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151.
Saroaut Noor M.A. Hakim S.S. Sikder S. Manjura Hoque Kazi Hanium Maria Per Nordblad 《Journal of Physics and Chemistry of Solids》2012,73(2):227-231
The effect of Cd-substitution on the variation of saturation magnetization Ms, Curie temperature Tc, and magnetic moments nB of Co1?xCdxFe2O4 (x=0.0–1.0 in steps of 0.1) ferrites have been investigated using SQUID magnetometer and impedance analyzer. The samples were prepared by conventional double sintering ceramic technique and found to be single-phase cubic spinel structure by X-ray diffraction. Saturation magnetization Ms, is found to increase with increase of Cd substitution attaining a maximum value at x=0.4 and decreases thereafter. Curie temperature decreases almost linearly with increasing x content up to x=0.7. Samples having x≥0.8 display complex magnetic behavior with competing antiferromagnetic and ferromagnetic interactions with the manifestation of large hysteresis at low temperature and no sign of saturation. Samples with x>0.8 show paramagnetic characteristic at T=5 K with no spontaneous magnetization revealed through Arrot-Belov-Kouvel (ABK) plots. 相似文献
152.
The crystal compound [N (CH3)4]2PdCl4 was crystallized in the orthogonal system and the space group is P4/mmm and the refined unit cell parameters are a = b = 8.831 Å, c = 11.415 Å. The structure, vibrational spectra and optical properties have been investigated. DSC studies indicate the presence of two phase transitions at higher temperature which confirm the thermal stability of the palladium-based compound. These transitions have been studied by Raman scattering on single crystals as a function of temperature which confirmed their nature. The assignment of the observed bands is discussed based in the theoretical calculated frequencies by the density functional theory (DFT) method using B3LYP/LanL2DZ basis in the GAUSSIAN-09 package of programs. The optical properties in the UV–visible region have been deduced and the energy gap has been determined which is equal to 3.11 eV. 相似文献
153.
Dr. S. M. A. Hakim Siddiki Dr. Abeda Sultana Touchy Dr. Kenichi Kon Prof. Ken‐ichi Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):6111-6119
Carbon‐supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant‐free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate‐limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. 相似文献
154.
155.
The [N(CH3)4][N(C2H5)4]ZnCl4 compound has been synthesized by a solution-based chemical method. The X-ray diffraction study at room temperature revealed
an orthorhombic system with P21212 space group. The complex impedance has been investigated in the temperature and frequency ranges 420–520 K and 200 Hz–5 MHz,
respectively. The grain interior and grain boundary contribution to the electrical response in the material have been identified.
Dielectric data were analyzed using the complex electrical modulus M
* for the sample at various temperature. The modulus plots can be characterized by full width at half height or in terms of
a non-exponential decay function ϕ(t) = exp[(−t/τ)
β
]. The detailed conductivity study indicated that the electrical conduction in the material is a thermally activated process.
The variation of the AC conductivity with frequency at different temperatures obeys the Almond and West universal law. 相似文献
156.
Liquid phase microextraction combined with ion‐exchange‐high performance thin layer chromatography has been developed for analysis of four plasticizers in aqueous samples. After their preconcentration by liquid phase microextraction, fast separation on thin layers of inorganic ion‐exchanger stannic silicate has been developed using a mixture of toluene + ethyl acetate (10:1, v/v) as mobile phase. Consequently, densitometric quantitative determination of the plasticizers has been made at λ = 280 nm in reflection–absorption mode by Camag TLC scanner‐3. The effects of type and volume of extraction solvent, stirring rate, extraction time, and ionic strength in the microextraction method have been also evaluated and optimized. The results show that the proposed method provides enhanced accuracy, linear range, LOD, and LOQ, and is very effective for analyzing the target compounds in water samples. Under the optimized conditions, preconcentration factor of 149–279 and extraction efficiency of 31–59% have been obtained. Repeatability (5.67–7.26%) and intermediate precision (6.21–8.17%) were in acceptable range. The relative recovery obtained for each analyte in different water samples was higher than 82.3% at three fortification levels with RSD <7.9%. 相似文献
157.
Optical Review - We propose an image reconstruction technique of a color 3-D object to perform image refocusing by combining information from bright-field image and digital holography. The key... 相似文献
158.
Versatile and Sustainable Synthesis of Cyclic Imides from Dicarboxylic Acids and Amines by Nb2O5 as a Base‐Tolerant Heterogeneous Lewis Acid Catalyst
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Md. Ayub Ali Dr. S. M. A. Hakim Siddiki Dr. Kenichi Kon Prof. Junya Hasegawa Dr. Ken‐ichi Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14256-14260
Catalytic condensation of dicarboxylics acid and amines without excess amount of activating reagents is the most atom‐efficient but unprecedented synthetic method of cyclic imides. Here we present the first general catalytic method, proceeding selectively and efficiently in the presence of a commercial Nb2O5 as a reusable and base‐tolerant heterogeneous Lewis acid catalyst. The method is effective for the direct synthesis of pharmaceutically or industrially important cyclic imides, such as phensuximide, N‐hydroxyphthalimide (NHPI), and unsubstituted cyclic imides from dicarboxylic acid or anhydrides with amines, hydroxylamine, or ammonia. 相似文献
159.
Supported metal nanoparticle catalysts are studied for alkylation of 2-methylquinoline with benzyl alcohol under additive-free conditions in N2 atmosphere. Among various metal-loaded Al2O3 catalysts and supported Pt catalysts, Pt metal nanocluster loaded-Al2O3 pre-reduced in H2 at 500 °C shows highest yield (82%) of the product (2-phenethyl-quinoline). The catalyst is reusable, shows higher turnover number than a previous homogeneous catalyst, and shows good to moderate yield for alkylation of 2-methylquinoline with various alcohols. The reaction is driven by the borrowing-hydrogen pathway, in which aldehyde formed by dehydrogenation of alcohol undergoes aldol condensation with 2-methylquinoline to give the alkene intermediate which is finally hydrogenated by Pt-H species. 相似文献
160.
Sustainable Heterogeneous Platinum Catalyst for Direct Methylation of Secondary Amines by Carbon Dioxide and Hydrogen
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Dr. Kenichi Kon Dr. S. M. A. Hakim Siddiki Wataru Onodera Dr. Ken‐ichi Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6264-6267
Pt and MoOx co‐loaded TiO2 is found to be highly effective for direct methylation of aliphatic and aromatic secondary amines by CO2 and H2 under solvent‐free conditions. This is the first additive‐free and reusable heterogeneous catalytic system with acceptable turnover number. 相似文献