Fiber Porosity Research Articles

Performance of Bamboo Bark Fiber Asphalt Mortar Modified with Surface-Grafted Nano-SiO2

In this study, the feasibility of using bamboo bark fibers as modifiers to enhance asphalt mortar performance was investigated. Bamboo bark fibers were modified with NaOH, KH570 silane coupling agent, and nano-SiO2, and their preparation methods were established. The modified fibers were assessed for their oil absorption, thermal stability, and hydrophobicity. The asphalt mortar was evaluated for three key indicators: rutting resistance, deformation resistance, and durability at high temperatures. The microscopic morphology and modification mechanisms of the fibers were also studied. The results showed that modification with NaOH increased fiber porosity and surface roughness, while KH570 and its hydrolysis products enabled nano-SiO2 grafting onto the fibers, improving their adsorption to asphalt. The NaOH-KH570-nano-SiO2 ternary-composite-modified bamboo bark fiber (NKSBF) demonstrated superior hydrophobicity, oil absorption, and thermal stability at the asphalt mixing temperature. Among the modified fibers, asphalt mortar containing 3% NKSBF showed the best performance based on three key indicators, increased the shear strength by 96.4% and the softening point by 7.1% compared to the base asphalt, and increased the ductility by 1% compared to lignin fiber asphalt mortar. The incorporation of 3% bamboo bark fibers improved the rutting resistance, deformation resistance, and durability of short-term-aged asphalt mortar, with NKSBF showing the most significant improvement.

NaCl aerosol filtration over filter media with intrafiber porosity: can filtrate capacity be increased by wicking into this pore volume?

This paper investigates a novel fiber-based filter media wherein a NaCl filtrate is collected and reservoired not only onto the surfaces of the fibers and within their inter-fiber voidage but also within the internal porosity of high pore volume nanoporous fibers or vapor grown carbon nanofibers (VGCF) floc used to fabricate the media. This transport process is shown to occur through a NaCl dissolution into the water-filled nanopores of the fiber and a subsequent intra-fiber wicking phenomenon. The study further elucidates two distinct NaCl accommodation mechanisms which are uniquely available to filter media containing nanoporous intrafiber porosity: (1) wicking and capillary condensation of liquid NaCl aerosols directly into the intrafiber pores at high RH, and (2) dissolution of otherwise solid NaCl aerosols deposited onto fiber surfaces (at low RH) into the interior nanopores of the fiber because these pores (when hydrophilic) are saturated with water (even at low RH). To investigate these two mechanistic regimes, various media were fabricated possessing multiscale porosity in the form of: (i) embedded flocs of VGCFs (4.108 cm3gm-1pore volume), (ii) hydrophilic and high pore volume activated carbon fibers (ACFs, 0.950 cm3gm-1) and (iii) solid graphite fibers. These media were then comparatively evaluated toward NaCl aerosol filtration at different relative humidities. Pressure drop measurements versus filtrate accumulation and SEM-EDAX VGCF demonstrated the location and transport of NaCl into the intrafiber voidage. Media containing both VGCF floc and ACF accumulated 1200% more NaCl at low RH (and a specified pressure drop) than similar media prepared from non-porous graphite fibers, with an additional 315% increase from low to high RH. A Gibbs free energy driving force model is provided to illustrate the driving forces favoring water condensation into the nanopores and solid NaCl aerosol dissolution into the water phase. Filtration efficiency and quality factor assessments for the various media are also systematically evaluated to demonstrate the observed mechanistics.

Mechanical property enhancement of flax fibers via supercritical fluid treatment

The desire for lightweight, carbon-negative materials has been increasing in recent years, particularly as the transportation sector reduces its global carbon footprint. Natural fibers, such as flax fiber and their composites, offer a compelling combination of properties including low density, high specific strength, and carbon negativity. However, because of the low modulus and high variability in performance, natural fibers can’t compete with glass fibers as structural reinforcements in polymer composites. In this study, flax technical fibers were treated in supercritical CO2 (scCO2), and the effects of this treatment on the morphology and properties of flax fibers are reported. Treatment in scCO2 successfully resulted in higher fiber modulus and strength by 33% and 40%, respectively. Fiber porosity was reduced by 50% and morphological changes to the fibers were observed. Specifically, fiber lumen collapsed during treatment and micro/mesoporosity was reduced by 27%. Treated flax fibers were used to create 30 vol% unidirectional flax-epoxy composites. ScCO2 treatment raised composite modulus and strength by 33% and 25%, respectively. Because of the dependence between technical fiber size and mechanical properties, the relationship between fiber modulus and fiber size were created and applied to the rule-of-mixtures. This relationship were found to be viable representations of the fiber performance within each composite. Overall, the treatment developed in this study has the potential to significantly improve natural fiber properties, enabling their consideration for use in lightweight, semi-structural composites.

Study on the performance of heat and mass transfer of moisture-conducting fibers for evaporative cooling

Moisture-conductive fibers exhibit potential to serve as evaporative medium in evaporative cooling systems. Their heat and mass transfer performance significantly influences the energy efficiency of evaporative cooling systems. This study evaluated the heat and mass transfer characteristics of moisture-conducting fibers through numerical simulation based on experimental validation. The experimental systems and numerical model with moisture-conducting fibers were developed. The microstructural parameters (porosity and permeability) of fibers were determined according to experimental data and theoretical analysis. The accuracy of parameters and model was verified by experiment. The differences in heat and mass transfer performance of various types of fibers and the effects of ambient air parameters (temperature, relative humidity and flow rate) on the heat and moisture transfer characteristics of fibers were investigated through simulation. The results indicated that the Coolmax fiber had superior heat and mass transfer performance compared to Coolpass, cellulose/PET and polyester fibers. The evaporative cooling efficiency between air and fibers was facilitated by increasing air temperature, decreasing air relative humidity and reducing air flow rate under other conditions unchanged. The results are beneficial to the optimization of the evaporative cooling medium and provide theoretical guidance for the selection of fibers for evaporative cooling.

Revealing pore size distribution in cellulose and lignin-cellulose man-made fibers – effect of draw ratio and lignin content

There are limited methods available for measurement of the porosity of cellulose fibers, even more so for obtaining a pore size distribution. Conventional pore analysis methods require dry samples, with intact pores. However, pores in cellulose fibers collapse when dried from water and thus present a challenge for sample analysis. Furthermore, the pore collapse is partially irreversible which should be accounted for in the analysis. In this study, analysis of pore structure was carried out in the wet state with thermoporometry and also for critical point dried samples, analyzed with N2 sorption. This study determines the effect of fiber lignin content and certain spinning parameters on the pore size distribution of spun fibers before and after drying. It could also be concluded that solvent exchange, drying from a non-polar solvent will result in an altered pore size distribution, with a total pore volume greater than if dried from water, however not representative of the never-dried state. It is concluded that thermoporometry together with the water retention value (WRV) measurement is a powerful combination to acquire insights to the pore size distribution of spun fiber.

The Characterization of Structures and Porosity of Abaca Fiber

Abstract Abaca fiber is one of the superior natural fibers in Indonesia. This fiber is also exported abroad as raw material for banknotes. Abaca fiber has superior mechanical properties including tensile strength and Young’s modulus test values. In this research, a more detailed characterization of abaca fiber has been carried out based on XRD, Gravimetry, SEM and BET analysis (Brunauer-Emmett-Teller). XRD characterization showed a relationship curve between intensity and 2θ resembling a cellulose curve. While gravimetric testing revealed three main components of abaca fibers in succession; cellulose 72.25%, hemicellulose 8.56% and lignin 8.69%. This high cellulose component caused abaca fiber to have high mechanical capabilities. BET analysis presented that abaca fiber has a Surface area 28.63 m2g−1, pore volume 0.09 ccg−1, and average pore size 4.94 nm. From the results of the analysis obtained proved that abaca fiber can be used as an alternative reinforcer in composite materials that can be applied as building materials (concrete) and acoustic materials (absorbers). In addition, abaca fiber is a natural fiber that is easily cultivated in Indonesia which is environmentally friendly and able to increase local wisdom if used scientifically.

Hierarchically porous electrospun carbon nanofiber for high-rate capacitive deionization electrodes

Capacitive deionization (CDI) is a promising technology that has gained interest for the desalination of brackish water. Hierarchically porous carbons are commonly used as electrodes for CDI due to their high surface areas and controlled pore size distributions that maximize ion adsorption capacity and rate. Electrospinning is an effective way of generating carbon nanofibers with high inter-fiber macroporosity that can be further modified to improve surface area, total pore volume, and pore size distribution. This work describes the use of sacrificial mesopore formers in tandem with a micropore etching technique to induce hierarchical porosity in electrospun fibers. Mesopores are formed via the dissolution of silica nanoparticles that are introduced into the fibers during the electrospinning step. After mesopore formation, micropores are etched into the resulting surface through KOH impregnation and thermal activation. This sequential technique creates a hierarchical network of pores from the inherent macroporosity of the fiber network, to the mesopores, and finally micropores to simultaneously maximize surface area and accessibility. Micropore formation is optimized to maximize specific surface area while maintaining physical integrity of the fibers. The combination of mesopores and micropores enables fast ion adsorption rates and capacity. Carbon fiber electrodes fabricated in this method achieve specific surface areas exceeding 1400 m2 g−1, with pore volumes exceeding 1.0 cc g−1. The pore size distributions are highly controlled, with 80 % of total pore volume coming from pores <20 nm in radius. In 500 ppm constant voltage CDI tests, these fiber electrodes obtain a salt adsorption capacity of over 14 mg g−1 at a salt adsorption rate of ∼4 mg g−1 min−1, showcasing the high capacity matched with high rate of these easily fabricated, inexpensive materials.

An efficient fabrication method of lightweight aramid nanofibrous aerogels for high-efficient sound absorption and thermal properties

The aramid nanofibrous aerogels (ANFs) have various application prospects due to their ultra-light, high porosity and excellent properties of aramid fibers. However, the preparation of ANFs requires long preparation time and their ultra-dense pore structure leads to poor sound penetration and high sound energy reflectivity, which ultimately makes the overall sound absorption performance of ANFs poor. Therefore, a strategy for synthesis of ANFs is designed to achieve light weight, excellent thermal insulation performance and significantly improve sound absorption properties. This strategy combines cell pulverizing, pump-filtration molding, and directional freezing to ensure structural strength of the aerogel without the addition of cross-linking agents, and this process enables the ANFs to introduce in macro-pores while keeping nano-pores. The structure of multi-layered pores effectively reduces the reflectivity of incident acoustic energy and improves the sound absorption coefficient. The interconnected macro-pores and interlaced small pores of ANFs provide good sound absorption performance (sound absorption average (SAA) = 0.338), excellent flame retardant and thermal insulation properties (thermal conductivity = 0.0635 W (m*K)−1) with ultralight (density = 40.5 mg cm−3) in a thinner thickness (15 mm), which extend the potential of ANFs in areas of noise control and thermal insulation. In addition, the structure of multi-scaled pores can also be formed inside other aerogels by using the method of cell pulverization and filtration preparation, which can be helpful for improving their properties of thermal insulation and sound absorption.

Functional properties and optimization of dietary fiber concentrate from sago hampas using response surface methodology

Sago hampas, whose major components are fiber and starch, is an underutilized by-product generated from starch extraction of sago stems. In order to increase its added value and applications, sago hampas could be developed into dietary fiber concentrate. This research purposed to obtain the optimum condition of enzymatic hydrolysis process of sago hampas to isolate the dietary fiber components. A central composite design of response surface methodology (RSM) was used to optimize processing variables, namely, sago hampas slurry concentration (0.1–0.2 kg/kg), reaction time (45–135 min), and enzyme concentration in the substrate (10–35 mL/kg). Enzymatic hydrolysis using α-amylase at 108 °C was employed to remove starch components (becoming maltodextrin), escalate dietary fiber content, and modify the crystallinity of fiber. The goals of optimization were to maximize total dietary fiber (TDF), water-holding capacity (WHC), and oil-holding capacity (OHC) of the dietary fiber concentrate and to maximize dextrose equivalent (DE) of the maltodextrin solution obtained. The optimum process condition was found when the variables sago hampas slurry concentration, reaction time, and enzyme concentration were 0.14 kg/kg, 121 min, and 25 mL/kg, respectively. The optimal condition was verified by laboratory experiment resulting in TDF, WHC, OHC, and DE of 92.98 %, 26.34 g of water per g of sample, 5.64 g of oil per g of sample, and 10.37 %, respectively. TDF increased while the starch decreased significantly following conversion to dietary fiber. It is associated with the improvement in the functional properties of dietary fiber. The OHC, cation exchange capacity, emulsifying activity, swelling capacity, and solubility all exhibited significant increases. The morphological structure of the dietary fiber concentrate revealed a fiber matrix degradation with a high level of fiber porosity while the crystallinity was decreased from 61 % to 42 %. The properties of dietary fiber concentrate indicate appropriate parameters for food industry applications.

Polymer composites with short recycled glass fibres manufactured by vacuum infusion

Recycling glass fibre reinforced thermoset composites remains a challenge despite years of research in the field. Among the barriers for a successful recycling, the properties of the recycled materials and their application in new products represent the main ones. With a pyrolysis recycling process, clean glass fibres can be extracted and separated from the polymer matrix. In this paper, recycled glass fibres are incorporated in a new polymer composite structure using both virgin and recycled glass fibres. Recycled glass fibres have a Young’s modulus comparable to virgin glass fibres. The objective is to identify a composite lay-up using virgin and recycled glass fibres, and where the Young’s modulus of recycled fibres is beneficial for the resulting composites mechanical properties. To do so, a sandwich structure composite with virgin fibres on the outer layer and recycled fibres in the inside is designed and manufactured. In order to produce flat panels despite the short and random fibres, a manufacturing procedure ensuring a good dispersion of the fibres and controlling the thickness of the panel is developed. Panels are produced incorporating two different weight fraction of recycled glass fibres. The quality of the panels are characterized using microstructure observations, fibre porosity analysis and mechanical testing. Results shows that the sandwich composites have a low porosity content and achieves higher bending stiffness than a composite only made of unidirectional virgin glass fibres.

Flammability and morphology of Agel leaf fibre- epoxy composite modified with carbon powder for fishing boat applications

Fibre Reinforced Polymer Composites have been extensively developed to construct fishing vessels. This study reports on the successful development of the Agel Leaf Fibre (ALF)-Epoxy composite reinforced with carbon powder and fabricated using the Vacuum Infusion method.The composites were prepared by varying the carbon powder filler content at volumes of 0%, 10%, and 30%. The fire resistance of the composites was investigated using a burning test according to ASTM D-3014 standards. The morphology of the composites was observed through SEM analysis and analysed using ImageJ software.The research findings reveal that adding 30% carbon powder in the HCP composite reduced the burning rate by 42.624 mm/sec and the time to ignition by 17.33 seconds, indicating improved fire resistance properties. The carbon powder inhibited flame propagation and reduced the combustion rate by 0.49%. The SEM examination confirmed that the fibre porosity decreased, resulting in a denser composite with enhanced fibre-matrix adhesion. Therefore, the implementation of fire-resistant composite materials in fishing vessel construction can be realised.The present study primarily examined the immediate effects of carbon powder additions on the morphology of the composites. However, it is crucial to consider these composites’ long-term stability and durability. Future research should investigate the ageing behaviour, considering environmental factors such as humidity, temperature, and UV radiation, to assess their impact on the morphology and flammability resistance of the composites. Additionally, it is essential to acknowledge that other factors, including fibre orientation, fibre length, and matrix properties, can significantly influence the overall performance of the composites.The enhanced flammability resistance of Agel Leaf Fibre-Epoxy composites with carbon powder additions holds significant benefits for fishing boat applications. In marine environments, the risk of fire incidents on fishing boats is high, making materials with good fire resistance highly desirable. Therefore, implementing fire-resistant composite materials in fishing boat construction can be realised to reduce the risk of fire incidents in high-seas fishing vessels.Composites with added carbon powder exhibited smaller flames, slower burning rates, and a lack of significant flame propagation. This suggests that adding carbon powder acts as an oxygen barrier and reduces the availability of fuel within the composite.

Degradation of petroleum hydrocarbon pollutants by a superhydrophobic/superoleophilic microbial immobilized core-shell bioreactor

Efficient elimination of petroleum hydrocarbon pollution from the environments has received extensive attention due to its severe environmental hazards. Herein, we designed and fabricated a composite bioreactor capable of rapidly and selectively adsorbing petroleum hydrocarbons, specifically diesel, followed by microbial degradation to treat oily wastewater simply and efficiently. Briefly, the bioreactor was prepared using a three-dimensional superhydrophobic/superoleophilic stainless steel mesh as the shell and mixed microbial immobilized kapok fibers as core. By a simple surface modification, the surface water contact angle of the composite bioreactor reaches up to 155°. The high-speed camera's super lipophilic description enables most of the diesel oil to be absorbed within 21 ms. The porosity of the reactor's super hydrophilic kapok fibers aerogel can reach 89%. After immobilized mixed microorganisms, the number of microorganisms increased within 48 h in a favorable environment. The internal space of the reactor shows positive biocompatibility. Afterward, the experimental results of adsorption and degradation for diesel oil show that the degradation rate can reach more than 90% after 204 h, which is about 40% higher than that of the free mixed microorganisms. Compared with the simple method of embedding microorganisms in aerogel, a new core-shell structure microbial reactor is constructed in this paper, which can effectively avoid the risk of microbial leakage and achieve the goal of biodegradation while absorbing oily wastewater. It has constructed a more stable and effective protection space for the continuous degradation of oiling wastewater, while effectively protecting microorganisms from harsh environment, thus showing great potential in various applications such as eliminating organic pollution, oil removal, and wastewater purification.

Effect of enzymatic treatment on Eucalyptus globulus vessels passivation

Hardwood vessel elements generate problems in industrial uncoated wood-free printing paper operation, causing vessel picking and ink refusal. These problems are mitigated using mechanical refining at the cost of paper quality. Vessel enzymatic passivation, altering its adhesion to the fiber network and reducing its hydrophobicity is a way of improving paper quality. The object of this paper is to study how the enzymatic treatment by xylanase and by an enzymatic cocktail containing cellulases and laccases affect elemental chlorine free bleached Eucalyptus globulus vessel and fiber porosities, bulk, and surface chemical compositions. Thermoporosimetry revealed the vessel structure to be more porous, surface analysis showed its lower O/C ratio and bulk chemistry analysis its higher hemicellulose content. Enzymes had different effects on porosity, bulk and surface composition of fibers and vessels, affecting vessel adhesion and hydrophobicity. Vessel picking count decreased 76% for papers containing vessels treated with xylanase and 94% for the papers with vessels treated with the enzymatic cocktail. Fiber sheet samples had lower water contact angle (54.1º) than vessels rich sheets (63.7º), that reduced with xylanase (62.1º) and cocktail (58.4º). It is proposed that differences in vessel and fiber porosity structures affect the enzymatic attacks, eventually causing vessel passivation.

Apparent thermal conductivity of PAN-based carbon fibre tow based on infrared thermography measurements

Currently, the apparent thermal conductivity of carbon fibre (CF) is measured using contact- and noncontact-type thermal conductivity methods. The contact-type method exhibits measurement non-uniformity in the CF thickness direction that does not allow uniform sampling; the error occurrence rate is known to be high. Meanwhile, in the noncontact-type method, the fibre porosity and tow gap results in a lower accuracy and similarly high error occurrence rate. Therefore, this study aims to provide a quantitative method of measuring the thermal conductivity of polyacrylonitrile (PAN)-based 12 K CF tows with a filament diameter of 7 µm using Fourier’s law of conduction and a thermal imaging camera. This method is expected to overcome the limitations of the conventional contact- and noncontact-type techniques. Using the proposed method, the average thermal conductivity of the PAN-based 12 K CF tow was measured to be approximately 21.28 W/m·K.

Integrating built-in fine alloying FeNi3 in carbon nanofiber reinforcing intermetallic synergy for PMS activation to degrade Bisphenol A

Heterogeneous peroxymonosulfate (PMS) activation for the mineralization of pollutants has attracted growing attention, while alloying bimetal catalysts afford big promises in synergetic catalysis. Here, by an alteration of electrospun precursor, one-dimensional carbon nanofiber (CNF) integrated with Prussian blue analogs (PBA)-derived alloyed fine plasmonic FeNi3 hybrid catalyst (FeNi3@CNF) was constructed by electrospinning technique with subsequent confinement calcination. The amount of PBA in fiber precursor and thermal treatment temperature were alternatively adjusted to control the distribution and concentration of alloyed FeNi3 in carbon nanofiber. This unique structure combines the advantages of abundant internal porosity of N-doping carbon fiber and uniforms active FeNi3 alloys with highly-exposed reactive sites, facilitating the electron transport and proximity of reactant molecules in catalytic oxidation. The synergistic and interfacial effect of optimal FeNi3@CNF endowed the ultra-fast degradation activity against bisphenol A (BPA) through rapid persulphate activation to generate four reactive active species. Specifically, 20 mg L−1 of BPA was completely degraded within 4 min with a reaction rate constant of 2.736 min−1. Impressively, by innovating the utilization of the Prussian blue precursor in electrospinning, the optimal FeNi3@CNF shows 18.5, 101.3, and 248.5 times activity enhancement in BPA degradation compared to that of Fe@CNF, Ni@CNF, and Fe&Ni@CNF, revealing the appreciable synergy of bimetallic alloys in PMS activation. In addition, the improved catalytic performance of FeNi3@CNF under light irradiation was also simulated, confirming that the enhanced photothermal conversion ability of plasmonic alloys and carbon fiber advance the degradation of BPA.

Efficient cathode for the hydrogen evolution reaction in alkaline membrane water electrolysis based on NiCoP embedded in carbon fibres

Porous carbon nano/microfibres (PCFs) modified by NiCoP nanoparticles (NiCoP/CF) were tested as gas diffusion cathodes in a zero-gap alkaline water electrolyser. Two types of precursors were used for the preparation of carbon fibres by needle-less spinning: polyacrylonitrile (PAN) and a combination of PAN and polyvinylpyrrolidone (PVP). The influence of the selected precursors on the morphology, porosity, and surface area of the carbon fibres was examined. Both samples NiCoP/CF_PAN and NiCoP/CF_PAN-PVP were characterised by means of (i) structural and phase composition, (ii) catalytic activity for the hydrogen evolution reaction (HER), and (iii) performance and stability under membrane alkaline water electrolysis (MAWE) conditions. The more porous, yet stable fibres of the NiCoP/CF_PAN outperformed the NiCoP/CF_PAN-PVP cathode. Nevertheless, both cathodes achieved high activity comparable to the Ni electrode modified by Pt/C catalyst, as well as exceptional stability for long-term intermittent electrolysis under MAWE conditions.

Effect of heat‐treatment on compressive response of 3D printed continuous carbon fiber reinforced composites under different loading directions

AbstractThis paper investigated the effects of heat‐treatment and loading directions on compressive properties of 3D printed continuous carbon fiber reinforced composites (CCFRC). After heat‐treatment at different conditions, specimens with different stacking sequences were compressed under different loading directions. The effect of heat‐treatment on the porosity and crystallinity of composites was investigated. The porosity of short carbon fiber reinforced composites decreased but that of CCFRC increased after heat‐treatment at 200°C. The compressive properties of specimens were investigated in combination with changes in porosity and crystallinity. It was found that the compressive properties of composites usually increased with decreasing porosity induced by heat‐treatment. While the fiber direction was parallel to the applied loading direction, the yield strength of C‐CCFRC and S‐CCFRC increased from 208.1 to 281.6 MPa and from 218.5 to 264.4 MPa, respectively, though the porosity increased. After heat‐treatment at 100°C for 4 h, the crack initiation of CCFRCs was delayed during compressive tests. Besides, heat‐treatment could change failure modes of CCFRC after heat‐treatment at 200°C for 4 h. More specifically, heat‐treatment at 200°C for 4 h could result in delamination and a decrease in energy absorption of C‐CCFRC (from 7.23 to 4.05 J).

Protein Carbonylation as a Reliable Read-Out of Urban Pollution Damage/Protection of Hair Fibers

(1) Background: Environmental factors, such as airborne pollutants and solar UV, induce oxidative damage to proteins and lipids on hair fibers, leading to decreased hair strength and shine, increased fiber porosity, brittleness, dryness, and stiffness. Traditional methods used for hair damage/protection/reparation assessment show limitations in sensitivity or specificity for evidencing the benefits to be gained from the protection/reparation of hair fibers against environmental stressors. (2) Methods: Ex vivo experimental models of hair fibers exposed to urban pollutants and UV irradiation were developed. Targeted proteomics approaches for the quantification of oxidatively damaged (carbonylated) proteins on hair fibers were optimized. (3) Results: A significant dose-dependent increase in carbonylation both in the cuticle and cortex proteins was observed upon exposure of hair fibers to particulate matter and UV-A radiation, at daily stress equivalent doses. Increased protein carbonylation on keratins and keratin-associated proteins led to loss of hair fiber structural integrity. The oxidative modification of proteins induced by urban pollution exposure led to hair cuticle structural damage revealed by an increased permeability. However, protein carbonylation was prevented in the presence of antioxidant compounds. (4) Conclusions: Protein carbonylation is an early event in hair fiber damage which can be used as a reliable biomarker for the efficacy of hair care interventions against environmental stressors.

Theoretical Study of the Effect of Fibre Porosity on the Heat Conductivity of Reinforced Gypsum Composite Material.

In recent years, there has been an increasing demand for engineering materials that possess good mechanical and thermal properties and are cheap an d environmentally friendly. From an industrial and academic point of view, there is a need to study the heat conductivity of newly developed polymer composites and the influence of porosity on the insulation performance of polymer composites. Experimental and theoretical studies were conducted on mainly sisal/glass fibre gypsum composites with different fibre volumes (0, 20, 25, 30, and 35 wt.%). The outcomes from the theoretical model in ANSYS have shown that there is a high possibility to simulate the experimental work and high accuracy for reflecting the experimental findings. Moreover, the results show that natural fibre polymer composites with a high-volume fraction of natural fibres have higher insulation performance than synthetic polymer composites with the same volume fraction of synthetic fibres. Furthermore, the results suggest and support that the improved performance of natural fibre-based composites was due at least in part to the internal porosity of the fibres.

Graphene-coated alumina nano/microfibers as filler for composites

The present work is focused on the preparation and characterization of composite nano/microfibers based on alumina applicable as fillers in ceramic-matrix composites. The graphene-coated Al2O3 microfibers have been prepared in the form of continuous alumina/graphene fibers from electrospun precursors using needle-less electrospinning, calcination, and catalyst-free chemical vapor deposition of graphene layers on the surface of the microfibers. The phase composition and morphology of the composite fibers were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning, and transmission electron microscopy (SEM and TEM). The porosity of the final fibers was evaluated by low-temperature nitrogen adsorption. The surface microstructures of composite fibers were rough and their diameters were in the range from 300 nm to 2 μm. The phase transformation at 1100 °C led to the formation of a mixture of γ-, δ-, and α-Al2O3. TEM results confirmed that the alumina fibers were covered by the 3–4 layers of graphene-based structure. The specific surface area of pure alumina fibers after carbon deposition slightly increased from the initial 40 m2/g to 45 m2/g, due to a slightly wavy surface of graphene layers. Raman spectroscopy and XPS analysis results showed that the surface layer of fibers is formed as graphene oxide. Between the graphene oxide and alumina grains a chemical bonding C–O–Al, C–O–O–Al was discovered as the nucleation of the graphene oxide sheet. The growth mechanism of graphene oxide layers on the surface edges of Al2O3 grains was described.