NCM계 리튬이온 배터리 양극재의 수소환원 거동

이소영,이소연,이대현,손호상 한국분말재료학회 2024 한국분말재료학회지 (KPMI) Vol.31 No.2

As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 °C and hydrogen partial pressure above 0.5 atm, Ni and Li2O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H2O, and Li2CO3, with about 0.02 wt% Al as an impurity.

볼 밀링한 CuO-Co₃O₄ 혼합분말의 수소환원 거동과 미세조직 특성

한주연,이규휘,강현지,오승탁,Han, Ju-Yeon,Lee, Gyuhwi,Kang, Hyunji,Oh, Sung-Tag 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5

The hydrogen reduction behavior of the $CuO-SCo_3O_4$ powder mixture for the synthesis of the homogeneous Cu-15at%Co composite powder has been investigated. The composite powder is prepared by ball milling the oxide powders, followed by a hydrogen reduction process. The reduction behavior of the ball-milled powder mixture is analyzed by X-ray diffraction (XRD) and temperature-programmed reduction at different heating rates in an Ar-10%H2 atmosphere. The scanning electron microscopy and XRD results reveal that the hydrogen-reduced powder mixture is composed of fine agglomerates of nanosized Cu and Co particles. The hydrogen reduction kinetics is studied by determining the degree of peak shift as a function of the heating rate. The activation energies for the reduction of the oxide powders estimated from the slopes of the Kissinger plots are 58.1 kJ/mol and 65.8 kJ/mol, depending on the reduction reaction: CuO to Cu and $SCo_3O_4$ to Co, respectively. The measured temperature and activation energy for the reduction of $SCo_3O_4$ are explained on the basis of the effect of pre-reduced Cu particles.

Reduction of SnO₂ with Hydrogen

Kim, Byung-Su,Lee, Jae-chun,Yoon, Ho-Sung,Kim, Soo-Kyung The Japan Institute of Metals 2011 Materials transactions Vol.52 No.9

<P>This study deals with the reduction of tin oxide by hydrogen in the temperature range of 773∼1023 K and the hydrogen partial pressure of 30.4∼101.3 kPa. It aims to investigate the kinetics of the reaction between tin oxide and hydrogen. The hydrogen reduction of tin oxide is to be related with the efforts to extract tin metal with decreasing the emission of carbon dioxide which causes global warming. The experiments were carried out under isothermal condition in hydrogen atmosphere using TGA equipment. The reduction rate of tin oxide to tin metal by hydrogen was found to be relatively fast under the whole conditions until the reduction ratio of SnO<SUB>2</SUB> approaches to about 0.95. As an example, at 1023 K under a hydrogen partial pressure of 101.3 kPa, almost 100% of tin oxide was reduced to tin metal in 10 min. The nucleation and growth model yielded a satisfactory fit to these experimental data. The reaction was first order with respect to hydrogen partial pressure and had an activation energy of 62.5 kJ/mol (15.0 kcal/mol).</P>

A Kinetics of Hydrogen Reduction of Nickel Oxide at Moderate Temperature

Dong Soo Lee,Dong Joon Min 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

Nano-metallic nickel powders are highly-valued materials applied in energy, electronic devices and aerospace, which isknown to be produced by the gaseous phase reduction method of NiCl 2 . In the case of a gaseous reduction method, sizecontrol is diffi cult due to the agglomeration of nickel powders. Therefore, a method of producing highly-valued nickel nanopowdersfrom Ni(OH) 2 has been proposed. Considering the reduction behavior of bulk nickel oxide has been reported tofollow the topo-chemical model. However, reduction behavior of nano-particle is expected to be unknown state. It is necessaryto clarify the mechanism of nickel oxide nano-particle reduction. Therefore, in this study, the temperature dependence andparticle size dependence on the reduction behavior of from micro scale to nano scale particle was confi rmed through TGAexperiment. Also, the reduction mechanism of nickel oxide powder was also investigated based on kinetic considerationsusing the grain topo-chemical model. It was confi rmed that the reduction reaction of nickel oxide powder undergoes throughthe 2nd Avrami model and reduction rate can be expressed by function of temperature and particle size of the powder. Dueto the part of the diff usion, the particle size of the powder also aff ects the rate constant of the reduction reaction. g(x) = k ⋅ f(d) ⋅ t

수소 주입 방식에 따른 세 고망간강의 수소 취화 거동 비교

이승용 ( Seung-yong Lee ),황병철 ( Byoungchul Hwang ) 대한금속ㆍ재료학회 2017 대한금속·재료학회지 Vol.55 No.10

In this study the hydrogen embrittlement characteristics of three high-manganese steels were tested using different hydrogen charging methods, and the results were compared with various Mn-containing steels. The results showed that the hydrogen embrittlement susceptibility of the high-manganese steels increased with increasing inherent strength because deformation mechanisms, such as deformation twinning, ε-martensite transformation, and shear- or micro-band formation, enhanced their sensitivity to hydrogen-induced cracking. The different hydrogen charging methods also affected their ability to achieve the critical hydrogen concentration needed for hydrogen-induced cracking under the stress fields of each microstructure. The relative reduction in ductility for different charging methods usually increased in the order of ex-situ electrochemically-charged, ex-situ high-pressure thermally-charged, and in-situ environment tensile testing, although it was somewhat dependent on the charging, testing and specimen conditions. Based on the results of the three high-manganese steels, it was found that the high-pressure thermally-charged steel specimens had higher relative reductions in ductility because a larger amount of hydrogen was uniformly injected into the steel specimens, which promoted hydrogen-induced cracking under smaller strain than that of the electrochemically-charged steel specimens. (Received May 18, 2017; Accepted June 20, 2017)

A study on the improvement of combustion and emission performance in an EGR-assisted gasoline engine bi-fueled with hydrogen

Young Choi,Changgi Kim,Seungmook Oh,Kernyong Kang 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Hydrogen addition to the typical transportation fuel promotes the combustion characteristics in internal combustion engines due to the wide flammability range and the fast flame speed. Lean combustion technology through hydrogen enrichment is expected to be able to satisfy the next generation emission standards and the green house gas regulation. 100% hydrogen is used to investigate the effect of hydrogen addition to a 2 liter gasoline engine equipped with the EGR supply system. The results show that hydrogen addition enables combustion to be stabilized in both lean condition and excess EGR operation. Hydrogen enrichment also reduces the harmful emissions such as nitric oxides (NOx), carbon monoxide (CO), and unburned hydrocarbon (THC) maintaining increased fuel conversion efficiency. Combustion stability is guaranteed through the hydrogen addition in spite of 32% of Exhaust Gas Recirculation (EGR), which ensures more than 90% of NOx reduction. The amount of emitted CO₂, representative green house gas from automobile, was reduced with the increase of hydrogen enhancement. i.e., more than 6%, 14%, 21% of CO₂ reduction rate was observed with the addition of 10%, 20%, 30% hydrogen energy fraction respectively.

Evaluation of hydrogen embrittlement behaviors of steel welds for pipelines in practical hydrogen environments using in-situ SP tests

Hyung-Seop Shin(신형섭),Juho Yeo(여주호),Jaewon Cho(조재원),Eunsu Min(민은수),Un-Bong Baek(백운봉) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5

Recently, ANU group has established a simple screening technique for hydrogen embrittlement compatibility of steels, which is adopting an in-situ small-punch (SP) test method and corresponding to the ‘external hydrogen’ condition, and proposed a characterizing factor which is suitable for the SP test. The technique is based on the quantitative evaluation of the hydrogen embrittlement (HE) behaviors of various structural steels for hydrogen energy facilities. To investigate the HE compatibility of metallic materials, the in-situ SP tests were carried out under a high-pressure hydrogen gas environment and at the temperature ranges sensitive to HE. Through the measurement of the reduction of thickness (ROT) at the fractured part of the specimen after SP tests under both H2 and inert gas environments, the relative reduction of thickness (RRT) due to HE can be obtained. The RRT has a similar physical meaning to the relative reduction of area (RRA) obtained by the conventional slow strain-rate tensile test (SSRT), since both factors are based on the ductility induced under hydrogen environments. In this study, it is tried to investigate the hydrogen embrittlement (HE) behaviors of pipeline steels and welds by the in-situ SP test. The ductility-based RRT obtained by in-situ SP tests was used to quantify the HE sensitivity of the base metal and welds under various test conditions corresponding to practical use environments of hydrogen devices. This study will contribute to confirm the validity of in-situ SP tests as a simple test method for the quantitative evaluation of the HE susceptibility of pipeline steel welds.

MoO₃-CuO 혼합분말의 볼 밀링 및 수소분위기 열처리에 의한 Mo-Cu 복합분말 제조

강현지,오승탁,Kang, Hyunji,Oh, Sung-Tag 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.4

The hydrogen reduction behavior of $MoO_3-CuO$ powder mixture for the synthesis of homogeneous Mo-20 wt% Cu composite powder is investigated. The reduction behavior of ball-milled powder mixture is analyzed by XRD and temperature programmed reduction method at various heating rates in Ar-10% $H_2$ atmosphere. The XRD analysis of the heat-treated powder at $300^{\circ}C$ shows Cu, $MoO_3$, and $Cu_2MoO_5$ phases. In contrast, the powder mixture heated at $400^{\circ}C$ is composed of Cu and $MoO_2$ phases. The hydrogen reduction kinetic is evaluated by the amount of peak shift with heating rates. The activation energies for the reduction, estimated by the slope of the Kissinger plot, are measured as 112.2 kJ/mol and 65.2 kJ/mol, depending on the reduction steps from CuO to Cu and from $MoO_3$ to $MoO_2$, respectively. The measured activation energy for the reduction of $MoO_3$ is explained by the effect of pre-reduced Cu particles. The powder mixture, hydrogen-reduced at $700^{\circ}C$, shows the dispersion of nano-sized Cu agglomerates on the surface of Mo powders.

Effect of Cu During Non-isothermal Hydrogen Reduction of

Kim Gil-Su,Kim Dae-Gun,Oh Sung-Tag,Suk Myung-Jin,Kim Young-Do 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The effect of Cu on the hydrogen reduction of powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of , which comprised the contained chemical vapor transport of . This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of to particles from or . Such an activated reduction process results in the deposition of Mo and particles on the surface of the Cu.

Supported Pd nanoparticle catalysts with high activities and selectivities in liquid-phase furfural hydrogenation

Nguyen-Huy, Chinh,Kim, Ji Sun,Yoon, Sinmyung,Yang, Euiseob,Kwak, Ja Hun,Lee, Man Sig,An, Kwangjin Elsevier Ltd 2018 Fuel Vol.226 No.-

<P><B>Abstract</B></P> <P>Highly dispersed and ultrafine Pd nanoparticles (NPs) deposited on carbon, silica, and alumina supports were prepared by chemical reduction (CR) using sodium borohydride, in the presence of trisodium citrate as a stabilizer. For comparison, supported Pd catalysts were also prepared through impregnation followed by thermal reduction (TR) and capillary inclusion of the colloidal Pd NPs (CI). The activities and selectivities of the prepared catalysts were evaluated in the liquid-phase furfural (FAL) hydrogenation reaction under 20 bar H<SUB>2</SUB> at 180 °C. Under these conditions, FAL was converted via two distinct pathways to produce either furan via decarbonylation or furfuryl alcohol (FA) via aldehyde hydrogenation. Subsequently, furan and FA were converted to tetrahydrofuran and tetrahydrofurfuryl alcohol (THFA), respectively, via ring hydrogenation. 2-Methylfuran was also produced from the hydration of FAL. To verify the efficiency of the preparation methods, the size of the Pd NPs, the degree of metal dispersion, and the type of supports were correlated with the catalytic conversions and selectivities of FAL hydrogenation. It was confirmed that the 5 wt% Pd/C catalysts possessed highly dispersed small Pd NPs with large metallic Pd surface areas, which resulted in high conversions and selectivities towards THFA in the FAL hydrogenation reaction compared to conventional supported catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultrafine Pd NPs deposited on carbon, silica, and alumina supports were prepared. </LI> <LI> The chemical reduction, impregnation, and capillary inclusion of the Pd NPs were used. </LI> <LI> The catalysts were evaluated in the liquid-phase hydrogenation of furfural. </LI> <LI> The 5 wt% Pd/C catalysts possessed highly dispersed small Pd nanoparticles. </LI> <LI> High conversions and selectivities towards tetrahydrofurfuryl alcohol were obtained. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>