scholarly journals An energy self-compensating phosphosilicate material applied to temperature sensors

RSC Advances ◽  
2018 ◽  
Vol 8 (67) ◽  
pp. 38538-38549
Author(s):  
Jiang Chen ◽  
Tiejun Li ◽  
Zhijing Zhang ◽  
Zhipeng Ci ◽  
Lili Han ◽  
...  
Keyword(s):  
Emission Intensity ◽  
Temperature Sensors ◽  
Increasing Temperature ◽  
Emission Loss

For years, researchers have been exploring effective methods of sustaining the emission intensity of phosphors with increasing temperature by suppressing emission loss.

YAG : R3+ (R = Ce, Dy, Yb) nanophosphor-based luminescent fibre-optic sensors for temperature measurements in the range 20–500 °C

2022 ◽  
Vol 52 (1) ◽  
pp. 94-99
Author(s):  
S K Evstropiev ◽  
V V Demidov ◽  
D V Bulyga ◽  
R V Sadovnichii ◽  
G A Pchelkin ◽  
...  
Keyword(s):  
Thermal Quenching ◽  
Signal Amplitude ◽  
Temperature Sensors ◽  
Yttrium Aluminium Garnet ◽  
Optical Fibres ◽  
Fibre Optic ◽  
Excitation Light ◽  
Yttrium Aluminium ◽  
Increasing Temperature ◽  
Silica Capillary

Abstract We report the development of a group of luminescent fibre-optic temperature sensors that use Ce3+-, Dy3+-, and Yb3+-doped yttrium aluminium garnet (YAG) nanophosphors as thermosensitive materials. The nanophosphors have been prepared in the form of powders with a crystallite size from 19 to 27 nm by a polymer ? salt method and exhibit bright luminescence at 550 (YAG : Ce3+), 400, 480 (YAG : Dy3+), and 1030 nm (YAG : Yb3+). The sensor design includes a silica capillary, partially filled with a nanophosphor, and two large-aperture multimode optical fibres located in the capillary, which deliver excitation light and receive and transmit the photoluminescence signal. The photoluminescence signal amplitude of all the sensors decreases exponentially with increasing temperature, pointing to characteristic thermal quenching of photoluminescence and adequate operation of the devices up to 500 °C. The highest temperature sensitivity among the fibre-optic sensors is offered by the YAG : Ce3+ nanophosphor-based devices.

Electrical performance of alumina films made in EB evaporation

2016 ◽  
Vol 30 (20) ◽  
pp. 1650260 ◽  
Author(s):  
Li-Jun He ◽  
Li-Yan Wang ◽  
Wei-Zhong Chen ◽  
Xing-Zhao Liu
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
High Temperature ◽  
Trap Depth ◽  
Temperature Sensors ◽  
Important Application ◽  
Electrical Performance ◽  
Alumina Films ◽  
Increasing Temperature ◽  
Made In

Alumina thin films deposited by electron beam (EB) evaporation are investigated with regard to their performance in high-temperature electrical insulators. The most important application is high-temperature sensors. The leakage behavior of EB-evaporated alumina thin films is investigated by analyzing the temperature dependence of the I–V characteristics of alumina thin films deposited on Pt/n-Si(100) substrates. The temperature is extending in the range from 300 K up to 1273 K. The results show that ln(J) increases linearly with the increasing electric field at high-temperature range, the trap depth of [Formula: see text] is 280 meV, the conductivity increases with the increasing temperature, while the resistivity decreases with the increasing temperature.

Temperature Dependence of the Sole Mn2+ Emissions in Manganese Doped ZnS:Mn Quantum Dots

2010 ◽  
Vol 159 ◽  
pp. 572-577
Author(s):  
Xiao Song Zhang ◽  
Gao Feng Zhang ◽  
Qing Song Huang ◽  
Feng Wei Wei ◽  
Yong Liang Zhou
Keyword(s):  
Quantum Dots ◽  
Temperature Dependence ◽  
Emission Intensity ◽  
Blue Shift ◽  
Average Diameter ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Broad Emission Band ◽  
Emission Energy ◽  
Increasing Temperature

ZnS:Mn Quantum dots (QDs) excess of [S2-] were synthesized by the wet chemical precipitation method with an average diameter of 3.9 nm. Temperature dependence photoluminescence measurements of ZnS:Mn QDs excited at 330nm only show a clear broad emission band with peak at ～595nm assigned to the 4T1→6A1 transition within the 3d5 configuration of Mn2+ in QDs. Through the temperature dependence of emission intensity, emission energy and full widths at half maximum (FWHM), the mechanisms are analyzed to explain the temperature behavior of Mn2+ emission observed here reasonably. The Mn2+ emission intensity decreases with increasing temperature. And the blue shift of the Mn2+ emission energy increase is also observed for increasing the temperature. Furthermore, the FWHM shows weak temperature dependence below 110 K and shows an increase with temperature increasing above 110 K. Consequently, the intrinsic mechanisms of temperature dependence photoluminescence are investigated.

Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

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