• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.846-848
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• 2009

Two modifications of the ${\alpha}\;and\;{\beta}$ forms of propyl mercaptan nickel(II) cluster, [$Ni_6(SCH_2CH_2CH_3)_{12}$], have been synthesized and their crystal structures have been determined by single-crystal X-ray diffraction. The alkyl groups are away from $Ni_6$ ring in $\alpha$ form whereas they are near to the Ni atom in $\beta$ form. The distance of Ni-H in $\beta$ form [2.576(5) $\AA$] is much shorter than that in $\alpha$ form [3.101(2) $\AA$]. In the crystal lattice of $\beta$ form, the whole structure forms a flower shape.

• Composites Research
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• v.29 no.4
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• pp.145-150
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• 2016

Polyvinylidene fluoride (PVDF) as a representative polymer with the piezoelectric property has been studied since the 1960s. Crystalline structure of poly(vinylidene fluoride) polymer is composed of five different crystal structure of the polymer as a semi-crystalline. Among the various crystal structures, ${\beta}-type$ crystal exhibits a piezoelectricity because the permanent dipoles are aligned in one direction. Generally ${\beta}-form$ crystal structure can be obtained through the transformation of the ${\alpha}-form$ crystal structure by the stretching and it can increase the amount through the after treatment as poling process after stretching. ${\beta}-form$ crystal structure the PVDF fibers produced by wet spinning is formed through a diffusion mechanism of a polar solvent in the coagulation bath. However, it has a disadvantage that the diffusion path of the solvent remains as pores in the fiber because the fiber solidification occurs simultaneously with the diffusion of the polar solvent. These pores play a role in reducing effect of poling process owing to effect of disturbances acting on the polarization by the electric field. In this work, the drying method using the microwave was introduced to remove more effectively the residual solvent and the pore within PVDF fibers produced through wet-spinning process and piezoelectric PVDF fibers was produced by transformation of the remaining ${\alpha}$ form crystal structure into ${\beta}-crystal$ structure through the stretching process.

• Journal of Pharmaceutical Investigation
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• v.41 no.6
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• pp.371-376
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• 2011

The objective of this work was to investigate the existence of new crystal forms of tulobuterol which is used to prevent morning asthma attacks by ${\beta}_2$ agonist and the transformation of crystal forms. Three crystal forms of tulobuterol have been isolated by recrystallization and Form 2 was transformed to Form 4 at 52% RH and 95% RH and these four crystal forms are characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis (TG). The DSC and PXRD patterns of four crystal forms of tulobuterol were different respectively. The dissolution patterns of these three crystal forms of tulobuterol were studied and they showed significant differences in the dissolution rate. After storage of 2 months at 0% RH (silica gel, $20^{\circ}C$), 52% RH (saturated solution of $Na_2Cr_2O_7{\cdot}2H_2O/20^{\circ}C$) and 95% RH (saturated solution of $Na_2HPO_4/20^{\circ}C$), Form 1 and Form 3 were not transformed. But Form 2 was transformed to Form 4 at 52% RH and 95% RH.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.737-742
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• 2015

An environmentally favorable solid oxidizer, guanidine dinitramide ($H_2C(NH_2)NH_2N(NO_2)_2$), with high purity and synthesis yield was prepared using guanidine carbonate ($NH_2C(=NH)NH_2{\cdot}1/2H_2CO_3$). Two different crystalline forms (${\alpha}$-form and ${\beta}$-form) were obtained depending on the solvent used and synthesis process. Despite of the same chemical composition, Raman-IR and TGA-DSC revealed that different structures existed between them. In particular, the thermal analysis showed the exothermic temperature of ${\alpha}$-form at $155.7^{\circ}C$ while $191.6^{\circ}C$ for ${\beta}$-form. The caloric value of ${\alpha}$-form was 536.4 J/g which was 2.5 times larger than that of ${\beta}$-form, 1310 J/g. In addition, ${\alpha}$-form was steeply decomposed with one-step variation, but ${\beta}$-form followed a two-step thermal decomposition pattern.

• Archives of Pharmacal Research
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• v.8 no.1
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• pp.1-6
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• 1985

The crystal structure or $\gamma$-hydroxy-$\betha$-aminobutyric acid was determined by MULTAN system with X-ray intensity data on a diffractometer and refined by the least-squares method to an R-value 0.034 for 711 reflections. The crystals were orthorhombic, space group $P2_{1}2_{1}2_{1}$, Z = 4, with a = 10.220, b = 8.257 and c = 6.556$\AA$. The molecule takes the zwitterionic form and skeletal conformation is trans-transform. The molecules are held together by intra-and intermolecular NH-O and OH--O hydrogen bonds.

• Archives of Pharmacal Research
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• v.14 no.2
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• pp.137-142
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• 1991

The structure of a $\beta$-allyl type phenylpropanoid was determined by single crystal X-ray diffraction analysis. The compound was recrystallized from a mixture of n-hexane and benzene in monoclinic crystal system with a = 24.782 (2), b = 10.537 (1), c = 7.871 (1) ${\AA}, \beta=95.74$ (1)$^\circ, $D_x$=1.216, $D_m$=1.22g/$cm^3$, space group $P2_1/a$, and Z=4. The structure was solved by direct method and refined by least-squares procedure to the final R value of 0.054 for 2824 observed reflections {$F{\geq}3\sigma(F)$}. The molecular geometry shows a most stable trans-form with respect to the bulky phenyls, and this conformation is settled by an intramolecular hydrogen bond. In the crystal, the molecules are arranged along with the screw axis, and stabilized by the $O{\cdot}H{\cdots}O$ type intermolecular hydrogen bonds. The other intermolecular contacts appear to be the normal van der Waals' interactions. The compound is a dimeric phenylpropanoid, and belongs to the neolignan analogues.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.626-631
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• 1997

AlSiCa powders were prepared from the domestic Hadong Kaolin ($Al_2O_3{\cdot}2SiO_2{\cdot}2H_2O$). As a result of the reaction of Hadong Kaolin and carbon powder at reducing atmosphere, $Al_2O_3{\cdot}SiC$ composite started to form at $1300^{\circ}C$ and completed at $1400^{\circ}C$. The optimum amount of carbon was 1:4 in mole ratio. It was found that only bright-green $\beta-SiC$ phase forms when the mixture was packed without carbon powder in alumina crucible.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.76-85
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• 1992

${\beta}-$Ag_2S$(high temperature phase) was grown by solid/vapour reaction growth based on solid -state electrochemisty. In S/V growth, one of the reactants, silver ion, is supplied to the growth surface through the solid $Ag_2S$ from one side and the other reactants, surfur, is transported in the phase of vapour from the other side. With the sufficient supply of S vapour, the growth rate increased as increasing $T_d$(decomposition temperature of $Ag_2S$) and ${\Delta}T$ between $T_d$ and $T_g$(temperature of growth surface). At low S vapour pressure, growth rate decreased with decreased vapour pressure and ${\beta}-$Ag_2S$ was grown in the form of whisker, when Ag+ion is sufficiently supplied. The measured values of electronic conductivity of ${\beta}-$Ag_2S$ showed that electronic conductivity of the poly crystal was larger than that of single crystal.

• Textile Coloration and Finishing
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• v.9 no.6
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• pp.18-25
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• 1997

The change of crystalline structure and mechanical properties of i-PP films which had before isothermally annealed at various temperature and times have been studied. The following results were abtain The crystallinity and crystallite size of the samples showed increasing above the annealing temperature of 13$0^{\circ}C$ and these are equilibrated after an annealing time of 30min. When the crystalline form was at annealling condition were below 13$0^{\circ}C$, 2min, subsequently achieving an $\alpha$, $\beta$ mixing form and at 13$0^{\circ}C$, 10min, the crystalline form entered an $\alpha$ form transition. It is achieved a typical $\alpha$ form at 15$0^{\circ}C$. The value of T'm was increasing until 13$0^{\circ}C$ but it was not founded at 15$0^{\circ}C$. The slopes which represented crystalline form in an Avrami plot differed from each other within the range of this experiment.

• Textile Coloration and Finishing
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• v.17 no.4 s.83
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• pp.41-47
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• 2005

Costume heritages of an excavated silk fabrics should be preserved without damage. In order to artificially restore the excavated silk fabrics, alkaline aqueous solution, as a simulated corpse, and two kinds of silk fabrics were used. Two kinds of silk fabrics were treated by aqueous alkaline solution according to strength retention value(100, 80, 60, 40, 20$\%$). The fine structure and physical properties of alkaline treated silk fabrics were investigated with various techniques such as wide-angle X-ray diffraction, tensile test, weight loss, shrinkage, SEM. and yellowness. As the alkaline treatment time increased tensile strength of silk fabrics decreased. However, weight loss and shrinkage slightly increased. The diffraction intensity of $\beta-form$ crystal declined and $\alpha-form$ crystal diffraction intensity disappeared with the treatment.