Materials Science and Nanotechnology I

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Authors: Zhi Juan Zhang
Abstract: The effects of Ce0.8Gd0.2O2-δ (CGO) doped manganese oxide as sintering additive on density and conductivity were studied. The experimental results indicated that relative density of CGO doped 2.0 mol% MnO1.333 (2Mn-CGO) increased within a certain temperature range because of the occurrence of viscous flow sintering, it was 89.5% at the sintering temperature of 1100 oC and higher 6.8% than that of CGO. Moreover, it can reach 91.1% for 2Mn-CGO at the sintering temperature of 1200 oC. The conductivity measured at 700 oC of 2Mn-CGO sintered at 1100 oC was 4.52×10-2 S/cm, which is higher than that of CGO. The value of 2Mn-CGO with the sintering temperature of 1200 oC was 5.24×10-2S/cm, which dropped slightly than that of CGO, this was caused by blocking of the migration of carriers.
362
Authors: Xing Guan Ma, Wen Juan Ji, Jun Ping Sun, Xiang Xin Xue, He Yang, Jin Xiang Fu
Abstract: Under the unique long-time low temperature conditions (average 8°C) of the northern winter in China, the effects of temperature on water quality and the performance of Powder activated carbon-I Membrane biological reactor (PAC-IMBR) were studied and demonstrated quantitatively by the NH4+-N value, chemical oxygen demand (CODCr) and transmembrane pressure (TMP). The results showed that the supernatant NH4+-N decrease from 1.20 mg·L-1 to 0.81 mg·L-1 with the temperature rising from 8°C to 20°C, while 30.8 mg·L-1 to 23.1 mg·L-1 for the CODCr. However, the temperature rising have no marked influence on the effluent NH4+-N and CODCr due to the filtration of membrane. TMP was measured to characterize membrane fouling and it is clear that the TMP and its increasing rate descend with the temperature rising, which demonstrates that the raising temperature is advantageous to prolong the cycle of PAC-IMRB and alleviate the membrane fouling.
368
Authors: Hai Bo Feng, Yi Qing Chen, Liang Chi Zhang
Abstract: This paper investigates the applicability of the dynamic friction polishing (DFP) technique to process the chemical vapour deposition (CVD) diamond surfaces. Two types of CVD diamond specimens were studied. A stepwise polishing process was introduced to minimise the cracking in CVD thin films. The investigation focused on the polished surface quality in relation to the polishing conditions and material remove rates. It was found that by selecting proper polishing parameters, surfaces of quality finish with a roughness of less than 70 nm Ra could be obtained in 15 minutes when the specimens were CVD diamond wafers with an initial roughness of 17 μm. The polishing time could be reduced to only 2.5 minutes in the case of diamond thin film specimens of initial roughness of 1.6 μm.
373
Authors: Guang De Li, Chang Rui Zhang, Hai Feng Hu, Yu Di Zhang, Si’an Chen, Xin Bo He, Min Mei
Abstract: C/SiC substrates and M3 bolts were prepared by precursor infiltration and pyrolysis (PIP) process firstly, then the joints with four joining methods (2 φ3mm soft pins, S-A; 2 M3 bolts, S-B; 2 φ3mm soft pins plus 8 φ1mm soft pins, S-C; 2 M3 bolts plus 8 φ1mm soft pins, S-D) were assembled, finally several PIP cycles were continued to finish densification. The influences of different joining methods and PIP cycles (3 or 6) on the stripping properties of C/SiC joints were investigated, and the fracture modes were analyzed. The stripping loads of the joints adopting 6 PIP cycles are almost two to six times the values adopting 3 PIP cycles, and the corresponding fracture modes are pins or bolts rupture and pull-out, respectively. When adopting 3 PIP cycles, the bearing ability of the joints with bolts (S-B and S-D) is about 51% higher than that of joints with pins (S-A and S-C), but when adopting 6 PIP cycles, the values with pins (S-A and S-C) is about 67% higher than that with bolts (S-B and S-D). Besides, the introduction of φ1mm pins enhances the bearing ability of the joints with 3 and 6 PIP cycles about 45% and 14%, respectively.
377
Authors: Gang Peng, Xiao Yan Yu, Ying Qiu Zhou, Guang Wang, Li Wang, Yan Lan He
Abstract: The desorption process for ambient atmosphere on electrical transport properties of bilayer graphene FET grown by CVD methods on SiO2/Si substrate was investigated in room temperature. With increasing the vacuum time of the device underwent, we found that the voltage of Dirac point decreased, the mobility of hole (electron) increased and the charged impurity density decreased. The results suggest that the atmospheric adsorbates (mainly oxygen and water molecules) are strongly influence the electrical transport properties of graphene FET.
383
Authors: Qiu Fang Wu, Si Si Wang, Feng Lan Yao, Chun Mei Zhang, Mi Dan Li
Abstract: The well-aligned nanoflower and nanorod films were synthesized using zinc acetate- sodium hydroxide aqueous solutions at different growth temperature. These microstructures were characterized with field emission scanning electron microscopy and the X-ray diffraction. The predominant c-axis growth of hexagonal lattice was observed in the ZnO films, and the growth temperature was found to play an important role in controlling the morphology of ZnO films. Mechanism of formation of varying morphologies was discussed.
388
Authors: Jie Song, Yan Qing Guo, Chao Song, Xiang Wang
Abstract: Since the visible photoluminescence (PL) in porous Si was observed by Canham, much attention has been paid to the light emission from silicon-based materials. In this work, luminescent amorphous silicon nitride films were prepared by very-high-frequency plasma enhanced chemical vapor deposition technique using ammonia, silane and hydrogen as source gases at a low temperature of 50 °C. It is found that the films exhibit strong visible light emissions with ranging from green to red region. Photoluminescence spectra show that the emission peaks as well as intensity strongly depends on the flow rates of ammonia. Combining with the analyses of Fourier transform infrared absorption spectra and the transmission spectra, it is suggested that the light emissions are originated from the radiative recombination in the band-tail states of amorphous silicon nitride.
392
Authors: Li Chun Hu, Hong Wei Zhao
Abstract: A series of bulk polycrystalline samples of La0.6Sr0.15Na0.10.15MnO3( represents vacancy)with Ag addition were prepared by conventional Sol-gel reaction processing in air.The mol proportion between La0.6Sr0.15Na0.10.15MnO3 and Ag is 1:x (x=0.00,0.016,0.04,0.1). This article focuses on the impact of Ag doping on the parent structure, magnetic properties and magnetoresistance. We have gotten the following experimental results:X-ray diffraction patterns show that a weak Ag phase appears when ;The Curie temperature of the doped samples is higher than that of the matrix sample and it reduces as x increases. The resistivity of the doped samples is bigger than that of the parent sample in zero field and it increases as x increases.In a quite wide temperature range (207K-286K), MR maintains the value of 5.08% (0.20%) when x=0.04. So the CMR temperature stability has been improved.
396
Authors: Wen Chao Dan, Ya Dong Jiang, Hui Ling Tai, Guang Zhong Xie, Xian Li, Chang Jie Fu, Ze Wu
Abstract: The pure conducting polymer P3HT film is less sensitive to the formaldehyde (HCHO), and the pure ZnO film needs a high temperature to militate the HCHO, as a result, the P3HT/ZnO composite was fabricated on the organic thin film transistor (OTFT) by spraying to detect the HCHO at room temperature, the electrical properties and sensing properties of all the prepared OTFT devices were measured by Keithley 4200-SCS source measurement unit. What is more, the effect of different P3HT/ZnO composite masses on the response of sensors were tested, all the sensors showed a remarkable response to HCHO, and the optimized composite mass of 1.0ml was obtained. Since most detecting methods for the HCHO vapor require an high temperature, the experiments and results in this paper showed the important significance for the field of HCHO detecting.
400
Authors: Tomáš Pospíšil, Jan Pěnčík, Libor Matějka, Libor Matějka, Alena Kalužová, Darina Dostálová
Abstract: In the process of sustainable construction is the emphasis placed on saving energy, reducing use of natural resources, increase the life cycle of materials by recycling, etc. Rising energy prices put increasing emphasis of builders and investors to better solution of thermal bridges. Solution can be done using a conventional materials, but also advanced materials meet the requirement of a sustainable construction and a reducing consumption of natural resources and extending of the life cycle of material. An example of such material is the thermal insulation composite material. This new developed material with low coefficient of thermal conductivity below the value of 0.100 W/mK is made of recycled waste polymer and recycled filler in the form of granules from recycled glass. In the paper are compared two variants of solution of thermal bridge under the opening in the cladding. In the first variant a wooden door opening in the perimetral cladding is deposited on a support structure for a doors threshold made of a thermal insulation composite material. In the second variant is used a lower shaped brick block. The variants of different foundation of a wooden door opening are compared in terms of a lowest surface temperature and of a temperature factor of the inner surface fRsi and its critical value fRsi,cr according to ČSN 73 0540-2 and ČSN EN ISO 10211.
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