High Dimensional Stability Research Articles

Robust superhydrophobic fluorinated fibrous silica sponge with fire retardancy for selective oil absorption in harsh environment

Water pollution caused by oil leaks is a global environmental problem, calling for high-performance superabsorbent materials for the selective removal and recovery of oil from water. Herein, a robust fluorinated silica fibrous sponge (Silica-GA-F) was developed as an efficient superabsorber for selective oil absorption in harsh environments. Silica fibrous sponge was fabricated by self-assembly electrospinning and calcination. Superhydrophobic Silica-GA-F was obtained after crosslinking and fluorination using glutaraldehyde (GA) and perfluorodecyltriethoxysilane (PDTS). The fluffy microscale fibrous structure and low surface energy of Silica-GA-F contributed to its low bulk density of 16 mg/cm3, relatively high surface area of 6.5 m2/g, and high water contact angle of 151°. The sagging of water interface along silica fiber profile led to an impregnated Cassie-Baxter wetting sate and a “rose petal” effect. The Silica-GA-F possesses an extraordinary absorption capacity of ~122 times of its weight toward various oils, excellent separation efficiency, and promising stability in harsh environments and repetitive use. The oil absorbed can be combusted due to the fire retardancy of Silica-GA-F. Moreover, the GA crosslinking renders the silica sponge with high dimensional stability and recoverability. These properties make the Silica-GA-F sponge an ideal selective superabsorbent material with superior robustness and stability for water remediation, especially in harsh environments.

Grinding performance and tribological behavior in solid lubricant assisted grinding of glass-ceramics

High dimensional stability of glass-ceramics is highly attractive to optical and precision engineering industries. This study aims to provide an efficient and stable grinding strategy for realizing high-quality surface and dimensional accuracy of glass-ceramics. The different solid additives (CeO2 and SiC) as lubricants and their performances were investigated regarding the grinding forces, friction coefficient, wheel wear and surface finish during grinding glass-ceramics. Friction and wear mechanism in solid lubricant assisted (SLA) grinding were analyzed. Three-body abrasive wear and chemical mechanical interaction were considered as the predominant lubrication mechanisms. The results showed that the low, stable grinding force and small friction coefficient can be obtained under SLA-SiC grinding. The study proved that the novel strategy can keep the wheel sharpness and improve the process performance.

Highly permselective tadpole-type ionic anion exchange membranes for electrodialysis desalination

A series of tadpole-type ionic ionomers PPO-DMODAs with long alkyl side chains designed for electrodialysis (ED) desalination were synthesized successfully from dimethyloctadecylamine (DMODA) and brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). The series of AEMs display stably low water uptakes ranging from 6.2% to 15.1% and high dimensional stabilities with swelling rations of 1.9%–4.8% at temperatures of 25 °C–60 °C. The nano-phase separated tadpole-type ionic structures ensure that the PPO-DMODAs membranes show excellent permselectivities with values above 94.6% and outstanding ED performances in the mostly reported desalination system of NaCl aqueous solutions. Especially, PPO-DMODA-3 surpasses commercial membrane TWEDA1 in ED competitions and ED-stability matches with current efficiency (η) of 88.7%, salt flux (J) of 80.61 mg m−2 s−1, energy consumption (EC) of per kg of NaCl of 2.56 kWh kg−1 and η retentions of the repeated runs higher than 97% of that of the origin run. Moreover, PPO-DMODA-3 membrane obtained from the ethanol solution exhibits stable aggregate structure and ED performances comparable to those of the PPO-DMODA-3 membranes cast with NMP and TCE solutions. Good solubility of PPO-DMODAs in ethanol offers an environmentally friendly green method to fabricate ED AEMs. In consideration of the advantages of low cost, simple synthesis process and green membrane casting technology, PPO-DMODA-3 membrane has a strong potential for ED-desalination application.

Cellulose nanofiber/elastomer composites with high tensile strength, modulus, toughness, and thermal stability prepared by high-shear kneading

An aqueous TEMPO-oxidized cellulose nanofiber (TOCN) dispersion and aqueous hydrogenated acrylonitrile-butadiene rubber (H-NBR) latex were mixed with or without applying high shear forces. The TOCN/H-NBR mixtures containing TOCN volume ratios of 0–10.0% were then converted to crosslinked composite sheets with peroxide between the H-NBR molecules by hot-pressing. When the aqueous TOCN/H-NBR mixtures were pretreated with high shear forces, the crosslinked TOCN/H-NBR composites exhibited concomitant high tensile strength, high tensile modulus, high ductility, high storage modulus, and high dimensional stability to temperature. These properties are better than those of H-NBR composites containing single-walled carbon nanotubes or carbon black at the same filler volume ratio. In the crosslinked TOCN/H-NBR comosites prepared with high shear fodrces as pretreatment, electron microscopy images showed that the TOCN elements were homogeneously dispersed in the H-NBR matrix without forming aggregates. Thermal and pulsed NMR analyses of the solvent-extracted residue of the non-crosslinked TOCN/H-NBR composite indicated that characteristic nanostructures formed in the TOCN/H-NBR interfacial phases, which may cause the excellent mechanical and thermal properties of the composite.

Effect of graphene-based nanofillers addition on the interlaminar performance of CFRP composites: An assessment of cryo-conditioning

Carbon fiber reinforced polymer (CFRP) composites are extensively being used as materials in aerospace and aircraft applications. For cryogenic applications, which require materials having high dimensional stability and low thermal conductivity, CFRP composites are an exquisite alternative to metals. These materials have to sustain and retain their promising mechanical properties which include high strength to weight ratio and stiffness at extremely low temperatures. This work involves the decoration of carbon fiber (CF) surface of carbon fiber epoxy (CF/E) composites with two types of graphene-based nanofillers. Graphene oxide (GO) and Graphene hydroxyl (GOH) were implemented onto the CF by electrophoretic deposition (EPD) technique. A comparative study of the effect of nanofillers on the interlaminar behavior of 3 CFRP composites (neat, GO-CF/E, GOH-CF/E) for different times of cryogenic conditioning was carried out. Modified CFRP laminates have shown an improvement of 15.6% and 11.42% with GO and G-OH respectively in interlaminar shear strength (ILSS) in the unconditioned state with respect to neat. The effect of fiber modification becomes less prominent with increasing time of cryo conditioning. GO was proposed to be a better modifying nanofiller than GOH. A dip in ILSS at 1 h of aging may be attributed to thermal shock and development of internal stresses. Recovery of ILSS values at higher times of aging was observed. Scanning electron microscopy was carried out to identify various modes of failure.

Research on the Properties of High-strength Gypsum Based Tile Adhesive in Interior Decoration

In this paper, a new early strength tile adhesive is prepared by using α- high strength gypsum and its properties are discussed. The research methods refer to relevant Chinese standards. The results show that the tensile bond strength of the adhesive can reach 0.6 MPa in one day and 1.5 MPa in 7 days, which is close to 80% of 28-day strength. It is indicating that the adhesive has high bond strength, rapid strength development, and high dimensional stability. It effectively solves the problems that the traditional cement-based tile adhesive is prone to hollowing, falling off, and cracking. Additionally, no interface treatment is required during the using process of this gypsum-based adhesive.

Mechanical and physical properties of binderless particleboard made from oil palm empty fruit bunch (OPEFB) with addition of natural binder

Malaysia produces a very high amount of oil palm biomass especially the oil palm empty fruit bunch (OPEFB) every year. The OPEFB in reality can be converted into value-added panels such as particleboard. The application may vary such as use for furniture, indoor building materials, door, window, floor, office partition and many more. Normally, the commercial particleboard were made from biomass with addition of formaldehyde based resins and it is harmful to the environment due to the formaldehyde released. In this study, the formaldehyde based resins were excluded and the binderless particleboard made from OPEFB with addition of natural binder such as corn, potato, tapioca and wheat starch were evaluated. These panels were manufactured with a target density of 0.8 g/cm3. The hot pressing temperature, hot pressing time, and pressing pressure used were 180 °C, 20 min, and 12 MPa respectively. From the results, the highest modulus of rupture (MOR) and modulus of elasticity (MOE) were found to be the panel with the addition of potato starch as the natural binder (15.33 MPa, 2078 MPa) following by wheat (14.41 MPa, 1823 MPa), tapioca (14.18 MPa, 1771 MPa) and corn starch (12.59 MPa, 1335 MPa) respectively. The highest dimensional stability was also found to be the panel with the addition of potato starch with the lowest water absorption (69%) and thickness swelling (50%) value. Overall results has met the Japanese Industrial Standard (JIS) for type-8 and type-13 except for water absorption and thickness swelling. Therefore, particleboard made from OPEFB without using any synthetic resin was successfully made with the addition of natural binder such as potato, wheat, tapioca and corn starch and probably can be replace as a substitute for conventional particleboard in future.

A Multifunctional Separator Enables Safe and Durable Lithium/Magnesium–Sulfur Batteries under Elevated Temperature

AbstractRechargeable metal–sulfur batteries encounter severe safety hazards and fast capacity decay, caused by the flammable and shrinkable separator and unwanted polysulfide dissolution under elevated temperatures. Herein, a multifunctional Janus separator is designed by integrating temperature endurable electrospinning polyimide nonwovens with a copper nanowire‐graphene nanosheet functional layer and a rigid lithium lanthanum zirconium oxide‐polyethylene oxide matrix. Such architecture offers multifold advantages: i) intrinsically high dimensional stability and flame‐retardant capability, ii) excellent electrolyte wettability and effective metal dendritic growth inhibition, and iii) powerful physical blockage/chemical anchoring capability for the shuttled polysulfides. As a consequence, the as constructed lithium–sulfur battery using a pure sulfur cathode displays an outstandingly high discharge capacity of 1402.1 mAh g−1and a record high cycling stability (approximately average 0.24% capacity decay per cycle within 300 cycles) at 80 °C, outperforming the state‐of‐the‐art results in the literature. Promisingly, a high sulfur mass loading of ≈3.0 mg cm−2and a record low electrolyte/sulfur ratio of 6.0 are achieved. This functional separator also performs well for a high temperature magnesium–sulfur battery. This work demonstrates a new concept for high performance metal–sulfur battery design and promises safe and durable operation of the next generation energy storage systems.

High-performance wood composites from desert shrub Salix psammophila

Salix psammophila (SP), a desert shrub willow, plays an important role in preserving local ecosystems, and it is regarded to have high potential as an alternative raw material in the wood industry. However, its inferior characteristics such as small diameter and difficulty of barking result in a low utilization rate and a low added value. In this study, flattening and separation (FS) technology combined with impregnation of resins and hot-pressing was applied to convert SP branch residues to high-performance wood composites. The effects of FS repetition, hot-pressing temperature, composite density and resin content on the physical–mechanical properties were investigated to find the optimum parameters for industrial production. The results indicated that SP can be used as a potential material for manufacturing greenwood composites with high mechanical strength and high dimensional stability.

Relationship between changes in ionic radius and lattice dimension of lithium manganese oxide spinels during lithium insertion/extraction

Dimensional stability is critical for the cyclability of Li insertion materials in Li-ion batteries. Thus, in this study, we characterize the dimensional change in a series of spinel-structured Li-Co-Mn oxides (LiCoxMn2-xO4) during Li insertion using ex-situ X-ray diffraction technique. We deduce that a change in the cubic lattice parameters of the LiCoxMn2-xO4 compounds during Li insertion depends on the solid-state redox reactions; in particular, a smaller dimensional change is observed for the Co3+/Co4+ redox reaction, while a larger change is observed for the Mn3+/Mn4+ redox reaction. Through our X-ray diffraction studies, a linear relationship between the change in ionic radii of the redox species and dimensional change in the lattice structure of the compounds was observed during the reactions, which can be adopted for other Li-Mn oxide spinels as well. Hence, this relationship provides useful insight for designing Li insertion materials with high dimensional stability for long-life Li-ion batteries.

Effect of hybrid reinforcement of carbon fiber and stable particles on pitch based carbon carbon composites

Carbon matrix carbon (c/c) composites were investigated to study the effect of incorporating stable particulate reinforcement along with chopped carbon fibers to check the effect of hybrid reinforcement. Robust c/c composites were fabricated by isotropic petroleum pitch matrix in single-step carbonization without re-impregnation process. Dense and rigid composites with density ranging from 1.65–1.75 g cm−3 were developed. Distinctive properties comprising coefficient of friction, coefficient of thermal expansion, high temperature dimensional and weight stability, shrinkage, hardness, weight loss, breaking energy and compressive strength were assessed and compared with the reference c/c composite. Secondary stable additives such as silicon carbide, molybdenum di-silicide, graphite, CNT, fly ash and alumina were added 5% by weight in the composites. Specimens containing advanced ceramic particles showed appreciable improvement in hardness, thermal, and mechanical response while composites with fly ash and graphite addition showed the converse effects. From the research, we were able to alter the properties and tailor them according to the application such as compression and friction coefficient was improved to have application in brake discs for automobiles. Also, the thermal shielding has been improved by incorporating thermally dormant material such as fly ash and Incorporation of hard and stable reinforcement has brought about noticeable changes consequently hybrid reinforcement improved the overall performance of the material even after ablation in oxy-acetylene flames.

О КОМПЛЕКСЕ МЕРОПРИЯТИЙ, ОБЕСПЕЧИВАЮЩИХ ПРОЧНОСТНОЙ РЕСУРС КОСМИЧЕСКИХ АППАРАТОВ ДЛЯ ДИСТАНЦИОННОГО ЗОНДИРОВАНИЯ ЗЕМЛИ

The subject of the work is the process of creating Earth remote sensing spacecraft (ERS SC) within the framework of solving the problem of obtaining a high-resolution optical system by achieving high temperature dimensional stability (TDS) while retaining the strength of load-bearing structures (LBSs) during SC operation in orbit. The purpose of the work is to substantiate the block diagram of a package of SC strength measures that has been developed and is being implemented at Yuzhnoye SDO in the process of creating ERS SC containing laminar composite materials in their load-bearing structures, in particular using in their LBSs laminar polymer composite materials (PCMs) with special patterns of reinforcing carbon fibers. Objectives of the work: to analyze the use of layered structures with a resulting coefficient of temperature linear elongation close to zero, including negative in the direction of developing a long-term satellite remote sensing; to consider options for compensating for the weakening of the stiffness and strength characteristics of nanocrystals for TRS layered structures, taking into account the properties of PCM, significantly different from the properties of metals and alloys in the direction of increasing the reliability of spacecraft at various stages of development; to evaluate the compensation for the high cost of spacecraft for remote sensing with the duration of the period of active work in orbit based on modern information technologies.The results consist in that the article formulates features of a package of measures directly linked with ensuring the strength, stiffness, durability, and operating life of LBSs in ERS SC. This package of the measures Yuzhnoye SDO has developed and been implementing in the last years has its first priority to attain the TDS of LBSs and covers the whole life cycle of SC: design, manufacture (technology), testing and service. The service includes storage, transportation, prelaunch tests, injection into orbit and operation in orbit. The scientific novelty consists in the fact that the package takes into account all possible technological processes, tests on several versions of mockups and models with maximally full imitation of standard service conditions according to the scheme: onboard equipment ® onboard systems ® SC in whole. Problems are solved using CALS-class information technologies, for the complete realization of which a super computer has been put into operation with a peak speed of 300 teraflops. This enables to continuously improve ERS SC using PCMs for the TDS of LBSs.

Synthesis and characterization of new sulfonated copolytriazoles and their proton exchange membrane properties

ABSTRACTThis work reports the synthesis and characterization of a series of new sulfonated copolytriazoles. The polymers were prepared by CuI catalyzed 1,3‐cycloaddition reaction of an equimolar amount of a dialkyne monomer, 1,3‐diethynylbenzene and a mixture of two diazide monomers, namely, 4,4′‐diazidodiphenyl ether and 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt. The copolymers showed high inherent viscosity indicating the formation of high molar mass product. The copolymers were characterized by Fourier transform infrared and proton nuclear magnetic resonance spectroscopic techniques. The copolymer membranes displayed moderate water uptake, high dimensional, mechanical, and thermal stability. Transmission electron microscopy micrographs displayed excellent phase‐separated morphology along with very fine ionic clusters. The copolymer PTEOSH‐90 (90% degree of sulfonation) showed much higher proton conductivity value which is up to 196 mS cm−1 at 80 °C in completely hydrated condition compared to that of Nafion (165 mS cm−1). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48514.

Optimization of 3D bioprinting of periodontal ligament cells

Three-dimensional (3D) bioprinting of cells is an emerging area of research but has been not explored yet in the context of periodontal tissue engineering. ObjectiveThis study reports on the optimisation of the 3D bioprinting of periodontal ligament cells for potential application in periodontal regeneration. MethodsWe systematically investigated the printability of various concentrations of gelatin methacryloyl (GelMA) hydrogel precursor using a microextrusion based three-dimensional (3D) printer. The influence of different printing parameters such as photoinitiator concentration, UV exposure, pressure and dispensing needle diameter on the viability of periodontal ligament cells encapsulated within the 3D bioprinted construct were subsequently assessed. ResultsThis systematic evaluation enabled the selection of the most suited printing conditions for achieving high printing resolution, dimensional stability and cell viability for 3D bioprinting of periodontal ligament cells. SignificanceThe optimised bioprinting system is the first step towards to the reproducible manufacturing of cell laden, space maintaining scaffolds for the treatment of periodontal lesions.

Enhanced wettability and electrolyte uptake of coated commercial polypropylene separators with inorganic nanopowders for application in lithium-ion battery

In this research, inorganic material type and content influence on coating of commercially available polypropylene (PP) separator were studied for improving its performance and safety as lithium ion battery separator. Heat-resistant nanopowders of Al2O3, SiO2 and ZrO2 were coated using polyvinylidene fluoride (PVDF) binder. Coating effects on the separators morphology, wettability, high temperatures dimensional stability and electrochemical properties were investigated via their scanning electron microscopy images, electrolyte contact angles, electrolyte uptakes, thermal shrinkages analysis and ion conductivities. Furthermore, their performances were studied as the lithium ion batteries separator. All the coated separators have lower thermal shrinkages compared to the commercial neat PP separator. In addition, almost all of the coated separators have shown higher porosities and electrolyte uptakes than those of the commercial neat PP separators. The coated separator with Al2O3 / binder ratio of 8 (MOA8) revealed highest improvement in electrolyte contact angle of 0 °, electrolyte uptake of 218 % (2.04 times increment), ion conductivity of 1.685 mS/cm (1.89 times increment), 52 % porosity compared with the neat PP separator due to proper coating surface morphology, interstitial cavities and a higher Al2O3 dielectric constant than SiO2. In terms of assembled battery discharge capacity reduction after 100 cycles, MOA8 separator showed better cyclic performance as 8.89 % compared with that of the neat PP separator as 16.6 %.

Large‐Area Aminated‐Graphdiyne Thin Films for Direct Methanol Fuel Cells

A two-dimensional (2D) carbon nanofilm with uniform artificial nanopores is an ideal material to ultimately suppress the fuel permeation in the proton exchange membrane fuel cells. Graphdiyne has great mechanical strength, high dimensional stability, and controllable nanopores, and has good prospects to play this crucial role. It is found that graphdiyne nanofilm with amino groups and natural nanopores can be easily prepared with high integrity. The aminated graphdiyne has good compatibility with the Nafion matrix owing to the acid-base interaction between them. The excellent comprehensive properties of graphdiyne in selectivity, dimensional stability, and integrity effectively improve the power performance and stability of fuel cells at wide temperature. Our results can be developed into a universal method that can easily realize the selective separation of ions and small molecules, and open a new way for the emerging applications in green energy.

New Type of Columnar Liquid Crystal Superlattice in Double-Taper Ionic Minidendrons.

Wedge-shaped molecules, such as dendrons, are among the most important building blocks for directed supramolecular self-assembly. Here we present a new approach aimed at widening the range and complexity of potential mesophases by introducing double-tapered mesogens. Two series of compounds are presented, both alkali metal salts (Li, Na, Cs) of 3,4,5-tris-alkoxybenzoic acid with a second tapered tris-alkoxyaryl group attached at the end of an alkoxy chain. The double-tapered compounds all display an unusual hexagonal columnar phase consisting of one ionic and three non-ionic columns per unit cell. The cation size has an unexpectedly drastic effect on unit cell size. Unlike most columnar phases, the current phases show unusually high dimensional stability on heating, and high stiffness in spite of being 80-85 % aliphatic, attributed to their molecular topology. The described approach may lead to co-assemblies of multifunctional materials, for example, parallel p- and n-semiconducting nanowires or parallel ionic and electronic conductors.

Novel proton exchange membranes based on sulfonated-phosphonated poly (p-phenylene-co-aryl ether ketone) terpolymers with microblock structures for passive direct methanol fuel cells

The development of fluorine-free proton exchange membranes (PEMs) to improve alcohol resistance and proton/methanol selectivity is a significant research direction for direct methanol fuel cells (DMFCs). In this work, a range of sulfonated-phosphonated poly (p-phenylene-co-aryl ether ketone) terpolymers with microblock structures are prepared by a Ni (0)-catalyzed coupling reaction at high yield. The experimental results reveal that the formation of P–O–P anhydride bridges by self-condensation in a hydrophilic domain can facilitate the connectivity of the proton conducting channels, through a mixed Grotthuss and Vehicle proton transport mechanism, and improve the alcohol resistance of terpolymers at the same time. The terpolymers have high conductivity (>0.01 S cm-1), which is superior to that of neat sulfonated or neat phosphonated aromatic polymers, and high dimensional stability at 80 °C and 40% relative humidity. A passive DMFC with a terpolymer membrane provides a high power density of 34.4 mW cm−2 at 25 °C, which is higher than that for l-SPP-co-PAEK 1.80 (27.1 mW cm-2) and Nafion®115 (29.3 mW cm-2). By controlling the ratio of phosphonic acid or sulfonic acid to regulate ion aggregation behavior and further construct connected (or cluster-free) proton channels, a new insight into the design PEMs with high proton/methanol selectivity is provided.

Comparison of the transformation behavior of cold rolling with aging and hot extrusion with aging processed Ni50.3Ti29.7Hf20 high temperature shape memory alloy

Among NiTiHf high temperature shape memory alloys, nickel rich ternary Ni50.3Ti29.7Hf20 (at%) alloy has been studied extensively and found to be promising for high temperature applications especially in aerospace industry. NiTiHf alloys have very high strength and transformation temperatures (TTs) proportional to their hafnium percentage. Therefore, these alloys are accepted as a hard to deform material. Hot extrusion at 900 °C and solutionizing at 1050 °C-1100°C treatments have been generally used in literature for the homogenization of the cast microstructure and chemistry and thus, the strength of the material eventually increases. In this study, one set of the as cast Ni50.3Ti29.7Hf20 alloy was hot extruded at 900 °C and then aged at 550 °C for 3 h and the other set was solutionized at 1050 °C for 2 h, cold rolled for 10% at room temperature and then aged at 550 °C for 3 h. The TTs of the hot extruded, hot extruded and aged, solutionized, solutionized-cold rolled and aged samples were measured using DSC and heating-cooling experiments under increasing stress magnitudes starting from 100 MPa and increasing up to 600 MPa were conducted on all thermal and thermo-mechanically treated samples in order to compare the shape memory characteristics such as actuation strain, irrecoverable strain and TTs. The samples which were hot extruded and aged and solutionized-cold rolled and aged showed very high dimensional stability with no irrecoverable strain values up to 500 MPa. However, the actuation strain magnitudes of the cold rolled with aging processed sample were half of the actuation strain values of the sample which was hot extruded and aging treated. Additionally, higher undercooling and overheating were necessary to achieve full transformation in the cold worked samples. These results might be due to the very high dislocation density and texture formation which was induced during cold rolling process.

Carboxylated nanocellulose/poly(ethylene oxide) composite films as solid–solid phase-change materials for thermal energy storage

Composite films of poly(ethylene oxide) (PEO) and 0%–20% surface-carboxylated cellulose nanofibrils (CNFs) were prepared by mixing the aqueous CNF dispersion and aqueous PEO solution at various weight ratios followed by casting and drying. The 20% CNF/PEO composite film was transparent, whereas the 100% PEO film was translucent. The addition of CNFs to the PEO matrix resulted in decreases of the crystallinity and crystal size of spherical PEO. The Young’s modulus and tensile strength of the 100% PEO film were 0.2 GPa and 6.1 MPa, respectively, and remarkably increased to 2.4 GPa and 86 MPa, respectively, with the addition of 20% CNF. The CNF/PEO composite films had clear melting and crystallization temperatures in the heating and cooling processes, respectively. Nevertheless, the coefficients of thermal expansion at temperatures above the melting point of PEO significantly decreased with the CNF addition. The CNF/PEO composite films are therefore promising solid–solid phase-change materials for energy storage with high film dimensional stability.