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Background: Oxalate ligand-based metal complexes have long been used for the thermal synthesis of metal oxides. Polymeric homo/heterometallic oxalate-based molecular materials of the general formula, {A]MIIMIII[C2O4]3]}∞, [A = organic cation, MII/MIII: di/trivalent transition metal ion; C2O4: oxalate ligand] provides a molecular source to prepare metal oxides through solid state thermal decomposition primarily due to the potential to tune the materials’ outcome by adjusting the molecular stoichiometry and composition. Objective: The study aims to explore the effect of mixing at the di- and trivalent metal sites of {N[n-C4H9]4]FeIIFeIII[C2O4]3]}∞ which decomposes to hematite, on the nature of thermal decomposition reaction as well as the nature of the obtained decomposed materials. Methods: Two series of materials {N[n-C4H9]4]FeII 1-xZnII xFeIII[C2O4]3]}∞ and {N[n- C4H9]4]FeIIFeIII 1-xCrIII x[C2O4]3]}∞ were prepared as precursors for non-isothermal thermogravimetry [TG] study. Model-free integral isoconversional method is employed to calculate the activation energy of decomposition, and hence the most probable reaction mechanism, as well as the reaction rate of thermal decomposition, was determined. Based on the kinetic parameters, the important thermodynamic parameters such as the changes of entropy, enthalpy, and Gibbs free energy are estimated for the activated complex formation from the precursors. Powder X-ray diffraction studies were made to identify the decomposed materials. Results: For materials with 0 < x ≤ 1 well-defined two-step and one-step decomposition process were observed for {N[n-C4H9]4]FeII 1-xZnII xFeIII[C2O4]3]}∞ and {N[n- C4H9]4]FeIIFeIII 1-xCrIII x[C2O4]3]}∞, respectively. For each series of materials, a systematic dependence of the activation energy on the extent of conversion indicates a systematic change in the reactivity. The thermal decomposition strongly depends on the extent of mixing at the di- and trivalent sites and proceeds through different reaction mechanisms at different rates. On the decomposition of these series of materials, a range of metal oxides was obtained. Possibly, during such extent of mixing dependent reactions, the reactant particles go through modifications in their reactivity by several factors. Conclusion: Present work may invoke interest in solid state synthesis of different metal oxides under controlled thermal decomposition by identifying the rate controlling the process through reaction kinetics study for better synthesis and manoeuvring.

The paper deals with the thermal decomposition of organometallic compound ferrocene carboxaldehyde [(C5H4CHO)Fe(C5H5)] in oxidative atmosphere, which leads to pure hematite nanoparticles, studied with non-isothermal thermogravimetry (TG) protocol. Deconvolution method with Fraser-Suzuki fit function is adopted to resolve the complex multistep TG profiles into six different reaction steps. Step-wise reaction kinetic parameters (activation energy, reaction mechanism function, reaction rate) are estimated based on the mathematical analysis of the multi-heating rate TG data primarily following model-free (integral isoconversional) approach and using master-plot method. The estimated kinetic parameters are utilised to reconstruct the conversion plots which successfully resemble the experimentally observed ones. A plausible reaction process leading to hematite on thermal decomposition of ferrocene carboxaldehyde as the end product is discussed. A comparative discussion on the thermal decomposition of two ferrocene derivatives have been made. The novelty of the present work lies in successful deconvolution of complex TG profiles and hence obtaining the step-wise reaction kinetic parameters demonstrating different reaction mechanisms involved in the thermal synthesis of hematite nanoparticles starting from ferrocene carboxaldehyde which have no prior reporting. Further, a satisfactory agreement between the reconstructed and experimental decomposition profiles establishes the correctness of the applied modelling approach as well as the methodology adopted.

Single crystal X-ray diffraction, magnetic and 57Fe Mossbauer spectroscopic studies of a new iron(II)-based spin transition complex – [Fe(3-bpp)2](CF3COO)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) are reported. The complex exhibits an incomplete thermal high spin (HS) low spin (LS) transition at ∼226 K which is not associated with any crystallographic transition. Only one of the two crystallographic iron(II) sites undergoes the spin transition, while the other HS site remains invariant of temperature down to 10 K. The origin of the incomplete spin transition is understood by analysing the nature of crystal packing below and above the transition temperature with special attention to the degree of distortion. The present study shows the role of the degree of distortion associated with the cations in the [Fe(3-bpp)2]2+ spin transition complexes.

Severity of exposure to whole-body vibration of vehicle drivers depends on multiple factors including type of vehicle suspension or quality of seats. The study presents analysis of seat vibrations of two different types of dumpers in opencast mines. Since health guidance provided in ISO 2631-1997 are only indicative, seat effective amplitude transmissibility factors along with one-third octave-band analysis of vibration signals have been considered as more effective information for control measures. Vibration characteristics of conventional seats ( n = 3) with rigid frame and those with pneumatic suspensions ( n = 3) have been compared during their use in mines. A(8) values ranged from 0.66 to 1.41 m/s2. All the six operators had shown moderate to higher health risk but this may vary since both intensity and durations of exposure frequently change during the operators’ employment. Vibration signals from a mono-axial accelerometer (z′) placed on the cabin floor was captured in addition to three channel vibration data (x, y and z) of a seat pad accelerometer placed on the vehicle seat. Transmissibility analysis of vibration signals from cabin floor to seat surface showed that the three pneumatic seats resonated in the range of 1.6–2.5 Hz in the z axis. There was significant attenuation of vibration energy ranging from 37% to 63% at 4 Hz which is important in the context of spinal injuries. The seat effective amplitude transmissibility values (%) in the resonating frequencies ranged from 119% to 173%. Interestingly, the conventional seats resonated at 4–5 Hz and the corresponding seat effective amplitude transmissibility (%) values were varying from 128% to 163%. This resonance at 4 Hz is in sharp contrast with the behaviour of pneumatic seats. It is recommended that vibration transmissibility should be considered as a major design parameter for mining vehicle seats.

Background: Melting of a pure crystalline material is generally treated thermodynamically which disregards the dynamic aspects of the melting process. According to the kinetic phenomenon, any process should be characterized by activation energy and preexponential factor where these kinetic parameters are derivable from the temperature dependence of the process rate. Study on such dependence in case of melting of a pure crystalline solid gives rise to a challenge as such melting occurs at a particular temperature only. The temperature region of melting of pure crystalline solid cannot be extended beyond this temperature making it difficult to explore the temperature dependence of the melting rate and consequently the derivation of the related kinetic parameters. Objective: The present study aims to explore the mechanism of the melting process of maleic anhydride in the framework of phase transition models. Taking this process as just another first-order phase transition, occurring through the formation of nuclei of new phase and their growth, particular focus is on the nucleation and growth models. Methods: Non-isothermal thermogravimetry, as well as differential scanning calorimetry studies, has been performed. Using isoconversional kinetic analysis, temperature dependence of the activation energy of melting has been obtained. Nucleation and growth models have been utilized to obtain the theoretical temperature dependencies for the activation energy of melting and these dependencies are then compared with the experimentally estimated ones. Conclusion: The thermogravimetry study indicates that melting is followed by concomitant evaporation, whereas the differential scanning calorimetry study shows that the two processes appear in two different temperature regions, and these differences observed may be due to the applied experimental conditions. From the statistical analysis, the growth model seems more suitable than the nucleation model for the interpretation of the melting mechanism of the maleic anhydride crystals.

Background: Thermal decomposition of iron-bearing organometallic complex acetyl ferrocene, (C5H4COCH3)Fe(C5H5), leads to hematite (α-Fe2O3) nanoparticles. Presence of maliec anhydride, C4H2O3 as co-precursor during thermal decomposition modifies the size of the particles as well as the quantity of the reaction product significantly. Objective: Kinetic analysis of the solid-state thermal reaction of acetyl ferrocene in the presence of varying amount of co-precursor maliec anhydride under inert reaction atmosphere has been studied in order to understand the reaction mechanism involved behind the formation of hematite and the role of co-precursor in the reaction process. For this purpose, reaction kinetic analysis of three mixtures of acetyl ferrocene and maliec anhydride has been carried out. Methods: Thermogravimetry under non-isothermal protocol with multiple heating rates has been employed. The data are analyzed using model-free iso-conversional kinetic techniques to estimate the activation energy of reaction and reaction rate. The most-probable reaction mechanism has been identified by master plot method. The kinetic triplets (activation energy, reaction rate, most probable reaction mechanism function) have been employed to estimate the thermodynamic triplets (ΔS, ΔH and ΔG). Observations: Acetyl Ferrocene (AFc) undergoes thermal decomposition in a four-step process leaving certain residual mass whereas maliec anhydride (MA) undergoes complete mass loss owing to melting followed by evaporation. In contrast, the (AFc1-x-MAx) mixtures undergo thermal decomposition through a two-step process, and the decompositions are completed at much lower temperatures than that in AFc. The estimated activation energy and reaction rate values are found strongly dependent on the extent of conversion as well as on the extent of mixing. Introduction of MA in the solid reaction atmosphere of AFc in one hand reduces the activation energy required by AFc to undergo thermal decomposition and the reaction rate, while on the other hand varies the nature of reaction mechanism involved. Results: The range of reaction rate values estimated for the mixtures indicate that the activated complexes during Step-I of thermal decomposition may be treated as ‘loose’ complex whereas ‘tight’ complex for the Step-II. From the estimated entropy values, thermal process of (AFc1-x-MAx) mixture for Steps I and II may be interpreted as ‘‘slow’’ stage. Conclusion: Variation of Gibb’s free energy with the fraction of maliec anhydride in the mixtures for Step-I and II indicate that the thermal processes of changing the corresponding activated complexes are non-spontaneous at room temperature.

The paper describes the physical characterization of CdS nanoparticles, green synthesized using Termitomyces heimii mushroom extract. The CdS samples obtained are wurtzite type. The amount of extract used for synthesis affects the particle size. FT-IR spectra confirmed the presence of proteins as well as the formation of CdS. A blue shift of the absorption maximum based on particle size was observed in the UV–Vis spectra. The size of the nanocrystallites estimated from the XRD and UV–Vis studies were in 3–5 nm range which is in conformity with the results obtained from the SEM and TEM studies. Electronic polarizability of the CdS samples has been estimated. The study presents a simple, cost effective and eco-friendly method of CdS nanoparticle (size

Present work reports a study on the electrical conduction properties of some composites of Gum Arabic biopolymer and magnetite nanoparticles as host and guest, respectively, synthesized in different weight percentages. The nanocomposites are found to be non-extrinsic type of semiconductors with guest content dependent trap distribution of charge carriers. Conductivity of these materials increases with increasing guest content along with a concomitant decrease in the activation energy. Percolation theory has been employed for the analysis of the electrical conductivity results to explore the effect of the guest on the electrical conductivity of the host.

In this study we report the solventless synthesis of iron oxide through thermal decomposition of acetyl ferrocene as well as its mixtures with maliec anhydride and characterization of the synthesized product by various comprehensive physical techniques. Morphology, size and structure of the reaction products were investigated by scanning electron microscopy, transmission electron microscopy and X-ray powder diffraction technique, respectively. Physical characterization techniques like FT-IR spectroscopy, dc magnetization study as well as 57Fe Mossbauer spectroscopy were employed to characterize the magnetic property of the product. The results observed from these studies unequivocally established that the synthesized materials are hematite. Thermal decomposition has been studied with the help of thermogravimetry. Reaction pathway for synthesis of hematite has been proposed. It is noted that maliec anhydride in the solid reaction environment as well as the gaseous reaction atmosphere strongly affect the reaction yield as well as the particle size. In general, a method of preparing hematite nanoparticles through solventless thermal decomposition technique using organometallic compounds and the possible use of reaction promoter have been discussed in detail.

Thermal decomposition of ferrocene [(C5H5)2Fe] in the presence of oxalic acid [(COOH)2·2H2O] samples—prepared by grinding the mixtures of ferrocene and oxalic acid at different weight ratios—is reported in this work. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetics as well as thermodynamic parameters. Model-free (integral isoconversional) methods are employed to analyze thermogravimetric data. The most probable reaction mechanisms for thermal reactions have been identified. Based on the values of the activation energy Eα* and reaction rate Aα for different steps of decomposition, the values of ΔS*, ΔH*, and ΔG* for the formation of activated complex from the precursor are estimated. Besides, this work has proposed reaction pathways indicating the formation of hematite (α-Fe2O3) as the solid end-product of thermal decomposition of the samples.

Magnetite and hematite nanoparticles (~ 20 nm size) have been synthesized by solventless thermal decomposition of iron(II)acetate in air under different reaction protocols. The structure of the decomposed materials is investigated by FT-IR and powder XRD, while the morphology of the particles formed was studied by SEM/TEM. The magnetic phases of the materials are quantitatively identified by 57Fe Mӧssbauer spectroscopy. EDX was used for elemental analysis. The results obtained from FT-IR, XRD and Mӧssbauer studies explicitly establish that the materials obtained are iron oxides (magnetite and hematite). The study shows a reaction time- and temperature-dependent conversion of magnetite to hematite. The underlying solid state reactions have been discussed. The present study comes across that a single organo-iron precursor can provide different pure phases of iron oxide nanoparticles depending on the reaction protocol.

Gum arabic (GA)-mediated chemical synthesis was carried out for obtaining ZnO nanoparticles (ZnO-NPs) (particle size of ZnO ≈ 40 nm) which, in turn, was used for preparing ZnO–biopolymer nanocomposites. The dielectric study of this synthesized products is reported in this paper. The synthesized products were characterized by X-ray diffraction, Fourier transform infrared, and transmission electron microscopy for their structure and morphology study. The frequency dependence of dielectric constant and dielectric loss of these GA–ZnO nanocomposites were analysed in the frequency range of 100 Hz–5 kHz. In addition, the dielectric property of these nanocomposites (0–15 wt% filler concentration) was analysed with respect to frequency in the temperature range 30–80°C. A high dielectric constant of 275 is achieved for the sample with 10 wt% of ZnO filler. The dielectric property of GA–ZnO nanocomposites is attributed to the interfacial and orientation polarization.

Physical aspects of tobacco samples, used in some commonly available Indian brands of cigarettes, with emphasis on their magnetic characterization before and after they get burnt into ashes, are described. The present work highlights the ultrafine nature of the cigarette ashes and provides a compositional insight of their constituent particulate matters as revealed by the XRD and SEM studies. Based on the EDX spectra, elemental distributions of different tobacco samples, before and after they get burnt, are presented. In this work, magnetic measurements of the un-burnt tobacco samples are reported. An attempt is made to shed light on the origin of magnetism observed in these samples.

A single-step thermal decomposition of ferrocene [(C5H5)2Fe] using nonisothermal thermogravimetry (TG) has been studied using single- as well as multiple-heating rate programs. Both mechanistic and nonmechanistic methods have been used to analyze the TG data to estimate the kinetic parameters for the solid state reaction. Two different isoconversional methods (improved iterative method and model-free method) have been employed to analyze the TG results to find out whether the activation energy of the reaction depends on the extent of decomposition and to predict the most probable reaction mechanism of thermal decomposition as well. A comparison of the activation energy values for the single-step thermal reaction of ferrocene estimated by different methods has been made in this work. An appraisal on the applicability of single-heating rate data for the analysis of single-step thermal decompositions over the recommendations by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) is made to look beyond the choice.

The paper presents a method to synthesize α-Fe, γ-Fe, magnetite and hematite through solventless thermal decomposition technique using an organo-metallic compound iron(III)citrate in two different atmospheres (N2 and O2) at different temperatures and the characteristics of these products. The solid state thermal reaction has been monitored by non-isothermal thermogravimetry. The FT-IR spectra and powder XRD pattern of the decomposed products reveal the type of materials formed and the SQUID measurements confirm those. Mossbauer spectroscopic study confirms the nature of magnetic structure of the synthesized materials. The SEM and TEM studies are used to study the shape and size of the particles formed. EDX technique has been employed to know the elemental composition. The solid state reaction processes involved in the synthesis have been proposed. The present study indicates that different types of iron/iron oxide particles in the range of nano-scale can be synthesized on thermal decomposition of iron(III)citrate depending on the decomposition temperature as well as the reaction atmosphere.

Magnetic studies into the effect of different hydrostatic pressures between ambient and 1.03 GPa on the high-spin (HS) i low-spin (LS) transition behavior of the dinuclear iron(II) compound [Fe II 2(PMAT)2](BF4)4·DMF (1, PMAT = 4-amino3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, DMF = N,N-dimethylformamide) have been carried out at 2– 300 K. Under ambient pressure, the sample studied exhibits a [HS–HS] to [HS–LS] half spin transition (ST) at T½ = 208 K without any thermal hysteresis. Increasing the pressure above 0.2 GPa causes an increase (initially rapid but above 0.5 GPa more gradual) of T½ as well as a matching reduction in the residual high-spin fraction at room temperature. This paper probes in detail how the increased pressure favors the

A multi-step thermal decomposition of a molecular precursor, {N(n-C4H9)4[FeIIFeIII(C2O4)3}? has been studied using non-isothermal thermogravimetry (TG) measurements in the temperature range 300 to ~800 K at multiple heating rates (5, 10 and 20 K min-1). The thermal decomposition of the oxalate-based complex proceeds stepwise through a series of intermediate reactions. Two different isoconversional methods, namely, improved iterative method and model-free method are employed to evaluate the kinetic parameters: activation energy and rate of reaction, and the most probable reaction mechanism of thermal decomposition is also determined. The different reaction pathways leading to different steps in the TG profile have also been explored which are supplemented by earlier experimental observations of the present authors.

Solid-state thermal decomposition reaction of a molecular material $$\{\hbox {As}(\hbox {C}_{6}\hbox {H}_{5})_{4}[\hbox {Fe}^{\mathrm{II}}\hbox {Fe}^{\mathrm{III}} (\hbox {C}_{2}\hbox {O}_{4})_{3}]\}_{\mathrm{n}}$$ has been studied using non-isothermal thermogravimetry (TG) in an inert atmosphere. By analyzing the TG data collected at multiple heating rates in 300 K–1300 K range, the kinetic parameters (activation energy, most probable reaction mechanism function and frequency factor) are determined using different multi-heating rate analysis programs. Activation energy and the frequency factor are found to be strongly dependent on the extent of decomposition. The decomposed material has been characterized to be hematite using physical techniques (FT-IR and powder XRD). Particle morphology has been checked by TEM. A solid-state reaction pathway leading the molecular precursor to hematite has been proposed illustrating an example of solventless synthesis of iron oxides utilizing thermal decomposition as a technique using innocuous materials.

Ferrite nanoparticles of ~40 nm size have been obtained under the thermal decomposition of {bis-(cyclopentadienyl)iron}—ferrocene in the presence of oxalic acid at ~453 K. The solventless solid state thermal reaction has been monitored by thermogravimetry. Morphology and structure of the ferrites obtained are investigated by scanning electron microscopy and X-ray powder diffraction technique, respectively, while the magnetic property of these materials are studied by dc magnetization study as well as 57Fe Mossbauer spectroscopy. The results, observed from X-ray powder diffraction, magnetization measurement and Mossbauer spectroscopy, establish unequivocally that the ferrite materials obtained are hematite. The solid state reaction process has been discussed too. To the best of our knowledge, the presently observed solid state reaction leading to the formation of hematite nanoparticles using ferrocene takes place at the lowest temperature reported so far.

Thermal decomposition of oxalate-based molecular precursors, namely \({\{{\rm N}(n{-} {\rm C}_{4} {\rm H}_{9})_{4}[{\rm Zn}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2} {\rm O}_{4})_{3}]\}_{\infty}, \{{\rm N}(n{-}{\rm C}_{4}{\rm H}_{9})_{4}[{\rm Co}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2}{\rm O}_{4})_{3}]\}_{\infty}}\) , and \({\{{\rm N}(n{-}{\rm C}_{4} {\rm H}_{9})_{4}[{\rm Fe}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2}{\rm O}_{4})_{3}]\}_{\infty}}\) , abbreviated as BuZnFe, BuCoFe, and BuFeFe, respectively, are studied using thermogravimetry (TG) in the temperature range from ~300 K to ~675 K at multiple heating rates. This study also deals with how the thermal decomposition of the complexes proceed stepwise through a series of intermediate reactions. The effect of the divalent metal MII on the nature of thermal decomposition of the complexes, reflected in their TG profiles in terms of number of steps involved, is reported in this study. The temperature range of thermal decomposition steps for BuZnFe, BuCoFe, and BuFeFe with the same heating rates are studied systematically. Two different isoconversional methods, namely an improved iterative method and a model-free method are employed to calculate the kinetic parameters, and thus the most probable reaction mechanism of thermal decomposition is determined. Based on kinetic parameters, the important thermodynamic parameters such as the changes of entropy, enthalpy, and Gibbs free energy are estimated for the activated complex formation from the precursors. Considering the mass loss during the different thermal decomposition steps of BuZnFe, BuCoFe, and BuFeFe, observed in the thermogravimetry profiles, the overall reactions of the thermal decompositions are demonstrated.

This paper reports on the physical nature of the fly ash sample of the Kolaghat Thermal Power Plant, India with an emphasis on its ultrafine nature. This paper also deals with the measurement of the magnetic properties of the fine particles of the fly ash sample. Particle sizes of this fly ash sample estimated from the SEM images lie within 0.16–5.50 μm, and the EDX spectral analysis indicates the presence of O, Al, Si, C, Fe, Mg, Na, K and Ti in this sample. From the XRD study, it is found that physical nature of conglomeration in the fly ash is crystalline and the major components are mullite (Al 6 Si 2 O 13 ) and quartz (SiO 2 ). Additionally, the presence of hematite, microcline, magnetite, maghemite and free iron in smaller fractions cannot be ruled out. A large magnetization observed at 5 K indicates the presence of magnetic components possibly due to superparamagnetism owing to very fine magnetic particles present. The hyperfine parameters obtained from the 57 Fe Mossbauer spectroscopy, in general, support the observations made from the XRD analysis and in particular, provides the quantitative estimation of the different iron ions present in the sample. Precisely, this report presents experimental data on physical aspects of the fly ash sample of a thermal power plant which consists of coarse, fine and ultrafine magnetic particulate materials (PMs) and deals with an in-depth analysis of it.

Electrical and magnetic properties of {[Ru(bpy) 3 ][Fe(dca) 3 ] 2 } n (bpy=2,2′-bipyridine, dca=dicyanamide) have been studied. The compound is a non-extrinsic type of semiconductor and paramagnetic in nature. Mossbauer spectroscopy has established the presence of high spin Fe(II) as one major species in this compound, and no high spin–low spin transition of Fe(II) was detected down to 80 K under dark. The photo-response of electrical conductivity with time shows interesting behavior with repeated exposure.

Thermal degradation of a mixed-valence oxalate based molecular material {N(n-C4H9)4[FeIIFeIII(C2O4)3]}∞ was investigated by thermogravimetric (TG) analysis. Considering the mass loss at each step of TG profile, possible step-wise thermal degradation reaction pathways of the precursor material are proposed which indicate the formation of hematite and magnetite as the solid end product of the degradation reaction. The IR spectroscopy and powder X-ray diffraction (XRD) studies of the thermally degraded samples supplement the proposed reaction pathways.

A series of dimeric lanthanide carboxylato complexes [La(5-Br-NIC)3(H2O)2]2·H2O (1); [Gd(5-Br-NIC)3(H2O)2]2 (2), [5-Br-NIC = 5-bromonicotinate] and [Sm(NIC)3(H2O)2]2 (3) [NIC = nicotinate], have been hydrothermally synthesized and structurally characterized by single crystal X-ray analysis. Complexes 1, 2 and 3 are of similar structure and consist of a basic unit [La(carboxylato)3(H2O)2]2. In compound 1 lanthanide cation is surrounded by one chelating 5-bromo-nicotinato ligand, two bridging oxygen atoms from 5-bromo-nicotinato and two water molecules, in which each La(III) ion is nine coordinated in a tricapped prismatic geometry. However, in compounds 2 and 3 four carboxylate groups link a pair of lanthanide atoms in the O,O′-bridging mode to generate a paddle-wheel-like centrosymmetric dimer. All the compounds exhibit excellent catalytic performance in olefin epoxidation reaction. The variable temperature magnetic susceptibility measurements showed that the magnetic interaction in [Gd(5-Br-NIC)3(H2O)2]2 (2), is antiferromagnetic (J = −0.048 cm−1), while compound [Sm(NIC)3(H2O)2]2 (3), showed a complicated low-temperature magnetic property.

Stone dust sample collected from a stone crushing industry situated at Muhammad Bazar in Birbhum, India, is studied for its physical characterization using various techniques. Morphology and compositional analysis of the stone dust by scanning electron microscopy (SEM) reveal that the dust is an agglomeration of many tiny particles (0.32–2.12 μm), mostly having sharp edges, as well show microstructure heterogeneity. Elements present in the sample are detected by energy dispersive X-ray spectrometry (EDX). The X-ray diffraction (XRD) pattern analysis shows that the sample mainly contains minerals like anorthite, augite, esseneite and albite. An overall antiferromagnetic interaction in this sample has been indicated by the nature of the thermal dependence of magnetization. The remnant magnetization study apparently indicates two magnetic transitions at low temperatures. 57 Fe Mossbauer spectroscopy has been employed to detect different possible iron sites as well as to estimate the respective site population. In general, Mossbauer spectroscopic results corroborate the observations made through XRD analysis in general.

Mixing of trans-[Mn(cyclam)Cl2]Cl (cyclam = 1,4,8,11-tetraazacyclotetradecane) and potassium hexacyanochromate (K3[Cr(CN)6]) aqueous solutions instantaneously yields a 1D infinite chain complex {[Mn(cyclam)(l-CN)2Cr(CN)4]� H2O}n (1). The crystal structure of 1, crystallizing in the monoclinic system with space group P21/n has been solved from X-ray powder diffraction data following direct space approach and refined by the Rietveld method. The structure analysis of 1 reveals alternating [Cr(CN)6] 3� and [Mn(cyclam)] 3+

This paper presents the characteristics of iron oxides obtained through thermal degradation of a molecular ferrimagnet, {N(n-C4H9)4[Fe II

Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and tunneling electron microscopy (TEM) studies of two solid vehicle wastes (pollutants) from petrol- and diesel-fueled engines of Kolkata (India) have detected a significant amount of ultrafine particles in the nanometer scale in these wastes. Both powder XRD and selected area electron diffraction from TEM have confirmed the existence of inhomogeneous distribution of nanocrystallites in these pollutants. Energy dispersive X-ray spectrometry shows that these wastes contain mainly carbon and oxygen as the constituent components. These pollutants are magnetic in nature as seen with SQUID magnetometry, and the presence of a high amount of carbon presumably is likely the origin of the magnetic property.

Electrical conduction properties of a molecular magnetic system {(cation)[Fe(II)Fe(III)(C2O4)3]}∞ with three different cations—N(n-C4H9)4+, N(n-C3H7)4+ and As(C6H5)4+ have been studied to understand the nature of electrical conduction in this molecular system as well as to explore any effect of the cation size on it. All the compounds are observed to be semiconducting in nature and their room temperature conductivity is of 10−15 S cm−1 order. Results indicate that the electrical conductivity as well as the activation energy of this system depends on the size of the cations used. Moreover, semiconducting iron oxide of hematite nature was obtained through the thermal degradation of {N(n-C4H9)4[Fe(II)Fe(III)(C2O4)3]}∞. The degraded material consisted of rod-like crystals of average length and diameter 350 and 140 nm, respectively.

Nano-sized crystals of maghemite iron oxide (γ-Fe 2 O 3 ) were synthesized onto the surface of NaY-zeolite crystals by immobilizing a polynuclear iron complex [Fe 4 O 2 (O 2 CCH 3 ) 7 (bpy) 2 ](ClO 4 ) (bpy = 2,2′-bipyridine) and subsequent calcination of the material in oxygen. Superparamagnetic γ-Fe 2 O 3 particles with sizes ∼5 nm were formed on the surface of the zeolite matrix. The nano-composite, γ-Fe 2 O 3 @NaY has been subsequently subjected for thorough characterization with several spectroscopic techniques as well as magnetic and transmission electron microscopic measurements. This confirms the formation of maghemite nanoparticles on a NaY-zeolite surface. γ-Fe 2 O 3 @NaY shows a remarkable catalytic efficiency in epoxidation reactions with various olefins using tert -BuOOH as oxidant. Notably, styrene shows a remarkable high conversion (90%) as well as epoxide selectivity (95%) while trans -stilbene is completely converted to its oxide with tert -BuOOH over a γ-Fe 2 O 3 @NaY catalyst.

We have attempted to characterize the magnetic and electrical properties of a new mixed-metal molecular material {NBu 4 [Ni(II) 0.5 Fe(II) 0.5 Fe(III)(ox) 3 ]} N synthesized by the use of trioxalatoferrate as the building block. Mossbauer spectroscopy was utilized in order to understand local spin structures in this compound. The results indicate that the compound is a semiconducting ferrimagnet with T N =30 K and room temperature conductivity of 6×10 −15 Ω −1 cm −1 along with 1.8 eV activation energy under dark. The compound has no appreciable electrical response towards illumination.

The reaction of M(NO 3 ) 2 · x H 2 O (M = Cu, Ni and Co; x = 3 for Cu and x = 6 for Co/Ni), imidazole (Im) and sodium dicyanamide (dca) afforded the complexes [M(Im) 2 (dca) 2 ] (where M = Cu for 1 , M = Ni for 2 , and M = Co for 3 ). All of them have been characterized structurally by single crystal X-ray diffraction measurements. X-ray analysis reveals that the dicyanamido ligand features the μ 1,3 bridging mode that led to the formation of two-dimensional structure of complex 1 while complexes 2 and 3 attribute an infinite one-dimensional chain like structure to generate the fascinating molecular assemblies. The {N(CN) 2 } − ligands present in the complexes 2 and 3 are coordinated in end-to-end (μ 1,5 ) fashion. All the complexes have distorted octahedral geometry around the central metal ion and coordinated by two amine nitrogen atoms from imidazole ligands and four nitrogen atoms from dca ligands. The variable temperature (2–300 K) magnetic susceptibility measurements showed that the magnetic interaction between the metal centers in the complex 1 is dominantly ferromagnetic while the metal ions in complex 3 are antiferromagnetically coupled. On the contrary, complex 2 is a simple paramagnet. The results of magnetic model are in good agreement with the experimental data.

Studies on the magnetic properties of the molecular antiferromagnetic material {N( n -C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ , carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mossbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Neel temperature and short-range correlations persisting high above T N . It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (Mn II –ox–Fe III A –...) and (Mn II –ox–Fe III B –...), where different responses of the Fe III A and Fe III B spin sites towards an external magnetic field might be responsible for the observation of the uncompensated magnetization in this compound at T T N . The present magnetic system is an S = 5/2 2-D Heisenberg antiferromagnet system with the intralayer exchange parameter J / k B = −3.29 K. A very weak interlayer exchange interaction was anticipated from the spin wave modeling of the magnetic heat capacity for T T N . The positive sign of the coupling between the layers has been concluded from the Mossbauer spectrum in the applied magnetic field. Frustration in the magnetic interactions gives rise to the uncompensated magnetic moment in this compound at low temperatures.

We have studied the high spin and low spin structural phases of the two-step spin transition compound [Fe(bpp) 2 ](NCS) 2 ·2H 2 O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) of different sample history with X-ray synchrotron ( λ ∼ 0.32 A) powder diffraction at different temperatures as well as with usual X-ray ( λ ∼ 1.54 A) powder diffraction at room temperature by performing rapid repeated scans at regular intervals of time. A structural phase transition occurs only during the first step of the spin transition. Time dependent interconversions of the two crystallographic phases have been observed at room temperature for this material. The results indicate that a soft X-ray (Cu-K α )-induced structural change occurs in this material at room temperature. Possible mechanisms for this unusual observation are discussed.

The (57)Fe Mossbauer spectroscopy of mononuclear [Fe(II)(isoxazole)(6)](ClO(4))(2) has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S = 0) and high-spin (S = 2) states.Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mossbauer spectra measured at various temperatures between 84 and 270 K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T(C)(down arrow) = 223 and T(C)(up arrow) = 213 K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The compound has three high-spin Fe(II) sites at the highest temperature of study of which two undergo spin transitions. The Compound seems to undergo a structural phase transition around the spin transition temperature, which plays a significant role in the spin crossover behaviour as well as the magnetic properties of the compound at temperatures below T(C). The present study reveals an increase in high-spin fraction upon hearing in the temperature range below T(C) and an explanation is provided. (C) 2008 Elsevier Ltd. All rights reserved.