• 한국세라믹학회지
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• 제34권2호
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• pp.195-201
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• 1997

본 논문은 kaolinite(Al2O3.2SiO2.2H2O)-aluminum trihydroxide(Al(OH3) 혼합물을 소결전에 planetary ball mill을 사용하여 건식 중에서 혼합분쇄한 후, 이 혼합물을 사용하여 소결하는 동안에 mullite의 생성거동을 연구한 것이다. 혼합물의 입자크기 감소는 분쇄 초기에 현저하였으며, 분쇄기간이 증가함에 따라 미립자들이 응집하는 현상을 보였다. 혼합물의 결정구조는 planetary ball milling에 의한 혼합분쇄에 따라 쉽게 비정질화되었으며, 비정질화되는 정도는 분쇄시간이 증가함에 따라 증가하였다. Kaolinite의 초기 분순물로 존재했던 anatase를 제외한 mullite상만이 상대적으로 낮은 소결온도인 1523K에서 혼합분쇄한 혼합물의 소결체에서 나타났다. 한편, 분쇄하지 않은 혼합물의 소결체의 경우는 이 온도에서 mullite 상 이외에 corundum, cristobalite, Al-Si spinel상이 공존하는 형태로 나타났다. 따라서, 혼합분쇄처리는 출발원료의 미소 규모에 있어서 균일혼합 및 분산을 촉진시키며, 또한 결정구조변화에 따른 열분해온도의 변화일으켜, 상대적으로 낮은 온도에서 고순도의 mullite를 직접 생성하는데 효과적이였다.

• Journal of Biosystems Engineering
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• 제31권1호
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• pp.33-38
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• 2006

This work was conducted to find the operating characteristics of an efficient wet grinding system designed to obtain fine rice husk ash powder. Once the rice husk was combusted and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement. Grinding time (15, 30, 45 min), impeller speed (250, 500, 750 rpm), and mixed ratio (6.7, 8.4, 11.l, 20.9) were three operating factors examined for the performance of a wet-type stirred ball mill grinding system. For the operating conditions employed, mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of $2.83{\sim}9.58{\mu}m,\;0.5{\sim}6.73kWh/kg,\;and\;0.51{\sim}3.27m^2/Wh$, respectively. With the wet-type stirred ball mill grinding system used in this study, the grinding energy efficiency decreased with the increase in total grinding time, impeller speed, and mixed ratio. The difference in specific surface area of powder linearly increased with logarithm in total number of impeller revolution and the grinding energy efficiency linearly decreased. Grinding time of 45 min, impeller speed of 500 rpm, and mixed ratio of 6.7 were chosen as the best operating condition. At this condition, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughput, and specific energy input were $2.84{\mu}m,\;2.28m^2/Wh,\;0.17kg/h$, and 2.03kWh/kg, respectively. Wet fine grinding which generates no fly dust causing pollution and makes continuous operation easy, is appeared to be a promising solution to the automatization of rice husk ash grinding process.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.39-46
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• 2000

This work was conducted to study the operating characteristics of a grinding system designed to obtain fine rice husk ash powder. To find better utilizing of rice husk, a valuable by-product from rice production, once the rice husk was incinerated and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement manufacturing . The rice husk ash grinding system consisted of a high speed centrifugal fan for the preliminary coarse milling and a dry-type stirred ball mill for the subsequent fine grinding . Total grinding time 9 5, 15, 30, 45 min), impeller speed (250, 500, 750 rpm) , and mixed ratio (4.8, 7.9, 14.9) were three operating factors examined for the performance of a stirred ball mill used for the fine grinding of ash. With the stirred ball mill used in this study, the minimum attianable mean diameter of rice husk ash powder appeared to be 2 ${\mu}{\textrm}{m}$. During the find grinding, the difference in specific surface area of powder showed an increase and the grinding energy efficiency decreased with the increase in total grinding time, impeller speed ,and mixed ratio. For the operating conditions employed , the resulting mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of 1.79 --16.04${\mu}{\textrm}{m}$, 0.072-5.226kWh/kg, an d1.11-12.15$m^2$/Wh, respectively. Grinding time of 30 min , impeller speed of 750 rpm, and mixed ratio of 4.8 were chosen as the best operating conditions of the stirred ball mill for fine grinding . At these conditions, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughtput, and specific energy input were 2.73${\mu}{\textrm}{m}$, 3.95$m^2$/Wh, 0.25kg/h, and 1.22kWh/kg, respectively.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.251-256
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• 1996

Effect of mixed grinding with a planetary ball mill of starting materials before heat treatment on the crystal structure and superconduction properties in the YBaCu composite oxide was studied. The size reduction of powders too place in the early stage of grinding, followed by aggregation of the resultant fine particles. The uniformity of the composition in the mixture was improved with grinding, which later decreased in the crystal grain size and well distribution of twin phase in the sintered bodies. The critical current density of the sintered bodies obtained from the mixture ground for 60 minutes showed the maximum value about 150 A/$\textrm{cm}^2$, while critical temperatures were around 90K and were independent of the grinding time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.633-634
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• 2012

• International journal of advanced smart convergence
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• 제5권4호
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• pp.66-70
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• 2016

When tooth grinding occurs, electrical stimulation is given at the same time, and tooth grinding stops on such stimulation. Electromyography signals are used as control signals of electrical stimulation to disturb tooth grinding. However because of the electrical stimulation, the M-waves are generated and mixed with spontaneous electromyogram. In this study, we designed an optimal filter to remove M-wave and conserve spontaneous electromyogram simultaneously. The inverse power method (IPM) showed that the optimal filter coefficient is the eigenvector corresponding to the minimum eigenvalue of the input covariance matrix. In order to evaluate the performance of the optimal filter, we compared using a conventional band pass filter and adaptive filter using least mean square algorithm. The experimental results show that the optimal filter can effectively remove the M-wave compared to the previously studied prediction error filter.

• 한국정밀공학회지
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• 제28권6호
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• pp.701-708
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• 2011

Although Titanium material has superior properties, it belongs to difficult-to-machine materials. The present research applies magnetic abrasive finishing to precision machining of internal-face of titanium pipes, and analyzed & assessed the influence of grinding conditions on magnetic abrasive effects through the removed amount and surface roughness of materials. There was the influence on grinding properties according to change of rotational speed, a total input of mixed powder and an input of grinding liquid, and when the total input, rotational speed and ratio of electrolytic iron versus magnetic abrasives are 8g and 1000rpm, it was most advantageous in aspects of surface roughness and material removal amount, and the grinding liquid remarkably improved the surface roughness and material removal amount only with addition of trace amounts of light oil rather than dry machining conditions. And a result of considering the influence on grinding properties by using an inert gas (Argon gas) for improving grinding properties of the internal-face of titanium pipe, the present research has obtained improvement effects in the removal amount and surface roughness through utilization of an inert gas.

• 한국재료학회지
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• 제23권2호
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• pp.89-97
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• 2013

The study of grinding behavior characteristics on aluminum powders and carbon nano tubes (CNTs) has recently gained scientific interest due to their useful effect in enhancing advanced nano materials and components, which significantly improves the property of new mechatronics integrated materials and components. We performed a series of dry grinding experiments using a planetary ball mill to systematically investigate the grinding behavior during Al/CNTs nano composite fabrication. This study focused on a comparative study of the various experimental conditions at several variations of rotation speeds, grinding time and with and without CNTs. The results were monitored for the particle size distribution, median diameter, crystal structure from XRD pattern and particle morphology at a given grinding time. It was observed that pure aluminum powders agglomerated with low rotation speed and completely enhanced powder agglomeration. However, Al/CNTs composites were achieved at maximum experiment conditions (350 rpm, 60 min.) of this study by a mechanical alloy process for Al/CNTs mixed powders because the grinding behavior of Al/CNTs composite powder was affected by addition of CNTs. Indeed, the powder morphology and crystal size of the composite powders changed more by an increase of grinding time and rotation speed.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.469-471
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• 2001

Dry grinding of a mixture of CaCO$_3$ and Ca(H$_2$PO$_4$)$_2$.$H_2O$ was conducted using a planetary ball mill in order to investigate solid state reaction for a synthesis of hydroxyapatite(Ca$_{10}$(PO$_4$)$_{6}$(OH)$_2$, HAp) through mechanochemical treatment method. The raw materials, which are composed of waste oyster and calcium biphosphate Ca(H$_2$PO$_4$)$_2$.$H_2O$, were mixed and then treated mechanochemically. The synthesis of hydroxyapatite(Ca$_{10}$(PO$_4$)$_{6}$(OH)$_2$, HAp) from the mixture was almost completed by about 60 minute grinding. The formation of HAp monophase in the ground mixture was characterized through X-ray diffraction (XRD) analysis. Moreover, the formation of HAp monophase depending on the grinding time was improved by increasing the grinding time.ime.ime.

• Journal of Applied Biological Chemistry
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• 제42권4호
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• pp.175-179
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• 1999

Grape seed oil was extracted using different preparatory treatments as follows: (1) grinding, (2) grinding and roasting, (3) grinding and wet- roasting, (4) grinding, roasting, and wet-roasting, and (5) grinding, wet-roasting, and wet-roasting. The highest antioxidant activity was obtained from the sample with the method (2). Initial states of oxidation were similar except method (1) that showed more oxidized state, being P.O.V.8. Acid values were observed in the range from 1.42 to 1.89. The lowest acid value was found as 1.42 in method (1) and those of others were somewhat higher, indicating that heating process of roasting produced some free fatty acids. From the results of sensory evaluation, the best odor and taste were obtained from the methods (2) and (3). Repetitive procedure of wet-roasting, like method 5, caused some loss of flavor components and decrease in the sensory evaluation score. Addition of grape seed oil (method 2) to soybean and perilla oil at the level of 20% retained considerable antioxidant activities as much as 4.3 and 5 times, respectively, than 100% soybean or perilla oil stored for 12 weeks. When soybean or perilla oil was mixed with 20% grape seed oils, P.O.V. decreased to half of that of unmixed oils.