The biomaterials most widely used for hard tissue implants (in orthopaedics, dental implants, and skull bones) are Ti-based biomaterials and Ti coated with hydroxiapatite (HAP). Because metallic biomaterials have some disadvantages as reported previously (mainly due to the difference between the mechanical characteristics of the human bone and the metallic implant), biocomposites have become an interesting solution to improve the hard tissue implants for the human body. This article presents the experimental results concerning the processing of HAP/Ti biocomposites by powder metallurgy technology. The initial powder mixture consists of HAP powder particles (<200 nm) reinforced with 100 μm titanium particles in the ratio 3:1 (wt%). Two different sintering routes are used: spark plasma sintering (SPS) at (1000-1100) • C for 10 or 20 min and two-step sintering (TSS) with the first step at 900 • C/1 min, followed by the second step at 800 • C for 300, 600, 900 or 1200 min. The ball-on-disc dry wear tests are developed using, as a moving counterpiece, DIN 100Cr6 tool steel balls (6 mm diameter; Ra < 3.2 μm; HRc 60-64; density >7.6 g/cm 3 ). The tribological behaviour of the processed biocomposites is appreciated on the basis of the coefficient of friction and wear rate, corroborated with the wear track depth. The final remarks of this article underline the potential use of SPS technology to obtain HAP/Ti biocomposites with comparable wear properties as similar materials processed by more complex technologies. Also, TSS allows processing HAP/Ti materials comparable with the SPS-ed ones from the point of view of the wear behaviour, except for the dwell time of the second step, which is critical for the wear behaviour.
The purpose of these researches was to determine the effect of silicon carbide particles (SiCp) proportion and the effect of some process parameters (temperatures and times of aging) on characteristics of Al-Cu/SiCp composites obtained by P/M route. The age-hardened composites and un-reinforced alloys solution treated at 515 ± 5°C, maintaining time 360 minutes, quenched in water and artificial aging at 150-190o C during respectively 240-720 minutes/ furnace cooled, were tested from hardness and microstructural point of view. The effect of SiCp proportion in matrix during cold compaction was observed on densification curves of all experimental powders mixtures Al-4Cu/ (5, 10, 15 and 20) wt.%SiC. The composites were analyzed using optical and electron microscopy (including ESEM-Enviromental Scanning Electron Microscopy), in terms of shape and size of grains, pores, ceramic particles, second phases and precipitates.
There are several innovations to be found in the inland waterway sector. European Federation of Inland Ports EFIP defines trends in Inland Ports and Current EU Policy Developments in 2014. The trends include urban logistics, biomass transports, as well as the transportation of heavy cargo. The Transport White Paper of 2011 targeted for freight transport to shift from road to rail and IWW by more than 50% by 2050. The described technological and organizational as well as logistic trends are linked and evaluated regarding their impact onto model variables of the different transport models and tools employed. Technological advancements have an impact on organizational and logistics issues and cannot be discussed independently from these topics. The analysis is performed for each trend individually and does not take into account the different maturities and interdependencies among the different trends evaluated.
The nanostructured biocomposites with hydroxyapatite (HAP) matrix reinforced by titanium (Ti), processed by two steps sintering (TSS) route in argon atmosphere, provide excellent wear behaviour when they are elaborated in specific sintering parameters. The wear tests, developed in steel ball-on-disc dry conditions, show low wear rates about 2x10-4 [mm3/Nm] when the biocomposites are processed at 750...8000oC for 450...600 min. in comparison with high wear rates 7x10-4 [mm3/Nm] in 700...7500oC for 300 min. as TSS parameters. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis outline the structural features that explain this wear behaviour.
The solid waste of Rapana thomasiana seashells both from domestic activities and natural waste on seashore can be used to obtain viable products for medical applications. However, conventional technologies applied for sintering the materials require massive energy consumption due to the resistance heating. Microwave heating represents an advanced technology for sintering, but the stability of the process, in terms of thermal runaway and microwave plasma arc discharge, jeopardizes the quality of the sintered products. This paper aims to present the results of research focused on viable heating technology and the mechanical properties of the final products. A comparative analysis, in terms of energy efficiency vs. mechanical properties, has been performed for three different heating technologies: direct microwave heating, hybrid microwave heating and resistance heating. The results obtained concluded that the hybrid microwave heating led to final products from Rapana thomasiana solid waste with similar mechanical properties compared with resistance heating. In terms of energy efficiency, the hybrid microwave heating was 20 times better than resistance heating.
The inland navigation sector makes a significant contribution to the growth of the global economy as well as to climate change due to pollutants emitted by diesel engines. NOx emissions are very high in port areas where, due to traffic, the ships run at idling regimes. Selective catalytic reduction (SCR) represents one of the most suitable technologies, in terms of cost effectiveness, but does not perform well if the temperature during vessel operation is lower than 180 °C. Microwave technology can support preheating of the ceramic core of SCR in order to increase the temperature towards the optimal interval for the best NOx reduction. Research has focused on coupling a magnetron head to a SCR device in order to evaluate to what extent the technology can meet the requirements of Stage V of the European Directive related to NOx emissions. Measurements of NOx emitted have been performed on engines with 603.5 kW nominal power and 1500 rpm that operate at a lower engine speed (700–1200 rpm) and output power (58–418 kW). The values recorded for emissions using microwave heating of ceramic core of SCR have decreased by 89% for a constant load of engine and idling engine speed.
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