Decrease In Deposition Rate Research Articles

Rotary Electrodeposition of High-Strength Nanotwinned Copper Foils

Due to the 2050 Net Zero Emissions becoming a major goal worldwide, electric vehicles have emerged as the future mainstream products. Among them, copper foils play a crucial role as the anode current collector in lithium-ion batteries (LIBs). Enhancing the strength and decreasing the thickness of copper foil are both important factors improving the lifespan of LIBs. The thickness of Cu foils can be reduced by rolling copper sheets, but it is challenging to achieve the required thinness below 10 micron for electronic applications. Direct current electroplating not only effectively increases the deposition rate but also reduces costs for thin Cu foils. In this study, we utilized a rotary direct current Cu-Ni co-electroplating method to enhance the mechanical strength of nanotwinned copper. The ultimate tensile strength (UTS) of nanotwinned copper-nickel alloy reached over 847.3 MPa (an increase of approximately 12.6 % compared to the maximum UTS of nanotwinned copper, which was 752.8 MPa) while maintaining excellent electrical conductivity similar to nanotwinned copper. Through potentiostat analysis, it was discovered that nickel ions inhibit copper growth, causing the reduction potential of copper to shift negatively, resulting in a decreased deposition rate and increased twin density. The nickel content, measured by ICP-MS, was found to be 0.467 ppm, suggesting that nickel acts as an impurity that refines grain size in copper foils. Therefore, this method not only significantly improves the strength of copper foils but also maintains low electrical resistance and low-cost characteristics. It provides a new material option for the anode current collector of the next-generation LIBs. Figure 1

Spatial and Size Distributions of Ti(C5H7O2)2[(CH3)2CHO]2 Mist Particles in a Tubular Furnace for Conformal and Uniform Deposition of Amorphous TiO2 Thin Films

The spatial and size distributions of titanium diisopropoxide bisacetylacetonate [(C5H7O2)2[(CH3)2CHO]2, also known as Ti(acac)2(OiPr)2] mist, diluted in CH3OH, are investigated in a tubular furnace using atmospheric‐pressure mist chemical vapor deposition (mist CVD). The focus is on the deposition of amorphous (a)‐TiO2 films with tubular furnace temperature and mesh bias as variables. When the furnace temperature reaches 350 °C, the number density of mist particles increases without significant changes in their size distribution, leading to a higher film deposition rate. Further, the deposition rate and average size of the mist particles with lower adhesion coefficient decrease with increasing spatial distance from the furnace inlet. Furthermore, applying a mesh bias results in an increase in the maximum number density of mist particles with a narrower size distribution; however, the overall film deposition rate decreases. These variations are attributed to the chemical reactivity of the mist precursors produced by pyrolysis and mesh bias. The fine mist precursors, which are strongly charged, coordinate with CH3OH and CHO groups through solvation, enhancing their chemical stability and lifetime. This process yields a dense and rigid a‐TiO2 network, improving the junction properties at the a‐TiO2/c‐Si interface.

An analytic description of electron thermalization in kilonovae ejecta

ABSTRACT A simple analytic description is provided of the rate of energy deposition by β-decay electrons in the homologously expanding radioactive plasma ejected in neutron star mergers, valid for a wide range of ejecta parameters – initial entropy, electron fraction {s0, Ye}, and scaled (time-independent) density ρt3. The formulae are derived using detailed numerical calculations following the time-dependent composition and β-decay emission spectra (including the effect of delayed deposition). The deposition efficiency depends mainly on ρt3 and only weakly on {s0, Ye}. The time te at which the ratio between the rates of electron energy deposition and energy production drops to 1 − e−1, is given by $t_e=t_{0e}\Big (\frac{\rho t^3}{0.5(\rho t^3)_0}\Big)^a$, where $(\rho t^3)_0=\frac{0.05\, {\rm M}_{\odot }}{4\pi (0.2c)^3}$, t0e(s0, Ye) ≈ 17 d, and 0.4 ≤ a(s0, Ye) ≤ 0.5. The fractional uncertainty in te due to nuclear physics uncertainties is $\approx 10~{{\ \rm per\ cent}}$. The result a ≤ 0.5 reflects the fact that the characteristic β-decay electron energies do not decrease with time (largely due to ‘inverted decay chains’ in which a slowly decaying isotope decays to a rapidly decaying isotope with higher end-point energy). We provide an analytic approximation for the time-dependent electron energy deposition rate, reproducing the numerical results to better than 50 per cent (typically $\lt 30~{{\ \rm per\ cent}}$, well within the energy production rate uncertainty due to nuclear physics uncertainties) over a 3–4 orders-of-magnitude deposition rate decrease with time. Our results may be easily incorporated in calculations of kilonovae light curves (with general density and composition structures), eliminating the need to numerically follow the time-dependent electron spectra. Identifying te, e.g. in the bolometric light curve, will constrain the ejecta density distribution.

Electrochromic Thin‐Film Nickel‐Oxide Coatings for Systems with Adjustable Light Transmission

In this study, results on the effect of technological parameters of the nickel(II)‐oxide thin‐film deposition process, obtained through chemical vapor deposition in an argon–oxygen environment using bis‐(ethylcyclopentadienyl)‐nickel (EtCp)2Ni, on their electrochromic properties, are presented. It is shown that the films lose ability to electrochromic coloring in alkaline environments as their thickness increases up to 170 nm. The introduction of small ozone additions of 0.1 vol% O3 into the gas phase leads to a decrease in the NiO films deposition rate, the formation of a rougher layer with an average grain size up to 71.4 nm, capable of coloring in light brown. Additional cathodic treatment of NiO films at a potential of −0.8 V for 30 s in alkaline environments containing fullerene C60(OH)24 leads to the modification of the surface layer and the formation of NiO–C carbon‐containing nanocomposite coatings with enhanced contrast and the ability to retain the colored state after polarization is turned off, i.e., possessing optical memory properties. Using NiO–C nanocomposite and indium–tin–oxide films, which have opposite coloring mechanisms, in the structure of an electrochromic device allows for an increase in the grade of glass darkening, significantly reducing energy consumption, improving operational characteristics, and life span.

Effect of N2 partial pressure on ZrN coating orientation and tribocorrosion behavior and mechanism

The ZrN coatings were prepared using multi-arc ion plating (MAIP) under different N2 partial pressures ranging from 10 % to 80 %. A comprehensive analysis of the microstructure, electrochemical behavior, and tribocorrosion properties of these coatings showed a gradual deposition rate decrease with rising N2 partial pressure. Analysis using GIXRD revealed higher N2 pressure led to a shift in crystal orientation from (111) to (200), initially increasing corrosion resistance but later declining. At 70 % N2 pressure, the ZrN coating exhibited the lowest values of capacitance Cpo (8.89 μF cm−2) and double-layer capacitance Cdl (1.14 × 10−7 F cm−2), with the highest values for the two-time constants τ recorded as 0.274 s and 5.749 s. The tribocorrosion behavior correlated closely with the corrosion performance, with the ZrN-70 % coating demonstrating superior tribocorrosion resistance and a minimal wear rate of 4.25 × 10−5 mm3/Nm. While the ZrN-80 % coating exhibited the lowest wear rate of 2.67 × 10−5 mm3/Nm, but was more susceptible to friction and corrosion synergy, causing localized failure. The outcomes reveal crystal texture significantly affected on the electrochemical and tribocorrosion characteristics of the coatings, primarily attributed to the robust passivation tendency and stability of the passivation film associated with the (200) crystal orientation. The dominant wear mechanism identified involves the interplay of adhesive, abrasive, and corrosion-erosion wear processes. Based on these results, ZrN coatings prepared using MAIP are expected to emerge as candidate materials for critical friction components in marine equipment or other corrosion-erosion environments.

Abundance, distribution and deposition of PM2.5-bound iron in northern China during 2021 dust and dust storm periods

Dust storms have the ability to transport and deposit contaminants and nutrients, such as iron (Fe), to downwind regions through atmospheric processes. However, there is a lack of reported data on the high-resolution variations and deposition of particulate iron in multiple locations during dust storms. This study aimed to address this gap by employing standardized analytical methods to measure the concentrations of PM10, PM2.5, and PM2.5-associated Fe in Taiyuan, Beijing, Tianjin, Ji'nan, and the Bohai Bay of China during the dusty events of 2021. A total of 13 blowing sand or dust storms were recorded, with average PM10 and PM2.5 concentrations of 262 ± 322 and 85 ± 652, 171 ± 403 and 53 ± 448, 153 ± 211 and 57 ± 315, and 207 ± 249 and 63 ± 301 μg/m3 at the above-mentioned sites, respectively. These elevated concentrations were attributed to stronger winds in northern China and severe wind erosion in the sand source areas. During these events, the average concentrations of PM2.5-bound Fe reached 2730.2 ± 4587.9, 2030.2 ± 3877.9, 1342.1 ± 2251.4, and 1785.1 ± 2536.6 ng/m3 in Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, with the highest concentrations recorded as 48.8, 48.0, 29.2, and 22.7 μg/m3. A significant positive correlation was observed between Fe and Si in PM2.5 in the four cities, with higher Fe/Si slopes recorded in or near the source regions, while the homogenized Fe/Si values were observed after long-distance transport. The mean dry deposition fluxes (FFe) of PM2.5-bound Fe were calculated as 0.34 ± 0.64, 0.31 ± 0.91, 0.21 ± 0.56, and 0.17 ± 0.28 mg/m2/d for Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, based on both hourly observation data and model-based calculations of dry deposition velocities. It is worth noting that FFe decreased from west to east in China, consistent with a previous study that showed a decrease in dust deposition rates with increasing transport distances. Peaks in FFe corresponded to the highest concentrations of PM2.5-associated Fe, indicating that these concentrations played a significant role in Fe. Furthermore, the atmospheric deposition of dissolved Fe from blowing sand or dust storm events was found to contribute to carbon fixation in the Bohai region of China, providing a range of 7.8 × 104–3.9 × 106 mol. This research provides valuable insights into the quantitative relationship between atmospheric deposition and marine productivity during dust events.

Mercury deposition to lake sediments near historic gold mines in northern Canada

Mercury (Hg) contamination in aquatic systems can lead to adverse human and environmental health outcomes. Yellowknife, a city in Canada’s Northwest Territories, is a historic mining community, with two large gold mines (Giant Mine and Con Mine) that used Hg amalgamation methods to extract gold between ∼1938 and 1960. We analyzed dated sediment cores from 20 small lakes to investigate the spatial and temporal Hg deposition patterns within 50 km of Giant Mine. Breakpoint analysis of the within-lake z-score normalized anthropogenic Hg flux indicates two significant time periods of changing emission rates. The first is a significant increase in Hg deposition rate (∼1925) during the time of gold exploration in the region and onset of Hg amalgamation (1938) and the second is a significant decrease in deposition rate that begins around the time of the cessation of Hg amalgamation at Giant Mine (∼1959). Sediment Hg concentrations exceeded the Canadian Council for Ministers of the Environment Interim Sediment Quality Guideline (ISQG) for Hg (0.17 mg/kg dw) in 55% of the lakes (n = 11) during mining (1948–1999). All lakes within 5 km of the Giant Mine roaster stack exceeded CCME ISQG during mining (n = 8), with a 4-fold increase in total Hg concentration observed during mining at these near-field (<5 km from stack) sites. We observed evidence of enriched Hg in near-field, mid-field, and far-field sites. The elevated sedimentary Hg concentrations during mining in near-field sites would have posed a hazard to human and wildlife health during the height of emissions, however the significant decrease in Hg concentrations since the closure of mines in the region demonstrate the potential for recovery in these aquatic ecosystems.

Reactive remote plasma sputtering of TiOx thin films and controlled growth of textured single-phase rutile using rf substrate biasing

Titanium oxide (TiOx) thin films were deposited by remote plasma sputtering (RPS) with the use of rf substrate bias onto unheated and water-cooled glass, Si, and Kapton substrates. The rf remote plasma power was kept constant (2.0 kW) and the properties of the films were studied as a function of deposition rate and substrate bias voltage. Four different reactive processes at four different deposition rates were developed under zero bias conditions by altering the target bias voltage and the flow of oxygen to give highly transparent TiOx films. These processes were studied with varying substrate bias voltage and the film structural, optical, and surface properties were investigated by GI-XRD, SEM, transmission, and sessile drop measurements. The changes in film structure and properties observed were related to the plasma conditions of the RPS system, investigated by dc electrical probe and OES measurements, and compared with other observations for films deposited under energetic conditions in the literature. All films deposited under zero bias conditions exhibited amorphous structures in GI-XRD and SEM images. Sufficient application of substrate bias was seen to promote columnar growth in cross-sectional SEM images and to crystallise phase pure rutile with no detection of the anatase phase in GI-XRD. Rutile bearing films were noted for their change in optical properties. Further increase of the substrate bias voltage caused a change in the texture of the rutile films from a low-energy [110] preferred orientation to a high-energy [101] and [002] preferred orientation. Contact angles of water with deposited films were found to increase with increasing substrate bias voltage and decreasing deposition rate. Film stress was also found to be influenced mainly by the substrate bias voltage process parameter.

Direct solar-driven thermochemical CO2-to-fuel conversion with efficiency over 39 % employing hierarchical triply periodic minimal surfaces biomimetic foam reactors

Solar-driven CO2 reforming of CH4 is considered a promising approach for achieving CO2 emission reduction and clean energy utilization simultaneously. However, reactors suffer from uneven temperature distribution and severe carbon deposition, leading to low solar-to-fuel efficiency. This study introduces a novel strategy for highly efficient solar-driven thermochemical CO2-to-fuel conversion based on hierarchical triply periodic minimal surfaces (TPMS) biomimetic foam reactors. The biomimetic hierarchical foam reactor exhibits a remarkably high light-to-fuel efficiency of 39.14 %, with CH4 and CO2 conversion rates reaching 72.6 % and 83.9 %, respectively, along with no obvious attenuation over 50 h. A 73.7 % reduction in temperature non-uniformity and a 96.9 % decrease in the carbon deposition rate are also demonstrated. The underlying mechanism is attributed to unique highly interconnected and smooth hierarchical pores, for which large pores promote the penetration of sunlight while small pores enhance fluid-solid energy transfer. Effects of solar irradiation conditions and foam thermal conductivity are investigated numerically, providing guides for further reactor optimization under different operating scenarios. This work presents a new approach for designing and manufacturing efficient direct solar-driven thermochemical CO2-to-fuel conversion reactors using hierarchical TPMS biomimetic foams.

An ab initio simulation on electron beam physical vapor deposition of Gd2Zr2O7 coating by density functional theory and kinetic Monte Carlo

AbstractWithout any experimental inputs, the electron beam physical vapor deposition (EB‐PVD) of Gd2Zr2O7 with much potential for thermal barrier coatings was investigated by use of the kinetic Monte Carlo, after fitting the potential function using lattice inversion method and “coarse‐grained” mapping on the cohesive energy calculated by density functional theory, to reveal the effect of critical processing parameters of EB‐PVD on the microstructures and porosity of the deposited coating, for example, substrate temperature, deposition rate and incident angle. Based on the lower energy barrier calculated by a nudged elastic band, intra‐layer diffusion is easier than interlayer diffusion, attributed to the fewer bonds in the former. Furthermore, the porosity of the coating decreases with the increase of temperature or decrease of deposition rate, with the gradual disappearing large gaps among columnar crystals and filled pores, because of the increase of transition probability and transition times. With the decreasing incident angle, the area of the shadow zone decreases and less particles can be blocked by previously deposited ones, making the columnar crystals disappear gradually, with more like laminated structures.

Ion current density on the substrate during short-pulse HiPIMS

A probe method for measuring the ion current density and theoretical calculations of the dynamics of neutral and charged plasma particles using the ionization region model (IRM) is used to study short and ultra-short pulse high-power impulse magnetron sputtering (HiPIMS). This paper studies reasons for the increase in the average ion current density on the substrate at shorter pulses, when the average discharge power does not change. HiPIMS pulses are applied to the copper target at constant values of average discharge power (1000 W) and peak current (150 А), respectively, while the pulse time of the discharge voltage ranges from 4 to 50 µs. A power supply with low output inductance is designed to generate ultra-short pulses. It is shown that shorter discharge pulses lead to a multiple growth (from 2 to 7 mA cm−2) in the average ion current density on the substrate and a growth in the peak intensity of Ar+, Cu+ and Cu2+ recorded by optical emission spectroscopy. A theoretical model of this effect is based on the spatially averaged IRM, which considers afterglow effects. According to theoretical calculations, the increase in the average ion current density on the substrate is determined by the plasma dissipation in the ionized region after the pulse ends. Also, a decrease in the copper deposition rate from 180 to 60 nm min−1 with decreasing pulse time from 40 to 4 µs is explored. A comparison of experimental data with those obtained earlier shows that the suggested dependences of the ion current density and deposition rate on the HiPIMS pulse time are typical for discharge systems with different cathode materials and configurations, i.e., for single- and dual-magnetron systems. This indicates a common nature of the phenomena observed and additionally confirms the results obtained.

A fluid model of pulsed direct current planar magnetron discharge

We simulated a pulsed direct current (DC) planar magnetron discharge using fluid model, solving for species continuity, momentum, and energy transfer equations, coupled with Poisson equation and Lorentz force for electromagnetism. Based on a validated DC magnetron model, an asymmetric bipolar potential waveform is applied at the cathode at 50–200 kHz frequency and 50–80% duty cycle. Our results show that pulsing leads to increased electron density and electron temperature, but decreased deposition rate over non-pulsed DC magnetron, trends consistent with those reported by experimental studies. Increasing pulse frequency increases electron temperature but reduces the electron density and deposition rate, whereas increasing duty cycle decreases both electron temperature and density but increases deposition rate. We found that the time-averaged electron density scales inversely with the frequency, and time-averaged discharge voltage magnitude scales with the duty cycle. Our results are readily applicable to modulated pulse power magnetron sputtering and can be extended to alternating current (AC) reactive sputtering processes.

Kinetic Monte Carlo simulation study of the early stages of epitaxial SiC (0001) growth

A kinetic Monte Carlo (kMC) simulation with a cluster-multiple labeling technique was carried out to study the dynamic behavior of Si-C clusters during the early stage of epitaxial growth. In the model, a crystal lattice was established to fix the physical location of atoms and interatomic bonding. Events, such as adatoms adsorption, diffusion on the planar surface, and attachment to and detachment from clusters of adatoms were considered in the model. The Si and C atoms were treated individually to achieve more elaborate information for dynamic behavior of the clusters in the crystal surface. Moreover, a cluster multiple labeling technique, also known as the Hoshen - Kopelman algorithm was used to identify Si-C clusters. Then the properties of the clusters were calculated and analyzed by the algorithm. The simulation results showed that the number of Si-C clusters gradually decreases with increasing substrate temperature and decreasing deposition rate, and that the average size of Si-C clusters at high temperatures is much larger than that at low temperatures. Furthermore, the Si:C ratio on the growing surface has a significant effect on the surface morphology. At Si-rich conditions, the cluster density is relatively high, and the cluster shape is not homogeneously distributed. While with the increase of C mole fraction, the cluster density gradually decreases and the cluster shape becomes more uniform. Therefore, a higher concentration of C in deposition flux is beneficial to the early stage of nucleation. These findings are consistent with predictions for the case of the epitaxial growth of SiC.

Effect of soot particle deposition on porous fouling formation and thermal characteristics of an exhaust gas recirculation cooler

Exhaust gas recirculation (EGR) systems have been successfully employed to reduce the NOx emissions in diesel engines. However, the fouling problem in EGR coolers challenges their capability to comply with stringent environmental regulations. A few numerical simulations have considered the fouling growth in EGR coolers. Those studies modeled the evolving fouling layer to be a solid medium, therefore, fluid flow and convection heat transfer within the fouling layer, which is well-documented to be a porous medium permeable to gas flow, have not been considered yet. As such, the present study investigates the simultaneous effects of the formation of the evolving porous fouling layer (EPFL) at the walls of an EGR cooler and fluid flow and convection heat transfer simulation within this EPFL to determine its coupled effects on the thermal performance of the EGR cooler. This study also investigates the possibility of formation of a steady fouling layer (SFL) because of the opposing effects of the fouling layer growth and deposition rate. The effects of two pertinent dimensionless parameters, namely Darcy number (10-4≤Da≤5×10-3) and Reynolds number (100≤Re≤400) on the time history of the fouling layer growth, deterioration of the thermal performance of the duct, and average Nusselt number ratio (Nuav/Nuavt=0) are studied. The results show that the thermal performance of the duct decreases as the EPFL grows, which agrees well with the available experimental data. It is shown that the steady fouling layer is obtained due to a decrease in thermophoretic force and deposition rate, as a result of the EPFL formation. Finally, a correlation is proposed in terms of Reynolds and Darcy numbers for the time at which the SFL occurs.

Numerical investigation of the effect of dust shields on accumulation of dust over PV panels

Dust accumulation on photovoltaic panels represents a major challenge for the operation of solar panels especially in the regions known by their high rate of dust and low frequency of rain. The objective of this study is to minimize dust accumulation on PV panels operating street light posts using dust shields. A novel dust shield having the same width of the panel, and subtending an angle of 120° with the panel, is proposed for dust mitigation. Numerical simulations are carried out to evaluate the influence of the dust shield on dust accumulation over the panel’s surface. It is found that using a dust shield decreases the dust deposition rate by more than 44%. Moreover, extending the panel’s surface at the lower edge with an extension plate together with the dust shield decreases the dust deposition rate better than using a dust shield only. Also, the effect of adding an air gap between the shield and the added extension plate is investigated, and it is found that the air gap induces air drafts over the panel’s surface, which acts as an air barrier that obstructs the approach of dust particles to the panel’s surface. These drafts get stronger as the air gap thickness increases, accordingly, less particles deposit on the panel. Finally, it is found that using a dust shield with a length smaller than the panel’s length in addition to an extension plate together and increasing the thickness of the air gap is an effective and efficient solution for dust mitigation, such that the percentage decrease in the dust deposition rate that might be more than 88%.

Experimental and mechanism investigation on flowability and wax deposition of waxy crude oil with dissolved CH4 by pressurized laboratory apparatus

In offshore oilfields, crude oils often contain dissolved gas, and are unavoidably transported under pressure. However, the flowability and wax deposition of crude oils with dissolved gas are rarely investigated. In this paper, Methane (CH4) was used as a similar substitute for the dissolved gas in crude oils, and a series of pressurized laboratory apparatuses were developed to study the influencing mechanism of dissolved CH4 on the flowability and wax deposition of Changqing waxy crude oil. It was found that with the increase of the dissolved CH4 pressure, the crude oil flowability was improved, and the wax deposition rate was inhibited. However, the wax appearance temperature (WAT), the average wax content of wax deposits, and the mass of wax diffused into wax deposits all increased accordingly. This was mainly attributed to the influence of dissolved CH4, which can effectively increase the intermolecular distance between wax molecules, decrease the intermolecular forces, and weaken the strength of wax crystals to overlap each other. The improvement of rheological properties, on the one hand, promotes the diffusion of wax molecules, which leads to the increase in the mass of wax diffused into wax deposits; on the other hand, it increases the wax content required for the formation of wax deposits according to the dynamic gelation mechanism, thus resulting in the decrease of wax deposition rate. Also, the wax stripping effect during the deposition and depressurization processes cannot be ignored. The research results have guiding significance for the optimal design of the gathering and transportation pipeline network and the calculation of wax deposition.

Nitrogen doped ZrO2 thin films: synthesis and characterization

To obtain ZrO2 and ZrO2+N2 thin films was used magnetron sputtering in radio frequency mode in a 10-6 mbar high vacuum deposition chamber. Silicon and carbon substrates measuring 12x15mm were used for deposition. The used magnetron system was composed of a single water-cooled cathode, provided with one circular targets of ZrO2 (2 mm thick and 50 mm in diameter) of high purity (99.95%). TDS Analysis of the films was performed. The desorbed species were observed with a QMG 220 Mass spectrometer provided with a W filament. It can be observed that in the case of the ZnO2 film, nitrogen desorption registers two maxima with signal intensity of 9.7x10-12 and 9.0x10-12, reached after 2000s and 4900s respectively. In the case of ZrO2+N2 film, nitrogen desorption shows a pronounced maximum with a signal intensity of 2.4x10-11 reached after 6000s. . The topology the ZrO2 and ZrO2+N2 samples deposited on Si substrates have been investigated by scanning electron microscopy (SEM) using a FEI Inspect S scanning electron microscope ( Hillsboro, Oregon, OR, USA) in high-vacuum modes. For the ZrO2 deposition, the surface appears to have grain-like topology, with a mean dimension of around 150 nm. These structures do not appear for the ZrO2+N2 deposition. Instead, for the ZrO2+N2 sample, small blisters (between 300 nm and 1.000nm) have formed on the surface, as a consequence of injecting N2 during the deposition. Cross-section measurements were also performed to establish the layer thickness. The ZrO2 sample has a measured thickness of 1950nm, while the introduction of N2 gas for the ZrO2+N2 sample had a poisoning effect on the magnetron target that led to a decrease (5 times) in deposition rate, giving this sample a final thickness of 365nm (compared to 1950nm) for the same deposition The crystalline structure was investigated using X-Ray Diffraction (XRD) method. The experimental set-up was composed of a diffractometer equipped with a Cu-Kα X-ray sourse, with a specific wavelength of 0.154nm, in a Bragg-Bretano type geometry. In this way, a crystalline phase corresponding to ZrO2 with a group symmetry Fm-3m (225)-face centered cubic was identified. At the same time, it is observed that the films deposited in the reactive atmosphere show a pronounced amorphization, this most likely being due to the retention of nitrogen which leads to the modification of the network parameters.

Effect of pH on Microstructure and Properties of Ultrasonic-Assisted Electroless Ni–P Coatings on Titanium Alloy

Ni–P coatings with various pH values (4.5–5.4) were fabricated on Ti-6Al-4V titanium alloy by ultrasonic-assisted electroless deposition. The effect of pH on the deposition rate and phosphorus content was studied, as well as pH on the surface morphology, phase structure and microhardness of the deposited Ni–P coatings. The results showed that the increasing pH enhanced the deposition reaction, and ultrasonic cavitation and mass transfer effect improved the catalytic activity of the substrate surface and the reaction system. So the deposition rate was increased. But the higher pH decreased the stability of the bath and precipitated NiHPO3, resulting in the decrease of deposition rate. With the increase of pH, the phosphorus content decreased at first and then kept stable (17 ± 0.45 wt%), while the microhardness enhanced at first and then kept stable (605 ± 2HV). The ultrasonic-assisted electroless Ni–P coatings had the typical cauliflower-like morphology and microcrystalline structure characteristics.

Probing the formation of ultrastable metallic glass from structural heterogeneity

• The structure underlying the unexpected stability of Zr-based TFMGs was tracked. • MGs with greater heterogeneity have a higher potential to form SMGs. • Slower deposition rates are required for ultrastability in more heterogeneous MGs. • The relaxation mechanism changes as the deposition rate decreases. • The geometry and distribution of loosely packed phases determines ultrastability. Ultrastable metallic glasses (SMGs) exhibit enhanced stability comparable to those of conventional glasses aged for thousands of years. The ability to understand why certain alloy compositions and processing conditions generate an SMG is an emerging challenge. Herein, amplitude-modulation dynamic atomic force microscopy was utilized for tracking the structure of Zr 50 Cu 50 , Zr 50 Cu 44.5 Al 5.5 and Zr 50 Cu 41.5 Al 5.5 Mo 3 thin film metallic glasses (TFMGs) that were produced by direct current magnetron sputtering at room temperature with the rate of deposition being the only variable. The transition in stability from bulk- to SMG-like behavior resides in the change of relaxation mechanism as the deposition rate is decreased. The formation of SMGs is directly linked with the degree of structural heterogeneity, whereby MGs with greater heterogeneity have a higher potential to form SMGs with more significant enhancement in stability. Slower deposition rates, however, are required to yield the more homogenous structure and lower energy state underlying the ultrastability. Ultrastability is closely linked with the geometric shape and distribution of loosely packed phases, whereby SMGs containing more slender loosely packed phases with a more skewed distribution achieve more significant improvements in stability. This work not only provides direct evidence of the structure of SMGs, but also opens new horizons for the design of SMGs. .

Formation of ilmenite-type single-crystalline MgTiO3 thin films by pulsed-laser deposition

Ilmenite structure is a good playground to explore magnetism in honeycomb lattices owing to the existence of an intriguing variety of magnetism in 3d transition metal compounds. Because of the absence of magnetic ions, ilmenite-type MgTiO3 is a promising candidate for d0 transparent insulators to reveal general features of TiO6 honeycomb layers. In this study, we found an optimum growth condition to synthesize ilmenite-type single-crystalline MgTiO3 thin films on Al2O3(0001) substrates by pulsed-laser deposition. By increasing oxygen pressure from roughly 10−6 to 10−1 Torr, we obtained (0001)-oriented MgTiO3 thin films with suppression of segregation of a Mg2TiO4 phase. On the triangular lattice of Al2O3, twin-domain formation is suppressed with decreasing deposition rate, resulting in the synthesis of single-crystalline MgTiO3 thin films. The bandgap of the MgTiO3 film was evaluated to be about 4.4 eV by optical absorption spectra, which implies d0 transparent insulator.