Nano-scaled multilayered TiAlN/VN coatings have been grown on stainless steel and M2 high speed steel substrates at U B =-85 V in an industrial, four target, Hauzer HTC 1000 coater using combined cathodic steered arc etching/unbalanced magnetron sputtering. X-ray diffraction (XRD) has been used to investigate the effects of process parameters (Target Power) on texture evolution (using texture parameter T*), development of residual stress (sin 2 method) and nano-scale multilayer period. The composition of the coating was determined using energy dispersive X-ray analysis. The thermal behaviour of the coatings in air was studied using thermo-gravimetric analysis, XRD and scanning electron microscopy. The bi-layer period varied between 2.8 and 3.1 nm and in all cases a {1 1 0} texture developed with a maximum value T* = 4.9. The residual stress varied between-5.2 and-7.4 GPa. The onset of rapid oxidation occurred between 62 and 645 C depending on the (Ti+Al):V ratio. After oxidation in air at 550 C AlVO4, TiO2 and V2O5 phases were identified by XRD with the AlVO4, TiO2 being the major phases. The formation of AlVO4 appears to disrupt the formation of Al2O3 which imparts oxidation resistance to TiAlN based coatings. Increasing the temperature to 600 and 640 C led to a dramatic increase in the formation of V2O5 which was highly oriented (001) with a plate-like morphology. At 640 C there was no evidence of the coating on XRD. Increasing the temperature to 670C led to further formation of AlVO4 and a dramatic reduction in V2O5.
Ni2`-and Al3`-exchanged montmorillonite are known to demonstrate Lewis and Bronsted acidity, respectively, when probed using the diagnostic base pyridine (C. Breen, Clay Miner., 1991, 26, 487). Thermogravimetric analysis (TGA) of pyridine saturated Al3`-and Ni2`-montmorillonite di †er whereas here it was found that cyclohexylamine (CHA) desorption proÐles were very similar, albeit CHA was held to a higher temperature on Ni2`-SWy-2 than on Al3`-SWy-2. Evolved gas analysis (EGA) of the desorbed products revealed signiÐcant di †erences in the amount of cyclohexylamine, cyclohexene, methylcyclopentene, benzene and aniline produced, which demonstrated di †erent decomposition pathways for CHA sorbed to Al3`-and Ni2`-exchanged SWy-2. For example, cyclohexene is produced over both exchange forms whereas aniline and methylcyclopentene were the major products over Ni2`-and Al3`-SWy-2, respectively. Variable-temperature DRIFTS was unable to distinguish between CHA-treated Al3`-and Ni2`-SWy-2 at temperatures \250 ¡C, but at 300 ¡C the Ni2`form exhibited a strong, intense band at 1648 cm~1 which identiÐes cyclohexylimine as a surface bound intermediate which transforms before desorption.
Samples of air-dried and heated Ni 21 -and Al 31 -exchanged bentonite (SWy-2) have been exposed to 3-cyanopyridine (3CYP) vapour for six days. The resulting intercalates were studied using variable temperature XRD, DRIFTS, thermogravimetry (TG) and TG-MS. The amount of water co-adsorbed with 3CYP did not influence the initial 13.2 A ˚spacing of the Al 31 -complex but the d-spacing of the heated Ni 21 -sample was ca. 5 A less that the 21.5 A ˚spacing of its air-dried counterpart. This difference in layer spacings suggests that 3CYP adopts an arrangement in which the plane of the aromatic ring is parallel with the aluminosilicate layer in the Al 31 -clay whereas in the Ni 21 -form the plane of the ring is perpendicular to the clay surface. TG-MS confirmed that 3CYP and water were the major species desorbed from all samples and that the contraction in the d-spacing upon heating the Ni 21 -3CYP complex arose from loss of these species. The appearance of a band near 1680 cm À1 in the VT-DRIFTS spectra at temperatures above 150 1C indicated the formation of amide(s). Correlation with TG-MS data confirmed the transformation of small quantities of 3CYP to nicotinamide. Some 3CYP was protonated in the Al 31 -samples.
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