Detailed Surface Properties Research Articles

Heat transfer enhancement of the f-MWCNT- Fe2O3/Water hybrid nanofluid with the combined effect of wire coil with twisted tape and perforated twisted tape

The impact of various variables on thermal conductivity and rheological behavior, such as nano particle weight concentration and temperature, and also the cumulative effects of coil ratio (CR = 3, 4) of wire coil insert and twist ratio (TR = 3, 4 and 5) of twisted tape (TT) and perforated twisted tape (PTT) on heat transfer coefficient and friction factor characteristics is explored. Nanofluids containing particles with weight percentages of 0.01%, 0.02%, and 0.03% were produced by dispersing functionalized multi-walled carbon nanotubes (f-MWCNTs) 60% by weight and Fe2O3 nanoparticles 40% by weight in distilled water and stabilizing them with an ultrasonic probe. The KD-2 Pro thermal analyzer and Rheometer are used to measure the thermal conductivity and viscosity of the hybrid nanofluids. The impact of various factors on the heat transfer and pressure drop is investigated, including Reynolds number, nanoparticle concentration, TR and CR of TT, PTT and WC. The findings clearly show that higher content of nanoparticles increases heat transfer as well as pressure drop. In contrast to the base coolant, the enhancement in heat transfer and friction factor is 21.66%–31.66% and 1.14 times, respectively. In comparison to a plain tube passing through 0.03 wt % hybrid nanofluid, the enhancements in heat transfer and friction are 32.31%–94.03%, 43.94%–141.07%, and 1.09 times, 1.13 times for the combined effect of TT and PTT having wire insert at ratio's of twist and coil are 3, respectively. Furthermore, UV–vis spectroscopy is being used to assess the stability of the prepared nanofluids, which is found to be acceptable. FESEM is used to determine the detailed surface properties.

MRS-Tex: A Magnetically Responsive Soft Tactile Device for Texture Display

Tactile devices provide an intuitive way for texture display, which allows users to perceive the detailed surface properties of virtual or remote objects. For existing tactile devices that create actual topographical transformations, it remains challenging to render surface textures with high spatial resolution due to the limitation of the size of actuators. To address this challenge, a magnetically responsive soft actuator with a diameter of 1 mm is proposed. Integrating the high-density soft actuator array and a soft membrane bracket, we develop a magnetically responsive soft tactile device (named MRS-Tex) for texture display. When a magnetic field is applied, the magnetic units will sink to form pits, and the soft membrane bracket resists the finger pressure so that users can perceive the rendered surface texture. Thanks to the proposed sunken solution, MRS-Tex is capable of rendering surface textures with millimeter-level resolution (1.5 mm) while providing a sufficient upward holding force. Moreover, we conduct quantitative experiments and two user studies to evaluate the performance of MRS-Tex. Experimental results show that MRS-Tex can generate pits with a depth of more than 0.20 mm, which is sufficient for rendering perceivable surface textures. The average discrimination accuracy of user study can reach up to 82% for both six basic texture patterns and four complex texture patterns.

Surface properties of heterogeneous polycyclic aromatic hydrocarbon clusters

In this paper we investigate the impact of molecular inhomogeneity on the surface properties of soot particles. Using replica exchange molecular dynamics and solvent-excluded surface analysis, we evaluate detailed surface properties directly from particles containing polycyclic aromatic hydrocarbon molecules of different sizes. The temperature-dependent behaviour of surface roughness and number densities of reactive sites are evaluated for particles from 1–5 nm in diameter. The percentage of carbon atoms and zig-zag sites on the particle surface are found to be independent of molecular composition, while molecule heterogeneity influences the accessible hydrogen atoms and free-edge sites. These relationships allow the prediction of surface composition for a given particle diameter. The surface densities of carbon and hydrogen atoms are explained by the morphological changes and molecule size contributions for solid-like and liquid-like configurations. Small molecules contribute significantly to the particle surface properties at low temperatures, regardless of the proportion of molecule sizes, which results in an increased density of accessible carbon atoms for heterogeneous particles. Interestingly, the surface density of edge carbon atoms and free-edge sites can be predicted from the average molecule size alone. The density of hydrogen atoms on the surface follows the average expected values from the constituent molecule sizes, suggesting that for particles containing many different molecule sizes the α parameter corresponding to the HACA mechanism converges to a linear temperature-dependent trend. This quantitative evaluation of the accessibility of reactive sites for heterogeneous particles provides important information for understanding soot particle growth and oxidation.

Heat transfer analysis using zinc Ferrite/water (Hybrid) nanofluids in a circular tube: An experimental investigation and development of new correlations for thermophysical and heat transfer properties

For heat transfer analysis, the thermal properties of the heat transfer fluid is aninterestingtopic of current research. The hybrid nanofluids have better effective thermal conductivity, which is being used to improve the heat transfer rate. This experimental study presents the heat transfer characteristic of aqueous Zinc Ferrite/water (ZnFe2O4/water) nanofluids. ZnFe2O4/waternanofluids were prepared, suspending hybrid nanoparticles in the basefluids with 0.01 wt% CTAB as surfactant with different weight concentrations i.e., (0.02, 0.05, 0.1, 0.2, 0.5 wt%). Detailed surface properties of ZnFe2O4/waternanofluids were characterized using EDS, TEM, and UV–vis spectroscopy. Experiments were conducted to find out the viscosity, thermal conductivity,and convective heat transfer coefficient of ZnFe2O4/waternanofluids using laminar flow in a tube geometry using constant heat flux (CHF) boundary condition. Results revealed 11.8% improvement in the thermal conductivity for ZnFe2O4/waternanofluids, whereas an enhancement of 42.99% was observed in the convective heat transfer coefficient using 0.5 wt% of the nanofluids.The thermal conductivity results indicate that ZnFe2O4/waternanofluids have higher thermal conductivity for all the studied nanofluids. From the experimental data, new correlations for finding the thermophysical properties and Nusselt number has been proposed. The novel correlation established will help scientists and engineers for further insight into future research.

Reactive sites on the surface of polycyclic aromatic hydrocarbon clusters: A numerical study

The surface growth of soot is a key process in its mass growth, depending crucially on surface properties. In this work, we directly extract the detailed surface properties, such as surface area, number density of reactive sites on a particle and parameter α, from the microscopic configuration of polycyclic aromatic hydrocarbon (PAH) clusters. Five representative PAHs, including pyrene (C16H10), coronene (C24H12), ovalene (C32H14), hexabenzocoronene (C42H18) and circumcoronene (C54H18), are used to build the model configurations of nascent soot. We develop a numerical scheme to determine the detailed surface properties based on the approximation of solvent-excluded surface. The assumption of spherical particles is found to introduce a large uncertainty in the estimation of the surface area, and the error can be a factor of 2.5 in the worst case. The number density of atoms or sites on cluster surfaces does not depend on the chemical composition of a particle larger than 2 nm in diameter, and our study indicates that the number density of hydrogen atoms is overestimated by a factor of 3 in the literature. Finally, we propose a new equation for parameter α, which includes the effects of the size of gaseous species in surface reaction, local temperature, particle size and chemical composition.

Study on surface properties of sodiumdodecyl sulfate and dodecyltrimethylammonium bromide mixed surfactants and their interaction with dyes

The antagonistic as well as synergetic interaction for dodecyltrimethylammonium bromide (DTAB) and sodiumdodecyl sulfate (SDS) mixed surfactants by using surface tension are investigated on the basis of the results obtained earlier, the efficiency of adsorption (pC20), aggregation number (N), ΓΓmax, effective Gibbs free energy (ΔGeffo) and CMCC20 are calculated additionally with three different temperatures at T = 293.15, 298.15 and 303.15 K as the detailed surface properties. The binding constants and standard free energy change of SDS and DTAB mixture with the interaction of (2.5× 10−5 mol L–1 of methyl orange, MO and methylene blue, MB) are carried out by using UV-Vis spectroscopy at room temperature by using different models. The closer values of the binding constants and standard free energy change for SDS and DTAB mixture with the interaction of MO and MB are included in our investigations.

Thermal conductivity of aqueous Al2O3/Ag hybrid nanofluid at different temperatures and volume concentrations: An experimental investigation and development of new correlation function

Nanofluids are a new group of materials with potentially broad applications in the industry, especially in the process of heat transfer. Recently, a new class of nanofluids called hybrid nanofluids are being used to enhance the heat transfer rate. In the present study, an experimental investigation on heat transfer characteristics of aqueous Al2O3/Ag hybrid nanofluids is presented. The main idea in producing hybrid nanofluids was to obtain better heat transfer rate compared to nanofluids dispersed with either of the dispersoids. The detailed surface properties of Ag and Al2O3 nanoparticles were performed by X-ray diffraction and transmission electron microscopy. Polyvinylpyrrolidone used to stabilize the nanoparticles (Al2O3/Ag) in water. Dynamic light scattering and zetapotential measurements measured the particle size distribution of the nanoparticles in the nanofluid and the surface charge formed on the surface of the nanoparticle by the polyvinylpyrrolidone. The hybrid nanofluid was prepared by dispersing Al2O3/Ag (50,50) in distilled water, and the thermal conductivity measurements were conducted for particle loading varying from 0.005 vol% to 0.1 vol% using transient hot-wire method. The results indicate that Al2O3/Ag hybrid nanofluids exhibit higher thermal conductivity enhancement compared to Al2O3 nanofluids alone. Based on the experimental data, a new correlation for predicting the thermal conductivity of aqueous Al2O3/Ag has been proposed.

Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes

Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/debinding dynamic properties. Here, we employ impedance spectroscopy to systematically characterize this specific noise component for its correlation to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen debinding) processes. This correlation is facilitated by applying our recently developed interfacial impedance model to ultrathin TiO2 layers grown by means of atomic layer deposition (ALD) on a TiN metallic electrode. With an excellent fitting of the measured noise power density spectra by the model for the studied TiO2 layers, we are able to extract several characteristic dynamic parameters for the TiO2 sensing surface. The observed increase of noise with TiO2 ALD cycles can be well accounted for with an increased average binding site density. This study provides insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.

A silver niobate photocatalyst AgNb7O18 with perovskite-like structure

Silver-containing niobate AgNb7O18 nanoparticles were prepared via sol-gel polymerized complex synthesis. The sample was given a good XRD Rietveld refinement in a typical perovskite-like structure. The detailed surface properties of AgNb7O18 nanoparticles were tested by SEM, EDS, TEM, nitrogen adsorption-desorption isotherms and XPS measurements. AgNb7O18 is characterized via a direct transition and the band energy is 2.76 eV. The hybridization between O 2p and Ag 3d states in valence band contributes to the narrowed band gap. The first principles electronic structure elucidation supports the narrow band gap of AgNb7O18. The sample shows an efficient degradation of methylene blue dye (MB) solutions. The trapping tests were performed to elucidate the real active species in the photocatalytic reactions. The results indicate that the superoxide radical is the main active species in the photocatalytic system, and the photocatalyst also shows a good stability and durability.

Layered oxide semiconductor In2Fe2CuO7: Optical properties and visible-light responsive photocatalytic abilities

Transition metal oxide In2Fe2CuO7 nanoparticles were prepared by the sol-gel film coating and subsequent sintering method. The phase formation was investigated by X-ray polycrystalline diffraction (XRD) measurement. The structure refinement confirmed that the sample has a pure hexagonal phase with the space group of P63/mmc. The detailed surface properties were characterized. In2Fe2CuO7 shows an efficient optical absorption in the region of visible wavelength and has a narrow band-gap of 1.91eV. Particularly, In2Fe2CuO7 presents the efficient photodegradation for methylene blue (MB) solutions under visible-light irradiation. The nanoparticles could be a potential photocatalyst for the photodegradation for organic pollution solutions.

A new bismuth vanadate photocatalyst of Bi23V4O44.5 nanoplates with layered δ-Bi2O3 based fluorite-type superstructures

The work reports the large-scale synthesis and photocatalytic activity of Bi23V4O44.5 nanoplates. The structural refinement was conducted in the layered δ-Bi2O3 based superstructuLre. The detailed surface properties were characterized. Bi23V4O44.5 shows efficient absorption in visible region with a band-gap of 2.384eV from the hybridization of Bi-6s and O-2p orbitals. Particularly, Bi23V4O44.5 shows an efficient photodegradation for methylene blue (MB). The photocatalysis benefits from the layered B–O structure characteristic and the codoped defects of V4+/V5+ ions in the lattices. Bi23V4O44.5 nanoplates could be a potential photocatalyst.

Insights into the surface property and blood compatibility of polyethersulfone/polyvinylpyrrolidone composite membranes: toward high-performance hemodialyzer

Applications of blood purification membranes are fuelled by diverse clinical needs, such as hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis, and plasma collection. For clinical usage, the adding of polyvinylpyrrolidone (PVP) is the general protocol for the design of antifouling and antithrombotic properties integrated artificial membranes. In the present work, to insight into the detailed surface properties and blood compatibilities of the PVP blended composite membranes, we synthesized a series of PVP polymers with different molecular weights using reversible addition fragmentation chain transfer polymerization and designed a series of polyethersulfone (PES)/PVP composite membranes by a physically blending method. The effects of PVP molecular weights and blending ratios on the surface properties and the blood compatibilities of the composite membranes were investigated in detail. The surface attenuated total reflection Fourier transform infrared spectra and scanning electron microscopy pictures indicated that the PVP was successfully immobilized into the membranes, and the composite membranes exhibited morphology transformation from finger-like structure to sponge-like structure, which indicated that the composite membrane had tunable porosity and permeability by adding PVP. The blood compatible tests revealed that the composite membranes showed increased hydrophilicity, decreased plasma protein adsorption, suppressed platelet adhesion, and prolonged blood clotting time compared with pristine PES membrane. These results indicated that the PES/PVP composite membranes exhibited enhanced antifouling and antithrombotic properties than the pristine PES membrane. Meanwhile, the results also suggested that the composite membranes with larger molecular weight PVP and higher blending ratios might show better blood compatibility. Copyright © 2014 John Wiley & Sons, Ltd.

Zeolite Surface As a Catalyst Support Material for Synthesis of Single-Walled Carbon Nanotubes

Preparation of single-walled carbon nanotubes (SWNTs) has been advanced by controlling several parameters including the catalyst and the catalyst support material. Although zeolite has been frequently used as a catalyst support material for the synthesis of SWNTs, detailed surface properties of previously employed zeolites and thus their role as a catalyst support material have not been sufficiently clarified yet. In this study, a clean b-plane surface of silicalite-1, which is a siliceous MFI-type zeolite, was used as a model substrate for the synthesis of SWNTs. The amount of active cobalt used for SWNT generation was smaller than the initially sputtered amount, and XPS measurements revealed diffusion of cobalt into the zeolite framework. The diffused cobalt was found to interact strongly with the silica framework of zeolite. The diffusion coefficient of cobalt in silicalite-1 zeolite was larger than that in thermally oxidized SiO2 formed on a Si substrate. This difference was ascribed to the microporou...

Phase imaging atomic force microscopy in the characterization of biomaterials

The phase imaging atomic force microscopy is a powerful tool in surface characterization of the biomaterials, and the resulting phase image is able to detect chemical variation and reveal more detailed surface properties than the morphological image. However, the chemical- and morphological-dependent phase images were still not distinguished well. In order to better understand actual occurring phase images, we examined non-carious human maxillary incisor, microphase separated polyurethane and self-assembling peptide nanofibres. We herein reported that phase image mainly plotted the morphological change: the phase peak corresponding to the morphological valley, and the morphological peak to the phase valley, and exhibited fine surface structures of materials. The chemical-dependent phase contrast was generally masked by their inherent roughness. For the sample being very rough and having great phase separation, its chemical-dependent phase contrast could be detected at the hard tapping mode ('Amp. Ref. "set point ratio"': -0.4 to -0.8), for the sample with medium roughness only at the light tapping mode ('Amp. Ref.': -0.1 to -0.4). These results will help us understand and determine actual occurring phase images of natural or fabricated biomaterials, even, other materials.

The Electromagnetic Field near a Metal Surface in the Semi-classical Infinite Barrier Model

The electromagnetic field has been calculated in the semi-classical infinite barrier model (SCIB). Since the conductivity tensor is discontinuous at the surface, the field component perpendicular to the surface is found to be discontinuous. In the surface region the field is modified due to single-particle excitations. This contribution to the vector potential is analyzed carefully and numerical results, as for the vector potential, is given. For certain angles of incidence and frequencies the transmitted wave propagates nearly parallel to the surface and the usefulness of the SCIB-model is questioned since it does not describe the detailed surface properties properly. Expressions and numerical results for the distribution of absorbed energy are given and a discussion of the local absorption of energy sometimes becoming negative.