Papers by Keyword: Quantitative Phase Analysis

Abstract: For cement-matrix materials, the microstructure plays a vital important role in the research. Recently, quantitative phase analysis of cementitious materials can be performed using the Rietveld method by fitting the calculated X-ray diffraction (XRD) profile with the observed one. The aim of this paper is to further perform the quantitative analysis by the Rietveld method and discuss the influence of testing factors on the Rietveld quantitative phase analysis. The factors included the collection range of pattern, step size and the scan time of per step. In this study, the chemical composition of the samples was determined by X-ray fluorescence (XRF) spectrometry. And their phase composition was calculated by X-ray powder diffraction and Rietveld analysis. The results showed that the collection range of pattern depended on the tested materials , and the scanning range should include the main diffraction peak of the sample. Smaller step size and longer scan time of each step made the fitting factor smaller, also the calculated pattern coincided with the measured pattern, better enhance the precision of the analyses.

Abstract: On the basis of the balance equations of chemical and phase composition of the Al-Mg-Li and Al-Cu-Li alloys developed a method of determining the amount of intermetallic phases from the experimentally measured value of the lattice parameter of α-solid solution. In alloys of Al-Mg (Cu)-Li the relative phase ratio of the δ'(Al₃Li) and S₁ (T₁) are determined by the atomic percentage ratio of the Li and Mg (Cu).

Abstract: The quantitative phase analyses of a slag have been successfully carried out by using both of the full-profile Rietveld and RIR methods from X-ray powder diffraction data. The qualitative phase analysis indicates that the slag contains mayenite (CaO)₁₂(Al₂O₃)₇, olivine Ca₂(SiO₄), gehlenite Ca₂Al (AlSiO₇), lemite Ca₂(SiO₄) and hibonite CaO(Al₂O₃)₆. The quantitative analysis from Rietveld refinement shows that the weight concentrations of mayenite, olivine, gehlenite, lemite and hibonite for the slag are 48.8(4) wt.%, 32.2(5) wt.%, 11.0(9) wt.%, 6.2(1.1) wt.% and 1.8 (1.2) wt.%, respectively. The quantitative phase analysis results obtained by Rietveld method are more precise then those by RIR method.

Abstract: Y₂O₃ is a common sintering additive of AlN ceramics to achieve densification and remove the oxygen impurity, resulting in a typically grain boundary phase (GBP) Y₃Al₅O₁₂ (YAG). Two AlN ceramics with 3wt% and 5wt% Y₂O₃ intended for thermal conductivity study were sintered at 1800 °C for 4h. X-ray diffraction (XRD) indicates that GBP could either be YAG or YAP (YAlO₃) phase, while the selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) in TEM identifies it as YAP instead of YAG. The electron back-scattering diffraction (EBSD) in SEM further confirms the general presence of YAP phase in both samples. In meanwhile, two types of Al-rich GBPs were also detected by TEM, which could account for extra dopant in the microstructure. GBP contents in the both samples were quantified by K-value method (XRD) and from backscattered electron images. Such analyses of GBPs are helpful to understand the sintering mechanism and evaluate their contribution to the thermal conductivity of AlN.

Abstract: Steelmaking dust, collected from four different steel plants, was examined by X-ray diffrac-tion powder technique using phase analysis. Some lead compounds, namely oxides, a silicate, a sul-phate and a chloride hydroxide, were identified. The quantities of the main phase components as franklinite, magnetite, hematite and zincite were determined, applying the Rietveld method. The importance of application of the microabsorption correction was shown.

Abstract: A study of the thermal decomposition sequence of a sample of natural arsenian plumbojarosite has been undertaken using in situ X-ray diffraction. The sample was heated to 900°C using an Anton-Paar heating stage fitted to an INEL CPS120 diffractometer. The data were analysed using a whole-pattern, Rietveld based approach for the extraction of quantitative phase abundances. The instrument configuration used required the development and application of algorithms to correct for aberrations in the (i) peak intensities due to differing path lengths of incident and diffracted beams in the sample and (ii) peak positions due to sample displacement. Details of the structural models used were refined at selected steps in the pattern and then fixed for subsequent analysis. The data sequence consists of some 110 individual data sets which were analysed sequentially with the output of each run forming the input for analysis of the next data set. The results of the analysis show a complex breakdown and recrystallisation sequence including the formation of a major amount of amorphous material after initial breakdown of the plumbojarosite.

Abstract: Application of the Rietveld method to quantitative phase analysis of fly ashes from Polish power stations is presented. The calculations of the fractions of crystalline components as well as non crystalline constituents have been done using SIROQUANT TM software. The power of the Rietveld refinement is shown when very small contents of minerals are detected and quantified.

Abstract: Two nanopowders with nominal compositions (Ca0.7La0.3)MnO3 (CLM) and (Ca0.7La0.3)(Mn0.8Ce0.2)O3 (CLMC) were synthesized by a modified glycine/nitrate procedure. XRD analysis revealed binary phase mixture in both samples. The influence of La and Ce on unit cell parameters, atom positions, and average bond distances were analyzed. According to these results and refined occupation factors of La and Ca, as well as quantitative phase analysis it was found that the CLM sample consists of 85 mass.% of Ca0.62La0.38MnO3 and 15 mass.% of Ca0.99La0.01MnO3, while the CLMC sample consists of 70 mass.% of Ca0.58La0.42MnO3 and 30 mass.% of CeO2. Microstructure size-strain analysis was performed and the Rietveld refinement gave crystallites of about 100 Å. TEM images showed particle sizes of about 100-500 Å.