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Results for “metallic diamond”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Effect of electronic structure of the diamond surface on the strength of the diamond-metal interface

A diamond surface undergoes a transformation in its electronic structure by a vacuum anneal at approximately 900 C. The polished surface has no electronic states in the band gap, whereas the annealed surface has both occupied and unoccupied states in the and gap and exhibits some electrical conductivity. The effect of this transformation on the strength of the diamond metal interface was investigated by measuring the static friction force of an atomically clean meta sphere on a diamond flat in ultrahigh vacuum. It was found that low friction (weak bonding) is associated with the diamond surface devoid of gap states whereas high friction (strong bonding) is associated with the diamond surface with gap states. Exposure of the annealed surface to excited hydrogen also leads to weak bonding. The interfacial bond is discussed in terms of interaction of the metal conduction band electrons with the band gap states on the diamond surface. Effects of surface electrical conductivity on the interfacial bond are also be considered.

Pepper, S. V.↗
DOE OSTI2025

Emission properties of a hybrid metallized diamond(001) photocathode

The spectral emission characteristics of a proof-of-concept hybrid metallized diamond(001) photocathode are presented. The quantum efficiency (QE) is shown to be determined by the photoinjection efficiency across the ohmic contact at the back metallized face, whereas the mean transverse energy (MTE) of the photoemitted electrons is consistent with an (optical)phonon-assisted and momentum-resonant Franck-Condon mechanism [Franck-Condon electron emission from polar semiconductor photocathodes, Phys. Rev. Appl. 23, 054065 (2025)] following electron drift transport to the untreated diamond(001) front emission face. Emission is observed from both the lower and upper conduction bands of diamond with positive and negative electron affinity, respectively. A potential route to the realization of a red-visible photocathode based on this concept with a sub-50 meV MTE and a QE greater than 0.1% is discussed.

Density of states↗
NASA NTRS1993

Bonding Diamond To Metal In Electronic Circuits

Improved technique for bonding diamond to metal evolved from older technique of soldering or brazing and more suitable for fabrication of delicate electronic circuits. Involves diffusion bonding, developed to take advantage of electrically insulating, heat-conducting properties of diamond, using small diamond bars as supports for slow-wave transmission-line structures in traveling-wave-tube microwave amplifiers. No fillets or side coats formed because metal bonding strips not melted. Technique also used to mount such devices as transistors and diodes electrically insulated from, but thermally connected to, heat sinks.

Jacquez, Andrew E.↗
NASA NTRS2000

Stable metallization for diamond and other materials

An adherent and metallurgically stable metallization system for diamond is presented. The big improvement in metallurgical stability is attributed to the use of a ternary, amorphous Ti--Si--N diffusion barrier. No diffusion between the layers and no delamination of the metallization was observed after annealing the schemes at 400.degree. C. for 100 hours and at 900.degree. C. for 30 minutes. Thermal cycling experiments in air from -65 to 155.degree. C. and adhesion tests were performed. Various embodiments are disclosed.

Bachli, Andreas↗
DOE OSTI2020

Metallization of diamond

Experimental discovery of ultralarge elastic deformation in nanoscale diamond and machine learning of its electronic and phonon structures have created opportunities to address new scientific questions. Can diamond, with an ultrawide bandgap of 5.6 eV, be completely metallized, solely under mechanical strain without phonon instability, so that its electronic bandgap fully vanishes? Through first-principles calculations, finite-element simulations validated by experiments, and neural network learning, we show here that metallization/demetallization as well as indirect-to-direct bandgap transitions can be achieved reversibly in diamond below threshold strain levels for phonon instability. We identify the pathway to metallization within six-dimensional strain space for different sample geometries. We also explore phonon-instability conditions that promote phase transition to graphite. These findings offer opportunities for tailoring properties of diamond via strain engineering for electronic, photonic, and quantum applications.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Experiments with diamond-turned metal X-ray mirrors

It is noted that the primary advantages of diamond turning technology for the fabrication of X-ray telescope mirrors is in the smoothness of the finished surface and the control of the position of the cutter afforded by the precision slides and computer-assisted positioners which form the surface. The paper summarizes the Caltech work in attempting to make Wolter Type I telescope mirrors using the diamond turning facilities at the Oak Ridge Y-12 laboratory. Attention is given to such factors as the use of aluminum with copper plating and electroless nickel coating. It is found that although the diamond turning capability of the Y-12 lab is capable of making good X-ray mirror contours, there are problems in the process which have limited the accuracy achieved by this technique.

Garmire, G. P.↗
DOE OSTI2023

Diamonds in the Rough: Direct Surface Enhanced Infrared Spectroscopic Evidence of Nitrogen Reduction on Boron-Doped Diamond Supported Metal Catalysts

In situ investigations of electrocatalytic processes of increasing societal interest such as the nitrogen reduction reaction (NRR) re-quire aggressive experimental conditions that are not readily compatible with surface sensitive techniques such as attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). A method for performing ATR-SEIRAS studies at very negative potentials where conventional IR-active films delaminate, and fail is reported. The method relies on a thin film of very robust boron-doped diamond deposited on a micromachined Si wafer, which provides extended mid-IR transparency at long wavelengths. SEIRAS activity is achieved by electrodepositing gold nanoparticles onto the conductive BDD layer. The Au@BDD layers are shown to sustain prolonged periods of electrolysis at negative potentials with no degradation of the modifying layer. The efficacy of these substrates for electrocatalysis is demonstrated by studying the reduction of N 2 at -1.5 V vs Ag/AgCl in an aqueous-based electrolyte. So under these conditions, direct spectroscopic evidence of both NH 3 and hydrazine formed from the nitrogen reduction reaction (NRR) is provided.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2001

Low Temperature Growth of Nanostructured Diamond Films on Metals

The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings, The choice of substrate used in most studies has typically been silicon. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress that often results in delamination of the film. To avoid this problem in conventional CVD deposition low substrate temperatures (less than 700 C) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture. Conventionally grown CVD diamond films are also rough and would require post-deposition polishing for most applications. Therefore, there is an obvious need to develop techniques for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. In our work, nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 C) for 30 minutes using a H2/CH4/N2 gas mixture in order to grow a thin (approx. 600 nm) nanostructured diamond layer and improve film adhesion. The remainder of the deposition involves growth at low temperature (less than 600 C) in a H2/CH4/O2 gas mixture. Laser reflectance Interferometry (LRI) pattern during growth of a nanostructured diamond film on Ti-6Al-4V alloy. The first 30 minutes are at a high temperature of 820 C and the rest of the film is grown at a low temperature of 580 T. The fringe pattern is observed till the very end due to extremely low surface roughness of 40 nm. The continuation of the smooth nanostructured diamond film growth during low temperature deposition is confirmed by in-situ laser reflectance interferometry and by post-deposition micro-Raman spectroscopy and surface profilometry. Similar experiments performed without the starting nanostructured diamond layer resulted in poorly adhered films with a more crystalline appearance and a higher surface roughness. This low temperature deposition of nanostructured diamond films on metals offers advantages in cases where high residual thermal stress leads to delamination at high temperatures.

Baker, Paul A.↗
NASA NTRS1972

Sintered diamond compacts using metallic cobalt binders

Method is developed for sintering diamond powder which uses metallic cobalt as binder. Present samples show maximum microhardness of over 3000 kg/sq mm on Knoop scale. Material may be used as hard surface coating or may compete with cubic boron nitride as abrasive grain.

Libby, W. F.↗
NASA NTRS1998

An Evanescent Microwave Probe for Super-Resolution Nondestructive Imaging of Metals, Semiconductors, Dielectrics, Composites and Biological Specimens

Using evanescent microwaves with decay lengths determined by a combination of microwave wavelength (lambda) and waveguide termination geometry, we have imaged and mapped material non-uniformities and defects with a resolving capability of lambda/3800=79 microns at 1 GHz. In our method a microstrip quarter wavelength resonator was used to generate evanescent microwaves. We imaged materials with a wide range of conductivities. Carbon composites, dielectrics (Duroid, polymers), semiconductors (3C-SiC, polysilicon, natural diamond), metals (tungsten alloys, copper, zinc, steel), high-temperature superconductors, and botanical samples were scanned for defects, residual stresses, integrity of brazed junctions, subsurface features, areas of different film thickness and moisture content. The evanescent microwave probe is a versatile tool and it can be used to perform very fast, large scale mapping of a wide range of materials. This method of characterization compares favorably with ultrasound testing, which has a resolution of about 0.1 mm and suffers from high absorption in composite materials and poor transmission across boundaries. Eddy current methods which can have a resolution on the order of 50 microns are restricted to evaluating conducting materials. Evanescent microwave imaging, with careful choice of operating frequency and probe geometry, can have a resolution of up to 1 micron. In this method we can scan hot and moving objects, sample preparation is not required, testing is non-destructive, non-invasive and non-contact, and can be done in air, in liquid or in vacuum.

Pathak, P. S.↗
NASA NTRS2001

Process for ultra smooth diamond coating on metals and uses thereof

The present invention provides a new process to deposit well adhered ultra smooth diamond films on metals by adding nitrogen gas to the methane/hydrogen plasma created by a microwave discharge. Such diamond coating process is useful in tribological/wear resistant applications in bio-implants, machine tools, and magnetic recording industry.

Vohra, Yogesh K.↗
NASA NTRS2003

Method of synthesizing metal doped diamond-like carbon films

A method of synthesizing metal doped carbon films by placing a substrate in a chamber with a selected amount of a metalorganic compound. An electron cyclotron resonance is applied to the chamber in order to vaporize the metalorganic compound. The resonance is applied to the chamber until a metal doped carbon film is formed. The metalorganic compound is preferably selected from the group consisting of an organic salt of ruthenium, palladium, gold or platinum.

Ueno, Mayumi↗
NASA NTRS2004

Triphasic Tooling with Small Oriented Diamond Tip for Turning and Smoothing Lightweight Mirrors

We are developing a new method for the growth of small diamond crystals at very high temperatures and pressures directly from a carbon melt. A prototype "Supercell" has been developed for this purpose. This system is capable of high rate crystal growth in relatively large working volumes. The resulting high quality diamond crystals will be incorporated into a triphasic diamond/titanium carbide/titanium composite tool, with an oriented diamond crystal at its tip. High pressure is needed to prevent degradation of diamond at high temperature, and to ensure the formation of a crack & composite structure. After grinding and polishing, the composite material will be joined to a steel holder, thus forming a diamond-tipped tool for turning and smoothing of a mirror surface. A properly oriented single-crystal diamond cuts and smoothes much better than a conventional polycrystalline diamond crystal. This is because the hardness depends on crystallographic orientation-the difference corresponds to 60-100 GPa on the Knoop scale. Our goal is to achieve surface roughness of about 1 nm, which will be accomplished by precision cutting and smoothing. The hardness of the functionally-graded diamond/titanium carbide/titanium composite tool varies from 100 GPa at its tip to 15 GPa at its base. Previous work has shown that the mass of machined material using an oriented-diamond tool is much larger than that for a standard diamond-metal composite tool.

Voronov, O. A.↗
NASA NTRS1980

Adhesion and friction of single-crystal diamond in contact with transition metals

An investigation was conducted to examine the adhesion and friction of single-crystal diamond in contact with various transition metals and the nature of metal transfer to diamond. Sliding friction experiments were conducted with diamond in sliding contact with the metals yttrium, titanium, zirconium, vanadium, iron, cobalt, nickel, tungsten, platinum, rhenium and rhodium. All experiments were conducted with loads of 0.05 to 0.3 N, at a sliding velocity of 0.003 m per minute, in a vacuum of 10 to the -8th Pa, at room temperature, and on the (111) plane of diamond with sliding in the 110 line type direction. The results of the investigation indicate that the coefficient of friction for diamond in contact with various metals is related to the relative chemical activity of the metals in high vacuum. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to the surface of diamond in sliding.

Miyoshi, K.↗
DOE OSTI2025

Simulations of Attosecond Metallization in Quartz and Diamond Probed with Inner-Shell Transient Absorption Spectroscopy

When dielectrics are hit with intense infrared (IR) laser pulses, transient metalization can occur. The initial attosecond dynamics behind this metallization are not entirely understood. Therefore, simulations are needed to understand this process and to help interpret experimental observations of it, such as with attosecond transient absorption (ATA). In this paper, we present first-principles simulations of ATA based on bulk-mimicking clusters and real-time time-dependent density functional theory (RT-TDDFT), with Koopmans-tuned range-separated hybrid functionals and Gaussian basis sets. Our method gives good agreement with the experiment for the breakdown threshold in silica and diamond. This breakdown voltage corresponds to a Keldysh parameter of approximately one and thus involves a transition to a regime where the dynamics are driven by tunneling. Pumping at an amplitude just below this value causes a mixture of multiphoton and tunneling excitations across the band gap to occur. The computed extreme ultraviolet and X-ray attosecond transient spectra also agree well with the experiment and show a decrease in optical density due to the transient population of the conduction band from the IR field. First-principles approaches such as this are valuable for interpreting the complicated modulations in a spectrum and for guiding future attosecond experiments on solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

High Current Density Diamond Photoconductive Semiconductor Switches With a Buried, Metallic Conductive Channel

Laterally configured diamond photoconductive semiconductor switches (PCSS) with a buried, metallic p+ current channel are reported. Above bandgap ( λ ≤ 226 nm) optical triggering enables responsivity of over 130 mA/W. The use of low-impurity semi-insulating diamond as an active absorption layer enables fast rise and fall times (~2 ns) and on/off ratios greater than 10 11 . The PCSS excited with a laser energy of 20 nJ per pulse passes a high current density (44 A/cm) under a DC bias of 60 V, thanks to the buried metallic p+ current channel. The reported devices promise high current carrying capacity without the need for filamenting while leveraging the excellent optical, electronic, and thermal properties of diamond.

42 ENGINEERING↗
NASA NTRS1982

Diamond Sheet: A new diamond tool material

Diamond sheet is termed a diamond tool material because it is not a cutting tool, but rather a new material from which a variety of different tools may be fabricated. In appearance and properties, it resembles a sheet of copper alloy with diamond abrasive dispersed throughout it. It is capable of being cut, formed, and joined by conventional methods, and subsequently used for cutting as a metal bonded diamond tool. Diamond sheet is normally made with industrial diamond as the abrasive material. The metal matrix in diamond sheet is a medium hard copper alloy which has performed well in most applications. This alloy has the capability of being made harder or softer if specific cutting conditions require it. Other alloys have also been used including a precipitation hardened aluminum alloy with very free cutting characteristics. The material is suitable for use in a variety of cutting, surfacing, and ring type tools, as well as in such mundane items as files and sandpaper. It can also be used as a bearing surface (diamond to diamond) and in wear resistant surfaces.

Mackey, C. R.↗