Grinding Duration Research Articles

Determining casson yield value, casson viscosity and thixotropy of molten Chocolate using viscometer

Flow properties of chocolate highly determine mouthfeel and consumer acceptance. Aside from these, they are also important factors in determining the incorporation of chocolate in food products. This work investigated the possibility of using viscometer to determine the flow properties of molten chocolate. The data obtained from viscometer was fitted to Casson Model. Afterwards, Casson yield value and Casson viscosity were then derived. To observe the homogeneity of molten chocolate, thixotropy value was also determined. In this study, molten chocolate was produced using a stone melanger as an alternative processing method. Four grinding durations, namely 4, 8, 12, and 16 hours, were used to produce 4 types of dark chocolate. The results showed that viscometer was able to determine the value of Casson Model parameters, eventhough the shear rate reached was only approximately 45 s−1. Using this approach, it can be observed that the Casson Yield Value and Casson Viscosity increased as the grinding durations were increased.

New flotation flowsheet for recovering combustible matter from fine waste coking coal

Fine waste coking coal (FWCC) is a high-ash-content by-product produced in large quantities during separation of raw coking coal and deposited in open air without treatment, causing environmental hazards and energy waste. The main objective of this study was to recover clean coal with ash content less than 12.5% by reprocessing FWCC at KaiLuan (Group) Limited Liability Corporation (KLLC) via spiral separation, grinding, and flotation processes. First, the physical characteristics of FWCC were investigated using particle-size analyses, washability analyses, and polarizing microscopy. Then, a spiral separator was used to remove materials with high ash content from the FWCC. Subsequently, spiral clean coal was ground in a roll mill for different grinding durations. Finally, flotation separated the products of grinding from the clean coal. Analyses of the physical characteristics showed that the FWCC could be pretreated using gravity in a spiral separator because it had a large amount of high-density materials. 46.28% spiral clean coal with 26.50% ash content was obtained and 53.72% of spiral tailings with 68.94% ash content were removed with a spiral separator under optimal conditions. The following flotation theoretical yield of clean coal increases with the grinding time. However, flotation experiments show that the maximum actual yield of clean coal first increases and then decreases on increasing the grinding time from 3.5 min to 15 min. Approximately 50% clean coal was obtained at grinding times between 3.5 and 5 min. This can be used for metallurgical plants and has economic value. A novel gravity-grinding-flotation separation flowsheet was developed and nearly 24% of the FWCC could be translated into qualified clean coal to realize comprehensive utilization of this waste resource. Engineering practice further confirm that deep processing of FWCC could generate an extra profit of $11.846 million per year for KLLC. These results indicate that deep processing of FWCC is reliable, economical, and promising for the coking coal industry, and therefore, cleaner production of coking coal is feasible.

Efficiency of wet-grinding on the mechano-chemical activation of granulated blast furnace slag (GBFS)

This work aims at evaluating the effect of wet grinding on the properties of blast furnace slag (BFS) and the properties of BFS-cement mixtures. Different grinding time are considered from 10 min to 50 min at intervals of 10 min. The morphology and structure properties of ground BFS and the physical properties of BFS slurries as the function of grinding duration are analyzed. BFS cement pastes with wet-grinding BFS content of 50% are characterized. Setting time, mechanical property, microstructure and hydration products analyses are performed to evaluate the performance of wet-grinding BFS. The results indicate that wet grinding is an effective method to treat BFS, which can decrease the average particle size to 2.95 μm after 50 min of grinding, but no significant influence on the bulk minimum particle size. Wet grinding not only gives rise to a transition of zeta potential value from minus to plus, but also cause the value to increase constantly with the treatment duration. Mixtures containing wet grinding BFS present high reactivity according to the shortening of setting time, improvement of mechanical strength and reduction of porosity and Ca(OH)2.

Activation of a Raw Clay by Mechanochemical Process-Effects of Various Parameters on the Process Efficiency and Cementitious Properties.

The efficiency of the mechanochemical activation (MCA) is influenced by various process parameters as well as by the properties of the treated material. The main objective of this research was to optimize the MCA process, gaining enhancement of the chemical reactivity of a Swedish raw clay, which is going to be used as an alkali-activated cementitious binder. The effects of the amount of water, the filling ratio, the rotation speed, and the grinding duration on the amorphization degree were evaluated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Generally, wet and dry processes showed an extensive amorphization of both kaolinite and muscovite minerals present in the studied clay. On the contrary, quartz was amorphized mainly by the wet grinding process. The efficiency of both dry and wet grinding processes was enhanced by the increased number of grinding media versus the amount of the activated material. However, longer processing times caused significant agglomeration while a higher rotational speed enhanced the amorphization. Preliminary tests have shown that alkali activation of the processed clays produced hardened samples. Furthermore, the increased amorphization corresponded to the increased compressive strength values.

Effects of soaking and grinding conditions on anti-nutrient and nutrient contents of soy milk

Although soy milk is a very good source of nutrient with high biological value, the presence of anti-nutritional factors affects its nutrition quality and limits bioavailability of the nutrients. The effects of soaking duration and combination of soaking and grinding (hot or cold) on phytate, lipoxygenase, urease, trypsin inhibitor activity, protein solubility and other nutrient contents were investigated. Soaking alone at 55 and 60oC for different durations was found effective for the reduction of lipoxygense activity. Combination of soaking, blanching (80oC for 10 min) and hot grinding (100oC) significantly (P>0.05) reduced urease activity, more than 80% phytate activity and deactivated trypsin inhibitor, but did not affect protein solubility. Meanwhile, protein solubility (10–15%) was increased due to hot grinding. Soy milk extracted from soaking at 55 and 60oC for 2, 4 and 6 h with hot grinding provided higher protein content compared to cold grinding. Increase in soaking temperature from 55 to 60oC increased the extracted solid content having a potential fraction of lipid. Increasing soaking time from 4 to 6 h did not show any significant difference in terms of phytate inhibition, urease activity reduction, trypsin inhibition and protein solubility except lipoxygenase activity. The results suggested that soaking of soybean at 60oC for 6 h and hot grinding (100oC) with blanching at 80oC for 10 min is the best for reducing anti-nutrient and retaining nutrient activity for soy milk and other soy-based products.J. Bangladesh Agril. Univ. 16(1): 158-163, April 2018

Surface coating copper powder with carbon nanotubes using traditional and stirred ball mills under various experimental conditions

We investigated the effect of the raw powder properties of carbon nanotube surface coatings on metal powder, with the goal of obtaining high-quality nanocomposites. The mechanical dry coating technique was used to fabricate CNT coatings (guest particles) on the surface of copper (Cu, host) particles using a traditional ball mill and a stirred ball mill. The coatings were produced under various experimental conditions (varying rotation speed and grinding duration, with a ball diameter of 5mm), and the effect of these conditions on the surface of the powder was determined. The coated surfaces were characterized using scanning electron microscopy and field emission scanning electron microscopy. We compared prolonged milling (48h) at a low rotation speed (50rpm), with a short milling period (12h) at high rotation speed. We found that for the TBM, successful CNT coating was achieved at 50rpm over 48h. In contrast, for the SBM, CNT coatings were obtained after a short milling period (12h) at low rotation speed (50rpm).

Self-hydration characteristics of ground granulated blast-furnace slag (GGBFS) by wet-grinding treatment

The aim of this paper is to evaluate the self-hydration characteristic of GGBFS activated by wet-grinding treatment (WGT). Three slag slurries with different fineness were prepared through milling with varying duration (20 min, 40 min and 60 min, abbreviated as S2, S4 and S6, respectively). The reaction kinetics, mechanical properties, hydration products and microstructure of hardened GGBFS pastes were analyzed to assess the effect of WGT on the self-hydration process of GGBFS. The results indicated that self-hydration was achieved after grinding without chemical activation and the rate of self-hydration was improved with the increased grinding duration. The setting times were dramatically shortened and the compressive strength was notably increased when prolonging the grinding time. The hydration process of GGBFS slurry after 20 min milling included incubation period, but the others did not. The electrical resistivity development of samples S2 and S4 decreased during the initial period, followed by setting, acceleration and deceleration stage. However, sample S6 exhibited an absence of the initial stage. The self-hydration products analyses indicated that the main products were calcium silicate hydrate, calcium aluminosilicate hydrate (C-A-S-H), hydrotalcite, akermanite and calcite.

Technology features of decellularization of human liver fragments as tissue-specific fine-grained matrix for cell-engineering liver construction

One of the problems when you create a bioengineered liver, as an alternative to transplantation of the donor liver in the treatment of end-stage liver failure, is the matrix, able to temporarily perform the functions of the natural extracellular matrix (ECM) and provide the necessary conditions to maintain the viability of the liver cells. The main disadvantage of resorbable biopolymer matrices is the absence of tissue specifi c properties and the impossibility of reproducing the unique structure of the ECM of the liver.Aim:to develop technology for decellularization of liver tissue fragments, saving the structural properties of native ECM of the liver.Materials and methods.The decellularization of mechanically grinded human liver fragments was carried out in three changes of buffer solution (pH = 7.4) containing 0.1% sodium dodecyl sulfate and increasing the concentration of Triton X100 (1%, 2% and 3%, respectively). During technology development were investigated the effects of duration, conditions (static, dynamic, rotary system, magnetic stirrer) washing and methods of liver tissue grinding on the completeness of removal of cellular elements and detritus preserving the the liver ECM structure. Slices of decellularized liver tissue samples were stained by hematoxylin and eosin, and Masson method for the detection of connective-tissue elements.Results.Histological analysis methods showed that the best from the point of view of effi ciency of decellularization and the safety of the structure of own human liver ECM, is a mode of washing of liver fragments for three days at room temperature in static conditions, accompanied by stirring by a magnetic stirrer for 2–3 times a day for one hour. Longer time or a large multiplicity of mixing mode is accompanied by increased risk of liver tissue damage. On the basis of the experimental results obtained the algorithm of preliminary study of donor human liver designed to optimize the process of obtaining decellularization fragments of liver tissue was elaborated.Conclusion.It was elaborated the algorithm and technology of obtaining of decellularized liver tissue fragments from the human donor liver which saved the structural properties of native ECM of the liver and complete removal of cellular elements and detritus.

Changing the quality of ground meat for sausage products in the process of grinding

Fine and thin grinding of meat to transform it into a homogeneous mass in sausage making was investigated. It is shown that meat raw materials with the same chemical composition but different degrees of grinding have different structural and mechanical characteristics that directly affect the quality of ground meat and the yield of finished products. The processes of thin grinding lead to high cutting speeds, which causes the raw materials temperature increase, denaturalization of proteins, change in the water-binding capacity and structural and mechanical properties of ground meat. The physicochemical properties of meat proteins were studied and the relationship between the physicochemical characteristics of ground meat, their effect on SMC, RP of ground meat in the meat grinding for boiled sausage products were determined, which made it possible to determine the optimum grinding duration, taking into account the cutting ability of cutters of different capacities. To this end, ground meat with different ratios of beef, pork and fatback, as well as production formulas for sausage products were used. It is shown that the degree of meat grinding affects the structure of muscle fibers, fat and connective tissues, protein solubility, strength, structure and moisture content of ground meat, which is crucial for obtaining high-quality sausages. It is proved that with increasing meat grinding duration above a certain extreme, the solubility of protein fractions decreases, structural and mechanical characteristics deteriorate, the moisture-binding capacity of ground meat decreases, which depends on the state of myofibrillar proteins forming a coagulation structure. The optimum grinding duration for a doctor’s sausage is 13 min at a humidity of WH=0.673 with the subsequent maximum yield and depends on the chemical composition of raw materials, formulation of sausage products, and type of grinding equipment. Changes in rheological characteristics, water-binding capacity and number of proteins that pass into the liquid phase of ground meat, correlate with each other. The influence of the grinding degree on the microstructure of ground meat from various meat tissues and their combinations was evaluated for the creation of meat grinding control devices and automation of the process.

Poly(3-hydroxybutyrate-co-hydroxyvalerate) and wheat straw fibers biocomposites produced by co-grinding: Processing and mechanical behavior

The main objective of this work was to explore for the first time the potential of the co-grinding process using a high-energy vibrated ball mill to prepare poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/wheat straw fibers biocomposites. Grinding conditions of virgin PHBV pellets were examined by focusing on the evolution of particle size, morphology, crystallinity, and molecular weight. Temperature and grinding duration were demonstrated to be the key parameters affecting PHBV milling. In a second step, mechanical properties of biocomposites prepared by cryo-co-grinding were discussed in relation to the processing conditions and the resulting structure of materials. Comparing to virgin PHBV, the reinforcing effect of wheat straw fibers was very poor, regardless of the good dispersion of fibers within the polymer matrix induced by co-grinding. The increased brittleness and decreased toughness of biocomposites were attributed to (a) a poor interfacial compatibility between wheat straw fibers and PHBV and (b) the degradation of PHBV during processing, as revealed by the decrease in molecular weight.

Influence of a Superplasticizer on Cement Grinding and Its Activity Reduction During Storage

The influence of the superplasticizer S-3 on the grindability of Portland cement and loss of its activity when it stored in air for a few weeks were investigated. The experimental results showed that the co-grinding of cement and a superplasticizer decreases the grinding duration and the absorption of moisture from the air during a long-term storage of cement. Combining the cement with a superplasticizer during the grinding process is a more effective method than introducing of an additive in the form of the dispersed powder to the binder. The mechanism of the interaction between cement and the chemical additive at various ways of combining them was considered. Сo-grinding of cement and a superplasticizer is recommended in the production of dry building mixtures to increase their shelf life and to produce cements which are suitable for transport and long-term storage.

Physical and Structural Transformations of Perlis Carbonate Rocks via Mechanical Activation Route

Carbonate rocks were mechanically activated in a high energy planetary ball mill using dry grinding method. The fine grinding test works were carried out with the same ball to powder ratio (9:1) at three levels of revolution speed (250rpm, 350rpm and 450rpm) and grinding time (30min, 60min, 90min) respectively. The chemical composition and elemental constituents of the raw dolomite and limestone samples were determined using X-ray fluorescence (XRF) and energy dispersive X-ray spectroscopy (EDX). The structural properties such as degree of crystallinity (DOC), crystallite sizes and lattice strains of non-activated and mechanically activated carbonate rocks were analyzed using X-ray diffraction (XRD) while the morphological analysis conducted using scanning electron microscopy (SEM). Results obtained showed that high revolution speed and longer grinding duration have pronounced effect on the grindability, increase in fineness, decrease in crystallite sizes and amorphization of Perlis dolomite compared to the limestone source. This might be due to the difference in material hardness and existence of appreciable amount of quartz content in limestones.

Effect of rice husk ash fineness on porosity and hydration reaction of blended cement paste

An experimental investigation on the effect of grinding fineness of rice husk ash (RHA) on the mechanical, hydration and porosity properties of RHA blended paste was launched. Locally produced RHA with six different grinding durations of 5, 10, 30, 60, 90 and 120min corresponding to mean particle size of 8.61, 8.15, 5.45, 6.25, 6.38 and 6.95μm, respectively, were used in this study. The physical and chemical properties of the ground RHAs were determined and results show that variations in chemical composition of RHAs with different grinding fineness are small. The pastes with water binder ration of 0.4 and cement substitution of 10% by ground RHAs were tested. Comparisons between pastes with SF, and control paste (only with ordinary Portland cement) were also presented. Mechanical properties, hydration reaction and porosity of paste were investigated by compressive strength, thermogravimetric analysis (TGA) and environment scanning electron microscope (ESEM) plus Image Pro Plus software analysis, respectively. Results show that incorporation of 30-min grinding RHA exhibits a strong, high hydration and low porosity paste due to the better dispersion, filling effect and pozzolanic activity.

Facile preparation of nanofiller-paper using mixed office paper without deinking

Mixed office paper (MOP) pulp without deinking with an ash content of 18.1 ± 1.5% was used as raw material to produce nanofiller-paper. The MOP pulp with filler was mechanically fibrillated using a laboratory stone grinder. Scanning electron microscope imaging revealed that the ground filler particles were wrapped by cellulose nanofibrils (CNFs), which substantially improved the incorporation of filler into the CNF matrix. Sheets made of this CNF matrix were densified due to improved bonding. Specific tensile strength and modulus of the nanofiller-paper with 60-min grinding reached 48.4 kN·m/kg and 8.1 MN·m/kg, respectively, approximately 250% and 200% of the respective values of the paper made of unground MOP pulp. Mechanical grinding duration did not affect the thermal stability of the nanofiller-paper.

Influence of the textural parameters of resorcinol–formaldehyde dry polymers and carbon xerogels on particle sizes upon mechanical milling

Abstract Porous carbons find various applications in catalysis, electrochemical storage or sorption. Prior to use, their particle sizes need however to be controlled according to the targeted application. In this study, the grinding behavior of materials prepared from aqueous resorcinol–formaldehyde mixtures and displaying different pore textures was studied in detail. Both dry polymer gels and pyrolyzed carbon xerogels were compared in terms of particle size distributions after planetary ball-milling. The results show that the pore texture and the qualitative hardness of the materials have a strong influence on the grinding behavior, especially if carbon xerogels pyrolyzed before grinding are considered. On the other hand, it appears that the milling of polymer gels, followed by a pyrolysis step, is the most efficient way to obtain homogeneous particle size distributions, for all of the investigated mesopore textures. In this case, carbon particles displaying a narrow grain size distribution centered on a mode value near 10 μm are successfully obtained after similar grinding durations, with retention of the mesopore texture of the starting materials. This work also demonstrates the possibility of using mercury intrusion porosimetry as an interesting tool to assess simultaneously the mesopore dimensions and the particle sizes of porous powders.

English

Several parameters governed the rheological properties as well as the nature of the constituents, to the process of implementation. One of the major solution is to master the milling time which is responsible for the fineness of the grains, which in turn, conditioned the correct handling of the sintering mechanism, and allows highlight of the correlation between the size of the powders and the rheological properties. The introduction of a powder in a liquid induces changes in the interface of the solid phase when it passes from the vapor phase, to the liquid phase. To improve this understanding, we studied the influence of these parameters on the good dispersion of particles and more particularly the grain size. To do this, four mixtures composed of clay, kaolin, feldspar and sand were considered. The difference between each mixture, is the substitution of kaolin by feldspar with a decreased of kaolin (8%) compared to the initial rate. Each mixture was to undergo three grinding duration (-1 h, 30 min, 1 h and 2 h). The analysis of the rheological properties allowed us to note that the best flow was obtained with mixtures C3, C4, C5, corresponding to a grinding duration of 1 h 30 min. We also observed a clear correlation between the grinding time and viscosity. After drying of the suspensions, the powders obtained are grounded according to three types of particle sizes (0.25 - 1 and 1.25 mm) then pressed in the form of ceramic tiles physical-mechanical, analyses were performed on the cooked products. After optimization and comparative study between the different mixtures, it was found that the M3 mixture, with grain size of 1.25 mm provides the best products. The measured values are in agreement with the requirements of manufacturing standards and offer a higher mechanical strength to the tiles manufactured industrially. Key words: Grinding, powder, stability, rheological parameters, ceramic tiles.

Study of morphology and magnetic properties of the HoNi3 crystalline and ball-milled compound

The morphology and magnetic properties of the HoNi3 crystalline and ball-milled intermetallic compounds are presented. The polycrystalline HoNi3 bulk compound crystallizes in the rhombohedral PuNi3 — type of crystal structure and indicates ferrimagnetic arrangement with the Curie temperature of TC=57±2K, the helimagnetic temperature Th=23±2K with the total saturation magnetic moment of 6.84μB/f.u. at 2K. The use of the ball-milling method leads to the formation of HoNi3 nanoflakes with typical thickness of less than 100nm prone to agglomeration upon milling. The increase of grinding duration leads to the reduction in crystallite size, which was confirmed by various complementary microscopical and diffraction studies. Moreover, the increase in milling duration results in the emergence of the relatively small coercivity (HC), remanence (Mr) and a variation of the saturation magnetization (MS).

Determinants of occupational exposure to metals by gas metal arc welding and risk management measures: A biomonitoring study

Welding fumes contain various toxic metals including chromium (Cr), nickel (Ni) and manganese (Mn). An assessment of the risk to health of local and systemic exposure to welding fumes requires the assessment of both external and internal doses. The aims of this study were to test the relevance in small and medium sized enterprises of a biomonitoring strategy based on urine spot-samples, to characterize the factors influencing the internal doses of metals in gas metal arc welders and to recommend effective risk management measures. 137 welders were recruited and urinary levels of metals were measured by ICP-MS on post-shift samples collected at the end of the working week. Cr, Ni and Mn mean concentrations (respectively 0.43, 1.69 and 0.27μg/g creatinine) were well below occupational health guidance values, but still higher than background levels observed in the general population, confirming the absorption of metals generated in welding fumes. Both welding parameters (nature of base metal, welding technique) and working conditions (confinement, welding and grinding durations, mechanical ventilation and welding experience) were predictive of occupational exposure. Our results confirm the interest of biomonitoring for assessing health risks and recommending risk management measures for welders.

Mechanical exfoliation of graphite in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) providing graphene nanoplatelets that exhibit enhanced electrocatalysis

A novel production method for graphene nanoplatelets (GPs) with enhanced electrocatalytic behaviour is presented. GPs show improvement in their oxygen reduction reaction (ORR) catalysis after prolonging the grinding of graphite in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). Nitrogen doping of the GPs has inferred a further increase in ORR. The ORR onset potential, cathodic current magnitude and electron transfer efficiency have all improved as a direct consequence of increasing the graphite grinding duration from 30 min to 4 h. Atomic force microscopy has confirmed a decrease in the GP diameter and height as the grinding increases. Raman spectroscopy indicates a higher level of defects present after prolonging the graphite grinding in BMIM-PF6, most likely a result of the increased edge plane exposure. This increased edge plane appears to promote a higher level of nitrogen incorporation as the graphite grinding duration increases, as confirmed by X-ray photoelectron spectroscopy analysis. The stability of the cathodic current assessed by chronoamperometry analysis is higher for the GP and nitrogen doped graphene nanoplatelet (N-GP) samples than the platinum on carbon black (Pt/C). This study presents a novel process for the production of nitrogen doped graphene nanoplatelets, constituting a strategy for the up-scaled production of electrocatalysts.

Mechanochemically Enhanced Degradation of Pyrene and Phenanthrene Loaded on Magnetite

The enhancement of the degradation of polycyclic aromatic hydrocarbons (PAHs), exemplified by pyrene and phenanthrene, using mild grinding in the presence of common minerals was investigated. Magnetite, birnessite, and Na- and Cu-montmorillonite samples were loaded with pyrene or phenanthrene and ground manually or in a ball mill for short periods of time. The ground samples were analyzed for PAHs and for their metabolites, using high-performance liquid chromatography and liquid chromatography-mass spectrometry. No degradation of pyrene occurred when it was in contact with Na-montmorillonite or birnessite. Sorption of pyrene on Cu-montmorillonite enhanced its degradation, but grinding of the loaded clay actually inhibited pyrene's degradation. Phenanthrene hardly degraded on Cu-montmorillonite. Grinding magnetite loaded with either PAH resulted in a significant degradation of both (∼50% after grinding for 5 min), while in the nonground samples, negligible degradation was detected. The extent of degradation increased with the duration of grinding. The degradation of either PAH loaded on magnetite yielded oxidized products. In soil samples contaminated with PAHs and mixed with magnetite, a similar grinding-induced degradation pattern was observed, but with a lower rate. A liquid phase was required to initiate degradation in the soil. The liquid phase apparently served as the medium through which the pollutants reached the surface of the degradation-enhancing mineral.