O-rich Layer Research Articles

Fabrication and Properties of Biodegradable Akermanite-Reinforced Fe35Mn Alloys for Temporary Orthopedic Implant Applications.

As a representative of the biodegradable iron (Fe)-manganese (Mn) alloys, Fe35Mn has been investigated as a promising biodegradable metal biomaterial for orthopedic applications. However, its slow degradation rate, though better than pure Fe, and poor bioactivity are concerns that retard its clinical applications. Akermanite (Ca2MgSi2O7, Ake) is a silicate-based bioceramic, showing desirable degradability and bioactivity for bone repair. In the present work, Fe35Mn/Ake composites were prepared via a powder metallurgy route. The effect of different contents of Ake (0, 10, 30, 50 vol %) on the microstructure, mechanical properties, degradation, and biocompatibility of the composites was investigated. The ceramic phases were found to be evenly distributed in the metal matrix. The Ake reacted with Fe35Mn and generated CaFeSiO4 during sintering. The addition of Ake increased the relative density of pure Fe35Mn from ∼90 to ∼94-97%. The compressive yield strength (CYS) and elastic modulus (Ec) increased with increasing Ake, with Fe35Mn/50Ake exhibiting the highest CYS of ∼403 MPa and Ec of ∼18 GPa. However, the ductility decreased at higher Ake concentrations (30 and 50%). Microhardness also showed an increasing trend with the addition of Ake. Electrochemical measurements indicated that higher concentrations of Ake (30 and 50%) could potentially increase the corrosion rate of Fe35Mn from ∼0.25 to ∼0.39 mm/year. However, all of the compositions tested did not show measurable weight loss after immersion in simulated body fluid (SBF) for 4 weeks, attributed to the use of prealloyed raw material, high sintered density of the fabricated composites, and the formation of a dense Ca-, P-, and O-rich layer on the surface. Human osteoblasts on Fe35Mn/Ake composites showed increasing viability with increasing Ake content, indicating improved in vitro biocompatibility. These preliminary results suggest that Fe35Mn/Ake can be a potential material for biodegradable bone implant applications, particularly Fe35Mn/30Ake, if the slow corrosion of the composite can be addressed.

Effect of Temperature Cycling Pretreatment on the Thermal Stability of Sm2(Co, Fe, Zr, Cu)17 Magnets in the Mild Temperature Range.

The irredeemable magnetic losses of Sm(Co, Fe, Zr, Cu)7.8 permanent magnets caused by oxidation are very important for their practical application. In this work, the simulated results with R2 ≥ 98% based on the data of the temperature cycling test and the long-term isothermal test for the original samples confirmed that the magnetic flux losses reached 9.38% after the 5000th cycle in range R.T.-300 °C, and 7.15% after oxidated at 180 °C for 10 years, respectively. Demagnetization curves showed that the low-temperature oxidation mainly led to the remanence attenuation, while the coercivity remained relatively stable. SEM observation and EDS analysis revealed that an oxide outer layer with a thickness of 1.96 μm was formed on the surface of the original sample at 180 °C for 180 days, in which there was no enrichment or precipitation of metal elements. However, once a Cu, O-rich outer layer with a thickness of 0.72 μm was grown by using a temperature cycling from -50-250 °C for three cycles, the attenuation of magnetic properties could be inhibited under the low-temperature oxidation. This work suggested that the magnetic attenuation of Sm2Co17-type permanent magnets in the low-temperature field could not be ignored, and provided a simple method to suppress this attenuation of magnetic properties below 300 °C.

Overcoming Voltage Losses in Vanadium Redox Flow Batteries Using WO3 as a Positive Electrode.

Vanadium redox flow batteries (VRFBs) are appealing large-scale energy storage systems due to their unique properties of independent energy/power design. The VRFBs stack design is crucial for technology deployment in power applications. Besides the design, the stack suffers from high voltage losses caused by the electrodes. The introduction of active sites into the electrode to facilitate the reaction kinetic is crucial in boosting the power rate of the VRFBs. Here, an O-rich layer has been applied onto structured graphite felt (GF) by depositing WO3 to increase the oxygen species content. The oxygen species are the active site during the positive reaction (VO2 +/VO2+) in VRFB. The increased electrocatalytic activity is demonstrated by the monoclinic (m)-WO3/GF electrode that minimizes the voltage losses, yielding excellent performance results in terms of power density output and limiting current density (556 mWcm-2@800 mAcm-2). The results confirm that the m-WO3/GF electrode is a promising electrode for high-power in VRFBs, overcoming the performance-limiting issues in a positive half-reaction.

High Wear Resistance and Mechanical Performance of NiAl Bronze Developed by Electron Beam Powder Bed Fusion

This work reports the additively manufactured NiAl bronze alloys via electron beam powder bed fusion (EB-PBF) that exhibit improved wear resistance without an increase of friction, exceeding those of conventional hot-rolled counterparts. High wear resistance is attributed to the formation of a Cu–O-rich transfer layer, and to exceptional mechanical strength induced by integrated effects including uniformly distributed precipitation, grain refinement, martensitic transformation around stacking faults, and a modulus mismatch between precipitates and the matrix. The simulation results indicate that the effect of the precipitate distribution on the internal stress field of the matrix is dependent on the external force direction. For the shear force, the uniformly distributed precipitates promote the overall stress concentration of the matrix, leading to its high work-hardening capability that plays a role in improving the wear resistance. This study reveals the potential of the EB-PBF technique to develop alloys with high wear resistance.

Tailoring electrolyte to enable high-rate and super-stable Ni-rich NCM cathode materials for Li-ion batteries

The detrimental effects on the electrochemical performances of high-capacity nickel-rich layered oxide cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Ni-rich NCM) are continuous irreversible phase transition, particle disintegration, and unstable cathode-electrolyte interface, which are usually induced by deleterious cathode-electrolyte reactions. Here, we report those side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. This CEI film not only eliminates the adverse cathode-electrolyte interface reaction and prevents the electrolyte penetration into the grain boundary but also hinders the formation of inactive rock-salt phase on the material surface. More significantly, it is demonstrated that this N, B, O-rich interface layer offers a fast Li + diffusion kinetic process to ensure a high-rate performance of the cathode, which is still a technical difficulty for the large application of Ni-rich NCM. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high-capacity retention over 92% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g −1 at the high rate of 20 C. Building a stable and effect Li + -ion conductive interface film by optimizing the electrolyte formula is a facial and effective approach to develop aggressive high-capacity cathodes for high-energy storage applications. A performance optimization mechanism induced by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high capacity retention over 90% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g −1 at the high rate of 20 C. • Side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface formed by electrochemical oxidation. • This N, B, O-rich interface layer hinders the formation of rock-salt phase on the cathode surface. • The CEI film formed by in-situ polymerization offers a fast Li + diffusion kinetic process to ensure a high-rate performance.

Three-dimensional Hydrodynamics Simulations of Precollapse Shell Burning in the Si- and O-rich Layers

Abstract We present 3D hydrodynamics simulations of shell burning in two progenitors with zero-age main-sequence masses of 22 and 27 M ⊙ for ∼65 and 200 s up to the onset of gravitational collapse, respectively. The 22 and 27 M ⊙ stars are selected from a suite of 1D progenitors. The former and the latter have an extended Si- and O-rich layer with a width of ∼109 cm and ∼5 × 109 cm, respectively. Our 3D results show that turbulent mixing occurs in both of the progenitors with the angle-averaged turbulent Mach number exceeding ∼0.1 at the maximum. We observe that an episodic burning of O and Ne, which takes place underneath the convection bases, enhances the turbulent mixing in the 22 and 27 M ⊙ models, respectively. The distribution of nucleosynthetic yields is significantly different from that in 1D simulations, namely, in 3D more homogeneous and inhomogeneous in the radial and angular direction, respectively. By performing a spectrum analysis, we investigate the growth of turbulence and its role of material mixing in the convective layers. We also present a scalar spherical harmonics mode analysis of the turbulent Mach number. This analytical formula would be helpful for supernova modelers to implement the precollapse perturbations in core-collapse supernova simulations. Based on the results, we discuss implications for the possible onset of the perturbation-aided neutrino-driven supernova explosion.

A study on the interfacial adhesion energy between capping layer and dielectric for cu interconnects

Recently, Cu interconnect and low-k materials have been applied to reduce the interconnect resistive-capacitive delay issue. However, as the process node size is reduced to a few nanometers, high leakage currents appear through the dielectric under high electric fields. Therefore, issues of Cu diffusion at the interface between the dielectric and the capping layer have been reported. This study investigated interfacial adhesion energy change at the film level between dielectric (low-k, tetraethyl orthosilicate (TEOS)) and capping layer (SiCN, SiN) taking into account the correlation between interfacial adhesion energy and interconnect reliability. In the capping layer/low-k interface, when low-k is applied to the top layer, it shows high interfacial adhesion energy (> 34.31 ± 3.49 J/m2) due to the presence of an O-rich thin layer. But when low-k is applied to the bottom layer, due to the SiC bond, it shows low interfacial adhesion energy (< 5.60 ± 2.46 J/m2). The interface between TEOS and SiN has high interfacial adhesion energy (> 32.54 ± 1.97 J/m2) regardless of the stacking order and CMP process. It clearly shows that low-k dielectrics will affect the deterioration of the interfacial adhesion energy and O-rich layer will greatly improve the interfacial adhesion energy in dielectric/capping layers.

Evaluating Solid-Electrolyte Interphases for Lithium and Lithium-free Anodes from Nanoindentation Features

Summary The morphology and mechanical property of SEIs for lithium anodes crucially affect the electrochemical cycling performance of Li-metal batteries such as Li-S and Li-O2 batteries. Herein, we establish the standards for rapidly assessing SEIs for Li and Li-free type of anodes by AFM nanoindentation features toward prediction of corresponding electrochemical performances. A series of single-layered and multi-layered SEIs with known composition and structures are purposely constructed. A set of unique nanoindentation features representative of mechanical properties of the basic SEIs are formed, serving as the standards for rapidly assessing the mechanical properties and electrochemical performances of unknown SEIs together with their Young’s modulus, smoothness, and thickness. To validate the applicability of the method, SEIs formed by electrochemical aging and formed on Cu substrates are further evaluated. Our work not only contributes to understanding the influence of SEIs on cycling performances but also provides a rapid way for screening SEIs.

Investigations on the formation of multi-modal size distribution of mechanochemically processed Cu-Y-CuO powders

Abstract In order to improve the high-temperature stability of copper (Cu) alloys, which have a range of applications because of their high conductivity, an in-situ mechanochemical process based on Mechanical Alloying (MA) and Hot Isostatic Pressing (HIP) was proposed and Cu-Y2O3 alloys were prepared. An interesting multi-modal distribution of particle size was observed in the high yttria (3/ 5 wt%) doped MA powders. Understanding the mechanism behind the above phenomenon will be important for preparing ODS-Cu by MA process. Thus, this paper investigates the formation of multi-modal distribution of particle size in the Cu-Y-CuO system. It was found that the finer the powder, the larger its lattice parameter, hardness, and oxygen content will be. On the basis of these data and the microstructural evolution of the powders with MA time, it was suggested that after CuO powder is mixed with Cu-Y alloyed powder, the high energy ball-milling will induce the formation of a hard and brittle O-rich shell on the surface of Cu-Y particles. With the continuing of MA, the high-energy collision between the balls will make the hard/brittle O-rich layer break into pieces. These results can provide helpful information to optimize the preparation of copper-based materials through process control.

Investigation of service life and corrosion mechanism of tubing in production well on polymer flooding

ABSTRACT The corrosion behaviour and the remaining safe service life of tubing in simulating production well of polymer flooding in Xinjiang oilfield which located in China was investigated using weight loss measurement and surface characterisation. The results showed that as the chloride ion concentration, temperature and H2S content increased, the corrosion rate of N80 steel gradually increased in the hydrolysis of anionic polyacrylamide (HPAM)/H2S/CO2 environment. The tubing of production well met the requirements of oilfield in polymer flooding. The corrosion scales had two layers: the outer O-rich layer and the inner S-rich layer. The chloride ion concentration and temperature affected the location and the thickness of the S-rich layer. The corrosion scales of N80 steel were composed of FeS, FeS2, FeCO3. Polyacrylamide adsorbed on the surface of steel to form a network film blocked the contact between metal and solution and then inhibited the anodic dissolution of metal.

Probing the Atomic-Scale Structure of Amorphous Aluminum Oxide Grown by Atomic Layer Deposition.

Atomic layer deposition (ALD) is a well-established technique for depositing nanoscale coatings with pristine control of film thickness and composition. The trimethylaluminum (TMA) and water (H2O) ALD chemistry is inarguably the most widely used and yet to date, we have little information about the atomic-scale structure of the amorphous aluminum oxide (AlOx) formed by this chemistry. This lack of understanding hinders our ability to establish process-structure-property relationships and ultimately limits technological advancements employing AlOx made via ALD. In this work, we employ synchrotron high-energy X-ray diffraction (HE-XRD) coupled with pair distribution function (PDF) analysis to characterize the atomic structure of amorphous AlOx ALD coatings. We combine ex situ and in operando HE-XRD measurements on ALD AlOx and fit these experimental data using stochastic structural modeling to reveal variations in the Al-O bond length, Al and O coordination environment, and extent of Al vacancies as a function of growth conditions. In particular, the local atomic structure of ALD AlOx is found to change with the substrate and number of ALD cycles. The observed trends are consistent with the formation of bulk Al2O3 surrounded by an O-rich surface layer. We deconvolute these data to reveal atomic-scale structural information for both the bulk and surface phases. Overall, this work demonstrates the usefulness of HE-XRD and PDF analysis in improving our understanding of the structure of amorphous ALD thin films and provides a pathway to evaluate how process changes impact the structure and properties of ALD films.

Facile Room Temperature Routes to Improve Performance of IGZO Thin-Film Transistors by an Ultrathin Al2O3Passivation Layer

Although oxide thin-film transistors (TFTs) have drawn great interests in flexible displays, a key obstacle is the requirement of high-temperature annealing to realized mobility>10 cm $^{2}/\text {V}\cdot \text {s}$ . In this paper, a fully room-temperature strategy, involving the deposition of ~10 nm In–Ga–Zn–O (IGZO) channel layer and ~4 nm Al2O3 passivation layer, is introduced. The as-prepared flexible TFT on polymide substrate exhibits a saturation mobility of 15.3 cm $^{2}/\text {V}\cdot \text {s}$ , $V_{{\text {th}}}$ of 3.08 V, and on/off current ratio of $2.3\times 10^{{\text {7}}}$ . Thickness-dependent analysis indicates that the interface between Al2O3 and IGZO is composed of negative O-rich layer, which impel the energy band bending inside the IGZO layers and release of electrons from traps. This paper opens up a route to achieve fully room-temperature fabrication of high-performance flexible TFT.

Rapid Growth of Crystalline Mn5O8 by Self-Limited Multilayer Deposition using Mn(EtCp)2 and O3.

This work investigates the use of ozone as a post-treatment of ALD-grown MnO and as a coreactant with bis(ethylcyclopentadienyl)manganese (Mn(EtCp)2) in ALD-like film growth. In situ quartz crystal microbalance measurements are used to monitor the mass changes during growth, which are coupled with ex situ materials characterization following deposition to evaluate the resulting film composition and structure. We determined that during O3 post-treatment of ALD-grown MnO, O3 oxidizes the near-surface region corresponding to a conversion of 22 Å of the MnO film to MnO2. Following oxidation by O3, exposure of Mn(EtCp)2 results in mass gains of over 300 ng/cm(2), which exceeds the expected mass gain for reaction of the Mn(EtCp)2 precursor with surface hydroxyls by over four times. We attribute this high mass gain to adsorbed Mn(EtCp)2 shedding its EtCp ligands at the surface and releasing Mn(II) ions which subsequently diffuse into the bulk film and partially reduce the oxidized film back to MnO. These Mn(EtCp)2 and O3 reactions are combined in sequential steps with (a) Mn(EtCp)2 reacting at the surface of an O-rich layer, shedding its two EtCp ligands and freeing Mn(II) to diffuse into the film followed by (b) O3 oxidizing the film surface and withdrawing Mn from the subsurface to create an O-rich layer. This deposition process results in self-limiting multilayer deposition of crystalline Mn5O8 films with a density of 4.7 g/cm(3) and an anomalously high growth rate of 5.7 Å/cycle. Mn5O8 is a metastable phase of manganese oxide which possesses an intermediate composition between the alternating MnO and MnO2 compositions of the near-surface during the Mn(EtCp)2 and O3 exposures.

Atomic transport property of Fe–O liquid alloys in the Earth’s outer core P, T condition

The self-diffusion and tracer diffusion coefficients and viscosity of non-magnetic liquid Fe–O alloys were determined at 100–350GPa and 4000–8000K on the basis of the ab initio molecular dynamics simulation method. Those of pure liquid iron are found to be consistent with the results of former studies. We confirmed that the self-diffusivity of Fe monotonically increases with increasing oxygen fraction. Meanwhile, the viscosity monotonically decreases with increasing oxygen fraction. On the other hand, the depth dependence of diffusivities and viscosity in the outer core are not great along the geotherm because pressure and temperature conversely affect the transport coefficients. The calculated diffusivity suggests that an O-rich stratified layer with a thickness of ∼70km could be produced at the uppermost layer of the outer core if the layer was created from the diffusion of O from the mantle.

Effect of Sn Addition on the Corrosion Performance of Cast X-52 in H&lt;sub&gt;2&lt;/sub&gt;S-Containing Environment at 60°C

The electrochemical behavior of cast X-52 with different Sn content ranging from 0 to 1 wt. % was investigated using the methods of potentiodynamic test, electrochemical impedance spectroscopy (EIS). The immersion tests involved to examine the relationship between Sn addition and corrosion performance of cast X-52. In addition, the morphology and the compositions of surface corrosion products were analyzed using scanning electron microscope (SEM)/ energy dispersive spectroscopy (EDS). Potentiodynamic polarization curves showed that the presence of Sn decreased the corrosion current density. EIS indicated that Sn-containing steels had higher polarization resistances. These results confirmed that Sn played a positive role in reducing corrosion rate in H2S-containing environment. However, the corrosion resistance decreased with increasing Sn addition. It was proved that Sn improved the corrosion resistance with only a small content and large amount of Sn might lead to an advance of the pit due to occurrence of more acidification. Moreover, a continuous inner O-rich layer adherent to the matrix was found for Sn-addition samples, which lead to a decrease of corrosion rate due to its compact characteristic, compared with porous sulfide formed on the outer surface.

The influences of plasma ion bombarded on crystallization, electrical and mechanical properties of Zn–In–Sn–O films

The quality of co-sputtering derived Zn–In–Sn–O (ZITO) film was adjusted by different gas (oxygen and argon) induced plasma ions bombarding (PIB) treatment. The result showed that the film conductivity could be improved after plasma bombardment. The increment of oxygen vacancies and plasma bombard-induced thermal energy were main reasons. Notably, the efficiency of Ar plasma bombarded for improved conductivity not only was better but also had a smoother surface morphology. Due to Ar ions will not react with metal atoms to form oxide and possessed a higher momentum. In addition, the O-rich layer on the ultra-surface not only was removed but also enhanced film reliability by plasma bombarded that could enhance the performance of optoelectronic devices.

Growth mechanisms forTiO2at its rutile (110) surface

Mechanisms for growth on the rutile (110) surface were investigated using a combination of ab initio, variable charge classical molecular dynamics and kinetic Monte Carlo (KMC) methods. Ab initio calculations were performed to determine relevant energy barriers, and these were used to parametrize a variable charge classical potential. Low-energy (10--40-eV) interactions of small ${\mathrm{Ti}}_{x}{\mathrm{O}}_{y}$ molecules with a rutile (110) substrate were then investigated, by molecular dynamics using the variable charge potential, with the aim of determining the influence of various parameters on surface growth and defect formation. Rutile growth was simulated through sequentially depositing randomly selected atoms and molecules with energies in the tens of eV range. Long-time scale evolution was approximated through heating the substrate and through on-the-fly KMC simulations, which could be used to simulate realistic experimental deposition times. The main growth mechanism was found to involve a fast kinetic effect to subplant interstitial Ti atoms, until an O-rich surface layer formed, followed by a slower diffusion of the Ti interstitials to the O-rich surface. Bombardment at an energy of around 20 eV in an oxygen-rich atmosphere with a high proportion of bombarding TiO, ${\mathrm{TiO}}_{2}$, as opposed to single atoms, was found to produce rutile growth with the best crystallinity.

Effect of Ce addition on the oxidation behaviour of Mo–Si–B–Al ultrafine composites at 1100 °C

Mo 73.4 Si 11.2 B 8.1 Al 7.3 ultrafine eutectic–dendrite composites undergo severe oxidation at 1100 °C in dry air, being transformed completely into mullite and cristobalite. However, the net mass loss is reduced by at least ∼ 40 % during 24 h exposure upon minor Ce addition to the alloy, indicating an unusual improvement in oxidation resistance. The presence of Ce hinders mullatization, and leads to the formation of a protective Si–O-rich layer in the scale. The relationship between oxide scale composition and the oxidation kinetics has been examined.

Extrinsic interface formation of HfO2 and Al2O3∕GeOx gate stacks on Ge (100) substrates

The extrinsic interfaces present at the HfO2∕GeOx∕Ge and Al2O3∕GeOx∕Ge gate stacks are investigated. The effective trapped charge density, estimated from hysteresis in capacitance-voltage characteristics, is higher for HfO2 than for Al2O3, implying qualitatively different charge trapping sources in each dielectric. Spectroscopic ellipsometry and medium energy ion scattering measurements reveal that HfO2 deposition induces the formation of a thicker germanate (intermixed) layer at the HfO2∕GeOx interface, where nonstoichiometric Ge-rich GeOx having significantly low bandgap (∼1.8eV) is present. In contrast, Al2O3 deposition leads to an abrupt and thinner O-rich GeOx interfacial layer without Ge-rich GeOx phase. The proposed band alignment indicates that Ge-rich GeOx layer at HfO2∕GeOx arises a significant band potential well trapping, while O-rich GeOx layer in Al2O3∕GeOx is responsible for a relatively lower charge trapping at band potential well. The combined results strongly suggest that the control of the GeOx interface layers is crucial to reduce the high charge trapping at high-κ∕GeOx∕Ge gate stacks.

Effects of two-step growth by employing Zn-rich and O-rich growth conditions on properties of (112¯) ZnO films grown by plasma-assisted molecular beam epitaxy on sapphire

The authors report properties of a-plane ZnO films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy in which two-step growth is employed. They show that the two-step growth is effective in improving structural and optical properties of a-plane ZnO films. Here, the two-step growth is preceded by growing the first layer under Zn-rich (O-rich) conditions and growing the second layer under O-rich (Zn-rich) conditions. All the grown samples show striated anisotropic morphology. The samples with the first, thin, O-rich layer plus the second, thick, Zn-rich layer show smaller root-mean-square (rms) roughness than those with the first, thin, Zn-rich layer plus the second, thick, O-rich layer. The sample with the 20-nm-thick first layer grown under O-rich condition shows the smallest rms roughness of 1.06nm, which is a smaller rms value than that of the sample grown under the single-step, stoichiometric condition. This sample shows the highest intensity of DX0 emission at 3.392eV and small full width at half maxima of (112¯0) and (101¯1) x-ray rocking curves, which indicate the good crystal quality.