Corrosion Characteristics of Electrodeposited Ni Mo P Alloy Immersed in NaCl Solution

用失重法、阳极极化曲线、Ｘ光电子能谱（ＸＰＳ）以及俄歇电子能谱（ＡＥＳ）研究了电沉积ＮｉＭｏＰ合金镀层在５％ＮａＣｌ溶液中的腐蚀特性．非晶态ＮｉＭｏＰ合金镀层比晶态ＮｉＭｏＰ合金镀层有较低的腐蚀速度．阳极极化曲线表明，ＮｉＭｏＰ合金镀层中，镍的摩尔分数为０．７１９～０．８６８时，随镀层中磷含量的增加，腐蚀电位正移；而活化区的峰电流随镀层中钼含量的增加而增加．磷含量对活化区的峰电流以及钼含量对腐蚀电位的影响均很小．ＸＰＳ和ＡＥＳ分析指出，经５％ＮａＣｌ溶液中浸渍后，ＮｉＭｏＰ合金镀层表面形成厚度约为５０ｎｍ的氧化膜．这层氧化膜主要由Ｎｉ２Ｏ３，ＭｏＯ３和ＰＯ４３－等构成，其在电解质溶液和合金间起着阻挡层的作用．The corrosion characteristics of electrodeposited Ni Mo P alloy immersed in 5wt.% NaCl solution were investigated using immersion, anodic polarization curves, XPS and AES analysis. The corrosion rates of amorphous Ni Mo P alloys are lower than that of crystalline Ni Mo P alloys. Anodic polarization curve experiments show that for the electrodeposited Ni Mo P alloys, the nickel mol fraction of which has in between 0.719 and 0.868, the corrosion potential moves to positive with the increase of P content, and the peak current value of active region increase with the increase of Mo content in alloys, though the effects of P content on the peak current of active region and of Mo content on the corrosion potential are insignificant. XPS and AES analyses indicate that after immersion in 5wt.% NaCl solution, an oxidation film of about 50 nm in thickness is formed on the surface of Ni Mo P alloys. This oxidation film is composed of Ni 2O 3,MoO 3 and PO 3- 4, and acts as a barrier between the alloy and the electrolyte.作者联系地址：湖南师范大学化学系,天津大学应用化学系Author's Address: Department of Chemistry, Hunan Normal University, Changsha, Hunan, 410006 Yao Suwei Guo Hetong Department of Applied Chemistry, Tiangjin University, Tianjin, 30007

Discovery of blue-emitting Eu2+-activated sodium aluminate phosphor with high thermal stability via phase segregation

Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of phase compositions in nominal Na2-xAl2B2O7:xEu (x = 0.02-2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through phase segregation combined with related analyses. The structure, phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO3 phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by phase transformation from Na2Al2B2O7:Eu2+ to NaAl11O17:Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na0.4Al2B2O7:1.6Eu and Na0.2Al(2)B(2)O(7):1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl11O17 and EuBO3 phase. The emission intensity for these two samples at 150 degrees C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively

Ultrafast Self-Crystallization of High-External-Quantum-Efficient Fluoride Phosphors for Warm White Light-Emitting Diodes

In this study, we used HF (as good solvent) to dissolve K₂GeF₆ and K₂MnF₆ and added ethanol (as poor solvent) to cause ultrafast self-crystallization of K₂GeF₆:Mn⁴⁺ crystals, which had an unprecedentedly high external quantum efficiency that reached 73%. By using the red phosphor, we achieved a high-quality warm white light-emitting diode with color-rendering index of <i>R</i>_a = 94, <i>R</i>9 = 95, luminous efficacy of 150 lm W^–1, and correlated color temperature at 3652 K. Furthermore, the good–poor solvent strategy can be used to fast synthesize other fluorides

Isolated Coordination Polyhedron Confinement in ABP2O7:Mn2+(A=Ba/Sr; B=Mg/Zn)

Many research efforts have focused on designing new inorganic phosphors to meet different application requirements. The structure-photoluminescence relationship between activator ions and the matrix lattice plays an irreparable role in designing target phosphors. Herein, a series of ABP2O7:Mn2+ (A = Ba/Sr; B = Mg/Zn) phosphors are prepared for a detailed study on the relationship between the luminescence performance and spatial structure and symmetry of the doping site of Mn2+. Due to the weak interaction between nearest B-B pairs, [BO5] is defined as an isolated coordination polyhedron whose structure and symmetry directly influence the photoluminescence of Mn2+. The emission wavelength of Mn2+ is ∼620 nm when it occupies the triangular bipyramid [MgO5] in BaMgP2O7. When Mn2+ occupies the quadrangular pyramid-typed [MgO5] or [ZnO5] in SrMgP2O7, SrZnP2O7, and BaZnP2O7, the emission wavelengths peak at ∼670 nm. We propose a conception of isolated coordination polyhedral confinement to clarify the luminescence performance of Mn2+ in the fivefold coordination configuration with different geometries, which has great theoretical research significance for designing inorganic phosphors

Ultrafast Self-Crystallization of High-External-Quantum-Efficient Fluoride Phosphors for Warm White Light-Emitting Diodes

In this study, we used HF (as good solvent) to dissolve K₂GeF₆ and K₂MnF₆ and added ethanol (as poor solvent) to cause ultrafast self-crystallization of K₂GeF₆:Mn⁴⁺ crystals, which had an unprecedentedly high external quantum efficiency that reached 73%. By using the red phosphor, we achieved a high-quality warm white light-emitting diode with color-rendering index of <i>R</i>_a = 94, <i>R</i>9 = 95, luminous efficacy of 150 lm W^–1, and correlated color temperature at 3652 K. Furthermore, the good–poor solvent strategy can be used to fast synthesize other fluorides

Suppression of Thermal Quenching for CsPbX₃ (X = Cl, Br, and I) Quantum Dots via the Hollow Structure of SrTiO₃ and Light-Emitting Diode Applications

All-inorganic perovskite quantum dots (PQDs, CsPbX3, X = Cl, Br, and I) show outstanding application prospects in the field of photoelectric devices. In recent years, the development of PQDs has greatly improved their stability to water, oxygen, and light. However, thermal quenching of PQDs greatly limits their practical application. Herein, we embed PQDs into ATiO3 (A = Ca, Ba, and Sr) of three different mesoporous spherical structures to explore the effect on thermal quenching of PQDs. Because of the unique mesoporous hollow microsphere structure and low thermal conductivity of SrTiO3, it can effectively block the heat transfer and improve the thermal quenching of PQDs. The photoluminescence (PL) intensity of CsPbBr3@SrTiO3 composites is 72.6% of the initial intensity after heating to 120 °C. Moreover, the PL intensity of CsPbBr3@SrTiO3 composites remains about 80% of the initial value even when stored in air for 20 days or irradiated by 365 nm UV light for 48 h. A neutral white light-emitting diode is assembled by a blue chip, CsPbBr3@SrTiO3 composites, and red phosphor of K2SiF6:Mn4+, which has a color temperature of 5389 K and a color gamut covered 133% of National Television Standards Committee (NTSC)

CaS:Eu2+@CaZnOS:Mn2+: A dual-UV/green-excited and dual-red-emitting spectral conversion with all-weather resistance

To pursue green ecological agriculture, long-life functionalized green house is looking for solar spectrum conversions with well spectral match, outstanding thermal and chemical stabilities, excellent anti-photobleaching and UV-conversion performance. CaS:Eu2+-based phosphors are widely known as a candidate for agricultural films with remarkable green-to-red conversion performance while they are also notorious for poor stabilities. In this work, a core-shell structured CaS:Eu2+@CaZnOS:Mn2+ composite phosphor was synthesized by a two-step solid state method. The coating layer of thermally and chemically inert oxysulfide prevents the sulfide core phosphor from hydrophilic, air-sensitive and heat-induced decompositions. Moreover, the addition of Mn2+ in CaZnOS shell qualifies the composite phosphor with strong UV absorption, which contributes to the improvement of the anti-photodegradation of the inner CaS:Eu2+ and the anti-aging of practical polymer films. The additional UV-to-orange red conversion resulting from CaZnOS:Mn2+ further extends the red components for the indoor plants. As a result, this dual UV/green excited and dual red-emitting super stable chalcogenide phosphor can be used as a general spectral conversion for plant cultivation

Redistribution of Activator Tuning of Photoluminescence by Isovalent and Aliovalent Cation Substitutions in Whitlockite Phosphors

Many strategies, including double substitution, addition of charge compensation, cation-size-mismatch and neighboring-cation substitution, have contributed to tuning photoluminescence of phosphors for white light-emitting diodes. These strategies generally involve modification of a certain special site where the activator occupies; tuning strategy based on multiple cation sites is very rare and desirable. Here we report that isovalent (Sr²⁺) and aliovalent (Gd³⁺) substitutions for Ca²⁺ tune the photoluminescence from one band to multiple bands in whitlockite β-Ca_3–<i>x</i>Sr_<i>x</i>(PO₄)₂:Eu²⁺ and β-Ca_{3–3<i>y</i>/7}Gd_2<i>y</i>/7(PO₄)₂:Eu²⁺ phosphors. The saltatory variation of the emission spectra is caused by the removal of Eu²⁺ from the site M(4) to other sites. Moreover, we found the mechanisms of dopant redistribution tuning the luminescence are different. The incorporation of Gd³⁺ makes the site M(4) empty according to the scheme 3Ca²⁺ = 2Gd³⁺ + □, while Sr²⁺ substitution causes the cation sites to be enlarged due to cation size mismatch. Additionally, the influence of the cation substitutions on the photoluminescence thermal stability of phosphors is researched. The strategies, emptying and enlarging sites, developed herein are expected to provide a general route for tuning luminescence of phosphors with multiple sites in the future

Changing Ce³⁺ Content and Codoping Mn²⁺ Induced Tunable Emission and Energy Transfer in Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Mn²⁺

A series of color-tunable Ce³⁺ single-doped and Ce³⁺, Mn²⁺ codoped Ca_2.5Sr_0.5Al₂O₆ phosphors were synthesized by a high-temperature solid-state reaction. The crystal structure, luminescent properties, and energy transfer were studied. For Ca_2.5Sr_0.5Al₂O₆:Ce³⁺ phosphors obtained with Al­(OH)₃ as the raw material, three emission profiles were observed. The peak of photoluminescence (PL) spectra excited at ∼360 nm shifts from 470 to 420 nm, while that of the PL spectra excited at 305 nm stays unchanged at 470 nm with the increase of Ce³⁺ content. Furthermore, the peak of PL spectra is situated at 500 nm under excitation at ∼400 nm. The relationship between the luminescent properties and crystal structure was studied in detail. Ce³⁺, Mn²⁺ codoped Ca_2.5Sr_0.5Al₂O₆ phosphors also showed interesting luminescent properties when focused on the PL spectra excited at 365 nm. Obvious different decreasing trends of blue and cyan emission components were observed in Ca_2.5Sr_0.5Al₂O₆:0.11Ce³⁺,<i>x</i>Mn²⁺ phosphors with the increase in Mn²⁺ content, suggesting different energy transfer efficiencies from blue- and cyan-emitting Ce³⁺ to Mn²⁺. Phosphors with high color-rendering index (CRI) values are realized by adjusting the doping content of both Ce³⁺ and Mn²⁺. Studies suggest that the Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Mn²⁺ phosphor is a promising candidate for near UV-excited w-LEDs