Liquid-Liquid Extraction of Vanadium(V) and Niobium(V) with Tris(2-ethylhexyl)phosphate: Mutual Separation of Vanadium(V), Niobium(V), and Tantalum(V), and Analysis of Steel Samples

Abstract

Tris(2-ethylhexyl)phosphate (TEHP) dissolved in toluene is used for selective extraction of vanadium(V) and niobium(V) from hydrochloric and hydrobromic acid solution. Vanadium is determined spectrophotometrically after backextraction from TEHP, whereas unstripped niobium is determined in the TEHP phase with thiocyanate. The probable extractable species is VOCl₃·2TEHP or NbOCl₃·2TEHP/NbOBr₃·2TEHP. The method permits mutual separation of vanadium(V), niobium(V), and tantalum(V), and provides analysis of vanadium and niobium in alloys with a high degree of accuracy and precision.     

Extraction Behavior of Uranium(VI) with Polyurethane Foam

Abstract

The extraction of uranium(VI) from aqueous solution with polyether-based polyurethane (PU) foam was studied. The effects of the kinds and concentrations of nitrate salts, uranium(VI) concentration, temperature, nitric acid concentration, pH, the content of poly(ethylene oxide) in the polyurethane foam, and the ratio of PU foam weight and solution volume on the extraction of uranium(VI) were investigated. The interferences of fluoride and carbonate ions on the extraction of uranium(VI) were also examined, and methods to overcome both interferences were suggested. It was found that no uranium was extracted in the absence of a nitrate salting-out agent, and the extraction behaviors of uranium(VI) with polyurethane foam could be explained in terms of an etherlike solvent extraction mechanism. In addition, the percentage extraction of a multiple stage was also estimated theoretically.     

Extraction and Adsorption Behavior of Co(II) on HTTA-Impregnated Polyurethane Foam

Abstract

The batch extraction of Co(II) from aqueous solutions with open cell polyethertype HTTA-loaded polyurethane (PU) foam has been studied using a radiotracer technique. The effect of pH, shaking time, and loading capacity has been investigated. The membrane properties of loaded PU foam sorbent offer unique advantage of adsorption. The fundamental studies of adsorption show that the classical Freundlich and Langmuir isotherms are followed in the entire concentration range of a 10^?5 to 10^?2 M solution of cobalt. The sorption mean free energy from the Dubinin-Radushkevich isotherm is found to be 13.8 kJ·mol^?1 and the loading capacity 4.44 mg·g^?1, suggesting that the ion-exchange or chemisorption mechanism operates. The kinetic parameters of adsorption also support a chemisorption mechanism and the first-order rate law. The rate constants and activation energies of sorption and desorption have been evaluated. The thermodynamic function of adsorption of ΔH, ΔS, ΔG, and equilibrium constant K _c have been calculated. The process of adsorption is established to be endothermic and chemisorption, stabilized through thermodynamic functions.     

聚氨酯/纳米纤维素/聚磷酸铵泡沫的制备与表征

依据理论计算和对聚氨酯泡沫形貌的单因素优化实验,将聚乙二醇(PEG)、三乙烯二胺、二甲基硅油、水、聚磷酸铵(APP)、纳米纤维素、正戊烷、多亚甲基多苯基多异氰酸酯(PAPI)分别按一定配比混合,室温静置发泡,分别得到聚氨酯泡沫、聚氨酯/APP泡沫、聚氨酯/纳米纤维素泡沫、聚氨酯/纳米纤维素/APP泡沫4种样品。分别对4种样品的表观密度、微观形貌、极限氧指数(LOI)等进行了表征。研究结果表明:4种样品主要是物理吸附,没有新物质生成;聚氨酯/纳米纤维素/APP泡沫的LOI为24.5%,接近聚氨酯/APP泡沫的LOI(24.6%);同等压缩率下,聚氨酯/纳米纤维素/APP泡沫的压缩强度高于聚氨酯/APP泡沫。     

Extraction of Alkali Metal Tetraphenylborates by Polyurethane Foam

Abstract

The extraction of alkali metal tetraphenylborates by polyurethane foam was investigated. The extractability sequences are K⁺ ≈ Rb⁺ > Cs⁺ and K⁺ ≈ Rb⁺ ≈ Cs⁺ for polyether and polyester foams, respectively. The high extraction of K⁺ by polyether foam can be explained by the cation chelation mechanism.     

聚氨酯(PU)泡沫塑料的受热过程

采用不同的加热方式,在升温速率为10 K/min时,研究聚氨酯泡沫塑料(PU)受热过程中的变化规律.采用热重-红外(TG-FTIR)联用测试方法,研究PU的热解特性,同时研究了其热分解过程中气体产物的释放规律.在烧结影像仪中观察试样加热过程中的膨胀收缩变形,确定其熔融和流动温度,试样受热过程中无熔融现象,最后炭化.     

微胶囊聚磷酸铵阻燃聚氨酯泡沫的阻燃性能研究

以三聚氰胺、甲醛为原材料,利用原位聚合法制备三聚氰胺-甲醛树脂(MF)微胶囊化聚磷酸铵;通过红外光谱、SEM图像研究包覆效果,并分别将两种微胶囊化APP添加到聚氨酯泡沫中,通过氧指数、垂直燃烧等研究泡沫的阻燃性能,通过万能试验机测试压缩强度来研究力学性能。研究得出微胶囊APP可以提高阻燃性能。MAPP的添加量为30%时,MAPP/PU氧指数达到30,并能通过V-0等级测试,此后增加缓慢,压缩性能达到50.5 Kpa。MCAPP的添加量为25%时,MCAPP/PU氧指数达到28,通过V-0等级测试,压缩性能达到57.7 Kpa。     

溶剂萃取过程自动控制技术在钽铌分离中的应用

介绍溶剂萃取过程自动控制技术在钽铌湿法分离过程中的应用。通过分析钽铌分离过程平衡浓度分布,确定敏感点并在线测量该点浓度,采用专家专家控制系统实现自动控制的方法及实践结果。     

聚氨酯泡沫夹层复合材料的制备及其吸波性能研究

根据电磁波阻抗匹配原理,制备了聚氨酯泡沫夹层结构复合吸波材料,研究了不同结构组成对材料吸波性能的影响。实验结果表明:当匹配层中加入质量分数15%的二氧化锰,聚氨酯泡沫夹芯层中加入质量分数5%的二氧化锰和10%的石墨和反射层中加入质量分数35%的石墨时,测试频段为8～18 GHz,聚氨酯泡沫夹层结构复合材料的最大吸收峰为12.9 GHz(R=-35.7 dB),R-10 dB的频宽为1.5 GHz。     

Preparation of Niobium(V) Oxide with Controlled Dispersity and Morphology

Glass and Ceramics - The effect of the annealing temperature and the chemical history of the precipitate on the morphology and phase composition of Nb2O5 powder was investigated. The precipitate...     

Synthesis of Niobium(V)-Stabilized Tetragonal Zirconia Nanocrystalline Powders

The polymer precursor method is very useful to prepare Nb⁵⁺-stabilized nanocrystalline powders of t -ZrO₂. The precursor solution is composed of zirconium oxalate, niobium tartrate, and poly(vinyl alcohol), which help to form a network matrix to disperse the metal ions homogeneously. Nb⁵⁺ is an effective agent to stabilize t -ZrO₂, and ease of formation of the tetragonal phase increases with increasing dopant concentration. Thermal stability of t -phase is found up to 1700°C having 15 mol% Nb⁵⁺, prepared at 600°C with particle sizes of 35 ± 5 nm.     

Solvent Extraction Separation of Niobium(V), Tantalutn(V) or Titanium(IV), and Vanadium(V) by 2′-Hydroxy-4-methoxy-5′-methyl Chalkone Oxime (HMMCO) from Their Binary Mixtures

Abstract

2′-Hydroxy-4-methoxy-5′-methyl chalkone oxime (HMMCO) has been used for the solvent extraction separation of Nb(V), Ta(V) or Ti(lV), and V(V) from their binary mixtures. V(V) can be quantitatively extracted with HMMCO from 9 M hydrochloric acid. The green-colored chloroform extractable V(V)-HMMCO complex absorbs at a maximum at 630 nm. Nb(V), Ta(V), and Ti(IV) are not extracted at these conditions. However, these metals can be extracted from strong hydrochloric acid medium in the presence of potassium thiocya-nate. The yellow-colored complexes of Nb(V), Ta(V), and Ti(IV) absorb at a maximum at 380, 390 and 390 nm, respectively. The method is simple, rapid, and selective, and affords a clean-cut separation of vanadium from niobium, tantalum, or titanium which are usually present in alloys and ores.     

聚氨酯泡沫材料的性能研究

聚氨酯泡沫具有多孔性、相对密度小、比强度高等特点,根据所用原料的不同和配方的变化可制成阻尼减震性能优异的材料。为了满足铝型材内填充材料的阻尼减震的要求,通过改变原料的组成和配比,制备了一种密度低、阻尼性能优异的聚氨酯泡沫材料。研究了发泡剂、N220和环氧树脂的含量对泡沫材料性能的影响,结果表明调节发泡剂用量可以改变材料的密度和粘接性能,N220和环氧树脂的加入可以提高聚氨酯泡沫的阻尼性能,所制得的聚氨酯泡沫材料可以满足铝型材填充材料的要求。     

铜尾矿和钽铌尾矿为主要原料的微晶玻璃的研究

以铜尾矿和钽铌尾矿为主要原料研制了性能优良的微晶玻璃，并研究了钽铌尾矿用量，晶核剂，CaO用量对核化和晶化过程的影响。     

Surface Segregation of Niobium and Tantalum in Titanium Dioxide. Overview

Segregation in crystals results in surface layer enrichment of selected lattice elements. The present work considers the phenomenon of segregation in solid solutions of TiO₂ doped with donor‐type elements, such as niobium and tantalum. The focus is on the effect of oxygen activity on segregation at elevated temperatures. It is shown that the effect of oxygen activity on the segregation‐induced enrichment may be used for engineering of oxide materials in general and TiO₂‐based materials in particular with controlled surface composition that is required to achieve the desired reactivity and photoreactivity for energy conversion in general and solar energy conversion in particular. The development of the related surface engineering procedures requires correct determination of oxygen activity during processing and the segregation‐induced concentration gradients within the surface layer.     

PFF与PUF热稳定性及燃烧性能研究

制备了酚醛泡沫和聚氨酯泡沫，并研究了酚醛硬泡与聚氨酯硬泡的热稳定性及燃烧性能。结果表明：和聚氨酯泡沫比较，酚醛泡沫的热失重小，热释放速率和热释放总量低。因此酚醛泡沫的热稳定性和阻燃性能明显优于聚氨酯泡沫。     

聚氨酯泡沫塑料老化问题研究进展

重点介绍了热老化、湿热老化和辐解老化对聚氨酯泡沫塑料的外部形态、内部构造及力学性能的影响,综述了聚氨酯泡沫塑料的防老化措施,并讨论了各种防老助剂的效果,最后,对各种防老助剂的研究近况进行了综述,以期为工业生产应用提供可靠的理论依据。     

泡沫聚氨酯防压垫的研制

介绍了泡沫型聚氨酯防压垫的配方和工艺过程。     

Monolayer-Mediated Deposition of Tantalum(V) Oxide Thin Film Structures from Solution Precursors

Integration of oxide thin films with semiconductor substrates is a critical technology for a variety of microelectronic memory and circuit applications. Patterned oxide thin film devices are typically formed by uniform deposition followed by postdeposition ion-beam or chemical etching in a controlled environment. This paper reports details of an ambient atmosphere technique which allows selective deposition of dielectric oxide thin layers without postdeposition etching. In this method, substrate surfaces are selectively functionalized with hydrophobic self-assembled monolayers of octadecyltrichlorosilane by microcontact printing (μ-CP). Sol-gel deposition of ceramic oxides on these functionalized substrates, followed by mild, nonabrasive polishing, yields high-quality, patterned oxide thin layers only on the unfunctionalized regions. A variety of micrometer-scale dielectric oxide devices have been fabricated by this process, with lateral resolutions as fine as 4 μm. In this paper, we describe the solution chemistry, evolution of microstructure, and electrical properties of Ta₂O₅ thin films, as well as the stress-related mechanism which enables selective de-adhesion and resultant patterning. Selectively deposited, 80-120 nm thick Ta₂O₅ thin film capacitors were crystallized on platinized silicon at 700-800°C, and had dielectric constants of 18-25 depending upon the processing conditions, with 1 V leakage current densities as low as 2 × 10⁻⁸ A/cm². The ability to selectively deposit Ta₂O₅ and other electrical ceramics (such as LiNbO₃ and PbTiO₃) on a variety of technologically important substrate materials suggests broad potential for integrated circuit and hybrid microelectronics applications.