Nitrogen In Glasses Research Articles

Thermally Induced Isomerization of Trilinolein and Trilinoelaidin at 250 °C: Analysis of Products by Gas Chromatography and Infrared Spectroscopy

The products formed by thermally induced isomerization of trilinolein and trilinoelaidin at 250 degrees C were studied by infrared spectroscopy and gas chromatography. The triglycerides of the 9c12c and 9t12t fatty acids, linoleic and linoelaidic acid respectively, were subjected to thermal treatment under nitrogen in glass. The products were removed at regular intervals and analysed by infrared spectroscopy using a single reflectance attenuated total internal reflectance crystal accessory. Trans-esterification of the products provided the corresponding fatty acid methyl esters which were studied by gas chromatography. The results show that the samples undergo decomposition and isomerization. Thermally induced 9c12c fatty acid (linoleic acid) molecules in the trilinolein molecules isomerize into 9c12t, 9t12c and 9t12t isomers. Thermally induced 9t12t fatty acid (linoelaidic acid) molecules in the trilinoelaidin molecules isomerize into 9c12t, 9t12c and 9c12c isomers. However, the concentration profiles are different for these two triglyceride samples. The rates of formation of isomers from linoleic acid are higher than the rates of formation of isomers from linoelaidic acid. In addition, these two fatty acids also isomerize into conjugated linoleic acids (CLAs). The profiles of the CLAs are identical in both cases.

Glasses in the D'Orbigny angrite

The angrites are a small and heterogeneous group of achondritic meteorites with highly unusual chemical and mineralogical features. The abundant presence of glasses in D'Orbigny makes this rock a unique member of the angrite group. Glasses fill open spaces, form pockets, and occur as inclusions in olivines. Their physical settings exclude an incorporation from an external source. Major and trace element (rare earth elements [REE], Li, B, Be, transition elements, N and C) contents of these glasses and host olivines were measured combining laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary-ion mass spectrometry (SIMS), Nuclear Reaction Analysis (NRA), and EMP techniques. Based on the major element composition, glasses filling voids could represent either a melt formed by melting an angritic rock or a melt from which angrites could have crystallized. Trace element contents of these glasses strongly indicate a direct link to the D'Orbigny bulk meteorite. They are incompatible with the formation of the glasses by partial melting of a chondritic source rock or by shock melting. The refractory elements (e.g., Al, Ti, Ca) have about 10 × CI abundances with CaO/TiO 2 and FeO/MnO ratios being approximately chondritic. Trace element abundances in the glasses appear to be governed by volatility and suggest that the refractory elements in the source had chondritic relative abundances. Although the glasses (and the whole rock) lack volatile elements such as Na and K, they are rich in some moderately volatile elements such as B, V, Mn, Fe (all with close to CI abundances), and Li (about 3–5 × CI). These elements likely were added to the glass in a sub-solidus metasomatic elemental exchange event. We have identified a novel mechanism for alteration of glass and rock compositions based on an exchange of Al and Sc for Fe and other moderately volatile elements in addition to the well-known metasomatic exchange reactions (e.g., Ca-Na and Mg-Fe). Because glass inclusions in olivine were partly shielded from the metasomatic events by the host crystal, their chemical composition is believed to be closer to the original composition than that of any other glasses. The relative trace element abundances in glasses of glass inclusions in olivine and glass pockets are also unfractionated and at the 10 to 20 × CI level. These glasses are chemically similar to the common void-filling glasses but show a much wider compositional variation. Inclusion glasses demonstrate that at least olivine grew with the help of a liquid. In analogy to olivines in carbonaceous chondrites, initial formation could also have been a vapor-liquid-solid condensation process. At that time, the glass had a purely refractory composition. This composition, however, was severely altered by the metasomatic addition of large amounts of FeO and other moderately volatile elements. The presence of volatile elements such as carbon and nitrogen in glasses of glass inclusions is another feature that appears to give these glasses a link with those hosted by olivines of carbonaceous chondrites. All these features point to an origin from a vapor with relative abundances of condensable elements similar to those in the solar nebula.

Nitrogen microanalysis of glass inclusions in chondritic olivines by nuclear reaction

Measured were the abundance and distribution of nitrogen in glasses of glass inclusions in olivines of CV3, CO3, CR, C4, CH3, and LL chondritic meteorites by means of the 14N(d, p) 15N nuclear reaction. Similar to what was observed with carbon, nitrogen is present in low concentrations (<20 ppm) in the structure of olivines but can by stored in variable amounts in glasses of glass inclusions. These primitive glasses, characterized by a Si-Al-Ca-rich composition, have highly variable nitrogen contents (30 to 1500 ppm) and highly inhomogeneous nitrogen distribution. Nitrogen contents are independent of the chemical composition of the glasses. The heterogeneous distribution is a common feature of all studied inclusions, as is evidenced by the variable contents of nitrogen in glass inclusions occurring in the same olivine grain. Nitrogen heterogeneity is suggestive of trapping of solid nitrogen carrier phases during formation of the constituents of chondrules. However, part of the originally trapped nitrogen appears to have been lost, possibly, by ulterior oxidation and subsequent transformation into volatile species.

Electron Probe Microanalysis of Nitrogen in Glasses and Glass Ceramics

A homogeneous (phosphate glass) and a heterogeneous (glass ceramic) material were chosen to develop a method for electron microprobe analysis of nitrogen in glasses and glass ceramics. The metaphosphate (50 mole-% P2O5, 25 mole-% BaO, 25 mole-% Rb2O) base glass and the silicate glass (composition of the base glass: 6.9 mole-% Al2O3, 21.3 mole-% MgO, 47.3 mole-% SiO2, 5.1 mole-% CaO, 19.4 mole-% AlN) were melted and cooled down to room temperature. In a second step, the two materials were nitrided by applying dry NH3 in a special tube furnace. Up to 5 wt.-% of nitrogen could be introduced. The ability of energy dispersive (EDX) as well as wavelength dispersive (WDX) electron probe microanalysis to analyze low contents of light elements in combination with highly concentrated heavy elements was tested both for glasses and for glass ceramics. Measuring conditions had to be optimized to get reliable analytical results as well as to avoid radiation damage of the glasses which may occur especially in the case of wavelength dispersive X-ray analysis.

Phosphorus oxynitride glasses

The properties and structural role of nitrogen in phosphorus oxynitride glasses are reported. Properties summarized for several compositions include the dissolution rate in water, thermal expansion coefficient, viscosity and refractive index. The bonding and coordination number of nitrogen in the glass network has been deduced from nuclear magnetic resonance, X-ray photoelectron spectroscopy and Raman spectroscopy. The existing evidence shows that nitrogen replaces oxygen in the PO 4 network as doubly coordinated (=N-) and triply coordinated (> N-) N 3− ions. The measured properties are consistent with these network structural features.

Nitrogen content of the intergranular glass phase in syalon ceramics

Syalon* ceramics are a series of biphase materials in which t3' grains, based on the /3-Si3N4 crystal structure with some substitution by A13+ and 02-, are contained in a semicontinuous matrix which is nominally a Y-Si-A1-O-N intergranular glass. Both low and high temperature properties of the Syalon composite are dependent on chemical composition of the glassy matrix phase. In particu- lar the limit to engineering application at elevated temperature is dependent upon the ability to crystallize the intergranular glass, which is also related to its chemical composition. The fine grain size of the/3' (~ 1 to 2 gm), and small matrix vol- ume fraction makes in situ analysis of the glass dif- ficult, although some work has been performed within the related Mg-Si-A1-O-N system, when specimens of unusually large glass volume fraction were prepared to facilitate analysis (1 ). Investigation of bulk glasses has related vari- ations in properties such as glass transition tempera- ture (Tg), viscosity, hardness and density to the nitrogen content, and such observations are noted to be consistent with a qualitative model in which N 3- substitutes for 02- in the glass network, there- by increasing the amount of crosslinking (2, 3). Although there is indirect evidence for the influence of glass nitrogen content on Syalon ceramic properties, no direct analytical data is available. Here we report the results of microanal- ysis which provides such direct evidence. Previous work on Syalon ceramics at Warwick (4), has utilized energy dispersive X-ray analysis (EDAX), on thin sections in the transmission elec- tron microscope (TEM), to obtain compositional data for the microstructural phases present. It has been demonstrated that an increase in the addition of a 21R polytypoid (close to A1N in composition) resulted in an increase in the A13+(and by infer- ence O z-) substitution level in the/3' phase. Calcu- *Syalon is a trade name of Lucas Cookson Syalon Ltd.