High-temperature Modification Research Articles

Characterization of temperature regulating, high-temperature rheological and anti-aging properties of asphalt mastic modified with SSPCMs

The objective of this study is to explore the potential of utilizing self-developed SSPCMs as additives for heat storage temperature regulation in asphalt mastic modification. To achieve this aim, a variety of asphalt mastics with different F-A volume ratios and SSPCM contents were formulated, and their high-temperature rheological properties, modification mechanisms, thermoregulation capabilities, and aging resistance performances were analyzed. The results of temperature regulation test indicated that the maximum cooling amplitude of asphalt mastic could reach 11.3°C, showing a great promising application for cooling asphalt pavements. Additionally, the incorporation of SSPCMs generally resulted in positive impacts on both the high-temperature rheological properties and temperature sensitivity of the asphalt mastics. Moreover, the aging indices GAI, ICO and ISO of the modified asphalt mastic with 30 % SSPCMs decreased by 5.6 %, 18.3 % and 8.7 %, respectively, compared with control asphalt mastic, implying that the incorporation of SSPCMs can retard the aging process of asphalt and enhance the thermal oxidative aging resistance of the asphalt mastics. In summary, the current study demonstrates the feasibility, improved performance, and effective thermoregulation properties of SSPCMs in asphalt mastics.

Native and TMT Chestnut Extractives as Hydrophobic and Photostabylizing Additives for Wood Surfaces

Wood extractives have proven strong anti-oxidative properties which may be used to mitigate surface deterioration caused by photolytic effects and free radical formations. An interesting challenge regarding wood extractives is understanding how they behave in terms of treating natural wood surfaces to reduce anti-oxidative processes that arise from exposure to the main environmental factors. In this study, the possible efficacy of chestnut (Castanea sativa Mill.) extractives derived from native (CH) and thermally modified wood (TMT CH), as a means of protecting against UV exposure in poplar (Populus spp.) and spruce (Picea abies Karst.) wood, was evaluated. Chestnut wood was first thermally modified at 180 °C for 3 h, and the extractives were obtained by the accelerated solvent extraction technique (ASE) and subsequently used to treat wood surfaces. Samples were immersed in extractive solutions and exposed to artificial UV-weathering exposure, then contact angle and colour stability were monitored during the process. An FTIR analysis of the photo-degradation process of poplar and spruce surfaces was also executed. Extractives of TMT chestnut changed the total colour variation in both poplar and spruce wood. A much darker colour compared to the extractives of native wood was observed and an increase in ∆E* from 9.75 to 30.76 and 6.24 to 22.97 in poplar and spruce was calculated. The stability of the colour depended both on the surface wood and the type of extractive. The initial contact angle remained almost unchanged in the poplar wood surface and only slightly increased in spruce regardless of whether they were treated with extractives from native or TMT chestnut wood. A strong reduction in contact angle after the accelerated UV exposure test was observed, especially in spruce treated with CH extractives. FTIR analysis confirmed the lower levels of chemical degradation of surfaces observed by colorimetry, where TMT CH extractives formed more stable chemical bonds than native extractives. The comparative analysis in this study clarified the complex relationships between the effects of high-temperature modification of wood and the potential protective role of TMT extractives on some wood surfaces.

Steerable droplet precise bouncing on a superhydrophobic surface with superhydrophilic stripes

The precise rebound of a droplet upon hitting a solid surface has garnered significant attention in recent years due to its critical applications in self-cleaning, printing industries, and the design of heat exchanger surfaces, among others. This study introduces an innovative approach that combines femtosecond laser processing with a high-temperature stearic acid modification to create surfaces that feature superhydrophilic (SHL) stripes on a superhydrophobic substrate. By controlling the offset distance between the droplet's impact point and the SHL stripe, we achieved a directional and precise rebound of the droplets. Our findings indicate that the lateral displacement of the droplet increases with the offset distance and always tilts toward the direction of the SHL stripe. This study also incorporates numerical simulations to validate the findings, shedding light on the energy conversion mechanisms at the liquid–solid interface during the impact, particularly during the retraction phase. This discovery is significant for more accurately predicting the specific landing spots of rebounding droplets.

On Chemical Bonding in ht-Ga3Rh and Its Effect on Structural Organization and Thermoelectric Behavior.

In the course of systematic studies of intermetallic compounds Ga3TM (TM─transition metal), the compound Ga3Rh is synthesized by direct reaction of the elements at 700 °C. The material obtained is characterized as a high-temperature modification of Ga3Rh. Powder and single-crystal X-ray diffraction analyses reveal tetragonal symmetry (space group P42/mnm, No. 146) with a = 6.4808(2) Å and c = 6.5267(2) Å. Large values and strong anisotropy of the atomic displacement parameters of Ga atoms indicate essential disorder in the crystal structure. A split-position technique is applied to describe the real crystal structure of ht-Ga3Rh. Bonding analysis in ht-Ga3Rh performed on ordered models with the space groups P1̅, P42nm, and P42212 shows, besides the omnipresent heteroatomic Ga-Rh bonds in the rhombic prisms ∞3[Ga8/2Rh2], the formation of homoatomic Ga-Ga bonds bridging the Rh-Rh contacts and the absence of significant Rh-Rh bonding. These features are essential reasons for the experimentally observed disorder in the lattice. In agreement with the calculated electronic density of states, ht-Ga3Rh shows temperature-dependent electrical resistivity of a "bad metal". The very low lattice thermal conductivity of less than 0.5 W m-1 K-1 at 300 K, being lower than those for most other Ga3TM compounds, correlates with the enhanced bonding complexity.

Properties, structure and mechanism of high-temperature modified steel slag based on solid waste

In this study, a composite modifier (CMCDL) containing coal gasification residue, dicyandiamide waste slag, and lake sediments was used to modify steel slag at high-temperature. Five kind of raw materials was analyzed in physicochemical properties, mineral composition and microstructure, cementitious properties and soundness, and particle size analysis, the same to steel slag after high-temperature modification (SHTM). The new mineral phases were found that tricalcium aluminate (C3A), gehlenite (C2AS), magnetite (Fe3O4), spinels (MgFe2O4), quartz (SiO2), celite (C6AF2) and diopside (CMS2) formed in the SHTM when the mass fraction increase from 10% to 30% in CMCDL. The HTM with CMCDL increases the glass phase and hydrated mineral (C3A, C3S, C2S) and in raw steel slag, promoting the disassembled of RO phase, turning the phase from FeO into MgFe2O4 and Fe3O4. MgFe2O4 and Fe3O4 have similar crystal structures, and they form mixed spinels. When the content of CMCCL (coal gasification residue: dicyandiamide waste slag: lake sediments =7:9:4) is 20%, the temperature is 1250 °C, result showed that the mass fraction of f-CaO in SHTM using CMCCL decreases from 4.81% to 1.86%, with a decrease of 61.3%, the 28-day activity index of SHTM increases up to 17.6% compared with raw steel slag, reaching 86.2%. Therefore, the CMCDL-blended SHTM can be applied harmlessly in cement and concrete, enabling low-energy fine grinding of steel slag.

High-temperature modifications of charged Casimir wormholes

In this work, we extend the investigation of the consequences of thermal fluctuations on the Casimir effect within the context of a traversable wormhole, recently proposed by Garattini & Faizal, arXiv:2403.15174 [gr-qc], subject to charge contributions. Specifically, we focus on scenarios where the plates exhibit both constant and radial variations. In our analysis, we initially concentrate on the high temperature approximation, considering solely the influence of charge on the thermal Casimir wormholes. Additionally, upon incorporating Generalized Uncertainty Principle (GUP) corrections to the Casimir energy, we obtain a new class of wormhole solutions. Notably, we establish that the flare-out condition remains consistently satisfied. Intriguingly, our findings reveal that both the charge and GUP contributions serve to further enlarge the throat's size in the radial variation.

Mechanistic study on the promotion of Ca2+ leaching in steel slag through high-temperature solid waste modification.

Indirect carbonation of steel slag is an effective method for CO2 storage, reducing emissions, and promoting cleaner production in the steel industry. However, challenges remain, such as low Ca2+ leaching rates and slag management complexities arising from variations in mineral compositions. To address this, a high-temperature modification process is proposed to alter the mineral composition and facilitate the synergistic utilization of calcium and iron. This study delves into the effects of various solid waste modifications on the leaching of Ca2+ and the total iron content within steel slag. Results show that high-basicity modified slag forms Ca2(Al, Fe)2O5, reducing calcium leaching. Low-alkalinity modified slag produces calcium-rich aluminum minerals and also reduces the leaching of Ca2+ ions. At a basicity of 2.5, coal gangue, fly ash, and blast slag achieve maximum Ca2+ leaching rates of 88.93%, 89.46%, and 90.17%, respectively, with corresponding total iron contents of 41.46%, 37.72%, and 35.29%. Upgraded coal gangue exhibits a 50.02% increase in calcium leaching and a 15.58% increase in total iron content compared to the original slag. This enhances CO2 fixation and iron resource utilization. Overall, the proposed indirect carbonation and iron enrichment modification offer a novel approach for the resource utilization and environmental stability of steel slag.

High temperature-resistance modification of the magnesium phosphate inorganic adhesive and its bond properties between CFRP sheets and concrete

The carbon fibre reinforced polymer (CFRP)-strengthened concrete structures are faced with the great threat of fire due to the vulnerability of the epoxy organic adhesive to high temperature. The traditional epoxy organic adhesives are thus urgently needed to be replaced by the alternatives with high-temperature resistance. This paper explored the feasibility of using magnesium phosphate inorganic adhesive (MPIA) to serve as the bonding material for the CFRP-strengthened concrete structures. To this end, the high-temperature resistance modification of MPIA was conducted through the addition of glass powder (GP) in this study. The effects of the GP content ranging from 0% to 15% on the temperature development, mechanical property degradation, phase evolution and microstructural characteristics of the MPIA after exposure to different temperatures were investigated. The results showed that the glass powder could effectively fill the pores caused by the decomposition of the hydration products and the cracks caused by the shrinkage of MPIA matrix at elevated temperatures, which improved the microstructure of MPIA significantly and thus alleviated its strength degradation under high temperature. In terms of the mechanical properties, the MPIA with 10% GP (hereinafter referred to as TRMPIA) yielded the best high-temperature resistance. In addition, the interfacial bond property test after high temperature was also conducted on the concrete members strengthened with the CFRP sheets pasted by TRMPIA, and the test results were also compared with the specimens with epoxy served as the bonding material. The results showed that even after exposure to 600°C, the in-plane shear strength of TRMPIA still remained 14.0% of that at room temperature, while the bond strength of epoxy had been completely lost, which highlighted the advantage of high-temperature resistance of the modified MPIA served as the bonding material of CFRP-strengthened concrete structures.

Experimental study on variation characteristics of combustion heat load in circulating fluidized bed under fuel high-temperature preheating modification

This study introduces an innovative application of fuel high-temperature preheating modification technology to circulating fluidized bed (CFB), intending to enhance the variable load rate of CFB and reduce its NOx emissions. The variable combustion heat load (CHL) experiments were conducted on a novel CFB experimental platform comprising a preheating modification device (PMD) and CFB. The findings indicate that implementing fuel high-temperature preheating modification technology allows the CFB to operate stably within the range of 30%–100% CHL while maintaining superior combustion efficiency. Moreover, it reduces NOx emissions by over 28% compared to conventional combustion. The decrease in NOx emissions can be attributed to the fuel's preheating modification process inhibiting NOx production and establishing conditions conducive to NOx reduction in CFB. Furthermore, after employing the fuel high-temperature preheating modification technology, the CHL change rate of CFB reached 1.79%/min and 2.27%/min for the transition from 50% CHL to 75% CHL and from 75% CHL to 100% CHL, respectively. These rates represent an increase of 1.59 and 1.80 times compared to the rates observed in conventional combustion processes. The increase in the CHL change rate of different CHL variation intervals is primarily due to the production of high-temperature coal gas and modified char following fuel preheating modification. High-temperature coal gas exhibits a rapid combustion rate, while modified char has a smaller particle size, more developed pore structure, and enhanced reactivity than raw coal.

CTAB modification bentonite for enhanced Re adsorption and diffusion suppression

Abstract 99Tc is a crucial high-yield fission product, characterized by its radiotoxicity, extended half-life, high solubility, and significant mobility in the environment. On the other hand, Re is employed as a substitute for Tc due to its analogous properties and non-radioactive nature. Bentonite is commonly used as a backfill material in repositories for high-level radioactive waste storage; however, it exhibits minimal adsorption capacity for Re(Tc). This study aims to enhance the adsorption capability of bentonite for Re(Tc) through modification with Cetyltrimethylammonium Bromide (CTAB). Modified bentonite exhibits excellent adsorption performance under various conditions, primarily driven by the interaction between the ReO4 − anion and the pyridinium ring of the CTA+. Its primary adsorption mechanism involves a chemical precipitation reaction between ReO4 − and CTA+. The adsorption capacity is approximately 30 times that of unmodified bentonite, and the adsorption process is characterized by spontaneous low-temperature chemical monolayer adsorption. Experimental results of the modification indicate that high-temperature and alkaline modification conditions contribute to enhanced adsorption capacity, with an optimal modification time of approximately 30 h and a maximum modifier addition of 250 % of the bentonite’s cation exchange capacity (CEC). Additionally, the incorporation of modified bentonite into natural bentonite significantly inhibits the diffusion behavior of ReO4 −. These findings highlight the substantial improvement in the adsorption capacity of bentonite for Re(Tc) through batch modification, leading to reduced mobility of ReO4 − within backfill materials.

Crystal structure and optical properties of Eu3+–doped and undoped complex sulfate KSc(SO4)2 produced by facile and efficient crystallization process

Both pristine and Eu3+-doped scandium-potassium complex sulfate KSc(SO4)2 has been obtained with 99% yield via crystallization from solutions. The high-temperature XRPD and thermal studies revealed an enantiotropic first-order phase transition at 700–725 K and standard pressure. In the temperature region 724–754 K, the low-temperature stable monoclinic polymorph, β-KSc(SO4)2 (sp.gr. С2/m), coexists with the high-temperature trigonal modification, α-KSc(SO4)2 (sp.gr. P321), with decomposition at ∼1120 K. DFT calculations confirmed this rank of polymorphs and a low hospitality of their Sc-sublattices for Eu3+ cations. Under UV excitation, the KSc0.98Eu0.02(SO4)2 sample exhibits Eu3+ luminescence at 570−720 nm. Heating of the sample from 298 K to 423 K leads to a luminescence fading of 13% and to its a sharp decline at elevated temperatures. Kinetic studies have shown that the lifetime depends on the chosen excitation wavelength and temperature. An Х-band resonance in the sample of KSc(SO4)2:Eu3+ has been detected in the temperature range of 299–500 K. The EPR spectra are interpreted assuming the presence of sulfate radicals.

Three Ways to (Pseudo)cubic Structure Models: Phase Transition and Pseudosymmetry in Orthorhombic Cs3MO4 (M = V, Nb, or Ta).

The new oxometalates Cs3NbO4 and Cs3TaO4 together with Cs3VO4 crystallize with the K3NO4 structure type [Pnma, a = 12.495(2) Å, b = 9.0183(14) Å, and c = 6.6529(10) Å for the V compound; a = 12.928(2) Å, b = 9.177(3) Å, and c = 6.739(4) Å for the Nb; and a = 12.963(4) Å, b = 9.122(2) Å, and c = 6.774(1) Å for the Ta compound]. Their crystal structures were evaluated on the basis of single-crystal and powder X-ray diffractometry, assisted by vibrational spectroscopy, thermoanalysis, and DFT calculations. The crystal structures contain tetrahedral [M5+O4]3- anions, representing the first occurrence of Nb and Ta in a tetrahedral oxidic environment. Many representatives of the orthorhombic K3NO4 structure type have been described in the literature with a cubic structure model with disordered O atomic positions. Based on studies on Cs3MO4 (M = P, V, Nb, or Ta), we show here three different effects which can lead to (pseudo)cubic data sets. Two of them are problems of crystallographic nature (overlooked twinning or adverse atomic form factor ratios), but the third one, phase transformation into a plastic crystalline high-temperature modification, leads to a "truly" cubic structure with dynamically disordered (freely rotating) oxometalate anions. This might be of interest with respect to a large and growing number of sulfido- and selenidometalate materials which are today in discussion as solid-state electrolytes and to the mechanism of the unusually efficient ion transport therein.

Microplastic removal from water using modified maifanite with rotating magnetic field affected

Magnetic separation of microplastics from water is a new generation technology that is cost effective and environmentally friendly, and can avoid secondary pollution. The influence of magnetic Maifanite on polystyrene removal from water was investigated under a magnetic field action time, solution pH, magnetic carrier dosage, and polystyrene concentration, using a developed rotating magnetic field generator. Additionally, the polystyrene removal mechanism by the rotating magnetic field was revealed based on characterization and process simulation. The results showed that Maifanite can increase the number of surface adsorption sites and improve the adsorption performance after high temperature and acid impregnated modification. Specifically, the surface morphology of the modified Maifanite exhibited skirted stripes and a multilayered pore structure. And the specific surface area increased from 3.26 to 20.83 m2/g. The removal process is based on chemical adsorption, supplemented by physical adsorption. The magnetic carrier is tightly wrapped around the polystyrene surface by π bonds between the metal and hydroxy groups, ensuring agglomeration strength. Additionally, the rotating magnetic field generator designed can provide a rotating dynamic magnetic field, and the magnetic particles in the mixed system present a multi-directional helical motion trajectory, thus the walking displacement increases and the capture time decreases. And the probability of collision with non-magnetic particles and the formation of magnetic agglomerates are greatly increased. Thus the adsorption and removal of microplastics are enhanced theoretically. The polystyrene removal efficiency from water using modified Maifanite by rotating magnetic field affected increased by 19.49 %, reaching 98.46 %, and stabilizing at 86.53 % over 25 operation cycles. This study holds promise for advancing magnetic separation technology for microplastics from water.

Synergistic calcium leaching and iron enrichment by indirect carbonation of thermally modified steel slag

Indirect carbonation of steel slag is an effective CO2 sequestration strategy, which is of great significance for reducing CO2 emissions of the iron and steel industry and achieving its green and low-carbon development. This paper proposed a process for high-temperature modification followed by indirect carbonation of steel slag, which enabled the separation and synergistic utilization of calcium and iron elements of the slag. The reactivity of various minerals in steel slag was initially studied at the level of ion coordination utilizing crystal structure theory. The results indicated that the O2- valence of β-Ca2SiO4 was unsaturated, resulting in high reactivity. In contrast, the O2- valence of Ca2Fe2O5 was relatively saturated, resulting in poor reactivity. The results of high-temperature modification and leaching experiments demonstrated that as the basicity of the steel slag decreased, the calcium component transformed into Ca2SiO4, while the iron component transformed into spinel minerals. When the basicity was too low, the Ca and Fe components recombined to form the poorly reactive Ca3Fe2(SiO4)3. As the basicity of the steel slag decreased, the Ca2+ leaching rate and the total iron content of leaching residue initially increased and then decreased. At a basicity of 2, both the Ca2+ leaching rate and the total iron content of leaching residue reached their maximum of 84.46% and 48.39%, respectively. This study significantly improved the Ca2+ leaching rate and the total iron content of leaching residue through high-temperature modification, thereby enhancing the CO2 sequestration capacity of the steel slag and the recovery level of iron resources The above strategy would be of great significance for promoting the green and low-carbon development of the iron and steel industry.

Galeite, Na15(SO4)5ClF4, and Schairerite, Na21(SO4)7ClF6: Phase Transitions, Thermal Expansion and Thermal Stability

In this study, galeite, Na15(SO4)5ClF4 and schairerite, Na21(SO4)7ClF6 were investigated via in situ single-crystal X-ray diffraction in the temperature range of 300–750 K. Galeite and schairerite are trigonal, P31m, a = 12.1903(2), c = 13.9454(2) Å, V = 1794.69(6) Å3, and Z = 3 (R1 = 0.0273, 300 K) for galeite and a = 12.1859(3), c = 19.3080(6) Å, V = 2483.04(14) Å3, and Z = 3 (R1 = 0.0334, 300 K) for schairerite. The crystal structures of galeite and schairerite are based upon frameworks consisting of alternating face- and corner-sharing fluorine- and chlorine-centered octahedra. Galeite and schairerite can be attributed to 5H (galeite) and 7H (schairerite) antiperovskite polytypes, respectively. It was observed that schairerite undergoes at least one reversible phase transition before it starts to lose its crystallinity at 750 K. This phase transition occurs in the temperature range of 550–600 K. The high-temperature modification of schairerite is trigonal, with the centrosymmetric space group P-3m1 and the unit-cell parameters a = 7.0714(2), c = 19.5972(7) Å, V = 848.66(6) Å3, and Z = 1. Galeite is stable up to 600 K. The crystal structures of minerals expand anisotropically, and, in both cases, the strongest thermal expansion was parallel to the modules of face-sharing anion-centered octahedra. The structural complexity analysis showed that galeite is complex (695.175 bits/cell) and that the LT-modification of schairerite is very complex (1064.990 bits/cell), whereas its HT-modification is intermediate in complexity (256.755 bits/cell). The complexities of LT- and HT-polymorphs of schairerite are consistent with the general observations regarding structures with positional disorder: complexity decreases with increasing temperature, and simpler polymorphs have lower physical density.

Effect of high-temperature mechanochemistry method modified TiO2 on the dispersibility and corrosion resistance of TiO2-epoxy coatings

PurposeThe purpose of this paper is to enhance the compatibility of titanium dioxide in epoxy resins and thus the corrosion resistance of the coatings.Design/methodology/approachIn this work, TiO2 was modified by the mechanochemistry method where mechanical energy was combined with thermal energy to complete the modification. The stability of modified TiO2 in epoxy was analyzed by sedimentation experiment. The modified TiO2-epoxy coating was prepared, and the corrosion resistance of the coating was analyzed by open circuit potential, electrochemical impedance spectroscopy and neutral salt spray test.FindingsHigh-temperature mechanical modification can improve the compatibility of TiO2 in epoxy resin. At the same time, the modified TiO2-epoxy coating showed better corrosion resistance. Compared to the unmodified TiO2-epoxy coating, the coating improved the dry adhesion force by 61.7% and the adhesion drop by 33.3%. After 2,300 h of immersion in 3.5 Wt.% NaCl solution, the coating resistance of the modified TiO2 coating was enhanced by nearly two orders of magnitude compared to the unmodified coating.Originality/valueThe authors have grafted epoxy molecules onto TiO2 surfaces using a high-temperature mechanical force modification method. The compatibility of TiO2 with epoxy resin is enhanced, resulting in improved adhesion of the coating to the substrate and corrosion resistance of the coating.

Enhanced sequestration of CO2 from simulated electrolytic aluminum flue gas by modified red mud

The aluminum industry is facing severe economic and environmental problems due to increasing carbon emissions and growing stockpiles of red mud (RM). RM is a strongly alkaline, high-emission solid waste from the alumina industry with potential for CO2 sequestration. However, the effectiveness of RM carbon sequestration is poor, and the mechanism behind it is not well understood. In this study, the effect of microwave and tube furnace activation of RM on CO2 sequestration in alumina was first investigated at different temperatures. The result showed that the CO2 sequestration capacity of unmodified RM (URM) was only 14.35 mg/g at ambient temperature and pressure, and the CO2 sequestration capacity could be increased to 52.89 mg/g after high-temperature activation and modification. Besides, high-temperature activation and modification will effectively improve the carbon sequestration capacity of RM. The carbonized RM was characterized by FT-IR, SEM, XRD, laser particle size, TG-DSC, and pH measurements. In addition, the mechanism of RM capturing CO2 was also proposed, which shows that CO2 was finally sequestered in the RM as CaCO3. The change in particle size distribution and the mineral phase in the RM indicated that high-temperature activation modification positively affects the application of RM to the sequestration of CO2. This study can provide a promising technology for the low-carbon and green development of the aluminum industry, as well as achieving the waste treatment and utilization objective.

Two-Component Rare-Earth Fluoride Materials with Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in 50 RF3-R'F3 (R = La-Lu) Systems.

The formation of materials with negative thermal expansion (NTE) based on a phase transition-type mechanism (NTE-II) in 50 T-x (temperature-composition) RF3-R'F3 (R = La-Lu) systems out of 105 possible is predicted. The components of these systems are "mother" RF3 compounds (R = Pm, Sm, Eu, and Gd) with polymorphic transformations (PolTrs), which occur during heating between the main structural types of RF3: β-(β-YF3) → t-(mineral tysonite LaF3). The PolTr is characterized by a density anomaly: the formula volume (Vform) of the low-temperature modification (Vβ-) is higher than that of the high-temperature modification (Vt-) by a giant value (up to 4.7%). In RF3-R'F3 systems, isomorphic substitutions chemically modify RF3 by forming R1-xR'xF3solid solutions (ss) based on both modifications. A two-phase composite (β-ss + t-ss) is a two-component NTE-II material with adjustable parameters. The prospects of using the material are estimated using the parameter of the average volume change (ΔV/Vav). The Vav at a fixed gross composition of a system is determined by the β-ss and t-ss decay (synthesis) curves and the temperature T. The regulation of ΔV/Vav is achieved by changing T within a "window ΔT". The available ΔT values are determined using phase diagrams. A chemical classification (ChCl) translates the search for NTE-II materials from 15 RF3 into an array of 105 RF3-R'F3 systems. Phase diagrams are divided into 10 types of systems (TypeSs), in four of which NTE-II materials are formed. The tables of the systems that comprise these TypeSs are presented. The position of Ttrans of the PolTr on the T scale for a short quasi-system (QS) "from PmF3 to TbF3" determines the interval of the ΔTtrans offset achievable in the RF3-R'F3 systems: from -148 to 1186 ± 10 °C. NTE-II fluoride materials exceed known NTE-II materials by almost three times in this parameter. Equilibrium in RF3-R'F3 systems is established quickly. The number of qualitatively different two-component fluoride materials with the giant NTE-II can be increased by more than ten times compared to RF3 with NTE-II.

Effect of high temperature modification on the highly adsorptive manufactured sand dust concrete

The production process of manufactured sand generates a large amount of dust, which poses a serious threat to the environment. In this study, we selected highly adsorptive manufactured sand dust of three lithologies (diabase, tuff, and basalt) for high temperature calcination. We evaluated its mechanical properties and microstructures after high temperature modification using various characterization methods to investigate its feasibility as a supplementary cementitious material (SCM). A comparative analysis of the manufactured sand dust before and after modification was conducted using thermogravimetric-differential scanning calorimetry (TG-DSC), laser particle size analysis, X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF) techniques, the results showed that high temperature modification can reduce the crystallinity of the mineral impurities in the manufactured sand dust. Furthermore, the average particle size of artificial sand dust from all three lithologies (diabase, tuff, and basalt) was reduced. However, the flowability of the mortars increased by 12.1%, 7.4%, and 6.4% respectively. The 28-day volcanic ash activity index reached 63%, 61%, and 60% respectively. In addition, we used the modified manufactured sand dust as a supplementary cementitious material in concrete. It was found that when 30% of cement was replaced with a 1:2 mixture of manufactured sand dust and fly ash, the compressive strength at 90 days reached a maximum of 90.6 MPa. These results demonstrate that the modified manufactured sand dust has certain economic benefits and can be used to partially replace cement in concrete. This provides a basis for the development and application of highly adsorptive manufactured sand in the long term.

X-ray Investigations of Sol–Gel-Derived GeO2 Nanoparticles

Germanium dioxide (GeO2) is a versatile material with several different crystalline polymorphs and interesting applications in, e.g., optics, microelectronics, and Li-ion batteries. In particular, many of the material’s properties depend on the size of the prepared crystallites, and thus, nanocrystalline GeO2 is of special interest. Here, GeO2 nanoparticles are prepared via sol–gel processes by the hydrolysis of Ge isopropoxide (Ge(OCH(CH3)2)4). The precipitated powders are dried at room temperature and annealed in ambient air using temperatures between 500 °C and 1000 °C from 3 to 24 h. The samples were characterized by X-ray diffraction, X-ray absorption fine structure spectroscopy, and scanning electron microscopy, providing the crystalline structures, the phase composition, as well as the morphology and crystallite size of the formed particles and their changes upon heating. According to the structural analysis, the samples are crystalline with a dominant β- (low temperature) quartz phase without any heat treatment directly after drying and increasing contributions of α- (high-temperature modification) quartz and quartz-like GeO2 structures with increasing temperature and annealing time were found. According to electron microscopy and the X-ray analysis, the particle size ranges from about 40 to 50 nm for the pristine particles and to about 100 nm and more for the annealed materials.