Low thermal expansion composites are difficult to obtain by using Al with larger positive thermal expansion coefficient(TEC) and the materials with smaller negative TECs. In this investigation, Y2Mo3O12 with larger ...Low thermal expansion composites are difficult to obtain by using Al with larger positive thermal expansion coefficient(TEC) and the materials with smaller negative TECs. In this investigation, Y2Mo3O12 with larger negative TEC is used to combine with Al to obtain a low thermal expansion composite with high conductivity. The TEC of Al is reduced by 19%for a ratio Al:Y2Mo3O12 of 0.3118. When the mass ratio of Al:Y2Mo3O12 increases to 2.0000, the conductivity of the composite increases so much that a transformation from capacitance to pure resistance appears. The results suggest that Y2Mo3O12 plays a dominant role in the composite for low content of Al(presenting isolate particles), while the content of Al increases enough to contact each other, the composite presents mainly the property of Al. For the effect of high content Al, it is considered that Al is squeezed out of the cermets during the uniaxial pressure process to form a thin layer on the surface.展开更多
Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Ra...Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of (ZrMg)6+ for Cr3+. The overall linear thermal expansion coefficient decreases with the increase of the (ZrMg)6+ content in an orthorhombic structure sample. The co-incorporation of Zr4+ and Mg2+ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4+ and Mg2+ than Cr3+, respectively.展开更多
Materials Lao.8Sro.2Gao.83Mgo.17_xCox03_6 with x = 0, 0.05, 0.085, 0.10, and 0.15 are synthesized by laser rapid solidification. It is shown that the samples prepared by laser rapid solidification give rise to unique ...Materials Lao.8Sro.2Gao.83Mgo.17_xCox03_6 with x = 0, 0.05, 0.085, 0.10, and 0.15 are synthesized by laser rapid solidification. It is shown that the samples prepared by laser rapid solidification give rise to unique spear-like or leaf-like microstructures which are orderly arranged and densely packed. Their electrical properties each show a general depen dence of the Co content and the total conductivities of Lao.8Sro.2Gao.83Mgo.085Coo.08503_6 prepared by laser rapid solidification are measured to be 0.067, 0.124, and 0.202 S.cm-1 at 600, 700, and 800 ℃, respectively, which are much higher than by conventional solid state reactions. Moreover, the electrical conductivities each as a function of the oxy gen partial pressure are also measured. It is shown that the samples with the Co content values 〈 8.5 mol% each exhibit basically ionic conduction while those for Co content values 〉 10 mol % each show ionic mixed electronic conduction under oxygen partial pressures from 10-16 atm (1 atm = 1.01325 x 105 Pa) to 0.98 atm. The improved ionic conductivity of Lao.sSro.2Gao.83Mgo.085Coo.08503 prepared by laser rapid solidification compared with by solid state reactions is attributed to the unique microstructure of the sample generated during laser rapid solidification.展开更多
A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm ...A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm (47) and exhibits negative thermal expansion (NTE) property with low anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) for a, b, and c axes are -1.41×10^-6 K^-1, -2.23×10^-6 K^-1, and -1.87×10^-6 K^-1, respectively. This gives rise to volume and linear CTEs of -3.10×10^-6 K^-1 and -1.03×10^-6 K^-1, respectively. Besides, it exhibits also intense photoluminescence from 360 nm to about 600 nm. The mechanism of NTE and the correlation of the PL with axial thermal expansion property are discussed.展开更多
Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grai...Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y2-x(ZnLi)xMo3O12(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn^2+ and Li+for Y^3+ in Y2Mo3O12 resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y2-x(ZnLi)xMo3O12 could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.展开更多
HfMgMo(3-x)WxO(12) with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structu...HfMgMo(3-x)WxO(12) with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structure for x≤2.0 and a monoclinic structure for x2.0. A near-zero thermal expansion(ZTE) is realized for HfMgMo(2.5)W(0.5)O(12) and negative coefficients of thermal expansion(NCTE) are achieved for other compositions with different values. The ZTE and variation of NCTE are attributed to the difference in electronegativity between W and Mo and incorporation of a different amount of W, which cause variable distortion of the octahedra and softening of the MoO4 tetrahedra, and hence an enhanced NCTE in the a- and c-axis and reduced CTE in the b-axis as revealed by Raman spectroscopy and x-ray diffraction.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974183 and 11104252)the Doctoral Fund of the Ministry of Education of China(Grant No.20114101110003)+2 种基金the Fund for Science&Technology Innovation Team of Zhengzhou,China(Grant No.112PCXTD337)the Industrial Science and Technology Research Projects of Kaifeng,Henan Province,China(Grant No.1501049)the Key Research Projects of Henan Higher Education Institutions,China(Grant No.18A140014)
文摘Low thermal expansion composites are difficult to obtain by using Al with larger positive thermal expansion coefficient(TEC) and the materials with smaller negative TECs. In this investigation, Y2Mo3O12 with larger negative TEC is used to combine with Al to obtain a low thermal expansion composite with high conductivity. The TEC of Al is reduced by 19%for a ratio Al:Y2Mo3O12 of 0.3118. When the mass ratio of Al:Y2Mo3O12 increases to 2.0000, the conductivity of the composite increases so much that a transformation from capacitance to pure resistance appears. The results suggest that Y2Mo3O12 plays a dominant role in the composite for low content of Al(presenting isolate particles), while the content of Al increases enough to contact each other, the composite presents mainly the property of Al. For the effect of high content Al, it is considered that Al is squeezed out of the cermets during the uniaxial pressure process to form a thin layer on the surface.
基金supported by the National Natural Science Foundation of China(Grant Nos.10974183 and 11104252)the Science Fund of the Ministry of Education of China(Grant No.20114101110003)+1 种基金the Fund for Science&Technology Innovation Team of Zhengzhou City,China(Grant No.112PCXTD337)the Postdoctoral Research Sponsorship in Henan Province,China(Grant No.2011002)
文摘Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of (ZrMg)6+ for Cr3+. The overall linear thermal expansion coefficient decreases with the increase of the (ZrMg)6+ content in an orthorhombic structure sample. The co-incorporation of Zr4+ and Mg2+ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4+ and Mg2+ than Cr3+, respectively.
基金supported by the National Natural Science Foundation of China(Grant No.10974183)the Fund for Science and Technology Innovation Team of Zhengzhou City,China(Grant No.2011-3)the Postdoctoral Research Sponsorship in Henan Province,China(Grant No.2011002)
文摘Materials Lao.8Sro.2Gao.83Mgo.17_xCox03_6 with x = 0, 0.05, 0.085, 0.10, and 0.15 are synthesized by laser rapid solidification. It is shown that the samples prepared by laser rapid solidification give rise to unique spear-like or leaf-like microstructures which are orderly arranged and densely packed. Their electrical properties each show a general depen dence of the Co content and the total conductivities of Lao.8Sro.2Gao.83Mgo.085Coo.08503_6 prepared by laser rapid solidification are measured to be 0.067, 0.124, and 0.202 S.cm-1 at 600, 700, and 800 ℃, respectively, which are much higher than by conventional solid state reactions. Moreover, the electrical conductivities each as a function of the oxy gen partial pressure are also measured. It is shown that the samples with the Co content values 〈 8.5 mol% each exhibit basically ionic conduction while those for Co content values 〉 10 mol % each show ionic mixed electronic conduction under oxygen partial pressures from 10-16 atm (1 atm = 1.01325 x 105 Pa) to 0.98 atm. The improved ionic conductivity of Lao.sSro.2Gao.83Mgo.085Coo.08503 prepared by laser rapid solidification compared with by solid state reactions is attributed to the unique microstructure of the sample generated during laser rapid solidification.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574276,51302249,and 11405028)the Fundamental Research Fund for the Central Universities,China
文摘A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm (47) and exhibits negative thermal expansion (NTE) property with low anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) for a, b, and c axes are -1.41×10^-6 K^-1, -2.23×10^-6 K^-1, and -1.87×10^-6 K^-1, respectively. This gives rise to volume and linear CTEs of -3.10×10^-6 K^-1 and -1.03×10^-6 K^-1, respectively. Besides, it exhibits also intense photoluminescence from 360 nm to about 600 nm. The mechanism of NTE and the correlation of the PL with axial thermal expansion property are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60976016,61350012,and 11574276)the Key Scientific Research Projects of Henan Province,China(Grant No.15B140004)+2 种基金Henan Science and Technology Development Project,China(Grant No.182102210241)Key Projects of Science and Technology Research of Henan Provincial Department of Education,China(Grant No.18A140014)Industrial Science and Technology Research Projects of Kaifeng,Henan Province,China(Grant No.1501049)
文摘Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y2-x(ZnLi)xMo3O12(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn^2+ and Li+for Y^3+ in Y2Mo3O12 resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y2-x(ZnLi)xMo3O12 could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.
基金supported by the National Natural Science Foundation of China(Grant Nos.10974183 and 11104252)the Key Natural Science Project of Henan Province,China(Grant No.142102210073)+1 种基金the Doctoral Fund of the Ministry of Education of China(Grant No.20114101110003)the Fund for Science & Technology Innovation Team of Zhengzhou,China(Grant No.112PCXTD337)
文摘HfMgMo(3-x)WxO(12) with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structure for x≤2.0 and a monoclinic structure for x2.0. A near-zero thermal expansion(ZTE) is realized for HfMgMo(2.5)W(0.5)O(12) and negative coefficients of thermal expansion(NCTE) are achieved for other compositions with different values. The ZTE and variation of NCTE are attributed to the difference in electronegativity between W and Mo and incorporation of a different amount of W, which cause variable distortion of the octahedra and softening of the MoO4 tetrahedra, and hence an enhanced NCTE in the a- and c-axis and reduced CTE in the b-axis as revealed by Raman spectroscopy and x-ray diffraction.