S. C. Mojumdar

Heat transfer through a textile layer composed of hollow fibres

Textiles are used as thermal isolating materials for technical and clothing applications. The paper generally deals with heat transfer through textile layers by conduction, convection, radiation and evaporation of humidity. This experiment evaluates heat transfer by conduction and radiation through textile layers containing hollow polyethylene terephthalate (PET) fibres. The environment created by a composite textile layer containing hollow PET fibres and air is not identical for every method of heat transfer. During heat transfer through a textile layer, we evaluate of the importance of macromorphological structure of the elementary fibres and textile layer, taking into account the thermo-physiological properties.

Synthesis and characterization of ultrafine spinel ferrite obtained by precursor combustion technique

Nanoparticles of the spinel ferrite, Co0.6Ni0.4Fe2O4 have been synthesized by the precursor combustion technique. This synthetic route makes use of a novel precursor viz. metal fumarato hydrazinate which decomposes autocatalytically after ignition to yield nanosized spinel ferrite. The X-ray powder diffraction of the “as prepared” oxide confirms the formation of monophasic nanocrystalline cobalt nickel ferrite. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been fixed as Co0.6Ni0.4Fe2(C4H2O4)3·6N2H4. The Curie temperature of the “as prepared” oxide was determined by ac susceptibility measurements.

Thermal and spectral properties and induction period, interfacial energy and nucleation parameters of solution grown anthracene

Anthracene crystals were grown by solution growth technique by adopting slow evaporation method from the solvents CS2, CCl4 and CHCl3. The induction period was measured at various super saturations, and hence the interfacial energies were evaluated. Using the interfacial tension value, the nucleation parameters such as radius of the critical nuclei (r*), the Gibbs free energy change for the formation of a critical nucleus (∆G*) and the number of molecules in the critical nucleus (i*) were also calculated for all these solvents at two different temperatures. The effect of surface tension, viscosity and density of these solvents are correlated with interfacial tension. The solution grown crystals were subjected to UV, FTIR, NMR and X-ray diffraction studies. The purity and high-thermal stability of the grown crystals were determined using thermal analysis.

Thermal properties of solid complexes with biologically important heterocyclic ligands

The stoichiometry of thermal decomposition of the complexes Ni(NCS)2(fpy)4 (I), Ni(NCS)2(bfpy)4 (II) and Ni(NCS)2(CF3Phfpy)4 (III) (where fpy=furopyridine, bfpy=benzo-[2,3]furo[3,2-c]pyridine, CF3Phfpy=2-(3-fluoromethylphenyl) furo[3,2-c]pyridine) have been investigated in nitrogen atmosphere from room temperature to 500°C by means of TG and DTG. The results revealed that release of the heterocyclic ligands occurs in two steps. IR data suggested that fpy, bfpy and CF3Phfpy ligands were coordinated to Ni(II) through the N atom of the respective heterocyclic rings and same is the case with the anionic NCS group.

Thermal properties of fillers based on organoclays in the polymeric materials

Nowadays, there is the widespread use of clay minerals as fillers in polymeric materials. One of the most widely used mineral is montmorillonite belonging to the smectite. We have prepared organically modified clays using two different types of accelerators TP and ZDT for sulfur vulcanization. Intercalation of these accelerators into the interlayer of clays was performed using a gas reaction at room temperature. They were examined (characterized) by thermal analysis (DTA, TG), X-ray analysis, and infrared spectroscopy (FTIR).

TG–DTA, XRD, SEM, EDX, UV, and FT-IR spectroscopic studies of l -valine thiourea mixed crystal

A new semi organic nonlinear optical (NLO) crystal, l-valine thiourea has been synthesized and good optical quality single crystals were grown by slow evaporation technique. The growth conditions of the crystals are studied and the grown crystals are confirmed by powder X-ray diffraction studies. The grown crystal was characterized using powdered XRD, FT-IR, UV–Vis–NIR, EDX, and TG–DTA. The crystalline nature and its various planes of reflections were observed by the powder XRD. The presence of various functional groups was confirmed by FT-IR spectra. The UV–Vis–NIR spectra indicate that the crystal has very good absorption in the entire visible and near IR region spectrum suggesting the suitability of the material for NLO applications. The decomposition temperatures and mass loss have been estimated from the thermogravimetric analysis.

Influence of Vo(II) doping on the thermal and optical properties of magnesium rubidium sulfate hexahydrate crystals

We have prepared pure and divalent vanadyl ion-doped magnesium rubidium sulfate hexahydrate crystals by using slow evaporation solution growth technique. It is interesting to observe that Vo(II) doping influences the physical properties of MRSH. Presence of Vo(II) ions in the doped specimen was confirmed by energy dispersive spectroscopy and electron paramagnetic resonance spectroscopy. FTIR studies reveal that the doping of vanadium ion has not altered the basic structure of MRSH. Scanning electron microscope studies of doped sample reveals that structure defect centers are formed in the crystals. Gradual decomposition patterns were observed for pure and doped specimens in thermogravimetry and differential thermogravimetry. The grown crystals were also characterized by powder X-ray diffraction. The second harmonic generation efficiency tested using Kurtz powder technique is not influenced by the added dopant.

Thermal properties of textile fabrics

Objective evaluation techniques were used in this study of thermal properties of textile fabric. The Alambeta, P tester, and Togmeter measure the passages of air which were used for evaluation of the physiological properties. Fibrous materials were prepared in the form of textile knitting fabric COOLMAX. It is clear from the measurement that there are considerable differences in the results of measurement with described methods. Device Alambeta is convenient for the measurement and evaluation of various thermal properties. Finally, it can be concluded that this field of measurements is developing and will be the subject of further research of other methods, more suitable for measurement of the various characteristics.

Influence of knitted structures on heat transfer

In this paper we studied the influence of knitted structures on heat transfer. The structure of the knitted fabric was expressed by geometric properties such as thickness, surface mass and bulked mass, and knitted structure. Heat transfer was experimentally measured on three types of devices. It was found that the measured structural properties do not have a significant effect on heat transfer of knitted fabrics. From three types of devices, the selected device was Alambeta as the most objective method for measuring thermal parameters. It was determined to be the most suitable of knitted structure which provided the best thermal insulation properties.

Synthesis growth and characterization of l-valine nickel (II) chloride

A new semi organic nonlinear optical crystal, l-valine nickel chloride has been synthesized and good optical quality single crystals were grown by slow evaporation technique. The growth conditions of the crystals are studied and the grown crystals are confirmed by powder X-ray diffraction studies. The grown crystal was characterized by using powdered XRD, FT-IR, UV–Vis–NIR, EDAX, and TG–DTA. The crystalline nature and its various planes of reflections were observed by the powder XRD. The presence of various functional groups was confirmed by FT-IR spectroscopic technique. The UV–Vis–NIR spectrum indicates that the crystal has very good absorption in the entire visible and near IR region spectrum suggesting the suitability of the material for NLO applications. The decomposition temperatures and mass loss have been estimated from the thermogravimetric analysis.