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Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a type of red mud/slag-based cenospheres/geopolymer foam was directly fabricated using the direct foaming method at room temperature. The effects of high-temperature exposure (700–1100 °C) on the phase evolution, pore structure, and properties of the foams were investigated. The results showed that the untreated foam was amorphous structure. The porosity of the foams increased from 36.4 ± 0.6% (1 wt%) to 71.9 ± 0.1% (5 wt%) with the addition of H 2 O 2. The compressive strength of the foams was 1.20–18.15 MPa, which was attributed to the good bond between the cenospheres and red mud/slag-based geopolymer matrix, the fractured spheres, and the crack deflection. After this high-temperature exposure, the foam crystallized mainly into the leucite and mullite phases. The density and compressive strength of the foams decreased as the exposure temperature increased. The thermal conductivity of the foams reached the lowest value of 0.169 W/(m⋅K) and 0.108 W/(m⋅K) with 5 wt% H 2 O 2 before and after the exposure, respectively. These foams have demonstrated good potential for application in the building insulation field. [ABSTRACT FROM AUTHOR]

Thermal protection has always been an important issue in the energy, environment and aerospace fields. Porous ceramics produced by the particle-stabilized foaming method have become a competitive material for thermal protection because of their low density and low thermal conductivity. However, the study of porous ceramics for composite systems using particle-stabilized foaming method was relatively rare. Here, silica-alumina composite porous ceramics were prepared by particle-stabilized foaming method, which was achieved by tailoring the surface charges of silica and alumina through adjustment of the pH. Porous ceramics exhibited porosity as high as 97.49% and thermal conductivity (25 °C) as low as 0.063 W m−1 K−1. The compressive strength of porous ceramics sintered at 1500 °C with a solid content of 30 wt% could reach 0.765 MPa. Based on the light weight and excellent thermal insulation properties, the composite porous ceramic could be used as a potential thermal insulation material in the spacecraft industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Macro PPBESK beads with hierarchical pores are fabricated via NIPS approach. • PPBESK beads have a good thermal insulation property in a wide temperature window. • The compression modulus of PPBESK beads is more than 50 times higher than PS foam. • The performance can be controlled by the composition of the coagulation bath. Preparation of porous materials from high-performance polymers holds great promise for various advanced engineering applications like thermal insulation. However, it is still a great challenge to fabricate them due to the difficulties in manufacturing them. Herein, a high performance polymer material poly(aryl ether sulfone ketone)s containing phthalazinone and biphenyl moieties (PPBESK) was utilized to fabricate porous materials via a frequently used and simple method named non-solvent induced phase separation (NIPS). Macro porous PPBESK beads have been fabricated in different non-solvent coagulation baths. The kinetics of the phase inversion processes are visualized by the optical microscope. The multi-scale porous structures formed inside the beads endow them an excellent thermal insulation performance in a wide temperature window and a high mechanical performance that the compression modulus is more than 50 times higher than Polystyrene (PS) foam. Therefore, these PPBESK beads provide an optimized combination of functionalities including high mechanical strength and good thermal insulation, which could turn out to be useful in harsh environmental applications. [ABSTRACT FROM AUTHOR]

This work focuses on the potential of agar from the seaweed Gracilaria fisheri to modify the properties of starch foam. The effects of different ratios of glycerol and agar on the properties of starch foams were investigated. All formulations used in this study produced easy-to-handle, smooth, single-use foam trays with no visible cracks. The addition of agar slightly affected the off-white color of the foam but red and yellow color values significantly decreased with increments of agar content. As the agar content was increased, the foam became less dense. A foam produced at a glycerol:agar ratio of 3:7 exhibited the highest values of flexural stress at maximum load (3.23 MPa), modulus (194.46 MPa) and hardness (97.50), and the highest temperature at maximum weight loss (T max) (337 °C). Therefore, starch foam modified with agar from Gracilaria fisheri showed suitable physical, mechanical and thermal properties for food packaging, and could possibly be used in the place of expanded polystyrene (EPS) foam. [ABSTRACT FROM AUTHOR]

Materials with complex inner structure can be challenging to characterise in an effective way. The effective material parameters significantly depend on the structure, and thus on the interface properties. In the present paper, we focus on metal matrix syntactic foams, and we attempt to determine their effective thermal parameters. We supplement the results with their mechanical properties as well. For thermal characterisation, we use the heat pulse experiment to study their transient thermal response. We observed deviation from Fourier's law in multiple situations, and thus we propose an evaluation procedure for such experimental data using the Guyer–Krumhansl heat equation. We provide an iterative procedure to efficiently find the effective thermal diffusivity values provided by the Guyer–Krumhansl and Fourier equations based on the measured transient response. Furthermore, we studied the effective parameters, the specific heat, mass density, thermal conductivity and thermal diffusivity. We found that the standard estimations significantly overestimate the thermal conductivity. Furthermore, we propose a method for deducing a more reliable thermal diffusivity and thermal conductivity based on the transient temperature history, i.e., we propose to estimate Fourier's thermal diffusivity based on averaging the parameters of the Guyer-Krumhansl equation according to the observed diffusive time scales. We also found that for such metal matrix syntactic foams, even with knowing the constituents, the contact thermal resistance makes more challenging to provide a prior estimate for the effective thermal conductivity, but this difficulty can be resolved using proper effective thermal diffusivity values. • Proposing an iterative evaluation procedure for the Guyer-Krumhansl equation. • Determining the effective thermal parameters of metal matrix synthetic foams. • Correlating the Fourier and Guyer-Krumhansl parameters. • Comparing the effective thermal conductivity estimations to the measured one. [ABSTRACT FROM AUTHOR]

Most of the thermal characterization methods using a uniform heating of a surface (Guarded Hot Plate, Transient Hot Plate, Fluxmeter Method) assume 1D transfer in the measurement area and neglect the in-plane heat transfer in the heating element. This results in limitations regarding the time interval for estimation, the thickness of samples or the possibility of simultaneously measuring thermal conductivity and capacity. To overcome these limits, a new 3D transient analytical model suited to isotropic materials and taking into account the convective lateral heat losses on the periphery of the samples as well as the 3D heat transfers in the heating element has been developed. It is first presented and then validated by comparison with 3D numerical simulations carried out with COMSOL. A study of the reduced sensitivities of the measured temperature to the various parameters and parameters estimations carried out on simulations obtained with the 3D model enable us to define an optimal estimation process. Finally, transient hot plate experiments were carried out on five extruded polystyrene samples with thickness ranging from 9.1 mm to 49.8 mm and on samples of PVC foam, PVC and of the reference anisotropic material IRMM-440. The results validate the theoretical study with a deviation lower than 5% compared to the known values of the thermal conductivity for the isotropic materials when using the 3D model, while the deviation may reach 77% using the1D model for the thickest sample of extruded polystyrene. The deviation reaches 11% for the thermal conductivity of IRMM-440 showing the need for a model taking into account the anisotropy for this type of materials. • 1D heat transfer is most often assumed in thermal characterization methods using plane source. • Experimental devices to ensure a 1D heat transfer are complex. • A 3D analytical model is developed for transient plane source methods. • The accuracy of thermal properties estimation using this 3D model is demonstrated. [ABSTRACT FROM AUTHOR]

The indiscriminate accumulation of plastic waste has prompted research that leads to obtaining biobased materials. The research aim was to evaluate the effect of incorporating fique bagasse microparticles (FBM) in a cassava starch-based foamed material. First, the FBM extraction conditions were established by acid hydrolysis, for which the effect of acid concentration (5, 10 and 15% H 2 SO 4), temperature (70, 80 and 90 °C) and extraction time (3, 5 and 7 h) on particle size, functional groups, color, and thermal properties was evaluated. The addition of FBM to the foamed material was then carried out. To do this, a completely randomized design with five treatments (0, 0.5, 0.75, 1.0 and 1.25% FBM) was evaluated. The response variables were the apparent density, expansion and spring index, compressibility, water absorption, thermal properties and FTIR. The results showed that the acid concentration, temperature and time had an effect on the morphological, chemical and thermal properties of FBM, with 10%, 70 °C and 7 h being the conditions that allowed obtaining the smallest particle size (61.69 ± 12.88 μm2). Moreover, the FBM concentration had a significant effect on the physical and mechanical properties of the foam, unleashing the treatment properties of 0.75%. This indicates that FBM have potential for use in obtaining biobased materials. • Fique bagasse can be valorized through the extraction of microparticles. • MBF are an important component for the development of bio-based materials. • MBF extraction conditions affect their properties. • MBF concentration influences the properties of starch-based foams. • The incorporation of 0.75% MBF positively affected the foam properties. [ABSTRACT FROM AUTHOR]

Graphene promises considerable application potentials in improving the thermal conductivity of polymeric composites due to its superior intrinsic thermal conductivity. However, the simple incorporation of graphene in polymeric composites usually fails to meet the requirements for simultaneously high thermal conductivity and electrical insulation. Herein, an epoxy-based composite with excellent thermal conductivity and electrical insulation has been produced by introducing a long-range ordered carbon/graphene/MgO ternary foam (CGMF) via surface modification and ice template method. The heat conduction shortcut provided by the vertically aligned structure of CGMF endows the composites with excellent thermal conductivity of 4.87 Wm−1K−1 (through-plane) at 12.96 vol% filler loading. Meanwhile, the barrier of MgO and PVA to the electron transmission in CGMF results in the composite with high surface electrical resistivity and volume electrical resistivity, which satisfies the requirement of electrical insulation. This work provides valuable insights into the fabrication of highly thermal conductive & electrically insulating composites. [ABSTRACT FROM AUTHOR]

• Shape-stable attapulgite/capric-myristic acid eutectic mix composite (attapulgite/C-M) was developed. • Attapulgite/C-M was used at 15, 30 and 45 wt% to produce foam concrete. • Solar thermoregulation performances of foam concretes were tested in laboratory and actual ambient conditions. • Foam concretes with acceptable mechanical properties can be used for internal temperature controlling. • Foam concretes save energy in buildings and decrease CO 2 emission. Thermal energy storage (TES) by means of phase change materials (PCM) is of great concern to decrease heating and cooling loads. In building envelopes, one of the most efficient TES methods is integration of PCMs with construction materials for preventing temperature fluctuations by taking advantage of energy storage/release feature of PCMs. Aim of this research was to develop novel foam concretes containing shape-stable attapulgite (ATP) based composite PCM as TES material. Shape-stable ATP/Capric-Myristic acid eutectic mix composite (ATP/C-M) was incorporated into foam concrete at three different ratios (15, 30 and 45 wt%) and characterized. Impacts of ATP/C-M inclusion on physico-mechanic and TES characteristics of foam concretes including composite PCM (FCPCM) were worked systematically. DSC results showed that ATP/C-M composite melts at 22.12 °C with latent heat storage capacity of 74.97 J/g, whereas FCPCM-45 melts at 21.05 °C with latent heat storage ability of 10.98 J/g. Inclusion of ATP/C-M instead of silica sand decreased flow diameter of foam concretes. Compared to reference mixture FCPCM-0, compressive strengths of FCPCM-15, FCPCM-30 and FCPCM-45 samples were reduced in the range of 11–46% while reduction in flexural strength was found to be about 35–57% at 28th day. All FCPCM samples showed lower thermal conductivity values than the specified value and could be defined as better insulation materials. Solar thermoregulation performances of foam concretes containing ATP/C-M were comparatively tested in laboratory and also actual ambient conditions. Results showed that foam concretes with acceptable mechanical properties can be used for internal temperature controlling and energy saving in buildings. [ABSTRACT FROM AUTHOR]

The incorporation of phase change microcapsule (microPCMs) substantially augmented the temperature regulation capacity of foams, endowing it with outstanding application potential in numerous industrial domains. However, interfacial compatibility issues between the capsule and the substrate always exist and affect foam performance. In this study, a milli-meter macrocapsule (macroPCMs) containing microPCMs was prepared using calcium alginate gel as the second layer wall to physically improve the interfacial compatibility. And poly (N-hydroxymethyl acrylamide) was in situ polymerized in the gel layer and provided active alcohol hydroxyl groups to form chemical grafting with the polyurethane raw materials, which further chemically improved the interfacial compatibility. These measures created a significantly improved foam microstructure and a greatly increased foaming capacity, which thus endow the composite foam with excellent thermal insulation performance and mechanical strength. Compared with conventional microPCMs-based foam, the foaming capacity of the macroPCMs-based foam increased by 40 folds, the temperature regulation duration increased by 7 folds, and the mechanical performance increased by 3 folds. Moreover, the insulated incubator fabricated with the macroPCMs-based foam exhibited two-fold greater thermal insulation efficiency than conventional models containing internal ice incubator, which validated the potential of employing macroPCMs-based polyurethane foam in cold chain logistics applications. [Display omitted] • Double-layered macrocapsules with reactive groups on the shell material was synthesized. • The double-layered microcapsules physically and chemically improved the capsules/foams interfacial compatibility. • The improved interfacial compatibility greatly enhanced the macroscopic performances of the composite foams. [ABSTRACT FROM AUTHOR]

Ultra-lightweight foam concrete (ULFC) is a relatively new construction material that has gained attention recently due to its unique properties. This material is not very heavy and low-density, making it easy to form into different shapes and sizes. Its excellent thermal insulation makes it popular for building walls, roofs, and floors. This review paper provides an in-depth examination of the properties and characteristics of ULFC. Its composition typically consists of cement, water, foam, additives, and the various manufacturing methods used to produce it—the mechanical properties of ULFC, including its compressive strength. The density of ULFC can vary greatly, usually falling between 100 and 600 kg/m3. The diversity of this can be affected by different factors, such as the kind and number of additives applied and the methods of foaming and thickening employed. The paper highlights the various applications of ULFC in the construction industry. Its use is as a TC material, which can help reduce heating and cooling costs; as a structural material, it can help reduce dead loads of structures. The review paper also discusses the challenges associated with ULFC production, including foam stability. Foam insulation concrete emits 302–508 kg CO 2 per cubic meter, primarily due to Portland cement, but enhances building energy efficiency, reducing household CO 2 emissions, while advanced recycled insulation materials offer superior thermal and acoustic properties with lower environmental impact. Additionally, we examine the current research on ULFC and suggest potential avenues for future investigation. This paper aims to introduce and put forward a range of cutting-edge and original recommendations and informative guidelines, with the ultimate objective of directing and shaping future research endeavors that focus on effectively exploiting and utilizing ultra-light foamed concrete. • Utilisation of Ultra-light foamed concrete for sustainable construction. • Mechanical properties and thermal insulation perspective incorporating Ultra-light foamed concrete. • The density of ULFC materials compared with normal concrete. • Microstructures properties of concrete incorporated with ULFC. • Recommendations and observations are advanced for future research in ULFC. [ABSTRACT FROM AUTHOR]

In this study, a new type of highly porous ceramic was successfully fabricated from α-Al 2 O 3 whiskers and nano-sized Al 2 O 3 particle slurry by vacuum infiltration with the subsequent annealing in air. It was found that with an increase in the alumina slurry amount or sintering temperature, the porosity of the foam ceramic decreased while its compressive strength increased. The optimal alumina slurry content and sintering temperature were equal to 4 g, and 1350 °C, respectively. The as-synthesised porous foam ceramic exhibited a low density of 0.65 g/cm3, high porosity of 83.51%, high compressive strength of 3.84 MPa, and low thermal conductivity of 1.37 W/m⋅K at room temperature, suggesting its potential applications in high-temperature gas filtration and thermal insulation materials. [ABSTRACT FROM AUTHOR]

In this paper, 3D-SiC network skeleton with different structures was successfully constructed by regulating the microstructure of SiC foam ceramic struts via polyurethane replication technology combined with reactive infiltration of Si and solid-state sintering. Then, SiC/Al composites with 3D-interpenetrated network structure (3D-SiC/Al) were fabricated via vacuum pressure infiltration of Al alloy into the 3D-SiC skeleton, for application as electronic packaging. The effects of different skeleton structures on the thermal conductivity (TC), coefficient of thermal expansion (CTE), and flexural strength of the composites were investigated in detail. Furthermore, representative volume element (RVE) models of the 3D-SiC/Al composites were developed and their heat transfer properties and dimensional stability were also comparatively analyzed by finite element (FE) simulations. The results showed that the 3D-SiC/Al composites exhibited high TC of 196 W/m·K, low CTE of 8.03 × 10−6 K−1, and excellent flexural strength of 272 MPa. Low thermal deformation parameter (TDP) and Ashby map demonstrated that the synergistic effect of a complete 3D network skeleton and a clean well-bonded interface in the 3D-SiC/Al composites facilitated the integration of low CTE and high TC even at a low SiC content of 30 vol%. The FE results revealed a 63.5 % reduction in thermal stress and nearly an order of magnitude increase in heat flux for the RVE model of 3D-SiC (30 vol%)/Al composite compared to the RVE model of SiC P (60 vol%)/Al composite. This work provides a novel and scalable method for designing and synthesizing various composites for electronic packaging. [ABSTRACT FROM AUTHOR]

To meet demand for lightweight and high-strength ceramic foams, in-situ self-reinforced Si 3 N 4 ceramic foams, with compressive strength of 13.2–45.9 MPa, were fabricated by protein foaming method combined with sintered reaction-bonded method. For comparison, ordinary protein foamed ceramics with irregular block microstructure were fabricated via reaction-bonded method, which had compressive strength of 3.6–20.5 MPa. Physical properties of these two types of samples were systematically compared. When open porosity was about 80%, both types of Si 3 N 4 ceramic foams had excellent thermal insulation properties (<0.15 W m−1 K−1), while compressive strength of in-situ self-reinforced samples increased by more than 158% compared with ordinary samples. Under high-temperature oxidation conditions, microstructures of both types of samples were deformed with increase in oxidation temperature. Moreover, after oxidation temperature was increased to 1400 °C, oxidation weight gain decreased from 18.07% for ordinary samples to only 2.18% for self-reinforced samples. Thus, high-temperature oxidation resistance of Si 3 N 4 ceramic foams was greatly improved. [ABSTRACT FROM AUTHOR]

This article presents a new application of a well-known theory concerning mixing. The introduction of boundary conditions was proposed, which allowed the determination of a universal formula for the k parameter of the system. A graphical method for solving the problem has been proposed, which is supported by studies of the synthesis of rigid polyurethane foam. Mixing tests were performed using a variable ratio of the diameter of the stirrer to the diameter of the mixing chamber. Block-shaped samples were obtained, which were then characterized in terms of mechanical properties - compressive strength, brittleness, in terms of thermal properties - Thermogravimetric analysis, differential calorimetry, in terms of qualitative and quantitative structure studies using SEM images, and in terms of chemical analysis using FTIR. The proposed method for determining the boundary parameters of blending systems was proved to be applicable to polyurethane blending system. • Analytical considerations regarding the mixing process. • Proposing a new approach to determining important boundary parameters for the polyurethane mixing process. • Proposal to improve polyurethane blending processes to reduce the energy intensity of the process. • Effect of stirrer-to-vessel diameter ratio on the structure and properties of rigid polyurethane foam. [ABSTRACT FROM AUTHOR]

Carbon fiber matrix composites have garnered significant attention due to their exceptional properties, finding wide-ranging applications in industries such as aerospace, transportation, and military. In this study, a novel approach involving the addition of nickel was explored to fabricate carbon fiber-reinforced thermoplastic polymer composites and composite materials filled with nylon 12, utilizing nickel foam as matrix. Subsequently, electromagnetic-thermal multiphysics coupling models were established to analyze the induction heating process. The study investigated the effects of nickel content, spatial location of the main heat source, coil current, and coil frequency on the temperature rise and heat generation. Additionally, a linear fit was applied to determine the material surface temperature and related factors during induction heating. Furthermore, a theoretical formula was derived for induction heating under ideal conditions, elucidating the heat transfer mechanism and the influence of various factors on heat generation. The findings of this research serve as a reference for optimizing the utilization of Joule heat in composites, thereby expanding the application of carbon fiber-reinforced polymer composites in temperature regulation and operational control. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Calcination to generate spider web-like distribution of SiC whiskers to control electrical and thermal conductivity. • SiC/C foam with maximum EAB of 6.9 GHz, perfect C-band coverage. • SiC/C foam combines thermal conductivity, Joule heating, mid-temperature microwave absorption and compression to support repeated mid-temperature heating. • SiC/C closed cell foam has potential for large-scale industrial application. Microwave-absorbing materials (MAMs) for applications such as aircraft protective layers and ship side panels often need to take into account the actual working conditions. Conventional MAMs are often difficult to take into account special functional requirements such as mechanics, high temperature, de-icing, etc. Therefore, there is an urgent need to develop MAMs with harsh environmental adaptability and multifunctional requirements. Here, we utilize SiO 2 microspheres and phenolic resin to prepare precursor foams, and through calcination, we have prepared closed-cell SiC/C foam composites with both microwave absorption properties, mechanical properties and thermal properties. The effective absorption bandwidth (EAB) of the samples is up to 6.9 GHz at a thickness of 7.3 mm, which can satisfy the perfect coverage of the C-band, and can be further broadened by structural design. The samples can satisfy the full coverage of the X-band at 200 °C. The samples have loaded properties, and the maximum compressive strength of the samples is up to 10.5 mm. The samples are loaded with a maximum compression strength of 8 MPa, support repeated medium-temperature heating, and maintain a compression performance of 5.7 MPa after heating. The samples have good thermal conductivity and Joule thermal properties, and the surface temperature can be rapidly increased under the condition of applying a heat source or applying a low pressure to cope with the cold and humid working conditions. The composites in this paper are simple to prepare and have the potential for mass production. [ABSTRACT FROM AUTHOR]

For polymer foams, a high expansion rate is often required to obtain a low thermal conductivity. However, polymer foams with high expansion ratio faces a difficulty of shape recovery. In this work, polystyrene (PS)/polymethyl methacrylate (PMMA)/carbon nanotubes (CNTs) composite foams were prepared by the synergy of ultrasound and H 2 O in supercritical carbon dioxide (scCO 2) foaming. The introduction of ultrasound and H 2 O is beneficial to improving expansion ratio. CNTs can enhance the melt strength of PS/PMMA, which also absorb part of the thermal radiation. Therefore, the PS/PMMA/CNTs foams with 0.5 wt% CNTs exhibits the high expansion ratio (80.7 times), low thermal conductivity (25.98 mW/mK) and 100% compression recovery in water at 85 °C after one compression. In addition, with the increasing of filler contents, the reusability of the foam is further improved. After ten compressions, the PS/PMMA/CNTs foams with 2 wt% CNTs still achieve the 99% recovery. This work provides a new way to prepare polymer foams with super-insulation and reusability. [Display omitted] [ABSTRACT FROM AUTHOR]

• Rigid polyurethane foam as the preferred thermal insulation. • Analysis of the influence of fly ash on material thermal conductivity. • Calculation of the heat balance for a wall with polyurethane insulation. • Study of the temperature field in the cross-section of the wall. Limitations in natural resource availability have a significant impact on prices of thermal energy. As a result, a growth of interest in the technology of insulation materials is observed. The paper presents a comparative analysis of rigid polyurethane foams, which are widely used as insulation materials. Rigid polyurethane foam with 10 wt.% addition of coal fly ash is compared to a reference foam, without any addition. The thermal conductivity coefficient of polyurethane materials was determined by the Hot Disk device. Heat transfer for both types of foams was modelled. As a result of the numerical modelling, the temperature field for the wall was obtained. The results of the computations have shown differences in energy losses. Conducted analyses demonstrate that the modified polyurethane foam (with the addition of coal fly ash) performs better as an insulation material. The reduction of heat requirement is 2.9 %. An environmental analysis of the insulation materials was also carried out. Using the SUBRAW index method it was calculated that embodied energy and the carbon footprint are lower in the case of the modified polyurethane compared to the unmodified foam. [ABSTRACT FROM AUTHOR]

Polymeric syntactic foams (PSF) are a kind of composite material, which consists of a polymer matrix reinforced by hollow thin wall glass micro-spheres. Because of their low density, low moisture absorption, relatively high specific strength and stiffness, PSF are often employed in aerospace and submarine applications in which they are subjected to a wide range of temperature conditions. Due to the temperature sensitivity of the polymer matrix, the physical and mechanical behaviour of PSFs is highly sensitive to temperature variations. Besides, their dynamic response is significantly affected by the strain rate. This research investigates the temperature and strain rate dependence of the mechanical behaviour of polyurethane, epoxy and nylon syntactic foams under compressive and tensile loads. The selected materials have in common that their mechanical characteristics, thermal properties, and dimensional stability make them suitable for both impact engineering and thermoforming applications. The experimental results, acquired over a temperature range from −25 °C to 100 °C at low and high strain rates, reveal a clear interplay between temperature and strain rate effects on the mechanical behaviour of the materials under investigation. This synergy is observed to vary based on both the matrix material and the loading mode. Notably, the rate dependency of polyurethane and nylon syntactic foams is significantly influenced by the testing temperature during compression, while in tension the influence of the temperature on the rate dependency is moderate or negligible. In contrast, the rate dependency of the epoxy syntactic foam remains largely unaffected by the testing temperature. Deformation and failure mechanisms were analysed by examining the failure surface of the tested samples using SEM micrographs. • A method to measure the dynamic response of polymeric syntactic foams is presented. • The interaction between the effects of temperature and strain rate is investigated. • The examined foams are characterised by a noticeable strength asymmetry. • The variation of strength and energy absorption in diverse conditions is examined. • The failure mechanisms of the materials is analysed via SEM micrographs. [ABSTRACT FROM AUTHOR]

In the field of material science, foaming agents common are commonly used for enhancing the thermal insulation and phase change materials (PCM) for heat storage. However, PCM tends to agglomerate in the cement slurry with the directly addition, presenting an obstacle to effective dispersion. Moreover, the addition of PCM leads to rapid defoaming. To overcome this issue, a novel nanoparticle-stabilized foam was designed in this study to create a three-component system that enhances the interaction of viscosity modifiers, surfactants, and foam stabilizers. The effect of cement density on thermal insulation was evaluated by analyzing thermal conductivity and heat transfer performance tests, as well as exploring the mechanical properties of the cement-based materials. Scanning electron microscope (SEM) images show that the foam designed in this study remarkably promotes the dispersion of PCM microcapsules, indicating the bridging interactions of foam in the cement paste. The result shows that the thermal conductivity of foam cement with 15 vol% PCM microcapsules drops from 0.11 W/m·k to 0.07 W/m·k compared to that without PCM addition, with a dry density around 600 kg / m 3. Furthermore, the specimens with the addition of PCM achieve the endothermic and exothermic peaks under experimental images. This discovery is of great significance to heat absorption ability of low-density concrete, where the addition of PCM leads to a slower foam bursting under the nanoparticle-reinforced foam system. The dispersion and connectivity of foams, as well as the physical characteristics of PCM, provide new perspectives for coexistence in a relatively stable system in this way. • Nanoparticle-stabilized foam remains stable within the cement slurry. • Stable foam contributes to the low thermal conductivity and superior insulation performance of foam cement. • The sustainable and environmentally friendly energy-saving effects of phase change materials microcapsules in foam cement. • A novel lightweight and eco-friendly cement with thermal regulation capabilities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sandwich panel with face sheet of CSB and core with PU and PU replaced with CH were studied. • PU replaced with CH at 10, 20, 30, 40 and 50 %, and material characterizations, mechanical, durability and acoustic property, thermal conductivity test were conducted. • Incorporation of CH at 10 and 20% with PU shows enhancement in various properties. • Regression analysis was conducted to validated by the suitable R2 threshold accuracy as R2 > 0.90. As the need for a sustainable solution increase, waste materials are gaining popularity in building applications to reduce the environmental impact. This study aims to utilize the waste Coconut Husk (CH) and Calcium Silicate Board (CSB) in a sandwich panel where Polyurethane Foam (PU) is used as a binding material which consists of A (isocyanate) and B (polyol) with a mixing ratio of A: B at 1:1.2. CH is obtained as a residue from the production of coconut shells aggregate. The PU has been replaced with CH at 10, 20, 30, 40 and 50 %, to identify the optimum replacement level. Sandwich panels of dimension 30 × 30 cm with a core thickness of 2 and 3 cm was prepared and tested to categorize their mechanical properties, thermal properties, durability properties, characterization study and sound absorption coefficient. The results show that the PU replaced with 20 % of CH has higher compression and flexural properties, owing as an optimum percentage. The inclusion of CH in the PU reduces the cell size and yields a significant improvement in acoustic behavior up to a frequency of 1600 Hz. The regression model was analyzed with the experimental data and validated by the suitable R2 threshold accuracy as R2 > 0.90. [ABSTRACT FROM AUTHOR]

• Properties of alkali-excited fly ash aerogel foam concrete were studied. • The microstructure of alkali-excited fly ash aerogel foamed concrete was analyzed. • Test variable included aerogel particles, fly ash, foam and polypropylene fiber. • Developed concrete exhibited excellent thermal performance and mechanical strength. • Aerogel used in concrete had excellent thermal insulation performance. With increasing focus on low-carbon energy conservation and environmental protection, there is a need to consider all aspects of life in future developments. To meet the concept and requirements of energy conservation and environmental protection in the building industry, we have developed alkali-excited aerogel-foamed concrete that exhibits excellent thermal insulation performance and mechanical strength. The variables involved in its production include fly ash, foam, aerogels, and polypropylene fibres. In this study, the microstructure and mechanical and thermal properties of alkali-excited fly ash aerogel foam concrete was analysed. The results indicated that fly ash can replace a portion of the cement, resulting in a reduction in the thermal conductivity of the concrete. The addition of aerogels and foams to the concrete can significantly decrease its thermal conductivity. Specifically, when the aerogel content reaches 12 % and the foam content reaches 75 %, the thermal conductivity of the concrete decreases from 0.498 W/m·K to 0.183 W/m·K and 0.19 W/m·K, respectively. However, this decrease in thermal conductivity comes at a cost of approximately 50 % reduction in the flexural and compressive strengths of the concrete. The findings reveal that the aerogel has excellent thermal insulation performance similar to that of the foam, but it has little influence on the mechanical properties of the concrete. Additionally, an increase in the polypropylene fibre content significantly improves the mechanical properties of alkali-excited fly ash aerogel concrete, but the thermal properties of the concrete remain mostly unaffected. [ABSTRACT FROM AUTHOR]

To promote environmentally sustainable behavior, it is meaningful to develop a simple preparation method of polyurethane foam (PUF) with excellent performance and degradability. Herein, PUF composites were economically and conveniently synthesized by mixed foaming of polyurethane prepolymer and cellulose nanocrystals (CNCs). After the hydrolysis of dissolving pulp fibers with formic acid (FA), hydrophobic ester groups were introduced in CNCs, thereby increasing the surface hydrophobicity of PUF composites. CNCs acted as a reinforcement agent capable can replace 10% up to 60% prepolymer for foaming, the modified PUF exhibiting gradient morphology structure and enhanced specific mechanical and thermal properties. When the CNCs replacement ratio was 50%, the maximum compressive stress was 1103.19 kPa, which is 21-fold that of the original foam. Remarkably, the addition of CNCs enhanced thermal insulation performance of the prepared foam, which of thermal conductivity decreased from 0.0780 W/mK to 0.0549 W/mK. The upgraded polyurethane foam composites promise to open exciting new windows on producing fire resistance PUF with enhanced performance. [Display omitted] • PUF composites were fabricated by polyurethane prepolymer and CNCs. • Maximum compressive stress reached 1103.19 kPa at 50% replacement rate of CNCs. • Thermal conductivity of foams decreased from 0.0780 W/mK to 0.0549 W/mK. • Sustainable and economically feasible method for producing fire resistance PUF. [ABSTRACT FROM AUTHOR]

• Starch foam composites were prepared with rubber seed shell particles. • The smallest rubber seed shell particles were from milling at 600 rpm for 40 min. • Ball milling affected the color parameters and whiteness of the rubber seed shell. • 5.0 wt% GRS loading produced starch foam with the best mechanical properties. Starch foam composites containing rubber seed shell particles of different sizes were prepared and characterized. The first objective was to prepare small particles of rubber seed shell using a planetary ball mill at different rotational speeds (300 and 600 rpm) and milling times (20, 40 and 60 min) to optimize the milling condition to achieve the smallest possible particle size. The second objective was to study the influence of the size of the rubber seed shell particles on the properties of the starch foam. Laser particle size analysis and morphological observation by scanning electron microscope (SEM) revealed the optimal milling condition to be 600 rpm for 40 min. The smallest average particle size obtained at this condition was 51.57 μm. Starch foam containing the smallest particles (GRS) exhibited greater flexural stress at maximum load and narrower cell size distribution and had a lower density than starch foam composite with crude rubber seed shell (CRS) at the same filler content. The small size and high surface area of GRS enabled a better dispersion of filler particles and the establishment of stronger interactions within the starch matrix. The change in the color parameters and whiteness values of the rubber seed shell particles can be attributed to exposure to the heat generated by ball milling and the reduction of the average particle size. The effect of the addition of GRS and CRS on the thermal properties of the composites was determined by simultaneous thermogravimetry – differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

In this work, a facile microwave-assisted foaming and thermal imidization treatment method was proposed to fabricate flexible polyimide (PI)/rGO composite foams with anisotropic pore structures. The PI/rGO composite foams (PIF/rGO) were used as the starting derivatives to prepare carbon foams that demonstrated excellent anisotropic thermal insulation and electromagnetic interference (EMI) shielding applications. The directional growth of pore structures during the foaming period resulted in the formation of aligned ellipsoidal strip-like pore structure in the horizontal direction (i.e., perpendicular to the pore growth direction), which was attributed to the escape of foaming gases such as tetrahydrofuran, methanol and H 2 O. The homogeneous dispersion of rGO in the PI-derived carbon skeleton endowed corresponding carbon foams with excellent mechanical and thermal stability, high thermal insulation and electrical conductivity (σ) as well as absorption dominated EMI shielding performance. The σ and EMI shielding effectiveness (SE) of carbon foams showed an increasing trend with increasing rGO content. The σ, EMI SE and specific EMI SE of the carbon foams reached up to 33.0 S/m, 49.0 dB and 8792.8 dB/(g/cm2) in the horizontal direction, respectively. Therefore, this work provided a facile strategy to fabricate lightweight and anisotropic pore structure rGO-containing PIFs and carbonized derivatives, which demonstrated promising applications in high-end industrial fields. [Display omitted] • A facile strategy was proposed to prepare PIF/rGO and CF/rGO. • The directional growth of pores endowed foams with anisotropic properties. • The foams showed excellent mechanical and thermal insulation properties. • CF/rGO showed absorption-dominated EMI shielding performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous ceramic was prepared by foamed cenosphere/geopolymer technology. • Compressive strength of the foamed composites was improved after crystallization. • Lowest thermal conductivity was obtained after crystallization. In order to enrich the porosity and high-temperature performance of geopolymer, a facile synthesis of foamed fly ash/slag-based cenosphere/geopolymer composite and its in-situ formation of porous ceramic via heat treatment were provided. The synergistic effects of H 2 O 2 and fly ash cenospheres (FACs) on the phase evolution, pore distribution and properties were investigated. Results showed that the foamed samples with amorphous structure could be synthesized at room temperature and fully crystallized to porous ceramics containing mullite and leucite after treated above 1000 °C. Porosity of the samples was enhanced with the increase of H 2 O 2 ratio (1–6 wt%) and treated temperature (600–1200 °C). Compressive strength of the whole composites was improved after treatment, which was attributed to the crystallization, good interface combination (between FACs and matrix), fractured spheres and crack deflection. The samples also showed lowest thermal conductivity of 0.115 W/(m⋅K) and 0.107 W/(m⋅K) before and after high-temperature treatment, respectively. It provided a strategy to prepare porous foam using solid waste and had the application to be used in insulation fields. [ABSTRACT FROM AUTHOR]

Ethylene propylene diene monomer (EPDM) rubber based bio-composites filled with silane-modified wood fiber (SiWF) were foamed by using chemical foaming method. The SiWF and the incorporation of dicumyl peroxide (DCP) generated crosslinking in the developed EPDM bio-composite foams, which showed much lower water absorption and improved thermomechanical properties. With SiWF and in situ cross-linking, the tensile strength and modulus of EPDM bio-composite foams exhibited up to 90% and 600% enhancement compared to the unfilled foam, respectively. The compressive strength and modulus individually showed up to 170% and 600% increase. The developed bio-composite foams also displayed lower apparent thermal conductivity than the unfilled EPDM foam over the heating temperature range, showing possible applications as insulation materials. [Display omitted] • Sustainable EPDM based bio-composite foams were designed and synthesized. • Silane-modified bio-composite foams showed much lower water absorption. • The bio-composite foams displayed cross-linking and improved properties. • The bio-composite foams displayed appealing insulation properties. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) were successfully fabricated through thermal foaming of polyester ammonium salt precursors (PEASs) with the addition of a pararosaniline base (PA) as a crosslinker. These foams exhibited good mechanical properties and thermal resistance. The construction of crosslinked structure derived from PA could improve melt viscosity and provide cell walls with sufficient strength to prevent shrinkage, which was conducive to elevating compressive properties. PIF BMP -2 (i.e., repeating unit was 2) exhibited optimal compressive strength of 1.76 and 1.25 MPa at room temperature (RT) and 200 °C, which were increased by 6.6 and 7.9 times compared to PIF BM (0.17 MPa (RT) and 0.11 MPa (200 °C)). Furthermore, a relationship between compressive strength and density was established, showing that the compressive strength is proportional to 2.34 and 2.13 powers of density at RT and 200 °C, respectively. Moreover, PIFs owned excellent thermal properties, the 5% weight loss temperature was higher than 458.9 °C in a nitrogen (N 2) atmosphere, and the glass transition temperature was up to 291.3 °C. Additionally, the thermal conductivities of the rigid polyimide foams (PIFs) ranged from 0.058 to 0.094 W m−1 K−1, which makes them highly suitable for potential applications in the fabrication of high-temperature resistant multifunctional composites, particularly in aerospace, defense, and transportation industries. [Display omitted] • Rigid polyimide foams were fabricated with pararosaniline base as a crosslinker. • Crosslinked structure could significantly improve mechanical properties of fabricated foams. • Relationship between PI chains and properties was investigated. [ABSTRACT FROM AUTHOR]

Thermoplastic polyester ether elastomer (TPEE) vitrimers with different dynamic crosslinked networks were synthesized via zinc (II) acetylacetonate-catalyzed epoxy chemistry. The effects of bond exchange within networks, characterized by number of catalytic centers per crosslink (CC), and the dynamic crosslinked topology, characterized by number of entanglement and crosslinking points per crosslink (EC), on thermal, rheological, and foaming properties of TPEE vitrimer were compared. The results show that increasing EC is more favorable for lower crystallization temperature than improving bond exchange owing to the bad structural symmetry but almost constant crystallinity owing to the branches. TPEE vitrimer with a complex dynamic crosslinked topology exhibited slow relaxation with a stronger relaxing response and steeper strain hardening than that with more bond exchanges, indicating better viscoelasticity. Moreover, the good foaming behavior of TPEE vitrimers was ascribed to the dynamic crosslinked networks, which promoted heterogeneous nucleation to increase the cell density, and strain hardening good for cell growth as it suppressed cell coalescence and rupture. Furthermore, increasing CC facilitates bond exchange, promoting more uniform heterogeneous nucleation and cell size dispersity than those afforded by a complex dynamic crosslinked topology achieved by increasing EC. The improvement of foaming behavior for TPEE vitrimer is quite different from that of branched polymer by enhancing cell growth rather than cell density. [Display omitted] • TPEE vitrimers were successfully synthesized based on epoxy-acid chemistry. • Complex dynamic crosslinked topology resulted in good viscoelasticity. • Dynamic crosslinked networks contributed to good foaming behavior. • Complex dynamic crosslinked topology resulted in higher expansion ratio of TPEE vitrimer foams. • Bond exchanges led to a more uniform cell size dispersity of TPEE vitrimer foams. [ABSTRACT FROM AUTHOR]

A foam ceramic was prepared using molybdenum tailings (97–99.5 wt%) as the raw material and SiC as the foaming agent. The results showed that with increasing SiC content, the liquid-phase viscosity decreased, which in turn enhanced the overall expansion of the system, leading to a decrease in the thermal conductivity. The effects of the SiC content on the bulk density, porosity, pore size, and thermal conductivity were investigated in detail. Moreover, the experimental results were compared with several analytical models, and we found that the parallel model closely agreed with the predictions. The sample prepared via sintering at 1150 °C using 2.5 wt% SiC and molybdenum tailings exhibited a low bulk density of 0.37 g/cm3, high porosity of 85.14%, and low thermal conductivity of 0.22W/m·K. Thus, the application of molybdenum tailings in the production of foamed materials is considered to have potential economic and environmental advantages. • The foam ceramic with high content (97–99.5 wt%) of molybdenum tailings. • The viscosity of molybdenum tailings with SiC during sintering process was characterized by high temperature microscope. • Effect of SiC content on the thermal conductivity of foam ceramic was investigated by theoretical models and actual test method. [ABSTRACT FROM AUTHOR]

Highlights • Eco-friendly fillers and phosphorus decreased the heat released in polyurethane foams. • Lignin acted as a charring agent in combination with phosphorus containing polyol. • Layered double hydroxides improved the quality of the char formed during combustion. Abstract Flexible polyurethane foams with densities of 40 ± 2 kg m−3 were prepared by combining different eco-friendly fillers such as layered double hydroxides (LDH) and kraft lignin (a byproduct of the pulp and paper industry) with a phosphorous polyol (E560) in order to study their effect on the mechanical performance and fire behavior of the foams. Two series of foams were prepared, some containing lignin or LDH separately, and some with a combination of both: one of the series was prepared without E560 (0E foam series) and the other with 5 parts per hundred of E560 polyol (5E series). The use of fillers resulted in increased viscosity of the reactive mixture, requiring higher blowing agent content in order to hold the density of the foams constant. It was observed that urea phase segregation was favored in the series of 0E foams due to their lower viscosity than the 5E series. This had consequent effects on the resilience, compression force deflection and compression set of these foams. In terms of fire behavior it was observed that while the limiting oxygen index decreased, cone calorimeter results showed that the combination of lignin, LDH and E560 decreased the heat release of the foams. In addition, the combination of fillers and E560 contributed to increase the viscosity of the pyrolysis products, preventing the dripping of the molten polymer, which is a key factor in flame propagation towards adjacent objects in fire scenarios. [ABSTRACT FROM AUTHOR]

It has been a great challenge to prepare high-expansion-ratio polylactide (PLA) foam with eminent thermal insulation and compression performance in packaging field. Herein, a naturally formed nanofiller halloysite nanotube (HNT) and stereocomplex (SC) crystallites were introduced into PLA with a supercritical CO 2 foaming method to improve foaming behavior and physical properties. The compressive performance and thermal insulation properties of the obtained poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA)/HNT composite foams were successfully investigated. At a HNT content of 1 wt%, the PLLA/PDLA/HNT blend foam with an expansion ratio of 36.7 folds showed a thermal conductivity as low as 30.60 mW/(m·K). Meanwhile, the compressive modulus of PLLA/PDLA/HNT foam was 115% higher than that of PLLA/PDLA foam without HNT. Moreover, the crystallinity of PLLA/PDLA/HNT foam was dramatically improved after annealing, thus the results showed that compressive modulus of the annealed foam increased by as high as 72%, while it still maintained good heat insulation with the thermal conductivity of 32.63 mW/(m·K). This work provides a green method for the preparation of biodegradable PLA foams with admirable heat resistance and mechanical performance. • The PLLA/PDLA/HNT composite foams with high expansion ratios were fabricated by scCO 2. • The thermal conductivity of PLLA/PDLA/HNT composite foams was as low as 30.60 mW/(m·K). • The annealing process further improved the compressive performance of PLLA/PDLA/HNT composite foams. [ABSTRACT FROM AUTHOR]

Hybrid coated open-cell foams have been proposed as an economical solution for obtaining tailored and application-optimized properties. These hybrid foams integrate commercially available metallic foams or cellular metallic solids with metallic coatings of different constituents and thicknesses to realize tailored elastic, yield, and thermal properties that can satisfy the needs of a wide range of multifunctional applications. This work aims to explore the range of tailored properties that can be obtained using a hybrid foam system that comprises copper coatings and the widely available aluminum open-cell foams. The elastic, plastic, and thermal conductive properties of the considered hybrid foam system are determined using computational tools for a range of porosities and coating thicknesses. Results show that the hybrid foam system can deliver significantly higher stiffness, yield strength, and thermal conductivity than its aluminum foam substrate. In few of the studied configurations, the stiffness and thermal conductivity of the hybrid foam system exceeded those of its aluminum foam substrate by more than 100%. Relative improvement in the hybrid foam properties correlated nonlinearly with the porosity of its aluminum foam substrate. Semi-empirical models were developed to predict the properties of hybrid coated open-cell foams. These models can assist engineers in selecting the hybrid foam parameters, such as coating constituent material and thickness, needed to obtain tailored elastic, yield strength, and thermal conductivity. • The multi-functional properties of hybrid aluminum-coated foams are investigated. • Multi-functional properties considered include effective elastic, yield, and thermal conduction. • Hybrid foams are shown capable of providing tunable multi-functional properties. • Models are developed to help in selecting the coating parameters required to obtain a desired multi-functional response. [ABSTRACT FROM AUTHOR]

Ceramic-polymer composites with an interpenetrating network structure have a lot of advantages, which can be achieved by connecting two quite different phases. Infiltration of liquid epoxy resin into the cellular alumina matrix is the most suitable way of producing this type of materials and offers an opportunity for a precise and simple fabrication method of ceramic-based interpenetrating composites. Alumina foams manufactured by “gel-casting” method were infiltrated by new tri-functional epoxy resin (triglycidylized para-aminophenol) designed for special aircraft applications. Combination of this new epoxy resin with high-porous alumina foams causes higher compressive strength and better flammability of ceramic/polymer composite than either individual component. Additionally, alumina/epoxy composites with partial pores filling ratio showed satisfactory acoustic absorption characteristics. Development of this type of composites is a result of need to research new, lightweight materials with increased mechanical strength, non-inflammable and another functional features, e.g. noise reduction ability, design for the aerospace industry. Therefore, presented paper investigates flammability, acoustic absorption and mechanical properties of resulted composites. [ABSTRACT FROM AUTHOR]

Open-cell phosphoric acid-based geopolymer foams with a homogeneous microstructure were synthesized by frothing using Triton X-100 as surfactant. When conducting the geopolymerization in a closed environment at 75 °C for 24 h, the frothing route enabled the production of geopolymer foams with a total porosity of ~78.3 vol%, open porosity as high as ~76.8 vol%, and possessing a compressive strength of ~0.64 MPa. [ABSTRACT FROM AUTHOR]

• Cone/plate structured evaporators have been designed for solar evaporation. • Cone/plate structures can effectively suppress thermal conduction-caused heat loss. • High evaporation rate of 2.21 kg m−2 h−1 with an efficiency of 131.4% was achieved. • High sea water evaporation capacity of 5.68 kg m−2 on a cloudy day was achieved. Solar-driven interfacial evaporation is a new and promising way to produce clean water. Suppression of heat loss is of great importance in solar-driven interfacial evaporators because it is the key to localizing solar-thermal energy. Up to date, most attention has been paid to suppressing heat loss by using materials with low thermal conductivity. Rare attention has been paid to suppressing heat loss by minimizing the contact area between photothermal conversion surfaces and other parts of evaporators, to the best of our knowledge. Herein, we develop a new design of cone/plate structure to suppress thermal conduction-caused heat loss by minimizing the contact area between photothermal film and its substrate. Under 1 sun illumination, the temperature gap between the top and side surfaces of a normal melamine foam evaporator is 12.3 °C, and it increases to 22.7 °C in a cone/plate structured evaporator, suggesting improved heat loss suppression and heat localization. In a normal melamine foam evaporator, an evaporation rate of 1.66 kg m−2 h−1 and a corresponding efficiency of 66.2% are obtained under 1 sun illumination. In the same condition, a high evaporation rate of 2.21 kg m−2 h−1 and a high corresponding efficiency of 131.4% can be achieved in a cone/plate structured evaporator. Meanwhile, cone/plate structured evaporators have high properties of dye water purification and seawater desalination. Simulated sea water evaporation tests show a high water evaporation capacity of 5.68 kg m−2 on a cloudy day, and the salinity in the condensed water (Na+ ions, 3.2 mg L−1) is below the WHO standards for drinkable water. Moreover, the cone/plate structured evaporator has low cost to produce, and can be easily scaled up for practical applications. [ABSTRACT FROM AUTHOR]

In this work, a phosphorus-containing soybean oil-based polyol (PSOP) was successfully synthesized from epoxidized soybean oil by a ring-opening reaction with dibutyl phosphate. A phosphorous polyol (HEDP-PO) was synthesized by polymerization between 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and propylene oxide (PO). The two new polyols were used together in the formation of flame-retardant polyurethane foams (FRPUF), which depicted good thermal stability and flame retardancy performance. The addition of PSOP/HEDP-PO polyols resulted in a reduction of cell size and an increasement of cell numbers of PUF composites, whose apparent density was observed to increase. Besides, the LOI value of PUF-80 could reach 23.7% and satisfy the V -0 rating in the vertical burning test. The cone calorimeter test showed a reduction in the heat release rate from 395 kW/m2 to 251 kW/m2 and the total heat release from 24.9 MJ/m2 to 18.0 MJ/m2. Polyurethane foam exhibited good flame retardancy because PSOP/HEDP-PO played a great free radical quenching effect in the gas phase by releasing the PO* and PO 2 * free radicals. Meanwhile, a more dense and complete carbon layer was formed to cut off the transfer of heat and oxygen between the matrix and the ambient. [Display omitted] • A new bio-based containing phosphorus (PSOP) was successfully synthesized. • Reactive phosphorus polyols (PSOP and HEDP-PO) were successfully synthesized. • PSOP/HEDP-PO in RPUF enhanced its flame retardancy. • The flame-retardant mechanism is proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-quality graphene prepared by electrochemical exfoliation. • Modification of graphene with dopamine. • Construction of PGF using metal ion-assisted gelation pathway. • The unidirectional freezing enables the foam to have a vertically aligned structure. • PGF/EP composite exhibits high thermal conductivity and excellent electrical insulation. Although graphene has aroused considerable interest in the thermal conductive enhancement of polymer composites for its superb intrinsic thermal conductivity, the enhancement efficiency is still limited by its production-induced defects, misalignment and intense phonon interface scattering. Herein, the three-dimensional (3D) polydopamine-graphene foam (PGF) with high orientation and good interfacial bonding has been prepared by electro-exfoliation, surface modification and unidirectional-freezing. This unique structure imparts excellent thermal conductivity, electrical insulation and good mechanical property to the PGF/epoxy (PGF/EP) composite. The highly arranged and compact stacked PDA-graphene sheets bound by metal ions provide heat conduction paths for effective phonon transport within the matrix. The manufactured PGF/EP shows enhanced through-plane thermal conductivity of 3.48 W/m·K with 3.02 vol% of PGF, excellent surface & volume electrical resistivity (2.7 × 1011 Ω and 1.65 × 1011 Ω·cm) and high mechanical strength (82.74 MPa), as well as the outstanding heat dissipation performance. Therefore, the PGF/EP composites prepared in the present study have a broad application prospect in advanced electronic packaging materials. [ABSTRACT FROM AUTHOR]

This study investigate the influence of gamma-irradiation (GI) doses from 0 up to 50 kGy on the polypropylene (PP) foams, mainly the impact on their structural and physical properties. It was found that structural properties were not significantly changed and the cellular structure of the PP foams sustain the same, while the thermal properties were significantly enhanced with increasing GI doses, due to the present cross-linking created within the irradiation. The cross-linking was confirmed also by the swelling measurements. The dielectric properties shows the three time increase of capacitance with increasing GI doses, due to the additional charges created in the foam voids by GI. Investigated mechanical properties in case of tensile tests as well as dynamical mechanical analysis proved, that enhanced behaviour was observed only in case of samples with irradiated by low doses, 1 kGy and 5 kGy, respectively, while the higher doses significantly decrease these ones, due to the present scission confirmed by FTIR and other investigations. Finally, it was found the competition between the cross-linking of the PP foam and present scission due to the applied GI and therefore the physical properties can be easily tailored. [ABSTRACT FROM AUTHOR]

• PVA fibre affects strength, rheology and fire resistance of geopolymer foam (GFC) • Compressive strength continuously increased with the PVA fibre dosage. • It highly improved the fire resistance until 200°C, above which the impact was mild. • A very high PVA dosage worsened the fire resistance above 200°C. • It increased the yield stress of interstitial paste more than the geopolymer slurry. This study presents the effects of Poly Vinyl Alcohol (PVA) fibre on the rheology and fire resistance of geopolymer foam concrete (GFC), which are important for the foam stability and elevated temperature performance of GFC respectively. The yield stress of fresh geopolymer slurry and the interstitial paste, the strength of the hardened GFC and their fire resistance were assessed and correlated to the fibre content. The results showed that the yield stress of geopolymer slurry and interstitial paste increased with the fibre dosage by up to 16 times. Adding fibre also continuously improved the compressive strength by up to 54%. Furthermore, the residual strength after exposure to elevated temperatures was improved with the fibre until 2% dosage; this was noticeable until 200°C. However, further increasing the fibre dosage deteriorated the residual strength. [ABSTRACT FROM AUTHOR]

Metallic foams, especially copper foams (CF), have been investigated to solve the problems of leaking and low thermal conductivity of phase change materials (PCMs), which helps to promote the application in solar thermal energy storage and thermal management. In this paper, the surface and pore structure of commercial CF was modified by in-situ formed copper nanowires and the introduction of flake graphite (FG). The copper nanowires and embedded FG not only provide greater capillary absorption force to prevent the leakage of liquid paraffin but also enhance the thermally conductive and photothermal conversion efficiency of the phase change composites. The thermal conductivity of the modified CF supported composite PCM reaches 4.1 W m−1 k−1, which is 1.6 times of the un-modified CF supported composite PCM and 20.5 times of paraffin. These results indicate the great application prospects in the fields of solar thermal energy storage and thermal management. • Modified Cu foam with a multi-scale pore structure is prepared for supporting PCM. • The Cu foam is also embedded with flake graphite to enhance the photo absorption property. • The composite PCM indicates good anti-leakage property. • The composite indicates thermal conductivity of 4.1 W m−1 k−1, which is 20.5 times higher than PW. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by thermal foaming of active cross-linkable units terminated polyester ammonium salts (PEAS) precursor powders. The active cross-linking strategy was realized by breaking C C bonds in maleic anhydride under heating treatment. Results showed that the formation of cross-linked structure before complete imidization effectively resisted matrix shrinkage and endowed PIFs with outstanding mechanical properties. The room temperature compressive strength and modulus of PIFs with four repeating units reached as high as 2.34 and 56.1 MPa, respectively. Moreover, the PIFs exhibited excellent thermal properties with onset decomposition temperatures ranging from 490 to 550 °C and the glass transition temperatures exceeding 290 °C. The PIFs displayed better thermal insulation, and the values of thermal conductivity fell within a range of 0.056–0.090 W m−1 K−1, which demonstrates potential application as high temperature resistant structural materials in aerospace and energy sectors. [Display omitted] • Rigid PIFs were fabricated by thermal foaming of active cross-linkable units terminated PEAS precursor powders. • Cross-linking structure was formed before complete imidization which endowed PIFs with outstanding mechanical properties. • Relationship between chain structure and properties of rigid PIFs were investigated. [ABSTRACT FROM AUTHOR]

Triply periodic minimal surfaces (TPMS) are employed to create novel cellular materials. They include Schwarz Primitive, Schoen IWP, Neovius, Schoen Gyroid, Fischer-Koch S, and Schwarz CLP geometries. Unit cells are studied using a finite element method with periodic boundary conditions in order to predict effective electrical/thermal conductivities and elastic moduli of these TPMS-based foams. The conductivities vary linearly with relative density. The conductivities of the Primitive-, IWP-, Neovius-, Gyroid-, and S-foams are very close to each other. The conductivity of the CLP-foam needs to be described by two values because of its geometrical asymmetry while the other foams are found to be isotropic when their conductivities are studied. The uniaxial, shear and bulk moduli, Poisson ratio and elastic anisotropy of these TPMS-foams are also computed and compared. When the mechanical properties are investigated, the CLP-foam is found to have highest anisotropy among the considered TPMS-foams. In addition, the Primitive-foam possesses highest shear modulus while the Neovius, IWP-, and Primitive-foams possess highest bulk moduli among the TPMS-foams. [ABSTRACT FROM AUTHOR]

Geopolymers have been a frequently studied topic during the last decades due to waste materials utilization, low energy demands, and low carbon dioxide emissions related to their production, which makes them very attractive within the current environmental trends. However, the original idea to use them as a concrete replacement showed to be unattainable in the nearest future, so other alternatives of geopolymers applications are being sought that could exploit the efforts spent and research progress made so far. This review paper summarizes the recent progress in the field of directly foamed geopolymers, as one of the alternatives, focusing on the material base, foaming and stabilization processes, and assessments of selected material parameters, as related to raw materials used and treatment techniques applied. As the main result, several gaps and challenges are identified that deserve more attention and deeper investigations, which can help to move the geopolymer foams closer towards their regular application in civil engineering. A detailed knowledge of hygric parameters and their influence on thermal properties, long-term performance analyses in real-world applications, or extension of the material base to achieve environmental more friendly solutions represent the most topical issues that are supposed to be addressed. • Recent progress in the field of directly foamed geopolymers is reviewed. • Foaming and stabilization processes are analyzed. • Material parameters are assessed and linked to raw materials and treatment techniques. • An overview of durability of geopolymer foams is given. • Several gaps in the current knowledge are identified that require deeper investigations. [ABSTRACT FROM AUTHOR]

• Unidirectional anisotropic PIAs have been prepared by freeze-drying. • The PIA shows excellent thermal stability and stable mechanical behavior. • The u -PIA-6 exhibits great strength, which is over twice as high as that of the TEEK-HH at 177 °C with a similar density. • The u -PIA shows great thermal insulation properties in anisotropic. Polyimide aerogels (PIAs) are the new type of high-performance lightweight material that combines the excellent thermal and mechanical behavior of polyimides with the highly porous and lightweight properties of aerogels. PIAs can meet the increasing material requirements of high-tech fields such as the aerospace and transportation industries. This study reports a series of all-aromatic anisotropic polyimide aerogels (p-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA)) with unprecedented behavior. These PIAs were synthesized using a random or unidirectional freeze-drying method followed by thermal imidization of the precursor solution. Their mechanical and thermal conductivity performance were anisotropic (u -PIA-8 strength: 1.86 and 0.14 MPa, thermal conductivity: 62.9 and 50.1 mW·m−1·K−1 along the axial and radial direction, respectively). Furthermore, the PIAs possessed excellent compression behavior in a wide temperature range from 25 °C to 316 °C, with a compressive strength over twice that of the commercial polyimide foam TEEK-HH (u -PIA-6 strength: 0.83 and 0.32 MPa at 177 and 316 °C, TEEK-HH strength: 0.31 MPa at 177 °C). These aerogels also demonstrated good thermal insulation performance after being held at 300 °C for 20 min (u -PIA-8: 76.3 °C at 25 mm). These highly anisotropic aerogels exhibit flexible thermal protection properties that extend the potential use of PIAs to applications such as high-temperature-resistant rocket fairings, sandwich structures, and arc-shaped structures for aerobats or the automobile industry. [ABSTRACT FROM AUTHOR]