Use Of Ultrasonic Treatment Research Articles

Synthesis of Ultrafine Oxide Powders by Hydrothermal-Ultrasonic Method

ABSTRACTIn the present work, a novel method of synthesis has been developed to obtain highly dispersed oxide powders. This method is based on the combination of hydrothermal and ultrasonic treatment and uses the effect of acoustic cavitation.Hydrothermal-ultrasonic treatment was carried out under the following conditions: T= 423 - 523 K, t = 10 min. -3 h. and ultrasonic frequency ν = 21.5 kHz. The control experiments (without ultrasound) were performed under the same conditions. The products were characterized by X-ray diffraction (XRD), thermal analysis (TGA), transmission electron microscopy (TEM). The specific surface area was determined by the BET method.It was found that high-temperature hydrolysis of cobalt (II) nitrate in ultrasonic field results in formation of considerably smaller particles of Co3O4 in comparison with conventional high-temperatures hydrolysis (mean particle size decreases from 600–650 nm to 60–70 nm). It must be noted that Co3O4 samples obtained by hydrothermal-ultrasonic treatment possess mesoporous structure.Ultrasonic-hydrothermal processing of amorphous gels of zirconyl and titanyl hydroxides leads to significant raise of the rate of crystallization process and formation of nanopowders of zirconia and titania (mean particle size 7–16 nm).It must be pointed that the use of ultrasonic treatment during hydrothermal processing of amorphous gel of zirconyl hydroxide and 0.3 M aqueous solution of H2TiO(C2O4)2 leads to increase of the content of thermodynamically stable phases in the products of synthesis.

Addendum to “Aeroacoustic integral methods, formulation and efficient numerical implementation”: [Aerospace Science and Technology 5 (2001) 457–468

The aim of this paper is to provide a methodology to study the influence of the molecular weight of polysaccharidic admixtures on mortar properties. A wide range of admixtures with different molecular weight and constant structure was prepared. This has been made possible by the use of ultrasonic treatment, a simple, effective, and without additive method. It appears that cellulose and guar gum derivatives, used as water retention agents, exhibit a significant molecular weight reduction according to the ultrasonic treatment duration. The water retention capacity of the mortars mixed with ultrasonically degraded admixture solutions increases with molecular weight for a same admixture. However, comparing water retention values obtained with similar molecular weight of a same family shows that effectiveness of polysaccharides as water retention agent is not linearly linked to their molecular weight.

An investigation of experimental methods used to determine free and total chloride contents

The free chloride content in cement pastes may be assessed by analysing the pore solution expressed under pressure using a pore press, or achieving an equilibrium between a known external solution and the pore solution, while the total chloride content is commonly determined using acid soluble extraction. A comparison of these techniques indicates that loosely bound chloride is released during pore solution expression under pressure and this may result in a significant overestimation of the free chloride content. Chloride binding relationships determined in this manner may produce errors when used in modelling chloride transport as the expressed pore solution concentration can be significantly greater than that in the contaminating solution. Furthermore acid soluble extraction may underestimate the total chloride content. The use of ultrasonic treatment to accelerate the achievement of equilibrium also results in the release of loosely bound chloride which in turn limits the chloride taken up by such samples.

Direct spectrophotometric determination of total boron in soils with ultrasonic leaching in automatic flow systems

Summary The direct introduction of solid samples proposed for flow-injection systems is based on the use of ultrasonic treatment to accomplish partial solubilization of the sample components. This approach is applied to the determination of total boron in soils, eliminating time-consuming prior dissolution steps. The derivatizing reagent used is azomethine-H. The results obtained are consistent with those provided by the manual curcumin method. The overall sampling rate is 25 h −1 .

Direct spectrophotometric determination of total boron in soils with ultrasonic leaching in automatic flow systems

The direct introduction of solid samples proposed for flow-injection systems is based on the use of ultrasonic treatment to accomplish partial solubilization of the sample components. This approach is applied to the determination of total boron in soils, eliminating time-consuming prior dissolution steps. The derivatizing reagent used is azomethine-H. The results obtained are consistent with those provided by the manual curcumin method. The overall sampling rate is 25 h−1.

Use of ultrasonic treatment for extraction of humic acid with inorganic reagents from soil

The use of ultrasonic vibrations (1 hr) on the extraction of humic acids (HA) from a brown soil has been compared with the extraction by mechanical stirring (24 hr) with two extractants: 0.5 N and 0.1 M Na 4P 2O 7, followed by extraction with 0.5 N NaOH. In the pyrophosphate extraction, ultrasonic and mechanical treatments produced the same yield of HA. Further extraction with NaOH and mechanical stirring gave higher yields. The elemental composition of HA changed remarkably with both ultrasonic and mechanical systems. The HA extracted with ultrasonic treatment showed a higher ash content and a lower content of COOH and phenolic OH groups. These HA's showed higher optical density at 260 and 450 nm when pyrophosphate-extracted, and lower optical density when NaOH-extracted. Moreover the ultrasonic-treated HA in both extractants showed a lower E 400/ E 600 ratio. Infrared examination confirmed the difference in chemical characteristics of extracted HA. The HA distribution in the different classes of nominal molecular weights by Sephadex gel filtration was influenced by both ultrasonic and mechanical systems, specially for molecular weights between 5000 and 150,000. It has been noted that the differences due to both systems are less marked than those caused by ssing different extractants.

Dispersion of Samples and Sample‐feeding for Counting Methods

AbstractThe currently used methods of sample preparation are examined and found to be unsatisfactory in case of counting methods for particle size analysis. It is the purpose of this paper to review the results of investigations of two different measuring principles (light extinction and electrical resistance change) by use of the same signal handling equipment. The commonly used techniques and units are compared with regard to the resulting density distributions of particle size below 0.25 mm. The final conclusions including recommendations to the use of ultrasonic treatment and to improvements of the sampling and the sample‐feeding units are valid for all counting methods.

SYNTHESIS OF GRANULAR LOW-MODULUS ZEOLITES FROM METAKAOLIN USING MECHANOCHEMICAL ACTIVATION AND ULTRASONIC TREATMENT

The process of synthesis of granular low-modulus zeolites from a mixture of metakaolin and solid sodium hydroxide depending on the method of pre-treatment (mechanochemical activation or ultrasonic treatment) has been investigated. The vibration roller-ring mill VM-4 (vibration frequency 930 min–1) was used for mechanochemical activation (MCA) of the powder mixtures. Ultrasonic treatment of the aqueous suspensions was carried out in the ultrasonic disperser UD-20 (oscillation frequency 22 kHz). X-ray diffraction analysis, IR spectroscopy and scanning electron microscopy have been used for the study. It was established that Na2Al2O4 and SiO2 are formed in the system after MCA as a result of leaching, and after UST, Na2Al2O4 is formed only. It was shown that thermal treatment at 650 °C of the mixture after mechanochemical activation and ultrasonic treatment leads to the synthesis of sodium aluminosilicates of cubic syngony, but with different parameters of the crystal lattice. Thermal treatment of the mixture without treatment gives the formation of sodium aluminosilicates and silicon oxide. It was found that after hydrothermal crystallization in NaOH solution with a concentration of 2 mol l–1, the LTA zeolite is synthesized. Crystallization in an alkali solution with a concentration of 6 mol l–1 gives the formation of SOD. It was ascertained that the use of ultrasonic treatment of the initial mixture results in the synthesis of a maximum amount of LTA zeolite (80 %) and SOD (98 %).