Efficient multi-barrier thin film encapsulation of OLED using alternating Al2O3 and polymer layers

Organic optoelectronic devices, especially for OLEDs, are extremely susceptibility to water vapor and oxygen which limit their widespread commercialization. In order to extend the shelf-lifetime of devices, thin film encapsulation is the most promising and challenging encapsulation process. In this study, dyad-style multilayer encapsulation structures based on alternating Al₂O₃ layer and parylene C have been discussed as gas diffusion barriers, in which dense and pinhole-free Al₂O₃ films were grown by atomic layer deposition (ALD) and flexible parylene C layers were deposited by chemical vapor deposition (CVD). We found the particle in ALD deposited Al₂O₃ films process is the key killer to barrier property. The thickness of Al₂O₃ films is the key factor which limit the amount of strain placed on barrier films. With three dyads of the optimal thickness of 30 nm Al₂O₃ film and 500 nm parylene C, WVTR value is lower than 10⁻⁵ g m⁻² per day. In addition, the lifetime of OLEDs with and without encapsulation was 190 h and 10 h, respectively. All the results show that this TFE structure has the effective encapsulated property and does not cause degradation of the OLED devices.

The work demonstrates the WVTR value of 3 dyads alternative 30 nm Al₂O₃ and 500 nm parylene C encapsulation structure is less than 10⁻⁵ g m⁻² per day. And this TFE technology successfully applies for OLED device encapsulation.     

Interface engineering of graphene–silicon Schottky junction solar cells with an Al2O3 interfacial layer grown by atomic layer deposition

The recent progress in graphene (Gr)/silicon (Si) Schottky barrier solar cells (SBSC) has shown the potential to produce low cost and high efficiency solar cells. Among the different approaches to improve the performance of Gr/Si SBSC is engineering the interface with an interfacial layer to reduce the high recombination at the graphene (Gr)/silicon (Si) interface and facilitate the transport of photo-generated carriers. Herein, we demonstrate improved performance of Gr/Si SBSC by engineering the interface with an aluminum oxide (Al₂O₃) layer grown by atomic layer deposition (ALD). With the introduction of an Al₂O₃ interfacial layer, the Schottky barrier height is increased from 0.843 V to 0.912 V which contributed to an increase in the open circuit voltage from 0.45 V to 0.48 V. The power conversion efficiency improved from 7.2% to 8.7% with the Al₂O₃ interfacial layer. The stability of the Gr/Al₂O₃/Si devices was further investigated and the results have shown a stable performance after four weeks of operation. The findings of this work underpin the potential of using an Al₂O₃ interfacial layer to enhance the performance and stability of Gr/Si SBSC.

One approach to improve Gr/Si SBSC performance is engineering the interface with an interfacial layer. We demonstrate the improved performance of Gr/Si SBSC upon engineering the interface with an aluminium oxide (Al₂O₃) layer grown by atomic layer deposition (ALD)..     

Effect of hydrogen diffusion in an In–Ga–Zn–O thin film transistor with an aluminum oxide gate insulator on its electrical properties

We fabricated amorphous InGaZnO thin film transistors (a-IGZO TFTs) with aluminum oxide (Al₂O₃) as a gate insulator grown through atomic layer deposition (ALD) method at different deposition temperatures (T_dep). The Al₂O₃ gate insulator with a low T_dep exhibited a high amount of hydrogen in the film, and the relationship between the hydrogen content and the electrical properties of the TFTs was investigated. The device with the Al₂O₃ gate insulator having a high H content showed much better transfer parameters and reliabilities than the low H sample. This is attributed to the defect passivation effect of H in the active layer, which is diffused from the Al₂O₃ layer. In addition, according to the post-annealing temperature (T_post-ann), a-IGZO TFTs exhibited two unique changes of properties; the degradation in low T_post-ann and the enhancement in high T_post-ann, as explained in terms of H diffusion from the gate insulator to an active layer.

We fabricated amorphous InGaZnO thin film transistors (a-IGZO TFTs) with aluminum oxide (Al₂O₃) as a gate insulator grown through atomic layer deposition (ALD) method at different deposition temperatures (T_dep).     

Modifying hydrophilic properties of polyurethane acryl paint substrates by atomic layer deposition and self-assembled monolayers

A process of atomic layer deposition (ALD) combined with self-assembled monolayers (SAMs) was used to investigate the possible modification of the wetting properties of polyurethane (PUR) paint surfaces without altering their original hue. First, we used an ALD process to produce thin and uniform Al₂O₃ coatings of these surfaces at temperatures as low as 80 °C. We then successfully achieved the addition of 16-phosphono-hexadecanoic acid (16-PHA) SAMs to the Al₂O₃-coated paint samples. Given initial hydrophobicity, which however was not stable over time, Al₂O₃ coatings reduced the contact angle of the PUR surfaces from 110 to 10°. Addition of SAMs on the Al₂O₃ coatings induced a sustained reduction in their contact angles to 60–70°, and aging of the samples revealed a further decrease to 25–40°. Testing of the Al₂O₃/16-PHA coating in a Weather-Ometer (WOM) revealed its durability even under harsh outdoor conditions. These experimental results show that by combining ALD with SAMs it is possible to produce durable coatings with modified hydrophilic/hydrophobic properties that are stable over time. The use of SAMs with different end-groups may allow fine-tuning of the coating''s wetting properties.

A process of atomic layer deposition (ALD) combined with self-assembled monolayers (SAMs) was used to investigate the possible modification of polyurethane (PUR) paint surface wetting properties without altering their original hue.     

Charge balance control of quantum dot light emitting diodes with atomic layer deposited aluminum oxide interlayers

We developed a 1.0 nm thick aluminum oxide (Al₂O₃) interlayer as an electron blocking layer to reduce leakage current and suppress exciton quenching induced by charge imbalance in inverted quantum dot light emitting diodes (QLEDs). The Al₂O₃ interlayer was deposited by an atomic layer deposition (ALD) process that allows precise thickness control. The Al₂O₃ interlayer lowers the mobility of electrons and reduces Auger recombination which causes the degradation of device performance. A maximum current efficiency of 51.2 cd A⁻¹ and an external quantum efficiency (EQE) of 12.2% were achieved in the inverted QLEDs with the Al₂O₃ interlayer. The Al₂O₃ interlayer increased device efficiency by 1.1 times, increased device lifetime by 6 times, and contributed to reducing efficiency roll-off from 38.6% to 19.6% at a current density up to 150 mA cm⁻². The improvement of device performance by the Al₂O₃ interlayer is attributed to the reduction of electron injection and exciton quenching induced by zinc oxide (ZnO) nanoparticles (NPs). This work demonstrates that the Al₂O₃ interlayer is a promising solution for charge control in QLEDs and that the ALD process is a reliable approach for atomic scale thickness control for QLEDs.

We developed a 1.0 nm thick aluminum oxide (Al₂O₃) interlayer as an electron blocking layer to reduce leakage current and suppress exciton quenching induced by charge imbalance in inverted quantum dot light emitting diodes (QLEDs).     

High-performance thin H:SiON OLED encapsulation layer deposited by PECVD at low temperature

Highly moisture permeation resistive and transparent single layer thin films for the encapsulation of hydrogenated silicon oxynitrides (H:SiON) were deposited by plasma-enhanced chemical vapor deposition (PECVD) using silane (SiH₄), nitrous oxide (N₂O), ammonia (NH₃), and hydrogen (H₂) at 100 °C for applications to a top-emission organic light-emitting diode (TEOLED). Addition of H₂ into the PECVD process of SiON film deposition afforded the hydrogenated SiON film, which showed not only improved optical properties such as transmittance and reflectance but also better barrier property to water permeation than PECVD SiON and even SiN_x. The H:SiON film with thickness of only 80 nm exhibited water vapor transmission rate (WVTR) lower than 5 × 10⁻⁵ g per m² per day in the test conditions of 38 °C and 100% humidity, where this WVTR is the measurement limit of the MOCON equipment. An additional coating of UV curable polymer enabled the H:SiON films to be flexible and to have very stable barrier property lower than 5 × 10⁻⁵ g per m² per day even after a number of 10k times bending tests at a curvature radius of 1R. The mild H:SiON film process improved the electrical properties of top-emission OLEDs without generating any dark spots. Furthermore, single H:SiON films having high water vapor barrier could maintain the original illumination features of TEOLED longer than 720 hours. These excellent properties of the H:SiON thin films originated from the structural changes of the SiON material by the introduction of hydrogen.

High-performance H:SiON single layer thin film encapsulation (TFE) was deposited by plasma enhanced chemical vapor deposition (PECVD) method. To control the characteristics of the SiON thin films, hydrogen gas was introduced during PECVD process.     

Layered Si–Ti oxide thin films with tailored electrical and optical properties by catalytic tandem MLD-ALD

Oxides with well-controlled optical and electrical properties are key for numerous advances in nanotechnology, including energy, catalysis, sensors, and device applications. In this study we introduce layer-by-layer deposition of silicon–titanium layered oxide (Si–Ti LO) thin films using combined MLD-ALD methodology (M/ALD). The Si–Ti LO film deposition is achieved by acid–base catalysis establishing an overall catalytic tandem M/ALD super cycle (CT-M/ALD). The catalytic nature of the process allows relatively fast deposition cycles under mild conditions compared with the typical cycle time and conditions required for ALD processes with silane precursors. The Si–Ti LO thin films exhibit tuneable refractive index and electrical conductivities. The refractive index is set by the stoichiometry of Si- to Ti-oxide phases simply by selecting the MLD to ALD proportion in the CT-M/ALD super cycle, with low and high refractive index, respectively. Thermal treatment of Si–Ti LO thin films resulted in conductive thin films with both graphitic and Magnéli oxide phases. Enhanced conductivity and reduced onset temperature for Magnéli phase formation were obtained owing to the unique Si–Ti layer structure and stoichiometry attained by the CT-M/ALD process and facilitated by breaking of Si–C bonds and Red–Ox reactions between the Si sub-oxide and TiO₂ phases leading to the conductive Magnéli phase. Hence, the embedded amine silane functions not only for catalysing Si–Ti LO deposition but also to further promote subsequent transformations during thermal processing. This work demonstrates the concept of embedding a meta-stable organic motif by the MLD step to facilitate transformation of an oxide phase by taking advantage of precise layer-by-layer deposition of alternating phases enabled by M/ALD.

Layer-by-layer deposition of Si–Ti layered oxide thin films are obtained using catalytic tandem M/ALD methodology. The films exhibit optical (RI) and electrical conductivities by selecting the MLD to ALD proportion in the super cycle.     

Development of moisture-proof polydimethylsiloxane/aluminum oxide film and stability improvement of perovskite solar cells using the film

A method for enhancing the moisture barrier property of polydimethylsiloxane (PDMS) polymer films is proposed. This is achieved by filling the PDMS free volume with aluminum oxide (AlO_x). To deposit AlO_x inside PDMS, thermal atomic layer deposition (ALD) is employed. The PDMS/AlO_x film thus produced has a 30 nm AlO_x layer on the surface. Its water vapor transmission rate (WVTR) is 5.1 × 10⁻³ g m⁻² d⁻¹ at 45 °C and 65% relative humidity (RH). The activation energy of permeability with the PDMS/AlO_x film for moisture permeation is determined to be 35.5 kJ mol⁻¹. To investigate the moisture barrier capability of the PDMS/AlO_x layer, (FAPbI₃)_0.85(MAPbBr₃)_0.15/spiro-OMeTAD/Au perovskite solar cells are fabricated, and encapsulated by the PDMS/AlO_x film. To minimize the thermal damage to solar cells during ALD, AlO_x deposition is performed at 95 °C. The solar cells exposed to 45 °C-65% RH for 300 h demonstrate less than a 5% drop in the power-conversion efficiency.

A method for enhancing the moisture barrier property of polydimethylsiloxane (PDMS) polymer films is proposed. This is achieved by filling the PDMS free volume with aluminum oxide (AlO_x).     

Thin film encapsulation for quantum dot light-emitting diodes using a-SiNx:H/SiOxNy/hybrid SiOx barriers

A facile thin film encapsulation (TFE) method having a triple-layered structure of a-SiN_x:H/SiO_xN_y/hybrid SiO_x (ASH) on QD-LEDs was performed utilizing both reproducible plasma-enhanced chemical vapor deposition (PECVD) and simple dip-coating processes without adopting atomic layer deposition (ALD). The ASH films fabricated on a polyethylene terephthalate (PET) substrate show a high average transmittance of 88.80% in the spectral range of 400–700 nm and a water vapor transmission rate (WVTR) value of 7.3 × 10⁻⁴ g per m² per day. The measured time to reach 50% of the initial luminance (T₅₀) at initial luminance values of 500, 1000, and 2000 cd m⁻² was 711.6, 287.7, and 78.6 h, respectively, and the extrapolated T₅₀ at 100 cd m⁻² is estimated to be approximately 9804 h, which is comparable to that of the 12 112 h for glass lid-encapsulated QD-LEDs. This result demonstrates that TFE with the ASH films has the potential to overcome the conventional drawbacks of glass lid encapsulation.

The extrapolated T₅₀ at 100 cd m⁻² for the a-SiN_x:H/SiO_xN_y/hybrid SiO_x (ASH)-encapsulated QD-LEDs is estimated to be 9804 h, which is compatible to that of 12112 h for glass lid encapsulated QD-LEDs.     

Improved resistive switching characteristics of a multi-stacked HfO2/Al2O3/HfO2 RRAM structure for neuromorphic and synaptic applications: experimental and computational study

Atomic Layer Deposition (ALD) was used for a tri-layer structure (HfO₂/Al₂O₃/HfO₂) at low temperature over an Indium Tin Oxide (ITO) transparent electrode. First, the microstructure of the fabricated TaN/HfO₂/Al₂O₃/HfO₂/ITO RRAM device was examined by the cross-sectional High-Resolution Transmission Electron Microscopy (HRTEM). Then, Energy Dispersive X-ray Spectroscopy (EDS) was performed to probe compositional mapping. The bipolar resistive switching mode of the device was confirmed through SET/RESET characteristic plots for 100 cycles as a function of applied biasing voltage. An endurance test was performed for 100 DC switching cycles @0.2 V wherein; data retention was found up to 10⁴ s. Moreover, for better insight into the charge conduction mechanism in tri-layer HfO₂/Al₂O₃/HfO₂, based on oxygen vacancies (V_OX), total density of states (TDOS), partial density of states (PDOS) and isosurface three-dimensional charge density analysis was performed using WEIN2k and VASP simulation packages under Perdew–Burke–Ernzerhof _Generalized Gradient approximation (PBE-GGA). The experimental and theoretical outcomes can help in finding proper stacking of the active resistive switching (RS) layer for resistive random-access memory (RRAM) applications.

Atomic Layer Deposition (ALD) was used for a tri-layer structure (HfO₂/Al₂O₃/HfO₂) at low temperature over an Indium Tin Oxide (ITO) transparent electrode.     

Low-resistance monovalent-selective cation exchange membranes prepared using molecular layer deposition for energy-efficient ion separations

The desalination of brackish water provides water to tens of millions of people around the world, but current technologies deplete much needed nutrients from the water, which is determinantal to both public health and agriculture. A selective method for brackish water desalination, which retains the needed nutrients, is electrodialysis (ED) using monovalent-selective cation exchange membranes (MVS-CEMs). However, due to the trade-off between membrane selectivity and resistance, most MVS-CEMs demonstrate either high transport resistance or low selectivity, which increase energy consumption and hinder the use of such membranes for brackish water desalination by ED. Here, we introduce a new method for fabrication of MVS-CEMs, using molecular layer deposition (MLD) to coat CEMs with ultrathin, hybrid organic–inorganic, positively charged layers of alucone. Using MLD enabled us to precisely control and minimize the selective layer thickness, while the flexibility and nanoporosity of the alucone prevent cracking and delamination. Under conditions simulating brackish water desalination, the modified CEMs provides monovalent selectivity with negligible added resistance—thereby alleviating the selectivity–resistance trade-off. Addressing the water-energy nexus, MLD-coating enables selective brackish water desalination with minimal increase in energy consumption and opens a new path for tailoring membranes'' surface properties.

The desalination of brackish water provides water to tens of millions of people around the world, but current technologies deplete much needed nutrients from the water, which is determinantal to both public health and agriculture.     

Water assisted atomic layer deposition of yttrium oxide using tris(N,N′-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii): process development,film characterization and functional properties

We report a new atomic layer deposition (ALD) process for yttrium oxide (Y₂O₃) thin films using tris(N,N′-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii) [Y(DPDMG)₃] which possesses an optimal reactivity towards water that enabled the growth of high quality thin films. Saturative behavior of the precursor and a constant growth rate of 1.1 Å per cycle confirm the characteristic self-limiting ALD growth in a temperature range from 175 °C to 250 °C. The polycrystalline films in the cubic phase are uniform and smooth with a root mean squared (RMS) roughness of 0.55 nm, while the O/Y ratio of 2.0 reveal oxygen rich layers with low carbon contaminations of around 2 at%. Optical properties determined via UV/Vis measurements revealed the direct optical band gap of 5.56 eV. The valuable intrinsic properties such as a high dielectric constant make Y₂O₃ a promising candidate in microelectronic applications. Thus the electrical characteristics of the ALD grown layers embedded in a metal insulator semiconductor (MIS) capacitor structure were determined which resulted in a dielectric permittivity of 11, low leakage current density (≈10⁻⁷ A cm⁻² at 2 MV cm⁻¹) and high electrical breakdown fields (4.0–7.5 MV cm⁻¹). These promising results demonstrate the potential of the new and simple Y₂O₃ ALD process for gate oxide applications.

A new water assisted atomic layer deposition (ALD) process was developed using the yttrium tris-guanidinate precursor which resulted in device quality thin films.     

Mesoporous TiO2 anatase films for enhanced photocatalytic activity under UV and visible light

Mesoporous TiO₂ films with enhanced photocatalytic activity in both UV and visible wavelength ranges were developed through a non-conventional atomic layer deposition (ALD) process at room temperature. Deposition at such a low temperature promotes the accumulation of by-products in the amorphous TiO₂ films, caused by the incomplete hydrolysis of the TiCl₄ precursor. The additional thermal annealing induces the fast recrystallisation of amorphous films, as well as an in situ acidic treatment of TiO₂. The interplay between the deposition parameters, such as purge time, the amount of structural defects introduced and the enhancement of the photocatalytic properties from different mesoporous films clearly shows that our easily upscalable non-conventional ALD process is of great industrial interest for environmental remediation and other photocatalytic applications, such as hydrogen production.

Mesoporous TiO₂ films with enhanced photocatalytic activity in both UV and visible wavelength ranges were developed through a non-conventional atomic layer deposition (ALD) process at room temperature.     

Stabilization of lithium anode with ceramic-rich interlayer for all solid-state batteries

The deposition of thin layers of polymer/ceramic on a lithium surface to produce a strong barrier against dendrites was demonstrated. Different forms (needle, sphere, rod) and types of ceramic (Al₂O₃, Mg₂B₂O₅) were tested and polymer/ceramic interlayers of a few micrometers (4 μm minimum) between the lithium and the PEO-based solid polymer electrolyte (SPE) were deposited. Interlayers with high amounts of ceramic up to 85 wt% were successfully coated on the surface of lithium foil. Compact “polymer in ceramic” layers were observed when Al₂O₃ spheres were used for instance, providing a strong barrier against the progression of dendrites as well as a buffer layer to alleviate the lithium deformation during stripping/plating cycles. The electrochemical performance of the lithium anodes was assessed in symmetrical Li/SPE/Li cells and in full all-solid-state LiFePO₄ (LFP)/SPE/Li batteries. It was observed for all the cells that the charge transfer resistance was significantly reduced after the deposition of the polymer/ceramic layers on the lithium surface. In addition, the symmetrical cells were able to cycle at higher C-rates and the durability at C/4 was even improved by a factor of 8. Microscopic observations of Li/SPE/Li stacks after cycling revealed that the polymer/ceramic interlayer reduces the deformation of lithium upon cycling and avoids the formation of dendrites. Finally, LFP/SPE/Li batteries were cycled and better coulombic efficiencies as well as capacity retentions were obtained with the modified lithium electrodes. This work is patent-pending (WO2021/159209A1).

Significant electrochemical performance improvement of symmetric Li/Li polymer cells at C/4 by using ceramic-rich coated lithium anodes.     

Low threshold room-temperature UV surface plasmon polariton lasers with ZnO nanowires on single-crystal aluminum films with Al2O3 interlayers

ZnO is one of the most promising optical gain media and allows lasing in ZnO nanowires at room temperature. Plasmonic lasers are potentially useful in applications in biosensing, photonic circuits, and high-capacity signal processing. In this work, we combine ZnO nanowires and single-crystalline aluminum films to fabricate Fabry–Perot type surface plasmon polariton (SPP) lasers to overcome the diffraction limit of conventional optics. High quality ZnO nanowires were synthesized by a vapor phase transport process via catalyzed growth. The ZnO nanowires were placed on a single-crystalline Al film grown by molecular beam epitaxy with an interlayer Al₂O₃ deposited by atomic layer deposition. The plasmonic laser is of metal-oxide-semiconductor (MOS) structure, compatible with silicon device processing. An optimal thickness of atomic layer deposited Al₂O₃ layer can lead to a low lasing threshold, 6.27 MW cm⁻², which is 3 times and 12 times lower than that of previous reports for ZnO/Al and Zno/Al₂O₃/Al plasmonic lasers, respectively, owing to low materials loss. Both the thickness and quality of insulating layers were found to critically influence the lasing threshold of the SPP nanolasers in the subwavelength regime. The simulation results also manifest the importance of the quality of the dielectric interlayer.

Ultralow threshold room-temperature UV surface plasmon polariton lasers using ZnO nanowires on single-crystal aluminum films with Al₂O₃ interlayers.     

Phase identification of vanadium oxide thin films prepared by atomic layer deposition using X-ray absorption spectroscopy

The chemical and local structures of vanadium oxide (VO_x) thin films prepared by atomic layer deposition (ALD) were investigated by soft X-ray absorption spectroscopy. It is shown that the as-deposited film was a mixture of VO₂ and V₂O₅ in disordered form, while the chemistry changed significantly after heat treatment, subject to the different gas environment. Forming gas (95% N₂ + 5% H₂) annealing resulted in a VO₂ composition, consisting mostly of the VO₂ (B) phase with small amount of the VO₂ (M) phase, whereas O₂ annealing resulted in the V₂O₅ phase. An X-ray circular magnetic dichroism study further revealed the absence of ferromagnetic ordering, confirming the absence of oxygen vacancies despite the reduction of V ions in VO₂ (V⁴⁺) with respect to the precursor used in the ALD (V⁵⁺). This implies that the prevalence of VO₂ in the ALD films cannot be attributed to a simple oxygen-deficiency-related reduction scheme but should be explained by the metastability of the local VO₂ structures.

X-ray absorption spectroscopy reveals the local structures of atomic-layer-deposited vanadium oxide films subject to heat treatments.     

High performance organic light-emitting diodes employing ITO-free and flexible TiOx/Ag/Al:ZnO electrodes

The broad application of flexible optoelectronic devices is still hampered by the lack of an ITO-free and highly flexible transparent electrode. Dielectric/metal/dielectric (DMD) transparent electrodes are promising candidates to replace ITO, especially in flexible devices due to their mechanical stability to bending, high optical transmittance and low sheet resistance (<6 Ω sq⁻¹). This paper reports on organic light emitting diodes (OLEDs) employing a DMD electrode, specifically TiO_x/Ag/Al:ZnO (doped with 2 wt% Al₂O₃) fabricated by sputter deposition, together with a solution-processed organic polymeric emitting layer. The electrodes were sputtered without substrate heating on rigid glass and flexible polyethylene terephthalate (PET). The results showed that the OLED devices on the DMD electrodes outperform the OLEDs on commercial ITO substrates in terms of maximum luminance as well as current efficacy. Specifically, DMD-based devices achieve up to 30% higher current efficacy on glass and up to 260% higher efficacy on PET, as compared to the ITO-based reference devices. Maximum luminance reaches up to 100 000 cd m⁻² for the DMD-based OLEDs on glass and 43 000 cd m⁻² for those on PET. This performance is due to the low sheet resistance of the electrodes combined with efficient light outcoupling and shows the potential of DMDs to replace ITO in optoelectronic devices. This outstanding type of optoelectronic device paves the way for the future high throughput production of flexible display and photovoltaic devices.

A flexible ITO-free structure based on nano-engineered transparent TiO_x/Ag/Al:ZnO electrodes is used for the first time in solution-processed OLEDs.     

Fabrication of graphene oxide/montmorillonite nanocomposite flexible thin films with improved gas-barrier properties

Nanocomposites are potential substitutes for inorganic materials in fabricating flexible gas-barrier thin films. In this study, two nanocomposites are used to form a flexible gas-barrier film that shows improved flexibility and a decreased water vapor transmission rate (WVTR), thereby extending the diffusion path length for gas molecules. The nanoclay materials used for the flexible gas-barrier thin film are Na⁺-montmorillonite (MMT) and graphene oxide (GO). A flexible gas-barrier thin film was fabricated using a layer-by-layer (LBL) deposition method, exploiting electronic bonding under non-vacuum conditions. The WVTR of the film, in which each layer was laminated by LBL assembly, was analyzed by Ca-test and the oxygen transmission rate (OTR) was analyzed by MOCON. When GO and MMT are used together, they fill each other''s vacancies and form a gas-barrier film with high optical transmittance and the improved WVTR of 3.1 × 10⁻³ g per m² per day without a large increase in thickness compared to barrier films produced with GO or MMT alone. Thus, this film has potential applicability as a barrier film in flexible electronic devices.

Nanocomposites are potential substitutes for inorganic materials in fabricating flexible gas-barrier thin films.     

Oxidation behavior of the TiAlN hard coating in the process of recycling coated hardmetal scrap

Recycling coated hardmetal scraps is becoming increasingly important for tungsten resource recovery. However, the coatings in these materials are one of the biggest problems, especially Al-containing coatings. In this study, discarded TiAlN-coated WC–Co hardmetal tool tips were isothermally oxidized at 900 °C in air, during which the final oxide, phase transition and microstructure evolution were investigated. Milled powders below 0.15 mm were completely oxidized in 180 min, and pieces of coatings were found in the final oxides. White WO₃ was mainly distributed on defect-rich areas of oxide scale surfaces. Furthermore, the final oxide scale was triple-layered, mainly consisting of the WO₃-concentrated outmost layer, the Al₂O₃-concentrated middle layer, and the TiO₂-concentrated inner layer. It is different from the bi-layered Al₂O₃/TiO₂ oxide scale that appeared for a new TiAlN-coated hardmetal during an oxidation resistance test. This was attributed to the defects in hardmetal scraps, which provided a fast pathway for element diffusion and volatilization of WO₃. Consequently, it was impossible to remove Al₂O₃ completely.

The final oxide scale was triple-layered, consisting of a WO₃-rich outmost layer, Al₂O₃-concentrated middle layer and TiO₂-concentrated inner layer.     

Effect of silane functionalized graphene prepared by a supercritical carbon dioxide process on the barrier properties of polyethylene terephthalate composite films

In this work, a simple and eco-friendly strategy to modify graphene nanoplatelets (GNs) with different silane coupling agents using a supercritical carbon dioxide (Sc-CO₂) process has been presented, and effect of the modified GNs on the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of GN/PET composite films was studied. FT-IR, SEM, EDX and TG results indicated that Sc-CO₂ process was an effective strategy to modify GNs with silane coupling agents. Addition of the modified GNs into PET matrix could greatly decrease the OTR and WVTR values of the GNs/PET composite films, and the WVTR of GNs560/PET composite film and OTR of GNs550/PET composite film were respectively decreased about 90.08% and 58.04%, as compared to those of GNs/PET composite film. It is found that the gas barrier property of GN/PET composites was attributed to not only the tortuous path effect caused by GNs themselves and the interfacial interaction, but also the affinity of binding bonds between GNs and the polymer to the gas molecules. It is believed that this work provided a strategy to design and prepare CN/polymer composites with high barrier properties.

Adding silane modified GNs prepared by a Sc-CO₂ process into a PET matrix could greatly enhance the barrier properties of the GNs/PET composites.The barrier performance of GNs/PET composites was greatly enhanced by modifying GNs with silane coupling agents via Sc-CO₂ process.