Sharifah Adzila

Doping Metal into Calcium Phosphate Phase for Better Performance of Bone Implant Materials

For many years calcium phosphate based materials have been used to create bone substitutes as alternatives to human transplant. Most calcium phosphate biomaterials are characterized by high biocompatibility and excellent ability to undergo varying degrees of resorbability. Numerous investigations have been made to study calcium phosphate ceramic materials as bone substitutes. This patent review however, focuses on metal-doped calcium phosphates produced by vari- ous methods for clinical applications. A variety of synthesis methods have been employed to produce metal-doped cal- cium phosphates and different methods may produce different final products and characteristics in terms of crystallinity, morphology and stoichiometry. There are many metal ions such as magnesium (Mg), strontium (Sr), manganese (Mn), iron (Fe), zinc (Zn) and silver (Ag) that have been doped successfully into calcium phosphates to enhance their mechani- cal and biological properties. These biomaterials can be served as scaffold for bone regeneration with adequate mechani- cal properties to restore bone defects and facilitate healing process. The significant improvement in certain metal-doped calcium phosphates in terms of physico-chemical, biological and mechanical properties has shown the relevance in the development of metal-doped HA for biomedical applications. This paper provides a review of doping of the most com- mon metals into calcium phosphate phase in order to optimize its performance as bone substitute materials. Some recent patents related to metal doped calcium phosphate ceramics are also reviewed.

Mechanochemical Synthesis of Nanosized Hydroxyapatite Powder and its Conversion to Dense Bodies

In this work, nanosized hydroxyapatite (HA) powder was synthesized via mechanochemical method by a dry mixture of calcium hydroxide Ca(OH)2 and di-ammonium hydrogen phosphate (NH4)2HPO4 powders. The effect of mechanochemical process on powder properties was investigated. Three rotation speeds of 170 rpm, 270 rpm and 370 rpm were chose with 15 hours milling time respectively. Characterization of nanopowders was accomplished by Fourier transform infra red (FTIR), X-ray diffraction (XRD) and nanosizer analysis. The green compacted powders with 200 MPa isostatically pressed were prepared and sintered in atmosphere condition at various temperatures ranging from 1150oC - 1350oC. The results showed that the rotation speed affected the obtained powders where the crystallite size was found increased with rotation speed (9 – 21 nm). In contrast, the particle size distribution decreased with rotation speed (322-192 nm). The sintering process has influenced the stability of powder by yielding TCP phase at a lower sintering temperature, 1150oC. However, powder synthesized at 370 rpm has showed a significant hardness, 5.3 GPa after compacted and sintered at 1250oC with the relative density of 95%. This phenomenon is believed to be related with the nanosize powder synthesized at high speed which has contributes the high strength of the sintered bodies.

Mechanochemical Synthesis of Hydroxyapatite Nanopowder: Effects of Rotation Speed and Milling Time on Powder Properties

Mechanochemical synthesis of two or more different precursors is a simple method to prepare metallic alloys, polymer and ceramic composite materials. This mechanical reaction based synthesis also has been employed to produce hydroxyapatite (HA) powder for bone implant application. In this present study, we employed mechanochemical method to synthesize hydroxyapatite nanopowder from dry mixture of calcium hydroxide (Ca (OH)2) and di-ammonium hydrogen phosphate [(NH4)2HPO4] powders. The effect of mechanochemical process on powder properties was investigated. Three rotation speeds of 170 rpm (M1), 270 rpm (M2) and 370 rpm (M3) were chose with 15 hours milling time respectively. The milling time at 370 rpm (M3) was extended to 30 hours (T1) and 60 hours (T2). Characterization of nanopowders were accomplished by Fourier transform infrared (FTIR), X-ray diffraction (XRD), nanosizer analysis, field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Rotation speed and milling time affected the obtained powders with nanocrystallite HA structure. The narrow peaks appeared with the incremental of crystallite size (9 – 21 nm) and crystallinity (21-59%) when the rotation speed was increased to 370 rpm (M3). However, particle size distribution (322-192 nm) was decreased with the rotation speed. Morphological evaluation indicated that the average particle size of resultant powder which consists of agglomerate crystals and irregular shapes reached about 17 - 36 nm. The as synthesized nanopowder showed that 370 rpm at 15 hours of milling is the suitable parameter to be applied for hydroxyapatite nanopowder synthesis in mechanochemical method.

Synthesis of hydroxyapatite through dry mechanochemical method and its conversion to dense bodies: preliminary result

Hydroxyapatite (HA) powder has been prepared through mechanochemical synthesis from a dry powder mixture of calcium hydroxide Ca(OH)2 and di-ammonium hydrogen phosphate (NH4)2HPO4. Three different rotation speeds of 170 rpm (M1), 270 rpm (M2) and 370 rpm (M3) were used in this method. The as synthesized powder analyzed by FTIR and XRD confirmed the formation of HA structure with nano crystallite size in all milling speeds. XRD results showed the wide broad peaks of HA powders narrowed and crystallinity increased (31.0-42.5%) when the milling speed was accelerated to 370 rpm. The powders were compacted using cold isostatic pressing at 200 MPa and then subjected to 1150 o C, 1250 o C and 1350 o C sintering. The sintered compacts were mechanically tested by Vickers microhardness indentation method. Powder synthesized at 370 rpm was found to have a significant hardness, 5.3 GPa obtained after 1250 o C sintering.

Mechanochemical Synthesis of Magnesium Doped Hydroxyapatite: Powder Characterization

In this study, the mechanochemical method was employed to synthesize hydroxyapatite (HA) and magnesium (Mg) doped hydroxyapatite (HA) powders. The effect of Mg2+ into the synthesized HA powder properties were investigated. Characterization of the synthesized HA and Mg doped HA at various concentrations (1% - 5% MgHA) were accomplished through X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses. nanosize of HA and Mg doped HA powders were successfully synthesized through the present method as indicated from the different peaks intensity and adsorption bands obtained in XRD pattern and FTIR respectively.

Assessment of Turbulence Model Performance Adopted Near Wall Treatment for a Sharp 90° 3-D Turning Diffuser

The primary aim of this paper is to assess the performance of k-e turbulence models by means of adopting various near wall treatments to simulate the flow within a sharp 90° 3-D turning diffuser. The Computational Fluid Dynamics (CFD) results were validated quantitatively and qualitatively with the experimental results (using Particle Image Velocimetry (PIV)). The standard k-e adopted curvature correction and enhanced wall treatment of y+ ≈ 1.2–1.7 appears as the best validated model, producing minimal deviation with comparable flow structures to the experimental cases.

PCL/PLA Polymer Composite Filament Fabrication using Full Factorial Design (DOE) for Fused Deposition Modelling

In this study, Polycaprolactone / Polylactice Acid (PCL/PLA) composite are used to fabricate filament wire with the specific diameter, which is in the range of 1.75 to 1.80 mm. Full factorial experimental design technique was used to study the main effects and the interaction effects between operational parameter which is (A) die temperature, (B) roller puller speed, (C) spindle speed and (D) inlet temperature. Besides that, there are two levels (-1 and +1) and the response are filament wire diameter. There are 16 numbers of runs and plus 8 centre points per blocks which makes the runs into 24 runs. From the experiment it shows that there are four factor that are significant effects on the filament wire diameter which is A, B, C and BC. The optimum parameter setting are also determined and there are 10 suggestions to achieve the target with different setting of parameter. The margin error for confirmation run is below than 15% when the parameter set at 6 Hz spindle speed, 4.99 rpm roller puller, 100.31 °C die temperature and 79.65 °C inlet temperature which can be noted that the confirmation run result is acceptable. The optimization parameter setting can use to continue in Fused Deposition Modelling (FDM). Filament wire from PCL/PLA are succesfully fabricated with acceptable diameter size and ready to be used for Fused Depotion Modelling process (FDM).

Characterization and Mechanical Analysis of PCL/PLA composites for FDM feedstock filament

In this research, characterization, and the mechanical properties of Polycaprolactone (PCL) and Polylactic Acid (PLA) composites with the objective of determining their suitability as biomaterials for an alternative composites material for Fused Deposition Modelling (FDM) was investigated. The percentage of PLA is varies from 10% to 50% by weight. The PCL/PLA composites were prepared by melting and mixing using Brabender Plastograph machine. The characterization of PCL/PLA composites was characterized using Fourier Transform Infrared (FTIR). Meanwhile, the mechanical properties were evaluated are the Tensile, Flexural and Impact. It demonstrate that by the addition of PLA it improve the mechanical properties of PCL and leads to a better processability of PCL/PLA composites. With the decrement of PLA content in PCL/PLA composites the Tensile Strength the Youngs Modulus and also the Impact Strength of the composites increased. The highest tensile strength was recorded at 10.00 Mpa and the Youngs Modulus was recorded at 118.26 Mpa. The highest Impact Strength was recorded at 1.33 J. However, the Flexural Strength and Flexural Modulus increased when the content of PLA decrease and it slightly drop when the content of PLA is at the 40%. The highest Flexural Strength and Flexural Modulus were recorded at 7.59 Mpa and 35.33 Mpa respectively. Overall it can be concluded that the PCL70PLA30 composites are the best formulation and it gives a better mechanical properties result.

Preparation and characterization of hydroxyapatite/sodium alginate biocomposites for bone implant application

In biomedical fields, synthetic scaffolds are being improved by using the ceramics, polymers and composites materials to avoid the limitations of allograft. Ceramic-polymer composites are appearing to be the most successful bone graft substitute in human body. The natural bones itself are well-known as composite of collagen and hydroxyapatite. In this research, precipitation method was used to synthesis hydroxyapatite (HA)/sodium alginate (SA) in various parameters. This paper describes the hydroxyapatite/sodium alginate biocomposite which suitable for use in bone defects or regeneration of bone through the characterizations which include FTIR, FESEM, EDS and DTA. In FTIR, the characteristi peaks of PO4−3 and OH− groups which corresponding to hydroxyapatite are existed in the mixing powders. The needle-size particle of hydroxyapatite/ alginate (HA/SA) are observed in FESEM in the range of 15.8nm-38.2nm.EDS confirmed the existence of HA/SA composition in the mixing powders. There is an endothermic peak whi...

Mechanochemical Synthesis of Hydroxyapatite Bioceramics through Two Different Milling Media

This work presents the wet mechanochemical synthesis of hydroxyapatite (HA) powder through two different milling mediums. The effect of milling mediums on powder properties was investigated. Two types of medium: water and ethanol were chosen with 370 rpm milling speed for 15 hours time. Characterization of synthesized powders was accomplished by X-ray diffraction (XRD) analysis. The green compacts were prepared and sintered in atmosphere condition at various temperatures ranging from 900oC - 1300oC. The mechanical and physical properties were evaluated under Vickers microhardness test and density measurement. Both of synthesis mediums yielded HA phases in the synthesized powders as detected by the peaks obtained in XRD analysis. Compacts synthesized in water medium (M1) showed a maximum density, 99% sintered at 1000oC and 1300oC. However, the hardness in water medium is closely similar to the ethanol medium as a function of sintering temperature where the maximum hardness was found in compacts synthesized in ethanol medium (M2) sintered at 1300oC (5.8GPa). The microstructure observed from SEM analysis was in line with the density obtained as the surface of sintered compacts synthesized in water medium (M1) contained less pores with large grain growth.