Search Results (93)

The deposition characteristics of coatings on a titanium alloy substrate were compared using two alternative surface preparation methods: Hollow Cathode Spaces (HCSs) and Ion Bombardment (IB). After deposition of ZrN coatings, the wear resistance of the samples increased by 50–70% compared to uncoated samples, while the HCS method provided 30% higher wear resistance than the IB method. Coated samples deposited using the HCS and IB methods demonstrated very similar friction coefficient values, with a slight (10–15%) decrease in this parameter for the HCS samples. Varying the bias voltage on the substrate (−900, −1200, and −1500 V) when using the HCS method significantly affected wear resistance. The calculated optimal value of the bias voltage when using the HCS method is −1126 V. During the pre-treatment of the substrate using the HCS and IB methods, a transition layer can be formed in the area of the coating–substrate interface; the thickness of this layer varies within the range of 15–400 nm, and the composition is a mixture of coating (zirconium) and substrate (titanium, aluminum, and vanadium) materials. Full article

In this study, the effects of plasma assistance on the electron beam physical vapour deposition (EB-PVD) process were investigated using an industrial coater (Smart Coater ALD Vacuum Technologies GmbH) equipped with a dual hollow cathode system. This configuration enabled the generation of a plasma environment during the deposition of the ceramic top coat onto a metallic substrate. The objective was to assess how plasma assistance influences the microstructure and thickness distribution of 7% wt. yttria-stabilised zirconia (YSZ) thermal barrier coatings (TBCs). Coatings were deposited with and without plasma assistance to enable a direct comparison. The thickness uniformity and columnar morphology of the 7YSZ top coats were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties of the deposited coatings were verified by the scratch test method. The results demonstrate that, in the presence of plasma, columnar grains become more uniformly spaced and exhibit sharper, well-defined boundaries even at reduced substrate temperatures. XRD analysis confirmed that plasma-assisted EB-PVD processes allow for maintaining the desired tetragonal phase of YSZ without inducing secondary phases or unwanted texture changes. These findings indicate that plasma-assisted EB-PVD can achieve desirable coating characteristics (uniform thickness and optimised columnar structure) more efficiently, offering potential advantages for high-temperature applications in aerospace and power-generation industries. Continued development of the EB-PVD process with the assistance of plasma generation could further improve deposition rates and TBC performance, underscoring the promising future of HC-assisted EB-PVD technology. Full article

To mitigate the high residual stress inherent in single-layer diamond-like carbon (DLC) films, we fabricate alternating soft/hard multilayer DLC thick films using a cage-type hollow cathode plasma-enhanced chemical vapor deposition (PECVD) system. The microstructure, mechanical properties, and corrosion resistance of these films were systematically investigated. Periodic film structures were characterized via scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), and X-Ray photoelectron spectroscopy (XPS). Adhesion and hardness were evaluated using a scratch tester and a nanoindentation tester, respectively, while corrosion resistance was assessed by dynamic potential polarization tests in a 3.5 wt% NaCl solution. Findings indicate that as the modulation period of the Si-DLC films increases, a greater proportion of high-energy carbon particles penetrate the non-biased layer under workpiece bias, ultimately disrupting the layered structure in the 90-layer film. This results in densification, reflected in three key improvements: (1) an increase in sp³-bonded carbon content and enhanced smoothness, (2) enhanced adhesion (from 34 N to 46 N) and nanohardness (from 4.94 GPa to 8.41 GPa), and (3) a tenfold reduction in corrosion current density (i_corr) compared to single-layer Si-DLC films. Full article

In this article, we present an overview of our investigations on the formation and behavior of space charge structures in an argon discharge plasma on gridded and smooth spherical hollow electrodes with and without orifices. Four experiments are described, in which we have used the following: (1) one spherical gridded sphere with one orifice, (2) one hollow smooth stainless steel sphere with two opposing orifices, (3) two smooth polished stainless steel spherical electrodes without orifices, (4) two smooth polished stainless steel spherical electrodes with opposing orifices. The experiments were conducted at the University of Innsbruck in a stainless steel cylindrical chamber (the former Innsbruck DP machine—IDP), and at the Alexandru Ioan Cuza University of Iaşi (Romania) in a Pyrex Vacuum Chamber (PCH). As diagnostics, we have used mainly optical emission spectroscopy to determine electron temperature and density. Full article

The rapid development of energy storage technologies has led to an increasing demand for high-performance electrode materials that can enhance both the energy density and the cycling stability of batteries. In this study, polypyrrole (PPy) nanorods with partial hollow features are utilized as a conductive and flexible framework for the in situ growth of VO₂ nanospheres via a simple hydrothermal method, forming a well-defined core–shell PPy/VO₂ nanocomposite. This hierarchical nanostructure combines the excellent electrical conductivity and mechanical flexibility of PPy with the high theoretical capacity of VO₂, creating a synergistic effect that significantly enhances the electrochemical performance. The well-integrated interface between PPy and VO₂ reduces interfacial resistance, promotes efficient electron and ion transport, and improves the overall energy conversion efficiency. Electrochemical testing reveals that the PPy/VO₂ nanocomposite delivers a high specific capacity of 413 mAh g⁻¹ at 100 mA g⁻¹ and retains 87.2% of its initial capacity after 1200 cycles, demonstrating exceptional rate capability and long-term cycling stability. This work provides a versatile strategy for designing high-performance cathode materials and highlights the promising potential of PPy/VO₂ nanocomposites for next-generation high-energy-density aqueous zinc-ion batteries. Full article

SiAlCN coatings were first obtained by the method of reactive evaporation of aluminum and plasma chemical activation of an organosilicon precursor in a hollow cathode arc discharge. The spectrum of discharge plasma was studied by optical emission spectroscopy under conditions of evaporation of Al in an Ar+N₂+hexamethyldisilazane vapor/gas medium, and it was shown that in the presence of a metal component in the plasma, not only did intensive activation of various components of the media occur but also an increased ionic effect on the surface of the coating was provided, with a deposition rate of up to 10.1 µm/h. The films had a dense and homogeneous structure and had a hardness of up to 31 GPa and good adhesion on stainless steel. The results of SEM, FTIR, and XRD showed that their structure was a nanocomposite consisting of an amorphous matrix based on SiCN and AlN with inclusions of AlCN nanocrystals. Full article

Iron-based phosphate is a promising cathode for sodium-ion batteries due to its low cost and abundant resources; however, the practical application is hindered by poor electronic conductivity, sluggish Na⁺ diffusion, and a lack of low-cost and scalable synthesis methods. To address such issues, herein, we present a low-cost and scalable spray-drying strategy to synthesize Na₄Fe₃(PO₄)₂P₂O₇@CNT (NFPP@CNT) hollow microspheres. The NFPP@CNT composite has the following advantages: highly conductive CNT can significantly improve the electronic conductivity of the cathode, and the flexible CNT-based microsphere architecture facilitates Na⁺ diffusion and guarantees excellent mechanical properties to mitigate structural degradation during cycling. These merits make the NFPP@CNT cathode display outstanding electrochemical performances: the NFPP@CNT-1% electrode demonstrates a high reversible capacity of 103.9 mAh g⁻¹ at 0.1 C and maintains a very high capacity retention of 99.9% after 1000 cycles even at a high rate of 5 C. Full article

Microbial fuel cell (MFC) can degrade pesticide wastewater and recovery energy simultaneously, and the activated carbon (AC) air cathode has great prospects for practical application. However, insufficient active sites and the limitation of multi-step electron transfer for oxygen reduction reaction (ORR) requires that AC should be modified by highly efficient electrocatalysts. Herein, busing the confinement effect of carbon-encapsulated metal and hollow carbon, we designed a unique ORR catalyst of Fe-Fe₃O₄-NC through utilizing the 2D leaf-like nanoplates of Zn-ZIF-L to load Prussian blue (PB) particles. The volatilization of low-boiled Zn and the catalysis of iron compounds led to the formation of confined walls of hollow carbon shell and carbon-encapsulated Fe/Fe₃O₄ particles on N-doped carbon substrate. Multivalent iron, a large surface area (368.11 m²·g⁻¹), N doping, a heterojunction interface, and the confinement effect provided all the Fe-Fe₃O₄-NC-modified AC air cathodes with excellent ORR activity. The optimal samples of AC-Fe-Fe₃O₄-NC-3 achieved a peak power density of 1213.8 mW·m⁻², demonstrating a substantial 82.8% increase over that of the bare AC. Furthermore, its efficiency in glyphosate removal reached 80.1%, surpassing the 23.2% of the bare AC. This study offers new ideas in constructing composite confined structures and the as-designed Fe-Fe₃O₄-NC is a promising modification candidate for the commercial adoption of AC air cathodes. Full article

The advantages of aluminum-ion batteries in the area of power source systems are: inexpensive manufacture, high capacity, and absolute security. However, due to the limitations of cathode materials, the capacity and durability of aluminum-ion batteries ought to be further advanced. Herein, we synthesized a nitrogen-doped tubular carbon material as a potential cathode to achieve advanced aqueous aluminum-ion batteries. Nitrogen-doped tubular carbon materials own an abundant space (367.6 m² g⁻¹) for electrochemical behavior, with an aperture primarily concentrated around 2.34 nm. They also exhibit a remarkable service lifespan, retaining a specific capacity of 78.4 mAh g⁻¹ at 50 mA g⁻¹ after 300 cycles. Additionally, from 2 to 300 cycles, the material achieves an appreciable reversibility (coulombic efficiency CE: 99.7%) demonstrating its excellent reversibility. The tubular structural material possesses a distinctive hollow architecture that mitigates volumetric expansion during charging and discharging, thereby preventing structural failure. This material offers several advantages, including a straightforward synthesis method, high yield, and ease of mass production, making it highly significant for the research and development of future aluminum-ion batteries. Full article

Metal air batteries have gradually attracted public attention due to their advantages such as high power density, high energy density, high energy conversion efficiency, and clean and green products. Reasonable design of oxygen reduction reaction (ORR) catalysts with high cost-effectiveness, high activity, and high stability is of great significance. Metal organic frameworks (MOFs) have the advantages of large specific surface area, high porosity, and designability, which make them widely used in many fields, especially in catalysis. This paper starts with regulating and optimizing the composition and structure of MOFs. A series of N, S co-doped electrocatalysts FeCuS-N-C were prepared by two high-temperature pyrolysis processes using N-doped carbon hollow nanorods derived from ZIF-8 as the substrate. The one-dimensional nanorod material derived from this MOF exhibits excellent electrocatalytic ORR performance (Eonset = 0.998 V, E_1/2 = 0.874 V). When used as the air cathode catalyst for zinc air batteries and assembled into liquid ZABs, the battery discharge curve was calculated and found to have a maximum power density of 142.7 mW cm⁻², a specific capacity of 817.1 mAh gZn⁻¹, and a cycling stability test of over 400 h. This study provides an innovative approach for designing and optimizing non-precious metal catalysts for zinc air batteries. Full article

In order to improve the wear and corrosion resistance of Ti6Al4V alloy, a Ti-N compound layer was formed on the alloy by plasma nitriding at a relatively low temperature (750 °C) and within an economical processing duration (4 h), in a mixture of NH₃ and N₂ gases with varying ratios. The influence of the gas mixture on the microstructure, phase composition, and properties of the Ti-N layer was investigated. The results indicated that the thickness of the nitrided layer achieved in a mixed atmosphere with optimal proportions of NH₃ and N₂ (with a ratio of 1:2) was substantially greater than that obtained in an atmosphere of pure NH₃. This suggests that appropriately increasing the proportion of N₂ in the nitriding atmosphere is beneficial for the growth of the nitrided layer. The experiments demonstrated that the formation of the surface nitrided layer significantly enhances the corrosion and wear resistance of the titanium alloys. Full article

Fluorinated carbon cathode materials have extremely high theoretical specific energy among known cathode materials of lithium primary batteries. Nevertheless, current fluorinated carbon cannot meet the performance demands of future applications due to the rate performance. This work innovatively applies hollow carbon spheres with a porous structure as carbon sources to prepare fluorinated hollow porous carbon spheres (FHPCS) with high energy density and power density. The porous structure provides more reaction sites for the fluorination process and also shortens the diffusion path of lithium ions during the discharge. Additionally, the hollow porous structure offers more interfacial contact areas and reduces volumetric expansion during discharge reactions. The Li/CF_x primary battery has a maximum specific energy of 2007 Wh kg⁻¹ and a maximum power density of 30,400 W kg⁻¹ and can have a capacity retention rate of 80.8% at a current density of 16 A g⁻¹. In addition, FHPCS also has the highest specific energy of 1999 Wh kg⁻¹ and 1711 Wh kg⁻¹ in Na/CF_x and K/CF_x primary batteries, respectively. The diffusion efficiency of an alkali metal ion is analyzed by the different discharge depths with electrochemical impedance spectroscopy and galvanostatic intermittent titration technique. This effort introduces a new high-performance fluorinated carbon featuring a hollow porous structure and puts forward an innovative approach to designing fluorinated carbon materials. Full article

Orifice Hollow Cathodes are electric devices necessary for the functioning of common plasma thrusters for space applications. Their reliability mainly depends on the success of a spacecraft’s mission equipped with electric propulsion. The development of plasma models is crucial in the evaluation of plasma properties within the cathodes that are difficult to measure due to the small dimensions. Many models, based on non-linear systems of plasma equations, have been proposed in the openiterature. These are solved commonly by means of iterative procedures. This paper investigates the possibility of solving them by means of the Particle Swarm Optimization method. The results of the validation tests confirm the expected trends for all the unknowns; the confidence bound of the discharge current as a function of mass flow rate is very narrow (2 ÷ 5) V); moreover, the results match very well the experimental data except at theowest mass flow rate (0.08 mg/s) and discharge current (1A), where the computations underpredict the discharge current to the utmost by 40%. The highest data dispersion regards the plasma density in the emitter region (±20% of the average value) and the wall temperatures (±50 K with respect to the average values) of the orifice and insert; those of the others variables are very tiny. Full article

High-density nitrogen plasma was produced using a high-power pulsed power modulator to sputter titanium targets for the preparation of titanium nitride film. The high-power pulsed sputtering discharge unit consisted of two targets facing each other with the same electrical potential. The titanium target plates were used as target materials with dimensions of 60 mm length, 20 mm height, and 5 mm thickness. The gap length was set to be 10 mm. The magnetic field was created with a permanent magnet array behind the targets. The magnetic field strength at the gap between the target plates was 70 mT. The electrons were trapped by the magnetic and electric fields to enhance the ionization in the gap. The nitrogen and argon gases were injected into the chamber with 4 Pa gas pressure. The applied voltage to the target plates had an amplitude from −600 V to −1000 V with 600 μs in pulse width. The target current was approximately 10 A with the consumed power of 13 kW. The discharge sustaining voltage was almost constant and independent of the applied voltage, in the same manner as the conventional normal glow discharge. The ion density and electron temperature at the surface of the ionization region were obtained as 1.7 × 10¹⁹ m⁻³ and 3.4 eV, respectively, by the double probe measurements. The vertical distribution of ion density and electron temperature ranged from 1.1 × 10¹⁷ m⁻³ (at 6 cm from the target edge) to 1.7 × 10¹⁹ m⁻³ and from 2.4 eV (at 6 cm from the target edge) to 3.4 eV, respectively. From the emission spectra, the intensities of titanium atoms (Ti I), titanium ions (Ti II), and nitrogen ions (N₂⁺) increased with increasing input power. However, the intensities ratio of Ti II to Ti I was not affected by the intensities from N₂⁺. Full article

In conventional lithium-ion batteries (LIBs), the active lithium from the lithium-containing cathode is consumed by the formation of a solid electrolyte interface (SEI) at the anode during the first charge, resulting in irreversible capacity loss. Prelithiation additives can provide additional active lithium to effectively compensate for lithium loss. Lithium oxalate is regarded as a promising ideal cathode prelithiation agent; however, the electrochemical decomposition of lithium oxalate is challenging. In this work, a hollow and porous composite microsphere was prepared using a mixture of lithium oxalate, Ketjen Black and transition metal oxide catalyst, and the formulation was optimized. Owing to the compositional and structural merits, the decomposition voltage of lithium oxalate in the microsphere was reduced to 3.93 V; when being used as an additive, there is no noticeable side effect on the performance of the cathode material. With 4.2% of such an additive, the first discharge capacity of the LiFePO4‖graphite full cell increases from 139.1 to 151.9 mAh g⁻¹, and the coulombic efficiency increases from 88.1% to 96.3%; it also facilitates the formation of a superior SEI, leading to enhanced cycling stability. This work provides an optimized formula for developing an efficient prelithiation agent for LIBs. Full article