Surface Chemical Properties Research Articles

A-site effects of titanate-perovskite (ATiO3)-based catalysts on dehydrogenation of N-heterocyclic molecules

Dehydrogenation reactions in liquid organic hydrogen carrier (LOHC) systems present significant challenges, particularly when aiming for low-temperature operations while ensuring that no hydrogen remains in the substrate molecules. Enhancing catalytic performance requires modifying the adsorption behavior of the reactants and products during dehydrogenation. Perovskites have emerged as promising catalyst supports because of their ability to modify the surface chemical properties by manipulating the cations present at the A- and B- sites. This study investigated the effects of A-site cations (Ca, Sr, and Ba) in titanate-type perovskite (ATiO3)—a prototypical perovskite—on the dehydrogenation activity in LOHC systems. Remarkably, Pd/SrTiO3 exhibited outstanding performance by completely converting octahydro-N-methylindole to N-methylindole and releasing 5.76 wt% hydrogen over 8 h. Additionally, it dehydrogenated dodecahydro-N-ethylcarbazole to N-ethylcarbazole with a hydrogen release of 5.70 wt%. Furthermore, the catalyst demonstrated a stable performance after recycling tests for three times without degradation or loss of activity. The chemical state of the catalyst surface was characterized through X-ray photoelectron spectroscopy, H2-temperature programmed reduction, and chemisorption using NH3, CO2, and H2. The results revealed that the exceptional dehydrogenation activity of Pd/SrTiO3 is due to the presence of suitable surface oxygen vacancies and abundant acid–base sites.

Glycerol-based H3PO4-activated carbon as a versatile adsorbent for removal of pollutants from wastewater: A novel synthesis protocol

Aiming at revaluing oversupplied glycerol as a result of biodiesel production, this approach introduces an authentic synthesis protocol for producing glycerol-based activated carbons holding suitable textural/surface properties for an efficient application in the methylene blue and Pb2+ adsorption processes. Typically, glycerol and phosphoric acid were submitted to a polycondensation reaction in order to insert manipulable fractions of C-O-P bridge bonds throughout the whole polymer chain in the form of mono, di and triesters before the traditional carbonization and activation steps. The physicochemical and surface chemistry properties of the ACPs were characterized by means of N2 adsorption/desorption isotherms, thermal analysis, elemental analysis, surface functional groups titration and pHpzc, X-rays diffraction, FTIR spectroscopy and scanning electron microscopy. Indeed, such strategy gave rise to a set of micro/mesoporous activated carbons (ACP) with surface area of up to 1056 m2/g and total acidity, constituted by thermally insensitive carbonyls-/phosphorus-containing functional groups, ranging from 1.63 to 2.32 mmol g−1. Adsorptive features of the obtained series of activated carbons were validated in the methylene blue and Pb2+ removal processes reaching out adsorption capacity of up to 543.3 and 26.5 mg g−1 at 298 K, respectively. Additionally, after confronting experimental data with several isothermal and kinetic theoretical models, it was demonstrated that the adsorption mechanism of both pollutants onto the ACPs is driven by chemisorption up to the monolayer coverage. The thermodynamic study indicated spontaneity of the adsorption processes and suggested a relation between the textural properties and surface functionalities of the ACPs with the enthalpic nature of the adsorbent-adsorbate interactions.

Anti-marine biofouling adhesion performance and mechanism of PDMS fouling-release coating containing PS-PEG hydrogel

Polystyrene microspheres compounded with polyethylene glycol–based hydrogel (PS-PEG)/polydimethylsiloxane (PDMS) coatings were prepared using the physical blending method. The chemical structure, surface and interface properties, interlayer adhesion, and tensile properties were tested in this paper. Furthermore, the antifouling performance was evaluated through bovine serum albumin fluorescent protein adsorption testing, marine bacteria adhesion testing, and benthic diatom adhesion testing. The results showed that the coating performance was best when 20 wt% PS-PEG hydrogel was added. Its surface energy was only 19.21 mJ/m2, the maximum breaking strength was 1.24 MPa, the maximum elongation rate was 675 %, the elastic modulus was 2.53 MPa, and the anti-stripping rate was 100 %. In addition, the coating with added 20 wt% PS-PEG hydrogel bacterial adherence rate was 5.36 % and 2.45 % after rinsing and washing, respectively, and the removal rate was 54.29 %. In the benthic diatom adhesion test, the chlorophyll concentration a-value was only 0.0017 mg/L after washing with added 20 wt% hydrogel, and the protein desorption rate was 84.19 % higher than PDMS in the fluorescent protein adsorption test. This coating has the ‘low adhesion’ and ‘desorption’ characteristics in the three growth stages of biofouling. Meanwhile, the low surface energy of the silicone is stable, and the hydrogel also dynamically migrates to the surface to gradually form a hydration layer, both are synergistic. When 20 wt% PS-PEG hydrogel was added, the coating demonstrated excellent antifouling performance due to its high hydration layer, low surface energy, high elasticity, and high interlayer adhesion. This research is expected to contribute to the practical applications of hydrogel coatings in marine antifouling.

Mechanism of Accelerated Deterioration of High-Temperature Vulcanized Silicone Rubber under Multi-Factor Aging Tests Considering Temperature Cycling.

High-temperature vulcanized silicone rubber (HTV-SR) employed for composite insulators is continuously subjected to a complex environment of alternating heat, corona discharge, humidity, etc. These stresses (especially alternating heat) complicate the aging mechanism of HTV-SR, which lacks systematic investigation. In this paper, a multi-factor aging platform considering temperature cycling, moisture, and corona discharge is established. Specifically, four temperature-cycling settings are employed, each of which lasts for 15 cycles. The surface morphology, hydrophobicity, and chemical, mechanical, and electrical properties of aged samples are methodically characterized. Experimental results show that the aging degree is correlated to the range of temperature cycling, which is attributed to diverse crosslink-degradation degrees with different temperature differences. Under a large temperature difference (70 °C), HTV-SR possesses a high crosslinking degree and a low degradation degree, making the material hard but easy to crack with alternating thermal stress. Then, severe defects and water condensation emerge on the HTV-SR surface, which promote the diffusion of corona products and water molecules into the material. The subsequent rise in crosslinking density caused by in-depth oxidation further exacerbates the aging of the material. Consequently, it brings about poor hydrophobicity, high interfacial polarization, and shallow trap energy levels in HTV-SR. This work provides a detailed analysis of the aging mechanism of HTV-SR in a simulated on-site environment.

Highly Efficient Solar-driven Dry Reforming of Methane on a Rh/LaNiO3 Catalyst through a Light-induced Metal-to-metal Charge Transfer Process.

As an energy-saving and green method, solar-driven dry reforming of methane (DRM) is expected to introduce new activation processes and prevent sintering and coking of the catalysts. However, it still lacks an efficient way to the coordinate regulation of activation of reactants and lattice oxygen migration. In this work, Rh/LaNiO3 is designed as a highly efficient photothermal catalyst for solar-driven DRM, which performs production rates of 452.3mmol h-1 gRh -1 for H2 and 527.6mmol h-1 gRh -1 for CO2 under a light intensity of 1.5W cm-2 , with an excellent stability. Moreover, a remarkable light-to-chemical energy efficiency (LTCEE) of 10.72% is achieved under a light intensity of 3.5W cm-2 . The characterizations of surface electronic and chemical properties and theoretical analysis demonstrate that strong adsorption for CH4 and CO2 , light-induced metal-to-metal charge transfer (MMCT) process and high oxygen mobility together bring Rh/LaNiO3 excellent performance for solar-driven DRM. This article is protected by copyright. All rights reserved.

Study on the synergistic effect of the binary compound system of cardanol sulfonate

Abstract In the present work, the anionic biomass surfactant cardanol sulfonate (CDS) was compounded in different molar fractions (α 1) with the commonly used amphoteric surfactant lauryl amidopropyl betaine (LAB) and the nonionic surfactant alkyl glycoside (APG), respectively. By measuring the surface tension of the binary compound system, the relationship between the surface chemical properties of the compound system and α 1 was investigated, and then the synergistic parameters and thermodynamic parameters of the compound system were calculated. The results showed that both CDS/LAB and CDS/APG systems exhibited non-ideal mixing behavior. The CDS/LAB compound system has the best synergistic effect when the two components were mixed in a 1:1 molar ratio, corresponding to a CMC of 3.06 × 10−4 mol L−1 and a γ CMC of 32.60 mN m−1. The formation of mixed micelles was a spontaneous exothermic process driven by enthalpy. The CDS/APG compound system at the molar ratio of n(APG): n(CDS) = 9:1 has a more significant synergistic effect, corresponding to a CMC of 1.13 × 10−4 mol L−1 and a γ CMC of 29.10 mN m−1. The application performance of the compound systems was the best at the optimal molar ratio, which confirms the existence of synergistic effect in the compound systems.

Tuning surface wettability of MoS2 to enhance solar‐driven evaporation rates

AbstractMolybdenum disulfide (MoS2), a promising two‐dimensional photothermal material, possesses the capability to convert solar irradiation into thermal energy. This conversion is beneficial for processes like wastewater treatment and seawater desalination. Nevertheless, the influence of the surface chemical properties of MoS2, particularly its wettability, on the evaporation rate of water confined to the surface remains unexplored. In our study, we demonstrate that the wettability degree of MoS2 significantly influences its water evaporation rate performance. Interestingly, this parameter can be simply and accurately modulated by altering the synthesis time of MoS2. We synthesized MoS2 via a simple hydrothermal method at three different durations: 16, 20, and 24 h, at 200°C. Subsequently, we impregnated the resultant MoS2 onto air‐laid paper (ALP), forming a solar‐driven evaporator system. We found that the MoS2 nanosheets synthesized within the shortest duration (MoS2‐16 h) exhibited the highest evaporation rate of 1.77 kg m−2 h−1, along with 92% energy efficiency. MoS2‐16 h resulted in MoS2 rich in defects, featuring the largest surface area and the smallest contact angle. The hydrophilic areas of MoS2‐16 h facilitated the continuous diffusion of water molecules through defect sites, treating them as contact lines. Additionally, the expansive surface area introduced a larger region for light absorption, enhancing water‐solid interactions. The presence of molybdenum oxide on the surface of the nanosheet system also contributed to superior wettability behavior. Notably, all the tested MoS2/ALP systems in this study displayed excellent performance in salt rejection and heavy metal ion concentration reduction.

Preparation of Thin Film Composite (TFC) Membrane with DESPs Interlayer and Its Forward Osmosis (FO) Performance for Organic Solvent Recovery.

To explore the application of forward osmosis (FO) technology in the organic solvent recovery field, we prepared a new solvent-resistant triple layer thin film composite (TFC) membrane on the PI (polyimide) substrate. The deep eutectic supramolecular polymers (DESPs) interlayer was constructed on the substrate to improve the separation performance and solvent resistance. DESPs interlayer was formed by mixing and heating with cyclodextrin as the hydrogen bond acceptor and L-malic acid as the hydrogen bond donor. The chemical changes, surface property and morphology of the composite membrane with DESPs interlayer were characterized. The separation performance and stability of the triple layer composite membrane in organic solvent FO were studied. For the monascorubrin-ethanol system, the permeation flux of TFC/DESPs5-PI membrane could reach 9.51 LMH while the rejection rate of monascorubrin was 98.4% (1.0 M LiCl/ethanol as draw solution), which was better than the pristine membrane. Therefore, this solvent-resistant triple layer composite FO membrane has good potential for the recovery of organic solvents.

Decontamination of biofilm-contaminated implant surfaces: An in vitro evaluation.

The aim of the present study was to evaluate the cleaning efficacy of two mechanical and two chemical protocols in the decontamination of implant surfaces. In total, 123 commercially available implants were mounted in plastic models mimicking peri-implant circumferential intra-bony defects. A multispecies biofilm was grown on implant surfaces. Mechanical (air-polishing (AP), rotating titanium brush (TiB)) and chemical decontamination (alkaline electrolyzed water, N-acetyl-L-cysteine) protocols were used. Cleaning efficacy in terms of residual biofilm area, chemical surface properties, and bacterial counts were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and quantitative polymerase chain reaction. Surface decontamination protocols including use of an AP device or a rotating TiB were superior in terms of biofilm removal and in reducing atomic% of Carbon on implant surfaces when compared to methods restricted to wiping with gauze. The use of chemical agents as adjuncts to the mechanical cleaning protocols provided no relevant overall benefit over saline. No treatment modality, however, resulted in complete biofilm removal. Air-polishing and rotating TiB were more effective implant surface decontamination protocols than wiping with gauzes. Use of chemical agents did not improve cleaning efficacy.

Multiresponse optimization in amylolytic desizing of viscose fabric in the copresence of ferrous ions and an anionic surfactant

Purpose This study aims to investigate the effect of the copresence of ferrous (Fe2+) ions and sodium dodecyl sulfate (SDS) on the activity of an amylase enzyme during the desizing of greige viscose fabric for potential industrial applications. The removal of starches is an essential step before processing the fabric for dyeing and finishing operations. The authors tend to accomplish it in eco-friendly and sustainable ways. Design/methodology/approach The experiments were designed under the Taguchi approach, and the results were analyzed using grey relational analysis to optimize the process. The textile properties of absorbency, reducing sugars, bending length, weight loss, Tegawa rating and tensile strength were assessed using the standard protocols. The control and optimized viscose specimens were investigated for certain surface chemical properties using advanced analytical techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). Findings The results demonstrate that the Fe2+ concentration and process time were the main influencing factors in the amylolytic desizing of viscose fabric. The optimized process conditions were found to be 0.1 mm Fe2+ ions, 3 mm SDS, 80°C, 7 pH and 30 min process time. The copresence of Fe2+ ions and SDS promoted the biodesizing of viscose fabric. The SEM, Fourier transform infrared spectroscopy, XRD and TGA results demonstrated that the sizing agent has efficiently been removed from the fabric surface. Practical implications The amylase desizing of viscose fabric in the presence of certain metal ions and surfactants is a significant subject as the enzyme may face them due to their prevalence in the water systems. This could also support the biodesizing and bioscouring operations to be done in one bath, thus making the textile pretreatment process both economical and environmentally sustainable. Originality/value The authors found no report on the biodesizing of viscose fabric in the copresence of Fe2+ ions and the SDS surfactant under statistical multiresponse optimization. The biodesized viscose fabric has been investigated using both conventional and analytical approaches.

Fabrication of CNTs-reinforced poly(vinyl alcohol) nanocomposite film with tailored structural, surface chemical and optical properties

Purpose This study aims to fabricate multiwalled carbon nanotubes (MWCNTs)-mediated polyvinyl alcohol (PVA) composite films using the solution casting approach. Design/methodology/approach The prepared films were evaluated for diverse structural, surface, optical and electrical attributes using advanced analytical techniques, i.e. electron microscopy for surface morphology, Fourier transform infrared spectroscopy for tracing chemical functionalities, x-ray diffraction (XRD) for crystal patterns, water contact angle (WCA) analysis for surface wettability and UV visible spectroscopy for optical absorption parameters. The specimens were also investigated for certain rheological, mechanical and electrical properties, where applicable. Findings The surface morphology results expressed a better dispersion of MWCNTs in the resultant PVA-based nanocomposite film. The XRD analysis exhibited that the nanocomposite film was crystalline. The surface wettability analysis indicated that with the inclusion of MWCNTs, the WCA of the resultant nanocomposite film improved to 89.4° from 44° with the pristine PVA film. The MWCNTs (1.00%, w/w) incorporated PVA-based film exhibited a tensile strength of 54.0 MPa as compared to that of native PVA as 25.3 MPa film. There observed a decreased bandgap (from 5.25 to 5.14 eV) on incorporating the MWCNTs in the PVA-based nanocomposite film. Practical implications The MWCNTs’ inclusion in the PVA matrix could enhance the AC conductivity of the resultant nanocomposite film. The prepared nanocomposite film might be useful in designing certain optoelectronic devices. Originality/value The results demonstrated the successful MWCNTs mediation in the PVA-based composite films expressed good intercalation of the precursors; this resulted in decreased bandgap, usually, desirable for optoelectronic applications.

Ginger oil and lime peel oil loaded PBAT/PLA via cast-extrusion as shrimp active packaging: Microbial and melanosis inhibition

Biodegradable active packaging for shrimp was produced via cast sheet extrusion of poly (butylene adipate terephthalate) and poly (lactic acid) (PBAT/PLA) at different ratios, incorporating ginger oil (GO) and lime peel oil (LPO). Surface chemistry, mechanical and barrier properties, volatile mass fraction, and antimicrobial activities were investigated. Microbial growth and melanosis of packaged shrimp were monitored. Gas chromatography-mass spectrometry indicated major volatile components of LPO and GO as D-limonene (40.55%) and L-zingiberene (19.85%), respectively. Essential oil loading improved polymer compatibility via C-H bonding and modified the polymer crystallinity, leading to improved film flexibility but reduced tensile strength. GO incorporation showed greater release of volatile mass fraction from the film matrix than LPO, with increased oxygen permeability and water contact angle. High PBAT film (PBAT70/PLA30) allowed greater release of essential oil than high PLA film (PBAT30/PLA70), with higher antimicrobial activity against Bacillus cereus. Film containing LPO was more effective in inhibiting microbial growth, while film containing GO showed superior prevention of melanosis in packaged shrimp. A linear correlation was found between microbial growth and degree of melanosis in shrimp packaged in PBAT/PLA packaging containing GO and LPO. Both LPO and GO effectively enhanced film functional properties and showed promise for seafood packaging with different mechanisms of ameliorating product bacterial degradation.

Influences analysis of Sb/Si dopant in TiO2 on NH3-SCR activity and low temperature SO2 resistance of V2O5/TiO2 catalysts

The Sb/Si doped TiO2 prepared by sol–gel method were used as supports of V2O5/TiO2 SCR catalysts in order to improve SCR activity and SO2 resistance. The type of dopant atoms changed catalyst physiochemical properties discriminatively. Surface chemical properties of catalysts played more important role in their catalytic performance. Simultaneous enhanced surface acidity and redox capacity leaded to the better SCR activity for V2O5/Sb-TiO2 compared with other catalysts. The low temperature SO2 resistance was improved for the support doped catalysts. The special electronic charge migration brought by surface sulfate species for V2O5/Sb-TiO2 even elevated its SCR activity during SO2 resistance test, which was due to the formation of new acid sites and enhancement of redox performance. Even though NOx conversion for V2O5/Si-TiO2 decreased, the relative stable efficiency was kept at low temperatures with SO2. The results proved hetero atom doping in TiO2 by sol–gel method was a useful method to improve low temperature SO2 resistance of catalysts. By contrast, Sb is a better choice for the development of support doped V2O5/TiO2 SCR catalyst used in a wide temperature range.

Comparative study on weld characterisation and corrosion performance of laser-welded NiTinol

ABSTRACT Laser welding of NiTinol is a promising fabrication method. An understanding of the effects of laser heat input on different surface properties and corrosion resistance behaviour is needed for laser-welded sea water-flooded components of NiTinol. Here the effect of laser heat input on various physical, chemical and mechanical surface properties along with the corrosion resistance behaviour of the laser welded samples was investigated. The corrosion resistance performance of the phase-separated samples was found to be inferior to the other laser-welded samples. The top surface showed a superior corrosion resistance performance because of the recirculation of the melt pool and Ti enrichment on top surface.

Electronic Structure and Surface Chemistry of Hexagonal Boron Nitride on HOPG and Nickel Substrates.

The effect of point defects and interactions with the substrate are shown by density functional theory calculations to be of significant importance for the structure and functional properties of hexagonal boron nitride (h-BN) films on highly ordered pyrolytic graphite (HOPG) and Ni(111) substrates. The structure, surface chemistry, and electronic properties are calculated for h-BN systems with selected intrinsic, oxygen, and carbon defects and with graphene hybrid structures. The electronic structure of a pristine monolayer of h-BN is dependent on the type of substrate, as h-BN is decoupled electronically from the HOPG surface and acts as bulk-like h-BN, whereas on a Ni(111) substrate, metallic-like behavior is predicted. These different film/substrate systems therefore show different reactivities and defect chemistries. The formation energies for substitutional defects are significantly lower than for intrinsic defects regardless of the substrate, and vacancies formed during film deposition are expected to be filled by either ambient oxygen or carbon from impurities. Significantly lower formation energies for intrinsic and oxygen and carbon substitutional defects were predicted for h-BN on Ni(111). In-plane h-BCN hybrid structures were predicted to be terminated by N-C bonding. Substitutional carbon on the boron site imposes n-type semiconductivity in h-BN, and the n-type character increases significantly for h-BN on HOPG. The h-BN film surface becomes electronically decoupled from the substrate when exceeding monolayer thickness, showing that the surface electronic properties and point defect chemistry for multilayer h-BN films should be comparable to those of a freestanding h-BN layer.

Fabrication of perovskite solar cells with PCE of 21.84% in open air by bottom-up defect passivation and stress releasement

The archetypical n-type semiconductor material, tin oxide (SnO2), is common and well-known electron transport layer (ETL) material in regular perovskite solar cells (PSCs) due to the superior electron mobility and suitable energy level alignment with perovskite. However, plentiful detrimental defects concentrated at perovskite/SnO2 ETLs interface and unfavorable residual stress within perovskite films, compromise and dampen the photovoltaic performance and shelf stability of PSCs. Herein, alkali metal salts (i.e., 2, 2′-biquinoline-4, 4′-dicarboxylic acid alkali metal salts (BCA-2H, BCA-2Na, and BCA-2K)) are employed as pre-buried modifiers in SnO2 films to achieve a holistic amelioration of ETLs, perovskite photoactive layer, and their interface heterojunction. The BCA modification facilitates crystal orientation and crystalline of SnO2 nanocrystals, instrumental in decreasing trap state densities within functional layers, releasing interfacial residual tensile strain, and upgrading perovskite film performance. In comparison to BCA-2H- and BCA-2Na-doped ETLs, the BCA-2K decoration corroborate better defect passivation and stress release effect originating from preferable interface enhancement and desirable surface chemical properties. Consequently, the PSCs based on SnO2-BCA-2K ETL fabricated under open-air conditions deliver the champion efficiency of 21.84% accompanied by negligible hysteresis. Moreover, the unpacked devices maintain 81.2% of its original value after 1200 h storage under an ambient condition of 55 ± 5% (relative humidity, RH) and 25 ± 5 ℃ with open-circuit conditions.

Assessment of Cr doping on TiO2 thin films deposited by a wet chemical method

Undoped and Cr-doped TiO2 thin films were synthesized by the dip-coating sol-gel process with titanium isopropoxide and chromium (III) chloride hexahydrate being used as the precursors. The chromium concentrations changed for different molar ratios, namely, 2, 4, and 8 wt.%. The samples, coated on glass substrates, were later annealed in air at 450 °C for 60 min. The influence of Cr doping on the structural, surface chemical, and optical properties of the samples was studied by several techniques, including EDS, Raman, UV–Vis, RT-PL, and XPS spectroscopies, as well as SEM and XRD. The diffraction patterns indicated that all the films displayed the anatase structure with the crystallite size decreasing with chromium doping. The same structure was confirmed by Raman spectroscopy measurements. UV–Vis absorption spectra of the samples showed a red shift of the fundamental absorption edge in the visible range following the increase of Cr doping concentration. In addition, the RT-PL study revealed that the dopant incorporation causes a decrease in the PL intensity. The EDS analysis revealed the presence of Ti, O, and Cr in the materials. Moreover, from high-resolution XPS Ti 2p spectra, titanium was found to be in the Ti4+ oxidation state evidencing the formation of TiO2, while the Cr 2p fitting analysis showed that chromium is present in the Cr (III) and Cr-metal states.

Investigation on structural, morphological and magnetic properties of Barium Cobaltite (BaCoO3) nanoparticle

Both the structural characteristics and the magnetic property of the polycrystalline BaCoO3(BCO) perovskite oxide have been thoroughly researched. The synthesis of polycrystalline BaCoO3 ceramics was accomplished using a solvothermal method. Through the use of thermogravimetric analysis, the thermal stability of BaCoO3 (TGA) was checked. In order to examine the crystal structures, microstructures, and surface chemical state properties of BCO ceramics, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) experiments were carried out. The XRD patterns indicate that the phases that were present in the calcined samples were hexagonal perovskite phases. The multilayer plated structure can be seen in SEM picturesand EDAX confirmed the elemental stoichiometry. Isothermal magnetization studies on the compound were carried out at room temperature (RT), and it was discovered that the complex possessed ferromagnetic properties. The deformed CoO6 that was found by Raman and XPS may be related to the oxygen defect known as perovskite. This faulty property suggests that BCO NPs have a ferromagnetic character.

Utilisation of raw oil shale as fine aggregate to replace natural sand in concrete: Microstructure, surface chemistry and macro properties

This study set out to examine the unconventional use of raw oil shale (OS) as fine aggregate in concrete instead of its traditional utilisation as a pollutant energy source aiming to hinder the depletion of natural resources. Oil shale particles have been used to replace sand in concrete with 30 wt.-% and 50 wt.-% ratios. Part of the used OS particles was treated with silane prior to their addition in concrete. The fresh, mechanical, and durability properties, along with the micro-properties and surface chemistry of mixtures, were analysed by running the slump, compressive strength, permeability, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR) tests, respectively. Five concrete mixtures consisting of 30 samples with the size of 150 mm x 150 mm x 150 mm were prepared to serve the testing programme of the study. The results revealed the formation of a well-bonded interfacial transition zone between untreated OS particles and the cementitious matrix due to the presence of pozzolanic materials in OS. However, micro cracks and enlarged capillary pores were witnessed in treated OS mixtures along with a weak interfacial transition zone between the treated OS and the cementitious matrix. Moreover, the use of 30 wt.-% untreated OS reduced the water absorption of concrete by 9% (absorption rate of 9.5%), while other mixtures experienced an increase in their water absorption with a maximum increase of 42% when using 50 wt.-% treated OS (absorption rate of 10.7%). All mixtures attained a reduction in their compressive strength compared to control sample when employing treated and untreated OS in concrete, with a minimum reduction of 13% when using 30 wt.-% untreated OS (compressive strength of 26 MPa). The strength reduction in untreated OS mixtures is due to the formation of free CaO and free SiO2, which promote concrete expansion. The interference between silane and kerogen in OS was the main reason behind the strength reduction in treated OS mixtures. However, this reduction in mixtures’ strength is considered minimal, allowing for their potential use in different construction applications like rigid pavement.

Post-annealing of hematite films: The changes in surface chemistry, lattice dynamics, and photoelectrochemical properties

This research deals with tracking changes in the surface chemistry and lattice dynamics of α-Fe2O3 (hematite) thin films upon post-annealing and its correlation with the photoelectrochemical (PEC) properties. The hematite thin films were prepared by the electric field-assisted liquid phase deposition (EA-LPD) method. The as-prepared thin films were heated at three different heating rates: 10, 22, and 80 ℃/min to 350 ℃; and kept for 15 min and then quenched in the air. The structural characterizations showed that the post-annealing process induces oxygen vacancies and the formation of hydroxyl groups on the surface. The extent of the changes in the surface chemistry strongly depends on the heating rate. Such changes in the surface chemistry possess a synergic effect on the PEC properties. Here the post-annealed photoanodes with an 80 ℃/min heating rate showed significantly improved PEC activity and exhibited a maximum photocurrent density ⁓ 0.73 mA.cm−2 at 1.23 V vs. RHE, 2.5 times higher than that for pristine sample. The lattice dynamics investigations suggested that the as-prepared photoanodes are composed of α-FeOOH. Upon post-annealing, α-FeOOH was partially converted into a proto-hematite intermediate phase. The longitudinal optical (LO) modes for the post-annealed samples enhanced as an indicator for the development of lattice disorder, as the results of induced oxygen vacancy defects and hydroxyl groups on the surface.