Results 1 - 10 of 35898
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[en] A series of interstitial ternary nitrides R2Fe17N3-δ has been prepared via a gas-solid reaction for R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y. These nitrides have structures related to the Th2Zn17 or Th2Ni17 structures of the R2Fe17 parent compounds, but the unit cell volumes are 6%--7% greater, and the Curie temperatures are approximately 400 K higher. The Fe-Fe exchange interactions are increased by a factor of 2.8 by nitrogenation, whereas the R-Fe exchange interactions are little changed. All compounds exhibit easy-plane anisotropy at room temperature, except for Sm2Fe17N3-δ, which shows strong uniaxial anisotropy and may be used to make permanent magnets. The Er and Tm compounds exhibit spin reorientations below room temperature. The anisotropy due to the iron sublattices is easy plane (K1 = -1.3 MJ/m3 at 4.2 K for Y2Fe17N3), but it changes sign to easy axis with cobalt substitution (K1 ∼ 1.0 MJ/m3 at 4.2 K for Y2(Fe1-xCox)17N3-δ when x≥0.2)
[en] This publication constitutes completion of the first phase in a program to update and upgrade the 1966 Databook, ''Engineering Properties of Ceramics'', (AFML-TR-66-52). The data are presented in the International System (SI) of units as well as in the engineering units used in the 1966 edition. Most data are referenced to the original source. Also, material and testing factors influencing each reported property are specified insofar as possible. The nitrides covered include these of alkaline earth metals, Al, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, rare earths, U, Pu, and Th. 1373 references
[en] Electronic emission spectra of several diatomic metal nitrides were obtained using a microwave discharge source. A survey of metals applicable to the experimental method produced nitrides of zirconium, vanadium, niobium, tantalum, molybdenum, aluminum, and boron. The nature of the carriers has been confirmed by isotopic substitution. Results of the rotational analysis are listed for ZrN, TaN, NbN, VN, MoN, BN, AlN, and TiN. (DLC)
[en] The cold cap floating on top of the molten glass pool in liquid fed joule-heated ceramic melter plays an important role for operation in the vitrification process. A series of such phenomena as evaporation, melting and thermal decomposition of HLLW (high-level liquid waste) takes place within the cold-cap. An understanding of the varied thermal decomposition behavior of many nitrates constituting of HLLW is necessary to elucidate a series of phenomena occurring through the cold-cap. In this study, the reaction rates of the thermal decomposition reaction of 13 kinds of nitrates including Na, Nd, Zr, Gd,Ce,Cs, Fe, La, Mn, Ba, Pr, Pd and Sr, which are main constituents of simulated HLLW, were investigated using thermogravimetric instrument in a range of room temperature to 1000 Celsius degrees. The reaction rates of the thermal decompositions of 13 kinds of nitrates were depicted according to composition ratio (wt%) of each nitrate in simulated HLLW (sHLLW). It was found that the thermal decomposition of sHLLW was able to be predicted by the reaction rates and reaction temperatures for the individual nitrates. The thermal decomposition of sHLLW with borosilicate glass system was also investigated. It was observed that the thermal decomposition of alkali metal and alkaline-earth metal nitrates were affected by the borosilicate glass. For other nitrates such as lanthanides, zirconium nitrate, iron nitrate and so on, the effects of their thermal decomposition in the presence of borosilicate glass were not observed. The above results will be able to provide a useful knowledge for understanding the phenomena occurring through the cold-cap
[en] The present work deals with the development of the model of interatomic interactions in nitrides, to the calculation of the parameters of the Mie-Grueneisen (MG) and the modified Morse (MM) potentials, to the calculation of p-V diagrams, and to comparing them with quantum mechanical calculations. A model of the interatomic interactions in cubic mononitrides is considered. The parameters of the Mie-Grueneisen potential and the modified, four-parameter Morse potential are determined. Calculated U-V and p-V dependence for ThN, UN, PuN, TiN, ZrN, HfN, VN, and CrN are given and compared to quantum mechanical calculations. Critical values of the pressure in the bulk that determine the ultimate strength under all-around tension and, correspondingly, the critical elastic deformation are established
[en] Single phase alloys of composition RFe11Ti with R=Y, Sm, and Dy were prepared by induction melting. The samples were nitrided by thermal cycling to 770 K, at a heating rate of 10 K/min, under an atmosphere of nitrogen in a thermopiezic analyzer (TPA). For YFe11TiN the x-ray diffraction (XRD) patterns give a=0.8611 nm and c=0.4802 nm for the tetragonal structure, space group I4/mmm. This represents a 3% volume expansion of the nitrogen-free unit cell. The amount of absorbed nitrogen corresponds to one nitrogen atom per formula unit indicating that RFe11TiN is a true nitrogen compound with the nitrogen atoms occupying the 2b site in the structure. The expansion of the unit cell is accompanied by a dramatic increase in the Curie temperature for all compounds
[en] It is proposed to use the multiperiod binanolayer composites (TiAlSi)N/MeN (Me-Zr, Nb, Cr, Mo) for controlling the structure, stress state and mechanical properties of a multi-element nitride (TiAlSi)N. The deposition of the layers was carried out by the method of vacuum-arc evaporation at different bias potentials on the substrate Ub = -110 and -200 V. It has been determined that mononitrides with a high Me-N binding energy in the binanolayer composite determine the crystallite growth in thin (nanometer) layers. The growth texture is formed in composites containing mononitrides based on transition metals with a relatively small atomic mass (Cr, Mo) at Ub = -110 V. The growth texture is formed at a larger Ub = -200 V when dealing with mononitride based on heavy metal (Zr). The greatest hardness is achieved in textured materials deposited at Ub = -200 V. This is typical both for a monolayer multi-element nitride (TiAlSi)N (hardness is 42.5 GPa) and for multiperiod nanolayer composites based on it (the highest hardness is 47.9 GPa for a composite (TiAlSi)N/ZrN).
[en] The hardnesses of various phases of group IVA and IVB nitrides (M3N4, M=C, Si, Ge, Sn, Ti, Zr or Hf; MN, M=Ti, Zr or Hf) were calculated using the bond electronegativity model for material hardness. The hardnesses of group IV nitrides increase with an increase in their average coordination numbers except for carbon nitrides, for which increasing the average coordination numbers results in a reduction in hardness. We suggest that for light-element compounds, the diamond-like structure represents the hardest one among all possible structures, whereas a high coordination number is generally required for heavy-element compounds to achieve high hardness values. This work provides a useful guide for designing novel nitride materials having excellent mechanical performances.