Type IIa Diamond Research Articles

Mechanical and tribological properties of Si and W doped diamond like carbon (DLC) under dry reciprocating sliding conditions

The mechanical and tribological properties of three types of diamond like carbon (DLC) coatings, i.e., non-doped, Si-doped, and W-doped DLC, are evaluated. Dry reciprocating sliding wear tests were performed to evaluate the effect of sliding frequency/velocity on friction, adhesion, and wear. The degree of graphitization of non-doped and W-doped DLC increases with sliding velocity, which results in a lower coefficient of friction (COF), and a decrease in wear rate. Si-doped DLC, however, exhibits distinct friction behaviour, with increasing COF and severe fluctuations in friction at higher sliding velocities. In Si-DLC frictional heating drives the formation of an oxide-rich tribofilm and large amounts of Si-rich oxide wear debris that are both adhesive and abrasive. The oxide-rich tribofilm, and lack of surface graphitization, result in the severe fluctuations of Si-DLC friction via stick-slip and surface fracture/wear mechanisms, and significantly increased COF and wear rates at higher sliding velocities.

Specifics of high-temperature annealing of brown CVD single crystal diamonds at graphite-stable and diamond-stable conditions

Changes in the set and concentration of optically active defects in brown single-crystal CVD diamonds under high-temperature annealing at low pressure (LPHT) and high pressure (HPHT) were studied by optical spectroscopy. It is established that the pink tint in diamond color, which appears after LPHT annealing and disappears after НРНТ annealing, is caused by NV centers. Transformation of nitrogen–vacancy centers observed in the course of annealing follows the NV → NVN → N3V pattern and is accompanied by a color change from dark brown to practically colorless. At the same time, the absorption spectrum takes the form typical of the IIa + Ib type diamonds with nitrogen concentration at the level of 1–2 ppm. The broadband luminescence present in all CVD diamonds studied is tentatively associated with some extended defects that do not disappear even during HPHT annealing. The set of charge carriers traps is sensitive to annealing parameters, and the high-temperature peak near 661 K appearing after the LPHT annealing on thermoluminescence is considered as promising for dosimetry of ionizing and UV radiations.

Mixed type Ib-IIa diamond from a Fe–Mg2Si3O8·5H2O–C system under high pressure and high temperature

The composition of the crystalline medium has an essential effect on the formation and properties of diamonds. Large single-crystal diamonds grown in a Fe–Mg2Si3O8·5H2O–C system by the temperature gradient method (TGM) at 5.8–6.3 GPa and 1400–1480 °C were investigated. It was found that as the Mg2Si3O8·5H2O content increased from 0 to 4 wt%, the synthesis pressure and temperature both increased, and more nitrogen-vacancy (NV) defect centers appeared in the diamond crystal. The nitrogen impurity concentration in type Ib diamonds synthesized in the pure FeC system was about 90 ppm, and the distribution of nitrogen impurities was uniform from core to rim. Furthermore, with a Mg2Si3O8·5H2O content of approximately 4.0 wt%, type Ib-IIa diamond was successfully synthesized. The infrared spectra (IR) results showed that the nitrogen content of the type Ib-IIa diamond was higher in the central zone of the crystal (79 ppm), decreased in the intermediate zone (42 ppm), and decreased further at the periphery (< 1 ppm). Thus, the type Ib-IIa diamond had significant heterogeneity in the distribution of nitrogen.

Raman electronic effect for non‐destructive boron calibration in type IIb semiconducting diamond

AbstractWhereas p type semiconducting diamond is well‐developed with boron doping, it is still challenge to directly determine boron content within type IIb diamonds in material science. In this work, we show a systematic study on analysis of electronic Raman effect in boron‐doped diamond (BDD) containing boron ranging from several to ~104 ppm. Beside a sharp peak near 5.2 cm−1, a shoulder associated with the Raman electronic effect near 12.1 cm−1 presents in the BDD samples and the intensity is observed to increase significantly with the increasing boron content. Our results demonstrate that the electronic line can be employed as an effective indication for simple, non‐destructive, accurate and broadly applicable boron calibration in semiconducting BDD samples.

Vacancy diffusion and nitrogen-vacancy center formation near the diamond surface

For the engineering of nitrogen-vacancy (NV) centers in diamond, vacancies have been introduced locally into a type Ib diamond (100–200 ppm nitrogen content) by implanting argon ions from a sub-500 nm focused beam. At an acceleration potential of 12 kV, different charge states (Ar n+, n={1,4,8,11}) result in kinetic energies of 12–132 keV. NV-centers were formed by a subsequent annealing step. A wide range of fluences from around one ion to several hundred ions was implanted per spot. It was found that, on average, between 0.04 (12 keV) and 0.79 (132 keV) NV-centers are created from the vacancies of a single implanted argon ion, depending on the ion energy, but not on the fluence. The different number of vacancies created at each energy alone cannot account for the difference in NV-center yield. However, the probability of a given vacancy to diffuse to the diamond surface during annealing, where it cannot contribute to NV-center formation, was simulated and can fully explain the NV-yield behavior. With this model, an upper bound of approximately 300 nm for the diffusion length of a single vacancy was found for an annealing temperature of 800 °C.

Semigenerated Carnot algebras and applications to sub-Riemannian perimeter

This paper contributes to the study of sets of finite intrinsic perimeter in Carnot groups. Our intent is to characterize in which groups the only sets with constant intrinsic normal are the vertical half-spaces. Our viewpoint is algebraic: such a phenomenon happens if and only if the semigroup generated by each horizontal half-space is a vertical half-space. We call semigenerated those Carnot groups with this property. For Carnot groups of nilpotency step 3 we provide a complete characterization of semigeneration in terms of whether such groups do not have any Engel-type quotients. Engel-type groups, which are introduced here, are the minimal (in terms of quotients) counterexamples. In addition, we give some sufficient criteria for semigeneration of Carnot groups of arbitrary step. For doing this, we define a new class of Carnot groups, which we call type (Diamond ) and which generalizes the previous notion of type (star ) defined by M. Marchi. As an application, we get that in type (Diamond ) groups and in step 3 groups that do not have any Engel-type algebra as a quotient, one achieves a strong rectifiability result for sets of finite perimeter in the sense of Franchi, Serapioni, and Serra-Cassano.

Predictor variables influencing merging speed change lane crash risk by interchange type in urban areas

The objective of this research is to model and examine the influence of predictor variables on merging speed change lane crash risk by interchange type in urban areas. Data for selected merging speed change lanes in Charlotte, North Carolina, USA, for five-years, were collected and used in this research. Multinomial logistic regression models were developed to examine the risk of getting involved in a fatal or injury crash and property damage only (PDO) crash by interchange type. The findings indicate that merging speed change lanes at multi-lane ramps are safer than single-lane ramps (odds ratio > 50). The ramp average daily traffic (ADT) and the speed difference between the freeway and the ramp influence merging speed change lane crash risk at a cloverleaf interchange while the freeway annual average daily traffic (AADT) and the speed change lane length influence merging speed change lane crash risk at a diamond interchange (odds ratio > 1.4). The risk of getting involved in a fatal-injury crash in the merging speed change lane increases (odds ratio > 1.6) if an upstream or downstream ramp is too close to the subject cloverleaf interchange ramp or if a downstream ramp is too close to the subject diamond interchange ramp. Contrarily, the upstream ramp distance does not influence the merging speed change lane PDO crash risk at a cloverleaf or diamond interchange. It can be concluded that predictor variables influencing the merging speed change lane crash severity risk are different for cloverleaf, diamond, and other interchange types.

Diamonds from the Mir Pipe (Yakutia): Spectroscopic Features and Annealing Studies

For this study, 21 samples of colorless octahedral diamonds (weighing 5.4–55.0 mg) from the Mir pipe (Yakutia) were investigated with photoluminescence (PL), infrared (IR), and electron paramagnetic resonance (EPR) spectroscopies. Based on the IR data, three groups of diamonds belonging to types IIa, IaAB, and IaB were selected and their spectroscopic features were analyzed in detail. The three categories of stones exhibited different characteristic PL systems. The type IaB diamonds demonstrated dominating nitrogen–nickel complexes S2, S3, and 523 nm, while they were less intensive or even absent in the type IaAB crystals. The type IIa diamonds showed a double peak at 417.4 + 418.7 nm (the 418 center in this study), which is assumed to be a nickel–boron defect. In the crystals analyzed, no matter which type, 490.7, 563.5, 613, and 676.3 nm systems of various intensity could be detected; moreover, N3, H3, and H4 centers were very common. The step-by-step annealing experiments were performed in the temperature range of 600–1700 °C. The treatment at 600 °C resulted in the 563.5 nm system’s disappearance; the interstitial carbon vacancy annihilation could be considered as a reason. The 676.5 nm and 613 nm defects annealed out at 1500 °C and 1700 °C, respectively. Furthermore, as a result of annealing at 1500 °C, the 558.5 and 576 nm centers characteristic of superdeep diamonds from São Luis (Brazil) appeared. These transformations could be explained by nitrogen diffusion or interaction with the dislocations and/or vacancies produced.

Realization of highly conducting n-type diamond by phosphorus ion implantation

We report on the formation of n-type ultra-nanocrystalline diamond exhibiting high electrical conductivity, σRT ∼104 Ω−1 m−1 by phosphorus ion implantation. The Raman study confirms the restoration of crystallinity upon high vacuum and high-temperature annealing post-implantation process at 850 °C. Varying the fluence enabled us to obtain a reduced thermal activation energy of Ea ∼8 meV with a very high carrier concentration of ne ∼1021 cm−3. Hall measurements confirm the n-type nature in phosphorus-implanted diamond at a high fluence of 1016 ions/cm2, and the nonlinear Hall effect reveals the signature of two band conduction mechanism, one via the impurity band and the other through the conduction band.

Representation of the Structural Types of Copper, Diamond and Tungsten in Terms of a Universal Building Unit

The structural types of copper, diamond and tungsten are represented by a linear union of four tetrahedrons over faces within solution of a general problem of representation of a crystal structure as a union of special atomic clusters. This union (a tetrablock) plays the role of a universal building unit, because it determines the generating clusters (building units) of the basic structural types considered. Spiral unions of these generating clusters are implemented in other structural types too, as well as in metallic liquids and glasses. Since symmetry is a geometrical equivalent for the physical requirement of minimal free energy in a system, the choice of such clusters is determined by purely symmetry (mathematical) considerations.

The effect of adding Cu on the nitrogen removal efficiency of Ti for the synthesis of a large type IIa diamond under high temperature and high pressure

The effect of adding Cu on the nitrogen removal efficiency of Ti for the synthesis of a large type IIa diamond under high temperature and high pressure

Unusual green Type Ib–Iab Dniester–type diamond from Ukrainian placers

Among placer diamond occurrences in Ukraine, a group of microdiamonds have been distinguished that have specific morphological, color and spectral characteristics, not observed in other natural diamonds. These diamonds, termed “Dniester–type diamonds”, have tetrahexahedroidal and rhombododecahedroidal morphologies, green coloration, and high concentrations of single–atom, unaggregated nitrogen in the form of C–centers (66–74% of all N atoms), along with low ratios of nitrogen aggregation (0–13% agrregation ratio) and high total nitrogen content (892–1493 atomic ppm). With these characteristics, Dniester–type diamonds are approximate the Type Ib-Iab classification. The predominance of single–atom, unaggregated nitrogen indicates a short residence time under high–temperature conditions. These Dniester–type diamonds have a narrow range of carbon isotopic compositions, from δ13С = -10.52‰ VPDB tо -12.82‰ VPDB (average δ13С = -11.85‰ VPDB). They are distributed in Quaternary and Neogene sediments of the southwestern part of the Ukrainian Shield. This distribution forms a local halo within the Dniester and Southern Bug rivers interfluve and Black Sea beach sediments, approximately 650 km in length. This implies their endemic character and the likely nearby presence of primary source(s) of unknown, possibly non–kimberlitic type.

Magnetic field noise analyses generated by the interactions between a nitrogen vacancy center diamond and surface and bulk impurities

We investigated the mechanism of magnetic noise due to both surface and bulk impurities. For surface noise, we apply the Langevin method to spin fluctuation theory to calculate the noise for paramagnetic surface impurities absorbed in a thin layer of water. We find that the mechanisms generating noise are spin flip and spin precession which depend on impurity spin relaxation and spin precession time. For the bulk noise, we consider carbon-13 and nitrogen as impurities and employ the correlated-cluster expansion to calculate noise. Carbon-13 noise is a few orders of magnitude larger than nitrogen due to the higher impurity density in the typical NV center diamond system. We also find that the noise in the secular approximation underestimates noise under low applied magnetic field. Overall, the major source of magnetic field noise is spin precession noise, which is more than five orders of magnitude larger than the spin flip noise.

Synthesis and evaluation of high-performance diamond films with multilayer structure on printed circuit board drills

Printed Circuit Board (PCB) filled with a large amount of Alumina ceramics has broad application prospects in the fifth-generation industry but is hard to drill. This work focuses on high-performance diamond films to improve the working life of drilling tools and holes quality of products. By utilizing hot filament chemical vapor deposition (HFCVD) methods, the monolayer microcrystalline diamond (MCD), bilayer micro-nanocrystalline diamond (MNCD), and four-layer diamond (MNMNCD) are coated on commercial PCB drills (WC-6% Co). Solid particle erosion tests are conducted to study erosive wear mechanism of diamond films impacted by ceramic powders/particles. Besides, cutting performances of diamond coated drilling tools are evaluated by performing high-speed drilling tests with PCB as workpieces. In Erosion tests, the monolayer MCD film presents intergranular fracture and shows the lowest erosive resistance. The MNCD and MNMNCD films have similar fracture forms, where curved boundaries and steps between layers indicate their discontinuous fracture, and minor deep cone holes on the surfaces demonstrate their high resistance to crack growth. Moreover, only one minor deep cone hole is observed on the four-layer film which indicates it has the best resistance to particle impinging. In drilling tests, the number of holes drilled by the diamond coated tools before failure is regarded as criteria of working life. Then surface and sectional morphologies of holes are also observed to evaluate the quality of products. The results indicate the number of holes machined by the four-layer MNMNCD coated drills reaches 10,000, while that of the monolayer and the bilayer MNCD ones are 3000– 4000 and 6000 respectively. More importantly, different from the other two types of diamond coated tools, almost no burrs with a height of over 20 μm are observed on the hole entrance using the four-layer diamond coated tools. Therefore, considering both the working life and holes quality, the MNMNCD films excel in the cutting performance of the new type of PCB drilling.

DIAMONDS OF UKRAINE: RESULTS AND GOALS

Diamonds from Ukraine were studied in terms of their separation into their geological and genetic types, distribution and occurrence, the ages of their host rocks, and their nature in Proterozoic and Neogene age sediments. The diamonds are variable in morphology, internal structure, concentration and degree of aggregation of nitrogen centers, carbon isotopes and mineral inclusions. Placer diamonds, primarily from Neogene sands, are anomalous in many respects. They are mostly extremely small, polyhedral, and morphologically diverse showing octahedral, rhombic dodecahedral and cubic forms and they have various colors. In addition to the large heterogeneity in nitrogen concentrations, many diamonds are characterized by a low degree of aggregation of nitrogen centers, which indicates short mantle residence times. Depending on the nitrogen impurity content, the degree of aggregation of nitrogen centers and the possible temperatures of crystallization, several types of diamonds are distinguished in the studied sedimentary placers. According to new isotope-geochemical data, placer diamonds are characterized by a wide range of carbon isotopic composition. This may indicate isotopic inhomogeneity of diamond carbon, different modes of formation and chemical variability in their source regions. Impact diamonds from meteorite craters and Neogene sedimentary deposits of Ukraine are paramorphoses from graphite with similar morphological, isotopic and structural characteristics. The goals of future research of Ukrainian diamonds are discussed.

Towards high-quality nitrogen-doped diamond single crystals for X-ray optics.

In this manuscript, characterization of single-crystalline (111) plates prepared from type-Ib diamonds with a nitrogen content of 100-150 ppm by means of high-resolution rocking-curve imaging (RCI) is reported. Contrary to common opinion regarding the intrinsically poor diffraction quality of type-I diamonds, RCI showed the presence of nearly defect-free areas of several millimetres squared in the central part of the diamond plates. The observed broadening of the rocking curves is a result of the cutting and polishing processes, causing strains around the edges of the plates and rare defects. An improvement of the preparation technique will thus allow single-crystalline diamond plates to be made for Laue and Bragg monochromators and beam splitters from type-Ib material with areas large enough to be used as optical elements at fourth-generation synchrotron facilities.

About Diamonds of the Ingul-Ingulets Domain (the Ukrainian Shield)

Three finds of diamonds on the Ingul-Ingulets domain of the Ukrainian Shield are considered: in breccia-like rocks of the Gruzke area, in eclogite-like rocks in the basin of the Ingul River and the Zeleny Gayi meteorite crater. A brief description of these diamonds is made, which represent their different geological and genetic types. Тhe veracity of these diamond findings and the origin of their crystals are appreciated. It is shown that 8 diamonds of the Gruzke area differ in size (0.2-1.4 mm), shape, colour, set of nitrogen centres and degree of preservation. According to infrared spectroscopy, all the studied crystals can be attributed to natural diamonds of the mantle type and distinguish them into separate groups, as they belong to several spectral types: IIa, IaAB, Iab and Ib. However, there are several doubts about the veracity of this finding: 1. Finding in small samples of the core wells of such a high concentration of diamonds. 2. A large variety of crystals in these samples by spectral types of physical classification. 3. Signs of mechanical wear on all crystals, which does not exclude the version of their origin from a diamond drill bit (a mixture of crystals of the natural and possibly synthetic diamond). The question of whether the found diamonds belong to the breccia-like rocks of the Gruzke area remains open. Small diamonds (up to 0.3 mm), which are found in eclogite-like rocks in the basin of the Ingul River on several grounds (mainly cubo-octahedral habit, manifestations of skeletal forms of growth, flat surface of the cube faces, yellow-green colour, inclusions) are very similar to crystals of synthetic HPHT diamond. However, the same small diamonds are found in the rocks of the Euro-Asian Alpine and the Ural and Central-Asian Caledonian ophiolite belts and the eruptions of modern volcanoes in Kamchatka. Such diamonds are also found in lamproite-like rocks of the Mriya pipe in the Azov Sea region, and they are found in weathering crusts and terrigenous deposits of Ukraine. It is necessary to find out the true nature of these findings. Therefore, it is necessary to audit all finds of such diamonds in Ukraine. It is shown that diamonds from the Zeleny Gayi meteorite crater are typical impact apographitic crystals - diamond paramorphoses on graphite. The conclusions of some researchers about the mantle nature of these diamonds from this crater are denied.

Identification of Natural Type IIa Colourless Diamond with 270 nm Absorption Peak of UV-Visible Spectrum

In this paper, the conventional gemmological and spectral characteristics of a type Ⅱa colourless diamond sample were analyzed. Gemmological characteristics of the diamond sample were tested by gem microscope; The DiamondViewTM observed the growth structure and photoluminescence of the diamond sample; UV-Vis spectrometer detected the UV-Visible absorption characteristics of the diamond sample; Fourier infrared spectrometer determined the type of the diamond sample; The confocal laser Raman spectrometer and PL-3000 portable laser Raman spectrometer analyzed the characteristic spectra of defects in the diamond sample. Based on the analysis of experimental data, it is concluded that the diamond sample is natural Ⅱa type colourless diamond with the characteristic peak at 270 nm in UV-Vis spectrum, which provided complete laboratory appraisal basis, and enriched the instruction and guidance for special type ultraviolet absorption type of natural type Ⅱa diamond for daily testing.

Multi-Response Optimization of Tensile Creep Behavior of PLA 3D Printed Parts Using Categorical Response Surface Methodology.

Three-dimensional printed plastic products developed through fused deposition modeling (FDM) endure long-term loading in most of the applications. The tensile creep behavior of such products is one of the imperative benchmarks to ensure dimensional stability under cyclic and dynamic loads. This research dealt with the optimization of the tensile creep behavior of 3D printed parts produced through fused deposition modeling (FDM) using polylactic acid (PLA) material. The geometry of creep test specimens follows the American Society for Testing and Materials (ASTM D2990) standards. Three-dimensional printing is performed on an open-source MakerBot desktop 3D printer. The Response Surface Methodology (RSM) is employed to predict the creep rate and rupture time by undertaking the layer height, infill percentage, and infill pattern type (linear, hexagonal, and diamond) as input process parameters. A total of 39 experimental runs were planned by means of a categorical central composite design. The analysis of variance (ANOVA) results revealed that the most influencing factors for creep rate were layer height, infill percentage, and infill patterns, whereas, for rupture time, infill pattern was found significant. The optimized levels obtained for both responses for hexagonal pattern were 0.1 mm layer height and 100% infill percentage. Some verification tests were performed to evaluate the effectiveness of the adopted RSM technique. The implemented research is believed to be a comprehensive guide for the additive manufacturing users to determine the optimum process parameters of FDM which influence the product creep rate and rupture time.

Rapid HPHT annealing of synthetic IB-TYPE diamonds

The paper provides the information on the effects of rapid (1 min) high pressure high temperature (RHPHT) annealing of synthetic Ib-type diamond plates at temperatures (1900 °C, 2100 °C, 2300 °C, 2500 °C, 2700 °C) and pressure of 8 GPa. The studies were carried out using the visual analysis, absorption and Raman spectroscopy, photoluminescence and cathodoluminescence. During RHPHT annealing the diamond plates in a high-pressure container were rapidly heated/cooled at a very non-uniform temperature and pressure distribution. All this caused the inhomogeneous plastic deformation of diamond plates. The plastic deformation of diamonds during RHPHT annealing was a powerful “generator” of vacancies. The electron transfer from individual atoms of substituting nitrogen to nitrogen-vacancy centers switched these centers to a negatively charged state. Another accompanying RHPHT annealing process was the diffusion of nitrogen atoms with the formation of it’s simple aggregates – H3 defects (at 2300 °C). At higher RHPHT annealing temperatures more complex aggregates containing three nitrogen atoms – N3 defects — were generated. RHPHT annealing led to the formation of identical nitrogen – vacancy defects, as did quasi stationary HPHT annealing, but the number of these defects was significantly greater after RHPHT annealing.