Mechanical Properties Of Silica Research Articles

The effect of initial temperature on the mechanical strength of tricalcium phosphate/Chitosan/Silica aerogels nanocomposites using molecular dynamics simulation

BackgroundChitosan is an organic polymer derived from chitin, showcasing commendable biocompatibility and biodegradability, while tricalcium phosphate emerges as an active ceramic with proven biocompatibility and superior compatibility with bone tissue. This composite material, endowed with a unique amalgamation of attributes including biocompatibility, porosity, and mechanical strength, proves highly applicable in diverse fields such as tissue engineering, drug delivery systems, wound repair, and as scaffolds for cell proliferation in regenerative medicine. MethodsThe focal point of this study is an exploration of the nuanced interplay between the mechanical properties of silica aerogel/chitosan tricalcium phosphate nanocomposites with increasing initial temperature. Employing molecular dynamics (MD) simulation, the research aims to unveil the temperature-induced variations in the critical properties. Significant FindingsThe results reveal that the ultimate strength and Young's modulus values are determined to converge to 772.28 MPa and 62.291 GPa, at 297 K. As the initial temperature escalates from 300 to 350 K, the US decreases from 72.28 to 714.47 MPa. The decrease in US could be due to higher temperatures, the increased thermal energy can lead to greater atomic vibrations within the material, which can promote easier dislocation movement and result in reduced resistance to deformation. The results reveal that as temperature increases to 320 K, YM increases to 67.134, and with further increase in temperature, YM decreases to 62.865 GPa

Transitional flaw size sensitivity of amorphous silica nanostructures analyzed by ReaxFF/SiO based molecular dynamics

This paper presents an investigation aimed at understanding the flaw size sensitivity in amorphous silica nanostructures. The investigation is carried out in LAMMPS via reactive molecular dynamics analyses by employing ReaxFF–SiO, a bond order-based force field. First, a validated procedure is developed to build the amorphous silica nanostructures via a melt, quench, and equilibration process. This procedure is seen to correctly reproduce the molecular structure as well as mechanical properties of silica. The best agreement to experimental data is obtained by using non-periodic boundary conditions with the isothermal–isobaric ensemble. The validated model is then used to analyze crack propagation in amorphous silica samples with varying flaw sizes subjected to mode I tensile fracture. The analyses reveal a marked transition from flaw sensitive to insensitive behavior with decreasing flaw size. The transition flaw size is found to be 20–25 Å. Fracture propagation is found to be accompanied by the formation of several single atom thick strands near the crack tip, previously reported as “stress fibers.” This is proposed as a viable mechanism causing blunting of an initially sharp crack, analogous to blunting of a macroscale crack by an inelastic damage zone. The nanoscale fracture process zone estimated by probing near crack tip stresses is found to nearly equal the transition flaw size, providing an explanation for the transitional behavior. A semi-empirical, transitional flaw size effect law rooted in quasibrittle fracture mechanics is derived based on asymptotic matching and is found to capture well the nanoscale transitional behavior.

The critical role of the interaction potential and simulation protocol for the structural and mechanical properties of sodosilicate glasses

We compare the ability of various interaction potentials to predict the structural and mechanical properties of silica and sodium silicate glasses. While most structural quantities show a relatively mild dependence on the potential used, the mechanical properties such as the failure stress and strain as well as the elastic moduli depend very strongly on the potential, once finite size effects have been taken into account. We find that to avoid such finite size effects, samples of at least 75,000 atoms for silica and 300,000 atoms for the sodosilicate are needed. Finally we probe how the simulation ensemble influences the fracture properties of the glasses and conclude that fracture simulations should be carried out in the constant pressure ensemble.

Effects of surface crack on the mechanical properties of Silica: A molecular dynamics simulation study

In this paper, fracture mechanism and the effects of surface crack on the mechanical properties (modulus and strength) of silica glass are studied through reactive all-atom molecular dynamics (MD) simulations. Tapered surface cracks of different length ranging from 0.25 to 10.0 nm are created by deleting atoms to study the crack length effects. Interatomic interactions are modeled with state-of-the-art reactive force field ReaxFF and fracture energy release rate is determined from discretized atomistic J-integral approach. Simulation results indicate that surface cracks have no effect on fiber modulus, however, fiber strength is significantly affected by surface crack. With the increase in crack length, strength decreases and MD predicted strength-crack length response is in good agreement with theoretical prediction. MD simulations project that about 35 nm size crack could reduce glass fiber strength to 3.5 GPa, which is experimentally observed fiber mean strength. MD simulations show that there is no inelastic process zone with cavities in front of the crack tip. Fracture mode is brittle type where crack growth initiates through Si-O bond breakage and it propagates through sequential bond ruptures.

Thermal and Mechanical Properties of Silica⁻Lignin/Polylactide Composites Subjected to Biodegradation.

In this paper, silica–lignin hybrid materials were used as fillers for a polylactide (PLA) matrix. In order to simulate biodegradation, PLA/hybrid filler composite films were kept in soil of neutral pH for six months. Differential scanning calorimetry (DSC) allowed analysis of nonisothermal crystallization behavior of composites, thermal analysis provided information about their thermal stability, and scanning electron microscopy (SEM) was applied to define morphology of films. The influence of biodegradation was also investigated in terms of changes in mechanical properties and color of samples. It was found that application of silica–lignin hybrids as fillers for PLA matrix may be interesting not only in terms of increasing thermal stability, but also controlled biodegradation. To the best knowledge of the authors, this is the first publication regarding biodegradation of PLA composites loaded with silica–lignin hybrid fillers.

Investigation on the Influence of Various Kinds of Soaps on the Mechanical Properties of Silica Filled Composites Based on Natural Rubber

The aim of this study was to investigate the influence that different fatty acid zinc salts had on the rheological, curing and mechanical properties of natural rubber based composites filled with silica and containing bi-functional organosilanes in the presence or absence of zinc oxide. The results demonstrated that the combination of zinc oxide and zinc soaps had a strongly pronounced anti-reversion effect. The absence of reversion in the cure curves of the rubber compounds comprising a combination of zinc oxide, stearic acid and zinc soaps, results in retention of their mechanical properties, even after overcure.

Mechanical properties of on/off-axis loading for hybrid glass fiber reinforced epoxy filled with silica and carbon black nanoparticles

In this study, mechanical properties of silica (SiO2) and carbon black nanoparticles (C) with different weight fractions embedded on epoxy matrix reinforced with two types of E-glass fiber was investigated. The hybrid glass fiber consists of woven glass fiber reinforced epoxy laminated between several layers of nonwoven glass tissue. The nanoparticles were incorporated into epoxy resin as a single nanoparticle (either SiO2 or C alone) or combining SiO2 and C nanoparticles simultaneously. Fatigue performance, on-axis and off-axis tensile behaviors of these hybrid composites were investigated. The incorporation of all nanoparticles contents leads to improvement in on/off axis ultimate tensile strength, failure strain, tensile modulus and toughness when compared to neat glass fiber reinforced epoxy composites except for the hybrid nanocomposites reinforced with 0·5 wt-% SiO2 and 0·5 wt-% C simultaneously. On/off-axis tensile properties were obviously improved with adding single SiO2 or C nanoparticles rather than with adding combined ones.

EFFECTS OF SURFACE TREATMENTS AND SILICA SIZE ON MECHANICAL PROPERTIES OF SILICA-REINFORCED ELASTOMERIC COMPOSITES

ABSTRACT The effect of surface treatments with atmospheric pressure flame plasma (APFP) and epoxy silane (ES) was studied experimentally to improve the mechanical properties of silica- (volume 40% and mean diameters of 2.2, 12.4, 26.6, and 110 μm) reinforced elastomeric composites. The tensile strength (TS) of the composites increased significantly with decreasing mean diameter. When the diameter was 2.2 μm, the TS of the composite was approximately 1.4 times higher than that of the matrix (2.52 MPa). In addition, the TS of the silica-reinforced composites treated with APFP and ES was increased by 8.8 to 13.3% and 9.9 to 12.5%, respectively, compared with that of the matrix. A larger particle size generally resulted in better surface treatment effects. When the diameter was 26.6 μm, the tensile modulus (TM) of the composite was increased approximately twofold compared with the matrix (0.88 MPa), and the TM of the silica-reinforced composites treated with APFP and ES was increased by 15.6 to 22.8% and 21.1 to 25.8%, respectively, compared with the matrix. Therefore, the importance of surface treatments increases with increasing filler particle size. A conventional silane-coupling agent treatment has few disadvantages, such as the use of organic solvents. Nevertheless, the APFP treatment is a fast, economic, and eco-friendly method for improving the mechanical properties.

Antibacterial Efficacy and Mechanical Properties of Silica Reinforced Natural Rubber (NR) with HPQM Based Neusilin

This work studied the antibacterial performance and mechanical properties of natural rubber (NR) compound reinforced with commercial silica at various silica loadings form 0, 20, 40 and 60 parts per hundred rubber (phr). 2-Hydroxypropyl-3-Piperazinyl-Quinoline carboxylic acid Methacrylate (HPQM) based Neusilin at loadings of 0, 3 and 5 phr were used as anti-bacterial agent against Escherichaia coli (E.coli) ATCC 25923 and Staphylococcus aureus (S.aureus) ATCC 25922. The antibacterial performance was reported as a clear zone radius by diffusion test and a percentage reduction of bacteria by Plate-Count-Agar (PCA) method. The results suggested that the increasing silica loading in the NR vulcanizates improved the tensile modulus and hardness, but decreased elongation which had optimal tensile strength at 20 phr of silica. Additionally, the HPQM based Neusilin did not affect the mechanical properties of the rubber vulcanizates. The antibacterial results showed that the inhibition zone radius and the percentage reduction increased with increasing HPQM based Neusilin, but decreased with silica filler content. The antibacterial efficacy was inversely related to the reinforcement level of the NR vulcanizates by the silica. The percentage reduction of bacteria of NR compound filled with 5 phr of HPQM based Neusilin achieved 99.9%.

シリカ粒子充てんスチレンブタジエンゴムの力学特性とパルスNMRによる界面領域の構造解析:シランカップリング剤前処理とインテグラルブレンドの比較

シランカップリング剤の添加方法が，シリカ粒子充てんスチレンブタジエンゴムの力学特性におよぼす影響について検討した。前処理法とインテグラルブレンド法を比較した。メルカプト基含有シランカップリング剤でアルコキシ基の数が2の場合,前処理法の200%モジュラスがより高かった。これに対して3では，インテグラルブレンド法の方がより高かった。この理由は以下である。アルコキシ基数2の前処理法では, シラン鎖はシリカ表面で直鎖状に成長するので，これとゴム分子鎖との絡み合いが起こりやすい。アルコキシ基数3のインテグラルブレンド法では，ネットワーク形成とゴム分子鎖との絡み合いが同時に進行する。 その結果，いずれも補強性の高い界面領域が形成したものと考えられる。ポリスルフィド系シランカップリング剤の場合の200%モジュラスは，インテグラルブレンド法より前処理法の方が高く,シラン分子中のイオウ原子の数が2より4の方がわずかに高かった。シラン分子中のイオウ原子が加硫反応に関与し，イオウ原子の多い方がこの効果がより高かったためである。未加硫ゴムの1Hパルス核磁気共鳴分析から，複合材料のシランカップリング剤による補強性を推定できることが分った。

Study on Impact Resistance of Silica Fume Concrete

It has important practical significance to research dynamic mechanical properties of silica fume concrete with silica fume concrete widely applying in civil engineering. Mechanical properties of silica fume concrete under impact loading were studied with the SHPB test device ofφ74mm to get its optimal design project and provided important bases and references for engineering applications.

A GaAs MEMS for AFM and spin injection

We investigate the mechanical and electrical properties of tip-less, GaAs micro-cantilevers on silica supports that are fabricated using a novel assembly approach. The resulting device is compatible with an atomic force microscope (AFM) and takes advantage of the electronic and optical properties of GaAs as well as the mechanical properties of silica. Mechanically, their resonant frequency and quality factor, as well as their AFM imaging capabilities (lateral resolution ∼10–20nm), are comparable to commercial silicon cantilevers despite the absence of micromachined tip. In the same AFM-like configuration, they can also function as novel spin-polarized electron injectors under excitation by a circularly polarized laser from the rear. Surface nitridation of the cantilever and deposition of a hydrophobic thin polymer film on the sample surface are found to stabilize the injected photocurrent, making them potentially useful for a variety of fundamental and applied investigations in atmosphere.

화염 플라즈마 및 실란 표면처리가 실리카 강화 고무복합재료의 기계적 특성에 미치는 영향

ABSTRACT The effect of surface treatments with the atmospheric pressure flame plasma (APFP) and epoxy silane (ES) is experimentally investigated to yield the best mechanical properties of silica (    ) reinforced elastomeric composites. The tensile strength of the composites is increased significantly with decrease the mean diameter. When the diameter is 2.2㎛, that of the composite is increased about 1.4 times compared to the matrix (2.52㎫). Also, the tensile strength of silica reinforced composites with APFP and ES treated is increased 8.8∼13.3%, 9.9~12.5%, respectively. When the diameter is 26.6㎛, the tensile modulus of the composite is increased about 2 times compared to the matrix (0.88㎫), and the tensile modulus of silica reinforced composites with APFP and ES treated is increased 15.6∼22.8%, 21.1~25.8%, respectively. Conventional silane coupling agent treatment have a few disadvantages because of using organic solvents. However APFP treatment is a fast, economic and eco-friendly method to improve the mechanical properties.

Atomistic-Continuum Modeling of the Mechanical Properties of Silica/Epoxy Nanocomposite

In this study, a hierarchical multiscale homogenization procedure aimed at predicting the effective mechanical properties of silica/epoxy nanocomposites is presented. First, the mechanical properties of the amorphous silica nanoparticles are investigated by means of molecular dynamics (MD) simulations. At this stage, the MD modeling of three-axial tensile loading of amorphous silica is carried out to estimate the elastic properties. Second, the conventional twp phase homogenization techniques such as finite elements (FE), Mori-Tanaka (M-T), Voigt and Reuss methods are implemented to evaluate the overall mechanical properties of the silica/epoxy nanocomposite at different temperatures and at constant weight ratio of 5%. At this point, the mechanical properties of silica obtained in the first stage are used as the inputs of the reinforcing phase. Comparison of the FE and M-T results with the experimental results in a wide range of temperatures reveals fine agreement; however, the FE results are in better agreement with the experiments than those obtained by M-T approach. Additionally, the results predicted by FE and M-T methods are closer to the lower bound (Reuss), which is due to lowest surface to volume ratio of spherical particles.

Preparation and Characterization of Silica Film on PBT Substrate by Sol-Gel Method Using Perhydropolysilazane

Silica, silica/polymethylmethacrylate (PMMA) hybrid, and silica-particle blend silica films were successfully prepared on polybutylene terephtalate (PBT) substrate by dip coating using perhydropolysilazane (PHPS) as a silica source. The effect of thermal treatment on conversion from PHPS to silica was investigated in detail by scanning electron microscopy and Fourier transform infrared spectroscopy. Mechanical properties of silica and silica/PMMA hybrid thin films also were examined by the pencil scratch hardness tests.

Effect of TAC (Triallyl Cyanorate) on Curing Characteristics and Mechanical Properties of Silica Filled EPDM Rubber

ABSTRACT In this research, the effects of formulation and the amount of triallyl cyanorate (TAC) as coupling agent on peroxide vulcanization and mechanical properties of the participated silica filled EPDM elastomer are investigated. The results of curing process and measuring mechanical properties (hardness, modulus, tensile strength, elongation at break, abrasion, resilience) of compounds show that silica accounts for mechanical properties improvement and TAC decreases Mooney viscosity and scorch time and also increases optimum curing time; therefore, it prevents compound scorching. In addition, results show that TAC improved rubber-filler interaction and apparent crosslink density, which reflected on mechanical properties under study and SEM photographs.

The effect of cyclic swelling (octamethylcyclotetrasiloxane) on the physical properties of silicone breast implant shells

Changes in the physical and mechanical properties of silica filled silicone elastomeric films were studied as a function of repeated sorption extraction cycling. The sorption of octamethylcyclotetrasiloxane (D4) on the properties of three silicone filled elastomeric films was analyzed. Two of the films, SILASTIC®I and SILASTIC®II, were shells of explanted breast implants and the third, a calendered film, prepared with similar composition to the elastomer used for the breast prosthesis were studied. The as-received (AR) SILASTIC®I and II films contained 20 and 26.5 wt% non-cross-linked material that was removed by extraction with hexane. The failure properties of the extracted films are significantly higher than those of the AR films. The amount of swelling, weight gain, volumetric change, and the stress- and strain-to-fail of the films were measured in the as-received condition, and after a series of extractions and swellings. Repeated cycling (up to 5 cycles) of extraction-swelling had essentially no effect on the failure properties of films when all the diluent was removed. The effect of diluent on the failure properties of all three films was quite large. The stress-to fail of the swollen film was reduced a factor of 6 compared to baseline extracted samples while the corresponding strain values were reduced a factor of 5. The energy to fail of the swollen compared to baseline films was reduced almost a factor of 50. However, the overall mechanical properties of the films are restored when the diluent was removed. The mechanical forces involved in the swelling process do not degrade the polymer even when cycled through five swell-extract cycles.

1718 シリカ粒子充填エポキシ樹脂の力学的特性に及ぼす不均質硬化の影響

1718 シリカ粒子充填エポキシ樹脂の力学的特性に及ぼす不均質硬化の影響

Basic Science in Silica Glass Polishing

ABSTRACTWater entered into oxides when the oxides were indented with diamond in the presence of water or water vapor. Similar water entry is expected during silica glass polishing because of the high stress concentration on the glass surface in contact with small abrasive particles. Both chemical and mechanical properties of silica glasses change with water content. Polishing rate of silica in oil-based slurry with diamond abrasive increased with water content in the silica. Since oil has no chemical reactivity with silica, mechanical property degradation with water incorporation must be responsible for the fast polishing rate of the water-containing samples. A plausible mechanism of the polishing of silica is, therefore, water entry into silica under stress and mechanical removal of the altered layer. In the presence of water this process repeats itself.

Strain Dependent Dynamic Mechanical Properties of Silica Filled Ethylene Vinyl Acetate Rubber

The dynamic mechanical properties of silica filled ethylene vinyl acetate (EVA) rubber have been studied at room temperature (25°C) at different frequencies (3.5 to 110 Hz) and varying dynamic strain amplitudes (0.07 to 5%). From the dynamic analysis it was found that the trend of variation of in-phase modulus, out-of-phase modulus, and tan δ with dynamic strain for lightly filled EVA vulcanizates is similar to that of the gum EVA vulcanizate. The changes in low strain dynamic properties can be ascribed to the mobility of amorphous chains. For highly filled vulcanizates, the nature of the variation of dynamic mechanical properties follows the pattern of filled conventional rub ber systems. For the systems with intermediate filler loading, the characteris tics follow a transition between those exhibited by the gum and the highly filled systems. The increase of high and low strain moduli with volume fraction of filler could be partly due to the hydrodynamic effect of filler dispersed in the rubber matrix and partly due to the enhanced adsorptive interaction between silica and EVA rubber.