Test Gas Research Articles

Ultra-small photonic crystal (PhC)-based test tool for gas permeability of polymers.

We present an ultra-small photonic crystal-based test tool for gas permeability of polymers. It features a fully-etched photonic crystal (PhC) structure occupying an area of 20 µm × 800 µm on silicon-on-insulator wafer. The light-matter interaction in the PhC cavity with deformed Polydimethylsiloxane (PDMS) under pressure difference was investigated with finite element method and finite-difference time-domain method numerically. Next, three PDMS membranes of different mixing ratios were utilized for the characterization of gas permeation flux. The feasibility and effectiveness of the proposed working mechanism are verified through clearly distinguishing the gas permeability of these three testing samples. Compared with conventional test tools, this proposed test tool has fast response while it consumes less testing gas volume in a testing system with reduced footprint. Potentially, it can be integrated into lab-on-a-chip devices to measure gas permeation in nano scale.

Full-scale 3D-modelling of the radiative heat transfer in rotary kilns with a present bed material

This work discusses the development and use of a detailed 3D radiative heat transfer model of a rotary kiln with a present bed material, used for iron ore pelletizing. A discrete ordinates method is used to solve the radiative heat transfer equation with radiative properties calculated using a weighted-sum-of-grey-gases (WSGG) model for gases and Mie and Rayleigh theory for particles including fuel, ash and soot. Measurement data gathered from a pilot-scale test furnace, comprising temperature, gas composition and particle concentration, is used in combination with temperature data and operation parameters gathered from a conventional rotary kiln to model a full-scale rotary kiln with a present bed material. The modelled cases have a thermal input of about 37 MWth and in addition to radiative heat transfer, conductive heat transfer within, as well as between, the bed and wall material are included in the model along with convective heat transfer from the gas and heat release from exothermic reactions in the bed. The model also considers the rotational wall and includes a simplified mixing model of the bed material as well as heat losses from the outside wall of the rotary kiln due to radiation and convection. For two different flames, one coal and one oil flame, surface temperatures are calculated on the inside and outside of the rotary kiln and compared to measurements. The model appears to predict the inner wall and bed surface temperatures well with errors less than 11%. The total heat transfer to the present bed material was also studied revealing that more than 80% originated from the radiative heat transfer within the furnace.

Reduction of fuel consumption of small gas turbines at idling under combined operation with adjustable compressor inlet and turbine outlet guide vanes

AbstractFor the experimental verification of the effect of adjustable compressor inlet guide vanes combined with adjustable turbine outlet guide vanes for reducing the fuel consumption at idling, an 8 kW test gas turbine was designed and built up. The data of the experiments with the test gas turbine was compared with experimental data acquired by the author from another gas turbine. Additionally, experimental data was compared with external data of other heat engines. Using the newly introduced dimensionless Kruschik number, the test gas turbine, two series gas turbines and an internal combustion engine was compared in terms of their required heat supply at idling.

Gas sensitivity of heterojunction TiO2NT/GO materials prepared by a simple method with low-concentration acetone

Graphene oxide (GO) was prepared using a modified Hummers' method, and titanium dioxide nanotubes (TiO2NT) were prepared by a hydrothermal method. The gas sensing material (graphene oxide-titanium dioxide nanotubes) was obtained by self-assembling composite GO and TiO2NT.Then the material was coated onto a gold electrode to prepare the device. This resultant device exhibits excellent response to low concentrations of acetone and high selectivity over other gases. Through SEM test analysis, TiO2NT was tiled on a sheet of GO to form a physically bonded heterojunction semiconductor composite. XRD analysis confirms that the anatase TiO2 was successfully produced and there was no impurity peak in the composite. During the gas sensing test, it was proved that the device exhibited an excellent response to 0.3 ppm of acetone at 250 °C. The heterojunction material still exhibits the resistance characteristics of the n-type semiconductor, and the material resistance is reduced in a gas environment by carrier conduction. The increase of sensitivity arises from the fact that the holes of GO and the carriers of TiO2NT are moved towards each other to form a space charge region, which causes the material to form a larger resistance difference in the test gas environment.

MEMS thermal gas flow sensor with self-test function

In this paper, the design, fabrication and characterization of a MEMS thermal gas flow sensor with self-test function are presented. The flow sensor is composed of a platinum heater and thermopiles, where the heater is served as a heat source and the thermopiles are used for voltage output. In order to improve the performance of the flow sensor, the heavily doped N/P-polysilicon is utilized to form the thermocouple and XeF2 front-side isotropic etching is adopted to realize thermal isolation of the device. At the same time, the effects of the chip position in the gas channel and heater voltage on device performance are also studied from both experiment and simulation. Moreover, a self-test method and corresponding test system based on the thermal flow sensor are proposed, which use an equivalent heater voltage to simulate the gas flow rate for monitoring the dynamic response of the flow sensor to the gas. This method is simple and effective compared with traditional methods for detecting the performance flow sensors. In addition, the basic output performance of the flow sensor using nitrogen as the test gas is characterized. The experimental results show that the flow sensor owns a relatively high sensitivity of 123.006 mV (m/s)−1 (no amplification), a low response time of about 250 ms and good accuracy of ±1.97%.

Constructing hierarchical SnO2 nanoflowers for enhanced formaldehyde sensing performances

In this work, the hierarchical structure SnO2 nanoflowers self-assembled by multilayer nanosheets were successfully prepared by a simple hydrothermal method. The sensor based on this material shows excellent performances, while the response toward 100 ppm formaldehyde (HCHO) is 34.6 at 300 °C, and the response for the other test gases is much lower. This is because the hierarchical structure can provide numerous oxygen adsorption sites and the gas efficient diffusion, which can ensure the sensing surfaces are immediately exposed to HCHO molecular because of the efficient diffusion pathway and make SnO2 be a highly conducting state in the same time.

Heat transfer rate and surface pressure measurements in short duration hypersonic flow

ABSTRACTExperiments were carried out with air as the test gas to obtain the surface convective heating rate and surface pressure distribution on blunt and sharp cone models flying at hypersonic speeds. Tests were performed in a hypersonic shock tunnel at two different angles of attack: ${0}^\circ$ and ${5}^\circ$ with angles of rotation $\phi = {0}^\circ, {90}^\circ$, and ${180}^\circ$. The experiments were conducted at a stagnation enthalpy of 1.4MJ/kg, flow Mach number of 6.56 and free stream Reynolds number based on the model length of $9.1 \times {10}^{5}$. The effective test time of the shock tunnel is 3ms. The results obtained for cone model with a bluntness ratio of 0.2 were compared with sharp cone models for $\alpha ={0}^\circ$. The measured stagnation heat transfer value matched well with the theoretical value predicted by the Fay and Riddell correlation and with the CFD results.

A highly selective sensor to acetylene and ethylene based on LaFeO3

Gas sensing using metal oxides can be a highly cost effective and reliable technology in a variety of medical and industrial applications. However, selectively sensing a specific gas in a complex gas mixture continues to be a significant challenge. Here, we focus on acetylene and ethylene sensing with LaFeO3 (LFO) based sensors with novel applications, such as online monitoring and maintenance of electrical power transformers, in mind. We prepared LFO’s via sol gel method at five different calcined temperatures (500–900 °C). X-ray diffraction (XRD) patterns showed that all five materials were single phased with a perovskite crystal structure. We then used these materials as active sensing layers during exposure to various test gases, including C2H2, C2H4, CH4, C2H6, CO, CO2 and H2 at different operating temperatures (150 °C, 200 °C, 250 °C and 300 °C). All of our sensors showed a significant response to unsaturated hydrocarbons, namely acetylene and ethylene, but not to the other gases. We further improved this high selectivity of our sensors, to only detect acetylene and not ethylene, by controlling the operating temperature. We then tested the effects of different backgrounds, such as humidity, and CO2 levels, on our LFO sensors. The sensors were saturated faster in humid than dry conditions, in particular at lower operating temperatures, and there was no influence of CO2. Therefore, our results demonstrate novel oxide-based sensors capable of distinguishing between acetylene and ethylene, enabling interesting new industrial applications.

Experimental study of forward-facing cavity with energy deposition in hypersonic flow conditions

Controlling nose surface peak heat fluxes is crucial to the design of hypersonic vehicles. In this study, we report a novel technique of convective heat flux reduction on the nose surface of a spherically blunted cone by employing a forward-facing cavity combined with heat energy deposition inside the cavity. The heat deposition is achieved by the exothermic reaction of a chromium film coated on the cavity surface. The experiments are performed in hypersonic shock tunnels using air as the test gas at free stream stagnation enthalpy conditions of 2.2 ± 0.08 MJ/kg (H1), 3.2 ± 0.018 MJ/kg (H2), and 5.4 ± 0.02 MJ/kg (H3), for a geometry of cavity length to diameter ratio of 1. Schlieren images of the flow are captured using a high-speed camera and a high-power pulsed diode laser light source. The surface heat flux measurements were performed using calibrated platinum thin film sensors. We observed that the heat deposition altered the cavity flow field significantly by lowering the flow oscillation frequency and increasing the shock standoff distances with higher oscillation amplitudes. The overall surface mean heat flux reduction is increased from ≈13% to ≈49% compared to the blunt body geometry, whose nose radius is 30 mm and enhanced with reference to the cavity without heat deposition from ≈15% to ≈35%. Chromium film surface reactions are studied using X-ray Photoelectron spectroscopy, and the results confirm that the exothermic surface reactions of the Cr thin film are attributed to the formation of oxides and nitrides of Cr.

Characteristics of wufeng-longmaxi formation shale gas sweet layer: a case study of weiyuan-rongchang block in the south of sichuan basin, China

Taking the typical shale well of the Wufeng-Longmaxi Formation in the Weiyuan shale gas block of the South Sichuan Basin as an example, based on core observation, core slice, ar-ion milling SEM, physical property test, X-ray diffraction, geochemical analysis and on-site gas content test, the author systematically evaluated the Wufeng-Longmaxi geological sweet layer from the aspects of petrology, mineral composition, organic geochemistry, hydrocarbon-generating organism, physical property, pore type and gas content.The research shows that the lithology of the geological sweet layer in Weiyuan area is mainly composed of black carbonaceous shale, and laminae are developed. Compared with the Jiaoshiba area, the carbonate mineral content is higher and the quartz mineral content is relatively lower. The sweet layer has high TOC, and is at a stage of high maturity. It is rich in hydrocarbon-generating organism such as graptolites, algae, sponge bones and bacteria. The inorganic pores and organic pores of the sweet layer are well developed. The inorganic pores are mainly clay mineral pores, feldspar alteration pores and intercrystalline pores of pyrite. In terms of gas content, it has the characteristics of high gas content and high Initial dissipation rate, which provides a possibility for high yield and stable production of fracturing in this layer.The geological sweet layer has high organic carbon content, is rich in hydrocarbon-generating organisms, has a large potential for gas generation, and generated enough gas after a period of high mature evolution; at the same time, a large number of inorganic pores and organic pores generated in diagenetic evolution, these pores provide space for shale gas generation, as the same time, it increases the permeability of the sweet layer. The study area has good preservation conditions, it has favorable top and bottom Stratum conditions, and does not have large destructive fractures and destructive fluid activities, The above factors make the shale gas enriched and preserved, which provides the possibility of high and stable yield after fracturing.

A new sensing mechanism of Si FET-based gas sensor using pre-bias

A new capacitive-type FET (CFET) gas sensor is proposed in this work and fabricated by using Si FET technology. Only five photomasks are used to prepare the CFET sensor and a ZnO thin film prepared by atomic layer deposition (ALD) is adopted as a sensing material. A diluted nitrogen dioxide (NO2) is used as a test gas and the sensing properties of the CFET gas sensor are measured at 180℃ by using pulse pre-bias method. It is verified that the response of the CFET sensor is significantly improved as the absolute value of the difference between pre-bias (Vpre) and gate read bias (VrCG) increases. However, the response is negligible when Vpre = VrCG. The drain current (ID) of the CFET gas sensor increases by 44.6% at a Vpre of −2 V while the ID decreases by 43.2% at a Vpre of 2 V under exposure to 0.5 ppm NO2 at a VrCG of 0 V at 180℃. The response and the recovery times are also investigated. The sensing mechanism is explained by using schematic energy band diagrams.

Increasing sensitivity of ZnO nanoparticles by hydrogenation and sensing reaction mechanism

Sensing reaction mechanism is decisive for improvement of the sensing property of metal oxide sensing materials. Herein, we demonstrated a conceptually different approach to improving sensing property of ZnO nanoparticles by increasing quantity of the surface unsaturated 3-coordinated Zn atoms through hydrogenation. The surface 3-coordinated Zn atoms play a pivotal role in sensing reaction. They can produce electrons, adsorb O2 and catalyze the gas sensing reaction between the adsorbed oxygen and test gas. A sensing mechanism of the unsaturated Zn atom serving as a sensing reactive site is presented for the first time. The mechanism provides a deep understanding for sensing and catalytic reaction mechanisms. In addition, the sensing performance of other sensing materials and reactive activity of catalysts may be enhanced by increasing concentration of surface unsaturated metal atom through hydrogenation.

MONITORING GAS DISTRIBUTION AND ORIGIN IN THE CULZEAN FIELD, UK CENTRAL NORTH SEA, USING DATA FROM A CONTINUOUS ISOTOPE LOGGING TOOL AND ISOTUBE AND TEST SAMPLES

The high pressure – high temperature Culzean field, UK Central North Sea, contains lean gas condensate in the Triassic Joanne sandstones and the Middle Jurassic Pentland sandstones. A comprehensive gas analysis programme was installed as an integrated part of field development in order to monitor gas composition, distribution and origin in the reservoirs and overburden pre‐ production start‐up. Isotube OUT and isotube IN gas samples were collected. The isotube IN data show that some gas is recycled, including alkenes representing contamination from the degradation of mud additives; but concentrations are minor, and do not seem to affect the isotope values derived from the C2 and C3 isotube OUT gases significantly. 13C‐enriched methane derived from drill‐bit metamorphism is recorded in the isotube IN gas, but likewise in low concentrations. Gas data were also acquired from a Continuous Isotope Logging Tool (CILT) which measures real‐time gas concentrations and isotope values of C1–C3 each foot through the entire drilled section. The CILT thus provides a continuous trend of methane isotope values versus depth, and this trend is useful in identifying changes in gas composition. However, concerns related to CILT include: (i) C1–C3 stable carbon isotope detection limits for isotube OUT gas analyses are considerable lower than for CILT; due to the lower isotube gas concentrations required for measurement of C3 isotopes, isotubes are able to map a shallower vertical thermogenic gas migration front in the overburden. (ii) Discrepancies between isotube OUT and CILT isotope values may be significant and cannot be assigned to analytical uncertainty; by contrast, test gas and isotube OUT isotope values are comparable. Hence, CILT isotope values from specific depths cannot stand in isolation but must be complemented by isotube OUT isotope measurements.Gas in the Pentland reservoir is the most coaly in composition due to self‐sourcing from the Pentland coals. The coals are the primary source rock for the gas encountered in the entire reservoir interval at Culzean, but the underlying Joanne sandstones contain contributions from highly mature marine shales in the Kimmeridge Clay Formation and/or Heather Formation. The Lower Cretaceous seal on top of the Pentland reservoir is relatively tight but some minor migration/leakage of thermogenic gas into the overburden is recorded by the detection of C3 isotopes. Thermogenic gas also occurs in high porosity intervals in the Upper Cretaceous succession but this gas is interpreted to have migrated laterally in porous carrier beds and did not enter these intervals at the well locations.

ANALISIS HASIL FERMENTASI PEMBUATAN BIOETANOL DENGAN VARIASI MASSA RAGI MENGGUNAKAN BAHAN (BERAS KETAN HITAM, BERAS KETAN PUTIH DAN SINGKONG)

This study aims to determine the levels of bioethanol from (black sticky rice, white sticky rice and cassava rice) with variations in yeast mass as much as 5 grams, 10 grams and 15 grams knowing the optimum time variation and knowing ethanol levels according to SNI. This research was carried out by hydrolysis or boiling of ingredients (black sticky rice, white sticky rice and cassava rice) using distilled water for 30 minutes, then fermentation using yeast saccharomyces cereviseae and distillation process using a complete destilator to obtain ethanol from fermented then tested with a pen refractometer to determine whether or not ethanol is formed from the distillation process. The selected sample was then tested for ethanol content using a gas chromatography tool. The results of this study are known by testing gas chromatography to find out the ethanol content contained in the distilled sample, the results of ethanol, black glutinous rice with 96 hours fermentation time 92.29% ethanol, and white glutinous rice with fermentation time 96 hours of 100% ethanol and cassava with 96 hours of fermentation time of ethanol content of 98.10%. Keywords: Black Sticky Rice, White Sticky Rice, Cassava, Fermentation, Ethanol

Experimental and numerical study of oxygen catalytic recombination of SiC-coated material

A combined experimental and numerical approach has been proposed to study the oxygen catalytic recombination coefficient of SiC-coated material for two different types of surface condition: roughened and pre-heated. For the experimental approach, the shock tube facility, which test gas consists of 21% oxygen and 79% argon by volume, is utilized to measure the oxygen catalytic recombination coefficient at near-room surface temperature. The coefficient is deduced from the local heat transfer measurement at the end-wall model of the shock tube via catalytic boundary layer theory. The experimental data indicated that the coefficient for the SiC-coated material varied between 0.0024 and 0.01, depending on the surface condition. The results suggested that even at low surface temperature, both the level of surface roughness and the oxidation due to the pre-heating should be considered carefully for the atomic recombination process. For the numerical approach, the finite rate catalytic modeling is elaborated in detail. The modeling is conducted to better understand the physical interaction for the recombination mechanism. Given the surface reactions considered in the modeling, the catalytic recombination coefficient was not significantly affected by the pressure at low wall temperature. Conversely, the variation in the coefficient was observed to be dependent on the activation energy and the number of active site concentrations at the surface.

Prediction of early postoperative desaturation in extreme older patients after spinal anesthesia for femur fracture surgery: a retrospective analysis.

BackgroundPostoperative desaturation in older individuals is rarely addressed in the literature. The objective of this retrospective study was to investigate whether a preoperative spirometric test and arterial blood gas analysis (ABGA) might predict postoperative desaturation after spinal anesthesia in extreme older patients.MethodsThe medical records of 399 patients (age ≥ 80 yrs) who were administered spinal anesthesia for a femur neck fracture surgery were retrospectively reviewed. Early postoperative desaturation was defined as a reduction of oxygen saturation (SpO2) below 90% within 3 days of surgery, despite O2 supply via a nasal prong. Binary logistic regression analysis was used to identify predictors of early postoperative desaturation.ResultsThe incidence of postoperative desaturation was 12.5%. Major morbidity rate was significantly higher in the desaturation group (n = 50) than that in the non-desaturation group (n = 349) (14% vs. 3.2%, P = 0.001) with more frequent postoperative stays in the intensive care unit (22% vs. 12%, P = 0.004). In a binary logistic regression analysis, preoperative ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2 ratio) (OR, 0.972; 95% CI 0.952–0.993; P = 0.010) and history of cardiovascular disease (OR, 2.127; 95% CI 1.004–4.507; P = 0.049) predicted postoperative desaturation.ConclusionsPreoperative PaO2/FiO2 ratio, but not preoperative spirometry, was predictive of the postoperative desaturation in older patients after being administered spinal anesthesia for femur fracture surgery. Based on our results, preoperative ABGA may be helpful in predicting early postoperative desaturation in these patients.

Effects of CeVO4 electrode morphology and oxygen content on ammonia sensing properties for potentiometric sensor

The influences of sensing electrode morphology, operating temperature and the oxygen content on NH3 sensing properties for the potentiometric gas sensor attached with CeVO4 sensing electrode were studied. With the increase of electrode sintering temperature, CeVO4 grains grow up gradually. The response/recovery time shows a decreasing trend, but the NH3 sensitivity reaches the highest when the sintering temperature reaches 1000 °C, this was determined by the amount of TPB and the ammonia concentration involved in the electrode electrochemical reactions. The NH3 sensitivity enhances with the increase of operating temperature in the range of 450–550 °C and presents the mixed-potential characteristic. When the temperature exceeds 600 °C, the curve between ΔV and logarithm of NH3 concentration presents a broken line relationship, and the concentration corresponding to the inflection point increases with the increase of operating temperature. The response and recovery rates accelerate but the NH3 sensitivity decreases with the increase of oxygen content in testing gas. When the oxygen is above 10 vol.% and NH3 is below 80 ppm, the response value is almost unaffected by the change of oxygen concentration. The broken line feature of the sensitivity curve under high operating temperatures and oxygen concentrations is mainly related to the gas phase catalytic reaction of NH3 by oxygen.

High-Temperature Unimolecular Decomposition of Diethyl Ether: Shock-Tube and Theory Studies

The unimolecular decomposition of diethyl ether (DEE; C2H5OC2H5) is considered to be initiated via a molecular elimination and a C-O and a C-C bond fission step: C2H5OC2H5 → C2H4 + C2H5OH (1), C2H5OC2H5 → C2H5 + C2H5O (2), and C2H5OC2H5 → CH3 + C2H5OCH2 (3). In this work, two shock-tube facilities were used to investigate these reactions via (a) time-resolved H-atom concentration measurements by H-ARAS (atomic resonance absorption spectrometry), (b) time-resolved DEE-concentration measurements by high repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS), and (c) product-composition measurements via gas chromatography/MS (GC/MS) after quenching the test gas. The experiments were conducted at temperatures ranging from 1054 to 1505 K and at pressures between 1.2 and 2.5 bar. Initial DEE mole fractions between 0.4 and 9300 ppm were used to perform the kinetics experiments by H-ARAS (0.4 ppm), GC/MS (200-500 ppm), and HRR-TOF-MS (7850-9300 ppm). The rate constants, ktotal (ktotal = k1 + k2 + k3) derived from the GC/MS and HRR-TOF-MS experiments agree well with each other and can be described by the Arrhenius expression, ktotal(1054-1467 K; 1.3-2.5 bar) = 1012.81±0.22 exp(-240.27 ± 5.11 kJ mol-1/RT) s-1. From the H-ARAS experiments, overall rate constants for the bond fission channels, k2+3 = k2 + k3 have been extracted. The k2+3 data can be well described by the Arrhenius equation, k2+3(1299-1505 K; 1.3-2.5 bar) = 1014.43±0.33 exp(-283.27 ± 8.78 kJ mol-1/RT) s-1. A master-equation analysis was performed using CCSD(T)/aug-cc-pvtz//B3LYP/aug-cc-pvtz and CASPT2/aug-cc-pvtz//B3LYP/aug-cc-pvtz molecular properties and energies for the three primary thermal decomposition processes in DEE. The derived experimental data is very well reproduced by the simulations with the mechanism of this work. With regard to the branching ratios between bond fissions and elimination channels, uncertainties remain.

CO2 Sensing Behavior of Calcium-Doped ZnO Thin Film: A Study To Address the Cross-Sensitivity of CO2 in H2 and CO Environment.

CO2, CO, and H2 are the major pollutants in the environment, which are primarily generated during the combustion of the organic compounds. Development of a smart sensor that could address CO2 sensing and its cross-sensitivity toward CO and H2 gases is highly advantageous. In this work, an advanced gas sensor is proposed and developed to address the cross-sensitivity of CO2 sensing in CO and H2 environment, which is based on calcium-doped ZnO (Ca_ZnO) thin films. The proposed sensors were successfully synthesized using wet chemical synthesis. We have reported that a 5 atomic weight % calcium-doped ZnO thin film exhibits an efficient sensing performance with a wide range of CO2 gas concentration (75 000-5000 ppm) at 350 °C. Additionally, mixed gas sensing characteristics have been carried out for various concentrations of CO (500-25 ppm) with CO2 and H2 (500-100 ppm) with CO2 gas at 350 °C. The response (%) was estimated as 53, 83, and 74% for 50 000 ppm CO2, 50 000 ppm CO2 + 500 ppm H2, and 50 000 ppm CO2 + CO gases, respectively. Furthermore, the enhancement of CO2 sensing was investigated using the Raman spectrum of calcium-doped ZnO thin films. Consequently, the cross-sensitivity of pure and mixed gases has been accomplished using principal component analyses, which shows a distinct cluster formation for each test gas. The proposed gas sensor can be potentially applied to biomass sensing, fuel combustion monitoring, and chemical industries.

Facile Synthesis of Nano-Diced SnO2–ZnO Composite by Chemical Route for Gas Sensor Application

The simple chemical bath deposition (CBD) method is used to synthesize SnO2–ZnO nanocomposite at room temperature. Formation of SnO2–ZnO nancomposite is confirmed by the x-ray diffraction (XRD) pattern of annealed films. Scanning electron microscopy (SEM) micrographs of nanocomposite SnO2–ZnO depict that morphological change from nanocubes to manifold hexagonal nanorods with an increase in ZnO content in a composite sample. Also, pure SnO2 sample exhibits interconnected nanospheres. Electron dispersive spectroscopy (EDS) is employed to confirm elemental compositions in composite films. SnO2–ZnO samples were applied as a sensor for different test gases, namely liquified petroleum gas (LPG), ethanol, ammonia (NH3), and hydrogen sulfide (H2S). The maximum response of 59.67% is observed for ethanol at an operating temperature of 275°C and 24 ppm gas concentration. Also, a composite sensor shows a quick response in comparison with a bare sensor. This superior performance of composite over pure sensor may be attributed to a n–n heterojunction at intergrain boundaries. The SnO2–ZnO sensor is found to be selective towards ethanol even at lower gas concentrations.