Journal of Thermal Analysis and Calorimetry

Narattha, Chalermphan; Chaipanich, Arnon

doi: 10.1007/s10973-020-09730-8pmid: N/A

Artificial aggregates, such as fly ash lightweight aggregates, can be used as eco-friendly alternatives to natural aggregates. This work aims to investigate the effect of curing time on the hydration and material properties (voids, shrinkage, crushing strength and pH) of cold-bonded high-calcium fly ash–Portland cement lightweight aggregate. Fly ash was used as a lightweight material (at 90% by mass), and Portland cement was used at 10% by mass. A 100% FA lightweight aggregate was also prepared for comparison. Thermogravimetry (TG) and derivative thermogravimetry (DTG) were performed at three different curing times (0, 3 and 28 days). Shrinkage test specimens were kept in sealed bags and exposed to air curing conditions and were measured at 3, 7, 14, 21 and 28 days. Calcium silicate hydrate, calcium hydroxide and calcium carbonate were observed in both mixes (100FA and 90FA10PC). The TG showed that the calcium silicate hydrate phase increased when 10% Portland cement was used compared to that of the 100FA mix. Furthermore, with increasing curing time, the calcium silicate hydrate phase increased while the calcium hydroxide phase decreased due to pozzolanic and hydration reactions. The shrinkage of fly ash lightweight aggregate with 10% Portland cement had a lower value than that of the 100FA mix for different curing conditions due to the effect of pore refinement.

Wang, Q.; Chen, H. M.; Li, M. X.; Geng, D. L.; Wang, H. P.

doi: 10.1007/s10973-020-09839-wpmid: N/A

The knowledge of specific heat for Ag–Si–Ge alloys in a broad temperature range would facilitate their practical applications in various branches of engineering. In this work, differential scanning calorimetry measurements were executed to determine specific heat of Ag–Si–Ge alloys from 123 K to high temperatures. For binary alloys, distinct troughs of specific heat are observed at eutectic Ag89Si11 and Ag75Ge25, when temperatures are larger than 500 K. Furthermore, specific heat of ternary Ag–Si–Ge alloys was predicted by four candidate principles based on the binary alloy’s data. Accordingly, the specific heat of 15 compositions of ternary Ag–Si–Ge alloys was determined to evaluate the predicted value. It is found that specific heat increases linearly with the rising Ag and Ge content in Si-rich alloys at low temperatures. Besides, alloys around Si–Ag75Ge25 pseudobinary line in Ag-rich area exhibit much lower specific heat at high temperatures. According to the comparison between measured and predicted specific heat of ternary alloys, the interpolation which employs data of pure elements, hypo-/hypereutectic alloys and the eutectic points, provides highest accuracy, especially at high temperatures. This rule may be applied to other eutectic systems.

Gouti, Imen; Litaiem, Hejer; García-Granda, Santiago

doi: 10.1007/s10973-020-09817-2pmid: N/A

Thermal analysis confirmed the presence of the phase transition at T = 320 K in the Cs2SeO4·H6TeO6 (CsSeTe) material. The structural study carried out at T = 360 K shows that this compound passes from the monoclinic system with the space group P21/c\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$P2_{1} /c$$\end{document} at room temperature, to the trigonal system with the space group R3¯m\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$R\bar{3}m$$\end{document}. At room temperature, the anionic groups are well ordered and stable, whereas after the transition at T = 320 K, the selenate groups change their orientation and the tellurate polyhedra change their positions. The high-temperature vibrational studies, carried out in a temperature range of 289–353 K, confirm the presence and nature of the transition detected by thermal analysis. The conductivity evolution versus temperature shows the presence of an ionic–protonic conduction phase transition at T = 490 K.

Anvari, Alireza; Javaherdeh, Kourosh

doi: 10.1007/s10973-020-09800-xpmid: N/A

In this work, the heat transfer of the non-Newtonian nanofluids inside a wavy microchannels heat exchanger (WMCHE) in cross-flow configuration has been experimentally and numerically studied. The Reynolds number (Re) does not have unique definition for non-Newtonian fluids. The non-Newtonian carboxyl methyl cellulose (CMC) aqueous solution containing 0.2 mass% CMC is used as base fluid (BF). The single-walled carbon nanotubes (CNT) and graphene nanoparticles (GNP) were added to the BF in 0.1 mass% as two other test fluids. Here, an equation based on the assumption of laminar flow is used in order to evaluate Re as a function of experimentally measured pressure drop. However, this assumption needs a similar form of friction factor relation to that of Newtonian fluids that is verified based on numerical simulation. In the presented work, finite element method (FEM) was utilized to perform the numerical modeling through Comsol Multiphysics software. Results show that as flowrate and relative waviness(2A/2L) increase, the convective heat transfer coefficient could be intensified. In terms of pressure drop, it was seen that with increasing the flowrate and relative waviness(2A/2L) of nanofluids, pressure drop was intensified. The results are compared to the experimental data and showed good agreement. The proposed performance index implies that GNP/BF nanofluid is the best one and both of two kinds of wavy configurations enhance the heat transfer efficiency, although the wavy two configurations are better.

Yang, Guochao; Liu, Jing; Xu, Bingbing; Liu, Zhijia; Ma, Fang; Zhang, Qiuhui

doi: 10.1007/s10973-020-09802-9pmid: N/A

In this paper, a new designed silicon-containing nitrogen and phosphorus flame-retardant system containing ammonium polyphosphate, modified molecular sieve and methylcellulose was used to prepare the flame-retardant corrugated cardboards (FRCCB). The samples before and after treatment were tested for combustion and thermal stability using vertical burning test (VBT), limiting oxygen index (LOI), cone calorimetric test (CCT) and thermogravimetry (TG). To further analyze the flame-retardant properties of the flame-retardant system, the microstructure, surface elements and functional groups of the materials were characterized by the scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the samples were tested to analyze the effect of flame-retardant treatment on the strength. The VBT and LOI tests showed that the samples after the flame-retardant treatment were able to self-extinguish after ignition, achieving the flame-retardant B-1 grade. The CCT tests showed that the total heat release of treated samples was reduced by 49.90%, and the total smoke production was decreased by 27.64%. TG tests showed that the thermal decomposition temperature of FRCCB decreased but the residual carbon content increased largely. FTIR tests showed that the functional group changed at different temperatures. After flame-retardant treatment, a dense carbon layer was formed on the surface of the treated sample, including N, P, Si and Cu, measured by SEM and EDS. Combining with various characterization methods, the flame-retardant system can retard flame by releasing nonflammable gases, forming covers and catalyzing char formation.

Narayanasamy, P.; Selvakumar, M.; Ramkumar, T.; Mohanraj, M.; Pillai, G. Pitchayya

doi: 10.1007/s10973-020-09834-1pmid: N/A

In this paper, the detailed characterization of mechanical, electrical and thermal properties of Ag nanoparticle-reinforced Al6061 alloy was studied. Four composites with Al6061 alloys and different mass percentages (3%, 6%, 9% and 12%) of Ag nanoparticles were processed by stir casting method. The chemical analysis was used to confirm the elemental composition. The microstructural examination was carried out using optical microscopy. The phase analysis of the samples was studied using X-ray diffraction technique. The density and hardness were measured as per ASTM standards. Four-point probe tester and differential scanning calorimetry were used to measure the electrical conductivity and specific heat. In addition, the thermal conductivity and thermal diffusivity were measured using laser flash method. The results reveal the presence of Ag nanoparticles can significantly enhance the mechanical, electrical and thermal properties.

Li, Xin; Liang, Dong; Li, Kai; Ma, Xuemei; Cui, Jianlan; Hu, Zhiyong

doi: 10.1007/s10973-020-09781-xpmid: N/A

A hypophosphorous acid-based ionic liquid [Bmim]H2PO2 (BMP) was synthesized and characterized by FTIR, 1HNMR, 13CNMR and 31PNMR. Moreover, a new intumescent flame-retardant system composed of BMP and expandable graphite (EG) was used to improve the flame retardancy of high-density polyethylene-based wood–plastic composites (WPC). The retardant properties and thermal decomposition behaviors were investigated by the limiting oxygen index (LOI) test, UL-94 vertical burning test, thermogravimetric analysis (TGA) and cone calorimeter test, respectively. When the mass ratio of BMP to EG was 1:2 and the total amount was kept at 30 mass%, WPC/EG-BMP composite passed UL-94 V-0 rating, and its LOI value increased to 31.5% from 21.4% for neat WPC. In addition, both the peak heat release rate and the total heat release of WPC/BMP-EG composite decreased significantly relative to WPC and WPC/EG composites according to cone calorimeter analysis. The TGA results suggested that BMP had good ability of char formation, and when combined with EG, it could greatly promote the formation of the protective char layer. The surface morphology and chemical structure of char residues were examined using scanning electron microscope–energy-dispersive spectrometer and Raman spectroscopy. It revealed that a compact and thick char layer was formed with the combination of BMP and EG, which hinder the transfer of heat flow and combustible gases in the condensed phase, thus exhibiting excellent flame retardancy. This study demonstrated that BMP and EG had a synergistic effect on the flame retardancy of WPC.

Moloney, Mícheál P.; Massoni, Nicolas; Grandjean, Agnès

doi: 10.1007/s10973-020-09823-4pmid: N/A

It is well known that the physical properties of nanoparticles can be tuned by controlling synthetic factors such as pH, temperature, reactant ratio or type of stabiliser used. In this work, the reactant ratio is varied to produce batches of copper(II) hexacyanoferrate(II) (Cu-HCF) with different cyano decomposition temperatures. This is accomplished by controlling the number of Fe(CN)64− site vacancies throughout the structure. By reducing the number of vacancies and consequently the need for water to complete the structure, the thermal decomposition temperature of Cu-HCF can be increased. In addition to this, we also note that the guest ion similarly contributes to the decomposition temperature. By exchanging K+ with Cs+, an increased resistance to thermal decomposition is realised. As the incorporation of Cs+ ions into the structure does not alter the number of Fe(CN)64− site vacancies, this enhancement is attributed to a change in the geometry of the copper coordination sphere.

Malekian, Navid; Moghadasi, Hesam; Bidabadi, Mehdi

doi: 10.1007/s10973-020-09791-9pmid: N/A

Owing to their safety, stability and controllability, diffusion flames have found extensive applications in medicine and power generation. Regarding the significance of recirculation impact on micro-combustors, an efficient method should be developed for better analysis of the micro-combustors performance. In this paper, an asymptotic method is developed to model diffusion flames propagation through a biofuel in counterflow configuration with the consideration of heat recirculation effect. The flame structure includes pre-heat, post-vaporization and oxidizer zones. Micron-sized lycopodium particles and air can be regarded as biofuel and oxidizer, respectively. Mass and energy conservation equations are investigated in each zone. For evaluation of the thermal recirculation impact, a specific term is included in the energy conservation equation. Furthermore, the effects of changes in the flame temperature, mass fraction of the gaseous fuel and oxidizer (relative to fuel and oxidizer Lewis numbers), mass particle content, particle radius and equivalence ratio were examined considering and ignoring the thermal recirculation effect. The results indicate that increase of heat recirculation coefficient will rise the flame temperature and shift the flame position to the fuel nozzle side. Also, consideration of thermal heat recirculation will enhance the gaseous fuel production in the pre-heat and post-vaporization zones.Graphic abstract[graphic not available: see fulltext]

Zhang, Yue-Fei; Mao, Jing-Jing; Zhou, Pei-Zhang

doi: 10.1007/s10973-020-09810-9pmid: N/A

A series of dicarboxylic dihydrazide compounds (DCDH-R-n) were prepared and used as nucleating agents for isotactic polypropylene (iPP). To investigate the relation between chemical structure of nucleating agents and nucleation effect in iPP, the influences of DCDH-R-n on crystallization and melting behaviors of iPP were analyzed by differential scanning calorimeter. The results showed some of dicarboxylic dihydrazide compounds were highly efficient for iPP. The nucleation efficiency of these nucleating agents depended on different substituent groups (R) and the number of methylene groups (n). When R is phenyl or cyclohexyl, the corresponding nucleating agents had relatively excellent nucleation effect. A nucleating agent was likely to have better nucleation effect as the number of methylene groups in the structure increases. In addition, the optimum addition amount of DCDH-R-n in iPP ranged from 0.10 to 0.20 mass% and the crystallization temperatures of nucleated iPP under optimum addition amount reached above 130.0 °C.