•HRTEM images revealed that the size of the nanoparticles are 100 nm and smaller.•Nanocrystalline Al2SiO5 particles can be partially amorphized under temperature.•The “triple point” in the DTA ...spectra is observed at 850 K.•At the cooling process the evaluated And – Sil transition stopped in small quantities.
DTA, TGA, and DTG methods were applied at different heating rates to comparative study of thermal parameters of nanocrystalline Al2SiO5particles. Hydroxyl groups on the surface of the nanoparticles and the process of their release under the influence of temperature were explained by the corresponding DSC spectra. Simultaneously, the size and composition of the nanoparticles were measured by HRTEM imaging and EDX analysis. Possible andalusite − sillimanitetransitionofAl2SiO5modifications, andamorphization processes under the influence of temperaturewere investigated by the DTA approach. Around 850 K “triple point” of Al2SiO5modifications was analyzed by the DSC spectroscopy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Substantial knowledge is available on the association of the indoor school environment and its effect among schoolchildren. In the same context, the SINPHONIE (School indoor pollution and health: ...Observatory network in Europe) conducted a study to collect data and determine the distribution of several indoor air pollutants (IAPs), physical and thermal parameters and their association with eye, skin, upper-, lower respiratory and systemic disorder symptoms during the previous three months. Finally, data from 115 schools in 54 European cities from 23 countries were collected and included 5175 schoolchildren using a harmonized and standardized protocol. The association between exposures and the health outcomes were examined using logistic regression models on the environmental stressors assessed in classroom while adjusting for several confounding factors; a VOC (volatile organic compound) score defined as the sum of the number of pollutants to which the children were highly exposed (concentration > median of the distribution) in classroom was also introduced to evaluate the multiexposure – outcome association. Schoolchildren while adjusting for several confounding factors. Schoolchildren exposed to above or equal median concentration of PM2.5, benzene, limonene, ozone and radon were at significantly higher odds of suffering from upper, lower airways, eye and systemic disorders. Increased odds were also observed for any symptom (sick school syndrome) among schoolchildren exposed to concentrations of limonene and ozone above median values. Furthermore, the risks for upper and lower airways and systemic disorders significantly increased with the VOCs score. Results also showed that increased ventilation rate was significantly associated with decreased odds of suffering from eye and skin disorders whereas similar association was observed between temperature and upper airways symptoms. The present study provides evidence that exposure to IAPs in schools is associated with various health problems in children. Further investigations are needed to confirm our findings.
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•Indoor air physical and comfort parameters in 114 schools across 23 European countries were measured.•PM2.5, radon and carbon dioxide concentrations were higher compared to air quality guidelines.•VOCs, particulate matter and physical parameters were positively and negatively associated with different disorders.
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This study investigates the effects of La2O3 on the mechanical, thermal, and physical characteristics and the ability of bismuth germinate glass with different compositions to protect against ...radiation. The glasses included ZnO, Na2O, Bi2O3, GeO2, and different concentrations of La2O3 (between 0 and 20 mol%). The glass density substantially increased from 3428 kg/m³ to 4412 kg/m³ as the concentration of La2O3 increased. This observation underscores the considerable influence of La2O3 on densification, which can be attributed to its higher coordination number and molecular weight. In addition, bridging oxygen atoms reduced the molar volume from 60.2 to 57.8 × 10−6 m3. This decrease suggests the synthesis of oxygen atoms, which increase the glass transition temperature from 536 to 573 K, improving the glass's thermal properties under investigation. As the amount of La2O3 increased, the ultrasonic velocity measurements indicated an increase in longitudinal and shear velocities from 3192 to 3611 m/s and 1884–2185 m/s, respectively. Longitudinal and shear ultrasonic velocity measurements can be utilized to determine the elastic moduli, Poisson's ratio, and Debye temperature. Correlations between these results and theoretical models highlighted the strengthening effect of La2O3 on the glass structure. Another important study area was radiation shielding efficiency, which showed that higher La2O3 content improved photon blocking. The study showed the potential of La2O3-enriched glasses in applications needing radiation protection by looking at the effective atomic number and neutron shielding. Overall, adding La2O3 strengthens the characteristics of bismuth-germinate glasses, increasing their suitability for certain applications in radiation-exposed areas.
•La2O3-doped bismuth-germanate glasses synthesized.•Improved mechanical and shielding properties.•Empirical and theoretical validations were conducted.•Outperforms heavy-weight concrete in shielding.
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Films of polyvinyl alcohol (PVA), Methacrylic Acid - Ethyl Acrylate (MAA:EA) copolymer and their blends PVA:MAA:EA of composition 80:20, 60:40, 50:50, 40:60, 20:80 (wt %) were prepared by using the ...solution cast technique. The prepared films were investigated by structural, optical and thermal studies. X-ray diffraction (XRD) scans revealed the semicrystalline nature of the blends for lower concentrations of PVA up to 60 wt % and the amorphous nature for higher ones. Fourier transform infra-red spectroscopy (FTIR) of blend samples indicates that there is a compatibility between PVA and MAA:EA copolymers through the formation of hydrogen-bonding between their polar groups. SEM image of polymer blend suggested the presence structural reorganization of polymer chains. UV-Visible spectral analysis revealed that the intensity of the shoulder around 271 nm decreases with increasing MAA:EA content. In DSC analysis, a single glass transition temperature for each blend was observed, which supports the existence of compatibility of such systems. From the observed results, 50:50 (wt %) PVA/MAA:EA is found to be the optimum blending ratio.
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•Challenges and mechanisms for engineering the thermal parameters of PCMs were summarized.•Design techniques of novel composite PCMs were systematically analyzed.•Recent advanced ...applications of composite PCMs were highlighted.•Developing multifunctional composite PCMs is demanding for practical applications.
The design of composite phase change materials (PCMs) for thermal energy storage has attracted increasing attention owing to their high latent heat storage capability, enhanced thermal transfer performance, and low volume variation in addition to being seepage free. This review aims to provide techniques for engineering the thermal parameters of composite PCMs (e.g., latent heat, thermal conductivity, durability, and thermal stability) for several advanced large-scale applications and for producing desired thermophysical, chemical, and mechanical properties. In addition, approaches and materials employed for composite synthesis are described. Challenges and factors influencing the thermal energy storage performance of composite PCMs are also analyzed. Furthermore, the recent advanced applications of composite PCMs (including medical, building, electronics, solar, and energy storage and conversion) as well as the potential for producing energy storage and conversion materials are indicated. This report is likely to provide a foundation for designing multifunctional organic composite PCMs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Binary ZnAl alloys are interesting alternatives when tensile strength and hardness performances are required. However, such alloys exhibit limitations on lubrication, ductility at room temperature ...and mechanical strength at high temperatures. It is known that small alloying additions of Cu to ZnAl alloys can modify the microstructure and properties such as creep and wear resistances, hardness, fluidity, and lubrication. In this sense, this work aims to study the effects of Cu additions on the solidification thermal parameters such as cooling and growth rates (ṪL/VL-liquidus isotherm and ṪE/VE-eutectic front), microstructure (dendritic and eutectic arrangements), and hardness of a hypereutectic Zn-8wt.%Al alloy. Techniques such as X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) were used to characterize the as cast samples. The results show that the resulting microstructures consist of a eutectic matrix (Zn) + (Al + Zn) with lamellar and fibrous morphologies and τ’-Al4Cu3Zn intermetallic particles disseminated within the (Zn) phase; pro-eutectic Al-rich (Al') dendrites containing alternating lamellae of Al and Zn phases, which resulted from the eutectoid transformation (Al')↔(Al) + (Zn). The Cu additions have coarsened the fibrous and lamellar eutectic of the binary Zn-8wt%Al alloy, with exception of the Zn-8 wt% Al-1.3 wt% Cu alloy, which showed a refinement of the fibrous eutectic for VE > 0.30 mm/s. Increase in hardness has been observed for both Cu-modified alloys due to the solid-solution strengthening mechanism and presence of the τ’-Al4Cu3Zn intermetallics. An expressive increase of about 73.4% has been observed due to the addition of 1.3% Cu, which is also related to lower eutectic fibrous spacings.
•Eutectic (fibrous and lamellar) and eutectoid structures predominated for the Zn-Al-xCu alloys.•1.3wt%Cu added to the Zn-8wt.%Al alloy induced the refinement of the fibrous eutectic.•A significant increase in hardness has been observed for the Zn-8wt.%Al modified by the addition of 1.3wt%Cu.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A reduced-order equivalent thermal parameters (ETP) model is adopted.•The model is simplified into a linearized form.•Free from uncertainty of the indoor mass temperature.•Free from being influenced ...by inconsistent sampling intervals.
Air conditioners (ACs) are considered to be one of the best candidates in demand response (DR) programs due to their heat/cold storage capacities. The potential of ACs in DR is to a great extent dependent on their thermal parameters. Existing ACs’ parameters estimation methods have difficulties in dealing with varying sampling intervals and unmeasurable mass temperature. To fill this gap, this paper proposes an ACs’ thermal parameters estimation method based on reduced-order equivalent thermal parameters (ETP) model, which is applicable of data with inconsistent sampling intervals and unknown mass temperature. After the model is converted into a linearized form, the parameters can be derived through least square (LS) or recursive least square (RLS) method. Testing results based on real ACs data verify the effectiveness of the proposed method.
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•We investigated the influence of high temperature on macro and micro morphology of CA-UHPC.•We investigated the influence of high temperature, coarse aggregates and steel fibers on thermal ...performance of CA-UHPC.•We proposed a simplified meso predictive model for high-temperature thermal properties of CA-UHPC.
Ultra-high performance concrete (UHPC) exhibits superior mechanical and durability performance with very high compressive strength. Compared with ordinary concrete, it is more environmentally friendly and has the great potential to be a practical solution to improve the sustainability of infrastructure. This study focuses on examining thermal properties of UHPC with coarse aggregates (CA-UHPC) subjected to temperature ranged from 20 °C ∼ 900 °C, including changes in macro and micro morphology before and after high temperatures, thermal conductivity, mass loss, specific heat and thermal expansion. The effects of high temperature, coarse aggregate and steel fiber content on the thermal performance of the material will be evaluated both qualitatively and quantitatively. Experimental results show that high temperature greatly affects thermal properties of CA-UHPC. Coarse aggregates also have a considerable influence on the thermal properties. Steel fibers, however, have little effect on the thermal properties. Based on the test results, meso calculation formulas are proposed to predict the thermal properties, which can be used in the design of structural components made of CA-UHPC.
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We present thermoelectric properties such as the Seebeck coefficient, thermal conductivity, electrical conductivity, figure of merit, and power factor of Tl2(Se, Te)Cl6 vacancy-ordered double ...perovskites obtained with use of the BoltzTraP code. For input files, structural and electronic properties were calculated with the full potential linearized augmented plane wave method within the Wien2k computational code. The mechanical and thermal parameters were computed for calculation of the lattice thermal conductivity. Both compounds were found to have indirect band gaps (2.976 eV for Tl2SeCl6 and 3.037 eV for Tl2TeCl6). The valence bands were observed to be flat, which results in large values of the Seebeck coefficient (S) of 183.50 μV/K for Tl2SeCl6 and 185.49 μV/K for Tl2TeCl6 at room temperature. In addition, positive values of S determined the p-type conductivity in these compounds. The power factor, figure of merit, and electrical conductivity were found to increase with temperature, while the thermal conductivity was found to decrease, hence confirming the semiconductor nature of Tl2(Se, Te)Cl6 compounds as predicted by their electronic properties. The figure of merit of these compounds was found to be higher than that of conventional metal halide perovskites. This makes the compounds investigated potential candidates for thermoelectric applications involving halide perovskites.
•Thermoelectric properties of Tl2(Se, Te)Cl6 were calculated with use of classical Boltzmann transport theory.•Tl2(Se, Te)Cl6 perovskites were found to be semiconductors.•The valence bands were observed to be flat, which results in high values of the Seebeck coefficient.•The electrical conductivity, power factor, and figure of merit were found to increase with temperature.•The figure of merit of these compounds was found to be higher than that of conventional metal halide perovskites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Thermal parameters of construction assemblies, e.g., the U-values of roofs, walls, floors, ground floors, windows and the solar heat gain coefficient (SHGC) of windows, are significant inputs for ...urban building energy models (UBEMs). However, estimating these values at the urban scale is difficult. A common practice to handle this issue is the use of archetypes. Additionally, there are three approaches in building-level studies, namely, 1) estimation based on technical documents, 2) in-situ measurements, and 3) prediction by machine learning. However, the lack of documentation or long-term testing of physical parameters restricts their applications at the urban scale. This paper presents a non-archetype approach that employs two learning algorithms, i.e., k-means and random forest classification (RFC), to predict thermal parameters of construction assemblies, with several urban & building (UB) factors selected as the inputs. The steps involve: 1) partitioning the thermal parameters in the dataset into k clusters using k-means, 2) assigning a Cluster_ID to the thermal parameters in cluster j and recording its centroid μj, 3) training the RFC, with UB factors as inputs and the Cluster_ID as outputs, 4) predicting the Cluster_ID of thermal parameters of investigated buildings via the trained model, 5) using corresponding centroids as their final thermal parameters, based on the predicted Cluster_ID. As a pilot study, the developed approach has an acceptable result, with the R2 greater than 0.6 and even 0.8. In addition, the study also introduces approaches for acquiring UB factors at the urban scale and demonstrates a case study in Nanjing.
•The relationship between thermal parameters and urban & building factors is analyzed.•Machine learning is employed to objectively reflect the relationship.•The algorithms and methods for acquiring urban & building factors are introduced.•The approach is in a non-archetype way that can predict the values for each building.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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