This paper presents a study on graphene-reinforced Al2O3-SiCw ceramic composites and the relationship between graphene oxide (GO) loading and the resulting mechanical and electrical properties. ...Well-dispersed ceramic-GO powders were fabricated using a colloidal processing route. Dense composites were obtained via spark plasma sintering, a technique that has the ability to reduce GO to graphene in situ during the sintering process. The mechanical properties of the sintered composites were investigated. The composite with only a small amount of graphene (0.5 vol.%) showed the highest flexural strength (904±56MPa), fracture toughness (10.6±0.3MPa·m1/2) and hardness (22±0.8GPa) with an extremely good dispersion of graphene within the ceramic matrix. In addition to these exceptional mechanical properties, the sintered composites also showed high electrical conductivity, which allows the compacts to be machined using electrical discharge machining and thus facilitates the fabrication of ceramic components with sophisticated shapes while reducing machining costs.
Abstract
The problems of micro-arc oxidation of titanium alloy parts Ti-6Al-4V produced by electron beam melting technology were considered. The phase composition, thickness and roughnessof the ...obtained coating have been evaluated.
Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powder of tantalum (20 vol%) as starting materials. Composites ...showed a fracture toughness value of 16 MPa m1/2 mainly due to crack bridging of the elastic–plastic deformations of ductile metal particles. This fracture toughness was accompanied by a simultaneous enhancement in damage tolerance and fatigue resistance of 3Y-TZP/Ta composites.
Besides exceptional mechanical properties, SPS sintered 3Y-TZP/Ta composites also showed the electrical conductivity suited to wire electrical discharge machining (WEDM). Therefore, they are suitable to be produced in mechanically performant, complex shape components with the required tolerance while reducing machining costs. The aim of this work was the study of the electrical properties of the materials as well as the characteristics of the machining process and the machined surfaces influence on the bending strength of composites. The results show that workpieces can be machined with high accuracy and without a drop in mechanical strength.
•Fully dense and homogeneous ceramic-metal composites were successfully fabricated.•Composites showed outstanding value of fracture toughness of 16 MPa m1/2.•3Y-TZP/Ta composites suited to wire electrical discharge machining (WEDM).•WEDM cut specimens showed insignificant degradation in the bending strength.
The electrochemical formation of ceramic-like coatings on D16 aluminum alloy was carried out using microarc oxidation method in phosphate (1.5 g/L NaOH + 9 g/L Na2SiO3 + 3 g/L Na3PO4) and molybdate ...(5 g/L NaOH + 30 g/L Na2SiO3 + 5 g/L (NH4)6Mo7O24) electrolytes. White and black ceramic-like coatings with thickness of 200-300 microns were obtained in phosphate and molybdate electrolytes, respectively.
The aim of this work was the comparative estimation of the efficiency of different variants of local ozone therapy in experimental burn wound. We conducted the experiments on 45 white Wistar rats ...being randomized for three groups. Every rat got contact thermal trauma (III degree; 20 bsp) of dorsal body surface on the area 20%. Rats of the first group received a Levomecol treatment of wound, animals of the second group were locally treated by ozonized oil, and the third group rats received a combination of ozone and oxygen gas mixture intracutaneously, and the wounds were treated with Levomecol locally. The character and particularities of post-traumatic regeneration were studied by histological investigation. Local treatment with reactive oxygen species at an early period after burning is revealed to lead to more pronounced manifestation of reparative processes in burn wounds (production of granulation tissue, epidermis regeneration) than when applying Levomecolointment, and that is accompanied by more pronounced initial manifestation of scab rejection. Applying reactive oxygen species in ointment compositions at these stages of treatment with the conjuncture of infected wounds does not contribute marked initiation of reparative processes and can even force the inflammation processes.
Large Al2O3–SiCw and Al2O3–SiCw–TiC composites disks (150mm diameter) were prepared in this work by using the spark plasma sintering technique. The main physical and mechanical properties of these ...composites were measured in different disk zones in order to test out the homogeneity of the sintering process. It has been found that the incorporation of TiC as reinforcing phase to the Al2O3–SiCw composite, improved densification, mechanical strength and hardness. This result was analyzed in terms of SEM microstructure observations showing that the presence of TiC inhibited the alumina grain growth.
Commercially pure titanium powder was modified by a two-step procedure involving attrition milling and subsequent coating with yttria by sol–gel. Lamellar titanium particles with a high aspect ratio ...were obtained by mechanical grinding. The existence of an yttria layer covering the milled titanium particles (shell–core structure) was corroborated by X-ray photoelectron spectroscopy. Zirconia/titanium (25vol% titanium) compact specimens were processed by a wet route using the modified titanium powder, spark plasma sintered, and then characterized in terms of mechanical strength and ageing. A reinforcement mechanism arises from the special shape and disposition of the metallic particles. The stable Y2O3 barrier prevents excessive formation of side products at the metal–ceramic interface. Hence, our innovative procedure allows to develop a new ceramic–matrix composite in the interesting zirconia/titanium system with improved mechanical properties and controlled ageing compared to the composites made with commercially pure titanium.
The effects of inhalation of singlet oxygen mixture, dry and humidified ozone-oxygen mixture, and ozonated oils on heart rate variability as well as on the rate and control mechanisms of ...microcirculation were examined in rats. The most optimal were the responses of systemic and regional hemodynamics to inhalation of the gas produced by a generator of singlet oxygen and humidified ozone-oxygen mixtures. Singlet oxygen stabilized the cardiac rhythm and augmented microcirculation via activation of “internal” (endothelial and neurogenic) regulatory mechanisms.
Alumina silicon carbide composites have been traditionally considered as one of the most interesting materials to be used for structural applications at high temperatures. The SiC nanoparticle ...content and its distribution in the alumina matrix are parameters of extreme importance controlling the operating deformation mechanisms at high temperature. Then, the processing of tailor-made microstructures is still challenging in order to find an optimal material.
Full dense alumina-nano silicon carbide composites were prepared by using Spark Plasma Sintering at relative low temperatures and sintering times. In this work, different composite microstructures with different SiC content and type of starting alumina powder were obtained by increasing the sintering temperature and dwell time. Different ratios of inter/intra granular alumina positions of SiC particles were controlled by a suitable selection of starting raw materials, composition and sintering conditions.
The anodic plasma-electrolyte modification of titanium alloy VT1-0 and low-carbon steel 20 for improvement their properties was carried out in nitrogen- and boronitrogen-containing electrolytes, ...respectively. Tribological and corrosion-protective properties of formed surface layers was investigated. The data of technical tests showing increase in the operational life of threaded fastening pair subjected toto plasma-electrolyte boronitriding are presented.
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