Discrete element method investigation of the milling characteristic in a rice mill

A milling chamber consisting of a rice sieve and a rotating roller plays critical roles in modulating the milling performance of rice grains. However, the mechanism of how the geometries of the rice sieve and rotating roller affect the particle collisions and the interaction time remains not fully understood. Our experimental results show that the milling degree and rate of broken rice of the octagonal rice sieve are largest among the hexagonal sieve, octagonal sieve, and circular sieve. Through the discrete element method, we illustrate that the peak milling degree at the octagonal sieve is attributed to the competition between the decreasing force and increasing milling time with the increase in edges. In addition, the geometries of the convex ribs of the rotating roller are investigated to optimize the structure of the milling chamber. In the left-hand spiral or right-hand spiral of the convex ribs, the rice particles are accumulated in the inlet or outlet regions, respectively, which leads to an uneven milling degree in the axial direction. The uniformity of a milling process can be promoted by increasing the number of convex ribs, which will reduce the milling degree on the other hand.

Effect of Ball Milling Time on the Performance of Phosphorous Building Gypsum

The use of phosphogypsum to prepare phosphorus building gypsum (PBG) is of great value to the resource utilization of phosphogypsum. In this study, PBG was ball-milled to obtain phosphorus building gypsum with good performance, which can meet the requirements of the Chinese standards for first-class building gypsum. Meanwhile, the changes of net slurry physical properties, mechanical properties, and particle size parameters of PBG under different treatment times were analyzed. With the increase of ball milling time, the particle size of PBG decreased rapidly and then stabilized, and the specific surface area gradually increased and then started to rise back. Ball milling can significantly reduce the standard consistency water requirement of phosphogypsum, resulting in a shorter setting time and higher strength of phosphogypsum. In the fixed water consumption test, the effect of ball milling time on the performance of phosphogypsum was small. Compared with sieving, washing, aging, and other means of PBG treatment, ball milling has the advantages of simplicity, environmental protection, and low cost, and it has some practical significance in production.

The effect of milling time on the alumina phase transformation in the AMCs powder metallurgy reinforced by silica-sand-tailings

This study aims to determine the effect of milling time and sintering temperature parameters on the alumina transformation phase in the manufacture of Aluminium Matrix Composites (AMCs) reinforced by 20 % silica sand tailings using powder metallurgy technology. The matrix and fillers use waste to make the composites more efficient, clean the environment, and increase waste utilization. The milling time applied to the Mechanical Alloying (MA) process was 0.5, 6, 24, 48, and 96 hours, with a ball parameter ratio of 15:1 and a rotation of 93 rpm. Furthermore, hot compaction was carried out using a 100 MPa two-way hydraulic compression machine at a temperature of 300 °C for 20 minutes. The temperature variables of the sintering parameter process were 550, 600 to 650 °C, with a holding time of 10 minutes. Characterization of materials carried out included testing particle size, porosity, X-Ray Diffraction (XRD), SEM-Image, and SEM-EDX. The particle measurement of mechanical alloying processed, using Particle Size Analyzer (PSA) instrument and based on XRD data using the Scherrer equation, showed a relatively similar trend, decreasing particle size occurs when milling time was increased 0.5 to 24 hours. However, when the milling time increases to 48 and 96 hours, the particle size tends to increase slightly, due to cold-weld and agglomeration when the Mechanical Alloying is processed. The impact is the occurrence of the matrix and filler particle pairs in the cold-weld state. So, the results of XRD and SEM-EDX characterization showed a second phase transformation to form alumina compounds at a relatively low sintering temperature of 600 °C after the mechanical alloying process was carried out with a milling time on least 24 hours

Microstructure and mechanical behavior of Al-xMg/5Al2O3 nanostructured composites

The effect of Mg content and milling time were investigated on the microstructure and microhardness values of Al-xMg/5Al2O3 (x = 0, 4, 8 and 12 wt %) nanostructured composite prepared via high energy milling technique. XRD results showed an acceleration of alloying process and formation of Al (Mg) ss by enhancing percentage of Mg element. Also, by increase in Mg percentage the grain size reduction was more considerable during milling treatment. Additionally, increment of the Mg content up to 12 wt%, causes the increase in micro-strain of the samples (from 0.31 to 0.82%). Increase in Mg concentration accelerates the mechanical milling process. According to SEM results a coaxial and circular morphology with a uniform distribution of powder particles has been formed. Up to 12 wt% (for each milling time), significant increase in microhardness (215 HV) was carried out due to solid solution hardening and crystallite refinement. From 10 to 15 h, a slight increase in microhardness up to 218 HV can be observed.

Optimization of Formulation and Operating Parameters for Ginkgo biloba Extract Nanosuspension by Wet Ball Milling Using a Box–Behnken Design

In the present work, the formulation of nanosuspension of Ginkgo biloba extract (GBE) and the operating parameters of wet ball milling (WBM) was optimized using the Box–Behnken design (BBD) method. The key formulation factors evaluated were GBE concentration, milling speed, milling time, and sodium dodecyl sulfate (SDS) concentration. A quadratic model with the correlation coefficient ( R 2 ) value of 0.9276 was established based on the experimental data, implying that this model is significant; meanwhile, the analysis of variance (ANOVA) showed that the SDS concentration was the most significant factor on particle size, followed by GBE concentration, milling speed, and milling time was the slighter significant factor. The GBE nanosuspension with the particles size of 171.2 nm was prepared under the optimized conditions of GBE concentration (7.459 g/L) in combination with milling time (1.492 h), milling speed (9.253 m/s), and SDS concentration (0.846 g/L). The freeze-dried nanosuspension exhibited spherical particle morphology with uniform size by scanning electron microscopy. In addition, the melting behavior of the raw material and milled GBE was analyzed by differential scanning calorimetry and it was found that the melting point decreased due to the decrease of particle size. Furthermore, the dissolution rates of the optimized GBE showed better dissolution properties than the unprocessed GBE. The results show that it is feasible to prepare GBE nanosuspension on a commercial scale by WBM to increase the bioavailability of GBE.

Prediction of Structural and Magnetic Properties of Nanocrystalline Mechanically Alloyed Fe-Ni Powders Using Multi-Gene Genetic Programming Approach

In this paper, a theoretical model based on multi-gene genetic programming (MGGP) approach has been applied to predict the structural and magnetic properties in nanocrystalline Fe–Ni powders prepared by mechanical alloying (MA) using a planetary ball mill. The MGGP model was used to correlate the input parameters (milling speed, chemical composition, and milling time), to output parameters (crystallite size and coercivity) of nanocrystalline Fe–Ni powders. The model obtained was tested with additional data to demonstrate its performance and prediction ability. The MGGP model is a robust and efficient method to find an accurate mathematical relationship between input and output data. A sensitivity analysis study was applied to determine the most influential milling parameters on the crystallite size and coercivity.

The Effect of Ball Milling Time on the Isolation of Lignin in the Cell Wall of Different Biomass

Ball milling technology is the classical technology to isolate representative lignin in the cell wall of biomass for further investigation. In this work, different ball milling times were carried out on hardwood (poplar sawdust), softwood (larch sawdust), and gramineous material (bamboo residues) to understand the optimum condition to isolate the representative milled wood lignin (MWL) in these different biomass species. Results showed that prolonging ball milling time from 3 to 7 h obviously increased the isolation yields of MWL in bamboo residues (from 39.2% to 53.9%) and poplar sawdust (from 15.5% to 35.6%), while only a slight increase was found for the MWL yield of larch sawdust (from 23.4% to 25.8%). Importantly, the lignin substructure of ß-O-4 in the MWL samples from different biomasses can be a little degraded with the increasing ball milling time, resulting in the prepared MWL with lower molecular weight and higher content of hydroxyl groups. Based on the isolation yield and structure features, milling time with 3 and 7 h were sufficient to isolate the representative lignin (with yield over 30%) in the cell wall of bamboo residues and poplar sawdust, respectively, while more than 7 h should be carried out to isolate the representative lignin in larch sawdust.

An Interdisciplinary Agent-based Evacuation Model: Integrating Natural Environment, Built environment, and Social System for Community Preparedness and Resilience

Previous tsunami evacuation simulations have mostly been based on arbitrary assumptions or inputs adapted from non-emergency situations, but a few studies have used empirical behavior data. This study bridges this gap by integrating empirical decision data from local evacuation expectations surveys and evacuation drills into an agent-based model of evacuation behavior for a Cascadia Subduction Zone community. The model also considers the impacts of liquefaction and landslides from the earthquake on tsunami evacuation. Furthermore, we integrate the slope-speed component from Least-cost-distance to build the simulation model that better represents the complex nature of evacuations. The simulation results indicate that milling time and evacuation participation rate have significant non-linear impacts on tsunami mortality estimates. When people walk faster than 1 m/s, evacuation by foot is more effective because it avoids traffic congestion when driving. We also find that evacuation results are more sensitive to walking speed, milling time, evacuation participation, and choosing the closest safe location than to other behavioral variables. Minimum tsunami mortality results from maximizing the evacuation participation rate, minimizing milling time, and choosing the closest safe destination outside of the inundation zone. This study's comparison of the agent-based model and BtW model finds consistency between the two models' results. By integrating the natural system, built environment, and social system, this interdisciplinary model incorporates substantial aspects of the real world into the multi-hazard agent-based platform. This model provides a unique opportunity for local authorities to prioritize their resources for hazard education, community disaster preparedness, and resilience plans.

Preparation of Expanded Graphite and Graphite Nanosheets for Improving Electrical Conductivity of Polyester Coating Films

Expanded graphite and graphite nanosheets were facilely prepared by the thermal expansion of expandable graphite at 800 °C and sand milling of expanded graphite in water, respectively. When the expandable graphite precursor was prepared by the oxidation and intercalation of natural graphite (5 g) using KMnO4 (6 g) as an oxidant in a concentrated sulfuric acid solution (120 mL) at room temperature (25 °C) for 8 h, the expanded graphite with a maximum volumetric rate of 317 mL g−1 was prepared after the thermal expansion of the expandable graphite precursor at 800 °C for 60 s. The oxidation extent of natural graphite with KMnO4 is crucial for the preparation of expanded graphite. The thicknesses of graphite nanosheets decreased from 8.9 to 3.2 nm when the sand milling time of the expanded graphite in deionized water was prolonged from 6 to 24 h. The prolonging of the sand milling time not only decreased the layer number of the graphite nanosheet but also increased the d002 spacing due to the shocking and shearing forces. The addition of the expanded graphite powder and graphite nanosheets in a polyester paint efficiently improved the electrical conductivity of the resultant polyester coating films.

New reaction paths for advanced SiAlON/TiN composites

<p>This thesis demonstrates how selected ceramic additives, including titanium nitride (TiN), impact upon the “chemistry ↔ microstructure ↔ properties” relationship as it applies to composites in the generic Sialon-TiN composite field. Examination and optimisation of this feedback loop enables control of industrially important thermal, electrical and engineering properties of β-Sialon based ceramics. The effects of a range of additives on the nitridation and sintering of β-Sialon composite bodies have been studied and the chemical and mechanical properties of the sintered bodies have been measured. The additives can be divided in three groups: nitridation additives which improve the yield and the rate of the reaction; sintering aids; and additives that improve resistance to thermal shock. A suite of additives consisting of a mixture of calcium aluminate cement, yttrium aluminium garnet and boron nitride was found to deliver an optimum set of mechanical properties with a fracture toughness achieved of over 4 MPa.m-1/2. This thesis also reports a new reaction path for the formation of a β-Sialon/TiN composite by the reaction bonding of aluminium powder coated with nanosized titania. In this novel technique, the aluminium reacts under an inert atmosphere with titania to form alumina and a TixAly intermediate which is then nitrided to form aluminium nitride and titanium nitride. The addition of a suitable silicon phase enables the formation of a β-Sialon phase under nitrogen at high temperature. The TiN was added in the range 1 to 10 wt% (0.6 to 6 vol%). The effects of milling time on the aluminium powder particle size distribution and reactivity have been studied, with a minimum of two days milling time required to modify the particle shape and reduce melting coagulation during firing. Firing parameters have been optimised, using XRD and MAS-NMR to monitor the samples’ composition and SEM to observe their microstructure. The reduction of titania by aluminium was completed at 900 ºC for 4 hours in an argon atmosphere and the nitridation of the titanium aluminide at 1400 ºC for 3 hours in a nitrogen flow. The nitridation and sintering of the β-Sialon/TiN composite were both performed in nitrogen at 1400 ºC and 1600 ºC, respectively. A low level of addition of TiN (1 wt%) has shifted the composition toward the AlN corner of the Sialon behaviour diagram, forming α-Sialon and AlN polytypes. Other levels of addition in the studied range formed a dense β-Sialon/TiN composite. The TiN inclusions are found at the grain boundaries but are of insufficient volume fraction to form a continuous network in the Sialon matrix. Mechanical and electrical properties of the newly fabricated β-Sialon/TiN composites have been measured. These properties were generally improved by the highest levels of TiN addition: Young’s modulus (up to 210 GPa), hardness (up to 17.7 GPa), fracture toughness (up to 3.3 MPa.m-1/2) and compressive strength (up to 188 MPa). However the presence of TiN had no impact on the resistance to thermal shock and electrical conductivity of the β−Sialon. Finally, the oxidation process for β-Sialon/TiN composites has been observed by a combination of XRD, SEM and Ion Beam Analysis techniques. The results show early enrichment of yttrium and titanium in the first 0.1 μm of the samples’ surface; replacement of nitrogen by oxygen to form crystalline phases on the surface and in the glassy phase up to 1.5 μm deep; and, major crystalline and chemical changes in an outer layer of about 100 μm thickness at 1200 ºC. The partial depletion of SiO species from the external sample surface during sintering firing leaves this surface zone more vulnerable to oxidation than the protected body of the ceramic. The oxidation of TiN forms a TiO₂ skin which acts as a protection from further oxidation. The outcome of this research is a novel reaction path to fabricate new advanced Sialon composites and an improved understanding of the effect of a broad range of additives on the nitridation and sintering behaviour of β-Sialon and β-Sialon/TiN composites.</p>