Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments / Albert Rimola;Dominique Costa;Mariona Sodupe;Jean-François Lambert;Piero Ugliengo. In: CHEMICAL REVIEWS. ISSN 0009-2665. STAMPA. 113:6(2013), pp. 4216-4313. Original Citation: Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

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Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

Silicon carbide (SiC) as both the most important non-oxide ceramic and promising semiconductor material grows stoichiometric SiO 2 as its native oxide. During passive oxidation, a surface transformation of SiC into silica takes place causing bulk volume and bulk mass increase. This review summarizes state-of-the-art information about the structural aspects of silicon carbide, silica, and SiC–SiO 2 interfaces and discusses physicochemical properties and kinetics of the processes involved. A special section describes the electronic properties of carbide–oxide interfaces, which are inferior compared to Si–SiO 2 interfaces, limiting the use of SiC-based electronics. In the oxidation of SiC there is a variety of parameters (e.g., porosity, presence of sintering aids, impurities, crystallographic orientation, surface treatment, and atmospheric composition) influencing the process. Therefore, the kinetics can be complex and will be discussed in detail. Nonetheless, a general linear-parabolic time-law can be foun...

Silica on Silicon Carbide

Cristobalite and tridymite are distinct forms of crystalline silica which, along with quartz, are encountered in industrial operations and industrial products. Because the International Agency for Research on Cancer has designated “crystalline silica” as an IARC Group 2A (probable carcinogen) and quartz and cristobalite as a Group 1 (carcinogen), it is important to properly identify and quantify the silica phase in all materials used in production and encountered in products. Opal is a form of hydrated silica which is also encountered in industry. Although some forms of opal mimic cristobalite and tridymite, they are not truly crystalline. The term “silica” in the industrial sense is used to mean any material whose composition is SiO2 whether it is crystalline or noncrystalline. Some people also consider silica to include hydrated SiO2. There are many forms of SiO2 which have both long-range and short-range order and are recognized as crystalline phases among which are quartz, cristobalite, and tridymite. The hydrated silicas, on the other hand, pose an enigma. Only a few forms show sufficient long-range and short-range order to be considered crystalline. The mineral silhydrite is an example. Opal in all its forms lacks sufficient order to be considered crystalline. Even opal-C, which produces a X-ray pattern similar to the diffraction pattern of cristobalite, lacks not only sufficient order to be considered crystalline but also contains water in the structural make-up. This paper discusses a classification and nomenclature for these forms which is critical to proper regulation. It also reviews the recent literature on tridymite, cristobalite, and opal, and provides an extensive bibliography. Modern studies have shown that opal-A is disordered, but opal-CT and opal-C contain ordered domains that mimic stacked sequences of cristobalite and tridymite sheets such that X-ray patterns show features similar to the crystalline cristobalite and tridymite. There is debate on whether the ordered regions have lost the water that characterizes the opals. In fact, heating studies have shown that all opals show changes on heating characteristic of materials that lose water in the process. The TEM evidence showing domains in the range 10–30 nm in a matrix of disordered opal suggest that the proper term for this system is paracrystalline analogous to inorganic and organic polymers.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0885715600009696

Opal, cristobalite, and tridymite: Noncrystallinity versus crystallinity, nomenclature of the silica minerals and bibliography

The autocorrelation function, Corr(α, ω′) = \({\int}_{{-}{\infty}}^{{\infty}}\) α(ω + ω′)α(ω)dω, may be used to parameterise effective line widths of absorption bands in IR spectra. It has the advantage of not requiring any peak fitting to the primary spectra and can be applied to individual bands or groups of bands in a spectrum. A new procedure for analysing autocorrelation spectra which result from the application of the autocorrelation function to primary spectra is presented. The approach is well suited for quantifying line width variations in powder absorption spectra from sequences of samples with varying composition, degree of cation order or structural state. Worked examples are set out to illustrate different applications of the approach, including the characterisation of structural phase transitions in tridymite, Al/Si ordering under non-equilibrium conditions in Mg-cordierite, short range Al/Ge order in BaAl 2 Ge 2 O 8 feldspar and mixing behaviour in the jadeite-augite solid solution.

Autocorrelation analysis of infrared spectra from minerals

Experimental investigation of thermomechanical behaviour of clay-rich sandstone at extreme temperatures followed by cooling treatments

Structural change of orthorhombic-I tridymite with temperature : A study based on second-order thermal-vibrational parameters

Two least-squares methods based on the Gram-Charlier expansion and the Edgeworth expansion were applied to a test structure to examine their usefulness in analysing multimodal density distribution of atoms. The Gram-Charlier expansion was more successful to reproduce the test structure than the Edgeworth expansion. The least-squares method based on the Gram-Charlier expansion was applied to the high temperature forms of tridymite to analyse density distribution of Ο atoms. The obtained density distribution of Ο was concave and nearly concentric at both 693 and 733 Κ (hexagonal), but clearly bimodal, at 493 Κ (orthorhombic), with the mean positions of low densities.

High-order thermal-motion tensor analyses of tridymite

単斜型6C tridymite(珪石レンガ,湯ケ原)と斜方型10C tridymite(石神山)の加熱変化を高温下でX線単結晶回折法と高温顕微鏡観察により検討した。珪石レンガ単斜型では室温から450℃ 間に5変態が存在し,貫井等の結果を確認した。また斜方10C型の加熱変化も貫井等の斜方5C型のそれと類似する。斜方10C型では,120～150℃ 間でO(6+I,1,1)相が室温相と共存しながら出現する。 また単斜型と斜方型の関係を調べるため,各tridymiteの加熱冷却実験を行なった。その結果,湯河原産単斜型は150℃ 以上の加熱冷却で斜方10C型に変化し,珪石レンガ単斜型は加熱急冷の場合のみ2C型に変化する。斜方型を加熱徐冷したが,単斜型への変化は観察されなかった。

Moritaka Imamura

Papers

Structural change of orthorhombic-I tridymite with temperature : A study based on second-order thermal-vibrational parameters

High-order thermal-motion tensor analyses of tridymite

Change of X-ray diffraction pattern of tridymite by heating and cooling