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81.
D. Dadarlat C. Neamtu M. Streza R. Turcu I. Craciunescu D. Bica L. Vekas 《Journal of nanoparticle research》2008,10(8):1329-1336
The suitability of the photopyroelectric (PPE) calorimetry in measuring the thermal parameters of nanofluids was demonstrated.
The main advantages of the method (concerning nanofluids) as compared to classical calorimetric techniques are: high sensitivity
and small amount of sample required. The thermal diffusivity and effusivity of some nanofluids based on Fe3O4 and CoFe2O4 type of nanoparticles (mean diameter 6.5 nm) were investigated by using two PPE detection configurations (back and front).
In both cases, the information is contained in the phase of the PPE signal. Due to the high accuracy of the results (within
±0.5%) thermal diffusivity was found to be particularly sensitive to changes in relevant parameters of the nanofluid as carrier
liquid, type and concentration of nanoparticles. 相似文献
82.
Daniela Filip Gheorghe Singurel Cristofor I. Simionescu Anisoara Socoliuc Adrian Bradu Doina Macocinschi 《Research on Chemical Intermediates》2002,28(1):1-11
An infrared analysis of phase transitions in three enantiotropic liquid crystalline acrylate monomers with different spacer lengths bearing urethane groups and cholesteryl as mesogen was carried out. Through heating and cooling, spectral modifications especially at the level of carbonyl, –NH– and urethane alkoxyl oxygen groups were found. These findings reveal the influence of hydrogen bonding on mesomorphic properties of the studied compounds mentioning that both liquid crystal transitions are evidenced by the spectral changes. For all the compounds studied, the values of the transition temperatures deduced from the spectral modifications are in good agreement with those obtained from DSC measurements. 相似文献
83.
Constantin Roşu Doina Mănăila-Maximean Rodica Bena Emil Petrescu Stanislav Klosowicz Krzysztof L. Czuprynski 《Czechoslovak Journal of Physics》2003,53(3):235-247
Polymer-dispersed-liquid-crystal films were obtained using the photopolymerization-induced-phase-separation method. The thermally stimulated depolarization current measurements indicate a space-charge-limited current. Conduction of electronic type was proven and the activation energy, specific to the conduction process, was calculated. Optical measurements have been performed simultaneously with the measurements of thermally stimulated currents and the nematic-isotropic phase transition was detected by the switch of the optical transmission. The change of the optical transmission versus applied a.c. voltage was the indication for the on-off switch behavior, useful in electro-optic applications. 相似文献
84.
The thermal properties of the Cr(III) complexes with the ligands glycine and glutamic acid were determined using TG, DTG and DTA techniques.The chromium(III)-glycine complex is more stable than the chromium(III)-glutamate complex. This behaviour is discussed in terms of different structures by IR and reflectance spectra as well as thermal data. 相似文献
85.
Doina MacocinschiDaniela Filip 《European Polymer Journal》2002,38(5):1025-1031
A poly(ether sulfone) and a copoly(ester sulfone) were synthesized and characterized using elemental analyses, IR, 1H-NMR spectrometry, GPC, thermogravimetric analyses. These polysulfones which show good thermal stability and flame retardancy were applied on textile materials and measurements for the evaluation of the flame retardant effect were carried out. 相似文献
86.
A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian
polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed
product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant
Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature
solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium
sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also
determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven
process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic
models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the
fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded
HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption
cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant
Red HE-3B from aqueous effluents.
相似文献
87.
88.
Doina Cioranescu Patrizia Donato Horia I. Ene 《Mathematical Methods in the Applied Sciences》1996,19(11):857-881
We study the Stokes system with non-homogeneous Fourier boundary conditions depending on a parameter, in a domain with periodic inclusions of the size of the period. Following the values of this parameter, we obtain at the limit a Darcy's law, a Brinkmann type equation or a Stokes type equation. We also present a physical model to which the results apply. This model describes the flow of an incompressible viscous fluid through a porous medium under the action of an exterior electric field. 相似文献
89.
Nilson C. Da Cruz Steven F. Durrant Mrio A. Bica De Moraes 《Journal of Polymer Science.Polymer Physics》1998,36(11):1873-1879
Films were produced by plasma enhanced chemical vapor deposition (PECVD) of tetramethylsilane (TMS)–helium–argon mixtures with either oxygen or nitrogen in a vacuum system fed with radiofrequency power. Actinometric optical emission spectroscopy was used to determine trends in the concentrations of plasma species of interest (H, CH, O, CO, and CN) as a function of the ratio of the inorganic reactive gas (oxygen or nitrogen) to the monomer (TMS) in the system feed. As the ratio of oxygen to TMS in the feed is increased, the degree of oxygenation of the deposited material, as revealed by transmission infrared spectroscopy, is also increased. Similarly, the degree of nitrogenation of the films increases with increasing nitrogen to monomer ratio in the feed. Strong correlations exist between the plasma concentrations of the above-mentioned plasma species and film structure and composition. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1873–1879, 1998 相似文献
90.