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Traditional methods of synthesis of metal-oxide gas sensing materials for semiconductor sensors are based on wet sol-gel processes. However, these processes lead to the formation of hydroxyl groups on the surface of oxide particles being responsible for the strong response of a sensing material to humidity. In this work, we investigated the possibility to synthesize metal-oxide materials with reduced sensitivity to water vapors. Dry synthesis of SnO2 nanoparticles was implemented in the gas phase by spark discharge, which allowed us to produce powder with specific surface area of about 40 m2/g after additional annealing at 610 °C. The drop of sensor resistance does not exceed 20%, when air humidity increases from 40 to 100%, whereas the response to 100 ppm of hydrogen is of a factor of 8 with very short response time of about 1 s.

This chapter proposes the interpretation of the concept of “power supply system efficiency” and a mathematical model that focuses on minimization of electricity supply expenses while observing the time criteria. The research examines the constituents of the specified time criteria, the calculations of power outage time, and the time of power supply restoration. In addition, this chapter describes the constituents of implementation time for a technological connection of rural consumers to electric networks and the statistical data on the time of inconsistency between power quality and regulatory requirements. Furthermore, this chapter investigates the applying possibility of the proposed mathematical model for the development of measures that can improve power supply system efficiency. In order to improve electricity supply reliability of rural consumers, the technical condition monitoring of power lines and electrical network automation is carried out.

During the topology creation by the selective laser sintering method experimental samples of microheater based on ruthenium dioxide micro-powder were made. The resulting structures were used as microheaters to measure changes in the thermal conductivity of gases. A power comparison of standard platinum spiral element widely used in catalytic thermal sensors and microheater produced by the new technology showed the advantage of the latter.

In this paper, a method of producing the metallization on the alumina ceramic substrate by micropowders of ruthenium dioxide sintering using laser radiation with 10.6 micrometers length (carbon dioxide laser) is described. During the work parameters of the mask, allowing to reduce the width of the laser spot as well as to get a mildly sloping profile of the radiation intensity, due to which more uniform sintering of the powders and pastes based on them takes place, are calculated.

We present a novel approach to the fabrication of MEMS devices, which can be used for gas sensors operating in harsh environment in wireless and autonomous information systems. MEMS platforms based on ZrO 2 /Y 2 O 3 (YSZ) are applied in these devices. The methods of ceramic MEMS devices fabrication with laser micromachining are considered. It is shown that the application of YSZ membranes permits a decrease in MEMS power consumption at 450 0 C down to ∼75 mW at continuous heating and down to ∼ 1 mW at pulse heating mode. The application of the platforms is not restricted by gas sensors: they can be used for fast thermometers, bolometric matrices, flowmeteres and other MEMS devices working under harsh environmental conditions.

The layout of experimental samples of microhotplate based on nanocomposite material consisting of ruthenium dioxide and borosilicate glass binder were formed by selective laser sintering method. The resulting structures were used as microhotplate to measure changes in thermal conductivity of gases. The comparison of power consumption of standard platinum wire coil element widely used in thermocatalytic (calorimetric) sensors and microhotplate produced by the new technology showed strong advantage of the latter one.

In this paper, we describe a novel cost-effective and simple technology for the production glass MEMS applied as microhotpalte platform for metal oxide gas sensors. The basis of the technology is magnetron sputtering of platinum heating layer followed by precise laser engraving and cutting used for heater patterning. As a result of the technology, we demonstrate the glass microhotplate cantilever with thickness of 30 μm equipped with platinum microheater with dimension of about 500×500 μm. The cantilever type MEMS microhotplate demonstrate very high stability at working temperatures up to 600 0C, which gives possibility to use it for the low-scale fabrication microhotplate of metal oxide gas sensors.

In this work we present the results on the application of additive technology that is aerosol and ink jet technique for the fabrication of high-temperature metal oxide gas sensors. The application of thin (12 μm) alumina membrane, aerosol jet printing of Pt microheater (line width 40–60 μm), printed sensing layer made of nanocristalline tin dioxide based material, laser cutting of the membrane enabled the fabrication of full-printed cantilever-shaped high-temperature sensor with optimal power consumption (~80 mW at 450 °C) applicable in wireless instruments for the detection of combustible and toxic gases including methane.

The application of thin LTCC is a very interesting and promising approach to the fabrication of ceramic MEMS gas sensors. The attempts to use this material were restricted till now by the thickness of commercial material (>50 μm). In this work, we found a possibility to fabricate thin LTCC membranes (20–30 μm) stretched on a frame made of 100 μm thick LTCC. Aerosol jet printed Pt microheater and laser cutting of the membrane gave a cantilever shaped microhotplate with hot spot of about 300 × 300 μm. Power consumption of the heater is ~150 mW at 450 °C.

The analysis of exhaled breath is drawing a high degree of interest in the diagnostics of various diseases, including lung cancer. Electronic nose (E-nose) technology is one of the perspective approaches in the field due to its relative simplicity and cost efficiency. The use of an E-nose together with pattern recognition algorithms allow 'breath-prints' to be discriminated. The aim of this study was to develop an efficient online E-nose-based lung cancer diagnostic method via exhaled breath analysis with the use of some statistical classification methods. A developed multisensory system consisting of six metal oxide chemoresistance gas sensors was employed in three temperature regimes. This study involved 118 individuals: 65 in the lung cancer group (cytologically verified) and 53 in the healthy control group. The exhaled breath samples of the volunteers were analysed using the developed E-nose system. The dataset obtained, consisting of the sensor responses, was pre-processed and split into training (70%) and test (30%) subsets. The training data was used to fit the classification models; the test data was used for the estimation of prediction possibility. Logistic regression was found to be an adequate data-processing approach. The performance of the developed method was promising for the screening purposes (sensitivity-95.0%, specificity-100.0%, accuracy-97.2%). This shows the applicability of the gas-sensitive sensor array for the exhaled breath diagnostics. Metal oxide sensors are highly sensitive, low-cost and stable, and their poor sensitivity can be enhanced by integrating them with machine learning algorithms, as can be seen in this study. All experiments were carried out with the permission of the N.N. Petrov Research Institute of Oncology ethics committee no. 15/83 dated March 15, 2017.

In this work, we demonstrated an open access Wi-Fi wireless system for environmental gas monitoring based on different types of gas sensors with SPI digital output. Digital sensors matrix consist of four sensors with especially developed data exchange protocol for digital intellectual sensors (DIS) giving possibility to work with any type of sensors. System architecture has also an advantage “hot swap” of sensors. Visualization of gas concentrations received from the matrix is possible through any web application available on any mobile device (laptop, smart phone, etc.).

The applicability of multisensor system based on a novel polymer nanocomposite material with parylene matrix including metal and/or semiconductive nanoparticles for the detection of low concentrations of ammonia gas, nitrogen dioxide, and hydrogen chloride is demonstrated. Nanocomposite films were synthesized by vacuum co-condensation method. It was shown that nanocomposite sensors demonstrate stable, fast, and reversible response at room temperature to target gases in ppm- and sub-ppm concentration ranges. Testing multisensor system using imitators of the odors of explosives (TNT) and drugs (heroin) showed the possibility of qualitative analysis of these odors as well.

We study dynamics of a nonlinear pendulum under a periodic force with small amplitude and slowly decreasing frequency. It is well known that when the frequency of the external force passes through the value of the frequency of the unperturbed pendulum's oscillations, the pendulum can be captured into the resonance. The captured pendulum oscillates in such a way that the resonance is preserved, and the amplitude of the oscillations accordingly grows. We consider this problem in the frames of a standard Hamiltonian approach to resonant phenomena in slow-fast Hamiltonian systems developed earlier, and evaluate the probability of capture into the resonance. If the system passes the resonance at small enough initial amplitudes of the pendulum, the capture occurs with necessity (so-called autoresonance). In general, the probability of capture varies between one and zero, depending on the initial amplitude. We demonstrate that a pendulum captured at small values of its amplitude escapes from the resonance in the domain of oscillations close to the separatrix of the pendulum, and evaluate the amplitude of the oscillations at the escape.

The target of this paper is answering the question about the minimum response time of metal oxide semiconductor gas sensors. This question is very important at the monitoring of sudden explosive emission of high concentrations of combustible gases in mines, chemical and oil refinery factories, nuclear power stations, etc. To reach this target, we eliminated the influence of internal and external diffusion to the sensor response time by the optimization of the thickness of sensing layer, deposition conditions, material, and working temperature of the sensor. As a result, it was possible to fabricate the sensor with very short response time ∼ 160 ms (hexane) in a concentration range up to 12 vol%. The response time of the sensor was compared with the response time of IR optic sensor based on LED (λ = 3.4 μm) using testing gas mixing installation equipped with ultra-fast valves. The effect of sensing layer thickness and the conditions necessary to exclude the influence of reagent and product diffusion through the sensing layer to the response time were studied in detail. It was shown that, if the thickness of thin film sensing layer exceeds 200 nm, the sensor response rate is diffusion limited, the diffusion coefficient corresponding to inter-grain diffusion at 550 °C was estimated as (1.5 ± 0.5)·10−10 cm2/s. The results were proven in field experiment with spike emission of petrol aerosol.

SnO2 chemical sensors were fabricated by two different methods. The first one was based on contacting individual nanowires by in situ nanofabrication in a Focused Ion Beam (FIB) microscope. The second one, the traditional sol-gel method, was based on tin dioxide nanopowder thermal agglomeration. Both types of sensors were capable of detecting air-diluted H2S to the parts per million level. The responses to this gas were studied at different concentrations and operating temperatures, showing up reproducible characteristics. Their performances were discussed in relation to the accepted mechanisms for H2S sensing in n-type metal oxides. Investigations were made on sensitivity and device stability, demonstrating that these nanowires have some advantages in comparison with sol-gel sensors.

We report a device for selective detection of ammonia. The device consists of a MOX sensor and a converter transforming ammonia into nitrogen dioxide. When the converter is switched off, the sensor mainly detects ammonia (donor signal), and when the converter turned on, the sensor detects nitrogen dioxide (acceptor signal). The analytical signal is a normalized difference between the sensor signals when the converter is working and when it is turned off. The main advantage of this method is high selectivity of ammonia detection. Another advantage is the solution of the problem of sensor drift.

We elaborated a logically closed theory of the conductivity of nano-structured semiconductor material (NSSM) valid in a large range of grain sizes a . It is shown that high sensitivity to electronegative gases (O 2 , F 2 , etc.) is observed, when the grain size lies in a range of aSH a aCR , where aCR – is a critical size of a grain, below this size charge carrier self-exhaustion regime takes place; aSH – is a grain size, below which the mechanism of superficial hopping conductivity predominates. This hopping mechanism excludes gas sensitivity of the material. Theorem of gas sensitivity of NSSM and the rules of the selection of nano-structures prospective for the fabrication of sensing MOXlayers are formulated.

Hybrid nanomaterials based on oxygen plasma treated multiwall carbon nanotubes decorated with tin oxide nanoclusters were synthesised by the precipitation of a SnO 2 colloidal suspension in the presence of carbon nanotubes dispersed in the mother solution of precursor tin (II) acetate in a water free acetic acid. TEM analysis revealed that the size of tin oxide nanoclusters anchored at the carbon nanotube sidewalls is about 5 nm. Hybrid nanomaterials with different carbon nanotube to tin oxide ratios were prepared and their gas sensing properties when operated at room temperature and at 150 °C were investigated and compared against the properties of pure tin oxide or pure oxygen plasma treated multiwall carbon nanotube sensors. When an appropriate ratio between the amount of plasma treated nanotubes and tin oxide precursors is employed, hybrid sensors show superior performance in the detection of nitrogen dioxide in the ppb range and carbon monoxide in the low ppm range. Furthermore, these optimised sensors show a significantly reduced moisture cross-sensitivity. Detection mechanisms are discussed.

An increase in the number of gases detectable by sensors based on Pd-SiO2-Si (MIS) and Pt-LaF3-Si3N4 -SiO2-Si (MEIS) structures was achieved by the application of an external catalyst element (CE). It was shown that as a result of the decomposition of hydrocarbon and fluorocarbon molecules on a Ni coil (CE), the products detectable by metal-insulator-semiconductor (MIS) and metal-electrolyte-insulator-semiconductor (MEIS) sensors are formed. The simultaneous catalytic oxidation of hydrocarbons and their thermal decomposition result in an optimum CE temperature of about 1050 K for propane. The kinetics of the thermal decomposition of gases on Ni were investigated. The activation energy of the reaction for C3 H8 and the enthalpy in the case of CF3-CCl were estimated

A silicon based semiconductor sensor structure Pd/LaF3/Si3N4/SiO2/Si was prepared using thin layer technology. The sensor can be used for hydrogen detection at room temperature. Therefore, the power consumption is reduced by a factor 106 compared to the best low power consumption hydrogen sensors. In contrast to other sensors it can be used for measurements at very low and high hydrogen partial pressure. The limit of detection was determined to be 0.5 ppm. Measurements at high concentrations near to and above the Lower Explosion Level (LEL) of 4 % hydrogen in air are demonstrated. A method to achieve long lifetime of the sensor was developed.

An LaF3 layer was shown to improve the characteristics of field-effect gas sensors for room-temperature hydrogen monitoring. The Pt/LaF3 interface leads to a Nernst-type response and a detection limit of 10-ppm hydrogen in atmospheric air. The response time was shown to be about 110 s and was independent of hydrogen concentration. A method for the stabilization of a long-term behavior of the sensor was successfully demonstrated. The mechanism of the sensor's response to hydrogen was shown to be different from that of the metal/insulator/semiconductor (MIS)-type sensors

Today, road-trains are one of the most widely-spread and multi-tonnage transport vehicles on road arteries interconnecting countries and cities. The concept of hybrid road-trains mostly meets the widely-spread policy for stepping up the rates of exhaust gas emissions and reducing specific hydrocarbon fuel costs but only an intermediate link in the development of more significant and important design – a driverless road-train. This article considers active trailers and their models with different design options for heavy tractor truck propulsion unit drive. The influence of trailer link drive on turning has been studied in “Universal gear” software. Special attention has been given to an electrical drive of active semi-trailer wheels as the most advanced one at the present moment. We have obtained the data intended to be used in design of active trailer chassis and identified the weight and size characteristics of energy accumulators required for movement of a road-train with active trailer. The efficiency factor for different semitrailer drives has been analyzed and calculated, in particular: Low EF of electrical drive. The relevancy of active trailer concept including that for driverless road-trains has been determined on the basis of received data.

This paper describes software and hardware solution that enables Global Navigation Satellite System (GNSS) data acquisition with ground based stations network. The solution relies on original data format and relational database management system. C++ library code and database schema SQL-structures are created automatically from Javads Receiver External Interface Specification (GREIS) with a C# application. This solution was used to create a real time ionosphere monitor service based on Feodorov Institute of Applied Geophysics ROSHYDROMET GNSS-receiver network.

A chemical semiconductor sensor for the temperature range up to 400°C was developed using silicon carbide with an epitaxial layer of SiC as the substrate. Thin layers of LaF 3 and Pt were deposited on the semiconductor/insulator structure to form a three-phase boundary with the gas under investigation. The sensor was shown to be sensitive to fluorine, hydrogen fluoride and different fluorocarbons. The influence of the operation temperature on the sensor response signal was investigated in the range from room temperature up to 400°C. For the fluorocarbons CF 3 CH 2 F, CF 3 CCl 3 , CHClF 2, CF 3 CH 2 Cl and CCl 3 F a selective detection was achieved at temperatures near to 400°C. The substantial role of the fluoride ion conducting material LaF 3 for the sensor detection principle was proven. A mechanism including the chemisorption of the fluorocarbon at the Pt surface and an insertion of fluorine into LaF 3 was discussed.

The growing interest in new under-water pipe lines for the delivery of natural gas (in Baltic Sea, Mediterranean region, Caspian Sea, Black Sea, etc.) needs a new instruments for the monitoring of leakage and/or possible destruction of the pipes, which could not only disturb fragile ecological systems of Baltic and other seas, but also can lead to the technological catastrophes. We plan to develop a prototype of the system consisting of pervaporation membrane and gas sensors. Overall system will be immersed into water and will be fabricated in two versions: as a stationary instrument dipped into sea water and as an instrument towed along the pipe line. Micromachined metal oxide semiconductor gas sensors used for the detection of methane concentrations is designed and fabricated using “nano-on-micro” approach. Overall system is optimized from the point of view of minimum power consumption, which is necessary to assure its long term operation under autonomous conditions.

Development and implementation of new Automatic Generation Control (AGC) algorithms requires testing them on a model that adequately simulates primary energetic, information and control processes. In this article an implementation of a test platform based on HRTSim (Hybrid Real Time Simulator) and SCADA CK-2007 (which is widely used by the System Operator of Russia) is proposed. Testing of AGC algorithms on the test platform based on the same SCADA system that is used in operation allows to exclude errors associated with the transfer of AGC algorithms and settings from the test platform to a real power system. A power system including relay protection, automatic control systems and emergency control automatics can be accurately simulated on HRTSim. Besides the information commonly used by conventional AGC systems HRTSim is able to provide a resemblance of Phasor Measurement Unit (PMU) measurements (information about rotor angles, magnitudes and phase angles of currents and voltages etc.). The additional information significantly expands the number of possible AGC algorithms so the test platform is useful in modern AGC system developing. The obtained test results confirm that the proposed system is applicable for the tasks mentioned above.

The problem of gas analyzers compatible with wireless networks can be solved by using sensors based on the “nano-on-micro” technology. The basis of this technology consists in nano-composite sensing metal oxide semiconductor or thermocatalytic materials deposited on a microhotplate fabricated using silicon or alumina microelectronic technology. As a result, the sensor combines the advantages of both technologies: on the one hand, high stability and sufficient selectivity of nano-composite materials, and, on the other hand, microprocessor compatibility, low-cost, mass-production possibilities, and low power consumption of microelectronic substrates. Two methods for the fabrication of microhotplates are the most promising: the silicon based technology of silicon oxide/silicon nitride membranes and the CeraMEMS technology of thin alumina films (TAF). The first technology enables the fabrication of microheaters with a power consumption around 20 mW for an operating temperature below 450°C. Advantages of CeraMEMS platforms are: (1) operation at temperature up to 600°C and, potentially, up to 800°C; (2) robustness compared with silicon chip with thin membrane; (3) perfect Pt and sensing layer adhesion without any adhesive layers; (4) low cost of middle scale production (104–107 chips per year) compared with the silicon technology. The CeraMEMS platform can be used for the fabrication of semiconductor and thermocatalytic gas sensors, as a source of IR radiation for optical gas sensors and as bolometers. The sensor withstands ∼7 × 106 on-off cycles. Heater resistance drift is below 3% per year at 550°C.

The properties of composite materials based on LaF 3 and polytetrafluoroethylene have been studied from the point of view of electrochemical sensor fabrication possibilities. The composite was obtained by pressing the mixture of LaF 3 particles (20–50 μm in diameter) and Teflon near 220 °C (in the thermal plasticity range of PTFE). The properties of the composite as a function of the quantity of the LaF 3 filler were investigated. The analysis of phase-frequency properties of the system, volt-amperic curves and conductivity activation energy showed the superionic character of conductivity which increases gradually with increase of the filler quantity. The ratio of conductivities σ e /σ i is as low as 10 −2 (60% vol. LaF 3 ). The degradation potential of the system is about 3.1 V. The self-discharge characteristics and the analysis of the system: SnF 2 (reversible electrode)/LaF 3 +Teflon/C(inert electrode) had been carried out. The advantages of this material from our point of view are good processability and fine mechanical properties of the composite. The possibility of using this material as a solid state electrolyte for electrochemical sensors of fluorine and hydrogen fluoride is studied. It is shown that composite material with more than 70% LaF 3 may be used in this case. The sensor properties of LaF 3− x O 0.5 x obtained by different ways and having different stoichiometry for the La/F/O ratio were also examined. This compound has conductivity of the electron type. The maximum sensitivity has been found for the samples with stoichiometry near to pure LaF 3 . The characteristic time for the desorption process is 25 sec for T=485 °C. A possible mechanism of sensitivity is discussed.

The target of this work is the demonstration of advanced approaches able to provide rapid prototyping by using laser technology ceramic MEMS platforms for chemical sensor operating under harsh environmental conditions and, on the other hand, to assure microhotplate stable at high temperature, which can be used for the deposition of high working temperature gas sensing materials, for example, oxides of tin, gallium, zirconium and hafnium. As substrate ceramic material in work using alumina oxide

In this work, we describe a new approach to the detection of pyrolysis gases produced at smoldering of organic materials using a single metal oxide gas sensors based on SnO 2 and operating in fast temperature scanning mode. The results of experimental comparison of the selectivity of standard electrochemical CO sensor and of the metal oxide gas sensors based on SnO 2 at smokeless pyrolysis of various organic materials are presented. The experiment showed high selectivity of metal oxide sensor at smoldering fire detection compared to the standard electrochemical sensor used in fire alarm system.

DC-biasing was applied as a method to enhance the performance of a capacitive type gas sensor with a polymer electrolyte layer. The sensor was constructed as a metal-electrolyte-insulator-semiconductor structure with a polymer electrolyte layer deposited on a Si-substrate with SiO2-dielectric layer and aluminum back electrode. The electrolyte was prepared from polyvinyl chloride polymer dissolved in water with adding H3PW12O40 to the mixture making it proton conductive. The device was finalized with a platinum top electrode. The sensor was shown to be sensitive to H2 with detection limit below 100-ppm concentrations in synthetic air at room temperature. The sensor was tested using ac voltages with 250-mV amplitude and frequency from 1 to 100 kHz. In addition, by dc biasing the device with voltages up to 2 V during the capacitive measurements, the response, and sensitivity of the sensor were increased by 70% and 50%, respectively, at the optimal measurement frequency (5 kHz).

The application of gas sensors in breath analysis is an important trend in the early diagnostics of different diseases including lung cancer, ulcers, and enteric infection. However, traditional methods of synthesis of metal oxide gas-sensing materials for semiconductor sensors based on wet sol-gel processes give relatively high sensitivity of the gas sensor to changing humidity. The sol-gel process leading to the formation of superficial hydroxyl groups on oxide particles is responsible for the strong response of the sensing material to this factor. In our work, we investigated the possibility to synthesize metal oxide materials with reduced sensitivity to water vapors. Dry synthesis of SnO2 nanoparticles was implemented in gas phase by spark discharge, enabling the reduction of the hydroxyl concentration on the surface and allowing the production of tin dioxide powder with specific surface area of about 40 m2/g after annealing at 610 &deg, C. The drop in sensor resistance does not exceed 20% when air humidity increases from 40 to 100%, whereas the response to 100 ppm of hydrogen is a factor of 8 with very short response time of about 1 s. The sensor response was tested in mixtures of air with hydrogen, which is the marker of enteric infections and the marker of early stage fire, and in a mixture of air with lactate (marker of stomach cancer) and ammonia gas (marker of Helicobacter pylori, responsible for stomach ulcers).

The most part of gas sensors based on tin dioxide semiconductor sensing material are fabricated by using sol-gel synthesis of SnO2. This process leads to the formation of highly sensitive sensing material; however, it forms hydroxyl groups on the surface of tin dioxide, leading, in turn, to strong parasitic sensitivity of the sensor to changing humidity. This sensitivity can be reduced by calcination of sensing material, but this treatment also reduces considerably the total response of the sensor to target gases. In this work, we investigated the possibility of the dry synthesis of tin dioxide nanoparticles by gas phase spark discharge. After the annealing at 610 degrees C, the specific area of the material synthesized by spark discharge was about 40 m(2)/g. The sensing layer resistance of the sensor decreases by only 20%, when relative humidity of a carrier air increases from 40 to 100%. At the same time, the hydrogen response of the sensor remains the same as for the material prepared by sol-gel synthesis, that is factor of 8 at 100 ppm concentration of H-2. Very important property of the sensor is short response time of similar to 1-2 s to both hydrogen and humidity.

The thesis is dedicated to the synthesis, comprehensive material science and some sensing properties of SnO2-MetOx oxide systems (where MetOx are IVB and IIIB metal oxides). The study was performed in comparison with blank SnO2, and SnO2 doped with noble metals (Pd, Pt, Rh and their binary mixtures). Results of 8 ex-situ (TEM, HRTEM, XRD, FTIR, UV-Vis, BET, XPS and element analysis), 5 in-situ (TGA, MS-analysis, DRIFT, TXRD, TPR) techniques and sensing properties characterization (DC measurements as a function of temperature and gas composition) are discussed regarding surface chemistry of SnO2 sensing phenomenon. The special attention is paid to the role of surface hydroxyls in the processes related with conductivity change of semiconductor adsorbents upon hydrogen chemisorption and oxidation in dry and humid air., Los principales objetivos de la presente investigación fueron la síntesis de las sistemas oxídicos SnO2-MetOx (donde MetOx corresponde a los óxidos de grupos IVB y IIIB), el estudio extensivo de sus propiedades fisicoquímicas y sus propiedades como sensores de gases. La investigación se ha basado en la comparación de estos materiales con el SnO2 puro y el SnO2 dopado con metales nobles (Pd, Pt, Rh y sus combinaciones binarias). Resultados de 8 estudios ex-situ (TEM, HRTEM, XRD, FTIR, UV-Vis, BET, XPS y MS-análisis de elementos), 5 estudios in-situ (TGA, MS-analysis, DRIFT, TXRD, TPR) y la caracterización de los sensores de gases (conductividad de los materiales semiconductores en función de la temperatura y los componentes de los gases compuestos) se analizan considerando las reacciones químicas superficiales del SnO2. Se ha prestado una especial atención en la participación de los grupos hidroxilo superficiales en el mecanismo de cambio de conductividad del adsorbente semiconductor durante la quimisorción u oxidación del hidrógeno en el aire seco o húmedo.