Pot Mill Research Articles

Role of Water in the Mechanochemical Reactions of MgO–SiO2Systems

The products of mechanochemical activation of mixtures in the magnesia–silica system ground in a planetary pot mill for up to 20 h. were found to depend on the water content of the siliceous starting materials. Mixtures containing silica gel produced no new products detectable by XRD and29Si MAS NMR, but their thermal reaction to form forsterite at 890°C was slightly enhanced by grinding. In contrast, mixtures containing more highly hydrated silicic acid produce a layer-lattice magnesium silicate with an 8.4-Å basal spacing and a29Si MAS NMR spectrum similar to that of the product obtained when the same mixture is subjected to hydrothermal reaction conditions. A possible explanation in terms of a mechanochemically induced hydrothermal reaction mechanism is discussed.

Grinding Effect of Powder on Thermal Expansion of Silica Glass Powder Compacts

A thermal expansion ten times larger than that of silica glass was observed for the pressed compacts of silica glass powder, which was ground with a planetary pot mill. The extent of the thermal expansion increased with increasing the grinding time. Since quartz powder compacts did not undergo much thermal expansion after grinding, such a large thermal expansion behavior of the silica glass powders seemed to be unique for the silica glass. Solid state 29Si NMR and IR spectra showed a reduction in the Si-O-Si bonding angle, which resulted due to a distortion of the silica glass network.

Preparation of a reference fallout material for activity measurements

Since the present environmental activity level is becoming extremely low, the quality control in determining fallout activities has become more important. So far, there is no reference material for fallout activity. In this paper, preparation of such a reference material is tried by using deposition samples collected at 14 stations throughout Japan in 1963–1979, which were preserved after the γ-activity measurement. About one-third of each deposition sample was combined and pulverised in a rolling pot mill. The obtained mixture was divided into about 1000 bottles, each of which contains 4 g of the sample. A homogeneity test was done by 137Cs determination. With this reference material, 90Sr, 137Cs and Pu isotopes were determined by several independent institutions. The results showed good accordance among the individual institutions, meaning that the sample can be used as a reference material for the measurement of the fallout activity.

Preparation of Calcium-Strontium Apatite through Mechanochemical Method

Abstract The formation of a calcium-strontium apatite solid solution precursor via mechanochemical method was described. The precursor is formed by a process of ball-milling of a slurry consisting of a mixture of the starting materials; CaHPO4·2H2O, CaCO3, SrHPO4 and Sr(OH)4·8H2O in a zirconia pot mill for 24 h in the presence of water at room temperature over the entire Ca/(Ca+Sr) compositional range. Calcium-stontium apatite precursor obtained from ball-milling began to change to calcium-stontium apatite upon heating at temperature over 500 °C.

ボールミル処理によるＳｎＯ２‐Ｓｂ２Ｏ３系半導性粒子の調整に及ぼすミル回転速度の影響

Semiconductive SnO2 fine powder, doped with Sb, was prepared by a mechano-chemical reaction during dry ball milling. The effects of the crystallinity of the SnO2 starting powder and the revolution rate of the pot mill were discussed in relationship to the doping reaction of Sb in SnO2 during ball milling by taking the milling mechanism into consideration.The results obtained are the following:(1) Ball milling at a high revolution rate was effective for the doping reaction of Sb in SnO2, so that the electrical conductivity of the powder mixture ball-milled at such a speed became higher compared with that of the powder mixture ball-milled at a low speed.(2) When the ball milling was carried out at a high revolution rate using well crystallized SnO2, the doping reaction of Sb was facilitated. However, at the same time, since particle size reduction was significant, the increase in the electrical conductivity was prevented. Thus, when the SnO2 starting powder was used, with a medium degree of crystallinity, the increase in the electrical conductivity was greatest due to competition between the particle size reduction and Sb doping reaction in SnO2.

Preparation of Trimagnesium Phosphate by Mechanochemical Reaction

Trimagnesium phosphate hydrate was synthesized by mechanochemical reaction of a slurry of magnesium hydrogen phosphate trihydrate and magnesium oxide with the molar ratio of 2:1 in a pot mill for a few hours. Mg3(PO4)2⋅8H2O was obtained by using a slurry with more than 60wt% water; Mg3(PO4)2⋅22H2O, with 40wt% water. The anhydrate of trimagnesium phosphate was obtained by heating Mg3(PO4)2⋅8H2O or Mg3(PO4)2⋅22H2O above 700°C.

A Consideration of the Differential Grinding of Quartz and Feldspar in Weathered Granite

An experimental study has been made to obtain the compressive strength and Martens scratching hardness of quartz, alkali feldspar and plagioclase particles. These minerals were sorted from weathered granite according to the weathering degree. The compressive strength and hardness of weathered plagioclase particles showed a prominent decrease due to argillization against the unweathered ones as compared with the other two minerals. The different behaviour of the compressive strength and hardness of each mineral suggests that the abrasive grinding mechanism may be more effective than compressive one for differential grinding.Laboratory scale mill tests were carried out with the samples of weathered granite by using pot mill, jet mill and hammer mill. The results of the differential grinding show that pot mill was more effective than jet and hammer mills in the amount of grinding for plagioclase particles.

Laboratory mill

Because pigments vary widely in their properties, various procedures for making them up into test formulations must be adopted. Thus, some require pot mill treatment, others can be ground on the laboratory roll mill, while a few respond to high speed stirrers. A further variation arises in the pigment response to a formulation, which may then involve a series of experiments to find the optimum formulation. The rows of pot mills in operation bear testimony to the daily permutations involved in product development in a laboratory.

Fine Grinding of Natural graphite in Dry Pot Mill

Fine Grinding of Natural graphite in Dry Pot Mill