8 research outputs found
CieÌncia Cognitiva, SisteÌmica e Filosofia Bergsoniana: uma reflexaÌo acerca da vida em sua capacidade organizativa
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Probing Structural Changes in a Phosphonate-based MetalâOrganic Framework Exhibiting Reversible Dehydration
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Probing Structural Changes in a Phosphonate-based MetalâOrganic Framework Exhibiting Reversible Dehydration
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Probing Structural Changes in a Phosphonate-based MetalâOrganic Framework Exhibiting Reversible Dehydration
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Probing Structural Changes in a Phosphonate-based MetalâOrganic Framework Exhibiting Reversible Dehydration
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Probing Structural Changes in a Phosphonate-based MetalâOrganic Framework Exhibiting Reversible Dehydration
A one-step hydrothermal
synthesis with small amines and 1,3,5-benzenetriphosphonic
acid was used to prepare single crystals of isostructural anionic
metalâorganic frameworks (MOF): Zn<sub>2.5</sub>(H)<sub>0.4â</sub><sub>0.5</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>1.9â2</sub>(NH<sub>4</sub>)<sub>0.5â0.6</sub> and Zn<sub>2.5</sub>(H)<sub>0.75</sub>(C<sub>6</sub>H<sub>3</sub>O<sub>9</sub>P<sub>3</sub>)Â(H<sub>2</sub>O)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>0.25</sub>. The ammonium ions are exchangeable
with lithium ions. The MOF exhibits reversible dehydration, and the
process was studied by two complementary methods: solid state NMR
and in situ X-ray diffraction. These experiments revealed three different
phases. The crystal structures of all phases have been determined,
showing loss in volume of the structure due to a phase change. The
ammonium ions remain in the structure and are forced to occupy the
larger pores due to a reduction in free volume. The change in positions
of the guest molecules in the framework has an effect on the potential
conductivity properties of the materials. Changes in framework and
guest molecules due to negative expansion have an effect on other
physical and chemical properties and need to be explored
Soft-Chemical Synthesis, Structure Evolution, and Insulator-to-Metal Transition in Pyrochlore-like λâRhO<sub>2</sub>
λ-RhO2, a prototype 4d transition metal
oxide,
has been prepared by the oxidative delithiation of spinel LiRh2O4 using ceric ammonium nitrate. Average-structure
studies of this RhO2 polytype, including synchrotron powder
X-ray diffraction and electron diffraction, indicate the room-temperature
structure to be tetragonal, in space group I41/amd, with a first-order structural transition
to cubic Fd3Ì
m at T = 345 K on warming. Synchrotron X-ray pair distribution
function analysis and 7Li solid-state nuclear magnetic
resonance measurements suggest that the room-temperature structure
displays local RhâRh bonding. The formation of these local
dimers appears to be associated with a metal-to-insulator transition
with a nonmagnetic ground state, as also supported by density functional
theory-based electronic structure calculations. This contribution
demonstrates the power of soft chemistry to kinetically stabilize
a simple binary oxide compound
Structural Evolution of Reversible Mg Insertion into a Bilayer Structure of V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O Xerogel Material
Functional
multivalent
intercalation cathodes represent one of
the largest hurdles in the development of Mg batteries. While there
are many reports of Mg cathodes, many times the evidence of intercalation
chemistry is only circumstantial. In this work, direct evidence of
Mg intercalation into a bilayer structure of V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O xerogel is confirmed, and
the nature of the Mg intercalated species is reported. The interlayer
spacing of V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O contracts upon Mg intercalation and expands for Mg deintercalation
due to the strong electrostatic interaction between the divalent cation
and the cathode. A combination of NMR, pair distribution function
(PDF) analysis, and X-ray absorption near edge spectroscopy (XANES)
confirmed reversible Mg insertion into the V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O material, and structural evolution
of Mg intercalation leads to the formation of multiple new phases.
Structures of V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O with Mg intercalation were further supported by the first
principle simulations. A solvent cointercalated Mg in V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O is observed for
the first time, and the <sup>25</sup>Mg magic angle spinning nuclear
magnetic resonance (MAS NMR) spectroscopy was used to elucidate the
structure obtained upon electrochemical cycling. Specifically, existence
of a well-defined MgâO environment is revealed for the Mg intercalated
structures. Information reported here reveals the fundamental Mg ion
intercalation mechanism in a bilayer structure of V<sub>2</sub>O<sub>5</sub>·<i>n</i>H<sub>2</sub>O material and provides
insightful design metrics for future Mg cathodes