Beta Phase Research Articles

Intracranial EEG signals disentangle multi-areal neural dynamics of vicarious pain perception

Empathy enables understanding and sharing of others’ feelings. Human neuroimaging studies have identified critical brain regions supporting empathy for pain, including the anterior insula (AI), anterior cingulate (ACC), amygdala, and inferior frontal gyrus (IFG). However, to date, the precise spatio-temporal profiles of empathic neural responses and inter-regional communications remain elusive. Here, using intracranial electroencephalography, we investigated electrophysiological signatures of vicarious pain perception. Others’ pain perception induced early increases in high-gamma activity in IFG, beta power increases in ACC, but decreased beta power in AI and amygdala. Vicarious pain perception also altered the beta-band-coordinated coupling between ACC, AI, and amygdala, as well as increased modulation of IFG high-gamma amplitudes by beta phases of amygdala/AI/ACC. We identified a necessary combination of neural features for decoding vicarious pain perception. These spatio-temporally specific regional activities and inter-regional interactions within the empathy network suggest a neurodynamic model of human pain empathy.

Development of Novel Antibacterial Ti-Nb-Ga Alloys with Low Stiffness for Medical Implant Applications.

With the rising demand for medical implants and the dominance of implant-associated failures including infections, extensive research has been prompted into the development of novel biomaterials that can offer desirable characteristics. This study develops and evaluates new titanium-based alloys containing gallium additions with the aim of offering beneficial antibacterial properties while having a reduced stiffness level to minimise the effect of stress shielding when in contact with bone. The focus is on the microstructure, mechanical properties, antimicrobial activity, and cytocompatibility to inform the suitability of the designed alloys as biometals. Novel Ti-33Nb-xGa alloys (x = 3, 5 wt%) were produced via casting followed by homogenisation treatment, where all results were compared to the currently employed alloy Ti-6Al-4V. Optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) results depicted a single beta (β) phase microstructure in both Ga-containing alloys, where Ti-33Nb-5Ga was also dominated by dendritic alpha (α) phase grains in a β-phase matrix. EDS analysis indicated that the α-phase dendrites in Ti-33Nb-5Ga were enriched with titanium, while the β-phase was richer in niobium and gallium elements. Mechanical properties were measured using nanoindentation and microhardness methods, where the Young's modulus for Ti-33Nb-3Ga and Ti-33Nb-5Ga was found to be 75.4 ± 2.4 and 67.2 ± 1.6 GPa, respectively, a significant reduction of 37% and 44% with respect to Ti-6Al-4V. This reduction helps address the disproportionate Young's modulus between titanium implant components and cortical bone. Importantly, both alloys successfully achieved superior antimicrobial properties against Gram-negative P. aeruginosa and Gram-positive S. aureus bacteria. Antibacterial efficacy was noted at up to 90 ± 5% for the 3 wt% alloy and 95 ± 3% for the 5 wt% alloy. These findings signify a substantial enhancement of the antimicrobial performance when compared to Ti-6Al-4V which exhibited very small rates (up to 6.3 ± 1.5%). No cytotoxicity was observed in hGF cell lines over 24 h. Cell morphology and cytoskeleton distribution appeared to depict typical morphology with a prominent nucleus, elongated fibroblastic spindle-shaped morphology, and F-actin filamentous stress fibres in a well-defined structure of parallel bundles along the cellular axis. The developed alloys in this work have shown very promising results and are suggested to be further examined towards the use of orthopaedic implant components.

Laser surface cladding of CoNiCrAlY as Bond Coat on INCONEL718 substrate for thermal barrier coating application

This study delves into laser surface cladding of CoNiCrAlY onto Inconel718 employing a 6.6 kW continuous wave diode laser with varying process parameters. The resulting microstructure, microhardness, and isothermal oxidation resistance are meticulously assessed. Laser surface cladding yields a defect free microstructure with the presence of gamma (γ), gamma prime (γ’) and beta (β) phases. There is negligible dilution at the interface with a minimum HAZ. The average microhardness of the clad zone ranges from 425 to 465 HV, increasing with increase in scan speed and decrease in power. The high temperature oxidation resistance property of the clad surface is superior to the same developed by high velocity oxy fuel spraying.

Beyond alpha band: prestimulus local oscillation and interregional synchrony of the beta band shape the temporal perception of the audiovisual beep-flash stimulus

Objective. Multisensory integration is more likely to occur if the multimodal inputs are within a narrow temporal window called temporal binding window (TBW). Prestimulus local neural oscillations and interregional synchrony within sensory areas can modulate cross-modal integration. Previous work has examined the role of ongoing neural oscillations in audiovisual temporal integration, but there is no unified conclusion. This study aimed to explore whether local ongoing neural oscillations and interregional audiovisual synchrony modulate audiovisual temporal integration. Approach. The human participants performed a simultaneity judgment (SJ) task with the beep-flash stimuli while recording electroencephalography. We focused on two stimulus onset asynchrony (SOA) conditions where subjects report ∼50% proportion of synchronous responses in auditory- and visual-leading SOA (A50V and V50A). Main results. We found that the alpha band power is larger in synchronous response in the central-right posterior and posterior sensors in A50V and V50A conditions, respectively. The results suggested that the alpha band power reflects neuronal excitability in the auditory or visual cortex, which can modulate audiovisual temporal perception depending on the leading sense. Additionally, the SJs were modulated by the opposite phases of alpha (5–10 Hz) and low beta (14–20 Hz) bands in the A50V condition while the low beta band (14–18 Hz) in the V50A condition. One cycle of alpha or two cycles of beta oscillations matched an auditory-leading TBW of ∼86 ms, while two cycles of beta oscillations matched a visual-leading TBW of ∼105 ms. This result indicated the opposite phases in the alpha and beta bands reflect opposite cortical excitability, which modulated the audiovisual SJs. Finally, we found stronger high beta (21–28 Hz) audiovisual phase synchronization for synchronous response in the A50V condition. The phase synchrony of the beta band might be related to maintaining information flow between visual and auditory regions in a top-down manner. Significance. These results clarified whether and how the prestimulus brain state, including local neural oscillations and functional connectivity between brain regions, affects audiovisual temporal integration.

Calcium Phosphate Coatings Deposited on 3D-Printed Ti–6Al–4V Alloy by Plasma Electrolytic Oxidation

In this article, the process of creating calcium phosphate coatings through plasma electrolytic oxidation was investigated. Calcium phosphate coatings were deposited onto titanium substrates fabricated via the selective laser melting (SLM) method. The correlation between the characteristics of the coating and the applied voltage (200, 250, and 300 V) of PEO was studied. The surface morphology analysis indicates that an increase in applied voltage results in a larger pore size. It was discovered that, when a voltage of 300 V was applied, a layer of hydroxyapatite formed. However, at 300 V, the coating cracked, producing a significantly rough surface. Our analysis of the elemental composition of sample cross sections indicates the presence of TiO2 layers that are enriched with calcium (Ca) and phosphorus (P). The coefficient of friction and wear rate are primarily influenced by the morphology, pore size, and density of the titanium dioxide layer. Furthermore, a rise in the quantity of the beta phase of the titanium on the surface can be noticed as the applied voltage increases. As a result, it also affects the mechanical and tribological characteristics of the coating. The sample treated to a voltage of 250 V demonstrates a higher resistance to wear and a lower elastic modulus in comparison to the other two coatings.

Lithium-Gold Electrochemical Alloying: Clarifying Reaction Pathways and Products Using Operando XRD

Gold electrodes are used in lithium-ion battery research despite their high cost and unclear reactivity with lithium. Many equilibrium phases of gold-lithium (Au-Li) exist—solid solutions alpha, beta, and delta, and intermetallic phases AuLi3 and Au4Li15. During the first alloying reaction, the equilibrium alpha and beta phases are seemingly bypassed; a phase, presumably delta, forms at a potential of 0.25 V (all potentials vs Li/Li+), followed by the formation of AuLi3 at 0.15 V at all conditions tested and Au4Li15 at 0.05 V in select conditions. Alloying reactions are reversible to (delta), followed by the formation of another phase near 0.3 V and a low Li content phase at potentials above 0.4 V during de-alloying. Observed diffraction peaks only partially align with previous reports for all phases other than Au4Li15. The second alloying/de-alloying cycle is reversible between a low Li content phase (not pure gold) and the terminal phase. Some reaction hysteresis is present at low Li content. While the (delta)/AuLi3 reaction had a consistent potential during alloying and de-alloying, the potential otherwise varied strongly with temperature, rate, and composition, implying that gold quasi-reference electrodes may not be suitable for lithium-ion battery research.

Temperature-dependent dielectric response of free standing PVDF-MoS2 nanocomposite films

Poly(vinylidene fluoride) (PVDF) and its copolymers are known for possessing the highest electroactive response including dielectric constant, piezoelectric and ferroelectric effects which has a wide range of applications such as in energy transfer, energy generation and storage, monitoring and control, and include the development of capacitors, sensors, actuators and so on. We report an enhancement in dielectric properties in PVDF generated by the addition of MoS2 nanosheets. The addition of 1 wt% MoS2 nanosheets as a filler in PVDF, stabilize its beta phase over the alpha phase, resulting in a significant increase in dielectric constant (ε’) across a wide range of frequencies (100 Hz to 1 MHz) and temperatures (140 K- 340 K). The high dielectric constant was achieved by the PVDF-MoS2 nanocomposite while maintaining a relatively low tangent loss factor of 0.94. Such properties in soft polymer-based piezoelectric materials were previously challenging and unachievable. The nanocomposite exhibits excellent ferroelectric properties with 11 times enhancement in remnant polarization compared to pristine PVDF in ambient conditions. The stored energy density (Us) is 39.43 mJ/cm3 for the PVDF-MoS2 film. These lead-free and soft polymer-based nanocomposites can bring remarkable advances in various flexible sensors, data storage, and energy harvesting applications.

Effect of Deposition Pressure and Temperature on Tungsten Thin-Film Heater for Phase-Change Switch Applications.

Tungsten (W) film is increasingly utilized in various microheater applications due to its numerous advantages. These advantages include a high melting point, positive constant temperature coefficient of resistance (TCR), good mechanical stability, and compatibility with semiconductor processes. In this paper, deposition parameters for enhancing the properties of W film were investigated, and an optimized microheater was fabricated. It was found that the deposition temperature and pressure can modify the TCR to be negative or positive and the crystalline phase of W films to be alpha phases or mixed with beta phases. A W film deposited under 650 °C with a pressure of 1 pa has a positive TCR and pure alpha phase crystalline structure. We applied this optimized W film as a microheater in an RF phase-change switch (RFPCS), and the maximum voltage of the optimized W microheater increased by at least 48% in this work. By optimizing the microheater, the phase-change switch can be successfully actuated in both on and off states, demonstrated by the Raman results of the phase-change material. A voltage pulse of 20 V/200 ns was enough to turn the switch off with MΩ, and 11 V/3 μs could turn the switch on with 138 Ω. The optimized microheater and device can cycle 500 times without failure. The insertion loss and isolation of the device at 20 GHz was 1.0 dB and 22 dB.

PVDF-Based Piezo-Catalytic Membranes-A Net-Zero Emission Approach towards Textile Wastewater Purification.

Among the various water purification techniques, advancements in membrane technology, with better fabrication and analysis, are receiving the most research attention. The piezo-catalytic degradation of water pollutants is an emerging area of research in water purification technology. This review article focuses on piezoelectric polyvinylidene difluoride (PVDF) polymer-based membranes and their nanocomposites for textile wastewater remediation. At the beginning of this article, the classification of piezoelectric materials is discussed. Among the various membrane-forming polymers, PVDF is a piezoelectric polymer discussed in detail due to its exceptional piezoelectric properties. Polyvinylidene difluoride can show excellent piezoelectric properties in the beta phase. Therefore, various methods of β-phase enhancement within the PVDF polymer and various factors that have a critical impact on its piezo-catalytic activity are briefly explained. This review article also highlights the major aspects of piezoelectric membranes in the context of dye degradation and a net-zero approach. The β-phase of the PVDF piezoelectric material generates an electron-hole pair through external vibrations. The possibility of piezo-catalytic dye degradation via mechanical vibrations and the subsequent capture of the resulting CO2 and H2 gases open up the possibility of achieving the net-zero goal.

Direct observations of dynamic and reverse transformation of Ti-6Al-4V alloy and pure titanium

This paper focused on the characterization and mechanism of the dynamic transformation from the alpha to beta phase during the hot deformation of Ti-6Al-4V alloy and pure titanium. The investigation employed in-situ neutron diffraction and atomistic simulations for a comprehensive understanding of the process. Dynamic transformations were observed during deformation of the Ti-6Al-4V alloy and pure titanium below the beta-transus temperatures (temperatures at which (alpha + beta) / alpha → beta). In the dynamic transformation of Ti-6Al-4V, the lattice parameters of the beta phase continuously increased during deformation in the tensile and transverse directions, a trend inconsistent with the behavior of flow stress. The anomalous variations in lattice parameters were attributed to element diffusion (i.e. a decrease in vanadium content in beta phase). During isothermal holding after unloading, the in-situ neutron diffraction results for Ti-6Al-4V and pure titanium indicated a sluggish reverse transformation from the beta to alpha phase. The mechanism of dynamic transformation was explored through in-situ neutron diffraction and atomistic simulations, which revealed twofold effects of deformation on dynamic transformation. Firstly, deformation led to a significant rise in the Gibbs energy of the alpha phase relative to the beta phase, expanding the beta phase region and diminishing the alpha phase region. Secondly, deformation lowered the energy barriers associated with dynamic transformation, facilitating the activation of dynamic transformation more readily than in the equilibrium state before deformation.

Energy storage and catalytic behaviour of cmWave assisted BZT and flexible electrospun BZT fibers for energy harvesting applications

High-performance lead-free Barium Zirconium Titanate (BZT) based ceramics have emerged as a potential candidate for applications in energy storage, catalysis for electro chemical energy conversion and energy harvesting devices as presented in this work. In the present study hybrid microwave sintered BZT are studied for dielectric, ferroelectric and phase transition properties. BZT ceramic exhibits tetragonal structure as confirmed by the Retvield refinement studies. XPS studies confirms the elemental composition of BZT and presence of Zr. Polarization versus electric field hysteresis loops confirms the ferroelectric behaviour of BZT ceramic. Encouragingly, the BZT showed a moderate energy storage efficiency of 30.7 % and relatively good electro chemical energy conversion (HER). Excellent catalytic activity observed for BZT electrode in acid medium with low Tafel slope 77 mV dec-1. Furthermore, electrospun nanofibers made of PVDF-HFP and BZT are used to make flexible piezoelectric nano generators (PENGs). FTIR studies show that the 16 wt% BZT composite ink exhibits a higher electroactive beta phase. The optimized open-circuit voltage and short circuit current of the flexible PENG exhibits 7Vpp and 750 nA under an applied force of 3N. Thus, flexible and self-powered BZT PENGs are alternative source of energy due to its reliability, affordability and environmental-friendly nature.

Phase of neural oscillations as a reference frame for attention-based routing in visual cortex

Selective attention allows the brain to efficiently process the image projected onto the retina, selectively focusing neural processing resources on behaviorally relevant visual information. While previous studies have documented the crucial role of the action potential rate of single neurons in relaying such information, little is known about how the activity of single neurons relative to their neighboring network contributes to the efficient representation of attended stimuli and transmission of this information to downstream areas. Here, we show in the dorsal visual pathway of monkeys (medial superior temporal area) that neurons fire spikes preferentially at a specific phase of the ongoing population beta (∼20 Hz) oscillations of the surrounding local network. This preferred spiking phase shifts towards a later phase when monkeys selectively attend towards (rather than away from) the receptive field of the neuron. This shift of the locking phase is positively correlated with the speed at which animals report a visual change. Furthermore, our computational modeling suggests that neural networks can manipulate the preferred phase of coupling by imposing differential synaptic delays on postsynaptic potentials. This distinction between the locking phase of neurons activated by the spatially attended stimulus vs. that of neurons activated by the unattended stimulus, may enable the neural system to discriminate relevant from irrelevant sensory inputs and consequently filter out distracting stimuli information by aligning the spikes which convey relevant/irrelevant information to distinct phases linked to periods of better/worse perceptual sensitivity for higher cortices. This strategy may be used to reserve the narrow windows of highest perceptual efficacy to the processing of the most behaviorally relevant information, ensuring highly efficient responses to attended sensory events.

Designing Architected Nickel Hydroxide Cathodes for Rechargeable Alkaline Nickel–Zinc Batteries

Now that dendrite-suppressing Zn sponge anodes developed at the U.S. Naval Research Laboratory [1] offer a safer route to aqueous batteries that can power a wide range of end uses including electric vehicles, portable electronic devices, and backup energy storage, we need better cathodes. With high rate capability and deep theoretical utilization of the zinc (DOD ≥ 40%) now routine in alkaline electrolytes, storing and delivering more than one electron per metal-centered active material in the cathode is next. We focus on moving the Ni cathode past the 0.8–0.9 electrons per Ni characteristic of fabricating the cathode using β-Ni(OH)2 to tap the extra capacity inherent to α-Ni(OH)2 (theoretical: 1.67 electrons/Ni). Substituting Al3+ into α-Ni(OH)2 stabilizes the alpha phase from conversion to beta phase upon contact with and cycling in aqueous KOH and shifts positive the cell voltage for oxygen evolution (OER), the parasitic charging reaction that affects coulombic efficiency and limits cycle life [2]. We have now redesigned a classic powder composite Ni cathode (carbon black + Ni(OH)2 + binder) into an architected Ni electrode to improve charging efficacy. Using microwave-assisted deposition of Al-substituted α-Ni(OH)2 nanosheets onto a freestanding carbon nanofiber paper electrode wires the active material in 3D to the current-collecting carbon throughout the volume of the electrode. The architected Ni cathodes are tested in alkaline cells versus zinc sponge anodes and demonstrate that architected electron-wiring improves the capacity, rate, and cycle stability of Ni cathodes relative to conventional powder-composite electrodes. Varying the synthetic conditions achieves mass loadings that approach technologically relevant values. The enhanced electrochemical performance of architected Ni cathodes and architected Zn anodes provides a pathway to energy dense, safe, rechargeable Ni–Zn batteries.[1] Parker, J.F.; Chervin, C.N.; Pala, I.R.; Machler, M.; Burz, M.F.; Long, J.W.; Rolison, D.R. Rechargeable Nickel–3D Zinc Batteries: An Energy-Dense, Safer Alternative to Lithium-Ion. Science 2017, 356, 415–418 (10.1126/science.aak9991).[2] Kimmel, S.W.; Hopkins,B.J.; Chervin, C.N.; Skeele, N.L.; Ko, J.S.; DeBlock, R.H.; Long, J.W.; Parker, J.F.; Hudak, B.M.; Stroud, R.M.; Rolison, D.R.;Rhodes, C.P.Capacity and Phase Stability of Metal-Substituted α-Ni(OH)₂ Nanosheets in Aqueous Ni–Zn Batteries. Mater. Adv. 2021, 2, 3060–3074 (10.1039/D1MA00080B).

Thalamo-cortical evoked potentials during stimulation of the dentato-rubro-thalamic tract demonstrate synaptic filtering

Essential tremor DBS targeting the ventral intermediate nucleus (Vim) of the thalamus and its input, the dentato-rubro-thalamic tract (DRTt), has proven to be an effective treatment strategy. We examined thalamo-cortical evoked potentials (TCEPs) and cortical dynamics during stimulation of the DRTt. We recorded TCEPs in primary motor cortex during clinical and supra-clinical stimulation of the DRTt in ten essential tremor patients. Stimulation was varied over pulse amplitude (2–10 ​mA) and pulse width (30–250 ​μs) to allow for strength-duration testing. Testing at clinical levels (3 ​mA, 60 ​μs) for stimulation frequencies of 1–160 ​Hz was performed and phase amplitude coupling (PAC) of beta phase and gamma power was calculated. Primary motor cortex TCEPs displayed two responses: early and all-or-none (<20 ​ms) or delayed and charge-dependent (>50 ​ms). Strength-duration curve approximation indicates that the chronaxie of the neural elements related to the TCEPs is <200 ​μs. At the range of clinical stimulation (amplitude 2–5 ​mA, pulse width 30–60 ​μs), TCEPs were not noted over primary motor cortex. Decreased pathophysiological phase-amplitude coupling was seen above 70 ​Hz stimulation without changes in power spectra and below the threshold of TCEPs. Our findings demonstrate that DRTt stimulation within normal clinical bounds does not excite fibers directly connected with primary motor cortex but that supra-clinical stimulation can excite a direct axonal tract. Both clinical efficacy and phase-amplitude coupling were frequency-dependent, favoring a synaptic filtering model as a possible mechanism of action.

Analysis of Face-Centered Cubic Phase in Additively Manufactured Commercially Pure Ti

Metal additive manufacturing is a developing technique with numerous advantages and challenges to overcome. As with all manufacturing techniques, the specific raw materials and processing parameters used have a profound influence on microstructures and the resulting behavior of materials. It is important to understand the relationship between processing and microstructures of Ti to advance knowledge of Ti-alloys in the additive field. In this study, a face-centered cubic (FCC) phase was found in grade 2 commercially pure titanium specimens, additively manufactured with directed energy deposition in an argon atmosphere. Two scanning speeds (500 and 1000 mm/min) and three scanning patterns (cross-hatched and unidirectional patterns) were investigated. Electron backscatter diffraction and energy-dispersive X-ray spectroscopy were used for microstructural and compositional analysis. Inverse pole figure, phase, and kernel average misorientation (KAM) maps were analyzed in this work. Larger amounts of the FCC phase were found in the unidirectional scanning patterns for the slower scanning speed, while the cross-hatched pattern for both scanning speeds showed a lower amount of FCC. Higher KAM averages were present in the faster scanning speed specimens. According to EDS scans, small amounts of nitrogen were uniformly distributed throughout the specimens, leading to the possibility of interstitial content as a contributing factor for development of the observed FCC phase. However, there is no clear relationship between nitrogen and the FCC phase. The formation of this FCC phase could be connected to high densities of crystalline defects from processing, plastic deformation, or the distribution of interstitials in the AM structure. An unexpected Kurdjumow–Sachs-type orientation relationship between the parent beta phase and FCC phase was found, as 110BCC∥111FCC, 111BCC∥110FCC.

New Powder Metallurgy Titanium Alloys with Built-In Antibacterial Capability

Amongst biomedical metallic materials, titanium alloys are normally used as structural permanent implants due to their favourable combination of mechanical properties and biocompatibility. However, commonly implanted titanium alloys are expensive and, unless purposely surface treated, generally cannot prevent surgical infections related to bacteria. Specifically, bacterial infection in biomedical protheses leads to inflammation, obstruction of the healing process, prevention of osteogenesis and, eventually, premature failure of the implant. This work therefore analysis the development of new ternary Ti-based alloys with built-in antibacterial capability as pathogenic bacterial infection occurring during surgery is a raising issue of metallic biomedical implants. The new Ti-based alloys were designed to be manufactured via powder metallurgy, which permits to successfully produce chemically homogeneous materials, key for a uniform antibacterial response, at lower cost. It is found that, primarily due to the stabilisation of the beta phase, the amount of the selected β stabilising alloying elements directly increases the mechanical performance and the antibacterial capability. Consequently, new ternary Ti-based alloys are promising candidates for structural prosthesis functionalised with antibacterial capability.

Improvement of mechanical, biological, and electrochemical properties of Ti6Al4V alloy modified with Nb and Ag for biomedical applications

This study aims to evaluate the mechanical and biological properties of a spark plasma-sintered (SPS) Ti6Al4V alloy modified with 5 and 10 wt% niobium (Nb) together with 2 wt% Ag. Five batches of Ti6Al4V, Ti6Al4V-5 Nb, Ti6Al4V-10 Nb, Ti6Al4V-5 Nb-2Ag, and Ti6Al4V-10 Nb-2Ag were sintered using SPS at 1400 °C for 5 min. X-ray diffraction (XRD) analysis was used to identify the phases of the specimens. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray mapping analyses were also utilized to study the powder morphology, microstructure, and fractured surfaces of the samples. Three-point flexural strength and Vickers microhardness tests were performed and the fracture toughness (K1 C) was calculated subsequently. The bulk parts showed a very high building density, which means that the plasma sintering parameters were optimal. X-ray diffraction (XRD) analysis confirmed the existence of alpha and beta phases by adding niobium and silver. Potentiodynamic, electrochemical impedance spectroscopy, MTT assay, and antibacterial tests were also conducted to evaluate the biological properties of the sintered samples. The maximum values of flexural strength and K1 C were obtained for Ti6Al4V-5 Nb samples up to 1943 ± 12 MPa and 63 ± 1.1 MPa.m0.5, respectively. The hardness values of samples showed no significant difference by adding Nb and Ag. The samples containing Nb exhibit a lower passive current density compared to the pure Ti6Al4V alloy, suggesting that the addition of Nb positively influences corrosion resistance. According to the results of the antibacterial test, Nb slightly deteriorated the antibacterial properties, while after adding Ag, this property improved. The results of the MTT assay revealed that adding niobium and silver had no toxic effect on the samples.

A study of gallium oxide by using the piezoelectric composite oscillator technique at a frequency of 100 kHz

The article presents the results of the study of the mechanical properties and defect structure of gallium oxide (Ga2O3) by using the piezoelectric composite oscillator technique. Bulk samples of the Ga2O3 beta phase in the form of single crystals and their intergrowths were obtained by growth from a melt with a shaper (Stepanov technique). The research involved studying the dependences of the longitudinal elastic modulus and the damping of elastic vibrations at a frequency of 100 kHz on the strain amplitude. Changes in the elastic and microplastic properties of the samples at different temperatures were attributed to possible relaxation phenomena in the structure of the material. Studying the defect structure in samples of pure and doped Ga2O3 is necessary to improve the technology for the production of large single crystals. The fundamental questions in this area are the influence of defects on the anisotropy of electrical conductivity, band structure, and other functional properties of the resulting semiconductor material. The purpose of this article is to establish the features of sample preparation, research, and interpretation of the results obtained by the piezoelectric composite oscillator technique for gallium oxide samples. In the studied samples, the first longitudinal vibration mode was excited, which corresponded to a length of about 27 mm and a small cross-section of the sample. The temperature dependences in the region of low and high strain amplitudes were determined separately. The crystalline quality of the prepared samples was assessed by X-ray diffraction with the analysis of the rocking curve. The value of Young’s modulus obtained along the growth axis (crystalline orientation &lt;010&gt;) in Ga2O3 crystals E≈260 GPa is in line with the results of previous studies. Relaxation peaks corresponding to various dislocation interactions were found on the temperature dependences of internal friction at a temperature of 280 K

Effects of fiber laser treatment on properties of Ti-64 alloy

Titanium (Ti) is a metal used extensively in aerospace, automotive industry and medical implants due to its exceptional combination of strength, corrosion resistance, and biocompatibility. The researchers have shown a lot of interest in exploring the areas for further enhancement of properties of Titanium alloy and to widen the range of applications. In current years, laser treatment has gained attention as an attractive method to modify the surface properties of these alloys, aiming to enhance their mechanical, chemical, and biological attributes. This study systematically examines the impact of various laser parameters, such as scan speed, and laser power, on the microstructural changes, mechanical properties, corrosion resistance, and surface wettability of titanium alloys. In the present research, laser treatment was performed on Ti alloy to study its effect on surface properties by Fiber laser heat treatment (LHT). The Ti-64 alloy (Ti-6Al-4 V) was selected LHT carried out and the surface integrity of the Ti alloy was analyzed before and after the laser process. The fiber laser of power 1600 W with a scanning speed of 7 mm/s and frequency 5000 Hz was used and nitrogen was used as shielding gas with a pressure of 10 bar. Micro Vickers hardness test, Optical Microstructure and Immersive Corrosion test have been carried out to scrutinize the impact of the laser surface heat treatment process. In the microstructure, the coarsened alpha phase in the matrix of the beta phase was transformed into an elongated alpha phase after laser treatment, increasing the grain boundary and hence the hardness. It was noticed that there was a 9 % increase in the hardness of Ti alloy after LHT in comparison with before LHT. The corrosion resistance of Ti alloy was enhanced significantly after LHT.

Managing the inevitable microstructural and property heterogeneity in powder bed fusion Ti-6Al-4V parts via heat treatment

This study investigates the effects of the commonly-observed microstructure heterogeneity from the metal electron beam powder bed fusion (PBF-EB) processes and how it evolves following the associated heat treatment (HT), on the tensile behaviour of Ti-6Al-4V alloy. A strain gradient crystal plasticity finite element (CPFE) method is employed using physically-based dislocation mechanics to capture the microstructure-sensitive size effect. Microstructural characterization is performed using electron backscatter diffraction (EBSD) of the as-built and post-HT specimens, with measurements of grain morphology, phase, and texture extracted from the bottom and top regions of specimens, used to construct the CPFE models. The dual-phase CPFE model represents α (hcp) and β (bcc) basket-weave morphology, typical in Ti-6Al-4V, with accurate PBF-induced texture definitions defined directly from the measured EBSD data. Key microstructural features exhibiting a gradient include lath width and phase fraction. The effects of as-built microstructural gradient in a single component include an increase of lath width by 43 %, and the beta phase fraction, from bottom to top. The CPFE models successfully predict the effect of HT and microstructural gradient on tensile response, specifically yield stress and initial hardening rate. The role of dislocation density and the associated influence of lath width on yield stress are empirically correlated for the structure-property design of PBF-EB metals. This study also demonstrates the homogenising effect of the heat treatment; effectively eradicating the microstructural gradient observed in as-built specimens.