Β-phase Fraction Research Articles

On the effect of energy input on microstructure evolution and mechanical properties of laser beam powder bed fusion processed Ti-27Nb-6Ta biomedical alloy

Additive manufacturing of pre-alloyed Ti-27Nb-6Ta powder by laser beam powder bed fusion (PBF-LB/M) employing a wide range of processing parameters is reported. An in-depth microstructure analysis along the whole process chain from powder feedstock material to additively manufactured bulk structures was conducted employing scanning electron microscopy (SEM) as well as X-ray and high-energy synchrotron diffraction. It is shown that near-fully dense parts (≥ 99.96%) with β+α’’ dual-phase microstructure and very homogenous element distribution are obtained in a large process window. In particular, a considerable influence of the energy input during PBF-LB/M on the solidification microstructure, i.e. phase composition and texture, is found. With increasing energy per unit area (EA) values both an increase in the volume fraction of the bcc β-phase and more pronounced texture components are seen. Furthermore, the mechanical behavior was evaluated under monotonic tensile loading. The PBF-LB/M processed Ti-27Nb-6Ta structures feature good mechanical properties with ultimate tensile strength (UTS) and strain to failure values of up to 768 MPa and 33.8 %, respectively. Due to the strong impact of the energy input during additive manufacturing on the microstructure evolution, however, a significant inverse strength-ductility behavior is observed. While UTS clearly decreases with increasing EA values, strain to failure increases at the same time. The underlying relationships between processing (energy input), microstructure and mechanical properties are explored and rationalized.

Fabrication of rare earth-doped ZnO-PVDF flexible nanocomposite films for ferroelectric response and their application in piezo-responsive bending sensors.

The present study covers the fabrication of flexible piezoelectric nanogenerators and their application towards sustainable power generation. The rod-like structure of erbium-doped ZnO (EZ) nanoparticles prepared by the hydrothermal synthesis route was successfully incorporated inside the polyvinylidene fluoride (PVDF) matrix using the solution casting method. Solution casting is an easy and cost-effective method for fabricating laminated, thin, flexible and lightweight EZ-PVDF nanocomposite films. The formation of the desired crystallographic phase of EZ-PVDF nanocomposite films and the presence of rod-like EZ nanoparticles inside the PVDF matrix were confirmed using X-ray diffraction and FESEM. The enhancement of the β-phase fraction of the EZ-PVDF nanocomposite films as compared to bare PVDF was estimated using FTIR spectroscopy. The presence of a ferroelectric phase in the EZ-PVDF nanocomposite films was found due to the formation of a large area of interfaces between the EZ nanoparticles and the PVDF matrix. The maximum polarizations of 0.00696 μC cm-2 and 0.00683 μC cm-2 for two samples (EZP1 and EZP2, respectively) were observed at an electric field of 1.25 kV cm-1. The piezoelectric voltages were observed at relatively low frequencies for both nanocomposite films. The maximum piezoelectric voltages of 18.9 V and 15.5 V were observed at a 1 Hz frequency for EZP1 and EZP2, respectively. The output piezoelectric current of 16.88 mA and the maximum power density of 7773.68 W m-3 for EZP1 ensure its potential as an efficient piezoelectric nanogenerator with greater efficiency than those reported previously in published articles. The change in the piezoelectric voltage response of the nanocomposite films as a function of mechanical movement of human external body parts renders them the most suitable candidate for human-machine interfacing (HMI) applications, such as bending sensors and human motion sensors.

Composite Nanoarchitectonics of Electrospun Piezoelectric PVDF/AgNPs for Biomedical Applications, Including Breast Cancer Treatment.

This study focused on preparing composite nanomats by incorporating silver nanoparticles (AgNPs) in polyvinylidene fluoride (PVDF) nanofibers through the electrospinning process. A short review of piezoelectric PVDF-related research is presented. PVDF is known for its biocompatibility and piezoelectric properties. Since electrical signals in biological tissues have been shown to be relevant for therapeutic applications, the influence of the addition of AgNPs to PVDF on its piezoelectricity is studied, due to the ability of AgNPs to increase the piezoelectric signal, along with providing antibacterial properties. The prepared samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. In addition, the biological activity of composites was examined using a cytotoxicity assay and an assessment of the antibacterial activity. The obtained results show that the incorporation of AgNPs into PVDF nanofibers further enhances the piezoelectricity (crystalline β-phase fraction), already improved by the electrospinning process, compared to solution-casted samples, but only with a AgNPs/PVDF concentration of up to 0.3%; a further increase in the nanoparticles led to a β-phase reduction. The cytotoxicity assay showed a promising effect of PVDF/AgNPs nanofibers on the MDA-MB-231 breast cancer cell line, following the non-toxicity displayed in regard to the healthy MRC-5 cell line. The antibacterial effect of PVDF/AgNPs nanofibers showed promising antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus, as a result of the Ag content. The anticancer activity, combined with the electrical properties of nanofibers, presents new possibilities for smart, multifunctional materials for cancer treatment development.

Advancements in Flexible Nanogenerators: Polyvinylidene Fluoride-Based Nanofiber Utilizing Electrospinning.

With the gradual miniaturization of electronic devices and the increasing interest in wearable devices, flexible microelectronics is being actively studied. Owing to the limitations of existing battery systems corresponding to miniaturization, there is a need for flexible alternative power sources. Accordingly, energy harvesting from surrounding environmental systems using fluorinated polymers with piezoelectric properties has received significant attention. Among them, polyvinylidene fluoride (PVDF) and PVDF co-polymers have been researched as representative organo-piezoelectric materials because of their excellent piezoelectric properties, mechanical flexibility, thermal stability, and light weight. Electrospinning is an effective method for fabricating nanofibrous meshes with superior surface-to-volume ratios from polymer solutions. During electrospinning, the polymer solution is subjected to mechanical stretching and in situ poling, corresponding to an external strong electric field. Consequently, the fraction of the piezoelectric β-phase in PVDF can be improved by the electrospinning process, and enhanced harvesting output can be realized. An overview of electrospun piezoelectric fibrous meshes composed of PVDF or PVDF co-polymers to be utilized is presented, and the recent progress in enhancement methods for harvesting output, such as fiber alignment, doping with various nanofillers, and coaxial fibers, is discussed. Additionally, other applications of these meshes as sensors are reviewed.

Advanced 3D-printed PVDF/BT piezoelectric energy harvester with a bio-inspired 3D structure for a self-powered smart mouse

Piezoelectric polymers such as poly(vinylidene fluoride) (PVDF) exhibit remarkable flexibility, lightweight, durability, and biocompatibility compared to their ceramic counterparts. This unique characteristic makes them highly suitable for harvesting mechanical vibrations. However, conventional manufacturing methods mainly result in two-dimensional (2D) piezoelectric energy harvester (PEHs) structures. This confines the internal stress and, as a result, limits their potential voltage output. This study introduces an innovative bio-inspired three-dimensional (3D) structure crafted through fused deposition modeling (FDM). Barium titanate (BT) nanoparticles were added as piezoelectric fillers to improve the performance of the PEH. The obtained nanocomposite was poled under optimal poling conditions, achieving a β-phase fraction of 95,72 %, a piezoelectric charge coefficient (d33) of 28 pC/N, and a permittivity of 24.2 at 100 Hz. A parametric study was performed through numerical analysis, resulting in an effective and optimized structural configuration. The combined excellent piezoelectric properties of the nanocomposite with the optimized structure enabled the PEH to generate an open-circuit voltage of 30.8 V, enabling it to charge a commercial 1 μF capacitor to 25 V in just 260 s. The bioinspired PEH demonstrates its practical application by powering an innovative device known as the "smart mouse," showcasing its utility and potential in real-world applications.

An integrated investigation of the effect of sub-transus treatment on the microstructure and corrosion behaviour of the LPBF Ti–6Al–4V alloy

Biomedical grade Ti–6Al–4V alloy, is the best candidate material for bioimplants due to its outstanding corrosion resistance. Additive manufacturing processes such as laser-based powder bed fusion (LPBF) are trending technologies that challenge conventional manufacturing methods in producing customized implants. However, the Ti–6Al–4V alloy fabricated by LPBF consists of a non-equilibrium phase (α′-martensite), that tends to degrade the corrosion resistance, and therefore a post-treatment is required to stabilize the phases. In this work, the annealing is done in the α+β range of the Ti–6Al–4V alloy. The corrosion performances of the as-built (AB) and annealed samples in 0.9 wt% NaCl solution are investigated through electrochemical measurements. The relationship between the microstructure and its corresponding corrosion behaviour is elucidated. The rate of corrosion increased by around 12 % following low temperature annealing, but decreased by more than 50 % following high temperature annealing above 850 ᵒC. Overall, the AB structure shows an inferior corrosion behaviour compared to the annealed ones. The electrochemical results show that post-annealing has a positive effect on corrosion performance that can be ascribed to various factors such as phase fraction, chemical composition, morphological features of microstructural and presence of defects. The findings show that a microstructure with increased β-phase fraction, a fine lamellar structure with low defect density, and a comparatively coarser grain size is beneficial in improving corrosion resistance. This can be achieved by annealing the Ti–6Al–4V alloy at 850 ᵒC or higher.

The influence of rapid-diffusive β-stabilizers on the microstructure formation and superplasticity of titanium-based alloys

The superplasticity of Ti-based alloys is improved due to grain refinement, an increase in grain size stability, and an increase in the β-phase fraction up to ∼0.5. Alloying with β-stabilizers reduces the β-transus temperature and increases the β-phase fraction at low forming temperatures, thus improving the superplasticity and lowering its temperature. Both grain growth and superplastic deformation mechanisms are diffusion-controlled phenomena, and, therefore, the diffusivity of the alloying elements should have a significant effect on superplasticity. This work deals with the influence of the high-diffusive elements Fe, Co, and Ni on the grain structure and superplasticity of titanium alloys. For this purpose, the Ti-Al-Mo-V alloy, and alloys with proportional replacement of low-diffusive Mo by Fe, Co, or Ni, exhibiting an interstitial diffusion mechanism, were studied. The alloying elements content was selected to ensure the same β-phase fraction at a deformation temperature of ∼875 °C. The microstructure evolution after thermomechanical processing, annealing, and superplastic deformation, as well as post-deformation room-temperature mechanical properties of the studied alloys, were compared. The actual phase ratio was reconstructed by comparing scanning electron microscopy images in backscattered electrons and electron backscatter diffraction data for the same fragments. It was found that Mo replacement for highly diffusive elements accelerated dynamic grain growth during superplastic deformation at an elevated temperature of 875 °C but improved superplasticity at a lower temperature of 775 °C. The results confirmed that alloying with high-diffusive elements is a promising strategy for the design of low-temperature superplastic forming alloys.

Processing and characterisation of hot rolling pressed PVDF films with enhanced field-induced polarisation

Poly (vinylidene fluoride) (PVDF) based polymers are good candidates for high-power energy storage in dielectric capacitors. So far, most studies reporting PVDF with high energy density are based on solution casting, a method ill-suited for large-scale production. In this work, we develop PVDF films with high crystallinity (47%) and ultrahigh β-phase (∼97%) using Hot Rolling Press (HRP). During HRP, the crystallinity, fraction of β-phase, internal stress, and the piezoelectric coefficient d33 increased with rolling temperature. The anisotropic stress imposed by two rollers led to a highly preferred orientation of the HRP film along the rolling direction. Notably, the HRP film exhibits an enhanced field-induced polarisation Pin-max value (0.16 C m−2) compared to conventional PVDF films (0.10 C m−2), with an energy density of 32.6 J cm−3 at 871 kV mm-1. The good low field dielectric (εr ∼19 @ 1 kHz) and piezoelectric (d33 ∼30 pC N-1) properties with high-temperature stability (up to 100 °C), and its suitability for in-line continuous production, make HRP PVDF films promising for low field dielectric and piezoelectric applications.

Process Investigation on Robust Electrospinning of Non-Aligned and Aligned Polyvinylidene Fluoride Nanofiber Mats for Flexible Piezoelectric Sensors.

Polyvinylidene fluoride (PVDF) nanofiber mats have played a significant role in wearable electronic devices that have been in great demand in recent decades. Although manifold PVDFbased freely stacked or well-aligned nanofiber mats created via the electrospinning process have been demonstrated to achieve multisensory capabilities with high sensitivity and long detection range, rarely have any of them proved their ability with a stable process and accurate processing parameters. In this work, we successfully developed freely stacked and well-aligned PVDF nanofiber mats with diameters ranging from micrometers to nanometers, providing stable performance for wearable electronic devices. Through in-depth investigations into material preparation, electrospinning, and fiber collection processes, we revealed the relationship between the nanofiber morphology, β-phase fraction, and piezoelectric output with various process parameters. Characterized by analytical methods, we have established a mature, reliable nanofiber mat fabrication system capable of mass-producing PVDF nanofibers with the required diameter and consistent properties. At 18 kV voltage and 60% RH humidity, the uniformity of the fiber diameter and β-phase content was maintained in a favorable range. When the drum speed increased to 2000 r/s, the fiber orientation and β-phase content increased. We assembled aligned PVDF nanofiber mats with conductive fabric in a flexible piezoelectric sensor that successfully monitored different body movements and produced an output voltage of 0.1 V. This study provides the necessary process parameters for the large-scale production of high-quality PVDF nanofiber mats and provides clear guidance for beginners in the field of nanofiber mat manufacturing.

Comprehensive Study on the Age-Strengthened Mg-Zn-Mn-Ca/ZnO Composites for Fracture Fixation: Microstructure, Mechanical, and In Vitro Biocompatibility Evaluation.

The present work investigates the use of age-strengthened Mg-Zn-Mn-Ca/xZnO as resorbable materials in temporary orthopedic implants. Quaternary Mg-Zn-Mn-Ca alloy, reinforced with zinc oxide particles, was stir-cast, followed by solution treatment and a range of aging treatments. Optical and electron microscopy, mechanical, electrochemical, immersion, and dynamic mechanical testing, with biocompatibility assessment were carried out. The observed 2θ shift in the (101) peaks of ZMX611/ZnO-ST and ZMX611/ZnO-H indicated lattice shrinkage. The formation of Mg7Zn3 and Ca2Mg6Zn3 in the grain boundary compositions was observed. ZMX611/ZnO-ST had a smaller β-phase fraction, indicating a finer microstructure. ZMX611/ZnO-H had the highest tensile yield strength (102.97 ± 3.92 MPa), and ZMX611/ZnO-ST showed the highest ultimate tensile strength (127.21 ± 7.48 MPa), indicating precipitation hardening of Zn enrichment. The uniformly dispersed secondary phases played a dual role in corrosion behavior. ZMX611/ZnO-ST showed a better cytocompatibility response among all samples. Composite materials exhibited satisfactory biocompatibility and mechanical compatibility as indicated by in silico results of deviatoric strain-based mechanical stimuli at the fracture interface.

High [formula omitted]-phase PVDF films formed by uniaxial compression

Polyvinylidene fluoride (PVDF) is a semicrystalline polymer with excellent ferroelectric properties. The β crystal form has the best piezoelectric properties among its five crystal forms. Conventionally, PVDF films with a high β-phase are produced by uniaxial stretching of α-phase PVDF films. Uniaxial compression of α-PVDF samples of thickness 3.2 mm was done to obtain β-PVDF films of thickness about 100μm, with biaxial orientation. The effects of temperature and compression ratio on the compressed PVDF films were studied using Raman spectroscopy, FTIR spectroscopy and cross-polarized optical microscopy. Uniaxial compression of the α-phase PVDF sample resulted in transformation to the β-phase, accompanied by distortion of the originally present Maltese cross structures in the optical micrographs. The compressed samples exhibited β-phase fraction anisotropy along the radial and thickness directions of the sample at lower compression ratios. PVDF samples with about 80% β-phase were obtained for compression ratios more than 12 at temperatures of 60 and 90 °C.

Constitutive modeling hot tensile behavior of Ti6Al4V alloy by considering phase transformation and damage mechanisms

The hot tensile and fracture behavior, as well as damage mechanisms of Ti6Al4V alloy are investigated by the hot tension tests and microstructure observation experiments. For comprehensively characterizing the hot tensile behaviors, a developed dislocation density-based constitutive model was established by coupling the flow softening, phase transformation and damage mechanisms. The results show that the flow stresses under the relatively high strain rates (0.01–1 s−1) easily peak at low strains and then decrease with the further straining. However, under the low strain rate (0.001 s−1), the flow stress tends to a continuously increasing trend until fractured. After hot deformation, the fraction of β phase greatly increases compared to that under the initial state. Meanwhile, β-phase fraction increases with the strain rate decreasing or the deformation temperature increasing. The great input thermal energy by the high temperature and the long deformation period under low strain rates promote the α-β phase transformation. Furthermore, the necking diffusion caused by dislocation motion enhances the homogeneous deformation under low strain rate or high temperature. The cavitations preferentially nucleate at the α/β phase interface due to the inconsistent strain. The comparison of the measured and calculated results confirms the excellent prediction ability of the established model in reproducing the hot tensile behavior, β-phase fraction and damage evolution under different processing parameters.

Physical, mechanical, and corrosion properties of Ti–12Mo and Ti–15Mo alloys fabricated by elemental blend and mechanical alloying techniques

Ti–Mo alloys have received increased attention and concern in several applications, especially in biomedical, because of their appropriate properties, non-toxicity, and reasonable cost. This work investigated the different Mo powder content (12 and 15 wt%) fabricated by elemental blended and mechanical alloying. The microstructure, density, microhardness, compressive, wear, and corrosion properties were characterized. It was found that the volume fraction of β-phase increases with increasing Mo content to around 85%, mainly due to the robust β-phase stabilizer effect. Moreover, the microhardness and compressive properties were enhanced with Mo addition and MA fabrication by 11.5 and 27%, respectively, mainly due to solid solution strengthening, plastic deformation, high dislocations, and lattice defects. However, the strain at failure decreased with decreasing sintered density and increasing porosity. From this study, the corrosion rate decreased with decreasing the porosity, reaching 0.226 × 10−3 mm/year for Ti–12Mo alloy fabricated by elemental blend with a minimum porosity of 3.6%. Ti–Mo alloys can also tolerate properties and impurities, making them suitable for biomedical applications.

Statistical Modeling and Optimization of Electrospinning for Improved Morphology and Enhanced β-Phase in Polyvinylidene Fluoride Nanofibers.

The fabrication of PVDF-based nanofiber mats with enhanced β-phase using electrospinning and post processing was optimized using Taguchi design methodology. The parameters studied include the concentration of PVDF in the DMF (Dimethylformamide) solvent, applied voltage, flow rate, and drum speed. A reliable statistical model was obtained for the fabrication of bead-free PVDF nanofibers with a high fraction of β-phase (F(β)%). The validity of this model was verified through comprehensive regression analysis. The optimized electrospinning parameters were determined to be a 23 wt% PVDF solution, 20 kV voltage, a flow rate of 1 mL/h, and a drum speed of 1200 revolutions per minute.

Mechanistic Study of Rhodamine B Piezocatalytic Decomposition Using Poly(vinylidene difluoride) and Related Polymers

Membranes of poly(vinylidene difluoride) (PVDF) and related polymers are used as piezoelectric materials to decompose rhodamine B (RhB) under low power sonication. The change in the visible spectrum of RhB allows determination of the rate constants for different polymer compositions and membrane thicknesses. The results indicate that the piezoelectric field generated by mechanical deformation of the polymers catalyzes the scission of the C–N bond in RhB. When PVDF is doped with transition-metal nitrates to increase the fraction of the piezoelectric β-phase, the rate constants increase, but the analysis is complicated by concurrent adsorption of RhB onto the membrane. A mechanism consistent with the observed data is proposed where the piezocatalytic effect of the membrane is to heterolytically cleave the C–N bond followed by formation of a C–Cl bond on the new xanthene ring.

Effect of Mo content on the microstructure, superplastic behavior, and mechanical properties of Ni and Fe-modified titanium alloys

Novel titanium-based alloys are required to increase the efficiency of superplastic forming technology and decrease energy consumption. For this purpose, the superplastic deformation behavior, strain-induced microstructure evolution in a temperature range of 625–775 °C, and post-deformation mechanical properties of Ti–4Al–1V–1Fe–1Ni-0.1B-xMo alloys (x = 1, 2.5, or 5 wt%) were investigated. The studied alloys demonstrated a stable flow with a high strain rate sensitivity coefficient m of 0.50–0.65 and an elongation-to-failure δ of 700–1000% at temperatures of 700–775 °C. Molybdenum insignificantly influenced superplastic deformation behavior at high temperatures due to a high fraction of the β phase of 22–62%. The Mo effect was significant at a low deformation temperature of 625 °C. At this temperature, an increase in Mo content from 1 to 5% provided the β-phase fraction above the critical value of ∼20% and increased the m-value from 0.4 to 0.5 and δ from ∼200 to ∼700%. Increasing Mo from 1 to 5% enhanced the post-deformation yield strength at room temperature by 180 MPa, the ultimate tensile strength by 170 MPa, and the ductility by 2.5%. Consequently, alloying Ti–4Al–1V–1Fe–1Ni-0.1B with 5% Mo provided an excellent combination of superplasticity at a low temperature of 625 °C and post-forming tensile mechanical properties.

PDMS/PVDF- MoS2 based flexible triboelectric nanogenerator for mechanical energy harvesting

A green energy generating device that can meet the energy requirements of future technologies without contaminating our environment is increasingly in demand. These devices can harvest energy from ambient sources that are already present in our surroundings. Triboelectric nanogenerator (TENG) has received a lot of attention as a potential sustainable source of power for smart devices, and numerous methods have been explored to enhance its output performance. In this work, we have fabricated a high performance TENG based on MoS2 filled PVDF for harvesting mechanical energy. Effect of MoS2 loading into the PVDF matrix was studied as a function of MoS2 wt% (0, 3, 5, 7, 10%). It has been observed that the fraction of crystalline β-phase and the dielectric constant of PVDF got enhanced after the addition of MoS2. In addition to the dielectric constant, the surface roughness of the MoS2 filled PVDF sample increases, which further contribute to the enhanced triboelectric performance. The TENG device with 7 wt % of MoS2 in PVDF matrix as one of the layer and PDMS as second layer in the vertical contact-separation geometry generates the maximum triboelectric output voltage and current of 189 V and 1.61 μA respectively, while the bare PVDF based TENG generates an output voltage and current of 107 V and 0.88 μA respectively. The TENG with 7 wt % of MoS2 also generates a maximum power density of 104.5 μWcm−2. Further, effect of the tapping frequency and the contact force was also analysed on the PDMS/PVDF-MoS2 based TENG with 7 wt% of MoS2. The triboelectric output voltage and current were also found to be increased with the rise in frequency and the contact force and generated a maximum voltage of ∼211 V. This study proposes an effective approach for enhancing the performance of triboelectric nanogenerator by changing the filler concentration. The fabricated TENG demonstrated the practical application, by powering electronic stopwatch and scientific calculator.

Effect of quenching temperature on microstructure and mechanical properties of Mg-35 wt%Sc alloy

In this work, the microstructure, microhardness and compressive mechanical properties of quenched Mg-35 wt%Sc alloy at 540 °С, 600 °С, and 630 °С were investigated. The microstructure of three specimen is mainly composed of α and β phases. With an increase in the quenching temperature, the fraction of β-phase is increased, indicating that the phase transformation occurs from α to β phase. On the other hand, the grain size of α-phase is reduced and the morphology of β-phase changes from needle-like to bulk structure. In addition, the texture intensity of β-phase is significant decreased, which suggests that the quenched alloy at 630 °С has a relatively random β texture. Among them, the specimen quenched at 630 °С exhibits the highest Vicker’s hardness of 113.3 ± 1 HV and ultimate compressive strength (UCS) of 551 ± 5 MPa, which is attributed to the solid solution strengthening effect of Sc and fine-grained strengthening of α-phase. Moreover, with the increase of β-phase in alloy, the plasticity is also increased from 26.8 ± 0.8% to 31.7 ± 0.9%. These researches on bcc-type Mg-Sc alloy provide a novel strategy for future structural magnesium alloy design.

Unleashing the piezoelectric potential of PVDF: a study on phase transformation from gamma (γ) to beta (β) phase through thermal contact poling.

Polyvinylidene fluoride (PVDF) is known for its piezoelectric properties. This material has different crystalline phases, alpha (α), beta (β) and gamma (γ), where the β-phase, in particular, is related to the piezoelectric behavior of PVDF. While the transformation from the α-phase to β-phase in PVDF is well-documented and widely studied, the transformation from γ- to β-phase has not yet been fully explored. However, when PVDF is produced by certain solution-based methods it can adopt its γ-form, which is not as piezoelectric as the β-phase. Hence, this study aims to bridge this gap by investigating the transformation from γ- to β-phase in PVDF nanocomposites films obtained from solution-based techniques. Our PVDF nanocomposite is made by solvent evaporation-assisted 3D printing of PVDF's nanocomposite with barium-titanate nanoparticles (BTO). To achieve the γ- to β-phase transformation, we first highlight the importance of annealing in the successful poling of PVDF samples. We then perform an in-depth analysis of the α-, β- and γ-crystallographic phases of PVDF-BTO using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). We observed that after annealing but before poling, the PVDF-BTO nanocomposite contains 76% of β + γ phases, the majority of which is the γ-phase. Poling of these samples resulted in the combination of the β + γ phases reaching 93% with the appearance of 40% of absolute fraction of the β-phase. We then demonstrated that the fraction of β-phase in the nanocomposite - as indicated by the 1275 cm-1 peak in PVDF's FTIR spectra - is not uniform on the surface area of the film. Additionally, the value of the absolute β-phase content also depends on the poling field's direction. Our work reveals that while considering PVDF's piezoelectric behavior, it is critical to be aware of these nuances and this article offers essential insights on how to address them. Overall, this study provides a step-by-step guideline to enhance the piezoelectricity of PVDF-based nanocomposites for sensing applications.

Analysis of hierarchical microstructural evolution in electron beam powder bed fusion Ti–6Al–4V alloys via time-of-flight neutron diffraction

Ti–6Al–4V alloys prepared via electron beam powder bed fusion (EB-PBF) generally exhibit a hierarchical microstructure consisting of columnar β-grains, an acicular α-matrix, and nanoscale β-precipitates at α-lath interfaces. In this study, we performed time-of-flight neutron diffraction measurements to investigate the texture and volume fraction of EB-PBF Ti–6Al–4V alloys via Rietveld texture analysis (RTA). The high-intensity neutron source enabled the analysis of the nanosized β-phase precipitates at the α-lath interfaces. The results indicate that the α- and β-textures of the as-built specimen can be ascribed to multiple Burgers orientation relationships among the prior β-phase, α-laths, and nanosized β-phase precipitates, which are not clearly understood. The as-built texture was maintained during post-processing, suggesting that texture manipulation in EB-PBF fabrication is important for controlling the crystallographic orientations of the built components, even after post-processing. RTA allowed a precise quantification of the β-phase fraction, which was found to have increased in post-processed specimens. The results would contribute to a comprehensive understanding of the microstructural evolution of such alloys, which is vital for the modeling and optimization of alloy performance.