Crystallization kinetics of amorphous Ga-Sb films extended for phase-change memory.

Performance of phase-change materials based on Ga-Te-Sb was found getting better with decreasing Te content in our earlier studies. We concerned much properties of Te-free, Sb-rich binary Ga-Sb, which has been known to possess extremely fast crystallization behavior. Non-isothermal and isothermal crystallization kinetics of amorphous Sb-rich Ga-Sb films were explored by temperature dependent electrical resistance measurements. The crystallization temperature (183 to 261 degrees C) increases with decreasing Sb content (91 to 77 at%). The activation energy and rate-factor vary with Sb contents and reach the maximum at Ga19Sb81. The kinetic exponent is smaller than 1.5 at Sb < 85 at% denoting that the mechanism is one-dimensional crystal-growth from nuclei. The temperature corresponding to 10-year data-retention, evaluated from films, is 180 degrees C (Ga19Sb81) and 137 degrees C (Ga13Sb87), respectively. We verified memory performance using test-devices made of Ga16Sb84 working at voltages with 100 ns pulse-width.

Graphene structure in carbon nanocones and nanodiscs.

Carbon nanoparticles, like nanocones and nanodiscs, can be obtained by mechanical treatment of carbon nanofilaments. Microstructural studies suggest that in nanocones the conical graphene stacking with progressively increasing apex (cone) angles does not fully agree with current theoretical geometry models, such as a closed cones model and a cone-helix model. The unusual stacking form of nanocones was taken into account in a modified cone-helix model. The formation mechanism of the distinctive microstructure is attributed to the inclined anchoring effect, and the relaxation of internal stresses, which were induced by the confined pyrolysis process, resulting in easier disintegration by sonication the nanofilaments. This is disclosed for the first time in literature regarding the attainment of uniform carbon nanoparticles.

Photo-luminescent hydroxyapatite coatings through a bio-mimetic process.

Hydroxyapatite (HAp) is the major inorganic component in natural bones. Because HAp has the advantages of excellent biocompatibility, free of cell toxicity, and forming strong bonding to bone osteoinductively, it has been widely studied and prepared in many forms for orthopedic and dental applications. In the recent years, silicon based bio-chip was extensively studied. To improve the biocompatibility and search for novel application of bio-chip are not only an important aim but also a challenge. In the previous literatures, it's reported that HAp is relatively difficult to be coated onto a Si(1 0 0) substrate. In this study, we successfully manufactured crystalline HAp on to Si(1 0 0) using simplified supersaturated solution and investigated the structural characteristics through the measurements of XRD, FTIR, FE-SEM, and XPS. The photo-luminescent properties of the coatings were also studied.

Preparation of gradually componential metal electrode on solution-casted Nafion membrane.

A typical ionic polymer-metal composite consists of a thin perfluorinated ionomer membrane and noble metal electrodes plated on both surfaces. It undergoes a large bending motion when an electric field is applied hence exhibits deformation by a certain amount of cation. With proper arrangement and package, a great number of "smart devices" are anticipated. In this study, a solution-cast route was used to prepare the electro-active polymer membrane and platinum electrodes were fabricated onto the membrane through electro-less plating. The ionic polymer used is the commercial Nafion, the perfluoro-sulfonated ionomer membrane, developed by DuPont Co. Nafion membrane was cast by the solution-casting route and then loaded with different weights simultaneously. The optimized processing conditions, membrane properties and electrodes behaviors were investigated. The results of shift in WAXD peaks showed that weights delineated the crystallinity of the solution-cast membranes. The number and size of the crystalline domains of solution-cast membrane decrease as studied by SAXS. The Young's modulus of solution-cast membrane decreases as increasing weight because of the loss of crystallinity (180-140 MPa). A finely dispersed platinum particle deeper and gradient penetrating within the near-boundary region with a smaller average particle size and more uniform distribution could be obtained through a reverse electro-less plating. Its surface roughness is 3 nm comparing to 52 nm of a typical process. But its surface resistance is too high (3.5 Omega) to activate the bending motion. To solve this problem, we coated the second Pt electrodes by a typical electro-less plating, and the resistance decreased to 0.7 Omega. The results depicted that the fabricated IPMC shows longer bending lifetime than typical IPMC. In a 0.09% NaCl solution, the device was able to vibrate for 8h under a 5 V, 0.1 Hz actuation.

Antimicrobial effects and human gingival biocompatibility of hydroxyapatite sol-gel coatings.

The sol-gel method was employed to synthesize hydroxyapatite (HAp) coatings modified with Ag or Zn ions onto Ti-6Al-4V substrate. A bacterial strain Streptococcus mutans (S. mutans) and a human gingival fibroblast (HGF-1) cell line were used to investigate the antimicrobial effect and biocompatibility, respectively. HAp coatings containing 100 ppm Ag(+) ions suppressed the growth of S. mutans. An apparent inhibition zone around the HAp coating was further observed at Ag(+) concentration up to 10,000 ppm. However, for coatings containing Zn(2+) ions, a clear inhibition zone was observed at Zn(2+) concentration of 10,000 ppm. Nevertheless, the results of HGF-1 cultivation demonstrated that the Zn(2+)-modified HAp coatings exhibited better attachment and spread of HGF-1 than did the Ag(+)-modified coatings. Zn(2+) modified HAp coatings also increased the plating efficiency of HGF-1 cells. The cytotoxicity associated with the addition of Ag and the cell-conductive capacity associated with the addition of Zn are proportional to the added concentration, from 100 to 10,000 ppm. The dosages of both Ag(+) and Zn(2+) ions that should be added to HAp coatings were considered to prevent infection and improve biocompatibility. The results of this study ensure that HAp coatings modified with a moderate amount of Ag/Zn efficiently resist microorganisms and improve biocompatibility.