Interphase Fraction Research Articles

Crosslinking of base-modified RNAs by synthetic DYW-KP base editors implicates an enzymatic lysine as the nitrogen donor for U-to-C RNA editing

Sequence-specific cytidine to uridine (C-to-U) and adenosine to inosine editing tools can alter RNA and DNA sequences and utilize a hydrolytic deamination mechanism requiring an active site zinc ion and a glutamate residue. In plant organelles, DYW-PG domain containing enzymes catalyze C-to-U edits through the canonical deamination mechanism. Proteins developed from consensus sequences of the related DYW-KP domain family catalyze what initially appeared to be uridine to cytidine (U-to-C) edits leading to this investigation into the U-to-C editing mechanism. The synthetic DYW-KP enzyme KP6 was found sufficient for C-to-U editing activity stimulated by the addition of carboxylic acids invitro. Despite addition of putative amine/amide donors, U-to-C editing by KP6 could not be observed in vitro. C-to-U editing was found not to be concomitant with U-to-C editing, discounting a pyrimidine transaminase mechanism. RNAs containing base modifications were highly enriched in interphase fractions consistent with covalent crosslinks to KP6, KP2, and KP3 proteins. Mass spectrometry of purified KP2 and KP6 proteins revealed secondary peaks with mass shifts of 319Da. A U-to-C crosslinking mechanism was projected to explain the link between crosslinking, RNA base changes, and the ∼319Da mass. In this model, an enzymatic lysine attacks C4 of uridine to form a Schiff base RNA-protein conjugate. Sequenced RT-PCR products from the fern Ceratopteris richardii indicate U-to-C base edits do not preserve proteinaceous crosslinks in planta. Hydrolysis of a protonated Schiff base conjugate releasing cytidine is hypothesized to explain the completed pathway in plants.

Theoretical framework to predict the balance of strength-ductility in graphene/metal nanocomposites

Grain size of metal phase and interphase property play an important role in enhancing the strength-ductility synergy of graphene/metal nanocomposites. In this work, we propose a theoretical framework to investigate the effects of different grain sizes and interphase properties on the strength and ductility of graphite nanoplatelet (GNP)/metal nanocomposites. The GNP/TC4 nanocomposites with various grain sizes are first fabricated by powder metallurgy. On the basis of the interphase model, dislocation density-based constitutive law, the field fluctuation method, and continuous damage theory, the micromechanics model for evaluating the balanced strength and ductility is established. Simultaneously, the accuracy of theoretical model is demonstrated by the tensile experiment of GNP/TC4 nanocomposites. To reveal how the strength and ductility of graphene/metal nanocomposites are enhanced synchronously, the influences of the major micromechanical variables including grain size of metal matrix, volume fraction and elastic modulus of interphase, as well as size distribution of GNPs on the strength and ductility are quantitatively assessed. Overall, the present work highlights the mechanisms governing the macro-mechanical properties of graphene/metal nanocomposites and furnishes a powerful analytical tool for their design.

Modeling of Electrical Conductivity for Polymer-Carbon Nanofiber Systems.

There is not a simple model for predicting the electrical conductivity of carbon nanofiber (CNF)–polymer composites. In this manuscript, a model is proposed to predict the conductivity of CNF-filled composites. The developed model assumes the roles of CNF volume fraction, CNF dimensions, percolation onset, interphase thickness, CNF waviness, tunneling length among nanoparticles, and the fraction of the networked CNF. The outputs of the developed model correctly agree with the experimentally measured conductivity of several samples. Additionally, parametric analyses confirm the acceptable impacts of main factors on the conductivity of composites. A higher conductivity is achieved by smaller waviness and lower radius of CNFs, lower percolation onset, less tunnel distance, and higher levels of interphase depth and fraction of percolated CNFs in the nanocomposite. The maximum conductivity is obtained at 2.37 S/m by the highest volume fraction and length of CNFs.

Micromechanics-based simulation of B4C-TiB2 composite fracture under tensile load

Micromechanics modeling was performed to study the effects of thermal residual stress, weak interphases, TiB2 volume fraction and particle size on the mechanical responses and fracture behaviors of B4C-TiB2 composites. Experimentally observed fracture behaviors including micro-cracking and crack deflection were successfully captured. The weak interphases at B4C-TiB2 boundaries and the thermal residual stress induced during cooling by the large CTE mismatch between B4C and TiB2 were identified as two major factors to promote micro-cracking that caused the enhanced progressive failure behavior. Micro-cracking was enhanced with higher TiB2 volume fraction due to higher fraction of weak interphase and material affected by thermal residual stress. Meanwhile, micro-cracking behaviors exhibited limited change with varying TiB2 particle sizes. This modeling study successfully captured the main fracture behaviors and their trends by varying micro-structures of B4C-TiB2 composites and can potentially aid microstructure design of tougher B4C-TiB2 composites in the future.

Investigation of the interphase structure in polyamide 6–matrix, multi-scale composites

In this study, we investigated the dispersion of carbon nanotubes and the interphases formed around them in nanocomposites with a polyamide 6 matrix (with carbon nanotube reinforcement) and hybrid composites with the same matrix, reinforced with carbon nanotubes and carbon fibers. Small-angle neutron scattering (SANS) experiments showed that carbon fibers effectively increased the dispersion of the carbon nanotubes. The average size of the carbon nanotube aggregates were significantly smaller, but the reinforcement–matrix interface area was larger in the hybrid composites than in the nanocomposites. Nanotube dispersion had a significant effect on the crystalline structure; the X-ray diffraction patterns showed that in the hybrid composites, the crystallites grew epitaxially on the surface of the well-dispersed carbon nanotubes, which resulted in decreased average crystallite size. In the hybrid composites, the smaller crystallites inferred a larger rigid amorphous fraction in the matrix. The larger interphase fraction in the hybrid composites also led to better mechanical performance.

Discrete element modeling of 3D irregular concave particles: Transport properties of particle-reinforced composites considering particles and soft interphase effects

Particles of complex morphologies and their surrounding soft interphase are main constituents that play a significant role in the transport properties of particle-reinforced composites (PRCs). It has been a crucial but unresolved issue how to derive the volume fraction of soft interphase around three-dimensional (3D) irregular concave particles, as well as it remains to be virgin to explore the effective transport properties of three-phase PRCs composed of homogeneous matrix, 3D irregular concave particles of a relatively high packing density and their surrounding soft interphase. To this end, this work initially develops a discrete element modeling (DEM) of 3D irregular concave particles with monodispersity in size to generate random dense packing structures, where an innovative mathematical-controllable parameterized method is proposed to devise diverse irregular concave particle shapes. The proposed particle design method is not only universal and controllable to generate a given particle shape, but also can be directly linked with an experimental measurement using digital scanning. In addition, an efficient two-step numerical strategy is presented to check the inter-particle contact detection and collision. Then, the volume fraction of soft interphase around monodisperse concave particles is numerically derived for the first time by using the Monte Carlo random point sampling simulation. The Monte Carlo simulation has good accuracy to obtain the soft interphase volume fraction, which is confirmed by comparing with the theoretical formulae for spherical particle systems. Next, a dual-probability-Brownian motion (DP-BM) scheme along with the level set algorithm is extended to investigate the effective transport properties like thermal conductivity of three-phase PRCs. Comparison against the finite element method (FEM), the proposed DP-BM scheme is more user-friendly and efficient to estimate the effective transport properties of PRCs within an accuracy level. The proposed DP-BM scheme can overcome the two intrinsic limitations of the classical effective medium approximations that one limitation is the ellipsoidal inclusion shape and another is a relative dilute level of inclusion volume fraction. Moreover, the effects of the concave particle shape and packing density, and the interphase dimension on the volume fraction of soft interphase and the effective normalized transport properties of PRCs are evaluated. The results elucidate rigorous component-structure–property relations, which can provide sound guidance for durability evaluation and material design of PRCs.

Bio-based semi-crystalline PEF: Temperature dependence of the constrained amorphous interphase and amorphous chain mobility in relation to crystallization

The temperature dependence of the constrained amorphous interphase or rigid amorphous fraction (RAF) in bio-based semi-crystalline poly(ethylene 2,5-furandicarboxylate) (PEF) was assessed. RAF, which is located in proximity of the basal crystal planes, was found to develop in parallel with the crystal phase during crystallization at the lowest investigated Tcs, i.e. 130 and 140 °C, at which the less stable α′-crystal phase grows. At higher Tcs, RAF does not vitrify during crystallization, but only upon the subsequent cooling down to Tg. The rigid amorphous fraction at Tg increases by decreasing the crystallization temperature, ranging approximately from 15 to 25%. This information is useful for the development of PEF products, since many RAF physical properties, for example mechanical and barrier properties, are different from those of the amorphous fraction far from the crystals. RAF decreases with increasing temperature, and becomes zero around 150 °C. The same temperature limit of 150 °C was found to influence the reversing crystallization/melting process at the lateral crystal surfaces, as well as the crystallization rate, which reaches its maximum at temperatures above 150 °C. In addition, singularly, the more ordered crystalline α-form was found to grow only at temperatures higher than 150 °C. The total absence of constraints on the amorphous segments mobility, identified at temperatures higher than 150 °C, also favors additional crystallization upon heating in the PEF samples crystallized at low Tcs, with also α-crystals development. The densities of the RAF connected to α′- and α-crystals were estimated at room temperature.

Three phase purification of milk clotting protease from Wrightia tinctoria fruit and studies on its casein subunit specificity

Crude aqueous extract of Wrightia tinctoria fruit was subjected to three phase partitioning (TPP) with three different ammonium sulphate concentrations (40, 60, 80%) and their effect on concentrating milk clotting proteases were examined with 1:1 ratio of crude extract to t-Butanol. Proteases that concentrated in the interphase (IP) fraction of 60 and 80% salt concentration exhibited high milk clotting activity. TPP contributed to reduction in Caseinolytic Activity (CA) and enhancement of Milk Clotting Index (MCI) in these IP fractions compared to the crude enzyme. Casein (whole and kappa) hydrolytic pattern was analyzed by tricine SDS PAGE. Electrophoretic pattern of hydrolysate after 1 hr incubation revealed hydrolysis of κ-CN by CE, IP 60 and IP 80 fractions. Appearance of two low molecular weight bands approximately around 15 kDa indicated the specific affinity and controlled hydrolytic behavior by the proteases. Study provides evidence towards the utility of TPP in concentrating these milk clotting proteases and in improving their MCI. Keywords : Milk clotting • Wrightia tinctoria • Proteases• cheese

Simultaneously enhanced strength-plasticity of graphene/metal nanocomposites via interfacial microstructure regulation

Interfacial microstructure characteristics (e.g., volume fraction, thickness, moduli) are crucial to the overall mechanical properties of graphene/metal nanocomposites. Herein, we investigate the effects of different interfacial characteristics on simultaneous improvement of strength and plasticity of nanocomposites. Graphene nanoplatelets (GNPs) reinforced Ti6Al4V composites with appropriate interfacial effects are first fabricated based on powder metallurgy. Combining the interphase model, the field fluctuation method, the second-order stress moment and continuous damage theory, the multiscale theoretical framework for predicting the entire stress-strain relations is developed, and its accuracy is verified by the tensile test results of GNP/Ti6Al4V nanocomposites. The effects of the micromechanical variables including volume fraction and stiffness of interphase, as well as geometrical size factor (ratio of interphase thickness to the GNP equivalent diameter) and aspect ratio of GNPs on the maximum strength and failure strain are quantitatively analyzed to demonstrate how the strength and plasticity of nanocomposites are enhanced concurrently. This work provides a new perspective for graphene/metal nanocomposites with excellent tensile properties by optimizing interfacial characteristics.

Effect of Processing Parameters on Interphase Precipitation and Mechanical Properties in Novel CrVNb Microalloyed Steel

Novel steel microalloyed with 0.73 (Cr + V + Nb) has been subjected to thermomechanical processing (TMP) with varying parameters to simultaneously maximise the steel strength and ductility. Optical and electron microscopy studies coupled with uniaxial tensile testing were carried out to analyse the processing-microstructure-properties relationship. For the suggested steel composition, the simultaneously highest yield stress (960 MPa), ultimate tensile strength (1100 MPa), and elongation to failure (25%) were achieved following simulated coiling at 650 °C and holding for 30 min. The variation in the finish rolling temperature affects the ferrite grain size and the ratio of precipitates formed in austenite and ferrite. If a significant amount of solute is consumed for precipitation in austenite and during subsequent growth of strain-induced precipitates, then a lower fraction of interphase and random precipitates forms in ferrite resulting in a lower strength. Extended time at a simulated coiling temperature resulted in the growth of interphase precipitates and precipitation of random ones in ferrite. Fine tuning of TMP parameters is required to maximise the contribution to strength arising from different microstructural features.

On the effect of stiffness/softness and morphology of interphase phase on the effective elastic properties of three-phase composite material

In the present study, Composite material consisting of an elastic homogeneous isotropic matrix in which are embedded coated elastic isotropic inclusions, widely used in many applications is investigate by homogenization approach coupled to the finite elements method. A finite element model is proposed to predict the Young and Shear modulus of the three-phase composite containing spherical inclusions surrounded by a spherical or ellipsoid interphase layer. Three cases of particles volume fractions and interphase was considered with addition of two interphase morphology. Young modulus of interphase region was varied from soft to hard than the matrix properties. We note that interphase morphology and properties plays an important role in the elastic properties of composite with increasing the volume fraction of inclusions and interphase. The results were compared to the first order bounds Voigt and Reuss, and the mean field homogenization techniques. A sensitive study of the effect of mesh density on the results of the von Mises stresses and elastic properties has been made.

DEM and dual-probability-Brownian motion scheme for thermal conductivity of multiphase granular materials with densely packed non-spherical particles and soft interphase networks

Shape-anisotropic granules and their surrounding interphase networks are significant constituents in granular materials. Structural and physical configurations of these constituents significantly affect the overall thermal performance of granular materials, specifically microstructure-dependent thermal conductive properties. It has been a key but unresolved issue how to quantitatively understand the microstructure evolution of conductive interphase interacted by densely packed non-spherical particles triggering the change of thermal conductivity of granular materials. In this work, we devise a powerful scheme by using the discrete element method (DEM) and the dual-probability-Brownian motion simulation (DP-BMS) to accurately and efficiently predict the effective thermal conductivity of granular materials composed of homogeneous matrix, conductive (soft) interphase around randomly-dispersed elliptical particles over a broad range of aspect ratios with widespread applications, such as cracks, pores, fibers, cellulose whiskers, silicate nanorods, and aggregates. Comparison against extensive numerical and theoretical data validates that such the scheme can well predict the effective thermal conductivity of multiphase granular materials with densely packed non-spherical particles that is just the intrinsic limitation of the classical micromechanical homogenization theories. In this scheme, the DEM provides a direct means of investigating the time-dependent microstructure evolution of granular materials with elliptical particles from a loose parking state to a dense packing state. The DP-BMS provides an effective technique for predicting the effective thermal conductive transport properties of multiphase granular materials. By comparing with traditional numerical strategies like the finite element method (FEM) and random walk model (RWM), the DP-BMS is more user-friendly and efficient to accurately predict the effective thermal conductivity. This scheme can be regarded as a general procedure that is readily applicable to predictions of other transport properties of two-dimensional or three-dimensional multiphase granular materials. Furthermore, we use the scheme to probe the influences of the shape and high packing density of particles and the thickness and fraction of soft interphase on the effective thermal conductivity of granular materials. The results elucidate rigorous component-structure–property relations, which can provide sound guidance for composite design and microstructure optimization.

Constrained Amorphous Interphase in Poly(l-lactic acid): Estimation of the Tensile Elastic Modulus.

The mechanical properties of semicrystalline PLLA containing exclusively α′- or α-crystals have been investigated. The connection between experimental elastic moduli and phase composition has been analyzed as a function of the polymorphic crystalline form. For a complete interpretation of the mechanical properties, the contribution of the crystalline regions and the constrained amorphous interphase or rigid amorphous fraction (RAF) has been quantified by a three-phase mechanical model. The mathematical approach allowed the simultaneous quantification of the elastic moduli of (i) the α′- and α-phases (11.2 and 14.8 GPa, respectively, in excellent agreement with experimental and theoretical data reported in the literature) and (ii) the rigid amorphous fractions linked to the α′- and α-forms (5.4 and 6.1 GPa, respectively). In parallel, the densities of the RAF connected with α′- and α-crystals have been measured (1.17 and 1.11 g/cm3, respectively). The slightly higher value of the elastic modulus of the RAF connected to the α-crystals and its lower density have been associated to a stronger chain coupling at the amorphous/crystal interface. Thus, the elastic moduli at Troom of the crystalline (EC), mobile amorphous (EMAF), and rigid amorphous (ERAF) fractions of PLLA turned out to be quantitatively in the order of EMAF < ERAF < EC, with the experimental EMAF value equal to 3.6 GPa. These findings can allow a better tailoring of the properties of PLLA materials in relation to specific applications.

The effect of molybdenum on interphase precipitation at 700 °C in a strip-cast low-carbon niobium steel

The effect of Mo on the clustering and interphase precipitation occurring during phase transformation has been investigated in a strip-cast low-carbon steel containing Nb. In this work, isothermal coiling treatments were performed at 700 °C for various times to form interphase precipitates. Transmission electron microscopy (TEM), small-angle neutron scattering (SANS) and atom probe tomography (APT) results show that the addition of Mo increases the number density and volume fraction of clusters and interphase precipitates but has a negligible effect on their size, and overall provides for greater strengthening in the Mo-containing alloy. APT analysis shows that the interphase precipitates are composed of Nb, C and N in both alloys. The segregation of Mo is also observed in the interphase precipitates in the Mo-containing alloy, which is believed to relieve the lattice misfit between the precipitate and the matrix. It is proposed that the reduced lattice misfit allows for precipitate nucleation to occur more easily in the Mo-containing alloy.

Влияние наводороживания на механические свойства и механизмы разрушения высокоазотистых хромомарганцевых сталей, подвергнутых дисперсионному твердению

Currently, many technical problems require a comprehensive study of the properties of materials operating in hydrogen-containing environments. The authors investigated the effect of age-hardening on the hydrogen embrittlement and fracture micromechanisms of high-nitrogen austenitic Fe-23Cr-17Mn-0.1C-0.6N (wt. %) steel. For this purpose, using heat treatments, the authors formed in specimens of Fe-23Cr-17Mn-0.1C-0.6N steel the structural phase states characterized by different distribution and content of dispersed phases. The experiment determined that the accumulation of hydrogen atoms occurs predominantly in the grains in solution-treated specimens without dispersed phases. This causes the effects of solid solution hardening and leads to a change in the micromechanism of steel fracture from a ductile dimple fracture in the absence of hydrogen to a transgranular fracture by the quasi-cleavage mechanism in hydrogen-charged specimens. It was established that the discontinuous decomposition of austenite with the formation of Cr 2 N cells and austenite depleted in nitrogen, predominantly along the grain boundaries causes the formation of a large fraction of interphase (austenite/Cr 2 N particles) boundaries. Cells of discontinuous decomposition promote hydrogen accumulation along the grain boundaries and cause brittle intergranular fracture of hydrogen-charged specimens during plastic deformation. The study showed that in specimens with the discontinuous decomposition of austenite both along the grain boundaries and spreading into the grain body, plenty of intragranular interphase boundaries (Cr 2 N plates in austenite) are formed, which causes the formation of a transgranular brittle fracture in the hydrogen-charged specimens.

Wear Resistance Mechanism of Ultrahigh-Molecular-Weight Polyethylene Determined from Its Structure–Property Relationships

Although it is generally believed that the extraordinarily high molecular weight plays a great role in the excellent wear resistance of ultrahigh-molecular-weight polyethylene (UHMWPE), the mechanism behind this effect remains poorly understood. In this study, we investigated the wear behavior of UHMWPE with respect to its microstructures, measured in terms of its crystallinity, lamellar thickness and crystallite size, entanglement, interphase fractions, and surface roughness. From these structure–property relationships, we conclude that the high wear resistance of UHMWPE can be attributed to its higher degree of entanglement and its high fraction content of interphase domains; the other parameters were either not significant or not relevant. Accordingly, we propose a mechanism in which the more greatly entangled molecular chain networks of UHMWPE protect the surface and subsurface layers from damage under stresses during sliding wear.

Generalized Formula of the Fraction of Interphase for Polydisperse Non-Spherical Particles: Theoretical and Numerical Models

Generalized Formula of the Fraction of Interphase for Polydisperse Non-Spherical Particles: Theoretical and Numerical Models

The fraction of overlapping interphase around 2D and 3D polydisperse non-spherical particles: Theoretical and numerical models

The fraction of interphase is an important microstructure parameter in the prediction of macroscopic properties of particulate composites. Currently, some researchers have presented theoretical and numerical investigations on the interphase fraction for spherical particle systems, and even quantify the influence of interphase fraction on the overall elastic and transport properties of particulate composites. However, the overlapping interphase fraction in polydisperse non-spherical particle systems is still an open issue. In this work, a generic theoretical model is formulated to derive the overlapping interphase fraction for polydisperse 2D non-circular and 3D non-spherical particle systems by means of the statistical geometry of composites. In this model, the morphology of interphase coated onto the surface of non-spherical particles can be characterized by circularity and sphericity of particles that are important parameters to describe the shape of particles. On the other hand, numerical simulations for the one-point probability function of interphase are presented to verify the proposed theoretical framework. In the numerical simulations, a novel algorithm is developed by reducing the problem of identifying the precise location between an arbitrary spatial point and interphase to the basic issue of finding the distance from the point to the surface of particles. If the distance is less than the interphase thickness, the point definitely locates inside interphase. In addition, the algorithm can be further used to detect the overlap between adjacent ellipsoidal particles (2D ellipses). Moreover, a variety of particle shapes (such as regular polygons and ellipses with the same circularity, and regular polyhedrons and ellipsoids with the same sphericity) are taken into account to generate particle packing structures. Then, the fraction of overlapping interphase in each packing structure is statistically obtained. Results show that statistical values are consistent with their theoretical values under the same conditions. This validates the reliability of the theoretical framework. Finally, the effects of particle size distributions and interphase thicknesses on the interphase fraction are investigated. It can be found that the interphase fraction increases with the increase of particle volume fraction, particle fineness and interphase thickness.

Structure and rheological behavior of polypropylene interphase at high carbon nanotube concentration

The structure of the interphase in polypropylene (PP)/multiwall carbon nanotube (MWNT) nanocomposite was characterized by thermal analysis and wide angle X-ray diffraction. The interphase was composed of non-covalently coated PP on acid functionalized MWNT (f-MWNT), where the volume of interphase increases with increased f-MWNT concentration from 1 wt% to 30 wt%. Larger lamella thickness, crystallinity, and smaller crystal size with respect to the bulk polymer were found at the interphase. Also, the thermal stability of the nanocomposite containing high volume fraction of interphase was demonstrated to be higher than that of the neat PP. Using designed thermal treatment, the interphase was successfully converted into a highly ordered crystalline structure with extended chain conformation. The understanding and control over the interphase formation at nanoscale afforded the observation of an unprecedented macroscopic rheological behavior where the viscosity and elastic modulus increased as temperature increased. A schematic showing polymer-CNT interaction at elevated temperature was proposed and verified. It is concluded that the constrained flow under high temperature originates from extended and immobile polymer chains at the interphase.

Tuning PVDF/PS/HDPE polymer blends to tri-continuous morphology by grafted copolymers as the compatibilizers

We reported a novel and effective strategy to achieve higher continuity at a lower volume fraction of interphase by using compatibilizers in ternary blend consisting of PVDF, PS and HDPE. PVDF-g-PS was synthesized by electron beam radiation induced free radical graft copolymerization reaction and PVDF-g-PS was characterized by FTIR, DSC and 1H NMR. PVDF-g-PS showed effective compatibilization in PVDF/PS binary blend. The phase size of PVDF/PS binary blend was decreased at addition of PVDF-g-PS. For phase morphology development, morphology of uncompatibilized PVDF/PS/HDPE (52/6/42 vol%) ternary blend revealed a part of PS droplets situated in PVDF/HDPE interface, the other part was located inside HDPE phase. Whereas, compatibilized blend showed more and more PS migrate to PVDF/HDPE interface. When adding 7% PVDF-g-PS, PS droplets formed into uniform layer self-assembly arrayed at interface, then tri-continuous morphology was formed and continuity of PS phase increased by 32%, ultralow percolation threshold ternary blend was successfully achieved.