R. Vik

Design of a singlet oxygen generator based on LED emitters

This article deals with the research of singlet oxygen generation using phthalocyanine photosensitizer. Singlet oxygen is extraordinary reactive and can be used in many applications such as photodynamic therapy, disinfection or chemical synthesis. For singlet oxygen generation, the photosensitized method in a new developed generator based on LED emitters was used. The amount of singlet oxygen generated by LED emitters was compared with laser excitation. The principle of measurement, design of a singlet oxygen generator and control unit are discussed in more detail.

Monitoring device of resin curing process

The presented article introduces a system for resin curing monitoring. The system is based on a combined sensor built on a ceramic substrate containing a heating element for independent surface heating, interdigital electrodes, and a Pt1000 thermistor for precise temperature measurements. The idea of the simple resin curing monitoring device is based on a small amount of tested resin being applied directly to the sensor surface. After the resin has been applied to the surface, a controlled heating process begins together with the measurement of the electrical properties of the resin, usually the impedance. The curing process is thus monitored and graphically plotted on the connected PC.

In-situ monitoring of resin curing process based on interdigital impedance sensors

The online monitoring of resin curing process is described in the presented article. There exists several monitoring technique useful for resin curing monitoring and consequently for the curing technology improving, at the present. The advantage of the described monitoring system and monitoring method is in the using a unique sensors directly inserted into the tested resin or technology part which allows observing the resin characteristics as well as the local temperature directly at the sensor area. The data acquisition is processed by the in-house developed portable curing monitoring device and wirelessly transfered to the PC for further analysis. The study describes the experimental work of using the monitoring system and sensors and also the curing process of resins and composites using electrical impedance magnitude.

Optimization of the curing process of epoxy resins using methods of structural analysis

Epoxy resins belong among materials frequently used for the production of impregnating composites especially for the construction of motors, generators, and transformers. During production, great emphasis must be focused on the proper curing process of these materials. Otherwise, it is not possible to guarantee the satisfactory properties of the final product. The paper is therefore focused on the analysis of the level of curing of epoxy resin by methods of structural analyses. The Fourier Transform Infrared Spectroscopy (FT-IR) and glass transition temperature evaluated from a reversible signal of heat flow measured by modulated differential scanning calorimetry (MDSC) were used. Curing process was performed in a laboratory oven. Partly and fully cured samples were analyzed during two independent experiments. These two experiments differ to each other especially by different times of sampling. The trend of the changes of infrared spectra measured on samples during the curing process corresponds well with the results of the glass transitions temperature measurements obtained by MDSC. Insufficient curing state is relatively well detectable by the presence of the spectral bands corresponding to the vibration of epoxy and anhydride groups (901, 1875, 1786 cm-1). Both methods are acceptable to detection of the curing level but with different sensitivity. While infrared spectroscopy is possible to use for prediction especially short times of curing, analysis of the glass transition is sensitive during the whole curing process.

Cross-sensitivity of humidity sensor layers based on organic materials

This article deals with the research of an impact of various gases and vapours on electrical parameters of phthalocyanine. Cross-sensitivity was researched in order to exclude a negative impact of organic vapours on humidity sensor. Thin layer of phthalocyanine was exposed to various vapours, and then responses of its electrical characteristics were measured. This suitable material for humidity sensors, was deposited from the liquid phase on a substrate with interdigital electrodes and than exposed to the effect of analytes. Subsequently, the impedance characteristic of this thin film layer was measured. The comparison of responses to various gases and vapours is discussed in more detail as well.

Organic materials for humidity detection

This article deals with the research of different types of diketopyrrolopyrroles (DPPs) for humidity detection. Thin layers of various DPPs are exposed to water vapors and then responses of electrical properties of these layers are measured. Potentially suitable materials are deposited on substrates with interdigital electrodes and subsequently impedance humidity characteristics are measured. Comparison of these materials, their features and responses to an ambient humidity are discussed in more detail as well.