Results 1 - 10 of 98
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[en] Claims have emerged recently, of high hydrogen storage capacities at room temperature and above, for carbons such as single-wall and multi-walled nanotubes. We have been unable to verify any claims of high capacities at room temperature and low pressure. For (10,10) single wall carbon nanotubes, we used a computer controlled Sievert's apparatus to measure an adsorption at RT of 0.07 wt% gravimetric density at 1 bar, typical of what is expected on the basis of BET surface area measurements for carbons. At high pressures of > 60 bar and temperatures of 80K gravimetric densities up to ∼ 8 wt% are obtained, but more typically ∼ 7 wt% after a few adsorption desorption cycles. These values and isotherm shapes can be attributed to rearrangement of the rope structure that is formed by condensed nanotubes. Certain fullerites can also exhibit adsorption/desorption cycle dependent capacity, ranging from 2.5 to 4 wt% at 80K and 120 bar. (author)
[en] Used as low-cost anode in the majority of lithium ion batteries, layered graphite has got critical issues. Owing to its low voltage operation, they reduce electrolyte by stealing lithium from cathode to form an SET (Solid Electrolyte Interphase), and pose fire risk from dendrite based short-circuit likely at times of fast charging or erroneous over-lithiation towards end of discharge. In this talk we are addressing this problems
[en] What existed first, the energy problem or the energy transition? For the clarification of this question the author gives a survey about the actual situation of our energy demand and the means and ways to its satisfaction. The reader learns to know the function of numerous energy transformers, from the wind mill via the automobile motor until the solar cell. The advantages and disadvantages of the different transformers are explained, just so their efficiencies and cost as well as the physical natural laws, which they must obey. A perpetuum mobile doesn't exist, but indeed an almost inexhaustible energy source, the sun, which can meet many thousandfold our demand, if we use it intelligently. Who has read this book can go confidently in each discussion about the energy problem and the energy transition.
[en] We have studied the sorption of hydrogen by 8 different carbon materials at pressures up to 11 MPa (1600 psi) and temperatures from -80oC to +500oC. Our samples include graphite flakes, Aldrich activated carbon, graphitized PYROGRAF vapor-grown carbon fibers (VGCF), etched PYROGRAF fibers, Showa-Denko VGCF, filaments grown from a FeNiCu alloy, and nanotubes from MER Corp. and Rice University. The results so far have been remarkably similar: very little hydrogen sorption. In fact, the sorption is so small that we must pay careful attention to calibration to get reliable answers. The largest sorption observed is less than 0.1 weight percent hydrogen at room temperature and 3.5 MPa. Furthermore, our efforts to activate these materials by reduction at high temperatures and pressures were also futile. These results cast serious doubts on any claims for large hydrogen sorption in carbon materials. (author)
[en] Phase change material (PCM) can store large amount of thermal energy at phase change temperature. Determination of thermophysical properties of PCM plays an important role in estimation of energy stored or released in storage device. Properties of PCM are key factors for designing a latent heat thermal energy storage system. This paper deals with the study of effect of heating/cooling rate on thermophysical properties, especially on melting temperature and latent heat of fusion /solidification. Results indicate that latent heat of fusion has more dependence on heating/cooling rate than onset, peak and end temperature. (author)
[en] Carbon, as a technologically important material, is attracting much attention due to its application in electrochemical devices based on energy storage/conversion. Carbon has the unique characteristics that comes from the fact that the simple change in its surface or local bonding give rise to a new type of carbon with entirely different performance. Carbon materials have a remarkable range of electrical, optical, and electrochemical properties which primarily depends on the texture and surface chemistry. Among carious carbon materials Graphene is attracting much attention in energy storage devices especially supercapacitors where charge storage takes place by accumulation of ionic charges at the surface and pseudo capacitance
[en] The thermal safety of batteries and of other energy storage devices (ESD) is among their most important characteristics. Thermal analysis and calorimetry testing, whether it aims at improving the thermal stability of ESD materials (cathodes, anodes, electrolytes, separators) or at determining heat management data (heat capacity, heat release) of ESD, is highly valuable from the point of view of thermal safety. Thermogravimetric Analysis (TGA) measures mass change of ESD materials as a function of temperature when they are heated, and detects materials reactivity. Its combination with evolved gas analysis techniques is particularly interesting for the investigation of the chemistry of the reaction, owing to the identification of the species evolved during the mass change
[en] Ionic Liquid (IL) [EMIMBF4] and lithium salt [LiPF6] based quasi solid-liquid electrolytes (QS-LEs; viz. Ionogels) were synthesized using physical imbibition process of IL-salt solution in ordered mesoporous SBA-15. Ionogel Electrolytes so prepared have high ionic conductivity and lithium transference number (tLi+). The synthesized quasi solid-liquid electrolytes were characterized by N2-sorption, SEM, TEM, TGA, and complex impedance spectroscopy techniques. N2-sorption technique, TEM and SEM results confirm the adsorption of ionic liquid and lithium salt in the ordered mesoporous channels and on the external surface of SBA-15
[en] Li-ion batteries are increasingly used in hybrid electric vehicles (HEV), electric vehicles (EV) and stationary storage applications. Those applications are significantly different in terms of storage capacity, life cycles and charging times from consumer type batteries such as mobile phones and handheld tools. Naturally, those HEV and EV Li-ion batteries also differ significantly in chemical composition and size. Coherently, a recycling concept has been developed for HEV, EV and stationary storage Li-ion batteries. This concept is based on the existing IME-ACCUREC recycling process for consumer type batteries. This work describes the whole process development including slag design, test series in a lab-scale electric arc furnace and a 1 t scale trial in a top blown rotary converter.