Fabrication Of Cold Spray Ti-O Coatings Engineered From Agglomerated Powders

Current attention has focused on the preparation of thick ceramic coating using nanostructured materials as feedstock materials using thermal spray process. Cold spray method has appeared as a promising process to form ceramic nanostructured coating without significantly changing the microstructure of the initial feedstock materials whereas many conventional thermal spray processes do due to its low processing temperature. However, deposition of ceramic powders by cold spray is not easy due to brittle characteristics of the material. Moreover, the bonding mechanism on how the ceramic coating was formed on the substrate is still unclear as this method requires plastic deformation of particles upon the impact onto the substrate. Therefore, in this study, focused have been made on the TiO2 nanostructured feedstock materials which were synthesized throughout of the study. The properties of the powders also have been altered by several conditions in order to make it suitable for cold spray deposition. The mechanism of coating deposition and properties of the feedstock powders were investigated in this study. The following results which obtained by this study were summarized as below: 1. In this work, the synthesis of agglomerated TiO2 powders, which are ready to be used as feedstock materials for a cold spray process after synthesis via a simple hydrolysis (TiO2-H) and hydrothermal (TiO2-HT) process, is described. The XRD patterns showed that single phase anatase TiO2 was able to be produced using a low temperature process for the hydrolysis and hydrothermal methods. However, the results showed that TiO2-H powders have a smaller crystallite size and broader peaks compared with TiO2-HT powders. SEM and TEM analysis confirmed that the TiO2-H powders were built up from nano-sized particles, and were further agglomerated into micrometer-size, which is a preferable size for the cold spray process. On the other hand, TiO2-HT powders showed a formation of agglomerated particles with minimal particle agglomeration which was revealed by the SEM image and the particle size analyzer. A preliminary study on coating deposition using cold spray showed that TiO2-H powders can be deposited onto ceramic tile substrate with a ~50μm thickness. Meanwhile for TiO2-HT powders, only particle embedment can be observed on the surface of the substrate. The results reveal that porosity contained in the agglomerated morphology is important in order to build up the coating by cold spray due to the tendency of the porous structure to break easily upon impact onto the substrate. 2. To further clarify the effect of porosity contain in the powder for the cold spray deposition, effect of low calcination on the as-synthesized TiO2 by hydrolysis method have been conducted. Then, as-synthesized TiO2 and calcined TiO2 powders were studied on coating deposition by cold spray process. The results of this study indicated that a post treatment on TiO2 powder improved powder deposition on ceramic tile substrate via the cold spray method. The cross-section of the obtained coating which was observed using SEM showed that nanoparticles TiO2 powders in the agglomerated form were able to be deposited on the substrate and formed a thick coating. A stacking of agglomerated TiO2 powders was found on the cross-section observation which is due to the breaking up of ceramic particles which was induced by porosity in the powder and is believed to be responsible for the formation of the coating. The results of this study also reveal that, when the feedstock powders have denser packing of particles and minimum number of porosity in the powder, breaking of particles during the spraying become more difficult. This hard and dense particle made them resistant to fragmentation and adherence on surface of the substrate. 3. Further study have been conducted by addition of ammonium sulfate; (NH4)2SO4 during the powder synthesis. Addition of structure-directing agent, (NH4)2SO4 promotes the agglomeration to occur with denser closed packing of particle arrangement which reduce the number of existing porosity in the synthesized powder. The addition of (NH4)2SO4 addition was found to be very effective to unite the nano-sized particles together to form agglomeration in order to form the tertiary particles. The preliminary study of coating formation depicted that the powder obtained could be used as the feedstock powder for cold spray process to make coating as it can be deposited onto the ceramic tile substrate. Once again, porosity in the powders was deduced as one of the crucial factors that contribute to better deposition of TiO2 coating by cold spray process. Plastic deformation also may contribute to the formation of coating due to the used of nanostructured powders which received high local compact pressure during the spraying process. 4. Further studies on the obtained coating have been investigated. The study reveals that the properties of the coating (hardness, roughness and porosity) also depend on the properties of the initial feedstock powders. Moreover, anatase phase was preserved as revealed by the XRD analysis. This finding proves that cold spray process is suitable process to fabricate TiO2 coating which can prevent phase transformation to occur due to low processing temperature. Details observation on the surface and cross-section of the coatings show that nanostructured particles from the feedstock powders were well-retained in the coating structure. 5. In order to study the individual particle impact morphologies, wipe tests were conducted on aluminum, copper and ceramic tile substrate. From the SEM observation, the results showed that the collided particles were plastically deformed and adhered on the hard ceramic tile substrate during deposition. However, in the case of aluminum and copper substrate, the splat diameters were smaller than the feedstock powder size and both particles and substrates were deformed during the collision. Moreover, many craters were observed on these metal substrates. It was found that the deposition behavior of TiO2 particle and the crater formation by the cold spray process was affected by the hardness and surface roughness of the substrate materials

Effect Of pH Condition During Hydrothermal Synthesis On The Properties Of Hydroxyapatite From Eggshell Waste

Hydroxyapatite (HA) powders were synthesized using eggshell waste through hydrothermal method to develop bioceramics materials for medical applications. The effects of the pH conditions during the synthesis on the phase behaviour, crystallite size, crystallinity and morphology of as-synthesized ceramic powders were evaluated. The XRD patterns showed that HA was the only main phase present in the as-synthesized powder after being calcined at 400°C. However, EDX measurement detected the presence of Mg as trace element which originated from the eggshell as starting materials. The crystallite size and crystallinity of the HA powders were increased when the powders were synthesized in acidic condition as compared to basic condition. FESEM images showed that HA powder with nano-sized rods and spherical morphologies were obtained from the powders that were synthesized at pH 5, while the powder particles synthesized at the basic condition at pH 9 produced elongated rodshape particles. The PSD results showed that the synthesized HA was in agglomerated form which was also confirmed by FESEM images

Calcium phosphate ceramics prepared from natural waste materials

Calcium phosphate bio-ceramics have widely been developed in biomedical applications due to their excellent biocompatibility, bioactivity and osteoconduction characteristics. These materials may be employed in many ceramic t(irms such as porous blocks, dense body, granular forms and hybrid composites to fill bone defects or voids. The main component of calcium phosphate ceramics is calcium. One of the means to produce calcium phosphate is by extracting it from natural sources such as eggshells. animal bones, cockles and coral as biogenic materials that are naturally available. Finer particles of the resulting powder promises better bioactivity and mechanical properties of bio-ceramic materials. This present research aims to synthesize calcium phosphate powders from raw materials, such as egg shell and bovine bone. The chemical and morphological properties of the materials arc studied and the phase stability and mechanical characteristics of the resulting granulated bin-ceramic material arc evaluated. The final products arc porous bioceramics used as ceramic scafi()lds for spongy bone application and dense ceramics used for load bearing applications

Mechanical and Morphological Properties of Polypropylene/Epoxidized Natural Rubber Blends at Various Mixing Ratio

This research is to investigate the effect of mixing ratio on the properties of polypropylene (PP) incorporated with epoxidized natural rubber (ENR). The blends of PP/ENR were prepared by melt compounding using an internal mixer and vulcanized through sulfur curing. Mechanical testing such as tensile test, hardness test and impact test were performed to characterize the properties of PP/ENR blends. It was clearly observed that the increase of the ENR percentage increases the toughness and flexibility of the PP/ENR blends. In comparison to the pure PP, the 40/60 PP/ENR blend showed an improvement of elongation at break and impact strength, up to 68% and 56%, respectively. In contrary, the tensile strength and hardness decreases as the amount of PP decreases. The changes were associated to the properties imparted by the elastic chains of cross-linked ENR. The obtained properties showed good correlation with fracture surfaces observed in microscopy analysis performed by Field Emission Scanning Electron Microscope at a magnification of 500 and 5000-x

Plasma-sprayed TiO2 coatings: Hydrophobicity enhanced by ZnO additions

Titanium dioxide (TiO2) powder mixed individually with 10 and 30 weight percentage (wt%) ZnO was thermally sprayed onto a grade B API 5 L carbon steel substrate by atmospheric plasma spraying. The effect of the addition of ZnO (10 wt% and 30 wt%) on the microstructures and wettability properties of the TiO2/ZnO coatings was investigated. The characterization of the coatings was carried out using scanning electron microscopy, X-ray diffraction (XRD), laser confocal microscope, and sessile droplet system. The XRD analysis of the coat�ing revealed that the anatase phase of TiO2 in the powder state transformed into rutile phases for the produced TiO2/ZnO coatings. Surface microstruc�ture analysis revealed that the coatings had typical micro-roughened surfaces of plasma spraying products. The coating with 30 wt% ZnO produced a coating with remarkable pores and microcracks compared with the TiO2 coating and coating with 10 wt% ZnO. Additionally, the increase in the wt% of ZnO increased the surface roughness value of the produced coatings and substantially changed the wettability properties of the TiO2 coating from hydrophilic to hydrophobic

In-Vitro Apatite Growth On Porous Â-Tricalcium Phoshpate Scaffolds Coated With PHVB

The bioactive properties of polyhydroxybutyrate-co-valerate (PHBV) coated beta-tricalcium phosphate (β-TCP) have been studied invitro. Porous β-TCP scaffolds have been prepared using a template method and sintered at 1450 °C.The bio ceramics were then coated with PHBV solution before being immersed for 6 weeks in a simulated body fluid (SBF)at 37°C.At the end of the immersion time, insignificant changes in the SBF pH value was observed, suggesting good stability against hydrolytic degradation. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed the presence of apatite.Morphological analysis by SEM showed the formation of apatite crystals in the form of flakes and globular deposits on the scaffold surface.This bonelike apatite indicates good biological activity of the bio ceramics scaffold with PHVB coating suggesting that the composite has potential for bone tissue engineering applications

FUNCTIONALISATION OF ETHYLENE-PROPYLENE COPOLYMER (EPM) BY MELT GRAFTING OF MALEIC ANHYDRIDE (MAH) USING HIGH SHEAR INTERNAL MIXER

MAH grafted EPM is a highly potential compatibiliser in EPDM based blend. This studyjs focusing on synthesizing peroxide-initiated MAH-g-EPM via melt grafting using a Haake intemal mixer at high shear rate. The effect of MAH and dicumyl (DCP) percentage on the grafting efficiency of MAH onto EPM chains was carried out through a 2-level factorial experimental design using the Design Expert 6.0.5 software. The MAH and DCP content were varied in the range of 1-5 phr and 0.1-0.3 phr, respectively. The grafting parameters were fixed at temperature of 180°C, rotor speed of 60 rpm for 5 minutes. The grafting efficiency was determined by Fourier Transform Infrared spectroscopy analysis based on cumulative absorbance of anhydrides characteristic peaks. It was observed to be highly 'j 'f influenced by the amount of MAH and DCP and the optimum funtionalisation was achieved at 5 phr MAH and 0.3 phr peroxide additio

Simulation of wire and arc additive manufacturing of 308L stainless steel with coldArc gas metal arc welding

This research focuses on the capabilities of coldArc GMAW in the behavior of heat input to the weld bead dimension. In this study, the effect of process GMAW of 308L stainless steel filler wire with a thickness of 1.2 mm and 304L stainless steel base plate, with a dimension of 120 mm x 25 mm x 10 mm (height x width x thickness) by applying WAAM. The data was collected using MATLAB of a Smart Weld Rosenthal’s Steady-State 3D Isotherms. A Taguchi response was used in the DOE method with Minitab software to analyze the effect of process parameters on height, width, and depth of weld bead dimension during GMAW. The experiments were conducted following the low, mid, and high input parameters will show the different structures of weld bead dimension, which include 70 A, 75 A, and 78 A (arc current), 15 V, 16 V, and 17 V (voltage), 400 mm/min, 600 mm/min, and 800 mm/min (welding speed). Hence, the optimum value is 75 A, 16 V, and 800 mm/min, and the most significant parameters to deposit stainless steel with coldArc GMAW were welding speed followed by arc current and voltage

Fabrication of Cold Spray Ti-O Coatings Engineered from Agglomerated Powders

豊橋技術科学大

Vero cell culture on magnesium doped biphasic calcium phosphate scaffolds

The bioactivity test on the performance of porous microcarriers of pure biphasic calcium phosphate (BCP) and Mg-doped BCP was conducted in spinner vessel with Vero cell lines for 90 hours. The findings revealed that all the porous microcarriers were biocompatible as the cells already attached on the microcarrier after 24 hours of culture. The presence of divalent cations including Mg2+ is encouraged the spreading and adhesivity of cells onto bioceramic matrices. Magnesium also believed to increase the solubility of BCP in vitro which is useful to establish cell-material interface and thus improved cell attachment and growth. Thus, higher cell attachment, growth, and migration of cell deep inside the pores were obtained on microcarriers of 10 mol% Mg-doped BCP compared to undoped BCP. The substitution of Mg into the BCP present several advantages related to metabolic cell behaviours as FESEM results showed that Mg substitution can induce a spread-like and irregular morphology which is quite different from the cell grown onto the pure BCP where the cells just remain on the surface of the scaffold, or in a localized area within the scaffold and proliferate there. This makes porous Mg-doped BCP substrate a promising candidate as a bone substitute and microcarrier