Oscillatory Ball Mill Research Articles

Evolution of grinding energy and particle size during dry ball-milling of silica sand

The energy efficiency of dry fine grinding process of powders dramatically declines with decreasing particle size, and represents a growing concern in various cutting-edge technical applications for pharmaceutical and cosmetic products, advanced-ceramics, and food industry. In this paper, we report on a detailed experimental analysis of the long-term grinding behavior of silica sand as a model material in an oscillatory ball mill for a broad range of the values of vibration frequency and amount of powder. We show that the re-agglomeration of fine particles unambiguously explains the anomalous increase of grinding power consumption. We also find that the agglomeration phenomena are correlated with the volume fraction of the class of finest particles. A nonlinear comminution model is shown to capture this effect for the prediction of the evolution of the specific surface area.

Prebiotic Sugar Formation Under Nonaqueous Conditions and Mechanochemical Acceleration.

Monosaccharides represent one of the major building blocks of life. One of the plausible prebiotic synthesis routes is the formose network, which generates sugars from C1 and C2 carbon sources in basic aqueous solution. We report on the feasibility of the formation of monosaccharides under physical forces simulated in a ball mill starting from formaldehyde, glycolaldehyde, DL-glyceraldehyde as prebiotically available substrates using catalytically active, basic minerals. We investigated the influence of the mechanic energy input on our model system using calcium hydroxide in an oscillatory ball mill. We show that the synthesis of monosaccharides is kinetically accelerated under mechanochemical conditions. The resulting sugar mixture contains monosaccharides with straight and branched carbon chains as well as decomposition products. In comparison to the sugar formation in water, the monosaccharides formed under mechanochemical conditions are more stable and selectively synthesized. Our results imply the possibility of a prebiotic monosaccharide origin in geochemical environments scant or devoid of water promoted by mechanochemical forces such as meteorite impacts or lithospheric activity.

Effect of different impact events in fine grinding mills on the development of the physical properties of dried Norway spruce (Picea abies) wood in pulverisation

The effect of different impact events, which occur in fine grinding mills, on the development of the physical properties of dry Norway spruce wood in pulverisation was studied. Dry Norway spruce wood with a median size d50=199μm (±6μm) was pulverised in an opposed jet mill and an oscillatory ball mill down to a d50 of approximately 20μm. In addition, knowledge from an earlier study was used to obtain information about high-speed rotor impact milling. The development of physical properties, such as aspect ratio, width of its distribution and cellulose crystallinity, as a function of particle size was significantly different using oscillatory ball milling compared to using jet milling. When pulverising to median sizes of approximately 20μm, oscillatory ball milling resulted in lower cellulose crystallinity and rounder, more uniform particle shapes than did jet and rotor impact milling. It is proposed that media mills are capable of imposing higher energies and, consequently, cause stronger physical changes for dry Norway spruce wood particles compared to impact-based non-media mills.

Effect of mild torrefaction on pulverization of Norway spruce (Picea abies) by oscillatory ball milling: particle morphology and cellulose crystallinity

Abstract The effects of mild torrefaction on the pulverization of Norway spruce sawdust have been studied. To this end, sawdust was dried and torrefied below 230°C for different periods of time to obtain samples with mass losses (ML) of 0.2%, 1.4%, and 2.8%, milled in an oscillatory ball mill, and the particle morphology and cellulose crystallinity of the powders were studied. The pretreatment leading to 0.2% ML had no effect on grindability, but that resulting in 1.4% ML improved grindability and a median particle size below 17.4±0.2 μm was attained. Torrefaction involving 2.8% ML reduced the specific energy consumption more than 21% when the targeted median particle size of the torrefied wood was between 18.7±0.5 and 79±3 μm. The mild torrefaction had a negligible influence on the aspect ratio distribution and cellulose crystallinity in the ball-milled wood.

Impact-based pulverisation of dried and screened Norway spruce (Picea abies) sawdust in an oscillatory ball mill

Abstract This study investigates the impact-based pulverisation of dried and screened Norway spruce (Picea abies) sawdust into a median particle size range of less than 100 μm in an oscillatory ball mill. Pulverisation is studied by considering the effects of impact energy, the number of impact events and the amount of feed on the size and shape properties of the pulverised wood. The impact energy is treated as the kinetic energy of the grinding ball and the impact event is considered as a period during which the grinding ball travels from one end-wall of the grinding jar to the other. Given a certain number of impact events, the use of higher impact energy lowers the particle sizes of the wood particles until a minimum size is attained. The minimum value for the median particle size is found between 13 μm and 20 μm. In the pulverisation, the aspect ratios of the wood particles decrease with the use of a higher impact energy and larger number of end-wall collisions. Within a certain range, the changes in the size and shape properties can be predicted from the total impact energy available for the pulverisation when the energy efficiency of the pulverisation remains constant. The energy efficiency of the pulverisation process can be affected by varying the amount of the feed. The pulverisation of dried Norway spruce sawdust from a median size range of 1 mm and 2 mm down to a median size below 100 μm is accomplished with the specific energy consumption of 0.36 kJ/g (100 kWh/t); reduction to a median size below 20 μm is accomplished with the specific energy consumption of 1.4 kJ/g (380 kWh/t).

Physical characterization and stability of amorphous indomethacin and ranitidine hydrochloride binary systems prepared by mechanical activation

Co-milling of γ-indomethacin and ranitidine hydrochloride form 2 at various weight ratios (1:2, 1:1 and 2:1) was investigated with a particular interest in the physicochemical properties and the stability of the milled mixed amorphous form. Co-milling was carried out using an oscillatory ball mill for various periods of time up to 60 min in a cold room (4 °C). The maximum temperature of the solid material was 42 °C during co-milling in a cold room. Results showed that both indomethacin and ranitidine hydrochloride were fully converted into the amorphous state after 60 min of co-milling. In contrast individually milled drugs remained partially crystalline after co-milling under the same conditions. During co-milling, the XRPD characteristic peaks of indomethacin were found to decrease faster than those of ranitidine hydrochloride. DSC results were in agreement with XRPD, and T gs of the fully converted amorphous mixtures of 29.3, 32.5 and 34.3 °C were measured for the 1:2, 1:1 and 2:1 mixtures, respectively. These T g values were in good agreement with the predicted T gs of the mixtures using the Gordon–Taylor equation. DRIFTS spectra of the co-milled amorphous samples showed peaks at 1610, 1679 and 1723 cm −1, that were not present in the individually milled samples and that are indicative of an interaction at the carboxylic acid carbonyl (HO–C O) and benzonyl amide (NC O) of the indomethacin molecule with the aci-nitro (C N) of ranitidine hydrochloride. Upon 30 days of storage, the 1:2 mixtures were found to crystallize; however, the amorphous 2:1 and 1:1 mixtures were stable when milled for 60 min and stored at 4 °C (for the 2:1 mixture) and at 4 and 25 °C (for the 1:1 mixture), respectively. Although XRPD, DSC and DRIFTS suggested an interaction between the two drugs, co-crystal formation was not observed between indomethacin and ranitidine hydrochloride.

Famotidine polymorphic transformation in the grinding process significantly depends on environmental humidity or water content

The effect of environmental humidity and additional water added on the polymorphic change of famotidine in the process of grinding was investigated. The famotidine form B powder with or without additional amount of water added was respectively ground for 30 min in an oscillatory ball mill under 25 ± 2 °C and three relative humidities (RH) (50 ± 5%, 75 ± 5% or 95 ± 5% RH). Each ground sample was periodically isolated for analytical determinations by using differential scanning calorimetry (DSC), thermogravimetric (TG) analysis and Fourier transform infrared (FT-IR) microspectroscopy. The results indicate that the higher environmental humidity might induce and promote the polymorphic transformation of famotidine from form B to form A in the process of grinding. Moreover, the more the amount of water externally added the easier the polymorphic transformation of famotidine from form B to form A obtained. In addition, the more grinding time spent the more formation of form A obtained. This study disavowed the results of other studies in which no polymorphic change of famotidine even by grinding. The apparent evidence shows that the solid-state polymorphic transformation of famotidine from form B to form A in the grinding process significantly depended on the relative humidity of atmosphere and the additional amount of water added.

Formation and physical stability of the amorphous phase of ranitidine hydrochloride polymorphs prepared by cryo-milling

The effect of cryo-milling on ranitidine hydrochloride polymorphs form 1 and 2 was investigated with particular interest in the formation and the stability of the amorphous phase. Cryo-milling was carried out using an oscillatory ball mill for periods up to 60 min, with re-cooling of the milling chamber with liquid nitrogen at 15 min intervals. Results showed that both ranitidine hydrochloride form 1 and form 2 could be fully converted to the amorphous form as determined by XRPD within 30 min. Upon 14 days storage, the amorphous samples crystallized back to their original forms. In the stability studies of amorphous drug with seeds, significant polymorphic transformation from form 1 to form 2 was not found when amorphous form prepared from form 1 was seeded with form 2 crystals by gentle physical mixing. In contrast, amorphous form prepared from form 1 seeded with form 2 crystals by ball milling for 1 min and simultaneous cryo-milling methods were found to transform amorphous form prepared from form 1 to crystalline form 2 under some storage conditions. The transformation was thought to be facilitated by interaction between seed crystals and amorphous drug and a storage temperature above the Tg. Amorphous form prepared from form 2 did not transform to crystalline form 1 under any conditions used in this study.

切削チップを用いたＭｇ‐Ａｌ‐Ｚｎ混合粉末のメカニカルアロイングにおける生成相

An aluminum and a zinc powder were mixed to machined chips of AZ31 alloy with various contents, and then the powder mixtures were mechanically alloyed for various milling times using planetary ball mill, for the purpose of recycling of the magnesium alloy. Crystal phase formed in the obtained powder were investigated by X-ray diffraction and Vickers hardness of the powder particles to confirm the formed phases. When Mg-Al system powder mixture was milled for 72 ks by the planetary ball mill, super-saturated solid solution α-Mg and intermetallic compound Mg17Al12 phase are formed, while by milling using the oscillatory ball mill 54 ks was necessary. In the case of mechanically alloyed Mg-2.5 mol% Zn powder, super-saturated α-Mg phase with 2.5 mol% Zn concentration forms. The structures of Mg-28 and 52 mol% Zn powder obtained by the mechanical alloying consist of Mg2Zn2 or MgZn2 and Mg7Zn3 phases and then these phases became amorphous by milling for further time. In the case of mechanical alloying for ternary Mg-Al-Zn system, an icosahedron Mg49(Al,Zn)32 phase, the quasi crystal, forms by the milling for 72 ks in the composition range as following; (30-50)mol% Mg with Al/Zn=(90/10-60/40) molar ratio, Mg-(30-50)mol% Al-20 mol% Zn and Mg-(10-30)mol% Al-40 mol% Zn.

アモルファス・ナノ結晶制御と高機能材料 メカニカルアロイングによるＡｌ‐Ｎｉ‐Ｚｒ三元系における非晶質相の生成

The formation of amorphous phase, which are invented by Al, Ni and Zr powder, were investigated. Oscillatory ball mill was used to carry out MA (mechanical alloying) in this investigation. DMA (Double Mechanical Alloying) method was also taken, where binary amorphous phases were firstly formed by MA, and the third element powder was added to those amorphous phases, and milled by MA again. The results of DMA were compared with the results of normal MA. For MA of Al-Zr mixed powder, amorphous phases were formed for 72ks in the case of Al-40-50 mol%Zr, while Ni-Zr amorphous phases were obtained at the same milling time for Ni-35-60 mol%Zr. Ternary Al-Ni-Zr amorphous phases were successively obtained by 72 ks of DMA for 30-40 mol%Al and MAed amorphous Ni-35-60 mol%Zr mixed powders. From these results, it was shown that the DMA method was more effective and prepare a wide range ternary amorphous phase than conventional MA method. Furthermore it was confirmed that the hardness of Al-Ni-Zr amorphous alloys decreased with increasing Ni/Zr and Al/(Ni-Zr) ratios, resulted in stable amorphous phases up to higher temperature.

Time and composition dependence of mechanical alloying of Fe1-xSnx.

Mixtures of powders of iron and tin with nominal compositions ${\mathrm{Fe}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sn}}_{\mathit{x}}$ (x=0.15, 0.20, 0.25, and 0.30) have been mechanically alloyed under argon atmosphere using a horizontal oscillatory ball mill for different times. It was observed that the time evolution of the system occurs in two main steps. In the first one ${\mathrm{FeSn}}_{2}$ forms until all tin is exhausted. In the second one ${\mathrm{FeSn}}_{2}$ decomposes and tin diffuses massively into iron to produce a composition modulated bcc solid solution. For x\ensuremath{\gtrsim}0.20, besides the bcc phase, the stationary state contains a tin-based solid solution. \textcopyright{} 1996 The American Physical Society.