Authors:G. Madhurambal, M. Mariappan, B. Ravindran, and S. C. Mojumdar
aqueous solutions. The bright and transparent crystals obtained were characterized. The TG and DTA studies confirm a two-stage decomposition of the compound when heated between 180 and 750 °C. The FTIR spectra show characteristic vibrational frequencies of
Authors:G. Madhurambal, M. Mariappan, and S. Mojumdar
A single crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent
crystals obtained were characterised by TG–DTA, UV and FTIR spectral analyses. A fitting decomposition pattern for the title
compound was formulated on the TG curve which shows a two stage mass loss between 200 and 750 °C. DTA curve shows exothermic
peaks supporting the formulated decomposition pattern in this temperature range. The UV and FTIR spectra show the characteristic
absorption, vibration frequencies due to urea–thiourea zinc chloride crystals. Detailed structural analysis of the compound
is under progress.
The novel two-step synthesis method decreasing
the calcining temperature necessary for formation of spinel lattice and as
well for reaching of bright and clear hue of the pigments prepared were investigated.
This work aims to utilization of DTA for synthesis monitoring. Influence of
raw materials and temperature of calcination on color properties were observed.
The characterization of the samples was performed by X-ray diffraction and
colorimetry in the CIE L*a*b* system. It
was proved that the black spinel pigment Cu2.3Mn2.8Cr4.9Ox can be prepared at finally temperature 700C as one-phase system with
high quality black hue.
The technique of crystal growth coupled with a stereophotocalorimetric method has been used in a series of supercooling measurements on pure refractory metals. The cooling history of these metals is recorded on photographic films which are calibrated as a function of the temperature. High absolute amounts of supercooling has been observed in W, Ta, Nb and Re liquid droplets. It is noted that the brightness traces of the solidification process for highly supercooled Re droplets evidence of two successive phase transformations (Re cfc to Re hc) shows.
Authors:G. Madhurambal, M. Mariappan, and S. Mojumdar
A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent
crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic
analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight
loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition
pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals.
Detailed structural analysis of the compound is under progress.
Authors:R. Jenkins, H. Grubbs, R. Newman, R. Bass, J. Brenizer, D. Jones, T. Williamson, D. Danehower, and R. Long
The use of instrumental neutron activation analysis (INAA) in determining selected elements in biological materials has been reported by numerous authors. Some of these have detailed the use of INAA to determine an elemental analysis in tobaccos of various geographical origins. This paper describes the first use of INAA to measure the distribution of selected inorganic elements within the tobacco leaf at a single plant stalk position for one tobacco curing routine. Three replicate plots of a common bright tobacco cultivar were grown under normal cultural conditions characteristic for the bright variety. The tobacco leaves were sampled at selected positions in the leaf. The brigh tobacco was cured in a conventional flue-curing barn using standard practices. Immediately after collection, each individual sample was freeze-dried, crushed and sampled. The leaf midrib samples were prepared using a similar procedure. A subsample of about 100 mg was taken from each sample, sealed in a polyethylene bag, irradiated in a thermal neutron flux of 2×1017 n·m–2·s–1 in a pneumatic rabbit system, and subsequently counted to obtain the reported data. A standard reference material was used as a comparator to yield relative elemental concentrations for Ca, Mg, Mn, Na, K, Cl and Br. The data show that chlorine, potassium, sodium and calcium have definite concentration trends within the tobacco leaf. The data also show that some elements, e.g. Mn, were more uniformly distributed throughout the leaf.
Authors:Žaneta Mesíková, Petra Šulcová, and M. Trojan
Inorganic pigments containing lanthanides based on pseudo cubic structure of SrSnO3 have been prepared by solid state reaction between SrCO3, SnO2 and lanthanide oxides (Tb4O7, Pr6O11, CeO2) in the temperature range 1300–1550°C. The resultant materials were characterised by XRD, TG-DTA and colourimetric techniques
were used. The most interesting colour properties were provided by SrTb0.4Sn0.6O3 prepared by firing at temperature 1500°C which has light yellow-green colour hue. The increase of temperature 1300–1500°C
caused the creation of pigments with deeper and brighter colour hue. Colour properties of the samples prepared by calcination
at 1550°C were of inferior quality due to structural changes from pseudo cubic to orthorhombic system.
Authors:Žaneta Dohnalová, Petra Šulcová, and M. Trojan
This work is focused on determination of the optimum firing temperature which leads to formation of the compounds LnFeO3 with good pigment-application properties (Ln=Gd, La, Yb, Tm, Lu). Based on results of thermal analysis the compounds were prepared by the solid-state reaction at temperature
900 and 1000°C. Colours of pigments vary depending on type of used lanthanoid (from light sienna to dark brown) and also on
the type of precursor. Generally, the compounds prepared from iron oxide have more interesting color properties. Colour of
these compounds is brighter and deeper. Increasing of the calcination temperature from 900 to 1000°C causes the darkening
of colour. The most problably, the darkening is connected with partial reduction of Fe3+ to Fe2+.
Authors:P. Thomas, K. Dwarakanath, K. Varma, and T. Kutty
A complex oxalate precursor, CaCu3(TiO)4(C2O4)8·9H2O, (CCT-OX), was synthesized and the precipitate that obtained was confirmed to be monophasic by the wet chemical analyses,
X-ray diffraction, FTIR absorption and TG/DTA analyses. The thermal decomposition of this oxalate precursor led to the formation
of phase-pure calcium copper titanate, CaCu3Ti4O12, (CCTO) at ≥680°C. The bright-field TEM micrographs revealed that the size of the as synthesized crystallites to be in the
30–80 nm range. The powders so obtained had excellent sinterability resulting in high density ceramics which exhibited giant
dielectric constants upto 40000 (1 kHz) at 25°C, accompanied by low dielectric losses, <0.07.
Two petroleum-derived aromatic hydrocarbon resins (HRs) were blended (1:1) with expanded polystyrene (EPS) waste and small
amounts (up to 10 mass%) of poly(vinyl chloride) (PVC) to increase both the lustrous carbon (LC) yield and softening point
of the blends without any deterioration of their rheological characteristics. The blends were prepared and tested for LC content,
softening points, shear stress and apparent viscosity to check their applicability as LC precursors under industrial conditions.
The properties of polystyrene compositions with bitumen fractions depend primarily on composition and viscosity of oil fraction.
Additional modification by poly(vinyl chloride) improves the blends’ properties, like bright coal content, softening point
and viscosity, and opens new possibilities of plastics’ wastes utilization.