Improvement in the microhardness and corrosion behaviour of Ti-14Mn biomedical alloy by cold working

β-titanium alloys are essential in many applications, particularly biomedical applications. Ti-14Mn β-type alloy was produced using an electric arc furnace from raw alloying elements in an inert atmosphere. The alloy was homogenized at 1000 °C for 8 hr to ensure the complete composition distribution, followed by solution treatment at 900 °C, then quenched in ice water. The alloy was subjected to cold deformation via cold rolling with different ratios: 10, 30, and 90%. The phases change, microstructure, mechanical properties, and corrosion resistance of Ti-14Mn alloys were evaluated before and after cold rolling. The results showed that the β-phase is the only existed phase even after a high degree of deformation. The microstructure shows a combination of twinning and slipping deformation mechanisms in the deformed alloy. Microhardness values indicated a linear increase equal to 30% by increasing the ratio of cold deformation due to the strain hardening effect. The corrosion resistance of Ti-14Mn alloy was doubled after 90% cold rolling.

Porous, multi-layered piezoelectric composites based on highly oriented PZT/PVDF electrospinning fibers for high-performance piezoelectric nanogenerators

Piezoelectric nanogenerators (PENGs) that can harvest mechanical energy from ambient environment have broad prospects for multi-functional applications. Here, multi-layered piezoelectric composites with a porous structure based on highly oriented Pb(Zr0.52Ti0.48)O3/PVDF (PZT/PVDF) electrospinning fibers are prepared via a laminating method to construct high-performance PENGs. PZT particles as piezoelectric reinforcing phases are embedded in PVDF fibers and facilitate the formation of polar β phase in PVDF. The multi-layered, porous structure effectively promotes the overall polarization and surface bound charge density, resulting in a highly efficient electromechanical conversion. The PENG based on 10 wt% PZT/PVDF composite fibers with a 220 µm film thickness outputs an optimal voltage of 62.0 V and a power of 136.9 µW, which are 3.4 and 6.5 times those of 10 wt% PZT/PVDF casting film-based PENG, respectively. Importantly, the PENG shows a high sensitivity of 12.4 V·N−1, presenting a significant advantage in comparison to PENGs with other porous structures. In addition, the composites show excellent flexibility with a Young’s modulus of 227.2 MPa and an elongation of 262.3%. This study shows a great potential application of piezoelectric fiber composites in flexible energy harvesting devices.

Effect of thermal cycling on mechanical and microstructural properties of heat-treated Ti-6Al-4V alloy

Titanium (Ti-6Al-4V) is an α+β phase-field alloy utilized in many industries due to its high strength-to-weight ratio and near-net shaping capability. Solution treated & aging, and stress relief annealing processes were performed on the samples to increase the strength and % of elongation. The heat-treated samples then thermally cycled for 500 cycles, 1000 cycles, and 1500 cycles to evaluate the microhardness and tensile properties. The presence of martensite and α2 precipitates in the thermally cycled samples was confirmed by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). In this investigation, at 1000 thermal cycles, all specimens show improvement in both hardness and strength when compared within the cycles. Solution-treated and aging (STA), stress relief annealing (SRA), and without any heat-treatment (WHT) processes have their highest hardness values recorded for 1000 thermal cycles, and the values are 471 HV0.5, 381 HV0.5, and 374.6HV0.5, respectively. For the SRA process, ultimate tensile strength (UTS) of 925 MPa and yield strength (YS) of 896 MPa have resulted in 1000 cycles. Similarly, at 1000 thermal cycle WHT processed samples yielded UTS of 920 MPa and YS of 885 MPa. STA process samples that are heat-treated for 1000 thermal cycles have better strength properties than SRA and WHT and had a UTS of 1530MPa and YS of 1420MPa. From a ductility point of view, a maximum elongation of 29% for the STA process has resulted. Compared to forged titanium alloy (base metal), an increase of 31% elongation and 41% ultimate tensile strength for solution treated and aging process at 1000 cycles has resulted in this investigation.

Vibrationally Resolved Absorption Spectra and Ultrafast Exciton Dynamics in the α-Phase and β-Phase Zinc Phthalocyanine Aggregates

The vibrationally resolved absorption spectra and ultrafast exciton dynamics in the α-phase and β-phase zinc phthalocyanine (ZnPc) aggregates are theoretically investigated by using a non-Markovian stochastic Schrödinger equation combined with...

Mechanical Properties and Microstructure Evolution of Mg-Gd Alloy during Aging Treatment

Rare-earth-containing Mg alloys are a group of widely investigated alloys due to the disperse nano-sized precipitations formed during heat treatment. The underlying formation and strengthening mechanisms of precipitation is critical for their industrial applications. In this work, we systematically studied the evolution of precipitations in a Mg-10Gd alloy, based on the atomic-scaled TEM and HAADF-STEM observations. Especially, the in-depth transition mechanism from G.P. Zone to β”, β’, βT and βM is proposed, as well as their relationships with mechanical properties. It is found that blocking effect of precipitations improves the strength significantly, according to the Orowan mechanism. The elliptic cylinder shaped β’ phase, with a base-centered orthorhombic lattice structure, provides significant strengthening effects, which enhance the hardness and ultimate tensile strength from 72 HV and 170 MPa to 120 HV and 300 MPa.

Effect of electrochemical modification of titanium hydride fraction on oxygen content in surface and deep layers

The paper presents a study of the microstructure and oxygen concentration in the surface and deep layers of fractions of unmodified titanium hydride and titanium hydride modified by electrodeposited layers of Ti and Cu at temperatures of 300-900 ° C. The composition of the oxide layer and the concentration of titanium and oxygen atoms are estimated. It is shown that an increase in the thickness and compaction of the oxide layer with increasing temperature prevents the penetration of oxygen into the deep layers of the unmodified fraction of titanium hydride. Modification of titanium hydride by electrochemical deposition of metallic titanium at a temperature of 700 °C reduces the oxygen concentration in titanium hydride at a layer depth of 50 μm from 35 wt% to 12.5 wt%. Electrodeposition of coatings based on titanium and copper at 700 °C reduces the oxygen concentration to 9.2 wt%, which may be due to the protective mechanism of the formed copper titanate layer. At 900 °C, in the modification layer based on titanium and copper, due to the eutectoid transformation of the β-phase of titanium, the process of contact melting occurs and a multiphase zone is formed. The oxygen concentration at a layer depth of 50 μm is no more than 12.4 wt%.

(100) Plane ß-Ga2O3 Flake Based Field Effect Transistor and Its Hydrogen Response

2-dimensional (100) plane β phase Ga2O3 (β-Ga2O3) flake based field effect transistor (FET) was fabricated, and its electrical characteristics was analyzed. The (100) plane β-Ga2O3 flake was mechanically exfoliated from the side wall of (2 ̅01) plane β-Ga2O3 bulk substrate. The minimum thickness of 57.3 nm was obtained for the very thin (100) plane β-Ga2O3 channel layer of the FET using inductively coupled plasma etching with BCl3/N2 chemistry. The current-voltage characteristics of the FET with various β-Ga2O3 channel thickness was investigated. The dependence of the channel thickness on the drain current density, threshold voltage, transconductance, and field effect mobility was studied. The hydrogen response of the (100) plane Ga2O3 flake based FET with catalytic Pt gate surface was measured in the range of 10-500 ppm at 400˚C, and modeled with a dissociative Langmuir isotherm. The device showed a reliable responsivity to the different concentration of hydrogen exposure, and the responsivity of 25.02% was observed for the 500 ppm hydrogen at 400˚C.

Antibacterial Ferroelectric Hybrid Membranes Fabricated via Electrospinning for Wound Healing

In the present study, wound healing ferroelectric membranes doped with zinc oxide nanoparticles were fabricated from vinylidene fluoride-tetrafluoroethylene copolymer and polyvinylpyrrolidone using the electrospinning technique. Five different ratios of vinylidene fluoride-tetrafluoroethylene to polyvinylpyrrolidone were used to control the properties of the membranes at a constant zinc oxide nanoparticle content. It was found that an increase of polyvinylpyrrolidone content leads to a decrease of the spinning solution conductivity and viscosity, causing a decrease of the average fiber diameter and reducing their strength and elongation. By means of X-ray diffraction and infrared spectroscopy, it was revealed that increased polyvinylpyrrolidone content leads to difficulty in crystallization of the vinylidene fluoride-tetrafluoroethylene copolymer in the ferroelectric β-phase in membranes. Changing the ratio of vinylidene fluoride-tetrafluoroethylene copolymer and polyvinylpyrrolidone with a constant content of zinc oxide nanoparticles is an effective approach to control the antibacterial properties of membranes towards Staphylococcus aureus. After carrying out in vivo experiments, we found that ferroelectric hybrid membranes, containing from five to ten mass percent of PVP, have the greatest wound-healing effect for the healing of purulent wounds.