共查询到20条相似文献,搜索用时 31 毫秒
1.
Ling Fei Yun Xu Zheng Chen Bin Yuan Xiaofei Wu Joshua Hill Qianglu Lin Shuguang Deng Paul Andersen Yunfeng Lu Hongmei Luo 《Materials Chemistry and Physics》2013
We report a surfactant-free chemical solution route for synthesizing one-dimensional porous SnO2 helical nanotubes templated by helical carbon nanotubes and two-dimensional SnO2 sheets templated by graphite sheets. Transmission electron microscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic discharge–charge analysis are used to characterize the SnO2 samples. The unique nanostructure and morphology make them promising anode materials for lithium-ion batteries. Both the SnO2 with the tubular structure and the sheet structure shows small initial irreversible capacity loss of 3.2% and 2.2%, respectively. The SnO2 helical nanotubes show a specific discharge capacity of above 800 mAh g−1 after 10 charge and discharge cycles, exceeding the theoretical capacity of 781 mAh g−1 for SnO2. The nanotubes remain a specific discharge capacity of 439 mAh g−1 after 30 cycles, which is better than that of SnO2 sheets (323 mAh g−1). 相似文献
2.
V.V. Bolotov P.M. KorusenkoS.N. Nesov S.N. PovoroznyukV.E. Roslikov E.A. KurdyukovaYu.A. Sten’kin R.V. ShelyaginE.V. Knyazev V.E. KanI.V. Ponomareva 《Materials Science and Engineering: B》2012,177(1):1-7
Hetero-phase nanocomposite layers based on porous silicon and nonstoichiometric tin oxide (por-Si/SnOx) were obtained by the chemical vapor deposition (CVD), magnetron sputtering, and molecular layer deposition methods. The structure, and the atomic and phase compositions of the nanocomposites were studied by means of transmission electron microscopy, energy-dispersive X-ray analysis (EDX), scanning electron microscopy, Raman spectroscopy, Auger spectroscopy, and X-ray photoelectron spectroscopy. The obtained data were indicative of the formation of por-Si/SnOx nanocomposite layers up to 2 μm thick with x = 1.0-2.0. According to EDX data, in magnetron sputtering process the formation of por-Si/SnOx nanocomposite layers proceeds on the externally exposed surface of polycrystalline por-Si skeleton elements with subsequent diffusion of tin atoms into the pores along the por-Si walls. The other two methods lead to formation of large SnOx islands covering pores in the por-Si structure. Enhanced diffusion of tin atoms into porous matrix with Deff ≈ 1 × 10−14 cm2/s was observed in samples annealed at 500 °C. Sensor heterostructures based on magnetron sputtered por-Si/SnOx nanocomposite layers show high sensitivity to NO2 environmental molecules and remarkable stability, thus offering promise in gas sensing applications. 相似文献
3.
Rutile structure SnO2 nano-single crystals have been synthesized using tin (IV) chloride as precursor by the modified hydrothermal method. Controllable morphology and size of SnO2 could be obtained by adjusting the concentration of the hydrochloric acid. The SnO2 nanoparticles were characterised by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical methods. The SnO2 nanoparticles as anode materials in lithium-ion batteries exhibit high lithium storage capacities. The reversible capacities are more than 630 mA h g− 1. 相似文献
4.
Yanbao Fu 《Materials Letters》2009,63(22):1946-1948
SnO2/multi-walled carbon nanotube (MWCNT) composite was prepared via a diffusion method. Firstly the MWCNT was sonicated in a filtrate which was derived from a tin dichloride solution mixed with AgNO3 solution. Then the SnO2/MWCNT composite was prepared whereby, after calcination in N2 atmosphere, the salts inside the MWCNT decomposed to SnO2. The resulting composite was characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, which indicated that SnO2 had infiltrated into the MWCNT and filled the interior. The subsequent evaluation of the electrochemical performance in lithium ion batteries showed that the SnO2/MWCNT composite had a reversible discharge capacity of 505.9 mAh?g− 1 after 40 cycles, as compared to 126.4 mAh?g− 1 for pure nano-SnO2. 相似文献
5.
Yanbai Shen Toshinari Yamazaki Zhifu Liu Dan Meng Toshio Kikuta 《Thin solid films》2009,517(21):6119-2463
Pd-doped SnO2 sputtered films with columnar nanostructures were deposited using reactive magnetron sputtering at the substrate temperature of 300 °C and the discharge gas pressures of 1.5, 12, and 24 Pa. Structural characterization by means of X-ray diffraction and scanning electron microscopy shows that the films composed of columnar nanograins have a tetragonal SnO2 structure. The films become porous as the discharge gas pressure increases. Gas sensing measurements demonstrate that the films show reversible response to H2 gas. The sensitivity increases as the discharge gas pressure increases, and the operating temperature at which the sensitivity shows a maximum is lowered. The highest sensitivity defined by (Ra − Rg) / Rg, where Ra and Rg are the resistances before and after exposure to H2, 84.3 is obtained for the Pd-doped film deposited at 24 Pa and 300 °C upon exposure to 1000 ppm H2 gas at the operating temperature of 200 °C. The improved gas sensing properties were attributed to the porosity of columnar nanostructures and catalytic activities of Pd doping. 相似文献
6.
Fast response detection of H2S by CuO-doped SnO2 films prepared was prepared by a simple two-step process: electrodeposition from aqueous solutions of SnCl2 and CuCl2, and oxidization at 600 °C. The phase constitution and morphology of the CuO-doped SnO2 films were characterized by X-ray diffraction and scanning electron microscopy. In all cases, a polycrystalline porous film of SnO2 was the product, with the CuO deposited on the individual SnO2 particles. Two types of CuO-doped SnO2 films with different microstructures were obtained via control of oxidation time: nanosized CuO dotted island doped SnO2 and ultra-uniform, porous, and thin CuO film coated SnO2. The sensor response of the CuO doped SnO2 films to H2S gas at 50–300 ppm was investigated within the temperature range of 25–125 °C. Both of the CuO-doped SnO2 films show fast response and recovery properties. The response time of the ultra-uniform, porous, and thin CuO coated SnO2 to H2S gas at 50 ppm was 34 s at 100 °C, and its corresponding recovery time was about 1/3 of the response time. 相似文献
7.
Faheem K. Butt Chuanbao Cao Waheed S. Khan Zulfiqar Ali Tariq Mahmood R. Ahmed Sajad Hussain Ghulam Nabi 《Materials Chemistry and Physics》2012
Here we report on the synthesis of novel SnO2 nanofibers bundle (NFB) by using ball milled Fe powders via chemical vapor deposition (CVD). The reaction was carried out in a horizontal tube furnace (HTF) at 1100 °C under Ar flow. The as prepared product was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction (SAED). The microscopy analysis reveals the existence of tubular structure that might be formed by the accumulation of nanofibers. The Raman spectrum reveals that the product is rutile SnO2 with additional peaks ascribed to defects or oxygen vacancies. Room temperature Photoluminescence (PL) spectrum exhibits three emission bands at 369, 450 and 466.6 nm. Using optical absorbance data, a direct optical bandgap of 3.68 eV was calculated. 相似文献
8.
Hierarchically porous intestine-like SnO2 hollow nanostructures of different dimension were successfully synthesized via a facile, organic template free, H2O2-assisted method at room temperature. The morphology as well as texture (congregated solid sphere, intestine-like solid nanostructure, hollow core–shell one, and intestine-like hollow one) of SnO2 materials can be controlled by varying H2O2 concentration and the size of intestine-like hollow SnO2 can be tuned in the range of 20–120 nm by changing SnSO4 concentration. The hierarchically porous intestine-like SnO2 has high specific surface area (142 m2 g−1). The gas-sensing behaviors of the intestine-like SnO2 material to different gas probes such as ethanol, H2, CO, methane, and butane have been investigated; among them a high selectivity to ethanol was achieved. 相似文献
9.
The synthesis of titanium porous microspheres by a combustion technique was studied under an argon atmosphere by using a TiO2 − 2.5Mg reactive mixture. The precursor, a fine TiO2 powder, was thermally treated in the range 600–1300 °C prior to the combustion experiments. TiO2 microspheres whose diameters were between 10 and 50 μm were obtained from precursor particles annealed in the range 900–1100 °C. A biphase product consisting of Ti and MgO phases was obtained when the TiO2 microspheres were reduced with Mg. The spherical morphology of the final particles was retained despite the relatively high combustion temperatures (1630–1670 °C) used in this study. Moreover, porous titanium microspheres were obtained when the MgO particles were dissolved using acid leaching. Scanning electron microscopy (SEM) images of the microspheres suggested that the spherical structure contained ∼0.5–2.0-μm-diameter porous windows. The Brunauer–Emmett–Teller (BET) surface area of the Ti microspheres was determined to be 2.8 m2 g−1. 相似文献
10.
The multi-walled carbon nanotube/SnO2 core-shell structures were fabricated by a wet chemical route. The electrochemical performance of the core-shell structures as anode materials of lithium-ion batteries was investigated. The initial discharge capacity and reversible capacity are up to 1472.7 and 1020.5 mAh g−1, respectively. Moreover, the reversible capacity still remains above 720 mAh g−1 over 35 cycles, and the capacity fading is only 0.8% per cycle. Such high capacities and good cyclability are attributed to SnO2 network structures, excellent mechanical property and good electrical conductivity of the multi-walled carbon nanotubes. 相似文献
11.
Preparation and electrochemical properties of multiwalled carbon nanotubes-nickel oxide porous composite for supercapacitors 总被引:1,自引:0,他引:1
Porous nickel oxide/multiwalled carbon nanotubes (NiO/MWNTs) composite material was synthesized using sodium dodecyl phenyl sulfate as a soft template and urea as hydrolysis-controlling agent. Scanning electron microscopy (SEM) results show that the as-prepared nickel oxide nanoflakes aggregate to form a submicron ball shape with a porous structure, and the MWNTs with entangled and cross-linked morphology are well dispersed in the porous nickel oxide. The composite shows an excellent cycle performance at a high current of 2 A g−1 and keeps a capacitance retention of about 89% over 200 charge/discharge cycles. A specific capacitance approximate to 206 F g−1 has been achieved with NiO/MWNTs (10 wt.%) in 2 M KOH electrolyte. The electrical conductivity and the active sites for redox reaction of nickel oxide are significantly improved due to the connection of nickel nanoflakes by the long entangled MWNTs. 相似文献
12.
A nanocomposite of manganese dioxide coated on the carbon nanotubes (MnO2/CNTs) was synthesized by a facile direct redox reaction between potassium permanganate and carbon nanotubes without any other oxidant or reductant addition. The morphology, microstructure and crystalline form of this MnO2/CNT nanocomposite were characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties are characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD). The results show that the facile prepared MnO2/CNTs nanocomposite shows specific capacitance of 162.2 F g−1 at the current density of 0.2 A g−1 and excellent charge/discharge property with 90% of its specific capacitance kept after 2000 cycles at the current density of 5 A g−1. 相似文献
13.
Aligned tin dioxide (SnO2) nanorods have been synthesized by high-frequency inductive heating. Nanorods were grown on silicon substrates vertically in less than 3 min, using SnO2 and graphite as the source powder. Scanning electron microscopy and transmission electron microscopy showed nanorod with diameters from 25 to 50 nm. The turn-on field needed to produce a current density of 10 μA/cm2 is found to be 1.6 V/μm. This type of SnO2 nanorods can be applied as field emitters in displays as well as vacuum electric devices. 相似文献
14.
Gang Zhu 《Materials Letters》2010,64(16):1763-1765
δ-MnO2 was synthesized by a facile low-temperature hydrothermal method with a mixed system of KMnO4 and CO(NH2)2 at 90 °C for 24 h. The obtained product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption. Results showed that the as-synthesized product had a layered structure and a high specific surface area of 230 m2 g− 1. Electrochemical characterization indicated that the prepared material exhibited an ideal capacitive behavior with the initial capacitance value of 265 F g− 1 in 1 mol L− 1 Na2SO4 aqueous solution at a scan rate of 5 mV s− 1 and excellent cycling behavior. 相似文献
15.
Branched structures of SnO2 one-dimensional nanomaterials have been successfully fabricated via a novel multi-step process. Scanning electron microscopy indicated that the SnO2 branches, which sprouted from the SnO2 stems, had diameters in the range of 30-120 nm. X-ray diffraction, high resolution transmission electron microscopy and selected area diffraction pattern revealed that the branches were single crystalline rutile SnO2 structures. Room temperature photoluminescence spectrum of the branched product exhibited visible light emission. We suggested that a Au-catalyzed vapor-liquid-solid growth mechanism was responsible for the growth of SnO2 branches on the SnO2 stems. 相似文献
16.
Hausmannite Mn3O4 polyhedral nanocrystals have been successfully synthesized via a simple solution-based thermolysis route using a three-dimensional hydrogen-bonded polymer as precursor. The as-obtained product was characterized by means of powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Possible formation mechanism of polyhedral nanocrystals was proposed based on the role of organic ligand dissociation from the polymer precursor at elevated temperature. The electrochemical capacitance performance of Mn3O4 electrode was investigated by cyclic voltammetry and galvanostatic charge/discharge measurements. A maximum specific capacitance of 178 F g−1 was obtained for the nanocrystals in a potential range from −0.1 to 0.8 V vs. SCE in a 0.5 M sodium sulfate solution at a current density of 0.2 A g−1. 相似文献
17.
Submicron layered LiNi0.5Mn0.5O2 was synthesized via a co-precipitation and solid-state reaction method together with a quenching process. The crystal structure and morphology of the materials were investigated by X-ray diffraction (XRD), Brunauer–Emmett and Teller (BET) surface area and scanning electron microscopy (SEM) techniques. It is found that LiNi0.5Mn0.5O2 material prepared with quenching methods has smooth and regular structure in submicron scale with surface area of 0.43 m2 g−1. The initial discharge capacities are 175.8 mAh g−1 at 0.1 C (28 mA g−1) and 120.3 mAh g−1 at 5.0 C (1400 mA g−1), respectively, for the quenched samples between 2.5 and 4.5 V. It is demonstrated that quenching method is a useful approach for the preparation of submicron layered LiNi0.5Mn0.5O2 cathode materials with excellent rate performance. In addition, the cycling performance of quenched-LiNi0.5Mn0.5O2 material was also greatly improved by AlF3 coating technique. 相似文献
18.
Synthesis of SnO2 hollow microspheres from ultrasonic atomization and their role in hydrogen sensing
Nanostructured SnO2 hollow microspheres were synthesized using ultrasonic atomization technique. It is interesting that hollow microspheres could be prepared from ultrasonic atomization technique without any aid of template and surfactant. X-ray powder diffraction (XRD) confirmed the material to be SnO2 having tetragonal structure. Average crystallite size calculated from X-ray diffractogram using Scherer's equation was found to be 8.45 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microscopic study of fine powder particles. Powder consists of hollow microspheres of average diameter of 0.58 μm as well as nanoparticles of average diameter of 6 nm. The sensors fabricated from such powder show high hydrogen (1000 ppm) response (S = 2379) under the optimized experimental conditions. Sensor performance merits, such as, high hydrogen response, high hydrogen selectivity, short response time (2 s) and quick recovery time (15 s) may be due to both nanocrystallites and hollow microspheres associated in SnO2 sensing material. The dramatic change in gas response was explained by the rapid diffusion of the target gas through the nano-porous structure of SnO2 hollow microspheres. 相似文献
19.
Well dispersed Fe3O4 nanoparticles with mean size about 160 nm are synthesized by a simple chemical method at atmosphere pressure. The products are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Raman spectrum. Electrochemical properties of the as-synthesized Fe3O4 nanoparticles as anode electrodes of lithium ion batteries are studied by conventional charge/discharge tests, showing initial discharge and charge capacities of 1140 mAh g−1 and 1038 mAh g−1 at a current density of 0.1 mA cm−2. The charge and discharge capacities of Fe3O4 electrode decrease along with the increase of cycle number, arriving at minimum values near the 70th cycle. After that, the discharge and charge capacities of Fe3O4 electrode begin to increase along with the increase of cycle number, arriving at 791 and 799 mAh g−1 after 393 cycles. The morphology and size of the electrode after charge and discharge tests are characterized by SEM, which exhibits a large number of dispersive particles with mean size about 150 nm. 相似文献
20.
Field emission from oriented tin oxide rods 总被引:1,自引:0,他引:1
Tin oxide (SnO2) films were grown on silicon substrates by a wet chemical route. It was found from scanning electron microscopy investigations that oriented SnO2 rods normal to the substrates were obtained. Field emission studies were carried out in diode configuration in an all metal ultra high vacuum chamber at a base pressure ∼ 1.33 × 10− 8 mbar. The ‘onset’ field required to draw 0.1 μA/cm2 current density from the emitter cathode was found to be ∼ 3.4 V/μm for SnO2 rods. The field emission current and applied field follows the Folwer-Nordheim relationship in low field regime. The observed results indicate that the field emission characteristics of chemically grown SnO2 structures are comparable to the vapor grown nanostructures. 相似文献