Papers by Keyword: Dispersion Stability

Abstract: This scientific study presents experimental results of particle agglomeration and dispersing processes under various physicochemical conditions, focusing on the effects of temperature, particle concentration, and medium viscosity. Using numerical approaches and experimental data, patterns describing the changes in agglomeration rate and the features of dispersing system stability were identified. The key findings of the research include: the influence of temperature on agglomeration, high particle concentration, medium viscosity, dispersion under low particle concentration conditions. It is noteworthy that the results also confirm an exponential dependence of the agglomeration rate on temperature. However, at high particle concentrations, this effect is mitigated by the dominance of interparticle interactions, such as Van der Waals forces and electrostatic effects. Furthermore, in systems with low particle concentration and elevated temperature, agglomeration processes significantly slow down, indicating improved dispersing stability. The study opens new perspectives for controlling particle agglomeration and dispersing based on temperature, concentration, and the physical properties of the medium. The obtained data can be useful for improving existing technologies and developing new ones in areas where controlling the behavior of dispersed systems is essential.

Abstract: A new organic phase change materials (PCM) for cool storage was developed for use in cold storage air-conditioning. The thermal properties of the new organic PCM were measured with a differential scanning calorimeter (DSC). To improve the thermal conductivity of the new organic PCM, the further research of using nanocomposite technology to the organic PCM SSW-4 was made. The effects of nanoparticles concentration on dispersion, ultrasonic time and consistence of dispersant in the best ultrasonic time on the dispersion were investigated by experiment. The results showed that the thermal conductivity of the nanocomposite PCM TiO₂ /SSW-4 increased by approximately 16.27% compared to that of the organic PCM SSW-4. The best dispersion condition of preparation for TiO₂ /SSW-4 was confirmed.

Abstract: Waterborne poly(carbonate urethane) dispersions (WPCUDs) have received much attention from both academia and the chemical industry due to their potential applications in high-performance volatile organic compound-free coatings and adhesives. Commercially, both the long-term stability and the mechanical properties of WPCUDs are extremely important because these are closely related to the storage life of the product. This study provides a detailed, real-time investigation into the dispersion stability of WPCUDs. Various WPCUDs with different ionic contents and containing polyols of different molecular weights were prepared, and their dispersion stabilities were monitored in real-time using Turbiscan measurements. The effect of temperature and concentration on dispersion stability was also examined. The thermal and mechanical properties of WPCUD were characterized by thermogravimetric analysis, differential scanning calorimetry, and universal testing machine, and the data were correlated to the dispersion stability data.

Abstract: A series of CeO₂-SiO₂ composite nanoparticles with different cerium and silica (Ce/Si) mole ratios were synthesized via a coprecipitation method using cerium nitrate, tetraethylorthosilicate and ammonia as raw materials. X-ray diffraction (XRD), fourier transform infrared spectrology (FT-IR), thermogravimetry-differential scanning calorimetry (TG/DSC), transmission electron microscopy (TEM) and energy dispersive analysis of X-ray (EDAX) were used to characterize the CeO₂-SiO₂ nanoparticles. With the increase of CeO₂ content, the crystal of CeO₂ grew up gradually and the average crystallite size of the CeO₂ decreased. There are Ce-O-Si bonds in the CeO₂-SiO₂ composite nanoparticles. The particle size of the CeO₂-SiO₂ composite nanoparticles with a Ce/Si mole ratio of 1 is about 20–30 nm. The dispersion stability of the CeO₂-SiO₂ composite nanoparticles with a Ce/Si mole ratio of 1 was studied. It was found that cationic and nonionic surfactant could obviously affect the dispersion stability of suspension, but not the anion surfactant. A suspension with CeO₂-SiO₂ composite nanoparticles at 0.1 wt% was added in 0.1 g/L cationic surfactant CTAB, and its pH value was adjusted within the range of 10-10.5. In this condition, the stable suspension without sedimentation time was successfully obtained.

Abstract: Three anionic sulfonic groups are used as monomers to synthesize sodium polyacrylic copolymers by radical polymerization process. The anionic sulfonic groups are: sodium acrylic sulfonate (SAS), sodium styrene sulfonate (SSS) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS), the redox initiator are ammonium persulfate and sodium bisulfite, the chain transfer agent is sodium bisulfite. The influence of different anionic sulfonic groups on dispersion stability of nanozinc oxide has been discussed.

Abstract: In order to apply nanofluids to ammonia-water absorption refrigeration, several groups of nanofluids mixing with rutile TiO₂(r-TiO₂) and ammonia-water were perpared by an optimizing method. Observation tests were carried out to investigate the effects of the kind and mass fraction of dispersant, mass fraction of ammonia-water basefluid and durations of supersonic vibration on the dispersion stability of nanofluids. The results show that, all three factors have influences on the dispersion. The optimal dispersing condition of 0.1wt% r-TiO₂ nanofluids was 0.1% of PAA in 25% ammonia water basefluid with 10 minutes of ultrasonic vibration.

Abstract: To improve the energy efficiency of refrigeration systems, carbon nanopowders, such as fullerene (C60) and carbon nanotubes (CNTs), are used widely because of their remarkable lubrication and heat transfer capacities. In this work, the dispersion stabilities of mineral oil with added C60, CNTs, and compound C60/CNTs nanopowders were investigated, respectively, by means of sedimentation observation and UV–visible scanning spectrophotometry. The results show that the two methods correspond well. C60 is more stable than CNTs with increasing time; the absorbency of fullerene nanorefrigeration oil displays increasing order with increased concentration, whereby 2 g/L is the inflection point; but a similar pattern appears in CNTs–oil only when the concentration is below 0.5 g/L, after which the concentration of the suspension cannot be measured by the absorbency because their values are alike. The agglomeration of CNTs in mineral refrigeration oil can be restored and it may not create any problems when employed in operational refrigeration systems. The different preparation procedures of compound C60/CNTs–oil exert a large influence on dispersion stability; by grinding fullerene first, one obtains the best dispersion stability of the complex nanorefrigeration oil, in comparison with other methods.

Abstract: In this paper an UV-curable character ink with high dispersion and stability was prepared based on acrylic resin, acrylic monomer, photo-initiator, pigment and other additives. The viscosity, particle size and surface tension of the ink were 18~22mPas, 310~330 nm and 22~25 mNm-1 at 25oC, respectively. These features showed the possibility to inkjet printing the ink on printed circuit board (PCB). Inkjet printing with high resolution can be achieved by varying the dried droplet diameter. Applied voltage and temperature during the jetting process influenced the diameter of dried droplet.

Abstract: Abstract. Adding dispersants like surfactants and polymers to modify nanoparticles surface is an effective way to enhance the dispersion stability of nanoparticles in refrigeration oil. In this paper, many groups of nano-CoFe₂O₄ refrigeration oil were prepared. In order to obtain the most effective kind of dispersant and the optimum additive amount, sedimentation observation method was employed for evaluation of the dispersion stability of CoFe₂O₄ nanoparticles in 3GS mineral lubricant. The spectral behavior of the surface modified nano-CoFe₂O₄ was studied by Fourier transform infrared (FT-IR) spectrometer. It was revealed that the optimized mass ratio between nano-CoFe₂O₄ and dispersant ratio is 2 to 5; a relatively appropriate dispersant for nano-CoFe₂O₄ would be Tween40, Tween60, Span80, Span80; Tween60 was the best. It was also illustrated in the infrared spectrum that nano-CoFe₂O₄ particles surface modified by Tween60 was connected by organic groups in Tween60. Thus, the particles changed from hydrophilic to lipophilic and performed good dispersity and high stability when dispersed in mineral refrigeration oil.

Abstract: TiO₂ nanoparticles are prone to aggregate in aqueous solution, which limits its extensive application. Several researches have been carried on the stability of TiO₂ suspensions. In this study, four common dispersants including ethanol, tetrahydrofuran (THF), polyvinylpyrrolidone (PVP), and sodium hexametaphosphate (SHMP) have been chosen to detect their effects on stability of TiO₂ aqueous suspensions. The experimental results showed that THF and SHMP were efficient dispersants for TiO₂ nanoparticles in aqueous solution.