Thermoreactivity of Sol-Gel Precursor for ZnO-Based Thin Films

The thermoreactivity of a zinc acetate non-alkoxide solution used for the preparation of ZnO-based thin films was investigated in the temperature range 20-600°C by TG-DTA, XRD and SEM data. We found that the formation in air of ZnO crystallites from the sol-gel precursor occurs above 150°C simultaneously with the decomposition of an intermediary compound, most probably carbonate hydroxide (sclarite and/or hydrozincite). At 200 °C, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although residual organic compounds and water were not yet fully removed and an amorphous phase coexists. A kinetic investigation on the thermal decomposition of sol-gel precursor from DTA data using Kissinger differential equation is also presented. Apparent activation energy values of about. 100 kJ mol-1 corresponding to the nonisothermal decomposition of solid precursors in the temperature range 170-250oC have been found.

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Photophysical Properties of CdS Nanoparticles in Thin Films for Opto-Chemical Sensing

MRS Proceedings ◽

10.1557/proc-820-o3.9 ◽

2004 ◽

Vol 820 ◽

Author(s):

Elena A. Guliants ◽

Barbara A. Haruff ◽

James R. Gord ◽

Christopher E. Bunker

Keyword(s):

Thin Films ◽

Organic Compounds ◽

Protective Coatings ◽

Photophysical Properties ◽

Sol Gel ◽

Liquid Solution ◽

Optical Signal ◽

Cds Nanoparticles ◽

Trap States ◽

Post Synthesis

AbstractIn recent years, II-VI compound semiconductor nanoparticles synthesized in a liquid solution have been shown to possess unique optoelectronic properties which are highly attractive for the fabrication of various sensors based on the optical signal readout scheme. The challenge has been to immobilize these nanoparticles into films on solid surfaces, i.e. on a chip, so that they do not suffer any property deterioration as a sensing medium. In the presented work, synthesis of CdS nanoparticles in reverse micelle solution using AOT surfactant as a stabilizer has led to particles with relatively bright photoemission identified as originating from both shallow and deep traps inside the bandgap. Moreover, slightly altering the preparation procedure has produced samples with two distinctive crystal structures. Both types of CdS nanoparticles suspended in commonly utilized solvents such as chloroform and hexane were subject to chemical quenching when various organic compounds were introduced into the solution, demonstrating the sensitivity of trap states to their chemical environment. However, the two structures have shown very different optical properties. While post-synthesis treatment had no effect on one type of particle, the other type was able to undergo a photochemical reaction via prolonged UV irradiation, which resulted in an increased luminescence quantum yield ÖL from 2% to 14%. The same particle type was also responsive to thermal treatment, showing even higher values of ÖL (∼40%). The CdS/AOT particles have been cast into thin films by spin-coating on a Si wafer. Coating parameters have been investigated in order to achieve optimal control over the film thickness, uniformity, overall film durability, etc. These nanostructured films capped with various porous polymeric and sol-gel protective coatings were exposed to a series of organic compounds. Photoluminescence data collected for these samples served for identification of the compounds and their concentrations. This paper offers the discussion of photophysical response in CdS nanoparticle-based thin films with respect to development of novel nanostructured opto-chemical sensors.

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Dielectric tunable characteristics of compositional-gradient BaTi1−xSnxO3 thin films

Journal of Advanced Dielectrics ◽

10.1142/s2010135x21500193 ◽

2021 ◽

Vol 11 (04) ◽

pp. 2150019

Author(s):

Chenjing Wu ◽

Manwen Yao

Keyword(s):

Thin Films ◽

Impedance Matching ◽

Sol Gel ◽

Temperature Stability ◽

Dielectric Behavior ◽

Compositional Gradient ◽

Dielectric Tunability ◽

Temperature Range ◽

Si Substrates ◽

Low Leakage

Compositional-gradient [Formula: see text][Formula: see text]O3 thin films on Pt(100)/Ti/SiO2/Si substrates are fabricated with sol–gel using spin coating. All of the structures of the prepared thin films are of single-phase crystalline perovskite with a dense and crack-free surface morphology. BTS10/15/20 thin film exhibits enhanced temperature stability in its dielectric behavior. The temperature coefficient of capacitance [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C and that of [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C. Furthermore, the thin films show low leakage current density and dielectric loss. High and stable dielectric tunable performances are found in BTS10/15/20 thin films: the dielectric tunability of the thin films is around 20.1% under a bias voltage of 8 V at 1 MHz and the corresponding dielectric constant is in the range between 89 and 111, which is beneficial for impedance matching in circuits. Dielectric tunability can be obtained under a low tuning voltage, which helps ensure safety. The simulated resonant frequency of the compositional-gradient BTS thin films depends on the bias electric field, showing compositional-gradient BTS thin films could be used in electrically tunable components and devices. These properties make compositional-gradient BTS thin films a promising candidate for dielectric tuning.

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Oxidation Behavior of β-Sialon Ultrafine Powders Prepared by the Combined Sol-Gel and Microwave Carbothermal Reduction Nitridation Method

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.281.34 ◽

2018 ◽

Vol 281 ◽

pp. 34-39

Author(s):

Fa Liang Li ◽

Fang Fu ◽

Li Lin Lu ◽

Hai Jun Zhang ◽

Shao Wei Zhang

Keyword(s):

Activation Energy ◽

Carbothermal Reduction ◽

Oxidation Behavior ◽

Oxidation Process ◽

Sol Gel ◽

Probable Mechanism ◽

Ultrafine Powders ◽

Isothermal Thermogravimetry ◽

Temperature Range ◽

Mechanism Function

Ultrafine powders of β-Sialon were prepared by the combined sol-gel and microwave carbothermal reduction nitridation method, and their oxidation process was studied by a non-isothermal thermogravimetry method. The results indicated that two different mechanism functions respectively corresponded to the initial and final oxidation stages. The reverse Jander equation with activation energy of 240.5 kJ/mol and the Avrami-Erofeev equation with activation energy of 410.7 kJ/mol were respectively identified as the most probable mechanism function for the initial and final oxidation stages in the temperature range of 1423-1623 K.

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Characteristics and thermal decomposition kinetics of wood-SiO2 composites derived by the sol-gel process

Holzforschung ◽

10.1515/hf-2016-0126 ◽

2017 ◽

Vol 71 (3) ◽

pp. 233-240 ◽

Cited By ~ 12

Author(s):

Ke-Chang Hung ◽

Jyh-Horng Wu

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Apparent Activation Energy ◽

Sol Gel ◽

Weight Percent Gain ◽

Weight Percent ◽

Decomposition Kinetics ◽

Thermal Decomposition Kinetics ◽

Sol Gel Process ◽

Kinetics Of

Abstract Wood-SiO2 composites (WSiO2Cs) were prepared by means of the sol-gel process with methyltrimethoxysilane (MTMOS) as a reagent, and the physical properties, structure and thermal decomposition kinetics of the composites has been evaluated. The dimensional stability of the WSiO2Cs was better than that of unmodified wood, especially in terms of the weight percent gain (WPG), which achieved values up to 30%. The 29Si-NMR spectra show two different siloxane peaks (T2 and T3), which supports the theory about the formation of MTMOS network structures. Thermal decomposition experiments were also carried out in a TG analyzer under a nitrogen atmosphere. The apparent activation energy was determined according to the iso-conversional methods of Friedman, Flynn-Wall-Ozawa, modified Coats-Redfern, and Starink. The apparent activation energy between 10 and 70% conversion is 147–172, 170–291, 189–251, and 192–248 kJ mol−1 for wood and WSiO2Cs with WPGs of 10, 20, and 30%, respectively. However, the reaction order between 10 and 70% conversion calculated by the Avrami theory was 0.50–0.56, 0.35–0.45, 0.33–0.44, and 0.28–0.48. These results indicate that the dimensional and thermal stability of the wood could be effectively enhanced by MTMOS treatment.

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Investigations of the Temperature Influence on Formation of Compounds from the BTEX Group During the Thermal Decomposition of Furan Resin / Badania wpływu temperatury na powstawanie związków z grupy BTEX podczas termicznego rozkładu żywicy furanowej

Archives of Foundry Engineering ◽

10.2478/afe-2013-0042 ◽

2013 ◽

Vol 13 (2) ◽

pp. 85-90 ◽

Cited By ~ 2

Author(s):

M. Kubecki ◽

M. Holtzer ◽

S. Żymankowska-Kumon

Keyword(s):

Thermal Decomposition ◽

Volatile Organic Compounds ◽

Organic Compounds ◽

Temperature Influence ◽

Temperature Range ◽

Furan Resin ◽

Volatile Organic ◽

Synthetic Resins ◽

Temperature Ranges ◽

The One

Abstract Organic binders applied in foundry plants based on synthetic resins, from the one side influence obtaining the required technological properties by the moulding sand and - in consequence - obtaining good quality castings, and on the other side are the source of volatile organic compounds (VOC). Together with synthetic resins their hardeners, which although added in very small amounts emit during their thermal decomposition substances negatively influencing the natural environment, are also used. Both, resins and hardeners only at the influence of high temperatures accompanying moulds pouring with liquid metal generate harmful volatile organic compounds including compounds from the BTEX group. Investigations of the temperature influence on the kind and amount of organic compounds formed during the thermal decomposition of selected binders and hardeners and their mixtures allow to determine temperature ranges the most favourable for emitting harmful substances as well as to compare their emission from the selected materials. The aim of this study was the determination the temperature influence on formation substances from the BTEX group, during thermal decomposition of the selected binder, its hardener and their mixture. The BTEX group emission constitutes one of the basic criteria in assessing the harmfulness of materials applied for moulding and core sands and it can undergo changes in dependence of the applied system resin-hardener. Investigations were carried out on the specially developed system for the thermal decomposition of organic substances in the temperature range: 500ºC - 1300ºC, at the laboratory scale. The investigations subject was the furan resin, its hardener and hardened furan resin. The assessment of the emission degree of the BTEX group in dependence of the system subjected to the temperature influence was performed, within the studies. The temperature range, in which maximal amounts of benzene, toluene, ethylbenzene and xylenes were emitted from tested materials - was defined. The qualitative and quantitative analysis of the BTEX group were carried out with using the gas chromatography technique coupled with the mass spectrometry (GC/MS).

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Relaxor Behavior in Ba0.8Sr0.2TiO3/ZrO2 Heterostructured Thin Films

MRS Proceedings ◽

10.1557/opl.2012.1254 ◽

2012 ◽

Vol 1454 ◽

pp. 89-96 ◽

Cited By ~ 1

Author(s):

Santosh K. Sahoo ◽

H. Bakhru ◽

Sumit Kumar ◽

D. Misra ◽

Y. N. Mohapatra ◽

...

Keyword(s):

Thin Films ◽

Activation Energy ◽

Oxygen Vacancies ◽

Sol Gel ◽

Single Layer ◽

Relaxor Behavior ◽

Bst Thin Films ◽

Si Substrates ◽

Sol Gel Process ◽

Loss Maximum

ABSTRACTBa0.8Sr0.2TiO3 (BST) thin films and Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films have been successfully fabricated on Pt/Ti/SiO2/Si substrates by a sol-gel process. The dielectric properties of these films were measured as a function of temperature in the frequency range of 1 kHz to 1 MHz. It is clearly observed that the dielectric peaks exist and shift to high temperature with the increase of frequency indicating the presence of relaxor-type behavior in the films. Also it is seen that one dielectric peak is observed in single layer BST thin films whereas two dielectric peaks are observed in BST/ZrO2 heterostructured thin films due to the presence of two dielectric layers having different band gap energies. The variation of peak temperature Tm, corresponding to dielectric loss maximum, with frequency and fitting to Arrhenius law gives activation energy of 1.24 eV which is very close to the activation energy of oxygen vacancies in BaTiO3. Hence, oxygen vacancies are the active defects which are contributing to the relaxation process in these films.

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The thermal decomposition of RDX at temperatures below the melting point. II. Activation energy

Australian Journal of Chemistry ◽

10.1071/ch9700749 ◽

1970 ◽

Vol 23 (4) ◽

pp. 749 ◽

Cited By ~ 17

Author(s):

JJ Batten ◽

DC Murdie

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Melting Point ◽

Kinetic Parameter ◽

Arrhenius Equation ◽

Kcal Mole ◽

Decomposition Products ◽

Sample Geometry ◽

Temperature Range ◽

Definition Of

The activation energy has been determined in the temperature range 170-198�. If the sample was spread the activation energy was independent of the definition of the kinetic parameter substituted in the Arrhenius equation and was 63 kcal mole-1. In the case of the unspread samples the activation energies of the induction, acceleration, and maximum rates were 49, 43, and 62 kcal mole-1 respectively. The effect that sample geometry has on the activation energy is attributed to gaseous decomposition products influencing the reaction.

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