Synthesis of polylactide/clay composites using structurally different kaolinites and kaolinite nanotubes

Polymer/clay nanocomposites receive much attention due to their interesting mechanical and thermal properties. Currently, the vast majority of plastics are made from petroleum-based synthetic polymers that do not degrade in a natural environment and their disposal poses a serious problem. An environmentally-conscious alternative is to design polymer nanocomposites that are biodegradable.In the present work the synthesis and properties of novel polymer/clay nanocomposites based on biodegradable polymer-polylactide (PLA) were investigated. Kaolinite nanotubes obtained by an intercalation/deintercalation method as well as platey kaolinites of different structural orders were used as fillers. Mechanical properties of composites (tensile strength (S_U) and Young's modulus (E)) were measured. The surface of the formed polymer derivatives was examined by AFM (Atomic Force Microscopy). The structural characterization was carried out using infrared spectroscopy (IR). Composites surface wettability was studied by measuring the water contact angle.The mechanical tests revealed that both S_U and E values increased significantly after addition of the nano-filler in comparison to the pure PLA. Regardless of the filler content the increase of S_U and E values was higher in the case of the nanotubular kaolinite. In particular, a threefold increase of the E value was noticed. For the most homogeneous kaolinite nanotubes/PLA nanocomposite S_U increased from ~ 29 MPa (pure PLA) to ~ 43 MPa, while E increased from ~ 0.7 GPa (pure PLA) to ~ 2.3 GPa. These mechanical parameters were comparable with the ones measured for polypropylene (S_U = 40 MPa; E = 1.5–2.0 GPa) and polystyrene (S_U = 40 MPa; E = 3.0–3.5 GPa). Differential IR spectra of the nanocomposites indicated an interaction of kaolinites inner surface hydroxyls with PLA which was confirmed by an intensity decrease of a band at ~ 3690 cm^? 1. The presence of highly dispersed nanotubular kaolinite particles in the polymer matrix which contributed to the improvement of PLA mechanical properties was observed using AFM. The contact angle measurements showed that the addition of kaolinites led to changes of wettability, yet the synthesized materials still possessed hydrophilic surfaces.     

Properties of a reactive‐graphitic‐carbon‐nanofibers‐reinforced epoxy

Our previous studies showed that herringbone graphitic GNFs surface‐derivatized with reactive linker molecules bearing pendant primary amino functional groups capable of binding covalently to epoxy resins. Of special importance, herringbone GNFs derivatized with 3,4′‐oxydianiline (GNF‐ODA) were found to react with neat butyl glycidyl ether to form mono‐, di‐, tri‐, and tetra‐glycidyl oligomers covalently coupled to the ODA pendant amino group. The resulting reactive GNF‐ODA (butyl glycidyl)_n nanofibers, r‐GNF‐ODA, are especially well suited for reactive, covalent incorporation into epoxy resins during thermal curing. Based on these studies, nanocomposites reinforced by the r‐GNF‐ODA nanofibers at nanofiber loadings of 0.15–1.3 wt% were prepared. Flexural property of cured r‐GNF‐ODA/epoxy nanocomposites were measured through three‐point‐bending tests. Thermal properties, including glass transition temperature (T_g) and coefficient of thermal expansion (CTE) for the nanocomposites, were investigated using thermal mechanical analysis. The nanocomposites containing 0.3 wt% of the nanofibers gives the highest mechanical properties. At this 0.3‐wt% fiber loading, the flexural strength, modulus and breaking strain of the particular nanocomposite are increased by about 26, 20, and 30%, respectively, compared to that of pure epoxy matrix. Moreover, the T_g value is the highest for this nanocomposite, 14°C higher than that of pure epoxy. The almost constant change in CTEs before and after T_g, and very close to the change of pure epoxy, is in agreement with our previous study results on a chemical bond existing between the r‐GNF‐ODA nanofibers and epoxy resin in the resulting nanocomposites. POLYM. COMPOS., 28:605–611, 2007. © 2007 Society of Plastics Engineers     

In situ preparation of polyimide/amino‐functionalized carbon nanotube composites and their properties

In order to improve the dispersion of carbon nanotubes (CNTs) in polyimide (PI) matrix and the interfacial interaction between CNTs and PI, 4,4′‐diaminodiphenyl ether (ODA)‐functionalized carbon nanotubes (CNTs‐ODA) were synthesized by oxidation and amidation reactions. The structures and morphologies of CNTs‐ODA were characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and thermal gravimetric analysis. Then a series of polyimide/amino‐functionalized carbon nanotube (PI/CNT‐ODA) nanocomposites were prepared by in situ polymerization. CNTs‐ODA were homogeneously dispersed in PI matrix. The influence of CNT‐ODA content on mechanical properties of PI/CNT‐ODA nanocomposites was investigated. It was found that the mechanical properties of nanocomposites were enhanced with the increase in CNT‐ODA loading. When the content of CNTs‐ODA was 3 wt%, the tensile strength of PI/CNT‐ODA nanocomposites was up to 169.07 MPa (87.11% higher than that of neat PI). The modulus of PI/CNTs‐ODA was increased by 62.64%, while elongation at break was increased by 66.05%. The improvement of the mechanical properties of PI/CNT‐ODA nanocomposites were due to the strong chemical bond and interfacial interaction between CNTs‐ODA and PI matrix. POLYM. COMPOS., 35:1952–1959, 2014. © 2014 Society of Plastics Engineers     

Local Structure Investigation in Multiferroic BiFeO3–BaTiO3 Ceramics by XAS Technique and Their Relevant Properties

The (1?x)BiFeO₃‐xBaTiO₃ (with x = 0.1, 0.2, 0.3, and 0.4) ceramics were fabricated successfully by solid‐state reaction method. Single‐phase perovskite was obtained in all ceramics, as confirmed by XRD technique. It was observed that 0.7BiFeO₃–0.3BaTiO₃ was the morphotropic phase boundary (MPB) between rhombohedral and cubic phases, as also revealed from ferroelectric and magnetic properties. The simulated and experimental X‐Ray Absorption Spectroscopy (XAS) study revealed that BT in 0.75BF‐0.25BT is possibly taken a rhombohedral structure. Furthermore, the rounded ferroelectric hysteresis loops observed for 0.9BiFeO₃–0.1BaTiO₃ and 0.8BiFeO₃–0.2BaTiO₃ compositions could be attributed to their microstructure and surface charge effects and electron transfer between Fe³⁺ and Fe²⁺ ions. It was also found that high dielectric constant of 0.9BiFeO₃–0.1BaTiO₃ composition was a result of grain and grain‐boundary effects, as observed in SEM micrographs. In addition, a strong signature of dielectric relaxation behavior was observed in this ceramic system with the activation energy 0.467 eV obtained from the Arrhenius' law. Finally, the local structure investigation with XAS technique provided additional information to better understand the electric and magnetic properties in the BF‐BT ceramic system.     

Flow Cytometry Analysis of Cytotoxicity In Vitro and Long‐Term Toxicity of HA‐40 wt% BaTiO3 Nanoparticles In Vivo

The development of new implantable biomaterials requires bone‐mimicking physical properties together with desired biocompatible property. In continuation to our earlier published research to establish compositional dependent multifunctional bone‐like properties and cytocompatibility response of hydroxyapatite (HA)‐BaTiO₃ composites, the toxicological property evaluation, both in vitro and in vivo, were conducted on HA‐40 wt% BaTiO₃ and reported in this work. In particular, this work reports in vitro cytotoxicity of mouse myoblast cells as well as in vivo long‐term tissue and nanoparticles interaction of intra‐articularly injected HA‐40 wt% BaTiO₃ and BaTiO₃ up to the concentration of 25 mg/mL in physiological saline over 12 weeks in mouse model. The careful analysis of flow cytometry results could not reveal any statistically significant difference in terms of early/late apoptotic cells or necrotic cells over 8 d in culture. Extensive histological analysis could not record any signature of cellular level toxicity or pronounced inflammatory response in vital organs as well as at knee joints of Balb/c mice after 12 weeks. Taken together, this study establishes nontoxic nature of HA‐40 wt% BaTiO₃ and therefore, HA‐40 wt% BaTiO₃ can be used safely for various biomedical applications.     

Highly Dense Amorphous Si2BC3N Monoliths with Excellent Mechanical Properties Prepared by High Pressure Sintering

The fabrication of dense amorphous Si–B–C–N monoliths is a processing challenge given that it is hard to avoid crystallization at the sintering temperatures needed to attain full density up to 1900°C for conventional hot pressing and SPS methods. We report here successful densification of amorphous Si₂BC₃N monoliths achieved by heating at 1100°C and 5 GPa. The relationships between microstructure, types of chemical bonding, and mechanical properties were investigated. The strong amorphous 3‐D networks of Si–C, C–B, C‐N (sp³), N‐B (sp³), and C–B–N bonds provide high densities at high applied pressure and thus amorphous Si₂BC₃N monoliths show high hardness of 29.4 GPa and elastic modulus of 291 GPa. The amorphous structure is lost with crystallization of β‐SiC and BN(C) reducing contributions from Si–C, C‐N (sp³), and C–B–N bond networks thereby decreasing mechanical properties.     

High‐performance fibers based on copolyimides containing benzimidazole and ether moieties: Molecular packing,morphology, hydrogen‐bonding interactions and properties

High‐performance copolyimide (co‐PI) fibers were prepared via the wet spinning process of co‐polyamide acid precursors based on 3,3′,4,4′‐biphenyldianhydride (BPDA) and a mixture of three diamines namely p‐phenylene diamine (p‐PDA), 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA), and 4,4′‐oxidianiline (ODA), followed by drawing and imidization at high temperatures. Effects of the ODA and BIA contents on the molecular packing, morphology, hydrogen‐bonding interactions, mechanical and thermal properties of the prepared fibers were investigated. The mechanical properties of the co‐PI fibers were improved with the addition of ODA and BIA, and they reached the optimum tensile strength of 2.7 GPa and modulus of 94.3 GPa. Wide‐angle X‐ray diffraction results (WAXD) showed that the co‐PI fibers exhibited highly oriented structure along the fiber direction with low degree of lateral packing orders in the transverse direction. Two‐dimensional small‐angle X‐ray scattering (2D‐SAXS) revealed that the incorporation of ODA resulted in the reduction in radius, length, misorientation, and internal surface roughness of the microvoids in the fibers. Fourier transform infrared (FTIR) results indicated that hydrogen‐bonding formed between the BIA and cyclic imide units effectively strengthened the intermolecular interactions. The co‐PI fibers exhibited excellent thermal and thermal‐oxidative stability, with a 5%‐weight‐loss temperature of 578°C under N₂ and 572°C in air. POLYM. ENG. SCI., 55:2615–2625, 2015. © 2015 Society of Plastics Engineers     

Ultra‐Broad Temperature Stability Obtained with Ce‐Doped BaTiO3‐Based Ceramics

Ce‐doped BaTiO₃‐based ceramics were prepared and studied to satisfy ultra‐broad temperature stability (from ?55°C to 300°C, capacitance variation rate based on C_20°C is within ±15%). The sample with 0.6 mol% CeO₂ succeeds to achieve this performance with a remarkably high ceiling temperature of 300°C. Meanwhile, the sample has good dielectric and electrical properties at room temperature (ε_r = 1667, tanδ = 1.478%, ρ_V = 5.9 × 10¹² Ω·cm). Ce ion can substitute for Ti ion as Ce⁴⁺ or Ba ion as Ce³⁺. The substitution decreases the spontaneous polarization of BaTiO₃, and then weakens the ferroelectricity of BaTiO₃. As a result, the temperature stability of samples is improved obviously. Besides, CeO₂ addition promotes the formation of exaggerated grains, which are consisting of Ba₆Ti₁₇O₄₀.     

Multifunctional Properties of Multistage Spark Plasma Sintered HA–BaTiO3‐Based Piezobiocomposites for Bone Replacement Applications

This work reports the processing–microstructure–property correlation of novel HA–BaTiO₃‐based piezobiocomposites, which demonstrated the bone‐mimicking functional properties. A series of composites of hydroxyapatite (HA) with varying amounts of piezoelectric BaTiO₃ (BT) were optimally processed using uniquely designed multistage spark plasma sintering (SPS) route. Transmission electron microscopy imaging during in situ heating provides complementary information on the real‐time observation of sintering behavior. Ultrafine grains (≤0.50 μm) of HA and BT phases were predominantly retained in the SPSed samples. The experimental results revealed that dielectric constant, AC conductivity, piezoelectric strain coefficient, compressive strength, and modulus values of HA‐40 wt% BT closely resembles with that of the natural bone. The addition of 40 wt% BT enhances the long‐crack fracture toughness, compressive strength, and modulus by 132%, 200%, and 165%, respectively, with respect to HA. The above‐mentioned exceptional combination of functional properties potentially establishes HA‐40 wt% BT piezocomposite as a new‐generation composite for orthopedic implant applications.     

Fabrication of piezoelectric particle-dispersed ceramic nanocomposite

The goal of this study is to fabricate perovskite type ferroelectric particles-dispersed ceramic nanocomposites though conventional hot-pressing or pulse electric current sintering (PECS). This type of nanocomposite is expected to show ferroelectricity or piezoelectricity with retaining mechanical properties. Magnesia (MgO) and barium titanate (BaTiO₃) were selected as a matrix and secondary phase dispersoid. From X-ray diffraction analysis, the BaTiO₃ was the phase compatible with the MgO matrix, and there were no reaction phases between the matrix and BaTiO₃. It was found that the BaTiO₃ enhanced the sinterability of the MgO ceramics. Relative density of pure MgO was lower than 80%, while dense MgO/10 vol% BaTiO₃ nanocomposites could be successfully prepared by sintering at 1200°C for 10 min through PECS method. Fine BaTiO₃ particles were homogeneously dispersed within the MgO matrix grain as well as at grain boundaries. Sintering behavior and microstructure development of the MgO/BaTiO₃ nanocomposites were discussed in terms of BaTiO₃ content and sintering temperatures.     

Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO₃ (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 μW/cm² (49.79 μW/cm³) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.     

Effect of atomic layer deposited aluminium oxide on mechanical properties of porous silicon carbide

Silicon carbide nanopowder was coated with amorphous alumina by atomic layer deposition (ALD), using trimethylaluminium Al(CH₃)₃ (TMA) and water as precursors. The ALD experiments were carried out at 300 ^°C, using variable cycle count or changing pulse times at constant cycle count. Depending on deposition conditions, hardness averaging at 14.8 GPa and corresponding reduced elastic modulus of 114 GPa were measured. Maximum hardness values and reduced moduli of elasticity reached 25–30 and 134–202 GPa, respectively, improving the mechanical properties of composites. Increased precursor flow had positive effect on mechanical properties – maximum values of hardness and elastic module reached 35–45 and 218–261 GPa, respectively. In the composites, the mechanical properties were improved compared to pure alumina films or silicon carbide and the brittleness characteristic of SiC particle tablets was decreased.     

Poly(methyl methacrylate) nanocomposites based on graphene oxide: a comparative investigation of the effects of surface chemistry on properties and foaming behavior

The effects of oxygen functional groups and alkyl chains at the surface of graphene oxide (GO) on the thermal stability, mechanical properties and foaming behavior of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. Alkyl‐functionalized GO (GO‐ODA) was prepared by grafting octadecylamine (ODA) on the surface of GO. PMMA/GO and PMMA/GO‐ODA nanocomposite were obtained by solution blending and were foamed using supercritical carbon dioxide (scCO₂). GO‐ODA, with the presence of alkyl chains, showed a better dispersion capability in PMMA matrix than GO with a large amount of oxygen functional groups. In addition, the good dispersion capability increased thermal stability and mechanical strength. In comparison with PMMA/GO samples foamed at 70 °C, PMMA/GO‐ODA nanocomposite foams displayed improved cell structures with higher cell density, smaller cell size and more homogeneous cell size distribution, which results from the strong heterogeneous nucleation due to alkyl chains on the GO surface. The foaming behaviors became more complicated at 80 °C as the GO might be intercalated and exfoliated with the aid of scCO₂, thus further enhancing the heterogeneous nucleation during the foaming process. The results indicated that the surface chemistry of GO was closely related to the properties and foaming behavior of the nanocomposites. © 2016 Society of Chemical Industry     

Porosity effect on microstructure,mechanical, and fluid dynamic properties of Ti2AlC by direct foaming and gel‐casting

In this study, Ti₂AlC foams were fabricated by direct foaming and gel‐casting using agarose as gelling agent. Slurry viscosity, determined by the agarose content (at a fixed solids loading), as well as surfactant concentration and foaming time were the key parameters employed for controlling the foaming yield, and hence the foam porosity after sintering process. Fabricated foams having total porosity in the 62.5‐84.4 vol% range were systematically characterized to determine their pore size and morphology. The effect of the foam porosity on the room‐temperature compression strength and elastic modulus was also determined. Depending on the amount of porosity, the compression strength and Young's modulus were found to be in the range of 9‐91 MPa and 7‐52 GPa, respectively. Permeability to air flow at temperatures up to 700°C was investigated. Darcian (k₁) and non‐Darcian (k₂) permeability coefficients displayed values in the range 0.30‐93.44 × 10^?11 m² and 0.39‐345.54 × 10^?7 m, respectively. The amount of porosity is therefore a very useful microstructural parameter for tuning the mechanical and fluid dynamic properties of Ti₂AlC foams.     

Structural evaluation and mechanical property of boron nitride fibers during melt‐drawn fabrication process

Boron nitride (BN) fibers were fabricated on a large scale through the melt‐drawn technique from low‐cost boric acid, NH₃, and N₂. Evolution of structure and properties of BN fibers during the fabrication process was studied by Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), scanning electron microscope (SEM), and X‐ray photoelectron spectroscopy (XPS). The mechanical properties of BN fibers were tested and analyzed. The results shown that both the mechanical properties and the crystallinity of BN fibers slightly increased with the temperature from 450 to 850°C, due to the combination of the fused‐B₃N₃. For BN fibers heat‐treated at 850 or 1000°C, the tensile strength (σ^R) and elastic modulus (E) were strongly increased because of the increase in crystallization of the BN phase. The meso‐hexagonal BN fibers with a diameter of 5.0 μm were fabricated at 1750°C, of which the tensile strength (σ^R) and elastic modulus (E) are 1200 MPa and 85 GPa, respectively. BN fibers with excellent mechanical properties and proper diameters were obtained by nitriding of green fibers during their conversion into ceramic.     

Processing and Properties of Eu3+‐Doped Barium Bismuth Titanate (BaBi4Ti4O15) Glass–Ceramic Nanocomposites

Precursor glasses for the ferroelectric barium bismuth titanate (BaBi₄Ti₄O₁₅) (BBiT) have been prepared by the melt‐quench technique in the SiO₂–K₂O–BaO–Bi₂O₃–TiO₂ (SKBBT) glass system with and without Eu₂O₃ doping. BBiT glass–ceramic (GC) nanocomposites have been derived from these glasses by controlled heat treatment. The structural properties of the GCs have been investigated using X‐ray diffraction (XRD), electron microscopy (FE‐SEM, TEM), and FT‐IR reflectance spectroscopy. FE‐SEM images show the formation of randomly oriented hexagonal rod‐shaped crystals of 200–400 nm and TEM images show 10–20 nm crystallites. FT‐IR spectra exhibit the characteristic bands of BBiT at 480, 585, and 680 cm^?1. The activation energy of crystallization (E_c) varies from 295 to 307 kJ/mol. The dielectric constants (ε_r) of glass and GC nanocomposites increase with an increase in frequency up to 3.0 MHz and then decrease up to 5.0 MHz. Heat‐treated GCs show higher ε_r values, in the range 25–55, compared to the precursor glasses (20–37). Dielectric losses (tan δ) for all the samples increase from 0.005 to 1.0 with an increase in frequency from 100 Hz to 5.0 MHz. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the ⁵D₀ → ⁷F₂ transition. An intense 466 nm excitation band corresponding to the ⁷F₀ → ⁵D₂ transition was observed. Emission spectra were then recorded by exciting the glass samples at 466 nm. Longer heat‐treatment times led to a 15‐fold increase in the intensity of the red emission at 612 nm, attributed to the segregation of Eu³⁺ ions into the low phonon energy BBiT crystallites. The hardness (3.8–5.1 GPa) and fracture toughness (1.8–3.5 MPam^0.5) values obtained in the GCs are high and suitable for structural applications.     

Fabrication and mechanical properties of Al2O3–TiC ceramic composites synergistically reinforced with multi-walled carbon nanotubes and graphene nanoplates

In this study, Al₂O₃–TiC composites synergistically reinforced with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were prepared via spark plasma sintering (SPS). The effects of the MWCNT and GNP contents on the phase composition, mechanical properties, fracture mode, and toughening mechanism of the composites were systematically investigated. The experimental results indicated that the composite grains became more refined with the addition of MWCNTs and GNPs. The nanocomposites presented high compactness and excellent mechanical properties. The composite with 0.8 wt% MWCNTs and 0.2 wt% GNPs presented the best properties of all analysed specimens, and its relative density, hardness, and fracture toughness were 97.3%, 18.38 ± 0.6 GPa, and 9.40 ± 1.6 MPa m^1/2, respectively. The crack deflection, bridging, branching, and drawing effects of MWCNTs and GNPs were the main toughening mechanisms of Al₂O₃–TiC composites synergistically reinforced with MWCNTs and GNPs.     

Preparation of siloxane–silsesquioxane hybrid thin films for large‐scale‐integration interlayer dielectrics with excellent mechanical properties and low dielectric constants

Several kinds of homogeneous organic–inorganic hybrid polymer thin films were designed with improved mechanical properties and low dielectric constants (<3.0). Novel soluble siloxane–silsesquioxane hybrid polymers were synthesized with cyclic and/or cage silane monomers, which had triorganosiloxy (R₃Si_1/2), diorganosiloxane (R₂SiO_2/2), and organosilsesquioxane (RSiO_3/2) moieties with ethylene bridges at the molecular level, by the hydrolysis and condensation of 2,4,6,8‐tetramethyl‐2,4,6,8‐tetra(trimethoxysilylethyl)cyclotetrasiloxane (a cyclic monomer). The electrical properties of these films, including the dielectric constant (～2.51), leakage current (6.4 × 10^?11 A/cm² at 0.5 MV/cm), and breakdown voltage (～5.4 MV/cm) were fairly good. Moreover, the mechanical properties of the hybrid films, including the hardness (～7 GPa), modulus (～1.2 GPa), and crack‐free thickness (<2 μm), were excellent in comparison with those of previous spin‐on‐glass materials with low dielectric constants. The excellent mechanical properties were proposed to be due to the high contents of Si? OH groups (>30%) and the existence of ethylene bridge and siloxane moieties in the hybrid polymer precursors. In addition, the mechanical properties of the hybrid films were affected by the contents of the cagelike structures. The more cagelike structures a hybrid film contained, the worse its mechanical properties were. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 626–634, 2003     

Biobased Polyester-Amide/Cellulose Nanocrystal Nanocomposites for Food Packaging

The worldwide plastic waste production is steadily increasing, since the use of polymeric materials continues to rise. One area of particular high plastic consumption is food packaging. Flexible and rigid packaging films are typically made from petrochemical-sourced polymers, which are utilized because of their low cost, ductility, melt-processability, and gas barrier properties, but a major downside is their inability to biodegrade in a reasonable time. Packaging-relevant properties of nanocomposites based on polyester-amides (PEAs) are reported, which are chosen on account of their tunable crystallinity, biobased starting materials, and biodegradability. These polymers are synthesized via melt polycondensation of a building block made from caprolactone and 1,4-diaminobutane, with the addition of 1,4-butanediol and dimethyl adipate. The fraction of the amide segment is varied between 25 and 75 mol%. The oxygen transmission rate (O₂TR) drops upon increasing the amide content from 1.6 × 10⁵ to 2.9 × 10⁻⁴ cm³ m⁻² d⁻¹ on account of increasing crystallinity. In order to improve the gas barrier properties further, nanocomposites of the PEAs and 1–10 wt% cellulose nanocrystals (CNCs) are prepared. These nanocomposites have indeed lower O₂TR values than the neat PEAs, with reductions of as much as 50% for a CNC content of 10 wt%.     

TiO2–BaTiO3 nanocomposite for electron capture in dye‐sensitized solar cells

Different compositions of TiO₂–BaTiO₃ nanocomposites are synthesized with various weight ratios for dye‐sensitized solar cell (DSSC) applications. TiO₂ and BaTiO₃ nanoparticles (NPs) are synthesized by sol‐gel and solvothermal methods, respectively and are employed as the photoanode electrodes. BaTiO₃ NPs have pure cubic perovskite crystal structure with an average size of 20‐40 nm, while TiO₂ NPs show pure anatase phase with 15‐30 nm size. The power conversion efficiency (PCE) enhancement of the cells is first attained by controlling the thickness of the films for light harvesting improvement. The fabricated DSSC composed of pure BaTiO₃ NPs with an optimal thickness of 25 μm shows efficiency of 6.83%, whereas that made of pure TiO₂ NPs with 14 μm thickness has cell efficiency of 7.24%. Further improvement of cell efficiency is achieved by preparation of binary oxide nanocomposites using TiO₂ and BaTiO₃ NPs with various weight ratios. The highest PCE of 9.40% is obtained for the nanocomposite with TiO₂:BaTiO₃=85:15 (wt%). The enhancement is assigned to less recombination of photo‐generated electrons and higher incident photon to current conversion yield as a result of rapid charge collection and higher dye sensitization.