Hasil untuk "Physical and theoretical chemistry"

Farizal Hakiki, Muhamad Raihan Al Fikri, Veni Dwi Amelia Putri et al.

Boecker Marcel, Marchesi D’Alvise Tommaso, Lander Sarah et al.

Judith de Paula Araújo, Maikel Y. Ballester, Mariana P. Martins et al.

The mathematics used in physical chemistry has changed greatly in the past forty years and it will certainly continue to change more quickly. Theoretical chemists and physicists must have an acquaintance with abstract mathematics if they are to keep up with their field, as the mathematical language in which it is expressed changes. Thinking about it, in this article, we want to show some of the most important concepts of Mathematical Analysis involved in obtaining analytical functions to represent the potential energy interaction for diatomic systems. A basic guide for the construction of a potential based on Dunham's coefficients and an example of a new potential obtained from this methodology is also presented.

Andrea Le Donne, Antonio Tinti, Eder Amayuelas et al.

Wetting and drying of pores or cavities, made by walls that attract or repel the liquid, is a ubiquitous process in nature and has many technological applications including, for example, liquid separation, chromatography, energy damping, conversion, and storage. Understanding under which conditions intrusion/extrusion takes place and how to control/tune them by chemical or physical means are currently among the main questions in the field. Historically, the theory to model intrusion/extrusion was based on the mechanics of fluids. However, the discovery of the existence of metastable states, where systems are kinetically trapped in the intruded or extruded configuration, fostered the research based on modern statistical mechanics concepts and more accurate models of the liquid, vapor, and gas phases beyond the simplest sharp interface representation. In parallel, inspired by the growing number of technological applications of intrusion/extrusion, experimental research blossomed considering systems with complex chemistry and pore topology, possessing flexible frameworks, and presenting unusual properties, such as negative volumetric compressibility. In this article, we review recent theoretical and experimental progresses, presenting it in the context of unifying framework. We illustrate also emerging technological applications of intrusion/extrusion and discuss challenges ahead.

Sainorudin Muhammad Hanif, Abdullah Nur Athirah, Asmal Rani Mohd Saiful et al.

The present study focused on the preparation of microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) from pineapple (Ananas comosus L.) leaves using chemical treatments followed by acid hydrolysis. Pineapple leaves could be used in medical applications such as drug delivery carriers. Advanced spectroscopy techniques such as Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to analyze the physical, chemical, and morphological features of the isolated MCC and NCC; the results indicated the needle-shaped form of nanostructures with good purity and high crystallinity index of 75.00 and 76.38%, respectively. In addition, inhibition of the treated MRC-5 cells with all the samples revealed that the percentage of cell viability was less than 30%, which is an interesting finding given their role in the cytotoxicity effect of MCC and NCC. It appears that MCC and NCC derived from pineapple leaves have lower toxicity. As a result, the developed MCC and NCC can be used in pharmaceutical applications as a novel drug delivery system. Molecular docking was performed to understand the non-bonding interaction of cellulose with human acid-beta-glucosidase (β-Glc) (PDB: 1OGS). The docking result shows that cellulose unit docked within the active pocket of the enzyme by forming hydrogen bonds against ASN19, THR21, and VAL17 with distances of 2.18, 1.93, and 2.92 Å, respectively, with binding energy (−5.0 kcal/mol) resulting in close interaction of cellulose unit with the receptor.

Daoyu Li, Zhen Shi, Huaping Xu et al.

In this work, the corrosion behavior of aluminum in carbon dioxide solutions with different concentrations at high temperature (50 oC) was studied. The corrosion of aluminum in the carbon dioxide solutions was inhibited to a certain extent compared to the corrosion in deionized water. It was found that an aluminum electrode in 0.84 pmol L''1 carbon dioxide solution with pH 4.35 had the lowest corrosion rate as observed from its lowest corrosion current, the most positive corrosion potential, and the maximum charge transfer impedance. The mechanism for aluminum corrosion inhibition was that HCO3- generated by carbon dioxide ionization developed an ordered charge field on the aluminum surface, shielding the diffusion of aluminum ions and inhibiting the dissolution of the oxide film on the aluminum surface. SEM, EDS and XRD confirmed that the corrosion products covering the surface of the aluminum electrode were Al(OH)3 and/or Al2O3. Based on the above, it was elucidated that the Pt grading electrodes of the high voltage direct current (HVDC) valve cooling system lower the scaling rate in solutions with a certain concentration of carbon dioxide, and it was shown that the concentration of aluminum ions in the inner cooling water is a crucial factor affecting the scaling of grading electrodes. Therefore, reducing the concentration of aluminum ions in the inner cooling water, in other words, inhibiting the corrosion of aluminum, is the fundamental means for solving the scaling problem of the grading electrode. This paper will contribute to the research on production improvement techniques used for HVDC valve cooling systems.

A.A. Chekannikov, A.A. Kuz’mina, T.L. Kulova et al.

Lithium-ion battery based on a new electrochemical system with a positive electrode based on composite of doped lithium iron phosphate with carbon (Li0.99Fe0.98Y0.01Ni0.01PO4/C) and a negative electrode based on doped lithium titanate (Li3.812Ti4.972Ga0.1O12) has been developed. The battery is intended for use in fixed energy storage units. The battery is characterized by the ability to operate at increased charging/discharging currents (up to 30 C). Specific power of the battery can reach about 1.5 kW kg-1.

Qiming Zhao, Xuanfen Zhang, Yinliang Bai et al.

In the present work, we develop a novel electrochemical strategy for immunoassay of neopterin by using screen-printed array as electrodes and Neopterin–alkaline phosphatase conjugation as label chemical. Electrochemical detection instead of traditional ELISA was employed, while the traditional plastic wells were replaced by screen-printed array electrodes. Various measurements were utilized for the detection of neopterin. Using the optimized electrochemical method, a limit. The obtained results show a possibility for the clinic diagnosis of vasculitis and a variety of other inflammatory diseases.

Wei Xiong, Ji Hoon Kang, Jin Kyeong Kang et al.

Nitrogen-doped porous carbons were synthesized from an aqueous solution of melamine and formaldehyde. The addition of potassium citrate to the solution mixture led to a tremendous increase in the surface area from 74 m2/g to 2718 m2/g, indicating that potassium citrate served as an excellent pore former. The nitrogen-doped carbon exhibited remarkable capacitive performance, such as a high capacitance of 320 F/g at 0.1 A/g, an excellent rate capability (70 % at 10.0 A/g), and a high cycling stability (94.6 % retention after 2000 cycles) in 6.0 M KOH aqueous solution. Furthermore, the nitrogen-doped carbon delivered a high energy density of 7.8 Wh/kg even at a high power density of 5000 W/kg. We believe that the synthesis strategy presented in this work could be used as a promising way to fabricate electrode materials for high-performance supercapacitors.

G. Roventi, G. Giuliani, M. Pisani et al.

Zn-Ni-ZrO2, Zn-Ni-Al2O3 and Zn-Ni-SiC nanocomposite coatings were obtained on mild steel substrate by electrodeposition technique from an alkaline bath. ZrO2, Al2O3 and SiC nanoparticles were added to the bath with concentrations of 5 and 10 g dm-3. The effect of current density and particles concentration on the deposit composition, morphology, structure and microharness was studied. The results show that the addition of nanoparticles to the plating solution does not affect significantly Zn-Ni electrodeposition process and alloy Ni percentage. X-ray diffraction patterns of the coatings show only the presence of cubic γ-phase Ni5Zn21. With ZrO2 or Al2O3 nanoparticles, homogeneous and compact deposits with low grain size were obtained. On the contrary, SiC nanoparticles incorporation perturbs the growth of the alloy matrix by reducing γ-phase orientation. ZrO2 and Al2O3 lead to an increase in the coating microhardness, whereas SiC leads to a decrease, due to the strong modification induced in the alloy structure.

Jian Lu, Jianling Li, Zhixun Zhu et al.

Porous Co3Mo3N nanorods were prepared by hydrothermal process combined with ammonia annealing and applied as catalyst in Li-O2 battery cell. The battery with the porous Co3Mo3N nanorods showed a higher initial discharge capacity of 7902.8 mAh/gc at current density of 100 mAh/gc than that with the pure Ketjen black. Moreover, the Co3Mo3N-based electrode displayed lower overpotential and better cycling performance than that of the carbon-only cathode. Such performance can be associated with the synergistic effects of high electrocatalytic activity and porous structure of the Co3Mo3N nanorods.

Chang Hwa Lee, Deok Yoon Kang, Min Ku Jeon et al.

The effect of fluoride compounds on Zr electrorefining is investigated for Zirlo cladding tubes in LiCl- KCl based molten salts. Cyclic voltammetric curves exhibit a modification of electrochemical behaviors of Zr ions from a two-step reduction process in LiCl-KCl-0.07 M ZrCl4 salts to one-step reduction by the addition of 0.84 M LiF. Morphological features of Zr deposits are found to also be changed from a powder type to a dendritic characteristic, thereby reducing the amount of incorporated salts and enhancing the crystallinity of electrorefined Zr. Quantitative measurement reveals that the Zr content in the deposit is increased by the addition of fluoride compounds, which is expected to enhance the recovery yield of Zr.