Incorporation Of Nanoclusters Research Articles

Comparison for Grain Growth Dynamics of Severely Deformed Austenite and Martensite NiTi Shape Memory Alloys after Complete Crystallization of Amorphous Phase

Severe plastic deformation (SPD) based on local canning compression is imposed on Ni-rich Ni50.7Ti49.3 (at.%) shape memory alloy (SMA) with B2 austenite phase and equiatomic Ni50Ti50 (at.%) SMA with B19′ martensite phase in order to induce the amorphization of the two alloys. SPD-processed Ni50.7Ti49.3 and Ni50Ti50 samples are annealed at 450°C for various times in order to comparatively investigate grain growth dynamics of severely deformed austenite and martensite NiTi SMAs after complete crystallization of amorphous phase. The grain growth exponent of B2 austenite Ni50.7Ti49.3 SMA is 2.78, whereas the grain growth exponent of B19′ martensite Ni50Ti50 SMA is 3.18. The results show that grain growth dynamics of amorphous NiTi samples is sensitive to the chemical composition. The grain growth of equiatomic B19′ martensite Ni50Ti50 sample is inhibited to a greater extent than that of Ni-rich B2 austenite Ni50.7Ti49.3 one. The mechanisms for grain growth of NiTi SMAs deal with formation of nano-clusters due to crystallization of amorphous phase, recovery of retained nanocrystalline grains containing dislocations under thermal driving force, growth of retained nanocrystalline grains as well as new nanocrystalline grains and incorporation of nano-clusters or smaller nanocrystalline grains into larger nanocrystalline grains. The grains of Ni50.7Ti49.3 sample absorb nano-clusters more readily than that Ni50Ti50 one during grain growth. Investigation on grain growth dynamics of severely deformed NiTi SMAs lays the foundation for fabricating nanocrystalline NiTi SMAs with tailored grain size.

Monodispersed ultrasmall NiMo metal oxide nanoclusters as hydrodesulfurization catalyst

In this study, we report the synthesis of ultrasmall NiMo bimetallic metal oxide nanoclusters (∼2nm), supported on γ-Al2O3 for hydrodesulfurization reaction. The metal oxide nanoclusters were prepared by colloidal synthesis using oleic acid and oleylamine as ligands, followed by incorporation of nanoclusters into the pores of γ-Al2O3. The nanocluster supported γ-Al2O3 was calcined to remove the ligands followed by sulfidation. Compared to the catalyst prepared using conventional wet impregnation method, the nanoclusters prepared using colloidal synthesis showed enhanced catalytic activity for the hydrodesulfurization of dibenzothiophene because of the ultrasmall size of the metal oxide nanoclusters supported on γ-Al2O3. In addition, we have evaluated the performance of our catalyst with a diesel sample (containing ∼14,700ppm sulfur) obtained from a crude distillation unit. The sulfur content of the feed was reduced to ∼35ppm at 335°C and LHSV 2h−1 showing the good catalytic activity.

Incorporation of Thiol-Stabilized CdTe Nanoclusters into Langmuir-Blodgett Films

The methods of incorporating thiol-stabilized CdTe nanoclusters into mono- and multilayer films produced by the Langmuir-Blodgett (LB) technique on the basis of anionic (behenic acid) and cationic (octadecyltrinonylammonium (ODTNA) iodide) surfactants were investigated. ‘Pressure-area’ isotherms, quartz crystal microbalance (QCM), FTIR, atomic force microscopy (AFM) and UV/Vis spectroscopy give evidence on the incorporation of the nanoclusters in LB films. The limiting surface area of the behenic acid monolayer increases with a simultaneous decrease of the film strength. The optical absorption of the films obtained through the incorporation of the clusters acquires the features of CdTe nanocrystals. The noticeable difference in the deposition process was observed for the two types of stabilizing ligands (thioglycerol and mercaptoethanol) used for the CdTe clusters. The bonding of the CdTe clusters with the carboxylic group of behenic acid monolayer is established for the thioglycerol-stabilized clusters.