Devices In Harsh Environments Research Articles

Designing barium titanate ceramics with high energy storage and mechanical properties

Designing the fine-grained ceramics with high recoverable energy storage density and excellent mechanical performance, still presents great challenges. Because the ceramics with large pore size and low relative density were obtained by the traditional sintering method, they always exhibit small breakdown strength and poor mechanical properties, which limits the miniaturization and operation of devices in harsh environments. In this article, we designed the barium titanate ceramics (BT) ceramics with grain size of 252 nm and relative density of 0.92 can be obtained via co-sintering of two sizes of BT particles at 1000 °C for 10 h. The cubic phase BT particles with 80 nm are doped in the tetragonal phase BT particles with 200 nm to obtain tetragonal phase fine-grained BT ceramics. When doped with 80 nm BT particles, the sintering of 200 nm BT particles is promoted. The enhanced sinterability is due to the phase transformation and metastability, which act as sintering aids. The obtained BT ceramics with nanodomains, high energy storage, and mechanical properties. The discharge energy density is of 0.81 J/cm3, and the Vickers hardness is 1.75 GPa.

Inverse-perovskites Sc3GaX (X = B, C, N): A comprehensive theoretical investigation at ambient and elevated pressures

We have made a comprehensive theoretical investigation of structural, mechanical, thermophysical, electronic, optical, thermodynamical and vibrational properties of inverse-perovskites Sc3GaX (X = B, C, N) as a function of pressure using density functional theory (DFT). Pressure dependent elastic constants are studied as regards mechanical stability, ductility, machinability and anisotropy of moduli. At ambient pressure, the density of states (DOS) at Fermi level of Sc3GaB is almost twice than that of Sc3GaC or Sc3GaN. This explains the predicted superconductivity of Sc3GaB. The nature of chemical bonding is studied via charge density distribution map. Calculated phonon dispersions exhibit dynamic stability of these compounds. The temperature and pressure dependent thermodynamic properties of Sc3GaB and Sc3GaN are investigated for the first time using quasi-harmonic Debye model. Debye and melting temperatures increase with increasing pressure which indicate that our studied compounds could be used for possible devices in harsh environments. Calculated minimum thermal conductivities of the compounds are much smaller than the optimum value (1.25 Wm−1K−1) up to 20 GPa. Hence the compounds are promising TBC materials over the entire pressure range considered. Optical properties of the compounds indicated several practical usefulness including the potential to be employed as coating materials to prevent solar heating.

Triboelectric polymer with excellent enhanced electrical output performance over a wide temperature range

Due to thermionic emission of triboelectric charge and degradation of mechanical stability of polymer tribomaterials (PTMs), PTMs based TENG (PTM-TENG) cannot maintain efficient electrical output and operate stably at high temperatures. Herein, a series of fatty acid doped PVDF-HFP (PH-FA) PTMs are fabricated. The introduction of FA lubricants dramatically increases the β-phase relative fraction, dielectric constant and surface charge potential of PTMs. Therefore, the PH-SA (stearic acid) based TENG shows improved electrical output over a wide temperature range, extraordinary stability, and durability. Particularly, the VT/VRoom, IT/IRoom and QT/QRoom of PH-SA at 100 °C are separately up to 231.10%, 251.46% and 234.01%, the output efficiency of PH-SA is still higher than 100% at 120 °C. This study not only provides pioneering reference for the development of advanced PTM-TENG with enhanced output performance over a wide temperature range, but also greatly promotes the application of PTM-TENG devices in harsh environments.

Influence of a Tailored Oxide Interface on the Quality Factor of Microelectromechanical Resonators

AbstractPiezoelectric microelectromechanical systems (MEMS) are used as sensors, actuators, energy harvesters, accelerometers, and communication modules. Aluminum nitride (AlN) is an especially attractive piezoelectric material because its fabrication process allows it to be integrated into semiconductor circuitry to deliver a fully integrated solution. Microelectromechanical resonators with AlN sandwiched between n‐type silicon (Si) and top metal electrode with and without a silicon oxide layer are designed and fabricated. The effect of the oxide film is up to a fourfold increase in quality factor (Q) that is consistent from very high frequency (VHF) to super high frequency (SHF). This effect is demonstrated using thin plate bulk acoustic wave modes from 70–80 MHz using the second contour mode and first width extensional mode and from 9.5–10.5 GHz using high overtone thickness modes. To explore potential applications of AlN‐transduced Q‐enhanced MEMS devices in harsh environments, measurements from −200 °C to +200 °C are performed. The Q enhancement is persistent across a wide temperature range for both VHF and SHF resonators with the added oxide layer. Furthermore, AlN‐on‐Si resonators that have a comparable temperature coefficient of frequency to silicon carbide‐based resonators in commercial applications are demonstrated.

Harsh Environmental-Tolerant and High-Performance Triboelectric Nanogenerator Based on Nanofiber/Microsphere Hybrid Membranes.

Triboelectric nanogenerator (TENG) can convert tiny mechanical energy into precious electrical energy. Constant improvements to the output performance of TENG is not only the driving force for its sustainable development, but also the key to expand its practical applicability in modern smart devices. However, most previous studies were conducted at room temperature, ignoring the influence of temperature on the output performance of TENG. Additionally, due to thermionic emission effect, the electrons transferred to a dielectric surface can be released into a vacuum after contact electrification. Therefore, TENG cannot maintain an effective electrical output under high-temperature conditions. Here, a series of high-temperature operatable flexible TENGs (HO-TENGs) based on nanofiber/microsphere hybrid membranes (FSHMs) was fabricated by electrospinning and electrospraying. The Voc of HO-TENG is 212 V, which is 2.33 times higher than that of control TENG. After 10,000 cycle stability tests, the HO-TENG shows excellent durability. Especially, this HO-TENG can maintain 77% electrical output at 70 °C compared to room temperature, showing excellent high-temperature operability. This study can not only provide a reference for the construction of advanced high-performance TENG, but also provide a certain experimental basis for efficient collection of mechanical energy in high-temperature environment and promote the application of TENG devices in harsh environments.

Highly compressible and environmentally adaptive conductors with high-tortuosity interconnected cellular architecture

Conductive hydrogels that are highly elastic, fatigue resistant and environmentally adaptive are promising materials in the fields of wearable electronics, bioelectronics and soft robotics. However, these materials are challenging to develop, especially for use in harsh environments including organic solvents and extreme temperatures. Here we report a simple method for the fabrication of highly compressible and fatigue-resistant conductive hydrogels with reinforced-concrete-type constituents and high-tortuosity interconnected cellular architecture through a self-assembly and two-stage in situ polymerization process. The obtained composites exhibit excellent mechanical compressibility with negligible residual strain at 50% strain for >104 cyclic loadings both in air and water. Due to the structure-favoured anisotropic response to tensile deformations coupled with elastic recovery, the hydrogel is endowed with sensing dimensions which allow the direction and velocity of movement on the sensor surface to be distinguished. In addition, by interpenetrating with an oleophilic polymer network, highly elastic and adaptive organohydrogels are developed with outstanding sensing performance in a wide variety of organic solvents and cryogenic temperatures. These materials may therefore be suitable for use in flexible and wearable devices in harsh environments.

High-temperature Pt–Al2O3 composite nano-thick interdigital electrodes for surface acoustic wave sensors

High-temperature stability of ultra-thin film electrodes is vital for surface acoustic wave (SAW) devices in harsh environments. This paper proposed the Pt–Al2O3 composite Nano-thick interdigital electrodes (IDEs) for langasite-based high-temperature SAW sensors. The sandwich structure of the IDEs was composed of Pt layers and Al2O3 armors. The armor consisting of barrier and coating layers was introduced to reduce the agglomeration, oxidation, and interdiffusion of IDEs at high temperatures. Capacitive bonding pads were proposed to transmit radiofrequency signals through the closed armor. The composite IDEs (226 nm thickness) had good structural stability and impurities concentration less than 1% at 1000 °C (3 h, air condition). Improved quality factors of 8805, and matched electrical impedance of 51 Ω and −16° were achieved through the electroacoustic optimized IDEs. Finally, multiple SAW temperature sensors using the composite IDEs presented fitting errors less than 1% and hysteresis errors below 4% in 80–1000 °C exceeded 9 h, which was 150 °C higher than existing ones. The proposed composite IDEs enable SAW devices to be applicated in 80–1000 °C.

Robust, fatigue resistant, self-healing and antifreeze ionic conductive supramolecular hydrogels for wearable flexible sensors

Ionic conductive hydrogel-based sensors have been capturing growing attention in various areas, but still cannot satisfy the operating requirements of next generation wearable electronics. Herein, inspired by biosystems, we demonstrate ionic conductive supramolecular hydrogels with simple one-step method based on salting-out effect and multiple hydrogen bond interactions. The supramolecular hydrogels exhibit high toughness and strength, quick self-recovery, high sensitive sensing performance as well as good self-healing, fatigue and frost resistances in mechanical and sensing properties, and can monitor large and subtle movements and physiological activities of the human body sensitively, quickly and stably. Thus, it provides a convenient and promising way to obtain stretchable sensors of excellent comprehensive properties, which have tremendous application potential as wearable electronic devices in harsh environments.

Mechanically Stable All Flexible Supercapacitors with Fracture and Fatigue Resistance under Harsh Temperatures

AbstractFor practical applications in the fields of aerospace and robotic engineering, flexible energy storage devices must be stable under environmental temperatures and different deformed situations. In this work, a mechanically stable supercapacitor (SC) at harsh ambient temperatures is synthesized by in situ polymerization of polyaniline(PANI) onto a double network hydrogel electrolyte from cross‐linked polyvinyl alcohol(PVA) and polyacrylamide/acrylic acid (PAM/AA) networks. The highly integrated structure endows the supercapacitor with unprecedented mechanical performance. The devices can endure 608% tensile strain and be stretched up to 50% without noticeable hysteresis, demonstrating fatigue and fracture resistance under thousands of cyclic loads. Benefiting from an all‐flexible configuration through seamless integration of the PANI electrode, the supercapacitor presents a high specific capacitance of 95.8 mF cm–2. It can also work as an all‐flexible device and maintain its stable output under complex deformations, even physical damages. Furthermore, the device delivers excellent environmental adaptability by steady electrochemical performance after operating at extreme temperatures from −60 to 100 °C. Such a versatile supercapacitor presents a potential application in integrated flexible electronic systems by powering functional devices in harsh environments.

Designing Barium Titanate Ceramics with High Energy Storage and Mechanical Properties

Designing the fine-grained ceramics with high recoverable energy storage density and excellent mechanical performance, still presents great challenges. Because the ceramics with large pore size and low relative density were obtained by the traditional sintering method, they always exhibit small breakdown strength and poor mechanical properties, which limits the miniaturization and operation of devices in harsh environments. In this paper, we designed the barium titanate ceramics (BT) ceramics with grain size of 252 nm and relative density of 0.92 can be obtained via co-sintering of two sizes of BT particles at 1000 °C for 10 h. The cubic phase BT particles with 80 nm are doped in the tetragonal phase BT particles with 200 nm to obtain tetragonal phase fine-grained BT ceramics. When doped with 80 nm BT particles, the sintering of 200 nm BT particles is promoted. The enhanced sinterability is due to the phase transformation and metastability, which act as sintering aids. The obtained BT ceramics with nanodomains, high energy storage and mechanical properties. The discharge energy density is of 0.81 J/cm3, and the Vickers hardness is 1.75 GPa.

Room‐Temperature Printing of Ultrathin Quasi‐2D GaN Semiconductor via Liquid Metal Gallium Surface Confined Nitridation Reaction

AbstractOutstanding wide‐bandgap semiconductor material such as gallium nitride (GaN) has been extensively utilized in power electronics, radiofrequency amplifiers, and harsh environment devices. Due to its quantum confinement effect in enabling desired deep‐ultraviolet emission, excitonic impact, and electronic transport features, 2D or ultrathin quasi‐2D GaN semiconductors have been one of the most remarkable candidates for future growth of microelectronic devices. Here, for the first time, the authors report a large area, wide bandgap, and room‐temperature quasi‐2D GaN synthesis and printing strategy through introducing the plasma medicated liquid metal gallium surface‐confined nitridation reaction mechanism. The developed direct fabrication and compositional process is consistent with various electronics manufacturing approaches and thus opens an easy going way for cost‐effective growth of the third‐generation semiconductor. In particular, the fully printed field‐effect transistors relying on the GaN thus made show p‐type switching with an on/off ratio greater than 105, maximum field‐effect hole mobility of 53 cm2 V−1 s−1, and a small sub‐threshold swing. As demonstrated, the present method allows to produce at room temperature the GaN with thickness spanning from 1 nanometer to nanometers. This basic method can be further extended, generalized, and utilized for making various electronic and photoelectronic devices in the coming time.

Ultra-Stretchable and Fast Self-Healing Ionic Hydrogel in Cryogenic Environments for Artificial Nerve Fiber.

Self-healing materials behave with irreplaceable advantages in biomimetic intelligent robots (BIR) for avoiding or reducing safety hazards and economic losses from accidental damage during service. However, the self-healing ability is unreservedly lost and even becomes rigid and fragile in the cryogenic environment where BIR are precisely needed. Here, the authors report a versatile ionic hydrogel with fast self-healing ability, ultra-stretchability, and stable conductivity, even at -80°C. The hydrogel is systematically optimized to improve a hydrogen-bonded network nanostructure, coordinated achieving a quick self-healing ability within 10min, large deformation tolerance of over 7000%, superior conductivity of 11.76 S cm-1 and anti-freezing ability, which is difficult to obtain simultaneously. Such a hydrogel provides new opportunities for artificial electronic devices in harsh environments. As a prospective application, they fabricate an artificial nerve fiber by mimicking the structure and functions of the myelinated axon, exhibiting the property of fast and potential-gated signal transmission. This artificial nerve fiber is integrated into a robot for demonstrating a real-time high fidelity and high throughput information interaction under big deformation and cryogenic temperature. The hydrogel and bionic device will bring pioneering functions for robots and open a broad application scenario in extreme conditions.

Ultrathin and Mechanically Robust Mussel Byssus‐Inspired MXene@Aramid Nanofibers Materials with Superior Endurance in Harsh Environments for Tunable EMI Shielding Performance

AbstractReducing the fire hazards caused by high power electromagnetic (EM) waves and maintaining operational status of EM interference (EMI) shielding devices in harsh environments have caught increasing eyesight. In this paper, a series of promising EMI shielding materials with mussel byssus‐inspired structure are accomplished via an efficient vacuum‐assisted filtration approach. The flexible multilayered MXene@ANF nacres reveal superior mechanical property compared with both self‐supporting MXene film and MXene@ANF mixture film. Meanwhile, these nacres exhibit both exceeding and tunable EMI shielding effectiveness (EMI SE) of 40–60 dB in 8.2–12.4 GHz with a thickness of ≈20 µm and the absolute SE (SSEt) accomplishes 36641.94 dB·cm2 g−1. Besides, the exceeding thermal insulation of ANF offers the MXene nacres with an outstanding flame‐stopping capacity, and it can still block 99.99% EM waves after 2 min burning. Furthermore, MXene nacres perform superior endurance in harsh environment and retain EMI SE of 42 dB after the ultralow temperature damage. The EMI SE and fire safety of MXene@ANF with two typical structures, composite films and foam, are also systematically investigated. Therefore, this work is promising to fabricate tunable EMI shielding products with low fire hazards and high endurance in harsh environments.

High Strain Rate Mechanical Properties of SAC-Q Solder for Extreme Temperatures After Exposure to Isothermal Aging Up to 90 Days

Abstract Electronic components are subject to high strain, during shock and vibration in many applications such as the automobile and aerospace. In many cases, this kind of electronic components will also be exposed to harsh temperatures of –65 °C to 200 °C. Electronic devices in harsh environments are often subject to strain rates of 1–100 per second. A large number of doped SAC solder alloys have emerged including SAC-Q, SAC-R, Innolot for electronic component interconnection. SAC-Q consists of inclusion of the Bi composition in Sn–Ag–Cu. For maximizing electronic package stability and high temperature storage and strain rates, the mechanical characteristic results and data for lead-free solder alloys are extremely significant. Thermal aging has been previously shown to cause modification of the mechanical properties at low strain rates. High strain-rate SAC-Q solder alloy data are not available for high temperature aging and testing at very low to high operating temperatures. For this analysis, the SAC-Q solder material was measured and analyzed at operating temperatures between –65 °C and 200 °C, at strain rates of up to 75 per second. Comparison with solder material SAC305, which has been tested under similar conditions, has also been made. When tensile experiments were carried out at various working temperatures, specimens for isothermal aging were preserved at 100 °C for up to 90 days after production and reflowing. The stress–strain curves are developed and described in this paper for a wide range of strain rates and test temperatures. Furthermore, the test results and data measured have been matched to the Anand viscoplasticity model and Anand constants have been determined by estimation of the high strain rate behavior measured in the broad range of working temperatures and stress levels.

Suppressing Thermal Negative Effect and Maintaining High-Temperature Steady Electrical Performance of Triboelectric Nanogenerators by Employing Phase Change Material.

Triboelectric nanogenerators (TENGs) are newly developed energy-harvesting mechanisms, which can efficiently transmute irregular mechanical energy into scarce electrical energy. However, the electrical performance of TENGs shows a decreasing tendency with the increase in temperature, and the negative effect caused by friction heat and operating environmental thermal stresses for the output performance, durability, and reliability are still a bottleneck, restricting the practical application of TENG electronic devices. Especially for wearable TENG devices, the heat-induced temperature rise evokes extreme discomfort and even hazards to human health. To effectively suppress the thermal negative effect and maintain the high-temperature steady electrical performance of TENGs, a novel thermo-regulating TENG (Tr-TENG) based on phase change materials (PCMs) is designed. The results state clearly that the Tr-TENG can maintain steady output performance without deterioration by the introduction of PCMs, during continuous heating and natural cooling, while the output performance of conventional TENG is decayed by 18.33%. More importantly, the Tr-TENG possesses high-efficiency thermal management ability, resulting in its improved durability, reliability, and thermal comfort. This study creates new possibilities for the development of advanced multifunctional TENGs with attractive characteristics and desirable performances and promotes the application of TENG electronic devices in harsh environments.

Microstructure-Based Fiber-To-Chip Coupling of Polymer Planar Bragg Gratings for Harsh Environment Applications.

This article proposes and demonstrates a robust microstructure-based fiber-to-chip coupling scheme for planar Bragg grating devices. A polymer planar Bragg grating substrate is manufactured and microstructured by means of a micromilling process, while the respective photonic structures are generated by employing a sophisticated single-writing UV-exposure method. A stripped standard single-mode fiber is inserted into the microstructure, which is filled with a UV-curable adhesive, and aligned with the integrated waveguide. After curing, final sensor assembly and thermal treatment, the proposed coupling scheme is capable of withstanding pressures up to 10 bar, at room temperature, and pressures up to 7.5 bar at an elevated temperature of 120 °C. Additionally, the coupling scheme is exceedingly robust towards tensile forces, limited only by the tensile strength of the employed single-mode fiber. Due to its outstanding robustness, the coupling scheme enables the application of planar Bragg grating devices in harsh environments. This fact is underlined by integrating a microstructure-coupled photonic device into the center of a commercial-grade carbon fiber reinforced polymer specimen. After its integration, the polymer-based Bragg grating sensor still exhibits a reflection peak with a dynamic range of 24 dB, and can thus be employed for sensing purposes.

Dielectric, mechanical and thermal properties of all-organic PI/PSF composite films by in situ polymerization

Abstract All-organic high dielectric materials are highly required in the field of modern electronic industry and energy storage. In this work, all-organic polyimide/polysulfone composite films with different amounts of PSF (PI/PSF-X) were prepared by in situ polymerization followed by film casting and thermal treatment. The dielectric, mechanical and thermal properties of these PI/PSF-X composite films are characterized by dielectric measurement, tensile test, thermogravimetric analysis and dynamic mechanical analysis. The results suggest that the PI/PSF-X composite films have good dielectric properties, good mechanical properties and excellent thermal properties, which are suitable for applications in electronic devices in harsh environments, especially in high-temperature environments.

Effects of Gamma Irradiation on Functional Response of Relaxor-Ferroelectric Thin Films.

This work investigates the radiation response of relaxor-ferroelectric, lead magnesium niobate-lead titanate (PMN-PT) thin films, as an alternative material for microelectromechanical system (MEMS) devices in harsh environments. PMN-PT (0.7Pb[Mg1/3Nb2/3]O3-0.3PbTiO3) thin films were fabricated via chemical solution deposition onto platinized Si wafers and exposed to gamma radiation doses up to 10 Mrad(Si). The functional response of the thin films was measured before and after irradiation, and the resulting changes were reported. Within the radiation dose range studied, dielectric permittivity, tunability, and saturated polarization showed <5% change, and saturated piezoelectric coefficient <10% change. Additionally, PMN-PT thin films showed equivalent or superior radiation tolerance compared with lead zirconate titanate thin films previously studied. Higher chemical heterogeneity and greater domain wall mobility are expected to contribute to overall greater radiation tolerance in PMN-PT thin films. Nonlinear trends were found in dielectric and piezoelectric response with increasing dose, showing enhanced response at low doses of radiation before degradation at high doses. However, such variations were also within the experimentally observed dispersion of the data. The results are expected to impact systems to be deployed in areas of high radiation exposure, including systems used in aerospace, medical physics, X-ray/high-energy source measurement tools, and continuous monitoring of nuclear power applications.

The piezoelectric and dielectric properties of flexible, nanoporous, self-assembled boron nitride nanotube thin films

Boron nitride nanotubes (BNNTs) are one-dimensional dielectric and piezoelectric nanomaterials with non-cytotoxic properties and superb chemical and thermal stabilities. Regarding practical applications, a flexible, nanoporous, self-assembled film is one of the most low-cost usable structures. Here, we reveal a unique nanocatalyst-assisted ink spray coating method to synthesize 4.69-eV optical bandgap NTs and an easy mechanical peeling method to obtain an attractive nanoporous freestanding NT thin film with high flexibility and 91.45% porosity. Importantly, the piezoelectric d33 coefficient of the 90-nm-radius NT is 41.12 pm V−1, more than triple the value reported previously, due to the inner bamboo structure, and this coefficient is a function of radius. The nanoporous bamboo-type NT film shows excellent dielectric properties, with a relation dielectric constant of 5.15 and a dielectric constant of 9.78 for the solid type (ignoring air), which is more than triple the value of the cylindrical type. Moreover, the capacitance loss and electrical conductance versus frequency have great potential for a dielectric layer under high-frequency capacitance. Hence, bamboo-type BNNTs and their films can reasonably be widely applied in flexible electronic devices, high-precision piezoelectric sensors, and intelligent bioelectronic devices in harsh environments.

On-Chip Curing by Microwave for Long Term Usage of Electronic Devices in Harsh Environments

Microwave-induced thermal curing is demonstrated to improve the reliability and to prolong the lifetime of chips containing nanoscale electron devices. A film containing graphite powder with high microwave absorbing efficiency was fabricated at low cost. The film is flexible, bendable, foldable, and attachable to a chip. A commercial off-the-shelf chip and a representative 3-dimensional (3D) metal-oxide-semiconductor field-effect transistor (MOSFET), known as FinFET, were utilized to verify the curing behaviors of the microwave-induced heat treatment. The heat effectively cured not only total ionizing dose (TID) damage from the external environment, but also internal electrical stress such as hot-carrier injection (HCI), which are representative sources of damages in MOSFET insulators. Then, the characteristics of the pre- and post-curing electron devices are investigated using electrical measurements and numerical simulations.