Hot Plate Temperature Research Articles

Extreme Chemical Reduction on Photoresist Stripping Process by Using Sulfuric Acid Ozone Mixture in Liquid Film

IntroductionSulfuric peroxide mixture (SPM) has been widely used in the photoresist (PR) stripping process of semiconductor manufacturing. However, the consumption of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) increase environmental burden such as water pollution. To reduce the chemical consumption, one of the ideas is that chemicals are supplied to the wafer until liquid film is formed and stopped during PR stripping process instead of continuous dispensing. It is concerned that chemical species in SPM become inactive while chemicals are stopped. Therefore, in this work, H2SO4 liquid film is formed on the wafer and then exposed to ozone (O3) atmosphere so that chemical species remain active. Peroxydisulfuric acid (H2S2O8) is generated by reacting H2SO4 with O3 and dissociates in peroxydisulfate ion (S2O8 2-) which is one of the chemical species for PR stripping. [1-2] In this study, PR removal efficiency and removal time of SOM in liquid film was evaluated and activation energy of the chemical species generated in SOM was calculated. ExperimentalSample: 435 nm thickness Boron (B) doped 5E+15 /cm2 5 keV KrF PR film was coated on 300mm Si wafer. And two kinds of 435 nm thickness KrF PR film, which were Arsenic (As) doped 1E+15 /cm2 10 keV and B-doped 1E+16 /cm2 10 keV, were coated on patterned 300mm Si wafer respectively. (Supported by AIST, Japan)Stripping process: SOM process was performed in a O3 gas chamber on a single coupon/wafer cleaning tool. Coupon size was 25mm x 25mm. H2SO4 was heated to 60°C and then supplied to the wafer. Hot plate was heated to 140~250°C. O3 concentration was 200 g/Nm3 and O2/O3 flow rate was 3 L/min. Experiment was conducted on coupon and 300 mm wafer with consumption of H2SO4 among 0.06ml to 0.5ml and 80ml respectively.Characterization: Stripping images of PR were observed by optical microscope (OM), and removal efficiency was calculated in image binarization method by using ImageJ software. PR residues were observed by scanning electron microscope (SEM). The activation energy of chemical species in SOM were verified by Ab initio calculation between S2O8 2- and peroxomonosulfate ion (HSO5 -). Results/discussionWith a little quantity of H2SO4, B-doped 5E+15 PR coupon with 0.3ml H2SO4 liquid film had the best removal efficiency between 0.06ml to 0.5ml. (Fig. 1) It was considered that quantity of H2SO4 should be moderate. With higher hot plate temperature, both As-doped and B-doped PR removal efficiency of patterned coupon were also higher with 0.3 ml H2SO4. At 250°C, the removal efficiency of As-doped 1E+15 was 99% and B-doped 1E+16 was 87% which was comparable to SPM with 170°C-H2SO4 and room temperature (RT) H2O2 mixture in the same process time. (Fig. 2) On 300 mm wafer, As-doped 1E+15 took 120 seconds for PR stripping by SOM in 80ml H2SO4 liquid film at 250°C and it was better than SPM with 90°C-H2SO4 and RT-H2O2 mixture. (Fig. 3) SEM images of the PR residues were observed in the dashed line block of OM images, and it was considered that PR collapse was the reason why PR residues were hardly removed. (Fig.4) By the Ab initio calculation, S2O8 2- had the activation energy of 0.78 eV which was lower than HSO5 -(1.79 eV). It’s implied that the reaction of S2O8 2- generation at higher rate was proved by the Ab initio calculation results. (Fig.5) ConclusionA novel PR stripping method of “expose H2SO4 to O3 atmosphere in liquid film” was developed to reduce the chemical consumption. This method was comparable to conventional SPM even though chemical consumption is lower, and it is expected to be next generation cleaning technology with smaller environmental burden.

The Effect of Blended Palm Oil Biodiesel Droplet Properties on Evaporation Characteristics

The evaporation characteristics of a single fuel droplet of diesel fuel (DF) and the Malaysian palm oil biodiesel-diesel blend (B10-B50) were studied experimentally. The fuel droplet properties consisted of different ratios of palm oil biodiesel mixtures which could influence the droplet behaviour when impinged on the heated surface. By employing the hot surface deposition test (HSDT) method, the droplets impinging on the heated surface of an aluminum alloy plate were observed to evaluate the droplet's evaporation characteristics including the evaporation lifetime and maximum evaporation point (MEP) of the tested fuels. Furthermore, the deposit’s surface temperature for dry condition (timp=7 seconds) and wet condition (timp=3 seconds) test were also measured during the deposition test. Finally, the deposit development on the heated surface was evaluated through a logarithmic expression of MR/mD = αNDβ. The results showed that the evaporation lifetime of each test fuel decreased with increasing hot plate surface temperature. Furthermore, the MEP was the highest for B30 (380°C), followed by B20 and B40 (375°C), B10 and B50 (365°C), and DF (360°C). In the dry condition test, the recorded average minimum and maximum deposit surface temperatures were observed to be within the range of Td=295°C to Td=325°C for DF and Td=290°C to Td=350°C for B10-B50 fuels. On the other hand, for the wet condition test, the recorded average minimum deposit surface temperatures for both DF and B10-B50 fuels were consistently lower than the hot plate temperature. DF exhibited the most variation, ranging from Td=200°C to Td=300°C, whereas, for B10-B50, the recorded deposit surface temperature was only ranging from Td=150°C to Td=200°C.

A source-to-surface model of heat and fluid transport in the Taupō Rift, New Zealand

We construct 2-D numerical models of bulk heat and water transport from the mid-crust (10 km depth) to the surface in a 20 km-wide continental rift, based on observations from the Taupō Rift in the central Taupō Volcanic Zone (TVZ) of New Zealand.The model represents a simplified geological setting with two low-permeability basement-like rock-types, the first defining the margins of the rift and the second a distinct ‘rifted basement’. The rift is overlain with a 2 km-thick, 20 km-wide layer of shallow volcanic infill. At the base of model there is a 10 km-deep heat source (the ‘hotplate’) with a specified TVZ-like heat flux of 0.77 Wm−2 and a ‘target’ average hotplate temperature of 700o to 900 °C, required to maintain the low melt fractions at ∼10 km depth inferred from geophysics.Parameterising the permeability of the rifted basement is a key part of the paper as it enables both the heat flux boundary condition and a temperature constraint to be satisfied at the hotplate. More generally, it allows the flexibility to control the depth of temperature contours which represent proxies for geophysical measurements. It is described as a power-law for log10(horizontal component of permeability, kh) with specified values of kh at two depths and a power law exponent as free parameters. Viable models which satisfy all constraints for the hydrothermal system beneath the TVZ rift have a power-law exponent less than ∼0.4, shallow (2 km deep) kh's of 10–14.0 to 10–13.0 m2, and deep (10 km) kh‘s <10–16.5 m2. The vertical component of the rifted basement permeability, kv, is ten times higher than kh.A generic feature of the models is that irregular, unsteady convection occurs in the upper ∼5 km of the rift. This results in temporal and spatial fluctuations in heat and fluid flow which are interpreted as high-temperature TVZ-like geothermal systems which have temperatures of ca. 300 °C at 2 km depth. Over the nominal simulation time of 3 Myr, approximately 40% of the geothermal systems are clustered within ∼2 km of the rift margins, with the remainder distributed roughly uniformly across the rift. Between the geothermal systems cool recharge from the surface occurs, with temperatures as low as 50 °C occurring at 5 km depth. The models successfully match temperature proxies for the depths of maximum seismicity (450 °C) and shallowest partial melt (> 700 °C) inferred from geophysical observations.Heat transport within the rift is dominated by convection. This is true even at 10 km depth, at the base of the geothermal systems, where kh in the rifted basement approaches 10−17 m2. In this situation, the relatively large value of vertical permeability kv, ∼ 10−16 m2, allows convection to occur. Conductive heat transport dominates in regions ∼1 km in vertical extent immediately above the hotplate and between the geothermal systems.The vigour of the hydrothermal systems is controlled by the permeability of the shallow volcanics, through which all cold surface recharge and hot outflows of fluid occur. Models with low permeability for the shallow volcanics produce longer lasting and higher temperature geothermal systems, and those with high permeability produce fewer and cooler geothermal systems.

Designing an Accurate Temperature Control System for Infrared Earth Simulators Using Semiconductor and Air Cooling Integration.

In a laboratory environment, in order to test the attitude recognition capability and accuracy of the satellite attitude sensor-the infrared Earth sensor-the infrared Earth simulator is fixed on a five-axis turntable to enable multi-angle testing. In the past, the temperature control system of the Earth simulator was water cooled, which not only affected the working accuracy of the Earth simulator but also affected its size and portability and made it more difficult to use on the turntable. Therefore, we designed a cooling method for the cold plate based on semiconductor cooling technology combined with air cooling, and we designed a fuzzy PID control algorithm to accurately control the temperature according to this cooling method. In this article, we use SOLIWORKS to build the system model for the system and use the ANAYS Workbench to perform temperature analysis of the Earth simulator. The results show that the cold plate temperature can be maintained at 20.089 °C when the hot plate temperature is 85 °C. The overall temperature uniformity of the hot plate is better than ±0.3 °C, which meets the index requirements of the Earth simulator. We found that this cooling method can replace water cooling, giving the simulator the advantage of being miniaturized, and it can be adaptable to the turntable, which can be widely used in various sizes of Earth simulators and in various complex environments and operating conditions.

Temperature Evolution and Heating Rates of Biomass undergoing Ablative Pyrolysis

The ablative reactor may be employed to enable fast pyrolysis to produce bio-oil from relatively large-sized biomass samples. Ablation mainly involves direct compressive force and conductive heat transfer between a hot surface and the biomass materials. Temperature evolution and heating rates are important operating factors in the biomass thermal conversion process. In this work, experimental and analytical investigations were carried out for different vertical dimensions of the biomass samples (2-20mm) and hot plate temperatures (400-550°C). It was shown that the thermal characteristics of the biomass were mainly affected by the transient conditions. It was observed that volatile release occurred during the transient heat transfer periods. It was found that at the maximum hot plate temperature of 550°C, the highest heating rate that could be achieved by ablation was more than 600°C/min.

Determination of toxic elemental levels in whey milk of different cattle and human using an innovative digestion method: risk assessment for children < 6.0 months to 5 years.

In present study, the toxic elements, arsenic (As), cadmium (Cd), and lead (Pb), were determined in whey milk samples obtained from various cattle (cow, goat, buffalo, sheep, camel) and human subjects of different areas of Sindh, Pakistan, based on consuming drinking water (exposed area) and surface water (control/non-exposed area). The whey milk was separated from casein by lowering the pH, and heating in an ultrasonic bath at 60 °C for 5 min and centrifuged. The whey milk samples were treated with deep eutectic solvent, prepared from choline chloride-oxalic acid (ChCl-Ox) at different mole ratio. Effects of different parameters on digestion efficiency of whey milk samples, including time and temperature of electric hot plate, mole ratio, and volumes of deep eutectic solvent were examined. The total levels of all selected toxic elements were also detected in whole milk samples of all exposed and nonexposed cattle and human, after acid digestion method. The validity of the proposed method was established by a conventional acid digestion method of selected whey milk samples and spiked certified standards in replicate real whey milk samples. The resulted elements obtained after proposed and conventional heating system were determined by inductively coupled plasma-optical emission spectrometry. The % of all three toxic elements found in whey milk samples were 24 to 50% of their total content in milk samples of different cattle and human. The As, Cd, and Pb contents in cattle and human milk consumed contaminated groundwater was significantly higher (2- to 3-fold) than those values observed for milk samples of cattle, who receive drinking water from fresh canal water (p < 0.01).Estimating the daily intake, hazard quotient and carcinogenic risk for <6 month to 5 years old children, based on the concentrations of toxic elements in milk samples of different cattle and human..

Cooperative Control of Recurrent Neural Network for PID-Based Single Phase Hotplate Temperature Control Systems

Cooperative Control of Recurrent Neural Network for PID-Based Single Phase Hotplate Temperature Control Systems

Co-precipitation synthesis of LaFe1-xAlxO3 (x = 0–0.2) on structure and electromagnetic properties

The synthesis of LaFe1-xAlxO3 (x = 0–0.2) on the structure and electromagnetic properties using the co-precipitation method were evaluated. LaFe1-xAlxO3 (x = 0–0.2) materials were synthesized using lanthanum chloride and natural iron sand powders. The mixing process of precursors was held with a hotplate temperature of 60 °C. The calcination process was done at 400 °C for 2 h. Then samples were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM), and CV meter. The XRD patterns result in two phases of LaFeO3 and Fe2O3. SEM images were performed that the powders are porous agglomerates. The particle size distribution is shown in the histogram that the samples are in the range of 50–500 nm, respectively. Then, the magnetic properties measurement of VSM analysis studied the substitution of Fe to Al ions decreases magnetic properties and BHmax in LaFe1-xAlxO3 (x = 0–0.2). The I-V measurements conducted the substitution of Fe to Al ions increase with a nonlinear reversal current in LaFeO3. These results show that LaFe1-xAlxO3 (x = 0–0.2) was recommended as the magnetic permanent material and perovskite material based on electromagnetic properties.

Determination of the ignition temperature of hay for the purposes of fire risk assessment on farms - Slovak case study

Hot surfaces are an integral part of the technological processes of agricultural crop processing. Their surface temperature at critical points can exceed the minimum ignition temperature. This paper aims to experimentally observe the behaviour of hay when exposed to radiant heat. The model presented here is implemented using a hot plate device. The hot plate has a defined temperature-time curve. Based on the above, the hot plate temperature is determined as the minimum ignition temperature of the investigated hay specimen. At the same time, the temperature inside the tested material was monitored. The heterogeneity of the above specimens significantly influenced the nature of the biomass thermal degradation. The ignition temperature of the hay (406 °C) can serve as a tool for fire risk assessment.

Effect of using natural and local environment contents on the thermal conductivity of building materials; case in Medina, Saudi Arabia

The previous literature indicated that thermal characteristics of the local environment of Medina were not addressed despite its apparent importance and abundant availability. The aim of this study is to investigate the use of local environment contents in buildings, its thermal effect and obtain the optimum content that minimizes energy cost. Experimental investigation on thermal conductivity of building materials was conducted on seven different samples at 60 °C hot plate temperature. Thermal conductivity values of volcanic tuff, rose, green and limestone rocks were found between 0.12 and 0.211 W/m k, 0.5195–1.1035 W/m k, 0.21–0.334 W/m k and 0.209–0.5582 W/m k respectively. It was concluded that the thermal conductivity of the mixture of cement with stones and sand extracted from the Medina region varied between 0.388 and 0.4155 W/m k, which showed a decrease of 37.75%–49.74% when compared with the reference value of cement at 0.78–1.1 W/m k.

Characteristics of self–ignition and smoldering of coal dust layer under inclination conditions

In many actual industrial scenes, the coal body and coal dust are not always in the tiled state, but in the inclined situation. A two – dimensional transient numerical model of coal oxidation reaction was established to study the self–ignition and smoldering characteristics of coal dust layers in the presence of inclination angle. The effects of gravity and thermal buoyancy were considered to solve the coupling problem of coal oxidation reaction and air flow. The results show that the growth coefficients of minimum ignition temperature of coal dust with thicknesses of 6.4 mm, 12.7 mm, 19.1 mm and 25.4 mm are 0.117 °C/°, 0.0467 °C/°, 0.033 °C/° and 0.033 °C/°, respectively. With the increase of hot plate temperature, the inclination of coal dust can greatly shorten the ignition delay time (IDT). The ΔIDT of coal dust inclination of 60° is 128 s/°C greater than that of 0°. The movement of high temperature point of coal dust in self–heating development stage is from the inside to the outside, and that in decaying stage is from the outside to the inside. In addition, some interesting phenomena in the process of coal self–ignition and smoldering have also been found. The influence of coal dust inclination on its self–heating is mainly reflected in the location of high temperature points and the spread of smoldering. This study is helpful to understand the characteristics of coal dust self–ignition and smoldering spread in inclined situation, and can guide the prevention of coal dust self–ignition.

Simulation Study of Ignition Characteristics of Impinging Sprays in Constant Volume Chamber

The present study involves the simulation of a constant volume, non-premixed, hot surface spray combustion of diesel fuel for a given set of injection pressure, compressed air pressure (cylinder air pressure) and hot surface temperature (hot plate temperature) and their effects on ignition delay period. Fuel injection pressure was varied from 100 bar – 300 bar in steps of 100 bar, cylinder air pressure in the range of 20 bar to 40 bar (in steps of 10 bar) and hot surface temperature from 623 K to 723 K (50 K steps). The problem was solved using 2D axisymmetric geometry. A structured mesh of about 1.24 lac nodal points was created and tested for grid independency. For solving flow behavior, a pressure solver was used with a turbulence model of k-ε with enhanced wall functions. While a volumetric eddy dissipation model was used to solve combustion phenomena. Ignition delay period was calculated with the help of static temperature versus time plot. It is found that keeping any two operating parameters constant, third operating parameter is inversely proportional to ignition delay period. The results of the present simulation study are in a fairly good agreement with the experimental studies at same operating conditions.

Modeling and Simulations of the Sulfur Infiltration in Activated Carbon Fabrics during Composite Cathode Fabrication for Lithium-Sulfur Batteries

During the manufacture of a composite cathode for lithium-sulfur (Li-S) batteries it is important to realize homogeneous infiltration of a specified amount of sulfur, targeted to be at least 5 mg cm−2 to achieve good battery performance in terms of high energy density. A model of the sulfur infiltration is presented in this study, taking into account the pore size distribution of the porous cathode host, phase transitions in sulfur, and formation of different sulfur allotropes, depending on pore size, formation energy and available thermal energy. Simulations of sulfur infiltration into an activated carbon fabric at a hot-plate temperature of 175 °C for two hours predicted a composite cathode with 41 wt% sulfur (8.3 mg cm−2), in excellent agreement with the experiment. The pore size distribution of the porous carbon host proved critical for both the extent and form of retained sulfur, where pores below 0.4 nm could not accommodate any sulfur, pores between 0.4 and 0.7 nm retained S4 and S6 allotropes, and pores between 0.7 and 1.5 nm contained S8.

The effect of data sampling time on the accuracy of maximum output power of a thermoelectric module

The instantaneous short-circuit current and open-circuit voltage of TEM (Thermoelectric Module) can be used to quickly estimate its maximum output power (P omax). Because of their instantaneous samples, the sampling time has a great influence on the accuracy of the estimated result. In this paper, the influence mechanism of sampling time is analysed systematically and a module of TEG1-127-2.8-1.2-250 is taken as a sample for verification. By means of either steady open-circuit/instantaneous short-circuit at mode A or steady short-circuit/instantaneous open-circuit at mode B, P omax can be estimated quickly. At single mode A or B, the shorter the sampling time is, the greater the relative error of the estimation of P omax has. This error varies with different temperature of hot plate, but the variation trend with sampling time is consistent. The valuations at model A and B are larger and smaller than the accurate values, respectively. When the sampling time is 600 to 1000ms, the error is the smallest (less than 3%). The accuracy of P omax is significantly improved by using the average results of mode A and B. In this way, the sampling time has little influence on the estimation error, and the shortest sampling time corresponds to the highest estimation accuracy.

Kinetic parameters identification of conductive enhanced hot air drying process of food waste

The efficient utilization of waste from food industry is possible after thermal treatment of the material. This treatment should be economically feasible and compromise the energy efficient drying process. The main goal of this investigation is to determine drying characteristics of nectarine pomace as a waste from food industry. The measurements were performed in an experimental dryer by combined conductive-convective drying method with disk-shaped samples of 5, 7, and 10 mm thickness and 100 mm in diameter at the air temperatures of 30, 40, 50, 60, and 70?C, hot plate temperatures of 50, 60, and 70?C and air velocity of 1.5 m/s. The drying curves were compared to a few semi-theoretical mathematical models. The Logarithmic model showed the best correlation. On the basis of experiments, it is determined that the drying process takes place in a falling rate period and it is accepted that the main mechanism of moisture removal is diffusion. The effective coefficient of diffusion was determined using experimental results by calculating the slope of the drying curves. Drying time and equilibrium moisture are determined for each experiment. Analysis of drying curves showed that the conductive-enhanced drying method reduces drying times and increases the diffusivity coefficient. The character of drying rate curves for conductive-enhanced drying was analysed and compared with pure convective drying of nectarine pomace.

Does social thermal regulation constrain individual thermal tolerance in an ant species?

In ants, social thermal regulation is the collective maintenance of a nest temperature that is optimal for individual colony members. In the thermophilic ant Aphaenogaster iberica, two key behaviours regulate nest temperature: seasonal nest relocation and variable nest depth. Outside the nest, foragers must adapt their activity to avoid temperatures that exceed their thermal limits. It has been suggested that social thermal regulation constrains physiological and morphological thermal adaptations at the individual level. We tested this hypothesis by examining the foraging rhythms of six populations of A. iberica, which were found at different elevations (from 100 to 2,000m) in the Sierra Nevada mountain range of southern Spain. We tested the thermal resistance of individuals from these populations under controlled conditions. Janzen's climatic variability hypothesis (CVH) states that greater climatic variability should select for organisms with broader temperature tolerances. We found that the A. iberica population at 1,300m experienced the most extreme temperatures and that ants from this population had the highest heat tolerance (LT50=57.55°C). These results support CVH's validity at microclimatic scales, such as the one represented by the elevational gradient in this study. Aphaenogaster iberica maintains colony food intake levels across different elevations and mean daily temperatures by shifting its rhythm of activity. This efficient colony-level thermal regulation and the significant differences in individual heat tolerance that we observed among the populations suggest that behaviourally controlled thermal regulation does not constrain individual physiological adaptations for coping with extreme temperatures.

Numerical model and analysis of heat transfer during microjets array impingement

In this paper heat and fluid flow characteristics during impingement of an array of microjets was numerically investigated. The numerical model which was based on the compressible steady-state Navier-Stokes equations and SST k-ω turbulence model was developed. Then an array of 8 × 8 microjets which impinged on a hot surface was analyzed. The influence of both a ratio of a distance between a nozzle and hot plate (H/d) as well as a microjet diameter-based Reynolds number (Red) on both the local and average temperature and heat transfer coefficient (HTC) on the surface of the hot plate were numerically studied. During simulations the ratio of the distance between the nozzle and hot plate to the microjet diameter was H/d = 3.125, 25 and 50, while the microjet diameter-based Reynolds number was equal to Red = 690, 1100 and 1510. It was found that the H/d ratio and Red significantly influenced flow patterns in the gap between the nozzle and hot plate as well as the temperature and HTC on the surface of the hot plate. With increase of the H/d ratio a more uniform distributions of the plate temperature and HTC were observed. Moreover, differences between extreme values of these parameters decreased. The optimal ratio of the distance between the nozzle and hot plate to the microjet diameter was calculated to be H/d = 25. Increasing or decreasing of this ratio resulted in the higher average temperatures and lower average values of the HTC on the hot plate. For the small value of the H/d ratio (i.e., H/d = 3.125) the influence of the microjet flow on adjacent microjets was vestigial. The area of the hot plate which was influenced by impinging microjets was small and degradation of the microjet velocity profile was negligible, i.e., high-speed microjets impinged the plate. Air from the microjet flowed above the hot plate and left the zone through spaces between adjacent microjets. For higher values of the H/d ratio influence of the microjet flow on adjacent microjets was observed. The microjet left the nozzle and greatly expanded, while its velocity profile was degraded. The area of the hot plate which was influenced by impinging microjets was large and the microjet velocity was low. Due to significant enlargement of the size of the microjet, it interacted with adjacent microjets, which resulted in the lost of their axisymmetric shape. Moreover, air from the microjet flowed above the hot plate and affected adjacent microjets. The rise in the Red intensified mentioned effects as well as heat transfer intensity on the hot plate. Moreover, the increase of the Red resulted in the decrease of the average temperature of the heater surface as well as the increase of the average HTC regardless the height of the microjet. Calculated average hot plate temperatures were also compered with experimentally measured temperatures and the good matching was found. However, much slower degradation of microjet profiles was observed in experiments than predicted numerically.

Propensity to self-heating ignition of open-circuit pouch lithium-ion battery pile on a hot boundary

The fire safety issue of Lithium-ion (Li-ion) batteries is an important obstacle for its market growth and applications. Although the open-circuit condition (e.g. storage, transport and disposal) accounts for the major part of battery lifespan, little research has investigated its self-ignition hazard during non-operating periods. In this work, we experimentally study the self-heating behavior of piled pouch Li-ion battery cells through the classical hot-plate experiments. Results show that the self-ignition of battery pile occurs under a hot plate temperature ranging from 199 °C to 265 °C, depending on the number of cells and environmental cooling. Thermal runaway always first occurs to the cell next to the hot plate and then propagates to upper cells. This critical temperature is increased by 20 °C under a good environmental cooling condition whereas it is reduced by 40 °C as the state of charge increases from 30% to 80%. Moreover, the critical plate temperature for self-ignition increases slightly with the height of battery pile, which is opposite to both hot-plate experiments of hydrocarbon materials and the oven experiments of battery. Therefore, the classical self-ignition theory may not be applicable for Li-ion batteries next to a hot boundary. This research reveals new self-ignition phenomena and helps understand the fire safety of Li-ion batteries in storage and transport.

SOI Based Low Power Thermocatalytic Sensor with Nanostructured Gas Sensitive Material

Introduction Catalytic gas sensors are essential devices for detection of combustive gases near lower explosion limit (LEL). As the minimum power dissipation of Pt coil based sensors (pellistors) are 120 - 150 mW [1] intensive research is devoted to reduce it to be better compatible with portable devices while preserving sensitivity and stability. The reported microheater structures can operate up to 600 oC at a cost of 20-50 mW power consumption [2]. Nowadays the research activity is focused on development of stablenanostructured catalyst layer effective at low temperature, whereas compatible with MEMS thick film technology. Gas Sensitive Catalytic Materials The approach of fabrication gas sensitive material for coil and silicon membrane sensors is different. In first case the catalyst is bulky and forms bead or cylinder with diameter 400-500µm. In MEMS structures the catalyst is deposited on a microhotplate with a characteristic diameter of 100µm, de facto forming 2D surface. In the present work nanodespersed Al2O3 and ZrO2 ceramic carriers were prepared as presented on figs.5 and 6, respectively. Each material was divided into two equal parts - an active catalytic layer from one part and a comparative element from the second part were made exhibiting equal surface area. .In order to impregnate the catalyst support with the catalyst metal, salts of palladium chloride (PdCl2) and platinum acid (H2PtCl6) were used. Having annealed at high temperature metal clusters were formed in the catalyst support. Finally the active and reference materials were mixed with an organic binder to make the paste suitable for drop-coating deposition to MEMS silicone microheater. SOI Based MEMS Microheater Uniform and reproducible crystalline Si filaments were formed from SOI (silicon on insulator) wafers, because the buried oxide provides uniform thickness of the device layer and guarantees identical geometry. Cantilevers are suspended on stress compensated SiO2-Si3N4 membrane to increase their mechanical stability and eliminate their bending out of the original plane (fig. 1-4). Thereby the reduced stress provides longer lifetime. The higher resistivity of device silicon ensures higher filament resistance at the same temperature compared to its thin film metal reference, therefore the cross section of the current routes should be increased to achieve the sufficient resistance. A plausible advantage of the single crystalline filament material and the design is the minimized degradation effect of electromigration, thereby the lifetime of the heater is expected to achieve 6000-8000 hours. Moreover, the heated area of filament can be completely covered with catalyst or passive material, similarly to the coil-type filament devices.The opened side chip design facilitates catalyst deposition. Results and Conclusions Significant issues arise when the design of thermocatalytic sensors are transferred from the volumetric to the microplanar approach. First of all, the catalytic gas-sensitive layer must provide chemical activities:3∙10-6÷10-5mW/μm3. The solution of the problem is to choose classical materials alreadybeen used for many years in coil types pellistors - catalysts of platinum group metals on Al2O3 or ZrO2 ceramic carriers. The stability and behavior of these materials at high working temperatures has been already tested over tens of years in real working conditions (mains, gas line pipes, leakage alarm systems and etc.). The decrease in the quantity of the catalytic material deposited on the microheater leads to insufficient catalytic activity of the sensor as a whole. An increase in the operating temperature can correct the situation, but it is limited by the long-term stability of the microheater and the transformation of the crystallographic phase of the ceramic catalyst carrier. The critical temperature is around 550 °C. The Pt-Pd mixed-catalysts can be applied in the microplanar structure if uniform hotplate temperature is provided and the active and the reference sensing layers are deposited such as to minimize imbalance between the two elements. Acknowledgement This research was sponsored by the Sponsored by the National Research, Development and Innovation Office Foundation, Hungary, funding No. 2017-2.3.4-TeT-RU-2017-00006, and the Ministry of Science and Higher Education of the Russian Federation founding with unique identifier RFMEFI58718X0053.

Study of droplet dynamics and condensation heat transfer on superhydrophobic copper surface

Superhydrophobic surface for dropwise condensation is prepared using hotplate solution immersion method on copper substrate. The preprocessed bare copper plate is immersed in a solution consist of 0.004-0.008 M ethanol (CH3-CH2-OH) and tetradecanoic acid (CH3(CH2)12COOH) then heating the plates in the solution at 30-50?C for 1-6 hours. The contact angle of water droplet on the prepared surface is measured using low bond axisymmetric drop shape analysis, which gives the maximum contact angle of 168? and average value of 166? ?2?. The maximum contact angle is obtained by adjusting the composition of the solution, temperature of the solution and immersion time to 0.006 M, 45?C and 4 hours, respectively. The various superhydrophobic surfaces are prepared by changing constituents of solution, hotplate temperature and processing time, respectively. Further dynamic behavior of water droplet on the prepared surfaces like jumping effect and rolling effect is presented in this work. In addition, experimental work is carried out on the prepared surface for dropwise condensation and the obtained results are com-pared with condensation on bare copper plate produces higher heat transfer coefficient.