P. S. Bassi

Comparative study of the thermal analyses of some transition metal(II) propionates. Part I

The thermal decomposition of the propionates of Co(II), Ni(II), Cu(II) and Zn(II) has been studied using non-isothermal techniques (DTG, DTA and TG). The final thermolysis products in all these compounds are the corresponding metal oxides as confirmed by chemical analysis and X-ray powder diffraction method. The TG data for dehydration were computerised to test the various decomposition models: the Erofeev-Avrami equation, i.e. [−1n(1-α)]r with r = 13 for a nucleation-and-growth-controlled mechanism, has been found to be the most suitable. Comparison of the Ti values led to the stability orders: Zn > Co > Cu > Ni and Zn > Co > Ni > Cu, for dehydration and decomposition processes, respectively.

Comparative study of the thermal analyses of some transition metal(II) maleates and fumarates

The thermal decompositions of maleates and fumarates of Cu(II) and Zn(II) have been studied by employing simultaneous non-isothermal techniques (DTG, DTA and TG). The end-products are the corresponding metal oxides, as characterized by chemical analysis and X-ray diffraction. Comparison of theTm values led to the stability sequences Cu(F)>Cu(M); Zn(F)>Zn(M) and Cu(M)≈ Cu(F); Zn(F)>Zn(M) for dehydration and decomposition, respectively.ZusammenfassungDie thermische Zersetzung von Maleaten und Fumaraten von Cu(II) und Zn(II) wurde mittels simultan angewandter nicht-isothermer Techniken (DTG, DTA und TG) untersucht. Die Endprodukte sind die entsprechenden Metalloxide, wie durch chemische Analyse und Röntgendiffraktometrie nachgewiesen wurde. Ein Vergleich der Tm-Werte ergab für die Stabilität in der Dehydratisierungs- bzw. Zersetzungsreaktion die Reihenfolgen Cu (F) > Cu (M); Zn (F) > Zn (M) bzw. Cu (M) ≈ Cu (F); Zn (F)>Zn (M).РезюмеСовмещенным неизоте рмическим методом ДТ Г, ДТА и ТГ изучено термичес кое разложение малеатов и фумаратов меди и цин ка. Конечными продуктам и реакции разложения являлись окиси соотв етствующих металлов, идентифицированных химическим анализом и рентгенофазовым ана лизом. Согласно значе ниямTm, устойчивость компле ксов располагается в ряд Cu (F)>Cu (M); Zn (F)>Zn (M) и Cu (M) ≈ Cu (F); Zn (F)>Zn (M), соотв етственно, для реакций дегидратаци и и разложения.

Mössbauer study of the thermal decomposition of some iron(III) monocarboxylates

Abstract The thermal decomposition of iron(III) succinate, Fe 2 (C 4 H 4 O 4 ) 2 (OH) 2 and iron(III) adipate pentahydrate, Fe 2 (C 6 H 8 O 4 ) 3 ·5 H 2 O, has been investigated at different temperatures for different time intervals in static air atmosphere using Mossbauer spectroscopy and nonisothermal techniques (DTG-DTA-TG). The reduction of iron(III) to iron(II) species has been observed at 533 K and 563 K in the case of iron(III) succinate and iron(III) adipate, respectively. At higher temperatures, α-Fe 2 O 3 is formed as the final thermolysis product.

Mössbauer study of the thermal decomposition of iron(III) citrate pentahydrate

The thermal decomposition of iron(III) citrate pentahydrate, Fe(C6H5O7) · 5 H2O, has been investigated at different temperatures in air using Mössbauer spectroscopy, nonisothermal techniques (DTA-TG) and X-ray diffraction. The reduction of iron(III) to iron(II) takes place at 553 K. At higher temperature the formation of α-Fe2O3 and γ-Fe2O3 as the ultimate thermal decomposition products has been confirmed.ZusammenfassungDie thermische Zersetzung des Pentahydrates von Eisen(III)-citrat in Luft wurde bei verschiedenen Temperaturen durch Mössbauer-Spektroskopie, nicht-isotherme Techniken (DTA, TG) und Röntgendiffraktometrie untersucht. Die Reduktion von Eisen(III) zu Eisen(II) erfolgt bei 553 K. Bei höheren Temperaturen entstehen α-Fe2O3 und γ-Fe2O3 als End-produkte der thermischen Zersetzung.РезюмеИспользуя неизотерм ические методы (ДТА-Т Г), мвссбауэровскую спе ктроскопию и рентгено-диффракци онный метод, было иссл едовано термическое разложе ние пятигидрата лимонно кислого железа (***) в атм осфере воздуха. При 553 К протек ает восстановление трех валентного железа до двухвалентного. Подт верждено, что при боле е высоких температура х имеет место совмест ное образование а-Fе2О3 и γ-Fe2O3. как конечных продуктов термическ ого разложения.

THERMAL DECOMPOSITION OF MAGNESIUM MALONATE TRIHYDRATE

The decomposition of magnesium malonate trihydrate has been studied isothermally and non-isothermally using TG, DSC, scanning electron microscope etc. The activation energy and frequency factor for isothermal dehydration are 100±5 kJ mol−1 and 1010 s−1 respectively and the corresponding values for decomposition from DSC are 332.9±113 kJ mol and 1017 s−1 respectively. The participation of liquid phase during dehydration is suggeseed while further decomposition is a solid state process. Final decomposition product at 673 K is crystalline magnesium oxide.ZusammenfassungMittels TG, DSC, Scanningelektronenmikroskop usw. wurde die Zersetzung des Trihydrates von Magnesiummalonat isotherm und nicht isotherm untersucht. Die Aktivierungsenergie und der Frequenzfaktor für die isotherme Dehydratation betragen 100±5 kJ·mol−1 bzw. 1010 s−1. Die entsprechenden DSC Werte für die Zersetzung betragen 332.9±113 kJ·mol−1 bzw. 1017 s−1. Während der Dehydratation scheint auch eine flüssige Phase aufzutreten, die weitere Zersetzung ist jedoch eine Feststoffreaktion. Das Endprodukt der Zersetzung bei 673 K ist kristallines Magnesiumoxid.РезюмеИспользуя методы ТГ, Д СК и сканирующую электронную микроск опию, изучено изотермическое и неи зотермическое разло жение тригидрата малоната магния. Значения энер гии активации и частотно го множителя для реак ции изотермической деги дратации составляли, соответственно, 100±5 кдж ·моль−1и 1010 сек−1, тогда как данные, полученные ме тодом ДСК, равнялись, соответст венно 332±113 кдж·моль−1 и 1017 сек−1. Установлено уч астие жидкой фазы в процессе дегид ратации, тогда как дал ьнейшее разложение является твердотельным процессом. Конечным п родуктом разложения при 673 К является кристаллич еский оксид магния.

Thermal analysis of lithium tris (malonato) ferrate(III) tetrahydrate

Thermal decomposition of lithium tris (malonato) ferrate (III) tetrahydrate i.e. Li3[Fe(CH2C2O4)3].4H2O has been studied in the temperature range of 353–873 K in static air atmosphere using Mössbauer, infrared spectroscopy and nonisothermal techniques (TG-DTG-DTA). The anhydrous complex decomposed into ferric oxide of varying particle sizes and alkali metal malonates/carbonates in succesive stages. Fimally a solid state reaction between α-Fe2O3 and alkali metal carbonate gives fine particles of lithium ferrite (LiFeO2) at a temperature lower than for oxalate precursor and for ceramic method.

Comparative study of the thermal analyses of some transition metal(II) iso- and terephthalates

Abstract The decomposition of iso- and terephthalates of Cu(II) and Zn(II) has been investigated employing simultaneous DTA, TG and DTG. The ultimate thermolysis products are the corresponding metal oxides as confirmed by chemical analysis and X-ray powder diffraction. The TG data for dehydration were computerised to test the various decomposition models. The equation −ln(1 − α) has been found to be the most appropriate in the case of iso- and terephthalates of Cu(II), while [−ln(1−α)] r ( r = 1 3 ) and ln(α/1−α) are most suitable for iso- and terephthalates of Zn(II), respectively. Comparison of the T i values led to the stability. orders: Zn(tere) ⪢ Zn(iso) ⪢ Cu(iso) ⪢ Cu(tere) and Zn(iso) ⪢ Cu(tere) ⪢ Cu(iso) ⪢ Zn(tere) for dehydration and decomposition processes, respectively.

Mössbauer study of the thermal decomposition of iron(III) benzoate and iron(III) fumarate

Abstract The thermal decomposition of iron(III) benzoate, Fe(C 7 H 5 O 2 ) 3 , and iron(III) fumarate pentahydrate, Fe 2 (C 4 H 2 O 4 ) 3 5 H 2 O, containing uni- and bidentate ligands, respectively, has been investigated at various temperatures for different intervals of time in a static air atmosphere. Thermolysis of these compounds leads directly to the formation of α-Fe 2 O 3 in the case of iron(III) benzoate and Fe 3 O 4 in the case of iron(III) fumarate as the ultimate products, thus without undergoing reduction to the iron(II) state.

Thermal Decomposition of Strontium and Barium Malonates

The thermal decomposition of strontium and barium malonates has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, DSC, XRD and IR spectroscopic techniques. DSC of these malonates has been recorded both in oxygen and nitrogen atmospheres. The decomposition is a single step process and the end product formed is carbonate. The energy of activation and frequency factor values for the decomposition of strontium malonate are 547 kJ mol−1 and 1041 s−1 respectively. The activation energy and frequency factor values for isothermal dehydration of barium malonate sester-hydrate are 57–111 kJ mol−1 and 107–1012 s−1 respectively and the corresponding values for decomposition from DSC are 499.5 kJ mol−1 and 1044 s−1 respectively. The higher thermal stability of strontium malonate as compared to that of barium salt is ascribed to its being anhydrous so that decomposition proceeds without restructuring. Their thermal stabilities have also been compared with that of respective oxalate salts.

Mössbauer studies on thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates

Thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates, i. e. M3 [Fe(CH2C2O4)3]·4H2O (M=Na, K) has been studied in the temperature range of 433–973 K in static air atmosphere using Mössbauer, IR and TG-DTG-DTA techniques. Mössbauer spectra are reported at different stages to study the mechanism of decomposition. The anhydrous complex decomposed into α-Fe2O3 of varying particle sizes and alkali metal malonate/carbonate in successive stages. In the final stage of remixing of cations, a solid state reaction between α-Fe2O3 and alkali metal carbonate/oxide gives fine particles of the respective ferrites at temperatures lower than for oxalate precursor or even for ceramic method. Thermal stability obeys the order: sodium > potassium > lithium tris(malonato) ferrate (III).