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Rubber surface is subjected to ultraviolet radiation (UV) in the presence of allylamine and radiation sensitizer benzophenone (BP). Fourier transform infrared spectral studies reveal the presence of allylamine on the surface. The presence of irregular needle shapes on the surface as observed in scanning electron micrographs also confirms the polymerized allylamine on the surface. Allylamine coatings have been further confirmed from atomic force microscopy (AFM) analysis. Thermogravimetric analysis (TGA) reveals that allylamine coating on the rubber surface lowers the thermal degradation rate. The contact angle between the water and rubber surface decreases for the modified rubber surface confirming the surface modification due to UV surface grafting. 相似文献
63.
C. Garcıa-Recio J. Nieves L. L. Salcedo 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):491-494
The construction of an extended version of the Weinberg-Tomozawa Lagrangian, in which baryons and mesons form spin-flavor
multiplets, is reviewed and some of its properties discussed, for an arbitrary number of colors and flavors. The coefficient
tables of spin-flavor irreducible representations related by crossing between the s-, t- and u-channels are explicitly constructed. 相似文献
64.
Poly(vinylidene fluoride), PVDF, in its β-phase is an electroactive polymer with many technological applications. There are two main ways to prepare this polymer in its electroactive β-phase: by high temperature stretching from the α-phase and directly from solution. In this paper, the influence of the processing methods in the thermal stability of the samples was studied by UV-VIS spectroscopy and thermogravimetric analysis. The number of chain defects was measured by 1H NMR. The results obtained were compared to a commercial β-PVDF sample. The number of head to head defects in the different samples is found to be between 6% and 9%. The onset temperature for thermal degradation and the average activation energy (∼76.5 kJ mol−1) of the process are approximately equal for the α-phase sample and the β-phase obtained from it. Larger values of the onset temperature and average activation energy (∼100 kJ mol−1) are found for the β-phase sample directly obtained from the solution and for the commercial β-phase sample. The thermal degradation of the samples occurs in two steps, independently of the phase of the sample, the degree of crystallinity and the processing method. 相似文献
65.
Physical characterizations of 4-tricyanovinyl-N,N-diethylaniline, TCVA, have been reported. The differential scanning calorimetry measurements of TCVA showed that this compound is stable up to 423 K. The temperature dependence of electrical conductivity, in the temperature range from 298 to 403 K, was studied on pellet samples of TCVA with evaporated ohmic Au electrodes. The electrical conductivity was found to be 7.01×10−9 Ω−1 cm−1 at room temperature. The temperature dependence of the electrical conductivity is typical for semiconducting compounds. The current density-voltage (J-V) characteristics of TCVA pellet samples have been investigated at different temperatures. In low-voltage region, the conduction current obeys Ohm's law while the charge transport phenomenon appears to be space-charge-limited current in the higher voltage regions. 相似文献
66.
We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum
cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal
conductance (G
th) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve
the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up
bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the G
th of QCLs were investigated. With 5 μm thick electroplated Au, the G
th is increased with the decrease of ridge width, indicating an improvement from G
th=177 W/K⋅cm2 at W=40 μm to G
th=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP
contact layer leads to a further improvement of 13% in G
th, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH
laser with InP contact layer leads to the highest G
th=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data. 相似文献
67.
Glasses in the La2O3−CaO−B2O3 ternary system were studied. The glass forming range as determined by the appearance of the annealed cast was found to match previously published findings. Clear glasses were formed in the composition range of 5.7−19.1 mol% La2O3 with constant B2O3 content of 71.4 mol%, and in glasses of constant La2O3:CaO ratio of 1:4 with B2O3 content in the range of 71.4-55.0 mol%. The non-linear optical crystalline phase La2Ca2B10O19 was crystallized from the clear glasses after heat treatments, as determined by powder XRD. Two types of the LaBO3 crystalline phases were detected in the partially and the fully crystallized glass compositions outside the glass forming range. Data are reported for the glass transition temperature (Tg), dilatometric softening point (Td), linear coefficient of expansion (α), onset crystallization temperature (Tx), exothermal peak temperature (TP), density (ρ) and index of refraction (nD) in the clear glasses. 相似文献
68.
The crystal growth kinetics of antimony trisulfide in (GeS2)0.1(Sb2S3)0.9 glass has been studied by microscopy and DSC. The linear crystal growth kinetics has been confirmed in the temperature range 492 ? T ? 515 K (EG = 405 ± 7 kJ mol−1). The applicability of standard growth models has been assessed. From the crystal growth rate corrected for viscosity plotted as a function of undercooling it has been found that the most probable mechanism is interface controlled 2D nucleated growth. The non-isothermal DSC data, corresponding to the bulk sample, can be described by the Johnson-Mehl-Avrami equation. 相似文献
69.
Amorphous ribbons of Fe77Nb7B15Cu1 prepared by melt-spinning and powders produced from them by ball-milling were characterized by means of calorimetry, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. Upon thermal treatment the amorphous alloy experiences a primary crystallization that leads to bcc-Fe nanocrystals dispersed in an amorphous matrix. Magnetic measurements indicate that this alloy in the amorphous and nanocrystalline state is a good soft magnetic material. Values of saturation magnetization and coercivity are 120 Am2/kg and 5 A/m respectively, for the alloy in the nanocrystalline state. Pre-annealing, post-relaxation and nanocrystallization as well as various milling parameters were explored and the structural and magnetic changes induced have been studied. The analysis of the particle size distribution and morphology of the powders show that the brittleness resulting from pre-annealing of the ribbons is very effective in reducing the particle’s size. Recovery of the high coercitive field induced by milling is achieved by post-annealing to an extent that depends mostly on the milling conditions. 相似文献
70.
Sujittra Daengsakul Charusporn Mongkolkachit Chunpen Thomas Sineenat Siri Ian Thomas Vittaya Amornkitbamrung Santi Maensiri 《Applied Physics A: Materials Science & Processing》2009,96(3):691-699
This study reports the new and simple synthesis of magnetic La0.7Sr0.3MnO3 (LSMO) nanoparticles by thermal decomposition method using acetate salts of La, Sr and Mn as starting materials. To obtain
the LSMO nanoparticles, thermal decomposition of the precursor is carried out at the temperatures of 600, 700, 800, 900, and
1000°C for 6 hours. The synthesized LSMO nanoparticles were characterized by XRD, FT-IR, TEM and SEM. Structural characterization
shows that the prepared particles consisted of two phases of LaMnO3 (LMO) and LSMO with crystallite sizes ranging from 18 to 55 nm. All the prepared samples have a perovskite structure which
changes from cubic to rhombohedral with the increase in the thermal decomposition temperature. Basic magnetic characteristics
such as saturation magnetization (M
S) and coercive field (H
C) are evaluated by sample vibrating magnetometry at room temperature (20°C). The samples show soft ferromagnetic behavior
with M
S values of ∼9–55 emu/g and H
C values of ∼8–37 Oe, depending on the crystallite size and thermal decomposition temperature. The relationship between the
crystallite size and the magnetic properties is presented and discussed. The cytotoxicity of synthesized LSMO nanoparticles
was also evaluated with NIH 3T3 cells and the result showed that the synthesized nanoparticles were not toxic to the cells
as determined from cell viability in response to the liquid extraction of LSMO nanoparticles. 相似文献