Purification of cadmium up to 5N+ by vacuum distillation

Cadmium was refined by vacuum distillation, a technique suitable for low boiling and melting point materials, to remove the heavy and low vapour pressure impurities at ppm level. The detailed analysis of the purified Cd as well as raw Cd was done by ICP-OES techniques for 27 impurity elements. Purification was carried out in an efficient high-yield vacuum distillation system designed and fabricated for purifying 3N+ purity indigenous cadmium to 5N+ (99.999%). Analysis confirmed the reduction of total impurity content from 134 ppm (3N7) for raw Cd to 3 ppm (5N7) upon vacuum distilled Cd. The present study shows that the analysis of impurities such as Fe, Mg and Ca are contributed from environmental effect, whereas impurities such as Pb, Bi, Ag, Ni, Cu, Zn and Tl require adaptation of elemental analysing technique to counter dilution effect. The Hg trace analysis can however be carried out by hydride generation techniques.     

The cadmium oxide-tungsten oxide phase system and growth of cadmium tungstate single crystals

The results of a further study of the cadmium oxide-tungsten oxide phase diagram are presented and the results of attempts to prepare single crystals of cadmium tungstate. The defects encountered in the crystals and attempts to eliminate them are described and the best conditions for growth of high-quality single crystals detailed. The relationship of the defects to the crystal growth mechanism is discussed.     

Aqueous nitrite ion determination by selective reduction and gas phase nitric oxide chemiluminescence

An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemilluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 microL) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100-microL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2% relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 microL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well.     

X-ray diffraction line broadening of cadmium oxide produced by cadmium hydroxide decomposition

A precise analysis of X-ray diffraction line broadening produced by cadmium oxide obtained by the thermal decomposition of Cd(OH)₂ is described. The influence of experimental conditions is considered. It is shown, using different methods of analysis, that the broadening of the reflections is due to size and microstrains effects, with a mean apparent size of 6 nm in a direction perpendicular to (1 10) planes.     

The effect of phase transition in quartz single crystal on its contact angle with lead melt

The temperature dependence of the contact angle between a quartz single crystal and lead melt has been studied in a temperature interval of 350–700°C. It is established that the contact angle exhibits a jumplike change at the point of phase transition in the crystal.     

The decomposition of cadmium carbonate in air and in vacuum

Cadmium carbonate powders were decomposed isothermally in air and in vacuum over the temperature range 563 to 773 K. The decomposition rates in vacuum were higher than those in air at corresponding temperatures. When decomposed in vacuum the carbonate phase experiences a total weight loss which is higher than that based on complete dissociation of CdCO₃. The excess weight loss is attributed to stoichiometric deviations and the evaporative dissociation of CdO. On the basis of first-order kinetics, the activation energies for the decomposition of the carbonate in vacuum and in air were calculated as 185 and 177 kJ mol^–1, respectively.     

Unusual toughening effect of graphene oxide on the graphene oxide/nylon 11 composites prepared by in situ melt polycondensation

Graphene oxide/nylon 11 composites were prepared by in situ melt polycondensation. These composites displayed better mechanical properties including stiffness and toughness than the pure nylon 11 matrix. The enhanced toughness was ascribed to the change of crystal form of nylon 11, namely the triclinic α crystal form to the pseudo-hexagonal δ′ crystal form transition trend with the incorporation of GO. Scanning electron microscopy and transmission electron microscopy images showed that GO bundles and stacks with an average thickness of 20 nm are homogeneously dispersed over the nylon 11 matrix with almost no large agglomerates.     

A novel nanostructure of cadmium oxide synthesized by mechanochemical method

Cauliflower-like cadmium oxide (CdO) nanostructure was synthesized by mechanochemical reaction followed calcination procedure. Cadmium acetate dihydrate and acetamide were used as reagents and the resulting precursor was calcinated at 450 °C for 2 h in air. The structures of the precursor and resultant product of the heating treatment were characterized using Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and elemental analysis, X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction pattern (ED). SEM and TEM images revealed the cauliflower-like morphology of the sample. This structure includes the bundles of rods and tubes in nanoscale, which combine with each other and form the resulting morphology with the average diameter, 68 nm of the components. ED pattern indicated the single crystal nature of the formed bundles.