Dispersive Raman Spectroscopy Research Articles

Nano selenium–alginate edible coating extends hydroponic strawberry shelf life and provides selenium fortification as a micro-nutrient

Although selenium nanoparticles (Nano Se) have gained attention for their anti-cancer and antioxidant activity, this nanomaterial's antimicrobial activity also has great potential. The aim of this study was to synthesize Nano Se edible coating solution through gamma irradiation technique with a bio-stabilizer of sodium alginate (Na-alg.), which is an ingredient commonly used in food preservation. Dynamic light scattering and transmission electron microscopy identified 94-nm-diameter Nano Se, and energy dispersive X-ray spectroscopy and Raman spectroscopy confirmed the formation of Nano Se. Antifungal studies revealed that Na-alg./Nano Se coating solution well inhibited both Neopestalotiopsis rosae and Fusarium oxysporum in single species culture conditions. The effectiveness of edible coatings containing Nano Se and Na-alg. on the physicochemical properties of strawberries at 24 ± 2 °C during 5-day storage period was evaluated. The results showed coated strawberries enhanced firmness by as much as 26% and a significantly less weight loss by as much as three fold compared to the control. The coating application was effective in maintaining a natural appearance and preserving half the amounts of vitamin C and B9 in the strawberries. In addition, the Na-alg./Nano Se coating was utilized as an additive to increase Se nutrient in strawberries. The Se content was supplemented from 0.28 to 0.56 μg per 100 g FW after coating. This study may potentially be used in the bio-preservation and Se-enrichment of various fresh fruits and other foods.

Study of lithium diffusion properties and electrochemical performance of SnSe/C and SnSe/MWCNT composite anode for Li-ion batteries

Herein, synthesis and electrochemical analysis of SnSe based alternative alloy anode and its composites with Super P (SnSe/C) and MWCNT (SnSe/MWCNT) have been attempted via a facile high-energy ball milling method. The X-ray diffraction (XRD) of the synthesized materials has been observed to confirm the phase formation. The morphological studies are analyzed using FESEM and TEM to see the shape, size and distribution of particles. In contrast, Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy confirm the homogeneous mixing of SnSe with Super P and MWCNT. Electrochemical analysis of all three compositions has been carried to explore the specific capacity, efficiency and cyclic performance. The lithium-ion diffusion coefficient is estimated using CV at different scan rates, EIS, and GITT for the SnSe, SnSe/C, and SnSe/MWCNT samples. For all three prepared anodes, the Li+ diffusion coefficient is calculated using EIS, CV, and GITT and it was found to be in the range of 10−15 cm2s−1, 10−14 to 10−15 cm2s−1 and 10−12 to 10−14 cm2s−1, respectively. Among all three anode materials, SnSe/MWCNT showed higher values of Li-ion diffusion coefficient, indicating that the SnSe/MWCNT electrode has superior kinetics over SnSe/C and SnSe.

Development of a Kilogram-Scale Synthesis of a Key Ulevostinag Subunit Part II: An Electrophilic Approach to Fluorinated Nucleosides

Ulevostinag (MK-1454) is a potent cyclic dinucleotide stimulator of interferon genes (STING) that was selected as a clinical candidate for evaluation in multiple solid tumor types. Nucleoside analogue 3′-deoxy-3′-α-fluroguanosine (3′FG) is one of two key monomeric subunits comprising Ulevostinag, and its efficient preparation was set as a key deliverable in the development of this novel therapeutic. We recently reported a novel synthetic approach to 3′FG, involving the aminocatalytic electrophilic fluorination and subsequent substrate-directed reduction of an isolable 2′-keto-nucleoside (i-Bu-3). Herein, we describe the process development of these key stereodefining steps, enabling the kilogram-scale preparation of i-Bu-3′FG (1). Key features of this process include (1) identification of commercially available l-leucine amide as an excellent fluorination catalyst, (2) development of a highly stereoselective (>95:5) intramolecular hydride delivery from the hindered nucleoside β-face, and (3) use of dispersive Raman spectroscopy to guide form control during the crystallization of 1.

Brass metallurgy in Urartu: Recent evidence from eastern Anatolia

Traditionally, the beginning of substantial and deliberate brass production through the cementation process has been placed to the Early Roman period. Sporadic early finds have accordingly been considered to be the result of various experimentations by eastern Mediterranean metallurgists at least since the Late Bronze Age. Several Anatolian finds, dated to the early first millennium BC, that were made from zinc rich alloys have been interpreted within this framework. In ancient Urartu, however, the mastery and application of advanced metal technologies of both casting and working of copper-alloys as well as blacksmithing are well documented. This study aims to provide a further understanding of this phenomenon by shedding light on the development of zinc metallurgy in eastern Anatolia based on recent finds unearthed during the rescue excavations at Murat Tepe and Murat Höyük in the Murat River basin in modern eastern Türkiye. In both cases the metal assemblages from stratified contexts were analysed by the means of multiple archaeometallurgical methods. The results from portable XRF (pXRF), metallography, micro-hardness, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) and Raman spectroscopy analyses have showed that zinc was intentionally used as an alloy additive in order to fabricate brass. Moreover, in one case, the chemical composition consisting of zinc (Zn), tin (Sn) and copper (Cu) was detected, which indicates different alloying practices for the production of different types of objects. These new observations raise further questions about the deliberate production and manufacturing of brass prior to the wide spread of this metal technology in the Roman period.

Mechanism of wear in zircaloy-4 under different loading conditions

Core components of nuclear reactor are generally made of zirconium alloys and some of them are prone to low amplitude vibration leading to material wear at contact interface. Reciprocating wear tests were conducted between zircaloy-4 (Zr-4) under dry and water-submerged conditions. To confirm the material transfer due to adhesion, wear tests were also conducted between Zr-4 and stainless steel. To understand the wear mechanism, worn surfaces were analyzed using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Coefficient of friction (COF) increases with increasing fretting duration and decreases with increasing frequency and displacement amplitude. Greater COF is observed under dry condition than that under submerged condition. The wear mechanism changes from adhesion to abrasion with increasing displacement amplitude.

Improved fracture response and electromagnetic interference shielding effectiveness of cementitious composites incorporating pyrolytic bagasse fibers and pine needles

The increasing amount of bagasse and pine needles have become a potential environmental threat to humans and wildlife, as they have serious consequences of catching fire or dumping on land. These wastes have been transformed for the first time into nano carbonaceous inerts via pyrolysis at 500 °C and 700 °C, respectively, in an inert atmosphere and utilized in the preparation of cementitious composites, to improve their strength, fracture response, and electromagnetic interference shielding. The pyrolysis temperature was decided based on thermogravimetric analysis of the selected Agro-wastes. Carbonized material produced by pyrolysis was ground to nano level and characterized through X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, laser granulometry, and UV–visible spectroscopy. Samples of cement mortar with cement to the sand ratio of 1:1.5 were prepared with the addition of 0.025 %, 0.05 %, 0.08 %, 0.20 %, 0.50 %, and 1.00 % pyrolyzed nano-inerts by wt. of cement after the effective dispersion in water. The uniform dispersion of carbonized particles in cementitious matrix was evidenced through the forensic analysis. Three-point bending test of mortar prisms was conducted at 0.1 mm/min strain rate in strain-controlled mode and the broken halves were tested in compression. A maximum increment of 25.36 % in compressive strength and 15.83 % in flexural strength was achieved due to the addition of 0.20 % pyrolyzed bagasse fibers and 1.00 % pyrolyzed pine needles respectively. A substantial increase of 114.15 % and 101.88 % was achieved in fracture toughness with the addition of 0.20 % carbonized bagasse fibers and 1.00 % carbonized pine needles, respectively. The improvement in strength and ductility is associated with supporting mechanics of crack branching, bridging, and crack contouring verified via SEM micrographs. The inertness of pyrolyzed particles in cementitious composites was verified by X-ray diffraction analysis. Furthermore, the cementitious samples were tested within the frequency range of 8–12 GHz in x-band to check electromagnetic interference shielding effectiveness (EMI-SE), and maximum improvement of 18.02 dB and 20.06 dB was attained with 0.50 % intrusion of pyrolytic bagasse fibers and pine needles, respectively.

Effect of Cu-Doped Carbon Quantum Dot Dispersion Liquid on the Lubrication Performance of Polyethylene Glycol

Energy saving and reduced consumption of key materials such as bearings in high-end equipment can be realized by synthesizing a new lubricating functional additive, copper-doped carbon quantum dot dispersion liquid (Cu-CQDs) via hydrothermal reaction with glycerol, cupric chloride dihydrate, and choline chloride as raw materials. The influence of the dispersion liquid containing Cu-CQDs nanoparticles on the lubricating properties of polyethylene glycol (PEG200) was investigated on a four-ball friction tester. The wear scars of steel balls after friction were analyzed using a scanning electron microscope accompanied by energy dispersive spectroscopy (SEM/EDS), photoelectron microscopy, and Raman spectroscopy. The results revealed the friction and wear mechanism of Cu-CQDs. Cu-CQDs dispersion liquid can significantly enhance the lubrication performance of PEG. The average friction coefficient of PEG containing 2.0 wt% Cu-CQDs dispersion liquid was 40.99% lower than that of pure PEG. The friction and wear mechanism can be ascribed to friction, inducing Cu-CQDs to participate in the formation of boundary lubricating film, resulting in a low friction coefficient and wear scar diameter.

Mechanical Reinforcement of ABS with Optimized Nano Titanium Nitride Content for Material Extrusion 3D Printing.

Acrylonitrile Butadiene Styrene (ABS) nanocomposites were developed using Material Extrusion (MEX) Additive Manufacturing (AM) and Fused Filament Fabrication (FFF) methods. A range of mechanical tests was conducted on the produced 3D-printed structures to investigate the effect of Titanium Nitride (TiN) nanoparticles on the mechanical response of thermoplastic polymers. Detailed morphological characterization of the produced filaments and 3D-printed specimens was carried out using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). High-magnification images revealed a direct impact of the TiN concentration on the surface characteristics of the nanocomposites, indicating a strong correlation with their mechanical performance. The chemical compositions of the raw and nanocomposite materials were thoroughly investigated by conducting Raman and Energy Dispersive Spectroscopy (EDS) measurements. Most of the mechanical properties were improved with the inclusion of TiN nanoparticles with a content of 6 wt. % to reach the optimum mechanical response overall. ABS/TiN 6 wt. % exhibits remarkable increases in flexural modulus of elasticity (42.3%) and toughness (54.0%) in comparison with pure ABS. The development of ABS/TiN nanocomposites with reinforced mechanical properties is a successful example that validates the feasibility and powerful abilities of MEX 3D printing in AM.

Mechanical and tribological characterization of graphene nanoplatelets/Al2O3 reinforced epoxy hybrid composites

This study aimed to determine the effects of varying Aluminum oxide (Al2O3) and Graphene Nanoplatelets (GNP) concentrations on epoxy-based polymer composites’ mechanical and tribological characteristics. Al2O3 (1 to 5 wt.%) and GNP (0 to 1 wt.%) reinforced epoxy matrix composites were produced with sonication and stirring magnetic route. Mechanical, microstructural and tribological properties of composites were investigated via X-ray diffraction (XRD), Archimedes’ Method, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Raman spectroscopy, hardness, impact, tensile, compressive and wear tests. The highest ultimate tensile strength and compressive strength were found at 62.83 and 137 MPa for 3 wt.% reinforced Al2O3 epoxy matrix composites, and it was observed that there was a 38% and 17% increase compared to neat epoxy, respectively. The highest impact strength was found for 3 wt.% Al2O3 and 1 wt.% GNP-reinforced composites and increased by 19% compared to neat epoxy. The best hardness was found for 3 wt.% reinforced Al2O3 and 0.25 wt.% GNP-reinforced composite, and there was a 22% increase in hardness compared to neat epoxy. Also, the highest wear resistance (1.686x10−6 mm3/Nm) and lowest Coefficient of Friction (COF, 0.13755) were determined for the same specimen.

Рост пленок SiC, AlN и GaN на кремниевых изделиях произвольной геометрии для микроэлектромеханических применений

A technique is proposed for the formation of epitaxial films of silicon carbide, gallium and aluminum nitrides on the surface of non-planar silicon parts. Using the technique, a GaN/AlN/SiC/Si heterostructure was grown on the surface of a silicon ring. The samples were studied by scanning electron microscopy, as well as raman and energy dispersive spectroscopy. It is shown that the preliminary deposition of a SiC layer on silicon by the atomic substitution method, in which (111) facets are inevitably being formed regardless of the local crystallographic orientation of the substrate surface, makes it possible to efficiently grow subsequent layers of III-nitrides of both wurtzite and sphalerite types on silicon parts.

CaZn(HPO3)2 and Ba2Zn(HPO3)3: novel alkaline-earth zincophosphites with diversified anionic frameworks.

Two novel alkaline-earth zincophosphites, namely CaZn(HPO3)2 and Ba2Zn(HPO3)3, were successfully synthesized under hydrothermal conditions. CaZn(HPO3)2 exhibits a three-dimensional (3D) anionic framework with a 6-connected uni-nodal pcu α-Po primitive cubic topology, constructed by unique Zn2O8 dimers and HPO3 pseudo-tetrahedra, while Ba2Zn(HPO3)3 displays one-dimensional (1D) [Zn(HPO3)3]4- anionic chains. It is worth mentioning that CaZn(HPO3)2 represents the first example of an alkaline-earth zincophosphite compound with a 3D framework structure. Our research also revealed the importance of both alkaline earth cation sizes and Zn/P ratios in anionic open-framework formation. The crystal structures of both compounds were further verified by energy dispersive spectroscopy, IR spectroscopy and Raman spectroscopy. Optical diffuse reflectance spectra, coupled with Tauc's fitting, revealed direct bandgaps with energy values of 4.33 and 4.48 eV for CaZn(HPO3)2 and Ba2Zn(HPO3)3, respectively, which differ from the prediction of theoretical calculations. Density of states calculations were conducted to reveal the origin of the bandgaps and bond interactions. Both compounds exhibited moderate birefringence values. This work may have implications for the design and synthesis of novel metal phosphites with desired properties.

Development of alumina-based hybrid composite coatings for high temperature erosive and corrosive environments

Low alloy steels are being used for structural applications exposed to extreme environmental conditions such as, high temperature, corrosive and erosive environment in petrochemical industry, turbomachinery, chemical reactors, and nuclear industry. These extreme environment conditions severely affect the performance of critical components. In this context, it is attempted to develop the alumina (Al2O3) based hybrid composite coatings on ASME SA387-22-2 steel to mitigate the effect of high temperature erosion and corrosion. High-velocity oxygen-fuel (HVOF) thermal spray technique is used to develop the coatings. The physical characteristics of the coatings are recorded in terms of density measurement, thermogravimetric analysis, and surface wettability analysis. Hardness and elastic modulus of the coatings are estimated at room temperature using nanoindentation and microhardness at high temperature (400 °C) using Vickers hardness tests. Metallurgical characterization and eroded surface analysis are done using Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and X-ray diffraction (XRD). High temperature (400 °C) erosion performance of the coatings is recorded using solid particle Air-jet erosion tester. The Corrosion performance of the coatings are analyzed using the potentiodynamic polarization technique and electrical impedance spectroscopy (EIS). Significant improvement in erosion performance (Erosion reduction: ≈ 96% at 30° and ≈63% at 90°) and corrosion resistance (≈92% reduction in corrosion rate) is recorded for the coating reinforced with 0.8 wt% ceria (CeO2) and 3 wt% hexagonal boron nitride hBN as compared to the bare steel. The improved erosive and corrosive characteristics of the coatings are attributed to the refined microstructural aspects, in-situ generation of hard second phases, and induction of hydrophobicity in the composite structure.

Modification of TiO2 nanotubes by graphene–strontium and cobalt molybdate perovskite for efficient hydrogen evolution reaction in acidic medium

Herein, we demonstrate that modification of TiO2 nanotubes with graphene–strontium and cobalt molybdate perovskite can turn them into active electrocatalysts for hydrogen evolution reaction (HER). For this purpose, a simple method of hydrothermal synthesis of perovskites was developed directly on the TiO2 nanotubes substrate. Moreover, the obtained hybrids were also decorated with graphene oxide (GO) during one-step hydrothermal synthesis. The obtained materials were characterized by scanning electron microscopy with energy dispersive X-ray analysis, Raman spectroscopy, and X-ray diffraction analysis. Catalytic properties were verified by electrochemical methods (linear voltammetry, chronopotentiometry). The obtained hybrids were characterized by much better catalytic properties towards hydrogen evolution reaction compared to TiO2 and slightly worse than platinum. The optimized hybrid catalyst (decorated by GO) can drive a cathodic current density of 10 mA cm−2 at an overpotential of 121 mV for HER with a small Tafel slope of 90 mV dec−1 in 0.2 M H2SO4.

Mobile Raman spectroscopy analysis of elephant ivory objects

AbstractRaman spectroscopy has been applied to the nondestructive study of ivory artefacts. Molecular Raman spectra of this material have been recorded previously using Fourier‐transform Raman spectroscopy (1064‐nm excitation), and attempts were made to differentiate between species of different origin. However, few attempts have been made to examine this interesting material using dispersive Raman spectroscopy, as when using shorter wavelength excitation, the fluorescence background signal tends to overwhelm the Raman signal. In this study, however, a mobile fibre‐optics Raman spectrometer, equipped with 1064‐nm excitation and an InGaAs detector, was used for the direct analysis of ivory artefacts. This approach opens opportunities for the fast and reliable analysis of this material, without the need to move the artefact to the laboratory, helping to act against the illegal trade of this endangered biomaterial.

Direct Measurement of Chocolate Components Using Dispersive Raman Spectroscopy at 1000nm Excitation.

Chocolate is a popular food around the world. Making chocolate-based confectionaries involve multiple processing steps including cocoa bean fermentation, cocoa bean roasting, grinding, and then a controlled crystallization, where the processing conditions yields the desirable polymorph V to give chocolate its characteristic snap and texture. Raman spectroscopy is well known as a technique that can provide a non-contact, non-destructive analysis of chemical composition and molecular structure. Yet, excitation in the visible and near-infrared (532-785nm) has not been possible for dark or milk chocolate because of the samples' overwhelming fluorescence. New technologies enabling Raman spectroscopy closer to shortwave infrared wavelengths, closer to 1000 nm, are likely to reduce fluorescence of chocolate and other highly fluorescent samples. Based on the successes of 1064nm excitation to understand chocolate blooming, we hypothesized that 1000nm excitation would also reduce fluorescence and enable Raman spectroscopy in dark and milk chocolates. We used dispersive Raman spectroscopy at 1000nm to measure white, milk, and dark chocolate and cocoa nibs. The use of 1000nm excitation effectively reduced fluorescence, enabling qualitative and quantitative Raman spectroscopy directly on chocolate samples. These feasibility studies indicate that 1000nm Raman spectroscopy can be used to measure chocolate in a laboratory or process environment.

Electrolyte contribution to the multifunctional response of cellulose carbon nanotube fibers

Flexible wearable multifunctional devices such as cellulose loaded with electroactive components are in the focus of modern research for electrochemical energy storage, sensors and actuators. In this report, the multifunctional response of cellulose with 50 wt% MWCNT formed into Cell-CNT composite fibers is demonstrated. The effect of (aqueous) electrolyte choice on the electro-mechanical response of Cell-CNT was studied. Aqueous electrolytes such as tetramethylammonium chloride (TMACl), sodium perchlorate (NaClO4), and 1-ethyl-2,3-dimethylimidazolium trifluoromethanesulfonate (EDMITF) were considered, with the resulting stress and strain decreasing in the order Cl− > ClO4− > TF−, matching the order of the size of the ions. Upon negative charging, the cations of the electrolytes showed electromechanical response in the order: TMA+ > EDMI+ > Na+, where the solvation strength of the cations had stronger influence than their size without solvation shell. The highest specific capacitance was shown by TMACl in the range of 74 mF cm−2 upon positive charging, with also the best retention of capacitance of 86% in long-term measurements. Chronopotentiometric measurements of Cell-CNT fibers where conducted to evaluate if the composites can also act as sensors for different electrolytes. The Cell-CNT fibers were characterized with scanning electron microscopy, energy dispersive X-ray, FTIR and Raman spectroscopy.

Study of modern Chinese cloisonné by means of small-spot energy dispersive X-ray fluorescence spectrometry and Raman spectroscopy

In this work, we studied the features of a modern Chinese cloisonné vase by means of small-spot energy dispersive X-ray fluorescence (EDXRF) and micro-Raman spectroscopy. Quantitative elemental results of enamel have been obtained after calibration of EDXRF instrumentation with certified reference materials. Up to eleven different coloured enamels have been recognized and analysed (black, pink, red, white, yellow and three shades of both blue and green). Enamel paste is mainly formed by the main identified elemental colouring agents - chromium, manganese, iron, cobalt, copper, antimony and cadmium– in a lead alkali silicate matrix.The body of the vase is made by copper with minor amounts of zinc and tin. Analysis of metallic decorations at the surface of the vase reveal the presence of metal coatings applied for the embellishment of the artwork. Thickness of layered metal structures have been obtained by XRF fundamental parameters assisted with data from pure metal spectra, thus revealing the gilded coatings consist of a thick layer made by silver-doped nickel.

Investigation of RF sputtered, n-Bi2Se3 heterojunction on p-Si for enhanced NIR optoelectronic applications

A significant deal of interest has been generated in heterojunctions made of 2D Bi-Chalcogenides and semiconducting materials due to the wide range of unique properties and functionalities that they exhibit. In this work RF magnetron sputtering technique was used to fabricate the high-quality n-Bi 2 Se 3 /p-Si heterojunction device. The structural properties of the grown Bi 2 Se 3 thin films were examined by XRD, SEM, Raman and Energy dispersive spectroscopy. The current-voltage (I–V) characteristic revealed the development of effective p-n junction with a greatest rectification ratio (RR) of 724 and significant figure of merit (FOM) of 1.11. A visible to near-infrared photodetector was successfully constructed using n-Bi 2 Se 3 /p-Si heterostructure exhibiting a strong response to 1100 nm irradiance and demonstrated outstanding photo-responsivity of 43.3 A/W, an excellent detectivity of 2.08 × 10 12 Jones and convincing photoconductive gain of 48.71. The fabricated n-Bi 2 Se 3 /p-Si heterojunction offers inexpensive optical detection, high performance broadband detector and tremendous potential for superior electrical and optoelectronic applications due to its convenient device fabrication and compatibility with silicon technology. • Using RF sputtering technique with high-quality epitaxial film offering low-cost optical detection. • n-Bi 2 Se 3 /p-Si heterojunction device for ultrafast optoelectronic devices for the future prospectus. • Excellent Responsivity (43A/W) and high Detectivity (2.08 × 10 12 ) from visible to near infrared region making it efficient for broadband detector.

Soft chemistry synthesis method of ZnAl2−xCrxO4 spinel: Structural, morphological, optical and photocatalytic properties

The precursor method was employed to prepare ZnAl 2-x Cr x O 4 (x = 0, 0.25, 0.5, 0.75, 1) using tartaric acid as a ligand. Five tartarate compounds were isolated as precursors for the obtaining of zinc aluminate and chromium-substituted zinc aluminate. These coordination compounds were characterized by elemental chemical analysis, infrared (IR) and ultraviolet visible (UV-Vis) spectroscopy, and thermal analysis. The influence of Cr 3+ substitution on the structure, morphology and optical properties of the synthesized mixed oxides was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), infrared, Raman and UV-Vis spectroscopy, and nitrogen adsorption – desorption analysis. The XRD patterns and Raman spectra confirmed the formation of spinel structure. The mean crystallite size varied from 18 to 22 nm. SEM and EDS showed uniform composition and microstructure of the ZnAl 2-x Cr x O 4 nanocrystalline powders. The values of the optical energy bandgap for the samples were found to be in the 3.92 – 2.85 eV range. The photocatalytic performance in the degradation reaction of Eosin Y (EY) under visible light irradiation was evaluated. The Eosin Y degradation efficiency values were obtained between 48 and 80% after 75 min. The best photocatalytic result was obtained for the sample with the highest amount of chromium.

Deep precision machining of SiC ceramics by picosecond laser ablation

Silicon carbide (SiC) ceramic is becoming widely used in multiple industrial applications, owing to its exceptional high-temperature properties. Yet it is still a challenge to machine SiC using traditional means without causing damage due to its high hardness and brittleness. In this study, a subtractive manufacturing technique based on the use of a fiber picosecond laser was employed to remove material from the reaction bonded SiC surface or create micro-patterns with the minimum damage to the surface, maximum surface quality and precision. Multiple laser processing parameters were investigated with the purpose of obtaining deep high-quality cuts with the minimum surface roughness and the minimum amount of the re-deposited material. The heat affected zone was analyzed by grazing angle X-ray diffractometry, cross-sectional scanning electron microscopy, energy dispersive and micro Raman spectroscopy techniques. The cut shape, depth, surface roughness as well as the kerf width and re-deposition height were assessed using a 3D laser scanning microscopy. The optimum values were established for the focal position, the laser power, linear speed, wobble frequency, wobble pattern, and number of passes. This study also identified the processing parameters for shallow and deep high-precision SiC cutting at a material removal rate of ∼2 mm3/min. The work demonstrated that the developed laser machining process is an efficient subtractive manufacturing tool that can be integrated into the automated precision cutting systems for machining hard ceramic materials such as SiC and alumina.