scholarly journals Measurements of delays of gas-phase compounds in a wide variety of tubing materials due to gas–wall interactions

2019 ◽  
Vol 12 (6) ◽  
pp. 3453-3461 ◽  
Author(s):  
Benjamin L. Deming ◽  
Demetrios Pagonis ◽  
Xiaoxi Liu ◽  
Douglas A. Day ◽  
Ranajit Talukdar ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Gas Phase ◽  
Atmospheric Measurements ◽  
Particle Sampling ◽  
Coated Metal ◽  
Different Types ◽  
Gas Surface Interactions ◽  
Teflon Tubing ◽  
Compound Concentration ◽  
Partitioning Behavior

Abstract. Losses of gas-phase compounds or delays on their transfer through tubing are important for atmospheric measurements and also provide a method to characterize and quantify gas–surface interactions. Here we expand recent results by comparing different types of Teflon and other polymer tubing, as well as glass, uncoated and coated stainless steel and aluminum, and other tubing materials by measuring the response to step increases and decreases in organic compound concentrations. All polymeric tubings showed absorptive partitioning behavior with no dependence on humidity or concentration, with PFA Teflon tubing performing best in our tests. Glass and uncoated and coated metal tubing showed very different phenomenology due to adsorptive partitioning to a finite number of surface sites. Strong dependencies on compound concentration, mixture composition, functional groups, humidity, and memory effects were observed for glass and uncoated and coated metals, which (except for Silonite-coated stainless steel) also always caused longer delays than Teflon for the compounds and concentrations tested. Delays for glass and uncoated and coated metal tubing were exacerbated at low relative humidity but reduced for RH >20 %. We find that conductive PFA and Silonite tubing perform best among the materials tested for gas-plus-particle sampling lines, combining reduced gas-phase delays with good particle transmission.

scholarly journals Measurements of Delays of Gas-Phase Compounds in a Wide Variety of Tubing Materials due to Gas-Wall Interactions

2019 ◽  
Author(s):  
Benjamin Deming ◽  
Demetrios Pagonis ◽  
Xiaoxi Liu ◽  
Douglas Day ◽  
Ranajit Talukdar ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Gas Phase ◽  
Surface Interactions ◽  
Atmospheric Measurements ◽  
Particle Sampling ◽  
Coated Metal ◽  
Different Types ◽  
Gas Surface Interactions ◽  
Teflon Tubing ◽  
Compound Concentration

Abstract. Losses of gas-phase compounds or delays on their transfer through tubing are important for atmospheric measurements and also provide a method to characterize and quantify gas-surface interactions. Here we expand recent results by comparing different types of Teflon and other polymer tubing, as well as glass, uncoated and coated stainless steel and aluminium, and other tubing materials by measuring the response to step increases and decreases in organic compound concentrations. All polymeric tubings showed absorptive partitioning behaviour with no dependence on humidity or concentration, with PFA Teflon tubing performing best in our tests. Glass and uncoated and coated metal tubing showed very different phenomenology due to adsorptive partitioning to a finite number of surface sites. Strong dependencies on compound concentration, mixture composition, functional groups, humidity, and memory effects were observed for glass and uncoated and coated metals, which (except for Silonite-coated stainless steel) also always caused longer delays than Teflon for the compounds and concentrations tested. Delays for glass and uncoated and coated metal tubing were exacerbated at low relative humidity but reduced for RH > 20 %. We find that conductive PFA and Silonite tubing perform best among the materials tested for gas plus particle sampling lines, combining reduced gas-phase delays with good particle transmission.

scholarly journals Effects of gas–wall interactions on measurements of semivolatile compounds and small polar molecules

2019 ◽  
Vol 12 (6) ◽  
pp. 3137-3149 ◽  
Author(s):  
Xiaoxi Liu ◽  
Benjamin Deming ◽  
Demetrios Pagonis ◽  
Douglas A. Day ◽  
Brett B. Palm ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Transmission Efficiency ◽  
Polar Molecules ◽  
Ionization Mass ◽  
Atmospheric Measurements ◽  
Wide Range ◽  
Teflon Tubing ◽  
Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multifunctional, semivolatile, and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C∗) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C∗, ranging from seconds to tens of minutes, except for the NO3- CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C∗ decreases, from less than a minute to >100 min. The delays caused by Teflon tubing vs. C∗ can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry's law constants instead of their C∗, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface–gas interactions.

scholarly journals 14C release from irradiated stainless steel

Radiocarbon ◽  
2018 ◽  
Vol 60 (6) ◽  
pp. 1671-1681 ◽  
Author(s):  
Eva de Visser-Týnová ◽  
Stephen W Swanton ◽  
Stephen J Williams ◽  
Marcel P Stijkel ◽  
Alison J Walker ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Radioactive Waste ◽  
Gas Phase ◽  
Near Field ◽  
Considerable Uncertainty ◽  
Dissolved Carbon ◽  
Carbon 14 ◽  
Fast Release ◽  
Potential Issue ◽  
Made In

ABSTRACTRadiocarbon (14C or carbon-14, half-life 5730 yr) is a key radionuclide in the assessment of the safety of a geological disposal facility (GDF) for radioactive waste. In particular, the radiological impact of gaseous carbon-14 bearing species has been recognized as a potential issue. Irradiated steels are one of the main sources of carbon-14 in the United Kingdom’s radioactive waste inventory. However, there is considerable uncertainty about the chemical form(s) in which the carbon-14 will be released. The objective of the work was to measure the rate and speciation of carbon-14 release from irradiated 316L(N) stainless steel on leaching under high-pH anoxic conditions, representative of a cement-based near field for low-heat generating wastes. Periodic measurements of carbon-14 releases to both the gas phase and to solution were made in duplicate experiments over a period of up to 417 days. An initial fast release of carbon-14 from the surface of the steel is observed during the first week of leaching, followed by a drop in the rate of release at longer times. Carbon-14 is released primarily to the solution phase with differing fractions released to the gas phase in the two experiments: about 1% of the total release in one and 6% in the other. The predominant dissolved carbon-14 releases are in inorganic form (as 14C-carbonate) but also include organic species. The predominant gas-phase species are hydrocarbons with a smaller fraction of 14CO (which may include some volatile oxygen-containing carbon-species). The experiments are continuing, with final sampling and termination planned after leaching for a total of two years.

Friction Coefficient and Wear Rate of Different Materials Sliding Against Stainless Steel

2013 ◽  
Vol 1 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Dewan Muhammad Nuruzzaman ◽  
Mohammad Asaduzzaman Chowdhury
Keyword(s):  
Stainless Steel ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Normal Load ◽  
304 Stainless Steel ◽  
Sliding Velocity ◽  
Stainless Steel 304 ◽  
Different Types ◽  
Pin On Disc ◽  
Ss 304

This paper examines the relation between friction/wear and different types of steel materials under different normal loads and sliding velocities and to explore the possibility of adding controlled normal load and sliding velocity to a mechanical process. In order to do so, a pin on disc apparatus is designed and fabricated. Experiments are carried out when different types of disc materials such as stainless steel 304 (SS 304), stainless steel 316 (SS 316) and mild steel slide against stainless steel 304 (SS 304) pin. Variations of friction coefficient with the duration of rubbing at different normal loads and sliding velocities are investigated. Results show that friction coefficient varies with duration of rubbing, normal load and sliding velocity. In general, friction coefficient increases for a certain duration of rubbing and after that it remains constant for the rest of the experimental time. The obtained results reveal that friction coefficient decreases with the increase in normal load for all the tested materials. It is also found that friction coefficient increases with the increase in sliding velocity for all the materials investigated. Moreover, wear rate increases with the increase in normal load and sliding velocity. At identical operating condition, the magnitudes of friction coefficient and wear rate are different for different materials depending on sliding velocity and normal load.

Solid C60 – How we Found It

1990 ◽  
Vol 206 ◽  
Author(s):  
Donald R. Huffman ◽  
Wolfgang Krätschmer
Keyword(s):  
Gas Phase ◽  
Mass Spectra ◽  
Scanning Tunneling ◽  
Spectral Features ◽  
Small Particles ◽  
Tunneling Microscopy ◽  
X Ray ◽  
Different Types ◽  
Interstellar Material ◽  
The Moment

ABSTRACTIn May of 1990, crystals of a new form of carbon were observed crystallizing from a solution of the newly-produced macroscopic quantities of fullerene molecules. This discovery followed many years of work we had done in producing and measuring the optical properties of small particles of graphitic carbon, a work which was aimed, in part, at a better understanding of the various spectral features of interstellar material. Among three distinctly different types of carbon particulates, distinguished by their differing ultraviolet and Raman spectra, was one that later proved to contain macroscopic quantities of C60 and C70. Evidence for fullerenes came from mass spectra, infrared spectra, and X-ray and electron diffraction. More, recent experiments with our collaborators have included scanning tunneling microscopy and gas phase emission spectroscopy in the infrared. At the moment, there is no obvious connection with interstellar spectral features.

scholarly journals Adhesion of Streptococcus mutans to Different Types of Brackets

2007 ◽  
Vol 77 (6) ◽  
pp. 1090-1095 ◽  
Author(s):  
William Papaioannou ◽  
Sotiria Gizani ◽  
Maria Nassika ◽  
Efterpi Kontou ◽  
Melachrini Nakou
Keyword(s):  
Stainless Steel ◽  
Streptococcus Mutans ◽  
Bacterial Species ◽  
Culture Technique ◽  
Orthodontic Brackets ◽  
Clinical Strain ◽  
Microbial Culture ◽  
Salivary Pellicle ◽  
Different Types ◽  
The Difference

Abstract Objective: To examine the difference in the adhesion of Streptococcus mutans to three different types of orthodontic brackets and the effect of the presence of an early salivary pellicle and Streptococcus sanguis on adhesion. Materials and Methods: Three adhesion experiments were performed using stainless steel, ceramic, and plastic orthodontic brackets. In the first experiment a clinical strain of S mutans adhered to the three different types of brackets (n = 6 for each). For the second, the brackets were treated with saliva before adhesion of S mutans (n = 6 per type of bracket). Finally, the third experiment concerned saliva coated brackets (n = 6 per type of bracket), but before S mutans, S sanguis bacteria were allowed to adhere. The bacteria were always allowed to adhere for 90 minutes in all the experiments. Adhesion was quantitated by a microbial culture technique by treating the brackets with adhering bacteria with trypsin and enumerating the total viable counts of bacteria recovered after cultivation. Results: There were consistently no differences in the adherence to stainless steel, ceramic, or plastic brackets. The presence of an early salivary pellicle and S sanguis reduced the number of adhering S mutans to all three types of brackets. Conclusions: Adhesion of bacteria to orthodontic brackets depends on several factors. The presence of a salivary pellicle and other bacterial species seem to have a significant effect on the adhesion of S mutans, reducing their numbers and further limiting any differences between types of brackets.

scholarly journals Corrosion Resistance of TIG Welded Joints of Stainless Steels

2017 ◽  
Vol 885 ◽  
pp. 190-195 ◽  
Author(s):  
Amanda Silveira Alcantara ◽  
Enikő Réka Fábián ◽  
Monika Furkó ◽  
Éva Fazakas ◽  
János Dobránszky ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Ferric Chloride ◽  
Stainless Steels ◽  
Welded Joints ◽  
Welding Process ◽  
Inert Gas ◽  
Tungsten Inert Gas Welding ◽  
Type Stainless Steel ◽  
Different Types

The aim of this work was to analyze the performance of joints made by TIG (Tungsten Inert Gas) welding process in austenitic and duplex stainless steels with special regards to their corrosion resistance. Three different types of stainless steel were butt welded with TIG method. Ferric-chloride test and electrochemical treatments revealed how does the TIG process affects the corrosion resistance depending upon the alloy used for welding the joint. This work focuses on the weldability of the 2304, 2404 and 304 type stainless steel heterogeneous welds.

Simple, Accurate Method for Evaluating the Amount of Fat and Protein Residue on a Food Contact Surface1,2

1984 ◽  
Vol 47 (10) ◽  
pp. 762-764
Author(s):  
H. E. HUFF ◽  
M. E. ANDERSON ◽  
R. T. MARSHALL
Keyword(s):  
Stainless Steel ◽  
Recovery Rate ◽  
Gravimetric Method ◽  
Accurate Method ◽  
Food Grade ◽  
Food Contact ◽  
Food Contact Surfaces ◽  
Different Types ◽  
Contact Surfaces ◽  
Pork Fat

The objective of this research was to evaluate a method for quantitatively removing pork fat and blood plasma from different food contact surfaces - glass, stainless steel, plastic and food grade belting. Two studies were conducted. In the first study, a mass balance procedure was used to determine whether the developed method could remove virtually all the fat or protein placed on stainless steel and glass. In the second study, a gravimetric method was used to verify that the amount of fat on test strips could be harvested and quantified as residue. A recovery rate of from 98% or 100% was achieved for the different types of food contact surfaces.

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