Structural Features of Niobium Carbide Disperse Particles in the Structure of Heat-Resistant Alloys Based on Fe–25Cr–35Ni System

2018 ◽  
Vol 9 (6) ◽  
pp. 1035-1043
Author(s):  
S. Yu. Kondratiev ◽  
E. V. Sviatysheva ◽  
S. N. Petrov
2012 ◽  
Vol 23 (08) ◽  
pp. 1240001 ◽  
Author(s):  
V. ALVIN SHUBERT ◽  
STEVEN P. LEWIS

Niobium carbide nanocrystals of ~1:1 stoichiometry have recently been observed for particle sizes ranging from Nb4C4 to Nb50C50 . Infrared (IR) spectroscopic measurements show that a new band of IR vibrational modes appears with increasing particle size at Nb9C9 . Using density-functional theory, we show that the vibrational modes in the new band involve structural features present only in nanocrystals with three or more atomic layers in every direction. The Nb9C9 nanocrystal is right at this structural threshold.


2002 ◽  
Vol 12 (4) ◽  
pp. 331-344 ◽  
Author(s):  
Patrick J.B Edwards ◽  
Geoffrey B Jameson ◽  
Kate P Palmano ◽  
Lawrence K Creamer

2021 ◽  
Vol 22 (4) ◽  
pp. 678-693
Author(s):  
G. P. Dmitrieva ◽  
T. S. Cherepova ◽  
T. V. Pryadko

This article represents the stages of the creation of new serial wear-proof and heat-resistant (at temperatures up to 1100 °C) cobalt–Nb-carbide cast eutectic alloys of the KhTN (XTN) grade at the G.V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, comparing them by their main properties, and use in aircraft engine engineering.


2019 ◽  
Vol 60 (11-12) ◽  
pp. 739-744 ◽  
Author(s):  
D. V. Masaylo ◽  
A. A. Popovich ◽  
V. Sh. Sufiyarov ◽  
A. V. Orlov ◽  
A. I. Shamshurin

2017 ◽  
Vol 254 (4) ◽  
pp. 191-209
Author(s):  
S.Yu. Kondratyev ◽  
E.V. Sviatysheva ◽  
G.P. Anastasiadi ◽  
M.A. Danilova

2016 ◽  
pp. 76-82 ◽  
Author(s):  
E. A. Lukina ◽  
◽  
S. V. Ovsepyan ◽  
E. A. Davydova ◽  
M. V. Akhmedzyanov ◽  
...  

2021 ◽  
Vol 2 ◽  
pp. 5-15
Author(s):  
Yu. A. Bondarenko ◽  
◽  
M. Yu. Kolodyazhnyy ◽  
V. A. V. A. ◽  
◽  
...  

The scientific, technical and technological aspects in the field of creating new high-temperature materials for the hot tract parts of gas turbine engines (GTE) with operating temperatures exceeding those existing in the GTE are considered. Investigated more refractory metal materials to create new high-temperature alloys used in the manufacture of working and nozzle blades and other parts of promising gas turbine engines based on Co – Cr, Pt – Al, Nb – Si, Mo – Si – B systems. In Co – Cr alloys, heat resistance is mainly ensured by hardening the Co matrix, including dispersed precipitates of the carbide phase (TaC) and the boride phase Cr2B. In alloys of the Pt – Al system, due to the doping of Cr, Al, Ti, Re ... and precipitates of the coherently embedded Pt3Al phase. In eutectic alloys of the Nb-Si system, this is due to complex hardening of the Nb solid solution and Nb5Si3 silicide, as well as the natural compositional structure. In Mo – Si – B alloys, high strength is achieved by doping a-Mo solid solution and the formation of intermetallic phases Mo3Si, Mo5SiB2, carbides Mo2C, TiC. Compositions were selected, analysis of their smelting methods was carried out, including directed crystallization, which provides a natural compositional structure, mechanical properties at room and high temperatures, oxidation resistance were evaluated, structural features were investigated, information was provided on technological equipment and the possibility of obtaining parts in various ways. It is shown that, depending on the composition of the selected matrix, the working temperature of heat-resistant alloys can increase to 1300 – 1500 °C, which significantly exceeds the existing nickel heat-resistant alloys. It is concluded that the materials under study are promising for use in aircraft engine building and the aerospace industry.


Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.


Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.


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