ABSTRACT
Rapid energy consumption stimulates the development of energy-saving materials. In this work, the L-S eutectic mixture used as a PCM was compounded with EP via vacuum adsorption to synthesize LS/EP CPCM. The maximum mass adsorption rate of EP on L-S is determined to be 70% via leakage experiments. The microscopic morphology, chemical, and crystal structure were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), respectively. The phase change properties were measured by differential scanning calorimetry (DSC). The melting temperature of LS/EP is 37.79 °C, with a latent heat of 126.05 J g-1, and it has a crystallinity of over 90%. The thermal decomposition was evaluated by TGA. The initial decomposition temperature is 132.20 °C for LS/EP. In addition, the results of accelerated phase change cycling experiments showed that LS/EP CPCM has good reliability.
ABSTRACT
Thermal properties, stability, and reliability of lauric acid-based binary eutectic mixtures for building energy efficiency were studied. The eutectic points and phase change performance of these binary PCMs were obtained as follows: (1) For lauric acid-myristic acid, the mass eutectic point is 70 wt % LA/30 wt % MA. (2) For lauric acid-palmitic acid, the eutectic point is 79 wt % LA/21 wt % PA. (3) For lauric acid-stearic acid, the eutectic point is 82 wt % LA/18 wt % SA. The eutectic PCMs have a melting enthalpy of 166.18, 183.07, and 189.50 J·g-1 and a melting temperature of 35.10, 37.15, and 39.29 °C for lauric-myristic acid, lauric-palmitic acid, and lauric-stearic acid binary eutectic PCMs, respectively. The experimental results are very close to the theoretical results. Moreover, from FT-IR and XRD investigations, we realized that during the preparation of the lauric acid-based binary eutectic fatty acids, no new functional groups were produced. Besides, the TG illustrated that the LA-MA eutectic PCMs, LA-PA eutectic PCMs, and LA-SA eutectic PCMs exhibit excellent thermal stability below 126.51, 135.7, and 110.08 °C, respectively. Finally, lauric acid-based binary eutectic PCMs still show excellent thermal properties and chemical structure after 500 hot and cold cycles. All in all, as a novel material for building energy conservation, lauric acid-based binary eutectic PCMs have broad prospects and good practicability.
ABSTRACT
In this work, a myristic acid (MA)-paraffin wax (PW) binary eutectic phase change material (PCM) was prepared by a melt-solution blending method. The eutectic point of the MA-PW binary system was determined to be 62 wt% MA-38 wt% PW using a cooling curve. In addition, the phase transition properties and thermal stability of MA-PW binary eutectic PCM were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG) analysis. The melting temperature and latent heat as well as starting temperature of decomposition for MA-PW binary eutectic PCM were 41.99 °C, 171.43 J g-1 and 137.86 °C, respectively. Besides, analysis of the chemical and crystal structures of MA, PW and MA-PW revealed no chemical reaction between MA and PW to produce a new molecular structure and no change in the crystal structure. Finally, MA-PW binary eutectic PCM still has good thermal properties and chemical stability after 500 cold-hot cycles.
ABSTRACT
A phase change material (PCM) has the characteristics of latent heat storage, controllable phase transition temperature (PTT), and chemical stability. It can naturally regulate the ambient temperature in a certain range and reduce the load of air conditioning operation. Therefore, it plays an important role in the field of energy-saving buildings, and the PTT of PCM is one of the decisive factors. In this paper, through analyzing PCM installed in solar buildings at various regions, a binary eutectic mixture (EM) was prepared from lauric acid (LA) and octadecanol (OD) by the method of mixed melting, and the PTT and enthalpy of the EM were 39.87 °C and 186.94 J/g, respectively. The PTT, latent heat, and EM ratio were determined by theoretical calculation, the step cooling curve, and DSC. FT-IR result shows that no chemical reaction occurs among the components of composites, and the molecular forces are uniform and stable. XRD results further proves that no other phases existed in the composites. Thermal cycles (500) and the TG test show that the EM has excellent thermal stability and heat resistance, which meets the engineering application. Due to the thermodynamic properties of the EM, it can be used in thermal cooling of electronic systems, building envelopes, and thermal storage in solar buildings to obtain a good energy-saving effect.
ABSTRACT
Turnip mosaic virus (TuMV) is the most prevalent viral pathogen infecting most cruciferous plants. MicroRNAs (miRNAs) are around 22 nucleotides long non-protein-coding RNAs that play key regulatory roles in plants. Recent research findings show that miRNAs are involved in plant-virus interaction. However we know little about plant defense and viral offense system networks throughout microRNA regulation pathway. In this study, two small RNA libraries were constructed based on non-heading Chinese cabbage (Brassica campestris ssp. chinensis L. Makino, NHCC) leaves infected by TuMV and healthy leaves, and sequenced using the Illumina-Solexa high-throughput sequencing technology. A total of 86 conserved miRNAs belonging to 25 known miRNA families and 45 novel ones were identified. Among them, twelve conserved and ten new miRNAs were validated by real-time fluorescence quantitative PCR (qPCR). Differential expression analysis showed that 42 miRNAs were down-regulated and 27 miRNAs were up-regulated in response to TuMV stress. A total of 271 target genes were predicted using a bioinformatics approach, these genes are mainly involved in growth and resistance to various stresses. We further selected 13 miRNAs and their corresponding target genes to explore their expression pattern under TuMV and/or cold (4°C) stresses, and the results indicated that some of the identified miRNAs could link TuMV response with cold response of NHCC. The characterization of these miRNAs could contribute to a better understanding of plant-virus interaction throughout microRNA regulation pathway. This can lead to finding new approach to defend virus infection using miRNA in Chinese cabbage.