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1.
In this study, Grf/Al composite was fabricated by liquid pressure method. The diffusion layer and the nucleation and growth of Al4C3 were observed at the interface of Grf/Al composites by TEM and HRTEM. The growth mechanism of Al4C3 was analyzed in detail by crystallography theory. It was found that Al4C3 had no phase relations with the carbon fiber. (0 0 0 1) layer of Al4C3 was parallel with main growth direction. Both the diffusion layer at the interface and crystal structure of Al4C3 affected the shape of Al4C3. At a certain position, Al4C3 could connect two fibers when the fibers were close to each other. 相似文献
2.
A. Siber J. Marien Th. Koch P. Ziemann 《Applied Physics A: Materials Science & Processing》1993,57(3):267-270
Al/Au multilayers (average composition Al2Au, individual layer thicknesses 1 nm Al and 0.71 nm Au) are prepared at 90 K by ion beam sputtering. The electrical resistance of the growing films is monitored in situ. From the results obtained in this way it can be concluded that interface reactions occur transforming the ultrathin layers into an amorphous phase, which is stable up to 255 K.For larger individual layer thicknesses (2.1 nm Au and 3 nm Al), the interface reaction into the amorphous state is incomplete. Based on a simple parallel-resistor model, one finds that the interface reaction into the amorphous phase is restricted to a thickness of less than 3.5 nm. The temperature dependence of the resistance of such thicker multilayers indicates the onset of interdiffusion of the yet unreacted material at T=200 K resulting in the crystalline Al2Au-phase. 相似文献
3.
4.
Alexander G. Sokol Yury M. Borzdov Yury N. Palyanov Alexander F. Khokhryakov 《高压研究》2015,35(2):139-147
Fusion and solidification of Al and Ag samples, as well as Fe93–Al3–C4, Fe56–Co37–Al3–C4, and Fe57.5–Co38–Al1–Pb0.5–C3 alloys (in wt%), have been investigated at 6.3?GPa. Heater power jumps due to heat consumption and release on metal fusion and solidification, respectively, were used to calibrate the thermal electromotive force of the thermocouple against the melting points (mp) for Ag and Al. Thus, obtained corrections are +100°C (for sample periphery) and +65°C (center) within the 1070–1320°C range. For small samples positioned randomly in the low-gradient zone of a high pressure cell, the corrections should be +80°C and +84°C at the temperatures 1070°C and 1320°C, respectively. The temperature contrast recorded in the low-gradient cell zone gives an error about ±17°C. The method has been applied to identify the mp of the systems, which is especially important for temperature-gradient growth of large type IIa synthetic diamonds. 相似文献
5.
This study investigates the effects of alloying elements on the microstructural evolution of Al-rich Al–Mn–Cu–(Be) alloys during solidification, and subsequent heating and annealing. The samples were characterised using scanning electron microscopy, energy dispersive X-ray spectroscopy, synchrotron X-ray diffraction, time-of-flight secondary-ion mass spectroscopy, and differential scanning calorimetry. In the ternary Al94Mn3Cu3 (at%) alloy, the phases formed during slower cooling (≈1?K?s?1) can be predicted by the known Al–Mn–Cu phase diagram. The addition of Be prevented the formation of Al6Mn, decreased the fraction of τ1-Al29Mn6Cu4, and increased the fraction of Al4Mn. During faster cooling (≈1000?K?s?1), Al4Mn predominantly formed in the ternary alloy, whereas, in the quaternary alloys, the icosahedral quasicrystalline phase dominated. Further heating and annealing of the alloys caused an increase in the volume fractions of τ1 in all alloys and Be4Al (Mn,Cu) in quaternary alloys, while fractions of all other intermetallic phases decreased. Solidification with a moderate cooling rate (≈1000?K?s?1) caused considerable strengthening, which was reduced by annealing for up to 25% in the quaternary alloys, while hardness remained almost the same in the ternary alloy. 相似文献
6.
通过自编软件建立了Fe-Cr-Al合金表面、氧化膜/基体界面模型,采用递归法计算了合金元素在Fe-Cr-Al合金表面、氧化膜/基体界面的环境敏感镶嵌能、亲和能、结合能、态密度等电子结构参数.从电子层次系统研究了Fe-Cr-Al合金氧化膜的形成机理、稀土元素和杂质硫对氧化膜形成过程及黏附性的影响机理.研究表明Fe-Cr-Al合金中Al的偏聚驱动力远大于Y,Cr.氧化初期氧从合金表面向合金内部扩散,合金内部Al向合金表面扩散,使合金形成富铝、氧表面层;氧与Al间的亲和力较大(亲和能低),氧原子容易与Al结合生成Al2O3保护膜;合金中加入Y后,Y在合金表面偏聚,抑制Al向合金表面扩散,氧化膜的横向生长得到有效控制,从而避免氧化膜皱褶形貌的发生,提高氧化膜的黏附性;合金内部的S通过扩散汇集在基体/氧化膜界面,S使界面区原子的总能增高,总态密度降低,减小了界面的稳定性,进而削弱氧化膜与合金基体的结合力.
关键词:
电子结构
高温氧化
Fe-Cr-Al合金 相似文献
7.
The growth of Co on thin Al2O3 layers on Ni3Al(1 0 0) was investigated by Auger electron spectroscopy, high resolution electron energy loss spectroscopy (EELS), and scanning tunneling microscopy. At 300 K, Co grows in three-dimensional clusters on top of the Al2O3 layer. A defect structure of the alumina layer plays a crucial role during the early stage of Co growth. After deposition of 10 Å of Co, a complete screening of the dipoles of the Al2O3 layer due to the Co film is found in the EELS measurements. Annealing the Co film reveals a process of coalescence of Co clusters and, above 700 K, diffusion of the Co atoms through the oxide film into the substrate takes place. 相似文献
8.
通过自编软件建立了铝氧化膜与基体铌界面的原子集团模型,用递归法计算了合金的原子埋置能、原子结合能等电子参数,从电子层面分析铌合金高温氧化机理.研究表明:铝通过晶界扩散偏聚在合金表面,并与氧结合生成致密的Al2O3氧化膜,阻挡氧向铌基体扩散.晶界和稀土元素能提高氧化膜与基体间的原子结合能,增加其界面的结合强度,加强氧化膜与基体铌间的黏附性.因此,通过在合金中添加稀土元素或细化合金晶粒均能提高铌合金的抗高温氧化性能. 相似文献
9.
The growth and oxidation of a thin film of Ni3Al grown on Ni(1 0 0) were studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and high resolution electron energy loss spectroscopy (EELS). At 300 K, a 12 Å thick layer of aluminium was deposited on a Ni(1 0 0) surface and subsequently annealed to 1150 K resulting in a thin film of Ni3Al which grows with the (1 0 0) plane parallel to the (1 0 0) surface of the substrate. Oxidation at 300 K of Ni3Al/Ni(1 0 0) until saturation leads to the growth of an aluminium oxide layer consisting of different alumina phases. By annealing up to 1000 K, a well ordered film of the Al2O3 film is formed which exhibits in the EEL spectra Fuchs-Kliewer phonons at 420, 640 and 880 cm−1. The LEED pattern of the oxide shows a twelvefold ring structure. This LEED pattern is explained by two domains with hexagonal structure which are rotated by 90° with respect to each other. The lattice constant of the hexagonal structure amounts to ∼2.87 Å. The EELS data and the LEED pattern suggest that the γ′-Al2O3 phase is formed which grows with the (1 1 1) plane parallel to the Ni(1 0 0) surface. 相似文献
10.
S. V. Bukin A. S. Shulakov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(1):67-70
The distribution of the phase and chemical composition at an Al2O3/Si interface is studied by depth-resolved ultrasoft x-ray emission spectroscopy. The interface is formed by atomic layer deposition of Al2O3 films of various thicknesses (from several to several nanometers to several hundreds of nanometers) on the Si(100) surface (c-Si) or on a 50-nm-thick SiO2 buffer layer on Si. L 2,3 bands of Al and Si are used for analysis. It is found that the properties of coatings and Al2O3/Si interfaces substantially depend on the thickness of the Al2O3 layer, which is explained by the complicated character of the process kinetics. At a small thickness of coatings (up to 10–30 nm), the Al2O3 layer contains inclusions of oxidized Si atoms, whose concentration increases as the interface is approached. As the thickness increases, a layer containing inclusions of metallic Al clusters forms. A thin interlayer of Si atoms occurring in an unconventional chemical state is found. When the SiO2 buffer layer is used (Al2O3/SiO2/Si), the structure of the interface and the coating becomes more perfect. The Al2O3 layer does not contain inclusions of metallic aluminum, does not vary with the sample thickness, and has a distinguished boundary with silicon. 相似文献
11.
《Journal of magnetism and magnetic materials》1987,69(2):158-162
We present measurements on the isostructural series CeCu5, CeCu4Al and CeCu3Al2, which demonstrate the supression of the antiferromagnetic phase transition at 4 K in CeCu5, due to the substitution of Cu by Al in CeCu4Al and CeCu3Al2. This substitution, however, is linked to a dramatic enhancement of properties reflecting the electronic density of states. 相似文献
12.
E. Popova N. Keller F. Jomard L. Thomas M.-C. Brianso F. Gendron M. Guyot M. Tessier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):69-74
Magnetic exchange coupling has been observed for ultrathin films of yttrium iron garnet (Y3Fe5O12 or YIG). Single-crystalline YIG films were prepared on yttrium aluminium garnet (Y3Al5O12 or YAG) substrates by pulsed laser deposition. (111) and (110) oriented substrates were used. Film thicknesses were varied
from 180 ? to 4600 ?. Epitaxial growth of YIG on YAG was obtained in spite of the lattice mismatch of 3%. Magnetic hysteresis
loops recorded for ultrathin YIG films have a “bee-waist” shape and show a coupling between two different magnetic phases.
The first phase is magnetically soft YIG. A composition study by secondary ion mass spectroscopy shows the second phase to
be Y3Fe5-xAlxO12 due to the interdiffusion of Fe and Al at the film/substrate interface. This compound is known to be magnetically harder
and to have weaker magnetization than YIG. The coupling of the two phases leads to a hysteresis loop displacement at low temperatures.
This displacement varies differently with film thickness for two substrate orientations. Assuming an interfacial coupling,
the maximal interaction energy is estimated to be about 0.17 erg/cm2 at 5 K for (111) oriented sample.
Received 3 June 2002 / Received in final form 7 October 2002 Published online 27 January 2003
RID="a"
ID="a"Presently at LPM, Université H. Poincaré, BP 239, 54506 Vandœuvre-lès-Nancy e-mail: popova@lpm.u-nancy.fr 相似文献
13.
《Composite Interfaces》2013,20(5):445-452
The surfaces of ellipsoidal Al2O3 particles with average size of 0.15 μm and the interfaces between the Al2O3 particles and 1070Al were investigated by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM).The results show that the surfaces of Al2O3 particles appear to be polyhedrons consisting of crystal planes with small angle, while every plane of the polyhedrons could be considered as a stepped structure composed of close-packed planes along the close-packed direction. The interfaces of the 0.15 μm Al2O3p/1070Al composite bond well, without any interfacial reaction products. It is proposed that there are several kinds of crystallographic orientation relationships between the aluminum matrix and Al2O3particles due to the polyhedral structure. In our study, such orientation relationships are found to be {110} Al ||{1100} Al2O3 and ?110? Al ||?1126? Al2O3 . 相似文献
14.
The effect of Si addition on the interfacial stability of Al-10Ti-5Cu-xSi (x = 0, 5, 10, 15) alloy/SiC is investigated. SiC and the Al-10Ti-5Cu-xSi alloys were compacted to obtain a stable interface with 10 wt% Si. Analysis of the processing conditions and the microstructures indicated that an excellent Ti3SiC2 phase had been formed and the deleterious Al4C3 phase had been eliminated successfully by the addition of 10 wt% Si to the Al-10Ti-5Cu alloy. Formation of Ti3SiC2 increased at first and then decreased, while the formation of Al4C3 was gradually inhibited with increasing Si content. Ti3SiC2 possesses good chemical stability, and flexibility. However, Al4C3 degrades within few days, in composites exposed to ambient conditions. The presence of Ti3SiC2 at the interface and the elimination of Al4C3 together ameliorate the bonding of Al-10Ti-5Cu-xSi alloy to SiC, thereby improving the interfacial stability of Al-10Ti-5Cu-xSi/SiC. 相似文献
15.
A quantitative phase-field approach for multiphase systems that is based upon CALPHAD free energies is used to model the aluminization of nickel wires, wherein vapour-phase alloying is used to deposit Al on the surface of the Ni wire and then the wire is annealed so that to remove all Al gradients and achieve a homogenous Ni-Al alloy. Both processes are modelled and numerical results are compared with experiments. It is found that the kinetics of both processes is controlled by bulk diffusion. During aluminization at 1273 K, formation and growth of intermetallics, Ni2Al3 NiAl and Ni3Al, are strongly dependent on the Al content in the vapour phase. Ni2Al3 growth is very fast compared with NiAl and Ni3Al. It is also found that an intermediate Al content in the vapour phase is preferable for aluminization, since the Ni2Al3 coating thickness is difficult to control. Ni2Al3 is found to disappear in a few minutes during homogenization at 1373 K. Thereafter, the NiAl phase, in which the composition is highly non-uniform after aluminization, continues growing until the supersaturation in this phase vanishes. Then, NiAl coating disappears concomitantly with the growth of Ni3Al, which disappears thereafter. Finally, the Al concentration profile in Ni(Al) homogenizes. 相似文献
16.
A. S. Shulakov A. P. Braiko S. V. Bukin V. E. Drozd 《Physics of the Solid State》2004,46(6):1145-1148
The extent and phase chemical composition of the interface forming under atomic layer deposition (ALD) of a 6-nm-thick Al2O3 film on the surface of crystalline silicon (c-Si) has been studied by depthresolved, ultrasoft x-ray emission spectroscopy. ALD is shown to produce a layer of mixed Al2O3 and SiO2 oxides about 6–8 nm thick, in which silicon dioxide is present even on the sample surface and its concentration increases as one approaches the interface with the substrate. It is assumed that such a complex structure of the layer is the result of interdiffusion of oxygen into the layer and of silicon from the substrate to the surface over grain boundaries of polycrystalline Al2O3, followed by silicon oxidation. Neither the formation of clusters of metallic aluminum near the boundary with c-Si nor aluminum diffusion into the substrate was revealed. It was established that ALD-deposited Al2O3 layers with a thickness up to 60 nm have similar structure. 相似文献
17.
A. S. Shulakov A. P. Braiko S. V. Bukin V. E. Drozd 《Physics of the Solid State》2004,46(10):1935-1939
The phase chemical composition of an Al2O3/Si interface formed upon molecular deposition of a 100-nm-thick Al2O3 layer on the Si(100) (c-Si) surface is investigated by depth-resolved ultrasoft x-ray emission spectroscopy. Analysis is performed using Al and Si L2, 3 emission bands. It is found that the thickness of the interface separating the c-Si substrate and the Al2O3 layer is approximately equal to 60 nm and the interface has a complex structure. The upper layer of the interface contains Al2O3 molecules and Al atoms, whose coordination is characteristic of metallic aluminum (most likely, these atoms form sufficiently large-sized Al clusters). The shape of the Si bands indicates that the interface layer (no more than 10-nm thick) adjacent to the substrate involves Si atoms in an unusual chemical state. This state is not typical of amorphous Si, c-Si, SiO2, or SiOx (it is assumed that these Si atoms form small-sized Si clusters). It is revealed that SiO2 is contained in the vicinity of the substrate. The properties of thicker coatings are similar to those of the 100-nm-thick Al2O3 layer and differ significantly from the properties of the interfaces of Al2O3 thin layers. 相似文献
18.
D.V. Suetin 《Physica B: Condensed Matter》2008,403(17):2654-2661
First principle calculations have been performed with the purpose to understand the peculiarities of the structural, elastic parameters and electronic properties and interatomic bonding for novel hexagonal carbide (W0.5Al0.5)C in comparison with binary phases WC and Al4C3. The geometries of all phases were optimized and their structural, elastic parameters and theoretical density were established. Besides, we have evaluated the formation energies (Eform) of W0.5Al0.5C for different possible preparation routes (namely for the reactions with the participation of simple substances (metallic W, Al and graphite, binary W or Al carbides and metallic Al and W, or binary W and Al carbides). The results show that the synthesis of the ternary carbide from simple substances is more favorable in comparison with the reactions with participation of W and Al carbides. Moreover, band structures, total and partial densities of states were obtained and analyzed systematically for (W0.5Al0.5)C, WC and Al4C3 phases in comparison with available theoretical and experimental data. The bonding picture in W0.5Al0.5C was described as a mixture of metallic, ionic and covalent contributions with the high anisotropy for the covalent W-C and Al-C bonds, where p-p like Al-C bonds become weaker than p-d like W-C bonds. 相似文献
19.
The system (Fe0.88Mn0.12
1–x
Al
x
has been investigated in a concentration range from 5 to 14 at.% Al. We applied Mössbauer spectroscopy in the temperature range from 4 up to 900 K and X-ray diffractometry at room temperature. The as-cast samples show a bcc phase for all concentrations and exhibit broadened six-line Mössbauer spectra typical for disordered alloys. The Mössbauer spectra during a high temperature treatment show dramatic changes. These are due to ordering processes appearing at temperatures above 700 K. As an example of the observed changes, we present results obtained for the alloy withx= 14 at.% Al. 相似文献
20.
《Surface science》2002,496(1-2):77-83
Soft X-ray photoelectron spectroscopy and resonant photoemission have been used to study the growth and electronic properties of Fe ultrathin films deposited on Al2O3 substrates. A simultaneous multilayer growth mode has been found for Fe growth at room temperature. For iron coverages below 1 ML, Fe2+ species are formed at the Fe/Al2O3 interface, followed by the formation of a metallic iron overlayer. The bonding of Fe at very low coverages occurs by charge transfer from Fe to surface oxygen atoms, and neither hybridisation of Fe and Al states nor reduction of the Al2O3 substrate are observed. The thermal stability of the interface has been also studied in the range 673–873 K. Annealing produces Fe agglomeration in such a way that some areas of the Al2O3 substrate become fully Fe-depleted. In these Fe-depleted areas, Fe2+ completely disappears and Al0 reduced species are formed. This behaviour would explain the decrease in the magnetoresistance performance of magnetic tunnel junctions after annealing above 573 K. 相似文献