A.U. Malik

Studies on the interaction of copper(I) halides with 2-mercaptobenzthiazole

2-Mercaptobenzthiazole forms a 1:1 yellow complex with cuprous ions. On the basis of conductometric and i.r. absorption studies it appears to be a polymeric species formed through S bridges in which Cu+ attains its normal coordination number of 4.

High temperature interactions of metal oxides with NaCl

Abstract The interaction of different metal oxides such as AL2O3, TiO2, ZrO2, SiO2, Nb2O5, Ta2O5, Cr2O3, MoO3, WO3, Fe2O3, Co3O4 and NiO with NaCl in the temperature range 800–1200 K in flowing oxygen has been studied. These oxides are present on the scales formed on Na2SO4 or NaCl during the initiation stage of hot corrosion attack and react with Na2SO4 or NaCl during the propagation stage by a fluxing reaction. Thermogravimetric, optical metallography, scanning electron microscopy, EDAX and X-ray diffraction techniques were used to identify and to determine the structure of various phases present in the solid state reaction products. The concentration of soluble metal and chloride species in the aqueous solutions of the reaction products of NaCl and metal oxides was determined using atomic absorption spectrophotometry and ion selective electrode analysis respectively. The solid state products usually contain a three-phase structure, i.e. Na2O.M2Ox, MO and Cl−. The concentration of various constituents varies according to the composition of interacting species, e.g. metal oxide and NaCl. The formation of Na2O.M2Ox depends upon the solid state solubility of metal oxides in the salt at high temperature.

High-temperature interactions of transition-metal carbides with Na2SO4

Abstract The high-temperature (900–1200 K) interaction of transition-metal carbides namely Cr 7 C 3 , Fe 3 C, TiC, ZrC, NbC, TaC, MoC, WC, VC and HfC with Na 2 SO 4 has been studied in a stream of pure and dried oxygen gas. Thermogravimetric studies were carried out by measuring the weight change as a function of time and mole fraction of Na 2 SO 4 in the reaction mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were discussed on the basis of metallography, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The quantitative determination of soluble metal species in the aqueous solutions of Na 2 SO 4 -transition-metal carbide products was carried out by atomic absorption spectroscopy. At high temperatures, transition-metal carbides interact with Na 2 SO 4 , forming metal oxides. The resulting metal oxide interacts with Na 2 SO 4 forming a soluble sodium metal oxide or a metal sulphide depending upon the local condition prevailing during the reaction.

Studies on the interactions of metal oxides and Na2 SO4 at 1100 and 1200 K in oxygen

The interaction of different metal oxides such as Co3O4, NiO, Al2O3, Cr2O3, Fe2O3 and SiO2 with Na2SO4 at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were carried out as a function of Na2SO4 in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM). The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined quantitatively using atomic absorption spectrophotometry.The high temperature interaction products usually contain a 3-phase structure namely, Na2O·M2Ox, M2Ox and metal sulphide and/or metal sulphate. The formation of Na2O·M2Ox depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility conditions Na2O·M2Ox is invariably formed, but as soon as this condition is relaxed the oxide. M2Ox, precipitates and forms a separate phase.

Studies on the interactions of bis thiourea bis chloro cobalt(II) complexes with hetrocyclic amines and phenyl arsonic acid

Abstract Mixed ligand complexes of Co(ii), viz, [Co(tu)o-Phen2Cl] Cl, [Co(tu)dipy2Cl] Cl, [Co(tu)-(PhOAs)2Cl] and [Co(tu)2py2Cl2] were prepared by the interaction of the tetrahedral complex, [Co(tu)2Cl2], with hetrocyclic amines and phenyl arsonic acid, respectively. The complex species were characterized as 6-coordinate products by their magnetic susceptibilities and electronic absorption spectra. In the heterocyclic amine substituted products, the bonding through sulphur and tertiary nitrogen has been inferred on the basis of i.r. studies, which show the presence of M=S and M=O bonds in the complexes. Kinetic studies on the substitution reactions involving the formation of the above mentioned species were carried out potentiometrically using AgAg2S as an indicator electrode. They indicate a second order overall process, first order with respect to both of the reactants.

Studies on mixed ligand complexes: Part III. Mechanism of the reaction of heterocyclic amines with tristhiourea copper(I) chloride and iodides

Summary The mechanism of the reactions of heterocyclic amines with tristhiourea copper(I) chloride and iodides has been studied potentiometrically using silver-silver sulphide as an indicator electrode. The interaction of pyridine and dipyridyl with tristhiourea copper(I) chloride and iodides results in the formation of complexes such as [Cu(Tu) 2 Py 2 ] + , and [Cu(Tu) 2 Dipy] + . The formation of [Cu(Tu) 2 Py 2 ]Cl and [Cu(Tu) 2 )Dipy]I takes place through a dissociative mechanism but that of [Cu(Tu) 2 Dipy]Cl proceeds by an associative mechanism.

Corrosion of Ni-Resist cast irons in sea water

AbstractThe corrosion behaviour of Ni-Resist cast irons in sea water has been investigated at various temperatures and dissolved oxygen concentrations. The investigations involved a case study of the failure of a Ni-Resist cast discharge column of a brine recycling pump from a sea water desalination plant and laboratory tests on two Ni-Resist cast irons. Weight loss measurements, electrochemical polarisation techniques, and metallographic methods of analysis were used to determine the corrosion rates and to investigate the nature of corrosion in Ni-Resist irons. It has been established that the discharge column of the brine recycling pump failed by stress corrosion cracking (SCC). The cracks initiated at pores and the cracking pattern was characterised by the emanation of fine cracks from large cracks. The region near the weld/base metal interface wasfound to be a preferential site for the initiation and propagation of SCC owing to the presence of higher concentrations of chromium carbide. The corrosion r...

Oxidation behaviour of silicate–chromate and oxide coated 303 steel in presence of ionic salts over temperature range 400–1000°C

AbstractThe oxidation behaviour of AISI303 steel coated with oxide and silicate–chromate coatings has been investigated in environments containing Na2SO4, Na2CO3, and NaCl, and mixtures thereof. The tests were carried out over the temperature range 400–1000°C, in air and oxidation behaviour was characterized by measuring the oxidation (weight gain) kinetics. The coated and uncoated steel specimens both follow parabolic rate kinetics over the temperature range 400–800°C, the coated steel having the better oxidation resistance. The silicate–chromate coated steel is much less severely attacked by Na2SO4 and Na2CO3 than the oxide coated steel. The addition of NaCl to Na2CO3 or Na2SO4 environments increases the aggressiveness of the melt, resulting in increased corrosion rates, although this effect is less pronounced for the oxide coated steel. These increased corrosion rates in the presence of NaCl are associated with intergranular attack of the alloy matrix by melts containing NaCl.

Coal-ash deposit corrosion of some steels and nimonic alloys

AbstractThe corrosion behaviour of some commercial austenitic steels and nimonic aalloys has been studied at 650, 800, 900 and 1000°C in air and in the presence of ash residues obtained from coals ...