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排序方式: 共有107条查询结果,搜索用时 31 毫秒
81.
Stadler A Brenner J Pauschitz A Wendrinsky J Schindel A Nauer GE 《Analytical and bioanalytical chemistry》2008,390(6):1527-1535
The aim of this study was to gain knowledge of tribological layers on a steel disc. This steel disc has been used in a transmission
system in the field. ATF-oil (automatic transmission fluid), which contains different surface-adhering additives, serves as
a lubricant and as a cooling fluid in the tribological system. Over time, the tribological characteristics of the system changed.
Special interest in this study lies in the modifications of the steel surface. The field-used disc was therefore compared
with model tested discs. In a disc-on-disc tribometer, all samples are tested for a short period of time to evaluate the actual
condition of the system regarding friction behaviour. Analysis and characterisation of surfaces and layer formation were carried
out with, among other techniques, 3D topography, SEM / EDX, AFM, XPS, and ToF-SIMS. Results indicate that in some regions
a complex composed tribological layer is formed. Differences were detected between the steel discs used in the field and the
model discs. This indicates the problem of evaluation of long-term behaviour exclusively by use of short or accelerated model
experiments. A combination of carefully selected and sophisticated analytical methods is necessary to trace small changes
of the system.
Figure Atomic force measurement of field used and model tested “new” friction discs 相似文献
82.
Yanqiu Lyu Dr. Jodie A. Yuwono Dr. Pengtang Wang Yanyan Wang Dr. Fuhua Yang Dr. Sailin Liu Dr. Shilin Zhang Prof. Baofeng Wang Prof. Kenneth Davey Dr. Jianfeng Mao Prof. Zaiping Guo 《Angewandte Chemie (International ed. in English)》2023,62(21):e202303011
Aqueous Zn-Iodine (I2) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm−2, 2 mAh cm−2. It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I−/I2. As a result, the Zn-I2 full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g−1 at 10 A g−1. We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I2 batteries. 相似文献
83.
褚富山 《理化检验(化学分册)》2000,36(8):337-338,340
试验以锡粒、纯铁、钨粒为助熔剂,用红外吸收测定铝质耐火材料中碳。通过加入碳酸钙进行回收率试验,回收率在95%~105%内,RSD在1%以下。在没有标样情况下,用合成标样或标准加入法计算样品结果与化学分析法基本一致。 相似文献
84.
The methods for increasing the production of ergothioneine (ERG) were investigated by using the mycelial culture of several
mushroom species, primarily Ganoderma neo-japonicum. We first found that ERG was accumulated at the different levels in mycelia and fruiting bodies, respectively, depending
on the mushroom species. As a result of adding various amino acids to the mycelial culture medium, methionine (Met) was shown
to be the most effective additive. The most preferable condition of the additive was the combination of 4 mM Met and 1 g/l
of yeast extract, and the maximum ERG production reached approximately 1.7 mg/l, which corresponds to 2.4 times (0.7 mg/l)
that in the basal medium without Met. Although the supplementation of Met enhanced the ERG production, the mycelial growth
was significantly inhibited. Furthermore, the analysis of amino acids in the culture medium revealed that the Met additive
reduced the consumption rates of most amino acids tested, probably due to the decrease in mycelial growth. Taking these results
into consideration, we suggest that the addition of Met to the mycelial culture medium is an efficient way to enhance the
ERG production in economically important mushroom species. 相似文献
85.
Amaury Cazenave-Gassiot Robert Boughtflower Jeffrey Caldwell Laure Hitzel Claire Holyoak Stephen Lane Paul Oakley Frank Pullen Stefan Richardson G. John Langley 《Journal of chromatography. A》2009,1216(36):6441-6450
The effects of increasing concentrations of ammonium acetate additive in supercritical fluid chromatography were studied on silica, 2-ethyl-pyridine and endcapped 2-ethyl-pyridine stationary phases. The study involved the addition of increasing concentrations of the ammonium acetate either in the mobile phase modifier (methanol) or in the sample solvent. The effects of ammonium acetate on retention and peak shape of the analytes were evaluated. Compounds that exhibited satisfactory chromatographic behaviour in the absence of the additive were virtually unaffected by its presence in the mobile phase or sample solvent. Nevertheless, compounds that exhibited late elution and strongly tailing peak shapes when pure methanol was used showed dramatically improved chromatographic behaviour in the presence of the additive. Shorter retention was observed not only when the modifier was introduced in the mobile phase but also when it was in the sample solvent. 相似文献
86.
Dr. D. Pukazhselvan Karakkadparambil Sankaran Sandhya Devaraj Ramasamy Aliaksandr Shaula Duncan Paul Fagg 《Chemphyschem》2020,21(11):1195-1201
The current work explores the in-situ formation of TiH2 additive in a Ti/MgH2 nanocomposite system. Mild mechanical milling leaves Ti chemically unchanged, while formation of stable TiH2–x occurs upon strong mechanical milling. TiH2–x further transforms to TiH2 upon recycling the powder (dehydrogenation and subsequent hydrogenation) and lowers the activation energy of MgH2 to 89.4 kJ (mol H2)−1 [Ea of as-received MgH2 is 153 kJ (mol H2)−1]. This work also reiterates that metallic Ti additive mixed MgH2 requires strong mechanical milling for better H2 ab/de-sorption performance. The current observations support the view that lattice strain may be an important factor in the catalysis of additives incorporated MgH2 hydrogen storage systems. 相似文献
87.
88.
Nishi K. Bhardwaj Sanjay Kumar Pramod K. Bajpai 《Colloids and surfaces. A, Physicochemical and engineering aspects》2005,260(1-3):245-250
The experiments have been carried out in the laboratory to investigate the interactions among negatively charged fibres, fines and positively charged polymer particles on two different papermaking slurries of old corrugated containers (OCC) pulp and mixed office waste (MOW) paper pulp. The effects of different wet-end chemicals such as polyacrylamide, polyamide amine and polyethylene amine on fibre surface chemistry have been followed by electrokinetic measurements (zeta potential) of papermaking stock to control the retention and drainage and see how well they perform in the wet-end of the paper machine. The flocculation behaviour has been investigated by different procedures: dewatering test and measuring the first pass retention. Treatment of pulps with chemical additives resulted in substantial improvement of drainage with increase in first pass retention. For OCC pulp, the best results were obtained with 0.5% polyacrylamide improving the drainage by 82% with corresponding first pass retention of 87.5% against 81.8% for the control pulp. However, for MOW pulp, the best results were obtained with 0.3% polyethylene amine improving the drainage by 63% with corresponding first pass retention of 86.0% against 74.2% for the control pulp. The studies on zeta potential of secondary fibres revealed the dependence of first pass retention and drainage on zeta potential of pulps. As the zeta potential approaches zero, the conditions approach optimum for first pass retention and drainage. This way, zeta potential control can lead to environmental protection and competitiveness by using secondary fibres more extensively. 相似文献
89.
火焰原子吸收法以其灵敏度高、选择性好等优点而广泛应用于各种基体中微量金属元素的测定 ,而不用于直接测定Cl- 。本文提出了采用火焰原子吸收法间接测定混凝土外加剂中微量Cl- 的方法 ,在待测液中加入过量的Ag 标液 ,通过测定与Cl- 定量反应后剩余的Ag 量从而换算出Cl- 的含量 ,本法进行了测定最佳酸度试验、精密度试验、在样品中加入Cl- 标准溶液回收试验 ,回收率为 96 %~ 10 4 %。经过实际样品测定 ,证明该方法具有样品预处理手续简单、测定周期短、干扰小等优点 ,最适合于测定基体较为复杂的混凝土外加剂中的微量Cl- 。称取样品 0 0 5~ 2g ,溶解后 ,用硝酸调节酸度 ,加入与之对应的Ag 标准溶液 ,放置 2h过滤后即可测定 ,所用仪器为澳大利亚GBC90 2型原子吸收光谱仪。 相似文献
90.
A nuclear magnetic resonance (NMR) methodology was assessed regarding the identification and quantification of additives in three types of polylactide (PLA) intended as food contact materials. Additives were identified using the LNE/NMR database which clusters NMR datasets on more than 130 substances authorized by European Regulation No. 10/2011. Of the 12 additives spiked in the three types of PLA pellets, 10 were rapidly identified by the database and correlated with spectral comparison. The levels of the 12 additives were estimated using quantitative NMR combined with graphical computation. A comparison with chromatographic methods tended to prove the sensitivity of NMR by demonstrating an analytical difference of less than 15%. Our results therefore demonstrated the efficiency of the proposed NMR methodology for rapid assessment of the composition of PLA. 相似文献