Search

ABSTRACT Snowmelt salts and deicing additives which are used to remove the snow/ice in winter make the pavement experience diverse and complex actions such as freeze-thaw (F-T) cycles and salt [...]

ABSTRACT Filler is the main component of asphalt mastic and its properties are closely associated with the performances of asphalt mastic. To investigate the relationship between properties of fillers and [...]

ABSTRACT The gradation of asphalt concrete affects the properties of pavement significantly. It is an important parameter for the design of asphalt mixture. So the planar gradation of asphalt concrete [...]

A series of double-limbs built-up I-section simply supported specimens subjected to compression were examined. The test columns contained 18 concentric compression columns and 12 eccentric compression columns with three section forms respectively. The influence of web stiffeners on buckling mode, ultimate bearing capacity and interaction between limbs were studied. It was shown that stiffeners in web effectively decreased the element width-to-thickness ratio and increased the bearing capacity of built-up I-section columns. But when larger eccentricity made the moment control the failure of eccentric compression specimens, the bearing capacity of the specimens was not improved obviously by web stiffeners. Distortional buckling could replace local buckling to control the failure modes of columns. Compared with double-limbs channel steel built-up open-sections with complex edge stiffeners under the same steel quantity and eccentricity, the load carrying capacity of double limb Σ-shaped channel built-up sections increased from 4.4% to 20.3%. While for double limb channel with V-type web stiffener sections, the increment was from 2.2% to 17.4%. Furthermore, parametric study of 90 Σ-shaped built-up section members was investigated to obtain the optimization proportion of the web sub-element and relationship of carrying capacity between single Σ-shaped section and double limb Σ-shaped I-section. Finally, the ultimate load-carrying capacity of built-up columns subjected to axial compression were calculated by two kinds of direct strength method formulas, which were compared with the tests values. The results showed that the method considered the interaction between distortional buckling and flexural buckling could obtain conservative results.

Biological soil crusts (BSCs) play an important role in soil development and ecological function, and it is more important for quantitatively analyzing the processes and trends of BSCs to identify the advantages and disadvantages of BSCs research for the development and application of BSCs theory. Bibliometric analysis of 2186 BSCs literatures from Web of Science showed an exponential growth trend, as China and the United States as the top 2 in terms of publication volume. High quality publications are mainly from European and American countries, such as the United States, Germany and Spain. The top 3 publishers are Journal of Arid Environments, Soil Biology & Biochemistry and Plant and Soil, and disciplines include ecology, environmental science, and soil science, etc. Research institutions mainly affiliate to the Chinese Academy of Sciences, United States Department of the Interior, United States Geological Survey, Hebrew University of Jerusalem, Consejo Superior de Investigaciones Cientificas, and Universidad Rey Juan Carlos. Authors mainly come from United States, Israel, Spain and China. Funds are mainly from the National Natural Science Foundation of China, Spanish Government, Chinese Academy of Sciences, and National Science Foundation of the United States. Biological soil crusts (biocrusts, cyanobacteria, lichens, moss crusts, bryophytes), drylands, climate change, photosynthesis and desert are high-frequency keywords. Future research will focus on the driving mechanisms of BSCs on global biogeochemical cycles, maintaining global biodiversity on important ecological processes, global C, N, and P cycles. The impact on biological invasion, sandstorms, and water balance, multifunctional and reciprocal mechanisms for maintaining the stability of desert and sandy ecosystems, and impact on the formulation of management policies for arid ecosystems, corresponding to global climate change, and the estimation of regional, local, and microscale distribution of BSCs based on machine deep learning modeling gradually focus on. The ecosystem service functions of BSCs, the soil and water conservation and soil stability mediated by BSCs in arid and semi-arid regions, and the excavation of stress resistant genes for BSCs will be emphasized.

The Dunhuang Mogao Grottoes are a significant cultural heritage site in the Silk Road, famous for its wonderful murals and statues. The rainfall causes the changes of humidity in the caves, which can easily activate the salts diseases of murals. In order to prevent the deterioration of the murals, the environmental monitoring tests were conducted to analyze the microclimate changes of the cave in rainfall weather, and proposed the risk prevention measures and suggestions. The results indicate that the temperature of caves has small change, but the humidity shows a clear trend of increase. The humidity and the duration of high humidity increases with the increase of the rainfall grade and frequency. The optimal starting time for environment control in the cave is when aatmand acaveare consistent, and the relative humidity is controlled below 62%. The caves with lower layer, larger degree of openness and small volume are most vulnerable to water vapour diffusion. The environment monitoring should pay more attention to the continuous rainfall weather and the vulnerable caves. The research has great significance for the prevention of ancient mural deterioration.

ABSTRACTIn the Mogao Grottoes of Dunhuang, China, the ambient relative humidity (RH) fluctuation in the caves is the main cause for the deterioration that has been observed, especially the deterioration of the earthen plaster and wall paintings linked to the presence of NaCl and Na2SO4salt contaminants. To help identify the mechanism responsible for this salt-related deterioration and provide a theoretical basis for the development of a preventive conservation regime, this study addressed the basic moisture adsorption mechanisms of earthen plaster with soluble salts by taking an experimental approach. It is shown that, as ambient RH increases, the moisture adsorption process of the plaster containing the soluble salts can be regarded to have three basic stages, as evidenced by the results of the moisture adsorption tests performed on earthen plaster samples with different NaCl or Na2SO4contents at various humidity levels. The moisture adsorption mechanism and its determining factors at each stage are also analysed. In addition, it is suggested that the hygroscopicity of the plaster structure and the interaction between the different kinds of salts in the plaster, which makes the dissolution or hydration of the salt in the plaster pores much easier, should be considered more seriously regarding increases in the ambient RH in the caves.

During the process of archaeological excavation in the regions of Southeast China, collapse of test square usually occurs due to poor site-specific conditions. In this paper, the fast Lagrangian analysis of continua in three dimensions (FLAC3D) is employed to reveal the behaviors of test square. Taking the archaeological works in Liangzhu prehistoric earthen sites as the research background, the paper first introduces the geological setting, excavation procedure and monitoring scheme of the studied test square. Then, the deformation of four sides of the test square is modeled using FLAC3D. By comparison, it shows that the numerical results are consistent with the results from field monitoring. The result suggests that the numerical simulation can be effectively applied to representing the actual behaviors of the test square, which is helpful for determination of excavation scheme and stability evaluation of the test square during archaeological excavation.

AbstractThe construction chronology of three of the earliest Dunhuang Mogao Grottoes (Caves 268, 272, and 275) has been the subject of ongoing debate for over half a century. This chronology is a crucial topic in terms of further understanding of the establishment of the Dunhuang Mogao Grottoes, early Buddhism in the Gansu corridor, and its relationship with Buddhism developed in the Central Plains. Building upon archaeological, art historical and radiocarbon (14C) dating studies, we integrate new 14C data with these previously published findings utilizing Bayesian statistical modeling to improve the chronological resolution of this issue. Thus, we determine that all three of these caves were constructed around AD 410–440, suggesting coeval rather than sequential construction.

The aim of this paper is to study the influence of atmospheric humidity and temperature on the mural paintings in the Mogao Grottoes of Dunhuang by measuring the weight of a simulated mural block. Under open conditions, the daily changes in the atmospheric humidity and temperature have an apparent effect on the water content of these murals. There exists an obvious water exchange between atmosphere and mural, that is, there is a ±43 g m−2moisture absorption–desorption ‘breathing’ process between the two. Evapotranspiration from the tree-belt, precipitation, and extremely dry weather also have an effect on the moisture associated with a mural painting. If the cave is closed, a comparable study finds that closure can make the effects of temperature and humidity changes disappear. The mural water content in this case remains stable and the harm due to water-salt deterioration is greatly reduced. Under closed conditions, artificial condensation dehumidification and control of the cave's temperature and humidity stabilizes water activity in the mural paintings very effectively. This is a clear indication of the future steps required to protect the cave's cultural relics.

The work reported here is a systematic study to evaluate the compatibility of using PS-F (potassium silicate with high modulus – fly ash) slurry in the conservation of adobe structures. Firstly, the optimum mixing proportion (0.47) was determined by flow meter. Then the experimental program was divided into two parts: one part studied changes in physical and mechanical properties with increase in setting time by means of the measurement of moisture content, compressive and flexural strength, elastic-wave velocity, density, and porosity; the other part studied the durability of PS-F slurry through temperature and humidity cycles, freeze–thaw cycles, water stability, tensile testing, and alkali resistivity tests. The results show that the consolidation process with the slurry can meet the requirements of conservation applications and provide a timely anchoring force, and the slurry and soil mass of adobe-based structures have good compatibility in physical and mechanical properties. In addition, the slurry can strongly resist freeze–thaw cycles, temperature-moisture cycles, and tensile stress and has a relatively weak resistance to alkali solutions and water immersion. In conclusion, PS-F with a mixing ratio of 0.47 is a suitable slurry for conservation of adobe structures.

The ramming technique is a traditional method used to improve the compactness of soil with impact and vibration energy. Based on the measured data of ramming force transmission and dissipation, this study reveals the mechanism of energy transfer and dissipation of single-layer ramming as well as the law of variation with ramming quality, laying thickness, and ramming times. It also establishes the ramming model and empirical formula of ramming quality, laying thickness, and ramming times, introduces the ramming layer changes associated with the constitutive relationship (elastic to elastoplastic parts) as a function of ramming times, and determines the influence depth and horizontal range based on real-time data monitoring. It was found that as the mass of the rammer increases, the range of influence of the impact stress inside the earth also increases proportionally, and this effect is more pronounced vertically. However, the dissipation rate of energy in horizontal direction is much greater than in the vertical direction. The traditional stacked ramming technique of “chong hai wo, hang yin ding” can effectively eliminate the defects of horizontal reversal upwelling impact and unevenness of the ramming layer during the ramming process. The research results provide a theoretical basis for evaluating the quality of the traditional ramming technique.

Earthen sites are important remains of past human societies. Weather-resistant measures comprise a major part of conservation efforts for earthen sites. Marked advancements in weather-resistant techniques have been made in recent years. Earthen sites are characterised by large numbers, large scales, various types, complex compositions, and diverse existing environments. Weather-resistant measures differ significantly in their environmental adaptability. The environmental adaptability of weather-resistant measures severely restricts further development and popularisation of weather-resistant technology at earthen sites. Based on the environmental and weathering characteristics of existing earthen sites in China, the consolidation and failure mechanisms of several weather-resistant measures (penetrating consolidation, sacrificial layers, soft capping, protective structures, and backfilling protection) were examined. The potential areas to increase the success of the different weather-resistant measures were obtained combined with the characteristics of various environmental boundaries.

Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civilization, but also possess important values for conservation and exhibition. Many researches and practices on their conservation and consolidation have been carried out; however, the consolidation effect is mainly judged by visual observation and expert evaluation. Scientific assessment of conservation and consolidation effects is a challenging issue. Many instruments in other fields cannot be directly applied to the conservation of cultural relics due to their peculiarity. In order to assess the effects of field conservation experiments, this paper tries to understand the consolidation effects at Liangzhu site using nondestructive or micro-damage methods, including thermo-physical parameters testing, infrared thermal imaging, high-density microelectrode resistivity testing, portable microscope observation, and hydrophilic and hydrophobic testing, and thereby explores the practicable methods for evaluating the properties of consolidation materials for earthen sites treatment.

AbstractIt is a challenge for the conservation of soil ruin sites that molds grow on the surface of damp soil ruins in soil ruin exhibition halls in high-humidity regions. The ventilation and lighting modes of soil ruin exhibition halls directly affect mold reproduction, but studies on the quantitative relationship between environmental factors and mold propagation on surfaces in damp soil ruins are insufficient. The Wenzhou Qiaolou soil ruin was selected as an example in this study, and rammed earth from this ruin was used as the experiment sample. For the ventilation and lighting modes as experimental variables, four ventilation and lighting environmental conditions were simulated for 56 days in a laboratory to compare differences in mold growth on samples of damp rammed earth surfaces. In this study, the difference of mold growth in different ventilation and lighting conditions were discussed, and some suggestions for the environmental management of soil ruin exhibition halls in high-humidity regions were given.

A novel white emitting phosphor Ca2PO4Cl:Dy3+was synthesized by a solid state method. The luminescence, concentration quenching and thermal stability of Ca2PO4Cl:Dy3+were investigated. Ca2PO4Cl:Dy3+showed three emission peaks, which were located at 483, 575 and 660 nm. Though the ratio of yellow to blue emission intensities showed a similar value, the intensities of yellow and blue peaks were influenced by Dy3+concentration, and the concentration quenching effect was observed. The emission intensity of Ca2PO4Cl:Dy3+as a function of temperature was explored and the emission intensity (at 150 °C) of Ca2PO4Cl:Dy3+was 90.0% of the value at 25 °C, and activation energy was 0.18 eV. The results indicated that Ca2PO4Cl:Dy3+might be conducive to development of white LEDs.

The Dunhuang Mogao Grottoes in China was designated as a world heritage site by UNESCO in 1987 and is famous for its cultural relics. Water is the most active factor that harms the relics in the caves as it damages the grotto murals and painted sculptures. Thus, determining the water sources and driving forces of water movement is a key issue for protecting these cultural relics. These issues have troubled relics protectors for a long time. In this study, the authors chose a representative cave in the Mogao Grottoes and, by completely sealing the cave to make a closed system, measured the water vapor from the surrounding rock. This was accomplished by installing a condensation-dehumidification temperature-humidity control system for the collection of water vapor. The results show that there is continuous evaporation from the deep surrounding rock into the cave. The daily evaporation capacity is determined to be 1.02 g/(d·m2). The water sources and driving forces of water movement were further analyzed according to the character of the water evaporation and by monitoring the temperature and humidity of the surrounding rock. It was found that the water vapor in the cave derives from phreatic water. Moreover, the yearly fluctuation of temperature in the surrounding rock and geothermal forces are the basic powers responsible for driving phreatic evaporation. Under the action of the yearly temperature fluctuations, decomposition and combination of bound water acts as a “pump” that drives phreatic water migration and evaporation. When the temperature rises, bound water decomposes and evaporates; and when it falls, the rock absorbs moisture. This causes the phreatic water to move from deep regions to shallow ones. Determining the source and dynamic foundation of the water provides a firm scientific basis for protecting the valuable cultural relics in the caves.

We have observed the formation of photorefractive spatial quasi-stead-state solitons in SBN:75 crystal by electric field with white beam as background and signal beam intensity of W magnitude. It was found that the electric field had obvious effect on the characteristics of laser beam propagation in crystal. It showed a performance of self-focusing that the output beam from the crystal is proportional to the voltage of the external electric field along the c-axis of the crystal. At the voltage of 900V(1800V/cm), (2+1) -dimensional bright spatial solitons formed. While applied voltage along the reverse of c-axis, the diffraction of spot on the output face of the crystal appeared obviously as a performance of self-defocusing.

The varied emitted color of Sr3La(PO4)3:Eu2+ phosphor was synthesized using a high temperature solid-state reaction method. The phosphor exhibits two emission bands at 418 and 500 nm corresponding to the 5d-4f transition of Eu2+ ions, which occupy two different crystallographic sites of Sr2+ in the Sr3La(PO4)3 structure. With increasing the Eu2+ doping concentration, the emission color changes the cyan into the purple, and the energy transfer takes place between Eu2+ activators. The experimental results and the analysis suggest that the energy transfer mechanism should occur due to dipole-dipole interaction with an energy-transfer critical distance of 2.56 nm. When Ce3+ ions are doped together, an efficient energy transfer from Ce3+ to Eu2+ ions exists in Sr3La(PO4)3:Ce3+, Eu2+ phosphor, the energy transfer mechanism is also d-d interaction, and the energy-transfer critical distance is 2.71 nm.

Trivalent terbium (Tb3+) doped double molybdate AGd(MoO4)2(A = Li+, Na+) phosphors have been synthesized by combustion reaction. The crystal structures and luminescent properties of the phosphors are investigated in this paper. The XRD patterns indicate that AGd(MoO4)2:Tb3+ phosphors take on single phase when the precursors are sintered at 700degC for 3 h. The average crystal size is about 2.0 um. LiGd(MoO4)2:Tb3+ and NaGd(MoO4)2:Tb3+ phosphors have the similar luminescent properties. The influences of urea and Tb3+ concentration on the luminescent properties of phosphor samples are also discussed in detail. The results show that Tb3+ activated LiGd(MoO4)2 phosphors is a potential candidate for green phosphor in ultraviolet (UV) -based white LED.

Earthen sites, which are mainly made of earth, are cultural heritages with historical, artistic and scientific values. Many extremely valuable earthen sites have been preserved in the arid areas in China. The earthen site of Jiaohe Ancient City is one of the earliest National Protected Important Cultural Heritage Sites. The Jiaohe Ancient City site exhibits all kinds of deteriorations, which can be found in the earthen sites in arid environments in China. Through a case study of the Jiaohe ancient earthen site, we present in this paper the comprehensive conservation technologies, including the mud bricklaying and reparation, wooden rod anchorage, crack grouting, surface potassium silicate (PS) penetration consolidation, and suspended steel beam ceiling, etc. Results of this case study showed that better conservation effects could be achieved by selecting proper PS penetration and crack grouting processes based on the deterioration characteristics of the earthen sites. The technology of mud bricklaying and reparation was also an effective method for preventing the earthen body from collapsing. Compared with traditional conservation technologies, the suspended steel beam ceiling technology could effectively reduce the negative impacts to the original state of the earthen site. As for unstable cliffs, a new method using composite anchor rod of bamboo and steel with massive loose earth was applied. Deformation monitoring and temporary supports were critical and indispensable measures for the safe of site conservation projects. Through years of monitoring and practical operation at the Jiaohe ancient earthen site, deterioration at the site has been effectively controlled.

A novel red phosphor, SrIn2O4:Eu3+, Sm3+, is synthesized by a combustion method. The 5D0 - 7F2 transition of Eu3+ is dominantly observed in the photoluminescence spectrum, leading to a red emission of the phosphor. The doped Sm3+ is found to be efficient to sensitize the emission of Eu3+ and be effective to extend and strengthen the absorption of near-UV light with wavelength of 400-405 nm, and the energy transfer from Sm3+ to Eu3+ occurs and is discussed. The effect of the molar concentration of Sm3+ on the emission intensities of the red phosphor SrIn2O4:Eu3+, Sm3+ is investigated. Moreover, the chromaticity coordinates and the emission intensities of SrIn2O4:Eu3+, Sm3+ are compared to those of the conventional red phosphor Y2O2S:Eu3+.

The Y2Si2O7:Tb3+phosphor was synthesized by high temperature solid state method. The crystal structure and luminescent properties of phosphors were studied by XRD pattern, excitation and emission spectra in this paper. XRD pattern showed that the sample was single phase Y2Si2O7crystal and the crystal lattice constants a=0.806nm, b=0.934 nm, and c=0.692 nm. The excitation spectrum is composed of a broad band centered 290nm and three narrow bands corresponding to 4� - 4� transition of Tb3+centered 378 nm, 400nm and 420nm, respectively. The emission peaks of phosphor were located at 487nm, 546nm, 584nm and 623nm, which were corresponding to 5D4-7F6, 5D4-7F5, 5D4-7F4and 5D4-7F3, respectively. The influences of Tb3+concentration on the luminescent intensity of Y2Si2O7:Tb3+phosphor was studied. The results indicated that this phosphor could act as a candidate green phosphor for UV-excited white LED.

Eu3+doped yttrium orthosilicate (Y2SiO5) phosphor was prepared by the sol-combustion method using citric acid as complexing agent in this experiment. The X-ray diffraction (XRD) pattern, excitation and emission spectra were used to investigate the crystal structure and luminescent properties of the phosphor. XRD pattern showed that pure Y2SiO5:Eu3+phosphor was obtained. The excitation spectrum was composed of a broad band from 200-350 nm and a series of narrow bands from 350-500 nm, in which the excitation peaks at 400 nm and 470 nm were stronger. The emission spectrum showed the most intense emission peak was located at 613 nm, which corresponded to the 5D0→7F2transition of Eu3+. The results showed that this phosphor could be excited by UV or blue light and emit red light. The luminescent intensity depends on the concentration of Eu3+and it reached the maximum when the molar concentration of Eu3+was 4 mol%. In this study, we found that the emission intensity reached maximum when the ratio of citric acid and Y3+was 1.5:1. The results indicated that Y2SiO5:Eu3+is a potential red-emitting candidate phosphor for white light-emitting diodes.

White light emission is generated by combining the blue and red emissions of and , respectively, and by adding the co-doping element in a single host lattice of . The effect of concentration on the emission intensity of is studied, and the emission intensity reaches a maximum at 1% . Energy migration over sites occurs, resulting in concentration quenching, and the concentration quenching mechanism is d-d interaction by Dexter theory. exhibits a high absorption in the near-UV region, and energy transfer from to occurs in . When is introduced in , a green emission band appears and white light is obtained. The results indicate that is an efficient "single host lattice phosphor" for solid-state lighting technology using a UV light emitting diode to generate white light.

Abstract: In the recent years, the competition of shortening the development cycle of new products is more and more fierce. Given the shortcomings of traditional scheduling algorithm in Intelligent Manufacturing, the architecture of multi-agent-based Intelligent Manufacturing System is put forward, which represents the basic processing entity. The architecture is based on the methodology of multi-agent systems (MAS) in distributed artificial intelligence (DAI). The multi-agent system has some common characteristics, such as distribution, autonomy, interaction and openness, which are helpful to transform the traditional architecture into a distributed and cooperative architecture in an Intelligent Manufacturing System. To develop a multi-agent-based scheduling system for Intelligent Manufacturing, it is necessary to build various functional agents for all the resources and an agent manager to improve the scheduling agility. In this paper, the proposed architecture consists of various autonomous agents that are capable of communicating with each other and making decisions based on their knowledge. The architecture of Intelligent Manufacturing, the scheduling optimization algorithm, the negotiation processes and protocols among the agents are described in detail. A prototype system is built and validated in an illustrative example, which demonstrates the feasibility of the proposed approach. The experiments prove that the implementation of multi-agent technology in Intelligent Manufacturing System makes the operations much more flexible, economical and energy-efficient. [Copyright &y& Elsevier]

Based on the research results and practical engineering experience pertaining to the protection and reinforcement of the cliff of the Mogao Grottoes in Dunhuang, China, this paper presents a method that is mainly based on the analytic hierarchy process (AHP) to evaluate the preservation state and risk of the Mogao cliff, a means that numerical simulation was conducted to quantitatively evaluate the stability and effectiveness of protective measures for the Mogao cliff, a set of reinforcement methods which integrate the key protection techniques based on propping, anchoring, grouting, and anti-weathering and the quality control measures based on assessing their effectiveness for surrounding rocks of the grottoes, and a set of methods for monitoring and warning based on risk theory throughout the entire reinforcement process. The four above-mentioned techniques complement and support with each other, and every stage is based on research. Additionally, the protection and reinforcement concepts implemented at the Mogao cliff are summarized in this paper. Finally, preventive protection and reinforcement techniques for sandy conglomerate grottoes were established based on the research, evaluation, calculation, and monitoring. The techniques presented in this paper can be used as a theoretical foundation and provide technical guidance for the protection and reinforcement of similar cultural heritage sites all over the world.

Mogao Grottos are located at the eastern foot of the Mingsha Mountain, 25 km southeast of Dunhuang City. The caves were excavated into the cliff on the west bank of the Daquan River. The wall paintings in the caves are subject to the severe deterioration generated by recrystallization of salt. It relates with the movement of water/moisture in rock formation. Through the satellite image analysis and geological survey, it has been clarified that the movement of ground water is governed by the fault system. The geographical nature is specified by the aggressive tectonic movement from the south.

The Ca2SiO4:Dy3+ phosphor was synthesized by the high temperature solid-state reaction method in air. The emission spectrum of Ca2SiO4:Dy3+ phosphor shows several bands at 486, 575, and 665 nm under the 365-nm excitation. The effects of Li+, Na+, and K+ on the emission spectrum of Ca2SiO4:Dy3+ phosphor were studied. The results show that the emission spectrum intensity is greatly influenced by Li+, Na+, and K+. The charge compensation concentration corresponding to the maximum emission intensity is different with different charge compensations.

Trivalent terbium (Tb3+) doped double molybdate AGd(MoO4)2(A = Li+, Na+) phosphors have been synthesized by combustion reaction. The crystal structures and luminescent properties of the phosphors are investigated in this paper. The XRD patterns indicate that AGd(MoO4)2:Tb3+phosphors take on single phase when the precursors are sintered at 700°C for 3 h. The average crystal size is about 2.0 μm. LiGd(MoO4)2:Tb3+and NaGd(MoO4)2:Tb3+phosphors have the similar luminescent properties. The influences of urea and Tb3+concentration on the luminescent properties of phosphor samples are also discussed in detail. The results show that Tb3+activated LiGd(MoO4)2phosphors is a potential candidate for green phosphor in ultraviolet (UV) -based white LED.

White light emission is generated by combining the blue and red emissions of Eu2+and Mn2+, respectively, and by adding the co-doping element Ba2+in a single host lattice of Sr2B2P2O10. The effect of Eu2+concentration on the emission intensity of Sr2B2P2O10:Eu2+is studied, and the emission intensity reaches a maximum at 1% Eu2+. Energy migration over Eu2+sites occurs, resulting in concentration quenching, and the concentration quenching mechanism is d-d interaction by Dexter theory. Eu2+exhibits a high absorption in the near-UV region, and energy transfer from Eu2+to Mn2+occurs in Sr2B2P2O10:Eu2+,Mn2+. When Ba2+is introduced in Sr2B2P2O10:Eu2+,Mn2+, a green emission band appears and white light is obtained. The results indicate that Sr2B2P2O10:Eu2+,Mn2+,Ba2+is an efficient “single host lattice phosphor” for solid-state lighting technology using a UV light emitting diode to generate white light.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.