• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.418-427
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• 1997

The effect of $La_2O_3$ as a dopant on the microstructure structure, crystal structure and electrical properties was studied. $0.05Pb(Sn_{0.5}Sb_{0.5})O_3＋0.11PbTiO_3＋0.84PbZroO_3＋0.4Wt%MnO_2$ (=0.05PSS ＋0.11PT＋0.84PZ+0.4wt%$MnO_2$) systems doped with 0, 0.1, 0.3, 0.5, 0.7, 1, 3, 5 mole% $La_2O_3$ were fabricated and investigated sintering density, crystal structure and micro-structure. The sintered 0.05PSS＋0.11PT＋0.84PZ+0.4wt%$MnO_2$ system doped with $La_2O_3$showed sintering density of the range of 7.683 g/㎤ of 0 mole% doping to 7.815 g/㎤ of 0 mole% doping. The average grain sizes in the range of 0 to 5 mole% $La_2O_3$were decreased from 9.0 $\mu\textrm{m}$ to 1.3 $\mu\textrm{m}$. X-ray diffraction investigation of sintered bodies showed that solid solutions were formed between 0.05PSS＋0.11PT＋0.84PZ+0.4wt%$MnO_2$ system and $La_2O_3$ in the range of 0 to 1 mole% but second phases were formed in case of 3, 5 mole%. Dielectric constants at 1 kHz were increased with 0 to 3 mlole% $La_2O_3$ before and after poling at the condition of 5 $KV_{DC}$/mm at $120^{\circ}C$ or $140^{\circ}C$ during 20 minutes. All Dielectric losses at 1 kHz were less than 1%, Curie temperatures were $208^{\circ}C$, $183^{\circ}C$, $152^{\circ}C$ and $127^{\circ}C$ at 0, 0.5, 1, 3 mole% $La_2O_3$ respectively. The values of $K_p$ were increased from 0 to 3 mole% $La_2O_3$ after poling at condition of 5 $KV_{DC}$mm at the condition of $120^{\circ}C$ or $140^{\circ}C$. The case of 0.7 mole% $La_2O_3$doped 0.05PSS＋0.11PT＋0.84PZ+0.4wt%$MnO_2$ system showed $K_p$ of 14.5% by poling at $140^{\circ}C$ during 20 minutes.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.187-196
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• 2005

Structural sites which cations can occupy in garnet structure are centers of the tetrahedron, octahedron, and distorted cube sharing edges with the tetrahedron and octahedron. Among them, the size of cation occuping at tetrahedral site (the center of tetrahedron) is closely related with the size of a unit cell of garnet. Accordingly, garnet containing iron with relative large ionic radii in tetrahedral site can be considered as a promising matrix for the immobilization of the elements with large ionic radii, such as actinides in radioactive wastes. We synthesized several garnets with the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$, and studied their properties and phase relations under various conditions. Mixed samples were fabricated in a pellet form under a pressure of $200{\~}400{\cal}kg/{\cal}cm^2$ and were sintered in the temperature range of $1100\~1400^{\circ}C$ in air and under oxygen atmospheres. Phase identification and chemical analysis of synthesized samples were conducted by XRD and SEM/EDS. In results, garnet was obtained as the main phase at $1300^{\circ}C$, an optimum condition in this system, even though some minor phases like perovskite and unknown phase were included. The compositions of garnet and perovskite synthesized from the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$ were ranged $[Ca_{l.2-1.8}Gd_{0.9-1.4}Ce_{0.3-0.5}]^{VIII}[Zr_{0.8-1.3}Fe_{0.7-1.2}]^{VI}[Fe_{2.9-3.1}]^{IV}O_{12}$ and $Ca_{0.1-0.5}Gd_{0.0-0.8}Ce_{0.1-0.5}\;Zr_{0.0-0.2}Fe_{0.9-1.1}O_3$, respectively. Ca content was exceeded and Ce content was depleted in the 8-coordinated site, comparing to the initial batch composition. This phenomena was closely related to the content of Zr and Fe in the 6-coordinated site.

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.37-40
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• 2009

In this study, we made a high efficiency x-ray detecting sensor using the lead oxide(PbO) that are used in direct method of x-ray detector. PbO with nano size particles is produced by sol-gel method for high efficiency. The produced PbO with nano size is deposited on ITO(Induim Tin Oxide) glass in several temperature using the PIB(particle-in-binder) method. The thickness of the deposited PbO is about $200{\mu}m$. Through the measurement of dark current, sensitivity and SNR(Signal To Noise Ratio), an electrical properties of the produced PbO film are analyzed. Therefore, we show that an electrical properties are changed according to a temperature and that the PbO film that was treated at $500^{\circ}C$ in O2 atmosphere is the most high efficiency x-ray detecting sensor.

• Resources Recycling
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• v.7 no.5
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• pp.19-25
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• 1998

High temperature thermal behaviors of EAF dust by coke at initial reaction stage were studied to obtain the fundamental data of EAF dust treatment process, that is Extended Arc Plasma Furnace System called RAPID system. In this study thermal behaviors including calcination of limestone, devolatilization of EAF dust itself, and reduction & devolatilization of mixture(EAF dust : coke : limestone = 80 : 10 : 10 wt.%) were investigated as functions of reaction temperature (1000~1300$^{\circ}C$) and reaction time (3~12 min), considering the 180% equivalence of carbon reduction and 1.7 bacisity for optimum reduction and melting of EAF dust in the RAPID system. Size of sample was about below 0.1 mm for these experiments. Limestone was completely calcined at above 1100$^{\circ}C$ within 1 minutes. In the case of devolatilization of EAF dust itself, weight loss of EAF dust was about 14% at 1300$^{\circ}C$ and 12 minutes, and partial sintering and melting were found in part of sample. Weight loss of mixtures increased with increasing reaction temperature and time, about 46% weight loss in it was occurred at 1300$^{\circ}C$ and 12 minutes. From these weight losses showing devolatilization and reduction of EAF dust, the treatment time of EAF dust inside.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.310-315
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• 2009

Perovskite-type ceramic powder, $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$, have been synthesized successfully by the citrate method. As a result of TGA for precursor, metal-citrate complex in precursor was decomposed in the temperature range of $150{\sim}650^{\circ}C$. XRD analysis showed the single perovskite structure was observed over $1,000^{\circ}C$ without impurities. Typical dense membrane with 1.6 mm thickness has been prepared using as-prepared powder by pressing unilaterally and sintering at $1,300^{\circ}C$. The electrical conductivity of $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ membrane increased with increasing temperature at atmosphere of air and then decreased over $600^{\circ}C$ due to oxygen loss from the crystal lattice. The oxygen flux of $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ membrane in the range of 700 to $950^{\circ}C$ increased with the increasing temperature from 0.045 to $0.415ml/cm^2{\cdot}min$. The activation energy for oxygen permeation was calculated to be 89.17 kJ/mol.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.259-265
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• 2011

This research was performed to stabilize heavy metals in mine tailing using fly ash and clay. Fly ash-clay-mine tailing system were investigated using XRD (X-ray diffractometer), XRF (X-ray fluorescence spectrometer), TG-DTA, SEM (Scanning Electron Microscope), Dilatometer and UTM with various mine tailing contents (~15 wt%). The fly ash used in this research was mainly composed of $SiO_2$ (33.01 wt%), $Al_2O_3$ (28.54 wt%), $K_2O$ (3.32 wt%), $Fe_2O_3$ (1.47 wt%), CaO(9.97 wt%). $SiO_2$ and $Al_2O_3$ composition of the clay was over 61 wt%. And the mine tailing have high composition of $SiO_2$ (26.91 wt%), CaO (24.25 wt%), $Fe_2O_3$ (22.97 wt%). Therefore, it was estimated that fly ash-clay-mine tailing have enough sintering characteristics. The shrinkage of specimens started at around $850^{\circ}C$ and changed little up to $1100^{\circ}C$, but increased markedly at above $1100^{\circ}C$. The shrinkage rate is strongly related to the decarbonization amount of coal fly ash. As the result of SEM, structure of the specimens with mine tailing addition showed more close than the one without mine tailing. Compressive strength of the specimens with mine tailing was highly increased to approximately 200~420 kgf/$cm^2$, it satisfied the first grade criterion for clay brick by KS L 4201. The specification of leaching characteristics of the sintered specimens were within the Korean regulation standard.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.

• Journal of the Korean Ceramic Society
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• v.42 no.1
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• pp.62-68
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• 2005

Oxidtion behavior of $Si_{3}N_{4}$ ceramics with the different porosity by the Nitrided Pressureless Sintering (NPS) were investigated in pure oxygen gas atmosphere at 1000 to $1300^{circ}C$. The thickness of formed oxide film on the surface of silicon nitride ceramics was increased with oxidation time and temperature. The oxide film thickness of 5A5Y5Si and 5A5Y10Si specimens for 100 h at 1300^{circ}C$ was about 10 $\mu$m and 20 $\mu$m, respectively. The oxidation of 5A5Y5Si and 5A5Y10Si specimens follows the parabolic behavior with an apparent activation energy of 215 kJ/mol and 104 kJ/mol, respectively. The flexural strength of 5A5Y5Si specimens after oxidation test for 500 h at 1300^{circ}C were maintained as-received value of 500 ma. On the other hand, that of 5A5Y10Si specimens were decreased about 100 MPa in as-received value.