• 한국광물학회지
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• 제27권3호
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• pp.115-124
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• 2014

금-은 함유 황화광물 정광으로부터 Au와 Ag를 용출시키기 위하여 황화광물 정광을 건식과 습식으로 전처리하였다. 전처리한 황화광물에 대하여 광물학적 연구와 티오요소 용출실험을 수행하였다. 평균입도와 등전위는 정광시료에서 보다 건식 전-처리 시료에서 낮게 나타났고, 건식 전-처리 시료 보다 습식 전-처리 시료에서 더 낮게 나타났다. XRD 분석결과, 습식 전-처리 시료에서만 비정질의 특성이 나타났다. 정광시료에서, 최대의 Au, Ag 용출인자는 1.0 g의 티오요소, 1.0 M의 황산제2철, 2.0 M의 황산 농도에서 그리고 $60^{\circ}C$의 용출온도에서였다. Au, Ag용출률은 건식 전-처리 시료에서 보다 습식 전-처리 시료에서 언제나 많이 그리고 빠르게 나타났다. 따라서, 향후 적당한 미분쇄 첨가제와 시간으로 전처리를 수행하고 비-시안 용매를 적용한다면 친환경적으로 Au, Ag를 용출시킬 수 있을 것으로 기대된다.

• Asian-Australasian Journal of Animal Sciences
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• 제30권10호
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• pp.1405-1409
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• 2017

Objective: This experiment was to determine proper physical traits in the diet for goats by investigating the effects of physically effective neutral detergent fiber (peNDF) content on dry matter intake (DMI), digestibility, and chewing activity in black goats fed with total mixed ration (TMR). Methods: Six growing wethers of Korean native black goats (Capra hircus coreanae) aged 8 months and weighing between 26.9 kg and 27.1 kg ($27.03{\pm}5.05kg$) were used in this experiment. Three diets of varying peNDF content were obtained by original TMR (T1), 12,000 rpm grinding (T2), and 15,500 rpm grinding (T3) of the same TMR diet. The $peNDF_{1.18}$ content of the experimental diets was 23.85%, 21.71%, and 16.22% for T1, T2, and T3, respectively. Results: Average daily gain (ADG) was higher in T2 group compared to those of the control and T3 groups, but ADG and DMI were not affected by the dietary particle size and peNDF content. Also, there was no difference between apparent nutrient digestibility of dry matter, crude fiber, ether extract, neutral detergent fiber, and acid detergent fiber. Although there was no significant difference, rumination and total chewing time were associated with decreased peNDF content. Conclusion: The feeding of peNDF-based TMR showed no impact on apparent nutrient digestibility and nitrogen balance. Further studies are required with a wider range of dietary peNDF level and particle size to better identify the effect of dietary peNDF and particle size on chewing activity and performance in goats.

• 한국세라믹학회지
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• 제22권5호
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• pp.47-53
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• 1985

In view of innovated utilization of Korean clay resources conventional techniques for pulverization are reviewed in comparison with fluid energy milling processes of fluidized-bed type. Throughout experiment indigenous halloysite ores (white grade) after usual pretreatment are employed as typical sample. It is evidenced that grinding by means of porcelain ball mills has limitation in reducing clay particles to less than 10${\mu}{\textrm}{m}$ in diameter regardless of whether it is processed in dry or wet. Upon use of tungsten carbide bull mill particulation to submicron sizes could be effected with relative ease but severe coloration in grey is attended indicating metallic contamination possibly from friction of the grinding apparatus itself. In contrast the modified fluid en ergy milling enables particulation to $\leq$10${\mu}{\textrm}{m}$ in diameter with simultaneous classification int olimited ranges of particle size distributions. Since this technique is in principle based on the interparticle collisions rather than on the frictions between particles and mill surfaces minimum impurity attendance would be an additional advantage. Evidence leads to the conclusion that the fluidized-bed type milling is regarded as highly effective in puverization as well as fractionation of the clay minerals under examination. This is especially so in contemplating high-value and/or high-purity clay products.

• 한국정밀공학회지
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• 제31권9호
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• pp.799-804
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• 2014

Hard turning is a machining process for hardened materials with high surface quality so that grinding process can be eliminated. Therefore, the hard turning is capable of reducing machining time and improving productivity. In this study, hardened AISI4140 (high-carbon chromium steel) that has excellent yield strength, toughness and wear resistance was finish turned using CBN tools. Wear characteristics of CBN tool was analyzed in dry and MQL mixed with nano-particle (Nano-MQL). The dominant fracture mechanism of CBN tool is diffusion and dissolution wear on the rake surface resulting in thinner cutting edge. Abrasive wear by hard inclusion in AISI4140 was dominant on the flank surface. Nano-MQL reduced tool wear comparing with the dry machining but chip evacuation should be considered. A cryogenically treated tool showed promising result in tool wear.

• Journal of Biosystems Engineering
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• 제39권2호
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• pp.122-133
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• 2014

Purpose: This study was to develop an effective process for fabricating biocompatible calcium phosphate powders (CPPs) using horse bones, and to investigate the characteristics of them. Methods: The characteristics of horse bone powders (HBPs) were investigated according to the different osseous tissue types (compact bone and cancellous bone), bone types (spine and tibia), pretreatment methods (cold water, $H_2O_2$, and hot water), sintering time (4, 8 and 12h), and sintering temperature (600, 900, 1100 and $1300^{\circ}C$). In addition, the grinding methods were compared based on the wet grinding (ball mill) and dry grinding (blade grinder) method to make it as powders. Finally, their cytotoxicity and cell viability were checked. Results: Regardless of the types of osseous tissues and bones, HBPs were well fabricated as biocompatible CPPs. It was also found that the pretreatment methods did not influence on the resultants, showing well-fabricated HBPs. Considering the processing time, the hot water method was the most suitable compared to other pretreatment methods. Further, 12h-sintering time was sufficient to remove residual organic compounds. The sintering temperatures greatly affected the properties of bone powders fabricated. The x-ray diffraction (XRD) peak of horse bone sintered at $600^{\circ}C$ was most closed to that of hydroxyapatite (HA). Our bioactivity study demonstrated that the HBPs fabricated by sintering horse bones at $1300^{\circ}C$ showed the best performance in terms of cell viability whereas the HBPs $1100^{\circ}C$ showed the cytotoxicity. Conclusions: Using various types of horse bone tissues, biocompatible CPPs were successfully developed. We conclude that the HBPs may have a great potential as biomaterials for various biological applications including bone tissue engineering.

• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3465-3474
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• 2014

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-$3{\mu}m$ silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

• Journal of the Korean Wood Science and Technology
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• 제24권2호
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• pp.42-45
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• 1996

A residue from the newsprint waste was investigated as a filler in adhesive for bonding southern pine plywood. The residue was prepared by drying the wet residue to 8% moisture content and grinding the dry material using a laboratory Wiley mitt with a 75-${\mu}m$(200-mesh) screen. The residue was compared to a commercial filler commonly used in structural plywood adhesives. A total of 48 three-ply panels. 12.7mm nominal thickness and 0.3 by 0.3 m in size, were fabricated at two press times(4 and 5 min) and three assembly times(20, 40 and 60 min). Evaluations of the residue were carried out by performance tension shear tests after two 4-hour boil accelerated aging tests on plywood. The test results included tension shear strength and estimated wood failure values. All plywood made with the residue filler were comparable to the control-bonded plywood. These results indicate that residue from the newsprint waste streams would be suitable as filler for plywood adhesives.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.899-904
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• 2011

A series of 5-indolylpyrimido[4,5-d]pyrimidinones (4a-h) were obtained by multi-component reaction of 3-formylindole (1), thiobarbituric acid/barbituric acid (2) and thiourea/urea (3) under microwave irradiation in dry media. Secondly, grinding together neat reactants also gave the titled compounds in good yields. All the synthesized compounds have been characterized on the basis of elemental analyses and spectral data (IR, $^1H$ NMR and Mass). Representative compounds were also evaluated for their antimicrobial activity against Rhizopus stolonifer, Fusarium oxysporum, Escherichia coli, and Pseudomonas aeruginosa at different concentrations. Some of the compounds showed promising activity.

• 한국입자에어로졸학회지
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• 제11권1호
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• pp.9-19
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• 2015

This study investigated the effects of ball mill operation condition on the morphology of raw powders in the dry-type milling process using three types of ball mills traditional ball mill, stirred ball mill and planetary ball mill. Furthermore, since spherical powders offer the best combination of high hardness and high density, the optimum milling condition to produce sphere-shaped powders was studied. The applied rotation speed ranged from 200rpm (low rotation speed) to 700rpm (high rotation speed). The used ball size ranged from 1mm to 5mm. The metal powder morphology was studied using SEM, XRD and PSA. The aimed spherical powders could be obtained under the optimum experimental conditions: traditional ball mill(200rpm, 1mm ball), planetary ball mill (500rpm, 1mm ball) and also planetary ball mill (700rpm, 1 and 3 mm ball). The results show to the development of new material using spherical type copper powder/CNT composites for air-craft and automotive applications.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.753-760
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• 2007

For protection of the cylinder wall of the ball mill for grinding raw ore. the inner side of the cylinder is covered with rubber liner. The rubber is easily worn down because the rubber relatively soft compared with raw ore. So the rubber liner in the ball mill cylinder must be replaced almost every year and the cost for replacing rubber liner formidable. In this paper, for reducing or excluding the cost of replacing rubber liner the basalt liner is designed. The basalt materials are generally harder than raw ore and the basalt liner in the ball mill does not wear down and so it can be used almost permanently. The concave surfaces are made on the liner of the ball mill and the liner in the cylinder wall plays also the role of raising the steel balls mixed in the raw ore. The section profiles of the concave surface have an important effect on the performance of the ball mill. The deep concave grooves raise the steel balls to high levels and give the large potential energy to the steel balls impacting to the raw ore. But if the concave grooves are too deep. the steel balls raised too high by the concave grooves fly along the parabolic path and reach to the other side of cylinder wall and so the steel balls do not play the roles of grinding the raw ore. The forces acting to a steel ball in a concave groove of the cylinder liner are also analyzed in this paper. The formulas calculating the height and the impact point of the steel ball are introduced and presented. Based to these formulas, the optimum section profiles of the basalt liner are presented.