No abstract

A simple and facile method was developed to fabricate functional bulk barium titanate (BaTiO3, BT) ceramics using the paste extrusion 3D printing technique. The BT ceramic is a lead‐free ferroelectric material widely used for various applications in sensors, energy storage, and harvesting. There are several traditional methods (eg, tape casting) to process bulk BT ceramics but they have disadvantages such as difficult handing without shape deformation, demolding, complex geometric shapes, expansive molds, etc. In this research, we utilized the paste extrusion 3D printing technique to overcome the traditional issues and developed printable ceramic suspensions containing BT ceramic powder, polyvinylidene fluoride (PVDF), N,N‐dimethylformamide (DMF) through simple mixing method and chemical formulation. This PVDF solution erformed multiple roles of binder, plasticizer, and dispersant for excellent manufacturability while providing high volume percent and density of the final bulk ceramic. Based on empirical data, it was found that the maximum binder ratio with good viscosity and retention for desired geometry is 1:8.8, while the maximum BT content is 35.45 vol% (77.01 wt%) in order to achieve maximum density of 3.93 g/cm3 (65.3%) for 3D printed BT ceramic. Among different sintering temperatures, it was observed that the sintered BT ceramic at 1400°C had highest grain growth and tetragonality which affected high performing piezoelectric and dielectric properties, 200 pC/N and 4730 at 103 Hz respectively. This paste extrusion 3D printing technique and simple synthesis method for ceramic suspensions are expected to enable rapid massive production, customization, design flexibility of the bulk piezoelectric and dielectric devices for next generation technology.

Wireless passive temperature sensors are receiving increasing attention due to the ever-growing need of improving energy efficient and precise monitoring of temperature in high temperature energy conversion systems such as gas turbines and coal-based power plants. Unfortunately, the harsh environment such as high temperature and corrosive atmosphere present in these systems has significantly limited the reliability and increased the costs of current solutions. Therefore, this paper presents the concept and design of a low cost, passive, and wireless temperature sensor that can withstand high temperature and harsh environments. The temperature sensor was designed following the principle of metamaterials by utilizing Closed Ring Resonators (CRR) in a dielectric ceramic matrix. The proposed wireless, passive temperature sensor behaves like an LC circuit, which has a temperature dependent resonance frequency. Full wave electromagnetic solver Ansys Ansoft HFSS was used to validate the model and evaluate the effect of different geometry and combination of Split Ring Resonator (SRR) structures on the sensitivity and electrical sizes of the proposed sensor. The results demonstrate the feasibility of the sensor and provide guidance for future fabrication and testing.

Abstract

This research studied multifunctional sensing capabilities on nanocomposites composed of poly(vinylidene) fluoride (PVDF), BaTiO 3 (BT), and multiwall carbon nanotubes (CNTs) fabricated by fused-deposition modeling 3D printing. To improve the dielectric property within BT/PVDF composites, CNTs have been utilized to promote ultrahigh polarization density and local micro-capacitor among BT and polymer matrix. The 3D printing process provides homogeneous dispersion of nanoparticles, alleviating agglomeration of nanoparticles, and reducing micro-crack/voids in matrix which can enhance their dielectric property. In this research, we demonstrated that by utilizing unique advantages of this material combination and a 3D printing technique, sensing capabilities for temperature and strain can be engineered with different content variations of included BT and CNTs. It is observed that the sensing capability for temperature change with respect to a 25-150 C range can be improved as both BT and CNTs' inclusions increase and is maximal with 1.7 wt.% CNTs/60 wt.% BT/PVDF nanocomposites, while the sensing capability for strain change in a 0-20% range is maximal with 1 wt.% CNTs/12 wt.% BT/PVDF nanocomposites. In addition, it is found that the best combination for mechanical toughness is 1 wt.% CNTs/12 wt.% BT/PVDF with 24.2 MPa and 579% in ultimate tensile strength and failure strain, respectively. These results show the technique to 3D print multifunctional nanocomposites with temperature and strain sensing capabilities as well as increased mechanical property. Furthermore, this research demonstrated the feasibility for large-scale multifunctional sensor device manufacturing with freedom of design, low-cost, and an accelerated process.