Cold spray synthesized hydroxyapatite-magnesium bioimplants physico-chemical behaviour, adherence and environmental compatibility

'^^^^'^'^mple and modified cold spray processwas developed In which hydroxyapatlte powderwas coated onto pure magnesium substrates preheated to 350°C or 550-C and ground to either 240 gnt or 2000 grit surface roughness, with standoff distances of 20 mm or 40 mm. The procedure was repeated five and ten times Afractional factorial design (2^') was applied to elucidate the process factors that significantly affected the thickness, nanohardness and elastic modulus of the coating sample. The overlaid method analysis was employed to determine trade off optimal values from multiple responses which is thickness, nanohardness and elastic modulus of the coating. Then, steepest method was used to reconfirm and relocate tee op ^ domain. The maximum mechanical properties of tee coating were determined at 30mm standoff distance, 926 4grit surface roughness and 456'C substrate heating temperature which accommodate t eop imum coating of 49.77pm thickness, 462.61 MPa nanohardness and 45.69 GPa elastic modulus. e hydroxyapatlte coatings did not show any phase changes at 550"C. Atomic force mlaoscopy revealed a uniform coating topography and scanning electron microscopy revealed good bonding ^ layers and tee substrates. The biodegradable study suggested that the bone-like apatite layer formed tee surface of the coatings at 1140 minutes may promote the bone bonding with living tissues and mcmase the ] longevity of coatings. The mass loss experiment concluded teat coated sample shows abetter bioachvity compare to uncoated sample. The adhesion test revealed teat reduction of bond strength comes mostly from tee continuation of chemical dissolution of coatings. At 1140 minutes of Immersion, tee bond ^t^^ng hwas 40 Mpa which satisfied the requirement for blolmplant application. The accelerated corrosion test concluded teat tee HAP coating remarkably protect and prevent from tee corrosion In tee corrosive environment. RU Gran

In-situ formation of NbC in mechanically alloyed Cu-Nb-C At different temperatures

In this study, a high-energy ball milling called mechanical alloying was applied to synthesis in- situ copper-based composite reinforced with niobium carbide particle. Cu, Nb and graphite powder mixture were mechanically alloyed for 32 h in a planetary ball with composition of Cu-11.77 %Nb-1.52 %C. The samples of the as-milled powder were compacted at 300 MPa to produce 10 mm diameter pellets. In order to investigate the effect of temperature on the carbide formation, the green compact were sintered in an argon atmosphere at different sintering temperature i.e. 600, 700, 800 and 900 °C. The change of phase and microstructure of the sintered compact were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The result from XRD shows that the NbC phase was not detected at sintering temperatures lower than 900 °C due to not having enough energy to initiate the reaction of Nb and C in Cu matrix. Cu shows an increase in the crystallite size while the internal strain decreases with increasing sintering temperature. The crystallite size of NbC was unresolved since the NbC peak is poorly defined at lower sintering temperature. From EDX analysis, higher oxide content was observed in Cu

Effect of alloying elements on properties of aluminide-base intermetallic material developed via powder metallurgy route.

The present study deals with the effect of additive element on structure and properties of Fe-Al intermetallic. FeAl-based intermetallic alloys with chromium or molybdenum addition were fabricated by s intering of mechanically alloyed powders

Comparison of Two Powder Processing Techniques on the Properties of Cu-NbC Composites

An in situCu-NbC compositewas successfully synthesized fromCu,Nb, and C powders using ball milling and high pressure torsion (HPT) techniques. The novelty of the new approach, HPT, is the combination of high compaction pressure and large shear strain to simultaneously refine, synthesize, and consolidate composite powders at roomtemperature.The HPTed Cu-NbC composite was formed within a short duration of 20 min without Fe contamination from the HPT’s die. High porosity of 3–9%, Fe and niobium oxidations, fromgrindingmedia and ethanol during ball milling led to low electrical conductivity of the milled Cu-NbC composite. The electrical conductivity of the HPTed Cu-NbC composite showed a value 50% higher than that of milled Cu-NbC composite of the same composition

Enhancing properties of fe-cr-alumina composites prepared by powder metallurgy / Saidatulakmar Shamsuddin ... [et al.]

Fe-based matrix composites have shown the potential for use as advanced materials for technological applications. In this study metal matrix composites (MMCs) of Fe-Cr –alumina were fabricated by powder metallurgy (PM). The effect of alumina content on the physical and mechanical properties of the composites was investigated. Scanning Electron Microscope (SEM) showed a homogeneous distribution of alumina in the matrix. Energy Dispersive X-ray (EDX) displayed the presence of Fe, Cr and alumina in the composites. Optimum condition of the composites was examined by evaluation of the parameters such as density, porosity, shrinkage, hardness, wear resistance and compressive strength. Results showed that addition of alumina greater than 5 wt. % decreased the density but increased porosity. Hardness and wear resistance of the composites increased with increasing alumina content to 20 wt. %. However, the compressive strength showed optimal value at 5 wt. % alumin

Studies on alumina dispersion-strengthened copper composites through ball milling and mechanical alloying method

Oxide dispersion-strengthened copper has the ability to retain most of its properties at elevated temperatures. Among various processes, powder metallurgy route is ideal because of its efficiency in dispersing fine oxide particles. In this study, copper-alumina composites is produced through powder metallurgy route whereby copper powder, which is the matrix, was mixed with alumina powder, which act as reinforcement. Powder mixtures with different compositions of alumina (2.5wt%, 5wt%, 7.5wt% and 10wt%) were prepared. The mixtures were then mixed either by (a) blending process for 45 minutes in a ball mill or (b) mechanical alloying for 45 minutes in a planetary mill. The mixture was then compacted at 200 MPa and sintered under argon atmosphere at 950°C for 1 hour. Results showed that mechanical alloying has produced Cu-Al2O3 composite with better hardness and lower electrical conductivity compared to those prepared by ball milling metho

Fabrication of in situ Fe-NbC composite by mechanical alloying

In this research we investigated the in situ formation mechanism of NbC in mechanically alloyed Fe-Nb-C mixture. Powders of iron, niobium and graphite with a composition Fe-20 %Nb was milled in a planetary mill for various milling times (i.e. 5, 10, 15 and 20 h) to investigate the influence of this variable on phase formation and properties of composite. The mixture was cold pressed and sintered at 1300°C for 1 h. Only phase of the initial raw materials was observed after milling, whilst NbC phase was detected after sintering. Increasing the milling time resulted in an increase in crystallite size and strain energy, which is beneficial for hardness and density improvement

In Situ Tungsten Carbide Formation in Nanostructured Copper Matrix Composite Using Mechanical Alloying and Sintering

In this study, an in situ nanostructured copper tungsten carbide composite was synthesized by mechanical alloying (MA) and the powder metallurgy route. The microstructure and phase changes of the composite were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Tungsten carbide phases (WC and W2C) were only present after MA and combination of sintering. Higher energy associated with a longer milling time was beneficial for the formation of WC. Formation of W2C and WC resulted from internal refinement due to heavy plastic deformation in the composite. The solubility of the phases in the as-milled and sintered composite was described by the changes of the lattice parameter of Cu. Chemical analysis of the surface of a composite of W 4f and C 1s revealed that the increased defects introduced by MA affect the atomic binding of the W-C interaction

Effect of dissolution times on compressive properties and energy absorption of aluminum foam

Aluminum foams were fabricated by sintering dissolution process (SDP) using sodium chloride (NaCl) as space holder. The compositions of space holder, used in this study were 40 and 60 wt. % with different dissolution times; 1, 2 and 3 h. The effect of different dissolution times on compressive behavior and energy absorption of foams were evaluated. The result showed that by increasing space holder and dissolution times, energy absorption capability increases. For aluminum foam contains 60 wt. % NaCl, longer dissolution times resulted in thinner cell wall and cell structure become more unstable which lead to lower plateau region