Preparation, scratch adhesion and anti-corrosion performance of TiO2-MgO-BHA coating on Ti6Al4V implant by plasma electrolytic oxidation technique

Bovine hydroxyapatite (BHA) (from cortical bone), was selected as the main electrolyte for plasma electrolytic oxidation (PEO) on Ti6Al4V implant. The prepared PEO coatings were examined by X-ray diffraction, field emission scanning electron microscope and energy-dispersive X-ray spectroscopy. The surface roughness, adhesion strength, wettability, surface energy and corrosion behaviour of the film were also investigated. The results show that the oxide layer (26 μm) formation on the Ti6Al4V was rough and porous. The micro-pores were filled with anatase TiO2, cubic MgO and hexagonal BHA particles. The porous structures and the compound particles were mainly composed of Mg, O, Ca, P, Ti, Na and Al. Unlike previous coatings produced from calcium and phosphorus inorganic solutions, the coating formation from a newly developed bovine bone-derived HA electrolyte revealed an additional MgO phase in the coating layer. Moreover, higher amount of single phase hexagonal crystalline BHA phase with a Ca/P ratio of 1.1 was achieved with a single PEO process. A film-to-substrate adhesion strength of 1862.24 mN and scratch hardness of about 4.1 GPa was achieved from this method. The TiO2/MgO/BHA film exhibited better wettability, higher surface energy and superior corrosion resistance compared to the bare Ti6Al4V substrate

Development of bovine hydroxyapatite coating on TI6AL4V implant by plasma electrolytic oxidation / Adeleke Sakiru Adekunle

Plasma electrolytic oxidation (PEO) is used to prepare bioactive hydroxyapatite ceramic coatings on light metals. The extensive literature reports on the bioactive hydroxyapatite-oxide coatings formed under a wide range of different electrical parameters and in various electrolyte concentrations. However, little work is available that investigates systematically the influence of hydroxyapatite concentration in the oxide film using a solitary sodium phosphate (NAP) electrolyte solution. In this present work, a single PEO process was used to produce film incorporating HA, and the aftermath effects of various HA concentrations in the oxide film on the Ti6Al4V alloy substrate were examined. The findings revealed that the oxide film was greatly influenced by the various hydroxyapatite particles. It was found that the amount of hydroxyapatite particles infiltrated into the coatings layer as well as the thickness and the surface roughness of the coating increased with increasing HA concentration. The porosity of the HA coatings indicated an inverse relationship with the concentration of HA particles in the NAP solution. The result also demonstrates that higher scratch adhesive strength was achieved using 1.5 g/L HA solution, producing a critical load of 2099 mN, while 0 g/L HA only produced a critical load of 1247 mN. The adhesion becomes independent of thickness when the concentration of HA exceeds 1.5 g/L. The failure of the coating was characterized by large periodic hemispherical chipping, while intermittent delamination was noticed with the coating embedded with HA particles. Due to the increasing demand to develop coatings with unique phase/elemental composition similar to hard bone tissues. The study also examined the coatings formed in a biologically friendly electrolyte containing natural bovine bone-derived HA (BHA) under a range of different voltage regimes, current density and time. The results indicated that the combination of a various voltage regime 225-325 V, current density of 500 mAcm-2 and deposition time of 5 mins produced a rough and porous surface coating. The surfaces of the coated layers were filled with anatase-TiO2, cubic-MgO and hexagonal-BHA particles. The coatings formed in a newly developed bovine-bone derived-HA revealed an additional MgO phase in the coating layer. A film-to-substrate adhesion strength of 2010 mN was achieved. Moreover, the PEO-BHA coatings significantly improved the wear performance of titanium alloy. However, the coefficient of friction (COF) for the coating at 325 V is almost the same with the one produced at 300 V due to porous layer of the coating formed at 325 V. A comparative study on the in vitro corrosion and bioactive performance of commercial hydroxyapatite (CHA) and BHA coatings was also studied. The corrosion and bioactivity properties were evaluated using potentiodynamic polarization and simulated body fluid, respectively. The electrochemical tests demonstrated that the oxide coatings containing different phases possess sufficient protection efficiency. The apatite layer formed on the PEO-BHA coating was more and denser than that of PEO-CHA coating, whereas apatite structure was completely formed on the two surfaces

Recent development of calcium phosphate based coating on titanium alloy implants

Titanium alloy implants are widely employed in biomedical devices and components, especially as hard tissue replacements as well as orthopaedic applications, owing to their favourable properties such as high-strength to weight ratio, low density, low Young’s modulus and biocompatibility. However, metallic implants cannot meet all of the clinical requirements. Therefore, in order to increase their clinical success and long term stability in the physiological environment, surface modification is often performed. This review focuses on the latest achievements in the field of surface modification techniques including sol-gel, thermal spray, magnetron sputtering, electrophoretic deposition and micro-arc oxidation of biocompatible calcium phosphates (CaP) based ceramics coatings for metallic implants with emphasis on the structure, morphological characterization, phase transformation and coating composition. A reflection on the results shows that CaP coatings can be grown with the each type of techniques and a stronger fixation can be enhanced with CaP fabrication on metallic implants. Advantages and limitations of the aforementioned techniques of CaP-based coatings from the point of view of the process simplicity as well as the most important challenges of each coating techniques are highlighted. Further, the most promising method for CaP deposition was identified and a specific area for improvement was discussed

Economics of Farm Households' Food Demand in Nigeria

In paper was used the panel data from the Nigeria General Household Survey and commodity prices from alternative sources between 2010-2016 to estimate farm households’ food and non-food demand in Nigeria. The commodity bundles of all the food groups were necessities goods, as their budget elasticities were positive and also inelastic. Animal products were a luxury good. There is no strong complementary and substitutive relationship existing between the commodity groups as the cross price elasticities estimated were smaller than the own price elasticities. Households’ expenditure on pulses is not affected by changes in their own prices. Policy issue such as stable food prices is important in ensuring that households are assisted in and encourage consuming balance diets

Evaluation of 0 ≤ M ≤ 8 earthquake data sets in African – Asian region during 1966–2015

This article evaluates the occurrence of 0 ≤ M ≤ 8 earthquake data sets for the period of 50 years (that is, January 1, 1966 to December 31, 2015) in African and Western Asia region. It is bounded by latitude 40° S to 40° N and longitude 30° W to 60° E with the focal depth of 0–700 km. Seventy seven thousand, six hundred and ninety-six data points were presented for the analysis. The data used were extracted from earthquake catalog of Advanced National Seismic system via http://quake.geo.berkeley.edu/cnss/, an official website of the Northern California Earthquake Data Centre, USA. Each datum comprised the earthquake occurrence date, time of the earthquake occurrence, epicenter’s coordinates, focal depth and magnitude. The Gutenberg-Richter’s relationship being the longest observed empirical relationship in seismology, analysis of variance and time series were used to analyze the seismicity of the study area. Annual distributions of earthquake occurrence based on magnitude variations with the limit 0 ≤ M ≤ 8 were presented. The two constants a and b in the Gutenberg-Richter’s equation, magnitude of completeness (MC) adjusted R-Square and F-value for the period of 1966–1975, 1976–1985, 1986–1995, 1996–2005, 2006–2015, and the entire period of investigation ranging from 1966 to 2015 were determined so as to investigate the variations of these parameters on earthquake occurrence over time. The histograms of earthquake occurrence against magnitude of earthquakes for the selected years (1966–1975, 1976–1985, 1986–1995, 1996–2005, 2006–2015, and 1966–2015), and the decadal frequency distributions of earthquake occurrence were also plotted. The focal depth occurrence for each magnitude bins (0–0.9, 1–1.9, 2–2.9, 3–3.9, 4–4.9, 5–5.9, 6–6.9, 7–7.9, 8–8.9) were grouped into shallow, intermediate, and deep depths ranging from 0 to 70, 71 to 300, and 301 to 700 km as being used in seismology. The neural network analysis was also applied to the magnitude of the earthquake. The network uses a time series magnitude data as input with the output being the magnitude of the following day. If the nature of the earthquakes time series is stochastic, modeling and prediction is possible. The earthquake data sets presented in this article can further be adopted in the study of seismicity pattern, b-value using series of models, earthquake prediction and variations of earthquake parameters on African and/or Arabian plates. When this approach is integrated with other technique(s), it can provide insights to stability of African lithospehric plates especially the coastal region of Africa. Keywords: African plates, Arabian plates, b-value, Gutenberg-Richter’s model, Artificial neural network, Earthquake magnitudes, Focal depth, Seismic events, Seismographs, Time series, Tectonic stres

The properties of hydroxyapatite ceramic coatings produced by plasma electrolytic oxidation

Calcium phosphate coatings produced on the surface of Ti6Al4V by plasma electrolytic oxidation (PEO) using different concentrations of hydroxyapatite (HA) in a 0.12 M Na3PO4 (NAP) electrolyte solution was investigated. It was found that the amount of calcium phosphate particles infiltrated into the coating layer as well as the thickness and the surface roughness of the coating increased with increasing HA concentration. The porosity of the ceramic coatings indicated an inverse relationship with the concentration of HA particles dispersed in the NAP solution. The result also demonstrates that higher scratch adhesive strength was achieved using 1.5 g/L HA solution, producing a critical load of 2099 mN, while 0 g/L HA only produced a critical load of 1247 mN. The adhesion becomes independent of thickness when the concentration of HA exceeds 1.5 g/L. The failure of the coating was characterized by large periodic hemispherical chipping, while intermittent delamination was noticed with the coating embedded with HA particles. This study demonstrate the viability of using PEO to produce a thin layer of HA ceramic coating on Ti6Al4V suitable for biomedical applications