Materials Science Forum Vol. 848

Abstract: By using Zr_6.5(Sb₂Te₃)_93.5 film, Te nanowires with a diameter of 5 to 30 nm were fabricated through annealing process. The results of the bright field TEM images, selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM) demonstrated that the nanowire fitted well with Te hexagonal Te (P3₁21) structure. The EDS mapping implies that Zr element bonded with Te element and induced the formation of single crystalline Te nanowire during the annealing process.

Abstract: In this paper, structures and electronic properties of atomic chains with 5 to 20 silicon atoms and different atomic distances (d = 1.652 ~ 2.752Å) were calculated by the tight-binding method based on density functional theory. The results showed that the majority of the silicon atomic chains were symmetrical structures. When the number of silicon atoms was small, the silicon atomic chains were linear, when the silicon atomic chains had seven or more silicon atoms zigzag structures appeared. With the increase of the distance between atoms, atomic chains were gathering. When the number of silicon atoms was between 10 and 20, the charges on the silicon atoms appeared as a symmetrical distribution. With the increase of the number of atoms, the energy of silicon atomic chains decreased gradually. As the distance between atoms and atomic number changed, HOMO (highest occupied molecular orbital electrons) -LUMO (lowest unoccupied molecular orbital electrons) energy gap changed as well.

Abstract: Ti-Ga co-doped ZnO (GTZO) ceramic targets were prepared by sintering in air at l300°C for 3 h. The morphologies, structure, densification behavior, mechanical and electrical properties of the sintered ceramic targets with different doping concentration were investigated. The optimal doping concentration was obtained. The results indicated that the sintered GTZO targets with total co-doping amount of 2wt% (1wt% Ga₂O₃ and 1wt% TiO₂) had the best properties combination, which was corresponding to an electrical resistivity of 1.56×10^-3Ω·cm, a relative density of 99%, a Vickers hardness of 378MPa and a bending strength of 99.4 MPa. The sintered targets were then used to deposit GTZO thin film by pulsed laser deposition. The electrical resistivity of the GTZO thin film achieved 3.78×10^-3 Ω·cm, and the optical transmittance was above 85% in the visible light region. This kind of GTZO ceramic has a potential to be used as a high-quality sputtering target to deposit ZnO-based transparent conductive films with good optical and electrical properties.

Abstract: The synthesis of silicon microspheres is of outmost importance, especially for the production of optical and electrical devices due to their unique properties displayed by this material. In this paper, we review the research on the synthesis of silicon microspheres, including one physical method, the drop method and several chemical methods, such as vapor-phase reaction, vapor-solid reaction, liquid phase reaction and magnesio-thermal reduction method. The formation mechanisms for silicon microsphere particles are also summarized.

Abstract: The n-type Cu₂O films were deposited on ITO substrate by three-electrode electrochemical deposition method in a CuSO₄-lactic acid electrolyte. The effects of electrolyte pH, bath temperature, and annealing treatment on films’ conductivity and their photoelectrochemical activity were investigated by X-ray diffraction (XRD), photocurrent (I-t) and mott-schottky (M-S) plots. The results show that the n-type Cu₂O could be electrodeposited at electrolyte pH of 8.5, 9 and 10, and the electrolyte temperature did not change the films’ conductivity. The highest n-type photocurrent density of 0.014 mA /cm² and carrier concentration of 2.3×10¹⁹ cm^-3 was obtained when the electrolyte pH was 8.5 and the bath temperature was 60°C. With increasing annealing temperature from 150°C to 400°C, the photocurrent density and carrier concentration of n-type Cu₂O thin films correspondingly increased, indicating that heat treatment is helpful to improve the photoelectrochemical activity.

Abstract: A well-defined poly [(ethylene glycol)-block-2-(dimethylamino) ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEG-b-DMA-b-DEA) triblock copolymer was synthesized via atom transfer radical polymerization (ATRP) by successively polymerization of DMA and DEA monomers using a PEG-based macroinitiator, and obtained copolymer was then converted to be PEG-b-P(DMA-co-QDMA)-b-PDEA copolymer with “clickable” moieties in the middle block by the quaternization with propargyl bromide. Those copolymers prepared were characterized by proton Nuclear Magnetic Resonance (¹H NMR) and Gel Permeation Chromatography (GPC), and its self-assembly behavior and subsequently fixation with bis-(azidoethyl) disulfide via click chemistry resulting reduction-sensitive shell-cross-linked (SCL) micelle in purely aqueous solution were investigated by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The results show the micellar structure could be effectively cross-linked via click chemistry and also be dissociated at reduction condition, which may realize it's potential application as novel drug delivery carriers.

Abstract: Titanium and its alloys have been widely used as implants replacing hard human tissues in biomedical fields. To improve the stability of implants in the surrounding bone tissues, the materials with porous structures were fabricated. In this paper powder metallurgy technique was employed to fabricate porous Ti-39Zr-6Nb (wt.%) alloys. The porous structures and mechanical properties of the porous alloys were examined by scanning electron microscopy (SEM) and compressive tests. The results showed that with increasing the sintering temperature the porosity of the alloys decreased and the compressive strength and the elastic modulus increased. The porosity of the alloys was in the range from 20.8% to 23.2%, and the pore sizes mostly centered in 10~30μm. The compressive strength and the elastic modulus were in the range from 110.4 to 292.4MPa and 4.7 to 12.4GPa respectively, which was close to human bone.

Abstract: In our previous work, silver nanoparticles (AgNPs) with ultrasmall sizes (4.3 ± 0.7 nm) can be in-situ obtained within the poly (vinyl alcohol) (PVA) fibers by mediating the electro-spun conditions. The obtained AgNPs “trapped” within the electro-spun PVA nanofibers were believed to be stable in the dry state, as the abundant PVA molecules could protect the dispersed AgNPs from agglomerating with each other. In this study, based on former study, aging tests about the nanohybrid mats were performed. Through ATR-FTIR spectra analysis, the formation mechanism of AgNPs within the PVA nanofiber by one-step electro-spun was confirmed. Atomic Absorption Spectroscopy analysis of the as-prepared PVA-Ag samples was performed in 14 h and the release of Ag⁺ was believed to be the main cause of its bactericidal effects. Scanning electron microscopy and transmission electron microscopy were used to characterize the nanofibers with AgNPs. After 4-month storage, the size of AgNPs doped in the PVA nanofiber became twice larger and the content of AgNPs was almost doubled.

Abstract: The aim of the current study was to improve the knowledge of the gelation process of injectable thermosensitive hydrogels comprising chitosan (CS) and β-glycerophosphate disodium salt (β-GP). The sol-gel transition process was precisely tracked by means of rheological measurement, in which the viscosity changed considerably with gelation time and temperature. The zero-order kinetics model was assumed to adequately describe the extent of gelation reaction. The reaction rate constant increased continuously with the increasing temperature and β-GP concentration. According to Arrhenius equation, the activation energies of gelation reaction for the chitosan injectable hydrogels were calculated as 64.38 KJ/mol, 101.68 KJ/mol and 140.92 KJ/mol for the samples containing 4% w/v, 6% w/v and 8% w/v of β-GP, respectively. It could be an effective way to study the gelation dynamics of injectable hydrogels, and provide references for clinical practice.

Abstract: Dendrimers and carbon nanotube took an important role in transport and delivery of drugs, gene, et al, however, to improve its functional properties is still a great challenge. Carbon nanotube not only has good biocompatibility but also hold optical adsorption in NIR. In biomimetic and biomedical fields, nanorobots or nanocarriers with external stimuli response for removal the organic pollutants and toxins or drugs in the living body are attractive for research and applications. In this paper, the self-assembly with CNTs containing –COOH and dendrimers having –NH₂ groups was carried out. A series of characterizations were performed by SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (X-ray diffraction), and Fourier-Transform Infrared (FTIR) spectra. The adsorption properties and releasing characteristics of CNTs modified with dendrimers were performed with simulating drugs. Some meaningful results were obtained. The photoconductivity response to visible light and 808 nm laser with low-power were studied based on interdigital electrodes of Au on flexible PET(polyethylene terephthalate) film substrate. The results indicated that CNTs modified with dendrimers showed good photo-response to visible light and 808 nm laser. It would be developing smart nanorobots with external stimuli response for removal the organic pollutants and toxins or drugs in the living body.