Grinding mechanical

It can be seen from Fig. 35(c) that MRR increases continuously with the solid concentration, which is consentaneous with the former results [41,106]. This may be due to the stronger mechanical grinding effect at the high particle concentration at which particles impact and grind the surfaces. 

When converting a conglomerate mass of relatively coarse particles into an aqueous dispersion (as in the manufacture of disperse dyes) there are two broad phases to be considered. In the first phase the dual aim is that of mechanically grinding the particles down to the required size and of obtaining as narrow a range of particle size as possible during the actual preparation of the dispersion. Maintaining these particles in a stabilised suspension constitutes the second phase. 

Above 140°C its exothermic decomposition to metal and carbon dioxide readily becomes explosive [1], A 1 kg batch which had been thoroughly dried at 50°C exploded violently when mechanical grinding in an end-runner mill was attempted [2], Explosions have been experienced when drying the oxalate as low as 80°C [6], It is a compound of zero oxygen balance. The explosion temperature of the pure oxalate is lowered appreciably (from 143 to 122°C) by application of an electric field [3], The salt prepared from silver nitrate with excess of sodium oxalate is much less stable than that from excess nitrate [4], Decomposition at 125°C in glycerol prevents explosion in the preparation of silver powder [5],... 

Lyse by mechanical grinding using a porcelain mortar and pestle. Add further LN2 as necessary during the grinding, until a fine, whitish powder is formed. The LN2 must not be allowed to evaporate completely or the cells will start to thaw and form an unmanageable paste. 

S. Orimo, H. Fujii, T. Yoshino, Reactive mechanical grinding of ZrNi under various partial pressures of hydrogen, J. Alloys Compd. 217 (1995) 287-294. 

S. Orimo, H. Fujii, Hydriding properties of the Mg Ni-H system synthesized by reactive mechanical grinding, /. Alloys Compd. 232 (1996) L16-L19. 

M.Y. Song, S.N. Kwon, S.H. Hong, D.R. Mumm, l.S. Bae, Improvement of hydrogen-sorption characteristics of Mg by reactive mechanical grinding with Cr Oj prepared by spray conversion, Int. J. Hydrogen Ener. 31 (2006) 2284-2291. 

J.-L. Bobet, B. Chevalier, M.Y. Song, B. Daniel, J. Etourneau, Hydrogen sorption of Mg-based mixtures elaborated by reactive mechanical grinding, J. Alloys Compd. 336 (2002) 292-296. 

H. Imamura, Y. Takesue, T. Akimoto, S. Tabata, Hydrogen-absorbing magnesium composites prepared by mechanical grinding with graphite effects of additives on composite structures and hydiiding properties, J. Alloys Compd. 293-295 (1999) 564-568. 

H. Imamura, S. Tabata, N. Shigetomi, Y. Takesue, Y. Sakata, Composites for hydrogen storage by mechanical grinding of graphite carbon and magnesium, J. Alloys Compd. 330-332 (2002) 579-583. 

W. Wang, C. Chen, L. Chen, Q. Wang, Change in structure and hydrogen storage properties of La,Mg,Ni alloy after modification by mechanical grinding in tetrahydrofuran, J. Alloys Compd. 339 (2002) 175-179. 

H. Fujii, S. Munehiro, K. Fujii, S. Orimo, Effect of mechanical grinding under Ar and atmospheres on structural and hydriding properties in LaNij, J. Alloys Compd. 330-332 (2002) 747-751. 

X. Liu, Y. Zhu, L. Li, Hydriding and dehydriding properties of nanostructured Mg Ni aUoy prepared by the process of hydriding combustion synthesis and subsequent mechanical grinding , /. Alloys Compd 425 (2006) 235-238. 

Tribochromism is a colour change brought about by mechanical grinding or fracture (tribochromic). 

High temperatures are generally needed in solid state synthesis to improve reaction rates and to facilitate solid state diffusion. Solid state diffusion is typically very slow. Thus, mechanical grinding steps are important to homogenize the sample and encourage complete reaction. It is important to realize, however, that some phases decompose at elevated temperatures. For example, Ba CujOy is unstable above about 1050°C (1) and the related phase, BajYCUjOg is only stable to 860°C in one atmosphere of oxygen (2). Thus, efforts to prepare these phases require a balance between the heat put in to speed the reaction kinetics and the stability limits of the desired phase. 

The simplest technique may be coprecipitation. In this method, a reagent is added to the stock solution that is destabilized and precipitated. Better mixing at a microscopic level is then achieved without mechanical grinding and mixing. Insoluble carboxylates such as citrates, oxalates and carbonates or hydroxides are the most suitable reagents. 

The various methods of preparation employed to prepare nanoscale clusters include evaporation in inert-gas atmosphere, laser pyrolysis, sputtering techniques, mechanical grinding, plasma techniques and chemical methods (Hadjipanyas Siegel, 1994). In Table 3.5, we list typical materials prepared by inert-gas evaporation, sputtering and chemical methods. Nanoparticles of oxide materials can be prepared by the oxidation of fine metal particles, by spray techniques, by precipitation methods (involving the adjustment of reaction conditions, pH etc) or by the sol-gel method. Nanomaterials based on carbon nanotubes (see Chapter 1) have been prepared. For example, nanorods of metal carbides can be made by the reaction of volatile oxides or halides with the nanotubes (Dai et al., 1995). 

Bead mills Mechanical grinding of cell suspensions with... 

POWDER. Any solid, dry material of extremely small particle size ranging down to colloidal dimensions, prepared either by comminuting larger units (mechanical grinding), combustion (carbon black, lampblack), or precipitation via a chemical reaction (calcium carbonate, etc ). Powders that are so fine that the particles cannot be detected by rubbing between... 

---