Nano-enhanced phase change materials (NePCMs) are composites made of an organic or inorganic PCM and nanoparticles (metal, metal oxide, carbon nanotube, graphite, graphene) capable of increasing their thermal capacity or conductivity.

PCMs are classified into three categories, namely organic, inorganic, and eutectic [1,2].

This study focuses on the patent analysis of organic NePCMs doped with carbon allotropes for thermal energy storage.

Patent searches were carried out using two databases (Espacenet, provided free of charge by the European Patent Office, and Orbit, a paid-for system provided by Questel) using precise and controlled keywords in the title/abstract/claims search fields with Boolean and proximity operators and classification codes.

Classification symbols were retrieved by means of the Espacenet classification search tool and the WIPO IPCCAT system.

China is the country with the highest number of patent applications filed for NePCMs with carbon allotropes, followed by the United States, Europe, and South Korea.

The number of patent applications filed increased from 2016 to 2022.

However, it should be noted that the figures for later years are not reliable, as applications are kept secret for the first 18 months after filing.

Graphene and its derivatives are the most frequently claimed compounds in applications and granted patents, followed by carbon nanotubes.

Fullerenes are rarely claimed (1.4% compared to graphene and derivatives), with an even smaller percentage claimed for other nanosized carbon materials (such as nano-onions, nanoscrolls, nanohorns, nanocones, nanowalls, and nanocoils).

Approximately 30% of the applications have either expired or been revoked or withdrawn.

Of the active patents, between 35% (for nanotubes) and 40% (for graphene) remain under examination.

The most commonly used PCMs in combination with carbon allotropes are paraffin, stearic and lauryl acids, and lauryl alcohol.

Materials based on α-NiSO₄·6H₂O (NSH) (sp. gr. P4₁2₁2, Z = 4) are used for lithium-ion batteries and UV filters for the solar-blind range. Their performance characteristics can be varied by introducing activator ions М. The behaviour of M in NSH depends on differences in crystallochemical characteristics of Mⁿ⁺ and Ni²⁺ ions, the way of introducing M ions into the solution, and the growth sectors of the crystals. The goal of this work is to establish the distribution of Y³⁺ ions over the growth sectors of NSH:Y crystals when they are introduced into a solution in extremely small quantities (c = 10 mM).

Two crystals were grown on NSH (001) plates: NSH:Y-1—perpendicular to <001> (32 g; growth duration 144 h); NSH:Y-2—parallel to <001> (269 g; growth duration 336 h). The habit (mmm) was found for NSH:Y-1, faceted by {001}, {101}, {011}, {012}, and {110} with face areas (S_face{hkl}) {101}>{011}>{012}>{001}>{110}. In the habit (mm2) of NSH:Y-2 crystals, new faces ((102), (12), and (1 )) with S_face(hkl) (101)>(012)>(102)>(011)>(001)>(1 2)>(1 )>(110) also appeared. The NSH:Y-2 crystal, by its (00) face, was at the bottom of the crystallizer during growth (uneven supply of the solution).

The c, Å tetragonal crystal parameter (X-ray diffraction of powdered crystals) decreased with the decrease in Y³⁺ content (с_м, ppm—mass spectrometry), c{101}>c{102}>c{001}, consistent with crystal morphology. Defect formation can be described by the quasi-chemical reaction 0V_Ni^n’+Y_i^m· and the composition (Ni²⁺_1-x[])(Y³⁺_i(x))SO₄]. In the {101}-{102}-{001} series, a decrease in Y³⁺ content is accompanied by a decrease in the Y³⁺ interstitials (Y_i^m·) and vacancies in the Ni²⁺ site (V_Ni^n’).

The compositions of the NSH:Y growth sectors, on which the functional properties depend, are important for the application of the material in the form of plates.

Funding: Ministry of Science and Higher Education of the Russian Federation, grant No. FSFZ-2024-0026.

The investigation of crystallization kinetics in supercooled melts has spanned more than a hundred years and is relevant to many areas of science and technology. Conventional techniques, however, limit the range of systems where this study is possible due to relatively slow crystallizers. As such, the nucleation kinetics in supercooled melt was accessed only for a few organic compounds.

Fast scanning calorimetry (FSC) allows us to greatly increase the range of molecules that can be supercooled by providing a cooling rate of thousands of degrees per second and beyond. FSC was extensively used to study nucleation and crystallization kinetics in polymers, but rather few applications of the method to small organic molecules are reported. Using the FSC technique, we have studied the nucleation and crystallization of benzocaine, a rapidly crystallizing molecule, from supercooled melt. The nucleation of benzocaine was observed at –70 °C (supercooling of about 160 degrees), which is more than 50 degrees below the glass transition of the compound. The crystallization half-times greatly depend on temperature and cover nearly five orders of magnitude.

Nucleation and crystal growth in the supercooled melt were also studied in tolbutamide. Compared to benzocaine, tolbutamide has lower critical cooling and heating rates, permitting the application of the two-stage nuclei development method based on FSC. In tolbutamide, the isothermal nucleation and crystallization kinetics were studied. A modified two-stage nuclei development technique was used to probe the nuclei stability and obtain an estimate of the lateral growth rate of the nuclei, providing a unique insight into the properties of crystal nuclei. The interplay between the nucleation, crystallization, and polymorphism of tolbutamide was also accessed.

The results of the measurements are discussed in the framework of the Classical Nucleation Theory.

Polymorphism in active pharmaceutical ingredients has been the subject of intense investigation in the drug industry due to its influence on the properties of a drug. A better understanding of the formation of different polymorphic forms and control mechanisms may improve crystallization process efficiency and reduce production costs [1-2].

In this study, para-aminobenzoic acid (pABA) was used as a model substance to investigate the crystallization control approach using additives. pABA has four polymorphic forms, in which there are different types of hydrogen bonding and aromatic interactions [3].

The polymorphic outcome of crystallization of pABA was explored under different conditions by performing evaporation and cooling crystallization from different solvents and in the presence of different additives. For the cooling crystallization, different cooling rates were used. Solid products obtained in the crystallization were characterized by powder X-ray diffraction. The solubility of different pABA polymorphic forms was determined in water and the presence of selected additive. Additionally, induction time measurements were performed to determine the effect of the selected additive on the crystal nucleation rates.

In most cases, the crystallization results with an additive present were the same as those from the pure solvent. However, polyacrylic acid has shown the potential to form a metastable form by cooling crystallization. In the crystallization using the fastest cooling rate, α or β form or their mixture was obtained, but when using the slower cooling rate pure metastable β form was achieved. The solubility of pABA α and β forms in the presence of polyacrylic acid is lower than in water. Additionally, polyacrylic acid slows down the nucleation of pABA.

References:

[1] Pudipeddi, M.; et al. J. Pharm. Sci. 2005, 94 (5), 929–939.

[2] Simone, E.; et. al. CrystEngComm 2015, 17 (48), 9370–9379.

[3] Cruz-Cabeza, et al. CrystEngComm 2019, 21 (13), 2034–2042.

Cobalt-substituted mixed spinel ferrites, used in various applications, have adjustable magnetic properties influenced by cation type and structural features. The theoretical framework for these materials assumes homogeneously magnetized, single-domain, non-interacting particles. However, recent studies reveal that nanoparticle systems are more complex, even with highly crystalline, monodisperse, non-interacting ensembles. Factors like spin disorder and dipolar interactions can significantly affect the material’s magnetic properties. In this study, we delve into the evolution of magnetic and structural properties within a series of oleate-capped manganese-substituted cobalt ferrites (denoted as Mn_xCo_1−xFe₂O₄) with varying Co/Mn molar ratios. The results can be interpreted solely based on their actual composition, independent of other parameters, thanks to the single-phase nanoparticles with similar crystallite and particle sizes (about 10 nm), size dispersity (14%), and weight percentage of capping oleate molecules (17%). The temperature and magnetic field dependences of the magnetization revealed magnetic anisotropy to be the key parameter affecting the magnetic parameters, including T_max, T_diff, T_b, H_c, H_K, and M_r/M_s, caused by different cobalt contents. Deviations from the ideal scenario of non-interacting NPs become evident in all samples when employing IRM-DCD protocols, showing negative ∆M peaks in Mn-rich samples (with a correlation between cobalt content and magnetic anisotropy), while positive ∆M is observed in the Co-enriched sample, possibly due to strong dipole–dipole interactions or surface spin phenomena. Small-Angle Polarized Neutron Scattering (SANSPOL) was then employed to study the quantitative distribution of magnetization within NPs, to reveal the presence of surface spin disorder, to access the surface anisotropy constant, and therefore to isolate the magnetocrystalline anisotropy and correlate it with the Mn content.

Background: Cone beam computed tomography ( CBCT) offers a comfortable breast examination accompanied by 3D breast representation, at the same or lower dose levels in comparison to classical mammography and its derivative tomosynthesis. In the case of dense breast, it provides specialists a reliable anatomical representation towards an accurate diagnosis of breast pathologies. CBCT system detector configuration usually is based on a CsI:Tl scintillator.

Materials and Methods: The purpose of this study was to instigate novel detector schemes applied to a simulated micro-CBCT system, with a view to designing future experimental setups. The energy spectrum of the CBCT system X-ray source ranged from 10 to 40 keV. The system relied on a 360° rotating table. Different detector materials, of the same size and shape, were simulated and investigated: LSO:Ce, LYSO:Ce, LuAG:Ce, GAGG:Ce, LaBr₃:Ce, LaCl₃:Ce, and CZT. A bone tissue capillary was used in order to investigate possible differences in the system’s spatial resolution. Further, a breast phantom was simulated in order to evaluate image quality, as it is derived from contrast-to noise ratios (CNRs) of specific ROIs (regions-of-interest). System simulation was based on GATE software. Images were reconstructed with FBP and OSEM. The evaluation was performed in conjunction to the standard CsI:Tl detector setup. All schemes were simulated with the same front-end electronic configuration.

Results: Image quality assessment depicted a dependence on detector material. LYSO:Ce, LuAG:Ce, GAGG:Ce, LaBr₃:Ce, and LaCl₃:Ce presented high CNRs for materials of different composition. CZT is a promising semiconductor energy converter in the case of a low-density bone tissue. Spatial resolution depends only on the reconstruction algorithm.

Conclusion: The aforementioned examined materials with increased CNRs could be an efficient alternative in a future CBCT system that will overcome further dense breast imaging limitations.

Introduction. The aim of this study was to examine the effective luminescence efficiency (ELE) and the spectral matching of a 10×10×10 mm³ cerium fluoride (CeF₃) single-crystal scintillator with various optical sensors. Numerous investigations have shown that CeF₃ crystals have a non-proportional response to gamma rays, and they have already been successfully used in high-rate calorimetry, including the Large Hadron Collider's high-luminosity phase experiments. However, the scintillation response of CeF₃ has not been systematically examined in the energy range covering medical imaging applications.

Methods. Measurements were performed with a CPI Inc. CMP 200 DR X-ray generator and the X-ray tube IAE SpA model RTM90HS in the range of 60–150 kVp and 63 mAs. Twenty mm of Al was added in addition to the inner filter of the X-ray tube to simulate attenuation from a human chest. The effective luminescence efficiency (ELE) and the spectral matching (SMF) of the scintillator wwere examined with various optical sensors.

Results. The effective luminescence efficiency increases continuously in the examined energy range (60-150 kVp), with the maximum value (0.812 efficiency units (EU) is the S.I. equivalent μWm^-2/(mGy/s)) at 150 kVp. With an emission maximum at 314 nm, the optimum effective efficiency was found for a multialkali photocathode (0.81 EU) and the flat-panel position-sensitive photomultiplier (PS-PMT) H8500D-03 (0.808). The corresponding spectral matching (SMF) values were equal to 0.97 for both the multialkali photocathode and the PS-PMT H8500D-03.

Conclusion. Within the examined energy range, the resulting values are considered low compared to those for typical materials used as X-ray radiation-t-light converters; thus, CeF3 could not be used in radiological applications covering this energy range. It is possibly worth studying CeF₃ crystals at higher energies considering that the luminescence efficiency did not reach the maximum value at 150 kVp (the maximum energy of the medical X-ray tube).

Background. Scintillators are used in a variety of applications, including modalities in environmental conditions of extreme temperature or radiation flux. Thus, knowledge of their luminescence performance under the influence of temperature or radiation flux is of paramount importance. In this framework, the aim of this study was to examine the influence of temperature on the luminescence efficiency of a hygroscopic cerium-doped lanthanum bromide (LaBr₃:Ce) single-crystal scintillator. The crystal output was compared with a cerium-doped lanthanum chloride (LaCl₃:Ce) crystal scintillator of equal dimensions, in similar experimental conditions.

Materials and Methods. The experimental setup comprised a CPI series CMP 200 DR medical X-ray source set to a fixed high voltage (90kVp) to expose the sample to X-ray radiation under temperature conditions in the range of 23–154 ^oC. LaBr₃:Ce is an extremely efficient crystal, with a high light yield of 63,000 photons/MeV and a fast decay time (25ns). The crystal was removed from the protective aluminum encapsulation (thickness 0.7 mm). Heating was performed using a Perel 3700-9 2000W heating gun. The temperature on the crystal surface was monitored using an Agilent Technologies U1253A digital multimeter, coupled to a U1185A thermocouple (J-Type) with a temperature probe adapter.

Results. The luminescence efficiency of LaBr₃:Ce decreases with increasing temperature, from 69.58 EU at 23.0^oC to 18.27 EU at 154^oC (EU is the S.I. equivalent μWm^-2/(mGy/s). The corresponding values for LaCl₃:Ce were 33.14 to 17.96 EU in the temperature range from 29 to 162 ^oC. The room-temperature absolute efficiency of LaBr₃:Ce, with the protective aluminum encapsulation, was 50.02 EU.

Conclusion. LaBr₃:Ce is an extremely efficient crystal scintillator and knowledge of its performance in various temperatures could be useful for various applications, from medical imaging to detectors for extreme environments.

Heusler alloys attract much attention due to their potential application in spintronic, magneto-optical and magnetocaloric devices [1-3]. In this work, we theoretically studied disorder effects in the electronic structure and magnetic properties of full Heusler Mn₂TiGe alloy, crystallized in the orthorhombic Ima2 structure within density functional theory (DFT). We calculated that Mn₂TiGe without defects exhibits metallic properties with a total magnetic value of 4.6 μ_B/f.u. and with partial magnetic moments of 3.2 μ_B/Mn, 1.3 μ_B/Ti and 0.1 μ_B/Ge. This value is higher than the value of 1.99 μ_B/f.u., reported recently from theoretical calculations for the L2₁ phase of Mn₂TiGe [4]. In our additional calculations for Mn2TiGe with the antisite defects Mn-Ge, the total magnetic moment was decreased to 1.3 μ_B/f.u. with 0.9 μ_B/Ti and a negligible Ge moment. An almost identically low value of the total moment 1.1 μ_B/f.u. was found in Mn₂TiGe with the antisite defects Mn-Ti; in this case, the partial moments gradually decreased. The largest effect on the magnetic moment is exhibited by the antisite change between Ti and Ge, because it provides further suppression of the Mn and Ti moments, causing the total magnetic moment to be equal to 0.6 μ_B/f.u. Also, in all cases, the Mn electronic states shift to lower energies, forming two peaks of states in the valence band in the electronic structure. Thus, we demonstrated that the investigated antisite disorder types result in a significant (by several times) reduction in the magnetic moment of the novel orthorhombic Mn₂TiGe alloy. This research was supported by the Russian Science Foundation, grant number RSF 22-42-02021.

[1] Phys. Rev. Mater. 3 (2019) 062401
[2] J. Magn. Magn. Mater. 398 (2016) 7
[3] J. Electron. Mater. 46 (2017) 2710
[4] J. Magn. Magn. Mater. 333 (2013) 162

Solid-phase synthesis of ZnS-based luminescent material enclosing the associative luminescence centres formed by the dopant atoms of copper and bromine Cu’Zn-BrS● is discussed. Annealing the powder mix of ZnS, CuCl, and NH4Br in reducing atmosphere provides the diffusion and volume distribution of Cu+ and Br- ions in the two-phase ZnS matrix.
It was stated experimentally in five series of the synthesized phosphors that ZnS:Cu,Br forms the combined sphalerite--wurtzite crystal structure and the intensity of radioluminescence given by the Cu’Zn-BrS● associates sharply increases at a certain content of the wurtzite phase in ZnS structure 1.
A description of this phenomenon can be provided by the percolation theory instruments. The formation of the long interphase boundary between sphalerite and wurtzite phases in the phosphor grain of ZnS matrix as a percolation infinite cluster analogue results in the grain boundary diffusion rate increasing and an improvement in the luminescence centres' forming ability on the intercrystalline borders. Associated defects migrating through the volume of the crystal to its surface provide the surface luminescence centres and improve tritium radioluminescence.
Computer modelling of the diffusion process in the discussed system was conducted and a descriptive model of structure defect migration through the two-phase phosphor structure was developed. The application of this approach in solid-state physical chemistry provides an additional tool for controlling the structure and properties of functional materials.