Mechanical Degradation Behavior of Single Crystal LiNixMnyCozO2 Cathode in Li-ion Battery by Indentation Analysis

LiNixMnyCozO2 (NMC) is among the most promising cathode materials for commercial Li-ion batteries due to its high electrochemical performance. However, NMC composite cathode is still plagued with limited cyclic performance, which is influenced by its structural stability during the cycling process. The cathode, which comprises of the active material, polymeric binder, and porous conductive matrix, often exhibits large structural variation during the electrochemical cycling process. This inevitably increases the challenge of measuring the mechanical properties of the material. Even though single crystal NMC possesses better stability as compared to the polycrystalline NMC, the electrochemical performance degradation of single crystal NMC cathode remains relatively unexplored. Different sample preparation methods are compared systematically in accordance to the previous report, and a new method of sample preparation is proposed. Nanoindentation instrument is used to measure the elastic modulus and hardness of the single crystal NMC particles. The measured elastic modulus and hardness of NMC particles, under different electrochemical environments, are dependent on a large number of nanoindentation experiments and statistical analysis of the result obtained from the carefully prepared samples. The sample preparation method is the key factor that can significantly influence the nanoindentation experiment results of the NMC particles. This work shows that the mechanical properties of the single crystal NMC particles degrade significantly with number of electrochemical cycles. The decreasing elastic modulus with the number of electrochemical cycles can be fitted using a two-parameter logarithm model.

Memory Trick Game Towards Students’ Enthusiasm In Learning Grammar

This was a qualitative research and aimed to investigate whether how memory trick game could improve students in learning grammar at SMPN 18 Mataram in the academic year of 2019/2020. The subject of this research was the second grade students of SMPN 18 Mataram that only one class consist of 15 students. This research was limited by the grammatical role only. The research instruments consisted of questionners, field note, and documentation. The data analyzed in transcript for the observation and taking note for shows that the students at SMPN 18 Mataram still low enthusiasm and comprehend the Memory Trick Game. The researcher took the research and has the provident which the questioner was looking for the students’ surface knowledge about the what is grammar and how enthusiasm student in learning grammar. The result of cycling process also shows that in the first cycle consist of three meetings, and the students were still need to be more concentrate in order to make them more understand in expanding their ideas into a good grammar. Then the cycle two was also consist of three meetings, the students’ score in this cycle was better than the cycle one. The memory trick game as the solution from the researchers also proved that there was an improvement from the first cycle to the second cycle.

Remobilization of Storage Nitrogen in Young Pear Trees Grafted onto Vigorous Rootstocks (Pyrus betulifolia)

The remobilization of storage nitrogen (N) is affected by growth characteristics of young pear trees. Aboveground parts of young pear trees grafted on P. betulifolia grew more vigorously than that on dwarfing rootstocks. Therefore, the remobilization of storage N within young pear trees on vigorous rootstocks may be different from that on dwarfing rootstocks. A 15N tracing experiment, including six groups of one-year-old pear trees grafted on vigorous rootstocks in 2016, was conducted to investigate the mobilization of storage N from 2016 to 2018. Results indicated that about 44%, 31.4% and 24.6% of storage N remobilized in new growth was derived from the trunk, shoots and roots, respectively. Most of storage N remobilized in new organs were supplied by trunks and shoots. About 82.2% of storage N withdrawn from senescent leaves were recovered in the trunk and shoots during autumn. The aboveground parts played a more important role than roots in the cycling process of storage N in young pear trees. However, as compared with young pear trees on dwarfing rootstocks, more storage N recovered in new organs were supplied by roots of that on vigorous rootstocks, due to vigorous growth and more nutrient requirement of aboveground parts.

Development of technology of gas condensate extraction from the formation in the conditions of retrograde condensation

The object of research is gas condensate fields at a late stage of their development under conditions of a decrease in reservoir pressure below the pressure of condensate separation from a gaseous state. Reservoir losses of condensate during the development of deposits in depletion mode can reach 78 %, which entails the need to use various methods of stimulating the reservoir system to remove it. The most acceptable method is the use of a cycling process by re-injection (recirculation) of the produced and separated gas into the formation. A significant disadvantage of the cycling process is the long-term conservation of gas reserves as a result of its re-injection into the reservoir and significant capital and operating costs for dry gas injection. From a technological point of view, the use of the cycling process is constrained by the low value of the sweep efficiency. Dry gas that is injected has a lower viscosity in terms of the gas-condensate mixture is withdrawn from the reservoir, and under the conditions of the heterogeneous structure of the reservoir, its rapid breakthrough from injection to production wells takes place and, as a result, a decrease in the efficiency of condensate recovery. As an alternative to the cycling process for extracting retrograde condensate from the reservoir, it has been proposed to squeeze it out with water. The paper proposes a unified waterflooding system, actually displacing condensate with water or a gas-water mixture. This is achieved by controlled operation of injection and production wells. First, gas is taken from the wells, and with the appearance of water in the product, methods of intensifying the transfer to the surface are used. If necessary, the wells are switched to forced production mode. The results of laboratory studies carried out on real samples of core material from the Andriyashivske gas condensate field (Ukraine) are presented. The directions of the implementation of gas-water repression in gas condensate fields with the parallel use of restrained reservoir gas available in the reservoir are substantiated. The technology allows to extract up to 50 % of the condensate dropped out in the reservoir.

Thermal Shock Behavior of Twill Woven Carbon Fiber Reinforced Polymer Composites

In the current research, the effect of cyclic temperature variation on the mechanical and thermal properties of woven carbon-fiber-reinforced polymer (CFRP) composites was investigated. To this, carbon fiber textiles in twill 2/2 pattern were used as reinforced phase in epoxy, and CFRPs were fabricated by vacuum-assisted resin-infusion molding (VARIM) method. Thermal cycling process was carried out between −40 and +120 °C for 20, 40, 60 and 80 cycles, in order to evaluate the effect of thermal cycling on mechanical and thermal properties of CFRP specimens. In this regard, tensile, bending and short beam shear (SBS) experiments were carried out, to obtain modulus of elasticity, tensile strength, flexural modulus, flexural strength and inter-laminar shear strength (ILSS) at room temperature (RT), and then thermal treated composites were compared. A dynamic mechanical analysis (DMA) test was carried out to obtain thermal properties, and viscoelastic properties, such as storage modulus (E’), loss modulus (E”) and loss factors (tan δ), were evaluated. It was observed that the characteristics of composites were affected by thermal cycling due to post-curing at a high temperature. This process worked to crosslink and improve the composite behavior or degrade it due to the different coefficients of thermal expansion (CTEs) of composite components. The response of composites to the thermal cycling process was determined by the interaction of these phenomena. Based on SEM observations, the delamination, fiber pull-out and bundle breakage were the dominant fracture modes in tensile-tested specimens.

Unveiling the abnormal capacity rising mechanism of MoS2 anode during long-term cycling for sodium-ion batteries

The capacity rising is due to the biphasic coexistence of MoS2 during the cycling and the progressive increase in the 1T-MoS2 content. Simultaneously, the layer spacing expanded from 0.62 nm to 1.03 nm during the cycling process.