X-ray diffraction study of amorphous Al77.5Mn22.5 and Al56Si30Mn14 alloys

The structure of amorphous sputtered Al_77.5Mn_22.5 and as-spun Al₅₆Si₃₀Mn₁₄ alloys is investigated by X-ray diffraction. Some distinct features are observed in the intensity profile, i.e. a pronounced prepeak atQ = 16 nm^–1 in both the alloys and a shoulder at the low-Q side in Al-Si-Mn. Also in the radial distribution functions, the first peak has a shoulder at the high-r side. This experimental evidence suggests the presence of a strong chemical short-range order persisting in the phase.     

An X-ray study of splat-quenched Sn-Bi and Cu-Sb alloys by energy-dispersive diffraction

A metastable shift of the solubility limit was produced by splat-quenching in Sn-Bi alloys containing 15, 20 and 25 at. % bismuth. Decomposition of the supersaturated a phase was investigated in the temperature range –40 to O° C. An activation energy of 39.8±3.0 kJ mol^–1 was obtained for the decomposition of Sn-25 at. % Bi. Splat-quenched Cu-Sb alloys with different compositions were also studied. The decomposition of the retained high-temperature phase was followed at 200 and 330° C. Neither an increase of solubility of copper into antimony nor new phases at the eutectic composition were observed in quenched foils.     

Study of microstructure in vanadium-palladium alloys by X-ray diffraction technique

Present study considers microstructural characterization of vanadium-based palladium (V-Pd) alloys, which are widely used in marine environment due to their high corrosion resistance. The X-ray diffraction line profile analysis (XRDLPA) have been used to assess the microstructure in body centred cubic (bcc) V-Pd alloys having four different nominal compositions in wt.%. X-ray diffraction line broadening analysis on V-Pd alloys has been performed by using different methods like the Warren-Averbach, double-Voigt and Rietveld methods. Finally microstructural defect parameters such as domain size (D), r.m.s. microstrain 〈ɛ ²〉^1/2, twin fault (β′), spacing fault (αɛ) and deformation stacking fault (α) were evaluated in these alloys by Fourier line shape analysis using Rietveld method in which the X-ray diffraction profiles of these alloys were described by the pseudo-Voigt function to fit the experimental data. From analysis it has been observed that twin fault, β′, and the spacing fault, αɛ, are totally absent in these bcc alloy systems because the twin fault, β′, has been observed to be either negative or very small (within experimental error limit) for these alloy systems and the spacing fault, αɛ, appears to be negative. This analysis also revealed that the deformation stacking fault, α, is significantly present in this alloy system and increases with Pd content.     

Structural study of superionic conducting glasses Agl-AgPO3 by X-ray diffraction

Atomic structures of (Agl) _x (AgPO₃O₃)_1–x glasses for x=0.0, 0.1, 0.2, 0.3 and 0.5 have been investigated by X-ray diffraction. Coordination numbers and atomic distances in the near-neighbour region were determined by the least-squares variational method. The coordination numbers of P-O, P-P and O-O pairs are unchanged with x, which suggests no modification of the connectivity of the PO₄ tetrahedral chains by doping with Agl. The coordination number of I^– around Ag⁺ linearly increases from 0 to 1.9 ± 0.2 with increase in x, while the coordination number of O^2– around Ag⁺ linearly decreases from 5.1±0.2 to 2.5±0.2. This also suggests that the Agl gets into the PO₄ chains while keeping the local environment of the Agi itself.     

Structural analysis of amorphous (Fe1-x Mn x )78B22 alloys by X-ray diffraction and electrical resistance

The structure of amorphous (Fe_1–x Mn _x ) alloys prepared by a single roller technique has been investigated in terms of X-ray diffraction and electrical resistance. The lattice parameter of the crystalline precipitates, which were-Fe and b c t (FeMn)₃B, was determined under different heat treatments. On heating up to 440° C where a mixture of amorphous and crystalline phases exists and up to 550° C corresponding to the completion of crystallization, the lattice parameter of the-Fe phase rises to that of pure-Fe with increasing manganese concentration. In samples annealed at 660° C for 5 h, the opposite behaviour is observed. These results can be explained on the basis of the position of the boron atom occupying the-Fe lattice, the pressure effect exerted by the environment, and the enhancement of the chemical short-range ordering between manganese and boron atoms with manganese concentration. In the b c t phase, which shows a reduction in lattice parameter with manganese concentration independent of heat treatment, the effect of redistribution of the atoms in the unit cell should be also taken into account.     

An X-ray study by Guinier diffraction camera of Al-Ge alloys rapidly quenched from the melt

Two Al-Ge alloys (6 and 30 at. % Ge) were levitation-melted and quenched in the rotary splat-quencher designed at Sussex University. X-ray diffraction patterns were obtained with crystal-monochromatized CuK ₁ in a precision Guinier camera, and further patterns were obtained after heating to various temperatures in a differential scanning calorimeter; the DSC was used to indicate when one of the metastable phases had completed its transformation. It was clear that there was more than one metastable phase in the concentrated (eutectic) alloy, possibly only one in the dilute alloy. Most of the lines matched those of the patterns reported by Raoet al. and by Köster; the agreement with Köster is very close, both as to lattice spacings and as to groupings of lines belonging to the different phases. Results published by other workers are completely at variance with ours. Köster's attribution of phases is confirmed by this study. (A recently developed iterative computer program was applied in an attempt to interpret the X-ray patternsab initio, but was not found useful.) This study illustrates the difficulty of identifying metastable phases, especially when more than one is present, and points to the importance of using a high-precision X-ray diffraction technique.     

X-ray diffraction study of an amorphous Al60Ge30Ni10 alloy

The ordinary X-ray diffraction profile and anomalous X-ray scattering profiles at nickel and germanium K absorption edges of amorphous Al₆₀Ge₃₀Ni₁₀ alloy have been determined. The results indicate the characteristic feature of the coexistence of nickel-rich highly ordered crystal-like regions and germanium-rich amorphous regions. From the environmental radial distribution function around germanium atoms, the coordination number around a germanium atom is estimated at about 4. Thus, an amorphous germanium-like structure may be quite feasible in this region.     

La掺杂的Bi4Ti3O12陶瓷的动态变温X射线衍射研究

利用动态变温X射线衍射技术,研究了La掺杂Bi4Ti3O12（BLT）陶瓷相的形成过程、微结构的变化及其与温度的关系。动态跟踪比较了不同物相的反应速率与消长规律。比较了大气与真空不同的气氛环境对BLT相结构形成的影响。初步给出了固态成相的温度范围和所需时间。     

A combined single crystal X-ray diffraction and electron diffraction study of the T2phase in Al-Li-Cu alloys

Both single crystal X-ray diffraction techniques and convergent beam electron diffraction have been employed to examine the structure of theT ₂ (Al₆CuLi₃) phase in three particular Al-Li-Cu alloys. It is shown thatT ₂ displays icosahedral symmetry both in a high purity laboratory melt and in two impure alloys which had been processed industrially. Possible reasons for the five-fold symmetry ofT ₂ are discussed.     

X-ray diffraction line broadening of cadmium oxide produced by cadmium hydroxide decomposition

A precise analysis of X-ray diffraction line broadening produced by cadmium oxide obtained by the thermal decomposition of Cd(OH)₂ is described. The influence of experimental conditions is considered. It is shown, using different methods of analysis, that the broadening of the reflections is due to size and microstrains effects, with a mean apparent size of 6 nm in a direction perpendicular to (1 10) planes.     

Phase fields in rapidly solidified MnTi and MnAlTi alloys studied by X-ray diffraction

While rapid solidification causes little modification of phase fields in Mn_x Ti_1–x alloys forx < 30at%, alloys richer in manganese present metastable phases. A structure intermediate between crystalline and quasi-crystalline phases is observed in the range 0.3 <x < 0.45. Aluminium addition is found to stabilize the C14 phase down to manganese contents as low as 35 at % and Mn₃₅ (AlTi)₆₅ is found to be single-phased C14. The ternary alloy's C14 phase field emerges due to aluminium substitution for manganese at low manganese contents.     

Anomalous X-ray scattering study of amorphous and icosahedral Al75Cu15V10 alloys

Atomic structures of amorphous and icosahedral Al₇₅Cu₁₅V₁₀ alloys were precisely examined by the ordinary and anomalous X-ray diffraction techniques. Some distinct features of intensity profiles, and coordination numbers and interatomic distances determined from the RDF analysis, indicate the presence of the icosahedral short-range ordering clusters in the as-quenched amorphous sample and other annealed amorphous samples, which are similar to the basic atomic structure constructing the icosahedral phase. The intensity differences of the amorphous and icosahedral phases obtained in the anomalous X-ray scattering (AXS) at the CuK-absorption edge suggest that copper atoms are homogeneously dispersed in the icosahedral short-range ordering clusters.     

The structure of amorphous aluminium phosphate by radial distribution functions derived from X-ray diffraction

An investigation of the molecular structure of amorphous aluminium phosphate, prepared from a recently discovered complex (AlPO₄ · HCl · 4C₂H₅OH), has been carried out using radial distribution function (RDF) techniques. Studies were made on two samples, one prepared by decomposing the solid complex and the other from powder produced by evaporating to dryness a solution of the complex in methanol and then decomposing and grinding the solid obtained. RDF curves were obtained from both samples, and were found to closely resemble that previously reported for vitreous silica. The short range order in both samples is similar to that in vitreous silica, with aluminium and phosphorous atoms occupying positions in aluminium phosphate similar to the positions of silicon atoms in silica. This structure is consistent with the crystal chemistry of aluminium phosphate.It is possible to assign all the peaks in the RDF plots out to values of r5 Å to known inter-atomic distances. The peak at 1.6 Å represents the Al-O and Al-P bond lengths, and is broader than the corresponding Si-O peak in vitreous silica, as the Al-O and P-O bonds are respectively slightly longer (Al-O) and shorter (P-O) than the equivalent Si-O bonds. Subsequent peaks result from the O-O distances ( 2.6 Å); the Al-Al, Al-P and P-P distances ( 3.1Å); the Al-second O and P-second O distances ( 4.2 Å), and O-second O, Al-second Al, P-second P and Al-second P distances ( 5.0 Å). The sample prepared from the methanolic solution shows some small additional peaks in the region 4 to 5 Å, indicating more order in the second neighbour distances.Analysis of the P-O and Al-O peak area indicates that both P and Al atoms are co-ordinated to four network oxygen atoms at a distance 1.6Å, and that absorbed water also co-ordinates to one or both atoms with a P-O and/or Al-O distance of 1.6 Å.     

X-ray diffraction study of ground talc Mg3Si4O10(OH)2

A structural analysis of talc ground under dry atmospheric conditions for different grinding times has been made by X-ray diffraction. The SiO₄ tetrahedra are found to remain unchanged in the ground talc samples by analysing the radial distribution function. On the other hand, with an increase of the grinding time a change in oxygen coordination number around magnesium has been quantitatively confirmed. This variation is attributed to the change of a hydroxyl induced by the prolonged grinding.