R. Prasad

Bhabha Atomic Research Centre, Mumbai, Mahārāshtra, India

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Publications (105)129.21 Total impact

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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 32(39).
  • ChemInform 01/2010; 29(22).
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 30(23).
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 31(28).
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    ABSTRACT: The Gibbs free energies of formation of Eu3RuO7(s) and Eu2Ru2O7(s) have been determined using solid-state electrochemical technique employing oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following solid-state electrochemical cells have been measured: Cell( I ):( - )Pt \mathord/ \vphantom ( - )Pt { Eu3 RuO7 ( s ) + Eu2 O3 ( s ) + Ru( s ) } { Eu3 RuO7 ( s ) + Eu2 O3 ( s ) + Ru( s ) }//CSZ//O2 ( p( O2 ) = 21.21 kPa ) \mathord/ \vphantom ( p( O2 ) = 21.21 kPa ) Pt( + ) Pt( + )Cell{\left( I \right)}:{{\left( - \right)}Pt} \mathord{\left/ {\vphantom {{{\left( - \right)}Pt} {{\left\{ {Eu_{3} RuO_{7} {\left( s \right)} + Eu_{2} O_{3} {\left( s \right)} + Ru{\left( s \right)}} \right\}}}}} \right. \kern-\nulldelimiterspace} {{\left\{ {Eu_{3} RuO_{7} {\left( s \right)} + Eu_{2} O_{3} {\left( s \right)} + Ru{\left( s \right)}} \right\}}}//CSZ//O_{2} {{\left( {p{\left( {O_{2} } \right)} = 21.21 kPa} \right)}} \mathord{\left/ {\vphantom {{{\left( {p{\left( {O_{2} } \right)} = 21.21 kPa} \right)}} {Pt{\left( + \right)}}}} \right. \kern-\nulldelimiterspace} {Pt{\left( + \right)}} Cell( II ):( - )Pt \mathord/ \vphantom ( - )Pt { Eu3 RuO7 ( s ) + Eu2 Ru2 O7 ( s ) + Ru( s ) } { Eu3 RuO7 ( s ) + Eu2 Ru2 O7 ( s ) + Ru( s ) }//CSZ//O2 ( p( O2 ) = 21.21 kPa ) \mathord/ \vphantom ( p( O2 ) = 21.21 kPa ) Pt( + ) Pt( + )Cell{\left( {II} \right)}:{{\left( - \right)}Pt} \mathord{\left/ {\vphantom {{{\left( - \right)}Pt} {{\left\{ {Eu_{3} RuO_{7} {\left( s \right)} + Eu_{2} Ru_{2} O_{7} {\left( s \right)} + Ru{\left( s \right)}} \right\}}}}} \right. \kern-\nulldelimiterspace} {{\left\{ {Eu_{3} RuO_{7} {\left( s \right)} + Eu_{2} Ru_{2} O_{7} {\left( s \right)} + Ru{\left( s \right)}} \right\}}}//CSZ//O_{2} {{\left( {p{\left( {O_{2} } \right)} = 21.21 kPa} \right)}} \mathord{\left/ {\vphantom {{{\left( {p{\left( {O_{2} } \right)} = 21.21 kPa} \right)}} {Pt{\left( + \right)}}}} \right. \kern-\nulldelimiterspace} {Pt{\left( + \right)}}The Gibbs free energies of formation of Eu3RuO7(s) and Eu2Ru2O7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given, respectively, by: { Df Go ( Eu3 RuO7 , s ) \mathord/ \vphantom ( Eu3 RuO7 , s ) ( kJ mol - 1 ) ±2.5 ( kJ mol - 1 ) ±2.5 ) = - 2,785.2 + 0.567 ( T \mathord/ \vphantom T K K ); ( 922.5 \leqslant T \mathord/ \vphantom 922.5 \leqslant T K \leqslant 1194.9 K \leqslant 1194.9 ).\left\{ {\Delta _{f} G^{o} } \right.\left. {{{\left( {Eu_{3} RuO_{7} , s} \right)}} \mathord{\left/ {\vphantom {{{\left( {Eu_{3} RuO_{7} , s} \right)}} {{\left( {kJ \cdot mol^{{ - 1}} } \right)} \pm 2.5}}} \right. \kern-\nulldelimiterspace} {{\left( {kJ \cdot mol^{{ - 1}} } \right)} \pm 2.5}} \right) = - 2,785.2 + 0.567 \cdot {\left( {T \mathord{\left/ {\vphantom {T K}} \right. \kern-\nulldelimiterspace} K} \right)}; {\left( {{922.5 \leqslant T} \mathord{\left/ {\vphantom {{922.5 \leqslant T} {K \leqslant 1194.9}}} \right. \kern-\nulldelimiterspace} {K \leqslant 1194.9}} \right)}. { Df Go ( Eu3 Ru2 O7 , s ) \mathord/ \vphantom ( Eu3 Ru2 O7 , s ) ( kJ mol - 1 ) ±2.9 ( kJ mol - 1 ) ±2.9 ) = - 2,256.6 + 0.579 ( T \mathord/ \vphantom T K K ); ( 995.3 \leqslant T \mathord/ \vphantom 995.3 \leqslant T K \leqslant 1260.6 K \leqslant 1260.6 ).\left\{ {\Delta _{f} G^{o} } \right.\left. {{{\left( {Eu_{3} Ru_{2} O_{7} , s} \right)}} \mathord{\left/ {\vphantom {{{\left( {Eu_{3} Ru_{2} O_{7} , s} \right)}} {{\left( {kJ \cdot mol^{{ - 1}} } \right)} \pm 2.9}}} \right. \kern-\nulldelimiterspace} {{\left( {kJ \cdot mol^{{ - 1}} } \right)} \pm 2.9}} \right) = - 2,256.6 + 0.579 \cdot {\left( {T \mathord{\left/ {\vphantom {T K}} \right. \kern-\nulldelimiterspace} K} \right)}; {\left( {{995.3 \leqslant T} \mathord{\left/ {\vphantom {{995.3 \leqslant T} {K \leqslant 1260.6}}} \right. \kern-\nulldelimiterspace} {K \leqslant 1260.6}} \right)}.The uncertainty estimates for Δf G o(T) include the standard deviation in e.m.f. and uncertainty in the data taken from the literature.
    Journal of Solid State Electrochemistry 01/2007; 11(2):291-295. · 2.28 Impact Factor
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    ABSTRACT: The Gibbs free energy of formation of Nd3RuO7(s) has been determined using solid-state electrochemical cell employing oxide ion conducting electrolyte. The electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured, in the temperature range from 929.3 to 1228.6K.Cell:(−)Pt/{Nd3RuO7(s)+Nd2O3(s)+Ru(s)}//CSZ//O2(p(O2)=21.21kPa)/Pt(+)The Gibbs free energy of formation of Nd3RuO7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by:{ΔfG°(Nd3RuO7,s)/(kJmol−1)±1.6}=−3074.3+0.6097(T/K);(929.3≤T/K≤1228.6).The uncertainty estimate for ΔfG°(T) includes the standard deviation in e.m.f. and the uncertainty in the data taken from the literature. The intercept and the slope of the above equation correspond to the enthalpy of formation and entropy, respectively, at the average experimental temperature of Tav.=1079K.
    Journal of Alloys and Compounds 01/2006; 420(1):283-285. · 2.73 Impact Factor
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    ABSTRACT: The Gibbs free energies of formation of Sm3RuO7(s), Sm2RuO5(s) and Sm2Ru2O7(s) have been determined using solid-state electrochemical cell employing oxide ion conducting electrolyte. The electromotive force (e.m.f.) of the following solid-state electrochemical cells have been measured:•Cell (I): (−)Pt/{Sm3RuO7(s) + Sm2O3(s) + Ru(s)}∥CSZ∥O2(p(O2) = 21.21 kPa)/Pt(+)•Cell (II): (−)Pt/{Sm3RuO7(s) + Sm2RuO5(s) + Ru(s)}∥CSZ∥(p(O2) = 21.21 kPa)/Pt(+)•Cell (III): (−)Pt/{Sm2RuO5(s) + Sm2Ru2O7(s) + Ru(s)}∥CSZ∥O2(p(O2) = 21.21 kPa)/Pt(+)The Gibbs free energies of formation of Sm3RuO7(s), Sm2RuO5(s) and Sm2Ru2O7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study can be given respectively by:{ΔfG0(Sm3RuO7,s)/(kJ mol−1)±3.1}=−3161.5+0.6528 (T/K); (969≤T/K≤1222.8),{ΔfG0(Sm3RuO7,s)/(kJ mol−1)±3.1}=−3161.5+0.6528 (T/K); (969≤T/K≤1222.8),{ΔfG0(Sm2RuO5,s)/(kJ mol−1)±2.6}=−2151.0+0.4544 (T/K); (917.1≤T/K≤1240.8),{ΔfG0(Sm2RuO5,s)/(kJ mol−1)±2.6}=−2151.0+0.4544 (T/K); (917.1≤T/K≤1240.8),{ΔfG0(Sm2Ru2O7,s)/(kJ mol−1)±3.1}=−2506.7+0.6345 (T/K); (1034.7≤T/K≤1221.1).{ΔfG0(Sm2Ru2O7,s)/(kJ mol−1)±3.1}=−2506.7+0.6345 (T/K); (1034.7≤T/K≤1221.1).The uncertainty estimates for ΔfG0(T) include the standard deviation in e.m.f. and uncertainty in the data taken from the literature.
    ChemInform 01/2006; 37(4).
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    ABSTRACT: The Gibbs free energy of formation of Nd3RuO7(s) has been determined using solid-state electrochemical cell employing oxide ion conducting electrolyte. The electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured, in the temperature range from 929.3 to 1228.6 K.Cell: (−)Pt/{Nd3RuO7(s) + Nd2O3(s) + Ru(s)}//CSZ//O2(p(O2) = 21.21 kPa)/Pt(+)The Gibbs free energy of formation of Nd3RuO7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by:{ΔfG°(Nd3RuO7, s)/(kJ mol−1) ± 1.6} = −3074.3 + 0.6097(T/K); (929.3 ≤ T/K ≤ 1228.6).The uncertainty estimate for ΔfG°(T) includes the standard deviation in e.m.f. and the uncertainty in the data taken from the literature. The intercept and the slope of the above equation correspond to the enthalpy of formation and entropy, respectively, at the average experimental temperature of Tav. = 1079 K.
    ChemInform 01/2006; 37(41).
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    ABSTRACT: The citrate-nitrate gel combustion route was used to prepare SrFe{sub 12}O{sub 19}(s) powder sample and the compound was characterized by X-ray diffraction analysis. A solid-state electrochemical cell of the type: (-)Pt, O{sub 2}(g)/(CaO(s)+CaF{sub 2}(s))//CaF{sub 2}(s)//(SrFe{sub 12}O{sub 19}(s)+SrF{sub 2}(s)+Fe{sub 2}O{sub 3}(s))/O{sub 2}(g), Pt(+) was used for the measurement of emf as a function of temperature from 984 to 1151K. The standard molar Gibbs energy of formation of SrFe{sub 12}O{sub 19}(s) was calculated as a function of temperature from the emf data and is given by: {delta}{sub f}G{sub m}{sup o} (SrFe{sub 12}O{sub 19}, s, T)/kJmol{sup -1} (+/-1.3)=-5453.5+1.5267x(T/K). Standard molar heat capacity of SrFe{sub 12}O{sub 19}(s) was determined in two different temperature ranges 130-325K and 310-820K using a heat flux type differential scanning calorimeter (DSC). A heat capacity anomaly was observed at 732K, which has been attributed to the magnetic order-disorder transition from ferrimagnetic state to paramagnetic state. The standard molar enthalpy of formation, {delta}{sub f}H{sub m}{sup o} (298.15K) and the standard molar entropy, S{sub m}{sup o} (298.15K) of SrFe{sub 12}O{sub 19}(s) were calculated by second law method and the values are -5545.2kJmol{sup -1} and 633.1JK{sup -1}mol{sup -1}, respectively.
    Materials Research Bulletin 02/2005; 40(2). · 1.97 Impact Factor
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    ABSTRACT: The citrate–nitrate gel combustion route was used to prepare SrFe12O19(s) powder sample and the compound was characterized by X-ray diffraction analysis. A solid-state electrochemical cell of the type: (−)Pt, O2(g)/{CaO(s) + CaF2(s)}//CaF2(s)//{SrFe12O19(s) + SrF2(s) + Fe2O3(s)}/O2(g), Pt(+) was used for the measurement of emf as a function of temperature from 984 to 1151 K. The standard molar Gibbs energy of formation of SrFe12O19(s) was calculated as a function of temperature from the emf data and is given by: ΔfGm∘(SrFe12O19, s, T)/kJ mol−1 (±1.3) = −5453.5 + 1.5267 × (T/K). Standard molar heat capacity of SrFe12O19(s) was determined in two different temperature ranges 130–325 K and 310–820 K using a heat flux type differential scanning calorimeter (DSC). A heat capacity anomaly was observed at 732 K, which has been attributed to the magnetic order–disorder transition from ferrimagnetic state to paramagnetic state. The standard molar enthalpy of formation, ΔfHm∘(298.15 K) and the standard molar entropy, Sm∘(298.15 K) of SrFe12O19(s) were calculated by second law method and the values are −5545.2 kJ mol−1 and 633.1 J K−1 mol−1, respectively.
    Materials Research Bulletin. 02/2005; 40(2):323–332.
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    ABSTRACT: The standard Gibbs free energies of formation of Sr2RhO4(s) and Sr4RhO6(s) have been determined using two types of solid-state electrochemical cells: one using CaF2(s) as the solid electrolyte, the fluoride cell and the other wherein calcia-stabilized zirconia (CSZ) has been used as the solid electrolyte, the oxide cell. The fluoride cell was operated in the temperature range from 895 to 1018 K and can be represented by and the oxide cell was operated in the temperature range from 1092 to 1267 K and can be represented by The standard Gibbs free energies of formation of Sr2RhO4(s) and Sr4RhO6(s) from elements in their standard state, calculated by combining results obtained from fluoride and oxide cells, can be given respectively by .
    Journal of Alloys and Compounds 01/2005; 381:58-62. · 2.73 Impact Factor
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    ABSTRACT: For Abstract see ChemInform Abstract in Full Text.
    ChemInform 08/2004; 35(32).
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    ABSTRACT: The standard Gibbs free energies of formation of Sr2RuO4(s) and Sr3Ru2O7(s) have been determined using two types of solid-state electrochemical cells: one using CaF2(s) as the solid electrolyte, the fluoride cell and the other wherein calcia-stabilized zirconia (CSZ) has been used as the solid electrolyte, the oxide cell. The standard Gibbs free energies of formation of Sr2RuO4(s) and Sr3Ru2O7(s) from elements in their standard state, calculated by combining results obtained from fluoride and oxide cells, can be given respectively by:ΔfGo[Sr2RuO4(s)](kJmol−1)(±1)=−1595.8+0.3588(T(K)).ΔfGo[Sr3Ru2O7(s)](kJmol−1)(±1)=−2546.7+0.6010(T(K)).The enthalpy increments of Sr2RuO4(s) measured using a high-temperature Calvet micro-calorimeter can be represented by the polynomial expression:Ho(T)−Ho(298.15K)(Jmol−1)=−69975.4+166.2(T/K)+0.554×10−1(T/K)2+46.18×105(K/T),310.4≤T(K)≤903.0.Molar heat capacity Cp,mo(T) of Sr2RuO4(s), was derived. The second law method gave the enthalpy of formation of Sr2RuO4(s) from elements in their standard state as ΔfHo(Sr2RuO4,s, 298.15K) = −1643.2kJmol−1.
    Journal of Alloys and Compounds 01/2004; 373(1):59-66. · 2.73 Impact Factor
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    ABSTRACT: The standard molar Gibbs energy of formations of BaFe12O19(s), BaFe2O4(s), Ba2Fe2O5(s), Ba3Fe2O6(s) and Ba5Fe2O8(s) have been determined using solid-state electrochemical technique employing CaF2(s) as an electrolyte. The reversible e.m.f. values have been measured in the temperature range from 970 to 1151K. The oxygen chemical potential corresponding to three phase equilibria involving technologically important compound BaFe12O19(s) has been determined using solid-state electrochemical technique employing CSZ as an electrolyte from 1048 to 1221K. The values of ΔfGm0(T) for the above ternary oxides are given byΔfGm0(BaFe12O19,s)/kJmol−1(±0.6)=−5431.3+1.5317(T/K)(970⩽T/K⩽1151)ΔfGm0(BaFe2O4,s)/kJmol−1(±1.3)=−1461.4+0.3745(T/K)(970⩽T/K⩽1151)ΔfGm0(Ba2Fe2O5,s)/kJmol−1(±1.4)=−2038.3+0.4433(T/K)(970⩽T/K⩽1149)ΔfGm0(Ba3Fe2O6,s)/kJmol−1(±1.5)=−2700.1+0.6090(T/K)(969⩽T/K⩽1150)andΔfGm0(Ba5Fe2O8,s)/kJmol−1(±1.6)=−3984.1+0.9300(T/K)(973⩽T/K⩽1150)The uncertainty estimates for ΔfGm0 includes the standard deviation in the e.m.f. and uncertainty in the data taken from the literature. An isothermal oxygen potential diagram for the system Ba–Fe–O was constructed at 1100K based on the thermodynamic data obtained in this study.
    Journal of Solid State Chemistry 01/2004; 177(4):1146-1156. · 2.04 Impact Factor
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    ABSTRACT: The Gibbs free energy of formation of CaRh2O4(s) has been determined using two techniques viz., quadrupole mass spectrometer coupled to a Knudsen cell and solid-state cell incorporating CaF2(s) as the solid electrolyte. In the former method, equilibrium O2(g) pressures were measured over the phase field Rh(s)+Rh2O3(s), in the temperature range 793.7–909.1K and over the three phase mixture CaRh2O4(s)+Rh(s)+CaO(s) was measured from 862.1 to 1022.7K.The Gibbs free energy of formation of Rh2O3(s) from elements in their standard state can be given by ΔfG°(Rh2O3(s))(kJmol−1±2.0)=−363.2+0.241T(K).The Gibbs free energy of formation of CaRh2O4(s) from elements in their standard state can be given by ΔfG°(CaRh2O4(s))(kJmol−1±2.0)=−1030.5+0.3437T(K).In the electrochemical technique, the cell configuration employed was (−)Pt/O2(g),{CaO(s)+CaF2(s)}//CaF2//{CaRh2O4(s)+Rh2O3(s)+CaF2(s)},O2(g)/Pt(+).The emf values were measured in the temperature range 879.7–1000K can be represented by the following expression: E(V)(±7.63×10−4)=0.3928−2.374×10−4T(K).From the measured emf of the cell and requisite ΔfG° values from the literature, ΔfG°(CaRh2O4(s)) from elements in their standard state has been calculated and can be represented by ΔfG°(CaRh2O4(s))(kJmol−1±2.0)=−1079+0.390T(K).The uncertainty estimates for ΔfG° include the standard deviation in the emf and uncertainty in the data taken from the literature. The slope and intercept of the above equation gives the entropy and enthalpy of formation of the compound at the average experimental temperature Tav=940K.
    Thermochimica Acta - THERMOCHIM ACTA. 01/2004; 417(1):59-65.
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    ABSTRACT: The standard Gibbs free energies of formation of Ba2U3O11(s) and BaU2O7(s) have been determined using a solid state electrochemical cell, wherein calcia stabilized zirconia (CSZ) was used as the solid electrolyte. The cells can be represented by: The standard Gibbs free energies of formation of Ba2U3O11(s) and BaU2O7(s) from elements in their standard state, can be given, respectively, by:
    ChemInform 01/2004; 35(47).
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    ABSTRACT: Two compounds, BaLa2Fe2O7(s) and BaLaFeO4(s) in the quaternary system Ba–La–Fe–O have been prepared by citrate-nitrate gel combustion route and characterized by X-ray diffraction analysis. Heat capacities of these two oxides were measured in the temperature range from 302 K to 832 K using a heat flux type differential scanning calorimeter. Two different types of solid-state electrochemical cells with CaF2 as the solid electrolyte were employed to measure the e.m.f. as a function of temperature. The standard molar Gibbs energy of formation of the above oxides was calculated as a function of temperature from the e.m.f. data. The standard molar enthalpy of formation at 298.15 K, ΔfHm∘(298.15K) and the standard entropy Sm∘(298.15K), of these two oxides were calculated by second law method. The values of ΔfHm∘(298.15K) and Sm∘(298.15K) obtained for BaLa2Fe2O7(s) are: −3446.4 kJ·mol−1 and 246.6 J·K−1·mol−1 whereas those for BaLaFeO4(s) are: −2080.4 kJ·mol−1 and 95.0 J· K−1·mol−1, respectively.
    Journal of Chemical Thermodynamics - J CHEM THERMODYN. 01/2004; 36(10):911-917.
  • R. Agarwal, R. Prasad, V. Venugopal
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    ABSTRACT: Enthalpy increments of ThO 2, (Th 0.9804U 0.0196)O 2, (Th 0.961U 0.039)O 2, (Th 0.941U 0.059)O 2, (Th 0.902U 0.098)O 2 and simfuel of (Th 0.9804U 0.0196)O 2 were measured using a high temperature Calvet drop calorimeter in the temperature range 375-991 K. The experimental values were used for calculating heat capacities of the compounds, which were compared with Neumann-Kopp's heat capacity values. On inter comparison of the heat capacity values of solid solution, (Th yU (1- y) )O 2, with variation in the fraction of ThO 2, a trend was observed. In the temperature range of the present experiments, the compound (Th 0.961U 0.039)O 2 showed minimum heat capacity values.
    Journal of Nuclear Materials 11/2003; 322(2):98-110. · 2.02 Impact Factor
  • R. Agarwal, R. Prasad, V. Venugopal
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    ABSTRACT: Enthalpy increments of ThO2, (Th0.9804U0.0196)O2, (Th0.961U0.039)O2, (Th0.941U0.059)O2, (Th0.902U0.098)O2 and simfuel of (Th0.9804U0.0196)O2 were measured using a high temperature Calvet drop calorimeter in the temperature range 375–991 K. The experimental values were used for calculating heat capacities of the compounds, which were compared with Neumann–Kopp’s heat capacity values. On inter comparison of the heat capacity values of solid solution, (ThyU(1−y))O2, with variation in the fraction of ThO2, a trend was observed. In the temperature range of the present experiments, the compound (Th0.961U0.039)O2 showed minimum heat capacity values.
    Journal of Nuclear Materials 11/2003; 322(s 2–3):98–110. · 2.02 Impact Factor
  • The Journal of Chemical Thermodynamics 05/2003; 35(5):851–858. · 2.30 Impact Factor