IR spectroscopic and electron microscopic investigations of colored lead silicate glasses

The information on obtaining colored transparent glasses of lead silicate composition is given in the article. Cr₂O₃, Mn₂O₃, Fe₂O₃, Ni₂O₃, Y₂O₃, Ce₂O₃, Nd₂O₃, and Er₂O₃ are used as colorants. Structural features of obtained glasses are investigated by methods of infrared spectroscopy and electron microscopy.     

Investigation of silicate mineral sanidine by vibrational and NMR spectroscopic methods

Sanidine, a variety of feldspar minerals has been investigated through optical absorption, vibrational (IR and Raman), EPR and NMR spectroscopic techniques. The principal reflections occurring at the d-spacings, 3.2892, 3.2431, 2.9022 and 2.6041 Å confirm the presence of sanidine structure in the mineral. Sanidine shows five prominent characteristic infrared absorption bands in the region 1200–950, 770–720, 590–540 and 650–640 cm⁻¹. The Raman spectrum shows the strongest band at 512 cm⁻¹ characteristic of the feldspar structure, which contains four membered rings of tetrahedra. The UV–vis–NIR absorption spectrum had strong absorption features at 6757, 5780 and 5181 cm⁻¹ due to the combination of fundamental OH– stretching. The bands at 11236 and 8196 cm⁻¹and the strong, well-defined band at (30303 cm⁻¹ attest the presence of Fe²⁺ and Fe³⁺, respectively, in the sample. The signals at g = 4.3 and 3.7 are interpreted in terms of Fe³⁺ at two distinct tetrahedral positions Tl and T2 of the monoclinic crystal structure The ²⁹Si NMR spectrum shows two peaks at −97 and −101 ppm corresponding to T2 and T1, respectively, and one peak in ²⁷Al NMR for Al(IV).     

The estimation of structural component contents in lead silicate glasses

The contents of structural components in lead silicate glasses were determined by the X-ray electron spectroscopy and thermodynamic analysis methods. Lead silicate glasses were described as solid solutions of lead and silicon oxides and lead silicates. The thermodynamic properties of metastable lead silicates were estimated. Thermal treatment in an inert or oxidizing atmosphere led to identical glass structures. High-lead glasses are based on metastable lead-oxygen structures containing 3–7 lead atoms. Such structures are absent in crystalline silicates.     

Thermal expansion of high lead silicate glasses in relation to structure

The thermal expansion of some binary and ternary high lead silicate glasses was measured from room temperature to above the softening temperature. The expansion curves for all the glasses showed similar characteristics. The increase of lead oxide content increased the thermal coefficient of expansion but to a lesser extent than the alkaline fluxes. The various proposed mechanisms of thermal expansion were advanced and the experimental results could be explained by considering the bond strengths and ionic sizes of the cations. The possible effects of compactness and phase separation of the structure were also examined.     

Low-temperature thermal degradation behaviour of non-wood soda lignins and spectroscopic analysis of residues

Journal of Thermal Analysis and Calorimetry - Soda lignins from three non-wood species, namely bamboo (Bambusa bambos), giant cane (Arundo donax) and pearl millet (Pennisetum glaucum) were studied...     

Study of the nature of the crystallization water in some magnesium hydrates by thermal methods

The nature of the crystallization water in MgSO₄·7H₂O, Mg(NO₃)₂·6H₂O and MgCl₂·6H₂O has been studied with the nonisothermal methods of thermogravimetry (TG), derived thermogravimetry (DTG) and differential thermal analysis (DTA). Analysis of the characteristic thermogravimetric data (T _M,W _∞) and the kinetic parameters (n, E _a), together with the DTA results, with CuSO₄·5H₂O as control sample, provided evidence of the existence of coordinated water and of the nature of the anions in these hydrates. The results are confirmed by the observation of a real compensation effect. For the compensation effect, the following equation is proposed: InA=0.220E-0.8 Structures explaining the presence of the coordinated water and the nature of the anions in these hydrates are also proposed.     

Characterization of 40-year-old calcium silicate pastes by thermal methods and other techniques

Differential thermal analysis, thermogravimetry and evolved gas analysis, as well as the X-ray diffraction, were used to identify and to quantify the products of dicalcium silicate hydration. The samples were 38 years stored in laboratory conditions. The calcium hydroxide, calcium carbonate and calcium silicate hydrate contents were determined and discussed in terms of the specific properties of initial anhydrous phases used.

     

Effect of boron oxide on the thermal conductivity of some sodium silicate glasses

The thermal conductivity of some ternary silicate glasses was measured by the steady-state method at 25°C. Experimental results show that introducing B₂O₃ to replace Na₂O or increasing the SiO₂ content of the glass increased the thermal conductivity. The results are discussed in terms of the possible variation in network structure with the change in glass composition, which may virtually affect the phonon mean-free-path.     

In situ FTIR spectroscopic study on crystallization process of isotactic polystyrene

The melt crystallization process of isotactic polystyrene (i-PS) was studied by means of in situ Fourier transform infrared (FTIR) spectroscopy, with a focus on the conformational changes during the induction period. The spectra obtained during the induction period suggested the occurrence of some ordered structure that is characterized by higher regularity and packing of the helical moieties than observed in the melt. This ordered structure was clearly different from the amorphous structure, and close to the crystal structure. The Avrami analysis indicated that the formation process of the ordered structure at the late stage of the induction period is similar to the growth process of the crystallites after the induction period. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1227–1233, 1998     

Concentration dependence of spectroscopic properties and energy transfer analysis in Nd3+ doped bismuth silicate glasses

A detailed investigation on 1.06 μm spectroscopic properties as a function of Nd³⁺ ions concentration in bismuth silicate glasses is reported. Judd–Ofelt analysis indicated that Nd₂O₃ has no substantial influence on glass structure. Based on the Judd–Ofelt intensity parameters, several radiative properties such as radiative transition probability, radiative lifetime, branching ratio and emission cross-section of Nd³⁺ ions have been derived. The 1.06 μm emission intensity increases firstly and then attains maximum at 0.5 mol% Nd₂O₃ and decreases with further increase of dopant concentration. The luminescence quenching behavior at higher Nd³⁺ concentration has been ascribed to the hopping migration assisted cross relaxation mechanism. The high emission cross section (2.33 × 10⁻²⁰ cm²) and large quantum efficiency (90.7%) suggests their potential for compact 1.06 μm lasers applications.     

Investigation of the compatibility between kaempferol and excipients by thermal,spectroscopic and chemometric methods

Journal of Thermal Analysis and Calorimetry - Compatibility is an important step in pre-formulation studies during the development of solid dosage forms. In the present study, we used thermal...     

Application and limitations on thermal and spectroscopic methods for shelf-life prediction

In medical products, shelf-life after thermoplastic processing and sterilization is important, and ionizing radiation has become a preferred sterilization mode for medical devices. We have employed successfully thermal analytical methods to predict shelf-life for many polyolefin materials. However, as the material of construction becoming more sophisticated: multiphase alloys and blends, multi-layer constructions etc., issues existed that require clarification as to what extent these methodologies are applicable. We have employed thermal analytical methods in conjunction with spectroscopic and morphological methods to study the applicability and limitation of these techniques. Results were combined with real life and simulated aging experiments and presented in this article.     

Study of complexation of styrylheterocycles with cavitands by spectroscopic methods

Russian Chemical Bulletin - The complexation of crown-containing or dimethoxy-substituted styrylheterocycles (guest molecules) with β-cyclodextrin (β-CD),...     

FTIR spectroscopic study on crystallization process of poly(ethylene-2,6-naphthalate)

In situ Fourier transform infrared (FTIR) measurements were carried out to elucidate conformation changes occurring during the isothermal melt crystallization of poly(ethylene-2,6-naphthalate) (PEN). Based on the band assignments for the components of the amorphous, α-crystal form, and β-crystal form of PEN in film samples, the in situ data was analyzed in terms of the amorphous- and crystal-trans conformations. It was observed at a higher isothermal crystallization temperature that the formation of amorphous-trans conformations precedes the growth of crystals. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2741–2747, 1997     

Compatibility studies of aceclofenac with retard tablet excipients by means of thermal and FT-IR spectroscopic methods

The compatibility of aceclofenac with various tableting excipients was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The excipients applied in the direct pressing retard tablets were Carbopol 940, hydroxypropyl-methyl-cellulose, microcrystalline cellulose, Aerosil 200 and magnesium stearate. The ingredients alone and their 1:1 (w/w) binary mixtures were investigated before and after accelerated storage. An interaction was observed only between aceclofenac and magnesium stearate. The DSC and FT-IR examinations indicated formation of the magnesium salt of aceclofenac. For the other mixtures, there was no incompatibility between the components.