Additive manufacturing of complex structures with spatially varying electromagnetic properties can enable new applications in high-technology sectors such as communications and sensors. This work ...presents the fabrication method as well as microstructural and dielectric characterization of bespoke composite filaments for fused deposition modeling (FDM) 3D printing of microwave devices with a high relative dielectric permittivity ϵ = 11 in the GHz frequency range. The filament is composed of 32 vol % of ferroelectric barium titanate (BaTiO 3 ) micro-particles in a polymeric acrylonitrile butadiene styrene (ABS) matrix. An ionic organic ester surfactant was added during formulation to enhance the compatibility between the polymer and the BaTiO 3 . To promote reproducible and robust printability of the fabricated filament, and to promote plasticity, dibutyl phthalate was additionally used. The combined effect of 1 wt % surfactant and 5 wt % plasticizer resulted in a uniform, many hundreds of meters, continuous filament of commercial quality capable of many hours of uninterrupted 3D printing. We demonstrate the feasibility of using the high dielectric constant filament for 3D printing through the fabrication of a range of optical devices. The approach herein may be used as a guide for the successful fabrication of many types of composite filament with varying functions for a broad range of applications.
High-entropy alloys (HEAs), based on equiatomic or near-equiatomic mixture of usually four or more elements, have attracted considerable attention as there are indications that along with surprising ...microstructural simplicity of some alloys, they may also offer intriguing combinations of mechanical and other properties. Amongst these properties, there is growing interest in the irradiation response of HEAs and their potential to withstand the neutron bombardment environment of future civil nuclear power plants. One of the first proposed HEAs is face-centred cubic CrMnFeCoNi, also known as the Cantor alloy, and the irradiation response of the Cantor alloy and its sub-systems are the focus of this review. Using irradiation analogues (electrons, heavy ions and He) to neutron bombardment and considering simulations, advanced microstructural analysis and property measurement, the Cantor alloy and its derivatives are shown to exhibit encouraging irradiation resistance that, in many instances, is superior to more traditional dilute alloys of the same elements. The beneficial aspects are high phase stability and resistance to radiation-induced segregation, smaller size but higher number density of dislocation loops, significantly lower extent of swelling and improved resistance to He bubble growth. The future research directions for irradiation resistant HEAs are also suggested.
The potential for MoO3 use as a supercapacitor electrode in aqueous electrolytes was investigated. α-MoO3 nanobelts were synthesized using a hydrothermal method and then thin-film electrodes were ...manufactured by spray deposition. Electrochemical testing in several aqueous electrolytes showed significant charge storage in 1M H2SO4 with a complex electrochemical activity that was further investigated by X-ray photoelectron spectroscopy and various electrochemical characterization methods. In a 0–1V (vs Ag/AgCl) electrochemical window, MoO3 was reduced to a mixture of lower valence oxides with concentrations varying as Mo (5+) > Mo (4+) > Mo (6+), with MoO2 as the main component at potentials below 0.185V (vs Ag/AgCl). The degree of redox reversibility was evaluated in order to optimize the electrochemical window for enhanced cyclability. A moderate capacitance of 8.8Fg−1 (64 μFcm−2) was fully retained for 720 cycles in an optimized electrochemical window of 0.26–0.43V (vs Ag/AgCl).
The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked ...a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.
Although the field of genetics has grown by leaps and bounds within the last decade due to the completion and availability of the human genome sequence, transcriptional regulation still cannot be ...explained solely by an individual's DNA sequence. Complex coordination and communication between a plethora of well-conserved chromatin modifying factors are essential for all organisms. Regulation of gene expression depends on histone post translational modifications (HPTMs), DNA methylation, histone variants, remodeling enzymes, and effector proteins that influence the structure and function of chromatin, which affects a broad spectrum of cellular processes such as DNA repair, DNA replication, growth, and proliferation. If mutated or deleted, many of these factors can result in human disease at the level of transcriptional regulation. The common goal of recent studies is to understand disease states at the stage of altered gene expression. Utilizing information gained from new high-throughput techniques and analyses will aid biomedical research in the development of treatments that work at one of the most basic levels of gene expression, chromatin. This chapter will discuss the effects of and mechanism by which histone modifications and DNA methylation affect transcriptional regulation.
•A model of acoustic streaming accounting for cavitation is implemented in OpenFOAM.•A 2D simulation matches the results of a water PIV experiment.•The net flow direction dependents on the transducer ...power, with upflow favoured at low power.•Acoustic streaming downflow is established at higher transducer powers.•Flow reversal is predicted to also occur in aluminium when the model is applied to liquid aluminium melt processing.
The acoustic streaming behaviour below an ultrasonic sonotrode in water was predicted by numerical simulation and validated by experimental studies. The flow was calculated by solving the transient Reynolds-Averaged Navier-Stokes equations with a source term representing ultrasonic excitation implemented from the predictions of a nonlinear acoustic model. Comparisons with the measured flow field from Particle Image Velocimetry (PIV) water experiments revealed good agreement in both velocity magnitude and direction at two power settings, supporting the validity of the model for acoustic streaming in the presence of cavitating bubbles. Turbulent features measured by PIV were also recovered by the model. The model was then applied to the technologically important area of ultrasonic treatment of liquid aluminium, to achieve the prediction of acoustic streaming for the very first time that accounts for nonlinear pressure propagation in the presence of acoustic cavitation in the melt. Simulations show a strong dependence of the acoustic streaming flow direction on the cavitating bubble volume fraction, reflecting PIV observations. This has implications for the technological use of ultrasound in liquid metal processing.
PDF
