Zirconium recovery from zircaloy shavings

A chlorination process for recovering Zr from zircaloy scrap has been studied. Zircaloy chlorination was possible at temperatures as low as 220 °C. The scale microstructure and its effect on the zircaloy reactivity was analysed using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and scanning electron microscopy (SEM) techniques. A solid-solid phase transformation took place into the oxide scale during the zircaloy chlorination. Zirconium, as ZrCl₄(g), was separated from the oxide scale and chlorides of Cr and Fe. The effect of the reaction temperature was also analysed.     

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

Abstract

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.     

Rigorous and approximate analysis of metallic gratings in soft X-ray and EUV regions

Abstract

In deep ultraviolet and soft X-ray regions the complex refractive indices of metals differ substantially from their values in the visible region of the spectrum. The implications of this fact are analysed for metallic gratings illuminated by electromagnetic fields with wavelengths ranging from soft X‐rays to near infrared, concentrating on short wavelengths. In particular, we study metal-stripe gratings (linear polarizers for visible light) by rigorous diffraction theory to determine the short-wavelength region in which a combination of the geometrical thin-element approximation and the theory of single-layer films can be applied. Then we study inductive grid filters for protection of X-ray detectors from infrared radiation in space applications.     

Grain refining mechanism in Mg–9Gd–4Y alloys by zirconium

Abstract

The effect of different zirconium contents on the grain size of Mg–9Gd–4Y alloys and the grain refinement mechanism of zirconium have been studied. The results reveal that zirconium can refine the grains of the alloys to a large extent, and the grains become finer with an increase of zirconium content. Microstructural analysis shows that there is at least one zirconium rich core in almost each grain in alloys with a high zirconium content, whereas the characteristic zirconium rich cores are not found in the alloy with a low zirconium content. It is suggested that the grain refinement mechanism of zirconium in the low zirconium alloy is different from that in the high zirconium alloys: the zirconium works mainly by restricting grain growth in the low zirconium alloy, and by generating nucleants in the high zirconium alloys.     

Features of the procedures to obtain ultrafine zirconium dioxide by mechanochemical method

The results of investigation of mechanochemical reactions in the mixtures of hydroxides and carbonates of alkaline and alkaline earth metals with zirconium oxychloride and oxynitrate are presented. It is shown that one of the features of interaction between the components is the formation of the salts of alkaline and alkaline earth metals along with X-ray amorphous zirconium-containing compound. It is demonstrated that the mechanical activation of the mixture of yttrium carbonate and zirconium oxynitrate, followed by thermal treatment of this mechanically activated mixture, results in the formation of solid solution ZrO₂-Y₂O₃ in cubic modification.     

Characterization of zirconium oxynitride films obtained by radio frequency magnetron reactive sputtering

Thin ZrN_xO_y films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon-oxygen-nitrogen mixture. The Φ_N2/Φ_{(Ar + N2 + O2)} ratio was varied in the range 2.5%-100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO₂, ZrN, ZrON and N-rich zirconium nitride which is correlated with the Φ_N2/Φ_{(Ar + N2 + O2)} values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution.     

Sondermetalle und ihre Anwendung im Chemieapparatebau

Refractory Metals and their Application in the Chemical Process Industry Special metals, such as titanium, zirconium and tantalum, are being used increasingly for chemical plant. The exceptional resistance of special metals to many corrosive chemicals - they show it even at high temperatures and pressures - arises not from natural immunity but from the formation of a protective oxide passive layer on the metal surface. Special metals are well suited for welding. Their reactions with gases of the atmosphere must be taken into account though. Welding is therefore possible only under inert gas or a high vacuum. Similarly, alloying with iron-based materials during welding must be avoided under all circumstances. It should be taken into consideration that the melting point of tantalum, for example, is about twice as high as that of steel. Tantalum and niobium are machined with high-speed cutting steels; the cutting speed and cutting angle are similar to those used for stainless steels. In detail, the outstanding properties of special metals in chemical plant are as follows:

• — the stability of titanium under oxidizing conditions
• — the stability of zirconium under reducing and alkaline conditions
• — the resistance of molybdenum to hydrofluoric acid and fluoride
• — the stability of tantalum under oxidizing and reducing conditions.

In pure mineral acids the passive behaviour generally improves in the order titanium - zirconium - tantalum. Except where molybdenum is concerned, the medium should not contain fluoride. The material with the widest range of applications is tantalum. The addition of niobium as an alloying element leads to favourably priced but similarly resistant materials whose prospects of becoming established in the chemical industry and playing a part similar in importance to that of tantalum itself are good.     

Kinetic Model of Metallocarbohedrene Formation in Arc Plasma Generator

Abstract

A kinetic model of the formation of stable metal-carbon clusters, which have been designated metallocarbohedrenes, is developed.

The metals chosen for the theoretical analysis were titanium and zirconium. An optimum starting composition of composite electrodes was found. The fullerene and Met-Car yields for different metal-to-carbon mass ratios were determined. The maximum yield of Ti₈C₁₂ was 0.4% while the maximum yield of Zr₈C₁₂ was 0.6%. The theoretical mass spectra of carbon and metallocarbon clusters were explored.     

ULTRAFINE OXIDE POWDERS PRODUCED BY RAPID THERMAL DECOMPOSITION OF PRECURSORS IN SOLUTION

ABSTRACT

The Rapid Thermal Decomposition of precursors in Solution (RTDS) process is described as an approach to nanoscale particle production. The RTDS method involves a brief (< 2 sec) exposure of an aqueous solution containing dissolved metal oxide precursors to hydrothermal conditions amenable to particle nucleation and growth. Particle growth is terminated by passing the solution through a pressure restrictor and into a cooled collection region. Initial RTDS results involving the production of iron, titanium, and zirconium oxide powders from aqueous solutions are described. Powders generated were characterized using transmission electron microscopy, powder X-ray diffraction, BET surface area analysis, and Mossbauer spectroscopy. Iron oxide (hematite phase) having crystallite sizes ranging from a few nanometers to tens-of-nanometers was produced (rom 0.1 M Fe(NO₃) ₃ and Fe(NH₄)(SO₄) ₂ solutions. Crystallite size in the hematite powders was found to be dependent on the temperature to which the solutions were exposed during RTOS processing. Anatase phase TiO₂ powders having crystallite sizes of 3 to 5 ran were generated from K₂TiO(C₂O₄) ₂solutions, and cubic phase ZrO₂ powders with 3.5 nm crystallites were produced using a solution containing a zirconium (IV) citrate ammonium complex.     

Integrated planning of acquisition,disassembly and bulk recycling: a case study on electronic scrap recovery

Abstract. Due to national and supranational legislation activities, the recovery of discarded products will attain an increasing momentum. Electronic equipment consists of many different parts and materials. Therefore, the related recovery process is often divided into disassembly to remove harmful substances or reusable parts and into bulk recycling to recover ferrous and non-ferrous metals. In order to consider the interactions between choice of scrap to be recovered (acquisition problem), disassembly and bulk recycling, a mixed-integer linear programming model for integrated planning of these stages is presented in this case study. It is applied to determine the daily allocation of products to processes for a major electronic scrap recovery centre that faces limited processing capacities and market restrictions. The optimization calculations covering typical discarded electronic products to be recycled in the related centre lead to a relevant improvement of the economic success. RID="*" ID="*" The authors would like to thank the German “Bundesministerium für Bildung und Forschung” (Federal Ministry of Education and Research) for supporting the research project “Substance Flow Oriented Closed Loop Supply Chain Management in the Electrical and Electronic Equipment Industry (STREAM)rdquo;. Correspondence to: T. Spengler     

Selective removal of Pb(II), Cd(II), and Zn(II) ions from waters by an inorganic exchanger Zr(HPO3S)2

The present study reported synthesis of a new inorganic exchanger, i.e., zirconium hydrogen monothiophosphate [Zr(HPO₃S)₂, denoted ZrPS] and its selective sorption toward Pb(II), Cd(II) and Zn(II) ions. ZrPS sorption toward all the three metals is dependent upon solution pH due to the ion-exchange nature. As compared to another inorganic exchanger zirconium phosphate [Zr(HPO₄)₂, denoted ZrP], ZrPS exhibits highly selective sorption toward these toxic metals from the background of calcium ions at great levels. Such sorption preference is mainly attributed to the presence of –SH group in ZrPS, as further demonstrated by FT-IR analysis and XPS study. Moreover, ZrPS particles preloaded with heavy metals could be efficiently regenerated with 6 M HCl for multiple use without any noticeable capacity loss. All the experimental results indicated that ZrPS is a promising sorbent for enhanced heavy metals removal from contaminated water.     

MORPHOLOGICAL ANALYSIS,TEN YEARS OF PROGRESS

ABSTRACT

The need for and the principles of morphological analysis as applied to particulate matter are briefly discussed. Applications of morphological analysis to a number of problems are cited. Topics include: relating morphology to the mechanisms of powder production; wear debris analysis by morphological analysis; and kinetic modeling of crystallization processes. Relationships between the behavior of particulate materials and the morphology of the particles are discussed in connection with: abrasive wear of metals; sedimentation In low flow regimes; measuring of bulk properties including internal angle of friction and flow times; dry separation technology; and scrap recovery techniques. The adaptation of the particle image analyzing system to analyze color as a morphic feature is presented. A number of examples of mixture analysis - classification studies are detailed and finally future work in packed and fluidized beds and slurry transportation is outlined.     

Mechanically alloyed metals

Abstract

Mechanical alloying involves the severe deformation of mixtures of powders until they form the most intimate of atomic solutions. Inert oxides can also be introduced to form a uniform dispersion of fine particles which strengthen the consolidated product. Large quantities of iron and nickel base alloys with unusual properties are produced commercially using this process. The theory describing the way in which the powders evolve into a solution is reviewed. There are some fundamental constraints which dictate how the microstructure must change during mechanical alloying for the process to be at all viable. The strange recrystallisation behaviour of the alloys can be understood if it is assumed that unlike normal metals, the grains in the mechanically alloyed sample are not topologically independent. Another topic discussed is the mechanical blending of microstructures containing different phases, both with and without a net reduction in free energy.     

Reduction of titanium and other metal oxides using electrodeoxidation

Abstract

Many reactive and refractory metals are currently produced industrially by reducing their compounds, including oxides, using a more reactive metal. In some cases, where there is substantial oxygen solubility in the metal, the oxygen is first removed by carbochlorination followed by reduction. Titanium and zirconium are made by reduction of the volatile tetrachlorides by magnesium. The processes consist essentially of two reduction steps: reducing magnesium chloride to magnesium metal and then reduction of the metal compound; this makes the overall reduction process relatively expensive. Electrodeoxidation is very simple in that the oxide to be reduced is rendered cathodic in molten alkaline earth chloride. By applying a voltage below the decomposition potential of the salt, it has been found that ionisation of oxygen is the dominant cathode reaction, rather than alkaline earth metal deposition. In the laboratory, this technique has been applied to reduce a large number of metal oxides to the metals, including titanium, zirconium, chromium, niobium, tantalum, uranium and nickel. Furthermore, when mixed oxides are used as the cathode, alloys or intermetallic compounds of uniform composition are obtained. This may offer advantages over conventional technology for those alloys that are difficult to prepare at present, owing to differences in either density or vapour pressure.     

Catalytic properties of composite materials based on mesoporous silica and zirconium hydrogen phosphate

We have synthesized composite materials based on SBA-15 mesoporous silica and zirconium phosphate. The materials have been characterized by scanning electron microscopy, transmission electron microscopy, inductively coupled plasma mass spectrometry, X-ray diffraction, BET measurements, ³¹P NMR spectroscopy, and thermogravimetry, and have been employed as catalysts for ethanol dehydration. Even though their catalytic activity is somewhat lower than that of fine-particle zirconium phosphates with layered and framework structures, they offer an increased ethylene yield at low temperatures.     

Raman spectra and structural analysis in ZrOxNy thin films

Raman spectroscopy has been used as a local probe to characterize the structural evolution of magnetron-sputtered decorative zirconium oxynitride ZrO_xN_y films which result from an increase of reactive gas flow in the deposition. The lines shapes, the frequency position and widths of the Raman bands show a systematic change as a function of the reactive gas flow (a mixture of both oxygen and nitrogen). The as-deposited zirconium nitride film presents a Raman spectrum with the typical broadened bands, due to the disorder induced by N vacancies. The recorded Raman spectrum of the zirconium oxide film is typical of the monoclinic phase of ZrO₂, which is revealed also by X-ray diffraction. Raman spectra of zirconium oxynitride thin films present changes, which are found to be closely related with the oxygen content in films and the subsequent structural changes.     

Microstructural development in plasma jet forming of sheet steels

Abstract

Plasma jet forming is a newly developed flexible forming process for sheet metals using plasma arc as the energy beam and CO₂ as the cooling jet. In this paper, two different metals, low carbon mild steel and Type 304 austenitic stainless steel, were formed using the developed experimental system with series parameters. Experiments showed that the difference in forming process of these two metals depended not only upon their physical properties, but also upon their phase transformation characters. The microstructural developments in the heat affected zone of these two metals were also observed and discussed.     

Erbium zirconium phosphate Er<Subscript>0.33</Subscript>Zr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> of the NaZr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> family. Structure contraction on heating

Erbium zirconium phosphate Er_0.33Zr₂(PO₄)₃, a member of the family of structural analogs of NaZr₂(PO₄)₃ (NZP), was prepared by the sol-gel process and studied by X-ray phase analysis, IR spectroscopy, and differential scanning calorimetry. The behavior of erbium zirconium phosphate on heating in the temperature interval from 25 to 625°C was studied by high-temperature X-ray diffraction. Expansion and contraction along different crystallographic directions and contraction of the structure as a whole were found. The overall contraction is due to higher contribution of the negative axial thermal expansion coefficients α _a and α _b to α_av and hence to the volume expansion of the phosphate. On heating to 900°C, the NZP structure is preserved.     

Preparation and characterization of precursors of Y2O3 stabilized ZrO2 by metal-organic compounds

8 mol% Y₂O₃-stabilized ZrO₂ has been prepared by four routes which involve yttrium and zirconium metal organic compounds as starting materials. The thermal decomposition of the precursors has been investigated by means of thermal analysis, X-ray diffraction and SEM technique with regard to their chemical homogeneity and phase composition. The possible reactions during precursor preparations are discussed.     

Physical-separation procedures for recovering metals from spent Ni–Cd batteries

While their heyday as the leading rechargeable cell system is probably over, Ni–Cd batteries remain the main sink for cadmium production and, at the same time, the major source of cadmium contamination to the environment. Whatever happens in the (near) future, there is an evident need for an abatement in such an input. This study deals with the initial (physical) stage of an integrated process for recovering Cd, Ni and Co from spent Ni–Cd batteries, namely with the granulometric separation by wet sieving of shred-to-pieces, scrap cells. Regardless of the shredder's output, the results point to a major separation around 2.8 mm for an intense flow. Generally speaking, toxic metals (Cd, Co, Ni) concentrate in the infra fractions, whereas ferrous and organic scrap are retained above. Upper fractions still contain a fair share of non-ferrous metals though, so an additional process like leaching is required. Infra fractions can proceed directly to the recovery stages downstream. The amount of material in the finest fractions (under 0.355 mm) is inversely proportional to the mesh of the shredder's output, yet this parameter appears to have no influence on their granulometry. Electronic Publication