Bericht über die 4. Tagung Steine und Erden in Aachen 29. und 30.4.54

Ohne ZusammenfassungDie Vorträge sollen ausführlich in den Fachzeitschriften: Tonindustriezeitung undZement, Kalk, Gips erscheinen.     

Vierte Schwebstofftechnische Arbeitstagung in Mainz am 29. und 30. September 1955

Ohne Zusammenfassung     

A new parameter to control heat transport in nanofluids: surface charge state of the particle in suspension

Although various conjectures have been proposed to explain the abnormal increase in thermal conductivity of nanofluids, the detailed mechanism has not been fully understood and explained. The main reason is due to the lack of knowledge of the most fundamental factor governing the mechanisms such as Brownian motion, liquid layering, phonon transport, surface chemical effects, and agglomeration. Applying a surface complexation model for the measurement data of hydrodynamic size, zeta potential, and thermal conductivity, we have shown that surface charge states are mainly responsible for the increase in the present condition and may be the factor incorporating all the mechanisms as well.     

Differences in the catalyst removal from single- and double-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapor deposition method showed partially incorporated metal catalysts inside the graphene walls. In order to remove the metal catalysts, acid and thermal treatments were successively carried out. The methods for effective catalyst removal in SWCNTs and DWCNTs were examined by means of thermogravimetric analysis, electron microscopy, and electron paramagnetic resonance. The DWCNTs showed distinctly different metal catalyst removal behavior from that of SWCNTs due to the double-wall structure. The acid treatment is less efficient for catalyst removal from DWCNTs, while catalysts in SWCNTs are effectively removed by acid treatment. Additional thermal treatment is quite effective to remove metal catalysts from DWCNTs.     

Effect of LiNi1/2Mn1/2O2 coating on the electrochemical performance of Li–Mn spinel

Lithium nickel manganese oxide (LiNi_1/2Mn_1/2O₂) was coated on spinel lithium manganese oxide (LiMn₂O₄) by a sol–gel process in an attempt to improve the high temperature cycling performance. The ratio of the coating sol to LiMn₂O₄ was adjusted to determine the relationship between the coating thickness and electrochemical performance. The crystal structure and morphology of the samples were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The charge and discharge characteristics, including cyclability and electrochemical properties of the bare and the coated LiMn₂O₄, were measured and compared. The results showed that a LiNi_1/2Mn_1/2O₂ coating on LiMn₂O₄ improves the rate capability at room temperature, and the cyclability at high temperatures.     

Ueber den Nachweis und die Bestimmung des Arsens

Ohne Zusammenfassung