Ind. Eng. Chem. Res. 1998, 37, 1815-1820
1815
Effects of Magnetic Field on the Electroless Nickel/Cobalt Deposition Chia-Chien Lee and Tse-Chuan Chou* Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, Republic of China 701
Effects of magnetic field on the electroless nickel/cobalt deposition using electroless nickel/γAl2O3 as the support and a hypophosphite ion as the reducing agent in the alkaline solution were studied. The active sites for electroless nickel/cobalt deposition were divided into three types in which the first type of active sites were occupied by both nickel ion and cobalt ion and the second and third types of active sites were occupied by the hypophosphite ion. Three exponential equations for the rate constants of nickel, cobalt, and hypophosphite ions were obtained, respectively. The plots of logarithms of rate constants were linear with the square of magnetic flux density. Based on the results of hydrogen gas evolution rate, the recombinations of Ni+a•/Ha• and Co+a•/Ha• radical pairs were affected by the magnetic field; however, the Ha• radicals did not separate from these radical pairs. 1. Introduction The effects of magnetic field on the electroless nickel deposition were well reported in our previous studies (Lee and Chou, 1994, 1995, 1996). These results indicated that the reaction order of the hypophosphite ion (Lee and Chou, 1994), the rate constants of electroless deposition of the nickel ion (Lee and Chou, 1995), and the rate constants of oxidation of hypophosphite ion (Lee and Chou, 1996) were affected by the magnetic field. These results revealed that the reaction behavior of electroless nickel deposition was affected by the magnetic field. Besides our previous studies (Lee and Chou, 1994, 1995, 1996), there are many reports on the magnetic field effects on electroless metal depositions (Chiba and Ogawa, 1989; Osaka et al., 1992; Takebayashi et al., 1993; Tabulina et al., 1993; Mogi et al., 1993). These results revealed that the deposition rate and the morphology of the deposit were affected by the magnetic field. The electroless nickel is a superior catalyst for hydrogenations (Ko and Chou, 1993, 1994; Ko et al., 1995; Lee and Chou, 1998). The morphology and size of electroless nickel grains on γ-Al2O3 were changed by the magnetic field (Lee and Chou, 1998). These changes were due to the magnetic field effect on the deposition rate of electroless nickel (Lee and Chou, 1993, 1994). The lower hydrogenation rates of cyclohexene and benzaldehyde catalyzed by the electroless nickel catalyst prepared within a magnetic field were due to the magnetic-field-induced changes of morphology and size of electroless nickel grains. Based on the magnetic field effects on the electroless nickel deposition in our previous studies (Lee and Chou, 1994, 1995, 1996), the electroless nickel/cobalt deposition was assumed to be affected by the magnetic field. Accordingly, the effects of magnetic field on the electroless nickel/cobalt deposition are explored in this study. 2. Theoretical Analysis The Langmuir-Hinshelwood adsorption model and the magnetic-induced spin rephasing were well applied * To whom correspondence should be addressed.
to reveal the magnetic field effects on the electroless nickel deposition in our previous studies (Lee and Chou, 1994, 1995, 1996). The electroless nickel/cobalt deposition was similar to electroless nickel deposition except that two metal ions, the nickel ion and the cobalt ion, coexisted in the deposition solution. Accordingly, the Langmuir-Hinshelwood adsorption model was applied to the nickel ion, cobalt ion, and hypophosphite ion, respectively. In our previous studies (Lee and Chou, 1994, 1995, 1996), the active sites were divided into two types that were occupied by the nickel ion and hypophosphite ion, respectively. The types of active sites were assumed to be four cases in the electroless nickel/ cobalt deposition. All the definitions of the rate constants in these four cases were similar to those in our previous studies (Lee and Chou, 1994, 1995, 1996). Case I: Two Types of Active Sites. The active sites were divided into two types in which the first type of active sites were occupied by the nickel ion and cobalt ion and the second type of active sites were occupied by the hypophosphite ion, respectively. The first type of active sites reacted with the second type of active sites, and the deposition rates of the nickel ion and cobalt ion are shown as eqs 1 and 2, respectively.
(
)
(
)
1 + kNi[Ni2+] + kCo[Co2+] 1 1 ) 1+ 2+ RNi KNikNi[Ni ] kP[H2PO2-]
(1)
1 + kNi[Ni2+] + kCo[Co2+] 1 1 ) 1+ 2+ RCo KCokCo[Co ] kP[H2PO2-]
(2)
Case II: Three Types of Active Sites with Each Site Occupied by One Element. The active sites were divided into three types in which each active site was occupied by one element. The first and second types of active sites were occupied by the nickel ion and cobalt ion, respectively. The third type of active sites were occupied by the hypophosphite ion. The first and second types of active sites reacted with the third type of active sites, and the deposition rates of nickel ion and cobalt ion are shown as eqs 3 and 4, respectively.
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1816 Ind. Eng. Chem. Res., Vol. 37, No. 5, 1998
( (
) )
1 + kNi[Ni2+] 1 1 ) 1+ 2+ RNi KNikNi[Ni ] kP[H2PO2-]
(3)
1 + kCo[Co2+] 1 1 ) 1+ RCo KCokCo[Co2+] kP[H2PO2-]
(4)
Case III: Three Types of Active Sites with Each Site Occupied by One or Two Elements. The active sites were divided into three types in which each active site was occupied by one or two elements. The first type of active sites were occupied by the nickel ion and cobalt ion and the second and third types of active sites were occupied by the hypophosphite ion. Formation of the second and third types of active sites was due to the nonuniform distribution of the nickel atom and cobalt atom in the electroless nickel/cobalt deposit. Two districts, the nickel-rich surface of the electroless nickel/ cobalt deposit as the second type and the cobalt-rich surface of the electroless nickel/cobalt deposit as the third type, coexisted on the surface of the electroless nickel/cobalt deposit. The first type of active sites reacted with the second or third types of active sites, and the deposition rates of nickel ion and cobalt ion are shown as eqs 5 and 6, respectively.
(
)
1 + kNi[Ni2+] + kCo[Co2+] 1 1 ) 1+ RNi KNikNi[Ni2+] kNi,P[H2PO2-]
(5)
(
)
1 + kNi[Ni2+] + kCo[Co2+] 1 1 ) 1+ 2+ RCo KCokCo[Co ] kCo,P[H2PO2-]
(6) Case IV: Four Types of Active Sites. The active sites were divided into four types in which two types of active sites were for the nickel ion and cobalt ion and the other two types of active sites were for the hypophosphite ion. The first and second types of active sites were occupied by the nickel ion and cobalt ion, respectively. The nickel-rich surface and the cobalt-rich surface of the electroless nickel/cobalt deposit were the third and fourth types of active sites, respectively, that were occupied by the hypophosphite ion. The first type of active sites reacted with the fourth type of active sites, and the second type of active sites reacted with the third type of active sites. For the pseudo steady ratio of the nickel atom and cobalt atom in the electroless nickel/ cobalt deposit, the first type of active sites would not react with the third type of active sites and the second type of active sites would not react with the fourth type of active sites. The deposition rates of the nickel ion and cobalt ion are shown as eqs 7 and 8, respectively.
( (
1 + kNi[Ni2+]
1 1 ) 1+ RNi KNikNi[Ni2+] kNi,P[H2PO2-] 1 + kCo[Co2+] 1 ) 1+ RCo K k [Co2+] k Co Co
) )
1 Co,P[H2PO2 ]
(7)
(8)
The most important characteristic of eqs 1 and 2 is that the rate constants kP determined from eqs 1 and 2 are the same and so are those of eqs 3 and 4. The rate constants kP in eqs 1 and 2 or eqs 3 and 4 are easily
Figure 1. Plots of the reciprocal of deposition rate of the nickel ion versus the reciprocal of concentration of the hypophosphite ion: [Ni2+]i ) 0.05 M, [Co2+]i ) 0.05 M, agitation rate ) 250 rpm, temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL.
determined by plotting the reciprocals of deposition rates of the nickel ion and cobalt ion with the reciprocal of the concentration of the hypophosphite ion, respectively. For cases I and II and cases III and IV, the rate constants of the hypophosphite ion, kNi,P and kCo,P, which were determined from eqs 5 and 6 or eqs 7 and 8, respectively, are different. The rate constants kNi,P and kCo,P in eqs 5 and 6 or eqs 7 and 8 are easily determined by plotting the reciprocals of deposition rates of the nickel ion and cobalt ion with the reciprocal of the concentration of the hypophosphite ion, respectively. 3. Experimental Section The reactor, reaction procedures, determination of the evolution rate of hydrogen gas, and control of magnetic flux density for the electroless nickel/cobalt deposition were the same as those of our previous studies (Lee and Chou, 1994, 1995, 1996). The preparation of the support, electroless nickel/γ-Al2O3, was described in our previous study (Lee and Chou, 1996), and the support loading was 0.01 g/mL. The electroless nickel/cobalt deposition solution was made with nickel sulfate, cobalt sulfate, and sodium hypophosphite. A 0.50 M ammonium sulfate and a 0.40 M sodium pyrophosphate were used as both the buffer and complexing agents, respectively, in the electroless nickel/cobalt deposition solution. The pH of the electroless nickel/cobalt deposition solution was adjusted to 9.50 by ammonium hydroxide. The concentrations of the nickel ion and cobalt ion of the electroless nickel/cobalt deposition solution were determined by X-ray fluorescence spectroscopy. 4. Results and Discussion 4.1. Concentration of the Hypophosphite Ion. The effects of the concentration of the hypophosphite ion on the deposition rates of the nickel ion and cobalt ion are shown in Figures 1 and 2, respectively. As shown in Figures 1 and 2, straight lines were obtained by plotting the reciprocals of the deposition rates of the nickel ion and cobalt ion versus the reciprocal of the concentration of the hypophosphite ion, respectively. The rate constants kNi,P and kCo,P determined from Figures 1 and 2, are listed in Table 1. Based on the theoretical analyses, the rate constants kP which were
Ind. Eng. Chem. Res., Vol. 37, No. 5, 1998 1817
Figure 2. Plots of the reciprocal of deposition rate of the cobalt ion versus the reciprocal of concentration of the hypophosphite ion: [Ni2+]i ) 0.05 M, [Co2+]i ) 0.05 M, agitation rate ) 250 rpm, temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL. Table 1. Effect of Magnetic Flux Density on kNi,P, kCo,P, and RNi/RCoa RNi/RCob B, T
kNi,P, 1/M
kCo,P, 1/M
0.10
0.20
0.30
0.40
0.00 0.15 0.20 0.25
4.682 3.699 2.540 2.489
10.431 7.113 3.869 2.467
1.73 1.99 2.55 2.95
1.98 2.11 2.77 3.11
2.17 2.44 3.03 3.02
2.22 2.98 2.94
0.50 2.52 2.75 2.83
a [Ni2+] ) 0.05 M, [Co2+] ) 0.05 M, agitation rate ) 250 rpm, i i temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL.b At various [H2PO2-]i, (M).
determined from eqs 1 and 2 and eqs 3 and 4 are the same. As shown in Table 1, the rate constants kNi,P and kCo,P determined from eqs 5 and 6 or eqs 7 and 8 are different. For example, the rate constants kNi,P and kCo,P were 4.682 and 10.431 min/mol, respectively, when the electroless nickel/cobalt deposition was proceeded without a magnetic field. Based on the results of Table 1 and the theoretical analyses, the reaction of the electroless nickel/cobalt deposition is Case III or IV because the rate constants kNi,P are different from the rate constants kCo,P. As shown in Table 1, the rate constants kNi,P and kCo,P were 4.682 and 10.431 min/mol, respectively, when the electroless nickel/cobalt deposition was proceeded without a magnetic field. However, the rate constants kNi,P and kCo,P are 2.489 and 2.467 min/mol, respectively, when the electroless nickel/cobalt deposition was proceeded with a magnetic flux density of 0.25 T. The results indicated that the differences of reactions of the hypophosphite ion with the nickel ion and cobalt ion were reduced by the magnetic field. The rate constants kNi,P and kCo,P shown in Table 1 were obtained according to the results of Figures 1 and 2; however, cases III and IV were not distinguished yet because the initial concentrations of the nickel ion and cobalt ion were constant. As shown in Figures 1 and 2, the deposition rates of the nickel ion and cobalt ion increase with the concentration of the hypophosphite ion. The ratio of the nickel atom to cobalt atom in the electroless nickel/cobalt deposit would change with the deposition rates of the nickel ion to cobalt ion. Consequently, the catalytic properties of active sites of the electroless nickel/cobalt
Figure 3. Plots of the logarithms of rate constants kNi,P, kCo,P, and KP versus the square of the magnetic flux density.
deposit would change with the ratio of the nickel atom to cobalt atom of the electroless nickel/cobalt deposit. The effects of magnetic flux density and concentration of the hypophosphite ion on the ratio of deposition rates of the nickel ion to cobalt ion are also shown in Table 1. The ratio of deposition rates of the nickel ion to cobalt ion were 1.73 and 2.95, respectively, when the electroless nickel/cobalt depositions were proceeded without a magnetic field and with a magnetic flux density of 0.25 T at an initial concentration of the hypophosphite ion of 0.10 M. Based on our previous studies (Lee and Chou, 1994, 1995, 1996), the surface of the electroless nickel deposit was renewed by the electroless deposited nickel. However, the surface renewing of the electroless nickel/ cobalt deposition was different with that of the electroless nickel deposition because of two metal atoms, the nickel atom and cobalt atom, in the electroless nickel/ cobalt deposit. Accordingly, the ratio of the nickel atom to cobalt atom of the electroless nickel/cobalt deposit played an important role in the catalytic properties of the electroless nickel/cobalt deposit. As shown in Table 1, the ratio of the deposition rates of the nickel ion to cobalt ion is between 2 and 3 which indicates that the ratio of the nickel atom to cobalt atom of the electroless nickel/cobalt deposit was affected insignificantly by both the magnetic flux density and the concentration of hypophosphite ion. That is to say, the catalytic properties of the electroless nickel/cobalt deposit were affected insignificantly by the ratio of the deposition rates of the nickel ion to cobalt ion. Based on our previous studies (Lee and Chou, 1995, 1996), the rate constants were exponential functions of the magnetic flux density. Accordingly, the rate constants kNi,P and kCo,P were assumed to be exponential functions of magnetic flux density. In our previous studies (Lee and Chou, 1995, 1996), plots of the logarithms of rate constants of the nickel ion versus magnetic flux density were linear. The logarithms of rate constants kNi,P and kCo,P were assumed to be linear with the square of the magnetic flux density because the nickel ion and cobalt ion coexisted in the electroless nickel/cobalt deposition solution. By plotting the logarithms of rate constants kNi,P and kCo,P versus the square of the magnetic flux density, two straight lines were obtained as shown in Figure 3. Two empirical exponential equations for rate constants kNi,P and kCo,P were
1818 Ind. Eng. Chem. Res., Vol. 37, No. 5, 1998
Figure 4. Plot of the ratio of deposition rates of the nickel ion to cobalt ion versus the ratio of initial concentrations of the nickel ion to cobalt ion: [H2PO2-]i ) 0.20 M, agitation rate ) 250 rpm, temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL.
Figure 5. Plots of the reciprocal of deposition rate of the nickel ion versus the reciprocal of concentration of the nickel ion: [H2PO2-]i ) 0.20 M, agitation rate ) 250 rpm, temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL.
obtained as shown in eqs 9 and 10, respectively. The
kNi,P ) 4.666 exp(-10.088B2)
(9)
kCo,P ) 10.894 exp(-23.918B2)
(10)
available magnetic flux density for the empirical exponential equations was in the range from 0.00 to 0.25 T. 4.2. Concentrations of the Nickel Ion and Cobalt Ion. The effects of the concentration of the hypophosphite ion on the deposition rates of the nickel ion and cobalt ion were studied in the previous section; however, the reactions of the nickel ion and cobalt ion were not clear. Equations 5 and 6 could be combined with eq 11 at the constant initial concentration of the hypophosphite ion, where KP ) (KNikNikNi,P[H2PO2-]i/
RNi [Ni2+] ) KP RCo [Co2+]
(11)
(1 + kNi,P[H2PO2-]i))/(KCokCokCo,P[H2PO2-]i/(1 + kCo,P[H2PO2-]i)). On the other hand, based on eqs 7 and 8, the reciprocals of the deposition rates of the nickel ion and cobalt ion were proportional to the reciprocals of the concentrations of the nickel ion and cobalt ion at the constant initial concentration of the hypophosphite ion as shown in eqs 12 and 13, respectively, where KNi,P
( (
1 1 ) KNi,P 1 + RNi kNi[Ni2+]
) )
1 1 ) KCo,P 1 + RCo kCo[Co2+]
(12)
(13)
) (1 + kNi,P[H2PO2-]i)/KNikNi,P[H2PO2-]i and KCo,P ) (1 + kCo,P[H2PO2-]i)/KCokCo,P[H2PO2-]i, respectively. Plots of the ratio of deposition rates of the nickel ion to cobalt ion versus the ratio of initial concentrations of the nickel ion to cobalt ion are shown in Figure 4. In addition, plots of the reciprocals of deposition rates of the nickel ion and cobalt ion versus the reciprocals of initial concentrations of the nickel ion and cobalt ion are shown in Figures 5 and 6, respectively. As shown in Figures 4 and 5, straight lines were obtained;
Figure 6. Plots of the reciprocal of deposition rate of the cobalt ion versus the reciprocal of concentration of the cobalt ion: [H2PO2-]i ) 0.20 M, agitation rate ) 250 rpm, temperature ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL.
however, straight lines were not obtained in Figure 6. The results of Figure 4 indicated that the reactions of the nickel ion and cobalt ion well correlated with case III of theoretical analyses. Based on eq 11, the rate constants kNi and kCo were indistinguishable and they were combined into the rate constant KP. The slopes of straight lines of Figure 4 were rate constants KP, which was assumed to be a function of the magnetic flux density, and the plot of the logarithm of rate constant KP versus the square of the magnetic flux density is also shown in Figure 3. The rate constant KP at 0.00 T was neglected because of the spin-orbit coupling at low magnetic flux density (Lee and Chou, 1996). Accordingly, an empirical exponential equation for the rate constant KP is shown as eq 14. The available magnetic
KP ) 2.175 exp(6.575B2)
(14)
flux density for the empirical exponential equation was in the range from 0.15 to 0.25 T. Based on the results of sections 4.1 and 4.2, the active sites for the electroless nickel/cobalt deposition were divided into three types in which the first type of active sites were occupied by
Ind. Eng. Chem. Res., Vol. 37, No. 5, 1998 1819 Table 2. Effect of Magnetic Flux Density and Ratio of Concentrations of Nickel Ion to Cobalt Ion on the Evolution Rate of Hydrogen Gasa rH,c mL at STP/min [Ni2+]i/([Ni2+]i + [Co2+]i)b
0.00
0.15
0.20
0.25
0.00 0.25 0.50 0.75 1.00
9.5 12.6 19.2 23.3 31.8
9.5 12.6 19.2 23.5 31.9
9.5 12.5 19.0 23.4 31.7
9.6 12.5 19.4 23.3 31.8
a [H PO -] ) 0.20 M, agitation rate ) 250 rpm, temperature 2 2 i ) 308 K, pH ) 9.5, support loading ) 0.01 g/mL. b [Ni2+]i + [Co2+]i ) 0.100 M. c At various B (T).
the nickel ion and cobalt ion and the second and third types of active sites were occupied by the hypophosphite ion. 4.3. Evolution Rate of Hydrogen Gas. The effects of the magnetic flux density and the ratio of concentrations of the nickel ion to cobalt ion on the evolution rate of hydrogen gas are shown in Table 2. The evolution rate of hydrogen gas increased from 9.5 to 31.8 mL at STP/min as the ratio of concentrations of the nickel ion to cobalt ion increased from 0 to 1 when the electroless nickel/cobalt deposition was proceeded without a magnetic field. As shown in Table 2, the evolution rate of hydrogen gas increased with the ratio of concentrations of the nickel ion to cobalt ion; however, the magnetic field effect on the evolution rate of hydrogen gas was insignificant. Based on the results of Figures 1 and 2, the deposition rates of the nickel ion were higher than those of the cobalt ion. That is to say, the catalytic activity of the nickel-rich surface was higher than that of the cobalt-rich surface of the electroless nickel/cobalt deposit. The higher ratio of the nickel atom to cobalt atom in the electroless nickel/cobalt deposit was due to the higher ratio of concentrations of the nickel ion to cobalt ion. Accordingly, the nickel-rich surface of the electroless nickel/cobalt deposit would catalyze more reaction of the hypophosphite ion resulting in a higher evolution rate of hydrogen gas. Based on our previous studies (Lee and Chou 1994, 1995, 1996), there were two radical pairs, Ni+a•/Ha• and Ha•/Ha•, in the electroless nickel deposition. However, there were three radical pairs, Ni+a•/Ha•, Co+a•/Ha•, and Ha•/Ha•, in the electroless nickel/cobalt deposition. The combination of Ha•/Ha• radical pair was not affected by the magnetic field because of the same g values of Ha• radicals; however, the combinations of Ni+a•/Ha• and Co+a•/Ha• radical pairs were affected by the magnetic field (Lee and Chou, 1995). The magnetic field would reduce the recombinations of Ni+a•/Ha• and Co+a•/Ha• radical pairs. The unreacted Ha• radicals could remain in the Ni+a•/Ha• and Co+a•/Ha• radical pairs and recombined to nickel, cobalt, and proton later. On the other hand, the unreacted Ha• radicals could separate from the Ni+a•/Ha• and Co+•/Ha• radical pairs and combined to hydrogen gas. In the former situation, the Ha• radicals did not separate from the Ni+a•/Ha• and Co+a•/ Ha• radical pairs. The evolution rate of hydrogen gas was not affected by the magnetic field because the relative amounts of Ni+a•/Ha•, Co+a•/Ha•, and Ha•/Ha• radical pairs changed insignificantly. In the latter situation, the Ha• radicals would separate from the Ni+a•/ Ha• and Co+a•/Ha• radical pairs and recombined to hydrogen gas. The relative amounts of Ni+a•/Ha•, Co+a•/ Ha•, and Ha•/Ha• radical pairs would change and the evolution rate of hydrogen gas would change with the
magnetic flux density. As shown in Table 2, the evolution rates of hydrogen gas changed with the magnetic flux density insignificantly. Accordingly, the recombinations of Ni+a•/Ha• and Co+a•/Ha• radical pairs were affected by the magnetic field; however, the Ha• radicals did not separate from the Ni+a•/Ha• and Co+a•/ Ha• radical pairs. 5. Conclusions A reaction mechanism based on the adsorption model was proposed, and the active sites for electroless nickel/ cobalt deposition were divided into three types. The first type of active sites were occupied by the nickel ion and cobalt ion and the second and third types of active sites were occupied by the hypophosphite ion. Based on the results of experiments and theoretical analyses, three empirical exponential equations for the rate constants of the nickel ion, cobalt ion, and the hypophosphite ion were obtained. The plots of logarithms of the rate constants were linear with the square of the magnetic flux density. The recombinations of Ni+a•/Ha• and Co+a•/Ha• radical pairs were affected by the magnetic field; however, the Ha• radicals did not separate from the Ni+a•/Ha• and Co+a•/Ha• radical pairs because the evolution rate of hydrogen gas changed with the magnetic flux density insignificantly. Acknowledgment The authors gratefully acknowledge the financial support provided by the National Science Council through Grant NSC 83-0416-E006-016 and National Cheng Kung University. Nomenclature B ) magnetic flux density, T K, k ) rate constants R ) deposition rate of the metal ion, M/min r ) evolution rate of hydrogen gas, mL at STP/min Subscripts a ) adsorption state Co ) cobalt ion H ) hydrogen gas Ni ) nickel ion P ) hypophosphite ion
Literature Cited Chiba, A.; Ogawa, T. Influence of Magnetic Fields on Electroless Nickel Plating. Hyman Gijitsu 1989, 40, 568-572. Ko, S.-H.; Chou, T.-C. Kinetics of the Liquid-Phase Hydrogenation of (-)-R-Pinene over Electrolessly-Deposited Ni-P/γ-Al2O3 Catalyst. Ind. Eng. Chem. Res. 1993, 32, 1579-1587. Ko, S.-H.; Chou, T.-C. Hydrogenation of (-)-R-Pinene over NickelPhosphorus/Aluminum Oxide Catalysts Prepared by Electroless Deposition. Can. J. Chem. Eng. 1994, 72, 862-873. Ko, S.-H.; Chou, T.-C.; Yang, T.-J. Selective Hydrogenation of (-)R-Pinene over Nickel Catalysts Prepared by Electroless Deposition. Ind. Eng. Chem. Res. 1995, 34, 457-467. Lee, C.-C.; Chou, T.-C. Effects of Magnetic Field on the Reaction Kinetics of Electroless Nickel Deposition. Electrochim. Acta 1994, 40, 956-970. Lee, C.-C.; Chou, T.-C. Influence of Magnetic Field on the Autocatalytic Reduction of Nickel Ion Supported by γ-Al2O3 Powder. Ind. Eng. Chem. Res. 1995, 34, 4290-4296. Lee, C.-C.; Chou, T.-C. Effects of Magnetic Field on NickelCatalyzed Oxidation of Hypophosphite Ion by Water/Deuterium Oxide. Ind. Eng. Chem. Res. 1996, 35, 3907-3914.
1820 Ind. Eng. Chem. Res., Vol. 37, No. 5, 1998 Lee, C.-C.; Chou, T.-C. Hydrogenations of Cyclohexene and Benzaldehyde over Electroless Ni/γ-Al2O3 Catalyst Prepared in the Presence of a Magnetic Field. J. Appl. Catal. 1998, submitted for publication. Mogi, I.; Okubo S.; Nakagawa, Y. Effect of High Magnetic Fields on Morphology in Electroless Deposition of Silver. Proc. Electrochem. Soc. 1993, 93, 136-146. Osaka, T.; Homma, T.; Saito, K.; Takekoshi, A.; Yamazaki, Y.; Namikawa, T. Co-Based Soft Magnetic Films Produced by Electroless Deposition. J. Electrochem. Soc. 1992, 139, 13111314. Tabulina, L. V.; Andryushchenko, T. N.; Dubin, V. M. Influence of a Magnetic Field and Low-Frequency Vibration on Electroless
Nickel Plating in Hypophosphite Solutions. Russ. J. Appl. Chem. 1993, 66, 761-764. Takebayashi, Y.; Kaneno, Y.; Yoshimura, S.; Yoshihara S.; Sato, E. Magnetic Field Effect on Electroless Nickel Plating: Photoacoustic Spectroscopy Observation. Hyman Gijitsu 1993, 44, 363-364.
Received for review October 6, 1997 Revised manuscript received February 2, 1998 Accepted February 7, 1998 IE970706A
