The study of phase,microstructure, and magnetocaloric properties in LaFe11.6*xSi1.4B0.1 alloys

The effect of Fe on the phase and magnetocaloric property of LaFe_11.6*xSi_1.4B_0.1 alloys with x = 1.0–1.4 have been studied. The results show that the excess of Fe will make the α-Fe phases increase, but the easy corrosion LaFeSi phase reduces in LaFe_11.6*xSi_1.4B_0.1 alloys. All LaFe_11.6*xSi_1.4B_0.1 alloys keep the first-order magnetic phase transition. The saturation magnetizations of LaFe_11.6*xSi_1.4B_0.1 alloys with x > 1 are much higher than LaFe_11.6Si_1.4B_0.1 alloy under 2T magnetic field. This results in the maximum isothermal magnetic entropy changes, and the relative cooling power of LaFe_11.6*xSi_1.4B_0.1 alloys is bigger than for LaFe_11.6Si_1.4B_0.1 alloys.     

Influence of surface and bulk layers on the crossover features for interaction parameters of a ferroelectric thin film

The phase diagram of a ferroelectric thin film is studied by using the usual mean-field approximation. The crossover features, from the ferroelectric-dominant phase diagram to the paraelectric-dominant phase diagram, for the physical parameters of the thin film are discussed. Special attention is devoted to the investigation of surface and bulk layers, and how to influence the crossover values of exchange interactions and transverse fields.     

Study on optical characterization of TGB and reentrant smectic-A phases in binary mixture of two liquid crystals

In this work, our investigation is to study the optical and thermal properties of the binary mixture of cholesteric and nematic compounds, namely, cholesteryl nonanoate and p-methoxybenzylidene-p-ethylaniline, which exhibits a very interesting liquid crystalline twisted grain boundary (TGB) phase and reentrant smectic-A phase. The chiral liquid crystalline TGB phases and reentrant smectic-A phases have been observed at different concentrations and at different temperatures. The existence of TGB and reentrant smectic-A phases is confirmed by differential scanning calorimetry and optical microscopic studies. The variation of optical anisotropy has been discussed. The helical pitch of the cholesteric phase has also been discussed.     

SYNTHÉSE DE THIOÉTHERS D'ACIDES PROPYLBORONIQUES S - BENZYLÉS

The protection of the hydroxy group of p-cresol 1 by o-silylation gives derivatives 2 and 3 , the methyl group of which can be brominated by NBS. The phase transfer catalysis applied to 4 and 5 is a good way which permits the mild introduction of the allylthio group ( 6 and 7 ). Hydroboration applied to silylated compounds 8 and 9 , followed by methanolysis and hydrolysis leads to target acids 10 and 11 in a good yield.

La protection du groupement hydroxy du p-crésol 1 par o-silylation donne les dérivés 2 et 3 ce qui permet de bromer le substituant méthyle par le N-bromosuccinimide (NBS). La catalyse par transfert de phase (CTP) appliquée aux produits 4 et 5 est une bonne méthode pour introduire un groupement allylthio (composés 6 , 7 ). L'hydroboration des composés silylés 8 et 9 , suivie d'une méthanolyse et d'une hydrolyse permet d'accéder aux acides cibles 10 et 11 avec de bons rendements.     

The Reaction Activity of Aromatic Carbonyl Compounds with Diphenylphosphine Oxide Studied by 31P NMR

Abstract

A series of α-hydroxyphosphine oxides were prepared by the reactions of diphenylphosphine oxide and aromatic carbonyl compounds and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, ESI-MS, and HR-MS spectra. The reaction rates and experimental conditions of aromatic aldehydes and aromatic ketones were obviously different due to the activity of their carbonyls. The different substituents of the aromatic aldehydes affected the reaction rate too, and the quantitative reactivity of their substituent conformed to the Hammett equation. The results were confirmed by ³¹P NMR spectroscopy.     

Solid-Phase Synthesis of 2-Arylamino-5-(4-hydroxyphenyl)-1,3,4-thiadiazole Derivatives Based on Resin-Bound Acylhydrazines

A highly efficient, solid-phase synthesis of 2-arylamino-5-(4-hydroxy-phenyl)-1,3,4-thiadiazole derivatives under mild conditions has been developed. The 1,3,4-thiadiazole derivatives were synthesized from resin-bound acylhydrazines in several steps, which gave 78–88% overall yields and excellent purities of the products.     

Reaction of Dithiophosphoric Acid Chloride Betaine with Bifunctional Compounds - A New Route to Cyclic Dithiophosphates

Abstract

Dithiophosphoric acid chloride pyrididium betaine, Py. PS₂Cl (1)¹, can be widely used for the synthesis of various organophosphorus compounds. 1 reacts in the presence of a base with an excess of nucleophiles like amines, alcohols or thiols to the corresponding disubstituted thiophosphoric acid derivatives^2–3.