High Efficiency Water Splitting using Ultrasound Coupled to a BaTiO 3 Nanofluid

To date, a number of studies have reported the use of vibrations coupled to ferroelectric materials for water splitting. However, producing a stable particle suspension for high efficiency and long-term stability remains a challenge. Here, the first report of the production of a nanofluidic BaTiO3 suspension containing a mixture of cubic and tetragonal phases that splits water under ultrasound is provided. The BaTiO3 particle size reduces from approximately 400 nm to approximately 150 nm during the application of ultrasound and the fine-scale nature of the particulates leads to the formation of a stable nanofluid consisting of BaTiO3 particles suspended as a nanofluid. Long-term testing demonstrates repeatable H2 evolution over 4 days with a continuous 24 h period of stable catalysis. A maximum rate of H2 evolution is found to be 270 mmol h–1 g–1 for a loading of 5 mg l–1 of BaTiO3 in 10% MeOH/H2O. This work indicates the potential of harnessing vibrations for water splitting in functional materials and is the first demonstration of exploiting a ferroelectric nanofluid for stable water splitting, which leads to the highest efficiency of piezoelectrically driven water splitting reported to date

Modified energy harvesting figures of merit for stress- and strain-driven piezoelectric systems

© 2019, The Author(s). Piezoelectrics are an important class of materials for mechanical energy harvesting technologies. In this paper we evaluate the piezoelectric harvesting process and define the key material properties that should be considered for effective material design and selection. Porous piezoceramics have been shown previously to display improved harvesting properties compared to their dense counterparts due to the reduction in permittivity associated with the introduction of porosity. We further this concept by considering the effect of the increased mechanical compliance of porous piezoceramics on the energy conversion efficiency and output electrical power. Finite element modelling is used to investigate the effect of porosity on relevant energy harvesting figures of merit. The increase in compliance due to porosity is shown to increase both the amount of mechanical energy transmitted into the system under stress-driven conditions, and the stress-driven figure of merit, FoM33X, despite a reduction in the electromechanical coupling coefficient. We show the importance of understanding whether a piezoelectric energy harvester is stress- or strain-driven, and demonstrate how porosity can be used to tailor the electrical and mechanical properties of piezoceramic harvesters. Finally, we derive two new figures of merit based on the consideration of each stage in the piezoelectric harvesting process and whether the system is stress- (FijX), or strain-driven (Fijx)

Additively Manufactured Ferroelectric Particulate Composites for Antimicrobial Applications

A polarized ferroelectric material can initiate the micro-electrolysis of water molecules which leads to the formation of reactive oxygen species (ROS) in an aqueous solution resulting in selective bacteria killing. This study presents the fabrication, characterization, and antimicrobial performance of poled ferroelectric particulate composites. Barium calcium zirconate titanate (BCZT) micro-powder is synthesized by a solid-state reaction and mechanically mixed with polycaprolactone (PCL) to be subsequently fed into the 3D bioprinter for the fabrication of porous PCL-BCZT structures at four different ceramic loadings (0, 10, 20, 30 wt%). For the examination of material's capacity to handle extremely high contamination, the composites are exposed to a high inoculum of bacteria (Escherichia coli ATCC 25922) ≈70% of E. coli degradation is recorded at the end of 15 min without any external intervention. The surface selective bacterial degradation can be attributed to the generated reactive oxygen species, the large surface area of the porous samples and polymer matrix's hydrophobic nature, behavior which can be reflected in the composites with 30 wt% of BCZT loading exhibiting the best antimicrobial performance among the other state-of-the-art ferroelectrics. Overall, these results indicate that the poled composites have a great potential as antimicrobial materials and surfaces

Functionally graded ferroelectric polyetherimide composites for high temperature sensing

High temperature ferroelectrics for thermally stable devices that can detect pressure and temperature are of great industrial interest. Here we describe composites of lead titanate (PT) particle-polyetherimide (PEI) polymers with stable dielectric and piezoelectric properties over a broad range of temperature and frequency. The reported materials have a low dielectric loss (tanδ ∼ 0.001 at 1 kHz) and a high piezoelectric voltage coefficient of 100 mV m N-1 at record temperatures of 175 °C. We demonstrate that a small ceramic loading leads to a significant change in thermally stable piezoelectric behavior, while the processability as well as mechanical properties remain comparable to those of the neat polymer. Careful design of the microstructure is performed by dielectrophoretic assembly of ferroelectric PT micro-particles to induce micro-wire configurations, which is shown to be a key element in attaining high functionality at low ceramic loading. Thermal imidization of the composites is performed in two steps, first partial imidization at 60 °C to form free standing films containing polyamic acid, followed by full imidization at 200 °C and 300 °C. The presence of highly polar polyamic acid results in higher dielectric permittivity and electrical conductivity that facilitate efficient poling. Upon complete imidization of the films at 300 °C the dielectric and piezoelectric properties are tested at elevated temperatures. A fully imidized composite contains completely closed imide groups, resulting in a thermally stable material with a very low dielectric loss that maintains more than 85% of its room temperature piezoelectric sensitivity up to 175 °C. The room temperature piezoelectric voltage coefficient shows more than 400% improvement over that of PT ceramics

Large area and flexible micro-porous piezoelectric materials for soft robotic skin

The need for flexible, highly sensitive tactile sensors that can fit onto curved surfaces is driving the conformable sensor materials research in the field of human–machine interactions. Here we report a new type of compliant piezoelectric active composite, a micro-porous polyurethane-PZT material, capable of generating a voltage output upon touch. The composites are synthesized with the aim of maximizing the piezoelectric sensitivity of particulate composite sensor materials. The goal is to reduce the dielectric constant of the polymer matrix and improve flexibility of conventional bulk piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system in the form of uniformly sized pores. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which increases the piezoelectric voltage sensitivity (g33) of the composite sensors significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The newly developed micro-porous composites show g33 value of 165 mV m/N that is twice that of the structured PZT-bulk PU composites (80 mV m/N) and more than five times the g33 value of bulk PZT ceramics (24–28 mV m/N). The capability of the flexible freestanding sensors for application in touch sensing devices for soft robotics is demonstrated

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere

Fractal Dimension Analysis of Grain Boundaries of 7XXX Aluminum Alloys and Its Relationship to Fracture Toughness

NovAMAMMAerospace Engineerin

Expanding the Functionality of Piezo-Particulate Composites

Novel Aerospace Material

Functionally graded ferroelectric polyetherimide composites for high temperature sensing

High temperature ferroelectrics for thermally stable devices that can detect pressure and temperature are of great industrial interest. Here we describe composites of lead titanate (PT) particle-polyetherimide (PEI) polymers with stable dielectric and piezoelectric properties over a broad range of temperature and frequency. The reported materials have a low dielectric loss (tan δ ∼ 0.001 at 1 kHz) and a high piezoelectric voltage coefficient of 100 mV m N−1 at record temperatures of 175 °C. We demonstrate that a small ceramic loading leads to a significant change in thermally stable piezoelectric behavior, while the processability as well as mechanical properties remain comparable to those of the neat polymer. Careful design of the microstructure is performed by dielectrophoretic assembly of ferroelectric PT micro-particles to induce micro-wire configurations, which is shown to be a key element in attaining high functionality at low ceramic loading. Thermal imidization of the composites is performed in two steps, first partial imidization at 60 °C to form free standing films containing polyamic acid, followed by full imidization at 200 °C and 300 °C. The presence of highly polar polyamic acid results in higher dielectric permittivity and electrical conductivity that facilitate efficient poling. Upon complete imidization of the films at 300 °C the dielectric and piezoelectric properties are tested at elevated temperatures. A fully imidized composite contains completely closed imide groups, resulting in a thermally stable material with a very low dielectric loss that maintains more than 85% of its room temperature piezoelectric sensitivity up to 175 °C. The room temperature piezoelectric voltage coefficient shows more than 400% improvement over that of PT ceramics.<br/