MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

A lightweight flexible thermally stable composite is fabricated by com-bining silica nanofiber membranes(SNM)with MXene@c-MWCNT hybrid film.The flexible SNM with outstanding thermal insulation are prepared from tetraethyl orthosilicate hydrolysis and condensation by electrospinning and high-temperature calcination;the MXene@c-MWCNT_(x:y)films are prepared by vacuum filtration tech-nology.In particular,the SNM and MXene@c-MWCNT_(6:4)as one unit layer(SMC_(1))are bonded together with 5 wt%polyvinyl alcohol(PVA)solution,which exhibits low thermal conductivity(0.066 W m^(-1)K^(-1))and good electromagnetic interference(EMI)shielding performance(average EMI SE_(T),37.8 dB).With the increase in func-tional unit layer,the overall thermal insulation performance of the whole composite film(SMC_(x))remains stable,and EMI shielding performance is greatly improved,especially for SMC_(3)with three unit layers,the average EMI SET is as high as 55.4 dB.In addition,the organic combination of rigid SNM and tough MXene@c-MWCNT_(6:4)makes SMC_(x)exhibit good mechanical tensile strength.Importantly,SMC_(x)exhibit stable EMI shielding and excellent thermal insulation even in extreme heat and cold environment.Therefore,this work provides a novel design idea and important reference value for EMI shielding and thermal insulation components used in extreme environmental protection equipment in the future.

Magneto-Transport Properties of Insulating Bulk States in Bi(111) Films

Magneto-transport properties of insulating bulk states in Bi（111） films are systematically investigated under the parallel field （BⅡ）. We find that the magnetotransport of the Bll field is a more powerful tool to distinguish the bulk states and the surface states. A large magnetoresistance （MR） up to 20% in the BⅡ field is induced by the insulating bulk states for the suppression of the backward scattering. With the increasing thickness, a positive MR（BⅡ） from magnetic induced boundary scattering appears in the semimetal films. As the thickness is reduced to 1Ohm, the positive MR（BⅡ） is induced by weak anti-localization from the surface states.

Test research on IR radiation characteristics control of space target using cryogenic vacuum multilayer insulation film structure

In order to achieve the objective of controlling IR radiation characteristics of space target,we design multilayer insulation film structure to cover the target.In space environment the structure comes to cryogenic vacuum multilayer insulation film structure.It can quickly lower the surface temperature of space target,approaching to the ultra-low temperature of the space environment.A vacuum simulation verification test was designed and performed.Through the analysis of test results,we can see that the surface temperature of space target covered by the structure changes with the ambient temperature,having no direct relationship with internal temperature of the target.Therefore,the designed cryogenic vacuum multilayer insulation film structure has excellent IR radiation control performance.It can reduce the target’s IR radiation intensity so as to reduce the probability of detection by IR detectors.

Confined states and spin polarization on a topological insulator thin film modulated by an electric potential

We study the electronic structure and spin polarization of the surface states of a three-dimensional topological insulator thin film modulated by an electrical potential well. By routinely solving the low-energy surface Dirac equation for the system, we demonstrate that confined surface states exist, in which the electron density is almost localized inside the well and exponentially decayed outside in real space, and that their subband dispersions are quasilinear with respect to the propagating wavevector. Interestingly, the top and bottom surface confined states with the same density distribution have opposite spin polarizations due to the hybridization between the two surfaces. Along with the mathematical analysis, we provide an intuitive, topological understanding of the effect.

Quantum spin Hall insulators in chemically functionalized As(110)and Sb(110)films

We propose a new type of quantum spin Hall （QSH） insulator in chemically functionalized As （110） and Sb （110） film. According to first-principles calculations, we find that metallic As （110） and Sb （110） films become QSH insulators after being chemically functionalized by hydrogen （H） or halogen （C1 and Br） atoms. The energy gaps of the functionalized films range from 0.121 eV to 0.304 eV, which are sufficiently large for practical applications at room temperature. The energy gaps originate from the spin-orbit coupling （SOC）. The energy gap increases linearly with the increase of the SOC strength λ/λ0. The Z2 invariant and the penetration depth of the edge states are also calculated and studied for the functionalized films.

Design of periodic metal-insulator-metal waveguide back structures for the enhancement of light absorption in thin-film solar cells

To increase the absorption in a thin layer of absorbing material （amorphous silicon, a-Si）, a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic （TM）-polarized light, but also for transverse electric （TE）-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.

Thermoelectric Transport by Surface States in Bi2Se3-Based Topological Insulator Thin Films

We develop a tractable theoretical model to investigate the thermoelectric （TE） transport properties of surface states in topological insulator thin films （TITFs） of Bi2Sea at room temperature. The hybridization between top and bottom surface states in the TITF plays a significant role. With the increasing hybridization-induced surface gap, the electrical conductivity and electron thermal conductivity decrease while the Seebeck coefficient increases. This is due to the metal-semiconductor transition induced by the surface-state hybridization. Based on these TE transport coefficients, the TE figure-of-merit ZT is evaluated. It is shown that ZT can be greatly improved by the surface-state hybridization. Our theoretical results are pertinent to the exploration of the TE transport properties of surface states in TITFs and to the potential application of Bi2Sea-based TITFs as high-performance TE materials and devices.

Infrared Nano-Imaging of Electronic Phase across the Metal–Insulator Transition of NdNiO_(3) Films

NdNiO_(3) is a typical correlated material with temperature-driven metal–insulator transition. Resolving the local electronic phase is crucial in understanding the driving mechanism behind the phase transition. Here we present a nano-infrared study of the metal–insulator transition in NdNiO_(3) films by a cryogenic scanning near-field optical microscope. The NdNiO_(3) films undergo a continuous transition without phase coexistence. The nano-infrared signal shows significant temperature dependence and a hysteresis loop. Stripe-like modulation of the optical conductivity is formed in the films and can be attributed to the epitaxial strain. These results provide valuable evidence to understand the coupled electronic and structural transformations in NdNiO_(3) films at the nano-scale.

Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Modification of the Hybridization Gap by Twisted Stacking of Quintuple Layers in a Three-Dimensional Topological Insulator Thin Film

Twisting the stacking of layered materials leads to rich new physics. A three-dimensional topological insulator film hosts two-dimensional gapless Dirac electrons on top and bottom surfaces, which, when the film is below some critical thickness, will hybridize and open a gap in the surface state structure. The hybridization gap can be tuned by various parameters such as film thickness and inversion symmetry, according to the literature. The three-dimensional strong topological insulator Bi(Sb)Se(Te) family has layered structures composed of quintuple layers(QLs) stacked together by van der Waals interaction. Here we successfully grow twistedly stacked Sb_2Te_3 QLs and investigate the effect of twist angels on the hybridization gaps below the thickness limit. It is found that the hybridization gap can be tuned for films of three QLs, which may lead to quantum spin Hall states.Signatures of gap-closing are found in 3-QL films. The successful in situ application of this approach opens a new route to search for exotic physics in topological insulators.

Weak avalanche multiplication in SiGe heterojunction bipolar transistors on thin film silicon-on-insulator

In this paper, we propose an analytical avalanche multiplication model for the next generation of SiGe silicon- on-insulator （SOI） heterojunction bipolar transistors （HBTs） and consider their vertical and lateral impact ionizations for the first time. Supported by experimental data, the analytical model predicts that the avalanche multiplication governed by impact ionization shows kinks and the impact ionization effect is small compared with that of the bulk HBT, resulting in a larger base-collector breakdown voltage. The model presented in the paper is significant and has useful applications in the design and simulation of the next generation of SiCe SOI BiCMOS technology.

超薄透明芳纶纳米纤维气凝胶膜的制备及隔热性能

为实现废弃芳纶高品质资源化利用,结合浸没沉淀相转化和冷冻干燥法,利用废弃芳纶成功制备了柔性、透明且隔热的芳纶纳米纤维(ANFs)超薄气凝胶膜。优化了ANFs气凝胶膜成型工艺,并借助FESEM、BET、FTIR、UV-Vis、TG及FLIR对所制ANFs薄膜的微观形貌、化学结构、透光性及热学性能进行分析。结果表明:ANFs被成功剥离,平均直径为18.32 nm;所制ANFs气凝胶膜成型良好,具有三维网络结构,其比表面积和孔隙率分别达52.73 m^(2)/g和92.43%;ANFs气凝胶膜具有超高的透明性和防紫外性(紫外透过率接近0%),在500~780 nm范围内透过率均大于70%,最高达90.70%;此外,所制ANFs气凝胶膜热稳定性良好,具有优异的隔热性能和柔性,四层薄膜隔热温差达28℃。该超薄透明ANFs气凝胶膜制备工艺简单且成本低,具有透光、防紫外及隔热特性,在防护膜领域具有广阔的应用前景。

(Ag,Cu)/TiO_(2)汽车玻璃隔热膜的制备与表征

利用磁控溅射技术制备由金属(Ag,Cu)膜、介质层TiO_(2)膜组成的双层汽车玻璃隔热膜样品。利用单因素分析法考察了溅射时间、溅射功率和Ar溅射流量三个因素对(Ag,Cu)/TiO_(2)汽车玻璃隔热膜透光隔热性能的影响。实验结果表明,在在本底真空度3×10^(-3) Pa,溅射气压2.1 Pa条件下,靶基距均为70 mm时,金属(Ag,Cu)膜溅射时间18 s,溅射功率80 W,Ar溅射流量20 sccm;介质层TiO_(2)膜溅射时间50 min,溅射功率115 W,溅射流量25 sccm时,(Ag,Cu)/TiO_(2)汽车玻璃隔热膜的透光隔热性能最佳。

辐射制冷膜对房式仓隔热效果研究

选取湖州拱板平房仓与荆门基建房式仓2种仓型,分别对其屋面和门窗粘贴辐射制冷膜处理、对仓墙做隔热改造,研究度夏期间屋面、仓内温度变化,分析房式仓隔热改造效果。结果表明:在相同外温下,试验仓仓顶温度比对照仓显著降低,回温速率比对照仓慢;湖州库试验仓拱板夹层温度平均低于对照仓11.3℃,在同时段空调运行时,荆门库试验仓比对照仓仓温温差最高可达8℃,隔热节能效果显著。

气凝胶薄膜材料的制备与应用研究进展

概述了用溶胶-凝胶法制备气凝胶薄膜的过程,重点介绍了各种薄膜成型工艺,如旋涂法、浸渍提拉法、喷涂法、浇铸法等。根据国内外相关研究报道,综述了近年来各类气凝胶薄膜在制备及应用方面所取得的突破性进展;同时指出,气凝胶薄膜材料的功能化基础研究体系还不够完善,在规模化实际应用方面亟待寻找成本低廉、便于生产的制备工艺。

微型电动汽车动力电池充电保温系统设计研究

为解决微型电动汽车在低温环境下充电困难的问题,提出了一种动力电池充电保温系统。通过对加热部件-加热膜、电路以及热管理系统控制策略3方面进行设计,实现了充电保温功能和充电保温等待功能,确保充电时保持动力电池温度在适宜范围内的效用。实验结果表明,该充电保温系统可有效实现温度的调节,保证充电的正常运转。

高温退火对合金衬底上PtW薄膜应变计性能影响研究

为实现航空发动机热端部件健康监测,采用磁控溅射技术在GH4169高温合金基板上制备了一种耐高温的PtW薄膜应变计。该应变计由NiCrAlY过渡层、热氧化生成TGO层、YSZ/Al_(2)O_(3)复合绝缘层和PtW功能层构成。采用SEM和EDS分析了退火前后PtW薄膜的微结构。研究结果表明,退火后PtW薄膜晶粒长大,电阻率下降,W元素含量减少且在晶界处发生富集。通过悬臂梁施加应变,研究了退火前后PtW薄膜应变计在室温~600℃下的应变敏感性能。结果表明,其应变灵敏系数均随温度升高而逐渐降低,且退火后薄膜应变计的应变灵敏系数随温度变化更为显著。该PtW薄膜应变计应变测量量程超过1400με且重复性良好,在航空航天高温部件表面应变测试领域具有广阔的应用前景。

五角星状ZrO_(2)改性聚酰亚胺的绝缘耐高温性能研究

新能源汽车工业的快速发展给汽车电机绝缘漆包线的耐温性能提出了更高要求,制备高性能且价格低廉的漆包线漆膜成为该领域的研究热点.本文提出用一步溶剂热法制备出五角星状ZrO_(2)纳米粉体,利用原位聚合法制备一种高性能、价格低廉的PI/五角星状ZrO_(2)复合薄膜.研究结果表明:制备的五角星状ZrO_(2)纳米粉体分布均匀,进而提高了ZrO_(2)在PI聚合物里的分散性;加入3%的五角星状ZrO_(2)纳米粉体后,相对于纯PI薄膜,PI/五角星状ZrO_(2)复合薄膜的疏水性能得到了提升,拉伸应力提高了4.8倍,初始热分解温度提高了8.30%,介电常数提高了3.2倍.可以看出,五角星状的ZrO_(2)对于纯PI薄膜绝缘、耐高温性能有显著提升.本工作对开发新型高性能漆包线新配方具有重要指导意义.

超大晶格二维纳米片调控聚酰亚胺基复合介质击穿和极化行为研究

为了改善二维纳米片在聚合物基体中的弱分散问题,提高复合材料的电学性能,采用水热法制备二维纳米扩层二硫化钼(E-MoS_(2))纳米片,通过原位聚合法制备聚酰亚胺(PI)基超大晶格二硫化钼纳米片(PI/E-MoS_(2))复合薄膜。利用扫描电子显微镜(SEM)对复合薄膜的表面和断面结构进行了表征,并用傅里叶红外光谱仪(FTIR)对复合薄膜的分子价键进行成分分析,用X射线衍射仪(XRD)研究复合薄膜的相结构。此外,测量了复合薄膜的介电常数、交流电导率和介质损耗因数,探讨了纳米片扩层晶格结构对薄膜击穿和极化行为的影响机理。结果表明:在PI薄膜中掺入少量的E-MoS_(2)纳米片,PI/E-MoS_(2)复合薄膜表面无明显团聚现象,其断面形貌无明显孔洞且结构缺陷数量较少,表明基体与填料相容性好。引入E-MoS_(2)纳米片可以增强复合薄膜内部的界面极化,显著提高薄膜的介电常数及电气强度,并降低其介质损耗。

SiC颗粒包覆氧化铝隔绝膜的性能

为了防止SiC颗粒与过渡金属在高温下混合应用时发生反应,使用流化床PECVD在名义粒度180μm SiC颗粒表面镀覆完整的Al_(2)O_(3)隔绝膜。通过SEM、XRD等对膜层的形态、组成和物相进行了表征,利用混合烧结法模拟SiC颗粒与过渡金属在高温下混合应用的状态。当膜层厚度在4μm以上,膜层主要成分为无定形氧化铝和少量含碳杂质。在700℃/1060℃的温度和空气氛围中保温12 h,膜层发生相变,生成γ-Al_(2)O_(3)/α-Al_(2)O_(3)。经高温真空腐蚀实验验证,证实膜层能有效防止SiC与Ni等过渡金属反应,提高了SiC颗粒高温应用的性能。