Photoelectron Spectroscopy Methods Research Articles

Reaction dynamics of the nonvalence bound states of the anions

Nonvalence bound state (NBS) is a unique anionic state where an excess electron is loosely bound to a neutral molecule in long-range potentials. Since Fermi and Teller first proposed that an electron could be bound in the dipolar field of a molecule, the physical and chemical properties of NBS in a variety of chemical systems have been investigated over recent decades. In this short review, recent notable studies aimed at thoroughly understanding the dynamics of NBS in various anionic chemical systems are elaborated. Photodetachment and photoelectron spectroscopic methods, particularly applied to cryogenically cooled anions, have been highly successful in providing detailed rovibronic structures of the NBS in many interesting chemical systems. Furthermore, real-time pump-probe photoelectron spectroscopy unraveled new dynamic aspects of anion physics and chemistry, offering deep insight into mode-specific autodetachment dynamics and the role of metastable NBS as a doorway into anionic chemical reactions. Autodetachment and/or nonvalence-to-valence (or vice versa) electron-transfer dynamics of NBS are found to be strongly mode-specific, presenting a challenge for theoretical explanations of their quantum-mechanical nature. The outlook for further exploration of NBS in various chemical or biological contexts as well as its potential exploitation in controlling chemical reaction is also provided.

Insights into Ultrafast Relaxation Dynamics of Electronically Excited Furfural and 5-Methylfurfural.

The ultrafast relaxation dynamics of furfural and 5-methylfurfural following excitation in the ultraviolet range is investigated using the femtosecond time-resolved photoelectron spectroscopy method. Specifically, the pump wavelength-dependent decay dynamics of electronically excited furfural and 5-methylfurfural is discussed on the basis of a detailed analysis of our measured time-resolved photoelectron spectroscopy spectra. Irradiation at all pump wavelengths prepares both furfural and 5-methylfurfural molecules with different vibrational levels in the first optically bright S2 (1ππ*) state, the lifetime of which is measured to be at least hundreds of femtoseconds. Besides the prominent deactivation channels of ring-opening and ring-puckering pathways for the S2(1ππ*) state, we propose that there is a minor decay channel of internal conversion from the initially prepared S2(1ππ*) state to the S1(1nπ*) state. The wavepacket decays out of the Franck-Condon region on the S2(1ππ*) state potential energy surface and bifurcates into different parts somewhere. A small fraction of the wavepacket funnels down to the S1(1nπ*) state via internal conversion. The subsequently populated S1(1nπ*) state contains large vibrational excess energy and decays over a lifetime of 2.5-2.8 ps. One of the deactivation channels of the S1(1nπ*) state is intersystem crossing to the 3ππ* triplet state. In addition, methyl substitution effects on the excited-state dynamics of furfural are also discussed. This experimental study provides new insights into the excitation energy-dependent decay dynamics of photoexcited furfural and 5-methylfurfural.

Designed magnetic nanoparticles for ferroptosis: Release of iron ions from metal-organic frameworks modified with iron oxides

The unique chemical properties of the catalytic and biocompatible metal organic framework MIL88b allow for considering it as prooxidant agent. The authors hypothesize whether additional modification of the MIL88b with an additional iron source as Fe3O4 nanoparticles can increase both pro-oxidant activity and provide magnetic properties contributing to target delivery. The prooxidant activity of the Fe3O4-MOF was studied using electron paramagnetic resonance spectroscopy and methylene blue degradation reactions in the presence of hydrogen peroxide. To understand the reaction mechanism, the authors studied the released iron ions, as well as the surface composition using the X-ray photoelectron spectroscopy method. The addition of iron oxide leads to a more prolonged release of iron ions and the production of hydroxyl radicals within 24 h. The native MIL88b demonstrates the highest Fenton reaction rate due to "sacrificial" behavior (despite lower concentration of iron ions in the composition and on the surface compared to the modified sample) and the blocking of the active centers of MIL88b by Fe3O4 on the surface.

Direct synthesis of Cu-TiO<sub>2</sub>-SBA-16 photocatalysts and its application for the oxidative desulfurization of fuel oil model

In this study, the Cu-TiO2-SBA-16 photocatalytic materials were successfully prepared by direct hydrothermal synthesis method. The products were characterized by X-ray diffraction (XRD), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) methods. The analysis illustrated that Cu-TiO2 nanocrystals were successfully incorporated into the SBA-16 mesopores. The photocatalytic activity of these Cu-TiO2-SBA-16 mesoporous materials have been tested by the oxidative desulfurization reaction of dibenzothiophene (DBT) using H2O2 as an oxidant under UV light irradiation. The results showed that the Cu-TiO2-SBA-16 mesoporous materials prepared at the Cu/Ti mole ratios of 0.05 showed higher photocatalytic activity than the rest due to the decrease in band gap energy.

Localization and other properties of electronic states in a semiconductor revealed by their response to surface doping and band-bending potential

Using photoelectron spectroscopy (PES), we study InAs(001) and InAs(110) surfaces, doped with Te atoms to induce strong band-bending phenomena and a formation of two-dimensional electron gases (2DEGs). The band structure of the 2DEGs as well as the coexisting 3D bulk electronic structure are investigated. We discuss several schemes to estimate the band-bending potentials at surfaces by PES methods, appropriate in different situations, e.g. in the presence of a significant band tailing. We use the Schroedinger–Poisson scheme as well as the Thomas–Fermi method to model the band-bending potential profiles and the 2DEG band energies. For the InAs crystal we find that the valence bands investigated with PES closely follow the band-bending potential which evidences that valence electronic states are localized to within few nm. In contrast, the conduction band is entirely insensitive to the band-bending potential, evidencing that the extent of electronic states within this band is at least 103nm.

Electrocatalytic efficiency of carbon nitride supported gold nanoparticle based sensor for iodide and cysteine detection

Extensive investigations are being conducted on gold nanoparticles focusing on their applications in biosensors, laser phototherapy, targeted drug delivery and bioimaging utilizing advanced detection techniques. In this work, an electrochemical sensor was developed based on graphite carbon nitride supported gold nanoparticles. Carbon nitride supported gold nanoparticles (Au–CN) was synthesized by applying a deposition-precipitation route followed by a chemical reduction technique. The composite system was characterized by X-ray diffraction and X-ray photo electron spectroscopy methods. Electron microscopy analysis confirmed the formation of gold nanoparticles within the size range of 5–15 nm on the carbon nitride support. Carbon nitride supported gold based sensor was employed for the electrochemical detection of iodide ion and l-cysteine. The limit of detection and sensitivity of the sensor was attained 8.9 μM and 0.96 μAμM⁻1cm⁻2, respectively, for iodide ion, while 0.48 μM and 5.8 μAμM⁻1cm⁻2, respectively, was achieved for the recognition of cysteine. Furthermore, a paper-based electrochemical device was developed using the Au–CN hybrid system that exhibited promising results in detecting iodide ions, highlighting its potential for economic and portable device applications.

EFFECT OF SNO2 POROUS STRUCTURE ON ITS OPTICAL AND PHOTOELECTROCHEMICAL PROPERTIES IN WATER AND WATER-METHANOL SOLUTIONS

Tin(IV) oxide is a wide-gap semiconductor material that is widely used in photooxidation reactions of organic compounds. However, the relationship between energetic and photoelectrocatalytic properties in the oxidation of small organic molecules has not yet been sufficiently explored. In this work, a series of tin oxides were synthesized using hydrothermal, sol-gel, and template methods. Polystyrene spheres with a size of 250 nm, as well as cetyltrimethylammonium bromide, were used as templates. X-Ray diffraction, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, Raman spectroscopy and diffuse reflectance spectroscopy methods were used to study the structure, surface composition, optical and energy characteristics. Using photoelectrochemical methods, the potentials of the conduction band and valence band were determined, and photocurrents in aqueous and aqueous-methanol solutions were studied depending on electrode polarization. It is shown that the preparation method (sol-gel or hydrothermal) does not affect the position of energy bands, while the use of a template during synthesis leads to an increase in the average pore diameter in the samples and an increase in photocurrent values in the presence of methanol. It has been established that for template-synthesized samples, the magnitude of photocurrents in a water-methanol mixture increases with an increase in the valence-band potential. The sample prepared by the hydrothermal method using a template showed the highest photocurrent values both in the background electrolyte (17.3 μA/cm2) and in the presence of methanol (26 μA/cm2), compared to the sample prepared without using a template in the electrolyte with the addition of methanol (7.6 μA/cm2) and without it (7.8 μA/cm2).

Copper-supported MOF-derived carbon materials for highly efficient antibiotics removal

Facing the escalating issue of antibiotic pollution and the emergence of bacterial resistance in water ecosystems, photocatalytic technology has been widely studied as one of the efficient methods to remove antibiotics in aquatic ecosystem. Herein, the bimetallic organic framework materials Cu/Zn-BTC were synthesized with varying proportions of copper and zinc as metal joints and 1,3,5-phthalic acid as organic ligands. Subsequently, the zinc elements within the MOF were eliminated through high pyrolysis to obtain carbon materials derived from Cu/Zn-BTC (referred to as 1.3CZC, 1.4CZC, and 1.5CZC based on the copper-to-zinc ratio). Notably, the presence of different valence copper species facilitated to form type II heterojunction within MOF-derived carbon materials, where internal Cu0/Cu+ species combined with oxygen vacancies to create localized bands that prolonged the lifetime of photogenerated carriers and enhanced photocatalytic activity. X-ray photoelectron spectroscopy, Brunauer-Emmett-Taylor and other characterization methods were used to analyze the difference in structure and performance of different catalysts. 1.4CZC showed excellent performance, upon exposure to visible light for 30 min, the removal rate of tetracycline significantly increased to an impressive 92.4 %, while extending the exposure time to 60 min further improved the removal rate of ciprofloxacin to approximately 82.6 %. It provides a highly efficient antibiotics removal pathway by MOF-derived carbon materials.

A Study on the Surface Oxidation Pretreatment and Nickel Plating Mechanism of Carbon Fiber.

This study explores the effects of various temperatures on the surface modification of carbon fibers, as well as the effect of differing voltages and currents on the morphology, deposition rate, and thickness of the Ni plating layers. Post-treatment characterization of the samples was conducted utilizing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods, thus facilitating a discussion on the mechanism of Ni plating. The findings demonstrate that at a temperature of 500 °C, the carbon fiber surface exhibits the highest concentration of functional groups, including hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O), resulting in the most efficacious modification. Specifically, exceeding 500 °C leads to significant carbon fiber mass loss, compromising the reinforcement effect. Under a stable voltage of 7.5 V, the Ni-plated layer on the carbon fibers appear smooth, fine, uniform, and complete. Conversely, at a voltage of 15 V, the instantaneous high voltage induces the continuous growth of Ni2+ ions along a singular deposition point, forming a spherical Ni-plated layer. In addition, a current of 0.6 A yields a comparatively uniform and dense carbon fiber coating. Nickel-plated layers on a carbon fiber surface with different morphologies have certain innovative significance for the structural design of composite reinforcements.

S-scheme TiO2/Bi2WO6 heterojunction for enhanced photocatalytic selective oxidation of toluene

Selective activation of saturated C–H bonds in hydrocarbons, such as the activation of the C–H bond in toluene, is an effective method for the production of high value-added chemicals. However, improving the C–H bond activation of toluene remains a challenge. In this study, S-scheme TiO2/Bi2WO6 composites were synthesized by loading TiO2 nanoparticles on Bi2WO6 flakes using a simple hydrothermal method. The physical and chemical properties of the prepared materials were characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectoscopy (FT-IR), Scanning Electronic Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and other characterization methods. Selective oxidation of toluene to benzaldehyde under visible light irradiation using air as an oxidizing agent. When the molar ratio of TiO2 and Bi2WO6 was 0.20, the composites exhibited excellent photocatalytic performance with a benzaldehyde production rate of 1725.41 μmol g−1 h−1, which was 2.31 and 1.91 times higher than that of TiO2 and Bi2WO6, respectively. This excellent performance is attributed to the formation of heterojunction structure by the loaded TiO2 nanoparticles, which improves the separation efficiency of photogenerated carriers and thus enhances its photocatalytic performance. In addition, the active substances involved in the photocatalytic reaction were identified by free radical trapping experiments as ·O2− and h+. Finally, the photocatalytic mechanism of S-scheme TiO2/Bi2WO6 composites was proposed by energy band structure analysis and radical trapping experiments. This study provides a simple design pathway for the construction of visible-light responsive bismuth tungstate-based heterojunction photocatalysts and some ideas for the development of new and efficient photocatalytic toluene selective oxidation catalysts.

Participation of Surface Oxygen in the Stabilization of the Rh/HOPG System with Respect to NO₂

In this work, using the method of X-ray photoelectron spectroscopy (XPS), a comparative study of the nature of the interaction of NO₂ at room temperature and a pressure of 10⁻⁵ mbar with two samples of highly oriented pyrolytic graphite (HOPG), on the surface of which rhodium was preliminarily deposited by vacuum deposition, was carried out. Before metal deposition, one of the HOPG samples was annealed in vacuum at 600°C, and the other was subjected to bombardment with argon ions, followed by exposure to air at room temperature for an hour in order to introduce strongly bound oxygen atoms into the surface composition. After deposition of rhodium on two samples of HOPG prepared, two model catalysts were obtained, designated as Rh/C and Rh/C(A)-O. It was found that the interaction of NO₂ with Rh/C led to the oxidation of graphite with the destruction of the surface layer. The Rh particles remained in the metallic state, but at the same time they were introduced into the near-surface layer of the carbon support. On the contrary, when the Rh/C(A)-O sample was treated with NO₂, the deposited rhodium was partially converted into RH₂O₃, while the graphite was oxidized to an insignificant degree and retained its original structure. The role of surface oxygen in the stabilization of graphite with respect to oxidation to NO₂ was discussed.

Influence of N 2, N 6-bis((3,5-dimethyl-1h-pyrazol-1-yl)methyl) pyridine-2,6-diamine on C35E steel corrosion in 1 M HCl medium: Experimental and theoretical studies

The inhibition effect of N 2, N 6-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridine-2,6-diamine (MH-PA) on the corrosion of C35E steel in 1 M HCl solution was investigated employing potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), contact angle, X-ray photoelectron spectroscopy (XPS) methods, UV-visible spectroscopy, and theoretical calculation methods. The inhibition efficiency increased with increasing MH-PA concentration and decreased with increasing temperature, attaining 98% inhibition efficiency at 10−3M under 303K. PDP studies indicated that MH-PA is a mixed-type corrosion inhibitor and its adsorption mode conforms to Langmuir isotherm. UV-visible and FTIR spectroscopy support MH-PA adsorption over the C35E steel surface. The surface analysis through SEM, EDS, AFM, and contact angle corroborates the formation of the protective layer of MH-PA molecules on the C35E steel surface. In addition, XPS analysis revealed the formation of an N-Fe bond. Thermodynamic properties revealed that MH-PA has both physical and chemical adsorption behavior. Molecular dynamics simulations manifest that MH-PA molecules adsorb parallel to the Fe (110) surface.

Indium-nickel oxide nanocomposite for room temperature H2 gas detection and its sensing mechanism

Lithium-ion batteries (LIBs) have a wide range of applications in energy storage power stations. However, thermal runaway of LIBs can lead to serious safety accidents and cause significant losses. Therefore, it is particularly important to carry out early security warning of LIBs. And H2 is generated along with the growth of lithium dendrites, which can serve as an effective indicator for detecting LIBs before TR. In this paper, In2O3/NiO nanocomposites were prepared, and five groups of samples were systematically prepared by adjusting the molar ratio of In and Ni. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and other test methods were used to characterize the prepared nanocomposites. Through experiments, the best samples among several groups of samples were determined. When the test gas is introduced, the resistance change of this optimal sensor is the greatest, indicating the best performance, which is significantly better than pure In2O3 and pure NiO samples. Furthermore, compared to other gases, this nanocomposite sensor exhibits significant selectivity towards H2. The results show that In2O3/NiO is a promising candidate material for room temperature H2 detection, and provide suggestions for the development of gas sensors with heterogeneous structures.

Biomimetic Bi3+ substituted borate bioactive glasses for bone tissue engineering via enhanced biological and antimicrobial activity

Biomimetic borate-based bioactive glasses (BAGs), substituted with metal oxides, serve as prominent candidates for the repair and regeneration of both hard and soft tissues. In the current study, bismuth mixed borate BAGs (60-X) B2O3–25CaO–15Na2O–XBi2O3 (X = 2, 4, 6, 8 & 10 mol.%) were synthesized using melt-quench method and systematically evaluated for their structural properties, followed by in-vitro biological performance and enhanced antimicrobial activity, using various characterization techniques and bioassays. The BAG structure was studied by Fourier transform infrared (FTIR), differential thermal analysis (DTA), and X-ray photoelectron spectroscopy (XPS) methods. The density and mechanical properties of the BAGs were found to increase with increase in bismuth content of the borate glass network. The XPS analysis confirmed the presence of Bi3+ ions embedded in the glass network. From DTA, it is noticed that the glass transition temperature (Tg) decreased and thermal stability (ΔT) values increased, with increased Bi2O3 content. Further, the bioactivity via hydroxy apatite (HAp) layer formation was confirmed by X-ray diffraction (XRD), FTIR, scanning electron microscopy- energy dispersive spectra (SEM-EDS) and Atomic force microscopy (AFM), both before and after soaking the glass samples in simulated body fluid (SBF) for 0, 7, 14, and 21 days. The results revealed that Bi3+ modified borate BAGs exhibited good HAp layer formation on their surfaces upon immersion in SBF solution. Moreover, the pH variation and degradation followed a trend, with increased in immersion time and decrease with Bi2O3 content. Lastly, in vitro cell culture tests on MG-63 osteoblast-like cells demonstrated that the as-developed BAGs were non-toxic and cytocompatible in nature; in addition, they also displayed demonstrable antibacterial activity against S. aureus and E. coli bacterial strains. Thus, the developed Bi2O3 mixed borate BAGs become suitable candidates for bone substitutes, especially for bone tissue regeneration and repair applications.

Direct electrocatalytic sensing of myoglobin using an annealed Au-implanted electrode

Ion implantation is a versatile and green material surface modification technology that modifies the structure of target-neat surface by bombardment of non-metal or heavy metal ions. A new Au nanoparticle loaded ITO (AuNPs/ITO) electrodes was prepared by ion implantation and thermal annealing method in this work. The obtained nanoparticles were characterized by Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods. The direct electrocatalysis of Myoglobin (MB) was reported. It was found that after annealing at 500 °C for 2 h, the damage part of the implanted sample was eliminated. The surface coverage of MB on the MB/AuNPs/ITO electrode and the MB/annealed-AuNPs/ITO electrode was 4.35× 10−11 mol·cm−2 and 1.23 × 10−10 mol·cm−2, respectively. The results show that this composite method can be used to fabricate an electrocatalytic biosensor.

Palladium nanocubes-mediated Fenton catalysis combined with chloride ion-amplified electro-driven catalysis for dye degradation

Electrochemical technology is frequently used to treat industrial dye wastewater. However, its degradation efficiency is restricted by pH, and the low current efficiency and high energy consumption limit its broader application. Based on this, we constructed an innovative electro-driven catalytic system by integrating nanotechnology with electric current. This system operates without pH constraints, has low energy consumption, and allows for the recycle and reuse of both electrodes and catalysts. Firstly, we synthesized palladium (Pd) cubes via a solvothermal method, and characterized their morphology, structural composition, and crystalline properties using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and other methods. The prepared Pd cubes possessed dual catalytic properties of electro-driven catalysis and Fenton catalysis, achieving a synergistic degradation effect under an electric field. Subsequently, the study explored how catalysts dosage, H2O2 concentration, pH and Cl− concentration affect the catalytic rate. The optimized system was able to degrade 99.17 % of MB within 1 h and was effective against various organic pollutants. After five cycles of reuse, the recovered catalysts maintained over 90 % degradation efficiency in decomposing MB. This process realizes efficient degradation with a low concentration of catalysts, offering a novel approach for nanotechnology in wastewater treatment under electro-driven conditions.

Crystal structure, composition and valence state of cations in mixed-valence A1-xCdxMnO3 (A=Pr, La) ceramics

Abstract Complex manganites A1−xCdxMnO3 (A = Pr, La) are synthesized by solid state reaction method. X-ray diffraction, scanning electron microscopy and energy-dispersive analysis are applied to study their crystal structure, surface morphology, elemental and phase composition. X-ray photoelectron spectroscopy (XPS) methods are used to study the charge states of Pr and La cations, as well as to quantify the fractions of coexisting Mn3+ and Mn4+ ions. La3d-, La4d-, Pr4d- и Mn2p-spectra of La3+, Pr3+, Mn3+ and Mn4+ ions are calculated in the isolated–ion approximation with accounting for multiplet splitting and charge transfer effect. Good agreement with the experiment is obtained. The relative fractions of trivalent and tetravalent manganese ions in La0.45Cd0.78Mn0,9O2.86 and Pr0.50Cd0.76Mn0.86O2.88 samples are determined by fitting the Mn2p spectra by superposition of experimental spectra containing only Mn3+, and only Mn4+ ions; they were found to be 0.71Mn3+/0.29Mn4+ and 0.54Mn3+/0.46Mn4+, respectively.

A novel arrangement of active and ultra-stable electrocatalyst based on iron/nickel/cobalt oxy/hydroxides for continuous oxygen evolution from alkaline seawater splitting

This research offers novel ideas for development a new class of materials with enhanced OER kinetics utilizing an easy electrochemical deposition technique. Here, the Ti/CoNiyOx/FeOOH electrocatalyst was prepared in two steps. First, CoNiyOx thin film was anodically electrodeposited on an activated titanium substrate. Then iron oxyhydroxide (FeOOH) nanosheets were cathodically electrodeposited on the first layer. The properties of this electrocatalyst was evaluated and compared with some monolayer electrocatalysts using field emission scanning electron microscopy (FE-SEM), Raman, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods. The Ti/CoNiyOx/FeOOH electrode requires an overpotential less than 330 mV at 100 mA/cm2 with Tafel constant of only 23.7 mV/dec for OER. The Ti/CoNiyOx/FeOOH electrode delivered long-term electrochemical stability in a solution containing corrosive chloride ions for more than 90 h at a constant current density of 100 mA/cm2 (with less than 9 % potential increase). Overall seawater splitting using the synthesized Ti/CoNiyOx/FeOOH electrode was performed at a current density of 100 mA/cm2 by a voltage as low as 1.58 V. The exceptional activity was ascribed to the synergistic effects of high electrochemical active sites and appropriate charge transfer ability found in CoNiyOx/FeOOH junction.

Facile purification of glass fiber powder by sedimentation for enhanced epoxy resin composites

Glass fiber powder contains two distinct forms: crumb-shaped and rod-shaped glass fiber powder particles. The shape and size of the particles in glass fiber powder have a great influence on its application. In order to separate rod-shaped glass fiber, the effects of different dispersants, such as SHMP, NaOL, and Na2SiO3 on them were investigated by settling experiments. Zeta potential, X-ray photoelectron spectroscopy (XPS), optical microscope, and other methods were used to analyze the adsorption behavior and settling mechanism. Three-point bending experiment and dynamic mechanical analysis (DMA) were used to evaluate the performance of epoxy resin composites reinforced with the raw glass fiber powder and the rod-shaped glass fiber powder. The results show that SHMP can effectively separate crumb-shaped glass fiber powder and rod-shaped glass fiber powder, leading to a notable increase in sedimentation recovery difference, up to Δ=51.08%. A preferential sedimentation separation mechanism is proposed to elucidate the settling mechanism. When the content of glass fiber powder and rod-shaped glass fiber is 5%, the glass transition temperature shifts significantly towards higher values, leading to the optimum comprehensive mechanical properties of the composites. Compared with the original epoxy resin, the flexural strength increased by 10.38% to 95.18 MPa and by 20.11% to 103.57 MPa. Similarly, the storage modulus increased by 14.14% to 2083 MPa and by 21.64% to 2220 MPa.

Optimization of electrical transport and magnetoresistance of La0.72Ca0.28-xPbxMnO3 ceramics by Pb2+ doping

Here, La0.72Ca0.28-xPbxMnO3 (LCPMO, 0 ≤ x ≤ 0.06) polycrystalline ceramics are prepared by the sol-gel method and the influence of Pb2+ doping on microstructure, chemical composition, and electrical transport properties of LCPMO ceramics is systematically investigated. The study was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and four-probe method. The four-probe test shows that all samples have MIT (metal-insulator transition) behavior, and the peak resistance gradually decreases with the increase of Pb2+ doping amount. With the increase of Pb2+ doping amount, the temperature coefficient of resistance (TCR) and magnetoresistance (MR) first increased and then decreased, the TCR increased from 24.6 % to 36.5 %·K−1, and the MR value increased from 47 % to 71.5 %, and both corresponded to high temperature direction. Referring to previous studies, higher TCR and MR values near room temperature are what researchers have been pursuing for a long time. it can be seen that the LCPMO ceramics prepared in this article can have good application prospects in infrared detection and magnetic storage.