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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Measurement and Analysis of Dose Rate Distribution in the Seismic Base-Isolation pit of the Electron Linac Oncology Facility - Paper 87

Recently electric linac oncology facilities incorporating seismic base-isolation structure have become very popular in Japan to prevent strong impact to the equipment by the earthquakes. When the boundary of the controlled area is set below the base-isolated foundations, additional shielding of iron plate is needed and the cost for shielding sometimes increases up to $1 M Since no one usually accesses underneath the treatment room, except short maintenance period for base-isolation structure, it is reasonable to set the boundary around the downstairs room (pit) by fence. However, it is very difficult to estimate the dose rate of new boundary by using the simple shielding calculation method, because of rotating gantry head and effect of scattering radiation in the base-isolation floor. In this study detail calculations by using Monte-Carlo calculation code MCNP5 have been performed to find out the practical shielding design. To be more specific, investigation for the complicated behavior of photons in the 'pit' have been performed by the analysis, i.e. (1) How much can we reduce the thickness of additional iron plate?, (2) Which angle of the beam direction will influence the most to the dose rate at the new boundary?, (3) Which component of the radiation is dominant at the new boundary? We also verified the calculated results by the measurement. We have performed the analysis of the behavior of photons in the pit and found out no additional iron shielding was necessary, which carried out an extreme reduction of costs. The main contribution to the dose rate at the boundary was scattered photons in the case of 0- degree beam direction. Good agreement between calculated and measured results were obtained, and passed the examination by the authority. It is concluded that the Monte-Carlo calculation code MCNP5 is very effective for the optimistic design of the electron linac oncology facilities incorporating seismic base-isolation structure. (authors)

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Facile synthesis of QD-anchored composite particles with magnetite cluster cores ({sup n}Fe{sub 3}O{sub 4}@SiO{sub 2}@QDs)

Highlights: ► Triple layered Fe{sub 3}O{sub 4}/SiO{sub 2}/QDs were designed as fluorescent magnetic nanocomposites. ► Magnetite cluster-embedded silica exhibited strong and controllable magnetism. ► Effective conjugation between QDs and magnetic silica occurred at pH3. - Abstract: Magnetism-controlled fluorescent composite particles ({sup n}Fe{sub 3}O{sub 4}@SiO{sub 2}@QDs) were prepared as QD-anchored silica nanoparticles with magnetite cluster cores. First, citrate-capped magnetites (C-Fe{sub 3}O{sub 4}) were prepared by the co-precipitation method and subsequently complexed with 3-aminopropyl-trimethoxysilane (APTMS) at room temperature, consequently leading to the formation of magnetite clusters (A-{sup n}Fe{sub 3}O{sub 4}) with alkoxy terminated interfaces. The sol–gel reaction between A-{sup n}Fe{sub 3}O{sub 4} and tetraethoxysilane (TEOS) produced the core-shell {sup n}Fe{sub 3}O{sub 4}@SiO{sub 2}. The resulting core-shell particles exhibited superparamagnetic properties and controllable magnetism simply by adjusting the thickness of nonmagnetic silica layer. After then, amine-terminated {sup n}Fe{sub 3}O{sub 4}@SiO{sub 2} (NH{sub 2}–{sup n}Fe{sub 3}O{sub 4}@SiO{sub 2}) was conjugated with carboxy quantum dots (QDs) using an EDC coupling agent. The QD conjugation with NH{sub 2}–{sup n}Fe{sub 3}O{sub 4}@SiO{sub 2} of lower pH exhibited the higher photoluminescence (PL) intensity, and the resulting composite particles ({sup n}Fe{sub 3}O{sub 4}@SiO{sub 2}@QDs) can be a useful biomedical agent. This chemical strategy can be further applied to prepare the core-shell magnetic nanostructure with various oxide layers for specific applications.

36 MATERIALS SCIENCE↗
NASA NTRS2013

Creating and Testing Simulation Software

The goal of this project is to learn about the software development process, specifically the process to test and fix components of the software. The paper will cover the techniques of testing code, and the benefits of using one style of testing over another. It will also discuss the overall software design and development lifecycle, and how code testing plays an integral role in it. Coding is notorious for always needing to be debugged due to coding errors or faulty program design. Writing tests either before or during program creation that cover all aspects of the code provide a relatively easy way to locate and fix errors, which will in turn decrease the necessity to fix a program after it is released for common use. The backdrop for this paper is the Spaceport Command and Control System (SCCS) Simulation Computer Software Configuration Item (CSCI), a project whose goal is to simulate a launch using simulated models of the ground systems and the connections between them and the control room. The simulations will be used for training and to ensure that all possible outcomes and complications are prepared for before the actual launch day. The code being tested is the Programmable Logic Controller Interface (PLCIF) code, the component responsible for transferring the information from the models to the model Programmable Logic Controllers (PLCs), basic computers that are used for very simple tasks.

Heinich, Christina M.↗
DOE OSTI2019

Design and thermomechanical properties of a γ' precipitate-strengthened Ni-based superalloy with high entropy γ matrix

A novel Ni-based superalloy was designed with γ' precipitate strengthening, controlled γ/γ' lattice misfit and high configurational entropy of the γ matrix for improved high temperature performance up to 800 degrees C. The alloy contains nano-sized γ' precipitates, MC and other grain boundary carbides. Three variants of the alloy were fabricated using vacuum induction melting, a computational-based homogenization cycle for reducing solidification segregation, and thermomechanical processing steps of forging followed by hot rolling to produce plates from which ASTM standard test specimens were extracted. Tensile testing at room temperature and elevated temperatures up to 800 degrees C revealed superior yield stress when compared to Nimonic 105 with good tensile strength values. Furthermore, the three alloys are machinable with maximum stresses comparable to standard practices as determined using deformation mechanisms maps obtained from Gleeble testing and EBSD analysis. Due to the composition of the experimental alloys falling outside the typical range used to populate thermodynamic databases, differences in phase predictions and related temperatures were observed between the experiment and Thermo-Calc predictions. Here, the γ' forming elements Ti and Nb had a similar effect on the γ' precipitates and indirectly contributed to changing the entropy of the γ matrix. Based on the results of this study, these alloys have the potential for use at 800 degrees C in energy structural applications. Definitions related to this novel class of alloys are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design of Graphene/Ionic Liquid Composites for Carbon Capture

Pore size is a crucial factor impacting gas separation in porous separation materials, but how to control the pore size to optimize the separation performance remains a challenge. Here, we propose a design of graphene/ionic liquid composites with tunable slit pore sizes, where cations and anions of ionic liquids are intercalated between graphene layers. By varying the sizes of the ions, we show from first-principles density functional theory calculations that the accessible pore size can be tuned from 3.4 to 6.0 Å. Grand canonical Monte Carlo simulations of gas sorption find that the composite materials possess high CO 2 uptake at room temperature and 1 bar (up to ~8.5 mmol/g). Further simulations of the sorption of gas mixtures reveal that high CO 2 /N 2 and CO 2 /CH 4 adsorption selectivities can be obtained when the accessible pore size is <5 Å. This work suggests a new strategy to achieve tunable pore sizes via the graphene/IL composites for highly selective CO 2 /N 2 and CO 2 /CH 4 adsorption.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Deformation T-Cup: A new multi-anvil apparatus for controlled strain-rate deformation experiments at pressures above 18 GPa

A new multi-anvil deformation apparatus, based on the widely used 6-8 split-cylinder, geometry, has been developed which is capable of deformation experiments at pressures in excess of 18 GPa at room temperature. In 6-8 (Kawai-type) devices eight cubic anvils are used to compress the sample assembly. In our new apparatus two of the eight cubes which sit along the split-cylinder axis have been replaced by hexagonal cross section anvils. Combining these anvils hexagonal-anvils with secondary differential actuators incorporated into the load frame, for the first time, enables the 6-8 multi-anvil apparatus to be used for controlled strain-rate deformation experiments to high strains. Testing of the design, both with and without synchrotron-X-rays, has demonstrated the Deformation T-Cup (DT-Cup) is capable of deforming 1–2 mm long samples to over 55% strain at high temperatures and pressures. To date the apparatus has been calibrated to, and deformed at, 18.8 GPa and deformation experiments performed in conjunction with synchrotron X-rays at confining pressures up to 10 GPa at 800 °C.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1980

Solar hot water system installed at Days Inn Motel, Dallas, Texas (Forrest Lane)

The solar system was designed to provide 65 percent of the total Domestic Hot Water (DHW) demand. The liquid flat plate (water) collector (1,000 square feet) system automatically drains into the 1,000 gallon steel storage tank located in the mechanical room when the pump is not running. Heat is transferred from the storage tank to DHW tanks through a tube and shell heat exchanger. A circulating pump between the DHW tanks and the heat exchanger enables solar heated water to help make DHW tank standby losses. All pumps are controlled by differential temperature.

Source record↗
DOE OSTI2021

Dynamic flow stress of pure polycrystalline aluminum: Pressure-shear plate impact experiments and extension of dislocation-based modeling to large strains

The dynamic thermo-mechanical behavior of pure aluminum has attracted renewed interest lately due to experimental observations of an anomalous increase in Hugoniot Elastic Limit (HEL) at incipient plasticity and elevated temperatures in polycrystalline pure metals. In context of current dislocation-mediated plasticity models for metals, this increase in dynamic strength is indicative of a transition in the rate controlling mechanism for dislocation glide from being thermally assisted to phonon-drag restricted due to increase in phonon viscosity at elevated temperatures. Though these studies have helped to shed light on these important mechanisms operative in FCC metals at incipient plasticity, the extent to which they contribute to flow stress, particularly at larger strains, remains unclear. Here, we address these questions through a combined experimental and modeling effort focused on investigating the evolution of dynamic flow stress in polycrystalline aluminum using experimental data gathered from a series of combined pressure-and-shear plate impact (PSPI) experiments designed to reveal the flow stress of pure aluminum at strain rates ~ 10 5 /s, plastic strains of up to 40% and temperatures ranging from room to 866 K. In all cases, the flow stress of aluminum, as inferred from the measured transverse particle velocity histories at the free surface of an elastic tungsten carbide target plate, reveals saturation with increasing plastic strains at stress levels that decrease with increasing test temperatures. Numerical simulations are performed to correlate the experimentally observed temperature and strain rate dependence of flow stress at small and large plastic strains using the Austin-McDowell dislocation-mediated plasticity model parametrized to normal plate impact experiments conducted in an earlier study by Zaretsky and Kanel (2012). Extensions to the model are made to better represent dynamic behavior of pure aluminum at larger plastic strains as observed in elevated temperature split Hopkinson Pressure bar (SPHB) experiments of Samanta (1971) and Lindholm and Yeakly (1965), and the combined pressure-and-shear plate-impact experiments conducted in the present study. The main theoretical extension to the Austin-McDowell model made in this paper is the introduction of a new rate- and temperature- dependent dynamic recovery function, which can potentially allow for an effective reduction in the rate of accumulation of dislocations at large plastic strains. The numerical predictions of the revised and re-calibrated plasticity model are brought into agreement with the experimental observations, correlating sufficiently well with dynamic yield stress at incipient plasticity and the flow stress levels at larger plastic strains, plastic strain rates in the range 10 3 – 10 6 /s, and elevated temperatures up to near melt. The model, in concert with the experimental measurements, suggests that at incipient plasticity the rate governing mechanism for plastic flow is phonon-drag restricted dislocation glide, whereas, at higher magnitudes of plastic strain, it transitions to stress-assisted thermally activated glide. The transition between these two rate governing mechanisms is controlled by the evolution of dislocations throughout the deformation process.

36 MATERIALS SCIENCE↗
DOE OSTI2019

P3HT-Based Polymer Solar Cells with 8.25% Efficiency Enabled by a Matched Molecular Acceptor and Smart Green-Solvent Processing Technology

Here, a novel molecular acceptor of TrBTIC (2,7,12-tris((2-(3-oxo-2,3-dihydroinden- 1-ylidene)malononitrile-7-benzothiadiazole-2-)truxene) is designed by attaching the 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrilebenzothiadiazole (BTIC) electron-deficient unit to an electron-rich truxene core. TrBTIC has excellent solubility in common solvents and features good energy level matching with poly(3-hexylthiophene) (P3HT). Interestingly, P3HT can be readily dissolved in warm 1,2,4-trimethylbenzene (TMB), a green solvent, but crystallizes slowly with long-term aging in TMB at room temperature. A prephase separation can thus occur before active blend film deposition, and the separation degree can be easily controlled by varying the aging time. After 40 min of aging, the resulting active blend has the most appropriate phase separation with uniform nanowires, which forms favorable interpenetrating networks for exciton dissociation and charge transport. As a result, the device performance is improved from 6.62% to 8.25%. Excitingly, 8.25% is a new record for P3HT-based solar cells. The study not only provides an efficient nonfullerene acceptor for matching P3HT donors but also develops a promising processing technology to realize high-performance P3HT-based polymer solar cells with an efficiency over 8%.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The inverse problems of wing panel manufacture processes

It is shown that inverse problems of steady-state creep bending of plates in both the geometrically linear and nonlinear formulations can be represented in a variational formulation. Steady-state values of the obtained functionals corresponding to the solutions of the problems of inelastic deformation and springback are determined by applying a finite element procedure to the functionals. Optimal laws of creep deformation are formulated using the criterion of minimizing damage in the functionals of the inverse problems. The formulated problems are reduced to the problems solved by the finite element method using MSC.Marc software. Currently, forming of light metals poses tremendous challenges due to their low ductility at room temperature and their unusual deformation characteristics at hot-cold work: strong asymmetry between tensile and compressive behavior, and a very pronounced anisotropy. We used the constitutive models of steady-state creep of initially transverse isotropy structural materials the kind of the stress state has influence. The paper gives basics of the developed computer-aided system of design, modeling, and electronic simulation targeting the processes of manufacture of wing integral panels. The modeling results can be used to calculate the die tooling, determine the panel processibility, and control panel rejection in the course of forming.

36 MATERIALS SCIENCE↗
NASA NTRS1991

A simulated lightning effects test facility for testing live and inert missiles and components

Details of a simulated lightning effects test facility for testing live and inert missiles, motors, and explosive components are described. The test facility is designed to simulate the high current, continuing current, and high rate-of-rise current components of an idealized direct strike lightning waveform. The Lightning Test Facility was in operation since May, 1988, and consists of: 3 separate capacitor banks used to produce the lightning test components; a permanently fixed large steel safety cage for retaining the item under test (should it be ignited during testing); an earth covered bunker housing the control/equipment room; a charge/discharge building containing the charging/discharging switching; a remotely located blockhouse from which the test personnel control hazardous testing; and interconnecting cables.

Craven, Jeffery D.↗
NASA NTRS2004

Advanced Control Surface Seal Development for Future Space Vehicles

NASA s Glenn Research Center (GRC) has been developing advanced high temperature structural seals since the late 1980's and is currently developing seals for future space vehicles as part of the Next Generation Launch Technology (NGLT) program. This includes control surface seals that seal the edges and hinge lines of movable flaps and elevons on future reentry vehicles. In these applications, the seals must operate at temperatures above 2000 F in an oxidizing environment, limit hot gas leakage to protect underlying structures, endure high temperature scrubbing against rough surfaces, and remain flexible and resilient enough to stay in contact with sealing surfaces for multiple heating and loading cycles. For this study, three seal designs were compared against the baseline spring tube seal through a series of compression tests at room temperature and 2000 F and flow tests at room temperature. In addition, canted coil springs were tested as preloaders behind the seals at room temperature to assess their potential for improving resiliency. Addition of these preloader elements resulted in significant increases in resiliency compared to the seals by themselves and surpassed the performance of the baseline seal at room temperature. Flow tests demonstrated that the seal candidates with engineered cores had lower leakage rates than the baseline spring tube design. However, when the seals were placed on the preloader elements, the flow rates were higher as the seals were not compressed as much and therefore were not able to fill the groove as well. High temperature tests were also conducted to asses the compatibility of seal fabrics against ceramic matrix composite (CMC) panels anticipated for use in next generation launch vehicles. These evaluations demonstrated potential bonding issues between the Nextel fabrics and CMC candidates.

DeMange, J. J.↗
NASA NTRS2003

Advanced Control Surface Seal Development for Future Space Vehicles

NASA's Glenn Research Center (GRC) has been developing advanced high temperature structural seals since the late 1980s and is currently developing seals for future space vehicles as part of the Next Generation Launch Technology (NGLT) program. This includes control surface seals that seal the edges and hinge lines of movable flaps and elevons on future reentry vehicles. In these applications, the seals must operate at temperatures above 2000 F in an oxidizing environment, limit hot gas leakage to protect underlying structures, endure high temperature scrubbing against rough surfaces, and remain flexible and resilient enough to stay in contact with sealing surfaces for multiple heating and loading cycles. For this study, three seal designs were compared against the baseline spring tube seal through a series of compression tests at room temperature and 2000 F and flow tests at room temperature. In addition, canted coil springs were tested as preloaders behind the seals at room temperature to assess their potential for improving resiliency. Addition of these preloader elements resulted in significant increases in resiliency compared to seals by themselves and surpassed the performance of the baseline seal at room temperature. Flow tests demonstrated that the seal candidates with engineered cores had lower leakage rates than the baseline spring tube design. However, then the seals were placed on the preloader elements, the flow rates were higher as the seals were not compressed as much and therefore were not able to fill the groove as well. High temperature tests were also conducted to assess the compatability of seal fabrics against cermaic matrix composite (CMC) panels anticipated for use in next generation launch vehicles. These evaluations demonstrated potential bonding issues between the Nextel fabrics and CMC candidates.

DeMange, Jeffrey J.↗
DOE OSTI2021

Light–matter coupling in large-area van der Waals superlattices

Two-dimensional (2D) crystals have renewed opportunities in design and assembly of artificial lattices without the constraints of epitaxy. However, the lack of thickness control in exfoliated van der Waals (vdW) layers prevents realization of repeat units with high fidelity. Recent availability of uniform, wafer-scale samples permits engineering of both electronic and optical dispersions in stacks of disparate 2D layers with multiple repeating units. In this study, we present optical dispersion engineering in a superlattice structure comprising alternating layers of 2D excitonic chalcogenides and dielectric insulators. By carefully designing the unit cell parameters, we demonstrate greater than 90% narrow band absorption in less than 4 nm of active layer excitonic absorber medium at room temperature, concurrently with enhanced photoluminescence in square-centimetre samples. These superlattices show evidence of strong light–matter coupling and exciton–polariton formation with geometry-tuneable coupling constants. Our results demonstrate proof of concept structures with engineered optical properties and pave the way for a broad class of scalable, designer optical metamaterials from atomically thin layers.

2D Crystals↗
DOE OSTI2023

Biologically Cooling the Planet: A BRISK Approach that Directly Connects the Ground to Deep Space

Climate change is a grave threat to our ability to thrive and prosper on Earth. Accumulation of greenhouse gases in the atmosphere stifle the Earth’s ability to cool itself, which leads to a rise of the average temperature – Global warming. The planetary cooling is exclusively radiative – thermal radiation escapes into cold outer space via a flux of photons at the low-infrared range. The penetration of these photons through Earth’s atmosphere is dictated by atmospheric transparency, which, serendipitously possesses a window centered around the peak of the Plank spectrum for a black body at about room temperature – the average temperature of Earth. This window spanning about 8 --13 μm wavelengths allows most of the photons in this range to escape into the Cosmos carrying our planet’s heat away. The efficiency of this outer heat flux – and thus planet’s cooling ability – can be controlled via emissivity – a function of wavelength which multiplies the fundamental Plank spectrum of a black body at a given temperature. In the presence of non-trivial atmospheric transparency it can be shown that radiative cooling can be enhanced with properly “designed” emissivity function. For the last 100 years, or so, people have been looking into ways to engineer materials to take advantage of such enhancement for various cooling applications, from making ice to cool clothes, and substantial progress has been achieved, including cooling in direct sunlight. The beauty if this approach is that it is entirely passive – no energy input is required. The objective of this project was to investigate whether biological systems possess such advanced cooling capacity, developed via millennia of evolution, to enhance plant’s adaptation to a hot environment, to increase cooling capability, and possibly modulate spectral emissivities on short or long time scales. We wanted to know if BRISK (Biological Radiative Sky Cooling) occurs and to what extent. It is unknown whether biological systems can perform this "spectral redistribution." It is reasonable to expect, however, that they might: in particular, desert plants under high heat stress and arid conditions might evolve this mechanism in order to maintain a tolerable internal temperature. Our intended approach was twofold: extensive literature search and supporting experimental investigations on select plants. We obtained the answers from the former, while the latter proved to be more complicated to perform with required accuracy in the timespan/budget of a small seedling project. After one year of research, we concluded that among the plant species studied there seem to be no evidence of BRISK, but it’s not the end of the story. Our planet’s biosphere is immense, and the evolution is continuing. With our preliminary results and a better understanding of what to look for further discoveries await, considering the accelerated pace of infrared imaging and spectroscopy technology development, from microscopic to satellite-based studies of plants and canopies. In the end, Earth’s energy balance is ultimately tied to radiative cooling so that further investigation into this problem is directly tied to solving the Climate Change challenge.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1988

The Berkeley extreme ultraviolet calibration facility

The vacuum calibration facilities of the Space Sciences Laboratory, University of California at Berkeley are designed for the calibration and testing of EUV and FUV spaceborne instrumentation (spectral range 44-2500 A). The facility includes one large cylindrical vacuum chamber (3 x 5 m) containing two EUV collimators, and it is equipped with a 4-axis manipulator of angular-control resolution 1 arcsec for payloads weighing up to 500 kg. In addition, two smaller cylindrical chambers, each 0.9 x 1.2 m, are available for vacuum and thermal testing of UV detectors, filters, and space electronics hardware. All three chambers open into class-10,000 clean rooms, and all calibrations are referred to NBS secondary standards.

Welsh, Barry Y.↗
NASA NTRS2005

Amateur Cleanrooms: Costs May Not Offset Benefits

Contamination and Coatings Branch During my career at NASA, I have encountered a variety of cleanroom systems. With many projects, cost pressures and lack of adequate facilities have forced the managers to resort to amateur cleanrooms to manufacture spacecraft and instruments. These rooms are usually spaces that have been used for other purposes that are converted to cleanroom, usually without the assistance of a contamination control specialist. Often, scientists and engineers are successful in converting an area for experimental use. However, when the area is used for production, countless difficulties are encountered. This paper will document some of the disasters that I have personally witnessed and offer some guidelines for contamination professionals to follow if you are called upon to assist in the development of new cleanrooms. Cleanroom come in all shapes and sizes from special purpose mini-environments (such as flow benches) to large, expansive production facilities. These areas may require a variety of unit operations to be carried out within a short range of each other. The design of the cleanroom should account for compatibilities of these operations to protect the product and personnel. The level of cleanliness has traditionally been associated with the method of ventilation. However, just because and =ea has HEPA filters and greater that 20 air changes per hour does not mean that it is a cleanroom. Airflow is extremely complex; the only way to properly design a cleanroom is through the use of a computer based model. In the aerospace industry, few engineered cleanrooms are modeled. Modeling has been perceived as expensive; however, modern programs and fast computers are changing perception. It is the lack of appreciation for how air flow and location within a cleanroom affects the product that causes most of the problems I have experienced. Currently, the rules defining the best air flow design practices are based on simplistic historical data that are often wrong. The performance of a cleanroom is defined by a set of complex interactions between the airflow, sources of contamination and heat, position of the air terminals and exhausts as well as the objects occupying the space in question. These subtleties are almost never appreciated in the setup of amateur cleanrooms (and sadly, in some engineered cleanroom as well). Experience with the room, measurement of air flows in the room, and black light inspections can be used to

Ramsey, W. Lawrence↗
DOE OSTI2013

New insights into designing metallacarborane based room temperature hydrogen storage media

Metallacarboranes are promising towards realizing room temperature hydrogen storage media because of the presence of both transition metal and carbon atoms. In metallacarborane clusters, the transition metal adsorbs hydrogen molecules and carbon can link these clusters to form metal organic framework, which can serve as a complete storage medium. Using first principles density functional calculations, we chalk out the underlying principles of designing an efficient metallacarborane based hydrogen storage media. The storage capacity of hydrogen depends upon the number of available transition metal d-orbitals, number of carbons, and dopant atoms in the cluster. These factors control the amount of charge transfer from metal to the cluster, thereby affecting the number of adsorbed hydrogen molecules. This correlation between the charge transfer and storage capacity is general in nature, and can be applied to designing efficient hydrogen storage systems. Following this strategy, a search for the best metallacarborane was carried out in which Sc based monocarborane was found to be the most promising H{sub 2} sorbent material with a 9 wt.% of reversible storage at ambient pressure and temperature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗