Brian G. Pazol

Design, fabrication, and properties of sonopanelTM 1–3 piezocomposite transducers

Abstract 1–3 piezocomposite materials, manufactured by PZT ceramic injection molding and marketed by Materials Systems under the trade name “SonoPanelTM”, have been adapted for operation under a wide variety of undersea conditions. These transducer materials have been modified to enhance specific performance characteristics by varying the PZT ceramic element type and layout, the polymer matrix properties, and by configuring the device to couple efficiently into water in both transmit and receive operation. Piezocomposite SonoPanelsTM have high and very broadband receiving voltage sensitivity (RVS). In one typical configuration (6mm thick 1–3 composite with 15 volume % PZT-5H, soft polymer matrix and stiff coverplates), the nonresonant RVS is −187 ± 2dB re IV/μPa from 0.1 to > 100kHz. The nonresonant transmit voltage response (TVR) of a 100mm square SonoPanelTM is 147dB at 50kHz, and increases linearly at 40dB per decade to 175dB at resonance. SonoPanelsTM have been driven at rms electric field levels up t...

1-3 piezocomposite smart panels for active surface control

A cost-effective technology has been developed for producing 1-3 piezoelectric ceramic/polymer composites for active surface control. SonoPanelTM 1-3 piezocomposite transducers consist of an array of piezoelectric ceramic rods in a polymer matrix. Stiff face plates are bonded to the composite for stress amplification when used as a sensor and to enhance surface response uniformity when used as an actuator. Many piezocomposite design variations have been produced for specific applications. The key technology in SonoPanelTM manufacturing is the PZT ceramic injection molding process. Using this process, an entire array of piezoelectric ceramic rods are molded in one operation using specially designed tooling. Injection molded PZT preforms are formed at a rate of one per minute. Several thousand components with excellent piezoelectric properties and part-to-part reproducibility have been manufactured to date. The piezocomposite fabrication process has been scaled up for low volume manufacturing. More than thirty 250 X 250 mm SonoPanelTM transducers have been produced and evaluated. The transducers show high receiving voltage sensitivity and transmitting voltage response as well as symmetrical beam patterns. Next generation SonoPanelTM transducers, with materials and designs optimized for Navy systems, are under development, including advanced panels for active surface control. The devices incorporate actuators, pressure sensors, and velocity sensors--all made from 1-3 composite materials--into an autonomous smart panel.

Large-area edge-bonded flat and curved sapphire windows

High strength edge bonds between individual sapphire components have been developed as a means to produce affordable large area windows. Several bonding methods have been demonstrated, with bond fracture strengths ranging from 100-200 MPa. When polished, the bonded windows show excellent transmittance with no degradation in transmitted wavefront quality. The bonding processes have recently been scaled up to 355mm wide, 10mm thick bond lines and multipane windows. Using singly-curved sapphire components for the individual panes, doubly-curved bonded sapphire components have also been produced and polished with excellent results. The edge bonding approach shows promise for fabricating affordable sapphire windows up to 750mm diameter. In addition, recent developments with index-matching glass coatings show the feasibility of substantial cost reductions in optical finishing of sapphire windows, particularly for transparent armor.

80-mm EFG sapphire dome blanks yield high-quality low-cost single-crystal domes

Close attention to crystal growth parameters and characterization of the crystals thermal environment during growth has led to improvement in the crystal structure of EFG grown dome blanks. These near net shape 80 mm sapphire blanks have been fabricated to produce high quality finished domes. New measurements of the coefficient of thermal expansion (CTE), thermal conductivity, optical scatter, rain erosion and the thermal coefficient of refractive index (dn/dT) as a function of wavelength have been performed and the data are presented.

Large-area flat and curved sapphire window blanks

With the objective of producing affordable large area windows, high strength edge bonds between individual sapphire components have been developed. Several bonding methods have been demonstrated, with bond fracture strengths ranging from 100 - 200 MPa. The directed energy process, which yields the strongest bonds, has produced bonded sapphire components 600 mm long and 3 mm thick with a 75 mm wide bond line. When polished, the bonded windows show no degradation in transmittance or transmitted wavefront quality. The processes have recently been scaled up to 355 m wide, 10 mm thick bonds lines and multipane window blanks. In addition, doubly-curved bonded sapphire components have been produced and polished with excellent results, using singly curved sapphire components for the individual panes. The edge bonding approaches shows promise for fabricating affordable sapphire windows up to 750 mm diameter.

High-strength edge-bonded sapphire windows

High strength edge bonds have been achieved between individual sapphire components, showing promise for fabricating window blanks up to 600 mm diameter or larger in size. Several bonding methods were investigated, with a directed-energy diffusion-bonding method yielding components with bond fracture strengths of 200 MPa. Bonded sapphire components 600 mm long and 3 mm thick with a 75 mm wide bond line have been produced. When polished, the bonded windows show no degradation in transmittance or transmitted wavefront quality. Process scale up to larger bonds lines is planned. Mechanical and optical characterizations of sub- scale edge-bonded sapphire windows are presented.

Titanium-doped silica aerogels for lightweighted optics

A process is presented for fabricating titanium doped silica aerogels. Aerogels were produced by the hydrolysis of TEOS and titanium isopropoxide in ethanol and then supercritically dried in a nitrogen overpressure. A detailed study of gelling and annealing was performed to minimize shrinkage and produce dried gels with densities less than 10% of ordinary glass. Lightweighted structures with densities between 0.16 g/cm3 and 0.06 g/cm3 were produced.