Glancing Angle X-ray Diffraction Research Articles

Fabrication perspective of Fe3O4-based cross-cell memristive device for synaptic applications

Neurotransmitter release in chemical synapses plays a pivotal role in a wide range of essential brain functions, including neural activity (potentiation/depression), learning, cognition, emotion, perception, and consciousness. In this study, we have presented the fabricated cross-cell memristive device that exhibits an analog resistive switching (ARS) device, with Silver (Ag) as active and Platinum (Pt) as inert metal electrodes. The energy bandgap, crystal structure, surface morphology, elemental composition, and electronic properties of the deposited metal-oxide thin film were examined by using UV–Vis spectroscopy, Glancing Angle X-ray diffraction (GAXRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), and Raman spectroscopy, respectively. The electrical characteristics of the fabricated resistive switching (RS) device have been studied by the Keithley 4200A SCS parameter analyzer by low triangular DC sweep voltage (-2V/+2V) at room temperature (RT). Furthermore, we have evaluated the outstanding performance of the fabricated cross-cell RS device at a read voltage of 0.1V, and we have also discussed its remarkable linearity. This work will aid researchers in realizing the synaptic behavior of cross-cell devices for neuromorphic computing applications.

Swift heavy ion irradiation effects on tungsten carbide films

Tungsten carbide (WC) is an important material to study for various applications in extreme environments due to its radiation-resistant properties and high mechanical strength. Due to its excellent properties such as high hardness, strength, and wear resistance, it is also being considered lately as a plasma facing component in nuclear fusion reactors. To study the response of this material in extreme radiation environments, WC films prepared using RF sputtering technique were irradiated with 100 MeV Ag8+ ions in the present work. The irradiation was carried out at three different fluences: 3 × 1012, 1 × 1013, and 3 × 1013 ions/cm2. Rutherford Backscattering Spectrometry (RBS) was performed to determine the stoichiometry and thickness of the pristine film. To study the irradiation-induced modifications, glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HRTEM), and Raman spectroscopy were performed on the pristine and irradiated samples. GAXRD of the pristine and irradiated samples revealed grain size reduction accompanied with reduced crystallinity with increasing ion fluence which was further manifested in HRTEM measurements and Raman spectroscopy measurements. Change in surface morphology due to the ion irradiation was observed in FE-SEM. These modifications have been explained using thermal-spike and TRIM simulations which showed that although the swift heavy ions irradiation did not result in track formation in the WC films, it caused radiation damage which may be attributed to the synergistic effect of electronic and nuclear energy loss mechanisms. These results might be crucial for a fundamental understanding of the radiation resistance of WC thin films and its application in different radiation environments.

Effect of the substrate treatment on the microstructure of CVD Ti(C,N)/α-Al2O3/TiN hard coatings

Although the use of protective Ti(C,N)/Al2O3 coatings produced by chemical vapour deposition (CVD) on cemented carbide (WC-Co) substrates is the state of the art in high-speed metal cutting, the effect of the substrate treatment on the microstructure of such coatings is not fully understood yet. In this study, the influence of the original substrate grain size (coarse-grained, fine-grained) and the substrate treatment (as-sintered, wet blasted, ground or polished) on the grain size, preferred orientation of crystallites and residual stress in Ti(C,N)/Al2O3 coatings was systematically investigated. The microstructure analyses carried out using scanning electron microscopy with electron backscatter diffraction and symmetrical X-ray diffraction (XRD) revealed that the utilization of fine-grained substrates and the substrate treatment reduce the grain size in both layers, and increase the preferred orientations 〈211〉 and 〈0001〉 of fcc-Ti(C,N) and α-Al2O3 crystallites, respectively. In α-Al2O3, the microstructure changes are mainly connected with the morphology of the bonding layer, as it follows the morphology of the fcc-Ti(C,N) facets. The residual stress analyses done using glancing angle X-ray diffraction (GAXRD) disclosed a reduction of the tensile thermal stress in α-Al2O3 layers that were deposited on coarse-grained substrates. The residual stress in fcc-Ti(C,N) was substantially less reduced in the whole fcc-Ti(C,N)/α-Al2O3 stacks than in the reference fcc-Ti(C,N) monolayers. Vice versa, fcc-Ti(C,N) in the full stacks contained less crystal structure defects and lower microstrain than in the reference fcc-Ti(C,N) monolayers, because they were exposed to higher temperatures.

Influence of thermal annealing on silicon negative ion implanted SiO2 thin films

SiO2 thin film of thickness 300 nm grown on p-type silicon substrate was implanted with 100 keV silicon negative ions with fluences varying from 5×1015 to 1×1017 ions cm−2. The implanted samples were annealed at the temperature of 500 °C under N2 ambient. Electron spin resonance (ESR), Fourier transform infrared (FTIR), Photoluminescence (PL), and glancing angle X-ray diffraction (GXRD) techniques have been used to investigate the implanted SiO2 thin film after thermal annealing. ESR studies revealed the absence of vacancy defects after thermal annealing. FTIR studies showed variations in the vibrational modes, attributed to the formation of new structures after annealing at 500 °C. PL studies showed the presence of a peak at 720 nm with an intensity higher than that observed for the unannealed SiO2 samples. This effect showed a decrease in the non-radiative defect centers with an increase in the radiative Si:SiO2 interface states after thermal annealing. The presence of an additional peak at 692 nm may be attributed to the radiative recombination centers associated with silicon nanoclusters formed after annealing at 500 °C. GXRD studies showed a decrease in the intensity of the spectra for the samples implanted with 1×1016 and 5×1016 ions cm−2 after thermal annealing at 500 °C. This result reveals the formation of new SiOx structures in SiO2 thin film.

Quantification of 1.75 MeV Xe5+ induced defects in zirconia doped ceria (Ce0.8Zr0.2O2)

This study investigates the structural stability of the CeO2-ZrO2 system when subjected to high doses of irradiation (a few hundred displacements per atom). The goal is to explore their potential use in safe immobilization of spent nuclear fuel and development of accident-tolerant fuels for next-generation nuclear reactors. Highly dense pellets were synthesized using a solid-state reaction and then irradiated with 1.75 MeV Xe5+ ions at ion fluences ranging from 1 × 1015 to 1 × 1017 ions/cm2. Structural and microstructural analyses were conducted using glancing angle x-ray diffraction, micro-Raman spectroscopy, and scanning electron microscopy. The results indicate that Ce0.8Zr0.2O2 has a high tolerance against irradiation-induced phase transformation or amorphization but does generate irradiation-induced point defects. Each energetic ion produced a deformed region with a voluminous swelling of ∼0.61 ± 0.09 nm and a damaged zone of ∼0.09 ± 0.02 nm, as calculated from the irradiation-caused peak broadening that is explained by a three-step damage accumulation model. The electron microscopy studies show that grain boundaries serve as a sink for defects, and an increase in grain size was observed due to defect accumulation inside the grain's volume. Overall, the study shows that polycrystalline fluorite-structured Ce0.8Zr0.2O2 is a promising nuclear material for advanced energy systems as it did not show significant structural damage such as amorphization and grain fragmentation, even on irradiation at a high dose of ∼428 dpa.

Bismuth Phase Dependent Growth of Superconducting NiBi3 Nanorods

We report a study on the growth of NiBi3 nanowires and nanorods during the preparation of superconducting NiBi3 films by co-evaporation of Ni and Bi. We find that NiBi3 films grown via co-evaporation of Ni and Bi metals achieve higher transition temperatures (4.4 K) compared even to the single crystal NiBi3. However, in certain parameter space, the film surfaces were spattered with nanoscale features, such as nanowires and nanorods. Ambient temperature deposition resulted in poly-crystalline NiBi3 nanorods which were controllable with the evaporation rate of Bi. Deposition at elevated temperatures promoted the emergence of long single crystalline NiBi3 nanorods. High resolution transmission electron microscopy measurements confirmed the crystalline behaviour of the nanorods. We believe that NiBi3 nanowires form in a process analogous to the well known vapor-liquid-solid process, as we observe an amorphous Bi cap on the nanorods. From glancing angle X-ray diffraction measurements we identify that the presence of trigonal Bi with hexagonal primitive cell in the film promotes the nucleation of nanorods. Electrical transport on a single NiBi3 nanowire shows a superconducting transition of 4.3 K.

Effect of Nitrogen Partial Pressure on Structure, Mechanical Property, and Corrosion Behavior of ZrNx Films Prepared by Reactive DC Magnetron Sputtering.

ZrNx films were deposited by DC magnetron sputtering with pure Zr target in different nitrogen partial pressure atmospheres (r = N2/[Ar + N2]). The structure and composition of the thin films were characterized as a function of r using scanning electron microscope, glancing angle X-ray diffraction, and X-ray photoelectron spectroscopy. The hardness, adhesive strength, and corrosion behavior of the coatings were measured by nanoindentation, microscratch, and potentiodynamic measurements in 3.5 wt% NaCl solution. The results show that the structure of the ZrNx films changes from a nearly stoichiometric ZrN with a typical columnar structure to mixed phases composited of ZrN and α-ZrNx with a dense glass structure as r increases from 12% to 50%. The mechanical properties including hardness, elastic modulus, and adhesion decrease with increasing r due to nonstoichiometric compound and glass phase structure of the coatings, while the dense glass structure significantly improves the corrosion inhibition.

Changes in the structure and D desorptive release from W-D co-deposit layers caused by thermal annealing

The annealing of ∼1 μm thick tungsten–deuterium co-deposit layers produced at 320 ± 25 K is found to induce changes in the desorptive release behavior and crystal structure. The changes in co-deposits were revealed by annealing in the temperature range 273–1273 K, examining the crystal structure with glancing angle X-ray diffraction, re-populating traps remaining following the anneal, by D plasma exposure at 373 K, then re-examining the co-deposits with glancing angle X-ray diffraction and scanning electron microscopy, before performing thermal desorption mass spectrometry to ascertain the effect of annealing on trap concentrations. The results indicate that low temperature W-D co-deposit layers are prone to the development of a significant fraction of deuterium retention sites, with a predominant thermal release that begins at ∼400 K and ceases approaching ∼1000 K. Increased annealing temperature is found to progressively depopulate and remove low temperature deuterium retention sites, as suggested by an inability to re-populate those sites with the deuterium plasma. Scanning electron micro-graphs show marked differences at the anneal temperature extremes, with surface conversion from a dendritic appearance at 320 K to a nodular appearance at 1273 K. X-ray diffraction reveals two W phases initially present as 320 K, namely the α-W BCC and β-W A15 crystal phases, the latter of which rapidly anneals out above 490 K leaving only increased Bragg reflection from the α-W phase at the higher annealing temperature.

Electrochemical noise energy generated by nickel electroplating process

AbstractThe effects of current density (Jk) and bath temperature on the structure of deposition layer of nickel and electrochemical noise energy (ED) are studied, and the relationship between the structure of the deposit and ED is also discussed in detail using electrochemical noise technique in coupled with the scanning electron microscopy and the glancing angle X-ray diffraction techniques. The results show that ED theoretically mainly reflects the severity or rate of the local cathodic reaction rather than the integral cathodic reaction, and is markedly influenced by the electroplating current density (Jk)-depended nucleation/growth kinetics of the nickel deposit film. The proceeding of the nucleation (or the formation of new phase)/growth process of crystal nucleus on a foreign substrate possesses much more effect on ED value than the subsequent homogenous growth of the already formed film particles, and the factors which can accelerate the drastic change of the electrode surface state should result in large ED value.

Fractal characterizations of MeV ion treated CaF2 thin films.

We present the morphological evolution and fractal characterizations of CaF2 thin-film surfaces modified by bombardment with 100 MeV Au+8 ions at various fluences. Atomic force microscopy (AFM) combined with line profile and two-dimensional power spectral density (2D-PSD) analysis was utilized to investigate the evolution of surface morphology as a function of fluence. The AFM images were utilized to investigate the relationship between fractal dimension, roughness exponent, lateral correlation length, and ion fluence. The surface erosion owing to sputtering was depicted using Rutherford backscattering spectrometry. The structural characteristics' dependency on fluence was explored with the help of glancing angle x-ray diffraction measurements on virgin and irradiated samples. Tensile stress calculated using a peak shift in the glancing angle x-ray diffractogram showed an increase in tensile stress with fluence that caused the surface to crack after the fracture strength of the surface was crossed. 2D-PSD analysis signified the role of sputtering over surface diffusion for the observed surface modifications. Fractal dimensions first increased and then decreased with ion fluence. The lateral correlation length decreased, while the roughness exponent increased with fluence after the threshold value.

Study of the structural, morphological and optical properties of ZnSe doped with Yb3+

A wurtzite phase of Zn 1−x Yb x Se (0 ≤ x ≤ 1.8) nanoparticles was synthesized through photo assisted chemical bath deposition. Glancing angle X-ray diffraction disclosed a hexagonal wurtzite crystal structure. The crystallite size (D) of undoped ZnSe was estimated 24.40 nm and then gradually decreased to 4.66 nm, after Yb 3+ doping. Scanning electron microscopy images revealed that with an increase in the Yb 3+ concentration, the thin film morphology transformed from Nano-flakes to spherical particles. The expected elements were confirmed by elemental energy X-ray dispersive analysis. Raman spectroscopy revealed the existence of two distinct optical phonon peaks induced by first- and second-order longitudinal vibration peak located at 257 and 500 cm -1 , respectively. UV–visible spectroscopy elucidated that the absorption spectra showed that the band gap energy for undoped ZnSe thin films can be tuned in the range of 2.76 - 3.12 by varying Yb 3+ concentration. Photoluminescence analysis revealed two emission and shoulder peaks located at 3.19 eV, 2.37 eV and 1.70 eV, which were ascribed to the band-to-band and imperfections of ZnSe, respectively. Chromaticity investigations revealed that the blue emission color was dependent on the concentration of Yb 3+ . The results suggest that Zn 1−x Yb x Se (0 ≤ x ≤ 1.8) is a promising candidate for blue-light emitting phosphor. The data that support the findings of this study are available from the corresponding author upon reasonable request.

A stearic acid/polypyrrole-based superhydrophobic coating on squeeze-cast Mg-Sr-Y-Ca-Zn alloys for improved salt-water corrosion

A polypyrrole (PPy) and stearic acid (SA)-based superhydrophobic coating was developed to improve the corrosion behavior of squeeze cast Mg-1.0 wt% Sr-1.0 wt% Y-0.6 wt% Ca-0.5 wt% Zn alloy in NaCl solution. The structure and morphology of the coating were analyzed using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), three-dimensional optical surface profilometer, glancing angle X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS) reveals variable coating thickness ranging from ~25–120 μm (depending on Mg alloy pretreatment with/without NaOH prior to coating) comprised of primarily Mg, C, O, Cl, and Zr species ascribed to a mixed composition of PPy, Mg(OH)2, and low amount of ZrO2 with mud-crack features and petal-like clusters. Although SA/PPy-based superhydrophobic coating (contact angle of static water droplets ~1640) can improve the corrosion resistance of bare Mg alloy drastically owing to the presence of thin air cushion between NaCl solution and Mg alloy surface preventing saltwater infiltration and advancement of Cl−-ions towards reactive Mg surface, however, the surface pretreatment in NaOH salt bath before superhydrophobic surface treatment has a profound effect on the interphase, bonding, and stability of the coating with Mg and associated corrosion phenomena. The Mg alloy without NaOH pretreatment (NPT) demonstrated excellent instantaneous corrosion resistance in 0.1 M NaCl confirmed by potentiodynamic polarization, polarization resistance (RP), and coating resistance (Rcoat) measured by electrochemical impedance spectroscopy (EIS). On the contrary, NaOH pretreated Mg alloys (1MPT, 5MPT) exhibited excellent corrosion protection ability (up to ~4-5 h) during long-term EIS study owing to the presence of Mg(OH)2 thick film deposited during pretreatment acting as a protective barrier preventing PPy degradation and Mg2+-ion diffusion to the outward surface. Overall, SA/PPy-based superhydrophobic coating juxtaposed with/or without surface pretreatment can shed new insight into the corrosion phenomena of squeeze cast Mg alloy in NaCl solution.

Role of IGZO thickness for oxygen reservoir control in stacked IGZO/ZrOx layers: Towards reliable, uniform performance of flexible random-access memories

For securing the enhanced properties in ZrOx based RRAMs, the roles of IGZO thickness in the switching window and stability of stacked IGZO/ZrOx RRAM devices are systematically investigated. The physical characteristics of the amorphous crystal structure of IGZO film and the variation of oxygen vacancy with IGZO thickness are validated by glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS) analysis. The reliable and uniform switching properties for bilayer RRAMs with (92 ± 2) nm IGZO films are obtained as a stable switching up to 103 cycles, ROFF/RON ratio (~102), and retention for 104 s. The improvement in the RRAM performances is interpreted with oxygen vacancy in the IGZO layer, which facilitates the role of oxygen reservoir owing to its oxygen-deficient composition to absorb/discharge oxygen ions. With respect to the switching mechanism, set cycles are governed by a trap-mediated space-charge-limited current (SCLC) conduction. Furthermore, the optimal IGZO thickness-based bilayer IGZO/ZrOx RRAM device on a flexible polyethylene terephthalate (PET) substrate is demonstrated with stable switching up to 103 cycles, ROFF/RON ratio (>10), and retention for 104 s, along with the stable performance under different bending radii. With the scheme of IGZO based oxygen vacancy control, IGZO/ZrOx bilayer-based RRAM devices are expected to be one of viable options for the flexible, wearable, and biomedical applications.

Surface Modification of 304L Stainless Steel and Interface Engineering by HiPIMS Pre-Treatment

A clean and defect-free substrate/coating interface is required to guarantee good adhesion of coatings under service conditions. For this purpose, an etching pre-treatment using High-Power Impulse Magnetron Sputtering (HiPIMS) was performed to modify the surface of 304L stainless steel. The effect of three etching procedures on the substrate properties, such as corrosion resistance and adhesion, was investigated with unprecedented spatial resolution and spectroscopic details. Glancing angle X-ray diffraction showed modification in phase content but no neoformation after steel etching. X-ray photoelectron spectroscopy confirmed the presence of etchant species (6–7 at.%) on the extreme surface of the substrate. Transmission Electron Microscopy and Atomic Probe Tomography showed that the interface was less than a few nanometers wide. Polarization curves in a nitric acid solution at boiling temperature showed, for the first time, that the Ti+ and Zr+ etchings decreased the corrosion current density compared to the untreated original surface. Scratch-test measurements indicated better substrate/coating adhesion using HiPIMS metal ion etching. Electrochemical characterization revealed that Zr etching and thin coating improve the anti-corrosion properties of stainless steel in strong nitric acid conditions.

Production of Antibacterial Activity and Bone Cell Proliferation by Surface Engineering of Ga‐ or Mn‐Doped Ceria‐Coated Biomedical Titanium Alloy

The present work reports a detailed interpretation of the role of Ga and Mn dopants, solid solubility mechanisms, charge compensation mechanisms, intervalence charge transfer, antibacterial performance, and cell attachment and proliferation. Sol–gel undoped and doped (1, 5, and 9 mol%) CeO2films are spin‐coated on 3D printed Ti6Al4V biomedical alloy substrates and annealed at 650 °C for 2 h in air. Material characterization includes scanning electron microscopy (SEM), 3D scanning laser confocal microscopy, glancing angle X‐ray diffraction (GAXRD), and X‐ray photoelectron spectroscopy (XPS). In vitro testing includes inhibition of bacterial growth, simulated body fluid (SBF) testing, and cell attachment and proliferation studies. The most significant outcome is that the bioactivity of ceria derives directly from the Ce3+concentration, which itself results from solid solubility (substitutional and interstitial) and charge compensation and redox. This challenges the common assumption of the dominance of oxygen vacancies in the performance of ceria. The antibacterial activity is dependent on the type, amount, and valence of the dopant, where opposite trends are observed for gram‐positiveStaphylococcus aureusand gram‐negativeEscherichia colibacteria. All of the doped samples result in enhanced cell proliferation, although this is greatest at the lowest dopant concentration. Surface hydroxyapatite formation on the samples is achieved by soaking in SBF at 2 weeks and 1 month.

Crystalline phase of TiO2 nanotube arrays on Ti–35Nb–4Zr alloy: Surface roughness, electrochemical behavior and cellular response

An investigation was made into the electrochemical, structural and biological properties of self-organized amorphous and anatase/rutile titanium dioxide (TiO 2 ) nanotubes deposited on Ti–35Nb–4Zr alloy through anodization-induced surface modification. The surface of as-anodized and heat-treated TiO 2 nanotubes was analyzed by field emission scanning electron microscopy (FE-SEM), revealing morphological parameters such as tube diameter, wall thickness and cross-sectional length. Glancing angle X-ray diffraction (GAXRD) was employed to identify the structural phases of titanium dioxide, while atomic force microscopy (AFM) was used to measure surface roughness associated with cell interaction properties. The electrochemical stability of TiO 2 was examined by electrochemical impedance spectroscopy (EIS) and the results obtained were correlated with the microstructural characterization. The in vitro bioactivity of as-anodized and crystallized TiO 2 nanotubes was also analyzed as a function of the presence of different TiO 2 polymorphic phases. The results indicated that anatase TiO 2 showed higher surface corrosion resistance and greater cell viability than amorphous TiO 2 , confirming that TiO 2 nanotube crystallization plays an important role in the material's electrochemical behavior and biocompatibility.

Corrosion Behavior of Mg(OH)2/Mg–Al Layered Double Hydroxides/AlO(OH) Composite Film Prepared by Steam Coating on Mg Alloy AZCa612

This study investigated the corrosion behavior of the corrosion-resistant films steam coated on AZCa612 magnesium alloy. The film samples were corroded by immersing them in 5 wt% NaCl aqueous solution for a predetermined time. The corroded films were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, glancing angle X-ray diffraction, Fourier transform infrared spectroscopy, potentiodynamic polarization measurements, hydrogen generation measurements, and electrochemical impedance spectroscopy. The amount of Mg–Al–CO3 layered double hydroxides (LDHs) in the film slightly decreased from the beginning of immersion to 120 h after immersion and gradually increased thereafter. Mg–Al–Cl LDHs were formed after 6 h of immersion and rapidly grew as the immersion progressed. In addition, even with the gradual decrease in the corrosion resistance of the film, there was no major damage observed on the substrates. These results indicate that the corrosion protection mechanism varied with the immersion time. The corrosion-resistant property under a short immersion time could be attributed to the high corrosion resistance of Mg(OH)2 and AlO(OH), whereas it is attributed to the coverage provided by the Mg–Al–Cl and Mg–Al–CO3 LDHs under a longer immersion duration.

Effect of Zr content on the structure and morphology of CrZrN thin films prepared by reactive DC magnetron co-sputtering method

In this research, nanostructured chromium zirconium nitride (CrZrN) thin film has been deposited on Si(100) substrates by reactive DC magnetron co-sputtering method without in situ substrate heating and post-deposition annealing. The effects of Zr content on thin film structure and morphology were investigated. The Zr content in the films were varied by applied the sputtering current of Zr target (Izr) in the range of 300 to 900 mA, whereas the current of Cr target was kept at 300 mA. The crystal structure, microstructure, morphology, thickness, and chemical composition were characterized by glancing angle X-ray diffraction (GA-XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques, respectively. The results showed that the increase of Izr not only increased the deposition rate, but also increased the Zr content of the as-deposited film ranging from 3.9 to 26.5 at%. The as-deposited thin films were formed as a (Cr,Zr)N solid solution, with fcc structure in (111) and (200) plane, where Cr atoms were replaced by Zr atoms in the CrN lattice. The 2θ diffraction peaks were shifted to the lower value as increase of Zr content which was obtained by increased Izr. The nanocrystalline CrZrN structure with crystal sizes smaller than 10 nm structure were calculated for as-deposited thin films. The lattice parameters increased from 4.187 to 4.381 Å, whereas the crystal size decreased from 8.3 to 6.4 nm. The FE-SEM images of all the CrZrN films exhibited compact columnar with dense morphology as a function of Zr content. Moreover, the thickness of the CrZrN thin films was increased of 302 – 421 nm.

Influence of helium ion radiation on the nano-grained Li2TiO3 ceramic for tritium breeding

Lithium titanium oxide (Li2TiO3) tritium breeder ceramic plates with nano- and coarse-grain size were fabricated. The preparation methods contained CTAB-modifying precursor, combining dry-pressing with isostatically cold-pressing, and calcinating at optimized sintering temperature in turn. Then their properties were characterized after radiation by 280 keV helium (He+) ion. Extensive characterization analyses were performed to reveal the changes in nano-grained and coarse-grained Li2TiO3 after radiation. They contained glancing angle X-ray diffraction (GIXRD), atomic force microscopy (AFM), electron spin resonance (ESR), and scanning electron microscopy (SEM). The results showed as follows, GIXRD peak position of the nano-grained Li2TiO3 was more stable than the coarse-grained Li2TiO3 after radiation. Nano-grained Li2TiO3 was less rough and swollen than the coarse-grained one after radiation. Nano-grained Li2TiO3 had more excellent structural stability and less defect concentration of Eʹ-center after radiation. As a result, nano-grained Li2TiO3 might have much better radiation tolerance than the coarse-grained one by comparing characterization results.

Effect of cerium-based conversion coating on corrosion behavior of squeeze cast Mg-4 wt% Y alloy in 0.1 M NaCl solution

Cerium-based conversion coating (CeCC) has been utilized to improve the corrosion resistance of squeeze cast Mg-4wt%Y alloy in 0.1 M NaCl solution. The morphology and composition of the coating analyzed using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), glancing angle X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS) demonstrate the formation of few microns thick pseudo-crystalline phase(s) composed of mainly Mg, O, C and Y species, assigned to hydrated Y(III) (Y(OH)3/Y2O3) CeO2, Mg(OH)2, and lower amount of PO43− ions with mud-crack morphology. The duration of the treatment in cerium nitrate salt bath has a pronounced effect on the evolution of the coating with 30 s treatment demonstrated the formation of uniform coating with dehydrated cracks that becomes loose and porous with nodular CeO2 precipitates for longer duration (1800 s). Potentiodynamic polarization (PDP) and mass loss test reveals that CeCC effectively reduces the corrosion rate by ~50–70% compared to base alloy, with the pitting corrosion around the second phase being the dominant mechanism due to the formation of the micro-galvanic couple between α-Mg phase and Mg24Y5 precipitates. The deep pit formation was severe around Y-rich cathodic sites due to the formation of Y(OH)3/Y2O3 as the corrosion products confirmed by EDX and elemental mapping. Electrochemical impedance spectroscopy revealed that corrosion protection was provided mainly by the barrier layer at the coating/Mg interface with a progressive increase in diameter of the capacitive loop up to 24 h commensurate with the surge in double-layer film resistance (RP) and free corrosion potential (Ecorr) shift towards noble value. Overall, cerium nitrate salt bath treatment in the presence of hydrogen peroxide for short duration is effective to retard the severe corrosion of Mg-4wt%Y alloy in 0.1 M NaCl solution.