The importance of materials for advanced energy technologies

Development of technology to meet the energy problems facing the industrialized countries depends strongly on the availability of improved constructional materials, in order to achieve more efficient conversion and utilization of energy. Due to the use of high temperatures and aggressive environments, ceramic and composite materials have to be considered, as well as steels and superalloys. In turn, the development of materials technology relies upon research into the relationships between structure and properties of materials.

This paper argues that scientific training for materials scientists is now much more urgently needed than in the past, in order to ensure the adequate and timely development of the required materials. Materials science should therefore be reassessed and its technological aspects emphasized. Finally, proposals are made for intensified international cooperation between materials laboratories and institutions to accomplish this task.     

Advanced pyroelectric materials for energy harvesting and sensing applications

Heat energy is among the most wasted energy in the environment which is available in an ample quantity. So, developing new technology for harvesting and detecting wasted thermal energy to produce electrical energy which may be used as reliable energy sources for ultra-low power devices like nanogenerators and self-powered sensor applications. In this approach, pyroelectric energy harvesting technology has gained a huge attraction for application in power generation and sensing systems. Currently, a class of pyroelectric and piezoelectric materials has drawn enormous attraction because of its pyroelectric effect caused by spontaneous polarization and successful thermal energy harvesting for producing electrical energy for application in many sensor networks. This review makes a comprehensive summary of the significance and physical application of pyroelectric materials including single crystal, inorganic films, ceramics, organic materials, polymers, and composites as energy harvesting devices for scavenging thermal energy from surrounding for sensing devices. Finally, the perspective for next-generation self-powered sensor technologies is described.     

Cyclic energy harvesting from pyroelectric materials

A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm(3), which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.     

Novel metal-hydride materials and technologies: Recent advances and further prospects

We present the review of joint works between the Physicomechanical Institute of the Ukrainian Academy of Sciences and the University of Birmingham on investigations of fundamental and applied aspects of the development of new intermetallic hydrides carried out in 1992–1997. Most attention is paid to the results of the following investigations: first experimental observations of the appearance of “anomalously bound” hydrogen in NdFeB permanent magnets during their brittle fracture in hydrogen environments; the use of hydrogen vibrodecrepitation in the synthesis of materials with advanced properties; new advanced hydrogen absorbers, their structure and magnetic properties; the application of the hydrogenation-disproportionation-desorption-recombination process to alloys of rare-earth metals and zirconium as hydrogen storages and permanent-magnet materials. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. School of Metallurgy and Materials, University of Birmingham, UK. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 4, pp. 39–52, July–August, 1997.     

Emerging X-ray imaging technologies for energy materials

With the growing need for sustainable energy technologies, advanced characterization methods become more and more critical for optimizing energy materials and understanding their operation mechanisms. In this review, we focus on the synchrotron-based X-ray imaging technologies and the associated applications in gaining fundamental insights into the physical/chemical properties and reaction mechanisms of energy materials. We will discuss a few major X-ray imaging technologies, including X-ray projection imaging, transmission X-ray microscopy, scanning transmission X-ray microscopy, tender and soft X-ray imaging, and coherent diffraction imaging. Researchers can choose from various X-ray imaging techniques with different working principles based on research goals and sample specifications. With the X-ray imaging techniques, we can obtain the morphology, phase, lattice and strain information of energy materials in both 2D and 3D in an intuitive way. In addition, with the high-penetration X-rays and the high-brilliance synchrotron sources, operando/in-situ experiments can be designed to track the qualitative and quantitative changes of the samples during operation. We expect this review can broaden readers’ view on X-ray imaging techniques and inspire new ideas and possibilities in energy materials research.     

Advanced triboelectric materials for liquid energy harvesting and emerging application

Triboelectric properties of materials play an essential role in liquid energy harvesting and emerging application. The triboelectric properties of materials can be controlled by chemical functionalization strategy, which can improve the utilization of liquid energy resources or reduce the hazards of electrostatic effects. Herein, the latest research progress in molecular modification based on chemical functionalization to control triboelectric properties of materials is systematically summarized. By introducing the mechanism of contact electrification between liquid and solid materials and the developmental history of liquid–solid contact electrification, the influence of solid surface charge density, wettability and liquid properties on contact electrification of liquid and solid materials is described. Research progress on chemical functionalization for improving the hydrophobicity of solid materials, surface charge density of solid materials and triboelectric properties of liquid materials is highlighted. The focus then turns to the significance of enhanced liquid–solid contact electrification in energy harvesting, self-powered sensors and metal corrosion protection. Recent advances in chemical functionalization strategies for weakening the triboelectric properties of solid and liquid materials are also highlighted. Finally, an outlook of the potential challenges for developing chemical functionalization strategies in the field of solid surface modification and liquid molecular modification is presented.     

用于锂离子电池的石墨烯材料——储能特性及前景展望

石墨烯具有独特的二维结构、优异的性能和各种潜在的应用价值,是当前材料科学领域研究的热点.通过简要评述石墨烯作为锂离子电池负极材料的结构与性能的关系,讨论了作为电极材料的石墨烯结构与功能调控的重要性,指出石墨烯基纳米材料是一种很有吸引力的锂离子电池电极材料,尤其针对高能量密度与高功率密度电池.     

Nanostructured materials for advanced energy conversion and storage devices

New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments in the discovery of nanoelectrolytes and nanoelectrodes for lithium batteries, fuel cells and supercapacitors. The advantages and disadvantages of the nanoscale in materials design for such devices are highlighted.     

Optimization and improvement of thermal energy harvesting by using pyroelectric materials

We deal with the thermal energy which is one of the ambient energy sources surely exploitable, but it has not been much interest as the mechanical energy. In this paper, our aim is to use thermal energy and show that it’s an important source for producing the electrical energy through pyroelectric effect which is the property of some dielectric materials to show a spontaneous electrical polarization versus temperature. In this context, we present a concept to harvest a thermal energy using infrared rays and pyroelectric effect.The pyroelectric material used in this work can generate an electrical voltage when it subjected to a temperature change which will be ensured by the use of infrared lamp. Our experimental results show that the electrical voltage, current and harvested power increased significantly when increasing the area of the pyroelectric element. The experimental results show also that with this simple concept we harvested a heavy amount value of power which will certainly be useful in an extensive range of applications, including sensors and infrared detection. These results shed light on the thermoelectric energy conversion by Ceramic lead zirconate titanate (PZT) buzzer having the pyroelectric property.     

Electromagnetic energy harvester for harvesting acoustic energy

This paper reports a suspended coil, electromagnetic acoustic energy harvester (AEH) for extracting acoustical energy. The developed AEH comprises Helmholtz resonator (HR), a wound coil bonded to a flexible membrane and a permanent magnet placed in a magnet holder. The harvester’s performance is analyzed under different sound pressure levels (SPLs) both in laboratory and in real environment. In laboratory, when connected to 50 Ω load resistance and subjected to an SPL of 100 dB, the AEH generated a peak load voltage of 198.7 mV at the resonant frequency of 319 Hz. When working under the optimum load resistance, the AEH generated an optimum load power of 789.65 µW. In real environment, the developed AEH produced a maximum voltage of 25 mV when exposed to the acoustic noise of a motorcycle and generated an optimum voltage of 60 mV when it is placed in the surroundings of a domestic electrical generator.     

A new piezoelectric energy harvesting design concept: multimodal energy harvesting skin

This paper presents an advanced design concept for a piezoelectric energy harvesting (EH), referred to as multimodal EH skin. This EH design facilitates the use of multimodal vibration and enhances power harvesting efficiency. The multimodal EH skin is an extension of our previous work, EH skin, which was an innovative design paradigm for a piezoelectric energy harvester: a vibrating skin structure and an additional thin piezoelectric layer in one device. A computational (finite element) model of the multilayered assembly - the vibrating skin structure and piezoelectric layer - is constructed and the optimal topology and/or shape of the piezoelectric layer is found for maximum power generation from multiple vibration modes. A design rationale for the multimodal EH skin was proposed: designing a piezoelectric material distribution and external resistors. In the material design step, the piezoelectric material is segmented by inflection lines from multiple vibration modes of interests to minimize voltage cancellation. The inflection lines are detected using the voltage phase. In the external resistor design step, the resistor values are found for each segment to maximize power output. The presented design concept, which can be applied to any engineering system with multimodal harmonic-vibrating skins, was applied to two case studies: an aircraft skin and a power transformer panel. The excellent performance of multimodal EH skin was demonstrated, showing larger power generation than EH skin without segmentation or unimodal EH skin.     

Toward energy harvesting using active materials and conversion improvement by nonlinear processing

This paper presents a new technique of electrical energy generation using mechanically excited piezoelectric materials and a nonlinear process. This technique, called synchronized switch harvesting (SSH), is derived from the synchronized switch damping (SSD), which is a nonlinear technique previously developed to address the problem of vibration damping on mechanical structures. This technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. Comparatively with standard technique, the electrical harvested power may be increased above 900%. The performance of the nonlinear processing is demonstrated on structures excited at their resonance frequency as well as out of resonance.