质子辐照CH3NH3PbI3基钙钛矿太阳能电池的损伤效应

针对钙钛矿太阳能电池(PSCs)的空间应用,研究了动能为0.1—20.0 MeV的质子在CH₃NH₃PbI₃(简称MAPbI₃)薄膜及其太阳能电池中引起的损伤效应.结果表明, PSCs具有良好质子辐照稳定性,当0.1 MeV(2.0 MeV)质子的注量超过1×10¹³ p/cm² (1×10¹⁴ p/cm²)时,才会引起电池光电性能的降低. PSCs载流子传输层的辐照退化可能是造成电池性能降低的主要原因. MAPbI₃中的有机成分MAI会在质子辐照作用下发生分解,分解产生的气态产物(NH₃和CH₃I)将最终导致PSCs表面金电极的剥落.对于具有更大离子射程的10 MeV和20 MeV质子,入射质子会在PSCs的玻璃基底中产生色心缺陷,造成玻璃对可见光透射率的降低.色心缺陷可以在室温或100℃条件下发生热退火,降低玻璃的透射损失.     

质子辐照对纯铝薄膜微观结构的影响

利用透射电子显微镜(TEM)详细分析了不同剂量的质子辐照纯铝薄膜样品的微观结构, 质子的能量E=160 keV.实验表明,质子辐照能够在Al薄膜中诱发空位位错圈,在实验范围内,位错密度随辐照剂量的增加而增加;质子辐照在1×10¹¹—4×10¹¹/mm²范围内随辐照剂量的增加,位错圈数量密度以及位错圈尺寸都随之增加.在较高剂量6×10¹¹/mm²辐照下,位错圈数量密度减小,但其尺寸显著 关键词： 质子辐照 空位簇缺陷 位错圈 微观结构     

氢离子注入对硅单晶电子辐照缺陷和氢泡形成的影响

以50keV和100keV能量的氢离子注入p型(100)直拉硅单晶薄膜。注入剂量为10¹⁵—2×10¹⁷H⁺/cm²。试样在HU-1300型超高压透射电子显微镜中进行电子辐照和原位加热动态观察。结果表明在20—300℃温度范围内与未注氢硅相比,注氢硅在相同的电子辐照条件下产生的电子辐照缺陷较少,电子辐照缺陷形成所需的潜伏时间较长。在电子显微镜中加热试样时于190℃开始观察到氢泡,190—220℃范围内氢泡逐渐产生并长大 关键词：     

碳、碳氮和硼碳氮纳米管场发射性能的比较研究

采用高温热解法在860℃分别制备出了碳、碳氮和硼碳氮纳米管，提纯后利用丝网印刷工艺分别将它们制备成薄膜，并测试了它们的场发射性能.结果表明：碳纳米管、碳氮纳米管和硼碳氮纳米管薄膜的开启电场分别为2.22，1.1和4.4V/μm，当电场增加到5.7V/μm时，它们的电流密度分别达到1400，3000μA/cm²和小于50μA/cm².碳和碳氮纳米管薄膜的场增强因子分别为10062和11521.可见，碳氮纳米管的场发射性能优于碳纳米管，而硼碳氮纳米管的场发射性能比前两者要差.解释了这三种纳米管场发射性能差别的原因. 关键词： 碳纳米管 碳氮纳米管 硼碳氮纳米管 场发射     

Mo/Si多层膜在质子辐照下反射率的变化

为了检验应用在极紫外波段空间太阳望远镜上Mo/Si多层膜反射镜在空间辐射环境下反射率的变化情况, 模拟了部分空间太阳望远镜运行轨道的辐射环境, 利用不同能量和剂量的质子对Mo/Si多层膜反射镜进行辐照实验.辐照前后反射率测量结果显示,由于带电粒子的辐照损伤,质子辐照会使Mo/Si多层膜反射镜的反射率降低,且质子能量越低、剂量越大,对多层膜的反射率影响越明显. 当质子能量E=160keV,剂量＝6×10¹¹/mm²时,反射率降低4.1%;能量E=100keV,剂量=6×10¹¹/mm²时, 反射率降低5.7%;能量E=50keV,剂量=8×10¹²/mm²时,反射率降低10.4%. 用原子力显微镜测量辐照后Mo/Si多层膜反射镜的表面粗糙度比辐照前明显增加,致使散射光线能量逐渐增大并最终导致反射率的降低. 关键词： 质子辐照 Mo/Si多层膜反射镜 辐照损伤     

快重离子辐照聚酰亚胺潜径迹的电子能损效应

快重离子辐照聚合物材料时，由于密集电离激发在其路径上产生几纳米直径的潜径迹，径迹形貌受离子种类、离子能量等多种因素的影响.为了研究电子能损对径迹形成所起的作用，利用1.158GeV 的Fe⁵⁶离子和 1.755GeV Xe¹³⁶离子在室温真空环境下辐照叠层聚酰亚胺(PI)薄膜，结合傅里叶转换红外光谱(FTIR)分析技术对辐照引起的化学变化进行了测量.聚酰亚胺官能团的降解及炔基的生成是离子辐照聚合物的主要特征，在注量1×10¹¹到6×10¹²/cm²范围及较宽的电子能损(dE/dX)_e范围 (Fe⁵⁶ 离子：2.2 到 5.2 keV/nm， Xe¹³⁶ 离子：8.6 到 11.3 keV/nm)对官能团的断键率及炔基生成率进行了研究. 红外结果显示在实验涉及的能损范围都有炔基生成，应用径迹饱和模型对实验结果进行拟合，不同能损下的平均损伤径迹半径及炔基生成径迹半径被得到，通过热峰模型对实验结果拟合，给出了离子在聚酰亚胺中产生潜径迹的能损阈值，实验给出的径迹形貌的电子能损效应曲线与热峰模型预言走势基本一致. 关键词： 离子辐照 潜径迹 红外光谱 热峰模型     

用20—1020 keV单能质子刻度CR-39固体核径迹探测器

用北京师范大学2×1.7MV串列加速器和400 kV高压倍加器产生的20—1020 keV单能质子束对CR-39固体核径迹探测器进行了刻度.为了保证质子的单能性和固体核径迹探测器上径迹密度不能超过10⁶/cm²的要求,对两台加速器分别采用了不同方法控制质子辐照数量.在串列加速器上采用了狭缝加转盘的方法,在高压倍加器上采用了100 ns单次高压脉冲扫描束流的方法,既保持了质子的单色性,又达到了质子注量小于10⁶/cm²的 关键词： 单能质子 固体核径迹探测器 CR-39     

增强型Cascode结构氮化镓功率器件的高能质子辐射效应研究

针对增强型共栅共源(Cascode)级联结构和耗尽型AlGaN/GaN功率器件,利用60 MeV能量质子开展辐射效应研究.获得了经质子辐照后器件电学性能的退化规律,并与常规耗尽型HEMTs器件辐照后的电学性能进行了比较,发现增强型Cascode结构器件对质子辐照更加敏感,分析认为级联硅基MOS管的存在是其对质子辐照敏感的主要原因.质子辐照使硅基MOS管栅氧化层产生大量净的正电荷,诱导发生电离损伤效应,使其出现阈值电压负向漂移及栅泄漏电流增大等现象.利用等效(60 MeV能量质子,累积注量1×10¹² p/cm²)剂量的⁶⁰Co γ射线辐射器件得到电离损伤效应结果,发现器件的电学性能退化规律与60 MeV能量质子辐照后的退化规律一致.通过蒙特卡罗模拟得到质子入射在Cascode型器件内诱导产生的电离能损和非电离能损,模拟结果表明电离能损是导致器件性能退化的主要原因.     

拟南芥胚的不同区域对MeV离子辐照的响应

利用不同能量的质子在大气环境中辐照拟南芥的含水种子，能量从1.1MeV到6.5MeV.根据模拟计算结果，相应能量的离子对种子的损伤区域分别为胚的浅层、胚的一半和整个胚.本实验中，具有较高能量的质子可以完全均匀地作用于拟南芥生长、发育及遗传密切相关的胚茎端分生组织，而能量较低的质子则不能直接作用于茎端分生组织.实验所用质子注量范围为4×10⁹ions/cm²—1×10¹⁴ions/cm².实验结果显示，虽然拟南芥种子的发芽率和幼苗存活率随离子注量增加都呈现下降的趋势，但对应于不同的胚损伤区域，即在不同的入射质子能量条件下，注量曲线具有各自的特征.实验结果显示，拟南芥种子中除了胚茎端分生组织作为对离子辐照敏感的辐射主靶外，茎端分生组织之外的胚区域可能作为离子辐射次靶，影响到最终的辐射生物学效应. 关键词： 离子辐照 拟南芥 胚区域 生物效应     

Ti/4H-SiC肖特基势垒二极管抗辐射特性的研究

本文采用γ射线、高能电子和中子对Ti/4H-SiC肖特基势垒二极管(SBD)的抗辐射特性进行了研究.研究发现对于γ射线和1 MeV电子辐照,-30 V辐照偏压对器件的辐照效应没有明显的影响.经过1 Mrad(Si)的γ射线或者1×l0¹³ n/cm²的中子辐照后,Ti/4H-SiC肖特基接触都没有明显退化;经过3.43×10¹⁴ e/cm²的1 MeV电子辐照后Ti/4H-SiC的势垒高度比辐照前轻微下降,这是由于高能 关键词： 碳化硅 肖特基 辐照 偏压     

Demetalization of single-walled carbon nanotube thin films with microwave irradiation

The microwave irradiation effects on purified HiPCO and CoMoCat single-walled carbon nanotube (SWNT) thin films are investigated. The surface conductivities of the SWNT films are extracted from the measured THz transmission coefficients to provide a direct indication of the metallic content in the films. The observed drastic conductivity decrease indicates a significant metallic content reduction after the microwave irradiation. Two different laser excitations are applied for Raman spectroscopy to reveal the response of different nanotube species. The Raman spectra of both HiPCO and CoMoCat thin films confirm the decrease of metallic carbon nanotubes. The observed microwave-induced effects may potentially lead to a convenient scheme for demetalization of single-walled carbon nanotube mixtures.     

质子辐照铝膜反射镜的慢正电子湮没研究

采用分光光度计测定了60keV质子辐照后铝膜反射镜反射光谱的变化规律.用慢正电子湮没等分析技术研究了辐照损伤的微观机制.结果表明，当质子辐照主要作用于反射镜铝膜层中时反射镜在200—800nm波长范围内反射率随辐照剂量增加而下降.入射质子可对铝膜中的缺陷产生填充作用，减小铝膜中电子密度，增加弱束缚电子带间跃迁.紫外至可见光能量较高的波段可引起带间激发跃迁，使相应的谱段反射率下降，导致反射镜光学性能的退化. 关键词： 反射镜 光学性能 质子辐照 慢正电子湮没     

Reduced graphene oxide/MWCNT hybrid sandwiched film by self-assembly for high performance supercapacitor electrodes

A reduced graphene oxide/multiwalled carbon nanotube (RGO/MWCNT) hybrid sandwiched film with different MWCNTs content was prepared by vacuum-assisted self-assembly from a complex dispersion of graphene oxide (GO) and MWCNTs followed by heat-treating at 200 °C for 1 h in a vacuum oven to reduce the GO into RGO. The free-standing RGO/MWCNT hybrid sandwiched film before heat-treatment showed a layered structure with an entangled network of MWCNTs sandwiched between the GO sheets. This unique structure not merely contribute to remove the oxygen-containing groups in GO during the heat-treatment, but also decrease the defects for electron transfer between RGO layers, which enhances the electrochemical capacitive performances of graphene-based films. A specific capacitance up to 379 F/g was achieved based on RGO/MWCNT with 30 % MWCNTs mass fraction at 0.1 A/g in a 6 M KOH electrolyte. The excellent performance of RGO/MWCNT hybrid sandwiched film signifies the importance of controlling the surface chemistry and sandwiched nanostructure of graphene-based materials.     

Effect of cross-linkable polymer on the morphology and properties of transparent multi-walled carbon nanotube conductive films

In this study, we fabricated optically transparent and electrically conductive multi-walled carbon nanotube (MWCNT) thin films using a spray-coating technique. The transparency and the electrical resistance of thin film are dependent on the nanotube content deposited on the polyethylene terephthalate (PET) substrate. Poly(acrylic acid) (PAA) and poly(N-vinyl pyrrolidone) (PVP) were used as adhesion promoters to improve MWCNT coating more significantly. The cross-linked polymer resulted in a superior bond between the MWCNTs and the substrates. The surface electrical resistance was significantly lower than the original sheet after nitric acid (HNO₃) treatment because of the removed surfactant and the increased interconnecting networks of MWCNT bundles, thus improving the electrical and optical properties of the films. Stronger interaction between the MWCNTs and the substrates resulted in lower decomposition of the polymer chain and less amounts of MWCNTs separated into the HNO₃ solution. The lower sheet electrical resistance of PVP/PAA-g-MWCNT conductive films on the PET substrate was because of a more complete conductive path with the cross-linked polymer than that without. Such an improved sheet of electrical resistance varied from 8.83 × 10⁴ Ω/□ to 2.65 × 10³ Ω/□ with 5.0 wt.% PVP/PAA-g-MWCNT sprayed on the PET after acid treatment.     

Effect of different microwave-based treatments on multi-walled carbon nanotubes

Three new methods for the functionalization of multi-walled carbon nanotubes (MWCNTs) are reported using microwave (MW) energy and water as a mild chemical agent. In the first method we reported the effect of MW irradiation on a dispersion of MWCNTs in deionized water, in the second method we studied the exposing of MWCNT to microwave irradiation in the presence of steam, and in the third method we used microwave oven-generated plasma for the functionalization of MWCNTs. We also performed thermal oxidation and acid treatment as two conventional methods for oxidative functionalization of carbon nanotubes, to compare their effect with our results. Transmission electron microscopy (TEM) and Raman spectroscopy results showed that although these microwave methods introduced some defects to the carbon nanotubes, the damage was less severe than conventional treatments. X-ray photoelectron spectroscopy (XPS) measurements confirmed that the functionalization of carbon nanotubes by these methods favored hydroxyl groups, which are useful when further functionalization is required.     

Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyacrylate composite films

Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in pure acrylic emulsion by ultrasonication to prepare MWCNT/polyacrylate composites applied on building interior wall for electromagnetic interference (EMI) shielding applications. The structure and surface morphology of the MWCNTs and MWCNT/polyacrylate composites were studied by field emission scanning microscopy (FESEM) and transmission electron microscopy (TEM). The electrical conductivity at room temperature and EMI shielding effectiveness (SE) of the composite films on concrete substrate with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in two different frequency ranges of 100-1000 MHz (radio frequency range) and 8.2-12.4 GHz (X-band). The experimental results show that a low mass concentration of MWCNTs could achieve a high conductivity and the EMI SE of the MWCNT/polyacrylate composite films has a strong dependence on MWCNTs content in both two frequency ranges. The SE is higher in X-band than that in radio frequency range. For the composite films with 10 wt.% MWCNTs, the EMI SE of experiment agrees well with that of theoretical prediction in far field.     

γ射线辐照下多壁碳纳米管结构转变过程研究

采用60Coγ射线辐照纯净的多壁碳纳米管,用高分辨透射电镜和拉曼光谱,研究了多壁碳纳米管由石墨结构向无定形结构转变的演化过程.发现在γ射线辐照下,碳纳米管的外部石墨层逐渐失去最初的有序结构而向无定形结构转变.而且,随着γ射线辐照剂量的增加,无定形结构不断推进,而石墨层结构则不断减小,直至使整个碳纳米管变为一个中空的无定形纳米线结构.用原子位移理论和溅射机理对这种转变过程进行了分析.γ射线轰击碳纳米管击出碳原子,碳原子停留在晶格的间隙位置上产生间隙原子,在它原来的平衡位置则留下一个空位.当轰击粒子动能足够大时导致碰撞级联效应,无序结构增加.多数空位和间隙原子可能相互复合而彼此退火,但仍有少数原子作为间隙原子而造成晶格进一步缺陷.辐射也可以引起碳原子的溅射,溅射出来的碳原子沉积在碳纳米管的外壁上形成一层无定形碳结构.     

3 MeV质子辐照对AlGaN/GaN高电子迁移率晶体管的影响

研究了AlGaN/GaN 高电子迁移率晶体管(HEMT)的质子辐照效应. 在3 MeV质子辐照下, 当辐照剂量达到1× 10¹⁵ protons/cm²时, 漏极饱和电流下降了20%, 最大跨导降低了5%. 随着剂量增加, 阈值电压向正向漂移, 栅泄露电流增加. 在相同辐照剂量下, 1.8 MeV质子辐照要比3 MeV质子辐照退化严重. 从SRIM软件仿真中得到不同能量质子在AlGaN/GaN异质结中的辐射损伤区, 以及在一定深度形成的空位密度. 结合变频C-V测试结果进行分析, 表明了质子辐照引入空位缺陷可能是AlGaN/GaN HEMT器件电学特性退化的主要原因.     

Study the effect of acetic acid on structural,optical and mechanical properties of PVA/chitosan/MWCNT films

Polyvinyl alcohol (PVA)/chitosan/multiwalled carbon nanotube (MWCNT) films were successfully prepared by using solution-casting method. Structural properties were studied using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopies. The effect of acetic acid (AA) concentration on the films optical parameters was studied by using absorbance and transmittance data recorded during ultraviolet-visible (UV–Vis) spectroscopy. The results indicated that increasing the AA concentration in MWCNT-reinforced PVA films caused an increase in their optical capability. We also evaluated mechanical properties such as stress-strain behavior, Young's modulus, tensile strength, elongation at break, etc. Mechanical indices have been modified by introducing carbon nanotubes, even though enhancing the AA concentration meets significant restrictions on higher percentages of AA concentration, which needs to be delicately considered. The porous structure of the films, such as porous pattern, materials’ diameter, and shape was examined by field emission electron microscopy (FESEM). Engineering analyses showed that the films reinforced with MWCNTs exhibited an interconnected homogenous structure in various acid concentrations.     

Functional multi-walled carbon nanotube/polysiloxane composite films as supports of PtNi alloy nanoparticles for methanol electro-oxidation

We demonstrate the use of molecular monolayers to enhance the nucleation of electrocatalytically active PtNi alloy nanoparticles onto the multi-walled carbon nanotubes (MWCNTs). After the siloxane was polymerized on the nanotube surfaces, the carbon nanotubes were embedded within the polysiloxane shell with a hydrophilic amino group situated outside. Subsequent deposition of PtNi nanoparticles led to high density of 3-10 nm diameter PtNi alloy nanoparticles uniformly deposited along the length of the carbon nanotubes. The presence of MWCNTs and PtNi in the composite films was confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersion X-ray spectra analysis (EDS). The electrocatalytic activity of the PtNi-modified MWCNT/polysiloxane (PtNi/Si-MWCNT) composite electrode for electro-oxidation of methanol was investigated by cyclic voltammetry (CV), and excellent electrocatalytic activity can be observed.