Materials Literature
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The temperature dependence of the photoluminescence (PL) spectra of Si nanocrystallites prepared using an inert-gas-ambient pulsed laser ablation technique was characterized. Although the PL intensity of as-deposited Si nanocrystallites was very weak at room temperature, it increased with annealing in N2 or O2 gas. Th…
Summary We have studied microstructural changes in montmorillonite and kaolinite, which were amended with organic debris (leaves of chestnut or beech), microbial inoculum and nutrients and subjected, for 30 days at 25°C, to alternate drying and wetting (D–W) or kept continuously moist at water‐holding capacity (WHC).…
Poly(2-vinylpyridine N -oxide) (P2VPNO) and poly(4-vinylpyridine N -oxide) (P4VPNO) were synthesized by the oxidation of the corresponding poly(vinylpyridine)s. They are soluble in water and have a characteristic fluorescence in aqueous solutions. The fluorescence intensities of P2VPNO were over 3 times that of P4VPNO…
Raman spectra of kaolinite and of the formamide-intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm-1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls m…
Abstract The manufacture of composites offers the greatest flexibility to convert and utilize waste plastics, paper and wood into high‐value products. This paper reports on two studies regarding the recycling of these materials. In one study, recycling was simulated by regrinding and injection‐moulding composites of p…
We develop and implement a direct computational method to obtain the structure and complete molecular electronic polarisability tensor directly from the first-principles–derived electron charge distributions of mesogens based on a plane-wave basis set approach. In our methods no semi-empirical bond polarisabilities or…
We numerically investigate phase separation kinetics of liquid crystalline polymers in a nematic state using time-dependent Ginzburg-Landau equations for the compositional and the orientational order parameters $\ensuremath{\varphi}$ and ${S}_{\mathrm{ij}}.$ The kinetics is significantly influenced by (i) the presence…
We investigate how plane-parallel and twisted alignment treatments influence the electrooptical properties of dye-doped polymer dispersed liquid crystal (PDLC) films. These films are transparent in the electric field-on state and opaque in the field-off state. The relationship between field-off state transmittance of…
Estimates for the thickness of the interface between poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and copolymers of styrene–acrylonitrile (SAN) and styrene–maleic anhydride (SMA) based on the theory of Helfand and Tagami are compared to neutron reflectivity (NR) measurements. Good agreement is found between the NR me…
Drape is a unique property that allows a fabric to be bent in more than one direction with double curvature. For many years, textile researchers studied this attribute in order to evaluate the drape quality and improve the drape appearance of garments. However, fabric drape can be more realistically investigated by co…
No presente trabalho, foi estudada a extração de substâncias húmicas (SH) de horizontes A de dois solos do Rio Grande do Sul (Latossolo Roxo (LR), e Brunizém vértico (B)) e de um lodo orgânico (LO), oriundo da fabricação de celulose, empregando-se dois métodos: (1) as SH foram extraídas com solução de NaOH 0,5 mol L-1…
Abstract The field of molecular based magnetism is an active area of research directed toward the design of new magnetic materials. The idea is to introduce molecular strategies in magneto‐chemistry. This can open completely new synthetic routes to materials with previously unknown physical properties. Spin carriers u…
Amorphous films of syndiotactic polystyrene were crystallized in dichloromethane, to obtain samples in the clathrate δ form; successively the samples were either annealed at temperatures below the glass transition temperature (Tg) or extracted with acetone. The samples obtained show, in the X-ray analysis, crystalline…
This paper presents a review of Electric Double Layered Magnetic Fluids (EDL-MF) based on spinel ferrite type [(M1-x+2Fex+3)]A [(Fe2-x+3 Mx+2)]BO4-2, with M(II) = Mn, Co, Ni, Cu and Zn. The chemical synthesis of the nanoparticles using hydrothermal techniques and their complete peptization in an aqueous medium results…
Variation of the number of crosslinks in polyvinylethylene (PVE) networks has a marked effect on the ${T}_{g}$-normalized temperature dependence (``fragility'') of the segmental relaxation times, even though the local chemical environment of virtually all repeat units is unchanged. Since the heat-capacity increment at…
To model the processes of cavitation inception, noise and damage, it is necessary to generate a model of the cavitation event rate which can then be coupled with the consequences of the individual events to produce a complete synthesis of the phenomenon. In this paper we describe recent efforts to connect the observed…
Silicon dioxide films were deposited in a parallel-plate electrode RF plasma-enhanced chemical vapor deposition (PECVD) system using hydrogen-free tetraisocyanatesilane (TICS) and oxygen. The deposition parameters were varied systematically, and the films were characterized by measuring infrared spectra, density, etch…
The thermal degradation behaviour of polymers and copolymers containing acrylic and methacrylic acid salt units has received much less attention than that devoted to the corresponding ester polymers from these acids. Whether present in a homopolymer or copolymer chain, however, these ionic salt units can have a major…
We propose a mechanism for breaking tilted nematic anchorings using an electric field normal to the plates. This breaking is a discontinuous first-order transition, unlike the known second-order breaking of planar anchorings. The elastic coupling of the tilted orientations on both plates is used to initialize the firs…
The three‐dimensional microstructural development of silicon nitride ceramics that exhibit superplastic elongation (up to ɛ = 1.34) was analyzed using a stereological analysis method. According to the microstructural change from randomly oriented grains to aligned grains along the tensile direction, the average orient…