This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in...This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.展开更多
Beamline BL16B1 at Shanghai Synchrotron Radiation Facility(SSRF) is dedicated to studying the microstructure and dynamic processes of polymers, nanomaterials, mesoporous materials, colloids, liquid crystals,metal mate...Beamline BL16B1 at Shanghai Synchrotron Radiation Facility(SSRF) is dedicated to studying the microstructure and dynamic processes of polymers, nanomaterials, mesoporous materials, colloids, liquid crystals,metal materials, etc. At present, SAXS, wide angle X-ray scattering(WAXS), simultaneous SAXS/WAXS,grazing incident SAXS, and anomalous SAXS techniques are available for end user to conduct diverse experiments at this beamline. The sample-to-detector distance is adjustable from 0.2 m to 5 m. The practicable q-range is 0.03–3.6 nm-1at incident X-ray of 10 ke V for conventional SAXS whilst a continuous q-region of0.06–33 nm-1can be achieved in simultaneous SAXS/WAXS mode. Time-resolved SAXS measurements in sub-second level was achieved by the beamline upgrating in 2013. This paper gives detailed descriptions about the status, performance and applications of the SAXS beamline.展开更多
The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incid...The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping （RSM）. It is confirmed that the measurement of （204） reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.展开更多
溶液法是新型光电器件制备的重要手段,然而以钙钛矿半导体材料为代表的薄膜样品制备通常需要在手套箱环境下完成,传统的实验表征大多在空气环境下进行,这显然很难反映薄膜结构与器件性能间的真实关联,因此急需对溶液成膜过程的微结构演...溶液法是新型光电器件制备的重要手段,然而以钙钛矿半导体材料为代表的薄膜样品制备通常需要在手套箱环境下完成,传统的实验表征大多在空气环境下进行,这显然很难反映薄膜结构与器件性能间的真实关联,因此急需对溶液成膜过程的微结构演变开展原位实时研究.为了实现溶液法成膜中的结构与形貌的同步辐射掠入射广角散射实时观测,本文结合上海同步辐射光源线站布局,报道了一种基于手套箱的原位成膜观测装置,可实现标准手套箱环境(c(H_(2)O,O_(2))<1×10^(-6))下远程控制薄膜旋涂、涂布及样品后处理,并实时可视化监测微结构和形貌演变.基于该装置进行的钙钛矿薄膜狭缝涂布大面积成膜结晶过程的原位GIWAXS/GISAXS(gtrazing incidence wide and small angle X-ray scattering)可视化测试揭示了薄膜微结构转变的内在驱动力:钙钛矿薄膜沉积界面层的优化对提升钙钛矿成核速率、诱导结晶择优取向、形成晶粒有序堆叠等具有“共性作用”,同时在成膜过程中的新生中间相显著提升软晶格薄膜质量和稳定性.基于各层均采用卷对卷全溶液狭缝涂布方法制备的大面积全柔性三维钙钛矿薄膜太阳能电池转换效率提升至5.23%(单个器件面积约15 cm^(2)),为迄今报道的这一体系该尺寸的全溶液狭缝涂布柔性钙钛矿器件的最高器件效率之一.因而,基于该同步辐射原位GIWAXS/S/GISAXS装置可以获得控制薄膜生长界面特性和薄膜品质的关键工艺,指导优化制备薄膜的最佳工艺条件.展开更多
SrTiO3 thin films are epitaxially grown on DyScO3, LaAlO3 substrates with/without buffer layers of DyScO3 and SrRuO3 using laser-MBE. X-ray diffraction methods, such as high resolution X-ray diffraction, grazing incid...SrTiO3 thin films are epitaxially grown on DyScO3, LaAlO3 substrates with/without buffer layers of DyScO3 and SrRuO3 using laser-MBE. X-ray diffraction methods, such as high resolution X-ray diffraction, grazing incident X-ray diffraction, and reciprocal space mapping are used to investigate the lattice structure, dislocation density, in-plane lattice strain distribution along film thickness. From the measurement results, the effects of substrate on film lattice quality and microstructure are discussed.展开更多
Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide...Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide angle X-ray diffraction and fourier transform infrared spectroscopy. The experimental results indicate that all of the three additives are compatible with PVC to some extent, but adipic acid＇s compatibility with PVC is less satisfactory. The three additives can improve PVC crystallinity, and acetanilide can decrease PVC glass transition temperature（T）and narrow PVC melting range, while adipic acid and potassium hydrogen phthalate rise T of PVC and widen its melting range. All additives do not affect PVC crystal system and all g samples are in orthorhombic system. All additives can improve （200）, （110）, （210） and （201, 111） planes growing. Moreover, acetanilide and adipic acid can shrink PVC spacings and improve the crystal perfection of PVC, but potassium hydrogen phthalate swells spacings and reduces the perfection of PVC crystal.展开更多
Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show th...Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer). The observation ofspherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than thoseof β-PP homopolymer.展开更多
It is found that ultrathin poly（3-hexylthiophene） （P3HT） film with a 2.5 nm-thick layer exhibits a higher mobility of 5.0× 10-2 cm2/V-s than its bulk counterpart. The crystalline structure of the as-fabricate...It is found that ultrathin poly（3-hexylthiophene） （P3HT） film with a 2.5 nm-thick layer exhibits a higher mobility of 5.0× 10-2 cm2/V-s than its bulk counterpart. The crystalline structure of the as-fabricated ultrathin P3HT layer is verified by atomic force microscopy as well as grazing incidence X-ray diffraction. Transient measurements of the as-fabricated transistors reveal the influence of the interface traps on charge transport. These results are explained by the trap energy level distribution at the interface manipulated by layers of polymer film.展开更多
The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） bac...The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.展开更多
Crystallographic dynamics of blend films of regioregular poly（3-hexylthiophene）（P3HT） mixed with [6-6-]-phenylC61-butyric acid methyl ester（PC61BM） treated by thermal annealing or by adding solvent 1,8-diiodooct...Crystallographic dynamics of blend films of regioregular poly（3-hexylthiophene）（P3HT） mixed with [6-6-]-phenylC61-butyric acid methyl ester（PC61BM） treated by thermal annealing or by adding solvent 1,8-diiodooctane（DIO） are characterized by 2D-grazing incidence x-ray diffraction（2D-GIXRD）. The results show that the P3 HT chains are primarily oriented with the thiophene ring edge-on to the substrate, with a small fraction of chains oriented plane-on. The interplanar spacing becomes narrow after being treated by DIO, and the coherence length of the P3 HT crystallites increases after being treated by thermal annealing or DIO, which is accompanied by a change in the orientation angle of the P3 HT lamellae. The increased ordering of P3 HT packing induced by thermal annealing or adding DIO contributes to enhanced photovoltaic performance.展开更多
BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible...BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible from renewable resources in the form of pure enantiomers. Thus it is used to synthesize main chain cholesteric thermotropic liquid crystalline polymers. Incorporation of phenyl hydroquinone into the backbone of the main chain frustrates chain packing, thus lowering the crystallinity and depressing the melting point below the degradation temperature, also improves the solubility due to disruption of packing and maintains the mechanical and thermal performance. RESULTS: Optical microscopy study reveals that more than 50% of isosorbide content with phenyl hydroquinone and terephthalic acid showed “yellow iridescent oily streaks” with a background of mosaic/marble texture. These are the typical textures of cholesteric liquid crystalline phase. Copolyesters based on phenyl hydroquinone, isosorbide and terephthalic acid are soluble in aprotic solvents like N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Solubility increases with the content of isosorbide percent. Thermal stability of all copolyesters was more than 300?C on the basis of 10% wt loss. CONCLUSIONS: It was found that main chain cholesteric thermotropic liquid crystalline polymers can be prepared form chiral cycloaliphatic diol such as isosorbide. Main chain cholesteric thermotropic liquid crystalline polyesters are prepared from phenyl hydroquinone, isosorbide and terephthalic acid showed thermal stability more than 300?C. Main chain cholesteric thermotropic liquid crystalline polymers are soluble in aprotic solvents like DMAC, DMSO, DMF and NMP.展开更多
Micro-sized copper powder(99.95%;O≤0.3)has been shock-processed with explosives of high detonation velocities of the order of 7.5 km/s to observe the structural and microstructural sub-strengthening.Axisymmetric shoc...Micro-sized copper powder(99.95%;O≤0.3)has been shock-processed with explosives of high detonation velocities of the order of 7.5 km/s to observe the structural and microstructural sub-strengthening.Axisymmetric shock-consolidation technique has been used to obtain conglomerates of granular Cu.The technique involves the cylindrical compaction system wherein the explosive-charge is in direct proximity with the powder whereas the other uses indirect shock pressure with die-plunger geometry.Numeric simulations have been performed on with Eulerian code dynamics.The simulated results show a good agreement with the experimental observation of detonation parameters like detonation velocity,pressure,particle velocity and shock pressure in the reactive media.A pin contactor method has been utilized to calculate the detonation pressure experimentally.Wide angled x-ray diffraction studies reveal that the crystalline structure(FCC)of the shocked specimen matches with the un-shocked specimen.Field emissive scanning electron microscopic examination of the compacted specimens show a good sub-structural strengthening and complement the theoretical considerations.Laser diffraction based particle size analyzer also points towards the reduced particle size of the shock-processed specimen under high detonation velocities.Micro-hardness tests conducted under variable loads of 0.1 kg,0.05 kg and 0.025 kg force with diamond indenter optical micrographs indicate a high order of micro-hardness of the order of 159 Hv.Nitrogen pycnometry used for the density measurement of the compacts shows that a compacted density of the order of 99.3%theoretical mean density has been achieved.展开更多
Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great impo...Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.展开更多
Fluorinated and nitrogen-doped graphdiyne(F/N-GDY)have been used in the active layer of perovskite solar cells(PSCs)for the first time.The introduction of heteroatoms turns out to be an effective method for boosted so...Fluorinated and nitrogen-doped graphdiyne(F/N-GDY)have been used in the active layer of perovskite solar cells(PSCs)for the first time.The introduction of heteroatoms turns out to be an effective method for boosted solar cells performance,which increases by 32.8%and 33.0%,better than the pristine or GDY doped PSCs.The enhanced performance can be attributed firstly to the superiority of F/N-GDY originated from the unique structure and optoelectronic properties of GDY.Then,both can further reduce surface defects and improve surface and bulk crystallinity than pristine GDY.What's more,efficiency increase caused by F-GDY is mainly attributed to the improvement of fill factor(FF),while the higher short-circuit current(Jsc)plays more important role by N-GDY doping.Most importantly,the detailed mechanism brought about by doping of F-GDY or N-GDY is expounded by systematical characterizations,especially the synchrotron radiation technique.Doping of F-GDY causes Pb and forms new Pb-F bonds between F-GDY and Pb ions.Doping of N-GDY or GDY brings about Pb(N-GDY doping induces more deviation than that of GDY due to the participation of imine N),improving its electron density and conductivity.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 60506001,60776047,60976045 and 60836003)the National Basic Research Programme of China (Grant No. 2007CB936700)the National Science Foundation for Distinguished Young Scholars,China (Grant No. 60925017)
文摘This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.
基金Supported by the National Basic Research Program of China(Nos.2011CB911104,2011CB606104,and 2011CB605604)National Natural Science Foundation of China(Nos.11305249,11005143,50903089,51273210,11405259,51303200,and 11305242)Knowledge Innovation Program of Chinese Academy of Sciences
文摘Beamline BL16B1 at Shanghai Synchrotron Radiation Facility(SSRF) is dedicated to studying the microstructure and dynamic processes of polymers, nanomaterials, mesoporous materials, colloids, liquid crystals,metal materials, etc. At present, SAXS, wide angle X-ray scattering(WAXS), simultaneous SAXS/WAXS,grazing incident SAXS, and anomalous SAXS techniques are available for end user to conduct diverse experiments at this beamline. The sample-to-detector distance is adjustable from 0.2 m to 5 m. The practicable q-range is 0.03–3.6 nm-1at incident X-ray of 10 ke V for conventional SAXS whilst a continuous q-region of0.06–33 nm-1can be achieved in simultaneous SAXS/WAXS mode. Time-resolved SAXS measurements in sub-second level was achieved by the beamline upgrating in 2013. This paper gives detailed descriptions about the status, performance and applications of the SAXS beamline.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60506001, 60776047, 60976045, and 60836003)the National Basic Research Programme of China (Grant No. 2007CB936700)the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 60925017)
文摘The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping （RSM）. It is confirmed that the measurement of （204） reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.
文摘溶液法是新型光电器件制备的重要手段,然而以钙钛矿半导体材料为代表的薄膜样品制备通常需要在手套箱环境下完成,传统的实验表征大多在空气环境下进行,这显然很难反映薄膜结构与器件性能间的真实关联,因此急需对溶液成膜过程的微结构演变开展原位实时研究.为了实现溶液法成膜中的结构与形貌的同步辐射掠入射广角散射实时观测,本文结合上海同步辐射光源线站布局,报道了一种基于手套箱的原位成膜观测装置,可实现标准手套箱环境(c(H_(2)O,O_(2))<1×10^(-6))下远程控制薄膜旋涂、涂布及样品后处理,并实时可视化监测微结构和形貌演变.基于该装置进行的钙钛矿薄膜狭缝涂布大面积成膜结晶过程的原位GIWAXS/GISAXS(gtrazing incidence wide and small angle X-ray scattering)可视化测试揭示了薄膜微结构转变的内在驱动力:钙钛矿薄膜沉积界面层的优化对提升钙钛矿成核速率、诱导结晶择优取向、形成晶粒有序堆叠等具有“共性作用”,同时在成膜过程中的新生中间相显著提升软晶格薄膜质量和稳定性.基于各层均采用卷对卷全溶液狭缝涂布方法制备的大面积全柔性三维钙钛矿薄膜太阳能电池转换效率提升至5.23%(单个器件面积约15 cm^(2)),为迄今报道的这一体系该尺寸的全溶液狭缝涂布柔性钙钛矿器件的最高器件效率之一.因而,基于该同步辐射原位GIWAXS/S/GISAXS装置可以获得控制薄膜生长界面特性和薄膜品质的关键工艺,指导优化制备薄膜的最佳工艺条件.
基金Supported by National Natural Science Foundation of China (10774065)Science Foundation for Excellent Youth Scholars of Huaiyin Normal University (08QNZCK 005)
文摘SrTiO3 thin films are epitaxially grown on DyScO3, LaAlO3 substrates with/without buffer layers of DyScO3 and SrRuO3 using laser-MBE. X-ray diffraction methods, such as high resolution X-ray diffraction, grazing incident X-ray diffraction, and reciprocal space mapping are used to investigate the lattice structure, dislocation density, in-plane lattice strain distribution along film thickness. From the measurement results, the effects of substrate on film lattice quality and microstructure are discussed.
基金Scientific and Technological Project of Hubei Province(No.2002AA105A01)
文摘Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide angle X-ray diffraction and fourier transform infrared spectroscopy. The experimental results indicate that all of the three additives are compatible with PVC to some extent, but adipic acid＇s compatibility with PVC is less satisfactory. The three additives can improve PVC crystallinity, and acetanilide can decrease PVC glass transition temperature（T）and narrow PVC melting range, while adipic acid and potassium hydrogen phthalate rise T of PVC and widen its melting range. All additives do not affect PVC crystal system and all g samples are in orthorhombic system. All additives can improve （200）, （110）, （210） and （201, 111） planes growing. Moreover, acetanilide and adipic acid can shrink PVC spacings and improve the crystal perfection of PVC, but potassium hydrogen phthalate swells spacings and reduces the perfection of PVC crystal.
文摘Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer). The observation ofspherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than thoseof β-PP homopolymer.
基金Project supported by the Special Funds for the Development of Strategic Emerging Industries in Shenzhen City,China(Grant No.JCYJ20120830154526537)the Start-up Funding of South University of Science and Technology of Chinathe Strategic Research Grant of City University of Hong Kong of China(Grant No.7002724)
文摘It is found that ultrathin poly（3-hexylthiophene） （P3HT） film with a 2.5 nm-thick layer exhibits a higher mobility of 5.0× 10-2 cm2/V-s than its bulk counterpart. The crystalline structure of the as-fabricated ultrathin P3HT layer is verified by atomic force microscopy as well as grazing incidence X-ray diffraction. Transient measurements of the as-fabricated transistors reveal the influence of the interface traps on charge transport. These results are explained by the trap energy level distribution at the interface manipulated by layers of polymer film.
基金Supported by the Science & Technology Development Program of Jilin Province,China(No.20100537)
文摘The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51272022 and 11474018)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120009130005)the Fundamental Research Funds for the Central Universities of China(Grant No.2012JBZ001)
文摘Crystallographic dynamics of blend films of regioregular poly（3-hexylthiophene）（P3HT） mixed with [6-6-]-phenylC61-butyric acid methyl ester（PC61BM） treated by thermal annealing or by adding solvent 1,8-diiodooctane（DIO） are characterized by 2D-grazing incidence x-ray diffraction（2D-GIXRD）. The results show that the P3 HT chains are primarily oriented with the thiophene ring edge-on to the substrate, with a small fraction of chains oriented plane-on. The interplanar spacing becomes narrow after being treated by DIO, and the coherence length of the P3 HT crystallites increases after being treated by thermal annealing or DIO, which is accompanied by a change in the orientation angle of the P3 HT lamellae. The increased ordering of P3 HT packing induced by thermal annealing or adding DIO contributes to enhanced photovoltaic performance.
文摘BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible from renewable resources in the form of pure enantiomers. Thus it is used to synthesize main chain cholesteric thermotropic liquid crystalline polymers. Incorporation of phenyl hydroquinone into the backbone of the main chain frustrates chain packing, thus lowering the crystallinity and depressing the melting point below the degradation temperature, also improves the solubility due to disruption of packing and maintains the mechanical and thermal performance. RESULTS: Optical microscopy study reveals that more than 50% of isosorbide content with phenyl hydroquinone and terephthalic acid showed “yellow iridescent oily streaks” with a background of mosaic/marble texture. These are the typical textures of cholesteric liquid crystalline phase. Copolyesters based on phenyl hydroquinone, isosorbide and terephthalic acid are soluble in aprotic solvents like N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Solubility increases with the content of isosorbide percent. Thermal stability of all copolyesters was more than 300?C on the basis of 10% wt loss. CONCLUSIONS: It was found that main chain cholesteric thermotropic liquid crystalline polymers can be prepared form chiral cycloaliphatic diol such as isosorbide. Main chain cholesteric thermotropic liquid crystalline polyesters are prepared from phenyl hydroquinone, isosorbide and terephthalic acid showed thermal stability more than 300?C. Main chain cholesteric thermotropic liquid crystalline polymers are soluble in aprotic solvents like DMAC, DMSO, DMF and NMP.
基金Defence Research and Development Organization(DRDO),India,for Grant-in-aid Project No.ERIP/ER/0703665/M/01/1044the University Grants Commission(UGC-New Delhi),India,for providing Research Fellowship No.F.4-1/2006(BSR)/11-08/2008.
文摘Micro-sized copper powder(99.95%;O≤0.3)has been shock-processed with explosives of high detonation velocities of the order of 7.5 km/s to observe the structural and microstructural sub-strengthening.Axisymmetric shock-consolidation technique has been used to obtain conglomerates of granular Cu.The technique involves the cylindrical compaction system wherein the explosive-charge is in direct proximity with the powder whereas the other uses indirect shock pressure with die-plunger geometry.Numeric simulations have been performed on with Eulerian code dynamics.The simulated results show a good agreement with the experimental observation of detonation parameters like detonation velocity,pressure,particle velocity and shock pressure in the reactive media.A pin contactor method has been utilized to calculate the detonation pressure experimentally.Wide angled x-ray diffraction studies reveal that the crystalline structure(FCC)of the shocked specimen matches with the un-shocked specimen.Field emissive scanning electron microscopic examination of the compacted specimens show a good sub-structural strengthening and complement the theoretical considerations.Laser diffraction based particle size analyzer also points towards the reduced particle size of the shock-processed specimen under high detonation velocities.Micro-hardness tests conducted under variable loads of 0.1 kg,0.05 kg and 0.025 kg force with diamond indenter optical micrographs indicate a high order of micro-hardness of the order of 159 Hv.Nitrogen pycnometry used for the density measurement of the compacts shows that a compacted density of the order of 99.3%theoretical mean density has been achieved.
基金Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515011071,2019A1515111093,and 2022A1515011614)the National Natural Science Foundation of China(Nos.62122034,61875082,61905107,62204107,and 62205138)+2 种基金Innovation Project of Department of Education of Guangdong Province(No.2019KTSCX157)Shenzhen Innovation Project(Nos.JCYJ20210324104413036 and JCYJ20190809152411655)Q.Q.W.and H.M.Z.acknowledge the support from China Postdoctoral Science Foundation(Nos.2021M691397 and 2021M691411).
文摘Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.
基金supported financially by the National Key Research and Development Program of China(Nos.2018YFA0703504 and 2017YFA0403403)the National Basic Research Program of China(No.2016YFA0203200)+1 种基金the National Natural Science Foundation of China(Nos.21971242,11705211,and U1532104)Young Scientist Innovative Foundation of IHEP(Nos.E05469U2 and Y95461C).
文摘Fluorinated and nitrogen-doped graphdiyne(F/N-GDY)have been used in the active layer of perovskite solar cells(PSCs)for the first time.The introduction of heteroatoms turns out to be an effective method for boosted solar cells performance,which increases by 32.8%and 33.0%,better than the pristine or GDY doped PSCs.The enhanced performance can be attributed firstly to the superiority of F/N-GDY originated from the unique structure and optoelectronic properties of GDY.Then,both can further reduce surface defects and improve surface and bulk crystallinity than pristine GDY.What's more,efficiency increase caused by F-GDY is mainly attributed to the improvement of fill factor(FF),while the higher short-circuit current(Jsc)plays more important role by N-GDY doping.Most importantly,the detailed mechanism brought about by doping of F-GDY or N-GDY is expounded by systematical characterizations,especially the synchrotron radiation technique.Doping of F-GDY causes Pb and forms new Pb-F bonds between F-GDY and Pb ions.Doping of N-GDY or GDY brings about Pb(N-GDY doping induces more deviation than that of GDY due to the participation of imine N),improving its electron density and conductivity.
