Increment In Surface Area Research Articles

Application of Cement Clinker as Ni-Catalyst Support for Glycerol Dry Reforming

The increase in biodiesel production inevitably yield plethora of glycerol. Therefore, glycerol has been touted as the most promising source for bio-syngas (mixture of H2 and CO) production. Significantly, coking on nickel-based catalysts has been identified as a major deactivation factor in reforming technology. Indeed, coke-resistant catalyst development is essential to enhance syngas production. The current work develops cement clinker (comprised of 62.0% calcium oxide)-supported nickel catalyst (with metal loadings of 5, 10, 15 and 20 wt%) for glycerol dry reforming (CO2). Physicochemical characterization of the catalysts was performed using XRD, XRF, BET, TGA and FESEM-EDS techniques. Subsequently, reaction studies were conducted in a 7-mm ID fixed-bed stainless steel reactor at 1023 K with various CO2 partial pressures at constant weight-hourly space velocity (WHSV) of 7.2×104 ml gcat-1 h-1. Gas compositions were determined using Agilent 3000 micro-gas chromatography (GC) and Lancom III gas analyzer. Results obtained showed an increment of BET surface area up to 32-fold with Ni loading which was corroborated by FESEM images. Syngas (H2 and CO) ratios of less than 2 were being produced at 1023 K. A closer scrutiny to the transient profile revealed that the presence of CO2 higher or lower than CGR 1:1 promotes the Boudouard reaction. © 2013 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Sol Gel Characterization of Nano Kaolin

Nano kaolin is product from kaolin also known as white clay. Kaolin was established as supplementary cementitious materials in concrete. The inclusion of kaolin in concrete enhances strength and durability properties and prolongs concrete life span. In this research, nanokaolin will be develop by using sol gel technique by that involves high energy milling. The process of milling been influenced by time of milling, ball and jar type. Ceramic type Zirconia (Zi) is been used as jar and ball type in this process. Time of milling was set from four (4) hours and one (1) days. Sample will be analyse by using particle size analyser to see the particle size and surface area of kaolin. From the result shows the optimum milling period for nanokaolin is one day base on particle size compare to 4 hours. Furthermore, one day milling produces a massive increment of surface area compare to others. In conclusion, one day can be considered as the optimum cycle time in the production of nano kaolin.

Surface thermodynamics reconsidered. Derivation of the Gokhshtein relations from the Gibbs potential and a new approach to surface stress

The terminology and definition of surface tension are discussed. In particular, the surface tension is defined as the partial derivative of the surface excess Gibbs energy with respect to an infinitesimal increment of surface area at constant temperature and pressure. The surface tension is also formulated as the sum of a stress-free component and a stress-containing component. The stress-containing component is defined as the surface stress. Finally, the case of charged surfaces is analyzed, and the Gokhshtein relations are derived from the Gibbs potential in the special case that the electrode/solution interface is ideally polarizable.

Enhancement of eucalypt chips’ enzymolysis efficiency by a combination method of alkali impregnation and refining pretreatment

A combination process of alkali impregnation and refining was used as a pretreatment to improve the production of fermentable sugar. The surface structures and crystallinities of wood samples were characterized to explain the relationships between the pretreatment action and enzymatic efficiency. After refining, the reducing sugar contents in hydrolyzates were analyzed by UV-Vis and HPLC. The results showed that the enzymatic efficiency could be improved by the combined pretreatment, due to the increment of specific surface area and the release of more free hydroxyls. Comparing to the sodium hydroxide and deionized water, the impregnation with magnesium hydroxide had low refining energy consumption and high yield of reducing sugar (glucose and xylose) in enzymolysis process, where about 560 kWh/t of the energy was saved in refining, and the yield of the reducing sugar was as high as 91.53%. And the enzymolysis could be improved by a certain amount of magnesium ions.

Effective optoelectronic and photocatalytic response of Eu3+-doped TiO2 nanoscale systems synthesized via a rapid condensation technique

Abstract

Geometrical effects of nanowire electrodes for amperometric enzyme biosensors

Enzymatic biosensor reactions follow the Michaelis–Menten kinetics, coupled with diffusion. The diffusion reaction processes for amperometric enzyme biosensors have been simulated to explore the geometrical effects of nanowire array electrodes (NWAEs) and nanowire array stack electrodes (NWASEs) from the viewpoint of enhanced mass transport and increased reaction surface area in two limiting cases. For practical analysis considering sensor fabrication, most samples are assumed to have the same unit square (1cm×1cm) footprint. In the reaction-controlled case, the surface area increment improves the sensitivity regardless of electrode geometry. However, in the diffusion-controlled case, well-controlled NWAE or NWASE geometries as well as the increased surface area improve the sensitivity when the peak current at an early stage of the reaction is measured. Peak current engineering by adjusting the geometric parameters of NWAEs and NWASEs will result in a highly sensitive amperometric enzyme biosensor in the diffusion-controlled case. In contrast to previous micro- and nanoelectrode array studies, we investigated NWASEs representing entangled nanowire network electrodes, and report significant improvements in both limiting cases.

Effect of phosphoric acid treatment on kaolinite supported ferrioxalate catalyst for the degradation of amoxicillin in batch photo-Fenton process

The effects of phosphoric acid treatment on kaolinite (Kaol) as catalyst support were investigated in this study. The results showed that as the acid concentration was increased from 5 to 10M, there was increment in the specific surface area from 18.78 in Kaol to 36.0 and 145.5m2g−1 in 5M acid treated Kaol supported catalyst (5M-AT-KaolCat) and 10M acid treated Kaol supported catalyst (10M-AT-KaolCat), respectively. Characterization results showed that 10M-AT-KaolCat has higher percentage of Fe than the 5M-AT-KaolCat due to the effect of acid treatment which provided larger surface area for its anchoring. Consequently, degradation efficiency is comparably faster in 10M-AT-KaolCat with about 99% of 40ppm amoxicillin degraded in 8min without pH adjustments while it takes 12min using 5M-AT-KaolCat. The degradation process showed initial enhanced degradation efficiency with increase in the catalyst loadings which later decreased due to the scavenging effect of excess catalyst loading on the reactive hydroxyl radical. The catalysts showed high resistance to leaching due to the presence of the ferrioxalate (FeOx) ligands and the effect of phosphoric acid modification which introduces monolayer of phosphate functional group on the catalyst support through which the FeOx ligands were properly anchored.

Thermoplastic polyurethane composites prepared from mechanochemically activated waste cotton fabric and reclaimed polyurethane foam

AbstractIn this study, thermoplastic polyurethane (PU) composites were successfully prepared from waste cotton fabric (WCF) and reclaimed PU foam derived from the shoe manufacturing industry through melt mixing. A pan‐mill‐type mechanochemical reactor made in our laboratory was applied to determine the mechanochemical activation of WCF. The intramolecular and intermolecular hydrogen bonds of WCF could be broken up through pan milling because of the fairly strong shearing and squeezing forces. Moreover, the simultaneous reduction of particle size and the large increment of the specific surface area of pan‐milled WCF benefitted its dispersion and the interfacial adhesion with the PU matrix. Mechanochemically activated WCF could be used as a low cost but effective functional additive to enhance the melt processability and mechanical properties of PU/WCF composites. With the addition of 75‐phr WCF, the heat shrinkage of the melt‐reprocessed PU decreased sharply from its original 11.4 to 0.3%. Meanwhile, the tensile strength of the composites was enhanced from 10.3 to 23.2 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Studying the morphology of hemispherical-grain polycrystalline silicon films

The effect of the deposition temperature on the morphology of hemispherical-grain polycrystalline silicon (HSG-Si) films obtained by low-pressure chemical vapor deposition (LPCVD) has been studied using atomic force microscopy. The dependences of the relative surface area increment, density of grains, average height and lateral size of grains, mean square roughness, and correlation length on the deposition temperature have been determined in an interval used for the LPCVD growth of HSG-Si films.

In situ synthesis and current-carrying characteristics of superconducting MgB2–B4C composites with MgB2 fractions ranging from 18% to 85%

Carbon is known to be the most effective dopant to enhance the high-field current-carrying capacity for high-power applications of MgB2 superconductors. Using B4C instead of B to synthesize MgB2 will be expected to produce superconducting MgB2 together with in situ carbon doping. By using just two reaction substances, B4C and Mg, superconducting MgB2–B4C composites with MgB2 fractions ranging from 18 to 85% were fabricated successfully by solid-state reaction. The influence of the grain size of the B4C raw material on the critical current density (Jc), the fraction of MgB2, and the critical transition temperature (Tc) of MgB2–B4C composites were investigated. Tc, Jc, and the fraction of MgB2 were increased with decrease in the grain size of the B4C raw material. Compared with a pure MgB2 superconductor, the critical transition temperature of the MgB2 composites fabricated with small B4C grain size was suppressed slightly, but the in-field current-carrying capacity was improved significantly. By using B4C raw material with a grain size of 2.5 μm, the resultant superconducting composite showed a critical transition temperature of 33.0 K, a high self-field Jc of 0.7 × 106 A cm−2, and a remarkable in-field current density value of 1 × 104 A cm−2 under 6 T at 10 K. These results indicate that the composites can be applied directly in high-power applications of superconductors. The enhancement of flux pinning in the superconducting MgB2–B4C composite is discussed and considered to be mainly due to the increment in the effective surface area of grain boundaries per unit volume.

Specific Surface Area Increment of Alumina Nanoparticles Using Mineral Fuels in Combustion Synthesis

Ammonium carbonate and ammonium sulfate have been proposed and used as two new fuels for synthesizing gamma alumina nanoparticles. The prepared samples have been characterized by X-ray diffraction (XRD), 2 N adsorption (BET) and Transmission electron microscopy (TEM). A comparison has been made between the properties of the nanoparticles synthesized by these two fuels and other conventional fuels. These two mineral fuels showed to be suitable for replacing organic fuels in combustion synthesis because they reduce the size and increase specific surface area of alumina nanoparticles effectively.

Waste Activated Sludge as an Additive for Increment of Lime Sorption Capacity

Lime was physically blended with Waste Activated Sludge (W.A.S) in various proportions. These blends were hydrated, dried, ground, and sieved to size of utmost 200 μm. The sorbents were then used in fixed-bed reactor for dry desulfurization tests. It was found that the blends had higher sorption capacities than lime alone which means that W.A.S augmented lime's sorption capacity. Higher surface area and porosity of the blended sorbents compared to lime was the main cause of the improved sorption capacity, a conclusion supported by Brunauer–Emmett–Teller surface area analysis (surface area increment with sorption capacity) and scanning electron microscopy imaging (rough morphology being formed). This higher surface area and porosity was caused by pozzolanic reaction between lime and the alumina silicate constituents of W.A.S. The products of this reaction are high surface area, complex calcium alumina silicates.

Size‐dependent aggregation behavior in monodisperse silica: a nitrogen adsorption study

AbstractThe present study focused on the aggregation behavior that resulted from surface interaction between monodisperse silicas synthesized with Stöber method using nitrogen adsorption method at cryogenic temperature (77 K). Specific surface area, pore size distribution and surface fractal dimension from adsorption isotherm were evaluated. For relatively large particle, (190 nm in diameter), it was observed that nitrogen adsorption isotherm could be classified to type I. However, others with small size (below 100 nm) have shown the characteristic of type IV with the evident character of hysteresis loop in the isotherm. The increment of specific surface area (SBET) changed with the decrease of particle size, which could be fitted with an exponential decay equation. Pore size distribution (PSD) indicated that there exist an amount of mesopore (between 2 and ∼50 nm) and shift toward the smaller with decreasing the size of silica. Surface fractal dimension (DSF) from thermodynamic method demonstrated that the DSF increased with the decreasing the size of silica. PSD and DSF clearly embodied the size‐dependent aggregation of monodisperse silica nanoparticle, which could be used to explain the inferior performance of polymer nanocomposite filled with smaller monodisperse silica. Copyright © 2011 John Wiley & Sons, Ltd.

Investigating Effects of Zeolites As an Agent to Improve Limestone Reactivity toward Flue Gas Desulfurization

Natural zeolite was utilized as an agent to increase the reactivity of lime for desulfurization. Due to the presence of hydrous silica−aluminates in zeolite, a pozzolanic reaction ensued which ended up with an increase in the surface area of lime thus making it more reactive. Tests were done in a pH-stat apparatus and a fixed bed reactor, representing wet and dry flue gas desulfurization (FGD), respectively, to check if lime reactivity was augmented by the addition of zeolite. It was found that zeolite amplifies reactivity of lime with the highest reactivity being achieved with a lime to zeolite ratio of 1:1 (by mass). This was confirmed by Brunauer−Emmett−Teller (BET) surface area analysis (surface area increment with the reactivity) and scanning electron microscopy (SEM) imaging (rough morphology being formed). Further optimization tests were conducted in the pH-stat apparatus with the aid of design expert software to quantify linear, quadratic, and interactive effects of four variables (temperature, lime to zeolite ratio, liquid to solid ratio, and stirring speed). Temperature as a variable had the highest effect, followed by lime to zeolite ratio. Stirring speed had the least effect on the reactivity.

Morphological and Physiological Responses of Weedy Red Rice (<i>Oryza sativa</i> L.) and Cultivated Rice (<i>O. sativa</i>) to N Supply

Red rice (Oryza sativa L.), a noxious weed in rice production, competes with cultivated rice for nutrients. Accumulation of more N in red rice than in cultivated rice may be due to a mechanism different from that of cultivated rice. To test this assumption, red rice and cultivated rice were grown in nutrient solution to compare their growth and physiological responses to N supply. Experimental design was a split-plot, where main plot factor was rice type (Stf-3, ‘Wells’); split-plot factor was N treatment [T1 (complete nutrient solution); T2 (–NH4NO3); T3 (+NH4NO3 for 24-h post-N deficiency); and T4 (+NH4NO3 for 48-h post-N deficiency)]. Nitrogen deficiency was defined as N sufficiency index (NSI) 4, Stf-3 showed higher increment in root length and surface area than Wells. Shoot tissue concentrations of N and total sugars were measured to determine physiological response in N-deficient and N-supplemented plants. Stf-3 had greater N and sucrose tissue concentrations at N-deficient conditions compared with Wells, implying a stress-adaptive molecular mechanism regulated by N and sucrose availability.

Templated fabrication of nanostructured Ni brush for hydrogen evolution reaction

We fabricated a nanostructured brush by carrying out Ni deposition on a through-channel anodic aluminum oxide (AAO) template, followed by removal of the AAO skeleton. The AAO was prepared by a two-step anodization process resulting in pore diameter and thickness of 350 nm and 40 μm, respectively. Subsequently, the AAO underwent an electroless deposition involving sensitization, activation, and Ni plating, in conjunction with polyethylene glycol used as the inhibitor to prevent premature closing of pore opening. After deliberate control in relevant parameters, we obtained a conformal Ni overcoat along every pore channel leading to a reduced average pore diameter of 78 nm. Afterward, the sample was immersed in a KOH solution to remove the AAO structure, forming freestanding Ni tubules in a brush configuration. The nanostructured brush revealed considerable enhancement for hydrogen evolution reaction in both current-potential polarization and galvanostatic measurements, which were attributed to the increment in apparent surface area.

The Effects of Organic Binders on Palladium Impregnated in TiO2Membrane Synthesis: X‐Ray Diffraction Analysis

This paper reports the effects of organic binders on the crystal microstructure of unsupported, Pd2+‐impregnated TiO2membranes. The organic binders used in this study were polyvinyl alcohol and hydroxypropyl cellulose. The use of the binders is important in the production of crack‐free membranes. However, the use of the binders influenced the microstructure of the unsupported TiO2membranes. X‐ray diffraction analysis utilized showed that the addition of binders has caused aggregation of palladium oxide (PdO) during its formation in the TiO2network. This phenomenon directly affects the effectiveness of PdO presence in the suppression of anatase–rutile phase transition. N2adsorb/desorption analysis was conducted to investigate the Pd2+–TiO2membrane morphology at different Pd2+loading. Based on the observation, the presence of 2 wt% Pd2+in the TiO2microstructure has significant impacts on the increment of surface area, pore volume, and average pore width from the original TiO2. However, the surface area shows decrement after the Pd2+loading was further increased from 2 to 6 and 10 wt%.

Surface Roughening During Deformation of Polycrystalline Aluminum and Titanium Alloys

The surface topography of aluminum and titanium alloys after plastic deformation is investigated using white-light interferometry. The surface profiles of tensile samples in the longitudinal and transverse directions are analyzed. The surface develops self-affine roughness on length scales up to a correlation length that is of the same order of magnitude as the grain size in the two directions. The difference in correlation lengths between the two directions is large for aluminum alloy and small for titanium alloy. Initially, the roughness values in the two directions remain the same and then become different with strain increase. It is shown that the strains in the two directions influence the profile. The relationship between the 3D surface roughness parameter (Sq) and strain appears to be linear, and a linear relation is also observed between surface area increment and strain.

On interaction of centrally-ignited, outwardly-propagating premixed flames with fully-developed isotropic turbulence at elevated pressure

A new apparatus for the study of turbulent premixed flames at atmospheric and elevated pressures is proposed. The apparatus includes a high-pressure fan-stirred cruciform burner, the inner chamber, which is resided in a relatively large pressure-absorbing safety chamber (the outer chamber). Both chambers are optically accessible, allowing direct visualization and measurement of flame and turbulence interactions. The inner burner applies the same turbulence generating mechanism as that previously reported by Shy et al. [10], capable of generating intense near-isotropic turbulence. The additional modification lies in its vertical vessel which has four sensitive pressure-releasing valves installed symmetrically, so that the pressure difference between the inner and outer chambers during explosion can be eliminated. Flame speed measurements for centrally-ignited, outwardly-propagating lean CH4–air flames at the equivalence ratio ϕ=0.8 under both quiescent and turbulent conditions are conducted over an initial pressure range of p=0.1–1MPa. It is found that, contrary to the popular scenario for laminar flames, the coupling influence of elevated pressure and turbulence significantly enhances turbulent flame speeds. Our experimental data show that the unstretched laminar burning velocities (SL) decrease with p−0.52, while turbulent burning velocities (ST) increase with p0.14 when a constant turbulent fluctuating velocity u′≈1.4m/s is applied. In terms of the power law relation proposed by Kobayashi and his co-workers, we found that ST/SL≈1.07[(u′/SL)(p/p0)]0.44 where p0 is the atmospheric pressure, showing a similar increasing trend but with much lower values of ST/SL to what they found in a Bunsen-type burner. It is suggested that ST∼p0.14 is attributed to further flame surface area increment induced by the enhancement of hydrodynamic instability due to the decrease of kinematic viscosity at elevated pressure.

Mechanochemical activation of cellulose and its thermoplastic polyvinyl alcohol ecocomposites with enhanced physicochemical properties

The focus of this work is to study the influence of mechanochemical treatment of cellulose on the physicochemical properties of its polyvinyl alcohol (PVA) composites. Cellulose fibers subjected to pan-milling could be mechanochemically activated by breaking up the intra- and inter-molecular hydrogen bonds through shearing and compressing forces. Reactive hydroxyl groups were exposed on the cellulose surface, which could establish new hydrogen bonds with PVA. Moreover, the simultaneous reduction of particle size and large increment of specific surface area of pan-milled cellulose would benefit its dispersion as well as the interfacial adhesion with polymer matrix. PVA/cellulose composites were successfully processed by the melt in the presence of plasticizers containing formamide and water. Tensile tests demonstrated positive results from mechanochemical treatment. As pan-milling cycles of cellulose increased, the tensile strength of PVA/cellulose composites increased from 8.8 MPa to 16.4 MPa, while elongation at break increased from 76.8% to 374%. The composite materials also exhibited enhanced thermal stability and better biodegradability.