High-density Storage Research Articles

Microencapsulated sodium nitrate with titanium-dioxide shell for high-temperature and high-density latent heat storage

In this study, a molten salt, i.e., sodium nitrate (NaNO3), that melts at 308 °C is microencapsulated with titanium dioxide (TiO2) shells via water-limited surfactant-free sol-gel processes for high-temperature and high-density thermal energy storage. The effects of the catalyst and precursor concentrations are examined to determine the optimal conditions for the two materials to achieve microcapsules with outstanding thermal performance and thermal reliability. The morphological characteristics of the core–shell structures of the microcapsule are investigated using scanning electron microscopy, whereas its chemical composition is analyzed using Fourier transform infrared spectroscopy to corroborate the synthesis of robust TiO2 shells. Calcination heat-treatment is performed at 300 °C to induce a transition from amorphous to anatase such that the shell robustness is enhanced and the thermal reliability of the NaNO3@TiO2 microcapsule is secured. The thermal performance of the NaNO3@TiO2 microcapsule is determined via differential scanning calorimetry between 220 and 360 °C. The encapsulation ratio is calculated to be 72.7–69.0 %. Finally, the thermal reliability of the NaNO3@TiO2 microcapsule is examined using DSC for 50 repeated heating and cooling cycles.

Preliminary experimental studies into the storage capacity of cryogenic hydrogen in aerogel blanket materials

The abundance and diversity of hydrogen applications necessitates continued and accelerated research into advanced storage technologies. Traditionally, hydrogen has been stored as either a high-pressure, warm gas; or a low-pressure, cryogenic liquid. Methods such as cryo-supercritical and cryo-adsorbed have been explored, but are not yet mainstream. Cryo-adsorbed is attractive because higher storage densities at higher temperatures than liquid may be achieved. Recently NASA, in partnership with Eta Space, Southwest Research Institute, the University of Central Florida, and Air Liquide, have been exploring the use of inexpensive, commercially available silica aerogel blanket materials for cryo-adsorbed hydrogen storage. Unlike most adsorbents, aerogel blanket is not a powder, but a robust, composite material that can be formed into complex shapes to aid in more efficient storage system designs, and has already been proven to uptake large quantities of fluids such as nitrogen and oxygen. Recent experimental efforts into the uptake of low-pressure hydrogen gas at 77 K, and liquid hydrogen at normal boiling point (NBP) will be discussed. Although preliminary in nature, the test results are promising, showing up to a 49% increase in storage density at 77 K over the gas alone, and greater than a one-to-one volume equivalency with NBP LH2.

A Single-Sized Metasurface for Image Steganography and Multi-Key Information Encryption

With the escalating flow of information and digital communication, information security has become an increasingly important issue. Traditional cryptographic methods are being threatened by advancing progress in computing, while physical encryption methods are favored as a viable and compelling avenue. Metasurfaces, which are known for their extraordinary ability to manipulate optical parameters at the nanoscale, exhibit significant potential for the revolution of optical devices, making them a highly promising candidate for optical encryption applications. Here, a single-sized metasurface with four independent channels is proposed for conducting steganography and multi-key information encryption. More specifically, plaintext is transformed into a ciphertext image, which is encoded into a metasurface, while the decryption key is discretely integrated into another channel within the same metasurface. Two different keys for steganographic image unveiling are also encoded into the metasurface and can be retrieved with different channels and spatial positions. This distributed multi-key encryption approach can enhance security, while strategically distributing images across distinct spatial zones serves as an additional measure to reduce the risk of information leakage. This minimalist designed metasurface, with its advantages of high information density and robust security, holds promise across applications including portable encryption, high-camouflaged image display, and high-density optical storage.

Conjugate heat transfer analysis of the transient thermal discharge of a metallic latent heat storage system

Thermal energy storage systems utilizing metallic phase change materials exhibit great potential as a technology for mobile applications, offering high storage densities and high thermal discharge rates. First experimental investigations show the functionality and performance characteristics of this system. For a deeper understanding of the thermal discharge, this paper presents a numerical model and analysis of the transient conjugate heat transfer. For validation of the numerical model, the results of the simulations are compared to the available experimental data. The investigated storage is based on an aluminum silicon alloy and a box-shaped graphite container design. In this system, heat extraction is achieved by forced convection of ambient air. The transient thermal discharge was simulated from 650 °C to 100 °C, and the solidification of the storage material at around 577 °C was simulated using an enthalpy-porosity approach. The discharge time and total heat flow show good agreement with the experimental data, indicating the model’s successful validation. An empirical study was carried out to determine the thermal contact resistance at the interface between the storage material and the graphite container. The present study contributes new physical insights regarding the thermal discharge of a novel metallic latent heat thermal energy storage system.

Synthesis of composite films for ZnO-based memristors with superior stability

Memristors have unique non-volatile characteristics that potentially can emulate biological synapses for applications in neural computing systems. However, the random formation of conductive filaments in these devices can cause various unreliability problems. In this work, films of a composite of ZnO nanoparticles and carbon nanotubes were prepared as functional layers for memristors by an in-situ growing strategy (ZnO@CNT-IS) using a straightforward high-temperature annealing treatment. This approach allowed for the formation of a high-quality films with uniform loading of ZnO nanoparticles on the carbon nanotubes, which contributed to a lower formation energy for oxygen vacancies and increased electron transfer rate. As a result, the memristors exhibited faster switching response speed, lower power consumption, and a stabilised switching ratio even after 2000 switching cycles. Based on the analog switching behaviour, the ZnO@CNT-IS-based devices showed significant biological synapse functions and plasticity, indicating their potential for high-density storage and neuromorphic computing.

Study on the impact of hydrogen storage temperature on iron-based thermochemical hydrogen storage technology

Thermochemical hydrogen storage technology based on iron-based materials has received significant attention owing to its low cost, safety features, and high volumetric hydrogen storage density. However, no consensus has been established on the optimal temperature range for hydrogen storage. This study investigated the impact of hydrogen storage temperature on hydrogen consumption capacity, hydrogen release capacity, and hydrogen storage energy consumption. The hydrogen storage temperature was optimized with the objectives of low energy consumption and high hydrogen storage density. The experiments were conducted using thermogravimetric analyzer and gram-scale packed-bed reactor setups, accompanied by thermodynamic and kinetic calculations. The research indicated that at 550 °C, the optimal hydrogen storage temperature, the lowest relative energy demand was 32.30 %, with the hydrogen consumption capacity reaching the theoretical maximum value of 4.8 %, and the hydrogen release capacity reaching 4.04 %. Furthermore, achieving the theoretical maximum value of hydrogen consumption capacity became exceedingly difficult when the hydrogen storage temperature exceeded 570 °C. Microstructural characterization and kinetic calculations revealed that this phenomenon was attributed to the formation of a dense iron layer on the particle surface, which impeded the solid-state diffusion of oxygen atoms. The formation of the intermediate phase wüstite was identified as the cause of the formation of the dense iron layer. Overall, this study provided theoretical support for iron-based thermochemical hydrogen storage processes and offered a perspective into the reaction behavior of the reduction of magnetite with hydrogen.

Optimal design and simulation investigation for high-density hydrogen storage tanks filled with rare earth-based (RE-Ca)(Ni-Co)5 optimized alloy

The slow kinetic rate due to strong thermal effect limits the practical application of metal hydride tanks in high-density hydrogen storage. In this work, we concentrate on a comprehensive experimental and numerical investigation of metal hydride beds with rare earth-based (RE-Ca)(Ni-Co)5 optimized alloy to explore faster reaction rates. Two different cylindrical tanks were manufactured to reflect de-/hydrogenation characteristics. A study on the temperature evolution in the loose powder bed was performed first, followed by five other different bed configurations: alternated powder layers with Al fiber layers, powder mixed with Al fibers, compacted discs (mixture of powder, resin and graphite), alternated compacts with Al fins and alternated Al foil-wrapped compacts with Al fins. Among them, the compacts provide good heat transfer capacity, with additional Al foils and fins for optimum thermal diffusion, reducing the reaction time by almost 50 %. Stress concentrations caused by powder accumulation can also be avoided thanks to the stable structure. Finally, the numerical model was adapted to simulate the de-/hydrogenation processes of the optimized bed and the experimental data matched well with the computational results, confirming the reliability of the model. It lays the foundation for the design and operation optimization of high-density hydrogen storage in the future.

Confining single Er3+ ions in sub-3 nm NaYF4 nanoparticles to induce slow relaxation of the magnetisation

Molecular systems known as single-molecule magnets (SMMs) exhibit magnet-like behaviour of slow relaxation of the magnetisation and magnetic hysteresis and have potential application in high-density memory storage or quantum computing. Often, their intrinsic magnetic properties are plagued by low-energy molecular vibrations that lead to phonon-induced relaxation processes, however, there is no straightforward synthetic approach for molecular systems that would lead to a small amount of low-energy vibrations and low phonon density of states at the spin-resonance energies. In this work, we apply knowledge accumulated over the last decade in molecular magnetism to nanoparticles, incorporating Er3+ ions in an ultrasmall sub-3 nm diamagnetic NaYF4 nanoparticle (NP) and probing the slow relaxation dynamics intrinsic to the Er3+ ion. Furthermore, by increasing the doping concentration, we also investigate the role of intraparticle interactions within the NP. The knowledge gained from this study is anticipated to enable better design of magnetically high-performance molecular and bulk magnets for a wide variety of applications, such as molecular electronics.

Study on hydrogen storage properties of Ti–V–Fe–Mn alloys by modifying Ti/V ratio

The high stability of hydride phase has limited the improvement for the hydrogen storage properties of Ti–V based alloy at room temperatures. In this work, the stability of hydride was reduced by designing a low-price Ti–V–Fe–Mn alloy, and the effect of Ti/V ratio on the crystal structure and hydrogen storage properties was systematically investigated. The Ti40-xV40+xFe15Mn5 (x = 0, 2, 4, 6, 8) alloys were synthesized using arc melting, and the as-prepared alloys are all composed of single BCC phase. The lattice constant and cell volume decrease linearly with a lessening in Ti/V ratio. The reduction of cell volume makes it difficult for hydrogen atoms to diffuse, resulting in a sluggish hydrogen absorption rate. The dehydrogenation plateau in PCI curve rises and corresponding thermodynamics is optimized with a decrease in the lattice constant, and the hydrogen atoms are more readily to release, especially for Ti32V48Fe15Mn5 alloy with the dehydrogenation capacity of 1.83 wt% at 373 K. The result indicates the thermodynamic properties can be optimized by adjusting the lattice constant of Ti–V–Fe–Mn alloys, and hydrogen storage capacity is improved effectively. This study provides a reference for composition design of Ti–V–Fe–Mn alloys for high-density hydrogen storage.

Fusion of memristor and digital compute-in-memory processing for energy-efficient edge computing.

Artificial intelligence (AI) edge devices prefer employing high-capacity nonvolatile compute-in-memory (CIM) to achieve high energy efficiency and rapid wakeup-to-response with sufficient accuracy. Most previous works are based on either memristor-based CIMs, which suffer from accuracy loss and do not support training as a result of limited endurance, or digital static random-access memory (SRAM)-based CIMs, which suffer from large area requirements and volatile storage. We report an AI edge processor that uses a memristor-SRAM CIM-fusion scheme to simultaneously exploit the high accuracy of the digital SRAM CIM and the high energy-efficiency and storage density of the resistive random-access memory memristor CIM. This also enables adaptive local training to accommodate personalized characterization and user environment. The fusion processor achieved high CIM capacity, short wakeup-to-response latency (392 microseconds), high peak energy efficiency (77.64 teraoperations per second per watt), and robust accuracy (<0.5% accuracy loss). This work demonstrates that memristor technology has moved beyond in-lab development stages and now has manufacturability for AI edge processors.

Application and Analysis of Liquid Organic Hydrogen Carrier (LOHC) Technology in Practical Projects

In contemporary times, the utilization of liquid organic hydrogen carriers (LOHCs) has gained prominence due to their high volumetric storage density and material properties closely resembling conventional fuels. Numerous countries are incorporating LOHCs in hydrogen demonstration initiatives, encompassing applications such as hydrogen refueling stations, hydrogen-powered ships, and trains. This paper conducts a comprehensive review of seventeen LOHC projects, spanning Germany, Europe, and other nations, presenting detailed project specifications. This review includes information on project consortiums, funding sources, covered supply chains, transport modalities, and employed technologies. Through a global evaluation of LOHC projects, this review underscores the promising and competitive nature of LOHCs as a viable option for the large-scale and long-distance storage and transportation of hydrogen. The future development of this field is discussed at in the last section.

Multilevel Information Encryption Based on Thermochromic Perovskite Microcapsules via Orthogonal Photic and Thermal Stimuli Responses.

Increasing modal variations of stimulus-responsive materials ensure the high capacity and confidentiality of information storage and encryption systems that are crucial to information security. Herein, thermochromic perovskite microcapsules (TPMs) with dual-variable and quadruple-modal reversible properties are designed and prepared on the original oil-in-fluorine (O/F) emulsion system. The TPMs respond to the orthogonal variations of external UV and thermal stimuli in four reversible switchable modes and exhibit excellent thermal, air, and water stability due to the protection of perovskites by the core-shell structure. Benefiting from the high-density information storage TPMs, multiple information encryptions and decryptions are demonstrated. Moreover, a set of devices are assembled for a multilevel information encryption system. By taking advantage of TPMs as a "private key" for decryption, the signal can be identified as the corresponding binary ASCII code and converted to the real message. The results demonstrate a breakthrough in high-density information storage materials as well as a multilevel information encryption system based on switchable quadruple-modal TPMs.

Effect of process parameters on quality of alfalfa block

To address the imbalance in the supply of grass resources caused by seasonality and regional factors, it is crucial to efficiently store and transport alfalfa. Exploring suitable grass feed processing techniques contributes to the stable transportation of grass blocks and long-term storage of nutritional components. The Central Composite Design response surface design was used to design experiments, with moisture content and compressive force as the test factors. Based on the experimental results, it was found that lower moisture content and a certain compressive force were beneficial for the stability, high density, and protein storage of alfalfa blocks. The microscopic examination of alfalfa particles revealed that a certain moisture content (15%) facilitates the formation of solid bridges between particles, leading to more stable alfalfa blocks. The final optimized process parameters were moisture content of 14.3% and compressive force of 34.8 kN. Under these conditions, the density of the molded alfalfa block was 1001 kg/m3, with R-CP at 96.96%, R-EE at 67.23%, and R-CF at 114.13%.

A universal strategy for electric field control of nonvolatile magnetization reversal

Achieving electric field control of nonvolatile magnetization reversal in van der Waals magnetic tunnel junctions (vdW MTJs) is of paramount importance for nanoscale spintronic devices with ultralow-power consumption and high-density storage. Here, a new and universal design strategy is proposed to realize nonvolatile magnetization reversal, which is based on electric field control of interlayer coupling. The nonvolatility benefits from the proposed special principle of vdW MTJ, in which the dependence of interlayer coupling energy on electric field strength follows a continuous odd function in mathematics. The feasibility of proposed strategy is proved by the MnBi2Te4/h-BN/Fe3GaTe2/h-BN/MnBi2Te4 junction. The magnetization state of Fe3GaTe2 can be reversed 180° by changing electric field directions. Moreover, the magnetization states can be preserved after removing electric field, demonstrating the nonvolatile magnetization reversal. Therefore, the present strategy provides an alternative approach to realize electric control of nonvolatile magnetization reversal in vdW MTJs for next-generation spintronic devices.

Nonvolatile behavior of resistive switching memory in Ag/WOx/TiOy/ITO device based on WOx/TiOy heterojunction

Two-terminal structure memristors are the most promising electronic devices that could play a significant role in artificial intelligence applications of the next generation and the post-Moore era. In this work, we fabricated the memristive device by depositing a heterojunction WOx/TiOy functional layer onto an indium tin oxide substrate using magnetron sputtering. The Ag/WOx/TiOy/ITO device exhibits improved memory behavior of bipolar resistive switching (RS) nonvolatile compared to TiOy-based single-layer memristors, enabling it to meet high-density information storage requirements. Moreover, our device exhibited the coexistence of the negative differential resistance effect and the behavior of the RS memory. Through a comprehensive analysis of conductivity on the curve of current–voltage (I–V), a physical model based on the mechanism of space charge-limited current, ohmic conduction, and Schottky emission was suggested to explain the behavior device RS memory. This study's findings demonstrate that including a heterojunction bilayer WOx/TiOy as a functional layer can significantly improve the performance of memristive devices. This advancement expands the potential application of ferroelectric metallic oxide heterojunctions within the field of memristors.

Ultrafine Pt particles on hollow hierarchical porous β zeolites for selective hydrogenation of naphthalene

It is crucial to develop effective heterogeneous catalysts for the production of decalin as a high-density liquid hydrogen storage material from naphthalene hydrogenation. In this work, hollow hierarchical Pt/Hβ catalysts with ultrafine Pt particles were successfully synthesized successfully. The construction of hollow cavity optimized the metal-support interaction and reduced the resistance of mass diffusion. The ultrafine Pt species could expose more active sites for effective hydrogenation of naphthalene. The optimized Pt/Hβ-2 with hollow structure catalyst displayed the remarkable catalytic performance with the naphthalene conversion of 94.2 % and the decalin yield of 81.4 % at 220 °C, which was superior to the reaction performance of the catalysts reported in the literature under similar reaction condition. Besides, Pt/Hβ-2 presents higher turnover frequency (25.4 h−1) and reaction rate constant (9.9 × 10-3 min−1), which is because of the relatively low activation energy (30.86 kJ mol−1) for the naphthalene hydrogenation.

2D Memory Selectors with Giant Nonlinearity Enabled by Van der Waals Heterostructures.

The integration of one-selector-one-resistor crossbar arrays requires the selectors featured with high nonlinearity and bipolarity to prevent leakage currents and any crosstalk among distinct cells. However, a selector with sufficient nonlinearity especially in the frame of device miniaturization remains scarce, restricting the advance of high-density storage devices. Herein, a high-performance memory selector is reported by constructing a graphene/hBN/WSe2 heterostructure. Within the temperature range of 300-80K, the nonlinearity of this selector varies from ≈103-≈104 under forward bias, and increases from ≈300-≈105 under reverse bias, the highest reported nonlinearity among 2D selectors. This improvement is ascribed to direct tunneling at low bias and Fowler-Nordheim tunneling at high bias. The tunneling current versus voltage curves exhibit excellent bipolarity behavior because of the comparable hole and electron tunneling barriers, and the charge transport polarity can be effectively tuned from N-type or P-type to bipolar by simply changing source-drain bias. In addition, the conceptual memory selector exhibits no sign of deterioration after 70000 switching cycles, paving the way for assembling 2D selectors into modern memory devices.

Performance comparison of a fixed-bed solar grain dryer with and without latent heat storage

Latent heat storage has gained attention as an energy storage method for solar drying due to its high storage density. However, its overall impact in drying performance has not been sufficiently investigated. This study presents detailed, validated mathematical models necessary for the transient simulation of a solar dryer with latent heat storage with the aim of assessing the effect that such storage has on the deep bed drying of wheat. Computer simulations were run with weather data from Germany. A fixed bed dryer with a capacity of one ton was assumed and the size of the solar air heater and latent heat storage unit was varied, as well as the type of phase change material. In drying wheat without storage from 22% to 13% w.b. (0.28 to 0.15 kg kg−1 d.b.), increasing solar collecting area from 6 to 15 m2 reduced drying time by around 50% but resulted in excessive temperatures. At equal collecting area, the use of latent heat storage changed drying time by −5% to +13.9% depending on component sizes, but the drying air temperature was limited effectively if solar collection and storage units are properly sized in relation to each other. Failure to do so can result in higher drying temperatures than recommended or bring little additional benefit. Moisture uniformity at the end of drying was slightly improved by up to 10% in the presence of the storage unit due to a reduction in the average drying temperature. The presented models and corresponding simulation programs are a useful tool to size the components of a solar dryer with and without latent heat storage.

Malicious Code Propagation Model Based on Sleep Monitoring Mechanism in Wireless Sensor Networks

&lt;p&gt;Wireless sensor networks (WSNs) are characterized by high node density and finite energy storage. Each node exchanges information with all its neighboring nodes frequently, which makes it easy for nodes to run out of energy, leading to paralysis of the WSNs when facing network malicious code attacks. To address this problem, a malicious code propagation model based on sleep-monitoring technology for WSNs is proposed. As a Multi-compartment propagation, sleep nodes and monitoring nodes are introduced to the conventional SIR model. Sleep nodes can turn the infected node into a dormant state and stop the dissemination of information to save energy. Monitoring nodes can contain malicious codes spread in wireless sensor networks by sharing prevention information in real time. Additionally, by calculating the equilibrium point and propagation threshold of the new feedback model, the corresponding Lyapunov function is constructed to prove the local stability and global stability of the equilibrium point. Finally, the results of numerical simulation experiments show that when the sleep rate is 0.3 and feedback rate is 0.0000005, the number of infected nodes in the wireless sensor network decreases by 43.45%. Therefore, adding sleep-monitoring technology can effectively control the spread of malicious code in the networks.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

FeFET-Based MirrorBit Cell for High-Density NVM Storage

FeFET-Based MirrorBit Cell for High-Density NVM Storage