Extreme Environment Applications Research Articles

Triple-shape memory polybenzoxazine resins and their composites

Shape memory polymer (SMP) as a new type of smart material can be programmed into a temporary shape by external excitation. Benzoxazine is a novel thermosetting resin with excellent heat resistance, high glass transition temperature (Tg) and mechanical properties. Here, triple-shape memory polybenzoxazines with high Tg were obtained by copolymerization of phenol/polyetheramine with phenol/furanamine benzoxazines. Electrically driven composites were prepared using multi-walled carbon nanotubes, and the SMP electrically driven function was achieved by forming a complete and continuous conductive permeable network inside the composites, shape recovery can be completed in 15 s at 60v. Furthermore, at high temperatures the carbon residue rate is increased to 45 % at 800 °C, demonstrating the high performance of electrically driven shape memory polymer composites. The realization of the triple and electrically induced shape memory properties of shape memory polybenzoxazines broadens the way for their application in extreme high-temperature environments in aerospace and aviation.

Laser Processing of Polyimide and Molybdenum Substrates for Extreme Environment Electronics

A desire in today’s electronic packaging technologies is to create more dense electronic packaging schemes. One method to achieve more dense electronic package integration is to use three-dimensional interconnects to minimize interconnect physical dimensions. Three-dimensional interconnect technologies, such as interposers, require a method of connecting electronics to electronic packages vertically. Thru silicon vias are a widely studied and explored vertical interconnect technology used in a variety of electronic packaging applications. Though silicon has high material hardness, the brittle nature of silicon substrates is a concern for robustness and reliability. These concerns only increase when the desired interconnect application is in extreme environments, such as cryogenic temperatures. A potential alternative to silicon in thru-via applications in extreme environments is molybdenum. Molybdenum is a commonly used material in many applications, such as automotive and aerospace, and has high material strength. Molybdenum is also a low coefficient of thermal expansion material, comparable to silicon, which in combination with high material strength lends to high reliability at extreme temperatures. A challenge of working with refractory metals such as molybdenum is that conventional CNC machining techniques require the use of machining coolants that may not be compatible with fabricated electronics and/or processes can become costly due to tool wear and the need for specialized equipment. Additionally, using molybdenum as a thru-via substrate requires the need for an electrically insulated layer, such as polyimide, within drilled molybdenum thru-holes to prevent the molybdenum substrate from shorting via connections. One potential solution to the above challenges is developing laser processing techniques to cut and drill molybdenum and polyimide. Laser processing is becoming a preferred method for inexpensive prototyping with high resolution and design versatility. This work seeks to meet the challenges described by developing laser cutting and drilling techniques for both molybdenum and polyimide for the use in cryogenic applications. This work will describe two laser processing configurations utilizing two different lasers to laser machine molybdenum and polyimide. This work will first describe the process strategies of laser cutting and drilling molybdenum as a stand-alone substrate. Aspects of laser processing on molybdenum, such as pattern repetitions and scanning speeds, will be described. Process parameter variations will be compared directly and evaluated. Additionally, post-laser processing steps, such as abrasive blasting, will be described and discussed. Next, the fabrication steps to achieve an insulating layer of polyimide in laser drilled holes as well as on each surface of the molybdenum will be detailed. Once polyimide has been cured, laser processing parameters to realize thru-holes in the polyimide-filled molybdenum drills will be presented. Adhesion of polyimide on the molybdenum substrate will be verified and demonstrated through the use of confocal scanning acoustic microscopy before and after polyimide laser processing. Cryogenic performance will be verified by completing confocal scanning acoustic microscopy after submersion in liquid nitrogen (~77 K) and compared with the pre-submersion microscopy images. Processes detailed in this work will open opportunities for future development of molybdenum-based interconnect structures for use in cryogenic applications. Acknowledgement We thank the Alabama Micro/Nano Science and Technology Center (AMNSTC) for providing access to fabrication and characterization facilities used in this work.

Recent Trends in High Reliability Timing and Frequency Control Devices for Extreme Environment Applications

Performance requirements for higher reliability extreme environment timing and Frequency control (TF) components have continued to evolve in the recent years. Bulk of this demand has been focused on specific performance attributes governed by system applications. Enhanced performance requirement has become the mainstream of requirements where SWaP (size, weight and power) improvement is interleaved with other critical parameters such as temperature range, frequency tolerance and long-term effects and in some cases the output spectral purity. Trendlines set by customer demand continues to be the main guide for more efficient solutions. Frequency Management International (FMI) has been in the forefront of advancing the performance attributes for Hi-Rel extreme environment components. We continue to proactively respond to the pressing needs and challenges for robust frequency control components that operate under extreme environmental conditions including extreme temperatures ranging from -200ºC to + 500ºC. The material in this writeup covers the more recent performance achievements tied to specific products and form-factors for high temperature applications.

Simulation-based analysis of total ionizing dose effects on low noise amplifier for wireless communications

The development of radiation-tolerant radio-frequency (RF) systems can be a solution for applications in extreme radiation environments, such as nuclear power plant monitoring and space exploration. Among the crucial components within an RF system, the low noise amplifier (LNA) stands out due to its vulnerability to TID effects, mainly relying on transistors as its main devices. In this study, the TID effects in the LNA using standard 0.18 μm complementary metal oxide semiconductors (CMOS) technology are estimated and analyzed. The results show that the LNA can withstand absorbed radiation up to 100 kGy. The S21, S11, noise figure (NF), stability (K), and linearity of the third input intercept point (IIP3) slightly shifted from the initial values of 0.8312 dB, 0.793 dB, 0.00381 dB, 1.34406, and 2.36066 dBm, respectively which are still comparable to the typical performances. Moreover, the standard 0.18 μ m technology has demonstrated its radiation tolerance, as it exhibits negligible performance degradation in the conventional LNA even when exposed to radiation levels up to 100 kGy. In this context, simulation approach offers a means to predict the TID effects and estimate the radiation exposure limit for electronic devices, particularly when transistors are used as the primary RF components.

Development of non-combustible weaveable yarn through oxidative control of a textile acrylic fibre

Acrylic fibre is considered to be artificial wool in the textile industry, but in contrast with natural wool, it vigorously burns producing black smoke and toxic gases. This not only has hindered its technical applications, but also poses safety risks to the end-users of acrylic-based products. This research aims at enhancing the fire-retardancy of acrylic yarns using a facile thermal stabilisation process which is based on controlling the oxidation temperature and residence period. To this end, acrylic yarns are thermally processed according to six different time and temperature profiles ranging from 220 to 280 °C, with residence periods ranging from 22 to 28 min. The oxidised yarns were characterised using FTIR, DSC, and TGA techniques and the effects of the oxidative thermal treatment on physical characterises, and surface morphology of yarns and fibres were discussed. The results showed that the acrylic yarn undergone the oxidation process based on 240–255–270–280 °C heating profile for 28 min at each step had a sufficiently high degree of cyclisation with an excellent fire retardancy. Furthermore, the stabilised acrylic yarn was strong enough to be woven into a plain weave fabric using a laboratory scale loom while displaying non-combustible behaviour during cyclic exposure to flame. These results present a novel pathway for the development of a low cost, non-combustible fabric ideally suited for applications in extreme environments.

Ionic conductive amylopectin hydrogels for biocompatible and anti-freezing wearable sensors

Conductive hydrogels with excellent flexibility, durability and functional diversity have great development prospects in the field of flexible strain sensors. However, most hydrogels inevitably lose their properties (such as elasticity, electrical conductivity, fatigue resistance, etc.) when frozen and crystallized in low temperature environments, severely hindering their application in extreme environments. Hence, the hydrogel was successfully prepared by introducing amylopectin, polyvinyl alcohol, lithium chloride and glycerol, which possessed the ability of freezing resistance and water retention. The interaction between amylopectin and polyvinyl alcohol formed hydrogen bonds, which endowed the hydrogel excellent tensile strain (608%) and stress (581 kPa). In addition, the hydrogel possessed significant water retention and excellent freeze resistance due to the introduction of glycerol and lithium chloride. Simultaneously, the PGLA hydrogel was placed into mice for 14 days without redness, swelling, allergy and other reactions, indicating the hydrogel with biocompatibility. More importantly, the PGLA hydrogel could detect not only the large strain caused via joint campaign but also the small strain exhibited by weak mastication. This research provides a new way to the development of wearable sensors with the ability to operate in low-temperature environments and biocompatibility.

Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron-Carbide Material.

A boron-rich boron-carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm-1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments.

3D printable, anti-freezing, and rapid self-healing violet phosphorene incorporated hydrogel-based sensors for human motion detection

Conductive self-healing hydrogels, as an emerging flexible material, have been extensively studied in flexible sensors which have great application potential in the field of wearable electronic devices. However, hydrogels are prone to freezing at low temperatures, resulting in reduced or even lost flexibility, conductivity and self-healing properties. Besides, manufacturing method, processing time and cost of hydrogel-based sensors remain extremely challenging, hindering their application in complex and extreme environments. The hydrogel with excellent strain-sensing properties and outstanding anti-freezing properties was fabricated by 3D printing technology and solvent displacement method. The VP-SPB-EG hydrogel has excellent anti-freezing performance (−80 °C). In particular, this hydrogel exhibits excellent self-healing performance (120 s) at −80 °C. In addition, VP-SPB-EG hydrogel-based has high stretchability (1850 %) and sensitivity (GF: 27.82) can be used to detect strain changes caused by human joint movements. Therefore, this flexible hydrogel-based sensor has broad application prospects for wearable devices in extreme environments.

Improvement of mechanical properties at cryogenic temperature of CoCrNi medium entropy alloy fabricated by hybrid additive manufacturing technology

The emergence of CoCrNi medium-entropy alloys (MEAs) holds great promise for applications in extreme service environments. However, fabricating CoCrNi MEA with an extraordinary combination of strength and ductility is urgently needed. Herein, we adopt a combination of laser direct energy deposition (L-DED) additive manufacturing and ultrasonic impact treatment (UIT) to fabricate CoCrNi additive parts. The optical microscopy results showed that the proportion of equiaxed crystals increased from 7.2% to 42.1% after UIT, while the proportion of columnar crystals with grain sizes greater than 31 μm decreased from 62.8% to 27.4%. The tensile test results at 298 and 77 K showed that the tensile strength increased by 7.0% and 27.6%, respectively, after UIT. Electron backscatter diffraction (EBSD) results indicated that the texture intensity of the XOY and XOZ planes in the additive parts decreased after UIT. The transmission Kikuchi diffraction (TKD) results showed that 29.9% of the FCC phase transformed into the HCP phase after the tensile test. Meanwhile, the volume fractions of the substructured, recrystallization, and deformation zones in the phase transformation zone and in the FCC structure were 21.2%, 58.7%, and 20.1% and 67.7%, 9.0%, and 23.3%, respectively. The enhanced transformation-induced plasticity effect contributed to the higher strength and ductility of the CoCrNi MEA treated by UIT.

Electrically-driven textiles using hierarchical aramid fiber

High strength and flexible electronic textiles show promise in aerospace, robotics, and extreme environment applications, while it is indispensable to develop functionally integrated fiber building blocks with durable materials performance. Here we report multifunctional sensory e-textiles driven by using copper-grafted polyaramid (Kevlar®) fiber networks for the integrated electromagnetic interference shielding, thermal and pressure sensing. The hierarchical structural design and synthesis of flexible conductive networks is accomplished via the synergistic coordination between molecular copper complex and Kevlar® fibers, which facilitate long-term cyclability, stability, and washability. Superior Joule heating capabilities with a rapid thermal response under a low driving voltage (with a heating rate of 6 ºC/s and a cooling-down rate of 5.8 ºC/s), together with a high level of EMI shielding (71 dB from 8 to 13 GHz), resulting from its multilayered, vertically-aligned structure with continuous percolation of conductive coating. This work presents a new and feasible grafting approach for the large-scale fabrication of multifunctional wearable e-textiles.

Spall characteristics of three-dimensional graphene networks with embedded copper: A molecular dynamics study

The phenomenon of shock-induced spallation has garnered significant interest in both scientific and industrial circles. Laminated graphene embedded in graphene-reinforced metal-matrix composites have been shown to improve mechanical properties. This study systematically investigates the dynamic response and spall failure of a three-dimensional graphene network (3DGN) with embedded copper composites (3DGCu) and its dependence on the grain sizes (D). Firstly, increasing the wt% of graphene results in significant increase of shock wave speed due to the intrinsic high modulus of graphene, whilst leading to a reduction in shock pressure. Spallation of 3DGCu at low shock velocity is observed, which is dominated by the bonded interaction at the graphene-metal interface. However, the 3DGCu with higher graphene content (smaller D) exhibits both low density and superior spall resistance. In particular, in the sample with 60 wt% graphene, the complete spallation has never occurred and still maintains a relatively high spall strength within the impact velocity of 3.0 km/s. This is due to the remarkable capacity for 3DGN to absorb the kinetic energy during tension. In addition, during shock loading, the graphene component is responsible to the tension loading, whereas the copper metal matrix undergoes compression, leading to a stable post-shock length. These findings offer a novel approach for tailoring the dynamic properties of advanced graphene-based nano-composites with potential applications in extreme environments.

Ultrafast high-temperature sintering (UHS) of ZrB2-based materials

ZrB2 is one of the most promising materials for extreme environment applications, especially in the aerospace field, due to the combination of superior thermophysical properties and low density. Nevertheless, pure ZrB2 is intrinsically hard to sinter, requiring either the application of intense external pressure or the use of sintering aids. In the present work, the feasibility of ultrafast high-temperature sintering (UHS) for the densification of commercial ZrB2 was explored. Thanks to the addition of B4C as a sintering aid, Densities up to 92–98% could be obtained in just 2 min. Hardness of 16.3–17.8 GPa was obtained for the UHS ZrB2-based ceramics, similar to what is reported in the literature using slower, more sophisticated and energy-consuming sintering approaches like spark plasma sintering. These first results show that UHS could provide a quick and simple way to produce high-performance ZrB2-based components with just a few minutes of processing time in pressure-less conditions.

An ultrathin polymer-derived UHTCs coating on CFRP substrate: Effective electromagnetic wave absorber

The utilization of carbon fiber-reinforced polymer (CFRP) materials in electronic equipment encounters notable challenges of electronic warfare operations and the risk of detection by various sensors. A novel ceramic coating comprising TiC/SiOC with added Al2O3 adhesive was formulated to address these issues. The TiC/SiOC-50 wt% Al2O3 coating demonstrated exceptional microwave-effective absorption bandwidth (EAB) of 13.5 GHz, effectively covering the entire Ka-band, while maintaining a thin thickness of 0.60 mm. The TiC/SiOC-80 wt% Al2O3 system exhibited remarkable EM characteristics, including a minimum reflection loss (RLmin) of −58.26 dB, an EAB of 10.74 GHz, and an ultra-thin thickness of 0.38 mm, which sets a new record as the thinnest reported coating in the existing literature. The outstanding electromagnetic performance, coupled with their lightweight and thin characteristics, positions these coatings as highly viable solutions for various electromagnetic shielding and absorption applications in extreme environments.

Improving Printability of Polytetrafluoroethylene (PTFE) with the Help of Plasma Pre-Treatment.

Polytetrafluoroethylene (PTFE) is a potential candidate for the fabrication of flexible electronics devices and electronics with applications in various extreme environments, mainly due to its outstanding chemical and physical properties. However, to date, the utilization of PTFE in printing trials has been limited due to the material's low surface tension and wettability, which do not ensure good adhesion of the printing ink at the level of the substrate. Within this paper, successful printing of PTFE is realized after pre-treating the surface of the substrate with the help of dielectric barrier discharge non-thermal plasma. The efficiency of the pre-treatment is demonstrated with respect to both silver- and carbon-based inks that are commercially available, and finally, the long-lasting pre-treatment effect is demonstrated for periods of time spanning from minutes to days. The experimental results are practically paving the way toward large-scale utilization of PTFE as substrate in fabricating printed electronics in harsh working environments. After 3 s of plasma treatment of the foil, the WCA decreased from approximately 103° to approximately 70°. The resolution of the printed lines of carbon ink was not time dependent and was unmodified, even if the printing was realized within 1 min from the time of applying the pre-treatment or 10 days later. The evaluation of the surface tension (σ) measured with Arcotest Ink Pink showed an increase in σ up to 40 < σ < 42 mN/m for treated Teflon foil and from σ < 30 mN/m corresponding to the untreated substrate. The difference in resolution was distinguishable when increasing the width of the printed lines from 500 μm to 750 μm, but when increasing the width from 750 μm to 1000 μm, the difference was minimal.

Phase stability, mechanical and thermodynamic properties of (Hf, Zr, Ta, M)B2 (M= Nb, Ti, Cr, W) quaternary high-entropy diboride ceramics via first-principles calculations

As the high-entropy design concept applied to the diboride ceramic system, high-entropy diboride ceramics with a wide range of composition control, is expected to become a new high-performance material for extreme high-temperature environments. Herein, the effects of four transition metal elements (Nb, Ti, Cr, W) on the phase stability and properties of (Hf, Zr, Ta)B2-based high-entropy diboride ceramics are systematically investigated via the first-principles calculations. All components were identified as thermodynamically, mechanically and dynamically stable from enthalpy of formation, elastic and phonon spectrum calculations. Among these, compared with the (Hf, Zr, Ta)B2 ceramics, the addition of Nb and Ti on the metal sublattice is beneficial to improve the mechanical properties of ceramics, including Young's modulus, hardness and fracture toughness, while the introduction of Cr and W weakens the strength of covalently and ionic bonds inside the material, reducing its mechanical properties. The predicted thermophysical properties show that the high-entropy diboride ceramics containing Nb and Ti have better high-temperature comprehensive performance, including higher Debye temperature, thermal conductivity and lower thermal expansion characteristics, which is conducive to the application in extreme high-temperature environments. This research will provide important guidance for the design and development of new high-performance high-entropy diboride ceramics.

A stretchable slippery surface fabricated by femtosecond laser direct writing

Surface conditions of flexible electronic devices can affect their accuracy, so it is necessary to keep surfaces clean and stable to ensure their correct-long-term operation. The Nepenthes-inspired slippery surface has excellent self-cleaning, stability, and self-healing properties. A slippery surface with stretching durability is significant for application to a flexible sensors surface. As an advanced micro-nanomanufacturing method, femtosecond laser has become an effective method for preparing porous structures to process a slippery surface. In this study, a femtosecond laser was used to prepare an interconnected porous structure on pre-stretched polydimethylsiloxane in one step. The slippery surface was prepared after being infused with lubricant, which maintained the slippery performance under tensile conditions and after hundreds of stretch cycles. Moreover, it exhibits remarkable self-cleaning and chemical stability. This stretchable slippery surface prepared by femtosecond laser direct writing presents good prospects for flexible electronic devices that require a stable surface in various extreme environmental applications.

Temperature Effects on Electrochemical Energy-Storage Materials: A Case Study of Yttrium Niobate Porous Microspheres.

Lithium-ion batteries (LIBs) are very popular electrochemical energy-storage devices. However, their applications in extreme environments are hindered because their low- and high-temperature electrochemical performance is currently unsatisfactory. In order to build all-climate LIBs, it is highly desirable to fully understand the underlying temperature effects on electrode materials. Here, based on a novel porous-microspherical yttrium niobate (Y0.5 Nb24.5 O62 ) model material, this work demonstrates that the operation temperature plays vital roles in electrolyte decomposition on electrode-material surfaces, electrochemical kinetics, and crystal-structure evolution. When the operation temperature increases, the reaction between the electrolyte and the electrode material become more intensive, causing the formation of thicker solid electrolyte interface (SEI) films, which decreases the initial Coulombic efficiency. Meanwhile, the electrochemical kinetics becomes faster, leading to the larger reversible capacity, higher rate capability, and more suitable working potential (i.e., lower working potential for anodes and higher working potential for cathodes). Additionally, the maximum unit-cell-volume change becomes larger, resulting in poorer cyclic stability. The insight gains here can provide a universal guide for the exploration of all-climate electrode materials and their modification methods.

Isoelectronic aluminum-doped gallium nitride alpha-voltaic cell with efficiency exceeding 4.5%

Although alpha-voltaic cells have shown great potential in unattended miniaturized systems for compact, long-lifetime and independence of external energy input, the power conversion efficiency of state-of the-art alpha-voltaic cells is still much lower than the theoretical limit. Here, an alpha-voltaic cell based on a gallium nitride transducer with PIN structure is designed and investigated. We find that isoelectronic aluminum-doping is an effective way for boosting the performance of the gallium nitride transducer by decreasing the unintentional doping concentration, deep trap concentration, and dislocation density in the gallium nitride epilayer. The isoelectronic aluminum-doped cell demonstrates a large depletion region of 1.89 μm and a charge collection efficiency of 61.6% at 0 V bias, resulting in a high power conversion efficiency of 4.51%, comparable to the best gallium nitride beta-voltaic cells. This work increases alpha-voltaic cell efficiency, bridging the gap between nuclear micro-batteries and real applications in extreme environments.

Microstructural and Mechanical Characterization of Colloidal Processed WC/(W5Vol%Ni) via Spark Plasma Sintering.

This study investigates the sintering behaviour and properties of WC-based composites in which WC was mixed with W5vol%Ni in concentrations of 10vol% and 20vol%. Colloidal processing in water and spark plasma sintering were employed to disperse the WC particles and facilitate sintering. The addition of W5vol%Ni improved the sintering process, as evident from a lower onset temperature of shrinkage determined through dilatometric studies. All samples exhibited the formation of tungsten monocarbide (W2C), with a more pronounced presence in the WC/20(W5vol%Ni) composite. Sintering reached its maximum rate at 1550 °C and was completed at 1600 °C, resulting in a final density exceeding 99.8%. X-ray diffraction analysis confirmed the detection of WC and W2C phases after sintering. The observed WC content was higher than expected, which may be attributed to carbon diffusion during the process. Macro-scale mechanical characterisations revealed that the WC/10(W5vol%Ni) composite exhibited a hardness of 18.9 GPa, while the WC/20(W5vol%Ni) composite demonstrated a hardness of 18.3 GPa. Increasing the W5vol%Ni binder content caused a decrease in mechanical properties due to the formation of W2C phases. This study provides valuable insights into the sintering behavior and properties of WC/W5vol%Ni composites, offering potential applications in extreme environments.

40 Years of Low‐Temperature Electrolytes for Rechargeable Lithium Batteries

AbstractRechargeable lithium batteries are one of the most appropriate energy storage systems in our electrified society, as virtually all portable electronic devices and electric vehicles today rely on the chemical energy stored in them. However, sub‐zero Celsius operation, especially below −20 °C, remains a huge challenge for lithium batteries and greatly limits their application in extreme environments. Slow Li+ diffusion and charge transfer kinetics have been identified as two main origins of the poor performance of RLBs under low‐temperature conditions, both strongly associated with the liquid electrolyte that governs bulk and interfacial ion transport. In this review, we first analyze the low‐temperature kinetic behavior and failure mechanism of lithium batteries from an electrolyte standpoint. We next trace the history of low‐temperature electrolytes in the past 40 years (1983–2022), followed by a comprehensive summary of the research progress as well as introducing the state‐of‐the‐art characterization and computational methods for revealing their underlying mechanisms. Finally, we provide some perspectives on future research of low‐temperature electrolytes with particular emphasis on mechanism analysis and practical application.