A strategy for designing microencapsulated composite phase change thermal storage materials with tunable melting temperature

Abstract(#br)Thermal energy storage technology with high temperature phase change materials (PCMs) plays an increasingly important role in the concentrated solar power plants and industrial waste heat recovery systems. In this study, a novel displacement reaction between tetraethoxysilane as SiO 2 source and molten raw Al powder was purposed to successfully prepare Al-Si/Al 2 O 3 high temperature composite PCMs. Interestingly, by proposed synthetic methodology, we not only achieved the in-situ synthesis of Al-Si alloy PCM and Al 2 O 3 shell, but also realized the controllability of Al-Si alloy composition and Al 2 O 3 shell layer thickness. Our results indicated that the melting temperature of the prepared composite PCMs depended on the composition of Al-Si alloy, and could be designed within a certain temperature range (from 574.0 °C to 641.4 °C), instead of a particular temperature point. The melting temperature adjustability of the prepared composite PCMs provided an additional flexibility in different working temperature conditions. Moreover, the prepared composite PCMs exhibited a relatively high thermal storage capacity (248.6 J/g to 331.0 J/g), good thermal stability, excellent repeatable utilization property and certain shell layer self-repairing ability in the working temperature range. Therefore, the prepared composite PCMs can prove to be promising thermal energy storage materials for improving the energy efficiency in various systems under different working temperature conditions

Thermal cycle stability of Co 64 V 15 Si 17 Al 4 high-temperature shape memory alloy

Abstract(#br)The microstructure, martensitic transformation and thermal cycle stability of Co 64 V 15 Si 17 Al 4 high-temperature shape memory alloy were studied. The results show that the martensite transformation of L2 1 /D0 22 occurred in the Co 64 V 15 Si 17 Al 4 alloy. In the Co 64 V 15 Si 17 Al 4 alloy, the transformation temperatures of forward transformation and reverse transformation are pretty high, reaching 589.6 °C and 649.1 °C, respectively. The temperatures of the martensitic transformation and the transformation heat show a neglectable difference after 200 thermal cycles in the alloy. This alloy exhibits good thermal stability during 200 thermal cycles between room temperature and 850 °C, in which the microstructure and martensitic transformation behavior have no obvious change

Novel core/void/shell composite phase change materials for high temperature thermal energy storage

Abstract(#br)Metallic solid-liquid phase change materials (SLPCMs) are crucial for the thermal energy storage technology of various industrial systems. However, the encapsulation of metallic SLPCMs is still technically difficult. In this pursuit, the present research envisaged the development of a novel technology to successfully prepare the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs by using Al/Bi immiscible alloy powders as starting material and tetraethoxysilane as SiO 2 source. The Al-Si alloy and Al 2 O 3 shell were in-situ synthesized by the displacement reaction between SiO 2 and molten Al. Interestingly, most of the Bi distributed in the shell of Al/Bi immiscible alloy powders could not only improve the activity of alloy powders and promote the formation of precursor shell, but also be recycled by evaporation to form the void layer during the calcination process of composite SLPCMs. The produced void layer provided a space buffer to alleviate the volume expansion of the core SLPCM, and thereby improving the thermal cycling stability of the prepared composite SLPCMs. The thermal cycling test results showed that after 300 thermal cycles, the melting latent heat reduction of the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs (24.3-31.7J/g) was much less than that of the core(=Al-Si)/shell(=Al 2 O 3 ) composite SLPCM (58.1J/g). Moreover, the prepared Al-Si/Bi/Al 2 O 3 exhibited an adjustable melting temperature (571.9℃ to 631.9℃) and average particle diameter (39.3μm to 112.6μm), relatively high thermal conductivity [2.068W(mK) -1 to 2.966W(mK) -1 ], and excellent thermal energy storage capacity (209.5J/g to 278.2J/g). Thus, the prepared Al-Si/Bi/Al 2 O 3 composite SLPCMs are potential thermal energy storage materials, which can be used to improve the energy efficiency of various industrial systems

Effect of Re on microstructure and mechanical properties of γ/γʹ Co-Ti-based superalloys

Abstract(#br)Three compositions of Re containing Co-Ti-based alloys with γ/γ′ two-phase microstructure were obtained based on the determined phase relationship in the Co-rich corner at 800 °C. The effect of Re on microstructure, elemental partition behavior, thermodynamic properties, lattice parameter misfits, mechanical properties and γ′ coarsening behavior of the Co-Ti-Re alloys were investigated. The γ/γ′ lattice parameter misfit of the alloys decreases from 0.72% to 0.50%, and the γ′ coarsening rate constant K of alloys decreases from 0.30 × 10 −27 m 3 s −1 to 0.073 × 10 −27 m 3 s −1 as Re content increasing form 1 at. % to 5 at. %. Additionally, the volume fraction of γ′ phase (V γ′ ) increases from 42.15% to 53.19% and the γ′ solvus temperature increases from 1059 °C to 1085 °C ( T solvus-γ′ ) with increasing Re content. Moreover, the 0.2% flow stresses and the 0.2% specific flow stresses of all three alloys exhibit negative temperature dependence at the temperatures ranging from room temperature to 900 °C. And both the 0.2% flow stresses and the 0.2% specific flow stresses increase with the Re content

Design and Fabrication of High Activity Retention Al-Based Composite Powders for Mild Hydrogen Generation.

Al-Bi-Sn-Cu composite powders for hydrogen generation were designed from the calculated phase diagram and prepared by the gas atomization process. The morphologies and structures of the composite powders were investigated using X-ray diffraction (XRD) and a scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) spectroscopy, and the results indicate that the Cu additive enhanced the phase separation between the Al-rich phase and the (Bi, Sn)-rich phase. The hydrogen generation performances were investigated by reacting the materials with distilled water. The Al-Bi-Sn-Cu powders reveal a stable hydrogen generation rate, and the Al-10Bi-7Sn-3Cu (wt%) powder exhibits the best hydrogen generation performance in 50 °C distilled water which reaches 856 mL/g in 800 min. In addition, the antioxidation properties of the powders were also studied. The Al-10Bi-7Sn-3Cu (wt%) powder has a good resistance to oxidation and moisture, which shows great potential for being the hydrogen source for fuel cell applications

Experimental Investigation of Diagram Equilibria in the Co-Nb-Re Ternary System

Abstract(#br)In this study, the isothermal sections of the Co-Nb-Re ternary system at 1200, and 1300 °C have been experimentally determined combining the means of electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The obtained experimental results showed that: (1) The Laves phase of λ3-Co2Nb (C36) was stable at 1300 °C. The temperature was beyond its stability limit in Co-Nb binary system. (2) The solubility of Re in the λ3 phase was so large that the nearest λ2-Co2Nb (C15) phase was essentially surrounded. (3) The solubility of Re in the μ-Co7Nb6 phase was 34.0 at.% at 1200 °C and 35.2 at.% at 1300 °C, respectively. (4) The liquid phase existed at 1300 °C dissolving about 4.0 at.% Re, but it was..

Unraveling the Regulatory Mechanism of Color Diversity in Camellia japonica Petals by Integrative Transcriptome and Metabolome Analysis

Camellia japonica petals are colorful, rich in anthocyanins, and possess important ornamental, edible, and medicinal value. However, the regulatory mechanism of anthocyanin accumulation in C. japonica is still unclear. In this study, an integrative analysis of the metabolome and transcriptome was conducted in five C. japonica cultivars with different petal colors. Overall, a total of 187 flavonoids were identified (including 25 anthocyanins), and 11 anthocyanins were markedly differentially accumulated among these petals, contributing to the different petal colors in C. japonica. Moreover, cyanidin-3-O-(6″-O-malonyl) glucoside was confirmed as the main contributor to the red petal phenotype, while cyanidin-3-O-rutinoside, peonidin-3-O-glucoside, cyanidin-3-O-glucoside, and pelargonidin-3-O-glucoside were responsible for the deep coloration of the C. japonica petals. Furthermore, a total of 12,531 differentially expressed genes (DEGs) and overlapping DEGs (634 DEGs) were identified by RNA sequencing, and the correlation between the expression level of the DEGs and the anthocyanin content was explored. The candidate genes regulating anthocyanin accumulation in the C. japonica petals were identified and included 37 structural genes (especially CjANS and Cj4CL), 18 keys differentially expressed transcription factors (such as GATA, MYB, bHLH, WRKY, and NAC), and 16 other regulators (mainly including transporter proteins, zinc-finger proteins, and others). Our results provide new insights for elucidating the function of anthocyanins in C. japonica petal color expression

Effect of Trace Boron on Microstructure and Mechanical Properties of Ti-9V-3Al-3Cr-3Zr-35Mo Alloy

Conference Name:2nd International Conference on Manufacturing Science and Engineering. Conference Address: Guilin, PEOPLES R CHINA. Time:APR 09-11, 2011.The effects of trace boron on microstructure and mechanical properties of beta type Ti-9V-3Al-3Cr-3Zr-3.5Mo (wt. %) alloy have been investigated in this study. Upon the addition of 0.02 wt. % boron, the grain size of the B-modified alloy was almost four times smaller than that of the B-free alloy. Accordingly, the tensile strength and elongation of B-modified alloy increased from 712 MPa and 14.6 % to 813 MPa and 17.9 %, respectively, mainly due to the effect of grain refinement

Associations of polysocial risk score with incident rosacea: a prospective cohort study of government employees in China

BackgroundThe associations between single risk factors and incident rosacea have been reported, but the effects of social risk factors from multiple domains coupled remain less studied.ObjectivesTo quantify the influence of social determinants on rosacea comprehensively and investigate associations between the polysocial risk score (PsRS) with the risks of incident rosacea.MethodsThis was a prospective cohort study of government employees undertaken from January 2018 to December 2021 among participants aged >20 from five cities in Hunan province of China. At baseline, information was collected by a questionnaire and participants were involved in an examination of the skin. Dermatologists with certification confirmed the diagnosis of rosacea. The skin health status of participants was reassessed every year since the enrolment of study during the follow-up period. The PsRS was determined using the nine social determinants of health from three social risk domains (namely socioeconomic status, psychosocial factors, and living environment). Incident rosacea was estimated using binary logistic regression models adjusted for possible confounding variables.ResultsAmong the 3,773 participants who completed at least two consecutive skin examinations, there were 2,993 participants included in the primary analyses. With 7,457 person-years of total follow-up, we detected 69 incident rosacea cases. After adjustment for major confounders, participants in the group with high social risk had significantly raised risks of incident rosacea with the adjusted odds ratio (aOR) being 2.42 (95% CI 1.06, 5.55), compared to those in low social risk group.ConclusionOur findings suggest that a higher PsRS was associated with an elevated risk of incident rosacea in our study population

Martensite stabilization and thermal cycling stability of two-phase NiMnGa-based high-temperature shape memory alloys

The martensite stabilization and thermal cycling stability of four types of two-phase NiMnGa-based high-temperature shape memory alloy, including Ni56+xMn25Ga19−x (x = 0, 1, 2, 3, 4), Ni56Mn25−yFeyGa19 (y = 4, 8, 9, 12, 16), Ni56Mn25−zCozGa19 (z = 4, 6, 8) and Ni56Mn25−wCuwGa19 (w = 2, 4, 8) alloys, were investigated. It is found that the martensite stabilization is closely related to the strength of the alloy and the volume fraction of γ phase; and increases as the alloy strength decreases. It is also found that in Ni56Mn25−yFeyGa19 alloys, with increasing Fe content to 12 and 16 at.%, the volume fraction of γ phase increases and the martensite stabilization decreases. The thermal cycling stability differs among different alloy systems and is related to the microstructural changes during thermal cycling and to the strength of the γ phase. Poor thermal cycling stability is observed in Ni56+xMn25Ga19−x (x > 0), Ni56Mn25−zCozGa19 and Ni56Mn25−wCuwGa19 alloys due to the formation of the ordered γ′ phase and the high strength of the γ phase. Results further show that Fe addition to Ni56Mn25Ga19 alloy can broaden the (bcc + γ) two-phase region and shift it to the Ni–Ga and Ni–Mn sides, hence stabilizing the two-phase region to lower temperatures. These effects can retard the formation of the ordered γ′ phase in the Ni56Mn25−yFeyGa19 system during thermal cycling, thus leading to good thermal cycling stability