Doctor Blade Research Articles

Preparation of a hierarchical porous activated carbon derived from cantaloupe peel/fly ash/PEDOT:PSS composites as Pt-free counter electrodes of dye-sensitized solar cells

Hierarchical porous activated carbon/fly ash/PEDOT:PSS composites (AC:FA) for a counter electrode (CE) were created using a doctor blade technique and applied in dye sensitized solar cells. Hierarchical porous activated carbon (AC) was produced using a potassium hydroxide (KOH) activation process from cantaloupe peels (Cucumis melo L. var. cantaloupensis). AC was introduced into fly ash at various mass ratios to enhance several physical and electrochemical characteristics. Compared to bare FA, the AC:FA electrode displayed a high electrocatalytic activity for the iodide/triiodide redox (I−/I3−) reaction. The test findings show that a higher proportion of AC has an impact on a CE's catalytic activity and charge transfer resistance. The power conversion efficiency (PCE) of the dye-sensitized solar cell (DSSC) attained 5.81 % using the AC:FA CE with AC in a mass ratio of FA in 3:1 (wt./wt.), which is very near the performance of manufactured DSSC's with a platinum (Pt)-based CE (5.91 %). The AC:FA CE stands out as a strong candidate to substitute for costly Pt CEs due to its enhanced electrochemical activity and charge transfer capabilities obtained with an inexpensive and simple production procedure.

Rheological Investigation of Highly Filled Copper(II) Oxide Nanosuspensions to Optimize Precursor Particle Content in Reductive Laser-Sintering

In this article, the particle concentration of finely dispersed copper(II) oxide nanosuspensions as precursors for reductive laser sintering (RLS) is optimized on the basis of rheological investigations. For this metallization process, a smooth, homogeneous and defect-free precursor layer is a prerequisite for adherent and reproducible copper structures. The knowledge of the rheological properties of an ink is crucial for the selection of a suitable coating technology as well as for the adjustment of the ink formulation. Different dilutions of the nanosuspension were examined for their rheological behavior by recording flow curves. A strong shear thinning behavior was found and the viscosity decreases exponentially with increasing dilution. The viscoelastic behavior was investigated by a simulated doctor blade coating process using three-interval thixotropy tests. An overshoot in viscosity is observed, which decreases with increasing thinning of the precursor. As a comparison to these results, doctor blade coating of planar glass and polymer substrates was performed to prepare precursor layers for reductive laser sintering. Surface morphology measurements of the resulting coatings using laser scanning microscopy and rheological tests show that homogeneous precursor layers with constant thickness can be produced at a particle–solvent ratio of 1.33. A too-high particle content results in an irregular coating layer with deep grooves and a peak-to-valley height Sz of up to 7.8 μm. Precise dilution control allows the fabrication of smooth surfaces with a Sz down to 1.5 μm.

Fabrication, characterization and application of W/N co-doped zinc oxide nanoparticles as a promising photoanode for dye-sensitized solar cells

In the present investigation, undoped, W doped, and W/N co-doped ZnO nanoparticles were prepared by sol–gel route. Here, the ZnO layers were fabricated via the doctor blade method. Hexagonal wurtzite structure is determined by XRD studies. The formation of a hexagonal wurtzite structure was observed from X-ray powder diffraction (XRD) resulting in a slight increase in crystallite size with an increase in doping content. The UV observation shows that W/N co-doping shifted the absorption spectra towards a higher wavelength and reduces the band gap energy. The EDS spectra confirms the high purity and triumphant doping of the W(tungsten) and N(nitrogen) into the ZnO lattice. The morphology of undoped and W/N co-doped ZnO nanoparticles was demonstrated by using FESEM and HRTEM. The 2 % W and 1.5 % N co-doped ZnO photoanode based DSSC (dye-sensitized solar cells) gained the highest short circuit current density of 8.44 mAcm−2 having an open-circuit voltage of 0.65 V, and PCE (power conversion efficiency) of 3.60 %.

The fabrication of integrated proton exchange membrane fuel cells: Excellent mechanical strength and electrochemical performance

Traditional membrane electrode assembly, prepared by catalyst coated electrodes (CCE) and catalyst coated membrane (CCM), has a huge interface between electrodes and membranes, which affects the mechanical adhesion, proton/electron transfer and gas/liquid transport in proton exchange membrane fuel cells (PEMFCs). In this study, an integrated membrane electrode assembly (I-MEA) was fabricated by the casting and doctor blade methods for low- and high-temperature PEMFCs, respectively. The results show that the maximum power density of I-MEALT is improved around 18% and its stripping force increased from 6.091 N to 7.387 N. I-MEAHT reached 0.418 W/cm2, which is 1.5 times higher than that of traditional MEAHT. Meanwhile, it achieved the maximum stripping force of 9.374 N.

Manufacturing supported loose-nanofiltration polymeric membranes with eco-friendly solvents on an R2R System

In this study, loose nanofiltration membranes made of polysulfone dissolved in co-solvents PolarClean and gamma-Valerolactone were prepared via slot die coating (SDC) on a roll-to-roll (R2R) system by directly coating them onto a support layer or free standing. A solution flow rate of 20 mL/min, substrate speed of 17.1 mm/s, and coating gap of 0.1 mm resulted in the formation of membranes without structural defects. Pre-wetting the support layer with dope solution minimized shrinkage of membrane layer thickness and improved interfacial adhesion. Membrane samples produced using SDC exhibited properties and performance consistent with bench-scale doctor blade extruded samples; pre-wetted and uncompressed samples (SDC-3) exhibited the highest rejection of bovine serum albumin (99.20% ± 1.31%) and along with adequate mean permeability during filtration (70.5 ± 8.33 LMH/bar). This study shows that combining sustainable materials development with SDC provides a holistic approach to membrane separations to bridge materials discovery and membrane formation.

Robust and wear-durable coating based on halloysite nanotubes/polymer composite for passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) is an efficient strategy to achieve cooling through spectrally selective emission and high solar spectrum reflection. Current preparation strategies for PDRC materials mainly involve doping inorganic micro-nanoparticles into polymers, but their solar reflectance is usually insufficient. Here, we designed a super-white inorganic coating on different substrates based on natural halloysite nanotubes (HNTs) through the doctor blade method. Polyvinyl alcohol (PVA) and water-based acrylic resin (AR) were introduced to increase the adhesion for obtaining robust inorganic coating. HNTs/PVA/AR composite coating shows excellent water resistance, wear resistance, and environmental tolerance, which is mainly due to the strong interfacial interactions between HNTs, PVA, and AR. Compared with the uncoated transparent plastic, the coated plastic exhibits a super-white appearance (whiteness of ∼95%) and maximum solar reflectance of ∼97%. The maximum temperature difference of the HNTs/PVA/AR coated and pristine copper sheet is 15 °C under simulated sunlight. The PDRC property is related to the high surface roughness of the coating composed of disordered high-aspect ratio nanotubes and the high whiteness of the raw halloysite materials. The composite coating can tolerate pH from 1–13, temperature change (−60∼250 °C), and different salt environments. The composite coating increases thermal stability, flame retardancy, and giving protective effect of dye against UV degradation. In addition, the HNTs/PVA/AR coated plastic as packaging materials can maintain good freshness of different fruits under strong solar irradiation. The robust HNTs/PVA/AR composite coating with high PDRC properties shows promising application in food packaging, building energy conservation, metal anticorrosive coating, and sunscreen products.

Synthesis and Characterization of Cerium Oxide Thin Films Fabricated via the Facile Doctor Blade Method

In this study, we present an in-depth investigation of cerium oxide (CeO2) thin films synthesized using the doctor blade approach, with polyethylene glycol employed as a binder. A comprehensive characterization employing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and atomic force microscopy (AFM) has been conducted to elucidate the structural, chemical, and morphological attributes of the fabricated films. The XRD analysis reveals distinctive wide diffraction peaks indicative of a face-centered cubic CeO2 crystalline structure existing in a singular phase. The morphological analysis using AFM delineates a mean square roughness of 34.54 nm, providing valuable insights into the surface topography of the CeO2 thin films. Additionally, the direct correlation between the material’s band gap, determined as 1.92 eV through UV-visible spectroscopy, and its nanostructural features is established using spectroscopic ellipsometry in conjunction with AFM studies. This approach offers a unique perspective on the optical characteristics of CeO2 films, enhancing our understanding of their nanostructures and facilitating the optimization of their performance for energy applications. Furthermore, the synergistic utilization of scanning electron microscopy (SEM) and spectroscopic ellipsometry contributes to a comprehensive understanding of the growth modes and surface characteristics of the thin films. The integration of these advanced techniques not only refines the fabrication process but also provides crucial insights into the intricate interplay between morphology and optical properties, crucial for optimizing thin films for various applications.

Microstructure and Electrochemical Performance of Supercapacitor Based on Nickel/Activated Carbon Composite Electrode

Supercapacitors are promising electrochemical energy storage devices because they have higher energy than conventional capacitors and higher power than rechargeable batteries. Based on material for supercapacitors, activated Carbon (AC) has large specific surface area, high conductivity, and chemical stability, but still shows less than optimal specific capacitance and energy density. In this work, AC was composited with nickel (Ni) and Carbon Black (CB) to modify microstructure and optimize its electrochemical performance. Initially, synthesis of Ni-AC (cathode) and AC (anode) slurry was carried out by blending method in different mass percentages of Ni (5, 10, 15, 20, 25 %). The slurry was coated using doctor blade on aluminum foil. Then, Ni-AC//AC was fabricated and tested by Galvanostatic Charge-Discharge (GCD) instrument to analyze the electrochemical performance changes of supercapacitor. Based on XRD pattern, AC peak was found at 26.5° and Ni-AC composite had additional peaks in 44.4°, 51.7°, and 76.2°. The crystal size and porosity of electrode were in range of 23.2 – 45.4 nm and 66.6 – 75.7%, respectively. Based on the electrochemical evaluation, addition of 20% Ni mass in activated carbon electrode has the optimum performance, which increases active sites of the electrode and ion electrolyte adsorption capacity. Further, the GCD revealed that the prepared Ni-AC//AC electrode have excellent capacitive behavior with specific capacitance of 56.6 F/g, power density of 308.8 W/kg, energy density of 20.8 Wh/kg, and specific retention of 69.6% until 50 cycles.

High-performance solid-state Li-ion batteries enabled by homogeneous, large-area ferroelectric PVDF-TrFE solid polymer electrolytes via horizontal centrifugal casting method

Solid polymer electrolytes (SPEs) have emerged as promising alternatives for enhancing the safety features of lithium-ion batteries (LIBs) while remaining compatible with established LIB manufacturing processes. However, a persistent challenge has been the relatively limited yield achieved via traditional fabrication techniques such as solution casting and doctor blade methods. In this study, we present a novel strategy to produce extensive and uniform films of solid polymer electrolytes using a ferroelectric polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) polymer. This approach employs horizontal centrifugal casting (HCC), a technique hitherto unutilized for SPE production. The substantial centrifugal forces generated during the HCC process yield SPE films characterized by uniform thickness across the surface and elevated ionic conductivity at ambient temperature. Compared to conventional solution casting techniques, the Li//Li cell featuring the SPE derived from HCC manifests stable electrochemical performance and increased cycle endurance. Additionally, a full cell incorporating a Li iron phosphate cathode displays consistent electrochemical behavior at room temperature. Notably, a 3 × 4 cm2 pouch cell maintains its performance attributes even under mechanical stress conditions such as folding and punching. These findings underscore the potential effectiveness of employing the HCC method in the development of high-performance SPE-based LIB systems.

Effects of tape thickness on the fabrication and performance of microtubular solid oxide fuel cells manufactured by tape casting

The role of tape thickness in the fabrication of microtubular anode supports for solid oxide fuel cells (SOFCs) by tape casting and isostatic pressing is investigated in this study. The anode support slurry of the same formulation is tape cast by varying the doctor blade gap (DBG) from 100 μm to 700 μm and the obtained tapes are wrapped at different lengths on a metal pin of 5 mm in diameter, while the appropriate tape length for each DBG is decided by considering anode support microtubes with a similar geometry for a reasonable comparison. The analyses reveal that the microstructure of the anode support microtube varies depending on DBG and in general delamination and crack formations occur in the supports at high DBGs. The resultant porosity and pore/grain sizes are also found to be different depending on DBG. Therefore, the supports and the cells with these supports show different mechanical and electrochemical performances. In this regard, DBG of 300 μm provides microtubular anode supports without any microstructural problems. The microtubular cell built on this support also exhibits the highest peak performance of 0.313 Wcm−2 at an operating temperature of 800 °C under 300 sccm hydrogen flow and open cathode condition.

The Influence of 2-Methoxyethanol as Capping Agent on WO3-Based Carbon Monoxide Gas Sensor Characteristics

Carbon monoxide (CO) gas detection using a modified WO3-based sensor is being developed. The solvent for solvothermal use, a combination of 2-Propanol and 2-Methoxyethanol, was employed as a capping agent before graphene was used as a component of nanocomposites. Following the creation of the powder, it is combined with ethyl glycol and applied to an alumina substrate using the Doctor Blade process.By X-ray diffraction research, it was discovered that the solvent combinations of 2-Propanol and 2-Methoxyethanol formed monoclinic WO3 in the amounts of 40-0 and 30-10, respectively, while the solvent combinations of 20-20 are thought to have produced W18O49 and 10-30, WO2.9, respectively. According to the SEM examination, the WO3 generated was first present as nanowires and nanorods before being calcined at 500 degrees Celsius, and it then appeared as nanoparticles. The sensor may work at a low temperature of 150°C, and the best sensitivity is found when the sensor is used at a temperature of 250°C, according to the CO gas test findings.

Investigating the Electrical and Mechanical Properties of Polystyrene (PS)/Untreated SWCNT Nanocomposite Films

This paper presents a study of the electrical and mechanical properties of polystyrene (PS)/carbon nanotube (CNT) composites prepared using the doctor blade technique. The nanocomposite films of PS/CNT were prepared by casting a composite solution of PS/CNT in tetrahydrofuran (THF) on a glass substrate using a doctor blade and drying in an oven. The nanocomposite films were then characterized using a tensile test and the four-point probe method to evaluate their mechanical properties and electrical conductivity. The experimental results were used to analyze the unpredicted behavior of the nanocomposite films. The experimental results showed that the electrical conductivity of the nanocomposite films became almost insensitive or unmeasurable with increasing CNT content for very dilute PS–THF solutions. In contrast, at higher PS concentrations, film conductivity increased to a given CNT threshold and then decreased. Based on PS–THF viscosity–concentration data, a discussion is elaborated that partially justifies the experimental results.

Integrated multimode optical waveguides in glass using laser induced deep etching.

Glass is an ideal material for optical applications, even though only a few micromachining technologies for material ablation are available. These microstructuring methods are limited regarding precision and freedom of design. A micromachining process for glass is laser induced deep etching (LIDE). Without generating micro-cracks, introducing stress, or other damages, it can precisely machine many types of glass. This work uses LIDE to subtractive manufacture structures in glass carrier substrates. Due to its transmission characteristics and refractive index, the glass substrate serves as optical cladding for polymer waveguides. In this paper, the described fabrication process can be divided into two sub-steps. The doctor blade technique and subsequent additive process step is used in manufacturing cavities with U-shaped cross-sections in glass in order to fill the trenches with liquid optical polymers, which are globally UV-cured. Based on the higher refractive index of the polymer, it enables optical waveguiding in the visible to near-infrared wavelength range. This novel, to the best of our knoowledge, manufacturing method is called LDB (LIDE-doctor-blade); it can be the missing link between long-distance transmissions and on-chip solutions on the packaging level. For validation, optical waveguides are examined regarding their geometrical dimensions, surface roughness, and waveguiding ability, such as intensity distribution and length-dependent attenuation.

Facile Synthesis and Characterization of TiO2/SnS Nanocomposites by Eco-Friendly Methods

The acid etching mechanism of FTO film using zinc powders has been explored, and sulfuric and hydrochloric acid solutions of different concentrations were tested as etching agents. Compact and mesoporous films of titanium dioxide were prepared by spin-coating and doctor blade techniques on FTO glass. Tin sulfide films were formed through a successive ionic layer adsorption and reaction (SILAR) process using different numbers of deposition cycles, and TiO2/SnS nanocomposites were synthesized. The thin films and the prepared composites were characterized using X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses. In this study, the principal characteristics of deposited tin sulfide films on two different types of TiO2 films are shown.

Long cycle‐life aqueous Zn battery enabled by facile carbon nanotube coating on Cu current collector

AbstractAs an alternative to Li‐ion batteries, aqueous Zn batteries have gained attention due to the abundance of Zn metal, low reduction potential (–0.76 V vs. standard hydrogen electrode), and high theoretical capacity (820 mAh g–1) of multivalent Zn2+ ion. However, the growth of Zn dendrites and the formation of irreversible surface reaction byproducts pose challenges for ensuring a long battery lifespan and commercialization. Herein, the Cu foil coated with a single‐walled carbon nanotube (SWCNT) layer using a facile doctor blade casting method is utilized. The SWCNT‐coated Cu foil demonstrates a significantly longer battery lifespan compared to the bare Cu in the half‐cell tests. Through operando optical microscopy imaging, we are able to provide intuitive evidence that Zn deposition occurs between the carbon nanotube (CNT) coating and Cu substrate, in agreement with the computational results. Also, with various imaging techniques, the flat morphology and homogeneous distribution of Zn beneath the SWCNT layer are demonstrated. In addition, the full‐cell using CNT‐coated Cu exhibits a long cycle life compared to the control group, thereby demonstrating improved electrochemical performance with limited Zn for the cycling process.

Sustainable additive manufacturing of polysulfone membranes for liquid separations

Membranes serve as important components for modern manufacturing and purification processes but are conventionally associated with excessive solvent usage. Here, for the first time, a procedure for fabricating large area polysulfone membranes is demonstrated via the combination of direct ink writing (DIW) with non-solvent induced phase inversion (NIPS). The superior control and precision of this process allows for complete utilization of the polymer dope solution during membrane fabrication, thus enabling a significant reduction in material usage. Compared to doctor blade fabrication, a 63% reduction in dope solution volume was achieved using the DIW technique for fabricating similarly sized membranes. Cross flow filtration analysis revealed that, independent of the manufacturing method (DIW vs. doctor blade), the membranes exhibited near identical separation properties. The separation properties were assessed in terms of bovine serum albumin (BSA) rejection and permeances (pressure normalized flux) of pure water and BSA solution. This new manufacturing strategy allows for the reduction of material and solvent usage while providing a large toolkit of tunable parameters which can aid in advancing membrane technology.

Impact of selenization with NaCl treatment on the physical properties and solar cell performance of crack-free Cu(In,Ga)Se2 microcrystal absorbers.

In this study, we developed an ink using hexanethiol and Cu(In,Ga)Se2 microcrystals (CIGSe MCs) to make thin films via doctor blade coating. Besides, crack-free thin films were obtained by optimizing CIGSe MC powder concentration and annealing temperature. Subsequently, single-step selenization was performed with and without sodium chloride (NaCl) surface treatment by carefully tuning the temperature. A crack-free surface with densely packed grains was obtained at 500 °C after NaCl treatment. Moreover, the structural parameters of the thin film (annealed at 350 °C) were significantly modified via selenization with NaCl at 500 °C. For instance, the FWHM of the prominent (112) plane reduced from 1.44° to 0.47°, the dislocation density minimized from 13.10 to 1.40 × 1015 lines per m2, and the microstrain decreased from 4.14 to 1.35 × 10-3. Remarkably, these thin films exhibited a high mobility of 26.7 cm2 V-1 s-1 and a low resistivity of 0.03 Ω cm. As a proof of concept, solar cells were engineered with a device structure of SLG/Mo/CIGSe/CdS/i-ZnO/Al-ZnO/Ag, wherein a power conversion efficiency (PCE) of 5.74% was achieved with exceptional reproducibility. Consequently, the outcomes of this investigation revealed the impact of selenization temperature and NaCl treatment on the physical properties and PCE of hexanethiol-based crack-free CIGSe MC ink-coated absorbers, providing new insights into the groundwork of cost-effective solar cells.

DSSC Fundamentals and Optimization Materials :A Review

Recently, researchers are focusing on renewable energy sources such as wind energy, Hydro-thermal energy, and solar energy. In this research article DSSC fundamentals and optimized materials are discussed and compared. The maximum efficiency reported by the researcher is 12% using Ru (II) dyes. The efficiency of DSSC depends on the various factors such as working electrode material, counter electrode material, dye used in preparation of solar cell are discussed. The simplest technique used for fabrication of DSSC solar cell is doctor blade method also discussed in this review article.

Innovative photovoltaic approach: Cd1-xBexTe mixed semiconductor crystals for novel dye-sensitized solar cells

This paper deals with the synthesis and properties of new ternary mixed Cd1-xBexTe (cadmium beryllium telluride) crystal-based electrodes for photovoltaic cells which is a modified version of dye- sensitized solar cells. We determined the thermal stability and photovoltaic performance of the obtained devices. Cd1-xBexTe crystals are grown using the Bridgman technique at high temperatures and pressure for different compositions. Using the modified doctor blade method, we fabricated dye-sensitized solar cells (DSSC) using Cd1-xBexTe-based film as working electrodes. The mixed crystals with the highest beryllium content (10 %) and the lowest (1 %) are used. At the same time, the counter electrode and polymer electrolytes are common. Comparative studies with standard DSSC are also undertaken to compare the stability and charge mechanism. As prepared, DSSC using ternary Cd1-xBexTe showed efficiency as high as 3.11 % at 1 sun condition. The life span measurement indicated promising results, and DSSC is stable up to 720 h with a reasonable decrease in fill factor from 84 to 55.

Electrochemical Properties of Activated Carbon Electrodes for Supercapacitor Application: The Effect of Various Electrolyte Concentrations of Na2SO4

To achieve the high accomplishment of the supercapacitor, various electrolyte concentrations of Na2SO4 (0.5 M, 1 M, and 2 M) were added to the activated carbon (AC) electrode. The AC has a moderate surface area of 1,500 m2/g and a pore size of 1 nm (micropore scale). The AC electrode was deposited from the mixture of AC, carbon black, and polytetrafluoroethylene (PTFE) with a weight ratio of 8:1:1 using the doctor blade method. Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD), and Electrical Impedance Spectroscopy (EIS) were used to characterize the electrodes electrochemically. Based on CV, GCD, and EIS characterizations, the measured specific capacitance of 17.2 F/g and ESR of 4.4 W exhibit the best performance due to their high ionic conductivity. We can conclude that 2 M Na2SO4 is a viable option for the ionic electrolyte of the microporous AC for the high performance of a supercapacitor.