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Vapor Deposition Method (vapor + deposition_method)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Growth of lead bromide polycrystalline films

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004
M. Giles
Abstract Lead bromide polycrystalline films were grown by the physical vapor deposition method (PVD). Glass 1,x1, in size, uncoated, and coated with Indium Tin Oxide (ITO), was used as substrate and rear contact. The starting material was evaporated at temperatures from 395°C to 530°C under high vacuum atmosphere (6 x 10 -3 Pa) and during 8 days. The substrate temperature was prefixed from 190°C to 220°C. Film thickness yielded values from 40 to 90 ,m. Optical microscopy and scanning electron microscopy (SEM) were performed on the films. Grain size resulted to be from 1.0 to 3.5 ,m. SEM and X-ray diffraction indicate that films grow with a preferred orientation with the (0 0 l) planes parallel to the substrate. The Texture Coefficient (TC) related to the plane (0 0 6) was 7.3. Resistivity values in the order of 1012 ,cm were obtained for the oriented samples, but a strong polarization indicates severe charge transport problems in the films. Film properties were correlated with the growth temperature and with previous results for films of other halides. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Growth of bismuth tri-iodide platelets by the physical vapor deposition method

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004
A. Cuña
Abstract The work reports the growth of single BI3 crystals with platelets habit. Platelets were grown by physical vapor deposition (PVD) in a high vacuum atmosphere and with argon, polymer or iodine as additives. Crystals grew in the zone of maximum temperature gradient, perpendicular to the ampoule wall. Crystals grown with argon as additive show a very shining surface, have hexagonal (0 0 l) faces, sizes up to 20 x 10 mm2 and thicknesses up to 100 ,m. They were characterized by optical microscopy and scanning electron microscopy (SEM). Dendritic-like structures were found to be their main surface defect. SEM indicates that they grow from the staking of hexagonal unities. Electrical properties of the crystals grown under different growth conditions were determined. Resistivities up to 2 x 1012 ,cm (the best reported value for monocrystals of this material) were obtained. X-ray response was measured by irradiation of the platelets with a 241Am source of 3.5 mR/h. A comparison of results according to the growth conditions was made. Properties of the crystals grown by this method are compared with the ones measured for others previously grown from the melt. Also, results for bismuth tri-iodide platelets are compared with the ones obtained for mercuric and lead iodide platelets. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Amperometric Nitrite Sensor Based on PVP-Os Entrapped in Titania Sol-Gel Matrix

ELECTROANALYSIS, Issue 19 2004
Yancai Li
Abstract A novel nitrite sensor was developed based on the immobilization of a partially quaternized poly(4-vinylpyridine) complexed with [Os(bpy)2Cl]+/2+ (PVP-Os) in a porous TiO2 sol-gel matrix by a vapor deposition method. The preparation process simplified the traditional sol-gel process and prevented the cracking of conventional sol-gel derived glasses. Electrochemical behavior of the sensor was characterized by cyclic voltammetry and shows excellent electrocatalytic response for the reduction of nitrite. Effect of operating potential on electrochemical responses of the sensor was explored for optimum analytical performance by using the amperometric method. The stability of the sensor was also evaluated. [source]

Synthesis and Optical Properties of Europium-Doped ZnS: Long-Lasting Phosphorescence from Aligned Nanowires,

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005
C. Cheng
Abstract Quasi-aligned Eu2+ -doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [010] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitons, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl, ions can serve not only as donors, producing a donor,acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4,min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ 4f65d1,4f7 intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths. [source]

Silicone Nanofilaments and Their Application as Superhydrophobic Coatings,

ADVANCED MATERIALS, Issue 20 2006

Silicone nanofilaments (see figure) are grown by a simple chemical vapor deposition method on different substrate materials. The filaments are flexible, and have lengths of up to several micrometers and diameters of up to 150,nm. The dense and entangled arrangement of these filaments yields a superhydrophobic coating that is also optically transparent and antireflective. [source]

Influence of carbon nanotube dispersion on the mechanical properties of phenolic resin composites

POLYMER COMPOSITES, Issue 2 2010
R.B. Mathur
Despite the much touted mechanical properties of carbon nanotubes, composites reinforced with nanotubes have failed to achieve mechanical properties which rival those present in conventional fiber reinforced polymer composites. This article describes an attempt to bridge this gap. Multi-walled carbon nanotubes (MWCNT) were synthesized using a chemical vapor deposition method and were dispersed in phenolic resin by both the wet and dry dispersion techniques before molding into composite bars (50 × 5 × 3 mm3). Although no improvement in the mechanical properties of the MWCNT/phenolic composites was observed over the neat resin value when wet mixing dispersion was employed, an improvement of nearly 158% (160 MPa as compared with 62 MPa for neat resin) was achieved in 5 vol% MWCNT containing phenolic resin prepared by the dry mixing. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]