| 1. |
- Liang, G-B, et al.
(författare)
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Modified regularization method applied to the inversion of particle size distribution from light scattering data
- 2006
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Ingår i: Guangdian Gongcheng. - 1003-501X. ; 33:12, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- Laser particle size analyzer is one of the instruments for particle size analysis. Recent developments focus on various algorithms for particle size analysis via light energy distribution based on the Mie scattering theory in the laser analyzer. The determination of the particle size distribution (PSD) from the analyzer requires the inversion of the Fredholm integral equation of the first kind. This equation is an ill-posed one, which can be analyzed by effective algorithms. This paper presents a modified regularization method applied to the inversion of the PSD with the independent models. The Generalized Cross-Validation (GCV) method was used for the selection of a regularization parameter. The Successive Over-Relaxation (SOR) iterative method was applied to improve the exactness and stability of the convergent result. The simulation with the models was carried out. The simulated results are in a good agreement with the data measured from nine standard particulate samples as well as their mixtures. It is indicated that this method can be feasible and effective for the simulation of the PSD from the corresponding light scattering data.
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| 2. |
- Wang, Hongdong, et al.
(författare)
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Superlubricity of Polyalkylene Glycol Aqueous Solutions Enabled by Ultrathin Layered Double Hydroxide Nanosheets
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:22, s. 20249-20256
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Tidskriftsartikel (refereegranskat)abstract
- It was previously proved that the existence of a large amount of hydrogen ions in water-based lubricants can easily lead to a superlubric state; however, it was also shown that these hydrogen ions could cause severe corrosion. As part of a large family of attractive clays, layered double hydroxides (LDHs) possess excellent tribological properties in water-based lubrication systems. In the present work, two different kinds of LDHs are dispersed in polyalkylene glycol (PAG) aqueous solutions, in two distinct forms: ultrathin nanosheets (ULDH-NS) of ca. 60 nm wide and ca. 1 nm thick (single or double layer) and nanoparticles (LDH-NP) of ca. 19.73 nm wide and ca. 8.68 nm thick. We find that the addition of ULDH-NS greatly shortens (as much as 85%) the running-in period prior to reaching the superlubricity regime and increases the ultimate load-bearing capacity by about four times. As compared to the fluid film thickness of the lubricating PAG solution, their ultrathin longitudinal dimension will not impair or influence the fluid film coverage in the contact zone. The analysis of sliding solid surfaces and the atomic force microscope microscale friction test demonstrate that the adsorption of ULDH-NS enables the sliding solid surfaces to be polished and protected because of their relatively weak interlayer interaction and increased adhesion effect. Owing to their superior tribological properties as lubricant additives, ultrathin LDH nanosheets hold great potential for enabling liquid superlubricity in industrial applications in the future.
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| 3. |
- Fan, Y., et al.
(författare)
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Mechanical preparation of nano titanium dioxide powder and its optical properties
- 2007
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Ingår i: Journal of the Chinese Ceramic Society. - 0454-5648. ; 35:7, s. 832-837
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Tidskriftsartikel (refereegranskat)abstract
- mechanical preparation of the nano-sized particles of TiO2 powder by a stirred bead mill was investigated. The particle sizes of the ground products were determined by the acoustic particle sizer, the nitrogen gas adsorption method and a scanning electron microscopy. The diameter of the nano-sized particles, which were obtained after milling for 7 h, is about 50 nm and the specific surface area is up to 70 m2/g. The surface and structure of the samples have been investigated with X-ray diffraction. It is indicated that an intense comminution in the mill leads to a progressive loss in crystallinity of TiO2. The catalytic degradation of methyl orange in water was also studied by a photometer. The results show that the nano-sized particles of TiO2 powder prepared by milling possess photocatalysis effect and are capable of absorption of ultraviolet radiation
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| 4. |
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| 5. |
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| 6. |
- He, Mingzhao, et al.
(författare)
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Parameter effects on wet ultrafine grinding of limestone through slurry rheology in a stirred media mill
- 2006
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Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 161:1, s. 10-21
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Tidskriftsartikel (refereegranskat)abstract
- Wet ultra-fine grinding of a limestone powder ( less than or equal 100 μm) has been investigated in a stirred media mill with respect to the effect of slurry rheology. The grinding results obtained by various parameters (i.e., molecular weight of a dispersant, solids concentration, additive dosage, addition method and beads load) are evaluated in terms of energy efficiency and the fineness of a product. A polymeric dispersant called Dispersant S40 with a molecular weight of 5500 gives the best grinding results. For a certain level of beads load, an optimal solids concentration exists. In the case of the additive dosage of Dispersant S40 at 0.1 wt.% or more, a smaller additive amount of Dispersant S40 gives a higher energy efficiency and a smaller median size at a lower level of specific energy input. However, the excessive amount of the dispersant could cause a cushion layer formed on milling beads and thus lowers stress intensities from the collisions of milling beads, leading to an inefficient milling operation. This can be avoided by either the multi-point addition of the dispersant or a higher beads load ( greater than or equal 83 vol.%). In addition, it was found that the higher the beads load, the better the cumulative energy efficiency, and the smaller the product size at the same specific energy consumption. For a given solids concentration, the relationships between the specific surface area and the particle size of an FP product and the additive amount of Dispersant S40 are explored, respectively. Furthermore, an empirical particle size-energy model provides a good fit (R2 > 0.991) to the grinding results under the experimental conditions investigated.
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| 7. |
- He, Mingzhao, et al.
(författare)
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Parameter studies on the rheology of limestone slurries
- 2006
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 78:2, s. 63-77
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Tidskriftsartikel (refereegranskat)abstract
- The influences of solids concentration, molecular weight of dispersant, particle size and distribution, and temperature on the rheological behaviour of limestone slurries have been investigated. The results reveal that when the solids concentration of a limestone slurry (< 100 μm) is increased from 60 wt.% (35.71 vol.%) to 78.5 wt.% (57.49 vol.%), the rheological behaviour of the slurry is transformed from a weakly dilatant characteristic to a pseudoplastic one with a yield stress, which is in combination with a thixotropic property at a higher solids concentration (i.e., ≥ 75 wt.% or 52.63 vol.%). At a certain shear rate, the apparent viscosity and the relative viscosity of the slurry increase exponentially with solids concentration. The extrapolated Bingham yield stress increases rather sharply in a power-law form with increasing solids concentration when the solids concentration of the slurry is larger than 70 wt.% (i.e., 46.36 vol.%)...
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| 8. |
- He, Mingzhao, et al.
(författare)
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Slurry rheology in wet ultrafine grinding of industrial minerals
- 2004
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Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 147:1-3, s. 94-112
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Tidskriftsartikel (refereegranskat)abstract
- Wet ultrafine grinding has been increasingly used for production of ultrafine powders in various industries. It has been known that slurry rheology significantly influences the grindability of industrial minerals in wet ultrafine grinding. This review represents some previous work with respect to slurry rheology in ultrafine grinding. In this review, some methods for the characterization of the slurry rheology and some empirical equations modelling rheological behaviours of slurries were presented. The semiempirical model incorporating slurry rheology, solids concentration, particle size and slurry temperature was described. In addition, on-line measurement for the slurry rheology control was also discussed. In the case of ultrafine grinding, various parameters (such as solid concentration, particle size and distribution, particle shape, temperature, rotation and pH, use of dispersants), which affect the slurry rheology, have been described. It was revealed that the optimization of the rheological behaviours of slurry in ultrafine grinding could increase throughput, energy efficiency and product fineness as well. It is suggested to further study the mechanisms of slurry rheology in the presence of chemical dispersants in wet ultrafine grinding. It is desired to develop a model, which can represent a relation among slurry rheology, comminution parameters, amount of dispersant, energy efficiency and particle size characterization.
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| 9. |
- He, Mingzhao, et al.
(författare)
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Ultrasonication-assisted synthesis of calcium carbonate nanoparticles
- 2005
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Ingår i: Chemical Engineering Communications. - : Informa UK Limited. - 0098-6445 .- 1563-5201. ; 192:11, s. 1468-1481
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a batch carbonation method with ultrasonication to synthesize monodispersed nanoparticles of calcium carbonate (CaCO3). The synthesis processes with and without ultrasonication were compared. The results showed that the application of ultrasonication into the synthesis caused a supersaturation of Ca2+ ions in the synthesis, leading to a rapid nucleation of calcium carbonate and improved the solute transfer as well as. It was also found that the effect of ultrasonication on the grain size of the nanoparticles synthesized was related to other synthesis conditions, such as initial temperature for carbonation, mass fraction of Ca(OH)2 suspension, and CO2 flow rate. The initial temperature applied for the carbonation was increased by at least 5°C when ultrasonication was applied. The nanoparticles formed in the presence of ultrasonication became smaller with a narrower particle size distribution at 6–12 wt.% of Ca(OH)2 suspension or at 1.28 l/h of CO2 consumed by per gram of Ca(OH)2 or more.
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| 10. |
- Liu, Qian, et al.
(författare)
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Graphenized pencil lead fiber : facile preparation and application in solid-phase microextraction
- 2014
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1325, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Graphenized pencil lead fiber was facilely prepared by in situ chemical exfoliation of graphite in pencil lead fiber to few-layered graphene sheets via a one-pot, one-step pressurized oxidation reaction for the first time. This new fiber was characterized and demonstrated to be a highly efficient but low-cost solid-phase microextraction (SPME) fiber. The extraction performance of the fiber was evaluated with four bisphenol analogs [bisphenol A (BPA), bisphenol S (BPS), bisphenol AF (BPAF), and tetrabromobisphenol A (TBBPA)] as model analytes in direct SPME mode. Unlike commercially available fibers, the graphenized pencil lead fiber showed an excellent chemical stability in highly saline, acidic, alkaline and organic conditions due to its coating-free configuration. The fiber also showed a very long lifespan. Furthermore, high extraction efficiency and good selectivity for the analytes with a wide polarity range could be obtained due to the exceptional properties of graphene. The detection limits (LODs) for the analytes were in the range of 1.1-25ng/L. The fiber was successfully applied in the analysis of tap water and effluent samples from a waste water treatment plant with spike recoveries ranging from 68.5 to 105.1%. Therefore, the graphenized pencil lead fiber provides a high performance, cheap, robust, and reliable tool for SPME.
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