jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: V. P. Vasiliev | Roman A. Manzhos | А. Г. Кривенко
Source: International Journal of Electrochemistry (article, 2019-04-28)
Field: Materials Science — Materials Chemistry

Electrical Conductivity of Films Formed by Few-Layer Graphene Structures Obtained by Plasma-Assisted Electrochemical Exfoliation of Graphite Current-voltage characteristics of few-layer graphene structures (FLGS) obtained by plasma-assisted electrochemical exfoliation of graphite in Na 2 SO 4 solution were measured. FLGS are shown to possess electronic conductivity, which indicates the predominant functionalization of the edges of graphene planes and the preservation of the structure of basal planes in obtained nanostructures as in the source graphite. The effect of humidity on the conductivity of FLGS films was studied. The resistance of films was found to increase with an increase in the relative humidity of the environment due to the shielding of FLGS flakes by a film of water. The effect of different solvents on the current-voltage characteristics of FLGS was analyzed. The conductivity of films significantly decreased in vapors of polar protic solvents, while there was a minor effect of nonpolar aprotic solvents on the conductivity of FLGS films. Graphene ; Exfoliation joint ; Conductivity ; Graphite ; Materials science ; Relative humidity ; Layer (electronics) ; Electrochemistry ; Electrical resistivity and conductivity ; Chemical engineering ; Composite material ; Polymer chemistry ; Nanotechnology ; Electrode ; Chemistry ; Physical chemistry Graphene research and applications ; Carbon Nanotubes in Composites ; Fiber-reinforced polymer composites
Authors: Zhiliang Xiong | Wenjian Zheng | Yanzhang Liu | Yanjun Kuang | Jianguo Yang
Source: Metals (article, 2019-09-03)
Field: Materials Science — Metals and Alloys

Hydrogen Diffusion Mechanism around a Crack Tip in Type 304L Austenite Stainless Steel Considering the Influence of the Volume Expansion of Strain-Induced Martensite Transformation Strain-induced martensite transformation (SIMT) commonly exists around a crack tip of metastable austenite stainless steels. The influence of the volume expansion of the SIMT on the hydrogen diffusion was investigated by hydrogen diffusion modeling around a crack tip in type 304L austenite stainless steel. The volume expansion changed the tensile stress state into pressure stress state at the crack tip, resulting in a large stress gradient along the crack propagation direction. Compared to the analysis without considering the volume expansion effect, this volume expansion further accelerated the hydrogen transport from the inner surface to a critical region ahead of the crack tip, and further increased the maximum value of the hydrogen concentration at the critical position where the strain-induced martensite fraction approximates to 0.1, indicating that the volume expansion of the SIMT further increased the hydrogen embrittlement susceptibility. Materials science ; Austenite ; Hydrogen embrittlement ; Martensite ; Hydrogen ; Volume expansion ; Volume fraction ; Volume (thermodynamics) ; Diffusion ; Metallurgy ; Stress (linguistics) ; Crack closure ; Austenitic stainless steel ; Metastability ; Composite material ; Thermodynamics ; Fracture mechanics ; Microstructure ; Chemistry ; Corrosion Hydrogen embrittlement and corrosion behaviors in metals ; Microstructure and Mechanical Properties of Steels ; Welding Techniques and Residual Stresses
Authors: Salisu Z.M. | Ishiaku S.U. | D. Abdullahi
Source: World Journal of Innovative Research (article, 2019-02-28)
Field: Chemistry — Analytical Chemistry

Recovery of Crude Oil from Aqueous Medium by Optimised Styrene/Kenaf Shive Graft-Based Sorbent Via Regeneration Method: Study of the Equilibrium, Kinetics and Activation Energy The area of research that cast the mind of many environmentalist is remediation of oil spilled environments. This paper addresses the development of new bio-based sorbent through ceric induced grafting. The effect studies of the individual and combine factors was carried out using a statistical experimental design matrix using five-level central composite design (CCD). Respond surface methodology (RSM) was used to optimise and develop equations of the variables (initiator concentration, monomer ratio and particle sizes). To the optimized sorbent, unmodified kenaf shive was compared with, it reveals a positive hydrophobic shift. However, instrumental analysis such as: XRD, FTIR, BET and DTA-TGA were carried out on the optimized sorbent. In addition, the capability of the oil sorption in water was reported and the kinetics and equilibrium isotherms employed fits respectively, the pseudo-second order and Langmuir isotherm with regression coefficient R 2 =0.9822 and R 2 =0.9900. The sorption property was found to be spontaneous and exothermic, however, the activation energy studies shows physic-sorption phenomenon with 25.6kJmol -1 and R 2 =0.9847. Sorbent ; Kenaf ; Kinetics ; Styrene ; Materials science ; Regeneration (biology) ; Activation energy ; Chemical engineering ; Aqueous solution ; Chemistry ; Composite material ; Copolymer ; Organic chemistry ; Polymer ; Fiber ; Adsorption ; Engineering Petroleum Processing and Analysis ; Enhanced Oil Recovery Techniques ; Catalysis and Hydrodesulfurization Studies
Authors: Yuqing Geng | Zhiwei Wang | Yahuan Wang | Jiayang Song | Zhimin Chen | Jiafu Chen | Yong Chen | Jianwei Fu
Source: SN Applied Sciences (article, 2019-09-19)
Field: Chemistry — Organic Chemistry

Amino-rich polymer-coated Fe–Fe2O3 nanoparticles with high adsorption capacity and rapid magnetic separation for anionic dye removal Adsorption ; Magnetic separation ; Polymer ; Nanoparticle ; Magnetic nanoparticles ; Chemical engineering ; Magnetite Nanoparticles ; Materials science ; Chemistry ; Nanotechnology ; Organic chemistry ; Metallurgy Nanomaterials for catalytic reactions ; Adsorption and biosorption for pollutant removal ; Environmental remediation with nanomaterials
Authors: Hongling Dai | Min Wang | Wendong Luo | Cheng Pan | Fengping Hu | Xiaoming Peng
Source: RSC Advances (article, 2019-01-01)
Field: Chemistry — Organic Chemistry

<i>In situ</i> fabrication of hierarchical biomass carbon-supported Cu@CuO–Al<sub>2</sub>O<sub>3</sub> composite materials: synthesis, properties and adsorption applications Hierarchical Cu-Al<sub>2</sub>O<sub>3</sub>/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu-Al<sub>2</sub>O<sub>3</sub> frame (H-Cu-Al/BC) for the removal of ammonium nitrogen (NH<sub>4</sub> <sup>+</sup>-N) from aqueous solutions. The as-synthesized samples were characterized <i>via</i> XRD, SEM, BET and FTIR spectroscopy. The BET specific surface area of the synthesized H-Cu-Al/BC increased from 175.4 m<sup>2</sup> g<sup>-1</sup> to 302.3 m<sup>2</sup> g<sup>-1</sup> upon the incorporation of the Cu-Al oxide nanoparticles in the BC surface channels. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the adsorption kinetics of NH<sub>4</sub> <sup>+</sup>-N obeyed the pseudo-second-order kinetic model. The static maximum adsorption capacity of NH<sub>4</sub> <sup>+</sup>-N on H-Cu-Al/BC was 81.54 mg g<sup>-1</sup>, which was significantly higher than those of raw BC and H-Al/BC. In addition, the presence of K<sup>+</sup>, Na<sup>+</sup>, Ca<sup>2+</sup>, and Mg<sup>2+</sup> ions had no significant impact on the NH<sub>4</sub> <sup>+</sup>-N adsorption, but the presence of Al<sup>3+</sup> and humic acid (NOM) obviously affected and inhibited the NH<sub>4</sub> <sup>+</sup>-N adsorption. The thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous in nature. H-Cu-Al/BC exhibited removal efficiency of more than 80% even after five consecutive cycles according to the recycle studies. These findings suggest that H-Cu-Al/BC can serve as a promising adsorbent for the removal of NH<sub>4</sub> <sup>+</sup>-N from aqueous solutions. Fabrication ; Composite number ; Carbon fibers ; Adsorption ; In situ ; Materials science ; Chemical engineering ; Nanotechnology ; Biomass (ecology) ; Chemistry ; Composite material ; Physical chemistry ; Organic chemistry ; Engineering Nanomaterials for catalytic reactions ; Supercapacitor Materials and Fabrication ; Catalytic Processes in Materials Science
Authors: Chansong Kim | Eunpyo Hong | Chae‐Ho Shin
Source: Preprints.org (preprint, 2019-09-21)
Field: Materials Science — Materials Chemistry

Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Re-oxidation Treatment The improvement of the methane combustion activity was observed in cyclic temperature-programmed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/re-oxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programmed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programmed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/re-oxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures. Isothermal process ; Catalysis ; Methane ; Combustion ; Anaerobic oxidation of methane ; Chemistry ; Catalytic combustion ; Temperature-programmed reduction ; Activation energy ; Redox ; Inorganic chemistry ; Chemical engineering ; Thermodynamics ; Organic chemistry Catalytic Processes in Materials Science ; Catalysis and Oxidation Reactions ; Industrial Gas Emission Control
Authors: Valeria Cuccia | SANDRO ROGÉRIO NOVAES SELES | Ana Cláudia Queiroz Ladeira
Source: Brazilian Journal of Radiation Sciences (article, 2019-02-06)
Field: Materials Science — Materials Chemistry

Removal of cobalt from lubricant oil by the use of bentonite: equilibrium, kinetic and adsorption preliminary studies Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator’s facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Bentonite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system’s kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assumption that the adsorption is due to chemisorption. Batch sorption tests were conducted and the results fitted to Langmuir and Freundlich sorption models. Both isotherm models chosen for this work did not fit to the experimental data. Thus, these are preliminary results and the studies must be repeated to evaluate data variability and better statistical inference. Other isotherm models must be evaluated to choose the best fitted one and describe the sorption of cobalt on bentonite in oil matrix. Even though, bentonite has considerable potential as sorbent for the removal of cobalt from lubricant oil. Finally, the results might be extended to other kinds of radioactive oils and radioactive organic wastes. Sorption ; Bentonite ; Sorbent ; Adsorption ; Freundlich equation ; Cobalt ; Lubricant ; Radioactive waste ; Waste management ; Human decontamination ; Langmuir ; Radionuclide ; Chemistry ; Materials science ; Environmental science ; Chemical engineering ; Nuclear chemistry ; Organic chemistry ; Engineering Graphite, nuclear technology, radiation studies ; Radioactive element chemistry and processing
Authors: Andrew Shamu | Henk Miedema | Kitty Nijmeijer | Zandrie Borneman
Source: Journal of CO2 Utilization (article, 2019-09-28)
Field: Materials Science — Polymers and Plastics

The effect of supercritical CO2 on the permeation of dissolved water through PDMS membranes Water vapor permeation under supercritical carbon dioxide (scCO2) conditions through dense polydimethylsiloxane (PDMS) was investigated up to pressure of 185 bars to evaluate the regenerability of scCO2 as desiccant to dehydrate fresh products that are prone to product deterioration during conventional drying. This study experimentally examined the impact of concentration polarization on the H2O vapor permeation through dense PDMS membranes in the presence of sub- and supercritical CO2. The results were compared to a system containing N2 instead of CO2. For the CO2 system, the residual mass transfer resistance, which excludes the membrane layer resistance, decreased down to zero with increasing feed pressure, at 90 bar. This is the result of the convergence of the H2O contents of the feed bulk and permeate, which leads to a change of the main H2O transport mechanism within the feed boundary layer from diffusion to convection. Here the H2O and CO2 molecules are transported with comparable speed towards the membrane surface. For the system with N2, the opposite trend was found, due to the maintained significant difference in transport speed between H2O and N2 even at elevated pressures. Consequently, the water vapor transport rate through the PDMS membrane is governed by the type of matrix fluid (CO2 or N2). Permeation ; Supercritical fluid ; Membrane ; Polydimethylsiloxane ; Water vapor ; Supercritical carbon dioxide ; Mass transfer ; Chemical engineering ; Materials science ; Chemistry ; Penetration (warfare) ; Chromatography ; Composite material ; Organic chemistry Polymer Foaming and Composites ; Phase Equilibria and Thermodynamics ; Membrane Separation and Gas Transport
Authors: Van C. Phan | Elizabeth A. Fry | Kurt W. Zilm
Source: Journal of Biomolecular NMR (article, 2019-08-12)
Field: Chemistry — Spectroscopy

Accounting for the temperature dependence of 13C spin–lattice relaxation of methyl groups in the glycyl–alanyl-leucine model system under MAS with spin diffusion The difficulties in quantitatively modeling the temperature dependence of spin-lattice relaxation in a model isotope-enriched peptide are explored as a prelude to obtaining dynamics parameters for motions in proteins from such measurements. The degree to which this can be handled by adding spin diffusion to a bath in standard rate matrix relaxation theory is studied using a small tri-peptide model system, glycyl-alanyl-leucine (GAL). We observe in this molecule that the relaxation of backbone carbons CO and Cα is not dominated by local fluctuations of the <sup>13</sup>C-<sup>1</sup>H dipolar couplings, but rather by <sup>13</sup>C-<sup>13</sup>C spin diffusion to nearby methyl relaxation sinks. A treatment of the methyl relaxation itself, which ignores <sup>13</sup>C-<sup>13</sup>C spin diffusion effects back to the otherwise slowly relaxing bath, provides poor agreement between theory and experimental data obtained for the temperature dependence of the methyl relaxation rates. Closed form approximate spectral densities and relaxation rates for a methyl group during magic angle spinning are obtained to compute the needed transition rates. These average computed rates, in conjunction with an extended form of the Solomon equations, are found to adequately model the temperature dependence of the methyl relaxation rates when spin diffusion is included. The barrier to rotation for the alanine methyl in GAL is determined to be 3.5 kcal mol<sup>-1</sup>. Chemistry ; Relaxation (psychology) ; Spin–lattice relaxation ; Methyl group ; Spin diffusion ; Diffusion ; Dipole ; Magic angle spinning ; Thermodynamics ; Nuclear magnetic resonance ; Nuclear magnetic resonance spectroscopy ; Physics ; Stereochemistry ; Group (periodic table) ; Organic chemistry Advanced NMR Techniques and Applications ; Electron Spin Resonance Studies ; NMR spectroscopy and applications
Authors: Dalia Bednarska | Marcin Koniorczyk
Source: Journal of Thermal Analysis and Calorimetry (article, 2019-05-15)
Field: Materials Science — Materials Chemistry

The influence of diol addition on water crystallization kinetics in mesopores Solidification of liquid occupying material’s pores is one of the main reasons of its skeleton deterioration. So far, it has been usually assumed that confined water undergoes phase transitions more rapidly than temperature changes, which indicates that the kinetic effects are negligible. However, this assumption is often infringed. The main object of this paper is to analyse the crystallization of commonly applied antifreeze, i.e. ethylene as well as propylene glycol, in water solutions contained in voids of mesoporous silica gel with average pore size equal to 11 nm. In case of both solutions, two concentrations are analysed, 5% and 10%. Additionally, the analysis is conducted also for deionized water. The experimental research has been conducted by means of differential scanning calorimetry with multiple cooling rate program applied. The activation energy is estimated according to the differential Friedman method. In order to pick the most appropriate kinetic model to analysed phenomenon, two approaches are applied: the one introduced by Málek as well as the one described by Perez-Maqueda et al., the so-called model-fitting method. The former indicates the Šesták–Berggren model, whereas the latter points to nth reaction order model. Both equations demonstrate high accordance with the experimental data. The Šesták–Berggren equation is an empirical formula, which does not provide any explanation about antifreeze solidification. However, the nth reaction order model belongs to the group of geometrical extension/contraction models. Differential scanning calorimetry ; Thermodynamics ; Crystallization ; Activation energy ; Kinetics ; Materials science ; Ethylene glycol ; Mesoporous material ; Antifreeze ; Kinetic energy ; Chemistry ; Chemical engineering ; Physical chemistry ; Organic chemistry ; Physics ; Catalysis Thermal and Kinetic Analysis ; Polymer crystallization and properties ; Thermochemical Biomass Conversion Processes
Authors: Ndepana A. Gaya | Victor Charles | Innocent Joseph | Hitler Louis
Source: Catalysis for Sustainable Energy (review, 2019-01-01)
Field: Materials Science — Materials Chemistry

A review on CO oxidation, methanol synthesis, and propylene epoxidation over supported gold catalysts Abstract The aim of this general review is to give an overview of the reaction pathways involving the transformation of carbon monoxide (CO), methanol synthesis and propylene epoxidation using gold (Au) and gold supported clusters. Over the catalyst system of Nano-gold (Au/SiO 2 ), the process of methane to methanol was also highlighted. A reaction mechanism proposed, indicated that molecular oxygen was consumed in the oxidation–reduction cycle. Consequently, methane oxidation to methanol can be achieved as a green chemical process. The system can also be used in other green chemical processes of liquid phase or gas phase oxidations. Methanol is expected to be a potential solution to the partial deployment of fossil source-based economies. Moreover, it is a recognized energy carrier that is better than other alternatives in terms of transportation, storage and reuse. New or improved catalysts for methanol production are likely to be discovered in the near future. Methanol ; Catalysis ; Carbon monoxide ; Methane ; Partial oxidation ; Chemistry ; Chemical engineering ; Materials science ; Inorganic chemistry ; Organic chemistry Catalytic Processes in Materials Science ; Catalysis and Oxidation Reactions ; Catalysis and Hydrodesulfurization Studies
Authors: Wiesław Apostoluk | Waldemar Robak
Source: SN Applied Sciences (article, 2019-06-27)
Field: Chemistry — Spectroscopy

Analysis of the aqueous solubility of trialkyl phosphates, dialkyl alkylphosphonates, dialkylphosphites and alkyl dialkylphosphinates Linear free energy relationship (LFER) analysis based on the molar intrinsic volume (Vx), McGowan hydrophile‒lipophile balance (HLB) and cumulative Kabachnik constants (Σσϕ) of considered solutes has been performed for the solubility of trialkyl phosphates, dialkyl alkylphosphonates, dialkyl phosphites and alkyl dialkylphosphonates in pure water (called also as their aqueous solubility). The descriptors mentioned above are known for all considered solutes and are strongly correlated with their aqueous solubility. From the correlation found for trialkyl phosphates, dialkyl alkylphosphonates and dialkyl phosphites it follows that the mean contribution of each methylene group in their structure (Δlog Sw) is a constant for these homologous series and equal to − 0.41. It means that within of homologous series the aqueous solubility of succeeding solutes decreases regularly. The established increment has been further used as a tool for the preliminary selection of solutes whose aqueous solubility at 25 °C is in agreement with this condition. The adequate model (further denoted as AR model) based on the accessible data of temperature effects upon the aqueous solubility of tributyl phosphate, dibutyl butylphosphonate and butyl dibutylphosphinate has been formulated and then tested with positive results for the other solutes whose solubility is known at a selected constant temperature, e.g. at 25 °C. It should noticed, however, that in this case there are some serious restrictions. First, the interpretation and formulation of conclusions for the solutes which aqueous solubility is known at one selected temperature (e.g. 25 °C) or if it has been determined at a few temperatures only, should be made with care. Second, the obtained results with AR model cannot be used for prediction of temperature effects upon the aqueous solubility of such solutes. Simultaneously, the results obtained with AR model have been compared with those following from the modified Abraham model. Such comparison has been possible due to a significant progress in the different application of Abraham model for several organophosphorus derivatives as monobasic dialkyl- and diarylphosphoric acids, dialkyl- and diphenylphosphinic acids, trialkyl- and triaryl phosphates, dimethyl methylphosphonate, dialkylphosphites and some of trialkyl- and triarylphosphine oxides, respectively. Solubility ; Chemistry ; Aqueous solution ; Molar solubility ; Homologous series ; Alkyl ; Methylene ; Phosphonate ; Molar volume ; Organic chemistry ; Inorganic chemistry ; Thermodynamics Analytical Chemistry and Chromatography ; Thermodynamic properties of mixtures ; Chemical and Physical Properties in Aqueous Solutions