• Title/Summary/Keyword: Preparation temperature

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Microwave Absorption Properties in Composite Microwave Absorberby Control of Preparing Temperature (복합형 전파흡수체에 있어 시편제작 온도에 따른 전파흡수 특성)

  • 송재만;김동일;김수정;옥승민;문상현;신승재
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2003.05a
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    • pp.97-101
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    • 2003
  • Mn-Zn ferrite microwave absorbers mixed with silicon for mobile phone were prepared and the effect of preparation temperature of specimens on absorption ability was studied. A sample with the thickness of 1 mm prepared at 70 $^{\circ}C$ showed excellent absorption ability of 3.4 ㏈ at 1.8 GHz which is a frequency band for mobile phone. A loss factor of tan $\delta$ > 1 is shifted toward lower frequency as increasing preparation temperature of specimens.

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Cellulose acetate membrane preparation by phase inversion to estimate optimized parameters and its performance study

  • Katariya, Heena N;Patel, Tejal M
    • Membrane and Water Treatment
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    • v.13 no.3
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    • pp.139-145
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    • 2022
  • Development in advanced separation processes leads to the significant advancement in polymeric membrane preparation methodology. Therefore, present research investigated the preparation and characterization of cellulose acetate membrane by phase inversion separation method to determine optimized operating parameters. Prepared CA membrane's performance was been analyzed in terms of % rejection and flux. Investigation was conducted to study effect of different parameters such as polymer concentration, evaporation rate, thickness of film, coagulation bath properties, temperature of polymer solution and of the coagulation bath etc. CA membrane was fabricated by taking polymer concentration 10wt% and 11wt% with zero second evaporation time and varying film thickness over non-woven polyester fabric. Effect of coagulation bath temperature (CBT) and casting solution temperature were also been studied. The experimental results from SEM showed that the surface morphology had been changed with polymer r concentration, coagulation bath and casting solution temperature, etc. Lower polymer concentration leads to lower precipitation time giving porous membrane. The prepared membrane was tested for advanced waste water treatment of relevant effluent stream in pilot plant to study flux and rejection behavior of the membrane.

Preparation of Iron Oxide Thin Films by Vacuum Evaporation Method and Its Electrical Properties (진공증착법에 의한 산화철박막의 제조 및 전기적특성)

  • 조경형;오재희
    • Journal of the Korean Ceramic Society
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    • v.22 no.6
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    • pp.87-93
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    • 1985
  • The hematite the magetite and the maghemite thin film were prepared by oxidation and reductino of the vaccum-evaporated iron thin film. Interre;atoms between film preparation process and the electrical properties were investigated. At room temperature the electrical conductivity of the iron the hematite the magnetite and the maghemite thin film were $1{\times}10^4\Omega^{-1}cm^{-1}$, 2{\times}10^{-5}\Omega^{-1}cm^{-1}$, $3{\times}10^{-5}\Omega^{-1}cm^{-1}$, and $4{\times}10^{-5}\Omega^{-1}cm^{-1}$, resp-ectively. The surface of each thin film was dense and homogeneous. At the temperature that the iron thin film was converted into the hematite thin film the electrical conductivity decreased rapidly and the electrical con-ductivity of the hematite thin film increased as temperature increased. The hematite thin film was reduced to the magnetite thin film in H2 atmosphere. The electrical conductivity decreased rapidly at the temperature that the maghemite thin film is formed by oxidation of the magnetite thin film and the electrical conductivity of the maghemite thin film increased as temperature increased.

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Preparation of Porous Glass by the Sintering (소결법에 의한 다공질유리의 제조)

  • 박용완;이준영
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.957-968
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    • 1994
  • Manufacturing process of porous glass by the filler method was studied. Commercial soda-lime-silicate glass powder was mixed with inorganic salt as the filler such as KCl, K2SO4, Na2SO4. Sintering shrinkages of mixed powders with the variation of sintering temperature were compared, and the effects of the fillers to shrinkages of mixed powder were increased in the order of Na2SO4${\mu}{\textrm}{m}$ of pore diameter were manufactured when the filler sizes 100~200 ${\mu}{\textrm}{m}$. The open pore volume of porous glass is determined by the quantity of filler and porous glasses having open pore volume between 30 and 70 vol% are available. Available sintering temperature range for preparation of porous glass is from the softening temperature of the glass powder to eutectic melting temperature of DTA curve of mixed powder.

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Direct Preparation of fine Powders of Bi-Pb-Sr-Ca-Cu-O by Ultrasonic Spray Pyrolysis (초음파 분무열분해에 의한 Bi-Pb-Sr-Ca-Cu-O의 미분체 제조)

  • 주명희;박도순;김윤수
    • Journal of the Korean Ceramic Society
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    • v.28 no.5
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    • pp.353-358
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    • 1991
  • Fine powders of the 2212 superconducting phase of bismuth system have been prepared directly from solution using ultrasonic spray pyrolysis. The fine superconducting powders produced by pyrolysis were characterized for the size, shape, and crystalline phase by SEM and XRD. The pyrolysis temperature, flow rate of the carrier gas, residence time of the droplets greatly influenced the size, shape, and crystalline phase. The optimum temperature and flow rate of the carrier gas for the preparation of fine powders of the 2212 superconduting phase were found to be 830$^{\circ}C$and 3ι/min, respectively.

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The Effect of the Acid Precipitate Conditions on the Size Distribution of Molybdenum Trioxide Particle

  • Tang, Jun-Li
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.171-172
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    • 2006
  • The effect of the preparation factors, such as the feeding mode and rate of raw materials, the reaction temperature and the surfactant on the size distribution of molybdenum trioxide particle were investigated by orthogonal test. The optimum conditions for the preparation of $MoO_3$ precursors are as following; opposite feeding fast, reaction temperature of $60^{\circ}C$ and adding dispersant.

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Microbiological Hazard Analysis and Preparation of Standard Recipe for Bellflower Roots with Seasonings Served in a University Foodservice Operation (대학급식에서 제공되는 통도라지 무침의 미생물학적 위해분석과 표준레시피 작성)

  • Ryu, Gyeong;Chae, Hyeon-Suk;Kim, Un-Ju
    • Journal of the Korean Dietetic Association
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    • v.12 no.2
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    • pp.157-171
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    • 2006
  • This study was intended to suggest HACCP-based standard recipe for bellflower roots, classified as no thermal cooking process, served in a university foodservice operation. The time-temperature and microbial contamination level in each cooking step were analyzed. The temperatures of bellflower root, peeled garlic and green onion at receiving were at 13.8$\pm$2.8, 12.6$\pm$2.9 and 13.7$\pm$$0.8^\circC$ respectively, which were above the temperature limit. The time consumed for pre-preparation was up to 90 min at room temperature having high microbial growth potential. The levels of total plate counts (TPC) of bellflower root and garlic were over the limit of $10^6$ CFU/g as were the numbers of coliforms in bellflower roots. There were no microbial reductions in pre-preparation and cooking, which resulted in over $10^5$- $10^6$ CFU/g of TPC at service step. Two CCPs identified were washing/sanitation at pre-preparation and service steps. The control measures were washing/sanitation and temperature control. It was verified that CCPs for no cooking process developed in preceding studies were applicable for the microbiological food safety of this menu item. The HACCP-based standard recipe was developed to produce a quantity for 100 servings by observing the critical limits established for CCPs. These results suggest that the selection of proper provider is imperative to control the microbial contamination of raw materials at purchasing step. Also, the sanitary education program should be developed for the employees to understand and comply the HACCP plan and standard recipe.

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The effect of precipitation conditions on the particle size and size distribution of zinc oxide prepared by high temperature precipitation (고온침전반응에 의한 산화아연 제조공정에서 입자의 형상 및 입도분포에 미치는 침전조건의 영향)

  • 주창식
    • Journal of the Korean Graphic Arts Communication Society
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    • v.16 no.2
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    • pp.11-22
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    • 1998
  • For the purpose of preparation of monodispersed spherical zinc oxide fine particles, an experimental research on the preparation of zinc oxide particles from zinc salts solutions by high temperature precipitation reaction was performed. Zinc oxide particles were precipitated from all the precipitation solutions tested if the precipitation temperature was higher than 60$^{\circ}$. As the precipitation temperature Increased until 80$^{\circ}$, the average particle diameter of zinc oxide particles decreased and the narrower particle size distribution were obtained. Spherical zinc oxide fine particles with relatively narrow particle size distribution were precipitated from the ZnSO$_4$ solutions with NaOH as precipitant. Final pH of precipitation solution had an effect on the amount of zinc oxide precipitated, but had no effect on the their particle size or size distribution.

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EFFECT of PREPARATION METHODS and CONDITIONS of PRECURSORS on the PROPERTIES of $BATIO_3$ ALKOXIDE FILMS

  • N., Korobova;Soh, Dea-Wha
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07b
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    • pp.714-718
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    • 2003
  • Usually for the commercial preparation of barium titanate films or ceramics the reaction atmosphere must be preferably in air. However, normally air is not used because it contains carbon dioxide, which can easily react with barium to form the undesired product barium carbonate, leading to unwanted second-phase formation in the (mal stages of the process. In the present work a series of perovskite barium titanate films was prepared by the sol-gel method, using a metal alkoxide solutions in the electrophoretic deposition (EPD). The influence of several process parameters, like sintering temperature of sol preparation before EPD and heat-treatment temperature and non-oxidized atmosphere, on the film properties is described.

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Preparation of Poly(lactic acid) Scaffolds by the Particulate Leaching (염 추출법에 의한 폴리락틱산 다공성 지지체 가공)

  • Lee, Ji-Hae;Lee, Jong-Rok;Kang, Ho-Jong
    • Journal of the Korean Applied Science and Technology
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    • v.20 no.4
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    • pp.324-331
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    • 2003
  • Particulate leaching method for the preparation of porous PLLA scaffolds was carried out and especially, the effect of PLLA/$CHCl_3$ solution concentration on the salt leaching rate and the pore structure of PLLA scaffolds were considered. It was found that maintaining lower PLLA/$CHCl_3$ concentration and higher $CHCl_3$ evaporation temperature in the preparation of PLLA/NaCl mixtures resulted in the enhancement of salt leaching rat e and higher porosity. This is understood that those conditions could minimize the formation of dense PLLA layer on the surface of PLLA/NaCl mixture as well as introducing better porosity on the surface. Higher salt leaching temperature accelerated the salt leaching rate but it seems that there is no influence on the porosity of PLLA scaffolds.