Dip Coating From Density Mismatching Mixture

Author(s):  
Bashir Khoda ◽  
AMM Nazmul Ahsan ◽  
SM Abu Shovon

Abstract Solid transfer technology from mixtures is gaining ever-increasing attention from materials scientists and production engineers due to their high potential in near net-shaped production of cost-effective engineering components. Dip coating, a wet deposition method, is an effective and straightforward way of thin-film/layers formation. The dipping mixtures are often embedded with inorganic fillers, nanoparticles, or clusters (d<30 nm) that produce a thin film ranging from nm to couple microns. An increase in the volume of solid transfer by the dipping process can open-up a novel 3D near-net-shape production. However, adding larger inorganic particle size (>1µm) or adding a higher solid fraction will increase the solid transfer but may result in a multi-phase heterogeneous mixture. In this work, the physical mechanism of an increased volume of solid transfer with a larger spherical particle size (>5 µm) is investigated. Polymer-based glue and evaporating solvent are mixed to construct the liquid carrier system (LCS). Moderate volume fraction of inorganic particles (20% < ?p < 50%) are added into the LCS solution as solid loading. Three levels of binder volume fraction are considered to investigate the effect of the solid transfer. Cylindrical AISI 304 steel wire with dia 0.81 mm is dipped and the coating thickness, weight, and the surface packing coverage by the particles are measured in our lab. The results presented the influence of volume fraction of inorganic particle and glue composition on the solid transfer from the heterogeneous mixture.

Author(s):  
Bashir Khoda ◽  
A. M. M. Nazmul Ahsan ◽  
S. M. Naser Shovon

Abstract Solid transfer technology from mixtures is gaining ever-increasing attention from both materials scientists and production engineers due to their high potential in near net shape production of cost-effective engineering components. Dip coating, a wet deposition method is an effective and straightforward way of thin-film/layers formation. It is extensively used as a coating method due to its simplicity, low cost, and reasonable control over the thickness. The dipping mixture can be homogeneous, composite, hybrid, or heterogeneous. The mixtures are often embedded with inorganic fillers, nanoparticles, or clusters (d < 30 nm) that produce a thin film ranging from nm to couple microns. An increase in the volume of solid transfer by the dipping process can open-up a novel technique for the 3D near-net-shape production process via sintering, robocasting or additive manufacturing, and material joining. Adding larger inorganic particle size (> 1μm) and/or by adding higher solid fraction will increase the solid transfer but may result in a multi-phase heterogeneous mixture or slurry. In this work, the physical mechanism of an increased volume of solid transfer with a larger particle size (> 5 μm) is investigated. The metallic particles are spherical in shape with an average diameter of 5.69 μm is considered as the coating material. Polymer-based glue and evaporating solvent are mixed to construct the liquid carrier system (LCS) for large inorganic hard particles. Moderate volume fraction (VF) of inorganic particles (20% < ϕp < 50%) are added into the LCS solution as solid loading. Cylindrical AISI 304 steel wire with dia 0.81 mm is used as the substrate for dipping and coating. The coating thickness (CT) and the surface packing coverage by the particles are measured in our lab. The results presented the influence of volume fraction of inorganic particle and glue composition on the solid transfer from the heterogeneous mixture.


2018 ◽  
Vol 9 (4) ◽  
pp. 777-782 ◽  
Author(s):  
Rupeshkumar V. Ramani ◽  
Bharat M. Ramani ◽  
Anjana D. Saparia ◽  
Chirag Savaliya ◽  
K.N. Rathod ◽  
...  

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Young Jung ◽  
Kyungkuk Jung ◽  
Byunggeon Park ◽  
Jaehyuk Choi ◽  
Donghwan Kim ◽  
...  

Abstract We present a highly elastic and wearable piezoresistive strain sensor based on three-dimensional, micro-porous graphene-coated polydimethylsiloxane (PDMS) sponge suitable for being attached on human skin. The proposed strain sensors are simply fabricated by a sugar templating process and dip coating method based graphene ink in a facile and cost effective manner. The fabricated graphene-coated PDMS sponge shows highly stable mechanical properties in various tensile stress–strain test. A graphene thin film coated onto the backbone of PDMS sponges is used as the sensing materials of piezoresisitve strain sensors. The changes in resistance of the devices are highly stable, repeatable, and reversible when various strain is applied. Furthermore, the strain sensors show excellent sensing performance under different strain rate and mechanically robustness enough to be worked stably under repeated loads without any degradation.


2021 ◽  
Author(s):  
S M Naser Shovon ◽  
Adeeb Alam ◽  
Bashir Khoda

Abstract Controlled delivery of inorganic microparticles by the dipping process can open up 3D near-net-shape production techniques through sintering, robocasting or additive manufacturing, and material joining. However, micro-scale inorganic particles (d>1 µm) have reduced surface area and higher density, making them negatively buoyant in dip-coating mixtures and challenging for high yield solid transfer through entrainment due to the density mismatch. In this work, the physical phenomenon of the particle transfer process under stirring energy with negatively buoyant, non-Brownian micro-particles from density mismatching mixture is investigated. Liquid carrier system (LCS) solution is prepared by the combination of a binder polymer and an evaporating solvent. Inorganic micro-particles are dispersed with the assistance of a magnetic stirrer to maintain the suspension characteristics of the mixture. The effect of solid loading and the binder volume fraction on solid transfer has been reported. Two coating regime is observed (i) heterogeneous coating where particles clusters are formed at a low capillary number and (ii) effective viscous regime, where full coverage can be observed on the cylindrical substrate. In our experiment, we have not observed ‘zero’ particle entrainment even at the low capillary number of the mixture, which can be attributed to the presence of binder and hydrodynamic flow of the particles due to the stirring of the mixture. The critical film thickness for particle entrainment is found as ℎ * = 0.16a for 6.5% binder and ℎ * = 0.26a for 10.5% binder, which are smaller than previously reported. Furthermore, the transferred particle matrices are compared with the analytical expression of density matching suspension. The finding of this research will help to understand the high-volume solid transfer technique and develop a novel manufacturing process.


Author(s):  
M. R. Pinnel ◽  
A. Lawley

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.


Author(s):  
M. E. Twigg ◽  
E. D. Richmond ◽  
J. G. Pellegrino

For heteroepitaxial systems, such as silicon on sapphire (SOS), microtwins occur in significant numbers and are thought to contribute to strain relief in the silicon thin film. The size of this contribution can be assessed from TEM measurements, of the differential volume fraction of microtwins, dV/dν (the derivative of the microtwin volume V with respect to the film volume ν), for SOS grown by both chemical vapor deposition (CVD) and molecular beam epitaxy (MBE).In a (001) silicon thin film subjected to compressive stress along the [100] axis , this stress can be relieved by four twinning systems: a/6[211]/( lll), a/6(21l]/(l1l), a/6[21l] /( l1l), and a/6(2ll)/(1ll).3 For the a/6[211]/(1ll) system, the glide of a single a/6[2ll] twinning partial dislocation draws the two halves of the crystal, separated by the microtwin, closer together by a/3.


2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.


2018 ◽  
Vol 5 (2) ◽  
pp. 16-18
Author(s):  
Chandar Shekar B ◽  
Ranjit Kumar R ◽  
Dinesh K.P.B ◽  
Sulana Sundar C ◽  
Sunnitha S ◽  
...  

Thin films of poly vinyl alcohol (PVA) were prepared on pre-cleaned glass substrates by Dip Coating Method. FTIR spectrum was used to identify the functional groups present in the prepared films. The vibrational peaks observed at 1260 cm-1 and 851 cm-1 are assigned to C–C stretching and CH rocking of PVA.The characteristic band appearing at 1432 cm-1 is assigned to C–H bend of CH2 of PVA. The thickness of the prepared thin films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD20) and cross checked by gravimetric method. XRD spectra indicated the amorphous nature of the films.Surface morphology of the coated films was studied by scanning electron microscope (SEM). The surface revealed no pits and pin holes on the surface. The observed surface morphology indicated that these films could be used as dielectric layer in organic thin film transistors and as drug delivery system for wound healing.


2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.


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