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A holographic recording medium comprising a conductive substrate, a photoconductive layer and an electrically alterable layer of a linear, low molecular weight hydrocarbon polymer has improved fatigue resistance. An acrylic barrier layer can be interposed between the photoconductive and electrically alterable layers.
A holographic recording medium comprising a conductive substrate, a photoconductive layer and an electrically alterable layer of a linear, low molecular weight hydrocarbon polymer has improved fatigue resistance. An acrylic barrier layer can be interposed between the photoconductive and electrically alterable layers.
Vacuum insulation panels (VIPs) have an extremely high thermal resistance of around R35/inch, which makes them ideal for building envelope retrofits and prefabricated construction with space constraints. However, the barrier film that maintains the vacuum and thermal performance of the panel can be easily damaged during transportation, installation, and service life. Oak Ridge National Laboratory (ORNL) has developed a self-healable barrier film for VIPs that instantly self-heals damages caused by punctures. The multi-layer barrier film is manufactured using roll-to-roll (R2R) methods. The self-healing barrier film prevents loss of vacuum in VIPs and maintains the exceptional thermal insulation performance. Enhanced durability of VIP by self-healable barrier film and establishing the commercialization path will increase the use of VIPs, thus reducing overall energy usage of buildings. This project has fine-tuned the slurry chemistry of the self-healing components and transitioned the R2R manufacturing trials from mid-scale lab equipment to large-scale industrial equipment for de-risking the technology for commercialization with our TCF CRADA partner, FLEXcon.
The plating sequences Pd-Cr-Cu and Pd-Ni-Cu are demonstrated. The surface was sensitized with a 50 A-thick Pd layer obtained from an immersion bath. After 15 min heating at 400 C in N2, a thin barrier layer of either Cr or Ni was deposited from electroless baths operated at temperatures around 90 C. The sintering process was repeated, and a thin copper layer of 500 A was deposited by electroless means. An electrolytic copper bath was used to build the copper layer to 3-4 micron thicknesses. Cells with good I-V curves were obtained, and the all-plated contacts had good adhesion. Preliminary cost estimates show that the process costs approximately 12 cents per watt excluding the cost of the masking procedure.
Current encapsulation architectures for thin-film metal halide perovskite do not adequately eliminate all ambient stressors. Here, we develop low transmission rate barrier layers using atomic layer deposited (ALD) aluminum oxide grown directly on the completed photovoltaic (PV) device stack to provide an additional seal, prior to full packaging. We investigate the effect of deposition temperature and oxidant chemistries on the barrier growth for protection of perovskite photovoltaic devices. We characterize the layers individually, then integrate into devices to detail the tradeoff between protection and deposition compatibility. To enhance compatibility and impermeability, we present an approach using water as the aluminum oxidant during nucleation and switching from water to ozone for the remainder of the growth. At 50 nm, the barrier results in a water vapor transmission rate (WVTR) of 4.5·10 −4 g/m 2 /day, and 1,000-hour device stability under 45°C with 85% relative humidity without further packaging. This barrier provides sufficient protection to enable minimal degradation of the perovskite solar cells while completely submerged in water for 140 minutes. Additionally, we characterize the oxygen transmission rate (OTR) to be 0.49 cm 3 /m 2 /day at 23°C and 0% relative humidity, which is 1.5 orders of magnitude improvement over the OTR of the current encapsulation.
A proof-of-concept device is being developed for hydrogen gas production based on water-splitting redox reactions facilitated by cobalt tetra-aryl porphyrins (Co[TArP]) catalysts stacked on carbon nanotubes (CNTs) that are grown on n-doped silicon substrates. The operational principle of the proposed device is based on conversion of photoelectron energy from sunlight into chemical energy, which at a later point, can be turned into electrical and mechanical power. The proposed device will consist of a degenerately n-doped silicon substrate with Si posts covering the surface of a 4-in. (approximately equal to 10cm) wafer. The substrate will absorb radiation, and electrons will move radially out of Si to CNT. Si posts are designed such that the diameters are small enough to allow considerable numbers of electrons to transport across to the CNT layer. CNTs will be grown on top of Si using conformal catalyst (Fe/Ni) deposition over a thin alumina barrier layer. Both metallic and semiconducting CNT will be used in this investigation, thus allowing for additional charge generation from CNT in the IR region. Si post top surfaces will be masked from catalyst deposition so as to prevent CNT growth on the top surface. A typical unit cell will then consist of a Si post covered with CNT, providing enhanced surface area for the catalyst. The device will then be dipped into a solution of Co[TArP] to enable coating of CNT with Co(P). The Si/CNT/Co [TArP] assembly then will provide electrons for water splitting and hydrogen gas production. A potential of 1.23 V is needed to split water, and near ideal band gap is approximately 1.4 eV. The combination of doped Si/CNT/Co [TArP] will enable this redox reaction to be more efficient.
ESA and NASA recently selected two 5 m cutoff Teledyne H2RG sensor chip assemblies (SCA) for flight on the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). These HgCdTe SCAs incorporate Teledynes improved barrier layer design that eliminates the degradation that affected earlier JWST H2RGs(Rauscher et al. 2012a). The better indium barrier, together with other design changes, has improved the performance and reliability of JWSTs SCAs. In this article, we describe the measured performance characteristics that most directly affect scientific observations including read noise, total noise, dark current, quantum efficiency (QE), and image persistence. As part of measuring QE, we measured the quantum yield as a function of photon energy,, and found that it exceeds unity for photon energies E (2.65.2) Eg, where Eg is the HgCdTe bandgap energy. This corresponds to. 2 m for NIRSpecs 5 m cutoff HgCdTe. Our measurements agree well with a previous measurement by McCullough et al. (2008) for. 1.3. For 1.3, we find a slower increase in with photon energy than McCullough et al. did. However, and as McCullough et al. note, their two state model of the yield process is not valid for large 1.
A method has been devised to enable the fabrication of lightweight pressure vessels from multilayer composite materials. This method is related to, but not the same as, the method described in gMaking a Metal- Lined Composite-Overwrapped Pressure Vessel h (MFS-31814), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 59. The method is flexible in that it poses no major impediment to changes in tank design and is applicable to a wide range of tank sizes. The figure depicts a finished tank fabricated by this method, showing layers added at various stages of the fabrication process. In the first step of the process, a mandrel that defines the size and shape of the interior of the tank is machined from a polyurethane foam or other suitable lightweight tooling material. The mandrel is outfitted with metallic end fittings on a shaft. Each end fitting includes an outer flange that has a small step to accommodate a thin layer of graphite/epoxy or other suitable composite material. The outer surface of the mandrel (but not the fittings) is covered with a suitable release material. The composite material is filament- wound so as to cover the entire surface of the mandrel from the step on one end fitting to the step on the other end fitting. The composite material is then cured in place. The entire workpiece is cut in half in a plane perpendicular to the axis of symmetry at its mid-length point, yielding two composite-material half shells, each containing half of the foam mandrel. The halves of the mandrel are removed from within the composite shells, then the shells are reassembled and bonded together with a belly band of cured composite material. The resulting composite shell becomes a mandrel for the subsequent steps of the fabrication process and remains inside the final tank. The outer surface of the composite shell is covered with a layer of material designed to be impermeable by the pressurized fluid to be contained in the tank. A second step on the outer flange of each end fitting accommodates this layer. Depending on the application, this layer could be, for example, a layer of rubber, a polymer film, or an electrodeposited layer of metal. If the fluid to be contained in the tank is a gas, then the best permeation barrier is electrodeposited metal (typically copper or nickel), which can be effective at a thickness of as little as 0.005 in (.0.13 mm). The electrodeposited metal becomes molecularly bonded to the second step on each metallic end fitting. The permeation-barrier layer is covered with many layers of filament-wound composite material, which could be the same as, or different from, the composite material of the inner shell. Finally, the filament-wound composite material is cured in an ov
Development, fabrication and applications of CdS solar cells are reviewed in detail. The suitability of CdS cells for large solar panels and microcircuitry, and their low cost, are emphasized. Developments are reviewed by manufacturer-developer. Vapor phase deposition of thin-film solar cells, doping and co-evaporation, sputtering, chemical spray, and sintered layers are reviewed, in addition to spray deposition, monograin layer structures, and silk screening. Formation of junctions by electroplating, evaporation, brushing, CuCl dip, and chemiplating are discussed, along with counterelectrode fabrication, VPD film structures, the Cu2S barrier layer, and various photovoltaic effects (contact photovoltage, light intensity variation, optical enhancement), and various other CdS topics.
The importance of thermal contact resistance between layers in heat transfer through two layer, plasma sprayed, thermal barrier coatings applied to turbine vanes was investigated. Results obtained with a system of NiCrAlY bond and yttria stabilized zirconia ceramic show that thermal contact resistance between layers is negligible. These results also verified other studies which showed that thermal contact resistance is negligible for a different coating system of NiCr bond calcia stabilized zirconia ceramic. The zirconia stabilized ceramic thermal conductivity data scatter presented in the literature is ?20 to -10 percent about a curve fit of the data. More accurate predictions of heat transfer and metal wall temperatures are obtained when the thermal conductivity values are used at the ?20 percent level.
We have performed a series of experiments using an ocean model to study the sensitivity of tropical Pacific Ocean to variations in precipitation induced freshwater fluxes. Variations in these fluxes arise from natural causes on all time scales. In addition, estimates of these fluxes are uncertain because of differences among measurement techniques. The model used is a quasi-isopycnal model, covering the Pacific from 40 S to 40 N. The surface forcing is constructed from observed wind stress, evaporation, precipitation, and surface temperature (SST) fields. The heat flux is produced with an iterative technique so as to maintain the model close to the observed climatology, but with only a weak damping to that climatology. Climatological estimates of evaporation are combined with various estimates of precipitation to determine the net surface freshwater flux. Results indicate that increased freshwater input decreases salinity as expected, but increases temperatures in the upper ocean. Using the freshwater flux estimated from the Microwave Sounding Unit leads to a warming of up to 0.6 C in the western Pacific over a case with zero net freshwater flux. SST is sensitive to the discrepancies among different precipitation observations, with root-mean-square differences in SST on the order of 0.2-0.3 C. The change in SST is more pronounced in the eastern Pacific, with differences of over 1 C found among the various precipitation products. Interannual variation in precipitation during El Nino events leads to increased warming. During the winter of 1982-83, freshwater flux accounts for about 0.4 C (approximately 10-15% of the maximum warming) of the surface warming in the central-eastern Pacific. Thus, the error of SST caused by the discrepancies in precipitation products is more than half of the SST anomaly produced by the interannual variability of observed precipitation. Further experiments, in which freshwater flux anomalies are imposed in the western, central, and eastern Pacific, show that the influence of net freshwater flux is also spatially dependent. The imposition of freshwater flux in the far western Pacific leads to a trapping of salinity anomaly to the surface layers near the equator. An identical flux imposed in the central Pacific produces deeper and off-equatorial salinity anomalies. The contrast between these two simulations is consistent with other simulations of the western Pacific barrier layer information.
Silicon carbide (SiC) based gas sensors have the ability to meet the needs of a range of aerospace propulsion applications including emissions monitoring, leak detection, and hydrazine monitoring. These applications often require sensitive gas detection in a range of environments. An effective sensing approach to meet the needs of these applications is a Schottky diode based on a SiC semiconductor. The primary advantage of using SiC as a semiconductor is its inherent stability and capability to operate at a wide range of temperatures. The complete SiC Schottky diode gas sensing structure includes both the SiC semiconductor and gas sensitive thin film metal layers; reliable operation of the SiC-based gas sensing structure requires good control of the interface between these gas sensitive layers and the SiC. This paper reports on the development of SiC gas sensors. The focus is on two efforts to better control the SiC gas sensitive Schottky diode interface. First, the use of palladium oxide (PdOx) as a barrier layer between the metal and SiC is discussed. Second, the use of atomically flat SiC to provide an improved SiC semiconductor surface for gas sensor element deposition is explored. The use of SiC gas sensors in a multi-parameter detection system is briefly discussed. It is concluded that SiC gas sensors have potential in a range of propulsion system applications, but tailoring of the sensor for each application is necessary.
Fabricated on InP substrates, devices operate at room temperature, emitting at wavelengths near 1.8 micrometers. By suitable modification of structure of devices, possible to achieve operation at any wavelength from 1.6 to 2.5 micrometers: this range important in lidar and in remote sensing of atmospheric gases. Quantum-well and barrier layers sandwiched between two 60-nm-thick layers of lattice-matched InGaAs. InGaAs layers sandwiched between two 150-nm-thick layers of InGaAsP. Those layers sandwiched, in turn, between InP substrate and InP cladding layer. Also layer of InGaAs atop InP cladding layers.
Using InGaAs for the base and InAlAs for the emitter and collector barriers, the first hot-electron transistor in this material system is fabricated. It is shown that 1.6 percent of the injected hot electrons can be transported ballistically through a 0.3 micron thick In(0.53)Ga(0.47)As plus 800-A-thick InAlAs barrier layer at 77 K giving rise to an average mean free path of 920 A. An energy spread of 130 MeV was observed for the ballistic electrons injected at about 700 MeV above the thermal equilibrium conditions. The value of collector barrier heights measured are in reasonable agreement with those deduced independently from thermionic emission studies in InGaAs gate, InAlAs/InGaAs capacitor structures.
In this study, the degradation of the solid-oxide fuel cell (SOFC) nickel-yttria stabilized zirconia anode under decamethyltetrasiloxane (L4) contamination is examined with experiments and modeling. A model is developed for the polarization losses based on the charge transfer coefficient,α, and diffusion layer thickness,δ, and fitted to the experimental data to understand how the siloxane degrades the SOFC performance with time. The results of the model indicate that the total polarization losses increase approximately 44% over the course of the 180 min experiment at 350 mA cm −2 . Activation losses dominate the polarization losses initially but decrease in their total contribution while concentration losses increase. Scanning electron microscopy (SEM) with wavelength dispersive X-ray spectroscopy (WDS) elemental mapping indicates that silicon deposition is highest at the outer edge of the anode and forms a barrier layer to fuel diffusion, increasing concentration losses. When the model is applied to other previous D4 and L4 siloxane experiments conducted over a period of 40 h, similar trends in polarization losses are observed. Polarization losses increase more rapidly with D4 compared to L4 siloxane contamination, with concentration losses increasing the fastest with both types of siloxane.
Electrochemical interfaces are dynamic systems, evolving based on their local environment and reactant surface structures. The electrode-electrolyte interface in Li-ion batteries can be protective, limiting parasitic reactions with the electrolyte to passivate the surface [1]. Additionally, this interphase has an impact on the Li-ion transport through that layer based on its composition, bonding environment, and thickness. These parameters are challenging to collect and may vary depending on the electrode surface site investigated relative to its spatial position in a coin cell. This study will detail a multiscale cryogenic electron microscopy approach where millimeter-scale cross-sections through the coin cell batteries were made using a cryogenic stage within a fs-laser plasma focused ion beam (laser PFIB) with complementary energy dispersive X-ray spectroscopy able to detect variations in the composition at electrode interfaces [2]. Microscale cross-sectioning and lamella sample preparation of battery electrodes was conducted at the Center for Integrated Nanotechnologies using a Ga-ion focused ion beam (FIB) with air-free and cryo-transfer [3], followed by nanoscale mapping of composition and bonding within the CEI through cryo-scanning transmission electron microscopy (cryo-STEM) electron energy loss spectroscopy [4]. This multiscale approach enabled identification of millimeter-scale features of a battery stack with visualization of degradation in electrodes such as cracks in cathode particles, gas evolution, and SEI evolution; microscale interfacial characteristics, such as heterogeneity in the SEI or barrier layer and identification of electrolyte networks to the electrode surfaces; and nanoscale measurement of the CEI thickness, mapping of transition metal bonding within the cathode particles to identify loss of active materials, and identification of beneficial electrolyte additives incorporated into the CEI structure. This multiscale approach allows for a statistical understanding of the primary mechanisms and parasitic degradation pathways that impact performance by limiting the ion transport pathways within Li+ batteries.
Understanding the onset of degradation in the air electrode within solid oxide electrolysis cells (SOECs), and the subsequent impact on cell performance, is a critical step in mitigating the performance losses and stability issues of SOECs. In an effort to identify early onset degradation phenomena, SOECs were characterized as fabricated and after testing potentiostatically at 1.3 V for 1000 h at 750 °C. SOEC air electrodes composed of a 1:1 composite of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (6428-LSCF) and Gd 0.1 Ce 0.9 O 1.95 (GDC) were studied using synchrotron X-ray diffraction (XRD), scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS), and X-ray absorption near-edge spectroscopy (XANES) to evaluate the changes in the air electrode structurally and chemically. These techniques show the migration of Sr species from the air electrode through pores in the GDC barrier layer, progressing to the electrolyte boundary, where it accumulates and reacts with (Zr 0.84 Y 0.16 )O 2–δ (YSZ) to form SrZrO 3 . Microscopy results are paired with atomistic simulations to better understand the relationship between the thermodynamic instability of 6428-LSCF and cell fabrication/testing conditions. First-principles calculations reveal that LSCF-6428 is not stable during cell manufacturing and testing conditions, which supports the experimental identification of secondary phases in both as-fabricated and tested cells. Together, these results demonstrate that the challenging environments encountered by SOECs during cell manufacturing and operation lead to instabilities of the target 6428-LSCF anode material and underscore the need for more durable, high-performing SOEC components.
Displacement damage from particle radiation increases the threshold current of semiconductor lasers, impeding the deployment of photonic systems in harsh radiation environments. Replacing conventional quantum well (QW) gain regions with quantum dots (QDs) has been shown to suppress the radiation-induced increase in threshold current owing to three-dimensional carrier confinement, which effectively segregates charge carriers away from radiation-induced defects. However, radiation-induced change in threshold current is also affected by extrinsic design elements of a laser, such as photon lifetime, and therefore provides only a partial assessment of the radiation hardness. In this work, we advance the understanding of the radiation resiliency of InAs QD lasers by extracting the change in the nonradiative recombination rate after radiation exposure, which provides a more fundamental assessment of the intrinsic radiation hardness of InAs QD gain regions. We find that carriers that populate InAs QD states have a nonradiative recombination rate that is over an order-of-magnitude less sensitive to neutron radiation relative to carriers in InGaAsP QWs. InAs QD lasers must be designed such that carriers primarily occupy QD states, preventing carrier spillover into surrounding barrier layers to obtain the maximum benefit. Furthermore, we show that enhanced radiation hardness is observed in InAs QD lasers grown on both highly lattice-mismatched silicon substrates and native GaAs substrates, further broadening the appeal of InAs QD lasers as reliable light sources for photonic systems operating in harsh radiation environments.