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Improving phase transition temperature of VO_(2) via Ge doping:a combined experimental and theoretical study

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Rare Metals 2021年第5期40卷 1337-1346页

作者： Lin Wang Yu-Qi Hao Wei Ma Sen Liang Ningxia Key Laboratory of Photovoltaic Materials Ningxia UniversityYinchuan 750021China

Enhancing the semiconductor-metal phase transition temperature(TSMT)of VO_(2) is of great consequence for further exploring the potential applications of VO_(2) at elevated *** this study,Ge^(4+)-doped VO_(2)(Ge_(x)V_(1-x)O_(2))samples were prepared by the hydrothermal and annealing approach.X-ray diffraction(XRD),high-resolution transmission electron microscopy(HRTEM),differential scanning calorimetry(DSC)and resistivity-temperature(R-T)analyses were used to investigate the influence of Ge doping on the lattice structures and phase transition properties of Ge_(x)V_(1-x)O_(2) *** found that the lattice parameter of Ge_(x)V_(1-x)O_(2) decreased with the Ge concentration increasing from 2 at%to 18 at%,which was further supported by density functional theory(DFT)-based first-principle *** firstly increased from 64.5 to 73.0℃ at 8 at% Ge and then decreased to 71.5℃ at higher Ge ***,DFT analysis revealed that the impact of lattice distortion induced by Ge doping rather than the changes in electronic structure is more pronounced on modulating TSMT of Ge_(x)V_(1-x)O_(2).The present work has pointed out the direction that the TSMT could be enhanced and illustrated the physical reason behind the regulation of TSMT in ionsdoped VO_(2) systems.

关键词： Vanadium dioxide phase transition temperature Germanium doping Lattice distortion

Effects of heat treatment conditions and Y-doping on structure and phase transition temperature of VO2 powders

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Transactions of Nonferrous Metals Society of China 2020年第4期30卷 1038-1045页

作者： Bin WANG Er-hu LI Jin-jing DU Jun ZHU Lin-bo LI Tian-tian ZHOU School of Metallurgy Engineering Xi’an University of Architecture and TechnologyXi’an 710055China Research Center of Metallurgical Engineering and Technology of Shaanxi Province Xi’an 710055China

The VO2 powders were prepared by hydrothermal *** effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were *** XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 *** temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of *** to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined *** curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.

关键词： VO2 powders hydrothermal synthesis heat treatment Y-doping phase transition temperature

New insights into the effects of molecular weight and end group on the temperature-induced phase transition of poly(N-isopropylacrylamide) in water

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Science China Chemistry 2013年第1期56卷 56-64页

作者： QIU XingPing KOGA Tsuyoshi TANAKA Fumihiko WINNIK Fran oiseM. Department of Chemistry and Faculty of Pharmacy University of MontrealCP 6128 Succursale Centre VilleMontrealQC H3C 3J7Canada Department of Polymer Chemistry Graduate School of EngineeringKyoto UniversityKatsuraKyoto 615-8510Japan Institute of Theoretical Polymer Science (ITPS) 5-19-2 Ozenji Asao-kuKawasaki 615-8510Japan World Premier International (WPI) Research Center Initiative International Center for Materials Nanoarchitectonics (MANA) and National Institute for Materials Science (NIMS)1-1 NamikiTsukuba 305-0044Japan

In an attempt to clarify issues related to the molecular weight dependence of the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in water,we prepared a library of PNIPAM samples of well-controlled molecular weight (7000 to 45000 g/mol) bearing identical groups on each chain *** polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) with a bifunctional chain tranfer agent and further end group *** effects of the end group chemical structure,hydroxyethyl (HE),propargyl (Pr),chloroethyl (CE),n-butyl (nBu),n-hexyl (nHe),and isobutylsulfanylthiosulfanyl (IBS) on the phase transition temperature of aqueous PNIPAM solutions were investigated by high-sensitivity differential scanning calorimetry (HS-DSC),yielding the enthalpy ΔH and the endotherm maximum temperature (T M),and turbidimetry,providing the cloud point (T CP) of each *** T CP and T M of the PNIPAM sample of lowest molar mass (M n 7,000 g/mol,0.5 g/L) ranged,respectively,from 38.8 to 22.5 °C and 42.2 to 26.0 °C,depending on the structure of the end-group,whereas H showed no strong end-group *** phase transition of all polymers,except,-di(n-butyl-PNIPAM),exhibited a marked dependence on the polymer molar mass.

关键词： poly(N-isopropylacrylamide) phase transition temperature high-sensitivity differential scanning calorimetry turbidimetry end group effect

Preparation and Properties of Smart Thermal Control and Radiation Protection Materials for Multi-functional Structure of Small Spacecraft

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Journal of Materials Science & Technology 2011年第10期27卷 879-884页

作者： shijie Zhang Xibin Cao Yingqiang Luan Xinxin Ma Xiaohui Lin Xianren Kong Research Center of Satellite Technology Harbin Institute of Technology Harbin 150080 China The Second System Design of the Second Research Academy of CASIC Beijing 100854 China

Considering the unique properties of small spacecraft, such as light weight, low power-consumption and high heat flux density, a new kind of lightweight boron carbide （B4C） radiation-protection coating material was proposed. New techniques for preparing LSMO thermal control coating and B4C radiation-protection coating were developed. The sample piece of multi-functional structure was manufactured by using the proposed materials, and a series of performance tests, such as thermal control and radiation-protection behaviors were evaluated. Test results show that： the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K. The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material. The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.

关键词： Coating material phase transition temperature temperature-dependent emissivity-variable Radiation-protection Spacecraft

SYNTHESES AND CHARACTERIZATION OF A NEW TYPE OF LIQUID CRYSTALLINE POLYESTERS

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Chinese Journal of Polymer Science 1994年第3期12卷 221-227页

作者：白如科吴承佩邹应芳孙武潘才元 Toshiyuki Uryu Department of Materials Science and Engineering University of Science and Technology of China Hefei Anhui 230026 Institute of Industrial Science Faculty of Engineering University of Tokyo Roppongi Minato-ku Tokyo 106 Japan

A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy andDSC.

关键词： New liquid crystalline polyesters Synthesis Interfacial polymerization phase transition temperature Texture of liquid crystalline polymers

Effect of hydrogenation on the microstructure of Ti-5.6Al-4.8Sn-2.0Zr alloy

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Rare Metals 2009年第4期28卷 343-345页

作者： LI Miaoquan LIN Yingying School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

The hydride phase in the Ti-5.6Al-4.8Sn-2.0Zr alloy after hydrogenation was investigated through TEM and XRD analysis. The experimental results show that the phase transition temperature of the hydrogenated Ti-5.6Al-4.8Sn-2.0Zr alloy is decreased approximately by 150-200℃. XRD analysis verifies that the hydrogenation treatment accelerates the phase transition process from α phase to β phase of the Ti-5.6Al-4.8Sn-2.0Zr alloy, so as to decrease the phase transition temperature of the alloy. Meanwhile, TiH2 hydride （8 phase） with strip structure appears in α phase and β phase.

关键词： titanium alloys hydrogenation hydride phase phase transition temperature

Multiferroic properties of Bi_(5.75)R_(0.25)Fe_(1.4)Ni_(0.6)Ti_(3)O_(18)(R=Eu,Sm,Nd,Bi and La)ceramics

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Journal of Rare Earths 2022年第1期40卷 112-117页

作者： Yongjie Yin Fei Liu Xiangyu Mao Wei Wang College of Physical Science and Technology Yangzhou UniversityYangzhou 225002China

An improved technique was used to prepare the ceramic samples of Bi_(5.75)R_(0.25)Fe_(1.4)Ni_(0.6)Ti_(3)O_(18)(BRFNT,R=Eu,Sm,Nd,Bi,and La).The five-layer Aurivillius phase of the samples was confirmed by X-ray diffraction(XRD)without detectable *** samples exhibit the pseudo-tetragonal except the orthorhombic BSmFNT *** characteristic plate-like morphology was revealed by field emission transmission electron microscopy(FETEM)*** ambient tempe rature,all the samples present both ferroelectric and magnetic properties and BEuFNT shows the best ferroelectric behavior with its remanent polarization as high as 14.9μC/cm^(2)under 155 kV/cm,which is three times higher than that of Bi_(5.75)R_(0.25)Fe_(1.4)Ni_(0.6)Ti_(3)O_(18).Moreover,the remanent magnetization of BEuFNT is increased up to 1.20 emu/g compared to that of Bi_(5.75)R_(0.25)Fe_(1.4)Ni_(0.6)Ti_(3)O_(18)which is only 0.53 emu/*** increasing radius of the introduced A-site ions,the ferroelectric phase transition temperature(T_(CE))is decreased while the magnetic phase transition temperature(T_(CM))*** decrease in both T_(CE)and T_(CM) corresponds to the upward shift of the related Raman modes and vice versa,indicating that the T_(CE)and the T_(CM) depend not only on the t factor,but also on the strength of the covalent bonds.

关键词： Ceramics Multiferroics phase transition temperature Rare earths Structure phase

Effect of thickness on infrared optical property of VO2 film deposited by magnetron sputtering

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Science China(Technological Sciences) 2020年第8期63卷 1591-1598页

作者： YANG ZhenHuai YANG QiuLing YANG Lei DAI Bing XIA Fei WANG Peng GUO Shuai GAO Gang XU LiangGe ZHANG YuMin ZHU JiaQi National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of TechnologyHarbin 150080China Key Laboratory of Micro-systems and Micro-structures Manufacturing Ministry of EducationHarbin 150080China Center of Analysis Measurement Harbin Institute of TechnologyHarbin 150080China

A series of VO2 films with different thicknesses(from about 25 nm to 250 nm)were prepared on sapphire substrates by radio frequency magnetron *** deposition times varied from 15 min to 150 *** metal to insulator transitions(MIT)of the films were *** optical transmittance of the films to infrared light(with a wavelength of 4.0μm)at room temperature(30℃)varied significantly with film thickness,ranging from 86.53%to 41.01%.The modulation property also changes with thickness,decreasing from 22.89%to 14.74%.The phase transition temperature remained approximately 70℃during heating,and approximately 53℃during cooling,despite a tenfold increase in the deposition time,and the resulting thickness of the *** spectroscopy of the films indicated that the intensities of the characteristic peaks corresponding to V2O5 increase with the increasing of film ***-dependent Raman spectroscopy indicated that the peaks corresponding to VO2 undergo reversible changes during heating and cooling of the films,while the peaks corresponding to V2O5 remain unchanged *** control of the V2O5 content of the films(by varying the duration of the deposition process)allows control over their transmittance and optical modulation properties without changes in the phase transition *** provides a new method of controlling the optical properties of these materials and shows promise for their potential applications in thermochromic windows.

关键词： Vanadium dioxide mid-infrared transmittance phase transition temperature magnetron sputtering

Synthesis and Characterization of Titania and Rare Earth Doped Titania Nanoparticles by Sol-gel Process

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Journal of Donghua University(English Edition) 2006年第5期23卷 108-112页

作者：林萍咸春颖毛志平郑利民 College of Chemistry and Chemical Engineering Donghua University

Titania sol has been prepared by the sol-gel process with Ti（OC4H9）4, as precursor. TiO2 gel was obtained through hydrolysis and condensation process. Rare earth such as La2O3, CeO2 and Gd2O3 were introduced into the nanostructure TiO2. After TiO2 and rare earth doped TiO2 powders were calcined at 400℃, 500℃, 600℃, 700℃ and 800℃ respectively, the characteristic analyses of the TiO2 samples were studied by UV-VIS, XRD and TEM etc. It was found that there are some stringer absorption peaks at 200 - 325 nm. The rare earth doping can increase the phase transition temperature convertin8 anatase phase into rutile phase, can decrease the grain size of TiO2particles and can improve the ann-UV capacity of the coating fabrics.

关键词： sol-gel rare earth doping phase transition temperature nanostructure TiO2 anti-UV caPacity.