Virtual Labs

Electron Micro Probe Analyses of Alloy for Precise Determination of Chemical Composition

Which type of X-ray emission is typically analyzed in EPMA for determining the composition of alloys?

a: Bremsstrahlung radiation Explanation

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b: Characteristic X-rays Explanation

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c: Auger electrons Explanation

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d: Secondary electrons Explanation

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In the context of EPMA, what is the purpose of performing a 'ZAF correction' when analyzing alloys?

a: To correct for surface roughness of the alloy Explanation

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b: To account for differences in atomic number, absorption, and fluorescence between the sample and standards Explanation

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c: To enhance the resolution of the X-ray detectors Explanation

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d: To increase the X-ray emission from the alloy Explanation

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In the analysis of a nickel-based superalloy using EPMA, the analyst observes anomalously high concentrations of a light element. Which factors could be responsible for this observation, and how should they be mitigated?

a: Contamination from the vacuum chamber; mitigate by thorough cleaning Explanation

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b: Beam-induced sample damage; mitigate by reducing the beam current Explanation

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c: X-ray fluorescence from neighboring elements; mitigate by using appropriate standards and applying corrections Explanation

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d: High electron dose; mitigate by using a lower accelerating voltage Explanation

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What role does the accelerating voltage play in determining the depth of analysis during EPMA of an alloy, and how does this influence the measured composition?

a: Higher accelerating voltage increases the analysis depth, potentially incorporating signals from underlying phases and affecting the measured composition Explanation

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b: Higher accelerating voltage reduces the analysis depth, leading to more surface-sensitive measurements Explanation

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c: Accelerating voltage has no impact on the depth of analysis Explanation

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d: Higher accelerating voltage decreases X-ray intensity, complicating compositional analysis Explanation

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In EPMA analysis of a multi-phase alloy, how can the presence of elements with very different atomic numbers in adjacent phases complicate the quantitative analysis, and what strategies can be employed to address this?

a: It can lead to underestimation of light elements; employ peak deconvolution and proper ZAF corrections to address this Explanation

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b: It results in beam scattering; reduce beam current and use low atomic number standards Explanation

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c: It enhances X-ray production; use a lower accelerating voltage to minimize this effect Explanation

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d: It complicates the focusing of the electron beam; use high-precision focusing techniques Explanation

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