n-Octadecane

Phase Change Nanocapsules Enabling Dual-Mode Thermal Management for Fast-Charging Lithium-Ion Batteries.[Pubmed:38637969]

ACS Nano. 2024 Apr 30;18(17):11300-11310.

The fast-charging performance of conventional lithium-ion batteries (LIBs) is determined by the working temperature. LIBs may fail to work under harsh conditions, especially in the low-temperature range of the local environment or in the high-temperature circumstances resulting from the release of substantial Joule heating in the short term. Constructing a thermal engineering framework for thermal regulation and maintaining the battery running at an appropriate temperature range are feasible strategies for developing temperature-tolerant, fast-charging LIBs. In this work, we prepare phase change nanocapsules as a thermal regulating layer on the cell surface. The polyurea shells of the nanocapsules are decorated with polyaniline, where the molecular vibration of polyaniline is enhanced under solar irradiation, enabling light-to-heat conversion that achieves an effective temperature increment at low temperatures. Based on the large latent heat storage capability of the n-Octadecane core in the nanocapsules, the thermal regulating layer is sufficient to modulate strong heat release when operating LIBs at a high current rate, which efficiently prevents strong side reactions at high temperatures or even the occurrence of thermal runaway. This work highlights the promise of optimizing the operating temperature with a thermal regulator to ensure the safety and performance stability of fast-charging LIBs.

Insights into Zwitterionic Surfactant Interactions at the Oil-Water Interface by Interferometry Experiments and MDS Calculations.[Pubmed:38326982]

Langmuir. 2024 Feb 7.

In this work, the interaction performance of zwitterionic surfactant [dodecyl dimethyl sulfopropyl betaine (DSB-12) and hexadecyl dimethyl sulfopropyl betaine (DSB-16)] at the n-Octadecane oil surface is investigated from experimental and simulation insights. For a macroscopic experiment, interfacial interferometry technology was developed for real-time monitor interaction performances and to obtain the quantitative interfacial thickness and mass results. The Langmuir model was characterized by thermodynamic analysis, deducing the aggregation spontaneity of DSB-16 > DSB-12 with DeltaG(agg(DSB-16)) = -5.94 kJ mol(-1) < DeltaG(agg(DSB-12)) = 24.08 kJ mol(-1). A three-step dynamic model (adsorption, arrangement, and aggregation) was characterized by kinetic analysis, indicating arrangement process as slow-limiting step with k(2(arr)) < k(1(ads)), k(3(agg)). For microscopic simulation, and molecular dynamic (MD) method was utilized to theoretically investigate interaction performances and obtain the interfacial configuration and energy results. The interaction stability and interaction strength were indicated to be DSB-16 > DSB-12 with differences of final energy DeltaE(fin) = 48-88 kcal mol(-1). The interaction mechanism was explained by proposing the model of "response enhancement" and "deposition activity" for DSB-16 interactions, and "response decrease" and "elution activity" for DSB-12 interactions. The different performances can be attributed to the different interaction forms and forces of surfactants. This work provided a platform for performance and mechanism investigation between the surfactant molecule and oil surface, which is of great significance in reservoir exploitation and enhanced oil recovery (EOR).

Polyurethane/n-Octadecane Phase-Change Microcapsules via Emulsion Interfacial Polymerization: The Effect of Paraffin Loading on Capsule Shell Formation and Latent Heat Storage Properties.[Pubmed:37834594]

Materials (Basel). 2023 Sep 28;16(19):6460.

Organic phase-change materials (PCMs) hold promise in developing advanced thermoregulation and responsive energy systems owing to their high latent heat capacity and thermal reliability. However, organic PCMs are prone to leakages in the liquid state and, thus, are hardly applicable in their pristine form. Herein, we encapsulated organic PCM n-Octadecane into polyurethane capsules via polymerization of commercially available polymethylene polyphenylene isocyanate and polyethylene glycol at the interface oil-in-water emulsion and studied how various n-Octadecane feeding affected the shell formation, capsule structure, and latent heat storage properties. The successful shell polymerization and encapsulation of n-Octadecane dissolved in the oil core was verified by confocal microscopy and Fourier-transform infrared spectroscopy. The mean capsule size varied from 9.4 to 16.7 microm while the shell was found to reduce in thickness from 460 to 220 nm as the n-Octadecane feeding increased. Conversely, the latent heat storage capacity increased from 50 to 132 J/g corresponding to the growth in actual n-Octadecane content from 25% to 67% as revealed by differential scanning calorimetry. The actual n-Octadecane content increased non-linearly along with the n-Octadecane feeding and reached a plateau at 66-67% corresponded to 3.44-3.69 core-to-monomer ratio. Finally, the capsules with the reasonable combination of structural and thermal properties were evaluated as a thermoregulating additive to a commercially available paint.

N-Octadecane Encapsulated by Assembled BN/GO Aerogels for Highly Improved Thermal Conductivity and Energy Storage Capacity.[Pubmed:37630901]

Nanomaterials (Basel). 2023 Aug 12;13(16):2317.

The rapid development of industry has emphasized the importance of phase change materials (PCMs) with a high latent-heat storage capacity and good thermal stability in promoting sustainable energy solutions. However, the inherent low thermal conductivity and poor thermal-cycling stability of PCMs limit their application. In this study, we constructed three-dimensional (3D) hybrid graphene aerogels (GBA) based on synergistic assembly and cross-linking between GO and modified hexagonal boron nitride (h-BN). Highly thermally conductive GBA was utilized as the supporting optimal matrix for encapsulating OD, and further implied that composite matrix n-Octadecane (OD)/GBA composite PCMs were further prepared by encapsulating OD within the GBA structure. Due to the highly thermally conductive network of GBA, the latent heat of the composite PCMs improved to 208.3 J/g, with negligible changes after 100 thermal cycles. In addition, the thermal conductivity of the composite PCMs was significantly enhanced to 1.444 W/(m.k), increasing by 738% compared to OD. These results sufficiently confirmed that the novel GBA with a well-defined porous structure served as PCMs with excellent comprehensive performance offer great potential for thermal energy storage applications.

Enhancing solar photothermal conversion and energy storage with titanium carbide (Ti(3)C(2)) MXene nanosheets in phase-change microcapsules.[Pubmed:37490836]

J Colloid Interface Sci. 2023 Nov 15;650(Pt B):1591-1604.

We propose to enhance photothermal conversion via doping titanium carbide (Ti(3)C(2)) MXene nanosheets on the surfaces of phase-change microcapsules consisted of the n-Octadecane core and styrene divinylbenzene copolymer shell. Detected by scanning electron microscopy, the microcapsules showed a usually circular form with an appropriate dispersion. The thermal properties of the microcapsules were characterized using the differential scanning calorimetry and thermal conductivity instruments, realizing an excellent phase-change enthalpy of around 140 J/g, high encapsulation ratio of over 64 %, good heat transfer of 0.294 +/- 0.003 W/(m.K), and great thermal reliability. More importantly, the microcapsules doped with Ti(3)C(2) MXene nanosheets reach a solar-to-heat conversion efficiency of 85 +/- 7 %, a substantial enhancement by 240 % in comparison with non-doping sample. The Ti(3)C(2) MXene-doped microcapsules with excellent heat storage and solar-to-heat conversion capabilities offer great potential for high-efficiency solar energy utilization and can be applied to thermal energy storage systems and direct absorption solar collectors.

Adaptive and Adjustable MXene/Reduced Graphene Oxide Hybrid Aerogel Composites Integrated with Phase-Change Material and Thermochromic Coating for Synchronous Visible/Infrared Camouflages.[Pubmed:36996266]

ACS Nano. 2023 Apr 11;17(7):6875-6885.

Although single-function camouflage under infrared/visible bands has made great advances, it is still difficult for camouflage materials to cope with the synergy detection spanning both visible and infrared spectra and adapt to complex and variable scenarios. Herein, a trilayer composite integrating thermal insulation, heat absorption, solar/electro-thermal conversions, and thermochromism is fabricated for visible and infrared dual camouflages by combining anisotropic MXene/reduced graphene oxide hybrid aerogel with the n-Octadecane phase change material in its bottom and a thermochromic coating on its upper surface. Benefiting from the synergetic heat-transfer suppression derived from the thermal insulation of the porous aerogel layer and the heat absorption of the n-Octadecane phase-change layer, the composite can serve as a cloak to hide the target signatures from the infrared images of its ambient surroundings during the day in the jungle and at night in all scenes and can assist the target in escaping visual surveillance by virtue of its green appearance. For desert scenarios, the composite can spontaneously increase its surface temperature via its solar-thermal energy conversion, merging infrared images of the targets into the high-temperature surroundings; meanwhile, it can vary the surface color from the original green to yellow, enabling the target to visually disappear from ambient sands and hills. This work provides a promising strategy for designing adaptive and adjustable integrated camouflage materials to counter multiband surveillance in complicated environments.

Hydrophobic aerogel-modified hemostatic gauze with thermal management performance.[Pubmed:36911208]

Bioact Mater. 2023 Feb 28;26:142-158.

Current hemostatic agents or dressings are not efficient under extremely hot and cold environments due to deterioration of active ingredients, water evaporation and ice crystal growth. To address these challenges, we engineered a biocompatible hemostatic system with thermoregulatory properties for harsh conditions by combining the asymmetric wetting nano-silica aerogel coated-gauze (AWNSA@G) with a layer-by-layer (LBL) structure. Our AWNSA@G was a dressing with a tunable wettability prepared by spraying the hydrophobic nano-silica aerogel onto the gauze from different distances. The hemostatic time and blood loss of the AWNSA@G were 5.1 and 6.9 times lower than normal gauze in rat's injured femoral artery model. Moreover, the modified gauze was torn off after hemostasis without rebleeding, approximately 23.8 times of peak peeling force lower than normal gauze. For the LBL structure, consisting of the nano-silica aerogel layer and a n-Octadecane phase change material layer, in both hot (70 degrees C) and cold (-27 degrees C) environments, exhibited dual-functional thermal management and maintained a stable internal temperature. We further verified our composite presented superior blood coagulation effect in extreme environments due to the LBL structure, the pro-coagulant properties of nano-silica aerogel and unidirectional fluid pumping of AWNSA@G. Our work, therefore, shows great hemostasis potential under normal and extreme temperature environments.

Phase-Change Microcapsules with a Stable Polyurethane Shell through the Direct Crosslinking of Cellulose Nanocrystals with Polyisocyanate at the Oil/Water Interface of Pickering Emulsion.[Pubmed:36614367]

Materials (Basel). 2022 Dec 21;16(1):29.

Phase-change materials (PCMs) attract much attention with regard to their capability of mitigating fossil fuel-based heating in in-building applications, due to the responsive accumulation and release of thermal energy as a latent heat of reversible phase transitions. Organic PCMs possess high latent heat storage capacity and thermal reliability. However, bare PCMs suffer from leakages in the liquid form. Here, we demonstrate a reliable approach to improve the shape stability of organic PCM n-Octadecane by encapsulation via interfacial polymerization at an oil/water interface of Pickering emulsion. Cellulose nanocrystals are employed as emulsion stabilizers and branched oligo-polyol with high functionality to crosslink the polyurethane shell in reaction with polyisocyanate dissolved in the oil core. This gives rise to a rigid polyurethane structure with a high density of urethane groups. The formation of a polyurethane shell and successful encapsulation of n-Octadecane is confirmed by FTIR spectroscopy, XRD analysis, and fluorescent confocal microscopy. Electron microscopy reveals the formation of non-aggregated capsules with an average size of 18.6 microm and a smooth uniform shell with the thickness of 450 nm. The capsules demonstrate a latent heat storage capacity of 79 J/g, while the encapsulation of n-Octadecane greatly improves its shape and thermal stability compared with bulk paraffin.

Interaction between indigenous hydrocarbon-degrading bacteria in reconstituted mixtures for remediation of weathered oil in soil.[Pubmed:36245697]

Biotechnol Rep (Amst). 2022 Oct 2;36:e00767.

It has been demonstrated that biostimulation is necessary to investigate the interactions between indigenous bacteria and establish an approach for the bioremediation of soils contaminated with weathered oil. This was achieved by adjusting the carbon (C)/nitrogen (N)/phosphorus (P) ratio to 100/10/1 combined with the application of 0.8 mL/kg Tween-80. In addition, three indigenous bacteria isolated from the same soil were introduced solely or combined concomitantly with stimulation. Removal of n-alkanes and the ratios of n-heptadecane to pristane and n-Octadecane to phytane were taken to indicate their biodegradation performance over a period of 16 weeks. One strain of Pseudomonas aeruginosa D7S1 improved the efficiency of the process of stimulation. However, another Pseudomonas aeruginosa, D5D1, inhibited the overall process when combined with other bacteria. One strain of Bacillus licheniformis D1D2 did not affect the process significantly. The Fourier transform infrared analysis of the residual hydrocarbons supported the conclusions pertaining to the biodegradation processes when probing the modifications in densities and stretching. The indigenous bacteria cannot mutually benefit from their metabolisms for bioremediation if augmented artificially. However, the strain Pseudomonas. aeruginosa D7S1 was able to perform better alone than in a consortium of indigenous bacteria.

Bioinspired Multilayer Structures for Energy-Free Passive Heating and Thermal Regulation in Cold Environments.[Pubmed:36206445]

ACS Appl Mater Interfaces. 2022 Oct 19;14(41):46569-46580.

Passive thermal regulation has attracted increasing interest owing to its zero-energy consumption capacity, which is expected to alleviate current crises in fossil energy and global warming. In this study, a biomimetic multilayer structure (BMS) comprising a silica aerogel, a photothermal conversion material (PTCM), and a phase change material (PCM) layer is designed inspired by the physiological skin structure of polar bears for passive heating with desirable temperature and endurance. The transparent silica aerogel functions as transparent hairs and allows solar entry and prevents heat dissipation; the PTCM, a glass plate coated with black paint, acts as the black skin to convert the incident sunlight into heat; and the PCM composed of n-Octadecane microcapsules stores the heat, regulating temperature and increasing endurance. Impressively, outdoor and simulated experiments indicate efficient passive heating (increment of 60 degrees C) of the BMS in cold environments, and endurance of 157 and 92 min is achieved compared to a single aerogel and PTCM layer, respectively. The uses of the BMS for passive heating of model houses in winter show an increase of 12.1 degrees C. COMSOL simulation of the BMSs in high latitudes indicates robust heating and endurance performance in a -20 degrees C weather. The BMS developed in this study exhibits a smart thermal regulation behavior and paves the way for passive heating in remote areas where electricity and fossil energy are unavailable in cold seasons.

Experimental Measurement and Thermodynamic Modeling of the Wax Disappearance Temperature (WDT) for a Quaternary System of Normal Paraffins.[Pubmed:35647458]

ACS Omega. 2022 May 13;7(20):16928-16938.

Normal paraffin (N-alkane)-based wax is well known as a severe problem in petroleum production, transportation, and processing. Implementing suitable solutions for wax-related problems requires vast technical knowledge and investigation of the wax disappearance temperature (WDT) of multicomponent systems in petroleum-dominated systems. In this study, the WDTs of a quaternary system comprising different mixtures of n-undecane + n-tetradecane + n-hexadecane + n-Octadecane were measured using a visual-based diagnosis apparatus under atmospheric pressure. On the other hand, the WDTs of the studied systems are predicted by applying a solid solution model without any adjustable parameter. Two approaches namely gamma-phi and gamma-gamma are assessed. In the (gamma-phi) approach, perturbed-chain statistical associating fluid theory (PC-SAFT) is applied for liquid phase modeling, while the solid phase is described using different activity coefficient models. In the (gamma-gamma) approach, nonidealities of both the liquid and solid phases are investigated using different combinations of activity coefficient models such as ideal solution, regular solution theory, predictive Wilson, predictive UNIQUAC, and UNIFAC. Comparison of experimental data and thermodynamic modeling results indicates that applying the predictive UNIQUAC model for describing the nonideality of the solid phase and the regular solution model for the liquid phase is the best combination for the aforementioned system with the average absolute deviation (AAD) of 0.8 K.

[Simultaneous determination of seven dimethylcyclosiloxanes in cosmetics of different formulation systems by gel permeation chromatography purification-gas chromatography-tandem mass spectrometry].[Pubmed:35616203]

Se Pu. 2022 Jun;40(6):576-583.

At present, the addition of dimethylcyclosiloxanes (DMCs) in cosmetics is being debated and no substantial progress has been made in their safety risk assessment because of the lack of a suitable analytical method. Therefore, it is of theoretical and practical significance to establish a method suitable for the determination of DMCs in cosmetics with different formulation systems. Accordingly, a method based on gel permeation chromatography (GPC) purification combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of seven DMCs in cosmetics. The cosmetic samples were extracted by ethyl acetate-cyclohexane (1ratio1, v/v), purified by gel permeation chromatography, separated on a DB-5ms column (30.0 mx0.25 mmx0.25 mum), confirmed and detected by gas chromatography-tandem mass spectrometry in the selected reaction monitoring (SRM) mode, and quantified by the internal standard method with n-hexadecane as the internal standard. Experiments were carried out using n-tetradecane, n-hexadecane, and n-Octadecane as the internal standards, and based on the retention time in GPC and GC, n-hexadecane was found to be the suitable choice for further analyses. The extraction efficiency for the target compounds was tested in different solvents such as methanol, n-hexane, acetonitrile, ethyl acetate, and ethyl acetate-cyclohexane (1ratio1, v/v). Given the high recovery, ethyl acetate-cyclohexane (1ratio1, v/v) was selected as the extraction solvent for analyses. Among the three purification methods (analysis without purification, solid-phase extraction (SPE), and GPC purification), GPC was selected as the best method because of the minimal matrix interference to the target compounds. Under the optimized conditions, the seven DMCs showed good linearities in the range of 0.05-1.0 mg/L. The correlation coefficients (r) were 0.994-0.998, which were greater than the required of the specification (r>/=0.990). The limits of detection (LODs, S/N=3) were 0.04-0.08 mg/kg, and the limits of quantification (LOQs, S/N=3) were 0.12-0.24 mg/kg. According to the cosmetic matrix in different formulation systems, standard addition recovery tests at three levels of low, medium, and high were carried out. The average recovery rates of the targets were 85.3%-108.8%. The relative standard deviations (RSDs, n=6) were 3.1%-9.4%. The established method was also employed for the analysis of cosmetics in the market, and octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) were detected at various levels in the cosmetics. The method established in this study has the advantages of operational simplicity, high sensitivity, and good reproducibility, and it allows for the determination of seven DMCs in cosmetics with different formulation systems. The establishment of this method provides a basis for the quality supervision and inspection of DMCs in cosmetics in China, in addition to providing technical support for follow-up health and safety evaluation.

Effects of Dopamine-Modified and Organic Intercalation on the Thermophysical Properties of Octadecane/Expanded Vermiculite Composite Phase Change Materials.[Pubmed:35559182]

ACS Omega. 2022 Apr 12;7(16):13538-13545.

For phase change materials (PCMs) confined in porous structure, the interface interaction between the PCM and the porous skeleton is the key factor to determine the thermal storage performance of PCM. In this study, the modified expanded vermiculite (EVM) was prepared by dopamine modification and DTA(+) intercalation method and a series of EVM-based composite phase change materials with form shape (fs-CPCMs) were prepared by physical impregnation using n-Octadecane as PCMs. The heat storage performance of the composite phase change materials were improved obviously, and the encapsulation ratio is increased to 84.7% and 83.1%. The nonisothermal crystallization process of prepared composite phase change material were further studied. The effects of dopamine modification and organic intercalation on the encapsulation performance of EVM-based fs-CPCMs were analyzed. The results of XRD, FT-IR, thermal cycle, and TGA tests showed that EVM-based composite phase change materials had good chemical compatibility, thermal reliability, and thermal stability. This study provides a theoretical basis for the preparation of EVM-based fs-CPCMs with high thermal stability and good heat storage performance.

Synthesis and Properties of Shape-Stabilized Phase Change Materials Based on Poly(triallyl isocyanurate-silicone)/n-Octadecane Composites.[Pubmed:35557688]

ACS Omega. 2022 Apr 21;7(17):14952-14960.

Triallyl isocyanurate (TAIC) was modified by hydrogen silicone oil (SO) via hydrosilylation reaction, generating the original TAIC-SO (TS) intermediate. After the cross-linking polymerization of TS (PTS), the shape-stabilized phase change materials (PCMs) consisting of n-Octadecane and silicone-modified supporting matrix were first synthesized by an in situ reaction. Remarkably, the novel three-dimensional PTS network effectively prevents the leakage of n-Octadecane during its phase transition, solving the prominent problem of solid-liquid PCMs in practical applications. Moreover, n-Octadecane is uniformly dispersed in the continuous and high-strength cross-linked network, contributing to excellent thermal reliability and structural stability of PTS/n-Octadecane (TSO) composites. Differential scanning calorimetry analysis of the optimal TSO composite indicates that melting and freezing temperatures are 29.05 and 22.89 degrees C, and latent heats of melting and freezing are 130.35 and 129.81 J/g, respectively. After comprehensive characterizations, the shape-stabilized TSO composites turn out to be promising in thermal energy storage applications. Meanwhile, the strategy is practical and economical due to its advantages of easy operation, mild conditions, short reaction time, and low energy consumption.

Enhanced Thermal Energy Storage of n-Octadecane-Impregnated Mesoporous Silica as a Novel Shape-Stabilized Phase Change Material.[Pubmed:35449958]

ACS Omega. 2022 Mar 31;7(14):12222-12230.

A series of n-Octadecane/mesoporous silica (C(18)/MS) shape-stabilized phase change materials (SSPCMs) with varying C(18) content were prepared, and the effects of adsorbed C(18) distributed within porous MS on the thermal properties were analyzed. As characterized, C(18) was first infiltrated into the mesoporous space, resulting in a SSPCM with a maximum of approximately 52 wt % C(18). Additional adsorption of C(18) occurred on the external surface of MS. Consequently, the optimum 70 wt % C(18) SSPCM had no C(18) leakage and exhibited a heat storage capacity of 135.6 J/g and crystallinity of 83.5%, which were much larger than those of 52 wt % C(18) SSPCM (60.2 J/g and 68.2%, respectively). The prepared C(18)/MS SSPCMs showed excellent thermal stability and thermal reliability up to 1000 accelerated thermal cycle tests. Moreover, the C(18)/MS SSPCM incorporated in gypsum effectively reduced the temperature changes compared with the original gypsum, suggesting the promising application of the prepared C(18)/MS SSPCM for energy-saving building applications.