Determination Of Surface Area Research Articles

Determination of Internal and External Surface Area of Atomistic Porous Carbons

In this work, we propose the computational algorithm to compute the temperature-independent specific surface area of atomistic models of porous carbons. Concisely, the method is to divide the simulation space into fine grid points, place the selected probe molecule on each grid point and then check whether that insertion is accessible or inaccessible regions based on molecular force field. Three models of porous carbon structures are chosen as examples for estimating internal and external specific surface areas and trend of surface curvature. By comparing the computational cost, our proposed technique significantly requires less time-consuming than the physisorption. Therefore, for atomistic models of porous carbons, we recommend that our proposed method be more efficient and accurate than the experimentally and computationally traditional physisorption.

Spatial characterization of heterogeneous nanopore surfaces from XCT scans of Niobrara shale

The multiphase fluid flow through natural and geo-architected nanopore structures is fundamentally controlled by the geometry of such nanopore structures, pore wettability and interfacial tension. Furthermore, multiphase fluid flow through the nanopore structures is compromised when the pore surfaces are heterogeneous, having surface regions of different composition, polarity, and wetting characteristics. In this regard, compositional analysis of the pore channel surface has been a big challenge in the past, since 3D analysis is required.Now, due to advances in nano X-ray CT, with a voxel resolution of 20 nm, it is possible to identify nanopore network structures and quantify their surface composition in 3D. In this paper, the development of procedures for detailed analysis to quantify the composition of the pore channel surface regions, including the corresponding area, is described using nanoCT images. Image analysis procedures, including preprocessing of the 3D tomographic images, correction for the partial volume effect (PVE), and the use of a new algorithm for determination of pore channel surface composition and area are discussed. Videos of the nanopore structure have been provided as supplementary information to further describe the heterogeneity of the nanopore surfaces.

USE OF CARBON MATERIAL WITH DEVELOPED SURFACE FOR SYNTHESIS OF HIGHER CHROMIUM CARBIDE

The paper presents experimental data on synthesis of finely dispersed powder of chromium carbide Cr3C2 . Chromium carbide was prepared by reduction of chromium oxide Cr2O3with nanofibrous carbon (NFC) in induction furnace in argon atmosphere. NFC is a product of catalytic decomposition of light hydrocarbons. The main characteristic of NFC is high specific surface area (~150,000 m2/kg), which is significantly higher than that of carbon black (~50,000 m2/kg). Content of impurities in NFC is at the level of 1 wt %. Based on analysis of state diagram of Cr – C system, composition of charge and the upper temperature limit of carbide formation reaction for obtaining chromium carbide in powder state are determined. Based on thermodynamic analysis, temperature of the onset of carbothermic reduction reaction of chromium oxide Cr2O3was determined at various CO pressures. Characteristics of chromium carbide were studied using X-ray diffraction analysis, pycnometric analysis, scanning electron microscopy using local energy dispersive X-ray microanalysis (EDX), lowtemperature nitrogen adsorption followed by determination of specific surface area by means of BET method, sedimentation analysis, synchronous thermogravimetry and differential scanning calorimetry (TG/DSC). The material obtained at optimal parameters is represented by a single phase – chromium carbide Cr3C2 . Powder particles were predominantly aggregated. Average size of particles and aggregates equaled 6.5 μm within a wide range of size distribution. Specific surface value of the obtained samples was 2200 m2/kg. Oxidation of chromium carbide began at temperature of ~640 °C and practically ends at ~1000 °C. Optimum parameters of synthesis are provided by ratio of reagents according to carbide of Cr3C2composition stoichiometry at temperature of 1300 °С and holding time of 20 minutes. It is shown that for this process nanofibrous carbon is an effective reducing agent and that chromium oxide Cr2O3is almost completely reduced to carbide Cr3C2 .

Thermal exfoliation of electrochemically obtained graphitic materials

The present work is devoted to the electrochemical formation and thermal exfoliation of graphite oxide (GO) and reduced graphite oxide (rGO). The main attention was paid on the correlation between cycling processes of GO formation followed by its electrochemical reduction and the stage of their exfoliation. For this purpose a natural graphite was overoxidized in 8 M HClO4 to form GO which was further cathodically reduced yielding rGO. Both processes were performed within one electrochemical process in three-electrode cell using a cyclic voltammetry method. To examine the reversibility of the coupled overoxidation of graphitic matrix and its two-stage reduction the above mentioned operations were three times repeated. The acquired results clearly showed that the properties of GO and rGO significantly change with number of performed cycles. The structure of graphite matrix gradually decreases disenabling the efficient intercalation of perchloric acid during renewed process proceeded during the further cycling. Thermal treatment of electrochemically obtained materials leads to their exfoliation thus contributing to significant modification of structure, morphology and chemical composition. The information on GO properties were provided by the determination of specific surface area, X-ray diffraction analysis (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy analysis (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy observations (SEM).

Removal of cationic surfactants from dilute solutions using nanoporous nickel phosphate: A structural, kinetic and thermodynamic study

The removal of cetylpyridinium chloride (CPC) (as a cationic surfactant) on nanoporous nickel phosphate (nano-NiPOx) particles is studied for the first time. The structure and morphology of the material are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and BET surface area determination. Various operating parameters, such as the initial CPC concentration, amount of NiPOx, shaking speed, pH and temperature, are investigated. The point of zero charge (PZC) for NiPOx in 0.1 M KCl solution is found to be 6.5. The adsorption of the CPC on the NiPOx follows pseudo-first-order kinetics. Furthermore, the experimental data follow the modified Frumkin adsorption isotherm. Important thermodynamic parameters, such as the free energy of adsorption at different temperatures, are extracted by fitting the experimental data with the isotherm model. The parameters obtained above suggest that there is a strong extent of adsorption of the CPC on the NiPOx surface.

Construction of BiOF/BiOI nanocomposites with tunable band gaps as efficient visible-light photocatalysts

A series of BiOF/BiOI heterojunction composites photocatalysts has been prepared via a simple coprecipitation method and characterized by using UV–vis (UV–vis) diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller for determination of the specific surface area and porosity (BET), high resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The enhanced photocatalytic activity for removal of the pharmaceutical compound Diclofenac Potassium commercially available as Voltfast sachets under visible light irradiation was demonstrated by comparing heterojunction prepared composites photocatalysts with that of pure BiOF and BiOI photocatalysts prepared under the same conditions. Based on the experimental conditions, the highest activity was achieved for the composite contains 40% BiOF and 60% BiOI showing comparable activities to that of pure BiOI. To the best of our knowledge, this study is the first to report the preparation of BiOF/BiOI composites photocatalysts and their use in the photocatalytic removal of Diclofenac Potassium from aqueous solution.

Enhanced adsorption and removal of urea from aqueous solutions using eco-friendly iron phosphate nanoparticles

This work reports of using iron phosphate nanoparticles (nano-FePh) as adsorbent for removing urea. Hence, the adsorption of urea on nano-FePh was investigated as a function of reaction time, temperature, catalyst weight, shaking speed and solution pH. Amorphous iron phosphate is synthesized by a cost-effective method reflux. The nano-FePh is characterized by different techniques including; X-ray diffraction (XRD), transmission electron micrograph (TEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray Spectroscopy (EDX), FT-IR and BET surface area determination. Highest adsorption extent obtained at pH range of 7–9 with uptake of urea equals to 1.2 × 102 mg/g (gram of nano-FePh). The reaction kinetics of the adsorption of urea follows a pseudo-first-order model. Application of homogenous film diffusion model and matrix diffusion model is carried out and analyzed. The model of the diffusion liquid film controls the process at the first adsorption step and then at the final stage is under control by matrix diffusion model. Frumkin adsorption isotherm is found to fit with the experimental data. The kinetics and thermodynamic parameters have been determined and analyzed. The nano-FePh adsorbent was stable and the adsorption capacity was remaining excellent after 10 cycles.

The Influence of Oxygen Concentration during MAX Phases (Ti₃AlC₂) Preparation on the α-Al₂O₃ Microparticles Content and Specific Surface Area of Multilayered MXenes (Ti₃C₂Tx).

The high specific surface area of multilayered two-dimensional carbides called MXenes, is a critical feature for their use in energy storage systems, especially supercapacitors. Therefore, the possibility of controlling this parameter is highly desired. This work presents the results of the influence of oxygen concentration during Ti3AlC2 ternary carbide—MAX phase preparation on α-Al2O3 particles content, and thus the porosity and specific surface area of the Ti3C2Tx MXenes. In this research, three different Ti3AlC2 samples were prepared, based on TiC-Ti2AlC powder mixtures, which were conditioned and cold pressed in argon, air and oxygen filled glove-boxes. As-prepared pellets were sintered, ground, sieved and etched using hydrofluoric acid. The MAX phase and MXene samples were analyzed using scanning electron microscopy and X-ray diffraction. The influence of the oxygen concentration on the MXene structures was confirmed by Brunauer-Emmett-Teller surface area determination. It was found that oxygen concentration plays an important role in the formation of α-Al2O3 inclusions between MAX phase layers. The mortar grinding of the MAX phase powder and subsequent MXene fabrication process released the α-Al2O3 impurities, which led to the formation of the porous MXene structures. However, some non-porous α-Al2O3 particles remained inside the MXene structures. Those particles were found ingrown and irremovable, and thus decreased the MXene specific surface area.

Superior photocatalytic activity of tungsten disulfide nanostructures: role of morphology and defects

Tungsten disulphide (WS2) nanostructures, WS2 nanosheets (WNS) and WS2 nanorods (WNR), were synthesized by varying the surfactant, N-cetyl-N, N,N-trimethyl ammonium bromide (CTAB), concentration using facile hydrothermal technique. Samples were characterized by high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) for morphology, X-ray diffraction (XRD) to confirm their phase and crystal structure, photoluminescence (PL) and Raman studies for the determination of defect density, Tauc plot for the determination of band gap, Fourier transform infra red (FTIR) spectroscopy for functional groups and bonds, and Brunauer–Emmett–Teller (BET) isotherms for the determination of pore size and surface area. A comparative study using WS2 nanostructures (WNS and WNR) was conducted to observe the photocatalytic degradation efficiency (ƞ) and degradation kinetics on methylene blue (MB) and 4-chlorophenol (4-CP). The superior photocatalytic performance of WNS over WNR is attributed to enhanced pore size and reduced defect density. High-performance liquid chromatography was carried out for the determination of intermediate products during photocatalytic degradation.

Electrochemical Determination of Porosity and Surface Area of Thin Films of Interconnected Nickel Nanowires

In this work, we demonstrate electrochemical methods for determination of porosity and surface area of thin films of interconnected nickel nanowires. While the standard porosimetry and gas adsorption methods lack sensitivity for characterization of thin metallic films, the electrochemical methods employing coulometry, cyclic voltammetry and electrochemical impedance spectroscopy can be applied to accurately determine textural properties of micron- and sub-micron thick nanostructured materials. Additionally, in this work we evaluated accuracy and precision of five electrochemical signals recorded during cyclic voltammetry and electrochemical impedance spectroscopy, which are commonly used for determination of electrochemical surface area (AECSA) of various nickel electrodes. By verifying the data with two independent surface characterization techniques, we found that the analysis based on surface-limited oxidation of nickel and on capacitive charging of nickel surface during hydrogen evolution reaction give the best accuracy and smallest errors. We also show that experimental conditions play a crucial role in the accurate determination of AECSA of nickel nanomaterials. If the influence of experimental conditions is not corrected for, the electrochemical surface area can differ by over 250% compared to the surface area determined with other methods.

Final report of CCQM-K153 Measurement of Specific Adsorption A [mol/kg] of N2 and Kr on nonporous SiO2 at LN temperature (to enable a traceable determination of the Specific Surface Area (BET) following ISO 9277)

CCQM key comparison K-153 Measurement of Specific Adsorption A [mol/kg] of N2 and Kr on nonporous SiO2 at LN temperature (to enable a traceable determination of the Specific Surface Area (BET) following ISO 9277) has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of specific adsorption, BET specific surface area) of nonporous substances (sorbents, ceramics, catalytic agents, etc) used in advanced technology.In this key comparison, a commercial nonporous silicon dioxide was supplied as a sample. Eight NMIs participated in this key comparison, but only five NMI's have reported in time. All participants used a gas adsorption method, here nitrogen and (or) krypton adsorption at 77.3 K, for analysis according to the international standards ISO 15901-2 and 9277.In this key comparison, the degrees of equivalence uncertainties for specific adsorption nitrogen and krypton, BET specific surface area were established.KEY WORDS FOR SEARCHnonporous SiO2, Specific Adsorption of N2 and Kr, BET specific surface areaMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A fast method for determination of surface area of zeolite-based catalysts and zeolites using near infrared emission spectroscopy

A new, fast and reagent-free method for determination of the surface area of zeolite-based catalysts and zeolites using direct spectral information from near infrared emission spectroscopy and chemometrics is described.

INVESTIGATION OF THE STRENGTH OF RUBBER CONCRETE ON THE BASIS OF MODEL OF THE SPECIFIC AREA OF FINE AGGREGATE

Стаття присвячена актуальним питанням дослідження міцності гумового бетону. Ґрунтуючись на мікроскопічному аналізі великої кількості гумового цементного розчину, була створена математична модель для якісного аналізу питомої поверхні гумового порошку, змішаного з дрібним агрегатом. На основі механізмів впливу методів змішування гумового порошку використовували різні розміри частинок для виконання випробування по визначенню опору бетону на стиск. Надано наукове пояснення логічних відмінностей, що існували в процесі попередніх досліджень гумового бетону. Проведено поглиблене дослідження впливу методів та параметрів змішування, розмірів частинок та інших факторів на стійкість бетону до стиснення. У даній роботі за допомогою великої кількості експериментальних досліджень на основі методу «Модель визначення площі поверхні бетону», який враховує коефіцієнт контакту між гумовою сумішшю та дрібним агрегатом, проведено глибоке вивчення механізмів впливу на гумовий бетон.

Synthesis of crystalline and amorphous iron phosphate nanoparticles by simple low-temperature method

A simple and well-designed route for controlled synthesis of crystalline iron phosphate (FePhcry) and amorphous iron phosphate (FePhamph) with simple reflux-based method at 90 °C is introduced. The method allows for mass production at low cost. The crystalline is formed at initial pH of 0.38 to final pH = 1.0 and the amorphous form is obtained at initial pH of 1.3 to final pH (after completed reflux) of 8.0. Characterization techniques such as FT-IR spectroscopy, energy dispersive x-ray analysis (EDS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and BET surface area determination are used for the investigation of the phase structure and morphological properties of the FePhcry and FePhamph nanomaterials. The average values of particle size are ∼50–100 nm and ∼5–15 nm with surface area of 16.013 m2 g−1 and 154 m2 g−1 for FePhcry and FePhamph, respectively. Based on the XRD pattern, the obtained phase structure of the FePhcry is FePO4.2H2O (80%) and Fe12 (OH)7.3 (PO4)8.4.7H2O (20%) with a monoclinic and orthorhombic crystallographic form, respectively. For the FePhamph sample the phase structure is completely amorphous with chemical structure of FePO4.

Mg-Al-La LDH-MnFe2O4 hybrid material for facile removal of anionic dyes from aqueous solutions

The urea hydrolysis method was applied to prepare Mg-Al-La layered double hydroxides (LDH) and its hybrids with different amounts of magnetic MnFe2O4 nanoparticles. The new hybrid materials were characterized by X-ray powder diffraction, FTIR and Raman spectroscopy, AFM, SEM, TEM/EDX microscopic methods, BET specific surface area determination and inductively coupled plasma (ICP). The AFM and TEM/EDX analyses clearly showed MnFe2O4 nanoparticles to be predominantly localized on the surface of LDH sheets. Almost two-fold increase of the specific surface area was observed for the Mg-Al-La LDH-MnFe2O4 hybrids compared to the pristine LDH. All synthesized hybrids were studied for their adsorption capacities of Acid orange 7 dye. The adsorption studies were measured at pH 4.0, 7.0 and 10.0. The resulting data were fitted by Langmuir and Langmuir-Freundlich models. The Langmuir isotherm model exhibited a maximum adsorption capacity of Acid orange 7 dye (687.9 mg/g) for Mg-Al-La LDH-MnFe2O4 hybrid material. The lower pH positively affected higher adsorption capacity of Acid orange 7 dye. The prepared Mg-Al-La LDH-MnFe2O4 hybrid materials thus showed to be new promising adsorbents of anionic dyes.

Green nanosilica@folic Acid (VB9) nanocomposite for engineered adsorptive water remediation of bivalent lead, cadmium and copper

Folic acid (VB9) was used as an eco-friendly sequestering chemical compound to modify and develop a novel nanocomposite via surface immobilization and chemical bonding with nanosilica (Nano-SiO2) in the chloride form to generate Nano-SiO2@VB9. The synthesized materials were investigated and characterized by several means of SEM, HR-TEM, TGA, FT-IR, XRD and surface area determination. The tendency of Nano-SiO2@VB9 nanocomposite to extract and remove bivalent lead, cadmium and copper ions was studied and optimized under various variables including pH of contact medium, nanocomposite dose, contact time, effect of metal ion concentration and interfering cations-anions. The highest determined capacity values were 562.1, 973.8 and 152.1 mg g−1 for Cd(II), Pb(ІІ) and Cu(II), respectively. The optimum contact time for sorption of metal ions was identified as 25 min, while 10.0 mg of Nano-SiO2@VB9 nanocomposite was the optimum dosage to establish the maximum capacity values. The adsorbed ions were arranged in a multilayer surface and the equilibrium up-take of metal ions by Nano-SiO2@VB9 nanocomposite was favorably characterized by the Freundlich adsorption isotherm model. The potential applications of Nano-SiO2@VB9 for removal and preconcentration of Cu(II), Pb(II) and Cd(II) from real water samples using multistage microcolumn were also studied to confirm excellent percentage extraction values 94–100%, 100% and 57–81%, respectively.

Coupling of WO3 with anatase TiO2 sample with high {001} facet exposition: Effect on the photocatalytic properties

A highly faceted {001} TiO2 catalyst was hydrothermally synthesized by using Ti(IV)-isopropoxide precursor with aqueous HF addition. WO3 was synthesized by following a reported method. Coupled TiO2-WO3 samples were synthesized by adding the corresponding amount of WO3 to fluorinated TiO2 gel followed by a hydrothermal treatment. Additionally the synthesized systems were characterized by using X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS) and N2-adsorption (BET) for specific surface area determination. The photocatalytic activity of the single and coupled oxides was measured by means of three model reactions: the photo-oxidation of phenol (as a colourless substrate) and methyl orange (as a dye) and the photoreduction of Cr(VI) as K2Cr2O7. The coupling of WO3 with a highly faceted {001} TiO2 makes it possible to optimize the photocatalytic properties of the faceted material. In fact, {001} faceted TiO2 by itself presents a substantial improvement with respect to commercial TiO2(P25), as it can implement its photoactivity after the incorporation of WO3 with promising results, which can reduce the limitations of TiO2 in terms of its photoactivity, taking advantage of a higher percentage of solar radiation.

Specific Surface Area Determination for Microporous/Mesoporous Materials: The Case of Mesoporous FAU-Y Zeolites.

A methodology for determining the micropore, mesopore, and external surface areas of hierarchical microporous/mesoporous materials from N2 adsorption isotherms at 77 K is described. For FAU-Y zeolites, the microporous surface area calculated using the Rouquerol criterion and the Brunauer-Emmett-Teller (BET) equation is in accord with the geometrical surface determined by the chord length distribution method. Therefore, BET surface area ( SBET) is the well representative of micropore surface areas of microporous materials and of total surface area of microporous/mesoporous materials. Mechanical mixtures of mesoporous MCM-41 and microporous FAU-Y powders of known surface areas were used to calculate the respective surface areas by weighted linear combination and the results were compared to the values obtained by the t-plot method. The first slope of the t-plot determined the mesopore and external surface areas ( Smes+ext). The linear fit of the first slope is in general in the range 0.01 < p/ p0 < 0.17 and contains the volumes and relative pressures at which all micropores are filled ( p/ p0 > 0.10). Overestimation of Smes+ext values was evident and appropriate corrections were provided. External surface areas ( Sext) were obtained from the second slope of the t-plot, without noting an overestimation of Sext, thus allowing the determination of mesopore surface areas ( Smes) by difference. Micropore surface areas were calculated by subtracting Smes+ext from the total surface area, SBET. As an example, this methodology was applied to characterize a family of hierarchical microporous/mesoporous FAU-Y (FAUmes) synthesized from H-FAU-Y (H-Y, Si/Al = 15) using C18TAB as the surfactant and different NaOH/Si ratios (0.05 < NaOH/Si < 0.25). By increasing the NaOH/Si ratio in the synthesis of FAUmes, it was shown that as the micropore surface area decreases, the mesopore surface area increases, whereas the micropore and mesopore surface area remains constant. This methodology allows accurate characterization of the surface areas of microporous/mesoporous materials.

관군 배열 형태에 따른 셸-앤-관 응축기의 설계

This paper carried out the thermal design of shell and tube condenser in ORC(Organic Rankine Cycle) using toluene as the working fluid. Heat exchanger design typically includes the determination of heat transfer surface area, number of tubes and tube length etc. In order to obtain the heat transfer surface area, shell and tube side heat transfer coefficients must be given to calculate the overall heat transfer coefficient. The simulation results show that the heat transfer coefficient for tube layout of 90o is higher than that of the other cases. In addition, it is found that the pressure drop and surface area for tube layout of 90o are lower than the other cases.

5-Na/ZnO doped mesoporous silica as reusable solid catalyst for biodiesel production via transesterification of virgin cottonseed oil

Abstract 5-Na/ZnO loaded SBA-15 has been prepared by one-pot method in atmospheric conditions (without employing hydrothermal treatment) and following wet impregnation method. The prepared catalyst was characterised by using several techniques viz., BET method for determination of surface area, FE-SEM for morphology of catalyst, XPS study to determine the oxidation state of constituent elements. The catalyst was utilised for transesterification from virgin cotton seed oil and the catalyst activity was dependant on its basic strength. Under optimal reaction conditions of catalyst amount 12 wt%, methanol to oil molar ratio of 24:1 at reaction temperature of 65 °C, the prepared catalyst yielded > 98% fatty acid methyl ester in 4 h of reaction duration. The catalyst was able to yield conversion level as good as ∼74% even in 5th cycle after regeneration. Leaching of