Synthesis of YAG∶Ce^(3+) Phosphor by Polyacrylamide Gel Method and Promoting Action of α-Al_2O_3 Seed Crystal on Phase Formation

YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.

Effects of alternating current imposition and alkaline earth elements on modification of primary Mg_2Si crystals in hypereutectic Mg-Si alloy

The effects of alternating current imposition and/or alkaline earth elements on modification of the primary Mg2Si crystals in the hypereutectic Mg-Si alloy were investigated.An alternating current of 60 A with frequency of 1 kHz was applied into the hypereutectic Mg-Si melt which was alloyed with alkaline earth elements or not in the fixed temperature range from 700 to 630℃. The results show that the primary Mg2Si crystals could be refined by imposing alternating current or adding alkaline elements. Compared with the samples treated by adding 0.4%Ca or 0.4%Sr,higher modification efficiency could be obtained for the samples treated by imposing alternating current.No further modification efficiency could be obtained for the samples treated by imposing alternating current combined with 0.4%Ca or 0.4%Sr addition.

Estimation of the Primary Magma Compositions of an Igneous Rock Series Petrogenetically Associated with Fractional Crystallization with Special Reference to Element Abundance Relationships

A primary magma not only represents the starting point of a fractional crystallization process,but also is the product of an equilibrium or fractional partial melting process in a mantle. Element abundance relation ships in the primary magma obey both the law of power function for fractional crystallization and the law of fractional linear function for Nullibrium partial melting. Based on this double nature of the primary magma, the authors advanced a principle to restore the primary magma composition from that of an igneous rock series with petrogenesis of fractional crystalization and put forward an approach of estimating the element abundance of the primary magma, exemplified by the rare-earth elements in the Andes volcanic rock series.

Relationship between Primary Crystal Temperature and Carbon Equivalent in Cast Iron

CE （=%C＋（1/3）x（%Si）） does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperature （Tc） and carbon equivalent （CEL） was investigated. The results show that Tc （Celsius degree） = 1650-110 × （%C） -25 × （%Si）＋3 × （%Mn） -35 × （%P） -71 × （%5）-2 × （%Ni） -7 × （%Cr）; CEL=%C ＋ 0.23×（%Si）-0.03× （%Mn）＋0.32×（%P）＋0.64×（%S） ＋0.02×（%Ni）＋0.06×（%Cr）. That is, in hypo eutectic composition, carbon equivalent should be calculated with CEL=%C＋ 0.23×（%Si）, not with CE=%C＋（1/3） x（%Si）.

EFFECT OF Ni CRYSTAL SIZE DISTRIBUTION ON THE ANTICOKING BEHAVIOR OF La-MODIFIED Ni/α-Al_2O_3 CATALYSTS

The crystal size distribution（CSD）was determined with small angle X-ray scattering technique.Theanticoking property of Ni-catalysts was investigated with the steam reforming of n-heptane in a TG-monitoredflow reactor.The results of this study show that the rate of coking on the supported Ni-catalysts depends main-ly on the percentage content of the large size fraction（25-70nm）of Ni-crystallites,and that the dispersion ofNi-crystallites and the anticoking property of the Ni/α-Al2O3 catalysts were promoted obviously by theLa2O3-modification method.The variation of the Ni-CSD and the anticoking property of the catalysts were fur-ther tested through different periods of hydrothermal treatment.It is found that the content of the largeNi-crystal size fraction and the coking rate pass correspondingly through a maximum.

Growth mechanism of primary silicon in cast hypoeutectic Al-Si alloys

The microstructural features of hypoeutectic AI-10%Si alloy were observed using optical microscopy and electron backscatter diffraction. The results show that primary silicon particles are frequently found in hypoeutectic alloys. Hence, the nucleation and growth mechanisms of the precipitation of primary silicon of hypoeutectic Al-10%Si alloy melts were investigated. It was discovered that Si atoms are easy to segregate and form Si-Si clusters, which results in the formation of primary silicon even in eutectic or hypoeutectic Al-Si alloys. In addition, solute redistribution caused by chemical driving force and large pile-ups or micro-segregation of the solute play an important role in the formation of the primary silicon, and the solute redistribution equations were derived from Jackson-Chalmers equations. Once Si solute concentration exceeds eutectic composition, primary silicon precipitates are formed at the front of solid/liquid interface.

微晶活性α-Al_2O_3微粉在耐火浇注料中的应用

介绍了新研制的微晶活性α-Al2O3微粉,并重点对产品的原晶粒度、吸水率以及其应用性能进行了研 究,结果显示具有极好的应用前景。

Determination of metastable zone and induction time of analgin for cooling crystallization

The solubility, metastable zone width, and induction time of analgin for unseeded batch cooling crystallization in ethanol–aqueous system were experimentally determined. The solubility data could be well described by the van't Hoff equation model. The metastable zone width at various cooling rates was measured, and some parameters of nucleation kinetic were calculated using the Ny'vlt theory. Furthermore, the induction period of various temperatures and supersaturation ratios was also measured. According to classical nucleation theory, some nucleation parameters and interfacial energy was calculated through the induction time(t_(ind)) data. Homogeneous nucleation tended to occur when the supersaturation is high, whereas heterogeneous nucleation was more likely to occur when the supersaturation is low.

Individual and synergistic effect of gamma alumina（γ-Al2O3） and strontium on microstructure and mechanical properties of Al-20Si alloy

An optimized combination of gamma alumina (4 wt.%) and strontium (0.1 wt.%) was incorporated in cast Al-20Si alloy to obtain fine form of silicon. During casting process, the amount of γ-Al2O3 was varied from 0.5.6 wt.% to refine primary Si and Sr was varied from 0.05.0.1 wt.% to modify eutectic Si. The results showed that the average size of primary Si is 24 μm for addition of 4 wt.%γ-Al2O3 to the alloy whereas 0.1 wt.% Sr resulted in sphericity of eutectic Si to ~0.6 and average length of ~1.2 μm. The thermal analysis revealed that γ-Al2O3 can act as potential heterogeneous nucleation sites. Moreover, simultaneous addition of γ-Al2O3 and Sr does not poison γ-Al2O3 particles and inhibit their nucleation efficiency as in the case of combined addition of phosphorous and strontium to Al-20Si alloy. Therefore, it was concluded that enhanced tensile strength, i.e., ultimate tensile strength (increase by 20%) and elongation (increase by 23%) in Al-20Si.4γ-Al2O3.0.1wt.%Sr alloy as compared to as-cast Al.20Si alloy can be attributed to refinement of primary Si, modification of eutectic Si and the presence of α(Al) in the alloy as evident from eutectic shift.

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during solidification.The grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the simulation.The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed.It is found that the growth of grains will be restrained in the location with higher nuclei density.The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification.The comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

HR-TEM and FIB-SEM characterization of formation of eutectic-like structure from amorphous GdAlO_3-Al_2O_3 system

The crystallization process of the eutectic composition of GdAlO_3-Al_2O_3 from the amorphous phase prepared by rapid-quenching of melt that leads to the formation of a cantaloupe skin-like microstructure was investigated using focused ion-beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (HR-TEM).The amorphous films were heat-treated at temperatures between 1000 °C and 1500 °C for up to 30min to form the eutectic phases of GdAlO_3 and Al_2O_3.The GdAlO_3 and Al_2O_3 crystal phases that formed from the amorphous phase were identified by FIB-SEM and HR-TEM.Both components began to crystallize and grow from the amorphous phase separately at different temperatures.The formation process of these crystal phases was different from that of the ordinary eutectic microstructure solidified from the GdAlO_3-Al_2O_3 system.Therefore,the observed structure is termed "eutectic-like" for distinction.The microstructures formed from the amorphous phases at sufficiently high temperatures consisted of ultra-fine microstructures of individually crystallized components and were similar to ordinary eutectic microstructures.By heat-treating the amorphous films at 1500 °C for either 2 min,8min or 30min,the ultra-fine components of GdAlO_3 and Al_2O_3 were found to crystallize following a eutectic-like stage after 8min of heat treatment.

Cubic Mesoporous Aluminosilicate with Primary Structure Units of Zeolite Beta in the Pore Wall

Mesoporous aluminosilicate with cubic ordered structure was synthesized by two-step crystallization, which showed stronger acid sites and more effective activity for catalytic alkylation of 2, 4-ditert-butylphenol with tert-butanol than conventional H-AlMCM-48 materials.

Unseeded Induction Period and Primary Nucleation of Lithium Carbonate

A set of laser apparatus was used to study induction period and primary nucleation of lithium carbonate in reactive crystallization.The results show that induction period increases with the decrease of supersaturation degree and temperature.Magnetic field has nearly no impact on it,while the use of ultrasound reduces it obviously.The impacts of some impurities and additives on primary nucleation were investigated.It is found that the presence of Na2SO4,NH4Cl,(NH4)2SO4 and EDTA disodium prolongs induction period,whereas KCl,NaCl,NaBr and CH4N2O can decrease it.Many important parameters of primary nucleation are also obtained,as temperature goes up from 283 to 313 K,interfacial tension decreases from 44.8 to 41.5 mJ/m2,contact angle varies from 82.9o to 88.7o,nucleation order is between 5.0 and 5.4,surface entropy factors are all above 5,suggesting that the growth mechanism is a spiral growth.Besides,both the homogeneous and heterogeneous primary nucleations were monitored with on-line focused beam reflectance measurement.

Influence of ultrasonic treatment on formation of primary Al_3Zr in Al-0.4Zr alloy

The effect of ultrasonic treatment on the formation of primary Al3Zr was investigated by applying ultrasound to an Al?0.4Zr alloy.Three temperature ranges were selected,i.e.,830to790°C(above liquidus),790to750°C(cross liquidus)and750to710°C(below liquidus)for ultrasonication.Using the scanning electron microscopy,both the size and morphology of the primary Al3Zr particles were examined.It was found that the size was significantly reduced and the morphology changed from large throwing-star shape to small compact tablet shape.The mechanisms for refinement of primary Al3Zr were discussed.It is suggested that sonocrystallization theory via activation of aluminium oxide particles is responsible for the refinement of primary Al3Zr when ultrasonic melt treatment(UST)is applied within the fully liquid state.The refinement of primary Al3Zr particles when UST is applied in the slurry(growth stage)is due to the sonofragmentation.

Synthesis of energetic coordination polymers based on 4-nitropyrazole by solid-melt crystallization in non-ionization condition

Based on the theory of crystallization,a solvent-free solid-liquid phase crystallization method called solid-melt crystallization was designed to prepare energetic coordination polymers.Two target compounds[Cu(NPyz)_(4)NO_(3)]·NO_(3)(ECPs-1)and Cu(NPyz)_(4)(ClO_(4))_(2)(ECCs-2)were prepared through programmed heating and cooling by using 4-nitropyrazole(NPyz),(Cu(NO_(3))_(2)·5H_(2)O and Cu(ClO_(4))_(2)·5H_(2)O) as raw materials.In addition,crystallization pre-experiments and annealing experiments also verified the feasibility of the method.Their structures were confirmed by IR,elemental analysis,single-crystal X-ray diffraction and powder X-ray diffraction.The physicochemical properties and sensitivity test results showed that ECCs-2 has better thermal stability(T_(d)=221℃),while ECPs-1 is less sensitive to mechanical stimuli(IS=12 J,FS=240 N).Calculations based on EXPLO5 and the Kamlet-Jacobs equation showed that ECCs-2 has more considerable detonation performance(P=25.2 GPa,D=7.5 km/s).In comparison,the more intuitive results from the HN test,flame test,thermal resistance test and lead plate explosion test revealed that ECCs-2 has an“acceptable”detonation performance.The laser detonation test also showed that ECCs-2 is a promising excellent laser detonation material(E=408 mJ,P=24 W,τ=17 ms).

Crystallography in Spaces E², E³, E⁴, E⁵… Study of Three Crystal Families of Space E⁵

In two previous papers, we explained the classification of all crystallographic point groups of n-dimensional space with n ≤ 6 into different isomorphism classes and we describe some crystal families. This paper mainly consists in the study of three crystal families of space E5, the (di-iso hexagons)-al, the hypercube 5 dim and the (hypercube 4 dim)-al crystal families. For each studied family, we explain their name, we describe their cell and we list their point groups which are classified into isomorphism classes. Then we give a WPV symbol to each group. (WPV means Weigel Phan Veysseyre). Our method is based on the description of the cell of the holohedry of each crystal family and of the results given by the Software established by one of us. The advantage to classify the point groups in isomorphism classes is to give their mathematical structures and to compare their WPV symbols. So the study of all crystal families of space E5 is completed. Some crystal families of space E5 can be used to describe di incommensurate structures and quasi crystals.

冰晶石-月壤熔盐体系初晶温度的研究

冰晶石熔盐电解法可实现月壤原位利用制备金属和氧气,研究冰晶石-月壤熔盐体系的初晶温度对电解槽稳定运行具有重要意义。本文以火山渣和玄武岩复配的NEU-1月壤仿真样为原料,与冰晶石、CaF_(2)混合配置电解质,将其作为待测试样,利用差热分析法测量了不同月壤仿真样添加量、不同分子比的冰晶石熔盐体系的初晶温度。结果表明,当分子比为2.2时,随着月壤仿真样添加量从0%增加至24%,冰晶石熔盐体系的初晶温度从974.9℃降低至932.0℃;每添加1%的月壤仿真样,冰晶石熔盐体系的初晶温度降低约1.79℃;当月壤仿真样添加量为8%时,随着分子比从2.2升高至2.7,冰晶石熔盐体系的初晶温度从960.0℃升高至979.4℃。

基于有限元模拟的水平连铸TP2铜管坯一次冷却结构优化研究

对比多种结晶器结构下温度场、速度场等分布状态及石墨模具内部温度变化趋势,探究其对铜套、石墨模具等易损件及铜管铸坯温度变化的影响。结果表明,在一次冷却结构增设12道Φ10 mm且倾斜角度为30°的流槽,可使冷却水流态平稳均衡,铜套受热均匀,有利于铸坯周向同时凝固。本文通过有限元软件模拟铜管水平连铸过程一次冷却结构优化对温度的影响,为生产企业改善产线冷却效果,提高产品质量,降低模具成本和延长使用寿命,提供了实验参照和理论指导。

铜管坯水平连铸水冷调控与实验分析

为实现传统铜管坯水平连铸水冷控制系统在线自动化精准控制,提高生产质量与精度,改善管坯组织性能,对现有铜管坯水平连铸一冷水控制进行分析。采用程序设计和物理实验验证的方法,开展了基于可编程逻辑控制器(PLC)闭环策略下石墨结晶器冷却水量自动控制的相关研究。实验结果表明,基于闭环控制逻辑的自动水冷控制系统可以将流量波动控制在±0.5 L/min范围内,离散系数为2.68×10^(-3),明显小于传统水冷控制系统,铜管坯水平连铸一次冷却水闭环控制系统可以实现连铸过程的精确控制。

压气机叶栅冰晶撞击特性的数值模拟研究

航空发动机吸入冰晶会导致推力损失甚至叶片损坏,对飞行安全构成潜在威胁。为了研究冰晶在压气机叶栅中的撞击特性,建立了一种分别计算颗粒撞击叶片压力面和吸力面时运动轨迹的方法,该方法可以避免冰晶颗粒轨迹交叉。在此基础上,对颗粒等效直径和形状对冰晶撞击特性的影响进行了数值模拟研究。结果表明,总收集系数随颗粒等效直径和长宽比的增加而增加。对于相同形状的颗粒,当颗粒直径从20μm增加到50μm时,总收集系数增加了44.1%;对于相同等效直径的颗粒,当颗粒长宽比从0.1增加到10时,总收集系数增加了39%。叶片压力面收集系数的增加是总收集系数增加的主要原因。冰晶撞击叶片前缘时发生破碎现象,撞击叶片表面时发生反弹现象。在叶片表面的大部分区域,冰晶颗粒发生非弹性反弹。就粒径而言,二次撞击后收集系数的分布趋势与一次撞击近似,二次收集系数的最大值减少了约70%。然而,就颗粒长宽比而言,叶片前缘处二次撞击收集系数的分布趋势与一次撞击相反,细长型冰晶颗粒撞击叶片前缘的二次收集系数反而低于粗短型冰晶颗粒撞击叶片前缘的二次收集系数。