Lithofacies Phases Analysis of Cover Flux in Tundish for Rare Earth Treated Steel

Lithofacies structure of commercial cover flux and experimental slags were analyzed,and states of rare earth oxides in cover flux were studied. The results show that under the experiment conditions,the mineral structures of original slags are mainly the calcium feldspar,a lot of magnesium olivine and Fe-bearing silicate. Rare earth oxides in the cover flux exist mainly as rare earth silicates. When the content of rare earth oxides reaches a certain value,rare earth oxides precipitate in molten cover flux. It means that the solubility of rare earth oxides is limited. Rare earth oxides may be partly substituted for CaO to form rare earth-silicate which may increase with the basicity reducing.

Effect of Rare Earth on Microstructure of Vacuum Melting Ni-Based Self-Fluxing Alloy Coatings

The Ni-based self-fluxing alloy coating containing RE was acquired by the technique of vacuum melting on the hypoeutectoid steel (Fe-0.45%C) matrix. By X-ray diffraction, SEM and EDX, the microstructure and phase structure of section of coating and the microstructure near the interface between coating and matrix were investigated, and the effect of RE on microstructure of coating was also discussed. The results show that the microstructure of the NiCrBSi alloy coating is composed of Ni-based solid solution and a lot of massive, globular and needle secondary phases CrB, Ni_3B, Cr_7C_3, Cr_(23)C_6 among the solid solution. The metallurgical binding between steel matrix and coating is realized. RE makes needle phase of alloy coating vanish. New phases of NiB and Cr_(6.5)Ni_(2.5)Si are precipitated from alloy coating, and secondary phases of alloy coating are sphericized. Consequently, RE also hinders the diffusion of Ni, Cr and Si atoms from coating to matrix and Fe atoms from matrix to coating, holds back the dilution of Fe for NiCrBSi alloy coating, and assures the chemical composition of the alloy coating.

Effect of CeO_2 on heat transfer and crystallization behavior of rare earth alloy steel mold fluxes

To improve the heat transfer capability and the crystallization property of the traditional mold flux, CaF_2 was replaced with B_2O_3. Then, the influences of CeO_2 on the heat transfer and the crystallization of the CaF_2-bearing mold flux and the new mold flux with 10 wt% B_2O_3 were studied using a slag film heat flux simulator and X-ray diffraction(XRD). The results revealed that the addition of CeO2 reduced the heat transfer by increasing the solid slag thickness and the crystallization of two mold fluxes. However, CeO_2 had less effect on the B_2O_3-containing mold flux compared with the CaF_2-bearing mold flux. According to the analyses, the CeO_2 contents in the CaF_2-bearing mold flux and the B_2O_3-containing mold flux should not exceed 8 wt% and 12 wt%, respectively. Therefore, these experimental results are beneficial to improve and develop the mold flux for casting rare earth alloy steels.

Effects of Rare Earth Oxide on Viscosity of Mold Fluxes for Continuous Casting

The effects of RE (rare earth) oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that: (1) The viscosity of mold fluxes is remarkably increased by RE oxide addition, especially when the mass fraction of RE oxide is more than 10%. (2) By addition of RE oxide, precipitation of the insoluble particles with high melting point from the molten slag with the decreasing of the temperature leads to the increase of viscosity. Viscosity curve shows that RE oxide is soluble in some extent in mold fluxes. When RE oxide is in a state of supersaturation, the existence of insoluble particles also makes the viscosity of mold fluxes increase. (3) Not only the viscosity of mold fluxes can be reduced, but also the capacity to dissolve and absorb RE oxide can be increased by Li_2O, B_2O_3 and BaO. However, the contents of Li_2O, B_2O_3, and BaO should be controlled to suitable levels. (4) The solidification temperature of mold fluxes can be increased by the addition of RE oxide, which is unfavorable to heat transfer and lubrication of mold fluxes between steel shell and mold.

稀土尾砂对超低温建筑瓷质砖性能的影响

以黑泥、金溪钠砂、稀土尾砂为主要原料超低温制备建筑瓷质砖。研究了稀土尾砂用量和烧成温度对样品性能的影响。探索了稀土尾砂在高利用率条件下,将稀土尾砂中的高CaO含量代替传统的硅灰石等原料,其引入多元复合熔剂降低样品烧结温度的可能性。研究结果表明:稀土尾砂中含有高CaO含量,参与构成的多元复合熔剂体系对降低坯体烧结温度,提高样品的烧结性能有积极作用。当稀土尾砂用量≤50%时,增大稀土尾砂用量,样品的烧结温度降低,烧结性能提升,当引入50%稀土尾砂可使坯体的烧结温度降低至1080℃,并表现出最优性能:吸水率为0.15%,烧成收缩为9.84%,体积密度为2.46 g/cm^(3),抗折强度为98.55 MPa,性能指标达国家标准。然而,继续增大稀土尾砂用量,样品的烧结温度上升,其性能反而降低。

Effect of fluxes on structure and luminescence properties of Y_3Al_5O_(12):Ce^(3+) phosphors

Ce3＋-activated yttrium aluminum garnet （YAG） was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied in detail, especially the fluxes of alkali fluorides, which could enhance the emission intensity and change the wavelength of emission peaks. Among these YAG：Ce phosphors, the phosphor sintered with H3BO3 and NaF exhibited the strongest emission. The emission peaks of phosphors prepared with fluxes from LiF to KF were shifted to long wavelength. The effect of NaF concentration on the emission intensity of YAG：Ce was also investigated. The value of emission intensity reached the maximum when the concentration of NaF was 0.5%.

Luminescence enhancement of BaMgSiO_4:Eu^(2+) by adding borate as flux

The luminescence of EU^2＋ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu^2＋ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was enhanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes （LED） combined with tricolor phosphors.

Characterization of Y_2O_2S∶Eu ^(3+), Mg^(2+), Ti^(4+) Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y2O2S ： Eu^3＋ , Mg^2＋ , Ti^4＋ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S： Eu^3＋ （0.01 ≤ x ≤0.10）. On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S： Eu^3 ＋ crystal structure, Eu^3＋ ions only replaced Y^3 ＋ ions＇ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm （5D1→^ 7F2 transition） to 626 nm （^5Do→^7TF2 transition）, and the maximum intensity was obtained when x = 0.09 in Y2O2S： Eu^3＋ （0.01 ≤x ≤0.10）. This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg^2＋ or Ti^4＋. ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg^2 ＋ and Ti^4 ＋ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence （LLP） was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye （0.32 mcd·m^-2）. Thus the LLP mechanism was analyzed.

离子型稀土多孔注液湿润体单向交汇入渗特征及关系模型

离子型稀土矿主要采用原地浸矿法实施资源回收,合理设置注液孔网可有效提高浸矿均匀性和浸矿液渗流速度。而合理孔网参数设定与多孔注液入渗过程中湿润体和湿润峰变化特征密切相关。对不同间距单向交汇入渗试验和单孔入渗试验进行了对比和分析。结果表明:湿润体交汇前,两种试验的湿润峰运移曲线基本重合,湿润体形状近似为八分之一椭球体;湿润体交汇后,交汇处湿润峰比注液孔正下方湿润峰运移快,湿润体形状逐渐变成椭圆柱体,交汇作用明显加快注液孔正下方湿润峰的运移,提高浸矿速度和浸矿的均匀性。交汇处和注液孔正下方湿润峰运移距离与入渗时间的关系曲线符合幂函数变化规律。在入渗过程中,湿润体体积和累计入渗量有明显的线性关系,且注液孔间距越小,湿润体含水率越高。基于Green-Ampt模型和质量守恒定律推导了单向交汇入渗条件下湿润峰运移距离与入渗时间关系模型,模型与试验结果吻合度高。

Effect of Flux on Properties of Structure and Luminescence of LaMgB_5O_(10)∶Ce^(3+), Mn^(2+)

The influences of the flux KCl or KF on the XRD spectra, cell parameters and crystal appearance, and spectral properties of the phosphor LaMgB_5O_(10)∶Ce^(3+), Mn^(2+) were studied. The results indicate that when 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5%KF are respectively added into phosphor (La_(0.85)Ce_(0.15)) (Mg_(0.9)Mn_(0.1))B_5O_(10), compared with the normal card of JCPDS (No 35-120), the intensity of XRD spectra is enhanced, the values corresponded to 17/28, 18/28, 16/28, 18/28 and 2/28 and the cell parameters diminish because of the flux KCl and KF. The use of 5% KCl a fraction of Cu monocrystals are observed in the phosphor. There are six hexagonal crystal-faces and eight triangular crystal-faces representing crystal-face index {100} and {111}. When 15% KCl is added to the phosphor, law of crystal plane and self-regulaton are formed, the emission intensity of Ce^(3+) 5d-4f ((()~2F_(5/2),) (()~2F_(7/2))) and Mn^(2+) ((()~4G) and (()~6S)) increases by 3.41 times and 2.36 times respectively.

Influence of Flux on Structure and Luminescence of LaMgB_5O_(10)∶Ce^(3+), Mn^(2+)

The influences of the flux KCl or KF on the XRD patterns, cell parameters, crystal morphology, and spectral properties of the phosphor LaMgB_5O_(10)∶Ce^(3+), Mn^(2+) are studied. The results indicate that as 4.2%, 8.6%, 12.8% KCl and 5.3%, 10.5% KF are added individually into the phosphor (La_(0.85)Ce_(0.15)) (Mg_(0.9)Mn_(0.1)) B_5O_(10), some peaks of the XRD patterns are intensified and cell volumes are decreased. A small amount of Cu mono-crystal typed phase appears as more than 5% KCl is added. There are six hexagonal crystal-faces and eight triangular crystal-faces attributed to the {100} and {111} respectively. When 15% KCl is added into the phosphor, multi-faced regular crystals are formed and the crystal self-regulation appears. The emission intensity of 5d→4f ((()~2F_(5/2),) (()~2F_(7/2))) of Ce^(3+) and (()~4G→()~6S) of Mn^(2+) increases up 3.41 and 2.36 times respectively.

Study on Effect of Flux on CeMgAl_(11)O_(19)∶Tb ^(3+) Phosphor

High calcination temperature is an important factor in the preparation process of CeMgAl 11O 19∶Tb 3+. To decrease the temperature, different fluxes (H 3BO 3, MgF 2 and AlF 3) were tested in order to compare their influence on the luminescence property and particle size distribution of CeMgAl 11O 19∶Tb 3+. The result shows that when the content of MgF 2 is 0.1 mol/mol, the intensity of luminescence can attain a maximum. Furthermore, MgF 2 can improve the particle size quality of the phosphor. So MgF 2 can take the place of the conventional flux H 3BO 3 to prepare high quality CeMgAl 11O 19∶Tb 3+ phosphor. In addition, the relation between phosphor property and content of AlF 3 was also studied. The crystal structure of the phosphor was analyzed by XRD method. The phase composition analysis shows that the reason of decrease of the brightness of CeMgAl 11O 19∶Tb 3+ phosphor is the emergence of TbAlO 3 and α-Al 2O 3 during the preparation process.

温度对热泵压缩机用稀土和铁氧体电机性能的影响与分析

使用Ansys Maxwell 2D对永磁电机进行仿真,对比分析不同温度下,铁氧体与稀土材料励磁性能的变化趋势,模拟热泵压缩机实际运行过程中温度对铁氧体和稀土电机效率的影响。通过仿真结果和实际测试验证,随着热泵压缩机内部运行环境温度的升高,稀土电机比铁氧体永磁电机的效率稳定性更高。

稀土熔剂对A356铝合金的作用

研究了一种含有稀土化合物的铝合金新型熔剂JDN I。结果表明 ,该熔剂通过发生一系列的物理和化学反应 ,不仅可使A3 5 6合金熔体 72 0℃时的含氢量由大于 0 .3 0mL/ 10 0 g(Al)下降到 0 .10mL/ 10 0g(Al)以下 ,除气效果显著 ,并使A3 5 6合金的室温抗拉强度提高 7.2 7% ,延伸率提高 85 .5 8%。该熔剂还具有细化晶粒和变质的作用 ,分析了该熔剂发生作用的机理 。

稀土熔剂对A356合金二次枝晶臂间距的影响

将含有稀土的熔剂JDN -Ⅰ用于覆盖处理A35 6合金。实验结果表明 ,该稀土熔剂对A35 6合金的二次枝晶臂间距dDAS值有着较大的影响。无熔剂覆盖时 ,水淬获得的dDAS值比空冷下降 30 .8% ;有JDN -Ⅰ熔剂覆盖时 ,水淬获得的dDAS值比空冷下降 88.2 % ;水淬时 ,有熔剂覆盖的dDAS值比无熔剂覆盖低 77.7% ;空冷时 ,有熔剂覆盖的dDAS值比无熔剂覆盖高 2 3.3%。分析认为 ,存在 2个临界冷速v1和v2 :当冷速v <v1时 ,dDAS值由液相线斜率决定 ;当v >v2 时 ,dDAS值由JDN -Ⅰ熔剂中的稀土含量决定 ;当v1<v <v2 时 。

助熔剂对Y_3Al_5O_(12)∶Ce荧光粉性能的影响

在还原气氛下采用高温固相反应法合成了白光LED用黄色荧光粉Y3Al5O12∶Ce(YAG∶Ce),研究了助熔剂对YAG∶Ce荧光粉发光特性的影响。XRD的测量结果表明加入合适的助熔剂有利于YAG∶Ce荧光粉的晶化,并且不引入杂相。选择BaF2和H3BO3同时使用效果要好于单独使用一种助熔剂。助熔剂的加入可增大YAG∶Ce荧光粉的激发和发射光谱强度,并能有效降低荧光粉的中心粒径(D50)控制粉体的粒径分布,适用于白光LED的制造。

铝熔体用稀土熔剂的使用效果及分析

针对我国在铝加工业存在能耗大、环境污染严重和含氢、含杂量高的问题 ,研究了一种新型熔剂JDN Ⅰ。结果发现 ,该熔剂具有多种功能 :覆盖隔热作用 ,既可保护铝合金免受潮湿大气的污染 ,又能节约能源 ;净化作用 ,可使铝熔体的含氢、含杂量降低到极低的水平 ,确保铝熔体的纯净化 ;细化变质作用 ,既可细化晶粒 ,又可使共晶硅变质 ;使用简便 ,不污染环境。在这种熔剂的作用下 ,可使A35 6铝合金的流动性大大提高 ,并使抗拉强度提高 7 2 5 % ,伸长率提高 85 5 8%。

LY12铝合金氧化膜与钎剂的反应机制

采用CsF AlF3中温无腐蚀钎剂能够去除LY12铝合金表面复杂的氧化膜,实现LY12铝合金的中温钎焊。研究发现:改进的CsF AlF3钎剂是以反应、溶解方式去除氧化膜的;在去膜过程中,CsF化合物起主要去膜作用,钎剂的高活性与NH4F、NH4AlF4及复合盐熔体等化合物的存在有关,它们的存在可提高CsF AlF3钎剂的去膜能力,而HF的生成则是诱发和加速反应、提高溶解去膜能力的关键;微量稀土元素镧未在界面出现富集现象,微量的稀土氟化物则起着"助溶"的作用。

镁合金熔炼的热力学

根据与镁合金化有关的金属元素的热力学数据,绘制与镁合金制备相关的金属氧化物、氯化物和氟化物的生成自由能随温度变化的关系图。从物理化学的角度,研究采用熔剂法制备镁合金铸锭熔剂处理的热力学原理,为合理选择熔剂配方提供理论依据。对稀土镁合金合金化存在的熔剂制备问题进行研究,指出了解决问题的方法。

添加稀土Er于熔剂中对铸态AZ91镁合金组织与性能的影响

研究了熔炼时在熔剂(42%MnCl2+53%LiCl+5%CaF2,质量分数,%)中添加稀土Er对铸态AZ91镁合金显微组织、力学性能、断口形貌以及腐蚀行为的影响。结果表明:在熔剂中添加稀土Er能够去除镁合金熔炼过程中产生的熔剂夹杂,净化镁合金熔体,提高铸态AZ91镁合金的拉伸性能和耐腐蚀性能;当熔剂中添加10%的稀土Er时,镁合金的抗拉强度σb和伸长率δ分别从156MPa和1.8%上升到最大值220MPa和4.1%;同时,镁合金在5%NaCl水溶液中的腐蚀速率从1.20mg/(cm2.d)下降到最小值0.15mg/(cm2.d);然而,随着稀土Er在熔剂中添加量的进一步提高,合金中开始有φ-(Al7ErMn5)和τ-(Al66.7Mg23.3Er10)等含有稀土Er的相生成,消耗了合金中的Al和Mn元素,改变了β-(Mg17Al12)相的形态;而且沿枝晶界附近分布的粗大φ-(Al7ErMn5)相降低了枝晶之间的结合力,使得合金的σb和δ下降;同时,部分网状的β-(Mg17Al12)相断裂,呈离散的块状,导致合金的腐蚀速率增加;熔剂中添加稀土Er不改变镁合金的断裂机理,断裂机制仍为准解理断裂。