FeO Content Research Articles

Fe3O4‐doped highly electromagnetically shielded PAN‐PVP composite porous carbon films

AbstractWith the wide application of modern electronic devices, the problem of electromagnetic pollution is becoming more and more serious, and the demand for efficient electromagnetic shielding materials is becoming more and more urgent. To address this problem, we homogeneously mixed polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and triiron tetraoxide (Fe3O4) nanoparticles by solution blending, and prepared composite precursor membranes by taking advantage of the magnetic properties and good electromagnetic loss characteristics of Fe3O4, as well as the high thermal stability and film‐forming properties of PAN and PVP. Subsequently, carbonized PAN‐PVP/ Fe3O4 composite films with different Fe3O4 contents were successfully prepared by carbonization under high temperature inert atmosphere to convert PAN and PVP into carbon materials. It was found that the PAN‐PVP/ Fe3O4 porous carbon film with 3 wt% Fe3O4 addition had a conductivity of 3.99 S·mm−1 at a thickness of 0.42 mm, and an average EMI SET of 78.9 dB, SEA of 64.8 dB, and SSEt of 1838 dB/(cm2·g−1) in the X‐band, which is a typical wave absorbing material and can meet commercial electromagnetic shielding requirements. This work provides new ideas and methods for the research and development of polymer‐based porous carbonized film as electromagnetic shielding materials.Highlights The carbon films with rich porous structure were prepared. Fe3O4 was successfully embedded into the carbon film. Carbon films have an efficient conducting network. Carbon film has excellent electromagnetic shielding performance. The main shielding mode of carbon film is absorption.

Influence of high‐iron bauxite on phase composition, microstructure, and properties of bauxite‐based homogenized grogs

AbstractInvestigation on the occurrence state of Fe2O3 in bauxite and its effect on the bauxite‐based homogenized grogs (BHG) is crucial for the utilization of high‐iron bauxite resources. BHG with different Fe2O3 contents incorporated in the form of high‐iron bauxite was prepared by maintaining the Al2O3 content around 82%. The effect of high‐iron bauxite addition (0, 25, 50 75, 100 wt.%) on the phase composition and microstructure evolution was studied using X‐ray diffractometer, scanning electron microscope, and Factsage software. The results show that part of the Fe2O3 in BHG is dissolved into crystalline phases, while the other part is present as a glass phase. The addition of high‐iron bauxite, coupled with a reduction in the SiO2 content, results in a rise in the corundum content within BHG from 55.0% to 93.6% and a decrease in the mullite content from 44.0% to 2.8%. This change results in a decline in the refractoriness under load of T0.6, dropping from 1593.5°C in the sample without high‐iron bauxite to 1430.7°C in the sample with 100% high‐iron bauxite addition. The microstructure of BHG evolves from the interconnected network of corundum and mullite phases to the structure of corundum bonded by the glass phase.

Remote sensing analysis and geodynamic setting of magmatic spessartine-almandine-bearing leucogranites, Um Addebaa area, southeastern Desert, Egypt: Bulk rock and mineral chemistry

This study aims to incorporate optical multispectral remote sensing, petrography, geochemical, and field investigations in producing mapping and surface abundance of garnet mineralization within Um Addebaa area, southeastern Desert of Egypt. Datasets of Landsat-8 OLI/TIRS, ASTER and Sentinel-2A (S2A) were handled and scaled enhanced to discriminate the units of lithologic rock and garnet mineralization. The spectral mapping techniques of constrained energy minimization (CEM) and matched filtering (MF) are used to detect the garnet-rich zones which confined to the leucogranites masses. These granites are spessartine-almandine-rich, certainly along the interaction with the ophiolitic mélange. Notably, they have high total alkalis, SiO2, and Al2O3, Rb, 104Ga/Al, Y, Zr, Pb, Rb/Sr, Al2O3/TiO2, and FeO/MgO, and strong Ti, Sr, and Ba depletion as well as low CaO/Na2O ratio (<0.3). These geochemical parameters reflecting calc-alkaline, and strongly peraluminous magma of S-type. They are derived by two episodes of partial melting clay-rich metapelite crustal rocks followed by extreme Fe-Ti oxides and feldspar fractionation. These leucogranites formed within extension tectonic regime during post-collisional episode, resulting raising of asthenosphere and partial melting of the crustal metasedimentary rocks. Garnet occurs as, aggregates and/or vein like-shape, subhedral to rounded grains, homogenous and rarely reveal weak zonation. It’s cracked and free of inclusions. It contains appreciated concentrations of FeO and MnO and minor amounts of CaO and MgO, dominantly spessartine-almandine end-member (Alm52-59Sps 31-36 Grs 8-12 Prp0.5-0.8 Adr0). Garnet chemical composition reflect it is magmatic origin with MnO- FeO-rich magma that is produced from in situ nucleation from strongly peraluminous magmas during post- collision setting.

Bedrock characterization and geochemical evolution of whole-rock weathering profile at GAG Ni laterite deposit, Southwest Papua, Indonesia

Abstract A series of laboratory analyses were conducted to investigate the correlation of petrography analyses of a bedrock coupled with microscope observation and X-Ray Diffraction (XRD) then compared with distribution of geochemical elements of whole-rock weathering profile by X-Ray Fluorescence (XRF). The microscope identification revealed that the bedrock was marked by the appearance of pyroxene predominantly surrounding olivine and serpentine, then magnetite, while XRD clarified that the bedrock was predominantly contained by a number of serpentine (lizardite), then pyroxene (enstatite), and magnetite. The geochemical evolution by bulk major-minor elements geochemistry as well as gain and losses of elements (τ) and compared with the equation from the ultramafic index alteration (UMIA) revealed that Fe2O3, NiO, Al2O3, CoO, Cr2O3 and MnO contents in the bedrock were 7.18wt%, 0.23 wt%, 1.23wt%, 0.01wt%, 0.35wt%, and 0.11wt%, respectively, then strongly increased towards the transition zone to 35.89wt%, 2.04wt%, 9.01wt%, 0.10wt%, 1.87wt%, and 0.51wt%, respectively. SiO2 and MgO revealed an inverted trend where it enriched in the bedrock then extremely decreased limonite layer with SiO2 (τ = ~ -0.92) and MgO (τ = ~ -0.99). The highest value of UMIA as well as consequently the highest degree of chemical weathering in this study was located in the upper limonite with a value of 63.87.

Air drying using Fe3O4-silica gel composite laminates and hollow tubes with magnetic induction heating based adsorbent regeneration

In the context of the chemical industry’s electrification, magnetic induction swing adsorption (MISA) has garnered attention in recent years, as it allows the direct conversion of renewable electrical energy into thermal energy. In this study, MISA was employed as an alternative technology for regenerating gas- and air drying adsorbents. For this purpose, composite adsorbents were synthesized, primarily composed of silica gel (as the adsorbent) and Fe3O4 (as the magnetic susceptor), and structured into either sheets or tubes. The inclusion of Fe3O4 reduced the surface area and mass adsorption capacity, but the hydrophilic character was retained, allowing for sustained water uptake. Additionally, the smaller particle size of silica gel in the composite material, compared to silica gel granules, enhanced the uptake kinetics, leading to faster saturation. Static experiments (without a convective gas flow) indicated that both the electric current and the Fe3O4 content significantly influenced heat generation and, consequently, the regeneration time. With a current of 49.4 A and 20 wt% Fe3O4, the temperature increased by 10 °C after 3600 s, removing 42 % of the adsorbed water. In contrast, at 100.7 A and 40 wt% Fe3O4, the temperature reached 250 °C in just 180 s, resulting in the removal of 92 % of the adsorbed water. The use of an convective flow over the material enhanced the regeneration efficiency to > 97 %. For the first time, a systematic analysis was conducted on the regeneration of integral water-saturated adsorbents using magnetic induction heating.

Geochemical suitability of Limestone for Cement making: A case study of Joldhal Formation

In this work, we investigate the industrial potentiality of limestone deposits in the Joldhal Formation of the Shimoga Schist Belt, Dharwar Craton. Based on their mineralogy, petrography, and geochemical characteristics. Twenty-five different limestone samples were collected from distinct locations and analyzed using X-ray fluorescence and X-ray diffraction techniques. Petrographically, these limestone deposits consist predominantly of calcite, quartz, chlorite, mica, micrites, etc. The X-ray diffraction studies indicated the dominance of calcite as an essential carbonate mineral, and quartz, kaolinite, chlorite, and mica/illite are major gangue minerals in the studied limestone. The results of the geochemical investigation of 25 samples indicated that the limestone from the study area exhibits a wide range of variation in LOI (27.99–42.82 wt%), SiO2 (0.21–19.60 wt%), CaO (27.80–55.50 wt%), Al2O3 (0.11–8.48 wt%), Fe2O3 (0.23–9.28 wt%), and MgO (0.51–9.79). Traces of K2O, Na2O, and TiO2 are found. This study illustrates how crucial it is to evaluate limestone's geochemical characteristics prior to cement making. Various factor analyses were calculated, like lime saturation factor, silica modulus, and alumina ratio, for suitable high-quality cement production. Bandigudda, Hanne, and Joldhal area valuable for cement manufacturing, unlike Medugondanahalli and Vitalapura, due to their impure quality and below-average parameter values. The results indicate suitability for cement production. The deposit's SiO2, Al2O3, and Fe2O3 content meet the ultimate moduli values of the raw material, indicating its suitability for cement production. This study emphasizes the significance of the geochemical evaluation of limestone for cement production

Harnessing Fe2O3 to improve HAP composites: Investigating radiation shielding, mechanical attributes, and magnetic field effects

Hydroxyapatite (HAP) bio-composites play a prominent role in addressing the reparative and replacement needs of human bone and dental tissues. Despite the suboptimal mechanical characteristics inherent in pure HAP, strength and durability enhancements have been achieved by incorporating various alloys and materials. The provided study delves into the radiation shielding and mechanical attributes of Fe2O3-reinforced HAP composites intended for use as implants, featuring Fe2O3 concentrations at 0.0, 2.5, 5.0, and 7.5 wt%. In addition, by leveraging the robust FLUKA Monte Carlo simulation code, the study explores the composites' response to the magnetic field. The findings suggest that augmenting the Fe2O3 content improves radiation shielding and mechanical properties in the chosen samples. Furthermore, in the absence of a magnetic field, the particles' spatial distribution (contour curves) exhibits symmetry along the X-axis. Nonetheless, a discernible pattern becomes apparent upon exposure to a magnetic field of Bx = 5 micro Tesla. The data extracted from this article can be used for medical and therapeutic applications and subsequent studies.

Potential engineering applications of volcanic scoria from Mount Cameroon area, Central Africa: evidence from petrography and geochemistry

This study was initiated to explore the suitability of volcanic scoria from Mount Cameroon along the Cameroon Volcanic Line (CVL) in engineering applications. The mineral composition has been obtained through thin sections observation and XRD method. The XRF analytical methods have been used to determine major element composition. The studied rocks are dark gray to reddish in color with a vacuolar structure and porphyritic microlithic texture recalling the Strombolian dynamism. They are mainly made up of pyroxene, olivine, plagioclase, opaque minerals, quartz, magnetite and iddingsite. The presence of phenocrysts of olivine and clinopyroxene is due to mantle contamination. The main chemical components of scoria of Mount Cameroon are silica, alumina, iron and calcium oxides. The abundant vitreous phases are responsible for the acidic character revealed by high SiO2 + Al2O3 contents. Fe2O3, MnO and MgO are hosted by ferromagnesian minerals while SiO2, Al2O3, K2O, NaO and P2O5 are found in acidic vitreous phases. The mineral and chemical composition of the scoria of Mount Cameroun is similar to those of scoria previously studied around the world. They can be used as absorbents for metals because of their high adsorption capacity and affinity for metals. The high SiO2 + Al2O3 + Fe2O3 contents and low LOI values show that the scoria from Mount Cameroon are suitable to the use in cement and concretes. They can improve the resistance to sulfate, and chlorite and alkali silica reaction. According to the chemical composition, the rocks are conforming to French standard NFP18310. Their high CaO contents are favorable to improve the quality of scoria blended cements.

Study on physical, electrical, magnetic and energy harvesting performances of eco-friendly piezoelectric ceramics (1 − x)[0.995BNKT–0.005LN]–xFe2O3 complex system

ABSTRACT In this work, the complex lead-free piezoelectric ceramics with formula (1 − x)[0.995 Bi0.5(Na0.80K0.20)0.5TiO3–0.005LiNbO3]–xFe2O3, where x = 0, 0.010, 0.015 and 0.020 mol fraction, have been prepared via a conventional solid-state method. The effects of Fe2O3 doping on the physical, microstructural electrical, energy harvesting and magnetic properties have been systematically investigated. All ceramics were sintered at 1150°C for 2 hours with obtained relative density of ~ 96-97%. The XRD and Raman data revealed the coexisting rhombohedral and tetragonal phases for all samples. SEM image presented angular grain packing with the average grain size range of 0.43–1.03 μm. The addition of Fe2O3 content improved in electrical properties of undoped sample particularly at a composition of x = 0.015. The maximum values of ε m = 6250, S max = 0.29, d*33 = 578 pm/V, d 33 = 211 pC/N and FOM = 3.54. All ceramics indicated ferromagnetic behavior with slim hysteresis shape. The results suggest a potential for its applications as an eco-friendly compound for further use in sensor, spintronic and microelectronic devices applications.

Mechanism and optimization of sintered ultra-lightweight aggregates with sand washing slurry and red mud

Sand washing slurry, red mud, and waste sawdust are major solid wastes produced by the construction, mining, and wood processing industries, respectively. Their accumulation poses significant environmental hazards and results in substantial wastage of resources. This study utilized a novel rapid roasting method to prepare ultra-lightweight ceramsite aggregates (ULC) using sand washing slurry, red mud, and sawdust as raw materials. A new process for preparing ultra-lightweight clay aggregates (ULCA) utilizing waste sand washing sludge is proposed, achieving a utilization rate of the wash sand sludge exceeding 60%. Ultra-lightweight clay aggregates with a loose bulk density of 264.3 kg/m3 were produced. The influence of material formulation on the performance of ultra-lightweight clay aggregates was studied. The phase changes and expansion mechanism of the clay aggregates were revealed from microscopic and chemical perspectives. The synergistic effect of red mud and sawdust significantly enhanced the foaming effect of the ceramsite (i.e., porosity), reducing its loose bulk density while slowing the rate of strength reduction. Additionally, increasing the content of red mud and sawdust promoted ceramsite expansion. When the mass ratio of sand washing slurry, red mud, and sawdust was 29: 12: 1, with Fe2O3 content at 13% and sawdust content at 3%, preheating at 500°C for 5 minutes followed by roasting at 1150°C for 5 minutes produced ultra-lightweight ceramsite with a compressive strength of 1.7 MPa. This study provides a promising method for producing ULC from industrial solid wastes.

Gamma-ray shielding effectiveness, optical, mechanical, dielectric properties of nanofiller-reinforced PVA/PVP polymeric blend nanocomposites

The aqueous solution cast method was used to create the biodegradable polymer nanocomposite (PNC) films from a blend of poly (vinyl alcohol) PVA and poly (vinyl pyrrolidone) PVP (70/30 wt %) and Fe2O3 nanoparticles (NPs). These PNC films were characterized using X-ray diffraction, scanning electron microscopy SEM, Fourier transform infrared spectroscopy FTIR, and ultraviolet-visible spectroscopy. XRD and FTIR results indicate that Fe+ 3 NPs interact with the host polymer. Optical, electrical, mechanical, and radiation shielding measurements were performed on the PNC films. From the optical measurements, the indirect optical band gap drops from 4.86 eV for the pure blend to 4.26 eV at the greatest NPs concentration. Optical limiting characterization shows that the output power of He-Ne and solid-state green laser beams is reduced from 22.98 to 3.6 mW and 6.59 to 1.4 mW, respectively, when the Fe2O3 NPs content in the blend matrix is increased to 6 wt %. The NGCal software was utilized to calculate nuclear radiation shielding properties. The findings demonstrated that when the concentration of Fe2O3 rose, the PNC films half-value layer and mean free path decreased. Mechanical measurements demonstrate that increasing the Fe2O3 content significantly improves nanocomposite films’ yield and tensile strength. Tensile strength is measured at 27.03 MPa for the composite film containing 6 wt % Fe2O3, which is significantly higher than the 8.66 MPa of the pure (PVA-PVP) film. Compared to the other samples under examination, the 6 wt % Fe2O3 sample yielded the best results (based on the analyzed optical, electrical, mechanical, and radiation shielding properties).

Photoelectric activity evaluation of surface-loaded ferroferric oxide/titanium dioxide composite prepared from ilmenite

This work demonstrates a surface-loaded Fe3O4/TiO2 composite with the magnetic Fe3O4 deposited on the surface of anatase TiO2 nanocrystal which can be directly prepared from the ilmenite using the coprecipitation method. After the acidolysis treatment with the 95% dissolution rate, the ilmenite will be first transformed into H2TiO3 and FeCl2, and the photoactive anatase TiO2 nanocrystals are obtained from the calcined H2TiO3 at 500[Formula: see text]C. Then a surface-loaded Fe3O4/TiO2 composite TF is finally achieved by the coprecipitation method, which is carefully elaborated to balance the magnetism and photoactivity of Fe3O4/TiO2 composite by the optimal contents of Fe3O4 and TiO2. It is encouraging to note that Fe3O4/TiO2 composite TF shows a good comprehensive performance in serial photodegradation experiments of Rhodamine B. The degradation rate of Rhodamine B is more than 99% during 60 min under the irradiation of both xenon lamp and sunlight. During at least six cycles, the composite TF can show stable photocatalytic activity and good durability together with the recovery and recycling potentials by using an external magnet.

Iron-bound organic carbon declined after estuarine wetland reclamation into paddy fields

Iron-bound organic carbon (Fe-OC) is a main pathway for the long-term maintenance of soil organic carbon (SOC), but research on its mechanism is still relatively weak. We investigated the coupling relationships among iron (Fe), carbon (C) and Fe-reducing bacteria (FeRB) in the soil of a reclaimed paddy field in comparison with natural Phragmites australis wetland in the Minjiang River estuary in southeastern China. The results showed that conversion of P. australis wetland to paddy cultivation changed the soil redox process. After reclamation, soil Fe(II), Fe(III), HCl-Fet, free iron oxide (Fed) and amorphous iron (Feo) contents and Fe(III)/Fe(II) decreased significantly (p < 0.05), while the content of complexed iron (Fep) increased. Nonmetric multidimensional scaling analysis (NMDS) demonstrated variability in FeRB across soil types (r = 0.900, p = 0.001). The lower Fe-OC concentration in soil after wetland reclamation may be the result of Fe reduction by dissimilatory FeRB (e.g., Bacillus, Anaeromyxobacter). On average, both Fe-OC and SOC contents decreased significantly (p < 0.05), while the contribution of Fe-OC to total SOC (fFe-OC) increased significantly (p < 0.05), after conversion to paddy cultivation. Structural equation modeling (SEM) showed that SOC, dissolved organic C, and Fe-OC were affected by FeRB and the speciation of Fe. In addition, Fe (III) concentration affected SOC concentration (r = 0.60, p < 0.05) and DOC concentration (r = 0.58, p < 0.05), and Fed affected DOC concentration (r = 0.69, p < 0.05). We conclude that after rice field reclamation in estuarine wetlands, Fe-reducing bacteria can mediate iron-bonded organic C decoupling, affecting SOC stabilization.

Synthesis of Fe3O4 Derived from Acid Mine Drainage (AMD) Sludge and Catalytic Degradation of Tetracycline.

Acid mine drainage (AMD) sludge is waste generated in the process of acid mine wastewater treatment, and the use of AMD sludge to prepare Fe3O4 to activate H2O2 degradation pollutants is an effective means of resource utilization. In this study, the heterogeneous catalyst Fe3O4-based composites were synthesized by a one-step method using AMD sludge as a raw material, and the Fe3O4-based materials before and after catalysis were characterized by powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The effects of several key factors (pH values, H2O2 content, TC concentration, and Fe3O4 content) of tetracycline (TC) degradation were evaluated. The results revealed that the TC removal rate reached up to 95% within 120 min under optimal conditions (pH 3; H2O2, 5 mmol/L; TC concentration, 25 mg/L; Fe3O4 content, 1g/L). Moreover, •OH and •O2- radicals were generated during the Fenton-like degradation process, and the plausible degradation mechanism was discussed. Besides, the Fe3O4 catalyst exhibited fantastic stability after five cycles. In conclusion, this study is expected to promote the resource utilization of industrial sludge and provide a new material for the treatment of antibiotic-contaminated wastewater.

Properties evaluation of electric smelting furnace slag: Viscosity and sulfide capacity under different FeO content

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO2-6wt.%MgO-10 wt%Al2O3-FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process.

Investigating the variation of iron-titanium content in lunar farside regolith along the route of the Yutu-2 rover with lunar penetrating radar.

Abstract The Chang’e-4 lander successfully landed in the Von Kármán crater on the farside of the Moon in 2019, collecting a large amount of scientific data to analyze the surface material and subsurface structures of the Von Kármán crater. In this study, we processed the high-frequency radar data from the first 25 lunar days collected by the Lunar Penetrating Radar along the route of the Yutu-2 rover. Using the peak frequency shift method, we calculated the loss tangent of the shallow regolith layer ranged from 3×10−3 to 5.5×10−3. The estimated TiO2 and FeO content in the regolith is 11.2 wt% - 14.7 wt%, revealing a heterogeneous distribution of iron and titanium content along the CE-4 landing site.

Size effects on the magnetic properties of a system of ε-Fe2O3 nanoparticles embedded in a SiO2 xerogel matrix

A representative series of samples consisting of fine ε-Fe2O3 nanoparticles uniformly distributed over the SiO2 xerogel matrix with an iron oxide content of 5–33 wt % has been synthesized and studied by mutually complementary physical methods. It has been shown by the X-ray diffractometry and high-resolution electron microscopy examination that, with increasing iron oxide concentration, the average particle size <d> increases from 4 to 11 nm. According to the X-ray diffractometry and Mӧssbauer spectroscopy data, the samples with an iron oxide content of 5–20 wt % are single-phase, while at the highest Fe2O3 concentration (33 wt %), the β-Fe2O3 and α-Fe2O3 phases arise. As the average particle size <d> increases, a monotonic increase in coercivity HC and remanent magnetization MR of the synthesized systems at room temperature is observed, which is indicative of their magnetic hysteresis. The magnetic transition known to occur in the ε–Fe2O3 oxide manifests itself in all the investigated samples as a drastic change in the HC and MR values at 150–75 K. At the same time, a thorough analysis of the temperature dependence of the real part of the ac magnetic susceptibility χ′ has shown that the particles with a size smaller than a critical value of dC ∼6.5 nm do not undergo the magnetic transition and have a much lower magnetic anisotropy constant as compared with coarser particles (d > dC). It has been found that, in the low-temperature region, the magnetic moments of these fine particles experience superparamagnetic blocking. It has been established that the size effects that arise in ultra-fine ε–Fe2O3 particles has a serious impact on the macroscopic magnetic properties of the highly dispersed systems based on them.

Polyaniline prepared by Fe3O4 catalysed eco-friendly synthesis as electrocatalyst for efficient water electrolysis

Preparing cost-effective and highly active catalysts for electrocatalytic hydrogen evolution reaction is crucial for developing hydrogen-based technologies. Hence, four conductive polyanilines, prepared by the environmentally-friendly approach using Fe3O4 nanoparticles/H2O2 as the catalyst/main oxidant system (PANI/Fe3O4), were investi¬gated for the first time as electrocatalysts for hydrogen evolution reaction (HER) in acidic media (0.1 M H2SO4) by using voltammetry and chronoamperometry. PANI/Fe3O4 electrodes exhibited Tafel slope values in the -171 to -246 mV dec-1 range depending on the synthesis conditions ‒ Fe3O4/aniline mass ratio and polymerization time. The sample PANI/Fe3O4-II(3) prepared with shorter reaction time and higher Fe3O4/aniline mass ratio showed the best electrocatalytic behaviour reflected in the lowest onset potential (-0.286 V), the lowest overpotential to reach a current density of -10 mA cm-2, the highest current density, the lowest HER activation energy (10 kJ mol-1), and the lowest charge-transfer resistance (5.3 Ω) under HER conditions. Materials were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photo¬electron spectroscopy and electrochemical impedance spectroscopy, and differences in their electrocatalytic HER performance were explained by differences in their content of Fe3O4, surface and electrical properties. Moreover, the possibility of using PANI/Fe3O4-II(3) as HER electrocatalyst in a wider range of pH (i.e. in alkaline media as well) and as a bifunc¬tional electrocatalyst, i.e., for oxygen evolution reaction beside HER, was also examined.

Effect of hot coil immersion cooling process on microstructure and properties of strip steel and oxide scales

ABSTRACT Coils obtained at the end of hot rolling of four different low carbon steels (DX54D, HX180YD, DX51D and HCT590X) were subjected to immersion in water for cooling (IC) as against the normal natural cooling (NC). IC produces significant improvements in the microstructure, scale formation, distribution of mechanical properties and surface quality. A model developed to simulate thermal history in the hot coil being cooled indicates that the 0.1°C/min core cooling rate in NC increased by over 7 times in IC, thereby decreasing the temper softening effects. Results of the tests performed exhibit a greater uniformity in the longitudinal properties and a 30–50% reduction in the band spread. The volume fraction of carbide on the DX54D steel is reduced by 20–30%, and the yield platform length is increased from 2.6 to 3.4%. The IC process was observed to significantly inhibit the formation of the banded structure in the HCT590X steel and the average yield strength of the coil increased by ∼30 MPa. The thickness of the oxide scale in all the steels decreased by 30–40% and the FeO content in the scale increased by 10–20%.

Protective role of reactive aluminum phases to stabilize soil organic matter against long-term cultivation in the humid tropics under volcanic influence

ABSTRACT Cultivation can cause rapid depletion of soil organic matter (SOM), particularly in the humid tropics. Understanding the factors controlling SOM storage is a key step toward effective soil management for sustainable crop production. While clay + silt content is known to be an important factor for soil organic carbon (SOC) storage, recent studies have shown greater importance of oxalate-extracted Al (Alo; roughly corresponds to short-range-order aluminosilicate minerals and organo-Al complexes) and Fe (Feo). However, the extent to which these mineralogical factors control the response of SOM pool to land-use changes remains unclear, especially in the tropics. This study aimed to clarify the factors regulating SOM content in croplands compared to secondary forests or home gardens in Negros Occidental, Philippines. Along two line transects having a wide range of Alo contents, soil samples were collected at a depth of 0 − 10 cm from sugarcane sites (n = 33; long-term continuous cultivation of >70 years) that were paired with either secondary forests (n = 10) or home gardens (n = 20). Sugarcane sites had significantly lower SOC and total nitrogen (N) contents than secondary forest and home garden sites, whereas there was no clear difference between the latter two land uses. Both SOC and total N contents showed significant positive correlations with Alo content and, to a much less extent, with Feo content, but not with clay + silt content. The slope of the regression line between SOC and Alo was indifferent between sugarcane and the other two land uses, while the intercept was significantly lower in the sugarcane sites. These results suggest the protective role of Alo phases in both agricultural and forest soils and the presence of unprotected SOM (e.g. plant litter) in the latter sites. Furthermore, δ13C analysis suggested that the proportion of forest (C3 plant) derived carbon remaining in the sugarcane soils ranged between 10% and 50% and increased with Alo content. Together, our study showed indirect evidence of Alo-induced stabilization of SOM against long-term cultivation under the humid tropical environment.