Nb Foils Research Articles

High Toughness Laminated Composites Fabricated from Ti3Al(Si)C2 Filled Preceramic Paper and Nb Foils: Formation Mechanism and Influence of Laminate Architecture

In this work high strength and tough metal‐ceramic laminated composites are fabricated by spark plasma sintering (SPS) of Ti3Al(Si)C2 MAX‐phase filled preceramic papers (TAC) and ductile Nb foils. The sintering is carried out at 1250 °C and 50 MPa for 5–20 min. Various stacking techniques are used to obtain Nb/TAC laminated composites with different architectures. SPS results in the formation of reaction layer (RL) with a complex composition, which changes the thickness insignificantly with increasing sintering time. The possible formation mechanism of RL is discussed. The bending strength of Nb/TAC composites is decreased from 410 to 350 MPa when lowering the thickness of ceramic layer. The maximum fracture toughness of 10.2 MPa·m1/2 is achieved for the composite with similar individual layers thickness. The toughening is explained by complex fracture mechanisms associated with deflection and branching of cracks at interfaces, delamination, plastic deformation of Nb layers, multiple cracking and crack deflection in ceramic TAC layers.

Innovative Approach to Producing Palladium-103 for Auger-Emitting Radionuclide Therapy: A Proof-of-Concept Study.

Auger-emitting radionuclides, exemplified by Pd-103, exhibit considerable therapeutic potential in cancer treatment due to their high cytotoxicity and localized biological impact. Despite these advantages, the separation of such radionuclides presents a complicated challenge, requiring intricate and time-intensive "wet chemistry" methods attributed to the exceptional chemical inertness of the associated metals. This study proposes an innovative solution to this separation challenge through the design and implementation of a piece of radionuclide separation equipment (RSE). The equipment employs a dry distillation approach, capitalizing on differences in partial vapor pressures between irradiated and resulting radioactive metals, with a diffusion-driven extraction method applied to separate Pd-103 radionuclides generated via the proton irradiation of Rh-103 at cyclotron. Our optimization endeavors focused on determining the optimal temperature for effective metal separation and adjusting the diffusion, evaporation, and deposition rates, as well as addressing chemical impurities. The calculations indicate 17% ± 2% separation efficiency with our RSE. Approximately 77 ± 2% and 49 ± 2% of the deposited Pd-103 were isolated on substrates of Nb foil and ZnO-covered W disc, respectively. The proposed innovative dry distillation method that has been experimentally tested offers a promising alternative to conventional separation techniques, enabling enhanced purity and cost-efficient cancer treatment strategies.

High temperature oxidation and thermal properties of laminated Ti3Al(Si)C2-TiC/Nb based composites obtained by spark plasma sintering

This paper describes high-temperature oxidation behavior and thermal properties of metal-ceramic laminated composites fabricated by spark plasma sintering of Ti3Al(Si)C2-filled preceramic papers (TAC) and Nb foils. The high-temperature oxidation tests were carried out in air at 800–1300 °C. The phase composition and microstructure of the oxide layers were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The thermal properties were measured by the laser flash method in the temperature range of 30–800 °C. The evolution of the microstructure of the reaction layer (RL) formed at TAC/Nb interfaces was studied. The passive oxidation of the surface TAC layers results in the formation of outer TiO2 and inner continuous Al2O3 phase at temperatures up to 1100 °C, while local accelerated oxidation occurs above 1100 °C. As a result of breakaway oxidation, a multilayer oxide structure consisting of TiO2, Al2TiO5, Al2O3 and SiO2 phases were formed. The oxidation of inner Nb layers from the side surface can lead to high volume expansion and generation of stresses in the ceramic and metal layers due to the formation of Nb2O5 oxide phase. The stress relaxation occurred by complex mechanisms, including plastic deformation of the Nb layers, delamination at the interfaces, and formation of cracks in the reaction and TAC layers. The high temperature exposure results in slight increase in columnar grains in the reaction layers at 1200 °C, while the thickness of RL remains unchanged. The TAC/Nb composites exhibit higher thermal conductivity and diffusivity compared to monolithic TAC ceramic composites.

Reconstruction of neutron spectrum emitted by portable 14 MeV neutron generator by a combination of different methods

The presented paper is a continuation of the Tikhonov Regularisation, Minimum Fisher Information, Maximum Entropy, and Maximum Likelihood methods application to unfolding the neutron spectra emitted by the fusion devices from activation measurement. The aim of the analysis is the evaluation of the possible uncertainty improvement. The developed algorithms and methodology were validated with 14 MeV portable neutron generators before application to the analysis of the neutron spectrum emitted from tokamak. The analysis concerns plasma-target generator did not provide satisfactory uncertainty of the results. The modification of the irradiation foils’ set and the improvement in the activity measurement precision progress the results. The sealed tube portable neutron generator irradiated the Al, Fe, Ni, Zr, Au, Mg, and Nb foils. The HPGe spectrometer measured the induced activity with an uncertainty of about 10 %. The synthetic data analysis was made to establish the ratio between the error of the spectrum reconstruction and the discrepancy between the input data and activities reconstructed for this spectrum by the FISPACT-II inventory code. Two bin structures were considered. One was compatible with the FISPACT-II code, but the energy resolution was not regular. The second was characterised by constant bin spacing connected with the modification requirement before simulation and additional uncertainty of about 5 %. The best results were obtained by calculation of the mean value from all methods. The corresponding reconstruction uncertainty is equal to 11 %. The reconstructed spectrum has a dominant deuterium tritium peak slightly shifted to the higher energies due to the beam-target reaction kinematics. The evaluation of the impact of the deuterium-deuterium reaction due to the long-term operation was not reachable due to the measured high intensity from scattered neutrons.

Microstructural evolution and mechanical properties of Zr-4 alloy joints diffusion bonded with Nb interlayer

To obtain a robust diffusion-bonded joint at a relatively low temperature, Nb foil was applied as an interlayer to the diffusion bonding of Zr-4 alloy, and a wide process parameter involving the bonding temperature of 720–820 °C and holding time of 30–120 min was investigated to reveal the evolution of interfacial structure and mechanical properties of the joints. The β-(Zr, Nb) and Widmanstädter microstructure formed at the interface induced by the eutectoid transformation of the diffused Zr and Nb at the bonding temperatures over 740 °C. The phase structure and the thickness of β-(Zr, Nb) layer were not considerably influenced by the increase in diffusion parameters while the Widmanstädter zone thickened significantly. Moreover, the tensile strength and elongation of the resultant joints could be stabilized above 433 MPa and 7.8%, respectively, when the bonding temperature exceeded 760 °C with a holding time of 30 min. By extending the holding time to 60 min at 760 °C, the tensile strength and elongation could reach 454 MPa and 12.6%, respectively, comparable to those obtained at an elevated temperature of 820 °C for 30 min. Additionally, the samples fractured at the diffusion layer were characterized by the in-situ tensile test under the scanning electron microscope, and it was discovered that the crack initiation and propagation process occurred mainly between the β-(Zr, Nb) and Widmanstädter diffusion zone.

Joining of graphite to Mo using Ti/Cu and Ti/Cu/Nb/Ti/Cu foils

Graphite/Mo joining has been carried out using Ti/Cu or Ti/Cu/Nb/Ti/Cu foils. The joining region in the joint using Ti/Cu foils is mainly composed of Ti3Cu4 and TiCu. The joining region using Ti/Cu/Nb/Ti/Cu foils contains a joining zone I, an Nb interlayer and a joining zone II. Both the joining zones I and II are made up of Ti3Cu4 and TiCu. The Nb foil diffuses and dissolves into the liquid fillers during the bonding. The joint using Ti/Cu/Nb/Ti/Cu foils shows higher shear strength than that using Ti/Cu foils, implying the contribution of Nb foil to the joint stress relief and to the joint strength promotion.

Study on Laser Overlap Welding of Titanium/Aluminum Dissimilar Metals Based on Niobium Microalloying

Brittle intermetallic compounds, formed during the welding process of titanium/aluminum (Ti/Al), lead to a significant reduction in joint mechanical properties. The purpose of this study is to mitigate the formation of brittle phases during the laser welding of dissimilar Ti/Al metals, thereby enhancing the mechanical properties of the joints. In this investigation, an innovative approach is adopted, utilizing Nb foil as an interlayer to effectively minimize the formation of brittle intermetallic phases during dissimilar welding. A comprehensive analysis of the microstructure of the transition layer was conducted using material characterization methods, including scanning electron microscope equipped with an energy dispersive X-ray spectrometer. The mechanical performance of the welded joints was assessed using tensile testing. The results indicate that the effective welding width and joint penetration depth at the joint interface were reduced in Ti/Al dissimilar metals when Nb was added as an intermediate layer, under the same welding process parameters, when compared to unalloyed weld seams. Furthermore, the utilization of a 0.05 mm Nb foil as the intermediate layer results in a significant 25% increase in the average shear strength compared to the other condition, with the average shear strength of the joint reaching its peak value at 192 N/mm. The unalloyed Ti/Al weld joint usually fractured along the melting zone, displaying complete brittle fracture characteristics. After Nb microalloying, the joint typically fractures along the transition zone and interface, exhibiting both cleavage and ductile fracture characteristics, indicating the combination of a brittle and toughness fracture. This study provides experimental evidence and new insights for welding Ti/Al composite structures, with significant theoretical and practical applications.

Towards the use of SDD as an absolute detector for high-energy neutron measurements

As of today, the standard method employed in tokamaks for the absolute measurement of the neutron flux (thus of the nuclear fusion power) is based on activation foils, being the most robust and unbiased technique for the absolute determination of neutron fluence. However, this technique is not able to provide real-time data useful for the control of future fusion plants like DEMO. In this paper, we present some preliminary results about the R&D activity aimed at developing the Single-crystal Diamond Detectors (SDD) used for fast neutron measurements into an absolute neutron flux monitor. Tests have been conducted at the new NILE neutron source of the Rutherford-Appleton Laboratory, a facility with compact neutron generators with a maximum yield of 109 n/s and 1010 n/s for 2.5 MeV and 14 MeV neutrons, respectively. A series of neutron spectra and flux measurements have been taken with different SDD and associated DAQ. Comparisons with standard activation foils (and namely Fe, Zr, Al and Nb foils for 14 MeV neutrons and In for 2.5 MeV neutrons) and with other reference detectors are presented and discussed. Also discussed is the stability of the SDD over time when employed at high neutron rates in realistic neutron environment, and the effects of neutron irradiation on both the counting rate and detector resolution.

Application of a flexible memristor in self-color electronics and its depth mechanism analysis

Memristor has a high-density information storage capability and can manipulate a large amount of data computing in parallel, so it can be applied in neuromorphic computing. The advanced intelligent applications are one of the major breakthroughs made in the past decade based on the memristor's research. In this work, amorphous Nb2O5 film as functional layers on flexible niobium (Nb) foil were fabricated by anodic oxidation in oxalic acid aqueous solution. A broad spectrum of well-defined color was acquired by varying the anodic voltage during oxidation of the Nb foil. The results of spectroscopic ellipsometry (SE) tests show that the Nb2O5 layers with various colors have different thickness. The willow yellow Nb2O5 film with a thickness of ∼85 nm based memristor show an excellent memristive memory behavior. Finally, it was proposed that the potential well of the ionization center tilts under the external electric field, which causes the probability of charge to escape along and against the direction of the external electric field to explain the memristive effect of the device. This work opens up a new method for fabricating the flexible memristor, which provides the potential applications for next generation self-color electronics.

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

We present the photoelectrochemical (PEC) water-splitting properties of pristine and reduced graphene oxide (rGO)-coated GaN nanocolumns (NCs) on flexible niobium (Nb) metal foils. The structural, optical, and electronic structure analyses of rGO-coated GaN-NCs on Nb foils revealed the formation of a rGO/GaN-NCs hybrid structure. Further, the valence-band studies of pure GaN-NCs shows valence-band maxima at ∼3.0 eV below the Fermi level, which decreased to ∼2.8 eV for rGO/GaN-NCs. The PEC measurement performed on pristine GaN-NCs under standard (1 Sun) conditions shows an effective photocatalytic nature with a photocurrent density of ∼60 μA/cm2 at 0.8 V (vs Ag/AgCl) in a 1 M oxalic acid electrolyte, which increases to ∼110 μA/cm2 for rGO/GaN-NCs. The efficient PEC characteristics of rGO/GaN-NCs are attributed to the effective charge separation/transport of photogenerated carriers. Furthermore, transient photocurrent measurement reveals that hybrid and pristine GaN-NCs on flexible metal foil have a fast and stable photoresponse in an aqueous solution. The development of a hybrid nitride nanostructure-based PEC device on flexible metal foils paves the way toward developing scalable PEC devices for hydrogen production applications.

Spark plasma sintering of Nb/Ti3Al(Si)C2-TiC laminated composites

This work describes novel Nb/Ti3Al(Si)C2-TiC laminated composites fabricated by spark plasma sintering (SPS) at 1250 °C, 50 MPa for 5 min. Preceramic papers filled with Ti3Al(Si)C2 MAX-phase and Nb foils were used as feedstock. Microstructure, phase composition and mechanical properties were evaluated by scanning electron microscopy, X-ray diffraction and three-point bending test, respectively. It was found that the reaction of preceramic paper-derived layers with Nb layers results in the formation of 16.5 µm-thick interlayers mainly composed of columnar Nb-Al intermetallic, Ti-Nb-Si and Nb-Si based phases. The laminated composites showed a brittle-ductile fracture behavior characterized by multiple deflection and branching of cracks at interfaces and plastic deformation of Nb layers. Crack deflection and delamination occur mainly near the interface between the reaction layer and ceramic layer due to the presence of more brittle silicide and carbide phases. The flexural strength of the fabricated composites was ∼350 MPa at 1.5% strain.

Variable energy X-ray fluorescence source

We detail the design of a variable energy, x-ray fluorescence source using a low activity (1.8×106 dpm) 99Tc β source that irradiates thin foils. By rotating the source among foils of Ti, Zn, Nb, Ag, and Au, the device produces x rays between 4 and 70 keV at a rate near 1 Hz. When the source is placed in a storage position, the external radiation is non-detectable. The design of the shielding and rotation mechanism permits use in vacuum and at liquid nitrogen temperature. The design is intended for the study of the low energy response to radiation impinging upon Ge detector surfaces. The source will be useful for understanding the detector response in large-scale Ge arrays such as Majorana and LEGEND.

Characterization of a Nb-Pb composite target

A thin Nb target on a Pb backing was fabricated using the rolling technique. In the present work, the characterization of the sample has been carried out using various techniques to study the surface morphology, crystallography, elemental analysis, thickness and electrical conductivity useful for the intended use of the target prepared. The thin Nb target was analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Rutherford back-scattering spectroscopy (RBS) techniques. The uniform and smooth surface of the sample was confirmed by SEM imaging. The presence of oxygen in the EDS spectra and peaks corresponding to crystal planes of PbO2 in the XRD spectrum confirms the oxidation of Pb foil. The XRD spectrum shows clear peaks corresponding to (011), (002), (112) crystal planes of pure Nb. The thickness of the thin Nb foil measured using the RBS techniques was found to be 0.8 mg/cm2. The current(I)-voltage(V) curve (relationship between the current flowing through an electronic device and the applied voltage across its terminals) at room temperature for the Pb and Nb/Pb foils was plotted and showed linear relationship between applied voltage and current flowing through the target foil. The measured electrical conductivity indicates an enhancement of 35.9 % for Nb/Pb foil relative to the conductivity measured for the Pb foil.

Effect of adding Nb foil on joint properties of laser fusion welding for TC4 titanium and 7075 aluminum alloy

It is difficult to gain effective Ti-Al fusion welding joints due to their differences in thermal properties and the appearance of brittle Ti-Al Intermetallic Compounds (IMCs). The experiments of laser fusion welding for TC4 titanium and 7075 aluminum alloy were carried out, temperature field and ductility/brittleness, as well as chemical potential of elements, were calculated, and the effect of adding Nb foil on mechanical properties of the weld was also investigated. The results suggested that Nb atoms tend to diffuse toward Al side, which is conducive to the participation of Nb in the metallurgical reaction and contributes to forming the Ti-Nb-Al IMC layer at the interface. As the thickness of Nb foil increases, the tensile-shear force of joint climbs first but then declines, and reaches the highest value of 1663 N with 0.10 mm-thickness Nb foil, representing 58.38% enhancement compared with the non-added one. Adding Nb foil slows down the heat transfer as a blocker, and thus both the melting amount of Al and the mixing area of Ti and Al decrease. In addition, Nb alloying reduces the brittleness of the Ti-Al compound. Hence, the joint properties of titanium/aluminum are improved with the addition of Nb foil.

Synergistic effect of oscillating laser-Nb foil on microstructure and mechanical properties of TC4/7075 dissimilar joints

Oscillating laser welding of TC4 titanium (Ti) to 7075 aluminum (Al) alloys with assistance of Nb foil was performed in an overlap Ti-on-Al configuration, and Nb foil was determined to improve the metallurgical reactions based on analysis from thermodynamic calculations. The synergistic effect of oscillating laser-Nb foil on microstructure and mechanical properties of TC4/7075 dissimilar joints was investigated. Results show that the reduction of Ti–Al joint properties is mainly due to the weak regions at Ti/Al interface composed of TiAl and TiAl3 compounds, where lattice distortion inside TiAl3 and the dislocations in Al matrix grains adjacent to TiAl3 are detected. A sound Ti/Al dissimilar joint is obtained under the beam rotation of oscillating laser assisted by Nb foil. The joint connection area is increased and interfacial heat input is reduced with the beam oscillation, which arises from the weakened heat transfer in penetration direction and heat absorption of Nb foil, thus it is beneficial to reducing the Al melting amount and preventing the overmixing and mutual diffusion between Ti and Al. At the optimal welding parameters, the maximum tensile-shear property of joints increases from 1663 N to 2131 N, representing a 28.14% enhancement compared with that of non-oscillation mode. Moreover, oscillating laser produces a significant effect on the metallurgical regulation of Nb foil, under which the phase composition at Ti/Al interface is replaced by Nb-containing Ti–Al compounds with lower brittleness, as well as some new phases like Ti2NbAl and NbAl3. However, when oscillation frequency is high, such as 100Hz, the melting amount of Nb foil is reduced, and the dual-interface joint is formed which is composed of Ti/Nb and Nb/Al interfaces, where the Nb metallurgy regulation is weakened.

Self-doping of Nb2O5NC by cathodic polarization for enhanced conductivity properties and photoelectrocatalytic performance

A simple novel electrochemical reduction approach was developed for the self-doping of Nb4+ in niobium oxide nanochannels (Nb2O5NC), changing the conductivity, optical properties, and photocatalytic properties of the material. Nb2O5NC was synthesized using different electrolytes: 0.4 wt% HF in 1 M H2SO4 (EI), 0.4 M NH4F in glycerol (EII), and 0.25 g NH4F with 4 vol% water in glycol at 50 °C (EIII). Field emission scanning electron microscopy (FEG-SEM) analysis showed well-organized arrays of Nb2O5 nanochannels produced on Nb foil, with varying tube diameters in the order EII < EI < EIII and film thickness in the order EI < EII < EIII, which drastically affected the photocurrent vs. potential curves. In order to self-dope the Nb2O5, the samples were electrochemically reduced in 0.1 M KH2PO4 buffer solution (pH 10) for 5 min, at −2.5 V vs. Ag/AgCl, resulting in the doped samples denoted P-EI, P-EII, and P-EIII. The results showed that reduction of Nb5+ to Nb4+ occurred for all the Nb2O5NC samples, leading to decreased surface charge transfer resistance between the Nb2O5NC and the electrolyte, as well as increases of the charge carrier density and photocurrent for all the self-doped samples, compared to undoped samples. Sample P-EI was also tested for the degradation of reactive red 120 (RR120) dye, achieving efficient photoelectrocatalytic degradation of a 10 mg L−1 dye solution. These results reveal that the self-doping approach can enhance the photoelectrocatalytic properties of Nb2O5 photoanode, offering an alternative way for the removal of reactive dyes.

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy.

Niobium metal foils were heat-treated at 900°C under different conditions and in situ investigated with time-resolved X-ray absorption fine-structure (EXAFS and XANES) measurements. The present study aims to mimic the conditions usually applied for heat treatments of Nb materials used for superconducting radiofrequency cavities, in order to better understand the evolving processes during vacuum annealing as well as for heat treatments in controlled dilute gases. Annealing in vacuum in a commercially available cell showed a substantial amount of oxidation, so that a designated new cell was designed and realized, allowing treatments under clean high-vacuum conditions as well as under well controllable gas atmospheres. The experiments performed under vacuum demonstrated that the original structure of the Nb foils is preserved, while a detailed evaluation of the X-ray absorption fine-structure data acquired during treatments in dilute air atmospheres (10-5 mbar to 10-3 mbar) revealed a linear oxidation with the time of the treatment, and an oxidation rate proportional to the oxygen (air) pressure. The structure of the oxide appears to be very similar to that of polycrystalline NbO. The cell also permits controlled exposures to other reactive gases at elevated temperatures; here the Nb foils were exposed to dilute nitrogen atmospheres after a pre-conditioning of the studied Nb material for one hour under high-vacuum conditions, in order to imitate typical conditions used for nitrogen doping of cavity materials. Clear structural changes induced by the N2 exposure were found; however, no evidence for the formation of niobium nitride could be derived from the EXAFS and XANES experiments. The presented results establish the feasibility to study the structural changes of the Nb materials in situ during heat treatments in reactive gases with temporal resolution, which are important to better understand the underlaying mechanisms and the dynamics of phase formation during those heat treatments in more detail.

Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures

Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of commercially available Nb foil samples affects their superconducting behavior. DC magnetization and AC susceptibility measurements at cryogenic temperatures and with magnetic fields of different amplitude and orientation are thus analyzed and reported. This study pays special attention to the surface superconducting layer that persists above the upper critical magnetic field strength Hc2, and disappears at a higher nucleation field strength Hc3. Characteristic changes were distinguished between the surface properties of the laser-irradiated samples, as compared to the corresponding reference samples (non-irradiated). Clear correlations have been observed between the surface nanostructures and the nucleation field Hc3, which depends on the relative orientation of the magnetic field and the surface patterns developed by the laser irradiation.

Enhancement of photocurrent response for self-ordered Nb2O5 nanotubes synthesized at room temperature

The major challenge regarding new photocatalysts is to obtain a semiconductor with high and stable photocurrent from inexpensive and abundant materials. Niobium oxide meets some of these requirements, but its photocurrent is usually very low. Therefore, this study introduces the synthesis and characterization of self-organized Nb2O5 nanotubes (Nb2O5Nt) presenting a high photocurrent density of 0.04 mA cm−2 under incidence of artificial sunlight, of 100 mW cm−2, and potential of 1.5 V without further surface modification. The best catalyst was obtained through anodization of a Nb foil at 90 V for 2 h in a one-compartment and two-electrodes cell at room temperature, using glycerol, H2O, and NH4F as the electrolyte, followed by annealing at 450 °C for 60 min. The water concentration was the most important factor to obtain the desired morphology with a good distribution of nanotube diameters, high UV absorption, low bang gap (3.2 eV) compared to the observed for the Nb2O5 semiconductor (3.4 eV), and great photocurrent density. Such properties turn the Nb2O5Nt into a promising catalyst for direct use in photochemical reactions or as a good platform yet to be combined in heterojunctions or applied for doping and decoration.

Self-induced growth of GaN nanorod assembly on flexible niobium metal foil using laser molecular beam epitaxy

Self-induced GaN nanorod (NR) growth on flexible niobium (Nb) metal foil has been reported using laser assisted molecular beam epitaxy (LMBE) technique. The role of growth temperature (600, 650 and 700 °C), laser repetition rate (10–30 Hz) and Nb foil pre-nitridation condition on the formation and properties of GaN NRs have been studied systematically. The dense (~2.42 × 109 cm−2) GaN NRs were grown on pre-nitridated Nb metal foil at growth temperature of 700 °C with length and diameter of ~550–640 nm and ~60–130 nm, respectively. The low growth temperature of 650 °C or the high laser repetition rate of 30 Hz increases the radial growth rate of GaN NRs on Nb foil which results the coalescence of NRs. The size and density of GaN NRs on Nb metal foil could be controlled with tuning of LMBE growth parameters. The GaN NRs obtained on bare and nitridated Nb foil have excellent optical properties with an intense near band emission peak position at ~3.40 eV and a narrow linewidth of 90–100 meV. The controlled growth of GaN NRs with excellent optical quality on Nb foil offers the possibility of realization of futuristic high efficient flexible III-nitride nanostructure-based optoelectronic devices.