INVESTIGATION OF PROCESS OF NATURAL GRAPHITE SPHEROIDIZATION

In this paper, the process of spheroidization of natural graphite powders on an original impact-reflecting mill with internal separation of particles was investigated. It was established that the process of spheroidization of natural graphite by impact depends both on the intensity and duration of mechanical activation. For the type of mill used, the critical linear velocity of the impact elements of the mill rotor, at which the graphite particles can be spheroidized, is 45 m/s. An increase in the linear rotational speed of the mill (intensity of impact) leads to a decrease in the average particle size, an increase in particle roundness, but significantly increases product losses. In the process of mechanical activation by impact, it is possible to increase the coefficient of roundness of the graphite particles to an average value of 0.8-0.9, which leads to compaction of graphite powders. The presence of ash impurities has a negative effect on the ability of natural graphite powders to compact. A mechanism is proposed for the process of spheroidization of graphite particles in a shock-reflecting mill. According to the proposed mechanism, at first, small-sized graphite plates are detached and deformed due to impact. As the free energy accumulates, agglomeration of deformed particles into spheres takes place. With increasing processing time, the surface of the particles is smoothed due to their friction with each other and against the wall of the mill. Powders of spherical graphite obtained by the proposed method have shown the possibility of their use as an anode material of lithium-ion batteries. The type of equipment investigated has made it possible to reduce the required number of pieces of equipment from 20 to 12 impact mills per line in comparison with foreign analogues. For citation: Yudina T.F., Blinichev V.N., Bratkov I.V., Gushchina Т.V., Melnikov A.G. Investigation of process of natural graphite spheroidization. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 48-52

Download Full-text

Influence of temperature and humidity on the angle of repose of wood bulk materials

Известия СПбЛТА ◽

10.21266/2079-4304.2016.217.158-165 ◽

2016 ◽

Author(s):

И.В. Бачериков ◽

Б.М. Локштанов

Keyword(s):

Field Experiments ◽

Bulk Material ◽

Average Particle Size ◽

Operating Conditions ◽

Angle Of Repose ◽

Wood Dust ◽

Average Particle ◽

Bulk Materials ◽

Technical Literature ◽

The Impact

При проектировании открытых и закрытых хранилищ измельченных сыпучих материалов древесных материалов, таких как щепа и опилки, большое значение имеет угол естественного откоса (статический и динамический) этих материалов. В технической литературе приводятся противоречивые сведения о величине этих углов, что приводит к ошибкам при проектировании складов. В справочных данных не учитываются условия, в которых эксплуатируются емкости для хранения сыпучих материалов, свойства и состояние этих сыпучих материалов. В свою очередь, ошибки при проектировании приводят к проблемам (зависание, сводообразование, «затопление» и т. д.) и авариям при эксплуатации бункеров и силосов на производстве. В статье представлены сведения, посвященные влиянию влажности и температуры на угол естественного откоса сыпучих материалов. На основании лабораторных и натурных экспериментов, проведенных с помощью специально разработанных методик и установок, была скорректирована формула для определения углов естественного откоса (статического и динамического) для измельченных древесных материалов в зависимости от их фракционного и породного состава, влажности (абсолютной и относительной) и температуры. При помощи скорректированной формулы можно определить угол естественного откоса древесных сыпучих материалов со среднегеометрическим размером частицы от 0,5 мм до 15 мм (от древесной пыли до технологической щепы) в различных производственных условиях. Статья может быть полезна проектировщикам при расчете угла наклона граней выпускающей воронки бункеров и силосов предприятий лесной отрасли и целлюлозо-бумажной промышленности. In the design of open and closed storage warehouses chopped wood materials for bulk materials such as wood chips and sawdust, great importance has an angle of repose (static and dynamic) of these materials. In the technical literature are conflicting reports about the magnitude of these angles, which leads to errors in the design of warehouses. In the referencesdoes not take into account the conditions under which operated capacities for storage of bulk materials, and properties and condition of the bulk material. The design errors lead to problems (hanging, arching, «flooding», etc.) and accidents in the operation of hoppers and silos at the mills. The article provides information on the impact of humidity and temperature on the angle of repose of granular materials. On the basis of laboratory and field experiments, conducted with the help of specially developed techniques and facilities has been adjusted formula for determining the angle of repose (static and dynamic) for the shredded wood materials depending on their fractional and species composition, humidity (absolute and relative) and temperature. It is possible, by using the corrected formula, to determine the angle of repose of loose wood materials with average particle size of from 0.5 mm to 15 mm (wood dust to pulpchips) in various operating conditions. The article can be helpful to designers in the calculation of the angle of inclination of the funnel faces produces bunkers and silos forest industries and pulp and paper industry.

Download Full-text

Preparation of LiFePO4 Powders by Ultrasonic Spray Drying Method and Their Memory Effect

Materials ◽

10.3390/ma14123193 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3193

Author(s):

Tu Lan ◽

Xiaolong Guo ◽

De Li ◽

Yong Chen

Keyword(s):

Spray Drying ◽

Memory Effect ◽

Electrode Materials ◽

Average Particle Size ◽

Lithium Ion ◽

Average Particle ◽

Preparation Process ◽

Drying Method ◽

Drying Temperature ◽

Ultrasonic Spray

The memory effect of lithium-ion batteries (LIBs) was first discovered in LiFePO4, but its origin and dependence are still not clear, which is essential for regulating the memory effect. In this paper, a home-made spray drying device was used to successfully synthesize LiFePO4 with an average particle size of about 1 μm, and we studied the influence of spray drying temperature on the memory effect of LiFePO4 in LIBs. The results showed that the increasing of spray drying temperature made the memory effect of LiFePO4 strengthen from 1.3 mV to 2.9 mV, while the capacity decreased by approximately 6%. The XRD refinement and FTIR spectra indicate that the enhancement of memory effect can be attributed to the increment of Li–Fe dislocations. This work reveals the dependence of memory effect of LiFePO4 on spray drying temperature, which will guide us to optimize the preparation process of electrode materials and improve the management system of LIBs.

Download Full-text

Toughening of Polypropylene-Ethylene Copolymer with Nanosized CaCO3 and Styrene-Butadiene-Styrene

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.121-123.1451 ◽

2007 ◽

Vol 121-123 ◽

pp. 1451-1454

Author(s):

Jian Feng Chen ◽

Guo Quan Wang ◽

Xiao Fei Zeng ◽

Hong Ying Zhao

Keyword(s):

Average Particle Size ◽

Average Particle ◽

Single Screw Extruder ◽

Roll Mill ◽

The Matrix ◽

Ethylene Copolymer ◽

Styrene Butadiene Styrene ◽

Styrene Butadiene ◽

The Impact ◽

Butadiene Styrene

Nanocomposites of nanosized-CaCO3/polypropylene-ethylene copolymer (PPE) and nanosized CaCO3/ PPE/ styrene-butadiene-styrene (SBS) were prepared by using two-roll mill and single screw extruder. The average particle size of nanosized CaCO3 was determined to be about 30 nm. By adding nanosized CaCO3 into PPE matrix, the toughness of the matrix improves significantly. At nanosized CaCO3 content of 12 phr (parts per hundred PPE resin by weight), the impact strength of CaCO3/PPE at room temperature reaches 61.6 KJ/m2, which is 3.02 times that of unfilled PPE matrix. In addition, the synergistic toughening effect of nanosized CaCO3 and SBS particles on PPE matrix was investigated.

Download Full-text

Commercial Cokes and Graphites as Anode Materials for Lithium - Ion Cells

MRS Proceedings ◽

10.1557/proc-496-575 ◽

1997 ◽

Vol 496 ◽

Cited By ~ 1

Author(s):

David J. Derwin ◽

Kim Kinoshita ◽

Tri D. Tran ◽

Peter Zaleski

Keyword(s):

Electron Microscopy ◽

Ethylene Carbonate ◽

Average Particle Size ◽

Chemical Properties ◽

Lithium Ion ◽

Reversible Capacity ◽

Bet Surface Area ◽

Average Particle ◽

Electrochemical Characteristics ◽

Wide Range

AbstractSeveral types of carbonaceous materials from Superior Graphite Co. were investigated for lithium ion intercalation. These commercially available cokes, graphitized cokes and graphites have a wide range of physical and chemical properties. The coke materials were investigated in propylene carbonate based electrolytes and the graphitic materials were studied in ethylene carbonate / dimethyl solutions to prevent exfoliation. The reversible capacities of disordered cokes are below 230 mAh / g and those for many highly ordered synthetic (artificial) and natural graphites approached 372 mAh / g (LiC6). The irreversible capacity losses vary between 15 to as much as 200 % of reversible capacities for various types of carbon. Heat treated cokes with the average particle size of 10 microns showed marked improvements in reversible capacity for lithium intercalation. The electrochemical characteristics are correlated with data obtained from scanning electron microscopy (SEM), high resolution transmission electron microscopy (TAM), X - ray diffraction (XRD) and BET surface area analysis. The electrochemical performance, availability, cost and manufacturability of these commercial carbons will be discussed.

Download Full-text

Preparation and Electrochemical Properties of Amorphous Tin-Copper Composite Oxide CuSnO3

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.535-537.31 ◽

2012 ◽

Vol 535-537 ◽

pp. 31-35

Author(s):

Tao Liu ◽

Rong Bin Du ◽

Xue Jun Kong

Keyword(s):

Electrochemical Properties ◽

Lithium Ion Batteries ◽

Anode Materials ◽

Average Particle Size ◽

Lithium Ion ◽

Average Particle ◽

Charge Capacity ◽

Composite Oxides ◽

Transmission Electron ◽

Copper Composite

Composite oxides materials CuSnO3as anode materials for lithium-ion batteries were synthesized by chemical coprecipitation method using SnCl4•5H2O, NH3•H2O and Cu(NO3)2•3H2O as raw materials.The precursor CuSn(OH)6and CuSnO3powders were characterized by thermogravimertric(TG) analysis and differential thermal analysis(DTA), X-ray diffraction(XRD), and transmission electron microscope (TEM). The electrochemical properties of CuSnO3powders as anode materials of lithium ion batteries were investigated comparatively by galvanostatic charge-discharge experiments. The results show the average particle size of amorphous CuSnO3is 70nm. The initial capacity during the ﬁrst lithium insertion is 1078 mA•h/g and the reversible charge capacity in first cycle is 775 mA•h/g. After 20 cycles, the charge capacity is 640 mA•h/g and this material shows moderate capacity fading with cycling. As a novel anode material for lithium ion batteries, amorphous CuSnO3demonstrates a large capacity and a low insertion potential with respect to Li metal.

Download Full-text

Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

Frontiers in Nutrition ◽

10.3389/fnut.2021.793009 ◽

2022 ◽

Vol 8 ◽

Author(s):

Ao Li ◽

Aixia Zhu ◽

Di Kong ◽

Chunwei Wang ◽

Shiping Liu ◽

...

Keyword(s):

Particle Size ◽

Soybean Lecithin ◽

Average Particle Size ◽

Soy Protein Isolate ◽

In Vitro Digestion ◽

Bimodal Distribution ◽

Average Particle ◽

Food Ingredients ◽

The Impact

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Download Full-text

Effect of adding TiO2 nanoparticles on the SEM morphology and mechanical properties of conventional heat-cured acrylic resin

Journal of Dental Research Dental Clinics Dental Prospects ◽

10.15171/joddd.2019.036 ◽

2019 ◽

Vol 13 (3) ◽

pp. 234-240

Author(s):

Elnaz Moslehifard ◽

Mahmood Robati Anaraki ◽

Saeed Shirkavand

Keyword(s):

Impact Strength ◽

Tio2 Nanoparticles ◽

Cross Sections ◽

Average Particle Size ◽

Acrylic Resin ◽

Mechanical Tests ◽

Average Particle ◽

Sem Images ◽

Tio2 Nps ◽

The Impact

Background. The current study evaluated the compressive, flexural and impact strengths of heat-cured acrylic resins reinforced by TiO2 nanoparticles (NPs). Methods. TiO2 NPs were provided and characterized using scanning electron microscopy (SEM) to determine their morphology and crystalline structure. For three mechanical tests, 12 acrylic resin groups (n=9), totaling 108 specimens, were prepared using a special mold for each test, with TiO2 nanoparticle contents of 0, 0.5, 1 or 2 wt% in different groups. After curing, the compressive, flexural and impact strengths of the specimens were examined according to ISO 1567. Results. In the SEM and XRD study of TiO2 NPs, anatase was identified as the major crystalline phase followed by rutile (average particle size: 20.4 nm). SEM images showed that the nanocomposite with 1 wt% NPs had a more homogenized blend. 1 wt% TiO2 nanocomposite exhibited a higher, but non-significant, impact strength compared to the controls. ANOVA showed significant differences in the impact and flexural strengths between nanocomposites with various contents of TiO2 NPs. Conclusion. The nanocomposite with 1 wt% TiO2 NPs exhibited fewer micro-pores and micro-cracks in the SEM cross-sections. A non-significant increase was also observed in the impact strength with TiO2 NPs at 1 wt%. Further increase in TiO2 NPs decreased both the impact and flexural strengths. The compressive strength of the heat-cured acrylic resin was not affected by the incorporation of NPs.

Download Full-text

Metallothermic Reduction at Low Temperature Synthesis of Ti4O7 Powder with Lithium Ion Insertion/Extraction Property

Materials Science Forum ◽

10.4028/www.scientific.net/msf.956.55 ◽

2019 ◽

Vol 956 ◽

pp. 55-66

Author(s):

Bei Lei Yan ◽

Wei Wei Meng ◽

San Chao Zhao

Keyword(s):

Reduction Method ◽

Average Particle Size ◽

Active Material ◽

Reduction Process ◽

Lithium Ion ◽

Thermal Reduction ◽

Average Particle ◽

X Ray Diffraction ◽

Metallothermic Reduction ◽

Extraction Property

In this work, a thermal reduction process via ultrafine titanium powder as the reducing agent under argon atmosphere is firstly used to prepare Ti4O7. Compared with the conventional method, this experiment process reduces the sintering temperature to 850°C. The phase transformation and the morphology of the as-prepared powders are examined by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). Besides, it is found that the Ti4O7 powders obtained by titanium thermal reduction method exhibited the crystal structure, distinctly possessing an average particle size around 750 nm. The as-prepared Ti4O7 nanoparticles are used as anode active material in lithium battery. The results demonstrate that the anode with Ti4O7 calcined at 850°C by titanium thermal reduction method exhibited insertion/extraction lithium ion property.

Download Full-text

ER Properties of a Suspension of Polymer Graft Carbon Black Particles

International Journal of Modern Physics B ◽

10.1142/s0217979299001673 ◽

1999 ◽

Vol 13 (14n16) ◽

pp. 1682-1688

Author(s):

Masayoshi Konishi ◽

Teruhisa Nagashima ◽

Yoshinobu Asako

Keyword(s):

Shear Stress ◽

Carbon Black ◽

Electric Field ◽

Silicone Oil ◽

Average Particle Size ◽

Average Particle ◽

Zero Field ◽

Average Value ◽

Time Period ◽

Micron Size

We newly developed ER particles with sub-micron size. The particle was polymer graft carbon black (GCB1) composed of carbon black particles and a polymer. The average particle size of GCB1 was found to be 81 nm. An ER suspension (ER1) was obtained by mixing GCB1 (30 wt%) with silicone oil (70 wt%). The ER1 showed excellent dispersion stability. Further, GCB1 particles did not settle under centrifuging at 9000G. The zero-field viscosity was 80 mPa·s at 25°C. The kinetic friction coefficient of ER1 was 0.15, while that of the silicone oil used was 0.23. When the electric field of 3 kV/mm (AC 1000 Hz) at the temperature of 25°C and the shear rate of 700 s -1 was applied to ER1, the shear stress of 116Pa was induced. The induced shear stress did not change for a long period of time period. In the temperature range between 25 and 150°C the induced shear stress and the current density were almost constant at any electric field. When 3 kV/mm (AC 50Hz) at 25°C and 700s-1 was applied to ER1, the shear stress of 88Pa was induced but the deviation of the induced shear stress from the average value was pluses and minuses 3 Pa.

Download Full-text

Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases

Polymers ◽

10.3390/polym11020320 ◽

2019 ◽

Vol 11 (2) ◽

pp. 320 ◽

Cited By ~ 4

Author(s):

Dries Devlaminck ◽

Paul Van Steenberge ◽

Marie-Françoise Reyniers ◽

Dagmar D’hooge

Keyword(s):

Particle Size ◽

Average Particle Size ◽

Miniemulsion Polymerization ◽

Monomer Conversion ◽

Water Soluble ◽

Explicit Calculation ◽

Average Particle ◽

Intermediate Radical ◽

Raft Agent ◽

The Impact

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical. To allow the identification of the nature of the RAFT retardation it is recommended to experimentally investigate in the future the impact of the average particle size (dp) on both the monomer conversion profile and the average polymer properties for a sufficiently broad dp range, ideally including the bulk limit. With decreasing particle size both a slow RAFT fragmentation and a fast RAFT cross-termination result in a stronger segregation and thus rate acceleration. The particle size dependency is different, allowing further differentiation based on the variation of the dispersity and end-group functionality. Significant RAFT cross-termination is specifically associated with a strong dispersity increase at higher average particle sizes. Only with an ideal exchange it is afforded in the modeling to avoid the explicit calculation of the RAFT intermediate concentration evolution.

Download Full-text