Replacement of conventional petroleum fuels with renewable fuels reduces net emissions of carbon and greenhouse gases, and affords opportunities for increased domestic energy security. Here, we present alkyl dialkoxyalkanoates (or DAOAs) as a family of synthetic diesel and marine fuel candidates that feature ester and ether functionality. These compounds employ pyruvic acid and fusel alcohols as precursors, which are widely available as metabolic intermediates at high titer and yield. DAOA synthesis proceeds in high yield using a simple, mild chemical transformation performed under air that employs bioderived and/or easily recovered reagents and solvent. The scalability of the synthetic protocol was proven in continuous flow with in situ azeotropic water removal, yielding 375 g of isolated product. Chemical stability of DAOAs against aqueous 0.01 M H2SO4 and accelerated oxidative conditions is demonstrated. The isolated DAOAs were shown to meet or exceed widely accepted technical criteria for sustainable diesel fuels. In particular, butyl 2,2-dibutoxypropanoate (DAOA-2) has indicated cetane number 64, yield soot index 256 YSI per kg, lower heating value 30.9 MJ kg−1 and cloud point < −60 °C and compares favorably to corresponding values for renewable diesel, biodiesel and petroleum diesel.
Plastic scintillators are widely used as radiation detection media in homeland security and nuclear physics applications. Their attributes include low cost, scalability to large detector volumes, and additive compounding to enable additional material and detection features, such as pulse shape discrimination (PSD), gamma-ray spectroscopy, aging resistance, and coincidence timing. However, traditional chemically cured plastic scintillators (CCS) require long reaction times, and hazardous wet chemical procedures performed by specially trained personnel, and can leave residual monomer, resulting in deleterious optical and material properties. Here, we synthesize melt blended scintillators (MBSs) in 2.5 days using easily accessible solid-state compounding of commercially-available poly(styrene) with 30-60 wt% fluorene-based compound 'P2' to create monolithic detectors with < 100 ppm residual monomer, in several form factors. The best scintillation performance was recorded for 60 wt% P2 in Styron 665, including gamma-ray light yield 139% of EJ- 200 commercial scintillator and PSD figure of merit (FOM) value of 2.65 at 478 keVee, approaching P2 organic glass scintillator (OGS). The capability of MBS to generate fog-resistant scintillators and poly(methyl methacrylate) (PMMA)-based scintillators for use in challenging environments is also demonstrated.
High-performance radiation detection materials are an integral part of national security, medical imaging, and nuclear physics applications. Those that offer compositional and manufacturing versatility are of particular interest. Here, we report a new family of radiological particle-discriminating scintillators containing bis(9,9-dimethyl-9H-fluoren-2-yl)diphe-nylsilane (compound 'P2') and in situ polymerized vinyltoluene (PVT) that is phase stable and mechanically robust at any blend ratio. The gamma-ray light yield increases nearly linearly across the composition range, to 16 400 photons/MeV at 75 wt.% P2. These materials are also capable of performing γ/n pulse shape discrimination (PSD), and between 20% and 50% P2 loading is competitive with the PSD quality of commercially available plastic scintillators. The 137Cs scintillation rise and decay times are sensitive to P2 loading and approach the values for 'pure' P2. Additionally, the radiation detection performance of P2-PVT blends can be made stable in 60 °C air for at least 1.5 months with the application of a thin film of poly(vinylalcohol) to the scintillator surfaces.
Sandia National Laboratories is developing a new method for detecting penetration of tamper - indicating enclosures (TIEs). This method incorporates the use of "bleeding" materials (analogous to visually obvious, colorful bruised skin that doesn't heal) into the design of TIEs. As designed, it will allow inspectors to use simple visual observation to detect attempts to penetrate the external surfaces of a TIE, without providing adversaries the ability to repair damage. A material of this type can enhance tamper indication of current TIEs used to support treaty verification regimes. Current TIE inspections are time - consuming and rely on subjective visual assessment by an inspector, equipment such as eddy current or camera devices, or involve approaches that may be limited due to application environment. The complexities and requirements that volumetric sealing methods (or TIEs) must address are: (1) enclosures that are non - standard in size/shape; (2) enclosures that may be inspectorate - or facility - owned; (3) finding tamper attempts that are difficult and time consuming for an inspector to locate; (4) enclosures that are reliable and durable enough to survive the conditions that exist in the operating environment (including facility handling); and (5) methods that prevent adversaries from repairing penetrations. Early project R&D [1] focused on encapsulated transition metals. Due to the challenges associated with the transition metal - based approach, a mitigation approach was investigated resulting in two separate research paths — one that involves fabricating custom TIE molds that meet the specific (size and shape) needs of safeguards equipment a nd one that can be deployed as a sprayed on or painted coating to an existing TIE or surface. The "custom mold" approach is based on creating thin layers of materials that , when penetrated, expose an inner material to O2 which causes an irreversible color change. The "in-situ coating" approach is based on applying a sensor solution containing color changing microcapsules that bleed when the microcapsule is ruptured. The anticipated benefits of this work are passive, flexible, scalable, robust , cost-effective TIEs with visually obvious responses to tamper attempts. This provides more efficient and effective monitoring , as inspectors will require little or no additional equipment and will be able to detect tamper without extensive time - consuming visual examination. Applications include custom TIEs (cabinets , equipment enclosures or seal bodies ), or spray-coating/painting onto facility-owned items, walls or structures, or circuit boards. The paper describes research and testing completed to-date on the method and integration of select system components.
Sandia National Laboratories is developing a way to visualize molecular changes that indicate penetration of a tamper-indicating enclosure (TIE). Such "bleeding" materials (analogous to visually obvious, colorful bruised skin that doesn't heal) allows inspectors to use simple visual observation to readily recognize that penetration into a material used as a TIE has been attempted, without providing adversaries the ability to repair damage. Such a material can significantly enhance the current capability for TIEs, used to support treaty verification regimes. Current approaches rely on time-consuming and subjective visual assessment by an inspector, external equipment, such as eddy current or camera devices, or active approaches that may be limited due to application environment. The complexity of securing whole volumes includes: (1) enclosures that are non-standard in size/shape; (2) enclosures that may be inspectorate- or facility-owned; (3) tamper attempts that are detectable but difficult or timely for an inspector to locate; (4) the requirement for solutions that are robust regarding reliability and environment (including facility handling); and (5) the need for solutions that prevent adversaries from repairing penetrations. The approach is based on a transition metal ion solution within a microsphere changing color irreversibly when the microsphere is ruptured. Investigators examine 3D printing of the microspheres as well as the spray coating formulation. The anticipated benefits of this work are passive, flexible, scalable, cost-effective TIEs with obvious and robust responses to tamper attempts. This results in more efficient and effective monitoring, as inspectors will require little or no additional equipment and will be able to detect tamper without extensive time-consuming visual examination. Applications can include custom TIEs (cabinets or equipment enclosures), spray-coating onto facility-owned items, spray-coating of walls or structures, spray-coatings of circuit boards, and 3D-printed seal bodies. The paper describes research to-date on the sensor compounds and microspheres.
Here we are investigating the inclusion of organotin compounds in polystyrene material to improve plastic scintillators full gamma-ray energy sensitivity with the ultimate goal of achieving spectroscopy. Accurate evaluation of the relative light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical processes used in the scintillators development and assess the scintillation efficiencies of the newly produced scintillators. Full gamma-ray energy peak in the measured gamma-ray spectrum, resulting from total absorption of gamma-ray energy, would be ideal in assessing the relative light yield. However, the significant number of new samples we are producing for investigation lead us to the possibility of using the Compton edge as an alternate spectral feature that can be exploited for expeditious characterization of the relative light yield in plastic scintillators. In this study we present a spectra gain matching approach, using a spectrum rebinning, for accurate relative light yield measurement using the Compton edge.
In this work, we report the synthesis and inclusion of rationally designed organotin compounds in polystyrene matrices as a route towards plastic scintillators capable of gamma-ray spectroscopy. Tin loading ratios of up to 15% w/w have been incorporated, resulting in photopeak energy resolution values as low as 10.9% for 662 keV gamma-rays. Scintillator constituents were selected based upon a previously reported distance-dependent quenching mechanism. Data obtained using UV-Vis and photoluminescence measurements are consistent with this phenomenon and are correlated with the steric and electronic properties of the respective organotin complexes. We also report fast scintillation decay behavior that is comparable to the quenched scintillators 0.5% trans-stilbene doped bibenzyl and the commercial plastic scintillator BC-422Q-1%. These observations are discussed in the context of practical considerations such as optical transparency, ease-of-preparation/scale-up, and total scintillator cost.
Currently we are investigating the inclusion of organotin compounds in polystyrene material to improve plastic scintillators full gamma-ray energy sensitivity with the ultimate goal of achieving spectroscopy. Accurate evaluation of light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical process used in the scintillators development. Full gamma-ray energy peak in measured gammaray spectrum, resulting from total absorption of gamma-ray energy, would be ideal in evaluating the light yield from the new scintillators. However, full energy sensitivity achieved thus far is not statistically viable for fast and accurate light yield energy calibration from the new scintillators. The Compton edge in measured gamma-ray spectrum has been found as an alternate gamma-ray spectrum feature that can be exploited for characterizing the light yield energy from the newly developed plastic scintillators. In this study we present technique implemented for accurate light yield energy calibration using the Compton edge. Results obtained were very encouraging and promise the possibility of using the Compton edge for energy calibration in detectors with poor energy resolution such as plastic and liquid scintillators.