Abstract: By using a combination of new technologies together with an unconventional use of different types of materials, specific mechanical properties and structures of the material can be achieved. Some possibilities are enabled by a combination of powder metallurgy in the preparation of a metal matrix with dispersed stable particles achieved by mechanical alloying and hot consolidation. This paper explains the thermomechanical properties of new generation of Oxide Dispersion Strengthened alloys (ODS) within three ranges of temperature with specified deformation profiles. The results show that the mechanical properties of new ODS alloys are significantly affected by the thermomechanical treatment.
Abstract: The alumosilicate ceramics with mullite crystalline phase are used in various branches of science and technique. The mullite refractory ceramics with high porosity serve as a heat insulator and as a constructional materials [1], [2]. The purpose of the work was to sinter high porosity ceramic and to increase the quantity of mullite phase in this mullite, mullite-corundum ceramics. Two types of compositions were prepared at during the experiment. The first type is compositions with commercial alumina and silica oxides. The second type is from mixing these oxides with 10, 20 and 30 wt.%. of kaolin. In all samples the Al2O3 and SiO2 were in 2.57:1 ratio, because that was conformed to mullite stechiometric compositions (3Al2O3.2SiO2). The types of alumina oxides were α-Al2O3 (d50=4µm) and γ-Al2O3 (d50=80µm). Ratios of α-: γ-Al2O3 were (1:1) or (1:3). The porous materials were prepared by slip casting of suspension of raw materials. The aluminium paste (0.18 wt.%) was used as a pore former. Water content in the suspensions was 26-47 wt.%. Pore formation occurred as a result of hydrogen formation in chemical reaction between aluminium paste and water [2]. The samples were sintered at the temperature of 1650°C and 1750°C for one hour. The increasing amount of kaolin, α-: γ-Al2O3 at the ratio (1:3) and sintering at the highest temperature raised the quantity of mullite phase. The mullite phase began to dominate over the corundum phase.
Abstract: Two novel hydrodesulfurization (HDS) catalysts:
FeN4/C and FeN2/C, were prepared using an impregnation-pyrolysis
method. The two materials were investigated as catalysts for
hydrodesulfurization (HDS) and hydrodearomitization (HDA) of
model compounds. The turnover frequency of the two FeN catalysts
is comparable to (FeN4/C) or even higher (FeN2/C) than that of
MoNi/Al2O3. The FeN4/C catalyst also exhibited catalytic activity
toward HDA.
Abstract: The paper relates to a catalyst, comprising copperchromium
spinel, coated on carrier γ-Al2O3. The effect of preparation
conditions on the active component composition and activity
behavior of the catalysts is discussed. It was found that the activity of
carbon monoxide, DME, formaldehyde and methanol oxidation
reaches a maximum at an active component content of 20 – 30 wt. %.
Temperature calcination at 500oC seems to be optimal for the γ–
alumina supported CuO-Cr2O3 catalysts for CO, DME, formaldehyde
and methanol oxidation. A three months industrial experiment was
carried out to elucidate the changes in the catalyst composition
during industrial exploitation of the catalyst and the main reasons for
catalyst deactivation.
It was concluded that the CuO–Cr2O3/γ–alumina supported
catalysts have enhanced activity toward CO, DME, formaldehyde
and methanol oxidation and that these catalysts are suitable for
industrial application. The main reason for catalyst deactivation
seems to be the deposition of iron and molybdenum, coming from the
main reactor, on the active component surface.
Abstract: The crystallization kinetics and phase transformation
of SiO2.Al2O3.0,56P2O5.1,8CaO.0,56CaF2 glass have been
investigated using differential thermal analysis (DTA), x-ray
diffraction (XRD), and scanning electron microscopy (SEM). Glass
samples were obtained by melting the glass mixture at 14500С/120
min. in platinum crucibles. The mixture were prepared from
chemically pure reagents: SiO2, Al(OH)3, H3PO4, CaCO3 and CaF2.
The non-isothermal kinetics of crystallization was studied by
applying the DTA measurements carried out at various heating rates.
The activation energies of crystallization and viscous flow were
measured as 348,4 kJ.mol–1 and 479,7 kJ.mol–1 respectively. Value of
Avrami parameter n ≈ 3 correspond to a three dimensional of crystal
growth mechanism. The major crystalline phase determined by XRD
analysis was fluorapatite (Ca(PO4)3F) and as the minor phases –
fluormargarite (CaAl2(Al2SiO2)10F2) and vitlokite (Ca9P6O24). The
resulting glass-ceramic has a homogeneous microstructure, composed
of prismatic crystals, evenly distributed in glass phase.