Electron Spectroscopy Analysis Research Articles

Assessing the Accuracy of Lithium Contents Determined by Combined Quantitative Backscattered Electron and X-ray Energy Dispersive Spectroscopy Analysis

Assessing the Accuracy of Lithium Contents Determined by Combined Quantitative Backscattered Electron and X-ray Energy Dispersive Spectroscopy Analysis

Revival of Degraded CsPbI3 Nanocrystals by Diselenide Ligand and Nanocrystal Self-Assembly on Nanofibrilar Ligand Template.

Among the lead halide perovskite (LHP) family, CsPbI3 is known to be significantly vulnerable to moisture, which hinders its use in real device applications. It is reported that chalcogen-based ligands can better stabilize CsPbI3 and revive nanocrystals (NCs). Here, diphenyl diselenide (DPhDSe) ligand is used to revive the degraded CsPbI3 NCs through a post-synthetic treatment of adding a small amount of DPhDSe in the degraded NC dispersion. DPhDSe in the dispersion formed nanofibrillar crystals at a low temperature through the π-π stacking of the phenyl ring. The nanofibrils played as a template on which the NCs self-assembled and they are attached side-by-side to form microfibers. The microfiber powder containing the NCs is optically stable at ambient conditions and morphologically self-healable by mild thermal annealing due to the dynamic Se─Se bond. The mechanism of the structural changes, optical transitions, and chemical changes has been systematically characterized through electron microscopy, diffraction, spectroscopy, and elemental analysis.

Amine-rich cyclotriphosphazene (P3N3) nano-cages for enhanced and selective Au(III) and Pd(II) recovery and hydrogen generation: Waste-to-resource tactics

Designing a new material for precious metals (PMs) recovery is of ultimate significance in the quest to explore highly efficient, selective, and stable adsorbents for a sustainable economy and green environment. Herein, novel amine-rich cyclotriphosphazene poly(tetrakis(4-aminophenyl)methane-co-cylotriphosphazene)- porous nano-cages (PTC-PNC) and microspheres (PTC-MS) were synthesized for adsorption and selective recovery of Au(III) and Pd(II) in aqueous solution. A combination of the abundant amine groups and the cage-like porous morphology of PTC-PNC makes it an ideal absorbent for recovery of the Au(III) (1592 mg g−1, pH 1.0, 60 oC) and Pd(II) (1372 mg g−1, pH 1.0, 60 oC) with high selectivity which was slightly decreased up to 8-11% even in the presence of 13 co-existing metals ions while an ultra-high recovery of 99% was obtained. The unique cage-like morphology of the PTC-PNC guarantees a fast adsorption equilibrium while the adsorption isotherm specifies a pseudo-second-order kinetic behavior and Langmuir isotherm. Amine groups were the most energetically favorable sites for the capturing and chelating of Au(III) and Pd(II) ions followed by their partial reduction to Au0 and Pd0. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron spectroscopy (HRTEM) analysis were employed to explore interactions and reduction mechanisms during the adsorption process. Adopting the waste-to-resource approach, after Au(III) and Pd(II) recovery, these adsorbents were applied for catalytic hydrogen generation from ammonia borane (AB) hydrolysis. Due to its favorable electronic structure, the PTC-PNC@Pd exhibited a higher hydrogen generation than PTC-PNC@Au. The as-synthesized PTC-PNC could be employed as a promising material for other MPs' selective recovery and green energy generation applications.

Remote plasma chemical vapor deposition of silicon oxycarbide film with a styrene-containing precursor and in situ O2 plasma treatment

In this paper, a study was conducted on silicon oxycarbide thin-film deposition using remote plasma chemical vapor deposition. A di-methyldimethoxysilane)2styrene (MDMS)2styrene precursor and CH4 plasma were used in the deposition process, and in situ oxygen plasma treatment was performed to control the carbon content and properties of the thin film. During the deposition process, the thin-film growth rate was found to be almost constant regardless of in situ plasma treatment. This means that in situ oxygen plasma treatment had no significant effect on thin-film growth itself. Auger electron spectroscopy analysis revealed that the carbon content of the deposited thin film was 43 % when only deposition was performed, but could be lowered to 3 % by in situ oxygen plasma treatment, which demonstrated that the carbon content can be controlled in a relatively wide range. X-ray photoelectron spectroscopy showed that it was possible to preserve SiC bonds even as the oxygen content increased with the number of in situ plasma treatments. The refractive index increased from 1.33 to 1.49, indicating a decrease in the number of pores and an increase in density. Meanwhile, the dielectric constant increased with the oxygen content, but did not exceed 3.9 due to the SiC bond structure. As the pore size decreased, the leakage current tended to decrease to 9.51 × 10−9 A/cm2 in an electric field of 1 MV/cm, and the breakdown voltage increased. Finally, it was possible to improve the etching characteristic through plasma treatment by lowering the wet etch rate from 78 to 19 Å/min.

Co-gasification of lignite and spent tea waste for the generation of hydrogen-rich syngas in a fluidized bed gasifier

The co-gasification of high moisture and high volatile content low-rank lignite (LG) coal and a common waste generated from the brewed tea leaves was studied in a fluidized bed gasification unit. Multiple experiments were conducted at different temperatures, ranging from 800 °C to 900 °C, at fixed operating parameters to elucidate the catalytic thermo-chemical impact on the gasifier performance parameters. The catalytic effect of alkali and alkaline earth metals (AAEMs), especially CaO, K2O, and Na2O present in the spent tea waste (STW) sample, on the product gas composition and performance parameters during the co-gasification experiments with LG was demonstrated. Mixed blends of LG and STW showed enhancement in the overall reactivity of the steam gasification runs, compared to the LG-only feed, primarily due to the change in the surface morphology, textures, and pore structures of the solid product ash samples, as identified with the electron spectroscopy analysis. Liquid and product samples were analyzed using characterization techniques such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) analytical techniques, along with the proximate, ultimate, and X-ray fluorescence (XRF) analysis of the gasification feed samples. An optimized blend ratio of 20 wt % of STW with LG sample enhanced the volumetric gas composition of H2 and CH4 gases from 52.03 % to 61.32 % and 3.98 %–5.45 % (on a dry-N2-free basis) with a relatively constant CO gas composition. It showed a reduced CO2 composition from 28.64 % to 18.25 % (on a dry-N2-free basis) for the gasification temperature of 900 °C. Even at the lower gasification temperatures of 800 °C and 850 °C with LG + STW feed, steam gasification experiments showed relatively comparable or superior performance to gasification experiments at 900 °C with LG-only feed. The present study indicated a holistic way to utilize the spent tea waste generated from millions of homes and commercial establishments in various parts of the world with potential application towards synergistic gasification process with other conventional carbon-source materials.

Development of fluorosilicon bivalve isocyanate microcapsules for multifunctional coatings with excellent self-repairing properties, enhanced hydrophobicity, and corrosion protection properties

This study first self-made TMP-IPDI tetramer, and then prepared a fluorine-modified silicon dioxide double shell isocyanate type self-healing microcapsule (CBS-X/TMP-IPDI@PU@F-SiO2) using TMP-IPDI tetramer, fluorescent agent 4,4-bis (2-disulfonic acid sodium styrene) biphenyl (CBS-X) as the core material, polyurethane (PU) as the single shell, and fluorine modified silicon dioxide (F-SiO2) as the double shell using interfacial polymerisation method. Then, it was added to waterborne polyurethane (WPU) to prepare self-healing coatings and coatings. The chemical structure, microstructure, self-healing self detection, and mechanical properties of TMP-IPDI, CBS-X/TMP-IPDI@PU@F-SiO2, and composite coatings were characterized by infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), particle size analysis (PSA), X-ray electron spectroscopy (XPS) analysis, contact angle testing, tensile testing, electrochemical impedance testing, and Ultraviolet photograph. The results showed that the TMP-IPDI tetramer was successfully prepared. The average particle size of CBS-X/TMP-IPDI@PU@F-SiO2 prepared is 29 μm. The contact angle, tensile strength, low-frequency impedance and Nyquist curve radius of the repaired spots increased with the increase of the amount of CBS-X/TMP-IPDI@PU@F-SiO2 in WPUs; the increasing trend slowed down when the amount of CBS-X/TMP-IPDI@PU@F-SiO2 was >5 %. When the CBS-X/TMP-IPDI@PU@F-SiO2 dosage is 5 %, the WPU coating has good self-repair and self-detection performance. The stress before and after repair were 12.89 MPa and 20.11 MPa, respectively, with a repair rate of 80.3 %. The contact angle at the repair site can reach 100.8°, and the coating has good corrosion resistance. The microcapsules prepared based on fluorine-modified silica (F-SiO2) as the wall material have good self-healing performance for WPU coatings, achieving secondary protection of the repaired material.

Effects of Spectrum Loading and break in period using molybdenum disulphide (MoS2) and zinc dialkyl dithiophosphate (ZDDP) as EP additives in lithium based grease

PurposeThe purpose of variable loading conditions (392 N-785N-392N-785N) with break-in period were used to study interactions between zinc dialkyl dithiophosphate (ZDDP) 0.1 P% (phosphorus) and fine-grade molybdenum disulfide (MoS2) 3%, in different mixtures of NLGI 2 lithium stearate grease. Four-ball wear tests were used to evaluate the tribological properties of different grease mixtures such as coefficient of friction and wear. ASTM 2266 as reported by earlier studies is useful, but it is not representative of real-life applications where variable loads and speeds and different break-in periods play a role and could change the results and the nature of tribofilms.Design/methodology/approachIn this study, chemical and mechanical properties of tribofilms were examined. Moreover, design of experiment was used to examine the data and shorten experimentation time. Research described here is investigating variable loading conditions for real-life applications by using a break-in period of 2 min at the start to minimize asperities and establish a clean surface. Design expert (DOE) analyzes responses to reveal those variables that are single factor and those that are multifactor whether synergistically or antagonistically.FindingsThe results indicated that spectrum loading with break-in period showed reduction in wear when tested in greases with ZDDP/MoS2 combinations. Ramping up or down the load every 7.5 min for a rotational speed of 1,200 rpm and a total of 36,000 revolutions or 30-min time slowed the wear properties of lithium-based grease under different MoS2 and ZDDP concentrations. Experiments indicated that wear was largely dependent on the loading condition and ZDDP additives during specific break-in period at 1,200 rotational speed. It is believed that MoS2 greases perform better under spectrum loading and under constant loading when mixed with ZDDP phosphorus.Originality/valueThis research indicates that there is a synergistic interaction between ZDDP, MoS2 and variable loading especially when a break-in period is applied. The results indicated that wear was largely dependent on the specific speed used with spectrum loading as presented in the energy dispersive spectroscopy and the Auger electron spectroscopy analysis, and thus a 3% MoS2 grease with ZDDP (phosphorus: 0.1 Wt.%) are needed to improve the wear resistance and improve the friction characteristics.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0016/

Fe-carbide/Fe-oxide-based nanocomposites synthesized as magnetic nanomaterials via laser ablation synthesis in solution (LASiS)

Magnetic nanostructured materials (MNMs) have gained prominence in materials technology developments owing to their potential biomedical applications for hyperthermia cancer treatment, and transplant organ cryopreservation. Herein, we report the facile and cost-effective synthesis of Fe-based composite MNMs, comprising both Fe@Fe2O3 and Fe3C@C core-shell nanoparticles (NPs), via Laser Ablation Synthesis in Solution (LASiS) using Fe targets ablated under acetone and toluene. Detailed materials characterizations using electron microscopy-based imaging, diffraction studies, and spectroscopic analyses - including Raman and Mössbauer spectroscopy - relate the structure-composition properties for different Fe-oxide/carbide phases in the aforesaid MNMs to their respective magnetic responses. Specifically, we confirm the presence of ultra-small (2–10 nm) amorphous Fe-oxide NPs, as well as Fe@Fe2O3 core-shell NPs (20–40 nm) in the samples synthesized by ablating Fe under acetone. In contrast, samples synthesized under toluene indicate a higher concentration of Fe3C@C core-shell NPs (20–40 nm) with a relatively low concentration of Fe2O3 NPs (2–10 nm). Furthermore, the crystallinity of the metallic phases and carbonaceous shell coatings are systematically increased by carrying out LASiS under heated toluene (up to ∼95 °C). Mössbauer spectroscopy results indicate that the elevation in toluene temperature leads to an increase in the concentrations of Fe3C@C NPs from ∼40 % to ∼53 % (at.).

The Impact of ZIF-8 Particle Size Control on Low-Humidity Sensor Performance

An accurate humidity measurement is essential in various industries, including product stability, pharmaceutical and food preservation, environmental control, and precise humidity management in experiments and industrial processes. Crafting effective humidity sensors through precise material selection is crucial for detecting minute humidity levels across various fields, ultimately enhancing productivity and maintaining product quality. Metal–organic frameworks (MOFs), particularly zeolitic imidazolate frameworks (ZIFs), exhibit remarkable properties and offer a wide range of applications in catalysis, sensing, and gas storage due to their structural stability, which resembles zeolites. The previous research on MOF-based humidity sensors have primarily used electrical resistance-based methods. Recently, however, interest has shifted to capacitive-based sensors using MOFs due to the need for humidity sensors at low humidity and the resulting high sensitivity. Nevertheless, further studies are required to optimize particle structure and size. This study analyzes ZIF-8, a stable MOF synthesized in varying particle sizes, to evaluate its performance as a humidity sensor. The structural, chemical, and sensing properties of synthesized ZIF-8 particles ranging from 50 to 200 nanometers were examined through electron microscopy, spectroscopic, and electrochemical analyses. The fabricated copper electrodes combined with these particles demonstrated stable and linear humidity sensing capabilities within the range of 3% to 30% relative humidity (RH).

Calculation of positron annihilation lifetime in diamond doped with B, Cr, Mo, Ti, W, Zr

Metal-matrix diamond composites have been extensively used and studied, but vacancies, doping, and other defects caused by the pretreatment of the diamond surface significantly affect the interface property between the metal base and diamond. Although techniques like transmission electron microscopy and spectroscopy analysis have been used to detect defects, they present certain limitations. Calculating the positron annihilation lifetime in diamond provides an accurate assessment of interface defect in the diamond. This study uses first-principles calculation methods and adopts various positron annihilation algorithms and enhancement factors, to compute the positron annihilation lifetimes in ideal diamond crystals, single vacancies, and diamond crystals doped with B, Cr, Mo, Ti, W, and Zr. The results, obtained by using local density functional in combination with Boronski & Nieminen algorithms and random-phase approximation restriction as annihilation enhancement factors, indicate that the computed positron annihilation lifetime of diamond is 119.87 ps, which is consistent closely with the experimental result in the literature. Furthermore, after B, Cr, Mo, Ti, W, and Zr atoms are doped into diamond (doping atomic concentration of 1.6%), the positron annihilation lifetimes change from a single vacancy 119.87 ps to 148.57, 156.82, 119.05, 116.5, 117.62, and 115.74 ps respectively. This implies that the defects due to doped atoms in diamond change their positron annihilation lifetimes, with the influence varying according to the different atoms doped. Based on the calculated electron density in diamond vacancies and doped atom areas, it is discovered that doping atoms do not cause severe distortion in the diamond lattice. However, after B and Cr atoms are doped, the positron annihilation lifetime increases significantly. The primary reason is that the relatively low positron affinity of B and Cr atoms results in an extended positron residence time in the vacancy, thereby increasing the annihilation lifetime. Overall, vacancies and doped atom defects in diamond will cause its positron annihilation lifetime to change. The above conclusions provide crucial theoretical references for detecting and identifying interface defects caused by doping treatment on the diamond surface during the preparation of metal-matrix diamond composites.

Multifaceted characterization of a Zn0.9Ca0.1Fe2O4/CeO2/NiFe2O4 nanocomposite electrode for battery-type supercapacitors

The majority of current energy application research is focused on the development of electrode materials for high-power devices. We investigated the electrochemical properties of a Zn0.9Ca0.1Fe2O4/CeO2/NiFe2O4 nanocomposite. The crystallographic characteristics of the produced nanocomposite were studied using X-ray diffraction (XRD). The structure of the material was confirmed using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Fourier transform infrared electron spectroscopy (FT-IR) analysis found two distinct vibrational bands at 699.65 and 545.02 cm−1, which can be attributed to metal-oxygen bond stretching in both tetrahedral and octahedral configurations. Magnetic measurements were done at room temperature using a vibrating sample magnetometer (VSM), and the magnetic behavior of the nanocomposite was found to be 33.82 emu/g. The results demonstrated battery-like behavior, with a specific capacity (Cs) of 266.7 C g−1 at 1 A/g. Notably, the prepared electrode had a significant capacity retention of 90 % even after 5000 cycles. These findings emphasize the nanocomposite's potential for a wide range of energy storage applications.

Dual surface/bulk engineering of Nb2O5 for high‐rate sodium storage

AbstractOrthorhombic Nb2O5 is a highly promising fast‐charging anode material for sodium‐ion capacitors. However, its poor intrinsic electronic/ionic conductivity limits its performance. Here, we developed a one‐step heat treatment method to create an N‐doped carbon coating on the outside and S‐doped Nb2O5 on the inside (CN‐SCN). Ionic liquids are used as the source of C/N/S, which synergistically enhance the surface and bulk electronic/ionic conductivity. The N‐doped carbon coating on the surface exhibits excellent electronic conductivity and a low ion‐diffusion barrier, thanks to the high nitrogen ratio and extremely low content (<2 wt%). Auger electron spectroscopy analysis confirms that S atoms detach from the carbon chain of the ionic liquids and enter the bulk Nb2O5, resulting in S‐doped Nb2O5, significantly facilitating reaction kinetics. The CN‐SCN electrodes exhibit outstanding rate capability, achieving a capacity of up to 94 mAh g−1 even at a high current rate of 50 C. When paired with activated carbon as the positive electrode, the sodium‐ion capacitor with the CN‐SCN anode exhibits a high‐energy density of up to 59 Wh kg−1 and a long cycle life with 73% capacity retention after 10,000 cycles. This work opens up possibilities for low‐cost and large‐scale production of high‐rate Nb2O5 for sodium‐storage applications.

Enhancing biochar properties through doping: A comparative study of sugarcane bagasse and chicken feather

This comparative study explores the production and characterization of biochar derived from a combination of sugarcane bagasse (SB) and chicken feathers (CF), with a doping strategy for each biomass in the other. Two biochars, SB92CF-BC (92% SB and 8% CF) and CF92SB-BC (92% CF and 8% SB), were produced using a top-lit updraft reactor, resulting in a yield of 34% and 27%, respectively. Fourier transform infrared spectroscopy (FTIR) analysis revealed characteristic functional groups in both biochars, with minimal impact from the doping process. Scanning electron spectroscopy (SEM) analysis showed distinct morphological features, with SB92CF-BC exhibiting a smoother surface and CF92SB-BC displaying an irregular and rough morphology. Energy dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of several elements in both biochars, with a higher nitrogen content in CF92SB-BC. Brunauer-Emmett-Teller (BET) analysis demonstrated significant specific surface areas for both biochars, exceeding those reported for unmodified SB and CF biochars. The findings suggest potential synergistic effects resulting from the doping strategy. The study expands knowledge on biochar production from diverse biomass sources and highlights the potential for utilizing lignocellulosic and non-lignocellulosic biomass waste materials for sustainable biochar production.

THE ROLE OF SULFUR-CONTAINING AMINO ACIDS IN THE PREVENTIVE NUTRITION OF WORKERS IN CONTACT WITH CHROMIUM

In the world, a large number of workers are exposed to fumes, mists and dusts containing Chromium and its compounds. One of the ways to prevent chromium intoxication is the enrichment of food rations with substances that have antioxidant and complexing ability. Attention is focused on the recommendations on the use of sulfur-containing amino acids and sulfur-rich proteins in the composition of food products for the prevention of intoxication in workers who come into contact with chromium in production. The mechanism of reduction of hexavalent chromium compounds by cysteine was considered. It has been shown that the process of reduction of chromates with cysteine is accompanied by the oxidation of cysteine to cystine and subsequent complexation with trivalent chromium. The structure of chromium III cystinate was confirmed by IR and electron spectroscopy and elemental analysis. It has been established that in the formed chelate complex [Cr(SNO2C3H6)6Cr], chromium (III) has a bond with cystine through the amino and carboxyl groups, LD50 is 2100 mg/kg and is less toxic than inorganic chromium (III) salts. The article analyzes protein raw materials rich in cysteine, which can be recommended to satisfy the daily requirement of cysteine, or to reduce chromium intoxication of workers working in a work area with a high content of chromium salts.

Cu(II), Ni(II) and Co(II) Complexes of Malonic Acid Dihydrazide with Bis-BrSalicylhydrazone

New complexes of Cu(II), Ni(II), and Co(II) with N1,N3-bis(5-bromo-2-hydroxybenzylidene)-malonohydrazide (LH4) have been synthesized. It was shown that, in the synthesized Cu(II) and Co(II) complexes with the LH4 ligand, coordination occurs according to the Schiff base type, while in the Ni(II) complex the oxygen atom of the amide (hydrazide) group in the enol form and the nitrogen atom of the azomethine group take part in the coordination groups. Based on the data of IR, electron spectroscopy, EPR, thermogravimetry and elemental analysis of the obtained complexes, the octahedral coordination of Cu(II) ions and the binuclear structure of the complexes are assumed. It was established that all obtained compounds have high bactericidal and fungicidal activity. After, the activities of the studied ligand and its metal complexes against various cancer proteins including breast, colon, and lung cancer were compared.

Heat Soaking for Improving Rollover From S at the Back of CIGSSe Solar Cells

A simple method of low-temperature heat-soaking (HS) treatment on copper indium gallium sulfur selenide (CIGSSe) solar cells is investigated for mitigating the rollover effect. Excessive sulfur accumulation on the backside of the CIGSSe absorber leads to downward valence band bending and forms a Schottky barrier, resulting in the rollover current–voltage characteristic at room temperature. HS treatment effectively reduces current saturation in the first quadrant of the current–voltage curves and improves cell efficiency on average by more than 6%. The depth profile on exfoliated CIGSSe absorbers from the Auger electron spectroscopy analysis demonstrates the elemental redistribution, indicating that HS treatment can change the profile gradient of sulfur. The width of sulfur accumulation is significantly reduced after HS, which enables Fowler–Nordheim tunneling by Schottky barrier width shortening. This study showcases a straightforward process and easy-to-implement strategy to reduce the second reverse diode effect caused from the sulfurization process.

CARBON MATERIALS FROM WASTE BIOMASS AS ANTI-BACTERIAL AIR FILTERS

Carbon materials from almond shells were developed for the adsorption of microorganisms from air. Samples were processed by means of a one-step process – high-temperature hydro-pyrolysis. Studies were carried out in a wide temperature range of 600-900 °C. As a result, carbonates with predominant micro- and mesopores were obtained. The samples were impregnated with zinc, silver, iron and copper 5% by weight. The obtained samples were characterized by XDR, BET, scanning electron spectroscopy and elemental analysis. The final products are distinguished by a moderate surface and the presence of nanosized metal particles. The antibacterial properties of the activated carbon composites were examined using standard methodology under dynamic contact conditions and Escherichia coli K12 as test microorganism. All tested composite materials exhibit strong antibacterial properties after 48 h of contact with microbial cells. Thus the application of these materials in filtering system will be possible solution for successful reduction of microbial cell number. It is assumed that a similar effect can be achieved in an air environment.

Engineering Conductivity and Performance in Electrorheological Fluids Using a Nanosilica Grafting Approach

Carbonization is considered an effective process for the preparation of carbon-rich solids for various applications. Raw carbonaceous particles however often possess high electrical conductivity, limiting their applicability in electrorheology. To address this drawback, the carbonaceous particles prepared from glucose through hydrothermal synthesis, followed by thermal carbonization in an inert atmosphere, were subsequently coated by compact and mesoporous nanosilica, giving rise to semiconducting particles. The successful coating was confirmed using transmission electron microscopy and spectroscopic analysis, and the composite particles were further used as a dispersed phase in electrorheological (ER) fluids of concentration 5 wt %. While an ER fluid based on pure carbonized particles caused a short circuit of the measuring device at the electric field of intensity 1 kV mm–1, the ER behavior of its analogue based on mesoporous silica-coated particles was successfully measured up to 3 kV mm–1, giving a high yield stress exceeding even the values estimated for ER fluids based on similar carbonaceous particles coated with a compact silica layer. Even though the conductivity decreased only about one order of magnitude after the coating process, the dielectric properties of the prepared ER fluid differed significantly, the relaxation process was shifted to lower frequencies, and most importantly, the dielectric relaxation strength increased, indicating an increased amount of interactions. The presence of mesoporous nanosilica further enhanced the sedimentation stability of the ER fluids when compared to its analogue with the compact silica coating, expanding the scope of practical applicability.

Effect of layer thickness on spatters oxidation of Hastelloy X alloy during powder bed fusion-laser beam processing

This study investigates the impact of powder layer thickness on spatter generation and oxidation behavior during the processing of Hastelloy X. In-situ monitoring using optical tomography reveals that thicker powder layers result in a higher number of hot spatters generated during laser-melt-powder interaction. Scanning electron microscopy and Auger electron spectroscopy analysis demonstrate the presence of different types of spatters that oxidize differently depending on their origin. X-ray photoelectron spectroscopy analysis further shows that the surface enrichment of oxide-forming elements such as Al, Ti, Cr, and Fe varies with the type of spatter particle. Additionally, depth profile analysis using X-ray photoelectron spectroscopy indicates that the average oxide layer thickness increases from ∼2.5 nm in virgin to ∼68 nm in spatters generated at 150 μm powder layer thickness. The findings suggest that powder layer thickness is a crucial factor in controlling spatter generation and oxidation behavior during powder bed fusion-laser beam processing.

Tuning the surface electronic structure of WS2 with Zn- and Cu-phthalocyanine for improved hydrogen evolution reaction: Experimental and DFT investigation

WS2 nanosheets have been successfully demonstrated to be promising materials for several important catalytic reactions including Hydrogen Evolution Reaction (HER) and Oxygen Reduction Reactions (ORR) either standalone or by functionalizing and as composites. Tungsten disulfide (WS2) is known to exist in two phases: 2H semiconducting and 1 T conducting. The 2H phase is commonly obtained by simple exfoliation of bulk WS2. Due to the semiconducting nature of the 2H phase, catalytic activity towards HER is very feeble compared to its 1 T counterpart. In this work, we have enhanced the activity of 2H WS2 nanosheets by interfacial modification through metal phthalocyanine (Pc) molecule (Cu-Pc and Zn-Pc) functionalization. We observe that the HER activity shows significant enhancement with the functionalization, with Zn-Pc showing better performance than the Cu-Pc. This functionalization creates an electronically coupled inorganic–organic heterostructure which shows improved response to HER. The WS2 functionalized nanosheets were studied in-depth with X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HRTEM) analyses. Electrochemical studies like linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) demonstrates that the heterostructures deliver enhanced charge transfer kinetics. The Zn-Pc functionalized nanosheets display an overpotential of 233 mV for attaining a current density of 10 mA.cm-2 and the overpotential decreased to 165 mV after cycling due to the surface reconstruction, when the stability was assessed with chronoamperometry. Density Functional Theory (DFT) studies reveal that the charge transfer due to the adsorption of Zn-Pc onto WS2 nanosheets is comparatively better than that of Cu-Pc. This work recounts that by simple metal phthalocyanine functionalization, charge transfer characteristics of WS2 can be markedly improved, thereby signifying the importance of interface modification in two-dimensional (2D) heterostructures.