Search

Aluminium nitride (AlN) materials are widely used in heat-dissipation substrates and electronic device packages. However, the application of aluminium nitride ceramics is hindered by the obvious anisotropy and high brittleness of its crystals, leading to poor material surface integrity and high grinding force. With the rapid development of microelectronics, the requirements for the material's dimensional accuracy, machining efficiency, and surface accuracy are increasing. Therefore, a new machining process is proposed, combining laser and ultrasonic vibration with grinding. The laser–ultrasonic-assisted grinding (LUAG) of aluminium nitride is simulated by molecular dynamics (MD). Meanwhile, the effects of different processing techniques on grinding force, stress distribution, matrix damage mechanism, and subsurface damage depth are systematically investigated and verified by experiments. The results show that laser–ultrasonic-assisted grinding produces 50% lower grinding forces compared to traditional grinding (TG). The microhardness of AlN can reach more than 1200 HV, and the coefficient of friction and wear is reduced by 42.6%. The dislocation lines of the AlN substrate under this process are short but interlaced, making the material prone to phase transformation. Moreover, the subsurface damage depth is low, realising the substrate's material hardening and wear resistance. These studies not only enhance the comprehension of material build-up and stress damage under the synergistic impact of laser, ultrasonic, and abrasive processing but also indicate that the proposed method can facilitate and realise high-performance machining of aluminium nitride substrate surfaces. [ABSTRACT FROM AUTHOR]

In this study, the complex aluminium nitride (AlN) components with performance comparable to those produced by conventional methods were fabricated through an improved additive manufacturing technique. The use of a novel surfactant (KMT3331) improved the dispersion of AlN powder in resin, enhancing the compatibility between the powder and the resin, resulting in a low-viscosity slurry with solid loading exceeding 60 vol.%. This approach improved the density and homogeneity of the green bodies, resulting in dense and microstructurally homogeneous AlN ceramics, as well as reduced the sintering shrinkage and grain size. Finally, by controlling oxygen impurities introduced from the debinding process, complex-shaped AlN ceramics with high thermal conductivity (184.56 ± 2.77 W·m−1·K−1), outstanding mechanical properties (bending strength of 458.09 ± 36.03 MPa, fracture toughness of 3.95 ± 0.26 MPa·m1/2) and high reliability (Weibull modulus of 14.89) were obtained, greatly broadening the prospect of AlN ceramics in advanced thermal management applications.

This study investigates the mechanical properties, surface integrity, and chemical configuration of PVD-coated high-speed steel (HSS) cutting tools, with a particular focus on titanium nitride (TiN) and titanium aluminium nitride (TiAlN) coatings. A range of characterisation methodologies were employed to examine the impact of pre-coating surface conditions on the resulting coatings. This impact includes the effects of gas bubble production and unequal distribution of elements, which are two unwanted occurrences. Notwithstanding these difficulties, coatings applied on surfaces that were highly polished exhibited more consistency in their mechanical and elemental characteristics, with a thickness ranging from 2 to 4 µm. The study of mechanical characteristics confirms a significant increase in hardness, from an initial value of roughly 1000 HV0.5 for untreated tools to 1300 HV0.5 for tools with physical vapour deposition (PVD) coatings. Although PVD coatings produced on an industrial scale might not exceed the quality of coatings manufactured in a laboratory, they do offer substantial enhancements in terms of hardness. This study highlights the significant importance of thorough surface preparation in achieving enhanced coating performance, hence contributing to the efforts to prolong the lifespan of tools and enhance their performance even under demanding operational circumstances. [ABSTRACT FROM AUTHOR]

The field of protective coatings for industrial applications is continuously evolving, driven by a need for materials that offer exceptional hardness, enhanced wear resistance, and low friction coefficients. Conventional methods of coating development, such as physical vapour deposition (PVD) and chemical vapour deposition (CVD), often face challenges like the necessity of vacuum conditions, slow growth rates, and weak substrate adhesion, leading to inadequate interface bonding. This study introduces a novel approach utilising an integrated laser/sol–gel method for synthesising aluminium nitride (AlN) coatings on EN43 mild steel substrates which overcomes these limitations. The technique employs a high-intensity diode laser with optimal power and translation speeds to consolidate a pre-applied thin layer of sol–gel slurry consisting of aluminium hydroxide, graphite, and urea on the substrate. Chemical thermodynamic calculations were used to predict the slurry composition, along with identifying the critical temperature range and the essential enthalpy needed for the synthesis of aluminium nitride. A three-dimensional heat transfer model was developed to predict the important process parameters, such as scanning speed and laser power density, required to achieve the temperature ranges necessary for a successful deposition process. Optical and scanning electron microscopy techniques were used to examine the surface morphology and microstructure of the coating. Elemental energy-dispersive X-ray spectroscopy and an X-ray diffraction analysis confirmed the synthesis of an aluminium nitride coating with a thickness ranging from 4 to 5 µm. Furthermore, the detection of sub-micron crystalline aluminium nitride structures yielding a metal matrix composite interlayer was indicative of strong metallurgical bonding. Microhardness testing indicated a hardness value of approximately 876 HV. The coated samples with the highest quality exhibited a surface roughness, Ra, ranging from 1.8 to 2.1 µm. Additionally, the coatings demonstrated an exceptionally low coefficient of friction, recorded at less than 0.1. These results represent a significant step forward in this field, offering a cost-effective, efficient, and scalable solution for producing high-quality coatings with superior performance characteristics. [ABSTRACT FROM AUTHOR]

A dense and smooth aluminium nitride thin film grown on a silicon (111) substrates using pulsed metal–organic chemical vapor deposition is presented. The influence of the pulsed cycle numbers on the surface morphology and crystalline quality of the aluminium nitride films are discussed in detail. It was found that 70 cycle numbers produced the most optimized aluminium nitride films. Field emission scanning electron microscopy and atomic force microscopy images show a dense and smooth morphology with a root-mean-square-roughness of 2.13 nm. The narrowest FWHM of the X-ray rocking curve for the AlN 0002 and 10–12 reflections are 2756 arcsec and 3450 arcsec, respectively. Furthermore, reciprocal space mapping reveals an in-plane tensile strain of 0.28%, which was induced by the heteroepitaxial growth on the silicon (111) substrate. This work provides an alternative approach to grow aluminium nitride for possible application in optoelectronic and power devices. [ABSTRACT FROM AUTHOR]

In this work, oxide-free AlN coating was fabricated using single-step, large throughput nitrogen-shrouded plasma spraying. Initially, Al/AlN composite feedstock powder was prepared by a ball-milling at a 70:30 wt% ratio to deposit the AlN coating. Microstructural evaluation revealed the formation of dominant c -AlN phase along with minor h -AlN without presence of any oxides or impurities in the coating. Hardness and elastic modulus (E) were observed to be ∼7.2 GPa and ∼280 GPa respectively. Furthermore, an investigation of tribological performance showed the wear rate ∼0.18 × 10−3 mm3/Nm and coefficient of friction (COF) 0.45 ± 0.02. In addition, the corrosion resistance behaviour of AlN coating in 3.5 wt% NaCl shows as low as 2.95 × 10−9 mm/s indicates the extended life of the coated components. Therefore, the fabricated plasma-sprayed AlN coating can be recommended for high-performing wear and anti-corrosive competitor for industrial applications. [ABSTRACT FROM AUTHOR]

Using band-structure calculations within the FLAPW (Full-Potential Linearized Augmented-Plane-Wave) model, information is obtained regarding the energy, charge and spatial characteristics of aluminium nitride and its solid solutions with oxygen and aluminium. As established, the formation of these solutions is accompanied by a reduction in electron density in their interatomic regions. The accompanying decrease in the covalence of interatomic interactions leads to both a reduction in binding energies and an increase in the volumes of elementary cells within the compounds. The transition from aluminium nitride to its energetically 'nearest' oxide is accompanied by a decrease in binding energy by 1.25 eV, which corresponds to over 14.5·103 K on the temperature scale. This correlation underscores the high resistance of aluminium nitride to oxidation processes. The formation of an alloy with aluminium incorporation becomes even less likely due to the larger decrease in binding energy by 2.84 eV. [ABSTRACT FROM AUTHOR]

Cyanogen gas has been reported to be poisonous and poses a great threat to human life when been exposed to its high concentration. Hence, the need to develop sensor materials that have the potential of detecting cyanogen gas is aroused. In this work, using the density functional theory (DFT)-based HSE, M06-2X, PBE0, and ωB97X-D/6-311G + + (d, p) functionals, the adsorption behaviour of cyanogen gas (CNG) on aluminium nitride (ALN), gallium-doped aluminium nitride (Ga@ALN), indium-doped aluminium nitride (In@ALN), and thallium-doped aluminium nitride (Tl@ALN) nanotubes as a sensor material was investigated. The calculation revealed that cyanogen gas was weakly adsorbed in the complex CNG@TlAlN with adsorption energy (− 23.01 kcal/mol), while stronger adsorption were observed for CNG@AlN (− 23.71 kcal/mol), CNG@InAlN (− 23.63 kcal/mol), and CNG@GaAlN (− 23.52 kcal/mol) at PBE0 functional. The HOMO–LUMO analysis calculations revealed that the complex CNG@InAlN (Eg = 0.2993 eV) has the highest conductivity and sensitivity. QTAIM and NCI examination revealed that the hydrogen bonding demonstrated a significant role in the interaction between the cyanogen gas and all the nanotubes. And, that CNG@AlN (− 67.861 kcal/mol) and CNG@InAlN (− 66.767 kcal/mol) have higher binding energy than other complexes. Based on these theoretical findings, it can be concluded that CNG@AlN and CNG@InAlN nanotubes are promising sensor materials for detecting cyanogen gas. [ABSTRACT FROM AUTHOR]

Chromenes belong to a group of heterocyclic compounds that feature a benzopyran ring system with an oxygen atom substitution. These compounds have been found to possess various pharmacological properties, such as anti-inflammatory, antioxidant, and antidiabetic effects. In this study, a novel heterogeneous nanocatalyst, aluminium nitride, was synthesized and characterized using XRD, UV–Vis, FT-IR, SEM, and TEM techniques. The prepared nanocatalyst was then utilized for the synthesis of chromeno[4, 3-b]chromenes under aerobic conditions. Additionally, the potential of aluminium nitride (ALN) nanocage for delivering the important antidiabetic drug, flutamide, was investigated using density functional theory calculations. The results showed that the highest interaction occurred when flutamide approached the Al atom of the fullerene surface from the carbonyl group, as evidenced by the calculated adsorption energies (Eads) of the flutamide onto pristine aluminium nitride. [ABSTRACT FROM AUTHOR]

In this investigation, aluminum alloy (AA2024) composite reinforced with ceramic particulates, namely alumina (Al2O3) and aluminum nitride (AlN), were designed and fabricated through a semi-automatic stir casting route. The ceramics are added complementary (0–4 wt% @ step of 1%), resulting in five composite specimens, namely ON04, ON13, ON22, ON31, and ON40. The composite specimens are then analyzed for their densities, mechanical, and tribological behavior (steady-state sliding wear analysis), adopting ASTM standards. The Taguchi design of experiment technique was adopted for planning test preliminaries and input sliding wear operating parameters (like sliding velocity, sliding distance, normal load, composition, and environment temperature) optimization using ANOVA. Worn surface morphology studies were reported using a scanning electron microscope (SEM) along with energy-dispersive X-ray spectroscopy (EDS) to understand prevalent wear mechanisms in real time. Additionally, a decision-making technique such as the preference selection index (PSI) system was used to analyze the alloy composites ranking. The theoretical densities vary 2.784–2.798 g/cc, while actual densities vary 2.539–2.546 g/cc, and voids fraction vary within the 0.5–9.3 % range. The hardness varies 71.6–85.4 HRB, impact strength varies 54–170 J, and tensile strength varies 190–265 MPa. The ranking orders of the significance of input operating factors are environment temperature > normal load > sliding velocity > reinforcement content > sliding distance. It has been found that the alloy composite sample ON22 with an equal presence of both ceramics exhibits overall optimum mechanical properties as well as superior steady-state behavior, which was consistent with the results of the PSI ranking method. [ABSTRACT FROM AUTHOR]

AlN films are prepared by reactive magnetron sputtering at a floating potential and at the bias –15 V on the substrate. It is found that ion-assisted deposition facilitates the formation of fiber texture AlN (104). This result can be explained by generation of compressive stress in films due to ion bombardment and preferred orientation (104) is favored for stressed films minimizing the elastic strain energy. Ion-assisted deposition provides dense and large-grained structure of AlN films due to high adatom mobility. [ABSTRACT FROM AUTHOR]

Aluminium nitride (AlN) materials are widely used in heat-dissipation substrates and electronic device packages. However, the application of aluminium nitride ceramics is hindered by the obvious anisotropy and high brittleness of its crystals, leading to poor material surface integrity and high grinding force. With the rapid development of microelectronics, the requirements for the material’s dimensional accuracy, machining efficiency, and surface accuracy are increasing. Therefore, a new machining process is proposed, combining laser and ultrasonic vibration with grinding. The laser–ultrasonic-assisted grinding (LUAG) of aluminium nitride is simulated by molecular dynamics (MD). Meanwhile, the effects of different processing techniques on grinding force, stress distribution, matrix damage mechanism, and subsurface damage depth are systematically investigated and verified by experiments. The results show that laser–ultrasonic-assisted grinding produces 50% lower grinding forces compared to traditional grinding (TG). The microhardness of AlN can reach more than 1200 HV, and the coefficient of friction and wear is reduced by 42.6%. The dislocation lines of the AlN substrate under this process are short but interlaced, making the material prone to phase transformation. Moreover, the subsurface damage depth is low, realising the substrate’s material hardening and wear resistance. These studies not only enhance the comprehension of material build-up and stress damage under the synergistic impact of laser, ultrasonic, and abrasive processing but also indicate that the proposed method can facilitate and realise high-performance machining of aluminium nitride substrate surfaces.

Secondary aluminum ash is a byproduct in the aluminum industry that contains valuable components, such as aluminum nitride (AlN) and aluminum oxide (Al2O3). AlN has excellent thermal and electrical properties and is widely used in various applications, making the recovery of AlN from secondary aluminum ash essential for both economic and environmental reasons. In this study, we developed a novel triboelectric separation technique to recover AlN from aluminum ash by investigating the tribocharging characteristics of the main components of secondary aluminum ash, Al2O3 and AlN. We studied the effects of tribocharging ball ratio, friction time, and stirring speed on the tribocharging of pure Al2O3 and AlN, using various materials such as polytef (PTFE), polypropylene (PP), polyvinyl chloride (PVC), copper (Cu), and stainless steel (SS) as tribocharging materials. We also examined the effects of friction medium ball ratio, friction medium material, rotational speed, and voltage on the triboelectric separation process. Our results showed that the charge-to-mass ratio for Al2O3 and AlN was 1.96 and −15.56 nC/g, respectively, the difference is largest, with a PTFE ball, a 1:5 ratio, a stirring speed of 290 n/min, and a tribocharging duration of 30 s. The triboelectric sequence of these friction materials was (+)PTFE, PP, Al2O3, SS, Cu, PVC, and AlN (-). To recover AlN from aluminum ash, PTFE should be chosen as the friction medium, and a friction medium ball ratio of 1:3, rpm rotation speed of 50, and voltage of 40kV should be used, resulting in an AlN grade of 89.25% and a significant increase in the recovery rate of AlN in the positive and negative electrode. Our findings demonstrate the feasibility of effective triboelectric separation of Al2O3 and AlN. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical properties, surface integrity, and chemical configuration of PVD-coated high-speed steel (HSS) cutting tools, with a particular focus on titanium nitride (TiN) and titanium aluminium nitride (TiAlN) coatings. A range of characterisation methodologies were employed to examine the impact of pre-coating surface conditions on the resulting coatings. This impact includes the effects of gas bubble production and unequal distribution of elements, which are two unwanted occurrences. Notwithstanding these difficulties, coatings applied on surfaces that were highly polished exhibited more consistency in their mechanical and elemental characteristics, with a thickness ranging from 2 to 4 µm. The study of mechanical characteristics confirms a significant increase in hardness, from an initial value of roughly 1000 HV0.5 for untreated tools to 1300 HV0.5 for tools with physical vapour deposition (PVD) coatings. Although PVD coatings produced on an industrial scale might not exceed the quality of coatings manufactured in a laboratory, they do offer substantial enhancements in terms of hardness. This study highlights the significant importance of thorough surface preparation in achieving enhanced coating performance, hence contributing to the efforts to prolong the lifespan of tools and enhance their performance even under demanding operational circumstances.

A dense and smooth aluminium nitride thin film grown on a silicon (111) substrates using pulsed metal–organic chemical vapor deposition is presented. The influence of the pulsed cycle numbers on the surface morphology and crystalline quality of the aluminium nitride films are discussed in detail. It was found that 70 cycle numbers produced the most optimized aluminium nitride films. Field emission scanning electron microscopy and atomic force microscopy images show a dense and smooth morphology with a root-mean-square-roughness of 2.13 nm. The narrowest FWHM of the X-ray rocking curve for the AlN 0002 and 10–12 reflections are 2756 arcsec and 3450 arcsec, respectively. Furthermore, reciprocal space mapping reveals an in-plane tensile strain of 0.28%, which was induced by the heteroepitaxial growth on the silicon (111) substrate. This work provides an alternative approach to grow aluminium nitride for possible application in optoelectronic and power devices.

The field of protective coatings for industrial applications is continuously evolving, driven by a need for materials that offer exceptional hardness, enhanced wear resistance, and low friction coefficients. Conventional methods of coating development, such as physical vapour deposition (PVD) and chemical vapour deposition (CVD), often face challenges like the necessity of vacuum conditions, slow growth rates, and weak substrate adhesion, leading to inadequate interface bonding. This study introduces a novel approach utilising an integrated laser/sol–gel method for synthesising aluminium nitride (AlN) coatings on EN43 mild steel substrates which overcomes these limitations. The technique employs a high-intensity diode laser with optimal power and translation speeds to consolidate a pre-applied thin layer of sol–gel slurry consisting of aluminium hydroxide, graphite, and urea on the substrate. Chemical thermodynamic calculations were used to predict the slurry composition, along with identifying the critical temperature range and the essential enthalpy needed for the synthesis of aluminium nitride. A three-dimensional heat transfer model was developed to predict the important process parameters, such as scanning speed and laser power density, required to achieve the temperature ranges necessary for a successful deposition process. Optical and scanning electron microscopy techniques were used to examine the surface morphology and microstructure of the coating. Elemental energy-dispersive X-ray spectroscopy and an X-ray diffraction analysis confirmed the synthesis of an aluminium nitride coating with a thickness ranging from 4 to 5 µm. Furthermore, the detection of sub-micron crystalline aluminium nitride structures yielding a metal matrix composite interlayer was indicative of strong metallurgical bonding. Microhardness testing indicated a hardness value of approximately 876 HV. The coated samples with the highest quality exhibited a surface roughness, Ra, ranging from 1.8 to 2.1 µm. Additionally, the coatings demonstrated an exceptionally low coefficient of friction, recorded at less than 0.1. These results represent a significant step forward in this field, offering a cost-effective, efficient, and scalable solution for producing high-quality coatings with superior performance characteristics.

In recent years, scientists have been actively exploring and expanding biosensor technologies and materials to meet the growing societal demands in healthcare and other fields. This study aims to revolutionize biosensors by using density functional theory (DFT) at the cutting-edge B3LYP-GD3BJ/def2tzsvp level to investigate the sensing capabilities of (Cu, Ni, and Zn) doped on Aluminum nitride (Al12N12) nanostructures. Specifically, we focus on their potential to detect, analyze, and sense the drug flutamide (FLU) efficiently. Through advanced computational techniques, we explore molecular interactions to pave the way for highly effective and versatile biosensors. The adsorption energy values of −38.76 kcal/mol, −39.39 kcal/mol, and −39.37 kcal/mol for FLU@Cu–Al12N12, FLU@Ni–Al12N12, and FLU@Zn–Al12N12, respectively, indicate that FLU chemically adsorbs on the studied nanostructures. The reactivity and conductivity of the system follow a decreasing pattern: FLU@Cu–Al12N12 > FLU@Ni–Al12N12 > FLU@Zn–Al12N12, with a band gap of 0.267 eV, 2.197 eV, and 2.932 eV, respectively. These results suggest that FLU preferably adsorbs on the Al12N12@Cu surface. Natural bond orbital analysis reveals significant transitions in the studied system. Quantum theory of atom in molecule (QTAIM) and Non-covalent interaction (NCI) analysis confirm the nature and strength of interactions. Overall, our findings indicate that the doped surfaces show promise as electronic and biosensor materials for detection of FLU in real-world applications. We encourage experimental researchers to explore the use of (Cu, Ni, and Zn) doped on Aluminum nitride (Al12N12), particularly Al12N12@Cu, for biosensor applications.

Micro-electromechanical system (MEMS) based piezoelectric ultrasonic transducers for acoustic imaging of the surroundings are known as piezoelectric micromachined ultrasonic transducers (PMUTs). This research proposes a structural design of the PMUT with four fixedguided beams. The beam is subjected to lateral loads, with vectors that are perpendicular to the longitudinal axis. This project simulated Piezoelectric Micromachined Ultrasonic Transducer (PMUT) with three different material properties i.e. Aluminium Nitride (AlN), Lead zirconate titanate (PZT) and Zinc Oxide (ZnO). Based on the study, it was found that reducing the beam dimensions and increasing the plate size will result in the first mode frequency reduction from 1.33×107 Hz to 3.74×106 Hz. Other than that, it was found that AlN PMUT experienced the maximum deflection of 6.3413 to 6.3478 µm when the loads applied in the range of 50 to 200 µN/m². When the piezoelectric material changed to PZT, we obtained the maximum deflections of 0.3771 to 0.3786 µm when the same loads range applied to the PMUT. As for the ZnO PMUT, the maximum deflections obtained were in between 0.1702 µm to 0.1772 µm with the loads are maintained as in the loads applied to the AlN and PZT. This study proved the significant impact of altering the structural dimensions and material properties of PMUTs on their operational characteristics, specifically the first mode frequency and deflection behavior. [ABSTRACT FROM AUTHOR]

Understanding and modeling plasma–surface interactions frame a multi-scale as well as multi-physics problem. Scale-bridging machine learning surface surrogate models have been demonstrated to perceive the fundamental atomic fidelity for the physical vapor deposition of pure metals. However, the immense computational cost of the data-generating simulations render a practical application with predictions on relevant timescales impracticable. This issue is resolved in this work for the sputter deposition of AlN in Ar/N2 discharges by developing a scheme that populates the parameter spaces effectively. Hybrid reactive molecular dynamics/time-stamped force-bias Monte Carlo simulations of randomized plasma-surface interactions/diffusion processes are used to setup a physics-separating artificial neural network. The application of this generic machine learning model to a specific experimental reference case study enables the systematic analysis of the particle flux emission as well as underlying system state (e.g. composition, density, point defect structure) evolution within process times of up to 45 min. [ABSTRACT FROM AUTHOR]

Al/AlN/p-Si diode was fabricated via thermal evaporation. The electrical properties of the structure were examined under various temperatures, illuminations, and frequencies. Temperature-dependent electrical properties were investigated using several different methods, which are the Thermionic Emission theory, Norde Function, and Cheung&Cheung Functions. The ideality factor, zero-bias barrier height, and series resistance values obtained from the Current–Voltage-Temperature plot of the diode were compared with each other. It was seen that the values obtained from three different methods were in good agreement with each other. Additionally, current–voltage measurements depending on the illumination intensity showed that the designed structure responds to light. The time-dependent photocurrent of the structure was examined with the switch on and off. The root mean square value for Aluminium nitride interfacial layer was found to be 4 nm from the Atomic Force Microscope measurements. Experimental results revealed that the fabricated structure is a candidate for sensing applications such as temperature or light sensors. [ABSTRACT FROM AUTHOR]

The role of BN, AlN and MnS particles on the degradation in creep life and rupture ductility has been investigated for 9 to 12Cr martensitic steels and 1Cr bainitic steel mainly at 550 to 650 oC. The BN particles form in Gr.92 and Gr.122 during normalising at around 1100 oC. The BN particles have nothing to do with the degradation in creep life. The AlN particles precipitate in the high-Al heats of 12Cr-1Mo-1 W-0.3 V steel during creep, reducing dissolved nitrogen and fine nitrides beneficial for the creep strength and degrading the creep life. The MnS particles have nothing to do with the degradation in creep life of 1Cr-1Mo-0.25 V steel. The BN, AlN and MnS particles are responsible for the degradation in reduction of area of the steels by accelerating the formation of creep voids at interfaces between the particles and alloy matrix. [ABSTRACT FROM AUTHOR]

A high concentration of trimethylamine (TMA) in the body can be converted to trimethylamine N-oxide (TMAO), which is a well-known proatherogenic substance capable of accelerating atherosclerosis disease in humans. Hence, there is a pressing need for the development of fast, accurate and reliable nanomaterials for the detection of TMA. In this study, the interaction of TMA with aluminium nitride nanotube (AlNNT) and gallium-doped aluminium nitride nanotube (AlNGaNT) was investigated using density functional theory at the M06-2X, B3LYP, ωB97XD at 6-311G(d)/6-31G(d) levels of theory. The results of the interaction energy between AlNGaNT and TMA for the 6-31G(d) increased remarkable in the order of M06-2X: −1.57 < B3LYP-D3:1.58 < ωB97XD: 1.89 kcal mol−1, while the 6-311G(d) showed higher interaction energy in the order of B3LYP-D3: −1.96 < M06-2X: −1.99 < ωB97XD: −2.03 kcal mol−1. Generally, the interaction of TMA with AlNNT and AlNGaNT increases the global reactivity parameter. From topological, a strong interaction was observed from −0.010 to −0.050 a.u. for signλ2(r)ρ(r) function and 0.000 to 0.00 to 0.400 for aRDG in TMA/AlNGaNT, where at signλ2(r)ρ(r) more scattered plot was observed between −0.050 to −0.020 a.u. While the small scattered plot was observed for TMA/AlNGaNT at 0.00 to −0.010 a.u. for signλ2(r)ρ(r) and aRDG of 0.00 to 0.400. Therefore, it was proposed that an electrostatic interaction is the mechanism between TMA and the AlNNC, and the strength of the interaction increase with the addition of Ga-atom as in AlNGaNT. [ABSTRACT FROM AUTHOR]

An AA2017-aluminum nitride composite was created through stir casting, and its tribological properties, like hardness and wear rate were examined by varying the aluminum nitride content from 5% to 15%. A numerical model was established to predict the wear rates of aluminum metal matrix composites (MMCs), and the accuracy of the model was confirmed through an analysis of variance (ANOVA). The findings demonstrated that the addition of aluminum nitride to AA2017 resulted in improved mechanical and wear characteristics for the composites. Furthermore, the utilization of sustainable materials and manufacturing techniques underscores the potential for environmentally responsible engineering solutions in material science and manufacturing processes. Aluminum nitride emerged as a critical component in enhancing the wear resistance of the metal matrix composites, contributing to their overall durability and sustainability.

Aluminium nitride (AlN) is an important technical ceramic with outstanding strength and thermal conductivity that has important applications for advanced heat sink materials and as a reinforcement for metal-based composites. In this study, we report a novel, straightforward and low-cost method to prepare AlN powder using a vacuum tube furnace for the direct nitridation of loose aluminium powder at low temperatures (down to 500 ∘ C) under flowing high-purity nitrogen. Small amounts of magnesium powder (1 wt.%), combined with aluminium, promote nitridation. Here, we characterise the effects of time (up to 12 h) and temperature (490 to 560 ∘ C) on nitridation with the aim to establish an effective regimen for the controlled synthesis of an aluminium nitride reinforcement powder for the production of metal matrix composites. The extent of nitridation and the morphology of the reaction products were assessed using scanning electron microscopy and X-ray diffraction analyses. AlN was detected for all nitriding temperatures ≥ 500 ∘ C, with the highest yields of 80% to 85% obtained at 530 ∘ C for times ≥ 1 h. At this temperature, nitridation proceeded rapidly, and there was extensive agglomeration of the reaction products making it difficult to reprocess into powder. At lower temperatures around 510 ∘ C, a relatively high proportion of AlN was attained (>73% after 6 h) while retaining excellent friability so that it could be manually reprocessed to powder. The synthesised reinforcement consisted of micro- or nano-crystalline AlN comingled with metallic aluminium. The ratio of AlN and metallic aluminium can be readily controlled by varying the nitriding temperature. This provides a flexible and accessible method for the production of AlN-reinforcement powders suited to the production of metal matrix composites. [ABSTRACT FROM AUTHOR]

Sensing systems are becoming less and less invasive. In this context, flexible materials offer new opportunities that are impossible to achieve with bulky and rigid chips. Standard silicon sensors cannot be adapted to curved shapes and are susceptible to big deformations, thus discouraging their use in wearable applications. Another step forward toward minimising the impacts of the sensors can be to avoid the use of cables and connectors by exploiting wireless transmissions at ultra-high frequencies (UHFs). Thin-film bulk acoustic wave resonators (FBARs) represent the most promising choice among all of the piezoelectric microelectromechanical system (MEMS) resonators for the climbing of radio frequencies. Accordingly, the fabrication of FBARs on flexible and wearable substrates represents a strategic step toward obtaining a new generation of highly sensitive wireless sensors. In this work, we propose the design and fabrication of a flexible gravimetric sensor based on an FBAR on a polymeric substrate. The resonator presents one of the highest electromechanical coupling factors in the category of flexible AlN-based FBARs, equal to 6%. Moreover, thanks to the polymeric support layer, the presence of membranes can be avoided, which leads to a faster and cheaper fabrication process and higher robustness of the structure. The mass sensitivity of the device was evaluated, obtaining a promising value of 23.31 ppm/pg. We strongly believe that these results can pave the way to a new class of wearable MEMS sensors that exploit ultra-high-frequency (UHF) transmissions. [ABSTRACT FROM AUTHOR]

Microchannel heat sinks (MCHSs) are among the most effective solutions for high-power heating elements; aluminium nitride (AlN) is widely used in various heat sinks owing to its high thermal conductivity. The study aims to investigate the effect of the spoiler column shape, number of rows, and position of the inlet/outlet on the temperature and pressure drop of AlN-based microchannel heat sink using a thermal fluid structure coupling simulation. The results showed that the circular spoiler column had the best dredging effect on the eddy current, which greatly improved the local Nusselt number and heat transfer efficiency. The maximum temperature of the heat sink with circular spoiler columns was 6.53 K lower than that without the spoiler column. The average flow velocity and heat transfer efficiency increased with an increase in the number of spoiler columns and the convective heat transfer area. However, the flow resistance and pressure drop between the inlet and outlet raised. When the inlet and outlet were arranged at the centreline, the flow velocity distribution in the heat sink is more uniform, and the maximum temperature was 160.78 K lower than that on the upper side. Heat transfer experiments were carried out by using three kinds of AlN-based microchannel heat sinks, which was machined by the pickling-assisted laser method. The heat transfer experiments showed that the error between simulation results and test data was less than 0.1%. [ABSTRACT FROM AUTHOR]

In this study, we inspect and analyse the effect of Al implantation into AlN by conducting confocal microscopy on the ion implanted regions, before and after implantation, followed by an annealing step. The independent effect of annealing is studied in an unimplanted control region, which showed that annealing alone does not produce new emitters. Through tracking individual locations in a lithographically patterned sample, we observe that point-like emitters are created in the implanted regions after annealing. The newly created quantum emitters show anti-bunching under ambient conditions and are spectrally similar to the previously discovered emitters in as-grown AlN. [Display omitted] • Aluminium implantation into MOCVD AlN generates single photon emitters after thermal annealing. • The creation of the new emitters is documented through tracking individual locations in a lithographically patterned sample. • Newly created emitters are spectrally comparable to the native emitters previously discovered in AlN. • The emitter creation seems to occur deeper than the created vacancy distribution, which was attributed to Al i diffusion. [ABSTRACT FROM AUTHOR]

The present study deals with the characterization of electrical and rheological behaviour of the Synthetic ester fluid incorporated with various concentration of Aluminium nitride (AlN) nanoparticles. Zeta potential measurement has shown an excellent stability of the ester fluid mixed with the nanoparticle. Corona inception voltage (CIV) measured using ultra-high frequency (UHF) technique and the results confirmed higher discharge resistance for nanofluid dispersed with 0.005% of AlN. Phase resolved partial discharge (PRPD) analysis with higher harmonic voltages has shown increase in pulse magnitude and number of discharges. Dielectric constant and tan $\delta $ measurements have revealed a slight marginal increase in its value with the inclusion of filler. Streaming current magnitude was found to increase with the disc rotational speed, concentration of nanoparticle and ambient temperature. Fluorescence spectroscopy analysis has shown increase in fluorophores intensity with filler dispersion in the ester fluid. Rheological properties of fluids mixed with nanoparticles are inspected with cone plane geometry configuration. Synthetic ester and its nanofluid exhibited Newtonian behavior of flow pattern and are independent of the applied shear rate. An exponential decay of viscosity of nanofluids was observed with temperature and it follows an Arrhenius law. The calculated activation energy has increased with the incorporation of filler concentrations. The complex modulus of AlN nanofluids was observed alongside exhibiting the viscous behavior where the loss modulus $\text{G}''$ is much larger than the storage modulus $\text{G}'$ , with the applied frequency.

In this paper, a novel vertically arranged double-electrodes A0 mode Lamb-wave AlN resonator on SOI substrate with a high electromechanical coupling coefficient and high figure of merit (FOM) is reported. The AlN resonator has a sandwich structure with aluminum and N-type doped silicon as electrode layers and a 500 nm thick AlN film as piezoelectric layer. The resonator has only two electrodes vertically arranged rather than horizontal interdigitated (IDT) electrodes which is common in conventional Lamb-wave resonators. The electrode gaps for the vertically arranged double-electrodes resonators are defined by AlN layer thickness rather than by photolithography for lateral field excitation resonators, which results in higher electric field strength and higher electromechanical coupling efficient ( k t 2 ). Compared with conventional thickness field excitation (TFE) resonators with floating bottom electrodes, the vertically arranged double-electrodes resonators have higher electric field strength as the potential difference is larger between the top electrode and bottom electrode than that between the IDT electrodes and floating electrode. As a result, a higher electromechanical coupling coefficient is achieved. Furthermore, the resonant frequency of the vertically arranged double-electrodes resonator presented in this work can be defined by photolithography by controlling the width of the silicon layer. The k t 2 of the vertically arranged double-electrodes resonator calculated from the measurement results of admittance versus frequency by numerically fitting with the Butterworth Van Dyke model shows an increase by 3.85 times, from 0.073% to 0.281% compared with conventional TFE resonators, and the FOM also increases by three times, from 2.66 to 7.99. This work provides a new structure to design future AlN Lamb-wave resonators on SOI substrate. [ABSTRACT FROM AUTHOR]

High-quality factor (Q m ) mechanical resonators are crucial for applications where low noise and long coherence time are required, as mirror suspensions, quantum cavity optomechanical devices, or nanomechanical sensors. Tensile strain in the material enables the use of dissipation dilution and strain engineering techniques, which increase the mechanical quality factor. These techniques have been employed for high-Q m mechanical resonators made from amorphous materials and, recently, from crystalline materials such as InGaP, SiC, and Si. A strained crystalline film exhibiting substantial piezoelectricity expands the capability of high-Q m nanomechanical resonators to directly utilize electronic degrees of freedom. In this work, nanomechanical resonators with Q m up to 2.9 × 10 7 made from tensile-strained 290 nm-thick AlN are realized. AlN is an epitaxially-grown crystalline material offering strong piezoelectricity. Nanomechanical resonators that exploit dissipation dilution and strain engineering to reach a Q m × f m -product approaching 10 13 Hz at room temperature are demonstrated. A novel resonator geometry is realized, triangline, whose shape follows the Al-N bonds and offers a central pad patterned with a photonic crystal. This allows to reach an optical reflectivity above 80% for efficient coupling to out-of-plane light. The presented results pave the way for quantum optoelectromechanical devices at room temperature based on tensile-strained AlN., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

The effective cross-plane thermal conductivity of AlN thin films is studied using 3ω method. AlN films 1-3 µm thick are synthesized on single-crystal Si and Al substrates without heating in a hybrid helicon-arc ion-plasma reactor with a helicon plasma source and plasma-arc accelerators combined in one process chamber. The resulting films at the interface with the substrate had a thin layer of disordered AlN about 200 nm thick. A high value of the thermal conductivity coefficient ⋅Si = 82.9 W/(m⋅K) is obtained for films synthesized on Si substrates. On Al substrates, the value λAl = 45.8 W/(m⋅K) is obtained, which is the highest among those known for Al metal substrates, which are widely used for cooling LED devices. The thermal resistance Rq of the boundary between AlN films and substrates, which is one of the most important parameters in the creation of a cooling system for electronic devices, is estimated. For the AlN/Si interface, the value Rq intSi = 2.3⋅10-8 (m²⋅K)/W is obtained, and for the AlN/Al interface, AlN/Al is Rq intAl = 4.3⋅10-8 (m² ⋅K/W). [ABSTRACT FROM AUTHOR]

An expanding agent (aluminum nitride) from the carbide and nitride group, less used in the cellular glass manufacturing process, was tested together with manganese dioxide in the experiment presented in the paper. The powder mixture of recycled residual glass and the two mentioned additives was thermally sintered and expanded by predominantly direct microwave irradiation at temperatures between 820-850 °C. The remarkable energy efficiency of the original heating technique allowed obtaining very economic specific energy consumptions between 0.80-0.95 kWh/kg. The optimal products had the apparent density between 0.35-0.43 g cm-3, porosity between 79.5-83.3 %, heat conductivity between 0.080-0.094 W (mK)-1, and compression strength in the range 4.0-6.7 MPa. The cellular material has the characteristics required for its using as a thermal insulation material in the building sector. [ABSTRACT FROM AUTHOR]

An expanding agent (aluminum nitride) from the carbide and nitride group, less used in the cellular glass manufacturing process, was tested together with manganese dioxide in the experiment presented in the paper. The powder mixture of recycled residual glass and the two mentioned additives was thermally sintered and expanded by predominantly direct microwave irradiation at temperatures between 820-850 ºC. The remarkable energy efficiency of the original heating technique allowed obtaining very economic specific energy consumptions between 0.80-0.95 kWh/kg. The optimal products had the apparent density between 0.35-0.43 g cm-3, porosity between 79.5-83.3 %, heat conductivity between 0.080-0.094 W (mK)-1, and compression strength in the range 4.0-6.7 MPa. The cellular material has the characteristics required for its using as a thermal insulation material in the building sector.

Demand for energy-efficient transportation has led to increased use of lightweight aluminium alloys due to their exceptional strength-to-weight. Meanwhile, aluminium-based metal matrix composites (MMCs) are being developed to enhance wear resistance and strength. However, traditional ceramic reinforcements often have poor bonding with the matrix, compromising performance. Here, we demonstrate the use of a novel ex-situ AlN reinforcement powder to enhance sintering and interfacial bonding for powder metallurgy preparation of Al/AlN MMCs. We compared two series of Al/AlN MMCs featuring 10 vol.% ex-situ AlN reinforcement, one prepared using commercial AlN powder, and the other using our novel AlN reinforcement prepared by low temperature direct nitridation of Al powder. Metallic Al contained in the synthesized reinforcement significantly improved interfacial adhesion between matrix and reinforcement and enhanced densification during sintering. This resulted in a substantial improvement in tensile mechanical properties, with an 11.5% increase in ultimate tensile strength and almost five-fold improvement in ductility compared to composites prepared using the conventional ceramic AlN reinforcement. This study provides a strategy for powder metallurgy production of advanced Al/AlN MMCs with superior physical and mechanical properties. • Nitrogen promoted in-situ AlN with increased tensile strength and improved ductility. • Al/AlN MMCs with ex-situ AlN from direct nitriding of Al gave five-fold improved tensile ductility. • Matrix-reinforcement adhesion enhanced by high lattice coherency. • Powder metallurgy enables tailoring of reinforcement characteristics for advanced Al/AlN MMCs. [ABSTRACT FROM AUTHOR]

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The additive composition of an AlN ceramic substrate material was optimized to achieve high strength and thermal conductivity. MgO-CaO-Al 2 O 3 -SiO 2 (MCAS) glass and Y 2 O 3 were used as basic additives for improved sintering properties and thermal conductivity, thereby allowing for AlN to be sintered at a relatively low temperature of 1600 °C without pressurization. Yttria-stabilized zirconia (YSZ) was added (0–3 wt%) to further improve the strength of the AlN ceramic. YSZ and Y 2 O 3 reacted with AlN to produce ZrN, Y 4 Al 2 O 9 , and Y 3 Al 5 O 12 secondary phases. The formation of these yttrium aluminate phases improved the thermal conductivity by removing oxygen impurities, while ZrN formed at the AlN grain boundaries provided resistance to grain boundary fractures for improved strength. Overall, the AlN ceramic with 1 wt% MCAS, 3 wt% Y 2 O 3 , and 1 wt% YSZ exhibited excellent thermal and mechanical properties, including a thermal conductivity of 109 W/mK and flexural strength of 608 MPa. [ABSTRACT FROM AUTHOR]

In this study, multi-walled carbon nanotubes (MWCNTs) are uniformly dispersed in aluminium nitride (AlN) powders, and the MWCNTs-doped AlN ceramics are sintered at 1500 °C with a holding time of 5 min by spark plasma sintering using Y 2 O 3 as the sintering additive. The effects of the MWCNTs content on the microstructure and mechanical properties of the as-obtained ceramic composites are investigated. The results reveal that many submicron pores are generated when protecting the structure of the CNTs, thereby reducing the density of the AlN ceramic. However, the gradual filling of the grain gap may compensate for the strengthening after CNT doping. The relative density and hardness reach the maximum values of 89.6% of the theoretical density and 7.0 ± 0.3 GPa, respectively, at the doping amount of 2.5 wt%. [ABSTRACT FROM AUTHOR]

Rolling bearings are important components of a mechanical structure; their state directly affects the operation of the whole mechanical system. To accurately and reliably evaluate the damage state of bearings, a wireless passive flexible strain sensor based on an aluminium nitride (AlN) film was proposed in this paper. The sensor was connected to the system using a plane inductor and an interdigital capacitor to form an LC loop, and the AlN film was deposited in the interdigital capacitor part to enhance the sensing performance. The structure of the sensor was optimised using a high-frequency structure simulator (HFSS), and the optimal coupling distance between the sensor and antenna was determined. The test results revealed that the resonant frequency of the sensor increases from 43.7089 to 43.735 MHz in a strain range of 0– $3000 ~\mu \varepsilon $ , and strain resolution is $20 ~\mu \varepsilon $. Moreover, the wireless strain sensor has a small size and high resolution. The flexible substrate can stick well to the part to be tested and can be applied to the bearing to detect micro-strain. Therefore, this sensor is applicable in fault prevention, condition monitoring, and non-destructive evaluation. [ABSTRACT FROM AUTHOR]

Objective(s): Aluminium nitride (AlN) could be used in implantable biomedical sensor devices, for which cytotoxicity analysis is of utmost importance. Materials and Methods: AlN nanoparticles were synthesized using a simple and effective solvothermal method. The X-ray diffraction results revealed the cubic phase of AlN, and the field emission scanning electron microscopy analysis demonstrated the structural morphology of the synthesized materials. In addition, the cytotoxicity of the AlN nanoparticles was assessed against healthy (HEK-293, HUVEC, and MCF10A) and cancerous cell line (HeLa). The intensity of the reactive oxygen species was also measured to determine the induced oxidative stress in the treated cells. Results: The cytotoxicity analysis indicated that the AlN nanoparticles were nontoxic against the cancerous and normal cell lines. No significant changes were observed between the low doses of the AlN nanoparticles in the treated and control cells. However, morphological changes were detected by a phase contrast microscope, while insignificant changes were observed similar to the control cells. Conclusion: The findings of this study could lay the groundwork for the development of AlN nanoparticles for further biomedical applications.

Aluminium nitride (AlN) is an important technical ceramic with outstanding strength and thermal conductivity that has important applications for advanced heat sink materials and as a reinforcement for metal-based composites. In this study, we report a novel, straightforward and low-cost method to prepare AlN powder using a vacuum tube furnace for the direct nitridation of loose aluminium powder at low temperatures (down to 500 ∘C) under flowing high-purity nitrogen. Small amounts of magnesium powder (1 wt.%), combined with aluminium, promote nitridation. Here, we characterise the effects of time (up to 12 h) and temperature (490 to 560 ∘C) on nitridation with the aim to establish an effective regimen for the controlled synthesis of an aluminium nitride reinforcement powder for the production of metal matrix composites. The extent of nitridation and the morphology of the reaction products were assessed using scanning electron microscopy and X-ray diffraction analyses. AlN was detected for all nitriding temperatures ≥ 500 ∘C, with the highest yields of 80% to 85% obtained at 530 ∘C for times ≥ 1 h. At this temperature, nitridation proceeded rapidly, and there was extensive agglomeration of the reaction products making it difficult to reprocess into powder. At lower temperatures around 510 ∘C, a relatively high proportion of AlN was attained (>73% after 6 h) while retaining excellent friability so that it could be manually reprocessed to powder. The synthesised reinforcement consisted of micro- or nano-crystalline AlN comingled with metallic aluminium. The ratio of AlN and metallic aluminium can be readily controlled by varying the nitriding temperature. This provides a flexible and accessible method for the production of AlN-reinforcement powders suited to the production of metal matrix composites.

Sensing systems are becoming less and less invasive. In this context, flexible materials offer new opportunities that are impossible to achieve with bulky and rigid chips. Standard silicon sensors cannot be adapted to curved shapes and are susceptible to big deformations, thus discouraging their use in wearable applications. Another step forward toward minimising the impacts of the sensors can be to avoid the use of cables and connectors by exploiting wireless transmissions at ultra-high frequencies (UHFs). Thin-film bulk acoustic wave resonators (FBARs) represent the most promising choice among all of the piezoelectric microelectromechanical system (MEMS) resonators for the climbing of radio frequencies. Accordingly, the fabrication of FBARs on flexible and wearable substrates represents a strategic step toward obtaining a new generation of highly sensitive wireless sensors. In this work, we propose the design and fabrication of a flexible gravimetric sensor based on an FBAR on a polymeric substrate. The resonator presents one of the highest electromechanical coupling factors in the category of flexible AlN-based FBARs, equal to 6%. Moreover, thanks to the polymeric support layer, the presence of membranes can be avoided, which leads to a faster and cheaper fabrication process and higher robustness of the structure. The mass sensitivity of the device was evaluated, obtaining a promising value of 23.31 ppm/pg. We strongly believe that these results can pave the way to a new class of wearable MEMS sensors that exploit ultra-high-frequency (UHF) transmissions.

Ash accumulation is a relevant problem due to the widespread use of coal-fired power plants and a very limited number of ash utilization technologies. Plasma processing of ash is a promising method of ash valorization for production of various useful products, which is limited by high energy consumption. In the current study, a mixture of waste ash from power plant and black carbon was processed using an original direct current plasma arc experimental setup in ambient air which allows lower energy consumption due to the absence of the vacuuming system. Four types of samples at different plasma exposure times were produced and together with the initial ash were studied by thermal analysis, X-ray diffractometry and scanning electron microscopy. The X-ray diffraction analysis identified the resulting phases of graphite, silicon carbide, and aluminum nitride in the synthesis products; at the same time, at the arc discharge energy increased from 26 to 105 kJ, the intensities of the maxima that correspond to metal and nonmetal oxides in the composition of the initial ash decreased to nearly zero. To remove graphite, the processed samples were annealed at 750 °C in air and studied. It was found that the applied approach made it possible to obtain a mixture of silicon carbide and aluminum nitride powders in direct current arc plasma initiated in ambient air, which reduced the energy consumption for ash processing by electric arc. [ABSTRACT FROM AUTHOR]

Aluminium nitride (AlN) is a futuristic material for efficient next-generation high-power electronic and optoelectronic applications. Sublimation growth of AlN single crystals with hetero-epitaxial approach using silicon carbide substrates is one of the two prominent approaches emerged, since the pioneering crystal growth work from 1970s. Many groups working on this hetero-epitaxial seeding have abandoned AlN growth altogether due to lot of persistently encountered problems. In this article, we focus on most of the common problems encountered in this process such as macro- and micro-hole defects, cracks, 3D-nucleation, high dislocation density, and incorporation of unintentional impurity elements due to chemical decomposition of the substrate at very high temperatures. Possible ways to successfully solve some of these issues have been discussed. Other few remaining challenges, namely low-angle grain boundaries and deep UV optical absorption, are also presented in the later part of this work. Particular attention has been devoted in this work on the coloration of the crystals with respect to chemical composition. Wet chemical etching gives etch pit density (EPD) values in the order of 105 cm-2 for yellow-coloured samples, while greenish coloration deteriorates the structural properties with EPD values of at least one order more. [ABSTRACT FROM AUTHOR]