ABSTRACT
The layered Nb5+-doped LiNi0.83Co0.11Mn0.06O2 (NCM) oxide cathode materials are successfully synthesized through introducing Nb2O5 into the precursor Ni0.83Co0.11Mn0.06(OH)2 during the lithiation process. The results refined by GSAS software present that the Nb5+-doped samples possess the perfect crystal structure with broader Li+ diffusion pathways. Moreover, the morphology characterized by scanning electron microscope displays the compact secondary particles packed by smaller primary particles under the effect of Nb5+. The excellent electrochemical properties are also acquired from the Nb5+-doped samples, in which the optimal rate performance and cycling stability are performed for NCM-1.0 when up to 1.0 mol % of Nb2O5 (based on the precursor) is added. Benefited from the introduction of Nb5+, the cell assembled with the NCM-1.0 electrode retains higher capacity retention of 86.6 % at 1.0 C and 25 °C, and 71.7 % at 1.0 C and 60 °C after 200cycles. Moreover, it also delivers higher discharge specific capacity of 154.6 mAh g-1 at 5.0 C. Therefore, the Nb5+-doping strategy may open an effective route for optimizing nickel-rich oxide cathode materials, which is worth popularizing for the enhancement of the electrochemical performance of nickel-rich cathodes for lithium-ion batteries.
ABSTRACT
CO2 injection and water alternating gas (WAG) injection are crucial to improve the oil recovery method and have optimized development in numerous oil fields. Many issues, such as gas channeling, water clogging, and a shortage of gas injection capacity, are addressed in the studies. Considering these conflicts, we suggest in this work a unique method of surfactant alternating gas (SAG) injection. Additionally, axisymmetric drop shape analysis and other approaches are utilized to explore the interface properties of a variety of systems, including CO2/carbonated water/water/surfactant/oil systems. SAG injection combines the advantages of surfactant and WAG injection. Although CO2 molecules have an effect on surfactant aggregation at the oil-water interface in the SAG system, carbonated water has little effect on surfactant performance in lowering oil-water interface tension. Pilot studies reveal that a SAG ratio of 3:2 at 74 °C and 0.5 wt% concentration significantly improves oil recovery.
ABSTRACT
WO3 as tungsten dopant is introduced into lithium nickel cobalt manganese (LiNi0.83Co0.11Mn0.06O2, NCM) layered oxide powders to synthesize W6+-doped NCM cathode materials during the lithiation process of the hydroxide precursor. Introducing W6+ into the lattice can lead to the diversities of the crystal structure, surface morphology, and electrochemical performance. The crystal structure confirmed by X-ray diffraction indicates that the W6+-doped oxide powders present a typical R-3m layered structure with larger interplanar distance and cell volume. Also, scanning electron microscope images reveal that the primary particles shrink forming a tighter surface under the effect of W6+, while the specific changes gradually aggravate with increase in the content of W6+ added. The excellent electrochemical stability of W6+-doped samples is observed, as the stable host structure is reinforced by the strong W-O bond. The stable structure does not only inhibit the anisotropic volume change caused by repetitive H2 â H3 phase transitions, but also sustains the integrated structure to impede the formation of microcracks and the appearance of more side reactions. This research provides an effective route on investigating the potential association between electrochemical performance and structure change for W6+-doped strategy.
ABSTRACT
Chemical flooding technology has been widely applied in medium- and high-permeability reservoirs. However, it is rarely applied in low-permeability reservoirs, which is mainly limited by reservoir physical properties, chemical agents, injection capacity, and so forth. In this paper, a novel chemical formula used in low-permeability reservoirs was developed. In response to the low-permeability reservoir geological characteristics, fluid properties, and water flooding development of the target block, some experimental studies and field project studies of polymer-surfactant flooding were carried out. The surfactant structure and polymer molecular weight were determined from laboratory experiments. The polymer-surfactant binary system was synthesized. It had good injectivity in low-permeability reservoirs, and its oil recovery efficiency increased over 10% in the laboratory experiment. The result was higher than that of single chemical flooding. After field implementation, initial results have been achieved with an increase in injection pressure. The chemical formula can effectively alleviate intra-layer and inter-layer contradictions in the reservoir. The project has increased oil output by 77,700 t and the recovery factor by 3.5%. The experience and lessons were of great significance for the development of chemical flooding in high-temperature, high-salinity, and low-permeability reservoirs.
ABSTRACT
The nitrogen-doped carbon (NC) coating encapsulating heterostructural Sn/SnO2 microcube powders (Sn/SnO2@NC) are successfully fabricated through hydrothermal, polymerization of hydrogel, and carbonization processes, in which the SnO precursor powders exhibit regular microcube structure and uniform size distribution in the presence of optimized N2H4·H2O (3.0 mL of 1.0 mol/L). Interestingly, the precursor powders are easily subjected to a disproportionated reaction to yield the desirable heterostructural Sn/SnO2@NC microcube powders after being calcined at 600 °C in N2 atmosphere in the presence of home-made hydrogel. The coin cells assembled with the Sn/SnO2@NC electrode present a high initial discharge specific capacity (1058 mAh g-1 at 100 mA g-1), improved rate capability (an excellent DLi+ value of 2.82 × 10-15 cm2 s-1) and enhanced cycling stability (a reversible discharge specific capacity of 486.5 mAh g-1 after 100 cycles at 100 mA g-1). The enhanced electrochemical performance can be partly ascribed to the heterostructural microcube that can accelerate the transfer rate of lithium ions by shortening the transmission paths, and be partly to the NC coating that can accommodate the volume effect and contribute to partial lithium storage capacity. Therefore, the strategy may be able to extend the fabrication of Sn/SnO2 heterostructural microcube powders and further application as promising anode materials in lithium ion batteries.
ABSTRACT
OBJECTIVE: To investigate the effectiveness and safety of clinical pharmacists-directed vancomycin dosing and therapeutic drug monitoring (TDM), and to promote the individualized medication of vancomycin. METHODS: Information of hospitalized patients treated by vancomycin admitted to Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from January 2011 to October 2017 was collected retrospectively during study period, the patients were divided into pharmacists intervention and non-pharmacists intervention groups according to pharmacist-directed vancomycin dosing guideline or not. The individualized dosing regimen of vancomycin for the patients in pharmacists intervention group was guided by clinical pharmacists, this guideline was that pharmacists offered the TDM guidance, made the individualized dosage regimen of vancomycin, etc., which based on the patients' pathophysiology, condition, and the adjustments of increased dose or 24-hour continuous infusion vancomycin were made for patients if the steady-state trough concentrations fell below the target level. Vancomycin dosage was made for patients in the non-pharmacists intervention group by physicians only based on vancomycin instructions or clinical experience. The vancomycin dosing, TDM, microorganism culture, renal function, 30-day mortality rate, and length of hospital stay were recorded. The appropriateness of TDM for vancomycin was defined as a blood collection within 1 hour of the next scheduled dose after steady state achieved. The rationality of the initial dosing regimen was determined based on the vancomycin application guidelines issued by Infectious Diseases Society of America (IDSA) in 2009. RESULTS: A total of 258 patients were enrolled, and there were 158 patients in the non-pharmacists intervention group and 100 in pharmacists intervention group. The appropriateness of TDM for vancomycin in pharmacists intervention group was significantly improved as compared with that in non-pharmacists intervention group [87.0% (87/100) vs. 69.6% (110/158), P < 0.01], the percentage of first trough serum concentrations drawn on day 3 after steady state achieved was significantly increased [51.0% (51/100) vs. 37.3% (53/142), P < 0.05]. Compared with the non-pharmacists intervention group, the percentages of patients who received appropriate initial dosing and attained the initial target therapeutic range in pharmacists intervention group were significantly increased [87.4% (76/87) vs. 68.2% (75/110), 51.7% (45/87) vs. 30.9% (34/110), both P < 0.01], the percentage of patients whose vancomycin dosing regimen was adjusted based on TDM results was also significantly increased [54.0% (47/87) vs. 15.5% (17/110), P < 0.01], the rate of vancomycin serum concentrations reaching the standard was increased [70.1% (61/87) vs. 32.7% (36/110), P < 0.01], and a lower number of patients in sub- or supra-therapeutic range was observed in pharmacists intervention group [27.6% (24/87) vs. 46.4% (51/110), 2.3% (2/87) vs. 20.9% (23/110), both P < 0.01]. In addition, a lower incidence of vancomycin-induced acute kidney injury (AKI) was observed in pharmacists intervention group as compared with that in non-pharmacists intervention group [0 (0/87) vs. 6.4% (7/110), P < 0.01]. No significant difference was observed in the microorganism culture, 30-day mortality rate or length of hospital stay between the two groups. Among the 87 patients in pharmacists intervention group, the vancomycin dosing was adjusted for 42 patients who did not attain the target therapeutic range, increasing the dose of vancomycin was made for 22 patients, 24-hour continuous infusion was made for 20 patients. Compared with the only increasing vancomycin dose group, vancomycin continuous infusion for 24 hours could significantly increase the serum trough concentration (mg/L: 18.0±6.7 vs. 12.5±5.8, P < 0.05), and reduce daily dosage (mg/kg: 27.1±7.1 vs. 36.6±9.2, P < 0.01). CONCLUSIONS: The implementation of a pharmacist-directed vancomycin dosing guideline based on TDM optimized vancomycin dosing regimen, improved the accuracy and timeliness of TDM for vancomycin, achieved a higher percentage of levels within the therapeutic range, and a lower incidence of vancomycin-induced AKI.
