Lattice Parameter Of Phase Research Articles

An Investigative Study on the effect of Dopants on Manganese Based Mixed Nano Ferrites Synthesized through Sol-Gel Method

The present article investigates the effect of different dopants on manganese based mixed nano ferrites synthesized through sol-gel method.MnF, MnCoF and MnCoMgF (MnFe2O4, Mn0.5Co0.5Fe2O4andMn0.5Co0.25Mg0.25Fe2O4) were synthesized by Sol-gel method. The structural, magnetic and optical properties of the samples were analysed through XRD(X-RayDiffractometer), VSM (Vibrating Sample Magnetometer,) and UV-Visible Spectroscopy. The phase identification and lattice parameter determination were carried out by using X-RayDiffraction and hence the crystallite size and X-Ray density were calculated. Peaks (220), (311), (400), (511), and (440) were obtained from the XRDpattern of the samples, which confirmed their single-phase cubic spinel structure. It was observed that because of the large ionic radius of Co2+ (0.745 Å) ions as compared to that of Fe3+ (0.645 Å) ions, lattice parameter of MnCoF increased in comparison with that of MnF but, the substitution of Mg2+ to MnCoF sample decreased the lattice constant. By investigating the hysteresis loops produced by the samples in the VSM analyses, it was found that the MnF have low coercivity and moderate saturation magnetization amongst the three. The substitution of Mg2+ in MnCoF sample decreased the value of saturation magnetization. UV-Visible analysis was used to determine bandgap energy of three samples.From the Tauc plot, we can observe bandgap energies of 3.202 eV, 3.180 eV and 3.239 eV, for MnF, MnCoF and MnCoMgF respectively.On substituting with the Co2+ in MnF the band gap of sample decreases indicating quantum confinement phenomenon.When substitution was done both Co2+ and Mg2+, the band gap energy value increases.

Evaluation of solid particle erosion and electrochemical corrosion of plasma-sprayed WC/8YSZ coating on SS316

Plasma spray coating enhances the corrosion and wear resistance of the stainless steel structures installed in marine applications. Hence, it is imperative to study the effectiveness of various coating combinations on the material’s performance. The present work investigates the effects of three different plasma-sprayed coatings on the wear and corrosive resistance of austenitic stainless steel (SS316). The three compositions of the coating were prepared using (i) Tungsten carbide (WC), (ii) 8 wt%. Yttria Stabilized Zirconia (8YSZ), and (iii) 50 wt%. Tungsten carbide (WC) with 50 wt%. Yttria Stabilized Zirconia (8YSZ). Experiments were conducted as per ASTM G76 to determine the erosive wear with a mixture of high-velocity air and Al2O3 abrasive particles. The corrosive medium used in the electrochemical polarisation tests was 3.5 wt%. NaCl. A scanning electron microscope (SEM) was used to examine the surface morphology of the eroded and corroded coatings. Energy Dispersive x-ray Analysis (EDAX) and X Ray Diffractrometry (XRD) analysis were carried out to reveal the phase composition, elemental distribution, and lattice parameters of uncoated and coated samples. The study reveals that the composite coating (WC + 8YSZ) have superior wear resistance when exposed to a high-velocity erodent. Due to the robust particle adhesion and cohesiveness of the (WC + 8YSZ) composite coating, crack initiation and propagation are rarely found on the surface of the composite coating, as evidenced by the surface wear morphology analysis. Further investigation reveals that the 8YSZ coating has excellent corrosion resistance. The SEM-based corrosive wear topography analysis reveals that the 8YSZ phase on the coated surface acts as a diffusion barrier to the electrolytic medium and a passive protective layer over the coating. Consequently, the micro-chipping of particles during exposure to the corrosive medium is prevented.

Synthesis of transition metal carbides and high-entropy carbide TiZrNbHfTaC5 in self-shielding DC arc discharge plasma

The paper shows the feasibility of synthesizing micro- and nano-sized particles of binary metal carbides (Me–C) and high-entropy carbide (HEC) TiZrNbHfTaC5 by vacuum-free electric arc method. The method is based on the effect of self-shielding of the reaction volume from atmospheric oxygen by carbon monoxide CO, which is generated during arcing in air. The synthesis results in a solid solution with a NaCl-type carbide with a cubic lattice, which simultaneously contains atoms of titanium, zirconium, niobium, hafnium, tantalum, and carbon. The lattice parameter of the HEC TiZrNbHfTaC5 phase is ∼4.532 Å that is in line with the known data on this compound. The synthesis product contains micro-sized particle agglomerates of transition metal carbides. The synthesis products also contain nano-sized particles with a shell-core structure, in which the core can consist of metal carbide (TiC, ZrC, NbC, HfC, TaC) or HEC TiZrNbHfTaC5, and the shell is a graphite phase.

Correlation between the Dendritic Structure and Lattice Parameter of γ'-Phase in Single-Crystalline Turbine Blades Made of Superalloys.

The dendritic structure and the distribution of the γ′-phase lattice parameter (aγ′) along selected lines of the longitudinal section in a model single-crystalline blade made of CMSX-4® nickel-based superalloy were studied. It was established that there is a correlation between the value of the aγ′ and the predomination of initial or ending fragments of the secondary dendrite arms. It is most noticed for the areas where the dendrite growth conditions are similar to steady. They are located in the center and near the root’s selector extension (SE) area. The correlation has been related to the dendritic segregation mechanism. It was shown that in the single-crystalline blades obtained by the directional crystallization using a spiral selector, the “walls” of the primary dendrite arms that grow at a low angle to the blade axis are created. It was found for the first time that the value of the lattice parameter aγ′ is decreased near such “walls”. Additionally, it was found that competitive growth of the dendrites may occur at a distance of even several millimeters from the bottom surface of the root. The first-time applied X-ray diffraction measurements of aγ′ made in a single-pass along the line allow the analysis of the dendritic segregation in the whole blade cast.

Sintering behavior, microstructure and mechanical properties of NbC-Ni alloys with different carbon contents

This work aims to study the influence of the carbon content in a (NbC-3vol%Mo2C)-12vol%Ni-0.5vol%WC alloy on the sintering process, and its resulting effect on the microstructure and mechanical properties. NbC cemented carbides with additions of Mo or C were sintered at 1450 °C for 1 h in the vacuum furnace of a dilatometer and of a TGA (Thermogravimetric Analysis) device. Liquid phase sintering temperature is decreased with addition of Mo or C, leading to an early densification which limits nickel evaporation. Swelling occurs during heating in the 3 phase (NbC + Ni + liquid) domain for the high carbon content alloys. A graphite phase is observed for largest carbon contents. The C/Mo ratio also affects the phase composition and lattice parameters. The lattice parameter variation of the carbide and Ni rich-binder is explained by the variation of the metallic solute contents as a function of the overall composition. Grain growth is globally enhanced by increasing the carbon content. A significant effect of C/Mo ratio on the mechanical properties of the alloy is also observed. The Vickers hardness (HV30) decreases while the toughness (KIc) exhibits a maximum value as the carbon content increases.

Super-hardening and localized plastic deformation behaviors in ZrB2 –TaВ2 ceramics

A systematic study of the Zr-Ta-B system was performed using thermodynamic and ab initio modeling, nanoindentation, and high-resolution TEM and XRD experiments. The phase diagram (convex hull) of the Zr-Ta-B system was constructed at 0 K, and phase stability, lattice parameters, and mechanical properties of ZrB2-TaB2 solid solutions were ascertained in silico. Dense ceramics were manufactured by the combination of combustion synthesis and hot pressing techniques. As opposed to theoretically predicted complete solubility in the ZrB2-TaB2 solid solution series, the highest experimentally attained Ta content in the ZrB2-based solution was 25–27 at%, suggesting that at higher Ta contents a non-equilibrium phase composition is formed during combustion synthesis and inherited during hot pressing. Single-phase ZrB2-TaB2 solid solutions displayed a super-hardness up to 70 GPa and coefficient of elastic recovery as high as 99.7%, which surpasses wurtzite and cubic boron nitride and rivals polycrystalline diamonds. In the non-equilibrium samples with multiple solid solutions, a “pop-in” (localized plastic deformation) effect was discovered and attributed to the formation of shearing bands, microtwins, and dislocation loops. The composition-dependent switching between super-hardened and locally plastic mechanical behavior allows the creation of a new generation of ultra-high temperature ceramic composites.

X-ray, IR and SEM studies on some Li-Cd ferrites

Lithium-Cadmium ferrites with general formula Li0.5-x/2 Fe2.5-x/2 Cdx O4 (with x = 0,0.1,0.2....,0.7) were prepared by standard ceramic method. X-ray diffraction studies confirms single phase formation and lattice parameters were calculated. The crystal structure is cubic and lattice parameter increases with increasing Cd content. The infrared absorption (IR) spectra of all the samples were recorded in the range 200-800 cm-1 at room temperature in the KBr medium. Lithium ferrite shows four principal bands and some shoulders have been observed. The force constants Kt and Ko were calculated using Waldron's analysis. Scanning electron microscopy studies shows increase in grain size up to x = 0.1 and then the grain size decreases with increase in cadmium content.

Effects of Ag modified TiO2 on local structure investigated by XAFS and photocatalytic activity under visible light

Silver modified titanium dioxide (Ag-TiO2) nanoparticles at different loading (3–10 mol%) were synthesized via dry and wet ball milling sol-gel method. Effects of doped Ag on local TiO2 structure were investigated. The presence of Ag+-ion in TiO2 structure was confirmed by XANES and EXAFS findings, resulting in Ag substitution and oxygen vacancy in TiO2. The phase transformation and modification of lattice parameters of anatase and rutile phases in the TiO2 structure following Ag doping were revealed by XRD and XANES and confirmed that Ag was successfully introduced into the TiO2 structure. When Ag doping content was increased from 3% to 10%, the number of Ag nanoparticles deposited on the TiO2 surface increased. The low Ag doping contents (3% and 5% Ag-TiO2) displayed better photocatalytic activity of 3.5 mg/L MB degradation under visible light than the high Ag doping contents (6% and 10% Ag-TiO2).

The effects of donor (Nb5+) and acceptor (Cu2+, Zn2+, Mn2+, Mg2+) doping at B-site on crystal structure, microstructure, and electrical properties of (Ba0.85Ca0.15)Zr0.1Ti0.9O3 ceramics

(Ba0.85Ca0.15)Zr0.1Ti0.9O3 (BCZT) ceramics with donor (Nb5+) and acceptor (Cu2+, Zn2+, Mn2+, Mg2+ ions) doping at B-site were fabricated in this study. The effects of crystal structure, microstructure, and chemical defects, on dielectric properties and piezoelectric coefficient (d33) of all samples, were observed. The addition of Mn2+ and Mg2+ ions could reduce the sintering temperature of BCZT from 1450 °C to 1300 °C; meanwhile, the others did not affect the microstructure of BCZT significantly. The ion substitution influenced the phase fraction, lattice parameters, and tetragonality of BCZT ceramic. The addition of Mg2+ ions decreased greatly Tm of BCZT from ~117 °C to ~76 °C. The addition of Nb5+, Cu2+, and Mn2+ shifted Tm of BCZT to higher temperature. The relationship between decrease of tetragonality and decrease of Tm was observed in these ceramics. The diffuse dielectric behavior of the doped BCZT was induced due to microscopic heterogeneity in the composition. The change in microstructure and the formation of chemical defects (A-site vacancies and oxygen vacancies) significantly affected the polling condition of BCZT ceramic. The crystal structure, microstructure, dielectric, and piezoelectric properties of BCZT ceramic could be modified using these dopants. The results here suggested that BCZT ceramics might become an alternative material for dielectric and piezoelectric devices.

Albumen-assisted Synthesis of Nanocrystalline Nickel Ferrite Photocatalyst

Abstract: As a simple step to remove the polluting dyes in aqua ecosystem, NiFe2O4 nanoparticles well known for their ferromagnetic properties, low conductivity and high electrochemical stability were prepared by simple auto combustion method using egg white as fuel via green synthesis route. The structural, morphological and magnetic properties of prepared NiFe2O4 was analyzed. The desirable phase purity of the prepared spinel ferrite was deliberated by X-ray Diffractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive and Vibrating Sample Magnetometer (VSM). XRD predicts the phase formation, particle size and lattice parameter of the spinel ferrite. The FTIR spectrum confirms the ferrite structure. The morphological and elemental analysis was made using SEM and EDAX. The hysteresis curve reveals the magnetic properties, such as remanence magnetization (Mr), coercivity (Hc) and saturation magnetization (Ms). The photocatalytic efficiency of the synthesized samples was determined from degradation of methylene blue dye. The whole process was monitored using spectrophotometer at regular intervals of time. The maximum photocatalytic degradation efficiency for NiFe2O4 is around 95.6 %. Keywords: NiFe2O4, Ferrite, Green synthesis, Egg white, Combustion, Photocatalyst.

Theoretical predictive screening of noble-metal-containing M3AuC2 (M = Ti, V, and Cr) MAX phases

Using first-principles density functional theory (DFT), the ground state physical properties of the newly synthesized noble-metal-containing Ti3AuC2 MAX phase have been investigated. The effect of transition-element Ti replacement (V and Cr) on physical properties, including structural, elastic, electronic, thermal, and optical are presented. The optimized lattice parameters of Ti3AuC2 MAX phase are in good agreement with the experimental values and decrease when we replace Ti with V and then Cr. The magnetic properties of M3AuC2 are predicted by using generalized gradient approximation (GGA) incorporating onsite electron correlation parameter (Hubbard U parameter) within DFT. Out of three studied MAX phases, V3AuC2 and Cr3AuC2 phases exhibit magnetism. The thermodynamical stability of M3AuC2 (M = Ti, V, and Cr) phases is discussed by the formation enthalpy with respect to their most competing phases. The electronic structure reveals that these phases have metallic nature and are electrically anisotropic. The M−element replacement has an effect on the bonding properties of M3AuC2. The bonding between M−C is in the order of Cr3AuC2 > V3AuC2 > Ti3AuC2 according to their peak positions and heights of density of states in the occupied site, which is also confirmed from the charge density distribution. The elastic properties indicate that M3AuC2 phases are ductile, machinable, less stiff, and better resistant to thermal shock and are elastically anisotropic. To understand the properties of M3AuC2 for the extreme environment, we employed a quasi-harmonic Debye model at the pressure and temperature range of 0–50 GPa and 0–1600 K, respectively. Additionally, we evaluated thermal conductivity and melting temperature to further understand the potential of these MAX phases in coating applications at elevated temperature. In relation to optical properties, these MAX phases have a reasonable absorption coefficient in the visible as well as in the ultra-violet regions. The reflectivity of M3AuC2 phases is polarization dependent and of 45 % against the visible region, which reveals its potential as coating material to minimize solar heating.

Crystallization and Dielectric Properties of BaO-SrO-PbO-TiO2-Nb2O5-SiO2 Glass-Ceramic Composites with La2O3 Addition

Glass-ceramic composite samples with different La2O3 content were prepared via melt-quenching followed by controlled crystallization. X-ray diffraction(XRD) analysis reveals that when the addition amount of La2O3 in the glass sample is less than 1mol%, two phases of perovskite structure and tungsten-bronze structure are formed after annealing at 1000°C for 3h. When the addition amount of La2O3 in the glass sample is increased to 2mol%, a new phase of pyrochlore structure is formed. Moreover, the addition of La2O3 causes the change in the lattice parameters of the glass-ceramic crystal phase. The microstructure observed that the ceramic phase grain size is in the nanometer level. The shape of some grains becomes an elongated structure when the La2O3 content in the sample increases to 2 mol%, and the grain size is increased significantly. The dielectric constant of the BaO-SrO-PbO-TiO2-Nb2O5-SiO2 glass-ceramic system is decreased with the increase of La2O3 addition, and the dielectric loss of the sample is decreased to the range of 0.003-0.008. The electric field stability of the dielectric constant was significantly improved with the addition of La2O3, indicating that adding a certain proportion of La2O3 to the BaO-SrO-PbO-TiO2-Nb2O5-SiO2 glass-ceramic system can effectively improve the dielectric properties, and it has a promising application as a dielectric material.

Depth profiling characterization of the nitride layers on gas nitrided commercially pure titanium

The thermochemical gas nitriding of the commercially pure titanium was conducted in a pure nitrogen atmosphere under the pressure of 2.5 × 105 and 4 × 105 Pa at the temperature ranging between 800 and 1323 K for 8 and 36 hours. The surface microstructures, chemical composition and hardness of the nitrided specimens were characterized using the scanning electron microscopy (SEM), Glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), X-ray photoelectron spectroscopy (XPS), and Vickers micro hardness tester. The nitrided layers, comprising TiN, Ti2N and TiN0.3 phases, as well as a solid solution of nitrogen in the titanium so called diffusion zone were formed during the gas nitriding process. The thickness of the nitrided layers and diffusion zone varied with the processing temperature and pressure. Furthermore, oxygen and carbon impurities were detected in the outermost titanium nitride layer. The influence of the processing temperature and pressure on the chemical and phase composition, microstructure development, lattice parameters, texture evolution, hardness and chemical state of the main elements in the nitrided layers have been discussed.

Effect of Carbon Partitioning and Residual Compressive Stresses on the Lattice Strains of Retained Austenite During Quenching and Isothermal Bainitic Holding in a High‐Silicon Medium‐Carbon Steel

The residual compressive stresses and dimensional changes related to the lattice strains of retained austenite (RA) phase in a high‐Si, medium‐carbon steel (Fe‐0.53C‐1.67Si‐0.72Mn‐0.12Cr) are investigated for samples austenitized and quenched for isothermal bainitic transformation (Q&B) in the range 5 s to 1 h at 350 °C. Also, samples are directly quenched in water (DWQ) from the austenitization temperature for comparison with Q&B samples. Field emission scanning electron microscopy (FE‐SEM) combined with electron backscatter diffraction (EBSD) analyses, and X‐ray diffraction are used to investigate the microstructural evolution, phase distribution, and lattice parameters of RA phase. While the Q&B samples showed formation of bainite and high‐carbon fresh martensite in conjunction with stabilization of various fractions of RA, the DWQ samples displayed nearly complete martensitic microstructure. For short holding durations (≪200 s), there was limited formation of bainite and the inadequate carbon partitioning to the adjacent untransformed austenite areas resulted in significant martensite formation and the associated c/a ratio of martensite resulted in high compressive residual stresses within the RA phase. While, at long isothermal holding times (≫ 200 s), there was a significant formation of bainite. The DWQ samples displayed maximum lattice strain in a small fraction of untransformed RA phase.

Investigation of the \u03b3\u2032 Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ/γ′ interface is strongly enriched in Co and Cr and depleted in Al.

In-situ XRD study of a Chromium doped LiNi0.5Mn1.5O4 cathode for Li-ion battery

This paper deals with structural (in-situ XRD) and electrochemical characterization of high-voltage lithium-ion cathode materials LiMn2O4 (LMO), LiNi0.5Mn1.5O4 (LNMO), and LiCr0.1Ni0.4Mn1.5O4 (LCNMO) prepared by solid-state synthesis. Structural in-situ X-ray diffraction spectra were measured by an affordable Rigaku diffractometer. Our synthesis route produced the samples with similar morphologies where the average particle sizes were 1.11 µm and 1.46 µm for LNMO and LCNMO respectively. Results of the Rietveld analysis brought detailed insight into two-phase structure transitions for LMO and three-phase transitions for LNMO and LCNMO. XRD study revealed differences in the structural behavior of LMO and LNMO prepared by solid-state synthesis compared to the results of other authors using the sol-gel synthesis route. In the case of chromium-doped LNMO, our results indicate ability of the chromium metal to effectively reduce Mn3+ content while the ordering of the structure increases. Chromium doping also promotes a larger lattice parameter in a fully delithiated state than in the case of undoped LNMO. Therefore, lowering of the volume changes was observed and faster phase II/III transition taking place, when Ni3+/Ni4+ redox pair was oxidized, was also identified. Cr doping of LNMO also promotes the reaching the lattice parameters of phases in both phase transitions and thus could reduce the internal stress of active material under high C-rate cycling. Results thus suggested that chromium doping can improve the stability of the inner structure and performance at higher charging C-rates even though the structure goes through a three-phase region during charging as undoped LNMO. The evaluation of diffusion coefficients of Cr-doped LNMO revealed increased diffusivity in a full discharge state and as the cathode underwent the cycling the differences in diffusivity seemed to be more pronounced.

Effect of Fe and Al on hydrogen storage properties of 75 V-Ti-Cr alloys

V-based hydrogen storage alloys are considered promising materials with high hydrogen capacity under ambient conditions. 75 V-Ti-15Cr alloys with different Fe and Al addition (1–3 at%) have been investigated. All the alloys are confirmed to show body-centered tetragonal (BCT) structure after dehydrogenated at room temperature. The PCT tests manifest that the hydrogen storage capacity decreases and desorption plateau pressure rises with the content of Fe or Al. The relationship between the hydrogen storage property and lattice parameters of BCT phase is discussed. Also, the relationship between hydrogen capacity and electron density is analyzed. Among the studied alloys, the 75 V-Ti-15Cr-1Al-1Fe alloy shows optimal hydrogen storage capacity (2.26 wt%) and plateau pressure (0.5 MPa) at room temperature. Cycle test proves that the optimized 75 V-Ti-15Cr-1Al-1Fe alloy possesses excellent durability and the retention rate of hydrogen capacity can achieve 97% after 100 cycles. The slight capacity attenuation possibly results from the derivation of lattice defects and small contraction of the hydrogen absorption phases.

The Influence of the Cooling Bores on Crystal Orientation and Lattice Parameter in Single-Crystalline Cored Turbine Blades.

The areas located near the cooling bores of single-crystalline cored turbine blades made of nickel-based CMSX-4 superalloy were studied. The blades were solidified by the vertical Bridgman technique in the industrial ALD furnace. Longitudinal sections of the blades were studied by Scanning Electron Microscopy, X-ray diffraction topography, X-ray diffraction measurements of the γ′-phase lattice parameter a, and the α angle of the primary crystal orientation. The local changes in α were analyzed in relation to the changes of the dendrite’s growth direction near the cooling bores. It was found that in the area approximately 3 ÷ 4 mm wide around the cooling bores, changes of α and a, both in the blade root and in the airfoil occurred. The local temperature distribution near the cooling bores formed a curved macroscopic solidification front, which caused changes in the chemical composition and, consequently, changes in the a value in a range of 0.002 Å to 0.014 Å. The mechanism of alloying elements segregation by tips of the dendrites on the bent solidification front was proposed. The multi-scale analysis that allows determining a relation between processes proceed both on a millimeter-scale and a micrometric and nanometric scale, was applied in the studies.

Microstructure and hydrogen storage properties of Ti10+xV80-xFe6Zr4 (x=0~15) alloys

The microstructure and hydrogen storage properties of Ti10+xV80-xFe6Zr4 (x = 0, 5, 10, 15) alloys have been studied. XRD and SEM analyses show that all alloys consist of a BCC main phase and a small fraction of C14 Laves secondary phase, in which the latter precipitates along the grain boundary of the former becoming network structure. With increasing Ti content in the alloy, the lattice parameter and cell volume of the BCC main phase of the alloy increase. The chemical composition of each phase is analysed by EDS, from which the lattice parameters of BCC phase have a good linear relationship with their average atomic radii. All bulk alloys have good activation behaviors and hydriding kinetics. With the increase of Ti content, the incubation time for activation decreases first and then increases under an initial hydrogen pressure of 4 MPa at 298 K. The incubation time of Ti15V75Fe6Zr4 alloy is only 12 s. It is one of the shortest incubation time in V-based solid solution alloys as far as we know, which may be related to the existence of C14 Laves phase. All the alloys have relatively high hydrogen absorption capacities of above 3 wt%, which increase first and then decrease as the Ti content increases, achieving the maximum capacity of 3.61 wt% at x = 10 at 298 K. With increasing x, the equilibrium plateau pressure of dehydrogenation of the samples at 353 K decreases owing to the expansion of unit cell of main phase, which is far below 0.1 MPa for x = 10 and 15. The maximum desorption capacity of 1.94 wt% (desorbed to 0.001 MPa) is obtained at x = 5, compared to that of 1.6 wt% (desorbed to 0.1 MPa) achieved at x = 0.

Enhancing the Corrosion Resistance of Austenitic Steel Using Active Screen Plasma Nitriding and Nitrocarburising.

AISI 316L steel was subjected to active screen plasma nitriding and nitrocarburising. The processes were carried out at 440 °C for 6 h. The nitriding process employed an atmosphere of nitrogen and hydrogen, while nitrocarburising was carried out in nitrogen, hydrogen and methane. The processes yielded structures consisting of nitrogen and nitro-carbon expanded austenite, respectively. Microhardness was measured via the Vickers method, surface roughness using an optical profilometer, microstructure by means of light microscopy, while a scanning electron microscope (SEM) served to determine surface topography. Phase composition, lattice parameter and lattice deformation tests were carried out using the X-ray diffraction (XRD) method. Corrosion resistance measurements were performed in a 0.5 M NaCl solution using the potentiodynamic method. The produced layers showed very high resistance to pitting corrosion, while the pitting potential reached 1.5 V, a value that has not yet been recorded in a chloride environment. After the passive layer was broken down, there was a clear deceleration of pitting in the nitrocarburised layer. It was found that in the case of nitro-carbon expanded austenite, pits are formed much slower compared to the nitrogen austenite layer.