Abstract
Reactions between zirconyl nitrate hydrate and condensed phosphates can be used to produce castable low CTE sodium zirconium phosphate (NZP) monoliths. Reaction between sodium nitrate, zirconyl nitrate hydrate and condensed phosphoric acid at room temperature (alkali nitrate method) produces monoliths having a heterogeneous microstructure, which are multiphasic in appearance. Except for the presence of crystalline sodium nitrate, they are X-ray amorphous. Differential thermal analysis revealed two distinct exothermic crystallization events when these materials are heated. The first event, with an onset temperature of 650 °C, is the result of NZP and ZrO2 crystallization. The second is the result of ZrP2O7 crystallization. Reaction between zirconyl nitrate hydrate and condensed sodium phosphate (condensed alkali phosphate method) results in a more homogeneous microstructure in which crystalline zirconium hydrogen phosphate hydrate and sodium nitrate are present. Two exothermic peaks, with onset temperatures of approximately 570 and 860 °C, are observed. The first exotherm is the result of NZP, ZrO2 and ZrP2O7 crystallization; the second exotherm is the result of a further NZP formation. After heating materials made by these two methods at 940 °C for 24 h, the condensed-alkali-phosphate-method-derived material converted to phase-pure NZP, while the alkali-nitrate-method-derived material contained ZrP2O7. The differences in phase evolution between the materials prepared by these two methods are attributable to the differences in chemical and microstructural homogeneity that result from the reactants used.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1809-1813 |
| Number of pages | 5 |
| Journal | Journal of Materials Science |
| Volume | 34 |
| Issue number | 8 |
| DOIs | |
| State | Published - Jan 1 1999 |
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
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Synthesis of castable sodium zirconium phosphate monoliths employing reactions between zirconyl nitrate hydrate and condensed phosphates. / Lynch, B. T.; Brown, P. W.; Hellmann, J. R.
In: Journal of Materials Science, Vol. 34, No. 8, 01.01.1999, p. 1809-1813.Research output: Contribution to journal › Article
TY - JOUR
T1 - Synthesis of castable sodium zirconium phosphate monoliths employing reactions between zirconyl nitrate hydrate and condensed phosphates
AU - Lynch, B. T.
AU - Brown, P. W.
AU - Hellmann, J. R.
PY - 1999/1/1
Y1 - 1999/1/1
N2 - Reactions between zirconyl nitrate hydrate and condensed phosphates can be used to produce castable low CTE sodium zirconium phosphate (NZP) monoliths. Reaction between sodium nitrate, zirconyl nitrate hydrate and condensed phosphoric acid at room temperature (alkali nitrate method) produces monoliths having a heterogeneous microstructure, which are multiphasic in appearance. Except for the presence of crystalline sodium nitrate, they are X-ray amorphous. Differential thermal analysis revealed two distinct exothermic crystallization events when these materials are heated. The first event, with an onset temperature of 650 °C, is the result of NZP and ZrO2 crystallization. The second is the result of ZrP2O7 crystallization. Reaction between zirconyl nitrate hydrate and condensed sodium phosphate (condensed alkali phosphate method) results in a more homogeneous microstructure in which crystalline zirconium hydrogen phosphate hydrate and sodium nitrate are present. Two exothermic peaks, with onset temperatures of approximately 570 and 860 °C, are observed. The first exotherm is the result of NZP, ZrO2 and ZrP2O7 crystallization; the second exotherm is the result of a further NZP formation. After heating materials made by these two methods at 940 °C for 24 h, the condensed-alkali-phosphate-method-derived material converted to phase-pure NZP, while the alkali-nitrate-method-derived material contained ZrP2O7. The differences in phase evolution between the materials prepared by these two methods are attributable to the differences in chemical and microstructural homogeneity that result from the reactants used.
AB - Reactions between zirconyl nitrate hydrate and condensed phosphates can be used to produce castable low CTE sodium zirconium phosphate (NZP) monoliths. Reaction between sodium nitrate, zirconyl nitrate hydrate and condensed phosphoric acid at room temperature (alkali nitrate method) produces monoliths having a heterogeneous microstructure, which are multiphasic in appearance. Except for the presence of crystalline sodium nitrate, they are X-ray amorphous. Differential thermal analysis revealed two distinct exothermic crystallization events when these materials are heated. The first event, with an onset temperature of 650 °C, is the result of NZP and ZrO2 crystallization. The second is the result of ZrP2O7 crystallization. Reaction between zirconyl nitrate hydrate and condensed sodium phosphate (condensed alkali phosphate method) results in a more homogeneous microstructure in which crystalline zirconium hydrogen phosphate hydrate and sodium nitrate are present. Two exothermic peaks, with onset temperatures of approximately 570 and 860 °C, are observed. The first exotherm is the result of NZP, ZrO2 and ZrP2O7 crystallization; the second exotherm is the result of a further NZP formation. After heating materials made by these two methods at 940 °C for 24 h, the condensed-alkali-phosphate-method-derived material converted to phase-pure NZP, while the alkali-nitrate-method-derived material contained ZrP2O7. The differences in phase evolution between the materials prepared by these two methods are attributable to the differences in chemical and microstructural homogeneity that result from the reactants used.
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U2 - 10.1023/A:1004563309860
DO - 10.1023/A:1004563309860
M3 - Article
AN - SCOPUS:0032665284
VL - 34
SP - 1809
EP - 1813
JO - Journal of Materials Science
JF - Journal of Materials Science
SN - 0022-2461
IS - 8
ER -