Raman investigation of ring configurations in vitreous silica

Sharma, Shiv K.; Mammone, Joseph F.; Nicol, Malcolm

doi:10.1038/292140a0

Cited by 333 publications

(174 citation statements)

References 28 publications

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“…5a) is almost identical to that of opal-A (Sodo et al, 2016). The broad band can be attributed to the Si-O-Si symmetric stretching mode (Sharma et al, 1981). In this study, a Raman spectrum, clearly distinguishable from opal-A, appeared at 465 cm −1 with the pressure and temperature treatment of 0.3 GPa and 100°C (Fig.…”

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 60%

“…5b). The most intense band of quartz lies at 464 cm −1 at ambient conditions (Sharma et al, 1981;Kingma and Hemley, 1994). According to the study of vibrational properties of quartz as a function of pressure and temperature (Schmidt and Ziemann, 2000), the frequency of the 464 cm −1 peak is estimated to increase 2 ± 1.0 cm −1 at 0.3 GPa at 100°C.…”

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 99%

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Pressure–induced crystallization of biogenic hydrous amorphous silica

Kyono

Yokooji

Chiba

et al. 2017

Journal of Mineralogical and Petrological Sciences

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Samples of the diatom Nitzschia cf. frustulum, collected from Lake Yogo, Siga Prefecture, Japan, were cultured in the laboratory. Organic components of the diatom cell were removed by washing with acetone and sodium hypochlorite. The remaining frustules were studied by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared (FTIR) spectroscopy, and synchrotron X-ray diffraction. The results showed that the spindle-shaped diatom frustule was composed of hydrous amorphous silica. Pressure-induced phase transformation of the diatom frustule was investigated by in situ Raman spectroscopic analysis. With exposure to 0.3 GPa at 100°C, the Raman band corresponding to quartz occurred at ν = 465 cm −1 . In addition, a characteristic Raman band for moganite was observed at 501 cm −1 . From the integral ratio of Raman bands, the moganite content in the probed area was estimated to be approximately 50 wt%. With increased pressure and temperature, the initial morphology of diatom frustules was totally changed to a characteristic spherical particle with a diameter of about 2 µm. Increasing pressure to 5.7 GPa at 100°C resulted in the appearance of a Raman band assignable to coesite at 538 cm −1 . That is, with compression and heating, hydrous amorphous silica can be readily crystallized into quartz, moganite, and coesite. First-principles calculations revealed that a disiloxane molecule with a trans configuration is twisted 60°with a close approach of a water molecule, which leads to a trans to cis configuration change. It is therefore reasonable to assume that during crystallization of hydrous amorphous silica, an Si-O-Si bridging unit with the cis configuration would survive as a structural defect, and could subsequently crystallize into moganite by maintaining that geometry. This hypothesis is adaptable to the phase transformation from hydrous amorphous silica to coesite as well, because coesite has four-membered rings and is easily formed from hydrous amorphous silica under high pressure and temperature conditions.

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Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 60%

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 99%

Pressure–induced crystallization of biogenic hydrous amorphous silica

Kyono

Yokooji

Chiba

et al. 2017

Journal of Mineralogical and Petrological Sciences

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“…The TOT1 feature envelops the vibrations of structural units formed by variable tetrahedra numbers building the aluminosilicate framework of the glass (Sharma et al, 1981 andMcMillan, 1984) and possibly of metal-oxygen polyhedra (Brawer and White, 1977). Therefore, band position and shape are expected to evolve as a result of the modification in glass composition and structure.…”

Section: Influence Of Glass Composition and Structure On Water Band Nmentioning

confidence: 99%

Quantification of water content and speciation in natural silicic glasses (phonolite, dacite, rhyolite) by confocal microRaman spectrometry

Muro

Villemant

Montagnac

et al. 2006

Geochimica et Cosmochimica Acta

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The determination of total water content (H 2 O T : 0.1-10 wt%) and water speciation (H 2 O molecular /OH) in volcanic products by confocal microRaman spectrometry are discussed for alkaline (phonolite) and calcalkaline (dacite and rhyolite) silicic glasses. Shape and spectral distribution of the total water band (H 2 O T ) at 3550 cm −1 show systematic evolution with glass H 2 O T , water speciation and NBO/T. In the studied set of silicic samples, calibrations based on internal normalization of the H 2 O T band to a band related to vibration of aluminosilicate network (TOT) at 490 cm −1 vary with glass peraluminosity. An external calibration procedure using well-characterized glass standards is less composition-dependent and provides excellent linear correlation between total dissolved water content and height or area of the H 2 O T Raman band. Accuracy of deconvolution procedure of the H 2 O T band to quantify water speciation in water-rich and depolymerized glasses depends on the strength of OH hydrogen bonding. System confocal performance, scattering from embedding medium and glass microcrystallinity have a crucial influence on accuracy of Raman analyses of water content in glass-bearing rocks and melt inclusions in crystals.

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“…Based on the suggestions of Sharma et al (1981) a three-step hierarchal regression analysis was conducted for each moderator, namely, the model variables were entered in the first step, the moderator variable was entered in the second step, and lastly, the interaction between the moderator and the independent variable was entered. The results of the hierarchical regression analysis discussed in table 7 which shows that when prior attitude towards brand is low, there is a significant influence of attitude towards advertisement on brand.…”

Section: Hierarchical Regression Analysesmentioning

confidence: 99%

The Impact of Source Credibility on Saudi Consumer’s Attitude toward Print Advertisement: The Moderating Role of Brand Familiarity

Sallam¹

2011

IJMS

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An endorser or a spokesperson is frequently used by marketers in their product advertisements as a credible source that is hoped to influence the attitude of consumers in the marketplace toward the shown advertisement, the brand and most importantly their purchase intentions. Corporate credibility C/C -the reputation of a company for honesty and expertise is another type of source credibility that is said to influence consumers' reaction to the shown product advertisements and shape their attitudes to brands. The present study assessed the impact of both source credibility (corporate credibility (C/C) and endorser credibility En/C) on Saudi consumers' attitude toward advertising (Aad), attitude toward brand (Ab), and purchase intention (PI) when brand familiarity is tested. A study carried out in Saudi Arabia using 150 respondents as consumers who used cover head product of (AL-Bassam). Path analysis confirmed that, attractiveness of endorser had strengthened impact on (Aad), then expertise, while no effect for endorser trustworthiness on (Aad). While trustworthiness is significant in all C/C relations with the other variables (i.e. Aad, Ab and PI), there is no effect for PAB on relationship between (Aad) and (Ab).Originality/value -In this study, the said relationships amongst the six variables are revisited. The difference lie in the use of Saudi consumers, a developing country compared to developed countries in past studies, in addition to the use of a real advertisement including (product, endorser and company) rather than make believe advertisement. This will provide the first insight on Saudi consumer's behaviour.Paper type -research paper

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Raman investigation of ring configurations in vitreous silica

Cited by 333 publications

References 28 publications

Pressure–induced crystallization of biogenic hydrous amorphous silica

Pressure–induced crystallization of biogenic hydrous amorphous silica

Quantification of water content and speciation in natural silicic glasses (phonolite, dacite, rhyolite) by confocal microRaman spectrometry

The Impact of Source Credibility on Saudi Consumer’s Attitude toward Print Advertisement: The Moderating Role of Brand Familiarity

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