Low-temperature heat capacities of the solid compound Zn（C4H7O5）2（s） were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in th...Low-temperature heat capacities of the solid compound Zn（C4H7O5）2（s） were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295？322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be （316.269±1.039） K, （11.194±0.335） kJ？mol-1, and （35.391±0.654） J？K-1？mol-1, respectively. The experimental values of the molar heat capacities in the temperature regions of 78？295 K and 322？374 K were fitted to two polynomial equations of heat capacities（Cp,m） with reduced temperatures（X） and [X = f（T）], with the help of the least squares method, respectively. The smoothed molar heat capacities and thermodynamic functions of the compound, relative to that of the standard reference temperature 293.15 K, were calculated on the basis of the fitted polynomials and tabulated with an interval of 5 K. In addition, the possible mechanism of thermal decomposition of the compound was inferred by the result of TG-DTG analysis.展开更多
Improved life assessment techniques will enable engineering components to be replaced before failure, thereby reducing the risk of industrial accidents as well as minimizing financial loss due to unscheduled outages. ...Improved life assessment techniques will enable engineering components to be replaced before failure, thereby reducing the risk of industrial accidents as well as minimizing financial loss due to unscheduled outages. For components operating at high temperatures, temperature measurement is very important. In many situations, the environmental conditions are too hostile for conventional techniques to be used. Researchers over the world have been looking for new techniques for temperature measurement and one such device, called Feroplug, has been developed previously by the and coworkers. The Feroplug has been patented in USA, UK and Europe by the British Technology Group. The underlying principle of the Feroplug is based on the transformation of ferrite in some specially designed duplex stainless steels. This paper describes a new invention called Sigmaplug which is a new development of the Feroplug but using an entirely different physical principle. It was discovered that the sigma phase in Fe展开更多
Main observation and conclusion Two new uranium(VI)phosphonate compounds,namely K_(8)[N(C_(2)H_(5))_(4)]_(2)(UO_(2))_(17)(H_(2)O)_(4)[CH_(2)(PO_(3))_(2)]_(8)[CH_(2)(PO_(3))(PO_(3)H)]_(4)·16(H_(2)O)(1)and[N(C_(2)H...Main observation and conclusion Two new uranium(VI)phosphonate compounds,namely K_(8)[N(C_(2)H_(5))_(4)]_(2)(UO_(2))_(17)(H_(2)O)_(4)[CH_(2)(PO_(3))_(2)]_(8)[CH_(2)(PO_(3))(PO_(3)H)]_(4)·16(H_(2)O)(1)and[N(C_(2)H_(5))_(4)]_(4)(H_(3)O)_(2)(UO_(2))_(10)[CH_(2)(PO_(3))_(2)]_(5)[CH_(2)(PO_(3))(PO_(3)H)]_(2)·10H_(2)O(2),have been synthesized under mild hydro/solvothermal condition.The structural analysis of the two compounds reveals that they both contain all three typical coordination geometries of the U(VI)ions,including UO;tetragonal,UO,pentagonal,and UOg hexagonal bipyramids.Moreover,compound 1 displays a tempera-ture-induced single crystal to single crystal phase transformation as confirmed by the Single-crystal X-ray diffraction data collected at different temperatures.Temperature-dependent fluorescence spectra presented herein illustrate the perturbation of the electronic structure of uranyl centers.展开更多
I. INTRODUCTION Calorimetry at very low temperatures is one of the useful tools for the investigation of magnetic properties of materials. Paramagnetic substances often exhibit
A new crystalline complex （C8H17NH3）2CdCI4（s） （abbreviated as CsCd（s）） is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffr...A new crystalline complex （C8H17NH3）2CdCI4（s） （abbreviated as CsCd（s）） is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P-1 and Z = 2. The lattice potential energy of the title complex is calculated to be UpoT （CsCd（s））=978.83 kJ.mol^-1 from crystallographic data. Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3±0.15 K, 10.15±0.23 kJ.mol^-1, and 33.054-0.78 J.K^-1.mol^-1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.展开更多
A series of high-k[(Na_(0.5)Bi_(0.5))_(x)Bi_(1-x)](W_(x)V_(1-x))O_(4)(abbreviated as NBWV(x value))solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at t...A series of high-k[(Na_(0.5)Bi_(0.5))_(x)Bi_(1-x)](W_(x)V_(1-x))O_(4)(abbreviated as NBWV(x value))solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at the temperature range of 680-760 C.A monoclinic(0≤x<0.09)to tetragonal scheelite(0.09≤x≤1.0)structural phase transition is confirmed by X-ray difraction(XRD),Raman,and infrared(IR)analyses.The effect of structural deformation and order-disorder caused by Na^(+)/Bi^(3+)/W^(6+) complex substitution on microwave dielectric properties is investigated in deail.The compositional series possess a wide range of variable relative permittivity(er=24.8-80)and temperature coefficient of resonant frequency(TCF value,-271.9-188.9 ppm/℃).The maximum permittivity of 80 and a high Qxf value of~10,000 GHz are obtained near the phase boundary at x=0.09.Furthermore,the temperature-stable dielectric ceramics sintered at 680 C with excellent microwave dielectric properties of ε_(r)=80.7,Qxf=9400 GHz(at 4.1 GHz),and TCF value=-3.8 ppm/℃ are designed by mixing the components of x=0.07 and 0.08.In summary,similar sinterability and structural compatibility of scheelite-like solid solution systems make it potential for low-temperature co-fired ceramic(LTCC)applications.展开更多
Raman and luminescence studies on the phase transition of europium orthoniobates （EuNbO4） under high pressure were performed. The pressure dependent Raman spectra revealed that an irreversible phase transition from ...Raman and luminescence studies on the phase transition of europium orthoniobates （EuNbO4） under high pressure were performed. The pressure dependent Raman spectra revealed that an irreversible phase transition from monoclinic phase to M＇-fergusonite phase of EuNbO4 occurred at 7.3 GPa, and the two phases coexisted over a pressure range from 7.3 to 13.7 GPa. An obvious discontinuity on luminescence intensity ratio between 5D0 →7F2 and 5D0→7F1 transitions was observed with increasing pressure, in- dicating also that a phase transition occurred at 7.3 GPa, which was in agreement with the high pressure Raman spectra data. Mean- while, the Raman and luminescence spectra in the temperature range of 20--300 K showed the structure stability at low temperatures.展开更多
基金the National Natural Science Foundation of China(No.20673050).
文摘Low-temperature heat capacities of the solid compound Zn（C4H7O5）2（s） were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295？322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be （316.269±1.039） K, （11.194±0.335） kJ？mol-1, and （35.391±0.654） J？K-1？mol-1, respectively. The experimental values of the molar heat capacities in the temperature regions of 78？295 K and 322？374 K were fitted to two polynomial equations of heat capacities（Cp,m） with reduced temperatures（X） and [X = f（T）], with the help of the least squares method, respectively. The smoothed molar heat capacities and thermodynamic functions of the compound, relative to that of the standard reference temperature 293.15 K, were calculated on the basis of the fitted polynomials and tabulated with an interval of 5 K. In addition, the possible mechanism of thermal decomposition of the compound was inferred by the result of TG-DTG analysis.
文摘Improved life assessment techniques will enable engineering components to be replaced before failure, thereby reducing the risk of industrial accidents as well as minimizing financial loss due to unscheduled outages. For components operating at high temperatures, temperature measurement is very important. In many situations, the environmental conditions are too hostile for conventional techniques to be used. Researchers over the world have been looking for new techniques for temperature measurement and one such device, called Feroplug, has been developed previously by the and coworkers. The Feroplug has been patented in USA, UK and Europe by the British Technology Group. The underlying principle of the Feroplug is based on the transformation of ferrite in some specially designed duplex stainless steels. This paper describes a new invention called Sigmaplug which is a new development of the Feroplug but using an entirely different physical principle. It was discovered that the sigma phase in Fe
基金the National Natural Science Foundation of China(21906113,21561018,21790374,and 22066014)the Priority Academic Pro-gram Development of Jiangsu Higher Education Institutions(PAPD)the Applied Basic Research Foundation of Yunnan Province(2017FH001-023).
文摘Main observation and conclusion Two new uranium(VI)phosphonate compounds,namely K_(8)[N(C_(2)H_(5))_(4)]_(2)(UO_(2))_(17)(H_(2)O)_(4)[CH_(2)(PO_(3))_(2)]_(8)[CH_(2)(PO_(3))(PO_(3)H)]_(4)·16(H_(2)O)(1)and[N(C_(2)H_(5))_(4)]_(4)(H_(3)O)_(2)(UO_(2))_(10)[CH_(2)(PO_(3))_(2)]_(5)[CH_(2)(PO_(3))(PO_(3)H)]_(2)·10H_(2)O(2),have been synthesized under mild hydro/solvothermal condition.The structural analysis of the two compounds reveals that they both contain all three typical coordination geometries of the U(VI)ions,including UO;tetragonal,UO,pentagonal,and UOg hexagonal bipyramids.Moreover,compound 1 displays a tempera-ture-induced single crystal to single crystal phase transformation as confirmed by the Single-crystal X-ray diffraction data collected at different temperatures.Temperature-dependent fluorescence spectra presented herein illustrate the perturbation of the electronic structure of uranyl centers.
文摘I. INTRODUCTION Calorimetry at very low temperatures is one of the useful tools for the investigation of magnetic properties of materials. Paramagnetic substances often exhibit
基金Project supported by the National Natural Science Foundations of China (Grant Nos. 20673050 and 20973089)
文摘A new crystalline complex （C8H17NH3）2CdCI4（s） （abbreviated as CsCd（s）） is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P-1 and Z = 2. The lattice potential energy of the title complex is calculated to be UpoT （CsCd（s））=978.83 kJ.mol^-1 from crystallographic data. Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3±0.15 K, 10.15±0.23 kJ.mol^-1, and 33.054-0.78 J.K^-1.mol^-1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.
基金supported by the National Natural Science Foundation of China(Grant Nos.61631166004 and 51902245)Hong Wang acknowledged the support of Shenzhen Science and Technology Program(Nos.KQTD20180411143514543 and JSGGZD20220822095603006)。
文摘A series of high-k[(Na_(0.5)Bi_(0.5))_(x)Bi_(1-x)](W_(x)V_(1-x))O_(4)(abbreviated as NBWV(x value))solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at the temperature range of 680-760 C.A monoclinic(0≤x<0.09)to tetragonal scheelite(0.09≤x≤1.0)structural phase transition is confirmed by X-ray difraction(XRD),Raman,and infrared(IR)analyses.The effect of structural deformation and order-disorder caused by Na^(+)/Bi^(3+)/W^(6+) complex substitution on microwave dielectric properties is investigated in deail.The compositional series possess a wide range of variable relative permittivity(er=24.8-80)and temperature coefficient of resonant frequency(TCF value,-271.9-188.9 ppm/℃).The maximum permittivity of 80 and a high Qxf value of~10,000 GHz are obtained near the phase boundary at x=0.09.Furthermore,the temperature-stable dielectric ceramics sintered at 680 C with excellent microwave dielectric properties of ε_(r)=80.7,Qxf=9400 GHz(at 4.1 GHz),and TCF value=-3.8 ppm/℃ are designed by mixing the components of x=0.07 and 0.08.In summary,similar sinterability and structural compatibility of scheelite-like solid solution systems make it potential for low-temperature co-fired ceramic(LTCC)applications.
基金Project supported by National Natural Science Foundation of China(11074232,11274288,21002097,11304300,11174265)the National Basic Research Program of China(2011CB932801,2009CB939901,2012CB933702)Ministry of Education of China(20123402110034)
文摘Raman and luminescence studies on the phase transition of europium orthoniobates （EuNbO4） under high pressure were performed. The pressure dependent Raman spectra revealed that an irreversible phase transition from monoclinic phase to M＇-fergusonite phase of EuNbO4 occurred at 7.3 GPa, and the two phases coexisted over a pressure range from 7.3 to 13.7 GPa. An obvious discontinuity on luminescence intensity ratio between 5D0 →7F2 and 5D0→7F1 transitions was observed with increasing pressure, in- dicating also that a phase transition occurred at 7.3 GPa, which was in agreement with the high pressure Raman spectra data. Mean- while, the Raman and luminescence spectra in the temperature range of 20--300 K showed the structure stability at low temperatures.
