Field of the Invention
One or more embodiments of the present invention relate to fluorine resistant, radiation resistant, and radiation detection alkali free fluorophosphate glass systems.
Description of Related Art
Conventional fluorophosphate-based glass systems are well known and have been in use for a number of years. Regrettably, existing conventional alkali free fluorophosphate-based glass systems that are radiation resistance do not provide a visible means for visually determining existence of radiation. That is, existing conventional alkali free fluorophosphate-based glass systems that are radiation resistance do not solarize, remain transparent within the visible portion of the electromagnetic spectrum, and scintillate outside the visible portion of the electromagnetic spectrum and hence, require external devices to be used in conjunction with the conventional glass systems to determine existence of radiation. For example, existing conventional alkali free fluorophosphate-based glass systems use Yb as a dopant and or co-dopant, which do not solarize, remain transparent within the visible spectrum, but generate scintillations within the infrared spectrum, which is obviously not detectable without the use of specialized devices. Non-limiting, non-exhaustive listing of examples of conventional alkali free fluorophosphate-based glass systems that are radiation resistance are disclosed in U.S. Pat. No. 7,608,551 to Margaryan et al., U.S. Pat. No. 7,637,124 to Margaryan et al., U.S. Pat. No. 7,989,376 to Margaryan, U.S. Pat. No. 8,356,493 to Margaryan, U.S. Pat. No. 8,361,914 to Margaryan et al., and U.S. Patent Application Publication 2010/00327186 to Margaryan et al., the entire disclosures of each and every one of which is expressly incorporated by reference in their entirety herein.
Further, existing conventional alkali free fluorophosphate-based glass systems are generally comprised of a base composition containing a maximum of only four raw compounds. However, the use of only four compounds limits the glass-forming domain, limiting the number of permutations for the glass formations (or types) that can be produced.
Additionally, existing conventional alkali free fluorophosphate-based glass systems with only four raw compounds have a generally low Z number (atomic number) by element. For example, the combined Z number of the conventional alkali free fluorophosphate-based glass system by element is approximately 50 to 56 for base glass composition:Ba(PO3)2—Al(PO3)3—BaF2—RFx-Dopants
wherein:
R is selected from the group comprising of Mg, Ca, Bi, Y, La;
x is an index representing an amount of fluorine (F) in compound RFX, and
Dopants may comprise of Yb, La.
It is well known that the lower the Z number for glass composition by element, the longer the excitation decay time is of an excitable element within the glass composition when irradiated. For example, in the case of the above composition, the excitation decay time of Yb dopant in response to emitted high-energy radiation is generally high, which would make the glass a somewhat poor choice for use in Positron Emission Tomography (PET) scans.
Furthermore, existing conventional alkali free fluorophosphate-based glass systems have low densities of about 4.1 grams per cubic centimeter (g/cm3) or less, which is mostly due to the overall lower Z number by element. In general, low-density conventional alkali free fluorophosphate-based glass systems have a lower radiation resistance and shielding when exposed to high-energy environments. Another drawback with existing conventional alkali free fluorophosphate-based glass systems with low density is their lack of ability to shield against high energy electromagnetic pulses (EMP). Further, optically, due to lower density, conventional glass systems have lower refractive index nD of about 1.57 (for wavelengths of about 589 nm—the visible light portion of the electromagnetic spectrum).
An additional drawback with existing conventional silica-based glass systems is that they have a poor or low resistance to fluorine, which means for example, they cannot be used as optical components in water treatment plants that utilize high levels of concentrations of fluorine without clouding up and pitting to the point that they are no longer transparent.
Accordingly, in light of the current state of the art and the drawbacks to current glass systems mentioned above, a need exists for glass systems that would have improved radiation resistance and shielding against high energy radiation and that would provide scintillations within the visible spectrum to provide a visible means for visually determining existence of high energy radiation. That is, a need exists for glass systems that would provide scintillations within the visible spectrum to provide visual indication of existence the of high energy radiation commensurate with duration thereof. In other words, a need exist for a glass system that would scintillate within the visible spectrum when irradiated (i.e., exposed to high energy environment). Further, a need exists for glass systems that would provide a greater (larger) glass-forming domain for larger number of permutations for the glass formations (or types) that may be produced. Additionally, a need exists for glass systems that would have a larger overall Z number by element, resulting in higher density, higher refractive index nD, and shorter excitation decay time. Additionally, a need exists for glass systems that would provide EMP shielding capabilities. Finally, a need exists for glass systems that would be fluorine resistance.
USPTO Backgrounds
USPTO Backgrounds