High accuracy capillary network representation in digital rock reveals permeability scaling functions

Permeability is the key parameter for quantifying fluid flow in porous rocks. Knowledge of the spatial distribution of the connected pore space allows, in principle, to predict the permeability of a rock sample. However, limitations in feature resolution and approximations at microscopic scales have so far precluded systematic upscaling of permeability predictions. Here, we report fluid flow simulations in capillary network representations designed to overcome such limitations. Performed with an unprecedented level of accuracy in geometric approximation at microscale, the pore scale flow simulations predict experimental permeabilities measured at lab scale in the same rock sample without the need for calibration or correction. By applying the method to a broader class of representative geological samples, with permeability values covering two orders of magnitude, we obtain scaling relationships that reveal how mesoscale permeability emerges from microscopic capillary diameter and fluid velocity distributions.Comment: Main article: 11 pages and 4 figures. Supplementary Information: 6 pages and 4 figures. Version 2 includes DOI for microCT datase

Lessons from the terra preta de índios of the amazon region for the utilisation of charcoal for soil amendment

peer-reviewedThe potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by international groups have contributed to the emergence of an awareness of the compositions and of the uses of these materials. In this contribution we report on chemical studies that are leading to the development of a scientific and technological awareness, and of innovations that will have value in finding novel uses in applications to soil of chars from organic wastes such as those from the biofuel industry, and from metallurgical and various coal plant residues

1H low- and high-field NMR study of the effects of plasma treatment on the oil and water fractions in crude heavy oil

AbstractThe chemical and physical properties of a Brazilian heavy oil submitted to plasma treatment were investigated by 1H low- and high-field nuclear magnetic resonance (NMR) combined to the characterization of rheological properties, thermogravimetry and measurement of basic sediments and water (BSW) content. The crude oil was treated in a dielectric barrier discharge plasma reactor, using natural gas, CO2 or H2 as working gas. The results indicated a large drop in the water content of the plasma-treated samples as compared to the crude oil, giving rise to a reduction in the viscosity. No significant chemical change was produced in the oil portion itself, as observed by 1H NMR. The water contents determined by 1H low-field NMR analyses agreed well with those obtained by BSW, indicating the low-field NMR methods as a useful tool for following the effects of plasma treatments on heavy oils, allowing the separation of the effects caused on the water and oil fractions

CONTRA: Improving the performance of dynamic investigations in natural abundance organic solids by mirror-symmetric constant-time CODEX

We present a minor but essential modification to the CODEX 1D-MAS exchange experiment. The new CONTRA method, which requires minor changes of the original sequence only, has advantages over the previously introduced S-CODEX, since it is less sensitive to artefacts caused by finite pulse lengths. The performance of this variant, including the finite pulse effect, was confirmed by SIMPSON calculations and demonstrated on a number of dynamic systems

New Li+ ion-conducting ormolytes

The preparation and characterization of two new families of lithium-conducting solid-state electrolytes is reported. Both systems are silica (SiO2) - polyethyleneglycol (PEGn) hybrid materials with (type I) or without (type II) covalent organic-inorganic chemical bonds. Their electrical conductivity has been studied by complex impedance spectroscopy between 20\u27°C and 100\u27°C in the frequency range 1 Hz to 10 MHz as a function of the polymer chain length (200 < n < 1900), polymer concentration and lithium concentration (4 < [O]/[Li] < 80). The highest room-temperature ionic conductivity (&sigma;&#8773; 6 x 10-2 S cm-1) has been found for type II material for ratios [O]/[Li] = 15 and PEG300/TEOS = 1.0. The effect of the chain length on the polymer mobility has been studied by nuclear magnetic resonance by measuring the Li+ line widths and the spin-lattice relaxation time T1 between -100\u27°C and + 100\u27°C, The bonded chain mobility increases with the chain length (type II) while the opposite occurs with unbonded chain material (type I). Both types of materials present high ionic conductivity at room temperature and are adequate as Li+-conducting electrolyte in all solid-state electrochemical devices

New Li+ ion-conducting ormolytes

The preparation and characterization of two new families of lithium-conducting solid-state electrolytes is reported. Both systems are silica (SiO2) - polyethyleneglycol (PEGn) hybrid materials with (type I) or without (type II) covalent organic-inorganic chemical bonds. Their electrical conductivity has been studied by complex impedance spectroscopy between 20'°C and 100'°C in the frequency range 1 Hz to 10 MHz as a function of the polymer chain length (200 < n < 1900), polymer concentration and lithium concentration (4 < [O]/[Li] < 80). The highest room-temperature ionic conductivity (&sigma;&#8773; 6 x 10-2 S cm-1) has been found for type II material for ratios [O]/[Li] = 15 and PEG300/TEOS = 1.0. The effect of the chain length on the polymer mobility has been studied by nuclear magnetic resonance by measuring the Li+ line widths and the spin-lattice relaxation time T1 between -100'°C and + 100'°C, The bonded chain mobility increases with the chain length (type II) while the opposite occurs with unbonded chain material (type I). Both types of materials present high ionic conductivity at room temperature and are adequate as Li+-conducting electrolyte in all solid-state electrochemical devices

NMR quadrupolar system described as Bose-Einstein-condensate-like system

This paper presents a description of nuclear magnetic resonance (NMR) of quadrupolar systems using the Holstein-Primakoff (HP) formalism and its analogy with a Bose-Einstein condensate (BEC) system. Two nuclear spin systems constituted of quadrupolar nuclei I=3/2 ((23)Na) and I=7/2 ((133)Cs) in lyotropic liquid crystals were used for experimental demonstrations. Specifically, we derived the conditions necessary for accomplishing the analogy, executed the proper experiments, and compared with quantum mechanical prediction for a Bose system. The NMR description in the HP representation could be applied in the future as a workbench for BEC-like systems, where the statistical properties may be obtained using the intermediate statistic, first established by Gentile. The description can be applied for any quadrupolar systems, including new developed solid-state NMR GaAS nanodevices.Brazilian Science Foundations CAPESCNPqFAPESPMillennium Institute for Quantum InformationLaboratorio Nacional de Luz Sincroton (LNLS

Investigation of new ion-conducting ORMOLYTES : structure and properties

Two families of hybrid organic-inorganic composites exhibiting Li+ ionic conduction (ORMOLYTES) have been prepared by the sol-gel process. The first family, prepared from a mixture of 3-isocyanatopropyltriethoxysilane, O,O\u27\u27Bis (2-aminopropyl)-polyethyleneglycol (or O,O\u27Bis (2-aminopropyl)-polypropyleneglycol) and lithium salt, presents chemical bonds between the organic and the inorganic phase and an ionic conductivity &sigma; higher than 10-4 S m-1 at room temperature. Their properties have been related to their structure using liquid state NMR measurements of 7Li between -100°C and +100\u27°C and the DMTA technique. In the second family, prepared by ultrasonic method from a mixture of tetraethoxysilane (TEOS), polyethyleneglycol (PEG) and lithium salt, the organic and inorganic phases are not chemically bonded. Ionic conductivity &sigma; has been studied as a function of the polymer chain length and concentration. Values of &sigma; up to 10-2S m-1 at room temperature have been obtained (with a silica-PEG300 system, PEG/TEOS=40% in weight). Again, structure was investigated by liquid state 7Li NMR measurements