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UNIVERSIDAD DEL ATLÁNTICOFACULTAD DE CIENCIAS BÁSICAS
DEPARTAMENTO DE FÍSICAGRUPO FÍSICA DE MATERIALES
MATERIALS PHYSICS GROUP
MATERIAL PHYSICS GROUP
DOCTORATE IN PHYSICAL SCIENCES
REGARDING THE DILEMMA OF THE PHYSICAL OR CHEMICAL NATURE OF THE TRANSFORMATIONS,
ABOVE ROOM TEMPERATURE, IN REPRESENTATIVE ACID SALTS OF THE MH2XO4, MHXO4 FAMILIES AND A
PROTOTYPE OF THEIR MIXTURES, MHXO4-MH2XO4, (M = K, Rb, Cs; X = Se, S, P): A POSSIBLE SOLUTION
ISMAEL ENRIQUE PIÑERES ARIZA
Director
EVER ORTIZ MUÑOZ, PhD
Co-Director
Rubén Vargas Zapata, PhD
MATERIALS PHYSICS GROUP
CONTENTS
PROBLEM STATEMENT
THEORETICAL FOUNDATIONS AND STATE OF THE ART
OBJECTIVES
GENERAL
SPECIFIC
METHODOLOGY
SCHEDULE
COMMUNICATION STRATEGIES
BIBLIOGRAPHY
BUDGET
MATERIALS PHYSICS GROUP
MATERIALS PHYSICS GROUP
THEORETICAL FOUNDATIONS AND STATE OF ART
MATERIALS PHYSICS GROUP
Fuel cell
2001 Haile et al. 2004 Boysen et al
Acid Salts
Baranov
research
CsH2PO4 (CDP) CsHSO4 (CHS)
When these compounds are heated
existence of a phase transition
from a low proton conduction to superprotonic conduction
monoclinic → tetragonal in CHS monoclinic → cubic in CDP
structural changes
MATERIALS PHYSICS GROUP
230 °C 141 °C
MATERIALS PHYSICS GROUP
theoretical models have been proposed
to establish a proton transport mechanisms
in the superprotonic phase of several acid salts
Grotthuss mechanism Interstitial proton sites
includes two steps
reorientation of the tetrahedronproton transfer
displacement along the chain of hydrogen bonds XO4
breakdown of the hydrogen bond group and redirection to a new HnXO4 position
MATERIALS PHYSICS GROUPGrotthuss mechanism
Figure 1. Grotthuss Mechanism
Proton conduction mechanism proposed by Baranov
CsHSO4
Proton diffusion can be explained without assuming any rotation of the HSO4 group
Postulated the occupation of interstitial proton sites
The proton hoping from normal hydrogen bond to the interstitial proton V position.
low conduction → superprotonic phase
symmetry increases and this leads to unification of proton positions.
MATERIALS PHYSICS GROUP
RbH2PO4 (RDP) KH2PO4 (KDP)
MH2XO4 family members
130 °C180 °C
heated through
structural transition: tetragonal → monoclinic occurs
superprotonic conduction phase
is not present
Botez
Chisholm
Suggest that the size of ionic radius of the metal ion play a role in the onset of the superprotonic phase
K+ Rb+ Cs+
Using XRD measurements but at 1GP of pressure
concluded that a proton conduction mechanism is independent of the metal ion.
(RDP and CDP)
Controversy
2.50 Å2.35 Å 2.72 Å
MATERIALS PHYSICS GROUP
partial decomposition process that starts at nucleation sites such as defects and impurities located on the surface of the crystals
Figure 2. Nuclei formation and growth of the decomposition product of the acid salts
Diametrically opposed to the interpretation of the existence of the phase transition.
This suggests that high electrical conductivities observed are the result of a
New Hypothesis
low proton conduction superprotonic conduction
MATERIALS PHYSICS GROUP
Haile Synthesized various mixtures CHS-CDP
Cs3(HSO4)2(H2PO4)
superprotonic phase transition at 111 ° C
has superprotonic phase
CHS CDP does not have superprotonic
phase
MATERIALS PHYSICS GROUP
DEBATEAbout the nature of the transformation above room temperature in acid salts
Baranov
HaileBoysen
Refute the existence of a superprotonic conduction
phase
Botez
Ho park Lee
Ortiz
PiñeresMellander
Vargas
assume the existence of a superprotonic conduction
phase
Nirsha
Chisholm
Tetsuya
Attempt to answer the following questions
Is the reported high proton conductivity, CsHSeO4 and in the prototype mixture - MHXO4 - MH2XO4, Cs3(HSO4)2(H2PO4), consequence of either, a physical or chemical transformation?
Are the reported transformations in KDP and RDP acid salts at 180 and 130 °C, respectively, consequence of either a physical nature (tetragonal → monoclinic) or otherwise a chemical nature (surface decomposition)?.
MATERIALS PHYSICS GROUP
Intrinsic ionic conduction in solids
Properties of Ionic conductors:
•Present a structure that mechanically holds the material as a solid.
•Have accessible positions in order to allow diffusion of ions through the material structure.
•The accessible positions of the ions should be energetically equal, or nearly equal, for the ones occupied by such ions in regular positions.
•The accessible position of the ions must be interconnected in order to form a continuous path (percolation) through the sample.
MATERIALS PHYSICS GROUP
Mobility and therefore the conductivity, depend on the probability of
jumping ions to neighboring positions.
probability is thermally activated
Arrhenius law Eσ is the activation energy of the ionic transport
long-range
MATERIALS PHYSICS GROUP
Figure 3. A plot of electrical conductivity Vs temperature of some ionic and superionic solids (Chandra….)
MATERIALS PHYSICS GROUP
Proton conductivity in acid salts
Figure 4. Dependence of the ionic conductivity with the temperature of some acid salts.
reaching values of 10-2 S cm-1
a certain temperature
Conductivity increases sharply
MATERIALS PHYSICS GROUP
a) CsHSO4
Figure 5. Anomalous behavior of the ionic conductivity Vs temperature a) CHS and b) CHSe indicated by an ellipses. (reference)
MATERIALS PHYSICS GROUP
KDP – Family: CsH2PO4, RbH2PO4 and KH2PO4
MATERIALS PHYSICS GROUP
Botez
Z. Li
Blinc
Lundén
XRD - Synchrotron
DSC – TGA – DTG
XRD – TGA
Conclude
Thermal event
180°C (KDP)
(98,5 ±31,5) °C (RDP)
Structural phase transition
Tetragonal → Monoclinic quasi-irreversible undergoing ultrasonic vibrations Or exposure to water vapor
transforms to the stable phase at room temperature
DSC
MATERIALS PHYSICS GROUP
monoclinic → cubicCDP
Bronowska
Baranov structural phase transition230 °C
low proton conduction → superprotonic conduction
Lee concluded that the thermal phenomena present in the CDP are not due to structural phase transitions.
chemical reaction:
nMH2XO4 → MnH2XnO(3n+1) (s) + (n-1) H2O (v)
(s) solid, (v) vapor phase.
He also suggests that the term Phase transition temperature could be changed by the beginning of partial polymerization sites distributed over the surface of
the acid salt.
CsH2PO4 (CDP)
Mixture systems CsHSO4-CsH2PO4
Haile
CDP → 230 °C
A chemical and not a physical transformation takes place.
A superprotonic conduction phase, takes place
CHS → 141 °C
Mix
What chemical properties are needed to stimulate the onset of the superprotónic transition?
Does phosphorous somehow prevent a compound from showing a superprotonic phase?
What structural features are needed?
OBJECTIVES
General
Experimental study of the thermal, electrical, structural, compositional and vibrational properties of acid salts CsHSeO4, KH2PO4, RbH2PO4 and Cs3 (HSO4)2(H2PO4), for temperatures above 25 °C, in order to contribute to the knowledge of the nature ( physical or chemical) of the transformation that these systems exhibit
Specifics
• Synthesize CsHSeO4, KH2PO4, RbH2PO4, and Cs3(HSO4)2(H2PO4) acid salts .
• Study the thermal stability of these compounds, using the thermo gravimetric analysis (TGA) technique.
• Analyze possible gas evolution, using the high resolution quadrupole mass spectrometry technique (QMS).
• Measure the enthalpie and temperature of thermal events associated with changes in the salts above room temperature, using differential scanning calorimetry (DSC).
• Perform electrical conductivity measurements as a function of temperature in the acid salts, using impedance spectroscopy technique (IS), to identify each of the protonic conduction phases
• Perform environmental electronic scanning microscopy measurements (ESEM) to obtain morphological and topographical high resolution images of the crystal surfaces at different temperatures.
• Perform EDS measurements to examine the composition of the surface of the salt crystals a difference temperatures.
• Perform Raman or FTIR spectroscopy measurements as function of temperature to obtain information about the molecular dynamics.
Note: Depending on the dynamics of the Research development it may be required to include other acid salts similar to those proposed in this project. However, it must be highlighted that it might not be necessary to use all experimental techniques for all of the studied salts.
METHODOLOGY
Synthesis of acid salts:
Crystals CsHSeO4 (CsHSe), RbH2PO4 (RDP), KH2PO4 (KDP) and Cs3(HSO4)2(H2PO4) will be synthesized using the method of slow evaporation of a saturated aqueous solution at room temperature under normal pressure.
Verification of the compound synthesis
XRD measurements will be used to verify that the synthesized compounds correspond to those desired in this research study.
Thermogravimetric Analysis (TGA)
Fresh samples synthesized systems will be subjected to various heating programs using a thermogravimetric balance, TA-Instruments 2950, in order to examine whether weight loss occurs as a function of the temperature around the temperature values which have been attributed phase transitions.
Differential Scanning Calorimetry (DSC)
It is a technique for obtaining temperatures and transformation enthalpies of thermal anomalies. If multiple samples from a single fresh salt batch are respectively heated to different heating rates it could shed light on the physical or chemical nature of the transformation. This experiment will be done in all salts using a TA-Instruments DSC 2920.
Modulated Differential Scanning Calorimetry (MDSC)
MDSC technique allows separation of the independent (specific heat) and dependent (kinetic) components from the DSC total signal.
MDSC measurements will be done for fresh salt samples using a TA-Instruments DSC 2920. Considering that the chemical reactions have a time-dependent basis, this technique will contribute to discern the nature of the transformations above room temperature.
Differential Scanning CalorimetryThermogravimetric Analysis Simultaneous with DSC-TGA (SDT)
This technique allows simultaneous measurement of weight and heat flow as a function of temperature on the same sample at the same time. The technique is very useful in the study of the thermal decomposition of solids since decomposition processes behaves different depending on its specific topological morphological and quality details.
This experiment was replicated in all salts using a SDT (simultaneous DSC-TGA) TA-2960 instruments.
Impedance Spectroscopy
Measurements of electrical impedance spectroscopy as a function of temperature will be done in the acid salts using a Solartron 1260A and Novocontrol equipment, in order to examine the relaxation processes in both, the superprotonic transition phase reported for CsHSeO4 and Cs3(HSO4)2(H2PO4) and to the quasi-irreversible transition tetragonal → monoclinic in KDP and RDP, respectively . Heating and cooling cycles will be programmed using settemp and ZPLOT software.
Simultaneous Thermogravimetric Analysis with Mass Spectroscopy, TG-MS
MS technique allows identifying the gas evolution in the studied sample, when it undergoes a chemical reaction.Simultaneous mass spectroscopy and thermogravimetric measurements will be carried out on fresh samples of the salts using a Balzers ThermoStar MS equipment in order to identify possible gaseous products of chemical reactions as a function of sample temperature..
Environmental scanning electron microscopy, ESEM
The technique is the same as SEM with the advantages of enabling the analysis of samples without non-metallic coating but it permits the analysis of hydrated samples working under water vapor atmosphere. With the use of this technique one can compare the evolution of the behavior of salts when heated through the transformation temperatures.
Energy dispersive spectrometry X-ray (EDS)
With the use of this technique we may do surface chemical composition analysis of the of the salt when heated through the transformation temperatures.
Raman or FTIR Spectroscopy.
Raman or FTIR spectroscopy measurements as a function of temperature will be carried out on fresh samples of the salts in order to obtain information on the molecular mechanics structural phase transition and / or the appearance of new normal modes of vibration which could be associated with surface thermal decomposition products.
X-ray diffraction, XRD
The evolution in each salt will be investigated as a function of temperature using XRD. With this measurements we expect to determine if the high temperature spectra show a new structural phase, or a mixture of decomposition products, or both.
trimester
activity
1 2 3 4 5 6 7 8
Literature Review
(Universidad del Atlántico-Universidad complutense de Madrid)X X X X X X X X
Sample preparation
(Universidad del Atlántico)X
Measurements of thermal analysis (DSC, TGA, MDSC, TG-MS, SDT)
(Universidad del Atlántico)X X
Electrical impedance spectroscopy (IS) (Universidad complutense de
Madrid y Universidad del Atlántico) X X X
Raman spectroscopy AND /OR FTIR
(Puerto Rico AND /OR SPAIN) X X
Measurements ESEM – EDS
(Universidad Industrial de Santander) X
XRD
(Universidad complutense de Madrid) X
Data Analysis
(Universidad complutense de Madrid and Universidad del Atlántico)
X X X X X
Writing articles and documentDoctoral Thesis X X X X X
SCHEDULE
COMMUNICATION STRATEGIES
• Thesis Document printed on paper and CD for dissemination through the network's website Materials Physics Group, Universidad Del Atlántico, and red Sue-Caribe.
• Participation in two scientific events in the field of Physics at the national and / or international level.
• Publication of at least three articles in international scientific journals.
• Publication in the Journal of the Faculty of Basic Sciences, University of the Atlantic.
RUBROS
Sources
TOTALUNIVERSIDAD DEL ATLÁNTICO
Other(Universidad Complutense de
Madrid y del Valle)
Cash Species Cash Species
Staff 81.600.000 16.000.000
97.600.000
Equipement 5.500.000 25.000.000 10.000.000 40.500.000
Software
Materials and Supplies 16.000.000 16.000.000
Field Trips 4.000.000 4.000.000
Literature Publications and records of
industrial or intellectual property
2.000.000 2.000.000
Technical Services 10.000.000 10.000.000
Travel 29.500.000 29.500.000
Maintenance 5.000.000 5.000.000
Administration
TOTAL
72.000.000 106.600.000 26.000.000 204.600.000
CASH VALUE FROM SUE CARIBE INSTITUTIONS 72.000.000
Budget
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• Ortiz E., Vargas R. A. and Mellander B. E. 1999, Solid State Ionics 125, 177.
• Ortiz E, Vargas R. A, Mellander B-E. 2006, J. Phys.: Condens. Matter 18.• Wang J., Chameides. 2007, Are Humans Responsible for Global
Warming? A REVIEW OF THE FACTS. Environmental Defense.• HirschenhoferJ.H,Stauffer
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Ionics. 77 91–6.• Nozik Yu Z, Lyakhovitskaya O I, Shchagina N M and Sarin V A 1990
Kristallografiya 35 658–60.• Belushkin A V, Carlile C J, David W I F, Ibberson R M and Suvalov L A
1991 Physica B 174 268.• Bronowska W., JCPDS – International Center for Diffraction Date (1997).
• Bronowska W. 2006, Materials Science-Poland, 24 (1), 229. • F. Roman, A. Novak. 1991, J. Mol. Struct. 263, 69.• W. Bronowska. 2001, J. Chem. Phys. 114, 611.• Haile S M., Chisholm C R. I., Sasaki w K, Boysen D A. and Udaz T, 2007,
Faraday Discuss.,134, 17.• Blinc R., Dimic V., Kolar D., Lahajnar G., Stepisnik J., Zumer S., Vene N. and
Hadzi D. J. 1968, Chem. Phys. 49, 4996.• Pham-Thi M., Colomban Ph., Novak A. and Blinc R.1985, Solid State Commun.
55, 265.• O´Keeffe M. and Perrino C. T. 1967, J. Phys. Chem. Solids 28, 211.• Grinberg J., Levin S., Pelah I., and Wiener E. 1967, Solid State Commun.5, 863.• Baranov A.I., Khiznichenko V.P., and Shuvalov L.A. 1989, Ferroelectrics. 100,135.• Cristian E Botez, Heber Martinez, Ronald J Tackett, Russell R Chianelli,
Jianzhong Zhang and Yusheng Zhao. 2009, J. Phys.: Condens. Matter 21 325401 (7pp).
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