Paraffin Matrix Research Articles

Optimization Design of the Multidimensional Heterostructure toward Lightweight, Broadband, Highly Efficient, and Flame-Retarding Electromagnetic Wave-Absorbing Composites.

A novel multidimensional electromagnetic wave-absorbing material was developed by combining carboxylated carbon nanotubes (CNT) with graphene oxide (GO) through multidimensional design, and cobalt/nickel-based metal organic frameworks (Co/Ni-MOF) were subsequently loaded onto the GO surface via its rich functional groups to form the composite absorbing material CNT-rGO-Co/Ni-MOF. Incorporating 25 wt % of CNT-rGO-Co/Ni-MOF into the paraffin matrix led to a remarkable RLmin value of -43 dB at 16.4 GHz, with an effective absorbing bandwidth (EAB) exceeding 4 GHz, all within a thickness of just 1.5 mm, showcasing its "lightweight, broadband, and high efficiency" characteristics. The exceptional electromagnetic wave absorption performance was attributed to multi-interface polarization loss, resistance loss, and magnetic medium loss. Furthermore, when incorporating 10 wt % of CNT-rGO-Co/Ni-MOF, the heat release capacity and peak heat release rate of EP/CNT-rGO-Co/Ni-MOF10 decreased by 59.2 and 52.6%, respectively.

Fe3C/Fe implanted hierarchical porous carbon as efficient electromagnetic wave absorber

The rapid development of communication technology has led to severe microwave pollution, which presents a challenge for microwave-absorbing composites. Current research suggests achieving superior microwave absorption requires the use of multi-component operation and ingenious structural design. Consequently, the present study has prepared continuous porous carbon (CPC) materials doped with large amounts of Fe3C/Fe nanoparticles (Fe@CPC) using carbonization and acid etching. By balancing the advantages of the above strategies, it is possible to address issues such as poor impedance match, single loss capacity, easy oxidation of magnetic metals/alloys, and the limited absorption bandwidth of conventional absorbing materials at the same time. The material exhibits a minimum reflection loss of −23.2 dB with an efficient absorption range of 5.3 GHz at 1.9 mm at a filler content of just 10 wt% in the paraffin matrix. In this paper, the samples with a continuous porous structure were prepared by a simple method, and the properties were excellent due to the appropriate preparation method and the synergistic effect of the multi-component composite. The porous structure facilitates the presence of a considerable number of active sites, which enables the loading of a substantial quantity of metal ions. Furthermore, nanoparticles are capable of aggregating and dispersing on the surface. This paper presents a theoretical framework for understanding the synergistic effect of microwave radiation through interfacial polarization and micro-scale magnetic interaction. Nevertheless, there are still obstacles to overcome in terms of achieving precise control over the structural design and ensuring the compatible integration of metal components.

Analysis of thermal storage behavior of composite phase change materials embedded with gradient-designed TPMS thermal conductivity enhancers: A numerical and experimental study

Phase change materials (PCMs) exhibit considerable potential for utilization in energy storage and temperature regulation applications, primarily attributed to their notable latent heat capacity. Nevertheless, the intrinsically limited thermal conductivity of PCMs necessitates the use of thermal conductivity enhancers (TCEs) that possess adjustable features to compensate for greater heat storage efficiency. Porous structures with flexible design freedom have garnered growing interest in contrast to traditional random foams, owing to their significantly larger surface areas and fully interconnected pore networks. This study fabricated three polar form-designed triply periodic minimal surfaces (TPMS) porous structures using selective laser melting (SLM) based on various radial density gradients, namely the uniform density, the linear gradient, and the Boltzmann gradient. The TPMS porous structures were incorporated as TCEs within a paraffin matrix to form composite TPMS-PCMs. The melting behavior of composite TPMS-PCMs during the charging process was investigated by employing both visual experiments and numerical methods. A thorough analysis was undertaken regarding the progression of solid-liquid phase interfaces, temperature distribution, convection distribution, and heat storage rate to elucidate the mechanisms that contribute to enhanced heat transfer. The findings indicate that the configuration of the density gradient has a notable impact on the melting behavior of composite TPMS-PCMs by tuning heat transfer paths. The heat storage rate of the linear gradient case is the highest among the three, reaching 12.1 W, 1.6 times that of the uniform density case, and twice that of the Boltzmann gradient case. Although the Boltzmann gradient case has the lowest heat storage rate, it demonstrates exceptional performance in terms of temperature uniformity. The average temperature gradient along the radius during melting is 348.6 °C/m, which is only 59% observed in the linear gradient case and 56% in the uniform density case. These findings substantiate the effectiveness of the radial gradient density design in the control of the thermal storage process of composite TPMS-PCMs. They serve as a reference for optimizing thermal storage and temperature control systems that rely on latent heat storage in the future.

Synthesis and broadband electromagnetic wave absorption for lightweight porous SiC/Si3N4 composite nanowires

As contemporary aerospace and radar-detecting technologies evolve, hypersonic vehicle components must avoid electromagnetic wave (EMW) detection in extremely harsh environments. In this study, lightweight porous SiC/Si3N4 composite nanowires (SiC/Si3N4 NWs), exhibiting excellent performance of broadband electromagnetic wave absorption (EWA), were successfully prepared via a facile electrostatic spinning and heat treatment in nitrogen atmosphere using phenol-formaldehyde resin (PR) and silica solution as precursors. The nanowire (NW) was composed of carbon-rich SiC and Si3N4 nanograins, and its microstructure and phase composition were regulated by carbon thermal reduction temperature. The EWA performance of the nanowires obtained through carbothermal reduction at 1300 °C, 1400 °C，and 1500 °C was investigated. The nanowires with 15 wt% obtained at 1500 °C were added to a paraffin matrix and the effective absorption bandwidth (EAB) was observed to cover almost the entire C, X, and Ku bands (4.2–18 GHz). Moreover, for a coating thickness of only 2.1 mm, the EAB was as high as 7.12 GHz (10.88–18 GHz), covering the entire Ku-band and achieving a minimum value of reflection loss (RLmin) of - 48 dB at 6.5 GHz. The 3D network structure of SiC/Si3N4 NWs with large specific surface areas and numerous mesopores extended the electromagnetic wave (EMW attenuation route and effectively improved the EWA performance through interfacial synergy between the carbon-rich SiC and Si3N4 nanograins). The strong absorption and wide EAB of the porous SiC/Si3N4 NWs rendered them highly suitable lightweight EMW absorbers in harsh, high-temperature environments.

A critical experimental evaluation of hexagonal boron nitride, graphene oxide and graphite as thermally conductive fillers in organic PCMs

Composite phase change materials (CPCMs), consisting of nanofillers embedded inside conventional PCMs such as salt hydrates or paraffins, are emerging candidates for large-scale latent heat storage systems or electrochemical applications. High thermal conductivity and thermal diffusivity of CPCMs are crucial prerequisites for practical utilization, in addition to good intrinsic enthalpy of fusion and volumetric heat capacity of the pristine PCMs. This paper presents an exclusive evaluation of graphite, hexagonal boron nitride (HBN), and graphene oxide nanoparticles as thermally conducting nanofillers across different loading ranges inside the paraffin matrix. The thermal performance of these CPCMs is compared by investigating multiple thermal properties, such as the melting temperature, degradation rate, and dispersion efficiency. Despite the similar intrinsic thermal properties of graphite, HBN and graphene oxide, their incorporation enhances the thermal performance of pure paraffin to different extents, by 137.6 %, 192.2 % and 344.1 % in thermal conductivity as well as by 189.0 %, 204.1 % and 202.1 % in thermal diffusivity, respectively, which is attributed to the conductive channels established by these nanofillers and the much-reduced thermal contact resistance across the interphase. Although these three types of particles possess analogously hexagonal structures, it was found that they interacted differently with the paraffin matrix at low (1 wt%) and high (15 wt%) filler loadings. The latent heat capacity of paraffin/GO was 3.8 % higher than that of paraffin/HBN and paraffin/graphite. Overall, this study provides a novel understanding of the transport mechanisms of heat carriers inside CPCMs, so the thermal performance for wider applications can be predicted, which will be invaluable for catering future sustainable energy needs.

P-219 Single-follicle spatial proteomics of the whole ovary by MALDI mass spectrometry imaging: towards the identification of protein-markers of the follicle's quality

Abstract Study question Can we improve our knowledge of the single-follicle proteome signature by MALDI mass spectrometry imaging? Summary answer We identified follicle-type proteins that function during follicle growth (NUMA1, TPM2), GV-to-MII transition (SFPQ, ACTBL, MARCS, NUCL), ovulation (GELS, CO1A2) and preimplantation development (TIF1B, KHDC3). What is known already The acquisition of oocytes developmental competence occurs through a bidirectional exchange of molecular information between the oocyte, the companion follicle cells, the stroma, and the vascular network. This reciprocal relationship is still poorly understood and particularly scarce is our knowledge of the proteins that are playing a regulative role during folliculogenesis. Matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) is a powerful tool that allows the study of the proteomic landscape of small morphological structures inside a tissue, but in the field of reproduction has been only used to analyse rodent spermatogenesis. Study design, size, duration Nano-scale liquid chromatography-electrospray ionisation-tandem mass spectrometry (nLC-ESI-MS/MS) was combined with MALDI-MSI to identify the proteomic landscape and to map the changes occurring throughout folliculogenesis. We performed single-follicle spatial proteomics on all the follicles, from the secondary to the fully-grown preovulatory, present in histological serial sections of an entire prepubertal 25-day-old mouse ovary. Cross-referencing our results with those obtained by previous proteomics and transcriptomics analyses allowed to strengthen their significance. Participants/materials, setting, methods A single 25-day-old mouse ovary was fixed in 10% formalin, dehydrated, embedded in paraffin, and sectioned to obtain 133 6-μm serial sections. After paraffin removal, trypsin digestion and matrix deposition, mass spectra were acquired using a rapifleX MALDI Tissuetyper™ (Bruker) with a raster sampling of 20 μm in both x and y axes. Then, tryptic peptides were extracted from sections and analysed with nLC-ESI-MS/MS using a Dionex-UltiMate-3000 LC-nano-system coupled with an Impact HD™ UHR-QqToF (Bruker). Main results and the role of chance This study proposes a spatial proteomics workflow to investigate the proteome of a whole prepubertal 25-day-old mouse ovary, preserving the spatial relationship of the peptides in this complex histological context. A total of 401 proteins were identified by nLC-ESI-MS/MS, 69 with a known function in ovary biology. Enrichment analysis highlighted significant KEGG and Reactome pathways, with apoptosis, developmental biology, PI3K-Akt, epigenetic regulation of gene expression, and extracellular matrix organisation being well represented. Then, correlating these data with the spatial information provided by MALDI-MSI on 276 follicles highlighted 94 proteins that were detected throughout the secondary to the pre-ovulatory transition. Of these, 37 proteins showed a gradual quantitative change during follicle differentiation, comprising 10 with a known role in follicle growth (NUMA1, TPM2), oocyte GV-to-MII transition (SFPQ, ACTBL, MARCS, NUCL), ovulation (GELS, CO1A2) and preimplantation development (TIF1B, KHDC3). The proteome landscape identified includes molecules of known function in the ovary, but also those whose specific role is emerging. Altogether, this work demonstrates the utility of performing spatial proteomics in the context of the ovary and offers sound bases for more in-depth investigations that aim to further unravel its spatial proteome. Limitations, reasons for caution A limitation of MALDI-MSI is its 20 µm/pixel resolution which 1) leads to the acquisition of spectra comprising follicular and extra-follicular tissue, particularly with small follicles (15-30µm in diameter); and 2) does not distinguish among the different follicular cell types, thus precluding its application for single-cell in situ proteomics. Wider implications of the findings MALDI-MSI is a potent technology to study the proteome of ovary specimens, but it could also be used for the analysis of their lipidic or metabolic profiles. Our pipelline aim to identify protein-markers of the follicle's quality and, in turn, of the oocyte's developmental competence. Trial registration number not appplicable

Biomass-based Co/C@Carbon composites derived from MOF-modified cotton fibers for enhanced electromagnetic attenuation

Recently, highly efficient electromagnetic attenuation materials are crucial for the development of modern electronics and telecommunications. Meanwhile, biomass-derived carbon materials have attracted widespread attention due to their availability and renewable characteristics. In this study, a composite with Co/C particles embedded in carbon networks was synthesized by pyrolysis of cotton fiber coated with ZIF-67, which are showing tunable and higher electromagnetic interference (EMI) shielding effectiveness (SE) than pure carbon networks. The remarkable performance originated from the aligned carbon networks and the Co/C particles connected by the carbon networks. The former can achieve the regulation of EMI SE by changing the angle between the fiber orientation direction and the direction of the incident EM-wave electric field, while the latter can play a role in catalytic graphitization and enhance the shielding performance. When decreasing the pyrolysis temperature and filling the composite powder with 30 wt% in the paraffin matrix, the minimum reflection loss (RLmin) can reach −58.8 dB at 5.12 mm. In addition, the effective absorption band (EAB) of the composite can cover the C-Ku band by adjusting the thickness from 3 to 7 mm. This work provides a potential guideline for efficient biomass-based electromagnetic attenuation materials.

Preparation of wax-based molecularly imprinted monolith for pipette-tip solid-phase extraction: a hybrid method.

The development of molecularly imprinted monolith (MIM) for pipette-tip solid-phase extraction (PT-SPE) forsample pretreatmentis challenging. In this work, a wax-based molecularly imprinted monolith (WMIM) was successfully prepared with a hybrid method by integration of the traditional packing SPE column and MIM, including preparation of the salt column inside the pipette, polymerization of wax-based imprinted column (WIC) outside the pipette, and immobilization of WIC inside the pipette tip. To ensure the penetration of samples and solvents during the PT-SPE, micrometer-range interconnected macropores were tailor-made via the salt-template sacrifice method. Forthe production of high affinity imprinted sites within the WIC, octadecanoic acid was used as functional monomer in the paraffin matrix. In terms of the adsorption property, the synthesized WIC exhibited a specific affinity to cardiovascular drugs, with an imprinting factor (IF) of 4.8 for the target analyte. Moreover, the WMIM-based PT-SPE was coupled with fluorescence spectrophotometry for the target propranolol determination (the excitation and emission wavelengths were 294nm and 343nm, respectively). This analytical method showed high recovery of target detection in different real samples (R > 90%), good sensitivity, and accuracy (R2 = 0.99, LOD = 0.03ngmL-1). We believe this work could provide a significant contribution for the fabrication of MIM and promote an emerging trend of developing elution-free materials for sample pretreatment.

Multifunctional flower-like Ni particles/silicon carbide nanowires for infrared radar compatible stealth performance

Alongside the rapid development of detection systems and improved detection accuracy, infrared/radar-compatible stealth materials have become the emphasis of current stealth technology research. Versatile flower-like Ni particles/silicon carbide nanowires (SiC NWs) composites for infrared radar stealth compatibility have been successfully prepared. Due to its special microstructure in combination with the multiple loss mechanisms of dielectric and magnetic, the minimum reflection loss (RLmin) achievable with the paraffin matrix mixture is −49.26 dB at a composite content of 50 wt%, which has a thickness of 1.9 mm and an effective absorption bandwidth (EAB) of 4.85 GHz. By increasing the absorbent content to 60 wt%, the EAB in the Ku band can attain 5.0 GHz at 1.8 mm thickness. Petal-shaped Ni particles are introduced to improve the impedance matching characteristics, increase interfacial polarisation and multiple scattering of electromagnetic (EM) wave, and enhance the microwave absorption properties. Simultaneously, the pure SiC NWs material can protect against infrared radiation emitted from the hand for more than 15 min, and the infrared (IR) reflectivity is improved in all three bands after the composite metal Ni particles. A novel formulation guide for the design of versatile and high-performance EM wave absorbing and infrared stealth materials is provided by this work.

Magnesium Spinel Ferrites Development for FDM 3D-Printing Material for Microwave Absorption

The magnesium nanosized ferrite powder with formula MgFe2O4 was synthesized via a pyrochemical sol–gel glycine–nitrate method and annealed consistently at temperatures of up to 1300 °C. The MgFe2O4 ferrite samples’ microstructure was studied by SEM and XRD methods. According to the results of the studies, the increase in MgFe2O4 nanoparticles size from about 15 nm to micron-sized particles was observed when increasing annealing temperatures. The DC electrical conductivity of MgFe2O4 also clearly shows the change in conduction behavior of samples with increased calcination temperatures. The electromagnetic microwave properties of micron-sized particles of MgFe2O4 ferrite powder for a 1200 °C annealing temperature were studied for composites in paraffin matrix with produced magnetic filler mass concentration at 40% and 50%. The filament composites of polymer polylactic acid with MgFe2O4 ferrite powder samples were prepared by the FDM 3D-printing process and their microwave-absorbing properties were investigated. The application of developed PLA–MgFe2O4 ferrite filament for fabricating magnetic microwave-absorbing components also was demonstrated.

Combustion performance of hybrid rocket fuels loaded with MgB2 and carbon black additives

Paraffin-based fuel has a great potential for several innovative missions, including space tourism, due to its safety, low environmental impact, high performance and low cost. Despite the fact that liquefying solid fuels increases the regression rate of hybrid rocket motors, incorporating energetic materials into solid fuel can still improve the performance. The objective and scope of this study is to increase the performance characteristics of the paraffin-based fuel by using magnesium diboride (MgB2) and carbon black (CB) additives. The cylindrical-port fuel grains were manufactured with various additives percentages in mass (wt%: CB-2% and MgB2-10%) and tested using a laboratory-scale ballistic hybrid motor under gaseous oxygen. The mechanical performance results revealed that adding CB and MgB2 improved the ultimate strength and elastic modulus of paraffin-based fuels. The addition of these fillers increased the hardness of fuel by developing a strong interaction in the paraffin matrix. Thermogravimetry (TG) results showed that CB inclusion improved the thermal stability of the paraffin matrix. The average regression rates of fuels loaded with CB and MgB2 were 32% and 52% higher than those of unmodified paraffin wax, respectively. The characteristic velocity efficiency was found in the range of 68%–79% at an O/F ratio of 1.5–2.6. The MgB2 oxidation/combustion in the paraffin matrix was described by a four-step oxidation process ranging from 473 K to 1723 K. Finally, a combustion model of MgB2 in the paraffin matrix was proposed, and four-step oxidation processes were discussed in detail.

Highly efficient electromagnetic wave absorption Fe-MOF-rGO based composites with enhanced flame retardancy

Ideal electromagnetic absorbing material should not only be light weight, broadband and high efficient, but also easily prepared and flame-retarding to satisfy the challenges from rapid development of electronic information technology. In present paper, a new type of electromagnetic absorbent (Fe-MOF-rGO) was prepared via a simple one-pot method to grow metal-organic framework (Fe-MOF) on the surface of in-situ reduced graphene oxide (rGO) by solvothermal method. When 25 wt% of Fe-MOF-rGO was incorporated into the paraffin matrix, the minimum reflection loss value (RL) reached to −43.6 dB at the thickness of 2 mm, and the effective absorption bandwidth (EAB) exceeded 5.0 GHz, which satisfied the goals of high efficiency, light weight and broadband. According the medium permittivity loss, magnetization loss and excellent resistance matching results, it was concluded that the conduction loss (excellent conductivity of rGO), magnetic loss (magnetic resonance of Fe nanoparticles) and interface polarization loss (heterostructure of two-dimensional rGO and three-dimensional Fe-MOF) of Fe-MOF-rGO jointly determined the electromagnetic absorbing performance. Moreover, the combustible behavior of Fe-MOF-rGO was also investigated. When 10 wt% of Fe-MOF-rGO was incorporated into the epoxy resin (EP), the heat release capacity (HRC) and peak heat release rate (PHRR) decreased by 42.1% and 42.3% respectively, which showed an excellent flame-retarding property. • A new type of electromagnetic absorbent was prepared via a simple one-pot method. • The absorbent was not only broadband and high efficient but also excellent flame retardancy. • The absorbing mechanism was conduction, magnetic and interface polarization loss.

Three-dimensional bamboo-like amorphous N/S co-doped carbon nanotubes encapsulated with Cu nanoparticles/carbon fiber heterostructures for boosting electromagnetic wave absorbing properties

Highly efficient and multifunctional electromagnetic wave (EMW) absorbers which can be easily processed are desirably required. Herein, cupric ammonia is creatively adopted as the catalyst precursor of the in-situ growth of carbon nanotubes (CNTs) onto carbon fiber (CF) during chemical vapor deposition. Typically, when prepared at 750 °C, N/S co-doped bamboo-like amorphous CNTs/CF was successfully synthesized, while some Cu nanoparticles were remained in CNT forests. The sample obtains an excellent absorption toward EMWs, demonstrating a minimal reflection loss of −59.28 dB at 14.1 GHz with an ultrathin thickness of 1.42 mm. Concurrently, it is over a relatively broad effective absorption bandwidth (EAB) of 3.3 GHz (12.3–15.6 GHz) with 31% loading in the paraffin matrix. And the EAB value of CA-700 reaches 3.7 GHz (14.3–18 GHz) at merely 1.45 mm. The satisfying attenuation performance mainly originates from the synergistic effects of continuous three-dimensional conducting networks, abundant interfaces, sufficient defects, and the well impedance matching. Moreover, all as-prepared samples could be potentially used as reinforcements of resin matrix composites with high strength. Therefore, a facile route is provided to produce thin, lightweight, superior and high-strength EMW absorbing materials based on CF and CNTs.

Polypyrrole/Schiff Base Composite as Electromagnetic Absorbing Material with High and Tunable Absorption Performance.

In recent years, Schiff base-related conjugated systems have received extensive attention, but little research has been done in the field of electromagnetic materials. In this work, an organic conjugated system based on polypyrrole/hydrazone Schiff base (PPy/HSB) composites was constructed via a Schiff base synthetic route and their electromagnetic behavior was investigated. The electromagnetic response of PPy/HSB complexes demonstrates fine electromagnetic absorption performance. When the filler loading is 30 wt% in a paraffin matrix, an absorption peak of −43.1 dB was achieved and its effective absorption bandwidth (EAB) was located in the range of 10.88−18.0 GHz. The electromagnetic response behavior of PPy/HSB complexes is explained by models involving electronic structure, multi-polarization and conductive network. The mechanisms of PPy/HSB complexes formation and HSB crystallization are also discussed through the compatibility of PPy/HSB and the structure of HSB. Moreover, the morphology transformation of HSB in the PPy/HSB systems has been studied. This study opens the exploration of organic–dielectric conjugated systems in the field of electromagnetic materials, and significantly broadens the application range of organic–dielectric–dielectric composites.

Dose Attenuation in Innovative Shielding Materials for Radiation Protection in Space: Measurements and Simulations.

Galactic cosmic rays (GCR) are among the main deterrents to manned space exploration. Currently, the most realistic way to reduce the dangers caused by GCR to acceptable levels is passive shielding. Light materials guarantee the strongest dose attenuation per unit mass. High-density polyethylene is considered the gold standard for radiation protection in space. Nevertheless, accelerator-based experimental campaigns already showed the advantages of more hydrogen-rich innovative shielding materials such as lithium hydride. The experimental campaigns of this work focused on the absorbed dose attenuation properties of lithium-based hydrides chemically stabilized with a paraffin matrix. Such materials were compared to pure lithium-based hydrides, polyethylene, structural materials such as spacecraft aluminum alloys and lithium batteries, and in situ shielding materials such as Moon regolith and its main components silicon and silicon dioxide. The experimental results were compared to simulations performed with PHITS, FLUKA, and Geant4, which are among the most used Monte Carlo codes for radiation protection in space. The simulations showed systematic differences and highlighted the pressing need for reliable nuclear cross-section models.

Tunable microwave absorption and shielding effectiveness in the nanocomposite of 3D hierarchical flower-like Co3O4 and rod-like polyindole

• 3D hierarchical composites of Co 3 O 4 /polyindole/paraffin were successfully prepared. • Electromagnetic properties of composites improved as the Co 3 O 4 /PIn ratio increased. • A 25 wt% Co 3 O 4 /PIn paraffined composite achieve RL = −21.5 dB and EAB = 3.5 GHz. • Total shielding effectiveness ( SE T ) was increased by the increase of Co 3 O 4 /PIn. • SE T of 25 wt% Co 3 O 4 /PIn paraffined composite was four times higher than 5 wt% one. Due to the rapid development of wireless electronic devices, achieving an excellent microwave absorber is crucial in modern life. The composite of flower-like Co 3 O 4 and rod-like polyindole (PIn) was embedded in the paraffin matrix for tunable microwave absorption performance and shielding effectiveness. Investigation of microwave absorption features of Co 3 O 4 /PIn paraffined composites in the X band frequency range revealed a good performance for 25 wt% Co 3 O 4 /PIn paraffined composite with reflection loss and an effective absorption bandwidth of −21.5 dB and 3.5 GHz (covered ∼ 83% X band). The pretty good microwave absorption performance of this composite originated from magnetic loss (by Co 3 O 4 ), dielectric loss (by PIn), and heat transfer capability (by paraffin). Shielding effectiveness was also increased with the increase of Co 3 O 4 /PIn loading percentage, with a total shielding effectiveness of 28.1 dB with the most contribution from shielding effectiveness for absorption. This work provides an easy and low-cost approach for tunable microwave absorption and shielding effectiveness for practical applications.

Filler dimensionality effect on the performance of paraffin-based phase change materials

HypothesisPhase change materials have the potential for use in high-density thermal energy storage. However, their low thermal conductivity and the need for shape stabilization restrict their performances and implementation in various fields. The inclusion of thermally conductive nanomaterial as a single or hybrid filling is expected to form 3D network that enhances the thermal performances of phase change materials. The encapsulation of the colloidal composites in a polymer matrix stabilizes the phase change material. ExperimentsA paraffin matrix was loaded with carbon-based fillers of various dimensionalities, namely, 1D-carbon nanotubes, 2D-graphene nanoplatelets, and 3D-graphite flakes. The thermal conductivity of the colloidal composite was measured by transient plane source and the latent heat capacity by differential scanning calorimetry techniques. Modeling the thermal conductivity by the effective medium approach predicts the experimental results. FindingsThe thermal conductivity of the phase change material loaded with fillers is enhanced from 0.2 to 11 W (m K)-1 (×55) compared with a filler-free paraffin matrix. We attribute this enhancement to the synergetic effect of the hybrid fillers (8 vol% graphite flakes and 12 vol% graphene nanoplatelets) and consequent compression (25 bar) of the colloidal composite. Moreover, the obtained phase change material is completely stable during charging and discharging cycles.

Mr Microwave absorption and electromagnetic interference shielding properties of carbon black/MnNiZn ferrite nanocomposites-filled paraffin wax in the frequency range (8.8–12 GHz)

In this present work, we offer the design of good, wideband microwave absorption materials (MAMs) based on CB/Mn0.1Ni0.5Zn0.4Fe2O4 (carbon black/MnNiZn ferrite). The ferrite is prepared by a self-combustion method using sucrose as fuel. The chemical is utilized for the synthesis of carbon black nanopowder is carbon black powder (2–8 μm). Then, the operation is continued via mixing carbon black and MnNiZn ferrite through the grinding balls. Four various weight ratios of CB/Mn0.1Ni0.5Zn0.4Fe2O4 (1:0, 1:1, 2:1, and 3:1) with various thicknesses (2–4–6 mm) are prepared. X-ray diffractometry and FTIR spectroscopy are utilized in order to characterize samples. The morphology of the powders is investigated by SEM. The electromagnetic interference (EMI) shielding and microwave absorption properties are measured in the frequency band of 8.8–12 GHz to accomplish the practical characterization. The MAMs show broad bandwidths under -10 dB in the range of 0.3–3.2 GHz and reasonable surface density in the range of 2.91–3.66 kg/m2 with a weight ratio within a paraffin matrix of 40% w/w. The MAM shows a minimal reflection loss of -18.3 dB at the frequency of 11.4 GHz for the thickness of 2 mm. The maximum shielding efficiency is 18.5 dB at 11.5 GHz for 2 mm thickness of the CB/F-21 nanocomposite sample.

Metal-coordination-driven self-assembly synthesis of porous iron/carbon composite for high-efficiency electromagnetic wave absorption

Hydrophilic-hydrophobic microphase separation is an important mechanism to promote aqueous polymer self-assembly. However, it is rarely used in the construction of magneto-dielectric absorbers in the interdisciplinary research involving organic polymer and inorganic hybrid material. Herein, a novel metal-coordination-driven self-assembly strategy is proposed for fabricating organic–inorganic composite co-assemblies by combining resorcinol–formaldehyde resin as carbon precursor and iron-containing polymer self-assemblies as soft template. Co-assemblies are then transformed into porous iron/carbon (Fe/C) composites with spherical Fe nanoparticles and micro-mesopores that form in graphited carbon matrix through high-temperature pyrolysis. The minimum reflection loss of Fe/C-800 composite in paraffin matrix with 10% filler loading can reach −57.8 dB, while the effective absorption bandwidth of 5.3 GHz can cover the whole X band. It is considered that the co-assemblies-derived microstructure and magneto-dielectric composition contribute to the multiple reflection, polarization loss, conductive loss, ferromagnetic resonance and eddy current loss for high-efficiency electromagnetic wave absorption. In general, this work opens up new prospects for designing and preparing high-performance magneto-dielectric absorbers via a novel metal-coordination-driven self-assembly strategy.

Application of multi-scale pore regulation for high thermal conductivity foam reinforcements in energy storage

A continuous diamond film layer was initially deposited on the surface of the foam skeleton by chemical vapor deposition (CVD), followed by the vertical growth of carbon nanotubes (CNTs) on diamond film using nickel particles as a catalyst. The CNTs extended into the interior of the pores inside the foam skeleton as a secondary heat transfer pathway. The effect of different pore densities on the thermal conductivity and latent heat of phase change composites (PCMs) was explored. The obtained diamond foam/carbon nanotube/paraffin composites (DF-CNT/PWs) was demonstrated to achieve an ultra-high conductivity of 5.3 W/m·K, which is 19.6 times that of the paraffin matrix. The latent heat of the DF-CNT/PWs is 83.37 J·g−1. In addition, finite element simulation confirmed that the thermal conductivity enhancer system could significantly improve the uniformity of heat transfer inside the foam skeleton.