Modification Of Matrix Research Articles

Modified Playfair cryptosystem for improved data security

Playfair is the earliest known classical block cipher which is capable of taking two characters as a unit in the process of encryption and decryption. However, the cipher is suffering from vulnerability to many cryptanalysis attacks due to a lack of confusion and diffusion properties, an inability to handle numbers and special characters in the process of encryption and decryption, and a host of other deficiencies. Although several modifications and improvements had been done by different researchers, the emphasis has been on the modification of the key matrix to accommodate more characters to increase the keyspace. No attention has been given to increment in the size of the block that the Playfair cipher can handle at a time. In this paper, a modified Playfair (MPF) cryptosystem that is capable of handling different block sizes with high diffusion and confusion properties is developed. cryptanalysis of the developed cryptosystem was carried out and the results show that the MPF cryptosystem is resistant to Known plaintext attack, chosen-plaintext attack, chosen ciphertext attack, frequency analysis attack, autocorrelation attack, differential cryptanalysis attacks, entropy attacks, brute force attack, and can handle variable block sizes.

Effect of Dispersing Multiwalled Carbon Nanotubes and Graphene Nanoplatelets Hybrids in the Matrix on the Flexural Fatigue Properties of Carbon/Epoxy Composites

The synergistic effect of applying hybrid nanoparticles in improving the fatigue property of fiber reinforced polymer composites has rarely been explored before. Hence the monotonic and fatigue flexure properties of the carbon fiber reinforced epoxy laminates with matrix modified by multiwalled carbon nanotubes and graphene nanoplatelets were experimentally studied herein. The nanofiller ratio applied in the matrix modification was considered as a variable in the experimental program to investigate the effect of nanofiller ratio on the studied mechanical properties. A synergistic index has been employed to evaluate the synergistic effect of hybrid nanoparticles on the studied properties successfully. Experimental results show that the laminates with matrix modified under a nanofiller ratio (multiwalled carbon nanotube: graphene nanoplatelet) of 9:1 have the higher monotonic and fatigue strengths than those modified under other nanofiller ratios. The monotonic flexural strength and fatigue limit of the specimens modified under a nanofiller ratio of 9:1 are higher than the neat laminate specimens by 9.3 and 11.0%, respectively. The fatigue limits of the studied nano-modified laminates increase with the static strengths. Adding hybrid nanoparticles under proper nanofiller ratios in the matrix can suppress the degradation of the stiffness, further increase the resistance to fatigue damage. Examining the fracture surfaces of fatigued specimens reveals that the pullout/bridging effects of carbon nanotubes and the crack deflection effect of graphene nanoplatelets are the main reinforcement mechanisms in enhancing the fatigue strength of the composites.

The impact of wormhole generation in carbonate reservoirs on CO2-WAG oil recovery

In this paper, the impact of CO2-carbonate interactions on hydrocarbon recovery from three initially oil-saturated heterogeneous carbonate core samples (with low and mid permeabilities) were investigated. Alternate injection of carbon dioxide (CO2) and synthetic formation brine was conducted after water flooding. X-ray computed tomography scanning of the core samples before and after core flooding was performed at ambient conditions. Extent of carbonate dissolutions and rock matrix modifications were observed from the change in porosities, permeabilities, and wormhole formations. Generally, the CO2-WAG injection resulted in more than 30% extra oil recovery from the three cores after water flooding scenario. As expected, the total recovery factor of the core with lowest initial permeability and porosity was the smallest, however the core permeability increased from 1.45 mD (pre-flood) to 1987.9 mD (post-flood). Considerable amount of oil was left behind in the core with initially low permeability and porosity due to preferentially flow of WAG fluid through the wormholes, bypassing the trapped oil in the pore spaces at the uninvaded region of the rock. The study suggests that low oil recovery from core with low initial permeability and porosity is principally due to formation of wormhole because of rapid rate of rock dissolution and faster rate of CO2-carbonate reactions. Compared to the mid permeability cores, the low permeable core slows down the WAG fluid flow and give more time for CO2-carbonate rock interactions and reactions because of the tightness of the pore spaces. Thus, facilitated more exposure time and effective contact between the carbonate rock fabrics and the CO2-saturated brine.

Targeting the IGF/PI3K/mTOR pathway and AXL/YAP1/TAZ pathways in primary bone cancer

Primary bone cancers (PBC) belong to the family of mesenchymal tumors classified based on their cellular origin, extracellular matrix, genetic regulation, and epigenetic modification. The three major PBC types, Ewing sarcoma, osteosarcoma, and chondrosarcoma, are frequently aggressive tumors, highly metastatic, and typically occur in children and young adults. Despite their distinct origins and pathogenesis, these sarcoma subtypes rely upon common signaling pathways to promote tumor progression, metastasis, and survival. The IGF/PI3K/mTOR and AXL/YAP/TAZ pathways, in particular, have gained significant attention recently given their ties to oncogenesis, cell fate and differentiation, metastasis, and drug resistance. Naturally, these pathways – and their protein constituents – have caught the eye of the pharmaceutical industry, and a wide array of small molecule inhibitors and antibody drug-conjugates have emerged. Here, we review how the IGF/PI3K/mTOR and AXL/YAP/TAZ pathways promote PBC and highlight the drug candidates under clinical trial investigation.

SIMULATIONS OF IMPROVED BLIND ELECTRONIC DIGITAL SIGNATURES 2D TYPE FOR INFORMATION PROTECTION SYSTEMS

The article considers aspects of application of matrix modifications of RSA cryptosystem for creation on the basis of matrix models and algorithms of cryptoconversions of images of blind electronic digital signatures (BEDS). The advantage of the proposed matrix models of RSA is to take into account the specifics of images and ease of adaptation to different types and formats of images. Formulas and algorithmic steps of BEDS creation procedures and intermediate steps of closing, encrypting and decrypting images are given. Model experiments in the Mathcad Professional software environment, screens from the created software modules demonstrate the functionality and advantages of procedures and algorithms for creating improved blind EDS of matrix type for textual documents (TGD) of a confidential nature. The results of modeling the processes of creating such signatures for large-format documents in the Mathcad software environment confirmed the adequacy of the proposed transformation models and the correct operation and verification of BEDS and allowed to determine the processing time and limitations of relevant cryptographic transformations. Improved BEDS take into account the specifics of TGD, adapt to different formats, have better temporal, histogram-entropy characteristics (shown an increase in the entropy of BEDS to 7.98 bits/el.).

Low velocity impact resistance of thin and toughened carbon fibre reinforced epoxy

This study investigates the effect of core-shell rubber nanoparticle and block copolymer matrix modifications on the low velocity impact resistance of thin (∼1.6 mm), multi-axial carbon fibre reinforced epoxy laminates. The results demonstrate a strongly enhanced damage resistance predominantly to impact energies of 9 J and 13 J. Lower impact energies do not sufficiently activate the energy dissipating capabilities of the applied toughening agents. In the case of 9 J impacts, it is found that the damage resistance increases with increasing modifier concentration by a successive reduction of the indentation depth. Once the impact causes large-scale fibre fracture (13 J), the damage mode changes and an increasing matrix toughness leads to a strong reduction of the damage area. However, a proper bonding between matrix and the embedded fibres is a mandatory precondition to take advantage of a core-shell rubber and block copolymer toughened matrix.

Hierarchically structured MoO2/dopamine-derived carbon spheres as intercalation electrodes for lithium-ion batteries

A hydrogen peroxide initiated sol-gel process involving molybdenum transformation in the presence of dopamine (Dopa) hydrochloride excess produced the metastable precipitate composed of polydopamine (PDopa) spheres coated with Dopa preintercalated molybdenum oxide, (Dopa)xMoOy@PDopa. The hydrothermal treatment (HT) of the (Dopa)xMoOy@PDopa precursor resulted in the simultaneous carbonization of Dopa and molybdenum reduction generating MoO2 nanoplatelets distributed and confined on the surface of the Dopa-derived carbon matrix (HT-MoO2/C). The consecutive annealing (An) of the HT-MoO2/C sample at 600 °C under Ar atmosphere led to the formation of MoO2 with increased Mo oxidation state and improved structural stability (AnHT-MoO2/C). Annealing had also further facilitated interaction between the molybdenum-derived and Dopa-derived components resulting in the modification of the carbon matrix confirmed by Raman spectroscopy. Morphology of both materials is best described as Dopa-derived carbon spheres decorated with MoO2 nanoplatelets. These integrated metal oxide and carbon structures were tested as electrodes for lithium-ion batteries in the potential window that corresponds to the intercalation mechanism of charge storage. The AnHT-MoO2/C electrode showed enhanced electrochemical activity, with an initial specific discharge capacity of 260 mAh/g and capacity retention of 67% after 50 cycles, compared to the HT-MoO2/C electrode which exhibited an initial specific discharge capacity of 235 mAh g−1 and capacity retention of 47% after 50 cycles. The rate capability experiments revealed that the capacity of 93 mAh/g and 120 mAh/g was delivered by the HT-MoO2/C and AnHT-MoO2/C electrodes, respectively, when the current density was increased to 100 mA/g. The improved specific capacity, electrochemical stability, and rate capability achieved after annealing were attributed to higher crystallinity of MoO2, increased oxidation state of Mo, and formation of the tighter MoO2/carbon contact accompanied by the annealing assisted interaction between MoO2 and Dopa-derived carbon.

Utilization of Reconstituted Whey Powder and Microbial Transglutaminase in Ayran (Drinking Yogurt) Production.

SUMMARYResearch backgroundIn industrial ayran production, milk is diluted to the desired protein content (2% (m/V)) prior to fermentation by yogurt starter cultures by partial replacement of cheese whey in reconstituted form with potable water. This may be an alternative way of protein recovery from cheese by-products as well as reducing the production costs since less milk is used in ayran production. On the other hand, the balance between milk caseins and whey proteins is disturbed when cheese whey is added to milk for ayran production, which likely leads to a time-dependent phase separation during cold storage. Modification of ayran matrix by enzymatic crosslinking of proteins may be a solution to overcome this potential physical instability of ayran. This topic has not been explored to date, and the present study was designed to investigate the possibilities of utilization of reconstituted whey powder (RWP) and microbial transglutaminase (MTG) in ayran production.Experimental approachMilk was diluted to obtain 2% protein level using RWP and potable water. The aim of utilization of RWP was to meet 5, 10 or 15% of the protein content of the final product. RWP solutions were obtained by calculating the amounts of whey powder required to meet the specified ratios and mixing it with the water required for dilution. We prepared eight different ayran samples divided in three groups, namely group A: prepared by partially diluting milk with RWP to obtain 5, 10 or 15% of total protein amount in the product, group AMTG: prepared by adding microbial transglutaminase (0.5 U per g of protein) to group A samples, and control group without RWP and with or without the addition of MTG. The gross composition, physical (phase separation and viscosity, chemical (volatile and peptide profiles and SDS-PAGE electrophoresis patterns) and sensory properties of the samples were evaluated throughout 15 days of storage with weekly intervals.Results and conclusionsSince the amounts of whey powder used to obtain RWP were different, dry matter levels of the samples differed. Using RWP in ayran production increased the phase separation slightly. Incorporation of MTG affected the physical properties of the ayran samples positively and prevented phase separation at a satisfactory level. SDS-PAGE electrophoretograms revealed that cross-linking between proteins triggered by MTG formed intense bonds at high molecular mass regions. The remaining parameters were not affected by MTG. Results revealed that the samples with 10% RWP with and without addition of MTG were determined as the formulations with the highest commercialization potential.Novelty and scientific contributionUtilizing RWP in the production of ayran to reduce the protein content of the final product to the desired level is a new approach. Since complete replacement of RWP with potable water to dilute milk to reach 2% (m/V) protein likely leads to lower sensory scores, we have investigated a possibility of partial replacement of RWP with potable water. A time-dependent phase separation is the major challenge of industrial ayran production. This physical problem was largely eliminated by means of MTG-mediated cross-linking of milk proteins. The proposed novel ayran production method offers dairy industry reduction of production costs and contributes to sustainability in milk production since smaller volume of milk is used to reach desired protein content in the final product.

Carbon nanotube enhanced carbon Fibre-Poly(ether ether ketone) interfaces in model hierarchical composites

Poly (ether ether ketone) (PEEK) has a high continuous service temperature, excellent mechanical properties, and good solvent and abrasion resistance, which can be further improved through the addition of carbon nanotubes (CNTs). CNT-PEEK nanocomposites are promising matrices for continuous carbon fibre composites; powder processing can mitigate the high melt viscosities in these systems. In this study, model single fibre (hierarchical) composites were produced by embedding sized and desized carbon fibres in nanocomposite CNT-PEEK powders followed by single fibre pull-out tests to assess interfacial characteristics. Carbon fibre-PEEK interfacial shear strength is typically 40–45 MPa. Increasing CNT loadings increased fibre-matrix interfacial shear strength linearly up to ∼70 MPa at 5.0 wt%, which was attributed to the CNT-based mechanical modification of the PEEK matrix. Apparent interfacial shear strength was inversely correlated with the embedded fibre length irrespective of carbon fibre sizing or CNT loading, indicating brittle fracture of the fibre-matrix interface. Pulled out carbon fibres were still coated with the matrix, which indicated strong adhesion at the interface in all samples, likely related to a transcrystalline region. Adhesion was, however, negatively affected by the presence of epoxy sizings. Frictional shear strength was independent of embedded fibre length and CNT content for all samples.

Synthesis, Structure and Properties of Barium Ferrites BaFe<sub>11</sub>M<sub>1</sub>O19 (M= Al, Ti and Mn) Ceramics

The article shows the results of a research in which barium hexaferrite samples of the BaFe11M1O19 (M= Al, Ti and Mn) composition were obtained by solid-state synthesis. Samples substituted with titanium, aluminum, and manganese were obtained in a tubular furnace at an exposure time of 5 hours at a temperature of 1350°C, the sample, substituted with manganese, it was obtained at a temperature of 1250°C. The chemical composition was controlled using electron microscopy the samples obtained correspond to the initial composition with sufficient accuracy. Hexagonal plates represent the structure of all the obtained samples. According to X-ray phase analysis, all samples are monophasic and have the structure of barium hexaferrite. Using the data of powder X-rays, the parameters of the unit cell of the studied samples were calculated, when iron atoms are substituted by titanium or aluminum or manganese atoms, the crystal lattice is distorted, while its change is not the same for different crystallographic directions. During the doping of barium hexaferrite with titanium, aluminum or manganese atoms, the Curie temperature decreases. This is due to a decrease in the exchange interaction forces during the modification of the barium hexaferrite matrix. The aim of this study was to study the structure and change of the lattice parameters, the Curie temperature, depending on the substitution element.

A glitch in the matrix: organ-specific matrisomes in metastatic niches.

Modification of the extracellular matrix (ECM) is a critical aspect of developing a metastasis-supportive organ niche. Recent work investigating ECM changes that facilitate metastasis has revealed ways in which different metastatic organ niches are similar as well as the distinct characteristics that make them unique. In this review, we present recent findings regarding how ECM modifications support metastasis in four frequent metastatic sites: the lung, liver, bone, and brain. We discuss ways in which these modifications are shared between metastatic organs as well as features specific to each location. We also discuss areas of technical innovation that could be advantageous to future research and areas of inquiry that merit further investigation.

Prednisolone and mesenchymal stem cell preloading protect liver cell migration and mitigate extracellular matrix modification in transplanted decellularized rat liver

IntroductionRegenerative medicine provides promising approaches for treating chronic liver diseases. Previous studies indicate that decellularized liver architecture is damaged by invading non-hepatic inflammatory cells. This study aimed to use anti-inflammatory and regenerative potency of bone marrow-derived mesenchymal stem cells (BM-MSC) and prednisolone for reducing fibrosis and balancing inflammatory cell migration into the decellularized liver scaffold.Material and methodThe liver was decellularized by perfusing Sodium Lauryl Ether Sulfate (SLES), and nuclei depletion and extracellular matrix (ECM) retention were confirmed by DNA quantification, histochemical, and immunohistochemical assessments. Scaffolds were loaded with BM-MSCs, prednisolone, or a combination of both, implanted at the anatomical place in the rat partial hepatectomized and followed up for 2 and 4 weeks.ResultsLabeled-MSCs were traced in the transplanted scaffolds; however, they did not migrate into the intact liver. Immunohistochemistry showed that the hepatoblasts, cholangiocytes, stellate, and oval cells invaded into all the scaffolds. Bile ducts were more abundant in the border of the scaffolds and intact liver. Stereological assessments showed a significant reduction in the number of lymphocytes and neutrophils in prednisolone-loaded scaffolds. The regeneration process and angiogenesis were significantly higher in the group treated with cell/prednisolone-loaded bioscaffolds. Collagen fibers were significantly reduced in the scaffolds pre-treated with cell/prednisolone, prednisolone, or BM-MSCs, compared to the control group.ConclusionLoading prednisolone into the scaffolds can be a worthy approach to restrict inflammation after transplantation. Although pre-loading of the scaffolds with a combination of cells/prednisolone could not alleviate inflammation, it played an important role in regeneration and angiogenesis.

The water uptake, thermal and mechanical properties, and aging resistance to thermo‐oxidation of phenylboronic acid‐modified benzoxazine‐glass fiber composites

AbstractPolybenzoxazines, also known as Benzoxazine (Bz) is one kind of high‐performance thermoset polymers. It manifests several advantages when used for thermal protection applications, such as thermal and dimensional stabilities, low rate of moisture absorption and near zero volatility in curing process. However, benzoxazine shows its drawbacks in terms of curing temperature, char yield at elevated temperature, and resin toughness. Thus, modification of Bz matrix would be essential in order to improve these unfavorable properties. In this study, a facile synthesis of phenylboronic acid‐modified (PBA) benzoxazine (PBz) and glass fibers (GF) composites with varied PBA ratios were prepared. Briefly, GF fabrics were impregnated with each of Bz or PBz/acetone solution and baked to form B‐staged prepregs. Then, the prepregs were stacked, molded and cured in a hot‐pressing machine to form composites. The present study shows the 10 wt% PBA modified‐Bz/GF composite is the optimal formulation as it exhibits minimal water uptake, enhanced char yield, decent thermomechanical stability in terms of glass transition temperature, exceptional interlaminar shear strength (ILSS) and highest flexural strength. Moreover, the PBz 10/GF composite subject to thermo‐oxidative aging still maintains good levels of shear and flexural properties for potential service as thermal protection layer.

BMSCs and Osteoblast-Engineered ECM Synergetically Promotes Osteogenesis and Angiogenesis in an Ectopic Bone Formation Model.

Bone mesenchymal stem cells (BMSCs) have been extensively used in bone tissue engineering because of their potential to differentiate into multiple cells, secrete paracrine factors, and attenuate immune responses. Biomaterials are essential for the residence and activities of BMSCs after implantation in vivo. Recently, extracellular matrix (ECM) modification with a favorable regenerative microenvironment has been demonstrated to be a promising approach for cellular activities and bone regeneration. The aim of the present study was to evaluate the effects of BMSCs combined with cell-engineered ECM scaffolds on osteogenesis and angiogenesis in vivo. The ECM scaffolds were generated by osteoblasts on the small intestinal submucosa (SIS) under treatment with calcium (Ca)-enriched medium and icariin (Ic) after decellularization. In a mouse ectopic bone formation model, the SIS scaffolds were demonstrated to reduce the immune response, and lower the levels of immune cells compared with those in the sham group. Ca/Ic-ECM modification inhibited the degradation of the SIS scaffolds in vivo. The generated Ca/Ic-SIS scaffolds ectopically promoted osteogenesis according to the results of micro-CT and histological staining. Moreover, BMSCs on Ca/Ic-SIS further increased the bone volume percentage (BV/TV) and bone density. Moreover, angiogenesis was also enhanced by the Ca/Ic-SIS scaffolds, resulting in the highest levels of neovascularization according to the data ofCD31 staining. In conclusion, osteoblast-engineered ECM under directional induction is a promising strategy to modify biomaterials for osteogenesis and angiogenesis. BMSCs synergetically improve the properties of ECM constructs, which may contribute to the repair of large bone defects.

Strengthening of ice with basalt materials

Practical approaches to controlling the strength and deformation properties of ice reinforced with basalt materials (rovings, fibres and nets) and/or modified by dopants of various groups are discussed in this paper. To carry out the entire research on the strength and deformation properties, approximately a thousand of ICMs samples were produced and tested. The three-point bending tests of ice beams and the compression tests of ice cylinders were carried out by authors. It was shown that the introduction of basalt rovings significantly improves the strength and deformation properties of freshwater ice. Ice reinforcement modifies the mechanism of cracks propagation and the overall nature of the specimens' failure. The major morphological and topological factors involved in the manufacture process of high strength ice composite materials were revealed. A combination of basalt rovings reinforcement and chemical modification of the ice matrix with dopants increases the strength properties of the tested ICM specimens by 4-6 times compared to freshwater ice samples. Based on collected experimental data the corresponding recommendations on the choice of reinforcement parameters are given dependent on the functional purpose of the ice composites being implemented.

A Modified Method for Beam-Forming Using Covariance Matrix in MIMO Radar System

A MIMO radar provides solution for beamforming, since transmit beampattern synthesis is well proven method for stimulating the antenna array to develop the beampattern. It is close to the desired one which can give minimum error between these two. A covariance matrix in beamforming contains the direction of invariable data and magnitude distribution in multidimensional space which decides the closeness with the desired beampattern. Here, selection of an optimal covariance matrix is constrained optimization problem with minimization of cost function. In high directivity radar systems, the antenna beam is needed to be steered to cover a large area for detection. In this proposed work, minimization of convex function and transmit beampattern synthesis is carried out with modifications of the covariance matrix ‘Rcov’ for minimum and maximum transmission power utilization constraints. The beampattern design problem is reformulated here, as semi-definite programming optimization problem and solved using convex optimization, with MATLAB simulation platform. The results show that the beampattern generated using this modified covariance matrix is optimally close to desired pattern.

A note on neighborhood first Zagreb energy and its significance as a molecular descriptor

The concept of graph spectra can be thought of as an approach to use linear algebra including, in particular, the well developed theory of matrices for unlocking a thousand secrets about graph theory and its applications. A novel neighborhood degree sum based matrix is proposed as a modification of classical adjacency matrix. Using the spectrum of this matrix, a graph energy and its Estrada index are introduced, and their role as a molecular structural descriptor in chemical graph theory is investigated. An algorithm is designed to make the computation of the energy and its Estrada index convenient. The relationship between the recently proposed matrix and its associated graph invariant is studied using the spectral moment. Several sharp bounds for spectral radius, energy, and Estrada index are computed, and the corresponding extremal graphs are characterized. The integral representation of the energy is also reported.

Mechanical properties of carbon fibre reinforced composites modified with star-shaped butyl methacrylate

This article presents the possibility of strength improvement and energy absorption of carbon fibre reinforced polymer composites by matrix modification. In this study, the mechanical properties of bisphenol-A epoxy matrix and carbon fibre reinforced polymer composites were modified with four different wt.% of star-shaped polymer n-butyl methacrylate (P n-BMA) block glycidyl methacrylate (PGMA). The tensile strength of the epoxy with 1 wt.% star-shaped polymer showed 128% increase in comparison to unmodified epoxy samples. Two different wt.% were then used for the modification of carbon fibre-reinforced polymer composite samples. Tensile tests and low-velocity impact tests were conducted for characterising modified samples. Tensile test results performed showed a slight improvement in the tensile strength and modulus of the composite. Low-velocity impact tests showed that addition of 1 wt.% star-shaped polymer additives increase composite energy absorption by 53.85%, compared to pure epoxy composite specimens. Scanning electron microscopy (SEM) analysis of post-impact specimens displays fracture modes and bonding between the matrix and fibre in the composites. These results demonstrate the potential of a novel star-shaped polymer as an additive material for automotive composite parts, where energy absorption is significant.

Experimental investigation of epoxy matrix and pine sawdust reinforced wood-polymer composite materials

Mechanical, thermal, and water absorption properties of the composites have been studied as a function of sawdust content, using different weight percentage. The characteristics properties of the composites were studied using differential scanning calorimetry and Fourier-transform infrared spectroscopy. Field emission scanning electron microscopy was used to understand the interfacial bonding. The obtained results showed that the 15 wt% composites exhibited the highest tensile strength (7.5 MPa) and flexural strength (8.9 MPa) compared with the 5 wt%, 30 wt%, 40 wt%, and 50 wt% composites. A good interfacial combination was formed between 15 wt% of sawdust and epoxy resin. In terms of the tensile and flexural strength, the differential scanning calorimetry analysis confirmed that matrix modification could improve the mechanical properties and thermal stability of the composites compared to neat resin. The Fourier-transform infrared spectroscopy spectrum showed the presence of functional groups pertaining to composites. The absorption data of the composite showed that the water uptake increased as the amount of sawdust in the composite increased. The 5 wt%, 15 wt%, 30 wt%, and 40 wt% sawdust composites also displayed less water absorption behavior (1.534%, 1.871%, 2.492%, and 4.127%, respectively) compared to the 50 wt% composite.

Micro/nano multiscale reinforcing strategies toward extreme high-temperature applications: Take carbon/carbon composites and their coatings as the examples

Carbon fiber reinforced carbon composites (C/Cs), are the most promising high-temperature materials and could be widely applied in aerospace and nucleation fields, owing to their superior performances. However, C/Cs are very susceptible to destructive oxidation and thus fail at elevated temperatures. Though matrix modification and coating technologies with Si-based and ultra-high temperature ceramics (UHTCs) are valid to enhance the oxidation/ablation resistance of C/Cs, it's not sufficient to satisfy the increasing practical applications, due to the inherent brittleness of ceramics, mismatch issues between coatings and C/C substrates, and the fact that carbonaceous matrices are easily prone to high-temperature oxidation. To effectively solve the aforementioned problems, micro/nano multiscale reinforcing strategies have been developed for C/Cs and/or the coatings over the past two decades, to fabricate C/Cs with high strength and excellent high-temperature stability. This review is to systematically summarize the most recent major and important advancements in some micro/nano multiscale strategies, including nanoparticles, nanowires, carbon nanotubes/fibers, whiskers, graphene, ceramic fibers and hybrid micro/nano structures, for C/Cs and/or the coatings, to achieve high-temperature oxidation/ablation-resistant C/Cs. Finally, this review is concluded with an outlook of major unsolved problems, challenges to be met and future research advice for C/Cs with excellent comprehensive mechanical-thermal performance. It's hoped that a better understanding of this review will be of high scientific and industrial interest, since it provides unusual and feasible new ideas to develop potential and practical C/Cs with improved high-temperature mechanical and oxidation/ablation-resistant properties.