Materials of the Western Trypillia Culture From the Settlements of Kamianets-Podilskyi, Tatarysky And Kubachivka

This paper presents the results of archaeological surveys at the Western Trypillia culture sites of Kamianets-Podilskyi, Tatarysky and Kubachivka in the 1990s and the 2000s. The article considers the history of research at these settlements from their discovery (in 1926 and 1947 respectively) until the present. The authors have specifically focused upon threats faced by the Kubachivka site, which keeps being destroyed by the eponymous quarry situated nearby. The study analyzes ceramics and flint and stone tools from the settlements. Ceramics from the Kamianets-Podilskyi, Tatarysky (3950—3900 ВСЕ) is represented by table and kitchen pottery. The first is decorated with a monochromic ornamental painting (black and brown colors); the most informative tableware are craters decorated with «face patterns» that are typical for the Mereșeuca local group, Stage BII (as per Taras M. Tkachuk). Tools are made from various raw materials including granitoids, Cenomanian and Turonian flint. The collection includes items related to the production of tools and other products (the attrition mill and the powder-crusher), waste and items of artifacts secondary processing. As far as Kubachivka settlement is concerned, the sample of ceramics materials is rather poor. The most of the items are not sufficiently intact. Upon having analyzed materials, we have been able to confirm the preliminary conclusions of prior researches. Stonework artifacts are also represented in a modest quantity of 9 pcs. These mostly include polished items as well as a hammered stone, plates, and suchlike. In our opinion, the ceramic artifacts discovered thereby should be ascribed to two chronological horizons, specifically: the BI—II and the BII stages. Further investigations will enable more precise chronologies.

Influence of excess alumina on mullite synthesized from pyrophyllite by spark plasma sintering

The influence of excess Al2O3 on 3:2 mullite produced from α-Al2O3 and pyrophyllite powder was examined. A mixture consisting of 28 wt.% dehydroxylated pyrophyllite and 72 wt.% α-Al2O3 was milled in an attrition mill. The milled powders were sintered by spark plasma sintering (SPS) at 1600°C for 10, 20 and 30 min. Subsequently, the samples were heated at 1350°C for 2 h to determine the influence of the excess Al2O3 on the microstructure. No glassy phase was detected in the sample containing 72 wt.% Al2O3 and sintered at 1600°C for 20 min. The sample with 72 wt.% Al2O3 had greater hardness and fracture toughness compared to 3:2 mullite. The greatest hardness and fracture toughness of 12.43 GPa and 2.71 MPa m–0.5, respectively, were obtained in the sample containing 72 wt.% Al2O3 sintered at 1600°C for 20 min.

Fine Comminution of Pine Bark: How Does Mechanical Loading Influence Particles Properties and Milling Efficiency?

The use of lignocellulosic plant biomass as an alternative to fossil feedstocks for chemistry, energy and materials often involves an intense dry comminution step, for which the energy consumed can vary significantly according to the process parameters, the particle size targeted, and the properties of the biomass. Here we studied the fine milling of maritime pine bark in an impact-mill configuration and in an attrition-mill configuration. The properties of the resulting powders (particle size distribution, particle shape, specific surface area, agglomeration level) obtained in each configuration were compared in relation to process energy consumption. Results evidenced that the agglomeration phenomena drive milling efficiency and limit the possibilities for reaching ultrafine particles. Interestingly, impact loading proved more effective at breaking down coarse particles but tended to generate high agglomeration levels, whereas attrition milling led to less agglomeration and thus to finer particles.

Reactivity of fly ashes milled in different milling devices

The effect of two different milling devices, namely attrition mill versus vibration mill, on the reactivity of fly ash was studied. High calcium fly ash from 4th Thermal power station of Ulaanbaatar (Mongolia) was used for the experiments. The raw and processed samples were characterized by XRD, SEM, Particle size distribution, BET, Blaine surface area and density measurements. The efficiency of 1 hour milling was evaluated with the Blaine surface area set to be more than 5000 cm2/g. The physical and chemical properties of the attrition milled fly ash changed not much compared to the vibration milled samples. For example the d50 particle size became reduced from 29 µm to 6 µm by attrition milling and in vibration milled fly ash it was reduced to 7 µm. The density increased from 2.44 g/cm3 of raw fly ash to 2.84 g/cm3 and 2.79 g/cm3 in attrition and vibration milled samples, respectively. Mechanical milling revealed not only a particle size reduction but also the formation of a denser microstructure. As a result the vibration milled fly ash showed a weaker interaction with the alkaline solution (8 M NaOH used here) compared to the attrition milled fly ash. Consequently, compressive strength of the binder prepared using the attrition milled fly ash was higher, 61 MPa, while for vibration milled fly ash it was 49 MPa. For comparison unmilled fly ash, it was 21 MPa.

The Effects of Ammonium Polyacrylate and Diammonium Citrate as Base and Acid Dispersion Agents on Yttria-Stabilized Zirconia (3Y-TZP) Dispersion Properties

Stable slurries in dispersions of 3Y-TZP in aqueous suspension with the addition of different concentrations of dispersants such as ammonium polyacrylate (APA) and diammonium citrate (DAC) were investigated. The dispersion properties were investigated by measuring the particle size, zeta potential, sedimentation, and viscosity as a function of the wt.% of the dispersant. Both dispersant agents were attached to the 3Y-TZP surface by the carboxylic group, as shown by the FTIR results. The addition of dispersants was found to produce more dispersed and stabilized aqueous suspension. As shown the viscosity result, that there is no being viscosity peak has been occurring and viscosity going decrease as the shear rates increasing which mean that the suspension has shear thinning behavior and there is no agglomeration as the shear rate is increased. It was determined that 3.5 wt.% of DAC and APA produced the best and most stable slurry; when 3.5 wt.% of DAC and APA was added, the zeta potential showed the largest value in the monodisperse condition. The low pH value of DAC has obtained the higher zeta potential value than APA, which was assumed due to low pH of DAC suspension. At low pH, the adsorption of the adsorbate will occur in a flat adsorbed, while at higher pH the polyelectrolyte will dangle into solution, thus reducing electrostatic repulsion as it is found in the case of APA addition. In this condition, the particle size was decreased to the lower value and the slurry’s stability was obtained with the lowest sedimentation height after the sedimentation test for 30 days. The sample was milled in an attrition mill at 1,000 rpm for four hours.

Effect of Mechanical Activation on the Synthesis of Ba-Celsian and Sr-Celsian using Precursor Mixtures Containing Coal Fly Ash

ABSTRACTBaAl2Si2O8 and SrAl2Si2O8 were synthesized by solid-state reaction of stoichiometric mixtures of either BaCO3 or SrCO3 with coal fly ash and Al2O3. The mixtures were mechanically activated in an attrition mill for up to 12 h and then reaction-sintered at 900-1300 °C, aiming to promote the formation of BaAl2Si2O8 and SrAl2Si2O8 as well as the conversion from their hexagonal (Hexacelsian) into their monoclinic (Celsian) forms, which is associated with improved mechanical properties in the sintered materials. Especially in the case of SrAl2Si2O8, the formation of Celsian was favored at relatively low sintering temperatures by increasing milling time. Although only the SrAl2Si2O8 composition was fully converted into Celsian, the Hexacelsian to Celsian conversions obtained for the mechanically-activated BaAl2Si2O8 composition were significantly higher than those previously reported in the literature for this compound. This could be attributed to the use of coal fly ash as raw material, which contains mineralizers that promote the mentioned conversion.

Effects of Mechanical Alloying on Microstructure and Properties of Powder Injection Moulded SiCp-Reinforced Aluminium Composite

This research investigated effects of mechanical alloying on microstructure and hardness of 30 vol.% SiCp - reinforced aluminium composites produced by powder injection moulding. Mechanical alloying was performed via an attrition mill prior to feedstock preparation at 52% and 55% solid loadings. Powder injection molding was operated at 170 oC followed by debinding and sintering at 680-740 oC. Experimental results showed that mechanical alloying aided better mixing of aluminium powder and SiCp such that certain amounts of SiCp was observed to be engulfed into deformable aluminium powder matrix. This in turn increased the interfaces between the two phases, thus facilitating sintering of the composite. By employing mechanical alloying, the effective sintering temperature has significantly reduced from 740 oC down to 700 oC. Improved sintered density and hardness were obtained by increasing % solid loading and sintering temperature.