Wan Sharuzi Wan Harun

A review of hydroxyapatite-based coating techniques: Sol-gel and electrochemical depositions on biocompatible metals.

New promising techniques for depositing biocompatible hydroxyapatite-based coatings on biocompatible metal substrates for biomedical applications have continuously been exploited for more than two decades. Currently, various experimental deposition processes have been employed. In this review, the two most frequently used deposition processes will be discussed: a sol-gel dip coating and an electrochemical deposition. This study deliberates the surface morphologies and chemical composition, mechanical performance and biological responses of sol-gel dip coating as well as the electrochemical deposition for two different sample conditions, with and without coating. The review shows that sol-gel dip coatings and electrochemical deposition were able to obtain the uniform and homogeneous coating thickness and high adherent biocompatible coatings even in complex shapes. It has been accepted that both coating techniques improve bone strength and initial osseointegration rate. The main advantages and limitations of those techniques of hydroxyapatite-based coatings are presented. Furthermore, the most significant challenges and critical issues are also highlighted.

Evaluation of ABS patterns produced from FDM for investment casting process

The paper presents the investigation of the Acrylonitrile Butadiene Styrene (ABS) pattern produced from Fused Deposition Modeling (FDM) for use as a pattern for an investment casting process. The investigations were carried out to establish the physical and collapsibility characteristics of an H-shape pattern produced from two different construction methods, i.e. hollow and solid, using rapid prototyping FDM2000 machine. Surface roughness, dimensional accuracy and distortion were evaluated to establish the physical characteristics of the pattern constructed. Results on surface roughness showed no significant variation between hollow and solid constructed patterns. As for dimensional accuracy, hollow patterns produced better accuracy compared to solid patterns. However, the result on distortion shows that hollow constructed patterns experienced 33.11% higher than solid constructed patterns. For collapsibility investigation, shell investment casting mould built from the two different pattern construction methods were fired to a temperature ranging from 300°C to 600°C. The moulds were weighted at a predetermine temperature intervals to establish the collapsibility characteristic of the patterns. ABS (P400) was found feasible to be used as an investment casting pattern material. Hollow pattern construction proved to be more viable than solid pattern construction in terms of dimensional accuracy, mould cleanliness, pattern collapsibility and no mould cracking at all temperatures.

A review of biocompatible metal injection moulding process parameters for biomedical applications

Biocompatible metals have been revolutionizing the biomedical field, predominantly in human implant applications, where these metals widely used as a substitute to or as function restoration of degenerated tissues or organs. Powder metallurgy techniques, in specific the metal injection moulding (MIM) process, have been employed for the fabrication of controlled porous structures used for dental and orthopaedic surgical implants. The porous metal implant allows bony tissue ingrowth on the implant surface, thereby enhancing fixation and recovery. This paper elaborates a systematic classification of various biocompatible metals from the aspect of MIM process as used in medical industries. In this study, three biocompatible metals are reviewed-stainless steels, cobalt alloys, and titanium alloys. The applications of MIM technology in biomedicine focusing primarily on the MIM process setting parameters discussed thoroughly. This paper should be of value to investigators who are interested in state of the art of metal powder metallurgy, particularly the MIM technology for biocompatible metal implant design and development.

Characteristic studies of collapsibility of ABS patterns produced from FDM for investment casting

Abstract A study was made of the collapsibility phenomenon of acrylonitrile butadiene styrene (ABS) P400 patterns tabulated using fused deposition modelling technique that will be used for investment casting process. There are two types of specimens: hollow (or hatching) and solid H shape ABS patterns. Results showed that the hollow patterns offered better results than the solid patterns in terms of mould cracking and internal mould cleanliness at temperature 300–500°C. However, all patterns demonstrated similar behaviour at temperatures of 550 and 600°C whereby no cracks were present and total decomposition of ABS was recognised. The results were strongly related to a fluidity phenomenon of the ABS material in conjunction with elevated temperature.

Critical Evaluation on Structural Stiffness of Porous Cellular Structure of Cobalt Chromium Alloy

In order to improve the stiffness characteristics of orthopedic devices implants that mimic the mechanical behavior of bone need to be considered. With the capability of Additive layer manufacturing processes to produce orthopedic implants with tailored mechanical properties are needed. This paper discusses finite element (FE) analysis and mechanical characterization of porous medical grade cobalt chromium (CoCr) alloy in cubical structures with volume based porosity ranging between 60% to 80% produced using direct metal laser sintering (DMLS) process. ANSYS 14.0 FE modelling software was used to predict the effective elastic modulus of the samples and comparisons were made with the experimental data. The effective mechanical properties of porous samples that were determined by uniaxial compression testing show exponential decreasing trend with the increase in porosity. Finite element model shows good agreement with experimentally obtained stress-strain curve in the elastic regions. The models prove that numerical analysis of actual prosthesis implant can be computed particularly in load bearing condition

Investigation of Mechanical Properties for Open Cellular Structure CoCrMo Alloy Fabricated by Selective Laser Melting Process

Orthodontic implants have been a major focus through mechanical and biological performance in advance to fabricate shape of complex anatomical. Designing the part with a complex mechanism is one of the challenging process and addition to achieve the balance and desired mechanical performance brought to the right manufacture technique to fabricate. Metal additive manufacturing (MAM) is brought forward to the newest fabrication technology in this field. In this study, selective laser melting (SLM) process was utilized on a medical grade cobalt-chrome molybdenum (CoCrMo) alloy. The work has focused on mechanical properties of the CoCrMo open cellular structures samples with 60 %, 70 %, and 80 % designed volume porosity that could potentially emulate the properties of human bone. It was observed that hardness values decreased as the soaking time increases except for bottom face. For compression test, 60 % designed volume porosity demonstrated highest ultimate compressive strength compared to 70 % and 80 %.

Electrochemical Deposited Nickel Nanowires: Influence of Deposition Bath Temperature on the Morphology and Physical Properties

This paper investigates the influence of the electrolytic bath temperature on the morphology and physical properties of nickel (Ni) nanowires electrochemically deposited into the anodic alumina oxide porous membrane (AAO). The synthesis was performed using nickel sulfate hexahydrate (NiSO4.6H2O) and boric acid (H3BO3) as an electrolytic bath for the electrochemical deposition of Ni nanowires. During the experiment, the electrolyte bath temperature varied from 40°C, 80°C, and 120°C. After the electrochemical deposition process, AAO templates cleaned with distilled water preceding to dissolution in sodium hydroxide (NaOH) solution to obtain free-standing Ni nanowires. Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDX) and X-ray Diffraction (XRD) analysis were employed to characterize the morphology and physical properties of the synthesized Ni nanowires. Finding reveals the electrodeposition bath temperature significantly influences the morphology and physical properties of the synthesized Ni nanowires. Rougher surface texture, larger crystal size, and longer Ni nanowires obtained as the deposition bath temperature increased. From the physical properties properties analysis, it can be concluded that deposition bath temperature influence the physical properties of Ni nanowires.

Effect of heat treatment on mechanical properties and microstructure of selective laser melting 316L stainless steel

Selective Laser Melting (SLM) has been one of the preferred Additive Manufacturing process to fabricate parts due to its merits in terms of design freedom, lower material waste and faster production when compare to the conventional manufacturing processes. However, due to the thermal gradient experienced during the process, the parts are exposed to the residual stress that leads to parts distortion. This work presents the effect of heat treatments on the micro-hardness of 316L stainless steel parts. In current study, SLM has been employed to fabricate 316L stainless steel compacts. Different heat treatments of 650°C, 950°C, and 1100°C for 2 hours were applied on the compacts. Hardness test were performed on the as-built and heat-treated compacts. The relationship between the microstructures and micro-hardness were discussed in this paper. The results revealed that the micro-hardness of the as-built compacts is between 209.0 and 212.2 HV, which is much higher than the heattreated compacts.

Study of Solvent Debinding Parameters for Metal Injection Moulded 316L Stainless Steel

Solvent debinding is one of a crucial stage in Metal Injection Moulding (MIM) process. This process begins with the removal of the soluble binder components by using solvents such as heptane or hexane. In solvent debinding process, unsuccessful to achieve maximum binder removal will cause a defect to the compact such as crack and swelling. So to have an optimum solvent debinding parameters are very important to improve the quality of the compact. Optimisation of solvent debinding process parameters for MIM of Stainless Steel 316L has been testified in this study. Gas atomised stainless steel 316L powder was mixed with a multicomponent binder in a twin blade mixer at a temperature of 150 °C for 90 minutes. The feedstock was successfully injected at the temperature of 150 °C. The green compacts were kept in n-heptane for eight different debinding times ranging between 30 to 240 minutes at temperatures of 40, 50, 60 and 70 °C to remove the primary binder components. From the result, the optimum temperature and time for solvent debinding were recorded at 60 °C and 240 minutes. Solvent debinding temperature and time give a significant effect on the rate of paraffin wax removal.

Effect of Sintering Temperature on Physical Properties & hardness of CoCrMo alloys fabricated by metal injection moulding process

Metal Injection Moulding (MIM) process is one of the Powder Metallurgy manufacturing techniques utilised to produce Cobalt Chromium Molybdenum (CoCrMo) compacts. The objective of this study is to determine physical properties and hardness of CoCrMo alloy compact sintered at three different sintering temperature at the similar soaking time. At the beginning, sample were fabricated by using Injection Moulding machine. Cobalt Chrome Molybdenum (CoCrMo) metal powder was selected for this study. A morphological study was conducted using optical microscope (OM) and micro-Vickers hardness testing. From the result obtained, it shows upward trend either on the hardness or physical properties of the samples. CoCrMo sintered compact become harder and volume of pores on surface become less due to the increase on sintering temperature. However, effect of increasing sintering temperature shows significant shrinkage of the sample, beginning losses in dimensional accuracy. It is discovered that a little change in sintering temperature gives significant impact on the microstructure, physical, mechanical of the alloy.