Boron Activation Research Articles

Investigation of the Diffusion Rate of Boron Atom in AISI D3 Steel

The present study reports on the kinetics of borided AISI D3 steel. Boriding thermochemical treatment was carried out in a solid medium consisting of B4C, SiC and KBF4 powders mixture at 1123, 1173 and 1223 K for 2, 4 and 6 h, respectively. The boride layer was characterized by optical microscopy, X-ray diffraction technique and micro-Vickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FeB, Fe2B, CrB and Cr2B compounds. The thickness of the boride layer increased with an increase of the boriding time and the temperature. The hardness of the boride compounds formed on the surface of the steels ranged from 1652 to 1984 HV0.05, whereas Vickers hardness values of the untreated the steels was 608 HV0.05. The boron activation energy (Q) was estimated as equal to 174.261 kJ/mol for the borided AISI D3 steel. The growth kinetics of boride layers forming on the borided AISI D3 steel was also analyzed.

Recycling Excessive Alkali from Reductive Soda Ash Roasted Ludwigite Ore: Toward a Zero-Waste Approach

During the soda ash calcining of ludwigite ore, sodium magnesium silicates are generated accompanying the activation of boron. This leads to the excessive consumption of soda ash and in turn enviro...

Mechanical properties and kinetics of boride layers on AISI D2 steel produced by plasma paste boriding

In the present study, the AISI D2 steel has been treated by the plasma paste boriding process using a gas mixture of 70% H2-30% Ar with 70% of borax and 30% SiC. The boriding treatment has been carried out at 700, 750 and 800 °C for an exposure time of 3 to 7 h. The plasma paste borided samples have been investigated by various techniques such as scanning electron microscopy, optical microscopy, XRD analysis, micro-hardness Vickers and the rockwell-C adhesion tests. The fracture toughness has also been measured on the plasma paste borided samples under different values of indentation load. From a kinetic point of view, the boride layers have obeyed the parabolic growth law. The value of boron activation energy for AISI D2 steel has been estimated as 130 kJ mol–1 using our experimental results. In addition, this obtained activation energy has been compared to the literature data.

Annealing of Boron-Doped Hydrogenated Crystalline Silicon Grown at Low Temperature by PECVD.

We investigate low-temperature (<200 °C) plasma-enhanced chemical vapor deposition (PECVD) for the formation of p–n junctions. Compared to the standard diffusion or implantation processes, silicon growth at low temperature by PECVD ensures a lower thermal budget and a better control of the doping profile. We previously demonstrated the successful growth of boron-doped epitaxial silicon layers (p+ epi-Si) at 180 °C. In this paper, we study the activation of boron during annealing via dark conductivity measurements of p+ epi-Si layers grown on silicon-on-insulator (SOI) substrates. Secondary Ion Mass Spectroscopy (SIMS) profiles of the samples, carried out to analyze the elemental composition of the p+ epi-Si layers, showed a high concentration of impurities. Finally, we have characterized the p+ epi-Si layers by low-temperature photoluminescence (PL). Results revealed the presence of a broad defect band around 0.9 eV. In addition, we observed an evolution of the PL spectrum of the sample annealed at 200 °C, suggesting that additional defects might appear upon annealing.

Modeling of the Growth Kinetics of Boride Layers in Powder-Pack Borided ASTM A36 Steel Based on Two Different Approaches

An indispensable tool to choose the suitable process parameters for obtaining boride layer of an adequate thickness is the modeling of the boriding kinetics. In this work, two mathematical approaches were used in order to determine the value of activation energy in the Fe2B layers on ASTM A36 steel during the iron powder-pack boriding in the temperature range of 1123–1273 K for treatment times between 2 and 8 h. The first approach was based on the mass balance equation at the interface (Fe2B/substrate) and the solution of Fick’s second law under steady state (without time dependent). The second approach was based on the same mathematical principles as the first approach for one-dimensional analysis under non-steady-state condition. The measurements of the thickness (Fe2B), for different temperatures of boriding, were used for calculations. As a result, the boron activation energy for the ASTM A36 steel was estimated as 161 kJ·mol−1. This value of energy was compared between both models and with other literature data. The Fe2B layers grown on ASTM A36 steel were characterized by use of the following experimental techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray Spectroscopy (EDS). Finally, the experimental value of Fe2B layer’s thickness obtained at 1123 K with an exposure time of 2.5 h was compared with the predicted thicknesses by using these two approaches. A good concordance was achieved between the experimental data and the simulated results.

Intermolecular Radical Addition to Ketoacids Enabled by Boron Activation

The intermolecular radical addition to the carbonyl group is difficult due to the facile fragmentation of the resulting alkoxyl radical. To date, the intermolecular radical addition to ketones, a valuable approach to construct quaternary carbon centers, remains a formidable synthetic challenge. Here, we report the first visible-light-induced intermolecular alkyl boronic acid addition to α-ketoacids enabled by the Lewis acid activation. The in situ boron complex formation is confirmed by various spectroscopic measurements and mechanistic probing experiments, which facilitates various alkyl boronic acid addition to the carbonyl group and prevents the cleavage of the newly formed C-C bond. Diversely substituted lactates can be synthesized from readily available alkyl boronic acids and ketoacids at room temperature merely under visible light irradiation, without any additional reagent. This boron activation approach can be extended to alkyl dihydropyridines as radical precursors with external boron reagents for primary, secondary, and tertiary alkyl radical additions. The pharmaceutically useful anticholinergic precursors are easily scaled up in multigrams under metal-free conditions in flow reactors.

Measuring the effects of heat treatment on SiC/SiC ceramic matrix composites using Raman spectroscopy

AbstractThe evolution of residual stresses found within a silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite through thermal treatments was investigated using Raman microspectroscopy. Constituent stress states were measured before, during, and after exposures ranging from 900 to 1300°C for varying times between 1 and 60 minutes. Silicon carbide particles in the as‐received condition exhibited average hydrostatic tensile stresses of approximately 300 MPa when measured at room temperature before and after heat treatment. The room temperature Raman profile of the silicon matrix was altered in both shape and location with heat treatment cycles due to increasing activation of boron within the silicon lattice as heat treatment temperatures increased. By accounting for boron activation in the silicon–boron system, little to no permanent change of any constituent stresses were observed, and the silicon matrix subsequently exhibited a complimentary average hydrostatic compressive stress of approximately 300 MPa at room temperature, measured before and after heat treatment. This result builds upon previous literature and offers increased insight into boron activation phenomena measured through Raman spectroscopy methods.

Extraction of Boron from Ludwigite Ore: Mechanism of Soda-Ash Roasting of Lizardite and Szaibelyite

Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, lizardite and szaibelyite were prepared and their soda-ash roasting behaviors were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) analyses, in order to shed light on the soda-ash activation of boron within ludwigite ore. Thermodynamics of Na2CO3-MgSiO3-Mg2SiO4-Mg2B2O5 via FactSage show that the formation of Na2MgSiO4 was preferential for the reaction between Na2CO3 and MgSiO3/Mg2SiO4. While, regarding the reaction between Na2CO3 and Mg2B2O5, the formation of NaBO2 was foremost. Raising temperature was beneficial for the soda-ash roasting of lizardite and szaibelyite. At a temperature lower than the melting of sodium carbonate (851 °C), the soda-ash roasting of szaibelyite was faster than that of lizardite. Moreover, the melting of sodium carbonate accelerated the reaction between lizardite with sodium carbonate.

Investigation of tribological behaviour and diffusion model of Fe2B layer formed by pack-boriding on SAE 1020 steel

In this study, a substitute boriding powder including boric acid as boron source was prepared and employed for boronizing of SAE 1020 steel. The boronizing processes were performed at 850, 900 and 950 °C for 4, 8 and 12 h. The formed boride layers were identified by varied experimental methods such as optical microscope, SEM and WDS analysis. As an outcome of the analyses, the boride layer containing only Fe2B phase with saw-tooth morphology was specified on surface of the samples. A diffusion model was proposed to estimate the coefficients of boron diffusion in the Fe2B layers. The value of boron activation energy for SAE 1020 steel was calculated as 183.14 kJ/mol and the result was contrasted with literature data. As a result of the microhardness measurements, the average hardness value of Fe2B layer was about between 1200 and 2000 HV0.1. The average hardness values of the transition zone and matrix zone were determined to be approximately 160 HV0.1 and 151 HV0.1, respectively. This study mainly concentrates on the tribological properties of borided SAE 1020 steel with using alternative boriding powder. Coefficient of friction graph was drawn for each sample and the wear rates were calculated. It was specified that specific wear rate of borided samples was roughly 47 times lower than that of unborided samples.

Modeling of the Growth Kinetics of Boride Layers during the Diffusion Annealing Process

In the current work, a diffusion model was suggested to estimate the boron activation energies for FeB and Fe2B layers on the gas-borided Armco iron at temperatures of 1073, 1173, and 1273 K for a treatment time varying between 1.33 and 4 h. This model takes into account the effect of boride incubation times during the formation of the FeB and Fe2B phases. The mass balance equations were reformulated to describe the evolution of boride layers after applying the diffusion annealing process. In addition, the time needed to completely dissolve the FeB phase in the boride layer was also predicted. This predicted time was influenced by the boriding parameters during the diffusion annealing process.

Growth kinetics and mechanical characterization of boride layers formed on β-type Ti-45Nb alloy

In this study, β-type Ti-45Nb alloy was borided by solid-state diffusion process in order to achieve a hard and adhered boride layer. Boriding was carried out in a solid medium consisting of amorphous boron, anhydrous borax and active carbon at temperatures between 850 and 1100 °C for time intervals of 3–24 h in order to determine boron diffusion kinetic and to achieve an optimum adhered layer thickness. Microstructure, mechanical properties, adhesion characteristic and growth kinetic of borided layers were investigated in detail by X-ray diffraction, GDOES and SEM-EDS analysis, microhardness and Rockwell-C adhesion tests. A layer consisting of monolithic TiB2·NbB2 phase with the hardness of about 34.3 GPa on the top and TiB whisker with the hardness of about 14.7 GPa beneath it was formed by boriding using optimum processing parameters. A diffusion model based on mass balance equations was used to estimate boron diffusion coefficients and activation energies in the boride layers. Activation energies in TiB2·NbB2 and TiB layers were determined to be 203.96 ± 2.4 kJ/mol and 138.33 ± 24.5 kJ/mol, respectively. Fracture toughness of the borided layer formed at 1000 °C for 24 h was found to be 2.84 ± 0.8 MPa m1/2. Multiple concentric cracks occurred at the peripheral zone of indent by Rockwell-C adhesion test. But no or very limited delamination or spalling occurred due to the result of deeper penetration of TiB whiskers.

Time evolution of boron deactivation with carbon coimplantation in preamorphized silicon

The influence of carbon on the evolution of boron deactivation was experimentally investigated. The peak profiles of implanted boron overlapped that of carbon in preamorphized silicon. Different annealing conditions were applied to modulate the injection of interstitials from end-of-range (EOR) defects to the recrystallized region. Transient enhanced diffusion was evident during rapid thermal annealing (RTA) at 600 °C while significant boron deactivation caused by carbon coimplantation was observed after solid-phase epitaxial regrowth. The degree of boron deactivation is proportional to the implantation doses of carbon and boron, indicating that the pairing of carbon and boron atoms prevents boron activation. However, carbon prevented further deactivation during additional furnace annealing at 750 °C after RTA because carbon blocked the reaction between boron and excess interstitials that were generated from the EOR defects.

Surface characterization and diffusion model of pack borided TB2 titanium alloy

In this work, TB2 alloy was successfully borided by pack boriding at the temperature range of 950–1100 °C for 5, 10, 20 and 30 h. The characteristics of boride layers were examined by X-ray diffraction, scanning electron microscopy, wavelength dispersive spectrometer, microhardness tester and micro vibration friction and wear tester. Based on the diffusion models of d2 = Dt and d = kt0.5, growth kinetics of the boride layers on TB2 alloy were investigated via the thickness of boride layers. There are dual boride layers on the surface of borided TB2 alloy, i.e. the outer TiB2 layer and the inner TiB layer. The microhardness and coefficients of friction (CoF) of borided TB2 alloy at 1100 °C for 30 h can reaches ~ 27.5 GPa and ~ 0.35, respectively. The diffusion model of d = kt0.5 is found to predict the thickness of boride layer more accurately. Therefore, the boron activation energies in TiB layer and TiB2 layer are 96.220 and 158.056 kJ mol−1, respectively. Finally, a comparison between the present boron activation energies and the reported available data was also made.

A Kinetic Model for the Boriding Kinetics of AISI D2 Steel During the Diffusion Annealing Process

In this work, a diffusion model was proposed to estimate the boron activation energies for FeB and Fe2B layers during the pack-boriding of AISI D2 steel at temperatures of 1223, 1253 and 1273 K for a treatment time varying between 2 and 10 h. This model considers the effect of boride incubation times during the formation of the FeB and Fe2B phases. To study the influence of diffusion annealing process on the boriding kinetics of AISI D2 steel, the mass balance equations were modified in order to follow the evolution of boride layers as a function of annealing time for the specified boriding parameters. Finally, the kinetic model was validated by a comparison of the experimental thicknesses of boride layers with the predicted ones at a temperature of 1243 K for 2, 4 and 6 h. A simple equation was then obtained for estimating the total time necessary to get a single boride layer (Fe2B) that depends on the boriding parameters and on the thickness of each boride layer prior to the diffusion annealing process.

Growth of the Fe2B layer on SAE 1020 steel employed a boron source of H3BO3 during the powder-pack boriding method

In this study, an alternative powder-pack boriding mixture containing H3BO3 as boron source was prepared and used for boriding of SAE 1020 steel. The boriding treatment was carried out in the temperature range of 850–950 °C for a treatment time ranging from 4 to 12 h. The generated boride layers were characterized by different experimental techniques such as optical microscope, SEM, XRD analysis and the Daimler-Benz Rockwell C indentation test. The powder-pack boriding mixture was analyzed by TGA and DTA methods and the possible chemical reactions that may be occurred during boriding were investigated. Furthermore, the growth kinetics of the boride layer forming on SAE 1020 steel substrates was investigated. A regression model based on a full factorial design was used to estimate the boride layers' thicknesses as a function of the boriding parameters. A single phase boride layer with saw-tooth morphology was formed on the steel samples. The value of boron activation energy for SAE 1020 steel was estimated as 183.15 kJ/mol. The comparisons were made between the empirical values of the boride layers' thicknesses with estimated ones. The contour diagrams were plotted for estimating the thickness of boride layer as a function of the temperature and time.

Microstructure, Growth Kinetics and Some Mechanical Properties of Boride Layers Produced on Pure Titanium by Molten-Salt Boriding

To modify the surface properties of pure titanium, boride layers had been fabricated by the boron molten-salt diffusion on pure titanium surfaces in the temperature range of 900-1100 °C for 5- to 30-h treatments. The results demonstrated that the boride layers were mainly composed of TiB whiskers and TiB2 layers without the rutile titanium oxide TiO2. Two diffusion models were introduced to model the growth kinetics of boride layers. The parabolic growth constants and the boron diffusion coefficients were obtained. The boron activation energies for TiB2 and TiB were 225.617 and 165.266 kJ mol−1, respectively. The surface microhardness of the borided titanium decreased with the increase in distance from the surface. The results of wear tests indicated that the wear properties had been improved significantly compared to the pure titanium under dry sliding conditions.

Kinetics of the Formation of Boride Layers on EN-GJL-250 Gray Cast Iron

In the present work, the EN-GJL-250 gray cast iron was pack-borided in a powder mixture consisting of 5 % B4C, 5 % NaBF4, and 90 % SiC. The boriding treatment was carried out in the temperature range 900°C–1000°C during 2, 4, and 6 h. The morphology of the generated boride layers was observed by an optical microscope and a scanning electron microscope. The phases in the borided layer were identified by X-ray diffraction (XRD) analysis, and Vickers microhardness testing was used to determine the microhardness profiles along the boride layers. The growth kinetics of boride layers was studied and the mass gain was estimated for the given boriding conditions. The regression model was also used to predict the total boride-layer thickness. As a result, the boron activation energy for EN-GJL-250 gray cast iron was estimated as 134.21 kJ mol−1 and compared with the literature data.

Germanium Junctions for Beyond-Si Node Using Flash Lamp Annealing (FLA)

ABSTRACTWe report on the formation of shallow junctions with high activation in both n+/p and p+/n Ge junctions using ion implantation and Flash Lamp Annealing (FLA). The shallowest junction depths (Xj) formed for the n+/p and p+/n junctions were 7.6 nm and 6.1 nm with sheet resistances (Rs) of 860 ohms/sq. and 704 ohms/sq., respectively. By reducing knocked-on oxygen during ion implantation in the n+/p junctions, Rs was decreased by between 5% and 15%. The lowest Rs observed was 235 ohms/sq. with a junction depth of 21.5 nm. Hall measurements clearly revealed that knocked-on oxygen degraded phosphorus activation (carrier concentration). In the p+/n Ge junctions, we show that ion implantation damage induced high boron activation. Using this technique, Rs can be reduced from 475 ohms/sq. to 349 ohms/sq. These results indicate that the potential for forming ultra-shallow n+/p and p+/n junctions in the nanometer range in Ge devices using FLA is very high, leading to realistic monolithically-integrated Ge CMOS devices that can take us beyond Si technology.

Characterization, Tribological and Mechanical Properties of Plasma Paste Borided AISI 316 Steel

The AISI 316 steel was treated by the plasma paste boriding by using a gas mixture of 70%H2–30%Ar with a boron source of 100% B2O3 in the temperature range of 700–800 °C for 3, 5 and 7 h. The boride layers formed on the samples were observed by scanning electron microscope. The iron borides were also identified by the use of an X-ray microanalyzer, equipped with energy dispersive X-ray spectroscopy. The XRD analysis was carried out to identify the iron and metallic borides present inside the boride layer. Based on the kinetic data, the value of boron activation energy for the AISI 316 steel was estimated as 118.12 kJ mol−1 and compared with the data available in the literature. A regression model based on ANOVA analysis was used to predict the boride layers’ thicknesses depending on the boriding parameters: the treatment time and the boriding temperature. A good correspondence was obtained between the experimental values and those predicted by the regression model. Furthermore, the wear behavior of the sample borided at 750 °C for 5 h was investigated. The significant increase in wear resistance of plasma borided layer was observed in comparison with the untreated AISI 316 steel. The nanomechanical properties of the sample, plasma paste borided at 700 °C for 7 h, were examined using the nanoindenter with a Vickers diamond tip. The load–displacement curves, as well as, Young’s moduli and hardness were shown for the selected measurements. The obtained results depended on the phase composition of the tested area.

Kinetics of boron diffusion and characterization of Fe2B layers on AISI 9840 steel

In this work, the AISI 9840 steel was subjected to the powder-pack boriding in the temperature range of 1123–1273 K for various times ranging from 2 to 8 h. A kinetic model based on the principle of mass conservation at the growing interface was used to estimate the boron diffusion coefficients through the Fe2B layers. The pack-borided samples were experimentally characterized by different techniques such as: Scaning electron microscopy, XRD analysis, Microhardness Vickers testing. The Daimler-Benz Rockwell-C indentation technique was used to assess the adhesion quality of boride coatings on AISI 9840 steel. Finally, the scratch and pin-on-disc tests for wear resistance were respectively performed using an LG Motion Ltd and a CSM tribometer under dry sliding conditions. The boron activation energy for the AISI 9840 steel was estimated as 193.08 kJ /mol by applying the present model. To confirm and extend the validity of the diffusion model, the experimental values of Fe2B layers thicknesses obtained for other boriding conditions were compared with the predicted values.