1,149 research outputs found
Developing Advanced Electrodes and Electrolytes for Energy Storage Beyond Li Ion Batteries
Electric vehicles, smart phones, and portable computers are all powered by lithium-ion batteries. This is because Li-ion batteries can store more energy in less space than other battery technologies. Also, they are rechargeable and last for a long time. The most recent 2019 Nobel prize in chemistry was awarded to John Goodenough, M. Stanley Whittingham and Akira Yoshino “for the development of lithium-ion batteries”. Through their work, they have made possible cars that do not burn fossil fuels and phones that are wireless and portable. Not only can Li-ion power your phone, it is an incredibly efficient way to store energy from renewable sources such as wind, solar, or hydroelectric.
From the introduction of the Li-ion Battery into the public market until now the fundamentals of the battery technology have remained relatively the same. This means a metal oxide electrode containing Co is combined with a Li containing electrolyte. Both Co and Li are rare elements that have sustainability issues. Replacing these components could make batteries more energy dense and sustainable for future generations.
The first part of this work describes an improved synthetic method to make battery electrodes from renewable organic materials and earth abundant elements. These electrodes were found to provide energy densities rivaling those found in current Li-ion technologies. The electrodes featured in this work make use of a type of material called metal organic frameworks (abbreviated as MOFs). The MOFs in this work were found to work well for Li batteries and last for over 1000 cycles. Spectroscopic techniques were used to prove that it is advantageous for both the metal and the organic component of the MOFs to store energy.
The other unsustainable component of the battery is the Li electrolyte. In this work Ca electrolytes were improved and developed. Ca is a highly abundant and nontoxic element that is found everywhere. These qualities make it a highly suitable alternative to Li. Ca electrolytes have different properties than Li. Here the very important contributions of the solvent used in the electrolyte are examined. Not very many Ca electrolytes currently work for batteries. In this dissertation a new working Ca electrolyte was discovered and fully tested for its ability to work in Ca batteries. Two full functioning Ca batteries were tested with different electrolytes and electrodes. These batteries are the most energy dense Ca batteries ever reported and are directly competitive with Li-ion batteries
Non-adiabatic Arbitary Geometric Gates in 2-qubit NMR Model
We study a 2-qubit nuclear spin system for realizing an arbitrary geometric
quantum phase gate by means of non-adiabatic operation. A single magnetic pulse
with multi harmonic frequencies is applied to manipulate the quantum states of
2-qubit instantly. Using resonant transition approximation, the time dependent
Hamiltonian of two nuclear spins can be solved analytically. The time evolution
of the wave function is obtained without adiabatic approximation. The
parameters of magnetic pulse, such as the frequency, amplitude, phase of each
harmonic part as well as the time duration of the pulse, are determined for
achieving an arbitrary non-adiabatic geometric phase gate. The derivation of
non-adiabatic geometric controlled phase gates and A-A phase are also
addressed.Comment: 7 pages, 1 figur
Iowa Swiss-type cheese
New types of cheese for Iowa have been receiving the attention of the Iowa Agricultural Experiment Station for a number of years. A previous publication (1) described the method of manufacture which has been used in the production of many thousands of pounds of Iowa Blue Cheese. This publication deals with the process used in the Iowa State College laboratories in manufacturing a Swiss-type cheese. In the course of these experiments a total of 25,136 lbs. of the cheese has been manufactured and marketed, utilizing approximately a quarter of a million pounds of milk
Thermal entanglement of spins in a nonuniform magnetic field
We study the effect of inhomogeneities in the magnetic field on the thermal
entanglement of a two spin system. We show that in the ferromagnetic case a
very small inhomogeneity is capable to produce large values of thermal
entanglement. This shows that the absence of entanglement in the ferromagnetic
Heisenberg system is highly unstable against inhomogeneoity of magnetic fields
which is inevitably present in any solid state realization of qubits.Comment: 14 pages, 7 figures, latex, Accepted for publication in Physical
Review
Orbits of quantum states and geometry of Bloch vectors for -level systems
Physical constraints such as positivity endow the set of quantum states with
a rich geometry if the system dimension is greater than two. To shed some light
on the complicated structure of the set of quantum states, we consider a
stratification with strata given by unitary orbit manifolds, which can be
identified with flag manifolds. The results are applied to study the geometry
of the coherence vector for n-level quantum systems. It is shown that the
unitary orbits can be naturally identified with spheres in R^{n^2-1} only for
n=2. In higher dimensions the coherence vector only defines a non-surjective
embedding into a closed ball. A detailed analysis of the three-level case is
presented. Finally, a refined stratification in terms of symplectic orbits is
considered.Comment: 15 pages LaTeX, 3 figures, reformatted, slightly modified version,
corrected eq.(3), to appear in J. Physics
A handbook for the determination of radon attenuation through cover materials
Radon emissions from bare and covered uranium mill tailings can be estimated by diffusion theory if appropriate diffusion coefficients are known. The mathematical basis for the diffusion theory expressions are herein presented, as is a general survey of previous and present research, as well as technological developments associated with randon transport through tailing cover systems. Research is presently being conducted to define more clearly the influences of moisture, porosity, pore size distribution and other factors, on the attenuative properties of cover materials. The results of these present investigations will be incorporated in a subsequent addendum to this handbook. The radon fluxes or cover thicknesses can be calculated by hand or by available computer programs. The equations and procedure for the hand calculations is in direct support of the methodology contained in Appendix P of the Generic Environmental Impact Statement on Uranium Milling. Several examples are given to demonstrate the methodology
Entanglement dynamics of two qubits under the influence of external kicks and Gaussian pulses
We have investigated the dynamics of entanglement between two spin-1/2 qubits
that are subject to independent kick and Gaussian pulse type external magnetic
fields analytically as well as numerically. Dyson time ordering effect on the
dynamics is found to be important for the sequence of kicks. We show that
"almost-steady" high entanglement can be created between two initially
unentangled qubits by using carefully designed kick or pulse sequences
High-fidelity simulations of CdTe vapor deposition from a new bond-order potential-based molecular dynamics method
CdTe has been a special semiconductor for constructing the lowest-cost solar
cells and the CdTe-based Cd1-xZnxTe alloy has been the leading semiconductor
for radiation detection applications. The performance currently achieved for
the materials, however, is still far below the theoretical expectations. This
is because the property-limiting nanoscale defects that are easily formed
during the growth of CdTe crystals are difficult to explore in experiments.
Here we demonstrate the capability of a bond order potential-based molecular
dynamics method for predicting the crystalline growth of CdTe films during
vapor deposition simulations. Such a method may begin to enable defects
generated during vapor deposition of CdTe crystals to be accurately explored
The exact Darwin Lagrangian
Darwin (1920) noted that when radiation can be neglected it should be
possible to eliminate the radiation degrees-of-freedom from the action of
classical electrodynamics and keep the discrete particle degrees-of-freedom
only. Darwin derived his well known Lagrangian by series expansion in
keeping terms up to order . Since radiation is due to acceleration the
assumption of low speed should not be necessary. A Lagrangian is suggested that
neglects radiation without assuming low speed. It cures deficiencies of the
Darwin Lagrangian in the ultra-relativistic regime.Comment: 2.5 pages, no figure
Computational Insights into Mg-Cl Complex Electrolytes for Rechargeable Magnesium Batteries
DFT calculations were conducted to provide insightful and unprecedented thermodynamic insights on tetrahydrofuran (THF) solvation, isomerization, chlorination, and complexation of possible Mg-Cl coordination species for the popular Mg-Cl electrolytes. Computational results using the M06-2x functional with the 6-31+G(d) basis set indicate trigonal bipyramidal e, e-cis-tbp-MgCl2(THF)3 dichloride species and octahedral [MgCl(THF)5]+ monochloride species are the dominant mononuclear species. These two can combine to form the active dinuclear species, [(ÎĽ-Cl)3Mg2(THF)6]+ with a free energy -6.30 kcal/mol, which is calculated to be the dominant Mg-Cl species in solution. Two mono-cation species, [(ÎĽ-Cl)3Mg2(THF)6]+ and [MgCl(THF)5]+ have comparable LUMO energies, thus both of them can act as active species for Mg deposition. However, the significant dominance of the dinuclear species in the electrolyte indicates that it is the primary species involved in reversible Mg deposition
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