Characterization of NTC thick film thermistor paste Cu0.2Ni0.5Zn1.0Mn1.3O4

A powder of Cu0.2Ni0.5Zn1.0 Mn1.3O4 composition for custom thermistor was prepared by using the respective mixture of metal oxides and solid state reaction at 1000 °C/4h in air. The obtained thermistor powder was milled in the planetary ball mill and agate mill for a prolonged time to achieve submicron powder. The prepared thermistor powder was further characterized by using XRD and SEM techniques. After that, the thermistor powder was pressed into small disc-shaped samples and sintered at 1150 °C/2h. The sintered samples were also characterized by using XRD and SEM. The main electrical properties such as nominal resistance R and thermistor exponential factor B were measured in the climatic test chamber. After that, the thick film paste was prepared using the same powder, an organic vehicle and a glass frit. The paste was printed on alumina substrate, dried at 150 °C /30 min and sintered in air at 850 °C /10 min in a hybrid conveyor furnace. Planar electrodes were printed on the sintered NTC thermistor layer using PdAg thick film paste. The electric properties of the sintered thick film thermistor were also measured in the climatic test chamber. The obtained results were used for development of novel self-heating thermistor applications

Three-Axis’ Heat Loss Anemometer Comprising Thick-Film Segmented Thermistors

NTC thick-film segmented thermistors were used as anemometer sensing devices. They were screen printed of thick-film thermistor paste based on modified NiMn2O4 fine powder, organic vehicle, and glass frit. Their electrical properties, such as resistance vs. temperature R(T) and thermistor exponential factor B were obtained using measurements in the climatic test chamber. A uniaxial anemometer was formed using a thick-film segmented thermistor, which was placed in the hole drilled in rectangular piece of thermally insulating material. The uniaxial anemometer was used for the optimization of operating point of segmented thermistors as self-heating/wind sensing devices. The dc supply voltage was correlated with the air temperature sub-ranges (RCV). The power save mode such as 30s self-heating/5 min pause was used to measure the thermistor response on stable wind blow. The three-axis' anemometer was formed using five sensor devices placed in five holes drilled in the cubical piece of thermally insulating material: three thermistor sensors measure wind speed on the x, y, z - axes, the fourth sensor Pt 1000 measures the air temperature T, while the fifth sensor (capacitive type) measures humidity H. The obtained sensitivity and inaccuracy were compared with respective ones of other anemometers

Characterization of NTC thick film thermistor paste Cu0.2 Ni0.5 Zn1.0 Mn1.3O4

A powder of Cu0.2Ni0.5Zn1.0 Mn1.3O4 composition for custom thermistor was prepared by using a certain mixture of metal oxides and solid state reaction at 1000 °C/4h in air. The obtained thermistor powder was milled in the planetary ball mill and agate mill for a prolonged time to achieve submicron powder. The prepared thermistor powder was further characterized by using XRD and SEM techniques. After that, the thermistor powder was pressed into small disc-shaped samples and sintered at 1150 °C/2h. The sintered samples were also characterized by using XRD and SEM. The main electrical properties such as nominal resistance R and thermistor exponential factor B were measured in the climatic test chamber. After that, the thick film paste was prepared using the same powder, an organic vehicle and a glass frit. The paste was printed on alumina substrate, dried at 150 °C / 30 min and sintered in air at 850 °C / 10 min in the hybrid conveyor furnace. The planar electrodes were printed on the sintered NTC thermistor layer using the PdAg thick film paste. The electric properties of sintered thick film thermistor were also measured in the climatic test chamber. The obtained results were used for development of novel self-heating thermistor applications

One-Step Synthesis of Biocompatible NaY0.65Gd0.15F4:Yb,Er Upconverting Nanoparticles for In Vitro Cell Imaging

There is a great technological interest in synthesis of lanthanide doped upconverting nanoparticles (UCNPs) with controlled crystal phase, morphology and intense luminescence properties suitable for biomedical use. A conventional approach for synthesis of such particles comprises decomposition of organometallic compounds in an oxygen-free environment, followed either with a ligand exchange, or biocompatible layer coating. Biocompatible NaY0.65Gd0.15F4:Yb,Er nanoparticles used in this study were synthesized through chitosan assisted one-pot hydrothermal synthesis and were characterized by X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and photoluminescence measurement (PL). Due to the presence of the amino groups at their surface, excellent biocompatibility and notably low cytotoxicity against MRC-5 cells (line of normal human fibroblasts) and A549 cells (human lung cancer cells) were detected using MTT assay. Furthermore, upon 980 nm laser irradiation, particles were successfully used in vitro for labeling of both, MRC-5 and A549 cells

One-Step Synthesis of Biocompatible NaY0.65Gd0.15F4:Yb,Er Upconverting Nanoparticles for In Vitro Cell Imaging

There is a great technological interest in synthesis of lanthanide doped upconverting nanoparticles (UCNPs) with controlled crystal phase, morphology and intense luminescence properties suitable for biomedical use. A conventional approach for synthesis of such particles comprises decomposition of organometallic compounds in an oxygen-free environment, followed either with a ligand exchange, or biocompatible layer coating. Biocompatible NaY0.65Gd0.15F4:Yb,Er nanoparticles used in this study were synthesized through chitosan assisted one-pot hydrothermal synthesis and were characterized by X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and photoluminescence measurement (PL). Due to the presence of the amino groups at their surface, excellent biocompatibility and notably low cytotoxicity against MRC-5 cells (line of normal human fibroblasts) and A549 cells (human lung cancer cells) were detected using MTT assay. Furthermore, upon 980 nm laser irradiation, particles were successfully used in vitro for labeling of both, MRC-5 and A549 cells

Three-Axis' Heat Loss Anemometer Comprising Thick-Film Segmented Thermistors

© 2001-2012 IEEE. NTC thick-film segmented thermistors were used as anemometer sensing devices. They were screen printed of thick-film thermistor paste based on modified NiMn2O4 fine powder, organic vehicle, and glass frit. Their electrical properties, such as resistance vs. temperature R(T) and thermistor exponential factor B were obtained using measurements in the climatic test chamber. A uniaxial anemometer was formed using a thick-film segmented thermistor, which was placed in the hole drilled in rectangular piece of thermally insulating material. The uniaxial anemometer was used for the optimization of operating point of segmented thermistors as self-heating/wind sensing devices. The dc supply voltage was correlated with the air temperature sub-ranges (RCV). The power save mode such as 30s self-heating/5 min pause was used to measure the thermistor response on stable wind blow. The three-axis' anemometer was formed using five sensor devices placed in five holes drilled in the cubical piece of thermally insulating material: three thermistor sensors measure wind speed on the x, y, z - axes, the fourth sensor Pt 1000 measures the air temperature T, while the fifth sensor (capacitive type) measures humidity H. The obtained sensitivity and inaccuracy were compared with respective ones of other anemometers

Modeling of the heat loss in a thermal sensor for water made of NTC thick film segmented thermistors

NTC thick film segmented thermistors were realized by screen printing of a low resistivity paste and conductive PdAg paste printed for electrodes. Two thick film thermistors as thermal sensors were placed in plastic tube housing connected to the water mains to form a calorimetric type of flow-meter, e.g. to measure the input water temperature and the thermistor self-heating temperature. Range constant voltage (RCV) was applied for self-heating thermistor power supply in different ranges of input water temperature. Modeling of the heat loss in the flow-meter for water was derived from heat balance equations for a self-heated thermistor in static water and in water flow conditions (static and dynamic thermistor temperature). Both temperatures (static and dynamic) were related to self-heating currents. The input water temperature was measured independently by a cold thermistor. Other parameters such as water thermal conductivity, thermistor exponential factor B and nominal thermistor resistance at room temperature were included in the thermistor heat balance equations. The logarithmic behavior of self-heating thermistors in the water flow enable modeling of heat loss as a function of static and dynamic currents related to static and dynamic thermistor temperatures. The model achieved was used in the fitting procedure of measured data of the flow-meter response