Mechanochemically synthesized powders

VII. Subsequent Heat Treatment of the Mechanochemically Synthesized Powders. .449... 

PZN)-barium titanate (BT) ceramics from mechanochemically synthesized powders. Mater. Res. Bull., 37 (15), 2491-2498. 

The solid-phase reactions starting from metal powders in conditions of friction (Examples 8 and 9) are described in two recent monographs [201,202] (see the scheme of the mechanochemical reactor in Ref. 202). In this respect, we note the possibility of a solid-state synthesis with the use of metal salts. In particular, mechanochemical syntheses are widely used for obtaining acetylacetonates [698-70Id] by the method of ligand exchange, for example (3.277) [701a] ... 

Fine LiMn204 powders with the size of 150 nm are synthesized by a mechanochemical/solvothermal treatment of LiOH and Mn02 in acetone / tetrahydrofran. Promoted nucleation relating to the chemical reduction of Mn02 contributes to the size reduction. The synthesized powder shows the improved cell capacity (90% of the theoretical value) and relatively good cycle performance. 

J. Ding, T. Tsuzuki, P. G. McCormick, Hematite Powder Synthesized by Mechanochemical Processing, NanoStructured Mater., 1997, 8 (6), 739. 

Ding, J., Tsuzuki, T., and McCormick, P.G., Hematite powders synthesized by mechanochemical processing, Nanostruct. Mater, 8, 739, 1997. 

Stability of nanocrystalline powder samples, synthesized in Sr-Ba-Fe-Co-0 system by the mechanochemical activation route in Ha atmosphere is investigated. Samples of various compositions were used to establish the main reasons of samples destruction. XRD, EPR and XPS methods were employed to characterize the samples before and after treatment in the Ha atmosphere (600 °C, 1 h). Essential content of cobalt in a sample was found to degrade its stability, whereas an insertion of additional amount of FeaOj at the end of the mechanochemical activation enhances stability. 

To elaborate the techniques of monoliths extrusion, the batches of powdered perovskites (up to 100 kg) were synthesized via mechanochemical route. In contrary to ceramic jierovskite powders, MA samples can be formed as rings without any addition of binder or peptizers into water-based pastes. However, after calcination at 500-900°C these rings have a rather low mechanical strength, which reaches an acceptable (ca 10 kg/cm ) level only after annealing at 1000°C. Any attempts to extrude micromonoliths without binders were imsuccessful. 

The application of mechanical alloying to the synthesis of rare-earth permanent magnets was first demonstrated by the work of Schultz and co-workers (Schultz et al. 1987). Subsequently, the magnetic properties of a number of rare-earth-transition-metal compounds synthesized by the mechanical alloying of elemental powders, mechanical milling of intermetallic compounds, or by mechanochemical reaction, using oxide and halide precursors, have been studied. 

The chemical functional group of the synthesized calcium phosphate powder was determined by using FTIR analysis. Figure 3 for example shows the FTIR spectra for HA powder through dry mechanochemical synthesis with different speeds. 

Abstract— Thermal analysis of hydroxyapatite formation through dry mechanochemical method has heen stndied. The calcium phosphate was synthesized using calcinm hydroxide and di-ammonium hydrogen phosphate as the precnrsors. The ball milling of 1/6 ball-powder mass ratio was employed on mixtures of calcium hydroxide and di-ammoninm hydrogen phosphate in three different speeds 170, 270 and 370 rpm for 15 h. As ball-milled powders were then sintered at 1150, 1250 and 1350°C for 2 h, then subjected to TGA, XRD and FTIR for phase characterization. Calcium phosphates with ammonium are phases of the material. The ammonium is trace of phosphorus precursor. Choosing condition of the process and type of precursors determines type of reactions and its products. 

Abstract. Highly-crystallized fine LiMn204 powders have been synthesized by a combination of the mechanochemical (MC) and solvothermal (ST) treatments of LiOH and MnOi in acetone. The MC product is amorphous, but, shows the formation of Mn-O-Li bond. The ST post treatment promotes the nucleation of LiMn204 by the chemical reduction of Mn to Mn. The estimated chemical compositions are LiMn(III)o.iiMn(IV)i.8904.45 (MC) and LiMn(III)o.76Mn(IV)i.i203.88 (MC/ST). The MC/ST powder crystallized at 800°C indicates the cell capacity of 119 mA.h.gThe dilution of acetone with tetrahydrofuran is effective to reduce the particle size. The MC/ST product using the diluent shows the fine particle size of 150 nm and the excellent cell capacity of 134 mA.h.g. ... 

Borothermic reduction was confirmed at a lower temperature, and the carbothermic reduction occurred at a higher temperature (33), which favors the production of high-purity powders. TiB2 and ZrBj powders were also synthesized by mechanochemical treatment of titania and zirconia powders with amorphous boron followed by a relatively low-temperature annealing (1100°C) (34). The occurrence of polymorphic transformations has been observed with milling time for both systems, together with a decrease upon annealing of the temperature of the boro-... 

Besides wet-synthesis methods, another two novel methods have been used to synthesize MA spinel powders. These are mechanochemical alloying and molten salt synthesis (MSS). 

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