Carbon Arc Research Articles

Capturing the Fused-Pentagon C74 by Stepwise Chlorination.

As a bridge to connect medium-sized fullerenes, fused-pentagon C74 is still missing heretofore. Of 14 246 possible isomers, the first fused-pentagon C74 with the Fowler-Manolopoulos code of 14 049 was stabilized as C74Cl10 in the chlorine-involving carbon arc. The structure of C74Cl10 was identified by X-ray crystallography. The stabilization of pristine fused-pentagon C74 by stepwise chlorination was clarified in both theoretical simulation with density functional theory calculations and experimental fragmentation with multistage mass spectrometry.

A brief report on the history of phototherapy

From ancient times, light has played a significant role in the treatment of diseases. The modern discoveries (eg, ultraviolet radiation) and modern inventions (eg, the electric generator or the electric lightbulb), as well as balneologic experiences of the treatment with sunlight, contributed to the transition from heliotherapy to artificial light phototherapy at the end of the 19th century.Nils Ryberg Finsen (1860-1904) was the founder of modern phototherapy. He is famous for applying an electric carbon arc torch in treating patients with lupus vulgaris using ultraviolet radiation. Subsequently, phototherapy using artificial light sources gained importance in the treatment of skin diseases with a noninfectious etiology. William Henry Goeckerman (1884-1954) chose an ultraviolet B light to treat psoriasis. Improvement in the effectiveness of dermatologic phototherapy occurred in 1947, when methoxypsoralen was isolated. During the 20th century, phototherapy was applied to new therapeutic areas, such as neonatology, psychiatry, and ophthalmology.

Structural variations of the cathode deposit in the carbon arc

Synthesis of various carbon nanostructures, including fullerenes, single-walled and multi-walled nanotubes and nanoparticles, by arc discharges relies on ablation of the graphite anode and deposition of synthesized carbonaceous products on the cathode surface and on the reactor chamber walls. For backbone all-carbon system, the cathode deposit plays a critical role in sustaining the arc discharge and thereby, the synthesis processes. This deposit usually exhibits spatially distinct structural variations with three different axially symmetrical morphologies. In particular, a rim of pyrolytic carbon separates the innermost core consisting of multi-walled carbon nanotubes from the outmost ring with powdery amorphous carbon soot. Experiments revealed a strong correlation between the current conducting arc attachment to the cathode deposit and the nanotube forming area in the deposit. Results suggest that particle and heat fluxes from the plasma are responsible for purity of nanotubes in this deposit core area. It appears that a better synthesis selectivity can be obtained in low ablation regime which is characterized by a nearly constant arc current density independent on the anode diameter.

Internalization and cytotoxicity effects of carbon-encapsulated iron nanoparticles in murine endothelial cells: Studies on internal dosages due to loaded mass agglomerates

Carbon-encapsulated iron nanoparticles (CEINs) qualified as metal-inorganic hybrid nanomaterials offer a potential scope for an increasing number of biomedical applications. In this study, we have focused on the investigation of cellular fate and resulting cytotoxic effects of CEINs synthesized using a carbon arc route and studied in murine endothelial (HECa-10) cells. The CEIN samples were characterized as pristine (the mean diameter between 47 and 56nm) and hydrodynamic (the mean diameter between 270 and 460nm) forms and tested using a battery of methods to determine the cell internalization extent and cytotoxicity effects upon to the exposures (0.0001–100μg/ml) in HECa-10 cells. Our studies evidenced that the incubation with CEINs for 24h is accompanied with substantial changes of Zeta potential in cells which can be considered as a key factor for affecting the membrane transport, cellular distribution and cytotoxicity of these nanoparticles. The results demonstrate that CEINs have entered the endothelial cell through the endocytic pathway rather than by passive diffusion and they were mainly loaded as agglomerates on the cell membrane and throughout the cytoplasm, mitochondria and nucleus. The studies show that CEINs induce the mitochondrial and cell membrane cytotoxicities in a dose-dependent manner resulting from the internal dosages due to CEIN agglomerates. Our results highlight the importance of the physicochemical characterization of CEINs in studying the magnetic nanoparticle–endothelial cell interactions because the CEIN mass agglomerates can sediment more or less rapidly in culture models.

(Invited) Novel Fullerenes and Their Photovoltaic Properties

Thousands fullerenes with even-numbered Cn (n > 20 but with exception of 22) were produced in the original gas-phase laser vaporization experiment conducted by Kroto, Curl and Smalley.[1] However, only a few fullerenes survive the ambient conditions and were isolated in the form of bare hollow fullerene. In recent years, tens labile fullerenes with novel cage configuration have been stabilized by exohedral chlorination or hydrogenation using carbon arc or combustion method in our lab, such as #271C50, #540C54, #864C56, #913C56, #916C56, #1,809C60, #1,804C 60, #4,169C66, #11,188C 72 and #23,863C 78.[2 -6 ] The availability of these unprecedented fullerenes provides experimental opportunities for scientists from a wide of variety of disciplines to expand their insight into the new world of these fullerenes. We have paid special attention to the possibility of using these novel fullerenes as electron acceptors in polymer solar cells. Cyclic voltammetric analysis revealed that C50H10 exhibited reversible cathodic behavior and useful reduced potentials for possible application in photovoltaic devices. The first reduction potential of C50H10 (-1.41 V vs Fc/Fc+ in acetonitrile/o-DCB) is about 0.34 V more negative than the corresponding value of C60 as well as its hydride C60H2. The LUMO of C50H10 (-3.37 eV) is about 0.34 eV higher than that of C60, with implication to utilize C50H10 as promising electron acceptor for making polymer solar cells with higher open circuit voltage.[ 7 ] In addition, two classes of novel C60 derivatives with higher LUMO energy levels were synthesized, including alkoxy substituted dihydronaphthyl-C60 derivatives and PCBM-C60 derivatives (PCBM = [6,6]- phenyl- C61- butyric acid methyl ester). Photovoltaic devices using each of these fullerene derivatives as acceptor in combination with poly(3-hexylthiophene) as donor were fabricated. Power conversion efficiencies of the device based on 2-methoxy-(5,8)-dihydronaphthyl-(6,7)-[6,6]-C60 is 4.58%, better than PCBM-based polymer solar cell.[ 8 ] The higher power conversion efficiency implies that photovoltaic performance of fullerene can be improved by chemically modified with electron-donating group(s), and lends credit to a bright future of more efficient polymer (or even perovskite) solar cells based on novel fullerenes.[9-11] [1] Kroto H. W., Heath J. R., O'Brien S. C., Curl R. F. and Smalley R. E., “C60: Buckminsterfullerene”, Nature, 318 (1985) 162-163. [2] Xie S.Y., Gao F., Lu X., Huang R. B., Wang C. R., Zhang X., Liu M. L., Deng S. L. and Zheng L. S., “Capturing the labile fullerene[50] as C50Cl10”, Science, 304 (2004) 699-699. [3] Tan Y.Z., Liao Z. J., Qian Z. Z., Chen R. T., Wu X., Liang H., Han X., Zhu F., Zhou S.J., Zheng Z. P., Xie S. Y, Lu X., Huang R.B. and Zheng L. S. “Two Ih-symmetry-breaking C60 isomers stabilized by chlorination”, Nature Mater ., 7 (2008) 790-794. [4] Tan Y.Z., Xie S.Y., Huang R.B. and Zheng, L.S., “The stabilization of fused-pentagon fullerene molecules”, Nature Chem., 1 (2009) 450-460. [5] Tan Y.Z., Li J., Zhu F., Han X., Jiang W. S., Huang R.B., Zheng Z. P., Qian Z. Z., Chen R. T., Liao Z. J., Xie S. Y, Lu X. and Zheng L. S. “Chlorofullerenes featuring triple sequentially fused pentagons”, Nature Chem., 2 (2010) 269-273. [6] Tan Y.Z., Chen R.T., Liao Z.J., Li J., Zhu F., Lu X., Xie S.Y., Li J., Huang R.B. and Zheng L.S. “Carbon arc production of heptagon-containing fullerene[68]”, Nature C ommun ., 2 (2011) 240. [7] Chen J.H., Gao, Z.Y., Weng Q.H., Jiang W.S., He Q., Liang H, Deng L.L., Xie S.L., Huang, H.Y., Lu X., Xie S.Y., Shi K., Huang R.B. and Zheng, L.S., “Combustion Synthesis and Electrochemical Properties of the Small Hydrofullerene C50H10”, Chem. Eur. J.,18 (2012) 3408-3415. [8] Deng L.L., Feng J., Sun L.C., Wang S., Xie S.L., Xie S.Y., Huang R.B. and Zheng, L.S., “Functionalized dihydronaphthyl-C60 derivatives as acceptors for efficient polymer solar cells with tunable photovoltaic properties” Sol. Energy Ma ter. Sol. Cells, 104 (2012) 113-120. [9] Deng L.L., Xie S.L., Yuan C., Liu R.F., Feng J., Sun L.C., Lu X., Xie S.Y., Huang R.B. and Zheng, L.S., “High LUMO energy level C60(OCH3)4 derivatives: Electronic acceptors for photovoltaic cells with higher open-circuit voltage” Sol. Energy Mater. Sol. Cells, 111 (2013) 193-199. [10] Tian C.B., Deng, L.L., Zhang Z.Q., Dai S.M., Gao C.L., Xie S.Y., Huang R.B. and Zheng, L.S., “Bis-adducts of Benzocyclopentane- and Acenaphthene-C60 Superior to Mono-adducts as Electron Acceptors in Polymer Solar Cells”, Sol. Energy Mater. Sol. Cells, 125 (2014) 198-205. [11] Chen W.Y., Deng, L.L., Dai S.M., Wang X., Tian C.B., Zhan X.X., et al. “Low-cost solution-processed copper iodide as an alternative to PEDOT:PSS hole transport layer for efficient and stable inverted planar heterojunction perovskite solar cells”, J. Mater. Chem. A, 3 (2015) 19353.

(Invited) Plasma-Based Technology for Mass Production of Graphene and Other 2D Layered Materials

Arc discharge plasma is as one of the most practical and efficient methods to synthesize various carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene with minimal defects and large yield. This is achieved due to the relatively high synthesis temperature and eco-friendly growth mechanism. Moreover, by introducing a magnetic field during synthesis process, large-scale graphene and high-purity SWCNT can be obtained in one step. In addition, the yield of graphene can be controlled by external parameters, such as the type and pressure of buffer gas, the temperature of substrate, and plasma density and temperature. Bulk graphene (graphene platelets, flakes) is usually characterized by several layer (2-20 nm) graphene pieces having characteristics sizes of about microns to ten microns. Currently, the main method for synthesis of bulk graphene is chemical exfoliation, where chemicals are utilized to separate the graphene sheets from the piece of graphite. Current production capability are quite limited and estimated to be around several tens of tons of material annually worldwide. This work is focused on development of novel highly efficient and low cost plasma-based method for graphene production in industrial quantities characterized by exceptional product properties. The synthesis is based on utilization of arc discharge supported by ablation of anode material at atmospheric pressures. Pure carbon anode (several millimeters in diameter) and arc current in the range 50-100A were utilized for the synthesis. The graphene was synthesized on the metal substrate and was mechanically remove using metallic brush immediately after the synthesis. The synthesized samples were characterized using SEM, TEM and Raman spectroscopy. Typical size of the graphene platelets was found to be about several microns. The graphene platelets down to ~2 layers were obtained. We present state-of-the-art experimental data on various attempts to employ the arc plasma technique for the graphene synthesis and consider growth mechanisms including precipitation, surface-catalyzed processes and a substrate-independent approach. The potential of arc synthesis for the growth of other types of 2D materials and future prospects are discussed.

Anode sheath transition in an anodic arc for synthesis of nanomaterials

The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

Puzzles in bonding and spectroscopy: the case of dicarbon.

The unstable molecule C₂ has been of interest since its identification as the source of the "Swan band" features observable in the spectra offlames, carbon arcs, white dwarf stars, and comets, and it continues to serve as a focal point for experimental and theoretical discovery. Recent spectroscopic work has identified a quintet state of the molecule for the first time, while new insights into the bond order of C₂ in its ground state have been provided by sophisticated computational methods based on valence bond theory. This article gives a review of spectroscopic and computational work on C₂ including both historical background and the most recent discoveries.

ОЦЕНКА ТЕХНИКО-ЭКОНОМИЧЕСКИХ ПОКАЗАТЕЛЕЙ РАЗЛИЧНЫХ СПОСОБОВ СОЕДИНЕНИЯ ДЕТАЛЕЙ КУЗОВА АВТОМОБИЛЯ

New methods of joining the body units widely used in foreign automotive industry and having a number of technical advantages are not used at the Volzhsky automobile plant. Among the major reasons, usually, the application of expensive materials and equipment are named. In this regard, this paper presents the results of the aggregated estimation of a number of specific economic indicators that allow comparing the traditional and the advanced methods of joining. The authors compared the indices of labor intensity, efficiency, and capital investments per unit, as well as the production cost of one meter of joining when applying spot welding, carbon dioxide welding, flame brazing, laser welding, arc and laser brazing. The calculations were carried out separately for short and elongated joints. It is shown, that the methods of joining new for the domestic automotive industry are quite competitive economically in relation to the traditionally used methods. Taking into account technical indicators, the authors formulated the recommendations on the selection of a method of joining. The current tendency to replace flame brazing can be explained by the high labor intensity and production cost of this method of joining. However, the replacement of flame brazing with welding in carbon dioxide is unequal, principally in terms of quality. Arc brazing is the most suitable method of body parts joining for short sections where the leak tightness, good appearance and the quality of the weld are required. To get the elongated joinings, laser brazing is the advanced method ensuring the maximum performance and minimum production cost in comparison with all the methods of joining considered, and the specific capital investments are comparable to other methods considered.

Atmospheric pressure arc discharge with ablating graphite anode

The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322–6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement.

Structural and nanomechanical properties of nanocrystalline carbon thin films for photodetection

This paper reports the effect of helium gas pressure upon the structural, nanomechanical, and photoconductive properties of nanocrystalline carbon thin (NCT) films deposited by the filtered cathodic jet carbon arc technique. High-resolution transmission electron microscopy images confirm the nanocrystalline nature of the deposited films with different crystallite sizes (3–7 nm). The chemical structure of the deposited films is further analyzed by x-ray photoelectron spectroscopy and Raman spectroscopy, which suggest that the deposited films change from graphitelike to diamondlike, increasing in sp3 content, with a minor change in the dilution of the inert gas (helium). The graphitic character is regained upon higher dilution of the helium gas, whereupon the films exhibit an increase in sp2 content. The nanomechanical measurements show that the film deposited at a helium partial pressure of 2.2 × 10−4 has the highest value of hardness (37.39 GPa) and elastic modulus (320.50 GPa). At a light intensity of 100 mW/cm2, the NCT films deposited at 2.2 × 10−4 and 0.1 mbar partial pressures of helium gas exhibit good photoresponses of 2.2% and 3.6%, respectively.

Core–shell structure carbon coated ferric oxide (Fe2O3@C) nanoparticles for supercapacitors with superior electrochemical performance

Core–shell structure carbon coated ferric oxide nanoparticles (Fe2O3@C) were fabricated by the oxidation of carbon coated iron nanoparticles (Fe@C) prepared by a direct current carbon arc discharge method. Porous activated-Fe2O3@C was prepared by KOH activation of Fe2O3@C at the temperature of 750°C. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the structure and morphology of the Fe2O3@C and activated-Fe2O3@C. The specific surface area and pore size distribution of the samples were also tested. The activated-Fe2O3@C electrodes exhibited good electrochemical performance with a maximum specific capacitance of 612Fg−1 at the charge/discharge current density of 0.5Ag−1 with 5M NaOH electrolyte. After 10,000 cycling DC tests at the charge/discharge current density of 4Ag−1, a high level specific capacitance of 518Fg−1 was obtained (90.6% retention of the initial capacity), suggesting excellent long-term cycling stability.

Effect of helium gas pressure on dc conduction mechanism and EMI shielding properties of nanocrystalline carbon thin films

This paper reports the effect of helium partial pressures ∼1.2 × 10−5 (base pressure), 1.4 × 10−4, 8.6 × 10−3 and 0.1 mbar on the variable range hopping conduction in nanocrystalline carbon thin films deposited by filtered cathodic jet carbon arc technique. High resolution transmission electron microscopy studies suggest the random distribution of nanocrystallites (∼3–7 nm) in the amorphous matrix. The DC conduction behavior of the deposited nanocrystalline films has been studied in the light of Mott's variable range hopping (VRH) model and found to obey three dimensional VRH conduction. The randomly distributed nanocrystallites in amorphous matrix may lead to change in the distribution of density of states near Fermi level and hence, the conduction behavior. The enhanced electrical conductivity of the deposited films due to the helium environment makes them suitable for electromagnetic interference shielding applications. The sample deposited at a helium partial pressure of 0.1 mbar has a value of shielding effectiveness ∼7.84 dB at 18 GHz frequency.

Self-organisation processes in the carbon arc for nanosynthesis

The atmospheric pressure carbon arc in inert gases such as helium is an important method for the production of nanomaterials. It has recently been shown that the formation of the carbon deposit on the cathode from gaseous carbon plays a crucial role in the operation of the arc, reaching the high temperatures necessary for thermionic emission to take place even with low melting point cathodes. Based on observed ablation and deposition rates, we explore the implications of deposit formation on the energy balance at the cathode surface and show how the operation of the arc is self-organised process. Our results suggest that the arc can operate in two different ablation-deposition regimes, one of which has an important contribution from latent heat to the cathode energy balance. This regime is characterised by the enhanced ablation rate, which may be favourable for high yield synthesis of nanomaterials. The second regime has a small and approximately constant ablation rate with a negligible contribution from latent heat.

Carbon encapsulated iron oxide nanoparticles surface engineered with polyethylene glycol-folic acid to induce selective hyperthermia in folate over expressed cancer cells

Carbon encapsulated iron oxide nanoparticles (CEIO-NPs) prepared by carbon arc method were successfully applied for in vitro magnetic hyperthermia. The CEIO-NPs were chemically oxidized and surface modified with PEG–FA for selective tumor localization in cancer cells that over expresses the folate receptors (FR+). The size, morphology, heating efficiency, biocompatibility and in vitro cell uptake of CEIO–PEG–FA NPs are extensively characterized. The as-prepared nanoparticles have generated quick heating (43–45°C) upon exposure to an alternating magnetic field (AMF) with the saturation magnetization of 25emu/g. The LDH cytotoxic assay demonstrated that the nanoparticle did not affect the viability of normal human fibroblast. The quantitative and cellular uptake studies by TEM confirmed the selective and increased uptake of CEIO–PEG–FA NPs when compared to the CEIO-nanoparticles. In conclusion, CEIO–PEG–FA NPs have the potential to induce magnetic hyperthermia in FR+ cells via the receptor mediated endocytosis uptake mechanism.

The First Man-Made Memristor: Circa 1801 [Scanning Our Past

This article reexamines the historical carbon arc discharge experiment conducted by Humphry Davy in 1801. We present experimental evidence which indicates that such a carbon arc discharge is not only the first artificial light source, but also the world's first man-made memristor ever reported in the scientific literature. The original carbon arc discharge experiment has been repeated with modern power supply equipment with bipolar excitation capability. The carbon arc discharge exhibits the three fingerprints of memristors, including the pinched hysteresis loops, the lobe area changing with operating frequency, and such lobe area approaching zero as the operating frequency increases.

Structural, nanomechanical and variable range hopping conduction behavior of nanocrystalline carbon thin films deposited by the ambient environment assisted filtered cathodic jet carbon arc technique

This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp3/sp2 ratio accompanied with the highest hardness of ∼18.34GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak (AD/AG) and the highest conductivity (∼2.23S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27×10−7S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport.

Preparation of carbon-coated iron nanofluid and its application in radiofrequency ablation.

Carbon-coated iron nanoparticles (Fe@C CCINs) were synthesized by carbon arc discharge method and were studied via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that CCINs have good core-shell structure and are in size of 40-50 nm. Also, carbon-coated iron nanofluid (CCINs-nanofluid) was prepared via two-step method by dispersing as-prepared CCINs and polyvinylpyrrolidone (PVP) into physiological saline. Its dispersion stability and thermal conductivity were detected by gravity sedimentation method and Hotdisk thermal constant analyzer respectively. The results indicated that CCINs-nanofluid possesses good dispersity and stability. Moreover, CCINs-nanofluid showed enhanced thermal conductivity compared with its base fluid physiological saline. The enhancement of thermal conductivity even reaches 41%. Additionally, CCINs-nanofluid injection aided radiofrequency ablation (RFA) was carried out. The relation between tissue temperature and ablation time revealed that by injecting CCINs-nanofluid into pork livers during RFA, target tissue temperatures were less than 100°C. Dissected pork livers showed that there was little or no tissue charring around the ablation probe. Results of ablation area calculation showed that the ablation area of CCINs-nanofluid injection aided RFA was 67% larger than that of saline injection aided RFA, indicating that a larger-volume tumor tissue necrosis at a single session can be achieved by CCINs-nanofluid injection aided RFA.

Colour fastnesses to ultraviolet carbon arc lamp light and perspiration of dyed cotton fabrics

Colour fastnesses to ultraviolet carbon arc lamp light and perspiration of dyed cotton fabrics

Role of the cathode deposit in the carbon arc for the synthesis of nanomaterials

The atmospheric pressure carbon arc in helium is an important method for the production of nanomaterials. Typical arcs operate in a dc mode between a graphite anode, which is consumed, and a cathode which may be a lower melting point material. During arc operation, a carbon deposit is formed on the cathode surface. This deposit may contain different forms of the synthesised fullerenes. It is shown that this deposit plays a crucial role in conducting the arc current. Temperature measurements demonstrate that a sufficiently large area of the cathode deposit is hot enough for thermionic emission to be the source of most of the arc current. Due to the deposit’s low thermal conductivity, the cathode behind the deposit does not reach its melting point. The role of the deposit in emitting electrons can probably be generalized for other arc synthesis methods with consumed anodes.