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1.
Sol–gel auto-ignition was used to prepare nano-scale magnesium aluminate spinel, using nitrate salts as an oxidizer and glycine–starch mixtures as the fuel. The glycine–starch mixture was varied to understand the effect of fuel mixing ratio on the structural characteristics of the resulting magnesium aluminate. The products were characterized by thermogravimetric-differential thermal analyses, Fourier-transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller surface area measurements, and transmission electron microscopy. The phase purity and crystallite size of the powder products depended on the fuel mixing ratio. The presence of starch in the fuel facilitated the preparation of pure nano-particles. To prepare nano-particles of uniform spherical morphology and diameter of <13 nm, the starch content should be optimized to avoid agglomeration.  相似文献   
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With an attempt to fabricate large-area OLED lighting panels, we investigate slot-die coating of a small molecule (SM) hole transport layer (HTL). It is observed that SM HTL films formed by spin coating exhibit pinhole-like surface, whereas the films by slot-die coating show micro-sized hillocks due to agglomeration. As the plate temperature of the slot coater is increased, smaller hillocks appear more densely. To tackle it, a small amount of a polymer HTL is added into the SM HTL (Hybrid HTL). By the aid of entangled polymer chains, small molecules are prohibited from migrating and thus agglomerations disappear. The peak-to-peak roughness of the slot-coated hybrid HTL films is measured to be about 11.5 nm, which is slightly higher than that (~7 nm) of the polymer HTL film, but much lower than that (~1071 nm) of the SM HTL film. Similar results are also observed in spin-coated films. It is also addressed that OLED with the hybrid HTL shows higher luminous efficacy, compared to OLED with the SM HTL or the polymer HTL. We have further demonstrated that the dissolution problem occurring between two stacked layers with different solvents during slot-die coating can be suppressed to a great extent using such a combination of materials in hybrid structure.  相似文献   
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Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a MSMPR reactor operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study.  相似文献   
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In this work the flow induced orientation and the governing mechanism of structural recovery of multi-walled carbon nanotube (MWCNT) filled polypropylene nanocomposites were investigated. A series of linear and nonlinear melt rheological measurements including stress growth and time sweep experiments were performed at different temperatures to study the structural breakdown, nanoparticles orientation, subsequent structural recovery and MWCNT loadings. The results showed that the structural recovery occurred in two stages. The first stage, initial agglomeration, showed a quick recovery which was independent of temperature, can be interpreted in terms of inter-particle van der Waals interactions. This structural recovery stage had major contribution in the storage modulus increment. The second stage of the recovery, secondary agglomeration, was slower and dependent on temperature, can be attributed to rotary diffusion of nanoparticles. This stage had minor contribution to the storage modulus increase. Storage modulus increment in both of these agglomeration was attributed to the increase of nanotube-nanotube contacts. Both of these stages were confirmed by transmission electron micrographs. These result were in a good agreement with those calculated using van der Waals and diffusion concepts.  相似文献   
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Airborne single-wall carbon nanotubes (SWCNTs) have a high tendency to agglomerate due to strong interparticle attractive forces. The SWCNT agglomerates generally have complex morphologies with an intricate network of bundles of nanotubes and nanoropes, which limits their usefulness in many applications. It is thus desirable to produce SWCNT aerosol particles that have well-defined, unagglomerated fibrous morphologies. We present a method to generate unagglomerated, fibrous particles of SWCNT aerosols using capillary electrospray of aqueous suspensions. The effects of the operating parameters of capillary electrospray such as strength of buffer solution, capillary diameter, flow rate, and colloidal particle concentration on the size distributions of SWCNT aerosols were investigated. Results showed that electrospray from a suspension of higher nanotube concentration produced a bimodal distribution of SWCNT aerosols. Monodisperse SWCNT aerosols below 100 nm were mostly non-agglomerated single fibers, while polydisperse aerosols larger than 100 nm had two distinct morphologies: a ribbon shape and the long, straight fiber. Possible mechanisms are suggested to explain the formation of the different shapes, which could be used to produce SWCNT aerosols with different morphologies.  相似文献   
7.
《Journal of Crystal Growth》1999,200(3-4):558-564
Grain size composition of precipitated Al(OH)3 is dependent on the mechanism of decomposition process of the caustic solution which determines crystal growth process, agglomeration process and secondary nucleation. Because the literature data shows that the growth rate is very low, the agglomeration process plays an important role in increasing the initial particle size. On the other hand, the agglomeration process enables the inclusion of impurities by the grain boundary of sticking Al(OH)3 particles, above all, the inclusion of soda Na2O.

In this paper we investigate the influence of caustic soda concentration Na2O(c), that is the supersaturation of the solution, seed charge and seed grain size on the agglomeration and secondary nucleation processes and total soda content in precipitated Al(OH)3. The results have shown that the factor which causes the increase of the agglomeration process also causes the increase of total soda content in precipitated Al(OH)3.  相似文献   

8.
Discrete element method(DEM) is used to studythe factors affecting agglomeration in three-dimensionalcopper particle systems during solid-state sintering.A newparameter is proposed to characterize agglomeration.Theeffects of a series of factors are studied,including particlesize,size distribution,inter-particle tangential viscosity,temperature,initial density and initial distribution of particleson agglomeration.We find that the systems with smallerparticles,broader particle size distribution,smaller viscosity,higher sintering temperature and smaller initial densityhave stronger particle agglomeration and different distributions of particles induce different agglomerations.This studyshould be very useful for understanding the phenomenon ofagglomeration and the micro-structural evolution during sintering and guiding sintering routes to avoid detrimental agglomeration.  相似文献   
9.
In order to improve the dispersion of detonation nanodiamonds (ND) in aqueous and non-aqueous media, a series of thermal treatments have been conducted in air ambient to modify ND surface. Small angle X-ray scattering (SAXS) technique and high resolution transmission electron microscopy (HRTEM) were introduced to observe the primary size of ND. Differential thermal analysis (DTA), X-ray diffraction (XRD) methodology, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were adopted to analyze the structure, bonds at surfaces of the treated ND. Malvern instrument Zetasizer3000HS was used for measuring the surface electric potential and the size distribution of ND. As thermal treatments can cause graphitization and oxidization of functional groups at the surface, ND treated at high temperature is correspondingly more negatively charged in an aqueous medium, and the increased absolute value of zeta potential ensures the electrostatic stability of ND particles. Specially, after being treated at a temperature more than 850 K, ND can be well dispersed in various media.  相似文献   
10.
This work addresses the adsorption of benzothiophene (BT), as a model heterocyclic and aromatic sulphur compound present in road fuels, over agglomerated zeolites with faujasite structure. Several adsorbents based on zeolites with FAU structure have been prepared with different Si/Al molar ratios and exchange cations and then agglomerated. The influence of the zeolite basicity has been studied, both in equilibrium and dynamic liquid phase adsorption experiments. Basicity of the adsorbent increased as the Si/Al molar ratio and the electronegativity of the exchange cation decreased. In equilibrium experiments, the affinity towards the adsorbent increased as the Si/Al molar ratio decreased, showing the highest affinity for exchanged low silica X zeolites with medium basicity (A-KLSX-02). Dynamic experiments showed that the less zeolite basicity, the higher fractional bed utilization and adsorption capacity at breakthrough time. Besides, zeolites with high basicity did not reach the equilibrium capacity due to the low diffusivity of BT into the micropores. Thermogravimetric analyses of the spent adsorbents showed a stronger BT adsorption onto the more basic zeolites. As main conclusion, adsorbents with medium basicity could present the best performance in fuel desulphurization due to their high affinity with sulphur compounds, although diffusion problems should be taken into account.  相似文献   
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