Presence Of Interphase Research Articles

Study of Gas Swelling Processes under Irradiation with Protons and He2+ Ions in Li4SiO4–Li2TiO3 Ceramics

One of the important areas of research in the energy sector is the study of the prospects for using new types of nuclear fuel, including tritium, which is one of the most promising types of fuel for thermonuclear energy. At the same time, for the production of tritium in the required quantities, the one that is the most optimal is the use of blanket materials based on lithium-containing ceramics. This is where tritium is released from lithium under the influence of neutron irradiation. The paper presents the results of an investigation of the influence of two-phase ceramics based on Li4SiO4–Li2TiO3 compounds on the resistance to external influences (mechanical loads) during the accumulation of hydrogen and helium (He2+) in the near-surface layer. The interest in such studies is primarily related to the search for solutions in the field of creating high-strength materials for tritium generation for its further use as nuclear fuel for thermonuclear fusion, as well as to the study of the mechanisms of the influence of different phases on the changes in the strength properties of ceramics, which provides an opportunity to expand fundamental knowledge in this area. The proposed method of obtaining two-phase ceramics by mechanical-chemical mixing and subsequent sintering into spherical particles enables the production of well-structured, high-strength ceramics of specified geometric dimensions (limited only by the dimensions of the mold) with a controlled phase ratio. During the experiments, it was found that increasing the content of Li4SiO4 phase in ceramics leads to an increase in strength characteristics (hardness, resistance to cracking) by 15–20% compared to single-phase ceramics. The most optimal composition of two-phase ceramics with high resistance to destructive embrittlement is the ratio of phases 0.75Li4SiO4–0.25Li2TiO3. One of the factors explaining the increase in resistance to destructive embrittlement under high-dose irradiation for two-phase ceramics is the increased dislocation density and the presence of interphase or intergranular boundaries, the high concentration of which leads to the creation of additional obstacles to the agglomeration of hydrogen and helium in the near-surface layer.

The Effect of Silica Particle Size on the Mechanical Enhancement of Polymer Nanocomposites

In the present work, SiO2micro/nanocomposites based on poly-lactic acid (PLA) and an epoxy resin were prepared and experimentally studied. The silica particles were of varying sizes from the nano to micro scale at the same loading. The mechanical and thermomechanical performance, in terms of dynamic mechanical analysis, of the composites prepared was studied in combination with scanning electron microscopy (SEM). Finite element analysis (FEA) has been performed to analyze the Young's modulus of the composites. A comparison with the results of a well-known analytical model, taking into account the filler's size and the presence of interphase, was also performed. The general trend is that the reinforcement is higher for the nanosized particles, but it is important to conduct supplementary studies on the combined effect of the matrix type, the size of the nanoparticles, and the dispersion quality. A significant mechanical enhancement was obtained, particularly in the Resin/based nanocomposites.

Effect of interphase on elastic and shear moduli of metal matrix nanocomposites

In the present work, the effect of interphase between nanofiller materials and base metal materials has been analyzed. The analysis has been performed to analyze the possible enhancement of mechanical properties in the presence of interphase between nanofiller material and base metal material of resultant nanocomposites. The carbon nanotube (CNT) and single-layer graphene sheet (SLGS) have been used as nanofiller materials. The 3-dimensional continuum solid modeling-based simulation approach has been considered for the analysis, which can easily model the bonding between base materials and interphase as well as bonding between interphase and nanofiller material. Also, the CNT/SLGS-based metal matrix composites are analyzed to analyze the effect of interphase due to variation in size of the nanofiller materials (variation in outer radius of CNTs and variation in width of the SLGSs) on the elastic and shear moduli of the metal matrix nanocomposites. The presented 3-dimensional continuum solid modeling-based simulation approach has been validated by comparing obtained results with the analytical results based on the continuum solid mechanics-based formulations (rule of mixture). The obtained results depict that the consideration of interphase between nanofiller material and base metal material enhances the elastic and shear moduli of resultant metal matrix nanocomposite. And, the variation in size of nanofiller material affects the overall mechanical properties of resultant metal matrix nanocomposites. Also, the obtained results depict that the effect of variation in outer radii of CNTs is found more significant compared to the variation in width of SLGSs. As the presented 3-dimensional continuum solid modeling-based simulation approach reduces the complexity of the analytical formulations, it is found to be an efficient tool for mechanical characterization of metal matrix nanocomposites in the presence of interphase.

Rheological behavior of polypropylene nanocomposites with tailored polymer/multiwall carbon nanotubes interface

Maleic anhydride grafted polypropylene (MA‐g‐PP) or polypropylene (PP) was noncovalently coated onto acid functionalized multiwall carbon nanotube (f‐MWNT) through solution mixing. These coated f‐MWNTs and pristine MWNT (p‐MWNT) were melt microcompounded with neat PP to form PP/f‐MWNT and PP/p‐MWNT nanocomposites at 0.1–1 wt% MWNT concentration. Complex viscosity and tan δ (ratio of loss modulus to storage modulus) behavior of these systems were studied using dynamic frequency sweep test, while relaxation time, activation energy, and melt homogeneity were also calculated and compared. Among the three types of samples, PP/f‐MWNT masterbatch‐based nanocomposite demonstrated not only the presence of interphase but also good processability. As a consequence, increase of both the crystallization rate in the presence of shear and the melt elasticity during annealing were found only in the masterbatch‐based samples but not in the PP/p‐MWNT. The mechanism of such increased melt elasticity was attributed to the formation of the space‐spanning network, which is consistent with the Cole–Cole plot showing similar behavior to the branched polymers in the literature. This has implications in polymer processing due to suggested changes in the balance between melt strength and polymer flow. Nanocomposite rheological behavior has also been correlated with the mechanical properties. POLYM. ENG. SCI., 59:1763–1777, 2019. © 2019 Society of Plastics Engineers

Effects of added SiO2 nanoparticles on the thermal expansion behavior of shape memory polymer nanocomposites

In this study, a unit cell–based micromechanical approach is proposed to analyze the coefficient of thermal expansion of shape memory polymer nanocomposites containing SiO2 nanoparticles. The interphase region created due to the interaction between the SiO2 nanoparticles and shape memory polymer is modeled as the third phase in the nanocomposite representative volume element. The influences of the temperature, volume fraction, and diameter of the SiO2 nanoparticles on the thermal expansion behavior of shape memory polymer nanocomposite are explored. It is observed that the coefficient of thermal expansion of shape memory polymer nanocomposite decreases with the increase in the volume fraction up to 12%. Also, the results reveal that with the increase in temperature, the shape memory polymer nanocomposite coefficient of thermal expansion linearly increases. The role of interphase region on the thermal expansion response of the shape memory polymer nanocomposite is found to be very important. In the presence of interphase, the reduction in nanoparticle diameter leads to lower coefficient of thermal expansion for shape memory polymer nanocomposite, while the variation of nanoparticles diameter does not affect the coefficient of thermal expansion in the absence of interphase. Based on the simulation results, the shape memory polymer nanocomposite coefficient of thermal expansion decreases as the interphase thickness increases. In addition, the contribution of interphase coefficient of thermal expansion to the shape memory polymer nanocomposite coefficient of thermal expansion is more significant than that of interphase elastic modulus.

Micromechanics-Based Thermoelastic Analysis of Polyimide Nanocomposites Containing 3D Randomly Oriented Carbon Nanotubes

The thermoelastic response of polyimide nanocomposites reinforced with randomly oriented carbon nanotubes (CNTs) is analyzed. For this purpose, a unit cell micromechanics model together with a proper representative volume element is employed. The interphase region created due to the non-bonded interaction between the CNT and surrounding polyimide matrix is taken into account in the modeling of nanocomposite. The effects of various parameters such as alignment and random orientation of CNTs into polyimide matrix, volume fraction and diameter of CNTs, size, adhesion exponent and material properties of the interphase region on the coefficient of thermal expansion (CTE) of polyimide nanocomposite are investigated. The results reveal that in the presence of interphase, the CTE nonlinearly increases with the reduction of CNT diameter, whereas without considering interphase, the change of diameter does not affect the thermoelastic properties of polyimide nanocomposite. Also, it is found that the CTEs of nanocomposite with interphase are higher than those of nanocomposite without interphase. Additionally, it is shown that the CTE of polyimide nanocomposite containing randomly oriented CNTs rises with increasing thickness, CTE and stiffness of interphase. The results of the presented model are in very good agreement with experimental data.

A Two‐Step Method Based on Micromechanical Models to Predict the Young's Modulus of Polymer Nanocomposites

A two‐step method is suggested to predict the Young's modulus of polymer nanocomposites assuming the interphase between polymer matrix and nanoparticles. At first, nanoparticles and their surrounding interphase are assumed as effective particles with core–shell structure and their modulus is predicted. At the next step, the effective particles are taken into account as a dispersed phase in polymer matrix and the modulus of composites is calculated. The predictions of the two‐step method are compared with the experimental data in absence and presence of interphase and also, the influences of nanoparticles size as well as interphase thickness and modulus on the Young's modulus of nanocomposites are explored. The predictions of the suggested model show good agreement with the experimental data by proper ranges of interphase properties. Moreover, the interphase thickness and modulus straightly affect the modulus of nanocomposites. Also, smaller nanoparticles create a higher level of modulus for nanocomposites, due to the large surface area at interface and the strong interfacial interaction between polymer matrix and nanoparticles.image

A nonlinear shear and elongation rheological study of interfacial failure in compatible bilayer systems

This work aims to examine whether or not interfacial failure can occur in a compatible polymer bilayer system under large shear and elongation deformations, as well as to probe the sensitivity of nonlinear transient rheology to the presence of interface/interphase at neighboring layers. For this, stress relaxation after a step strain and fast startup in simple shear and uniaxial extension experiments have been performed on healed and coextruded poly(methyl methacrylate)/poly(vinylidene fluoride) bilayers with the presence of a robust diffuse interphase as evaluated by energy dispersive X ray. For unhealed bilayers, interfacial failure occurred in shear flows at intermediate deformations, while for healed bilayers the interphase greatly delayed the onset of interfacial failure to larger deformation steps and to a higher deformation rate in the startup shear. Extensional rheology demonstrated that the presence of an interphase in the bilayers greatly enhanced the transient extensional viscosity ηE+(t) as well as the tensile relaxation modulus E(t) of the structure, even though the entanglement density was relatively low. Moreover, models are presented to predict the nonlinear relaxation behavior of bilayers and to estimate the relaxation behavior of the interphase. Fitting of the tube model to the shear relaxation indicates a dilated tube diameter in the interphase, confirming its weak entanglement intensity and its readiness to flow-induced disentanglement under large external deformations. Finally, the physics of the interfacial failure was assessed based on some recent molecular dynamic theories.

Numerical and analytical modeling of the stiffness of Polymer–Clay Nanocomposites with aligned particles: One- and two-step methods

This paper studies one- and two-step homogenization models for predicting the stiffness of Polymer–Clay Nanocomposites (PCN) with aligned particles. In particular, the influence of the Effective Particle (EP) concept central to two-step models is assessed for numerical as well as analytical modeling. This study covers intercalated PCN, as well as exfoliated morphologies in the presence of interphase. The predictions of analytical and simplified numerical homogenization models were compared against detailed 3D Finite Element (FE) simulations where the PCN layered microstructure is explicitly simulated. The Representative Volume Element (RVE) was rigorously determined. The theoretical predictions were also compared against experimental data extracted from the literature. It was found that both numerical and analytical two-step methods may significantly diverge from the FE simulations of the detailed microstructures. In general, the analytical multi-coated inclusions model delivers more reliable results than two-step methods. Despite their higher computational costs, one-step FE models are necessary, depending on the PCN microstructure and the desired accuracy. It was also found that the more the EP is different from the nanoclay, in terms of rigidity and aspect ratio, or the higher the volume fraction is, the more the accuracy of two-step numerical models is deteriorated.

Understanding the effect of CNT characteristics on the tensile modulus of CNT reinforced polypropylene using finite element analysis

The focus of this study is to understand the reinforcing efficiency of carbon nanotubes (CNT) in polymers through finite element modeling. The novelty of our work is that the probability distribution functions of CNT diameter, orientation, dispersion and waviness, determined through image analysis, are incorporated in the finite element model allowing thus for fundamental understanding of how the CNT characteristics affect the tensile modulus of CNT reinforced polypropylene (PP) composites. The presence of interphase, confirmed by atomic force microscopy, is also accounted for in our model. The image analysis approach utilizes scanning electron microscopy images of the CNT/PP composites made by melt mixing and injection molding. Model predictions are compared with the data obtained experimentally according to ASTM D638. A good agreement between the model predictions and experimental data is observed.

Micro-Crack Propagation in Particulate Composite with Different Types of Matrix

Particulate composites with polymer matrix and solid fillers are one of important types of materials. Generally, these materials are usually used as construction materials, high-performance engineering materials or protective organic coatings. The main aim of a present paper is an estimation of the micro-crack behavior in the particulate composite with non-linear polymer matrix. The polymer matrix filled by magnesia-based mineral filler is investigated by means of the finite element method. A non-linear material behavior of the matrix was obtained from experiment as well as properties of mineral filler. Numerical model on the base of representative plane element (RPE) was developed. The results show that the presence of interphase between particle and matrix can improve fracture toughness of polymer particle composite through debonding process. The conclusions of this paper can contribute to a better understanding of the behavior of micro-crack in particulate composites with respect to interphase.

Effects of repeated maternal oral exposure to low levels of trichlorfon on development and cytogenetic toxicity in 3-day mouse embryos

Trichlorfon is a widely used broad-spectrum agricultural insecticide. Few studies have evaluated the effects of trichlorfon on developing fetuses, especially at early stages of development after low-level maternal exposures. In this study, we evaluated the direct effects of trichlorfon on preimplantation mouse embryos after 30days of maternal exposure (2, 10 and 50mg/kg/day) via drinking water.On gestation day 3 (dg3), blastocysts were collected and evaluated for changes in gross morphology; cell number; the presence of interphase, metaphase, micronuclei (MN) cells and fragmented and pycnotic nuclei. Embryos in the 50mg/kg/day group had a significantly reduced mean cell number per embryo. Furthermore, there was a significant increase in the frequency of pycnotic nuclei and an absence of metaphase cells in the 50mg/kg/day treated group. None of the developmental endpoints evaluated were observed in the 2 and 10mg/kg/day trichlorfon-treated groups. A simultaneous decrease in the cell number and an increase in the frequencies of absent metaphases and pycnotic nuclei indicate that embryonic developmental deficits observed in the 50mg/kg/day exposure group were associated with cytotoxicity.

Effect of Interphase Modulus and Nanofiller Agglomeration on the Tensile Modulus of Graphite Nanoplatelets and Carbon Nanotube Reinforced Polypropylene Nanocomposites

This study investigates the effect of filler content (wt%), presence of interphase and agglomerates on the effective Young's modulus of polypropylene (PP) based nanocomposites reinforced with exfoliated graphite nanoplatelets (<TEX>$xGnP^{TM}$</TEX>) and carbon nanotubes (CNTs). The Young's modulus of the composites is determined using tensile testing based on ASTM D638. The reinforcement/polymer interphase is characterized in terms of width and mechanical properties using atomic force microscopy which is also used to investigate the presence and size of agglomerates. It is found that the interphase has an average width of ~30 nm and modulus in the range of 5 to 12 GPa. The Halpin-Tsai micromechanical model is modified to account for the effect of interphase and filler agglomerates and the model predictions for the effective modulus of the composites are compared to the experimental data. The presented results highlight the need of considering various experimentally observed filler characteristics such as agglomerate size and aspect ratio and presence and properties of interphase in the micromechanical models in order to develop better design tools to fabricate multifunctional polymer nanocomposites with engineered properties.

Influence of interfacial phenomena on the mechanical properties of particulate composite membranes

AbstractNew models are proposed to describe the mechanical behavior of particulate composite membranes. The mechanical properties of particulate composite membranes are strongly influenced by interfacial phenomena. When adhesion between the filler particles and matrix is poor, the mechanical properties of composite membranes deteriorate with the addition of filler to the matrix. The addition of filler particles to the matrix has a reinforcement effect when adhesion between the particles and matrix is good. The presence of interphase (interfacial shell) around the particles can strongly influence the mechanical properties of particulate composite membranes. Some of the key factors affecting the mechanical properties of composite membranes are interphase‐to‐matrix moduli ratio, core‐to‐shell moduli ratio, and shell‐to‐core radii ratio. Theproposed models are verified using 15 sets of experimental data on the mechanical properties of particulate composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Probing the properties of particle-matrix interphase in reactive rubber-grafted polybenzoxazine resins by atomic force microscopy

Atomic force microscopy (AFM) is employed to study the amine-terminated poly (butadiene-co-acrylonitrile) (ATBN) rubber-modified polybenzoxazine resin. Topographic mapping of the fracture surface is performed in conjunction with lateral force microscopy (LFM) and force–distance curve measurements (F–d). Matrix T g reduction is attributed to the dissolved rubber and the increased mechanical damping (tan δ) is derived from the phase-separated rubber. Saturation of the rubber in the matrix is defined at 6 wt% above which the matrix T g is not influenced upon rubber loading. The solubility limit of the reactive rubber in the matrix phase is determined from the fractured surface using LFM. The torsional force analyzed in the matrix phase increases upon the addition of rubber and levels off at 6 wt%. The results provide a direct correlation between bulk properties acquired by DMA and fractured surface probed by AFM. The presence of interphase between the separated rubbery domain and the continuous matrix phase is confirmed and its thickness is quantified from F–d curves. Moreover, it is found that interphase properties exhibit a strong rubber-concentration dependence.

Mechanism of coagulation of disperse elements in media isolated from external actions

A physical model of the experimentally observed coagulation (the mutual approach) of spherical liquid, solid, and gaseous disperse elements (of diameter of up to1 cm) in polar liquid and viscoelastic thixotropic matrices when the system is completely isolated from the external forces and the gradient temperature and concentration fields is proposed. It is shown that a weak stress-field gradient is formed in a polar liquid or viscoelastic matrix in the presence of interphase at the matrix-spherical disperse element interface, i.e., when the capillary pressure is negative at the convex boundary of the matrix. If the second disperse particle enters into this field, the resulting force acts on it in the direction of the first particle, thus ensuring their coagulation over large time lapses.

Dynamic mechanical spectrometry for the study of multiphase polymer materials

AbstractThe dynamic mechanical behaviour of multiphase polymer materials depends on two factors: (i) properties of each phase and (ii) geometric arrangement of these phases (so‐called morphology). Analysis of experimental results has been performed in order to separate these two factors; it leads to informations about morphology, presence of interphase between main phases, chemical composition of different domains and possible changes in physical properties of one phase, induced by its neighbours. The interest in such an analysis based on mechanical spectrometry appears important because of difficulties in direct investigations (low contrast in Electron Microscopy, poor information provided by X‐ray measurements on amorphous polymers … )