Earticle

Conventional phase change materials (PCMs) are typically composed of pure water combined with superabsorbent polymers (SAPs), raising concerns regarding environmental sustainability, complex synthesis processes, and high material costs. In this study, we propose a pulp-water composite as an eco-friendly and cost-effective alternative to traditional PCMs. Recycled paper pulp (1-5 wt%) was incorporated into water-based PCMs to investigate its effects on thermal retention and phase transition behavior. The use of pulp offers advantages over SAP-based PCMs, including simpler synthesis, lower production costs, and easier material availability. Thermal and chemical properties were analyzed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and data loggers. The results indicate that a 3 wt% pulp-water mixture extends temperature retention by 70 minutes compared to pure water. These findings suggest that pulp-enhanced water-based PCMs can serve as a sustainable, biodegradable, and economically viable alternative to conventional SAP-based PCMs, providing improved thermal performance while minimizing environmental impact.

본 연구에서는 PCM 공융혼합물의 열 저장 용량 향상에 대한 고분자 물질의 적용 가능성을 평가하기 위해 PEG와 BDO의 다양한 함량을 조사하여 이들의 열적 특성과 열 안 정성을 평가하였다. FT-IR의 결과에서 BDO의 OH기와 PEG600의 Ether기가 수소결합을 형성하며 고정되는 효과 로 인해 혼합물이 더욱 높은 안정성을 띄는 것을 확인하였 고, XRD 분석을 통해 PEG와 BDO 혼합물의 결정화도가 증가하여 높은 열 용량을 갖을 수 있다는 것을 확인하였다. 또한, DSC 결과와 온도-시간 그래프를 비교하여 고분자가 사용된 PEG600-BDO 혼합물은 상변화 온도의 변화 및 높 은 온도 지속 시간이 관찰되었다. 이는 고분자를 이용하여 공융혼합물을 제조할 때 혼합물의 온도 유지 시간이 단일 물질보다 개선되어 열 에너지 저장에 유리함을 알 수 있다. 그러나, 공융점 혼합물이 아닌 경우 PEG의 분자량 분포로 인한 넓은 온도 유지 구간과 과냉각 현상 등의 문제가 발 생하였다. 공융점이 형성된 PEG600(68)-BDO(32)의 경우, 재사용성 실험에서 100회까지 잠열과 상변화온도의 변화 없이 우수한 재사용성을 나타내었다. 본 연구 결과를 통하 여 공융혼합물 PCM의 열 저장 용량 및 열 안정성을 동시 에 확보하기 위하여 고분자 물질의 사용 및 최적의 공융비 율 확보가 중요함을 알 수 있다. 한편, 고분자 물질을 사용 한 공융혼합물의 실제 사용을 위해 분자량 분포의 영향을 최소화하는 등의 연구를 통하여 넓은 온도의 공융온도 유 지와 과냉각 현상 문제 해결이 필요하다.

Current cold chain logistics relying on organic or eutectic materials within the 2~8°C range as secondary fluids often face limitations in heat storage capacity, necessitating high energy consumption and large volume capacity. An effective approach to address this challenge is by incorporating polymers to enhance the heat storage capacity of eutectic materials. In this study, we investigated the impact of polyethylene glycols (PEGs) on phase change materials using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), analyses of endothermic and exothermic phase change processes, and an accelerated thermal cycling test. Our findings indicate that the introduction of PEGs into the phase change materials can lead to improvements in latent heat, thermal conductivity, and 2~8oC retention time. This enhancement is attributed to the high latent heat and thermal conductivity of the polymer, along with its ability to inhibit crystal formation in the eutectic mixture.

본 연구의 목적은 크실리톨과 상전이 물질의 흡열반응을 활용하여 수화열 저감에 관한 영향을 알아보고자 하는 연구이다. 실험을 실시하기 위하여 크실리톨 0.2 와 0.3%를 혼입하였으며, PCM재료는 황산나트륨, 질산칼슘, 인산 나트륨을 2%를 혼입하여 모르타르를 제작하였다. 그리고 비교 시험체로 기준모르타르와 고로슬래그 미분말을 30%혼입한 저발열 배합을 제작하였다. 평가항목은 수화열측정, 길모아침, 압축강도 및 휨강도를 측정하였다. 그 결과, 황산을 혼입한 시편의 초결이 가장 빨랐으며, 크실리톨 0.3%를 혼입한 시편의 초결이 가장 늦게 나타났다. 또한 PCM재료와 크실리톨을 사용한 시편들이 OPC와 저발열 배합에 비하여 수화열이 저감하였으며, 최고온도 도달시간도 늦게 나타났다. 압축강도와 휨강도 역시 PCM재료와 크실리톨을 사용한 시편들이 OPC와 저발열 배합에 비하여 높은 압축강도 발현을 보였다.

The purpose of this study is to investigate a hydration heat property of mortar using endothermic reaction of xylitol and phase change materials(PCM). For this reason, this study is to control the hydration heat by replacing mineral admixture or adding xylitol and Sodium sulfate dodecahydrate, calcium nitrate tetrahydrate, sodium phosphate dibasic dodecahydrate as PCM. Mortar to produce 0.2% or 0.3% of the amount of xylitol, sodium sulfate dodecahydrate, calcium nitrate tetrahydrate, sodium phosphate dibasic dodecahydrate, respectively, 2% of the full amount of cement were made. Also, plain mortar and mortar containing blast-furnace slag (30%) were made, in order to compare with mortar using PCM and xylitol. A gillmore needle, measurement of hydration heat, compressive strength and tensile strength were tested. From the test results, a initial setting of mortar containing 0.2% xylitol and 2% sodium phosphate dibasic dodecahydrate was found to become fast. And a initial setting of mortar containing 0.3% xylitol was found to become slow. Also, mortar containing xylitol and PCM can reduce of maximum temperature and increase compressive and tensile strength compared to the plain mortar and mortar containing blast-furnace slag.

The purpose of this study is to investigate a hydration heat property of mortar using endothermic reaction of xylitol and phase change materials(PCM). For this reason, this study is to control the hydration heat by replacing mineral admixture or adding xylitol and Sodium sulfate dodecahydrate, calcium nitrate tetrahydrate, sodium phosphate dibasic dodecahydrate as PCM. Mortar to produce 0.2% or 0.3% of the amount of xylitol, sodium sulfate dodecahydrate, calcium nitrate tetrahydrate, sodium phosphate dibasic dodecahydrate, respectively, 2% of the full amount of cement were made. Also, plain mortar and mortar containing blast-furnace slag (30%) were made, in order to compare with mortar using PCM and xylitol. A gillmore needle, measurement of hydration heat, compressive strength and tensile strength were tested. From the test results, a initial setting of mortar containing 0.2% xylitol and 2% sodium phosphate dibasic dodecahydrate was found to become fast. And a initial setting of mortar containing 0.3% xylitol was found to become slow. Also, mortar containing xylitol and PCM can reduce of maximum temperature and increase compressive and tensile strength compared to the plain mortar and mortar containing blast-furnace slag.

This study examines the effectiveness of nighttime passive cooling strategies in residential buildings located in warm climate zones, with a specific focus on integrating Phase Change Materials (PCM) with natural ventilation. The research conducts an empirical analysis of PCM's thermal performance during nighttime cooling and evaluates different specific heat calculation methods for PCM, determining that the heat balance equation method which is proposed previously provides the most accurate results with error margins below 0.5°C compared to measured data. The research utilized field measurements in a wooden single-story building in Kumagaya, Japan, analyzing PCM cold storage performance during nighttime ventilation over different seasonal periods. Results indicate that PCM's cooling capacity varies significantly with weather conditions, showing optimal performance during moderate temperature months (May) compared to warmer months (June, September). The study also demonstrates that building orientation significantly impacts cooling efficiency, with west-facing rooms or east-facing rooms shaded from morning solar radiation exhibiting superior performance in maintaining cooler indoor temperatures. The findings suggest that while PCM combined with nighttime ventilation shows promising potential for reducing cooling energy demand in temperate climates, optimal results are achieved when this passive cooling strategy is integrated with complementary passive design approaches or mechanical systems rather than implemented as a standalone solution. Future research should focus on determining optimal phase change temperature ranges for specific climate conditions and exploring hybrid passive-active cooling systems that maximize PCM's thermal storage capabilities.

This study was aimed at developing a low cost cold storage system for agricultural products. Three kinds of slurries: K1, K2, and K3 slurries were developed using phase change materials (PCMs) such as tetradecane, octadecane, and sodium polyacrylate to maintain the desired temperature ranges. The slurries were manufactured by in-situ polymerization. Tetradecane and octadecane were capsulated in a core with melamine at the surface. The thermodynamic characteristics of the slurries were measured and analyzed. The latent heats of the K1, K2, and K3 slurries at the melting points were 206.41, 186.88, and 147.91 kJ/kg, respectively. A transportable cold storage container was built to investigate the performance of the slurries as thermal storage media. The temperatures at the insides of the container could be maintained in the ranges of 0-5, 5-10, and 10-15oC for more than 23, 27, and 60 hr with the K1, K2, and K3 slurries, respectively.

Electrical optical switching and structural transformation of $Ge_{15}Sb_{85}$, $Sb_{65}Se_{35}$ and N2.0 sccm doped $Sb_{83}Si_{17}$ were studied to investigate the phase change characteristics for PRAM application. Sb-based materials were deposited by a RF magnetron co-sputtering system and the phase change characteristics were analyzed using an X-ray diffractometer (XRD), a static tester and a four-point probe. Doping Ge, Se or Si atoms reinforced the amorphous stability of the Sb-based materials, which affected the switching characteristics. The crystallization temperature of the Sb-based materials increased as the concentration of the Ge, Se or Si increased. The minimum time of $Ge_{15}Sb_{85}$, $Sb_{65}Se_{35}$ and N2.0 sccm doped $Sb_{83}Si_{17}$ for crystallization was 120, 50 and 90 ns at 12 mW, respectively. $Sb_{65}Se_{35}$ was crystallized at $170^{\circ}C$. In addition, the difference in the sheet resistances between amorphous and crystalline states was higher than $10^4{\Omega}/{\gamma}$.

상변화물질(phase change material, PCM)은 외부온도변화에 따른 상변화에 따라 흡열과 방열성을 반복적으로 나타내는 물질로서 건축, 우주항공분야 등에서 열전달매체나 열조절시스템에 응용되어 왔다. 이러한 PCM의 응용방법은 PCM을 미세한 입자(직경이 약 100$\mu\textrm{m}$)로 만들어 직접 운반유체 속에 분산시켜 이용하거나, PCM을 심물질로 하는 마이크로캡슐을 제조하여 이용하는 방법을 들 수 있다. (중략)

To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

본 연구에서는 상전이 온도가 36 $^{\circ}C$인 n-eicosnae을 열가소성 폴리올레핀 고분자인 폴리프로필렌과 블렌드하였으며, 또한 최근의 형태안정성 PCM(SSPCM)의 연구검토를 통하여 폴리프로필렌과 n-eicosnae의 특성과 잠열저장체로서의 적용 가능성을 확인하였다. 상전이 온도가 36 $^{\circ}C$인 n-eicosane과 폴리프로필렌을 멜팅방법과 흡수방법을 이용하여 시료를 제조하였다. 제조된 형태안정성 PCM(SSPCM)을 DSC, WAXD, FTIR spectroscopy, ARES로 분석결과 형태안정성, 열용량의 향상을 확인하였다.

Phase change materials based on polypropylene blended with n-eicosane were studied in this paper. In addition, this paper reviews recent studies on the preparation of shape stabilized phase change materials (SSPCM), such as SSPCM from polypropylenes and n-eicosane, their basic properties and possible applications to latent heat storage. The preparation methods used were the melting method and absorption methods. Shape stabilized PCM(SSPCM) prepared for DSC, WAXD, FTIR spectroscopy, ARES, results of the analysis of shape stability heat capacity to improve were identified.

We prepared polymer-PCM gels such as prepared frozen gel from polypropylene and n-Paraffin for thermal storage and release materials, their basic properties and possible applications especially in latent heat storage. The preparation methods are used to melting method and absorption method respectively. The composition and properties of prepared frozen gels from polypropylene and n-Paraffin were observed by DSC, FT-IR spectra, ARES and Elemental analysis. We can prepare frozen gels in different temperature for latent heat storage materials as controlling composition of phase change material as well as using different incorporating phase change materials. These frozen gels can be used to latent heat storage materials for several applications.

We prepared polymer-PCM gels such as prepared frozen gel from polypropylene and n-Paraffin for thermal storage and release materials, their basic properties and possible applications especially in latent heat storage. The preparation methods are used to melting method and absorption method respectively. The composition and properties of prepared frozen gels from polypropylene and n-Paraffin were observed by DSC, FT-IR spectra, ARES and Elemental analysis. We can prepare frozen gels in different temperature for latent heat storage materials as controlling composition of phase change material as well as using different incorporating phase change materials. These frozen gels can be used to latent heat storage materials for several applications.

Phase change thermal storage devices can effectively solve the shortcomings of solar energy such as intermittency anduncertainty, and realize the efficient use of renewable energy. However, the low thermal conductivity of phase changematerials makes it a research priority to increase the melting rate of heat storage units. In this paper, the melting performanceenhancement of the phase change thermal storage device is investigated. A numerical model is constructed for the phasechange process of the device at different inclination angles and heating boundaries, and parameters such as the completemelting time, the melting fraction, the phase interface and the temperature fields are discussed. The results show that thephase change heat storage rate is optimal at 90° inclination, which reduces the complete melting time by 14.05% comparedto 0° inclination. In addition, the increase of inclination angle not only increases the melting rate, but also reduces the areaof refractory region and improves the melting uniformity.

For thermal adaptable fabrics, the polyurethane-urea microcapsules containing phase-change materials (PCMs: hexadecane, octadecane and eicosane) were successfully synthesized by interfacial polycondensation using 2,4-toluene diisocyanate (TDI)/poly(ethylene glycol) (PEG400)/ethylene diamine (EDA) as shell monomers and nonionic surfactant NP-12 in an emulsion system under stirring rates of $3,000{\sim}13,000$ rpm. The mean particle size of microcapsule decreased significantly with increasing the stirring rate up to 11,000 rpm, and then leveled off. The mean particle size increased with increasing the content and molecular weight (eicosane > octadecane > hexadecane) of PCMs at the same stirring rate. The mean particle sizes of microcapsules were found to decrease with increasing the NP-12 content up to 1.5 wt%, and thereafter increased a little. It was found that the melting temperature ($T_m$) and crystallization temperature ($T_c$) of three kinds of encapsulated PCMs and their enthalpy changes (${\Delta}H_m,{\Delta}H_c$) increased with increasing PCM contents. The encapsulation efficiencies (Ee) of hexadecane microcapsule linearly increased with increasing the content of hexadecane. It was found that the stable microcapsule containing 50 wt% of hexadecane could be obtained in this study. However, Ee of octadecane and eicosane microcapsules increased with increasing PCM's contents up to 40 wt%, and then decreased a little. By considering the encapsulation efficiency, it was found that the maximum/optimum contents of octadecane and eicosane microcapsules were about 40 wt%. By the dynamic thermal performance test, it was found that the maximum buffering levels of Nylon fabrics coated with hexadecane, octadecane, and eicosane microcapsules were about $-2.4/+2.9^{\circ}C,\;-3.6/+3.6^{\circ}C\;and\;-4.0/+4.7^{\circ}C$, respectively.

The crystallization behavior and physical properties of Si-doped Sb2Te3(Si : ST) materials applicable to phase change random access memory (PCRAM) was studied with the purpose of overcoming their current weaknesses regarding use in PCRAM. Phase change materials were prepared by DC magnetron sputtering. Si-doped Sb2Te3materials have anSb2Te3(ST) rhombohedral structure regardless of Si content and a segregated region consisting of Si was founded. The Si amorphous phase located at grain boundaries interrupted grain growth, therefore the grain size became smaller. These crystal structures and their bonding characteristics were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Increasing the amount of Si in Sb2Te3 increased the sheet resistance, crystallization temperature (Tc) and crystallization activation energy (Ea), which was confirmed by a 4-point probe measurement. Furthermore, Metal-Insulator-Metal (MIM) devices based on ST and Si : ST were fabricated and the measured threshold voltage (Vth) of Si : ST was higher than ST. These results showed that Si doping improved thermal stability.

Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

A novel TPC-PEG-TPC with active end-groups was obtained from the end-groups of polyethylene glycol (PEG) modified by terephthaloyl chloride (TPC). These active end-groups can link up with a rare earth ion, which is a luminescent center of a rare earth fluorescent complex. Complexes of Eu-PEG with novel ligands (TPC-PEG-PTC) were synthesized by the coordination of the active reactant (as the first ligand) and phenanthroline (as the second ligand) with $Eu^{3+}$.IR, $^1H$-NMR, element analysis, DSC, WAXD, fluorescent spectroscopy, TGA, and SEM were used to characterize the structure and properties of these complexes. The results showed that this type of complex is a heat storage material with the phase change character of polyethylene glycol (PEG) and the luminescent properties of europium. There was no thermal decomposition of the complex of Eu-PEG until $300^{\circ}C$. SEM showed that the complex of Eu-PEG can be dispersed in PE.

A numerical analysis of solid-liquid phase change was performed on a heat transfer module which consisted of circulating water path (BRINE), heat transfer plate (HTP) and phase change material (PCM) layers, such as high temperature PCM (HPCM, $78{\sim}79^{\circ}C$) and low temperature PCM (LPCM, $28{\sim}29^{\circ}C$). There were five arrangements, consisting of BRINE, HTP, LPCM and HPCM layers in the heat transfer module. The time and heat transfer rate for melting/solidification was compared to their arrangements, against each other. As results, the numerical time without convection was longer than the experimental one for melting/solidification. Moreover, the melting/solidification with the BRINE I-LPCM-BRINE II-HPCM arrangement was faster(10 hours) than the others; HPCM-BRINE-LPCM, BRINE I-HPCM-LPCM-BRINE II one.