Simulations of the surfaces of soda lime aluminoborosilicate glasses exposed to water

Molecular dynamics simulations of 7 compositionally different sodium calcium alumino‐borosilicate glasses showed formation of ⁴B and ⁵Al more consistent with experimental data without compromising the other structural features that match experimental results observed in recent simulations of these glasses. Analysis of the dry surfaces of these glasses show a lack of ⁴B in the top 5‐6 Å of the surface in comparison to the bulk concentration for all glasses and no ⁵Al. Upon exposure to water, the simulations show that the ³B in the top 5‐6 Å of the glasses are preferentially attacked, decreasing the number of B bonds to O originally from the glass, indicating a change in the glass network. Inclusion of all B–O bonds in the top 5‐6 Å (i.e., including O from water) shows a decrease in ³B but an increase in ⁴B that is consistent with NEXAFS analysis, which the simulations show are hydroxylated. There is an increase in the concentration of ³Al in the dry surface in comparison to the bulk, but exposure to water converts almost all of these ³Al to ⁴Al. Hydroxyl concentrations vary from 2.6/nm² to 4.1/nm², with SiOH and BOH dominating these surface hydroxyls. Upon exposure to water, network linkages to B are preferentially ruptured. This, and the preferential loss of the nonbridging oxygen sites attached to Na, provide atomistic evidence of the initial stages of removal of B and Na from glass surfaces exposed to water.     

Detection of Phase Separation by FTIR in a Liquid-Crystal-Display Substrate Aluminoborosilicate Glass

The effect of heat treatment on the Fourier transform infrared spectrometry (FTIR) reflection peak position of the Si–O structural band near 1087 cm⁻¹ of a liquid-crystal-display substrate glass was investigated. The FTIR peak position shifted more slowly with heat-treatment time, and to a greater extent than expected, for the fictive temperature change. The isochronal shift of the FTIR peak as a function of the heat-treatment temperature exhibited a good correlation with the change of chemical durability in an HCl solution, suggesting that the infrared peak shift was the result of the phase separation induced by the heat treatment. The separated phase, with spherical particles ∼50 nm in diameter, was observed by scanning electron microscopy in a glass sample heat-treated at 750°C for 2500 h. The FTIR peak shift measurement appears to be a sensitive method for detecting the early stage of the glass-in-glass phase separation for borosilicate glasses.     

Chemical structure and mechanical properties of soda lime silica glass surfaces treated by thermal poling in inert and reactive ambient gases

This study employed thermal poling at 200°C as a means to modify the surface mechanical properties of soda lime silica (SLS) glass. SLS float glass panels were allowed to react with molecules constituting ambient air (H₂O, O₂, N₂) while sodium ions were depleted from the surface region through diffusion into the bulk under an anodic potential. A sample poled in inert gas (Ar) was used for comparison. Systematic analyses of the chemical composition, thickness, silicate network, trapped molecular species, and hydrous species in the sodium‐depleted layers revealed correlations between subsurface structural changes and mechanical properties such as hardness, elastic modulus, and fracture toughness. A silica‐like structure was created in the inert gas environment through restructuring of Si–O–Si bonds at 200°C in the Na‐depleted zone; this occurred far below T_g. This silica‐like surface also showed enhancement of hardness comparable to that of pure silica glass. The anodic thermal poling condition was found so reactive that O₂ and N₂ species can be incorporated into the glass, which also alters the glass structure and mechanical properties. In the case of the anodic surfaces prepared in a humid environment, the glass showed an improved resistance against crack formation, which implies that abundant hydrous species incorporated during thermal poling could be beneficial to improve the toughness.     

Study on the leaching behavior of salt waste forms prepared by using zeolite and lime glass

When the reaction of salt and zeolite was used to minimize the free salt in waste forms (r = 0.1), Cs showed the lowest leaching rate, 1.015 × 10⁻¹ g/m² d. Because alkali chloride is chemically stable, the reaction that alkali elements become components of glass does not happen and thus the leach resistance of the waste form solidified with soda glass was not much different from that solidified with borosilicate glass. The crystalline phase containing Cl was sodalite, but the tendency that Cs exists prior to sodalite phase was not confirmed. From a result of a long-term leaching, the predicted leaching fraction of Cs in 900 days was as high as 5.13%, but that of Sr was as low as 0.24%. The leaching experiment with a varying pH showed the major nuclides such as Cs, Sr, and Li in salt waste had different leaching characteristics each other.     

Molecular dynamics study of correlations between IR peak position and bond parameters of silica and silicate glasses: Effects of temperature and stress

In the IR spectra of the silica and silicate glasses, the shifts of the maximum intensity position of the ν_{Si–O–Si,as} band upon heating or applying mechanical stress could be attributed to changes in the distribution of bond parameters such as bond length and bond angle. Upon heating, isotropic expansion occurs and the density changes; upon applying mechanical stress, anisotropic strain is induced and a significant change in the Si–O–Si bond angle is observed. From molecular dynamics simulations of a silica glass, we show that the peak position shift correlates better with the asymmetric change in the Si–O bond length distribution, rather than the Si–O–Si bridge angle, the O–Si–O tetrahedral angle, or the density change. This new finding provides an insight into how and why the ν_{Si–O–Si,as} IR peak of soda lime silica (SLS) glass shifts upon chemical strengthening via ion exchange and thermal tempering.     

A fourier transform infrared spectroscopy study of the effect of temperature on soy lecithin-stabilized emulsions

The effect of temperature on soy lecithin-stabilized emulsions was studied using Fourier transform infrared spectroscopy (FTIR). Oil-in-water (o/w) 4% (wt/vol) soy lecithin emulsions were prepared in 6% (vol/vol) medium-chain triglycerides and 94% (vol/vol) water using a two-stage homogenizer set at a pressure of 3000 psig. Three types of emulsions were used in this study: emulsions containing Lecigran and Lecimulthin as emulsifiers and a control emulsion, with no emulsifier added. After preparation, the emulsions were cooled to 4°C, held at this temperature, and spectra were collected after 1 h. The emulsions and reference water were raised to room temperature (22°C) and held at that temperature for 1 h and the spectra collected. The temperature was raised 15°C over the temperature range of 22 to 82°C, and spectral data were collected similarly. The four regions used for this determination in the subtracted spectra of the emulsion were those contributing to -OH vibration, -CH₂ stretching, H-O-H bending vibrations, and P=O, C-O-C, and P-O-C vibrations. The control emulsion was greatly affected at temperatures other than room temperature. This was due to the lack of lecithin as an emulsifier, resulting in a destabilization of the emulsion with temperature increases. The vibrational peaks for the emulsion containing Lecimulthin were found to be lower than those for the emulsion made with Lecigran due to greater water bonding. The control had the highest peaks at the -OH regions because of reduced interaction at the oil-water interface. Both of the emulsions with phospholipids remained stable throughout the temperature range. FTIR is a potentially powerful tool that could be used in the rapid determination of emulsion stability in food systems by measuring emulsifier-water interactions.     

Correlation between IR peak position and bond parameter of silica glass: Molecular dynamics study on fictive temperature (cooling rate) effect

The fictive temperature of glass is a consequence of its thermal history (cooling rate, primarily) and has a direct effect on physical and chemical properties of the glass. But, it is not easy to measure. The ability to nondestructively and spectroscopically measure it at room temperature would be of great benefit. Although empirical correlations have been established between fictive temperature and selected absorption peaks in the infrared spectra of silica glass, the fundamental understanding for this correlation has not been reported. Here, we use molecular dynamics simulations to show that the blue shift in the Si–O–Si asymmetric stretching peak of pure silica glass, which is known to correlate with a decrease in fictive temperature, can be attributed to a decrease in the average length of the Si–O bond in the silica network, not changes in the density or the Si–O–Si bond angle. The decrease in density at higher fictive temperatures of silica is associated with a decreased population of 5‐ and 6‐membered rings and broadening of the ring‐size distribution, and an increase in the average Si–O–Si bond angle.     

Roughness of oxide glass subcritical fracture surfaces

An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable subcritical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self‐affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al (J Non‐Cryst Solids, 353, 1582‐1591, 2007) on the effect of the material's heterogeneity on the crack tip stresses with the self‐affine nature of the fracture surfaces.     

应用非线性回归理论探讨钠钙玻璃高温电阻率的计算

钠钙玻璃高温电阻率计算是玻璃电熔设计中最重要的参数之一,作者在多年工作与收集大量资料的基础上,运用非线性回归与数理统计理论,重新探讨并提出新的钠钙玻璃高温电阻率计算式.这些回归式与原苏联学者提出的计算式相比,或精度更高、或更加简便,并已经实际应用在玻璃电熔的研究与设计工作中.     

Silicones on glass surfaces

X-Ray photoelectron spectroscopy can be applied to the study of the bonding of highly functionalised silicones on to E-glass fibres. The adsorption of six types of silicones (hydrido, epoxy, unsaturated imino, methacryl. ‘terminal’ amino and ‘pendant’ amino) from dilute toluene solutions were compared with that of a standard silane coupling agent. The calcium concentration was found to be an effective determinant of surface coverage by the siloxanes. as well as enabling the thicknesses of the adsorbed layers to be determined.     

Hydrolysis and condensation of alkoxysilanes investigated by internal reflection FTIR spectroscopy

The hydrolysis of a series of alkyl-substituted alkoxysilanes and an antimicrobial quaternary ammonium silane was investigated in water-acetone solvents by Fourier transform infrared (FTIR) spectroscopy. An internal reflectance cell was employed for the investigation. Rates of sequential hydrolysis of the first, second, and in one case the third alkoxy groups were extracted by nonlinear regression of curves of methanol concentration plotted versus time using data obtained from the FTIR spectra of the reaction mixture. Acid catalysis of the hydrolysis was observed. Condensation of the silanol groups produced by the hydrolysis was investigated using similar techniques and rate data are presented.     

Study of light scattering on a soda lime glass eroded by sandblasting

In Saharan areas of Algeria, sandstorms can damage vehicles windshields inducing incidental light diffusion that affects the driver's visibility. Vehicles technical controllers find some difficulties with damaged windshields. The control being made visually with the naked eye, it is therefore difficult to judge when a damaged windshield is no more valid to use. In this context, we studied the influence of the surface state of a soda lime glass on the scattering of a white light. The varying parameters considered are the projected sand mass, the opening of the light beam and the distance sample-receptor. By increasing the projected sand mass up to 200 g, the optical transmission falls from 91.6 to 13% and the roughness increases from 0.035 up to 2.27 μm and then tends toward a constant level. For the as-received state, the image obtained using a CCD camera presents a net boundary and the transmission profile shows a saturation plateau. By damaging the surface, the image boundary deforms and becomes diffuse. For the highly damaged states, the image become completely blurred and the transmission profile disappears. The variation of the transmission according to roughness shows an inflection point at T = 73% and R_a = 1.5 μm. This point seems to separate two domains: a transparent field (R_a < 1.5 μm) and a blur field (R_a > 1.5 μm). The visibility limit obtained in our tests conditions is estimated at about 73%.     

Nondestructive evaluation of polymer coatings by mirage–FTIR spectroscopy: A tool for surface characterization

We demonstrate the unusual applications of the recently developed mirage–Fourier transform infrared (FTIR) spectroscopy for nondestructive characterization of polymer coatings, especially on absorbing substrates or very thin coatings, where conventional FTIR techniques tend to fail. The mirage–FTIR has been briefly described. A few specific examples have been given to demonstrate the potential of this technique as a tool for surface characterization. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1249–1252, 1998     

Conformational changes in the induction period of crystallization as measured by FT-IR

The isothermal crystallization behaviors of poly(bisphenol A-co-decane ether) (BA-C10) at different temperatures were studied in situ by means of Fourier transform infrared spectroscopic (FT-IR) measurements. Conformational changes during the induction period were investigated in details. The results suggest that conformational changes of polymer chains always take place before the start of changes in the characteristic FT-IR peaks of the crystalline phase.     

SBS改性沥青紫外老化研究

将不同老化时间、老化方式的SBS改性沥青的饱和分、芳香分、胶质、沥青质和SBS改性剂分离出来,用傅立叶红外光谱分析各组分的结构变化以研究SBS改性沥青的紫外老化机理.结果表明：紫外老化后,SBS改性沥青的饱和分和芳香分含量下降、胶质和沥青质含量上升、胶体不稳定指数上升;羧基和亚砜基含量增加,说明光氧化产生了极性官能团.     

Hybrid Microwave Sintering of Infrared Transparent Nano‐Y3Al5O12 Synthesized by a Modified Combustion Technique

Infrared transparent ceramics found to have numerous civilian and defense applications. In the present work, Y₃Al₅O₁₂ nanoparticles were synthesized by an auto‐igniting modified single‐step combustion method. The structure and morphology of the as‐prepared powder revealed the phase purity and ultrafine nature of the powder having an average crystallite size of 16 nm and well‐defined lattice planes. Coupling of the resistive and microwave heating at precise proportion leads to a sintered density of the powder with 99.3% of the theoretical density at a temperature as low as 1470°C for a soaking duration of just 20 min. Marked reduction in grain size and the porosity was also observed for the hybrid sintered pellets. An average grain size of 167 nm was measured for the sintered pellets, which also showed a high transmittance of 80% in the UV–vis region and 82.5% in the mid‐IR region.     

Electrical properties of soda lime silica glass using electrolysis at 600°C between molten tin and lead electrodes

The electrolysis of a soda lime silicate glass has been studied using liquid metal electrodes of lead and tin at 600°C and voltages up to 300 V in a N₂/10% H₂ atmosphere. The behaviour observed was dependent upon the applied voltage. At less than 2.5 V, the square of the current was inversely proportional to the electrolysis time but at higher voltages, up to 100 V, the current was inversely proportional to the time for periods up to 300 ms. At voltages greater than 100 V, the behaviour could not be expressed by a simple equation, the currents passing were high and finally, electrical breakdown occurred at 300 V.It is proposed that in the range 2.5 to 100 V the glass behaves as a dielectric with charge separation in a thin surface layer. At higher voltages, near breakdown, the heat liberated at the surface is sufficient to disrupt the surface layer and then the conduction is governed by the electrical properties of the bulk glass.     

几种光谱方法(FTIR、FT-Raman,NMR)在橡胶分析中的应用

综述了傅里叶变换红外光谱 ,傅里叶变换拉曼光谱以及核磁共振波谱在橡胶结构的定性、定量分析中的应用     

Influence of triacylglycerol characterics on the determination of free fatty acids in vegetable oils by fourier transform infrared spectroscopy

A rapid and direct Fourier transform infrared (FTIR) spectroscopic method using a 25-μm NaCl transmission cell was developed for the determination of free fatty acids (FFA) in six important vegetable oils (corn, soybean, sunflower, palm, palm kernel, and coconut oils) that differ in fatty acid profile. The calibrations were established by adding either standard FFA (oleic, lauric acids) or a representative mixture of FFA obtained after saponification of the refined oils. For all oils, up to a FFA level of 6.5% for coconut oil, the best correlation coefficient was obtained by linear regression of the free carboxyl absorption at 1711 cm⁻¹. All correlation coefficients were greater than 0.993, and no significant difference between the calibration methods could be detected. Upon validation of the calibration, no significant difference (α=0.05) between the “actual” and the “FTIR predicted” FFA values could be observed. The calibration models developed for the six oils differed significantly and indicate the need to develop a calibration that is specific for each oil. In terms of repeatability and accuracy, the FTIR method developed was excellent. Because of its simplicity, quick analysis time of less than 2 min, and minimal use of solvents and labor, the introduction of FTIR spectroscopy into laboratory routine for FFA determination should be considered.