Regioselective Approach to Characterizing Increased Edge Availability in Layered Crystal Materials following Layer Expansion: Reaction of Kaolinite with Octadecyltrimethylammonium Salts

In this paper, the regioselective reactions of kaolinite and methoxy-modified kaolinite (MeO-Kaol), methanol-expanded kaolinite, with octadecyltrimethylammonium salts are compared. This study mainly concerns the reactions of kaolinite or MeO-Kaol with octadecyltrimethylammonium chloride (C18TAC) in methanol and the subsequent exhaustive washing of the resultant products with ethanol. X-ray diffraction patterns of the products reveal no intercalation of C18TAC between pristine kaolinite layers. Additionally, intercalation and subsequent deintercalation of C18TAC proceed in the product using MeO-Kaol. In the Fourier-transform infrared spectra, the intensities of CH2 stretching bands of the product prepared using MeO-Kaol drastically increase compared to those using kaolinite. In addition, CH2 stretching bands of the product using kaolinite are hardly observed without enlarging the spectrum. The product using MeO-Kaol also displays mass loss in the range of 200–300 °C in the thermogravimetric curve and a nitrogen content with 0.15 mass% estimated using the CHN analysis. These results therefore demonstrate an increase in the available reactive edges in the layered crystal material following an expansion of the stacked layers.

Sulbactam pivoxil powder attributes and compatibility study with excipients

Background Sulbactam pivoxil is an irreversible β-lactamase inhibitor that can be used with β-lactam antibiotics to improve antibacterial therapy by the oral route. Relevant properties of this drug for pharmaceutical manufacturing are not available in the open literature. In this work, a solid-state characterization of sulbactam pivoxil at the molecular, particle, and bulk levels was performed. Results Particles exhibited a mean diameter of about 350 μm, irregular shape crystals, and good flow properties. This work presents for the first time the crystal structure of this β-lactamase inhibitor obtained by X-ray diffraction analysis. Fourier-transform infrared results showed the characteristic bands of aliphatic hydrocarbons and ester groups. The differential scanning calorimetry curve exhibited a sharp endothermic peak at 109 °C corresponding to sulbactam pivoxil melting. The thermogravimetric curve revealed a mass loss at 184 °C associated with a decomposition process. This powder showed a moisture content of 0.34% and a water activity of 0.463. Potential interactions between sulbactam pivoxil and common pharmaceutical excipients were evaluated by thermal analysis. The endothermic peak and the enthalpies of melting were preserved in almost all the analyzed mixtures. Conclusion The powder was constituted by micro-sized crystals of sulbactam pivoxil that had suitable physicochemical properties for processing in controlled humidity environments. Thermal analyses suggested that sulbactam pivoxil is compatible with most of the evaluated excipients. The information obtained in the present study is relevant for the development, manufacturing, and storage of formulations that include sulbactam pivoxil.

Study of Growth and Sublimation of Germanium Nitride Using the Concept of Tedmon's Kinetic Model

The paper gives a mathematical model of a thermogravimetric curve for the growth of scale on a metal surface with its simultaneous sublimation is presented and considers the case of the growth-sublimation of scale being preceded by the process of gas etching of the monocrystal surface. The obtained equations are used to describe the kinetic curve of the mass change of a germanium sample when a nitride layer is formed on it in a medium of hydrazine vapors.

Effects of Shellac Treatment on Wood Hygroscopicity, Dimensional Stability and Thermostability

Dimensional stability proves to be an important factor affecting the quality of wooden products. As a sort of crude and thermoplastic resin, shellac excreted by lac insects demonstrates water-repellent and environmental-friendly features. The research impregnated shellac with wood at room temperature and with a vacuum-pressure procedure. Efforts were made to examine how shellac treatment affected the dimensional stability, moisture absorption, chemical structure, thermostability, as well as morphological characteristics of wood. Results indicated that shellac treatment was a type of efficient solution useful in the enhancement of the dimensional stability of wood. Shellac solution had good permeability in the wood, and the weight percentage gain reached 13.01% after impregnation. The swelling coefficients of treated wood in the tangential and radial directions decreased by 20.13% and 24.12%, respectively, indicating that impregnation could improve wood dimensional stability. The moisture absorption of shellac-treated wood was reduced by 38.15% under 20 °C and 65% relative humidity. Moreover, shellac treatment significantly modified wood structure, although there were no drastic changes in the spectra. Specimens for shellac treatment ran across two decomposition peaks at 350 and 390 °C, and specimens in the control group saw one more common derivative thermogravimetric curve when the sharp peak approached 355 °C. After impregnation of shellac into wood, the shellac blocked pits and hardened on the intrinsic layer of the wood for fear of hygroscopicity. The practice was applicable to a variety of wood products, such as buildings, furniture, and landscape architecture.

Study of thermal degradation behavior and kinetics of ABS/PC blend

This work investigated kinetics and thermal degradation of acrylonitrile butadiene styrene and polycarbonate (ABS/PC) blend using thermogravimetric analysis in the range of 25 to 520°C. For thermal degradation of blend, activation energy (Ea) and pre-exponential factor (A) were calculated under various heating rates as 5, 10, 15 and 20°C/min using iso-conversional model-free methods (Kissinger, Flynn-Wall- Ozawa and Friedman). Mass loss of the blend as a function of temperature was plotted as thermogravimetric curve (TG) while derivative values of mass loss were drawn as derivative thermogravimetric (DTG) curve. Using Kissinger method, Ea was 51.4 kJ/mol, while values calculated from FWO and Friedman method were 86–161 and 30–251 kJ/mol respectively. Results showed increasing trend of Ea with higher conversion values indicating different degradation mechanisms at the initial and final stages of the experiment. Thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy (ΔG) and entropy change (ΔS) were also calculated.

Crystal structure of bis(N,N′-dimethylthiourea-κS)bis(thiocyanato-κN)cobalt(II)

During systematic investigations on the synthesis of coordination polymers with Co(NCS)2 involving different thiourea derivatives as coligands, crystals of the title compound Co(NCS)2(N,N′-dimethylthiourea)2, or [Co(C3H8N2S)2(NCS)2], were obtained. These crystals were non-merohedric twins and therefore, a twin refinement using data in HKLF-5 format was performed. In the crystal structure of this compound, the CoII cations are coordinated by two N-terminally bonded thiocyanate anions as well as two S-bonding N,N′-dimethylthiourea molecules, forming two crystallographically independent discrete complexes each with a strongly distorted tetrahedral geometry. An intricate network of intermolecular N—H...S and C—H...S hydrogen bonds can be found between the complexes. The thermogravimetric curve of the title compound shows two discrete steps in which all coligand molecules have been emitted, which is also accompanied by partial decomposition of the cobalt thiocyanate. If the measurement is stopped after the first mass loss, only broad reflections of CoS can be found in the XRPD pattern of the residue, which proves that this compound decomposes completely upon heating. However, at lower temperatures an endothermic signal can be found in the DTA and DSC curve, which corresponds to melting, as proven by thermomicroscopy.

Application of Percolation Theory in Thermokinetics

The present paper focuses on the infiltration of random fluid particles through a porous wall. The thermogravimetric curve is assumed to be a non-eroded interface so that the random fluid particle can pass through the discrete boundary of it. The node on the thermogravimetric plane is denoted by the three-dimensional lattice, which has unit thickness. The Lattice Boltzmann method is implemented to determine the variation of the remaining mass fraction (X) with respect to time. The kinetic model is correlated with the Lattice Boltzmann method to determine the kinetic parameters. The practical situation of Moka coffee maker is applied to determining the kinetic parameters.

Evaluation of Two Kurdistan-Iraq Crude Oil (T-21A, PF2) by Derivatographic Method

Evaluation of crude oil and its residue using derivatography, is one of the most common physical and chemical methods analytical research. Crude oil residues 350+ obtain from two Iraq-Kurdistan crudes (Tawke T-21A well and Shekhan PF2 well) by using atmospheric distillation after removing all volatile fractions. The sample characterized by direvatographic method. The thermo analysis, reactions were carried out at temperature range 20- 700℃ for reaction time 68 min. These derivatograph curves show the weight change and heat energy (Enthalpy) change as the function of time and temperature. It shows that the crude oil residues have different composition. The curve which marks the weight changes of the sample heated is the thermogravimetric curve, TGA. Whereas the curve, which records heat energy or enthalpy changes during thermal decomposition is the DTA or differential thermoanalytic. By means of the derivatograph, it is possible to record simultaneously curve of weight change (TG), and enthalpy change (DTA) as a function of temperature. This method analysis shows good evaluation of these two crude oil well.

MODIFICATION OF EXPANDED PERLITE WITH ORTHOPHENANTHROLINE FOR FORMATION OF ACTIVE SITES FOR ACID DYES: PREPARATION AND CHARACTERIZATION

The expanded perlite (aluminosilicate naturally acid) has been modified with orthophenanthroline (Lewis base). The material was characterized by TG/DTA, XRD and IR. The thermogravimetric curve of the modified expanded perlite presented a lower thermal stability due to the orthophenanthroline and showed 13,6% of mass loss total. However, pure expanded perlite presented only 2,3% of the mass loss. The DTA curve showed endothermic event characteristic of the presence of orthophenanthroline. For XRD analysis is visualized, the presence of reflections in the diffractogram relating to the modified material of orthophenanthroline peaks of crystallinity since no modification perlite is an amorphous material. The band regarding absorption vibration of Si-O group appears at lower wavenumbers than in the unmodified material. So there was an interaction between the OH groups of silanols of perlite groups with unshared electron pairs of nitrogen atoms and C=C bonds (also rich in electrons) in the chemical structure of orthophenanthroline as a result of a hydrogen bond between these groups. thus perlite was modified through the interaction of its acid sites (Si-OH) with Lewis basic sites of orthophenanthroline.