Synthesis, growth and thermal and Fourier transform infrared spectral characterization of tetraethylammonium tetrachloro manganate (II) monohydrate crystals

Single crystals of a novel tetraethylammonium tetrachloro manganate (II) monohydrate (TEATC-Mn) were grown by slow evaporation solution technique at room temperature. These crystals belong to a class of interesting ferroelectric materials. The grown crystals were characterized through powder X-ray diffraction (XRD), thermogravimetry, differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC) studies and Fourier transform infrared (FTIR) spectra. While the results of the elemental analysis of the compound agree with the stoichiometry, its crystallinity is confirmed by the powder X-ray diffraction pattern. The weight losses observed were suitably explained based on the formulated decomposition pattern. The differential thermal analysis of the compound conforms to the thermogravimetric study. The endothermic peak observed in the high temperature differential scanning calorimetry suggests the occurrence of a phase transition in the compound between 300 and 370 °C while the corresponding low temperature study shows thermal anomalies at −41.7, −51.7 and at −52.4 °C. This suggests the occurrence of both first and second order phase transitions. The characteristic absorptions in the FTIR spectrum further characterize the compound. Further investigations on the ferroelectric behaviour of the compound at low temperatures are in progress.     

Enhanced Dissolution of Ursodeoxycholic Acid from the Solid Dispersion

Abstract

Solid dispersions of a very slightly water-solubte drug, ursodeoxycholic acid (UDCA), were prepared using urea, mannitol, and PEG 6000 as a carrier, and the solubility of UDCA was determined in water-ethanol (1:1) mixed solvent as a function of UDCA-carrier ratio. The solubility of UDCA was slightly improved when urea or PEG 6000 was used as a carrier. The powder x-ray diffraction measurements revealed that UDCA did not exist in the crystalline state in the solid dispersions. Differential scanning calorimetry (DSC) studies showed that UDCA was able to dissolve in the melt of urea, mannitol, and PEG 6000. The effect of carriers of solid dispersions on the UDCA dissolution rate was examined. The dissolution rate of UDCA was markedly increased from the solid dispersions of urea, PEG 6000, and mannitol, respectively.     

Differential Thermal Analysis of Polyethylene Glycol and Glycerol Monostearate Suppository Bases Containing Theophylline

Water soluble polyethylene glycol 4000 (PEG4) suppositories were prepared containing 4% (w/w) theophylline. Various concentrations of polyethylene glycol 1000 (PEG1) and glycerol monostearate (GMS) were also added. Differential thermal analysis (DTA) of the PEG4 and PEG1 combination suppositories showed no melting endotherm for theophylline. But when theophylline concentration in the base was 12% (w/w) and above, sharp endothermic peak of theophylline was obtained. In contrast, when GMS was added as a base material above 50% (w/w) with PEG4, the melting endotherm of theophylline (4%, w/w) appeared at 273-274°C. The melting endotherm of the suppository bases increased up to 2 to 4°C due to storage at 4°C for six months.     

Characteristics of Ti–Ni–Pd shape memory alloy thin films

Ti–Ni–Pd thin films were deposited by RF magnetron sputtering. Microstructure and phase transformation behaviors were studied by X-ray diffraction (XRD), by transmission electron microscopy and by differential scanning calorimeter (DSC). Also tensile tests and the internal friction characteristics were examined. Annealing at 750 °C followed by subsequent annealing at 450 °C resulted in relatively homogeneous microstructure and uniform martensite/austenite transformation. The results from DSC showed clearly the martensitic transformation upon heating and cooling, the transformation temperatures are 112 °C (M* peak) and 91 °C (M peak), respectively. The transformation characteristics are also found in strain–temperature curves and internal friction–temperature curves. The film had shape memory effect. The frequency had no effect on the modulus, but the internal friction decreased with increasing frequency.     

Enhanced Dissolution of Ursodeoxycholic Acid from the Solid Dispersion

Solid dispersions of a very slightly water-solubte drug, ursodeoxycholic acid (UDCA), were prepared using urea, mannitol, and PEG 6000 as a carrier, and the solubility of UDCA was determined in water-ethanol (1:1) mixed solvent as a function of UDCA-carrier ratio. The solubility of UDCA was slightly improved when urea or PEG 6000 was used as a carrier. The powder x-ray diffraction measurements revealed that UDCA did not exist in the crystalline state in the solid dispersions. Differential scanning calorimetry (DSC) studies showed that UDCA was able to dissolve in the melt of urea, mannitol, and PEG 6000. The effect of carriers of solid dispersions on the UDCA dissolution rate was examined. The dissolution rate of UDCA was markedly increased from the solid dispersions of urea, PEG 6000, and mannitol, respectively.     

A temperature study on critical micellization concentration of the novel platelet-activating factor receptor antagonist E5880 in water by electric conductivity measurements

To clarify the behavior of the novel platelet-activating factor (PAF) receptor antagonist E5880 in aqueous solution, electric conductivity was measured at different temperatures (every 5°C), ranging from 15°C to 50°C. Critical micellization concentration (CMC) of E5880 was dependent on the temperature; at 30°C, the CMC value was smallest (0.143 mM). Below that temperature, the enthalpy for formation of the micelle (Δ H⁰_m) was positive, and the formation of micelles was endothermic; above that temperature, Δ H⁰_m was negative, and the formation of micelles was exothermic.     

Thermal behaviour of 82Ni-18P amorphous powder alloy in hydrogen atmosphere

By the methods of differential scanning calorimetry and X-ray diffraction it was shown that chemically prepared 82Ni-18P amorphous powder alloy is an active hydrogen absorber in the temperature range 120–250 ° C, and that in the temperature range 340–450 °C it passes into the crystalline state. The processes of hydrogen absorption and crystallization were analyzed, and the kinetic and thermal parameters of both processes were determined.     

Thermal behavior of hydroxyapatite in structural and spectrophotometric characteristics

The thermal behavior of stoichiometric hydroxyapatite(HAp) in structural and spectrophotometric characteristics was investigated to make clear the relation between the difference of optical properties by heat treatment and radical formation seemed to be caused by appearance of vacancy in apatitic structure and to grasp the characteristics of photoexcitation connected with photocatalytic behavior of HAp. The basic apatitic structure of the HAp sample scarcely varied often by heating up to 1150°C in air. The structural water left the lattice at 1150°C from the results of XRD and FTIR spectra. The coloring of the HAp sample occurred with heat treatment, especially, at 1150°C. The strong UV absorption under 400 nm was observed after heating at 1150°C. ESR signals appeared after heating at 900°C and 1150°C. The g-values of the ESR signals were assigned as O₂⁻ species, and it is assumed that the vacancy site move in the crystalline as well as TiO₂. The strong oxidation would influence to the HAp sample with heating at 1150°C from the results that the phase of the signal of Mn²⁺ after heating at 1150°C was reverse compared with those at less than 900°C.     

Polymorphism and Crystal Growth of Phenylbutazone in Semisolid Preparations. Part One: Characterisation of Isolated Crystals from Commercial Creams of Phenylbutazone

It has been observed that a commercial product of phenylbutazone cream (o/w type) shows gritty appearance. Large Crystals up to 1000 μm in diameter have been isolated from unexpired batches. New batches from the same product show crystal size up to 150 μm in diameter. Investigation of the physical characters of the isolated crystals have been done in comparison with a pure phenylbutazone sample (99.5%). UV-Spectrophotometric analysis of the isolated crystals indicates phenylbutazone content of 90%. However, TLC examination and UV, IR and NMR Spectra examinations indicate the absence of decomposition products. Oily material has been separated from the isolated crystals by phosphate buffer solution (pH. 6.90).

DSC examinations of the isolated crystals show two endothermic peaks at 76°C and 100.1°C and one exothermic peak at 81°C. The endothermic peak at 76°C is interpreted as a result of the interaction between phenylbutazone and the oily material.

The examination of the isolated crystals before and after isothermal transformation and during melting by both hot stage microscope, ESM, (IR) and DSC indicates that the presence of phenylbutazone in the crystals is not a mechanical entrapment. It suggests that phenylbutazone interacts with the fatty base on the molecular level and both crystallise out from the cream.     

Characterization of poly(ethylene oxide) as a drug carrier in hot-melt extrusion

Poly(ethylene oxide) (PEO) as a drug carrier in hot-melt extrusion was studied by using a model drug, nifedipine, in a twin-screw extruder. Binary mixtures of PEO and nifedipine have been shown to be amenable to hot-melting at a temperature as low as 70°C, well below nifedipine's melting point (172°C). Hot-stage microscopy provided visual evidence that nifedipine can form a miscible dispersion with PEO at 120°C. Complete loss of nifedipine crystallinity when extrudated at and above 120°C with a drug loading of 20% (w/w) was further confirmed by differential scanning calorimetry (DSC) and X-ray diffraction. Cross-sectional imaging of the extrudates using scanning electron microscopy indicated homogeneous drug distribution inside PEO when the processing temperature was above 120°C. Raman spectroscopy confirmed drug-PEO interactions at a molecular level. Cryo-milled extrudates showed significant improvement in dissolution rate compared to either pure nifedipine or the physical mixture of PEO and nifedipine. A state of supersaturation was achieved after 10-minute release in pH 6.8 phosphate buffer. Finally, stability study demonstrated that the solid dispersion system is chemically stable for at least 3 months under the conditions of both 25°C/60% RH and 40°C/75% RH. Overall, PEO appears to be a promising aid/carrier to solublize poorly soluble drugs through the formation of solid dispersion via hot-melt extrusion, thereby improving dissolution and absorption.     

Physicochemical characterization of glybuzole polymorphs and their pharmaceutical properties

Systematic polymorphic screening tests were performed using 11 kinds of solvents and 6 kinds of preparation methods, and the three specific modifications of glybuzole (forms I and II and amorphous form) were identified by X-ray diffractometry and differential thermal analysis (DTA). The physicochemical properties of forms I and II and amorphous forms were measured using X-ray diffractometry, differential scanning calorimetry (DSC), thermogravimetry (TG), scanning electron microscopy (SEM), solubility tests, and others. The solubilities of all modifications in JP XII, first and second fluid (pH 1.2 and 6.8, respectively) were evaluated at 37°C. Forms I and II and the amorphous form showed almost equivalent solubilities. Forms I and II were stable polymorphic forms at 0% and 75% relative humidity (RH), respectively, at 40°C for 2 months, but the amorphous form was not stable. The crystallization rates of the amorphous form at 0% and 75% RH at 40°C were estimated by X-ray diffraction analysis based on the Jander equation, and the rate at 0% RH was 364 times slower than that at 75% RH.     

Abnormal optical behaviour of InAsSb quantum dots grown on GaAs substrate by molecular beam epitaxy

InAs(Sb) quantum dots (QDs) samples were grown on GaAs (001) substrate by Molecular Beam Epitaxy (MBE). The structural characterization by Atomic Force Microscopy (AFM) of samples shows that InAsSb islands size increases strongly with antimony incorporation in InAs/GaAs QDs and decreases with reducing the growth temperature from 520 °C to 490 °C. Abnormal optical behaviour was observed in room temperature (RT) photoluminescence (PL) spectra of samples grown at high temperature (520 °C). Temperature dependent PL study was investigated and reveals an anomalous evolution of emission peak energy (EPE) of InAsSb islands, well-known as “S-inverted curve” and attributed to the release of confined carriers from the InAsSb QDs ground states to the InAsSb wetting layer (WL) states. With only decreasing the growth temperature, the S-inverted shape was suppressed indicating a fulfilled 3D-confinement of carriers in the InAsSb/GaAs QD sample.     

A Cubic-Phase Oral Drug Delivery System for Controlled Release of AG337

AG337 is a novel thymidylate synthase inhibitor possessing potent antitumorogenic activity which was designed using protein structure-based techniques. It is currently undergoing clinical trials as both N and oral formulations. Based on AG337's short in vivo half-life, an oral controlled-release formulation is desired. The feasibility of using cubic liquid crystalline phases formed from monoolein for controlled release of AG337 has been investigated in this study. AG337 (m.p. = 298®C) was triturated with glycerol and then dissolved in monoolein using mild heat. The resulting gel was liquified by further heating to 65®C, then cooled to RT to yield a clear viscous solution. Samples of the formulation were exposed to water for up to 48 hr at 25®C. Thermal analysis of this system was undertaken in order to determine the effect of hydration state on the liquid crystalline structure. The differential scanning colorimetry (DSC) profile of samples not exposed to water showed no distinct endo- or exothermic transitions. However, samples exposed to water exhibited multiple endothermic transitions from 80° to 120°C. These data demonstrate a thermal response to time-dependent water uptake in the formulation as might occur in vivo after oral dosing, due to changes in physical properties of the system. In vitro release rates of AG337 from this formulation were evaluated.     

The effects of mischmetal, cooling rate and heat treatment on the hardness of A319.1, A356.2 and A413.1 Al–Si casting alloys

The present study investigated the effect of mischmetal as a modifier, as well as the effects of cooling rate and heat treatment on the hardness of non-modified and Sr-modified A319.1, A356.2 and A413.1 Al–Si casting alloys. The main aim of the study was to determine the effect of mischmetal in terms of mischmetal-containing intermetallic phases, as well as the effects of the chemical composition of the alloys, cooling rate and heat treatment on the corresponding hardness values obtained for the alloys in question. Two cooling rates were employed to provide estimated hardness levels of 85 and 110–115 BHN, levels conforming to levels most commonly observed in commercial applications of these alloys.

The hardness measurements revealed that the hardness values of the as-cast alloys were higher at high cooling rates than at low cooling rates. Non-modified alloys (i.e. those with no Sr addition) displayed slightly higher hardness levels compared to the Sr-modified alloys. Also, the hardness decreased with the addition of mischmetal at both cooling rates.

Two peak hardness values were observed at 200 °C/5 h and 240 °C/5 h at high cooling rates in the non-modified A319.1 alloy after aging at different temperatures between 155 °C/5 h and 240 °C/5 h, while the Sr-modified alloy showed only one peak at 200 °C/5 h. Two maximum hardness values were observed at 155 °C/5 h and 180 °C/5 h in both non-modified and Sr-modified alloys at low cooling rates. The alloys containing 0 and 2 wt% mischmetal additions exhibited the highest hardness values at both cooling rates; the hardness decreased with further mischmetal additions.

Peak hardness was observed at 180 °C/5 h in the non-modified and Sr-modified A356.2 alloys under both cooling rate conditions after aging at different temperatures between 155 °C/5 h and 240 °C/5 h. The alloys free of mischmetal exhibited relatively higher levels of hardness than those containing mischmetal. The hardness decreased with increasing mischmetal addition. At the high cooling rates, the non-modified alloys displayed higher hardness values than the Sr-modified alloys, while an opposite trend was observed at the low cooling rate.

The decrease in the hardness values may be attributed to the interaction of the mischmetal with the alloying elements Cu and Mg to form the various intermetallic phases observed. In tying up these elements, the volume fraction of the precipitation-hardening phases formed in the A319.1 and A356.2 alloys (i.e. the Al₂Cu and Mg₂Si phases) is significantly reduced, thereby decreasing the hardness. The addition of mischmetal was also reported to change the precipitation sequence of the Mg₂Si phase in the A356.2 alloy. In the case of the A413.1 alloy, the low content of alloying elements resulted in a weak response of the alloy to the age-hardening process at all aging temperature/time conditions (155 °C/5 h–240 °C/5 h), and at both cooling rates. Thus, no peak hardness was observable in these alloys.     

Thermal oxidation of InAs

The growth rate and chemical composition of thermally grown oxides on 111 InAs are presented. The oxide was found to grow very slowly at 350°C but the growth was rapid at 450 °C. The oxides grown at 350 °C contained approximately equal concentrations of As₂O₃ and In₂O₃ and no detectable elemental arsenic. The As₂O₃ concentration decreased and the elemental arsenic concentration increased with increasing growth temperature. The oxides were amorphous unless the growth temperature was 475 °C or above.     

Thermal Analysis Studies of Glass Dispersion Systems

Glass dispersion systems were examined using differential scanning calorimetry. The addition of a crystalline additive to a glassy vehicle resulted in a reduction of the vehicle's glass transition temperature. Mixtures of glassy materials were immiscible, partially miscible, or completely miscible. The results can be explained using the concept of miscibility among liquids. By combining two miscible glasses in the proper ratio, it was possible to obtain greater physical stability than with either of its glassy components. This was demonstrated with a 1:1 mixture of citric acid and acetaminophen which showed no changes in its thermogram after seven weeks of storage at 23°C. The glass transition of this mixture is about 18° C.     

Thermal stability and crystallization kinetics of sputtered amorphous Si3N4 films

The crystallization of thin silicon nitride (Si₃N₄) films deposited on polycrystalline SiC substrates was investigated by X-ray diffractometry as a function of annealing time. The amorphous Si₃N₄ films were produced by means of reactive r.f. magnetron sputtering. Annealing at temperatures between 1300 and 1700 °C led to the formation of crystalline films composed of -Si₃N₄ and β-Si₃N₄. The fraction of β-Si₃N₄ in the films reaches approximately 40% at temperatures above 1550 °C. Both polymorphic modifications were formed simultaneously during the crystallization process. A transformation of -Si₃N₄ to β-Si₃N₄ could not be observed in the time and temperature range investigated. The crystallization process of amorphous Si₃N₄ can be described according to the Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism, assuming a three-dimensional, interface controlled grain growth from pre-existing nuclei. The rate constants show an Arrhenius behaviour with an activation enthalpy of approximately 5.5 eV.     

Dynamics of absorbed water in model composites of polyamide 6 and carbon fibre evaluated by differential scanning calorimetry

The crystallization and subsequent melting behaviour of absorbed water in the model composites of polyamide 6 (PA6) and carbon fibre were investigated by differential scanning calorimetry (DSC) in comparison with those in neat PA6, using the small rectangular specimens exposed to water at 90 °C. In the DSC curves of PA6 any exothermic peaks of crystallization and endothermic ones of melting were not observed, but a step corresponding to glass transition was observed at about −30 °C during the heating process. Thus water absorbed by neat PA6 was recognized as non-freezing bound water which does not crystallize, probably due to the strong interaction with the polyamide chains. On the other hand, for the model composite several exothermic peaks were clearly observed at temperatures ranging from −10 to −20 °C, and their intensity was increased with increasing the fibre content. The distinct endothermic peaks were detected around at 0 °C during the reversed heating process. The glass transition temperature was not affected by adding the carbon fibre. Comparing with the result of neat PA6 indicates that in the model composite water exists in a state near free water, besides the non-freezing bound water dispersed in the matrix polyamide. It is further implied that water is mainly accumulated in the matrix/fibre interfacial region with some microstructural heterogeneties or defects, in which the water molecules can easily move under much weaker interaction with the polyamide chains.     

Domestic refrigerators with absorption-diffusion units and heat-transfer panels

The possibility of essential increasing of absorption-diffusion cooler set refrigerating power by means of separating cold transmission and distribution processes in the inner refrigerator volumes from cold generation processes has been shown. The problem is solved by using heat-transfer panels on the base of heat tubes and vaporization thermosiphons. The construction developed on the ‘Kristall’ type domestic cooler basis has attained a low temperature of −15°C in the 155-1 volume at the ambient temperature of 20°C and at the ambient temperature of 43°C it was allowed to reach −1°C temperature without using additional heat insulation.     

Low ductility at intermediate temperature of Ni–base superalloy M963

Tensile behavior of a cast Ni–base superalloy M963 under solution treatment and age treatment was studied in the temperature range from 20 to 1100 °C. Extensive TEM investigations were performed after tensile test to fracture. Furthermore, the fracture surfaces were studied in the SEM. The yield and tensile strengths under the two conditions initially increase with temperature and reach a peak at around 800 °C. Beyond this temperature, a sharp decrease of both yield and tensile strengths was observed. A ductility minimum was observed at 800 °C under solution treatment and disappeared under age treatment. With the increment of temperature, the following sequence of deformed substructure features was observed: dislocation pairs → connected slip bands within matrix channel under solution treatment and homogeneous interface dislocations under age treatment → homogeneous dislocation network within matrix channel. The fracture surface observation indicated that localized slip which leading to glide plane decohesion caused the poor ductility of M963 alloy.