Nitride Surface Research Articles

High-rate etching of silicon oxide and nitride using narrow-gap high-pressure (3.3 kPa) hydrogen plasma

We investigated the etching behavior of silicon oxide (SiO x ) and silicon nitride (SiN x ) in narrow-gap, high-pressure (3.3 kPa) hydrogen (H2) plasma under various etching conditions. Maximum etching rates of 940 and 240 nm min−1 for SiO x and SiN x , respectively, were obtained by optimizing the H2 gas flow rate. The dependence of the etching rate on gas flow rate implied that effective elimination of etching products is important for achieving high etching rates because it prevents redeposition. The sample surfaces, especially the oxide surfaces, were roughened and contained numerous asperities after etching. Etching rates of both SiO x and SiN x decreased as the temperature was raised. This suggests that atomic H adsorption, rather than H-ion bombardment, is an important step in the etching process. X-ray photoelectron spectroscopy revealed that the etched nitride surface was enriched in silicon (Si), suggesting that the rate-limiting process in high-pressure H2 plasma etching is Si etching rather than nitrogen abstraction. The etching rate of SiO x was three times higher than that of SiN x despite the higher stability of Si–O bonds than Si–N ones. One reason for the etching difference may be the difference between the bond densities of SiO x and SiN x . This study presents a relatively non-toxic, low-cost, and eco-friendly dry etching process for Si-based dielectrics using only H2 gas in comparison with the conventional F-based plasma etching methods.

A synergistic strategy for the removal and secondary utilization of Cu(II) organic complexes in wastewater for the efficient degradation of tetracycline

Heavy metals in industries such as electroplating plants and semiconductor industries usually exist in the form of heavy metal organic complexes, and the removal of heavy metal organic complexes is troubled by the difficulty of decomplexation as well as the complexity of the treatment process of the free heavy metal ions after decomplexation. In this study, we proposed a synergistic strategy for the removal and secondary utilization of Cu(II) organic complexes (Cu-EDTA) in wastewater through mixed pyrolysis of carbon nitride precursor and Cu-EDTA, and the resulted product was used for the efficient degradation of tetracycline (TC). The unique electronic structure of carbon nitride and abundant surface defects anchor Cu during pyrolysis, which effectively realizes the removal of Cu-EDTA from wastewater. In addition, the Cu and O co-doped carbon nitride (Cu/O-CN) catalyst constructed by this strategy was proved to be effective in peroxydisulfate activation TC degradation, with a removal efficiency of 91.5% in 20 min, a degradation rate of 0.1643 min−1, and a TOC removal efficiency of 53%. X-ray Photoelectron Spectroscopy (XPS) and density functional theory (DFT) calculation revealed Cu+ active center constructed by the strong metal support interaction between Cu and carbon nitride in Cu/O-CN and the 1O2 dominated nonradical degradation pathways of TC. This study demonstrated a synergistic strategy for the efficient removal and secondary utilization of Cu-EDTA in wastewater, providing new insights into the use of environmentally friendly and cost-effective methods for the removal and recovery of heavy metal organic complexes from wastewater.

Surface Modification of 42CrMo Steels: A Review from Wear and Corrosion Resistance

This work reviews surface modification techniques for improving the wear and corrosion resistance of 42CrMo steel. The advantages and disadvantages of various methods, including thermal spraying, deposition, hardfacing, laser cladding, nitriding, and laser surface treatment, are discussed. The review elaborates on the materials commonly employed in laser cladding technology, including iron-based, cobalt-based, nickel-based, and high-entropy alloys and reinforced composite coatings. Furthermore, the mechanisms and methods of improving the wear and corrosion resistance of 42CrMo steel are summarized. Finally, this review presents research shortcomings and future opportunities of surface modification techniques. This review also provides a theoretical guide for the application of 42CrMo steel.

Flexible phase change materials based on hexagonal boron nitride (hBN) surface modification and styrene-butadiene-styrene (SBS)/low-density polyethylene (LDPE) crosslinking for battery thermal management applications

In battery thermal management (BTM), flexible phase change materials (FPCMs) emerge as highly promising substances, owing to their simple installment and low contact thermal resistance. However, FPCMs based on high thermal conductivity fillers and polymers always suffer from the enduring challenges of poor high-temperature resistance and poor filler-matrix compatibility. To solve these problems, a novel strategy is reported in this work, wherein FPCMs with excellent filler-matrix compatibility and satisfactory high-temperature resistance are synthesized by two steps: functionalizing the hexagonal boron nitride (hBN) surface and inducing the inter crosslinking between Styrene-Butadiene-Styrene(SBS) and Low-density polyethylene(LDPE). Vinyltrimethoxysilane (VTMS) molecules were introduced on the surface of raw hBN by hydroxylation and silanization surface modification to improve the compatibility of hBN with the matrix. Concluding from the results, the addition of 6.7 wt% LDPE doubled the high-temperature resistance of FPCMs, enabling them to maintain their structural integrity even at 200 °C for 1 h. The prepared FPCMs also exhibited higher thermal conductivity (increased by 20.5 %), low leakage rate (<0.6 wt% after 70 heating–cooling cycles), high enthalpy (122 J g−1), and strong adhesion (>0.1 MPa), etc. In terms of BTM performance, the FPCMs-based passive cooling BTM presents remarkable temperature control capabilities (maximum temperature reduction by 16.3 ℃) and uniform temperature performance (maximum temperature difference < 2.5 ℃). Collectively, this work will provide a promising approach for the fabrication of high-performance FPCMs in BTM and other thermal management applications for electronic devices.

Role of Surface Chemistry of Ta Metal Foil on the Growth of GaN Nanorods by Laser Molecular Beam Epitaxy and Their Field Emission Characteristics.

This study investigates the influence of surface nitridation of Ta metal foil substrates on the growth of GaN nanorods using the laser molecular beam epitaxy (LMBE) technique and the field emission characteristics of the grown GaN nanorod ensemble. Surface morphology examinations underscore the pivotal role of Ta foil nitridation in shaping the dimensions and densities of GaN nanorods. Bare Ta foil fosters the formation of high-density, vertically self-aligned GaN nanorods at a growth temperature of 700 °C. Furthermore, the density of these nanorods is directly related to the duration of Ta foil nitridation, with increased duration leading to a reduced nanorod density. X-ray Photoelectron Spectroscopy (XPS) studies reveal that the transition of the Ta foil surface from tantalum oxide to tantalum nitride during nitridation emerges as a crucial factor influencing GaN nanorod growth. Photoluminescence (PL) spectroscopy at ambient temperature reveals a strong near-band-edge (NBE) emission peak with negligible defect-related peaks, displaying the high optical quality of the GaN nanorods. The highly dense vertically aligned GaN nanorod ensemble growth without Ta prenitridation exhibits the most favorable field emission performance, featuring a turn-on field of 2.1 V/μm, a field enhancement factor of 2480, and a stable long-term operation at the emission current density of 2.26 mA/cm2. This study advances the understanding of the role of the surface chemistry of metal foil in determining GaN nanorod growth and opens up exciting possibilities for tailoring advanced optoelectronic devices for specific application requirements.

Surface Reconstruction on Metal Nitride during Photo-oxidation.

The efficient conversion and storage of solar energy for chemical fuel production presents a challenge in sustainable energy technologies. Metal nitrides (MNs) possess unique structures that make them multi-functional catalysts for water splitting. However, the thermodynamic instability of MNs often results in the formation of surface oxide layers and ambiguous reaction mechanisms. Herein, we present on the photo-induced reconstruction of a Mo-rich@Co-rich bi-layer on ternary cobalt-molybdenum nitride (Co3 Mo3 N) surfaces, resulting in improved effectiveness for solar water splitting. During a photo-oxidation process, the uniform initial surface oxide layer is reconstructed into an amorphous Co-rich oxide surface layer and a subsurface Mo-N layer. The Co-rich outer layer provides active sites for photocatalytic oxygen evolution reaction (POER), while the Mo-rich sublayer promotes charge transfer and enhances the oxidation resistance of Co3 Mo3 N. Additionally, the surface reconstruction yields a shortened Co-Mo bond length, weakening the adsorption of hydrogen and resulting in improved performance for both photocatalytic hydrogen evolution reaction (PHER) and POER. This work provides insight into the surface structure-to-activity relationships of MNs in solar energy conversion, and is expected to have significant implications for the design of metal nitride-based catalysts in sustainable energy technologies.

Novel high-efficiency plasma nitriding process utilizing a high power impulse magnetron sputtering discharge

Lifetime and biocompatibility of orthopedic implants are crucial in meeting the new challenges brought about by the fall in the patient age and the aging population. The high-load surfaces in contact with the biological environment must display enhanced tribological properties, biocompatibility, and reduced metal ion release in long-term clinical performance. Surface modification techniques such as nitriding can significantly improve the in-service behavior of the medical-grade alloys in current use. We report on a novel approach for nitriding of CoCrMo alloys using high power impulse magnetron sputtering (HIPIMS) discharge. The new nitriding process has been successfully carried out at the National HIPIMS Technology Centre at Sheffield Hallam University, UK, in an industrial size Hauzer 1000-4 system enabled with HIPIMS technology. While the nitriding ion flux is controlled by the HIPIMS magnetron plasma source, the ion energy can be independently set via the substrate bias. Implementing the HIPIMS source allows reducing the operational pressure by one order of magnitude compared to conventional dc plasma nitriding (DCPN). Plasma analyses have identified significantly enhanced production of ions of molecular nitrogen (N2+), atomic nitrogen (N+), and N2H+ radicals in the HIPIMS discharge compared to DCPN. Because of the low pressure of operation of the HIPIMS process, the energy of ions is similar to the bias voltage, whereas the high pressures used in DCPN cause severe losses in ion energy due to scattering collisions within the sheath. The high flux and high ion energy are primarily responsible for achieving a fourfold increase in process productivity as compared to state-of-the-art plasma nitriding processes. The nitrided surface layers exhibit excellent mechanical and tribological properties, which bring about significant improvements in hardness, fracture toughness, and wear. The protective function of the nitrided layer against corrosion in the aggressive environments of simulated body fluid is remarkably augmented. The barrier properties of the nitrided layer have been demonstrated through a reduction in metal ion release by as much as a factor of 2, 4, and 10 for Co, Cr, and Mo, respectively.

Tribocorrosion assessment of low-temperature plasma nitrided super duplex stainless steel

The tribocorrosion of low-temperature plasma nitrided UNS S32750 super duplex stainless steel was investigated according to procedures for passivating materials. Nitrided and non-treated samples were compared through two reciprocating sliding tests in NaCl solution: the continuous test, without significant passive layer growth, and the intermittent one, with repassivation. Open circuit potential and linear polarization resistance (LPR) characterized the electrochemical response. LPR was successfully introduced to evaluate the polarization resistance evolution during the continuous test. Corrosion and mechanical wear components were quantified. The mechanical wear dominated, and nitrided samples showed lower wear volume loss. After the intermittent test, their values were further reduced. Such improvement was explained by the higher load bearing capacity and repassivation ability of the nitrided surfaces.

Mechanically tailored surface of titanium based alloy (Ti6Al4V) by laser surface treatment

In this study, laser surface treatment (LST) of Ti6Al4V carried out by melting within a narrow regime of optimum process parameters for the formation of a surface with improved wear and tribo-corrosion resistance is presented. The effect of applied power and shrouding gas on the microstructure, phase, surface hardness, residual stress, dry wear (against tungsten carbide, WC) and tribocorrosion resistance (against ZrO2 in Hank's solution) is established. LST in argon atmosphere leads to the formation of a composite structure consisting of acicular α’ martensite and α. LST in nitrogen atmosphere causes the formation of titanium nitride (TiN and Ti2N) dispersed in α matrix. Due to LST, there is an increase in surface microhardness both under argon (435–630 VHN) and nitrogen atmosphere (839–1327 VHN) when compared to untreated Ti6Al4V (278 VHN). There is a marginal decrease in wear rate (against WC ball) due to laser surface melting (5.17–5.81 × 10−3 mm3/Nm) under argon and a substantial decrease in wear rate when melting was conducted under nitrogen atmosphere (1.91–4.94 × 10−3 mm3/Nm) as compared to Ti6Al4V (5.93 × 10−3 mm3/Nm). The mechanism of wear is established. On the other hand, the tribo-corrosion rate is found to decrease for laser surface melting (3.5–4.8 × 10−3 mm3/Nm) and nitriding (1.3–3.2 × 10−3 mm3/Nm) as compared to Ti6Al4V (5.7 × 10−3 mm3/Nm). Bioactivity in terms of calcium phosphate deposition followed by dipping in Hank's solution was found to increase due to both melting and nitriding, though nitriding offered a marginally higher bioactivity than only melting.

In-situ formation of ultra-hard titanium-based composite coatings on carbon steel through electro-spark deposition in different gas media

In the current study, ultra-hard TiC, TiN, and Ti(C,N) layers were in-situ formed on carbon steel substrate using pure titanium electrode via electro-spark deposition (ESD) in argon, nitrogen, argon/nitrogen, and air atmospheres. The synthesized coatings were characterized using various techniques, including FE-SEM/EDS, X-ray diffractometry, Raman spectroscopy, microhardness and nanoindentation tests, and surface roughness measurement. Also, a thermodynamic simulation was executed to estimate the phase-stability. Fe5C2, TiN, Fe3N, and Ti2O3 were determined as the major phases formed under the argon, nitrogen, Ar/N2, and air atmospheres, respectively. The formation of martensite at the interface of the coating and substrate in all atmospheres indicates the capability of the ESD process for surface hardening. The observed discrepancies between the empirically formed phases and the thermodynamics prediction can be related to the non-equilibrium conditions of the ESD process. It was revealed that gaseous media such as argon and nitrogen serve as a protective/active environment in the titanium/steel system. It is proposed that the electro-sparking of titanium under the active nitrogen medium follows an avalanche plasma regime. Under the argon flow, FeTi intermetallic layer is formed. Whilst, electro-sparking in ambient air leads to the formation of various Fe-Ti-O compounds, as well as different TiOn oxides. On the other hand, the utilization of nitrogen gas during the ESD increases the surface roughness and the thickness of the coating, rather than the deposition under the argon flow, due to the extra heat of reactions. The dynamic reactions occur between pure titanium, nitrogen, carbon, and oxygen, leading to the initial formation of Ti(C,N) at the top surface, followed by the production of titanium oxides in the middle layer. The coexistence of the super-hard Ti(C,N) with a hardness of 3130 HV at the top surface and titanium nitrides beneath it in a gradient mode effectively impedes the crack propagation.

Effect of process parameters on the growth and wear resistance of CrAlN coating on silicon nitride surface

PurposePreparing CrAlN coatings on the surface of silicon nitride bearings can improve their service life in oil-free lubrication. This paper aims to match the optimal process parameters for preparing CrAlN coatings on silicon nitride surfaces, and reveal the microscopic mechanism of process parameter influence on coating wear resistance.Design/methodology/approachThis study used molecular dynamics to analyze how process parameters affected the nucleation density, micromorphology, densification and internal stress of CrAlN coatings. An orthogonal test method was used to examine how deposition time, substrate temperature, nitrogen-argon flow rate and sputtering power impacted the wear resistance of CrAlN coatings under dry friction conditions.FindingsNucleation density, micromorphology, densification and internal stress have a significant influence on the surface morphology and wear resistance of CrAlN coatings. The process parameters for better wear resistance of the CrAlN coatings were at a deposition time of 120 min, a substrate temperature of 573 K, a nitrogen-argon flow rate of 1:1 and a sputtering power of 160 W.Originality/valueSimulation analysis and experimental results of this paper can provide data to assist in setting process parameters for applying CrAlN coatings to silicon nitride bearings.

A Comparison Study on the Microstructure, Mechanical Features, and Tribological Characteristics of TiN Coatings on Ti6Al4V Using Different Deposition Techniques

Titanium alloys are considered lightweight alloys and are widely applied across various industries. However, their low hardness, poor wear resistance, and limited oxidation resistance restrict their prospects for wider application. In this paper, nitride coatings were prepared using three preparation processes, namely laser surface nitriding (LSN), physical vapor deposition (PVD), and plasma ion implantation (PII). Their microstructure, microhardness, tribological behavior, and high-temperature oxidation characteristics were compared. The experimental results revealed that nitrided coatings were successfully prepared using the three methods. However, a comparison of these data shows that the LSN coating exhibited superior comprehensive performance. It achieved the maximum thickness within the shortest preparation time: the thickness was about 280 μm and the deposition rate of the LSN method was 2250 and 90,000 times higher than those of the PVD and PII methods. Nitrides have high hardness, but the carrying capacity could be attributed to the thickness of the coatings: the PVD coating could withstand a force of 500 g, while the PII coating only withstood a force of less than 25 g. In addition, as hardness is the most important factor for excellent wear resistance, the average volumetric wear rate of the LSN and PVD coatings was about 9 × 10−6 mm3/m·N, and their relative wear resistance was 49.2 times that of Ti6Al4V. Meanwhile, the excellent bond between the LSN coating and the substrate was evidenced by a high-temperature oxidation test during a rapid heating–cooling cycle.

Four‐Dimensional Design Space of High‐Q Second‐Order Distributed Feedback Perovskite Lasers

AbstractSecond‐order distributed feedback (DFB) resonators are widely used for thin‐film lasers as they combine low lasing thresholds with ease of manufacturing. Here, the grating design parameters are varied to map the lasing characteristics of lead halide perovskite films deposited on a single substrate that contains hundreds of high‐quality silicon nitride surface gratings. The lowest lasing threshold (≈130 µJ cm−2) is identified through the aid of near‐field and far‐field imaging spectroscopy in a four‐dimensional design space composed of grating period, duty cycle, active layer thickness, and cavity length. Moreover, it is shown that antisymmetric modes support high‐quality lasing (Q up to ≈10800) in the second‐order DFBs. The multi‐dimensional experimental analysis is accompanied by a thorough theoretical study with a semi‐empirical model based on coupled wave equations, which is used to investigate the lasing characteristics beyond the manufacturing range. The results can be applied to a broad range of thin‐film DFB resonators, enabling the design of more complex laser stack configurations including light‐emitting devices for current‐injection lasing.

Influence of screen height and bias voltage on the active screen plasma nitriding of shot-peened Ti-6Al-4V titanium alloy

The effects of screen height and bias voltage on the active screen plasma nitriding (ASPN) of Ti-6Al-4V titanium alloy were investigated in this paper. Before nitriding, the Ti-6Al-4V alloy was pretreated by shot peening to allow the ASPN performed at a low temperature of 500 °C. The ASPN process variables concerned in this paper included screen height (20 and 100 mm) and bias voltage (0, 400 and 1100 V). The results show that the increase in active screen height effectively increased the yield of nitride particles transferred to the specimen surface by expanding the screen sputtering area and promoted the thickening of the nitrided layer. When the bias voltage increased from 0 V to 1100 V, the nitrided layer thickness and surface hardness of the nitrided Ti-6Al-4V showed a tendency of increasing first and then decreasing. Among the three selected bias voltages (0 V, 400 V, 1100 V), the thickest and hardest nitrided layer was obtained at 400 V, which balanced better between the deposition of nitride particles and the sputtering thinning of the nitrided layer. Meanwhile, the thickness and hardness of the nitrided layer on the shot-peened Ti-6Al-4V specimens were greatly improved compared to the original specimen. The thickest (5.30 μm) and hardest (1672 HV) nitrided layer was obtained on the shot-peened specimen at ASPN 500 °C–20 h with a bias voltage of 400 V and a screen height of 100 mm.

High-yield synthesis of hydroxylated boron nitride nanosheets and their utilization in thermally conductive polymeric nanocomposites.

Hexagonal boron nitride nanosheets (BNNSs) possess remarkable potential for various applications due to their unprecedented properties. However, the scalable production of BNNSs with both expansive surface and high solubility continues to present a significant challenge. Herein, we propose an innovative and efficient two-step method for manufacturing hydroxyl-functionalized BNNSs (OH-BNNSs). Initially, hydroxyl groups are covalently attached to bulk hexagonal boron nitride (h-BN) surfaces through H2O2 treatment. Then, the hydroxyl-functionalized h-BN undergoes exfoliation on account of a sudden increase in interlayer gas pressure generated by the vigorous decomposition of H2O2 in alkali solutions, resulting in the creation of OH-BNNSs. This approach produces relatively large flakes with an average dimension of 1.65 μm and a high yield of 45.2%. The resultant OH-BNNSs exhibit remarkable stability and dispersibility in a range of solvents. Their integration into thermoplastic polyurethane (TPU) significantly enhances both thermal conductivity and stability, attributed to the excellent compatibility with the resin matrix. This study represents a significant advancement in the functionalization and exfoliation of h-BN, opening new avenues for its promising applications in polymer composites.

Improving surface hardness of AISI 1045 steels using melamine derived from urea

ABSTRACT AISI 1045 steels are medium carbon steels used in applications that require greater strength and hardness such as gears, railway wheels and tracks, crankshafts, rolls, axles and other structural components. Although AISI 1045 steels are highly demanded engineering materials, they suffer from deformation and wear resistance when these applications are used. The hardness and wear resistance of the material are improved using a surface hardening method. Pack nitriding is the cheapest and easiest method of surface hardening method implemented in this work. The surface hardness of AISI 1045 steel is improved by the diffusion of nitrogen from the nitrogen-bearing material (melamine) to the surface of the steel and forms a metal nitride compound, which has strong hardness and wear resistance. This work reports that substantial surface hardening of AISI 1045 steel was achieved by the pack nitriding method using melamine obtained by in situ reaction of urea. The surface hardness increases manifold with the amount of melamine used, soaking time and temperature. The microscopic investigations of the nitrided surfaces of the metal show the formation of two distinct layers. The microstructural properties and hardness of the samples before and after nitriding were thoroughly investigated and interpreted.

Optimization and Mechanism of SiO2-Based Slurry Components for Atomically Smooth Gallium Nitride Surface Obtained Using Chemical Mechanical Polishing Technique

With the ongoing progress of mobile communication and new energy technologies, the market interest in high-frequency and high-power semiconductor devices has risen. Gallium nitride (GaN), a wide bandgap semiconductor material, has become a popular area of research in relevant fields. A sufficiently flat material surface can significantly enhance the device’s performance. Therefore, this paper explores the effect of oxidants on the quality of GaN surface during chemical mechanical polishing (CMP). Atomic force microscopy (AFM) was employed to examine the surface morphology of GaN after each CMP experiment. The aim was to evaluate the effect of specific slurry components on GaN surface quality. The results revealed that the introduction of oxidizers, particularly the potent oxidizer potassium persulfate (K2S2O8), was advantageous in reducing the surface roughness Sq and thus, enhancing the surface quality of GaN. The surface roughness (Sq) of GaN was reduced from 7.7 nm to 0.78 nm after the CMP process with the optimal components. AFM tests were conducted on different areas of the GaN surface within a range of 1 μm2, which revealed that clear images of the GaN atomic steps can be obtained, and the Sq can reach as low as 0.26 nm.

Self-brushing for nanopatterning: achieving perpendicular domain orientation in block copolymer thin films.

The self-assembly of thin films of block copolymers (BCPs) with perpendicular domain orientation offers a promising approach for nanopatterning on a variety of substrates, which is required by advanced applications such as ultrasmall transistors in integrated circuits, nanopatterned materials for tissue engineering, and electrocatalysts for fuel cell applications. In this study, we created BCPs with an A-b-(B-r-C) architecture that have blocks with equal surface energy (γair) and that can bind to the substrate, effectively creating a non-preferential substrate coating via self-brushing that enables the formation of through-film perpendicular domains in thin films of BCPs. We employed a thiol-epoxy click reaction to functionalize polystyrene-block-poly(glycidyl methacrylate) with a pair of thiols to generate an A-b-(B-r-C) BCP and tune γair of the B-r-C block. The secondary hydroxyl and thiol ether functionality generated by the click reaction was utilized to bind the BCP to the substrates. Scanning electron microscopy revealed that perpendicular orientation was achieved by simply annealing a thin film of the BCP on the bare substrate without the usual extra step of coating a random copolymer brush on the substrate. The self-brushing capability of the BCP was also examined on gold, platinum, titanium, aluminum nitride, and silicon nitride surfaces. These results demonstrate that self-brushing is a promising approach for achieving perpendicular domain orientation in thin films of BCP for nanopatterning on a variety of useful surfaces.

APPLICATION OF A NON-SELF-SUSTAINED GLOW DISCHARGE INITIATED BY A FOCUSED ELECTRON BEAM IN THE FOREVACUUM PRESSURE REGION FOR NITRIDING THE INNER SURFACE OF NARROW METAL TUBES

We have explored some of the features of ion-plasma nitriding the inner surface of narrow extended metal tubes by the plasma of a non-self-sustained glow discharge initiated by a focused electron beam in the forevacuum pressure range. The influence of electron beam current on the discharge parameters was determined. We found a non-monotonic dependence of plasma density, nitrogen content in the nitrided surface layer, and layer microhardness on discharge burning voltage. The microhardness of the inner surface of the nitrided tubes reaches values of 1500 kgf/mm&lt;sup&gt;2&lt;/sup&gt; for AISI 321 stainless steel and 700 kgf/mm&lt;sup&gt;2&lt;/sup&gt; for alloy carbon steel AISI 5135.

From microkinetic model to process: understanding the role of the boron nitride surface and gas phase chemistry in the oxidative dehydrogenation of propane

In the oxidative dehydrogenation of propane over boron nitride, propylene selectivity is lost due to unselective gas-phase chemistry.