Diamond Materials Research Articles

Analysis and Test: Impregnated Diamond Cutters for Oil Drilling Bit

Systematic testing methods of the performance of diamond/metal composite drilling segments (impregnated diamond cutters) have not come into being. This article tries to test the mechanical properties, structures and component of a certain number of impregnated diamond cutters; focuses on analysis of the relationship between the performance of typical composite diamond cutters and materials’ structures, intends to study the testing methods of impregnated diamond cutters’ performance.

Nanodiamond Foils for H- Stripping to Support the Spallation Neutron Source (SNS) and Related Applications

ABSTRACTThin diamond foils are needed in many particle accelerator experiments regarding nuclear and atomic physics, as well as in some interdisciplinary research. Particularly, nanodiamond texture is attractive for this purpose as it possesses a unique combination of diamond properties such as high thermal conductivity, mechanical strength and high radiation hardness; therefore, it is a potential material for energetic ion beam stripper foils. At the ORNL Spallation Neutron Source (SNS), the installed set of foils must be able to survive a nominal five-month operation period, without the need for unscheduled costly shutdowns and repairs. Thus, a single nanodiamond foil about the size of a postage stamp is critical to the entire operation of SNS and similar sources in U.S. laboratories and around the world. We are investigating nanocrystalline, polycrystalline and their admixture films fabricated using a hot filament chemical vapor deposition (HFCVD) system for H- stripping to support the SNS at Oak Ridge National Laboratory. Here we discuss optimization of process variables such as substrate temperature, process gas ratio of H2/Ar/CH4, substrate to filament distance, filament temperature, carburization conditions, and filament geometry to achieve high purity diamond foils on patterned silicon substrates with manageable intrinsic and thermal stresses so that they can be released as free standing foils without curling. An in situ laser reflectance interferometry tool (LRI) is used for monitoring the growth characteristics of the diamond thin film materials. The optimization process has yielded free standing foils with no pinholes. The sp3/sp2 bonds are controlled to optimize electrical resistivity to reduce the possibility of surface charging of the foils. The integrated LRI and HFCVD process provides real time information on the growth of films and can quickly illustrate growth features and control over film thickness. The results are discussed in the light of development of nanodiamond foils that will be able to withstand a few MW proton beam and hopefully will be able to be used after possible future upgrades to the SNS to greater than a 3MW beam.

Concluding remarks: there's nowt so queer as carbon electrodes.

This contribution provides a personal overview and summary of Faraday Discussion 172 on "Carbon in Electrochemistry", covering some of the key points made at the meeting within the broader context of other recent developments on carbon materials for electrochemical applications. Although carbon electrodes have a long history of use in electrochemistry, methods and techniques are only just becoming available that can test long-established models and identify key features for further exploration. This Discussion has highlighted the need for a better understanding of the impact of surface structure, defects, local density of electronic states, and surface functionality and contamination, in order to advance fundamental knowledge of various electrochemical processes and phenomena at carbon electrodes. These developments cut across important materials such as graphene, carbon nanotubes, conducting diamond and high surface area carbon materials. With more detailed pictures of structural and electronic controls of electrochemistry at carbon electrodes (and electrodes generally), will come rational advances in various technological applications, from sensors to energy technology (particularly batteries, supercapacitors and fuel cells), that have been well-illustrated at this Discussion.

In Situ Tribo-Electrochemical Evaluation of Wear of Diamond Composites

Real-time detection of wear between a rubbing pair is of critical significance for the performance and safety of industrial systems. In this research, a tribo-electrochemical method is developed to in situ monitor the friction and wear of diamond materials. The electrochemical impedance and current density were measured under the influence of friction between a pin against a disk of the same diamond composite. It was discovered that the current density is a function of the excitation voltage in a sinusoidal pattern. This was due to the synergetic effects of the amorphization-wear process of diamond. The amplitude and period of the sinusoidal pattern reflect the intensity and the frequency of the process. This electrochemical approach could be used to evaluate the friction and wear of an insulating material in situ, which has not been possible until this study. This research proposes new avenue in the evaluation of electrochemical wear of a hard diamond composite.

Sub-diffraction imaging of nitrogen-vacancy centers in diamond by stimulated emission depletion and structured illumination

Stimulated emission depletion (STED) and structured illumination (SIM) are two commonly used techniques for super-resolution imaging. However, the performance of these two techniques has never been quantitatively compared side-by-side. Taking advantage of the non-photobleaching characteristic of NV centres in fluorescent nanodiamond (FND), we performed a comparative study for the resolution of these two methods with 35 nm FNDs at the single particle level, as well as with FND grown in bulk diamond material. Results show that STED provides more structural details, whereas SIM provides a larger field of view with a higher imaging speed. SIM may induce deconvolution smooth and orientational artifacts during its post-processing.

Finite Element Simulation of Nano-indentation of DLC Coated HSS Substrate

Surface coatings like diamond like carbon (DLC) films provide excellent surface properties on substrate. By using technique like finite element simulation, the coating performance under load can be estimated and thus provided valuable information, for the design and the use of coatings for different applications. Aim of present study was to model and simulate nanoindentation process on DLC coated high speed steel (HSS) by finite element method and to compare its results with experimental nanoindentation results. A two-dimensional (2D) and three-dimensional (3D) axisymmetric model was modeled/meshed in HYERMESH and analyzed in ANSYS software. The indenter was modeled as rigid body of diamond material. The models have the ability to simulate the loading-unloading curves and the development of plastic deformation during indentation. Developed load-displacement curve from FE models are compared with load-displacement curves measured by the experiments. The FE simulation results show that they are in good agreement with the experiment results.

Study of Radiation Damage in Diamond Film Implanted by B Ion

The radiation damage and its distribution in the type-Ib diamond film implanted by B ion have been investigated by means of Raman scattering and X-ray diffraction spectra. It is of significance during the applications of diamond materials due to several phenomena related to B-doped diamond, such as the superconductivity, the conversion of p-type to n-type conductivity and the low resistivity. The Raman scatting spectra indicated that the radiation damage in implantation layer was various with implantation depth. The top layer was damaged badly and graphitized completely. There existed small damage in nether layer, which resulted in partly amorphous carbon. It was noted that the volume was expanded in diamond film implanted by B ion. By x-ray diffraction pattern, it was reckoned that the lattice parameter was enlarged in B-implanting diamond layer, which expanded the volume of diamond film.

New textural evidence on the origin of carbonado diamond: An example of 3-D petrography using X-ray computed tomography

Three-dimensional textural observations of inclusion and porosity patterns in a 23carat carbonado diamond using high-resolution X-ray computed tomography reveal new information bearing on the nature and origin of this enigmatic material. A prominent patinaed surface is texturally linked to a banding and grading of inclusions and pore space beneath, extending several millimeters into the specimen. In situ observation demonstrates that almost all inclusions are polymineralic and show replacement textures, corroborating previous work indicating that the pore network is fully three-dimensionally (3-D) connected, and that virtually all macroinclusions are secondary. Large metal inclusions are only found immediately adjacent to the margin of the specimen, and are thus also likely to be secondary or even tertiary. However, we also report pseudomorphs after a phase forming pristinely euhedral rhombic dodecahedra, individually and in clusters from 0.3 to 1 mm in diameter; although we could fi nd no evidence of this phase persisting, it nevertheless represents the fi rst “true” macro-inclusion reported in carbonado, which almost certainly formed syngenetically with the diamond material. The pore system is essentially trimodal, consisting of single and clustered pseudomorphs, oblate pores 0.1‐0.3 mm in length with a clear preferred orientation, and 20 µm to <1 µm pores that form the connected network. Our observations support recent work suggesting that carbonado crystallized from a carbon-supersaturated fl uid and suggest that the second stage may correspond with the creation of the pore alignment fabric. We further postulate that, although the present-day macroinclusions are certainly secondary, the bulk material that comprises them may not be, and may instead be broken-down remains of the original included phase(s). While further verifi cation is needed, a model built around this hypothesis may provide the simplest explanation to many of the unusual features of carbonado.

Recent Developments and Applications of Nanodiamonds as Versatile Bioimaging Agents

AbstractThe first demonstration of nanodiamonds (NDs) for cellular fluorescence imaging was reported in 2005. It has since then aroused considerable interest among scientists working in the field of diamond and related materials. A large number of researches have been conducted, aimed to develop this novel nanomaterial as diagnostic, imaging, and therapeutic agents in biomedicine. There have been more than 20 review articles and book chapters published on this topic in the past 8 years. With the recent development of nanotechnologies and photonics, the ND‐based bioimaging has been taken to a new level. In this topic review, we will focus our attention on the recent advances in the development of NDs as versatile bioimaging agents for both in vitro and in vivo applications. Emerging new technologies including multiphoton excitation imaging, superresolution imaging, optically detected magnetic resonance imaging, cathodoluminescence imaging, and photoacoustic imaging are discussed.

Simulation of beam induced lattice defects of diamond detectors using FLUKA

Diamond is more and more used as a detector material for particle detection. One argument for diamond is its higher radiation hardness compared to silicon. Since various particles have different potentials for radiation damage at different energies, a scaling rule is necessary for the prediction of radiation damage. For silicon detectors the non-ionising energy loss (NIEL) is used for scaling the effects of different particles. A different way of predicting the radiation damage is based on the Norget–Robinson–Torrens theorem to predict the number of displacements per atom (DPA). This provides a better scaling rule since recombination effects are taken into account. This model is implemented in the FLUKA Monte Carlo simulations package for protons, neutrons and pions. We compare simulation results of NIEL and DPA for diamond and silicon material exposed to protons, neutrons and pions for a wide range of energies.

Measurement of the full stress tensor in a crystal using photoluminescence from point defects: The example of nitrogen vacancy centers in diamond

We introduce a method for measuring the full stress tensor in a crystal utilising the properties of individual point defects. By measuring the perturbation to the electronic states of three point defects with C3v symmetry in a cubic crystal, sufficient information is obtained to construct all six independent components of the symmetric stress tensor. We demonstrate the method using photoluminescence from nitrogen-vacancy colour centers in diamond. The method breaks the inverse relationship between spatial resolution and sensitivity that is inherent to existing bulk strain measurement techniques, and thus, offers a route to nanoscale strain mapping in diamond and other materials in which individual point defects can be interrogated.

Study on Thermal Influence of Grinding Process on LiTaO&lt;sub&gt;3&lt;/sub&gt;

As a typical multi-functional single crystal material, Lithium tantalate (LiTaO3 or LT) exhibits its excellent electro-optical, pyroelectric and piezoelectric properties, and has now been widely applied into many applications, especially in the telecommunication field. However, the most critical issue in the process is its pyroelectric effect and piezoelectric effect which potentially leads to crack initiation during grinding. Because it is rich in plasticity, LT demands larger specific energy for material removal. As the most machining energy is eventually converted into heat, LT undergoes a rapid rise in temperature during the grinding process, thus highly risks in thermal shock. In order to clarify the thermal influence on the grinding process of LiTaO3, the effects of coolant temperature, diamond grinding wheel geometry and material of substrate are investigated in this research. The experimental results show that the increasing rate of grinding torque (or force) and surface roughness are two major factors dominating the crack initiation during grinding of LT wafers. Via a DOE (design of experiment) analysis, coolant temperature and wheel type stand out as the main factors influencing on the increasing rate and wafer surface roughness.

Element six focuses diamond R&amp;D on Harwell

Element Six, the industrial synthetic diamond subsidiary of De Beers, has consolidated its R&D operations at a UK site close to the Rutherford Appleton laboratories in the hope that by bringing a number of teams together it will open up more applications for diamond and similar ultra-hard materials. With three high-temperature presses already in place able to develop pressures up to 8GPa - today commercial synthetic diamonds are made with pressures of less than 6GPa -the centre has space for eight and will install a 10GPa-capable machine in the near future. As a result, services such as power played a key role in site selection.

Facile Fabrication of Single‐Crystal‐Diamond Nanostructures with Ultrahigh Aspect Ratio

A robust and facile approach for making single-crystal-diamond MEMS and NEMS devices is presented. The approach relies entirely on commercial diamond material and standard cleanroom processes. As an example, batch fabrication of cantilever beams of thickness down to 45 nm and aspect ratios exceeding 2000:1 is demonstrated.

Application of Materials Studio Modeling in Crystal Structure

Modeling of crystal structure in material science curriculum was practiced and applied to keep it simple and understandable by using MS. The unit cells and atomic configurations are produced to show the theory system of geometry description of crystal structure. Many examples, as diamond, graphite, nanomaterial and advanced carbon materials, are employed to describe the main application of MS in material science teaching. According to these atomic modeling configurations, crystal structures exhibit a clearly and understandable appearance for us. So, the meaning of learning and understanding the related parameters of geometry description of crystal structure was explored with the point which helped students to realize and master the abstract concepts of crystal structure.

Timekeeping with electron spin states in diamond

Frequency standards based on atomic states, such as Rb or Cs vapors, or single-trapped ions, are the most precise measures of time. Here we propose and analyze a precision oscillator approach based upon spins in a solid-state system, in particular, the nitrogen-vacancy defect in single-crystal diamond. We show that this system can have stability approaching portable atomic standards and is readily incorporable as a chip-scale device. Using a pulsed spin-echo technique, we anticipate an Allan deviation of ${\ensuremath{\sigma}}_{y}={10}^{\ensuremath{-}7}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$ limited by thermally-induced strain variations; in the absence of such thermal fluctuations, the system is limited by spin dephasing and harbors an Allan deviation nearing $\ensuremath{\sim}{10}^{\ensuremath{-}12}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$. Potential improvements based upon advanced diamond material processing, temperature stabilization, and nanophotonic engineering are discussed.

Artificial diamonds as radiation-hard detectors for ultra-fast fission-fragment timing

In the framework of the construction of the double time-of-flight spectrometer VERDI, where we aim at measuring pre- and post-neutron masses directly and simultaneously, ultra-fast time pick-up detectors based on artificial diamond material were investigated for the first time with fission fragments from 252Cf (0.5MeV/u<E/A<2MeV/u). Signal stability under a high radiation fluence was determined up to at least 109 fission-fragments/cm2 together with more than 3.5×109neutrons/cm2 and 3×1010α-particles/cm2. This fluence is characteristic for fission experiments. The pre-requisite for the observed signal stability is the application of priming of the diamond material with a strong β-source for about 48h. The intrinsic timing resolution of a 100μm thick polycrystalline CVD diamond detector with a size of 1×1cm2 was determined to σint=(283±41)ps by comparison with Monte-Carlo simulations. Using broadband pre-amplifiers, 4-fold segmented detectors of same total size and with a thickness of 180μm show an intrinsic timing resolution of σint=(106±21)ps. This is highly competitive with the best micro-channel plate detectors. Due to the limited and batch-dependent charge collection efficiency of poly-crystalline diamond material, the detection efficiency for fission fragments may be smaller than 100%.

Surface Uniformity of CVD Diamond Film Polishing by Catalytic Polishing Method

CVD diamond is the main trend of future diamond materials. Surface uniformity of CVD diamond film polishing is one of the key technologies to expand the application of CVD diamond. Based on the catalytic polishing method, rotation velocity of the planet wheel is achieved when the lapping plate is in different rotation velocity and different bias distance by mechanics analysis. The lapping surface uniformity is analyzed to find out the best bias distance and velocity ratio by simulating the lapping times of different CVD diamond film with different velocity ratio and bias distance. At last, the lapping planet velocity and bias distance are achieved when polishing is in the best condition. The high uniformity surface can be achieved when polishing is carried out in these parameters.

Research on the diamond MISFET

Based on the hydrogen-terminated surface channel diamond material, a 1 μm gate length diamond metal—insulator—semiconductor field-effect transistor (MISFET) was fabricated. The gate dielectric A12O3 was formed by naturally oxidated thin Al metal layer, and a less than 2 pA gate leakage current was obtained at gate bias between −4 V and 4 V. The DC characteristic of the diamond MISFET showed a drain-current density of 80 mA/mm at drain voltage of −5 V, and a maximum transconductance of 22 mS/mm at gate—source voltage of −3 V. With the small signal measurement, a current gain cutoff frequency of 2.1 GHz was also obtained.

Suppression of abnormal grain growth in fine grained polycrystalline diamond materials (PCD)

During the sintering of fine grained (0.5μm) polycrystalline diamond (PCD) composite materials under high pressure-high temperature (HPHT) conditions, abnormal grain growth (AGG) of the diamond was observed. These abnormally grown diamond grains were up to several hundreds of microns in diameter. Diamond enhanced carbide substrates were used to suppress the abnormal grain growth. Electron backscattered diffraction was used to obtain grain orientation of the single crystals. The AGG was explained in a framework of the changed driving forces of the grain growth due to different initial carbon concentrations in the melt, particle size distribution and growth mechanisms.