University of Wollongong

About: University of Wollongong is a education organization based out in Wollongong, New South Wales, Australia. It is known for research contribution in the topics: Population & Graphene. The organization has 15674 authors who have published 46658 publications receiving 1197471 citations. The organization is also known as: UOW & Wollongong University.

Understanding the Reaction Chemistry during Charging in Aprotic Lithium–Oxygen Batteries: Existing Problems and Solutions

Abstract: The aprotic lithium-oxygen (Li-O2 ) battery has excited huge interest due to it having the highest theoretical energy density among the different types of rechargeable battery. The facile achievement of a practical Li-O2 battery has been proven unrealistic, however. The most significant barrier to progress is the limited understanding of the reaction processes occurring in the battery, especially during the charging process on the positive electrode. Thus, understanding the charging mechanism is of crucial importance to enhance the Li-O2 battery performance and lifetime. Here, recent progress in understanding the electrochemistry and chemistry related to charging in Li-O2 batteries is reviewed along with the strategies to address the issues that exist in the charging process at the present stage. The properties of Li2 O2 and the mechanisms of Li2 O2 oxidation to O2 on charge are discussed comprehensively, as are the accompanied parasitic chemistries, which are considered as the underlying issues hindering the reversibility of Li-O2 batteries. Based on the detailed discussion of the charging mechanism, innovative strategies for addressing the issues for the charging process are discussed in detail. This review has profound implications for both a better understanding of charging chemistry and the development of reliable rechargeable Li-O2 batteries in the future.

Viscoelastic properties of MR elastomers under harmonic loading

Abstract: This paper presents both experimental and modeling studies of viscoelastic properties of MR elastomers under harmonic loadings. Magnetorheological elastomer (MRE) samples were fabricated by mixing carbonyl iron power, silicone oil, and silicone rubber and cured under a magnetic field. Its steady-state and dynamic properties were measured by using a parallel-plate rheometer. Various sinusoidal loadings, with different strain amplitude and frequencies, were applied to study the stress responses. The stress–strain results demonstrated that MR elastomers behave as linear visocoelastic properties. Microstructures of MRE samples were observed with a scanning electron microscope. A four-parameter linear viscoelatic model was proposed to predict MRE performances. The four parameters under various working conditions (magnetic field, strain amplitude, and frequency) were identified with the MATLAB optimization algorithm. The comparisons between the experimental results and the model predictions demonstrate that the four-parameter viscoelastic model can predict MRE performances very well. In addition, dynamic properties of MRE performances were alternatively represented with equivalent stiffness and damping coefficients.

Reversible structural evolution of sodium-rich rhombohedral Prussian blue for sodium-ion batteries.

Abstract: Iron-based Prussian blue analogs are promising low-cost and easily prepared cathode materials for sodium-ion batteries. Their materials quality and electrochemical performance are heavily reliant on the precipitation process. Here we report a controllable precipitation method to synthesize high-performance Prussian blue for sodium-ion storage. Characterization of the nucleation and evolution processes of the highly crystalline Prussian blue microcubes reveals a rhombohedral structure that exhibits high initial Coulombic efficiency, excellent rate performance, and cycling properties. The phase transitions in the as-obtained material are investigated by synchrotron in situ powder X-ray diffraction, which shows highly reversible structural transformations between rhombohedral, cubic, and tetragonal structures upon sodium-ion (de)intercalations. Moreover, the Prussian blue material from a large-scale synthesis process shows stable cycling performance in a pouch full cell over 1000 times. We believe that this work could pave the way for the real application of Prussian blue materials in sodium-ion batteries. Here the authors deploy a scalable synthesis route to prepare sodium-rich Na2−xFeFe(CN)6 cathode materials for sodium-ion battery. The highly reversible structural evolution during cycling between rhombohedral, cubic and tetragonal phases is the key to enable the good performance.

The ACOS CO 2 retrieval algorithm – Part II: Global X CO 2 data characterization

Abstract: . Here, we report preliminary estimates of the column averaged carbon dioxide (CO2) dry air mole fraction, XCO2, retrieved from spectra recorded over land by the Greenhouse gases Observing Satellite, GOSAT (nicknamed "Ibuki"), using retrieval methods originally developed for the NASA Orbiting Carbon Observatory (OCO) mission. After screening for clouds and other known error sources, these retrievals reproduce much of the expected structure in the global XCO2 field, including its variation with latitude and season. However, low yields of retrieved XCO2 over persistently cloudy areas and ice covered surfaces at high latitudes limit the coverage of some geographic regions, even on seasonal time scales. Comparisons of early GOSAT XCO2 retrievals with XCO2 estimates from the Total Carbon Column Observing Network (TCCON) revealed a global, −2% (7–8 parts per million, ppm, with respect to dry air) XCO2 bias and 2 to 3 times more variance in the GOSAT retrievals. About half of the global XCO2 bias is associated with a systematic, 1% overestimate in the retrieved air mass, first identified as a global +10 hPa bias in the retrieved surface pressure. This error has been attributed to errors in the O2 A-band absorption cross sections. Much of the remaining bias and spurious variance in the GOSAT XCO2 retrievals has been traced to uncertainties in the instrument's calibration, oversimplified methods for generating O2 and CO2 absorption cross sections, and other subtle errors in the implementation of the retrieval algorithm. Many of these deficiencies have been addressed in the most recent version (Build 2.9) of the retrieval algorithm, which produces negligible bias in XCO2 on global scales as well as a ~30% reduction in variance. Comparisons with TCCON measurements indicate that regional scale biases remain, but these could be reduced by applying empirical corrections like those described by Wunch et al. (2011b). We recommend that such corrections be applied before these data are used in source sink inversion studies to minimize spurious fluxes associated with known biases. These and other lessons learned from the analysis of GOSAT data are expected to accelerate the delivery of high quality data products from the Orbiting Carbon Observatory-2 (OCO-2), once that satellite is successfully launched and inserted into orbit.