In this study, S-doped NbSea （NbSo.aSel.8） powders were fabricated, and the corresponding Cu-based composites （Cu/NbSo.eSe1.8） were obtained by powder metallurgy technique. The phase compositions, physical, and tr...In this study, S-doped NbSea （NbSo.aSel.8） powders were fabricated, and the corresponding Cu-based composites （Cu/NbSo.eSe1.8） were obtained by powder metallurgy technique. The phase compositions, physical, and tribological properties of Cu-based composites were investigated systematically. The results show that Cu matrix reacts with NbSo.2Sel.8 to produce Cu2Se and Cu0.38NbSo.2Se1.8 during sintering process, which influences the physical and tribological properties of Cu-based composites significantly. Specially, with NbS0.2Se1.8 content increasing, the density of Cu/ NbSo.2Se1.8 composites decreases, and the hardness increases firstly and then decreases, while the electric resistivity in- creases slightly. In addition, the incorporation of NbSo.2Se1.8 enhances the tribological properties of Cu greatly, which is attributed to the lubricating effect of Cuo,38NbSo.2Se1.8 and the reinforcement effect of Cu2Se. In particular, when the content of NbSo.2Sel.8 is 6 wt%, the Cu-based composite has the best tribological properties.展开更多
In this paper, phase composition of the Mn＋l- AXn phases by self-propagating high-temperature synthesis （SHS） was determined using Ti, Cr, A1, and carbon black as raw materials. And, phase composition and micro- st...In this paper, phase composition of the Mn＋l- AXn phases by self-propagating high-temperature synthesis （SHS） was determined using Ti, Cr, A1, and carbon black as raw materials. And, phase composition and micro- structures of the Mn＋1AXn phases-contained bulk by SHS with the pseudo-hot isostatic pressing （SHS/PHIP） were investigated in Ti-Cr-AI-C systems raw materials. Riet- veld XRD refinement was introduced to study the lattice parameters and phase composition of the resultant phases from the SHSed and SHS/PHIPed samples. Ti2A1Cx, Ti3A1C2, and Cr2A1Cx by SHS were detected in the Ti-Cr- A1-C systems, as well as the binary carbide of TiC and intermetallics. The mechanical properties of the synthe- sized bulk samples were determined, exhibiting a high strength and toughness compared with the typical mono- lithic Mn＋1AXn phase ceramics. It is indicated that the samples prepared by SHS/PHIP are identified to be a strategy for improving the mechanical properties of monolithic Mn＋1AXn phase.展开更多
Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosp...Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosphors are studied. Results show that the phase com-position changes from strontium-rich phase to aluminum- rich phase with the decrease of Sr/AI： when the rate of Al/Sr changes from 3：1 to 1：1, the main crystal phase of samples is Sr3Al206, and it exhibits the characteristic fluorescence of Eu^3＋ in the lattice of Sr3Al206; when the rate of Al/Sr is between 1：2 and 2：7, phase composition is the mixture of SrAl204 and SrAl4OT, and it emits the characteristic fluorescence of Eu^2＋ in SrAl204 but not in SrAl4OT; when Al/Sr decreases to 1：4 or even 1：12, the main crystal phase of samples transform into SrAl12019, and the characteristic emission peak is about 470 nm, which corresponds to the characteristic emission of Eu2＋ in SrAl12019. At the end of the article, the influence laws of two different synthesis methods on phase composition of samples between high-temperature solid method and combustion method are compared. Compared with the high-temperature solid method, the rule of influence is similar, but the mole ratio of Al/Sr in products is always higher than the initial ratio of the raw material, and com-pounds like Sr4Al14025 are not obtained by combustion method.展开更多
The calcia-stabilized zirconia grains with different sizes and the calcia-stabilized zirconia powder were used as main starting materials,m-ZrO2 micropowder and Y2O3 powder as additives,and sulphite liquor as binder. ...The calcia-stabilized zirconia grains with different sizes and the calcia-stabilized zirconia powder were used as main starting materials,m-ZrO2 micropowder and Y2O3 powder as additives,and sulphite liquor as binder. The specimens with the dimension of 50 mm×50 mm were prepared under 150 MPa,dried at 110 ℃ for 24 h,then fired at 1 700 ℃ and 1 750 ℃ in air,respectively. The phase composition,microstructure and properties of specimens were analyzed with XRD,SEM,and other test methods. The results indicate that：（1） the appropriate amount of m-ZrO2 micropowder and Y2O3 powder can promote the sintering property of calcia-stabilized zirconia products,and the sintering property is better when m-ZrO2 micropowder addition in matrix is 5%-10% and Y2O3 powder addition in matrix is 1%; （2） the main phase compositions of zirconia products fired at 1 700 ℃ are c-ZrO2 and m-ZrO2,no t-ZrO2 is found; （3） the microstructure of the specimen containing additives is obviously different with the specimen without additives after firing at 1 700 ℃. The matrix grains rearrange and grow in the specimens containing additives forming permeable network gas pore,and the process of the grain growth helps the gas release during sintering. So the relative density is bigger in fired specimens containing an appropriate amount of additives.展开更多
基金financially supported by the National Nature Science Foundation of China(Nos.51405199 and21301075)the Natural Science Foundation of Jiangsu Province(Nos.BK20140551 and BK20140562)+4 种基金the Postdoctoral Science Foundation of China(No.2014M561579)the Postdoctoral Science Foundation of Jiangsu Province(No.1401106C)the Opening Foundation of Jiangsu Province Material Tribology Key Laboratory(No.Kjsmcx201304)the Senior Intellectuals Fund of Jiangsu University(No.13JDG099)the Industry-Academy-Research Union Foundation of Jiangsu Province(No.BY2013065-05)
文摘In this study, S-doped NbSea （NbSo.aSel.8） powders were fabricated, and the corresponding Cu-based composites （Cu/NbSo.eSe1.8） were obtained by powder metallurgy technique. The phase compositions, physical, and tribological properties of Cu-based composites were investigated systematically. The results show that Cu matrix reacts with NbSo.2Sel.8 to produce Cu2Se and Cu0.38NbSo.2Se1.8 during sintering process, which influences the physical and tribological properties of Cu-based composites significantly. Specially, with NbS0.2Se1.8 content increasing, the density of Cu/ NbSo.2Se1.8 composites decreases, and the hardness increases firstly and then decreases, while the electric resistivity in- creases slightly. In addition, the incorporation of NbSo.2Se1.8 enhances the tribological properties of Cu greatly, which is attributed to the lubricating effect of Cuo,38NbSo.2Se1.8 and the reinforcement effect of Cu2Se. In particular, when the content of NbSo.2Sel.8 is 6 wt%, the Cu-based composite has the best tribological properties.
基金financially supported by the National Natural Science Foundation of China(Nos.11302068 and 51172057)China Postdoctoral Science Foundation(No.2013M541261)
文摘In this paper, phase composition of the Mn＋l- AXn phases by self-propagating high-temperature synthesis （SHS） was determined using Ti, Cr, A1, and carbon black as raw materials. And, phase composition and micro- structures of the Mn＋1AXn phases-contained bulk by SHS with the pseudo-hot isostatic pressing （SHS/PHIP） were investigated in Ti-Cr-AI-C systems raw materials. Riet- veld XRD refinement was introduced to study the lattice parameters and phase composition of the resultant phases from the SHSed and SHS/PHIPed samples. Ti2A1Cx, Ti3A1C2, and Cr2A1Cx by SHS were detected in the Ti-Cr- A1-C systems, as well as the binary carbide of TiC and intermetallics. The mechanical properties of the synthe- sized bulk samples were determined, exhibiting a high strength and toughness compared with the typical mono- lithic Mn＋1AXn phase ceramics. It is indicated that the samples prepared by SHS/PHIP are identified to be a strategy for improving the mechanical properties of monolithic Mn＋1AXn phase.
基金financially supported by the National Natural Science Foundation of China(No.NSFC50962001)the Scientific Research Foundation of Beifang Ethnic University for Nationalities(No.2010Y042)
文摘Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosphors are studied. Results show that the phase com-position changes from strontium-rich phase to aluminum- rich phase with the decrease of Sr/AI： when the rate of Al/Sr changes from 3：1 to 1：1, the main crystal phase of samples is Sr3Al206, and it exhibits the characteristic fluorescence of Eu^3＋ in the lattice of Sr3Al206; when the rate of Al/Sr is between 1：2 and 2：7, phase composition is the mixture of SrAl204 and SrAl4OT, and it emits the characteristic fluorescence of Eu^2＋ in SrAl204 but not in SrAl4OT; when Al/Sr decreases to 1：4 or even 1：12, the main crystal phase of samples transform into SrAl12019, and the characteristic emission peak is about 470 nm, which corresponds to the characteristic emission of Eu2＋ in SrAl12019. At the end of the article, the influence laws of two different synthesis methods on phase composition of samples between high-temperature solid method and combustion method are compared. Compared with the high-temperature solid method, the rule of influence is similar, but the mole ratio of Al/Sr in products is always higher than the initial ratio of the raw material, and com-pounds like Sr4Al14025 are not obtained by combustion method.
文摘The calcia-stabilized zirconia grains with different sizes and the calcia-stabilized zirconia powder were used as main starting materials,m-ZrO2 micropowder and Y2O3 powder as additives,and sulphite liquor as binder. The specimens with the dimension of 50 mm×50 mm were prepared under 150 MPa,dried at 110 ℃ for 24 h,then fired at 1 700 ℃ and 1 750 ℃ in air,respectively. The phase composition,microstructure and properties of specimens were analyzed with XRD,SEM,and other test methods. The results indicate that：（1） the appropriate amount of m-ZrO2 micropowder and Y2O3 powder can promote the sintering property of calcia-stabilized zirconia products,and the sintering property is better when m-ZrO2 micropowder addition in matrix is 5%-10% and Y2O3 powder addition in matrix is 1%; （2） the main phase compositions of zirconia products fired at 1 700 ℃ are c-ZrO2 and m-ZrO2,no t-ZrO2 is found; （3） the microstructure of the specimen containing additives is obviously different with the specimen without additives after firing at 1 700 ℃. The matrix grains rearrange and grow in the specimens containing additives forming permeable network gas pore,and the process of the grain growth helps the gas release during sintering. So the relative density is bigger in fired specimens containing an appropriate amount of additives.
