scholarly journals A Novel Method for Estimation of Transition Temperature for Polymorphic Pairs in Pharmaceuticals Using Heat of Solution and Solubility Data

2002 ◽  
Vol 50 (2) ◽  
pp. 263-267 ◽  
Author(s):  
Koji Urakami ◽  
Yasushi Shono ◽  
Atsuya Higashi ◽  
Kazuichi Umemoto ◽  
Masayuki Godo
Keyword(s):  
Transition Temperature ◽  
Solubility Data ◽  
Heat Of Solution ◽  
Novel Method

scholarly journals A Novel Method for Notable Reducing Phase Transition Temperature of VO2 Films for Smart Energy Efficient Windows

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 58 ◽  
Author(s):  
Huan Guan ◽  
Dongping Zhang ◽  
Yu Yang ◽  
Yi Liu ◽  
Aihua Zhong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Carrier Concentration ◽  
Phase Transition Temperature ◽  
Energy Efficient ◽  
Measurement Results ◽  
High Transition ◽  
Novel Method ◽  
Parameters Measurement

Although Vanadium dioxide (VO2) has a potential application value for smart energy efficient windows because of its unique phase transition characteristic, there are still many obstacles that need to be overcome. One challenge is to reduce its high transition temperature (ζc = 68 °C) to near room temperature without causing its phase transition performance degradation. In this paper, a novel method was employed that covered a 3 nm ultra-thin heavy Cr-doped VO2 layer on the pure VO2 films. Compared with the as-grown pure VO2, obviously, phase transition temperature decreasing from 59.5 °C to 48.0 °C was observed. Different from previous doping techniques, almost no phase transition performance weakening occurred. Based on the microstructure and electrical parameters measurement results, the mechanism of ζc reducing was discussed. The upper ultra-thin heavy Cr-doped layer may act as the induced role of phase transition. With temperature increasing, carrier concentration increased from the upper heavy Cr-doped layer to the bottom pure VO2 layer by diffusion, and induced the carrier concentration reach to phase transition critical value from top to bottom gradually. The present method is not only a simpler technique, but also avoids expensive alloy targets.

scholarly journals Frost-Resistant Epoxy-Urethane Binders Containing Diglycidyl Urethane

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Vladimir N. Strel’nikov ◽  
Valeriy Yu. Senichev ◽  
Alexey I. Slobodinyuk ◽  
Anna V. Savchuk ◽  
Elena R. Volkova
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Elastic Materials ◽  
Novel Method

A novel method for developing frost-resistant epoxy-urethane binders is proposed that is based on mixtures of epoxy-urethane oligomers and diglycidyl urethane formed during synthesis. The microheterogeneous elastic materials obtained by curing these mixtures by the cycloaliphatic amines have a low glass transition temperature and high mechanical properties.

Estimation of Transition Temperature of Pharmaceutical Polymorphs by Measuring Heat of Solution and Solubility

2002 ◽  
Vol 75 (6) ◽  
pp. 1241-1245 ◽  
Author(s):  
Koji Urakami ◽  
Yasushi Shono ◽  
Atsuya Higashi ◽  
Kazuichi Umemoto ◽  
Masayuki Godo
Keyword(s):  
Transition Temperature ◽  
Heat Of Solution

scholarly journals Morphology and Properties of Aminosilane Grafted MWCNT/Polyimide Nanocomposites

2008 ◽  
Vol 2008 ◽  
pp. 1-15 ◽  
Author(s):  
Siu-Ming Yuen ◽  
Chen-Chi M. Ma ◽  
Chin-Lung Chiang ◽  
Chih-Chun Teng
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Percolation Threshold ◽  
Multiwalled Carbon ◽  
Mwcnt Content ◽  
Glass Transition Temperatures ◽  
Novel Method ◽  
Polyimide Composites

This investigation presents a novel method for modifying multiwalled carbon nanotubes (MWCNTs). The morphology, electrical resistivity, and percolation threshold of MWCNT/Polyimide nanocomposites were studied. Acid-modified MWCNTs reacted with (3-aminopropyl)triethoxysilane by ionic bonding, and were then mixed with polyamic acid via imidization. TEM microphotographs reveal that silane-grafted MWCNTs were connected to each other. The electrical resistivity of silane-grafted MWCNT/polyimide decreased substantially below than that of acid-treated MWCNTs when the silane-modified MWCNT content was lower than 2.4 wt%. The percolation threshold of the MWCNT/polyimide composites is 1.0 wt% for silane-modified MWCNT and exceeds 7.0 wt% for acid-modified MWCNT. The acid-modified MWCNT/polyimide composites possess slightly higher glass transition temperatures than that of pure polyimide. The glass transition temperature of the polyimide increased significantly with silane-modified MWCNT content. Tensile properties of the polyimide have been improved with the MWCNTs content.

Superconducting energy gap of NbS2

1984 ◽  
Vol 62 (8) ◽  
pp. 776-779 ◽  
Author(s):  
R. J. Kennedy ◽  
B. P. Clayman
Keyword(s):  
Magnetic Susceptibility ◽  
Transition Temperature ◽  
Energy Gap ◽  
Far Infrared ◽  
The Novel ◽  
Superconducting Transition ◽  
Small Particles ◽  
Energy Gaps ◽  
Superconducting Energy Gap ◽  
Novel Method

The superconducting energy gaps of small particles (1–10 μm) of 2H–NbS2 and 2H–NbSe2 have been measured by far-infrared (FIR) transmission spectroscopy. Comparison of these results with previous FIR measurements made on millimetre-size single crystals of 2H–NbSe2 validates the use of the novel method of sample preparation used here. Comparison of the gap frequencies (νg) with the superconducting transition temperature (Tc) determined by magnetic susceptibility measurements indicates that 2H–NbS2, unlike 2H–NbSe2, exhibits non-Bardeen–Cooper–Schrieffer (BCS)-like behaviour, with hνg/kTc = 2.3.

scholarly journals Solubility of a Pharmacological Intermediate Drug Isatin in Different Solvents at Various Temperatures

2013 ◽  
Vol 17 ◽  
pp. 36-46 ◽  
Author(s):  
Shipra Baluja ◽  
Rahul Bhalodia ◽  
Mehul Bhatt ◽  
Nayan Vekariya ◽  
Ravi Gajera
Keyword(s):  
Thermodynamic Parameters ◽  
Atmospheric Pressure ◽  
Water Solubility ◽  
Chlorinated Solvents ◽  
Solubility Data ◽  
Heat Of Solution ◽  
Maximum Solubility ◽  
Carbon Tetra

The solubility of isatin in different solvents was studied by a gravimetrical method from (298.15 to 318.15) K under atmospheric pressure and the solubility data were correlated against temperature. The solvents selected for the present study are: water, methanol, ethanol, 1-butanol, dichloromethane, dichloroethane, chloroform and carbon tetra chloride. Among chlorinated solvents, solubility is observed to be maximum in 1, 2-dichloroethane and minimum in dichloromethane whereas in alcohols, maximum solubility is observed in methanol. In water, solubility is found to be minimum. Further, some thermodynamic parameters such as Gibb’s energy (ΔGsol), heat of solution (ΔHsol) and entropy of solution (ΔSsol) have also been evaluated.

scholarly journals An Insight into Thermodynamic Relationship Between Polymorphic Forms of Efavirenz

2012 ◽  
Vol 15 (2) ◽  
pp. 234 ◽  
Author(s):  
Renu Chadha ◽  
Poonam Arora ◽  
Anupam Saini ◽  
Dharamvir Singh Jain
Keyword(s):  
Transition Temperature ◽  
Fusion Rule ◽  
Solution Calorimetry ◽  
Enthalpy Of Fusion ◽  
Solubility Data ◽  
Enthalpies Of Solution ◽  
Thermally Induced ◽  
Preferential Formation ◽  
Polymorphic Forms ◽  
Stable Forms

Purpose: The aim of the work is to study the crystallization of efavirenz to understand the preferential formation of various polymorphic forms, to establish their identity, to study the transformation between the polymorphic forms on heating and to determine their free energy. Methods: Slow crystallization from different solvents under controlled conditions was employed to prepare various crystalline forms. The TGA and DSC were used to study their thermal behavior and inter-conversion of these forms. The calorimetrically determined enthalpies of solution and solubility data are utilized to determine the transition temperatures. Results: Six polymorphic forms of efavirenz are identified and characterized completely. The TGA scans of all the forms did not show any mass loss indicating absence of hydrate or solvate. The thermally induced transformations are observed in the DSC scans of five forms II-VI indicating them to be metastable which are converted to stable higher melting forms. The melting temperature and enthalpy of fusion of lower melting (FormL) and higher melting forms (FormH) reveal that four of these polymorphic pairs are monotropically related. The enthalpies of solution of FormL are found to be more exothermic as compared to corresponding FormH. The transition temperature (Tt) determined using enthalpy of solution and solubility data was found to be higher than the melting of both the forms except for polymorphic pair VIL/VIH. The effect of ΔCp on transition temperature is also reported. Conclusions: The form I is found to be thermodymanically most stable but least soluble. The forms II-V are metastable and are converted irreversibly to stable forms. The enthalpy of fusion rule and virtual transition temperature provided complementary evidence for the existence of monotropy in these polymorphic pairs. However, enantiotropy is demonstrated in VIL/VLH pair and is well established in our study. Novelty: The present study reveals the thermodynamic aspects of various isolated polymorphic forms of efavirenz. Solution calorimetry along with other techniques is used to study the transformation of one form to another. The emphasis is laid on determination of transition temperature of various polymorphic pairs which has not been reported earlier. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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