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A comprehensive study on the processing of Co:ZnO nanostructured ceramics:Defect chemistry engineering and grain growth kinetics

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Journal of Materials Science & Technology 2023年第7期138卷 221-232页

作者： R.T.da Silva J.M.Morbec G.Rahman H.B.de Carvalho Universidade Federal de Ouro Preto-UFOP Ouro PretoMG 35400-000Brazil School of Chemical and Physical Sciences Keele UniversityKeele ST55BGUnited Kingdom Department of Physics Quaid-i-Azam UniversityIslamabad 45320Pakistan Universidade Federal de Alfenas-UNIFAL Alfenas 37130-000Brazi

In this report,we present a systematic study on the preparation of Co:ZnO ceramics via a standard solid-state route from different Co precursors(Co_(3)O_(4),CoO,and metallic Co)and atmospheres(O_(2)and Ar).Particular emphasis is given to defect chemistry engineering and the sintering growth kinetics.First-principles calculations based on density functional theory are employed to determine the formation en-ergy of the main point defects in ZnO and Co:ZnO systems.Based on the theoretical results,a set of chemical reactions is proposed.Detailed microstructural characterization is also performed to determine the degree of Co incorporation into the ZnO lattice.The samples prepared in Ar atmosphere and metal-lic Co present the highest Co solubility limit(lower apparent Co incorporation activation energy)due to the incongruent ZnO decomposition.Determination of the parameters of the sintering growth kinetics reveals that Co_(3)O_(4)is the best sintering additive to achieve larger grain sizes,and possible higher densi-ties,in both sintering atmospheres,while metallic Co is the best to achieve the smallest grain size with higher Co concentration and homogeneous spatial distribution for a subsequent reduction of dimension-ality.The results show that the sintering in O_(2)effectively promotes zinc vacancies in the ZnO structure,while the sintering in Ar promotes zinc interstitial defects.Our findings contribute to understanding the preparation of Co-doped ZnO ceramics and the sintering growth kinetics,which may improve the state of the art in processing the material at both bulk and nanometric scales.

关键词： Multifunctionality Zinc oxide Defect engineering growth kinetics

growth kinetics of Nanocrystals and Nanorods by Employing Small-angle X-ray Scattering (SAXS) and Other Techniques

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Journal of Materials Science & Technology 2008年第4期24卷 615-627页

作者： Kanishka BISWAS Neenu VARGHESE C.N.R.Rao Chemistry and Physics of Materials Unit DST Nanoscience Unit and CSIR Centre of Excellence in ChemistryJawaharlal Nehru Centre for Advanced Scientific ResearchJakkur P.O.Bangalore 560064India Solid State and Structural Chemistry UnitIndian Institute of ScienceBangalore 560012India Chemistry and Physics of Materials Unit DST Nanoscience Unit and CSIR Centre of Excellence in ChemistryJawaharlal Nehru Centre for Advanced Scientific ResearchJakkur P.O.Bangalore 560064India

In this article, we report the results of our detailed investigations of the growth kinetics of zero-dimensional nanocrystals as well as one-dimensional nanorods by the combined use of small angel X-ray scattering （SAXS）, transmission electron microscopy （TEM） along with other physical techniques. The study includes growth kinetics of gold nanocrystals formed by the reduction of HAuCl4 by tetrakis（hydroxymethyl） phosphonium chloride in aqueous solution, of CdSe nanocrystals formed by the reaction of cadmium stearate and selenium under solvothermal conditions, and of ZnO nanorods formed by the reaction of zinc acetate with sodium hydroxide under solvothermal conditions in the absence and presence of capping agents. The growth of gold nanocrystals does not follow the diffusion-limited Ostwald ripening, and instead follows a Sigmoidal rate curve. The heat change associated with the growth determined by isothermal titration calorimetry is about 10 kcal·mol^-1 per I nm increase in the diameter of the nanocrystals. In the case of CdSe nanocrystals also, the growth mechanism deviates from diffusion-limited growth and follows a combined model containing both diffusion and surface reaction terms. Our study of the growth kinetics of uncapped and poly（vinyl pyrollidone）（PVP）-capped ZnO nanorods has yielded interesting insights. We observe small nanocrystals next to the ZnO nanorods after a lapse of time in addition to periodic focusing and defocusing of the width of the length distribution. These observations lend support to the diffusion-limited growth model for the growth of uncapped ZnO nanorods. Accordingly, the time dependence on the length of uncapped nanorods follows the L3 law as required for diffusion-limited Ostwald ripening. The PVP-capped nanorods, however, show a time dependence, which is best described by a combination of diffusion （L^3） and surface reaction （L^2） terms.

关键词： growth kinetics Gold nanocrystals CdSe nanocrystals ZnO nanorods Small angle X-ray scattering Transmission electron microscopy Ostwald ripening and sigmoidal growth

Superior compound coatings prepared by low-temperature vanadium-nitrocarburizing duplex treatment

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Rare Metals 2024年第4期43卷 1828-1835页

作者： Gen Jin Fang-Fang Xu Xun-Xun Hu Yue Xu School of Chemistry Beihang University Guobiao (Beijing) Testing and Certification Co. Ltd School of Materials Science and Engineering Beihang University

Superior compound coatings were prepared on CK45 steel surface by vanadium-nitrocarburizing duplex treatment in low-temperature salt bath.In this study,the microhardness,the phase constitution and the compositional distribution in the coatings prepared under different conditions were systematically characterized.The results indicated that the reactions among activated vanadium,carbon and nitrogen atoms occurred on the steel surface,leading to the formation of compound coatings composed of outermost and compound layers.The mechanism for the formation of compound layer as well as the growth kinetics of the layer was also discussed.Upon the duplex treatment,the wear and corrosion resistances of steel surface were significantly improved.It was found that the growth kinetics of compound layer obeyed the parabolic law,with the activation energy of 122.82 kJ·mol-1.

关键词： Vanadium-nitrocarburizing duplex treatment Compound coatings Microstructure Formation mechanism growth kinetics

A growth kinetics model of rate decomposition for Si_(1-x)Ge_x alloy based on dimer theory

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Chinese Physics B 2014年第1期23卷 284-288页

作者：戴显英吉瑶郝跃 School of Microelectronics Xidian Universily Xi'an 710071 China

According to the dimer theory on semiconductor surface and chemical vapor deposition（CVD） growth characteristics of Sil_xGex, two mechanisms of rate decomposition and discrete flow density are proposed. Based on these two mech- anisms, the Grove theory and Fick＇s first law, a CVD growth kinetics model of Sil-xGex alloy is established. In order to make the model more accurate, two growth control mechanisms of vapor transport and surface reaction are taken into account. The paper also considers the influence of the dimer structure on the growth rate. The results show that the model calcuated valne is consistent with the experimental vahles at different ternnerntllres.

关键词： dimer theory rate decomposition discrete flow density mechanisms growth kinetics

HIGH-TEMPERATURE TEM IN SITU STUDY OF growth kinetics OF BAINITE IN β BRASS

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Acta Metallurgica Sinica(English Letters) 1992年第5期5卷 309-313页

作者： YANG Yanqing LIU Donghui KANG Mokuang Northwestern Polytechnical University,Xi’an,ChinaSUN Yuan Beijing Centre of Physical and Chemical Analysis,Beijing,China Northwestern Polytechnical Univ Xi'an China

In situ observation of the growth process of bainitic plate in βbrass by means of high-temper- ature TEM is conducted.The lengthening and thickening kinetics of bainitic plate is analysed with Trivedi's model and Zener-Hillert's model,respectively.It is found that the stacking fault substructure exists just in the growth tip of fresh bainitie plate and so does the shear stress in the matrix around the tip.The measured lengthening rate of bainitic plate is not con- sistent with Trivedi's model.The thiekening process is only macroscopieally controlled by vol- ume diffusion but its nature is a shear process.

关键词： β-brass bainite growth kinetics shear volume diffusion

Formation and growth kinetics of Intermediate Phases in Ni-Al Diffusion Couples

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Journal of Wuhan University of Technology(Materials Science) 2009年第5期24卷 787-790页

作者：任晓周文龙 National Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology School of Materials Science and Engineering Dalian University of Technology

Formation and growth of the intermediate phases in the Ni-Al diffusion couples prepared by pouring technique were investigated. Electron probe microanalysis, scanning electron microscopy and X-ray diffraction were used to characterize the product phases in the joints. The results show that two intermediate phases form in the sequence of NiAl3 and Ni2Al3 during solidification. After annealed, Ni2Al3 and NiAl3 still exist in the joints of the couples. The reasons for the formation of Ni2Al3 and NiAl3, as well as the absence of NiAl, Ni5Al3 and Ni3Al were discussed, respectively. The growth kinetics of both product phase layers indicates that their growth obeys the parabolic rate law. The activation energies and frequency factors for NiAl3 and Ni2Al3 phases were also calculated according to the Arrhenius equation.

关键词： Ni-Al diffusion couple growth kinetics intermediate phase parabolic rate law

growth kinetics of Vegetative and Reproductive Organs of Guava(Psidium guajava L.)in Iguala Guerrero,Mexico

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Agricultural Sciences 2014年第14期5卷 1468-1475页

作者： Agustin Damian Nava Victor A.Gonzalez Hernandez Manuel Nava Jaimes Elias Hernandez Castro Dolores Vargas Alvarez Gemima Diaz Villasenor Francisco Palemon Alberto Blas Cruz Lagunas Academic Unit of Agricultural and Environmental Sciences The Autonomous University of GuerreroGuerreroMéxico Institute of Genetic Resources and Productivity Graduate CollegeTexcocoMexico

In the Mexican tropics the guava trees can grow and produce in any season, so they can be har-vested out of the period of high competition marketing (Summer). It?studied the growth kinetics of leaves and fruits of guava trees at the dry tropical conditions of the State of Guerrero, in guava trees of four years old and was evaluated a non-destructive method for measuring leaf area from November to May. 100 sheets of 10 randomly selected trees were cut. It was found that leaf length X the width X 0.72581647 (conversion factor) gave an estimated leaf area which?was significantly correlated with that obtained by the integrator of leaf area. Both in length and width the leaf growth kinetics were sigmoid with three growth stages: In Stage I (15 days) leaves grew 21.2% and 21.5%;in Stage II (26 days) grew 73.6% and 68%;and in Stage III (30 days). They Increased 5.2% and 10.5% in the primary and secondary sprouts. The fruit growth in its equatorial and polar diameters corresponded to a double sigmoid kinetics. In Stage I (61 days) it reached 1.9 and 2.3 cm;in Stage II (62 - 102 days) it reached 3.09 and 3.62 cm;and in Stage III (103 to 126 days) it reached 4.63 and 5.13 cm, as well the physiological maturity of fruit.

关键词： Psidium guajava growth kinetics Phenological Events

Modeling of growth kinetics of Conifer Trees

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Open Journal of Forestry 2015年第1期5卷 21-27页

作者： Alexander S.Kholmanskiy Institute of Electrification of Agriculture MoscowRussian Federation

The kinetics of growth of conifers is modeled by the dependence of the area of tree rings on time. The data on the growth of 46 coniferous trees varying in age from 35 to 242 years, found in the literature are analysed. To identify the common patterns in the growth kinetics, we investigate the series of standard increments of tree rings for pine, spruce, and larch. The curves obtained reflect adequately the ontogeny of trees. These allow the analysis of the environmental effects’ on the physiology of trees. In such a way the accelerated growth of trees in the Tunguska meteorite explosion zone is established. The proposed method of dendrochronology based on the area of tree rings is more adequate and informative than the method based on tree-rings’ widths.

关键词： Tree-Ring Area growth kinetics Area of Tree Rings Phytohormones Conifer

Characterization of sulfide oxidation and optimization of sulfate production by a thermophilic Paenibacillus naphthalenovorans LYH-3 isolated from sewage sludge composting

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Journal of Environmental Sciences 2023年第3期125卷 712-722页

作者： Li Chen Weiguang Li Yi Zhao Shumei Zhang Liqiang Meng Yujie Zhou School of Environment Harbin Institute of TechnologyHarbin 150090China State Key Laboratory of Urban Water Resource and Environment Harbin Institute of TechnologyHarbin 150090China Institute of Microbiology Heilongjiang Academy of SciencesHarbin 150010China

The sulfur-containing odor emitted from sludge composting could be controlled by sulfide oxidizing bacteria, yet mesophilic strains show inactivation during the thermophilic stage of composting. Aimed to investigate and characterize the thermotolerant bacterium that could oxidize sulfide into sulfate, a heterotrophic strain was isolated from sewage sludge composting and identified as Paenibacillus naphthalenovorans LYH-3. The effects of various environmental factors on sulfide oxidation capacities were studied to optimize the sulfate production, and the highest production rate (27.35%±0.86%) was obtained at pH 7.34, the rotation speed of 161.14 r/min, and the inoculation amount of 5.83%by employing BoxBehnken design. The results of serial sulfide substrates experiments indicated that strain LYH-3 could survive up to 400 mg/L of sulfide with the highest sulfide removal rate (88.79%±0.35%) obtained at 50 mg/L of sulfide. growth kinetic analysis presented the maximum specific growth rateμm(0.5274 hr-1) after 22 hr cultivation at 50℃. The highest enzyme activities of sulfide quinone oxidoreductase (0.369±0.052 U/mg) and sulfur dioxygenase (0.255±0.014 U/mg) were both obtained at 40℃, and the highest enzyme activity of sulfite acceptor oxidoreductase (1.302±0.035 U/mg) was assessed at 50℃. The results indicated that P. naphthalenovorans possessed a rapid growth rate and efficient sulfide oxidation capacities under thermophilic conditions, promising a potential application in controlling sulfur-containing odors during the thermophilic stage of sludge composting.

关键词： Sulfide oxidizing bacteria Paenibacillus naphthalenovorans Thermophilic strains Optimization growth kinetics Bacterial isolation