effect in fine-grain ceramics,and expands current knowledge on DGG and grain size effect in polycrystalline materials.
基金This work is financially supported by the National Key Research of Development Program of China(Grant No.2016YFD0702004)the National Natural Science Foundation of China(Grant No.51605196)+3 种基金the Jiangsu Key Research and Development Program of China(Grant No.BE2016356)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20160532)the National Science Foundation for Post-doctoral Scientists of China(Grant No.2016M591788)Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,China(Grant No.17KJB416003).
文摘Mechanical shear resistance of wheat grain is a significant concern for the designers and researchers related to the design of threshing,handling and processing machinery of the field crops.The grain mechanical properties directly affect the machine geometry and its operational parameters.The present study was carried out to determine the shear resistance of five wheat varieties(Locally names;TD-02,Sindhu-1105,Benazir,China and SKD-118)influenced by moisture content(16.7%,18.7%and 19.5%)and loading rate(3 mm/s,6 mm/s and 9 mm/s).However,some physio-dimensional properties(length,width,thickness,slenderness ratio,surface area and sphericity)were obtained at different moisture contents.The results showed that the shear resistance reduced by increasing the moisture content and loading rate.The average shear resistance decreased from 10.45 N to 3.74 N for 3-9 mm/s loading rate at moisture content of 16.7%to 19.5%.Thus,the maximum correlation(r=0.905)of shear resistance obtained at 16.7%,whereas minimum correlation(r=0.692)obtained at 19.5%.The shear resistance of wheat grain was highly significant(p<0.05)at 9 mm/s for 19.5%.Shear resistance decreased with an increase in the moisture content in the grain whereas deformation is increasing with the increase of moisture content.However,the maximum bulk density of wheat grain obtained at 19.5%for SKD-118,while the minimum obtained at 16.7%for TD-02.It is recommended that the design and modification of wheat grain processing equipment should be executed on the physio-mechanical properties of grain varieties.
