Structure Of Composite Films Research Articles

Incorporation of Phase Change Materials into the Surface of Aluminum Structures for Thermal Management.

This article explores the concept of generating a porous anodic layer on the surface of a metallic component to host a phase change material (PCM) aiming to reduce the peak temperatures that the host structure will experience. The conditions to fabricate a porous anodic layer on top of an aluminum substrate were determined through varying anodization conditions: solution concentration, voltage employed, and anodization times. Pore sizes were characterized using scanning electron microscopy. The alkane n-eicosane was selected as PCM, introduced within the porous anodic annealed layer using vacuum impregnation and the thin film composite structure sealed. Epoxy resin and a metallic paste were tested as sealants. Thermal tests were performed to compare the behavior of aluminum alloy substrates anodized and sealed with and without PCM. The results showed pores with diameters in the 5–85 nm range, with average values that increased as the time of anodization was extended. The aluminum alloy impregnated with n-eicosane presents lowered surface peak temperatures during heating cycles than the samples that were only anodized or than the base alloy, demonstrating the potential of PCM incorporated in the superficial microstructure of anodic structures to manage, to a certain extent, peak transient thermal loads.

Structure and properties of flexible starch-based double network composite films induced by dopamine self-polymerization

Starch-based packaging materials are being developed to alleviate environmental pollution and greenhouse gas emissions associated with plastic-based ones. However, the high hydrophilicity and poor mechanical properties of pure-starch films limit their widespread application. In this study, dopamine self-polymerization was used as a strategy to improve the performance of starch-based films. Spectroscopy analysis showed that strong hydrogen bonding occurred between polydopamine (PDA) and starch molecules within the composite films, which significantly altered their internal and surface microstructures. The composite films had a greater water contact angle (> 90°), which indicated that the incorporation of PDA reduced their hydrophilicity. Additionally, the elongation at break of the composite films was 11-fold higher than pure-starch films, indicating that PDA improved film flexibility, while the tensile strength decreased to some extent. The composite films also exhibited excellent UV-shielding performance. These high-performance films may have practical applications in food and other industries as biodegradable packaging materials.

Nano‐silica/fluorinated polyacrylate composites as surface protective coatings for simulated stone cultural relic protection

AbstractStone cultural relics are widely distributed globally and have significant historical and cultural significance and research value. However, most of them have suffered severe weathering and erosion due to the physical and chemical effects of different climatic conditions. Herein, a series of nano‐silica/fluorinated polyacrylate composites as surface protective coatings to protect simulated stone cultural relics were prepared with dodecafluoroheptyl methacrylate (DFMA), acrylates, and different contents of nano‐silica. The storage stability, mechanical stability, coagulum rate, and surface tension of the composite coatings were measured. The UV absorption, chemical structure, surface morphology, and thermal properties of composite films were characterized. When the nano‐silica content was 6 wt%, the optimal nano‐silica/fluorinated polyacrylate (Si‐F‐3) composite with excellent comprehensive properties was applied in the protection of simulated stone cultural relics. Compared with the uncoated original stone samples, the simulated stone cultural relics treated with Si‐F‐3 composite not only had freeze–thaw resistance but also could slow down sulfate erosion and freeze–thaw coupling cycle (SEFTCC) test damage. To conclude, the nano‐silica/fluorinated polyacrylate composites could be a desirable solution for protecting stone cultural relics.

Design and construction of an immobilized Z-scheme Fe2O3/CuFe2O4|Cu photocatalyst film for organic pollutant degradation with simultaneous hydrogen production

An immobilized Z-scheme Fe2O3/CuFe2O4|Cu photocatalyst composite film was prepared by using an incomplete solid-state chemical reaction method. In the designed composite film, the copper foil is used not only as a photocatalyst carrier, but also as a reactant to generate CuFe2O4. Based on the unique structure of the photocatalyst composite film, the electrons can be transferred to the other surface of the copper foil. Therefore, photocatalytic degradation and hydrogen production reactions can be carried out simultaneously on both sides of the copper foil. The structure and properties of the photocatalyst composite film were studied by various characterization techniques. Some factors such as calcination time and calcination temperature on the photocatalytic activity of the composite film in organic pollutant degradation and hydrogen production were investigated. The crystal violet degradation ratio and hydrogen production amount reached 88.22 % and 375.00 µmol/dm2, respectively, under simulated sunlight irradiation for 120 min. The cyclic experiments were carried out to investigate the stability and reusability of the composite film. The species and properties of the active species generated in the photocatalytic reaction were studied by trapping experiments and electron spin resonance. This study may provide an idea for large-scale photocatalytic treatment of wastewater and hydrogen production.

Effect of Annealing on the Structure of Composite Passivation Films Prepared by Magnetron Sputtering Deposition on the Surface of HgCdTe

In this study, the structural evolution of the CdTe/ZnS composite passivation films on the surface of infrared HgCdTe material before and after annealing was comparatively explored. The surface morphology and microstructure of the passive films before and after annealing were characterized by scanning electron microscope, X-ray diffraction, atomic force microscopy, and Raman and X-ray photoelectron spectroscopy to determine the effects of the annealing process on the surface crystal defects of the films. The results show that annealing at 320 °C for three hours can improve crystal quality, ameliorate the surface density, and reduce the dislocation density of grains, while the Hg grains inhibited by tellurium-rich growth during the annealing process return to the normal growth state, and the S signal can be detected near the surface after annealing. This finding indicates that high-temperature annealing promotes the inhibited grain growth and also causes diffusion of surface elements, thus smoothing the compositional gradient at the passivation interface of the films.

Zein composite film with excellent toughness: Effects of pyrolysis biochar and hydrochar microspheres

The novelty of this study is providing a new toughening strategy in terms of the challenge of improving the poor toughness of zein film. Two types of biochar, pyrolysis biochar (PB) and hydrochar microspheres (HM), were blended into the zein system through solution casting to develop zein composite films with excellent toughness. The effects of biochar types and contents on the mechanical properties of the resulting composite films were investigated. The results indicated that better compatibility of zein composite films was achieved due to the hydrogen bond formed by biochar and hydrophilic amino acid in zein. A better surface structure of HM composite films was obtained than PB composite films by the uniform size and regular shape of HM. Better thermal stability shown in PB contributed to better thermal properties in the zein system than HM. Mechanical properties showed that tensile strength and modulus were increased with increasing PB or HM contents. Although increasing PB or HM contents decreased the elongation at break, the elongation at break reached a maximum of 475.47% at 0.1 g HM added composite film showing excellent toughness due to the strong interface binding and micro-nano size effect. The composite films prepared in this study have broad application prospects in packaging and agricultural films.

Excellent Lubricity of PVA/PEG/CS Composite on Ceramic Surface and Stainless Steel Friction Pair

At present, polymers such as polyethylene glycol (PEG) and chitosan (CS) are widely studied because of their excellent lubricating properties. Herein, powder combinations of different mass ratios are obtained by changing the mass of CS, and polymer films are obtained by hot pressing on the surface of the aluminum disk after microarc oxidation (MAO). The structure and crystallinity of the polymer composite film are characterized by X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR), and X‐ray photoelectron spectroscopy (XPS), which show that there is no chemical reaction between various substances. The tribological properties of the composite film are evaluated. Experiments show that when the mass ratio of polyvinyl alcohol (PVA), PEG, and CS is 5:5:1.5, the composite film has excellent lubrication performance, and the friction coefficient reaches 0.068 under long‐time running in. This effect meets the social requirements for lubrication performance to a certain extent and is expected to replace some mature solid lubricants.

Composite film with hollow hierarchical silica/perfluoropolyether filler and surface etching for performance enhanced triboelectric nanogenerators

Triboelectric nanogenerators (TENGs), capable of harvesting distributed energy from the environment, have provided a viable solution for self-powered wearable electronics. However, their low power density and susceptibility to contamination still severely limit their practical application. Herein, we reported a “two-step” strategy to implement a waterproof self-powered wearable electronic device based on TENG. Firstly, Perfluoropolyether (PF) and hollow hierarchical silica (H-SiO2) as fillers significantly improve the dielectric properties of polydimethylsiloxane (PDMS) composite films (PFS films) through polarization effect. Then the nano bumps of 10–30 nm are created on the surface of the films by surface etching, the bumps can increase the contact area of TENG. The voltage of TENG is improved from ∼ 67 V to ∼ 910 V and the current is improved from ∼ 1 μA to ∼ 25 μA. What’s more, the investigation of the surface structure of the PFS composite films by Atomic Force Microscope (AFM) revealed that the synergistic combination of multiple nanoscales (10–30 nm, 60–80 nm, 300–500 nm) is more favorable to achieve high performance of TENG. The surface structure composed of multiple nanoscales endows PFS with excellent superhydrophobicity. The PFS films remained fine performance after 40,000 drops of water and 90 days. This work achieves high performance and water resistance of TENG, demonstrating great potential in the field of self-powered wearable electronic devices.

Effects of Surfactants on Zein Cast Films for Simultaneous Delivery of Two Hydrophilic Active Components.

In order to prepare edible films with outstanding antimicrobials and antioxidants utilized in applications of food and pharmaceutics, in this study, effects of surfactants on zein cast films for simultaneous delivery of lysozyme (LY) and ascorbic acid (AA) were investigated, where sodium alginate (SA), soy lecithin (SL), and Pluronic f-68 (PF-68) were selected as surfactants. FT-IR tests indicated that SL or PF-68 dramatically changed secondary structure of zein composite films, which heightened the irregularity of the composite film and inhibited LY crystallization. Mechanical tests showed that highly flexible films exhibiting elongations between 129% and 157% were obtained when adding PF-68. Compared with the film without emulsifier, zein film containing SL and PF-68 showed approximately 7.51 and 0.55 times lower initial release rates for LY and AA respectively, which significantly improved the controlled release and heightened the anti-microbial and anti-oxidant activities of the film. Finally, emulsified mechanisms of the surfactants in zein films were proposed.

Circularly Polarized Luminescent Chiral Photonic Films Based on the Coassembly of Cellulose Nanocrystals and Gold Nanoclusters.

In this work, we studied the formation and properties of composite films coassembled by cellulose nanocrystals (CNCs) and bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs). The influences of the BSA-AuNC concentration on the structure and optical properties of CNC-based composite films were further studied. It was found that the composite film retained the chiral nematic structure and optical activity. The self-assembled CNC and BSA-AuNC helical superstructures can produce strong, left-handed, circularly polarized luminescence with dissymmetry factors up to 0.287. Meanwhile, the third component, polyethylene glycol, was introduced without affecting the structural color and fluorescence characteristics of the composite film to enhance the flexibility of the film. The simplicity of the film preparation, the abundance of CNCs, and the flexibility and stability of the composite films pave the way for the production of functional materials with integrated functions.

Effect of Molar Ratio on Structure of PPy-PVA Composite Film

A chemical oxidation method is used to synthesize pyrrole with ferric chloride as oxidant to prepare polypyrrole. Multiple chemical oxidations were carried out using various molar ratios. A stock solution of PolyVinyl Alcohol was produced to form composites of polymers. The PPy-PVA composites were achieved with the help of solution casting method to obtained free standing films. These composites films were characterized using SEM, FTIR and XRD techniques. The result of SEM, FTIR, and XRD reveals that the surface morphology varies as per the molar ratio. Along with the surface morphology molar ratio the conductivity of composite films was studied in the temperature range 303 K-343 K using two probe conductivity method. It has been observed that molar ratio also plays an important role in the conductivity of composite films.

Effect of Molar Ratio on Structure of PPy-PVA Composite Film

Effect of Molar Ratio on Structure of PPy-PVA Composite Film

Active gelatin/cress seed gum-based films reinforced with chitosan nanoparticles encapsulating pomegranate peel extract: Preparation and characterization

The aim of this study was to evaluate the effect of chitosan nanoparticles (CSNPs) incorporating pomegranate peel extract on properties of composite gelatin/cress seed gum films. The moisture barrier properties of active films were improved by 65% as function of adding CSNPs. Water contact angle (WCA) measurement exhibited hydrophobic surfaces with WCA of 108–119°. Reinforced films with 6% CSNPs showed enhanced mechanical properties, as tensile strength and elongation at break were significantly increased and decreased, respectively by 50%. Moreover, the films exhibited 85% light transmittance (T600) compared to that of control film (94%). Scanning electron microscopy revealed homogenous distribution of nanoparticles within film matrix. Atomic force microscopy showed a considerable increase in the roughness of nanocomposite films, where average surface (Ra) and root mean squared (Rq) roughness indices were increased from 0.4 and 0.5 nm in the neat gelatin film to 11.8 and 16.0 nm in gelatin/gum films with 6% CSNPs. X-ray diffraction analysis indicated that the semi-crystalline structure of composite films was not changed as function of adding CSNPs. Thermal stability of nanocomposite films was enhanced when higher contents of CSNPs were added, attributing to the interaction of CSNPs with gelatin matrix. Nanocomposite films showed no appreciable antimicrobial properties, whereas they revealed strong DPPH radical-scavenging activities.

Influence of chitin nanofibrils ultrasonic treatment on structure and properties of chitosan-based composite materials

The influence of ultrasonic treatment parameters of chitin nanofibrils aqueous suspension on structure, strength and deformation properties of chitosan-based composite films and fibers was investigated. Model calculations of ultrasound-induced cavitation parameters in the aqueous suspension of the chitin nanofibrils showed that an increase in the field power up to 630 W led to destruction of the cavity, to an increase in the temperature in the vicinity of cavitation area (up to 507 °C) and, as a consequence, to destruction of chitin glycoside ring (which is confirmed by the IR data). The results of light scattering, IR spectroscopy, and electron microscopy investigations indicated that the optimal duration of ultrasonic treatment of the chitin nanofibrils aqueous solution was 4–10 min (depending on oriented state of the scaffold). Tensile strength of the composites was 130 ± 11 MPa (films), 226 ± 4.8 MPa (fibers); deformation at break was 43 ± 7.5% (films), 10 ± 0.6% (fibers).

Efficiency and stability improvements for room light dye-sensitized solar cells in the presence of electrochemically fabricated composite counter electrodes

Electrochemical methodologies including constant current, constant potential and cyclic voltammetry (CV), as well as the sputter coating, are utilized to fabricate the poly(3,4-ethylene dioxythiophene) (PEDOT), platinum (Pt), and their composite films with layer-by-layer (Pt/PEDOT) and homogenous (PEDOT-Pt) structures. These films are utilized as counter electrodes of dye-sensitized solar cells (DSSCs). To achieve high cell efficiencies, the thickness of Pt and PEDOT, as well as the structure of composite films are regulated. The results show that PEDOT/Pt and PEDOT-Pt films demonstrate, respectively, the best and worst cell efficiencies. The X-ray diffraction and X-ray photoelectron spectroscopy analysis indicate that PEDOT and Pt have slight interaction in the PEDOT/Pt film, and the Pt preserves a crystalline structure. On the contrary, the interaction of PEDOT and Pt in the PEDOT-Pt film is high, resulting in an amorphous Pt structure. The crystalline Pt and its interaction with PEDOT are considered to be the main reason resulting in the high efficiencies of the corresponding cells. By applying this PEDOT/Pt counter electrode on DSSCs, the charge transfer at the counter electrode/electrolyte interface is significantly increased, and the cells can achieve efficiencies as high as 8.97% and 15.35%, respectively, under one-sun and room-light (200 lux) conditions. • PEDOT/Pt counter electrodes (CEs) is prepared using electrochemical methods. • This CE has the uniform layer of PEDOT/Pt and high surface area. • The PEDOT/Pt CE has high electrocatalytic activity towards I 3 − ions reduction. • The DSSCs using the PEDOT/Pt CE achieves an efficiency of 15.35%. • The cells using the PEDOT/Pt CE has high stability.

Composition, Structure and Properties of CrAlN-DLC Hard Composite Films Deposited by Arc Ion Plating

Composition, Structure and Properties of CrAlN-DLC Hard Composite Films Deposited by Arc Ion Plating

Effect of nanotubes on the electrical and mechanical properties of chitosan films

Using the methods of X-ray diffraction and scanning electron microscopy, the structure of composite films based on chitosan and single-wall carbon tubes has been studied. It is shown that the introduction of carbon nanotubes leads to the ordering of the chitosan structure. Increase in concentration of nanotubes (from 0 to 3%) causes rise in the value of storage modulus from 3 to 4 GPa (DMA data), increase in electrical conductivity of samples (from 10-11 to 102 S/m), and some changes in their dielectric permittivity (from 5.5. to 26 at an electrical field frequency of 1 kHz). Data on the ionic and electronic components of the conductivity of the composite film are presented. Keywords: chitosan, electrical conductivity, nanotubes, dielectric constant, composite.

Влияние углеродных нанотрубок на электрические и механические свойства хитозановых пленок

Using the methods of X-ray diffraction and scanning electron microscopy, the structure of composite films based on chitosan and single-wall carbon tubes has been studied. It is shown that the introduction of carbon nanotubes leads to the ordering of the chitosan structure. Increase in concentration of nanotubes (from 0 to 3%) causes rise in the value of storage modulus from 3 to 4 GPa (DMA data), increase in electrical conductivity of samples (from 10-11 to 102 S/m), and some changes in their dielectric permittivity (from 5.5. to 26 at an electrical field frequency of 1kHz). Data on the ionic and electronic components of the conductivity of the composite film are presented.

The ion migration process and cyclic stability of voltage-induced vanadium dioxide phase transition

The composite film structure of LiF/VO2 can effectively suppress the ion capture problem in single layer VO2, thereby improving the phase transition capability of voltage-induced ion-gated VO2.

Development of hydroxypropyl methylcellulose film with xanthan gum and its application as an excellent food packaging bio-material in enhancing the shelf life of banana

A novel film composed of xanthan gum (XG) and hydroxypropyl methylcellulose (HPMC) was prepared (XH). The films were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The light transmittance, mechanical properties and water vapor transmission rate (WVTR) indicated the good compatibility between XG and HPMC with hydrogen-bond interaction and XG had a significant effect on the chemical structure, crystalline texture and microstructure of the XH composite film. The best XH sample with optimum XG concentration of 2 g/L was used as food packaging via coating onto banana, whereby the weight loss rate on banana was able to decreased from 25 ± 3% (without XH coating) to 16 ± 4% (with XH coating). Consequently, the release of flavor substances was also decreased. Banana shelf life has qualitatively improved with XH composite film for food preservation and affirmed the uses in food packaging applications.