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Effective hydrogen gas sensor based on palladium nanoparticles dispersed on graphene sheets by spin coating technique

Inpaeng Saowaluk, Muangrat Worawut, Tedsree Karaked, Pfeiler Wolfgang, Chodjarusawad Thanawee, Issro Chaisak

Materials Science Poland

2020

Vol. 38, No. 2

305--311

A room-temperature hydrogen gas (H2) sensor was successfully fabricated by dispersion of palladium nanoparticles (Pd NPs) on graphene sheets (GRs) (hereafter referred to as “Pd NPs/GRs”). GRs and Pd NPs were synthesized by chemical vapor deposition technique and by polyol process, respectively. A colloidal solution of Pd NPs with an average diameter of 11 nm was then dispersed onto the GRs by spin coating technique. The density of dispersed Pd NPs on GRs was controlled by varying the volume of the dispersed solution within the range of 50 – 150 μL. The fabricated Pd NPs/GRs sensors exhibited a high sensitivity for H2 gas with a concentration of 1500 – 6000 ppm at room temperature. Upon H2 exposure, the Pd NPs/GRs sensors showed an increase in electrical resistance, which could easily be measured. The relationship between sensor response and H2 concentration is in correspondence with the Langmuir adsorption model. The H2 detection limit is estimated to be 1 ppm. The results demonstrate that the Pd NPs/GRs sensor is an easily fabricated, but very effective means for room-temperature detection of H2 at ppm level.

Static stability analysis of mass sensors consisting of hygro-thermally activated graphene sheets using a nonlocal strain gradient theory

Selvamani Rajendran, Mahaveer-Sreejayan Madasamy, Ebrahimi Farzad

Engineering Transactions

2020

Vol. 68, iss. 3

269--295

This paper develops a nonlocal strain gradient plate model for buckling analysis of graphene sheets under hygro-thermal environments with mass sensors. For a more accurate analysis of graphene sheets, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. The graphene sheet is modeled via a two-variable shear deformation plate theory that does not need shear correction factors. Governing equations of a nonlocal strain gradient graphene sheet on the elastic substrate are derived via Hamilton’s principle. Galerkin’s method is implemented to solve the governing equations for different boundary conditions. Effects of different factors, such as moisture concentration rise, temperature rise, nonlocal parameter, length scale parameter, nanoparticle mass and geometrical parameters, on buckling characteristics of graphene sheets are examined and presented as dispersion graphs.

Effect of graphene as anti-settling agent for magnetorheological fluid

Thanikachalam J., Nagaraj P., Hikku G. S.

Journal of Achievements in Materials and Manufacturing Engineering

2016

Vol. 77, nr 2

49--56

Purpose: Magnetorheological fluids are field-responsive fluids containing magnetic particles suspended in a suitable medium. In this proposed work, the iron powder was dispersed in silicone oil to obtain magnetorheological fluid. These fluids can be transformed from liquid-like state to solid-like state within milliseconds by applying magnetic field and vice versa. The particles arrange as chain like pattern with the application of magnetic field, increasing the yield strength of the fluid. However, when the shear stress reaches the critical value, the chain like pattern breaks causing reduction in yield strength. One of the major limitations of these fluids is that the suspended particles settle down quickly forming cake like structure at the bottom, which is very difficult to re-disperse. Design/methodology/approach: The present study focuses on increasing the Sedimentation time of the fluid by adding suitable Nano additives. For this purpose graphene nanoparticles with atomic thickness were introduced as an additive to decrease the sedimentation of the fluid. The added graphene sheets (gap-fillers) filled the interspaces of Iron particles and improved the sedimentation resistance. Different quantities of graphene were added (0.5 g, 1.5 g, 2.5 g and 3.5 g) and their normalized height was calculated with time. Interpolation method was also done to find the sedimentation values with Graphene addition which were not done experimentally. Findings: The prepared samples were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope, Optical Microscopy, Viscometer etc. Contour plot was interpreted to understand the effect of graphene addition towards the normalized height and viscosity of the fluid.