Книги по разным темам Pages:     | 1 | 2 |

Collisions between the particles in the near-cathode porous body under application of electric field. Assuming region may change the particle trajectory promoting or the particles in the near-cathode region as porous bodies, preventing the particle movement to the cathode. Moreover, the ionic species move through this bodyУ due to the Ф the particle in the electrolyte may collide with the particle electric field in the plating solution. In its turn, the ion trapped by the cathode and prevent embedment. flow exerts the pressure upon the particles and assists the Electric forces. The ions in the double layer around the particle movement toward the cathode surface. It should particle interact with the electric field in the plating solution. be mentioned that the electroosmotic motion of particle is This results in the particle motion along the lines of electric influenced by those parameters as for electrophoretic motion field. The motion is affected by the fluid permitivity, particle (see above).

size, intensity of electric field in the particle place, and Molecular forces. At the immediate vicinity of a cathode zeta potential. The sign and value of the zeta potential surface the van der Waals attraction force appears. It occurs is determined by both the particle nature and the electrolyte with all types atoms or molecules. It arises from the charge constitution and can be changed by addition of surfactants fluctuations within an atom or molecule that is associated into the plating solution. In the near-cathode region, the with the motion of its electrons.

cathode itself affects ambiguosly the electrophoretic particle A strong repulsive force appears at short distances, when motion. On the one hand, modification of the electric field the electrolyte concentration exceeds a certain value. This lines in the near-cathode region slows down the particle force is called the structural or hydration force. It originates movement, and on the other hand, the cathode surface itself from the fact that the thin solvent layer presents near the increases the intensity of the electrophoretic movement. It interfaces. This solvent layer is ordered by hydration of should be emphasized that it is not possible measurement of cations adsorbed onto surfaces as the interfaces approaches zeta potential in the near-cathode region because it depends each other. The hydration force results from change in the on many factors and can change no only value but the structure of solvent between the interfaces and prevents the sign as well. Therefore, it is difficult task to evaluate interfaces from close approach.

the contribution of electrophoretic particle motion into the As particles aggregate approaches the near-cathode recodeposition process. gion, the force field increases. If these forces exceed In the near-cathode region, the osmotic pressure of the a certain certain critical value, which keeps the particles electrolyte affects the particle motion. The electroosmotic in the aggregated state, the aggregates are disintegrated.

motion is the phenomenon of liquid movement through Further, the solitary particles and the aggregate chips interact Физика твердого тела, 2004, том 46, вып. 684 V.I. Kurmachev, Y.V. Timoshkov, T.I. Orehovskaja, V.Y. Timoshkov with the cathode and can be adsorbed weakly onto the important. The solution of the trybology problem for highcathode. The weak adsorption step assumes the interaction tech devices can be made by joint efforts of scientists between the particle and cathode surface through adsorbed working in the field of nanodiamond manufacture, design layers of ions and solvent molecules. Further, the electric of the devices, technology of composite coatings.

field helps to uncover the particle. The thin interlayer 6) Application of composite electrochemical coatings and between the cathode surface and particle disappears. It layers, in general, and nanodiamonds, in particular, solves leads to the strong field-assisted adsorption and the particle the tribology problem. As for MicroElectroMechanical is overgrown with deposit. systems application of composite coatings and layers is the only way.

Related to functionality, the most important ptoperties 7) Particle incorporation of the fine, compared with are friction and wear resistance. For the composite geometric limits, homogeneous sizes for mechanical highsystems, mechanical properties are determined by the phase tech devices Ч the key task to apply the composite coatings composition of materials, i. e. the matrix / particle ratio.

in the moveable micromechanical systems.

The dependence of the amount of codeposited diamond particles on particle concentration in the plating bath (Fig. 4) shows that the investigated system may be described by References GuglielmiТs model [10]. The evolution of the coefficient of friction is shown in Fig. 4. Among the coatings tested, [1] Proc. 3rd Int. Conf. Tribology of Information Storage DeviФ composite nickel coatings containing ultra-fine diamond cesУ. Sendai, Japan (2001).

particles show the lower coefficient of friction. The wear [2] Yu.V. Timoshkov, A.M. Giro, V.A. Khomenok. In: Proc. Conf.

State and prospective of microelectronics developmentУ.

volume for pure Ni and composite coatings is shown for Ф Minsk (1985). P. 218.

fretting tests operated for 100 000 cycles. The amount of [3] V.I. Kurmashev, Yu.V. Timoshkov, T.I. Orekhovskaya, particles in the coatings affects the wear rate. The friction P.M. Brylyakov. J. of Magn. Soc. Jap. 15, 52, 767 (1991).

behaviour of multiphase materials has been described in the [4] Yu.V. Timoshkov, T.M. Gubarevich, I.S. Molchan, S.V. Laliterature. The main problem with these approaches is that bunov, V.I. Kurmashev, J. Franzaer, J.-P. Celis. Surf. Mod.

they are static ones and applied to ideal surfaces because Technol. XI, 991 (1998).

during wear of a multiphase material the topography [5] Yu.V. Timoshkov, T.M. Gubarevich, T.I. Orekhovskaya, changes in practice continuously. Localised wear of the I.S. Molchan, V.I. Kurmashev. Galvanotechn. and Surf. Techmatrix takes place in the first phase. After that, the particles nol. 7, 2, 20, (1999). [in Russian].

become more loaded. This dynamic process may lead to an [6] Tetsuya Osaka, Takayuki Homma. The Electrochemical Society Interface (1995).

increased wear resistance of composite materials. Of course, [7] L. Romankiw. Plating & Surface Finishing. January, the fretting wear properties of coatings are also influenced (1997).

by the size, shape and distribution of the reinforcing phase.

[8] USSR Patent No 1 694 710, CO1B, (1991).

Some composite elements of the magnetic recording [9] J. Fransaer, J.-P. Celis, J.-R. Roos. J. Electrochem. Soc. 139, systems are shown in Fig. 5.

413 (1992).

[10] N. Guglielmi. J. Electrochem. Soc. 119, 1009 (1972).

[11] Yu.V. Timoshkov, O.N. Kudanovich, T.I. Orekhovskaya, 4. Conclusion L.G. Palevskaya, V.I. Kurmashev. In: Proc. Int. Conf. Modern Ф means of communicationУ. News of Belarus Engineering This investigation on composite coatings containing nanoAcademy 2, 14/2, 14 (2002). [in Russian].

diamond particles has led to the following scientific results and common conclusions.

1) The grain size of electrolytic nickel coatings is affected by the codeposition of ultra-fine diamond particles.

Nanocrystalline Ni deposits may be formed by codeposition of ultra-fine diamond particles.

2) The microhardness of the composite coatings increases up to 420 kg mm-3 (250 for pure metal).

3) Embedment of ultra-fine diamond particles results in both decreasing the coefficient of friction from 0.43 to 0.and increasing the wear resistance by a factor of 2.

4) Composite films with nanodiamond particles obtained may be applied for components of magnetic recording devices and elements of the MicroElectroMechanical systems.

5) Tribology problem (friction, wear, lubrication) for high-tech devices, in general, and for magnetic recording systems, in particular, is the fundamental problem. In future the place of micro- and nano-tribology will be more Физика твердого тела, 2004, том 46, вып. Pages:     | 1 | 2 |    Книги по разным темам