铪元素及其同位素的发现：技术进步和思想发展的共同结晶

1869年，门捷列夫在第一张元素周期表中的锆元素后留出原子量为180的元素位置，预测铪与锆同族。1913年，原子序数和莫斯莱定律的提出揭示了铪元素在周期表中位置排列的实质，为铪元素的发现提供理论基础。20世纪20年代，玻尔理论的发展证实铪与锆同族，指导科学家从锆矿石中寻找铪元素。1923年，赫维西和科斯特借助X射线光谱技术发现铪元素，彰显了X射线光谱技术的独特价值。20世纪30年代以后，同位素理论和质谱技术促成了铪同位素的发现，使人们对铪元素有了新的认识。总之，铪元素及其同位素的发现是技术进步和思想发展的共同结晶。     

锆铪催化添加剂对PX液相氧化过程的影响

向对二甲苯(PX)催化氧化体系加入锆铪离子可有效地加速该反应过程．对锆铪离子与Co-Mn-Br催化剂体系的协同催化机理作了简要阐述，并对添加不同浓度下锆铪离子的催化作用进行了动力学实验．考察了添加锆和铪离子对主反应和燃烧副反应的影响，获得了锆铪离子添加剂对PX氧化过程的影响规律．研究发现，在实验所考察的温度与催化剂组成条件下，添加锆铪离子对反应过程中不同阶段的加速效果各不相同．且两种离子对燃烧副反应过程也有不同程度的加速作用．     

A simple method for the preparation of pure hafnium

The separation of zirconium and hafnium by fractional precipitation as pyrophosphate¹ has been extended for the preparation of pure hafnium. The favourable uptake of hafnium, in spite of the decreasing tendency of partition factor when hafnium concentration is high, is maintained for all concentration of hafnium (relative to zirconium). Particularly significant is the fact that at very high concentrations of hafnium (at≈84%) the uptake of zirconium sharply falls. So pure hafnium can be prepared from natural zirconium by a simple process of eight or nine stages of fractional precipitations as pyrophosphate. This process yields reactor grade zirconium on the one side and pure hafnium on the other side.     

A rapid procedure for the simultaneous determination of zirconium and hafnium in high-temperature alloys by means of a spectrophotometric masking approach

Data are presented for a refined spectrophotometric procedure for the simultaneous determination of zirconium and hafnium based on the combined effects of hydrogen peroxide, sodium sulphate, and excess of zirconium ion on the hafnium and zirconium complexes with Xylenol Orange in 0.2M perchloric acid. Isolation procedures for the hafnium/zirconium content of complex high-temperature alloys which result in an ionic substrate compatible with the spectrophotometric masking method were devised.     

Determination of zirconium and hafnium with xylenol orange and methylthymol blue

Both Xylenol Orange and Methylthymol Blue are highly selective and sensitive reagents for zirconium and hafnium forming intensely red complexes in an acidic medium. The factors affecting the color formation have been studied. The properties of the complexes have been determined and compared. In general, zirconium forms a more stable complex with the two dyes than hafnium, and Xylenol Orange forms a stronger complex with either zirconium or hafnium than Methylthymol Blue. Hydrogen peroxide can completely mask the zirconium complexes of either dye but only slightly affects the hafnium complex of Xylenol Orange. Zirconium and hafnium can both be determined without separation using peroxide as a masking agent and sulfate as a demasking agent. A bleaching reaction was observed when small amounts of hafnium were added to the red zirconium complex of Methylthymol Blue in 2.4 N perchloric acid or a small amount of zirconium was added to the red hafnium complex of Methylthymol Blue solution at pH 2 to 3.     

Group IV imino-semiquinone complexes obtained by oxidative addition of halogens

An isostructural series of titanium, zirconium, and hafnium complexes, M[ap] 2L 2 (M = Ti, Zr, Hf; L = THF, pyridine), of the redox-active 4,6-di- tert-butyl-2- tert-butylamidophenolate ligand ([ap] (2-)) have been prepared. The zirconium and hafnium derivatives react readily with halogen oxidants such as XeF 2, PhICl 2, and Br 2, leading to products in which one-electron oxidation of each [ap] (2-) ligand accompanies halide addition to the metal center. Iodine proved to be too weak of an oxidant to yield the corresponding oxidative addition product, and under no conditions could halogen oxidative addition products be obtained for titanium. According to X-ray crystallographic studies, the zirconium and hafnium oxidation products are best formulated as MX 2[isq.] 2 ([isq.] (-) = 4,6-di- tert-butyl-2- tert-butylimino-semiquinonate; M = Zr, Hf; X = F, Cl, Br) species, in which the molecule is symmetric with each redox-active ligand in the semiquinone oxidation state. Temperature-dependent magnetization measurements suggest a singlet ( S = 0) ground-state for the diradical complexes with a thermally accessible triplet ( S = 1) excited state. Solution electron paramagnetic resonance (EPR) spectra are consistent with this assignment, showing both Delta m s = 1 and Delta m s = 2 transitions for the antiferromagnetically coupled electrons.     

High-temperature oxidation of titanium, zirconium, and hafniyum in steam

The influence exerted by the nature of titanium, zirconium, and hafnium on the kinetic parameters of oxidation and on the diffusion mechanism of scale formation in steam at 973–1473 K is analyzed. The results obtained are compared with the data for the air medium.     

The influence of dissociation on simultaneous determination of zirconium and hafnium with Xylenol Orange

The molar absorptivities of the zirconium and hafnium Xylenol Orange (1:1) complexes are said to be similar in the acidity range 0.1-2.0M HCl. However, the absorbances obtained for the zirconium-Xylenol Orange complex in the acidity range 0.5-2.0M HCl are much higher than those for the same concentrations of hafnium. The absorbance differences are generally due to the higher stability of the zirconium complex at such acidities. Calculations based on the conditional stability constants of these complexes show the influence of dissociation on the results of simultaneous determination of zirconium and hafnium with Xylenol Orange.     

Separation of zirconium and hafnium from early actinides and rare earth elements with eichrom’s pb resin in HCl

The separation of zirconium and hafnium isotopes from the early actinides and rare earth elements (REE) with Eichrom’s Pb resin has been studied. Batch studies were performed to characterize the behavior of actinium, thorium, zirconium, hafnium, lutetium, and yttrium on Pb resin from HCl solutions (0.001 M to 11 M). The early actinides and REE had no affinity for the resin at any concentration of HCl, but zirconium and hafnium showed a moderate uptake at high concentrations of HCl with a maximum extraction at 11 M HCl. Several column separations were tested, including with only tracer isotopes and with mass. Rapid, simple separations of zirconium from actinium, thorium, protactinium, and the REE with high yields and low elution volumes are presented with applications for tracer isotope production and fission product separations. The resin is less suitable for hafnium separations as hafnium tends to bleed off the resin even at high concentrations of HCl.

     

X-ray determination of traces of hafnium in zirconium metal or traces of zirconium in hafnium metal after separation by ion exchange

A method is proposed for the determination of traces of hafnium in zirconium metal or zirconium in hafnium metal. The trace metals are first separated from the matrix metals on an ion-exchange column and then determined by X-ray analysis.     

Application of zone-melting technique to metal chelate systems-XI Refining of tetrakis(di-n-propionylmethanato)zirconium(IV) from hafnium and trace amounts of some other metals

The zone-melting method was applied to purification of tetrakis(di-n-propionylmethanato)zirconium(IV) which contained copper(II), nickel(II), cobalt(II and III), iron(III) and hafnium(IV) in the forms of their chelates with the common ligand. All minor components having effective distribution coefficients < 1 in the zirconium(IV) chelate were concentrated toward the terminal end of the refining column. When an aqueous solution of zirconium(IV) containing zinC(II) and manganese(II) in addition to the metal contaminants above was treated with di-n-propionylmethane to precipitate the chelate complexes, only zinc, iron and hafnium were found in the precipitated zirconium chelate. The first two were ettectively removed by zone-melting. Though the separation of hafnium was poorer, the technique was efficient enough for practical purposes.     

Extraction of zirconium and hafnium thiocyanate with polyurethane foam

Conditions for the extraction of zirconium and hafnium thiocyanate by polyether-type polyurethane foam were studied in detail. The composition of the extractable species was found to be dependent on both the thiocyanate and metal-ion concentrations. The extraction efficiency for zirconium and hafnium depended on the size of the counter-cation as well as on the type of anion.     

Development of a high-resolution inductively-coupled argon plasma apparatus for derivative spectrometry and its application to the determination of hafnium in high-purity zirconium oxide

A high-resolution apparatus for inductively-coupled plasma emission spectrometry (ICPES) has been developed, based on an echelle spectrometer modified for wavelength modulation with a quartz refractor plate. The selectivity of the technique is thus improved, and small amounts of hafnium in high-purity zirconium oxide can be determined directly without prior separation or preconcentration. A straight-line calibration curve passing through the origin is obtained without any correction for the interference from zirconium which exists in large excess. The detection limit for hafnium is 0.06 microg/ml, and the relative standard deviation (10 replicates) for hafnium at the 1.2 microg/ml level is about 3%.     

Analysis of niobium alloys

An ion-exchange method was applied to the analysis of synthetic mixtures representing various niobium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titanium, molybdenum, tungsten and tantalum. Mixtures containing zirconium or hafnium, tungsten, tantalum and niobium were separated by means of a single short column. Coupled columns were employed for the resolution of mixtures containing vanadium, zirconium or titanium, molybdenum, tungsten and niobium. The separation procedures and the methods employed for the determination of the alloying elements in their separate fractions are described.     

Cation-exchange separation of hafnium and zirconium from accompanying ions

Hafnium and zirconium are not retained on the strongly acidic cation-exchange resin Dowex 50 from a mixture consisting of methanol and 12M nitric acid (19:1) which is 0.1M in trioctylphosphine oxide. On the other hand most other elements investigated are strongly adsorbed on the resin from this medium so that they are readily separated from hafnium and zirconium. These elements include titanium, rare earths, alkali metals, alkaline earth metals, iron, cobalt, manganese and zinc. This separation technique has been found to be suitable for the separation of tracer and milligram amounts of hafnium and zirconium from accompanying metal ions. If in place of methanol other organic solvents such as acetone, tetrahydrofuran and methyl glycol are used the selectivity of the separation of zirconium and hafnium from the other elements is decreased. The same effect is observed when hydrochloric acid is used in the mixtures instead of nitric acid.     

Simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

A simple analytical procedure is described for determining zirconium or hafnium in molybdenum-base alloys by formation of the Arsenazo III complex of zirconium or hafnium in 9 M hydrochloric acid medium. The absorbance is measured at 670 nm. Molybdenum (10 mg), titanium (1 mg), and rhenium (10 mg) have no adverse effect. No prior separation is needed. The relative standard deviation is 1.3-2.7%.     

On the microscopic distinction of zirconium and hafnium

A method has been worked out for the microscopic distinction of zirconium and hafnium by means of the reagent of MARTINI, quinoline and ammonium thiocyanate. When using this reaction exactly as described by MARTINI, there generally is a difference in the shape of the primarily formed crystals. When using 25% formic acid as a solvent instead of HCl 1:2, hafnium, always gives a good reaction, whereas the zirconium reaction is prevented.     

Determination of hafnium by neutron activation, and variation in the Zr/Hf ratio of some granite masses

A fairly quick method for the separation of hafnium from irradiated rock samples is described and results of the hafnium determinations are reported. The distribution of zirconium and hafnium and the variation of the Zr/Hf ratio in three calc-alkali granite masses are discussed. Reasons are suggested for the observed decrease in the Zr/Hf ratio during the crystallization of igneous rocks.     

Anomalies in the spectrophotometric and extractive behaviour of zirconium and hafnium: evidence of a synergistic effect

In this work, some observations that confirm non-specific interactions between zirconium and hafnium are presented. This phenomenon, which induces significant differences between the spectrophotometric and extractive behaviour of the isolated elements related to their mixtures, indicates the existence of an important synergistic effect on the depolymerisation reactions involved in the aqueous chemistry of the elements. All experimental evidences suggest that the presence of zirconium can minimise the polymerisation of hafnium, favouring its reaction with the studied complexing agent.     

Synthesis of nanosized group IV borides in ionic melts of anhydrous sodium tetraborate

The preparation of nanosized Group IV metal diborides by reacting powdery titanium, zirconium, and hafnium with fine-grained boron in Na₂B₄O₇ ionic melts in the temperature range 600–850°C has been studied. Nanosized titanium, zirconium, and hafnium diborides are formed at temperatures of at least 750°C.