Improving the luminescence properties and powder morphologies of red-emitting Sr0.8Ca0.19AlSiN3:0.01Eu2+ phosphors for high CRIs white LEDs by adding fluxes

Red-emitting Sr_0.8Ca_0.19AlSiN₃:0.01Eu²⁺ phosphor with halide fluxes for use in the production of white light-emitting diodes (white LEDs) with high-colour rendering indices (CRIs) was prepared through the high-temperature solid-state method. Fluoride (NaF, SrF₂, BaF₂, CaF₂, AlF₃·3H₂O and CeF₃), chloride (NH₄Cl, BaCl₂, MgCl₂, NaCl and LiCl) and composite fluxes (NaF + SrF₂, SrF₂+NH₄Cl and NaF + NH₄Cl) were applied in the phosphors. NaF, SrF₂, NH₄Cl and NaF + SrF₂ fluxes had prominent effects on the characteristics of Sr_0.8Ca_0.19AlSiN₃:0.01Eu²⁺ phosphors. Sr_0.8Ca_0.19AlSiN₃:0.01Eu²⁺ phosphors with various powder morphologies can be obtained through the addition of fluxes, which are conducive for phosphor formation. The powder morphologies of phosphors incorporated with NaF + SrF₂ were preferable to those of powders incorporated with other fluxes. This result indicated that the incorporation of NaF + SrF₂ into Sr_0.8Ca_0.19AlSiN₃:0.01Eu²⁺ yielded phosphors with high luminescent intensity and quantum efficiency, excellent thermal stability, narrow full widths at half-maximum (FWHM, 75.2 nm), uniform rod-like morphologies with large particle sizes (D₅₀ = 16.99 μm) and good particle dispersion. White LEDs with high CRIs were obtained by combining prepared phosphors (NaF + SrF₂ additive) with the commercial green-emitting phosphors Y₃(Al,Ga)₅O₁₂:Ce³⁺ and (Sr,Ba)₂SiO₄:Eu²⁺. White LEDs with Y₃(Al,Ga)₅O₁₂:Ce³⁺ and (Sr,Ba)₂SiO₄:Eu²⁺ phosphors had correlated colour temperatures (CCTs) of 3064 and 3023 K, respectively, and CRIs of 81.8 and 92.4, respectively. Therefore, NaF + SrF₂ can be used as a favourable flux for the production of Sr_0.8Ca_0.19AlSiN₃:0.01Eu²⁺.     

Physical modeling of the electrical double layer effects on multispecies ions transport in cement-based materials

The transport of ions through cement-based materials is described at a microscopic scale with a pore modeled by two infinitely large flat plates. The theory of the electrical double layer (EDL) shows that (i) the overlapping between the diffuse layers occurring in the pore is more important as the pore diameter will be small (low than the Debye length) and the pore walls will be strongly charged, (ii) the fluxes of coions and counterions will be respectively increased and attenuated in such pores. The gel pores of cement based materials have similar characteristics. As the capillary pores of the cement based materials with low porosity are connected between them by the pores gel, the transport of ions at a macroscopic scale could be greatly influenced by the overlapping effect of the diffuse layers.     

结晶器保护渣对超低碳钢连铸坯表面渗碳的影响

通过超低碳钢渗碳的理论解析和实验测定，研究连铸保护渣对超低碳钢铸坯表面渗碳的影响。在稳态浇注条件下，超低碳钢铸坯表面渗碳量和渗碳深度很小；在非稳态浇注时期，超低碳钢铸坯表面渗碳量和渗碳深度很大。保护渣中含石墨的连铸坯表面渗碳量和渗碳深度最大，碳黑次之，活性炭最小。     

电子器件用的中温钎料的进展

概述了用于电子器件中的中温钎料(450～600℃)的特点及应用条件,回顾中温钎料近40年来的发展,指出非晶态中温钎料在电子器件中的应用的可能性。     

无铅波峰焊设备的特点

相对于传统的Sn-Pb焊料,无铅焊料需要较高的焊接温度,而且润湿性差,另外免清洗助焊剂和水溶性助焊剂的固体含量低,活性温度高和活性区间窄。无铅焊料和助焊剂的特性决定了无铅波峰焊设备在结构和材料选用上有很大不同。通过对无铅波峰焊设备的各个部分的特点进行分析,为传统的旧波峰焊设备的改造提供参考。     

抗吸潮碱性烧结焊剂的试验研究

介绍了一种新型高强钢埋弧焊用碱性烧结焊剂(SJ—K1)。该焊剂具有良好的工艺性能,电弧燃烧稳定,尤其是具有较强的抗吸潮性,这种焊剂配合H08A,H10Mn2或其它合金焊丝可用于低合金高强度钢焊接,并可获得氧含量和扩散氢含量低、却贝冲击韧性高的焊缝金属。     

Sampling frequency and accuracy of SPM flux estimates in two contrasted drainage basins

The present paper is based on discharges and suspended particulate matter concentrations from a 9-years high-resolution database for the Garonne River (large plain river) covering contrasted hydrologic years, and a 12-months high frequency sampling for the Nivelle River (small mountainous river). Annual SPM fluxes in the Garonne River range from 0.6 x 10(6) t year(-1) (1997) to 3.9 x 10(6) t year(-1) (1996). In contrast, the Nivelle River transported 11 x 10(3) t year(-1) from December 1995 to December 1996. From the long-term observation of the Garonne River an empirical relation between SPM* (discharge-weighted mean annual SPM concentrations) and annual discharge was established. This relation allows estimating annual SPM fluxes for the Garonne River with less than 30% deviation from reference values for the whole range of mean annual discharge observed during the past decade. Specific (=area-normalized) annual SPM fluxes (YSPM) range from 11 to 74 t km(-2) year(-1) for the Garonne River. Comparison of these results with YSPM of the Nivelle River (69 t km(-2) year(-1) in 1996) suggests that interannual hydrological variations may have a greater impact on fluvial SPM transport than basin-specific parameters. By extracting individual SPM concentrations and corresponding discharge values from the database, different sampling frequencies were simulated and resulting SPM fluxes were then compared to reference fluxes derived from the complete database. If a deviation of simulated flux estimates from reference fluxes lower than +/-20% is accepted, the Garonne River (large plain river) must be sampled at least every 3 days (10 samples per month) and the Nivelle River every 7 h (approx. 100 samples per month). For the Garonne River this minimum sampling frequency is valid for all contrasted hydrologic years of the observation period. Below these minimum sampling frequencies, annual SPM flux estimates may greatly differ from reference fluxes (up to 200%) and there is high probability of systematic underestimation. Consequently, annual SPM flux estimates for the Garonne River derived from the empirical relation (SPM*-annual discharge) are likely to be more satisfactory (errors <30%) than estimates based on sampling frequencies lower than the minimum frequency. These findings underline the need of adapted sampling strategies for erosion assessment, reliable chemical (e.g. nutrients and pollutants) mass balances and characterisation of fluvial transport mechanisms in the world's contrasted watersheds.     

Historical contamination of Yukon Lake sediments by PCBs and organochlorine pesticides: influence of local sources and watershed characteristics

PCBs and other persistent organochlorine (OC) pesticides were analyzed in sediment cores collected from six lakes in Yukon Territory and one in northern British Columbia, Canada, with the objective of establishing sources and historical trends of these contaminants. DDT was found to be the most prominent OC in the sediment profiles of most of the lakes. Maximum sigmaDDT levels (3.47-2680 ng g(-1) dw) were observed in sediment slices dated to the 1950s from lakes near populated areas. In contrast, in more remote lakes (Hanson, Kusawa and Lindeman), the maximum sigmaDDT concentrations were observed in the sediments dated to the 1970s. Highest sigmaPCB and sigmaDDT concentrations were measured in sediments from Watson Lake, near a suspected PCB waste disposal site and in a region where DDT was heavily applied in the 1950s and 1960s. Elevated sigmaPCB concentrations [16.1-93.6 ng g(-1) dry weight (dw)] were also observed in sediments from lakes situated near populated areas, relative to Kusawa and Lindeman (11.1 and 12.7 ng g(-1) dw, respectively). Recent sigmaPCB fluxes ranged from 621 ng m(-2) y(-1) in Kusawa Lake to 16400 ng m(-2) y(-1) in Little Atlin Lake. The extremely high sedimentation rate (2050 g m(-2) y(-1)) in glacial fed Lindeman Lake gave rise to elevated fluxes of sigmaPCB (2410 ng m(-2) y(-1)) and other OCs, despite much lower concentrations in the sediment. Levels of hexachlorocyclohexanes (sigmaHCH), chlordane-related compounds (sigmaCHL), and chlorobenzenes (sigmaCBz) were in the low ng g(-1) (dw) range in all lake sediments, similar to concentrations previously reported for Arctic lakes in Canada, indicating that their major source was long range atmospheric transport. Contamination of the lakes with PCBs and DDT near populated areas of the Yukon Territory appears to be a result of regional activities rather than long range transport and deposition. The results also point to glacial runoff as a significant source of OCs to small, high elevation lakes (Lindeman), but not to larger lakes within the Yukon River drainage basin that are also affected by glacial sources (Kusawa, Laberge).     

黑河流域湿地、农田、草地生态系统碳通量变化特征及驱动因子分析

为了认识黑河流域湿地、农田、草地生态系统不同时间尺度的碳通量特征及与环境因子的关系,并为干旱区生态系统碳源/汇效应评估提供理论依据.采用涡度相关技术对黑河流域湿地、农田、草地生态系统进行长达7 a的碳通量、气象因子观测,分析了净生态系统生产力(NEP)、生态系统呼吸(Reco)、总初级生产力(GPP)在日际、季节、年际...     

新型无公害镁合金熔剂的研制

新研制成功的镁合金用熔剂以多种碱金属的氯化物、氟化物为主要成分 ,添加少量无机物 ,使熔剂的熔点、密度、粘度、造渣性达到最佳状态 ,特别是该熔剂加到镁液表面时体积会膨胀 ,释放出惰性气体 ,既减慢了熔剂下沉又增强阻燃效果。 5年的实际使用表明该熔剂使用中释放出来的有害气体远低于规定的排放标准 ,有利于环境保护和操作者健康