Advanced Materials Research Vols. 47-50

Abstract: CuMgAl hydrotalcite-like compounds with MII/MIII=1 and Cu/Mg molar ratios 3:1, 1:1, 1:3 and 1:19 were synthesized by coprecipitation and characterized by elemental analyses, XRD, SEM, FT-IR, TG-DTA and BET surface area test. XRD of all samples showed that Cu/Mg/Al hydrotalcites without any detectable impurity phase could be obtained at Cu/Mg molar ratios 1:3 and 1:19, however, at high Cu/Mg molar ratios 3:1 and 1:1, Al(OH)3 and copper hydroxides or oxides were obtained in the products besides the hydrotalcites, owing to the strong Jahn-Teller effect of Cu2+. It was also found that the crystallinity of the solids increased with an increase in copper content. IR results showed that the symmetry of carbonate was reduced from D3h to lower symmetry at high copper content. The thermal stability of the compounds decreased with increasing copper content, as indicated by TG-DTA measurements. Further thermal decomposition analyses showed that the surface area reached the maximum at calcination temperature of 500 ° C and mixed metal oxides with crystalline MgO, amorphous Al2O3 and highly dispersed CuO were obtained.

Abstract: Copper sulfide (CuS) nanocrystals with flower-like and tubular morphology have been successfully synthesized via a facile and convenient hydrothermal route at 75 °C by using CuCl2·2H2O as Cu-precursor, C2H5NS as S-source and CTAB as template molecules. The effect of concentration of reactants and template molecules on morphology has been discussed. X-ray diffraction pattern suggests that the CuS crystals are pure hexagonal phase. The morphology of the products has been studied by scanning electron microscope analysis. The absorption peaks of CuS in UV and near-IR regions indicate that the as-prepared CuS are promising in the development of photoelectric devices.

Abstract: The growth behaviour of the intermetallic compounds (IMCs) in Pb-free solder bump is investigated. The Pb-free micro-bump, Sn-50%Bi, was fabricated by binary electroplating for flip-chip bond. The diameter of the bump is about 506m and the height is about 60 6m. In order to increase the reliability of the bonding, it is necessary to protect the growth of the IMCs in interface between Cu pad and the solder bump. For control of IMCs growth, SiC particles were distributed in the micro-solder bump during electroplating. The thickness of the IMCs in the interface was estimated by FE-SEM, EDS, XRF and TEM. From the results, The IMCs were found as Cu6Sn5 and Cu3Sn. The thickness of the IMCs decreases with increase the amount of SiC particles until 4 g/cm2. The one candidate of the reasons is that the SiC particles could decrease the area which be reacted between the solder and Cu layer. And another candidate is that the particle can make to difficult inter-diffusion within the interface.

Abstract: It is very important to study the effects of various factors on synthesis of carbon nanofibers for controlled synthesis, which plays a significant role in realizing desired nanostructures or nanodevices for applications. In this report, we employed different carbon source and different catalyst precursor solution, respectively, and studied the effects of those on carbon nanofibers that were synthesized by catalytic combustion process. We have characterized the as-grown carbon nanofibers by employing scanning electron microscopy (SEM) for deep understanding.

Abstract: This paper aims at providing a preliminary understanding in biomechanics with respect to the effect of the particle size of Fully Porous-Coated (FPC) dental implant on osseointegration. 2D multiscale finite element models are created for a typical dental implantation setting. Under a certain mastication force (<200N), a global response is first obtained from a macro-scale model (without considering morphological details on the coated surface), and then it is transferred to micro-scale models (with coated surface morphology details in three different particle sizes). An equivalent strain is analyzed to investigate the effect of particle size of the FPC materials on osseointegration and initiation of bone remodelling. The result reveals that increasing particle sizes has a significant effect on biomechanical and bone remodelling responses.

Abstract: We described a facile approach to controllably synthesize silver nanoparticles with various morphologies using N, N-dimethylformamide (DMF) in the presence of poly (vinyl pyrrolidone) (PVP). Triangular/hexagonal nanoplates, chain-like nanoplate assemblies, and nanobelts could be selectively obtained. On the basis of the experimental results, the concentration of poly (vinyl pyrrolidone) and AgNO3, reactive temperature and time were the vital factors to determine the shape of final products. Reasonable mechanisms for the formation of silver nanoparticles with various morphologies were proposed. Fluorescence modulation of dye rhodamine B (RhB) and fluorescein (FI) in the presence of silver nanoparticles were studied. Addition of silver nanoparticles could produce fluorescence enhancement and show self-quenching release of RhB, while the fluorescence intensity of FI decreased due to the presence of the silver nanoparticles. The effects of silver nanoparticles on the fluorescence properties of dyes were dependent on the competition between the local field enhancement and non-radiation energy transfer from the molecule to the metallic nanoparticles.

Abstract: The present research’ goal is the fabrication of Fe-based composite reinforced with oxide particles with special characteristics (wear, friction coefficient) for friction applications usually the Fe-based composite are obtained through melting and castings followed by other finishing operations. These technologies do not ensure a homogeneous distribution of reinforcement particles and that is why, the authors approached a PM specific technologies to obtained Fe-based composite. The Fe-based powder reinforcement with oxide particles obtained through mechanical alloying the powder was analyzed and characterized and then underwent the operation of milling in the planetary milling with ball, pressing and sintering at different temperatures and durations. SEM analysis had of identifying the distribution compounds into the Fe- matrix, their quantitative evolution and the influence of different parameters. The mechanical characteristics, wear and friction coefficient, were determined.

Abstract: Strontium is one of metallic elements found in bones and teeth. It is an essential substance in preventing osteoporosis and has the ability to regenerate, preserve, and even restore bone growth. Synthesizing Sr-doped HA powder is of great importance accordingly. Here we present Sr-doped HA powders prepared via sol-gel procedure using calcium nitrate and diammonium hydrogen phosphate as the precursors. Strontium nitrate was used as the dopant source, and its concentration was varied from 2~15 %. An ammoniacal solution was heated until a white gel was obtained. The obtained gel was then dried and subsequently subjected to 900°C calcination. Characterization on the obtained powder was conducted using XRD, FTIR, and FESEM. XRD measurement had shown that the powder contained hydroxyapatite phase only. Morphological evaluation by FESEM measurement shows that the particles of the Sr -doped HA agglomerates are globular in shape with an average size of 1-2 µm in diameter. Meanwhile, the primary particles have a diameter of 50-150 nm in average. It is likely Sr has played an important role as a calcination or sintering additive, causing more progressive densification of particles.

Abstract: Hydroxyapatite porous materials for cancellous bone applications were prepared via polymeric sponge method. Suspensions of the nanostructured hydroxyapatite powders were prepared via stirring of the mixture of hydroxyapatite powder, water, and dispersing agent. The stirring time was adjusted at 4 and 20 hours. After soaking cellulosic sponges into the suspension, the sponges were dried and then subjected to heat-treatment at 600°C, followed by sintering at 1250°C for 1 h. No additional phases were identified in the sintered porous hydroxyapatite. This result showed that the sintering process did not alter the hydroxyapatite phase composition. The study found that the apparent density of the porous bodies varied from 1.69 g/cm3 to 2.03 g/cm3 with 35.6 – 46.2 % porosities and 100-500 microns macropore size depending on the composition of slurry and the stirring time. Longer stirring time resulted in the breakdown of HA agglomerates and the slurry obtained tends to be more homogeneous, leading to higher density and better compressive strength of the sintered porous bodies. The measurement of compressive strength provided the values of 4.3 MPa and 10 MPa for 4 h and 20 h stirring time, which is in the range of mechanical strength of human cancellous bone.

Abstract: Porous barium strontium titanate−titania (BST−TiO2) nanocomposite was developed by the combination of electrochemical anodization and hydrothermal synthesis. Self organized titania nanotube arrays were first fabricated by electrochemical anodization of titanium foil in 0.2 wt.% HF. The as-anodized titania was then used as a template and was subject to a hydrothermal treatment in the solution mixture of barium hydroxide and strontium hydroxide with different molar ratios. Well crystallized barium strontium titanate was developed directly from the titania nanotubes. Annealing was carried out to transform residual amorphous titania to crystallized anatase, resulting in the porous BST−TiO2 nanocomposite. The surface morphology and structure of the nanocomposite were characterized. The photoelectrochemical response of the BST−TiO2 composite was investigated and the photocatalytic property was evaluated through the photo-decomposition of an organic dye solution. The effect of hydrothermal parameters on the surface morphology and the photocatalytic activity of the nanocomposite was studied.