Thermal Properties Research Papers - Academia.edu (original) (raw)

Bisthiourea Zinc Acetate (BTZA) a semi organic material has been synthesized by slow evaporation method using water as a solvent. The solubility studies have been carried out in aqueous solution in the temperature range 25 ˚C – 45 ˚C.... more

Bisthiourea Zinc Acetate (BTZA) a semi organic material has been synthesized by slow evaporation method using water as a solvent. The solubility studies have been carried out in aqueous solution in the temperature range 25 ˚C – 45 ˚C. Crystals have been grown from low temperature solution method by slow evaporation of saturated aqueous solution at room temperature. Single Crystal X-ray diffraction study has been carried out to determine the lattice parameter of the grown crystal. The spectral bands have been compared with similar thiourea complexes using FTIR spectrum in the range 400 – 4000 cm-1. Optical transmittance and absorption percentage of the grown crystal have been measured from UV-Vis studies. The thermal behavior has been investigated by thermogravimetric (TGA) and Differential Thermogram analyses (DTA). The mechanical strength and work hardening coefficient of the grown crystal have been analyzed by Vicker’s microhardness method. Keywords: Growth from solutions; X-ray d...

Stability of drugs and products has a great practical interest, which is facing to strict regulation. Thermal studies, besides the determination of the thermal properties of the investigated product allow the verification of possible... more

Stability of drugs and products has a great practical interest, which is facing to strict regulation. Thermal studies, besides the determination of the thermal properties of the investigated product allow the verification of possible interactions between the drug substances and excipients. The objective of this work was to obtain solid pre-formulates of paracetamol (PC) by spray drying (SPDR), as well as to investigate their thermal behavior. Dynamic and isotherm TG, conventional DSC and DSC-photovisual coupled methods were used to characterize the conventional and pre-formulated mixtures obtained by SPDR. The results of both DSC investigations showed slight alterations in melting temperatures, which suggests incompatibilities. The TG decomposition data of the mixtures evidenced that the dry process via SPDR leads to stability enhancement of the pre-formulated mixtures.

Bone ablation using different pulse parameters and four emission lines of 9.3, 9.6, 10.3, and 10.6 μm of the CO2 laser exhibits effects which are caused by the thermal properties and the absorption spectrum of bone material. The ablation... more

Bone ablation using different pulse parameters and four emission lines of 9.3, 9.6, 10.3, and 10.6 μm of the CO2 laser exhibits effects which are caused by the thermal properties and the absorption spectrum of bone material. The ablation mechanism was investigated with light- and electron-microscopy at short laser-pulse durations of 0.9 and 1.8 μs and a long pulse of 250 μs. It is shown that different processes are responsible for the ablation mechanism either using the short or the long pulse durations. In the case of short pulse durations it is shown that, although the mineral components are the main absorber for CO2 radiation, water is the driving force for the ablation process. The destruction of material is based on explosive evaporation of water with an ablation energy of 1.3 kJ/cm3. Histological examination revealed a minimal zone of 10–15 μm of thermally altered material at the bottom of the laser drilled hole. Within the investigated spectral range we found that the ablation threshold at 9.3 and 9.6 μm is lower than at 10.3 and 10.6 μm. In comparison the ablation with a long pulse duration is determined by two processes. On the one side, the heat lost by heat conduction leads to carbonization of a surface layer, and the absorption of the CO2 radiation in this carbonized layer is the driving force of the ablation process. On the other side, it is shown that up to 60% of the pulse energy is absorbed in the ablation plume. Therefore, a long pulse duration results in an eight-times higher specific ablation energy of 10 kJ/cm3.

Using an electronic apparatus simulating a bird roosting in a nest at night, we examined the insulating qualities of Eurasian Tree Sparrow (Passer montanus) nests built in nest boxes under winter conditions. Nests of different... more

Using an electronic apparatus simulating a bird roosting in a nest at night, we examined the insulating qualities of Eurasian Tree Sparrow (Passer montanus) nests built in nest boxes under winter conditions. Nests of different construction were compared with an empty box, and with roosting in open air. Energy savings in an empty box accounted for 18%, in boxes with

Two series of organic–inorganic hybrid films were prepared from epoxidised castor oil (ECO) and the inorganic precursor 3-aminopropyltriethoxysilane (APTES), and the combination of APTES with tetraethoxysilane (TEOS) with different... more

Two series of organic–inorganic hybrid films were prepared from epoxidised castor oil (ECO) and the inorganic precursor 3-aminopropyltriethoxysilane (APTES), and the combination of APTES with tetraethoxysilane (TEOS) with different organic to inorganic proportions. Films were pre-cured at room temperature under inert atmosphere and subsequently submitted to thermal curing. The macro- and microscopic properties of the films, including adhesion, hardness, microstructure and thermal properties, were determined as a function of the proportion of ECO to inorganic precursors. Morphologic studies showed that the hybrid films were microscopically homogeneous. The hardness and tensile strength of the films increased with increased concentrations of inorganic precursor. All of the films exhibited good adhesion to an aluminium surface and worked as an efficient barrier against corrosion.

Ultra-thin fibers are obtained from polyacrilonitrile co-polymer (PAN-CP)/N,N-dimethylformamide (DMF) solution by electro-spinning technique. The different wt. content of PAN-CP solution is electrospun with varying processing parameters... more

Ultra-thin fibers are obtained from polyacrilonitrile co-polymer (PAN-CP)/N,N-dimethylformamide (DMF) solution by electro-spinning technique. The different wt. content of PAN-CP solution is electrospun with varying processing parameters to get nanofibers. The morphology of nanofibers is studied by scanning electron microscopy (SEM) and thermal properties are primarily investigated by DSC and TGA. The polymer nanofibers are stabilized and carbonized to get carbon nanofibers, after stabilization and carbonization nanofibers are characterized by FTIR, XRD, SEM and SPM. It is found that the diameter of nanofibers varies from 150 to 1300 nm, that increases with increasing polymer concentration and decreases with increasing the tip to collector distance and collector speed. The DSC studies show that the exothermic peak occurs at two different temperatures 275 and 320 °C in case of nanofibers. While in case of micron fiber single exothermic peak occurs at ∼275 °C. This might be due to the alignment of polymeric chain along the fiber direction. This is due to the stretching and whipping that occurs during the electrospinning process. As a consequence, increase in thermal stability and decrease in weight of nanofibers is confirmed by TGA. However, in the nanofibers of diameter >1000 nm, weight loss pattern is found to be similar as that of micron fibers. This could be due to the entrapping of solvent between polymeric chains. On stabilization and carbonization there is a decrease in fiber diameter in all the cases. The extent of decrease is higher in case of 10 wt.% electrospun fibers, from 350–400 nm to 100 nm. The SPM investigations reveal that the surface area and roughness changes due to the transverse shrinkage of nanofibers.