Chittagong University of Engineering & Technology

About: Chittagong University of Engineering & Technology is a education organization based out in Chittagong, Bangladesh. It is known for research contribution in the topics: Renewable energy & Dielectric. The organization has 1200 authors who have published 1444 publications receiving 10418 citations. The organization is also known as: Engineering College, Chittagong & Bangladesh Institute of Technology, Chittagong.

Enhanced dielectric properties of prospective Bi0.85Gd0.15Fe1−xCrxO3 multiferroics

Abstract: Scientific endeavor for tailoring properties of functional materials offers a significant urge to material scientists. The driving force is to facilitate the current understanding that may create new pathway to alternative materials. BiFeO3 is inherently multiferroic and its exploitation for applications in diversified fields are still required extensive investigations in different perspectives. In this context, we synthesized new Bi0.85Gd0.15Fe1−xCrxO3 multiferroics prepared by wet chemical method using high purity metal salts. We mainly focused on the investigation of dielectric properties, ac electrical conductivity and complex electrical modulus of the synthesized materials. Crystallographic measurements confirmed its rhombohedral structure which gradually transforms towards orthorhombic structure with increasing Cr dopants. The grain size of the synthesized samples was found to vary from 68 to 22 nm depending on doping concentration. Dielectric properties of sintered samples were studied in the frequency range of 100 Hz–1 MHz. Frequency dependent dielectric constant has shown to display dielectric dispersion behavior. At higher frequencies ( ⩾ 10 5 Hz), due only to electronic and ionic polarizations the dielectric constant has shown to be independent of frequency. Complex impedance showed a semicircular arc due to the dominant grain boundary resistance and the electric modulus confirms the existence of electrical relaxation. The AC conductivity ( σ AC ) has shown to obey a power law. Obtained improved properties suggested that the synthesized Bi0.85Gd0.15Fe1−xCrxO3 ceramic by partial substitution of A and B sites by Gd 3 + and Cr 3 + shows added advantage in application over the pure BiFeO3 counterpart.

Printable Single-Unit-Cell-Thick Transparent Zinc-Doped Indium Oxides with Efficient Electron Transport Properties.

Abstract: Ultrathin transparent conductive oxides (TCOs) are emerging candidates for next-generation transparent electronics. Indium oxide (In2O3) incorporated with post-transition-metal ions (e.g., Sn) has been widely studied due to their excellent optical transparency and electrical conductivity. However, their electron transport properties are deteriorated at the ultrathin two-dimensional (2D) morphology compared to that of intrinsic In2O3. Here, we explore the domain of transition-metal dopants in ultrathin In2O3 with the thicknesses down to the single-unit-cell limit, which is realized in a large area using a low-temperature liquid metal printing technique. Zn dopant is selected as a representative to incorporate into the In2O3 rhombohedral crystal framework, which results in the gradual transition of the host to quasimetallic. While the optical transmittance is maintained above 98%, an electron field-effect mobility of up to 87 cm2 V-1 s-1 and a considerable sub-kΩ-1 cm-1 ranged electrical conductivity are achieved when the Zn doping level is optimized, which are in a combination significantly improved compared to those of reported ultrathin TCOs. This work presents various opportunities for developing high-performance flexible transparent electronics based on emerging ultrathin TCO candidates.

Potential of Wind and Solar Electricity Generation in Bangladesh

Abstract: Wind and solar energies are the alternative energy sources that can be used to supplement the conventional energy sources particularly in Bangladesh. In this work, the aim is to assess the current wind and solar energy potential in Bangladesh. The wind data for the five stations obtained from Local Government Engineering Department have been assessed, but only two of them seem to be eligible for energy production. Annual average, monthly average, and hourly average wind speeds and wind power densities were calculated from the wind data. The Weibull distribution parameters (c and k), the dominant wind directions, and the frequency distributions were also determined. Experimentally measured solar radiation data are not available over Bangladesh. Measured climatological data such as cloud cover and sunshine duration data of Bangladesh Meteorological Department from 1992 to 2001 used for the estimation of global solar radiation as they are correlated. Technoeconomic feasibility analysis is done for 100 kW grid connected wind and solar photovoltaic (PV) systems. Renewable-energy-based system will bring more environmental benefits than conventional power in terms of human health, reduction of air pollution, and decrease of noise, and so forth. However, in the above estimation, these were not considered.

Electronic and optical properties of non-hexagonal Dirac material S-graphene sheet and nanoribbons

Abstract: In this paper, we have critically explored the electronic, magnetic and optical properties of stable non-hexagonal carbon allotrope S-graphene (SG). The band structure of SG sheet exhibits two Dirac cones at distinct k → points. The ab-initio molecular dynamics study reveals the dynamical stability of the system up to 600 K. Besides, the sheet possesses appreciable mechanical stability. Furthermore, the electronic properties of the ribbons strongly depend on the edge geometry and width. The A-type S-graphene nanoribbons (SGNRs) with even N exhibit width-dependent direct bandgap semiconducting nature. Whereas, A-SGNRs with odd N are semi-metallic. In contrary, B-SGNRs are uniformly semi-metallic except for extremely narrow N = 1 and 2 case. Besides, the unexpected occurrence of Dirac point for the N = 4.5 C-SGNR has been explored. Moreover, the optical response of the sheet and nanoribbons are highly anisotropic. We have critically obtained the plasma frequency for the collective electron oscillation of the sheet at 5.37 eV under parallel incidence of electromagnetic waves. Besides, the effective number of electrons participating in direct interband transitions in sheet show a quasi-saturation between 3-10 eV. We thus expect these theoretical predictions will provide a basic understanding of the opto-electronic responses towards possible application of this non-hexagonal graphene network with multiple Dirac cones.