Softening Of Matrix Research Articles

Cu-Hemin Nanosheets and Indocyanine Green Co-Loaded Hydrogel for Photothermal Therapy and Amplified Photodynamic Therapy

Near-infrared (NIR) organic small molecule indocyanine green (ICG) could respond well to 808 nm laser to promote local high temperature and ROS generation for realizing photothermal therapy (PTT)/photodynamic therapy (PDT). However, the high content of GSH in the tumor microenvironment (TME) limited the further therapeutic performance of ICG. Herein, injectable agarose in situ forming NIR-responsive hydrogels (CIH) incorporating Cu-Hemin and ICG were prepared for the first time. When CIH system was located to the tumor tissue through local injection, the ICG in the hydrogel could efficiently convert the light energy emitted by the 808 nm laser into thermal energy, resulting in the heating and softening of the hydrogel matrix, which releases the Cu-Hemin. Then, the over-expressed GSH in the TME could also down-regulated by Cu-Hemin, which amplified ICG-mediated PDT. In vivo experiments validated that ICG-based PDT/PTT and Cu-Hemin-mediated glutathione depletion could eliminate cancer tissues with admirable safety. This hydrogel-based GSH-depletion strategy is instructive to improve the objective response rate of PDT.

Microstructure and high-temperature sliding wear performance of Fe-Co-Mo alloy coating fabricated by plasma cladding

A Fe-Co-Mo alloy coating was successfully fabricated on 40Cr steels by plasma cladding with water-atomized powders. The coating exhibited a good metallurgical bonding with substrate and possessed no cracks or apparent pores, being particularly suited for plasma cladding. The microstructure of the as-cladded coating contained α-Fe matrix and netlike micrometer-sized strengthening phases comprising μ-intermetallic phases and a few η-carbide phases caused by substrate dilution and introduction of carbon element. Besides, Fe-Co-Mo coating could be hardened to the remarkable microhardness (849 HV0.2, 3.5 times as much as the substrate) after aging at 600 °C (the peak-aging temperature) by the precipitation of nanometer-sized μ phases. Meanwhile, the superior aggregation resistance and size stability of strengthening intermetallics at elevated temperatures could impede dislocation motion, postpone matrix softening and endow the coating with outstanding temper resistance. The high temper resistance could delay the change from slight wear to severe wear during high-temperature wear, making the wear mechanism mainly mild abrasive and oxidative wear. Therefore, the coating showed outstanding wear resistance and its superiorities became more pronounced as the temperature rises, with a wear rate of only 17 % of widely-used AISI H13 hot-working steels at 800 °C.

Microstructure and mechanical properties of 1000 MPa grade steel plate for hydropower station in different quenching processes

AbstractStrength and toughness of the ferrum‐1.2manganese‐1.4nickel steel plates in the DQT (direct quenching→tempering) and DQQT (direct quenching→reheated quenching→tempering) processes were investigated. This ferrum‐1.2manganese‐1.4nickel which possessed a relatively low alloy content and improved purity was used as the 1000 MPa grade high‐strength steel plates for hydropower station. The flat prior austenite grains with the dislocation density of 4.86×1014 m−2 and nano‐scaled precipitates were acquired in the DQT process. The grains and precipitates grew up and the dislocation density decreased to 4.26×1014 m−2 as a result of reheated quenching in the DQQT process. After tempering, the yield strength of the specimen treated by the DQT process was ∼996 MPa, which was ∼34 MPa higher than that of the DQQT sample. The difference of yield strength between these two quenching processes was primarily ascribed to grain boundary strengthening and partly caused by dislocation strengthening or precipitation strengthening. Due to the circular propagation path of cracks and matrix softening, the impact energy at −60 °C in the DQQT process was superior to that of the DQT process.

Coreflood Effluent and Shale Surface Chemistries in Predicting Interaction between Shale, Brine, and Reactive Fluid

Summary Field and laboratory observations to date indicate that the efficiency of hydraulic fracturing, as it relates to hydrocarbon recovery, depends significantly on geochemical alterations to rock surfaces that diminish accessibility by partial or total plugging of the pore and fracture networks. This is caused by mineral scale deposition, such as coating of fracture surfaces with precipitates, particle migration, and/or crack closure, because of dissolution under stress. In reactive flow-through experiments, mineral reactions in response to acidic fluid injection significantly reduced system porosity and core permeability. The present study focuses on changes to fluid chemistry and shale surfaces (inlet and fracture walls) resulting from shale-fluid interactions and integrates these findings for an improved estimate of transport-related consequences. The pre- and post-reaction shale surfaces were examined by spatially resolved scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis. Importantly, inductively coupled plasma-mass spectrometry/optical emission spectroscopy (ICP-MS/OES) was utilized to probe the chemical evolution of the coreflood effluents. The three study cores selected from the Marcellus formation represent different mineralogies and structural features. In flow-through experiments, laboratory-generated brine and HCl-based fracture fluid (pH = 2) were injected sequentially under effective stress (up to 500 psi) at reservoir temperature (80°C). SEM-EDS results confirmed by the ICP concentration trends showed significant Fe hydroxide precipitates in the clay- and pyrite-rich outcrop sample because of partial oxidation of Fe-bearing phases in the case of intrusion of low salinity water-based fluids. Porosity reduction in the Marcellus Shale Energy and Environmental Laboratory (MSEEL) carbonate-rich sample is related to compaction of cores under stress because of matrix softening with substantial dissolution, and pore filling by hydroxides, as well as secondary barite and salts. Despite the same fluid compositions and experimental conditions used for both MSEEL samples, barite precipitation was much more intense in the MSEEL clay-rich sample because of its greater sorption capacity and additional sulfate source as well as its fissile nature with multiple lengthwise cracks. ICP tests revealed time-resolved concentration behavior in produced brine and reactive fluids that in turn complemented the pre/post-reaction SEM-EDS observations. The greatest release of metal ions into brine was in clay-rich systems indicating the importance of chemical compatibility between in-situ shale and nonequilibrated injection solutions. A thorough examination of surface and effluent data pointed to the substantial influence of formation brine in the shales, mixing of brine with fracture fluid during flow, and shale mineralogy on mineral dissolution and scale formation that significantly affect flow efficiency.

A mesomechanics-based analysis on the flexural behavior of ultra-high-performance concrete (UHPC) with different steel fiber lengths

This study investigates the flexural behavior of UHPC materials containing steel fibers of varying lengths. Mesomechanical analysis is performed according to the analytical pullout model, using actual measured fiber distributions. The flexural behavior of UHPC after cracking is simulated by superposing the fiber bridging and matrix softening curves. Subsequently, the evolution of stress–strain along the axial crack of UHPC is evaluated under different loading conditions. The obtained results indicate that longer steel fibers can efficiently improve the flexural behavior of UHPC. Moreover, the actual fiber orientation and pullout length distributions can be well fitted by two-parameter probability distribution (PDF) and Gaussian functions, respectively. Based on the micromechanical analysis, the fiber bridging behavior is overestimated under the assumption of 2D random fiber distribution, and it is underestimated under the assumption of 3D random fiber distribution. Interestingly, the length of the shear lag zone is independent of the fiber length, which is about 20.16 mm. The obtained results demonstrate that the compressive stress and strain at the top of the tested specimen gradually transform into tensile stress and strain at the opposite side. Interestingly, the stress of the specimens with fiber length of 20 mm are slightly higher than the specimens with fiber lengths of 6 and 13 mm, and the strain just lower than the specimens with fiber lengths of 6 and 13 mm in all crack propagation stages, respectively. This indicates that, in addition to the number of steel fibers, the stress/strain dispersion depends on fiber length.

The effect of thickness on the compression failure of composite laminates in fire

This paper presents an experimental and modelling study that determined the influence of thickness on the softening-rate, composite damage initiation and propagation, and structural survivability of composite structures in fire. Fire-under-compression load tests were conducted using glass fibre reinforced vinyl-ester laminates of varying thicknesses to quantify the influence of thickness on fire structural survivability. The matrix softening and degradation rates decreased as the composite thickness increased. The laminate thickness variations had a strong influence on the fire-under-compression load performance and failure mode. The analysis reveals complex multi-mode failure mechanisms involving global buckling and transitioning into shear dominated failure as the composite thickness increased. A thermal–mechanical model that can predict the time-to-failure of glass fibre reinforced composite subjected to a combined compression and fire load was developed and its validity was assessed by comparing the theoretical predictions to the experimental data.

High-throughput screening the micro-mechanical properties of polyimide matrix composites at elevated temperatures

In this work, a novel high-throughput methodology based on combinations of nanoindentation, indentation creep and push-in methods, is proposed to measure in-situ the micro-mechanical properties of typical polymer matrix composites at a wide temperature range. The Young's modulus and strain rate sensitivity of a polyimide matrix and the interfacial shear strength in a quartz fiber reinforced polyimide matrix composite are measured at 25–350 °C for the first time. The results highlight a linear softening of the polyimide matrix at high temperatures, which is evidenced by the approximate linear decrease of Young's modulus from ≈5.0 GPa at 25 °C to ≈1.1 GPa at 350 °C. In comparison, the strain rate sensitivity of the polyimide matrix is increased, from ≈0.032 at 25 °C to ≈0.062 at 350 °C. This evidences a stronger visco-plasticity of polyimide at higher temperatures. The shear strength of the fiber/matrix interface is also temperature dependent. As the testing temperature increases from 25 to 300 °C, the shear strength is decreased from ≈147 MPa to ≈40 MPa. Specially, the interfacial strength is extremely low at 350 °C (≈4 MPa), evidencing a failure of the composite at this temperature.

Failure-mode dependence of the strengthening effect in Ti3AlC2/10 vol.% Al2O3 composite

Abstract The high-temperature mechanical properties of both Ti3AlC2 and Ti3AlC2/10 vol.%Al2O3 composite, including compressive strength, bending strength, and fracture behavior, were investigated. The strengthening effect caused by Al2O3 strongly depended on the mode of failure: significant enhancement in strength was only observed under the brittle mode of failure; whereas under the ductile mode of failure the strengthening effect was impaired due to Ti3AlC2 matrix softening and stress relaxation.

Effect of steel fiber-volume fraction and distribution on flexural behavior of Ultra-high performance fiber reinforced concrete by digital image correlation technique

This paper investigated the effect of steel fiber-volume fraction (0.5%, 1.0%, 1.5%, and 2.0%) and distribution on the flexural behavior of ultra-high performance fiber reinforced concrete (UHPFRC). Digital image correlation (DIC) was used to obtain the crack propagation behavior of UHPFRC under bending load. With increasing fiber-volume fraction, the crack-propagation path becomes more zigzagged. Based on the flexural response of UHPFRC and fiber distribution on the crack plane, a correlation between fiber distribution characteristics and flexural behavior was discussed. The fibers number per unit area for S0.5, S1.0, S1.5, and S2.0 were 7, 14, 21, and 31, respectively. The fiber pull-out length in cracked zone with different fiber-volume fractions was about 3.56 mm. The fiber orientation factor (ηθ) of S0.5, S1.0, S1.5, and S2.0 were 0.80, 0.79, 0.69 and 0.61 respectively. A quadratic relationship between the ηθ and the fiber pull-out number is proposed. The flexural-tensile strength ratio (β) is about 2.52 for UHPFRC exhibiting deflection hardening behavior. Finally, the post-cracking tensile behavior of UHPFRC was analyzed based on the matrix softening and fiber bridging curve models by the inverse analysis method. The tension softening curves obtained from the tri-linear softening curve analysis exhibited good agreement with the experimental results.

Plasticity improvement and radiation hardening reduction of Y doped V-4Cr-4Ti alloy

In current work, V-4Cr-4Ti and V-4Cr-4Ti-2Y alloys are prepared using mechanical alloying and spark plasma sintering. Sequential-beam irradiation of 30 keV H+ and 50 keV He+ ions, are carried out at 450 ℃ to the peak damage of 0.18 dpa. The influence of Y on the microstructure, mechanical properties, radiation induced defect and radiation-hardening are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical test, and nano-indentation test. Two kinds of Y-rich particles precipitated in Y added alloy, one is Y2O3 phase with a mean size of 60 nm, the other is YVO4 with a diameter of ∼10 nm, but no carbide of Y is observed. The results show that Y can significantly improve plasticity of V base alloy, reduce the size and number density of radiation induced dislocation loops, limit radiation hardening. Two different fitting process with different initial values and boundary conditions are used to analysis radiation hardening, the fitting results indicate a slight softening of matrix near damage layer which named softened layer. This softened layer can affect nanoindentation test results especially for shallow irradiation. A plausible explanation for the formation of this softened layer could be the oxygen diffuses from unirradiated region to damage layer.

Effect of workpiece preheating on tool wear and delamination at the hole exit in high feed drilling of carbon fiber reinforced plastics with diamond-coated tools

High feed drilling of carbon fiber reinforced plastics (CFRP) poses a risk of serious tool wear and delamination caused by high drilling thrust force despite improving productivity. However, by taking advantage of the proper thermal softening of the epoxy matrix in CFRP, a decrease in forces related to tool wear and delamination is achievable under high feed. Through this study, thermal softening of epoxy matrix by preheating was effective in reducing thrust force and tool wear in the drilling of CFRP with diamond-coated tools. Hole exit delamination factors decreased by adjusting workpiece temperature to the proper value using a developed preheating system under high feed (0.2 mm/rev).

Geometry effect of copper nanoparticles and nanowires on polyetheretherketone-matrix nanocomposites: Thermal conductivity, dynamic mechanical properties and wear resistance

Polyetheretherketone (PEEK)-matrix nanocomposites filled with copper nanowires (Cu NWs) and copper nanoparticles (Cu NPs) were prepared by hot compaction method. The effects of Cu NWs and Cu NPs on the thermal conductivity, dynamic mechanical performance, and tribological property of PEEK-matrix nanocomposites were investigated. Results indicate that Cu NPs and Cu NWs with different geometry exhibit different influences on the crystallization behavior, melting behavior, dynamic mechanical properties, and friction and wear behavior of PEEK matrix. Namely, Compared to Cu NPs, Cu NWs can more efficiently better dissipate heat and transfer stress at PEEK/nanofiller interface. Moreover, the friction and wear behavior of the PEEK-matrix nanocomposites is also related to the geometry of the Cu nanofillers to some extent. This is because Cu NPs can act as roll bearings to reduce friction; and Cu NWs with a high thermal conductivity can prevent softening of PEEK matrix and increase the wear resistance via well dissipating friction heat away from the sliding interface. In one word, the comprehensive properties of PEEK-matrix nanocomposites are closely related to the geometry effect of Cu NPs and Cu NWs, which could be of significance for revealing the relation between the micro morphology and the macro application of inorganic nanofillers.

Dynamic mechanical response and damage mechanisms of nacre-inspired 2024Al/B4C composite at elevated temperature

In this study, the nacre-like 2024Al/B4C composites with a lamellar-interpenetrated architecture, virtually free of pores and cracks, were fabricated through combining freeze casting with pressure infiltration, and their quasi-static and dynamic compressive properties were investigated over the temperature ranged from 25 to 500 °C. The dynamic compressive strength and strain were greater than quasi-static ones due to strain-rate hardening and adiabatic heating softening mechanisms. Regardless of strain rates, the compressive strength decreased with temperature, while the failure strain increased. This could be explained by four main fracture phenomena including cracking of B4C and intermetallic compounds (IMCs), matrix deformation and interfacial debonding. The matrix deformation prevailed actively at high temperatures, with a reduced overall trend towards cracking and interfacial debonding. The interfacial debonding and particle cracking acted as the dominant factors that deteriorated the compressive behavior, whereas the soften matrix induced by elevated test temperatures effectively blocked the crack propagation that favorably worked for the strain. As the temperature was raised, the softened matrix destabilized particle skeleton with the deformation behavior of the composites determined by the alloy matrix. However, recrystallization occurred within the alloy matrix, accompanied by a reduction in dislocation density, which degraded the strength of the composites. The elevated temperatures significantly enhanced the strain rate sensitivity of the composites because of the matrix softening yielding a greater proportionate enhancement of particle stress at high temperature than at low temperature.

Boson-peak-like anomaly caused by transverse phonon softening in strain glass

Strain glass is a glassy state with frozen ferroelastic/martensitic nanodomains in shape memory alloys, yet its nature remains unclear. Here, we report a glassy feature in strain glass that was thought to be only present in structural glasses. An abnormal hump is observed in strain glass around 10 K upon normalizing the specific heat by cubed temperature, similar to the boson peak in metallic glass. The simulation studies show that this boson-peak-like anomaly is caused by the phonon softening of the non-transforming matrix surrounding martensitic domains, which occurs in a transverse acoustic branch not associated with the martensitic transformation displacements. Therefore, this anomaly neither is a relic of van Hove singularity nor can be explained by other theories relying on structural disorder, while it verifies a recent theoretical model without any assumptions of disorder. This work might provide fresh insights in understanding the nature of glassy states and associated vibrational properties.

Effect of nickel-based filler metal types on creep properties of dissimilar metal welds between Inconel 617B and 10% Cr martensitic steel

Creep rupture behaviors of dissimilar metal welds (DMWs) between Inconel 617B and 10%Cr martensitic steel with two different filler metals Inconel 617 and 82 were comparatively investigated at 600 °C to study the effect of nickel-based filler metal types on creep properties. Both the crept DMWs ruptured on the steel side prematurely compared to steel base metal (BM). The failure mode of DMW shifts from interfacial failure at weld metal (WM)/steel interface to Type Ⅳ crack in the intercritical heat-affected zone (ICHAZ) of steel with longer rupture life at the same creep condition by replacing Inconel 617 filler metal with Inconel 82. Type Ⅳ crack was related to matrix softening and fine prior austenite grain boundaries (PAGBs) scarcely decorated by precipitates in the ICHAZ. Interfacial failure was controlled by creep voids nucleation, growth and coalescence at the interface, while oxide notch only triggered crack initiation. The failure mode shift is because Inconel 82 filler metal compared to Inconel 617 can achieve slighter creep deformation concentration in the HAZ closely adjacent to interface and avoid interfacial failure of the DMW due to the lower creep strength gradient across the interface it induced. Based on this study, creep strength compatibility should be considered when selecting nickel-based filler metals for similar DMWs to obtain prolonged creep life.

On the tensile properties and failure mechanisms of 3D six-directional braided composites at elevated temperatures

Three-dimensional six-directional (3D6d) braided composites with different braiding angles were prepared, and the influences of temperature and braiding angle on tensile properties and failure mechanisms were studied. The results show that both temperature and braiding angle have significant effects on the tensile properties of 3D6d braided composites. As temperature increases, due to the weakening of the fiber/matrix interface, the stress-strain curve shows a nonlinear upward trend and the tensile properties decrease. As braiding angle increases, the curve declines, and both the tensile strength and modulus diminish. At high temperatures, the damage pattern is mainly braiding fibers multiple shear fracture, fifth fibers tensile fracture, sixth fibers torn, showing expansion outwards, matrix softening and peeling off from the fiber bundles. At 150 °C, the composite shows shear fracture, as the braiding angle increases, the shear fracture characteristics along the braiding angle become prominent. At 200 °C, the composite distorts and expands outwards overall. The fibers pull-out feature become obvious with increasing the braiding angle.

Matrix stiffness changes affect astrocyte phenotype in an in vitro injury model

Injury to the central nervous system (CNS) usually leads to the activation of astrocytes, followed by glial scar formation. The formation of glial scars from active astrocytes in vivo has been found to be dependent on the cell microenvironment. However, how astrocytes respond to different microenvironmental cues during scar formation, such as changes in matrix stiffness, remains elusive. In this work, we established an in vitro model to assess the responses of astrocytes to matrix stiffness changes that may be related to pathophysiology. The investigated hydrogel backbones are composed of collagen type I and alginate. The stiffness of these hybrid hydrogels can be dynamically changed by association or dissociation of alginate chains through adding crosslinkers of calcium chloride or a decrosslinker of sodium citrate, respectively. We found that astrocytes obtain different phenotypes when cultured in hydrogels of different stiffnesses. The obtained phenotypes can be switched in situ when changing matrix stiffness in the presence of cells. Specifically, matrix stiffening reverts astrogliosis, whereas matrix softening initiates astrocytic activation in 3D. Moreover, the effect of matrix stiffness on astrocytic activation is mediated by Yes-associated protein (YAP), where YAP inhibition enhances the upregulation of GFAP and contributes to astrogliosis. To investigate the underlying mechanism of matrix stiffness-dependent GFAP expression, we also developed a mathematical model to describe the time-dependent dynamics of biomolecules involved in the matrix stiffness mechanotransduction process of astrocytes. The modeling results further indicate that the effect of matrix stiffness on cell fate and behavior may be related to changes in the cytoskeleton and subsequent activity of YAP. The results from this study will guide researchers to re-examine the role of matrix stiffness in reactive astrogliosis in vivo and inspire the development of a novel therapeutic approach for controlling glial scar formation following injury, enabling axonal regrowth and improving functional recovery by exploiting the benefits of mechanobiology studies.

Plasmon-driven light harvesting in poly(vinyl alcohol) films for precise surface topography modulation.

Efficient light harvesting is essential for advanced photonic devices. Complex micro/nano surface relief structures can be produced via light-triggered mechanical movement, but limited in organic active molecular units. In this Letter, we propose to embed noble-metal particles into light-inactive polyvinyl alcohol matrix to construct a light harvesting system driven by plasmon for inscription of surface relief gratings. Ultra-small-sized silver nuclei are generated in the polymer by pre-thermal treatment, acting as an accelerator for the subsequent photoinduced particle growth, hydrogen group cleavage, and matrix softening. Based on such properties, a complex plasmonic array carrying ultra-high-density information is achieved with peristrophic multiplexing holography. This Letter paves a bright way to realize data storage, information encryption, and optical microcavity.

Creep rupture mechanisms and life prediction of IN617 for VHTR applications

The creep rupture mechanisms of IN617 were systematically investigated by establishing the relationship between microstructural characteristics and creep performance, including rupture time, percentage elongation, microhardness, and minimum creep rate. The Wilshire equation was employed to extrapolate long-term creep life by normalizing the stress, σ , using the ultimate tensile strength, σ TS . The results indicated that at temperatures ≤950 °C, when σ / σ YS values were >0.2 ( σ YS = yield strength), the creep rupture mechanism involved the sliding and migration of recrystallized grain boundaries, leading to matrix softening and necking fractures. When applied stresses ranged from 0.12 σ TS to 0.2 σ YS , creep voids along the grain boundaries became a pronounced feature, implying the rupture mechanism of the weakening of the grain boundaries without sufficient secondary-phase pinning. At a low stress level ( σ / σ TS < 0.12), creep ruptures were governed by a composite mechanism of microstructural degradation and internal oxidization, which was reflected in the brittle fractures caused by the connection of cracks along carbide networks and internal oxidized voids. A temperature–stress–rupture mechanism map was constructed by combining a comparison and summary from the literature. The Wilshire extrapolation curve described the creep rupture times well with temperatures and stresses, and the turning point of the curve suggested that microstructural degradation and internal oxidization increased the minimum creep rates and accelerated creep rupture.

High-Temperature Creep Behavior and Microstructural Evolution of a Cu-Nb Co-Alloyed Ferritic Heat-Resistant Stainless Steel

The creep behavior of Fe–17Cr–1.2Cu–0.5Nb–0.01C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa. The evolution of precipitates after creep deformation was analyzed by scanning electron microscopy, energy dispersion spectrum, and transmission electron microscopy. The minimum creep rate decreased with the decrease in the applied load and temperature, thereby extending the rupture life. Cu-rich phase and Nb-rich Laves particles were generated in dominant quantities during the creep process, and the co-growth relationship between them could be detected. Creep rupture was featured by ductile fracture with considerable necking. As increasing the temperature and decreasing the stress, the softening of the metal matrix was accelerated, showing more obvious plastic flow. The true stress exponent and activation energy were 4.9 and 375.5 kJ/mol, respectively, indicating that the creep deformation was dominated by the diffusion-controlled dislocation creep mechanism involving precipitate-dislocation interactions. Based on the creep rupture data obtained, the Monkman–Grant relation and Larson-Miller parameter were established, which described the creep rupture life for the studied steel well.