JOURNAL OF CHEMICAL THERMODYNAMICS
·
2019
·
IF 2.29
Zhan-Ping Qiao,Meng-Yao Su,Yuan-Lin Dang,Qi-Chao Yang
The phase diagrams of the Mg(NO 3 ) 2 –Ln(NO 3 ) 3 (Ln = Nd, Sm, Eu, Tb)–HNO 3 –H 2 O systems in the (∼20%) HNO 3 regions at T = 298.15 K were determined by using an isothermal solution saturation method. The Schreinemaker’s wet residues method was used to determine the compositions of solid-phases. Both Mg(NO 3 ) 2 –Nd(NO 3 ) 3 –HNO 3 –H 2 O and Mg(NO 3 ) 2 –Sm(NO 3 ) 3 –HNO 3 –H 2 O systems are complicated with three equilibrium solid phases Mg(NO 3 ) 2 ·6H 2 O, Mg 3 Ln 2 (NO 3 ) 12 ·24H 2 O and Ln(NO 3 ) 3 ·6H 2 O (Ln = Nd, Sm). But the systems Mg(NO 3 ) 2 –Eu(NO 3 ) 3 –HNO 3 –H 2 O and Mg(NO 3 ) 2 –Tb(NO 3 ) 3 Tb–HNO 3 –H 2 O are simple eutonic type. The two new solid-phase compounds Mg 3 Nd 2 (NO 3 ) 12 ·24H 2 O and Mg 3 Sm 2 (NO 3 ) 12 ·24H 2 O are congruently soluble in an average medium of ∼20 mass % HNO 3 , and they were identified and characterized by the methods of powder X-ray diffraction, X–ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric. The XRD diffraction patterns for the two new solid-phase compounds are identical due to their isomorphic structure. They belong to hexagonal systems, with space group R 3 . For Mg 3 Nd 2 (NO 3 ) 12 ·24H 2 O, a = b = (1.0993 ± 0.0005) nm, c = (1.7211 ± 0.0007) nm, V = (1.8012 ± 0.0013) nm 3 , D c = (4.2532 ± 0.0024) g·cm −3 , Z = 3; for Mg 3 Sm 2 (NO 3 ) 12 ·24H 2 O, ( a = b = 1.1198 ± 0.0004) nm, c = (1.7257 ± 0.0006) nm, V = (1.8742 ± 0.0011) nm 3 , D c = (4.1201 ± 0.0012) g cm −3 , Z = 3. The standard molar enthalpies of solution of the compounds Mg 3 Nd 2 (NO 3 ) 12 ·24H 2 O and Mg 3 Sm 2 (NO 3 ) 12 ·24H 2 O in water (aq) were measured to be (101.26 ± 0.77) kJ mol −1 and (80.27 ± 0.81) kJ mol −1 , and their standard molar enthalpies of formation were calculated to be – (12214.13 ± 2.5) kJ mol −1 and – (12183.6 ± 2.5) kJ mol −1 , respectively.
研究领域:
化学
·
物理化学
·
材料科学
✓ 已验证
DOI
高影响因子
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
·
2019
·Vol. 43
·期 3
·1121-1132
·
IF 3.343
Yue Zhang,Jinhe Sun,Guixiang Ma,Zhao Wang,Shaolei Xie,Yan Jing,Yongzhong Jia
Summary Expanded graphite (EG) has shown excellent performances in compression resilience, thermal conductivity, and adsorption ability. EG can adsorb liquid phase change materials (PCMs) mainly because of capillary action; however, EG is hydrophobic, which makes it less compatible with hydrated salts. Herein, hydrophilic EG (HEG) was prepared with Triton X-100 (TX-100) as surface modifier. The HEG–magnesium nitrate hexahydrate (HEG-MNH) composite as a PCM was investigated for thermal energy storage (TES) to understand the effect of hydrophilic modification on thermophysical properties. The powder-state HEG is added into MNH to prepare HEG-MNH composite PCM, which contains 1.71 wt% of TX-100, 7.29 wt% of EG, and 91.00 wt% of MNH by control variable method. The melting point and latent heat of HEG-MNH composite PCM were 89.05°C and 137.28 J/g, respectively. The endothermic enthalpy change of HEG-MNH composite PCM only decreased by 0.90%, along with the exothermic values of HEG-MNH composite that increased by 3.80% after 100 cycles. The thermal conductivity is higher 5.17 times than that of the pure MNH. Our work suggests that the HEG-MNH composite PCM has a great potential to be used as a PCM for TES.
研究领域:
材料科学
·
能源存储
✓ 已验证
DOI
高影响因子
JOURNAL OF APPLIED ELECTROCHEMISTRY
·
2018
·Vol. 48
·期 10
·1131-1138
·
IF 2.262
Ling Ziye,Li Suimin,Zhang Zhengguo,Fang Xiaoming,Gao Xuenong,Xu Tao
Abstract Household water heating systems incorporating phase change materials (PCMs) can store solar thermal energy and reduce energy consumption. MgCl 2 ·6H 2 O–Mg(NO 3 ) 2 ·6H 2 O eutectics have a melting point near 60 °C with a large energy storage density suitable for use in the thermal energy storage unit of a water heating system. However, the low thermal conductivity of the eutectic limits its heat extraction rate. In this study, we combine the eutectic and expanded graphite (EG) to prepare a high thermal conductivity composite PCM and study its cycling performance over 200 thermal cycles. The thermal conductivity of the composite PCM increased from 0.5 to 3.7 W m −1 K −1 , ensuring faster heating and cooling. The images obtained from scanning electron microscopy and leakage testing showed that the maximum loading mass fraction of the eutectic in the EG reached 85 wt %. Infrared spectra and X-ray diffractometry patterns confirm that composites with compositions between those of EG and the eutectic were composed of the physical mixture. Thermogravimetric analysis indicated that the composite PCM lost less mass at 300 °C compared to the pure eutectic, and differential scanning calorimetry demonstrated that the composite PCM had a melting point of 52.3 °C and a small subcooling degree of 2.7 °C, compared to 56.6 and 18.4 °C for the pure eutectic, respectively. All these measurements demonstrated that the composite PCMs changed less after 200 thermal cycles than the pure eutectic, which had an observable stratification caused by phase separation. The composite PCM developed was thermally conductive, shape-stabilized, and more thermally stable during cycling than the pure eutectic. Graphical Abstract
研究领域:
能源材料
·
热能工程
✓ 已验证
产品关联
DOI
高影响因子
SOLAR ENERGY MATERIALS AND SOLAR CELLS
·
2017
·
IF 4.784
Ziye Ling,Junwan Liu,Qianhao Wang,Wenzhu Lin,Xiaoming Fang,Zhengguo Zhang
MgCl 2 ·6H 2 O-Mg(NO 3 ) 2 ·6H 2 O eutectic has a proper melting point and high latent heat for solar water heating systems with latent heat storage . In this paper, the exact composition of the eutectic and the corresponding phase change temperature are determined by measuring the phase change characteristics of mixtures of MgCl 2 ·6H 2 O and Mg(NO 3 ) 2 ·6H 2 O in various ratios. MgCl 2 ·6H 2 O-Mg(NO 3 ) 2 ·6H 2 O eutectics, the melting temperature of which is around 58 °C, can be obtained with the mass fraction of MgCl 2 ·6H 2 O ranging from 35% to 50%. The eutectics are composited with porous fumed silica to improve its thermo-physical properties. The eutectic/SiO 2 composite retains a similar melting point of the pure eutectic, is of no liquid leakage even after melting while the SiO 2 weighs more than 15 wt%, and the specific enthalpy reaches 88.13 kJ kg −1 . The eutectic/SiO 2 composite has a thermal conductivity 5% higher than pure eutectics and better thermal stability and cycle stability. The thermogravimetric analysis shows its weight loss is 8.03% less than pure eutectic at 300 °C. And the eutectics suffers a decrease in phase change enthalpy after 100 thermal cycles by 9.2%, much lower compared with the 37.23% for pure eutectics due to the phase separation during the thermal cycles. Thermo-physical properties and stability of MgCl 2 ·6H 2 O-Mg(NO 3 ) 2 ·6H 2 O eutectic have been enhanced by fumed silica.
研究领域:
材料科学
·
能源工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Energy Storage
·
2022
·
IF 8.907
Hui Wang,Enda Ci,Xiaoqing Li,Ying Zhang,Zhenying Zhang,Jianqiang Li
A new eutectic mixture phase change material containing magnesium nitrate hexahydrate and lithium nitrate has been successfully prepared, which can be applied in the field of residential radiator heating due to the suitable phase change temperature and high latent heat. Further, by physical blending magnesium nitrate hexahydrate/lithium nitrate eutectic mixtures and expanded graphite, the new composites were prepared. The crystalline structure, thermal properties, corrosion performance of eutectic phase change materials were systematically measured. The results showed that the best eutectic mixtures had a phase change temperature of 72.35 °C and latent heat of 170.32 kJ/kg, with a little supercooling degree. The thermal conductivity was effectively improved by adding expanded graphite. Meanwhile, corrosion tests suggested aluminum and stainless steel 304 could be the preferred choices as the container. Overall, the prepared eutectic composite materials with superior performances could be a promising candidate for the residential radiator heating field.
研究领域:
材料科学
·
热能存储技术
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）