Surfactant-assisted hydrothemial synthesis of fluoridated hydroxyapatite nanorods

Fluoridated Hydroxyapatite (FHA) nanorods were synthesized using Apricot Tree Gum (ATG) as a novel surfactant and then compared with Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Sodium Dodecyl Sulfate (SDS) as conventional surfactant agents under hydrothermal condition (70 degrees C and 1 atm). The effects of pH values and various types of surfactants on the formation of the FHA nanorods, crystalline phase, and chemical compositions were investigated using Field Emission Scanning Electron Microscopy (FESEM) equipped by Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The findings indicated application of the presented ATG as surfactant is able to produce the hexagonal nanorods of FHA along their c-axis direction. Moreover, it is illustrated that diameter and length of nanorods which is obtained by ATG surfactant are bigger than EDTA and SDS. In addition, it is demonstrated that pH values can play a major role on formation of hexagonal FHA nanorods. The increase of pH transformed the shape of synthesized FHA from particles to rods. Ultimately, based on the similarity of synthesized FHA nanorods to the shape, structure, and composition of enamel; it is suggested for its potential to be used for dental applications

Effect of pretreatment parameters on surface roughness and cobalt removal of tungsten carbide before diamond coating

Chemical vapor Deposition (CVD) is one of diamond synthesis process and it is widely applied to cutting tools to enhance wear resistance and increase tool life. The presence of excessive Co on the substrate of cemented tungsten carbide has a negative influence on the deposition diamond. Single step pretreatment leading to both Co removal and the roughening of the substrate surface can improve adhesion levels of the diamond coatings deposited onto WC-Co substrates. The effect of cobalt content on the diamond adhesion on WC [6%Co] is well documented. However, very limited research has been reported on WC [12%Co]. In this present work, an attempt is made to study the effect of pretreatment parameters namely temperature and time on cobalt removal and surface roughness of WC [12%Co]. Full factorial experimental design followed by Response Surface Methodology (RSM) is employed in this study to plan and analyze the experiment. The surface roughness (Ry) and cobalt removal are the independent response variables. Empirical models are successfully developed to predict amount of cobalt removal and surface roughness of the substrate using both Genetic Algorithm (GA) and design of experiments (DOE) methods. Experimental results show that the temperature is the most significant factor followed by the etching time for predicted surface roughness (Ry). Whereas for interaction of time and temperature are not significant to influence Ry. In contrast time of etching is more significant than temperature for cobalt removal during pretreatment process. Moreover, interaction of time and temperature is also significant to influence cobalt remova

A comparison of optimization methods in cutting parameters using Non-Dominated Sorting Genetic Algorithm (Nsga-Ii) and Micro Genetic Algorithm (Mga)

Since cutting conditions have an influence on reducing the production cost and time and deciding thequality of a final product the determination of optimal cutting parameters such as cutting speed, feedrate, depth of cut and tool geometry is one of vital modules in process planning of metal parts. Withuse of experimental results and subsequently, with exploitation of main effects plot, importance ofeach parameter is studied. In this investigation these parameters was considered as input in order tooptimized the surface finish and tool life criteria, two conflicting objectives, as the processperformance simultaneously. In this study, micro genetic algorithm (MGA) and Non-dominated SortingGenetic Algorithm (NSGA-II) were compared with each other proving the superiority of Non-dominated Sorting Genetic Algorithm over micro genetic since Non-dominated Sorting GeneticAlgorithm results were more satisfactory than micro genetic algorithm in terms of optimizingmachining parameters

Effects of HA-Coating on the Surface Morphology and Corrosion Behavior of a Co-Cr-Based Implant in Different Conditions

The corrosion behavior and surface morphology of a Co-Cr-based implant after HA-coating using the sol-gel method were investigated. Sintering was performed at four different conditions. Surfaces of the samples were characterized and evaluated using field emission scanning electron microscopy. Atomic force microscope was used to measure the surface roughness and to collect the micrographs of the HA-coating layer. The x-ray diffraction results confirmed the formation of a crystalline phase of HA on the surface of the substrates. To measure the corrosion resistance, the samples were dip-coated with two different thicknesses (78 and 142 µm), and then tested by potentiodynamic polarization and spectroscopy (EIS) in SBF at 37 °C after sintering process. This study revealed that the thickness of the HA-coating layer affects the corrosion rate of the substrate, but the sintering condition of the HA-coating layer plays a remarkably more significant role in improving the corrosion resistance of Co-Cr-based implants. Moreover, the sample sintered at 600 °C for 20 min with thickness of 142 µm showed considerably enhanced surface morphology and superior corrosion resistance compared with the bare material and other treated samples

Effect of post-treatment techniques on corrosion and wettability of hydroxyapatite-coated Co–Cr–Mo Alloy

This study is a comparison between the effect of sintering and alkaline post-treatment techniques on calcium phosphate-coated Co–Cr–Mo alloy in terms of electrochemical corrosion behavior and wettability. The Co–Cr–Mo substrates were electrophoretically coated by calcium phosphate in a solution of Ca(NO3) · 4H2O and NH4H2PO4. The sintering and alkaline post-treatment techniques were then conducted to convert an as-deposited dicalcium phosphate dihydrate phase to crystalline hydroxyapatite (HA). The coated layers were characterized in terms of phase, crystallinity and composition using X-ray diffraction, Fourier transform infrared spectroscopy and energy-dispersive spectroscopy. In addition, morphology and thickness of coated layers were evaluated using a scanning electron microscope. The results indicate HA-coated samples with a sintering post-treatment technique exhibit more improvement in corrosion parameters, such as corrosion potential (Ecorr) and corrosion current density (Icorr), but lower enhancement in hydrophilicity. However, the HA-coated samples with an alkaline post-treatment technique reveal higher hydrophilicity with lower improvement in corrosion resistance

The application of surface response methodology to the pretreatment of WC substrates prior to diamond coating

High cobalt (Co) content greater than 10% in tungsten carbide is desirable because Co improves the toughness of the cutting tool. However, the additional Co poses a huge challenge in surface preparation given that the Co content must be reduced to less than 1% on the substrate surface prior to applying a diamond coating. The excessive presence of Co on the substrate surface during coating suppresses diamond nucleation and causes the deterioration of diamond film adhesion. Many attempts have been made to overcome this issue, including the use of chemical etching, mechanical blasting, and heat treatment, but the successful pretreatment of WC-12%Co is still very limited. In this paper, a single-step chemical pretreatment using a mixture of sulfuric acid and hydrogen peroxide solutions was carried out on WC-12%Co. Two independent variables, i.e., etching time and acid temperature, were varied in the experiments to reduce Co contents as well as to roughen the substrate surface. The experimental plan was based on a central composite design. Variance analysis was employed to verify the precision of the mathematical models and their relative parameters. The predicted models generated by the response surface methodology (RSM) were compared with the experimental results, and close agreement was observed. The models demonstrated the significance of both factors, namely, acid temperature and etching time, in reducing Co contents to less than 1% as well as a roughening of the substrate surface within the desirable range

Evaluating hydrothermal synthesis of fluorapatite nanorods: pH and temperature

In this study, the fluorapatite was synthesised by a hydrothermal technique in different pH and temperature using apricot tree gum surfactant. The fluorapatite was synthesised in different shapes such as spherical, Chrysanthemum flower and rod. The effect of two factors (pH and temperature) on the shape and dimension of synthesised fluorapatite was investigated through the full factorial design. An experimental strategy was developed based on the analysis of variance to create mathematical models for the shape and dimension of synthesised fluorapatite. Findings revealed that the pH of hydrothermal solution is more significant factor than temperature in terms of shape and dimension of the synthesised fluorapatite. It was illustrated that similar nanorods structure to the human tooth enamel can be achieved in pH of 10 and temperature of 70 °C The transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) spectroscopy were carried out for characterisation of synthesised fluorapatite

Effect of electrophoretic deposition parameters on the corrosion behavior of hydroxyapatite-coated cobalt–chromium using response surface methodology

Cobalt–chromium (Co–Cr)-based alloys have been used extensively as medical implants, but the ion release and the corrosion products can affect their mechanical integrity and biocompatibility. One of the solutions is to surface coat the substrate with hydroxyapatite via electrophoretic deposition technique. Two variables—pH of electrolyte and current density—were used to examine the electrochemical behavior of the coated sample. An experimental strategy was developed based on the response surface methodology together with the analysis of variance to verify the precision of the mathematical models and their relative parameters. Close agreement was observed between the predicted models and the experimental results. The pH value of electrolyte was a more significant factor than current density in increasing the corrosion potential (Ecorr) of the substrate. The maximum Ecorr was obtained with a current density of 12 mA cm−2 and a pH value of 4.71

Optimizing Material Removal Rate (MRR) in WEDMing Titanium Alloy (Ti6Al4V) Using the Taguchi Method

Abstract: Selection of optimal cutting parameters has always been a critical issue to achieve high-quality in the machining process. In this study Design of Experiment (DOE) method for selection of optimal cutting parameters during WEDM of titanium alloy (Ti6Al4V) is experimentally studied. Moreover, the behaviour of three control parameters such as Pulse ON Time (A), Pulse OFF Time (B) and Peak Current (C) on machining performance, including Material Removal Rate (MRR) and Surface Roughness (SR) is studied using Analysis of Variance (ANOVA). This study has been establishedasa second-order mathematical model based on the Response Surface Methodology (RSM). The experimental plan was based on the face cantered, Central Composite Design (CCD). The residual analysis and confirmation runs indicate that the proposed models could adequately describe the performance of the factors that are being investigated. The results are particularly useful for scientists and engineers to determine which subset of the process variable has the greatest influence on the process performance

Fluoridated hydroxyapatite nanorods as novel fillers for improving mechanical properties of dental composite: Synthesis and application

© 2015 Elsevier Ltd. Fluoridated hydroxyapatite (FHA) in nanorod morphology and hexagonal cross section were synthesised via hydrothermal process using Apricot Tree Gum (ATG) as a surfactant. The synthesised FHA nanorods were then used as reinforcement in bisphenol A-glycol dimethacrylate (Bis-GMA) as base monomer of composite matrix. The FHA nanorods with different ratios were incorporated in the matrix to examine fluoride ion release and pH changes in the Simulated Body Fluid (SBF) and their mechanical properties. The resin without FHA reinforcement was used as the control sample. The Diametral Tensile Strength (DTS), Flexural Strength (FS), and Flexural Modulus (FM) of the reinforced composite were found to be higher compared to the control sample; the values increased from 34.8 to 45.4. MPa, 76.5 to 99.4. MPa, and 1.7 to 2.5. GPa, respectively. Moreover, findings revealed that the pH is reduced by releasing the fluoride ions into the SBF which can be effective for preventing secondary caries. The most optimum mechanical properties were achieved with 0.2. wt% of FHA reinforcement. The FHA nanocomposite meets the minimum standard requirements for dental applications and compared to other dental composites has advantage of preventing formation of secondary caries due to release of fluoride