Browsing by Author "Kumar, Ajay"

In current study, the variation of sub-capping thickness of InGaAs strain reducing layer (SRL) of InAs quantum dot heterostructure using digital alloy approach is presented. The thickness of 6 nm SRL of conventional structure (sample A) is divided equally with 2 nm thickness (sample B) by using digital alloy approach. Further, using such approach, this thick 6 nm capping is divided in unequal fashion for sample C (1 nm, 2 nm and 3 nm) and sample D (3 nm, 2 nm and 1 nm) from InAs QD towards top GaAs layer. The In-content inside the SRL of the sample A is 15%, whereas, In-content inside the divided-SRL is considered as 45%, 30% and 15% for all other samples. Such composition of SRLs helps in reducing the In-out diffusion, minimizing the lattice mismatch at InAs QD-SRL and SRL-top GaAs layer interfaces, and also reduces the strain inside the overall heterostructures. Two strains, namely hydrostatic and biaxial are calculated by using Nextnano for all the structures and compared simultaneously. The hydrostatic strain inside the QD of sample D is reduced by 4.74%, 1.07% and 2.269% and the biaxial strain inside the QD of sample D is improved by 1.66%, 0.696% and 1.276% as compared to that of samples A, B and C, respectively. The computed PL emission of samples A, B, C and D are observed to be 1305 nm, 1365 nm, 1349 nm and 1375 nm, respectively. Hence, sample D is the optimum choice for fabricating future opto-electronic devices.

Plastic has changed the human life by frequent usage in daily needs due to its practical features compared to other materials. In addition, the ability to get easily molded and low production cost make it better a choice than other materials. Industry 4.0 concepts and technologies are playing vital role in manufacturing sector. Among the available processes extrusion molding is popularly used for producing the plastic products. The production time and quality of the product in extrusion blow molding is greatly affected by material selection, pressure, temperature, cooling time and extrusion speed. The optimum parameters selection is very crucial to increase the productivity with low cost of the product. The present work investigates the effect of various parameters such as extruder pressure, die temperature along with extruder speed on production time for 20-L bottle made up of low-density polyethylene (LDPE) material using extrusion molding process. Design of experiments using response surface methodology is used to obtain experimental results. The main and interaction effect of process parameters are studied successfully using central composite design (CDD). The individual main effect graphs and 3D surface plots are used to understand the effect of input parameters on the process timing.

HKUST-1 Metal-Organic Framework (MOF), due to its coordinatively unsaturated metal sites, high surface area and microporosity, is one the most prominent MOF candidates. Our study investigates the consequence of doping iron into HKUST-1 MOF on its hydrostability, and demonstrates its usability for Pb(II) removal. A simple one-pot solvothermal process was used to synthesize Fe doped HKUST-1 MOF with varying dopant concentrations of Fe (5–20 mol%). Through various characterisation techniques (XPS, XRD, FTIR, ICP-OES) and MD simulations we demonstrated the incorporation of Fe into the HKUST-1 framework, which happened through Fe substituting the Cu(II) sites. Water stability studies using experimental and modelling approaches demonstrated that partial substituted Fe-HKUST-1 MOFs have a greater surface area retention with very little loss in crystallinity as compared to pristine HKUST-1 MOF. Fe substitution of as low as 5 mol% yielded a significant enhancement in the hydrostability of HKUST-1 MOFs, wherein the structure was intact for up to 10 hrs of water treatment. Similarly, 5 mol% Fe doping had a 53% reduction in the amount of Cu being leached out from the HKUST-1 MOF framework. Fe doped HKUST-1 MOFs showed exceptionally high Pb(II) selectivity, Pb(II) removal efficiency of > 90%, and a high Pb(II) adsorption capacity of 565 mg g⁻¹. This study opens up the possibility of using doping as a strategy to enhance the hydrostability of HKUST-1 MOF and in the process improve its applicability for environmental remediation applications.

meta-Aminophenols are formed by the action of DBU on 3-amino-2-chlorocyclohex-2-en-1-ones at room temperature in MeCN. The chloro compounds are generated by treating 3-aminocyclohex-2-en-1-ones with the easily prepared halogenating agent BnNMe3·ICl2 in MeOH-CH2Cl2. The amino group must carry two substituents, either two aryl, one aryl and one alkyl, or two alkyl groups; 3-aminocyclohex-2-en-1-ones of this type are readily made from cyclohex-2-en-1-one and a primary or secondary amine.