Mn-Cu/Al₂O₃ 촉매 상에서 NO, CO 및 CH₄ 동시 산화

정지은 ( Ji Eun Jeong ),이창용 ( Chang-yong Lee ) 한국공업화학회 2024 공업화학 Vol.35 No.1

NO, CO 및 CH₄의 동시 산화를 위한 4 종의 Mn-M/Al₂O₃ (M = Cu, Fe, Co, Ce) 촉매를 제조하여 산화 활성을 비교하고, 동시 산화활성이 가장 높은 Mn-Cu/Al₂O₃ 촉매에 대해 XRD, Raman, XPS, O₂-TPD 분석을 수행하였다. XRD 분석 결과, Mn-Cu/Al₂O₃ 촉매에서는 담지된 Mn과 Cu는 복합산화물로 존재하였다. Raman 및 XPS 분석을 통해 Mn-Cu/Al₂O₃ 촉매는 Mn-O-Cu 결합의 형성 과정에서 Mn 이온과 Cu 이온 간의 전자 수수가 일어남을 알 수 있었다. XPS O 1s 및 O₂-TPD 분석을 통해 Mn-Cu/Al₂O₃ 촉매는 Mn/Al₂O₃ 촉매에 비해 이동성이 우수한 흡착산소 종이 증가했음을 알 수 있었다. Mn-Cu/Al₂O₃ 촉매의 높은 동시 산화 활성은 이러한 결과에 기인한다고 판단된다. Mn-Cu/Al₂O₃ 촉매 상에서 NO는 CO와 CH₄ 산화를 촉진하지만, NO 산화는 억제되었다. 이는 NO로부터 산화된 NO₂가 CO 및 CH₄의 산화제로 사용되었기 때문이라고 추측된다. CO와 CH₄의 산화 반응은 경쟁하지만 촉매 활성 온도가 다르기 때문에 그 효과가 두드러지지 않았다. Mn-M/Al₂O₃ (M = Cu, Fe, Co, and Ce) catalysts were prepared for simultaneous oxidation of NO, CO, and CH₄, and their oxidation activities were compared. The Mn-Cu/ Al₂O₃ catalyst with the best simultaneous oxidation activity was characterized by XRD, Raman, XPS, and O₂-TPD analysis. The result of XRD indicated that Mn and Cu existed as complex oxides in the Mn-Cu/Al₂O₃ catalyst. Raman and XPS results showed that electron transfer between Mn ions and Cu ions occurred during the formation of the Mn-O-Cu bond in the Mn-Cu/Al₂O₃ catalyst. The XPS O 1s and O₂-TPD analyses showed that the Mn-Cu/Al₂O₃ catalyst has more adsorbed oxygen species with high mobility than the Mn/Al₂O₃ catalyst. The high simultaneous oxidation activity of the Mn-Cu/Al₂O₃ catalyst is attributed to these results. Gas-phase NO promotes the oxidation reactions of CO and CH₄ in the Mn-Cu/Al₂O₃ catalyst while suppressing the NO oxidation reaction. These results were presumed to be because the oxidized NO was used as an oxidizing agent for CO and CH₄. On the other hand, the oxidation reactions of CO and CH₄ competed on the Mn-Cu/Al₂O₃ catalyst, but the effect was not noticeable because the catalyst activation temperature was different.

K₂O-MgO-Al₂O₃ 3성분계에서 K⁺-β/β"-Al₂O₃의 합성 및 상관계

함철환,임성기,이충기,유승을,Ham, Choul-Hwan,Lim, Sung-Ki,Lee, Chung-Kee,Yoo, Seung-Eul 한국공업화학회 1999 공업화학 Vol.10 No.7

$K_2O-MgO-Al_2O_3$의 3성분계로부터 $K^+-{\beta}/{\beta}"-Al_2O_3$를 직접 고상반응법에 의하여 합성하였다. 합성시 초기조성, 합성온도, 합성시간 및 분쇄매체가 ${\beta}/{\beta}"-Al_2O_3$ 상형성 및 상관계에 미치는 영향에 대하여 분석하였으며 최대 분율의 ${\beta}"-Al_2O_3$ 상형성을 위한 최적 합성조건을 연구하였다. 조성범위로서 $K_2O$와 $Al_2O_3$상형성의 몰비를 1:5에서 1:6.2로, 안정화제로 사용된 MgO는 4.2 wt % 에서 6.3 wt % 사이에서 변화시켰으며 합성온도는 $1000^{\circ}C$에서 $1500^{\circ}C$까지 취하였다. ${\beta}/{\beta}"-Al_2O_3$상은 ${\alpha}-Al_2O_3$와 $KAlO_2$가 결합하는 $1000^{\circ}C$ 부근에서 형성되기 시작하여 점차 증가하다가 $1200^{\circ}C$ 부근에서 ${\alpha}-Al_2O_3$가 모두 사라지면서 균일화되었다. ${\beta}"-Al_2O_3$ 상분율은 $K_{1.67}Mg_{0.67}Al_{10.33}O_{17}$의 조성과 함께 $1300^{\circ}C$ 부근에서 최대값을 보였다. $1300^{\circ}C$ 이상의 합성 온도에서는 높은 potassium의 증기압에 따른 $K_2O$의 손실에 의하여 ${\beta}"-Al_2O_3$ 상분율이 감소하였으며 합성시간은 5시간 정도가 적당하였다. 분쇄 및 혼합을 위한 분산매체로는 증류수보다는 아세톤의 효과가 뛰어났다. $K^+-{\beta}/{\beta}"-Al_2O_3$ in the ternary system $K_2O-MgO-Al_2O_3$ was directly synthesized by solid state reaction. The phase formation and phase relation were carefully investigated in relation to starting composition, calcining temperature and time, and dispersion medium. The optimal synthetic condition was also examined for the formation of ${\beta}"-Al_2O_3$ phase with a maximum fraction. As a composition range, the mole ratio of $K_2O$ to $Al_2O_3$ was changed from 1:5 to 1:6.2 and the amount of MgO used as a stabilizer was varied from 4.2 wt % to 6.3 wt %. The calcining temperature was selected between $1000^{\circ}C$ and $1500^{\circ}C$. At $1000^{\circ}C$, the ${\beta}/{\beta}"-Al_2O_3$ phases began to form resulted from the combining of ${\alpha}-Al_2O_3$ and $KAlO_2$ and increased with temperature rising. All of ${\alpha}-Al_2O_3$ phase disappeared to be homogenized to the ${\beta}/{\beta}"-Al_2O_3$ phase at $1200^{\circ}C$. Near the temperature at $1300^{\circ}C$, the fraction of ${\beta}"-Al_2O_3$ phase showed a maximum value with the composition of $K_{1.67}Mg_{0.67}Al_{10.33}O_{17}$. At temperatures above $1300^{\circ}C$, the fraction of ${\beta}"-Al_2O_3$ phase decreased gradually owing to $K_2O$ loss caused by a high potassium vapor pressure, and the appropriate calcining time was about 5 hours. Acetone was more effective than distilled water as a dispersion medium for milling and mixing.

재활용원료의 첨가량과 입경에 따른 재생 ${Al_2}{O_3}$ 세라믹스의 소결 특성

신대용,한상목,김경남 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.12

재활용 $Al_2$O$_3$분말인 구조재료용 $Al_2$O$_3$세라믹스의 분쇄분말과 폐Al$_2$O$_3$흡착제의 첨가량과 입경에 따른 재생 $Al_2$O$_3$세라믹스의 소결특성을 조사하였다. 1,$650^{\circ}C$에서 5시간 소결한 순수 $Al_2$O$_3$시편을 급랭하여 분쇄한 -40과 +40$\mu$m의 $Al_2$O$_3$분말과 폐Al$_2$O$_3$흡착제를 순수한 $Al_2$O$_3$분말에 10~50wt% 첨가한 후, 재소결하여 재생 $Al_2$O$_3$세라믹스를 제조하였다. 재활용 $Al_2$O$_3$분말의 첨가량과 입경에 관계없이 소결온도가 증가함에 따라 시편의 밀도와 3점곡강도는 증가하였으나, 동일 소결온도에서는 재활용 $Al_2$O$_3$분말의 첨가량이 증가함에 따라 밀도와 3점곡강도는 감소하였다. ~30wt%의 $Al_2$O$_3$분쇄분말(-40$\mu$m), ~20wt%의 $Al_2$O$_3$분쇄분말(+40$\mu$m) 및 10wt%의 폐Al$_2$O$_3$흡착제를 첨가한 시편의 3점곡강도는 200MPa 이상이었다. 재생 $Al_2$O$_3$시편의 치밀화를 위하여 5~20wt%의 폐유리분말을 첨가하여 1200~1$650^{\circ}C$에서 5시간 소결한 시편은 폐유리분말의 첨가량이 증가함에 따라 최대 밀도와 3점곡강도를 나타내는 온도는 감소하였으나, 140$0^{\circ}C$이상에서는 페유리분말을 첨가하지 않은 시편에 비하여 밀도와 3점곡강도가 감소하여 재생 $Al_2$O$_3$세라믹스의 소결성 향상에는 기여하지 못하였다. The sintering behaviors of the renewed $Al_2$O$_3$ceramics were investigated as functions of the addition amount and particle size of recycling $Al_2$O$_3$powder, such as crushed powder of structural $Al_2$O$_3$ceramics and waste $Al_2$O$_3$adsorbent, were investigated. Pure $Al_2$O$_3$sample was fabricated by sintered at 1,$650^{\circ}C$ for 5h and it was crushed into powder (-40${\mu}{\textrm}{m}$and +40${\mu}{\textrm}{m}$ in particle size) by thermal shock treatment and crushing. Then, 10~50wt% of crushed $Al_2$O$_3$powder and waste $Al_2$O$_3$adsorbent were mixed with pure $Al_2$O$_3$powder and were subjected to re-sintering to renewed $Al_2$O$_3$sample. The density and the 3-point bending strength increased with increasing the sintering temperature without regard to the addition amount and particle size of recycling $Al_2$O$_3$powder, and that of the samples at the same sintering temperature decreased with increasing the addition amount and particle size of recycling $Al_2$O$_3$powder. Samples over 200 Mpa of 3-point bending strength were obtained by mixing ~30wt% of crushed $Al_2$O$_3$powder(-40${\mu}{\textrm}{m}$), ~20wt% of crushed $Al_2$O$_3$powder (+40${\mu}{\textrm}{m}$) and 10wt% of waste $Al_2$O$_3$adsorbent. 5~20wt% of waste glass powder containing renewed $Al_2$O$_3$samples for densification were fabricated by sintered at 1200~1$650^{\circ}C$ for 5h. The temperature of maximum density and 3-point bending strength decreased with increasing the addition amount of waste glass powder, however, these samples at above 140$0^{\circ}C$ showed lower density and bending strength than renewed $Al_2$O$_3$samples. The addition of waste glass powder did not improved the densification of renewed $Al_2$O$_3$sample.

Effects of heat treatment on the dielectric properties of aerosol-deposited Al2O3-polyimide composite thick films for room-temperature fabrication

Hyung-Jun KIM,Song-Min NAM 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.6

Al2O3-polyimide composite thick films for integrated substrates were successfully fabricated at room temperature by an aerosol deposition method (ADM). When using as-received a-Al2O3 as a starting powder, the Al2O3-polyimide composite thick films exhibited a high dielectric loss and high frequency dependence. The relative permittivity and tan δ of the Al2O3-polyimide composite thick films using as-received Al2O3 powder were 6.7 and 0.026 at 1MHz, respectively. However, their dielectric loss was remarkably decreased from 0.026 to 0.007 at 1MHz after post-annealing at 100℃ although their relative permittivity did not change. It was determined that the decreases of dielectric loss mainly depended on the state of the Al2O3. Based on these results, the heat treatment of the Al2O3 starting powder was carried out in order to fabricate Al2O3-polyimide composite films with a low dielectric loss at room temperature. As a result, their tan δ was also decreased from 0.026 to 0.007 without a long post-annealing. It was confirmed that the preparation of the ceramic Al2O3 starting powder was important for the roomtemperature fabrication of the aerosol deposited Al2O3-polyimide composite thick films with a low dielectric loss. Al2O3-polyimide composite thick films for integrated substrates were successfully fabricated at room temperature by an aerosol deposition method (ADM). When using as-received a-Al2O3 as a starting powder, the Al2O3-polyimide composite thick films exhibited a high dielectric loss and high frequency dependence. The relative permittivity and tan δ of the Al2O3-polyimide composite thick films using as-received Al2O3 powder were 6.7 and 0.026 at 1MHz, respectively. However, their dielectric loss was remarkably decreased from 0.026 to 0.007 at 1MHz after post-annealing at 100℃ although their relative permittivity did not change. It was determined that the decreases of dielectric loss mainly depended on the state of the Al2O3. Based on these results, the heat treatment of the Al2O3 starting powder was carried out in order to fabricate Al2O3-polyimide composite films with a low dielectric loss at room temperature. As a result, their tan δ was also decreased from 0.026 to 0.007 without a long post-annealing. It was confirmed that the preparation of the ceramic Al2O3 starting powder was important for the roomtemperature fabrication of the aerosol deposited Al2O3-polyimide composite thick films with a low dielectric loss.

연소합성법에 의한 $MoSi_2-Al_2O_3$ 복합재료의 특성에 미치는 $Mo/MoO_3$ 몰비의 영향

장윤식,이윤복,김용백,김인술,박흥채,오기동 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.11

MoSi2-Al2O3 composites were prepared by thermal explosion mode of self-propagating high temperature syn-thesis (SHS) using element powders of MoO3 Mo Si and Al. The combustion products of MoSi2 which have 10, 20, 30 and 40 wt% Al2O3 showed the molten state in the range of Mo to MoO3 6:1-9.5:1, 2:1-8:1, 1:1-5:1, and 1:1-3:1 (molar ratio) respectively. The combustion products which made least seperation the molten phase from the slag phase were in Mo/MoO3=9, 5:1, 8:1, 5:1 and 3:1 (molar ratio) respectively. Particles size of MoSi2 and Al2O3 in the combustion product were decreased as the molar ratio of Mo to MoO3 increase. By XRD analysis only MoSi2 and $\alpha$-Al2O3 peaks were identified in the combusion products, In case of MoSi2 containing 20wt% Al2O3 5.1wt% Al existed into MoSi2 grains and 30.7wt% Si and 7.7wt% Mo existed into Al2O3 grains. The relative density of MoSi2 containing 10, 20, 30 and 40 wt% Al2O3 were 82.7, 85.2, and 81.9% respectively. The fracture strength of MoSi2-Al2O3 composites increased with increasing Al2O3 and that of MoSi2-20wt% Al2O3 composite was 195 MPa.

Al₂O₃ Passivation Effect in HfO₂·Al₂O₃ Laminate Structures Grown on InP Substrates

Kang, Hang-Kyu,Kang, Yu-Seon,Kim, Dae-Kyoung,Baik, Min,Song, Jin-Dong,An, Youngseo,Kim, Hyoungsub,Cho, Mann-Ho American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.20

<P>The passivation effect of an Al2O3 layer on the electrical properties was investigated in HfO2-Al2O3 laminate structures grown on indium phosphide (InP) substrate by atomic-layer deposition. The chemical state obtained using high-resolution X-ray photoelectron spectroscopy showed that interfacial reactions were dependent on the presence of the Al2O3 passivation layer and its sequence in the HfO2-Al2O3 laminate structures. Because of the interfacial reaction, the Al2O3/HfO2/Al2O3 structure showed the best electrical characteristics. The top Al2O3 layer suppressed the inter diffusion of oxidizing species into the HfO2 films, whereas the bottom Al2O3 layer blocked the outdiffusion of In and P atoms. As a result, the formation of In-O bonds was more effectively suppressed in the Al2O3/HfO2/Al2O3/InP structure than that in the HfO2-on-InP system. Moreover, conductance data revealed that the Al2O3 layer on InP reduces the midgap traps to 2.6 X 10(12) eV(-1) cm(-2) (compared to that of HfO2/InP, that is, 5.4 X 10(12) eV(-1) cm(-2)). The suppression of gap states caused by the outdiffusion of In atoms significantly controls the degradation of capacitors caused by leakage current through the stacked oxide layers.</P>

Highly-impermeable Al₂O₃/HfO₂ moisture barrier films grown by low-temperature plasma-enhanced atomic layer deposition

Kim, Lae Ho,Jang, Jin Hyuk,Jeong, Yong Jin,Kim, Kyunghun,Baek, Yonghwa,Kwon, Hyeok-jin,An, Tae Kyu,Nam, Sooji,Kim, Se Hyun,Jang, Jaeyoung,Park, Chan Eon Elsevier 2017 Organic Electronics Vol.50 No.-

<P><B>Abstract</B></P> <P>Polymer substrates are essential components of flexible electronic applications such as OTFTs, OPVs, and OLEDs. However, high water vapor permeability of polymer films can significantly reduce the lifetime of flexible electronic devices. In this study, we examined the water vapor permeation barrier properties of Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films on polymer substrates. Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> films deposited by plasma-enhanced atomic layer deposition were transparent, chemically stable in water and densely amorphous. At 60 °C and 90% relative humidity (RH) accelerated condition, 50-nm-thick Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> had water vapor transmission rate (WVTR) = 1.44 × 10<SUP>−4</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>, whereas single layers of Al<SUB>2</SUB>O<SUB>3</SUB> had WVTR = 3.26 × 10<SUP>−4</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP> and of HfO<SUB>2</SUB> had WVTR = 6.75 × 10<SUP>−2</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>. At 25 °C and 40% RH, 50-nm-thick Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> film had WVTR = 2.63 × 10<SUP>−6</SUP> g m<SUP>−2</SUP> d<SUP>−1</SUP>, which is comparable to WVTR of conventional glass encapsulation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>, HfO<SUB>2</SUB>, and Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were deposited by plasma-enhanced atomic layer deposition (PEALD). </LI> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were prepared by alternating deposition of Al<SUB>2</SUB>O<SUB>3</SUB> and HfO<SUB>2</SUB> (one layer of each per cycle). </LI> <LI> Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films had densely-packed amorphous structure due to Al<SUB>2</SUB>O<SUB>3</SUB> and high chemical stability due to HfO<SUB>2</SUB>. </LI> <LI> All Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> mixed oxide films were less permeable to moisture than were single Al<SUB>2</SUB>O<SUB>3</SUB> or HfO<SUB>2</SUB> films. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

$Al/SiC/Al_{2}O_{3}$복합재료의 기계적 성질 및 마멸특성

임흥준,김영한,한경섭 대한기계학회 1993 대한기계학회논문집 Vol.17 No.10

$Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.

시멘트 구성성분을 이용한 시멘트/Fe(Ⅱ)의 TCE 환원성 탈염소화 반응의 유효반응 성분 규명

김홍석,정유연,황인성 한국지하수토양환경학회 2008 지하수토양환경 Vol.13 No.1

Experimental studies were conducted to identify the active agents for reductive dechlorination of TCE in cement/Fe(II) systems focusing on cement components such as CaO, Fe2O3, and Al2O3. A hematite that was used to simulate an Fe2O3 component in cement was found to have degradation efficiencies (k = 0.641 day-1) equivalent to that of cement/Fe(II) systems in the presence of CaO/Fe(II), only when it contained an aluminum impurity(Al2O3). When the effect of Al2O3 content of hematite/CaO/Al2O3/Fe(II) system was tested, the mole ratio of Al2O3 to CaO affected the rate of TCE degradation with an optimum ratio around 1 : 10 that resulted in a rate constant of 0.895 day-1. In the SEM images of hematite/CaO/Al2O3/Fe(II) systems, acicular crystals were also found that were also observed in cement/Fe(II) systems. Thus it was suspected that these crystals were reactive reductants and that they might be goethite or ettringite that are known to have acicular structures. An EDS element map analysis revealed that these crystals were not goethite crystals. A subsequent experiment that tested reactivities of compounds formed during the ettringite synthesis showed that ettringite and minerals associated with ettringite formation are not reactive reductants. These observations conclude that a mineral containing CaO and Al2O3 with a acicular structure could be a major reactive reductant of cement/Fe(II) systems. 본 연구는 시멘트 구성성분 중 CaO, Fe2O3, Al2O3를 중심으로 하여 시멘트/Fe(II) 시스템에서 TCE의 환원성 탈염소화에 관여하는 유효반응성분을 규명하기 위하여 수행되었다. Al2O3를 함유하는 것으로 밝혀진 hematite(Fe2O3)를 포함하는 hematite/CaO/Fe(II) 시스템에서 시멘트/Fe(II) 시스템과 유사한 TCE 분해능이 나타나는 것을 확인할 수 있었다. Hematite/CaO/Al2O3/Fe(II) 시스템에서 Al2O3의 첨가량의 영향을 알아보는 실험을 수행한 결과 Al2O3 : CaO의 비율이 1:10을 유지한 시스템에서 최고의 분해능(k = 0.895 day-1)을 보이는 것으로 보아 1 : 10이 최적의 반응비율인 것을 알 수 있었다. SEM 분석 결과 시멘트/Fe(II) 시스템에서 나타났던 막대결정을 hematite/CaO/Al2O3/Fe(II) 시스템에서도 관찰할 수 있었다. 이러한 막대결정을 TCE 분해의 유효성분으로 추정하고 막대나 침상 결정으로 알려진 goethite와 ettringite를 유효성분 후보군으로 판단하였다. EDS element map을 살펴본 결과, 막대 결정은 Ca를 주성분으로 하고 있었기 때문에 Fe 성분을 다량 함유하고 있는 goethite를 배제하였다. 추가적으로 시멘트 수화반응 중 ettringite가 생성되는 과정을 재연한 실험 결과, ettringite가 생성되는 반응 중 혹은 생성 후에도 TCE 분해능이 발현되지 않았다. 이러한 결과를 바탕으로 하여 시멘트/Fe(II) 시스템의 유효반응성분은 CaO와 Al2O3를 주성분으로 하는 막대모양의 결정일 것으로 판단된다.

X-Ray 영상을 위한 Gd3Ga2Al3O12: Sm3+ or Tb3+ 형광체의 제조와 발광특성 연구

오명진,정동경,김홍주 한국물리학회 2018 새물리 Vol.68 No.7

Sm$^{3+}$- or Tb$^{3+}$-doped gadolinium gallium aluminum garnet (Gd$_3$Ga$_2$Al$_3$O$_{12}$) phosphors were fabricated by using a solid-state reaction with gadolinium oxide, gallium oxide and aluminum oxide as host materials, as well as samarium oxide and terbium oxide as doping materials. The powders were processed at 1300 $^\circ$C for 5 hours in a horizontal furnace. For this study, Gd$_3$Ga$_2$Al$_3$O$_{12}$:Sm$^{3+}$, Tb$^{3+}$ phosphors were characterized by XRD (X-ray diffraction). In addition, the properties of X-ray- and UV-induced luminescences were studied. The emission spectra of Gd$_3$Ga$_2$Al$_3$O$_{12}$: Sm$^{3+}$ and Gd$_3$Ga$_2$Al$_3$O$_{12}$: Tb$^{3+}$ for X-rays and UV light were in the wavelength range from 500 to 800 nm. Gd$_3$Ga$_2$Al$_3$O$_{12}$ has a high effective Z-number (Z$_{eff}$ = 51) and is sensitive to X-rays and gamma-rays. Therefore, Gd$_3$Ga$_2$Al$_3$O$_{12}$:Sm$^{3+}$or Tb$^{3+}$ phosphors are promising candidates in diagnostic X-ray imaging. 이 실험에서 Gd$_2$O$_3$, Ga$_2$O$_3$, Al$_2$O$_3$ 등의 모체와 도핑 물질인 Sm$_2$O$_3$, Tb$_4$O$_7$ 등을 고체반응법을 이용하여 Gd$_3$Ga$_2$Al$_3$O$_{12}$: Sm$^{3+}$와 Gd$_3$Ga$_2$Al$_3$O$_{12}$: Tb$^{3+}$ 형광체를 제조하였다. 이 형광체를 제조하기 위하여 전기로를 이용하여 1300 $^\circ$C에서 5시간 동안 소결하였으며 Gd$_3$Ga$_2$Al$_3$O$_{12}$: Sm$^{3+}$ or Tb$^{3+}$ 형광체의 구조를 분석하기 위하여 XRD를 사용 하였다. 그리고 X-ray와 UV 선원을 이용하여 Gd$_3$Ga$_2$Al$_3$O$_{12}$: Sm$^{3+}$와 Gd$_3$Ga$_2$Al$_3$O$_{12}$: Tb$^{3+}$ 형광체의 발광스펙트럼을 측정한 결과 500 $\sim$ 800 nm 사이의 긴 파장을 보여주었다. 한편, Gd$_3$Ga$_2$Al$_3$O$_{12}$: Sm$^{3+}$ or Tb$^{3+}$ 형광체는 유효원자번호 (Z$_{eff}$ = 51)가 높기 때문에 X-선과 감마선에 대해 매우 감도가 높으므로 X-선 영상 진단 분야에 적용될 수 있다.