Anodic Dissolution Behavior of Zr-Nb Alloy in Chloride-based Molten Salts

Jungho Hur,Yeonghwan Jeon,Seungmin Ohk,Jaeyeong Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Zirconium(Zr) alloys are commonly used in the nuclear industry for applications such as fuel cladding and pressure tubes. To minimize the levels and volumes of radioactive waste, molten salts have been employed for decontaminating Zr alloys. Recently, a two-step Zr metal recovery process, combining electrolysis and thermal decomposition, has been proposed. In the electrolysis process, potentiostatic electrorefining is utilized to control the chemical form of electrodeposits(ZrCl). Although Zr metals are expected to dissolve into molten salts, reductive alloy elements can also be co-dissolved and deposited on the cathode. Therefore, a better understanding of the anodic side’s response during potentiostatic electrorefining is necessary to ensure the purity of recovered Zr and long-term process operation. As the first step, potentiodynamic polarization curves were obtained using Zr, Nb, and Zr-Nb alloy to investigate the anodic dissolution behavior in the molten salts. Nb, which has a redox potential close to Zr, and Zr exhibit active or passivation dissolution mechanisms depending on the potential range. It was confirmed that Zr-Nb alloy also has a passivation region between -0.223 to -0.092 V influenced by the major elements Zr and Nb. Secondly, active dissolution of Zr-Nb was performed in the range of -0.9 to -0.6 V. The dissolution mechanism can be explained by percolation theory, which is consistent with the observed microstructure of the alloy. Thirdly, passivation dissolution of Zr, Nb, and Zr-Nb alloy was investigated to identify the pure passivation products and additional products in the Zr-Nb alloy case. K2ZrCl6 and K3NbCl6 were identified as the pure passivation products of the major elements. In the Zr-Nb alloy case, additional products, such as Nb and NbZr, produced by the redox reaction of nanoparticles in the high viscous salt layer near the anode, were also confirmed. The anodic dissolution mechanism of Zr-Nb alloy can be summarized as follows. During active dissolution, only Zr metal dissolves into molten salts by percolation. Above the solubility near the anode, passivation products begin to form. The anode potential increases due to the disturbance of passivation products on ion flow, leading to co-dissolution of Nb. When the concentration of Nb ion exceeds the solubility, a passivation product of Nb also forms. In this scenario, a high viscous salt layer is formed, which traps nanoparticles of Zr metal, resulting in redox behavior between Zr metal and Nb ion. Some nanoparticles of Zr and Nb metal are also present in the form of NbZr.

Optical and Thermal Characteristics of Zr-O Solar Selective Coatings

이길동 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.4

Zr-O (Zr-ZrO2) cermet solar selective coatings with a double cermet layer film structure on Al-coated glass substrates for solar collectors used at in high temperatures were prepared by using direct-current magnetron sputtering technology. The typical film structure from the surface to the bottom substrate was an Al2O3 anti-reflection layer on a double Zr-O cermet layer on an Al-metal infrared reflection layer. The deposited Zr-O cermet solar selective coatings had a solar absorptance of α = 0.94 – 0.96 and a thermal emittance of " = 0.07 – 010 (100 ˚C), depending on the sputtering conditions. The absorption layers of the Zr-O cermets coatings on glass and silicon substrates were identified as being amorphous by using X-ray diffraction. Surface roughness measurements of coating layers by using atomic force microscopy showed that the cermet films were very smooth and that their root-mean-square roughness (rms) was approximately 0.1 nm. The composition of the cermet coatings was determined by using X-ray photoelectron spectroscopy. A chemical shift of the photoelectron binding energy occurred due to a change in the structure of the deposited Zr-O cermet coating with increasing oxygen flow rate. The results of the thermal stability test for the thermal characteristics analysis showed that solar selective coating of the Zr-O cermet was stable at temperatures under 350 ˚C. Zr-O (Zr-ZrO2) cermet solar selective coatings with a double cermet layer film structure on Al-coated glass substrates for solar collectors used at in high temperatures were prepared by using direct-current magnetron sputtering technology. The typical film structure from the surface to the bottom substrate was an Al2O3 anti-reflection layer on a double Zr-O cermet layer on an Al-metal infrared reflection layer. The deposited Zr-O cermet solar selective coatings had a solar absorptance of α = 0.94 – 0.96 and a thermal emittance of " = 0.07 – 010 (100 ˚C), depending on the sputtering conditions. The absorption layers of the Zr-O cermets coatings on glass and silicon substrates were identified as being amorphous by using X-ray diffraction. Surface roughness measurements of coating layers by using atomic force microscopy showed that the cermet films were very smooth and that their root-mean-square roughness (rms) was approximately 0.1 nm. The composition of the cermet coatings was determined by using X-ray photoelectron spectroscopy. A chemical shift of the photoelectron binding energy occurred due to a change in the structure of the deposited Zr-O cermet coating with increasing oxygen flow rate. The results of the thermal stability test for the thermal characteristics analysis showed that solar selective coating of the Zr-O cermet was stable at temperatures under 350 ˚C.

Zr-Nb계 합금의 석출물 특성과 산화 특성에 미치는 마지막 열처리 온도의 영향

윤영균,정용환,박상윤,위명용,Yun, Yeong-Gyun,Jeong, Yong-Hwan,Park, Sang-Yun,Wi, Myeong-Yong 한국재료학회 2001 한국재료학회지 Vol.11 No.8

Nb 첨가 Zr합금인 Zr-lNb합금과 Zr-lNb-lSn-0.3Fe함금의 석출물 및 산화 특성에 미치는 마지막 열처리 온도의 영향을 알아보기 위하여 최종 열처리 온도를 $450^{\circ}C$에서 $800^{\circ}C$까지 변화시켜 미세조직 및 산화 특성을 조사하였다. 부식 시험은 $400^{\circ}C$ , 수중기 분위기에서 270 일 동안 실시하였으며 X-선 회절법을 이용하여 산화막 결정 구조를 분석하였다. 마지막 열처리 온도가 $600^{\circ}C$ 이상일 때 두 합금 모두 $\beta$-Zr이 관찰되었으며 모두 재결정 이후 마지막 열처리 온도가 상승할수록 석출물의 면적 분율이 증가하는 경향을 나타내었다. 모든 열처리 온도 구간에서 Zr-lNb합금의 부식 저항성이 Zr-lNb-lSn-0.3Fe 합금에 비해 우수하였으며 두 합금 모두 재결정 이후 부식 저항성이 급격히 나빠졌다. 이는 $600^{\circ}C$ 이후 형성된 $\beta$-Zr의 영향으로 밝혀졌다. Effects of final annealing temperature on the precipitate and oxidation were investigated for the Zr-lNb and Zr-lNb-lSn-0.3Fe alloys. The microstructure and oxidation of both alloys were evaluated for the optimization of final annealing process of these alloys in the annealing temperature regime of 450 to $800^{\circ}C$. The corrosion test was performed under steam at $400^{\circ}C$ for 270 days in a static autoclave. The oxide formed was identified by low angle X-ray diffraction method. The $\beta$-Zr was observed at annealing temperature above $600^{\circ}C$. Above $600^{\circ}C$, the precipitate area volume fraction of Zr-lNb and Zr-1Nb-lSn-0.3Fe alloys appeared to be increased with increasing the final annealing temperature. The corrosion resistance of Zr-lNb was higher than that of Zr- lNb-lSn-0.3Fe alloy. The corrosion rate of both alloys were accelerated due to the formation and growth of $\beta$-Zr with increasing the annealing temperature.

Zr, Zircaloy-4, Zr-Nb 합금의 미세조직 및 재결정 거동에 관한 연구

이명호,최병권,백종혁,정용환,Lee, Myeong-Ho,Choe, Byeong-Gwon,Baek, Jong-Hyeok,Jeong, Yong-Hwan 한국재료학회 2000 한국재료학회지 Vol.10 No.6

Zr 합금의 재결정 거동 및 미세조직 변화에 미치는 열처리 온도 및 시간의 영향의 조사하기위하여 순수 Zr과 Zircaloy-4, Zr-0.88n-0.4Nb-0.4Fe-0.2Cu, Zr-1Nb 합금을 냉간가공한 후 $400^{\circ}C$~$900^{\circ}C$에서 각각 30분~5000분 동안 열처리하였다. 열처리 온도에 따른 Zr합금의 경도, 미세조직 및 석출물 특성을 미소경도기, 광학 현미경 및 투과 전자 현미경을 이용하여 조사하였다. 냉간 가공채는 $400^{\circ}C$에서 $600^{\circ}C$ 범위에서 재결정이 일어났는 데 합금원소가 증가함에 따라 재결정온도가 상승했고 결정립 성장이 억제되었다. 그리고 합금원소 증가에 따른 경도증가 영향이 재결정 이후에도 지속되었다. 열처리 온도 및 시간에 비례하여 재결정 이후 결정립 크기는 증가한 반면 경도변화는 상대적으로 미미하였다. Fe나 Cu가 Zr에 첨가될 경우 회복중 경도증가가 수반되는데, 이는 회복중 생성과 관련이 있는 것으로 사료된다. To investigate the effect of annealing temperature and time on the recrystallization behavior and microstructure of Zr-based alloys, the specimens of Zr-0.8Sn-0.4Nb-0.4Fe-0.2Cu, Zr-1Nb, Zircaloy-4, and unalloyed Zr were cold-worked and annealed at 400, 500, 600, 700, 800, $900^{\circ}C$ for 30 to 5000 minutes. The hardness, microstructure and precipitate of the specimens were investigated by using micro-hardness tester, optical microscope and transmission electron microscope, respectively. The recrystallization of Zr-based alloys occurred between $400^{\circ}C$ and $600^{\circ}C$. As the content of alloying elements increased, the hardness and recrystallization temperature of the alloys increased though the grain sizes after recrystallization decreased. It was supposed that the hardness of Zr-based alloy with Fe or Cu increased during recovery by the formation of Fe or Cu precipitates.

HTPB/AP/Zr 추진제의 연소 특성

민병선,임유진,현형수 한국추진공학회 2005 한국추진공학회지 Vol.9 No.3

Zirconium(Zr) addition to formulation of HTPB/AP propellants, was shown to be less specific impulse than aluminum(Al) by the theoretical calculation because of the lower flame temperature and higher molecular weight of Zr oxide. It was found that the burning rate was faster with the finer size of Zr and the more content of 2㎛ Zr the faster burning rate is in HTPB/AP/Zr propellants caused by the more conduction energy transfer from Zr flame to the burning surface. Also the burning rate of HTPB/AP/Zr propellant could be reduced by addition of 150nm Al, depending on AP size distribution in formulation with Butacene and 1㎛ AP. HTPB/AP의 성능을 이론적 계산에 의해 분석한 결과, Zr 함유 추진제는 Al 추진제보다 비추력이 낮은 데 그 이유는 화염온도가 낮고, Zr 산화물의 분자량이 크기 때문이었다. HTPB/AP/Zr 추진제에서 Zr의 입도가 작을수록 연소속도가 증가하며, 입도가 작은 2㎛ Zr은 함량이 증가할수록 금속화염으로부터 연소표면으로 전달되는 열량이 증가하여 연소 속도가 빨라지는 것으로 나타났다. 150nm 크기의 Al을 HTPB/AP/Zr 추진제에 적용하면 연소 속도가 증가하지만, 연소속도 증진 효과가 매우 좋은 Butacene 및 1㎛ AP가 함께 함유된 추진제에서는 AP의 입도 분포의 영향에 의해 nano Al으로 인하여 연소속도가 감소할 수도 있다는 것을 알게 되었다.

Heteropolyacid supported on Zr-Beta zeolite as an active catalyst for one-pot transformation of furfural to γ-valerolactone

Winoto, Haryo Pandu,Fikri, Zuhroni Ali,Ha, Jeong-Myeong,Park, Young-Kwon,Lee, Hyunjoo,Suh, Dong Jin,Jae, Jungho Elsevier 2019 Applied Catalysis B Vol.241 No.-

<P><B>Abstract</B></P> <P>A novel bifunctional catalyst that enables an efficient one-pot conversion of furfural into γ-valerolactone (GVL) has been developed by anchoring heteropolyacid (HPA) on Zr-Beta zeolite. The catalysts were prepared by a post-synthesis procedure, which consists of the dealumination of Al-Beta, incorporation of Zr into the beta framework through solid-state ion-exchange and impregnation of the HPA. Zr-Beta is used as a Lewis acid catalyst to catalyze the transfer hydrogenation of furfural and levulinic acid/ester using 2-propanol as a hydrogen donor. To deal with the inability of Zr-Beta to catalyze the hydrolytic ring-opening of furans toward GVL, phosphotungstic acid (HPW) and silicotungstic acid (HSiW) were introduced to the Zr-Beta as BrØnsted acid sites. The characterization of the catalysts using XRD, UV–vis and XPS as well as TPD of ammonia and FT-IR spectroscopy of the adsorbed pyridine revealed that the HPA/Zr-Beta possesses both isolated Lewis and BrØnsted acid sites. When they were applied to the one-pot cascade conversion of furfural, the initial activity of the HPA/Zr-Beta toward GVL production were 2–3 times greater than that for Zr-Beta due to the enhanced hydrolytic ring-opening of the furans promoted by the added BrØnsted acidity. Especially, HPW loaded Zr-Beta demonstrated a remarkable GVL yield of ∼70% at 433 K after 24 h due to its high thermal stability and stronger BrØnsted acidity, and its activity far surpasses that of the conventional Sn-Al-Beta zeolite (∼40%). Overall, this study demonstrates that an incorporation of HPA into Lewis acid Sn- or Zr-Beta zeolites is an effective strategy to create isolated Lewis and BrØnsted acid sites within a single catalyst, thereby allowing the selective cascade catalysis for the cost-effective production of high-value chemicals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heteropolytungstae (HPW)-loaded Zr-Beta is synthesized via a simple post-synthesis method. </LI> <LI> The method consists of dealumination of Al-Beta followed by sequential incorporation of Zr and HPW. </LI> <LI> HPW/Zr-Beta zeolite possesses both isolated Lewis and Brønsted acid sites. </LI> <LI> Transfer hydrogenation and ring-opening reactions is effectively combined using a single catalyst. </LI> <LI> One-pot cascade conversion of furfural to GVL with a high yield (∼70%) is achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Study of Coercivity Origin in Mechanically Alloyed Co-Zr System

I. C. Jeong,H. W. Kwon 한국자기학회 2007 Journal of Magnetics Vol.12 No.1

Co100-XZrX (x=10-40) alloys were prepared by using a mechanical alloying technique. Phase constitution of the crystallised material depended on the annealing temperature. The Co?₂Zr₁? alloy crystallised at lower temperature around 550℃ consisted of Co₂₃Zr?, Co?Zr and fcc-Co phases, while the alloy crystallised at higher temperature around 800℃ consisted of Co₂₃Zr? and fcc-Co phases. Phase constitution of the crystallised material also depended on the chemical composition of the alloy. The material with lower Zr content less than 10 at% Zr consisted of Co₂₃Zr? and fcc-Co, and the material with higher Zr-content over 30 at% consisted of Co₂Zr phase. The material containing 15-20 at% Zr consisted of Co₂₃Zr?, Co?Zr and fcc-Co. Only the material containing Co?Zr phase exhibited substantial coercivity, and it was confirmed that coercivity in the mechanically alloyed Co-Zr alloy was originated from the Co?Zr phase.

Identification and structures of the X-ray induced luminescence centers in the zeolites Zr,X,Cs,Na-LTA, X = Cl, Br, and I

Kim, Joon Young,Lim, Hyeon Seung,Heo, Nam Ho,Kim, Hong Joo,Seff, Karl Elsevier 2019 Microporous and mesoporous materials Vol.278 No.-

<P><B>Abstract</B></P> <P>Zr<SUP>4+</SUP> and halide anions were introduced into zeolite A (LTA) by treating Cs,Na-A with ZrX<SUB>4</SUB>(<I>g</I>), X = Br and I, under anhydrous conditions. The crystal structures of Zr,Br,Cs,Na-A and Zr,I,Cs,Na-A were determined by single-crystal crystallography with compositional confirmation by scanning electron microscopy energy-dispersive X-ray (SEM-EDX) analysis. Their X-ray induced luminescence (XIL) properties were throughly studied. These structures and XIL properties were compared with those of previously reported Zr,Cl,Cs,Na-A. In both structures, most Na<SUP>+</SUP> and Cs<SUP>+</SUP> ions occupy positions similar to those found in Cs,Na-A and Zr,Cl,Cs,Na-A. About 9% of the large cavities of Zr,Br,Cs,Na-A are centered by ZrBr<SUB>6</SUB> <SUP>2−</SUP> ions. In Zr,I,Cs,Na-A, about 6% are centered by ZrI<SUB>6</SUB> <SUP>2−</SUP>. These octahedral ZrX<SUB>6</SUB> <SUP>2−</SUP> ions are each held in place and stabilized in their large cavities by 24 bonds between all six of its halide ions and eight surrounding Cs<SUP>+</SUP> ions. They are further bridged by 8-ring Cs<SUP>+</SUP> ions to form a cubic 3-dimensional Cs<SUB>11</SUB>ZrX<SUB>6</SUB> <SUP>9+</SUP> continuum in the surface volume of the crystal. Their XIL domain peaks have red-shifted from 495 nm for Zr,Cl,Cs,Na-A, to 520 nm for Zr,Br,Cs,Na-A, and to 640 nm for Zr,I,Cs,Na-A. This may be because the self-trapped excitons (STE) of ZrBr<SUB>6</SUB> <SUP>2−</SUP> and ZrI<SUB>6</SUB> <SUP>2−</SUP> have smaller band gaps than that of ZrCl<SUB>6</SUB> <SUP>2−</SUP>, a result of the valence band maximum 4p energy level in Br<SUP>−</SUP> being higher (5p in I<SUP>−</SUP> even higher) than the 3p energy level in Cl<SUP>−</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Extraframework Zr<SUP>4+</SUP> and the halide anions were introduced into zeolite A (LTA) to prepare Zr,X,Cs,Na-A, X = Br and I. </LI> <LI> The crystal structures of Zr,X,Cs,Na-A were determined by single-crystal crystallography using synchrotron X-radiation. </LI> <LI> X-ray induced luminescence (XIL) properties of Zr,X,Cs,Na-A were thoroughly studied. </LI> <LI> ZrX<SUB>6</SUB> <SUP>2−</SUP> (X = Cl, Br, and I) ions in the large cavities of Zr,X,Cs,Na-A appear to be the luminescent centers. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

가동 시간에 따른 Zr-2.5Nb 압력관의 크립속도

김영석(Kim Young Suk),서용찬(Suh Yong Chan),안상복(Sang Bok Ahn),정용무(Cheong Yong Moo),임경수(Im Kyung Soo) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3

With a view to assessing a change in the creep rate of the Zr-2.5Nb pressure tubes operating in the reactor with the operation time, Zr-2.5Nb sheets were made with four different kinds of manufacturing process to simulate a microstructural change of the pressure tubes with time. The creep tests were conducted on the Zr-2.5Nb sheets at temperatures ranging from 623 to 673 K and constant stress of 120 ㎫. As an indirect evaluation of the Nb content dissolved in the α-Zr grains, the Nb content in the β-Zr phase of Zr-2.5Nb sheets made with 4 different processes was measured using a replica method. Zr-2.5Nb made with process P1 had the lowest creep rate while that made with process P3 or P4 had the highest creep rate. By correlating the Nb content in the α-Zr grains with the creep rate and strength of the Zr-2.5Nb sheets, we conclude that the Nb contents dissolved in the the c-Zr grains governs the creep rate and strength of Zr-2.5Nb alloy. A change in the creep rate of the Zr-2.5Nb pressure tubes was discussed on the basis of a fact that α-Zr grains in the Zr-2.5Nb pressure tubes have the Nb content decreasing with the operation time increasing.

SO₂로부터 원소 황 회수를 위한 Ce_(1-x)Zr_(x)O₂ 촉매반응연구

김봉석,이종대,박노국,류시옥,이태진,김재창 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.5

Ce_(1-x)Zr_(x)O₂ 촉매상에서 CO에 의한 SO₂의 촉매환원으로부터 원소 황 회수 반응에 대하여 연구하였다. Ce_(1-x)Zr_(x)O₂ 촉매는 Ce/Zr 조성비를 x=1, 0.8, 0.5, 0.2, 0과 같이 조절하여 제조하였으며 반응온도(400-450℃), 공간속도(10,000-70,000 h^(-1)) 변화에 따른 SO₂전화율과 원소 황(S)선택도를 조사하였다. Ce_(1-x)Zr_(x)O₂촉매의 최적반응온도는 425℃ 이었으며 공간속도 50,000 h^(-1)에서 Ce_(0.8)Zr_(0.2)O₂와 Ce_(0.5)Zr_(0.5)O₂ 촉매의 SO₂ 전환율이 93%, 원소 황 선택도 98%로 CeO₂, Ce_(0.2)Zr_(0.8)O₂ 촉매보다 반응성이 높았다. Ce_(1-x)Zr_(x)O₂촉매에 Zr의 첨가량이 증가할수록 CeO₂의 환원률이 증가되었으며, 이러한 결과는 산소 저장성이 우수한 CeO₂에 Zr를 첨가함으로써 산소이동성이 증가되었기 때문인 것으로 판단된다. 본 연구에서 Zr의 첨가로부터 Ce-based 촉매의 격자산소 환원과 비어있는 격자산소 자리의 재산화에 영향을 주어 redox 반응특성을 개선할 수 있음을 확인하였다. The catalytic reduction of SO₂ to elemental sulfur with CO over Ce_(1-x)Zr_(x)O₂ was studied. The Ce_(10x)Zr_(x)O2 catalysts were prepared by changing the Ce/Zr mole ratio(x=1, 0.8, 0.2, 0). The reactivity of Ce_(1-x)Zr_(x)O₂ in accordance with experimental conditions, such as reaction temperature(400-450??), space velocity (GHSV: 10,000-70,000 h^(-1)) were investigated. The conversion of SO2 and the selectivity to elemental sulfur in the recovery of elemental sulfur from SO2 using Ce_(0.8)Zr_(0.4)O₂ and Ce_(0.5)Zr_(0.5)O₂ catalysts were respectively about 93% and 98% at temperature about 425 ??, which were superior to other catalysts. It seems that the reactivity is influenced by the Ce/Zr mole ratio. From these results, it was concluded that the oxygen mobility of catalysis was increased with inserting the Zr. Because the reduction of lattice oxygen and reoxidation of Ce-based catalysts was improved by the adding Zr, it is possible to improve the redox characteristic.