Indian Institute of Technology Guwahati

About: Indian Institute of Technology Guwahati is a education organization based out in Guwahati, Assam, India. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 6933 authors who have published 17102 publications receiving 257351 citations.

Microscopic origin of lattice contraction and expansion in undoped rutile TiO 2 nanostructures

Abstract: We have investigated the microscopic origin of lattice expansion and contraction in undoped rutile TiO2 nanostructures by employing several structural and optical spectroscopic tools. Rutile TiO2 nanostructures with morphologies such as nanorods, nanopillars and nanoflowers, depending upon the growth conditions, are synthesized by an acid-hydrothermal process. Depending on the growth conditions and post-growth annealing, lattice contraction and expansion are observed in the nanostructures and it is found to correlate with the nature and density of intrinsic defects in rutile TiO2. The change in lattice volume correlates well with the optical bandgap energy. Irrespective of growth conditions, theTiO2 nanostructures exhibit strong near infrared (NIR) photoluminescence (PL) at 1.43?eV and a weak visible PL, which are attributed to the Ti interstitials and O vacancies, respectively, in rutile TiO2 nanostructures. Further, ESR study reveals the presence of singly ionized oxygen vacancy defects. It is observed that lattice distortion depends systematically on the relative concentration and type of defects such as oxygen vacancies and Ti interstitials. XPS analyses revealed a downshift in energy for both Ti 2p and O 1s core level spectra for various growth conditions, which is believed to arise from the lattice distortions. It is proposed that the Ti4+ interstitial and F+ oxygen vacancy defects are primarily responsible for lattice expansion, whereas the electrostatic attraction between Ti4+ interstitial and O2? interstitial defects causes the lattice contraction in the undoped TiO2 nanostructures. The control of lattice parameters through the intrinsic defects may provide new routes to achieving novel functionalities in advanced materials that can be tailored for future technological applications.

A Dual-Material Gate Junctionless Transistor With High- $k$ Spacer for Enhanced Analog Performance

Abstract: In this paper, we present a simulation study of analog circuit performance parameters for a symmetric double-gate junctionless transistor (DGJLT) using dual-material gate along with high- k spacer dielectric (DMG-SP) on both sides of the gate oxides of the device. The characteristics are demonstrated and compared with DMG DGJLT and single-material (conventional) gate (SMG) DGJLT. The DMG DGJLT presents superior transconductance (Gm), early voltage (VEA), and intrinsic gain (GmRO) compared with SMG DGJLT. The values are further improved for DMG-SP DGJLT, because high- k spacer enhances the fringing electric fields through the spacer.

Effect of cellulose nanocrystal polymorphs on mechanical, barrier and thermal properties of poly(lactic acid) based bionanocomposites

Abstract: Cellulose nanocrystals (CNCs) using different polymorphs of cellulose were fabricated from raw bamboo pulp through alkali treatment followed by acid hydrolysis. The effect of CNC polymorphs, namely CNC I, CNC II and CNC:I → II (CNC II from cellulose I), on morphology, crystal structure, degree of hydrogen bonding and thermal stability were studied. These polymorphs were dispersed in polylactic acid (PLA) films using a casting evaporation approach and their effect on the structural, thermal, mechanical and barrier properties of the PLA were investigated. The CNC polymorphs differ significantly in their reinforcement capability and ability to form percolated networks. Incorporation of CNC II and CNC:I → II significantly improved the Young's modulus of composites (by ∼72%). However, their elongation at break significantly decreased compared to CNC I, due to high hydroxyl functionality, which forms an entangled hydrogen bonded network within the polymer matrix, leading to improvement in mechanical as well as barrier properties. The theoretically calculated moduli of composites using Halpin–Kardos, Cox–Krenchel and Ouali models showed good agreement for CNC I, CNC II and CNC:I → II, albeit at higher aspect ratio. All three CNCs showed the ability to form percolated networks, the occurrence and stability of which varied with the type of polymorph. Therefore, the current study provides an insight towards selection of appropriate polymorphs for fabrication of CNC reinforced high performance poly (lactic acid) based bionanocomposites.

Application of artificial neural network and response surface methodology for the removal of crystal violet by zinc oxide nanorods loaded on activate carbon: kinetics and equilibrium study

Abstract: The present work discusses the removal of crystal violet dye from aqueous solution by ultrasound assisted adsorption using zinc oxide nanorods loaded on activate carbon as an adsorbent The said adsorbent was prepared and characterized using field emission scanning electron microscopy, X-ray diffraction and Fourier transform infrared analysis The important process parameters, such as initial crystal violet concentration (8–24 mg/L), solution pH (30–70), adsorbent doses (0005–0025 g), and sonication time (2–6 min) were optimized using design of experiments The optimum removal efficiency of crystal violet onto adsorbent was determined as 9982% at pH 70, 0025 g adsorbent dosage, 24 mg/L initial crystal violet concentration and 50 min sonication time Analysis of variance showed a high coefficient of determination ( R 2 = 0992) The present analysis suggests that the predicted values are in good agreement with experimental data Also, the artificial neural network model was used for predicting removal (%) of crystal violet dye based on experimental data Equilibrium data was fitted well with the Langmuir model having maximum adsorption capacity of 11364 mg/g The adsorption of crystal violet followed the pseudo-second order kinetic model This study clearly showed that response surface methodology was one of the appropriate methods to optimize the operating conditions