Novel technique to suppress hydrocarbon contamination for high accuracy determination of carbon content in steel by FE-EPMA

In multiphase steels, control of the carbon contents in the respective phases is the most important factor in alloy design for achieving high strength and high ductility. However, it is unusually difficult to determine the carbon contents in multiphase structures with high accuracy by electron probe microanalysis (EPMA) due to the unavoidable effect of hydrocarbon contamination during measurements. We have investigated new methods for suppressing hydrocarbon contamination during field emission (FE) EPMA measurements as well as a conventional liquid nitrogen trap. Plasma cleaner inside the specimen chamber results in a improvement of carbon-content determination by point analysis, increasing precision tenfold from the previous 0.1 mass%C to 0.01 mass%C. Stage heating at about 100 °C dramatically suppresses contamination growth during continuous point measurement and mapping. By the combination of above two techniques, we successfully visualized the two-dimensional carbon distribution in a dual-phase steel. It was also noted that the carbon concentrations at the ferrite/martensite interfaces were not the same across all interfaces, and local variation was observed. The developed technique is expected to be a powerful tool for understanding the mechanisms of mechanical properties and microstructural evolution, thereby contributing to the design of new steel products with superior properties.

Determination of Lewis and Brönsted acid sites by gas flow-injection technique

Gas flow-injection technique pyridine-FTIR was studied for determination of Lewis and Brönsted acid sites on the solid super acid catalysts. The system consists of stainless steel gas cell which can be heated up to 623 K, CaF2 windows, pyridine injection port and double liquid nitrogen trap for removal of moisture. Pure nitrogen gas and pyridine were used as a carrier and probe molecule. Pyridine was injected to the sysem at 423 K followed by flushing of N2 gas through double liquid nitrogen trap at 423 for 1 h and at 573 K for 30 min. All spectra were recorded at room temperature. This technique gave similar results to those of taken by vacuum system for HZSM-5, Pt/SO4 2--ZrO2, Al2O3 catalysts.

A New Automated Extraction System for 14C Measurement for Atmospheric Co2

The radiocarbon content of atmospheric CO2 (Δ14CO2) has long been of interest to atmospheric and Earth system researchers. Recent improvements in 14C measurement precision and reduction in sample size requirements have now made it possible to measure Δ14CO2 within existing trace gas sampling networks, most notably as a method to quantify recently added fossil-fuel-derived CO2 in the atmosphere. At INSTAAR, in collaboration with NOAA/ESRL, ∼600 atmospheric samples from around the globe are prepared each year, and that number is anticipated to grow in connection with various monitoring and data assimilation efforts. To accommodate the growing demand and reduce per sample costs, we developed an automated extraction system to quantitatively isolate CO2 from whole air for AMS 14C analysis. Twenty samples can be extracted in 1 fully automated run, taking 10–12 hr to complete and requiring only about 1 hr of operator time, a substantial improvement over the manual extraction system. CO2 is extracted cryogenically by flowing the whole air over a liquid nitrogen trap, after first removing water in a trap at –85 °C. Large volume vacuum lines are used to extract ∼30 μmol of CO2 in less than 10 min, keeping contamination from leaks to a minimum and allowing rapid processing and greater throughput. δ13C measurements on the resultant CO2 demonstrate that extraction is quantitative, and extractions of 14C-free air show that no significant modern contamination occurs. Replicate analyses of standard materials indicate that both mean values and precision are comparable to those for the manual extraction system.

Use Tungsten Shadowing to Study Biological Macromolecules

Shadowing is widely used for biological macromolecules and their complexes structure determination . It has been shown that tungsten shadowing produces fine granularity and good structural detail resolution. We have developed a working prototype of an electron beam evaporator (“electron gun“) based on the principle described by V. Vasiliev. The electron gun has characteristics that allow us to deposit high quality films of carbon or even pure tungsten. in addition we have constructed a prototype sample handling apparatus for freeze drying and shadowing. The prototype allows tilting of +/- 90° in 2° increments, rotation (if desired) at 6 rpm, controlled heating at a rate of 1-2° per min, and cooling using a liquid nitrogen trap attached to the device. The system is vacuumed by 480 1/sec maglev turbomolecular pump with scroll pump at the first stage. It produces oil-free vacuum in 2-5*10-7 torr range, which we believe, is sufficient for good quality shadowing.

An IR cell for vacuum and high temperature

Much interest has been shown in IR cells capable of maintaining one or more samples at constant temperature, constant water vapour or gas pressure, or under vacuum conditions (Farmer, 1974). This note describes a cell capable of maintaining a vacuum between 10-3 torr and 10-4 tort from room temperature to 1000°C whilst the spectrum is being recorded; such cells have been constructed previously but for less severe conditions.The cell and associated vacuum system are shown schematically in Fig. 1. The vacuum in the cell body is produced by an Edwards rotary pump and a normal mercury diffusion pump. To obtain a vacuum of 10-3 to 10-4 torr, a liquid nitrogen trap and foreline trap are used. The trap is filled with activated alumina. The O-ring seals in the cell are made of Viton. The constant vacuum control is obtained with Pirani and Penning gauges.