Paraffin Wax Research Articles

Ice templated honeycomb-like porous copper foam to improve the anisotropic thermal transfer property of phase change composites

This study explores the use of copper foam (CF) as a thermally conductive scaffold for phase change materials (PCMs), enhancing shape stability. Employing the ice template method (ITM), we fabricate a CF with a low-density, honeycomb structure and anisotropy from flake copper powders. The resulting phase change composites (PCCs), infused with paraffin wax (PW), showcase high thermal conductivity and shape retention compared to pure PW, with anisotropic heat flow due to directional channels in the CF. With a 34.4 wt% filling ratio, the PCCs achieve axial and lateral thermal conductivities of 2.85 W m−1 K−1 and 1.51 W m−1 K−1, respectively, and a thermal storage enthalpy of 158.18 J g−1. This work presents a novel method for advanced thermal energy storage and management, indicating the promise of ITM-derived CF in high-performance PCCs for diverse applications.

Characterization and identification of long-chain hydrocarbon-degrading bacterial communities in long-term chronically polluted soil in Ogoniland: an integrated approach using culture-dependent and independent methods

Escalating oil consumption has resulted in an increase in accidental spills of petroleum hydrocarbons, causing severe environmental degradation, notably in vulnerable regions like the Niger Delta. Complex mixture of these hydrocarbons particularly long-chain alkanes presents unique challenges in restoration of polluted environment due to their chemical properties. This study aimed to investigate the long-chain hydrocarbon-degrading bacterial communities within long-term chronically polluted soil in Ogoniland, by utilizing both traditional cultivation methods and modern culture-independent techniques. Results revealed that surface-polluted soil (SPS) and subsurface soil (SPSS) exhibit significantly higher total organic carbon (TOC) ranging from 5.64 to 5.06% and total petroleum hydrocarbons (TPH) levels ranging from 36,775 ppm to 14,087 ppm, compared to unpolluted soil (UPS) with 1.97% TOC and 479 ppm TPH, respectively. Analysis of carbon chain lengths reveals the prevalence of longer-chain alkanes (C20-28) in the surface soil. Culture-dependent methods, utilizing crude oil enrichment (COE) and paraffin wax enrichment (PWE), yield 47 bacterial isolates subjected to a long-chain alkane degradation assay. Twelve bacterial strains demonstrate significant degradation abilities across all enriched media. Three bacterial members, namely Pseudomonas sp. (almA), Marinomonas sp. (almA), and Alteromonas (ladA), exhibit genes responsible for long-chain alkane degradation, demonstrating efficiency between 50 and 80%. Culture-independent analysis reveals that surface SPS samples exhibit greater species richness and diversity compared to subsurface SPSS samples. Proteobacteria dominates as the phylum in both soil sample types, ranging from 22.23 to 82.61%, with Firmicutes (0.2–2.22%), Actinobacteria (0.4–3.02%), and Acidobacteria (0.1–3.53%) also prevalent. Bacterial profiles at genus level revealed that distinct variations among bacterial populations between SPS and SPSS samples comprising number of hydrocarbon degraders and the functional predictions also highlight the presence of potential catabolic genes (nahAa, adh2, and cpnA) in the polluted soil. However, culture-dependent analysis only captured a few of the dominant members found in culture-independent analysis, implying that more specialized media or environments are needed to isolate more bacterial members. The findings from this study contribute valuable information to ecological and biotechnological aspects, aiding in the development of more effective bioremediation applications for restoring oil-contaminated environments.

Solid Foam Insertion to Increase PCM-Based Thermal Energy Storage System Efficiency: Experimental Test and Numerical Simulation of Spherical Macrocapsules

Phase change materials (PCMs) are an interesting solution to increase the efficiency of thermal energy storage (TES) systems. The present work explores, with an experimental and computational study, the behavior of a paraffin wax encapsulated in a spherical containment system during the melting and solidification phases. The experimental tests were conducted by immersing the spherical capsule in a thermostatic water bath at different temperatures and measuring the temperatures at four different points inside the capsule. A two-dimensional CFD model of the sphere was then applied to investigate the effect of the insertion of a solid foam into the sphere to increase the system’s responsiveness under demanding conditions. In addition, an analysis of the solidification process considering two different wall materials (HDPE and aluminum) with different thermal conductivity was performed. The results suggest that embedded foams can represent a useful tool to increase the efficiency of a PCM-based TES, but, at the same time, they also highlight that a considerable increase in thermal conductivity is required to achieve significant advantages with respect to pure PCM systems.

A Numerical Study of the Effect of Water Speed on the Melting Process of Phase Change Materials Inside a Vertical Cylindrical Container

The present work offers a thorough analysis of the impact of water velocity on phase change material (PCM) melting in a vertical cylindrical container. A detailed quantitative analysis uses sophisticated numerical techniques, namely the ANSYS/FLUENT 16 program, to clarify the complex relationship between enthalpy and porosity during the melting process. The experimental focus is on phase transition materials based on paraffin wax, particularly Rubitherm RT42. This study’s primary goal is to evaluate the effects of different water velocities (that is, at velocities of 0.01 m/s, 0.1 m/s, and 1 m/s) on the PCM’s melting behavior at a constant temperature of 333 K. This work intends to make a substantial contribution to the development of thermal energy storage systems by investigating new perspectives on PCM behavior under various flow circumstances. The study’s key findings highlight the possible ramifications for improving PCM-based thermal energy storage devices by revealing significant differences in melting rates and behavior that correlate to changes in water velocities. Future research is recommended to explore the impact of temperature variations, container geometries, and experimental validation to improve the accuracy and practicality of the results and to advance the creation of sustainable and effective energy storage solutions.

The influence of palm oil-derived plasticizers and lubricants on the rheological and mechanical properties of styrene butadiene rubber

Researchers have recently focused on green processing aids made from plants and vegetables to avoid the high concentration of polycyclic aromatic hydrocarbons (PAHs) from petroleum-based processing oils, which is hazardous to human health. This paper focuses on the effect of lubricants and plasticisers produced from palm oil on the rheological, mechanical and thermal aging properties of styrene-butadiene rubber (SBR). These lubricants and plasticisers are known as glycerol trioleate (GTO), n-butyl stearate (NBS), ethylene bis-steramide (EBS), ethylene bis-oleamide (EBO), pentaerythritol tetrastearate (PETS) and stearyl stearate. The abrasion performance, visual inspection appearance, and cure characteristics of the lubricants and plasticisers on SBR were examined and compared to processing oil-treated distillate aromatic extract (TDAE), paraffin wax, microcrystalline wax, polyethylene (PE) wax, epoxidised soybean oil (ESBO), and stearic acid. It discovered that rubber compounds based on GTO, stearic acid, and EBS exhibited better abrasion resistance and cure properties than rubber compounds based on processing oil. These samples were selected and subjected to mechanical properties, thermal aging effects analysis and comparison with processing oil. Tensile strength shows that SBR with EBS (22.49 MPa) and EBS with GTO (EBS/GTO; 21.25 MPa) are closely similar to SBR compounds with processing oil (21.02 MPa). The findings imply that EBS and EBS/GTO, green plasticisers and lubricants, are viable alternatives to petroleum-based processing oils while being cost-effective for tire production.

Correlation study of thermal charging, discharging, and efficiency of graphene oxide-reinforced paraffin wax for thermal energy storage system

Nanocomposites, produced through mechanical blending, serve to enhance thermal performance of heat exchangers, solar collectors, and photovoltaic-thermal systems. This work employs an experimental methodology to assess the thermal charging (TC) and thermal discharging (TDC) of a composite generated by mixing graphene oxide (GO) and paraffin wax. TC and TDC of the GO-reinforced paraffin wax-based phase change material (PCM) have been examined across different flow rates (0.375, 0.75, and 1.5 L/min) and concentrations of GO (ranging from 0.25 to 1.00 vol%). The results exhibit a direct correlation between TC, TDC and efficiency, and reaction parameters (flow rate and volume concentration of GO). The experimental and predicted values of TCs, TDCs, and efficiencies fell ±15% (for TC and TDC), and ±9% for thermal efficiency, demonstrating a satisfactory level of agreement. This holds a practical application and valuable predictive tool for estimating TC, TDC, and thermal efficiency on known flow rates and concentrations of GO in wax-based PCMs.

Placental Vimentin Expression in Preeclampsia and Gestational Diabetes Mellitus

OBJECTIVE: This study investigated vimentin expression in placentas of patients with preeclampsia and gestational diabetes mellitus (GDM). STUDY DESIGN: Placentas of preeclamptic women (n=25), women with GDM (n=25), and control cases (n=25) were enrolled in this study. Placental samples were fixed in zinc-formalin and further processed for paraffin wax tissue embedding. Demographic and laboratory parameters of patients were recorded. Vimentin immune activity was analyzed in the placental sections with immunohistochemistry. Sections were imaged and analyzed under a light microscope. A semiquantitative measurement was done between groups by comparing the Vimentin signal and significance was calculated. Network construction and pathway enrichment analysis were conducted using Cytoscape (v3.10.1) and ShinyGO, respectively. RESULTS: Vimentin expression was high in the placental sections of the control group. The preeclampsia group showed positive Vimentin expression in cytotrophoblast and syncytiotrophoblast cells and connective tissue of placental villi in the preeclampsia group. Vimentin expression was generally recorded as negative in placental villi, fibrinoid substances, and connective tissue cells in the GDM group. Bioinformatic analysis showed that the AGE-RAGE signaling pathway and cancer-related pathways were mainly observed in Vimentin-associated pathways, which finally activate inflammatory pathways in both preeclampsia and GDM. CONCLUSION: Vimentin expression patterns in placental tissue sections reveal nuanced regulatory mechanisms, emphasizing the need for further exploration into the functional roles of vimentin in placental physiology and pathology.

Thermal Performances and Stability of Capric Acid–Stearic Acid–Paraffin Wax Adsorbed into Expanded Graphite in Vacuum Conditions

Thermal Performances and Stability of Capric Acid–Stearic Acid–Paraffin Wax Adsorbed into Expanded Graphite in Vacuum Conditions

Predicting Solvation Free Energies from the Minnesota Solvation Database Using Classical Density Functional Theory Based on the PC-SAFT Equation of State.

We critically assess the capabilities of classical density functional theory (DFT) based on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state to predict the solvation free energies of small molecules in various hydrocarbon solvents. We compare DFT results with experimental data from the Minnesota solvation database and utilize statistical methods to analyze the accuracy of our approach, as well as its weaknesses. The mean absolute error of the solvation free energies is 3.7 kJ mol-1 for n-alkane solvents, ranging from pentane to hexadecane, with 473 solute-solvent systems. For solvents consisting of cyclic hydrocarbons (cyclohexane, benzene, toluene, and ethylbenzene) with 245 solute-solvent systems, we report a slightly larger mean absolute error of 4.2 kJ mol-1. We identify three possible sources of errors: (i) the neglect of solute-solvent and solvent-solvent Coulomb interactions, which limits the applicability of PC-SAFT DFT to nonpolar and weakly polar molecules; (ii) the solute's Lennard-Jones parameters supplied by the general AMBER force field, which are not parametrized toward solvation free energies; and (iii) the application of the Lorentz-Berthelot combining rules to the dispersive interactions between a segment of the PC-SAFT solvent and a Lennard-Jones interaction site of the solute. The approach is more accurate than standard implementations of phenomenological models in common chemistry software packages, which exhibit mean absolute errors larger than 9.12 kJ mol-1, even though newer phenomenological models achieve a mean absolute error of about 2 kJ mol-1. PC-SAFT DFT is more computationally efficient than state of the art explicit molecular simulations in combination with free energy perturbation methods. It is predictive with respect to solvation free energies, i.e., the input for the model is the (element-specific) molecular force field, the solute configuration from molecular dynamics simulations, and the (substance-specific) PC-SAFT parameters. The PC-SAFT parametrization uses pure-component data and does not require experimental solvation free energies. The PC-SAFT equation of state, without applying a DFT formalism, can also be used to calculate solvation free energies, provided that the PC-SAFT parameters for the solute are available. A large number of substances was recently parametrized by members of our group (Esper, T.; Bauer, G.; Rehner, P.; Gross, J. Ind. Eng. Chem. Res. 2023, 62), which enables a comparison to the DFT approach for 103 substances. Accurate results are obtained from the PC-SAFT equation of state with an MAE below 2.51 kJ mol-1. The DFT approach does not require PC-SAFT parameters for the solute and can be applied to all solutes that can be represented by the molecular force field.

The effect of heat flux on enhancement heat transfer mechanism in copper metal foam composite paraffin wax during melting process: Experimental and simulation research

To investigate the effect of heat flux on the enhanced heat transfer in phase change materials (PCMs) composed of copper metal foam (CMF) and paraffin wax (PX), a semi-cylindrical visualized heat storage device with a varied heat flux of 7.3 kW/m2, 8.5 kW/m2, 9.7 kW/m2, and 10.9 kW/m2 was established in this paper. Moreover, a 3-D mathematical model of composite phase change materials (CPCMs) was established using hybrid grid to study the temperature distribution, imbalance effect, flow, heat transfer mechanisms, and heat storage performance during the melting process. The results showed that the melting time of the CPCMs decreased as the heat flux increased. Compared with a heat flux of 7.3 kW/m2, the melting time was shortened by 10.05 %, 20.71 %, and 27.21 %, respectively. In addition, the Rayleigh number (Ra) increased with the increase in heat flux, and the amplitudes of Ra were 1.45×108,1.54×108,1.61×108, and 1.74×108, respectively, which indicated that the higher the heat flux, the larger the amplitudes. Moreover, the heat transfer mechanism during the melting process was dominated by conduction; however, with the increase in heat flux, the maximum flow velocity of the liquid paraffin increased, which caused the proportion of natural convection to increase from 27.80 % to 31.30 %. Hence, the integrated heat transfer coefficient of CPCMs increased from 5.69 W/(m·K) to 5.81 W/(m·K). However, the temperature imbalance effect of the CPCMs was exacerbated, as evidenced by the increased maximum temperature difference in the vertical direction of the center of the CPCMs from 24.7 K to 35.6 K. Besides, the heat storage performance was enhanced. Compared with a heat flux of 7.3 kW/m2, the heat storage capacities of the CPCMs increased by 4.21%, 9.46%, and 12.66 % with increasing heat flux, and the heat storage rates of the CPCMs increased by 15.3 %, 34.9 %, and 52.3 %, respectively. Furthermore, the relative error of the overall melting time was 3.4 %, indicating that the model provided reasonable predictions.

Photocatalytic dye decomposition by bio-enzyme enriched TiO2/g-C3N4 nanocomposite and assessment of toxicity of resultant water using Catla catla fish

Nanocomposite of TiO2/g-C3N4 enriched with enzyme prepared from bio-wastes (fruit and vegetable peels) was synthesized for the photocatalytic decomposition of toxic dye solution and the toxicity, if any, of the resultant water obtained after treatment was tested by exposing freshwater Catla catla fish to the treated water. The result was compared with the toxicity of the untreated test dye solution. The bio-enzyme powered TiO2/g-C3N4 nanocomposite exhibits enhanced degradation efficiency of 99% for methylene blue (MB) and 95% for methyl orange (MO) in 45 min, whereas the bare TiO2/g-C3N4 exhibits efficiencies of only 92% for MB and 90% for MO. The quantitative study showed that enzymes present in the system viz., protease, peroxidase, cellulase, amylase and lipase act as supporting catalyst and thereby improve the photocatalytic ability of the synthesized nanocomposite for effective dye degradation. The results showed the combined effects of composite partners and the bio-cocatalyst. Characterization of the prepared samples was performed using XRD, FTIR, SEM, RAMAN, UV, EDS and XPS and the results are correlated with the application concerned. The histology study was performed through paraffin wax method to evaluate the toxic effects of the industrial dyes on Catla catla fish by exposing the fish to different aquarium systems (Dye, Control and Treated water).

Experimental study of phase change material (PCM) based spiral heat sink for the cooling process of electronic equipment

Today, every device that a person uses depends on electronic equipment, frequent and long-term use of it causes to heat up and as a result, slow down the speed and performance of that device. In more important and sensitive equipment such as medical equipment, slow speed and reduced performance cause irreparable damage. Therefore, to cool these devices, their internal electronic equipment must be cooled. In studies by others, the simultaneous use of several phase change materials and airflow in the form of layer-by-layer contact was usually less studied. In this study, using CNC machining, a heatsink consisting of 2 spirals was produced. In the first spiral, PCM Paraffin Wax with different volume percentages and in the second spiral, the presence or absence of forced airflow in heat transfer rate 2.9 W to 3.7 W was tested with a step of 0.4 W and the results were that by adding %50 PCM and adding 100 % PCM to the system, its performance increases by 7.19 % and 44.91 %, respectively, which shows using the maximum volume capacity of PCM increases efficiency. Also, by adding forced airflow to the system, its performance has increased by 7.71 %. It can be said that if the forced airflow in the system is used layer by layer, it prevents the heat from concentrating in certain parts of the heatsink and the circuit, which results in the same heating of the whole system and the heat is evenly distributed throughout the heatsink.

Enhancement of solar evacuated tube unit filled with nanofluid implementing three lobed storage unit equipped with fins

This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.

Growth and characterization of 6LiI:Ag crystal scintillators for thermal and epithermal neutron detection on the lunar surface

This paper discusses crystal growth and characterization of 1.0-inch 6LiI:Ag scintillators for thermal and epithermal neutron detection on the lunar surface as part of the Lunar Vehicle Radiation Dosimeter project. Zone purification method was employed to purify the raw material of 6LiI, and the crystals were grown using the Bridgman method. X-ray luminescence spectrum was measured to confirm the presence of Ag+ in the crystal lattice of 6LiI. The feasibility of neutron detection under 252Cf fast neutron irradiation was investigated. A hydrogen-rich paraffin wax moderator was used to slow down fast neutrons to obtain thermal and epithermal neutrons. The charge comparison method was used to perform pulse shape discrimination. The maximum value of the Figure of Merit was obtained to be 1.3, which demonstrates the capability of using 6LiI:Ag crystal scintillators in high neutron and gamma mixed fields. The energy resolution of the thermal neutron peak varied with the thickness of scintillators, achieving 12.0 % for the 0.5 cm thick samples. The potential for further improvement of the scintillation performance of 6LiI:Ag crystal relies on reducing impurities and color centers.

Efficient simulation of bitter gourd drying in active solar dryer: A state-of-the-art model

Greenhouse drying system is used to dry agricultural products or low-temperature thermal drying using a greenhouse structure. In this paper, an experimental and simulation study is carried out to evaluate the drying performances of an active solar greenhouse dryer using COMSOL Multiphysics. The experimental setup includes a compact thermal storage-based greenhouse dryer (1.5 m × 1.0 m x 0.5 m) equipped with a black gravel-covered Aluminium jacket and 35 kg of paraffin wax for heat retention which is located on the floor of the dryer. The experiments were conducted in Ranchi, India (23.34 °N, 85.30 °E) under clear sky conditions in the month of May. The amount of solar radiation (global solar radiation) varied from (630 W/m2 to 1052 W/m2) with an average of 936 W/m2, ambient air temperature (30.2 °C–38.2 °C), air relative humidity (31.6 %–34.6 %), and wind speed (0.9–1.0 m/s). The inside dryer temperature, humidity, wind speed, and floor temperature were also measured every hour. The average values of these parameters were 59.1 °C, 30.2 %, 0.91 m/s, and 69.1 °C, respectively. The FE (finite element) modelling finds out the maximum temperature in drying products, floor and dryer's outlet is 55.3 °C,72.4 °C and 67.4 °C, respectively at 13:00 h. The proposed dryer costs 19633.50 INR with an embodied energy of 1358.01 kW h. The proposed dryer has a break-even period of 1.87 years, and its lifespan is 35 years. During this time, the net CO2 emission was found to be 21.45 tonnes, and the earned carbon credit varies from 1505.01 to 30030.00 INR. The result shows that the drying efficiency is 42.52 %, reducing the initial moisture content from 88.64 % to 2.28 % within five consecutive hours. The energy and exergy efficiencies of the dryer are found to be 61.84 % and 56 % respectively. The system is a viable, sustainable choice for the large-scale production of bitter gourd flakes.

Molecular Dynamics Study of Nanoribbon Formation by Encapsulating Cyclic Hydrocarbon Molecules inside Single-Walled Carbon Nanotube.

Carbon nanotubes filled with organic molecules can serve as chemical nanoreactors. Recent experimental results show that, by introducing cyclic hydrocarbon molecules inside carbon nanotubes, they can be transformed into nanoribbons or inner tubes, depending on the experimental conditions. In this paper, we present our results obtained as a continuation of our previous molecular dynamics simulation work. In our previous work, the initial geometry consisted of independent carbon atoms. Now, as an initial condition, we have placed different molecules inside a carbon nanotube (18,0): C5H5 (fragment of ferrocene), C5, C5+H2; C6H6 (benzene), C6, C6+H2; C20H12 (perylene); and C24H12 (coronene). The simulations were performed using the REBO-II potential of the LAMMPS software package, supplemented with a Lennard-Jones potential between the nanotube wall atoms and the inner atoms. The simulation proved difficult due to the slow dynamics of the H abstraction. However, with a slight modification of the parameterization, it was possible to model the formation of carbon nanoribbons inside the carbon nanotube.

Analysis of Solar Water Heater with Modification Absorber Plate Integrated Thermal Storage

In various countries worldwide, solar water heater systems (SWHs) are utilized as devices that harness solar energy as a primary energy source. This study investigates the performance of SWHs numerical simulation by integrating phase change material (PCM) paraffin wax onto an absorber plate collector at the bottom for thermal storage. This study presents the thermal performance of a SWHs that uses an absorber plate with PCM for thermal energy storage. In this test, four variations of the model tested, namely a) standard flat plate (SFP), b) standard flat plate with PCM storage thickness 10mm (SFP+PCM 10mm), c) standard flat plate with PCM storage thickness 7mm (SFP+PCM 7mm), and d) standard flat plate with PCM storage thickness 4mm (SFP+PCM 4mm), were investigated using numerical simulation. Initially, an analytical investigation was conducted to examine the material qualities of paraffin wax utilised for phase change material (PCM) storage. The SWH systems were subsequently imported and simulated under three different levels of continuous solar radiation: 400 W/m2 700 W/m2 and 1000 W/m2. The simulation incorporates the use of computational fluid dynamics (CFD) tools. The results of the study revealed that the collector of the SWH system, which utilised an absorber plate containing phase change material (PCM) storage, demonstrated exceptional performance. Models with a thickness of 7mm PCM or SFP+PCM 7mm have the highest efficiency compared to other models with an efficiency value of 64%. There is a 3-4% increase in efficiency with variations in models that use PCM thermal storage compared to models that do not use PCM thermal storage.

Alterations in paraffin wax crystal networks induced by asphaltenes and pour point depressants, investigated by atomic force microscopy

Wax crystallization in pipelines in cold environments is a key factor affecting flow assurance during crude oil production. Polar crude oil components, such as asphaltenes, and polymeric pour point depressants (PPDs) have been demonstrated to interact with wax during gelation and crystallization through complex formation during nucleation or crystal growth alteration which leads to co-crystallization. This study introduces a methodology based on atomic force microscopy (AFM) to characterize features of solid surfaces precipitated from model wax, wax-PPD, wax-asphaltene and asphaltene systems. Height data collected from AFM measurements enabled the quantification of modifications in crystal sizes and shapes induced by the presence of asphaltenes and PPDs. The 2D Fourier transform of the height was used to generate statistics for the frequency of height amplitude, revealing information about the pore size and the height patterns. A stiffness/elasticity analysis was used to calculate the Young Modulus of the upper layers. In wax and wax-asphaltene systems, two nano-scale layers with different Young Modulus profiles emerged. The nano-scale layer on the top was softer and corresponded to more amorphous wax crystal networks with trapped dissolved wax. The nano-scale layer on the bottom was stiffer, comprising of more crystalline structures, corresponding to wax crystals with lower deviations from full crystallinity, with properties independent of asphaltene concentration. A bilayer did not form in the presence of PPD, which prevented the formation of amorphous phases with trapped dissolved wax or gel. After a methodology for model systems was established, the focus moved to systems based on production wax i.e. recovered from deposits. This was complemented by a comparison between model precipitation conditions and precipitation by cold finger, resembling industrial processes. Results highlighted the effect of change in chemical composition on topography, elasticity and adhesion of the surface. AFM provided new insights into wax crystallization patterns in the presence of inhibitors, which can be used to quantify the extent of wax-inhibitor interactions and project it on production systems. The method could be used to explain macro-scale rheological properties of oils during flow assurance in the future.

Carbonized-wood based composite phase change materials loaded with alumina nanoparticles for photo-thermal conversion and energy storage

The integration of photo-thermal conversion and thermal energy storage is an efficient way to improve the solar energy utilization. Phase change material (PCM) with excellent thermal storage ability is often used in solar energy storage systems. However, PCMs suffer from liquid leakage, low thermal conductivity and insensitivity to light. This work used sol-gel and high-temperature calcination to modify the carbonized-wood (CW) by alumina nanoparticles loaded in the pores to improve the above issues. The combined microscopic and macroscopic test results showed that the modified carbonized-wood provided a good support structure for the paraffin wax (PW) to prepared carbonized-wood based composite phase change materials (CCPCMs). The CCPCMs exhibit noticeable hydrophobicity as well. The thermophysical properties of the CCPCMs were tested and the results showed that the CCPCMs possessed excellent encapsulation rate (85.98 %–91.65 %), enthalpy of phase transition (166.3–176.6 J/g), and good thermal reliability. By high-temperature carbonization and loading of alumina nanoparticles, the photo-thermal conversion efficiency of CCPCMs was optimized to 95.13 % and the surface overheating was weakened. In the simulation experiment of glass chamber, CCPCMs can store heat while maintaining the uniformity of the chamber's temperature. In conclusion, the novel CCPCMs developed in this work are highly promising in the field of solar thermal utilization and storage.

Vitrimeric phase change material facilitating 3D-structured boron nitride network for reliable thermal conductive interface materials

Phase change materials (PCMs) shows great promise as thermal interface materials (TIMs) due to their compliance and thermal management properties from solid-liquid phase transition characteristics. However, the significantly reduced thermal conductivity resulting from that randomly dispersed thermal conductive fillers susceptible to localized volume change by solid-liquid phase transition deteriorates the reliable heat transfer of TIM but is often overlooked. In this work, 3D-structured network of boron nitride (BN) fillers is created in vitrimeric PCM (vPCM) consisting of dynamic covalent crosslinked polyolefin elastomer (POE)/paraffin wax (PW) blends. The resulted composites with interconnected BN network show a through-plane thermal conductivity (κ⊥) of 3.08 W m−1 K−1 at 29.8 vol% BN. Significantly, the composites can keep the BN network continuous when heated, and remain κ⊥ of about 1.4 W m−1 K−1 after the solid-liquid phase transition of PW, which ensures reliable heat transfer when achieving thermal management by melting endotherm of PW. Moreover, the composites conform to the surface topography of sandwiching surfaces through solid plasticity under low stress when the crosslinked network rearranges via the exchange of dynamic covalent bonds activated by the melting of POE, reducing the thermal contact resistance. When the composites are used as TIM through thermally triggered reconfigurable package procedures at 80 °C and 50 kPa, the heat dissipation is better than a commercial thermal pad with κ⊥ of 3.86 W m−1 K−1. Vitrimeric PCM facilitates reliable 3D-structured BN network and thermally triggered conformability, paving a promising way for high-performance TIM with excellent heat dissipation.