This paper proposed a two-stage thermal processing method combined with the reduction-reoxidation procedure. Samples were firstly sintered in a reducing atmosphere by two stages and then reoxidized in air. Such two-stage thermal processing method was used to adjust density and grain size of ceramics separately. Finally, nanocrystalline semiconducting donor-doped BaTiO3 ceramics were first successfully prepared. Samples with average grain size of 340 nm exhibited unexpectedly low room resistivity of 136 Ω cm and a significant PTCR effect, with a resistance jump of 4 orders of magnitude. In addition, depletion layer thickness of 40 nm and surface acceptor-state densities of 9.52 × 1013 cm−2 were also calculated. Such good properties had not been reported in former publications. It also means that smaller components based on semiconducting BaTiO3 ceramics could be produced and more extensive application field could be proposed in the trend of miniaturization of electronic devices.

Nanocrystalline semiconducting donor-doped BaTiO3 ceramics for laminated PTC thermistor

Abstract Accurate knowledge of pore and fracture pressures is essential for drilling wells safely with the desired mud weight (MW). Overpressure occurs when the pore pressure is higher than the normal hydrostatic pressure. There is a challenge regarding the pressure studies domain in an oilfield in SW Iran, where lack of geo-mechanical data limits exact mud window calculation. Also, the reservoir generally consists of carbonate rocks and contains no shale interbeds, so mechanical stratigraphy based on Gamma ray could not be applied. This study is to provide safe drilling considering MW to prevent the flow or loss in the vicinity of the new wells in the studied field. In this research, the formation pressures and mud window models are determined by combining geostatistical, intelligent, and conditional programming models and compared with real data. The conditional programming was also used to correct small out-of-range data. The highest correlation between the final effective pressure and velocity cube was observed in lower Fahliyan Formation with 0.86 and Ilam with 0.71.The modeled MW difference ranged between 2.5 and 30 PCF. Also, the maximum modeled MW is 150 PCF in the upper Fahliyan Formation. Heavy mud of more than 130 PCF is suggested for drilling the Khalij member and continues to the end of stratigraphy column. Best observed correlation comparing the drilled and modeled MW, especially achieved in the Fahliyan reservoir Formation with more than 100 PCF and the Ilam Formation with 80–100 PCF. Finally, 3D formation pressures are presented and recommended for further safe drillings. 

/pdf/determining-the-drilling-mud-window-by-integration-of-2uwks5ja.pdf

Determining the drilling mud window by integration of geostatistics, intelligent, and conditional programming models in an oilfield of SW Iran

This paper presents experimental findings on heat and mass transfer, phase transitions, and chemical reactions during the interaction of CO2 hydrate in powder granules and tablets with burning liquid fuels and oil. The experiments involved CO2 hydrate tablets and spheres made of pressed granules. The fire containment and suppression times were established experimentally. Using the gas analysis data, we studied the effects of the mitigation of anthropogenic emissions from the combustion of liquids and their suppression by gas hydrates. We also compared the performance of water aerosol, foaming agent emulsion, snow, ice, and CO2 hydrate samples as laboratory-scale fire suppressants. The paper further describes the numerical modeling of the CO2 hydrate dissociation during liquid fuel combustion. The rapid carbon dioxide release is shown to prevent the oxidizer from the combustion zone. The suppression of a flame using powder with a granule size of 3 mm requires 20-times less carbon dioxide hydrate than in the case of pressed tablets. Effective conditions are identified for using CO2 hydrates to extinguish fires involving flammable liquids and most common fuels.

/pdf/pool-fire-suppression-using-co2-hydrate-22horm2q.pdf

Pool Fire Suppression Using CO2 Hydrate

This paper investigated the effects of sintering temperature on the microstructure and electrical properties of ZrO
 2
-doped zinc oxide (ZnO) varistor ceramics. The results show that, the additive ZrO
 2
 exists as independent second phase between ZnO grains, which can limit the growth of ZnO grains and improve the voltage gradient. With the increasing of ZrO
 2
, the content of extrinsic elements (Mn, Sb, Co, Cr) in the grain boundary layers tends to increase first and then decease. When ZrO
 2
 content is more than 1.0mol%, the electrical performance of ZnO varistors decreases sharply. With the increasing of sintering temperature, the ZnO grain size increases and the voltage gradient decreases. When the sintering temperature is larger than 1200°C, more monoclinic ZrO
 2
 phase transformed into cubic phase, and more micropores are generated, causing the non-linear coefficient to decrease and the residual voltage ratio and leakage current to increase. With a sintering temperature of 1150°C and a ZrO
 2
 content of 1.0mol%, the ZnO varistors can reach the overall optimum electric performance, exhibiting a breakdown voltage of E
 1mA
 = 420V/mm, a nonlinear coefficient of α = 58, a residual voltage ratio of CR = 1.87, and a leakage current of I
 L
 = 4μA. The studies in this paper can give reference for the development of high quality ZnO arresters.

Influence of Sintering Temperature and ZrO 2 Dopants on the Microstructure and Electrical Properties of Zinc Oxide Varistors

The aim of this paper was to study the suppression influence of water mist on oil pool fires, taking diesel fires and n-heptane fires as experimental objects. The effects of spray pressure and temperature on water mist suppression were examined, and an experimental platform for the suppression of water mist in a small space was set up. Their fire prevention performance and fire extinguishing mechanisms were analyzed by comparing the flame temperature and extinguishing time of diesel and n-heptane pool fire. Three types of spray pressure were set. Water mist was designed at different temperatures and design experiments were carried out for this purpose. The change process of smoke concentration, thermocouple temperature, and flame combustion under different working conditions were analyzed, and the factors affecting the fire extinguishing effect of water mist on oil pool fire were discussed. The results show that 20 °C water mist is more effective at medium and high pressure than at low pressure. Moreover, 80 °C water mist at 9 MPa is more effective in extinguishing n-heptane fire. The flame extinction time is about 10 s, which is more than 40 s higher than that of cold water.

/pdf/influence-of-water-mist-temperature-approach-on-fire-1uz188xl.pdf

Influence of Water Mist Temperature Approach on Fire Extinguishing Effect of Different Pool Fires

Study on the effect of mist flux on water mist fire extinguishing

Fracture stratigraphy and mechanical stratigraphy in sandstone: A multiscale quantitative analysis

Numerical study on the influence mechanism of different types of burst disc on high pressure hydrogen spontaneous combustion in tube

The aqueous film-forming foam (AFFF) extinguishing agent is suitable for fighting various hydrocarbon fuel fires due to its dual fire-fighting effect of foam and liquid film. Because the action law and microscopic mechanism of inorganic salts on the stabilization process of surfactant-generated AFFF are not perfect, this paper employs an experimental approach to investigate the effects of inorganic salt types and concentrations on sodium dodecyl sulfate-containing foam systems (SDS). Prior to critical micelle concentration (CMC), increasing inorganic salt concentration decreased solution surface tension, but the opposite was true after CMC. The CMC value of an SDS solution decreases as inorganic salt concentration increases, and the "salting effect" of inorganic salt cations also has an effect on the CMC value. Based on the resistance of the liquid film at the gas-liquid interface affecting gas transport, the foam evolution was divided into three stages: foam generation, liquid drainage, and gas transfer. The effect of inorganic salts on these three stages was studied at the molecular level, and it was discovered that the addition of NH4Cl and MgCl2 could improve the saturation adsorption at the gas-liquid interface, reduce the surface tension of the surfactant solution, and improve foam stability. Meanwhile, inorganic salts can change the force of gas molecules, so the equilibrium force of gas across the liquid membrane increases as inorganic salt concentration increases. Additionally, the addition of inorganic salts raises the diffusive drainage coefficient, but the gravity drainage coefficient still reigns supreme in the predecay period.

Experimental Study of the Influence of Inorganic Salts on Foam Stability.

Experimental study on heat transfer and propagation speed of spill fire on porous media substrate with micro-inclination

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