Nb Tubes Research Articles

Manufacturing of PAV-ONE, a Permeator against Vacuum Mock-Up with Niobium Membrane

The Permeator Against Vacuum (PAV) is one of the proposed technologies for the Tritium Extraction System of the WCLL BB (Water-Cooled Lithium-Lead Breeding Blanket) of the EU DEMO reactor. In this paper, the manufacturing of the first PAV mock-up with a niobium membrane with a cylindrical configuration is presented. This work aimed to demonstrate the possibility of manufacturing a relevant-size PAV to be later tested in the TRIEX-II facility. The adopted prototypical solutions are described in detail, starting with the methodology developed to join the Nb tubes with a 10CrMo9-10 (A182 F22) plate. Dedicated manufacturing and welding procedures, based on vacuum brazing with a nickel-based brazing alloy, were developed to solve the problem. This new kind of brazing was first analyzed to check the morphology of the joint and then tested to check its capability to withstand the TRIEX-II operative conditions. In parallel, the compatibility with a lithium-lead environment was analyzed by exposing samples of niobium and 10CrMo9-10 (A335 P22) to a flow of the eutectic alloy at 500 °C up to 4000 h. Finally, the PAV mock-up was installed in the TRIEX-II facility.

Corrosion behavior of Cr-coated zirconium alloy cladding in LiOH/H3BO3-containing water at 360 ℃

The corrosion behaviors of Cr-coated zirconium alloy (Zr-0.9 Nb) tube were investigated in 70 ppm Li and 3.5 ppm Li+ 1000 ppm B aqueous solutions at 360 °C/18.6 MPa by static autoclave tests, respectively. Results show that Cr coating improves the corrosion resistance of Zr-0.9 Nb under LiOH and Li+B conditions. The corrosion products of Cr coating were Cr2O3 and Cr(OH)3, while the Cr2O3 was more easily transformed into Cr(OH)3 under LiOH conditions. Some of the Cr(OH)3 dissolved in the late stage of corrosion, resulting in the thinning of the oxide film. Data availabilityThe raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

Thermal stability model of power coupler niobium tube for accelerator based on multi-field coupling analysis

The power coupler is the key component of superconducting accelerator, and its thermal stability will seriously affect the stable operation of the superconducting cavity. The niobium (Nb) tube at the end of the power coupler directly connected to the superconducting cavity is taken as the research object, and a one-dimensional thermal stability model based on multi-field coupling analysis is established. The coupling relationship between the electromagnetic field, liquid helium boiling heat transfer and temperature field is considered. The finite difference method was used to discretize the control equations of the model, and the Newton-Raphson method was used to handle the influence of material parameters and internal heat sources nonlinearity on the accuracy and stability of the discrete equations. The results show that the thermal stability of the Nb tube can be improved by controlling the upstream heat leakage and maintaining the upstream temperature below 9.2 K. Under transient conditions, timely recovery of the upstream cooling capacity can stop the quench caused by the decrease of cooling capacity and restore the superconducting state. The maximum quench propagation speed caused by the increase of magnetic field is 0.188 m/s, which is higher than that caused by the decrease of cooling capacity. When the local region of the liquid helium contact enters the film boiling 0.0034 s, the entire region will enter the film boiling, and the maximum temperature will reach 11.3 K, which will cause the thermal quench of the superconducting cavity. The model can accurately analyze the factors affecting the thermal stability of Nb tube and provide a reliable theoretical basis for the thermal design and stable operation of this type of power coupler.

Microstructure and texture evolution of pure niobium in cold-drawn Mg+B/Nb/Cu wires

In this study, Mg+B wires were prepared by powder in tube method using Nb and Cu tubes as barrier and sheath, respectively, followed by cold drawing. Microstructural, textural, and mechanical properties of the Nb barrier at different drawing strains (ε d) were investigated. The results showed that the Nb barrier demonstrated a saturation hardness of 159.4 HV. The microstructure of the Nb barrier became elongated along the drawing direction increasing ε d. Sub-grains existing inside the deformed grains rotated from low-angle grain boundaries to high-angle grain boundaries and developed into new grains. The main textural components of the Nb barrier were {111} γ-fiber and {hkl}〈110 〉 α-fiber. Recrystallized grains exhibited a low maximum orientation distribution function intensity, weak {100}〈110 〉 α-fibers, and strong {111}〈110 〉 γ-fibers as compared to those of the deformed grains. The relationship between the microstructure evolution and mechanical properties of the Nb barrier and the changes in the cross-sectional area fractions of the materials constituting the Mg+B composite wire are discussed. The current study provides details about the misorientation profile inside deformed grains and continuous dynamic recrystallization mechanism of the cold-drawn Nb barrier.

Effect of extrusion ratios on hardness, microstructure, and crystal texture anisotropy in pure niobium tubes subjected to hydrostatic extrusion

Nb tubes were fabricated through hydrostatic extrusion at extrusion ratios of 3.1 and 6.1 at ambient temperature, and then their microstructure, texture, and Vickers hardness were investigated based on electron back-scattered diffraction (EBSD) data. The fraction of low-angle boundaries (LABs) largely decreased with a sharp decrease in mean grain sizes after hydrostatic extrusion and was not proportional to extrusion ratios, assuming that mixed-asymmetrical junctions forming LABs dissociate at high extrusion ratios from the external stress (>981 MPa) with thermal activation by the generated heat. The correlation between grain size and Vickers hardness followed the Hall−Petch relationship despite the texture gradient of the 〈111〉 cyclic fiber textural microstructure at low extrusion ratios and the 〈100〉 true fiber textural microstructure at high extrusion ratios. The increase in hydrostatic pressure on the Nb tubes contributed to texture evolution in terms of extrusion ratios due to the difference between {110}〈111〉 and {112}〈111〉 components based on EBSD data.

Mechanical and Microstructural Evolution of the Mg-B Powder/Nb/Cu Cladding Using Hydrostatic Extrusion and Subsequent Drawing Process.

The paper introduces the mechanical and microstructural evolution of Mg-B powders/Nb/Cu claddings fabricated using only drawing process and hydrostatic extrusion plus drawing process. We found that the Mg-B powder of the claddings during the latter process was more densified than that of the former process because of larger reduction rate in the process of hydrostatic extrusion. The claddings created by the latter process exhibited a little higher Vickers hardness values and lower grain size than those of the former process in Nb tubes. The refined microstructure of Nb tube by the latter process had higher image quality (IQ) value corresponding to lower dislocation density due to higher misorientation angles between grains than that of the former process, thereby demonstrating the broadly distributed (110) fiber texture.

Effect of strains on textural evolution of hydrostatically extruded niobium tubes

The influence of tube strains on tube deformation ratios and textural evolution during the deformation of pure Nb tubes subjected to hydrostatic extrusion was investigated. The tube deformation ratios increased with increasing tube strains. A very strong <111> fibre texture at a lower strain transformed to a dual strong <100> and weak <111> fibre texture at a higher strain. The texture evolution led to an increase in the Taylor factor at the drawing tensor.

Exploration of Multi-Component Vanadium and Titanium Pnictides Using Flux Growth and Conventional High-Temperature Methods.

The flux growth method was successfully employed to synthesize millimeter-sized single crystals of the ternary barium vanadium pnictides Ba5V12As19+x (x ≈ 0.02) and Ba5V12Sb19+x (x ≈ 0.36), using molten Pb and Sb, respectively. Both compositions crystallize in space group P3m and adopt a structure similar to those of the barium titanium pnictides Ba5Ti12Pn19+x (Pn = Sb, Bi), yet with a subtly different disorder, involving the pnictogen and barium atoms. Attempts to obtain an arsenide analog of Ba5Ti12Pn19+x using a Pb flux technique yielded binary arsenides. High-temperature treatment of the elements Ba, Ti, and As in Nb or Ta tubes resulted in side reactions with the crucible materials and produced two isostructural compositions Ba8Ti13−xMxAs21 (M = Nb, Ta; x ≈ 4), representing a new structure type. The latter structure displays fcc-type metal clusters comprised of statistically distributed Ti and M atoms (M = Nb, Ta) with multi-center and two-center bonding within the clusters, as suggested by our first-principle calculations.

RETRACTED ARTICLE: Experimental and Numerical Investigation of VMR and HPTR Pilgering of Zr–1.5%Nb Tubes

Due to role of the sequence of cold pilger rolling processes with intermediate heat treatments in regular Zr cladding tube productions, the precise study of such processes and their effects on the material properties, geometry and deformation behavior of the tube can be very important. Therefore, a unique set of experimental and finite element simulation examinations were carried out to investigate the mechanical properties, microstructure, hydrides fraction (F) and deformation behavior of Zr–1.5%Nb by employing a series of vertical mass ring die mill and roll cold reduction mill (Holodnoj Prokatki Trub Rolikami: HPTR) processes. Furthermore, it was important to optimize the process parameters and the resulting mechanical properties of the cold-rolled cladding tubes. Therefore, the effects of the main process parameters (feed rate and turn angle) on the damage build-up during the pilgering process were also studied. To determine the optimum process parameters, a new revised Latham–Cockcraft damage was calculated for different conditions by introducing the new subroutine, which considered the compressive stresses on the formula. It is shown that the proposed model is completely reliable. Then, based on its results, the optimum values of process parameters could be obtained. Besides, it is concluded that the annealing process could change the orientations of zirconium hydrides from the radial direction to the circumferential one. The different Fn values in the internal and external surfaces of the samples were related to the basal planes orientations at these two layers.

Heat Treatment Effect on the Microstructure and Properties of a High-Strength and High-Conductivity Cu–Nb–Cu Microcomposite

Cu–Nb–Cu microcomposite reinforced by Nb tube was successfully fabricated by accumulative drawing and bundling process. When the strength of the Cu–Nb–Cu composite reaches above 1 GPa, the conductivity can reach 67% International Annealed Copper Standard (IACS). The annealing effects on the microstructure and properties of the Cu–Nb–Cu microcomposite have been thoroughly discussed. Annealing temperature at 750 °C can lead to an obvious change of microstructures. Both the partial spheroidization and further coarsening of niobium filaments in Cu–Nb–Cu microcomposite have been revealed. The influences of the microstructure changes on the mechanical and electrical properties have also been analyzed.

Effect of Rolling Speed on Microstructural and Microtextural Evolution of Nb Tubes during Caliber-Rolling Process

This study investigated the fabrication of Nb tubes via the caliber-rolling process at various rolling speeds from 1.4 m/min to 9.9 m/min at ambient temperature, and the effect of the caliber-rolling speed on the microstructural and microtextural evolution of the Nb tubes. The caliber-rolling process affected the grain refinement when the Nb tube had a higher fraction of low angle grain boundaries. However, the grain size was identical regardless of the rolling speed. The dislocation density of the Nb tubes increased with the caliber-rolling speed according to the Orowan equation. The reduction of intensity for the &lt;111&gt; fiber texture and the development of the &lt;112&gt; fiber texture with the increase of the strain rate are considered to have decreased the internal energy by increasing the fraction of the low-energy Σ3 boundaries.

Sr/Eu cation doping and thermoelectric properties of the compound Ca&amp;lt;sub&amp;gt;9&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;4.5&amp;lt;/sub&amp;gt;&amp;lt;sub&amp;gt;&amp;minus;&amp;lt;/sub&amp;gt;&amp;lt;sub&amp;gt;&amp;lt;italic&amp;gt;&amp;delta;&amp;lt;/italic&amp;gt;&amp;lt;/sub&amp;gt;Sb&amp;lt;sub&amp;gt;9&amp;lt;/sub&amp;gt; (0&amp;lt;&amp;lt;italic&amp;gt;&amp;delta;&amp;lt;/italic&amp;gt;&amp;lt;0.5)

Previous studies suggested that Zintl phases related to the Ca9Zn4.5− δ Sb9 (0 δ x Cu x Sb9 indicated that they could achieve an optimized zT around 0.7. Especially for Ca9Zn4.5− δ Sb9, a very recent report suggested that a high zT of 1.1 at 875 K could be obtained in combination of various secondary phases introduced by the variation of Zn contents, which provided a chemical potential to change the composition. However, to change the composition of Ca9Zn4.5− δ Sb9 is actually very difficult to implement owing to the narrow homogeneity range. In this work, with Ca substituted by big cations such as Eu2+ and Sr2+, the unit cell of Ca9Zn4.5− δ Sb9 was expanded, and similar significant enhancement on the thermoelectric performance was resulted. All syntheses were handled inside a glovebox, then the reactants were loaded in the Nb tube and arc-welded, which were enclosed in a fused silica tube. The reactions were firstly heated to 1173 K in 6 h and then maintained at this temperature for 24 h. After the homogeneity process, the furnace was slowly cooled down to 873 K at a rate of 6 K/h, followed by another dwelling for 6 hours and finally cooled down to 573 K at a rate of 10 K/h. At last, the furnace was shut down and the reactions were opened in the glovebox. The compound were fully characterized by single-crystal X-ray diffraction (SXRD) and powder X-ray diffraction(PXRD), Energy dispersive spectrometer (EDS) and Hall effect measurement, etc. Single-crystal X-ray diffraction (SXRD) proves that with the increase of Sr component, the crystal parameters are slightly increasing. Hall effect measurement show that the substitution of Ca by Eu or Sr can both lead to an obvious decreasing on the carrier (holes) concentration, and the resultant mobility for Sr/Eu-doped materials is very similar if compared by the same doping level. It is also noted that neither the carrier concentration nor the mobility seems to vary linearly with the Eu/Sr-doping contents, which means a saturated state will be eventually approached. This phenomenon is consistent with the speculation above that the changes on the properties should predominantly originate from the change of interstitial Zn content, which the size effect dominated. While the decreasing carrier concentrations as well as the increasing mobility and lattice thermal conductivity all point to a structure modification, the crystal structures of these doped materials were systematically verified through the single crystal X-ray diffraction. In conclusion, although a direct measurement on such a small composition variation is very difficult (the X-ray diffraction results prove it), the significantly reduced carrier concentration and increased mobility as well as lattice thermal conductivity can still provide some useful hints on understanding the property optimization of these materials. For material Ca8.2Eu0.8Zn4.5− δ Sb9, high figure of merit with ZT ~0.81 has been achieved at 873 K.

Crystal Chemistry of RE6MgxCd23–xPb [0.6(1) ≤ x ≤ 3.2(1); RE = La and Ce]. New Mixed‐Metal Derivatives of the RE6Cd23T Phases (T = Group 14/15/16 Element)

Synthesis and crystal structure determinations are reported for six quaternary phases with the general formula RE6MgxCd23–xPb [RE = La, Ce; 0.6(1) ≤ x ≤ 3.2(1)]. These compounds were prepared by high temperature reactions of the elements in sealed Nb tubes. As revealed by powder and single‐crystal X‐ray diffraction, their crystal structures are of the cubic Zr6Zn23Si system (cF120, Fm3m, Z = 4), itself an interstitially filled variant of the Th6Mn23 structure type. Rather than distributing equally across the entire Cd23 sub‐structure, Mg displayed a tendency to accumulate at specific sites (most notably 4a); charge differences between sites within the sub‐structure, as revealed by computational methods, are the likeliest explanation.

An intermetallic powder-in-tube approach to increased flux-pinning in Nb3Sn by internal oxidation of Zr

We report on the development of multifilamentary Nb3Sn superconductors by a versatile powder-in-tube technique (PIT) that demonstrates a simple pathway to a strand with a higher density of flux-pinning sites that has the potential to increase critical current density beyond present levels. The approach uses internal oxidation of Zr-alloyed Nb tubes to produce Zr oxide particles within the Nb3Sn layer that act as a dispersion of artificial pinning centres (APCs). In this design, SnO2 powder is mixed with Cu5Sn4 powder within the PIT core that supplies the Sn for the A15 reaction with Nb1Zr filament tubes. Initial results show an average grain size of ∼38 nm in the A15 layer, compared to the 90–130 nm of typical APC-free high-Jc strands made by conventional PIT or Internal Sn processing. There is a shift in the peak of the pinning force curve from H/Hirr of ∼0.2 to ∼0.3 and the pinning force curves can be deconvoluted into grain boundary and point-pinning components, the point-pinning contribution dominating for the APC Nb-1wt%Zr strands.

Superconducting shielding with Pb and Nb tubes for momentum sensitive measurements of neutral antimatter

In this paper we report on measurements and simulations of superconducting tubes in the presence of inhomogeneous externally applied magnetic fields in a cryogenic environment. The shielding effect is studied for two different tube materials, Pb and Nb, employing Hall sensors in a tabletop experiment. The measured internal and external fields of the tubes agree with the theory of the Meissner-Ochsenfeld effect [1], field trapping of type 2 superconductors, phase transitions and tube geometries. The obtained measurements are compared to a finite element simulation. Next, the simulation model is applied to estimate the shielding effect in the vicinity of a cryogenic Penning trap experiment. The controlled suppression of external magnetic fields is important for future precision experiments in atomic and antimatter physics in cryogenic environments.

Development of a multi-scale simulation model of tube hydroforming for superconducting RF cavities

This work focuses on finite element modeling of the hydroforming process for niobium tubes intended for use in superconducting radio frequency (SRF) cavities. The hydroforming of tubular samples into SRF-relevant shapes involves the complex geometries and loading conditions which develop during the deformation, as well as anisotropic materials properties. Numerical description of the process entails relatively complex numerical simulations. A crystal plasticity (CP) model was constructed that included the evolution of crystallographic orientation during deformation as well as the anisotropy of tubes in all directions and loading conditions. In this work we demonstrate a multi-scale simulation approach which uses both microscopic CP and macroscopic continuum models. In this approach a CP model (developed and implemented into ABAQUS using UMAT) was used for determining the flow stress curve only under bi-axial loading in order to reduce the computing time. The texture of the materials obtained using orientation imaging microscopy (OIM) and tensile test data were inputs for this model. Continuum FE analysis of tube hydroforming using the obtained constitutive equation from the CP modeling was then performed and compared to the results of hydraulic bulge testing. The results show that high quality predictions of the deformation under hydroforming of Nb tubes can be obtained using CP-FEM based on their known texture and the results of tensile tests. The importance of the CP-FEM based approach is that it reduces the need for hydraulic bulge testing, using a relatively simple computational approach.

ChemInform Abstract: Redetermination of the Crystal Structure of NbF4.

AbstractSingle crystals of NbF4 are prepared by disproportionation of Nb2F5 (Nb Tube in evacuated silica tubes, 1273 K, 2 d) and by solid state reaction of Nb and NbF5 (1073 K, 2 d; heating rate of 16 K/h).

ChemInform Abstract: Ternary Aurides RE4Mg3Au10 (RE: La, Ce, Pr) and RE4Cd3Au10 (RE: Y, La—Nd, Sm, Gd—Dy) — Ordering Variants of the Zr7Ni10 Type.

AbstractLn14Mg3Au10 (Ln1: La, Ce, Pr) and Ln24Cd3Au10 (Ln2: Y, La—Nd, Sm, Gd—Dy) are prepared by induction melting of the elements (Nb tubes, 1.

ChemInform Abstract: Ba3Pt4Al4 — Structure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units.

AbstractThe title compound is prepared from the elements (Nb tube, 1073 K, 7 d) and characterized by powder XRD, XPS, 27Al MAS NMR spectroscopy, magnetic measurements, and DFT band structure calculations.

Bulge testing of copper and niobium tubes for hydroformed RF cavities

The heat treatment, tensile testing, and bulge testing of Cu and Nb tubes has been carried out to gain experience for the subsequent hydroforming of Nb tube into seamless superconducting radio frequency (SRF) cavities for high energy particle acceleration. In the experimental part of the study samples removed from representative tubes were prepared for heat treatment, tensile testing, residual resistance ratio measurement, and orientation imaging electron microscopy (OIM). After being optimally heat treated Cu and Nb tubes were subjected to hydraulic bulge testing and the results analyzed. In the final part of the study finite-element models (FEM) incorporating constitutive (stress–strain) relationships analytically derived from the tensile and bulge tests, respectively, were used to replicate the bulge test. As expected, agreement was obtained between the experimental bulge parameters and the FEM model based on the bulge-derived constitutive relationship. Not so for the FEM model based on tensile-test data. It is concluded that a constitutive relationship based on bulge testing is necessary to predict a material's performance under hydraulic deformation.