Conductivity Of Films Research Articles

Composite coatings of poly(methyl methacrylate) with silicon dioxide nanoparticles for capacitive sensors of nickel content control in water

Pollution of the environment, in particular water sources, with heavy metals is a serious environmental problem. In this regard, it is relevant to develop new sensor systems that allow rapid tests and are not inferior in analytical parameters to classical methods for detecting heavy metals. Promising materials for creating such sensor systems are composite coatings based on polymer compounds with inorganic nanoparticles. The article presents the results of using poly(methyl methacrylate) (PMMA) coatings and PMMA nanocomposites with silicon dioxide nanoparticles (SiO2 NPs) to develop capacitive sensors for analyzing the content of Ni2+ ions in water. The structural and morphological characteristics of a conductive nickel layer and nanostructured films based on poly(methyl methacrylate) were studied using atomic force microscopy. Based on the experimental data on the dependence of the capacitance characteristics of sensors on the concentration of Ni2+ in solutions, the operating characteristics of sensors were established: response time is 5 min; working range of concentrations of Ni2+ ions: 1 ‧ 10–3 – 50 mM; lower detection limit ≈ 0.06 mg/l (maximum nickel concentration limit in water is 0.1 mg/l). It has been shown that the formation of a coating of the composition PMMA + NPs-SiO2 (1 : 41.7 mol) on a conductive nickel layer using the spin-coating method leads to increasing the sensitivity of a sensor and its service life (up to seven cycles).

Thermal Conductivity and Flame Retardancy of Nacre-like Cellulose-based Composite Films Reinforced with Flame-retardant Functionalized Graphene Nanoplatelets by One-Step Ball Milling

Thermal Conductivity and Flame Retardancy of Nacre-like Cellulose-based Composite Films Reinforced with Flame-retardant Functionalized Graphene Nanoplatelets by One-Step Ball Milling

Electrochemical polymer synthesis using thiophene and pyrrole/carbazole: Their electrochemical behaviours and capacitor performance

In this study, carbazole-derived monomers were synthesized on ITO-coated PET via electrochemical reactions and conductivity measurements of the resulting polymeric films were performed by UV, FT-IR, NMR, TG-DTG, SEM and AFM analyses. Their spectroelectrochemical properties were investigated. The carbazole (C) based thiophene (Th) polymer abbreviated as pThC and its copolymer with pyrrole (Py), named as pThC-Py were obtained by electrochemical polymerization method. The surface stability of the resulting polymer films was good depending on time. The contact angle (CA) between the water and theco- polymer surface was determined by dropping 6.09 μL of pure water and CA average was calculated as 68.19° < 90°. According to the thermal analysis data of the polymers, the thermal stability of the pThC-Py was better than pThC as it had higher thermal decomposition temperature. Comparisons of electrical conductivity measurements of the polymer films were made depending on the temperature (25, 50 and 90 °C). Due to increasing temperature, the electrical conductivity of pThC-Py film was read as 29.3 S/cm at 90 °C, and also the electrical conductivity values of the pThC-Py were determined as 1.92 × 10−2 S/cm at 25 °C and 14.2 S/cm at 50 °C. Because of the high electrical conductivity of the pThC-Py, its capacitor performance was tried to be determined from cyclic voltammetric measurements. According to the voltammetric results, the power density (P) and the energy density (E) values of the synthesized substance were calculated as 290.532 W/g and 9.684 Wh/g, respectively. This indicates that the amount of energy the material storable is relatively high. Moreover, it is possible to say that it can be included in the classical capacitor class and in the supercapacitor category by improving its features. Moreover, since the electrical conductivity of pThC-Py is quite good, it is thought that it may be suitable for use in electronic devices.

Simultaneous determination of the phase boundary thermal resistance and thermal conductivity in phase-separated TiO2 thin films

Phase boundaries, most often between crystalline and amorphous phases of a material, are ubiquitous lattice imperfections in thin films, particularly deposited by low temperature processes such as atomic layer deposition (ALD). Thermal resistances from these boundaries may impede phonon transport and reduce thermal conductivity. However, to date, there have been no reports on the direct measurement of the phase boundary thermal resistance, due in part to challenges associated with fabricating an atomically flat yet geometrically planar interface between different phases within a film. Here, we present a systematic study to simultaneously determine the phase boundary thermal resistance and thermal conductivity in a series of phase-separated titanium oxide (TiO2) thin films prepared via plasma-enhanced ALD (PEALD). A precise implementation of per-cycle plasma treatment enables extremely localized crystallization—i.e., plasma-assisted atomic layer annealing (ALA)—and the fabrication of crystalline/amorphous layered structures with their respective thicknesses systematically varied. Frequency-domain thermoreflectance measures the effective thermal conductivity of each film and its top and bottom interfaces, confirmed independently using time-domain thermoreflectance. We simultaneously solve a system of linear equations generated by applying a series resistor model to each film, yielding the phase boundary thermal resistance of 5.1 m2 K GW–1 between crystalline and amorphous TiO2, as well as the thermal conductivities of 5.1 and 2.1 W m–1 K–1 for crystalline and amorphous TiO2, respectively. The results suggest that the crystalline/amorphous phase boundary acts like a layer of crystalline (amorphous) TiO2 with equivalent thickness ∼26 (∼11) nm.

Covalent bond-assisted continuous interface structure for high thermal conductive polyimide composite films

Polyimide (PI) is widely used in electronic, electrical and communication fields because of its outstanding mechanical properties, electrical insulation and thermal stability. However, the lower thermal conductivity limits their application. Here, PI composite films with high thermal conductivity are obtained by utilizing reactive groups on the carbon nitride nanosheets (CNNS) surface to form covalent bond with PI matrix. The thermal conductivity of CNNS/PI composite films can reach 5.84 W∙m−1∙K−1, which is about 10 times higher than that of pure PI (0.56 W∙m−1∙K−1). This is attributed to the covalent bond between CNNS and PI matrix acting as a “thermal bridge” to connect the discontinuities at the interface, thereby reducing the interfacial thermal resistance between CNNS and PI. The heat transfer mechanism of composite film is further revealed by finite element analysis. This work provides a viable solution to improve the thermal conductivity of PI, allowing for a wide range of potential applications for PI in electronic devices.

A room-temperature ammonia gas sensor based on the h-MoO3@Graphene composite film with fast response time

The release of ammonia (NH3) in industry or daily life is harmful to human health. A gas sensor was developed using h-MoO3 nanorods and graphene film to detect and eliminate this. The h-MoO3 nanorods were first synthesized by chemical bath deposition using ammonium molybdate tetrahydrate (NH4)6Mo7O24•4H2O and HNO3 and then deposited on the graphene film transferred to SiO2/Si substrate by electrochemical bubbling method. Subsequently, gas-sensitive h-MoO3@Graphene composite films were prepared and analyzed using Raman, XRD, SEM, and UV–vis. The gas sensor's performance was evaluated to detect NH3 at a room temperature concentration range of 1–60 ppm. Compared with graphene, the conductivity of the composite film with 10 mg/ml h-MoO3 nanorods was increased by 40 % and the sensitivity increased by 10 times. The sensor h-MoO3@G-10 showed the best sensing performance to 1 ppm NH3. Sensor sensitivity, response and recovery time are 1.1 %, 46.8 s and 17.8 s.

Identification and Compensation Method of Unbalanced Error in Driving Chain for Rate-Integrating Hemispherical Resonator Gyro.

The accuracy of the signal within a driving chain for the rate-integrating hemispherical resonator gyro (RI-HRG) plays a crucial role in the overall performance of the gyro. In this paper, a notable and effective method is proposed to realize the identification and compensation of the unbalanced error in the driving chain for the RI-HRG that improved the performance of the multi-loop control applied in the RI-HRG. Firstly, the assembly inclination and eccentricity error of the hemispherical resonator, the inconsistent metal conductive film layer resistance error of the resonator, the coupling error of the driving chain, and the parameter inconsistency error of the circuit components were considered, and the impact of these errors on the multi-loop control applied in the RI-HRG were analyzed. On this basis, the impact was further summarized as the unbalanced error in the driving chain, which included the unbalanced gain error, equivalent misalignment angle, and unbalanced equivalent misalignment angle error. Then, a model between the unbalanced error in the driving chain and a non-ideal precession angular rate was established, which was applicable to both single channel asynchronous control and dual channel synchronous control of the RI-HRG. Further, an unbalanced error identification and compensation method is proposed by utilizing the RI-HRG output with the virtual precession control. Finally, the effectiveness of the proposed method was verified through simulation and experiments in kind. After error compensation, the zero-bias instability of the RI-HRG was improved from 3.0950°/h to 0.0511°/h. The results of experiments in kind demonstrated that the proposed method can effectively suppress the non-ideal angular rate output caused by the unbalanced error in the driving chain for the RI-HRG, thereby further improving the overall performance of the RI-HRG.

Improving corrosion and conductivity of Ti-doped amorphous carbon film coated on 316L stainless steel bipolar plates by nitrogen atoms doping

Amorphous carbon films have recently attracted extensive attention as surface functional films for bipolar plates with excellent conductivity and anti-corrosion properties. In this research, to determine the influence of the amorphous carbon film doped with titanium and nitrogen on the efficiency of proton exchange membrane fuel cells (PEMFCs) and clarify the effect of N atoms on Ti doped amorphous carbon, a series of Ti, N co-doped amorphous carbon films are built on 316L stainless steel at different N2 flow rates. This study provides detailed research about the influence of N atoms content on the microstructure, morphology evolution, corrosion resistance and interfacial contact resistance (ICR) of Ti, N co-doped amorphous carbon films. The results reveal that the N doping of the Ti-doped amorphous carbon film has the potential to enhance the C-sp2 content and refine the grain. The characterization results indicate that introducing N atoms into Ti doped amorphous carbon can reduce the ICR of the film to 2.38 mΩ cm2. The introduction of N atoms can also enhance the anti-corrosive characteristics of the titanium singly doped amorphous carbon film. The Ti, N co-doped film can be used as candidate materials applied to metal bipolar plates.

The impact of lithium concentration on the optical properties of colloidal ZnO nanocrystals

In this work, Li-doped ZnO nanocrystals (LZO) were synthesized via the sol–gel method. The concentration of zinc acetate has been set at 2 M in order to prepare the highly concentrated Li-doped ZnO sol. The generated LZO sol’s optical characteristics were assessed using UV–visible absorption and photoluminescence spectroscopy, while the ZnO nanopowders’ lithium doping process was assessed using XRD and Raman spectroscopy. The experimental findings indicate that the concentration of Li+ ions in the synthesized zinc oxide nanocrystals has reached the maximum solid solubility limit. The inclusion of Li+ ions results in a reduction in the size of ZnO nanocrystals, accompanied by a notable increase in violet-blue emission, distinguishing them from other materials reported in the literature. As can be found, Li+ ions cannot change the type of conductivity in thin ZnO films, and they have n-type conductivity.

Flexible CNT-based composite films with amorphous SiBCN-inhibited ultrafine SiC grains for high-temperature electromagnetic shielding

Lightweight, flexible and highly conductive electromagnetic interference (EMI) shielding materials are of great importance for protecting flexible electronics and telecommunication devices under extremely high temperature conditions. A potential solution is to incorporate ceramic phases with highly conductive flexible carbon nanotube films to improve their thermal stability. However, the grain size of the ceramic phase generally increased significantly as the temperature increased which led to brittleness. In this work, a highly flexible carbon nanotube (CNT) film with controllable ceramic nanocrystals was prepared by precursor infiltration and pyrolysis. The silicon carbide (SiC) grain size in the nanocomposites was inhibited by the spatial confinement effects of CNT networks and a second amorphous SiBCN phase. The SiC grain size in the composite film decreased with the increase of the SiBCN content and the elongation at break of the nanocomposites improved significantly by 45 %. Moreover, the initial thermogravimetric temperature of the prepared films has been significantly improved to exceed 600 °C compared to the raw CNT film. Importantly, the nanocomposite film exhibited an average EMI shielding effectiveness of ∼40 dB from 8.2 to 12.4 GHz. Benefiting from the ultrafine grain size, the nanocomposite films could be folded and extended without micro-cracks over 1000 times. Combining the performance and mechanical properties of the nanocomposite film, this approach provides important guidance for designing high-performance CNT-based electromagnetic shielding materials with superior flexibility at elevated temperatures.

Design of interconnected graphene loaded thermoplastic elastomeric blend composite films for minimizing electromagnetic radiation and efficient heat management

AbstractIn this work, electrically conductive thermoplastic elastomeric blend composite films based on polystyrene (PS)/ethylene‐co‐methyl acrylate (EMA) filled with functionalized graphene were developed via the solution mixing technique. Morphological analysis revealed that selective localization of amine‐functionalized reduced graphene oxide (G‐ODA) sheets in the EMA phase of co‐continuous binary blend formed a well‐connected dense conductive pathway by graphene sheets ultimately facilitating the double percolation phenomenon. The electrical percolation threshold was achieved at ~2 wt% of G‐ODA loading which was much lower than that for both single polymer composites. An electrical conductivity of 0.9 S/cm was obtained for blend composite film with 10 wt% of graphene concentration whereas for the same filler loading, PS and EMA composites exhibited electrical conductivity of 1.9 × 10−1 and 2.3 × 10−1 S/cm, respectively. The obtained thermal conductivity of the blend composite with 10 wt% of G‐ODA loading was 0.95 W/m K with 400% enhancement compared to the neat blend system. The same composite exhibited increased real and imaginary permittivity of 92 and 83, respectively. The electrical percolation threshold is well‐correlated with the percolation concentration found from storage modulus and thermal conductivity data. The fabricated PS/EMA blend composite film exhibited absorption‐dominant electromagnetic interference SE of −25 and − 35 dB in X‐band frequency (8.2–12.4 GHz) for 10 wt% of graphene loading with a sample thickness of 0.5 and 1 mm, respectively.

Flexible Piezoelectric Sensor With a Sandwich Structure Composed of Ionic Conductive Hydrogel and PVDF Film

Flexible Piezoelectric Sensor With a Sandwich Structure Composed of Ionic Conductive Hydrogel and PVDF Film

Enhanced current-carrying capability in YBCO coated conductor bilayers for high-field applications

We have investigated the impact of bilayer structures on the critical current density, J c, of YBa2Cu3O6+x (YBCO) coated conductor films, i.e. films grown on buffered metal substrates, under varying temperature and magnetic field conditions. The bilayers consisted of a YBCO layer free of artificial pinning centers and 8 wt% BaZrO3-added (BZO) layer on top, where the thickness percentage of the layers was varied from 0 to 100 %. The results reveal that the bilayer configuration enhances J c at temperatures below 60 K, with a significant improvement in high magnetic fields (5–8 T) and temperatures ≤20 K. The optimal BZO-added layer thickness was found to be approximately 70 %, reaching 80 % at 8 T. Structural examinations indicate improved growth of YBCO and BZO nanorods in the bilayer structure with BZO-added layer thickness ≤80 %. Theoretical model of the bilayer structure considering the layers as two parallel superconductors with different properties was developed. It was found that the model adequately explains all the experimentally observed tendencies, and thus the observed maximum in J c is due to better growth of the BZO-added layer. The study provides valuable insights for designing optimal bilayer structures for diverse applications operating in different temperature and magnetic field regimes.

Fabrication and application of multifunctional conductive hydrogel film for wearable sensors via efficient freeze-thaw cycling and annealing process

Conductive hydrogel films, as integral elements of flexible sensors, hold promising applications across diverse fields. However, their cost-effective and straightforward production, ensuring both excellent mechanical properties and conductivity, remains a formidable challenge. In our research, we developed a multifunctional conductive hydrogel film using a freeze-thaw cycling-annealing method. That process applied freeze-thaw cycling to reorganize the hydrogel’s cross-linking structure and improve the polyvinyl alcohol molecules’ crystallinity through annealing. The thickness of the fabricated film was approximately 100 μm, and the limit of detection and sensitivity for glucose were 2.82 μM and 117.6 μA /mM*cm2 respectively, and the sensitivity factor during the bending process was 2.61, which demonstrated excellent biocompatibility, mechanical properties, and electrochemical properties. It also facilitates wireless, real-time electrophysiological signal monitoring and sweat glucose tracking in the human body. In summary, the freeze-thaw cycling/annealing approach simplified and accelerated hydrogel film preparation. This development is poised to resolve the intricacies of existing hydrogel film production methods and broaden the application scope of such films in wearable devices.

Laser-assembled conductive 3D nanozyme film-based nitrocellulose sensor for real-time detection of H2O2 released from cancer cells

In this work, a nanostructured conductive film possessing nanozyme features was straightforwardly produced via laser-assembling and integrated into complete nitrocellulose sensors; the cellulosic substrate allows to host live cells, while the nanostructured film nanozyme activity ensures the enzyme-free real-time detection of hydrogen peroxide (H2O2) released by the sames. In detail, a highly exfoliated reduced graphene oxide 3D film decorated with naked platinum nanocubes was produced using a CO2-laser plotter via the simultaneous reduction and patterning of graphene oxide and platinum cations; the nanostructured film was integrated into a nitrocellulose substrate and the complete sensor was manufactured using an affordable semi-automatic printing approach. The linear range for the direct H2O2 determination was 0.5–80 μM (R2 = 0.9943), with a limit of detection of 0.2 μM. Live cell measurements were achieved by placing the sensor in the culture medium, ensuring their adhesion on the sensors' surface; two cell lines were used as non-tumorigenic (Vero cells) and tumorigenic (SKBR3 cells) models, respectively. Real-time detection of H2O2 released by cells upon stimulation with phorbol ester was carried out; the nitrocellulose sensor returned on-site and real-time quantitative information on the H2O2 released proving useful sensitivity and selectivity, allowing to distinguish tumorigenic cells. The proposed strategy allows low-cost in-series semi-automatic production of paper-based point-of-care devices using simple benchtop instrumentation, paving the way for the easy and affordable monitoring of the cytopathology state of cancer cells.

2D Graphene Oxide: A Versatile Thermo‐Optic Material

AbstractEfficient heat management and control in optical devices, facilitated by advanced thermo‐optic materials, are critical for many applications such as photovoltaics, thermal emitters, mode‐locked lasers, and optical switches. Here, a range of thermo‐optic properties of 2D graphene oxide (GO) films are investigated by precisely integrating them onto microring resonators (MRRs) with control over the film thicknesses and lengths. The refractive index, extinction coefficient, thermo‐optic coefficient, and thermal conductivity for the GO films with different layer numbers and degrees of reduction, as well as reversible reduction and enhanced optical bistability induced by the photo‐thermal effects, are comprehensively characterized. Experimental results show that the thermo‐optic properties of 2D GO films vary widely with the degree of reduction. In addition, significant anisotropy is observed for the thermo‐optic response, enabling efficient polarization‐sensitive devices. The versatile thermo‐optic response of 2D GO substantially expands the scope of functionalities and devices that can be engineered, making it promising for a diverse range of thermo‐optic applications.

Chemical, Structural, and Electrical Changes in Molecular Layer-Deposited Hafnicone Thin Films after Thermal Processing.

Post deposition annealing of molecular layer-deposited (MLD) hafnicone films was examined and compared to that of hafnium oxide atomic layer-deposited (ALD) films. Hafnicone films were deposited using tetrakis(dimethylamido)hafnium (TDMAH), and ethylene glycol and hafnia films were deposited using TDMAH and water at 120 °C. The changes in the properties of the as-deposited hafnicone films with annealing were probed by various techniques and then compared to the as-deposited and annealed ALD hafnia films. In situ X-ray reflectivity indicated a 70% decrease in thickness and ∼100% increase in density upon heating to 400 °C yet the density remained lower than that of hafnia control samples. The largest decreases in thickness of the hafnicone films were observed from 150 to 350 °C. In situ X-ray diffraction indicated an increase in the temperature required for crystallization in the hafnicone films (600 °C) relative to the hafnia films (350 °C). The changes in chemistry of the hafnicone films annealed with and without UV exposure were probed using Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy with no significant differences attributed to the UV exposure. The hafnicone films exhibited lower dielectric constants than hafnia control samples over the entire temperature range examined. The CF4/O2 etch rate of the hafnicone films was comparable to the etch rate of hafnia films after annealing at 350 °C. The thermal conductivity of the hafnicone films initially decreased with thermal processing (up to 250 °C) and then increased (350 °C), likely due to porosity generation and subsequent densification, respectively. This work demonstrates that annealing MLD films is a promising strategy for generating thin films with a low density and relative permittivity.

Conductive graphene-containing biocompatible films

Conductive graphene-containing biocompatible films

ZnO nanoarrays/Cu nanowires composite films with high haze value

In this work, we worked on compositing Cu nanowires (NWs) with ZnO nanoarrays (NAs) to enhance the light trapping abilities of transparent conductive films. A well-dispersed, crosslinked network of Cu NWs with appropriate light trapping ability was formed on the surface of the ZnO NAs, and the ZnO NAs/Cu NWs composite structures were obtained ultimately. The Cu NWs on the surface of the composite structures maintained excellent transparency and conductivity while preventing agglomeration phenomena. The ZnO NAs/Cu NWs composite films exhibited low average sheet resistance (59 Ω/sq) and high haze value (0.53) at 550 nm with uniform conductivity and exceptional light trapping performance. The composite films not only demonstrate enhanced light trapping abilities, but also exhibit improved electrical properties, making it an outstanding candidate for transparent front electrode materials in solar cell applications.

Ultra-Mild Fabrication of Highly Concentrated SWCNT Dispersion Using Spontaneous Charging in Solvated Electron System.

The efficient dispersion of single-walled carbon nanotubes (SWCNTs) has been the subject of extensive research over the past decade. Despite these efforts, achieving individually dispersed SWCNTs at high concentrations remains challenging. In this study, we address the limitations associated with conventional methods, such as defect formation, excessive surfactant use, and the use of corrosive solvents. Our novel dispersion method utilizes the spontaneous charging of SWCNTs in a solvated electron system created by dissolving potassium in hexamethyl phosphoramide (HMPA). The resulting charged SWCNTs (c-SWCNTs) can be directly dispersed in the charging medium using only magnetic stirring, leading to defect-free c-SWCNT dispersions with high concentrations of up to 20 mg/mL. The successful dispersion of individual c-SWCNT strands is confirmed by their liquid-crystalline behavior. Importantly, the dispersion medium for c-SWCNTs exhibits no reactivity with metals, polymers, or other organic solvents. This versatility enables a wide range of applications, including electrically conductive free-standing films produced via conventional blade coating, wet-spun fibers, membrane electrodes, thermal composites, and core-shell hybrid microparticles.