The main achievements of the project are:
-1 Production of an original paste for the sensing element : The high detection performances of alumina have been demonstrated and the thick film technic has been indicated as the valid choice for the elaboration of the material. An original paste which is a mixture of alumina, of a binder (glass) and of an organic vehicle has been developed for the deposition of the sensing material by the screen printing method. The electrical performances of the thick films have been investigated under gases (CO, NO and NO(2)). The sensitivities depend largely on the temperature and consequently selective detection is possible.
-2 Development of a demonstration model : The nature and the design of each constituents (substrate, heater element, connections...) of the sensor substrates have been studied. The development has been focused on a model which can be used at high temperature for the exhaust application. The problems which have been solved are related to the compatibility, the mechanical properties and the thermal behaviour of the different materials. The thick film technology allows to produce strongly build sensors. The improvements to be perform concern principally the exact control of the temperature of the sensing material.
-3 Tests of the sensors prototypes : Two special testing benches have been developed, on one hand a laboratory bench including the possibility to test the sensing material and the sensors both under gases (CO, NO and NO(2)) in the concentration range from few ppm to few % and at different temperatures (200 to 700°C), and on the other hand an industrial bench for the evaluations of several sets of sensors especially in regards to their reproducibility and stability. A part of the obtained files have been used for the development of a mathematical model for the discrimination of gas mixtures on the basis of the selectivity possibility with the temperature : NO(2) at low temperature (350°C) and CO at high temperature (650°C).
-4 Tests on cars : The instrumentation of a car has been achieved with on board computer and gas analysers. This car has been used with success to test the sensors for both applications : air quality in passenger compartment and control of exhausts. The experiments realised in the exhausts have demonstrated the possibilities of the ECONOX sensors to produce a signal which seems in correlation with the nature and the concentrations of the gases. A major result is connected to the dual behaviours of the sensors which are very similar to the responses of the sensors measured on testing bench. The experiments inside the car have demonstrated the capability of the sensors to be used for the control of the air quality and to be insert in electronic device for automatic regulation of the air circulation. The experiments realised with sensors on motor bench are more difficult to explain and this can be due to the high complexity of the gas mixture which is produce by the motor.
The object of the proposed research is to develop a device for the selective detection of CO and NOx. The applications most immediately envisaged relate to the quality of the air inside the passenger compartment of motor vehicles and the control of exhaust emissions. Unlike semi-conductor sensors, which are insensitive to the simultaneous action of CO and NOx, the devices developed in the course of this study operate according to an original electrochemical principle. These sensors, utilising beta alumina, are capable, after analysis of the signal, of providing selective information for the detection of the two gases in question in the applications envisaged.
These sensors are manufactured by sintering or by deposition of thick layers by dip-coating or screen printing.
Experimental models using one or more types of sensors are constructed in the laboratory, then in the form of industrial prototypes. Electrical tests are performed on these models on the basis of signal analysis, at least in the case of the multisensor devices. Validation tests are carried out directly on motor vehicles specially equipped for this purpose.
The objectives are to develop:
- An immediately usable device to control the quality of the air inside the passenger compartment
- an industrial model for the measurement and regulation of emissions.
The results of this research will be available for exploitation in other fields related to the urban environment, industrial hygiene and safety.
Funding SchemeCSC - Cost-sharing contracts
10129 Torino (Turin)