Optimization and Application of NTC Thick Film Segmented Thermistors

NTC thermistor paste for printing thermal sensors on alumina was formed of very fine Ni0.5Cu0.2Zn1.0Mn1.3O4 thermistor powder obtained by a combined mechanical activation/thermal treatment process, organic vehicle and glass frit. Sheet resistivity was measured using an R-test matrix and it was much lower than the value determined for pure nickel manganite thermistors. The thermistor exponential coefficient was calculated from the R[ diagram measured in the temperature range-30 to +120°C in a climatic chamber. Thick film segmented thermistors with reduced dimensions (optimized construction) were printed sequentially layer by layer, dried and fired at 850°C/10 min in air. Electrodes were printed of PdAg conductive and solderable paste. The samples obtained were characterized by electrical and thermal measurements. The obtained NTC segmented thermistors with reduced dimensions were applied in a thermal sensor for water flow in the water mains. It contained a cold thermistor for measuring input water temperature and a self-heating thermistor for measuring the dependence of water current on water flow rate at a set input voltage power. Initial measurements show that the thermal sensor system requires a low input voltage power making it much easier and safer for operation

Aeroallergen survey of Vukovar-Srijem County using a burkard volumetric spore trap

The analysis of air was performed through the collection of pollen and spores using a Burkard Volumetric Spore Trap and was conducted during 2017 in Vukovar (Croatia). The relationship between investigated fungal spores, and pollen genera, and selected meteorological parameters were examined. Ambrosia and Urticaceae were the major contributors to the total pollen airspora, followed by Poaceae and Betula. Fungal spores showed one period of high sporulation, from June to September. Cladosporium was by far the most abundant spore identified, followed by Alternaria. Weather conditions play an integral role in the passive and active discharge of spore and pollen

Comparison of selected bioactive compounds and antioxidative capacity in different broccoli cultivars

Numerous recent publications have compared different cultivars of broccoli and different cultivation conditions suggesting that great variations in the content of phytochemicals among cultivars are due to genetic, and many environmental factors. The purpose of the present work was the quantification of glucosinolates, phenolic compounds, carotenoids, and antioxidant capacity in the florescences of 13 genotypes from freshly harvested broccoli grown under uniform agroecological practices. The present results showed a significant variation in the level of bioactive compounds and consequently potential health benefits of broccoli (total glucosinolates 12.04–22.48 μmol g−1 d.w., the total phenolic content 15.54–26.92 mg g−1 d.w., total carotenoid content 0.19 mg g−1–0.46 mg g−1 d.w.). Studied cultivars were different in the level of the individual bioactive compounds, although some cultivars had higher content of all three analysed bioactive compounds such as Marathon, Ironman and General cultivar. In addition, these three cultivars showed excellent marketable properties and we choose them for the further breeding program in order to study variation among bioactive compounds in more details

Preparation and characterization of Cu and Zn modified nickel manganite NTC powders and thick film thermistors

A simple ball milling/thermal treatment procedure was applied to obtain fine thermistor powders. Three different powder compositions were analyzed–Cu0.2Ni0.5Zn1.0Mn1.3O4, Cu0.25Ni0.5Zn1.0Mn1.25O4 and Cu0.4Ni0.5Mn2.1O4. XRD analysis showed that all three powder compositions had a cubic spinel structure. Correlation between the sintering temperature, structure and resulting electrical properties was analyzed on bulk samples. Thick film pastes were composed and segmented thick film thermistors were screen printed on alumina, dried and fired. SEM analysis revealed a typical dendrite structure with small grains and a developed surface area. Thick film sheet resistance was measured on a test matrix and the resistance decreased with increasing Cu content. The temperature dependence of sample resistance was measured in a climatic chamber enabling calculation of the material constant and activation energy. Aging of the obtained segmented thermistors was analyzed and the resistivity drift was 0.23% for the Cu0.2Ni0.5Zn1.0Mn1.3O4 NTC thick film thermistor confirming greater stability of thermistors containing Zn and Cu that in combination with the determined good thermistor characteristics make them good candidates for temperature and heat loss sensor applications