Increment In Surface Area Research Articles

Molecular dynamics study of the nanoscale boiling heat transfer process on nanostructured surfaces

In this study, the effects of nanostructures on nanoscale water boiling heat transfer are investigated using nonequilibrium molecular dynamics simulations. The nanostructured substrates show great superiority over the smooth surface. The bubble nucleation time is advanced and the heat transfer efficiency is enhanced on structured surfaces. Besides, the heat transfer enhancement differs on surfaces with different nanostructures with the same nanostructure volume. Through calculation, it is found that the solid-liquid interfacial area varies with the surface structure configuration and the square nanogroove case which achieves the best heat transfer performance among the nanostructured systems has the largest solid-liquid contact area. To prove the hypothesis that the heat transfer efficiency increases with the interfacial surface area, a solid-liquid-solid system is developed to measure the interfacial thermal resistance between the different solid surfaces and water molecules. The interaction energy per unit area is also calculated to explain the heat transfer variations. Results show that with the increment of surface area which adsorbs more water molecules at the interface could increase the interaction energy per unit area, thereby decreasing the interfacial thermal resistance. The results in this study could provide some insight into the nanostructure design to enhance the heat transfer involving boiling.

Atomistic Approximation of Solid Surface Energy and Its Anisotropy

The anisotropic surface energy of solid surfaces is mainly calculated using electron-based analyses. Experimental measurements are both difficult and subject to numerous errors. In this communication, by quantifying the surface area increment accompanying a vacancy formation process on solid surfaces, the anisotropic solid surface energy is approximated. Further analyses on the dependence of solid surface energy on planar packing fraction show that, however, the electron-based data may seem unrealistic in some cases.

Investigations on porous carbon derived from sugarcane bagasse as an electrode material for supercapacitors

The porous carbon is prepared utilizing the sugarcane bagasse via pre-treatment process using chemical agents like K2CO3, KOH and NaOH, followed by carbonization at 650 °C. The non-pre-treated (NPSB) and pre-treated (PSB1, PSB2, PSB3) samples were prepared. The resulting pre-treated carbon shows the increment in specific surface area from 476 to 725 m2 g-1, which is further examined for electrochemical performances. The highest specific capacitance was recorded of 241 Fg-1 at 10 mVs−1 and 265 Fg-1 at 0.2 Ag-1 for the pre-treated K2CO3 sample (PSB1) from Cyclic Voltammetry (CV) and Galvanostatic charge-discharge (GCD) measurements, respectively. The efficiency of 98.63% shows almost constant specific capacitance up to 15,000 cycles for the PSB1 sample. The electrochemical impedance spectroscopy (EIS) curve of PSB1 sample shows the decrease in equivalent series resistance (ESR) from 3.54 to 1.76 Ω with improved electrical conductivity. It has been found that the PSB1 sample has preserved the moderate specific energy of 6.26 WhKg−1 with a specific power of 234 WKg-1. The above results show that porous carbon derived from sugarcane bagasse can be utilized as an electrode material for energy storage devices.

Ni-Bi co-doped TiO2 as highly visible light response nano-photocatalyst for CO2 photo-reduction in a batch photo-reactor

Photocatalytic reduction of CO2 is considered as a promising strategy for production of a wide range of renewable hydrocarbon fuels by solar energy. In this investigation, a series of Ni and Bi doped TiO2 catalysts with different Ni and Bi contents were synthesized by the conventional sol-gel method and tested for CO2 photo-reduction under visible light irradiation. Synthesized nano-photo-catalysts were characterized by XRD, FESEM, TEM, DRS, PL, FTIR and BET analyses. BET results indicated that the doping of Ni or/and Bi in the TiO2 framework resulted in BET specific surface area increment with respect to pure TiO2. DRS analysis showed that Ni doped TiO₂, Bi doped TiO2, and co-doped samples had narrower band gap energy and consequently considerably higher light absorption in the visible region compared with pure TiO₂. Doping Ni and Bi in TiO2 suppressed the rate of electron-hole recombination as indicated by PL spectra. CO2 adsorption capacity were increased in presence of Bi ions in comparison with pure TiO2 and Ni doped sample as a result of reactant adsorption increase on the surface of catalyst. The yield of methane considerably increased in the presence of Ni and Bi doped samples. The highest methane production (21.13 μmol/gcat) was obtained for 1 wt% Ni–3 wt% Bi co-doped TiO₂, which was almost 6.5 times greater than that for pure TiO2.

INFLUENCE OF CARBONISATION TEMPERATURE ON THE SURFACE PORE CHARACTERISTICS OF ACID-TREATED OIL PALM EMPTY FRUIT BUNCH ACTIVATED CARBON

Carbonisation process affects the surface physical and chemical properties of an activated carbon. Therefore, this work aims to investigate the influence of carbonisation temperature from 400 to 550°C during activation with 85% phosphoric acid (H3PO4) on the surface pore characteristics of activated carbon produced from oil palm empty fruit bunch (EFB) for nitric oxide (NO) removal from gas streams. Pore and morphological characterisation showed that EFB carbonised at 400°C (EFBC-400) is microporous and has a uniform pore structure with 98% micropore volume. Increasing carbonisation temperature resulted in pore enlargement from 2.8 to 4.7 nm and increment in pore heterogeneity and BET surface area from 215 to 759 m2/g. However, the NO breakthrough experiment indicated that EFBC-400 is more favourable for low-temperature NO removal, due to the importance of microporosity in adsorption of NO. Further study will look at the kinetics of NO removal and the adsorbent regeneration.

Pore wall functionalized ultrasonically synthesized cooperative MOF for luminescence sensing of 2,4,6-trinitrophenol

Adjustments of morphology and surface area increment with the help of ultrasonic method for tunability of Luminescent MOFs make them more attractive to detection applications. More incoming guest analytes interact with the surface led to the enhanced sensitivity and selectivity of MOFs. Here in, we evaluated fluorescence quenching of bulk and nanostructure ultrasonically synthesized (nanorod) cooperative TMU-33 ([Cd3(BDC)3(OPP) (DMF)2].2DMA), (OPP:N,N’-(oxybis (1,4-phenylene)) bis(1-(pyridin-4yl) methanimine)) in the presence of nitro analytes. This strategy combined the advantages of fluorescent cooperative TMU-33 and nanoscale structures, which not only provide simultaneously imine functional group and open metal site but also promoted the interaction of the analyte with recognition sites in the pore channel. The nanorod TMU-33 demonstrated a superior selective quenching ability in the presence of 2,4,6-Trinitrophenol (TNP) with the high quenching constant (9.3 ​× ​105 ​M−1), which is 10.6 times better than of bulk TMU-33. This unprecedented selectivity could be attributed to effective interaction of guest with accessible free Brønsted base N atoms of imine sites of nanorod TMU-33. The PXRD patterns of the structures indicate the high stability of this compound after 3 times sensing. This study shows the effect of nanostructures in helping to the detection of TNP by the MOF and could be a path for further studies in this area.

Cerium Oxide Nanoparticles: Recent Advances in Tissue Engineering.

Submicron biomaterials have recently been found with a wide range of applications for biomedical purposes, mostly due to a considerable decrement in size and an increment in surface area. There have been several attempts to use innovative nanoscale biomaterials for tissue repair and tissue regeneration. One of the most significant metal oxide nanoparticles (NPs), with numerous potential uses in future medicine, is engineered cerium oxide (CeO2) nanoparticles (CeONPs), also known as nanoceria. Although many advancements have been reported so far, nanotoxicological studies suggest that the nanomaterial’s characteristics lie behind its potential toxicity. Particularly, physicochemical properties can explain the positive and negative interactions between CeONPs and biosystems at molecular levels. This review represents recent advances of CeONPs in biomedical engineering, with a special focus on tissue engineering and regenerative medicine. In addition, a summary report of the toxicity evidence on CeONPs with a view toward their biomedical applications and physicochemical properties is presented. Considering the critical role of nanoengineering in the manipulation and optimization of CeONPs, it is expected that this class of nanoengineered biomaterials plays a promising role in the future of tissue engineering and regenerative medicine.

Tea wastes as an Alternative Sustainable Raw Material for Ethanol Production

Integrating sustainability in life became an urgent necessity. Currently tea sectors play important role in adopting new technologies in order to reduce tea wastes .Collection of these wastes for production of ethanol will contribute to the improvement of life and the environment. Simple technique was proposed for saccharification of spent tea leaves either by cellulase or fermentation with baker's yeast. Scanning electron microscope analysis showed certain modification for the morphology of both green and black tea leaves. Brunauer Emmett Teller analysis confirmed the increment in surface area of both tea leaves. X- Ray Diffraction analysis proved the amorphous nature of their cellulose with little crystallinity. This nature eases their saccharification because cellulose is usually susceptible to degradation in its amorphous form. The percentage of produced ethanol was 74.4% from spent green tea leaves and 80.7% from spent black tea leaves after 24 h at mild temperature. The habit of drinking tea in Egypt shed the light on a promising approach relies on the production of ethanol from tea wastes especially spent tea leaves.

Preparation and utilization of Keggin-type polyoxometalate intercalated Ni–Fe layered double hydroxides for enhanced adsorptive removal of cationic dye

The Ni–Fe layered double hydroxide (LDH) intercalated by Keggin-type polyoxometalate (POM) of SiW12O404− was investigated for the first time. The synthesized Ni–Fe LDH and Ni–Fe POM were characterized by XRD, FT-IR, and N2 adsorption–desorption isotherm to identify the intercalation process as well as their surface morphology. The obtained results indicated that after intercalated by POM, the interlayer distance of the LDH expanded due to the insertion of POM anion and removal of some native NO3− anion in the interlayer space. Moreover, the increment of the BET surface area of the material after intercalation indicated the opening of the interlayer space that beneficial for the adsorption process. The study on the malachite green adsorption onto the synthesized materials showed that POM intercalated LDH has better adsorption capacity than the original LDH, where the adsorption kinetic was better described by pseudo second order model than the pseudo first order model.

Lightweight, flexible NiO@SiO2/PVDF nanocomposite film for UV protection and EMI shielding application

A series of silica coated nickel oxide nanoparticles incorporated PVDF nanocomposite films have been successfully prepared by solution casting method and the dielectric properties along with EM shielding hasalso been studied. Higher loading of the well-dispersed NiO@SiO2 nanoparticles inthe PVDF matrix leads to the increment of the effective surface area resulting enhancement of the dielectric and ferroelectric properties of the nanocomposite films. The nanocomposite films successfully block the harmful UV radiations. The sample PSNO15 (for 15 wt% loading of the NiO@SiO2 nanoparticles can almost completely block the UV radiation. As the effective surface area and the interfaces are increased due to the SiO2 coating of the NiO nanoparticles, the electromagnetic waves are reflected and scattered for multiple times from these interfaces. These NiO@SiO2/PVDFnanocomposite films are proposed to be used as UV and EMI shielding technology to get rid of EM hazards of the human civilizations.

Continuous and ordered surface microtexturing on Cu and Ni-based alloys by novel electrochemical dissolution

The present study discusses the formation of surface micro-texture on flat samples of Cu-based and Ni-based alloys by two-step electrochemical dissolution. Prior to the electrochemical dissolution, laser marking only on the araldite coating has been carried out for effective dissolution of the selectively exposed metal surfaces along the laser cut regions. After second stage dissolution, the circular truncated conical grids with average base diameter of 210.7 μm for the Cu-based alloy and truncated square pyramid like grids with base width of 203.2 μm for the Ni-based alloy have formed. Similarly, maximum dissolution depths of 61.8 and 39.3 μm for the Cu-based and Ni-based alloys, respectively, could be observed. Moreover, excellent hydrophobicity of the textured Cu-based as well as Ni-based alloys correlating to grid dimensions along with air entrapment beneath the water droplet has been analysed with the help of Wenzel and Cassie-Baxter models. Nano-hardness of the as-received alloys as well as the textured alloy surfaces shows minor variation. Similarly, the micrographs of the flat surfaces of the as-received alloys and cross-sectional microstructure of the textured alloys have also portrayed little difference suggesting negligible heat or stress affected zone after dissolution process. Moreover, the textured surfaces have showed significant increment in surface area: ∼62.7% for the Cu-based alloy and ∼71.4% for the Ni-based alloy as compared to the flat specimens.

Nitrogen oxide reduction through absorbent solutions containing nitric acid and hydrogen peroxide in hollow fiber membrane modules

Emissions of nitrogen oxides such as NO and NO2, which are commonly known as NOx, are threats to human existence and cause environmental problems. Mainly, two techniques have been developed to drastically reduce these emissions, which are dry and wet processes. The wet process has several advantages, major identifiable advantages are the adaptability to the flue gas, low operating temperatures and no poisoning and inactivation catalyst. Also, a mixture of hydrogen peroxide and nitric acid are used as absorbents solution for NOx reduction in the wet process. The advantages of using this mixture include the ability to reduce the negative effect of NOx and does not contaminate the scrubbing solution. In addition, nitric acid has an economical advantage in the process considering the fact that it is produced in the process. Finally, it can be conducted at ambient temperature. This study furthermore used a mixture of hydrogen peroxide and nitric acid solutions as an absorbent to reduce NOx in hollow fiber membrane modules. The hydrogen peroxide oxidized HNO2 to nitric acid, while enhances the oxidation through an autocatalytic reaction. The effects of the feed gas flow rate, hydrogen peroxide concentrations and number of fibers on the NOx reduction, absorbed NOx and flux were varied to study. The experimental results showed that the increase in the feed gas flow rate from 100 to 200 mL/min decreased NOx reduction from about 98 to 94% but increased the absorbed NOx and flux from about 0.13 to 0.255 mmol/h and 0.85–1.63 mmol/m2.h, respectively The increase in proportion of NOx in the feed gas effect was dominant than the increase in absorbed NOx. An increase in hydrogen peroxide concentration from 0.5 to 10 wt.% in the absorbent solutions increased NOx reduction, absorbed NOx and flux from about 94 to 98%, 0.257–0.267 mmol/h and 1.09–1.13 mmol/m2.h, respectively. Additionally, the H2O2 plays an important role in enhancing HNO2 oxidation to HNO3. Furthermore, an increase in the number of fibers from 50 to 150 in the membrane module increased NOx reduction and absorbed NOx from 86 to 97% and 0.23–0.27 mmol/h. Flux decreased from 2.98 to 1.13 mmol/m2.h due to increment in the gas-liquid contact surface area.

Investigation on gas plasma and liquid plasma treatment for polyether ether ketone (PEEK) surface for wettability enhancement

The results of liquid and gas plasma treatment on polyether ether ketone PEEK surfaces are reported. The experiments were conducted by using variation of treatment time (5 s to 60 s) using Helium as its working gas. The results were obtained by measuring the water contact angle (WCA) and the studying the surface morphology of the PEEK surface. Comparisons of WCA and Scanning Electron Microscopy (SEM) analysis were conducted for samples which undergone gas plasma treatment and liquid plasma treatment. After gas plasma treatment, WCA of the PEEK surface decreased from 65° to 21°. Results of WCA for liquid plasma treatment showed decrement from 65° to 45°. Images from SEM showed PEEK surface area after gas and liquid plasma showed surface area increment of 40% for gas plasma and 20% for liquid plasma. The decrement of WCA and increment of surface area showed that PEEK surface properties changed from hydrophobic to hydrophilic via wettability enhancement.

Excellent performance of porous carbon from urea-assisted hydrochar of orange peel for toluene and iodine adsorption

In order to promote the physicochemical properties and the pollutants adsorption capacities of porous carbon, a novel urea-assisted hydrothermal method was developed to produce N-doped hydrochar as an ideal precursor from orange peel waste. Different from the modification technologies for nitrogen doping, the highly porous carbon prepared by KOH activation of the urea-assisted hydrochar contained extremely low N content. But such sample showed ultra-high specific surface area up to 3053 m2/g, with 63% and 39% higher than the porous carbons through conventional N-free method and hydrochar-urea mixing activation method respectively. In-depth study revealed that during 600–800 °C activation procedure, the N-containing groups including pyridinic-N, pyridonic-N and graphitic-N in the urea-assisted hydrochar reacted sufficiently with K2CO3, an intermediate of KOH activation, and generated NH3, creating richer porous structures in carbon. Particularly, there was a good linear relationship between the relative increment of specific surface area and the relative reduction of N content in porous carbon when the activation temperature increasing. This connection can be served as a reference to increase the porosity of porous carbon through the activation of N-doped carbonaceous precursor. As for pollutants adsorption, the highly porous carbon from urea-assisted hydrochar possessed excellent toluene adsorption capacity up to 724 mg/g and iodine adsorption capacity up to 2252 mg/g.

High Impact Exercise Improves Bone Microstructure and Strength in Growing Rats

Physical activity is beneficial for skeletal development. However, impact sports during adolescence, leading to bone growth retardation and/or bone quality improvement, remains unexplained. This study investigated the effects of in vivo low (LI), medium (MI), and high (HI) impact loadings applied during puberty on bone growth, morphometry and biomechanics using a rat model. 4-week old rats (n = 30) were divided into control, sham, LI, MI, and HI groups. The impact was applied on the right tibiae, 5 days/week for 8 weeks mimicking walking (450 µε), uphill running (850 µε) and jumping (1250 µε) conditions. Trabecular and cortical parameters were determined by micro-CT, bone growth rate by calcein labeling and toluidine blue staining followed by histomorphometry. Bio-mechanical properties were evaluated from bending tests. HI group reduced rat body weight and food consumption compared to shams. Bone growth rate also decreased in MI and HI groups despite developing thicker hypertrophic and proliferative zone heights. HI group showed significant increment in bone mineral density, trabecular thickness, cortical and total surface area. Ultimate load and stiffness were also increased in MI and HI groups. We conclude that impact loading during adolescence reduces bone growth moderately but improves bone quality and biomechanics at the end of the growing period.

Tracing chirality, diameter dependence, and temperature-controlling of single-walled carbon nanotube non-covalent functionalization by biologically compatible peptide: insights from molecular dynamics simulations.

Biological applications of single-walled carbon nanotubes (SWCNTs), including drug delivery, require their functionalization with various functional groups such as peptides. Recently, a biologically compatible peptide (named PW3 with the sequence of NH2-Trp-Val-Trp-Val-Trp-Val-Lys-Lys-COOH) has been introduced as a good candidate for modification of carbon nanotubes due to its high affinity toward the exterior surface of these nano-carriers. In order to optimize the process of SWCNT peptide functionalization, the effects of chirality and diameter of SWCNTs as well as the temperature on PW3 adsorption were systematically investigated using molecular dynamics (MD) simulation. It was found that modification of chiral/zigzag SWCNT by PW3 peptide was more suitable compared with the armchair system due to the strong peptide-nanotube interactions and more water solubility at 310K which can be well explained by microscopic structural investigations. Regarding the enhanced peptide-chiral nanotube interactions at the low temperature of 277K, chiral nanotubes can be effective structures for SWCNT functionalization process at reduced temperatures. Our analysis indicated that disrupted PW3 and SWCNT hydration patterns and fewer internal interactions within the peptide could be responsible for the stronger peptide modification of SWCNT at higher temperatures. Additionally, "PW3/SWCNT" systems containing larger tube diameters formed more stable complexes owing to their effective surface area increment.

Experimental and numerical investigation of heat transfer augmentation in heat sinks using perforation technique

Extended surfaces are commonly adopted as a thermal management technique for heat transfer augmentation owing to their ability to facilitate an increment in the available surface area, and hence, the total heat dissipation. This study aims at experimentally and numerically evaluating the performance of fins with and without perforated geometry under forced convection heat transfer. The effect of the circular perforations at different perforation number and size, airflow velocity, and different input powers on the thermal and hydraulic performance of those fins, at a constant perforation area of 24 cm2, has been examined. An excellent agreement has been observed between the experimental and numerical results. The findings of this investigation show that the thermal performance of the perforated fins is superior over the non-perforated ones with a reduction in fin temperature up to 8.5 °C. Further, increasing the size and number of perforations promotes the convective heat transfer process. On the other hand, the perforated fins offer an outstanding hydraulic performance compared to the solid ones since the flow friction factor and the required pumping power will be less, particularly with the increased number of perforations. Adopting the perforation technique has been discussed in detail, as well as significant experimental and numerical information has been reported in this article.

Electrochemical fabrication of reusable pencil graphite electrodes for highly sensitive, selective and simultaneous determination of hydroquinone and catechol

In the present study, we here report a simple, cost-effective and highly sensitive electrochemical sensor for the selective determination of hydroquinone (HQ) and catechol (CC) using electrochemically pretreated pencil graphite electrode (PPGE). The electrochemical pretreatment of pencil graphite electrode (PGE) was done in phosphate buffer solutions (PBS) and characterized by FT-IR, XRD, SEM and EDX. FT-IR and EDX analysis shows the introduction of oxygen functionalization on the PPGE surface. Further the electrodes were electrochemically characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 0.1M KCl containing K4[Fe(CN)6] as redox probe. Interestingly, The PPGE shows a significant enhancement in the redox peak current of Fe2+/3+, owing to the effective increment in the electroactive surface area at PPGE (1.22cm2) compared with the PGE (0.29cm2). Then the PPGE was utilized for the electrochemical determination of HQ and CC in 0.1M PBS (pH7.0). A reversible electrochemical redox peak for HQ and CC were occurred at PPGE, while PGE doesn't efficiently catalyze the HQ and CC redox reaction under identical experimental conditions. The oxidation current response of HQ and CC at PPGE were increased three and four times respectively compared with the PGE. Further, the DPV analysis displays a wide range of linear responses from 2 to 200μM with a limit of detection (LOD) of 1.17μM for HQ and 1.32μM for CC (S/N=3), respectively. Consequently, the concentration of HQ and CC were successfully determined in the presence of major interferents (10 folds) such as, glucose, ascorbic acid and uric acid. The practical utilization of as-fabricated PPGE was tested in water samples; the obtained results demonstrated that PPGE can be used as a potential candidate for environmental sensor application.

Influence of mechanical activation of fly ash in presence of polynaphthalene sulfonate superplasticizer on rheology and hydration kinetics of cement – fly ash pastes

Abstract In this study fly ash was milled in three types of mills up to the same median particle size ∼6 µm. The milling was performed in presence of polynaphthalene sulfonate (PNS) superplasticizer and apart of it. It is shown that the introduction of PNS during the milling allows to prevent adverse agglomeration of the particles, while increment of the specific surface area is independent of the presence of PNS. Cement – fly ash pastes prepared with PNS introduced during the fly ash activation exhibit a reduction of the yield stress by 35%, plastic viscosity by 25% and the induction period of hydration by 30% in comparison to the paste prepared with PNS introduced with the mixing water.

Synthesis and characterization of ZnZr composites for the photocatalytic degradation of phenolic molecules: addition effect of ZrO2 over hydrozincite Zn5(OH)6(CO3)2

AbstractBACKGROUNDThe composite materials ZrO2/Zn5(OH)6(CO3)2 were prepared in only one step by chemical co‐precipitation and thermal hydrolysis of urea. ZrO2 was added at 5, 8 and 10 mol%. The samples were dried at 80 °C and characterized by adsorption–desorption of N2 isotherms, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, and diffuse reflectance (DRS), UV–visible, Fourier‐transform infrared (FTIR) and X‐ray photoelectron (XPS) spectroscopies. The materials were assessed in the photodegradation of phenol and polychlorinated phenolic molecules under UV‐light irradiation. The possible mechanism was discussed from studies that corroborated or discarded the formation of the species •OH, •O2− and h+.RESULTSThe addition of ZrO2 to Zn5(OH)6(CO3)2 resulted in a composite material with high photoactivity. The material containing 8 mol% of ZrO2 (ZnZr‐8.0%) was the sample with the best percentages of photodegradation and mineralization. The photodegradation enhancement was achieved partly by an increment in the specific surface area and principally due to localized states originating in the composite interphase which improved charge transfer. XPS study revealed that the ZrO2 addition increases the oxygen vacancies which enhanced the organic molecule photodegradation via direct hole attack.CONCLUSIONThe ZnZr composite system constitutes an excellent alternative for the photodegradation of persistent organic pollutants due to the low cost, high stability and null toxicity of the support Zn5(OH)6(CO3)2. © 2019 Society of Chemical Industry