Determination of elastic constants of functionalized graphene-based epoxy nanocomposites: A molecular modeling and MD simulation study

The effect of carboxyl (–COOH) functionalized graphene (FG) on the mechanical properties of its epoxy-based nanocomposites has been investigated by Molecular Dynamics (MD) simulations. Simulations cells of nanocomposites with varying wt% of FG (1, 2 & 3 wt%) were constructed using Material Studio 6.0. Obtained MD simulation results show improved mechanical properties such as elastic modulus, bulk modulus, shear modulus, and the Poisson ratio of the FG/epoxy nanocomposites than that of pure epoxy. Moreover, the computational results of nanocomposites have also been validated well with existing experimental data. Therefore, the current MD simulation shows a decent computational sign for the existing experimental and simulation outcomes on mechanical properties of FG/epoxy nanocomposites.

Computer-aided molecular design of 2-anilino 4-amino substituted quinazolines derivatives as malarial inhibitors

Quantitative structure–activity relationship studies conducted on forty-five (45) derivatives of 2-anilino 4-amino substituted quinazolines as malaria inhibitors to determine the structures responsible for their antimalarial properties and design novel derivatives with improved activities. The molecular descriptors generated were selected to develop the theoretical model using the genetic approximation component of the material studio. The developed model found to be a function of ATSC8c, GATS8i, SpMin1_Bhi, JGI10, and TDB6u descriptors, shows excellent statistical parameters (R2 = 0.7913, R2adj = 0.7553, Q2cv = 0.7112, LOF = 0.2125, and R2pred = 0.7650). The mean effect (MF) analysis revealed the descriptor SpMin1_Bhi, as the most influential by its largest percentage contribution (54%) to the developed model. The descriptor decodes the information on the first ionization potentials and was found to have positive MF. Hence, activity increases with increases the descriptor value. Structural modifications of the template (compound 13; pEC50 = 7.387) using electron-withdrawing groups increases the descriptor value (first ionization potentials) of the template, which by extension increases the antimalarial activity lead to the design of ten (10) novel theoretical derivatives with improve antimalarial activities. Compound 3, N4-(3-bromo-5-fluorobenzyl)-N2-(4-fluorophenyl)-6,7-dimethoxyquinazoline-2,4-diamine was found to have the highest antimalarial activities among all the designed derivatives (pEC50 = 8.0515).

Simple and Rapid Preparation of MIL-121 with Small Particles for Lithium Adsorption from Brine

A novel method to generate an aluminum-based MOF material named as MIL-121 was investigated. MIL-121, [Al(OH)(H2BTEC)·(H2O)]n is a prototypal aluminum MOF with 1,2,4,5-benzenetetracarboxylic acid (BTEC) linkers, which was normally produced by the hydrothermal method. Different from the hydrothermal method, the developed novel method does not involve high temperature and high pressure, instead the MOF material was produced by the traditional cooling crystallization method at ambient pressure and low temperature below 100 °C. The MIL-121 obtained by the novel method possesses the same lithium adsorption performance as that obtained by hydrothermal method, but with lower energy consumption and more environmentally friendly. Compared with hydrothermal method, this method has more advantage to be scaled up to industrialized production. The formation mechanism of MIL-121 in the novel method including nucleation and growth process of MOF crystal was studied. The results indicated that the size and morphology of MIL-121 crystals were influenced by the temperature and additives, respectively. As the reaction temperature increased to 100 °C, the operation time can be shortened to 2–5 h. The crystal habit that was predicted by Material studio software using BFDH, which is a model for crystal habit prediction proposed by Bravais, Friedel, Donnay, and Harker based on the crystal lattice parameters and crystal symmetry in the Morphology module, the simulated morphology of MIL-121 was in accord with that of the products obtained by cooling crystallization. The thermal stability of MIL-121 obtained by cooling crystallization is better than that obtained by the hydrothermal method.

A theoretical study of (9, 0) Singlewalled Carbon Nanotubes using quantum mechanical techniques

First principles simulation studies using the density functional theory have been performed on (9, 0) Zigzag Singlewalled Carbon Nanotube (SWCNT) to investigate its electronic, optical and thermodynamic properties using CASTEP (Cambridge Sequential Total Energy Package) and DFTB (Density Functional based Tight Binding) modules of the Material Studio Software version 7.0. Various functionals and sub-functionals available in the CASTEP Module (using Pulay Density Mixing treatment of electrons) and various eigen-solvers and smearing schemes available in the DFTB module (using smart algorithm) have been tried out to chalk out the electronic structure. The analytically deduced values of the band gap obtained were compared with the experimentally determined value reported in the literature. By comparison, combination of Anderson smearing scheme and standard diaogonalizer produced best results in DFTB module while in the CASTEP module, GGA (General Gradient approximation) functional with RPBE (Revised-perdew-Burke-Ernzerh) as Sub-functional was found to be the most consistent. These optimized parameters were then used to determine various electronic, optical and thermodynamic properties of (9, 0) Singlewalled Nanotube. (9, 0) Singlewalled Nanotube, which is extensively being used for sensing NH3, CH4 & NO2, has been picked up in particular as it is reported to exhibit a finite energy band gap in contrast to its expected metallic nature. The study is of utmost significance as it not only probes and validates the simulation route for predicting suitable properties of nanomaterials but also throws light on the comparative efficacy of the different approximation and rationalization quantum mechanical techniques used in simulation studies.

Effect of Temperature on Diffusivity of Monoethanolamine (MEA) on Absorption Process for CO2 Capture

iffusion coefficient study gains an interest to know the mass transfer properties of molecules especially in study of the absorption process. The main objective of this study is to investigate the effect of temperature on diffusivity of MEA absorption process for CO₂ capture. Three different values of process temperature were chosen for simulation was carried out at 25°C, 40°C. The MD simulation was carried out at NVE (200ps) and NPT (INS) ensemble in Material Studio 7.0 software.

Screening of gallate-based metal-organic frameworks for single-component CO2 and CH4 gas

Adsorption using porous adsorbents is widely applied in carbon dioxide (CO2) capture due to its potential energy saving with low operating cost. Metal-organic frameworks (MOFs) are preferable over conventional adsorbents as MOFs have tunable structure properties. Organic linkers from phytochemical-based give a new idea in forming MOFs. Gallic acid is classified under phytochemicals can act as an alternative organic linker in a new family of hybrid framework materials due to low cost, low toxicity, easy availability and naturally abundant. Due to unique property of MOFs that can be tailored, screening using systematic tool is very important. Molecular modeling is proven to play a crucial role in providing an estimation on adsorption capacity, selectivity and adsorbent selection. Grand Canonical Monte Carlo (GCMC) method via Sorption module in Material Studio was performed to compute loading curves of CO2 and methane (CH4) in MOFs. Based on the simulation results, it shows that gallate-based MOFs can be a new promising adsorbent in CO2 capture as the predicted CO2 loading is significantly higher than CH4. The highest predicted CO2 adsorption capacity is achieved by Mg-gallate and the lowest is by Ag-gallate with 7.79 mmol/g and 6.35 mmol/g respectively. The applicability of gallic acid to act as an alternative linker is relevant for practical applications.

Metal-Organic Frameworks: Screening M-MOF-74 (M = Co, Cr, Cu, Fe, Mg, Mn, Ni, Ti, and Zn) Based for Carbon Dioxide Adsorption

The release of carbon dioxide in the environment is increasing yearly due to human activities and it will affect greenhouse gas. To overcome this issue, adsorption technology found to be the best candidate due to its performance to capture high CO2 with lower capital cost. Much attention has focused on metal-organic framework (MOF) due to high potential of CO2 capture compared with conventional adsorbents. More research has been done on MOF-74 due to presence of the open-metal site that favors CO2 binding. The presence of metal in MOF-74 able to give higher surface area and porosity of the molecules thus result in higher adsorption of CO2. However, there is limited research related to metal in MOF-74 where most focused on the Mg-MOF-74 due to its ability to adsorb twice of CO2 compared with zeolites. Yet, Mg-MOF-74 found to lose stability in presence of water where it's only able to recover 15% from initial adsorption. Synthesizing MOF-74 requires high cost and providing not a promising result for each synthesizes. Thus, this paper introduces to screen MOF-74 for different metal centers using modeling approach by Material Studio. As result, Ni-MOF-74 shows the highest adsorption of CO2 with 12.35mmol/g compared to other metals.

Effect of introduction of fluoromonomer copolymerization on properties of polyimide hollow fibers

The novel copolymerization polyimide (PI) hollow fibers (HFs) of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) containing –CF3 groups were prepared and investigated through both simulation and experiment. To demonstrate the alteration attributable to the introduction of fluoromonomers, the condensed states of pyromellitic dianhydride (PMDA)/4,4′-oxybisbenzenamine (ODA), PMDA/6FDA/ODA, and 6FDA/ODA PI were constructed by Material Studio, and we simulated the mobility of molecular chain, free volume fraction, and O2/N2 dissolution–diffusion process. The molecular dynamics simulation results demonstrated that the properties of the copolymerized PI system with 6FDA were significantly improved, while the selectivity remained almost unchanged. Then, the films of copolymerized PI and HFs were prepared by the two-step method, and O2/N2 permeability of the PI copolymer films was characterized, indicating that although the gas permeation performance was greatly improved, the selectivity was not so satisfactory. However, the selection factor increased heavily after polydimethylsiloxane coating.

Molecular dynamics simulation of bamboo heat treatment with cellulose based on molecular different weight fractions of water

Eight groups of cellulose amorphous region models in which the mass fraction of water was separately 0%, 1%, 2%, 3%, 4%, 5%, 6%, and 7% were established using a molecular dynamics software material studio. The PCFF force field was selected to simulate the molecular dynamics of the model under the constant-pressure and constant-temperature (NPT) ensemble. The simulated temperature was set to 433.15 K. The experiment showed that the hydrogen bonds between cellulose chains affected the structure of cellulose, which led to the change of the end-to-end distance of the cellulose chain and the overall size of a cell. The diffusion degree of water molecules was closely related to the number of hydrogen bonds between cellulose and water. In the process of heat treatment of bamboo, the present simulation results suggest that the structure of bamboo may be damaged when the mass fraction of water vapor reaches or exceeds 7%.

Study on synthesis and application of tetrabasic lead sulfate as the positive active material additive for lead-acid batteries

Tetrabasic lead sulfate (4BS) was used as a positive active material additive for lead-acid batteries, which affirmatively affected the performance of the battery. Herein, tetrabasic lead sulfate was synthesized from scrap lead paste that was formed through the production process of the lead-acid batteries. This solves the disposing problem of the scrap lead paste that is challenging in the production of the lead-acid batteries. Scrap lead paste was first pre-treated and the 4BS with high purity and crystalline was synthesized by sintering at the temperature of 450°C and hold time of 7 h. As demonstrated by X-ray diffraction and scanning electron microscopy test and Material Studio software calculation, the purity of synthesized 4BS is higher than 98 wt%, small particles have pillar forms and are evenly distributed. Moreover, the synthesized 4BS of 1 wt% was added to the positive lead paste and then valve-regulated lead-acid battery was made after the pasting, curing and formation processes. The effectiveness of the lead-acid batteries after adding 4BS as crystal seeds was evaluated, and the 100% charge–discharge cycle life of the new battery (523 times) was about 1.4 times higher than that of general lead-acid batteries (365 times).