Monochromatic Diffraction-Absorption Technique for Direct Quantitative X-Ray Analysis

Lennox, D. H.

doi:10.1021/ac60125a008

Cited by 19 publications

(6 citation statements)

References 5 publications

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“…A Pearson VII deconvolution was used to calculate the area under the diffraction peaks for crystallite size information. To determine the copper content within each sample, the spiking method developed by Lennox et al 37 was utilized to quantitatively analyze the samples through XRD. For each spiking run, approximately 0.1 g of Cu 2 O powders was successively added to 1 g of the powder samples.…”

Section: Methodsmentioning

confidence: 99%

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

et al. 2012

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We present a study of powder agglomeration and thermal conductivity in copper-based nanofluids. Synthesis of the copper powders was achieved by the use of three different surfactants (polyvinylpyrrolidone, oleic acid, and cetyl trimethylammonium bromide). After careful determination of morphology and purity, we systematically and rigorously compared all three of the surfactants for the production of viable copper-based nanofluids using dynamic light scattering. Our results show that the use of surfactants during synthesis of copper nanopowders has important consequences on the dispersion of the powders in a base fluid. The oleic-acid-prepared powders consisted of small particles of ∼100 nm that did not change with the addition of dispersant. The CTAB-prepared powders exhibited the best dispersion characteristics, as they formed small particles of approximately 80 nm in the presence of SDBS. The thermal conductivity enhancement in our nanofluids exhibited a linear relationship with powder loading for an average particle size of ∼100 nm and similar particle size distributions that range from ∼50 to 650 nm, but independent of crystallite size and with all other factors maintained constant (surface area, surface additives, levels of oxidation) such that a 0.55 vol % loading results in a thermal conductivity enhancement of 22% over water and a 1.0 vol % loading results in a thermal conductivity enhancement of 48% over water. This study is the first to decouple the effect of a carefully characterized particle size distribution using dynamic light scattering versus crystallite size from X-ray line broadening on the thermal conductivity enhancement of a nanofluid.

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Section: Methodsmentioning

confidence: 99%

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

et al. 2012

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“…The amount of Cu 2 O precipitated by the HT phase annealed at 450 °C was determined to be 19.8 mass %; that is, the composition of the HT phase was Cu 1.03 ZnGeO 3.515 ( R 2 = 0.9906), by the standard addition method (Figure S3). − The composition of the sample annealed at 500 °C, which was calculated using the same method, was Cu 0.81 ZnGeO 3.405 ( R 2 = 0.9931). Figure shows the XRD patterns of the LT phase (initial Cu 2 ZnGeO 4 ) and HT phase (sample annealed in the vacuum-sealed ampule at 450 °C) and the simulated XRD patterns of Cu I 2– x ZnGeO 4– x /2 with copper deficiencies of x = 0, 0.5, and 1 using the lattice parameters of the HT phase.…”

Section: Resultsmentioning

confidence: 99%

Phase Transformation of Metastable Cu₂ZnGeO₄ with a Wurtz–Kesterite Structure at Elevated Temperatures

et al. 2022

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The thermal stability and high-temperature phase transformation of metastable Cu2ZnGeO4 were investigated in an Ar atmosphere by thermogravimetry, differential thermal analysis, and high-temperature X-ray diffraction. Three Cu-deficient CuI 2–x ZnGeO4–2/x phases with a wurtzite-related structure were observed, with varying amounts of copper deficiency. The metastable Cu2ZnGeO4 was stable at approximately 275 °C and transformed into intermediate phases. The intermediate phases had a wurtz–kesterite structure with a small number of copper and oxygen vacancies, which later transformed into a high-temperature phase at approximately 425 °C. The crystal structure of the high-temperature phase was assumed to be a deficient wurtzite-related structure with hexagonal closely packed oxygen and deficient copper sites on the order of tens of a percent. The high-temperature phase decomposed into stable Cu2O, GeO2, and Zn2GeO4 phases above 550 °C. The mechanism for the formation of the phase with a large amount of copper deficiency is discussed, leading to an understanding of the formation process for the copper-deficient phase of complex compounds containing monovalent copper.

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“…Fortunately, as shown below, density related factors cancel out in the fi nal expression for A(θ) and sample density evaluations are not required. By comparison, quantifi cation methods based on direct measurements of sample absorption coeffi cients are experimentally complicated and prone to systematic errors (e.g., Lennox 1957). Next, in taking mass absorption into account in the actual diffraction experiment, we consider that the radiation is transformed in successive steps as: (1) incident beam intensity, I o , (2) surviving incident intensity at depth d within the sample, after mass absorption removal, (3) scattering (both modifi ed and unmodifi ed) of the latter local incident radiation by the material at depth d, per elementary volume of material at depth d, and (4) surviving outgoing scattered radiation, after an additional mass absorption on exit from depth d within the sample.…”

Section: Mass Absorption Factormentioning

confidence: 99%

Absolute quantification by powder X-ray diffraction of complex mixtures of crystalline and amorphous phases for applications in the Earth sciences

Rancourt

2005

American Mineralogist

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Monochromatic Diffraction-Absorption Technique for Direct Quantitative X-Ray Analysis

Cited by 19 publications

References 5 publications

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

Phase Transformation of Metastable Cu₂ZnGeO₄ with a Wurtz–Kesterite Structure at Elevated Temperatures

Absolute quantification by powder X-ray diffraction of complex mixtures of crystalline and amorphous phases for applications in the Earth sciences

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Monochromatic Diffraction-Absorption Technique for Direct Quantitative X-Ray Analysis

Cited by 19 publications

References 5 publications

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

Phase Transformation of Metastable Cu2ZnGeO4 with a Wurtz–Kesterite Structure at Elevated Temperatures

Absolute quantification by powder X-ray diffraction of complex mixtures of crystalline and amorphous phases for applications in the Earth sciences

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Phase Transformation of Metastable Cu₂ZnGeO₄ with a Wurtz–Kesterite Structure at Elevated Temperatures