Size Of Final Products Research Articles

Effect of cooling modes on microstructure and electrochemical performance of LiFePO4

LiFePO4 was prepared by heating the pre-decomposed precursor mixtures sealed in vacuum quartz-tube. Three kinds of cooling modes including nature cooling, air quenching, and water quenching were applied to comparing the effects of cooling modes on the microstructure and electrochemical characteristics of the material. The results indicate that the water quenching mode can control overgrowth of the grain size of final product and improve its electrochemical performance compared with nature cooling mode and air quenching mode. The sample synthesized by using water quenching mode is of the highest reversible discharge specific capacity and the best cyclic electrochemical performance, demonstrating the first discharge capacity of 138.1 mA·h/g at 0.1C rate and the total loss of capacity of 3.11% after 20 cycles.

Pure LiFePO 4 with high energy density prepared by water quenching treatment

A compound “vacuum firing and water quenching” technique was presented in the synthesis of LiFePO 4 cathode powder. The sample was prepared by heating the pre-decomposed precursor mixtures sealed in vacuum quartz-tube, followed by water quenching at the sintering temperature. The results indicate that using the “fast quenching” treatment can succeed in controlling overgrowth of the grain size of final product and improving its utilization ratio of active material. The sample synthesized by this technique has the high reversible discharge specific capacity and good cyclic electrochemical performance.

Recrystallisation, Grain Growth and Texture Evolution in Nonoriented Electrical Steels

The magnetic properties of nonoriented electrical steels are influenced by grain size and texture of final products. The key technology in the commercial production of nonoriented electrical steels is to grow grains with {hk0}<001> texture up to the optimum size in the final annealing process. The problems related to grain size control have been extensively investigated, while texture control has received much less attention. Therefore, there is enough room to improve the magnetic properties through the control of texture. In this study, systematic investigations on the texture evolution during both recrystallization and grain growth have been made. The formation of recrystallization texture is explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientation to all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation angle of 25∼55° with the surrounding deformed matrices. During the progress of grain growth, the Goss texture component continues to decrease because the Goss grains have a high percentage of low angle, low mobility grain boundaries. The grains of Goss orientation have a smaller grain size than those of random orientation.

Investigation of primary nucleation phenomena of acetylsalicylic acid crystals induced by ultrasonic irradiation—ultrasonic energy needed to activate primary nucleation

The purpose of our study is to clarify ultrasonic primary nucleation phenomena for controlling final product size by adjusting the number of primary nuclei. In our previous study, the effect of ultrasonic irradiation on the number of nuclei was investigated under the same supersaturated condition, as a result two novel phenomena were observed. First, there is a region where ultrasonic irradiation inhibits primary nucleation. Second, a specific amount of energy is needed to activate primary nucleation. From this result, it was expected that the ultrasonic energy needed to activate primary nucleation has a certain relationship to the energy necessary to form a stable nucleus. Therefore, we investigated the following: whether ultrasonic irradiation inhibits and activates primary nucleation at various degrees of supersaturation, whether final crystal size relates to the number of nuclei, and whether the ultrasonic energy needed to activate primary nucleation relates to the energy necessary to form a stable nucleus. First, we found that ultrasonic irradiation inhibits and activates primary nucleation at various supersaturated degrees. Second, we found that final crystal size increases or decreases depending on the number of nuclei. Therefore, it was indicated that ultrasonic energy could yield the desired crystal size by inducing suitable nucleation. Third, we found that the ultrasonic energy needed to activate primary nucleation decreases with a decrease in the energy necessary to form a stable nucleus. From this, we can propose criteria for determining the effect of ultrasonic irradiation on primary nucleation by showing diagrams correlating Δ G crit with E crit.

The influence of cavity deformation on the shrinkage and warpage of an injection-molded part

As soon as the gate solidifies or the nozzle is closed, the amount of melt inside a cavity remains constant. At this moment, the cavity deformation affects the final product shape and size. A set of simulation procedures has been developed in this study to estimate the cavity deformation which arises during an injection-molding process. A mold-filling program was applied to calculate the molding variables. The estimated cavity pressure, temperature distribution, and clamping force were employed as the boundary conditions in the mold-deformation analysis. A structural analysis program was developed to predict the cavity deformation. Molding experiments were carried out for polymethyl methacrylate (PMMA) wedge-shaped parts. To verify the structural analysis, a strain gauge was installed on the sidewall of the mold. The measured strains agreed with the simulated results. A commercial simulation software package was also used to predict the shrinkage and warpage of injection-molded parts. Numerical results showed the improvement in predicting the shape and size of a final product by taking the cavity deformation into account. The influences of the packing pressure, mold temperature, or melt temperature on shrinkage and warpage were also investigated.

Preparation of Size and Aggregation Controlled Nickel Oxalate Dihydrate Particles from Nickel Hydroxide

Abstract. Nickel oxalate nanoparticles as nickel precursor were synthesized from nickel hydroxide (Ni(OH) 2 ) slurry by mixing H 2 C 2 O 4 solution. Precipitates of nickel oxalate dihydrate (NiC 2 O 4 ·2H 2 O) were formed by adding H 2 C 2 O 4 solution of pH 1. The NiC 2 O 4 ·2H 2 O particles with rectangular parallelepiped shape of ca. 440 nm sizes were prepared from the Ni(OH) 2 slurry at 298 K by dropping H 2 C 2 O 4 solution at a rate of 1 ml min -1 . The NiC 2 O 4 ·2H 2 O particles of rectangular parallelepiped shape were formed at 298-333 K, and was finely dispersed without aggregation. The size of the particle was controllable by preparation temperature. Introduction Interest in synthesizing nickel nanoparticles has increased considerably in recent years, largely in line with its growing applications such as magnetic recording medium, battery, internal electrodes of multi-layer ceramic capacitors and so on. The size and morphology control of nanoparticles is very important for their use in nanotechnology applications. A number of methods are considered for preparing nickel particle. Main methods of preparation, however, have so far been chemical reduction procedures and decomposition of metal carbonyl nickel compounds. In particular, the chemical reduction in aqueous system can prepare only a spherical nanoparticle, but the aggregation of particles is often serious [1-6]. We developed fabrication process of nickel nanoparticle to control the morphology and size. The process consists of two-step, i.e., synthesis of nickel oxalate as nickel precursor by precipitation reaction between nickel ammoniate ion, and oxalate ion and thermal decomposition of the nickel oxalate precursor. The morphology of the precursor is controllable as rectangular parallelepiped shape, rod-like, and needle-like by controlling coordination number of nickel ammoniate ion [7]. Then, needle-like nickel particle is obtained by the heat treatment of the needle-like precursor under inert atmosphere [8]. The main part of this process is morphology and size controls of nickel oxalate precursor, because those of the precursor determine the morphology and size of final products. In the preparation of nickel oxalate precursor in aqueous solution, aggregation of the

Effect of ultrasonic irradiation on the number of acetylsalicylic acid crystals produced under the supersaturated condition and the ability of controlling the final crystal size via primary nucleation

The purposes of this study were to investigate the effects of ultrasound irradiation on the number of crystals formed in an acetylsalicyclic acid crystallization process and to assess the controllability of the final product size via the number of primary nuclei. The number of crystals present after primary nucleation was counted and the relationship between the final product size and the number of crystals was examined. Additionally, the growing ASA crystals were observed, since ultrasound energy not only may control primary nucleation but may also the perfection of the crystal shape. At a high level of ultrasonic energy, ultrasound irradiation increased the average number of crystals, an effect that has been reported often; however, at a low level of ultrasonic energy it decreased the average number of crystals, and moreover, these opposing ultrasonic effects on the number of crystals interchanged at a specific energy threshold. These results reveal two novel phenomena—that there is an energy region where ultrasonic irradiation inhibits primary nucleation, and that a specific amount of ultrasonic energy is needed to activate primary nucleation. On the other hand, the final product size almost depended upon the number of primary nuclei, indicating that the final product size could be controlled via the number of crystals influenced by ultrasound irradiation. According to the photographs of crystals, they were not destroyed by the process. Therefore, it was proposed that ultrasound energy does not destroy the perfection of the crystal shape but only controls primary nucleation under the condition: both short irradiation time and low supersaturated condition.

Shape-controlled synthesis and properties of uniform spinel cobalt oxide nanocubes

Inorganic nanoparticles with controlled size and shape seem especially technologicallyimportant due to the strong correlation between these parameters and their magnetic,electrical, and catalytic properties. Herein we demonstrate that uniform spinel cobalt oxide(Co3O4) nanocubes can be successfully synthesized on a large scale via a facile hydrothermalsynthetic route under mild conditions. The size and shape of final products can be readilytuned in a wide range by tuning process parameters such as hydrothermal time, reactiontemperature, surfactant, concentration, and molar ratios of starting material.

Change of luminescent properties of phosphors through pH and Rw control in sol-gel reaction

In this paper, we describe the luminescent properties of the phosphors synthesized via sol-gel technique. When the phosphor prepared by sol-gel technique, reaction factors, such as pH condition, <TEX>$R_w$</TEX> and drying temperature affected the luminescent intensity, particle size and morphology of final product. Therefore, we attempt to control these reaction factors in order to improve the luminescent efficiency of phosphors. As a result of our study, when the acid catalyst (HCl) was used, emission intensity was higher than the case of base catalyst <TEX>$(NH_4OH)$</TEX>. The product prepared at <TEX>$R_w=60$</TEX> indicated the maximum intensity. As the increase of the <TEX>$R_w$</TEX> value, the particle was agglomerated and emission intensity was decreased. Finally, optimum drying temperature of gel was found to be<TEX>$ 180^{\circ}C$</TEX>.

Synthesis and characterization of nanocrystalline cerium oxide powders by two-stage non-isothermal precipitation

Nanocrystalline CeO 2 particles were firstly prepared by two-stage non-isothermal precipitation, i.e. precipitating at 70 °C and aging at another temperature. Experimental results showed that the intermediates at the end of precipitation stage were needle-like mixtures of Ce 3+–Ce 4+ compounds. The subsequent aging temperature played an important role on the shape and size of final products. As the aging temperature suddenly reduced to 0 °C, the resultant particles retained their original needle-like structure via the topotactic mechanism, which cannot be obtained by isothermal precipitation. As raising the aging temperature above 50 °C, the products were hexagonal and grown up with increasing temperature via the dissolution–recrystallization mechanism. Moreover, all products were cubic-fluorite structured CeO 2 with negligible Ce 3+ content. As compared to the nanohexagons (aged at 90 °C), the nanoneedles (aged at 0 °C) exhibited an unordinary red shift in the UV absorption and possessed a smaller bandgap energy.

GRINDING PROCESS SIMULATION BASED ON ROSIN-RAMMLER EQUATION

In many grinding cases, mainly during the last stages of the process, the cumulative particle size distribution is found to follow the Rosin-Rammler equation (RR), the parameters of which can be used as essential criteria to the operation progress. This article presents a method for developing a simplified, easy-to-use process model by utilizing data from laboratory grinding of limestone and clinker and applying some appropriate mathematical transformations to the RR. The proposed simulation model follows the evolution of the particle size range below 200 µm and allows for adequate precision during the last, most energy-consuming grinding stages. These process stages are also the most decisive in defining the final product size distribution profile. By applying the model, in laboratory and industrial scale, it is possible to combine the characteristics of the materials of interest and the grinding equipment with the RR parameters, the latter expressed as process-time or energy consumption functions.

Effect of seeded surface area on crystal size distribution in glycine batch cooling crystallization: a seeding methodology

In batch cooling crystallization, if the seeding process is not carefully carried out, the crystal size distribution (CSD) is dispersed. The aim of this work is to determine the optimal conditions for seeding operations. Results show that the CSD is controlled if the seed surface area reaches a specific value called critical surface Sc. Nevertheless, Sc is not the only parameter to be considered. The mean crystal size of the product obtained actually depends on the size of the seeds used because of the growth rate distribution. In fact, seeds behave differently according to their crystal sizes, which accounts for the difference in crystal growth rates. Rules are proposed for seeding with the view to obtain a uni-modal CSD and a final product size predefined by the seed crystals.

Mechanochemical–hydrothermal synthesis of hydroxyapatite from nonionic surfactant emulsion precursors

Nanocrystalline hydroxyapatite [HA, Ca10(PO4)6(OH)2] powders were synthesized by the mechanochemical–hydrothermal method using emulsion systems consisting of aqueous phase, petroleum ether (PE) as the oil phase and biodegradable Tomadol 23–6.5 as the nonionic surfactant. (NH4)2HPO4 and Ca(NO3)2 or Ca(OH)2 were used as the phosphorus and calcium sources, respectively. The calcium source and emulsion composition had significant effects on the stoichiometry, crystallinity, thermal stability, particle size and morphology of final products. Disperse HA crystals with a 160nm length and aspect ratio of ca. 6 were formed in an emulsion system containing 10wt% PE, 60wt% water and 30wt% surfactant. The HA particles had needle morphology with a specific surface area of 190m2/g. With this technique, HA nanopowders with specific surface areas in the range of 72–231m2/g were produced.

Roll deformation and stress distribution under thermo-mechanical loading in cold rolling

Tool deformation in metal forming is an important phenomenon that is critical not only for controlling the shape and size of final product but also for minimizing its cost. Under the assumption of an elastic roller and including the heat transfer effects, in this paper we determine the distribution of elastic deformation of the roller when it comes in contact with the strip in cold rolling. Using a coupled approach, the heat transfer phenomenon between roll and strip has been modeled analytically to predict roll temperature distribution by simulating non-uniform heat flux at the interface. This temperature distribution along with the mechanical load results in roll deformation with large localized stresses. Roll deformation has been modeled by using a thermo-elastic finite element method. Thermal and deformation models have been coupled and an iterative procedure has been developed to calculate optimum roll diameter. Finally, the deformed roll radius is utilized for calculating the exit strip thickness. It is found that the calculated thickness under thermo-mechanical load agrees very well with the experimental value reported in the published literature. The developed combined analytical–numerical model can easily be implemented on a personal computer and takes less memory and computational time, which is a marked advantage over pure numerical schemes.

Study of batch crystallization and determination of an alternative temperature-time profile by on-line turbidity analysis — application to glycine crystallization

On-line information is valuable for the supervision of crystal size and crystal size distribution (CSD) in batch-cooling crystallizers. A spectral turbidimetric method was used to measure crystal size on-line during the cooling crystallization of glycine in water. In order to control CSD and crystal size several temperature–time profiles can be used in batch-cooling processes. The kinetic parameters of nucleation and crystal growth were first studied and used to calculate the convex optimal temperature–time profile. A comparison of simulated and real turbidities allowed to display secondary nucleation and to devise a new alternating cycle of temperature (ACT) obtained from turbidimetry. The results achieved while comparing the CSDs obtained by three different profiles (convex, linear and alternative) on glycine-seeded batch crystallization showed that the alternative temperature–time profile improves the final mean particle size and CSD. It allowed to reduce the coefficient of variation from 32 to 12%. The final product size is largely regular, 95% of crystals having a size between 1.0 and 1.6 mm. Moreover, fine particle concentration was less than 3%. Furthermore, an analogy between experimental and estimated turbidity time evolution showed that crystal growth prevails over the nucleation process throughout crystallization.

Estimation of crystallization kinetics from batch cooling experiments

AbstractA direct optimization method to estimate nucleation and crystal growth rate parameters from seeded batch cooling crystallization experiments is evaluated. The experimental information applied comprises the concentration of the solution and the temperature as functions of time and the final product size distribution. Parameters in kinetic equations are determined by nonlinear optimization of a dynamic model of the experiment, by which intermediate approximations of experimental data are avoided. The optimization objective function includes both solution concentration data and product size distribution data. Kinetics are estimated for succinic acid crystallizing in aqueous solutions. Results from several different cooling crystallizations are simultaneously supplied into one single optimization to determine seven parameters.

The possibility of the production of reaction bonded aluminium oxide using microwave energy

Recently many investigations of the use of microwaves in the area of material processing have been conducted. One of them involves the use of microwave energy to make metal-ceramic composites [1, 2]. Metal is known to reflect microwaves, but when fine metal powders are used, metal-ceramic powder mixtures can be heated due to the surface ohmic current of metal powder. Conventional ceramic sintering usually results in large shrinkage (15-20%), which causes problems such as fracture, and leads to difficulty in predicting the size of final products and in forming complicated shapes. Many processes have been developed to reduce this large shrinkage, one of which is the production of reaction bonded aluminium oxide (RBAO) [3]. Using this process, it is possible to produce low-shrinkage alumina, because the volume expansion of A1 powders during oxidation in A1-A1203 mixture can reduce the shrinkage during sintering. Since the starting powder of the RBAO process is metal-ceramic powder mixture which is suitable for heating in the microwave cavity, we investigated the possibility of making RBAO using microwave energy and the effects of the powder characteristics on the oxidation and sintering behaviour. Microwave processing experiments were carried out in air using a domestic microwave oven (Daewoo KOR111, 2.45 GHz, 650 W). The alumina powder used was reagent grade (99.6 wt% purity, A-12, IKEI Co., Japan) agglomerate, with average particle size of 16/xm, consisting of small alumina grain ( -0 .9 /xm) . The A1 powder was reagent grade (99.9 wt % purity, Junsei Chemical Co. Ltd, Japan) with average particle size of 23/~m and flake-like shape. The AI:A1203 ratio was 35:65 (vol %). After weighing, the A1-AI203 mixture was stirred by magnetic bar, then mixed using a mortar and pestle for 1 h. In order to prevent hydration and oxidation, ethanol was used as the mixing solvent. After drying, the powders were pressed into 4 g cylindrical pellets under 1.5 tonnes in a 10 mm diameter cylindrical die. For the oxidation experiment, a low temperature insulating brick was placed on the bottom of the microwave cavity, with a high temperaute insulating brick placed above. A hole a little larger than the size of the specimen was drilled in the middle of the top surface of the insulating brick, and another insulating brick was placed as a cover. For the sintering experiment an SiC plate was placed above the high temperature insulating brick as a heater,

Preparation and characterization of vanado-, ferri-, and gallosilicate catalysts in the presence of fluoride ions

Vanado-, ferri-, and gallosilicate catalysts were prepared from the mixtures containing colloidal silica, corresponding metal source, tetrapropylammonium bromide, and NH4F by hydrothermal crystallization at 175°C for 7 days. The pH value of the reaction mixture was low (pH 10). The size distribution and the size of final products were found to be more homogeneous and larger than those of metallosilicates prepared in strong alkaline media. The characterization of metallosilicates with IF!, X-ray diffraction, SEM, EPR, and29Si MAS NMR, indicated that corresponding metal atoms were successfully incorporated into the tetrahedral lattice sites of the ZSM-5 structure.

Production of alumina fibre through jute fibre substrate

Alumina fibre has been produced using jute fibre as substrate material at temperatures lower than 1600‡ C in a reducing atmosphere. Processed jute fibre was chemically pretreated by saturation with Al2Cl6 · 12H2O, coked and then pyrolysed to obtain alumina fibre. Chemical pretreatment conditions have been determined by following weight loss measurements of the jute fibre at 0.1 to 0.6 N solutions of NaOH, KOH, NH4OH, Na2CO3, K2CO3, HCl and acetic acid. The effect of heat treatment on the jute fibre and jute fibre + aluminium salt has been studied from 150 to 1600‡ C. Trace elements present (Fe2O3, SiO2, K2O, Na2O, CaO, MgO, ZnO, MnO, V2O5, P2O5, CuO) on heat-treated products have been determined by atomic absorption spectrometry. Optical and scanning electron micrographs of representative samples showing growth mechanism are presented. The effect of copper, nickel and platinum catalysts and fluxing agents such as K2O and Na2O in fibre formation has also been examined. Particle size and surface area analyses of intermediate and final products have been carried out. Changes in 2θ values are plotted for various products from X-ray diffraction studies. It is conceived that the porous surface of cellulosic fibrils in the jute fibre adsorbs the AlCl3 molecules which decompose to oxide and are gradually shaped to the fibrous form during the course of thermal treatment in a reducing atmosphere and due to the high surface area.

粉砕を伴う回転円錐型容器による微細造粒粒子の連続生成 造粒粒子径に及ぼす操作条件の影響

A continuous granulation process for the smaller and more spherical granules is developed by using a single rotating conical vessel in which a simultaneous operation of granulation, grinding and separation might be performed with grinding media.It is experimentally confirmed by granulating CaCO3-powder with water that the final granule size (_??_1mm) is affected by the feed ratio of the binder to powder and grinding conditions. The experimental results can be explained by a granulation process model of the simultaneous operation in a continuous rotating conical vessel. The present model is based on the following granulation characteristics: (1) The amount of the larger granules increases with the feed ratio, (2) the larger granules segregate toward the grinding zone near the wider end of the vessel and are selectively ground into smaller granules, the size of which is given by the grinding intensity, and (3) the final product size is given by the amount and size of granules ground in the wider end and rounded in the narrower one of the vessel.As a result, the final granule size decreases with a larger grinding effect and increases with a smaller grinding effect on the larger granules, as the feed ratio increases.