Thermal Decomposition Of Precursor Research Articles

Effect of Active Phase Precursor on Structural, Textural and Catalytic Properties of the Model NiOx/CeO2 System Active in Dry Reforming of Methane

The current paper is devoted to the synthesis of ceria-supported nickel-based catalysts starting from different precursors of the nickel active phase. Thermal decomposition of metal-containing precursors, deposited onto stable supports by dry impregnation, belongs to the industrially preferred, simple ways of catalyst preparation. The synthesized series of NiOx/CeO2 catalysts have been tested in dry methane reforming (DMR), in which two greenhouse gases, i.e., CO2 and CH4, are simultaneously converted into syngas. Both reaction progress and stability of the catalyst strongly depend on nickel speciation, which in turn can be determined by the nature of the chosen precursor. Contrary to relatively many studies focused on the importance of synthetic methods and conditions on nickel speciation, the effect of precursor nature on structural, textural, and functional properties of catalytic systems has neither been discussed much nor fully understood. The main goal of this paper was to elucidate the effect of precursors on the properties of NiOx/CeO2. Consequences of the use of various nickel precursors (simple inorganic salts, organometallic complexes, and chelates) have been analyzed in detail from the viewpoint of their beneficial influence on the catalytic performance of NiOx/CeO2 system (containing 3 wt. % of Ni) tested in DMR.

Chemical Vapor Deposition of Elemental Crystallogen Thin Films

A consolidation of the fundamentals of elemental crystallogen chemical vapor deposition (CVD) is a necessity in view of the extensive evidence accumulated over the last few decades. An in-depth understanding of deposition mechanisms via hydrides asks for a discerning understanding of molecular hydrogen dissociative adsorption, precursor thermal decomposition, and CVD growth rates. With those, a groundbreaking paradigm shift comes to light. GR activation energy E(GR) fingerprints the surface energy. SE ≈ 2 × E(GR)/(a×a), where SE is surface energy, E(GR) activation energy, a lattice parameter. Hydride precursor thermal decomposition consistency with the corresponding solid growth kinetics is demonstrated. Heterogeneous TD kinetics captures a solid deposition and not a gas phase molecular reaction. Thermodynamic equilibrium is achieved during the heterogeneous thermal decomposition of silicon precursors. The popular split between mass-transfer and kinetic regimes is not supported by evidence. Three mechanisms are apparent. The first is controlled by a Si–H bond dissociation energy. The second is controlled by an H–H bond dissociation energy. The last is controlled by a Si–Si bond dissociation energy as lattice sites are sealed off with Si–H bonds.

Precursor decomposition mechanism of In2O3 powder for oxide ceramic targets

In this study, precursor decomposition as well as nucleation and growth processes during the preparation of In2O3 powders via chemical precipitation were investigated. This is to provide guidance for the preparation of high-quality In-based oxide target powders. In-situ phase and microstructure evolution during thermal decomposition of precursors were analyzed. In addition, decomposition behavior of precursors at different heating rates was explored. Results show that amorphous In(OH)3 precursor powder gradually decomposes and transforms into crystalline In2O3 powder during heating process. Its degree of crystallinity increases with the increase in temperature. Fine and homogeneous In2O3 powder with average grain size of 54.46 nm was obtained by holding the powder at 770 °C for 3 h. The decomposition of precursors at any given heating rate can be divided into two stages: (i) dehydration and (ii) nucleation and crystallization. However, higher heating rate clearly results in temperature hysteresis effect, the occurrence of decomposition reaction at higher temperature, and an increase in the maximum reaction rate of decomposition reaction. Moreover, activation energy of thermal decomposition was obtained using model-free transformation method. Decomposition reaction model of In(OH)3 precursor was established using model-fitting method. It was deduced that first-stage reaction mechanism is three-dimensional diffusion. Reaction rate in this stage is controlled by product layer diffusion. Furthermore, second-stage reaction mechanism is random nucleation and subsequent growth. Reaction rate in this stage is controlled by nucleation and growth rates.

CO2 Hydrogenation to Methanol on CuO-ZnO/SiO2 and CuO-ZnO/CeO2-SiO2 Catalysts Synthesized with β-Cyclodextrin Template

A series of mixed copper (II)—zinc oxide catalysts supported on unmodified and ceria-modified silica supports were synthesized using β-cyclodextrin as a template. The novelty of this work lies in the use of cyclosextrins for the template synthesis of catalyst supports. The obtained samples were analyzed by XRD, SEM-EDX, low-temperature nitrogen physisorption, XPS, and EPR. The magnetic properties of the catalysts were also measured. The thermal decomposition of precursors was analyzed by TGA combined with mass-spectrometric analysis of the evolved gases. The effects of the support pore size, the nature of the active phase and its loading, as well as the sequence of component deposition on the catalyst performance in the CO2 conversion to methanol were studied. The catalysts with cerium added at the gelation stage demonstrated the best performance. The selectivity of these samples reaches values of more than 90% over a fairly ide temperature range, with the productivity reaching 480 g/kg cat·h at 300 °C.

Evolution of microstructure and electromagnetic interference shielding performance during the ZrC precursor thermal decomposition process

Evolution of microstructure and electromagnetic interference shielding performance during the ZrC precursor thermal decomposition process

Thermal decomposition of trimethylindium and indium trisguanidinate precursors for InN growth: An abinitio and kinetic modeling study.

Indium nitride (InN) is an interesting material for future electronic and photonic-related applications, as it combines high electron mobility and low-energy band gap for photoabsorption or emission-driven processes. In this context, atomic layer deposition techniques have been previously employed for InN growth at low temperatures (typically <350 °C), reportedly yielding crystals with high quality and purity. In general, this technique is assumed to not involve any gas phase reactions as a result from the time-resolved insertion of volatile molecular sources into the gas chamber. Nonetheless, such temperatures could still favor the precursor decomposition in the gas phase during the In half-cycle, therefore altering the molecular species that undergoes physisorption and, ultimately, driving the reaction mechanism to pursue other pathways. Thence, we herein evaluate the thermal decomposition of relevant In precursors in the gas phase, namely, trimethylindium (TMI) and tris(N,N'-diisopropyl-2-dimethylamido-guanidinato) indium (III) (ITG), by means of thermodynamic and kinetic modeling. According to the results, at T = 593K, TMI should exhibit partial decomposition of ∼8% after 400s to first generate methylindium and ethane (C2H6), a percentage that increases to ∼34% after 1h of exposure inside the gas chamber. Therefore, this precursor should be present in an intact form to undergo physisorption during the In half-cycle of the deposition (<10s). On the other hand, the ITG decomposition starts already at the temperatures used in the bubbler, in which it slowly decomposes as it is evaporated during the deposition process. At T = 300 °C, the decomposition is a fast process that reaches 90% completeness after 1s and where equilibrium, at which almost no ITG remains, is achieved before 10s. In this case, the decomposition pathway is likely to occur via elimination of the carbodiimide ligand. Ultimately, these results should contribute for a better understanding of the reaction mechanism involved in the InN growth from these precursors.

A New Approach to the Synthesis of Nanocrystalline Cobalt Boride in the Course of the Thermal Decomposition of Cobalt Complexes [Co(DMF)6]2+ with Boron Cluster Anions

In the course of the study, nanocrystalline cobalt monoboride was prepared by thermal decomposition of precursors [Co(DMF)6][An], where [An] = [B12H12]2- (1), [trans-B20H18]2- (2) or [B10Cl10]2- (3) in an argon atmosphere. Three new salt-like compounds 1-3 were prepared when Co(NO3)2 was allowed to react with (Et3NH)2[An]. Compound 1 is new; the structures of compounds 2 and 3 have been previously reported. Samples 1-3 were annealed at 900 °C in argon to form samples 1a-3a, which were characterized by single crystal XRD for 1 and powder XRD for 1-3. Powder XRD on the products showed the formation of BN and CoB for 1a in a 1:1 ratio; 2a gave a higher CoB:BN ratio but an overall decreased crystallinity. For 3a, only CoB was found. IR spectra of samples 1a-3a as well as X-ray spectral fluorescence analysis for 3a confirmed these results. The nanoparticular character of the decomposition products 1a-3a was shown using TEM; quite small particle sizes of about 10-15 nm and a quite normal size distribution were found for 1a and 2a, while the decomposition of 3 gave large particles with 200-350 nm and a broad distribution.

Impact of Precursor Thermal Decomposition Reactions on YSZ Coatings Deposited with a Low-Power Plasma Torch at Short Spray Distance

Impact of Precursor Thermal Decomposition Reactions on YSZ Coatings Deposited with a Low-Power Plasma Torch at Short Spray Distance

Facile Synthesis of Highly Uniform ZnMn2O4 Hollow Nanospheres with Excellent Lithium Storage Properties

Abstract Hollow nano/micron-structured transition metal oxides (TMOs) hold great potential as electrodes for rechargeable batteries, due to abundant electrochemically active sites, shortened ion diffusion length, and robust architecture. Herein, a facile solvothermal approach combined with post annealing is reported for synthesizing highly uniform ZnMn2O4 hollow nanospheres. The one-pot solvothermal reaction is the key step to form a hollow interior. With solvothermal reaction processing, the precursor solid nanospheres are formed firstly, which gradually evolve into core-shelled structures and finally hollow structures via a self-templated process. Then, the ZnMn2O4 nanospheres with well-inherited hollow interior are obtained by the thermal decomposition of precursors. When evaluated as an electrode, the ZnMn2O4 hollow nanospheres show lithium storage properties superior to solid counterparts, in view of high reversible capacity (735.0 mAh g−1 after 200 cycles at 0.1 A g−1), and ultralong cyclic stability (up to 1000 cycles at 1 A g−1). A dominant pseudocapacitive contribution of 60.0% is identified for the ZnMn2O4 hollow electrode, leading to excellent rate performance. This work provides a new path for preparing TMOs with hierarchically hollow structure.

Impact of Preparation Method and Y2O3 Content on the Properties of the YSZ Electrolyte

This study is an effort to cover and interconnect multiple aspects of the fabrication of the yttria-stabilized zirconia (YSZ) from powder preparation to a solid electrolyte suitable for utilization in solid oxide cells. Thus, a series of YSZ electrolytes was prepared, differing in the content of the Y2O3 dopant and in the method of preparation. Combustion synthesis along with the thermal decomposition of precursors was used for YSZ powder synthesis with a dopant content of 8 to 18 mol.%. Post-synthesis treatment of the powder was necessary for achieving satisfactory quality of the subsequent sintering step. The morphology analyses of the YSZ powders and sintered electrolytes produced proved that small particles with a uniform size distribution are essential for obtaining a dense electrolyte. Furthermore, the conductivity of YSZ electrolytes with different Y2O3 contents was examined in the temperature range of 400 to 800 °C. The lowest conductivity was found for the sample with the highest Y2O3 content. The obtained results enable the preparation methods, YSZ powder morphology, and composition to be connected to the mechanical and electrochemical properties of the YSZ electrolyte. Thus, this study links every step of YSZ electrolyte fabrication, which has not been sufficiently clearly described until now.

Fabrication of minimal capital‐intensive scratch‐resistant and hydrophobic tungsten oxide film on stainless steel through spray pyrolysis

In this contribution, a pure and robust tungsten oxide (WO3) film was accomplished on stainless steel (SS) substrate at 400°C through a minimal capital intensive, simplistic spray pyrolysis method by utilizing a precursor comprising tungsten hexachloride and 2‐methoxyethanol. Thermal analysis revealed the precursor's thermal decomposition and crystallization at ~230°C and 255°C, respectively. The fabricated polycrystalline (monoclinic crystal structured) film was uniform and dense in nature, exhibiting surface porosity and average surface roughness of 4.7 % and 15.9 nm, respectively. The average grain size and thickness of film were 360 ± 70 nm and ~3.6 μm, respectively. W, O elemental presence with a close atomic ratio of 1:3 on the film's surface was acquired along with 91 % lattice oxygen. Regardless of applied normal load in the range of 5 to 15 N, an increment of ~22 % in scratch hardness was gained in WO3‐coated SS compared to uncoated one. Hydrophilic natured WO3 film (water contact angle, WCA, of ~31°) was efficaciously transformed into hydrophobic (WCA, 136°) by chemical modification with octadecyltrichlorosilane to create a self‐assembled monolayer on the surface of the film. The hydrophobicity of octadecyltrichlorosilane (OTS)‐treated film was found to be preserved even after 100 days.

Effect of the Synthesis Method, Complexing Agent and Solvent on the Physicochemical Properties of LaNiO3 Nanopowders

LaNiO3 nanopowders are synthesized by sol–gel and sol-gel combustion methods using citric acid, ascorbic acid and sucrose as chelating agents, and ethanol and water as solvents. The precursor thermal decomposition towards the final solid was analyzed by X-ray diffraction, differential thermal analysis and thermogravimetric techniques which were also used to provide the adequate temperature of calcination (800and#176;C) for achievement of the final perovskite. After calcination, the nanocomposites were characterized by powder size distribution, Fourier transform infrared spectroscopy and X-ray diffraction.

Coprecipitation of actinide peroxide salts in the U-Th and U-Pu systems and their thermal decomposition.

The uranium and plutonium co-conversion process constitutes a continuous subject of interest for MOx fuel fabrication. Among the various routes considered, chemical coprecipitation by the salt effect has been widely investigated regarding its simplicity of integration between the partitioning and purification steps of the PUREX process, and the straightforward recovery of precursors that are easily converted into oxide phases by thermal decomposition. The present study focuses on the coprecipitation behavior of U-Th and U-Pu actinide peroxide mixed systems by examining the precipitation yields and settling properties for nitric acidity in the range of 1 to 3 M and hydrogen peroxide concentration in the range of 4.5 to 7 M. The precipitated solids have been characterized by powder XRD, IR and Raman spectroscopy, laser granulometry and SEM-EDS analyses revealing the synthesis of studtite and actinide(IV) peroxo-nitrates as aggregated particles. The actinide solid phases are uniformly distributed within the filtered cakes. The precursor thermal decomposition results in the formation of oxide phases at low temperature according to a sequential release of water molecules, peroxide ligands and nitrate ions. The calcination step has a limited effect on the morphology of the powders which remain highly divided. The high precipitation rate of actinides makes this chemical route potentially interesting as a co-precipitation process.

Cadmium Telluride Nanocomposite Films Formation from Thermal Decomposition of Cadmium Carboxylate Precursor and Their Photoluminescence Shift from Green to Red

This study focuses on the investigation of a CdTe quantum dots (QDs) formation from a cadmium-carboxylate precursor, such as cadmium isostearate (Cd(ISA)2), to produce CdTe QDs with tunable photoluminescent (PL) properties. The CdTe QDs are obtained by the thermal decomposition of precursors directly in the polymer matrix (in situ method) or in solution and then encapsulated in the polymer matrix (ex situ method). In both approaches, the time course of the CdTe QDs formation is followed by means of optical absorption and PL spectroscopies focusing on viable emission in the spectral interval between 520 and 630 nm. In the polymeric matrix, the QDs formation is slower than in solution and the PL bands have a higher full width at half maximum (FWHM). These results can be explained on the basis of the limited mobility of atoms and QDs in a solid matrix with respect to the solution, inducing an inhomogeneous growth and the presence of surface defects. These achievements open the way to the exploitation of Cd(ISA)2 as suitable precursor for direct laser patterning (DPL) for the manufacturing of optoelectronic devices.

Cadmium Telluride Nanocomposite Films Formation from Thermal Decomposition of Cadmium Carboxylate Precursor and Their Photoluminescence Shift from Green to Red

Cadmium Telluride Nanocomposite Films Formation from Thermal Decomposition of Cadmium Carboxylate Precursor and Their Photoluminescence Shift from Green to Red

Synthesis, structural, magnetic, textural, optical investigation and photocatalytic performance of undoped and doped cobaltite nanoparticles

The present work deals with the synthesis and characterization of pure and transition metal (Ni, Cu and Fe) doped spinel Co3O4 nanoparticles (NPs), which are well known for their physical and chemical features. These transition metal doped Co3O4 NPs were tailored through thermal decomposition of precursors synthesized by simple co-precipitation, the simple and cost-effective strategy of fabricating mesoporous spinel cobalt oxide. This study investigates the photocatalytic degradation of industrial dyes Rhodamine B (RhB) and Methyl Orange (MO) under sunlight by using NPs as catalysts. Among the different nanocatalysts, Ni doped Co3O4 NP exhibited the highest efficiency in degrading the environmentally harmful dyes, proving the positive correlation between surface area and photodegradation efficiency. The structures and optical properties were investigated by Powder X-Ray Diffraction (PXRD), X-ray Photoelectron Spectroscopy (XPS), High-Resolution Transmission Electron Microscopy (HR-TEM), Ultraviolet-Diffuse Reflectance Spectroscopy (UV-DRS) and Photoluminescence (PL) under dopant control. The morphology and polycrystallinity of the samples were studied using SEM-EDS and SAED patterns, respectively. The doped ferromagnetic samples showed unsaturation in hysteresis loops which specified the oxygen vacancy.

A comparative study for degradation of RB5 dye using Ti/Ir0.15–Ru0.15–Sn0.6–Sb0.1 electrodes fabricated by employing two different thermal decomposition methods

A comparison of electrochemical degradation efficiency of Ir- and Ru-based mixed metal oxide electrodes fabricated by two different methods, i.e. polymeric precursor thermal decomposition (PPTD) and standard thermal decomposition (STD), was carried out on Reactive Black 5 (RB5) dye. The electrolysis experiments were performed with 100 mg/L RB5 at initial pH 2, a current density 50 mA/cm2, and 4 mg/L NaCl dosage. The results of the study were evaluated in terms of reduction in colour, COD, and TOC. The result showed higher RB5 degradation rate constants obtained on the PPTD electrode during kinetic study, compared to the STD electrode. A better performance of the PPTD electrode compared to the STD electrode may be attributed to its higher Sn content and its different morphologies observed in characterization using SEM with EDX analysis. Although proven efficient, the service life of PPTD-coated electrode was found only ~ 76 h, compared to ~ 895 h of STD-coated electrode. Experimental results demonstrated that coating method influenced the performance and service life of the electrodes. A comparison of the MTC, ICE, and energy consumption of the two electrodes prepared by STD and PPTD methods demonstrated that PPTD-coated electrodes were more efficient with a shorter life-span.

Synthesis, characterization and studies of BaFe2O4/PMMA nanocomposite

Synthetic nanotechnology has attracted a great deal of attention from researchers for the synthesis of assorted materials at nanoscale dimension. Researchers are more attracted to microwave-assisted route for the synthesis of ferrite nanomaterials due to its simplicity. Barium ferrite (BF) nanomaterials are prepared by two strategies: the barium oxalate and the iron oxalate strategy. Thermal decomposition of barium oxalate precursor and ferrous oxalate precursor has been done using polyvinyl alcohol (PVA) as a fuel. Self-propagating combustion reaction of metal oxalates takes place with fuel, which controls the size of the particle. Solvent casting method is used for the preparation of barium ferrite-dispersed poly(methyl methacrylate) (BF–PMMA) nanocomposite. The structure of the as-prepared samples was carried out by X-ray diffraction (XRD) study and particle morphology of the sample done by scanning electron micrograph (SEM) technique. The presence of barium and iron metals in the sample is confirmed by EDX analysis. Bonding nature of the ferrite is studied by Fourier transform (FT-IR) tool. Thermal and electrical studies of the samples are also undertaken to know the thermal electrical behaviour. UV absorbance study of the said composite is also undertaken.

High compressibility of synthetic analogous of binary iridium–ruthenium and ternary iridium–osmium–ruthenium minerals

Hcp–Ir0.24Ru0.36Os0.40 and fcc–Ir0.84Ru0.06Os0.10 ternary alloys as well as binary hcp–Ir0.33Ru0.67 and fcc–Ir0.75Ru0.25 ones were prepared using thermal decomposition of [IrxRu1-x(NH3)5Cl][OsyIr(1-y)Сl6] single-source precursors in hydrogen flow below 1070 K. These single-phase alloys correspond to ternary and binary peritectic phase diagrams and can be used as synthetic models for rare iridosmine minerals. Thermal decomposition of parent bimetallic precursor [Ir(NH3)5Cl][OsСl6] has been investigated using in situ powder X-ray diffraction in inert and reductive atmospheres. In reductive atmosphere, [Ir(NH3)5Cl][OsСl6] forms (NH4)2[OsСl6] as crystalline intermediate; Ir from its cationic part is reduced by hydrogen with a formation of defect fcc-structured metallic particles; the final product is a metastable hcp–Ir0.5Os0.5 alloy. In inert atmosphere, the salt decomposes at higher temperature without a formation of any detectable crystalline intermediates; two-phase fcc+hcp mixture forms directly above 800 K. Room temperature compressibility up to 50 GPa has been studied for all prepared alloys in diamond anvil cells. Investigated ternary and binary alloys do not show any phase transitions upon compression at room temperature. In contrast with other investigated ultra-incompressible refractory alloys with osmium and iridium, hcp–Ir0.33Ru0.67, fcc–Ir0.75Ru0.25 binary and fcc–Ir0.84Ru0.06Os0.10 ternary alloys show higher compressibility in comparison with pure metals. Fcc–Ir0.75Ru0.25 alloy shows several magnetic phase transitions (at approx. 3.4 K, 135 K and 233 K) that could be related to different magnetic phases.

Formation of TiO2 particles during thermal decomposition of Ti(NO3)4, TiOF2 and TiOSO4

In the paper, impact of the precursor decomposition conditions on the morphological and structural characteristics of TiO2 particles was discussed. The novelty and significance of the researches lay in the ability to control morphological features of the synthesized powder particles so that enhanced properties of the sintered ceramics can be obtained. The research program covered thermal decomposition of titanium nitrate, titanium oxyfluoride and titanium oxysulphate at different temperatures, with and without organic additive. Obtained titanium dioxide powder underwent analysis, namely, its phase composition, particle shape and dimensions were measured using X-ray and IR-spectra, as well as scanning electron microscopy. Activity of the obtained particles during sintering process was analyzed using dilatometer and microhardness measurement after sintering. It was found that spherical TiO2 nanoparticles of anatase and rutile phases can be obtained from decomposition of titanium nitrate at 700 °C. Thermal decomposition of other precursors, titanium oxyfluoride and oxysulfate, synthesized only anatase phase with particles of 200 and even 300 nm. Obtained spherical particles were smaller when temperature of decomposition was lower or the activator OP9 was added. However, lower decomposition temperature and additive had negative effect on sintering activity of the obtained particles, decreasing the microhardness of sintered specimens.