Nanowhiskers Research Articles

Waste electric porcelain-based refractory bricks with significantly enhanced mechanical properties: preparation, characterization and mechanism

Using waste electric porcelain to produce refractory bricks is a viable technology. However, these bricks currently have lower mechanical strength compared to those made from mineral raw materials. This study optimized the proportions and sintering process to develop high-strength refractory bricks from waste electric porcelain. The impact of physical phase, crystallinity, sintering temperature, and fly ash content on the bricks properties was examined. The research found that low crystallinity in waste electric porcelain leads to disorganized growth of mullite nano whiskers at high temperatures, reducing mechanical strength due to insufficient support structures and stress concentration zones. The addition of fly ash promotes the formation of uniformly dispersed mullite columns through non-uniform nucleation, significantly improving mechanical properties by creating a collective tetrahedral structure. Bricks with 20 wt% fly ash sintered at 1440 °C achieved a flexural strength of 77.3 MPa, a compressive strength of 156 MPa, and an apparent porosity of 10.89%. High-temperature simulations indicate that these bricks exhibit good compressive strength and deformation resistance, with no adhesion observed. These high strength refractory bricks have promising potential for use in various high-temperature applications, including kiln linings, high-temperature flue, high-temperature support components and other industrial processes where durability and thermal stability are critical.

Biopolymers and their Nanocomposites: Current Status and Future Prospects

Abstract: For many years, petroleum-based polymers have been successfully enhanced by the addition of nanoparticles as additives. Carbon nanotubes, graphene, nanoclays, 2-D layered materials, and cellulose nano whiskers are a few of the several nanoreinforcements that are currently being researched. In comparison to unmodified polymer resin, the use of these nanofillers with bio-based polymers could improve a wide range of physical properties, including barrier, flame resistance, thermal stability, solvent uptake, and rate of biodegradability. This nano-reinforcement is a very appealing method to create new functional biomaterials for a variety of applications because these enhancements are typically achieved at minimal filler content.

Preparation and characterization of porous reaction bonded silicon nitride by paraffin emulsified suspension

Porous Si3N4 ceramics with an interconnected pore structure were prepared by a paraffin emulsified suspension method. The effects of the volume ratio of paraffin to silicon and Y2O3 addition on the structure and properties of porous Si3N4 were studied. Uniform dispersed pores introduced by the emulsified paraffine droplets can be observed in the green samples. With the increase of the volume ratio of paraffin to silicon, the bulk density and the strength of the sample were decreased, and the apparent porosity and Darcy permeability were increased. The formation of α-Si3N4 whiskers could be promoted by the addition of the Y2O3 during the nitriding process, and numerous nano whiskers could be obtained in the pores left by the paraffine droplets with suitable addition of the Y2O3. The porous Si3N4 with interconnected whiskers prepared via the paraffin emulsion method exhibited potential application for hot gas particular matter filtration.

Exploring the antibacterial and dermatitis-mitigating properties of chicken egg white-synthesized zinc oxide nano whiskers.

Zinc oxide nanoparticles (ZnO-NPs) have garnered considerable interest in biomedical research primarily owing to their prospective therapeutic implications in combatting pathogenic diseases and microbial infections. The primary objective of this study was to examine the biosynthesis of zinc oxide nanowhiskers (ZnO-NWs) using chicken egg white (albumin) as a bio-template. Furthermore, this study aimed to explore the potential biomedical applications of ZnO NWs in the context of infectious diseases. The NWs synthesized through biological processes were observed using electron microscopy, which allowed for detailed examination of their characteristics. The results of these investigations indicated that the NWs exhibited a size distribution ranging from approximately 10 to 100 nm. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) mapping analyses successfully corroborated the size, dimensions, and presence of biological constituents during their formation. In this study, XTT assay and confocal imaging were employed to provide evidence of the efficacy of ZnO-NWs in the eradication of bacterial biofilms. The target bacterial strains were Staphylococcus aureus and Escherichia coli. Furthermore, we sought to address pertinent concerns regarding the biocompatibility of the ZnO-NWs. This was achieved through comprehensive evaluation of the absence of cytotoxicity in normal HEK-293T and erythrocytes. The findings of this investigation unequivocally confirmed the biocompatibility of the ZnO-NWs. The biosynthesized ZnO-NWs demonstrated a noteworthy capacity to mitigate the dermatitis-induced consequences induced by Staphylococcus aureus in murine models after a therapeutic intervention lasting for one week. This study presents a comprehensive examination of the biosynthesis of zinc oxide nanowhiskers (ZnO-NWs) derived from chicken egg whites. These findings highlight the considerable potential of biosynthesized ZnO-NWs as a viable option for the development of therapeutic agents targeting infectious diseases. The antibacterial efficacy of ZnO-NWs against both susceptible and antibiotic-resistant bacterial strains, as well as their ability to eradicate biofilms, suggests their promising role in combating infectious diseases. Furthermore, the confirmed biocompatibility of ZnO-NWs opens avenues for their safe use in biomedical applications. Overall, this research underscores the therapeutic promise of ZnO-NWs and their potential significance in future biomedical advancements.

AgNP anchored carbon dots and chitin nanowhisker embedded soy protein isolate films with freshness preservation for active packaging

Biodegradable substitutes to the commonly practiced packaging materials are always in high demand. Active biopolymer film was obtained from soy-protein isolate (SPI) and the antibacterial properties were introduced by incorporating silver nanoparticles. Active bio-composite films incorporating silver nanoparticles (AgNP) are much sought after in the food packaging industry owing to their ability to extend the shelf life of fresh foods. But the toxicity of the ingredients used for preparation (mainly the reducing agents) and the poor stability limits their usage for the aforementioned application. Herein, to counter these limitations, we have adopted an environment-friendly method where carbon dot (CD) prepared from soy protein isolate was used to prepare AgNPs. AgNPs (1% wt.) and different concentrations of chitin nano whisker (CNW) (2–10% wt.) were added to soy protein isolate to fabricate nanocomposite films. The subsequent effect on the latter’s tensile property, moisture content, thermal property and morphological characteristics were noted. Here, for the first time, the steam explosion technique was used for the preparation of CNW which resulted in highly crystalline CNW with good antibacterial properties. It was observed that the mechanical strength and thermal stability of SPI film were significantly increased and the moisture content decreased with the addition of CNW and AgNP. The synergistic effect of AgNP and CNW imparted excellent antioxidant, antibacterial and antifungal properties to the SPI film thus enabling the SPI film to extend the shelf life of the food material that was packed using the same. Commercial production of such SPI films would revolutionize the food packing industry given its health benefits and its cost-effectiveness.

Coupled continuum and network model framework to study catalyst layers of polymer electrolyte fuel cells

The nanostructured thin film (NSTF) catalyst layers which have demonstrated high power densities, mass activities, and exceptional metal and support stability can have limited operational robustness due to their thin thickness and the hydrophilicity of the metal-coated nano whiskers. The dispersed nanostructured thin film (dNSTF) catalyst layers have been developed by dispersing the NSTF Pt whiskers with ionomer and carbon support to increase the thickness and hydrophobicity. Continuum and network models (NM) are coupled through boundary conditions to study the polymer electrolyte fuel cell with a dNSTF cathode catalyst layer. The coupled model combines the computational efficiency of the continuum model with the pore-scale information in the dNSTF cathode catalyst layer of the NM. It captures the special morphology of the partially ionomer/water covered cylindrical whiskers, as well as water percolation through the pore structures and their impact on the cell performance. We observe optimal ionomer coverage on whiskers to be 0.5, ionomer to carbon ratio to be 0.9 and higher whisker to carbon ratios to be desired.

Surface modification of the cellulose nanocrystals through vinyl silane grafting

Incompatibility of nanocellulose with non-polar polymer matrices disrupts the interfacial interaction and results in aggregation and phase separation. In this study a facile and environmentally friendly method was used to partially substitute the surface hydroxyl groups by attaching polysiloxane to impart hydrophobic properties. The silanization reaction proceeded with hydrolysis of triethoxyvinylsilane (TEVS) into reactive silanols followed by condensation to form the branched polymer. These polysiloxane oligomers were chemically grafted to form alkoxy silane bonds on the surface of CNCs. A suitable degree of hydrophilic-hydrophobic balance of the modified CNCs was achieved which improved their dispersion in hydrophobic matrix poly(butylene adipate-co-terephthalate) (PBAT). FTIR, NMR (13C and 29Si) and XPS demonstrated successful surface chemical modification and confirmed extent of silanization as a function of silane concentration. XRD showed successful grafting of the vinyl silane agent and confirmed polymorph structure of the nanocellulose was retained. The results from TEM and AFM demonstrated successful coating of nano whiskers at 5 wt% silane loading. The successful grafting of the silane agent with pendant vinyl groups improved surface hydrophobicity. These results show that this facile method produces adequately surface modified CNC which can be used as filler in hydrophobic matrices of bioplastics.

PH indicator films fabricated from soy protein isolate modified with chitin nanowhisker and Clitoria ternatea flower extract

Sensor films are finding wide range of applications. Different type of sensing films is fabricated for the identification of chemicals, ions, heavy metals, changes in the pH, etc. The present report is on the fabrication of pH sensitive films from completely natural sources-soy protein isolate, chitin nano whiskers and flower extract. The highly crystalline chitin nano whiskers (CNW) were extracted from prawn shell under neutral condition via steam explosion technique. Multifunctional Soy protein isolate (SPI) films were prepared by adding chitin nanowhisker and Clitoria ternatea flower extract and its effect on thermal, mechanical and moisture properties of SPI film was investigated. The isolated CNW presented a needle like morphology with a diameter of 10–50 nm and a crystallinity index of 99.67%. The extracted chitin nanowhisker was used to prepare biodegradable films with soy protein isolate immobilized with anthocyanin from Clitoria ternatea flower extract. The prepared Soy protein -chitin nanowhisker films was found to have a tensile strength of about 15.45 ± 0.97 MPa with 8% chitin nanowhisker addition. The addition of CTE was found to decrease the tensile strength of SPI-CNW film but was found to make the film pH sensitive. The developed indicator film showed visible color changes in acidic and basic medium and hence can be used to monitor the freshness of food materials.

Utilization of Thermally Treated SiC Nanowhiskers and Superplasticizer for Cementitious Composite Production.

Nanomaterials are potential candidates to improve the mechanical properties and durability of cementitious composites. SiC nanowhiskers (NWs) present exceptional mechanical properties and have already been successfully incorporated into different matrices. In this study, cementitious composites were produced with a superplasticizer (SP) and 0–1.0 wt % SiC NWs. Two different NWs were used: untreated (NT-NW) and thermally treated at 500 °C (500-NW). The rheological properties, cement hydration, mechanical properties, and microstructure were evaluated. The results showed that NWs incorporation statistically increased the yield stress of cement paste (by up to 10%) while it led to marginal effects in viscosity. NWs enhanced the early cement hydration, increasing the main heat flow peak. NWs incorporation increased the compressive strength, tensile strength, and thermal conductivity of composites by up to 56%, 66%, and 80%, respectively, while it did not statistically affect the water absorption. Scanning electron microscopy showed a good bond between NWs and cement matrix in addition to the bridging of cracks. Overall, the thermal treatment increased the specific surface area of NWs enhancing their effects on cement properties, while SP improved the NWs dispersion, increasing their beneficial effects on the hardened properties.

Electrorheological response behavior of H2Ti2O5@MoS2@SiO2 core-shell nanoparticles

In this paper, a novel H2Ti2O5@MoS2@SiO2 ternary composite material was prepared by a combination of dual hydrothermal method and controlled hydrolysis method, in which H2Ti2O5 nanotubes are tightly combined with hierarchical molybdenum disulfide, and the unique structure of titanate nano whiskers, including the loosely bound alkali metal ions between the titanate layers with high dielectric constant and the large aspect ratio, which induce active response to the electric field. Flower-like molybdenum disulfide provides electrical conductivity, and silicon dioxide as a insulative coating layer can suppress excessive the electrical conductivity of the two-dimensional material. The morphological evolution was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of showed that the sheet-shaped molybdenum disulfide coated with curved H2Ti2O5 nanotubes showed a honeycomb structure with uniform size. Silicon oxide acts as a cladding layer to increase the thickness of the flakes. The existence of H2Ti2O5, molybdenum disulfide and silicon dioxide is confirmed by X-ray powder diffractometer (XRD) and Fourier transform infrared spectroscopy (FT-IR). The prepared product was confirmed by XPS, BET test and electrorheological rheometer. Core/shell nanoparticles not only exert the active response characteristics of titanate nanoparticles and molybdenum disulfide to electric field, but also inherit the excellent characteristics of a core-shell structure produced by the interface polarization and the synergistic effect of the polar groups on the surface of the two-dimensional material further enhance the electrorheological effect.

Utility of whiskerized carbon fabric surfaces in resistive heating of composites

AbstractIn the present study, the embedding ZnO nano‐whiskers (NWs) on carbon fiber (CF) surface was carried out to study the changes in Ohmic heating and mechanical stability of carbon fabric reinforced green epoxy composite laminates. The ZnO NWs were grown onto the CF surface by hydrothermal method and subsequently the laminate composites with different number of carbon woven layers were prepared. To study the resistive heating behavior of the laminate composites, the temperature versus time curves were analyzed in three sections, from which the temperature response rate, the maximum temperature, and the electrical power efficiency were estimated. Later, the effects of Ohmic heating action on the structural damage and mechanical stability of the composites were examined by dynamic mechanical analysis and X‐ray micro computerized tomography. Multilayer ZnO/carbon woven composites were found to be rapidly heating, less power consumption, and have improved mechanical and structural stability over bare carbon woven composites. This indicated that ZnO NWs enhanced the adhesion between the fibers and matrix, meanwhile acting as a heat barrier to avoid degradation of the epoxy at the interface of the fiber and matrix during Ohmic heating.

Exploring (1overline{1}2)-related ordered structure in oxidation-synthesized \u03b1-Fe2O3 nanowhiskers

Hematite (α-Fe2O3) nanowhiskers (NWs) synthesized via oxidation of iron-based substrates are a promising photoanode material for photoelectrochemical water splitting. Such synthesized α-Fe2O3 NWs have been found to contain ordered axial structures. Herein, we reveal that the known (1overline{1}2)-related ordered structure actually exists in bicrystalline α-Fe2O3 NWs instead of single-crystalline α-Fe2O3 NWs and that it is associated with another known (3overline{3}0)-related ordered structure. Through a spherical aberration (CS)-corrected high-resolution transmission electron microscopy (HR-TEM) investigation, the microstructural characteristic of the (1overline{1}2)-related ordered structure is verified to be periodic atomic column displacements serving as tensile strain accommodation. The HR-TEM observation are also supported by a monochromated O K-edge EELS analysis, which indicates that α-Fe2O3 NWs hosting the (1overline{1}2)-related ordered structure are indeed associated with lattice expansion. In sum, our microstructural study elucidates the root cause of the long-asserted relationship between the (1overline{1}2)-related ordered structure and oxygen vacancy ordering.

On the use of cellulose nanowhisker as reinforcement in all‐cellulose composite membrane from corn stalk

AbstractAll‐cellulose composite (ACC) membranes were prepared with cellulose and cellulose nano whisker (CNW) extracted from corn stalk by using NaOH/thiourea as solvent. CNW was isolated via acid hydrolysis method and the yield, size distribution and morphology of CNW were investigated. ACC Membranes were characterized via SEM, XRD, TGA as well as water flux and were further plasticized with glycerol aqueous solution. The mechanical property and transparency of ACC membranes before and after plasticization were compared. CNW prepared with 63% sulfuric acid for 60 min of hydrolysis time had the biggest ratio of length to diameter and moderate yield. ACC membrane with 5% CNW content had the highest tensile strength and the structure of ACC membranes was observed clearly in SEM images. TGA testing indicated that the initial degradation temperature tended to lower after CNW was introduced into membrane. ACC membrane had good optical transmittance and good flexibility after plasticization.

Nanorods of α-Bi2O3 for photocatalytic degradation of methylene blue

In this study, monoclinic bismuth oxide (α-Bi2O3) was synthesized using in the presence and absence of surfactant, and its performance was compared for the photocatalytic degradation of methylene blue. The usage of surfactant alters the morphology of α-Bi2O3/P123 as nanorods. XRD and Raman Spectroscopy analysis confirms the monoclinic phase of the prepared catalyst and the SEM shows cubes with nano whiskers. TEM image confirms nanorods for the surfactant aided synthesis of α-Bi2O3/P123 which plays a significant role in the degradation of methylene blue. Nanorods of α-Bi2O3/P123 shows 95% photo catalytic degradation of methylene blue than compared to 84% for α-Bi2O3 and 78% for P25. The effect of catalyst loading, kinetics of degradation and the comparison of performance with the standard catalyst were reported.

Properties of cellulose reinforced composites: A review

This paper provides a review of cellulose, sources, extraction, molecular structure, cellulose whiskers, preparations, and morphology. The mechanical and thermal properties of cellulose reinforced composites are also discussed. Detail structure of Nano whiskers is also reported. As a renewable biomaterial, the most common source of cellulose is the plant. These plants include fruit fibers (coir), seed fibers (cotton), wood, leaf fibers (sisal), bast fibers (jute, kenaf, and hemp). Other sources of cellulose are from micro-organisms such as fungi, tunicates, bacteria, and algae. Cellulose whiskers are isolated from cellulose fibers by acid hydrolysis. Cellulose micro fibril structures are made of both amorphous and crystalline regions. The amorphous regions are vulnerable to hydrolysis by acids compared to the crystalline domains. Several techniques among which are Field Emission Scanning Electron Microscopy (FESEM), Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) have been used to study the morphology of cellulose whiskers. An interface between cellulose whisker and matrix is a transition zone between the matrix and the cellulose whiskers. It plays an important role in the overall mechanical properties of the composites. A soft interface domain will yield a greater resistance to fracture, while the composite will be low in stiffness and strength. On the other hand, a stiffer interface domain may cause the composite to be strong and stiff and less resistant to fracture. The addition of CW into polymers matrices has little or no effect on the glass transition temperature, (Tg) except on the modification of CW.
 Keywords: Cellulose, whiskers, mechanical, thermal, properties, biomaterials

A Systematic Study on Au-Capped Si Nanowhiskers for Size-Dependent Improved Biosensing Applications

Reducing the distance between the fluorescence molecules and noble metal (resonant) nanostructures is known to advance the process of electromagnetic coupling and energy transfer, which in return yields fluorescence enhancement particularly exploited for improved biomedical applications. In this study, Au-capped Si nanowhiskers (NWs) at various sizes were fabricated using a vapor–liquid–solid (VLS) mechanism for systematically investigating the dependence of the size of the Au-capped Si NWs on the fluorescence enhancement factor with respect to the fluorescence emission from Rhodamine 6G (Rh-6G) fluorophore. Opposite to what is anticipated from the literature, the maximum enhancement was obtained for the sample for which the Au-nanoparticle (NP) capping is well isolated from the fluorophore and the vertical distance between the fluorophore and the plasmonic metal nanoparticle is largest. Numerical simulations using the finite element method (FEM) were shown to support the experimental optical response results. Four-point probe I-V measurements also show that the Schottky ideality factor of Au-capped Si NWs decays exponentially upon the rise in the fluorescence enhancement factor. Graphical abstract

Hydrothermal-solid state synthesis of Gadolinium aluminate nano whiskers with alkaline mineralizer

Gadolinium aluminate (GdAlO3, GAP) nano whiskers were synthesized by the hydrothermal-solid state method, Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermogravimetry-differential thermal analysis (TG-DTA) were employed to analyze the phase change and the nucleation mechanism of GAP during calcing process. The results show that the precursor of GAP prepared by hydrothermal is (NH4)xGdAl(OH)y(NO3)z·nH2O. When the calcination temperature is higher than 900 °C, the precursor recrystallizes, forming the needle shape GAP under the synergistic effect factors. The best preparation conditions are as follows: ammonia water as mineralizer, pH = 9, calcination temperature 1100 °C and holding time 3 h.

Physical and bioactivities of biopolymeric films incorporated with cellulose, sodium alginate and copper oxide nanoparticles for food packaging application

The present work prepared the antibacterial polymeric film (APF) using the different combination of sodium alginate (SA) and cellulose nano whisker (CNW) embedded with copper oxide nanoparticles (CuO NPs). Here, the SA acts as a plasticizer and provides flexibility. The CNW improves barrier properties of the film to limit moisture penetration into food. CuO NPs prevent the microbial contamination to food. Cross-linking and functional relationship of SA-CNW-CuNPs film were confirmed by adopting characterization including SEM, FTIR, EDS and XRD. The film composed with CNW (0.5%)-SA (3%)-CuNPs (5 mM) exhibited promising antibacterial activity against several pathogens in terms of higher zone of inhibition against S. aureus (27.49 ± 0.91 mm), E. coli (12.12 ± 0.58 mm), Salmonella sp. (25.21 ± 1.05 mm), C. albicans (23.35 ± 0.45 mm) and Trichoderma spp. (5.31 ± 1.16 mm). In addition, CNW (0.5%)-SA(3%)-CuO NPs (5 mM) film showed the challenging antioxidant activity in terms of DPPH and ABTS scavenging. Also, the optimized composition of film composed with CNW (0.5%)-SA (3%)-CuO NPs (5 mM) was preventing the microbial contamination in fresh cut pepper (FCP). Therefore, APF composed with CNW (0.5%)-SA (3%)-CuO NPs (5 mM) is proved to be an active food packaging system (FPS) for its utility in food industry to overcome the limitations in conventional food packaging.

Understanding ordered structure in hematite nanowhiskers synthesized via thermal oxidation of iron-based substrates

Hematite (α-Fe2O3) nanowhiskers (NWs) with (001) basal faces synthesized via thermal oxidation of iron-based substrates are known to contain an ordered structure. The ordered structure has been identified to be related to oxygen vacancy ordering. However, the cause of its formation remains a mystery. In this study, with a high-resolution transmission electron microscopy (HR-TEM) investigation based on negative-Cs imaging (NCSI) and atomic-column position analysis, we observed tensile strain in the above-mentioned α-Fe2O3 NWs and revealed that the ordered structure was actually periodic interplanar gap expansions induced by oxygen vacancy accumulations. These findings were further confirmed in a monochromated electron energy loss spectroscopy (EELS) analysis of the α-Fe2O3 NWs. The EELS data indicated that, in comparison to pristine α-Fe2O3, the α-Fe2O3 NWs possessed expanded average FeO and OO interatomic distances and were oxygen-deficient. Clarifying oxygen deficiency in the α-Fe2O3 NWs was not attributed to an insufficient oxygen supply during the NW growth, we concluded the ordered structure formed to accommodate tensile strain in the α-Fe2O3 NWs. This work demonstrates the applicability of integrating NCSI and monochromated EELS for the examination of strain-induced microstructural and microchemical variations in lightly strained metal oxides.

Controllable Combustion Synthesis of SiC Nanowhiskers in a Si-C-N System: The Role of the Catalyst

Silicon carbide (SiC) nanowhiskers (NWs) constitute an important type of optical and structural materials. Herein, SiC NWs were successfully combustion synthesized (CSed) in a Si-C-N system using tungsten (W) as a catalyst. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were used to characterize the SiC NWs. Results of morphological characterization indicated that the W-catalyzed CSed SiC NWs products were fluffy from surface to the core, and they were about several hundred micrometers in length with diameters less than 1 μm. For the comprehensive understanding of the initial growing progress of W-catalyzed CSed SiC NWs, the absorption behavior of C, N, and Si atoms on the crystal planes of W (100), W (110), and W (111) surfaces was investigated by using first-principles calculations. The calculated surface energy (Esurf) of the studied W surfaces and the absorption energy of C, N, and Si atoms on different sites, indicate that the C atom has a priority to sink to the nanometer catalysts grain of W, and the pre-sunk C atom then reacts with Si atom to form NWs.