106 research outputs found
Aluminum- and Iron-Doped Zinc Oxide Nanorod Arrays for Humidity Sensor Applications
Metal-doped zinc oxide (ZnO) nanorod arrays have attracted much attention due to improvement in their electrical, structural, and optical properties upon doping. In this chapter, we discuss the effects of aluminum (Al)- and iron (Fe)-doping on ZnO nanorod arrays properties particularly for humidity sensor applications. Compared to Fe, Al shows more promising characteristics as doping element for ZnO nanorod arrays. The Al-doped ZnO nanorod arrays showed dense arrays, small nanorods diameter, and high porous surface. The I-V characteristics showed that Al-doped sample possesses higher conductivity. From the humidity sensing performance of the samples, Al-doped ZnO nanorod arrays possess the superior sensitivity, more than two times higher than that of the undoped ZnO nanorod arrays sample, demonstrating great potential of Al-doped ZnO nanorod arrays in humidity sensor applications
Synthesis of Titanium Dioxide Nanorod Arrays Using a Facile Aqueous Sol-Gel Route for Ultraviolet Photosensor Applications
In this chapter, we review the state of the art of aqueous sol-gel route for ultraviolet (UV) photosensor applications based on the nanostructured TiO2. The performance of UV photosensor is associated with the high surface-to-volume ratio, porosity, surface defects, light trapping, and the intensity of the UV radiation. One-dimensional (1D) growth of TiO2 nanorod arrays (TNAs) offers an enhance charge carrier mobility to overcome the photocurrent loss due to the existence of multiple grain boundaries in granular-like and porous nanostructures. Photoelectrochemical cell (PEC)-based device structure is preferred in TNA-based UV photosensor due to its low cost, facile fabrication process, high contact area, low recombination of the excitonic charge carriers, high photocurrent gain, and fast response and recovery times. It also could work in applied bias mode, as well as in “self-powered” mode. Our study has introduced a new one-step method to deposit a thin film TNA on an FTO-coated glass substrate at low temperature and a rapid process using a facile glass container. The fabricated PEC-based UV photosensor using the deposited TNAs has successfully shown its potential in the application of UV photosensor
A Study on the Expropriation Behavior of Controlling Shareholders of China’s Listed Companies
传统的公司治理理论研究的是在贝利-米恩斯式的公司中解决股东与经理层之间的利益冲突,设计一种激励约束兼容的制衡机制使得经理层的行为符合公司及股东利益最大化的要求。但是20世纪80年代,学者们发现相对集中或高度集中的股权结构是许多国家上市公司的主要特征,公司治理的主要矛盾已经转变为控制性股东与中小股东之间的利益冲突。我国上市公司控制性股东通过控制股东大会及董事会进而侵害中小股东及上市公司利益的事例时有发生,并日益受到广泛的关注。因此,弄清控制权这一具有巨大价值的权力在公司治理中所起到的作用,设计一种制衡控制性股东利益的制度,与解决所有权与经营权的委托代理关系同等重要。这是完善公司治理,建立现代企业...The principal-agent relation between managements and shareholders used to be the focus of the study on corporate governance in those companies whose ownership were dispersive.However,the results of some newly research show that most listed companies’ ownership structures are relatively concentrative in many countries over the world, which results in interest conflict between the controlling shareh...学位:经济学硕士院系专业:经济学院经济系_经济思想史学号:1532006115078
ZnO Nanorod Arrays Synthesised Using Ultrasonic-Assisted Sol-Gel and Immersion Methods for Ultraviolet Photoconductive Sensor Applications
Thermomechanical Properties of Jute/Bamboo Cellulose Composite and Its Hybrid Composites: The Effects of Treatment and Fiber Loading
Jute cellulose composite (JCC), bamboo cellulose composite (BCC), untreated hybrid jute-bamboo fiber composite (UJBC), and jute-bamboo cellulose hybrid biocomposite (JBCC) were fabricated. All cellulose hybrid composites were fabricated with chemical treated jute-bamboo cellulose fiber at 1 : 1 weight ratio and low-density polyethylene (LDPE). The effect of chemical treatment and fiber loading on the thermal, mechanical, and morphological properties of composites was investigated. Treated jute and bamboo cellulose were characterized by Fourier transform infrared spectroscopy (FTIR) to confirm the effectiveness of treatment. All composites were characterized by tensile testing, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Additionally, surface morphology and water absorption test was reported. The FTIR results revealed that jute and bamboo cellulose prepared are identical to commercial cellulose. The tensile strength and Young’s modulus of composites are optimum at 10 weight percentage (wt%) fibers loading. All cellulose composites showed high onset decomposition temperature. At 10 wt% fiber loading, JBCC shows highest activation energy followed by BCC and JCC. Significant reduction in crystallinity index was shown by BCC which reduced by 14%. JBCC shows the lowest water absorption up to 43 times lower compared to UJBC. The significant improved mechanical and morphological properties of treated cellulose hybrid composites are further supported by SEM images
Synthesis of zinc oxide nanostructures on graphene/glass substrate by electrochemical deposition: effects of current density and temperature
The electrochemical growth of zinc oxide (ZnO) nanostructures on graphene on glass using zinc nitrate hexahydrate was studied. The effects of current densities and temperatures on the morphological, structural, and optical properties of the ZnO structures were studied. Vertically aligned nanorods were obtained at a low temperature of 75°C, and the diameters increased with current density. Growth temperature seems to have a strong effect in generating well-defined hexagonal-shape nanorods with a smooth top edge surface. A film-like structure was observed for high current densities above -1.0 mA/cm2 and temperatures above 80°C due to the coalescence between the neighboring nanorods with large diameter. The nanorods grown at a temperature of 75°C with a low current density of -0.1 mA/cm2 exhibited the highest density of 1.45 × 109 cm-2. X-ray diffraction measurements revealed that the grown ZnO crystallites were highly oriented along the c-axis. The intensity ratio of the ultraviolet (UV) region emission to the visible region emission, IUV/IVIS, showed a decrement with the current densities for all grown samples. The samples grown at the current density below -0.5 mA/cm2 showed high IUV/IVIS values closer to or higher than 1.0, suggesting their fewer structural defects. For all the ZnO/ graphene structures, the high transmittance up to 65% was obtained at the light wavelength of 550 nm. Structural and optical properties of the grown ZnO structures seem to be effectively controlled by the current density rather than the growth temperature. ZnO nanorod/graphene hybrid structure on glass is expected to be a promising structure for solar cell which is a conceivable candidate to address the global need for an inexpensive alternative energy source
Palm oil as the carbon source for the synthesis of carbon nanotubes using floating catalyst - chemical vapour deposition method
CNTs were synthesized using floating catalyst by dual‐furnace thermal chemical vapour deposition method at 800–1000° C. Cooking oil made of palm oil was used as the carbon precursor. Ferrocene in the presence of 0.05 M zinc nitrate and a p‐type silicon wafer was used as a catalyst precursor and a sample target, respectively. The deposition temperature was varied from 800–1000° C. Nitrogen gas was used as a gas carrier with a constant flow rate of 150 sccm/min. Field emission scanning electron micrographs show the formation of CNTs together with other carbons formed on the silicon substrate. Raman spectroscopy studies were also supported the formation of CNTs
Effect of Growth Pressure on Structural Properties of SiC Film Grown on Insulator by Utilizing Graphene as a Buffer Layer
Heteroepitaxial growth of silicon carbide (SiC) on graphene/SiO2/Si substrates was carried out using a home-made hot-mesh chemical vapor deposition (HM-CVD) apparatus. Monomethylsilane (MMS) was used as single source gas while hydrogen (H2) as carrier gas. The substrate temperature, tungsten mesh temperature, H2 flow rate and distance between mesh and substrate were fixed at 750 °C, 1700 °C, 100 sccm and 30 mm, respectively. The growth pressures were set to 1.2, 1.8 and 2.4 Torr. The growth of 3C-SiC (111) on graphene/SiO2/Si were confirmed by the observation of θ-2θ diffraction peak at 35.68°. The diffraction peak of thin film on graphene/SiO2/Si substrate at pressure growth is 1.8 Torr is relatively more intense and sharper than thin film grown at pressure growth 1.2 and 2.4 Torr, thus indicates that the quality of grown film at 1.8 Torr is better. The sharp and strong peak at 33° was observed on the all film grown, that peak was attributed Si(200) nanocrystal. The reason why Si (200) nanocrystal layer is formed is not understood. In principle, it can’t be denied that the low quality of the grown thin film is influenced by the capability of our home-made apparatus. However, we believe that the quality can be further increased by the improvement of apparatus design. As a conclusion, the growth pressures around 1.8 Torr seems to be the best pressures for the growth of heteroepitaxial 3C-SiC thin film
Thermomechanical Properties of Jute/Bamboo Cellulose Composite and Its Hybrid Composites: The Effects of Treatment and Fiber Loading
Jute cellulose composite (JCC), bamboo cellulose composite (BCC), untreated hybrid jute-bamboo fiber composite (UJBC), and
jute-bamboo cellulose hybrid biocomposite (JBCC) were fabricated. All cellulose hybrid composites were fabricated with chemical
treated jute-bamboo cellulose fiber at 1 : 1 weight ratio and low-density polyethylene (LDPE).The effect of chemical treatment and
fiber loading on the thermal, mechanical, and morphological properties of composites was investigated. Treated jute and bamboo
cellulose were characterized by Fourier transform infrared spectroscopy (FTIR) to confirm the effectiveness of treatment. All
composites were characterized by tensile testing, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).
Additionally, surface morphology and water absorption test was reported.The FTIR results revealed that jute and bamboo cellulose
prepared are identical to commercial cellulose. The tensile strength and Young’s modulus of composites are optimum at 10 weight
percentage (wt%) fibers loading. All cellulose composites showed high onset decomposition temperature. At 10 wt% fiber loading,
JBCC shows highest activation energy followed by BCC and JCC. Significant reduction in crystallinity index was shown by BCC
which reduced by 14%. JBCC shows the lowest water absorption up to 43 times lower compared to UJBC. The significant improved
mechanical and morphological properties of treated cellulose hybrid composites are further supported by SEM images
Heterogeneous SnO2/ZnO nanoparticulate film: Facile synthesis and humidity sensing capability
Highly sensitive and extremely thin tin oxide/zinc oxide (SnO2/ZnO) heterojunction films were prepared via a two-step solution-based method for humidity-sensing application. The average diameters of the ZnO and SnO2 nanoparticles were 26 and 6 nm, respectively. The deposition of SnO2 for 3 min reduced film resistance from 6.74 MΩ to 0.40 MΩ. Remarkably, the humidity-sensing performance of the heterojunction sensors was critically dependent on deposition time, and sensors subjected to 3 min deposition exhibited the highest sensitivity (90.56) to humidity, which was significantly higher than that of bare ZnO. This study indicates that the use of SnO2/ZnO heterojunction has a great potential in humidity sensing applications
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