Composite Thick Films Research Articles

Preparation and Characterization of SiO2-PMMA and TiO2-SiO2-PMMA Composite Thick Films for Radiative Cooling Application

Preparation and Characterization of SiO2-PMMA and TiO2-SiO2-PMMA Composite Thick Films for Radiative Cooling Application

CsPbBr3 and Cs2AgBiBr6 Composite Thick Films with Potential Photodetector Applications

This paper investigates the optoelectronic properties of CsPbBr3, a lead-based perovskite, and Cs2AgBiBr6, a lead-free double perovskite, in composite thick films synthesized using mechanochemical and hot press methods, with poly(butyl methacrylate) as the matrix. Comprehensive characterization was conducted, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectroscopy (UV–Vis), and photoluminescence (PL). Results indicate that the polymer matrix does not significantly impact the crystalline structure of the perovskites but has a direct impact on the grain size and surface area, enhancing the interfacial charge transfer of the composites. Optical characterization indicates minimal changes in bandgap energies across all different phases, with CsPbBr3 exhibiting higher photocurrent than Cs2AgBiBr6. This is attributed to the CsPbBr3 superior charge carrier mobility. Both composites showed photoconductive behavior, with Cs2AgBiBr6 also demonstrating higher-energy (X-ray) photon detection. These findings highlight the potential of both materials for advanced photodetector applications, with Cs2AgBiBr6 offering an environmentally Pb-free alternative.

Cytotoxicity and biocompatibility of a material based in recycled polyvinyl butyral PVB and high-density polyethylene HDPE determined in human peripheral leukocytes

Abstract Polyvinyl butyral (PVB) is a polymer resin byproduct of the automotive industry. Separation and recycling of PVB from automotive windshield production lines solve waste management issues and might be used in biomedicine implants, particularly when blended with high-density polyethylene (HDPE). Materials designed for biological applications must undergo pre-clinical safety evaluation, including in vitro biocompatibility and cytotoxicity testing. This study evaluated in vitro the biocompatibility and cytotoxicity of thick composite films made of recycled PVB (rPVB), HDPE, and composites made of concentrations of both polymers using peripheral blood mononuclear cells (PBMCs) from healthy donors. The microstructure and elemental analysis revealed no potential concerns regarding mechanical damage to the cell cultures. After culturing the PBMCs in the presence of the polymers and their blends, we observed no acute release of the proinflammatory cytokines TNF-α and IL1-β, nor evidence of cell death, measured by the release of nucleosomes to the extracellular medium at 24 h nor at 7 days of culture. We also found no damage to the cell monolayer. The stimulation with lipopolysaccharide (LPS), used here as proinflammatory control, induced the significant release of both cytokines and caused damage to the cell monolayer. In conclusion, the pure recycled PVB, pure HDPE, and their composites are safe and biocompatible.

Cold Sprayed Copper-Diamond Composites for Thermal Management of Semiconductor Packages

Thermal management is key to enabling increasingly powerful chips and heterogeneous integrated 2.5D/3-D systems. Composite materials with high thermal conductivities that can be placed at different levels of proximity to the die provide new solutions for heat dissipation. Here we report the fabrication of thick copper-diamond composite films using cold spray, which is a high-throughput, low-thermal-budget deposition technology. In cold spray, feedstock micro powder is accelerated in a specially designed nozzle by a heated pressurized gas and adheres to the substrate upon high-speed impingement. This process achieves higher deposition rates than other methods used in semiconductor manufacturing (such as electroplating). It also produces films that are denser and much less porous than ones produced by conventional thermal spray techniques. In this work, we first use process and thermal simulations to determine the requirements of the micro diamond powder feedstock, including the diamond core size, metal-clad thickness, core-clad interfacial resistance, and volume fraction to enable the cold spray of copper-diamond composites with thermal conductivities that are higher than copper. Subsequently, we perform a systematic characterization of the diamond powders from several suppliers, including the purity, metal oxygen content, particle morphology, and metal-clad adhesion. This characterization reveals the challenges of meeting all the specs using currently available diamond powders. Finally, we cold spray copper-diamond composite films on a variety of substrates with tunable thicknesses between 100 mm and 2 mm, achieving a thermal conductivity that is approximately 10% higher than cold-sprayed pure copper. Further improvement of the thermal properties relies on continued innovation in powder surface modification and powder storage/shipping methods.

Luminescence enhancement behavior of KSr1.96Sm0.04Nb5O15/PVDF composite thick film after electric polarization

A novel composite thick film exhibiting luminescent enhancement behavior was prepared using Sm3+ doped KSr2Nb5O15 ferroelectric microcrystals and polyvinylidene difluoride (PVDF) polymer via a tape-casting technology. After compositing with PVDF, the thick film retained the ferroelectric polarization behavior, and the PVDF phase had negligible impact on the reflectivity and optical absorption edge of ferroelectric microcrystals. The photoluminescent emission intensities of the characteristic transitions of Sm3+ exhibited significant enhancement after electric polarization, with a maximum modulation ratio exceeding 200 %. The underlying luminescence modulation mechanism is discussed. This work proposed a novel strategy for fabrication of flexible composite thick films with coupling behavior between luminescent and ferroelectric properties.

Enhancing β-phase and dielectric properties of BCZT lead-free reinforced in PVDF-HFP composite thick films for eco-friendly energy harvesting

Barium titanate doped with calcium and zirconium (BCZT) relaxor ferroelectric ceramics enhance energy storage capabilities due to their excellent ferroelectric and dielectric properties. In this investigation, BCZT particles (Ps) were incorporated into poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) using the solvent casting method to prepare biocompatible composite films with varying BCZT Ps contents. The uniform dispersion and distribution of BCZT Ps throughout the polymer matrix results in robust interfacial interactions, promoting improved nucleation of the β-phase in PVDF-HFP and increased thermal stability with higher BCZT Ps loading. The Young's modulus and tensile strength of the composites experienced respective increases of 78.2 % and 41.8 % with the addition of 20 wt% BCZT Ps. While the dielectric constant was improved from 12 to 31. This research contributes to the development of flexible composite films with different BCZT Ps contents, to promote an innovative and environmentally friendly energy harvesting technology. This innovation captures environmental vibrations and converts them into electrical energy to supply a variety of sensors.

Subtractive manufacturing of polymer-derived ceramic composite thick film sensor based on ultrafast laser etching

Polymer-derived ceramics (PDCs) are increasingly recognized as promising materials for high-temperature thin/thick film sensors (HTTFSs). However, a large linewidth and poor dimensional accuracy have severely restricted the practical application of PDCs HTTFSs. Our study employed a picosecond laser to precisely pattern the polymer-derived ceramic (PDC) thick film while applying no obvious damage to the interface between ceramic and substrate. Through parameters optimization, the laser-affected area was minimized to 6 μm wide, and a minimum feature size of about 30 μm was achieved. Furthermore, 7 rounds of high-temperature tests of the patterned film revealed good temperature-resistance repeatability within a temperature range of up to 800 °C. To demonstrate practical application potential, we successfully fabricated a heat flux sensor, and it exhibited a sensitivity of 1.32 mV/(kW/m2), a response time of 600 ms, and excellent repeatability over a range of 0–75.4 kW/m2. In summary, this paper proposes a novel approach toward miniaturizing the linewidth of the polymer-derived ceramics thick film sensor, showing significant potential for precise measurements in extreme environments.

Quenching induced modified nanoarchitectonics in the dielectric and energy storage behavior of poly (vinylidene fluoride)/Ba0.7Sr0.3TiO3 composites thick films

Quenching induced modified nanoarchitectonics in the dielectric and energy storage behavior of poly (vinylidene fluoride)/Ba0.7Sr0.3TiO3 composites thick films

Sustainable super-hard and thick nanodiamond composite film deposited on cemented carbide substrates with an interfacial Al-interlayer

Super-hard nanodiamond composite (NDC) films, synthesized via cathodic arc plasma deposition on unheated WC − Co substrates, offer an eco-friendly solution for cutting tools. A 100 nm-thick Al-interlayer mitigates Co catalytic effects, improving adhesion and yielding smooth and dense 10 µm-thick films at a deposition rate of 3.3 μm/hr. These grain-boundary-rich nanostructured films, with an impressive 58 GPa hardness attributed to a substantial 70 % C sp3 fraction, prove optimal for hard coatings. The Al-interlayer effectively suppresses Co catalytic effects, forming a dense Al-oxide layer, enhancing film hardness and adhesion (Lcr = 18.6 N). NDC films present a promising eco-friendly option for high-performance hard coatings.

산화아연 나노입자 유형이 카라기난 기반 복합 필름의 구조, 기계적 및 항균 특성에 미치는 영향

In this study, zinc oxide nanoparticles (ZnONPs) were synthesized using three distinct zinc salts: zinc acetate, zinc chloride, and zinc nitrate. These ZnONPs were subsequently utilized in the fabrication of carrageenan-ZnONPs (Car-ZnONPs) composite films. The study assessed influence of the various ZnONPs on the morphological, water vapor barrier, color, optical, and antimicrobial properties of the Car-ZnONPs composite films. The surface morphology and UV-blocking attributes of the composite films were affected by the type of ZnONPs used, but their surface color, transparency, and chemical structure remained unaltered. The composite film's thickness and elongation at break (EB) significantly increased, while the tensile strength significantly decreased. In contrast, film’s elastic modulus (EM) and water vapor permeability coefficient (WVP) showed no significant difference. All the composite films with added ZnONPs demonstrated potent antibacterial activity against Escherichia coli O157:H7 and Listeria monocytogenes. Among the carrageenan-based composite films, Car-ZnONPsZC showed the highest antibacterial and UV-blocking properties, and its elongation at break was significantly higher than that of the pure carrageenan films. This suggests that ZnONPs composite films have the potential to be used as an active packaging film, preserve the safety of the packaged food and extend shelf life.

Enhanced Absolute Recovered Energy under Low Electric Field in All-Inorganic 0-3 Nanocomposition Thick Films.

Inorganic thick-film dielectric capacitors with ultrahigh absolute recovered energy at low electric fields are extremely desired for their wide application in pulsed power systems. However, a long-standing technological bottleneck exists between high absolute energy and large recovered energy density. A new strategy is offered to fabricate selected all-inorganic 0-3 composite thick films up to 10µm by a modified sol-slurry method. Here, the ceramic powder is dispersed into the sol-gel matrix to form a uniform suspension, assisted by powder, therefore, the 2µm-thickness after single layer spin coating. To enhance the energy-storage performances, the composites process is thoroughly optimized by ultrafine powder (<50nm) technique based on a low-cost coprecipitation method instead of the solid-state and sol-gel methods. 0D coprecipitation powder has a similar dielectric constant to the corresponding 3D films, thus uneven electrical field distributions is overcome. Moreover, the increase of interfacial polarization is realized due to the larger specific surface area. A maximum recoverable energy density of 14.62Jcm-3 is obtained in coprecipitation thick films ≈2.2 times that of the solid-state powder and ≈1.3 times for sol-gel powder. This study provides a new paradigm for further guiding the design of composite materials.

Optical and structural properties of Fe2O3-ZnO composite thick films obtained by ultrasonic spray pyrolysis

Optical and structural properties of Fe2O3-ZnO composite thick films obtained by ultrasonic spray pyrolysis

Scintillation properties of composite films based on CsPbBr3 nanocrystals embedded in PMMA

Transparent composite films of polymethylmethacrylate with embedded CsPbBr3 colloidal nanocrystals (CsPbBr3-PMMA) were obtained. The optical, photoluminescent, and scintillation properties of the composite films were studied. The CsPbBr3-PMMA films had an intense photoluminescence signal and a nanosecond-range photoluminescence decay time (2 ns). The scintillation characteristics of CsPbBr3-PMMA films of different thicknesses were studied upon excitation by α-radiation of radionuclides 239Pu (Eα = 5.15 MeV) and 238Pu (Eα = 5.46 MeV). The sensitivity and minimum detectable activity of the composite films were calculated from the pulse-height spectra. The estimation of the absolute light yield according to the IEC 62372:2021 standard (determining the intrinsic resolution of scintillator) and calculation of the light collection coefficient showed that the 200-μm thick composite film emitted about 860 photons per 1 MeV of absorbed energy. Under α-excitation, the films revealed a fast scintillation response with average decay time of about 1.4 ns.

Fabrication and performance of ultrathin and adhesive composite film with high out-of-plane thermal conductivity using 3D printing and microwire-cutting assistance

This study presents the development of a highly thermally conductive adhesive film based on an epoxy matrix filled with high-oriented graphite films (GFs). The film was fabricated using a 3D-printed framework to fix aligned GFs in a parallel configuration, followed by the infusion of liquid epoxy. A diamond microwire cutting technique was employed to obtain a 0.4 mm thick epoxy composite film. The resulting film exhibits an impressive apparent out-of-plane thermal conductivity of 20 Wm-1K−1 and a notable tensile shear strength of 5.91 MPa, with a GF volume fraction of 75 %. Finite element simulations were employed to accurately predict the TC, which is found to be in excellent agreement with experimental results. The unprecedented combination of high out-of-plane TC and adhesive performance in such a thin adhesive film opens up opportunities for its utilization in various thermal management applications, including electronic packaging, LED systems, etc.

Breaking Boundaries in LED Technology: Exploring the Revolutionary Diode Characteristics of Screen Printed (TiO2)1−x (CuO)x Thick Films

A thick TiO2-CuO composite film is deposited on a Si substrate by a low-cost screen printing method. Both anatase and CuO-doped TiO2 are characterized for diode applications. X-ray Diffraction (XRD) confirms that the composite film exists as an anatase phase of TiO2 and a monoclinic phase of CuO with a maximum diffraction of (101) plane. SEM images depict the less severe agglomeration of particles for the doped TiO2 as compared to the anatase TiO2. The UV–visible spectra reveal a direct band gap shift of 3.35 eV (pure TiO2) to 3.26 eV (doped TiO2). From the PL study, the blue shaded emission is perfectly derived for anatase TiO2 while the color is seen to change to the white zone supporting TiO2-CuO composite formation as depicted by the CIE diagram. The diode parameters such as ideality factor (n) and barrier height (Φb) are calculated with the help of I–V characteristics. This only reported novel effort on screen-printed TiO2-CuO thick film may help in manufacturing possible LEDs for optoelectronic applications.

Coercivity mechanism and long-range coupling of anisotropic Nd-Dy-Fe-Co-B/Fe composite thick film

In the present work, the long-range coupling between soft- and hard-magnetic layers and a dual enhancement of coercivity and polarization are achieved in anisotropic Nd-Dy-Fe-Co-B/Fe composite thick film with Ta spacer layers. It has been found that the coercivity mechanism dominated by the pinning mechanism is enhanced with increasing the periodic number of multilayers. The effect of the Ta spacer layer isolating the hard-magnetic phase grains leads to an increase in the coercivity. Continuous irreversible distribution confirms the coherent reversal of the soft and hard magnetic phases. The increase of polarization is caused by the dipole interactions acting in the long-range coupling between the layers.

Investigation of Structural and Electrical Properties of Al2O3/Al Composites Prepared by Aerosol Co-Deposition

As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al2O3 is widely present in electronic applications as a protective coating or as an electrical and thermal insulator due to its mechanical and thermal stabilities and chemical inertness. Al2O3 is also an important dielectric material, with high resistivity and stable permittivity over a wide range of temperatures and electric fields, but its modest permittivity necessitates large effective areas or extremely thin layers when a large capacitance is desired. Composites consisting of discrete conducting phases within an insulating matrix can produce large capacitance via Maxwell–Wagner polarization. In this work, Al2O3/Al composite thick films with different volume ratios of Al were prepared using the aerosol deposition method. A relative dielectric permittivity (εr′) of 800 at 1 MHz was achieved at 27 vol% of Al, a sixty-sevenfold enhancement compared to Al2O3. On the other hand, dielectric losses, tan(δ), at 1 MHz increased from 0.01 for Al2O3 up to 0.58 for the composite with 27 vol% of Al. A finite-element model of the composites was implemented, supporting the nonlinear electrical behavior of the composites as function of vol% of Al. Our results show novel possibilities for the applications of Al2O3-based materials in the microelectronic industry, especially for temperature-sensitive applications, for which the integration strengths of aerosol deposition are valuable.

Application of Low Temperature Processed 0-3 Composite Piezoelectric Thick Films in Flexible, Non-planar, High Frequency Ultrasonic Devices.

Low-temperature, flexible, 0-3 composite piezoelectric materials can decrease the size, cost, and complexity of high-frequency acoustic devices on temperature sensitive substrates such as those in catheter based ultrasonic devices and acoustooptic sensors. In this paper, the application of low-temperature 0-3 connected composite thick films in flexible, non-planar, high frequency ultrasonic devices is reported. A flexible high-frequency ultrasound transducer and an acousto-optic radio-frequency (RF) field sensor are demonstrated utilizing PZT-based composite thick films. Flexible composite films have been fabricated with thicknesses between 20-100μm utilizing screen-printing, stencil-printing, and dip-coating techniques. Composite films' piezoelectric d33 coefficient is measured, with results between 35-43 pC/N. Ultrasonic transducers utilizing these films demonstrate broadband acoustic response. A composite transducer is fabricated on flexible polyimide and wrapped around a 3mm catheter. Pulse-echo experiments demonstrate viability of these films as both as an actuator and a sensor in flexible devices. The composite material is further dip-coated onto an optical fiber Bragg grating to form a flexible acousto-optic RF field sensor. The sensor demonstrates RF field sensing in the 20-130 MHz range. The results from these experiments indicate significant potential for future flexible, high frequency ultrasonic devices utilizing low temperature 0-3 composite piezoelectric materials on temperature sensitive substrates.

CuInS2 Nanocrystals Embedded PMMA Composite Films: Adjustment of Polymer Molecule Weights and Application in Remote-Type White LEDs.

The commercial application of colloidal semiconductor nanocrystals has been realized owing to the development of composite film technology. Here, we demonstrated the fabrication of green and red emissive CuInS2 nanocrystals embedded polymer composite films of equal thickness by using a precise solution casting method. The impacts of polymer molecular weight on the dispersibility of CuInS2 nanocrystals were then systematically studied through evaluating the decrease in transmittance and red shift of emission wavelength. The composite films made from PMMA of small molecular weights exhibited higher transmittance. Applications of these green and red emissive composite films as color converters in remote-type light-emitting devices were further demonstrated.

The influence of pregelatinized starch on the rheology of a gellan gum-collagen IPN hydrogel for 3D bioprinting

Hydrogel scaffolds infused with stem cells are valuable alternatives to skin grafts in replacement of lost host tissues. In a prior study, we developed an adipose-derived stem cells (ADSC)-laden gellan gum-collagen interpenetrating network (IPN) hydrogel with enhanced wound healing properties upon application on murine full thickness burn wounds. With the perspective of enabling the clinical translation and healthcare adaptation of the hydrogel wound-dressing, we report a novel ADCS-laden collagen-gellan gum full IPN hydrogel formula compatible with 3D bioprinting technology. The stable new bio-ink showed improved printability for extrusion-based 3D biofabrication and preserved scaffold quality for stem cell proliferation. Pregelatinized starch (PGF, PREGEFLO®PI10) and glycerol were successfully incorporated to the bio-ink as molecular lubricant and hydrophilic plasticizer. When subjected to rheological measurements, the new glycerol-PGF-gellan gum composite hydrogel demonstrated good shear recovery ability, improved resistance to step-strain deformations and adequate stiffness as cell-conducive environment. Subsequently, a dual-head two-step temperature-guided 3D bioprinting methodology was developed to extrude ADSC-laden collagen into the composite hydrogel thick film to achieve in-situ polymer interpenetration. After their fabrication, the printed cell-laden hydrogel constructs were able to maintain high shape fidelity and stability after 21 days of incubation in cell culture media. Results from cell proliferation assay (MTS) and confocal laser scanning microscopy (CLSM) suggested that ADSC retained their normal cellular functions of adhesion, proliferation, and migration within the 3D bioprinted hydrogel scaffold. Taken together, our study brings forward the use of PREGEFLO®PI10 in upgrading the ADSC-laden IPN hydrogel formula towards potential clinical translation of synthetic skin grafts.