Sputtering Deposition Technique Research Articles

Tailored nanocones arrays on cellulose fiber: A higher-performance flexible SERS substrate for trace chemical detection

This study presents the successful fabrication of silver nanocone surface-enhanced Raman spectroscopy (SERS) substrate on flexible 70 GSM paper using the Direct Current (DC) magnetron sputter deposition technique. XRD analysis confirmed the crystalline nature and face-centered cubic structure of the Silver Nanocone (AgNC) substrate. SEM analysis revealed the fabricated AgNC substrate shows nanocones arrayed on the cellulose fibers. UV–visible spectral analysis validates the surface plasmon resonance peak of the AgNC substrate at 406 nm. Furthermore, SERS spectral analysis showed excellent detection abilities by accurately identifying rhodamine 6G and methylene blue dyes and fipronil pesticides at concentrations of 10−9 M, 10−8 M, and 10−6 M respectively. In addition, the substrate detects fipronil (pesticide) sprayed on tomatoes and nicotine (energy booster) mixed with tea for commercial applications. The substrate exhibits enhancement factor values for rhodamine 6G, methylene blue, fipronil, and nicotine as 1.3 × 107, 1.2 × 106, 2.6 × 105, and 5.8 × 104, respectively. Theoretical validation using density functional theory confirms the experimental Raman and SERS peaks show good similarity. Considering that the charge transfer mechanism shown in the study of the frontier molecular orbitals allowed for the identification of the interaction between the analyte molecules and silver cluster. The fabricated SERS substrate exhibited remarkable stability and reproducibility.

Investigation of crystalline and band alignment properties of NiO/GaN and Ni0.5Co0.5O/GaN heterojunctions using synchrotron radiation based techniques

Epitaxial layers of NiO and Ni0.5Co0.5O have been deposited on GaN templates using RF magnetron sputtering deposition technique. The epitaxial relationship in out-of-plane and in-plane directions for NiO and Ni0.5Co0.5O layers with respect to GaN is [111]NiO(Ni0.5Co0.5O)∥[0001]GaN and [1̅10]NiO(Ni0.5Co0.5O)∥[1̅21̅0]GaN, respectively. The epi-layers are found to have two triangular domain structures oriented along [111] direction with an in-plane rotation of 60° with respect to each other. Photoelectron spectroscopy (PES) has been used to determine the valence band offset (∆EV) and the band alignment at the heterojunctions (HJs). The ∆EV at NiO/GaN and Ni0.5Co0.5O/GaN HJs are 1.2 ± 0.2 eV and 1.8 ± 0.2 eV, respectively. The conduction band offsets (∆EC) have also been estimated using the determined values of optical band gap (NiO: Eg = ∼ 3.5 eV; Ni0.5Co0.5O: Eg = ∼ 3.3 eV) from optical transmission measurements. The values of ∆EC are found to be 1.5 ± 0.2 eV and 1.9 ± 0.2 eV at NiO/GaN and Ni0.5Co0.5O/GaN HJs, respectively. A type-II band alignment is observed at both the HJs. Higher values of valence band and conduction band offsets are observed at Ni0.5Co0.5O/GaN HJ in comparison to NiO/GaN. These experimentally determined values of band offsets can be used to design wide band gap HJ based devices like photodetectors, where higher values of band off-set at the Ni0.5Co0.5O/GaN HJ can be utilized to confine the carriers.

Enhanced corrosion resistance of graphite-like carbon coatings via dense ta-C interlayer encapsulating

Taking the combination of atomic bond density, in this work, the tetrahedral amorphous carbon (ta-C) layer with high sp3 bond were especially introduced into the sp2-riched graphite-like carbon (GLC) coatings, using a hybrid filtering cathodic arc and magnetron sputtering deposition technique. The focus was elaborated on the electrochemical behavior of coatings against the stimulated chloride solutions for marine applications. Results showed that inserting dense ta-C layer significantly encapsulated the intrinsic pore defects within GLC growth, thereafter enhancing the corrosion resistance remarkably. In particular, the coating porosity was reduced from 10.84 % for pristine GLC system to 3.19 % for GLC with ta-C sealing layer, accompanying with a reduction in corrosion current to 7.8 × 10−9 A/cm2 and an increment in protective efficiency to maximum value of 95.49 %. The small angle X-ray scattering (SAXS) analysis evidenced qualitatively that the coating porosity was suppressed greatly, which were well consisted with the enhanced corrosion resistance of GLC coating with ta-C sealing layer. Furthermore, the balance between pores sealing and interfacial matching could be tailored by controlling the thickness ratio of ta-C and GLC layers, enabling the achievement of both the compact structure and the superior corrosion resistance. These observations offer a new promising strategy to develop the protective coatings for harsh marine environment that required both excellent capability against corrosion and friction with long lifetime.

Nanovoid formation mechanism in nanotwinned Cu

Nanotwinned metals have been intensely investigated due to their unique microstructures and superior properties. This work aims to investigate the nanovoid formation mechanism in sputter-deposited nanotwinned Cu. Three different types of epitaxial or polycrystalline Cu films are fabricated by magnetron sputtering deposition technique. In the epitaxial Cu (111) films deposited on Si (110) substrates, high fractions of nanovoids and nanotwins are formed. The void size and density can be tailored by varying deposition parameters, including argon pressure, deposition rate, and film thickness. Interestingly, nanovoids become absent in the polycrystalline Cu film deposited on Si (111) substrate, but they can be regained in the epitaxial nanotwinned Cu (111) when deposited on Si (111) substrate with an Ag seed layer. The nanovoid formation seems to be closely associated with twin nucleation and film texture. Based on the comparative studies between void-free polycrystalline Cu films and epitaxial nanotwinned Cu films with nanovoids, the underlying mechanisms for the formation of nanovoids are discussed within the framework of island coalescence model.Graphical abstract

Highly sensitive self-powered solar-blind ultraviolet photodetectors based on n-Zn1-xFexO/p-Si heterojunctions

The pristine and iron-doped ZnO thin films were fabricated on p-type silicon and glass substrates using the radio-frequency magnetron sputter deposition technique. The structural, morphological, and electrical properties of the deposited thin films were analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and I-V characteristics. XRD analysis revealed the preferential growth of ZnO along the c-axis, with lattice parameter (c) values of 5.216, 5.234, and 5.241 Å for the pristine ZnO, Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films, respectively. The crystallite sizes were measured to be 13.2 nm, 16.2 nm, and 18.3 nm for the respective films. The elemental analysis of the deposited films was done under X-ray photoelectron spectroscopy (XPS), which revealed the concentrations of iron Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films were 2.93 at% and 5.14 at%, respectively. Raman spectroscopy confirmed the presence of the hexagonal wurtzite structural form in the deposited films. The I-V characteristics of the deposited films confirmed the formation of a heterojunction between the film and the silicon substrate. Furthermore, the constructed heterojunction devices were evaluated for their ability to detect ultraviolet (UV) radiations of wavelengths 365 nm and 254 nm. The devices exhibited response and recovery times of less than 1 s. The detectivity values were found to be 0.321 ×1011, 1.051 ×1011, and 2.992 ×1011 Jones for the ZnO/p-Si, Zn0.97Fe0.03O/p-Si, and Zn0.95Fe0.05O/p-Si devices, respectively, under a fixed illumination intensity of 0.812 mW/cm2 for a UVA source with a wavelength of 365 nm. These results confirm the excellent photodetection ability of the constructed devices. The mechanism of UV radiation detection by the devices has also been extensively discussed.

Direct Growth of Low Thermal Conductivity WTe2 Nanocrystalline Films on W Films.

WTe2 has attracted much attention because of its layered structure and special electronic energy band structure. However, due to the difficulty of evaporating the W element itself and the inactivity of the Te element, the obtained large-area WTe2 thin films are usually accompanied by many defects. In this paper, WTe2 nanocrystalline films were successfully prepared on quartz substrates using magnetron sputtering and chemical vapor deposition techniques. Various analytical techniques such as X-ray Diffraction, Raman spectra, X-ray Photoelectron Spectroscopy, Scanning Electron Microscope, and photoluminescence spectra are employed to analyze the crystal structure, composition, and morphology. The effects of different tellurization temperatures and tellurization times on the properties of WTe2 thin films were investigated. WTe2 nanocrystalline films with good crystallinity were obtained at 600 °C for 30 min. The thermal conductivity of the WTe2 films prepared under this condition was 1.173 Wm-1K-1 at 300 K, which is significantly higher than that of samples prepared using other methods.

Study of optical and structural properties of CZTS thin films using copper capping layer and sulfurization to correct stoichiometry

Non-toxic, environment friendly and low cost Cu2ZnSnS4 (CZTS) thin films were deposited on sodalime glass substrates by radio frequency magnetron sputter deposition technique. Stoichiometry analysis revealed that the as-deposited films were Cu deficient. Hence, Cu capping layer was deposited, to study its’ effect on optical and structural properties of the films. These films were subsequently sulfurized in a quartz setup. Ultimately, stoichiometric CZTS films with improved Cu content up to 27.4% were obtained. The kesterite CZTS phase was identified in the samples using x-ray diffraction measurements. The morphological studies revealed that, grain size varies as a function of the thickness of Cu capping layer. The formation of undesired Cu2S and ZnS phases were also observed in the film with Cu content above and below the optimum range. Optical bandgap (Eg) of the films could also be optimized by controlling the Cu content in the film. An optimal Cu content between 24% and 26% was found to be appropriate for achieving a desired bandgap within a range of 1.55 to 1.4 eV, suitable for application in thin film solar cells. The CZTS films with corrected stoichiometry have a charge carrier density in the rage of ∼1021 cm−3, which are much better than values reported so far in the literature.

(Invited) Leading-Edge Diamond FET, MEMS, and Photodetector Devices

Diamond is a candidate material for next-generation power electronics, micro-electro mechanical systems (MEMS), and solar-blind deep-ultraviolet (DUV) photodetector devices with excellent thermal stability and radiation hardness, which operate under extreme environment. In order to use an advantage of high-density hole channel of hydrogenated diamond (H-diamond) surface, we have developed the high-k stack gate dielectrics and AlN heterojuction gate for H-diamond FETs, such as HfO2/HfO2, LaAlO3/Al2O3 Ta2O5/Al2O3, and ZrO2/Al2O3, AlN/Al2O3 prepared by a combination of sputter-deposition (SD) and atomic layer deposition (ALD) techniques [1,2]. We also demonstrated the artificial diamond Fin-FETs with high-current level [3] and the nanolaminate insulator gate metal-oxide-gate FETs (MOSFETs) with k value as high as 100 [4], and the new transistor concept named by metal-insulator-metal-semiconductor field-effect transistor (MIMS-FET) to achieve normally-off operation by combining the advantages of MOSFET and metal-semiconductor FET [5]. In addition, we developed the routine ion-implantation process for preparing the diamond cantilever with a resonant frequency quality factor as high as one million [6,7]. We have also developed thermally stable Schottky barrier photodiode (SPD), metal-semiconductor-metal photodetector (MSMPD), and MSM-type SPD (IDF-SPD) with a large photoconductivity gain in DUV wavelength and a large discrimination ratio between DUV/visible light responsivity [8,9]. In this presentation, we will review the comprehensive our work on the diamond FET, MEMS, and photodetector devices. Acknowledgements: This work was in collaboration with J-W. Liu, M. Imura, M-Y. Liao, J. Alvarez in NIMS and A. Ouchiero and E. Obaldia in University of Taxes, Dallas, and partly supported by JSPS KAKENHI Grant Number 20H00313.

Corrosion-Resistant and Electrically Conductive Oxide Coatings for Metal Bipolar Plates for PEM Electrolyzers

The PEM electrolyzers are considered a promising alternative to alkaline water electrolyzers, as the advantages of PEM technology are high efficiency, high power density, a wide range of power inputs, low operating temperatures, relatively quick start-up, and easy scale-up. The ability of PEM electrolyzers to function dynamically makes them particularly appealing in energy capture and storage systems where electrical energy is derived from renewable sources such as solar and wind power. The bipolar plates (BPPs) are essential components of the PEM electrolyzer stacks and account for the main fraction of the total weight and cost. The BPPs must be electrically conductive, highly corrosion-resistant, and maintain a low interface contact electrical resistance (ICR). The root causes of the BPPs corrosion issues are non-conductive oxides formation increasing electrical resistance, and metal ions out-diffusion poisoning the catalyst and electrolyte membrane. The US Department of Energy has set targets for bipolar plates in fuel cells, including corrosion current densities < 1 µA/cm2 and ICR < 10 mΩ·cm2. Even though these targets do not apply to BPPs in PEM electrolyzers, they provide an indication of acceptable values. The problems outlined above are being overcome or minimized by applying corrosion-resistant and simultaneously electrically conductive coatings.This work, therefore, investigates various corrosion-resistant and electrically conductive oxide coatings prepared by reactive high-power impulse magnetron sputtering (HiPIMS) on SS316L substrates. Reactive HiPIMS is an advanced and progressive magnetron sputter deposition technique suitable for preparing high-quality oxide coatings. The main advantage of HiPIMS is a high degree of ionization of sputtered particles in the discharge plasma and the associated high ion-to-atom ratio in particle flux toward the substrate. This allows one to achieve coating densification and crystallinity at low substrate temperature and without applying a substrate bias voltage. In our case, the native oxide on the SS316L substrate surface was removed by employing plasma etching prior to the coating deposition utilizing HiPIMS-generated ions accelerated towards the substrate by an applied bias voltage. The oxide coatings were deposited using an unbalanced magnetron with a directly water-cooled planar target with a diameter of 100 mm in argon-oxygen gas mixtures at the argon pressure of 1 Pa in an ultra-high vacuum chamber. The oxygen partial pressure was controlled by a PID regulator at a given power density in a pulse. This allowed the deposition of the coatings with different stoichiometries and, thus, different electrical conductivity and corrosion resistance.The electrical resistivity of oxide coatings was measured by a four-point probe system on a non-conductive glass substrate. The compaction pressure dependence of ICR between the test plate and a gas diffusion layer (GDL) was measured in a range from 0.3 to 2.0 MPa on a custom-designed device using gold-coated cylindrical copper electrodes. All electrochemical measurements were performed in an H2SO4 electrolyte solution with an acidity of pH 5.5, fluorine ions concentration of 5 ppm, and a temperature of 60 ℃ to simulate the PEM electrolyzer environment. Accelerated corrosion tests were carried out in extreme anodic conditions of the PEM electrolyzer via potentiostatic polarization at a potential of 2 V vs SHE. Open circuit potential, corrosion current, Tafel slopes, and polarization resistance were determined from potentiodynamic polarization curves measured from 0 to 2 V vs SHE recorded at a scan rate of 1 mV/s, this range should cover most of the potentials experienced inside a PEM electrolyzer. Potentiodynamic polarization and ICR versus compaction pressure were measured before and after the accelerated corrosion test.

Effect of Film Thickness on Microstructural and Magnetic Properties of Lithium Ferrite Films Prepared on Strontium Titanate (001) Substrates

Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission electron microscope and a magnetic measurement device. It was found that the formation of structural defects can be influenced by the thickness of the film. In addition to misfit dislocations, orientation domains form in thinner films and twin boundaries appear in thicker films, respectively, contributing to the misfit strain relaxation in the heterosystem. The magnetic measurement showed that the thinner films have enhanced magnetization and a relatively lower coercive field compared with the thicker films containing antiferromagnetic twin boundaries. Our results provide a way of tuning the microstructure and magnetic properties of lithium ferrite films by changing the film thickness.

Cadmium sulfides: Electrochemical CO2 reduction and Fischer–Tropsch synthesis pathways

The development of electrocatalysts is a pivotal aspect of advancing electrochemical (EC) CO2 recycling. In this research, we incorporated cadmium sulfide (CdS) onto a cadmium (Cd) support and subsequently enhanced it with the deposition of Au, Ag, and Cu using sputter deposition techniques. These modified catalysts were then rigorously evaluated for their performance in EC CO2 reduction. The primary products were formate, CO, and H2. Notably, CdS/Cd demonstrated significantly superior performance in EC CO2 reduction compared to the unmodified Cd catalyst. Furthermore, the deposition of transition metals drastically suppressed H2 production, while Ag and Cu deposition enhanced CO production in NaHCO3 conditions. For Au/CdS/Cd in phosphate condition, CH4 and alkane-dominant C2–7 hydrocarbons were significantly produced and explained by the conventional Fischer–Tropsch synthesis paths. After EC CO2 reduction, CdS/Cd surface was observed to be recrystallized to CdCO3 with a morphology of cubes. Photocatalytic CO2 reduction over CdS/Cd produced CO, CH4, CH3OH, and alkene-dominant C2–6 hydrocarbons. Additionally, a zinc sulfide (ZnS) on Zn electrode was prepared and tested, which showed H2 and CO as main products, but no formate was observed.

Magnetic field tunable piezoelectric resonator for MEMS applications

In this report, the Ni0.50Mn0.35In0.15/Pb0.96La0.04Zr0.52Ti0.48O3 (Ni-Mn-In/PLZT) bulk acoustic wave (BAW) resonator has been fabricated using the sputtering deposition technique. The magnetoelectric effect in the Ni-Mn-In/PLZT resonator has been investigated. The increase in magnetoelectric coupling coefficient (MECC) with the increment in the frequency of applied HAC is observed. The potential of the Ni-Mn-In/PLZT BAW resonator as a magnetic sensor is tested by measuring the shift in the resonant frequency of the reflective (S11 parameter) response in the presence of the externally applied magnetic field. The Ni-Mn-In/PLZT resonator exhibits a frequency shift of 730 MHz in the 1200 Oe magnetic field, among the largest magnetic field-induced frequency shifts in literature. The rarely reported complete dependence of acoustic velocity, coupling coefficients, magnetic sensitivity, and frequency peak shift on the strength of the external magnetic field is investigated. The acoustic velocity increases from 1237 m/s to 1394 m/s, and the electromechanical coupling coefficient increases from 0.0199 % to 0.0206 % after applying the 1200 Oe magnetic field. The reflective responses have been fitted using the Modified-Butterworth Van Dyke (MBVD) model in terms of hardly reported RLC equivalent circuits. The experimental results and extracted parameters from MBVD modeling exhibit high accuracy. This interaction between multiferroic orders and elastic resonance peaks opens a new window for highly sensitive future magnetic field sensors, wireless communication devices, and magnetic field tunable filters.

(TiZrNbTaMo)N nanocomposite coatings embedded with silver nanoparticles: imparting mechanical, osteogenic and antibacterial traits to dental implants

Designing highly osteogenic and effective antibacterial biomaterials with a prolonged service life for oral implants remains an ongoing challenge. In this work, the multi-element (TiZrTaNbMo)N high entropy nitride (HEN), with different concentrations of Ag, was co-deposited onto surgical grade commercially pure titanium by a reactive sputter-deposition technique using a double cathode glow discharge plasma system. The effects of Ag concentration on the microstructure and mechanical properties of the HEN-Ag nanocomposite coatings were investigated by various testing methods. Potentiodynamic polarization measurements were used to evaluate the corrosion resistance of the coatings in simulated body fluid. The antibacterial activity of the HEN-Ag nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The cytocompatibility and osteogenesis activity of the HEN nanocomposite coatings using MC3T3-E1 cells were evaluated by a CCK-8 assay and an alkaline phosphatase quantitative assay. These studies demonstrate that the Ag-free HEN coating was composed of a face-centered-cubic (FCC) nitride phase, which displays good mechanical properties, anti-corrosion performance and osteogenic function, but no antibacterial properties were observed. In contrast, the HEN0.9Ag0.1 coating, composed of amorphous/nanocrystalline high-entropy nitride embedded with silver nanoparticles ∼10 nm in diameter, displays good mechanical and anti-corrosion performance, together with the excellent cell compatibility and antibacterial performance, which offer potential for providing outstanding protective efficiency for dental implants. Although the HEN0.8Ag0.2 nanocomposite coating exhibited superior antibacterial efficacy, potential for in vitro cytotoxicity was identified.

3D binder-free nanoarchitecture design of porous silicon/graphene fibers for ultrastable lithium storage

Enhancing the stability and fast-charging capability of battery electrodes is of paramount importance in the field of battery technology. Silicon (Si), renowned for its high specific capacity, has emerged as a promising candidate for anodes. However, the limited structural stability and electron/ion conductivity of silicon-based anodes have raised significant concerns, including fractures and the continuous formation of unstable solid-electrolyte interphase (SEI) layers, leading to rapid capacity decay. In this study, we introduce a comprehensive approach to fabricating a binder-free and free-standing anode electrode paper using a combination technique of employing electrospinning, magnetron sputtering, and chemical vapor deposition (CVD) techniques. This developed paper electrode incorporates a 3D interconnected network of nitrogen-doped vertical graphene nanosheets (VGs) that connect porous carbon fibers (PCFs) with uniformly distributed Si nanoparticles (VGs@Si@PCFs). The as-fabricated VGs@Si@PCFs paper effectively addresses the mechanical and chemical stability issues commonly associated with Si anodes. The VGs@Si@PCFs anode demonstrates a remarkable reversible capacity of 2205 mAh g-1 at 0.1 A g-1 and exhibits exceptional cycling performance with 83.5% capacity retention at 1.0 A g-1 after 3000 cycles. This design leverages the nanoporous carbon fibers and nitrogen-doped vertical graphene nanosheets as flexible and conductive supports, enhancing the robustness and flexibility of the electrode. Additionally, mechanical modeling reveals that the overall Mises strain in the porous VGs@Si@PCFs structure is significantly lower compared to nonporous cases, potentially minimizing low-cycle fatigue. Our free-standing Si/C composite anode introduces a new class of low-strain Si-based materials, showcasing significantly improved stabilities and fast-charging capabilities.

Enhancement of the efficiency of solar collector by SiO2, TiO2, and ZnO thin films layers

Most scientific researchers are motivated to develop alternative energy applications and raise their efficiency as a result of rising global warming and pollution from traditional energy sources. In this study, Nanocoating thin films of ` have been prepared on different substrates (stainless steel 316 L, commercially pure Ti, Si-Wafer(100) and glass). Magnetron sputtering deposition technique at 2.8 × 10–7 Torr vacuum has been used to synthesize the nanocoated thin films. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Atomic Force Microscopy (AFM), and UV–visible radiation tests have been used to characterize the thin films deposited. The investigation results showed that the thin films deposited do not have microcracks or defects with a uniform and homogenous structure at 400 nm magnification. It has a nanoparticle grain size of 60–90 nm with a crystal structure for TiO2, SiO2, and ZnO films. ZnO films have coarser grain and more aggregation than the other films. The highest efficiency of the collector was recorded for a collector integrated with ZnO thin-film. The efficiency of the ZnO-coated collector was about 66 % at midday compared to the conventional system (no thin film), which was 39 %.

High-performance thermochromic YSZ/[formula omitted]/YSZ coatings for energy-saving smart windows

The reversible semiconductor-to-metal transition of vanadium dioxide (VO2) makes VO2-based coatings a promising candidate for thermochromic smart windows, reducing the energy consumption of buildings. We report on a scalable sputter deposition technique for fast preparation of strongly thermochromic YSZ/V0.986W0.014O2/YSZ coatings, where YSZ denotes Y-stabilized ZrO2, on conventional soda-lime glass at a relatively low substrate surface temperature (350 °C) and without any substrate bias voltage. The thermochromic V0.986W0.014O2 layers and the antireflection YSZ layers were deposited using a controlled high-power impulse magnetron sputtering of a single V–W and Zr–Y target, respectively. A coating design utilizing a second-order interference in the YSZ layers was applied to increase both the integral luminous transmittance (Tlum) and the modulation of the solar energy transmittance (ΔTsol). We present the phase composition (X-ray diffraction) and microstructure (high-resolution transmission electron microscopy) of the coatings and their optical properties (spectrophotometry and spectroscopic ellipsometry). The YSZ/V0.986W0.014O2/YSZ coatings exhibit a transition temperature of 33–35 °C with Tlum = 64.5% and ΔTsol = 7.8% for a V0.986W0.014O2 thickness of 37 nm, and Tlum = 46.1% and ΔTsol = 13.2% for a V0.986W0.014O2 thickness of 67 nm. The results constitute an important step to a cost-effective and high-rate preparation of large-area thermochromic VO2-based coatings for future smart-window applications.

Detailed pathway for a fast low-temperature synthesis of strongly thermochromic W-doped VO2 films with a low transition temperature

We report the discharge characteristics, and population of chosen atomic neutral (V, O and Ar) and ionic (V+, V2+, O+ and Ar+) species in the discharge during low-temperature (350 °C) depositions of W-doped VO x films onto a 170 nm thick Y-stabilized ZrO2 layer on a 1 mm thick conventional soda-lime glass. The depositions were performed using reactive deep oscillation magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputter V-W target. The pre-selected critical values of the oxygen partial pressure were in the range from 82 mPa to 92 mPa. Optical emission spectroscopy proved a relatively high density of O atoms in front of the substrate, which is important for production of the W-doped VO2 films. It was found that setting of the amount of O2 in the gas mixture determines not only the elemental and phase composition of the films and their deposition rate but also the crystallinity of the thermochromic VO2 phase in them. The crystalline W-doped VO2 films with a low transition temperature of 28 °C exhibited a high modulation of the solar energy transmittance of 8.9%. The results are important for further improvement of this new scalable sputter deposition technique for a fast (53 nm min−1 at a target-substrate distance of 100 mm in this work) low-temperature synthesis of high-performance durable thermochromic VO2-based multilayer coatings designed for smart-window applications.

Low-cycle fatigue behavior of zirconium fuel cladding with Cr coatings deposited by High-power Impulse Magnetron Sputtering

In this paper, the work reports on finding of an experimental investigation of the low cycle fatigue performance of Cr-coated zirconium fuel cladding. Cr coatings were fabricated by utilizing High-power Impulse Magnetron Sputtering (HiPIMS) and Direct Current Magnetron Sputtering (DCMS) deposition techniques, respectively. The experimental results have indicated that, due to the different discharge characteristics of DCMS and HiPIMS, the microstructure and mechanical performances of the deposited Cr coating are significantly different. The film morphology alter from columnar for DCMS-Cr coating to dense for HiPIMS-Cr coating, and the hardness of HiPIMS-Cr coating is higher than the values of DCMS-Cr coating. The low cycle fatigue performance of HiPIMS-Cr coated zirconium fuel cladding is better than that of DCMS-Cr coated ones, which revealed that the dense Cr coating benefitted the low-cycle fatigue life of the zirconium alloy cladding tube.

Optimizing the Performance of Low-Loaded Electrodes for CO2-to-CO Conversion Directly from Capture Medium: A Comprehensive Parameter Analysis.

Gas-fed reactors for CO2 reduction processes are a solid technology to mitigate CO2 accumulation in the atmosphere. However, since it is necessary to feed them with a pure CO2 stream, a highly energy-demanding process is required to separate CO2 from the flue gasses. Recently introduced bicarbonate zero-gap flow reactors are a valid solution to integrate carbon capture and valorization, with them being able to convert the CO2 capture medium (i.e., the bicarbonate solution) into added-value chemicals, such as CO, thus avoiding this expensive separation process. We report here a study on the influence of the electrode structure on the performance of a bicarbonate reactor in terms of Faradaic efficiency, activity, and CO2 utilization. In particular, the effect of catalyst mass loading and electrode permeability on bicarbonate electrolysis was investigated by exploiting three commercial carbon supports, and the results obtained were deepened via electrochemical impedance spectroscopy, which is introduced for the first time in the field of bicarbonate electrolyzers. As an outcome of the study, a novel low-loaded silver-based electrode fabricated via the sputtering deposition technique is proposed. The silver mass loading was optimized by increasing it from 116 μg/cm2 to 565 μg/cm2, thereby obtaining an important enhancement in selectivity (from 55% to 77%) and activity, while a further rise to 1.13 mg/cm2 did not provide significant improvements. The tremendous effect of the electrode permeability on activity and proficiency in releasing CO2 from the bicarbonate solution was shown. Hence, an increase in electrode permeability doubled the activity and boosted the production of in situ CO2 by 40%. The optimized Ag-electrode provided Faradaic efficiencies for CO close to 80% at a cell voltage of 3 V and under ambient conditions, with silver loading of 565 μg/cm2, the lowest value ever reported in the literature so far.

Palladium-based membranes for potential application in bio-jet fuel production unit

ABSTRACT The hydrogen in the vent gas stream of the hydrocracker (used to produce bio-jet fuel) cannot be reused since it has many impurities. The metal membrane can be a potential candidate for recovering hydrogen from this vent gas. In this work, the authors report the development of a composite palladium membrane and its application, for the first time, in the recovery of hydrogen from a simulated vent gas environment. A dense thin film (thickness ∼3 µm) of Pd metal was coated on a ceramic support tube by the sputter deposition technique. The hydrogen permeance of the Pd membrane was found to be 18.75 × 10−6 mol·m−2·h−1·Pa−1, which was reduced to 3.25 × 10−6 mol·m−2·h−1·Pa−1, with an exposure of 100 h in the simulated bio-jet fuel environment. To avoid the loss of permeability, a thin layer of Pt can be coated over the Pd membrane. The present study used MATLAB software to simulate the Pt-coated Pd composite membrane performance in the bio-jet fuel production environment. Simulation studies confirmed that a membrane area of ∼95 cm2 (250 mm length and 12 mm OD) is sufficient for the complete recovery of hydrogen from the vent gas stream of hydrocracker at a feed velocity of 0.075 m/s.