Materials Solutions (United Kingdom)

Thermochemical energy storage (TCES) utilizes chemical reactions to store thermal energy, offering a promising solution for efficient energy management. However, a significant challenge in application of TCES materials, particularly with crystal-to-crystal chemical transformations, is the mechanical degradation of reactive particles during repeated cycles connected with the constant re-modeling of crystals due to consecutive hydration-dehydration steps. This degradation leads to increased pressure drops in packed beds due to swelling and fracturing of salt particles, complicating their practical application. To address this issue, this study investigates the effect of a polymeric network as stabilizing element within TCES particles to enhance mechanical stability. Using potassium carbonate hydrate (K2CO3·1.5H2O) as a model thermochemical material and thermoplastic polymers for reinforcement, composite particles were developed to resist disintegration over multiple cycles. The incorporation of polymeric networks from polyamide (PA11), polyetherimide (PEI) and polyvinylidene fluoride (PVDF) resulted in improved mechanical properties at relatively high porosity, which contributes to higher hydration rate. The developed stabilization method is compatible with existing scalable particle production methods like tableting and compacting.

In this work we utilize different electromagnetic interference (EMI) environments to test near field absorber performance as well as absorber placement. We use in-house designed test fixtures to mimic some of the real-world EMI environments: shield cans and metal shielding screens. The near field test results are compared to the reflection loss, one of the most used absorber metrics.

Magnetic microrobots can be spatiotemporally steered by manipulating external magnetic fields, achieving rapid locomotion. However, for high-speed magnetic microrobots, steering stability is crucial to control actuation speeds along predetermined trajectories. Herein, we discover that nanoscale distribution of magnetic nanoparticles is key to ensuring the steering stability of agile magnetic microrobots. A model system comprising two different processing methods is implemented to induce either macroscopic phase separation or nanoscale distribution of nanoparticles within thermoplastic nanocomposites-based magnetic microrobots. The dispersive and distributive mixing of magnetic nanoparticles is evaluated via systematic investigation on magnetic, thermal, and rheological properties. According to the spatial distribution states of the magnetic nanoparticles, magnetic microrobots exhibit stark differences in motion uniformity and trajectory regularity during agile pivoting motion. Our findings elucidate the correlations among nanocomposite processing, nanoparticle distribution, physical properties, and magnetic actuation, providing valuable insights for designing stimuli-responsive miniaturized robots with enhanced locomotion control.

For use as a heat storage material, CaCl 2 is often impregnated into porous materials. This is done to stabilize the salt against conglomeration and its dissolution due to the low deliquescence relative humidity. However, CaCl 2 has overlapping temperature and water vapor pressure conditions for its trito- and monohydrate, which are kinetically hindered against each other creating path-dependent (de-)hydration steps. These pathways may change under the influence of confinement. These changes can influence the temperature output for heat batteries using CaCl 2 composites and could make the taken pathways for hydration and dehydration either more complex or simpler than the pure salt. So, in this research, the hydration and dehydration steps of CaCl 2 inside different clays (Vermiculite, Halloysite, and Sepiolite) and silica gels were investigated with respect to their transformations compared to the bulk salt. Therefore, the kinetic phase transition onsets were determined with isobaric TGA measurements together with PXRD in situ experiments to confirm or identify the crystalline phases. This showed that inside pores, CaCl 2 forms the monohydrate rather than the tritohydrate. The decrease of pore diameter leads to easier formation of monohydrate over tritohydrate. This trend can be explained by the crystal structures of the hydrates and their unit cell volumes considering that larger crystals are difficult to form in the limited space inside the pore systems. This change in phase transition steps influences the transition temperatures, which affects its application for heat storage.

A promising candidate for thermochemical energy storage (TCES) is calcium oxalate. As calcium oxalate is part of the earth alkali oxalate group, other earth alkali oxalates such as magnesium oxalate, strontium oxalate, and barium oxalate are investigated for their applicability in thermochemical energy storage. It is observed that only calcium oxalate shows reversible (de)hydration behavior whereas as magnesium oxalate, strontium oxalate, and barium oxalate show irreversible behavior; rehydration is not possible. The irreversible behavior is linked to the crystal structures of the materials. Calcium oxalate remains in an open structure during dehydration whereas magnesium oxalate, strontium oxalate, and barium oxalate transition into dense network structures, hindering the access of water vapor into the material. This work opens the horizon to explore other metal oxalates and find a solution to the irreversibility challenges addressed in this work.

Due to climate change and the energy transition, energy storage applications are being studied and developed. One energy storage application is a heat storage battery, which needs materials that can store and release heat with high energy storage capacity. One such material is a salt hydrate. The hydration pathways of salt hydrates can have different numbers of steps. There are salts with single-hydrate steps like for CuCl2 (0-2) and LiBr (0-1) and multihydrate steps like for MgCl2 (0-2-4-6) and SrCl2 (0-1-2-6). Additionally, there are also salts with complex hydration-dehydration pathways like for CaCl2 (0-1/3-2-1-0). Little is known about the hydrate steps of CaBr2. The crystal structures of the CaBr2 nona-, hexa-, and anhydrate are known, but there are no intermediate steps and conditions for these transitions. The hexahydrate and anhydrate have the same structure as CaCl2 except for the unit cell size due to the different anions. Additionally, the equilibria were determined for the hexa-, tetra-, and dihydrate transitions. However, the intermediate steps are debated. The hydrates 3, 1.5, 1, and 0.5 were all proposed but are disputed and not verified. Therefore, the hydration and dehydration pathways of CaBr2 from the anhydrate to the dihydrate and back were examined in this study for both the bulk salt and the confinement of mesoporous silica gels. The kinetic phase transition onsets and equilibrium lines were measured for the bulk salt. Powder X-ray diffractograms were used to ensure that the same structures were formed every time during hydration and dehydration. Single-crystal analysis was used to determine the crystal structures of the hydrates. These experiments showed only a stable monohydrate phase between the anhydrate and dihydrate during hydration and dehydration. Furthermore, the dihydrate has the same crystal structure as the dihydrate of CaCl2 except for the size, while the monohydrate differs from the CaCl2 monohydrate. Additionally, the composites' kinetic onsets and powder diffractograms were measured, which showed that CaBr2 performs the same hydrate steps in confinement as in bulk form.

To evaluate the feasibility and efficacy of diffusion tensor imaging (DTI) for detecting early brain microstructure alterations in germinal matrix-intraventricular hemorrhage (GMH-IVH) rat model. This study used a postnatal day 5 (PND 5) rat model of GMH-IVH. T2-weighted imaging and DTI were performed during acute (6 h and 24 h) and subacute (3d and 7d) phases after GMH-IVH. Four DTI parameters including fractional anisotropy (FA), mean diffusion (MD), axial diffusion (AD) and radial diffusion (RD) were collected in 9 specific brain regions to assess the brain microstructure alterations. Early and long-term neurological function tests were evaluated. Transcriptome sequencing analysis was also performed to investigate possible underlying mechanisms. Regional abnormalities after GMH-IVH were observed in T2-weighted images that showed significant hypointense in striatum region which close to the germinal matrix. DTI parameters also observed changes in striatum region in GMH-IVH. Alterations in other regions of brain including hippocampus, thalamus, external capsule and motor cortex also noted, which were associated with the abnormalities observed in behavioral experiments. Long-term behavioral tests show that compared to sham group, rats in GMH-IVH group caused abnormal motor function. In addition, at 24 h after GMH-IVH, transcriptome analysis results showed that the highly expressed differential genes encode hemoglobin components and down-regulate neurodevelopment-related pathways. DTI imaging allows the early assessment of neurological alteration in GMH-IVH rat pups, and providing great value in evaluating long-term behavioral deficits.

This research assesses the potential of a mobile thermochemical storage system, the mobile heat battery (M-HB), for decarbonizing a low-temperature district heating (DH) system in the Netherlands. The assessment is built on a case study where the M-HB is used to transport waste heat from different sources to a neighborhood interface of a DH system. This case study utilizes a simulation-based methodology to calculate the emissions from grid electricity, DH, and M-HB transport and charging. Building performance simulation is used as the main experimental method in combination with both empirical data and theoretical assumptions. Various system operational strategies and uncertain factors are explored, and waste heat sources are screened by different decarbonization targets. Findings indicate that using the M-HB can reduce the operational carbon emissions by up to 80 %, from approximately 60–70 KgCO2/GJ of the system without M-HB to around 13 KgCO2/GJ in optimal scenarios. Emissions from M-HB transport and charging are identified as more influential to the decarbonization potential than other considered factors, which addresses the significance of choosing proper waste heat sources. Despite some limitations from data availability and assumptions, this work identifies both opportunities and challenges for using M-HB to decarbonize DH systems.

Salt hydrates are thermochemical materials capable of storing and releasing heat through reversible reaction with water vapor. In a heat battery, salt hydrate tablets of millimeter size are necessary to ensure a sufficient permeability of the packed bed. A profound understanding of the hydration process of these tablets is required to improve their kinetic performance. In this study we show that the hydration timescale of salt tablets is transport limited and that it depends primarily on the porosity and on the driving force (Δp). From gravimetric measurements done on SrBr2·6H2O and CaC2O4 we derived the intrinsic reaction and effective diffusion coefficients (k and Deff) and found that they validate a front-diffusion limited hydration hypothesis. In particular, the obtained Deff values (0.8–4.5 mm2 s−1) only depend on the tablets' porosities. Based on these parameters, we calculated the second Damköhler number (DaII) and proved that many other hydration reactions are diffusion limited. In the case of identical structures, the power output is therefore controlled only by the driving force. Its variation could be predicted by calculation of a so-called power scaling factor (Λ) for a selection of salts. This power scaling factor depends on the enthalpy (ΔH) and entropy (ΔS) of the reaction. For a temperature output of 40 °C and at 12 mbar most hydration reactions fall in the interval 0<Λ<30 and Λ exceeds 30 only in very few cases. This parameter establishes therefore another important constraint to the selection of the most ideal salt. Suitable strategies to circumvent the diffusion limitation will lead to the development of next generation salt hydrate tablets for thermochemical energy storage.

We investigate the influence of inherited glacier structures on the development of moraine dam morphology over 61 years on four glacial lake dams in the Eastern Himalaya. We compare glacier structures from 1962 Corona imagery with current dam features from 2023 Maxar imagery at Imja, West Barun, Melung and Dang Pu glaciers. From the Corona imagery, maximum glacier extents were identified, along with discrete flow units, ice cliffs, transverse structures, and supraglacial ponds at a 2.5 m resolution. In the Maxar imagery, key dam components were identified including extent of dead ice, hummocky moraines, thermokarst, and surface drainage features and surface structures, mapped at 1 m resolution. Our analysis revealed that former glacier flow unit boundary locations coincide with the development of hydrological features on the dam surface. This was augmented with further analysis of surface elevation change, thermokarst, and surface drainage development using historical aerial imagery, satellite imagery, and DEMs for Imja from 1962 to 2023. We propose that hydrological features exploit relict flow unit boundaries and conclude that inherited glacier structures are key in understanding the development of lake dams that contain dead ice. The glaciological influences on dam features should be included in integrated hazard assessments in glacial settings.