The Experts below are selected from a list of 1830 Experts worldwide ranked by ideXlab platform
Raul Quijada - One of the best experts on this subject based on the ideXlab platform.
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preparation and characterization of porous microfiltration membranes by using tailor made propylene 1 Octadecene copolymers
Desalination, 2008Co-Authors: Wilfredo Yave, Raul QuijadaAbstract:Tailor-made isotactic polypropylene (iPP) and propylene/1-Octadecene (CiPP-OD) copolymers synthesized via a metallocene catalyst were used for membrane preparation by the thermally induced phase separation (TIPS) process. Although the resulting morphology of the membranes and porosity were found similar, the water permeability for propylene/1-Octadecene copolymer membrane (1.0 mol-% of 1-Octadecene) was twofold higher compared to iPP membranes. Further increase of 1-Octadecene in the polypropylene did not improve the performance of membrane (decrease of permeability). This behaviour was attributed to the compressibility of the pores due to the ductile behaviour of the copolymer. Thus, the presence of a small amount of 1-Octadecene (1.0 mol-%) in the polypropylene chain can lead to obtain membranes with improved water permeability for the microfiltration process.
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metallocenic copolymers of isotactic propylene and 1 Octadecene crystalline structure and mechanical behavior
Macromolecular Chemistry and Physics, 2005Co-Authors: Humberto Palza, Raul Quijada, Rosario Benavente, Ernesto Perez, Juan M Lopezmajada, Maria L CerradaAbstract:A set of copolymers of isotactic propylene and 1-Octadecene (CiPOD) and the corresponding isotactic poly(propylene) homopolymer (iPP) have been synthesized using a metallocene catalyst. The influence of the incorporation of this long chain comonomer on the structure and final properties exhibited by iPP has been examined. Wide-angle X ray diffraction and optical microscopy have been used to analyze the effect of introducing 1-Octadecene comonomer within the iPP backbone. The initial monoclinic crystal lattice with a well-developed lamellar morphology is transformed into a mesomorphic modification showing very small entities. All these structural changes significantly influence the mechanical behavior of these copolymers. Thus, stiffness and microhardness are diminished and the brittle-ductile transition can be observed by simply varying composition when deformation takes place at room temperature. On the other hand, the intensity of the process associated with cooperative movements within the amorphous phase (β relaxation) significantly goes up with the incorporation of 1-Octadecene and its location is shifted to lower temperature because of the decrease in the crystallinity content.
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structural evaluation of copolymers of ethylene and 1 Octadecene by using the temperature rising elution fractionation technique
Journal of Applied Polymer Science, 2001Co-Authors: Raul Quijada, Ana Narvaez, Marcus Dal Pizzol, Susana Alcira Liberman, Adilson A Da Silva Filho, Griselda B GallandAbstract:Three samples of ethylene-Octadecene copolymers having different quantitative composition were analyzed structurally and in terms of their thermal behavior. The samples were fractionated by temperature rising elution fractionation, presenting different chemical composition distributions (CCD) that are essentially the result of the proportion of incorporated Octadecene. The CCD profiles were relatively wide for samples generated by metallocene catalysts. The analyses of the fractions showed that the melting and crystallization temperatures decrease with increasing comonomer incorporation, but this relation is affected by the average molecular weight of the chains. The melting thermograms of those fractions having higher proportions of Octadecene may be divided into two characteristic regions: the first one, at a higher temperature, originates from the melting of the least modified chains, which crystallize more perfectly. The second one is formed by the melting of chains having a high degree of comonomer incorporation, which melt in a diffuse manner over a wide range of temperatures. It is probable that the morphology of the crystals formed in this region does not follow the folded chain model, and are better represented by a model involving the alignment of chain segments (bundling). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 221–227, 2001
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synthesis and characterization of copolymers of ethylene and 1 Octadecene using the rac et ind 2zrcl2 mao catalyst system
Macromolecular Chemistry and Physics, 1999Co-Authors: Raul Quijada, Griselda B Galland, Ana Narvaez, Rene S Rojas, Franco M Rabagliati, Raquel Santos Mauler, Rosario Benavente, Ernesto Perez, Jose M Perena, Antonio BelloAbstract:The copolymerization of ethylene and 1-Octadecene using a bridged metallocene was studied in order to observe the effect of the comonomer on the catalytic activity. A noticeable increase in activity is seen as the concentration of 1-Octadecene in the reaction medium increases. 13 C NMR analysis shows 6.4 mol-% incorporation of comonomer at the highest 1-Octadecene concentration in the feed used here. The molecular weight of the copolymers shows a drastic decrease that may be attributed to chain termination by transfer or β-elimination of the comonomer. As to the molecular weight distribution, it remains within a narrow range, as expected with metallocene catalysts. The melting temperature and the enthalpy of melting of the copolymers show a decrease with increasing comonomer content. As usual for ethylene copolymers, the X-ray crystallinities are higher than those determined from the enthalpy of melting.
Gui Yin Fang - One of the best experts on this subject based on the ideXlab platform.
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preparation and thermal properties of n octadecane molecular sieve composites as form stable thermal energy storage materials for buildings
Energy and Buildings, 2012Co-Authors: Zhi Chen, Feng Shan, Lei Cao, Gui Yin FangAbstract:Abstract The n-octadecane/molecular sieve 5A composites as form-stable thermal storage materials were prepared by adsorbing liquid n-octadecane into the molecular sieve 5A. In the composites, the n-octadecane was used as thermal storage material, and the molecular sieve 5A acted as the supporting material. Fourier transformation infrared (FT-IR) spectroscope and scanning electronic microscope (SEM) were used to determine the chemical structure and microstructure of the n-octadecane/molecular sieve 5A composites. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetry analyzer (TGA). The FT-IR analyses indicated that there is no chemical interaction between the n-octadecane and molecular sieve 5A. The SEM results showed that the n-octadecane was well adsorbed into the porous network of the molecular sieve 5A and there is no leakage of the n-octadecane from the composites even when it is in the melting state. The DSC results indicated that the n-octadecane/molecular sieve 5A composites exhibited the same phase change characteristics as the n-octadecane and their latent heats increased with the increase of the n-octadecane content in composites. The TGA results presented that the molecular sieve 5A can improve the thermal stability of the composites as form-stable thermal energy storage materials.
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synthesis and characteristics of form stable n octadecane expanded graphite composite phase change materials
Applied Physics A, 2010Co-Authors: Xu Liu, Gui Yin FangAbstract:N-octadecane/expanded graphite composite phase-change materials were prepared by absorbing liquid n-octadecane into the expanded graphite. The n-octadecane was used as the phase-change material for thermal energy storage, and the expanded graphite acted as the supporting material. Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal diffusivity measurement were used to determine the chemical structure, crystalline phase, microstructure and thermal diffusivity of the composite phase-change materials, respectively. The thermal properties and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results indicated that the composite phase-change materials exhibited the same phase-transition characteristics as the n-octadecane and their latent heat increased with the n-octadecane content in composite phase-change materials. The SEM results showed that the n-octadecane was well absorbed in the porous network of the expanded graphite, and there was no leakage of the n-octadecane from the composites even when it was in the molten state.
Xiaodong Wang - One of the best experts on this subject based on the ideXlab platform.
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new approach for sol gel synthesis of microencapsulated n octadecane phase change material with silica wall using sodium silicate precursor
Energy, 2014Co-Authors: Fang He, Xiaodong Wang, Dezhen WuAbstract:A new silica encapsulation technique toward n-octadecane PCM (phase change material) was developed through sol–gel synthesis using sodium silicate as a silica precursor. Fourier transform infrared spectra confirm the chemical composition of the synthesized microcapsules, and wide-angle X-ray scattering patterns indicate good crystallinity for the n-octadecane inside silica microcapsules. Scanning electric micrographs demonstrate that the microencapsulated n-octadecane obtained at pH 2.95∼3.05 presents a perfect spherical morphology and a well-defined core–shell microstructure. Because the pH value of reaction solution determines the silica condensation rate and, thus, influences the balance between the self-assembly and polycondensation of silica precursors on the surface of n-octadecane droplets, the microcapsules could achieve a smooth and compact surface at pH 2.95∼3.05. The microencapsulated n-octadecane also exhibits good phase change performance and achieves a high encapsulation rate and high encapsulation efficiency in this synthetic condition. The encapsulation of n-octadecane with compact and thick silica wall can impart a high thermal conductivity and a good anti-osmosis property to the microcapsules, and can also improve the thermal stability of the microcapsules by preventing inside n-octadecane from thermally evaporating. Owing to the easy availability and low cost of sodium silicate, this synthetic technique indicates a high feasibility in industrial manufacture for the microencapsulated PCMs with inorganic walls.
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microencapsulation of n octadecane phase change material with calcium carbonate shell for enhancement of thermal conductivity and serving durability synthesis microstructure and performance evaluation
Applied Energy, 2014Co-Authors: Shiyu Yu, Xiaodong Wang, Dezhen WuAbstract:A sort of new phase change material (PCM) microcapsules based on n-octadecane core and calcium carbonate (CaCO3) shell was synthesized through a self-assembly method to enhance the thermal conductivity and serving durability. Fourier transform infrared spectra confirmed that the CaCO3 wall material was successfully fabricated upon the n-octadecane core. Scanning electric micrographs demonstrated that the n-octadecane microcapsules presented a perfect spherical morphology and a well-defined core-shell microstructure. Wide-angle X-ray scattering patterns indicated that the CaCO3 shell was formed in the crystalline phase of vaterite while the n-octadecane core inside microcapsules still preserved good crystallinity. The microencapsulated n-octadecane also exhibited good phase-change performance and achieved a high thermal storage capability, and however, their encapsulation ratio and encapsulation efficiency were determined by the core/shell mass ratio. Thermogravimetric analysis showed that the microencapsulation of n-octadecane improved the thermal stability by upgrading the evaporating temperature of n-octadecane inside the CaCO3 shell. The thermal conductivity of n-octadecane microcapsules was significantly improved due to the fabrication of highly thermally conductive CaCO3 shell, and the anti-osmosis property and serving durability were also enhanced under the protection of compact CaCO3 shell. Owing to the easy availability and low cost of calcium carbonate, this synthetic technique indicates a high feasibility and a good prospect in industrial manufacture for the microencapsulated PCMs with inorganic shells.
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Fabrication of microencapsulated phase change materials based on n-octadecane core and silica shell through interfacial polycondensation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011Co-Authors: Huanzhi Zhang, Shuangyue Sun, Xiaodong WangAbstract:Abstract In order to enhance the thermal transfer and phase change properties of microencapsulated phase change materials (micro-PCMs), a new micro-PCM based on n-octadecane core and silica shell was synthesized through interfacial polycondensation in different conditions. Fourier transform infrared spectra confirm the successful encapsulation of n-octadecane with inorganic silica. The silica microcapsules show a pronounced dependence of morphology and microstructure on the acidity of reaction solution in terms of the scanning electric microscopy observation, although all of them exhibit a well-defined core–shell structure. It is found that the microcapsules formed at pH 2.89 achieve a compact silica shell with fairly smooth surface as well as a large mean particle size of about 17.0 μm. Wide-angle X-ray scattering patterns indicate that the crystalline nature of the microencapsulated n-octadecane is maintained despite the confinement of silica shell. Thermogravimetric analysis shows that the silica microcapsules perform a typical two-step degradation process and present a good thermal stability. Differential scanning calorimetry investigation indicates that the silica-microencapsulated n-octadecane can achieve good phase change properties and high encapsulation efficiency by controlling the acidity of the reaction solution as well as the loading content of core material in synthesis. The thermal conductivity of the silica microcapsules is also significantly improved due to the presence of high thermal conductive silica shell. Encapsulation of n-octadecane with the silica shell material through interfacial polycondensation can be a perspective way to prepare the micro-PCMs with enhanced thermal transfer and phase change properties for potential applications to thermal-regulating textiles and fibers.
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silica encapsulation of n octadecane via sol gel process a novel microencapsulated phase change material with enhanced thermal conductivity and performance
Journal of Colloid and Interface Science, 2010Co-Authors: Huanzhi Zhang, Xiaodong Wang, Dezhen WuAbstract:Abstract A novel microencapsulated phase-change material (PCM) based on an n-octadecane core and an inorganic silica shell was designed to enhance thermal conductivity and phase-change performance. These silica microcapsules were synthesized by using TEOS as an inorganic source through a sol–gel process. Fourier transform infrared spectra confirm that the silica shell material was successfully fabricated onto the surface of the n-octadecane core. Scanning electronic microscopy images suggest that the silica microcapsules exhibit a spherical morphology with a well-defined core–shell microstructure. Furthermore, the silica microcapsules synthesized at pH 2.45 display a smooth and compact surface. These microcapsules also present a large particle size range of 7–16 μm. Wide-angle X-ray scattering patterns indicate that the n-octadecane inside the silica microcapsules still retains a good crystallinity. Thermogravimetric analysis shows that these silica microcapsules are degraded in two distinct steps, and have good thermal stability. The silica-microencapsulated n-octadecane can achieve good phase-change performance, high encapsulation efficiency, and good antiosmosis property by controlling the loading of core material and acidity of the reaction solution during the sol–gel process. The thermal conductivity of the microencapsulated n-octadecane is also significantly enhanced due to the presence of the high thermal conductive silica shell.
Dezhen Wu - One of the best experts on this subject based on the ideXlab platform.
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new approach for sol gel synthesis of microencapsulated n octadecane phase change material with silica wall using sodium silicate precursor
Energy, 2014Co-Authors: Fang He, Xiaodong Wang, Dezhen WuAbstract:A new silica encapsulation technique toward n-octadecane PCM (phase change material) was developed through sol–gel synthesis using sodium silicate as a silica precursor. Fourier transform infrared spectra confirm the chemical composition of the synthesized microcapsules, and wide-angle X-ray scattering patterns indicate good crystallinity for the n-octadecane inside silica microcapsules. Scanning electric micrographs demonstrate that the microencapsulated n-octadecane obtained at pH 2.95∼3.05 presents a perfect spherical morphology and a well-defined core–shell microstructure. Because the pH value of reaction solution determines the silica condensation rate and, thus, influences the balance between the self-assembly and polycondensation of silica precursors on the surface of n-octadecane droplets, the microcapsules could achieve a smooth and compact surface at pH 2.95∼3.05. The microencapsulated n-octadecane also exhibits good phase change performance and achieves a high encapsulation rate and high encapsulation efficiency in this synthetic condition. The encapsulation of n-octadecane with compact and thick silica wall can impart a high thermal conductivity and a good anti-osmosis property to the microcapsules, and can also improve the thermal stability of the microcapsules by preventing inside n-octadecane from thermally evaporating. Owing to the easy availability and low cost of sodium silicate, this synthetic technique indicates a high feasibility in industrial manufacture for the microencapsulated PCMs with inorganic walls.
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microencapsulation of n octadecane phase change material with calcium carbonate shell for enhancement of thermal conductivity and serving durability synthesis microstructure and performance evaluation
Applied Energy, 2014Co-Authors: Shiyu Yu, Xiaodong Wang, Dezhen WuAbstract:A sort of new phase change material (PCM) microcapsules based on n-octadecane core and calcium carbonate (CaCO3) shell was synthesized through a self-assembly method to enhance the thermal conductivity and serving durability. Fourier transform infrared spectra confirmed that the CaCO3 wall material was successfully fabricated upon the n-octadecane core. Scanning electric micrographs demonstrated that the n-octadecane microcapsules presented a perfect spherical morphology and a well-defined core-shell microstructure. Wide-angle X-ray scattering patterns indicated that the CaCO3 shell was formed in the crystalline phase of vaterite while the n-octadecane core inside microcapsules still preserved good crystallinity. The microencapsulated n-octadecane also exhibited good phase-change performance and achieved a high thermal storage capability, and however, their encapsulation ratio and encapsulation efficiency were determined by the core/shell mass ratio. Thermogravimetric analysis showed that the microencapsulation of n-octadecane improved the thermal stability by upgrading the evaporating temperature of n-octadecane inside the CaCO3 shell. The thermal conductivity of n-octadecane microcapsules was significantly improved due to the fabrication of highly thermally conductive CaCO3 shell, and the anti-osmosis property and serving durability were also enhanced under the protection of compact CaCO3 shell. Owing to the easy availability and low cost of calcium carbonate, this synthetic technique indicates a high feasibility and a good prospect in industrial manufacture for the microencapsulated PCMs with inorganic shells.
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silica encapsulation of n octadecane via sol gel process a novel microencapsulated phase change material with enhanced thermal conductivity and performance
Journal of Colloid and Interface Science, 2010Co-Authors: Huanzhi Zhang, Xiaodong Wang, Dezhen WuAbstract:Abstract A novel microencapsulated phase-change material (PCM) based on an n-octadecane core and an inorganic silica shell was designed to enhance thermal conductivity and phase-change performance. These silica microcapsules were synthesized by using TEOS as an inorganic source through a sol–gel process. Fourier transform infrared spectra confirm that the silica shell material was successfully fabricated onto the surface of the n-octadecane core. Scanning electronic microscopy images suggest that the silica microcapsules exhibit a spherical morphology with a well-defined core–shell microstructure. Furthermore, the silica microcapsules synthesized at pH 2.45 display a smooth and compact surface. These microcapsules also present a large particle size range of 7–16 μm. Wide-angle X-ray scattering patterns indicate that the n-octadecane inside the silica microcapsules still retains a good crystallinity. Thermogravimetric analysis shows that these silica microcapsules are degraded in two distinct steps, and have good thermal stability. The silica-microencapsulated n-octadecane can achieve good phase-change performance, high encapsulation efficiency, and good antiosmosis property by controlling the loading of core material and acidity of the reaction solution during the sol–gel process. The thermal conductivity of the microencapsulated n-octadecane is also significantly enhanced due to the presence of the high thermal conductive silica shell.
Su Gwang Jeong - One of the best experts on this subject based on the ideXlab platform.
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analysis on phase transition range of the pure and mixed phase change materials pcm using a thermostatic chamber test and differentiation
Journal of Thermal Analysis and Calorimetry, 2018Co-Authors: Seong Jin Chang, Su Gwang Jeong, Sumin KimAbstract:A phase change material (PCM) is a type of thermal storage material. The thermal performance of PCMs is evaluated by latent heat capacity and phase change temperature range. The phase change temperature of the phase change materials (PCM) is a critical factor in selecting a PCM. In this study, the conditions of physical and chemical bonding of PCMs including n-octadecane, n-docosane, palm wax, and two types of mixed PCMs were analyzed using the differential scanning calorimetry and the Fourier transform infrared. The phase change temperature range of these PCMs were analyzed using a thermostatic chamber test. In addition, the analysis method of the phase transition range of these PCMs was studied using the first and second derivatives. As a result, the phase changes of n-octadecane, n-docosane, and palm wax occurred at 27, 43, and 45–62 °C, respectively. It is not possible to determine the exact temperature at which phase change occurs with palm wax because palm wax includes various acids. Also, the results of the mixed PCM of n-octadecane and palm wax indicate several peaks. Finally, through a second derivative, it proved that the mixed PCM of n-octadecane and palm wax melts at 18.3–29.1 and 35.1–42.9 °C and freezes at 48.4–51.8, 31.8–34.1, and 23.7–26.9 °C.
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development of thermal enhanced n octadecane porous nano carbon based materials using 3 step filtered vacuum impregnation method
Thermochimica Acta, 2017Co-Authors: Jongki Lee, Su Gwang Jeong, Seong Jin Chang, Sumin KimAbstract:In this study, n-octadecane/porous nano carbon-based materials (OPNCs) were thermally enhanced using a 3-step filtered vacuum impregnation method. n-octadecane as phase change materials (PCMs) and supporting materials of C-300, C-500, Activated carbon (AC), Expanded graphite (EG) and Exfoliated graphite nanoplatelets (xGnP) made of the same raw material. Through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis, n-octadecane was well impregnated in carbon-based materials not a chemical bonding. Thermal conductivities of OPNCs were increased up to 580% compared with n-octadecane by TCi. Dfferential scanning calorimetry (DSC) analysis was used to verify thermal performance of OPNCs, the latent heat capacities of OPNCs were measured from 220J/g to 393J/g. Analysis of thermal stability by thermogravimetric analysis (TGA) showed that the impregnation ratio of OPNCs was about 56% and that of EG was 88.53%. 3-step filtered vacuum impregnation method manufactured a stable and thermally enhanced OPNCs.
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preparation of energy efficient paraffinic pcms expanded vermiculite and perlite composites for energy saving in buildings
Solar Energy Materials and Solar Cells, 2015Co-Authors: Okyoung Chung, Su Gwang JeongAbstract:Abstract This paper deals with the preparation, characterization, thermal properties and thermal reliability of form-stable composite phase change materials (PCMs), composed of n-octadecane, expanded vermiculite, and perlite for thermal energy storage. The composite PCMs were prepared by incorporation of liquid n-octadecane within the expanded vermiculite (eVMT) and expanded perlite (ePLT), using a vacuum impregnation method. The microstructures of n-octadecane/expanded vermiculite and pearlite were characterized by scanning electron microscopy (SEM). Analysis of Fourier transform infrared spectroscopy (FT-IR) of the prepared composite PCMs showed good compatibility between n-octadecane and the expanded vermiculite and pearlite. The thermal conductivities of composites were reduced, based on the TCi results. Differential scanning calorimetry (DSC) analysis indicated that the n-octadecane/eVMT and n-odtadecane/ePLT composites maintained their large latent heat capacity and original phase change temperatures, due to large surface area and good dispersion of the eVMT and ePLT. TGA analysis revealed that the prepared composite PCMs had good thermal durability in the working temperature ranges. Therefore, n-octadecane based composite PCMs can be considered as suitable candidates for latent heat thermal energy storage, with high thermal performance.
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thermal performance enhancement of mortar mixed with octadecane xgnp sspcm to save building energy consumption
Solar Energy Materials and Solar Cells, 2014Co-Authors: Sughwan Kim, Su Gwang Jeong, Songyee Paek, Jeong Hun Lee, Sumin KimAbstract:Abstract The octadecane/exfoliated graphite nanoplatelets (xGnP) shape-stabilized PCM (SSPCM) was prepared by impregnating octadecane as the PCM into xGnP in a vacuum. Fourier transform infrared spectroscopy determined that the heat storage characteristics of octadecane could integrate into the structure of xGnP due to its physical bonding, without a change in its chemical properties. Scanning electron microscopy images revealed that octadecane was evenly dispersed in the pores of xGnP. Differential scanning calorimeter analysis displayed that the melting temperature range of the SSPCM was similar to that of pure octadecane. Thermo gravimetric analysis measurements of the octadecane/xGnP SSPCM determined that the percentage of impregnated octadecane into xGnP was 55.9%, with 110.9 J/g of latent heat storage energy. In addition, mortar with the prepared SSPCM was investigated, in terms of developing advanced building materials with thermal energy storage properties. The purpose was to improve the thermal properties of mortar by using the latent heat storage of the octadecane/xGnP SSPCM. In consequence, mortar preserved with the SSPCM could be utilized as a construction material that stored thermal energy, to result in saving in buildings energy consumption.
