scholarly journals Using Graphene Sulfonate Nanosheets to Improve the Properties of Siliceous Sacrificial Materials: An Experimental and Molecular Dynamics Study

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4824 ◽  
Author(s):  
Hongyan Chu ◽  
Zifei Wang ◽  
Yu Zhang ◽  
Fengjuan Wang ◽  
Siyi Ju ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
High Performance ◽  
Pore Diameter ◽  
Water Molecules ◽  
Scanning Calorimetry ◽  
Optimal Amount ◽  
Cement Based Materials ◽  
Decomposition Enthalpy ◽  
Sacrificial Materials

The fabrication of high-performance cement-based materials has benefited greatly from the extensive use of graphene and its derivatives. This paper studies the effects of graphene sulfonate nanosheets (GSNSs) on sacrificial cement paste and mortar (the tested materials) and other siliceous sacrificial materials, especially their ablation behaviors and mechanical properties. Decomposition temperatures and differential scanning calorimetry were used to examine how different contents of GSNSs determines the corresponding decomposition enthalpy of the tested materials and their ablation behaviors. Molecular dynamics was also used to clarify the mechanism how the GSNSs work in the CSH (calcium silicate hydrated)/GSNSs composite to increase the resistance to high temperature. The experimental results show that: (1) the contents of GSNSs at 0.03 wt.%, 0.1 wt.%, and 0.3 wt.% brought an increase of 10.97%, 22.21%, and 17.56%, respectively, in the flexural strength of siliceous sacrificial mortar, and an increase of 1.92%, 9.16%, and 6.70% in its compressive strength; (2) the porosity of siliceous sacrificial mortar was decreased by 5.04%, 9.91%, and 7.13%, respectively, and the threshold pore diameter of siliceous sacrificial mortar was decreased by 13.06%, 35.39%, and 24.02%, when the contents of GSNSs were 0.03 wt.%, 0.1 wt.%, and 0.3 wt.%, respectively; (3) a decline of 11.16%, 28.50%, and 61.01% was found in the ablation velocity of siliceous sacrificial mortar, when the contents of GSNSs were 0.03 wt.%, 0.1 wt.%, and 0.3 wt.%, respectively; (4) when considering the ablation velocities and mechanical properties of siliceous sacrificial materials, 0.1 wt.% GSNSs was considered to be the optimal amount; (5) the GSNSs contribute to the reinforced effect of GSNSs on CSH gel through the grab of dissociated calcium and water molecules, and the chemical reaction with silicate tetrahedron to produce S–O–Si bonds. These results are expected to promoting the development of new kinds of siliceous sacrificial materials that contain GSNSs.

scholarly journals Simultaneous Enhancement of Strength and Toughness of PLA Induced by Miscibility Variation with PVA

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1178 ◽  
Author(s):  
Yanping Liu ◽  
Hanghang Wei ◽  
Zhen Wang ◽  
Qian Li ◽  
Nan Tian
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Fracture Strain ◽  
Electrospun Fiber ◽  
Structural Evolution ◽  
Amorphous Structure ◽  
Poly Lactic Acid ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
Strength And Toughness

The mechanical properties of poly (lactic acid) (PLA) nanofibers with 0%, 5%, 10%, and 20% (w/w) poly (vinyl alcohol) (PVA) were investigated at the macro- and microscale. The macro-mechanical properties for the fiber membrane revealed that both the modulus and fracture strain could be improved by 100% and 70%, respectively, with a PVA content of 5%. The variation in modulus and fracture strain versus the diameter of a single electrospun fiber presented two opposite trends, while simultaneous enhancement was observed when the content of PVA was 5% and 10%. With a diameter of 1 μm, the strength and toughness of the L95V5 and L90V10 fibers were enhanced to over 3 and 2 times that of pure PLA, respectively. The structural evolution of electrospun nanofiber was analyzed by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Although PLA and PVA were still miscible in the concentration range used, the latter could crystallize independently after electrospinning. According to the crystallization behavior of the nanofibers, a double network formed by PLA and PVA—one microcrystal/ordered structure and one amorphous structure—is proposed to contribute to the simultaneous enhancement of strength and toughness, which provides a promising method for preparing biodegradable material with high performance.

A Potential High-Throughput Route to Collagen-Mimicked Carbon Nanotube Fiber via Domino Pushing and Ion Bombardment

2020 ◽  
Vol 87 (6) ◽  
Author(s):  
Qifang Yin ◽  
Kun Geng ◽  
Yanan Yuan ◽  
Zuoqi Zhang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Elastic Modulus ◽  
Mass Production ◽  
High Performance ◽  
Ion Bombardment ◽  
Weak Interface ◽  
Carbon Nanotube Fiber ◽  
Economic Technology ◽  
Dynamics Simulations

Abstract Carbon nanotubes (CNTs) have been shown owning extraordinary mechanical properties for decades, but to date, their wide application as load-bearing structural materials has not been realized mainly due to the critical obstacles of weak interface, poor distribution and alignment, and lack of economic technology for mass production and processing. In order to overcome these obstacles, we proposed a potential route from as-grown CNT forest to collagen-mimicked CNT films with covalently crosslinked CNTs arranged in a staggered alignment. To consolidate the foundation of the route, its critical step of ion bombardment to construct the intertube crosslinks in CNT films was simulated using molecular dynamics simulations. Results show that the ion bombardment can efficiently construct the intertube crosslinks and greatly improve the elastic modulus and strength of CNT films by as much as 24% and 660%, respectively, with comparison to the nonbombarded ones. The influences of the number and the kinetic energy of the incident particles were systematically investigated and the corresponding contours were presented, suggesting the optimal energy and number of the incident particles for the elastic modulus and strength of collagen-mimicked CNT films. The work not only provides a novel route to mass fabrication of high-performance CNT fibers but also gives useful guidelines on the optimization of processing design.

Thermo-mechanical characterization of discontinuous recycled/repurposed carbon fiber reinforced thermoplastic organosheet composites

2021 ◽  
pp. 002199832110157
Author(s):  
Philip R Barnett ◽  
Stephen A Young ◽  
Vivek Chawla ◽  
Darren M Foster ◽  
Dayakar Penumadu
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
High Performance ◽  
Thermomechanical Properties ◽  
Polyphenylene Sulfide ◽  
Single Fiber ◽  
Thermoplastic Resin ◽  
Scanning Calorimetry ◽  
Post Process ◽  
Process Annealing

The integration of repurposed and recycled carbon fibers into high-performance composites is essential to the adoption of composites for automotive structures due to their low-cost, high formability, and reduced environmental impact. When high areal density nonwovens of these fibers are infused with a semi-crystalline thermoplastic resin, organosheets offering competitive mechanical properties can be produced. This study examined the optimization of such composites through multiscale material characterization and post-process annealing. Single fiber tensile tests were used to characterize repurposed and recycled fiber formats. The thermomechanical properties of the polyphenylene sulfide matrix and resulting composites subjected to different post-process annealing conditions were characterized using differential scanning calorimetry, dynamic mechanical analysis, and nano-indentation. Single fiber push-in testing was conducted to evaluate the fiber–matrix interface as a function of annealing. It was shown that statistical methods based on the bootstrap principle successfully identify the effects of post-process annealing, which are otherwise masked by material inhomogeneity. Post-process annealing was shown to be an effective method of improving the resulting mechanical properties of repurposed and recycled carbon fiber organosheet composites, thereby optimizing their properties for use as a high-performance automotive structural material.

scholarly journals Nanoindentation on the bio-inspired high-performance nature composite by molecular dynamics method

2019 ◽  
Vol 28 ◽  
pp. 096369351986016 ◽  
Author(s):  
Amin Nouroozi Masir ◽  
Abolfazl Darvizeh ◽  
Asghar Zajkani
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Elastic Modulus ◽  
Composite Structures ◽  
High Performance ◽  
Inorganic Materials ◽  
Atomic Scale ◽  
Small Scale ◽  
Different Temperatures ◽  
Research Findings

The determination of mechanical properties at the nanoscale is of such importance today that researchers pay special attention to it. Discovering the mechanical properties of biological composite structures in the nanoscale is much interesting today. Top neck mollusk shells are among biomaterial nanocomposites that their layered structures are composed of organic and inorganic materials. Since the nanoindentation process is known as an efficient method to determine mechanical properties like elastic modulus and hardness in small scale, therefore, due to some limitations of considering all peripheral parameters, particular simulations of temperature effect in the atomic scale are considerable. The present article provides a molecular dynamics approach for modeling the nanoindentation mechanism with three types of pyramidal, cubic, and spherical indenters at different temperatures of 173, 273, 300, and 373°K. Based on load-indentation depth diagrams and Oliver–Pharr equations, research findings indicate that the temperature has weakened the power between the biological atoms; this leads to reduced mechanical properties. An increase in temperature causes a reduction in elastic modulus and hardness. There was correspondence between the results obtained from the spherical indenter and experimental data. This study can be regarded as a novel benchmark study for further research studies which tend to consider structural responses of the various bio-inspired nanocomposites.

scholarly journals Preparation and Characterization of pH Sensitive Chitosan/3-Glycidyloxypropyl Trimethoxysilane (GPTMS) Hydrogels by Sol-Gel Method

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1326 ◽  
Author(s):  
Chi-Ping Li ◽  
Mao-Chi Weng ◽  
Shu-Ling Huang
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Diffusion Mechanism ◽  
Sol Gel ◽  
Swelling Kinetics ◽  
Water Molecules ◽  
Crosslinking Reaction ◽  
Buffer Solution ◽  
Scanning Calorimetry ◽  
Hybrid Hydrogels

pH responsive chitosan and 3-Glycidyloxypropyl trimethoxysilane (GPTMS) hydrogels were synthesized by the sol-gel crosslinking reaction. GPTMS was introduced to influence several behaviors of the chitosan hydrogels, such as the swelling ratio, mechanical properties, swelling thermodynamics, kinetics, and expansion mechanism. The functional groups of Chitosan/GPTMS hybrid hydrogels were verified by FT-IR spectrometer. Differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) were used to analyzed the thermal behavior of water molecules, the expansion of thermodynamics, and the content of water molecules in the hydrogel. The results show that hydrogel consists of 50 wt.% GPTMS (CG50) and has good mechanical properties and sensitivity to pH response characteristics in the acidic/alkaline buffer solution. The increase of GPTMS content leads to the increase of hydrophobic groups in the hydrogel and causes the decrease of the overall water content and the freezing bond water content. When the hydrogels were immersed in acid solution, the interaction force parameter was smaller than that of DI-water and alkaline. It means that the interaction forces between hydrogel and water molecules are relatively strong. The swelling kinetics of hybrid hydrogels were investigated to inspect the swelling mechanism. The result is consistent with the Fisk’s diffusion mechanism, meaning that the rate of water penetration is adjustable. The biodegradable hydrogel (CG50) in this study has good environmental sensitivity and mechanical properties. It is suitable to be applied in the fields of drug release or biomedical technology.

scholarly journals Molecular Dynamics Investigation of the Thermo-Mechanical Properties of the Moisture Invaded and Cross-Linked Epoxy System

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 103
Author(s):  
Can Sheng ◽  
Gai Wu ◽  
Xiang Sun ◽  
Sheng Liu
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Hydrogen Bonds ◽  
Epoxy Polymer ◽  
Uniaxial Tensile ◽  
Cross Linking ◽  
Water Molecules ◽  
Moisture Concentration

In spite of a high market share of plastic IC packaging, there are still reliability issues, especially for the effects of moisture. The mechanism between moisture and epoxy polymer is still obscure. A multi-step cross-linking approach was used to mimic the cross-linking process between the DGEBA resin and JEFFAMINE®-D230 agent. Based on the molecular dynamics method, the thermo-mechanical properties and microstructure of epoxy polymer were analyzed. In this paper, the degree of cross-linking ranged from 0% to 85.4% and the moisture concentration ranged from 0 wt.% to 12 wt.%. The hydrogen bonds were investigated in the moisture invaded epoxy polymer. Although most of the hydrogen bonds were related to water molecules, the hydrogen bonds between the inside of epoxy polymer were reduced only a little as the concentration of moisture increased. The diffusion coefficient of the water molecules was found to increase with the increase of moisture concentration. When the moisture concentration was larger than 12 wt.% or smaller than 1.6 wt.%, the diffusion coefficient was less affected by the epoxy polymer. In addition, the free volume and the thermal conductivity of the epoxy polymer were considered. It was found that the moisture could increase the thermal conductivity from 0.24 to 0.31 W/m/K, identifying a coupling relationship between moisture and thermal properties. Finally, the mechanical properties of epoxy polymer were analyzed by uniaxial tensile simulation. The COMPASS and DREIDING force fields were used during the uniaxial tensile simulation. A better result was achieved from the DREIDING force field compared with the experiment. The degree of cross-linking was positively correlated with mechanical properties. For the system with the largest degree of cross-linking of 85.4%, the Young’s modulus was 2.134 ± 0.522 GPa and the yield strength was 0.081 ± 0.01 GPa. There were both plasticizing and anti-plasticizing effects when the water molecules entered the epoxy polymer. Both the Young’s moduli and yield strength varied in a large range from 1.38 to 2.344 GPa and from 0.062 to 0.128 GPa, respectively.

Microstructural Aspects of High-Performance Cement-Based Materials

1994 ◽  
Vol 370 ◽  
Author(s):  
W. Jiang ◽  
D.M. Roy
Keyword(s):  
Mechanical Properties ◽  
Image Analysis ◽  
Radioactive Waste ◽  
Future Development ◽  
High Performance ◽  
Fiber Composites ◽  
Process Models ◽  
Strengthening Mechanisms ◽  
Computer Image Analysis ◽  
Cement Based Materials

AbstractThe goal of this research is to improve the physical properties, mechanical properties and durability of cement-based materials by controlling chemistry and processing to produce the desired microstructures and properties. An accompanying initiative is to establish the basic scientific understanding relating processing and microstructure with physical and mechanical behavior, for the future development of new, special purpose, high performance cement-based materials. The research involves both experimentation and theory elucidating fundamental strengthening mechanisms for materials such as warm-pressed, MDF, DSP, polymer, and fiber composites. SEM and computer image analysis were used. Of interest are creating process models that serve as a basis for real applications such as in the following areas: High-performance highway concrete, and the immobilization of radioactive waste.

Assessment of a Polyamide Used in Flexible Pipes After Aging in Deoxygenated Water

2020 ◽  
Author(s):  
Danyelle Costa ◽  
Geovanio Oliveira ◽  
Leilane Cirilo ◽  
Marysilvia Costa
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
High Performance ◽  
Accelerated Aging ◽  
Volumetric Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polyamide 12 ◽  
Flexible Pipes ◽  
Indentation Tests

Abstract A high-performance polyamide grade of easy processability which presents excellent thermal and mechanical properties such as resistance to fatigue and creep is studied in this work. An accelerated aging of Polyamide 12 samples was performed in stainless steel autoclaves at 120°C in deoxygenated water at pH 8.7 in order to shorten the aging time and avoid oxidation. The samples were retrieved at distinct aging times which were enough to reach the asymptotic portion of the curve of corrected inherent viscosity (CIV) versus aging time. CIV measurements track modifications of the molecular weight due to hydrolysis. Afterwards, the samples were analyzed through their cross section in the core and edge layer in order to investigate changes due to diffusion effects. Differential scanning calorimetry (DSC) analysis assesses the degree of crystallinity and melting temperature. Thermogravimetric analysis (TGA) was employed in order to investigate changes in the thermal stability and the stage of degradation of the samples. Unlike conventional volumetric analysis techniques, the instrumented indentation tests (IIT) in micro-scale were performed to measure the mechanical properties such as elastic modulus (EIT) and hardness (HIT) along the thickness aiming to detect properties gradient between surface and core. The CIV measurements showed a decrease of 46.3% in the aged sample during the maximum aging time compared to the reference material.

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