Applied Mechanics and Materials Vols. 110-116

Abstract: A nanomachine is an assembly of a discrete number of supramolecular components designed to perform mechanical like movements as a consequence of appropriate external stimuli. In this research work we wish report synthesis of a part of nanomachines are based on interlocked macrocycle named rotaxanes, catenanes, pseudorataxane and knots, that Bis aza thiacrown compound (5) was synthesized by macrocyclic diamide (4) and 2, 6-dicarbonyldicholoride pyridine in dry CH2Cl2 and was refluxed in presence of Et3N in good yield. The structures of these compounds were confirmed by IR, 1H NMR, 13C NMR and elemental analysis.

Abstract: Rubber/Ca-montmorillonite (Ca-MMT) nanocomposites with exfoliated Ca-MMT layers was prepared by a new preparation method named masterbatch method, in which the masterbatch was prepared by co-coagulating nature rubber latex and bis [3-triethoxysilylpropyl-] tetrasulfide (TESPT) modified Ca-MMT aqueous suspension and then the masterbatch accompanied with carbon black (N220) were used in the system of SBR and ENR. The properties of TESPT in-situ modified Ca-MMT were investigated by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The results showed that the TESPT has reacted with the surface groups of Ca-MMT. The dispersion of the Ca-MMT in masterbatch and vulcanized sample was characterized by X-ray diffraction. The results showed that in the masterbatch an exfoliated structure was obtained and in the vulcanized sample a coexistence of intercalated-exfoliated structure was obtained. The influence of the Ca-MMT loading on the structure and properties of the nanocomposites were studied. It was found that the incorporation of Ca-MMT hindered the vulcanization, improved mechanical properties, thermal properties and aging resistance properties. The dynamic mechanical analysis results showed a decrease of tanδ max when the Ca-MMT is added.

Abstract: Organo-montmorillonite (OMMT) was compounded with Hydrogenated Nitrile-Butadiene Rubber （HNBR）(50% epoxidation) to prepare nanocomposites by melt mixing method. The nanometer scales of organoclays in rubber matrix were determined by X-ray diffraction testing, the exfoliated/intercalated structures of OMMT in HNBR were confirmed by transmission elector microscopy. The increases in tensile module and strength of HNBR/OMMT nanocomposites vulcanizaters were caused by the better interactions between rubber macromolecule chains and organoclay layers. The air-aging properties of nanocomposites enhanced by the increasing content of OMMT, which was leaded by the barrier characterize of nanodisperse OMMT layers. DMA test showed that the Tgs of HNBR/OMMT shifted to a higher temperature, as verified by the crosslinking density determination.

Abstract: The strong local property of surface plasmon polaritons can break through the diffraction limit, and reduce the propagation of corner scattering on nanoscale. The nanoantenna structure based on the plasmon resonant effect can collect the light energy effectively, and the local field enhancement effects of the structure have extensive application prospect. The field distribution and field enhancement effects of optical antenna under nanoscale are calculated with finite-difference time-domain (FDTD) method. Several different structures of nanooptical antenna are studied, and their enhancement properties are compared in this paper.

Abstract: Carbon nanotube has attracted tremendous scientific and industrial interests due to its exceptional mechanical, electrical and thermal properties. In this paper, classic molecular dynamic simulations are carried out to investigate the buckling behaviors and mechanical properties of single-walled carbon nanotubes under axial compression, both for perfect and imperfect ones introducing atomic vacancies. The effect of chirality, diameter, quantity and position of vacancy are systematically studied. The simulation results reveal that their mechanical properties such as Young’s modulus, critical strain and stress suffering a significant decline as the increasing numbers of vacancies. It is also found that the critical stress and strain are sensitive to position of atomic vacancy. Carbon nanotubes with vacancies located at the center have lower critical strain and are easier to reach the failure stage than those with vacancies at both sides.

Abstract: In this study, we report the fabrication and characterization of a novel nanohetero junction structure (NHJ) UV photodetectors (PDs) on flexible polyethylene terephthalate (PET). The ZnO nanowires (NWs) were grown by 2-step hydrothermal growth (HTG) onto p-type nickel oxide (p-NiO) film deposited PET flexible substrate. For enhancing the quality and reliability of the fabricated UV PDs, the PET substrate was treated with a beforehand thermosetting process to refine its toughness and flatness. By switching the illumination UV light “on” and “off”, the fabricated UV PDs biased under-5 V have an on-off current ratio of 16. After over 100 times 90^o bend, the transient measurement almost has the same reversibility but on-off current ratio reducing to 10. These results suggest that the proposed n-ZnO-NWs/p-NiO NHJs on PET flexible PET substrate not only have a fairly good response to UV light but also have good endurance within suitable bend. The present optoelectronic UV sensor would provide an effective and simple way for future developments of flexible optoelectronic devices.

Abstract: Beta-spodumene glass-ceramic powder was prepared by Sol–gel route. Tetraethyl orthosilicate (TOES), aluminum nitrate, lithium carbonate were used as starting materials. X-ray powder diffraction (XRD), thermal expansion coefficient (TEC), scanning electron microscope (SEM) and transmission electron microscope (TEM) were utilized to characterize the dried LAS gels and glass-ceramic blocks. The results suggest beta-spodumene is the only crystals phase in the prepared LAS glass-ceramics powder when sintering temperature is 950 °C. The average particle size of the beta-spodumene crystal is about 30 nm with a narrow size distribution both in prepared LAS glass-ceramics powder and block. The thermal expansion coefficient of moulding pressed blocky LAS glass-ceramics is lower than 0.6×10^{-6 o}C^-1.

Abstract: The purpose of this project is to study the nanotechnology researchers’ information needs and information retrieval behavior. Its Methodology is questionnaire survey. Research instrument was a researcher-made questionnaire whose reliability was calculated through Cronbach α (α= 0,914) and whose content validity was analyzed and approved through expert opinions.1225 researchers in nanotechnology are included as the research population out of whom 291 researchers, based on Krejcie and Morgan table, were selected using cluster random sampling method. Out of distributed questionnaires (500), 243 of them (84% of the sample) were returned completed. Statistical analyses were carried out in SPSS and Excel environments. The results of research indicate that, 69.7 % researchers mainly use articles, 58.8 % of them e-journals, and a few of them use bibliographies as formal sources. Their ideal type of resource is e-resources. Their motives to use information are mainly conducting research projects and updating their field-related information. Academic centers are where they usually refer to address their information needs. The major problems to access information are inappropriate internet services and lack of access to certain data bases due to subscription issues.

Abstract: The construction industry uses concrete to a large extent. currently, the most active research areas dealing with cement and concrete are: understanding of the nanostructural properties of cement and the use of nano–particles, here, Ti nanoparticles in these mixtures. We have synthesized nanoparticles with sol-gel method at 500°C in ambient media and studied their nanostructures with using SEM (scanning Electron Microscopy) technique. The obtained results show that nanosilica can make more stable structure of concrete and/ or cement mixtures.

Abstract: Using the resistive heated method, TiO₂/Ag/TiO₂ thin files (Transparent heat windows) in vertical deposition angle were deposited on SiO₂ substrate, in high vacuum (HV) condition and 100°c. The thickness of TiO₂ on glass substrate was 50°A, Silver film 125°A and 225°A and the upper layer TiO₂ with 115°A. All other deposition conditions were same for both samples .Atomic force microscope (AFM), and spectrophotometric methods were used to study the nanostructures of these samples in the range of FTIR. The purpose of this work is to find and produce the structure with the least energy waste.