Layer-dependent charge density wave phase transition stiffness in 1T-TaS2 nanoflakes evidenced by ultrafast carrier dynamics

Novel physical properties emerge when the thickness of charge density wave(CDW)materials is reduced to the atomic level,owing to the significant modification of the electronic band structure and correlation effects.Here,we investigate the layer-dependent CDW phase transition and evolution of the nonequilibrium state of 1T-TaS₂nanoflakes using pump-probe spectroscopy.Both the low-energy single-particle and collective excitation relaxations exhibit sharp changes at?210 K,indicating a phase transition from commensurate CDW to nearly commensurate CDW state.The single particle process reveals that the phase transition stiffness(PTS)is thickness-dependent.Moreover,a small PTS is observed in thin nanoflakes,which is attributed to the reduced thickness that increases the fluctuation and inhibits the nucleation and growth of discommensurations.In addition,the phase mode vanishes when the discommensuration network appears.Our results suggest that the carrier dynamics could be an efficient operational approach to measuring the quantum phase transition in correlated materials.     

Microstructural evolution of a Ni-Co based superalloy during hot compression at γ'sub-/super-solvus temperatures

The effects of strain rate on the microstructural evolution and deformation mechanism of a Ni-Co based superalloy were investigated by isothermal compression tests performed at γ'sub-solvus(1090℃)andγ'super-solvus temperatures(1150℃)with a wide strain rate range from 0.001 to 10 s-1 under a true strain of 0.693.Electron backscatter diffraction(EBSD),electron channeling contrast imaging(ECCI)and transmission electron microscope(TEM)techniques were used to characterize the microstructures.The results revealed that the dynamic recrystallization(DRX)volume fraction increased and stored energy of the γ matrix grains decreased with increasing the strain rate during γ'sub-solvus temperature defor-mation,while the opposite phenomena were observed during γ'super-solvus temperature deformation.The comprehensive effect of initial grain size,primary y'phase,twins and adiabatic temperature rise led to these results.The primary γ'particles undergone the deformation behavior within itself and obviously accelerated the DRX of the matrix.The microstructural evolution proved that discontinuous dynamic recrystallization(DDRX)was the dominant mechanism during the hot deformation carried out at both γ'sub-solvus and γ'super-solvus temperatures.Primary γ'particles obviously accelerated the nucleation step and retarded the growth step of DDRX during γ'sub-solvus temperature deformation.Besides,the acceleration effect of primary γ'particles on DDRX increased with the increase of strain rate.Continuous dynamic recrystallization(CDRX)was confirmed to be an assistant mechanism during γ'super-solvus temperature deformation and was promoted with the increase of strain rate.     

Investigation of the pore-size dependent microwave absorption properties of honeycomb SnO2

Journal of Materials Science: Materials in Electronics - In this work, the honeycomb-like SnO2 with excellent microwave absorbing (MA) capability was successfully prepared by a template method....     

纳米二氧化硅补强可生物降解聚酯弹性体的制备与性能

通过原位聚合和界面改性,制备出SiO2含量0phr～20phr(质量份数)的纳米SiO2/聚(癸二酸-丙三醇-柠檬酸)酯复合材料,并研究了其结构与性能。力学性能测试结果表明,改性纳米SiO2对弹性体表现出了优异的补强效果,拉伸强度可从0.9MPa提高到5.3MPa;扫描电镜(SEM)和透射电镜(TEM)表明,SiO2以纳米网络状态分散于基体中,与基体间界面结合良好;X射线衍射(XRD)谱图从分子短程相互作用的角度反映出SiO2的存在不利于有序结构的生成;差示扫描量热(DSC)曲线显示,随SiO2含量增加,材料的Tg向低温方向移动;降解性能测试表明,SiO2的加入有助于调节材料的降解速度。     

Selection of single-walled carbon nanotubes according to both their diameter and chirality via nanotweezers

Diameter- and chirality-dependent interactions between aromatic molecule-based nanotweezers and single-walled carbon nanotubes (SWNTs) are revealed by density functional theory calculations. We found that the threshold diameter of selected SWNTs is determined by the end-to-end distance of the nanotweezer. Large-diameter SWNTs are preferred by a nanotweezer with an obtuse folding angle, whereas small-diameter SWNTs are favored by a nanotweezer with an acute folding angle. The adsorption can be further stabilized by the orientational alignment of the hexagonal rings of the nanotweezer and the SWNT sidewall. Therefore, by taking advantage of the supramolecular recognition ability of the aromatic molecule-based nanotweezer, SWNTs can be enriched with both controllable diameter and chirality.      

聚偏氟乙烯/碳纳米管复合材料的制备及性能研究

通过溶剂蒸发成膜法,研究了多壁碳纳米管(MWNTs)对聚偏氟乙烯(PVDF)结晶行为、热行为及力学性能的影响。研究表明,随MWNTs的加入PVDF中α相逐渐减少,而β相晶体含量逐渐增加。且随着MWNTs含量增加,PVDF晶体体积减小,颗粒增多,完善度下降。表明MWNTs作为成核点有利于PVDF结晶,晶体颗粒明显增多,但另一方面,晶体相互制约,晶体尺寸减小。     

胡柚精油纳米乳的制备及品质评价

研制了胡柚精油纳米乳并对其进行了品质评价。利用伪三元相图法优选配方,直接以胡柚精油为油相,从Span系列和Tween系列中筛选出Span-80与Tween-80作为混合表面活性剂,选用丙三醇为助表面活性剂,加入蒸馏水制备胡柚精油纳米乳。通过染色法鉴定染色法该乳液属于O/W型,清澈透明有明显的丁达尔现象,经激光粒度仪测得分散相平均粒径为21 nm,且粒径大小集中,影响因素实验表明该胡柚精油纳米乳有良好的稳定性。     

己酸菌、窖泥与浓香型白酒之间的关系

己酸菌和窖泥与浓香型白酒关系密切,在一定程度上说,是它们在决定着浓香型白酒的质量及风格。就己酸菌与窖泥、己酸菌与甲烷菌、窖泥与清香、浓香、凤香等白酒之间的关系作了详细阐述,分析了浓香型白酒生产中窖泥退化的原因及防治措施,并就人工窖泥培养的配方、原料选择、工艺操作及管理等方面作了介绍。     

自然波纹织物的开发

介绍了自然波纹织物的设计理念、工艺过程及产品特征。织物外观具有自然波纹,效果独特,滑爽轻薄,既有较理想的服用性能又有良好的视觉效果,适宜制作春夏季高档轻薄面料。