2015

A new E -plane filtering structure suitable for very high-power telecom satellite applications is presented. The conceived configuration exploits the design flexibility provided by cascading highly integrated step/stub resonators with pseudoelliptic frequency responses. Several design examples of filters and diplexers in Ku-, K-, and Q-band are reported and supported by experimental tests campaigns. The components have been designed with a full-wave 2-D spectral element method. Prototypes have been realized in aluminum clam-shell technology.

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency.

In order to develop ceria-stabilized zirconia (Ce-TZP) ceramics suitable for biomedical applications, composite materials should be developed. In this work, three different Ce-TZP-based composites were prepared by adding rounded α-Al2O3 grains and two kinds of elongated particles, SrAl12O19 and CeMgAl11O19. Composite powders were prepared through a surface coating route, which allowed a precise tailoring of chemical and phase composition as revealed by HRTEM. A limited cerium diffusion inside zirconia grains was revealed when CeMgAl11O19 was added to zirconia matrix.

In order to fulfill the clinical requirements for strong, tough and stable ceramics used in dental applications, we designed and developed innovative zirconia-based composites, in which equiaxial α-Al2O3 and elongated SrAl12O19 phases are dispersed in a ceria-stabilized zirconia matrix. The composite powders were prepared by an innovative surface coating route, in which commercial zirconia powders were coated by inorganic precursors of the second phases, which crystallize on the zirconia particles surface under proper thermal treatment.

Ceramic nanocomposites are attracting growing interest, thanks to new processing methods enabling these materials to go from the research laboratory scale to the commercial level. Today, many different types of nanocomposite structures are proposed in the literature; however, to fully exploit their exceptional properties, a deep understanding of the materials’ behavior across length scales is necessary. In fact, knowing how the nanoscale structure influences the bulk properties enables the design of increasingly performing composite materials.

Zirconia toughened alumina (ZTA) materials are frequently used in mechanical engineering and biomedical applications due to their enhanced toughness, strength and wear resistance compared to monolithic alumina. In this study, a submicron size alumina powder was modified via wet chemical route: the alumina particles surface was coated with zirconium chloride, to yield 10 vol% zirconia by subsequent thermal treatment. From this powder, several ZTA materials were produced by slip casting, sintered at different temperatures from 1475 to 1575 °C.

An Al2O3/5 vol%·ZrO2/5 vol% Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix.

In this work, the synthesis of RKKP bioactive glass composition by an aqueous sol-gel method is reported. A complete and systematic characterisation of the produced material was carried out. Characteristic functional groups were detected by Fourier transform infrared (FT-IR) spectroscopy, the thermal behaviour was investigated by simultaneous thermogravimetric and differential thermal analysis (TG-DTA), crystallisation kinetics and phase evolution were followed by X-ray diffraction (XRD) analyses.

Titanium aluminide alloys are good candidates for structural applications thanks to their low density and good balance of properties up to relatively high temperatures. However, their application is still limited by significant oxidation. Four γ-TiAl alloys with different content of aluminum and niobium were produced by electron beam melting: Ti-45Al-2Cr-2Nb, Ti-48Al-2Cr-2Nb, Ti-45Al-2Cr-8Nb, and Ti-46Al-2Cr-8Nb.