Si3 N4 Research Articles

Microstructural and mechanical characterization of AA2124 aluminum alloy matrix composites reinforced with Si3 N4 particulates fabricated by powder metallurgy and high-energy ball milling

Microstructural and mechanical characterization of AA2124 aluminum alloy matrix composites reinforced with Si3 N4 particulates fabricated by powder metallurgy and high-energy ball milling

Improved Thermal and Chemical Stability of Oxynitride Phosphor from Facile Chemical Synthesis for Vehicle Cornering Lights.

Orange Eu2+ -doped phosphors are essential for light-emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow-orange-red emitting SrAl2 Si3 ON6 :Eu2+ oxynitride phosphors, derived from the SrAlSi4 N7 nitride iso-structure by replacing Si4+ -N3- with Al3+ -O2- . The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air-stable raw materials SrCO3 , Eu2 O3 , AlN and Si3 N4 . SrAl2 Si3 ON6 has a smaller band gap and lower structure rigidity than SrAlSi4 N7 (5.19 eV vs 5.50 eV, Debye temperature 719 K vs 760 K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi4 N7 . Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2 hours or being immersed in water for 20 days, implying both of the thermal and chemical stability of SrAl2 Si3 ON6 :Eu2+ phosphors. The strategy of oxynitride-introduction from nitride promotes the development of low-cost thermally and chemically stable luminescent materials.

Controllable Fabrication and Rectification of Bipolar Nanofluid Diodes in Funnel-Shaped Si3 N4 Nanopores.

Solid-state nanopores attract widespread interest, owning to outstanding robustness, extensive material availability, as well as capability for flexible manufacturing. Bioinspired solid-state nanopores further emerge as potential nanofluidic diodes for mimicking the rectification progress of unidirectional ionic transport in biological K+ channels. However, challenges that remain in rectification are over-reliance on complicated surface modifications and limited control accuracy in size and morphology. In this study, suspended Si3 N4 films of only 100nm thickness are used as substrate and funnel-shaped nanopores are controllably etched on that with single-nanometer precision, by focused ion beam (FIB) equipped with a flexibly programmable ion dose at any position. A small diameter 7nm nanopore can be accurately and efficiently fabricated in only 20ms and verified by a self-designed mathematical model. Without additional modification, funnel-shaped Si3 N4 nanopores functioned as bipolar nanofluidic diodes achieve high rectification by simply filling each side with acidic and basic solution, respectively. Main factors are finely tuned experimentally and simulatively to enhance the controllability. Moreover, nanopore arrays are efficiently prepared to further improve rectification performance, which has great potential for high-throughput practical applications such as extended release of drugs, nanofluidic logic systems, and sensing for environmental monitoring and clinical diagnosis.

A Coupled 3d Morphological Reconstruction Approach for Surface Microcrack in Si3 n4 Ceramic Bearing Roller Based on Adaptive Nano Feature Extraction & Multiscale Depth Fusion.

To extract the fuzzy contour features, tiny depth features of surface microcracks in the Si3 N4 ceramic bearings roller. An adaptive nano feature extraction and multiscale deep fusion coupling method is proposed, to sufficiently reconstruct the three-dimensional morphology characteristics of surface microcracks. Construct an adaptive nano feature extraction method, form the surface microcrack image scale space and the Gaussian difference pyramid function equation, realize the detection and matching of global feature points. The sparse point cloud is obtained. Through polar-line correction, depth estimation, and fusion of feature points on the surface microcracks image, a multiscale depth fusion matching cost pixel function is established to realize a dense point cloud reconstruction of surface microcracks. The reconstruction results show that the highest value of the local convex surface reconstructed by the dense point cloud reaches 1183nm, and the lowest local concave surface is accurate to 296nm. Compared with the measurement results of the confocal platform, the relative error of the reconstruction result is 24.6%. The overall feature-matching rate of the reconstruction reaches 93.3%. It provides a theoretical basis for the study of surface microcrack propagation mechanism and the prediction of bearing life.

Tex Se1- x Photodiode Shortwave Infrared Detection and Imaging.

Short-wave infrared detectors are playing an increasingly important role in the fields of autonomous driving, food safety, disease diagnosis and scientific research. However, the mature short-wave infrared camera such as InGaAs has the disadvantage of complexly heterogeneous integration with complementary metal-oxide-semiconductor (CMOS) readout circuits, leading to high cost and low imaging resolution. Herein, we report a low-cost, high-performance, and high-stability Tex Se1- x short-wave infrared photodiode detector. The Tex Se1- x thin film is fabricated through CMOS-compatible low-temperature evaporation and post-annealing process, showcasing the potential of direct integration on the readout circuit. The device demonstrates a broad-spectrum response of 300-1600nm, a room-temperature specific detectivity of 1.0 × 1010 Jones, a -3dB bandwidth up to 116kHz, and a linear dynamic range of over 55dB, achieving the fastest response among Te-based photodiode devices and a dark current density 7 orders of magnitude smaller than Te-based photoconductive and field-effect transistor devices. With a simple Si3 N4 packaging, the detector shows high electric stability and thermal stability, meeting the requirements for vehicular applications. Based on the optimized Tex Se1- x photodiode detector, we demonstrate the applications in material identification and masking imaging. Our work paves a new way for CMOS-compatible infrared imaging chips. This article is protected by copyright. All rights reserved.

Tailoring Dense, Orientation-Tunable, and Interleavedly Structured Carbon-Based Heat Dissipation Plates.

The controllability of the microstructure of a compressed hierarchical building block is essential for optimizing a variety of performance parameters, such as thermal management. However, owing to the strong orientation effect during compression molding, optimizing the alignment of materials perpendicular to the direction of pressure is challenging. Herein, to illustrate the effect of the ordered microstructure on heat dissipation, thermally conductive carbon-based materials are fabricated by tailoring dense, orientation-tunable, and interleaved structures. Vertically aligned carbon nanotube arrays (VACNTs) interconnected with graphene films (GF) are prepared as a 3D core-ordered material to fabricate compressed building blocks of O-VA-GF and S-VA-GF. Leveraging the densified interleaved structure offered by VACNTs, the hierarchical O-VA-GF achieves excellent through-plane (41.7W m-1 K-1 ) and in-plane (397.9W m-1 K-1 ) thermal conductivities, outperforming similar composites of S-VA-GF (through-plane: 10.3W m-1 K-1 and in-plane: 240.9W m-1 K-1 ) with horizontally collapsed carbon nanotubes. As heat dissipation plates, these orderly assembled composites yield a 144% and 44% enhancement in the cooling coefficient compared with conventional Si3 N4 for cooling high-power light-emitting diode chips.

Structure-Dependent Electrical Conductance of DNA Origami Nanowires.

Exploring the structural and electrical properties of DNA origami nanowires is an important endeavor for the advancement of DNA nanotechnology and DNA nanoelectronics. Highly conductive DNA origami nanowires are a desirable target for creating low-cost self-assembled nanoelectronic devices and circuits. In this work, the structure-dependent electrical conductance of DNA origami nanowires is investigated. A silicon nitride (Si3 N4 ) on silicon semiconductor chip with gold electrodes was used for collecting electrical conductance measurements of DNA origami nanowires, which are found to be an order of magnitude less electrically resistive on Si3 N4 substrates treated with a monolayer of hexamethyldisilazane (HMDS) (∼1013 ohms) than on native Si3 N4 substrates without HMDS (∼1014 ohms). Atomic force microscopy (AFM) measurements of the height of DNA origami nanowires on mica and Si3 N4 substrates reveal that DNA origami nanowires are ∼1.6 nm taller on HMDS-treated substrates than on the untreated ones indicating that the DNA origami nanowires undergo increased structural deformation when deposited onto untreated substrates, causing a decrease in electrical conductivity. This study highlights the importance of understanding and controlling the interface conditions that affect the structure of DNA and thereby affect the electrical conductance of DNA origami nanowires.

The Influence of the Different Gain Material on the Loss Compensation of Hybrid Plasmonic Waveguide

The influence of different gain materials and waveguide parameters on propagation properties are analyzed in detail. In this paper, three materials including Al2 O3 , Si3 N4 , and Polymethylmethacrylate (PMMA) as low index materials are introduced instead of SiO2 which is used in many experiments. The results obtained via simulations showed that by increasing the width of metal, field confinement increased and for widths larger than 450 nm the filed profile was completely confined in below the metal (zone I). In addition to, simulation results showed that Al2 O3 and Si3 N4 are more efficient than SiO2 whereas PMMA is completely similar to SiO2 in loss compensation. It was attributed to the fact that the refractive index of PMMA is close to the refractive index of SiO2 . Moreover, the effect of InGaAsP as high index gain material instead of Si is analyzed. In this case, InGaAsP also reveals a loss compensation effect similar to Si due to their close refractive indexes. Therefore, the configuration with new different gain materials potentially offers an appealing solution to provide lossless light transport via low compensation gain, hence opening venues for ultra-compact active plasmonic devices.

Combustion Synthesis of Si3N4-BN-SiC Composites by in-situ Introduction of BN and SiC

Combustion Synthesis of Si₃N₄-BN-SiC Composites by <i>in-situ</i> Introduction of BN and SiC

Modification of steel surface layer by electroslag surfacing using compounds with high melting point

The authors have studied the effect of alloying on the structure, microhardness and abrasive wear resistance of electroslag surfacing layers on low-alloy structural steel 09G2S. For modification, mixtures of Si3 N4 + FeSi2 + Si powders obtained in the Department of Structural Macrokinetics of the Tomsk Scientific Centre SB RAS by the method of SHS synthesis, as well as powder compositions based on TiC, were used. A molten electrode was made of low-alloy steel St3, on which modifying compositions Si3 N4 + FeSi2 + Si were poured out, in the first case, and modifying compositions Si3 N4 + FeSi2 + Si, located below, in the second case. Metallography and X-ray microanalysis methods were used to determine the structure and to analyze the composition of the deposited layers, heat-affected zone (HAZ) and the base metal, on the basis of which assumptions were made about the nature of the formation of coating properties – hardness and wear resistance. It is shown that the main influence on the wear resistance is exerted by structure of the surfacing metal. There is a positive effect of modifying coatings by alloying materials with the alloys Si3 N4 + FeSi2 + Si + St3 and TiC + St3. In the molten layer, many new crystallization centers are released in the form of dispersed TiC particles. Dispersed TiC particles with a high melting point (3180 °C) are the first to fall out of the melt and not only serve as multiple crystallization centers, but also prevent the growth of austenitic grains, which ensures the formation of dispersed structure. The coatings contain TiC carbide particles, as well as inclusions of other phases. At the same time, an increase in hardness of the deposited layer containing titanium carbide inclusions is observed in direction of the boundary with the base. Wear resistance of the layer increases when a TiC-based coating is formed. The obtained data can be used to create deposited layers on the metal surface with high resistance against abrasive wear.

Understanding Electrical Conduction and Nanopore Formation During Controlled Breakdown.

Controlled breakdown has recently emerged as a highly appealing technique to fabricate solid-state nanopores for a wide range of biosensing applications. This technique relies on applying an electric field of approximately 0.4-1 V nm-1 across the membrane to induce a current, and eventually, breakdown of the dielectric. Although previous studies have performed controlled breakdown under a range of different conditions, the mechanism of conduction and breakdown has not been fully explored. Here, electrical conduction and nanopore formation in SiNx membranes during controlled breakdown is studied. It is demonstrated that for Si-rich SiNx , oxidation reactions that occur at the membrane-electrolyte interface limit conduction across the dielectric. However, for stoichiometric Si3 N4 the effect of oxidation reactions becomes relatively small and conduction is predominately limited by charge transport across the dielectric. Several important implications resulting from understanding this process are provided which will aid in further developing controlled breakdown in the coming years, particularly for extending this technique to integrate nanopores with on-chip nanostructures.

Stretchable and Compressible Si3 N4 Nanofiber Sponge with Aligned Microstructure for Highly Efficient Particulate Matter Filtration under High-Velocity Airflow.

Particulate matter (PM) is one of the most severe air pollutants and poses a threat to human health. Air filters with high filtration efficiency applied to the source of PM are an effective way to reduce pollution. However, many of the present filtration materials usually fail because of their high pressure drop under high-velocity airflow and poor thermal stability at high temperatures. Herein, a highly porous Si3 N4 nanofiber sponge (Si3 N4 NFS) assembled by aligned and well-interconnected Si3 N4 nanofibers is designed and fabricated via chemical vapor deposition (CVD). The resulting ultralight Si3 N4 NFS (2.69mg cm-3 ) processes temperature-invariant reversible strechability (10% strain) and compressibility (50% strain), which enables its mechanical robustness under high-velocity airflow. The highly porous and aligned microstructure result in a Si3 N4 NFS with high filtration efficiency for PM2.5 (99.97%) and simultaneous low pressure drop (340Pa, only <0.33%of atmospheric pressure) even under a high gas flow velocity (8.72 m s-1 ) at a high temperature (1000°C). Furthermore, the Si3 N4 NFS air filter exhibits good long-term service ability and recyclability. Such Si3 N4 NFS with aligned microstructures for highly efficient gas filters provides new perspectives for the design and preparation of high-performance filtration materials.

Graphene/chitosan/Ag+- doped hydroxyapatite triple composite fiber coatings on new generation hybrid titanium composite by electrospinning

In this work, The hybrid hydroxyapatite (HaP), chitosan (CH) and graphene nanosheets (GNS) mixtures were applied by electrospinning on the surface of GNS and Si3N4 (SN) binary powder reinforced hybrid titanium (Ti) metal composites surface to improve composite biosurface functionallity. The surfaces of coated materials were characterized and antibacterial tests were carried on for their suitability in the industry by performing artificial body fluid tests. The hybrid nano fiber coatings formed a homogeneous structure on the composite. According to bioactivity tests and microstructure analysis, it was seen that HaP, which has the best results in the change of pH (pH= 11.80) values. The lowest mass change (0.0005 g) was observed on the 10th day of pure titanium. The highest mass change (0.0210 g) was obtained as on the HaP coated hybrid titanium composite. According to the antibacterial test result the hybrid nanofiber containing silver (Ag+) doped HaP on Ti composites showed the best antibacterial property aganist the E.coli. The fabricated electrospin coated hybrid composites can be a potantial candidate for dental, orthopedic implant applications and tissue engineering.

All Si3 N4 Nanowires Membrane Based High-Performance Flexible Solid-State Asymmetric Supercapacitor.

Recently, much attention has been drawn in the development of flexible energy storage devices due to the increasing demands for flexible/portable electronic devices with high energy density, low weight, and good flexibility. Herein, vertically oriented graphene nanosheets (VGNs) are in situ fabricated on the surface of free-standing and flexible Si3 N4 nanowires (NWs) membrane by plasma-enhanced chemical vapor deposition (PECVD), which are directly used as flexible nanoscale conductive substrates. NiCo2 O4 hollow nanospheres (HSs) and FeOOH amorphous nanorods (NRs) are finally prepared on Si3 N4NWs @VGNs, which are served as the positive and negative electrodes, respectively. Profiting from the structural merits, the synthesized Si3 N4NWs @VGNs@NiCo2 O4HSs and Si3 N4NWs @VGNs@FeOOHNRs membrane electrodes exhibit remarkable electrochemical performance. Using Si3 N4NWs membrane as the separator, the assembled all Si3 N4NWs membrane-based flexible solid-state asymmetric supercapacitor (ASC) with a wide operating potential window of 1.8 V yields the outstanding energy density of 96.3 Wh kg-1 , excellent cycling performance (91.7% after 6000 cycles), and good mechanical flexibility. More importantly, this work provides a rational design strategy for the preparation of flexible electrode materials and broadens the applications of Si3 N4NWs in the field of energy storage.

Selective laser melting of stainless steel and silicon nitride fibre metal matrix composites

Metal matrix composites are formed by adding certain filler particles to selected base metals to combine the good properties of both in the resulting composite and were proved to be quite promising in numerous applications. The main bottleneck lies in the processing methods, as the traditional solutions often lead to a loss of control on the dispersion of the filler material. The point-by-point consolidation mechanisms typical of additive manufacturing are proposed here as a possible means of enhancing this control over the composition of the metal matrix composites. Selective laser-melted composites with stainless steel 316L as the base metal and Si3 N4 as the filler phase are evaluated in the current study. The results clearly indicated that the dispersion of the filler particles is more controlled, as they are pushed and segregated around the solid front boundaries. The tensile strength of the composites is better than the pure 316L when laser-melted under appropriate process conditions. The surface quality is also substantially enhanced with the metal matrix composites.

Design of Extremely Sensitive Refractive Index Sensors in Infrared for Blood Glucose Detection

Simple and easy to fabricate sensors with high sensitivity, high quality-factor $(\chi)$ , large figure of merit (FOM), and narrow bandwidth are highly desirable for immediate point of care testing. In this article, we introduce a one-dimensional periodic array of barium flint glass on active plasmonic material, a thin gold film on silicon nitride (Si3 N4) substrate. Reflection spectrum of the proposed structure exhibits a clear rejection of certain wavelength on normal incidence due to the coupling between incident plane wave and plasmonic wave. The effect of ambient refractive index or glucose concentration has been studied to measure the plasmonic sensitivity of the designed structure in blood glucose detection. After optimizing geometric parameters, the designed sensor achieved sensitivity and quality factor as high as ~ 2600 nm RIU −1 (refractive index unit) and ~1500 respectively. The calculated sensitivity, quality factor and FOM are much higher than the reported structures with a similar geometry in IR. Owing only one rejection band with narrow bandwidth, the designed structure can also be realized for optical filtering applications. Wide spectral tunability in the IR, close to 100% peak absorbance and narrow bandwidth make the designed structures as an ideal candidate for surface-enhanced infrared absorption (SEIRA) spectroscopy.

Fretting corrosion of Si3 N4 vs CoCrMo femoral heads on Ti-6Al-V trunnions.

Fretting corrosion at the head-neck taper junction was compared between silicon nitride (Si3 N4 ) and commercially available cobalt chrome (CoCrMo) femoral heads on titanium (Ti-6Al-4V) trunnions. An electrochemical setup was used to capture the fretting currents (characterized by oxide abrasion and repassivation) during cyclic loading. Onset load, pull-off force (disassembly load), short term and long term (1 million cycles) fretting currents were used to compare the fretting corrosion performance between the test group (Si3 N4 /Ti-6Al-4V) and the control group (CoCrMo/Ti-6Al-4V). Incremental cyclic fretting corrosion tests showed that the Si3 N4 /Ti-6Al-4V combination had statistically lower (P < .05) average fretting current of 0.189 µA (SD = 0.114 µA) compared to 0.685 µA (SD = 0.630 µA) for CoCrMo/Ti-6Al-4V for cyclic load of 3200 N. Similarly, for the one million cycle fretting corrosion tests, the Si3 N4 /Ti-6Al-4V couples had statistically lower (P < .05) average current (0.048 µA, SD = 0.025 µA) vs CoCrMo/Ti-6Al-4V couples (0.366 µA, SD = 0.143 µA). The Si3 N4 heads also had higher onset loads (P < .05) for fretting (vs CoCrMo, 2200 N vs 1740 N) indicating a difference in surface contact mechanics between the two groups. Scanning electron microscopy with energy dispersive spectroscopy confirmed material transfer from the trunnions to the heads for both groups tested, and from head to trunnion for the CoCrMo heads. Minimal Si3 N4 transfer was noted. The electrochemical, mechanical, and microscopic inspection data supported the hypothesis that Si3 N4 /Ti-6Al-4Vcombination had better fretting corrosion performance compared to CoCrMo/Ti-6Al-4V.

The choice of coating for the ceramic end mill, taking into account the stress-strain state of its blade. Part 2

It was found that the TiC coating is more effective than the TiN coating and stabilizes the temperature distribution and structural stress heterogeneity in the surface layer of Si3 N4 ceramic adjacent to the coating. It is recommended to apply TiC coating to end mills made of Si3 N4 -ceramic intended for milling of spatially complex surfaces on nickel alloy billets. Ill. 4. Ref. 25.

Nitride Spinel: An Ultraincompressible High-Pressure Form of BeP2 N4.

Owing to its outstanding elastic properties, the nitride spinel γ‐Si3N4 is of considered interest for materials scientists and chemists. DFT calculations suggest that Si3N4‐analog beryllium phosphorus nitride BeP2N4 adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite‐type BeP2N4 by single‐crystal synchrotron X‐ray diffraction and report the phase transition into the spinel‐type phase at 47 GPa and 1800 K in a laser‐heated diamond anvil cell. The structure of spinel‐type BeP2N4 was refined from pressure‐dependent in situ synchrotron powder X‐ray diffraction measurements down to ambient pressure, which proves spinel‐type BeP2N4 a quenchable and metastable phase at ambient conditions. Its isothermal bulk modulus was determined to 325(8) GPa from equation of state, which indicates that spinel‐type BeP2N4 is an ultraincompressible material.

Comparison of Si3N4-SiO2 and SiO2 Insulation Layer for Zero-Bias CMUT Operation Using Dielectric Charging Effects.

In this letter, we report the characteristics of zero-bias capacitive micromachined ultrasonic transducers (CMUTs) in various aspects, considering the transmission and reception sensitivity and evaluation of the long-term stability with ac transmission in immersion. The main idea of the zero-bias CMUT implementation is that the charge is injected by the dielectric charging effects in an insulation layer in the pull-in state. The CMUT was fabricated by a local oxidation of silicon (LOCOS) process, and the insulation layer consists of Si3 N4 -SiO2 and SiO2, which have been commonly used in previous studies. A study on the charging effects is reported to quantitatively observe the voltage shift by charge transfer with time dependence at different temperatures and collapsing time dependence. Therefore, we successfully implemented a zero-bias CMUT with a transmission efficiency of 4.62 kPa/V at a center frequency of 7.53 MHz in Si3 N4-SiO2 and a transmission efficiency of 6.78 kPa/V at a center frequency of 7.86 MHz in SiO2 immersion.