Jerzy J . Sobczak

For the first time, experimental data on the high-temperature interaction of liquid Mg with pure Ag are presented. The study was performed by the sessile drop method and capillary purification procedure. The test was carried out under isothermal conditions at 720 °C in a protective atmosphere of Ar + 5 wt.% H2. The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). Under the used conditions, immediately after contact with the Ag substrate, liquid Mg drop showed a good wetting (θ0 ~ 65°) followed by fast spreading over the substrate in subsecond time to form the final contact angle of θf ~ 31°.SEM/EDS analysis showed that θf is apparent because of a deep crater (200 μm) formed in the substrate under the drop by the dissolution of Ag in liquid Mg. SEM/EDS observations of complex structural transformations in the Mg/Ag couple due to high-temperature contact and subsequen...

Graphene-based aerogels (GA) have a high potential in the biomedical engineering field due to high mechanical strength, biocompatibility, high porosity, and adsorption capacity. Thanks to this, they can be used as scaffolds in bone tissue engineering, wound healing, drug delivery and nerve tissue engineering. In this review, a current state of knowledge of graphene (Gn) and graphene oxide (GO) aerogels and their composites used in biomedical application is described in detail. A special focus is paid first on the methods of obtaining highly porous materials by visualizing the precursors and describing main methods of Gn and GO aerogel synthesis. The impact of synthesis parameters onto aerogel microstructure and porosity is discussed according to current knowledge. Subsequent sections deal with aerogels intended to address specific therapeutic demands. Here we discuss the recent methods used to improve Gn and GO aerogels biocompatibility. We explore the various types of GA reported t...

The wetting behavior of liquid magnesium drop on pure tungsten substrates was investigated, for the first time, with the sessile drop method combined with non-contact heating and capillary purification of a Mg drop from a native oxide film. A specially designed apparatus dedicated to the investigation of the high-temperature interaction of dissimilar materials was used. The comparative experiments were performed under isothermal conditions at temperatures of 700 °C and 740 °C using two atmospheres: Ar + 5 wt.% H2 and pure Ar, respectively. During high-temperature tests for 180 s, the images of the Mg/W couples were recorded with CCD cameras (57 fps) from two directions of observation. The solidified drop/substrate couples were subjected to structural characterization using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Under the applied measurement conditions, liquid Mg revealed non-wetting behavior on W substrates (a contact angle θ >...

This paper discusses some theoretical aspects of the design of ultralight materials. Potential appli-cation of syntactic foams in the fabrication of composites lighter than air is also analyzed. Carbon allotropic forms (fullerenes, colossal carbon tubes) and some non-carbon matters are considered as components of ultralight composites. Calculations for the size of fullerenes, the number of carbon atoms in their structure and thickness of reinforcing phase are presented. It is concluded that 3D carbon molecules (fullerenes) and colossal carbon tubes are the most promising components for design of ultralight metallic materials which can be lighter than air. Key words: ultralight materials, composites, syntactic foams, carbon allotropic forms Streszczenie W artykule omówiono wybrane teoretyczne aspekty projektowania ultralekkich materiałów kompozy-towych. Przeanalizowano potencjalne zastosowanie pian syntektycznych w produkcji kompozytów lżejszych od powietrza. Uwzględniono alotropowe ...

Popioły lotne jako faza zbrojąca kompozytów metalowych na osnowie stopów metali lekkich Cz. 3. Wpływ składu chemicznego na charakterystyczne temperatury topliwości węglowych popiołów lotnych Fly ash as a reinforcement of light metal matrix composites Part 3. The influence of a chemical composition on characteristic fusibility temperatures of coal fly ashes

Reduction in CO2 emissions from coal-fired power plants is one of the major challenges in order to decrease global warming effect. In energy sector, the aim to reduce CO2 emission can be achieved by increasing the operating temperature (and pressure) of water steam system, which results in an increase in overall coal fired power plant efficiency. Currently the main components of coal fired power plants are made from the materials designed years ago; to meet harsh eco criteria such materials are not suitable for harsh conditions of modern coal-fired power plant. Subcritical power stations are main contributor in CO2 emission globally, with high CO2 emission and low efficiency ~ 37 %. The next-gen coal-fired power plants have potential to reach 55% efficiency, taking into account, that 1% increase in absolute efficiency results in as much as 3% reduction in CO2 emissions, 55 % of CO2 lower emission achieved. Modern, advanced coal fired power stations operating under Ultra Super Critic...

The sessile drop method was adopted to investigate the effect of multiple re-melting and casting of metal matrix composite on the structural stability of metal-ceramic slurry. Commercial aluminum matrix composite made of the A359Al alloy reinforced with about 20 vol. % Al2O3 particles was produced by DURALCAN and next re-melted and recast ten times using two casting methods, i.e. conventional gravity casting and squeeze casting. The samples taken from all composite ingots produced after every cycle of re-melting and re-casting were used for high temperature tests at a temperature of 850°C for 30 min, under vacuum conditions. Both direct observations of the behavior of composite samples placed on alumina substrates during their contact heating and at the test temperature as well as the detailed structural characterization of solidified droplets have shown high structural stability of the metalceramic slurry, irrespective of the number of re-melts and type of casting process used afte...

Właściwości temperaturowe popiołu lotnego są ściśle skorelowane ze składem chemicznym i proporcjami głównych związków chemicznych, wchodzących w skład materiału odpadowego. Przeprowadzone w pracy ujęcie statystyczne danych otrzymanych w trakcie prowadzonych analiz temperaturowych wykazało dużą korelację temperatur charakterystycznych od składu chemicznego, zwłaszcza w przypadku temperatur topnienia i płynięcia dla popiołów o wysokiej zawartości tlenku krzemu i tlenku glinu. Duża ilość zgromadzonych danych doświadczalnych pozwoliła na wiarygodne i potwierdzone w badaniach wyznaczenie wzorów matematycznych, opisujących charakterystyki temperaturowe w funkcji udziału danego pierwiastka w składzie chemicznym.

This study shown possibilities of Rapid Prototyping techniques (RP) and metal casting simulation software (MCSS), including non inertial reference systems. RP and MCSS have been used in order to design and produce essential elements for artificial heart. Additionally it has been shown possibilities of Fused Deposition Modeling (FDM) technique and DodJet technology using prototyped elements of rotodynamic pump. MAGMASOFT® software allowed to verify the cast kit heart valves model. Optical scanner Atos III enabled size verification of experimental elements supplied by rapid prototyping together with metal casting elements. Due to the selection of ceramic materials and assessment of molten metal – ceramic reactivity at high temperatures together with pattern materials selection model it was possible to design, manufacture a ceramic mould for titanium based alloys. The casting structure modification has been carried out by means of high isostatic pressure technique (HIP). The quality as...

... odwzorowaniu kształtu i powierzch-ni, co pozwala na ograniczenia niezbędnej obróbki wiórowej i wykańczającej [12]. ... Zaprezentowana powyżej technologia wytwarzania kompozytów zbrojonych cenos-ferami pozwala na otrzymywanie lekkiego materiału konstrukcyjnego o ...

This chapter deals with the concept of graded material and main technologies for their production. The technologies for metallic graded materials are divided into two general groups. A sequence of eighth basic production methods is discussed in more details. I.1 Materials of Graded Structure The idea of Functionally Graded Materials (FGMs) was substantially advanced in the early 1980’s in Japan, where this new material concept was proposed to increase adhesion and minimize the thermal stresses in metallic-ceramic composites developed for reusable rocket engines [1]. Meanwhile, FGMs concepts have triggered world-wide research activity and are applied to metals, ceramics and organic composites to generate improved components with superior physical properties [2]. Depending on the application and the specific loading conditions, varying approaches can be followed to generate the structure gradients. Consequently, coatings have been deposited by different techniques involving physical v...

An attempt to develop a mathematical model for the simultaneous growth of the gas pore and the solid phase in gasar technology was offered in the paper “A theoretical study of Gasarite eutectic growth”. Unfortunately the paper incorporates mistakes which have led to erroneous results and incorrect conclusions. In order to rectify this, the most important ones are analyzed by

ABSTRACT High temperature investigation of wetting behavior and interface formation during interaction of dense polycrystalline Y2O3 substrates with liquid Ni (99.95%) and its alloys NiCo10, NiCr10, NiW10, NiAl12, Inconel 740 (IN740) and Haynes 282 (H282) was performed by a sessile drop method. Specially developed procedure was used for in situ opening of the metal/ceramic interface at the test temperature allowing pushing a metal drop to another position on a substrate directly during wettability test. The results show that the contact angle on Y 2 O 3 substrate decreases in the following order: NiW10(121°)>NiCr10(117°)>NiCo10(115°)>NiAl12(114°)>IN740(104°)>Ni(95°)>H282(67°). Other findings are: 1) substrate recrystallization in the vicinity of triple line with NiCo10, NiW10 and NiAl12 drops, 2) interfacial failure in IN740/Y 2 O 3 ; 3) failure in ceramic in H282/Y 2 O 3 ; 4) mixed failure in NiW10/Y 2 O 3 and NiAl12/Y 2 O 3 ; 4) colorization (green) of the substrate surface near Cr-containing drops (NiCr10, IN740, H282) related with the formation of Cr 2 O 3-rich layer; and 5) segregation of Al, Cr and Mo into interfacial region of H282/Y 2 O 3.

The microstructural characteristics of aluminium matrix AK12 composites containing of fly ash particles (precipitator), obtained by gravity and squeeze costing techniques, pitting corrosion behaviour and corrosion kinetics are presented and discussed. It was found that: (1) in comparison with gravity casting, squeeze casting technology is advantageous for obtaining higher structural homogeneity with minimum possible porosity levels, good interfacial bonding and

Functionally graded materials, including their characterization, properties and production methods are a new rapidly developing field of materials science. The aims of this review are to systematize the basic production techniques for manufacturing functionally graded materials. Attention is paid to the principles for obtaining graded structure mainly in the metal based functionally graded materials. Several unpublished results obtained by the authors have been discussed briefly. Experimental methods and theoretical analysis for qualitative and quantitative estimation of graded properties have also been presented. The article can be useful for people who work in the field of functionally graded structures and materials, and who need a compact informative review of recent experimental and theoretical activity in this area.

The nature very often demonstrates “smart” solutions of specific problems of biosphere, which allow meeting contradictory requirements for materials and constructions. Porous structure can be found in many biological objects (plants and animals) where combination of strength and lightness are necessary. Nowadays a lot of porous materials are designed and utilized in engineering constructions and machines. The majority of them are produced by special processing of liquid metals and alloys. Gasars are relatively new class of porous materials, which are object of enlarging investigations and applications. Firstly such materials are obtained in Ukraine by V. I. Shapovalov about 25 years ago and used in Russian automotive, oil and space industries. The name “gasar” is abbreviation of Russian words and means “gas reinforced”. In 1993 Shapovalov reserved the rights in USA by Patent No. 5,181,549. During the last decade of previous century Prof. H. Nakajima and coworkers from Osaka Universi...

ABSTRACT Wetting behavior of liquid Sn (99.99%) on graphene coated Cu substrate was investigated by the sessile drop method using two testing procedures: 1) classical contact heating (CH) of a couple of materials; 2) capillary purification (CP) allowing non-contact heating accompanied with squeezing the Sn droplet through a hole in an alumina capillary. The tests were performed in vacuum (p < 1.80 ×10-6 mbar) at 360 °C for 300 s. The images of Sn/substrate couples were recorded by high-resolution high-speed CCD camera. The results of this study evidenced that graphene layer is transparent for liquid Sn and after 300 s interaction, it forms the contact angles (θ) similar to those on pure Cu substrates, both in CH (θ = 59°) and CP (θ = 32°) tests. However, with liquid Sn, apparently the same effect of graphene wetting transparency is more complicated than that with water and it is caused by different mechanism, most probably, accompanied with reconstruction of the graphene layer.