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Hybrid aerosol deposition (HAD) is a new coating method to deposit homogeneous nano-structured ceramic coatings. An accurate evaluation of the fabricated coating properties is required. In this study, α-Al2O3 fine powder was sprayed by HAD. The obtained coatings were dense and uniform with a nanocrystalline structure. An X-ray diffraction measurement revealed that the fabricated HAD Al2O3 coatings mainly consisted of α-Al2O3 phase. The hardness and Young's modulus of the HAD Al2O3 coatings were evaluated by a micro-Vickers method and a nanoindentation method using the Weibull distribution. The hardness of HAD Al2O3 coatings measured by micro-Vickers was ~1400 HV (~15 GPa). The variation of mechanical properties of HAD coatings measured by the nanoindentation method was extremely small compared to those of plasma-sprayed coatings, which also indicates that HAD coatings contain less pores and cracks than plasma-sprayed coatings.

Deposition of protective dense environmental barrier layers is a promising solution to improve the reliability and environmental durability of the next-generation turbines and other industrial applications. In this context, spraying of fine particles could enhance the formation of fine dense coating microstructures with improved properties. In AIST we are focusing on the spraying of the fine particles via different spraying technologies including suspension plasma spraying, as well as deposition of the fine solid particles directly by aerosol deposition (AD) and plasma-assisted aerosol deposition (so-called Hybrid Aerosol Deposition; HAD. The HAD is a new coating window to spray the fine ceramic particles via the implementation of a low-power rf-plasma source to assist the aerosol deposition at room temperature. This study introduced the feasibility of utilization of HAD as an outstanding technology for deposition of dense ceramic coatings on different substrate materials and 3D deposition capability. Highly dense and well-adhered Al2O3 coatings without obvious observable cracks and bulk-like properties were successfully fabricated on different substrate materials of SUS 304, Aluminium, Al2O3 and glass, via HAD of fine particles. The substrate material and its hardness significantly influenced the first deposition step, which determined the coating adhesion and properties. Furthermore, homogeneously uniform, dense, and crack-free coating with a strong adhesion has been fabricated successfully on cylindrical substrates with 6.3 mm diameter. During HAD spraying the plasma activated the surface of the particles without reaching to the molten state, then the activated particles impact and stuck with the substrate by room temperature impact consolidation mechanism. Therefore, the fabricated coatings had the same crystal structure as the starting feedstock powder, and the activated surface act as glue and improved the deposition efficiency and 3D capabilities. Herein, the deposition phenomena of HAD makes it as a promising candidate technology for development of environmental and sealing layers of highly dense microstructure, with the targeted crystalline phase structure, without stoichiometric composition nor phase transformation and improved deposition efficiency on multi-shape components in different fields such as environmental, thermal barrier coatings (TBCs), environmental barrier coatings (EBCs) and gas turbine applications.

Technological innovations in manufacturing processes are critical for devices that require high-quality thick piezoelectric ceramic films. However, ceramic films synthesized by conventional methods usually suffer from mechanical failures, poor adhesion, reliability, and rough interfaces. Furthermore, with traditional piezoelectric thin film methods, such as sputtering, sol-gel, pulsed laser, and etc., it is difficult to synthesize piezoelectric films with complex material compositions and with multiple dopants in a short deposition time and over a large surface area, in general. The aerosol deposition (AD) process is a unique approach for depositing thick piezoelectric ceramic films to overcome these technological hurdles. In this process, (sub)-micron ceramic particles fluidized by gas flow are accelerated in a low-vacuum environment at velocities of up to 100–300 m/s to be impacted on the desired substrates. The impact results in a thick, dense, uniform, and homogeneous polycrystalline ceramic film formed at room temperature without the need for any additional heating to solidify the resulting film. The process is extremely cost-effective and requires comparatively simple equipment installation that is integratable with modern industrial fabrication facilities. This technique is particularly useful for fabricating piezoelectric thick films for microactuators, sensors, and energy-harvesting devices. This chapter describes the mechanisms and features of the AD process, followed by applications of AD for fabricating piezoelectric materials and devices.

Titanium dioxide (TiO2) films were irradiated with a femtosecond laser beam to alter their electrical resistances. The TiO2 film was produced by aerosol beam deposition. The wavelength, pulse duration, and repetition rate of the femtosecond laser scanned across the sample surface were 800 nm, 100 fs, and 1 kHz, respectively. By attenuating the laser fluence on the TiO2 film, a range was found in which the electrical resistance of the TiO2 film was varied even though the morphology of the film surface was not changed.

The infrared reflectivities of crystalline forsterite (Mg 2 SiO 4 ) were measured for the temperature range 295-50 K for each crystal axis, between wavenumber 5000 and 100 cm -1 . The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K.

By observing light emissions from flares, we systematically investigated transient phenomena from glow to arc discharges under designated durations. To describe properly the discharge flare behavior, we introduced a parameter νa defined as (electrode gap)/(flare traveling time). The main findings are as follows. The parameter νa is proportional to the initial electrode voltage. The maximum value of νa is obtained at a certain gas pressure and it falls on the Paschen curve. The flare behavior follows Townsend’s theory at each instant, therefore, it is governed by the state of the electrolytic dissociation of the gas.

Ultra-fine particles of metal and ceramic materials jetting with the velocities of several hundreds m/s is accumulated on the substrate based on impact adhesion. Recently, the application of this phenomenon for micro electro mechanical systems and micro devise has been investigated. In this paper, the deposition method based on ultra-fine particle beam and possibilities of its application as HARMST are reported.

We have developed a fabrication technology for realization of three-dimensional microstmctures composed of different materials using excimer laser ablation and ultrafine particle (UFP) jet molding. We have named this technology the jet molding system (JMS). This method enables the production of three-dimensional microdevices composed of actuator, sensor materials (PZT), and electrodes (metal). Insertmolding and mask-deposition methods were applied to obtain these structures. SEM observation as well as density and electrical property measurements showed good pattern transfer fidelity with sufficient deposited layer quality (density of better than 85%, dielectric constant of deposited PZT layer of 760). The deposition rate of PZT was much faster than that obtained using any other deposition technique, and a PZT layer up to 40 μm of thick was formed with the desired metal electrode structure.

By using the magnetic lithography technique previously reported, an optical grating can be easily formed not only on a plane, but also on a convex or concave surface. since the optical characteristics of this relief-type grating depend on its cross-sectional shape, it is important to investigate the factors determining the shape of the grating in magnetic lithography so that this technology can be applied to an encoder plate. In order to improve the encoder's performance, it is necessary to control the crosssectional shape of the grating and to try to produce a grating that has no Fraunhofer zeroth-order diffraction light spot by means of magnetic lithography. Results show that the characteristics of the gratings have good repeatability in production. Conditions for developement of such gratings are investigated.

Aerosol deposition (AD) is a unique approach for depositing ceramic films, where submicron ceramics particles (both oxide and non-oxide) are accelerated by gas flow up to 100–500 m/s and then impacted on a substrate. It can rapidly form a thick, dense, uniform and hard ceramic layer at room temperature without additional heating for solidifying ceramic powders, even in low vacuums, using relatively cheap and simple production facilities. It is expected to reduce energy and costs, ease the fabrication of thin or thick film with complicated material compositions, and reduce the number of processes during fabrication of electronic devices, as well as to improve substantially their performance. This technique is particularly useful for fabricating piezoelectric thick films and producing micro-actuator devices. This chapter deals with the mechanism and features of the AD process first, followed by its application for piezoelectric materials and devices.

A new method, previously reported, for fabricating optical diffraction gratings involves writing a periodic magnetic pattern in a magnetic memory medium and using a magnetic fluid as magnetic toner to render the pattern visible. Using this method, an optical grating can easily be prepared even on convex and concave surfaces. Because the optical characteristics of such relief-type gratings are determined by the cross-sectional shape, it is important that the cross-sectional shape be studied prior to application of the method in encoder plates or optical components. When the grating constant is small, the positions at which the magnetic fluid is deposited change from domain walls to magnetic domains. By analyzing the Fraunhofer diffraction pattern of such gratings, the relationship between cross-sectional shape and developing conditions was investigated. According to the results, the shape is that of a sinusoidal or circular arc when the grating constant is less than 10 ?m.

Ceramic tribo-coating continues to be one of the major research areas in tribology, especially in relation to recent developments in smart structured devices and micro-electro mechanical systems (MEMS), as well as for their use in advanced machines operating in extreme or hostile environments. This paper is a report on current state-of-the-art topics in ceramic tribe-coatings that the authors have interest in and for which they believe further focus in required.

PZT films were deposited on 4 inch silicon wafer substrate by aerosol deposition, based on room temperature impact consolidation (RTIC). A nozzle that blowed out aerosol beam scanned the wafer. The film thickness was evaluated through the measurements with step height of masked edges. The aerosol deposited films showed relatively good uniformity of thickness of 1.4%. The surface roughness was Ra 59 nm.

Preparation of Bi:YIG films, using aerosol deposition method (ADM), onto low temperature resistant substrates such as polycarbonate is demonstrated. In ADM, sub-micrometer particles of Bi:YIG mixed with a carrier gas in the flow is ejected through a micro-orifice nozzle. SEM and XRD are used to determine the surface roughness and structure of the film, respectively. The saturation magnetization and coercivity of the films are evaluated to be 250 G and 50 Oe, respectively. The magneto-optical effect in the film is also investigated.

Integrating and embedding various passive components like capacitors, and inductors, in one system module, is one of the attractive ways to achieve down-sizing, cost-reduction and higher performance in RF wireless communication products. Because the unique aerosol deposition (AD) method, we developed creates a dense ceramic film, that can be deposited at room temperature, and that possesses electric properties that are close to that of bulk ceramics, we can offer a module with passive components by incorporating different materials with various process temperatures. In this paper, we have presented our novel approach to RF modules compared with other processes and methods. We also examined the microstructure and dielectric properties of high Q ceramic dielectric film for microwave filter applications and high K ceramic dielectrics deposited by the AD method at RT. As a result, a 500 dielectric constant and a 450 Q value at 10GHz were clearly attained with our ceramic AD films deposited on FR4 substrates at RT. Decoupling capacitors embedded in epoxy-based substrates fabricated as prototypes using AD film indicated about 300nF/cm/sup 2/. By developing other various functional ceramic dielectric films with the AD method and increasing the dielectric properties of those films, we can expect to attain our target: a small RF integrated module incorporating a lot of functions.

A simple, low-cost technique for measuring the velocity of particles for spray coating methods is presented. The accuracy of measurement is determined by the precision of the only quantity of geometrical size of the deposited layer. Self-selection of the particles with parameters suitable for deposition occurs. For typical deposition conditions, a velocity of 650 m/s was detected. This technique allows in situ velocity monitoring during process.

Through ionization waves (striation), the transition of glow discharge to arc discharge was observed and relevant electron temperatures were determined experimentally. The velocity of ionization waves in a cathode flare increased from twofold to threefold that in an anode flare. It was assumed that the electron temperature of an anode flare was 4.0-fold to 8.4-fold higher than that in a dark space, and the typical electron temperatures in a dark space and an anode flare were 1.8×103 and 1.0×104K, respectively. The electron temperature of the anode flare agreed well with the theoretical value of a positive column in steady glow discharge.

A new method to make an optical diffraction grating has been developed using the Bitter method. A periodic magnetic pattern like 0101 ... is written in a magnetic memory medium, and a magnetic fluid is used as magnetic toner to visualize this pattern. To enhance the contrast of the grating, an interfacial active agent in the magnetic fluid is destroyed by a certain organic solvent, and a DC magnetic bias field is applied to the memory medium to thicken the pattern. When a transparent grating is required, Au film is deposited on it as a parting agent after the formation of a magnetic toner pattern. After separation of the epoxy resin film from the memory medium, Au film is chemically etched. A sharp diffraction image is observed by projecting a laser diode onto the diffraction grating. Using this method, an optical grating can easily be made even on a convex or concave surface.