Dip-coating Parameters Research Articles

Development of Photocatalytically Active Anodized Layers by a Modified Phosphoric Acid Anodizing Process for Air Purification

One of the key urban air quality issues is pollution by nitrogen oxides (NOx). To reduce NOx, facade cladding could be provided with photocatalytic properties by incorporating titanium dioxide nanoparticles. For this purpose, a modified phosphoric acid anodizing process (MPAA) was developed for the facade alloy EN AW-5005, in which highly ordered anodized structures with a low degree of arborization and tortuosity were produced. Pore widths between 70 nm and 150 nm and layer thicknesses of about 2–3 μm were obtained. The subsequent impregnation was carried out by dip coating from water-based systems. Depending on the dip-coating parameters and the suspension used, the pores can be filled up to 60% with the TiO2 nanoparticles. Photocatalytic tests according to ISO 22197-1 certify a high photocatalytic activity was obtained with rPCE values > 8 and with rPCE > 2, achieving “photocatalytically active for air purification”. Tests on the corrosion resistance of the anodized coatings with a commercially available aluminum and facade cleaner confirm a protective effect of the anodized coatings when compared with nonanodized aluminum material, as well as with compacted anodized layers.

One-step sintering for anti-fouling piezoelectric α-quartz and thin layer of alumina membrane

Lead-free piezoelectric ceramics are attracting significant attention in the construction of separation membranes because they offer a self-cleaning function and have no risk of lead leaching from the materials. In this study, the fabrication of cost-sensitive and self-cleaning ceramic composite membranes via co-sintering of a porous α-quartz green support and an alumina microfiltration layer is reported. The α-quartz green support prepared by aqueous gel-casting has benign wettability and flexural strength, which is beneficial for forming a thinner and homogeneous membrane layer by dip-coating. The effects of the co-sintering temperature and dip-coating parameters on the pore size, permeance, mechanical and chemical stabilities, and piezoelectric properties were further investigated. The optimal membrane had an average pore size of 190 nm by co-sintering at 1200 °C and a strongest ultrasound response of 15 mV at an alternating voltage (AV) of 100 V. Finite element analysis showed that the composite membrane generated a beneficial displacement and acoustic pressure (acpr) for cavitation effect. In-situ mitigation of fouling was demonstrated during 500 ppm oil-in-water (O/W) emulsion filtration, which resulted in a stationary flux (Jstat) of 190 L m−2 h−1·bar−1, increased by 65.7% at 100 V AV.

Highly efficient doping of carbon nanotube films with chloroauric acid by dip-coating

Single-walled carbon nanotube (SWCNT) based transparent and conductive films (TCFs) are one of the most prospective materials for novel flexible and stretchable electronic devices. Development of reproducible and scalable doping procedure is the key step towards the widespread implementation of SWCNT TCFs. Here, we thoroughly investigate a dip-coating technique for SWCNT doping as a promising approach for the practical manufacturing of SWCNT films with high performance. We examine the effect of dip-coating parameters on optical and electrical properties of the films using HAuCl4 solution in isopropyl alcohol (IPA) and in situ investigate doping effects. This method appeared to easily fine-tune the optoelectronic parameters of SWCNT films and achieve a record sheet resistance value of 36 Ohm/sq. at the 90% transmittance in the middle of visible spectral range by increasing a work function value from 4.8 (for pristine SWCNTs) to 6.0 eV. The proposed approach allows efficient, uniform, and reproducible fabrication of highly conductive and transparent SWCNT films and opens an avenue for precise tailoring of SWCNT Fermi level for optoelectronic devices.

The effect of dip-coating parameters on the thickness and uniformity of BCZYZ electrolyte layer on porous NiO-BCZYZ tubular supports

The effect of dip-coating parameters on the coating thickness and uniformity have been investigated for BaCe0.7Zr0.1Y0.16Zn0.04O3-δ (BCZYZ) electrolyte on porous NiO-BCZYZ tubular supports. The calculated thicknesses of electrolyte using both pre-fired and full fired tubes' dimensions and both wet and dry weight gains have been compared to the measured ones using Scanning Electron Microscopy (SEM) analysis after full firing. The calculated thicknesses using pre-fired tubes’ dimensions using both wet and dry weight gains are found in a good agreement with the measured thicknesses. The minimum coating thickness of 20.49 ± 3.36 μ with 16% standard deviation (StDev) is achieved using 1.91 mm s−1 (20 step.s-1) withdrawal speed and 30 s dwell time. The most uniform coating layer is obtained using that withdrawal speed and 60 s dwell time, leading 23.14 ± 1.69 μ coating thickness and the minimum StDev% of 7%. Using the polynomial fit between StDev% and dwell time, the minimum StDev% can be achieved at that withdrawal speed has been determined as 80 s. The coating parameters have been optimized as 1.91 mm s−1 withdrawal speed and 80 s dwell time for BCZYZ electrolyte on porous Ni/NiO-BCZY tubular supports.

Carboxymethyl cellulose/polyethersulfone thin-film composite membranes for low-pressure desalination

Herein, we report the fabrication of carboxymethyl cellulose (CMC)/polyethersulfone (PES) thin-film composite nanofiltration membranes using a dip-coating method with glutaraldehyde (GA) as the crosslinking agent. The effects of crosslinking degree and the dip-coating parameters, including CMC concentration and dipping time, on the performance and morphology of the fabricated membranes were investigated. The properties of the prepared membranes were analyzed by ATR-FTIR, AFM, FE-SEM, and water contact angle analysis. The optimized membrane containing 0.2 wt% CMC, crosslinking degree of 20% by the dipping time of 10 min represented a rejection efficiency of 91.90%, 68.63%, and 45.90% towards the Na2SO4, MgSO4, and NaCl solutions (100 mg/L), respectively. The pure water flux of the optimal membrane was 47.90 ± 1.77 L/m2 h under a low transmembrane pressure of 0.4 MPa. The flux recovery ratio of the nanofiltration membrane was 63% higher than the PES support membrane, indicating an improvement in fouling resistance.

Enhanced Ordering of Block Copolymer Thin Films upon Addition of Magnetic Nanoparticles.

The influence of magnetite nanoparticles coated with poly(acrylic acid) (Fe3O4@PAA NPs) on the organization of block copolymer thin films via a self-assembly process was investigated. Polystyrene-b-poly(4-vinylpyridine) films were obtained by the dip-coating method and thoroughly examined by X-ray reflectivity, transmission electron microscopy, atomic force microscopy, and grazing incidence small-angle scattering. Magnetic properties of the films were probed via superconducting quantum interference device (SQUID) magnetometry. It was demonstrated that due to the hydrogen bonding between P4VP and PAA, the Fe3O4@PAA NPs segregate selectively inside P4VP domains, enhancing the microphase separation process. This in turn, together with employing carefully optimized dip-coating parameters, results in the formation of hybrid thin films with highly ordered nanostructures. The addition of Fe3O4@PAA nanoparticles does not change the average interdomain spacing in the film lateral nanostructure. Moreover, it was shown that the nanoparticles can easily be removed to obtain well-ordered nanoporous templates.

Preparation and Characterization of Electrospun Polyurethane Nanofibrous Microfiltration Membrane

Herein, the preparation of polyurethane nanofibrous microfiltration membranes, with electrospinning and then dip-coating methods was reported. The study of process parameters (i.e. needle-free electrospinning and dip-coating condition) on the membrane properties was also conducted. The different pore sizes of the prepared MF membranes (e.g. 0.23, 0.33, and 0.47 μm) is orchestrated through the adjustment of various electrospinning and dip-coating parameters. The capability of these membranes to simultaneously eliminate the sources of water pollution, i.e. micro-particles and bacteria, has been demonstrated. Specifically, the prepared membranes could thoroughly reject the E. coli BL21 (DE3) bacteria (~ 97–99%) as well as micro-particles through size extrusion mechanism (~ 95–99%), while they retained a high permeation flux (~ 65,400, ~ 40,000 and ~ 25,700 (L/m2 h bar) for 0.46, 0.33, and 0.25 μm pore size, respectively). In addition, a comparison between nanofibrous MF membranes and their commercial counterparts from both utility and effectiveness standpoint was conducted and the obtained result indicated the supreme performance of these membranes in comparison with the commercial membranes of the same mean pore size, also with almost double or triple higher flux.

Adjustable self-assembly in polystyrene-block-poly(4-vinylpyridine) dip-coated thin films

This work studies the influence of dip-coating parameters on self-assembly in ultra-thin films of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers from a 1-chloropentane solution using a combination of several experimental techniques. Small-Angle X-ray Scattering, Atomic Force Microscopy, Grazing Incidence Small Angle X-ray Scattering and Transmission Electron Microscopy were used to characterize the fabricated films. We have shown a facile fabrication route to smooth films with a wide range of thicknesses. Arranged domains of P4VP oriented perpendicularly to the substrate were observed. The domain sizes and spacing varied in the range from 13 up to 35 nm and from 39 to 115 nm, respectively.

Graphene‐Coated Spandex Sensors Embedded into Silicone Sheath for Composites Health Monitoring and Wearable Applications

This study presents a low-cost, tunable, and stretchable sensor fabricated based on spandex (SpX) yarns coated with graphene nanoplatelets (GnP) through a dip-coating process. The SpX/GnP is wrapped into a stretchable silicone rubber (SR) sheath to protect the conductive layer against harsh conditions, which allows for fabricating washable wearable sensors. Dip-coating parameters are optimized to obtain the maximum GnP coating rate. The covering sheath is tailored to achieve high stretchability beyond the sensing limit of 104% for SpX/GnP/SR sensors. Adjustable sensitivity is attained by manipulating SpX immersion times broadening its application for a wide range of strains: Gauge factors as high as two orders of magnitude are achieved at tensile strains greater than ≈40%. The fabricated sensors are tested for two applications: First, the SpX/GnP sensors are integrated into composite fabrics (with no negative impact on the structural integrity of the part) for screening the yarn displacements, resin flow, solidification during the hot press forming process, and structural health monitoring under mechanical loads with minimal cross-sensitivity to temperature/humidity. Second, the capability of SpX/GnP/SP sensors in detection of a wide range of bodily motions (from the joint motion to arterial blood pressure) is demonstrated.

Corrosion protection properties of inhibitor containing hybrid PEO-epoxy coating on magnesium

A hybrid PEO-epoxy coating was developed for magnesium. A highly-efficient corrosion inhibitor (3-methysalicylate) was impregnated into the anodized layer, which was sealed by an epoxy layer through dip-coating process. Influence of dip-coating parameters on coating properties was investigated. The corrosion performance was evaluated through general and localized electrochemical techniques. As a result, the epoxy layers registered superior resistance, whereas the anodized layer suppressed corrosion expansion. Longer immersion and triple-dipping favored the production of better sealed epoxy layer. The active protection mechanism was achieved by suppression the re-deposition of detrimental impurity and/or adsorption upon the exposed surface from incorporated inhibitor.

Large-Area Self-Assembly of Silica Microspheres/Nanospheres by Temperature-Assisted Dip-Coating.

This work reports a temperature-assisted dip-coating method for self-assembly of silica (SiO2) microspheres/nanospheres (SPs) as monolayers over large areas (∼cm2). The area over which self-assembled monolayers (SAMs) are formed can be controlled by tuning the suspension temperature (Ts), which allows precise control over the meniscus shape. Furthermore, the formation of periodic stripes of SAMs, with excellent dimensional control (stripe width and stripe-to-stripe spacing), is demonstrated using a suitable set of dip-coating parameters. These findings establish the role of Ts, and other parameters such as withdrawal speed (Vw), withdrawal angle (θw), and withdrawal step length (Lw). For Ts ranged between 25 and 80 °C, the morphological analysis of dip-coatings shows layered structures comprising of defective layers (25-60 °C), single layers (70 °C), and multilayers (>70 °C) owing to the variation of SP flux at the meniscus/substrate assembling interface. At Ts = 70 °C, there is an optimum Vw, approximately equal to the downshift speed of the meniscus (Vm = 1.3 μm/s), which allows the SAM formation over areas (2.25 cm2) roughly 10 times larger than reported in the literature using nanospheres. Finally, the large-area SAM is used to demonstrate the enhanced performance of antireflective coatings for photovoltaic cells and to create metal nanomesh for Si nanowire synthesis.

Porous Gold Films Fabricated by Wet-Chemistry Processes

Porous gold films presented in this paper are formed by combining gold electroless deposition and polystyrene beads templating methods. This original approach allows the formation of conductive films (2 × 106 (Ω·cm)−1) with tailored and interconnected porosity. The porous gold film was deposited up to 1.2 μm on the silicon substrate without delamination. An original zirconia gel matrix containing gold nanoparticles deposited on the substrate acts both as an adhesion layer through the creation of covalent bonds and as a seed layer for the metallic gold film growth. Dip-coating parameters and gold electroless deposition kinetics have been optimized in order to create a three-dimensional network of 20 nm wide pores separated by 20 nm thick continuous gold layers. The resulting porous gold films were characterized by GIXRD, SEM, krypton adsorption-desorption, and 4-point probes method. The process is adaptable to different pore sizes and based on wet-chemistry. Consequently, the porous gold films presented in this paper can be used in a wide range of applications such as sensing, catalysis, optics, or electronics.

Silicon carbide-based membranes with high soot particle filtration efficiency, durability and catalytic activity for CO/HC oxidation and soot combustion

We report here the solution coatings of Diesel Particulate Filter (DPF) with allylhydridopolycarbosilane (AHPCS)-based polymers leading to supported silicon carbide (SiC)-based membranes with high temperature soot particle filtration efficiency, durability and catalytic activity. In a first part of the present study, our objective was to reduce the pore size of DPF to filtrate finer particles without altering filtration efficiency by coating DPF with an additional fine porous AHPCS-derived SiC membrane. The latter is produced by dip-coating AHPCS on DPF following by a pyrolysis of the AHPCS membrane-modified DPF at 1000°C under argon. We investigated the influence of dip-coating parameters and viscosity of different AHPCS solutions on the SiC membrane-coated DPF by SEM, mercury porosimetry, XRD and high-temperature thermogravimetric analysis. The evolution of the filtration capacity has been determined with a synthetic gas bench. An additional fine SiC membrane (∼150nm in thickness) prepared from a 10vol% of AHPCS in THF deposited on DPF allowed maintaining filtration efficiency as high as the virgin DPF while the pore size of the SiC membrane coated-DPF decreased to filter finer particles. Results are confirmed using a commercially-available polysiloxane (Si–C–O precursor). Furthermore, the SiC membrane acted as a thermal barrier coating and provided a better durability to the DPF by preventing apparition of cracks after heat-treatment to 1500°C under argon. The use of mixed oxide and metallic phases formed in-situ in SiC constitutes one of the solutions to generate new and effective catalytic performances to membranes. Within this context, in a second part of the study, we applied a reverse AHPCS-based microemulsion to combine SiC and oxide phases in the same additional porous membrane. As a proof of concept, we have prepared catalytically active Ce–O–Fe–Pt/SiC membrane coated DPF after dip-coating and pyrolysis under argon. These materials have been characterized and tested with regard to CO/HC oxidation and soot combustion. Ce–O–Fe–Pt/SiC membrane coated DPF showed an activity for CO conversion reaching a light-off temperature T50=270°C and the presence of the catalytic phase allowed burning soot at 486°C.

Preparation and Characterization of Al<sub>2</sub>O<sub>3</sub>-Based Composite Membranes by Sol-Gel Method

Porous Al2O3-SiO2-ZrO2 ceramic composite membranes were fabricated by the sol-gel method. The effects of constitution of the composite sol, dip-coating parameters and calcination parameters on the morphology, phase composition, pore size distribution and BET surface area of the membranes were investigated extensively. The thermogravimetric analysis (TGA)/differential scanning calorimeters (TG/DSC), scanning Electron Microscopy (SEM), XRD analysis and N2 adsorption-desorption analysis was employed for the membranes characterization. TG/DSC curve shows that the suitable calcination temperature of Al2O3-SiO2-ZrO2 membranes is 1000°C. The SEM morphology displays a smooth and free-crack layer of Al2O3-SiO2-ZrO2 composite membranes on the surface of the support after calcination at 1000°C. Furthermore, the membranes were also successfully coated with a good adhesion to the support. The optimal composite membranes were obtained when the moral ratio of Al2O3-SiO2-ZrO2 was 10:2.3:1, the dip-coating parameters were four times dip-coating with every time of 60s respectively.

Preparation of Polymer-Derived Ceramic Coatings by Dip-Coating

Polysilazane-based coatings were prepared on dense and porous substrates by dip-coating. Both the pure, liquid polymer and polymer solutions in cyclohexane were investigated. Relevant properties of the coating solutions, including rheological properties and surface tension, were determined and used to predict the resulting layer thickness as a function of dip-coating parameters on dense borosilicate glass substrates. A good correlation between existing model (Landau and Levich) and experiment was found for the pure polymer. In the presence of a solvent, evaporation phenomena led to a predicted coating thickness that is much less than the experimental value for all dip coating withdrawal spends. The introduction of a correction factor was found to adequately describe the deviation. In case of porous substrates, the coating thickness could not be predicted using the model due to infiltration of the base structure, resulting in an interpenetrating ceramic composite layer after pyrolytic conversion of the preceramic polymer compound. When preparing polymer-derived ceramic films on porous base materials, e.g. for membrane applications, this phenomenon has to be taken into account.

Influence of Thickness on Performances of YBa$lt;inf$gt;2$lt;/inf$gt;Cu$lt;inf$gt;3$lt;/inf$gt;O$lt;inf$gt;7-δ$lt;/inf$gt; Films Prepared by Metal Organic Solution Deposition

Trifluoroacetate metal organic deposition (TFA-MOD) is one of the most promising technology routes for fabrication of YBa2Cu3O7-δ (YBCO) coated conductors. In this paper, high-boiling point organic solvent diethanolamine (DEA) was added to modulate and to improve the properties of precursor solution by suppression the defect in the final films. And the thickness of single coated film was increased by increased concentration of the metal ions in the precursor solution. It is revealed that an exponential relationship was found between the thickness of precursor film after low-temperature decomposition and the ion concentration, as well as the viscosity of precursor solution vs the ion concentration. Optimizing the ion concentration and dip-coating parameters, smooth and crack-free YBCO films after crystallization are achieved with the thickness more than 1.3 μm. The films show homogeneous microstructures while dispersive heterogeneous particles appear in the surface of the thick films. Critical current density (Jc) measurement shows a decrease of Jc due to the increase of the thickness of YBCO films prepared by high concentration precursor solution, while critical currents (Ic) are distinctly improved. For instance, the Ic value of YBCO film prepared by 2.5 mol/L precursor solution is 4.7 times of that by 1.0 mol/L precursor solution. 1168 无 机 材 料 学 报 第 29 卷

Titania nanocomposite polyethersulfone ultrafiltration membranes fabricated using a low temperature hydrothermal coating process

Thin mesoporous coatings of TiO 2 nanoparticles were developed for in-house and commercial PES membranes of varying pore sizes using a low temperature hydrothermal (LTH) approach. Titania sol–gel particles were dip-coated onto membrane substrates, followed by heat and UV treatments to extract the residual organic templates. Dip-coating parameters such as drying and holding time, dipping and withdrawal velocities, and the number of coating cycles were varied to optimise the microstructure and surface properties of the coating. Coated membranes exhibit a dual level hierarchical roughness and hydrophilicity which was maintained without continuous UV illumination. The organic templating agent (Pluronics F127) enhanced adhesion of the particles; however the heat treatment collapsed some pores in the tighter ultrafiltration membranes. Results showed that the coatings were mechanically robust and photoactive. Passive protein adsorption was reduced significantly on the TiO 2 coated surfaces. Filtration performance of coated and uncoated 500 kDa membranes was also investigated with humic acid as a model foulant, and an increase in flux recovery was observed during multiple fouling and cleaning cycles with the titania coated membrane. The LTH approach provides a platform for further surface functionalization of polymeric membranes to generate photoactive coatings, tuneable hydrophilicity, low fouling surfaces and novel surface architecture.

Um procedimento simples e barato para a construção de um equipamento "dip-coating" para deposição de filmes em laboratório

In this work we show how to build a piece of equipment for depositing thin films by the dip-coating process, using inexpensive components easily found on the market. This equipment allows us to control the dipping and pulling velocity at which the substrate is put in the film precursor solution, two very important parameters for obtain thin films. This article discusses the construction of the mechanical and electric parts of the equipment, a simple method to interface it to a computer and the development of the software to control the dip-coating parameters.