Thermogravimetry and differential thermal analysis have been used to study the resistance to the air oxidation of high-density samples of Ti
3
AlC
2
, Ti
2
AlC and Ti
2
Al(C
1−
x
N
x
) solid ...solutions. It has been shown that the Ti
3
AlC
2
samples are more stable than Ti
2
AlC and Ti
2
Al(C
1−
x
N
x
) solid solutions and as the nitrogen content of the solid solution increases to
x
= 0.75, the oxidation resistance decreases. The following characteristics have been exhibited by the material containing 89 wt % Ti
3
AlC
2
(the rest being Al
2
O
3
and TiC) having density 99% of theoretical: bending strength
R
bm
= 500 MPa, compressive strength
R
cm
= 700 MPa, fracture toughness
K
I
c
= 10.2 MPa·m
0.5
, hardness
HRA
= 70 GPa,
H
V
= 4.6 GPa, Young modulus = 149.4 ± 28.7 GPa. After sintering with diamonds or cBN (50 wt %) at 5.5–7.7 GPa and 1350–1960°C for 0.07–1.0 h the Ti
3
AlC
2
MAX phase decomposes to form TiC and TiAl or TiB
2
and a thin layer of Al
4
C
3
forms at the interface with diamond. The Al
4
C
3
decomposition in a composite material due to the interaction with the air moisture results in the crack initiation along the diamond perimeter, which brings about the material fracture in 1–2 weeks. It has been found that the Ti
3
AlC
2
powder is efficient for polishing natural and synthetic jewelry crystals and competitive in polishing efficiency and quality with ACM 2/1 grade diamond.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A structural Auger spectroscopy study of MgB sub(2) thin ( similar to 140 nm) oxygen-containing polycrystalline films produced by magnetron sputtering and 99% dense MgB sub(2) bulks synthesized at 2 ...GPa allows us to conclude that j sub(c) of MgB sub(2) depends to a high extent on the amount and distribution of oxygen in the material matrix. j sub(c) reached 7.8-2.7 MA/cm super(2) below 1T at 20 K in the films and 0.3-0.9 MA/cm super(2) (depending on the boron used) in the bulks. The higher j sub(c) in MgB sub(2) thin films can be associated with finer oxygen-enriched Mg-B-O inclusions and their higher density in the film structure compared to the bulk. Calculations of the total electron density of states (DOS) in MgB sub(2), MgB sub(1.75)O sub(0.25), MgB sub(1.5)O sub(0.5) and MgBO showed that all the compounds are conductors with metal-like behaviour. The DOS is even higher in MgB sub(1.5)O sub(0 5) than in MgB sub(2) and the binding energy is similar. So, the experimentally found presence of some dissolved oxygen in MgB sub(2) does not contradict its high SC performance. The introduction of a high amount of oxygen into the MgB sub(2) structure does not dramatically reduce the material's T sub(c) and allows obtaining highjc as observed in our MgB sub(2) films and bulks.
High-resolution
in situ X-ray powder diffraction applying synchrotron radiation has been used to examine the occurring crystal structures and the thermal behaviour of the solid solution Pr
1−
x
La
x
...AlO
3 in a wide temperature range 12–1173
K. At room temperature all studied samples in the whole composition range of the pseudo-binary system PrAlO
3–LaAlO
3 adopt a rhombohedral perovskite structure. The phases Pr
1−
x
La
x
AlO
3 with
x=0.56 and 0.66 undergo a sequence of three phase transitions
I2/
m↔
Imma↔
R3¯
c↔
Pm3¯
m. For the sample with
x=0.24 a series of four (
I4/
mcm↔I2/
m↔
Imma↔
R3¯
c↔
Pm3¯
m) phase transitions has been observed and for
x=0.86 two transformations were apparent (
I2/
m↔
R3¯
c↔
Pm3¯
m). Crystal structure parameters for all studied compositions Pr
1−
x
La
x
AlO
3 have been determined. Based on
in situ powder diffraction and DTA/DSC data, the phase diagram of the pseudo-binary system PrAlO
3–LaAlO
3 has been constructed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Виконано екологічне оцінювання сучасного стану якості води річки Гапа на основі класифікації якості поверхневих вод суші за трьома блоками показників: сольового складу, трофо-сапробіологічних ...(еколого-санітарних) показників та показників специфічних речовин токсичної дії. Визначено величину інтегрального (екологічного) індексу. Встановлено, що поверхневі води р. Гапа відповідають ІІ класу 3 категорії якості води та характеризуються, як «добрі» за станом і «досить чисті» за ступенем чистоти.
The volume pinning force, F p(max), increases with increasing synthesis or sintering pressure (0.1 MPaa2 GPa) in materials prepared at high temperature (1050 degree C) while it stays practically ...unchanged in those prepared at low temperature (800 degree C). The position of F p(max) can be shifted to higher magnetic fields by: (1) increasing the manufacturing pressure or decreasing the temperature (2) additions (Ti, SiC, or C, for example), and (3) in-situ preparation. Grain boundary pinning (GBP) dominates in materials prepared at low temperatures (600a800 degree C), while high-temperature preparation induces strong point pinning (PP) or mixed pinning (MP) leading to outstanding properties. In materials produced by spark plasma sintering (SPS), the position of F p(max) is higher than expected for both grain boundary and point pinning. The distribution of boron and oxygen in MgB2 based material, which can changed by additions or the preparation conditions, significantly affects the type and strength of pining.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Phase diagram of the PrAlO3-GdAlO3 system Basyuk, T; Berezovets, V; Trots, D ...
European Powder Diffraction Conference; August 2010, Darmstadt, Germany,
2015, Volume:
1
Book Chapter
Nanostructural superconducting MgB 2 -based materials contain a great quantity of O, which gives grounds to assign them to Mg-B-O compounds. The quantity of O in these materials is not an obstacle ...for attaining high critical current density (j c =10 6 A/cm 2 in 1 T at 20 K), upper critical magnetic fields (B c2 (0 K)= 42 T, B c2 (22 K)= 15 T) and the fields of irreversibility (B ρ (0 K)= 32.5 T, B ρ (18.5 K)= 15 T). Our recent studies have shown that by changing manufacturing conditions (temperature, pressure, adding Ti, SiC) is possible to affect oxygen and boron distribution in the structure of Mg-B-O ceramic materials and purposefully change the type of pinning, superconducting properties, thus varying their behavior in magnetic fields.
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