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

Structural features of near equiatomic FeCo-2V semi-hard magnetic alloy prepared by MIM technology

The structural properties of a magnetically semi-hard near equiatomic FeCo-2wt%V (FeCoV) alloy produced by Powder Injection Moulding (PIM) (option by fine metal powder - Metal Injection Moulding (MIM) technology) were investigated in this paper. Starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology was completed by high-temperature sintering for 3.5 hours at temperatures from 1370 OC to 1460 OC in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics. The influence of sintering temperature was investigated concerning the aspects of the processes of structural transformation by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The appearance of an intense diffraction peak of the α'-FeCo phase (crystal structure type B2) was registered for all investigated samples. Structural parameters particle size Dmax, Feret X, and Feret Y exhibit constant increase with increase of sintering temperature

Magnetic features of MnZn ferrite for electronic applications

MnZn ferrites are one of the most common soft magnetic materials for application in microelectronics as a material for microwave components (transformers, transducers, inductors, magnetic fluids, sensors,). MnZn ferrites attracted attention due to wide range of relative magnetic permeability values (from 103 to 104), high resistivity (consequently low magnetic losses) as well as high thermal stability (high saturation magnetic flux density at high temperatures (Bs > 0.4 T at 100 OC) and a relatively high Curie temperature of about 230 OC).Recently, a variety of technologies have been examined for MnZn ferrite production: powder/ceramic injection moulding (PIM/CIM), chemical co-precipitation method, conventional ceramic processing, sol-gel or microemulsion. In this study a toroidal samples of MnZn ferrites with dimensions appropriate for applications in electronic industry (i.e. microelectronics: inner diameter 3.5 mm, outer diameter 7 mm, height 2 mm) were investigated. Magnetic properties were measured by hysteresis graph (B-H curve at level of magnetic excitation up to 1 kA/m and at different frequencies from 5 Hz to 10 kHz). Relative magnetic permeability as well as magnetic power (active) losses was analyzed as frequency dependent. Very stable maximum magnetic permeability was observed for magnetic field of 200 A/m in the frequency range from 50 Hz (μr ≈ 480) to 10 kHz (μr ≈ 450). Active power referred to unit mass of about 30 W/kg was recorded at frequency of 1 kHz (@ 280 mT). As the hysteresis losses are proportionally to the frequency (~ f) and eddy-current losses are proportionally to the square of frequency (~ f2) it was performed separation between these two components from total magnetic power (active) losses. Numerical fitting of this functionality on frequency were performed and analysed. The results obtained were compared with the catalogue data for other MnZn ferrite components for applications in electronics

Frequency behaviour of Co-based amorphous wire MI-element

This study presents magnetoimpedance (MI) effect of Co-based amorphous wire investigated at driving frequency range f [50 Hz – 5 MHz]. The XRD pattern and EDX analysis confirmed amorphous structure and the main element content of CoFeSiB alloy. The critical frequency of about 7 kHz was observed as the point with the initial increase of magnetoimpedance. A maximum MI-ratio [Z(0) - Z(Hmax)] / Z(Hmax) of 334 % is attained at driving frequency of 900 kHz@ Hmax 4.63 kA/m

The influence of mechanochemical activation and thermal treatment on magnetic properties of the BaTiO3 -FexOy powder mixture

Powder mixture of 50 mass % of barium titanate (BaTiO3) and 50 mass % of iron (Fe) was prepared by solid-state reaction technique, i.e. ball milled in air for 60 min, 80 min, 100 min, 120 min and 150 min. During mechanochemical activation it was observed the iron powder transitsion to iron oxides. Depending on the activation time the content of iron oxides FeO, Fe2 O3 and Fe3O4 varies. Simultaneously, with the content change of the activated system, magnetic properties change as well. The XRD analysis of milled samples shown that as the activation time increase, the iron oxide percentage increases to, whereby the percentage of BaTiO3 in a total sample mass decreases. The percentage of iron oxides and BaTiO3 in annealed samples changes depending on annealing temperature. The thermomagnetic measurements performed by Faraday method shown that the powder mixture milled for 100 minutes exhibit maximum magnetization prior to annealing. The increase of magnetization maximum was observed after annealing at 540 oC with all milled samples, and at room temperature it has enhancement from 10 % to 22 % depending on the activation time. The samples milled for 100 min and 150 min and then sintered at 1200 oC exhibit magnetoelectric properties. © 2015 International Institute for the Science of Sintering (IISS). All rights reserved

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

Ispitivanje strukturnih svojstava legure FeCoV metodom skenirajuće elektronske mikroskopije - SEM

U radu su ispitivani strukturna svojstva legure 49Fe49Co2V proizvedene PIM/MIM tehnologijom, tako što je polazni granulat pripremljen mešanjem FeCoV praha sa niskoviskoznim vezivom. Nakon brizganja sirovi uzorci su najpre tretirani rastvaračem a zatim i termički s istim ciljem odstranjivanja veziva. MIM tehnologija je završena visokotemperaturskim sinterovanjem tokom 3,5 sata na temperaturama od 1370 °C do 1460 °C u atmosferi vodonika, kojim se obezbedjuju potrebne magnetne i mehaničke karakteristike. Strukturna svojstva veličine čestica Dmax, Feret X, Feret Y su ispitivana u zavisnosti od temperature sinterovanja

Structural properties of FeCoV alloys produced by PIM / MIM technology

FeCoV alloys with high saturation magnetization and high Curie temperature, making them useful for high-temperature and power-dense applications (e. g. aviation device). In this study, we report the results of observing the structural properties of 49Fe49Co2V alloy produced by PIM / MIM technology. The starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the raw “green” samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology is completed by high-temperature sintering of “brown” samples for 3.5 hours at temperatures from 1370 OC to 1460 OC in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics. Depending on the sintering temperature, structural parameters of particle size Dmax, Feret X, Feret Y were investigated and analysed

Correlation of crystallization process and thermal dilatation behavior in FeCrMoGaPCB bulk metallic glass

Uzorci amorfne masivne metalne legure sastava Fe65.5Cr4Mo4Ga4P12C5B5.5 dobijeni su tehnologijom livenja rastopa u bakarne kalupe prečnika 1,5 mm i 1,8 mm. DTA analizom je utvrdjena temperatura kristalizacije TX = 810 K. S ciljem ispitivanja procesa termičkog širenja (dilatacije) sprovedeni su višestruki termički tretmani do oko 200 K iznad temperature kristalizacije. Uticaj procesa kristalizacije na termičko širenje je izučavan preko temperaturske zavisnosti koeficijenta termičkog širenja koji pokazuje evidentne promene tokom kristalizacije za razliku od skoro konstantne vrednosti kod legure u iskristalisanom stanju. Stereološkom i XRD analizom su praćene promene strukture iz amorfne u mikrokristalnu. S obzirom na sastav legure kojim se težilo poboljšanju mehaničkih svojstava sprovedena su kontrolna merenja tvrdoće koja su pokazala povećanje HV1 sa vrednosti od oko 713 u amorfnom stanju do preko 876 u mikrokristalnom stanjuBulk metallic glass with nominal composition Fe65.5Cr4Mo4Ga4P12C5B5.5 was prepared by cooper mold casting with 1.5 mm and 1.8 mm diameter cylinders. Crystallization temperature TX= 810 K was observed by DTA analysis. Repeated thermal treatments were performed to about 200 K over the crystallization temperature in order to investigate thermal dilatation effects. Structural changes were examined by optical microscopy and XRD analysis. Intensive changes of thermal dilatation coefficient was observed during crystallization process of amorphous structure. However, during the second heating run already crystalline structure exhibit almost constant value of thermal dilatation coefficient. Hardness test shows the increase of HV1 value from about 713 for as-cast samples to about 876 in microcrystalline state

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