CHEMICAL STRUCTURE AND FUNCTIONAL PROPERTIES OF AMORPHOUS BORON CARBONITRIDE FILMS

Journal of Structural Chemistry - We report a comprehensive study of the effect of the chemical structure of boron carbonitride films on the variability of their functional characteristics. The...     

DIELECTRIC LAYERS BCxNy: SYNTHESIS BY THE DECOMPOSITION OF VAPORS OF ORGANOBORON COMPOUNDS,COMPOSITION AND CHEMICAL STRUCTURE

Journal of Structural Chemistry - Composition, chemical structure, and dielectric characteristics of boron carbonitride films BCxNy prepared by chemical vapor deposition upon thermal and plasma...     

Effect of cyclic cooling to low temperatures on the adhesive strength of fiber-thermoplastic matrix joints

The adhesive strength of the interface between the polyarylene sulfone PSK-1 and a steel wire 150 mm in diameter was measured using a pull-out technique after cyclic cooling of the joints from room temperature down to liquid nitrogen temperature. All specimens were prepared under isothermal conditions (300 °C, 30 min) without applying pressure. The number of cycles N of plunging in liquid nitrogen reached 900. All measurements were taken at room temperature with constant loading rate. The joint areas S were varied within a wide range. It was found that ten cooling cycles do not cause any appreciable change in the values of (Figs. 1–3). After 100 cooling cycles, the adhesive strength losses reached 30–45% (Figs. 1–3). After 810 cycles, the fiber-matrix interface is almost totally destroyed (Fig. 1). As the number of cycles N increases, the character of the dependence of the adhesive strength on the joint area changes: when N < 100, the values of are reduced as the interfacial surface area increases; when N = 810, the adhesive strength does not depend on S. The main factor that governs the reduction in adhesive strength is assumed to be residual thermal stresses. Analysis of the data obtained here and earlier shows that the behavior of polymer-fiber systems after cyclic cooling down to low temperatures is the same for both network and linear polymer matrices. The origin of this behavior also seems to be the same for all polymer-fiber adhesive joints.Report presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 2, pp. 156–162, March–April, 1995.This work was done with the support of the International Science Foundation (the G. Soros Foundation), grant NED000.     

Speciation of BCxNy films grown by PECVD with trimethylborazine precursor

Films of BC _x N _y were produced in a plasma-enhanced chemical vapor deposition process using trimethylborazine as precursor and with H₂, He, N₂, and NH₃, respectively, as auxiliary gas. These films deposited on Si(100) wafers or fused quartz glass substrates were characterized chemically by X-ray photoelectron spectroscopy and by synchrotron radiation-based total-reflection X-ray fluorescence combined with near-edge X-ray absorption fine structure. Independent of the auxiliary gas, the B–N bonds are dominating. Furthermore, B–C and N–C bonds were identified. Oxygen, present in the bulk (in contrast to the surface layer of some nanometers, where molecular oxygen and/or water are absorbed) as an impurity, is bonded to boron or to carbon, respectively. The relation of boron and nitrogen changes with the character of the auxiliary gas: c _B/c _N ≈ 4:3 (for H₂ and He) and c _B/c _N ≈ 1 (for N₂ or NH₃). Furthermore, physical properties such as the refractive index and the optical band-gap energy were determined.     

Influence of Precursor Gas Flow Rate on Fluoropolymer Coating Growth Rate During Hot Wire Chemical Vapor Deposition

The formation of a fluoropolymer coating by chemical deposition has been studied experimentally. It has been found that increasing the flow rate of the precursor gas leads to a decrease in the growth rate of the coating. Deposition conditions were analyzed, and the gas-dynamic parameters of the process were estimated. The estimates are consistent with experimental data.     

Comparison of structures of gold nanoparticles synthesized by pulsed laser ablation and magnetron sputtering

We present the results of studying the structure of gold nanoparticles synthesized on the silicon surface by two techniques: pulsed laser ablation and magnetron sputtering. The surface morphology is examined by scanning electron microscopy. The structure of the obtained gold nanoparticles is analyzed by transmission electron microscopy and electron diffraction. It is shown that nanoparticle sizes and crystal structures can be controlled by their thermal annealing. Mechanisms occurring during annealing of thin gold films and also their effect on the formation of nanoparticles with different structures are investigated.     

X-ray photoelectron and auger spectroscopic study of the chemical composition of BC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> films

X-ray photoelectron and Auger spectroscopy are used to investigate the chemical composition of BC _x N _y films synthesized by PECVD from different initial gas mixtures in the temperature range 473–723 K. Main principles and features of the film formation are found. It is shown that the chemical composition of BC _x N _y films significantly depends on the synthesis parameters, which enables targeted control of their physical properties. The obtained data are discussed.