Volume 12, Issue 4, April 2021

Progress and Perspectives of Photodetectors Based on 2D Materials

Wenkai Zhu; Faguang Yan; Quanshan Lv; Ce Hu; Kaiyou Wang

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-3
DOI: 10.5185/amlett.2021.041616

Photodetectors based on two-dimensional (2D) materials and their heterostructures have been attracting immense research interests due to their excellent device performances, such as ultrahigh photoresponsivity, ultrafast and broadband photodetection, polarized sensitivity, flexibility, and Complementary Metal-Oxide-Semiconductor (CMOS) compatibility. Here, we firstly compare the device performance of several photodetectors based on Schottky junctions and p-n junctions, such as photoresponsivity and response time. Then, we provide an overview of the recent progress on 2D material-based photodetectors, emerging strategies to improve device performances by structure optimization and bandgap engineering as well. Finally, we discuss the challenges and perspectives on the exploration of 2D materials and their heterostructures for future application in electronics and optoelectronics.

Synthesis and Characterization of Platinum and Platinum based Alloy Nanoparticles Anchored on Various Carbon Materials for Methanol Oxidation in a DMFC – A Short Review

Richa Baronia; Jyoti Goel; Sunil K. Singhal

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-22
DOI: 10.5185/amlett.2021.041617

In the fabrication of direct methanol fuel cells (DMFCs) having high performance the essential conditions are (i) the design and construction of a suitable anode electrocatalyst comprising of Pt or a Pt based alloy nanoparticles methanol oxidation reaction (MOR) efficiently and effectively (ii) nature of support materials onto which these nanoparticles are anchored. In MOR one of the major problems is the adsorption of poisoneous carbonmoxide and other similar intermediates near the active surface of Pt active leading to its deactivation and also the crossover of methanol solution towards the cathodic side. All these factors, therefore, lower the overall electrochemical performance of the electro-catalysts. In the present review paper we report some of our important results of the synthesis of different Pt and Pt based anode electro-catalysts (Pt, PtCo alloys, PtCu alloys) anchored on different support materials such as reduced graphene oxide (rGO), Nitrogen doped rGO and a hybrid of rGO/CNTs for MOR and compared with few of those already reported recently. A detailed characterization of raw materials and the electro-catalysts synthesized in this work is also discussed using XRD, FT-IR, SEM, TEM etc. The electrochemical measurements were made using cyclic voltammetry in acidic medium at room temperature.

Influence of Processing Induced Morphology on the Performance of PP Injected Intricate Pieces Modified with MWCNT as a Painting Aide

Alejandra Costantino; Leandro Ramajo; Julio Viana; Caren Rosales; Antonio Pontes; Valeria Pettarin

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-10
DOI: 10.5185/amlett.2021.041618

Carbon nanotubes are currently added to polymers to avoid extra-stages in the electrostatic painting process. However, the attained particle network after processing a final part could affect the mechanical properties and thermal stability of nanocomposites. It is then important to evaluate not only the functional properties, but also the overall performance of these pieces. In this work, boxes of polypropylene (PP) modified with multi-walled carbon nanotubes (MWCNT) were injection molded. Morphology induced by processing was characterized at different locations of the moldings to correlate the influence of in-homogeneities and flow pattern with the overall performance of the molded boxes. PP/MWCNT presented a better aesthetic quality and a markedly better thermal stability than pure PP. It was confirmed that the nanocomposite has high dielectric permittivity, low dielectric losses and relatively good DC conductivity. Regarding mechanical properties, MWCNT induced a slight improvement in flexural elastic modulus. Although fracture initiated at practically the same loading levels for both materials, the propagation energy was deteriorated by MWCNT presence. Differences in both electrical and mechanical behavior were found trough out the PP/MWCNT pieces as result of distinct MWCNT orientation and distribution. It was then concluded that processing has a great influence on parts performance.

Inhibitive Effect on the Rate of Hydrolysis of Tetracaine by the Surfactant-Coated Magnetic Nanoparticles (Fe3O4)

Mohd Shaban Ansari; Kashif Raees; M. Z. A. Rafiquee

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-7
DOI: 10.5185/amlett.2021.041619

The influence of the magnetic nanoparticles Fe3O4 and surfactant coated nanoparticles on the rate of alkaline hydrolysis of tetracaine were investigated spectrophotometrically. The Fe3O4 nanoparticles were synthesized by co-precipitation method. These synthesized nanoparticles were characterized by physical techniques. The XRD patterns showed the crystalline nature and the presence of two bands at 635 cm -1 and 585 cm -1 were assigned to the Fe-O bond vibrations in Fe3O4. The SEM and TEM studies confirmed the spherical structure of nanoparticles. The VSM studies show the magnetic nature. The reaction rate increased linearly with increase in [NaOH]. The rate constant values decreased with the increase in the SDS coated Fe3O4 nanoparticles from 4.0 × 10 -4 s -1 to 1.1 × 10 -4 s -1 in the presence of PEG 1500. Similarly, the increase in the amount of CTABr coated Fe3O4 nanoparticles decreased the rate constant values from 4.0 × 10 -4 s -1 to 1.02 × 10 -4 s -1 in the presence of PEG 1500. The binding constant and rate constant were found to be lower in SDS coated nanoparticles than the CTABr coated particles. The observed results for - [surfactant] in the presence of magnetic nanoparticles and surfactant coated nanoparticles were treated using the pseudophase kinetic model.

Multi-Energy System Based on Ocean Thermal Energy Conversion

Zhihao Li; Jiapeng Su; Hui Yu; Anjun J. Jin; Jin Wang

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-7
DOI: 10.5185/amlett.2021.041620

The ocean thermal energy is abundant. The global total is about 40 billion kW. The ocean thermal energy conversion (OTEC) is clean and renewable, the power generation is stable, and the energy storage has high capacity. Active exploitation of ocean thermal energy resources is of great significance to realize the strategy of maritime power. In view of the efficiency limit of a traditional OTEC, authors propose an approach of a multi-energy complementary OTEC system that they can improve the efficiency of this system. The approach sets parameters at the system level and integrates solar energy, wind energy, energy storage and OTEC. For example, a 1MW integrated power generation system is designed and simulated by means of computer aided design and of conducting a model-based simulation, respectively. The efficiency of the complementary OTEC system with solar heating can reach 13.12%. In this article, the basic principle and working process of the approach are analyzed, and the system efficiency is calculated. The results show that, in comparison to the traditional OTEC, the complementary system of OTEC can improve the ratio of power generation output efficiency, stability and ocean energy utilization.  

Synthesis of Nitrogen-doped KTaTeO6 with Enhanced Visible Light Photocatalytic Degradation of Methylene Blue

Mannepalli Sudheera; Perala Venkataswamy; Gundeboina Ravi; Kadari Ramaswamy; Nalluri Chitti Babu; Muga Vithal

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-10
DOI: 10.5185/amlett.2021.041621

Anion doping is one of the efficient ways to tailor the bandgap of photocatalysts for the treatment of polluted water. The present work describes the improved photocatalytic activity of defect pyrochlore, KTaTeO6 (KTTO), upon nitrogen doping, towards the degradation of methylene blue under visible light irradiation. The parent KTaTeO6 was synthesized by solid-state method. The N-doped KTaTeO6 (N-KTTO) was prepared by nitridation method using NH3. Techniques such as the XRD, N2 adsorption-desorption, FE-SEM/EDX/EDS elemental mapping, TEM-HRTEM, UV-Vis DRS, XPS, Raman, and PL were employed to characterize the physicochemical properties of photocatalysts. The N-doping in KTTO has resulted in enlarged surface area, narrowed the bandgap, and reduced the recombination of photogenerated electron-hole pairs, leading to enhanced photocatalytic activity compared to parent KTTO. The active species trapping experiments were conducted to elucidate the mechanism of photodegradation. The N-KTTO is chemically stable and can be used at least up to five cycles.

Structural Evolution and Enhanced Energy Density, Ferroelectric Property Investigation in Gd Substituted NBT – BT Lead Free Ferroelectric Ceramics

K.S.K.R. Chandra Sekhar; M.L.V. Mahesh; Y. Rama Krishna; K. Chandra Mouli; R. Ramchandra Kiran; Patri Tirupathi

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-6
DOI: 10.5185/amlett.2021.041622

Gd substituted 0.94(Na0.5Bi0.5-xGdxTiO3) – 0.06 BaTiO3 (x = 0.00, 0.01, 0.02 and 0.03) lead free ferroelectric ceramics were synthesized by a conventional solid-state synthesis. Room temperature XRD reveals the formation of perovskite structure without secondary impurity peaks. Rietveld refinement pattern confirms the coexistence of dual phase i.e., major monoclinic (Cc) and minor tetragonal (P4mm). More tetragonality and slim ferroelectric properties were noted with increasing Gd content in NBT-BT solid solutions. A collective Gd substitution stimulates the transition of PE loop shape from square to slim with slanted leads to suit for high energy density storage applications. The optimum energy storage properties can be achieved for x = 0.03 ceramic showed a recoverable energy density 1.59 J/cm3 and a remarkably best energy efficiency of 67% under 65 kV/cm at room temperature.

Designing of 10 Wt. % Graphite Particulate Hot Forged AA7075 Composites and its Loss Factor Analysis

N.B. Dhokey; A.G. Jadhav; S.S. Nimbalkar; V. Nimbalkar

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-7
DOI: 10.5185/amlett.2021.041623

The composite material is an emerging opportunity for improving the loss factor. In the present context, AA7075 was fabricated in induction furnace using elemental addition such as Zn, Mg and Cu and ex-situ reinforcement of 10wt. % graphite particulates with three types of composites viz 3 to 10 μm (C1), 53 to 66 μm (C2) and 106 to 150 μm (C3). The melt was poured at 780 o C and cast into the steel mold then hot forged at a strain rate of 3- 5x10-3 s-1 in three stages with net cross-section reduction in the range of 30-33%. Solutionizing at 470 o C was followed by artificial aging at 120 o C. Characterization was carried out by SEM and DMA at two selected frequencies 0.1Hz and 1Hz over the temperature range of 30 to 250 o C. Significant improvement in storage modulus (E’) and loss modulus (E”) noticed in C2 as compared to the C1, C2 and monolithic alloy. A threshold value of the volume to the surface of graphite reinforcement has arrived for an improved loss factor. A generalized experimental model formulated to account for 12 influencing parameters and the significance of damping capacity with the response to graphite content has been established.

Positron Annihilation Spectroscopy of Basaltic Rocks from Plio-Qaternary Volcanics, Sana’a-Amran Volcanic Field, Yemen

K. R. Mahmoud; Mohamed Th. S. Heikal

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-5
DOI: 10.5185/amlett.2021.041624

We focus a new application of positron annihilation lifetime spectroscopy and Doppler broadening techniques at the annihilation sites have been applied on some basaltic rocks from inactive volcano related to Sana’a-Amrana volcanic Field (SAVF). A brief geologic set up and the main petrographic signature of this inactive volcano are given. To gain an insight into geological environment, open nanospaces in the well-characterized basaltic rocks were investigated by positron annihilation spectroscopy. The analysis of the lifetime spectra yielded two lifetime components. The olivine basalt samples contain less mono- vacancies than those found in the trachybasalt and vesicular basalt samples. The overall defect (vacancy) concentration and its variation in the samples were estimated using the mean positron lifetime (τm). The Doppler broadening parameters (S and W-Parameters) were measured. A little variation of the S-parameter values has been observed for all the studied samples indicating that the valance electron contribution to annihilation is not significant.