Search Results (1,706)

For the first time, the kinetics of isothermal curing and thermal degradation of polyethylene glycol maleate (pEGM)–based systems and their composites with mineral fillers were investigated in the presence of a benzoyl peroxide/N,N-Dimethylaniline redox-initiating system. DSC analysis revealed that the curing process at 20 °C can be described by the modified Kamal autocatalytic model; the critical degree of conversion (α_c) decreases with increasing content of the unsaturated polyester pEGM and in the presence of fillers. In particular, for unfilled systems, α_c was 0.77 for pEGM45 and 0.60 for pEGM60. TGA results demonstrated that higher pEGM content and the incorporation of fillers lead to increased thermal stability and residual mass, along with a reduction in the maximum decomposition rate (dTGₘₐₓ). Calculations using the Kissinger–Akahira–Sunose and Friedman methods also confirmed an increase in the activation energy of thermal degradation (E_a): E_KAS was 419 kJ/mol for pEGM45 and 470 kJ/mol for pEGM60, with the highest values observed for pEGM60 systems with fillers (496 kJ/mol for SiO₂ and 514 kJ/mol for CaCO₃). Rheological studies employing three-interval thixotropy tests revealed the onset of thixotropic behavior upon filler addition and an increase in structure recovery after deformation of up to 56%. These findings underscore the potential of pEGM-based systems for low-temperature curing and for the design of composite materials with improved thermal resistance. Full article

According to the production process requirements of oriented silicon steel in a certain steel mill, optimization of the slag composition ratio is studied through thermodynamic calculations. The CaO-SiO₂-Al₂O₃-FeO-MgO slag system is studied using FactSage thermodynamic software (FactSage 8.1), and a slag optimization plan is proposed based on industrial experiments involving changes in the composition ratio of the slag, calculation and analysis of the melting characteristics of RH refining slag, further verification through orthogonal experiments, and observations of the slag state, temperature, and composition relationship through phase diagrams. This study provides theoretical guidance for finding a suitable slag composition ratio based on the influence of slag on dissolved aluminum in steel liquid. Research has shown that, combined with thermodynamic analysis, slag melting characteristics, component content calculations, and industrial experiments, the range of RH refining slag composition suitable for production in this steel mill is slag in the range of 1.3~1.5 alkalinity, 25~30% Al₂O₃, 5~6% MgO, and 1–2% FeO. Full article

The potential for creating composite cements by incorporating fly ash is demonstrated. Analysis revealed that the fly ash examined consists of 69.66 wt. % silicon oxide, 21.34 wt. % aluminum oxide, 1.57 wt. % calcium oxide and 2.78 wt. % iron oxide. Fly ash mainly consists of quartz (SiO₂), goethite (FeO(OH)) and mullite (3Al₂O₃·2SiO₂). The properties of the cement composition containing 5 to 25 wt. % fly ash were studied. Incorporating fly ash enhances system dispersion, promotes mixture uniformity, and stimulates the pozzolanic reaction. Compositions of composite cements consisting of 90% CEM I 42.5 and 10% fly ash were developed. The cement stone based on the obtained composite cement had a compacted structure with a density of 2.160 g/cm³, which is 9.4% higher than the control sample. It is shown that when composite cement containing 10% fly ash interacts with water, hydration reactions of cement minerals (C₃S, C₂S, C₃A and C₄AF) begin first. This is accompanied by the formation of hydrate neoplasms, such as calcium hydroxide (Ca(OH)₂) and calcium hydrosilicates (C-S-H). Fly ash particles containing amorphous silica progressively participate in a pozzolanic reaction with Ca(OH)₂, leading to the formation of additional calcium hydrosilicates phases. This process enhances structural densification and reduces the porosity of the cement matrix. After 28 days of curing, the compressive strength of the resulting composite cements ranged from 42.1 to 54.2 MPa, aligning with the strength classes 32.5 and 42.5 as specified by GOST 31108-2020. Full article

The Weimei Formation, the most complete Upper Jurassic sedimentary sequence in the Tethyan Himalaya, is crucial for understanding the tectono-sedimentary evolution of the northern Indian margin. However, its depositional environment remains debated, with conflicting shallow- and deep-water interpretations. This study integrates sedimentary facies, petrography, zircon geochronology, and geochemical analyses to constrain the provenance, depositional environment, and tectonic setting of the Weimei Formation. The results reveal that the sedimentary system primarily consists of shoreface, delta, and shelf facies, with locally developed slope-incised valleys. Detrital zircon ages are concentrated at ~468 Ma and ~964 Ma, indicating a provenance mainly derived from the Indian continent. Geochemical characteristics, such as high SiO₂, low Na₂O–CaO–TiO₂ contents, right-leaning REE patterns, and significant negative Eu anomalies, suggest the derivation of sediments from felsic upper crustal recycling within a passive continental margin. Stratigraphic comparison between southern and northern Tethyan Himalayan sub-zones reveals a paleogeographic “uplift–depression” pattern, characterized by the coexistence of shoreface–shelf deposits and slope-incised valleys. This study provides key evidence for reconstructing the Late Jurassic paleogeography of the northern Indian margin and the tectonic evolution of the Neo-Tethys Ocean. Full article

This study investigates the mechanism behind the heat-induced color change (brown to yellowish green) in Mn- and Fe-rich elbaite tourmaline under reducing atmosphere at 500 °C. A combination of analytical techniques including gemological characterization, electron microprobe analysis (EMPA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and ultraviolet–visible (UV-Vis) spectroscopy was employed. Chemical analysis confirmed the samples as intermediate members of the elbaite–fluorelbaite series, with an average formula of ^X(Na₀.₆₆ □₀.₂₆ Ca₀.₀₈) _Σ1.₀₀^Y(Li₁.₂₉Al₁.₁₀Mn₀.₃₁ Fe²⁺₀.₁₅Ti₀.₀₁Zn₀.₀₁) _Σ2.₈₇ ^ZAl₆^T[Si₆O₁₈] (BO₃)₃^V(OH)₃.₀₀^W(OH₀.₅₁F₀.₄₉) _Σ1.₀₀, enriched in Mn (17,346–20,669 μg/g) and Fe (8396–10,750 μg/g). Heat treatment enhanced transparency and induced strong pleochroism (yellowish green parallel c-axis, brown perpendicular c-axis). UV-Vis spectroscopy identified the brown color origin in the parallel c-axis direction: absorption bands at 730 nm (Fe²⁺ d–d transition, ⁵T_2g → ⁵E_g), 540 nm (Fe²⁺→Fe³⁺ intervalence charge transfer, IVCT), and 415 nm (Fe²⁺→Ti⁴⁺ IVCT + possible Mn²⁺ contribution). Post-treatment, the 540 nm band vanished, creating a green transmission window and causing the color shift parallel the c-axis. The spectra perpendicular to the c-axis remained largely unchanged. The disappearance of the 540 nm band, attributed to the reduction of Fe³⁺ to Fe²⁺ eliminating the Fe²⁺–Fe³⁺ pair interaction required for IVCT, is the primary color change mechanism. The parallel c-axis section of the samples shows brown and yellow-green dichroism after heat treatment. A decrease in the IR intensity at 4170 cm⁻¹ indicates a reduced Fe³⁺ concentration. The weakening or disappearance of the 4721 cm⁻¹ absorption band of the infrared spectrum and the near-infrared 976 nm absorption band of the ultraviolet–visible spectrum provides diagnostic indicators for identifying heat treatment in similar brown elbaite–fluorelbaite. Full article

Myanmar blue jadeite jade is a rare and highly prized gemstone, yet its coloration and formative mechanisms remain poorly understood. In this study, petrographic analysis, ultraviolet–visible (UV–Vis) spectroscopy, electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed on a sample of Myanmar blue jadeite with small white blocks to investigate its mineral composition, trace element distribution, and coloration mechanisms. Most of the sample was found to be blue, with surrounding white areas occurring in small ball-shaped blocks. The main mineral component in both the blue and white domains was jadeite. Although both areas underwent recrystallization, their textures differed significantly. The blue areas retained primary structural features within a medium- to fine-grained texture, reflecting relatively weaker recrystallization. The white areas, however, were recrystallized into a micro-grained texture, reflecting relatively stronger recrystallization, with the superimposed effects of external stress producing a fragmented appearance. The blue jadeite had relatively higher contents of Ti, Fe, Ca, and Mg, while the white jadeite contained compositions close to those of near-end-member jadeite. It was noted that, while white jadeite may have a high Ti content, its Fe content is low. UV–Vis spectra showed a broad absorption band at 610 nm associated with Fe²⁺-Ti⁴⁺ charge transfer and a gradually increasing absorption band starting at 480 nm related to V⁴⁺. Combining the chemical composition and the characteristics of the UV–Vis spectra, we infer that the blue coloration of jadeite is attributed to Fe²⁺-Ti⁴⁺ charge transfer; i.e., the presence of both Ti and Fe in blue jadeite plays a key role in its color formation. V⁴⁺ exhibited no significant linear correlation with the development of blue coloration. Prominent oscillatory zoning was observed in the jadeite, transitioning from NaAlSi₂O₆-dominant cores to Ca-Mg-Fe-Ti-enriched rims, reflecting the trend of fluid evolution during blue jadeite crystallization. Petrographic analysis indicated that the formation of the Myanmar blue jadeite occurred in two or three stages, with the blue regions forming earlier than the white regions. The blue jadeite also underwent significant recrystallization. Our findings contribute to the understanding of the formation of blue jadeite and the diversity of colors in jadeite jade. Full article

To reduce the proliferation of greenhouse gases in the construction industry, ternary blended concrete comprising fly ash (FA) powder, waste glass (WG) powder, and ordinary Portland cement (OPC) was developed such that the WG to total binder varied from 0 to 20% at intervals of 5% (C₈₀FA_20-xWG_x:x = WG/(WG + FA + OPC)). The developed concrete was investigated for water absorption, workability, 28-day compressive strength, binder phases, bond characteristics, microstructure, and elemental composition of the concrete. The mixture proportions of C₈₀FA₁₅WG₅ and C₈₀FA₁₀WG₁₀ exhibited better consistency and water absorption than the OPC concrete (C₁₀₀FA₀WG₀). Furthermore, the 28 d strength of C₈₀FA₁₅WG₅ marginally outperformed those of C₈₀FA₁₀WG₁₀ and C₈₀FA₂₀WG₀. The sample with equal proportions of FA and WG (C₈₀FA₁₀G₁₀) was more amorphous owing to the disappearance of the hedenbergite phase (CaFeSi₂O₆) and conversion of tobermorite (CSH) to C-A-S-H. C₈₀FA₁₀WG₁₀ also exhibited better microstructural stability than FA + OPC concrete (C₈₀FA₂₀G₀), owing to the pore-filling of the microcracks within the matrix. Finally, higher Si/Ca, Ca/Al, and Si/Al ratios were recorded in C₈₀FA₁₀WG₁₀ than in the case of FA preponderating WG in ternary blending. Finally, structural concrete can be produced through the ternary blending of glass waste, fly ash, and OPC, thereby promoting the valorization of solid waste and a sustainable environment. Full article

Kimberlite has attracted considerable interest among geologists as the primary source of natural gem-quality diamonds. The term “transitional kimberlite” was previously introduced to categorize rocks that exhibit bulk geochemical and Sr–Nd isotopic characteristics intermediate between those of archetypal kimberlite (formerly Group-I) and orangeite (formerly Group-II). Nevertheless, the petrogenesis of transitional diamond-bearing kimberlites remains poorly understood due to limited research. The diamondiferous transitional Wafangdian kimberlite in the North China Craton (NCC) thus provides a valuable opportunity for a detailed case study. We investigated fresh hypabyssal transitional Wafangdian kimberlites using bulk-rock major and trace element geochemistry to constrain near-primary parental magma compositions and decipher their petrogenesis. Geochemical compositions identify samples affected by crustal contamination based on elevated SiO₂, Pb, heavy rare earth element (HREE) concentrations, and Sr isotopic ratios. Compositional variations among macrocrystic samples (MgO: 29.7–31.5 wt.%; SiO₂: 30.6–34.7 wt.%; CaO: 3.9–7.5 wt.%; Mg^# [atomic Mg/(Mg + Fe²⁺) × 100]: 85–88) result from substantial entrainment and partial assimilation of peridotite xenoliths (up to 35%). In contrast, variations within aphanitic samples (MgO: 24.0–29.7 wt.%; SiO₂: 27.7–30.9 wt.%; CaO: 6.0–11.8 wt.%; Mg^#: 81–85) are attributed to fractional crystallization of olivine and phlogopite (~1–32%). Based on these constraints, the near-primary parental magma composition for the Wafangdian kimberlite is estimated as ~29.7 wt.% SiO₂, ~29.7 wt.% MgO, and Mg^# 85. Trace element concentrations in the transitional Wafangdian kimberlites resemble those of archetypal kimberlites globally (e.g., Nb/U > 26, La/Nb < 1.4, Ba/Nb < 16, Th/Nb < 0.25), indicating a shared convective mantle source. However, the Wafangdian kimberlites exhibit distinct characteristics: ε_Nd(t) values ranging from −3.44 to −1.77, higher Al₂O₃ and K₂O contents, and lower Ce/Pb ratios (10–20) compared to archetypal kimberlites. These features suggest the mantle source region was profoundly influenced by deeply subducted oceanic material. Full article

In this work, γ-irradiated poly(tetrafluoroethylene) (i-PTFE) and short carbon fibre (SCF) along with different types of ceramic inorganic nanoparticles (i.e., SiC, SiO₂, ZnO, TiO₂, and CaCO₃) were employed to improve the mechanical and tribological performance of polyphenylene sulphide (PPS) composites. The results showed that the flexural strength and modulus of PPS composites increased with the addition of inorganic nanoparticles. Moreover, the inorganic nanoparticles not only exhibited a ‘micro-bearing’ effect during friction tests, but also promoted the formation of high-quality transfer film on the surface of a friction pair, significantly improving the self-lubricating performance of PPS composites. XPS analysis confirmed the occurrence of friction-induced chemical reactions during the friction process in nanoparticle-containing PPS/i-PTFE/SCF composites, which was helpful in improving the tribological performance. PPS/i-PTFE/SCF/SiC composite demonstrated an average friction coefficient of 0.083 and specific wear rate of 9.04 × 10⁻⁶ mm³/Nm, which was the best among the studied systems. This work provided valuable insights for developing high-performance self-lubricating polymer composites that can be applied in high-end engineering sectors. Full article

The thermodynamic equilibrium of the CaO-TiO₂-SiO₂ system plays a crucial role in the design of ceramic materials. CaO-TiO₂-SiO₂ ternary systems were thermodynamically evaluated and optimized using the CALculation of PHAse Diagram (CALPHAD) method. The liquid phase was modeled with the ionic two-sublattice model, represented as (Ca⁺²,Ti⁺²,Ti⁺³)_P(O⁻²,Va,O,TiO₂,SiO₂,SiO₄⁻⁴)_Q, and the ternary compound was described using the compound energy formalism (CEF) model. A set of self-consistent thermodynamic parameters was obtained for the CaO-TiO₂-SiO₂ system. The complete parameters are listed, which reliably could describe the phase equilibria and thermodynamic properties of the ternary system. This thermodynamic description provides a valuable foundation for developing larger thermodynamic databases for multicomponent silicate systems. Full article

This study investigates the combustion characteristics and ash behavior of coal–biomass co-combustion using Zhujixi coal and corn straw in a fixed-bed system. The research analyzes combustion stage division, gas release patterns, and mineral evolution of ash under varying blending ratios. Results indicate that biomass addition modifies the dynamic features of the combustion process by advancing the CO₂ release peak; extending the release of CO, CH₄, and H₂; and enhancing the completeness of char oxidation. At moderate blending levels (20–60%), oxygen utilization is significantly improved and combustion stability is strengthened. Ash fusion temperatures exhibit a consistent decline with increasing biomass proportion due to the formation of low-melting eutectic phases such as KAlSiO₄ and K, Ca-based phosphates. Mineralogical analysis further reveals that coal ash components promote the immobilization of alkali metals, thereby suppressing potassium volatilization. A blending ratio of 40% demonstrates the most favorable balance between burnout performance, oxygen efficiency, and alkali fixation, surpassing both pure coal and high-ratio biomass conditions. This optimized ratio not only improves energy conversion efficiency but also reduces slagging and corrosion risks, offering practical guidance for cleaner coal power transformation, stable boiler operation, and long-term reduction of carbon and pollutant emissions. Full article

Foamed concrete has been widely applied in construction engineering; however, the performance requirements vary across different structural components. Its production typically involves a substantial consumption of cement, which imposes both environmental and economic burdens. Therefore, this study examined foamed concrete with dry apparent densities of 500–1000 kg/m³, in which cement was partially replaced (0–30%) by recycled powder from construction and demolition waste. Macroscopic performance was evaluated through drying shrinkage, compressive strength, softening coefficient, carbonation coefficient, and thermal conductivity, while microstructural analysis was conducted to clarify the underlying mechanisms. The results indicate that the internal composition of the recycled powder primarily consists of SiO₂, CaCO₃, and C-S-H gel. When recycled powder is used to replace cement, the microstructure of the resulting paste gradually deteriorates compared to that of the control group without recycled powder, and a significant amount of inert SiO₂ is introduced. As the replacement ratio of recycled powder increases, the compressive strength of foamed concrete across various density grades exhibits a gradual decline. Notably, when the replacement ratio reaches 30%, the reduction in mechanical performance becomes more substantial. However, the incorporation of recycled powder can effectively mitigate the drying shrinkage of foamed concrete. Moreover, the incorporation of recycled powder exerts minimal influence on the thermal conductivity and porosity of foamed concrete, demonstrating its favorable compatibility and potential for application in foamed concrete systems. Full article

Background and Objectives: Chairside bleaching can alter enamel morphology and mineral content. This in vitro study compared surface changes and elemental shifts after three in-office protocols using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Materials and Methods: Forty-two human premolars/molars were sectioned; matched halves served as control or received Opalescence Quick 45% carbamide peroxide (CP), Opalescence Boost 40% hydrogen peroxide (HP), or BlancOne Ultra+ 35% HP with light activation. Gels were applied per manufacturers’ instructions. SEM assessed topography (×500–×1100); EDS quantified atomic percent of O, Ca, P, C and trace elements. One-way ANOVA compared Ca and P between bleached groups (α = 0.05). Results: Controls showed compact surfaces with preserved Ca and P. After Quick, SEM revealed roughness, fissures and microcracks; Ca fell from 11.5 to 12.5 to 9.53–11.73 at% and P from 7.5 to 8.9 to 7.41–8.59 at%. Boost produced mild superficial restructuring and granular deposits with variable Ca 13.80–27.94 at% and P 7.32–14.65 at%. BlancOne Ultra+ caused diffuse erosion and loss of prismatic clarity with marked demineralization (Ca 1.42–7.85 at%, P 1.22–6.71 at%); C rose locally to 46.61 at%. Across bleached groups, Ca and P differed significantly (both p < 0.001). Oxygen remained dominant (~39–50 at%) in all spectra; occasional Al/Si/Cl/K likely reflected residues or preparation artifacts. Conclusions: All protocols produced surface and compositional alterations, with a severity gradient: BlancOne Ultra+ > Boost > Quick. High-concentration, light-activated HP yielded the largest Ca/P losses. Clinically, neutral-pH, non-activated or chemically activated regimens and immediate post-bleach remineralization should ideally be used when feasible, particularly before adhesive procedures. Full article

In this study, gangue-based solid waste was utilized as the primary raw material to prepare filling materials using a composite alkali activator comprising calcium oxide (CaO) and sodium metasilicate (Na₂SiO₃). By varying the proportions and total content of the alkali activators, with the total content fixed at 12 wt% of coal gangue, the resulting filling materials were systematically investigated. The mineralogical composition, morphology, and hydration degree of the materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). In addition, the compressive strength of the materials was measured. The results demonstrated that both the type and dosage of alkali activators significantly influenced the mineral phases and surface morphology of the filling materials. CaO and Na₂SiO₃ exhibited distinct effects on the degree of hydration, and the curing age was also found to be a critical influencing factor. For single-component activators, the compressive strength of the filling materials initially increased and then decreased with increasing activator content, with optimal values observed at CaO contents between 6% and 9% and Na₂SiO₃ content around 2%. In the case of the composite CaO–Na₂SiO₃ system, the uniaxial compressive strength exhibited a similar trend, increasing first and then decreasing with the CaO-to-Na₂SiO₃ ratio, with the optimal ratio determined to be 3:1. Furthermore, a positive correlation between curing age and compressive strength was observed. This study elucidates the synergistic mechanism of CaO and Na₂SiO₃, identifies optimal mix proportions, and quantifies empirical relationships between raw material properties, reaction conditions (activator ratio/content, curing age), and compressive strength. These relationships serve as core data for subsequent construction of a “raw material–reaction condition–strength” correlation model, providing support for formulation optimization of gangue-based filling materials. Full article

A fine-grained nepheline sample from Egan Chutes, Ontario, with the chemical composition (K_1.32▯_0.68)(Na_6.05Ca_0.22)[Al_7.77Si_8.21O₃₂], where ▯ represents vacancies, was studied through in situ synchrotron powder X-ray diffraction (XRD) data and Rietveld structure refinement from 26 to 900 °C on heating and cooling. The average structure was refined in the space group P6₃. The satellite reflections in nepheline give rise to order–disorder transitions. The average <Al,Si-O>{4} distances in nepheline indicate a partially ordered Al-Si distribution, especially in the Al2 and Si2 sites at room T before heating. The nepheline structure shows that except for the positional disorder of the O1 oxygen atom, the other atoms are well defined and contain no unusual features. Vacancies, ▯, occur at the K site. Different satellite (s) reflections arise from (1) positional order of the O1 atoms to 299 °C (s1 disappears), (2) K-▯ order to 486 °C (s2 and s3 disappear), and (3) some Al-Si order 900 °C, where some satellite reflections are present. Complete Al-Si order is obtained at room T on cooling. Full article