Performance of ZrB2–Cu composite as an EDM electrode

The low wear resistance of electrodes like Cu, Cu alloys and graphite is a major problem for electrical discharge machining (EDM) operation. Here an attempt has been made to develop a metal matrix composite (ZrB2–Cu) to get an optimum combination of wear resistance, electrical and thermal conductivity. The ZrB2–Cu composite have been developed by adding different amounts of Cu and tested as a tool material at different process parameters of EDM during machining of mild steel. The ZrB2–40 wt.% Cu composite shows more metal removal rate (MRR) with less tool removal rate (TRR) than commonly used Cu tool. But the diameteral overcut and average surface roughness are found to be lesser in case of Cu tool than composite tool. The tools and workpiece surfaces are analyzed by scanning electron microscope (SEM)/EDS and XRD technique

Big data analytics in healthcare: a systematic literature review

The current study performs a systematic literature review (SLR) to synthesise prior research on the applicability of big data analytics (BDA) in healthcare. The SLR examines the outcomes of 41 studies, and presents them in a comprehensive framework. The findings from this study suggest that applications of BDA in healthcare can be observed from five perspectives, namely, health awareness among the general public, interactions among stakeholders in the healthcare ecosystem, hospital management practices, treatment of specific medical conditions, and technology in healthcare service delivery. This SLR recommends actionable future research agendas for scholars and valuable implications for theory and practice

Orbital interactions and chemical reactivity of metal particles and metal surfaces

A review is presented with 101 refs. on chem. bonding to metal surfaces and small metal particles demonstrating the power of symmetry concepts to predict changes in chem. bonding. Ab-initio calcns. of chemisorption to small particles, as well as semiempirical extended Hueckel calcns. applied to the study of the reactivity of metal slabs are reviewed. On small metal particles, classical notions of electron promotion and hybridization are found to apply. The surroundings of a metal atom (ligands in complexes, other metal atoms at surfaces), affect bonding and reactivity through the prehybridization they induce. A factor specific for large particles and surfaces is the required localization of electrons on the atoms involved in the metal surface bond. At the surface, the bond energy is found to relate to the grou8p orbital local d. of states at the Fermi level. The use of this concept is extensively discussed and illustrated for chemisorption of CO and dissocn. of NO on metal surfaces. A discussion is given of the current decompn. schemes of bond energies and related concepts (exchange (Pauli)-repulsion, polarization, charge transfer). The role of non-orthogonality of fragment orbitals and of kinetic and potential energy for Pauli repulsion and (orbital) polarization is analyzed. Numerous examples are discussed to demonstrate the impact of those concepts on chem. bonding theor

Interpenetrated Magnesium–Tricalcium Phosphate Composite: Manufacture, Characterization and In Vitro Degradation Test

Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test.Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test

Application of new tool material for electrical discharge machining (EDM)

In EDM, Cu and graphite are commonly used as tool materials. The poor wear resistance is the drawback of these tools. In the current study, an attempt has been made to develop a ZrB2-Cu composite as an EDM tool material to overcome this problem. Initially, the ZrB2 powder is prepared by self-propagating high-temperature synthesis (SHS) technique and synthesized powder is mixed with different amounts of Cu powder. Dense composite is developed by a pressureless sintering at 1250°C. The composites are tested as tool material at different EDM process parameters during machining of mild steel. The ZrB2-40 wt% Cu composite shows highest metal removal rate (MRR) with significant tool removal rate (TRR) than other composites. The performance of ZrB2-40 wt% Cu composite is compared to conventional Cu tool. The composite shows higher MRR with less TRR than Cu tool but it shows more average surface roughness and diameteral overcut than Cu tool

Double SHS of ZrB2 powder

Production of ZrB2 powder through self-propagating high-temperature synthesis (SHS) from ZrO2, Mg and H3BO3 mixture often leads to incomplete conversion. A new technique, called DSHS (double SHS) has been developed, wherein the reaction product of the first SHS is mixed with calculated amounts of Mg and H3BO3 powder and subjected to a second SHS. The ZrB2 powder produced by DSHS technique yields increased conversion. The NaCl is used as a diluent during SHS to control the particle size of the product. The average particle size of SHS ZrB2 powder found to be 75–125 nm in range, which decrease to 25–40 nm after DSHS

Sintering behaviour of ultra-fine titanium diboride powder prepared by self-propagating high-temperature synthesis (SHS) technique

A systematic study on the sintering behaviour of titanium diboride (TiB2) powder of different particle sizes prepared by a SHS route is carried out in the temperature range of 1973–2173 K. The decrease of particle size increases the densification of the TiB2 powder compacts and a maximum densification of 93% of the theoretical density is achieved after sintering at 2173 K. The activation energies for sintering are observed to vary within 76 to 85 kJ/mol for the different particle sizes that indicate the boron diffusion in Ti as the possible rate-controlling process for sintering. The time dependent variation of densification under isothermal condition indicates the surface diffusion or vapour phase condensation mechanisms operative in the system. The microstructure and microhardness of different sintered samples reflect the densification behaviour of sintered pellets