Tungsten Filament Research Articles

Fostering prospective teacher-students to contextualize blackbody radiation in astrophysics

Abstract In astrophysical concepts, a star can be treated as a blackbody. However, teaching blackbody radiation in physics classrooms is not often relevant to astrophysical contexts. Therefore, prospective teacher-students need to have experiences contextualizing blackbody radiation in astrophysics. This study aimed to investigate how the inquiry lesson activities for teaching blackbody radiation in an astrophysics context, including the design of a simple experimental setup and the worksheets. The experimental setup was designed using affordable equipment like a tungsten bulb, a basic meter, a small piece of compact disk, and a smartphone application called lux meter. By manipulating the voltage across the tungsten filament and measuring the current and intensity using a lux meter, students can calculate its temperature, analyze the spectrum through PHET simulation, and construct a graph of wavelength vs intensity. The method of this study combines a qualitative analysis to describe the resulted spectral by the apparatus, lesson design, and description of the implementation. In addition, quantitative analysis using a quasi-experimental one-group pre-test and post-test design was conducted with prospective teacher-student participants who had taken the astronomy course and are still taking the modern physics course. The results show that inquiry lesson using simple apparatus model and materials positively fosters prospective teacher-students understanding of how to contextualize the blackbody radiation concept in astrophysics.

Advancing CubeSats Capabilities: Ground-Based Calibration of Uvsq-Sat NG Satellite’s NIR Spectrometer and Determination of the Extraterrestrial Solar Spectrum

Uvsq-Sat NG is a French 6U CubeSat (10 × 20 × 30 cm) of the International Satellite Program in Research and Education (INSPIRE) designed primarily for observing greenhouse gases (GHG) such as CO2 and CH4, measuring the Earth’s radiation budget (ERB), and monitoring solar spectral irradiance (SSI) at the top-of-atmosphere (TOA). It epitomizes an advancement in CubeSat technology, showcasing its enhanced capabilities for comprehensive Earth observation. Scheduled for launch in 2025, the satellite carries a compact and miniaturized near-infrared (NIR) spectrometer capable of performing observations in both nadir and solar directions within the wavelength range of 1100 to 2000 nm, with a spectral resolution of 7 nm and a 0.15° field of view. This study outlines the preflight calibration process of the Uvsq-Sat NG NIR spectrometer (UNIS), with a focus on the spectral response function and the absolute calibration of the instrument. The absolute scale of the UNIS spectrometer was accurately calibrated with a quartz-halogen lamp featuring a coiled-coil tungsten filament, certified by the National Institute of Standards and Technology (NIST) as a standard of spectral irradiance. Furthermore, this study details the ground-based measurements of direct SSI through atmospheric NIR windows conducted with the UNIS spectrometer. The measurements were obtained at the Pommier site (45.54°N, 0.83°W) in Charentes–Maritimes (France) on 9 May 2024. The objective of these measurements was to verify the absolute calibration of the UNIS spectrometer conducted in the laboratory and to provide an extraterrestrial solar spectrum using the Langley-plot technique. By extrapolating the data to AirMass Zero (AM0), we obtained high-precision results that show excellent agreement with SOLAR-HRS and TSIS-1 HSRS solar spectra. At 1.6 μm, the SSI was determined to be 238.59 ± 3.39 mW.m−2.nm−1 (k = 2). These results demonstrate the accuracy and reliability of the UNIS spectrometer for both SSI observations and GHG measurements, providing a solid foundation for future orbital data collection and analysis.

Calculation and error analysis of virtual cathode caused by a thermionic cathode

The relative errors of virtual cathodes calculated by using the one-dimensional virtual cathode theory are analyzed and discussed. The studies of the error analysis show that the cathode temperature is the major factor affecting the calculated results of virtual cathodes, especially for calculations of the virtual cathode width. The smaller the virtual cathode produced by a hot cathode, the more significant the relative error of the virtual cathode caused by the uncertainties of electron emission parameters. Using the accurate cathode temperature, the potential barrier and the spatial width of virtual cathodes generated by a tungsten filament are calculated with experimental and theoretical electron emission parameters. The calculated results show that there is a strong linear correlation between the potential barrier of the virtual cathode and the heating current of the tungsten filament, which is independent of the electron collection current. With the increase in the heating current, the variation of the virtual cathode width is very sensitive to the relation between the electron collection current and the heating current.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia. A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05). The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3mm and 0.7mm thicknesses showed strong negative correlations between Sa and RTP00. The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased. For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

Tungsten Wire—From Lamp Filaments to Reinforcement Fibers for Composites in Fusion Reactors

The use of drawn tungsten wire marked a breakthrough in electric lighting which led to a significant advancement in human society and technology. Nowadays, thermal light sources using tungsten filaments are being more and more replaced by semiconductor‐based light‐emitting diodes (LEDs). Despite the lower visibility of incandescent lamps in everyday life, new markets and applications for drawn tungsten wires are opening up, which makes this complex material a highly‐studied subject. One of these applications is the use of heavily drawn tungsten wires as high‐performance reinforcement fibers for new composites that can withstand the extreme environment present in a nuclear fusion reactor. The main advantage of tungsten wires for this class of composites is their ductility and high strength. It can be used to increase the high‐temperature strength of copper‐based heat sink materials as well as the fracture toughness of bulk tungsten considered for the use of highly loaded reactor wall components. These new applications for tungsten wire has also given new impetus to the study of their fundamental properties.

Incandescent Lamp from Black Body Perspective

The incandescent lamp from black body perspective was investigated using commercial lamps of various watts. The major component of the incandescent lamp is the tungsten filament. The resistance of the tungsten filament was measured using a digital multimeter at an initial laboratory temperature. Light produced from lamp was separated into visible colours by an equilateral triangular glass prism. Deduced resistances were used to obtain equivalent temperatures by power-law parameterization. The Wien’s displacement law was used to estimate Peak wavelengths at different temperatures. The diameter of the tungsten was measured after dissecting the lamp, and this was used to determine its cross-sectional area. Both Wien’s displacement law and Stefan-Boltzmann expressions were applied in determining the filament’s spectral emissive power (SEP) in comparison with that of the visible spectrum. Planck’s graph of intensity using peak wavelength of tungsten filament as reference was juxtaposed with the intensity of visible spectrum using OriginPro 2016 SR0 b9.3.226. The maximum temperature attained was 2852.87 K with (SEP) of 1478955.24 Wm-2 for the 200W lamp. For the 100W lamp, the (SEP) obtained was 749347.9078 Wm-2 at 2489.14 K. Both temperatures, and even as low as 1250 K, were in agreement with Wien’s displacement law. The percentage estimation of visible spectrum in the radiation was about fourteen percent (14 %) while the rest was infra red radiation. This low visible light produced may be as a result of the non-ideal black body nature of the tungsten filament; and so, the incandescent lamp may be considered a quasi-black body.

Inline CT-Analysis of the Melting Area during Fused Filament Fabrication

In the 21st century, 3D printing has become a mainstream process for prototyping and low-volume production. Fused Filament Fabrication is the most commonly used process for 3D printing plastics. A plastic filament is melted in a nozzle and a component is built up layer by layer. As with all manufacturing processes, there is an interest in continuously optimizing and improving the FFF process. One approach is based on process simulation, which provides a better understanding of the process. Subsequently, it is always necessary to validate the simulation models with the real process. This validation has only been possible to a limited extent in the case of FFF. In this work, a method is presented that allows a non-destructive investigation of the melt behaviour during the printing process. For this purpose, a 3D printer nozzle with an extruder was integrated into an X-ray computed tomography system. Thus, a computed tomography scan can be performed during the extrusion process. By using highly absorbent tungsten filaments, sufficient contrast can be created between the metal nozzle and the plastic filament to allow analysis of the melt behaviour. This setup makes it possible to distinguish between the solid filament area and the melt area, as well as to determine the contact between the filament and the die wall. In doing so, simulations can be validated and nozzle geometries can be improved.

A low-energy MHz repetition rate short-pulse electron gun

An electron gun that can produce MHz repetition rates and nanosecond pulses is described. The gun uses a Pierce grid in combination with an anode to extract electrons from a tungsten filament cathode. The electrons emerging from the anode are accelerated and focused using two triple-aperture lenses to form a beam. By applying a high slew rate grid pulse that transitions through the extraction voltage region of the grid/anode combination, pulses of electrons are produced from the gun that have temporal widths less than 5 ns. The pulsed beams are produced at both the rising and falling edges of the driving pulse. The characteristics of the emerging electron beams have been determined using an (e, 2e) coincidence spectrometer, and examples where they are used for time of flight decay measurements are presented.

Influence of the Incorporation of Nd in ZnO Films Grown by the HFCVD Technique to Enhance Photoluminiscence Due to Defects

In this work, optical–structural and morphological behavior when Nd is incorporated into ZnO is studied. ZnO and Nd-doped ZnO (ZnO-Nd) films were deposited at 900 °C on Silicon n-type substrates (100) by using the Hot Filament Chemical Vapor Deposition (HFCVD) technique. For this, pellets were made by from powders of ZnO(s) and a mixture of ZnO(s):Nd(OH)3(s). The weight percent of the mixture ZnO:Nd(OH)3 in the pellet is 1:3. The gaseous precursor generation was carried out by chemical decomposition of the pellets using atomic hydrogen which was produced by a tungsten filament at 2000 °C. For the ZnO film, diffraction planes (100), (002), (101), (102), (110), and (103) were found by XRD. For the ZnO-Nd film, its planes are displaced, indicating the incorporation of Nd into the ZnO. EDS was used to confirm the Nd in the ZnO-Nd film with an atomic concentration (at%) of Nd = 10.79. An improvement in photoluminescence is observed for the ZnO-Nd film; this improvement is attributed to an increase in oxygen vacancies due to the presence of Nd. The important thing about this study is that by the HFCVD method, ZnO-Nd films can be obtained easily and with very short times; in addition, some oxide compounds can be obtained individually as initial precursors, which reduces the cost compared to other techniques. Something interesting is that the incorporation of Nd into ZnO by this method has not yet been studied, and depending on the method used, the PL of ZnO with Nd can increase or decrease, and by the HFCVD method the PL of the ZnO film, when Nd is incorporated, increases more than 15 times compared to the ZnO film.

Low power silicon evaporation source—Construction, performances, and applications

The construction of a low power silicon evaporation source for thin film deposition applications is proposed in this article. A few differently shaped tungsten filaments were mounted inside a quartz glass crucible, which assured an effective heating of silicon wafer pieces. The sublimation process was monitored at filament powers in the range of 8–22 W, which corresponds to temperatures far below the melting point of Si. The operation of the evaporation source requires only the use of a low voltage power supply. All considered models of evaporation sources are characterized by an easy construction. The measurements carried out with the use of a quartz crystal microbalance sensor enabled to determine the deposition rate at different filament powers for all constructed Si sources and confirm the long-term stability of the silicon flux. The experimental data exhibit the Polany–Wigner dependence of the deposition rate as a function of inverse of power at higher filament powers. Auger electron spectroscopy was used to monitor the deposition of Si on Ag(100) under constant silicon flux. The Auger signal recorded from Si and Ag reflects the growth of subsequent silicon layers. This enabled the determination of the Frank–van der Merwe growth mode of Si on Ag(100) at early stages of growth, the formation time of one Si monolayer, and, thus, the deposition rate. The presented designs of the Si source exhibit long time stable evaporation fully controlled by the applied filament power, which is crucial in the precise adsorption of ultrathin Si layers.

Potential impact of surface microstructure change on reduction of emission current in tungsten filament

When a helium beam is extracted, a significant decrease in arc current is observed in the filament arc ion source of the Neutral Beam Injector. Microstructural changes in the tungsten filament surface of the ion source are observed by electron microscopy to investigate the cause of the reduction of arc current. Helium bubbles with 100–800nm diameters appear immediately beneath the surface within 1μm, and the bubbles develop into surface hole structures with surface erosion by sputtering. The decrease in arc current with helium beam extraction can be explained by a reduced effective surface area, due to the increase in hole porosity. It has been shown that the reduction of the arc current can be recovered by removing the helium-irradiation-affected layer by sputtering with argon discharge.

Development and application of a high-temperature imaging system for in-situ scanning electron microscope

In-situ scanning electron microscope (SEM) is essential for investigating materials' properties. In this study, a custom-built in-situ heating system was developed to improve SEM imaging at elevated temperatures. A heater equipped with a double helical tungsten filament was specifically designed to achieve unprecedented high temperatures for heating materials. A bias-voltage control system was proposed to suppress thermal electrons during heating. Additionally, a high-temperature secondary-electron detector was developed and equipped with a variable visible-light filter to mitigate the impact of visible and infrared light at high temperatures. The heater and detector worked within a high vacuum environment with a pressure level below 1×10−3 Pa. Two in-situ heating experiments were conducted using the heating system to observe the melting and crystallizing processes of cobalt and the phase transformation of carbon steel. The results exhibited the remarkable capability of the heating system to image at temperatures as high as 1500 °C, offering a resolution of 40 nm. This heater is anticipated to advance materials characterization, providing comprehensive insights into their behavior at high temperatures and opening new avenues for developing material properties.

Effects of propellant species on the discharge characteristics of glow discharge hollow cathode

Hollow cathodes are the key sources of electrons for the operation of space electric thrusters. Traditionally, hollow cathodes utilize heating elements to raise the temperature of low work function materials to produce electrons. To accommodate the development of small satellites, researchers around the world have developed alternative neutralizer technologies such as radio frequency neutralizers, electron cyclotron resonance neutralizers, and coiled tungsten filaments cathode neutralizers to simplify the cathodes design and operation. In this work, a lower current glow discharge hollow cathode (GDHC) is developed, which can generate a discharge current of 10–100 mA. By testing with xenon, krypton, and argon propellants, it is found that GDHC has lower discharge voltage and power consumption with argon propellant. Simulation analysis reveals that during argon propellant discharge, the secondary electron emission coefficient on the cathode surface is larger, the electron density in the cathode sheath area is higher, and the high mobility of argon ions increases the conductivity within the cathode sheath. In addition, there are low and high extraction modes for GDHC electron extraction, depending on whether the keeper electrode absorbs or emits electrons.

Study on microstructure of 42CrMo steel by ultrasonic surface rolling process

To explore the microstructure formation mechanism of 42CrMo steel under the strengthening of ultrasonic surface rolling process (USRP), the combination of theoretical analysis and experiment was used to conduct in-depth research on USRP. Firstly, according to contact mechanics and Hertz contact theory, the calculation model of contact stress distribution and elastoplastic strain between the rolling ball and the part during USRP is obtained. Secondly, the USRP processing test was carried out by single-factor experimental design method, and the microstructure of 42CrMo steel after USRP was analyzed by LEXT OLS5100 3D laser surface topography instrument and VEGA3 tungsten filament scanning electron microscopy, which found that with an increase in static pressure, residual stress and plastic strain gradually increase, the hardness firstly increases and then decreases, while surface roughness exhibits an initial decrease followed by an increase. The results show that USRP produces violent plastic deformation inside the material under the superposition of high-frequency impact and static pressure, at the same time, it refines the grains, so as to improve the surface performance of the part and improve its fatigue resistance.

Exploring the Potential of a Thermionic LaB6 Virtual Source Mode Electron Gun for a High Angular Current Density and a Narrow Energy Distribution.

To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%.

Two-color thermal imaging of the melt pool in powder-blown laser-directed energy deposition

This work demonstrates an experimental technique to image melt pool temperature fields with a commercial color camera for laser-directed energy deposition (L-DED) processes. The technique relies on two-color thermography to construct spatially-resolved temperature fields and is demonstrated on 316L stainless steel (SS) melt pools from solidus to near-boiling temperatures. This two-color thermal imaging system negates the need for a priori knowledge of melt pool emissivity or the camera’s view factor and was validated with a calibrated tungsten filament lamp between temperatures of 1220 K and 2850 K. In-situ temperature measurements are combined with ex-situ cross-sectional geometry to determine the material’s effective absorptivity and coefficient of temperature-dependent surface tension, which is responsible for Marangoni convection, in a multi-physics computational fluid dynamics (CFD) model. Measured peak melt pool temperatures are important for understanding the molten convection within the melt pool, and measured cooling rates can be related to the resulting part microstructure. Peak temperatures from 1750 K to 3000 K show that below the boiling point, temperature increases with increasing laser power density and decreases with increasing scanning velocity. Thermal images are used to estimate cooling rates in the melt pool tail, which increase with the ratio of scanning velocity to power. Our thermal imaging strategy will advance measurement science in L-DED processes by validating multi-physics CFD models, quantifying cooling rates, providing real-time feedback control, and allowing process mapping of critical melt pool behaviors.

WO3 work function enhancement induced by filamentous films deposited by resistive heating evaporation technique

Tungsten trioxide (WO3) films are of great interest due to their electronic properties which can be tuned by surface nanostructuring leading to enhanced efficiency for gas sensing, energy storage or electrochromic applications. Resistive heating of tungsten (W) filaments at pressures of few Pa in an oxygen O2 atmosphere has already demonstrated its capability to form porous, micro/nano-structured, cheap and fast films making it suitable for industrial applications. This work presents stoichiometric WO3 films produced by applying a current into a W filament for pressures in the range of 2–20 Pa. The increase of the pressure above 7.5 Pa led to amorphous WO3 films with a newly filamentous morphology. As a function of the pressure, the work function (WF) of the films was determined in-vacuo by aims of Ultraviolet Photoelectron Spectroscopy (UPS). In addition to the high surface to volume ratio of the films, the WF exhibited an increase from 5.8 eV, for a conventional WO3 film, to a maximum of 8.7 eV at 20 Pa. This change corresponds to an increase of the WF of about 50% compared to 5.8 eV making our films suitable for a large variety of applications. The highering of the WF is mainly induced by the change of morphology to filamentous structures, the defect induced by the amorphous structure and the nanometric size of the filaments leading to the confinement of the electrons in the valence band for our WO3 films. Additionally, a change from p to n-type polarity is reported in-vacuo when increasing the pressure from 7.5 to 20 Pa with the formation of an intermediate band at around 0.8 eV below the Fermi level. Additionally, molybdenum trioxide (MoO3) and vanadium pentoxide (V2O5) filamentous films were deposited via the resistive evaporation technique in an O2 atmosphere. Similarly, copper, aluminium and molybdenum wires were used, leading to the formation of islands having foam-like structures analogous to the WO3.

Ultraviolet metalens for photoacoustic microscopy with an elongated depth of focus.

Ultraviolet photoacoustic microscopy (UV-PAM) can achieve in vivo imaging without exogenous markers and play an important role in pathological diagnosis. However, traditional UV-PAM is unable to detect enough photoacoustic signals due to the very limited depth of focus (DOF) of excited light and the sharp decrease in energy with increasing sample depth. Here, we design a millimeter-scale UV metalens based on the extended Nijboer-Zernike wavefront-shaping theory which can effectively extend the DOF of a UV-PAM system to about 220 μm while maintaining a good lateral resolution of 1.063 μm. To experimentally verify the performance of the UV metalens, a UV-PAM system is built to achieve the volume imaging of a series of tungsten filaments at different depths. This work demonstrates the great potential of the proposed metalens-based UV-PAM in the detection of accurate diagnostic information for clinicopathologic imaging.

Study of electrodeposited zinc selenide (ZnSe) nanostructure thin films for solar cell applications

Electrodeposition approach was used to grow the ZnSe nanostructure on indium doped tin oxide (ITO) layered glass substrate. Due to low cost and high degree of absorption, binary semiconductors made from chalcogens such as CdSe, ZnO, ZnS and ZnSe provide significant features in photovoltaic and photoelectrochemical cells. The structural and morphological properties of deposited nanostructures were examined by XRD and SEM. X-ray diffraction analysis informed about cubic structure with a preferred orientation and the calculated crystal size was approximately 75 nm. The optical properties were examined by UV–visible absorbance spectra and optical band gap was measured using Tauc plot. The deposited ZnSe nanostructure has direct band gap ∼2.52 eV at room temperature which was less than 2.82 eV which is the band gap of bulk ZnSe. Investigations also focused on additional qualities like excellent optical transmission, low electrical resistance, and good photosensitivity. Because of the presence of defect states in the deposited nanostructure, the band gap energy is smaller than that of bulk material. The current-voltage characteristics were measured in dark mode and under illumination of normal tungsten filament light and LED. There was notable change in the current for both normal light and LED in comparison to dark mode. The findings of all the characterization methodologies suggested that for the production of solar cells low cost ZnSe may be used as an alternative environment friendly Cd-free window layer.

Water and Hydroxyl Reactivity on Flat and Stepped Cobalt Surfaces

Hydroxyl adsorbates generally appear as transient species during water formation from adsorbed oxygen and hydrogen atoms on a metal surface, a reaction that is part of the catalytic cycle in various important surface-catalyzed reactions such as Fischer–Tropsch synthesis. In the present work, temperature-programmed desorption and in situ synchrotron XPS were used to study water adsorption and OH reactivity on a flat and a stepped cobalt single crystal surface. Water adsorbs intact on the flat Co(0001) surface and desorbs around 160 K. Electrons induce dissociation of water and produce OH species at low temperature. Hydroxyl species can also be formed by the reaction between Oad and H2O, but only for high initial oxygen coverage while low coverage Oad appears largely unreactive. Reactive hydrogen species (H atoms) produced by a hot tungsten filament hydrogenate adsorbed oxygen atoms at low temperature already and both OHad and H2O are formed. In all cases, hydroxyl adsorbates react around 190 K to form water via 2 OHad → H2O (g) + Oad associated with an activation barrier of 40–50 kJ mol–1. Water readily dissociates on the step sites exposed by vicinal Co(10–19). A part of the OHad species recombine to form water and oxygen between 200 and 300 K, while decomposition of OHad into Oad and Had dominates above 370 K. For catalysis, the high reactivity of step sites for water dissociation and the high stability of OHad at these sites implies that O removal from these sites may be difficult and may limit the overall rate of Fischer–Tropsch synthesis on cobalt catalysts.