Hilfe2 RECENT ACHIEVEMENTS ON NANOCRYSTALLINE MATERIALS FOR SOLID STATE HYDROGEN STORAGE G. Principi, F. Agresti, A. Khandelwal, A. Maddalena, S. Lo Russo VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009
Diapositiva 1 Hilfe2 Diese Folie enthält zwei Mastergruppen (Master und Titelmaster), welche den Corporate-Design-konformen Auftritt definieren. Der jetzt zugewiesene Empa-Master 1 sieht für die Titelfolie das Empa-Logo vor. Den weiteren Folien ist kein Logo zugewiesen. Für längere Vorträge mit Zwischentiteln empfehlen wir, den Folien mit Zwischentiteln den Empa-Master 2 (mit Logo unten rechts) zuzuweisen. Dazu öffnen Sie via Ansicht > Aufgabenbereich > Foliendesign-Entwurfsvorlage rechts die Masterauswahl. Nun markieren Sie im linken Ansichtsfenster die Folien, denen Empa-Master 2 zugewiesen werden soll (mindestens zwei, ansonsten für den ganzen Satz Empa-Master 1 verwendet wird). Weitere Hilfe erhalten Sie bei Monika Ernst, 4995 (Empa, Dübendorf) M. Ernst; 04/02/2005
The problem of hydrogen storage Maggiore capacità volumetrica di idrogeno: Max 30 Kg/m 3 in high pressure cylinders 70 Kg/m 3 in liquid hydrogen Up to 150 Kg/m 3 in metal hydrides More safety with respect to high pressure cylinders and cryostats Less energy loss with respect the classic systems VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 2
Outline Hydrogen storage studies in MgH 2 pellets Mechano-chemical synthesis of LiBH 4 starting from LiH and B Dispersion of LiBH 4 on modified MWCNT VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 3
Scaling up effects of MgH 2 6 A 6 B 5 5 Hydrogen, wt.% 4 3 2 1 Storage degradation Kinetics degradation 4 3 2 1 cycle 8 cycle 14 cycle 20 0 0 5000 10000 15000 20000 Time, s 0 0 5000 10000 15000 Time, s Compaction of the powder in various regions of the tank, implying different thermal conductivity in various regions that leads to kinetic and storage degradation* *M. Verga et. al, Scaling up effects of Mg hydride in a temperature and pressure controlled hydrogen storage device, Int. J. Hydrogen Energy 34 (2009) 4602 VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 4
Pellets of catalyzed MgH 2 MgH 2 + 0,5 mol% Nb 2 O 5 BM 20 h 0.7 cm 0.7 cm wt% H 2 6 5 4 3 2 320 C 1,2 atm 1 2 3 4 5 6 7 8 9 10 1 0 0 200 400 600 800 1000 t (s) MgH 2 with 0.5 mol % Nb 2 O 5 and 1 wt% Graphite, ball milled for 20 hrs Pellets prepared by compacting the milled powder at the pressure of 230 MPa VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 5
Pellets of catalyzed MgH 2 + Al Hydrogen (wt %) 6 5 4 3 2 1 0 Pellet with 5wt% Al preheated at 450 O C 320 C 1,2 atm 0 400 800 1200 t (sec) 1 5 10 15 20 25 30 35 40 45 50 The desorption behaviour becomes almost stable just after 10 cycles and the pellet remains mechanically very consistent and hard even after 50 cycles VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 6
Pellets of catalyzed MgH 2 + Al intensity (a.u.) Data Rietveld fit βmgh 2 MgO Al χ Al 3 Mg 2 Al 12 Mg 17 Al 3 Nb χ χ 20 30 40 50 60 70 80 90 2θ XRD shows the presence of Mg-Al phases in the absorbed sample VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 7
Pellets of catalyzed MgH 2 + Al SEM micrographs Surface cracks of the order of ~100 µm after cycles are not interconnected VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 8
Conclusions #1 Problem of degradation of kinetic and storage proprieties during scaling up studies can be avoided by using pellets in place of powder MgH 2 pellets + 5 wt % Al show a very interesting stability VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 9
Outline Hydrogen storage studies in MgH 2 pellets Mechano-chemical synthesis of LiBH 4 starting from LiH and B Dispersion of LiBH 4 on modified MWCNT VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 10
Why LiBH 4? Most used compound in organic chemistry as reducing agent for aldehydes, ketones, acid chlorides, esters etc. One of the most studied complex metal hydride for hydrogen storage Theoretical gravimetric hydrogen storage capacity = 18.4 wt % Decomposition reaction: LiBH 4 LiH +B + 3/2 H 2 (>400 C) Practical maximum hydrogen storage capacity = 13.4 wt% due to high stability of LiH up to 730 O C VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 11
Mechano-chemical synthesis of LiBH 4 starting from LiH and B Milling Milling LiH powder and B pieces with stoichiometric ratio of 1:1 SPEX 8000M mill Stainless steel vial Stainless steel and WC balls Ball to powder ratio = 30:1 H 2 Pressure inside vial = 3, 4.5 and 10 atm Milling time: 12, 30, 120 and 138 hrs Separation and re-crystallization Dissolved in methyl tert-butyl ether and filtered Re-crystallised using vacuum evaporation F. Agresti and A. Khandelwal, Evidence of formation of LiBH 4 by high energy ball-milling of LiH and B in a hydrogen atmosphere, Scripta Mater. 60 (2009) 753 VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 12
Mechano-chemical synthesis of LiBH 4 starting from LiH and B T ( C) 550 500 450 400 350 300 250 200 150 Sample A Sample B Sample C Sample D Sample E 3,5 3,0 2,5 2,0 1,5 1,0 Desorbed H 2 (wt%) Intensity (a.u.) as milled LiH WC Sample holder 100 50 0 0,5 0,0 decomposed 0 100 200 300 400 time (min) 20 30 40 50 60 70 80 2θ (deg) Sample A: SS balls - 3 atm H 2-12 hrs Sample B: SS balls - 3 atm H 2-30 hrs Sample C: SS balls - 4.5 atm H 2-120 hrs Sample D: SS balls - 10 atm H2-138 hrs Sample E: WC balls - 10 atm H 2-138 hrs VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 13
Mechano-chemical synthesis of LiBH 4 starting from LiH and B 500 12 DSC (a.u.) pure LiBH 4 as milled Exo. Endo. orthorhombic to hexagonal LiBH 4 phase transition LiBH 4 melting Intensity (a.u.) T ( C) 400 300 200 100 0 0 0 50 100 150 200 250 300 time (min) 10 LiBH 4 (orthorhombic) 8 6 4 2 Desorbed H 2 (wt%) recrystallized sample holder 50 75 100 125 150 175 200 225 250 275 300 T ( C) 10 20 30 40 50 60 70 80 90 2θ (deg) All the identified peaks in re-crystallized specimen belong to orthorhombic LiBH 4 VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 14
Conclusions #2 Synthesis of LiBH 4 starting from LiH and B has been presented for the first time The amorphous-like state of LiBH4 and the chemical surrounding in the asmilled samples seem to considerably reduce the decomposition temperature A yield of formation of LiBH 4 is calculated to be about 27 % by weight VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 15
Outline Hydrogen storage studies in MgH 2 pellets Mechano-chemical synthesis of LiBH 4 starting from LiH and B Dispersion of LiBH 4 on modified MWCNT VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 16
Liquid dispersion of LiBH 4 in modified MWCNT BET Surface Area (m 2 /g) 260 250 240 230 220 210 200 0 50 100 150 200 250 300 350 Ball Milling Time (min) hydrogen (wt %) 0-2 -4-6 -8-10 -12 LiBH 4 LiBH 4 :CNT 0.11g:0.2g LiBH 4 :CNT 0.11g:0.1g LiBH 4 :CNT 0.11g:0.05g 100 200 300 400 500 T ( o C) Commercial MWCNT modified by high energy ball milling LiBH 4 solved in MTBE and dispersed on MWCNT by evaporating the solvent VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 17
Conclusions #3 LiBH 4 solved in MTBE and dispersed on MWCNT show a reduced decomposition temperature with respect to the pure material Work is under progress to better characterize the material VII CONVEGNO NAZIONALE INSTM SULLA SCIENZA E TECNOLOGIA DEI MATERIALI, Tirrenia (PI) 9-12 Giugno 2009 18
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