Putting Confidence in Ultrasound

Glossary of Abbreviations

 

= Acoustic attenuation in nepers/cm. To convert units to dB/cm, multiply by 8.686 ¥ f2 where f is the frequency of interest in Hz. This conversion assumes that the attenuation increases with the square of frequency and is only valid for low loss materials such as glass.

Loss = Acoustic attenuation in dB/cm at the stated frequency in MHz.

V / T = Change in acoustic velocity per change in temperature in m/s°C referenced to 25°C

Tc = Curie temperature in °C

r = Realitive dielectric constant, multiply by 8.84 ¥ 10-12 for MKS units

kt = Electromechanical coupling coefficient between E3 and thickness mode of vibration

kp = Planar (radial) mode coupling coefficient

= Density in g/ml

tan = Loss tangent

Qm = Mechanical quality factor

V3D = Piezoelectrically stiffened velocity in piezoelectric material. Corresponds to antiresonant frequency (parallel resonance)

V3E = Velocity in piezoelectric material with electric field in the material fixed to zero. Corresponds to resonant frequency (series resonance)

VL = Longitudinal wave velocity in mm/µs

VS = Shear wave velocity in mm/µs

= Poisson’s ratio given by (1 - 2X ) / (2 * (1 - X ) where X = (VS / VL)2

ZL = Longitudinal wave impedance ( ¥ VL) ¥10-6 in kg/m2s

ZS = Shear wave impedance ( ¥ VS) ¥ 10-6 in kg/m2s

Alumina = Aluminum oxide for thin layer chromatography. Obtained from Chemistry Stores at Stanford University.

C5W = A Li Tungsten product, the 6 to 10 micron powder

DEH = Dow epoxy hardner

LP3 = A liquid polysulfide resin from Thiokol Corporation

DER = Dow epoxy resin

MPDA = Meta-phenaline-diamine, a good epoxy hardner. Use vendors D, handle, or rather don’t handle with care. This product can be difficult to obtain fresh, should arrive in the form of whiteish flakes. When handling, take care to use gloves and apron, do not breath the powder. It is best stored in jars filled with dry nitrogen at 0C. When opening a new jar, allow it to equilibrate to RT first.

PHA = Parts per hundred parts by weight of A

PHE = Parts per hundred parts by weight of mixed epoxy

PHR = Parts per hundred parts by weight of RESIN, as opposed to total weight etc.

R1 = Recipe 1: Heat the resin to 70C, add the MPDA and keep the mixture in the oven until the MPDA melts. Sift the W through a 100 mesh screen and add to the epoxy. Stir thoroughly, and outgas the mixture to a 100 micron vacuum. Cure at 40°C for 1 hour, then leave in oven over night at 70°C.

R2 = Recipe 2: Mix alumina to resin. Alumina is very light and fluffy and does not need to be sifted first. It is so light in fact, that any mixture having more than about 100PHR of it will be fixatropic and hard to pour. Next add the hardner, then stir thoroughly and outgas to 200 microns. Use an engraving tool on the beaker to facilitate pouring. Cure at RT for 48 hours.

R3 = Recipe 3: Sift the W through a 100 mesh screen before adding to the resin at RT. Stir and outgas the mixture to 150 microns vacuum. Add the hardner, stir and outgas again. We have noted that epoxy hardened by DEH20, if exposed to the atmospheric moisture, will still be sticky after curing. This is called blushing and usually does not effect the experiment.

R4 = Recipe 4: Mix parts A and B and filler together, outgas to 100 microns vacuum, bake over night at 70C.

R5 = Recipe 5: Vacuum impregnation. To make these materials a vessel is required which is vacuum tight at the bottom and open at the top, i.e. a test tube or jig. The jig is mold released and the filler material is poured into it, usually no more than a third of the way to the top. Next the jig is warmed in an oven to the specified temperature to preheat it and bake on the mold release. The resin is melted, usually in the same oven at this time, and then the MPDA is added and allowed to melt into the resin. Thiokol may also be added at this time if specified. The mixture is stirred, then poured over the filler material, usually no more than two thirds of the way to the top. This assembly is outgassed till a vacuum of 100 microns is reached, usually in about 10 minutes depending on the size of the jig etc. When the vacuum is broken, the epoxy is forced into the filler material by atmospheric pressure. Bake at 70°C overnight.

R6 = Recipe 6: Parts A and B are stirred together, outgas to 100 microns vacuum, bake at 60°C overnight.

R7 = Recipe 7: Same as R6 but the material is post baked at 200°C overnight. Material turns from red to black and the loss increases.

R8 = Recipe 8: Stir components together thoroughly, outgas to 200 microns, pour into a jig at room temperature, leave at RT for about an hour, then place jig in 72°C oven overnight.

R9 = Recipe 9: Stir components together thoroughly, outgas to 200 microns, pour in to a preheated jig and bake at 90°C overnight.

R10 = Recipe 10: Melt resin, mix in alumina, outgas mix to 1mm, add DEH20, stir, outgas again to 1mm.

R11 = Recipe 11: Stir W into RTV 560 and outgas Then add the DBT, stir and outgas again. Pour or scrape into jig mold released with “Heavy Duty Silicon Mold Release” from Sprayon Products, Anaheim, CA. Let stand at room temperature for 4 hours to let cure, then bake at 40°C overnight. Immediate baking will cause material to stick through the mold release.

RT = Room temperature, or about 20°C

SiC = Silicon carbide, 325 mesh or about 10 to 20 microns diameter, Cerac product number S1169.

T1167 = 325 mesh tungsten from Cerac, product number T1167.

V140 = Versamid V140

W = Tungsten powder, 1 to 2 microns diameter, Cerac product number T1168. This material is very fine and does not settle out of a heavier epoxy resin such as DER317 at RT.

WO3 = 1-5µm size 99.9% pure tungsten oxide. This material does not conduct electrically - unlike pure tungsten or tungsten carbide.

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