Investigation on etching selectivity and microstructure of Ag doped Sb2Te thin film for dry lithography

Dry lithography is a promising micro/nanomanufacturing method owing to its advantages of solution-free, absence of undercut and resist swelling. However, heat-mode resist suitable for dry lithography is less reported. This work reported Ag doped Sb2Te thin film as heat-mode resist, and its etching selectivity and microstructures are investigated in detail. It is found that Ag1.44Sb2.19Te thin film possesses high etching selectivity in CHF3/O2 mixed gases and can act as a heat-mode resist. In order to elucidate the mechanism of high etching selectivity, the microstructures of the Ag doped Sb2Te thin films are analyzed according to XRD, Raman spectra, XPS, and TEM methods. Results implies that the etching selectivity is attributed to the phase separation of Ag1.44Sb2.19Te film and formation of Sb phase after laser exposure, leading to the reduction of etching resistance in CHF3/O2 mixed gases. Besides, the pattern transfers from Ag1.44Sb2.19Te to SiO2 and Si substrates are achieved successfully and the etching selectivity of Si or SiO2 to Ag1.44Sb2.19Te are both higher than 2:1. This work may provide a useful guide for the research of dry lithography without wet development.

Effect of Hydrogen in Mixed Gases on the Mechanical Properties of Steels—Theoretical Background and Review of Test Results

This review summarizes the thermodynamics of hydrogen (H2) in mixed gases of nitrogen (N2), methane (CH4) and natural gas, with a special focus on hydrogen fugacity. A compilation and interpretation of literature results for mechanical properties of steels as a function of hydrogen fugacity implies that test results obtained in gas mixtures and in pure hydrogen, both at the same fugacity, are equivalent. However, this needs to be verified experimentally. Among the test methods reviewed here, fatigue crack growth testing is the most sensitive method to measure hydrogen effects in pipeline steels followed by fracture toughness testing and tensile testing.

An Analytical Method for Gas Flow Measurement Using Conservative Chemical Elements

Mass flow meters (MFMs) are widely used to secure reliable flow rates based on the mass value of the gas being measured. However, chemical reactions produce various kinds of gases, and their composition also changes in real time. Thus, there may be a large deviation in the gas flow if the gases’ composition and its mixing ratio are not known. In this study, we derived a gas flow rate measurement method using a chemically stable chemical specie and verified the precision of the proposed method through comparative analysis with an MFM. The flow rate by this method showed reliable results in both single and mixed gases. Notably, the results were within ±2.74% of the injected flowrate values in the gas mixtures. This method is expected to be able to fundamentally overcome the limitations of the mechanical flowmeter because it is not affected by changes in gas composition or mixing ratio during the reaction.

Spectroscopic Identification on CO2 Separation from CH4 + CO2 Gas Mixtures Using Hydroquinone Clathrate Formation

The formation of hydroquinone (HQ) clathrate and the guest behaviors of binary (CH4 + CO2) gas mixtures were investigated by focusing on an application to separate CO2 from landfill gases. Spectroscopic measurements show that at two experimental pressures of 20 and 40 bar, CO2 molecules are preferentially captured in HQ clathrates regardless of the gas composition. In addition, preferential occupation by CO2 is observed more significantly when the formation pressure and the CH4 concentration are lower. Because the preferential occupation of CO2 is found with binary (CH4 + CO2) gas mixtures regardless of the composition of the feed gas, a clathrate-based process can be applied to CO2 separation or concentration from landfill gases or (CH4 + CO2) mixed gases.

A Molecular Simulation Study of Silica/Polysulfone Mixed Matrix Membrane for Mixed Gas Separation

Polysulfone-based mixed matrix membranes (MMMs) incorporated with silica nanoparticles are a new generation material under ongoing research and development for gas separation. However, the attributes of a better-performing MMM cannot be precisely studied under experimental conditions. Thus, it requires an atomistic scale study to elucidate the separation performance of silica/polysulfone MMMs. As most of the research work and empirical models for gas transport properties have been limited to pure gas, a computational framework for molecular simulation is required to study the mixed gas transport properties in silica/polysulfone MMMs to reflect real membrane separation. In this work, Monte Carlo (MC) and molecular dynamics (MD) simulations were employed to study the solubility and diffusivity of CO2/CH4 with varying gas concentrations (i.e., 30% CO2/CH4, 50% CO2/CH4, and 70% CO2/CH4) and silica content (i.e., 15–30 wt.%). The accuracy of the simulated structures was validated with published literature, followed by the study of the gas transport properties at 308.15 K and 1 atm. Simulation results concluded an increase in the free volume with an increasing weight percentage of silica. It was also found that pure gas consistently exhibited higher gas transport properties when compared to mixed gas conditions. The results also showed a competitive gas transport performance for mixed gases, which is more apparent when CO2 increases. In this context, an increment in the permeation was observed for mixed gas with increasing gas concentrations (i.e., 70% CO2/CH4 > 50% CO2/CH4 > 30% CO2/CH4). The diffusivity, solubility, and permeability of the mixed gases were consistently increasing until 25 wt.%, followed by a decrease for 30 wt.% of silica. An empirical model based on a parallel resistance approach was developed by incorporating mathematical formulations for solubility and permeability. The model results were compared with simulation results to quantify the effect of mixed gas transport, which showed an 18% and 15% percentage error for the permeability and solubility, respectively, in comparison to the simulation data. This study provides a basis for future understanding of MMMs using molecular simulations and modeling techniques for mixed gas conditions that demonstrate real membrane separation.

Mixed and single gas permeation performance analysis of amino-modified ZIF based mixed matrix membrane

Dense and translucent CA/PEG 1000/ZIF membranes were synthesized in acetone, utilizing solution casting. Membrane characterization was carried out using FT-IR, SEM and tensile testing. SEM proved presence of dense membranes and increase in the filler amount may have formed voids, raising the permeability of both gases. Single and mixed gas (CO2/CH4) permeation testing showed an increased permeability, on addition of more filler, which is probably due to formation of nano-gaps. A maximum selectivity of 39.49 and 34.86 for single and mixed gases respectively, and maximum permeabilities of 49.7685 and 1.41 barrers were observed. Tensile testing showed that strength peaked then decreased on increased loading, due to agglomeration on adding more ZIF, which introduced defects in structure. To conclude, selectivity of higher loaded membranes is favourable whereas tensile strength of lower loaded membrane is superior, but we have a trade-off between selectivity and tensile strength, so a higher-loaded membrane is most suitable. [Formula: see text]