The change of electroless Ni‐Mo‐P alloy films was investigated using a pulse heating method that provided a very high heating rate (up to 106 K min−1) and a very short heating time (200 ms). Both amorphous and crystalline Ni‐Mo‐P alloy films under “as‐plated” conditions were prepared by controlling the Na2MoO4 concentration in the plating baths. The heat change properties of both amorphous and crystalline films during the pulse heating were compared with those during conventional long‐time annealing, by measuring the specific resistance, the temperature coefficient of resistance, and the saturation magnetization. For both amorphous and crystalline Ni‐Mo‐P alloy films under “as‐plated” conditions, the crystallization and the phase transformation processes which occurred during the pulse heating were different from the corresponding processes observed in the conventionally annealed films. Furthermore, the film structure after the higher‐power pulse heating was also found to be different from that after conventional annealing at 700°C for 1h. The Ni‐Mo‐P alloy film after the pulse heating was very stable against change in the later conventional annealing at 700°C for 1h.
A B S T R A C T A n electroless Ni-Zr-P c o m p o s i t e film a n d a Ni-Nb-P c o m p o s i t e film were plated a n d their heat~treating b e h a v i o r s were investigated. The addition of 20g d m -3 of metallic p o w d e r resulted in a c o m p o s i t e film t h a t c o n t a i n e d 21.2 w e i g h t perc e n t (w/o) of Zr, [13.8 a t o m p e r c e n t (a/o)], or 4.8 w/o of Nb, (2.9 a/o), respectively. B o t h metallic p o w d e r s were d i s p e r s e d uniformly t h r o u g h o u t the films. T h e metallic Ni f o r m e d by t h e crystallization of t h e Ni-P m a t r i x diffused into t h e metallic powders, a n d t h e a m o r p h o u s Ni-Zr a n d Ni-Nb p h a s e s were f o r m e d by h e a t -t r e a t m e n t at 500 ~ or 300~ S o m e parts of t h e a m o r p h o u s Ni-Zr p h a s e s a n d t h e metallic Ni p h a s e s c o m b i n e d to form intermetallic c o m p o u n d s by h e a t -t r e a t m e n t at 600~ T h e nickel-rich parts of the a m o r p h o u s Ni-Nb p h a s e were c o n v e r t e d into a m e t a s t a b l e Ni-Nb p h a s e (4 phase) or a Ni-Nb solid solution b y h e a t -t r e a t m e n t at 700~ T h e longer h e a t i n g t i m e at 400~ i n c r e a s e d t h e a m o u n t of t h e Ni-Zr amorp h o u s phase: however, it d e c r e a s e d the reactivity of t h e a m o r p h o u s Ni-Zr phase. T h e s a m e h e a t -t r e a t m e n t of 400~ did n o t give t h e c o n s i d e r a b l e c h a n g e on t h e a m o r p h o u s Ni-Nb phase. Recently, c o m p o s i t e films c o m p o s e d of a metallic plated matl:ix a n d inert particles h a v e b e e n actively i n v e s t i g a t e d b y m a n y w o r k e r s (1, 2) to i m p r o v e t h e i r wear a n d a b r a s i o n resistance (3). N o n m e t a l l i c particles, s u c h as BN, SiC, SiO2, a n d A120~, are c o m m o n l y used as t h e d i s p e r s i o n for this purpose. S o m e w o r k e r s h a v e u s e d metallic p o w d e r s s u c h as Cr, Ni, or Cu, for t h e d i s p e r s i o n (4-6); while others h a v e a t t e m p t e d to t h e r m a l l y treat t h e c o m p o s i t e film to create a n e w alloy (7-9), especially in electroless plating (9). It is also possible to create a n e w material by t h e r m a l l y t r e a t i n g an electroless c o m p o s i t e film, w h e r e t h e d i s p e r s i o n particles of h a r d l y electroless-deposited m e t a l react w i t h t h e plating matrix. This p a p e r describes t h e t h e r m a l treating b e h a v i o r of t h e electroless-plated Ni-P c o m p o s i t e films w i t h Zr or N b m e t a l p o w d e r s w h i c h have n o t b e e n u s e d as t h e dispersion. M o r e o v e r , we discuss the solid-state reaction bet w e e n t h e Ni-P m a t r i x a n d each m e t a l powder. Experimental Electroless Ni-P m a t r i x films were d e p o s i t e d to a thickness of 2 ~m by controlling t h e plating t i m e from a general a m m o n i a c a l alkaline bath. T h e c o m p o s i t i o n a n d t h e operating c o n d i t i o n s of t h e b a t h are listed in Table I. Prio...
The corrosion behaviour of carbon steel under combined water treatment (CWT) conditions was investigated for the purpose of determining the minimum adequate oxygen concentration. Corrosion tests were carried out in owing water (pH 9 . 0) under simulated CWT conditions at 250°C for 500 h, and electrochemical measurements were also carried out during these test periods. The corrosion potential of carbon steel shifted in the noble direction and the polarisation resistance increased with increasing oxygen concentration in the range of 5 to 15 l g L 1 . The corrosion rate calculated from weight loss measurements in oxygenated water containing 15 l g L 1 of dissolved oxygen was less than that in deaerated water. In the case of the water containing 25 l g L 1 of dissolved oxygen, the corrosion loss was much smaller than that for deaerated water. In addition, no signi cant change of corrosion behaviour was observed for oxygen concentrations in the range 25 to 100 l g L 1 . The present work has shown that the oxygen dosing concentration for CWT could be decreased, the minimum oxygen concentration required to maintain protective oxide lms having been estimated to be in the range 15 -25 l g L 1 .
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