Morphological Study of hydroxypropyl cellulose films prepared from thermotropic melt under shear

A strain-induced crystallization behavior of hydroxypropyl cellulose (HPC) from the thermotropic liquid-crystalline state is described based on morphological observations by electron microscopy. It is shown that originally round-shaped particles behave as a structure unit in formation of a variety of supermolecular architectures of HPC films prepared from the thermotropic melt under shear. In an oriented HPC film obtained under weak shear, many round particles are elongated and aligned in the direction of shear (SD), but with their bodies bent to some degree. As deformation increases further, fibrillation occurs on the surface of the elongated particles, and then the resulting fibrils are arranged in a zigzag fashion along the SD to form a banded structure. In some cases, a pleated arrangement of fibrils is noticeable between bands. The structural transformation mechanism of thermotropic HPC under shear is discussed in detail on the basis of the morphological evidence.     

twins in Mo-doped TiSi 2 thin films with the C54 structure

The defect structures in orthorhombic C54 crystallites in thin films of Mo-doped TiSi 2 produced by co-sputtering have been investigated by transmission electron microscopy. Almost all C54 crystallites contain a twin boundary parallel to (101), dividing a crystallite into two regions, each of which also contains many thin twins with the habit plane parallel to (001), which is inclined by about 45° from (101). Both of the two regions divided by the twin boundary parallel to (101) tend to have facets on (001) as well as thin twins with the habit plane parallel to (001). As a result, C54 crystallites exhibit a characteristic shape just like an oak leaf. While twins with the (001) habit plane have been observed in C54 crystallites in both binary and Mo-doped TiSi 2 thin films, those with the (101) habit plane are present only in Mo-doped TiSi 2 thin films. The twinning elements for (101) twins are determined to be K 1 = (101), , K 2 = (001) and m2 = [100]. The origin of (101) twins in Mo-doped TiSi 2 is discussed in terms of the change in the c / a axial ratio upon alloying TiSi 2 with Mo.     

Correlation of fluctuation field and temperature coefficient of coercivity in a CoCrPtB thin film

The effect of the ratio of fluctuation field (H_f) to coercivity (H_c) on the temperature coefficient of coercivity [α(H_c)] was investigated for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr, Co₆₉Cr₁₉Pt₉Ta₃/Cr, and Co₈₆Cr₁₀Ta₄/Cr thin films (longitudinal recording media) with very small average grain volume (V_phy). α(H_c) increases markedly with increase in temperature between near 250 and 350 K for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr thin films. α(H_c) is approximately proportional to the ratio H_f/H_c for all thin films, as in the case of advanced data backup tapes prepared from ultrafine particles. α(H_c) and the ratio H_f/H_c increase as V_phy decreases. Smaller H_f/H_c values are necessary for small α(H_c) values, which is very important for the thermal stability of high-density recording media with very small V_phy.     

Aerobic oxidation of alcohols using bismuth bromide as a catalyst

We developed an environmentally friendly method for aerobic oxidation of alcohols using a commercially available, relatively benign bismuth salt as a catalyst. We found that the catalytic combination of BiBr₃ with nitric acid is key for enhancing the reactivity. The reaction proceeds well under air, making the use of pure oxygen unnecessary. Each of the primary or secondary alcohols tested was oxidized to the corresponding aldehydes or ketones using this protocol.     

Fabrication of fluorine-doped silica glasses by the sol-gel method

Fluorine-doped silica glasses are produced by the sol-gel method for optical fiber preforms. In order to dope fluorine into silica glass, fluorinated silicon alkoxide, Si(OC₂H₅)₃F, is titrated into SiO₂ sol solutions. The fluorine content in silica glass depends on: the fluorine concentration in the gel, the specific surface area of SiO₂ particles and the heating rate in the sintering process. Fluorine-doped silica glass with a maximum relative refractive index difference of −0.93% is obtained. Using this technique, optical fibers with a triangular refractive index profile are fabricated with a minimum optical loss of 1.6 dB/km at 1.69 μm wavelength.     

Novel one-pot approach to synthesis of indanones through Sb(V)-catalyzed reaction of phenylalkynes with aldehydes

Catalytic SbF5 and the use of EtOH as an additive efficiently converted a mixture of phenylalkynes and aldehydes to indanone compounds in one pot, and the reaction stereoselectively afforded the corresponding 2,3-disubstituted indanones as a single trans-isomer.     

Iron-catalyzed enyne cross-coupling reaction

In the presence of 0.5-1 mol % of FeCl(3) with lithium bromide as a crucial additive, alkynyl Grignard reagents, prepared from the corresponding alkynes and methylmagnesium bromide, react with alkenyl bromides or triflates to give the corresponding conjugated enynes in high to excellent yields. The reaction shows wide applicability to various terminal alkynes and alkenyl electrophiles.