Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An <i>in situ</i> time-resolved X-Ray diffraction and mass spectroscopy study

Hu, Enyuan,Bak, Seong Min,Senanayake, Sanjaya D.,Yang, Xiao-Qing,Nam, Kyung-Wan,Zhang, Lulu,Shao, Minhua Elsevier 2015 Journal of Power Sources Vol.277 No.-

<P><B>Abstract</B></P> <P>Thermal stabilities of a series of blended LiMn<SUB>2</SUB>O<SUB>4</SUB> (LMO)–LiNi<SUB>1/3</SUB>Co<SUB>1/3</SUB>Mn<SUB>1/3</SUB>O<SUB>2</SUB> (NCM) cathode materials with different weight ratios were studied by <I>in situ</I> time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25 °C–580 °C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn<SUB>3</SUB>O<SUB>4</SUB> phase at around 250 °C. Formation of MnO with rock-salt structure started at 520 °C. This observation is in contrast to the previous report for chemically delithiated LMO in air, in which a process of λ-MnO<SUB>2</SUB> transforming to β-MnO<SUB>2</SUB> was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO<SUB>2</SUB> profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO<SUB>2</SUB> profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO<SUB>2</SUB> release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermal stability of blended LiMn<SUB>2</SUB>O<SUB>4</SUB>(LMO)–LiNi<SUB>1/3</SUB>Co<SUB>1/3</SUB>Mn<SUB>1/3</SUB>O<SUB>2</SUB>(NCM) is studied. </LI> <LI> Blending of LMO with NCM leads to lower gas releasing temperature of CO<SUB>2</SUB> and O<SUB>2</SUB>. </LI> <LI> During heating the NCM decomposes first followed by the LMO. </LI> <LI> MnO, NiO and possibly CoO were formed at temperatures higher than 500 °C. </LI> </UL> </P>

Temporal and spatial characteristics of coal-mine microseism based on single-link cluster

Zhibo Zhang,Enyuan Wang,Enyuan Wang 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.2

Single-link cluster is introduced into mine microseism monitoring from a seismology point of view. The changes in spatial correlation length of mine microseismic events at different spatial scales are analyzed, and the underlying mechanisms are explained. The results show that large-energy microseismic events often occur after the spatial correlation length drops to a low value when the spatial scale is large. The larger the energy of microseismic events is, the more obvious the law is. Large-energy microseismic events occur after the spatial correlation length exhibits the power-law growth phenomenon, when the spatial scale becomes small. The smaller the spatial scale is, the more obvious the law is. The reason for this property is that microseismic events exhibit the space aggregation phenomenon before a large-energy microseismic event occurs, resulting in decreases in spatial correlation length when the spatial scale is large. By contrast, when the spatial scale is small, the spatial correlation degree of regional microseismic sources is high. Small-energy microseismic events occur gradually with concentration in low-intensity regions, and a large number of small cracks are produced before a large microseismic event occurs. The microseismic source is dispersed again once the regional stress is released. The entire system achieves a critical state. There is small cracks coalescence at a particular moment, which triggers a large-energy microseismic event. Therefore, it exhibits the phenomenon of power-law growth of the correlation length before the occurrence of the large-energy microseismic event. Moreover, statistical analysis of the bond length and frequency of SLC is performed. The result is that three non-scale ranges are identified. The turning points of the first two nonscale ranges are 180 m and 240 m, respectively, while the turning points of the second and third non-scale ranges are both approximately 450 m. The difference between the first turning points is due to the artificial disturbance, while the second turning point is affected by the geological environment.

Coal and gas outburst hazards and factors of the No. B-1 Coalbed, Henan, China

Liang Chen,Enyuan Wang,Jianchun Ou,Jiangwei Fu 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.1

Coal and gas outburst disaster of the No. B-1 Coalbed, Henan, China, have lasted for nearly 60 years, and the threat will become more and more serious as mining depths continuously increase. However, coal and gas outburst characteristics and factors of the coalbed have not been studied in detail. To effectively prevent and control coal and gas outburst, we analyzed the type, intensity, location and precursors of coal and gas outburst occurring in the No. B-1 Coalbed. Moreover, the effects of geological conditions (burial depth, faults, folds, coalbed thickness and dip) and mining disturbances on coal and gas outburst were studied. The results showed that these outburst accidents were mostly typical, small-sized and medium-sized outburst, which mainly occurred at the coal roadway working faces. There were many precursors such as blasting sound, changes in coal structure, and abnormal gas emission prior to the accidents. Within a burial depth of 500 m, the average outburst intensity had a stronger correlation with the burial depth, which was more obvious at a burial depth of 301~400 m, and less obvious at a burial depth of 401~500 m. However, the distribution of these outbursts barely changed within the burial depth. Up to 99.15% of coal and gas outburst occurred at faults, folds, and areas with changes in coalbed thickness and dip. Up to 68.25% were induced by blasting and 18.04% occurred during shelving, coal-shoveling and no operation. The No. B-1 Coalbed was characterized by delayed outbursts. Moreover, specific suggestions were recommended for the prevention and control of coal and gas outburst. The study is useful to government regulators and staffs engaged in the prevention and control of coal and gas outburst.

The exhumation along the Kenyase and Ketesso shear zones in the Sefwi terrane, West African Craton: a numerical study

Xiaojun Feng,Enyuan Wang,Jérôme Ganne,Roland Martin,Mark Jessell 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.3

High-grade (amphibolite–granulite facies) tectono-metamorphic domains in the Sefwi terrane of Ghana are separated from adjacent lower-grade (greenschist facies) greenstone belts by two main shear zones. The high-grade rocks presumably exhumed along the sinistral shear zones during the D2 ENE-WSW transtension (~2073 Ma). To better understand the role boundary conditions and the spatial relationship of faults play in the exhumation of partially molten lower crust in the Sefwi terrane, ten 3D thermomechanical models have been constructed. The results show that the normal component of velocity boundary conditions mainly controls the exhumation (8–10 km) of the lower crust along pre-existing faults, while the exhumation in the relay zones between faults is controlled by the obliquity between the applied extensional velocity vector and the vertical wall on which it is applied. The strike of the exhumation belt made of partially molten lower crust rocks in the relay zone is sub-orthogonal to the horizontal maximum stretching axis. The isostatic compensation from low-density upper mantle to overlying crust (thinning) is higher under transtension than under extension. The lower crust exhumation influenced by inherited shear zones (ductile) can be used to better understand the loci of the high-grade rocks in the Sefwi terrane. We suggest that the Kukuom-Juaboso domain composed of amphibolite–migmatite facies rocks probably resulted from the concentration of partially molten rocks in the relay zone between the Ketesso and Kenyase shear zones during the D2 ENE-WSW transtension. The two shear zones probably underwent two main stages for growth and maturation from the D1 to D2 phases. The regional exhumation of the high-grade rocks in the Sefwi terrane probably occurred within < 5 Ma.

중의 약재로부터 피부 미백제의 탐색

( Guixin Chou ),( Enyuan Zhu ),이수연 ( Su Yeon Lee ),김영희 ( Young Heui Kim ),박선기 ( Sun Ki Park ),오선택 ( Sun Tack Oh ),김기호 ( Ki Ho Kim ) 대한화장품학회 2009 대한화장품학회지 Vol.35 No.4

본 연구에서는 미백 화장품 원료를 개발하기 위해 중국에서 전통적으로 사용되어 오던 47종의 천연약재 또는 복합처방 중에서 멜라닌 생성 저해 효과를 지닌 원료를 찾고자 하였다. 그 중 버섯 티로시나제 활성 실험에서는 저해효과를 보이지 않았으나, B16-F10 멜라닌 생성세포(B16-F10 melanoma cell)를 이용하여 류기노와 단삼을 선별하였으며 단삼에서 단삼소(丹蔘素, α,3,4-trihydroxybenzenepropanoic acid sodium salt)를 분리하여 B16-F10 멜라노마 세포를 이용하여 멜라닌 생성 억제에 관한 실험을 실시하였다. 류기노와 단삼소는 농도에 따라 멜라닌 생성을 억제하였으며, 류기노는 300 μg/mL의 농도에서 약 60%, 단삼소는 100 μg/mL의 농도에서는 약 50 %의 멜라닌 생성 저해 효과를 보였다. 따라서 연구 결과로써 얻어진 2종의 원료는 새로운 천연 미백 소재로 적용할 수 있을 것으로 기대된다. In order to search for new whitening cosmetic ingredients from Chinese herbal extracts including Chinese herbs and complex prescriptions from TCM (Traditional Chinese Medicine), we screened about 47 TCM extracts collected from China. We tested their inhibitory effects on melanogenesis by using in vitro tyrosinase inhibition assay and B16 melanoma cells. We selected Siphonostegia chinensis and Salvianic miltiorrhiza Bunge. We isolated Danshensu (α,3,4-trihydroxybenzenepropanoic acid sodium salt) from Salvianic miltiorrhiza Bunge extract and tested its inhibitory effect on melanin formation in B16-F10 melanoma cells. Danshensu suppressed melanin synthesis up to about 50 % at a concentration of 100 μg/mL. Siphonostegia chinensis suppressed melanin synthesis up to about 60 % at a concentration of 300 μg/mL. The results showed that these extracts could be used as new natural active ingredients for whitening cosmetics.

Effect of pre-existing faults on the distribution of lower crust exhumation under extension: numerical modelling and implications for NW Ghana

Xiaojun Feng,Enyuan Wang,Prince O. Amponsah,Jérôme Ganne,Roland Martin,Mark W. Jessell 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6

3D thermo-mechanical models have been constructed to explore the influence of pre-existing faults on the temporalspatial distribution of high-grade amphibolite-granulite facies metamorphic rocks during extension. The different dip amounts of three pre-existing faults (refer to the Bole-Nangodi shear zones, the Jirapa shear zone and the Bulenga shear zone in the study area) are studied in models. The results show the lower crust exhumes occur at a relatively low rate prior to attaining a Stretching Factor = 4.2%. The partially molten lower crustal rocks tend to move (up to 20 km) towards the center of the model and focus exhumation in regions where pre-existing faults intersect. The high-strain corridors in models are used to understand the loci of exhumation in the Bole-Bulenga domain of NW Ghana. Accordingly, in the eastern and western parts of the high-grade rock corridors in NW Ghana, partially molten rocks exhumed from the lower into middle-upper crustal levels are interpreted to have been dominantly facilitated by the km-scale high-strain corridors. In the central part of the Bole-Bulenga domain, the high-grade rocks are interpreted to have been exhumed because of a coupling between two mechanisms: (1) The exhumation of partially molten rocks between the Jirapa and Bole-Nangodi faults increases in spatially due to the reduction in space from north to south. (2) The exhumation of lower partially molten rocks in the central part, as a result of inherited orthogonal (E-W) structures.

Numerical simulation of pressure relief in hard coal seam by water jet cutting

Song, Dazhao,Wang, Enyuan,Xu, Jiankun,Liu, Xiaofei,Shen, Rongxi,Xu, Wenquan Techno-Press 2015 Geomechanics & engineering Vol.8 No.4

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

Structural Changes and Thermal Stability of Charged LiNi_<i>x</i>Mn_<i>y</i>Co_<i>z</i>O₂ Cathode Materials Studied by Combined <i>In Situ</i> Time-Resolved XRD and Mass Spectroscopy

Bak, Seong-Min,Hu, Enyuan,Zhou, Yongning,Yu, Xiqian,Senanayake, Sanjaya D.,Cho, Sung-Jin,Kim, Kwang-Bum,Chung, Kyung Yoon,Yang, Xiao-Qing,Nam, Kyung-Wan American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.24

<P>Thermal stability of charged LiNi<SUB><I>x</I></SUB>Mn<SUB><I>y</I></SUB>Co<SUB><I>z</I></SUB>O<SUB>2</SUB> (NMC, with <I>x</I> + <I>y</I> + <I>z</I> = 1, <I>x</I>:<I>y</I>:<I>z</I> = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined <I>in situ</I> time-resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and the larger amount of oxygen release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3<I>a</I> octahedral sites of a layered structure (<I>R</I>3̅<I>m</I>) but Co ions prefer to migrate to the 8<I>a</I> tetrahedral sites of a spinel structure (<I>Fd</I>3̅<I>m</I>) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. This systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-24/am506712c/production/images/medium/am-2014-06712c_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am506712c'>ACS Electronic Supporting Info</A></P>

EMR: An effective method for monitoring and warning of rock burst hazard

Song, Dazhao,Wang, Enyuan,Li, Zhonghui,Qiu, Liming,Xu, Zhaoyong Techno-Press 2017 Geomechanics & engineering Vol.12 No.1

Rock burst may cause serious casualties and property losses, and how to conduct effective monitoring and warning is the key to avoid this disaster. In this paper, we reviewed both the rock burst mechanism and the principle of using electromagnetic radiation (EMR) from coal rock to monitor and forewarn rock burst, and systematically studied EMR monitored data of 4 rock bursts of Qianqiu Coal Mine, Yima Coal Group, Co. Ltd. Results show that (1) Before rock burst occurrence, there is a breeding process for stress accumulation and energy concentration inside the coal rock mass subject to external stresses, which causes it to crack, emitting a large amount of EMR; when the EMR level reaches a certain intensity, which reveals that deformation and fracture inside the coal rock mass have become serious, rock burst may occur anytime and it's necessary to implement an early warning. (2) Monitored EMR indicators such as its intensity and pulses amount are well and positively correlated before rock bursts occurs, generally showing a rising trend for more than 5 continuous days either slowly or dramatically, and the disaster bursts generally occurs at the lower level within 48 h after reaching its peak intensity. (3) The rank of EMR signals sensitive to rock burst in a descending order is maximum EMR intensity > rate of change in EMR intensity > maximum amount of EMR pulses > rate of change in the amount of EMR pulses.

Study on the Safety of Tunnel Structure Vibration in Dry Ice Powder Thermal Shock Rock Breaking

Xiaofei Wang,Shaobin Hu,Enyuan Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.11

The application of explosive blasting for rock breaking works was not possible in densely populated areas, which caused problems in urban tunnel construction. In the application of dry ice powder thermal shock breaking in tunnel excavation, a vibration monitoring system was employed to monitor the vibration response of the tunnel structure during the breaking process, and it was used to extract the signal characteristics by Hilbert-Huang transformation. Experimental results are as follows: 1) The peak vibration speed was below 50 mm/s for concrete structures safe as long as it was farther than 10 m from the burst hole in the support concrete. 2) Aggregate decay of vibration velocities caused by thermal shock breaking of rock with dry ice powder corresponded to the decay law of the power function. The range of influence of the vibration was considerably smaller compared to that of drilling and blasting the rock; 3) The new rock-breaking technology induced damage can be divided into three regions, with radial fractures generated by high-energy fluids dominating. 4) Hilbert Huang transform extracted signal features more objectively and accurately, with excellent reference for the safety monitoring of tunnel structures.