Formation of Aligned α-Si3N4 Microfibers by Plasma Nitridation of Si (110) Substrate Coated with SiO2

Plasma nitridation of an amorphous SiO2 layer on Si (110) substrate can form well-aligned α-Si3N4 crystallites in fibrous morphology. Nitriding is performed at a temperature in the range of 800–1000 °C by using microwave plasma with a gas mixture of N2 and H2. Raman spectroscopy shows the characteristics of an α-Si3N4 phase without other crystalline nitrides. As shown by scanning electron microscopy, the formed α-Si3N4 microfibers on the Si substrate can be in a dense and straight array nearly along with Si <11¯0>, and can have a length over 2 mm with a diameter in the range of 5–10 μm. Structural characterization of scanning transmission electron microscopy in cross section view reveals that the elongated α-Si3N4 crystallites are formed on the surface of the nitrided SiO2/Si (110) substrate without any interlayers between Si3N4 and Si, and the longitudinal direction of α-Si3N4 appears mainly along <112¯0>, which is approximately parallel to Si <11¯0>.

IMINATION OF CHITOSAN NANOFIBERS IN A HETEROGENEOUS SYSTEM. SYNTHESIS OPTIMIZATION AND IMPACT ON FIBER MORPHOLOGY

The paper aimed to prepare imino-chitosan fibers by the imination reaction in a heterogenous system, targeting the improvement of anti-pathogenic activity. To this end, porous neat chitosan fibers were prepared by electrospinning of the polyethylene glycol/chitosan blend, followed by polyethylene glycol removal. Imination of the neat chitosan fibers was carried out in three liquid phase systems using solvents of different polarity and, consequently, different ability to swell the solid phase chitosan fibers. The successful imination was qualitatively and quantitatively assessed by FTIR and 1H-NMR spectroscopy, and the impact of the liquid phase on the fibers’ morphology was evaluated by SEM, POM and AFM microscopy. Further, the antimicrobial activity of the imino-chitosan fibers was investigated on relevant bacterial and fungal strains. It was concluded that the prior swelling in water of the fibers improved the imination degree, while the use of a less polar solvent, such as toluene, favored the preservation of the fibrous morphology. The imination with an antimicrobial aldehyde endowed the chitosan fibers with the ability to create a physical barrier against pathogens.

The Effect of Ozone Treatment on the Physicochemical Properties and Biocompatibility of Electrospun Poly(ε)caprolactone Scaffolds

Ozonation has been proved as a viable surface modification technique providing certain properties to the scaffolds that are essential in tissue engineering. However, the ozone (O3) treatment of PCL scaffolds in aqueous environments has not yet been presented. O3 treatment performed in aqueous environments is more effective compared with traditional, executed in ambient air treatment due to more abundant production of hydroxyl radicals (•OH) within the O3 reaction with water molecules. During interaction with •OH, the scaffold acquires functional groups which improve wettability properties and encapsulate growth factors. In this study, a poly(ε)caprolactone (PCL) scaffold was fabricated using solution electrospinning and was subsequently ozonated in a water reactor. The O3 treatment resulted in the expected occurrence of oxygen-containing functional groups, which improved scaffold wettability by almost 27% and enhanced cell proliferation for up to 14 days. The PCL scaffold was able to withhold 120 min of O3 treatment, maintaining fibrous morphology and mechanical properties.

Biodegradable and conductive PVA/CNT nanofibrous membranes used in nerve conduit applications

The recovery of impaired peripheral nerves is often not as expected, which makes the development of nerve conduits trendy nowadays. To enable the neural messages effectively being delivered as well as to prevent the secondary damage during the removal of nerve conduits, the conductivity and biodegradability are two essential requirements for ideal nerve conduits. In this study, electrospinning is used to produce polyvinyl alcohol (PVA)/carbon nanotubes (CNT) electrospun films, after which the morphology analysis, electrical property, water contact angle, and biological characteristics of the membranes are investigated, thereby determining the optimal nerve conduits based on the employment of electrospinning, PVA, and CNT. The test results indicate that with 0.25 wt% of PVA, the electrospun films exhibit comparatively lower resistance of 25.3 ohm, good fibrous morphology with a diameter being 1 μm. In addition, the electrospun films are cytotoxicity-free and facilitate the growth of cells. It is observed in the MMT assay that after co-cultured with cells for three days, PVA/CNT electrospinning fibrous membranes exhibit a cellular viability that is 18.5 times greater than that of the control group on Day 1. According to all property evaluations, PVA/CNT electrospinning fibrous membranes are a qualified candidate for the use of nervous conduits.

Advances in Fabricating the Electrospun Biopolymer-Based Biomaterials

Biopolymers formed into a fibrous morphology through electrospinning are of increasing interest in the field of biomedicine due to their intrinsic biocompatibility and biodegradability and their ability to be biomimetic to various fibrous structures present in animal tissues. However, their mechanical properties are often unsatisfactory and their processing may be troublesome. Thus, extensive research interest is focused on improving these qualities. This review article presents the selection of the recent advances in techniques aimed to improve the electrospinnability of various biopolymers (polysaccharides, polynucleotides, peptides, and phospholipids). The electrospinning of single materials, and the variety of co-polymers, with and without additives, is covered. Additionally, various crosslinking strategies are presented. Examples of cytocompatibility, biocompatibility, and antimicrobial properties are analyzed. Special attention is given to whey protein isolate as an example of a novel, promising, green material with good potential in the field of biomedicine. This review ends with a brief summary and outlook for the biomedical applicability of electrospinnable biopolymers.

Activation of Peroxymonosulfate by Chrysotile to Degrade Dyes in Water: Performance Enhancement and Activation Mechanism

An environmentally friendly activation method of peroxymonosulfate (PMS) provides a promising advanced oxidation processes for the degradation of organic wastewater. In this article, chrysotile, extracted from asbestos tailings, was found to be a kind of one-off catalyst relying on hydroxyl groups to activate PMS. Furthermore, the activation performance of the chrysotile had been greatly improved by the mean of calcining at 850 °C (850CC). It is worth mentioning that 850CC could not only realize three effective cycles, but also the mineralization ratio of Rhodamine B (RhB) could be impressively higher than 60%. According to characterization results, it was discovered that the chrysotile had transformed into forsterite with a fibrous morphology after calcination at 850 °C due to the loss of hydroxyl groups and the recombination of silicon, oxygen and magnesium atoms. Besides, the main active species produced by 850CC activating PMS were singlet oxygen and sulfate radicals. Further studies uncovered that PMS was successfully activated by a large number of unsaturated coordination oxygen on 850CC surface, and the activation mechanism was further elucidated. This study provides a new route for the comprehensive utilization of chrysotile and a valuable strategy for the degradation of hazardous organic pollutants in wastewater by PMS activation.

CO2-Induced Fibrous Zn Catalyst Promotes Electrochemical Reduction of CO2 to CO

The electrochemical reduction of CO2 is a promising strategy to achieve efficient conversion and utilization. In this paper, a series of Zn catalysts were prepared by electrodeposition in different atmospheric conditions (N2, CO2, H2, CO). A fibrous Zn catalyst (Zn-CO2) exhibits high electrochemical activity and stability. The Zn-CO2 catalyst shows 73.0% faradaic efficiency of CO at −1.2 V vs. RHE and the selectivity of CO almost did not change over 6 h in −1.2 V vs. RHE. The excellent selectivity and stability is attributed to the novel fibrous morphology, which increases the electrochemical active surface area. X-ray diffraction (XRD) results show that Zn-CO2 catalyst has a higher proportion of Zn (101) crystal planes, which is considered to be conducive to the production of CO. The search further demonstrates the importance of morphology control for the preparation of highly active and stable catalysts.

Drainage in a Screw Press and Utilization of the Recovered Fibres after Thermo-Hydrolytic Disintegration of Waste Fibreboards

A thermo-hydrolytic disintegration process qualifies as a promising option for recycling the waste MDF and preserving the fibrous morphology of the recovered lignocellulosic fibre material. This study aims to include a drainage process between the thermo-hydrolytic disintegration and the further utilization of the recovered fibres (RF) obtained using a screw press for removing the disintegration water (DW). In this context, the chemical properties of the RF (pH, nitrogen content, formaldehyde emissions) and the DW (pH, formaldehyde, reducing sugars and equivalents and nitrogen contents) were analyzed. Moreover, the RF material was utilized to produce recycled MDF panels, solely containing the RF (100%) and hence supplanting 50% of the virgin fibres (VF). The recycled MDF portrayed significant reductions in the internal bond strength (IB), and flexural properties (MOR, MOE): in the case of MDF made from 100% recycled fibres, about half the strength was reduced, and in the case of MDF made from 50% recycled fibres, the strength was reduced by 20-25%. The Thickness swelling (TS) of the recycled MDF panels was similar, while the water uptake (WA) was higher than that of the original MDF. The recycled MDF panels also exhibited a higher content of formaldehyde and emission. The findings recommend the application of a screw press process for prompter drainage of the RF and to utilize the RF obtained in combination with the VF to achieve adequate mechanical properties rather than using the RF separately for the manufacturing of the recycled MDF panels.