Diamond Research Articles

Simultaneous Evaluation of Heat Capacity and In-plane Thermal Conductivity of Nanocrystalline Diamond Thin Films

ABSTRACT As wide bandgap electronic devices have continued to advance in both size reduction and power handling capabilities, heat dissipation has become a significant concern. To mitigate this, chemical vapor deposited (CVD) diamond has been demonstrated as an effective solution for thermal management of these devices by directly growing onto the transistor substrate. A key aspect of power and radio frequency (RF) electronic devices involves transient switching behavior, which highlights the importance of understanding the temperature dependence of a material’s heat capacity and thermal conductivity when modeling and predicting a devices electro-thermal response. Due to the complicated microstructure near the interface between CVD diamond and electronic material, it is difficult to measure both properties simultaneously. In this work, we use time-domain thermoreflectance (TDTR) to simultaneously measure the in-plane thermal conductivity and heat capacity of a 1-µm-thick CVD diamond film via multi-frequency analysis. We obtain temperature dependent thermal properties by using the pump beam to heat the sample according to increasing power. This mitigates the need for a more complicated setup using a thermal stage but has limited upper temperature boundaries based on the sample geometry and thermal properties. The results show that the in-plane thermal conductivity varied slightly with an average of 103 W/m-K over a temperature range of 302–327 K, while the specific heat capacity has a strong temperature dependence over the same range and compares well with heat capacity data of natural diamond in literature.

Non-invasive sampling of bats reflects their potential as ecological indicators of elemental exposure in a diamond mining area, northern Limpopo Province, South Africa

Bats have been proposed as reliable bioindicators for monitoring bioaccumulation of elements and chemicals in natural and transformed ecosystems. Non-invasive methods are becoming more popular as research moves away from destructive methodologies. We present the first concentrations of 23 elements in Mops condylurus and Tadarida aegyptiaca (Molossidae) fur and blood from an opencast diamond mine and reference area using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of B, K, Rb and Cd in the bats’ fur were significantly higher in the mining footprint compared to the reference area (P < 0.05). Other elements such as Zn and Hg were significantly higher in the blood of bats from the mining footprint than the reference area (P < 0.05), whereas Mn was significantly higher in the blood of bats from the reference area than from the mining footprint (P < 0.05). Sixteen of the 22 elements above the limit of detection, with the exception of Ba, were significantly higher in the fur samples than in the blood due to elements being incorporated over time into the fur as it grows, whereas blood reveals short-term exposure to elements. Concentrations of most of the elements were reasonably low except Al, Fe and Zn. In general, the element concentrations particularly in the fur samples were comparable with other international studies reporting elemental fur concentrations from anthropogenically impacted and natural areas. Fur and blood have the potential to be viable indicators of environmental toxicity, but research is required on toxic thresholds and physiological and ecological unknowns around element concentrations in bat tissues and organs.

Surface quality control of thin SiN layer by optical measurements

Fiber optic interferometers have a wide range of applications including biological and chemical measurements. Nevertheless, in case of a reflective interferometer setup, standard silver mirrors cannot be used in every measurement, due to their chemical activity. In this work, we investigate the surface quality of a thin optical layer of silicon nitride (SiN) which can serve as an alternative material for silver mirrors. We present measurements carried out with a Fabry-Perot fiber optic interferometer working in a reflective mode. Measurement results allow us to determine the surface quality of the investigated layer. Full Text: PDF ReferencesK. Karpienko, M.S. Wróbel, M. Jedrzejewska-Szczerska, "Determination of refractive index dispersion using fiber-optic low-coherence Fabry-Perot interferometer: implementation and validation", Opt Express, 53, 077103 (2014). CrossRef Jedrzejewska-Szczerska M., Gnyba M., Kosmowski B. B. "Low-coherence fibre-optic interferometric sensors", Acta Phys. Pol. A 120, 621 (2011). CrossRef M. Jedrzejewska-Szczerska "Response of a new low-coherence Fabry-Perot sensor to hematocrit levels in human blood",Sensors 14(4), 6965 (2014). CrossRef M. Kosowska, D. Majchrowicz, K.J. Sankaran, M. Ficek, K. Haenen, M. Szczerska, "Doped Nanocrystalline Diamond Films as Reflective Layers for Fiber-Optic Sensors of Refractive Index of Liquids", Materials 12, 2124 (2019). CrossRef Shou-YiChang, Yi-Chung Huang, "Analyses of interface adhesion between porous SiO2 low-k film and SiC/SiN layers by nanoindentation and nanoscratch tests", Microelectron. Eng. 84(2), 319 (2007). CrossRef X. Wang, C. Wang, X. Shen, F. Sun, "Potential Material for Fabricating Optical Mirrors: Polished Diamond Coated Silicon Carbide". Appl. Opt. 56, 4113 (2017). CrossRef G. Coppola, P. Ferraro, M. Iodice, S. De Nicola, "Method for measuring the refractive index and the thickness of transparent plates with a lateral-shear, wavelength-scanning interferometer", Appl. Opt. 42, 3882 (2003). CrossRef H. Mäckel, R. Lüdemann, "Detailed study of the composition of hydrogenated SiNx layers for high-quality silicon surface passivation", J. Appl, Phys. 92, 2602 (2002). CrossRef N. Atman, M. Krzywinski, "Visualizing samples with box plots", Nat. Methods, 11(2), 119 (2014). CrossRef M. Vignesh, R. Balaji, "Data analysis using Box and Whisker Plot for Lung Cancer", International Conference on Innovations in Power and Advanced Computing Technologies,(2017). CrossRef

More on Diamonds and De Beers

The author develops and supplements his previous analysis of a long period of Moscow’s confidential cooperation with South African diamond cartel De Beers, both forced and mutually beneficial, initially in the 1920s, then from late 1950s to early 1990s (Journal of the Institute for African Studies №3(40),2017). According to recently released documents such cooperation also continued between these two periods. It provided Soviet enterprises with imported industrial diamonds for precision instruments and augmented the country’s defense potential during the period of toughest Western Cold war sanctions in 1949–1953, before the discovery and extraction of rich deposits of Yakut diamonds. The article contains some interesting evidence of Russian diaspora involvement in South African industrial development. The author also calls for greater objectivity in historic analysis of the period of South African internal colonialism and anti-apartheid struggle.

Main results of the diamond, precious metal, and base metal mineral resource base reproduction using the declarative principle of licensing

The article presents the results of geological exploration for diamonds, precious metals, and base metals, conducted in the Russian Federation in consistence with licenses granted based on the declarative principle, beginning from the moment this mechanism was introduced. Key aspects of changes in the legislative regulation of this mechanism are represented. The information on the planned and factual financing of these works, on the number of the issued licenses, and on the respective increase in the resources and reserves of precious metals is provided. Specific (unit) indicators of the mineral reserve increase and of the respective costs were proposed, based on which the effectiveness of geological exploration was determined for projects performed in administrative subjects of the Russian Federation in consistence with the licenses granted by the declarative principle. Problems in implementation of the mechanism were identified. Recommendations for elimination of these problems are proposed.

A comparison of traditional orthodontic polishing systems with composite polishing systems following orthodontic debonding

IntroductionAt the completion of treatment, the orthodontic practitioner’s goal is to effectively remove all traces of adhesive and return enamel to its initial state. With the advent of new polishing systems being released each year, there may be one product that is superior to others. AimThe purpose of this study is to determine the efficacy of new polishing systems (in the last 5–10 years) used in general dentistry on enamel surface roughness following debond utilizing profilometery and scanning electron microscopy and compare them to established orthodontic polishing systems results. MethodsFifty-two mandibular incisors were randomly assigned to one of five test groups (N = 10) and two incisors (untreated enamel) were used for profilometer and scanning electron microscopy analysis at the end of testing. After bracket removal, the teeth were polished using traditional polishing products (Komet H48L bur, Reliance ‘Renew’ point) and newer polishing products (Coltene Spiral Composite Plus Polisher, Ultradent Jiffy Composite Polishing Spiral or 3M Sof-Lex™ Diamond Polishing System). The results were evaluated using a profilometer and scanning electron microscopy images. ResultsThe results of a one-way analysis of variance (ANOVA) determined that the mean change in enamel surface roughness was not statistically different both in the traditional and novel groups. Tukey’s Honestly Significant Difference (HSD) test found that there was no statistically significant difference in the change in enamel surface roughness between instrument groups. ConclusionsThere was no statistically significant difference in enamel surface roughness after polishing between traditional orthodontic polishing systems and the selected novel polishing systems. SEM analysis revealed similar findings. This supports previous research suggesting that a wide variety of polishing systems or none at all, may be used to restore enamel smoothness after removal of orthodontic appliances.

Experimental verification of the field theory of specific heat with the scaling in crystalline matter

The field (geometrical) theory of specific heat is based on the universal thermal sum, a new mathematical tool derived from the evolution equation in the Euclidean four-dimensional spacetime, with the closed time coordinate. This theory made it possible to explain the phenomena of scaling in the heat capacity of condensed matter. The scaling of specific heat of the carbon group elements with a diamond lattice is revisited. The predictions of the scaling characteristics for natural diamond and grey tin are verified with published experimental data. The fourth power in temperature in the quasi-low temperature behaviour of the specific heat of both materials is confirmed. The phenomenon of scaling in the specific heat, previously known only in glassy matter, is demonstrated for some zincblend lattice compounds and diamond lattice elements, with their characteristic temperatures. The nearly identical elastic properties of grey tin and indium antimonide is the cause for similarity of their thermal properties, which makes it possible to make conjectures about thermal properties of grey tin.

Diamond growth and characteristics in the metal-silicate-H2O-C system at HPHT conditions

The detailed phase composition and characteristics of diamond crystals grown in the metal-silicate-H2O-C system at 5.5 GPa and 1385 °C are reported in this paper. The conversion efficiency of the graphite-to-diamond in the metal-silicate-C system is lower than that in the metal-C system, which significantly decreases the growth rate of crystal. As the Mg2Si3O8·5H2O content increases to 1.5 wt%, growth pits and {110} related features of trigonal pyramids, skeletal structure, rhombic dodecahedron, and {110} dendrites exhibit in sequence. Simultaneously, the content of graphite and metal inclusions inside the crystal increases. These systematic changes are accompanied by the appearance of CH, CO, and CO bonds and a decrease of nitrogen content from ⁓210 ppm to ⁓60 ppm. It is speculated that H2O will further decompose and bond with carbon atoms and finally enter the diamond structure. The formation of CH and CO bonds will terminate the extension of the three-dimensional network of CC bonds. These defects will accumulate along the [111] direction and form {110} related characteristics. These chemical bonds also compete with the nitrogen in the system during entering into the diamond lattice. Our experimental model may provide implications for the morphology and formation environment of natural diamonds.

Rehabilitation of kimberlite tailings in the afro‐alpine zone of Lesotho: seed germination and plant performance of native grassland species across different topsoil mixtures

Environmental rehabilitation is mandatory for mining operations in many countries, including Lesotho. At Letšeng Diamond Mine in Lesotho, waste residues of kimberlite tailings create a hostile environment for the establishment of plant species during vegetation restoration. In this study, we investigated seed germination of native grassland species and tested the best performing species on different topsoil mixtures with kimberlite tailings in the Afro‐alpine zone in Lesotho. Rapid germination tests showed highly significant differences in the number of seedlings that emerged for different plant species: the grass Tenaxia disticha (% mean ± SE: 80 ± 17%; n = 36) and the forb Hesperantha schelpeana (56 ± 14%) were highest but nonsignificantly different to each other, while other species were significantly lower and nonsignificantly different to each other. In all treatments, seed germination of T. disticha was significantly higher than the experimental control, while the treatments that were covered with topsoil did not differ significantly. In addition, T. disticha seedling height and basal width varied significantly over time with seedlings in all the treatments growing significantly taller than those in the experimental control. Also, seedling basal width showed significant increase during the third growing season while height remained constant. We concluded that kimberlite tailings ameliorated with topsoil encourage plant establishment and performance of T. disticha, and this medium could be used to stabilize disturbed mine landscapes in the Afro‐alpine zone of Lesotho.

Where did the largest diamonds grow? The experiments on percolation of Fe-Ni melt through olivine matrix in the presence of hydrocarbons

Recently it was found that large natural diamonds can grow from a metal liquid. One of the principal issues of the proposed hypothesis is the formation of so-called “pockets” filled with Fe-Ni melt and hydrocarbons in the Earth's mantle. The existing models of Fe migration imply percolation of liquid melt through interconnected interstices between silicate minerals, although these models face several fundamental problems in explaining the process of penetration of Fe melt between solid crystalline phases like silicate and oxide minerals. The aim of the present study is to contribute to the mechanism of Fe-Ni melt migration, and to elucidate the evolution of the “pockets” in the presence of hydrocarbons. The experiments were performed using a high-pressure apparatus “BARS” at pressures 3 and 5 GPa, and temperature 1600 °C. A silicate matrix consisting of natural olivine grains was used. The interstices in olivine were filled with anthracene that decomposes under high P-T into a complex hydrocarbon fluid. Percolation of Fe-Ni (64/36 wt%) melt through the interstices was demonstrated which occurred at relatively high rates. The basis of the proposed mechanism is “solubility-enhanced infiltration”: Fe-Ni occupies the space filled with light elements or substances that are soluble in the melt. It is suggested that the following simple, but efficient mechanism supports the growth of large diamonds as well as their resorption and storage within silicate mantle of the Earth for a long time.

TAMAN WORKSHOP TAMBANG INTAN MODERN DI CEMPAKA

Banjarbaru City is one of the areas in South Kalimantan which is widely known to the public as a diamond-producing area. Many wilah in the city of Banjarbaru that are used as mining locations, PT Galuh Cempaka is one of them. At PT Galuh Cempaka's diamond mine, there are many abandoned diamond mining equipment that will eventually become a pile of scrap metal. The workshop equipment still has an economic and aesthetic selling point. In this case, it becomes interesting to develop a tourist attraction with the concept of a workshop equipment park. So that we need a place that can provide information for the community to raise awareness of the negative impacts of mining. To realize the development of a diamond mining workshop, PT Galuh Cempaka Banjarbaru has become a memorial park that can provide information on the negative impacts of mining. Layering method is used with the principle of superimposition to accumulate special interest tourism activity programs and information galleries.

Unusual optical centres in fancy brown diamonds

Background. Natural brown diamonds with fancy yellow, orange, red and green tints are valuable jewelry raw materials. Their colour is associated with post-crystallisation plastic deformation occurring during transportation from the mantle to the Earth’s surface.Aim. To study point defects in plastically deformed diamonds using optical and IR spectroscopy.Materials and methods. Faceted brown diamonds with fancy tints presented on the Russian market were studied spectroscopically. Selected samples were examined using UV-visible optical absorption spectroscopy and IR spectroscopy.Results. We discovered unusual optical centres in the absorption spectra of the UV-visible region. In addition, the known continuous absorption increasing from the red to the ultraviolet region of the spectrum, as well as the N3 and H3 nitrogen centres and a band at 550 nm, were revealed. In the spectra of yellowish-brown diamonds, the bands at 512.9 nm and 519.9 nm and an accompanying broad band with a maximum of 480 nm were found. The appearance of a yellowish tint of crystals was associated with these optical centres. The bands 506.5 nm, 516.1 nm and 679.7 nm were established in the spectrum of orange-brown diamond samples. An additional absorption continuum associated with single nitrogen atoms and centres (NV)– were observed in greenish-brown diamond samples. Their simultaneous presence causes the appearance of a greenish tint in the diamond colour.Conclusion. The information obtained using IR spectroscopy indicates that an intense brown colour can occur not only in the most common Ia type crystals according to the physical classification of diamonds, but also in relatively rare Ib + IaA type diamonds.

Micro topography, organic amendments and an erosion control product for reclamation of waste materials at an arctic diamond mine

Building a suitable soil is the foundation for successful revegetation and ecosystem development following disturbance. Mines produce large amounts of waste materials, which are important resources for soil building where it is lacking, although their potential on their own to support plants is often low. The objective of this research was to evaluate the effectiveness of built micro topography, organic amendments and an anionic polymer erosion control product (Soil Lynx) in improving plant community establishment on substrates of diamond mine waste materials (crushed rock, processed kimberlite, lakebed sediment) in the Northwest Territories, Canada. In general, micro topography and organic amendments worked independently to enhance revegetation. Built micro topography only enhanced plant establishment on processed kimberlite with highest plant density, cover and height in depressions. Plant response was considerably less on this substrate than on the others. Crushed rock had at least eight times the plant density and cover of processed kimberlite and double that of lakebed sediment. Sewage sludge incorporated 5–10 cm into surface substrates significantly improved plant establishment, growth and frequency of seed heads. Soil Lynx provided no benefit for plants. After 4 years, crushed rock with sewage sludge showed the greatest potential for use in reclamation. Seeded grasses dominated all treatments, although moss and lichen cover were increasing with time on crushed rock. Gravel disturbances are common in arctic regions and the ability to accelerate plant community development through use of novel soil building materials can ensure ecosystem resilience.

Optical Quality Laser Polishing of CVD Diamond by UV Pulsed Laser Irradiation

AbstractIt is a great technical challenge to precisely polish diamond substrates due to their extremely high hardness, especially for micro‐optics fabrication. Here, a simple laser polishing process is demonstrated for the optical quality surface finish of chemical vapor deposition diamond using a 355 nm nanosecond laser. Raman spectroscopy and surface profile analyses reveal that the laser polishing is an ablation‐based process that consists of laser graphitization and the subsequent laser ablation of the graphitized layer. An optimized strategy is proposed to realize the high‐quality polishing by combining the ablation effect and defocusing laser irradiation. The polishing strategy can effectively reduce the peak‐to‐valley height difference of a rough surface and automatically enables the laser fluence at a low level close to the ablation threshold. Laser polishing at such critical laser fluence can greatly avoid harmful effects caused by high laser fluence and achieve precision materials’ removal while maintaining optical surface quality. The approach is capable of delivering an average roughness Ra down to 8.02 nm and a high transmittance up to 80% of mechanically polished diamond in the visible spectrum. High optical performances make it possible to directly fabricate micro‐optical components on diamond substrates using this novel laser polishing approach.

Atom-by-Atom and Sheet-by-Sheet Chemical Mechanical Polishing of Diamond Assisted by OH Radicals: A Tight-Binding Quantum Chemical Molecular Dynamics Simulation Study.

Ultraflat and damage-free single-crystal diamond is a promising material for use in electronic devices such as field-effect transistors. Diamond surfaces are conventionally prepared by the chemical mechanical polishing (CMP) method, although the CMP efficiency remains a critical issue owing to the extremely high hardness of diamond. Recently, OH radicals have been demonstrated to be potentially useful for improving the CMP efficiency for diamond; however, the underlying mechanisms are still elusive. In this work, we applied our previously developed CMP-specialized tight-binding quantum chemical molecular dynamics simulator to comprehensively elucidate the CMP mechanisms of diamond assisted by OH radicals. Our simulation results indicate that the diamond surface is oxidized by reactions with OH radicals and then a concomitant surface reconstruction takes place due to the distorted and unstable nature of the oxidized diamond surface structure. Furthermore, we interestingly reveal that the reconstruction of the diamond surface ultimately leads to two distinct removal mechanisms: (i) gradual atom-by-atom removal through the desorption of gaseous molecules (e.g., CO2 and H2CO3) and (ii) drastic sheet-by-sheet removal through the exfoliation of graphitic ring structures. Hence, we propose that promoting the oxidation-induced graphitization of the diamond surface may provide a route to further improving the CMP efficiency.

Monolith Dental Bridge by Soft Machining of Dried Ceramic Dough

All-ceramic fixed restorations are gaining popularity because of increased esthetic consciousness in the younger population. Monolith ceramic crowns and bridges are preferred to withstand masticatory loads where the availability of occlusal height is limited. Machining green blanks of ceramic with organic binders have been studied to reduce loss of final strength, cost, and wastage associated with milling partial sintered and sintered blanks. Notches on the surface/edge associated with green milling will disappear after sintering in contrast to sintered state machining where diamond polishing is essential. In this study, we explored a novel ceramic dough process to form a green body of alumina or 3 Mol% yttria-stabilized zirconium oxide (YSZ), and computer numerical control (CNC) machining was performed on the dried dough. Micro Computer Tomography analysis of the bridges after sintering revealed a negligible void volume, 0.06–0.08% of the total volume, with randomly dispersed voids. Precision analysis of the sintered bridges with respect to the reference file resulted in a deviation range of +0.56 to −0.79 mm, with negligible deviation on the cementation surface. The green machined surface had a roughness profile of 1.2–1.7 μm after machining and 2.2–2.4 μm after sintering, as revealed by 3D profilometry.

Ultrashort-laser electron\u2013hole plasma and intragap states in diamond

The article discusses the implementation of ultrafast broadband excitation of A-band luminescence of natural diamond by femtosecond-laser pulses with low-energy near-IR photons. Such regime provides A-band luminescence yield with the fourth-power nonlinearity at low laser intensities and second-power nonlinearity at higher laser intensities. These nonlinear dependences of A-band intensity on laser intensity can be related to quasi-resonant four-photon excitation at lower laser intensities and impact excitation of corresponding optical centers at higher intensities, or to similar nonlinear processes in electron–hole plasma relaxing to trapping donor-acceptor centers.Graphic abstract

Theoretical and experimental investigation of material removal rate in shape adaptive grinding of HVOF sprayed WC-Co coating

Shape adaptive grinding (SAG) is conducted on the ground tungsten carbide-cobalt coating using diamond polishing pad. A material removal rate (MRR) model is proposed by considering the indentation of active abrasive particle, cross-sectional area and actual length of the finishing grooves. The effects of tool speed, tool compression, backing pad hardness and abrasive particle size of the polishing pads on the normal force, MRR and surface roughness are investigated. With an increase of the tool compression, the contact pressure increases and the surface peaks get sheared off at an enhanced rate that results in a higher MRR and lower surface roughness. On the other hand, SAG with harder tool (i.e., higher backing pad hardness) produces many deep finishing grooves owing to the aggressive mechanical interaction with the workpiece surface and that increases the surface roughness. Therefore, it is perceived that the harder SAG tool is not suitable as the final finishing step for precision finishing of cermet coating. The effect of tool speed on normal force is found to be insignificant as the contact area or pressure does not vary much with the tool speed. The polishing pad with lower particle size gets partially loaded at a higher tool compression and that impedes the reduction rate of surface roughness. By performing SAG with the polishing pads of reducing particle sizes in sequence, areal surface roughness (Sa) of 7 nm is attained. The residual stress of the finished coating is reduced to - 81 ± 7 MPa (compressive) which is around 29% of the ground surface. No abnormality is observed in the sub-surface of the finished coating.

Femtosecond-laser-excited luminescence of the A-band in natural diamond and its thermal control

Ultrafast visible-range excitation in natural diamond produces UV-VIS A-band photoluminescence with marginal zero-phonon line and intense regular multi-peak optical-phonon progression. The A-band photoexcitation can occur via band-center, center-center and band-band transitions, being related to two-photon (center-terminated), or interband three-photon and impact-ionization processes. Minor thermal pre-heating of the diamond (&lt; 55 °C) demonstrates strong damping of A-band progression intensities with two different activation energies.

Biomechanical performances of PCL/HA micro- and macro-porous lattice scaffolds fabricated via laser powder bed fusion for bone tissue engineering

The present experimental study aims to extend know-how on resorbable polycaprolactone/hydroxyapatite (PCL/HA, 70/30 wt%) scaffolds, produced by Laser Powder Bed Fusion (LPBF) technology, to geometrically complex lattice structures and micro porous struts. Using optimized LPBF printing parameters, micro- and macro-porous scaffolds for bone tissue regeneration were produced by regularly repeating in space Diamond (DO) and Rhombic Dodecahedron (RD) elementary unit cells. After production, scaffolds were submitted to structural, mechanical, and biological characterization. The interaction of scaffolds with human Mesenchymal Stem Cells (hMSCs) allowed studying the degradative processes of the PCL matrix. Biomechanical performances and biodegradation of scaffolds were compared to literature results and bone tissue data. Mechanical compression test, biological viability up to 4 days of incubation and degradation rate evidenced strong dependence of scaffold behavior on unit cell geometry as well as on global geometrical features.