Kinetics and mechanism of thermal decomposition of copper hypophosphite

On the basis of an elaborate investigation of the thermal decomposition reaction for crystalline copper hypophosphite by kinetic, radiospectroscopic and optical methods, and by a study of the peculiarities of the copper hypophosphite structure and defects, it has been found possible to suggest the mechanisms by which the decomposition kinetics are regulated.     

Influence of preliminary UV irradiation on the thermal decomposition of copper hypophosphite

The effect of the influence of preliminary UV irradiation on the kinetics of the thermal decomposition of crystalline copper hypophosphite has been discovered, revealing a decrease in the induction period. Spectral dependence of the effect was determined by absorption of copper hypophosphite in the 255 nm charge transfer band. Comparison of the quantum efficiency of the disappearance of ions of bivalent copper 10^?1–10^?2 ions per quantum and the quantum output of hydrogen 10^?4–10^?5 mole per quantum as well as acid formation during photolysis shows that a proton (acid) as well as the univalent copper is the main primary product of photolysis. Formation of acid in the course of photolysis participating in the nucleation during the investigated topochemical process of thermal decomposition is the reason for the discovered effect.     

Dewetting of thin liquid films near soft elastomeric layers

Thin liquid film instabilities driven by van der Waals forces and in the proximity of soft elastomeric layers are considered in this work through two model problems: (i) a liquid film resting on an elastomeric layer and (ii) a liquid film bounded from one side by a rigid substrate and from the other side by an elastomeric layer. The elastomeric layers are modeled as linear viscoelastic solids, van der Waals forces are assumed to act only in the liquid, and lubrication theory and linear stability analysis are applied. For a liquid film resting on an elastomeric layer, substrate deformability has a destabilizing effect, as evidenced by an increase in the maximum growth rate and range of unstable wavenumbers. The destabilization worsens for thicker solid layers and is due to a lowering of the effective liquid-air interfacial tension. For an elastomeric layer resting on a liquid film, layer deformability has a stabilizing effect for thin layers but a destabilizing effect for thicker layers, with the former due to an enhancement and the latter due to a reduction of the effective solid-air interfacial tension. The results presented here suggest the possibility of exploiting the dewetting of thin liquid films to create topographically patterned surfaces on soft polymeric solids.     

Investigation of thermal decomposition of solids

Practical aspects of the studies of stages of thermal dissociation of solids, of the kinetics of the stages, and of utilization of general regularities of the process for verification of kinetic studies are discussed.

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Zusammenfassung Die praktischen Aspekte der Untersuchungen über die Stufen der thermischen Dissoziation von Festkörpern und ihrer Kinetik weiterhin über die Anwendungsmöglichkeiten der RegelmÄssigkeiten der Verifikation der kinetischen Untersuchungen werden erörtert.

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Investigation of thermal decomposition of phosphonic acids

The paper compares building and decomposition pathways of two phosphonic acids, amino trimethylene phosphonic acid (ATMP) and 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP).The theoretical formation reactions were composed using elementary reactions and compared to reaction routes published in literature. As result, summary reaction pathways for both phosphonic acids are proposed which only vary in the number of reaction steps required. These reaction steps include carbonyl reactions, S_N2-reactions, and ionic reactions. The synthesis of ATMP proceeds in three reaction steps, whereas HEDP is formed in one reaction. The thermal decomposition of both phosphonic acids in solid state was examined by combination of thermogravimetry coupled with infrared spectroscopy as well as pyrolysis gas chromatography coupled with mass spectrometry. Decomposition mechanisms were deduced and compared to the theoretical findings resulting in the conclusion that the decomposition processes of ATMP and HEDP follows the formation mechanism.Thus, the suitability of theoretical considerations for the understanding of thermal decomposition processes is shown.     

Investigation of thermal decomposition of rice husk

Studies on the thermal decomposition of untreated rice husk and that treated with HCl and H₂SO₄ of various concentrations were carried out by TG, DTG and DTA. The mass loss occurred in three distinct stages, namely, removal of moisture, release of volatile matter and burning of combustible material. The corresponding temperature ranges for untreated husk were 40–150, 215–350 and 350–690°C. The final temperature of combustion decreased with acid-treatment of the husk. The thermal decomposition of the husk was found to be an exothermic process.     

Investigation of thermal decomposition kinetics of taurine

The non-isothermal thermal decomposition of taurine was investigated by means of thermogravimetric analysis (TG) and differential thermal analysis (DTA). The experimental data were treated using Flynn–Wall–Ozawa, Doyle, Kissinger, and ?atava–?esták methods, respectively. The results show that the non-isothermal thermal decomposition mechanism of taurine is classified as phase boundary reaction, and the mechanism function is the Mampel Power law with n = 1. The forms of both integral and differential for the mechanism function are $ G(\alpha ) = \alpha $ and $ f(\alpha ) = 1 $ , respectively. The activation energy and the pre-exponential factor are 167.88 kJ mol^?1 and 1.82 × 10¹³min^?1, respectively.     

Nonlinear evolution of thin liquid films dewetting near soft elastomeric layers

The nonlinear evolution of thin liquid films dewetting near soft elastomeric layers is examined in this work. Evolution equations are derived by applying the lubrication approximation and assuming that van der Waals forces in the liquid cause the dewetting and that the solid can be described as a linear viscoelastic material. Two cases are examined: (i) a liquid layer resting on an elastomer bounded from below by a rigid substrate, and (ii) an elastomer overlying a thin liquid film bounded from below by a rigid substrate. Linear stability analysis is carried out to obtain asymptotic relations which are then compared against solutions of the full characteristic equations. In the liquid-on-solid case, numerical solutions of the evolution equations show that van der Waals forces cause thinning of the liquid film and thickening of the elastomeric solid beneath film depressions. Inclusion of a short-range repulsive force suggests that regular patterns may form in which ridges of fluid rest on depressions in the solid. In the solid-on-liquid case, the van der Waals forces cause the solid layer to break up before the liquid film can dewet. The results presented here support the idea that the dewetting of thin liquid films might be exploited to create topographically patterned surfaces on soft polymeric solids.     

Investigation of thermal decomposition of hydrated aluminium oxide

The composition of a hydrated aluminium oxide was determined and the course of its thermal decomposition was investigated. The stages of the dissociation were established and all the solid and gaseous intermediates of the decomposition were identified. A correlation was observed between the peak temperatures for boehmite and the particle size and degree of crystallinity.

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Zusammenfassung Die Zusammensetzung eines hydratisierten Aluminiumoxids wurde bestimmt und der Verlauf der thermischen Zersetzung dieses Oxids untersucht. Die Dissoziationsstufen wurden ermittelt und alle gasförmigen und festen Zwischenprodukte der Zersetzung identifiziert. Es wurde eine Korrelation zwischen den Peak-Temperaturen für Böhmit und der Partikelgrö\e und dem Kristallisationsgrad beobachtet.

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Mechanism of thermal decomposition of hydrated copper nitrate in vacuo

The general scheme of three-stage thermal decomposition of Cu(NO₃)₂·3H₂O to CuO has been refined based on evolved-gas-analysis data with a quadrupole mass analyzer (Jackson et al., Spectrochim. Acta Part B, 50 (1995) 1423). Quantitative evaluation of the composition of the gaseous products shows that the first stage involves primarily deaquation, and the second stage, primarily denitration of the original hydrated nitrate. The basic nitrate formed in the second stage most probably has the formula Cu(NO₃)₂·3Cu(OH)₂. It has been established that the molecular oxygen observed in the third stage of decomposition is produced by catalytic decomposition of NO₂ on the surface of CuO. The presence of Cu-containing ions in all stages of the process is consistent with the gasification mechanism of thermal decomposition.     

Synthesis and characterization of metallic copper nanoparticles via thermal decomposition

Copper oxalate was used as a precursor to prepare metallic copper nanoparticles by thermal decomposition. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. XRD analysis revealed broad pattern for fcc crystal structure of copper metal. The particle size by use of Debye–Scherrer’s equation was calculated to be about 40 nm.     

Evolution of yttrium trifluoroacetate during thermal decomposition

A detailed analysis of the thermal decomposition of yttrium trifluoroacetate under different atmospheres is presented. Thermogravimetry, differential thermal analysis, and evolved gas analysis have been used for this in situ analysis. Solid residues at different stages have been characterized by means of X-ray diffraction, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The first decomposition stage (310 °C) is exothermic and involves the complete removal of carbon (organic part) and the formation of yttrium fluoride. This process is characterized by a fast mass loss rate. Afterwards, yttria (Y₂O₃) is formed at 1200 °C through a slow process controlled by the out diffusion of fluorine that involves the formation of yttrium oxyfluoride as an intermediate. The evolution of the mass during the decomposition and the structure of the yttria particles is not affected by the presence of oxygen or water. However, when the oxygen (water) partial pressure is as low as 0.02% (<0.002%), the kinetics and final particle structure are strongly affected.     

Investigation of thermal decomposition of anthranilates of alkali metals

The thermal properties of the anthranilates of the alkali metals Li, Na, K, Rb and Cs were studied. Thermal, chemical and X-ray analyses and infrared spectroscopy were used to determine the reactions of decomposition of these compounds. The thermal properties of the anthranilates of the alkali metals were compared with those of other metals.This work was done within Project 01.17: New Methods in Analytical Chemistry and Their Application in the National Economy.     

The thermal decomposition of N,N-dimethyl-3-oxaglutaramic acid and the kinetics of its second-stage thermal decomposition reaction

N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by ¹H-NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The kinetic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1?α)^1/3?1]^?1, 203.75 kJ·mol^?1 and 10^17.95s^?1, respectively. The values of ΔS ^≠, ΔH ^≠ and ΔG ^≠ of the reaction are 94.28 J·mol^?1·K^?1, 203.75 kJ·mol^?1 and 155.75 kJ·mol^?1, respectively.     

The thermal decomposition of N,N-dimethyl-3-oxa-glutaramic acid and the kinetics of its second-stage thermal decomposition reaction

N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by 1H-NMR, Fourier transform in-frared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The ki-netic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1-α) 1/3-1]-1, 203.75 kJ-mol-1 and 1017.95s-1, respec-tively. The values of ΔS≠, ΔH≠ andΔG≠ of the reaction are 94.28 J-mol-1-K-1, 203.75 kJ-mol-1 and 155.75 kJ-mol-1, respectively.     

Isokinetic relationships at the thermal decomposition of tetranuclear copper(II)-complexes

A dependence of the activation energy upon the extent of conversion has been discovered for the thermal decomposition of Cu₄OCl₆L₄ with piperidine (1), morpholine (2), and triphenylphosphine oxide (3) as the ligand (L). Within the interval of conversions 0–0.3 the process shows a decrease in the activation energy (230–130 (1), 130–50 (2), and 200–100 (3) kJ mol^?1). The processes considered show an isokinetic relationship with T_iso = 255 ± 15 K which corresponds to a vibrational frequency of v_iso = 177 ± 10 cm^?1. This value accords well with IR absorption bands assigned to the stretching vibration in the trigonal CuCl₃ chromophore as predicted by theory. Based on this, an assumption about the CuCl₃-group as a central site of the reaction can be made. The IR- and X-ray data are presented to support the assumption made. © 1995 John Wiley & Sons, Inc.