196,068 research outputs found
Silicon carbide based thermal spray powder, method of preparation and use
No full textA silicon carbide-based thermal spray powder contains at least one boride chosen from zirconium boride, titanium boride and hafnium boride. The powder is prepared by mixing and aggregation of powders containing the compounds in question. Said thermal spray powder is used to deposit, via the plasma spraying technique, a silicon carbide-based coating on a metallic or non-metallic substrate. The figure shows the X-ray crystallogram obtained, for a silicon carbide-based powder, according to the invention, after thermal spraying. The substantial identity of this crystallogram with the one obtained prior to thermal spraying demonstrates that the silicon carbide has been deposited on the substrate without decomposing
Silicon carbide-based thermal spray powder, method of preparation and use
No full textA silicon carbide-based thermal spray powder contains at least one boride chosen from zirconium boride, titanium boride and hafnium boride. The powder is prepared by mixing and aggregation of powders containing the compounds in question. Said thermal spray powder is used to deposit, via the plasma spraying technique, a silicon carbide-based coating on a metallic or non-metallic substrate. The figure shows the X-ray crystallogram obtained, for a silicon carbide-based powder, according to the invention, after thermal spraying. The substantial identity of this crystallogram with the one obtained prior to thermal spraying demonstrates that the silicon carbide has been deposited on the substrate without decomposing
Process for the realisation of ceramic matrix composite layers and related composite material
No full text
Process for the manufacturing of ceramic-matrix composite layers and related composite material
No full textHigh pressure reactive plasma spray synthesis of titanium nitride based coatings
No full textThe term thermal spray covers a wide range of fabrication methods for surface engineering applications. A very promising thermal spray,process involves the production of protective coatings or freestanding components by reactive plasma spray (RPS) techniques. Using reactive gases such as nitrogen or methane it is possible to synthesise hard nitride and carbide phases in reactive metals such as Ti, Cr, and Al. In this investigation RPS was used to produce composite titanium nitride/titanium coatings. Commercially pure titanium powders were used as raw materials and sprayed in a nitrogen atmosphere at up to 300 kPa. The process was carried out by means of a controlled atmosphere plasma spray system, allowing spraying in the pressure range 10-400 kPa. The effects of chamber pressure, plasma gas composition, and spraying distance on the scope of the expected reactions were evaluated. Phase analysis, measurements of nitrogen content and Vickers microhardness, and metallographic investigation of the as sprayed coatings revealed that titanium hard phases were synthesised during spraying and became embedded in the titanium matrix. High pressure significantly enhanced nitride formation (Ti2N, TiN, TiN1-x) in the titanium matrix. Microhardness values up to 1433 HV0.3 were obtained, with maximum nitrogen content of about 11.1 wt-%. Studies on sprayed particles showed that TiN was the dominant phase formed during flight, suggesting that diffusion processes play an important role in the substrate. Compared with pure titanium deposits, coatings produced by RPS are much harder and have better tribological properties
Do mergers and acquisitions create shareholder value in the infrastructure and utility sectors? Analysis of market perceptions
No full textThrough an analysis over a 20-year period from 1997 to 2017 for a global sample of listed infrastructure
companies, 80% of which were utilities, this study shows that target companies’ Cumulative Average Abnormal
Returns (CAARs) are positive and statistically significant, while acquirer firms earn positive but not statistically
significant CAARs. The results obtained must be viewed in light of the restructuring that has distinguished the
last 20 years by strongly modifying the infrastructure environment and facilitating the diffusion of mergers and
acquisitions (M&A). Our results support the financial reasonableness and potential efficiency of M&A transactions
in the infrastructure and public utility sectors, with specific reference to target companies
Mechanical properties of ceramic matrix composite for high temperature applications obtained by plasma spraying
No full textNose and wing leading edges for future generations space vehicles will withstand very high temperature in an oxidizing environment. UHTC (Ultra High Temperature Ceramics) materials are very promising candidate materials for such applications. An innovative, proprietary methodology was developed to produce, by plasma spraying deposition, a ceramic composite containing SiC particles (25 wt%) dispersed in a ZrB2 matrix. With such a technique both coatings and self standing parts were fabricated. In the present paper, the results of mechanical characterisations, carried out on self standing samples, are presented. Tensile and bending properties were determined by mechanical tests on as sprayed samples and on samples exposed at high temperature (2173 K) in oxidising conditions. Experimental results clearly evidenced the possibility to use the plasma spraying technology and suggest that the so fabricated ZrB2-SiC material is suitable to be adopted as protective coating
Titanium matrix reinforced composites produced by H.I.P. of plasma sprayed preforms
No full textThe present work has been focussed on the fabrication of long fibre reinforced titanium composites by hot isostatic pressing (HIP) of plasma sprayed preforms. Silicon carbide long fibers were used together with two different metallic matrices, the first being a Ti-6Al-2Sn-4Zr-2Mo alloy and the second a Ti-4.5Al-3V-2Mo-2Fe alloy also named SP700. All the spraying trials were performed by using a Controlled Atmosphere Plasma Spraying equipment (CAPS), allowing deposition processes also in the high pressure range. After optimisation of the plasma spraying procedure, on the basis of results obtained with preliminary spraying trials carried out according to a DOE methodology composite multilayers were fabricated by HIP with different comibinations for the process parameters temperature/time/applied pressure, in the range 850-940°C, 30-45 min, 1200 bar They were then qualified by microstructural investigations and tensile testing at room and high temperature (up to 600°C). Obtained results are reported and discussed with particular reference to differences evidenced for the two titanium matrices
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