Enhancement of photoluminescence in Sr_2CeO_4 phosphors by doping with non-rare earth impurities

Non-rare earth impurity doped Sr2CeO4：X （X ：Zn, Hg, Al, Ag, Cr） phosphors are prepared by using the combustion method. The structural and photoluminescent properties of the as-prepared phosphors are investigated by X-ray diffraction （XRD） and photoluminescence at room temperature. Experimental results show that zinc addition and firing processing can effectively enhance the photoluminescence of Sr2CeO4 phosphors.

Determination of Non-Rare Earth Impurities in High Purity Lanthanum Oxide by Inductively Coupled Plasma Atomic Emission Spectrometry after HPLC Separation Using P507 Resin

A new method for the determination of trace non-rare earth elements (NREEs) impurities in high-purity lanthanum oxide by HPLC combined with ICP-AES is proposed. The chromatographic retention behaviors of matrix (La) and NREEs were studied using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (P507) chelating resin as the stationary phase and dilute nitric acid as the mobile phase. It is found that the use of pH 1.7 nitric acid enables effective elution of NREEs from HPLC column, but the lanthanum remains on the column. The experimental results show that a favorable separation between matrix lanthanum and NREEs can be obtained within 15 min. The method proposed is applied to the determination of 8 NREEs impurities in high-purity La2O3. The recoveries of 8 NREEs are in the range of 90 % similar to 110 %.

Modification Behavior of Trace Rare Earth on Impurity Phases in Commercial Purity Aluminum

Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity aluminum were studied with the aids of SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth (RE) is an effective modifying agent, which makes the coarse Fe rich impurity phases transform into complex compounds of tiny, sphere/short stick form, thus improving mechanical properties of this material; its modifying mechanism is in that RE gathering in front of solid/liquid interface enters into the impurity phases, forming complex (AlFeSiRE) compounds; or is adsorbed in the impurity phases surface, impeding the growth of impurity phases; however, excessive RE will result in the increasing of RE compounds (secondary phases), and plasticity reduction of this material. Therefore, its addition amount should be less than 0 07% (mass fraction).

Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

The model of dislocations was used to construct the model of grain boundary (GB) with pure rare earths, and rare earth elements and impurities. The influence of the interaction between rare earth elements and impurities on the cohesive properties of 5.3° low angle GB of Fe was investigated by the recursion method. The calculated results of environment sensitive embeding energy( E ESE ) show that the preferential segregation of rare earth elements towards GBs exists. Calculations of bond order integrals (BOI) show that rare earth elements increase the cohesive strength of low angle GB, and impurities such as S, P weaken the intergranular cohesion of the GB. So rare earth element of proper quantity added in steel not only cleanses other harmful impurities off the GBs, but also enhances the intergranular cohesion. This elucidates the action mechanism of rare earth elements in steel from electronic level and offers theoretical evidence for applications of rare earth elements in steels.

Direct Determination of Rare Earth Impurities in High Purity Europium Oxide by ICP-MS

A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide (Eu_2O_3) was developed. The spectral interference,matrix effect,instrument parameters fluctuation were investigated and the optimized experimental conditions were established. Under the selected conditions,the detection limits of the method are 3～7 ng·L (-1),the RSD is varied between 2.1%～8.4%,and the percentage recovery is ranged from 90% to 113% for the analytes. The solid detection limit for gross amount of 13 rare earth impurities is 0.19 μg·g (-1) when the matrix (Eu) concentration of 0.1 mg·ml (-1) was chosen. Compared with the reported methods in the literature,this method has several attractive features: simple,small sample amount required,no internal standard and matrix matching requirements.

Quenching Study on Iron Impurity in Eu^(2+), Dy^(3+) Doped Strontium Aluminate Phosphor Prepared by Nano-Coating Process

A series of long afterglow phosphors, Eu2+, Dy3+, with different iron content were prepared by nano-coating process. The resulted precursors were characterized by Transmission Electron Microscope (TEM), which suggested that the precursor particles had nanometer size distribution. The optical quenching of iron impurity on the phosphor powders were investigated by X-Ray powder Diffraction (XRD) and photoluminescence methods. The XRD indicates that a pure monoclinic SrAl2O4∶Eu2+, Dy3+ was formed at 1200 ℃ and iron impurity up to 296.36×10-4% had no effect on the SrAl2O4∶Eu2+, Dy3+ phase structure. However, the luminescence intensity were strongly dependent on the trace iron impurity, which might be explained that iron displace the aluminium and form Fe-O bond, which competed energy with Eu2+ and transfer red them to infrared sites.

基于高温HF/H_(2)法的YF_(3)∶Yb^(3+),Er^(3+)上转换发光性能增强研究

近年来,稀土材料因其独特的上转换光致发光特性备受关注。采用共沉淀法制备了掺杂Yb^(3+)和Er^(3+)的YF_(3)上转换发光材料。为了提高晶体结晶度和消除氧杂质的影响,采用500℃高温和HF/H_(2)气氛进行脱水除氧处理。通过X射线衍射(XRD)、氧分析仪、红外吸收光谱和荧光光谱等手段进行全面表征。结果表明:经过HF/H_(2)气氛高温脱氧处理的样品具有更高的结晶度和更优异的发光性能,表现出更高的量子产率。揭示了氧杂质对YF_(3)∶Yb^(3+),Er^(3+)上转换发光材料性能的负面影响,而采用高温HF/H_(2)气氛处理是提高发光性能的有效途径,为类似发光材料的研究提供了新思路。

从离子型稀土镁盐富集物中提取稀土工艺初探

以MgO为沉淀剂沉淀MgSO_(4)稀土浸出母液时,得到的稀土镁盐富集物REO总量较低,需要进一步除去杂质以沉淀富集稀土。以离子型稀土镁盐富集物为原料,进行碳化—酸溶—中和除杂—沉淀等工艺初步探索研究。结果表明:REO在碳化过程中的损失很少甚至可以忽略不计,有24.33%~30.9%MgO由稀土镁盐富集物转化进入碳化后液,在中和除杂过程中Fe去除率约99.5%,Al去除率约98.6%。以碳化后液为沉淀剂沉淀中和除杂后液得到碳酸稀土,经过灼烧,获得了符合《GB/T 20169—2015离子型稀土矿混合稀土氧化物》标准质量要求的稀土氧化物,该工艺总渣率为19.81%~23.22%,REO总收率平均89.43%。为了从离子型稀土镁盐富集物中提取稀土的工艺形成成套工艺技术,获取最优的工艺技术参数,有待于后续深入研究和优化。

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察消解酸量、温度、时间,氧气反应气流量,稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱(ICP-MS/MS)法直接测定氧化铕中13种稀土杂质元素的分析方法。采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试。通过对氧化铕标准物质(GBW02902)直接测定,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数(r)均大于0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于2.0%,13种元素的测定值都在认定值的不确定度范围之内。方法操作简单、测定稳定、效率高,为实验室进行氧化铕材料中REE杂质的准确测定提供思路和借鉴。

Simultaneous Determination of Trace Rare Earth Elements and Other Elements in High Purity Terbium Oxide (Tb_4O_7) by ICP-AES After HPLC Separation Using P507 Resin

This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.

Magnetic property improvement of niobium doped with rare earth elements

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-Ⅱ superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

Effects of Ce and Impurities on Percentage Elongation and Recrystallization in Al-Li Alloys

The effects of the contents of Ce and deleterious impurities on the ductility and recrystallized microstructure have been investigated for Al Li based alloys 2090 and 8090 sheets. The relationships between the parameters of recrystallized microstructure and percentage elongation( δ ) in the transverse orientation of the sheets have been obtained. The beneficial behavior of Ce microalloying can be markedly shown in the alloy 2090 containing a certain amount of impurities Fe and Si or in the alloy 8090 containing a certain amount of impurities Na and K. Ce microalloying can still improve δ to a certain degree, even though impurities Fe, Si, Na and K coexist and their concentration is rather high in the alloy 8090. When the recrystallized volume, coarse grained volume and grain average width increase because of the variation in the contents of Ce element and impurities, δ decreases for the alloys 2090 and 8090. When the grain aspect ratio increases, δ increases for the alloy 2090 and decreases for the alloy 8090.

Effect of Impurities and Cerium on Stress Concentration Sensitivity of Al-Li Based Alloys

A notch sensitivity factor was derived in order to evaluate the stress concentration sensitivity of Al Li based alloys. The factor values for the Al Li alloy sheets containing various contents of impurities and cerium addition were evaluated by determining the mechanical properties. It is found that the impurities Fe, Si, Na and K significantly enhance the stress concentration sensitivity of the alloys 2090 and 8090, whereas cerium addition reduces the stress concentration sensitivity to a certain degree for the high strength alloys. However, an excess amount of cerium addition in the high ductility alloy 1420 can significantly increase the stress concentration sensitivity. As compared with conventional aluminum alloys, the Al Li based alloys generally show high stress concentration sensitivity. Therefore, a special attention must be paid to this problem in the practical application of Al Li based alloys.

磷石膏杂质脱除、稀土回收及资源化利用研究进展

磷石膏是磷矿湿法产酸的工业副产物,主要由二水硫酸钙和氟硅酸钠组成,产量大、组分复杂。目前我国磷石膏堆存量高达8亿t,其大量堆存不仅造成了严重的土地资源浪费,还导致了江河水质劣化及大气污染等生态环境问题,而其利用率仅为10%~30%,远未达到产用平衡。对磷石膏中磷、氟等杂质的脱除工艺、稀土元素的回收技术及其在建筑、农业、化工等行业的资源化利用研究现状进行了综述,以期为磷石膏大宗化、高值化利用研究及产业化应用提供参考。

赤泥磷酸浸出液中稀土的萃取行为研究

赤泥是铝土矿生产氧化铝过程中产生的固体残渣,含有铁、硅、铝、钛及稀土等多种有价组分。在已预先分离赤泥中大部分铁、硅、铝、钛的前提下,采取溶剂萃取的方式对赤泥磷酸浸出液中的稀土作进一步分离与纯化,研究了在中性磷型萃取剂TBP、酸性磷型萃取剂P204和P507分别作用下,稀土La、Ce、Sc、Y以及主要杂质组分Al、Fe、Ti、Ca的萃取行为,结果表明:TBP对稀土的萃取效果较差,P507对稀土Sc、Y及杂质Fe、Ti的萃取能力较强,P204萃取稀土的能力优于P507;采用质量分数2%P204作为萃取剂,在溶液pH为1.5、相比为1∶3的条件下,磷酸浸出液中Sc、Y的萃取率分别为90%、99%,La、Ce及杂质Fe、Al、Ti、Ca萃取率均低于5%;将P204质量分数升至20%,La、Ce萃取率可分别达到85%、95%。因此可通过采用P204分步萃取的方式有效分离磷酸浸出液中的稀土。

从废旧稀土抛光粉中回收稀土研究新进展

随着稀土抛光粉在玻璃抛光等行业的应用,产生的废旧失效的稀土抛光粉量逐年增加。稀土是不可或缺也不可再生资源,从废旧失效的稀土抛光粉中回收稀土已成为必然,国内外科技工作者对此进行了大量的研究,取得一定成效。本文就废旧稀土抛光粉稀土及杂质元素的化学组成和物相组成,尤其是Al、Si等的赋存状态进行分析,综述了近几年最新分离提取Ce、La等稀土的回收工艺,分析了分离过程中稀土元素的物相转变和杂质元素的浸出行为及深度除杂路径,并对从废旧稀土抛光粉中回收稀土发展方向进行总结和展望。

Effect of impurity ions on preparation of novel saponifier for rare earth extraction

Magnesium bicarbonate, prepared by the carbonation of magnesium hydroxide slurry, was used as a novel saponifier to eliminate the ammonia nitrogen pollution in the rare earth extraction separation process. The effect of impurity ions introduced by system on the carbonation reaction of magnesium hydroxide was studied in the work. The results showed that the presence of Ca2＋could lead to side reactions so as to reduce the conversion rate of magnesium hydroxide, and a small number of rare earth ions would have great influence on the carbonation reaction. What’s more, there was no influence on carbonation reaction with the low concen-tration of Na＋or Mg2＋, the conversion rate of magnesium hydroxide could reach above 96%. This paper showed a practical theory which could provide scientific guidance for the preparation of novel saponifier in rare earth extraction separation process.

Adjacent stage impurity ratio in rare earth countercurrent extraction process

Impurity components decrease stage by stage in a cascade of rare earth （RE） extraction separation, and adjacent stage impurity ratio （ASIR） which is defined as the ratio of an impurity＇s contents in the aqueous/organic phase of two adjacent stages can be used to evaluate the capacity of impurity removal for the two stages. On the basis of extraction equilibrium and mass balance, the ASIR in a two-component extraction separation was deducted and its simplified expressions were given for different process sections according to reasonable assumptions. The calculation simulation was then carried out to obtain the ASIR distribution in the cascade. The results showed that in both the extraction and scrubbing sections the ASIR principally increased with the decrease of the molar proportion of the impurity but along with a flat appearing in the purification zone located in the middle of the cascade. The ASIR intuitively exhibits the running status of RE extraction separation and purification, which could provide a theoretic guide for investigating the influence factors of RE extraction separation process in practical industry.

Development of non-rare earth grain boundary modification techniques for Nd-Fe-B permanent magnets

The magnetic performance of Nd-Fe-B magnets depends on their grain boundary structure.Intergranular addition and grain boundary diffusion(GBD)process are effective approaches for enhancing coercivity with low material cost.This review summarizes the development of grain boundary modification techniques with emphasis on our recent work using cost-effective non-rare earth(non-RE)sources for GBD.Up to now,heavy rare earth(HRE)based compounds,metals and light rare earth(LRE)based alloys have been successfully employed as the diffusion sources for coercivity enhancement.Inspired from the previous investigations on the intergranular addition of non-RE compounds and alloys for Nd-Fe-B magnets,in 2015,we firstly proposed a novel GBD process based on diffusion source of Mg O.After that,various non-RE diffusion sources have been developed.The fundamentals of non-RE additives and non-RE diffusion sources for hard magnetic properties enhancement of Nd-Fe-B magnets are summarized here based on both the experimental and computational results.In particular,the properties-microstructure relationships of non-RE GBD modified magnets are discussed.The non-RE alloys or compounds modify the composition and structure of the grain boundary by diffusing into the intergranular regions,resulting in enhanced coercivity and corrosion resistance.Recently,we used Al-Cr coatings for both coercivity enhancement and surface protection,which shortens the production process and makes non-RE diffusion sources more competitive.The opportunity and future directions for non-RE GBD are also discussed in this review.

Leaching kinetics of ionic rare-earth in ammonia-nitrogen wastewater system added with impurity inhibitors

Ammonia-nitrogen wastewater is produced during the dressing and smelting process of rare-earth ores.Such wastewater includes a very high concentration of NH4＋, as well as other ions（e.g., NH4＋, RE3＋, Al3＋, Fe3＋, Ca2＋, Cl–, and Si O32–） with a p H of 5.4–5.6.Its direct discharge will pollute, yet it can be recycled and used as a leaching reagent for ionic rare-earth ores.In this study, leaching kinetics studies of both rare earth ions and impurity ion Al3＋ were conducted in the ammonia-nitrogen wastewater system with the aid of impurity inhibitors.Results showed that the leaching process of rare-earth followed the internal diffusion kinetic model.When the temperature was 298 K and the concentration of NH4＋ was 0.3 mol/L, the leaching reaction rate constant of ionic rare-earth was 1.72 and the apparent activation energy was 9.619 k J/mol.The leaching rate was higher than that of conventional leaching system with ammonium sulfate, which indicated that ammonia-nitrogen wastewater system and the addition of impurity inhibitors could promote ionic rare-earth leaching.The leaching kinetic process of impurity Al3＋ did not follow either internal diffusion kinetic model or chemical reaction control, but the hybrid control model which was affected by a number of process factors.Thus, during the industrial production the leaching of impurity ions could be reduced by increasing the concentration of impurity inhibitors, reducing the leaching temperature to a proper range, accelerating the seepage velocity of leaching solution, or increasing the leaching rate of rare earths.