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Structural and Diffuse Reflectance Study of Cr-Doped ZnO Nanorod-Pigments Prepared via Facile Thermal Decomposition Technique
摘要： Ceramic coloured nanopigments are promising for commercial cool paint applications. This study was carried out to examine the near infrared (NIR) reflectivity of Cr-doped ZnO nanopigments prepared by simple thermal decomposition of zinc acetate dihydrate and chromium(III) acetate hydroxide as precursors of Zn and Cr, respectively. XRD, FTIR and SEM have been used to characterize the microstructure and morphological properties of the synthesized nanopigments. The obtained results referred to ZnO wurtzite hexagonal structure in absence of other ZnO phases or any phases based on chromium. The obtained particles of the investigated samples are uniform rod-like shape with average diameter about 50 nm. The diffuse reflectance measurements exhibited the decrease in NIR reflectance with increasing Cr content. The sample with lower content of Cr, 0.5 wt% of Cr precursor to Zn precursor, exhibited a maximum value of NIR solar reflectance (R*) of 53.1% with respect to the other doped samples. The optical energy gap (Eg) of the investigated nanopigments were calculated using diffuse reflectance spectrum in view of Kubelka–Munk assumptions and the obtained average value of Eg is 3.219 eV with small standard deviation ± 0.015 eV.
关键词： Thermal decomposition technique,ZnO,Structure and optical properties,Pigments
更新于2025-09-23 15:23:52
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Thermal oxidative decomposition estimation combining TGA and DSC as optimization targets for PMMA
摘要： Thermal analysis techniques play a key role to determine and characterize solid phase thermal decomposition. In this sense, Simultaneous Thermal Analysis (STA, i.e. TGA and DSC tests carried out simultaneously) are widely employed, since it provides information about how mass is lost and energy released while the temperature of the sample increases. Fire computer models combined with methods numerical methods are widely used to represent the results from tests and to achieve the values of the kinetic and thermal parameters. Previous works looked forward achieving those parameters using, as unique optimization target, the mass loss curve (TGA) or its derivative (DTGA). As the study of heat release rate is a decisive element to characterize the material properly, most recent works were adding additional measures. These extra measurements concern the heat transfer and the energy required or released during temperature programmed heating, such as heat rate release, heat of gasification, or the surface temperatures of the samples. The information about the energy is provided by the Differential Scanning Calorimetry curve (DSC). Despite of the employment of the information provided by the DSC, this information usually is not used as a target to approach the DSC simulated curve to the experimental one as TGA does. Based on the lack of use of the DSC curve as numerical approaching process to set the kinetic properties, we decide to explore the possibility of adding this as a new target in the process. Therefore, kinetic and thermal properties might be achieved fitting experimental and simulated curves simultaneously, which should allow us to take into account the decomposition process and their energy released. Results obtained in the present work reveal the major challenge of getting a set of parameters, which can fit DSC curve. The level of accuracy reached when only TGA is utilized as target to approach is higher than the level of accuracy of DSC curve. This fact makes increase the value of the errors when both curves are used as targets to approach. In other words, an approach to both curves simultaneously cannot be directly made. With this consideration in mind, this paper proposes an alternative methodology in order to fit TGA curve considering the optimization of the DSC curve. The methodology proposed in the present work is applied to the analysis of poly(methyl methacrylate) (PMMA).
关键词： DSC,numerical methods,TGA,CFD,Thermal decomposition,PMMA,optimization methods,solid phase chemistry
更新于2025-09-23 15:23:52
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CdO Nanoparticles by Thermal Decomposition of a Cadmium- Hexamethylenetetramine Complex
摘要： CdO nanoparticles have been prepared by the thermal decomposition of a precursor complex. A simple and cost effective room temperature synthetic technique allows the preparation of the precursor complex from hexamethylenetetramine and cadmium nitrate in ethanol. The precursor, characterized by elemental analysis, mass spectrometry, Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis, had the composition [{Cd(HMTA)(NO3)2(H2O)2}n]. It was calcined at 500 oC for 2 h, and the cadmium oxide nanoparticles obtained was characterized by X-ray diffraction (XRD), scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), Nitrogen adsorption and physisorption, and Selected Area Electron Diffraction (SAED). XRD shows that the CdO obtained is pure and crystalline. The particles obtained had a cubic morphology and are mesoporous.
关键词： thermal decomposition,hexamethylenetetramine,nanoparticles,cadmium oxide
更新于2025-09-23 15:22:29
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Evolution of Size and Optical Properties of Upconverting Nanoparticles during High Temperature Synthesis
摘要： We investigated the growth of β-phase NaYF4:Yb3+,Er3+ upconversion nanoparticles synthesized by the thermal decomposition method using a combination of in situ and offline analytical methods for determining the application-relevant optical properties, size, crystal phase, and chemical composition. This included in situ steady state luminescence in combination with offline time-resolved luminescence spectroscopy, as well as small-angle X-ray scattering (SAXS) transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and inductively coupled plasma optical emission spectrometry (ICP-OES). For assessing the suitability of our optical monitoring approach, the in situ collected spectroscopic data, that reveal the luminescence evolution during nanocrystal synthesis, were compared to measurements done after cooling of the reaction mixture of the as-synthesized particles. The excellent correlation of the in situ and time-resolved upconversion luminescence with the nanoparticle sizes determined during the course of the reaction provides important insights into the various stages of nanoparticle growth. This study highlights the capability of in situ luminescence monitoring to control the efficiency of UCNP synthesis, particularly the reaction times at elevated temperatures and the particle quality in terms of size, shape and crystall structure, as well as luminescence lifetime and upconversion quantum yield.
关键词： thermal decomposition,XRD,ICP-OES,TEM,in situ luminescence,SAXS,upconversion nanoparticles
更新于2025-09-23 15:21:01
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Synthesis and characterization of CdS@ZnO nanoribbon@quantum dot and their enhanced visible-light-driven photocatalytic activities
摘要： CdS/ZnO nanoribbon/quantum dot was prepared using thermal decomposition method. Size and distribution of ZnO quantum dots on CdS nanobelt were controlled by concentrations of zinc acetate ethanol solution and thermal decomposition temperature. The structure and optical properties of CdS nanobelts and CdS/ZnO heterostructures are studied by XRD, TEM, PL and Raman scattering and UV–Vis absorption spectra. The photocatalytic performances of CdS nanobelts and CdS/ZnO heterostructures are tested by photocatalytic degradation of RhB aqueous solution under visible light irradiation. Compared with that (83.57%) of CdS nanobelts, the degradation rate (88.66%) of RhB using CdS/ZnO heterostructures as catalyst is significantly improved, which suggests better development prospect in photocatalytic technology and photoelectric device.
关键词： photocatalytic activities,thermal decomposition method,CdS@ZnO nanoribbon@quantum dots,optical properties
更新于2025-09-23 15:19:57
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Theoretical evaluation of thermal decomposition of dichlorosilane for plasma-enhanced atomic layer deposition of silicon nitride: the important role of surface hydrogen
摘要： Silicon nitride (SiN) thin films have been widely employed for various applications including microelectronics, but their deposition presents a challenge especially when highly conformal layers are necessary on nanoscale features with high aspect ratios. Plasma-enhanced atomic layer deposition (PEALD) has been demonstrated to be a promising technique for controlled growth of SiN thin films at relatively low temperatures (o400 1C), in which thermal decomposition of Si-containing precursors on a N-rich surface is a critical step. Based on periodic density functional theory calculations, we present potential underlying mechanisms leading to facile thermal decomposition of dichlorosilane (DCS, SiH2Cl2) on the N-rich b-Si3N4(0001) surface. Our study highlights the importance of high hydrogen content on the N-rich surface, rendering primary and secondary amine groups. When the N-rich b-Si3N4(0001) surface is fully hydrogenated, the molecular adsorption of DCS is predicted to be exothermic by 0.6 eV. In this case, DCS decomposition appears to be initiated by nucleophilic attack by an amine lone-pair on the electrophilic Si, leading to the formation of a DCS-amine adduct intermediate followed by release of a Cl(cid:2) anion and a proton. The predicted activation barrier for the DCS decomposition reaction is only 0.3 eV or less, depending on its adsorption configuration. We also discuss the formation and desorption of HCl, the subsequent formation and nature of Si–N bonds, and the interaction between adsorbed DCS molecules. While clearly demonstrating the advantageous features of DCS as a Si precursor, this work suggests that the thermal decomposition of Si precursors, and in turn the ALD kinetics and resulting film quality, can be strongly influenced by surface functional groups, in addition to product accumulation and precursor coverage.
关键词： silicon nitride,plasma-enhanced atomic layer deposition,dichlorosilane,surface hydrogen,thermal decomposition,density functional theory
更新于2025-09-19 17:15:36
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Optical and structural-chemistry of SnS nanocrystals prepared by thermal decomposition of bis(N-di-isopropyl-N-octyl dithiocarbamato)tin(II) complex for promising materials in solar cell applications
摘要： Mixed ligand precursor complex bis(N-di-isopropyl-N-octyl dithiocarbamato)tin(II) complex was synthesized from its respective dithiocarbamate ligands, characterized and thermalized through thermogravimetric analysis to yield tin sulfide (SnS) nanocrystals. The thermal decomposition pattern was recorded as a function of the required temperature for the formation of the SnS nanocrystals at 360 °C. The SnS nanocrystals were characterized using optical, vibrational, structural and morphological analyses instruments. The obtained orthorhombic phase SnS nanocrystals showed indirect and direct optical energy band gaps close to the 1.5 eV of the bulk SnS.
关键词： SnS nanocrystals,Thermal decomposition pattern,Mixed ligand precursor complex,Orthorhombic phase,Thermogravimetric analysis
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Growth of Large-Area, Uniform, Few-Layer Tungsten Disulphide by Thermal Decomposition of Ammonium Tetrathiotungstate
摘要： Two-dimensional transition metal dichalcogenides (2D-TMDCs) such as molybdenum disulphide (2D-MoS2) and tungsten disulphide (2D-WS2) are now established as a class of nanomaterials that can be used in numerous applications due to their tuneable physical and chemical properties [1]. However, in terms of electrical characteristics and photoluminescence efficiency, WS2 typically exhibits superior performance compared with the molybdenum analogue [2,3]. Nevertheless, synthesis of continuous, uniform and thickness controllable 2D-WS2 films for (opto)electronic device fabrication is more challenging compared with better established 2D-MoS2 growth protocols. Therefore, the search for alternative precursors and synthesis approaches of 2D-WS2 that can provide mass production with excellent quality at low cost is highly desirable [1]. In this work, we tackle this issue by refining the solvents recipe with n-methylpyrrolidone, n-butylamine and 2-aminoethanol, which significantly improves the continuity, uniformity and thickness controllability for the spin-coated precursor films. This enables the large-area growth of few-layer WS2 films using thermal decomposition via two-step high temperature annealing without sulphurisation. The few-layer WS2 films were characterised by optical and atomic force microscopy to confirm the continuity and two-dimensional nature of the deposited WS2 films. Raman, photoluminescence and x-ray photoelectron spectroscopy indicate growth of highly crystalline films with an optimum composition of WS2. The electrical response of the WS2 films grown by this method was investigated by interrogating a back-gate thin film transistor utilising a WS2 channel as shown in Figure 1.
关键词： ammonium tetrathiotungstate,Tungsten disulphide,few-layer,large-area growth,thermal decomposition
更新于2025-09-16 10:30:52
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Synthesis and characterization of Mono-disperse Carbon Quantum Dots from Fennel Seeds: Photoluminescence analysis using Machine Learning
摘要： Herein, we present the synthesis of mono-dispersed c-QDs via single-step thermal decomposition process using the fennel seeds (Foeniculum vulgare). As synthesized c-QDs have excellent colloidal, photo-stability, environmental stability (pH) and do not require any additional surface passivation step to improve the fluorescence. The C-QDs show excellent PL activity and excitation-independent emission. Synthesis of excitation-independent c-QDs, to the best of our knowledge, using natural carbon source via pyrolysis process has never been achieved before. The effect of reaction time and temperature on pyrolysis provides insight into the synthesis of c-QDs. We used Machine-learning techniques (ML) such as pcA, McR-ALS, and nMf-ARD-So in order to provide a plausible explanation for the origin of the pL mechanism of as-synthesized c-QDs. ML techniques are capable of handling and analyzing the large pL data-set, and institutively recommend the best excitation wavelength for pL analysis. Mono-disperse c-QDs are highly desirable and have a range of potential applications in bio-sensing, cellular imaging, LeD, solar cell, supercapacitor, printing, and sensors.
关键词： Machine learning,Fennel seeds,Thermal decomposition,Photoluminescence,Carbon quantum dots
更新于2025-09-16 10:30:52
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[IEEE 2019 3rd International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT) - Ankara, Turkey (2019.10.11-2019.10.13)] 2019 3rd International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT) - Manufacturing Graphene via Laser Heating
摘要： This study focuses on the investigation of an alternative method for graphene production. There are various ways of manufacturing graphene sheets. Each method has it is own advantages and disadvantages. However, the common problem is about the cost and time associated with these particular routes. In this study, we have developed an alternative mechanism that utilizes laser beam as heating source to help thermal decomposition of silicon carbide in order to obtain graphene sheets. The manufactured samples were compared with graphene sheets that were prepared with traditional thermal decomposition method using a high temperature furnace. The results showed that the alternative way of manufacturing has promise for graphene formation since Raman spectrum showed graphene peaks in corresponding locations with satisfactory shapes. This could lead to potentially single layer graphene on a large scale after optimizing the manufacturing setup and, consequently, could either reduce the fabrication costs or reduce the time required for epitaxial growth process. Few rearrangements such as laser power, flow rate of the gas or pressurizing the chamber could make the process an applicable approach.
关键词： epitaxial growth,laser-heating,thermal decomposition,graphene
更新于2025-09-12 10:27:22