Vladimir Sleptsov

Water permeability of poly(ethylene) terephthalate track membranes modified in plasma

Abstract The properties of poly(ethylene) terephthalate track membranes (PET TM) subjected to effect of plasma of the RF-discharge in air have been investigated. The influence of conditions of a plasma treatment on the surface properties and hydrodynamic characteristics of the membranes has been studied. It has been found that the effect of the air plasma on the membranes studied results in a formation of asymmetric track membranes with a higher flow rate; the structure and chemical composition of their superficial layer are changed. It was shown that the presence of the modified layer on the membrane surface caused changing in their hydrodynamic characteristics — the water permeability of the membranes, processed in plasma, in a greater degree depends upon pH of a filtered solution.

Production of asymmetric track membranes by gas-discharge method

An investigation of the structure and surface of poly(ethylene) terephthalate (PET) track membranes (TM) treated with a plasma RF-discharge in non-polymerizing gases has been performed. It was arranged that the effect of non-polymerizing gas plasma on the TM results in etching a surface layer of the membranes. The membrane pore size and the shape change in this case. It is shown that it is possible to change the structure of track membranes directly by gas-discharge etching. Depending on the choice of discharge parameters, it is possible to achieve etching conditions either in part of the channel or along the whole length of the pore channels. In both cases membranes with asymmetric pores are formed, which possess a higher porosity and flow rate.

Production of asymmetric track membranes with a high permeability and separation selectivity

Abstract An investigation of the structure and surface properties of poly(ethylene) terephthalate track membranes (PET TM) with a changed pore profile subjected to the plasma RF-discharge is performed. It was arranged that effect of the non-polymerizing gas plasma on the membranes of researched sample leads to formation of asymmetric membranes possessing a higher flow rate. Choice of optimal discharge parameters allows one to etch the membrane in its layer. In this case in the membrane layer not affected by plasma, the mean pore diameter remains at its initial level. Preserving the initial (nominal) pore diameter allows one to perform the filtration processes with no decrease of separation selectivity. It is shown that the introducing of the polymerizing gas, cyclohexane, into the composition of plasma-forming gas provides improved hydrodynamic properties of asymmetric membranes.

LED-based NDIR natural gas analyzer

A new generation of the light-emitting diodes (LEDs) and photodiodes (PDs) was used recently to develop an open path non-dispersive infrared (NDIR) methane analyzer. The first open path detector prototype was constructed using LEDs for measurement and reference channels, accordingly, and first measurements for methane gas have been performed using optical paths of the order of several meters [3]. The natural gas consists of several first alkanes, mainly methane, and it is important to have a possibility of measuring all of them. In the present work we report the results of NDIR measurements for propane-butane mixture and new measurements of methane using LEDs for measurement and reference channels at 2300 and 1700 nm wavelengths, accordingly. The necessity of the double beam scheme is demonstrated and obtained results for methane and propane-butane mixture are compared.

Design of smart dust sensor node for combustible gas leakage monitoring

In this work we present the results of design of smart dust sensor platform for combustible gas leakage monitoring. During the design process we took into account a lot of combustible gas sensor specific problems such as their huge power consumption, the necessity to work in explosive environment and sensor parameters degradation. To decrease power consumption we designed specific energy efficient algorithms for measurements. The resulting average power consumption of the node is low enough for one year autonomous lifetime. The methods and algorithms which was designed are very promissing for catalytic combustible gas sensors.

Plasma-chemical modification of the structure and properties of poly(ethylene terephthalate) track membranes

A process of extraction of the low-molecular products of the synthesis from the poly(ethylene terephthalate) track membranes modified by plasma has been investigated. It is shown that the deposition of a thin polymeric hydrocarbon film by cyclohexane plasma on the membrane surface with preliminary treatment in a plasma of non-polymerizing gases, for example oxygen, allows one to produce membranes possessing a high productivity. Their advantages are much better hydrodynamic properties and a small amount of the low-molecular products of the synthesis extracted by organic solvents.

Multicomponent hydrocarbons monitoring by infrared LED arrays

The use of new infrared LED arrays for NDIR multicomponent gas analysis is considered. Model spectra for bi component gas mixtures are simulated and the concentration reconstruction method is discussed.

Modification of Poly(Ethylene Terephthalate) Track Membrane Properties by Plasma Chemical Method

Properties of poly(ethylene terephthalate) track membrane (PET TM) exposed to an allyl alcohol radiofrequency plasma after pre-activation its surface in an oxygen plasma were studied. The influence of plasma treatment conditions on basic membrane characteristics, i.e. pore size and shape, wettability, and water permeability, was studied. It has been shown that the plasma treatment of membrane can significantly improve its performance characteristics.

A Multisource Energy Harvesting Platform for Wireless Methane Sensor

Sensors used for detecting combustible gases consume significant amounts of power. Energy management for these sensors can become an important issue when they are used as part of a wireless sensor network. This is because of the fact that wireless sensors are usually powered by batteries. Batteries have a finite lifetime and their replacement can take a considerable amount of time in a gas monitoring application where thousands of sensor nodes are deployed to measure the concentration of flammable gases. Moreover, the battery replacement procedure can turn into a more complicated task if the gas monitoring network is located in a harsh environment. Energy harvesting is a method which can increase the operation time of wireless gas sensor networks. In this article, we present a multisource harvesting circuit for a wireless gas sensor node. As for ambient sources, we have chosen solar and wind energy. Energy from ambient sources is stored in supercapacitors which have a capacity of 400 F. We prove that a catalytic gas sensor can operate for 2 days without batteries by using the developed scheme.

X-ray study of silicon distortion on deposition of diamond-like films

Abstract Diamond films are of special interest for passivation, because of their chemical stability and electric characteristics. However, the problem of about crystal surface distortion on film deposition is crucial for microelectronics applications. An X-ray study of radiation defects created in the silicon subsurface region during ion plasma etching and covering the crystal with diamond-like carbon films has been carried out. The distorted layer thickness (several nanometres) has been determined to be close to the ion penetration depth and the main radiation defects near the crystal surface turn out to be interstitial like. It has been found that the silicon crystal surface under the diamond-like film, deposited by magnetron sputtering of graphite in argon at the optimal bias voltage equal to -100 V, is very smooth on an atomic scale (the damaged layer thickness was equal to 3.7 A).