Granulometric activation of densified silica fume (CSF) by sonication
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A sonication process was developed by means of which the deagglomeration of the particles of commercial densified silica fume (CSF) was achieved: an increase in the amount of submicrometric particles was obtained, which finally yielded a larger specific surface area. Sonicated silica fume (SSF) (prepared with an ultrasound probe, working in a water/silica fume suspension) was obtained starting from different tests in which parameters such as treating time and power level of sonication were varied. After sonication treatment, the commercial CSF (with 59.64 μm mean particle diameter) was converted to samples with mean particle diameter of about 5 μm, with an increase of the volume percentage of particles with diameter lower than 1 μm (more than 50%). With a longer sonication time and higher sonication power level it was possible to obtain a greater quantity of submicrometric particles. A threshold power level was identified below which the sonication process was not effectiveKeywords:
Sonication
Silica fume
Suspension
Particle (ecology)
Specific surface area
The effect of the content of silica fume on the structure and property of the cement mortar and property of the cement paste were investigated.The results shows that the early stage rate of hydrated reaction is reduced to decrease the content of hydrated product and make the structure sparse,so that the early strength of cement mortar is reduced by adding silica fume to cement.The late stage rate of hydrated reaction is improved to increase the content of hydrated product and increase compactness of cement mortar,so that the late age strength of cement mortar is increased by adding proper content of silica fume to cement.The hydrated reaction can continue for long time,so that the long age strength of cement mortar is increased by adding proper content of silica fume to cement.The optimized content of silica fume is 8%.The flowability of cement paste is reduced and the setting time of cement is increased but the soundness is acceptable by adding silica fume to cement.
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We demonstrate the use of novel type of sonication method, focused sonication, with added advantages over bath and probe type of sonication for the dispersion of single walled carbon nanotubes (SWNT). Di-chloro benzene was used as the solvent for dispersion of SWNT. Results from focused sonication and bath sonication were compared and found that focused sonication results in better dispersion. Also Raman spectroscopy was analysed to ascertain if focused sonication causes any damage to the tubes and it was found that there was no damage to the SWNT. We believe that with the added advantages like in-situ temperature control and large sample volume processing, focused sonication would prove to be the most proficient method of sonication for dispersion of nanoparticles.
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Cellulose nanocrystals (CNCs) are promising biomaterials, but their tendency to agglomerate when dried limits their use in several applications. Ultrasonication is commonly used to disperse CNCs in water, bringing enough energy to the suspension to break agglomerates. While the optimized parameters for sonication are now well defined for small volumes of low concentration CNC suspensions, a deeper understanding of the influence of the dispersing process is needed to work with larger volumes, at higher concentrations. Herein, rheology is used to define the distribution and dispersion states upon ultrasonication of a 3.2 wt% CNC suspension. After considering the importance of the measurement sampling volume, the behavior of a more concentrated suspension (6.4 wt%) is examined and compared with a never-dried suspension of the same concentration to validate the dispersion state.
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As the first step of studies related to production of chitooligosaccharides by physical methods, chitosan solution were sonicated with 20 kHz and various treatment effects were examined to present fundamental data of sonicated chitosan solution. Intrinsic viscosity of chitosan solution sharply decreased from 3.76 dl/g to 2.90 dl/g until 5 minutes of sonication and then slowly decreased. With low volume of chitosan solution, sonication was very effective and temperature of chitosan solution slightly affected the efficiency of sonication. In case of changing the solvent, no significant differences were observed on the effect of sonication, however, acetate buffer had highest sonication effect among various solvents. The sonication effect was increased as the increasement of the value of pH, on the contrary, ionic strength and type of counterions showed no effect on sonication. With these results, we assumed that optimal sonication treatment would be as follows, solution volume was , temperature range was , pH value of solution was 4.5 and type of solvent was acetate buffer.
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Injectable poly-l-lactic acid (PLLA) carries the risk of nodule or microlump formation. Various methods including sonication have been tried to minimize these adverse effects of PLLA.This study investigated the change in size, distribution, and properties of PLLA particles after sonication, and the duration of sonication needed to reach the ideal particle size.Two indicators, the average size of PLLA particles and diameter at 90%, were measured at each timepoint: at 0, 10, 60, 120, and 240 minutes of sonication. The characteristics and particle shape were assessed at 0 and 240 minutes.The average particle size and the diameter at 90% decreased drastically until 10 minutes of sonication and then increased slightly at 60 minutes. After 60 minutes, the average size and the diameter at 90% gradually decreased over time and reached 42.2 μm and 75.7 μm, respectively, at 120 minutes. After 240 minutes of sonication, the average particle size was 35.9 μm, much smaller than the smallest proper size required (40 μm). Standard deviation decreased gradually over time, which means that a more even distribution was obtained. Crystalline remnants were significantly less left with 120 minutes sonication compared to those with 120 minutes hydration only. PLLA particles were more cracked at the center, and microcrystals were more loosely distributed at the periphery after 120 minutes sonication.Sonication help reduce the average size of PLLA particles and achieve more even distribution. Therefore, we believe sonication may attribute to the safer use of PLLA.
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The comparison experiments are carried out at different silica fume dosage between the silica fume with pre-treatment and the silica fume without pre-treatment. The results show that the pre-treatment of silica fume improved the strength greatly and the silica fume dosage corresponding to the strength peak somewhat moved forward from 0.20 for the cement-based materials with pre-treatment of silica fume to 0.21 for the cement-based materials without pre-treatment of silica fume. The particles distribution experiment results indicate that after the pre-treatment of silica fume, the average particle diameter of silica fume reduced from 2.865μｍto 0.151μｍ. Based on Aim-Goff model, it is concluded that the increase in the compressive strength and flextural strength of cement-based materials with pre-treatment of silica fume, are attributed to the dispersion of silica fume agglomeration and the increase in the packing density of the cement-based materials.
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一半顺序的重新组合离子的自我补充肽 CH3CO-Pro-Ser-Phe-Cys-Phe-Lys-Phe-Glu-Pro-NH2 被报导，它能进稳定的 nanofibers 自我装配、形成 hydrogel 由组成 >99% 水。在这研究， nanofiber 支架是由超声的房间 disruptor 的 sonicated。sonication 的效果被通报检测二色性(CD ) ，原子力量显微镜学(AFM ) ，和流变学。AFM 图象说明了 sonicated 碎裂，这能快速重新集合进 nanofibers，当形态学从原来的是可区分的时。CD 光谱表明变换主要在常规海滨之间发生了结构和弄歪的海滨结构。Rheological 分析证明在在 sonication 以后的第 7 天的肽解决方案的存储模量(G) 在 sonication 前与解决方案的值相比在将近 40% 减少了。最后，一个嘴巧的变换模型被建议解释重新组合过程。
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