Absorption Materials Research Articles

Underwater sound absorption characteristics of water-saturated porous materials

In this research, the underwater sound absorption performance of porous media saturated with water is investigated through long straight tubes (LSTs) with circular cross-section and sintered fibrous metals (SFMs) containing complex pores, and effective underwater sound absorption capability is demonstrated theoretically, numerically and experimentally. Specifically, the theoretical model for LSTs, verified by direct numerical simulations (DNSs), reveals that much smaller pore diameter and much larger layer thickness of porous material is needed to gain high waterborne sound absorption coefficient than to obtain large airborne sound absorption coefficient. Besides, to examine the sound absorption capacity of realistic porous materials, SFMs backed with a finite cavity are experimentally measured under 7 different hydrostatic pressures in a water-filled tube, and numerically characterized via multi-physics couplings. Insensitivity of effective sound absorption capability to high pressure is established, which stems from the different underwater wave energy consumption mechanism (i.e. viscous-thermal effect) of porous materials from conventional rubber kind of underwater sound absorption materials. Physically, porous materials possess great potential in developing the next generation of high-performance underwater sound absorption materials.

Broadband microwave absorption and antibiosis effect of Cu@C@Fe3O4 nanocomposites

Metal Cu nanoparticles have been recognized as the long-standing presence in the fields of antibacterial and low-induced bacterial resistance, however, the uncontrollable Cu ion concentration from Cu nanoparticle leads to the unstable release of copper ions, limiting their controllable antibacterial application. Based on stable release of copper ions from Cu@C nanocapsules, herein, we report a novel A/B/C structure Cu@C@Fe3O4 nanocomposite to present integrated functionalities of highly controllable antibiosis and electromagnetic wave (EMW) absorption to realize a bifunctional EMW absorption system. With stable concentration, the Cu@C@Fe3O4 nanocomposite can slowly release Cu ions to experience an efficient reactive oxygen species process to realize extreme stable antibiosis behavior and long-term antibacterial effect that is 100 % bactericidal effect. With the sustained antibacterial conditions, the Cu@C@Fe3O4 with magnetic component simultaneously exhibits a good impedance matching to lead a broad microwave absorption with a bandwidth of 5.87 GHz. Considering above two functions, the multifunctional Cu@C@Fe3O4 provides a pathway for multifunctional EMW absorption materials exploration in antibacterial and microwave absorption applications. This strategy also indicates the possibility to functionalize magnetic nanocapsules towards even broader applications.

Integrated design of multifunctional lightweight magnetic cellulose-based aerogel with 1D/2D/3D hierarchical network for efficient microwave absorption

Developing electromagnetic wave absorption materials that are both multifunctional and high-performance, while using rational dimensional design and component strategies, remains extremely challenging. Herein, multidimensional, gradient porous, electrically, and magnetically conductive carbon nanocellulose aerogels composed of nanocellulose and highly oriented Ni chains are prepared through freeze-drying and subsequent low-temperature annealing. Interestingly, the Ni/CNCA composite achieves exceptional microwave absorption with a minimum reflection loss (RLmin) value of −62.0 dB and a maximum effective absorption bandwidth (EAB) of 6 GHz, covering the entire Ku-band. The superior electromagnetic wave absorption stems from 1D/2D/3D double-supported interpenetrating network with satisfactory impedance matching, dielectric/magnetic losses, interface/dipole polarization, and multiple/reflection scattering. Furthermore, the Ni/CNCA exhibits a low density, excellent mechanical adaptability, hydrophobicity, and corrosion resistance. This work introduces innovative approaches for developing lightweight, multifunctional microwave absorbers for practical applications.

Advanced acoustic design: 3D printed thermoplastic folded core sandwich structures with porous materials and microperforations for enhanced sound absorption

This study introduces a novel sound-absorbing sandwich structure with a folded core, created through 3D printing technology, to address the challenge of weak sound absorption in the low-frequency range in sound absorption materials (SAMs). The structure comprises chopped carbon fiber–dispersed thermoplastic polyamide (CF-PA), continuous carbon fiber (CCF) filaments, and polyurethane (PU) foam coated with graphene oxide (GO). Simulation studies revealed that optimized structural parameters and microperforation diameters resulted in enhanced sound absorption coefficient (SAC) of 99 % or more at 1250 Hz, within the low-frequency range (160–1600 Hz). The GO-coated PU foam SAMs demonstrated excellent sound absorption performance measured in the high-frequency range (1600–6000 Hz), achieving 99 % SAC at 2400 Hz. Furthermore, the manufactured folded core structure exhibited outstanding sound absorption performance, achieving SAC of 99 % at 732 Hz measured in the low-frequency (160–1600 Hz) band and 99 % at 600 Hz, showcasing broad absorption capabilities measured in the high-frequency band (160–6000 Hz). Additionally, a flatwise compression test on the structure filled with GO-coated PU foam demonstrated a 32 % improvement in compressive load, indicating the structure’s versatility for various applications.

MXene-derived titanate heterojunctions with lightweight and heat-resistant properties for electromagnetic wave absorption

The development of high-efficiency titanate-based electromagnetic wave (EMW) absorbers presents a significant challenge, primarily due to the limited number of loss mechanisms available in such materials. Herein, an innovative approach has been employed, utilizing g-C3N4 as a connecting bridge linking KTi8O16.5 nanorods with Fe2O3 nanoparticles, thereby crafting a KTO/Fe2O3–CN absorber with a dual heterojunction architecture. This sophisticated structure is realized through a detailed freeze-drying process followed by heat treatment. In this structure, g-C3N4 and KTi8O16.5 originate from melamine and MXene precursors, respectively, while Fe2O3 component is derived from the thermal decomposition of FeSO4. The integrated KTO/Fe2O3–CN system fosters enhanced interfacial and dipole polarization, as well as conduction and magnetic loss, all collaboratively aiding in the attenuation of EM waves. In addition, the specially designed EMW absorber is notable for its lightweight nature, along with impressive heat dissipation and resistant performance. It demonstrates exceptional thermal stability, capable of withstanding temperatures as high as 500 °C and sustaining repeated thermal cycles at 400 °C. This strategy not only elevates the efficacy of titanate-based EMW absorbers but also paves the way for the conceptualization of high-performance, multifunctional EMW absorption materials. Such advancements hold the promise of transforming a wide range of applications that necessitate effective EM wave attenuation, marking a significant leap forward in the field.

Hierarchical porous SiCnws/SiC composites with one-dimensional oriented assemblies for high-temperature broadband wave absorption

The research on high-performance electromagnetic wave absorption materials with high-temperature and oxidative stability in extreme environments is gaining popularity. Herein, the lightweight silicon carbide nanowires (SiCnws)/SiC composites are fabricated with in-situ SiC interface on one-dimensional oriented SiCnws skeleton, which collaborative configuration by 3D printing and freeze casting assembly. The constructed porous structure optimizes the impedance matching degree and scattering intensity, the maximum effective absorption bandwidth (EABmax) of 5.9 GHz and the minimum reflection loss (RLmin) of −41.4 dB can be realized. Considering the inherent oxidation resistance of SiC, the composites present well-maintained absorption performance at 600 °C. Even at 1100 °C, the EABmax of 4.9 GHz and RLmin of −30.4 dB also demonstrate the high-temperature absorption stability of the composites, indicating exceptional wave absorption properties and thermal stability. The slight attenuation can be attributed to the decrease in impedance matching capability accompanying the elevated dielectric constant. This work clarifies the impact of structure and component synergy on wave absorption behavior, and offers a novel approach to producing high-performance and high-temperature resistance ceramic-based electromagnetic wave absorption materials suitable for extreme environments.

Broadband absorptive metamaterials enhanced by magnetic rubber to broaden bandwidth

A method to extend the operational bandwidth of metal-dielectric-metal (MDM) type absorptive metamaterials is proposed. An ultrathin, five-band absorptive metamaterial with wide-angle absorption and polarization sensitivity in the X-band is designed. The total absorption bandwidth across the five bands, with reflection losses below −10 dB (absorption rate greater than 90 %), is nearly 1 GHz. The physical mechanisms of absorption are analyzed through the distributions of surface current, electric field, and magnetic field. Samples were fabricated and tested, and the results were consistent with the simulation outcomes. To enhance the bandwidth of the absorptive metamaterial and its application prospects, magnetic materials such as barium ferrite and carbonyl iron were introduced into a rubber vulcanization layer, which was then combined with the ultrathin absorptive material to create a novel absorptive material. When the magnetic material content in the rubber layer was 50 wt%, the frequency range with reflection losses below −10 dB increased by approximately nine times, covering 69.5 % of the C-Ku band. This significantly broadens the bandwidth of the pure MDM-type absorptive metamaterial, providing a feasible solution for the design of broadband ultrathin absorptive materials.

Template‐Made Ultrahigh, Broadband, and Omnidirectional Light Absorption Surface for Enhanced Solar Energy Harvesting and Utilization

AbstractThe practical application of solar energy harvesting urgently calls for the facile preparation of high‐performance ultrablack surfaces with broadband and omnidirectional light absorption performance; however, some roadblocks still need to meet these requirements simultaneously. Herein, cone‐array ultrablack (CAUB) surfaces are prepared by combining feasible template replication and blade coating techniques. The elaborate micro‐sized cone structure and high absorptive materials (polydimethylsiloxane@carbon black, PDMS@CB) offer the CAUB extremely high, broadband, and omnidirectional light absorption over the solar spectrum with an average absorbance of 99.35%. Under one sun irradiation, the CAUB can efficiently absorb solar energy, reaching a surface temperature as high as 75 °C. A solar‐thermal‐electric generator (STEG) made from the CAUB film demonstrates real‐time solar‐heat‐electric conversion, achieving a high output power density of 330 µW cm−2. The CAUB film possesses excellent water repellency, flexibility, chemical solvent resistance, and potential for large‐scale production, satisfying the application requirements of solar energy harvesting and utilization.

Ultralight Hierarchical Fe3O4/MoS2/rGO/Ti3C2Tx MXene Composite Aerogels for High-Efficiency Electromagnetic Wave Absorption.

Aerogel-based composites, renowned for their three-dimensional (3D) network architecture, are gaining increasing attention as lightweight electromagnetic (EM) wave absorbers. However, attaining high reflection loss, broad effective absorption bandwidth (EAB), and ultrathin thickness concurrently presents a formidable challenge, owing to the stringent demands for precise structural regulation and incorporation of magnetic/dielectric multicomponents with synergistic loss mechanisms within the 3D networks. In this study, we successfully synthesized a 3D hierarchical porous Fe3O4/MoS2/rGO/Ti3C2Tx MXene (FMGM) composite aerogel via directional freezing and subsequent heat treatment processes. Owing to their ingenious structure and multicomponent design, the FMGM aerogels, featured with abundant heterogeneous interface structure and magnetic/dielectric synergism, show exceptional impedance matching characteristics and diverse EM wave absorption mechanisms. After optimization, the prepared ultralight (6.4 mg cm-3) FMGM-2 aerogel exhibits outstanding EM wave absorption performance, achieving a minimal reflection loss of -66.92 dB at a thickness of 3.61 mm and an EAB of 6.08 GHz corresponding to the thickness of 2.3 mm, outperforming most of the previously reported aerogel-based absorbing materials. This research presents an effective strategy for fabricating lightweight, ultrathin, highly efficient, and broad band EM wave absorption materials.

The effect of natural waste filter on dimethyl ether production from low calorific coal gasification

In Indonesia, rapid population growth has increased energy demand, especially in the transportation and power generation sectors. The Indonesian government has been active in promoting the use of renewable energy, but the transition from fossil energy is still faced with various challenges, including limited technology and adequate infrastructure. Apart from that, Indonesia's large potential in coal is the main factor slowing down this energy transition. One promising alternative is to convert coal into Dimethyl Ether (DME) through the gasification process, which is a thermochemical process for converting solid fuel into gas, producing syngas containing H2, CO, and CH4. Synthesis purification is essential to produce high-purity DME. This process involves the use of filter materials such as zeolite and rice husk charcoal to remove contaminants such as sulfur. Zeolite, with its chemical absorption properties and regular pore structure, is effective in absorbing H2S from syngas. Meanwhile, rice husk charcoal, which is an agricultural waste rich in silica and has a porous structure, has shown potential as an absorbent material to reduce H2S content in gas. In research on the use of various filter material compositions in the up-draft type coal gasification process with CuO–ZnO–Al2O3 and ZSM-5 catalysts, it was found that a 3:7 ratio for zeolite and rice husk charcoal provided optimal performance. This ratio not only increases CH4 and CO levels in syngas, but is also effective in reducing H2S content. The research results showed that the highest DME production reached 90.10% at a ratio of 3:7, while at a ratio of 2:8 and 5:5, production was 81.61% and 73.64% respectively. These findings emphasize the importance of using diverse filter materials in improving syngas quality and DME synthesis efficiency, strengthening steps to accelerate the energy transition towards more sustainable solutions in Indonesia.

The role of glycerol in manufacturing freeze-dried chitosan and cellulose foams for mechanically stable scaffolds in skin tissue engineering

Various strategies have extensively explored enhancing the physical and biological properties of chitosan and cellulose scaffolds for skin tissue engineering. This study presents a straightforward method involving the addition of glycerol into highly porous structures of two polysaccharide complexes: chitosan/carboxymethyl cellulose (Chit/CMC) and chitosan/oxidized cellulose (Chit/OC); during a one-step freeze-drying process. Adding glycerol, especially to Chit/CMC, significantly increased stability, prevented degradation, and improved mechanical strength by nearly 50%. Importantly, after 21 days of incubation in enzymatic medium Chit/CMC scaffold has almost completely decomposed, while foams reinforced with glycerol exhibited only 40% mass loss. It is possible due to differences in multivalent cations and polymer chain contraction, resulting in varied hydrogen bonding and, consequently, distinct physicochemical outcomes. Additionally, the scaffolds with glycerol improved the cellular activities resulting in over 40% higher proliferation of fibroblast after 21 days of incubation. It was achieved by imparting water resistance to the highly absorbent material and aiding in achieving a balance between hydrophilic and hydrophobic properties. This study clearly indicates the possible elimination of additional crosslinkers and multiple fabrication steps that can reduce the cost of scaffold production for skin tissue engineering applications while tailoring mechanical strength and degradation.

Electrospinning fabrication of hollow C@TiO2/Fe3C nanofibers composites for excellent wave absorption at a low filling content

In order to face the challenge of achieving high-efficiency and lightweight wave absorption materials, we prepared the poly-m-phenylene isophthalamide (PMIA)/TiO2/Fe3C (PTF) composites with hollow structure by coaxial electrospinning and carbonization process. PMIA as the carbon source provided a three-dimensional (3D) conductive network, using TiO2 and Fe3C to improve the impedance matching, reinforce the hollow structure, and increase the absorption mechanism of composites. Significantly, the minimum reflection loss (RLmin) value of optimal material is −58.1 dB at 14.88 GHz and the effective absorption bandwidth (EAB) of 6 GHz with the matching thickness of 2.3 mm, and the filling content is only 13 wt%. The excellent absorption property is maintained even after heating, immersing, and long-term use. This work provides the reference of hollow carbon nanofiber absorbers with excellent comprehensive properties and has more powerful practicability in a variety of environmental conditions.

Effect of tubular-typed charcoal height variations on efficiency in passive interfacial solar desalination

Passive solar desalination is a process of reducing the salt content of salt water to produce fresh water by utilizing solar heat. In recent years, interfacial heating has been proposed as an alternative to evaporation by creating localized heat on the water surface. Charcoal is an absorbent, heat storage, and wettability material, so the evaporation process not only occurs on the surface of seawater but also on the surface of the charcoal, which results from this wettability. The height of the charcoal indicates the distance the steam travels to reach the glass surface for the condensation process, thereby speeding up evaporation. The experiment was carried out in 4 single-slope-type basins using tubes filled with charcoal as high as 30, 40, and 50 mm for 8 hours in the sun. The results showed that adding heat-absorbing material to the basin was able to accelerate seawater to reach its boiling point so that it could evaporate. The temperature and humidity in each basin also have a similar changing trend where temperature is strongly influenced by solar radiation. The use of charcoal can also increase the rate of convection and evaporation heat transfer in the basin, as well as the maximum efficiency in basin 4 with an efficiency value of 56.40%, basin 2 at 53.17%, basin 3 at 51.62%, and basin 1 44.17%. Efficiency is obtained from the desalination efficiency equation, namely the ratio of the latent heat of vaporization to the solar energy entering the system

Study of the thermal diffusivity in low-response optical systems combining a thermal lensing approach with a standard addition method

Abstract Thermal lensing is a local effect produced by the incidence of a light beam that heats a part of an absorbent material. Mathematical modeling of this photothermal phenomenon allows the determination of the medium’s thermal diffusivity. A pumping-modulated laser (405nm) induces the thermal lensing effect, and a test laser (650nm) generates the photothermal signal measured as a function of the modulation. The thermal diffusivity is obtained from a curve fit of the signal (calibrated for ethanol). In this work, the thermal diffusion coefficients of low-absorbance nanoparticle suspensions are established. This was achieved through the application of a standard addition method. The added analyte, enhance the optical response of SiO 2 nanoparticle suspensions. Different aliquots of tartrazine (analyte) resulted in different values for the thermal diffusion of the samples. It was found that the experimental coefficients of this colloids agree with the theoretical model. Finally, a linear regression allowed to find the thermal coefficient in the zero concentration point.

(B4C+Al2O3)/Al composites with excellent high temperature strength and thermal stability prepared by sintering in air atmosphere

B4C/Al composites are commonly used as neutron absorption materials. The introduction of amorphous Al2O3 through surface oxidation of Al powder can significantly enhance the mechanical properties of the composites; however, the thermal stability of the composite is compromised due to the inherent instability of amorphous Al2O3. In this study, (B4C + Al2O3)/Al composites were sintered in an air atmosphere with high pressure for the first time, generating stable γ-Al2O3. It was found that in comparison with the conventional vacuum sintering process, (B4C + Al2O3)/Al sintered in an air atmosphere exhibited increases in ultimate tensile strength of 42 % at room temperature and 90 % at 350 °C. Furthermore, due to the reaction between Al and oxygen, the composite exhibited exceptional thermal stability when subjected to annealing at 620 °C, demonstrating an ultimate tensile strength of 144 MPa at 350 °C, surpassing values reported in other studies.

Construction of three-dimensional aerogels from electrospun cellulose fibers as highly efficient and reusable oil absorbents

The escalating environmental impact of oil pollution has necessitated the development of efficient and sustainable absorbent materials. Considering the large surface area and good flexibility of electrospun fibers, in this work, we aim to construct three-dimensional interconnected porous structures by using electrospun cellulose fibers as building blocks to allow highly efficient and repeatable oil absorption. Specifically, electrospun cellulose fibers were dispersed in water and assembled by covalently crosslinking, followed by a silanization process to improve the hydrophobicity of the fibrous matrices. The structure and properties of the assembled aerogels were studied by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, water contact angle (WCA) measurement, and compression test. All the aerogels exhibited multiscale morphological structures composed of major pores (up to 20 μm), minor pores (up to 1 μm), and semi-micron scaled fibers as the building blocks, and were capable of absorbing diversified oils and organic solvents owing to their three-dimensional interconnected porous structures (porosity > 93.5 %). In particular, Aerogel 1–1 exhibited exceptional oil absorption capacities (up to 37.82 g/g) and superior reusability as evidenced by the minimal changes in its absorption capacity and compressive strength after 20 absorption-compression cycles. Therefore, this work highlights the potential of the electrospun cellulose fiber-constructed aerogels for efficient oil pollution remediation and industrial wastewater treatment.

Experimental and numerical investigations with multifunctional heat transfer fluid to evaluate the performance of a thermal energy storage system

In the upcoming decades, concentrated solar power (CSP) technology is expected to be one of the most promising methods of producing electricity.Along with the reduction in energy waste coupled with an increase in efficiency, the thermal energy storage (TES) systems are vital in refining the dependability and efficacy of the energy infrastructure and in reducing gap between supply and demand. This study aims to evaluate a parabolic trough collector by means of experimental investigation and mathematical modelling. Nanofluid is employed as an energy absorption material and transport medium from concentrating tube to storage tank. At consistent flow rate of 3.0 L per minute, a comparative evaluation is conducted between water and ZnS/ water-quantum dots at different volume concentrations (0.1, 0.2, 0.3, and 0.4 %). Heat exchanger-delivered sensible heat, thermal efficiency, heat removal factor, and energetic efficiency are used to examine the qualitative and quantitative performance of the system. The ZnS/ water-quantum dots ratio of 0.3 % (wt%) has been found to yield the maximum thermal and energetic efficiencies. At a solar intensity of 1210 W/m2, the highest thermal efficiency of 57.81 % is reflected by the experimental observations. At the same intensity, there is a 20.63 % increase in the energy efficiency. The charge and discharge of phase-changing material (PCM) are highly influenced by the flow rate of heat transfer fluid (HTF). By increasing the HTF flow rate from 1 to 3 L per minute, the solidification and melting times are shortened by 30 % and 10 %, respectively. This study emphatically reflects a high potential of employing nanofluid in TES to enhance the performance of energy infrastructure coupled with energy waste reduction.

Ant‐Nest‐Inspired Biomimetic Composite for Self‐Cleaning, Heat‐Insulating, and Highly Efficient Electromagnetic Wave Absorption

AbstractThe pursuit of eco‐friendly electromagnetic wave absorption (EMWA) materials with multifunctional capabilities has garnered significant attention in practical applications. However, achieving these desired qualities simultaneously poses a significant challenge. This study introduces a single‐step calcination and chemical polymerization process to obtain an environmentally friendly ant‐nest‐inspired hybrid composite by optimizing conductive polypyrrole nanotubes (PNTs) within a 3D carbonaceous structure. The biomimetic composite forms a highly efficient conductive network, providing a pathway for free electrons within the carbonaceous barriers and enhancing the conduction loss. Remarkably, the EMWA performance of the composite achieves ultrathin (1.6 mm), wide effective absorption band (5.4 GHz), and strong absorption intensity (−67.6 dB) features. Moreover, due to the complex and intertwined 3D continuous network, the obtained samples exhibit excellent thermal insulation and superhydrophobic behavior by inhibiting heat transfer and preventing localized areas from being prone to water absorption. These findings not only offer a sustainable and low‐cost production route for biomimetic carbonaceous composites but also demonstrate a high‐efficiency absorber with great multifunctionality as a green alternative to traditional EMWA materials.

Template-sacrificing synthesis of hollow Co@C nanorods for excellent microwave absorption

Metal organic frameworks (MOFs) have been widely used as microwave absorption (MA) materials owing to their varied structures and large specific surface area. However, it is still challenging to endow MOF derivatives with a rational structure to achieve outstanding microwave absorption. In this work, the hollow Co@C nanorods (HCCN) with lots of winding carbon nanotubes on the surface are obtained based on a template-sacrificing method which employs ZnO nanorods as templates and ZIF67 nanoparticles as ornaments. The HCCNs possess large pore size and specific surface area, efficiently improving the impedance matching. The 1D structure, abundant heterointerfaces and defects trigger strong conduction loss, interfacial and dipole polarization, respectively. Therefore, HCCNs exhibits excellent MA properties: the strong reflection loss of −66.8 dB at the thickness of 2.1 mm and the effective absorption bandwidth of 5.68 GHz at 2.5 mm. Radar cross section (RCS) simulation results have confirmed the practicality of HCCNs. This study proposes an inspiration for the structural designing of MOF materials and derivatives to realize amazing MA performance.

Lightweight and robust electrospun zirconia fiber reinforced carbon aerogel composites for efficient microwave absorption and heat insulation

Carbon aerogel (CA) is recognized as a promising microwave absorption (MA) material, but it remains greatly challenging to integrate the multiple functions of MA, mechanical strength, and heat insulation. In this work, a novel zirconia fiber reinforced CA (ZF/CA) composite is successfully fabricated via electrospinning technology coupled with a sol-gel impregnation process for the first time. The density (0.132–0.206 g/cm3) of the obtained ZF/CA composites can be regulated by simply varying the initial sol concentration, thus effectively tuning their performance. Notably, the ZF/CA composites display excellent MA properties, with a strong absorption of −80.30 dB at the thickness of merely 1.71 mm and the optimal effective absorption bandwidth reaches 5.16 GHz, which is a significant improvement compared to CA (−11.70 dB, 0.58 GHz). Simultaneously, the brittleness and cracking problems of CA are effectively addressed by the soft reinforcement strategy of electrospun zirconia fibers, and superior mechanical strength is obtained. Furthermore, the nanopore structure and hierarchical design endow the ZF/CA composites with low thermal conductivity (0.029–0.038 W m−1 K−1) and favorable heat insulation performance. Outstanding MA capacity and excellent heat insulation properties along with lightweight construction and high strength make ZF/CA composites a great candidate for efficient MA and heat insulation.