Thermodynamic investigation on the Al2O3–BaO binary system

The Al₂O₃–BaO binary system has been studied using the CALPHAD technique in this paper. The modeling of Al₂O₃ in the liquid phase is modified from the traditional formula with the liquid phase represented by the ionic two-sublattice model as (Al³⁺, Ba²⁺)_P (AlO₂¹⁻, O²⁻)_Q. Based on the measured phase equilibrium data and experimental thermodynamic properties, a set of thermodynamic functions has been optimized using an interactive computer-assisted analysis. A comparison between the calculated results and experimental data is presented.     

Reduction and re-oxidation of molybdena and vanadia: DFT cluster model studies

Catalytic properties of oxide-based catalysts strongly depend on the mobility and reactivity of surface oxygen as well as on oxide ability to provide oxygen as a reactant and its facility to undergo re-oxidation process. To understand the whole process one of the most important information concerns energetics of creation and annihilation of surface oxygen vacancies. In order to obtain such data theoretical calculations by means of DFT method are carried out. Catalytic activity of different surface species that contain oxygen (surface O centers, surface OH and H₂O groups, adsorbed O₂) in MoO₃ and V₂O₅ systems are examined using cluster model. In addition, tendency towards an aggregation of surface oxygen vacancies is studied.     

放电等离子烧结快速制备高钪含量铝钪合金

采用放电等离子烧结技术制备高钪含量Al-Sc合金,利用扫描电子显微镜、能谱仪和X射线衍射仪等设备对球磨前后Al-Sc合金粉末的形貌、相组成以及不同温度快速烧结样品的显微组织结构进行观察和分析,研究烧结温度对Al-Sc合金显微组织的影响。结果表明:球磨后粉末的形状较规则,其颗粒尺寸为25~45mm,并初步实现了机械合金化,除Al、Sc相以外,有少量Al3Sc和AlSc2相生成。放电等离子烧结可实现高钪含量铝钪合金的快速致密化,成功制备出钪含量30%(质量分数)的铝钪合金,通过调整烧结工艺参数,烧结样品的相对密度可达92.19%;当烧结温度高于500℃时,所得样品致密,无孔洞,且无明显晶界;随着烧结温度的提高,Sc相与第二相融合,形成Al3Sc、AlSc2等第二相,存在于合金中,且Al3Sc相呈现逐渐增强的趋势。     

Green and red phosphor for LED backlight in wide color gamut LCD

Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent developments in crystal structure,luminescence and applications of phosphors for wide color gamut LED backlight are introduced.As novel red phosphors,Mn~(4+)activate fluoride and aluminate phosphors are advanced in quantum efficiency,thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission.The crystal structure and fluorescence properties of Mn~(4+)doped fluosilicate,fluorogermanate,fluotitanate,as well as Sr_4 Al_(14)O_(25),CaAl_(12)O_(19) and BaMgAl_(10)O_(17) phosphors are discussed in detail.A serial of narrow-band red-emitting Eu~(2+),Eu~(3+)and Pr~(3+)-doped nitride silicates and molybdate phosphors are also introduced.Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation,narrow emission,high quenching temperature,high quantum efficiency,such as β-sialon:Eu~(2+),Ba_3Si_6O_(12)N_2:Eu~(2+),MSi_2O_2N_2:Eu~(2+)(M=Ca,Sr,Ba),y-AlON:Mn~(2+)and Ca_3Sc_2Si_3O_(12):Ce~(3+).All above phosphors demonstrate their adaptability in wide color gamut LCD display.Especially for Mn~(4+)doped fluosilicate red phosphor and β-sialon:Eu~(2+)green phosphor.To achieve an ultra-high color gamut in white LED backlight and against the OLED,innovative narrow-band-emission red and green phosphor materials with independent intellectual property rights are continuously pursed.     

Thermodynamic Description of $${\hbox{SrO-Al}_{2}\hbox{O}_{3}}$$ System and Comparison with Similar Systems

The Al₂O₃-SrO binary system has been studied using the CALPHAD technique in this paper. The modeling of Al₂O₃ in the liquid phase is modified from the traditional formula with the liquid phase represented by the ionic two-sublattice model as (Al³⁺, Sr²⁺) _P (, O²⁻) _Q . Based on the measured phase equilibrium data and experimental thermodynamic properties, a set of thermodynamic functions has been optimized using an interactive computer-assisted analysis. The calculated results are compared with experimental data. A comparison between this system and similar systems is also given.     

Characterization and alkaline decomposition/cyanidation of beudantite–jarosite materials from Rio Tinto gossan ores

Jarosite-type minerals are the major silver carriers in the gossan ores from Rio Tinto (Spain). Two types of minerals were found: one corresponding to beudantite variable enriched in sulfate; the other is potassium jarosite containing various amounts of arsenate and lead. They are isostructural with cell parameters intermediate between those reported for end members. Silver is present in both jarosites as dilute solid solution (230 ppm Ag in average). The cyanidation of potassium jarosite in saturated Ca(OH)₂ at 70–100°C consists of two step in series: a slow step of alkaline decomposition followed by a fast step of Ag complexation from the decomposition solids. The alkaline decomposition is characterized by the simultaneous removal of sulfate and K ions and the formation of an amorphous hydroxy-arsenate of Fe, Pb and Ca. The kinetics are chemically controlled, with an activation energy of 86.5 kJ mol⁻¹. The nature of the alkaline decomposition of beudantite was similar but extremely slow at ≤100°C.     

Re-determination of the crystal structure of Ca₂Y₈Si₆O₂₆ and study on the luminescent properties of Ca₂Y₈Si₆O₂₆:Tb³⁺

The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal,space group P63/m,a=0.93515 nm,c=0.67872 nm,α=β=90°,γ=120°,V=0.5138692 nm3.Three strong peaks located at 32.079o,32.595o,and 50.104o with d=2.7903,2.74649,1.8194 was in accordance with,(112),and(213) planes.The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+.The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm.The photoluminescence measurements showed that the green emission originated from 5D4-7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.     

银基钎料真空钎焊钛/钢接头组织与性能研究

采用Ag-28Cu银基钎料对钛/钢进行真空钎焊。研究钛/钢钎焊接头的拉剪强度、界面微观组织演变与断裂行为的特征,确定不同钎焊工艺对接头拉剪强度和成分分布的影响。结果表明,钛/钢结合界面形成不同的金属间化合物,如CuTi、CuTi2、Cu4Ti3、FeTi等,并且接头微观组织对钎焊试样的拉剪强度有显著影响。接头最高拉剪强度可达100 MPa。不同钎焊条件下断口形貌发生变化,但断裂都是发生在钛/银基合金界面上。     

粉末冶金结合热轧制备高硼铝合金组织与性能研究

采用粉末冶金结合热轧成形工艺制备含硼质量分数为7%与12%的中子屏蔽用高硼铝合金（Al-7% B与Al-12% B），并对不同工艺条件下铝硼合金的组织与性能进行研究。结果表明:在机械球磨5 min+放电等离子烧结条件下，Al-7% B合金中AlB₂体积分数高于Al-12% B合金，且分布更加均匀。放电等离子烧结后进行热轧有利于提高试样的相对密度，减少硼粉团聚。在450℃固溶处理2 h，Al-7% B合金试样的拉伸强度和屈服强度达到峰值，分别为145.7 MPa和99.4 MPa。由10B面密度理论计算结果可知，厚度相近时，热轧后高硼铝合金10B面密度均可达到BoralTM水平。