Ferrite Type Research Articles

Effect of Aggressive Anions on the Stress Corrosion Cracking of Stainless Steel in Hot Pressurized Alkaline Water

Abstract U-bend stress corrosion cracking (SCC) testing of low Cr ferritic (Type 409) and austenitic (Type 304L) stainless steel was conducted in a hot pressured alkaline water to study the effect of aggressive anions (Cl− and HS−) on the relative susceptibility. SCC was only observed in Type 304L when immersed in the solution that contained both aggressive anions. Critical factors were identified based on cross-section examination of the U-bends after exposure using complementary electron microscopy techniques. These factors include: (i) preferential oxidation of deformation bands (arising from cold working), (ii) Ni-S compound formation at the oxide/metal interface and (iii) S and Cl incorporation into the inward growing Cr-rich oxide. These critical factors were considered within an overall slip dissolution-type mechanism to account for the SCC observed.

Experimental validation of nonreciprocal metasurface using simple structure

AbstractThe non‐reciprocity of electromagnetic waves is a technology garnering significant attention for its applications in electromagnetic security and the mitigation of electromagnetic interference, serving to control radio waves in space. This article outlines a comprehensive design approach for a novel non‐reciprocal structure that integrates ferrite and metal patches. Additionally, it presents experimental results utilizing two types of ferrites. The experiments demonstrated the attainment of 15 dB isolation at both 6.25 GHz and 6.5 GHz.

Comparative study of two mesoporous magnetic and MCM-41 supported Cu complex: High-performance heterogeneous catalysts for aqueous synthesis of tetrazole

The effects of the carrier were studied in the synthesis of tetrazole. Copper catalysts supported on CoFe2O4 and MCM-41 with serine ligands were prepared. Two mesoporous catalysts, CoFe2O4/Ser/Cu and MCM-41/Ser/Cu, (denote Serine with (Ser)) were synthesized and compared the activity of these catalysts in converting nitrile to tetrazole. The prepared material was characterized using powder X-ray diffraction (XRD),field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), elemental mapping, vibrating-sample magnetometer (VSM), and nitrogen adsorption–desorption isotherm. The relation between the textural properties of the catalysts and the catalytic performance was investigated. The X-ray diffraction patterns showed the spinel ferrite type for CoFe2O4/Ser/Cu and amorphous SiO2 for MCM-41/Ser/Cu. The distinctive diffraction peaks in the diffraction curves of CoFe2O4/Ser/Cu, and MCM-41/Ser/Cu were identical to those of CoFe2O4, and MCM-41, confirming the preservation of these phases of supports throughout the functionalization processes and formation of -Ser/Cu moiety on the crystalline CoFe2O4 structure and non-crystalline silica structure. FE-SEM images showed the particles in CoFe2O4/Ser/Cu had an average diameter of 20–50 nm and in MCM-41/Ser/Cu had an average diameter of 50–250 nm. The images showed the uniformity and well-ordering of the particles. The slight aggregation in CoFe2O4/Ser/Cu particles implied that their clustering may be the result of modest attraction forces between them. MCM-41/Ser/Cu sample exhibited a type IV isotherm with an H1-type hysteresis loop and diagrams of the CoFe2O4/Ser/Cu showed a type IV isotherm (type H2 hysteresis loop). The MCM-41/Ser/Cu and CoFe2O4/Ser/Cu showed a mesoporous structure and capillary condensation occurred in the nearly cylindrical and ink bottle channels with non-uniform size or shape. The CoFe2O4/Ser/Cu showed surface area by BET and t-plot of 71.17 m2/g and 64.92 m2/g respectively, mean pore size of 14.06 nm, and pore volume of 0.250 cm3/g. The MCM-41/Ser/Cu showed surface area by BET and t-plot of 639.2 m2/g and 484.6 m2/g respectively, with a mean pore size of 5.44 nm, and pore volume of 0.869 cm3/g. The BJH pore size distribution was between 1 and 10 nm for the MCM-41/Ser/Cu and 1–20 nm for the CoFe2O4/Ser/Cu. Two catalysts were used for the synthesis of tetrazole. The CoFe2O4/Ser/Cu shows better activity in the synthesis of 5–substituted 1H-tetrazoles than the MCM-41/Ser/Cu sample despite its lowest surface area (71.17 m2/g). There is no reduction in the conversion of nitrile to tetrazole after the 6 cycles for CoFe2O4/Ser/Cu and after the 4 cycles for MCM-41/Ser/Cu.

Investigating the influence of post-deposition heat treatment (PDHT) on the characteristic changes in wire arc additively manufactured 410 martensitic stainless steel thin-wall structure

Obtaining the desired material characteristics of an as-deposited martensitic stainless steel (MSS) structure fabricated by wire arc additive manufacturing (WAAM) is challenging due to several factors like inhomogeneity, precipitation, phase transition, etc. This investigation elucidates the impact of post-deposition heat treatment (PDHT) on the microstructural and mechanical properties of the WAAM-processed 410 MSS thin-wall structure and compares it with the as-deposited 410 thin-wall structure. The MSS thin-wall structure consists of retained austenite (γ), delta (δ) ferrite, martensite laths and Cr-rich M23C6 type carbide. The M23C6 volume fraction increases by up to 18 %, and the γ-phase fraction reduces by up to 40 % by applying PDHT. The PDHT process significantly changed the texture from {110}<011> to {001}<110>. The PDHT process increases the dislocation density (1.974 × 10−15 m−2) than the as-deposited condition (0.924 × 10−15 m−2). The total low energy boundary (LAGB+CSL) contribution of the as-deposited sample is 19.5 %, whereas the PDHT sample demonstrated a higher fraction of low energy boundaries of 32.4 %. The PDHT sample showed a much smaller distribution of grains with an average grain size of 11 μm compared to the as-deposited condition. The overall hardness increases from 468 HV to 487 HV after PDHT compared to the as-deposited condition with lower inhomogeneity across the build direction. The mean 0.2 % proof stress, ultimate tensile stress, and elongation of the PDHT sample increased by 17 %, 5 %, and 60 %, respectively, compared to the as-deposited sample.

Zinc Extraction from Primary Lead Smelting Slags by Oxidant Alkaline Leaching

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a single aqueous medium, where oxidant alkaline leaching with NaOH and NaClO was used. The parameters evaluated during the experiment were as follows: percentage of solids, NaOH/NaClO ratio, and temperature. The maximum amount of recovered Zn obtained during the leaching was 58%. This percentage was achieved by using the following optimal conditions: temperature of 60 °C, 0.22 of NaOH/NaClO ratio, 10% of solids, and a reaction time of 40 min. The calculated values of activation energy confirmed that the rate-limiting step of the reaction using the decreasing particle model is diffusion. The maximum percentage of zinc obtained could only have been achieved if the zinc oxide and part of the zinc sulfide (both present in almost equal proportions in the sample) were leached into the alkaline aqueous medium in the presence of NaClO.

Supercapacitor properties of Ni2+ incrementally substituted with Co2+ in cubic spinel NixCo1-xFe2O4 nanoparticles by sol-gel auto combustion method

The nanoparticle powder of Ni1-xCoxFe2O4 (x = 0.00, 0.25, 0.50, 0.75, 1.00) spinel ferrite was successfully prepared by the sol-gel auto-combustion method. The synthesized nanomaterials were used to prepare spinel ferrite supercapacitor electrode material. The structured phase of prepared nanoparticle powders was studied using XRD which shows the prepared sample consists of nanocrystalline single phase, with cubic spinel ferrite. Furthermore, using FESEM surface morphology of prepared samples was investigated. Ni1-xCoxFe2O4 nanoparticles spinel ferrite structure was verified by FT-IR, which detected distinctive vibrational bands at octahedral and tetrahedral locations.The spinel ferrite type materials are good active electrode materials. In this study, the prepared Ni1-xCoxFe2O4 electrode material is used as cathode material for supercapacitor. The electrochemical behavior of prepared samples was studied and compared by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. An electrochemical measurement study of prepared samples shows excellent performance and desirable cycling stability for supercapacitors. The prepared Ni0.5Co0.5Fe2O4 spinel ferrite gives the highest specific capacitance of 1282 F/g at a current density of 5 mA/cm2 with corresponding energy density of 30 Wh/kg and power density of 301 W/kg. Also, they exhibited outstanding cycling stability for 5000 cycles with 91.24 % capacity retention.

Praseodymium dysprosium co-doped M-type strontium ferrite: Intentionally manufacturing heterophase growth to improve microwave absorption performance

When excessive praseodymium and dysprosium ions are doped with M-type strontium ferrite, heterophases with different magnetic and electrical properties will be formed. We use this to intentionally induce different heterogeneous growth in the Pr–Dy co-doped strontium ferrite system. While maintaining the dielectric loss of the main phase, the produced heterogeneous phase acts as a companion for dielectric and magnetic losses. The synthesized SrFe12-2xPrxDyxO19 ferrite demonstrates its potential as a microwave absorbing material, exhibiting excellent absorption effects over a wide range of Pr–Dy doping (x = 0.05–1.5). The XRD results show that the synthesized materials include both pure M-phase and coexistence of M-phase and heterophases, and the generated heterophases are mainly perovskite type ferrite and garnet type ferrite. SEM and EDS results indicate that Pr–Dy co-doping can significantly refine the grain size, reduce the grain size of the main and heterophases, and lead to a decrease in oxygen content. The XPS analysis shows that some praseodymium ions are in the Pr4+ oxidation state, leading to the existence of Fe2+ ions and oxygen defects (Od). The VSM results indicate that at different calcination temperatures, the saturation magnetization decreases and the coercivity shows an increasing trend as the Pr–Dy doping amount increases. Pr–Dy doping not only increases the dielectric and magnetic losses of the M phase, but also generates heterophases that can enhance the dielectric and magnetic losses of the material, jointly improving the absorption effect. This results in excellent absorption performance of the material within a large range of praseodymium dysprosium doping contents (x = 0.05–1.5, RLmin = −52.51 dB, EABmax = 4.81 GHz).

Effect of Sn4+–Co2+ co-substitution on structural and magnetic properties of SrFe12-2xSnxCoxO19 M–type strontium ferrite

With the continuous improvement of the performance of M–type ferrite, it has been paid more attention to and become more and more popular, and it has been applied to social production and development. For improving the magnetic properties of ferrite, the most common method used by researchers is ion replacement. This method of improving magnetic properties is the mainstream of research. In this study, SrFe12-2xSnxCoxO19 (x = 0, 0.05, 0.1, 0.15, 0.2) strontium ferrite with Sn4+ and Co2+ co-substitution was prepared using ceramic technology. The influence of Sn4+ and Co2+ co-substitution on the structure and magnetism of strontium ferrite were analyzed. X-ray diffraction analysis shows that as the substitution amount of Sn4+ and Co2+ ions increased, the main structure of strontium ferrite remained hexagonal. The morphology of the samples was analyzed by scanning electron microscope, and the results showed that the morphology of ferrite was mainly hexagonal strontium ferrite. Magnetic property show that the remanence (Br), coercivity (Hcj) and saturation magnetization (Ms) of the sample first increased and then decreased with the Sn4+- Co2+ ions increase of doping amount. When the substitution amount x = 0.15, the Ms reaches its maximum value of 83.8 emu/g, the Br reaches its maximum value of 405.4 mT. And when the substitution amount x = 0.05, Hcj reaches its maximum value of 312.5 kA·m−1.

Influence of Pr-cations on structural, spectral, elemental, and electrical features of Zr2–R type ferrites

Hexagonal ferrites have gained much attraction due to extensive applications in telecommunication and stealth fields. R-type hexagonal ferrites are rare hexagonal ferrites used in various technological applications. In the current work, the sol-gel auto-combustion method was used to prepare samples of R-type hexagonal ferrites with the chemical formula BaZr2Fe4-xPrxO11 (x = 0.00, 0.03, 0.06, and 0.09) respectively. The impact of substituting Praseodymium (Pr) on its structural, electrical, dielectric, and magnetic properties was investigated. X-ray diffraction (XRD) patterns suggest all samples exhibit a single phase. The lattice parameters and unit cell volume experienced alterations with varying Praseodymium (Pr3+) substitution levels. The atomic dynamics study of the Pr-doped R-type hexagonal ferrites was evaluated using FTIR analysis. Two absorption bands in the infrared spectroscopy were utilized to designate the tetrahedral and octahedral sites. X-ray photoelectron spectroscopy (XPS) findings verified the presence of all metal ions alongside their respective electronic states. Jonscher's power law elucidates the conduction mechanism of charge carriers in the synthesized ferrite samples. Impedance analysis was employed to investigate the influence of relaxation time and grain boundaries on the electrical characteristics of the fabricated nanomaterials. Impedance Cole-Cole plots provide evidence that all samples demonstrate multiple relaxation processes of a non-Debye nature. The minimum reflection loss (RL) of −32.46 dB at 3.27 GHz was achieved for x = 0.09. Pr-doped R-type hexagonal ferrite has potential applications in microwave high-frequency applications.

The Electrical Conductivity, EMI Absorption Shielding Performance, Curing Process, and Mechanical Properties of Rubber Composites.

Three types of composites were tested for electromagnetic interference (EMI) absorption shielding effectiveness, the curing process, and their physical-mechanical properties. For the first type of composites, nickel-zinc ferrite, manganese-zinc ferrite, and both fillers in their mutual combinations were incorporated into acrylonitrile-butadiene rubber. The overall content of the filler, or fillers, was kept at 200 phr. Then, carbon black or carbon fibers were incorporated into each rubber formulation at a constant loading of-25 phr, while the content of magnetic fillers was unchanged, at -200 phr. This work focused on the understanding of correlations between the electromagnetic shielding parameters and electrical conductivity of composites in relation to their EMI absorption shielding effectiveness. The absorption shielding abilities of materials were evaluated within a frequency bandwidth from 1 MHz to 6 GHz. This study revealed good correlation among permittivity, conductivity, and EMI absorption effectiveness. Although the absorption shielding efficiency of composites filled only with ferrites seems to be the highest, the absorption maxima of those composites reached over 6 GHz. The application of carbon-based fillers resulted in the higher electrical conductivity and higher permittivity of composites, which was reflected in their lower absorption shielding performance. However, the composites filled with ferrites and carbon-based fillers absorbed electromagnetic radiation within the desired frequency range. The presence of carbon-based fillers caused improvement in the tensile behavior of composites. This study also demonstrated that the higher the ratio of nickel-zinc ferrite in combined magnetic fillers, the better the absorption shielding efficiency.

Preparation of spinel ferrites-based flexible electrodes for high electrochemical performances

In this study, we synthesized two different types of spinel ferrites as CoFe2O4 and NiFe2O4 nanocomposites by thermal decomposition method to improve the performance of supercapacitor research. Numerous physicochemical characterization tests, including X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectroscopy (EDS), UV–Vis DRS, and Fourier Transform Infrared Spectroscopy (FTIR) analyses, have been conducted to investigate the structural, morphological, and elemental composition of the manufactured ferrite electrodes. Three-electrode systems have each been used in the electrochemical investigations for the electrodes utilizing 3 M KOH as the electrolyte. The nickel ferrite and cobalt ferrite nanocomposites had a maximum specific capacitance of 1096 Fg−1 and 836 Fg−1 at a current density of 1 A g−1. A high energy density is also delivered by the assembled symmetric CoFe2O4 and NiFe2O4 nanocomposites. In addition, the nanocomposites exhibit Pseudo capacitance with excellent cyclic stability of 87.4 % and 80.5 % capacitance retention for 5000 cycles. The fabricated CoFe2O4 and NiFe2O4 electrodes showed a strong reduction in the Rct value than the pristine nanocomposites. The materials have demonstrated promising potential as electrodes for energy conversion and storage.

Electrical and magnetic properties of MF/CuAl nanocomposites

Abstract This study investigated the effects of CuAl2O4 (CuAl) on four types of spinel ferrites: CoFe2O4 (CoF), NiFe2O4 (NiF), MgFe2O4 (MgF), and ZnFe2O4 (ZnF) with regards to their electrical characteristics and microscopic magnetic behavior. According to the Seebeck coefficient (φ), the nanocomposites have a mixture of positive and negative charge carriers, except for CoF/CuAl, which has a positive charge carrier only. Depending on the temperature, the DC conductivity of all MF/CuAl nanocomposites has a conductor and semiconductor behavior. The dielectric properties were studied at different frequencies (100–10^8 Hz) and temperatures (300–673 K). The results demonstrated how temperature and frequency affect AC operating mechanisms. The high values of dielectric loss for all nanocomposites confirm their applicability in high-frequency microwave devices. The impedance study revealed that the equivalent circuit for all MF/CuAl nanocomposites is a mixture of R, L, and C. Temperature-magnetization graphs were obtained for all nanocomposites, indicating ferrimagnetic behavior except ZnF/CuAl. The magnetic transition temperature (T Cm), the Curie–Weiss constant (θ CW), and the effective magnetic moments (μ eff) for all nanocomposites were determined. The MF/CuAl samples were analyzed using ESR spectroscopy at room temperature. The spectra were distorted but remained distinct, potent, and sweeping. The g-factor values deviate from the free electron, which suggests that the Fe3+–O–Fe3+ superexchange interaction has changed. In addition, the interaction effect between MF and CuAl is discussed.

An Attractive Route to Benzothiazole or Benzoxazole-Sulfide Aryls: CuFe2O4 NPs as a Highly Efficient Recoverable Nanocatalyst for Three-Component Coupling Reaction of Benzoazoles with Aryl Iodides and Sulfur Source in ChCl-Urea

Magnetic nanoparticles are efficient catalytic systems for various reactions because of their high efficiency and easy separation. Amongst magnetic nanoparticles, copper ferrite (CuFe2O4 NPs) is one of the different types of ferrites, which is widely used in catalytic reactions because of its magnetic properties. On the other hand, deep eutectic solvents (DESs) consisting of a hydrogen bond acceptor component and a hydrogen bond donor component have recently attracted the attention of many researchers as green solvents. ChCl-urea is considered a green DES that has been reported several times to carry out chemical reactions. In recent years, research on the synthesis of 2-thioaryl-benzothiazoles and 2-thioaryl-benzoxazoles (compounds containing C-S aryls and benzothiazoles and benzoxazoles scaffolds) has become an attractive challenge in organic chemistry. In this research, we report the synthesis of 2-thio-benzothiazoles and 2-thioaryl-benzoxazoles by CuFe2O4 NPs in ChCl-urea as an efficient nanocatalyst. These compounds were synthesized via a one-pot, three-component coupling reaction of benzoxazoles or benzothiazoles with aryl iodides and S8 as a sulfur source in the presence of KOAc as a base.

Photocatalytic reduction of 4-nitrophenol over eco-friendly NixCuxFe2O4 without an additional reducing agent in water

Organic pollutants such as 4-nitrophenol (4-NP) pose serious environmental extortions due to their chemical stability for which efficient catalytic materials are indispensable in treating them. In this regard, the present work involves the synthesis of two different types of ferrites (NiFe2O4, and CuFe2O4), and a combination of NixCuxFe2O4 with various ratios that systemically work as efficient photocatalysts without any additional reducing agents is reported. The structural, and morphological properties of NiFe2O4, CuFe2O4, and NiCuFe2O4 were characterized by XRD, FT-IR, SEM, and HRTEM techniques. Then, the catalytic role of individual ferrite catalysts was evaluated towards catalytic reduction of 4-NP under visible light. The progress dye reduction was examined via UV–vis spectrophotometry. The effect of various concentrations, and reduction time were investigated. The kinetic rate constants determined for NiFe2O4, CuFe2O4, and NixCuxFe2O4 revealed that Ni and Cu in bimetallic ferrites promoted the reduction reaction under visible light. The results demonstrated that the photo-reduction efficiency of the Ni0.7Cu0.3Fe2O4 catalyst over 4-NP (conc. 10 ppm) to 4-AP was determined as 82 % under 120 miniutes with good recyclability up to six cycles. The mechanism of photocatalytic reduction of ferrites without the use of a reducing agent was studied. Such facile and productive ferrite materials could be employed as efficient photocatalysts for the reduction of toxic organic contaminants in environmental treatment.

MEEHANITE SFP500

Abstract Meehanite SFP500 is a ductile iron that has a minimum tensile strength of 500 MPa (73 ksi) and a minimum elongation of 8%, when measured on test pieces machined from separately cast samples. This Meehanite grade possesses a mixed matrix of ferrite and pearlite, with the ferrite predominating. It offers a compromise between the relatively soft, low tensile, high ductility ferritic types and the harder, higher tensile, lower ductility pearlitic grades. Meehanite SFP500 is a good all-round material providing a degree of toughness coupled with a higher tensile strength in the as-cast condition. This datasheet provides information on physical properties, hardness, elasticity, tensile properties, and compressive strength as well as fatigue. It also includes information on casting and heat treating. Filing Code: CI-108. Producer or source: Meehanite Metal Corporation.

Microstructural Evolution and Its Influence on Low‐Temperature Toughness of Simulated Heat‐Affected Zone in Super Duplex Stainless Steel Welded Joint

The microstructures of heat‐affected zone (HAZ) during multipass welding procedure of super duplex stainless steel (DSS) are simulated by a thermomechanical simulator. The influences of ferritization, 1st‐reheating, and 2nd‐reheating process on the microstructural evolution and toughness of the HAZ are studied. The results show that the alternating bands of ferrite and austenite are transformed into coarse equiaxed ferrite and different types of primary austenite (γ1). The austenite content significantly decreases and a great number of Cr2N precipitate in the ferritized HAZ comparing with as‐received super DSS. In addition, the 1st‐reheating temperature has significant influence on microstructure of the ferritized HAZ. The austenite content increases but the precipitation tendency of Cr2N reduces with the raising of 1st‐reheating temperature. Secondary austenite (γ2) is prone to precipitate after the 1st‐reheating at 1000 °C. A combined precipitation behavior of γ2 and Cr2N is clarified during the reheating process. Furthermore, the 2nd‐reheating at 900 °C promotes Cr2N precipitation again as well as austenite formation. The toughness is mainly related with ductile austenite content, hard‐brittle Cr2N amount, and N supersaturation degree in the ferrite. In order to raise toughness of the ferritized HAZ, it is recommended to reheat at above 1200 °C.

THE EFFECT OF ABRASIVE GRAIN SHAPES ON QUALITY OF FERRITE MAGNETS GRINDING PROCESS

A research was conducted on the grinding process of ferrite magnet with Strontium ferrite type (SrO.6 (Fe2O3)) using electroplated single layer grinding wheels. Many cracks have been found on work pieces during this work, which is coming from grinding processes. Research is conducted starting from chemical composition test and the effect of the shape and size of the abrasive grain of grinding wheels to the quality of grinding process results by measuring crack ratio of the work piece. In this experiment, 3 (three) model design of grinding wheels with three different size and shape of abrasive grains are made. All of processing parameters are set at the same value as ordinary process. The experimental results shown that 3rd model have the best results from the outputs number and also the lowest reject crack ratio compared to 1st and 2nd models. This is because the 3rd model has blocky shape which its distribution structure is denser and more uniform compared to the irregular shape, so that continuous grinding on hard and brittle work pieces is more stable and suitable

Dielectric Performance of UHMWPE-MgFe2O4 Composites Depending on Polymer Crystallinity, and the Concentration and Size of Mechanochemically Synthesized Ferrite Particles

Mechanochemically synthesized particles of two types of magnesium ferrites, one of which with structural distortions and an average size of 170 nm, and another that is highly crystalline with an average size of 900 nm, were introduced into a matrix of ultra-high-molecular-weight polyethylene via the milling processing. The final material has been formed by hot pressing mechanocomposites based on ultra-high-molecular-weight polyethylene and magnesium ferrite particles of various fineness and concentration. Structural characteristics were studied using scanning electron microscopy, differential scanning calorimetry and X-ray diffraction analysis. The dielectric properties of the obtained composites were analyzed by testing the frequency dependence of the permeability, dielectric losses, and conductivity. The effect of filler concentration and particle size, as well as the crystallinity of the polymer, on the dielectric properties of the composite material were studied.

Web crippling resistances of cold-formed stainless steel sections: A proposal for EN 1993-1-4

The current EN 1993-1-4 does not have supplementary web crippling design provision for cold-formed stainless steel sections under local transverse forces. Therefore, designers are generally referring to the guidance in EN 1993-1-3 for cold-formed carbon steel sections. Over the past decades, quite a substantial number of tests have been carried out worldwide to study the behaviour of cold-formed stainless steel sections undergoing web crippling, among which the majority of the data were focused on C-sections as well as square and rectangular hollow sections (SHS and RHS). To this end, tailor-made design provisions for these stainless steel sections can be developed. In this study, up-to-date web crippling test data on cold-formed stainless steel C-sections and SHS/RHS were firstly collected. The applicability of the web crippling design provisions as per the new version of EN 1993-1-3 to stainless steel sections was assessed. New design provisions for cold-formed stainless steel unstiffened C-sections (unlipped channels), stiffened C-sections (lipped channels) as well as SHS and RHS under local transverse forces are proposed in this study. The newly developed web crippling design provisions for C-sections and SHS/RHS were derived based upon reliability requirements as regulated in EN 1990 using available experimental data reported on austenitic, ferritic and duplex stainless steel types of various grades. The proposed design provisions for stainless steel sections have been made in line with the development of the new version of EN 1993-1-3 provisions and therefore are recommended to EN 1993-1-4 for calculating web crippling resistances under local transverse forces.

Thermodynamics and electronic structure characteristics of MFe2O4 with different spinel structures: A first-principles study

In recent years, spinel ferrites with chemical formula MFe2O4, have attracted much attention due to their impressive photocatalytic and electrocatalytic performances, which are significantly influenced by their spinel structures. However, it is still a big challenge to distinguish or predict spinel structures for spinel ferrites. As an attempt to address this issue, this paper presents a first-principles study of the thermodynamics and electronic structures for six spinel ferrites with different spinel structures. The configurational free energy of these spinel ferrites at different inversion degrees is calculated to determine the equilibrium inversion degree for each spinel, which successfully predicts the spinel structure type of these spinel ferrites. The partial density of states is obtained for six spinel ferrites assuming they are normal or inverse spinels. The electronic states close to the Fermi energy of each spinel ferrite are carefully examined, showing that normal spinels have weak interactions between M and Fe states, while strong interactions exist in mixed or inverse spinels. Our results offer an insightful understanding of different spinel structures, and provide a reliable approach to determine the spinel structure of spinel ferrites.