Thermal Decomposition Process Research Articles

Influences of Saponification Time on the Physical Properties of Mineral Oil-Based Magnetorheological Grease

This study was conducted to investigate the influences of saponification time on the physical properties of mineral oil-based magnetorheological greases(MRGs). Three types of mineral oil-based MRG were prepared by applying different saponification time in this work. Then the physical properties, thermal stability and colloidal performance were tested. Besides, the micro-morphology was observed to analyze the microstructures of MRGs. The experimental results prove the formation of entanglement soap fibers micro-network. The oil separation on pressure and worked penetration of MRG decrease with the increase of saponification time, while the centrifugal stability becomes better. DSC-TG-DTG tests exhibit three endothermic peaks and reveal a double-stage thermal decomposition process. It also indicates that the MRG under 2 hours saponification has the smallest thermal decomposition and highest decomposition temperature, which demonstrates a good thermal stability.

Thermal decomposition behavior, thermal stability and thermal explosion risk evaluation of a novel green hydroxylamine ionic liquid salt

Hydroxylamine salts are important chemical raw materials to a wide range of applications ranging from the synthesis of caprolactam, to pesticides and medicine. However, challenging setbacks associated with environmental pollution, equipment corrosion and explosive safety hazards are inevitably encountered with traditional hydroxylamine salts due to the release of strong acids and their poor thermal stability. In order to address those mentioned above environmental and safety challenges, an acidic ionic liquid, instead of inorganic acids, was introduced to stabilize hydroxylamine. Hence, a novel green chemical-hydroxylamine 1-sulfobutyl-3-methyl imidazole hydrosulfate salt ((NH2OH)2·[HSO3-b-mim]·HSO4) was created. It is essential to systematically study thermal decomposition behavior, thermal stability and safety of the novel hydroxylamine ionic liquid salt. This study used the thermogravimetric method to investigate the thermal decomposition process of (NH2OH)2·[HSO3-b-mim]·HSO4. The mechanism of thermal decomposition function and kinetic model were obtained by the Coats-Redfern method. The thermal explosion risk of (NH2OH)2·[HSO3-b-mim]·HSO4 under adiabatic conditions was evaluated using a differential scanning calorimeter (DSC) and an accelerated adiabatic calorimeter (ARC). The results indicate that (NH2OH)2·[HSO3-b-mim]·HSO4 exhibits good thermal stability and safety, providing an avenue for the future production, storage and application of this eco-friendly hydroxylamine product.

Catalytic properties of a composite material based on belarusian dolomites in relation to the decomposition of pyrolysis tar

The paper discusses results of an experimental study of the thermal decomposition of pyrolysis tar in a homogeneous process and in the presence of a catalyst. Experiments on thermal decomposition of pyrolysis tar were carried out under isothermal conditions in a laboratory setup at temperatures of 300, 400, 450 and 500 °C. The rate of the homogeneous process of thermal decomposition of tar and maximal degrees of decomposition were determined. According to the data of this work, the activation energy of the homogeneous process was 320 kJ/mol. It was found that the rate of thermal decomposition of the tar increases in the case of introducing samples of natural dolomites into the reaction zone, as well as a composite material based on them. This increase is due to the occurrence of a heterogeneous catalytic decomposition reaction of the pyrolysis tar. The apparent activation energy of this process was 210 kJ/mol (when using dolomites) and 202 kJ/mol (when using composites). It was noted that the composite material has significantly more favorable mechanical properties than dolomite. Based on the established data, it was concluded that the creation of composite catalysts for the thermal decomposition of heavy hydrocarbons formed in the processes of thermochemical conversion of biomass is promising.

Application of model-free and multivariate nonlinear regression methods for evaluation of the kinetic scheme and kinetic parameters of thermal decomposition of low density polyethylene

A sort of low density polyethylene (LDPE) was characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), thermal analysis methods (TG, DTG, DTA) in nitrogen flow at constant heating rates of 2.50, 5.00, 9.91, 14.98 and 19.92 K min−1 and at other five temperature programs, coupled TG + FTIR analysis, and DSC analysis in nitrogen flow. The kinetic analysis of TG data has been performed using an algorithm consisting of the following three successive steps: (1) the application of model-free (isoconversional) methods for evaluation of apparent activation energy dependence on the conversion degree, (2) the processing of the TG data recorded at constant heating rates to assess the possible kinetic schemes and the corresponding kinetic parameters, and (3) the selection of the kinetic scheme characteristic of the thermal decomposition of LDPE by comparing the experimental TG curves with the reconstructed ones corresponding to the temperature programs used. It has been pointed out that the overall process of thermal decomposition of LDPE consists of four successive stages with the Avrami-Erofeev kinetic models (An) - reaction order (Fn) -reaction order (Fn) - three-dimensional diffusion (D3). This kinetic scheme and corresponding kinetic parameters is suitable for prediction of thermal behavior of LDPE in some temperature programs and can be used for the design of pyrolysis reactors necessary for the conversion of LDPE waste into low molecular mass chemicals, which can be used as raw materials for chemical and petrochemical industry.

Self-assembly of broadband-emitting SnOx nanodots for efficient Cr(VI) detection

Chromium is a metal commonly used in the manufacturing industry. However, when present in industrial wastewater and refuse, chromium causes serious water pollution. In this study, we synthesized a high-efficiency low-cost SnOx (SnO/SnO2) nanodot (ND) photocatalyst using monobutyltin trichloride (MBTC) using a one-step thermal decomposition process. SnOx NDs not only exhibit strong broadband and multicolor fluorescence emission (λem ranging from 450 nm to 585 nm), but also emit white light under ultraviolet irradiation. We also found that, under visible-light irradiation, SnOx NDs exhibited a photocurrent response that improved photocatalytic activity. In addition, we used electrochemical impedance spectroscopy (EIS) to detect Cr(VI) over a concentration range of 5–1000 ppb, with a detection limit of 0.006 ppb under light. This detection limit is lower than the maximum limit of 50 ppb for human water consumption, as stipulated by the European Union.

Study on Combustion Characteristics and Thermodynamic Parameters of Thermal Degradation of Guinea Grass (Megathyrsus maximus) in N2-Pyrolytic and Oxidative Atmospheres

This study provides an extensive investigation on the kinetics, combustion characteristics, and thermodynamic parameters of the thermal degradation of guinea grass (Megathyrsus maximus) in N2-pyrolytic and oxidative atmospheres. A model-fitting technique and three different iso-conversional techniques were used to investigate the kinetics of the thermal process, after which an analysis of the combustion characteristics and thermodynamic parameters was undertaken. Prior to this, experiments on the physico-chemical characterization, thermogravimetric, and spectroscopic analyses were carried out to provide insight into the compositional structure of the guinea grass. The volatile matter, fixed carbon, and total lignin contents by mass were 73.0%, 16.1%, and 21.5%, respectively, while the higher heating value was 15.46 MJ/kg. The cellulose crystallinity index, determined by XRD, was 0.43. The conversion of the GG in air proceeded at a relatively much higher rate as the maximum mass-loss rate peak in a 20 K/min read was −23.1 and −12.3%/min for the oxidative and the pyrolytic, respectively. The kinetics investigation revealed three distinctive stages of decomposition with their corresponding values of activation energy. The average values of activation energy (FWO) at the latter stages of decomposition in the pyrolytic processes (165 kJ/mol) were higher than those in the oxidative processes (125 kJ/mol)—an indication of the distinctive phenomenon at this stage of the reaction. The Coats–Redfern kinetic model revealed that chemical reactions and diffusional models played a predominant role in the thermal decomposition process of the GG. This study showed that the thermodynamic parameters varied with the conversion ratio, and the combustion performance increased with the heating rates. The use of GG as an energy feedstock is recommended based on the findings from this work.

Experimental and Kinetic Studies on Tobacco Pyrolysis under a Wide Range of Heating Rates.

In the present work, experimental and kinetic studies are conducted to explore and model tobacco pyrolysis characteristics under a wide range of heating conditions. First, thermal decomposition processes of a tobacco sample were investigated using thermogravimetric analysis/difference thermogravimetry (TGA/DTG) experiments under a wide range of heating rates (10–500 K/min), and the TGA/DTG profiles were compared to highlight the effect of heating rate on the pyrolysis characteristics. The results showed that the tobacco sample was sufficiently devolatilized at 1173.15 K (900 °C) and the final volatiles yields were not sensitive to the heating rate. Moreover, it was illustrated that the DTG curve presents a polymerization trend with the increase in heating rate. Then, kinetic parameters, including total component mass fraction, preexponential factor, and activation energy, were derived by deconvolution from TG/DTG profiles for each component with a one-step kinetic framework, and the correlations between kinetic parameters and heating rates were further explored and modeled. The results illustrated that four subpeaks can be found in the deconvolution, indicating the four components (volatile components, hemicellulose, cellulose, and lignin). In addition, the activation energy of each component was found to be insensitive with heating rate (with standard deviation less than 20%). Therefore, an average activation energy was used for each component to avoid the compensation effect and a power correlation between the heating rate and the preexponential factor could be found. A posteriori analysis also confirmed the validity of this correlation.

A facile approach for the synthesis of porous hematite and magnetite nanoparticles through sol-gel self-combustion.

Porous magnetite (Fe3O4) and hematite (α-Fe2O3) nanoparticles were prepared via the sol-gel auto-combustion method. The gels were prepared by reacting ferric nitrates (as oxidants) with starch (as fuel) at an elevated temperature of 200 °C. Different ratios (Φ) of ferric nitrates to starch were used for the synthesis (Φ = fuel/oxidant). The synthesized iron oxides were characterized by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET) and vibrating sample magnetometer (VSM) analysis techniques. The crystal structure, morphology, and specific surface area of the iron oxide nanoparticles (Fe3O4 and α-Fe2O3) were found to be dependent on the starch content. The FT-IR, XRD and VSM analysis of the iron oxides for Φ = 0.3 and 0.7 confirmed the formation of the α-Fe2O3 core, whereas at Φ = 1, 1.7, and 2 showed that Fe3O4 cores were formed with the highest saturation magnetization of 60.36 emu/g at Φ = 1. The morphology of the Fe3O4 nanoparticles exhibited a quasi-spherical shape, while α-Fe2O3 nanoparticles appeared polygonal and formed clusters. The highest specific surface area was found to be 48 m2 g-1 for Φ = 1.7 owing to the rapid thermal decomposition process. Type II and type III isotherms indicated mesoporous structures.

Pyrolysis Kinetics of a Lignin-Modified Cellulose Composite Film.

Cellulose is the most abundant natural biopolymer material, which has been widely used in film making and food packaging in recent years. However, lignin, a natural bioaromatic material, is always applied as a waste resource due to its low utilization efficiency. In this study, a ZnCl2/CaCl2/cellulose mixed system was used to prepare film materials via a regeneration method. The chemical structure and corresponding properties were characterized. The thermal decomposition process of film materials showed that with an increase of the heating rate, the maximum weight loss temperature gradually shifted to the higher-temperature region. Additionally, the combination of lignin with cellulose as composite films can effectively improve thermal stability. Furthermore, kinetics methods such as Kissing–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman were used to calculate the average activation energy (E). This study proposed a facile method for preparing biobased multifunctional composite films using two kinds of naturally renewable materials.

Fast-Setting Permeable Alkyd/Polyester Composites: Moulding Sands.

This paper presents the outcomes of extensive research targeting the development of high-performance alkyd and polyester resins used as binders in mould- and core-making permeable composite materials designated for large-size/complex-shape, heavy alloy-steel and cast-iron castings (0.5 to 50 tonnes): steam turbine casings (e.g., 18K360 condensing turbine), naval engine blocks and heavy machinery. The technology was implemented by Zamech/ALSTON Power. The key issues discussed here are: (1) control of resin crosslinking kinetics; slow or rapid strength development, (2) shelf-life control of pre-mixed composite, (3) improved thermo-mechanical stability; (4) kinetics of gaseous by-product emission. Optimised composite formulations (resins, crosslinkers and catalysts) allow for the flexible control of material properties and mould-/core fabrication, i.e.,: shelf-life: 10–120 min; mould stripping time: 10 min to 24 h; compressive strength: 4–6 MPa (with post-cure: 10–12 MPa); tensile strength: up to 3 MPa (after post-cure). The moulding sands developed achieved thermal resistance temperatures of up to 345 °C, which exceeded that of 280 °C of comparable commercial material. The onset of the thermal decomposition process was 2–3 times longer than that of furan or commercial alkyd/polyester resin. The technology developed allows for the defect-free manufacture of castings (no pinholes) and binder contents minimisation to 1.2–1.5% with quartz and 1.2% with zirconium or chromite sand.

Zirconium metal recovery from irradiated radioactive zirconium alloy via chloride‐basedelectrorefining and thermal decomposition ofZrCl

Chloride salt–based decontamination methods for neutron-irradiated radioactive zirconium alloys have been designed to directly recover metallic Zr. Previous studies have shown that ZrCl is co-deposited with Zr at a low current density on the cathode, while sparse and low-purity Zr is obtained with the application of a high current density. We propose a process to prepare high-purity Zr metal involving the electrochemical recovery of ZrCl and thermal decomposition of ZrCl to Zr. Electrodeposition of ZrCl in a LiCl-KCl-ZrCl4 system by controlling the cathode potential at −1.1 V (vs Ag/AgCl, −2.3 V vs Cl2/Cl−) was performed at 723 K to produce ZrCl and confirm the morphology of deposition. Dense and layered depositions adhered to the cathode were introduced to a vacuum distillation furnace after washing with pyridine solvent. The optimized condition of the thermal decomposition process was deduced by experimental results using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and inductively coupled plasma-optical emission spectrometry. Furthermore, the crystallographic phase transition of Zr into a face-centered cubic structure during the thermal decomposition was also observed by crystallographic analysis. Quantitative evaluation of electrodeposition of ZrCl and production Zr by thermal decomposition was discussed.

Studies on thermal and combustion properties of thermoplastic vulcanizates composites modified by polyhedral oligomeric silsesquioxane

ABSTRACT PP/EPDM (TPV) is a common thermoplastic elastomer with excellent performance and a wide range of uses. Polyhedral oligomeric silsesquioxane (POSS) with its own functional organic group (OV-POSS) was used to improve the combustion performance of TPV systems. 1 wt%, 3 wt% and 5wt% OV-POSS were added to TPV respectively, and their mechanical properties and thermal stability were tested. The results showed that the TPV mechanics performance of OV-POSS was slightly reduced, but the thermal stability was improved. Cone test results showed a 53% reduction in the heat release rate of TPV containing 5wt% OV-POSS compared with TPV without adding OV-POSS. The release of CO and CO2 also decreased significantly, and the amount of carbon formation increased from 1.1% to 14.8%. As can be seen from TG-IR analysis, the addition of OV-POSS slows down the thermal decomposition process of hydrocarbons. OV-POSS was added to improve flame-retardant properties and reduces fire risk of TPV.

Applying Feasibility Investigation of Resin Modifying Agent in Asphalt Pavement Materials

In order to promote the resin modifying agent applied into pavement materials, a type of resin modifying agent was selected as the modifier to prepare modified asphalt. The molecular crystal structure of the modifying material was characterized by using the X-ray diffraction test (XRD). The microstructure and element composition of PA6 was investigated through focused ion beam scanning electron microscopy (FIB-SEM). The thermal property and functional groups of PA6 were studied by thermogravimetric analysis-Fourier infrared spectroscopy (TG-FTIR) test. The physical property and rheological properties of PA modified asphalt were evaluated to confirm the applying feasibility of PA6 in asphalt. The results indicated that PA6 was the semicrystalline polymer and the existence of γ crystal form might improve the toughness of asphalt materials effectively. The thermal decomposition process of PA6 could be divided into three stages roughly: inert weight loss stage, rapid weight loss stage, and stable stage. The amount of PA6 modifier should be appropriately controlled during the application process to ensure the comprehensive effect of PA6 on high-temperature performance and low-temperature performance. The corresponding initial modulus attenuation value of PA modified asphalt was less than 70# asphalt under the same test conditions.

Insights into the thermal degradation mechanisms of polyethylene terephthalate dimer using DFT method

The thermal degradation mechanisms of polyethylene terephthalate (PET) dimer were studied by the B3P86 density functional theory (DFT) approach at 6–31++G (d, p) base set in this paper. Seven possible reaction paths were designed and analyzed, and the thermodynamic parameters for all reactions were computed. The calculated results indicate that the bond dissociation energy values (BDEs) of C–C bonds on the main-chain are the smallest, followed by those of C–O bonds. The kinetics analysis indicates that the concerted reactions are obviously liable to occur rather than radical reactions in the initial thermal decomposition process. In the processes of initial reactions, all concerted reactions occurred by six-membered cyclic transition states (TSs) are more prone to carry out than those happened by four-membered cyclic transition states. The research results show that the primary products of PET dimer pyrolysis are terephthalic acid, vinyl terephthalate, CH3CHO and divinyl terephthalate. CH3CHO is mainly formed by a concerted reaction in the initial degradation process, and CO2 is mainly produced by the decarboxylation via a concerted reaction and CO is mainly produced by the decarbonylation of a radical in secondary degradation.

Effect of Variations in Pyrolysis Reactor With Glass Wool Equipped and Without Glass Wool on the Weight of the Oil Produced

Currently, plastic waste is a very serious threat because plastic waste pollution can harm all living things around and also harm the environment. The increasing volume of plastic waste is due to the lack of processing technology, so that the volume of plastic waste is increasing day by day. Plastic is a material that is difficult to decompose because it is non-biodegradable. One application of plastic waste processing technology offered in this study is to use the pyrolysis principle. Pyrolysis is a method of converting plastic into fuel oil through a thermal decomposition process without the use of oxygen. The pyrolysis process used with a variety of reactors equipped with glass wool and reactor variations without glass wool. The purpose of this study was to compare the yield of pyrolysis oil with a variety of reactors equipped with glass wool and reactors without glass wool. The plastic used is OPP (oriented polypropylene), with a constant reactor heating temperature of 200° C. The pyrolysis process is carried out for 1 hour each test, and the condenser cooling temperature is 28° C. Based on the results of the research, the reactor variation with glass wool got the highest oil weight of 175 grf, while the reactor variation without glass wool got the lowest oil weight of 17 grf. With a variety of reactors equipped with glass wool, the heat generated is more concentrated into the reactor core, resulting in higher oil weight and a more efficient pyrolysis process.

Iron reduction from concentrates of hydrometallurgical dressing

The article presents results of theoretical and experimental studies of the processes of iron solid-phase reduction from an iron-containing concentrate obtained as a result of hydrometallurgical dressing of ferromanganese and polymetallic manganese-containing ores with coals of grades D (long-flame) and 2B (brown). The method of thermodynamic modeling using TERRA software complex was used to study the reducing properties of hydrocarbons by calculating equilibrium compositions in the temperature range of 373 - 1873 K. The authors obtained the dependences of compositions and volume of the gas phase formed as a result of the release of volatile components during heating on the temperature for the coals of the grades under consideration. As a result of thermodynamic modeling, the optimal temperatures and consumption are determined, which ensure the complete iron reduction from an iron-containing concentrate. The results of experimental studies were obtained by modern research methods using laboratory and analytical equipment, as well as methods of statistical processing. Results of the coals analysis carried out using the Setaram LabSys Evo thermal analyzer showed that the process of thermal decomposition of coals of the studied grades proceeds according to general laws. The process of thermal decomposition of long-flame coal proceeds less intensively than of brown coal. The results of an experimental study of the processes of thermal decomposition of reducing agents have shown that volumes of the gas phases, formed when coals are heated to a temperature of 1173 K in an argon atmosphere, practically coincide with the calculated values. As a result of thermodynamic modeling and experimental study, the optimal consumption of D and 2B grades of coal is determined at a temperature of 1473 K. The best reducing agent with a minimum specific consumption is long-flame coal of D grade. When determining the optimal amount of reducing agent in charge mixtures during the study of metallization processes, it was found that with an excess of reducing agent, it is possible to achieve almost complete extraction (98 - 99 %) of iron from the concentrate.

Thermal Performances and Fluidity of Biodegradable Poly(L-lactic acid) Filled with N, N'-Oxalyl Bis(piperonylic acid) Dihydrazide as a Nucleating Agent

N, N'-oxalyl bis(piperonylic acid) dihydrazide (PAOD) was obtained through the amination of piperonylic acid chloride and its structure was characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance. Melting blend technology was used to prepare the modified poly(L-lactic acid) (PLLA) containing the various loading PAOD as a new organic nucleating agent. The thermal performances including crystallization, melting behavior and thermal decomposition process, as well as the fluidity of PAOD-nucleated PLLA were investigated via a series of tests. The DSC results showed that, in comparison to DSC curve of the virgin PLLA, the DSC curves of all PLLA/PAOD appeared the sharp melt-crystallization peak, and a higher PAOD concentration caused the melt-crystallization to occur in the higher temperature region and reduced the negative effect of the high cooling rate on the melt-crystallization process. However, with increasing of PAOD concentration, the cold-crystallization enthalpy decreased from 24.4 J/g to 16.7 J/g. The melting peak after melt-crystallization depended on the heating rate and the PAOD concentration; and the double melting peaks appeared after isothermal crystallization in low temperature region was thought to be due to the melting-recrystallization. The addition of PAOD decreased the onset decomposition temperature of PLLA, but the onset decomposition temperature was determined by the PAOD concentration and the intermolecular interaction of PLLA and PAOD. Additionally, the PAOD could considerably improve the fluidity of PLLA.

Comparative Studies on Thermal Decompositions of Dinitropyrazole-Based Energetic Materials.

Dinitropyrazole is an important structure for the design and synthesis of energetic materials. In this work, we reported the first comparative thermal studies of two representative dinitropyrazole-based energetic materials, 4-amino-3,5-dinitropyrazole (LLM-116) and its novel trimer derivative (LLM-226). Both the experimental and theoretical results proved the active aromatic N-H moiety would cause incredible variations in the physicochemical characteristics of the obtained energetic materials. Thermal behaviors and kinetic studies of the two related dinitropyrazole-based energetic structures showed that impressive thermal stabilization could be achieved after the trimerization, but also would result in a less concentrated heat-release process. Detailed analysis of condensed-phase systems and the gaseous products during the thermal decomposition processes, and simulation studies based on ReaxFF force field, indicated that the ring opening of LLM-116 was triggered by hydrogen transfer of the active aromatic N-H moiety. In contrast, the initial decomposition of LLM-226 was caused by the rupture of carbon-nitrogen bonds at the diazo moiety.

Study of the Potential Uses of Hydrochar from Grape Pomace and Walnut Shells Generated from Hydrothermal Carbonization as an Alternative for the Revalorization of Agri-Waste in Chile

A myriad of resources and efforts have been devoted to assessing the possibilities of using locally sourced biomass to produce energy, reduce CO2 emissions, and, in turn, lower dependance on petroleum. Grape pomace (GP) and walnut shells (WS) are organic waste generated in Chile. Within the last decade, the potential benefits and application of biomass have received significant attention, both in terms of producing functionalized carbon materials, and the various potential applications in the field of energy storage and environmental protection. The proposed research motivation is on the development of carbonous materials through thermal decomposition processes. Few researchers have addressed the idea of developing a multipurpose carbonaceous matrix from hydrochar, and there remains a need for an efficient method to obtain hydrochar specially from grape pomace. Hence, the general objective of this research is to study the potential of grape pomace and walnut shells treated with hydrothermal carbonization (HTC) as an alternative low-cost and efficient carbonous matrix. Proximate and elemental analysis was determined to distinguish the nature of the feedstock along with the hydrochar produced. Yield and reaction severity were also studied to study the impacts of temperature and residence time for both feedstocks. Successful results from the proposed work have broad applications for increasing the sustainability biomass applications, contributing to a positive economic impact.

Thermal decomposition of ferroan dolomite: A comparative study in nitrogen, carbon dioxide, air and oxygen

The mechanism and kinetics of the process of thermal decomposition of low-manganese ferroan dolomite were investigated by non-isothermal derivative thermogravimetric analysis in this work. The study of the effect of the composition of gaseous phase on the mechanism and kinetics of thermal decomposition process includes the kinetics experiments performed in nitrogen, carbon dioxide, air and oxygen. While the process of endothermic decomposition takes place in one-step in a carbon dioxide-free atmosphere or in air, three separate reactions take place in carbon dioxide. The activation energy of these three reactions is also significantly higher than that of the thermal decomposition of ferroan dolomite in nitrogen, oxygen or air.