Additively manufactured lead zirconate titanate–polymer composites with sheet-based triply periodic minimal surface structures
Creators: name: XU, Hu
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400510
subject: Structural engineering

description: The rapid development of the world economy has led to a sharp increase in energy consumption. With the depletion of non-renewable energy and the seriousness of the environment, everyone is looking for sustainable clean energy. Wind energy, light energy, solar energy, etc., have gradually attracted people's attention. This article introduces piezoelectric ceramic materials. Piezoelectric ceramics are polycrystals formed by oxides (oxides, lead oxides, titanium oxides, etc.) through high-temperature sintering and solid-phase reactions, which have piezoelectric effect after direct current high-voltage polarization treatment. It is a significant functional material and an available ceramic material that can convert mechanical energy and electrical energy to each other. When the mechanical pressure or vibration signal is induced, there will be a voltage signal at both ends of the piezoelectric ceramic electrode. Conversely, piezoelectric materials can also convert electrical energy into vibration signals when applying electrical signals to piezoelectric ceramics. Using these two characteristics, many components with special functions can be designed. With the continuous research and improvement of materials and processes, with the development of modern science and technology, the production technology and application development of piezoelectric materials will be a hot topic that people pay attention to.

 Since the appearance of piezoelectric materials in the 20th century, due to their unique properties, fast response speed, high measurement accuracy, stable performance and other advantages, they have gradually become an essential part of the material field. However, single-phase piezoelectric materials are incredibly restricted in practical applications due to their apparent shortcomings. With the development of high-tech areas such as electronics, navigation and biology, people have higher and higher requirements for the performance of piezoelectric materials. At present, the research and development of new piezoelectric composite materials must start from the structure and use new processes to prepare various piezoelectric composite materials.  Piezoelectric ceramic-polymer composites have attracted substantial interest owing to their distinct piezoelectric performance, excellent mechanical durability, and low acoustic impedance in energy harvesting applications. This paper investigates the dependence of their output voltage on the volume fraction and structure of the ceramic component, together with the type of stimulus, using finite element analysis. When the ceramic parts of piezocomposites are shaped into structures with a topology of triply periodic minimum surface such as Schwarz Primitive surface, Gyroid surface, and Neovius surface, they exhibit much better piezoelectric performance than existing piezocomposites under both the compressive strain and the shear strain. Compared to a piezocomposite with three intersecting ceramic cuboids, Schwarz piezocomposite with the same volume fraction of 50% can increase output voltage by approximately 50% under compressive strains 2%-8%. With 16% ceramic material and under a compressive strain of 8%, Neovius piezocomposite demonstrates ~17-fold and ~6,000-fold enhancement of output voltage than that of the piezocomposite in the 3-3 mode (connected and irregularly-shaped ceramic component) and in the 0-3 mode (disconnected ceramic particles), respectively. Under simple shear, the performance superiority of Neovius piezocomposite to that of the 3-3 mode piezocomposite becomes more significant as output voltage can be enhanced up to approximately 30-fold. Computational analysis shows that high von Mises stress helps to enlarge the difference between positive and negative electrical potential, and therefore output voltage is enhanced. The findings in this work also reveal that output voltage is inversely proportional to strain energy stored in piezocomposites. Because Schwarz composite has the largest bulk modulus with minimum strain energy under compression, it can reach the highest output voltage.

Subsequently, designing piezoelectric ceramic Shellular structures with triply periodic minimal surface (TPMS) sheet is a novel approach for piezoelectric composite. Unlike the current 3-3 mode (connected and irregularly-shaped ceramic component) and 0-3 mode (disconnected ceramic particles), TPMS Shellular structures are composed of continuous and smooth shells, allowing for large surface areas straight internal channels. This paper also investigates the piezoelectric properties of four types of TPMS sheet structures (Primitive, Gyroid, Diamond and Neovius) under compression strain. Finite element analysis reveals the TPMS Shellular architecture presents a continuous pathway for load transfer to break the load transfer scaling law seen in the conventional composites with low-dimensional ceramic fillers. Four types of TPMS sheet structures exhibits exceptional piezoelectric characteristics under compression strain. With 16% ceramic material and under a compressive strain of 8%, Neovius piezoelectric composite demonstrates ~18-fold and ~7,000-fold enhancement of output voltage than that of the piezoelectric composite the 3-3 mode and in the 0-3 mode, respectively.

The current 3D printing companies are in the preliminary research stage and cannot realise the additive manufacturing of PZT materials. In this experimental project research, we expound the use of sol-gel technology to fabricate 3D PZT composites and using additive manufacturing technology to prepare a 3D polymer model. Then, the sintered PZT ceramic structure is immersed in the prepared PDMS model and solidified to form a new piezoelectric composite. Fabrication of the TPMS sheet structures is challenging because of the complex geometries, especially on a small scale. Finally, the manufactured composite samples are subjected to compression testing and compared and analysed the experimental data and simulated values.