Unmodified Matrix Research Articles

Mechanical enhancement of natural-fiber-reinforced composites modified with recycled thermoset composite fillers

Synthetic-fiber-reinforced thermoset composites pose a significant threat of environmental pollution owing to their nonbiodegradable nature. To address this issue, it is essential to establish an adequate recycling strategy to reduce composite waste. In this study, we prepared flax-fiber-reinforced thermoplastic composites and modified a liquid thermoplastic resin (Elium 188 O) with recycled thermoset composite fillers. The introduction of 15% silane-treated fillers into the polymer matrix resulted in a substantial increase in the energy release rate and fracture toughness at the fracture initiation stage in modes I and II. Specifically, compared with the unmodified matrix, the energy release rate and fracture toughness were enhanced by 44.8% and 42.8% (for mode I) and 40.5% and 85.4% (for mode II), respectively. Similarly, the flexural strength and modulus increased by 25.1% and 34.8%, respectively. Furthermore, the mechanical properties of thermoplastic composites will deteriorate significantly because of the low bonding strength between virgin and recycled materials. However, the flax-fiber-reinforced composites with a 15% silane-treated filler-modified polymer matrix maintained Young’s modulus and tensile strength of 89.9% and 91.2%, respectively, after 20 cycles of recycling. Overall, the strategy of inducing chemical-treated powdered composite wastes is a sufficient and low-labor-cost method to mitigate environmental pollution and improve the sustainability of recycled composite structures.

The Effect of Carbon-Based Nanofillers on Cryogenic Temperature Mechanical Properties of CFRPs.

In the present work, the effects of carbon-based nanofillers (0.5 wt%), i.e., graphene nanoplatelets (GNPs), carbon nanofibers (CNFs), and carbon nanotubes (CNTs), on the cryogenic temperature (77 K) mechanical properties of carbon fiber reinforced polymers (CFRPs) were investigated. The study utilized an ex situ conditioning method for cryogenic tests. The nanofillers were mixed with the epoxy matrix by a solvent-free fluidized bed mixing technique (FBM), while unidirectional carbon fibers were impregnated with the resulting nanocomposites to manufacture CFRP samples. Optical microscopy was employed to analyze the dispersion of the carbon-based fillers within the matrix, revealing a homogeneous distribution in nanocomposites containing GNPs and CNFs. Fracture toughness tests confirmed the homogeneity of the GNP-loaded systems, showing an improvement in the stress intensity factor (KC) by 13.2% and 14.7% compared to the unmodified matrix at RT (25 °C) and 77 K, respectively; moreover, flexural tests demonstrated a general increase in flexural strength with the presence of carbon-based nanofillers at both temperature levels (RT and 77 K). Additionally, interlaminar shear strength (ILSS) tests were performed and analyzed using the same ex situ conditioning method.

Mechanical properties and strengthening mechanism of SiC particle reinforced porcelain

AbstractMechanical properties of porcelain based on feldspar porcelain as a matrix with SiC particles as a reinforcing phase were studied in terms of the effects of SiC content, firing temperature, and holding time. A maximum flexural strength of 122 ± 4 MPa was achieved for a sample with 8 wt% SiC content treated at 1260°C for 30 min, which is 90.6% as high as than that of the unmodified matrix (64 ± 5 MPa). The fracture toughness and elastic modulus of the former sample were 1.71 MPa · m1/2 and 89.975 GPa, respectively. Because the thermal expansion coefficient of SiC (4.40 × 10−6/°C) is smaller than that of the glass phase (6.60 × 10−6/°C), the SiC particles remain in a state of compressive stress after the porcelain cooling. This characteristic restricts crack growth and offsets the tensile stress of the glass phase, restraining crystal growth owing to the tensile stress pinning the grains, such that the mechanical properties are improved.

Mechanical analysis and machinability evaluation of a new EDM-turning hybrid machining process

This study developed an accurate electrical discharge-assisted turning (EDAT) technique for Ti–6Al–4 V alloy and a precise EDAT cutting force prediction model considering theoretical multi-physics fields with metallurgical transformation. A heat-fluid coupled model of multi-pulse discharge in the EDAT process was developed to obtain the thickness of the removal layer (RL) and modified layer (ML) together with the temperature field of the cutting layer. Subsequently, the shear flow stresses under different machining parameters were obtained using the oblique cutting and flow softening constitutive models. Within the cutting layer, the pure thermal softening effect reduces the flow stresses by more than 25% in the unmodified matrix layer (UML) and by more than 60% in the ML, which is dominated by the metallurgical transformation softening (MTS) effect. Finally, the cutting force model of EDAT under multi-physical fields was established and the accuracy was verified by relevant experiments. The results showed that the increase in discharge number accelerated the rise of workpiece surface temperatures, and the small cutting parameters were favorable to the machining performance of the EDAT. The MTS effect significantly reduces cutting forces while improving the quality of the machined surface.

Preparation of TiO2-deposited silica-based catalysts for photocatalytic decomposition of chloro-pesticide to environmentally less toxic species

Herein, titanium (IV) oxide (TiO2) loaded into montmorillonite (MK10) and sand is presented as an efficient heterogeneous catalyst for the degradation of 1,4-dichlorobenzene (DCB) as a model organic pollutant in the aqueous phase. The catalyst was synthesized by incorporating titanium isopropoxide as a precursor into MK10 through a simple solvent impregnation method, followed by direct calcination. The same protocol was applied to a clean quartz matrix. The resulting catalysts were characterized in detail using a variety of techniques. The TiO2 deposited MK10 and sand exhibited photochemical removal of DCB (>99% of 100 mg L−1) from the aqueous phase; this process followed a pseudo second-order kinetic model values in the range of Qe:111–113 mg g−1 and K2: 4–5 × 10−4 g mg−1 min−1. The kinetic plots indicate that after 30 min, the intermediates start to decrease and complete degradation occurs in 180 min. The modified materials showed fast DCB degradation kinetics under photochemical reaction conditions and adsorption under dark reaction conditions. The unmodified matrix adsorbed 99.12–99.88% of the DCB under both dark and light reaction conditions. These photocatalysts are stable, reusable, and least amount of titanium leaching. The simple two step synthesis, and high photocatalytic performance (with 10 mg of the catalyst without any oxidants) of our catalysts can be promising in environmental applications to treat similar organic pollutants in wastewater. These catalysts have enhanced activity and durability for environmental catalytic pollutant degradation reactions and can provide insights beyond single metal oxide catalysts for heterogeneous catalysis at diverse operating conditions.

Sustainable microwave-assisted hydrothermal synthesis of carbon-supported ZrO2 nanoparticles for H2O2 electrogeneration

This work proposes the use of a novel green and fast (<1h) route for the construction of electrocatalysts by microwave-assisted hydrothermal synthesis using carbon-supported metal oxide for H2O2 electrogeneration. Using ZrO2 supported on carbon black Printex L6 (PL6C) as a non-toxic model catalyst, the present study evaluated different synthesis conditions and their effects on ORR activity and selectivity via the application of the rotating ring-disk electrode (RRDE) and gas diffusion electrode (GDE) techniques. RRDE results showed that the optimized ZrO2/PL6C catalyst presented improvements in catalytic performance of 140 mV in the E1/2 for ORR and in selectivity for H2O2 production of 88.8% compared to the unmodified PL6C (78%). The improved electrocatalytic performance was attributed to the high dispersion of small ZrO2 nanoparticles (~7 nm) in direct contact with the carbon support which helped increase the ECSA values. GDE results showed that ZrO2/PL6C was responsible for doubling the kapp values of H2O2 production and for the reduction of energy consumption by about 150 kWh g−1 compared to the unmodified matrix. Key insights related to the construction of carbon-based metal oxide catalysts and the optimization of ORR are discussed further in the work aiming at providing useful contributions for future investigations and applications.

Research on Performance of BRA Modified Asphalt

For estimating the performance indexes of Buton rock asphalt (BRA) modified asphalt and the influence of different Buton asphalt content on the property of BRA modified asphalt, an indoor pitch performance index experiment was carried out. The test study uses Buton asphalt as the modifier, and the percentage of Buton asphalt relative to the total asphalt is used as the mixing ratio (namely internal mixing method), with 5% as the interval, select 10%, 15%, 20%, 25% and 30% five blending ratios to prepare BRA modified pitch. In addition, related tests will be done on the prepared BRA modified asphalt, and the high temperature property, low temperature property and durability of Buton asphalt modified pitch were evaluated. The analysis of the test results shows that the function of the BRA modified asphalt prepared by adding the base asphalt to Buton asphalt has changed. With the increase of Buton asphalt content, the high temperature property of BRA modified asphalt is significantly improved, but the low temperature property decreases with the increase of the content, and the durability performance is roughly the same as that of the unmodified matrix asphalt.

Morphological and Semi-empirical Study of the Pluronic F68/Imogolite/Sudan III Intersurfaces Composite for the Controlled Temperature Release of Hydrophobic Drugs.

Some PluronicF68 (F68) triblock copolymer properties demonstrate surprising applications in selective drug administration, such as the transportation of hydrophobic anti-inflammatories through epithelial barriers. Nuclear magnetic resonance (1H-NMR) spectroscopy was carried out for micelle precursor dispersions and F68 films modified with a synthetic imogolite (IMO) biocompatible hydrogel. Theoretical calculations and morphological assessment for the process of morphogenesis of dendritic crystallization were performed by molecular docking and atomic force microscopy (AFM) of the Sudan III-IMO-F68 composite, which was more hydrophobic than Sudan III-F68 and carried out the prolonged release of the Sudan III “drug” captured by a water–octanol interface determined by standard absorbance. Surface fusions were measured and compared to the unmodified matrix. However, despite the superior properties of the composite, the critical micelle concentration (CMC) was practically unmodified because solitary IMO strands attached to Sudan III formed Sudan III-IMO. These strands unraveled in a stable manner by expanding like a “spiderweb” in hydrophilic interfaces according to NMR analysis of the hydrogen one H1 polarization of Sudan III and F68 methyl, whose correlation relates hydrophobicity of Sudan III-IMO-F68 with dendrite properties from F68 concentrations. CMC and surface fusions equivalent to F68 surface properties, calculated by differential scanning calorimetry and dynamic Raman spectroscopy, were determined by AFM and high-resolution ellipsometry. Our results show highly specialized pharmacological applications since micelle surfaces expand, triggering maximum deliveries of “Drugs” from its interior to the physiological environment. The implanted sensor prototype determined equilibria reached Sudan III according to temperature (32–50 °C) and time it took to cross the membrane model 1-octanol (48 h). The findings suggest that the targested design of a F68-IMO-“Drug” would function as a microdevice for the prolonged release of hydrophobic drugs. In addition, the said microdevice could regenerate the damaged tissue in the central nervous system or other organs of the body. This is due to the fact that it could perform both tasks simultaneously, given the properties and characteristics acquired by the compatible material depending on the temperature of the physiological environment.

Ibuprofen incorporated into unmodified and modified mesoporous silica: From matrix synthesis to drug release

Abstract Aiming to rationalize the release profile of an incorporated pharmaceutical drug in terms of its mobility, driven by guest-host interactions, the poorly water-soluble Ibuprofen drug was loaded in a mesoporous inorganic silica matrix with unmodified (MCM-41) and modified surface (MCM-41sil) by post-synthesis silylation, both having pore sizes ∼ 3 nm. The single calorimetric detection of a broad glass transition step for both ibuprofen composites indicates full drug amorphization, confirmed by the only appearance of an amorphous halo in the powder XRD patterns. Moreover, a gradient profile is disclosed by the heat flux derivative plot in the glass transition, in coherence with the thermogravimetric profile that shows a multi-step decomposition trace for confined ibuprofen in these matrixes. While identical guest dynamics, as probed by dielectric relaxation spectroscopy, were found in both dehydrated composites, a significant molecular population with faster relaxation exists in the hydrated state for the drug inside the unmodified matrix. This was rationalized as the concurrence of true confinement effects, which manifest under nanometer dimensions, and greater water affinity of the unmodified matrix, forcing the drug molecules to be placed mostly in the pore core. Finite size effects are also felt in both dehydrated composites, however guest-host interactions give origin to a dominant population with slowed down mobility that governs the overall guest dynamics. In spite of an inferior number of active sites for drug adsorption in the silylated matrix, a faster Ibuprofen delivery in phosphate buffer (pH = 6.8) was observed when the drug is released from unmodified MCM-41 in the hydrated state. Therefore, our results suggest that a relevant role is played by water molecules, which impair a strong guest adsorption in the host surface more efficiently than the limited surface modification, influence the higher ratio of a faster population in the pore core and facilitate the diffusion of the aqueous releasing media inside pores.

Effect of the Oxidative Modification and Activation of Templates Based on Poly(ethylene terephthalate) Track-Etched Membranes on the Electroless Deposition of Copper and the Catalytic Properties of Composite Membranes

Treatment conditions (oxidation, number of activation procedures) of a polymer template based on poly(ethylene terephthalate) track-etched membranes (PET TeMs) on the efficiency of the electroless deposition of copper, the structure of the synthesized copper nanotubes, and their catalytic activity in the liquid-phase reduction of p-nitrophenol are studied. It is shown that oxidative premodification contributes to an increase in the catalytic activity of the composite membrane by 20% compared with a sample synthesized in accordance with the standard procedure (etched PET TeM, single activation). In addition, it is found that the repeated implementation of the sensitization and activation stages leads to an increase in the reaction rate constant by 35 and 15% in the case of the etched and oxidized membranes, respectively. The properties of the catalysts in the temperature range of 16–35°C are studied; the activation energy Ea is calculated. The lowest Ea value is obtained for a sample synthesized in an unmodified matrix: electroless deposition into the polymer template without additional oxidative modification makes it possible to synthesize composite catalysts exhibiting relatively low catalytic activity; however, membranes of this type remain active in five test runs (p-nitrophenol conversion and reaction rate constant decrease by 26 and 44%, respectively).

Polymer composites based on functionalized carbon nanotubes

The present paper considers the efficiency of using carbon nanotubes (CNTs) functionalized by titanium stearate groups for modifying of polyethylene and polypropylene. For this purpose, the strength characteristics, Shore hardness, thermal diffusivity and conductivity of the obtained nanocomposites were determined. The weak effect of the CNTs (0.01-1.5 wt.%) on the values of thermal conductivity coefficients and thermal diffusivity was revealed. It was found that compared to the unmodified matrix, nanocomposites containing 0.01-0.1 wt.% of the titanium stearatefunctionalized CNTs demonstrate, an increase in the Shore hardness by 12.5-14.5%, a decrease in the weight wear by 54.2%, and the daily water absorption - to the values below the threshold of sensitivity of the standardized method of determination. The functionalization by the titanium stearate groups made it possible to reduce the CNTs mass fraction in the composition of polyethylene and polypropylene composites by more than 10 times compared with the pristine nanotubes.

KNbO3 soportado en zeolita BETA: evaluación del método de incorporación

Los óxidos mixtos presentan propiedades catalíticas, sin embargo, exhiben baja área superficial, lo que limita su uso como catalizadores. Con el fin de aumentar su superficie específica, se prepararon materiales a partir de la incorporación del óxido mixto sobre materiales de elevada área superficial evaluando dos métodos de incorporación. La actividad catalítica de los materiales se evaluó en la oxidación de Metil Fenil Sulfuro.&#x0D; Los materiales resultantes se caracterizaron mediante técnicas fisicoquímicas. El área superficial disminuyó respecto la matriz sin modificar como resultado de bloqueo de los poros y/o la ubicación de las partículas dentro de los poros de las zeolitas. Mediante difracción de rayos X se determinó que la muestra obtenida por mezcla mecánica presentó las señales de la zeolita pero con una disminución de la intensidad; la muestra “in-situ” no presentó estructura zeolítica ni cristalinidad. Los resultados de evaluación catalítica demostraron la importancia de la estructura y cristalinidad.

Study of the Surface Integrity and High Cycle Fatigue Performance of AISI 4340 Steel after Composite Surface Modification

In the field of materials science, the fabrication of a material with severe surface plastic deformation and a good surface state is an issue encountered in the development of counterbalanced gradient materials. For this paper, AISI 4340 steel was first processed with abrasive water jet peening (AWJP) and then with ultrasonic surface rolling (USRE) to obtain a good surface state while maintaining large plastic deformation. The AISI 4340 steel composite surface was therefore modified, and the surface integrity and cycle fatigue performance were analyzed. The results show that the plastic deformation layer of the modified composite surface of the 4340 steel was 310 µm from the surface of the sample, the grain size 40 µm from the surface layer was refined to 70 nm, and the maximum surface roughness Ra is 0.06. The fatigue limit of the modified composite surfaces obtained by the tensile fatigue test was 595.7 MPa, which was 85.7 MPa higher than the 510 MPa fatigue limit of the unmodified matrix, indicating that the method of composite surface modification can produce a deep deformation layer while maintaining good surface conditions. The results show that work hardening caused by a composite surface treatment is the most important factor for improving the fatigue performance of materials.

Numerical Analysis of Transient Pressure Behaviors with Shale Gas MFHWs Interference

After the large-scale horizontal well pattern development in shale gas fields, the problem of fast pressure drop and gas well abandonment caused by well interference becomes more serious. It is urgent to understand the downhole transient pressure and flow characteristics of multi-stage fracturing horizontal well (MFHW) with interference. Therefore, the reservoir around the MFHW is divided into three regions: fracturing fracture, Stimulated reservoir volume (SRV), and unmodified matrix. Then, multi-region coupled flow model is established according to reservoir physical property and flow mechanism of each part. The model is numerically solved using the perpendicular bisection (PEBI) grids and the finite volume method. The accuracy of the model is verified by analyzing the measured pressure recovery data of one practical shale gas well and fitting the monitoring data of the later production pressure. Finally, this model is used to analyze the effects of factors, such as hydraulic fractures’ connectivity, well distance, the number of neighboring wells and well pattern arrangement, on the transient pressure and seepage characteristics of the well. The study shows that the pressure recovery double logarithmic curves fall in later part when the well is disturbed by a neighboring production well. The earlier and more severe the interference, the sooner the curve falls off and the larger the amplitude shows. If the well distance is closer, and if there are more neighboring wells and interconnected corresponding fracturing segments, the more severe interference appears among the wells. Moreover, the well interference may still exist even without interlinked fractures or SRV. Especially, severe interference will affect production when the hydraulic fractures are connected directly, and the interference is weaker when only SRV induced fracture network combined between wells, which is beneficial to production sometimes. When severe well interference occurs, periodic well shut-in is needed to help restore the reservoir pressure and output capacity. In the meanwhile, the daily output should be controlled reasonably to prolong the stable production time. This research will help to understand the impact of well interference to gas production, and to optimize the well spacing and achieve satisfied performance.

Functionalized nanoparticles as adjuvant to increase the cytotoxicity of metallodrugs toward tumor cells

Silica nanoparticles increasing the cytotoxicity of copper(ii) and zinc(ii) metallodrugs.

Longitudinal and transverse compressive properties of alumina nanoparticles filled epoxy/unidirectional glass fiber composite laminate under in-plane loading

In this work, alumina nanoparticles at various concentrations were used to modify the epoxy system to develop the composites along with unidirectional (UD) glass-fibers. In order to understand the influence of alumina nanoparticles over the directional compressive properties, tests were performed along longitudinal and transverse directions of the laminate using a universal testing machine. To generate the base line data the laminates with the unmodified matrix are also tested. The maximum enhancement of compressive properties were seen in the composite having 1.0wt% of alumina nanoparticles. The compressive modulus and compressive strength was found to be 17.76% and 19.43% in the transverse direction where as it found to be 2.89% and 3.44% in the longitudinal direction respectively. Results of the present study showed that glass-fiber reinforced nano-modified polymers (GFRP) exhibit significantly improved compressive properties such as compressive strength and compressive modulus along the transverse direction while the properties along the longitudinal direction were not affected much by the nano-fillers, due to the dominating effect of the fiber-reinforcement. The graphs and figures are employed to explain the results.

Microstructure and mechanical properties of newly developed SiC-C/C composites under atmospheric conditions

The purpose of this study is to investigate the relationship between its microstructure and bending strength of SiC-C/C (carbon-carbon) composites. By using the phenolic resin and carbon fiber bundle, the carbon fiber reinforced plastics (CFRP) precursor was prepared by employing filament winding technique. To modify the phenolic resin, the micro-sized glass fiber was added. The CFRP precursor was charred at high temperature at Argon atmosphere to obtain SiC-C/C composites. The matrix of composites was densified by resin impregnation done by cold isostatic pressing (CIP) method. The detail observation of matrix after charred revealed that when precursor resin was modified with glass fiber, the direction of thermal crack at matrix showed complex manner, while thermal crack at un-modified matrix only appeared along fiber direction. Because of the presence of complex thermal crack, the matrix of SiC-C/C composite showed high porosity at un-densified condition and effectively densified by CIP to promoting resin flow toward thermal crack. The bending and compression test results showed that bending strength and inter-laminar shear strength of SiC-C/C composites was increased by densification. Moreover, the fractured surface observations suggested that the presence of synthesized SiC nano-whisker at inter-laminar enhances the apparent shear strength due to mechanical bridging between laminar.

Mechanical strength of epoxy/organoclay/carbon fiber hybrid composites

The influence of organoclay (bentonite BS) modified with quaternary ammonium (QAS) and phosphonium salts (QPS) on the mechanical properties of epoxy/organoclay/carbon fiber hybrid composites was investigated. The longitudinal flexural strength of the composites containing 1 wt % ­BSQAS and BSQPS increased by 4 and 10 %, respectively, compared to the reference sample (epoxy resin/carbon fiber). Moreover, there was also a significant improvement, up to 13 %, of Young's modulus and transverse elastic modulus for the composites with modified bentonites. On the basis of the atomic force microscopy cross-section analysis (AFM), it was found that the composites with matrix containing the modified bentonites were characterized with larger interfacial surface, about 50 %, than that of unmodified matrix (epoxy resin/carbon fiber).

Effect of Compaction Pressure and Sintering Time on the Properties of Sintered Cu-10Sn Bronze

Bronze-based composite materials are well known for use as friction materials. They are produced by powder metallurgy techniques from bronze powder, which acts as a matrix, and various friction modifying additives. The objective of this work was to study the effect of compaction pressure and sintering time on the properties of the unmodified bronze matrix. The bronze powder used was prealloyed with a composition of Cu-10Sn. The specimens were pressed by uniaxial die compaction with pressures of 282 to 339 MPa. The sintering experiments were conducted in an alumina tube furnace at 800 °C with sintering times of 30, 45, and 60 min under a vacuum pressure of 2.25x10-2 Torr. From the results, it was found that the density of the samples increased with increasing compaction pressure. A microstructural examination of the samples for the different sintering times showed them to look very similar. Finally, the highest sintered density of 7.30 g/cm3 was obtained at 800 °C for 60 min.

Thermal properties of polyethylene glycol/carbon microsphere composite as a novel phase change material

Polyethylene glycol (PEG) as phase change materials has been extensively studied. However, it is difficult to uniformly disperse the PEG in the unmodified matrix material owing to the impregnation problem. It is therefore challenging to overcome the shortcoming of low thermal conductivity. In order to solve this problem, carbon microspheres (CMPs) prepared by the hydrothermal method is firstly proposed as the supporting matrix for preparation of PEG composite. The PEG/CMPs composite is prepared via a mutual diffusion methodology in a high-temperature environment. The test result shows the CMPs nano-material has rich oxygen-based functional groups and can be uniformly dispersed in the PEG phase. As the carbon content increases, the CMPs become gradually connected in the PEG/CMPs composite, which can result in a network with good thermal conductivity. Compared with the thermal conductivity of pure PEG, the thermal conductivity of the composite is increased by 65.07%. Owing to the existence of hydrogen bonds in the composite, the crystallinity fraction of the PEG is in the range of 102–105%. It means that the test result is higher than the theoretical value of latent heat for the composite. Finally, its cycling performance was measured. After 500 thermal cycles, the phase transition temperature of the composite remains almost constant, and the latent heat values of the melting and freezing decrease by 1.05 and 1.45%, respectively. The PEG/CMPs composite would be a promising material for thermal energy storage applications and can be used in various engineering disciplines.