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Recently, ion-substituted hydroxyapatite (HAP) is gaining popularity due to the additional advantages obtained by the presence of other elements. In the current work, zinc-substituted nano-hydroxyapatite powder (Zn-HAP) has been synthesized through wet chemical synthesis process. The synthesized nano-powders were analyzed by scanning electron microscopy and X-ray diffractometry (XRD). From the results, it was evident that the produced powders were in the nano-level and without impurities. Furthermore, the XRD analysis of heated powders (1000 °C) revealed the presence of β-TCP, which was an indication that the produced powder was calcium deficient due to the substituted Zn. The results were also compared with pure HAP. Using XRD data, Rietveld refinement was carried out to assess the parameters of the unit cell and positions of ions in the Zn-HAP. The synthesized Zn-HAP powders were tested for antimicrobial properties by exposing them to two different bacterial strains; Sporosarcina pasteurii(S. pasteurii) and Escherichia coli(E. Coli). From the results, Zn-HAP was observed with a higher potential toward inhibiting the growth of the bacterium compared with that of pure HAP.

Ion-substituted hydroxyapatite (HAP) offers several advantages compared with pure HAP. Since the calcium amount is relatively lower compared with the stoichiometric ratio of pure HAP, the resulting calcium deficiency in ion-substituted HAP leads to higher degradation in the physiological environment. Therefore, ion-substituted HAP has promising applications in the biomedical industry, particularly in drug delivery systems. In the present work, strontium-substituted HAP (Sr-HAP) was prepared by wet chemical precipitation method. The powders were characterized by X-ray diffraction (XRD) method and scanning electron microscopy (SEM). The crystallite size of Sr-HAP was calculated as ˜?9 nm. Furthermore, structural characterization of Sr-HAP was done by Rietveld refinement and the substituting atomic sites and occupancies were obtained. The atomic positions occupied by the substituted Sr atoms in the calcium (Ca) atomic positions in the hcpunit cell were identified. The unit cell parameters of synthesized Sr-HAP were precisely calculated. The synthesized Sr-HAP powders were compacted and the antimicrobial properties were assessed by using Escherichia coli(E. coli) and Sporosarcina pasteurii(S. pasteurii). From the antimicrobial studies, it was understood that Sr-HAP has shown lower viability of these strains compared with pure HAP which is an indication of antimicrobial properties of Sr-HAP.

The tribological characteristics of Electroless Ni-P and Ni-P/D (diamond) coatings were studied and analysed against AISI 52100 steel ball under dry reciprocating sliding conditions. Low and High Phosphorus Ni-P alloy coatings were deposited on steel substrate by Electroless deposition technique. Diamond particles were successfully reinforced into Ni-P matrix to produce Ni-P/D composite coatings. All coatings were subjected to heat treatment at 400°. The micro-hardness, surface features and elemental composition of the coatings was analysed. The surface morphology of Ni-P and Ni-P/D coatings is detailed. Presence of dia mond particles in Ni-P matrix was confirmed by EDS analysis. Dry sliding wear tests showed a significant enhancement in wear resistance of Ni-P/D composite coatings compared to Ni-P coatings. Experimental results indicate that combined effect of diamond particles reinforcement and heat treatment play a crucial role in modifying the surface characteristics and tribological performance of the Ni-P coatings.

AZ91 Mg alloy was considered and friction stir processing (FSP) was adopted to achieve grain refinement to investigate the effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds. Super saturated AZ91 Mg alloy was obtained after FSP and the grain refinement was achieved from (166.5±8.7) µm to (21.7±13.5) µm. Surprisingly, hardness reduced for FSP AZ91 Mg alloy (88.95±6.1) compared with AZ91 alloy (108.2±15.6), which was attributed to the reduced secondary phase. However, the mean cutting force for FSP-treated (FSPed) AZ91 Mg alloy was marginally increased. The edge damage of the drilled holes was lower for FSPed AZ91 Mg alloy compared with unprocessed AZ91 Mg alloy. Hence, it can be understood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achieved in machining of AZ91 Mg alloy.

WC-Co coatings were produced on SS 410 plates and subjected to heat treatment at different temperatures (from 300 to 900 °C). The microstructural studies and structural analysis of the coatings before and after heat treatment were carried out by electron microscopy and X-ray diffraction analysis. From the Vickers indentation method, hardness values were measured, and higher microhardness was observed for the coatings after heat treatment. The sample that was heat-treated at 750 °C exhibited the highest hardness. From the sliding wear test results, the wear resistance of the coatings was observed as increased after the heat treatment. However, it was found that the heat-treated coatings at 600 °C exhibited higher wear resistance. Cracking and fracture were the dominant wear mechanisms observed for the heat-treated coatings, along with coating delamination and oxidation.

Titanium (Ti) suffers from lack of ability to establish strong bonding with the local tissue when used as implant material. Higher level of bone-implant interactions promotes osseointegration which is essentially desirable in artificial joint replacements and dental implants. Hence, for such targeted applications, transforming the surface of Ti implants to exhibit more bioactive nature in addition to antimicrobial properties is one of the prime research fields in materials engineering. Several surface treatments and coatings which alter the surface microstructure and chemical composition have been widely adopted to functionalize the Ti surface to impart special properties suitable for biomedical usage. The current review aims to present the recent developments and the state of the art in developing surface functionalized Ti through different processing routes with a brief discussion on the limitations and the potential of these techniques.