Search Results (74)

This study employed an in-situ displacement technique to eliminate the oxide layer present on the surface of micron aluminum (μAl). Utilizing the exposed metallic aluminum, we facilitated the displacement of copper and nickel nanoparticles. These nanoparticles, approximately 90 nanometers in size, were densely adhered to the surface of the μAl particles. The elemental composition and structural characteristics of the composite particles were meticulously analyzed using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Vibrating Sample Magnetometry (VSM), and X-Ray Photoelectron Spectroscopy (XPS). Subsequently, thermal analysis and combustion performance assessments were conducted to elucidate the catalytic effects of the composite particles ([nCu+nNi]/μAl) on the thermal decomposition and combustion efficiency of ammonium perchlorate (AP). The results elucidate that the nanoparticles immobilized on the surface of μAl are unequivocally metallic copper (nCu) and metallic nickel (nNi). Following the application of nCu and nNi, the oxidation reaction of μAl accelerated by nearly 400 °C; furthermore, the incorporation of [nCu+nNi]/μAl raised the thermal decomposition peak temperature of AP by approximately 130 °C. Notably, the thermal decomposition activation energy of raw AP reached as high as 241.7 kJ/mol; however, upon doping with [nCu+nNi]/μAl, this activation energy significantly diminished to 161.4 kJ/mol. The findings of the combustion experiments revealed that both the raw AP and the AP modified solely with μAl were impervious to ignition via the hot wire method. In contrast, the AP doped with [nCu+nNi]/μAl demonstrated pronounced combustion characteristics, achieving an impressive peak flame temperature of 1851 °C. These results substantiate that the nCu and nNi, when deposited on the surface of μAl, not only facilitate the oxidation and combustion of μAl but also significantly enhance the thermal decomposition and combustion dynamics of ammonium perchlorate. Consequently, the [nCu+nNi]/μAl composite shows considerable promise for application in high-burn-rate hydroxyl-terminated polybutadiene (HTPB) propellants. Full article

This study designed Al_xCrFeNi (x = 0.8, 1.0, 1.2) medium-entropy alloys featuring a BCC + B2 dual-phase structure to systematically investigate the effects of Al content variation and heat treatment on microstructure evolution and corrosion behavior. Microstructural characterization revealed that all investigated alloys maintained the BCC + B2 dual-phase labyrinth structure. Electrochemical tests showed that as the Al content increased, the corrosion current density and corrosion rate in a 3.5 wt% NaCl solution increased. Synergistic analysis of post-corrosion morphology (through electrochemical testing and in-situ immersion) combined with XPS analysis of the passive films revealed that the initial stage of corrosion was primarily pitting. Subsequently, due to the loose and porous Al₂O₃ passive layer formed by the NiAl-rich phase, which was easily attacked by Cl⁻ ions, the corrosion progressed into selective corrosion of the NiAl phase. Notably, heat treatment at 1000 °C induced microstructural refinement with enhanced coupling between chunky and labyrinth structures, resulting in improved corrosion resistance despite a 4–6% reduction in Vickers hardness due to elemental homogenization. Among the investigated alloys, the heat-treated Al_0.8CrFeNi exhibited the most promising corrosion resistance. Full article

V/Fe multilayers were prepared on naturally oxidized Si(100) substrates at room temperature (RT) by UHV magnetron sputtering. Mixing effects at the Fe–V interfaces were investigated in-situ, directly after deposition, by means of X-ray photoelectron spectroscopy (XPS). The results of systematic in-situ XPS studies of the integral intensity of the Fe-2p peak, as a function of the nominal thickness of the Fe sublayer deposited on vanadium, allowed us to estimate the thickness of the pure iron layer that forms the mixed layer at about 0.4 nm. Assuming the same thickness of the vanadium layer that forms the mixed layer, the estimated thickness of the mixed layer near the Fe–V interface was about 0.8 nm. In the analysis of magnetic hysteresis loops, in addition to the bilinear (J₁) and biquadratic (J₂) coupling constant, the contribution of the cubic exchange constant (J₃) was taken into account, which also contributed significantly to the total energy. Higher order interactions (J₂ and J₃) are particularly important for V spacer thicknesses greater than 7 atomic monolayers. Hydrogen absorption in V/Fe multilayers at RT and a pressure of about 1 bar causes an increase in the biquadratic coupling constant J₂, while the values of J₁ and J₃ are reduced. A comparison of the obtained experimental results and available theoretical models leads to the conclusion that the mechanism of “fluctuating thickness of the non-magnetic spacer” could be responsible for the biquadratic exchange coupling. On the other hand, the “loose spins” model can explain the cubic coupling in the V/Fe multilayers. The modification of the interlayer exchange coupling using hydrogen is fully reversible. Full article

In the environmental field, the advancement of new high-efficiency heavy metal adsorption materials remains a continuous research focus. A novel composite, covalent organic framework-modified biochar (RH-COF), was fabricated via an in-situ polymerization approach in this study. The COF-modified biochar was characterized by elemental analysis, BET analysis, SEM, FT-IR, and XPS. The nitrogen and oxygen content in the modified material increased significantly from 0.96% and 15.50% to 5.40% and 24.08%, respectively, indicating the addition of a substantial number of nitrogen- and oxygen-containing functional groups to the RH-COF surface, thereby enhancing its adsorption capacity for Cd from 4.20 mg g⁻¹ to 58.62 mg g⁻¹, representing an approximately fourteen-fold increase. Both the pseudo-second-order model and the Langmuir model were suitable for describing the kinetics and isotherms of Cd²⁺ adsorption onto RH-COF. The adsorption performance of Cd²⁺ by RH-COF showed minimal sensitivity to pH values between 4.0 and 8.0, but could be slightly influenced by ionic strength. Mechanistic analysis showed that the Cd²⁺ adsorption on RH-COF was dominated by surface complexation and chelation, alongside electrostatic adsorption, surface precipitation, and Cπ–cation interactions. Overall, these findings suggest that the synthesis of COF-biochar composite may serve as a promising remediation strategy while providing scientific support for applying COF in environmental materials. Full article

As photoelectrochemical catalyst material, Z-scheme heterojunction 3D WO₃@Co₂SnO₄ composites were designed through a hydrothermal-calcination method. The morphology and structure were characterized by SEM, EDS, XRD, XPS, DRS, and Mott–Schottky analysis, and the photoelectrochemical properties were explored with the transient photocurrent and electrochemical impedance. The construction of Z-scheme heterojunction markedly heightened the separation efficiency of photogenerated electron-hole pairs of WO₃ and enhanced the light absorption intensity, retaining the strong redox ability of the photocatalyst. The 3D WO₃@Co₂SnO₄ was used as a photocathode for production of H₂O₂. Under the optimal reaction conditions, the yield of H₂O₂ can reach 1335 μmol·L⁻¹·h⁻¹. The results of free radial capture and rotating disc test revealed the existence of direct one-step two-electron and indirect two-step one-electron oxygen reduction to produce H₂O₂. Based on the excellent H₂O₂ production performance of the Z-scheme heterojunction photoelectrocatalytic material, 3D WO₃@Co₂SnO₄ and stainless-steel mesh were used to construct a dual-cathode photoelectric-Fenton system for in-situ degradation of a variety of pollutants in water, such as dye (Methyl orange, Rhodamine B), Tetracycline, sulfamethazine, and ciprofloxacin. The fluorescence spectrophotometry was used to detect hydroxyl radicals with terephthalic acid as a probe. Also, the photocatalytic degradation mechanism was revealed, indicating the dual-cathode photoelectron-Fenton system displayed satisfactory potential on degradation of different types of environmental pollutants. This work provided insights for designing high-activity photoelectrocatalytic materials to produce H₂O₂ and provided possibility for construction of a photoelectric-Fenton system without extra additions. Full article

This work presents a new ultra-high vacuum cluster tool to perform systematic studies of the early growth stages of atomic layer deposited (ALD) ultrathin films following a surface science approach. By combining operando (spectroscopic ellipsometry and quadrupole mass spectrometry) and in situ (X-ray photoelectron spectroscopy) characterization techniques, the cluster allows us to follow the evolution of substrate, film, and reaction intermediates as a function of the total number of ALD cycles, as well as perform a constant diagnosis and evaluation of the ALD process, detecting possible malfunctions that could affect the growth, reproducibility, and conclusions derived from data analysis. The homemade ALD reactor allows the use of multiple precursors and oxidants and its operation under pump and flow-type modes. To illustrate our experimental approach, we revisit the well-known thermal ALD growth of Al₂O₃ using trimethylaluminum and water. We deeply discuss the role of the metallic Ti thin film substrate at room temperature and 200 °C, highlighting the differences between the heterodeposition (<10 cycles) and the homodeposition (>10 cycles) growth regimes at both conditions. This surface science approach will benefit our understanding of the ALD process, paving the way toward more efficient and controllable manufacturing processes. Full article

Composites made from carbon and nanominerals show great potential for thermal phase change materials, environmental water treatment, and biomass conversion. In 2019, a micro and nano-quartz-carbon ore was discovered in Feng-cheng City, Jiangxi Province. The study of the structural and physicochemical changes of quartz-carbon ore (QZC) during calcination is essential for the preparation of QZC-based composites and to broaden their application areas. Firstly, the SiO₂ crystal structure evolution of QZC during calcination was investigated using in-situ X-ray diffraction (XRD), ²⁹Si magic-angle sample spinning nuclear magnetic resonance (MAS NMR), and Fourier transform infrared FTIR spectroscopy. Then, the changes in carbon during calcination were investigated using Raman spectroscopy, ¹³C MAS NMR, and X-ray photoelectron spectroscopy (XPS). In addition, changes in the QZC morphology were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Finally, the evolution of the physicochemical properties of QZC during calcination was revealed using thermogravimetric (TG), Brunauer–Emmet–Teller (BET), resistivity, thermal conductivity, and zeta potential techniques. Full article

An advanced strategy was developed for the synthesis of molecular sieve-supported Pd catalysts. In this method, reductant containing C=C was in-situ prepared and pre-dispersed in the pore of the zeolites. The C=C group in the reductant can reduce the Pd²⁺ to Pd⁰ efficiently, leading to the formation of small and uniform Pd nanoparticles (~2 nm). The physical and chemical properties of the catalyst were characterized by XRD, TEM, XPS (ICP-OES), N₂ isothermal adsorption-desorption, and H₂-TPR. These catalysts showed high catalytic performance for the hydrogenation of nitrobenzene to aniline. All the TOFs for 1.5 Pd/Y, 1.5 Pd/ZSM-5, and 1.5 Pd/MOR with 1.5 wt% Pd loading are higher than 1000 h⁻¹ at 30 °C and 0.1 MPa H₂. Meanwhile, kinetic analysis for 2.0 Pd/Y was carried out, and an apparent activation energy of 28.88 kJ mol⁻¹ was obtained, which is lower than most of the reported values in the literature. Furthermore, these catalysts were stable and recyclable. Full article

Phenolic resin-modified materials partially reduce the toughness of the wood. In this study, organic–inorganic composite modifiers were used to modify the wood. Silica sol/phenolic resin was prepared through in-situ polymerization, and poplar wood was modified using a vacuum pressure impregnation process, enhancing its toughness. Orthogonal experiments were conducted, and the impact toughness of the modified poplar wood was used as the evaluation index. Through orthogonal experiments, using the impact toughness of modified poplar as the evaluation indicator, it was found that when the average particle size of the silica sol is 8–15 nm, the pressure is 1.2 MPa, and the pressurization time is 3 h, the impregnation-modified poplar’s impact toughness reaches its optimum, improving by 84.1% and 135.4% compared to the raw material and phenolic resin impregnated wood, respectively. The Fourier Transform Infrared Spectroscopy (FT-IR) results indicated that the characteristic absorption peak of Si-O-Si appears in the poplar wood after impregnation, confirming the formation of new silicon-oxygen (Si-O) chemical bonds. X-ray Photoelectron Spectroscopy (XPS) analysis revealed that a chemical reaction occurs between the impregnation liquid and the wood, generating Si-O-C. Subsequently, through Dynamic Mechanical Analysis (DMA) and Thermogravimetric (TGA) analysis, it was understood that this chemical reaction significantly enhances the thermal stability and toughness of the impregnated material, making it superior to the original poplar material. The TGA further unveiled that, compared to untreated poplar, the thermal stability of the impregnated material has been notably improved. Lastly, Scanning Electron Microscopy (SEM) analysis demonstrated that the composite impregnation liquid successfully permeates and fills the interior of the poplar cells. Full article

Pre-treated silica with a plasma-deposited (PD) layer of polymerized precursors was tested concerning its compatibility with Natural Rubber (NR) and its influence on the processing of silica-silane compounds. The modification was performed in a tailor-made plasma reactor. The degree of deposition of the plasma-coated samples was analyzed by ThermoGravimetric Analysis (TGA). In addition, Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM) were performed to identify the morphology of the deposited plasma polymer layer on the silica surface. PD silica samples were incorporated into a NR/silica model compound. NR compounds containing untreated silica and in-situ silane-modified silica were taken as references. The silane coupling agent used for the reference compounds was bis-(3-triethoxysilyl-propyl)disulfide (TESPD), and reference compounds with untreated silica having the full amount and 50% of silane were prepared. In addition, 50% of the silane was added to the PD silica-filled compounds in order to verify the hypothesis that additional silane coupling agents can react with silanol groups stemming from the breakdown of the silica clusters during mixing. The acetylene PD silica with 50% reduced silane-filled compounds presented comparable properties to the in-situ silane-modified reference compound containing 100% TESPD. This facilitates processing as lower amounts of volatile organic compounds, such as ethanol, are generated compared to the conventional silica-silane filler systems. Full article

Polymeric surfaces have been increasingly plasma-activated to adopt adequate chemistries, enabling their use in different applications. An unavoidable surface oxygen insertion upon exposure to non-oxygen-containing plasmas was always observed and mainly attributed to in-plasma oxidation stemming from O₂ impurities in plasma reactors. Therefore, this work investigates exclusive in-plasma oxidation processes occurring on polyethylene surfaces by purposely admixing different O₂ concentrations to medium-pressure Ar and N₂ dielectric barrier discharges (base pressure: 10⁻⁷ kPa). Hence, distinctive optical emission spectroscopy and in-situ X-ray photoelectron spectroscopy (XPS) data were carefully correlated. Pure N₂ discharge triggered an unprecedented surface incorporation of large nitrogen (29%) and low oxygen (3%) amounts. A steep rise in the O-content (10%) at the expense of nitrogen (15%) was detected upon the addition of 6.2 × 10⁻³% of O₂ to the feed gas. When the added O₂ exceeded 1%, the N content was completely quenched. Around 8% of surface oxygen was detected in Ar plasma due to high-energy Ar metastables creating more surface radicals that reacted with O₂ impurities. When adding only 6.2 × 10⁻³% of O₂ to Ar, the surface O content considerably increased to 12%. Overall, in-plasma oxidation caused by O₂ impurities can strikingly change the surface chemistry of N₂ and Ar plasma-treated polymers. Full article

Photocatalytic degradation plays a crucial role in wastewater treatment, and the key to achieving high efficiency is to develop photocatalytic systems that possess excellent light absorption, carrier separation efficiency, and surface-active sites. Among various photocatalytic systems, S-type heterojunctions have shown remarkable potential for efficient degradation. This work delves into the construction of S-type heterojunctions of ternary indium metal sulfide and bismuth ferrite nanofibers with the introduction of sulfur vacancy defects and morphology modifications to enhance the photocatalytic degradation performance. Through the impregnation method, BiFeO₃/ZnIn₂S₄ heterojunction materials were synthesized and optimized. The 30% BiFeO₃/ZnIn₂S₄ heterojunction exhibited superior photocatalytic performance with higher sulfur vacancy concentration than ZnIn₂S₄. The in-situ XPS results demonstrate that the electrons between ZnIn₂S₄ and BFO are transferred via the S-Scheme, and after modification, ZnIn₂S₄ has a more favorable surface morphology for electron transport, and its flower-like structure interacts with the nanofibers of BFO, which has a further enhancement of the reaction efficiency for degrading pollutants. This exceptional material demonstrated a remarkable 99% degradation of Evans blue within 45 min and a significant 68% degradation of ciprofloxacin within 90 min. This work provides a feasible idea for developing photocatalysts to deal with the problem of polluted water resources under practical conditions. Full article

The content of Cu²⁺ in lubricants is an essential indicator for determining the quality of the lubricant and predicting mechanical failure. Finding an effective and sensitive method for detecting Cu²⁺ in lubricants is of great importance in oil monitoring. In this work, AgInS₂ (AIS) and AgInS₂-ZnS (ZAIS) nanoparticles (NPs) were synthesized by a simple one-step approach via in-situ surface modification by oleylamine. The as-synthesized AIS and ZAIS NPs exhibit good dispersion stability in various apolar media. The photoluminescence (PL) of AIS and ZAIS NPs as lubricating additives could reflect and monitor the lubrication state of steel-copper pairs due to the quenching effect of Cu²⁺ from the friction process. With an optimum concentration of 0.5 wt% in paraffin oil, the friction coefficient of the AIS and ZAIS NPs at 100 N was decreased by 56.8 and 52.1% for steel-steel contacts, respectively. ZAIS was observed to be more effective than AIS in improving anti-wear (AW) and extreme pressure (EP) properties, with a load-bearing capacity of up to 1100 N. Characterization of the wear tracks by SEM and XPS indicates that a tribofilm composed of metal sulfides and oxides was formed during the lubricating process. This work not only reveals AIS and ZAIS NPs as a new class of promising candidates for lubricating additives but also unveils their potential for monitoring lubricant conditions and exploring lubricant service life. Full article

Biochar derived from waste biomass has proven to be an encouraging novel electrode material in supercapacitors. In this work, luffa sponge-derived activated carbon with a special structure is produced through carbonization and KOH activation. The reduced graphene oxide (rGO) and manganese dioxide (MnO₂) are in-situ synthesized on luffa-activated carbon (LAC) to improve the supercapacitive behavior. The structure and morphology of LAC, LAC-rGO and LAC-rGO-MnO₂ are characterized by the employment of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), BET analysis, Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical performance of electrodes is performed in two and three-electrode systems. In the asymmetrical two-electrode system, the LAC-rGO-MnO₂//Co₃O₄-rGO device shows high specific capacitance (SC), high-rate capability and excellent cycle reversibly in a wide potential window of 0–1.8 V. The maximum specific capacitance (SC) of the asymmetric device is 586 F g⁻¹ at a scan rate of 2 mV s⁻¹. More importantly, the LAC-rGO-MnO₂//Co₃O₄-rGO device exhibits a specific energy of 31.4 W h kg⁻¹ at a specific power of 400 W kg⁻¹. Overall, the synergistic effect between the ternary structures of microporous LAC, rGO sheets and MnO₂ nanoparticles leads to the introduction of high-performance hierarchical supercapacitor electrodes. Full article

Photovoltaics are being transformed by perovskite solar cells. The power conversion efficiency of these solar cells has increased significantly, and even higher efficiencies are possible. The scientific community has gained much attention due to perovskites’ potential. Herein, the electron-only devices were prepared by spin-coating and introducing the organic molecule dibenzo-18-crown-6 (DC) to CsPbI₂Br perovskite precursor solution. The current-voltage (I-V) and J-V curves were measured. The morphologies and elemental composition information of the samples were obtained by SEM, XRD, XPS, Raman, and photoluminescence (PL) spectroscopies. The distinct impact of organic DC molecules on the phase, morphology, and optical properties of perovskite films are examined and interpreted with experimental results. The efficiency of the photovoltaic device in the control group is 9.76%, and the device efficiency gradually increases with the increase of DC concentration. When the concentration is 0.3%, the device efficiency is the best, reaching 11.57%, short-circuit current is 14.01 mA/cm², the open circuit voltage is 1.19 V, and the fill factor is 0.7. The presence of DC molecules effectively controlled the perovskite crystallization process by inhibiting the in-situ generations of impurity phases and minimizing the defect density of the film. Full article