Fabricating a highly sensitive graphene nanoplatelets resistance-based temperature sensor

Purpose This study aims to present an efficient and reliable graphene nanoplatelets (GNPs)-based temperature sensor. Design/methodology/approach A high-quality dispersion of GNPs was dropped by casting method on platinum electrodes deposited on a polyethylene terephthalate (PET) substrate. The GNPs were characterized by scanning electron microscope, Raman spectroscopy and X-ray diffraction spectra to ensure its purity and quality. The temperature sensing behavior of the fabricated sensor was examined by subjecting it to different temperatures, range from room temperature (RT) to 150 °C. Findings Excellent resistance linearity with temperature change was achieved. Temperature coefficient of resistance of the fabricated sensor was calculated as 1.4 × 10–3°C. The sensor also showed excellent repeatability and stability for the measured temperature range. Good response and recovery times were evaluated at all the measured temperatures. With measuring the sensor response, the ambient temperature can be determined. Originality/value The present work presents a new simply and low cost fabricated temperature sensor based on GNPs working at a wide temperature range.

An Effective Method for Hybrid CNT/GNP Dispersion and Its Effects on the Mechanical, Microstructural, Thermal, and Electrical Properties of Multifunctional Cementitious Composites

This paper reports a study undertaken to achieve a compatible and affordable technique for the high-quality dispersion of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) in an aqueous suspension to be used in multifunctional cementitious composites. In this research work, two noncovalent surfactants with different dispersion mechanisms (Pluronic F-127 (nonionic) and sodium dodecylbenzene sulfonate (SDBS) (ionic)) were used. We evaluated the influences of various factors on the dispersion quality, such as the surfactant concentration, sonication time, and temperature using UV-visible spectroscopy, optical microscopic image analysis, zeta potentials, and particle size measurement. The effect of tributyl phosphate (TBP) used as an antifoam agent was also evaluated. The optimum suspensions of each surfactant were used to produce cementitious composites, and their mechanical, microstructural, electrical, and thermal behaviors were assessed and analyzed. The best dispersed CNT+GNP aqueous suspensions using Pluronic and SDBS were obtained for concentrations of 10% and 5%, respectively, with 3 hours of sonication, at 40°C, with TBP used for both surfactants. The results also demonstrate that cementitious composites reinforced with CNT+GNP/Pluronic showed better mechanical performance and microstructural characteristics due to the higher quality of the dispersion and the increasing hydration rate. Composites prepared with an SDBS suspension demonstrated lower electrical and thermal conductivities compared to those of the Pluronic suspension due to changes in the intrinsic properties of CNTs and GNPs by the SDBS dispersion mechanism.

Passive seismic recording of cryoseisms in Adventdalen, Svalbard

A series of transient seismic events were discovered in passive seismic recordings from 2D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images through an innovative source localisation approach, based on apparent offset resorting and inter-trace delay minimisation, followed by cross-correlation beamforming dispersion imaging. The dispersion images are highly analogous to surface wave studies of pavements and display a complex multimodal dispersion pattern. Supported by theoretical modelling based on a highly simplified arrangement of horizontal layers, we infer that a ~ 3.5–4.5 m thick, stiff, high-velocity layer overlies a ~ 30 m thick layer that is significantly softer and slower at our study site. Based on previous studies we link the upper layer with syngenetic ground-ice formed in aeolian sediments, while the underlying layer is linked to epigenetic permafrost in marine-deltaic sediments containing unfrozen saline pore water. Comparing events from spring and autumn shows that temporal variation can be resolved via passive seismic monitoring. The transient seismic events that we record occur during periods of rapidly changing air temperature. This correlation along with the spatial clustering along the elevated river terrace in a known frost polygon, ice-wedge area and the high proportion of surface wave energy constitutes the primary evidence for us to interpret these events as frost quakes, a class of cryoseism. In this study we have proved the concept of passive seismic monitoring of permafrost in Adventdalen, Svalbard.

Associations between Vehicle Exhaust Particles and Ozone at Home Address and Birth Weight

We have studied the associations between exhaust particles and birth weight. Adjustments were made for ozone and potential confounding factors at the individual level. The study included all singletons conceived between August 2003 and February 2013 with mothers living in Greater Stockholm. We obtained record-based register data from the Swedish Medical Birth Register. Data concerning the parents were provided by Statistics Sweden. Exposure levels for nearly 187,000 pregnancies were calculated using a validated air quality dispersion model with input from a detailed emission database. A higher socioeconomic status was associated with higher levels of exhaust particles at the home address. In this region, with rather low air pollution levels, the associations between levels of exhaust particles and birth weight were negative for all three of the studied exposure windows (i.e., first and second trimester and full pregnancy). For the entire pregnancy, the linear decrease in birth weight was 7.5 grams (95% CI−12.0; −2.9) for an increase in exposure, corresponding to the inter quartile range (IQR = 209 ng/m3). We also found that the risk of being born small for gestational age increased with the level of exhaust particles in all three exposure windows, but these associations were not statistically significant.

Study of the Effect of Composite Fillers on the Rheological Properties of Polymers to Create a Biodegradable Film

The modern aspects of some rheological characteristics of polymeric materials obtained using starch of substandard wheat grains and sugar beet pulp are considered. The main factors affecting mixing are discussed, which ensures high-quality dispersion and distribution of particles in the matrix in order to obtain a homogeneous mixture and the required properties of biopolymers. A study on the selection of the percentage ratio of fillers (starch and sugar beet pulp) allowed us to develop compositions for biodegradable films. The main objective of the research is to reduce the biodegradation period of polymeric material based on starch from substandard wheat grains and sugar beet pulp.

In situ polymerization approach to poly(arylene ether nitrile)-functionalized multiwalled carbon nanotube composite films: thermal, mechanical, dielectric, and electrical properties

Poly(arylene ether nitrile) (PEN)-functionalized multiwalled carbon nanotube (MWNT) composites were successfully prepared via anin situpolymerization method based on the combination of nucleophilic aromatic substitution polymerization with simple acylate-functionalized MWNTs (MWNTs-COCl) in the presence of nitrile monomers. The structure and morphology of PEN-MWNT composites were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The improvement in the thermal stability and mechanical properties of PEN-MWNT films was achieved because of the good-quality dispersion of MWNTs and strong interfacial interaction between the PEN matrix and MWNTs. The most important result is that the dielectric constant and electrical conductivity can be remarkably enhanced by a high MWNT content.

Group velocity estimation of Rayleigh wave of crust and upper mantle based on the broadband seismic data in Vietnam East Sea

In this study, the Rayleigh wave group velocity (Vgr) of Vietnam East Sea is determined by using 36,195 broadband velocity seismograms recorded by 95 seismic stations from 381 events with magnitude larger than 6.0, depth lower than 100 km, from 2000 to 2016 and applying the multiple filter analysis, integrated into Computer Program Seismology (CPS) by Herrmann and Ammon (2002). Using 2,600 high quality dispersion curves of Vrg passing through the Vietnam East Sea, the results show that: (i) The dispersion curves of Vgr in the continent region have the function graph of grade 3 with a minimum (at Vrg ≈ 2.8 km/s; T = 20 - 26 s) and a maximum (at Vrg ≈ 3.9 km/s; T = 50 - 90 s) and the dispersion curves of Vgr in the ocean have the function graph of grade 2 with a maximum (≈ 3.9 km/s; T = 40 - 90 s); (ii) At the period lower than 40s, the Vrg in Vietnam East Sea is from 2.8 km/s to 4.0 km/s and reaches a maximum at the center area; (iii) At the period over 50s, the Vrg in Vietnam East Sea is from 3.2 km/s to 4.2 km/s and the low Vgr area appears along the Red river, Con Co island, Dai Loan island, Visayas, Philippines and Borneo island.