• Journal of the Korean Wood Science and Technology
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• 제50권2호
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• pp.104-112
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• 2022

Indoor air quality is a very important environmental factor in modern society. However, air pollutants generated from various interior construction materials significantly affect the human body, including formaldehyde (HCHO) and volatile organic compounds that threaten public health by deteriorating indoor air quality. Effective in removing these harmful substances are porous materials, such as woodceramics. In this study, charcoal, a porous material, was added to rice husk, an agricultural by-product, and sawdust generated during the sawing process to prepare boards and ceramics at different mixing ratios, and the HCHO deodorization performance and far-infrared emission characteristics were measured. As the mixing ratio of charcoal increased, the deodorization rate of the boards and ceramics tended to increase. Overall, the deodorization rate was measured to be 80% to 90%, indicating that the boards and ceramics prepared with charcoal are suitable to be used for the purpose of deodorization. The effect of the material mixing ratio on far-infrared emissivity and emission power was insignificant.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.652-657
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• 2001

Vanadate glasses containing 10~20mol% glass former, P$_2$O$_{5}$ were prepared by melting the batch in platinum crucible and quenching on the copper plate. Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ glass-ceramics having LiV$_3$O$_{8}$ were obtained by heat-treatment of this glass in crystallization temperature. The glass-ceramics showed singnificantly good capacity and long cycles life according to heating condition. In this paper, we described electrochemical properties during crystallization process and found the best crystallizaton condition of Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ glass as cathode material. Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ glass-ceramics heat-treated at 233$^{\circ}C$ for 3 hors showed good rechargeable capacity of 220mAh/g in the cycling range between 2.0 and 3.9V.en 2.0 and 3.9V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.76-79
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• 2000

The $Ba(Zn_{1/3}Ta_{2/3})O_3$ ceramics were prepared by conventional mixed oxide method. The structural properties of the BZT ceramics with the sintering temperature were investigated by XRD, SEM. The BZT ceramics have a complex-perovskite structure. The BZT ceramics sintered at $1550^{\circ}C$ had a superstructure plane of BZT(100). Increasing the sintering temperature, the bulk density and ordering were increased. The bulk density of the BZT ceramics sintered at $1550^{\circ}C$ was $7.50[g/cm^3]$. Increasing the sintering temperature, the average grain size were increased and pore were decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.629-633
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• 2002

The degradation behaviour of ZPCCL-based varistor ceramics composed of 97.5 mol%ZnO-0.5 mol% $Pr_6O_{11}-1.0$ mol% $Cr_2O_3-0.5$ mol% $La_2O_3$ was investigated under various DC accelerated aging streses. The varistor ceramics sintered for 1 h exhibited excellent nonlinearity, in which the nonlinear exponent is 81.6 and the leakage current is $0.2{\mu}A$. It was found that this varistor ceramics possess high stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current are -1.14%, -3.7%, and 85.0%, respectively, against DC accelerated aging stress. On the contrary, the varistor ceramics sintered for 2 h also exhibited high nonlinearity and stability, but they were bad characteristics, compared with the varistor ceramics sintered for 1 h.

• 한국군사과학기술학회지
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• 제25권6호
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• pp.580-585
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• 2022

In this study, the high-temperature dielectric constant of Si₃N₄ ceramics, a representative non-oxide-based radome material, was evaluated and the cause of the dielectric constant change was analyzed in relation to the oxidation behavior. The dielectric constant of Si₃N₄ ceramics was 7.79 at room temperature, and it linearly increased as the temperature increased, showing 8.42 at 1,000 ℃. As results of analyzing the microstructure and phase for the Si₃N₄ ceramics before and after heat-treatment, it was confirmed that oxidation did not occur at all or occurred only on the surface at a very insignificant level below 1,000 ℃. Based on this, it is concluded that the increase in the dielectric constant according to the temperature increase of Si₃N₄ ceramics is irrelevant to the oxidation behavior and is only due to the activation of charge polarization.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.104-104
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• 2009

In this study, both structural, dielectric and piezoelectric properties of the NKN-0.96BNT-0.04BT ceramics were investigated. All samples of the NKN-0.96BNT-0.04BT ceramics were fabricated by conventional mixed oxide method with Pt electrodes. We report the improved dielectric and piezoelectric properties in the perovskite structure composed of the NKN, BNT and the BT ceramics. We investigated the effects of NKN, BT on the structural and electrical properties of the NKN-0.93BNT-0.07BT ceramics. The dielectric properties and piezoelectric properties of the NKN-0.93BNT-0.07BT ceramics were superior to those of single composition NKN, NKN-BNT and those values for the NKN-0.93BNT-0.07BT ceramics were 861 and 1.12%.

• 한국전기전자재료학회논문지
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• 제15권10호
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• pp.870-875
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• 2002

Ba(Zn$_1$-xCox)TaO$_3$[BZCT] ceramics were Prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of 1450∼1550$\^{C}$ for 5 hr in air. The crystal structure of BZCT ceramics was investigated by the XRD. The microstructure of the specimens were observed by SEM. The structural properties of BZCT specimens were investigated as a function of composition and sintering temperature. All BZCT ceramics sintered over 1550$\^{C}$ were showed a polycrystalline complek perovskite structure without second phases and any unreacted materials. The density of BZCT (70/30) specimen sintered at 1550$\^{C}$ was 6.31g/㎤. In the case of the BZCT(70/30) ceramics sintered at 1550$\^{C}$ for 5 hours, dielectric constant, qualify factor and temperature coefficient of resonant frequency for microwave dielectrics application were a good value of 29, 16,468 at 10㎓ and -4.4 ppm/$\^{C}$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.183-186
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• 1994

Porous piezoelectric ceramics of P7T have been newly developed to apply for transducers in an echo sounder PZT powders were prepared by the molten salt synthesis method. The porous PZT was prepared from a mixture of PZT and polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The piezoelectric and acoustic properties with various PVA wt.% have studied. The density of porous PZT ceramics was decreased linearly with increasing the PVA sphere wt.%. Piezoelectric coefficient d$\_$33/ of porous PZT ceramics was almost same to that of single phase PZT ceramics. The thickness mode coupling factor k$\_$t/ was ranged over 0.53∼0.59 comparable with the single phase PZT ceramics(k$\_$t/=0.7).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.291-295
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• 2002

Ceramics are very difficult-to-cut materials because of its high strength and hardness. Their machining process can be characterized by cracking and brittle fracture. Generally, ceramics are machined using traditional method such as grinding and polishing. However, such processes are generally costly and have low material removal rate. In this paper, to develop machinable ceramics those have good machinability without losing their material properties, machinability evaluations are performed by applying the experimental design method. In this paper, to evaluate the machinability of the developed ceramics, various workpieces are machined on the CNC machining center, and surface roughness are measured under predefined process parameters obtained using Taguchi method. And the experimental results are investigated to derive optimum cutting parameters for the given materials.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.180-181
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• 2014

Optically translucent Sialon ceramics was fabricated by hot pressed sintering method. The Sialon ceramics was laser textured and their tribological performance was observed. Starved lubrication method was applied on Sialon ceramics with different dimple spacing under a load of 10N and at room temperature. The material having high dimple spacing ($200{\mu}m$) shows low coefficient of friction. The material shows mild wear and therefore, wear rate of steel ball (meeting partner) was observed to measure wear rate. Different phases Sialon ceramics were analyzed by XRD patterns. Moreover, the mechanical properties of the Sialon ceramics were observed.