Diamond Pyramid Research Articles

Determination of performance properties of galvanic coatings based on cobalt

Abstract. Problem. An effective solution to the problem of the durability of construction materials is the application of protective coatings, which allow tosignificantly expand the scope of use and service life of products. The purpose of the work was to determine the performance characteristics of electrolytic coatings with Co-Ni-Zr alloy, namely adhesion and microhardness. Methodology The microhardness of the coatings was determined by the indentation depth of the diamond pyramid. Coating adhesion was determined by the fracture method. The chemical composition of the obtained coatings was determined by the X-ray fluorescence method using the SPRUT portable spectrometer. The analysis was carried out at least in 3 points with subsequent averaging of the obtained values. Electrodeposition was carried out with a unipolar current in stationary and pulsed modes (ti/tр=2/2) while varying the current density. Originality. There are no signs of delamination of the coatings on the sandpaper, which emphasizes strong adhesion to the base. The results of metallographic studies proved that Co-Ni-Zr coatings have good adhesion to the substrate material and retain it under mechanical loads. The highest value of microhardness – 850.0 MPa was obtained in the galvanostatic mode at i = = 6 A/dm2, while the zirconium content in the alloy is 1.5 wt.%. From the results of the experiments, it can be concluded that the zirconium content does not affect the microhardness of the Co-Ni-Zr coating. When the current density increases, the microhardness of the deposit decreases, which can be explained by reaching the maximum density of the deposition current. The optimal deposition current density for the galvanostatic mode is 6 A/dm2, pulsed 6 A/dm2 for obtaining coatings with high microhardness

Thermohydraulic Performance and Flow Structures of Diamond Pyramid Arrays

Abstract Surface features are a common heat transfer enhancement method used in a myriad of applications including gas turbines and heat exchangers. One such style of surface feature is diamond pyramids, which offer significant heat transfer augmentation for moderate increases in overall pressure losses. This study investigated a suite of additively manufactured pyramids in a variety of sizes and arrangements at relevant scale contained in test coupons. Designs were printed with low surface roughness relative to typical additive components (Ra < 5 μm), and pyramids were printed within 100 μm of the design intent. Experimental and computational results indicate that the pressure penalty and heat transfer increased as the pyramids increased in size with aligned pyramids on both channel walls having higher values than staggered pyramids. It was found that implementing the pyramids onto a rough surface had a lesser impact on the friction factor than implementing it on a smooth surface, but that the relative increase in heat transfer was the same regardless of the roughness of the endwall. The greatest enhancement to local heat transfer and pressure loss was offset from the location of the minimum flow area due to local acceleration around the wake regions. The vortices formed in the wake of the pyramid structures enhanced the endwall heat transfer and shear stress. The performance of the pyramids investigated in this study follows a similar trend to prior studies investigating smooth rib geometries, though certain rib designs had higher heat transfer at lower pressure losses.

Multi-Pass Laser Polishing of As-Built Directed Energy Deposition Surfaces

Abstract Laser polishing (LP) provides a fast and efficient way of remelting part surfaces manufactured by additive manufacturing to alter both their geometric as well as physical properties. Depending on the laser parameters, remelted surfaces with different properties are achieved, with a majority exhibiting lower surface roughness compared to the original surface. In this study, a high-power continuous fiber laser is used to polish Inconel 718 (IN718) surfaces produced by depositing a single layer of clads on a steel substrate by the powder-blown directed energy deposition (DED) process. Polishing was performed under different sets of parameters, namely, laser power, beam diameter, feed rate or feed, hatch spacing, and the number of polishing passes. Their effects on the surface roughness profiles and the microstructural properties of the sample cross section were analyzed after one and two polishing passes. Optical microscopic images of the sample's cross sections show the presence of supersaturated γ phase particles, γ′+γ″ precipitates, Laves phases, and δ phase needles. The combined effect of high-temperature gradients and lower solidification rates in certain regions within the cross section results in undercooled regions and pseudo-heat treatment of unmelted regions close to the undercooled regions. These results are corroborated by indenting the various regions of the IN718 sample cross section with a pyramidal diamond indenter in the form of a grid, resulting in different micro-hardness values due to different densities of precipitate and phase transformed δ particles.

Analysis of micromechanical and tribotechnical properties of fluoropolymers during friction on 40Kh steel

The paper presents the results of micromechanical and tribotechnical tests of samples of polytetrafluoroethylene, radiation-modified (PTFE – RM according to modes A and B), coked in comparison with the PTFE standard (Fluoroplast -F4). The influence of the surface roughness of a 40Kh steel counter-tile on the coefficients of friction against time at a constant sliding speed is considered. Micromechanical tests were carried out using the method of instrumental indentation with a triangular Berkovich diamond pyramid. Tribotechnical tests were performed on a friction machine with a vertical axis of rotation of the spindle according to the scheme “the end of the sample of the fluoropolymer disk is the end of the counter-flange of the annular sleeve (steel 40Kh)” without lubrication and when the friction pair is lubricated with MGE-10A hydraulic oil. It was found that during friction without lubrication, PTFE samples had the maximum friction coefficients, and F4K20 samples had the minimum friction coefficients when working with 40X steel counter-tiles treated with P180 sandpaper. PTFE-RM (A) samples had the best wear resistance, followed by decreasing F4K20, PTFE – RM (B) and PTFE under friction without lubrication. In the presence of lubricant, the samples of the PTFE standard were inferior in wear resistance to the F4K20 samples, but were 5-7% better than the samples of PTFE-RM (B) and (A), respectively.

Exploring Cyber Threats and Threat Actors in the Financial Sector: A Comprehensive Study

This paper aims to discuss the recent activities of Financially motivated Threat actors and gather IOCs and Threat Intelligence based on the same. Common TTPs are mapped for 18 FIN threat actor groups along with known mitigations as per MITRE Attack Framework. In particular, FIN 7 is discussed in detail, including the lifecycle of Qakbot Malware and malwares are analyzed to gather IOCs using Static Analysis. Intrusion Detection Systems (Snort and YARA) are drafted for Qakbot. A comprehensive analysis on Diamond Model, Kill Chain and Pyramid of Pain is performed for Qakbot Malware and mitigations are mapped to MITRE ATTACK framework. Threat intelligence is gathered on the 1000 latest samples of Qakbot to deep dive into most commonly used delivery methods, malware file types and a timeline analysis is conducted. Advanced tools like OpenCTI and Cuckoo Sandbox are utilized to give an overall analysis on Financially motivated threat actors

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks

BackgroundTo study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale.MethodsSeven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials.ResultsThe nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 μm and increased after 3 months storage in distilled water to between 0.28 and 3.46 μm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found.ConclusionThe PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Indenting glasses with indenters of varying stiffness and sharpness

In this study, the effects of both indenter sharpness and stiffness on the indentation response of oxide glasses have been investigated. Using five different indenters, the indentation response in terms of glass deformation mechanism, cracking behavior, and hardness has been examined for three glasses (sodium silicate, sodium borate, and sodium borosilicate). For right square-based pyramidal diamond indenters with varying tip angle, increased indenter sharpness reduces the magnitude of the indentation size effect. Additionally, increased indenter sharpness lowers the crack initiation resistance, which is linked to a reduction of densification. For indenters with the same geometry but made of different materials, the effect of the indenter material is insignificant when the indenter is substantially stiffer than the specimen. When the stiffness of the indenter is only slightly higher or similar to that of the sample, substantial deformation of the indenter occurs, reducing the effective indenter sharpness and hence affecting the indentation response.

A theoretical model to predict the anisotropic characteristics in grinding of diamond conical indenter

Mechanical grinding of a high-precision diamond conical indenter is difficult due to the strong grinding removal rate anisotropy. In the existing literature, theoretical models have been established to predict the strength anisotropy of diamond on the (100), (110) and (111) planes, which provide a theoretical basis for the fabrication of pyramid diamond indenters, such as Berkovich, Vickers or Knoop indenters. However, investigations on the anisotropic characteristics in processing of diamond curved surface are rarely carried out. To solve the anisotropy problem in grinding of diamond conical indenter, this work contributes a theoretical model to predict the anisotropic characteristics in grinding of diamond cone face, and provides an effective method to optimize the grinding direction for enhancing the fabrication precision. Based on a proposed grinding-ability factor model, a general method is developed to analyze the grinding ability along different directions according to the formation process of the cone face. The results suggest that the optimized mechanical grinding direction can be determined by minimizing the standard deviation of the grinding-ability factors of the crystal planes. The proposed method is validated by grinding experiments on indenters, with the <100> or <111> orientation along the indenter axis. The experimental observations confirm that the optimized grinding direction can weaken the pyramid phenomenon, yielding a roundness error of 0.12 μm. In addition, the grinding removal rate-dependent roughness petal phenomenon is suppressed, which considerably enhances the conical surface quality.

Study of some thermo-mechanical parameters in Se70Te30-xMx (x = 0, 2; M = Cd, Ag, and Zn) alloys

Vickers microhardness has been determined by performing micro-indentation experiments on Chalcogenide glasses (ChGs) of Se70Te30, and Se70Te28M2 (M = Cd, Ag, and Zn) alloys using micro-indentation and optical microscopic techniques. Vickers micro-hardness is directly observed by the diagonal lengths of the indentation marks of a pyramidal diamond indenter. Thermally-induced glass transition was noticed by the DSC technique. Mechanical property such as modulus of elasticity (E), is calculated by well-known empirical relations. The minimal energy of micro-void (Eh), micro void volume (Vh), and covalence character of the glassy system are discussed in terms of microhardness (Hv). Physical parameters i.e., overall mean bond energy, density, molar volume, and compactness have been also carried out.

Effect of Aging on the Microhardness of Different Resin-based Fluoride-releasing Fissure Sealants: An In Vitro Study

The aim of the present study was to evaluate the effect of aging on the microhardness score [Vickers hardness number (VHN)] of different resin-based fluoride-releasing sealants compared to non-fluoride resin-based sealants. A total of 48 extracted sound molars that were sectioned mesiodistally were used. In the current study, four types of sealants were compared: Group A, a resin-based non-fluoride-releasing pit and fissure sealant (Eco-S sealant) served as a control. Groups B, C, and D received resin-based fluoride-releasing pit and fissure sealants Helioseal F, Fissurit F, and Embrace™ WetBond, respectively. Subsequently, each group was further divided into immediate and aged subgroups. The samples had been evaluated regarding their microhardness using a pyramidal diamond indenter of a Vickers hardness test at two-time intervals: Immediately and after the aging process through thermocycling. There were no statistically significant differences between mean VHN and material types (p = 0.72). Aging appeared to significantly increase the mean VHN (p = 0.001). The interaction model between material type and time factor showed that the effect of aging differs by the material type, where the VHN of the Embrace™ group increased significantly after aging from 24.33 ± 5.60 to 31.70 ± 3.59 (p = 0.001). While there were no significant differences in the microhardness of commonly used fluoride-releasing fissure sealants, time appears to significantly increase the mean microhardness score (VHN), especially in the Embrace™ group. Embrace™ WetBond fissure sealant showed a significant improvement in the mean microhardness score (VHN) with time. However, clinical studies with long-term follow-up are needed to confirm our results.

Low loss optical structure for directional and efficient photon emission using nitrogen-vacancy center in diamond

Nitrogen-vacancy center in diamond based photonic structures are appealing in the field of quantum technology as they offer single photon emission with an efficient directional output beam. In this paper, we report a nano-range waveguide design which is capable of producing ~70% photon collection efficiency with a NA of 1. We have utilized the pyramidal diamond structure onto a rectangular diamond substrate with the NV center positioned on top surface of this optical structure. A stable and directional emission of a far field pattern is achieved even with a wide range of dipole positions. Less power coupling inside the optimized device helps to enhance the efficiency near NV emission spectra. This optical waveguide can be employed in various applications in the NV based magnetometers and quantum devices

Experimental study of strength and fracture toughness of laser-blasted glass

The use of glass in structural applications has been increasing during last years. Nevertheless, the generalized use of surface-modified bearing glass is precluded by the lack of knowledge about their mechanical performance. This experimental investigation carries out the assessment of the fracture toughness and strength of glass subjected to laser blasting. Annealed glass and heat strengthened glass plates were subjected to mid-infrared laser surface treatment to increase the surface roughness and improve the slip resistance in wet conditions. The fracture toughness and fracture surface energy were experimentally determined from the observed radial cracks after micro-indentation with a pyramidal diamond indenter, and the results were analyzed in correlation to the laser processing conditions and the obtained surface roughness. The Weibull graph and the cumulative failure probability of the as-received and laser-modified glass were obtained by the four-point bending test.

Investigation of nanoscratch anisotropy of C-plane sapphire wafer using friction force microscope

In this study, nanoscratch experiments using side-forward multiple scans by friction force microscope with triangular pyramidal monocrystalline diamond tip were conducted on a (0001) plane sapphire wafer substrate to clarify the ductile-regime machining mechanism including its anisotropy. Various characteristics, such as scratch force, depth and specific energy for each scratch direction on C-plane of sapphire, were manifested by a friction force microscope, and the specific scratch energy showed a trend of three-fold symmetry. Subsequently, cutting chips which adhere to the diamond tip exhibited plastic deformations features were testified by a scanning election microscope. Based on slip/twinning systems of sapphire, Schmid factor was calculated for each scratch direction using the resultant force, and the calculated Schmid factors on the rhombohedral planes became the highest. Following the results, the resolved shear stresses along the twinning directions on the rhombohedral planes were calculated using a simple chip formation model, and they were several times larger than the critical resolved shear stress for rhombohedral twinning. As a result, it was found that when the scratch direction is set so that one of the three faces of the diamond tip is close to parallel to one of the rhombohedral planes, the rhombohedral plane acts as the chip shear plane and the specific scratch/cutting energy can be minimized. The cross-sectional transmission electron microscope images of scratched sub-surface also distinctly displayed the existence of subsurface damages consisting of twins and stacking faults relating rhombohedral planes.

Halide-modulated self-assembly of metal-free perovskite single crystals for bio-friendly X-ray detection

Halide-modulated self-assembly of metal-free perovskite single crystals for bio-friendly X-ray detection

Single-Crystal Diamond Needle Fabrication Using Hot-Filament Chemical Vapor Deposition.

Single-crystal diamonds in the form of micrometer-scale pyramids were produced using a combination of hot-filament (HF) chemical vapor deposition (CVD) and thermal oxidation processes. The diamond pyramids were compared here with similar ones that were manufactured using plasma-enhanced (PE) CVD. The similarities revealed in the morphology, Raman, and photoluminescent characteristics of the needles obtained using the hot-filament and plasma-enhanced CVD are discussed in connection with the diamond film growth mechanism. This work demonstrated that the HF CVD method has convincing potential for the fabrication of single-crystal diamond needles in the form of regularly shaped pyramids on a large surface area, even on non-conducting substrates. The experimental results demonstrated the ability for the mass production of the single-crystal needle-like diamonds, which is important for their practical application.

Evaluation of surface hardness of NiCr coating using Finite Elements Analysis

Introduction: To enhance resistance to surface damage of materials due to mechanical actions, there have been created many procedures that allow its modification for different needs. This leads to researches conducted to determine the changes achieved in the properties due to said procedures. One method commonly applied is, for example, physical means of vapor deposition of thin films on a surface. In recent years, many rational and empirical models have been proposed for the study of said properties. One of these models is computational analysis, which allows determining a great number of properties while avoiding applying destructive tests, achieving to reduce experimental time spent and costs of manufacture of test tubes as well as the test itself. In this research, the hardness of a surface coating of Nichrome (NiCr 80-20) was determined with an indentation test modeled in Ansys, based on the finite elements' method. Objective: To design a computational model that allows determining the surface hardness of material with coating Method: The realization of this project was made with the software for engineering analysis ANSYS, and the model was made based on the Vickers Indentation Test regulation given by the ASTM, which states that the test must be done with a pyramidal diamond indenter, applying forces greater than 1 kgf. Results: By running the respective numerical analysis for both the substrate and the coating, a surface hardness of 197.5073 VH was obtained for NiCr coating and surface hardness of 160.5809 VH for the S235 Steel (hardness of the interface). Conclusions: It was determined that the model proposed is correct seeing as the values obtained for the Vickers' Hardness is approximately the same as the experimental value with an error of 0.7501% for the coating layer and 0.2605% for the substrate. It was also concluded that it is possible to use this same procedure to obtain the surface hardness for different materials than those treated in this article by using this tool. In this research the hardness of a surface coating of Nichrome (NiCr 80-20) was determined with an indentation test modeled in Ansys, based on the finite elements’ method [1]. Objective: To design a computational model that allows to determine the surface hardness of a material with coating Method: The realization of this project was made with the software for engineering analysis ANSYS, and the model was made based on the Vickers Indentation Test regulation given by the ASTM [2], which states that the test must be done with a pyramidal diamond indenter, applying forces greater than 1 kgf. Results: By running the respective numerical analysis for both the substratum and the coating, a surface hardness of 197.5073 VH was obtained for the S235 Steel (hardness of the interface) and a surface hardness of 160.5809 VH for the NiCr coating. Conclusions: It was determined that the model proposed is correct seeing as the values obtained for the Vickers’ Hardness is approximately the same as the experimental value with an error or 0.7501% for the substratum and 0.2605% for the coating layer. It was also concluded that it is possible to use this same procedure to obtain the surface hardness for different materials than those treated in this article by using this tool.

Microdistortions, Hardness, and Young’s Modulus of Multicomponent Bcc Solid Solutions

The phase composition, type II microstresses, and coherent scattering domains (CSDs) of multicomponent (medium- and high-entropy) bcc solid solutions with an average electron concentration, Csd, ranging from 4.6 to 5.47 e/a were studied. The effect of these characteristics on the hardness and Young’s modulus was analyzed. The alloys were melted in a MIFI-9 vacuum arc furnace using components with a purity of at least 99.5 wt.%; the ingots were remelted six times. The hardness and Young’s modulus of the alloys were determined from nanoindentation curves plotted with a Micron Gamma unit under a load from 0.98 to 2.94 N using a Berkovich diamond pyramid under automated loading and unloading. A relatively small change in the quantitative chemical composition of the samples led to a noticeable change in the lattice parameter, type II microstresses, CSDs, microhardness, and Young’s modulus. The greatest possible type II microstresses and minimum CSD sizes were observed for the alloys characterized by high average mismatch between the atomic sizes of their constituent elements. Increase in the electron concentration in the alloys led to higher hardness and Young’s modulus and lower lattice parameter. Increase in the type II microstresses was also accompanied by higher hardness and Young’s modulus. The microhardness H of alloys significantly exceeded that calculated with the mixture rule, Hmix, and was determined by solid-solution hardening (∆H = H – Hmix ranging between 2.9 and 6.4 GPa). Type II microstresses precisely calculated from the X-ray line width can be used for measuring the distortion of the solidsolution lattice and assessing solid-solution hardening. The relationship between the magnitude of solid-solution hardening, Young’s modulus, and lattice microdistortions (type II microstresses) was proposed.

Peróxido de Hidrógeno al 35% y su efecto sobre la microdureza dental

Peroxides are currently the most widely used products for tooth whitening, when peroxide decomposes it produces a decrease in the pH in the medium in which it is found, immediately in the enamel produces acid etching that varies depending on the pH of the product, contact time and concentration. Objectives: To know the effect of hydrogen peroxide at 35% on dental microhardness. Methodology: Experimental, transversal, descriptive study. Using 50 teeth that were cut 1 mm below the amelocemental junction to create two vestibular and palatal faces. The teeth were lightened with 35% hydrogen peroxide to find out how much micro-hardness the enamel loses, the Vickers unit of measurement. The microhardness was measured after making 3 indentations in different surfaces of the enamel at a force of 50 grams and a time of 20 seconds with a diamond tip that left a trace observed under the microscope in the form of a pyramidal diamond; based on the vertical and horizontal diagonals, the Vickers microhardness was determined. Contribution: According to the results obtained, we found that the application of 35% hydrogen peroxide decreased dental microhardness by 25.08%.

Analysis Of Load Variations On ST 60 Steel Using Vickers Method

The use of metal in the industrial world, especially ST60 Steel, is a very vital need, this can be seen from the increasing number of machine or equipment components or construction parts made of steel. Hardness is one of the mechanical properties that is often used as a guide in selecting materials for an equipment component. To find out the hardness price of a material, various testing methods can be used, including the Vickers method, which is tested by applying a force to the indented diamond pyramid against the material for which the hardness value is determined. The amount of hardness value is determined by the magnitude of the loading force divided by the area of indentation. In this study, what was investigated was the effect of force on the hardness of the Vickers method. The results showed that the load variation had little effect on the results of the Vickers hardness value, especially for high loads (100 Kgf). The average hardness value for the mild steel being tested is 163 HV and 168 HV, the highest hardness value is 174 HV and the lowest hardness value is 156 HV, so that a tolerance of ± 10 HV commonly used in the Vickers test is sufficient.Keywords: Hardness, ST 60 Steel , Loading Variations, Vickers Test

Evaluation of the Elastic Compliance of the Hardness Tester in Instrumented Indentation Tests

The elastic compliance of the instrument (hardness tester) should be taken into account when determining the mechanical properties of materials by means of instrumented indentation with registration of indentation diagrams. The values of Young’s modulus of the tested materials significantly depend on the method for evaluating and accounting for elastic compliance. Therefore, the methods should be verified during instrumented indentation of materials with known but very different Young’s moduli. Successful experience in evaluating and accounting for elastic compliance of the instrument during the instrumented indentation of materials with a diamond pyramid has already been accumulated to date. This is reflected in the relevant standards. However, this experience cannot be applied to instrumented indentation with a steel ball or hard-metal ball without additional research and experimental verification. We propose a method for evaluating the elastic compliance of the hardness tester using the instrumented diagram of ball indentation based on the Hertz equation in the case of elastic contact of the ball with the plane. It is found that additional elastic deformations of the links of instrument are directly proportional to the indentation load; this dependence is typical of each instrument and the diameter of the ball does not affect it. This dependence allows one to take into account the elastic compliance of the instrument using software when registering and processing diagrams of ball indentation. Experiments to determine Young’s modulus and hardness by instrumented ball indentation of various materials (steel, aluminum alloy, magnesium alloy, and titanium alloy) using the known and proposed methods to account for the elastic compliance of the instrument are performed. The main criterion confirming the reliability of the method is the coincidence or proximity of the values ​​of Young’s modulus of the same material determined from the diagram of ball indentation and the diagram of tension of the sample. The advantages and disadvantages of the known and proposed methods are described. Practical recommendations for use of these methods are given.