Researches and applications of the ultrasonic emulsifications and dispersions Li Quanlu,a) Zhang Yinhong, and Wu Jing Institute of Applied Acoustics, School of Physics and Information Technology, Shaanxi Normal University, #199, Chang’an South Road, Xi’an, Shaanxi 710062, China
(Received 22 May 2012; revised 17 May 2013; accepted 25 September 2013) This paper defines power ultrasonics and their two important directions: Ultrasonic emulsification and dispersion from a practical point of view, brief reports on recent research results are ultrasonic emulsification to be used for the preparation of composite electrorheological fluid, and ultrasonic dispersion to be used dispersion as a new type cold cloud catalytic agent metaldehyde ½CH3 CH4-6 (this is used for artificial rain), etc., and produce good results or gain progress. Then, the principle and applications of power ultrasonics (including magnetostriction type ultrasonic transducer and piezoelectric type ultrasonic transducer) in the emulsification or dispersion, are pointed out. Also, ultrasonic extensive applications in chemistry, materials, and life sciences are briefly introduced. C 2013 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4824490] V PACS number(s): 43.35.Bf, 43.38.Ct, 43.38.Ar, 43.35.Vz [JDM] I. INTRODUCTION
Ultrasonic emulsification and dispersion are some of the applications of ultrasonic power, and they belong to the category of sonochemistry. The origin of the sonochemistry effect is the phenomenon of acoustic cavitations in liquids. Sonochemistry is the application of ultrasonics to chemical reactions and processes. Ultrasonics is the part of the sonic spectrum which ranges from about 20 kHz to 10 MHz and can be roughly subdivided into three main regions: Low frequency, high power ultrasound (20 to 100 kHz); high frequency, medium power ultrasound (100 kHz to 1 MHz); and high frequency, low power ultrasound (1 to 10 MHz). The range from 20 kHz to around 1 MHz is used in sonochemistry whereas frequencies far above 1 MHz are used for medical and diagnostic ultrasound. Power ultrasonics can be used as a means of mechanical vibration energy to produce emulsification and dispersion effects, etc., in related solutions. Generally, power ultrasonics is also a process in which the energy of ultrasonic vibration is made use of to change the structure, states, characteristics, and functions, etc., of substantial organizations or can be used to speed up these changes. To have an active applied technology of dynamic applications is an outstanding characteristic of power ultrasonics, which has larger acoustic power and higher acoustic intensity. The first successful and ripe application of power ultrasonics was the use of ultrasonic cleaning machines (techniques) as early as the 1940s to 1950s. In this paper, ultrasonics is used for the emulsification and dispersion of new types of smart material (i.e., composite electrorheological fluid, abbreviated as composite ERF), the cold cloud catalytic agent of artificial rain (i.e., metaldehyde ½CH3 CH4-6 , etc.). Also, some new developments and applications of power ultrasonics and sonochemistry are discussed.
Pages: 3546–3550
II. BASIC PRINCIPLE AND METHOD OF ULTRASONIC TREATMENT
In broad applications of ultrasonic treatment, generally electroacoustical ultrasonic equipment or instruments are used. The schematic diagram of the working principle of the ultrasonic treatment with electroacoustical ultrasonic equipment is illustrated in Fig. 1. (The substance to be processed is mixed in a solution. The mixing solution is poured into a beaker and the smaller end of the concentrator of the ultrasonic equipment is inserted into the solution, starting ultrasonic emulsification or ultrasonic dispersion, etc.). In this work, we have adopted electroacoustical ultrasonic equipment, where there is a key device used as an electroacoustic transducer (for receiving waves from an electrical system and delivering waves to an acoustic system, or vice versa). These include magnetostrictive ultrasonic transducers (see Fig. 2) and piezoelectric ultrasonic transducers (see Fig. 3), used in ultrasonic emulsification and dispersion, etc., and have produced better effects in an actual application. Applying an alternating electric field to a piezoelectric transducer normally generates ultrasonic waves, or a magnetic field to a magnetostrictive one. These techniques are capable of producing coherent pulses of ultrasound over a very wide frequency range (Table I) and have been applied in temperatures such as, for example, the Curie point of nickel (385 C), quartz (576 C), or PZT (lead zirconate-titanate ceramics, generally at 310 C or so). They are likely to remain in common use, but since only a limited range of dielectrics are piezoelectric and only a few metals and ferrites are ferromagnetic, these transducers have to be acoustically bonded in most instances to the material under investigation. As is shown in Table I on piezoelectricity (or piezomagnetic effect), acoustic wave and device applications were, are, and will be a general development status. A. Ultrasonic emulsification is used in the preparations of composite ERF
a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
3546
J. Acoust. Soc. Am. 134 (5), November 2013
Composite ERF with high multi-property is prepared in this work.
0001-4966/2013/134(5)/3546/5/$30.00
C 2013 Acoustical Society of America V
FIG. 1. Schematic diagram of the working principle of electroacoustical ultrasonic equipment.
1. Preparing methods of composite ERF
Materials designing ! selecting raw material, get the materials ready ! according to the component part of designing composite ERF which is to compound it ! for the composite ERF treated with ultrasonic emulsification ! packaging of ERF and setting up the electrodes for it ! alternatively applied electric field and other factors to make an experiment with ERF ! measuring the performance parameter of ERF ! analyze, compare, and determine the best ERF material samples. The preparation steps are roughly as follows [when the composite ERF is made up, the ultrasonic emulsification is useful to the composite ERF (special is very useful for the liquid crystal) to keep a homogeneous system and to prevent the precipitation of dispersing grains in composite ERF]: (1) The main dispersing grains in the ERF are processed by using strongly polarized piezoelectric ceramic (such as FD3 -PZT or FD4 -PZT), which is ground to 50 lm or so by machines, and then to less than 10 lm by ultrasonic dispersion. The other, in the preparation of composite ERF, ultrasonic dispersion, and emulsification with the ultrasonic vibration system shown in Fig. 3, ultrasonic dispersion and emulsification both obtained good results there. (2) Strongly polarized piezoelectric liquid crystal materials1 are selected as an additive for the liquid phase of ERF. (3) The third phase included organic silicone oil and mineral oil, used as a dispersing medium of composite ERF, made up of the single- or multi-component (series).
FIG. 3. Schematic diagram of the working principle of a piezoelectric ultrasonic transducer.
(4) Then, one selects the activator and stabilizer of composite ERF: Halogenated hydrocarbon, alcohol, amine, etc., and some surface-active agent. (5) In proportion to the designed part-component, whose volume percentage concentration of the disperse phase is at 10% to 30%, compound composite ERF is prepared in groups and is then treated with ultrasonic emulsification, which prevents the precipitation of dispersing grains in composite ERF. In the present work, we mainly used the ultrasonic vibration system shown in Fig. 3 to treat the compound composite ERF; we also adopted an ultrasonic cleaner to treat the compound composite ERF. A sandwich piezoelectric transducer is stuck on the outside bottom-center of the cleaning trough (with a special type epoxy resin cementing agent) to form an ultrasonic cleaner. Then, the composite ERF is poured into the cleaning trough to be treated. The transducer frequency is 23 kHz; power is 70 W; each time the treating time is 15 to 20 min. The ultrasonic emulsification is to improve the quality and properties of the composite ERF which took an important effect. The ultrasonic emulsification is mainly caused by ultrasonic cavitations effect and ultrasonic depolymerizing action of chemical effect, etc., in a related solution.2,3 (6) To design and process the packages of ERF, and to set up the electrodes for the packages of ERF. The composite ERF is grouped to pack in the packaging of ERF.
FIG. 2. Schematic diagram of the structural principle of a magnetostrictive ultrasonic transducer. Notes: l ¼ 288.6 mm; D ¼ 562 mm; d ¼ 188.4 mm; the sound velocity of stainless steel is 5790 m s1.
J. Acoust. Soc. Am., Vol. 134, No. 5, November 2013
Quanlu et al.: Ultrasonic emulsification and dispersion
3547
(7) To test the basic performance parameter of the composite ERF. (8) To perform experiments with electric field (frequency and other conditions) alternatively on ERF, measuring properties of the composite ERF (at ac is 1 to 41 kV, at dc is 1 to 30 kV). 2. Principal properties of composite ERF in present work
Principal properties of this composite ERF are as follows: Viscosity g0 < 100 mPa S (at zero electric field); Yield stress sy < 4 k Pa (at E ¼ 3.5 kV mm1 ); Current density J > 100 mA cm2 (at E ¼ 3.5 kV mm1 ); Response time t < 1 mS. Anti-precipitate, nonpoisonous, and the composite ERF do not contain water (Note: In the present work we do not treat the samples of the composite ERF by ultrasonic dispersion and emulsification, dispersing grains in the ERF which are precipitated formidably). 3. General applications of ERF
The researchers concerned all over the world generally think highly of the ERF, which has broad applied prospects in electrical controlled driver; exciter, brake, clutches recoilless equipment, and varied shock-absorber and damper. These applications can be found in the fields of national defense, electronics, aviation-spaceflight, machinery, traffic, chemical industry, robot, and medical equipment. In the present work, the composite ERF is used for the research and development of the intelligent structure (a new actuator combining piezoelectric ceramic and ERF).2 B. Ultrasonic dispersion of metaldehyde [CH3 CH]4-6 is used as a cold cloud catalytic agent of artificial rain
kind of method of artificial climate control, and refers to selecting suitable weather conditions by artificial rain through a cloud layer seeding catalytic agent. Artificial rain (and hail prevention, extinguish a forest fire, dispelling dense fog of sky over airfield, etc.) has been developed faster in some developed countries, such as America, England, and France, etc. Their technique level and measures are also relatively advanced. Now, in some countries a new type of cold cloud catalytic agent metaldehyde ½CH3 CH4-6 is used and has attempted to replace the conventional cold cloud catalytic agent, e.g., dry-ice {i.e., carbon dioxide (CO2 ), sodium chloride (NaCl), silver iodide (AgI) and urea [COðNH2 Þ2 ]}, etc. In the raining effect of metaldehyde there exists a great difference between metaldehyde of natural crystalloid and dispersed powder of metaldehyde. The methods of dispersing metaldehyde have already been tried and used in mechanical grinding, high speed airflow dispersion, and launching smoke bombs, etc. The grains are all above 10 lm and uneven with these methods. The fineness and evenness of metaldehyde’s grains directly affect the increase of metaldehyde to be formed at the ice-nucleus rate of artificial rain (it is directly proportional to the number of catalytic agent grains, that is fineness of grain) in rain and saving raw materials. In the present work ultrasound is used for the dispersion of metaldehyde. With this new method, the grains of metaldehyde are mostly smaller than 4 lm and the evenness is greatly improved. The test results made by Meteorological Bureau of Shaanxi Province in a cloud chamber show that the formed ice-nucleus rate of ultrasonic dispersing metaldehyde in rain is raised 2 orders of magnitude compared with other methods (such as “micronizer” grinding, airflow dispersing, and launching smoke bomb, etc.). (a)
(b)
The principle of ultrasonic dispersion is that an ultrasonic cavitations effect and a machine-agitated action in liquid mediums are produced when ultrasound waves propagate in liquid. For ultrasonic treatment of a new type of cold cloud catalytic agent metaldehyde [CH3 CHO]34-6 : (1) With the ultrasonic instrument, CFS-250 W ultrasonic generator and magnetostrictive transducer
Artificial precipitation (including rainfall and snow; excluding channel water spray irrigation on the ground), is a TABLE I. Referenced frequency ranges for design of acoustics transducer and receiver. Infrasonics
Sonics
Ultrasonics
Microsonics
Lightwave ultrasonics
(hypersonics) (Hz)104
102
1
GENERATORS Explosives Whistles and sirens Electrodynamic devices! Mechanical vibrations RECEIVERS
102
104
106
108
1010
1012
1014
Piezoelectric transducers! — Heat pulses — ! Electromagnetic transducers! Magnetostrictive transducers! — Piezoelectric —! —Electromagnetic detectors —
— !
—
—
Magnetic vibration pickups! Resistance strain gauges
3548
Radiation Optical diffraction and scattering! Pressure Bolometers
J. Acoust. Soc. Am., Vol. 134, No. 5, November 2013
Quanlu et al.: Ultrasonic emulsification and dispersion
(see Fig. 2), their frequency fr ¼ 19:6 kHz; the concentrator is a stepped horn; its amplification factor is 10.24, in which the optimum effect is obtained. The transducer and the stepped horn are welded together at 400 C by welding flux. The transducer is equipped with a cooling water jacket and is then connected with an ultrasonic generator. (2) Metaldehyde ½CH3 CH4-6 grains, their length is approximately 80 to 180 lm, and their thickness is approximately 50 lm; they are needle-like white formless crystals, not dissolved in water, and the subliming point is 112 C. (3) Medium is used as tap water. Metaldehyde ½CH3 CH4-6 grains are dispersed into tap water; both mixing percentage by weight is at 50%. The mixture of metaldehyde ½CH3 CH4-6 grains and water is poured into a beaker, and the tip of the horn of the ultrasonic vibration system is inserted into and always located at the central position of the mixture (i.e., the tip of the horn is at 3 cm from the surface of the mixing solution, then the ultrasonic vibration system is electrified and the mixture is started with ultrasonic treatment). (4) Treating time is 15 to 20 min. (5) Results. After the ultrasonic treatment, the length of metaldehyde ½CH3 CH4-6 grains are less than 4 lm; they make up 92% of the total, and are less than 10 lm and those greater than 4 lm make up about 6%. Dispersing effects of different grinding methods are listed in Table II. In present work, we have also adopted the piezoelectric ultrasonic vibration system to treat the metaldehyde ½CH3 CH4-6 grains repeatedly (see Fig. 3); its dispersing results are basically the same as that with the magnetostrictive ultrasonic vibration system (see Fig. 2).
C. Ultrasonic dispersion of other inorganic materials
The method of ultrasonic dispersion can be not only used for reference for [NO2 C6 H4 C : CHCOOH] and [C6 H3 ðOHÞ3 2H2 O], etc., these better recent discoveries of organic cold cloud catalytic agent, but also can be used for dispersion of other inorganic materials. In the present work, inorganic substances such as antimony trioxide (Sb2 O3 ) and aluminum hydroxide [AlðOHÞ3 ], etc., have been dispersed by the ultrasonic transducer vibration system, coupled with a horn. The length of the dispersed substance’s grains is all less than 2 lm. The dispersed samples
are use to solve a difficult problem of additions in some research items (about aviation materials), in which superfine powder is required. In addition, application of ultrasonic transducer of a special design allows receiving a small-dispersed aerosol from liquid. This process is used for uniform irrigation of some object or for powder production in pharmaceutical and chemical industries. Powder dispersion of different oxides (Al2O3, TiO2, SiO2, ZrO2, Fe3O4, etc.) is made with ultrasonics. Dispersion is made in ultrasonic reactors on the base of a ring magnetostrictive ultrasonic transducer. III. DISCUSSION
The present work has obtained the good results on ultrasonic emulsifying composite ERF and ultrasonic dispersing metaldehyde, etc. The development and spreading applications of the composite ERF and metaldehyde, etc., provided a certain scientific basis and applied prospects, for emulsification and dispersion of similar substances. Also are provided new methods for reference. At the same time, the present work opens and suggests further broad and new applied fields for sonochemistry and power ultrasonics. However, in developments and research of power ultrasonics and sonochemistry there are technologically difficult problems that require further research work and solutions. For example, ultrasonic emulsification and the ultrasonic dispersion need automatic temperature control systems to solve the problem of vibrating system frequency drift and its temperature rise, whether a piezoelectric ultrasonic vibration system or a magnetostrictive ultrasonic vibration system. It is necessary to develop truly high-power ultrasonic treating equipment (including high-power piezoelectric ultrasonic transducer and its high-power piezoelectric materials, and high-power magnetostrictive ultrasonic transducer and its high-power piezomagnetic materials, etc.). In the present work there are some problems which have been discovered and must be pointed out: The emulsifying and dispersing results of different materials with ultrasonics show that not all materials be applicable emulsified or dispersed by ultrasonics; water is a commonly used medium for ultrasonic dispersion (of course, the emulsified materials must be in a solution; and the dispersed materials must not be dissolved in water. And, water is practical and saves money.). It is pointed out that a piezoelectric ultrasonic transducer and its piezoelectric transducer materials, and magnetostrictive transducer and its piezomagnetic materials of acoustoelectrical devices and its materials cannot replace each other in some important applications and will coexist for a
TABLE II. Dispersing results of different methods for metaldehyde.
Dispersing method “Micronizer” grinding Airflow dispersion Launching smoke bomb Ultrasound dispersion
Grain size (lm) after dispersion
Metaldehyde grain number per gram
Measured and counted by
Merits and demerits
>10 >10 >6
1010 1010 1011
(Received 22 May 2012; revised 17 May 2013; accepted 25 September 2013) This paper defines power ultrasonics and their two important directions: Ultrasonic emulsification and dispersion from a practical point of view, brief reports on recent research results are ultrasonic emulsification to be used for the preparation of composite electrorheological fluid, and ultrasonic dispersion to be used dispersion as a new type cold cloud catalytic agent metaldehyde ½CH3 CH4-6 (this is used for artificial rain), etc., and produce good results or gain progress. Then, the principle and applications of power ultrasonics (including magnetostriction type ultrasonic transducer and piezoelectric type ultrasonic transducer) in the emulsification or dispersion, are pointed out. Also, ultrasonic extensive applications in chemistry, materials, and life sciences are briefly introduced. C 2013 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4824490] V PACS number(s): 43.35.Bf, 43.38.Ct, 43.38.Ar, 43.35.Vz [JDM] I. INTRODUCTION
Ultrasonic emulsification and dispersion are some of the applications of ultrasonic power, and they belong to the category of sonochemistry. The origin of the sonochemistry effect is the phenomenon of acoustic cavitations in liquids. Sonochemistry is the application of ultrasonics to chemical reactions and processes. Ultrasonics is the part of the sonic spectrum which ranges from about 20 kHz to 10 MHz and can be roughly subdivided into three main regions: Low frequency, high power ultrasound (20 to 100 kHz); high frequency, medium power ultrasound (100 kHz to 1 MHz); and high frequency, low power ultrasound (1 to 10 MHz). The range from 20 kHz to around 1 MHz is used in sonochemistry whereas frequencies far above 1 MHz are used for medical and diagnostic ultrasound. Power ultrasonics can be used as a means of mechanical vibration energy to produce emulsification and dispersion effects, etc., in related solutions. Generally, power ultrasonics is also a process in which the energy of ultrasonic vibration is made use of to change the structure, states, characteristics, and functions, etc., of substantial organizations or can be used to speed up these changes. To have an active applied technology of dynamic applications is an outstanding characteristic of power ultrasonics, which has larger acoustic power and higher acoustic intensity. The first successful and ripe application of power ultrasonics was the use of ultrasonic cleaning machines (techniques) as early as the 1940s to 1950s. In this paper, ultrasonics is used for the emulsification and dispersion of new types of smart material (i.e., composite electrorheological fluid, abbreviated as composite ERF), the cold cloud catalytic agent of artificial rain (i.e., metaldehyde ½CH3 CH4-6 , etc.). Also, some new developments and applications of power ultrasonics and sonochemistry are discussed.
Pages: 3546–3550
II. BASIC PRINCIPLE AND METHOD OF ULTRASONIC TREATMENT
In broad applications of ultrasonic treatment, generally electroacoustical ultrasonic equipment or instruments are used. The schematic diagram of the working principle of the ultrasonic treatment with electroacoustical ultrasonic equipment is illustrated in Fig. 1. (The substance to be processed is mixed in a solution. The mixing solution is poured into a beaker and the smaller end of the concentrator of the ultrasonic equipment is inserted into the solution, starting ultrasonic emulsification or ultrasonic dispersion, etc.). In this work, we have adopted electroacoustical ultrasonic equipment, where there is a key device used as an electroacoustic transducer (for receiving waves from an electrical system and delivering waves to an acoustic system, or vice versa). These include magnetostrictive ultrasonic transducers (see Fig. 2) and piezoelectric ultrasonic transducers (see Fig. 3), used in ultrasonic emulsification and dispersion, etc., and have produced better effects in an actual application. Applying an alternating electric field to a piezoelectric transducer normally generates ultrasonic waves, or a magnetic field to a magnetostrictive one. These techniques are capable of producing coherent pulses of ultrasound over a very wide frequency range (Table I) and have been applied in temperatures such as, for example, the Curie point of nickel (385 C), quartz (576 C), or PZT (lead zirconate-titanate ceramics, generally at 310 C or so). They are likely to remain in common use, but since only a limited range of dielectrics are piezoelectric and only a few metals and ferrites are ferromagnetic, these transducers have to be acoustically bonded in most instances to the material under investigation. As is shown in Table I on piezoelectricity (or piezomagnetic effect), acoustic wave and device applications were, are, and will be a general development status. A. Ultrasonic emulsification is used in the preparations of composite ERF
a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
3546
J. Acoust. Soc. Am. 134 (5), November 2013
Composite ERF with high multi-property is prepared in this work.
0001-4966/2013/134(5)/3546/5/$30.00
C 2013 Acoustical Society of America V
FIG. 1. Schematic diagram of the working principle of electroacoustical ultrasonic equipment.
1. Preparing methods of composite ERF
Materials designing ! selecting raw material, get the materials ready ! according to the component part of designing composite ERF which is to compound it ! for the composite ERF treated with ultrasonic emulsification ! packaging of ERF and setting up the electrodes for it ! alternatively applied electric field and other factors to make an experiment with ERF ! measuring the performance parameter of ERF ! analyze, compare, and determine the best ERF material samples. The preparation steps are roughly as follows [when the composite ERF is made up, the ultrasonic emulsification is useful to the composite ERF (special is very useful for the liquid crystal) to keep a homogeneous system and to prevent the precipitation of dispersing grains in composite ERF]: (1) The main dispersing grains in the ERF are processed by using strongly polarized piezoelectric ceramic (such as FD3 -PZT or FD4 -PZT), which is ground to 50 lm or so by machines, and then to less than 10 lm by ultrasonic dispersion. The other, in the preparation of composite ERF, ultrasonic dispersion, and emulsification with the ultrasonic vibration system shown in Fig. 3, ultrasonic dispersion and emulsification both obtained good results there. (2) Strongly polarized piezoelectric liquid crystal materials1 are selected as an additive for the liquid phase of ERF. (3) The third phase included organic silicone oil and mineral oil, used as a dispersing medium of composite ERF, made up of the single- or multi-component (series).
FIG. 3. Schematic diagram of the working principle of a piezoelectric ultrasonic transducer.
(4) Then, one selects the activator and stabilizer of composite ERF: Halogenated hydrocarbon, alcohol, amine, etc., and some surface-active agent. (5) In proportion to the designed part-component, whose volume percentage concentration of the disperse phase is at 10% to 30%, compound composite ERF is prepared in groups and is then treated with ultrasonic emulsification, which prevents the precipitation of dispersing grains in composite ERF. In the present work, we mainly used the ultrasonic vibration system shown in Fig. 3 to treat the compound composite ERF; we also adopted an ultrasonic cleaner to treat the compound composite ERF. A sandwich piezoelectric transducer is stuck on the outside bottom-center of the cleaning trough (with a special type epoxy resin cementing agent) to form an ultrasonic cleaner. Then, the composite ERF is poured into the cleaning trough to be treated. The transducer frequency is 23 kHz; power is 70 W; each time the treating time is 15 to 20 min. The ultrasonic emulsification is to improve the quality and properties of the composite ERF which took an important effect. The ultrasonic emulsification is mainly caused by ultrasonic cavitations effect and ultrasonic depolymerizing action of chemical effect, etc., in a related solution.2,3 (6) To design and process the packages of ERF, and to set up the electrodes for the packages of ERF. The composite ERF is grouped to pack in the packaging of ERF.
FIG. 2. Schematic diagram of the structural principle of a magnetostrictive ultrasonic transducer. Notes: l ¼ 288.6 mm; D ¼ 562 mm; d ¼ 188.4 mm; the sound velocity of stainless steel is 5790 m s1.
J. Acoust. Soc. Am., Vol. 134, No. 5, November 2013
Quanlu et al.: Ultrasonic emulsification and dispersion
3547
(7) To test the basic performance parameter of the composite ERF. (8) To perform experiments with electric field (frequency and other conditions) alternatively on ERF, measuring properties of the composite ERF (at ac is 1 to 41 kV, at dc is 1 to 30 kV). 2. Principal properties of composite ERF in present work
Principal properties of this composite ERF are as follows: Viscosity g0 < 100 mPa S (at zero electric field); Yield stress sy < 4 k Pa (at E ¼ 3.5 kV mm1 ); Current density J > 100 mA cm2 (at E ¼ 3.5 kV mm1 ); Response time t < 1 mS. Anti-precipitate, nonpoisonous, and the composite ERF do not contain water (Note: In the present work we do not treat the samples of the composite ERF by ultrasonic dispersion and emulsification, dispersing grains in the ERF which are precipitated formidably). 3. General applications of ERF
The researchers concerned all over the world generally think highly of the ERF, which has broad applied prospects in electrical controlled driver; exciter, brake, clutches recoilless equipment, and varied shock-absorber and damper. These applications can be found in the fields of national defense, electronics, aviation-spaceflight, machinery, traffic, chemical industry, robot, and medical equipment. In the present work, the composite ERF is used for the research and development of the intelligent structure (a new actuator combining piezoelectric ceramic and ERF).2 B. Ultrasonic dispersion of metaldehyde [CH3 CH]4-6 is used as a cold cloud catalytic agent of artificial rain
kind of method of artificial climate control, and refers to selecting suitable weather conditions by artificial rain through a cloud layer seeding catalytic agent. Artificial rain (and hail prevention, extinguish a forest fire, dispelling dense fog of sky over airfield, etc.) has been developed faster in some developed countries, such as America, England, and France, etc. Their technique level and measures are also relatively advanced. Now, in some countries a new type of cold cloud catalytic agent metaldehyde ½CH3 CH4-6 is used and has attempted to replace the conventional cold cloud catalytic agent, e.g., dry-ice {i.e., carbon dioxide (CO2 ), sodium chloride (NaCl), silver iodide (AgI) and urea [COðNH2 Þ2 ]}, etc. In the raining effect of metaldehyde there exists a great difference between metaldehyde of natural crystalloid and dispersed powder of metaldehyde. The methods of dispersing metaldehyde have already been tried and used in mechanical grinding, high speed airflow dispersion, and launching smoke bombs, etc. The grains are all above 10 lm and uneven with these methods. The fineness and evenness of metaldehyde’s grains directly affect the increase of metaldehyde to be formed at the ice-nucleus rate of artificial rain (it is directly proportional to the number of catalytic agent grains, that is fineness of grain) in rain and saving raw materials. In the present work ultrasound is used for the dispersion of metaldehyde. With this new method, the grains of metaldehyde are mostly smaller than 4 lm and the evenness is greatly improved. The test results made by Meteorological Bureau of Shaanxi Province in a cloud chamber show that the formed ice-nucleus rate of ultrasonic dispersing metaldehyde in rain is raised 2 orders of magnitude compared with other methods (such as “micronizer” grinding, airflow dispersing, and launching smoke bomb, etc.). (a)
(b)
The principle of ultrasonic dispersion is that an ultrasonic cavitations effect and a machine-agitated action in liquid mediums are produced when ultrasound waves propagate in liquid. For ultrasonic treatment of a new type of cold cloud catalytic agent metaldehyde [CH3 CHO]34-6 : (1) With the ultrasonic instrument, CFS-250 W ultrasonic generator and magnetostrictive transducer
Artificial precipitation (including rainfall and snow; excluding channel water spray irrigation on the ground), is a TABLE I. Referenced frequency ranges for design of acoustics transducer and receiver. Infrasonics
Sonics
Ultrasonics
Microsonics
Lightwave ultrasonics
(hypersonics) (Hz)104
102
1
GENERATORS Explosives Whistles and sirens Electrodynamic devices! Mechanical vibrations RECEIVERS
102
104
106
108
1010
1012
1014
Piezoelectric transducers! — Heat pulses — ! Electromagnetic transducers! Magnetostrictive transducers! — Piezoelectric —! —Electromagnetic detectors —
— !
—
—
Magnetic vibration pickups! Resistance strain gauges
3548
Radiation Optical diffraction and scattering! Pressure Bolometers
J. Acoust. Soc. Am., Vol. 134, No. 5, November 2013
Quanlu et al.: Ultrasonic emulsification and dispersion
(see Fig. 2), their frequency fr ¼ 19:6 kHz; the concentrator is a stepped horn; its amplification factor is 10.24, in which the optimum effect is obtained. The transducer and the stepped horn are welded together at 400 C by welding flux. The transducer is equipped with a cooling water jacket and is then connected with an ultrasonic generator. (2) Metaldehyde ½CH3 CH4-6 grains, their length is approximately 80 to 180 lm, and their thickness is approximately 50 lm; they are needle-like white formless crystals, not dissolved in water, and the subliming point is 112 C. (3) Medium is used as tap water. Metaldehyde ½CH3 CH4-6 grains are dispersed into tap water; both mixing percentage by weight is at 50%. The mixture of metaldehyde ½CH3 CH4-6 grains and water is poured into a beaker, and the tip of the horn of the ultrasonic vibration system is inserted into and always located at the central position of the mixture (i.e., the tip of the horn is at 3 cm from the surface of the mixing solution, then the ultrasonic vibration system is electrified and the mixture is started with ultrasonic treatment). (4) Treating time is 15 to 20 min. (5) Results. After the ultrasonic treatment, the length of metaldehyde ½CH3 CH4-6 grains are less than 4 lm; they make up 92% of the total, and are less than 10 lm and those greater than 4 lm make up about 6%. Dispersing effects of different grinding methods are listed in Table II. In present work, we have also adopted the piezoelectric ultrasonic vibration system to treat the metaldehyde ½CH3 CH4-6 grains repeatedly (see Fig. 3); its dispersing results are basically the same as that with the magnetostrictive ultrasonic vibration system (see Fig. 2).
C. Ultrasonic dispersion of other inorganic materials
The method of ultrasonic dispersion can be not only used for reference for [NO2 C6 H4 C : CHCOOH] and [C6 H3 ðOHÞ3 2H2 O], etc., these better recent discoveries of organic cold cloud catalytic agent, but also can be used for dispersion of other inorganic materials. In the present work, inorganic substances such as antimony trioxide (Sb2 O3 ) and aluminum hydroxide [AlðOHÞ3 ], etc., have been dispersed by the ultrasonic transducer vibration system, coupled with a horn. The length of the dispersed substance’s grains is all less than 2 lm. The dispersed samples
are use to solve a difficult problem of additions in some research items (about aviation materials), in which superfine powder is required. In addition, application of ultrasonic transducer of a special design allows receiving a small-dispersed aerosol from liquid. This process is used for uniform irrigation of some object or for powder production in pharmaceutical and chemical industries. Powder dispersion of different oxides (Al2O3, TiO2, SiO2, ZrO2, Fe3O4, etc.) is made with ultrasonics. Dispersion is made in ultrasonic reactors on the base of a ring magnetostrictive ultrasonic transducer. III. DISCUSSION
The present work has obtained the good results on ultrasonic emulsifying composite ERF and ultrasonic dispersing metaldehyde, etc. The development and spreading applications of the composite ERF and metaldehyde, etc., provided a certain scientific basis and applied prospects, for emulsification and dispersion of similar substances. Also are provided new methods for reference. At the same time, the present work opens and suggests further broad and new applied fields for sonochemistry and power ultrasonics. However, in developments and research of power ultrasonics and sonochemistry there are technologically difficult problems that require further research work and solutions. For example, ultrasonic emulsification and the ultrasonic dispersion need automatic temperature control systems to solve the problem of vibrating system frequency drift and its temperature rise, whether a piezoelectric ultrasonic vibration system or a magnetostrictive ultrasonic vibration system. It is necessary to develop truly high-power ultrasonic treating equipment (including high-power piezoelectric ultrasonic transducer and its high-power piezoelectric materials, and high-power magnetostrictive ultrasonic transducer and its high-power piezomagnetic materials, etc.). In the present work there are some problems which have been discovered and must be pointed out: The emulsifying and dispersing results of different materials with ultrasonics show that not all materials be applicable emulsified or dispersed by ultrasonics; water is a commonly used medium for ultrasonic dispersion (of course, the emulsified materials must be in a solution; and the dispersed materials must not be dissolved in water. And, water is practical and saves money.). It is pointed out that a piezoelectric ultrasonic transducer and its piezoelectric transducer materials, and magnetostrictive transducer and its piezomagnetic materials of acoustoelectrical devices and its materials cannot replace each other in some important applications and will coexist for a
TABLE II. Dispersing results of different methods for metaldehyde.
Dispersing method “Micronizer” grinding Airflow dispersion Launching smoke bomb Ultrasound dispersion
Grain size (lm) after dispersion
Metaldehyde grain number per gram
Measured and counted by
Merits and demerits
>10 >10 >6
1010 1010 1011
