Electron beam degradation of Ca-A zeolite

Acosta, Dwight; Vázquez‐Polo, G.; Garcia, Ramiro; Castaño, V. M.

doi:10.1080/10420159308219896

Cited by 15 publications

(9 citation statements)

References 5 publications

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“…Using strong-beam and weak-beam techniques in the TEM to study naturally strained quartz, they observed that vitrification began at dislocations and spread outward from the dislocation core. A similar link to defects has been postulated for zeolite structures~Bursill et al, 1980structures~Bursill et al, , 1981Acosta et al, 1993!. Beryl~Be 3 Al 2 Si 6 O 18 !, cordierite~Mg 2 Al 2 Si 5 O 18 !, CsAlSi 5 O 12 , and sphene~CaTiSiO 5 ! have been studied Vance et al, 1986!.…”

Section: Other High-energy Irradiation Studies Of Silicatessupporting

confidence: 62%

“…Similar to observations in a-quartz and in zeolites, disordered areas such as dislocations seemed to be a source of enhanced vitrificatioñ Bursill et al, 1980Bursill et al, , 1981Hobbs & Pascucci, 1980;Carter & Kohlstedt, 1981;Pascucci et al, 1983;Acosta et al, 1993!. However, unlike a-quartz, in which the crystallineamorphous boundary progresses at a constant rate from the dislocation core~Carter & Kohlstedt, 1981!, the loss of long-range order around dislocations in MCM-41 seems to progress quickly at first, then slows or stops. Similar to observations in a-quartz and in zeolites, disordered areas such as dislocations seemed to be a source of enhanced vitrificatioñ Bursill et al, 1980Bursill et al, , 1981Hobbs & Pascucci, 1980;Carter & Kohlstedt, 1981;Pascucci et al, 1983;Acosta et al, 1993!. However, unlike a-quartz, in which the crystallineamorphous boundary progresses at a constant rate from the dislocation core~Carter & Kohlstedt, 1981!, the loss of long-range order around dislocations in MCM-41 seems to progress quickly at first, then slows or stops.…”

Section: Effect Of Structural Defectssupporting

confidence: 60%

“…An intriguing aspect of the damage mechanism is the role of defects on the loss of long-range order. Similar to observations in a-quartz and in zeolites, disordered areas such as dislocations seemed to be a source of enhanced vitrificatioñ Bursill et al, 1980Bursill et al, , 1981Hobbs & Pascucci, 1980;Carter & Kohlstedt, 1981;Pascucci et al, 1983;Acosta et al, 1993!. However, unlike a-quartz, in which the crystallineamorphous boundary progresses at a constant rate from the dislocation core~Carter & Kohlstedt, 1981!, the loss of long-range order around dislocations in MCM-41 seems to progress quickly at first, then slows or stops. This behavior is particularly clear in Figure 3.…”

Section: Effect Of Structural Defectssupporting

confidence: 60%

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Electron Radiation Damage of MCM-41 and Related Materials

Blanford

Carter

2003

Microsc Microanal

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The article compares the relative stability of MCM-41 and related mesoporous materials in electron beam at an accelerating voltage of 100-300 kV. The work encountered in electron microscopy presents a comparison with similar research that has been carried out on nonporous and microporous silicates, especially a-quartz and zeolite Y. The trends in stability are analyzed, classifying the effects of sample preparation, organic and inorganic moieties, and electron accelerating voltage on beam stability. A higher synthesis temperature, the use of an acid catalyst in the synthesis, and the presence of additional organic or inorganic material within the channels were all found to stabilize these materials. The dose required to completely disrupt the structure increased with accelerating voltage for nearly all samples, suggesting a primarily radiolytic damage mechanism.The exception, MCM-41 containing nanometer-sized titania particles in its channels, was found to be almost insensitive to accelerating voltage.

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Section: Other High-energy Irradiation Studies Of Silicatessupporting

confidence: 62%

Section: Effect Of Structural Defectssupporting

confidence: 60%

Section: Effect Of Structural Defectssupporting

confidence: 60%

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Electron Radiation Damage of MCM-41 and Related Materials

Blanford

Carter

2003

Microsc Microanal

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“…These species appear with gamma irradiation and they are due to the presence of small alumina particles or aluminum and oxygen dangling radicals [17]. It would be a local amorphization similar to the one proposed by Acosta [18] and Gu et al [12,19,20] when zeolites are irradiated with an electron beam. Note that, although we found consistence with the results of Acosta and Gu, they used smaller ionizing doses and the nature of radiation was different.…”

Section: Crystalline Samples Prepared With Csclmentioning

confidence: 96%

Cesium leaching from γ-irradiated CsA and CsX zeolites

Lima

Ibarra

Lara

et al. 2008

Journal of Hazardous Materials

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“…Electron beam-induced damage can be significant even when conventional operating conditions are used in BSE analyses of bone Jones 1996, Vajda et al 1998). This damage includes the disruption of chemical bonds, the production and dispersal of molecular fragments, and mass loss (Acosta et al 1993, Fryer and McConnell 1992, Isaacson 1977, Thach and Thach 1971, von Zglinicki 1993. In BSE images of bone, Boyce et al (1990) described this observable damage as "bleaching" since image gray levels became notably brighter (Fig.…”

Section: Introductionmentioning

confidence: 99%

Mineral content changes in bone associated with damage induced by the electron beam

Bloebaum¹,

Holmes²,

Skedros³

2006

Scanning

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Summary:Energy-dispersive x-ray (EDX) spectroscopy and backscattered electron (BSE) imaging are finding increased use for determining mineral content in microscopic regions of bone. Electron beam bombardment, however, can damage the tissue, leading to erroneous interpretations of mineral content. We performed elemental (EDX) and mineral content (BSE) analyses on bone tissue in order to quantify observable deleterious effects in the context of (1) prolonged scanning time, (2) scan versus point (spot) mode, (3) low versus high magnification, and (4) embedding in poly-methylmethacrylate (PMMA). Undemineralized cortical bone specimens from adult human femora were examined in three groups: 200× embedded, 200× unembedded, and 1000× embedded. Coupled BSE/EDX analyses were conducted five consecutive times, with no location analyzed more than five times. Variation in the relative proportions of calcium (Ca), phosphorous (P), and carbon (C) were measured using EDX spectroscopy, and mineral content variations were inferred from changes in mean gray levels ("atomic number contrast") in BSE images captured at 20 keV. In point mode at 200×, the embedded specimens exhibited a significant increase in Ca by the second measurement (7.2%, p < 0.05); in scan mode, a small and statistically nonsignificant increase (1.0%) was seen by the second measurement. Changes in P were similar, although the increases were less. The apparent increases in Ca and P likely result from decreases in C: -3.2% (p < 0.05) in point mode and -0.3% in scan mode by the second measurement. Analysis of unembedded specimens showed similar results. In contrast to embedded specimens at 200×, 1000× data showed significantly larger variations in the proportions of Ca, P, and C by the second or third measurement in scan and point mode. At both magnifications, BSE image gray level values increased (suggesting increased mineral content) by the second measurement, with increases up to 23% in point mode. These results show that mineral content measurements can be reliable when using coupled BSE/EDX analyses in PMMA-embedded bone if lower magnifications are used in scan mode and if prolonged exposure to the electron beam is avoided. When point mode is used to analyze minute regions, adjustments in accelerating voltages and probe current may be required to minimize damage.

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Electron beam degradation of Ca-A zeolite

Cited by 15 publications

References 5 publications

Electron Radiation Damage of MCM-41 and Related Materials

Electron Radiation Damage of MCM-41 and Related Materials

Cesium leaching from γ-irradiated CsA and CsX zeolites

Mineral content changes in bone associated with damage induced by the electron beam

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