Advanced Materials Research Vol. 771

Abstract: Under the generalized gradient approximation (GGA), the structural and electronic properties of armchair GaN nanoribbons with AlN edges have been investigated by using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. The results reflect that the band gaps of the armchair GaN nanoribbons (AGaNNRs) are vibrated with the increasing ribbon width. For Al, Ga, H and N atom, the successively increasing electronegativity of 3.04, 2.1, 1.81 and 1.61 causes the successive increase of the charge density. These results are very useful for the applications of the AGaNNRs.

Abstract: The objective of this work is to study the viscoelastic properties by which nanofillers produce mechanical reinforcement in polymers using dynamic mechanical analysis (DMA). To this purpose, waterborne polyurethane (WBPU) and cellulose nanocrystals (CNCs) composites films with various filler contents were prepared by ultrasonic dispersion followed by emulsion casting process. In frequency sweep tests, the storage modulus and loss modulus were recorded and modeled by the Power Law equation. CNCs precipitation significantly increased the steady state viscous properties of cellulose nanocoposite films but decreased the dynamic viscoelastic properties and frequency sensitivity of nanocomposite films.

Abstract: Nano-rods hydroxyapatite (HA) was synthesized by hydrothermal method using Ca(NO₃)₂·4H₂O and H₃PO₄ as precursors and cationic surfactant (CTAB) as a template. The effect of pH value and reaction temperature on the phase and morphology of HA were investigated. HA samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that high pH values resulted in high purity of HA. HA morphology changed from irregular round shape to nano-rod shape with the increase of the reaction temperature from 80°C to 120°C. The prepared HA was utilized as adsorbent to remove copper ion from aqueous solution. The adsorption results showed that nano-rod HA had a rapid Cu²⁺ adsorption rate and good removal efficiency (>99%).

Abstract: An experimental study of oxidation of nano aluminum (Al) powders in CO₂ and O₂ is described. The oxidation is studied using thermogravimetric (TG) measurements from room temperature to 1500°C. Partially oxidized samples are recovered and their compositions are analyzed using X-ray diffraction. The oxidation product morphology was examined using SEM. Dimensional properties of aluminum particles have a significant influence on the oxidation processes. The nano aluminum reaction onset temperature was much lower than micro aluminum. Distinctly different oxidation properties of nano aluminum powders were shown between CO₂ and O₂. nano aluminum powders could ignite in O₂ at fairly low temperatures around 530 °C. However ignition for nano aluminum powders in CO₂ didn't appeared below 1500 °C. There was a weight loss in the TG curves at around 1200 °C for nano Al-CO₂ system. It was thought that small amount of carbon formed in the oxidation process. The XRD showed that both the nano aluminum oxidation products were α-Al₂O₃ in CO₂ and O₂.

Abstract: Nanotechnology has heralded the advent of next major techno-paradigm shift that will have pervasive impacts on a wide-range of high-tech sectors. International collaboration will exert important influences over the development of nanotechnology. Patents encompass valuable technological information and collaborative efforts. Therefore, this paper studies international collaboration of nanotechnology from the perspective of patent analysis. The results show that encouraged by the rapid development and ardent enthusiasm for nanotechnology globally, internationally collaborative nanotechnology patents grow steadily. The share of internationally collaborative patents in the world increases from 3.70% in 1991 to 6.52% in 2010. Among the top 20 countries/regions owning nanotechnology patents, the U.S. has the largest number of patents and internationally collaborative patents. However, the share of internationally collaborative patents in the whole U.S. patents is relatively low, which is below 10%. Such is also the case in Japan, South Korea and Taiwan. In the other countries, the domestic share of internationally collaborative patents varies, ranging from less than 20% to more than 50%. The highest domestic share of internationally collaborative patents (56.1%) is found in Russia. International collaboration in the field of nanotechnology has yet found globally significant in terms of patent quantity, it does nevertheless play an active role in the improvement of citation impacts of nanotechnology patents for most of the top 20 countries, especially China.

Abstract: Aqueous nanofluids composed of SiO₂ nanoparticles with different sizes (15 nm, 30 nm, 50 nm) at a low volume concentration were prepared by a two-step method. The suspension and dispersion characteristics were experimentally examined by the zeta potential, average size and absorption spectrum. The thermophysical properties, such as viscosity, thermal conductivity, surface tension and latent heat of vaporization were experimentally measured. A lot of thermophysical data of SiO₂ nanofluids were obtained. The influences of the particle size, particle volume concentration and temperature on thermophysical properties were discussed briefly.

Abstract: Lock-in Amplifier is very useful in many weak signals processing systems. To lower down the system cost and to raise the speed of the system, a digital Lock-in Amplifier processor with nanosize electronic technology based on FPGA chip and the algorithm appropriate for hardware to implement was introduced. The frequency of the signal which can be lock-in amplified by the processor is up to 158 KHz, and the error in the experiment is less than 1.27. Also, the cost of the system is much lower than the system scheme based on DPS chips.

Abstract: The n-ZnO nanorods/p-Si nanowires heterojunction was fabricated by chemical method. The microstructure of the epitaxially grown ZnO nanorod was characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The photoluminescence of the nanostructure showed a typical UV emission band and a defect-related emission band. Further, the electroluminescence of the nanostructure were measured, and the mechanism was discussed based on the band diagram of the n-ZnO nanorods/p-Si nanowires heterojunction.

Abstract: This paper reports a surface functional polymer- poly(N-isopropylacrylamide) (PNIPAM) was grafted on the surface of zinc oxide (ZnO) nanoparticles. It has been demonstrated that Reversible addition fragmentation chain-transfer (RAFT) agent was successfully grafted onto the surface of ZnO. PNIPAM chains were successfully grafted from the surface of ZnO via RAFT process by using RAFT agent immobilized on ZnO. The effect of surface modification on the size, structure, morphology, and properties of ZnO nanoparticles was investigated. The thickness of a PNIPAM monolayer bound to the ZnO core is somewhat larger than the size of the random coil of the corresponding free PNIPAM in aqueous solution, which suggests that the conformation of a PNIPAM chain bound to the ZnO core is extended.

Abstract: To better master the development law of flight safety for flight materials, the spectral analysis method is introduced to analyze the cycle fluctuation of flight accident for flight materials. The basic principle of spectrum analysis of cycle fluctuation is first introduced, and then the calculation method of spectral density function is given. The actual example of flight accident shows that the method is an effective and feasible for analyzing the cycle fluctuation of flight accident. The research also has both theoretical and applicable value of flight safety management for flight materials.