Two-dimensional cycle-resolved exhaust valve temperature measurements in an optically accessible internal combustion engine using thermographic phosphors

Phosphor thermometry was employed to measure the temperature distribution of the exhaust valves in an optically accessible direct injection internal combustion engine. A CMOS high-speed camera was used to two-dimensionally resolve the temperature dependent luminescence decay of the phosphor Gd₃Ga₅O₁₂:Cr. Measurements were performed under motored and fired conditions for several degrees crank angle to determine the temperature distributions within cycles. Additionally, several binders have been tested in terms of survivability and signal strength to guarantee ideal phosphor coating.     

A novel blue magnesium strontium aluminate-based phosphor for PDP application

A novel blue light-emitting phosphor, Eu²⁺-doped magnesium strontium aluminate (MgSrAl₁₀O₁₇:Eu²⁺), for plasma display panel (PDP) application was developed. X-ray diffraction (XRD) patterns disclosed that the phosphor annealed at 1500 °C for 5 h was a pure MgSrAl₁₀O₁₇ phase. Field emission scanning electron microscopy (FE-SEM) images showed the particle size of the phosphor was less than 3 μm. The phosphor shows strong and broad blue emission under vacuum ultraviolet (VUV) light excitation. After baking at 400-600 °C and irradiation with VUV light for 300 h, the phosphor still keep excellent VUV luminescence properties exhibiting good stability against high temperature baking and VUV irradiation. The decay time was short as 1.09 μs and the quantum yield was high to 0.77±0.02. All the characteristics indicated that MgSrAl₁₀O₁₇:Eu²⁺ would be a promising blue phosphor for PDP application.     

Morphology and photoluminescence of BaAl12O19:Mn2+ green phosphor prepared by flux method

This paper reports that the green phosphor BaAl11.9O19:0.1Mn2+ is prepared by a flux assisted solid state reaction method.The effect of flux systems on the crystal structure,morphology and luminescent properties of the phosphor are studied in detail.The samples are characterized by the application of x-ray diffraction patterns,scanning electron microscopy patterns,luminescent spectra and decay curves.The results show that a pure phase BaAl12O19 can be achieved at the firing temperature above 1300℃ by adding the proper flux system,the firing temperature is reduced at least 200℃ in comparison with the conventional solid state reaction method.Maximum photoluminescence emission intensity is observed at 517 nm for(AlF3+Li2CO3) flux system under vacuum ultraviolet region(147 nm) excitation.The photoluminescence emission intensity and the decay time of these phosphor is found to be more superior to that of the corresponding sample prepared by the conventional solid state reaction method implying the suitability of this route for the preparation of display device worthy phosphor materials.     

Synthesis, characterization, optical absorption, luminescence and defect centres in Er3+ and Yb3+ co-doped MgAl2O4 phosphors

The Er³⁺–Yb³⁺ co-doped MgAl₂O₄ phosphor powders have been prepared by the combustion method. The phosphor powders are well characterized by X-ray diffraction (XRD) and energy dispersive (EDX) techniques. The absorption spectrum of Er³⁺/Er³⁺–Yb³⁺ doped/co-doped phosphor powder has been recorded in the UV–Vis–NIR region of the electro-magnetic spectrum. The evidence for indirect pumping under 980 nm excitation of Er³⁺ from Yb³⁺ was observed in the MgAl₂O₄ matrix material. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermally stimulated luminescence (TSL) process in MgAl₂O₄:Er³⁺ phosphor. Three defect centres were identified in irradiated phosphor by ESR measurements which were carried out at room temperature and these were assigned to an O^? ion and F⁺ centres. O^? ion (hole centre) appears to correlate with the low temperature TSL peak at 210 °C and one of the F⁺ centres (electron centre) is related to the high temperature peak at 460 °C.     

A novel white light-emitting diode (w-LED) fabricated with Sr<Subscript>6</Subscript>BP<Subscript>5</Subscript>O<Subscript>20</Subscript>:Eu<Superscript>2+</Superscript> phosphor

Sr₆BP₅O₂₀:Eu²⁺ phosphor was prepared by the solid-state reaction method under a weak reductive atmosphere and the photoluminescence properties were studied systematically. The bluish-green emission band of Sr₆BP₅O₂₀:Eu²⁺ phosphor is peaking at 475 nm, and the excitation bands are broad with peaks at about 290 and 365 nm with a shoulder around 390 nm, respectively. By combining with Ga(In)N-based near-ultraviolet LEDs, a bluish-green LED was fabricated based on the Sr₆BP₅O₂₀:Eu²⁺ phosphor, and a novel intense white LED was fabricated based on the bluish-green phosphor Sr₆BP₅O₂₀:Eu²⁺ and the red phosphor (Sr,Ca)₅(PO₄)₃Cl:Eu²⁺,Mn²⁺. When this two-phosphor white LED is operated under 20-mA forward-bias current at room temperature, the Commission Internationale de l’Eclairage(CIE) chromaticity coordinates (x,y), the correlated color temperature Tc, and the color rendering index Ra are calculated to be (0.3281,0.3071), 5687 K, and 87.3, respectively. The dependence of the bluish-green and two-phosphor white LEDs on different forward-bias currents from 5 mA to 50 mA shows a similar behavior. As the current increases, the relative intensity simultaneously increases. The CIE chromaticity coordinates (x,y) of the two-phosphor white LED tend to decrease. Consequently, the correlated color temperature Tc increases from 3800 K to 9400 K and the color rendering index Ra of the two-phosphor white LED increases from 83.4 to 91.8 simultaneously. PACS 07.60.-j; 42.70.-a; 71.55.Eq     

Generation of phosphor nanoparticles for temperature sensing by laser ablation in liquid

Nano-size phosphor particles of Y_2.97Ce_0.03(Al_1?x Gd _x )₅O₁₂ were fabricated by ablating commercial micron-size powders in deionized water. We show that these colloidal phosphor nanoparticles suspended in deionized water can be used as a liquid sensor for all-optical, non-contact measurements of temperature with nanosecond time resolution. The nanophosphors can be used as temperature-sensing reporters in many applications where real-time measurements of temperature are necessary to understand physical processes, such as the mechanisms of temperature–time profiles in laser ablation.     

Luminescent properties of PEG-added nanocrystalline YVO4:Eu phosphor prepared by a hydrothermal method

In an effort to obtain enhanced luminescence under photoexcitation as well as to clarify the underlying correlation between non-radiative sites and a surface modifier in a nanoscale phosphor, YVO₄:Eu³⁺ was synthesized via a polyethylene glycol (PEG)-assisted hydrothermal process. The temperature variable photoluminescence reveals that the overall emission behaviors of PEG-added YVO₄:Eu³⁺ phosphor was similar to those of a post-annealed sample without PEG addition. This polymeric agent induces a rough thin layer onto the YVO₄:Eu³⁺ nanoparticle during synthetic procedure, resulting in the prevention of surface-adsorbed species known as non-radiative sites such as NH₄⁺ as well as hydroxyl groups.     

Preparation and luminescence properties of Y2(WO4)3: Eu3+

A red-emitting Y₂(WO₄)₃: Eu³⁺ phosphor (orthorhombic high temperature phase, anhydride) is prepared by two different methods: the firing of mixtures of constituent oxides and that of precipitates from aqueous solutions. After optimizing preparation conditions, the cathodoluminescence brightness reaches 56% that of Y₂O₂S: Eu³⁺, a commercial red phosphor for color TV. Formation of a high temperature phase below the reported transition temperature is noted in the fired precipitates. This phase occurrence is shown to depend on the treatment of the precipitates to be fired. Reflection difference measurement of Eu-doped and undoped samples assigns an excitation band of about 245 nm to the Eu-O charge transfer band. Different by-products in the two preparation methods are identified by measuring emission spectra under selective excitation. Reversible hydration-dehydration of the phosphor is demonstrated by successively measuring photoluminescence first in vacuum and then in air at various temperatures. No deterioration of luminescence efficiency is observed after repeating this reversible structural change.     

Thermally stable luminescence of blue LiSrPO4:Eu2+ phosphor for near-UV light-emitting diodes

Blue phosphor, LiSrPO₄:Eu²⁺, was prepared by solid-state reaction method under a weak reductive atmosphere and investigated by means of photoluminescence, concentration quenching process, and temperature dependence of luminescence. These results show that LiSrPO₄:Eu²⁺ can be efficiently excited by the UV-visible light of 250–440 nm and exhibits bright blue emission. Furthermore, Eu²⁺-doped LiSrPO₄ phosphor shows high thermally stable luminescence comparable to commercial phosphor BaMgAl₁₀O₁₇:Eu²⁺ (BAM). Two bright blue LEDs were fabricated by incorporating an InGaN-based near-UV chip with the obtained phosphor LiSrPO₄:Eu²⁺ and BAM, respectively. Their luminescence properties were compared based on different forward-bias currents. All the characteristics suggest that LiSrPO₄:Eu²⁺ is a good blue phosphor candidate for creating white light in phosphor-conversion white LEDs.     

Eu-doped B2O3–ZnO–PbO glass phosphor powders with?spherical shape and fine size prepared by spray pyrolysis

Eu-doped B₂O₃–ZnO–PbO glass phosphor powders with spherical shape and fine size were directly prepared by spray pyrolysis. The glass phosphor powders prepared at a temperature of 1100°C had broad XRD peak at around 28°. One glass phosphor powder was formed from one droplet at the preparation temperature range from 900 to 1100°C. The mean size of the glass phosphor powders was 0.75 μm. The glass transition temperature (T _g ) of the glass phosphor powders prepared by spray pyrolysis was 378.5°C. The excitation spectrum of the glass phosphor powders prepared at the optimum preparation temperature of 1100°C had bands at 362, 381, 392, 463, 525, and 532 nm. The glass phosphor powders had emission spectra with bands at 579, 614, and 653 nm. The glass phosphor powders with doping concentration of Eu of 7 wt% had the maximum photoluminescence intensity. The glass phosphor layer formed from the glass phosphor powders had high transparencies above 90%.     

Synthesis and thermoluminescence characterization of Na6Mg(SO4)4:RE (RE = Ce,Tb) phosphors

Thermoluminescence (TL) properties of sulfate-based phosphors activated by different rare earths have received tremendous attention to the field of radiation dosimetry. Those TL materials based on CaSO₄ have been widely applied for medical and environmental dosimetry. Taking this fact into account we have synthesized Na₆Mg(SO₄)₄ doped with Ce and Tb by wet chemical method. The prepared phosphor was characterized by XRD, FTIR, photoluminescence (PL) and thermoluminescence. For TL study, the phosphor is irradiated with γ-rays from ⁶⁰Co source. For studying luminescence properties, the prepared phosphor was annealed at different temperatures and effects of these annealing temperatures on Na₆Mg(SO₄)₄ samples are investigated and quantified. The changes in the glow curve and PL emission spectrum are also investigated as a function of annealing temperature and the annealing temperature was optimized. For calculation of trapping parameters various methods such as peak shape (PS) method, initial rise (IR) method, various heating rate (VHR) method, and computerized glow curve deconvolution (CGCD) are employed.     

Synthesis and optimum luminescence of monodispersed spheres for BaWO4-based green phosphors with doping of Tb

Monodispersed spheres for Tb³⁺-doped BaWO₄ (BWO:Tb) phosphors were prepared by a hydrothermal method. X-ray diffraction (XRD) and field-emission scanning electron microscopy were used to characterize the resulting samples. Emission and excitation spectra were studied using xenon excited spectroscopic experiments at room temperature. Because 12 at% BWO:Tb phosphor exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO₄:Ce,Tb), it is considered to be a new promising green phosphor for fluorescent lamps application.     

Piston engine driven by a cw laser

The construction and operating principles of a piston laser engine driven by a cw laser and its indicator diagrams are considered under various operating conditions. Equations are given for the indicator efficiency of the engine as a function of the opening angle of the obturator that controls the entry of the laser energy into the cylinder, and recommendations are made for the choice of the optimal regime. Engines with working volumes 2.5 and 45 cm³ driven by a 1-kW CO₂ laser were constructed. The former reached 3600 rpm.Translated from Trudy Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 120, pp. 100–105, 1980.     

溶胶-凝胶法制备BaGd1-xEuxB9O16红色磷光粉的发光

采用溶胶-凝胶法制备出BaGd_1-xEu_xB₉O₁₆红色磷光粉,对过程的物料配比、前驱体处理和晶化温度等制备条件进行了讨论。结果表明,样品在850 ℃下开始晶化,900 ℃时就能够获得较好的晶化产物,结合不同晶化温度下的发光强度比较确定,晶化温度为950 ℃时,BaGd_1-xEu_xB₉O₁₆磷光粉具有较高的结晶状态和发光强度。当Eu浓度x=0.9时具有最大的发光强度;初始原料配比硼酸须按计量过量15%。所得荧光粉的激发光谱峰值为264,394,465,534 nm等,分别归属于Eu-O电荷迁移带及Eu³⁺的⁷F₀-⁵L₆、⁷F₀-⁵D₂和⁷F₀-⁵D₁跃迁,发射光谱呈Eu³⁺的特征红光,最强的发射峰位于614 nm,归属于⁵D₀-⁷F₂跃迁。进一步研究表明该磷光粉中存在着Gd³⁺对Eu³⁺的能量传递。     

Photoluminescence properties of BaMgAl10O17:Eu phosphor prepared by the flux method

BaMgAl₁₀O₁₇:Eu²⁺ phosphors were synthesized by the flux method. When the appropriate amounts of fluxes are added, the synthesis temperature reduced by at least 200 °C compared with the conventional solid-state reaction method. SEM images demonstrated that addition of the flux in the process of phosphor synthesis benefitted the size and morphology of BaMgAl₁₀O₁₇:Eu²⁺ phosphor particles. Photoluminescence measurements under VUV excitation indicated that the luminescent intensity of the phosphor enhanced by adding the flux system (BaF₂+Li₂CO₃). Addition of the flux system can not only enhance the luminescence efficiency and improve the stability, but also control the morphology and grain size of the phosphor. Replacement of Ba²⁺ by Li⁺ could generate traps, which result in slightly longer decay time.     

An adaptive multi-grid chemistry (AMC) model for efficient simulation of HCCI and DI engine combustion

There is a need to reduce the computational expense of practical multidimensional combustion simulations. Simulation of Homogeneous Charge Compression Ignition (HCCI) engine processes requires consideration of detailed chemistry in order to capture the ignition and combustion characteristics. Even with relatively coarse numerical meshes and reduced chemistry mechanisms, calculation times are still unacceptably long. For the simulation of Direct Injection (DI) engines, fine meshes are needed to achieve the resolution required by the spray and mixing models, and they are computationally expensive even with reduced chemistry. In addition, the increasing application of CFD for engine design optimization is pushing the demand to reduce computational time. In current design optimizations, depending on the size of the parametric space, hundreds of individual simulations are needed.

This work presents an efficient Adaptive Multi-grid Chemistry (AMC) model that can be used in engine CFD codes for simulations of HCCI and DI engines with detailed chemistry. It was found that the number of cells computed with the chemistry solver can be reduced by two orders of magnitude for HCCI engines. The results predicted by the present KIVA AMC code are also consistent with those calculated by the original code using every cell.

In the method, progressively coarser grids are used for cells with similar gas properties in the chemistry calculation (up to four neighbour levels) or in the global method, cells are grouped without regard for their locations in the cylinder. Averaged and gradient-preserving remapping techniques used in multi-zone engine simulations were also explored. A parametric study was conducted for determining the model variables, such as the degree of local homogeneity for the multi-grid solvers.

The simulation results were compared with experimental data obtained from a Honda engine operated with n-heptane under HCCI conditions for which directly measured in-cylinder temperature and H₂O mole fraction data are available. In addition, simulation results were found to agree well with experimental data from a DI diesel engine operated under PCCI conditions with ultra-high EGR rates. It was found that computer time was reduced by a factor of ten for HCCI cases and two to three for DI cases without losing prediction accuracy.     

Upconversion mechanisms and thermal effects of Er3+ in Er3+ doped yttria nanocrystals

Efficient Er³⁺:Y₂O₃ phosphor is synthesized by the sol–gel method. Rate equations for Er³⁺ energy level populations are used to investigate pump power and temperature dependences of upconversion intensity as well as the fluorescence decay profiles. Excited state absorption cross section of Er^{3+ 4}I_13/2 of 6.8×10^?27 m² and cross relaxation rate of 6200 s^?1 are determined from comparison between theoretical predictions and experimental data. In addition, it is found that effect of temperature on the phonon-assistant absorption cannot be neglected. This work provides references for the prediction of the upconversion behavior in Er³⁺ singly doped matrix.     

KBaPO4:Ln (Ln=Eu, Tb, Sm) phosphors for UV excitable white light-emitting diodes

This letter reports the novel three emission bands based on phosphate host matrix, KBaPO₄ doped with Eu²⁺, Tb³⁺, and Sm³⁺ for white light-emitting diodes (LEDs). The phosphors were synthesized by solid-state reaction and thermal stability was elucidated by measuring photoluminescence at higher temperatures. Eu²⁺-doped KBaPO₄ phosphor emits blue luminescence with a peak wavelength at 420 nm under maximum near-ultraviolet excitation of 360 nm. Tb³⁺-doped KBaPO₄ phosphor emits green luminescence with a peak wavelength at 540 nm under maximum near-ultraviolet excitation of 370 nm. Sm³⁺-doped KBaPO₄ phosphor emits orange-red luminescence with a peak wavelength at 594 nm under maximum near-ultraviolet excitation of 400 nm. The thermal stabilities of KBaPO₄:Ln (Ln=Eu²⁺, Tb³⁺, Sm³⁺), in comparison to commercially available YAG:Ce³⁺ phosphor were found to be higher in a wide temperature range of 25-300 °C.     

Effect of the geometric shape of Lu 2 O 3 : Eu spherical nanocrystals on their spontaneous luminescence

Monodisperse red phosphor particles 100 nm in diameter with the Lu_1.90Eu_0.10O₃ composition have been prepared using the developed technique for synthesizing spherical colloidal lutetium oxide particles with a size dispersion in the range 10–15%. The structure of spherical nanoparticles has been investigated, their excitation and photoluminescence spectra have been analyzed, and the lifetime of the ⁵ D ₀ excited state of Eu³⁺ ions has been considered. It has been found that the luminescence decay time for spherical particles increases by a factor of 1.39 compared to that for a powdered phosphor Lu₂O₃: Eu (5 at %) prepared and treated under the same temperature conditions as the Lu₂O₃: Eu (5 at %) spherical particles. This effect has been associated with the change in the photonic local density of states in spherical optical cavities consisting of particles of the phosphor.     

Mechanoluminescence and lyoluminescence characterization of Li2BaP2O7:Eu phosphor

In this work mechanoluminescence and lyoluminescence properties of Li₂BaP₂O₇: Eu phosphor are reported. Phosphor was synthesized through high temperature solid state diffusion method. Analysis of phosphor was made through various characterization techniques such as mechanoluminescence (ML), lyoluminescence (LL), x-ray powder diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL). It was observed that ML intensity showed good enhancement with variation in time, concentration of dopant Eu, mass of piston and impact velocity. Lyoluminescence intensity was also found to increase with change in time and mass of the sample. Variation in gamma doses imparted to Li₂BaP₂O₇: Eu phosphor was observed to affect both the ML and LL intensities' respectively. Both the ML and LL intensity attain a maximum value I_m at a particular time t_m but afterwards, it decreases and finally disappears. Morphology of Li₂BaP₂O₇: Eu luminescent material was also studied using scanning electron microscope technique. The average particle size in Eu doped lithium barium diphosphate phosphor was around 2 μm.