Surface Chemical Elements Research Articles

Magnetic Nitrogen-Doped Fe<sub>3</sub>C@ c Catalysts for Efficient Activation of Peroxymonosulfate for Degradation of Organic Pollutants

Recoverable and stable nanocatalysts are essential for peroxymonosulfate - based advanced oxidation processes (AOPs) in wastewater purification treatment. In this paper, Fe3C nanorods @ nitrogen-doped carbon composites (N-Fe3C@C) with core-shell architecture were fabricated by the co-precipitation and calcination methods, and characterized and analyzed in terms of their crystal structure, microscopic morphology, and surface chemical elements. In addition, N-Fe3C@C-4 degraded 85.36% of tetracycline in 10 min under PMS, which was much higher than the catalytic ability of Fe3O4 (42.03% in 10 min). Both the active radical trapping and EPR experiments verified that 1O2 played a key role for degradation of organic dyes in PMS system. The investigation on the degradation mechanism revealed that the presence of the carbon layer facilitated to adsorb TC, accelerate free radical generation and promote the redox cycle of Fe2+/Fe3+ in the nanocatalyst. This study offers novel ideas for multifunctional catalysts for advanced wastewater purification treatment.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

Enhanced catalytic oxidation of naproxen via activation of peroxymonosulfate by Fe-based metal–organic framework aerogels functionalized with Ag nanoparticles

In this study, Ag3PO4 and Fe-based metal–organic frameworks (MOFs)-functionalized three-dimensional (3D) porous gelatin aerogels (Ag/Fe@GMA) were fabricated and used as adsorbents and catalysts for the activation of peroxymonosulfate (PMS) for naproxen (NPX) removal from water. The morphology, crystallinity, surface functional groups, and surface chemical element compositions of the fabricated Ag/Fe@GMA was evaluated using various analytical techniques. Our results showed that as an adsorbent, Ag/Fe@GMA showed a 18.0 % higher NPX adsorption capacity compared with the pristine aerogels. This can be attributed to the well-embedded Ag3PO4 and MOFs, indicating a stronger interaction between functionalized aerogels and NPX. After adsorption, 99.9 % of total NPX removal was achieved within 15 min by activating PMS and effectively generating •OH and •SO4− in water. The PMS/Ag/Fe@GMA aerogel system also showed high removal performance for rhodamine B (99.5 %) and tetracycline (93.7 %). Moreover, the Ag/Fe@GMA aerogels showed excellent reusability to achieve 95.7 % NPX removal efficiency after six times of recycling. This study revealed that the Ag/Fe@GMA aerogels had good potential for PMS activation and NPX removal. In particular, as an alternative to powdery materials, 3D shape of Ag/Fe@GMA with excellent reusability facilitates its application in the treatment of water contaminated with organic contaminants.

Determination of conduction type in high-resistivity silicon by combining spreading resistance profiling (SRP) with hydrofluoric acid treatment

The effect of hydrofluoric acid (HF) treatment on the surface electrical properties was observed in high-resistivity bulk silicon by the spreading resistance profiling (SRP) technique. It is found that the near-surface resistivity decreased in n-type silicon and increased in p-type silicon after HF treatment according to the SRP measurement. The variation of surface chemical elements and energy bands of HF-treated n-type and p-type (100) silicon has been characterized by x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements. The results indicate that the surface Fermi level is shifted toward the conduction band minimum after HF treatment. The surface energy band bending caused by the surface electronegative groups (–F and –OH) was investigated by the method of First-principles calculation. Based on these findings, a method combining the SRP measurement with HF treatment to determine the conduction type of high-resistivity silicon was proposed, which is critical for the development of high-resistivity CZ silicon crystal growth.

Effects of different pretreatments combined with steam explosion on the properties of bamboo fibers

Bamboo pretreatment is a key technology for the preparation of bamboo fibers (BFs) for composites. This study examined the properties of BFs prepared by steam explosion (SE) BFs following pretreatment by enzyme, alkali, and salt. The microstructure, functional groups, crystallinity, and surface chemical elements of BFs were characterized by environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that bamboo could be separated into fiber bundles through SE after pretreatment. The separation of BFs pretreated by enzyme and alkali were better, but colloid remained and was able to stick the fibers together. Through performing different pretreatments before SE, the lignin and hemicellulose of BFs were partially removed, and alkali pretreatment had the best effect on lignin removal. The crystal structure of the BFs did not change significantly, and the crystallinity of BFs was highest at 2 MPa and 6 min when pretreated by alkali. The XPS results showed that the effect of alkali pretreatment at 2 MPa for 6 min was the best.

Nitrogen-doped graphene oxide with enhanced bioelectricity generation from microbial fuel cells for marine sewage treatment

With the increasing demand for clean water and energy, microbial fuel cell (MFC) as a promising technology for obtaining energy from wastewater has attracted great research interest in the last two decades. The performance of the anode electrode is the most critical factor limiting the large-scale application of MFC. Graphene materials as a suitable candidate have been successfully used as the anode due to their excellent biocompatibility and efficient extracellular electron transfer (EET) ability. Here, nitrogen-doped graphene oxide (NGO) was prepared by a simple one-step hydrothermal method. X-ray photoelectron spectroscopy (XPS) was used to analyse the valence states of the surface chemical elements and their associated molecular species. Fourier transform infrared spectroscopy (FTIR) was used to identify the surface functional groups, and Raman spectroscopy was used to analyse the information about surface defects. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the increased electrochemical activity and rapid EET ability from the NGO electrodes. Scanning electron microscopy demonstrated the two-dimensional layered structure of the NGO with some wrinkled texture. MFCs equipped with the modified NGO anode achieved the highest power density of 708.3 mW/m2 with an output voltage of 498.6 mV in comparison with the other graphene-based electrodes, i.e., graphene and graphene oxide. Moreover, the chemical oxygen demand (COD) removal rate increased significantly from 18.1% to 45.6%. The analysis of the bacterial community using a high-throughput sequencing indicated that the relative abundance of the electricigens increased on the NGO electrode biofilim, and the relative expression of ccoN gene coding cytochrome-c oxidase (Cco) was markedly up-regulated. These results demonstrated that NGO modification effectively enhanced the bio-electrocatalytic activity of MFC with improved wastewater treatment capacity.

Evolution Toward the Observational Features of a Stripped Envelope Type IIb Supernova in a Binary System

Type IIb supernovae (SNe IIb) that have a thin layer of hydrogen left in their outer envelope have been believed to belong to core collapse supernovae. Mass transfer via Roche lobe overflow can significantly change the nucleosynthesis and surface chemical elements of the progenitors of SNe IIb. We aim to explore what conditions a close binary can meet with the observational features of SNe IIb. We find that an observed low mass SN IIb cannot be produced by a low mass isolated star with M < 20 M ⊙ due to the existence of a thick hydrogen envelope regardless of rotation. Binaries dominate as progenitors in the mass interval (i.e., M < 20 M ⊙) considered in this paper. The 16 M ⊙ primary with a 14 M ⊙ companion in a binary system with ∼10 days < P orb < 720 days can reproduce observational features of SNe IIb (i.e., T eff, , M He, M H, etc.). With the decrease of the hydrogen-rich envelope mass, the radius of the progenitor shrinks. The associated types of SN IIb progenitors from RSGs and YSGs to BSGs are closely related to the amount of hydrogen left in the envelopes. Rotation can bring the production of the CNO reaction to the stellar surface at an early phase, which would explain the nitrogen-rich circumstellar material of SN 1993J and can also explain the large He/H ratio of supernova ejecta. Rotation can increase the corresponding region of the orbital period which can produce an SN IIb.

Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite

The surface treatment of carbon fibers (CFs) was carried out using a self-synthesized sizing agent. The effects of sizing agent on the surface of CFs and the interface properties of CF/polymethyl methacrylate (PMMA) composites were mainly studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and static contact angle were used to compare and study the CFs before and after the surface treatment, including surface morphology, surface chemical element composition, and wettability of the surface. The influence of sizing agent on the mechanical properties of CF/PMMA resin composite interface was investigated. The results show that after sizing treatment, the CF surface O/C value increased by 35.1% and the contact angles of CF and resin decreased by 16.2%. The interfacial shear strength and interlayer shear strength increased by 12.6%.

A novel π bridging method to graft graphene oxide onto carbon fiber for interfacial enhancement of epoxy composites

Based on the inherent crystallite structure of carbon fiber, a novel and facile method was presented to balance the tedious steps and effectiveness of graphene oxide/carbon fiber (GO/CF) hierarchical reinforcement, by establishing π bridging of GO and CF under the assistance of pyrene-containing compounds, which was performed without chemical treatment of CF and GO. The surface chemical elements, functional groups, wettability, morphologies and surface structures of obtained reinforcements were characterized through XPS, FT-IR, dynamic contact angle, SEM and Raman spectroscopy, respectively. This method could implement at room temperature without causing damage to CF as indicated by filament tensile strength test. The resulted composites with a bridging agent of 72 mmol/L have the highest interlaminar shear strength, transverse fiber bundle strength and interfacial shear strength which increased by 49.3%, 117.1% and 59.1%, respectively, compared to pristine CF composites.

Imparting antibacterial activity, UV-protection properties and enhancing performance of casein modified polyester fabrics

Polyester fibres are extensively used in the textile industry because of their durability, low-cost, easy-care and compatibility properties. The hydrophobic nature of polyester is adversely affecting the level of comfort and restricts its use in most textile applications like sportswear, underwear, and bedding. Thus, the demands for improving polyester properties to meet market needs are gaining increased research interest. In the present work, casein was used as a surface-coating material for woven and knitted polyester fabrics to impart new desired properties. The fabrics were pretreated with sodium hydroxide followed by treating with various concentrations of casein using pad-dry-cure technique, as well the fabrics were treated with casein directly in presence of epichlorohydrin as cross-linker. The apparent viscosity of the different concentrations of the dissolved casein biopolymer was studied. The morphological structure and the surface chemical elements of the untreated and treated polyester fabrics were investigated using field emission scanning electron microscopy (FE-SEM) and dispersive X-ray spectroscopy (EDX), respectively. The base combining capacity of the untreated and treated fabrics was evaluated and compared, in addition to studying their physical and mechanical properties to evaluate their performance. Also, the antibacterial activity of the treated fabrics compared to the untreated one was investigated. The results revealed that all treated polyester fabrics exhibited better moisture regain, UPF, antistatic and antibacterial activity compared to the untreated fabrics. Woven and knitted polyester samples treated with casein only achieved higher strength properties, lower surface roughness and improved electrostatic charges. Even so, the woven samples pretreated with sodium hydroxide followed by casein had increased air permeability values, while the knitted samples showed decreased values and increased stiffness. The overall comparison between the significant properties of all treated polyester fabrics clarified that, the woven sample pretreated with 10% NaOH then 7% casein and knitted sample treated with 4% casein only achieved the best functional performance.

Modification of hydroxyapatite surface properties by electron irradiation

In the present work, the modification of wetting properties of EB irradiated HA ceramics are studied under air and N2 gas atmospheres. We show a noticeable increase of the hydrophily of electron irradiated HA ceramics in an air gas atmosphere and a lesser increase when the samples are irradiated in an N2 atmosphere, such a phenomenon is correlated to a modification of grain morphology obtained under the 2 atm. With a progressive water saturation of the ceramics, the wetting angles increase progressively until they reach plateau values different from each set of samples (irradiated under air, irradiated under N2 atmosphere and pristine). Profilometry, SEM/EDX, XRD and Raman spectrometry analysis do not show differences between irradiated and pristine samples which indicates that the EB irradiation modifies the surface chemical elements related to the surface wetting properties and not those analysed by the above techniques.

Use of Sustainable Energy as a Heating Source to Improve Dyeability and Other Properties of Wool and Polyamide-6 Fabrics with Nano-Silica

This study deals with the utilization of silicon dioxide nanoparticles (SiO2 NPs) to treatment of wool and polyamide 6 fabrics. The fabrics treated with different concentrations of SiO2 NPs (5- 20 g/l) using pad-dry- cure technique. The size of nano silicon dioxide particles measured with TEM. The surface morphology and surface chemical elements of treated and untreated fabrics were characterized through high-resolution Scanning Electron Microscopy (SEM) and Dispersive X-Ray spectroscopy (EDX), respectively. The untreated and treated wool and polyamide fabrics were characterized by FTIR. The effect of the treatment on dyability of both wool and polyamide 6 fabrics using different dyestuffs such as acid, basic and direct dyes is studied with applying innovation technique to save energy, water and time. For comparison, the same dyeing technique was carried out by using conventional heating technique. The colour strength and the fastness tests of the untreated and treated wool and polyamide 6 fabrics were evaluated. The effects of SiO2 NPs on the physical and multifunctional properties of the treated sample such as weight, thickness, UPF, antibacterial activity and moisture regain % were determined. The obtained results indicate that the optimization of dyeing process parameters as well as optimized treatment of both wool and polyamide fabrics with SiO2 NPs has a significant influence on the obtained shades and fastness properties.

Friction stability and cellular behaviors on laser textured Ti–6Al–4V alloy implants with bioinspired micro-overlapping structures

The grain structure and surface morphology of bio-implants act as a pivotal part in altering cell behavior. Titanium alloy bone screws, as common implants, are prone to screws loosening and complications threat in the physiological environment due to their inferior anti-wear and surface inertia. Manufacturing bone screws with high wear resistance and ideal biocompatibility has always been a challenge. In this study, a series of overlapping morphologies inspired by the hierarchical structure of fish scales and micro bulges of shrimp were structured on Ti–6Al–4V implant by laser texturing. The results indicate that the textured patterns could improve cell attachment, proliferation, and osteogenic differentiation. The short-term response of human bone marrow-derived mesenchymal stem cells (hBMSCs) on the textured surface are more sensitive to the microstructure than the surface roughness, wettability, grain size and surface chemical elements of the textured surfaces. More importantly, the friction-increasing and friction-reducing type overlapping structures exhibit excellent friction stability at different stages of modified simulated body fluid (m-SBF) soaking. The overlapping structure (Micro-smooth stacked ring: MSSR) is more beneficial to promote the formation of apatite. Deposited spherical-like apatite particles can act as a “lubricant” on the MSSR surface during the friction process to alleviate the adhesion wear of the surface. Meanwhile, apatite particles participate in the formation of friction film, which plays an effective role in reducing friction and antiwear in corrosion solution (m-SBF) for a long time. These features show that the combination of soaking treatment in m-SBF solution with laser-textured MSSR structure is expected to be an efficient and environmentally friendly strategy to prolong the service life of bone screws and reducing the complications of mildly osteoporotic implants.

Effect of ceria concentration of Strontium titanate on the structural, optical, dielectric and electrical properties

The present investigation, pure and ceria (CeO2) doped strontium titanate (SrTiO3) powders have been synthesized by the solid-state reaction method. In addition, the effect of ceria (0, 1, and 3%) on the variation of crystallite size, crystalline nature, surface particle shape, optical absorption, optical band gap, dielectric constant, dielectric loss and electric conductivity of SrTiO3 material through physico-chemical characterization like powder X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), UV–Visible spectra and impedance spectroscopy have been investigated. The powder XRD display confirms the evolution of the single phase with cubic structure of SrTiO3 material. Further, we confirmed the formation of strontium titanate material through spectral studies like Fourier Transforms Infrared (FTIR), Raman spectrum and Energy dispersive X-rays studies. X-rays photoelectron spectroscopy (XPS) explains the surface chemical elements and their binding energy of pure and 3% ceria doped strontium titanate. The optical band gap values of SrTiO3 decreases emphasized a red shift with increasing the ceria concentration. Dielectric constant, dielectric loss and electrical conductivity of pure and ceria doped SrTiO3 have been comparatively discussed in detail.

Functional Finishing of Polyester Fabric Using Bentonite Nano-Particles

This work is devoted to increase the functional properties of polyester fabric such as UPF, moisture regain, tensile strength at break and dyeability towards basic dye. To achieve this purpose polyester fabric were modified with different concentrations bentonite nano-particles (BNPs) using pad – dry curing technique and IR dyeing machine. The effect of the (BNPs) on the physical and mechanical properties of the treated fabrics such as moisture regain, tensile strength at break, elongation percentage and thickness were investigated. Topographical investigation of the said nano-particles was conducted using transmission electron microscopy (TEM). The surface morphology and surface chemical elements of the treated as well as the untreated fabrics were investigated using field emission scanning electron microscopy and dispersive X-ray spectroscopy, respectively. FTIR, thermogravimetric analysis and UPF of the treated polyester fabrics compared to the untreated one were assessed. The colour strength of dyed polyester fabrics with both disperse and cationic dyestuffs as well as the fastness properties were evaluated. Excellent results of the treated fabrics toward physical and coloration properties were obtained.

Lotus-Inspired Multiscale Superhydrophobic AA5083 Resisting Surface Contamination and Marine Corrosion Attack.

The massive and long-term service of 5083 aluminum alloy (AA5083) is restricted by several shortcomings in marine and industrial environments, such as proneness to localized corrosion attack, surface contamination, etc. Herein, we report a facile and cost-effective strategy to transform intrinsic hydrophilicity into water-repellent superhydrophobicity, combining fluorine-free chemisorption of a hydrophobic agent with etching texture. Dual-scale hierarchical structure, surface height relief and surface chemical elements were studied by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), successively. Detailed investigations of the wetting property, self-cleaning effect, NaCl-particle self-propelling, corrosion and long-term behavior of the consequent superhydrophobic AA5083 surface were carried out, demonstrating extremely low adhesivity and outstanding water-repellent, self-cleaning and corrosion-resisting performance with long-term stability. We believe that the low cost, scalable and fluorine-free transforming of metallic surface wettability into waterproof superhydrophobicity is a possible strategy towards anti-contamination and marine anti-corrosion.

Development of some functional properties on viscose fabrics using nano kaolin

Nanoclays are among the more important industrial minerals. They are inexpensive, widely available in nature, and environment friendly. Nano kaolin (NK) is used to impart additional values of viscose fabrics. The mentioned fabrics were treated with different concentrations of NK using pad-dry cure technique. The surface morphology and surface chemical elements of treated as well as untreated fabrics were investigated using scanning electron microscopy and dispersive X-ray spectroscopy, respectively. Tensile strength and elongation, thickness, bending length, moisture regain and antimicrobial activity of the treated fabrics were evaluated. New colouring material (Thiazolidin), direct and reactive dyes were used for dyeing the treated and untreated fabrics. K/S and washing fastness of the dyed fabrics were assessed and statistically compared using t test. The effect of treatment and dying on performance properties of garments were evaluated by calculating quality factor for each fabric.

Superhydrophobic surface decorated with vertical ZnO nanorods modified by stearic acid

Static and dynamic wettability of the ZnO nanorod surface prepared by a facile and inexpensive route is reported. The wettability of the ZnO surface was controlled and tuned by post hydrophobization using different stearic acid concentrations. The surface of the ZnO nanorods modified with 8mM stearic acid showed a static water contact angle of 152° and sliding angle of 9°, which indicates superhydrophobicity. This suggests that the combination of the rough structures achieved by the ZnO nanorods and low surface energy provided by stearic acid modification results in superhydrophobicity and a very low sliding angle. The crystal structure, surface chemical elements, surface morphology, surface roughness, and static and dynamic water contact angles of the ZnO coatings were studied in detail. Further, the surface properties were assessed by calculating the surface free energies and work of adhesion for unmodified and stearic-acid-modified ZnO nanostructure surfaces. These coatings can find potential industrial applications in the electronic industry.

The Production and Properties of Electrolytic Zn-Ni Layers Deposited by Pulse Current Method

The Zn-Ni layers were obtained by electrolytic method in the conditions of pulse current with symmetric current pause. The austenitic steel (OH18N9) was used as the cathode. The morphology, phase and surface chemical composition of the layers deposited at reduction current densities ic = 5 – 25 mAcm2, were defined. The surface morphology of deposited layers and surface chemical elements distribution were studied using a scanning electron microscope (JEOL JSM-6480). On the basis on this research, the possibility of deposition of Zn-Ni layers contained about 8 – 10 % at. Ni was exhibited. The optimal pulse current condition of Zn-Ni layers deposition were proposed namely ic=20mA•cm2, ton = toff = 2ms. It was stated, that surface chemical composition of Zn-Ni layers is independent on pulse current densities of deposition, whereas development of Zn-Ni surface increases with the increase in the pulse current density of deposition. The corrosion resistance investigations showed that passivation and heat treatment improved the corrosion resistance of Zn-Ni layers in 5% NaCl solution. Higher corrosion resistance of heated Zn-Ni layers is caused by the creation of Ni5Zn21 intermetallic phase. Moreover the heated Zn-Ni layers are characterized by slightly higher corrosion resistance compared with metallic Cd. Microhardness of the layers was investigated by Vickers diamond testing machine.

The Influence of Sodium Molybdate on the Properties of Zn-Ni Layers Obtained by Electrolytic Deposition

This study was undertaken in the aim to try the limit of extraction of Zn from Zn-Ni system. The aim was realized by the addition of MoO42- ions into the galvanic bath containing Ni2+ and Zn2+ ions. Zn-Ni-Mo layers were deposited under galvanostatic conditions on (OH18N9) austenitic steel substrate. The influence of Na2MoO4 concentration in a bath on the surface morphology, chemical and phase composition and the corrosion resistance of obtained layers, was investigated. The properties of Zn-Ni-Mo layers were compared to the properties of electrolytic Zn-Ni layer. Structural investigations were performed by the X-ray diffraction (XRD) method. The surface morphology and chemical composition and surface chemical elements distribution of deposited layers were studied using a scanning electron microscope. Electrochemical corrosion resistance investigations were done by classical Stern method and electrochemical impedance spectroscopy. The potentiodynamic curves in the range of  0.05V to the potential of open circuit, were obtained. On the base of these curves the parameters like corrosion potential- Ecor, corrosion current density- icor and the polarization resistance- Rp were determined. These values served as a measure of the corrosion resistance of obtained layers. Results of impedance investigations were presented on the Nyquist Z”= f (Z’) and the Bode log Z = f (log) and  = f (log), diagrams. On the basis on this research, it was exhibited that surface morphology, chemical composition of Zn-Ni-Mo layers are dependent on Mo contents. The optimal content of Na2MoO4 in the bath for the sake of corrosion resistance in 5% NaCl, is found to be 1.2 gdm-3.