Mellander Check

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


CONTENTS

PROBLEM STATEMENT

THEORETICAL FOUNDATIONS AND STATE OF THE ART

OBJECTIVES

GENERAL

SPECIFIC

METHODOLOGY

SCHEDULE

COMMUNICATION STRATEGIES

BIBLIOGRAPHY

BUDGET



THEORETICAL FOUNDATIONS AND STATE OF ART


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


230 °C 141 °C


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.


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


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


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


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)?.


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.


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


Figure 3. A plot of electrical conductivity Vs temperature of some ionic and superionic solids (Chandra….)


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


a) CsHSO4

Figure 5. Anomalous behavior of the ionic conductivity Vs temperature a) CHS and b) CHSe indicated by an ellipses. (reference)


KDP – Family: CsH2PO4, RbH2PO4 and KH2PO4


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


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

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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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