摘要: Silicon nitride materials with low dielectric properties were prepared using nano and micron
silicon nitride powders as raw materials and the green bodies were sintered with cordierite as sintering
additive in flowing nitrogen. The additives of cordierite powders prepared by sol-gel method and solidstate
reaction method could greatly decrease the sintering temperature. The dielectric constant of
materials decreased as sintering temperature fell, whereas the strength showed relatively low as the low
sintering temperature. XRD analysis showed the main phase of material was Si2N2O, which indicated that
the Si3N4 could be integrated with SiO2. Porous structures were observed by SEM, showing compact
sintering cannot be achieved at these temperatures, explaining the low strength.
摘要: The sintering dynamics, microstructures and microwave dielectric properties of Bi2O3 and
MnO2 co-doped [(Pb,Ca) La](Fe,Nb)O3 (PCLFN) ceramics were investigated. Bi2O3 and MnO2
dopants effectively enhanced bulk densities and reduced sintering temperatures by about 100~140°C.
Sintering procedure had significant effect on grain size and porosities of ceramics. Investigation of
microstructures revealed that the grain growth was controlled by either volume diffusion or
second-order interface mechanism in present ceramics. The potential microwave dielectric properties
of εr=91.1,Qf=4870GHz and τf=18.5ppm/°C could be obtained when the mass ratio of Bi2O3/MnO2
(k) was 1, the doping content w=1wt% and sintered at 1050°C for 4h.
摘要: A novel piezoelectric actuator used for transporting some living cells in micro fluidic systems
is presented. The mechanism of the living cell transportation is studied based on the acoustics principles.
The structural resonant model and a solid-liquid coupling analysis are obtained by FEM. The works will
be useful for design optimization of some corresponding actuators and their applications.
摘要: This study dealt with the Maxwell stress effect of waterborne polyurethane (WPU)/
conductive filler nanocomposite, which was a promising candidate for a material to be used in
dielectric elastomer actuator electrode. Conductive nanocomposites were produced by using three
types of conductive filler such as carbon black (CB), vapor grown carbon fiber (VGCF), and silver
powder (Ag). Among them, conductive nanocomposite containing VGCF exhibited the lowest
threshold concentration. And the blend of CB and VGCF (CB/VGCF) filler had a synergistic effect to
electrical conductivity. Actuation test showed that CB/VGCF nanocomposite electrode had the
largest displacement. Then it could be stated that the improvement of the displacement in CB/VGCF
nanocomposite electrode was originated from the increase in relative dielectric constant. In addition, a
unique feature of the hysteresis in the bending deformation was described. The feature is that the prior
application of an electric field significantly improves the bending speed in the successive application.
摘要: The influence of electro-mechanical operation conditions on the actuation capabilities of the
piezoelectric bimorph is investigated in this paper. The objective is to compare the performance of the
piezoelectric bimorph in different operation conditions and to determine the optimum operating
conditions. An experimental set-up is built, and a series of experiments are presented to investigate the
static and dynamic characteristics of the bimorph, including tip displacements of the bimorph under
different preloads, dynamic response at different drive frequencies, step response and creep. Some
properties such as displacement output, force output and hysteresis of the piezoelectric bimorph under
different operating conditions are evaluated. Experimental results indicate strong dependence of both
elastic and piezoelectric properties of the bimorph on the operating conditions.
摘要: The responses of the piezoelectric stack actuator under electro-mechanical loading are
investigated. Two types of tests are performed: influences of the preload on characteristics of the stack
and dynamic test. Experimental results indicate strong dependence of the stack properties on the
electro-mechanical loading conditions. The displacement output is initially enhanced with an increase of
the mechanical preload, and the maximum value is obtained at the preload of about 0.4 kN. But much
higher preload will cause the decrease of the displacement output. The effective piezoelectric coefficient
and the hysteresis degree are employed to describe the variations of the stack’s performances caused by
the mechanical preload. The effective piezoelectric coefficient under different preloads can be calculated
by using experimental results of the displacement output and input voltage. Within low frequency band of
about 400 Hz, the displacement magnitude of the stack is nearly constant, and the phase lag increases with
the increase of the driving frequency at the applied sine sweep voltage with the amplitude of 150V.
摘要: The dynamic behavior of a vibration converter of an ultrasonic motor is described using finite
element method. Tetrahedral finite elements with three dimensions are formulated with the effects of
piezoelectric coupling. And the solution of the coupled electroelastic equations of dynamic motion is
presented. The simulated response of the vibration converter is calculated, and shows excellent
consistency with experimental results, which proved that finite element modeling is a good approach to
optimize piezoelectric apparatus design. A gradual optimized method is employed to ascertain the most
摘要: The paper presents a novel structure cylinder driving USM (ultrasonic motor). Through
development and experimentation, the torque and rotational speed of the prototype were tested, which
proves that this type of USM has a very simple structure, self-adjusting pre-tightening force and
compensation for wear. The results verify the theoretical feasibility and provide instructions for the
industrialization of this type of USM.
摘要: Conducting polymer (CP) actuators undergo volumetric changes due to the movement of
dopant ions into the film during the electrical oxidation process. However, it may be an impediment for
practical use of polypyrrole actuator that polypyrrole usually requires electrolyte solution for actuation.
To solve this problem, solid polymer electrolyte(SPE) was introduced in CP actuator instead of
electrolyte solution. And PPy/SPE/PPy electroactive tri-layer actuator was prepared by the
electrochemical polymerization of pyrrole and the actuation characteristics were studied. An all-solid
actuator, consisting of two polypyrrole films and a solid polymer electrolyte based on polyurethane,
clearly showed a reversible displacement in an atmosphere when a voltage was applied.
摘要: This article describes out-of-plane resonant modes of a piezoelectric disc structure. A new type
of micro ultrasonic motor using the resonant mode B11 (Bmn, where m is the number of nodal circles, n is
the number of nodal diameters) has been studied. The motor is a wobble-type motor. The stator of the
motor uses this structure, consisting of a hollow metal cylinder and a piezoelectric ceramic disc bonded
with a metal one, which is excited in the vibration mode by two electrical signals. The stator exhibits
wobble displacement and transfers rotation to a rod rotor by the cylinder. The behavior of the stator has
been simulated by the finite element analysis. The simulation results have been checked with laser
scanning by a laser scanning vibrometer. The article closes with the introduction of the new micro
ultrasonic motors based on this vibration mode with high rotation speed.