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1.
刘启佳  邵勇  吴真龙  徐洲  徐峰  刘斌  谢自力  陈鹏 《物理学报》2009,58(10):7194-7198
利用金属有机物化学气相沉积(MOCVD)方法在c面蓝宝石(α-Al2O3)衬底上外延生长了铝镓铟氮(AlGaInN)四元合金薄膜.合金薄膜的生长温度设置为800,850,900 ℃,对获得的样品进行对比分析发现:随着生长温度的升高,合金中的In组分单调降低,而Al组分则基本保持恒定.当合金薄膜的生长温度升高到850 ℃时,薄膜表面开始出现V型缺陷;生长温度进一步升高到900 ℃时,偏析In原子的脱吸附作用加剧,V型缺陷成核被弱化,使V型缺陷的特征尺 关键词: AlGaInN 金属有机物化学气相沉积 生长温度  相似文献   

2.
高纯度和高产率的制备碳纳米管是碳纳米管研究的一个重点。目前制备碳纳米管的方法有电弧法、激光蒸发法、化学气相沉积法(又称CVD法)和模板法等。本文主要介绍采用PECVD化学气相沉积法制备碳纳米管,并对该种方法制备碳纳米管进行了系统的研究和探讨。  相似文献   

3.
采用巨正则蒙特卡罗方法(GCMC)研究了单壁氮化硼纳米管(SWBNNTs)和单壁碳纳米管(SWCNTs)的物理吸附储氢性能,主要对比研究了纳米管的管径、温度和手性对二者物理吸附储氢量的影响. 研究结果表明:在低温下,SWBNNTs的物理吸附储氢性能优于相应的SWCNTs;但是随着温度的升高,二者的物理吸附储氢性能差别越来越小,在常温下,SWBNNTs不具备有比SWCNTs更强的物理吸附储氢性能,而是和相同条件下的SWCNTs相差不大,只是在高压下的物理吸附储氢量稍稍大于SWCNTs,并给出了合理的理论解释 关键词: 巨正则蒙特卡罗方法(GCMC) 单壁氮化硼纳米管(SWBNNTs) 单壁碳纳米管(SWCNTs) 储氢  相似文献   

4.
研究了多壁碳纳米管(MWNTs)薄膜的湿敏特性,实验所用的多壁碳纳米管是用热灯丝化学气相沉积法(CVD)合成的.分别对未修饰和修饰的多壁碳纳米管膜温度和湿度特性进行研究后发现,修饰的多壁碳纳米管对温度和湿度非常敏感,且对湿度的响应时间和恢复时间短,重复性好.而未修饰的多壁碳纳米管对温度和湿度不太敏感.对修饰多壁碳纳米管的湿敏特性进行了理论分析,给出了其理论表示式. 关键词: 多壁碳纳米管 化学修饰 湿敏特性 物理吸附  相似文献   

5.
秦杰明  曹建明  蒋大勇 《物理学报》2013,62(13):138101-138101
本文利用金属有机气相沉积法(MOCVD)生长单一立方相Mg0.57Zn0.43O (记作立方MZO)合金薄膜, 以及该合金薄膜在后期热处理过程中质量和热稳定性的关系. 通过X射线衍射等测试发现, 后期热处理对于立方MZO合金薄膜质量具有较大的影响. 其中在500–850℃的条件下, 合金薄膜的结晶质量和表面形貌随温度的增加得到明显的改善, 吸收截止边逐渐蓝移,带隙展宽, 但仍保持单一立方结构. 当温度达到950℃时立方MZO合金薄膜出现混合相. 通过对立方MZO合金薄膜制备的MSM型单元器件进行光响应的测试表明, 在外加15 V的偏压下, 器件的响应峰值在260 nm附近,紫外/可见抑制比大约为4个数量级, 饱和响应度为3.8 mA/W, 暗电流值为5 pA左右. 关键词: MOCVD 0.57Zn0.43O')" href="#">Mg0.57Zn0.43O 热处理 光响应  相似文献   

6.
采用微波等离子体化学气相沉积法,用高纯氮气(99.999%)和甲烷(99.9%)作反应气体,在单晶Si(100)基片上沉积C3N4薄膜.利用扫描电子显微镜观察薄膜形貌,表明薄膜由密排的六棱晶棒组成.X射线衍射和透射电子显微镜结构分析说明该薄膜主要由β-C3N4和α-C3N4组成,并且这些结果与α-C3N4相符合较好.由虎克定律近似关 关键词: 3N4')" href="#">C3N4 微波等离子体化学气相沉积法 薄膜沉积  相似文献   

7.
基于化学气相沉积(CVD)法制备的铯铅溴钙钛矿薄膜具有优异的光电特性,然而薄膜通常存在CsPbBr3和CsPb2Br5两个不同的相结构区域。本文通过CVD法制备了铯铅溴钙钛矿薄膜,并利用X射线衍射(XRD)、扫描电镜(SEM)、电子能谱仪(EDS)及荧光光谱仪研究了反应气压与N2流量对其中的CsPb2Br5相结构的影响。实验结果表明,反应气压的变化对CsPb2Br5相结构无影响;与此不同,随着N2流量的减少,薄膜中部分CsPb2Br5相结构逐渐转变为CsPbBr3相结构,其发光也由以~630 nm为主的宽带发射转变为以~530 nm为主的窄带发射。实验表明,N2流量是调控CsPb2Br5相结构和发光特性的有效手段。  相似文献   

8.
马立安  郑永安  魏朝晖  胡利勤  郭太良 《物理学报》2015,64(23):237901-237901
采用化学气相沉积法系统研究了合成温度和N2/O2流量对生长在碳纤维衬底上的SnO2纳米线形貌及场发射性能的影响规律. 利用扫描电镜(SEM)、透射电镜(TEM), X射线衍射(XRD)及能谱仪(EDS)对产物细致表征, 结果表明, SnO2纳米线长径比随反应温度的升高而增大; 随N2/O2流量比值的增大先增大后变小, 场发射测试表明, 合成温度780 ℃, N2/O2流量比为300 : 3 时SnO2纳米线阵列具有最佳的场发射性能, 开启电场为1.03 V/μm, 场强增加到1.68 V/μm时, 发射电流密度达0.66 mA/cm2, 亮度约2300 cd/m2.  相似文献   

9.
氢的物理和化学吸附是氢存储的基本形式,而H2分子的解离能垒是决定可逆储氢动力学性能的重要因素.纳米团簇是研究材料储氢性能的重要物质层次,研究氢与Na-Al团簇的相互作用性质能够了解纳米尺度的Na-Al氢化物的储氢性能.本文利用密度泛函理论,计算研究了H2分子在较小的合金团簇Na2Al6上的吸附与解离性能.结果表明H2分子在Na2Al6团簇上是弱的物理吸附,但很容易发生解离.氢分子的解离能垒很低,解离可以在环境温度下发生,纳米结构的Na2Al6团簇具有良好的化学储氢性能.  相似文献   

10.
以金属W和Ta为热丝,采用热丝化学气相沉积 ,在250℃玻璃衬底上沉积多晶硅薄膜.研究了热丝温度、沉积气压、热丝与衬底间距等沉积参数对硅薄膜结构和光电特性的影响,在优化条件下获得晶态比Xc>90%,暗电导率σd=10-7—10-6Ω -1cm-1,激活能Ea=0.5eV,光能隙Eopt≤1.3 eV的多晶硅薄膜. 关键词: 多晶硅薄膜 热丝化学气相沉积 光电特性  相似文献   

11.
Haiyan Zhu 《Ionics》2011,17(7):641-645
SnS nanoparticles were mechanochemically synthesized and fabricated into electrodes with two kinds of conductive agents, acetylene black and multi-wall carbon nanotubes (MWNTs), respectively. The morphology and structure of as-synthesized SnS powder were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of as-prepared electrodes were investigated by discharge–charge test, cyclic voltammogram, and electrochemical impedance spectrum. By comparing the variation of the charge-transfer impedance R ct at different discharge states, it was found that the value of R ct of the electrode with MWNTs as conductive agent was less than that of the electrode with acetylene black as conductive agent. The electrode with MWNTs as conductive agent had preferable cycling performances, which was believed to be attributed to the tenacity and good conductivity of MWNTs.  相似文献   

12.
Hydrogen storage in multi-wall carbon nanotubes using samples up to 85 g   总被引:3,自引:0,他引:3  
Hydrogen storage in carbon nanotubes (CNTs) is investigated at ambient temperature and pressures of 0–12 MPa, using 35–85 g multi-wall carbon nanotube (MWNT) samples that were synthesized in a nano-agglomerate fluidized bed reactor. The volume of hydrogen gas released by the CNTs was measured by a volumetric flow meter. The capability of H2 storage in the CNT samples of mass of up to 85 g can be obtained with a precision of 0.01 wt.%. MWNTs with average diameters ranging from 10–30 nm and were pretreated using nitric acid or a sodium hydroxide solution wash and a high temperature treatment. The influence of the hydrogen pressure, hydrogen storage time and treatment method were studied. All data show that the amount of hydrogen released by the MWNTs at room temperature is no more than 0.30 wt.%, while hydrogen released by MWNT at 77 K can reach 2.27 wt.%. PACS 61.46.+w; 68.43.-h; 84.60.Ve  相似文献   

13.
Carbon nanotubes (CNTs) are synthesized by the catalytic decomposition of acetylene using low pressure chemical vapour deposition method (LPCVD) at 800 °C and at a chamber pressure of 10 Torr over a supported catalyst film of Fe70Pd30. Morphology of these CNTs is studied using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM). From HRTEM image of these multi-walled carbon nanotubes (MWNTs), it is clear that these MWNTs do not possess a co-axial cylindrical structure, but are composed of imperfect and broken graphite cylinders of different sizes. The average diameter and length of the nanotubes varies between 20–70 nm and 5–60 μm respectively. Electrical transport measurements of these MWNTs are studied over a temperature range of 298–4.2 K. The results have been interpreted in terms of variable-range hopping (VRH) over the entire temperature range of 298–4.2 K. Three-dimensional variable-range hopping (VRH) is suggested for the temperature range (298–125 K), while two-dimensional VRH is observed for the temperature range (125–4.2 K).  相似文献   

14.
The functionalization of carbon nanotubes (CNTs) was carried out by using different chemical treatment methods. These functionalized CNTs were characterized by TEM image and FT-IR spectra. The CNT electrodes are measured by thermal resistivity and cyclic voltammetry experiments. The results showed that two important factors controlled the electrochemical properties of the CNT film electrode: one is the active functional group; another is activation energy of the CNT film. From our experiments, we have found the electrode of 10 min nitric acid treated CNTs have the optimal peaks in relation to carboxylic acids, the highest redox peak currents, the biggest value of k0 and well-defined quasi-reversible voltammograms for redox of iron couples, in which the two factors best match.  相似文献   

15.
Flexible polyethylene terephthalate (PET) electrodes based on pristine single-walled carbon nanotubes (SWCNTs) and acid-treated single-walled carbon nanotubes (A-SWCNTs) were prepared by spray coating technique. Flexible A-SWCNTs electrodes showed enhanced electrochemical properties compared to the pristine SWCNTs electrodes. The electrochemical properties of the flexible A-SWCNTs electrodes were optimized with various types of aqueous electrolytes including sulfuric acid (H2SO4), sodium sulfate (Na2SO4), potassium chloride (KCl), sodium hydroxide (NaOH), and potassium hydroxide (KOH). The electrochemical performance of the A-SWCNTs electrodes as a function of bending to 30° were evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) measurements in 1 M H2SO4. The specific capacitance value of the unbent A-SWCNTs electrode was 67 F g?1, which decreased to 63 F g?1 (94% retention) after 1000 GCD cycles. Interestingly, the specific capacitance of the unbent A-SWCNTs electrode with application of the 1000 GCD cycles was retained even after 500 bending to 30° with 6000 GCD cycles.  相似文献   

16.
Using low-pressure chemical vapour deposition (LPCVD), multi-walled carbon nanotubes (MWNTs) are grown on nanocrystalline Fe70Pt30 film. The Fe70Pt30 nanocrystalline film is deposited by vapour condensation technique. The size of the nanoparticles varies from 5–10 nm, as inferred from SEM micrographs of Fe70Pt30 film. SEM and TEM observations of as-grown CNTs film reveal that these are multi-walled and their diameter varies from 30–80 nm and length is of the order of several micrometers respectively. There is a structural change from ordinary geometry of CNTs to bamboo shaped as suggested by TEM image. Raman spectra shows sharp G and D bands with a higher intensity of G band showing the presence of graphitic nature of the nanotubes. An experimental study of the temperature dependence of electrical conductivity of MWNTs film is done over a wide temperature range from (293–4 K). The measured data gives a good fit to variable-range hopping (VRH) and the results are interpreted using Mott's (VRH) model. The conduction mechanism of the MWNTs film shows a crossover from the exp[ -(To/T)1/4] law in the temperature range (293–110 K) to exp[ -(Tm/T)1/3] in the low temperature range (110–4 K). This behaviour is attributed to temperature-induced transition from three-dimension (3D) to two-dimension (2D) VRH. Various Mott's parameters like characteristic temperature (Tm), density of states at Fermi level N(EF), localization length (ξ), hopping distance (R), hopping energy (W) have also been calculated using above-mentioned model.  相似文献   

17.
LiFePO4-positive electrode material was successfully synthesized by a solid-state method, and the effect of storage temperatures on kinetics of lithium-ion insertion for LiFePO4-positive electrode material was investigated by electrochemical impedance spectroscopy. The charge-transfer resistance of LiFePO4 electrode decreases with increasing the storage temperatures. This suggests that it has a high electrochemical activity at high temperature. The diffusion coefficient of lithium ion is greatly increased with increasing the storage temperatures, indicating that the kinetics of Li+ and electron transfer into the electrodes were much fast at high storage temperature.  相似文献   

18.
The catalytic pyrolysis of waste plastics with iron-based catalyst can produce H2 rich gas, liquid oil and carbon nanotube (CNTs) together. While the catalytic pyrolysis mechanism is still unclear, in this study, the catalytic pyrolysis of polypropylene (PP) was explored in depth, and the influence of catalyst and temperature was distinguished. The results indicated that a lower temperature led to the generation of waxes, while a higher temperature promoted the formation of aromatic hydrocarbons when plastic pyrolysis was performed without a catalyst. In addition, a large number of carbon deposits, mainly in the form of spheres, were collected when the temperature was over 800 ℃. These carbon spheres originated from the agglomeration of aromatic hydrocarbons. Once catalysts were introduced, a large amount of liquid oil was transferred into carbon deposits at both lower and higher catalytic temperatures, simultaneously, leading to more light gases releasing, like hydrogen. At a lower temperature (≤ 800 ℃), it was mainly CNTs while carbon spheres are the main solid product at higher temperatures (> 800 ℃). In addition, two different mechanisms of CNTs formation were also concluded that the base-growth model dominated the of generation CNTs at 600 °C whereas the CNTs followed the tip-growth model at 800 ℃. The results show that the optimized temperature for the catalytic process should be around 800 o℃ where approximately 35 mmol/gplastic hydrogen, 50% hydrogen efficiency and over 320 mg/gplastic carbon nanotubes (CNTs) were obtained.  相似文献   

19.
Magnetic carbon nanotubes consisting of multi-wall carbon nanotubes (MWNTs) core and Fe3O4 shell were successfully prepared by in situ thermal decomposition of Fe(acac)3 or FeCl3 or Fe(CO)5 in 2-pyrrolidone containing acid treated MWNTs at 240 °C with the protection of nitrogen gas. The samples were characterized by TEM, XRD, SEAD, XPS and superconducting quantum interference device. Also, their biocompatibility was compared with naked carbon nanotubes. The results showed that after coated with Fe3O4 nanoparticles, the obtained magnetic carbon nanotubes show superparamagnetic characteristic at room temperature, and their blocking temperature is about 80 K. The magnetic properties of the nanotubes are relevant to the content of magnetic particles, increasing content of magnetic nanoparticles leads to higher blocking temperature and saturation magnetization. The results of antimicrobial activities to bacterial cells (Escherichia coli) showed that the MWNTs have antimicrobial activity, while the magnetic nanotubes are biocompatible even with a higher concentration than that of MWNTs.  相似文献   

20.
Supercapacitor (SC) electrodes fabricated with the combination of carbon nanotubes (CNTs) and metal oxides are showing remarkable advancements in the electrochemical properties. Herein, NiO decorated CNT/ZnO core-shell hybrid nanocomposites (CNT/ZnO/NiO HNCs) are facilely synthesized by a two-step solution-based technique for the utilization in hybrid supercapacitors. Benefitting from the synergistic advantages of three materials, the CNT/ZnO/NiO HNCs based electrode has evinced superior areal capacity of ~67 µAh cm−2 at a current density of 3 mA cm−2 with an exceptional cycling stability of 112% even after 3000 cycles of continuous operation. Highly conductive CNTs and electrochemically active ZnO contribute to the performance enhancement. Moreover, the decoration of NiO on the surface of CNT/ZnO core-shell increases the electro active sites and stimulates the faster redox reactions which play a vital role in augmenting the electrochemical properties. Making the use of high areal capacity and ultra-long stability, a hybrid supercapacitor (HSC) was assembled with CNT/ZnO/NiO HNCs coated nickel foam (CNT/ZnO/NiO HNCs/NF) as positive electrode and CNTs coated NF as negative electrode. The fabricated HSC delivered an areal capacitance of 287 mF cm−2 with high areal energy density (67 µWh cm−2) and power density (16.25 mW cm−2). The combination of battery type CNT/ZnO/NiO HNCs/NF and EDLC type CNT/NF helped in holding the capacity for a long period of time. Thus, the systematic assembly of CNTs and ZnO along with the NiO decoration enlarges the application window with its high rate electrochemical properties.  相似文献   

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