Investigation of interfacial shear strength in SiC/Si3N4 composites

NASA Technical Reports Server (NTRS)

Eldridge, J. I.; Bhatt, R. T.; Kiser, J. D.

1991-01-01

A fiber push-out technique was used to determine fiber/matrix interfacial shear strength (ISS) for silicon carbide fiber reinforced reaction-bonded silicon nitride (SiC/RBSN) composites in the as-fabricated condition and after consolidation by hot isostatic pressing (HIPing). In situ video microscopy and acoustic emission detection greatly aided the interpretation of push-out load/displacement curves.

Feasibility study of silicon nitride protection of plastic encapsulated semiconductors

NASA Technical Reports Server (NTRS)

Peters, J. W.; Hall, T. C.; Erickson, J. J.; Gebhart, F. L.

1979-01-01

The application of low temperature silicon nitride protective layers on wire bonded integrated circuits mounted on lead frame assemblies is reported. An evaluation of the mechanical and electrical compatibility of both plasma nitride and photochemical silicon nitride (photonitride) passivations (parallel evaluations) of integrated circuits which were then encapsulated in plastic is described. Photonitride passivation is compatible with all wire bonded lead frame assemblies, with or without initial chip passivation. Plasma nitride passivation of lead frame assemblies is possible only if the chip is passivated before lead frame assembly. The survival rate after the environmental test sequence of devices with a coating of plasma nitride on the chip and a coating of either plasma nitride or photonitride over the assembled device is significantly greater than that of devices assembled with no nitride protective coating over either chip or lead frame.

Processing and Properties of Silicon Carbide Reinforced Reaction Bonded Silicon Nitride Composites

DTIC Science & Technology

1992-11-30

work as well as of polymer derived and composite parts will be discussed. 3. Mechanical Behavior of a Continuous SiC Fiber Reinforced RBSN, S.V...Silicon carbide paniculate composites exhibited improved fracture toughnesses and evidence of R-Curve behavior. Composites made with SiC (w...i£L LIST OF TABLES Page No. 1. Summary of mechanical properties measured for RBSN and RBSN/ SiC 7 composites 2. Summary of characteristics for

3500-hour durability testing of ceramic materials for automotive gas turbine engines

NASA Technical Reports Server (NTRS)

Carruthers, W. D.; Richerson, D. W.; Benn, K. W.

1980-01-01

A two-year durability program was performed by AiResearch Phoenix to evaluate four commercially available ceramic materials under simulated automotive gas turbine combustor discharge conditions. These conditions included extended cyclic thermal exposures up to 2500 F and 3500 hr. The four materials selected for evaluation were Norton NCX-34 hot pressed silicon nitride, AiResearch RBN 101 reaction bonded silicon nitride, Carborundum pressureless sintered alpha-SiC and Pure Carbon Co. (British Nuclear Fuels, Ltd.) Refel reaction sintered silicon carbide. These materials were initially exposed to 350 hr/1750 cycles at 1200 and 1370 C. Subsequent exposures to 1050, 2100 and 3500 hr were performed on those materials maintaining 50% of baseline strength after the initial exposure. Additional evaluations of exposed bars included dimensional and weight changes, dye penetrant, specific damping capacity changes, SEM fractography, and X-ray diffraction.

Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

2000-01-01

Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

Chip PCR. I. Surface passivation of microfabricated silicon-glass chips for PCR.

PubMed Central

Shoffner, M A; Cheng, J; Hvichia, G E; Kricka, L J; Wilding, P

1996-01-01

The microreaction volumes of PCR chips (a microfabricated silicon chip bonded to a piece of flat glass to form a PCR reaction chamber) create a relatively high surface to volume ratio that increases the significance of the surface chemistry in the polymerase chain reaction (PCR). We investigated several surface passivations in an attempt to identify 'PCR friendly' surfaces and used those surfaces to obtain amplifications comparable with those obtained in conventional PCR amplification systems using polyethylene tubes. Surface passivations by a silanization procedure followed by a coating of a selected protein or polynucleotide and the deposition of a nitride or oxide layer onto the silicon surface were investigated. Native silicon was found to be an inhibitor of PCR and amplification in an untreated PCR chip (i.e. native slicon) had a high failure rate. A silicon nitride (Si(3)N(4) reaction surface also resulted in consistent inhibition of PCR. Passivating the PCR chip using a silanizing agent followed by a polymer treatment resulted in good amplification. However, amplification yields were inconsistent and were not always comparable with PCR in a conventional tube. An oxidized silicon (SiO(2) surface gave consistent amplifications comparable with reactions performed in a conventional PCR tube. PMID:8628665

Preparation and evaluation of silicon nitride matrices for silicon nitride-SiC fiber composites. M.S. Thesis Final Technical Report

NASA Technical Reports Server (NTRS)

Axelson, Scott R.

1988-01-01

Continuous silicon carbide (SiC) fiber was added to three types of silicon nitride (Si3N4) matrices. Efforts were aimed at producing a dense Si3N4 matrix from reaction-bonded silicon nitride (RBSN) by hot-isostatic-pressing (HIP) and pressureless sintering, and from Si3N4 powder by hot-pressing. The sintering additives utilized were chosen to allow for densification, while not causing severe degradation of the fiber. The ceramic microstructures were evaluated using scanning optical microscopy. Vickers indentation was used to determine the microhardness and fracture toughness values of the matrices. The RBSN matrices in this study did not reach more than 80 percent of theoretical density after sintering at various temperatures, pressures, and additive levels. Hot-pressing Si3N4 powder produced the highest density matrices; hardness and toughness values were within an order of magnitude of the best literature values. The best sintering aid composition chosen included Y2O3, SiO2, and Al2O3 or AlN. Photomicrographs demonstrate a significant reduction of fiber attack by this additive composition.

Silicon nitride films fabricated by a plasma-enhanced chemical vapor deposition method for coatings of the laser interferometer gravitational wave detector

NASA Astrophysics Data System (ADS)

Pan, Huang-Wei; Kuo, Ling-Chi; Huang, Shu-Yu; Wu, Meng-Yun; Juang, Yu-Hang; Lee, Chia-Wei; Chen, Hsin-Chieh; Wen, Ting Ting; Chao, Shiuh

2018-01-01

Silicon is a potential substrate material for the large-areal-size mirrors of the next-generation laser interferometer gravitational wave detector operated in cryogenics. Silicon nitride thin films uniformly deposited by a chemical vapor deposition method on large-size silicon wafers is a common practice in the silicon integrated circuit industry. We used plasma-enhanced chemical vapor deposition to deposit silicon nitride films on silicon and studied the physical properties of the films that are pertinent to application of mirror coatings for laser interferometer gravitational wave detectors. We measured and analyzed the structure, optical properties, stress, Young's modulus, and mechanical loss of the films, at both room and cryogenic temperatures. Optical extinction coefficients of the films were in the 10-5 range at 1550-nm wavelength. Room-temperature mechanical loss of the films varied in the range from low 10-4 to low 10-5 within the frequency range of interest. The existence of a cryogenic mechanical loss peak depended on the composition of the films. We measured the bond concentrations of N - H , Si - H , Si - N , and Si - Si bonds in the films and analyzed the correlations between bond concentrations and cryogenic mechanical losses. We proposed three possible two-level systems associated with the N - H , Si - H , and Si - N bonds in the film. We inferred that the dominant source of the cryogenic mechanical loss for the silicon nitride films is the two-level system of exchanging position between a H+ and electron lone pair associated with the N - H bond. Under our deposition conditions, superior properties in terms of high refractive index with a large adjustable range, low optical absorption, and low mechanical loss were achieved for films with lower nitrogen content and lower N - H bond concentration. Possible pairing of the silicon nitride films with other materials in the quarter-wave stack is discussed.

Engine materials characterization and damage monitoring by using x ray technologies

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1993-01-01

X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results from one-, three-, five-, and eight-ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber-matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. In situ film radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction-bonded silicon nitride matrix. It is concluded that pretest, in situ, and post-test x ray imaging can provide greater understanding of ceramic matrix composite mechanical behavior.

Reaction of Si(100) with NH3: Rate-limiting steps and reactivity enhancement via electronic excitation

NASA Astrophysics Data System (ADS)

Bozso, F.; Avouris, Ph.

1986-09-01

We report on the low-temperature reaction of ammonia with Si(100)-(2×1). The dangling bonds in the clean Si surface promote NH3 dissociation even at temperatures as low as 90 K. The N atoms thus produced occupy subsurface sites, while the H atoms bind to surface Si atoms, tie up the dangling bonds, and inactivate the surface. Thermal or electronic-excitation-induced hydrogen desorption restores the dangling bonds and the reactivity of the surface. Silicon nitride film growth is achieved at 90 K by simultaneous exposure of the Si surface to NH3 and an electron beam.

Durability characterization of ceramic materials for gas turbines

NASA Technical Reports Server (NTRS)

Carruthers, W. D.; Lindberg, L. J.

1987-01-01

The strength retention of ceramic materials during extended high-temperature cyclic exposure is critical to their widespread application in gas turbine engines. During a continuing NASA funded program initated in 1979, reaction bonded silicon nitride (RBSN), sintered silicon carbide (SSC), reaction sintered silicon carbide (RSSC), and sintered silicon nitride (SSN) materials were evaluated following simulated gas turbine engine exposures. Exposures were performed by cycling specimens five times per hour between a high velocity burner discharge and a rapid air quench. The retained flexural strengths were determined following up to 3500 hours of exposure at temperatures up to 1370 C. Post-exposure strengths have been correlated with fractography and surface examination using SEM. Results illustrate excellent strength retention of SSC materials after 3500 hours of exposure to 1370 C. At 1200 C, RBSN and RSSC also demonstrate significant strength retention. Although SSN materials typically suffer significant strength losses during exposures at 1200 C, a new composition, which has improved high-temperature strength, also shows improved durability. In the majority of the materials, strength loss is typically associated with flaw formation in the protective SiO2 layer.

Thermo-Oxidative Degradation Of SiC/Si3N4 Composites

NASA Technical Reports Server (NTRS)

Baaklini, George Y.; Batt, Ramakrishna T.; Rokhlin, Stanislav I.

1995-01-01

Experimental study conducted on thermo-oxidative degradation of composite-material specimens made of silicon carbide fibers in matrices of reaction-bonded silicon nitride. In SiC/Si3N4 composites of study, interphase is 3-micrometers-thick carbon-rich coat on surface of each SiC fiber. Thermo-oxidative degradation of these composites involves diffusion of oxygen through pores of composites to interphases damaged by oxidation. Nondestructive tests reveal critical exposure times.

Cryogenic High Pressure Sensor Module

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams, Qamar A. (Inventor); Powers, William T. (Inventor)

1999-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Cryogenic, Absolute, High Pressure Sensor

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

2001-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Silicon-nitride and metal composite

DOEpatents

Landingham, R.L.; Huffsmith, S.A.

A composite and a method for bonding the composite are described. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi/sub 2/ indirectly bonding the composite together. The method includes contacting the layer of MoSi/sub 2/ with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400/sup 0/C; and, simultaneously, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

Silicon-nitride and metal composite

DOEpatents

Landingham, Richard L.; Huffsmith, Sarah A.

1981-01-01

A composite and a method for bonding the composite. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi.sub.2 indirectly bonding the composite together. The method includes contacting the layer of MoSi.sub.2 with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400.degree. C.; and, simultaneously with the heating, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

Heat Treatment Effects on the Tensile Properties and Microstructures of a SiC/RBSN Composite in Nitrogen

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1995-01-01

The room-temperature tensile properties and constituent microstructures of a unidirectionally reinforced SiC/reaction bonded silicon nitride (RBSN) composite have been investigated after heat treatments at 1400, 1600, or 1800 C in nitrogen for up to 100 hr. The composite consisted of approximately 24 vol% of aligned 140 micron diameter, continuous length, chemically vapor deposited SiC fibers in an approximately 40% porous silicon nitride matrix. The composites heat treated at 1400 C for up to 100 hr showed elastic modulus, first matrix cracking strength, and ultimate tensile strength values similar to those of the as-fabricated composites, but those heat treated for 1 hr beyond this temperature displayed losses in all three properties. Recrystallization of the SiC fibers, reaction between the carbon-rich interface coating on the fibers and the RBSN matrix, and dissociation of the RBSN matrix are the reasons for the loss of mechanical properties.

Effect of milling and leaching on the structure of sintered silicon

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Glascow, T. K.; Herbell, T. P.

1980-01-01

Sintering was performed in He for 16 hours at 1200, 1250, and 1300 C. Compacts of as-received Si did not densify during sintering. Milling reduced the average particle size to below 0.5 micrometer and enhanced densification (1.75 g/cc). Leaching milled Si further enhanced densification (1.90 g/cc max.) and decreased structural coarsening. After sintering, the structure of the milled and leached powder compacts appears favorable for the production of reaction bonded silicon nitride.

Advanced ceramic material for high temperature turbine tip seals

NASA Technical Reports Server (NTRS)

Vogan, J. W.; Solomon, N. G.; Stetson, A. R.

1980-01-01

Forty-one material systems were evaluated for potential use in turbine blade tip seal applications at 1370 C. Both ceramic blade tip inserts and abradable ceramic tip shoes were tested. Hot gas erosion, impact resistance, thermal stability, and dynamic rub performance were the criteria used in rating the various materials. Silicon carbide and silicon nitride were used, both as blade tips and abradables. The blade tip inserts were fabricated by hot pressing while low density and honeycomb abradables were sintered or reaction bonded.

Nested potassium hydroxide etching and protective coatings for silicon-based microreactors

NASA Astrophysics Data System (ADS)

de Mas, Nuria; Schmidt, Martin A.; Jensen, Klavs F.

2014-03-01

We have developed a multilayer, multichannel silicon-based microreactor that uses elemental fluorine as a reagent and generates hydrogen fluoride as a byproduct. Nested potassium hydroxide etching (using silicon nitride and silicon oxide as masking materials) was developed to create a large number of channels (60 reaction channels connected to individual gas and liquid distributors) of significantly different depths (50-650 µm) with sloped walls (54.7° with respect to the (1 0 0) wafer surface) and precise control over their geometry. The wetted areas were coated with thermally grown silicon oxide and electron-beam evaporated nickel films to protect them from the corrosive fluorination environment. Up to four Pyrex layers were anodically bonded to three silicon layers in a total of six bonding steps to cap the microchannels and stack the reaction layers. The average pinhole density in as-evaporated films was 3 holes cm-2. Heating during anodic bonding (up to 350 °C for 4 min) did not significantly alter the film composition. Upon fluorine exposure, nickel films (160 nm thick) deposited on an adhesion layer of Cr (10 nm) over an oxidized silicon substrate (up to 500 nm thick SiO2) led to the formation of a nickel fluoride passivation layer. This microreactor was used to investigate direct fluorinations at room temperature over several hours without visible signs of film erosion.

High temperature resistant cermet and ceramic compositions

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

Mechanical properties of SiC fiber-reinforced reaction-bonded Si3N4 composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1985-01-01

The room temperature mechanical and physical properties of silicon carbide fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) have been evaluated. The composites contained 23 and 40 volume fraction of aligned 140 micro m diameter chemically vapor deposited SiC fibers. Preliminary results for composite tensile and bend strengths and fracture strain indicate that the composites displayed excellent properties when compared with unreinforced RBSN of comparable porosity. Fiber volume fraction showed little influence on matrix first cracking strain but did influence the stressed required for matrix first cracking and for ultimate composite fracture strength. It is suggested that by reducing matrix porosity and by increasing the volume fraction of the large diameter SiC fiber, it should be possible to further improve the composite stress at which the matrix first cracks.

Role of interfacial thermal barrier in the transverse thermal conductivity of uniaxial SiC fiber-reinforced reaction bonded silicon nitride

NASA Technical Reports Server (NTRS)

Bhatt, H.; Donaldson, K. Y.; Hasselman, D. P. H.; Bhatt, R. T.

1992-01-01

The transverse thermal conductivity of reaction-bonded Si3N4 is significantly affected by an interfacial barrier at the interface formed with SiC reinforcing fibers. A comparative study of composites with and without reinforcing-fiber carbon coatings found the coating to reduce effective thermal conductivity by a factor of about 2; this, however, is partially due to a thermal expansion-mismatch gap between fiber and matrix. HIPing of composites with coated fibers led to an enhancement of thermal conductivity via improved interfacial thermal contact and greater grain size and crystallinity of the fibers.

Infrared bolometers with silicon nitride micromesh absorbers

NASA Technical Reports Server (NTRS)

Bock, J. J.; Turner, A. D.; DelCastillo, H. M.; Beeman, J. W.; Lange, A. E.; Mauskopf, P. D.

1996-01-01

Sensitive far infrared and millimeter wave bolometers fabricated from a freestanding membrane of low stress silicon nitride are reported. The absorber, consisting of a metallized silicon nitride micromesh thermally isolated by radial legs of silicon nitride, is placed in an integrating cavity to efficiently couple to single mode or multiple mode infrared radiation. This structure provides low heat capacity, low thermal conduction and minimal cross section to energetic particles. A neutron transmutation doped Ge thermister is bump bonded to the center of the device and read out with evaporated Cr-Au leads. The limiting performance of the micromesh absorber is discussed and the recent results obtained from a 300 mK cold stage are summarized.

Steel bonded dense silicon nitride compositions and method for their fabrication

DOEpatents

Landingham, R.L.; Shell, T.E.

1985-05-20

A two-stage bonding technique for bonding high density silicon nitride and other ceramic materials to stainless steel and other hard metals, and multilayered ceramic-metal composites prepared by the technique are disclosed. The technique involves initially slurry coating a surface of the ceramic material at about 1500/sup 0/C in a vacuum with a refractory material and the stainless steel is then pressure bonded to the metallic coated surface by brazing it with nickel-copper-silver or nickel-copper-manganese alloys at a temperature in the range of about 850/sup 0/ to 950/sup 0/C in a vacuum. The two-stage bonding technique minimizes the temperature-expansion mismatch between the dissimilar materials.

Steel bonded dense silicon nitride compositions and method for their fabrication

DOEpatents

Landingham, Richard L.; Shell, Thomas E.

1987-01-01

A two-stage bonding technique for bonding high density silicon nitride and other ceramic materials to stainless steel and other hard metals, and multilayered ceramic-metal composites prepared by the technique are disclosed. The technique involves initially slurry coating a surface of the ceramic material at about 1500.degree. C. in a vacuum with a refractory material and the stainless steel is then pressure bonded to the metallic coated surface by brazing it with nickel-copper-silver or nickel-copper-manganese alloys at a temperature in the range of about 850.degree. to 950.degree. C. in a vacuum. The two-stage bonding technique minimizes the temperature-expansion mismatch between the dissimilar materials.

High temperature resistant cermet and ceramic compositions. [for thermal resistant insulators and refractory coatings

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

High temperature oxidation resistance, high hardness and high abrasion and wear resistance are properties of cermet compositions particularly to provide high temperature resistant refractory coatings on metal substrates, for use as electrical insulation seals for thermionic converters. The compositions comprise a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride are also described.

Fabricating capacitive micromachined ultrasonic transducers with a novel silicon-nitride-based wafer bonding process.

PubMed

Logan, Andrew; Yeow, John T W

2009-05-01

We report the fabrication and experimental testing of 1-D 23-element capacitive micromachined ultrasonic transducer (CMUT) arrays that have been fabricated using a novel wafer-bonding process whereby the membrane and the insulation layer are both silicon nitride. The membrane and cell cavities are deposited and patterned on separate wafers and fusion-bonded in a vacuum environment to create CMUT cells. A user-grown silicon-nitride membrane layer avoids the need for expensive silicon-on-insulator (SOI) wafers, reduces parasitic capacitance, and reduces dielectric charging. It allows more freedom in selecting the membrane thickness while also providing the benefits of wafer-bonding fabrication such as excellent fill factor, ease of vacuum sealing, and a simplified fabrication process when compared with the more standard sacrificial release process. The devices fabricated have a cell diameter of 22 microm, a membrane thickness of 400 nm, a gap depth of 150 nm, and an insulation thickness of 250 nm. The resonant frequency of the CMUT in air is 17 MHz and has an attenuation compensated center frequency of approximately 9 MHz in immersion with a -6 dB fractional bandwidth of 123%. This paper presents the fabrication process and some characterization results.

Effect of milling and leaching on the structure of sintered silicon

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Glasgow, T. K.; Herbell, T. P.

1980-01-01

The effects of attrition milling and acid leaching on the sintering behavior and the resultant structures of two commercial silicon powders were investigated. Sintering was performed in He for 16 hours at 1200, 1250, and 1300 C. Compacts of as-received Si did not densify during sintering. Milling reduced the average particle size to below 0.5 microns and enhanced densification (1.75 g/cc). Leaching milled Si further enhanced densification (1.90 g/cc max.) and decreased structural coarsening. After sintering, the structure of the milled and leached powder compacts appears favorable for the production of reaction bonded silicon nitride.

Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okada, H.; Kato, M.; Ishimaru, T.

2014-02-20

Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma is investigated. Feasibility of precursors of triethylsilane (TES) and bis(dimethylamino)dimethylsilane (BDMADMS) is discussed based on a calculation of bond energies by computer simulation. Refractive indices of 1.81 and 1.71 are obtained for deposited films with TES and BDMADMS, respectively. X-ray photoelectron spectroscopy (XPS) analysis of the deposited film revealed that TES-based film coincides with the stoichiometric thermal silicon nitride.

Materials development and evaluation for the ceramic helical expander

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landingham, R.L.; Taylor, R.W.

The supporting role of the materials program for the ceramic helical expander program is described. The materials problems for this rotory expander in an extremely severe environment-a direct coal-fired Brayton topping cycle is defined. Readily available materials and methods for possible solution to these material problems as well as initiating some longer-range studies to improve reliability were evaluated. A preliminary screening of materials in hot coal-fired environments to select candidate materials and coating was made. More detailed evaluations of these candidate materials-reaction-bonded silicon nitride (RBSN) and Si--Al--O--N (Sialon) system- and coatings-chemical-vapor-deposited silicon nitride (CVD-Si/sub 3/N/sub 4/) and CVD-Sialon need tomore » be performed. Termination of the helical expander program abruptly stopped the materials program during this evaluation.« less

Materials development and evaluation for the ceramic helical expander

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landingham, R.L.; Taylor, R.W.

The supporting role of the materials program for the ceramic helical expander program is described. The materials problems for this rotory expander in an extremely severe environment - a direct coal-fired Brayton topping cycle is defined. Readily available materials and methods are evaluated for possible solution to these material problems as well as initiating some longer-range studies to improve reliability. A preliminary screening of materials in hot coal-fired environments to select candidate materials and coating, was made, but there is a need to perform more detailed evaluations of these candidate materials-reaction-bonded silicon nitride (RBSN) and Si--Al--O--N (Sialon) system- and coatings-chemical-vapor-depositedmore » silicon nitride (CVD-Si/sub 3/N/sub 4/) and CVD-Sialon. Termination of the helical expander program abruptly stopped the materials program during this evaluation.« less

Interfacial phenomena in high-kappa dielectrics

NASA Astrophysics Data System (ADS)

Mathew, Anoop

The introduction of novel high-kappa dielectric materials to replace the traditional SiO2 insulating layer in CMOS transistors is a watershed event in the history of transistor development. Further, replacement of the traditional highly-doped polycrystalline silicon gate electrode with a new set of materials for metal gates complicates the transition and introduces further integration challenges. A whole variety of new material surfaces and interfaces are thus introduced that merit close investigation to determine parameters for optimal device performance. Nitrogen is a key component that improves the performance of a variety of materials for the next generation of these CMOS transistors. Nitrogen is introduced into new gate dielectric materials such as hafnium silicates as well as in potential metal gate materials such as hafnium nitride. A photoemission study of the binding energies of the various atoms in these systems using photoemission reveals the nature of the atomic bonding. The current study compares hafnium silicates of various compositions which were thermally nitrided at different temperatures in ammonia, hafnium nitrides, and thin HfO2 films using photoelectron spectroscopy. A recurring theme that is explored is the competition between oxygen and nitrogen atoms in bonding with hafnium and other atoms. The N 1s photoemission peak is seen to have contributions from its bonding with hafnium, oxygen, and silicon atoms. The Hf 4f and O 1s spectra similarly exhibit signatures of their bonding environment with their neighboring atoms. Angle resolved photoemission and in-situ annealing/argon sputtering experiments are used to elucidate the nature of the bonding and its evolution with processing. A nondestructive profilitng of nitrogen distribution as a function of composition in nitrided hafnium silicates is also constructed using angle resolved photoemission as a function of the take-off angle. These results are corroborated with depth reconstruction obtained using medium energy ion scattering (MEIS). A comparison of samples nitrided at progressively increasing temperatures in an ammonia environment shows substitution of oxygen with nitrogen atoms and increasing penetration of nitrogen into the gate stack. Trends in the binding energy of the the as-prepared hafnium silicates suggest that they are non-phase separated, and the binding energy of the hafnium and silicon track the relative composition. Upon being subject to rapid thermal annealing, the samples are observed to show behavior consistent with phase separation. There is also the evidence of charges at the oxide/Si interface that modify the expected behavior of the shifts in binding energy. In another set of experiments, a one-cycle atomic layer deposition (ALD) growth reaction on the water terminated Si(100) -- (2x1) surface is shown to lead to successful nucleation, high metal oxide coverage, and an abrupt metal-oxide/silicon interface as confirmed by photoemission, reflection high energy electron diffraction (RHEED), and Rutherford back scattering (RBS) measurements. Photoemission results confirm the coordination states of the hafnium and oxygen atoms. A Hf 4f core level shift is observed and assigned to the presence of the Si-O-Hf bonding environment with the more electronegative Si atom inducing the binding energy shift. This Hf 4f shift is smaller than that reported previously for silicates because of the difference of the semiconductor bonding environment. The subspecies *(O)2HfCl2 and *OHfCl3 are seen to be the predominant intermediate species in these reactions and photoemission results provide corroborative evidence for their presence. Experiments indicate that the hydroxyl sites bound to Si(100) are active for adsorption. The abrupt interface could be useful for aggressive Effective Oxide Thickness (EOT) scaling.

Detection of antibody-antigen reaction by silicon nitride slot-ring biosensors using protein G

NASA Astrophysics Data System (ADS)

Taniguchi, Tomoya; Hirowatari, Anna; Ikeda, Takeshi; Fukuyama, Masataka; Amemiya, Yoshiteru; Kuroda, Akio; Yokoyama, Shin

2016-04-01

Biosensors using ring resonators with silicon nitride (SiN) slot waveguides have been fabricated. The temperature coefficient of the resonance wavelength of the SiN resonator is 0.006 nm/°C, which is one order of magnitude smaller than that of Si. The sensitivity of the biosensor has been improved by using slot waveguide together with Si-binding protein (designated as Si-tag), which bonds to SiN or SiO2 surface, as an anchoring molecule to immobilize bioreceptors on the SiN rings in an oriented manner. Furthermore, the protein G, which strongly bonds to many kinds of mammalian antibodies only by mixing the antibody solution, is used to efficiently immobilize the antigen on the sensor surface. By means of these devises the sensitivity of the biosensor has been improved by factor of 10-100 compared with that of normal Si ring resonator sensors without slot. Then the detection of prostate specific antigen (PSA) with the sensitivity of ~1×10-8 g/ml, which is the concentration of strongly suspicious for the prostate cancer, has been achieved.

Improved reaction sintered silicon nitride. [protective coatings to improve oxidation resistance

NASA Technical Reports Server (NTRS)

Baumgartner, H. R.

1978-01-01

Processing treatments were applied to as-nitrided reaction sintered silicon nitride (RSSN) with the purposes of improving strength after processing to above 350 MN/m2 and improving strength after oxidation exposure. The experimental approaches are divided into three broad classifications: sintering of surface-applied powders; impregnation of solution followed by further thermal processing; and infiltration of molten silicon and subsequent carburization or nitridation of the silicon. The impregnation of RSSN with solutions of aluminum nitrate and zirconyl chloride, followed by heating at 1400-1500 C in a nitrogen atmosphere containing silicon monoxide, improved RSSN strength and oxidation resistance. The room temperature bend strength of RSSN was increased nearly fifty percent above the untreated strength with mean absolute strengths up to 420 MN/m2. Strengths of treated samples that were measured after a 12 hour oxidation exposure in air were up to 90 percent of the original as-nitrided strength, as compared to retained strengths in the range of 35 to 60 percent for untreated RSSN after the same oxidation exposure.

Process for producing high purity silicon nitride by the direct reaction between elemental silicon and nitrogen-hydrogen liquid reactants

DOEpatents

Pugar, Eloise A.; Morgan, Peter E. D.

1990-01-01

A process is disclosed for producing, at a low temperature, a high purity reaction product consisting essentially of silicon, nitrogen, and hydrogen which can then be heated to produce a high purity alpha silicon nitride. The process comprises: reacting together a particulate elemental high purity silicon with a high purity nitrogen-hydrogen reactant in its liquid state (such as ammonia or hydrazine) having the formula: N.sub.n H.sub.(n+m) wherein: n=1-4 and m=2 when the nitrogen-hydrogen reactant is straight chain, and 0 when the nitrogen-hydrogen reactant is cyclic. High purity silicon nitride can be formed from this intermediate product by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours to form a high purity alpha silicon nitride product. The discovery of the existence of a soluble Si-N-H intermediate enables chemical pathways to be explored previously unavailable in conventional solid state approaches to silicon-nitrogen ceramics.

Process for producing high purity silicon nitride by the direct reaction between elemental silicon and nitrogen-hydrogen liquid reactants

DOEpatents

Pugar, E.A.; Morgan, P.E.D.

1987-09-15

A process is disclosed for producing, at a low temperature, a high purity reaction product consisting essentially of silicon, nitrogen, and hydrogen which can then be heated to produce a high purity alpha silicon nitride. The process comprises: reacting together a particulate elemental high purity silicon with a high purity nitrogen-hydrogen reactant in its liquid state (such as ammonia or hydrazine) having the formula: N/sub n/H/sub (n+m)/ wherein: n = 1--4 and m = 2 when the nitrogen-hydrogen reactant is straight chain, and 0 when the nitrogen-hydrogen reactant is cyclic. High purity silicon nitride can be formed from this intermediate product by heating the intermediate product at a temperature of from about 1200--1700/degree/C for a period from about 15 minutes up to about 2 hours to form a high purity alpha silicon nitride product. The discovery of the existence of a soluble Si/endash/N/endash/H intermediate enables chemical pathways to be explored previously unavailable in conventional solid-state approaches to silicon-nitrogen ceramics

An evaluation of strain measuring devices for ceramic composites

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bartolotta, Paul A.

1991-01-01

A series of tensile tests was conducted on SiC/reaction bonded silicon nitrides (RBSN) composites using different methods of strain measurement. The tests were used to find the optimum strain sensing device for use with continuous fiber reinforced ceramic matrix composites in ambient and high temperature environments. Bonded resistance gages were found to offer excellent performance for room temperature tests. The clip-on gage offers the same performance, but less time is required for mounting it to the specimen. Low contact force extensometers track the strain with acceptable results at high specimen temperatures. Silicon carbide rods with knife edges are preferred. The edges must be kept sharp. The strain measuring devices should be mounted on the flat side of the specimen. This is in contrast to mounting on the rough thickness side.

Development of silicon nitride of improved toughness

NASA Technical Reports Server (NTRS)

Brennan, J. J.

1979-01-01

The application of reaction sintered Si2N4 energy absorbing surface layers to hot-pressed Si3N4 was investigated. The surface layer was formed by in-place nitridation of silicon powder. It was found that reaction sintered Si3N4 layers of 1 mm thickness, fabricated from either -100, +200, -200, or -325 mesh Si powder and nitrided in 96% N2/4% H2 so that approximately 20-25 vol % unnitrided Si remained in the layer, resulted in a sevenfold increase in ballistic impact resistance of a 0.64 cm thick hot-pressed SI3N4 substrate from RT 1370 C. Both NC-132 SI3N4, with MgO additive, and NCX-34 Si3N4, with Y2O3 additive, were evaluated as substrate material. The finer grain size -200 and -325 mesh nitrided Si layers were for their smoothness and relatively high density. It was found that nitriding in N2/H2 mixtures, rather than pure N2, resulted in a microstructure that did not substantially degrade the strength of the hot-pressed Si3N4 substrate. Thermal cycling tests on the RSSN/HPSN combinations from 200 C to 1370 C for 75 cycles in air did not degrade the impact resistance nor the interfacial bonding, although a large amount of internal silica formation occurred within the RSSN layer. Mach 0.8, 5 hr, hot gas erosion tests showed no surface recession of RSSN layers at 1200 C and slight surface recession at 1370 C.

Apparatus for silicon nitride precursor solids recovery

DOEpatents

Crosbie, Gary M.; Predmesky, Ronald L.; Nicholson, John M.

1995-04-04

Method and apparatus are provided for collecting reaction product solids entrained in a gaseous outflow from a reaction situs, wherein the gaseous outflow includes a condensable vapor. A condensate is formed of the condensable vapor on static mixer surfaces within a static mixer heat exchanger. The entrained reaction product solids are captured in the condensate which can be collected for further processing, such as return to the reaction situs. In production of silicon imide, optionally integrated into a production process for making silicon nitride caramic, wherein reactant feed gas comprising silicon halide and substantially inert carrier gas is reacted with liquid ammonia in a reaction vessel, silicon imide reaction product solids entrained in a gaseous outflow comprising residual carrier gas and vaporized ammonia can be captured by forming a condensate of the ammonia vapor on static mixer surfaces of a static mixer heat exchanger.

Method for silicon nitride precursor solids recovery

DOEpatents

Crosbie, Gary M.; Predmesky, Ronald L.; Nicholson, John M.

1992-12-15

Method and apparatus are provided for collecting reaction product solids entrained in a gaseous outflow from a reaction situs, wherein the gaseous outflow includes a condensable vapor. A condensate is formed of the condensable vapor on static mixer surfaces within a static mixer heat exchanger. The entrained reaction product solids are captured in the condensate which can be collected for further processing, such as return to the reaction situs. In production of silicon imide, optionally integrated into a production process for making silicon nitride caramic, wherein reactant feed gas comprising silicon halide and substantially inert carrier gas is reacted with liquid ammonia in a reaction vessel, silicon imide reaction product solids entrained in a gaseous outflow comprising residual carrier gas and vaporized ammonia can be captured by forming a condensate of the ammonia vapor on static mixer surfaces of a static mixer heat exchanger.

Untangling the Energetics and Dynamics of Boron Monoxide Radical Reactions (11BO; X2Sigma+)

DTIC Science & Technology

2015-04-15

Reaction products of isoelectronic boron monoxide (BO), cyano (CN), ethynyl (CCH), and silicon nitride (SiN) radicals with acetylene and ethylene. 3.10...Isoelectronicity in the Reactions of the Cyano (CN), Boron Monoxide (BO), Silicon Nitride (SiN), and Ethynyl (C2H) Radicals with Unsaturated Hydrocarbons...AFRL-OSR-VA-TR-2015-0111 Untangling the Energetics and Dynamics of Boron Monoxide Radical Reactions Ralf Kaiser UNIVERSITY OF HAWAII SYSTEMS HONOLULU

The effect of preparation conditions on the structure and mechanical properties of reaction-sintered silicon nitride

NASA Technical Reports Server (NTRS)

Heinrich, J.

1980-01-01

The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.

Mechanical Properties of Porous, High Temperature Structural Materials: Sources of Toughness in Reaction Bonded Silicon Nitride.

DTIC Science & Technology

1995-10-15

tensile extension. At each level of externally imposed displacements, internal equilibrium was achieved by a conjugate gradient method of energy...indentation cracks viewed by TEM. This could be due to either weaker grain boundaries or due to grain level internal stresses of misfit. The fact... internally using the conjugate gradient method until the overall elastic strain energy function 4 was minimized for a unit level of border displacement which

Corrosion Issues for Ceramics in Gas Turbines

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Opila, Elizabeth J.; Tortorelli, Peter F.; More, Karren L.; Nickel, Klaus G.; Hirata, Takehiko; Yoshida, Makoto; Yuri, Isao

2000-01-01

The requirements for hot-gas-path materials in gas turbine engines are demanding. These materials must maintain high strength and creep resistance in a particularly aggressive environment. A typical gas turbine environment involves high temperatures, rapid gas flow rates, high pressures, and a complex mixture of aggressive gases. Figure 26.1 illustrates the requirements for components of an aircraft engine and critical issues [1]. Currently, heat engines are constructed of metal alloys, which meet these requirements within strict temperature limits. In order to extend these temperature limits, ceramic materials have been considered as potential engine materials, due to their high melting points and stability at high temperatures. These materials include oxides, carbides, borides, and nitrides. Interest in using these materials in engines appears to have begun in the 1940s with BeO-based porcelains [2]. During the 1950s, the efforts shifted to cermets. These were carbide-based materials intended to exploit the best properties of metals and ceramics. During the 1960s and 1970s, the silicon-based ceramics silicon carbide (SiC) and silicon nitride (Si3N4) were extensively developed. Although the desirable high-temperature properties of SiC and Si3N4 had long been known, consolidation of powders into component-sized bodies required the development of a series of specialized processing routes [3]. For SiC, the major consolidation routes are reaction bonding, hot-pressing, and sintering. The use of boron and carbon as additives which enable sintering was a particularly noteworthy advance [4]. For Si3N4 the major consolidation routes are reaction bonding and hot pressing [5]. Reaction-bonding involves nitridation of silicon powder. Hot pressing involves addition of various refractory oxides, such as magnesia (MgO), alumina (Al2O3), and yttria (y2O3). Variations on these processes include a number of routes including Hot Isostatic Pressing (HIP), gas-pressure sintering, sinter-HIPing, and Encapsulation-HIPing. It is important to note that each process involves the addition of secondary elements, which later were shown to dramatically influence oxidation and corrosion behavior. As dense bodies of silicon-based ceramics became more readily available, their desirable high temperature properties were confirmed. These materials retained strength to very high temperatures (i.e. 1300-1400 C). Further, they were lightweight and made from abundant materials. SiC and Si3N4 therefore emerged as leading ceramic candidates for components in heat engines, designed to operate at higher temperatures for better performance and fuel efficiency. The first US programs for ceramics in heat engines have been reviewed [6]. Selected programs on ceramic engine parts are summarized here in regard to their contributions to understanding the corrosion behavior of a heat engine environment.

Assessment of damage in ceramics and ceramic matrix composites using ultrasonic techniques

NASA Technical Reports Server (NTRS)

Chu, Y. C.; Baaklini, G. Y.; Rokhlin, S.I.

1993-01-01

This paper addresses the application of ultrasonic sensing to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock or oxidation at elevated temperatures, which often results in elastic anisotropy. This damaged-induced anisotropy is determined by measuring the velocities of ultrasonic waves in different propagation directions. Thermal shock damage is assessed in ceramic samples of reaction bonded silicon nitride (RBSN). Thermal shock treatment from different temperatures up to 1000 C is applied to produce the microcracks. Results indicate that most microcracks produced by thermal shock are located near sample surfaces. Ultrasonic measurements using the surface wave method are found to correlate well with measurements of degradation of mechanical properties obtained independently by other authors using destructive methods. Oxidation damage is assessed in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400 C, for 100 hr. The Youngs' modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600 C but retains its original value at temperatures above 1200 C. This agrees well with the results of destructive tests by other authors. On the other hand, the transverse moduli obtained from ultrasonic measurements decrease continually until 1200 C. Measurements on the shear stiffnesses show behavior similar to the transverse moduli. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

Effect of attrition milling on the reaction sintering of silicon nitride

NASA Technical Reports Server (NTRS)

Herbell, T. P.; Glasgow, T. K.; Yeh, H. C.

1978-01-01

Silicon powder was ground in a steel attrition mill under nitrogen. Air exposed powder was compacted, prefired in helium, and reaction sintered in nitrogen-4 v/o hydrogen. For longer grinding times, oxygen content, surface area and compactability of the powder increased; and both alpha/beta ratio and degreee of nitridation during sintering increased. Iron content remained constant.

Effect of attrition milling on the reaction sintering of silicon nitride

NASA Technical Reports Server (NTRS)

Herbell, T. P.; Glasgow, T. K.; Yeh, H. C.

1978-01-01

Silicon powder was ground in a steel attrition mill under nitrogen. Air-exposed powder was compacted, prefired in helium, and reaction-sintered in nitrogen-4 v/o hydrogen. For longer grinding times, oxygen content, surface area and compactability of the powder increased; and both alpha/beta ratio and degree of nitridation during sintering increased. Iron content remained constant.

Silicon nitride: A ceramic material with outstanding resistance to thermal shock and corrosion

NASA Technical Reports Server (NTRS)

Huebner, K. H.; Saure, F.

1983-01-01

The known physical, mechanical and chemical properties of reaction-sintered silicon nitride are summarized. This material deserves interest especially because of its unusually good resistance to thermal shock and corrosion at high temperatures. Two types are distinguished: reaction-sintered (porous) and hot-pressed (dense) Si3N4. Only the reaction-sintered material which is being produced today in large scale as crucibles, pipes, nozzles and tiles is considered.

Joining engineering ceramics

NASA Astrophysics Data System (ADS)

Loehman, Ronald E.

Methods for joining ceramics are outlined with attention given to their fundamental properties, and some examples of ceramic bonding in engineering ceramic systems are presented. Ceramic-ceramic bonds using no filler material include diffusion and electric-field bonding and ceramic welding, and bonds with filler materials can be provided by Mo-Mn brazing, microwave joining, and reactive nonmetallic liquid bonding. Ceramic-metal joints can be effected with filler material by means of the same ceramic-ceramic processes and without filler material by means of use of molten glass or diffusion bonding. Key properties of the bonding processes include: bonds with discontinuous material properties, energies that are positive relative to the bulk material, and unique chemical and mechanical properties. The processes and properties are outlined for ceramic-metal joints and for joining silicon nitride, and the factors that control wetting, adhesion, and reaction on the atomic scale are critical for establishing successful joints.

A study of vapor-phase deposition of silicon nitride layers by ammonolysis of dichlorosilane at lowered pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manzha, N. M., E-mail: magazine@miee.ru

2010-12-15

Deposition kinetics of silicon nitride layers at lowered reactor pressures of 10-130 Pa and temperatures in the range 973-1073 K has been studied. The equilibrium constant of the bimolecular reaction of dichlorosilane with ammonia has been calculated. The apparent activation energies calculated taking into account the experimental growth rate nearly coincide with the experimental data. Recommendations for improving the quality of silicon nitride layers are made.

Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Kiser, Lames D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Thermal effects on the mechanical properties of SiC fiber reinforced reaction bonded silicon nitride matrix (SiC/RBSN) composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Phillips, R. E.

1988-01-01

The elevated temperature four-point flexural strength and the room temperature tensile and flexural strength properties after thermal shock were measured for ceramic composites consisting of 30 vol pct uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The elevated temperature strengths were measured after 15 min of exposure in air at temperatures to 1400 C. Thermal shock treatment was accomplished by heating the composite in air for 15 min at temperatures to 1200 C and then quenching in water at 25 C. The results indicate no significant loss in strength properties either at temperature or after thermal shock when compared with the strength data for composites in the as-fabricated condition.

Surface reaction of silicon chlorides during atomic layer deposition of silicon nitride

NASA Astrophysics Data System (ADS)

Yusup, Luchana L.; Park, Jae-Min; Mayangsari, Tirta R.; Kwon, Young-Kyun; Lee, Won-Jun

2018-02-01

The reaction of precursor with surface active site is the critical step in atomic layer deposition (ALD) process. We performed the density functional theory calculation with DFT-D correction to study the surface reaction of different silicon chloride precursors during the first half cycle of ALD process. SiCl4, SiH2Cl2, Si2Cl6 and Si3Cl8 were considered as the silicon precursors, and an NH/SiNH2*-terminated silicon nitride surface was constructed to model the thermal ALD processes using NH3 as well as the PEALD processes using NH3 plasma. The total energies of the system were calculated for the geometry-optimized structures of physisorption, chemisorption, and transition state. The order of silicon precursors in energy barrier, from lowest to highest, is Si3Cl8 (0.92 eV), Si2Cl6 (3.22 eV), SiH2Cl2 (3.93 eV) and SiCl4 (4.49 eV). Silicon precursor with lower energy barrier in DFT calculation showed lower saturation dose in literature for both thermal and plasma-enhanced ALD of silicon nitride. Therefore, DFT calculation is a promising tool in predicting the reactivity of precursor during ALD process.

Characterization of Reaction Sintered Silicon Nitride Radomes

DTIC Science & Technology

1977-10-01

A. Ossin , "A Three Dtraenslonal Stress Analysis on the Effects of a Laser Induced Local Hot Spot on a Silicon Nitride Shell, " Martin Marietta...not stated by Ossin , et al, these boundary conditions are extremes and bracket the realistic case. ** In cases where only a few large flaws limit

Synthesis of fine-grained .alpha.-silicon nitride by a combustion process

DOEpatents

Holt, J. Birch; Kingman, Donald D.; Bianchini, Gregory M.

1990-01-01

A combustion synthesis process for the preparation of .alpha.-silicon nitride and composites thereof is disclosed. Preparation of the .alpha.-silicon nitride comprises the steps of dry mixing silicon powder with an alkali metal azide, such as sodium azide, cold-pressing the mixture into any desired shape, or loading the mixture into a fused, quartz crucible, loading the crucible into a combustion chamber, pressurizing the chamber with nitrogen and igniting the mixture using an igniter pellet. The method for the preparation of the composites comprises dry mixing silicon powder (Si) or SiO.sub.2, with a metal or metal oxide, adding a small amount of an alkali metal azide such as sodium azide, introducing the mixture into a suitable combustion chamber, pressurizing the combustion chamber with nitrogen, igniting the mixture within the combustion chamber, and isolating the .alpha.-silicon nitride formed as a reaction product.

Early stages of plasma induced nitridation of Si (111) surface and study of interfacial band alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shetty, Satish; Shivaprasad, S. M., E-mail: smsprasad@jncasr.ac.in

2016-02-07

We report here a systematic study of the nitridation of the Si (111) surface by nitrogen plasma exposure. The surface and interface chemical composition and surface morphology are investigated by using RHEED, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). At the initial stage of nitridation two superstructures—“8 × 8” and “8/3 × 8/3”—form, and further nitridation leads to 1 × 1 stoichiometric silicon nitride. The interface is seen to have the Si{sup 1+} and Si{sup 3+} states of silicon bonding with nitrogen, which suggests an atomically abrupt and defect-free interface. The initial single crystalline silicon nitride layers are seen to become amorphous at higher thicknesses.more » The AFM image shows that the nitride nucleates at interfacial dislocations that are connected by sub-stoichiometric 2D-nitride layers, which agglomerate to form thick overlayers. The electrical properties of the interface yield a valence band offset that saturates at 1.9 eV and conduction band offset at 2.3 eV due to the evolution of the sub-stoichiometric interface and band bending.« less

Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Rhatt, R. T.; Phillips, R. E.

1988-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2)sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Phillips, Ronald E.

1990-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

Gibbs free energy of reactions involving SiC, Si3N4, H2, and H2O as a function of temperature and pressure

NASA Technical Reports Server (NTRS)

Isham, M. A.

1992-01-01

Silicon carbide and silicon nitride are considered for application as structural materials and coating in advanced propulsion systems including nuclear thermal. Three-dimensional Gibbs free energy were constructed for reactions involving these materials in H2 and H2/H2O. Free energy plots are functions of temperature and pressure. Calculations used the definition of Gibbs free energy where the spontaneity of reactions is calculated as a function of temperature and pressure. Silicon carbide decomposes to Si and CH4 in pure H2 and forms a SiO2 scale in a wet atmosphere. Silicon nitride remains stable under all conditions. There was no apparent difference in reaction thermodynamics between ideal and Van der Waals treatment of gaseous species.

Boron nitride - Composition, optical properties, and mechanical behavior

NASA Technical Reports Server (NTRS)

Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

1987-01-01

A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at. percent. The carbon and oxygen impurities were in the 5 to 8 at. percent range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

Boron nitride: Composition, optical properties and mechanical behavior

NASA Technical Reports Server (NTRS)

Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

1987-01-01

A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

A Porous Ceramic Interphase for SiC/Si(sub 3)N(sub 4) Composites

NASA Technical Reports Server (NTRS)

Ogbuji, Linus U. J. T.

1995-01-01

A suitable interphase material for non-oxide ceramic-matrix composites must be resistant to oxidation. This means it must exhibit a slow rate of oxidation, and its oxidation product must be such as to ensure that the system survives oxidation when it does occur. Because the current benchmark interphase materials, carbon and boron nitride, lack these qualities, a porous fiber coating was developed to satisfy both the mechanical and oxidative requirements of an interphase for the SiC/SiC and SiC/Si2N4 composites that are of interest to NASA. This report presents the interphase microstructure achieved and the resulting characteristics of fiber push-out from a matrix of reaction-bonded silicon nitride (RBSN), both as-fabricated and after substantial annealing and oxidation treatments.

Isolation and characterization of a uranium(VI)-nitride triple bond

NASA Astrophysics Data System (ADS)

King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

2013-06-01

The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

Facile CO Cleavage by a Multimetallic CsU2 Nitride Complex.

PubMed

Falcone, Marta; Kefalidis, Christos E; Scopelliti, Rosario; Maron, Laurent; Mazzanti, Marinella

2016-09-26

Uranium nitrides are important materials with potential for application as fuels for nuclear power generation, and as highly active catalysts. Molecular nitride compounds could provide important insight into the nature of the uranium-nitride bond, but currently little is known about their reactivity. In this study, we found that a complex containing a nitride bridging two uranium centers and a cesium cation readily cleaved the C≡O bond (one of the strongest bonds in nature) under ambient conditions. The product formed has a [CsU2 (μ-CN)(μ-O)] core, thus indicating that the three cations cooperate to cleave CO. Moreover, the addition of MeOTf to the nitride complex led to an exceptional valence disproportionation of the CsU(IV) -N-U(IV) core to yield CsU(III) (OTf) and [MeN=U(V) ] fragments. The important role of multimetallic cooperativity in both reactions is illustrated by the computed reaction mechanisms. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hollow Cathode Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using Pentachlorodisilane.

PubMed

Meng, Xin; Kim, Harrison Sejoon; Lucero, Antonio T; Hwang, Su Min; Lee, Joy S; Byun, Young-Chul; Kim, Jiyoung; Hwang, Byung Keun; Zhou, Xiaobing; Young, Jeanette; Telgenhoff, Michael

2018-04-25

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSi 2 Cl 5 ), was investigated for the growth of silicon nitride (SiN x ) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270-360 °C. At identical process conditions, PCDS not only demonstrated approximately >20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (Si 2 Cl 6 ), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiN x films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (<1 at. %; below the detection limit). Fourier transform infrared spectroscopy spectra suggested that N-H bonds were the dominant hydrogen-containing bonds in the SiN x films without a significant amount of Si-H bonds originating from the precursor molecules. The possible surface reaction pathways of the PEALD SiN x using PCDS on the surface terminated with amine groups (-NH 2 and -NH-) are proposed. The PEALD SiN x films grown using PCDS also exhibited a leakage current density as low as 1-2 nA/cm 2 at 2 MV/cm and a breakdown electric field as high as ∼12 MV/cm.

High performance SONOS flash memory with in-situ silicon nanocrystals embedded in silicon nitride charge trapping layer

NASA Astrophysics Data System (ADS)

Lim, Jae-Gab; Yang, Seung-Dong; Yun, Ho-Jin; Jung, Jun-Kyo; Park, Jung-Hyun; Lim, Chan; Cho, Gyu-seok; Park, Seong-gye; Huh, Chul; Lee, Hi-Deok; Lee, Ga-Won

2018-02-01

In this paper, SONOS-type flash memory device with highly improved charge-trapping efficiency is suggested by using silicon nanocrystals (Si-NCs) embedded in silicon nitride (SiNX) charge trapping layer. The Si-NCs were in-situ grown by PECVD without additional post annealing process. The fabricated device shows high program/erase speed and retention property which is suitable for multi-level cell (MLC) application. Excellent performance and reliability for MLC are demonstrated with large memory window of ∼8.5 V and superior retention characteristics of 7% charge loss for 10 years. High resolution transmission electron microscopy image confirms the Si-NC formation and the size is around 1-2 nm which can be verified again in X-ray photoelectron spectroscopy (XPS) where pure Si bonds increase. Besides, XPS analysis implies that more nitrogen atoms make stable bonds at the regular lattice point. Photoluminescence spectra results also illustrate that Si-NCs formation in SiNx is an effective method to form deep trap states.

Silicon cantilever functionalization for cellulose-specific chemical force imaging of switchgrass

DOE PAGES

Lee, Ida; Evans, Barbara R.; Foston, Marcus B.; ...

2015-05-08

A method for direct functionalization of silicon and silicon nitride cantilevers with bifunctional silanes was tested with model surfaces to determine adhesive forces for different hydrogen-bonding chemistries. Application for biomass surface characterization was tested by mapping switchgrass and isolated switchgrass cellulose in topographic and force-volume mode using a cellulose-specific cantilever.

Silver-hafnium braze alloy

DOEpatents

Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

2003-12-16

A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

Method for making circular tubular channels with two silicon wafers

DOEpatents

Yu, Conrad M.; Hui, Wing C.

1996-01-01

A two-wafer microcapillary structure is fabricated by depositing boron nitride (BN) or silicon nitride (Si.sub.3 N.sub.4) on two separate silicon wafers (e.g., crystal-plane silicon with [100] or [110] crystal orientation). Photolithography is used with a photoresist to create exposed areas in the deposition for plasma etching. A slit entry through to the silicon is created along the path desired for the ultimate microcapillary. Acetone is used to remove the photoresist. An isotropic etch, e.g., such as HF/HNO.sub.3 /CH.sub.3 COOH, then erodes away the silicon through the trench opening in the deposition layer. A channel with a half-circular cross section is then formed in the silicon along the line of the trench in the deposition layer. Wet etching is then used to remove the deposition layer. The two silicon wafers are aligned and then bonded together face-to-face to complete the microcapillary.

Surface Defect Passivation and Reaction of c-Si in H2S.

PubMed

Liu, Hsiang-Yu; Das, Ujjwal K; Birkmire, Robert W

2017-12-26

A unique passivation process of Si surface dangling bonds through reaction with hydrogen sulfide (H 2 S) is demonstrated in this paper. A high-level passivation quality with an effective minority carrier lifetime (τ eff ) of >2000 μs corresponding to a surface recombination velocity of <3 cm/s is achieved at a temperature range of 550-650 °C. X-ray photoelectron spectroscopy (XPS) confirmed the bonding states of Si and S and provides insights into the reaction pathway of Si with H 2 S and other impurity elements both during and after the reaction. Quantitative analysis of XPS spectra showed that the τ eff increases with an increase in the surface S content up to ∼3.5% and stabilizes thereafter, indicative of surface passivation by monolayer coverage of S on the Si surface. However, S passivation of the Si surface is highly unstable because of thermodynamically favorable reaction with atmospheric H 2 O and O 2 . This instability can be eliminated by capping the S-passivated Si surface with a protective thin film such as low-temperature-deposited amorphous silicon nitride.

Experimental evidence of trap level modulation in silicon nitride thin films by hydrogen annealing

NASA Astrophysics Data System (ADS)

Seki, Harumi; Kamimuta, Yuuichi; Mitani, Yuichiro

2018-06-01

The energy level of electron traps in silicon nitride (SiN x ) thin films was investigated by discharging current transient spectroscopy (DCTS). Results indicate that the trap level of the SiN x thin films becomes deeper with decreasing composition (N/Si) and shallower after hydrogen annealing. The dependence of the trap level on the SiN x composition and the modulation of the trap level by hydrogen annealing are possibly related to the change in the number of Si–H bonds in the SiN x thin films.

Heterogeneous integration of lithium niobate and silicon nitride waveguides for wafer-scale photonic integrated circuits on silicon.

PubMed

Chang, Lin; Pfeiffer, Martin H P; Volet, Nicolas; Zervas, Michael; Peters, Jon D; Manganelli, Costanza L; Stanton, Eric J; Li, Yifei; Kippenberg, Tobias J; Bowers, John E

2017-02-15

An ideal photonic integrated circuit for nonlinear photonic applications requires high optical nonlinearities and low loss. This work demonstrates a heterogeneous platform by bonding lithium niobate (LN) thin films onto a silicon nitride (Si₃N₄) waveguide layer on silicon. It not only provides large second- and third-order nonlinear coefficients, but also shows low propagation loss in both the Si₃N₄ and the LN-Si₃N₄ waveguides. The tapers enable low-loss-mode transitions between these two waveguides. This platform is essential for various on-chip applications, e.g., modulators, frequency conversions, and quantum communications.

Preceramic Polymers for Use as Fiber Coatings

NASA Technical Reports Server (NTRS)

Heimann, P. J.; Hurwitz, F. I.; Wheeler, D.; Eldridge, J.; Baranwal, R.; Dickerson, R.

1996-01-01

Polymeric precursors to Si-C-O, SI-B-N and Si-C were evaluated for use as ceramic interfaces in ceramic matrix composites. Use of the preceramic polymers allows for easy dip coating of fibers from dilute solutions of a polymer, which are then pyrolyzed to obtain the ceramic. SCS-0 fibers (Textron Specialty Materials, Lowell, MA) were coated with polymers from three systems: polysilsesquioxanes, polyborosilazanes and polycarbosilanes. The polysilsesquioxane systems were shown to produce either silicon oxycarbide or silicon oxynitride, depending on the pyrolysis conditions, and demonstrated some promise in an RBSN (reaction-bonded silicon nitride) matrix model system. Polyborosilazanes were shown, in studies of bulk polymers, to give rise to oxidation resistant Si-B-N ceramics which remain amorphous to temperatures of 1600 C, and should therefore provide a low modulus interface. Polycarbosilanes produce amorphous carbon-rich Si-C materials which have demonstrated oxidation resistance.

Properties of RBSN and RBSN-SiC composites. [Reaction Bonded Silicon Nitride

NASA Technical Reports Server (NTRS)

Lightfoot, A.; Ker, H. L.; Haggerty, J. S.; Ritter, J. E.

1990-01-01

Strengths, fracture toughnesses, hardnesses, and dimensional changes have been measured for RBSN and RBSN/SiC composites. Samples were made from mixtures of Si and either Si- or C-rich SiC powders. For pure, 75 pct dense RBSN dispersed with octanol, strengths up to 858 MPa have been achieved. Improved strengths result from a combination of microstructural perfection and increased fracture toughness. The mechanical properties of the composites were approximately equal to those of methanol processed RBSN but not quite equal to those of the octanol-processed RBSN. Results are discussed in terms of observed microstructural features.

Crack healing behavior of hot pressed silicon nitride due to oxidation

NASA Technical Reports Server (NTRS)

Choi, S. R.; Tikare, V.

1992-01-01

It is shown that limited oxidation of an MgO-containing, hot-pressed silicon nitride ceramic at 800 deg C and above results in increased strength due to crack healing. Slight oxidation of the surface produces enstatite and cristobalite which fills in cracks. More extensive oxidation leads to strength degradation due to the formation of new flaws by the evolution of N2 gas at the surface. The apparent fracture toughness also increased at 800 deg C and above due to oxidation. Bonds formed between the two surfaces of the crack during oxidation leads to a reduction in stress intensity at the crack tip, suggesting that valid high-temperature toughness values cannot be obtained in an air environment. The increase in strength due to crack healing by oxidation can be achieved without compromising the fatigue properties of the silicon nitride ceramic.

A new active solder for joining electronic components

DOE Office of Scientific and Technical Information (OSTI.GOV)

SMITH,RONALD W.; VIANCO,PAUL T.; HERNANDEZ,CYNTHIA L.

Electronic components and micro-sensors utilize ceramic substrates, copper and aluminum interconnect and silicon. The joining of these combinations require pre-metallization such that solders with fluxes can wet such combinations of metals and ceramics. The paper will present a new solder alloy that can bond metals, ceramics and composites. The alloy directly wets and bonds in air without the use flux or premetallized layers. The paper will present typical processing steps and joint microstructures in copper, aluminum, aluminum oxide, aluminum nitride, and silicon joints.

Method for making circular tubular channels with two silicon wafers

DOEpatents

Yu, C.M.; Hui, W.C.

1996-11-19

A two-wafer microcapillary structure is fabricated by depositing boron nitride (BN) or silicon nitride (Si{sub 3}N{sub 4}) on two separate silicon wafers (e.g., crystal-plane silicon with [100] or [110] crystal orientation). Photolithography is used with a photoresist to create exposed areas in the deposition for plasma etching. A slit entry through to the silicon is created along the path desired for the ultimate microcapillary. Acetone is used to remove the photoresist. An isotropic etch, e.g., such as HF/HNO{sub 3}/CH{sub 3}COOH, then erodes away the silicon through the trench opening in the deposition layer. A channel with a half-circular cross section is then formed in the silicon along the line of the trench in the deposition layer. Wet etching is then used to remove the deposition layer. The two silicon wafers are aligned and then bonded together face-to-face to complete the microcapillary. 11 figs.

Silicon technology-based micro-systems for atomic force microscopy/photon scanning tunnelling microscopy.

PubMed

Gall-Borrut, P; Belier, B; Falgayrettes, P; Castagne, M; Bergaud, C; Temple-Boyer, P

2001-04-01

We developed silicon nitride cantilevers integrating a probe tip and a wave guide that is prolonged on the silicon holder with one or two guides. A micro-system is bonded to a photodetector. The resulting hybrid system enables us to obtain simultaneously topographic and optical near-field images. Examples of images obtained on a longitudinal cross-section of an optical fibre are shown.

Low temperature synthesis of silicon nitride thin films deposited by VHF/RF PECVD for gas barrier application

NASA Astrophysics Data System (ADS)

Lee, Jun S.; Shin, Kyung S.; Sahu, B. B.; Han, Jeon G.

2015-09-01

In this work, silicon nitride (SiNx) thin films were deposited on polyethylene terephthalate (PET) substrates as barrier layers by plasma enhanced chemical vapor deposition (PECVD) system. Utilizing a combination of very high-frequency (VHF 40.68 MHz) and radio-frequency (RF 13.56 MHz) plasmas it was possible to adopt PECVD deposition at low-temperature using the precursors: Hexamethyldisilazane (HMDSN) and nitrogen. To investigate relationship between film properties and plasma properties, plasma diagnostic using optical emission spectroscopy (OES) was performed along with the film analysis using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). OES measurements show that there is dominance of the excited N2 and N2+ emissions with increase in N2 dilution, which has a significant impact on the film properties. It was seen that all the deposited films contains mainly silicon nitride with a small content of carbon and no signature of oxygen. Interestingly, upon air exposure, films have shown the formation of Si-O bonds in addition to the Si-N bonds. Measurements and analysis reveals that SiNx films deposited with high content of nitrogen with HMDSN plasma can have lower gas barrier properties as low as 7 . 3 ×10-3 g/m2/day. Also at Chiang Mai University.

New Oxide Ceramic Developed for Superior High-Temperature Wear Resistance

NASA Technical Reports Server (NTRS)

Sayir, Ali; Miyoshi, Kazuhisa; Farmer, Serene C.

2003-01-01

Ceramics, for the most part, do not have inherently good tribological properties. For example friction coefficients in excess of 0.7 have been reported for silicon nitride sliding on silicon nitride or on bearing steel (ref. 1). High friction is always accompanied by considerable wear. Despite their inherently poor tribological properties, the high strength and high toughness of silicon nitride (Si3N4) ceramics has led to their successful use in tribological applications (refs. 1 to 4). The upper temperature limit for the application of Si3N4 as wear-resistant material is limited by reaction with the tribological environment (ref. 3). Silicon nitride is known to produce a thin silicon dioxide film with easy shear capability that results in low friction and low wear in a moist environment (ref. 5). At elevated temperatures, the removal of the reaction product that acts as lubricant causes the friction coefficient to increase and, consequently, the wear performance to become poor. New materials are sought that will have wear resistance superior to that of Si3N4 at elevated temperatures and in harsh environments. A new class of oxide ceramic materials has been developed with potential for excellent high-temperature wear resistance. The new material consists of a multicomponent oxide with a two-phase microstructure, in which the wear resistance of the mixed oxide is significantly higher than that of the individual constituents. This is attributed to the strong constraining effects provided by the interlocking microstructures at different length scales, to the large aspect ratio of the phases, to the strong interphase bonding, and to the residual stresses. Fretting wear tests were conducted by rubbing the new ceramic material against boron carbide (B4C). The new ceramic material produced a wear track groove on B4C, suggesting significantly higher wear resistance for the oxide ceramic. The new material did not suffer from any microstructural degradation after the wear test. The wear rate of the new ceramic material at 600 C was determined to be on the order of 10-10 mm3/N-m, which is 3 to 5 orders of magnitude lower than that for the current state-of-theart wear-resistant materials (Si3N4and B4C). The friction coefficient of the new ceramic materials is on the order of 0.4, which is significantly lower than that of silicon nitride. This new class of oxide materials has shown considerable potential for applications requiring high wear resistance at high temperatures and in harsh environments. New understanding of the wear behavior of ceramic materials is emerging as a result of the surprisingly high wear resistance of two-phase oxide ceramics. There is excellent potential for further improvements in the wear resistance of oxide ceramics through optimizing the microstructure and altering the crystallographic properties of specific oxide materials as a second phase to reduce the coefficient of friction at elevated temperatures.

Durable silver coating for mirrors

DOEpatents

Wolfe, Jesse D.; Thomas, Norman L.

2000-01-01

A durable multilayer mirror includes reflective layers of aluminum and silver and has high reflectance over a broad spectral range from ultraviolet to visible to infrared. An adhesion layer of a nickel and/or chromium alloy or nitride is deposited on an aluminum surface, and a thin layer of silver is then deposited on the adhesion layer. The silver layer is protected by a passivation layer of a nickel and/or chromium alloy or nitride and by one or more durability layers made of metal oxides and typically a first layer of metal nitride. The durability layers may include a composite silicon aluminum nitride and an oxinitride transition layer to improve bonding between nitride and oxide layers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Custer, Jonathan S.; Fleming, James G.; Roherty-Osmun, Elizabeth

Refractory ternary nitride films for diffusion barriers in microelectronics have been grown using chemical vapor deposition. Thin films of titanium-silicon-nitride, tungsten-boron-nitride, and tungsten-silicon-nitride of various compositions have been deposited on 150 mm Si wafers. The microstructure of the films are either fully amorphous for the tungsten based films, or nauocrystalline TiN in an amorphous matrix for titanium-silicon-nitride. All films exhibit step coverages suitable for use in future microelectronics generations. Selected films have been tested as diffusion barriers between copper and silicon, and generally perform extremely weH. These fiIms are promising candidates for advanced diffusion barriers for microelectronics applications. The manufacturingmore » of silicon wafers into integrated circuits uses many different process and materials. The manufacturing process is usually divided into two parts: the front end of line (FEOL) and the back end of line (BEOL). In the FEOL the individual transistors that are the heart of an integrated circuit are made on the silicon wafer. The responsibility of the BEOL is to wire all the transistors together to make a complete circuit. The transistors are fabricated in the silicon itself. The wiring is made out of metal, currently aluminum and tungsten, insulated by silicon dioxide, see Figure 1. Unfortunately, silicon will diffuse into aluminum, causing aluminum spiking of junctions, killing transistors. Similarly, during chemical vapor deposition (CVD) of tungsten from ~fj, the reactivity of the fluorine can cause "worn-holes" in the silicon, also destroying transistors. The solution to these problems is a so-called diffusion barrier, which will allow current to pass from the transistors to the wiring, but will prevent reactions between silicon and the metal.« less

Silicon-based sleeve devices for chemical reactions

DOEpatents

Northrup, M. Allen; Mariella, Jr., Raymond P.; Carrano, Anthony V.; Balch, Joseph W.

1996-01-01

A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

Silicon-based sleeve devices for chemical reactions

DOEpatents

Northrup, M.A.; Mariella, R.P. Jr.; Carrano, A.V.; Balch, J.W.

1996-12-31

A silicon-based sleeve type chemical reaction chamber is described that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis. 32 figs.

Microfabricated sleeve devices for chemical reactions

DOEpatents

Northrup, M. Allen

2003-01-01

A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and non-silicon based materials to provide the thermal properties desired. For example, the chamber may combine a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

Transferrable monolithic III-nitride photonic circuit for multifunctional optoelectronics

NASA Astrophysics Data System (ADS)

Shi, Zheng; Gao, Xumin; Yuan, Jialei; Zhang, Shuai; Jiang, Yan; Zhang, Fenghua; Jiang, Yuan; Zhu, Hongbo; Wang, Yongjin

2017-12-01

A monolithic III-nitride photonic circuit with integrated functionalities was implemented by integrating multiple components with different functions into a single chip. In particular, the III-nitride-on-silicon platform is used as it integrates a transmitter, a waveguide, and a receiver into a suspended III-nitride membrane via a wafer-level procedure. Here, a 0.8-mm-diameter suspended device architecture is directly transferred from silicon to a foreign substrate by mechanically breaking the support beams. The transferred InGaN/GaN multiple-quantum-well diode (MQW-diode) exhibits a turn-on voltage of 2.8 V with a dominant electroluminescence peak at 453 nm. The transmitter and receiver share an identical InGaN/GaN MQW structure, and the integrated photonic circuit inherently works for on-chip power monitoring and in-plane visible light communication. The wire-bonded monolithic photonic circuit on glass experimentally demonstrates in-plane data transmission at 120 Mb/s, paving the way for diverse applications in intelligent displays, in-plane light communication, flexible optical sensors, and wearable III-nitride optoelectronics.

Temperature control apparatus

DOEpatents

Northrup, M. Allen

2003-08-05

A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and non-silicon based materials to provide the thermal properties desired. For example, the chamber may combine a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

A three-mask process for fabricating vacuum-sealed capacitive micromachined ultrasonic transducers using anodic bonding.

PubMed

Yamaner, F Yalçın; Zhang, Xiao; Oralkan, Ömer

2015-05-01

This paper introduces a simplified fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using anodic bonding. Anodic bonding provides the established advantages of wafer-bondingbased CMUT fabrication processes, including process simplicity, control over plate thickness and properties, high fill factor, and ability to implement large vibrating cells. In addition to these, compared with fusion bonding, anodic bonding can be performed at lower processing temperatures, i.e., 350°C as opposed to 1100°C; surface roughness requirement for anodic bonding is more than 10 times more relaxed, i.e., 5-nm rootmean- square (RMS) roughness as opposed to 0.5 nm for fusion bonding; anodic bonding can be performed on smaller contact area and hence improves the fill factor for CMUTs. Although anodic bonding has been previously used for CMUT fabrication, a CMUT with a vacuum cavity could not have been achieved, mainly because gas is trapped inside the cavities during anodic bonding. In the approach we present in this paper, the vacuum cavity is achieved by opening a channel in the plate structure to evacuate the trapped gas and subsequently sealing this channel by conformal silicon nitride deposition in the vacuum environment. The plate structure of the fabricated CMUT consists of the single-crystal silicon device layer of a silicon-on-insulator wafer and a thin silicon nitride insulation layer. The presented fabrication approach employs only three photolithographic steps and combines the advantages of anodic bonding with the advantages of a patterned metal bottom electrode on an insulating substrate, specifically low parasitic series resistance and low parasitic shunt capacitance. In this paper, the developed fabrication scheme is described in detail, including process recipes. The fabricated transducers are characterized using electrical input impedance measurements in air and hydrophone measurements in immersion. A representative design is used to demonstrate immersion operation in conventional, collapse-snapback, and collapse modes. In collapsemode operation, an output pressure of 1.67 MPa pp is shown at 7 MHz on the surface of the transducer for 60-Vpp, 3-cycle sinusoidal excitation at 30-V dc bias.

PECVD silicon-rich nitride and low stress nitride films mechanical characterization using membrane point load deflection

NASA Astrophysics Data System (ADS)

Bagolini, Alvise; Picciotto, Antonino; Crivellari, Michele; Conci, Paolo; Bellutti, Pierluigi

2016-02-01

An analysis of the mechanical properties of plasma enhanced chemical vapor (PECVD) silicon nitrides is presented, using micro fabricated silicon nitride membranes under point load deflection. The membranes are made of PECVD silicon-rich nitride and low stress nitride films. The mechanical performance of the bended membranes is examined both with analytical models and finite element simulation in order to extract the elastic modulus and residual stress values. The elastic modulus of low stress silicon nitride is calculated using stress free analytical models, while for silicon-rich silicon nitride and annealed low stress silicon nitride it is estimated with a pre-stressed model of point-load deflection. The effect of annealing both in nitrogen and hydrogen atmosphere is evaluated in terms of residual stress, refractive index and thickness variation. It is demonstrated that a hydrogen rich annealing atmosphere induces very little change in low stress silicon nitride. Nitrogen annealing effects are measured and shown to be much higher in silicon-rich nitride than in low stress silicon nitride. An estimate of PECVD silicon-rich nitride elastic modulus is obtained in the range between 240-320 GPa for deposited samples and 390 GPa for samples annealed in nitrogen atmosphere. PECVD low stress silicon nitride elastic modulus is estimated to be 88 GPa as deposited and 320 GPa after nitrogen annealing.

Improved performance of silicon nitride-based high temperature ceramics

NASA Technical Reports Server (NTRS)

Ashbrook, R. L.

1977-01-01

Recent progress in the production of Si3N4 based ceramics is reviewed: (1) high temperature strength and toughness of hot pressed Si3N4 were improved by using high purity powder and a stabilized ZrO2 additive, (2) impact resistance of hot pressed Si3N4 was increased by the use of a crushable energy absorbing layer, (3) the oxidation resistance and strength of reaction sintered Si3N4 were increased by impregnating reaction sintered silicon nitride with solutions that oxidize to Al2O3 or ZrO2, (4) beta prime SiA1ON compositions and sintering aids were developed for improved oxidation resistance or improved high temperature strength.

Structure analysis of aluminium silicon manganese nitride precipitates formed in grain-oriented electrical steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernier, Nicolas, E-mail: n.bernier@yahoo.fr; Xhoffer, Chris; Van De Putte, Tom, E-mail: tom.vandeputte@arcelormittal.com

We report a detailed structural and chemical characterisation of aluminium silicon manganese nitrides that act as grain growth inhibitors in industrially processed grain-oriented (GO) electrical steels. The compounds are characterised using energy dispersive X-ray spectrometry (EDX) and energy filtered transmission electron microscopy (EFTEM), while their crystal structures are analysed using X-ray diffraction (XRD) and TEM in electron diffraction (ED), dark-field, high-resolution and automated crystallographic orientation mapping (ACOM) modes. The chemical bonding character is determined using electron energy loss spectroscopy (EELS). Despite the wide variation in composition, all the precipitates exhibit a hexagonal close-packed (h.c.p.) crystal structure and lattice parameters ofmore » aluminium nitride. The EDX measurement of ∼ 900 stoichiometrically different precipitates indicates intermediate structures between pure aluminium nitride and pure silicon manganese nitride, with a constant Si/Mn atomic ratio of ∼ 4. It is demonstrated that aluminium and silicon are interchangeably precipitated with the same local arrangement, while both Mn{sup 2+} and Mn{sup 3+} are incorporated in the h.c.p. silicon nitride interstitial sites. The oxidation of the silicon manganese nitrides most likely originates from the incorporation of oxygen during the decarburisation annealing process, thus creating extended planar defects such as stacking faults and inversion domain boundaries. The chemical composition of the inhibitors may be written as (AlN){sub x}(SiMn{sub 0.25}N{sub y}O{sub z}){sub 1−x} with x ranging from 0 to 1. - Highlights: • We study the structure of (Al,Si,Mn)N inhibitors in grain oriented electrical steels. • Inhibitors have the hexagonal close-packed symmetry with lattice parameters of AlN. • Inhibitors are intermediate structures between pure AlN and (Si,Mn)N with Si/Mn ∼ 4. • Al and Si share the same local arrangement; Mn is incorporated in both Mn{sup 2+} and Mn{sup 3+}. • Oxygen incorporation is invoked to account for the thermal stability of (Al,Si,Mn)N.« less

Nanostructured silicon nitride from wheat and rice husks

NASA Astrophysics Data System (ADS)

Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Wollmershauser, J. A.; Feng, C. R.

2016-04-01

Nanoparticles, submicron-diameter tubes, and rods of Si3N4 were synthesized from the thermal treatment of wheat and rice husks at temperatures at and above 1300 °C in a nitrogen atmosphere. The whole pattern Rietveld analysis of the observed diffraction data from treatments at 1300 °C showed the formation of only hexagonal α-phase of Si3N4 with an R-factor of 1%, whereas samples treated at 1400 °C and above showed both α- and β-phases with an R-factor of 2%. Transmission electron microscopy showed the presence of tubes, rods, and nanoparticles of Si3N4. In a two-step process, where pure SiC was produced first from rice or wheat husk in an argon atmosphere and subsequently treated in a nitrogen atmosphere at 1450 °C, a nanostructured composite material having α- and β-phases of Si3N4 combined with cubic phase of SiC was formed. The thermodynamics of the formation of silicon nitride is discussed in terms of the solid state reaction between organic matter (silica content), which is inherently present in the wheat and rice husks, with the nitrogen from the furnace atmosphere. Nanostructures of silicon nitride formed by a single direct reaction or their composites with SiC formed in a two-step process of agricultural byproducts provide an uncomplicated sustainable synthesis route for silicon nitride used in mechanical, biotechnology, and electro-optic nanotechnology applications.

Crystal growth in supercritical ammonia using high surface area silicon nitride feedstock

NASA Astrophysics Data System (ADS)

Kaskel, Stefan; Khanna, Meikh; Zibrowius, Bodo; Schmidt, Hans-Werner; Ullner, Dirk

2004-01-01

The use of amorphous high surface area silicon nitride is proposed as a raw material for crystallization experiments in supercritical ammonia. Compared with earlier studies, the use of highly dispersed solids results in the crystallization of inorganic nitrides under relatively mild conditions (673 K). Mineralizers such as amides (LiNH 2, NaNH 2, KNH 2) are found to be effective crystallization aids. The crystalline products, detected using powder X-ray diffraction, are either MSi 2N 3 (M=Li, Na) or Si 2N 2NH. Si 2N 2NH is also characterized using 29Si MAS NMR. The spectrum shows a narrow line located at -44.7 ppm, whereas for amorphous silicon nitride-based materials the line is broad. The ammonothermal reaction of NaAl(NH 2) 4 and high surface area silicon nitride at 673 K affords a new orthorhombic phase, isostructural with NaSi 2N 3, but with extended lattice constants ( a=9.634, b=5.643, c=5.011 Å). Effective crystallization is also achieved using fluoride mineralizers (KF, CsF) at 673 K. A new small scale autoclave, suitable for laboratory syntheses at temperatures up to 873 K, is presented that can be loaded under inert gas.

Study program to develop and evaluate die and container materials for the growth of silicon ribbons. [for development of low cost solar cells

NASA Technical Reports Server (NTRS)

Addington, L. A.; Ownby, P. D.; Yu, B. B.; Barsoum, M. W.; Romero, H. V.; Zealer, B. G.

1979-01-01

The development and evaluation of proprietary coatings of pure silicon carbide, silicon nitride, and aluminum nitride on less pure hot pressed substrates of the respective ceramic materials, is described. Silicon sessile drop experiments were performed on coated test specimens under controlled oxygen partial pressure. Prior to testing, X-ray diffraction and SEM characterization was performed. The reaction interfaces were characterized after testing with optical and scanning electron microscopy and Auger electron spectroscopy. Increasing the oxygen partial pressure was found to increase the molten silicon contact angle, apparently because adsorbed oxygen lowers the solid-vapor interfacial free energy. It was also found that adsorbed oxygen increased the degree of attack of molten silicon upon the chemical vapor deposited coatings. Cost projections show that reasonably priced, coated, molten silicon resistant refractory material shapes are obtainable.

Ultrasonic and micromechanical study of damage and elastic properties of SiC/RBSN ceramic composites. [Reaction Bonded Silicon Nitride

NASA Technical Reports Server (NTRS)

Chu, Y. C.; Hefetz, M.; Rokhlin, S. I.; Baaklini, G. Y.

1992-01-01

Ultrasonic techniques are employed to develop methods for nondestructive evaluation of elastic properties and damage in SiC/RBSN composites. To incorporate imperfect boundary conditions between fibers and matrix into a micromechanical model, a model of fibers having effective anisotropic properties is introduced. By inverting Hashin's (1979) microstructural model for a composite material with microscopic constituents the effective fiber properties were found from ultrasonic measurements. Ultrasonic measurements indicate that damage due to thermal shock is located near the surface, so the surface wave is most appropriate for estimation of the ultimate strength reduction and critical temperature of thermal shock. It is concluded that bonding between laminates of SiC/RBSN composites is severely weakened by thermal oxidation. Generally, nondestructive evaluation of thermal oxidation effects and thermal shock shows good correlation with measurements previously performed by destructive methods.

X-Ray Photoelectron Spectroscopy and Ultrahigh Vacuum Contactless Capacitance-Voltage Characterization of Novel Oxide-Free InP Passivation Process Using a Silicon Surface Quantum Well

NASA Astrophysics Data System (ADS)

Takahashi, Hiroshi; Hashizume, Tamotsu; Hasegawa, Hideki

1999-02-01

In order to understand and optimize a novel oxide-free InP passivation process using a silicon surface quantum well, a detailed in situ X-ray photoelectron spectroscopy (XPS) and ultrahigh vacuum (UHV) contactless capacitance-voltage (C-V) study of the interface was carried out. Calculation of quantum levels in the silicon quantum well was performed on the basis of the band lineup of the strained Si3N4/Si/InP interface and the result indicated that the interface should become free of gap states when the silicon layer thickness is below 5 Å. Experimentally, such a delicate Si3N4/Si/InP structure was realized by partial nitridation of a molecular beam epitaxially (MBE) grown pseudomorphic silicon layer using an electron cyclotron resonance (ECR) N2 plasma. The progress of nitridation was investigated in detail by angle-resolved XPS. A newly developed UHV contactless C-V method realized in situ characterization of surface electronic properties of InP at each processing step for passivation. It was found that the interface state density decreased substantially into the 1010 cm-2 eV-1 range by optimizing the nitridation process of the silicon layer. It was concluded that both the surface bond termination and state removal by quantum confinement are responsible for the NSS reduction.

A novel passivation process of silicon nanowires by a low-cost PECVD technique for deposition of hydrogenated silicon nitride using SiH4 and N2 as precursor gases

NASA Astrophysics Data System (ADS)

Bouaziz, Lamia; Dridi, Donia; Karyaoui, Mokhtar; Angelova, Todora; Sanchez Plaza, Guillermo; Chtourou, Radhouane

2017-03-01

In this work, a different SiNx passivation process of silicon nanowires has been opted for the deposition of a hydrogenated silicon nitride (SiNx:H) by a low-cost plasma enhanced chemical vapor deposition (PECVD) using silane ( SiH4 and nitrogen ( N2 as reactive gases. This study is focused on the effect of the gas flow ratio on chemical composition, morphological, optical and optoelectronic properties of silicon nanowires. The existence of Si-N and Si-H bonds was proven by the Fourier transmission infrared (FTIR) spectrum. Morphological structures were shown by scanning electron microscopy (SEM), and the roughness was investigated by atomic force microscopy (AFM). A low reflectivity less than 6% in the wavelength range 250-1200nm has been shown by UV-visible spectroscopy. Furthermore, the thickness and the refractive index of the passivation layer is determined by ellipsometry measurements. As a result, an improvement in minority carrier lifetime has been obtained by reducing surface recombination of silicon nanowires.

Brittle Materials Design, High Temperature Gas Turbine

DTIC Science & Technology

1976-10-01

f7<psBCsqRf°?^PM^ppRi^Sq^PMip««niS! V Modulus of Rupture tests were conducted on 274 specimens of hot pressed silicon nitride to investigate the...Reaction Sintered 813^ 4. 3 Nitriding Developments 4.4 Sialon Materials 4. 5 Silicon Milling Studies 5. References v Page No. 1 ii...iv v vi ix 1 3 5 7 7 14 17 19 19 21 38 48 65 66 73 75 87 89 97 101 103 .:,:.o:^ -.. ...•• ._ . .- —~ «-«aa. m

AIN-Based Packaging for SiC High-Temperature Electronics

NASA Technical Reports Server (NTRS)

Savrun, Ender

2004-01-01

Packaging made primarily of aluminum nitride has been developed to enclose silicon carbide-based integrated circuits (ICs), including circuits containing SiC-based power diodes, that are capable of operation under conditions more severe than can be withstood by silicon-based integrated circuits. A major objective of this development was to enable packaged SiC electronic circuits to operate continuously at temperatures up to 500 C. AlN-packaged SiC electronic circuits have commercial potential for incorporation into high-power electronic equipment and into sensors that must withstand high temperatures and/or high pressures in diverse applications that include exploration in outer space, well logging, and monitoring of nuclear power systems. This packaging embodies concepts drawn from flip-chip packaging of silicon-based integrated circuits. One or more SiC-based circuit chips are mounted on an aluminum nitride package substrate or sandwiched between two such substrates. Intimate electrical connections between metal conductors on the chip(s) and the metal conductors on external circuits are made by direct bonding to interconnections on the package substrate(s) and/or by use of holes through the package substrate(s). This approach eliminates the need for wire bonds, which have been the most vulnerable links in conventional electronic circuitry in hostile environments. Moreover, the elimination of wire bonds makes it possible to pack chips more densely than was previously possible.

Investigation of Oxygen and Hydrogen Associated Charge Trapping and Electrical Characteristics of Silicon Nitride Films for Mnos Devices.

NASA Astrophysics Data System (ADS)

Xu, Dan

Silicon nitride (Si_3N _4) and silicon oxynitride (SiO _{rm x}N_ {rm y}) films in the form of metal -nitride-oxide-silicon (MNOS) structures were investigated to determine the correlation between their electrical characteristics and the nature of the chemical bonding so as to provide guidelines for the next generation of nonvolatile memory devices. The photoionization cross section of electron traps in the oxynitride films of MNOS devices were also measured as a function photon energy and oxygen concentration of the silicon oxynitride films. An effective photoionization cross section associated with electron traps was determined to be between 4.9 times 10 ^{-19} cm^2 to 10.8 times 10^ {-19} cm^2 over the photon energy of 2.06 eV to 3.1 eV for silicon oxynitride films containing 7 atomic % to 17 atomic % of oxygen. The interface state density of metal-nitride-oxide -silicon (MNOS) devices was investigated as a function of processing conditions. The interface state density around the midgap of the oxide-silicon interface of the MNOS structures for deposition temperature between 650^ circC to 850^circC increased from 1.1 to 8.2 times 10 ^{11} cm^ {-2}eV^{-1}, for as-deposited silicon nitride films; but decreased from 5.0 to 3.5 times 10^ {11} cm^{-2} eV^{-1}, for films annealed in nitrogen at 900^circC for 60 minutes; and further decreased and remained constant at 1.5 times 10^{11 } cm^{-2}eV ^{-1}, for films which were further annealed in hydrogen at 900^ circC for an additional 60 minutes. The interface state density increase was due to an increase in the loss of hydrogen at the interfacial region and also due to an increase in the thermal stress caused by differences in thermal expansion coefficients of silicon nitride and silicon dioxide films at higher deposition temperatures. The interface state density was subject to two opposing influences; an increase by thermal stress, and a reduction by hydrogen compensation of these states. The photocurrent-voltage (photoI-V) technique in combination with internal photo-electric technique were employed to determine the trapped charge density and its centroid as a function of processing conditions. Results showed that the trapped charge density was of the order of 10^{18} cm ^{-3}. However, the charge trapping density increased about 30% as the atomic percentage of hydrogen decreased from 6 to 2 atomic %.

Vertical integration of high-Q silicon nitride microresonators into silicon-on-insulator platform.

PubMed

Li, Qing; Eftekhar, Ali A; Sodagar, Majid; Xia, Zhixuan; Atabaki, Amir H; Adibi, Ali

2013-07-29

We demonstrate a vertical integration of high-Q silicon nitride microresonators into the silicon-on-insulator platform for applications at the telecommunication wavelengths. Low-loss silicon nitride films with a thickness of 400 nm are successfully grown, enabling compact silicon nitride microresonators with ultra-high intrinsic Qs (~ 6 × 10(6) for 60 μm radius and ~ 2 × 10(7) for 240 μm radius). The coupling between the silicon nitride microresonator and the underneath silicon waveguide is based on evanescent coupling with silicon dioxide as buffer. Selective coupling to a desired radial mode of the silicon nitride microresonator is also achievable using a pulley coupling scheme. In this work, a 60-μm-radius silicon nitride microresonator has been successfully integrated into the silicon-on-insulator platform, showing a single-mode operation with an intrinsic Q of 2 × 10(6).

Influence of interfaces density and thermal processes on mechanical stress of PECVD silicon nitride

NASA Astrophysics Data System (ADS)

Picciotto, A.; Bagolini, A.; Bellutti, P.; Boscardin, M.

2009-10-01

The paper focuses on a particular silicon nitride thin film (SiN x) produced by plasma enahanced chemical vapor deposition (PECVD) technique with high deposition rate (26 nm/min) and low values of mechanical stress (<100 MPa). This was perfomed with mixed frequency procedure varying the modulation of high frequency at 13.56 MHz and low frequency at 308 kHz of RF power supply during the deposition, without changing the ratio of reaction gases. Low stress silicon nitride is commonly obtained by tailoring the thickness ratio of high frequency vs. low frequency silicon nitride layers. The attention of this work was directed to the influence of the number of interfaces per thickness unit on the stress characteristics of the deposited material. Two sets of wafer samples were deposited with low stress silicon nitride, with a thickness of 260 nm and 2 μm, respectively. Thermal annealing processes at 380 and 520 °C in a inert enviroment were also performed on the wafers. The Stoney-Hoffman model was used to estimate the stress values by wafer curvature measurement with a mechanical surface profilometer: the stress was calculated for the as-deposited layer, and after each annealing process. The thickness and the refractive index of the SiN x were also measured and charaterized by variable angle spectra elliposometry (VASE) techinique. The experimental measurements were performed at the MT-LAB, IRST (Istituto per la Ricerca Scientifica e Tecnologica) of Bruno Kessler Foundation for Research in Trento.

Uranium azide photolysis results in C-H bond activation and provides evidence for a terminal uranium nitride

NASA Astrophysics Data System (ADS)

Thomson, Robert K.; Cantat, Thibault; Scott, Brian L.; Morris, David E.; Batista, Enrique R.; Kiplinger, Jaqueline L.

2010-09-01

Uranium nitride [U≡N]x is an alternative nuclear fuel that has great potential in the expanding future of nuclear power; however, very little is known about the U≡N functionality. We show, for the first time, that a terminal uranium nitride complex can be generated by photolysis of an azide (U-N=N=N) precursor. The transient U≡N fragment is reactive and undergoes insertion into a ligand C-H bond to generate new N-H and N-C bonds. The mechanism of this unprecedented reaction has been evaluated through computational and spectroscopic studies, which reveal that the photochemical azide activation pathway can be shut down through coordination of the terminal azide ligand to the Lewis acid B(C6F5)3. These studies demonstrate that photochemistry can be a powerful tool for inducing redox transformations for organometallic actinide complexes, and that the terminal uranium nitride fragment is reactive, cleaving strong C-H bonds.

High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Pramod; Washiyama, Shun; Kaess, Felix

2016-04-14

In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on Al{sub x}Ga{sub 1-x}N (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where E{sub g}(AlGaN) > E{sub g}(Si{sub 3}N{sub 4}). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that atmore » free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si{sup 0/−1}) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si{sub 3}N{sub 4}/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si{sub 3}N{sub 4}/n-GaN to the valence band in Si{sub 3}N{sub 4}/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.« less

Process for producing organic products containing silicon, hydrogen, nitrogen, and carbon by the direct reaction between elemental silicon and organic amines and products formed thereby

DOEpatents

Pugar, E.A.; Morgan, P.E.D.

1988-04-04

A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about O/degree/C up to about 300/degree/C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200-1700/degree/C for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Process for producing organic products containing silicon, hydrogen, nitrogen, and carbon by the direct reaction between elemental silicon and organic amines

DOEpatents

Pugar, Eloise A.; Morgan, Peter E. D.

1990-04-03

A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about 0.degree. C. up to about 300.degree. C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Nitriding kinetics of Si-SiC powder mixtures as simulations of reaction bonded Si3N4-SiC composites

NASA Technical Reports Server (NTRS)

Lightfoot, A.; Sheldon, B. W.; Flint, J. H.; Haggerty, J. S.

1989-01-01

The nitriding kinetics of Si and Si plus SiC powder mixtures were studied to simulate the fabrication of RBSN-SiC ceramic matrix composites. Very clean, assynthesized, and solvent-exposed powders were studied; C-rich and Si-rich SiC 0.04-0.05 micron diameter powders were mixed in varying concentrations with SiH4-derived 0.2-0.3 micron diameter Si powder. Complete nitridation is achieved with C-rich SiC powders in 140 min at 1250 C, and in the centers of Si-rich SiC powders in 15 min. The effects on the incubation periods, fast reaction periods, and slow reaction periods that characterize these nitriding processes were studied to explain unusual reverse reaction gradients and other effects of contamination.

First-principles investigation of band offsets and dielectric properties of Silicon-Silicon Nitride interfaces

NASA Astrophysics Data System (ADS)

Pham, Tuan Anh; Li, Tianshu; Gygi, Francois; Galli, Giulia

2011-03-01

Silicon Nitride (Si3N4) is a possible candidate material to replace or be alloyed with SiO2 to form high-K dielectric films on Si substrates, so as to help prevent leakage currents in modern CMOS transistors. Building on our previous work on dielectric properties of crystalline and amorphous Si3N4 slabs, we present an analysis of the band offsets and dielectric properties of crystalline-Si/amorphous Si3N4 interfaces based on first principles calculations. We discuss shortcomings of the conventional bulk-plus line up approach in band offset calculations for systems with an amorphous component, and we present the results of band offsets obtained from calculations of local density of states. Finally, we describe the role of bonding configurations in determining band edges and dielectric constants at the interface. We acknowledge financial support from Intel Corporation.

Silicon nitride/silicon carbide composite powders

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-06-11

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Hydrogen passivation of polycrystalline silicon thin films

NASA Astrophysics Data System (ADS)

Scheller, L.-P.; Weizman, M.; Simon, P.; Fehr, M.; Nickel, N. H.

2012-09-01

The influence of post-hydrogenation on the electrical and optical properties of solid phase crystallized polycrystalline silicon (poly-Si) was examined. The passivation of grain-boundary defects was measured as a function of the passivation time. The silicon dangling-bond concentration decreases with increasing passivation time due to the formation of Si-H complexes. In addition, large H-stabilized platelet-like clusters are generated. The influence of H on the electrical properties was investigated using temperature dependent conductivity and Hall-effect measurements. For poly-Si on Corning glass, the dark conductivity decreases upon hydrogenation, while it increases when the samples are fabricated on silicon-nitride covered Borofloat glass. Hall-effect measurements reveal that for poly-Si on Corning glass the hole concentration and the mobility decrease upon post-hydrogenation, while a pronounced increase is observed for poly-Si on silicon-nitride covered Borofloat glass. This indicates the formation of localized states in the band gap, which is supported by sub band-gap absorption measurments. The results are discussed in terms of hydrogen-induced defect passivation and generation mechanisms.

Room-Temperature Synthesis of GaN Driven by Kinetic Energy beyond the Limit of Thermodynamics.

PubMed

Imaoka, Takane; Okada, Takeru; Samukawa, Seiji; Yamamoto, Kimihisa

2017-12-06

The nitridation reaction is significantly important to utilize the unique properties of nitrides and nitrogen-doped materials. However, nitridation generally requires a high temperature or highly reactive reagents (often explosive) because the energies of N-N bond cleavage and nitrogen anion formation (N 3- ) are very high. We demonstrate the first room-temperature synthesis of GaN directly from GaCl 3 by nanoscale atom exchange reaction. Nonequilibrium nitrogen molecules with very high translational energy were used as a chemically stable and safe nitrogen source. The irradiation of molecular nitrogen to the desired reaction area successfully provided a gallium nitride (GaN) nanosheet that exhibited a typical photoluminescence spectrum. Because this process retains the target substrate room temperature and does not involve any photon nor charged ion, it allows damage-less synthesis of the semiconducting metal nitrides, even directly on plastic substrates such as polyethylene terephthalate (PET).

Ceramic-bonded abrasive grinding tools

DOEpatents

Holcombe, C.E. Jr.; Gorin, A.H.; Seals, R.D.

1994-11-22

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Ceramic-bonded abrasive grinding tools

DOEpatents

Holcombe, Jr., Cressie E.; Gorin, Andrew H.; Seals, Roland D.

1994-01-01

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Enhanced adhesion by high energy bombardment

NASA Technical Reports Server (NTRS)

Griffith, Joseph E. (Inventor); Qiu, Yuanxun (Inventor); Tombrello, Thomas A. (Inventor)

1984-01-01

Films (12) of gold, copper, silicon nitride, or other materials are firmly bonded to insulator substrates (12) such as silica, a ferrite, or Teflon (polytetrafluorethylene) by irradiating the interface with high energy ions. Apparently, track forming processes in the electronic stopping region cause intermixing in a thin surface layer resulting in improved adhesion without excessive doping. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters.

Silicon nitride/silicon carbide composite densified materials prepared using composite powders

DOEpatents

Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

1997-07-01

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, Eugene E.; Cohen, Marvin L.; Hansen, William L.

1992-01-01

Novel crystalline .alpha. (silicon nitride-like)-carbon nitride and .beta. (silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate.

Friction and Wear of Monolithic and Fiber Reinforced Silicon-Ceramics Sliding Against IN-718 Alloy at 25 to 800 C in Atmospheric Air at Ambient Pressure

NASA Technical Reports Server (NTRS)

Deadmore, Daniel L.; Sliney, Harold E.

1988-01-01

The friction and wear of monolithic and fiber reinforced Si-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C was measured. The monolithic materials tested were silicon carbide (SiC), fused silica (SiO2), syalon, silicon nitride (Si3N4) with W and Mg additives, and Si3N4 with Y2O3 additive. At 25 C fused silica had the lowest friction while Si3N4 (W,Mg type) had the lowest wear. At 800 C syalon had the lowest friction while Si3N4 (W,Mg type) and syalon had the lowest wear. The SiC/IN-718 couple had the lowest total wear at 25 C. At 800 C the fused silica/IN-718 couple exhibited the least total wear. SiC fiber reinforced reaction bonded silicon nitride (RBSN) composite material with a porosity of 32 percent and a fiber content of 23 vol percent had a lower coefficient of friction and wear when sliding parallel to the fiber direction than in the perpendicular at 25 C. The coefficient of friction for the carbon fiber reinforced borosilicate composite was 0.18 at 25 C. This is the lowest of all the couples tested. Wear of this material was about two decades smaller than that of the monolithic fused silica. This illustrates the large improvement in tribological properties which can be achieved in ceramic materials by fiber reinforcement. At higher temperatures the oxidation products formed on the IN-718 alloy are transferred to the ceramic by sliding action and forms a thin, solid lubricant layer which decreases friction and wear for both the monolithic and fiber reinforced composites.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, E.E.; Cohen, M.L.; Hansen, W.L.

1992-05-05

Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

Thermodynamics of Volatile Species in the Silicon-Oxygen-Hydrogen System Studied

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Opila, Elizabeth J.; Copland, Evan H.; Myers, Dwight

2005-01-01

The volatilization of silica (SiO2) to silicon hydroxides and oxyhydroxides because of reaction with water vapor is important in a variety of high-temperature corrosion processes. For example, the lifetimes of silicon carbide (SiC) and silicon nitride (Si3N4) - based components in combustion environments are limited by silica volatility. To understand and model this process, it is essential to have accurate thermodynamic data for the formation of volatile silicon hydroxides and oxyhydroxides.

High temperature alkali corrosion of ceramics in coal gas: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pickrell, G.R.; Sun, T.; Brown, J.J. Jr.

1994-12-31

There are several ceramic materials which are currently being considered for use as structural elements in coal combustion and coal conversion systems because of their thermal and mechanical properties. These include alumina (refractories, membranes, heat engines); silicon carbide and silicon nitride (turbine engines, internal combustion engines, heat exchangers, particulate filters); zirconia (internal combustion engines, turbine engines, refractories); and mullite and cordierite (particulate filters, refractories, heat exchangers). High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and highmore » efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, and zirconia. The study consists of identification of the alkali reaction products and determination of the kinetics of the alkali reactions as a function of temperature and time. 145 refs., 29 figs., 12 tabs.« less

Multifunctional silicon surfaces: reaction of dichlorocarbene generated from Seyferth reagent with hydrogen-terminated silicon (111) surfaces.

PubMed

Liu, Wenjun; Sharp, Ian D; Tilley, T Don

2014-01-14

Insertion of dichlorocarbene (:CCl2), generated by decomposition of the Seyferth reagent PhHgCCl2Br, into the Si-H bond of a tertiary silane to form a Si-CCl2H group is an efficient homogeneous, molecular transformation. A heterogeneous version of this reaction, between PhHgCCl2Br and a silicon (111) surface terminated by tertiary Si-H bonds, was studied using a combination of surface-sensitive infrared and X-ray photoelectron spectroscopies. The insertion of dichlorocarbene into surface Si-H bonds parallels the corresponding reaction of silanes in solution, to produce surface-bound dichloromethyl groups (Si-CCl2H) covering ∼25% of the silicon surface sites. A significant fraction of the remaining Si-H bonds on the surface was converted to Si-Cl/Br groups during the same reaction, with PhHgCCl2Br serving as a halogen atom source. The presence of two distinct environments for the chlorine atoms (Si-CCl2H and Si-Cl) and one type of bromine atom (Si-Br) was confirmed by Cl 2p, Br 3d, and C 1s X-ray photoelectron spectroscopy. The formation of reactive, halogen-terminated atop silicon sites was also verified by reaction with sodium azide or the Grignard reagent (CH3MgBr), to produce Si-N3 or Si-Me functionalities, respectively. Thus, reaction of a hydrogen-terminated silicon (111) surface with PhHgCCl2Br provides a facile route to multifunctional surfaces possessing both stable silicon-carbon and labile silicon-halogen sites, in a single pot synthesis. The reactive silicon-halogen groups can be utilized for subsequent transformations and, potentially, the construction of more complex organic-silicon hybrid systems.

Adhesion enhancement of titanium nitride coating on aluminum casting alloy by intrinsic microstructures

NASA Astrophysics Data System (ADS)

Nguyen, Chuong L.; Preston, Andrew; Tran, Anh T. T.; Dickinson, Michelle; Metson, James B.

2016-07-01

Aluminum casting alloys have excellent castability, high strength and good corrosion resistance. However, the presence of silicon in these alloys prevents surface finishing with conventional methods such as anodizing. Hard coating with titanium nitride can provide wear and corrosion resistances, as well as the aesthetic finish. A critical factor for a durable hard coating is its bonding with the underlying substrate. In this study, a titanium nitride layer was coated on LM25 casting alloy and a reference high purity aluminum substrate using Ion Assisted Deposition. Characterization of the coating and the critical interface was carried out by a range of complementing techniques, including SIMS, XPS, TEM, SEM/EDS and nano-indentation. It was observed that the coating on the aluminum alloy is stronger compared to that on the pure aluminum counterpart. Silicon particles in the alloy offers the reinforcement though mechanical interlocking at microscopic level, even with nano-scale height difference. This reinforcement overcomes the adverse effect caused by surface segregation of magnesium in aluminum casting alloys.

A hybrid density functional study of silicon and phosphorus doped hexagonal boron nitride monolayer

NASA Astrophysics Data System (ADS)

Mapasha, R. E.; Igumbor, E.; Chetty, N.

2016-10-01

We present a hybrid density functional study of silicon (Si) and phosphorus (P) doped hexagonal boron nitride (h-BN). The local geometry, electronic structure and thermodynamic stability of Si B , Si N , P B and P N are examined using hybrid Heyd-Scuseria- Ernzerhof (HSE) functional. The defect induced buckling and the local bond distances around the defect are sensitive to charge state modulation q = -2, -1, 0, +1 and +2. The +1 charge state is found to be the most energetically stable state and significantly reduces the buckling. Based on the charge state thermodynamic transition levels, we noted that the Si N , Si N and P B defects are too deep to be ionized, and can alter the optical properties of h-BN material.

Method for producing silicon nitride/silicon carbide composite

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-07-23

Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.

Radiation Hardened Silicon-on-Insulator Structures with N+ Ion Modified Buried SiO2 Layer

NASA Astrophysics Data System (ADS)

Tyschenko, I. E.; Popov, V. P.

2009-12-01

Radiation-resistant silicon-on-insulator structures were produced by N+ ion implantation into thermally grown SiO2 film and subsequent hydrogen transfer of the Si layer to the nitrogen-implanted substrate under conditions of vacuum wafer bonding. Accumulation of the carriers in the buried SiO2 was investigated as a function of fluence of nitrogen ions in the range (1-6)×1015 cm2 and as a function of total radiation dose ranging from 104 to 107 rad (Si). It was found that the charge generated near the nitrided bonding interface was reduced by a factor of four compared to the thermal SiO2/Si interface.

Method and apparatus for stable silicon dioxide layers on silicon grown in silicon nitride ambient

NASA Technical Reports Server (NTRS)

Cohen, R. A.; Wheeler, R. K. (Inventor)

1974-01-01

A method and apparatus for thermally growing stable silicon dioxide layers on silicon is disclosed. A previously etched and baked silicon nitride tube placed in a furnace is used to grow the silicon dioxide. First, pure oxygen is allowed to flow through the tube to initially coat the inside surface of the tube with a thin layer of silicon dioxide. After the tube is coated with the thin layer of silicon dioxide, the silicon is oxidized thermally in a normal fashion. If the tube becomes contaminated, the silicon dioxide is etched off thereby exposing clean silicon nitride and then the inside of the tube is recoated with silicon dioxide. As is disclosed, the silicon nitride tube can also be used as the ambient for the pyrolytic decomposition of silane and ammonia to form thin layers of clean silicon nitride.

Colloidal characterization of ultrafine silicon carbide and silicon nitride powders

NASA Technical Reports Server (NTRS)

Whitman, Pamela K.; Feke, Donald L.

1986-01-01

The effects of various powder treatment strategies on the colloid chemistry of aqueous dispersions of silicon carbide and silicon nitride are examined using a surface titration methodology. Pretreatments are used to differentiate between the true surface chemistry of the powders and artifacts resulting from exposure history. Silicon nitride powders require more extensive pretreatment to reveal consistent surface chemistry than do silicon carbide powders. As measured by titration, the degree of proton adsorption from the suspending fluid by pretreated silicon nitride and silicon carbide powders can both be made similar to that of silica.

Effects of Fe2O3 addition on the nitridation of silicon powder

NASA Technical Reports Server (NTRS)

Hasegawa, Y.; Inomata, Y.; Kijima, K.; Matsuyama, T.

1977-01-01

The reaction of silicon powder and nitrogen was studied in the range of 1300-1400 C. When an addition of Fe2O3 was more than 0.8wt%, the reaction was linear and compared to samples with no Fe2O3, the reaction velocity increased 5 to 10 times. The reactions were mediated by the process of peeling and cracking in a thin layer of Si2N4 formed on the silicon particles or on the surface of the Fe-Si melts. As the addition of Fe2O3 increased, the reaction activation energy for highly pure samples decreased. Fe2O3 which exceeded the Si3N4 solubility limits was finally converted to d-Fe.

Investigation of isochronal annealing on the optical properties of HWCVD amorphous silicon nitride deposited at low temperatures and low gas flow rates

NASA Astrophysics Data System (ADS)

Muller, T. F. G.; Jacobs, S.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Arendse, C. J.

2015-06-01

Hydrogenated amorphous silicon nitride (a-SiNx:H) is used as anti-reflection coatings in commercial solar cells. A final firing step in the production of micro-crystalline silicon solar cells allows hydrogen effusion from the a-SiNx:H into the solar cell, and contributes to bulk passivation of the grain boundaries. In this study a-SiNx:H deposited in a hot-wire chemical vapour deposition (HWCVD) chamber with reduced gas flow rates and filament temperature compared to traditional deposition regimes, were annealed isochronally. The UV-visible reflection spectra of the annealed material were subjected to the Bruggeman Effective Medium Approximation (BEMA) treatment, in which a theoretical amorphous semiconductor was combined with particle inclusions due to the structural complexities of the material. The extraction of the optical functions and ensuing Wemple-DeDomenici analysis of the wavelength-dependent refractive index allowed for the correlation of the macroscopic optical properties with the changes in the local atomic bonding configuration, involving silicon, nitrogen and hydrogen.

Silicon surface passivation by silicon nitride deposition

NASA Technical Reports Server (NTRS)

Olsen, L. C.

1984-01-01

Silicon nitride deposition was studied as a method of passivation for silicon solar cell surfaces. The following three objectives were the thrust of the research: (1) the use of pecvd silicon nitride for passivation of silicon surfaces; (2) measurement techniques for surface recombination velocity; and (3) the importance of surface passivation to high efficiency solar cells.

Silicon nitride ceramic having high fatigue life and high toughness

DOEpatents

Yeckley, Russell L.

1996-01-01

A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

Rolling-element fatigue life of silicon nitride balls: Preliminary test results

NASA Technical Reports Server (NTRS)

Parker, R. J.; Zaretsky, E. V.

1972-01-01

Hot pressed silicon nitride was evaluated as a rolling element bearing material. The five-ball fatigue tester was used to test 12.7 mm (0.500 in.) diameter balls at a maximum Hertz stress of 800,000 psi at a race temperature of 130 F. The fatigue spalls in the silicon nitride resembled those in typical bearing steels. The ten-percent fatigue life of the silicon nitride balls was approximately one-eighth to one-fifth that of typical bearing steels (52100 and M-50). The load capacity of the silicon nitride was approximately one-third that of typical bearing steels. The load capacity of the silicon nitride was significantly higher than previously tested ceramic materials for rolling element bearings.

New R-SiC extends service life in kiln furniture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sonntag, A.

1997-11-01

Silicon carbide kiln furniture systems are an essential part of modern high-temperature technology. SiC ceramics have exceptional high-temperature stability and thermal shock resistance., They show no plastic deformation (creep) under mechanical load and maintain their geometry after each high-temperature cycle. Therefore, various new kiln systems with light and open setting patterns can be realized where more fired goods can be produced with less kiln furniture ballast and within shorter firing cycles. The fast-firing technology of porcelain is an opportunity for new SiC kiln furniture ceramics. The new SiC ceramic systems available include: (1) recrystallized SiC (R-SiC); (2) silicon-infiltrated reaction-bonded SiCmore » (SiSiC); and (3) nitride-bonded SiC (NSiC). The new SiC ceramics have an important production criterion in common. They show practically no shrinkage during production. This is important for the manufacture of large shapes, such as beams, rollers and setter plates, as well as tailored geometries that allow light and open kiln furniture construction. Because of the extraordinarily high thermal shock resistance, high strength and high-temperature creep stability of these SiC ceramics, delicate and precise kiln furniture configurations have been introduced. One application is the fast firing of tableware with automatic setting robots.« less

Surface Area, and Oxidation Effects on Nitridation Kinetics of Silicon Powder Compacts

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Palczer, A. R.

1998-01-01

Commercially available silicon powders were wet-attrition-milled from 2 to 48 hr to achieve surface areas (SA's) ranging from 1.3 to 70 sq m/g. The surface area effects on the nitridation kinetics of silicon powder compacts were determined at 1250 or 1350 C for 4 hr. In addition, the influence of nitridation environment, and preoxidation on nitridation kinetics of a silicon powder of high surface area (approximately equals 63 sq m/g) was investigated. As the surface area increased, so did the percentage nitridation after 4 hr in N2 at 1250 or 1350 C. Silicon powders of high surface area (greater than 40 sq m/g) can be nitrided to greater than 70% at 1250 C in 4 hr. The nitridation kinetics of the high-surface-area powder compacts were significantly delayed by preoxidation treatment. Conversely, the nitridation environment had no significant influence on the nitridation kinetics of the same powder. Impurities present in the starting powder, and those accumulated during attrition milling, appeared to react with the silica layer on the surface of silicon particles to form a molten silicate layer, which provided a path for rapid diffusion of nitrogen and enhanced the nitridation kinetics of high surface area silicon powder.

Silicone-containing composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, Mustafa

A silicone-containing composition comprises the reaction product of a first component and an excess of an isocyanate component relative to the first component to form an isocyanated intermediary. The first component is selected from one of a polysiloxane and a silicone resin. The first component includes a carbon-bonded functional group selected from one of a hydroxyl group and an amine group. The isocyanate component is reactive with the carbon-bonded functional group of the first component. The isocyanated intermediary includes a plurality of isocyanate functional groups. The silicone-containing composition comprises the further reaction product of a second component, which is selectedmore » from the other of the polysiloxane and the silicone resin. The second component includes a plurality of carbon-bonded functional groups reactive with the isocyanate functional groups of the isocyanated intermediary for preparing the silicone-containing composition.« less

The Effect of Polymer Char on Nitridation Kinetics of Silicon

NASA Technical Reports Server (NTRS)

Chan, Rickmond C.; Bhatt, Ramakrishna T.

1994-01-01

Effects of polymer char on nitridation kinetics of attrition milled silicon powder have been investigated from 1200 to 1350 C. Results indicate that at and above 1250 C, the silicon compacts containing 3.5 wt percent polymer char were fully converted to Si3N4 after 24 hr exposure in nitrogen. In contrast, the silicon compacts without polymer char could not be fully converted to Si3N4 at 1350 C under similar exposure conditions. At 1250 and 1350 C, the silicon compacts with polymer char showed faster nitridation kinetics than those without the polymer char. As the polymer char content is increased, the amount of SiC in the nitrided material is also increased. By adding small amounts (approx. 2.5 wt percent) of NiO, the silicon compacts containing polymer char can be completely nitrided at 1200 C. The probable mechanism for the accelerated nitridation of silicon containing polymer char is discussed.

Finishing Techniques for Silicon Nitride Bearings

DTIC Science & Technology

1976-03-01

finishing procedures. Rolling contact fatigue lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order...grinding. Rolling contact fatigue lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order of magnitude...lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order of magnitude longer than those

Method for forming fibrous silicon carbide insulating material

DOEpatents

Wei, G.C.

1983-10-12

A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

Method for forming fibrous silicon carbide insulating material

DOEpatents

Wei, George C.

1984-01-01

A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

Methods of repairing a substrate

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2011-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Matrix density effects on the mechanical properties of SiC/RBSN composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Kiser, James D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates

DOEpatents

Sarin, V.K.

1991-07-30

A process is disclosed for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900--1500 C and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates

DOEpatents

Sarin, Vinod K.

1991-01-01

A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900.degree.-1500.degree. C. and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

A density functional theory model of mechanically activated silyl ester hydrolysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pill, Michael F.; Schmidt, Sebastian W.; Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel

2014-01-28

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutralmore » reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ mol{sup −1}, which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters.« less

Features of the phase composition and morphology of the particles of sialon synthesized from silicon and aluminum nitrides

NASA Astrophysics Data System (ADS)

Ivicheva, S. N.; Lysenkov, A. S.; Ovsyannikov, N. A.; Titov, D. D.; Kargin, Yu F.

2018-04-01

The phase composition and morphological features of sialons were studied under the same conditions of firing (duration, temperature) using different initial components, silicon nitride, aluminum nitride, and a mixture of silicon nitrides and aluminum with the application of nitrides of the corresponding oxide (aluminum or silicon) sol-gel method. The effect of the initial reagents composition on the phase composition of the final product and the morphological features of the sialon powders obtained in a single firing step in a nitrogen atmosphere is shown.

Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics

DOEpatents

Becher, Paul F [Oak Ridge, TN; Lin, Hua-Tay [Oak Ridge, TN

2011-06-28

A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.

Stability and rheology of dispersions of silicon nitride and silicon carbide

NASA Technical Reports Server (NTRS)

Feke, Donald L.

1987-01-01

The relationship between the surface and colloid chemistry of commercial ultra-fine silicon carbide and silicon nitride powders was examined by a variety of standard characterization techniques and by methodologies especially developed for ceramic dispersions. These include electrokinetic measurement, surface titration, and surface spectroscopies. The effects of powder pretreatment and modification strategies, which can be utilized to augment control of processing characteristics, were monitored with these technologies. Both silicon carbide and nitride were found to exhibit silica-like surface chemistries, but silicon nitride powders possess an additional amine surface functionality. Colloidal characteristics of the various nitride powders in aqueous suspension is believed to be highly dependent on the relative amounts of the two types of surface groups, which in turn is determined by the powder synthesis route. The differences in the apparent colloidal characteristics for silicon nitride powders cannot be attributed to the specific absorption of ammonium ions. Development of a model for the prediction of double-layer characteristics of materials with a hybrid site interface facilitated understanding and prediction of the behavior of both surface charge and surface potential for these materials. The utility of the model in application to silicon nitride powders was demonstrated.

Photochemical Reactions of (n(5)-Pentamethylcyclpentadienyl)-Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond and Implications for the Mechanism of Transition Metal-Catalyzed Hydrosilation of Alkenes.

DTIC Science & Technology

1985-12-11

RD-R162 462 PHOTOCHEMICAL REACTIONS OF(N(S)-P NTANETNYLCVCLPENTADIENYL)-DICARRONVLIR.. (U) MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY...34 Photochemical Reactions of (n5-Pentamethylcyclpentadienyl)- Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond...Chemical Society) PHOTOCHEMICAL REACTIONS OF (n5-PENTAMETHYLCYCLOPENTADIENYL)- DICARBONYLIRON-ALKYL AND -SILYL COMPLEXES: REVERSIBLE ETHYLENE INSERTION INTO

Effect of the hexagonal phase interlayer on rectification properties of boron nitride heterojunctions to silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teii, K., E-mail: teii@asem.kyushu-u.ac.jp; Ito, H.; Katayama, N.

2015-02-07

Rectification properties of boron nitride/silicon p-n heterojunction diodes fabricated under low-energy ion impact by plasma-enhanced chemical vapor deposition are studied in terms of the resistive sp{sup 2}-bonded boron nitride (sp{sup 2}BN) interlayer. A two-step biasing technique is developed to control the fraction of cubic boron nitride (cBN) phase and, hence, the thickness of the sp{sup 2}BN interlayer in the films. The rectification ratio at room temperature is increased up to the order of 10{sup 4} at ±10 V of biasing with increasing the sp{sup 2}BN thickness up to around 130 nm due to suppression of the reverse leakage current. The variation ofmore » the ideality factor in the low bias region is related to the interface disorders and defects, not to the sp{sup 2}BN thickness. The forward current follows the Frenkel-Poole emission model in the sp{sup 2}BN interlayer at relatively high fields when the anomalous effect is assumed. The transport of the minority carriers for reverse current is strongly limited by the high bulk resistance of the thick sp{sup 2}BN interlayer, while that of the major carriers for forward current is much less affected.« less

COATED CARBON ELEMENT FOR USE IN NUCLEAR REACTORS AND THE PROCESS OF MAKING THE ELEMENT

DOEpatents

Pyle, R.J.; Allen, G.L.

1963-01-15

S>This patent relates to a carbide-nitride-carbide coating for carbon bodies that are to be subjected to a high temperature nuclear reactor atmosphere, and a method of applying the same. This coating is a highly efficient diffusion barrier and protects the C body from corrosion and erosion by the reactor atmosphere. Preferably, the innermost coating is Zr carbide, the middle coatlng is Zr nitride, and the outermost coating is a mixture of Zr and Nb carbide. The nitride coating acts as a diffusion barrier, while the innermost carbide bonds the nitride to the C body and prevents deleterious reaction between the nitride and C body. The outermost carbide coating protects the nitride coating from the reactor atmosphere. (AEC)

In situ X-ray monitoring of damage accumulation in SiC/RBSN tensile specimens

NASA Technical Reports Server (NTRS)

Baaklini, George Y.; Bhatt, Ramkrishna T.

1991-01-01

The room-temperature tensile testing of silicon carbide fiber reinforced reaction-bonded silicon nitride (SiC/RBSN) composite specimens was monitored by using in-situ X-ray film radiography. Radiographic evaluation before, during, and after loading provided data on the effect of preexisting volume flaws (high density impurities, and local density variations) on the fracture behavior of composites. Results from (O)1, (O)3, (O)5, and (O)8 composite specimens showed that X-ray film radiography can monitor damage accumulations during tensile loading. Matrix cracking, fiber-matrix debonding, and fiber pullout were imaged throughout the tensile loading history of the specimens. Further, in-situ film radiography was found to be a helpful and practical technique for estimating interfacial shear strength between the SiC fiber and the RBSN matrix by the matrix crack spacing method. It is concluded that pretest, in-situ, and post-test radiography can provide for a greater understanding of ceramic matrix composite mechanical behavior, a verification of related experimental procedures, and a validation and development of related analytical models.

In-situ x-ray monitoring of damage accumulation in SiC/RBSN tensile specimens

NASA Technical Reports Server (NTRS)

Baaklini, George Y.; Bhatt, Ramakrishna T.

1991-01-01

The room-temperature tensile testing of silicon carbide fiber reinforced reaction-bonded silicon nitride (SiC/RBSN) composite specimens was monitored by using in-situ x ray film radiography. Radiographic evaluation before, during, and after loading provided data on the effect of preexisting volume flaws (high density impurities, and local density variations) on the fracture behavior of composites. Results from (0)1, (0)3, (0)5, and (0)8 composite specimens, showed that x ray film radiography can monitor damage accumulations during tensile loading. Matrix cracking, fiber-matrix debonding, and fiber pullout were imaged throughout the tensile loading history of the specimens. Further, in-situ film radiography was found to be a helpful and practical technique for estimating interfacial shear strength between the SiC fiber and the RBSN matrix by the matrix crack spacing method. It is concluded that pretest, in-situ, and post-test radiography can provide for a greater understanding of ceramic matrix composite mechanical behavior, a verification of related experimental procedures, and a validation and development of related analytical models.

Silicon Nitride Photonic Integration Platforms for Visible, Near-Infrared and Mid-Infrared Applications

PubMed Central

Micó, Gloria; Pastor, Daniel; Pérez, Daniel; Doménech, José David; Fernández, Juan; Baños, Rocío; Alemany, Rubén; Sánchez, Ana M.; Cirera, Josep M.; Mas, Roser

2017-01-01

Silicon nitride photonics is on the rise owing to the broadband nature of the material, allowing applications of biophotonics, tele/datacom, optical signal processing and sensing, from visible, through near to mid-infrared wavelengths. In this paper, a review of the state of the art of silicon nitride strip waveguide platforms is provided, alongside the experimental results on the development of a versatile 300 nm guiding film height silicon nitride platform. PMID:28895906

Feasibility study of silicon nitride regenerators

NASA Technical Reports Server (NTRS)

Fucinari, C. A.; Rao, V. D. N.

1979-01-01

The feasibility of silicon nitride as a regenerator matrix material for applications requiring inlet temperatures above 1000 C is examined. The present generation oxide ceramics are used as a reference to examine silicon nitride from a material characteristics, manufacturing, thermal stress and aerothermodynamic viewpoint.

High Temperature Corrosion of Silicon Carbide and Silicon Nitride in Water Vapor

NASA Technical Reports Server (NTRS)

Opila, E. J.; Robinson, Raymond C.; Cuy, Michael D.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Silicon carbide (SiC) and silicon nitride (Si3N4) are proposed for applications in high temperature combustion environments containing water vapor. Both SiC and Si3N4 react with water vapor to form a silica (SiO2) scale. It is therefore important to understand the durability of SiC, Si3N4 and SiO2 in water vapor. Thermogravimetric analyses, furnace exposures and burner rig results were obtained for these materials in water vapor at temperatures between 1100 and 1450 C and water vapor partial pressures ranging from 0.1 to 3.1 atm. First, the oxidation of SiC and Si3N4 in water vapor is considered. The parabolic kinetic rate law, rate dependence on water vapor partial pressure, and oxidation mechanism are discussed. Second, the volatilization of silica to form Si(OH)4(g) is examined. Mass spectrometric results, the linear kinetic rate law and a volatilization model based on diffusion through a gas boundary layer are discussed. Finally, the combined oxidation and volatilization reactions, which occur when SiC or Si3N4 are exposed in a water vapor-containing environment, are presented. Both experimental evidence and a model for the paralinear kinetic rate law are shown for these simultaneous oxidation and volatilization reactions.

Comparison of the surface charge behavior of commercial silicon nitride and silicon carbide powders

NASA Technical Reports Server (NTRS)

Whitman, Pamela K.; Feke, Donald L.

1988-01-01

The adsorption and desorption of protons from aqueous solution onto the surfaces of a variety of commercial silicon carbide and silicon nitride powders has been examined using a surface titration methodology. This method provides information on some colloidal characteristics, such as the point of zero charge (pzc) and the variation of proton adsorption with dispersion pH, useful for the prediction of optimal ceramic-processing conditions. Qualitatively, the magnitude of the proton adsorption from solution reveals small differences among all of the materials studied. However, the results show that the pzc for the various silicon nitride powders is affected by the powder synthesis route. Complementary investigations have shown that milling can also act to shift the pzc exhibited by silicon nitride powder. Also, studies of the role of the electrolyte in the development of surface charge have indicated no evidence of specific adsorption of ammonium ion on either silicon nitride or silicon carbide powders.

Fatigue life of high-speed ball bearings with silicon nitride balls

NASA Technical Reports Server (NTRS)

Parker, R. J.; Zaretsky, E. V.

1974-01-01

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. The five-ball fatigue tester was used to test 12.7-mm- diameter silicon nitride balls at maximum Hertz stresses ranging from 4.27 x 10 to the 9th power n/sq m to 6.21 x 10 to the 9th power n/sq m at a race temperature of 328K. The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

Two different ways for waveguides and optoelectronics components on top of C-MOS

NASA Astrophysics Data System (ADS)

Fedeli, J. M.; Jeannot, S.; Kostrzewa, M.; Di Cioccio, L.; Jousseaume, V.; Orobtchouk, R.; Maury, P.; Zussy, M.

2006-02-01

While fabrication of photonic components at the wafer level is a long standing goal of integrated optics, new applications such as optical interconnects are introducing new challenges for waveguides and optoelectronic component fabrication. Indeed, global interconnects are expected to face severe limitations in the near future. To face this problem, optical links on top of a CMOS circuits could be an alternative. The critical points to perform an optical link on a chip are firstly the realization of compact passive optical distribution and secondly the report of optoelectronic components for the sources and detectors. This paper presents two different approaches for the integration of both waveguides and optoelectronic components. In a first "total bonding" approach, waveguides have been elaborated using classical "Silicon On Insulators" technology and then reported using molecular bonding on top off Si wafers. The S0I substrate was then chemically etched, after what InP dies were moleculary bonded on top of the waveguides. With this approach, optical components with low loses and a good equilibrium are demonsrated. Using molecular bonding, InP dies were reported with no degradation of the optoelectronic properties of the films. In a second approach, using PECVD silicon nitride or amorphous silicon coupled to PECVD silicon oxide, basic optical components are demonstrated. This low temperature technology is compatible with a microelectronic Back End process, allowing an integration of the waveguides directly on top of CMOS circuits. InP dies can then be bonded on top of the waveguides.

Probabilistic Micromechanics and Macromechanics for Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; Shah, Ashwin R.

1997-01-01

The properties of ceramic matrix composites (CMC's) are known to display a considerable amount of scatter due to variations in fiber/matrix properties, interphase properties, interphase bonding, amount of matrix voids, and many geometry- or fabrication-related parameters, such as ply thickness and ply orientation. This paper summarizes preliminary studies in which formal probabilistic descriptions of the material-behavior- and fabrication-related parameters were incorporated into micromechanics and macromechanics for CMC'S. In this process two existing methodologies, namely CMC micromechanics and macromechanics analysis and a fast probability integration (FPI) technique are synergistically coupled to obtain the probabilistic composite behavior or response. Preliminary results in the form of cumulative probability distributions and information on the probability sensitivities of the response to primitive variables for a unidirectional silicon carbide/reaction-bonded silicon nitride (SiC/RBSN) CMC are presented. The cumulative distribution functions are computed for composite moduli, thermal expansion coefficients, thermal conductivities, and longitudinal tensile strength at room temperature. The variations in the constituent properties that directly affect these composite properties are accounted for via assumed probabilistic distributions. Collectively, the results show that the present technique provides valuable information about the composite properties and sensitivity factors, which is useful to design or test engineers. Furthermore, the present methodology is computationally more efficient than a standard Monte-Carlo simulation technique; and the agreement between the two solutions is excellent, as shown via select examples.

Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2009-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, Richard A.

1994-01-01

A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.

Nanoparticles, submicron-diameter tubes, and rods of Si{sub 3}N{sub 4} were synthesized from the thermal treatment of wheat and rice husks at temperatures at and above 1300 °C in a nitrogen atmosphere. The whole pattern Rietveld analysis of the observed diffraction data from treatments at 1300 °C showed the formation of only hexagonal α-phase of Si{sub 3}N{sub 4} with an R-factor of 1%, whereas samples treated at 1400 °C and above showed both α- and β-phases with an R-factor of 2%. Transmission electron microscopy showed the presence of tubes, rods, and nanoparticles of Si{sub 3}N{sub 4}. In a two-step process, where pure SiC wasmore » produced first from rice or wheat husk in an argon atmosphere and subsequently treated in a nitrogen atmosphere at 1450 °C, a nanostructured composite material having α- and β-phases of Si{sub 3}N{sub 4} combined with cubic phase of SiC was formed. The thermodynamics of the formation of silicon nitride is discussed in terms of the solid state reaction between organic matter (silica content), which is inherently present in the wheat and rice husks, with the nitrogen from the furnace atmosphere. Nanostructures of silicon nitride formed by a single direct reaction or their composites with SiC formed in a two-step process of agricultural byproducts provide an uncomplicated sustainable synthesis route for silicon nitride used in mechanical, biotechnology, and electro-optic nanotechnology applications.« less

Elevated temperature mechanical behavior of monolithic and SiC whisker-reinforced silicon nitrides

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Choi, Sung R.; Sanders, William A.; Fox, Dennis S.

1991-01-01

The mechanical behavior of a 30 volume percent SiC whisker reinforced silicon nitride and a similar monolithic silicon nitride were measured at several temperatures. Measurements included strength, fracture toughness, crack growth resistance, dynamic fatigue susceptibility, post oxidation strength, and creep rate. Strength controlling defects were determined with fractographic analysis. The addition of SiC whiskers to silicon nitride did not substantially improve the strength, fracture toughness, or crack growth resistance. However, the fatigue resistance, post oxidation strength, and creep resistance were diminished by the whisker addition.

Crystallization of the glassy grain boundary phase in silicon nitride ceramics

NASA Technical Reports Server (NTRS)

Drummond, Charles H., III

1991-01-01

The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

Rolling-element fatigue life of silicon nitride balls. [as compared to that of steel, ceramic, and cermet materials

NASA Technical Reports Server (NTRS)

Parker, R. J.; Zaretsky, E. V.

1974-01-01

The five-ball fatigue tester was used to evaluate silicon nitride as a rolling-element bearing material. Results indicate that hot-pressed silicon nitride running against steel may be expected to yield fatigue lives comparable to or greater than those of bearing quality steel running against steel at stress levels typical rolling-element bearing application. The fatigue life of hot-pressed silicon nitride is considerably greater than that of any ceramic or cermet tested. Computer analysis indicates that there is no improvement in the lives of 120-mm-bore angular--contact ball bearings of the same geometry operating at DN values from 2 to 4 million where hot-pressed silicon nitride balls are used in place of steel balls.

Solid-Liquid Interdiffusion Bonding of Silicon Carbide to Steel for High Temperature MEMS Sensor Packaging and Bonding

NASA Astrophysics Data System (ADS)

Chan, Matthew Wei-Jen

Complex engineering systems ranging from automobile engines to geothermal wells require specialized sensors to monitor conditions such as pressure, acceleration and temperature in order to improve efficiency and monitor component lifetime in what may be high temperature, corrosive, harsh environments. Microelectromechanical systems (MEMS) have demonstrated their ability to precisely and accurately take measurements under such conditions. The systems being monitored are typically made from metals, such as steel, while the MEMS sensors used for monitoring are commonly fabricated from silicon, silicon carbide and aluminum nitride, and so there is a sizable thermal expansion mismatch between the two. For these engineering applications the direct bonding of MEMS sensors to the components being monitored is often required. This introduces several challenges, namely the development of a bond that is capable of surviving high temperature harsh environments while mitigating the thermally induced strains produced during bonding. This project investigates the development of a robust packaging and bonding process, using the gold-tin metal system and the solid-liquid interdiffusion (SLID) bonding process, to join silicon carbide substrates directly to type-316 stainless steel. The SLID process enables bonding at lower temperatures while producing a bond capable of surviving higher temperatures. Finite element analysis was performed to model the thermally induced strains generated in the bond and to understand the optimal way to design the bond. The cross-sectional composition of the bonds has been analyzed and the bond strength has been investigated using die shear testing. The effects of high temperature aging on the bond's strength and the metallurgy of the bond were studied. Additionally, loading of the bond was performed at temperatures over 415 °C, more than 100 °C, above the temperature used for bonding, with full survival of the bond, thus demonstrating the benefit of SLID bonding for high temperature applications. Lastly, this dissertation provides recommendations for improving the strength and durability of the bond at temperatures of 400 °C and provides the framework for future work in the area of high temperature harsh environment MEMS packaging that would take directly bonded MEMS to temperatures of 600 °C and beyond.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, R.A.

1994-04-05

A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks

PubMed Central

Meng, Xin; Byun, Young-Chul; Kim, Harrison S.; Lee, Joy S.; Lucero, Antonio T.; Cheng, Lanxia; Kim, Jiyoung

2016-01-01

With the continued miniaturization of devices in the semiconductor industry, atomic layer deposition (ALD) of silicon nitride thin films (SiNx) has attracted great interest due to the inherent benefits of this process compared to other silicon nitride thin film deposition techniques. These benefits include not only high conformality and atomic-scale thickness control, but also low deposition temperatures. Over the past 20 years, recognition of the remarkable features of SiNx ALD, reinforced by experimental and theoretical investigations of the underlying surface reaction mechanism, has contributed to the development and widespread use of ALD SiNx thin films in both laboratory studies and industrial applications. Such recognition has spurred ever-increasing opportunities for the applications of the SiNx ALD technique in various arenas. Nevertheless, this technique still faces a number of challenges, which should be addressed through a collaborative effort between academia and industry. It is expected that the SiNx ALD will be further perceived as an indispensable technique for scaling next-generation ultra-large-scale integration (ULSI) technology. In this review, the authors examine the current research progress, challenges and future prospects of the SiNx ALD technique. PMID:28774125

Porous silicon technology for integrated microsystems

NASA Astrophysics Data System (ADS)

Wallner, Jin Zheng

With the development of micro systems, there is an increasing demand for integrable porous materials. In addition to those conventional applications, such as filtration, wicking, and insulating, many new micro devices, including micro reactors, sensors, actuators, and optical components, can benefit from porous materials. Conventional porous materials, such as ceramics and polymers, however, cannot meet the challenges posed by micro systems, due to their incompatibility with standard micro-fabrication processes. In an effort to produce porous materials that can be used in micro systems, porous silicon (PS) generated by anodization of single crystalline silicon has been investigated. In this work, the PS formation process has been extensively studied and characterized as a function of substrate type, crystal orientation, doping concentration, current density and surfactant concentration and type. Anodization conditions have been optimized for producing very thick porous silicon layers with uniform pore size, and for obtaining ideal pore morphologies. Three different types of porous silicon materials: meso porous silicon, macro porous silicon with straight pores, and macro porous silicon with tortuous pores, have been successfully produced. Regular pore arrays with controllable pore size in the range of 2mum to 6mum have been demonstrated as well. Localized PS formation has been achieved by using oxide/nitride/polysilicon stack as masking materials, which can withstand anodization in hydrofluoric acid up to twenty hours. A special etching cell with electrolytic liquid backside contact along with two process flows has been developed to enable the fabrication of thick macro porous silicon membranes with though wafer pores. For device assembly, Si-Au and In-Au bonding technologies have been developed. Very low bonding temperature (˜200°C) and thick/soft bonding layers (˜6mum) have been achieved by In-Au bonding technology, which is able to compensate the potentially rough surface on the porous silicon sample without introducing significant thermal stress. (Abstract shortened by UMI.)

Microstructures of BN/SiC coatings on nicalon fibers

NASA Technical Reports Server (NTRS)

Dickerson, R. M.; Singh, M.

1995-01-01

The microstructures of Nicalon silicon carbide (SiC) fibers and layered coatings of boron nitride (BN) followed by chemical vapor infiltrated silicon carbide (CVI-SiC) were characterized using optical and electron microscopy. Two different precursors and reactions were used to produce the BN layers while the deposition of CVI silicon carbide was nearly identical. Coated tows were examined in cross-section to characterize the chemistry and structures of the constituents and the interfaces. One BN precursor yielded three sublayers while the other gave a relatively homogeneous nanocrystalline layer.

RF sputtered silicon and hafnium nitrides as applied to 440C steel

NASA Technical Reports Server (NTRS)

Grill, A.; Aron, P. R.

1984-01-01

Silicon nitride and hafnium nitride coatings were deposited on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. The coatings and the interface between the coating and substrate were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. Oxide was found at all interfaces with an interface width of at least 600 A for the oxidized substrates and at least 300 A for the unoxidized substrates. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C. Coatings of both nitrides deposited at 8 mtorr were found to have increased adhesion to both oxidized and unoxidized 440C over those deposited at 20 mtorr.

Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

2002-01-01

A fiber-reinforced silicon-silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon-silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

1999-01-01

A fiber-reinforced silicon--silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon--silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

Silicon micromachined waveguides for millimeter and submillimeter wavelengths

NASA Technical Reports Server (NTRS)

Yap, Markus; Tai, Yu-Chong; Mcgrath, William R.; Walker, Christopher

1992-01-01

The majority of radio receivers, transmitters, and components operating at millimeter and submillimeter wavelengths utilize rectangular waveguides in some form. However, conventional machining techniques for waveguides operating above a few hundred GHz are complicated and costly. This paper reports on the development of silicon micromachining techniques to create silicon-based waveguide circuits which can operate at millimeter and submillimeter wavelengths. As a first step, rectangular WR-10 waveguide structures have been fabricated from (110) silicon wafers using micromachining techniques. The waveguide is split along the broad wall. Each half is formed by first etching a channel completely through a wafer. Potassium hydroxide is used to etch smooth mirror-like vertical walls and LPCVD silicon nitride is used as a masking layer. This wafer is then bonded to another flat wafer using a polyimide bonding technique and diced into the U-shaped half wavelengths. Finally, a gold layer is applied to the waveguide walls. Insertion loss measurements show losses comparable to those of standard metal waveguides. It is suggested that active devices and planar circuits can be integrated with the waveguides, solving the traditional mounting problems. Potential applications in terahertz instrumentation technology are further discussed.

Advanced ceramic material for high temperature turbine tip seals

NASA Technical Reports Server (NTRS)

Solomon, N. G.; Vogan, J. W.

1978-01-01

Ceramic material systems are being considered for potential use as turbine blade tip gas path seals at temperatures up to 1370 1/4 C. Silicon carbide and silicon nitride structures were selected for study since an initial analysis of the problem gave these materials the greatest potential for development into a successful materials system. Segments of silicon nitride and silicon carbide materials over a range of densities, processed by various methods, a honeycomb structure of silicon nitride and ceramic blade tip inserts fabricated from both materials by hot pressing were tested singly and in combination. The evaluations included wear under simulated engine blade tip rub conditions, thermal stability, impact resistance, machinability, hot gas erosion and feasibility of fabrication into engine components. The silicon nitride honeycomb and low-density silicon carbide using a selected grain size distribution gave the most promising results as rub-tolerant shroud liners. Ceramic blade tip inserts made from hot-pressed silicon nitride gave excellent test results. Their behavior closely simulated metal tips. Wear was similar to that of metals but reduced by a factor of six.

Tensile strength of aluminium nitride films

NASA Astrophysics Data System (ADS)

Zong, Deng Gang; Ong, Chung Wo; Aravind, Manju; Tsang, Mei Po; Loong Choy, Chung; Lu, Deren; Ma, Dejun

2004-11-01

Two-layered aluminium nitride (AlN)/silicon nitride microbridges were fabricated for microbridge tests to evaluate the elastic modulus, residual stress and tensile strength of the AlN films. The silicon nitride layer was added to increase the robustness of the structure. In a microbridge test, load was applied to the centre of a microbridge and was gradually increased by a nano-indenter equipped with a wedge tip until the sample was broken, while displacement was recorded coherently. Measurements were performed on single-layered silicon nitride microbridges and two-layered AlN/silicon nitride microbridges respectively. The data were fitted to a theory to derive the elastic modulus, residual stress and tensile strength of the silicon nitride films and AlN films. For the AlN films, the three parameters were determined to be 200, 0.06 and 0.3 GPa, respectively. The values of elastic modulus obtained were consistent with those measured by conventional nano-indentation method. The tensile strength value can be used as a reference to reflect the maximum tolerable tensile stress of AlN films when they are used in micro-electromechanical devices.

Process for producing amorphous and crystalline silicon nitride

DOEpatents

Morgan, P.E.D.; Pugar, E.A.

1985-11-12

A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of whiskers'' or needles is heated at temperature ranging from about 900 C to about 1,200 C to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900 C. 6 figs.

Process for producing amorphous and crystalline silicon nitride

DOEpatents

Morgan, Peter E. D.; Pugar, Eloise A.

1985-01-01

A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korolev, D. S.; Mikhaylov, A. N.; Belov, A. I.

The composition and structure of silicon surface layers subjected to combined gallium and nitrogen ion implantation with subsequent annealing have been studied by the X-ray photoelectron spectroscopy, Rutherford backscattering, electron spin resonance, Raman spectroscopy, and transmission electron microscopy techniques. A slight redistribution of the implanted atoms before annealing and their substantial migration towards the surface during annealing depending on the sequence of implantations are observed. It is found that about 2% of atoms of the implanted layer are replaced with gallium bonded to nitrogen; however, it is impossible to detect the gallium-nitride phase. At the same time, gallium-enriched inclusions containingmore » ∼25 at % of gallium are detected as candidates for the further synthesis of gallium-nitride inclusions.« less

Resistance of Silicon Nitride Turbine Components to Erosion and Hot Corrosion/oxidation Attack

NASA Technical Reports Server (NTRS)

Strangmen, Thomas E.; Fox, Dennis S.

1994-01-01

Silicon nitride turbine components are under intensive development by AlliedSignal to enable a new generation of higher power density auxiliary power systems. In order to be viable in the intended applications, silicon nitride turbine airfoils must be designed for survival in aggressive oxidizing combustion gas environments. Erosive and corrosive damage to ceramic airfoils from ingested sand and sea salt must be avoided. Recent engine test experience demonstrated that NT154 silicon nitride turbine vanes have exceptional resistance to sand erosion, relative to superalloys used in production engines. Similarly, NT154 silicon nitride has excellent resistance to oxidation in the temperature range of interest - up to 1400 C. Hot corrosion attack of superalloy gas turbine components is well documented. While hot corrosion from ingested sea salt will attack silicon nitride substantially less than the superalloys being replaced in initial engine applications, this degradation has the potential to limit component lives in advanced engine applications. Hot corrosion adversely affects the strength of silicon nitride in the 850 to 1300 C range. Since unacceptable reductions in strength must be rapidly identified and avoided, AlliedSignal and the NASA Lewis Research Center have pioneered the development of an environmental life prediction model for silicon nitride turbine components. Strength retention in flexure specimens following 1 to 3300 hour exposures to high temperature oxidation and hot corrosion has been measured and used to calibrate the life prediction model. Predicted component life is dependent upon engine design (stress, temperature, pressure, fuel/air ratio, gas velocity, and inlet air filtration), mission usage (fuel sulfur content, location (salt in air), and times at duty cycle power points), and material parameters. Preliminary analyses indicate that the hot corrosion resistance of NT154 silicon nitride is adequate for AlliedSignal's initial engine applications. Protective coatings and/or inlet air filtration may be required to achieve required ceramic component lives in more aggressive environments.

Microwave Integrated Circuit Amplifier Designs Submitted to Qorvo for Fabrication with 0.09-micron High Electron Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC)

DTIC Science & Technology

2016-03-01

Fabrication with 0.09-µm High-Electron-Mobility Transistors (HEMTs) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC) by John E Penn...for Fabrication with 0.09-µm High-Electron-Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide by John E Penn...µm High-Electron-Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

Suppression of carbon desorption from 4H-SiC by irradiating a remote nitrogen plasma at a low temperature

NASA Astrophysics Data System (ADS)

Shimabayashi, Masaharu; Kurihara, Kazuaki; Sasaki, Koichi

2018-05-01

We remotely irradiated a nitrogen plasma onto the carbon-side surface of 4H-SiC at a low temperature, and examined the effect of sample cooling on the characteristics of the nitride layer. An improved nitride layer, which had higher concentrations of carbon and silicon and a lower concentration of oxygen, was formed in the region at depths of more than 0.6–0.9 nm from the top surface. The depth of the fragile nitride layer in the top region, where no improved characteristics of the nitride layer were observed, became smaller with sample cooling. In addition, on the basis of the experimental results, we discussed the difference in the activation energy of the nitriding reaction of 4H-SiC supported by atomic nitrogen and molecular nitrogen in the metastable \\text{A}3Σ \\text{u} + state.

A comparison of ground-based and space flight data: Atomic oxygen reactions with boron nitride and silicon nitride

NASA Technical Reports Server (NTRS)

Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.; Koontz, S. L.

1990-01-01

The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) have been studied in low Earth orbit (LEO) flight experiments and in a ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed the materials coated over thin (approx 250 Angstrom) silver films whose electrical resistance was measured in situ to detect penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the in-flight and ground-based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the in-flight or ground-based experiments. The ground-based results show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground-based facility in terms of reproducing LEO flight results.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, Stephen M.; Tao, Hongyi; Todd-Copley, Judith A.

1991-01-01

A process for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, S.M.; Tao, H.; Todd-Copley, J.A.

1991-06-11

A process is disclosed for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength. 1 figure.

Formation of carbon nitride — a novel hard coating

NASA Astrophysics Data System (ADS)

Chubaci, J. F. D.; Ogata, K.; Fujimoto, F.; Watanabe, S.; Biersack, J. P.

1996-08-01

Increasing efforts have been reported on the formation of carbon nitride. Vapor deposition and simultaneous ion bombardment from accelerators or plasmas (IBAD) proved to be a successful technique for the preparation of this material. In our preparation, the properties of the films were controlled by varying the nitrogen ion energy and the flux composition ratio {C}/{N}. The deposited films with high nitrogen incorporation ( {C}/{N} = 0.6 ˜ 0.7 ) and low implantation energies (< 1.0 keV) showed high Knoop hardnesses of up to 63 GPa. XPS and FT-IR measurements indicated a high fraction of triple bonded CN. X-ray diffraction showed an amorphous structure. Computer simulations by the dynamic TRIM code are used to study the formation parameters, nitrogen ion energy and {C}/{N} ratio. This turned on to be useful in understanding the formation process of the carbon nitride films grown on silicon wafers, fused silica and tungsten carbide substrates.

Adhesion, friction, and wear of plasma-deposited thin silicon nitride films at temperatures to 700 C

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Pouch, J. J.; Alterovitz, S. A.; Pantic, D. M.; Johnson, G. A.

1988-01-01

The adhesion, friction, and wear behavior of silicon nitride films deposited by low- and high-frequency plasmas (30 kHz and 13.56 MHz) at various temperatures to 700 C in vacuum were examined. The results of the investigation indicated that the Si/N ratios were much greater for the films deposited at 13.56 MHz than for those deposited at 30 kHz. Amorphous silicon was present in both low- and high-frequency plasma-deposited silicon nitride films. However, more amorphous silicon occurred in the films deposited at 13.56 MHz than in those deposited at 30 kHz. Temperature significantly influenced adhesion, friction, and wear of the silicon nitride films. Wear occurred in the contact area at high temperature. The wear correlated with the increase in adhesion and friction for the low- and high-frequency plasma-deposited films above 600 and 500 C, respectively. The low- and high-frequency plasma-deposited thin silicon nitride films exhibited a capability for lubrication (low adhesion and friction) in vacuum at temperatures to 500 and 400 C, respectively.

Use of anionic surfactants for selective polishing of silicon dioxide over silicon nitride films using colloidal silica-based slurries

NASA Astrophysics Data System (ADS)

Penta, Naresh K.; Amanapu, H. P.; Peethala, B. C.; Babu, S. V.

2013-10-01

Four different anionic surfactants, sodium dodecyl sulfate, dodecyl benzene sulfonic acid (DBSA), dodecyl phosphate and Sodium lauroyl sarcosine, selected from the sulfate, phosphate, and carboxylic family, were investigated as additives in silica dispersions for selective polishing of silicon dioxide over silicon nitride films. We found that all these anionic surfactants suppress the nitride removal rates (RR) for pH ≤4 while more or less maintaining the oxide RRs, resulting in high oxide-to-nitride RR selectivity. The RR data obtained as a function of pH were explained based on pH dependent distributions of surfactant species, change in the zeta potentials of oxide and nitride surfaces, and thermogravimetric data. It appears that the negatively charged surfactant species preferentially adsorb on the positively charged nitride surface below IEP through its electrostatic interactions and form a bilayer adsorption, resulting in the suppression of nitride RRs. In contrast to the surfactants, K2SO4 interacts only weakly with the nitride surface and hence cannot suppress its RR.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1988-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C.E.; Benson, D.K.

1984-07-20

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate prior to metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Microelectromechanical-System-Based Variable-Focus Liquid Lens for Capsule Endoscopes

NASA Astrophysics Data System (ADS)

Seo, Sang Won; Han, Seungoh; Seo, Jun Ho; Kim, Young Mok; Kang, Moon Sik; Min, Nam Ki; Choi, Woo Beom; Sung, Man Young

2009-05-01

A liquid lens based on the electrowetting phenomenon was designed to be cylindrical to minimize dead area. The lens was fabricated with microelectromechanical-system (MEMS) technology using silicon thin film and wafer bonding processes. A multiple dielectric layer comprising Teflon, silicon nitride, and thermal oxide was formed on the cylinder wall. With a change of 11 Vrms in the applied bias, the lens module, including the fabricated liquid lens, showed a focal length change of approximately 166 mm. A capsule endoscope was assembled, including the lens module, and was successfully used to take images of a pig colon at various focal lengths.

X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation. Ph.D. Thesis - Cleveland State Univ., 1991

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1992-01-01

The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. Further in-situ radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction bonded silicon nitride matrix. It is concluded that pretest, in-situ, and post test x ray imaging can provide for greater understanding of ceramic matrix composite mechanical behavior.

Synchrotron Radiation Damage Mechanism of X-Ray Mask Membranes Irradiated in Helium Environment

NASA Astrophysics Data System (ADS)

Arakawa, Tomiyuki; Okuyama, Hiroshi; Okada, Koichi; Nagasawa, Hiroyuki; Syoki, Tsutomu; Yamaguchi, Yoh-ichi

1992-12-01

The mechanism of X-ray mask membrane displacement induced by synchrotron radiation (SR) has been discussed. Silicon nitride (SiN) and silicon carbide (SiC) membranes were irradiated by SR in a 1 atm helium ambient. SR-induced displacement for both membranes was 25-97 nm (σ). Oxygen concentration in both SiN and SiC was below 0.01 in O/Si atomic ratio. Although an increase in dangling bond density of SiN was observed, no remarkable increase in spin density was detected in SiC. Moreover, the most important finding was that thin oxides were grown on the membrane surface after SR irradiation. From these results, it is considered that the oxide growth on SiC membrane surfaces, and both the oxide growth and the increase of dangling bond density in SiN play an important role in the SR-induced displacement for the X-ray mask membranes.

Infrared Dielectric Properties of Low-stress Silicon Nitride

NASA Technical Reports Server (NTRS)

Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

2012-01-01

Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

Effect of oxygen plasma on nanomechanical silicon nitride resonators

NASA Astrophysics Data System (ADS)

Luhmann, Niklas; Jachimowicz, Artur; Schalko, Johannes; Sadeghi, Pedram; Sauer, Markus; Foelske-Schmitz, Annette; Schmid, Silvan

2017-08-01

Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

Rhodium-catalyzed synthesis of silafluorene derivatives via cleavage of silicon-hydrogen and carbon-hydrogen bonds.

PubMed

Ureshino, Tomonari; Yoshida, Takuya; Kuninobu, Yoichiro; Takai, Kazuhiko

2010-10-20

The rhodium-catalyzed synthesis of silafluorenes from biphenylhydrosilanes is described. This highly efficient reaction proceeds via both Si-H and C-H bond activation, producing only H(2) as a side product. Using this method, a ladder-type bis-silicon-bridged p-terphenyl could also be synthesized.

Foreign Object Damage Behavior of Two Gas-turbine Grade Silicon Nitrides by Steel Ball Projectiles at Ambient Temperature

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Pereira, J. Michael; Janosik, Lesley A.; Bhatt, Ramakrishna T.

2002-01-01

Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through strength testing of flexure test specimens impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (K(sub IC)). Additionally, the FOD response of an equiaxed, fine-grained silicon nitride (NC132) was also investigated to provide further insight. The NC132 silicon nitride exhibited the lowest fracture toughness of the three materials tested, providing further evidence that K(sub IC) is a key material parameter affecting FOD resistance. The observed damage generated by projectile impact was typically in the forms of well- or ill-developed ring or cone cracks with little presence of radial cracks.

Wetting behaviour of carbon nitride nanostructures grown by plasma enhanced chemical vapour deposition technique

NASA Astrophysics Data System (ADS)

Ahmad Kamal, Shafarina Azlinda; Ritikos, Richard; Abdul Rahman, Saadah

2015-02-01

Tuning the wettability of various coating materials by simply controlling the deposition parameters is essential for various specific applications. In this work, carbon nitride (CNx) films were deposited on silicon (1 1 1) substrates using radio-frequency plasma enhanced chemical vapour deposition employing parallel plate electrode configuration. Effects of varying the electrode distance (DE) on the films' structure and bonding properties were investigated using Field emission scanning electron microscopy, Atomic force microscopy, Fourier transform infrared and X-ray photoemission spectroscopy. The wettability of the films was analyzed using water contact angle measurements. At high DE, the CNx films' surface was smooth and uniform. This changed into fibrous nanostructures when DE was decreased. Surface roughness of the films increased with this morphological transformation. Nitrogen incorporation increased with decrease in DE which manifested the increase in both relative intensities of Cdbnd N to Cdbnd C and Nsbnd H to Osbnd H bonds. sp2-C to sp3-C ratio increased as DE decreased due to greater deformation of sp2 bonded carbon at lower DE. The films' characteristics changed from hydrophilic to super-hydrophobic with the decrease in DE. Roughness ratio, surface porosity and surface energy calculated from contact angle measurements were strongly dependent on the morphology, surface roughness and bonding properties of the films.

Second-harmonic generation in substoichiometric silicon nitride layers

NASA Astrophysics Data System (ADS)

Pecora, Emanuele; Capretti, Antonio; Miano, Giovanni; Dal Negro, Luca

2013-03-01

Harmonic generation in optical circuits offers the possibility to integrate wavelength converters, light amplifiers, lasers, and multiple optical signal processing devices with electronic components. Bulk silicon has a negligible second-order nonlinear optical susceptibility owing to its crystal centrosymmetry. Silicon nitride has its place in the microelectronic industry as an insulator and chemical barrier. In this work, we propose to take advantage of silicon excess in silicon nitride to increase the Second Harmonic Generation (SHG) efficiency. Thin films have been grown by reactive magnetron sputtering and their nonlinear optical properties have been studied by femtosecond pumping over a wide range of excitation wavelengths, silicon nitride stoichiometry and thermal processes. We demonstrate SHG in the visible range (375 - 450 nm) using a tunable 150 fs Ti:sapphire laser, and we optimize the SH emission at a silicon excess of 46 at.% demonstrating a maximum SHG efficiency of 4x10-6 in optimized films. Polarization properties, generation efficiency, and the second order nonlinear optical susceptibility are measured for all the investigated samples and discussed in terms of an effective theoretical model. Our findings show that the large nonlinear optical response demonstrated in optimized Si-rich silicon nitride materials can be utilized for the engineering of nonlinear optical functions and devices on a Si chip.

Microstructure and Mechanical Properties of Reaction-Formed Joints in Reaction Bonded Silicon Carbide Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

A reaction-bonded silicon carbide (RB-SiC) ceramic material (Carborundum's Cerastar RB-SIC) has been joined using a reaction forming approach. Microstructure and mechanical properties of three types of reaction-formed joints (350 micron, 50-55 micron, and 20-25 micron thick) have been evaluated. Thick (approximately 350 micron) joints consist mainly of silicon with a small amount of silicon carbide. The flexural strength of thick joints is about 44 plus or minus 2 MPa, and fracture always occurs at the joints. The microscopic examination of fracture surfaces of specimens with thick joints tested at room temperature revealed the failure mode to be typically brittle. Thin joints (<50-55 micron) consist of silicon carbide and silicon phases. The room and high temperature flexural strengths of thin (<50-55 micron) reaction-formed joints have been found to be at least equal to that of the bulk Cerastar RB-SIC materials because the flexure bars fracture away from the joint regions. In this case, the fracture origins appear to be inhomogeneities inside the parent material. This was always found to be the case for thin joints tested at temperatures up to 1350C in air. This observation suggests that the strength of Cerastar RB-SIC material containing a thin joint is not limited by the joint strength but by the strength of the bulk (parent) materials.

Trapped Atoms in One-Dimensional Photonic Crystals

DTIC Science & Technology

2013-08-09

a single silicon -nitride nanobeam (refractive index n = 2) with a 1D array of filleted rectangular holes along the propagation direction; atoms are...trapped in the centers of the holes (figure 1( a )). The second waveguide consists of two parallel silicon nitride nanobeams, each with a periodic array...the refractive index of silicon nitride is approximately constant across the optical domain, we adopt the approximation based on a frequency

Dimensional Analysis and Extended Hydrodynamic Theory Applied to Long-Rod Penetration of Ceramics

DTIC Science & Technology

2016-07-01

thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test...of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron ...since the mid 20th century. Popular candidate ceramics for such systems include alumina, aluminum nitride, boron carbide, silicon carbide, and titanium

Process for producing silicon nitride based articles of high fracture toughness and strength

DOEpatents

Huckabee, Marvin; Buljan, Sergej-Tomislav; Neil, Jeffrey T.

1991-01-01

A process for producing a silicon nitride-based article of improved fracture toughness and strength. The process involves densifying to at least 98% of theoretical density a mixture including (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 .mu.m and a surface area of about 8-12 m.sup.2 /g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 .mu.m and a surface area of about 2-4 m.sup.2 /g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. Optionally, the mixture may be blended with a binder and injection molded to form a green body, which then may be densified by, for example, hot isostatic pressing.

Process for producing silicon nitride based articles of high fracture toughness and strength

DOEpatents

Huckabee, M.; Buljan, S.T.; Neil, J.T.

1991-09-10

A process for producing a silicon nitride-based article of improved fracture toughness and strength is disclosed. The process involves densifying to at least 98% of theoretical density a mixture including (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 [mu]m and a surface area of about 8-12 m[sup 2]/g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 [mu]m and a surface area of about 2-4 m[sup 2]/g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. Optionally, the mixture may be blended with a binder and injection molded to form a green body, which then may be densified by, for example, hot isostatic pressing.

Power mixture and green body for producing silicon nitride base articles of high fracture toughness and strength

DOEpatents

Huckabee, M.L.; Buljan, S.T.; Neil, J.T.

1991-09-17

A powder mixture and a green body for producing a silicon nitride-based article of improved fracture toughness and strength are disclosed. The powder mixture includes (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 [mu]m and a surface area of about 8-12m[sup 2]g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 [mu]m and a surface area of about 2-4 m[sup 2]/g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. The green body is formed from the powder mixture, an effective amount of a suitable oxide densification aid, and an effective amount of a suitable organic binder. No Drawings

Method for one-to-one polishing of silicon nitride and silicon oxide

NASA Technical Reports Server (NTRS)

Babu, Suryadevara V. (Inventor); Natarajan, Anita (Inventor)

2009-01-01

The present invention provides a method of removing silicon nitride at about the same removal rate as silicon dioxide by CMP. The method utilizes a polishing slurry that includes colloidal silica abrasive particles dispersed in water and additives that modulate the silicon dioxide and silicon nitride removal rates such that they are about the same. In one embodiment of the invention, the additive is lysine or lysine mono hydrochloride in combination with picolinic acid, which is effective at a pH of about 8. In another embodiment of the invention, the additive is arginine in combination with picolinic acid, which is effective at a pH of about 10.

Process for manufacture of semipermeable silicon nitride membranes

DOEpatents

Galambos, Paul Charles; Shul, Randy J.; Willison, Christi Gober

2003-12-09

A new class of semipermeable membranes, and techniques for their fabrication, have been developed. These membranes, formed by appropriate etching of a deposited silicon nitride layer, are robust, easily manufacturable, and compatible with a wide range of silicon micromachining techniques.

Devitrification and delayed crazing of SiO2 on single-crystal silicon and chemically vapor-deposited silicon nitride

NASA Technical Reports Server (NTRS)

Choi, Doo Jin; Scott, William D.

1987-01-01

The linear growth rate of cristobalite was measured in thin SiO2 films on silicon and chemically vapor-deposited silicon nitride. The presence of trace impurities from alumina furnace tubes greatly increased the crystal growth rate. Under clean conditions, the growth rate was still 1 order-of-magnitude greater than that for internally nucleated crystals in bulk silica. Crystallized films cracked and lifted from the surface after exposure to atmospheric water vapor. The crystallization and subsequent crazing and lifting of protective SiO2 films on silicon nitride should be considered in long-term applications.

Effect of partial nitridation on the structure and luminescence properties of melilite-type Ca2Al2SiO7:Eu2+ phosphor

NASA Astrophysics Data System (ADS)

Luo, Yi; Xia, Zhiguo

2014-09-01

Ca1.97Al2-xSi1+xO7-xNx:0.03Eu2+ (x = 0-0.4) phosphors have been prepared by using the high temperature solid-state reaction. The effect of phase structures, photoluminescence (PL) properties and the thermal stabilities have been investigated based on the substitution of Al-O bond in Ca2Al2SiO7:Eu2+ phosphor with Si-N bond. The XRD Rietveld refinement and 29Si NMR analysis results verify the introduction of partial Si-N bonds. It is found that the PL spectra shift to the blue region abnormally from 530 to 515 nm, and the possible mechanism has been proposed. The activation energy becomes large along with the nitridation process, which coincides with the explanation of configuration coordinate diagram.

Irradiation resistance of silicon carbide joint at light water reactor–relevant temperature

DOE PAGES

Koyanagi, T.; Katoh, Y.; Kiggans, J. O.; ...

2017-03-10

We fabricated and irradiated monolithic silicon carbide (SiC) to SiC plate joints with neutrons at 270–310 °C to 8.7 dpa for SiC. The joining methods included solid state diffusion bonding using titanium and molybdenum interlayers, SiC nanopowder sintering, reaction sintering with a Ti-Si-C system, and hybrid processing of polymer pyrolysis and chemical vapor infiltration (CVI). All the irradiated joints exhibited apparent shear strength of more than 84 MPa on average. Significant irradiation-induced cracking was found in the bonding layers of the Ti and Mo diffusion bonds and Ti-Si-C reaction sintered bond. Furthermore, the SiC-based bonding layers of the SiC nanopowdermore » sintered and hybrid polymer pyrolysis and CVI joints all showed stable microstructure following the irradiation.« less

Use of silicon in liquid sintered silicon nitrides and sialons

DOEpatents

Raj, Rishi; Baik, Sunggi

1984-12-11

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

Reversible Silylene Insertion Reactions into Si-H and P-H σ-Bonds at Room Temperature.

PubMed

Rodriguez, Ricardo; Contie, Yohan; Nougué, Raphael; Baceiredo, Antoine; Saffon-Merceron, Nathalie; Sotiropoulos, Jean-Marc; Kato, Tsuyoshi

2016-11-07

Phosphine-stabilized silylenes react with silanes and a phosphine by silylene insertion into E-H σ-bonds (E=Si,P) at room temperature to give the corresponding silanes. Of special interest, the process occurs reversibly at room temperature. These results demonstrate that both the oxidative addition (typical reaction for transient silylenes) and the reductive elimination processes can proceed at the silicon center under mild reaction conditions. DFT calculations provide insight into the importance of the coordination of the silicon center to achieve the reductive elimination step. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of improved coating for advanced carbon-carbon components

NASA Technical Reports Server (NTRS)

Yamaki, Y. R.; Brown, J. J.

1984-01-01

Reaction sintered silicon nitride (RSSN) was studied as a substitute coating material on the carbon-carbon material (RCC) presently used as a heat shield on the space shuttle, and on advanced carbon-carbon (ACC), a later development. On RCC, RSSN showed potential in a 538 C (1000 F) screening test in which silicon carbide coated material exhibits its highest oxidation rate; RSSN afforded less protection to ACC because of a larger thermal expansion mismatch. Organosilicon densification and metallic silicon sealing methods were studied as means of further increasing the oxidation resistance of the coating, and some improvement was noted when these methods were employed.

Method for selective CMP of polysilicon

NASA Technical Reports Server (NTRS)

Babu, Suryadevara V. (Inventor); Natarajan, Anita (Inventor); Hegde, Sharath (Inventor)

2010-01-01

A method of removing polysilicon in preference to silicon dioxide and/or silicon nitride by chemical mechanical polishing. The method removes polysilicon from a surface at a high removal rate while maintaining a high selectivity of polysilicon to silicon dioxide and/or a polysilicon to silicon nitride. The method is particularly suitable for use in the fabrication of MEMS devices.

Colloidal characterization of silicon nitride and silicon carbide

NASA Technical Reports Server (NTRS)

Feke, Donald L.

1986-01-01

The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

On the photon annealing of silicon-implanted gallium-nitride layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seleznev, B. I., E-mail: Boris.Seleznev@novsu.ru; Moskalev, G. Ya.; Fedorov, D. G.

2016-06-15

The conditions for the formation of ion-doped layers in gallium nitride upon the incorporation of silicon ions followed by photon annealing in the presence of silicon dioxide and nitride coatings are analyzed. The conditions of the formation of ion-doped layers with a high degree of impurity activation are established. The temperature dependences of the surface concentration and mobility of charge carriers in ion-doped GaN layers annealed at different temperatures are studied.

Paralinear Oxidation of Silicon Nitride in a Water Vapor/Oxygen Environment

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Opila, Elizabeth J.; Nguyen, QuynhGiao; Humphrey, Donald L.; Lewton, Susan M.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Three silicon nitride materials were exposed to dry oxygen flowing at 0.44 cm/s at temperatures between 1200 and 1400 C. Reaction kinetics were measured with a continuously recording microbalance. Parabolic kinetics were observed. When the same materials were exposed to a 50% H2O - 50% O2 gas mixture flowing at 4.4 cm/s, all three types exhibited paralinear kinetics. The material is oxidized by water vapor to form solid silica. The protective silica is in turn volatilized by water vapor to form primarily gaseous Si(OH)4. Nonlinear least squares analysis and a paralinear kinetic model were used to determine both parabolic and linear rate constants from the kinetic data. Volatilization of the protective silica scale can result in accelerated consumption of Si3N4. Recession rates under conditions more representative of actual combustors are compared to the furnace data.

An Array of Layers in Silicon Sulfides: Chain-like and Ground State Structures

NASA Astrophysics Data System (ADS)

Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino

While much is known about isoelectronic materials related to carbon nanostructures, such as boron nitride layers and nanotubes, rather less is known about equivalent silicon based materials. Following the recent discovery of phosphorene, we here discuss isoelectronic silicon monosulfide monolayers. We describe a set of anisotropic ground state structures that clearly have a high stability with respect to the near isotropic silicon monosulfide monolayers. The source of the layer anisotropy is related to the presence of Si-S double chains linked by some Si-Si covalent bonds, which lie at the core of the increased stability, together with a remarkable spd hybridization on Si. The involvement of d orbitals brings more variety to silicon-sulfide based nanostructures that are isoelectronic to phosphorene, which could be relevant for future applications, adding extra degrees of freedom. Spanish Ministry of Economy and Competitiveness MINECO, Basque Government (ETORTEK Program 2014), University of the Basque Country (GrantGrant No. IT-366-07) and MPC Material Physics Center - San Sebastián.

Doping of silicon by carbon during laser ablation process

NASA Astrophysics Data System (ADS)

Raciukaitis, G.; Brikas, M.; Kazlauskiene, V.; Miskinis, J.

2007-04-01

Effect of laser ablation on properties of remaining material was investigated in silicon. It was established that laser cutting of wafers in air induced doping of silicon by carbon. The effect was found to be more distinct by the use of higher laser power or UV radiation. Carbon ions created bonds with silicon in the depth of silicon. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion was performed to clarify its depth profile in silicon. Photo-chemical reactions of such type changed the structure of material and could be a reason for the reduced quality of machining. A controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.

BN Bonded BN fiber article and method of manufacture

DOEpatents

Hamilton, Robert S.

1981-08-18

A boron nitride bonded boron nitride fiber article and the method for its manufacture which comprises forming a shaped article with a composition comprising a bonding compound selected from boron oxide and boric acid and a structural fiber selected from the group consisting of boron oxide, boron nitride and partially nitrided boron oxide fibers, heating the composition in an anhydrous gas to a temperature above the melting point of the compound and nitriding the resulting article in ammonia gas.

Use of silicon in liquid sintered silicon nitrides and sialons

DOEpatents

Raj, R.; Baik, S.

1984-12-11

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

Use of free silicon in liquid phase sintering of silicon nitrides and sialons

DOEpatents

Raj, R.; Baik, S.

1985-11-12

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

Use of free silicon in liquid phase sintering of silicon nitrides and sialons

DOEpatents

Raj, Rishi; Baik, Sunggi

1985-11-12

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

Thermal conversion of an iron nitride-silicon nitride precursor into a ferromagnetic nanocomposite

NASA Astrophysics Data System (ADS)

Maya, L.; Thompson, J. R.; Song, K. J.; Warmack, R. J.

1998-01-01

Iron nitride films, FeN, in a pure form and in the form of a nanocomposite in silicon nitride were prepared by reactive sputtering using iron or iron disilicide, respectively, as targets in a nitrogen plasma. Iron nitride decomposes into the elements by heating in vacuum to 800 °C. Intermediate phases such as Fe2N or Fe4N form at lower temperatures. The nanocomposites contain the iron phases as particles with an average size of ˜5 nm dispersed in the amorphous silicon nitride matrix. The magnetic properties of the nanocomposites were established. The precursor FeN-Si3N4 film is paramagnetic, while the Fe-Si3N4, obtained by heating in vacuum, is ferromagnetic and shows typical superparamagnetic behavior. These films are of interest as recording media with superior chemical and mechanical stability and may be encoded by localized heating.

Fabrication of porous silicon nitride ceramics using binder jetting technology

NASA Astrophysics Data System (ADS)

Rabinskiy, L.; Ripetsky, A.; Sitnikov, S.; Solyaev, Y.; Kahramanov, R.

2016-07-01

This paper presents the results of the binder jetting technology application for the processing of the Si3N4-based ceramics. The difference of the developed technology from analogues used for additive manufacturing of silicon nitride ceramics is a method of the separate deposition of the mineral powder and binder without direct injection of suspensions/slurries. It is assumed that such approach allows reducing the technology complexity and simplifying the process of the feedstock preparation, including the simplification of the composite materials production. The binders based on methyl ester of acrylic acid with polyurethane and modified starch were studied. At this stage of the investigations, the technology of green body's fabrication is implemented using a standard HP cartridge mounted on the robotic arm. For the coordinated operation of the cartridge and robot the specially developed software was used. Obtained green bodies of silicon powder were used to produce the ceramic samples via reaction sintering. The results of study of ceramics samples microstructure and composition are presented. Sintered ceramics are characterized by fibrous α-Si3N4 structure and porosity up to 70%.

Fabrication of turbine components and properties of sintered silicon nitride

NASA Technical Reports Server (NTRS)

Neil, J. T.; French, K. W.; Quackenbush, C. L.; Smith, J. T.

1982-01-01

This paper presents a status report on the injection molding of sinterable silicon nitride at GTE Laboratories. The effort involves fabrication of single axial turbine blades and monolithic radial turbine rotors. The injection molding process is reviewed and the fabrication of the turbine components discussed. Oxidation resistance and strength results of current injection molded sintered silicon nitride as well as dimensional checks on sintered turbine blades demonstrate that this material is a viable candidate for high temperature structural applications.

Property Screening and Evaluation of Ceramic Turbine Materials

DTIC Science & Technology

1984-04-01

Unless otherwise indicated, the upper and lower spans were 0.875 and 1.750 in., respectively. For room-temperature tests, a stainless steel fixture...Silicon Nitride High Temperature Properties Silicon Carbide Silicon Ceramics Transformation-Toughened Zirconia Structural Ceramics Mechanical Properties...3ilicon carbide and silicon nitride, that have potential as structural components in"advanced gas turbine engines, were evaluated. Thermal and

Silicon nitride reinforced with molybdenum disilicide

DOEpatents

Petrovic, John J.; Honnell, Richard E.

1991-01-01

Compositions of matter comprised of silicon nitride and molybdenum disilicide and methods of making the compositions, where the molybdenum disilicide is present in amounts ranging from about 5 to about 50 vol. %.

Towards the development of micromechanics equations for ceramic matrix composites via fiber substructuring

NASA Technical Reports Server (NTRS)

Murthy, P. L. N.; Chamis, C. C.

1992-01-01

A generic unit cell model which includes a unique fiber substructuring concept is proposed for the development of micromechanics equations for continuous fiber reinforcement ceramic composites. The unit cell consists of three constituents: fiber, matrix, and an interphase. In the present approach, the unit cell is further subdivided into several slices and the equations of micromechanics are derived for each slice. These are subsequently integrated to obtain ply level properties. A stand alone computer code containing the micromechanics model as a module is currently being developed specifically for the analysis of ceramic matrix composites. Towards this development, equivalent ply property results for a SiC/Ti-15-3 composite with 0.5 fiber volume ratio are presented and compared with those obtained from customary micromechanics models to illustrate the concept. Also, comparisons with limited experimental data for the ceramic matrix composite, SiC/RBSN (Reaction Bonded Silicon Nitride) with a 0.3 fiber volume ratio are given to validate the concepts.

Evaluation of microcrack thermal shock damage in ceramics: Modeling and experiment

NASA Technical Reports Server (NTRS)

Chu, Y. C.; Hefetz, M.; Rokhlin, S. I.

1992-01-01

In this paper we present an experimental and theoretical study of the effect of microcrack damage on ceramic properties. For the experimental investigation, ceramic samples of aluminum oxide and reaction bonded silicon nitride (RBSN) are used. Thermal shock treatment from different temperatures up to 1000 C is applied to produce the microcracks. Both surface and bulk ultrasonic wave methods are used to correlate the change of elastic constants to microstructural degradation and to determine the change in elastic anisotropy induced by microcrack damage. For the theoretical investigation, damage mechanics, which relates microstructural damage to material service life and mechanical failure, is used. The change in elastic properties due to microcrack damage calculated from the theoretical model is compared with the experimental results for determination of the applicability of damage theory. It is shown that two independent experimental methods (bulk wave and surface wave) give the same results for shear moduli of damaged ceramics. The experimental results aagree reasonably well with the moduli predicted from the cracked solid model.

Modeling of stress/strain behavior of fiber-reinforced ceramic matrix composites including stress redistribution

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Murthy, Pappu L. N.; Chamis, Christos C.

1994-01-01

A computational simulation procedure is presented for nonlinear analyses which incorporates microstress redistribution due to progressive fracture in ceramic matrix composites. This procedure facilitates an accurate simulation of the stress-strain behavior of ceramic matrix composites up to failure. The nonlinearity in the material behavior is accounted for at the constituent (fiber/matrix/interphase) level. This computational procedure is a part of recent upgrades to CEMCAN (Ceramic Matrix Composite Analyzer) computer code. The fiber substructuring technique in CEMCAN is used to monitor the damage initiation and progression as the load increases. The room-temperature tensile stress-strain curves for SiC fiber reinforced reaction-bonded silicon nitride (RBSN) matrix unidirectional and angle-ply laminates are simulated and compared with experimentally observed stress-strain behavior. Comparison between the predicted stress/strain behavior and experimental stress/strain curves is good. Collectively the results demonstrate that CEMCAN computer code provides the user with an effective computational tool to simulate the behavior of ceramic matrix composites.

Silicon Nitride for Direct Water-Splitting and Corrosion Mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Head, J.; Turner, J.A.

2006-01-01

Todays fossil fuels are becoming harder to obtain, creating pollution problems, and posing hazards to people’s health. One alternative to fossil fuels is hydrogen, capable of serving as a clean and efficient energy carrier. Certain semiconductors are able to harness the energy of photons and direct it into water electrolysis in a process known as photoelectrochemical water splitting. Triple junction devices integrate three semiconductors of different band gaps resulting in a monolithic material that absorbs over a broader spectrum. Amorphous silicon (a-Si) is one such material that, when stacked in tandem, possesses water-splitting capabilities. Even though a-Si is capable ofmore » splitting water, it is an unstable material in solution and therefore requires a coating to protect the surface from corrosion. A stable, transparent material that has the potential for corrosion protection is silicon nitride. In this study, silicon nitride thin films were grown using DC magnetron sputtering with varying amounts of argon and nitrogen added to the system. X-ray diffraction indicated amorphous silicon nitride films. Current as a function of potential was determined from cyclic voltammetry measurements. Mott-Schottky analysis showed n-type behavior with absorption and transmission measurements indicated variation in flatband potentials. Variation in band gap values ranging from 1.90 to 4.0 eV. Corrosion measurements reveal that the silicon nitride samples exhibit both p-type and n-type behavior. Photocurrent over a range of potentials was greater in samples that were submerged in acidic electrolyte. Silicon nitride shows good stability in acidic, neutral, and basic solutions, indicative of a good material for corrosion mitigation.« less

Doping of silicon with carbon during laser ablation process

NASA Astrophysics Data System (ADS)

Račiukaitis, G.; Brikas, M.; Kazlauskienė, V.; Miškinis, J.

2006-12-01

The effect of laser ablation on properties of remaining material in silicon was investigated. It was found that laser cutting of wafers in the air induced the doping of silicon with carbon. The effect was more distinct when using higher laser power or UV radiation. Carbon ions created bonds with silicon atoms in the depth of the material. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion to clarify its depth profile in silicon was performed. Photochemical reactions of such type changed the structure of material and could be the reason of the reduced machining quality. The controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.

Method of joining ceramics

DOEpatents

Henager, Jr., Charles H.; Brimhall, John L.

2000-01-01

According to the method of the present invention, joining a first bi-element carbide to a second bi-element carbide, has the steps of: (a) forming a bond agent containing a metal carbide and silicon; (b) placing the bond agent between the first and second bi-element carbides to form a pre-assembly; and (c) pressing and heating the pre-assembly in a non-oxidizing atmosphere to a temperature effective to induce a displacement reaction creating a metal silicon phase bonding the first and second bi-element carbides.

Power mixture and green body for producing silicon nitride base & articles of high fracture toughness and strength

DOEpatents

Huckabee, Marvin L.; Buljan, Sergej-Tomislav; Neil, Jeffrey T.

1991-01-01

A powder mixture and a green body for producing a silicon nitride-based article of improved fracture toughness and strength. The powder mixture includes 9a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon mitride powder of an average particle size of about 0.2 .mu.m and a surface area of about 8-12m.sup.2 g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 .mu.m and a surface area of about 2-4 m.sup.2 /g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified articel an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. The green body is formed from the powder mixture, an effective amount of a suitable oxide densification aid, and an effective amount of a suitable organic binder.

Tensile test of pressureless-sintered silicon nitride at elevated temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Fujisawa, Y.; Takahara, K.

1985-01-01

Uniaxial tensile strength tests of pressureless sintered silicon nitride were carried out in air at temperatures ranging from room temperature up to 1600 C. Silicon nitrides containing Y2O3, Al2O3, Al2O3-MgO, or MgO-CeO2 additives were tested. The results show that the composition of the additive used influences the strength characteristics of the silicon nitride. The tensile strength rapidly decreased at temperatures above 1000 C for the materials containing MgO as the additive and above 1000 C for the material with Y2O3. When the temperature increased to as high as 1300 C, the strength decreased to about 10 percent of the room temperature strength in each case. Observations of the fracture origin and of the crack propagation on the fracture surfaces are discussed.

Passivation coating for flexible substrate mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1990-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors. Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention.

Microstructural and Mechanical Evaluation of a Cu-Based Active Braze Alloy to Join Silicon Nitride Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.; Asthana, Rajiv; Varela, F. M.; Martinez-Fernandez, J.

2010-01-01

Self-joining of St. Gobain Si3N4 (NT-154) using a ductile Cu-Al-Si-Ti active braze (Cu-ABA) was demonstrated. A reaction zone approx.2.5-3.5 microns thick) developed at the interface after 30 min brazing at 1317 K. The interface was enriched in Ti and Si. The room temperature compressive shear strengths of Si3N4/Si3N4 and Inconel/Inconel joints (the latter created to access baseline data for use with the proposed Si3N4/Inconel joints) were 140+/-49MPa and 207+/-12MPa, respectively. High-temperature shear tests were performed at 1023K and 1073 K, and the strength of the Si3N4/Si3N4 and Inconel/Inconel joints were determined. The joints were metallurgically well-bonded for temperatures above 2/3 of the braze solidus. Scanning and transmission electron microscopy studies revealed a fine grain microstructure in the reaction layer, and large grains in the inner part of the joint with interfaces being crack-free. The observed formation of Ti5Si3 and AlN at the joint interface during brazing is discussed.

Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, J. Douglas

2007-01-01

A robust joining approach is critically needed for a Micro-Electro-Mechanical Systems-Lean Direct Injector (MEMS-LDI) application which requires leak free joints with high temperature mechanical capability. Diffusion bonding is well suited for the MEMS-LDI application. Diffusion bonds were fabricated using titanium interlayers between silicon carbide substrates during hot pressing. The interlayers consisted of either alloyed titanium foil or physically vapor deposited (PVD) titanium coatings. Microscopy shows that well adhered, crack free diffusion bonds are formed under optimal conditions. Under less than optimal conditions, microcracks are present in the bond layer due to the formation of intermetallic phases. Electron microprobe analysis was used to identify the reaction formed phases in the diffusion bond. Various compatibility issues among the phases in the interlayer and substrate are discussed. Also, the effects of temperature, pressure, time, silicon carbide substrate type, and type of titanium interlayer and thickness on the microstructure and composition of joints are discussed.

Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

1990-01-01

The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

Laser-induced amorphization of silicon during pulsed-laser irradiation of TiN/Ti/polycrystalline silicon/SiO2/silicon

NASA Astrophysics Data System (ADS)

Chong, Y. F.; Pey, K. L.; Wee, A. T. S.; Thompson, M. O.; Tung, C. H.; See, A.

2002-11-01

In this letter, we report on the complex solidification structures formed during laser irradiation of a titanium nitride/titanium/polycrystalline silicon/silicon dioxide/silicon film stack. Due to enhanced optical coupling, the titanium nitride/titanium capping layer increases the melt depth of polycrystalline silicon by more than a factor of 2. It is found that the titanium atoms diffuse through the entire polycrystalline silicon layer during irradiation. Contrary to the expected polycrystalline silicon growth, distinct regions of polycrystalline and amorphous silicon are formed instead. Possible mechanisms for the formation of these microstructures are proposed.

Strengthening of oxidation resistant materials for gas turbine applications. [treatment of silicon ceramics for increased flexural strength and impact resistance

NASA Technical Reports Server (NTRS)

Kirchner, H. P.

1974-01-01

Silicon nitride and silicon carbide ceramics were treated to form compressive surface layers. On the silicon carbide, quenching and thermal exposure treatments were used, and on the silicon nitride, quenching, carburizing, and a combination of quenching and carburizing were used. In some cases substantial improvements in impact resistance and/or flexural strength were observed. The presence of compressive surface stresses was demonstrated by slotted rod tests.

Conformal chemically resistant coatings for microflow devices

DOEpatents

Folta, James A.; Zdeblick, Mark

2003-05-13

A process for coating the inside surfaces of silicon microflow devices, such as electrophoresis microchannels, with a low-stress, conformal (uniform) silicon nitride film which has the ability to uniformly coat deeply-recessed cavities with, for example, aspect ratios of up to 40:1 or higher. The silicon nitride coating allows extended exposure to caustic solutions. The coating enables a microflow device fabricated in silicon to be resistant to all classes of chemicals: acids, bases, and solvents. The process involves low-pressure (vacuum) chemical vapor deposition. The ultra-low-stress silicon nitride deposition process allows 1-2 .mu.m thick films without cracks, and so enables extended chemical protection of a silicon microflow device against caustics for up to 1 year. Tests have demonstrated the resistance of the films to caustic solutions at both ambient and elevated temperatures to 65.degree. C.

Silicon nitride photonics: from visible to mid-infrared wavelengths

NASA Astrophysics Data System (ADS)

Micó, Gloria; Bru, Luis A.; Pastor, Daniel; Doménech, David; Fernández, Juan; Sánchez, Ana; Cirera, Josep M.; Domínguez, Carlos; Muñoz, Pascual

2018-02-01

Silicon nitride has received a lot of attention during the last ten years, for applications such as bio-photonics, tele/datacom, optical signal processing and sensing. In this paper, firstly an updated review of the state of the art of silicon nitride photonics integration platforms will be provided. Secondly, our developments on a moderate confinement Si3N4 platform in the near-infrared will be presented. Finally, our steps towards establishing a Si3N4 based platform for broadband operation spanning from visible to mid-infrared wavelengths will be introduced.

Octave-spanning supercontinuum generation in a silicon-rich nitride waveguide.

PubMed

Liu, Xing; Pu, Minhao; Zhou, Binbin; Krückel, Clemens J; Fülöp, Attila; Torres-Company, Victor; Bache, Morten

2016-06-15

We experimentally show octave-spanning supercontinuum generation in a nonstoichiometric silicon-rich nitride waveguide when pumped by femtosecond pulses from an erbium fiber laser. The pulse energy and bandwidth are comparable to results achieved in stoichiometric silicon nitride waveguides, but our material platform is simpler to manufacture. We also observe wave-breaking supercontinuum generation by using orthogonal pumping in the same waveguide. Additional analysis reveals that the waveguide height is a powerful tuning parameter for generating mid-infrared dispersive waves while keeping the pump in the telecom band.

Hot isostatic pressing of silicon nitride Sisub3n4 containing zircon, or zirconia and silica

NASA Technical Reports Server (NTRS)

Somiya, S.; Yoshimura, M.; Suzuki, T.; Nishimura, H.

1980-01-01

A hydrothermal synthesis apparatus with a 10 KB cylinder was used to obtain a sintered body of silicon nitride. The sintering auxiliary agents used were zircon (ZrSiO4) and a mixture of zirconia (ZrO2) and silica (SiO2). Experiments were conducted with the amounts of ZrSi04 or ArO2 and SiO2 varying over a wide range and the results compared to discover the quantity of additive which produced sintering in silicon nitride by the hot pressing method.

The elevated temperature mechanical properties of silicon nitride/boron nitride fibrous monoliths

NASA Astrophysics Data System (ADS)

Trice, Rodney Wayne

A unique, all-ceramic material capable of non-brittle fracture via crack deflection has been characterized from 25sp°C through 1400sp°C. This material, called fibrous monoliths (FMs), was comprised of unidirectionally aligned 250 mum diameter cells of silicon nitride surrounded by 10 mum thick cell boundaries of boron nitride. Six weight percent yttria and two weight percent alumina were added to the silicon nitride to aid in densification. TEM experiments revealed that the sintering aids used to densify the silicon nitride cells were migrating into the boron nitride cell boundary during hot-pressing and that a fine network of micro-cracks existed between basal planes of boron nitride. Elevated temperature four point bending tests were performed on fibrous monolith ceramics from room temperature through 1400sp°C. Peak strengths of FMs averaged 510 MPa for specimens tested at room temperature through 176 MPa at 1400sp°C. Work of fractures ranged from 7300 J/msp2 to 3200 J/msp2 under the same temperature conditions. The interfacial fracture energy of boron nitride, GammasbBN, as a function of temperature has been determined using the Charalambides method. The fracture energy of boron nitride is approximately 40 J/msp2 and remained constant from 25sp°C through 950sp°C. A sharp increase in GammasbBN, to about 60 J/msp2, was observed at 1000sp°C-1050sp°C. This increase in GammasbBN was attributed to interactions of the crack tip with the cell boundary glassy phase. Subsequent measurements at 1075sp°C indicated a marked decrease in GammasbBN to near 40 J/msp2 before plateauing at 17-20 J/msp2 in the 1200sp°C-1300sp°C regime. The Mode I fracture toughness of silicon nitride was also determined using the single edge precracked beam method as a function of temperature. The He and Hutchinson model relating crack deflection at an interface to the Dundurs' parameter was applied to the current data set using the temperature dependent fracture energies of the boron nitride and the silicon nitride. A more refractory fibrous monolith was fabricated in an effort to extend the high temperature properties of SN/BN fibrous monoliths. Only 4 wt.% yttria was added to the silicon nitride to aid in densification. The presence of residual carbon following binder burnout was proposed to be responsible for the formation of melilite, a phase known to undergo severe oxidation between 900sp°C-1100sp°C. When residual carbon was removed prior to hot-pressing with a post-binder burnout heat treatment at 400sp°C in air this phase was not present. A room temperature strength of 553 MPa and a work of fracture of 6700 J/msp2 was observed. A strength of 293 MPa was measured at 1400sp°C.

Development of a continuous spinning process for producing silicon carbide - silicon nitride precursor fibers

NASA Technical Reports Server (NTRS)

1985-01-01

An apparatus was designed for the continuous production of silicon carbide - silicon nitride precursor fibers. The precursor polymer can be fiberized, crosslined and pyrolyzed. The product is a metallic black fiber with the composition of the type C sub x Si sub y n sub z. Little, other than the tensile strength and modulus of elasticity, is known of the physical properties.

Nitridation of silicon by nitrogen neutral beam

NASA Astrophysics Data System (ADS)

Hara, Yasuhiro; Shimizu, Tomohiro; Shingubara, Shoso

2016-02-01

Silicon nitridation was investigated at room temperature using a nitrogen neutral beam (NB) extracted at acceleration voltages of less than 100 V. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of a Si3N4 layer on a Si (1 0 0) substrate when the acceleration voltage was higher than 20 V. The XPS depth profile indicated that nitrogen diffused to a depth of 36 nm for acceleration voltages of 60 V and higher. The thickness of the silicon nitrided layer increased with the acceleration voltages from 20 V to 60 V. Cross-sectional transmission electron microscopy (TEM) analysis indicated a Si3N4 layer thickness of 3.1 nm was obtained at an acceleration voltage of 100 V. Moreover, it was proved that the nitrided silicon layer formed by the nitrogen NB at room temperature was effective as the passivation film in the wet etching process.

Ab initio design of nanostructures for solar energy conversion: a case study on silicon nitride nanowire.

PubMed

Pan, Hui

2014-01-01

Design of novel materials for efficient solar energy conversion is critical to the development of green energy technology. In this work, we present a first-principles study on the design of nanostructures for solar energy harvesting on the basis of the density functional theory. We show that the indirect band structure of bulk silicon nitride is transferred to direct bandgap in nanowire. We find that intermediate bands can be created by doping, leading to enhancement of sunlight absorption. We further show that codoping not only reduces the bandgap and introduces intermediate bands but also enhances the solubility of dopants in silicon nitride nanowires due to reduced formation energy of substitution. Importantly, the codoped nanowire is ferromagnetic, leading to the improvement of carrier mobility. The silicon nitride nanowires with direct bandgap, intermediate bands, and ferromagnetism may be applicable to solar energy harvesting.

Preparation and mechanical properties of carbon nanotube-silicon nitride nano-ceramic matrix composites

NASA Astrophysics Data System (ADS)

Tian, C. Y.; Jiang, H.

2018-01-01

Carbon nanotube-silicon nitride nano-ceramic matrix composites were fabricated by hot-pressing nano-sized Si3N4 powders and carbon nanotubes. The effect of CNTs on the mechanical properties of silicon nitride was researched. The phase compositions and the microstructure characteristics of the samples as well as the distribution of carbon nanotube in the silicon nitride ceramic were analyzed by X-ray diffraction and scanning electron microscope. The results show that the microstructure of composites consists mainly of α-Si3N4, β-Si3N4, Si2N2O and carbon natubes. The addition of proper amount of carbon nanotubes can improve the fracture toughness and the flexural strength, and the optimal amount of carbon nanotube are both 3wt.%. However the Vickers hardness values decrease with the increase of carbon nanotubes content.

Substrate nitridation induced modulations in transport properties of wurtzite GaN/p-Si (100) heterojunctions grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhat, Thirumaleshwara N.; Rajpalke, Mohana K.; Krupanidhi, S. B.

Phase pure wurtzite GaN films were grown on Si (100) substrates by introducing a silicon nitride layer followed by low temperature GaN growth as buffer layers. GaN films grown directly on Si (100) were found to be phase mixtured, containing both cubic ({beta}) and hexagonal ({alpha}) modifications. The x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy studies reveal that the significant enhancement in the structural as well as in the optical properties of GaN films grown with silicon nitride buffer layer grown at 800 deg. C when compared to the samples grown in the absence of silicon nitridemore » buffer layer and with silicon nitride buffer layer grown at 600 deg. C. Core-level photoelectron spectroscopy of Si{sub x}N{sub y} layers reveals the sources for superior qualities of GaN epilayers grown with the high temperature substrate nitridation process. The discussion has been carried out on the typical inverted rectification behavior exhibited by n-GaN/p-Si heterojunctions. Considerable modulation in the transport mechanism was observed with the nitridation conditions. The heterojunction fabricated with the sample of substrate nitridation at high temperature exhibited superior rectifying nature with reduced trap concentrations. Lowest ideality factors ({approx}1.5) were observed in the heterojunctions grown with high temperature substrate nitridation which is attributed to the recombination tunneling at the space charge region transport mechanism at lower voltages and at higher voltages space charge limited current conduction is the dominating transport mechanism. Whereas, thermally generated carrier tunneling and recombination tunneling are the dominating transport mechanisms in the heterojunctions grown without substrate nitridation and low temperature substrate nitridation, respectively.« less

Silicon nitride films deposited with an electron beam created plasma

NASA Technical Reports Server (NTRS)

Bishop, D. C.; Emery, K. A.; Rocca, J. J.; Thompson, L. R.; Zamani, H.; Collins, G. J.

1984-01-01

The electron beam assisted chemical vapor deposition (EBCVD) of silicon nitride films using NH3, N2, and SiH4 as the reactant gases is reported. The films have been deposited on aluminum, SiO2, and polysilicon film substrates as well as on crystalline silicon substrates. The range of experimental conditions under which silicon nitrides have been deposited includes substrate temperatures from 50 to 400 C, electron beam currents of 2-40 mA, electron beam energies of 1-5 keV, total ambient pressures of 0.1-0.4 Torr, and NH3/SiH4 mass flow ratios of 1-80. The physical, electrical, and chemical properties of the EBCVD films are discussed.

Broadband wavelength conversion in hydrogenated amorphous silicon waveguide with silicon nitride layer

NASA Astrophysics Data System (ADS)

Wang, Jiang; Li, Yongfang; Wang, Zhaolu; Han, Jing; Huang, Nan; Liu, Hongjun

2018-01-01

Broadband wavelength conversion based on degenerate four-wave mixing is theoretically investigated in a hydrogenated amorphous silicon (a-Si:H) waveguide with silicon nitride inter-cladding layer (a-Si:HN). We have found that enhancement of the non-linear effect of a-Si:H waveguide nitride intermediate layer facilitates broadband wavelength conversion. Conversion bandwidth of 490 nm and conversion efficiency of 11.4 dB were achieved in a numerical simulation of a 4 mm-long a-Si:HN waveguide under 1.55 μm continuous wave pumping. This broadband continuous-wave wavelength converter has potential applications in photonic networks, a type of readily manufactured low-cost highly integrated optical circuits.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharlamov, Alexey; Bondarenko, Marina, E-mail: mebondarenko@ukr.net; Kharlamova, Ganna

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists ofmore » weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.« less

Photoluminescence of amorphous and crystalline silicon nanoclusters in silicon nitride and oxide superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shuleiko, D. V., E-mail: shuleyko.dmitriy@physics.msu.ru; Zabotnov, S. V.; Zhigunov, D. M.

2017-02-15

The photoluminescence properties of silicon nitride and oxide superlattices fabricated by plasmaenhanced chemical vapor deposition are studied. In the structures annealed at a temperature of 1150°C, photoluminescence peaks at about 1.45 eV are recorded. The peaks are defined by exciton recombination in silicon nanocrystals formed upon annealing. Along with the 1.45-eV peaks, a number of peaks defined by recombination at defects at the interface between the nanocrystals and silicon-nitride matrix are detected. The structures annealed at 900°C exhibit a number of photoluminescence peaks in the range 1.3–2.0 eV. These peaks are defined by both the recombination at defects and excitonmore » recombination in amorphous silicon nanoclusters formed at an annealing temperature of 900°C. The observed features of all of the photoluminescence spectra are confirmed by the nature of the photoluminescence kinetics.« less

Effects of varying oxygen partial pressure on molten silicon-ceramic substrate interactions

NASA Technical Reports Server (NTRS)

Ownby, D. P.; Barsoum, M. W.

1980-01-01

The silicon sessile drop contact angle was measured on hot pressed silicon nitride, silicon nitride coated on hot pressed silicon nitride, silicon carbon coated on graphite, and on Sialon to determine the degree to which silicon wets these substances. The post-sessile drop experiment samples were sectioned and photomicrographs were taken of the silicon-substrate interface to observe the degree of surface dissolution and degradation. Of these materials, silicon did not form a true sessile drop on the SiC on graphite due to infiltration of the silicon through the SiC coating, nor on the Sialon due to the formation of a more-or-less rigid coating on the liquid silicon. The most wetting was obtained on the coated Si3N4 with a value of 42 deg. The oxygen concentrations in a silicon ribbon furnace and in a sessile drop furnace were measured using the protable thoria-yttria solid solution electrolyte oxygen sensor. Oxygen partial pressures of 10 to the minus 7 power atm and 10 to the minus 8 power atm were obtained at the two facilities. These measurements are believed to represent nonequilibrium conditions.

Kinetic Control in the Cleavage of Unsymmetrical Disilanes.

PubMed

Hevesi, Làszlò; Dehon, Michael; Crutzen, Raphael; Lazarescu-Grigore, Adriana

1997-04-04

A series of 12 phenyl-substituted arylpentamethyldisilanes 1a-l have been synthesized in order to examine the regioselectivity of their nucleophilic Si,Si bond cleavage reactions under Still's conditions (MeLi/HMPA/0 degrees C). It has been found that the sensitivity of these reactions to the electronic effects of the substituents in the phenyl ring could be described by the Hammett-type equation log(k(A)/k(B)) = 0.4334 + 2.421(Sigmasigma); (correlation coefficient R = 0.983). The k(A)/k(B) ratio represents the relative rate of attack at silicon atom A (linked to the aryl ring) or at silicon atom B (away from the aryl ring) of the unsymmetrical disilanes. Thus, the present investigation shows that the earlier belief according to which the nucleophilic cleavage of unsymmetrical disilanes always produces the more stable silyl anionic species (thermodynamic control) should be abandoned, or at least seriously amended: kinetic factors appear to exert a primary influence on the regioselectivity of such reactions. Since the two major kinetic factors (i.e., electrophilic character of and steric hindrance at a given silicon atom) have opposite effects on the orientation of the reaction, it may happen that kinetic and thermodynamic control lead to the same result. For some of the unsymmetrical disilanes studied, the major reaction path was not the Si,Si bond cleavage; instead, Si-aryl bond breaking occurred, producing the corresponding aryl anions.

Process Development and Property Evaluation of Organosilicon Infiltrated Reaction Sintered Silicon Nitride (RSSN).

DTIC Science & Technology

1982-01-01

Battelle) (5) Prepolymer based on methyltrichlorosilane and ammonia (Battelle) (6) Polysilastyrene (Professor West, University of Wisconsin) (7...These types of materials are not commercially available, but are produced from commercial intermediates (methyldichlorosilane and ammonia ) and have been...methyltrichlorosilane and ammonia is a low melting, solid resin which has been shown to yield 72 percent residue by thermogravimetric analysis (TGA) in our work

Bolometric Array Detectors for Space-Borne Astronomy

NASA Technical Reports Server (NTRS)

Lange, Andrew E.

2000-01-01

Funding from the NASA Innovative Research Grant was used to develop bolometric detectors. As described in the proposal, silicon nitride micromesh ('spider-web') absorbers had been demonstrated at U.C. Berkeley but not developed to be flight-worthy devices. We proceeded to first fabricate bolometers with Neutron Transmutation Doped (NTD) Ge thermistors that demonstrated high optical coupling (Church et al. 1996) and were developed for a ground-based millimeter-wave receiver (Mauskopf et al. 1997). The next generation of devices used In bump-bonded thermistors to achieve devices with performance product NEP*sqrt(tau) = 3e - 18 j at 300 mK, demonstrating a full order of magnitude improvement over pervious devices. These devices achieved an NEP = 1e-18 W/rtHz (Murray et al. 1996) as promised in the proposal. Sensitivities as good as 1e - 19 W/rtHz appear achievable with the silicon nitride architecture (Bock et al. 1997). Finally, arrays of micromesh bolometers were shown to be feasible in the last year of the program by etching a large number of devices on a single silicon wafer (75 mm). Full arrays were subsequently demonstrated for selection on the ESA/NASA Far-Infrared Space Telescope (FIRST) in competition with detectors provided by CEA in France and GSFC in the US Micromesh bolometer arrays are now baselined for both the ESA/NASA Planck and FIRST missions.

Thermal oxidation and nitridation of Si nanowalls prepared by metal assisted chemical etching

NASA Astrophysics Data System (ADS)

Behera, Anil K.; Viswanath, R. N.; Lakshmanan, C.; Polaki, S. R.; Sarguna, R. M.; Mathews, Tom

2018-04-01

Silicon nanowalls with controlled orientation have been prepared using metal assisted chemical etching process. Thermal oxidation and nitridation processes have been carried out on the prepared silicon nanowalls under a control flow of oxygen/nitrogen gases independently at 1050°C for 900s. The morphology and structural properties of the as-prepared, oxidized and nitridated silicon nanowalls have been studied using the scanning electron microscopy and the Grazing incident X-ray diffraction techniques. The results obtained from the analysis of X-ray diffraction patterns and the microscopy images are discussed.

Fabrication of sinterable silicon nitride by injection molding

NASA Technical Reports Server (NTRS)

Quackenbush, C. L.; French, K.; Neil, J. T.

1982-01-01

Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

Processing study of injection molding of silicon nitride for engine applications

NASA Technical Reports Server (NTRS)

Rorabaugh, M. E.; Yeh, H. C.

1985-01-01

The high hardness of silicon nitride, which is currently under consideration as a structural material for such hot engine components as turbine blades, renders machining of the material prohibitively costly; the near net shape forming technique of injection molding is accordingly favored as a means for component fabrication. Attention is presently given to the relationships between injection molding processing parameters and the resulting microstructural and mechanical properties of the resulting engine parts. An experimental program has been conducted under NASA sponsorship which tests the quality of injection molded bars of silicon nitride at various stages of processing.

Microstructure and Mechanical Properties of Reaction-Formed Silicon Carbide (RFSC) Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.; Behrendt, D. R.

1994-01-01

The microstructure and mechanical properties of reaction-formed silicon carbide (RFSC) ceramics fabricated by silicon infiltration of porous carbon preforms are discussed. The morphological characterization of the carbon preforms indicates a very narrow pore size distribution. Measurements of the preform density by physical methods and by mercury porosimetry agree very well and indicate that virtually all of the porosity in the preforms is open to infiltrating liquids. The average room temperature flexural strength of the RFSC material with approximately 8 at.% free silicon is 369 +/- 28 MPa (53.5 +/- 4 ksi). The Weibull strength distribution data give a characteristic strength value of 381 MPa (55 ksi) and a Weibull modulus of 14.3. The residual silicon content is lower and the strengths are superior to those of most commercially available reaction-bonded silicon carbide materials.

Multibit Polycristalline Silicon-Oxide-Silicon Nitride-Oxide-Silicon Memory Cells with High Density Designed Utilizing a Separated Control Gate

NASA Astrophysics Data System (ADS)

Rok Kim, Kyeong; You, Joo Hyung; Dal Kwack, Kae; Kim, Tae Whan

2010-10-01

Unique multibit NAND polycrystalline silicon-oxide-silicon nitride-oxide-silicon (SONOS) memory cells utilizing a separated control gate (SCG) were designed to increase memory density. The proposed NAND SONOS memory device based on a SCG structure was operated as two bits, resulting in an increase in the storage density of the NVM devices in comparison with conventional single-bit memories. The electrical properties of the SONOS memory cells with a SCG were investigated to clarify the charging effects in the SONOS memory cells. When the program voltage was supplied to each gate of the NAND SONOS flash memory cells, the electrons were trapped in the nitride region of the oxide-nitride-oxide layer under the gate to supply the program voltage. The electrons were accumulated without affecting the other gate during the programming operation, indicating the absence of cross-talk between two trap charge regions. It is expected that the inference effect will be suppressed by the lower program voltage than the program voltage of the conventional NAND flash memory. The simulation results indicate that the proposed unique NAND SONOS memory cells with a SCG can be used to increase memory density.

Fabrication of Robust, Flat, Thinned, UV-Imaging CCDs

NASA Technical Reports Server (NTRS)

Grunthaner, Paula; Elliott, Stythe; Jones, Todd; Nikzad, Shouleh

2004-01-01

An improved process that includes a high-temperature bonding subprocess has been developed to enable the fabrication of robust, flat, silicon-based charge-coupled devices (CCDs) for imaging in ultraviolet (UV) light and/or for detecting low-energy charged particles. The CCDs in question are devices on which CCD circuitry has already been formed and have been thinned for backsurface illumination. These CCDs may be delta doped, and aspects of this type of CCD have been described in several prior articles in NASA Tech Briefs. Unlike prior low-temperature bonding subprocesses based on the use of epoxies or waxes, the high-temperature bonding subprocess is compatible with the deltadoping process as well as with other CCD-fabrication processes. The present improved process and its bonding, thinning, and delta-doping subprocesses, are characterized as postfabrication processes because they are undertaken after the fabrication of CCD circuitry on the front side of a full-thickness silicon substrate. In a typical case, it is necessary to reduce the thickness of the CCD to between 10 and 20 m in order to take advantage of back-side illumination and in order to perform delta doping and/or other back-side treatment to enhance the quantum efficiency. In the prior approach to the fabrication of back-side-illuminated CCDs, the thinning subprocess turned each CCD into a free-standing membrane that was fragile and tended to become wrinkled. In the present improved process, prior to thinning and delta doping, a CCD is bonded on its front side to a silicon substrate that has been prefabricated to include cutouts to accommodate subsequent electrical connections to bonding pads on the CCD circuitry. The substrate provides structural support to increase ruggedness and maintain flatness. At the beginning of this process, the back side of a CCD as fabricated on a full-thickness substrate is polished. Silicon nitride is deposited on the back side, opposite the bonding pads on the front side, in order to define a relatively thick frame. The portion of the CCD not covered by the frame is the portion to be thinned by etching.

Method of high purity silane preparation

DOEpatents

Tsuo, Y. Simon; Belov, Eugene P.; Gerlivanov, Vadim G.; Zadde, Vitali V.; Kleschevnikova, Solomonida I.; Korneev, Nikolai N.; Lebedev, Eugene N.; Pinov, Akhsarbek B.; Ryabenko, Eugene A.; Strebkov, Dmitry S.; Chernyshev, Eugene A.

2000-01-01

A process for the preparation of high purity silane, suitable for forming thin layer silicon structures in various semiconductor devices and high purity poly- and single crystal silicon for a variety of applications, is provided. Synthesis of high-purity silane starts with a temperature assisted reaction of metallurgical silicon with alcohol in the presence of a catalyst. Alcoxysilanes formed in the silicon-alcohol reaction are separated from other products and purified. Simultaneous reduction and oxidation of alcoxysilanes produces gaseous silane and liquid secondary products, including, active part of a catalyst, tetra-alcoxysilanes, and impurity compounds having silicon-hydrogen bonds. Silane is purified by an impurity adsorption technique. Unreacted alcohol is extracted and returned to the reaction with silicon. Concentrated mixture of alcoxysilanes undergoes simultaneous oxidation and reduction in the presence of a catalyst at the temperature -20.degree. C. to +40.degree. C. during 1 to 50 hours. Tetra-alcoxysilane extracted from liquid products of simultaneous oxidation and reduction reaction is directed to a complete hydrolysis. Complete hydrolysis of tetra-alcoxysilane results in formation of industrial silica sol and alcohol. Alcohol is dehydrated by tetra-alcoxysilane and returned to the reaction with silicon.

Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides.

PubMed

Ikeda, Kazuhiro; Saperstein, Robert E; Alic, Nikola; Fainman, Yeshaiahu

2008-08-18

We introduce and present experimental evaluations of loss and nonlinear optical response in a waveguide and an optical resonator, both implemented with a silicon nitride/ silicon dioxide material platform prepared by plasma-enhanced chemical vapor deposition with dual frequency reactors that significantly reduce the stress and the consequent loss of the devices. We measure a relatively small loss of approximately 4dB/cm in the waveguides. The fabricated ring resonators in add-drop and all-pass arrangements demonstrate quality factors of Q=12,900 and 35,600. The resonators are used to measure both the thermal and ultrafast Kerr nonlinearities. The measured thermal nonlinearity is larger than expected, which is attributed to slower heat dissipation in the plasma-deposited silicon dioxide film. The n2 for silicon nitride that is unknown in the literature is measured, for the first time, as 2.4 x 10(-15)cm(2)/W, which is 10 times larger than that for silicon dioxide.

Modification of silicon nitride surfaces with GOPES and APTES for antibody immobilization: computational and experimental studies

NASA Astrophysics Data System (ADS)

Dien To, Thien; Nguyen, Anh Tuan; Nhat Thanh Phan, Khoa; Thu Thi Truong, An; Doan, Tin Chanh Duc; Mau Dang, Chien

2015-12-01

Chemical modification of silicon nitride (SiN) surfaces by silanization has been widely studied especially with 3-(aminopropyl)triethoxysilane (APTES) and 3-(glycidyloxypropyl) dimethylethoxysilane (GOPES). However few reports performed the experimental and computational studies together. In this study, surface modification of SiN surfaces with GOPES and APTES covalently bound with glutaraldehyde (GTA) was investigated for antibody immobilization. The monoclonal anti-cytokeratin-FITC (MACF) antibody was immobilized on the modified SiN surfaces. The modified surfaces were characterized by water contact angle measurements, atomic force microscopy and fluorescence microscopy. The FITC-fluorescent label indicated the existence of MACF antibody on the SiN surfaces and the efficiency of the silanization reaction. Absorption of APTES and GOPES on the oxidized SiN surfaces was computationally modeled and calculated by Materials Studio software. The computational and experimental results showed that modification of the SiN surfaces with APTES and GTA was more effective than the modification with GOPES.

Helium ion beam induced electron emission from insulating silicon nitride films under charging conditions

NASA Astrophysics Data System (ADS)

Petrov, Yu. V.; Anikeva, A. E.; Vyvenko, O. F.

2018-06-01

Secondary electron emission from thin silicon nitride films of different thicknesses on silicon excited by helium ions with energies from 15 to 35 keV was investigated in the helium ion microscope. Secondary electron yield measured with Everhart-Thornley detector decreased with the irradiation time because of the charging of insulating films tending to zero or reaching a non-zero value for relatively thick or thin films, respectively. The finiteness of secondary electron yield value, which was found to be proportional to electronic energy losses of the helium ion in silicon substrate, can be explained by the electron emission excited from the substrate by the helium ions. The method of measurement of secondary electron energy distribution from insulators was suggested, and secondary electron energy distribution from silicon nitride was obtained.

New Approaches to the Synthesis of Novel Organosilanes.

DTIC Science & Technology

1983-10-01

through" electrode composed of RVC ( reticulated vitreous carbon ), a highly conductive sponge of carbonized material. Both of these flow systems...effective in promoting silicon- carbon bond cleavage and reformation to give cyclic and cage compounds readily and in good yields: (tA*3-9)(CŖ). n 2-S...silicon to carbon bonds and has broad based applications in research and industrial labs. The increase in reaction rate and yield with ultrasonic waves

Surface modification of titanium nitride film by a picosecond Nd:YAG laser

NASA Astrophysics Data System (ADS)

Gakovic, B.; Trtica, M.; Batani, D.; Desai, T.; Panjan, P.; Vasiljevic-Radovic, D.

2007-06-01

The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a polycrystalline titanium nitride (TiN) film was studied. The TiN thin film was deposited by physical vapour deposition on a silicon substrate. The titanium nitride/silicon system was modified with an energy fluence from 0.2 to 5.9 J cm-2. Multi-pulse irradiation was performed in air by a focused laser beam. Surface modifications were analysed after 1 100 successive laser pulses. Depending on the laser pulse energy and pulse count, the following phenomena were observed: (i) increased surface roughness, (ii) titanium nitride film cracking, (iii) silicon substrate modification, (iv) film exfoliation and (v) laser-induced periodical surface structures on nano- (NPSS) and micro-dimensions (MPSS).

Surface characterization of polydimethylsiloxane treated pharmaceutical glass containers by X-ray-excited photo- and Auger electron spectroscopy.

PubMed

Mundry, T; Surmann, P; Schurreit, T

2000-12-01

The siliconization of pharmaceutical glass containers is an industrially frequently applied procedure. It is done by spreading an aqueous silicone oil emulsion film on the inner surface and successive heat curing treatment at temperatures above 300 degrees C for 10-30 min. It was often proposed that a covalent bonding of PDMS to the glass or branching of the linear PDMS occurs during heat treatment. The present study was performed for a detailed investigation of the glass and silicone (polydimethylsiloxane = PDMS) chemical state before and after heat-curing treatment and analysis of the bond nature. Combined X-ray excited photoelectron (XPS) and Auger electron spectroscopy as well as angle resolved XPS-measurements were used for analysis of the glass samples. The silicon surface atoms of the borosilicate container glass were transformed to a quartz-like compound whereas the former linear PDMS had a branched, two-dimensional structure after the heat curing treatment. It was concluded that the branching indicates the formation of new siloxane bonds to the glass surface via hydroxyl groups. Further evidence for the presence of bonded PDMS at the glass surface can be found in the valence band spectra of the siliconized and untreated samples. However, this bond could not be detected directly due to its very similar nature to the siloxane bonds of the glass matrix and the organosilicon backbone of PDMS. Due to the high variation of data from the siliconized samples it was concluded, that the silicone film is not homogeneous. Previously raised theories of reactions during heat-curing glass siliconization are supported by the XPS data of this investigation. Yet, the postulation of fixing or baking the silicone on the glass surface is only partially true since the bonded layer is very thin and most of the silicone originally on the surface after heat curing can be removed by suitable solvents. This fraction can therefore still interact with drug products being in contact to the siliconized container wall.

Efficient nitrogen incorporation in GaAs using novel metal organic As-N precursor di-tertiary-butyl-arsano-amine (DTBAA)

NASA Astrophysics Data System (ADS)

Sterzer, E.; Beyer, A.; Duschek, L.; Nattermann, L.; Ringler, B.; Leube, B.; Stegmüller, A.; Tonner, R.; von Hänisch, C.; Stolz, W.; Volz, K.

2016-04-01

III/V semiconductors containing small amounts of nitrogen (N; dilute nitrides) are discussed in the context of different solar cell and laser applications. The efficiency of these devices is negatively affected by carbon (C) incorporation, which comes either from the direct C-N bond in the N precursor unsymmetrical 1,1-dimethylhydrazine (UDMHy) used conventionally or from the alkyl groups of the conventional precursors for gallium (Ga), indium and arsenic (As) containing carbon. This C is incorporated together with the N due to the strength of the C-N bond. A further important issue in dilute nitride growth is the very low N incorporation efficiency in the crystal from UDMHy, which can be as little as 1% of the N supplied in the gas phase. Therefore, new metal organic chemicals have to be synthesized and their growth characteristics and suitability for dilute nitride growth have to be explored. This work presents the chemical di-tertiary-butyl-arsano-amine (DTBAA), which was synthesized, purified and tested as an N precursor for metal organic vapor phase epitaxy (MOVPE). Computational investigations show β-hydrogen and isobutane elimination to be the main reaction channel in the gas phase with high reaction barriers and absence of small fragments containing C as products. The loss of N via N2, as in UDMHy, can be excluded for unimolecular reactions of DTBAA. The Ga(NAs)/GaAs heterostructures were grown by MOVPE as initial test material and a systematic N incorporation study is presented in this paper. It is shown that high quality Ga(NAs) can be grown using DTBAA. The N incorporation was confirmed by high resolution X-ray diffraction and photoluminescence studies. All samples grown exhibit as grown room temperature photoluminescence and smooth surface morphologies. Furthermore, DTBAA shows extremely high N incorporation efficiency, which makes this molecule a very promising candidate for further research into dilute nitride material growth.

Environmental Barrier Coatings for Silicon-Based Ceramics

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Fox, Dennis S.; Robinson, Raymond C.; Bansal, Narottam P.

2001-01-01

Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based ceramics, however, suffer from rapid surface recession in combustion environments due to volatilization of the silica scale via reaction with water vapor, a major product of combustion. Therefore, application of silicon-based ceramic components in the hot section of advanced gas turbine engines requires development of a reliable method to protect the ceramic from environmental attack. An external environmental barrier coating (EBC) is considered a logical approach to achieve protection and CP long-term stability. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 Wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program (5). They consist of three layers, a silicon first bond coat, a mullite or a mullite + BSAS (BaO(1-x)-SrO(x)-Al2O3-2SiO2) second bond coat, and a BSAS top coat. The EPM EBCs were applied on SiC/SiC CMC combustor liners in three Solar Turbines (San Diego, CA) Centaur 50s gas turbine engines. The combined operation of the three engines has accumulated over 24,000 hours without failure (approximately 1,250 C maximum combustor liner temperature), with the engine in Texaco, Bakersfield, CA, accumulating about 14,000 hours. As the commercialization of Si-based ceramic components in gas turbines is on the horizon, a major emphasis is placed on EBCs for two reasons. First, they are absolute necessity for the protection of Si-based ceramics from water vapor. Second, they can enable a major enhancement in the performance of gas turbines by creating temperature gradients with the incorporation of a low thermal conductivity layer. Thorough understanding of current state-of-the-art EBCs will provide the foundation upon which development of future EBCs will be based. Phase stability and thermal conductivity of EPM EBCs are published elsewhere. This paper will discuss the chemical/environmental durability and silica volatility of EPM EBCs and their impact on the coating's upper temperature limit.

Improved growth of GaN layers on ultra thin silicon nitride/Si (1 1 1) by RF-MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Mahesh; Roul, Basanta; Central Research Laboratory, Bharat Electronics, Bangalore 560013

High-quality GaN epilayers were grown on Si (1 1 1) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation at high temperatures, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. The material quality of the GaN films was also investigated as a function of nitridation time and temperature. Crystallinity and surface roughness of GaN was found to improve when the Si substrate was treated under the new growth process sequence. Micro-Raman and photoluminescence (PL) measurement results indicate that the GaN filmmore » grown by the new process sequence has less tensile stress and optically good. The surface and interface structures of an ultra thin silicon nitride film grown on the Si surface are investigated by core-level photoelectron spectroscopy and it clearly indicates that the quality of silicon nitride notably affects the properties of GaN growth.« less

Monolithic microcircuit techniques and processes

NASA Technical Reports Server (NTRS)

Kennedy, B. W.

1972-01-01

Brief discussions of the techniques used to make dielectric and metal thin film depositions for monolithic circuits are presented. Silicon nitride deposition and the properties of silicon nitride films are discussed. Deposition of dichlorosilane and thermally grown silicon dioxide are reported. The deposition and thermal densification of borosilicate, aluminosilicate, and phosphosilicate glasses are discussed. Metallization for monolithic circuits and the characteristics of thin films are also included.

Hafnium nitride buffer layers for growth of GaN on silicon

DOEpatents

Armitage, Robert D.; Weber, Eicke R.

2005-08-16

Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

Sintering silicon nitride

NASA Technical Reports Server (NTRS)

Bansal, Narottam P. (Inventor); Levine, Stanley R. (Inventor); Sanders, William A. (Inventor)

1993-01-01

Oxides having a composition of (Ba(1-x)Sr(x))O-Al2O3-2SiO2 are used as sintering aids for producing an improved silicon nitride ceramic material. The x must be greater than 0 to insure the formation of the stable monoclinic celsian glass phase.

Silicon nitride ceramic development in Thales Alenia Space : qualification achievement and further developments for future applications

NASA Astrophysics Data System (ADS)

Cornillon, L.; Devilliers, C.; Behar-Lafenetre, S.; Ait-Zaid, S.; Berroth, K.; Bravo, A. C.

2017-11-01

Dealing with ceramic materials for more than two decades, Thales Alenia Space - France has identified Silicon Nitride Si3N4 as a high potential material for the manufacturing of stiff, stable and lightweight truss structure for future large telescopes. Indeed, for earth observation or astronomic observation, space mission requires more and more telescopes with high spatial resolution, which leads to the use of large primary mirrors, and a long distance between primary and secondary mirrors. Therefore current and future large space telescopes require a huge truss structure to hold and locate precisely the mirrors. Such large structure requires very strong materials with high specific stiffness and a low coefficient of thermal expansion (CTE). Based on the silicon nitride performances and on the know how of FCT Ingenieurkeramik to manufacture complex parts, Thales Alenia Space (TAS) has engaged, in cooperation with FCT, activities to develop and qualify silicon nitride parts for other applications for space projects.

Silicon nitride ceramic development in Thales Alenia Space: qualification achiement and further developments for future applications

NASA Astrophysics Data System (ADS)

Cornillon, L.; Devilliers, C.; Behar-Lafenetre, S.; Ait-Zaid, S.; Berroth, K.; Bravo, A. C.

2017-11-01

Dealing with ceramic materials for more than two decades, Thales Alenia Space - France has identified Silicon Nitride Si3N4 as a high potential material for the manufacturing of stiff, stable and lightweight truss structure for future large telescopes. Indeed, for earth observation or astronomic observation, space mission requires more and more telescopes with high spatial resolution, which leads to the use of large primary mirrors, and a long distance between primary and secondary mirrors. Therefore current and future large space telescopes require a huge truss structure to hold and locate precisely the mirrors. Such large structure requires very strong materials with high specific stiffness and a low coefficient of thermal expansion (CTE). Based on the silicon nitride performances and on the know how of FCT Ingenieurkeramik to manufacture complex parts, Thales Alenia Space (TAS) has engaged, in cooperation with FCT, activities to develop and qualify silicon nitride parts for other applications for space projects.

Powder Injection Molding of Ceramic Engine Components for Transportation

NASA Astrophysics Data System (ADS)

Lenz, Juergen; Enneti, Ravi K.; Onbattuvelli, Valmikanathan; Kate, Kunal; Martin, Renee; Atre, Sundar

2012-03-01

Silicon nitride has been the favored material for manufacturing high-efficiency engine components for transportation due to its high temperature stability, good wear resistance, excellent corrosion resistance, thermal shock resistance, and low density. The use of silicon nitride in engine components greatly depends on the ability to fabricate near net-shape components economically. The absence of a material database for design and simulation has further restricted the engineering community in developing parts from silicon nitride. In this paper, the design and manufacturability of silicon nitride engine rotors for unmanned aerial vehicles by the injection molding process are discussed. The feedstock material property data obtained from experiments were used to simulate the flow of the material during injection molding. The areas susceptible to the formation of defects during the injection molding process of the engine component were identified from the simulations. A test sample was successfully injection molded using the feedstock and sintered to 99% density without formation of significant observable defects.

Demonstration of slot-waveguide structures on silicon nitride / silicon oxide platform.

PubMed

Barrios, C A; Sánchez, B; Gylfason, K B; Griol, A; Sohlström, H; Holgado, M; Casquel, R

2007-05-28

We report on the first demonstration of guiding light in vertical slot-waveguides on silicon nitride/silicon oxide material system. Integrated ring resonators and Fabry-Perot cavities have been fabricated and characterized in order to determine optical features of the slot-waveguides. Group index behavior evidences guiding and confinement in the low-index slot region at O-band (1260-1370nm) telecommunication wavelengths. Propagation losses of <20 dB/cm have been measured for the transverse-electric mode of the slot-waveguides.

Corrosion Characteristics of Silicon Carbide and Silicon Nitride

PubMed Central

Munro, R. G.; Dapkunas, S. J.

1993-01-01

The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000 °C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags. PMID:28053489

Nanotribological performance of fullerene-like carbon nitride films

NASA Astrophysics Data System (ADS)

Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan; Chiñas-Castillo, Fernando; Espinoza-Beltrán, Francisco Javier

2014-09-01

Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ∼ 0.009-0.022) that is lower than amorphous CNx films (CoF ∼ 0.028-0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp3 CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery.

Ceramic Composite Intermediate Temperature Stress-Rupture Properties Improved Significantly

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Hurst, Janet B.

2002-01-01

Silicon carbide (SiC) composites are considered to be potential materials for future aircraft engine parts such as combustor liners. It is envisioned that on the hot side (inner surface) of the combustor liner, composites will have to withstand temperatures in excess of 1200 C for thousands of hours in oxidizing environments. This is a severe condition; however, an equally severe, if not more detrimental, condition exists on the cold side (outer surface) of the combustor liner. Here, the temperatures are expected to be on the order of 800 to 1000 C under high tensile stress because of thermal gradients and attachment of the combustor liner to the engine frame (the hot side will be under compressive stress, a less severe stress-state for ceramics). Since these composites are not oxides, they oxidize. The worst form of oxidation for strength reduction occurs at these intermediate temperatures, where the boron nitride (BN) interphase oxidizes first, which causes the formation of a glass layer that strongly bonds the fibers to the matrix. When the fibers strongly bond to the matrix or to one another, the composite loses toughness and strength and becomes brittle. To increase the intermediate temperature stress-rupture properties, researchers must modify the BN interphase. With the support of the Ultra-Efficient Engine Technology (UEET) Program, significant improvements were made as state-of-the-art SiC/SiC composites were developed during the Enabling Propulsion Materials (EPM) program. Three approaches were found to improve the intermediate-temperature stress-rupture properties: fiber-spreading, high-temperature silicon- (Si) doped boron nitride (BN), and outside-debonding BN.

Deposition of reactively ion beam sputtered silicon nitride coatings

NASA Technical Reports Server (NTRS)

Grill, A.

1982-01-01

An ion beam source was used to deposit silicon nitride films by reactively sputtering a silicon target with beams of Ar + N2 mixtures. The nitrogen fraction in the sputtering gas was 0.05 to 0.80 at a total pressure of 6 to 2 millionth torr. The ion beam current was 50 mA at 500 V. The composition of the deposited films was investigated by auger electron spectroscopy and the rate of deposition was determined by interferometry. A relatively low rate of deposition of about 2 nm. one-tenth min. was found. AES spectra of films obtained with nitrogen fractions higher than 0.50 were consistent with a silicon to nitrogen ratio corresponding to Si3N4. However the AES spectra also indicated that the sputtered silicon nitride films were contaminated with oxygen and carbon and contained significant amounts of iron, nickel, and chromium, most probably sputtered from the holder of the substrate and target.

Reactions of Hydrogen Chloride and Boron Trichloride with Trimethylsilylamino Groups

DTIC Science & Technology

1989-04-04

SUPPLEMENTARY NOTATION 17, COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and kientify by block number) FIELD ,,GROUP SU8 -GROUP...nitride preceramic polymers . Due to the low yield multistage synthesis, alternate routes to isomeric compositions and intermediates needed to be...Organo- metallic Polymers , Zeldin, M., Wynne, K. J., Allcock, H. R.; Ed, ACS Symposium Series 360. (4) Ebsworth, E.A.V. Volatile Silicon Compounds

Surface-Micromachined Microfluidic Devices

DOEpatents

Galambos, Paul C.; Okandan, Murat; Montague, Stephen; Smith, James H.; Paul, Phillip H.; Krygowski, Thomas W.; Allen, James J.; Nichols, Christopher A.; Jakubczak, II, Jerome F.

2004-09-28

Microfluidic devices are disclosed which can be manufactured using surface-micromachining. These devices utilize an electroosmotic force or an electromagnetic field to generate a flow of a fluid in a microchannel that is lined, at least in part, with silicon nitride. Additional electrodes can be provided within or about the microchannel for separating particular constituents in the fluid during the flow based on charge state or magnetic moment. The fluid can also be pressurized in the channel. The present invention has many different applications including electrokinetic pumping, chemical and biochemical analysis (e.g. based on electrophoresis or chromatography), conducting chemical reactions on a microscopic scale, and forming hydraulic actuators. Microfluidic devices are disclosed which can be manufactured using surface-micromachining. These devices utilize an electroosmotic force or an electromagnetic field to generate a flow of a fluid in a microchannel that is lined, at least in part, with silicon nitride. Additional electrodes can be provided within or about the microchannel for separating particular constituents in the fluid during the flow based on charge state or magnetic moment. The fluid can also be pressurized in the channel. The present invention has many different applications including electrokinetic pumping, chemical and biochemical analysis (e.g. based on electrophoresis or chromatography), conducting chemical reactions on a microscopic scale, and forming hydraulic actuators.

Silicon nitride having a high tensile strength

DOEpatents

Pujari, Vimal K.; Tracey, Dennis M.; Foley, Michael R.; Paille, Norman I.; Pelletier, Paul J.; Sales, Lenny C.; Willkens, Craig A.; Yeckley, Russell L.

1996-01-01

A silicon nitride ceramic comprising: a) inclusions no greater than 25 microns in length, b) agglomerates no greater than 20 microns in diameter, and c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa.

Hydrogenated amorphous silicon formation by flux control and hydrogen effects on the growth mechanism

NASA Astrophysics Data System (ADS)

Toyoda, H.; Sugai, H.; Kato, K.; Yoshida, A.; Okuda, T.

1986-06-01

The composition of particle flux to deposit hydrogenated amorphous silicon films in a glow discharge is controlled by a combined electrostatic-magnetic deflection technique. As a result, the films are formed firstly without hydrogen ion flux, secondly by neutral flux only, and thirdly by all species fluxes. Comparison of these films reveals the significant role of hydrogen in the surface reactions. Hydrogen breaks the Si-Si bond, decreases the sticking probability of the Si atom, and replaces the SiH bond by a SiH2 bond to increase the hydrogen content of the films.

Covalently Bound Monomolecular Layers on Si Single Crystals

NASA Astrophysics Data System (ADS)

Chidsey, Christopher E. D.

1996-03-01

Methods and reagents borrowed from the molecular synthetic chemistry of silicon compounds have been used to form covalently bound monomolecular layers on silicon single crystals. Organic monolayers bound covalently to silicon could form the basis for silicon/organic interfaces useful in sensor structures. In a representative reaction, alkyl monolayers with densities approaching that of crystalline polyethylene have been prepared by the radical-initiated insertion of 1-alkenes into the Si-H bonds of hydrogen-terminated Si(111) surfaces footnote M. R. Linford, P. Fenter, P. M. Eisenberger and C. E. D Chidsey, J. Am. Chem. Soc. 117, 3145-3155 (1995). It has recently been found that this insertion reaction can also be initiated by illumination with UV light having sufficient energy to break the Si-H bond. Synchrotron-based high-resolution photoelectron spectroscopy and diffraction have demonstrated the expected Si-C bond in such monolayers footnote J. H. Terry, R. Cao, P. A. Pianetta, M. R. Linford and C. E. D. Chidsey, unpublished results. An alternate approach to similar monolayers has been found to be the chlorination of hydrogen-terminated Si(111) with Cl_2, followed by the nucleophilic displacement of chlorine with alkyl lithium reagents. The well-behaved chemical transformations of the hydrogen-terminated silicon surfaces appear to result from the essentially bulk termination of the silicon lattice with closed-shell silicon hydride "functional groups" on the surface. In addition to the formation of novel organic layers, a full understanding of the reactivity of the hydrogen-terminated silicon surfaces should lead to better control of key technological silicon interfaces such as Si/SiO_2, Si/epi-Si, and Si/metal.

Dry Lubrication of High Temperature Silicon Nitride Rolling Contacts.

DTIC Science & Technology

1980-11-01

comparable to M50 bearing steel [2]. Quality control measures were implemented in the areas of raw material inspection as well as non-destructive evaluation...to oil lubricated bearing steels . Due to the apparent success of graphite at high tem- perature, three vendors were selected that manufacture graph...hybrid bearings ( steel rings and silicon nitride balls) to establish solid lubricant/cage design practices. High temperature bearing tests with silicon

Silicon Nitride Equation of State

NASA Astrophysics Data System (ADS)

Swaminathan, Pazhayannur; Brown, Robert

2015-06-01

This report presents the development a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4) . Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonalβ-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products and then combined with the single component solid models to study the global phase diagram. Sponsored by the NASA Goddard Space Flight Center Living With a Star program office.

Silicon nitride having a high tensile strength

DOEpatents

Pujari, V.K.; Tracey, D.M.; Foley, M.R.; Paille, N.I.; Pelletier, P.J.; Sales, L.C.; Willkens, C.A.; Yeckley, R.L.

1996-11-05

A silicon nitride ceramic is disclosed comprising: (a) inclusions no greater than 25 microns in length, (b) agglomerates no greater than 20 microns in diameter, and (c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa. 4 figs.

Method and apparatus for forming conformal SiN.sub.x films

DOEpatents

Wang, Qi

2007-11-27

A silicon nitride film formation method includes: Heating a substrate to be subjected to film formation to a substrate temperature; heating a wire to a wire temperature; supplying silane, ammonia, and hydrogen gases to the heating member; and forming a silicon nitride film on the substrate.

Experimental study of three-dimensional fin-channel charge trapping flash memories with titanium nitride and polycrystalline silicon gates

NASA Astrophysics Data System (ADS)

Liu, Yongxun; Matsukawa, Takashi; Endo, Kazuhiko; O'uchi, Shinichi; Tsukada, Junichi; Yamauchi, Hiromi; Ishikawa, Yuki; Mizubayashi, Wataru; Morita, Yukinori; Migita, Shinji; Ota, Hiroyuki; Masahara, Meishoku

2014-01-01

Three-dimensional (3D) fin-channel charge trapping (CT) flash memories with different gate materials of physical-vapor-deposited (PVD) titanium nitride (TiN) and n+-polycrystalline silicon (poly-Si) have successfully been fabricated by using (100)-oriented silicon-on-insulator (SOI) wafers and orientation-dependent wet etching. Electrical characteristics of the fabricated flash memories including statistical threshold voltage (Vt) variability, endurance, and data retention have been comparatively investigated. It was experimentally found that a larger memory window and a deeper erase are obtained in PVD-TiN-gated metal-oxide-nitride-oxide-silicon (MONOS)-type flash memories than in poly-Si-gated poly-Si-oxide-nitride-oxide-silicon (SONOS)-type memories. The larger memory window and deeper erase of MONOS-type flash memories are contributed by the higher work function of the PVD-TiN metal gate than of the n+-poly-Si gate, which is effective for suppressing electron back tunneling during erase operation. It was also found that the initial Vt roll-off due to the short-channel effect (SCE) is directly related to the memory window roll-off when the gate length (Lg) is scaled down to 46 nm or less.

Predicting the structural and electronic properties of two-dimensional single layer boron nitride sheets

NASA Astrophysics Data System (ADS)

Li, Xiao-Dong; Cheng, Xin-Lu

2018-02-01

Three two-dimensional (2D) single layer boron nitride sheets have been predicted based on the first-principles calculations. These 2D boron nitride sheets are comprised of equivalent boron atoms and nitride atoms with sp2 and sp bond hybridization. The geometry optimization reflects that they all possess stable planar crystal structures with the space group P 6 bar 2 m (D3h3) symmetry. The charge density distribution manifests that the B-N bonds in these boron nitride sheets are covalent in nature but with ionic characteristics. The tunable band gaps indicate their potential applications in nanoscale electronic and optoelectronic devices by changing the length of sp-bonded Bsbnd N linkages.

Improved toughness of refractory compounds. [with elimination of the grain boundary phase

NASA Technical Reports Server (NTRS)

Wright, T. R.; Niesz, D. E.

1974-01-01

The concept of grain-boundary-engineering through elimination of the grain-boundary silicate phase in silicon nitride was developed. The process involved removal of the silica from the nitride powder via a thermal treatment coupled with the use of nitride additives to compensate the remaining oxygen. Magnesium and aluminum nitrides are found to be the most effective additive for use as oxygen compensators. Strength decreases at elevated temperatures are not observed in the alumina containing material. The creep rate of a dual additive sialon composition was two orders of magnitude lower at 1400 C than commercial silicon nitride. A cursory analysis of the creep mechanism indicate that grain-boundary sliding is avoided through elimination of the grain-boundary silicate phase.

Enhanced Electroluminescence from Silicon Quantum Dots Embedded in Silicon Nitride Thin Films Coupled with Gold Nanoparticles in Light Emitting Devices

PubMed Central

Muñoz-Rosas, Ana Luz; Alonso-Huitrón, Juan Carlos

2018-01-01

Nowadays, the use of plasmonic metal layers to improve the photonic emission characteristics of several semiconductor quantum dots is a booming tool. In this work, we report the use of silicon quantum dots (SiQDs) embedded in a silicon nitride thin film coupled with an ultra-thin gold film (AuNPs) to fabricate light emitting devices. We used the remote plasma enhanced chemical vapor deposition technique (RPECVD) in order to grow two types of silicon nitride thin films. One with an almost stoichiometric composition, acting as non-radiative spacer; the other one, with a silicon excess in its chemical composition, which causes the formation of silicon quantum dots imbibed in the silicon nitride thin film. The ultra-thin gold film was deposited by the direct current (DC)-sputtering technique, and an aluminum doped zinc oxide thin film (AZO) which was deposited by means of ultrasonic spray pyrolysis, plays the role of the ohmic metal-like electrode. We found that there is a maximum electroluminescence (EL) enhancement when the appropriate AuNPs-spacer-SiQDs configuration is used. This EL is achieved at a moderate turn-on voltage of 11 V, and the EL enhancement is around four times bigger than the photoluminescence (PL) enhancement of the same AuNPs-spacer-SiQDs configuration. From our experimental results, we surmise that EL enhancement may indeed be due to a plasmonic coupling. This kind of silicon-based LEDs has the potential for technology transfer. PMID:29565267

Chemical Stability of the Fiber Coating/Matrix Interface in Silicon-Based Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Jacobson, Nathan S.

1995-01-01

Carbon and boron nitride are used as fiber coatings in silicon-based composites. In order to assess the long-term stability of these materials, reactions of carbon/Si3N4 and BN/SiC were studied at high temperatures with Knudsen effusion, coupon tests, and microstructural examination. In the carbon/Si3N4 system, carbon reacted with Si3N4 to form gaseous N2 and SiC. The formation of SiC limited further reaction by physically separating the carbon and Si3N4. Consequently, the development of high p(N2) at the interface, predicted from thermochemical calculations, did not occur, thus limiting the potential deleterious effects of the reaction on the composite. Strong indications of a reaction between BN and SiC were shown by TEM and SIMS analysis of the BN/SiC interface. In long-term exposures, this reaction can lead to a depletion of a BN coating and/or an unfavorable change of the interfacial properties, limiting the beneficial effects of the coating.

Research and Development for Continued Performance Improvement in Flexible a-Si PV

DTIC Science & Technology

2010-12-14

accomplished, however, at low temperatures silicides tend to form on the surface of the filament, which affected filament lifetime and deposition rate...considered. Titanium Nitride, sputtered As an alternative to the hot wire deposition of silicon, samples were prepared with various thicknesses of...Silicon 21 Insitu DC Sputtering Titanium Nitride 22 Metal Machine 2 ឈ> RF Oxygen Plasma Silicon Dioxide 20. Oxygen Etch Table A.4.1 Open circuit

Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide

NASA Astrophysics Data System (ADS)

Yao, Wang; Zhang, Yu-Min; Han, Jie-cai; Zhang, Yun-long; Zhang, Jian-han; Zhou, Yu-feng; Han, Yuan-yuan

2006-01-01

Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions.

Characterization of Subsurface Defects in Ceramic Rods by Laser Scattering and Fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J. M.; Sun, J. G.; Andrews, M. J.

2006-03-06

Silicon nitride ceramics are leading materials being evaluated for valve train components in diesel engine applications. The surface and subsurface defects and damage induced by surface machining can significantly affect component strength and lifetime. In this study, a nondestructive evaluation (NDE) technique based upon laser scattering has been utilized to analyze eight transversely ground silicon nitride cylindrical rods before fracture tests. The fracture origins (machining cracks or material-inherent flaws) identified by fractography after fracture testing were correlated with laser scattering images. The results indicate that laser scattering is able to identify possible fracture origin in the silicon nitride subsurface withoutmore » the need for destructive fracture tests.« less

Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application

PubMed Central

2009-01-01

We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160–200 nm and a height of 140–150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen. PMID:20596409

TEM Analysis of Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

NASA Technical Reports Server (NTRS)

Ozaki, T.; Hasegawa, Y.; Tsuda, H.; Mori, S.; Halbig, M. C.; Asthana, R.; Singh, M.

2017-01-01

SiC fiber-bonded ceramics (SA-Tyrannohex: SA-THX) diffusion-bonded with TiCu metallic interlayers were investigated. Thin samples of the ceramics were prepared with a focused ion beam (FIB) and the interfacial microstructure of the prepared samples was studied by transmission electron microscopy (TEM) and scanning TEM (STEM). In addition to conventional microstructure observation, for detailed analysis of reaction compounds in diffusion-bonded area, we performed STEM-EDS measurements and selected area electron diffraction (SAD) experiments. The TEM and STEM experiments revealed the diffusion-bonded area was composed of only one reaction layer, which was characterized by TiC precipitates in Cu-Si compound matrix. This reaction layer was in good contact with the SA-THX substrates, and it is concluded that the joint structure led to the excellent bonding strength.

Multimillion atom simulations of dynamics of oxidation of an aluminum nanoparticle and nanoindentation on ceramics.

PubMed

Vashishta, Priya; Kalia, Rajiv K; Nakano, Aiichiro

2006-03-02

We have developed a first-principles-based hierarchical simulation framework, which seamlessly integrates (1) a quantum mechanical description based on the density functional theory (DFT), (2) multilevel molecular dynamics (MD) simulations based on a reactive force field (ReaxFF) that describes chemical reactions and polarization, a nonreactive force field that employs dynamic atomic charges, and an effective force field (EFF), and (3) an atomistically informed continuum model to reach macroscopic length scales. For scalable hierarchical simulations, we have developed parallel linear-scaling algorithms for (1) DFT calculation based on a divide-and-conquer algorithm on adaptive multigrids, (2) chemically reactive MD based on a fast ReaxFF (F-ReaxFF) algorithm, and (3) EFF-MD based on a space-time multiresolution MD (MRMD) algorithm. On 1920 Intel Itanium2 processors, we have demonstrated 1.4 million atom (0.12 trillion grid points) DFT, 0.56 billion atom F-ReaxFF, and 18.9 billion atom MRMD calculations, with parallel efficiency as high as 0.953. Through the use of these algorithms, multimillion atom MD simulations have been performed to study the oxidation of an aluminum nanoparticle. Structural and dynamic correlations in the oxide region are calculated as well as the evolution of charges, surface oxide thickness, diffusivities of atoms, and local stresses. In the microcanonical ensemble, the oxidizing reaction becomes explosive in both molecular and atomic oxygen environments, due to the enormous energy release associated with Al-O bonding. In the canonical ensemble, an amorphous oxide layer of a thickness of approximately 40 angstroms is formed after 466 ps, in good agreement with experiments. Simulations have been performed to study nanoindentation on crystalline, amorphous, and nanocrystalline silicon nitride and silicon carbide. Simulation on nanocrystalline silicon carbide reveals unusual deformation mechanisms in brittle nanophase materials, due to coexistence of brittle grains and soft amorphous-like grain boundary phases. Simulations predict a crossover from intergranular continuous deformation to intragrain discrete deformation at a critical indentation depth.

The Electrochemical Fluorination of Organosilicon Compounds

NASA Technical Reports Server (NTRS)

Seaver, Robert E.

1961-01-01

The electrochemical fluorination of tetramethylsilane, hexamethyl-disiloxane, diethyldichlorosilane, amyltrichlorosilane, and phenyltri-chlorosilane was conducted in an Inconel cell equipped with nickel electrodes. A potential of approximately 5.0 volts and a current of approximately 1.0 ampere were used for the electrolysis reaction. In all cases the fluorinations resulted in considerable scission of the carbon-silicon bonds yielding hydrogen and the various fluorinated decomposition products; no fluoroorganosilicon compounds were identified. The main decomposition products were silicon tetrafluoride, the corresponding fluorinated carbon compounds, and the various organofluorosilanes. It is suggested that this is due to the nucleophilic attack of the fluoride ion (or complex fluoride ion) on the carbon-silicon bond.

Molybdenum disilicide composites

DOEpatents

Rodriguez, Robert P.; Petrovic, John J.

2001-01-01

Molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z, wherein z=a number from greater than 0 to about 5, composites are made by use of in situ reactions among .alpha.-silicon nitride, molybdenum disilicide, and aluminum. Molybdenum disilicide within a molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z eutectoid matrix is the resulting microstructure when the invention method is employed.

Growth kinetics for temperature-controlled atomic layer deposition of GaN using trimethylgallium and remote-plasma-excited NH3

NASA Astrophysics Data System (ADS)

Pansila, P.; Kanomata, K.; Miura, M.; Ahmmad, B.; Kubota, S.; Hirose, F.

2015-12-01

Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH3 are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 104 Langmuir (L), where 1 L corresponds to 1.33 × 10-4 Pa s (or 1.0 × 10-6 Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH3 on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH3.

Method of producing novel silicon carbide articles. [Patent application

DOEpatents

Milewski, J.V.

1982-06-18

A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

Method of producing silicon carbide articles

DOEpatents

Milewski, John V.

1985-01-01

A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

Demonstration of a silicon nitride attrition mill for production of fine pure Si and Si3N4 powders

NASA Technical Reports Server (NTRS)

Herbell, T. P.; Glasgow, T. K.; Orth, N. W.

1984-01-01

To avoid metallic impurities normally introduced by milling ceramic powders in conventional steel hardware, an attrition mill (high-energy stirred ball mill) was constructed with the wearing parts (mill body, stirring arms, and media) made from silicon nitride. Commercial silicon and Si3N4 powders were milled to fine uniform particles with only minimal contamination - primarily from wear of the sintered Si3N4 media.

Silicon nitride equation of state

NASA Astrophysics Data System (ADS)

Brown, Robert C.; Swaminathan, Pazhayannur K.

2017-01-01

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

BN Bonded BN fiber article from boric oxide fiber

DOEpatents

Hamilton, Robert S.

1978-12-19

A boron nitride bonded boron nitride fiber article and the method for its manufacture which comprises forming a shaped article with a composition comprising boron oxide fibers and boric acid, heating the composition in an anhydrous gas to a temperature above the melting point of the boric acid and nitriding the resulting article in ammonia gas.

Feasibility of Actively Cooled Silicon Nitride Airfoil for Turbine Applications Demonstrated

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

2001-01-01

Nickel-base superalloys currently limit gas turbine engine performance. Active cooling has extended the temperature range of service of nickel-base superalloys in current gas turbine engines, but the margin for further improvement appears modest. Therefore, significant advancements in materials technology are needed to raise turbine inlet temperatures above 2400 F to increase engine specific thrust and operating efficiency. Because of their low density and high-temperature strength and thermal conductivity, in situ toughened silicon nitride ceramics have received a great deal of attention for cooled structures. However, the high processing costs and low impact resistance of silicon nitride ceramics have proven to be major obstacles for widespread applications. Advanced rapid prototyping technology in combination with conventional gel casting and sintering can reduce high processing costs and may offer an affordable manufacturing approach. Researchers at the NASA Glenn Research Center, in cooperation with a local university and an aerospace company, are developing actively cooled and functionally graded ceramic structures. The objective of this program is to develop cost-effective manufacturing technology and experimental and analytical capabilities for environmentally stable, aerodynamically efficient, foreign-object-damage-resistant, in situ toughened silicon nitride turbine nozzle vanes, and to test these vanes under simulated engine conditions. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. With cooling, the surface temperature decreased to approximately 1910 F--a drop of approximately 440 F. This preliminary study demonstrates that a near-net-shape silicon nitride airfoil can be fabricated and that silicon nitride can sustain severe thermal shock and the thermal gradients induced by cooling and, thus, is a viable candidate for cooled components.

Development and evaluation of die materials for use in the growth of silicon ribbons by the inverted ribbon growth process, task 2. LSSA project

NASA Technical Reports Server (NTRS)

Duffy, M. T.; Berkman, S.; Moss, H. S.; Cullen, G. W.

1978-01-01

The results of emission spectroscopic analysis indicate that molten silicon can remain in contact with hot-pressed Si3N4 (99.2 percent theoretical density) for prolonged periods without attaining the impurity content level of the nitride. Although MgO was used as binder, Mg was not found present in the silicon sessile drop in quantities much above the level initially present in the silicon source material. Preliminary experiments with EFG-type dies coated with CVD Si3N4 or CVD SiOxNy indicate that capillary rise does not occur readily in these dies. The same was found to be true of hot-pressed and reaction-sintered Si3N4 obtained commercially. However, when dies were formed by depositing CVD layers on shaped silicon slabs, a column of molten silicon was maintained in each CVD die while being heated in contact with a crucible of molten silicon. Preliminary wetting of dies appears necessary for EFG growth. Several ribbon growth experiments were performed from V-shaped dies.

Pressureless sintered beta prime-Si3N4 solid solution: Fabrication, microstructure, and strength

NASA Technical Reports Server (NTRS)

Dutta, S.

1977-01-01

Si3N4, AlN, and Al2O3 were used as basic constituents in a study of the pressureless sintering of beta prime-Si3N4 solid solution as a function of temperature. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 MPa were achieved at moderate temperature (1000 C), but decreased to 228 MPa at 1380 C. This substantial strength loss was attributed to a glassy grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

Additive Effects on Si3n4 Oxidation/Volatilization in Water Vapor

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Robinson, R. Craig; Fox, Dennis S.; Wenglarz, Richard A.; Ferber, Mattison K.

2002-01-01

Two commercially available additive-containing silicon nitride materials were exposed in four environments which range in severity from dry oxygen at 1 atm pressure, and low gas velocity to an actual turbine engine. Oxidation and volatilization kinetics were monitored at temperatures ranging from 1066 to 1400 C. The main purpose of this paper is to examine the surface oxide morphology resulting from the exposures. It was found that the material surface was enriched in rare earth silicate phases in combustion environments when compared to the oxides formed on materials exposed in dry oxygen. However, the in situ formation of rare earth disilicate phases offered little additional protection from the volatilization of silica observed in combustion environments. It was concluded that externally applied environmental barrier coatings are needed to protect additive-containing silicon nitride materials from volatilization reactions in combustion environments. Introduction Si3N4 is proposed for use as components, such as vanes, in turbine applications. Tens of thousands of hours of life are needed for both land-based turbines and aeropropulsion applications. Additive-containing SisN4 materials are

Silicon nitride boundary lubrication: Effect of oxygenates

NASA Astrophysics Data System (ADS)

Gates, Richard S.; Hsu, Stephen M.

1995-07-01

A ball-on-three-flat (BTF) wear tester was used to investigate the boundary lubricating characteristics of oxygenates on a commercial silicon nitride. A wide variety of oxygen-containing compounds containing hydroxyl functioal groups were more effective compared to a base case of neat paraffin oil. Decreases of up to 58% in friction coefficient, and 95% in wear were obtained. In most cases, films were obseved in and around the wear scar, suggesting chemical reactions had taken place in the contact. Additional wear tests, conducted using neat shorter-chain linear primary alcohols, i.e., 6-10 carbons, demonstrated boundary lubrication protection, with longer chain length providing better antiwear performance. A study of several C8 compounds with specific oxygen-containing functional groups (primary alcohol, secondary alcohols, acid, aldehyde, and ketone) demonstrated that the primary alcohol had the strongest boundary lubricating effect. Varying the amount of water in the alcohols had little effect on friction and wear, suggesting that the boundary lubrication effects observed were not merely due to dissolved water in these fluids, but some characteristic chemical interaction with the hydroxyl functional group of the alcohols and acids.

Swing arm profilometer: high accuracy testing for large reaction-bonded silicon carbide optics with a capacitive probe

NASA Astrophysics Data System (ADS)

Xiong, Ling; Luo, Xiao; Hu, Hai-xiang; Zhang, Zhi-yu; Zhang, Feng; Zheng, Li-gong; Zhang, Xue-jun

2017-08-01

A feasible way to improve the manufacturing efficiency of large reaction-bonded silicon carbide optics is to increase the processing accuracy in the ground stage before polishing, which requires high accuracy metrology. A swing arm profilometer (SAP) has been used to measure large optics during the ground stage. A method has been developed for improving the measurement accuracy of SAP using a capacitive probe and implementing calibrations. The experimental result compared with the interferometer test shows the accuracy of 0.068 μm in root-mean-square (RMS) and maps in 37 low-order Zernike terms show accuracy of 0.048 μm RMS, which shows a powerful capability to provide a major input in high-precision grinding.

Low-temperature crack-free Si3N4 nonlinear photonic circuits for CMOS-compatible optoelectronic co-integration

NASA Astrophysics Data System (ADS)

Casale, Marco; Kerdiles, Sebastien; Brianceau, Pierre; Hugues, Vincent; El Dirani, Houssein; Sciancalepore, Corrado

2017-02-01

In this communication, authors report for the first time on the fabrication and testing of Si3N4 non-linear photonic circuits for CMOS-compatible monolithic co-integration with silicon-based optoelectronics. In particular, a novel process has been developed to fabricate low-loss crack-free Si3N4 750-nm-thick films for Kerr-based nonlinear functions featuring full thermal budget compatibility with existing Silicon photonics and front-end Si optoelectronics. Briefly, differently from previous and state-of-the-art works, our nonlinear nitride-based platform has been realized without resorting to commonly-used high-temperature annealing ( 1200°C) of the film and its silica upper-cladding used to break N-H bonds otherwise causing absorption in the C-band and destroying its nonlinear functionality. Furthermore, no complex and fabrication-intolerant Damascene process - as recently reported earlier this year - aimed at controlling cracks generated in thick tensile-strained Si3N4 films has been used as well. Instead, a tailored Si3N4 multiple-step film deposition in 200-mm LPCVD-based reactor and subsequent low-temperature (400°C) PECVD oxide encapsulation have been used to fabricate the nonlinear micro-resonant circuits aiming at generating optical frequency combs via optical parametric oscillators (OPOs), thus allowing the monolithic co-integration of such nonlinear functions on existing CMOS-compatible optoelectronics, for both active and passive components such as, for instance, silicon modulators and wavelength (de-)multiplexers. Experimental evidence based on wafer-level statistics show nitride-based 112-μm-radius ring resonators using such low-temperature crack-free nitride film exhibiting quality factors exceeding Q >3 x 105, thus paving the way to low-threshold power-efficient Kerr-based comb sources and dissipative temporal solitons in the C-band featuring full thermal processing compatibility with Si photonic integrated circuits (Si-PICs).

Surface wet-ability modification of thin PECVD silicon nitride layers by 40 keV argon ion treatments

NASA Astrophysics Data System (ADS)

Caridi, F.; Picciotto, A.; Vanzetti, L.; Iacob, E.; Scolaro, C.

2015-10-01

Measurements of wet-ability of liquid drops have been performed on a 30 nm silicon nitride (Si3N4) film deposited by a PECVD reactor on a silicon wafer and implanted by 40 keV argon ions at different doses. Surface treatments by using Ar ion beams have been employed to modify the wet-ability. The chemical composition of the first Si3N4 monolayer was investigated by means of X-ray Photoelectron Spectroscopy (XPS). The surface morphology was tested by Atomic Force Microscopy (AFM). Results put in evidence the best implantation conditions for silicon nitride to increase or to reduce the wet-ability of the biological liquid. This permits to improve the biocompatibility and functionality of Si3N4. In particular experimental results show that argon ion bombardment increases the contact angle, enhances the oxygen content and increases the surface roughness.

Near-infrared gallium nitride two-dimensional photonic crystal platform on silicon

NASA Astrophysics Data System (ADS)

Roland, I.; Zeng, Y.; Han, Z.; Checoury, X.; Blin, C.; El Kurdi, M.; Ghrib, A.; Sauvage, S.; Gayral, B.; Brimont, C.; Guillet, T.; Semond, F.; Boucaud, P.

2014-07-01

We demonstrate a two-dimensional free-standing gallium nitride photonic crystal platform operating around 1550 nm and fabricated on a silicon substrate. Width-modulated waveguide cavities are integrated and exhibit loaded quality factors up to 34 000 at 1575 nm. We show the resonance tunability by varying the ratio of air hole radius to periodicity, and cavity hole displacement. We deduce a ˜7.9 dB/cm linear absorption loss for the suspended nitride structure from the power dependence of the cavity in-plane transmission.

Near-infrared gallium nitride two-dimensional photonic crystal platform on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roland, I.; Zeng, Y.; Han, Z.

We demonstrate a two-dimensional free-standing gallium nitride photonic crystal platform operating around 1550 nm and fabricated on a silicon substrate. Width-modulated waveguide cavities are integrated and exhibit loaded quality factors up to 34 000 at 1575 nm. We show the resonance tunability by varying the ratio of air hole radius to periodicity, and cavity hole displacement. We deduce a ∼7.9 dB/cm linear absorption loss for the suspended nitride structure from the power dependence of the cavity in-plane transmission.

Review of corrosion behavior of ceramic heat exchanger materals: Corrosion characteristics of silicon carbide and silicon nitride. Final report, September 11, 1992--March 11, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munro, R.G.; Dapkunas, S.J.

1993-09-01

The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags.

229 nm UV LEDs on aluminum nitride single crystal substrates using p-type silicon for increased hole injection

NASA Astrophysics Data System (ADS)

Liu, Dong; Cho, Sang June; Park, Jeongpil; Seo, Jung-Hun; Dalmau, Rafael; Zhao, Deyin; Kim, Kwangeun; Gong, Jiarui; Kim, Munho; Lee, In-Kyu; Albrecht, John D.; Zhou, Weidong; Moody, Baxter; Ma, Zhenqiang

2018-02-01

AlGaN based 229 nm light emitting diodes (LEDs), employing p-type Si to significantly increase hole injection, were fabricated on single crystal bulk aluminum nitride (AlN) substrates. Nitride heterostructures were epitaxially deposited by organometallic vapor phase epitaxy and inherit the low dislocation density of the native substrate. Following epitaxy, a p-Si layer is bonded to the heterostructure. LEDs were characterized both electrically and optically. Owing to the low defect density films, large concentration of holes from p-Si, and efficient hole injection, no efficiency droop was observed up to a current density of 76 A/cm2 under continuous wave operation and without external thermal management. An optical output power of 160 μW was obtained with the corresponding external quantum efficiency of 0.03%. This study demonstrates that by adopting p-type Si nanomembrane contacts as a hole injector, practical levels of hole injection can be realized in UV light-emitting diodes with very high Al composition AlGaN quantum wells, enabling emission wavelengths and power levels that were previously inaccessible using traditional p-i-n structures with poor hole injection efficiency.

From melamine sponge towards 3D sulfur-doping carbon nitride as metal-free electrocatalysts for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Xu, Jingjing; Li, Bin; Li, Songmei; Liu, Jianhua

2017-07-01

Development of new and efficient metal-free electrocatalysts for replacing Pt to improve the sluggish kinetics of oxygen reduction reaction (ORR) is of great importance to emerging renewable energy technologies such as metal-air batteries and polymer electrolyte fuel cells. Herein, 3D sulfur-doping carbon nitride (S-CN) as a novel metal-free ORR electrocatalyst was synthesized by exploiting commercial melamine sponge as raw material. The sulfur atoms were doping on CN networks uniformly through numerous S-C bonds which can provide additional active sites. And it was found that the S-CN exhibited high catalytic activity for ORR in term of more positive onset potential, higher electron transfer number and higher cathodic density. This work provides a novel choice of metal-free ORR electrocatalysts and highlights the importance of sulfur-doping CN in metal-free ORR electrocatalysts.

Preparation of a silicon surface for subsequent growth of dilute nitride alloys by molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Lazarenko, A. A.; Berezovskaya, T. N.; Denisov, D. V.; Sobolev, M. S.; Pirogov, E. V.; Nikitina, E. V.

2017-11-01

This article discusses the process of preparation of a silicon surface for subsequent growth of dilute nitride alloys by molecular-beam epitaxy. The method of preparation of Si (100) and Si (111) substrates was developed. This method provides reproducible high-quality silicon surface for molecular-beam epitaxy of Si-GaP heterostructures. As a result, it managed to reduce the eviction oxide temperature below 800 °C, which is an important parameter for the MBE technology.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O

NASA Astrophysics Data System (ADS)

Kharlamov, Alexey; Bondarenko, Marina; Kharlamova, Ganna; Fomenko, Veniamin

2016-09-01

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C3N4. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets.

Effect of hydrogen on the strength and microstructure of selected ceramics

NASA Technical Reports Server (NTRS)

Herbell, Thomas P.; Eckel, Andrew J.; Hull, David R.; Misra, Ajay K.

1990-01-01

Ceramics in monolithic form and as composite constituents in the form of fibers, matrices, and coatings are currently being considered for a variety of high-temperature applications in aeronautics and space. Many of these applications involve exposure to a hydrogen-containing environment. The compatibility of selected ceramics in gaseous high-temperature hydrogen is assessed. Environmental stability regimes for the long term use of ceramic materials are defined by the parameters of temperature, pressure, and moisture content. Thermodynamically predicted reactions between hydrogen and several monolithic ceramics are compared with actual performance in a controlled environment. Morphology of hydrogen attack and the corresponding strength degradation is reported for silicon carbide, silicon nitride, alumina, magnesia, and mullite.

A Thermodynamic Model to Estimate the Formation of Complex Nitrides of Al x Mg(1- x)N in Silicon Steel

NASA Astrophysics Data System (ADS)

Luo, Yan; Zhang, Lifeng; Li, Ming; Sridhar, Seetharaman

2018-06-01

A complex nitride of Al x Mg(1- x)N was observed in silicon steels. A thermodynamic model was developed to predict the ferrite/nitride equilibrium in the Fe-Al-Mg-N alloy system, using published binary solubility products for stoichiometric phases. The model was used to estimate the solubility product of nitride compound, equilibrium ferrite, and nitride compositions, and the amounts of each phase, as a function of steel composition and temperature. In the current model, the molar ratio Al/(Al + Mg) in the complex nitride was great due to the low dissolved magnesium in steel. For a steel containing 0.52 wt pct Als, 10 ppm T.Mg., and 20 ppm T.N. at 1100 K (827 °C), the complex nitride was expressed by Al0.99496Mg0.00504N and the solubility product of this complex nitride was 2.95 × 10-7. In addition, the solution temperature of the complex nitride increased with increasing the nitrogen and aluminum in steel. The good agreement between the prediction and the detected precipitate compositions validated the current model.

Atmospheric pressure scanning transmission electron microscopy.

PubMed

de Jonge, Niels; Bigelow, Wilbur C; Veith, Gabriel M

2010-03-10

Scanning transmission electron microscope (STEM) images of gold nanoparticles at atmospheric pressure have been recorded through a 0.36 mm thick mixture of CO, O2, and He. This was accomplished using a reaction cell consisting of two electron-transparent silicon nitride membranes. Gold nanoparticles of a full width at half-maximum diameter of 1.0 nm were visible above the background noise, and the achieved edge resolution was 0.4 nm in accordance with calculations of the beam broadening.

Nanomanufacturing of silicon surface with a single atomic layer precision via mechanochemical reactions.

PubMed

Chen, Lei; Wen, Jialin; Zhang, Peng; Yu, Bingjun; Chen, Cheng; Ma, Tianbao; Lu, Xinchun; Kim, Seong H; Qian, Linmao

2018-04-18

Topographic nanomanufacturing with a depth precision down to atomic dimension is of importance for advancement of nanoelectronics with new functionalities. Here we demonstrate a mask-less and chemical-free nanolithography process for regio-specific removal of atomic layers on a single crystalline silicon surface via shear-induced mechanochemical reactions. Since chemical reactions involve only the topmost atomic layer exposed at the interface, the removal of a single atomic layer is possible and the crystalline lattice beneath the processed area remains intact without subsurface structural damages. Molecular dynamics simulations depict the atom-by-atom removal process, where the first atomic layer is removed preferentially through the formation and dissociation of interfacial bridge bonds. Based on the parametric thresholds needed for single atomic layer removal, the critical energy barrier for water-assisted mechanochemical dissociation of Si-Si bonds was determined. The mechanochemical nanolithography method demonstrated here could be extended to nanofabrication of other crystalline materials.

Clarifying coverages on the basis of tapes SnO2, SiO2, Si3N4 for photodiodes of ultraviolet and visible range

NASA Astrophysics Data System (ADS)

Dobrovolsciy, Yu. George; Perevertaylo, Vladimir L.; Shabashcevich, Boris G.; Pidkamin, Leonid J.

2009-10-01

It is shown, what coverage of dioxide of tin is instrumental in the rise of sensitiveness of photodiodes sensible in the ultraviolet region of spectrum on the basis of selenid zinc and phosphide of gallium to 0,12 A/W and 0,2 A/W accordingly in the maximum of spectral description of sensitiveness. All so it is shown, that tape of nitrid silicon - dioxide of silicon a bit better clarifies silicon photodiode, especially on a wave-length 700 nm. Gluing composition, in general, worsens admission of tapes, and in a greater degree the admission of tape of nitrid silicon - dioxide of silicon.

Nano-Welding of Multi-Walled Carbon Nanotubes on Silicon and Silica Surface by Laser Irradiation.

PubMed

Yuan, Yanping; Chen, Jimin

2016-02-24

In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm²) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on silica, after 3 s irradiation, nanoscale welding with good quality can be achieved due to breaking C-C bonds and formation of new graphene layers. While welding junctions can be formed until 10 s for the MWCNTs on silicon, the difference of irradiation time to achieve welding is attributed to the difference of thermal conductivity for silica and silicon. As the irradiation time is prolonged up to 12.5 s, most of the MWCNTs are welded to a silicon substrate, which leads to their frameworks of tube walls on the silicon surface. This is because the accumulation of absorbed energy makes the temperature rise. Then chemical reactions among silicon, carbon and nitrogen occur. New chemical bonds of Si-N and Si-C achieve the welding between the MWCNTs and silicon. Vibration modes of Si₃N₄ appear at peaks of 363 cm -1 and 663 cm -1 . There are vibration modes of SiC at peaks of 618 cm -1 , 779 cm -1 and 973 cm -1 . The experimental observation proves chemical reactions and the formation of Si₃N₄ and SiC by laser irradiation.

Hot corrosion of silicon carbide and silicon nitride at 1000 C

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Jacobson, Nathan S.; Smialek, James L.

1990-01-01

The sodium sulfate hot corrosion of silicon-based ceramics at 1000 C has been extensively studied. Deposition of the sodium sulfate corrodant from combustion products is discussed in relation to sodium air impurity and sulfur fuel impurity content. Corrosion occurs by the combined processes of oxidation to form protective silica scales and dissolution of these scales to form nonprotective sodium silicates. The chemical corrosion mechanisms are presented in terms of acidic/basic dissolution of oxides in molten salts. The reactions are strongly influenced by the presence of free carbon in the ceramic. Strength reductions have been measured and are attributed to pitting in SiC and grain boundary attack in Si3N4. Initial results of burner corrosion of two ceramic matrix composites are consistent with the models developed for monolithic ceramics.

Silicon Nitride Antireflection Coatings for Photovoltaic Cells

NASA Technical Reports Server (NTRS)

Johnson, C.; Wydeven, T.; Donohoe, K.

1984-01-01

Chemical-vapor deposition adapted to yield graded index of refraction. Silicon nitride deposited in layers, refractive index of which decreases with distance away from cell/coating interface. Changing index of refraction allows adjustment of spectral transmittance for wavelengths which cell is most effective at converting light to electric current. Average conversion efficiency of solar cells increased from 8.84 percent to 12.63 percent.

Slip casting and nitridation of silicon powder

NASA Technical Reports Server (NTRS)

Seiko, Y.

1985-01-01

Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

Tunable Patch Antennas Using Microelectromechanical Systems

DTIC Science & Technology

2011-05-11

Figure 28, was selected as most suitable to this application. MetalMUMPs is a surface micromachining process with polysilicon , silicon nitride, nickel...yields. MEMS Variable Capacitor Design The MEMS capacitors reported here were an original design that features nickel and polysilicon layers as...the movable plates of a variable parallel plate capacitor. The polysilicon layer was embedded in silicon nitride for electrical isolation and suspended

Synthesis of nanowires and nanoparticles of cubic aluminium nitride

NASA Astrophysics Data System (ADS)

Balasubramanian, C.; Godbole, V. P.; Rohatgi, V. K.; Das, A. K.; Bhoraskar, S. V.

2004-03-01

Nanostructures of cubic aluminium nitride were synthesized by DC arc-plasma-induced melting of aluminium in a nitrogen-argon ambient. The material flux ejected from the molten aluminium surface was found to react with nitrogen under highly non-equilibrium conditions and subsequently condense on a water-cooled surface to yield a mixture of nanowires and nanoparticles of crystalline cubic aluminium nitride. Both x-ray diffraction and electron diffraction measurements revealed that the as-synthesized nitrides adopted the cubic phase. Fourier transform infrared spectroscopy was used to understand the bonding configuration. Microstructural features of the synthesized material were best studied by transmission electron microscopy. From these analyses cubic aluminium nitride was found to be the dominating phase for both nanowires and nanoparticles synthesized at low currents. The typical particle size distribution was found to range over 15-80 nm, whereas the wires varied from 30 to 100 nm in diameter and 500 to 700 nm in length, depending upon the process parameters such as arc current and the nitrogen pressure. The reaction products inside the plasma zone were also obtained theoretically by minimization of free energy and the favourable zone temperature necessary for the formation of aluminium nitride was found to be {\\sim } 6000 K. Results are discussed in view of the highly non-equilibrium conditions that prevail during the arc-plasma synthesis.

Fabrication and Characterization of Diffusion Bonds for Silicon Carbide

NASA Technical Reports Server (NTRS)

Halbig, Michael; Singh, Mrityunjay; Martin, Richard E.; Cosgriff, Laura M.

2007-01-01

Diffusion bonds of silicon carbide (SiC) were fabricated using several different types of titanium (Ti) based interlayers between the SiC substrates. The interlayers were an alloyed Ti foil, a pure Ti foil, and a physically vapor deposited (PVD) Ti coating. Microscopy was conducted to evaluate the cross-sections of the resulting bonds. Microprobe analysis identified reaction formed phases in the diffusion bonded region. Uniform and well adhered bonds were formed between the SiC substrates. In the case where the alloyed Ti foil or a thick Ti coating (i.e. 20 micron) was used as the interlayer, microcracks and several phases were present in the diffusion bonds. When a thinner interlayer was used (i.e. 10 micron PVD Ti), no microcracks were observed and only two reaction formed phases were present. The two phases were preferred and fully reacted phases that did not introduce thermal stresses or microcracks during the cool-down stage after processing. Diffusion bonded samples were evaluated with the non-destructive evaluation (NDE) methods of pulsed thermography and immersion ultrasonic testing. Joined SiC substrates that were fully bonded and that had simulated bond flaws in the interlayer were also evaluated using immersion ultrasound. Pull testing was conducted on the bonds to determine the tensile strength. To demonstrate the joining approach for a complex multilayered component for a low NOx injector application, the diffusion bonding approach was used to join three 4" diameter SiC discs that contained complex fuel and air flow channels.

MEMS Microshutter Array System for James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Li, Mary J.; Adachi, Tomoko; Allen, Christine; Babu, Sachi; Bajikar, Sateesh; Beamesderfer, Michael; Bradley, Ruth; Denis, Kevin; Costen, Nick; Ewin, Audrey;

Fracture Behavior of Ceramics Under Displacement Controlled Loading

NASA Technical Reports Server (NTRS)

Calomino, Anthony; Brewer, David; Ghosn, Louis

1994-01-01

A Mode I fracture specimen and loading method has been developed which permits the observation of stable crack extension in monolithic and in situ toughened ceramics. The developed technique was used to conduct room temperature tests on commercial grade alumina (Coors' AD-995) and silicon nitride (Norton NC-132). The results of these tests are reported. Crack growth for the alumina remained subcritical throughout testing revealing possible effects of environmental stress corrosion. The crack growth resistance curve for the alumina is presented. The silicon nitride tests displayed a series of stable (slow) crack growth segments interrupted by dynamic (rapid) crack extension. Crack initiation and arrest stress intensity factors, K(sub Ic) and K(sub Ia), for silicon nitride are reported. The evolution of the specimen design through testing is briefly discussed.

A conceptual design study of a high temperature solar thermal receiver (added tasks 6 and 7)

NASA Technical Reports Server (NTRS)

Robertson, C. S.; Mccreight, L. R.; Gatti, A.; Semon, H. W.

1980-01-01

The key component of this concept is a coiled tube of silicon nitride which acts as a heat exchanger appears to be ideal from the standpoint of utilizing structural ceramics at around 2500 F under severe thermal shock conditions. However the size and configuration of this coil are beyond the state of the art for fabricating such materials as silicon nitride and carbide. A two-task program to develop and demonstrate the feasibility of extruding and forming a section of thin walled silicon nitride tubing was undertaken as an addition to the original program. A promising polyvinyl butyral-based binder lubricant was identified. Fourteen full size extrusion experiments were conducted. Two trial firings of 1-1/4 turn helices were made.

Fabrication of thermal microphotonic sensors and sensor arrays

DOEpatents

Shaw, Michael J.; Watts, Michael R.; Nielson, Gregory N.

2010-10-26

A thermal microphotonic sensor is fabricated on a silicon substrate by etching an opening and a trench into the substrate, and then filling in the opening and trench with silicon oxide which can be deposited or formed by thermally oxidizing a portion of the silicon substrate surrounding the opening and trench. The silicon oxide forms a support post for an optical resonator which is subsequently formed from a layer of silicon nitride, and also forms a base for an optical waveguide formed from the silicon nitride layer. Part of the silicon substrate can be selectively etched away to elevate the waveguide and resonator. The thermal microphotonic sensor, which is useful to detect infrared radiation via a change in the evanescent coupling of light between the waveguide and resonator, can be formed as a single device or as an array.

Joining of Silicon Carbide-Based Ceramics by Reaction Forming Method

NASA Technical Reports Server (NTRS)

Singh, M.; Kiser, J. D.

1997-01-01

Recently, there has been a surge of interest in the development and testing of silicon-based ceramics and composite components for a number of aerospace and ground based systems. The designs often require fabrication of complex shaped parts which can be quite expensive. One attractive way of achieving this goal is to build up complex shapes by joining together geometrically simple shapes. However, the joints should have good mechanical strength and environmental stability comparable to the bulk materials. These joints should also be able to maintain their structural integrity at high temperatures. In addition, the joining technique should be practical, reliable, and affordable. Thus, joining has been recognized as one of the enabling technologies for the successful utilization of silicon carbide based ceramic components in high temperature applications. Overviews of various joining techniques, i.e., mechanical fastening, adhesive bonding, welding, brazing, and soldering have been provided in recent publications. The majority of the techniques used today are based on the joining of monolithic ceramics with metals either by diffusion bonding, metal brazing, brazing with oxides and oxynitrides, or diffusion welding. These techniques need either very high temperatures for processing or hot pressing (high pressures). The joints produced by these techniques have different thermal expansion coefficients than the ceramic materials, which creates a stress concentration in the joint area. The use temperatures for these joints are around 700 C. Ceramic joint interlayers have been developed as a means of obtaining high temperature joints. These joint interlayers have been produced via pre-ceramic polymers, in-situ displacement reactions, and reaction bonding techniques. Joints produced by the pre-ceramic polymer approach exhibit a large amounts of porosity and poor mechanical properties. On the other hand, hot pressing or high pressures are needed for in-situ displacement reactions and reaction bonding techniques. Due to the equipment required, these techniques are impractical for joining large or complex shaped components.

Effect of Pr Valence State on Interfacial Structure and Electrical Properties of Pr Oxide/PrON/Ge Gate Stack Structure

NASA Astrophysics Data System (ADS)

Kato, Kimihiko; Sakashita, Mitsuo; Takeuchi, Wakana; Kondo, Hiroki; Nakatsuka, Osamu; Zaima, Shigeaki

2011-04-01

In this study, we investigated the valence state and chemical bonding state of Pr in a Pr oxide/PrON/Ge structure. We clarified the relationship between the valence state of Pr and the Pr oxide/Ge interfacial reaction using Pr oxide/Ge and Pr oxide/PrON/Ge samples. We found the formation of three Pr oxide phases in Pr oxide films; hexagonal Pr2O3 (h-Pr2O3) (Pr3+), cubic Pr2O3 (c-Pr2O3) (Pr3+), and c-PrO2 (Pr4+). We also investigated the effect of a nitride interlayer on the interfacial reaction in Pr oxide/Ge gate stacks. In a sample with a nitride interlayer (Pr oxide/PrON/Ge), metallic Pr-Pr bonds are also formed in the c-Pr2O3 film. After annealing in H2 ambient, the diffusion of Ge into Pr oxide is not observed in this sample. Pr-Pr bonds probably prevent the interfacial reaction and Ge oxide formation, considering that the oxygen chemical potential of this film is lower than that of a GeO2/Ge system. On the other hand, the rapid thermal oxidation (RTO) treatment terminates the O vacancies and defects in c-Pr2O3. As a result, c-PrO2 with tetravalent Pr is formed in the Pr oxide/PrON/Ge sample with RTO. In this sample, the leakage current density is effectively decreased in comparison with the sample without RTO. Hydrogen termination works effectively in Pr oxide/PrON/Ge samples with and without RTO, and we can achieve an interface state density of as low as 4 ×1011 eV-1·cm-2.

Push-out tests on a new silicon carbide/reaction-bonded silicon carbide ceramic matrix composite

NASA Technical Reports Server (NTRS)

Curtin, William A.; Eldridge, Jeffrey I.; Srinivasan, Gajawalli V.

1993-01-01

Fiber push-out tests have been performed on a ceramic matrix composite consisting of carborundum-sintered SiC fibers, with a BN coating, embedded in a reaction-bonded SiC matrix. Analysis of the push-out data, utilizing the most complete theory presently available, shows that one of the fiber/coating/matrix interfaces has a low fracture energy (one-tenth that of the fiber) and a moderate sliding resistance of about 8 MPa. The debonded sliding interface shows some continuous but minor abrasion, which appears to increase the sliding resistance, but overall the system exhibits very clean smooth sliding. The tensile response of a full-scale composite is then modeled using data obtained here and known fiber strengths to demonstrate the good composite behavior predicted for this material.

Development and Characterization of the Bonding and Integration Technologies Needed for Fabricating Silicon Carbide Based Injector Components

NASA Technical Reports Server (NTRS)

Halbig,Michael C.; Singh, Mrityunjay

2008-01-01

Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding technology, titanium interlayers (coatings and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness, and processing time were investigated. Electron microprobe analysis was used to identify the reaction formed phases. In the diffusion bonds, an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner interlayers of pure titanium and/or longer processing times resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Nondestructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

Brittle Materials Design, High Temperature Gas Turbine

DTIC Science & Technology

1975-10-01

White Army Material and Mechanics Research Center E. M. Lenoe, R. N. Katz, D. R. Messier, H. Priest m ’■ V ..W.*.il.’■.■,:;.-M V -^.’ -i.-■..::.■ f.:irjU...Stator Vane Development 6.1.1 Design and Analysis v 6.1.2 Static Rig Testing 6.1.3 Vane Fabrication 6.1.4 Heat Transfer Tests Progress on Materials...Oxidation on the Strengths of Hot- Pressed Silicon Nitride and Silicon Carbide Properties of Yttria Hot-Pressed Silicon Nitride i ii iii iv v x 1

Penetration Resistance of Armor Ceramics: Dimensional Analysis and Property Correlations

DTIC Science & Technology

2015-08-01

been reported in experimental studies. Particular ceramics analyzed here are low- and high-purity alumina, aluminum nitride, boron carbide, silicon...analyzed here are low- and high-purity alumina, aluminum nitride, boron carbide, silicon carbide, and titanium diboride. Data for penetration depth...include high hardness, high elastic stiffness, high strengths (static/dynamic compressive, shear, and bending), and low density relative to armor steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shanmin; Yu, Xiaohui; Zhang, Jianzhong

Here, we report synthesis of single-crystal VN and CrN through high-pressure ionexchange reaction routes. The final products are stoichiometric and have crystallite sizes in the range of 50-120 mu m. We also prepared VN and TiN crystals using high-pressure sintering of nitride powders. On the basis of single-crystal indentation testing, the determined asymptotic Vickers hardness for TiN, VN, and CrN is 18 (1), 10 (1), and 16 (1) GPa, respectively. Moreover, the relatively low hardness in VN indicates that the metallic bonding prevails due to the overfilled metallic a bonds, although the cation-anion covalent hybridization in this compound is muchmore » stronger than that in TiN and CrN. All three nitrides are intrinsically excellent metals at ambient pressure. In particular, VN exhibits superconducting transition at T-c approximate to 7.8 K, which is slightly lower than the reported values for nitrogen-deficient or crystallinedisordered samples due to unsuppressed "spin fluctuation" in the well-crystallized stoichiometric VN. The magnetostructural transition in CrN correlates with a metal metal transition at T-N = 240(5) K and is accompanied by a similar to 40% drop in electrical resistivity. Additionally, more detailed electronic properties are presented with new insights into these nitrides.« less

Synthesis, Hardness, and Electronic Properties of Stoichiometric VN and CrN

DOE PAGES

Wang, Shanmin; Yu, Xiaohui; Zhang, Jianzhong; ...

2015-11-09

Here, we report synthesis of single-crystal VN and CrN through high-pressure ionexchange reaction routes. The final products are stoichiometric and have crystallite sizes in the range of 50-120 mu m. We also prepared VN and TiN crystals using high-pressure sintering of nitride powders. On the basis of single-crystal indentation testing, the determined asymptotic Vickers hardness for TiN, VN, and CrN is 18 (1), 10 (1), and 16 (1) GPa, respectively. Moreover, the relatively low hardness in VN indicates that the metallic bonding prevails due to the overfilled metallic a bonds, although the cation-anion covalent hybridization in this compound is muchmore » stronger than that in TiN and CrN. All three nitrides are intrinsically excellent metals at ambient pressure. In particular, VN exhibits superconducting transition at T-c approximate to 7.8 K, which is slightly lower than the reported values for nitrogen-deficient or crystallinedisordered samples due to unsuppressed "spin fluctuation" in the well-crystallized stoichiometric VN. The magnetostructural transition in CrN correlates with a metal metal transition at T-N = 240(5) K and is accompanied by a similar to 40% drop in electrical resistivity. Additionally, more detailed electronic properties are presented with new insights into these nitrides.« less

Interface bonding in silicon oxide nanocontacts: interaction potentials and force measurements.

PubMed

Wierez-Kien, M; Craciun, A D; Pinon, A V; Roux, S Le; Gallani, J L; Rastei, M V

2018-04-01

The interface bonding between two silicon-oxide nanoscale surfaces has been studied as a function of atomic nature and size of contacting asperities. The binding forces obtained using various interaction potentials are compared with experimental force curves measured in vacuum with an atomic force microscope. In the limit of small nanocontacts (typically <10 3 nm 2 ) measured with sensitive probes the bonding is found to be influenced by thermal-induced fluctuations. Using interface interactions described by Morse, embedded atom model, or Lennard-Jones potential within reaction rate theory, we investigate three bonding types of covalent and van der Waals nature. The comparison of numerical and experimental results reveals that a Lennard-Jones-like potential originating from van der Waals interactions captures the binding characteristics of dry silicon oxide nanocontacts, and likely of other nanoscale materials adsorbed on silicon oxide surfaces. The analyses reveal the importance of the dispersive surface energy and of the effective contact area which is altered by stretching speeds. The mean unbinding force is found to decrease as the contact spends time in the attractive regime. This contact weakening is featured by a negative aging coefficient which broadens and shifts the thermal-induced force distribution at low stretching speeds.

Interface bonding in silicon oxide nanocontacts: interaction potentials and force measurements

NASA Astrophysics Data System (ADS)

Wierez-Kien, M.; Craciun, A. D.; Pinon, A. V.; Le Roux, S.; Gallani, J. L.; Rastei, M. V.

2018-04-01

The interface bonding between two silicon-oxide nanoscale surfaces has been studied as a function of atomic nature and size of contacting asperities. The binding forces obtained using various interaction potentials are compared with experimental force curves measured in vacuum with an atomic force microscope. In the limit of small nanocontacts (typically <103 nm2) measured with sensitive probes the bonding is found to be influenced by thermal-induced fluctuations. Using interface interactions described by Morse, embedded atom model, or Lennard-Jones potential within reaction rate theory, we investigate three bonding types of covalent and van der Waals nature. The comparison of numerical and experimental results reveals that a Lennard-Jones-like potential originating from van der Waals interactions captures the binding characteristics of dry silicon oxide nanocontacts, and likely of other nanoscale materials adsorbed on silicon oxide surfaces. The analyses reveal the importance of the dispersive surface energy and of the effective contact area which is altered by stretching speeds. The mean unbinding force is found to decrease as the contact spends time in the attractive regime. This contact weakening is featured by a negative aging coefficient which broadens and shifts the thermal-induced force distribution at low stretching speeds.

Self-assembled monolayer and method of making

DOEpatents

Fryxell, Glen E [Kennewick, WA; Zemanian, Thomas S [Richland, WA; Liu, Jun [West Richland, WA; Shin, Yongsoon [Richland, WA

2003-03-11

According to the present invention, the previously known functional material having a self-assembled monolayer on a substrate has a plurality of assembly molecules each with an assembly atom with a plurality of bonding sites (four sites when silicon is the assembly molecule) wherein a bonding fraction (or fraction) of fully bonded assembly atoms (the plurality of bonding sites bonded to an oxygen atom) has a maximum when made by liquid solution deposition, for example a maximum of 40% when silicon is the assembly molecule, and maximum surface density of assembly molecules was 5 silanes per square nanometer. Note that bonding fraction and surface population are independent parameters. The method of the present invention is an improvement to the known method for making a siloxane layer on a substrate, wherein instead of a liquid phase solution chemistry, the improvement is a supercritical phase chemistry. The present invention has the advantages of greater fraction of oxygen bonds, greater surface density of assembly molecules and reduced time for reaction of about 5 minutes to about 24 hours.

Self-assembled monolayer and method of making

DOEpatents

Fryxell, Glen E.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon

2004-05-11

According to the present invention, the previously known functional material having a self-assembled monolayer on a substrate has a plurality of assembly molecules each with an assembly atom with a plurality of bonding sites (four sites when silicon is the assembly molecule) wherein a bonding fraction (or fraction) of fully bonded assembly atoms (the plurality of bonding sites bonded to an oxygen atom) has a maximum when made by liquid solution deposition, for example a maximum of 40% when silicon is the assembly molecule, and maximum surface density of assembly molecules was 5 silanes per square nanometer. Note that bonding fraction and surface population are independent parameters. The method of the present invention is an improvement to the known method for making a siloxane layer on a substrate, wherein instead of a liquid phase solution chemistry, the improvement is a supercritical phase chemistry. The present invention has the advantages of greater fraction of oxygen bonds, greater surface density of assembly molecules and reduced time for reaction of about 5 minutes to about 24 hours.

Self-Assembled Monolayer And Method Of Making

DOEpatents

Fryxell, Glen E.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon

2004-06-22

According to the present invention, the previously known functional material having a self-assembled monolayer on a substrate has a plurality of assembly molecules each with an assembly atom with a plurality of bonding sites (four sites when silicon is the assembly molecule) wherein a bonding fraction (or fraction) of fully bonded assembly atoms (the plurality of bonding sites bonded to an oxygen atom) has a maximum when made by liquid solution deposition, for example a maximum of 40% when silicon is the assembly molecule, and maximum surface density of assembly molecules was 5 silanes per square nanometer. Note that bonding fraction and surface population are independent parameters. The method of the present invention is an improvement to the known method for making a siloxane layer on a substrate, wherein instead of a liquid phase solution chemistry, the improvement is a supercritical phase chemistry. The present invention has the advantages of greater fraction of oxygen bonds, greater surface density of assembly molecules and reduced time for reaction of about 5 minutes to about 24 hours.

Self-Assembled Monolayer And Method Of Making

DOEpatents

Fryxell, Glen E.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon

2005-01-25

According to the present invention, the previously known functional material having a self-assembled monolayer on a substrate has a plurality of assembly molecules each with an assembly atom with a plurality of bonding sites (four sites when silicon is the assembly molecule) wherein a bonding fraction (or fraction) of fully bonded assembly atoms (the plurality of bonding sites bonded to an oxygen atom) has a maximum when made by liquid solution deposition, for example a maximum of 40% when silicon is the assembly molecule, and maximum surface density of assembly molecules was 5 silanes per square nanometer. Note that bonding fraction and surface population are independent parameters. The method of the present invention is an improvement to the known method for making a siloxane layer on a substrate, wherein instead of a liquid phase solution chemistry, the improvement is a supercritical phase chemistry. The present invention has the advantages of greater fraction of oxygen bonds, greater surface density of assembly molecules and reduced time for reaction of about 5 minutes to about 24 hours.

Vacuum-based surface modification of organic and metallic substrates

NASA Astrophysics Data System (ADS)

Torres, Jessica

Surface physico-chemical properties play an important role in the development and performance of materials in different applications. Consequently, understanding the chemical and physical processes involved during surface modification strategies is of great scientific and technological importance. This dissertation presents results from the surface modification of polymers, organic films and metallic substrates with reactive species, with the intent of simulating important modification processes and elucidating surface property changes of materials under different environments. The reactions of thermally evaporated copper and titanium with halogenated polytetrafluoroethylene (PTFE) and polyvinyl chloride (PVC) are used to contrast the interaction of metals with polymers. Results indicate that reactive metallization is thermodynamically favored when the metal-halogen bond strength is greater than the carbon-halogen bond strength. X-ray post-metallization treatment results in an increase in metal-halide bond formation due to the production of volatile halogen species in the polymer that react with the metallic overlayer. The reactions of atomic oxygen (AO) and atomic chlorine with polyethylene (PE) and self-assembled monolayers (SAMs) films were followed to ascertain the role of radical species during plasma-induced polymer surface modification. The reactions of AO with X-ray modified SAMs are initially the dominated by the incorporation of new oxygen containing functionality at the vacuum/film interface, leading to the production of volatile carbon containing species such as CO2 that erodes the hydrocarbon film. The reaction of atomic chlorine species with hydrocarbon SAMs, reveals that chlorination introduces C-Cl and C-Cl2 functionalities without erosion. A comparison of the reactions of AO and atomic chlorine with PE reveal a maximum incorporation of the corresponding C-O and C-Cl functionalities at the polymer surface. A novel method to prepare phosphorous-containing polymer surfaces through ion implantation of trimethyl phosphine onto PE is presented. Air exposure of the resulting P-implanted PE leads to the surface selective oxidation of phosphorous moieties. P-containing hydrocarbon films are used to model the surface chemical changes of P-containing polymers exposed to AO. Results indicate that oxidized phosphorous species protect the film from AO-induced erosion. The low temperature (<150 K) oxidation of nitrided iron surfaces exposed to oxygen reveal the formation of iron oxynitride (FexNyO z, nitrosonium ions (NO+) as well as nitrite/nitrito and nitrate type species. The production of nitrite/nitrito and nitrate species is taken as evidence for the existence of oxygen insertion chemistry into the iron nitride lattice under these low temperature oxidation conditions. Upon annealing the oxidized iron nitride surface, nitrogen desorbs exclusively as nitric oxide (NO).

Back scattering involving embedded silicon nitride (SiN) nanoparticles for c-Si solar cells

NASA Astrophysics Data System (ADS)

Ghosh, Hemanta; Mitra, Suchismita; Siddiqui, M. S.; Saxena, A. K.; Chaudhuri, Partha; Saha, Hiranmay; Banerjee, Chandan

2018-04-01

A novel material, structure and method of synthesis for dielectric light trapping have been presented in this paper. First, the light scattering behaviour of silicon nitride nanoparticles have been theoretically studied in order to find the optimized size for dielectric back scattering by FDTD simulations from Lumerical Inc. The optical results have been used in electrical analysis and thereby, estimate the effect of nanoparticles on efficiency of the solar cells depending on substrate thickness. Experimentally, silicon nitride (SiN) nanoparticles have been formed using hydrogen plasma treatment on SiN layer deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD). The size and area coverage of the nanoparticles were controlled by varying the working pressure, power density and treatment duration. The nanoparticles were integrated with partial rear contact c-Si solar cells as dielectric back reflector structures for the light trapping in thin silicon solar cells. Experimental results revealed the increases of current density by 2.7% in presence of SiN nanoparticles.

Further Investigations of Hypersonic Engine Seals

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; DeMange, Jeffrey J.

2004-01-01

Durable, flexible sliding seals are required in advanced hypersonic engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures of 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA's Glenn Research Center is developing advanced seals and preloading devices to overcome these shortfalls. An advanced ceramic wafer seal design and two silicon nitride compression spring designs were evaluated in a series of compression, scrub, and flow tests. Silicon nitride wafer seals survived 2000 in. (50.8 m) of scrubbing at 2000 F against a silicon carbide rub surface with no chips or signs of damage. Flow rates measured for the wafers before and after scrubbing were almost identical and were up to 32 times lower than those recorded for the best braided rope seal flow blockers. Silicon nitride compression springs showed promise conceptually as potential seal preload devices to help maintain seal resiliency.

Transmission of Free Radicals through and Damage to Freestanding Single and Multilayer Dielectric Film

NASA Astrophysics Data System (ADS)

Choudhury, Faraz Anwar

A high concentration of free radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Measuring the types and concentrations of free radicals present in the plasma is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups and often modifications to the plasma reactor. In this work, we present a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye that is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma, which is indicated by degradation of its fluorescence. As plasma power was increased, the quenching of the fluorescence significantly increased. Both immobilized and non-immobilized fluorophore dyes were used and the results indicate that both states function effectively under vacuum conditions. Using radical-sensitive dyes and free-standing films, the transmission of oxygen radicals through silicon nitride and silicon dioxide dielectric films is measured and their absorption lengths are determined. The absorption lengths were found to be 33, 37 and 40 nm for 15, 30 and 45-minute oxygen plasma exposures respectively. FTIR and XRR measurements show that a silicon oxynitride-like layer forms on the surface of the film which has a lower density than silicon nitride. The increase in absorption length with plasma-exposure time is attributed to the formation of the surface layer. In silicon dioxide films, the absorption length of oxygen radicals was found to be 70 nm after 20 minutes of plasma exposure. After 30 minutes of plasma exposure under the same conditions, the absorption length was reduced to 66 nm. XRR and FTIR measurements both reveal that the oxygen plasma exposure leads to surface oxidation of the silicon dioxide film and the formation of a denser surface layer which restricts the transmission of the radicals through the film. It was found that the extent of modification of the film partially depends on the radical dose. The calculated enthalpies of the reactions show that they are all exothermic reactions, however, the radicals need enough energy to overcome the activation energy for the reaction to take place.

Highly nonlinear sub-micron silicon nitride trench waveguide coated with gold nanoparticles

NASA Astrophysics Data System (ADS)

Huang, Yuewang; Zhao, Qiancheng; Sharac, Nicholas; Ragan, Regina; Boyraz, Ozdal

2015-05-01

We demonstrate the fabrication of a highly nonlinear sub-micron silicon nitride trench waveguide coated with gold nanoparticles for plasmonic enhancement. The average enhancement effect is evaluated by measuring the spectral broadening effect caused by self-phase-modulation. The nonlinear refractive index n2 was measured to be 7.0917×10-19 m2/W for a waveguide whose Wopen is 5 μm. Several waveguides at different locations on one wafer were measured in order to take the randomness of the nanoparticle distribution into consideration. The largest enhancement is measured to be as high as 10 times. Fabrication of this waveguide started with a MEMS grade photomask. By using conventional optical lithography, the wide linewidth was transferred to a <100> wafer. Then the wafer was etched anisotropically by potassium hydroxide (KOH) to engrave trapezoidal trenches with an angle of 54.7º. Side wall roughness was mitigated by KOH etching and thermal oxidation that was used to generate a buffer layer for silicon nitride waveguide. The guiding material silicon nitride was then deposited by low pressure chemical vapor deposition. The waveguide was then patterned with a chemical template, with 20 nm gold particles being chemically attached to the functionalized poly(methyl methacrylate) domains. Since the particles attached only to the PMMA domains, they were confined to localized regions, therefore forcing the nanoparticles into clusters of various numbers and geometries. Experiments reveal that the waveguide has negligible nonlinear absorption loss, and its nonlinear refractive index can be greatly enhanced by gold nano clusters. The silicon nitride trench waveguide has large nonlinear refractive index, rendering itself promising for nonlinear applications.

Identification and characterization of monomeric, volatile SiCl3NH2 as product of the reaction between SiCl4 and NH3: an important intermediate on the way to silicon nitride?

PubMed

Himmel, Hans-Jörg; Schiefenhövel, Nils; Binnewies, Michael

2003-03-17

We studied the reaction of SiCl(4) with NH(3) by mass spectrometry and IR spectroscopy. By means of mass spectrometry, SiCl(3)NH(2) was for the first time identified as an intermediate generated in significant amounts in the course of the reaction. In additional experiments, SiCl(3)NH(2) was formed as a stable gaseous product of the ammonolysis of SiCl(4), and the product was identified and characterized in detail by IR spectroscopic methods (gas phase and matrix isolation) in combination with quantum-chemical calculations. The calculations also gave access to important thermodynamical data.

Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma

NASA Technical Reports Server (NTRS)

Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

1983-01-01

Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

Silicon rich nitride ring resonators for rare - earth doped telecommunications-band amplifiers pumped at the O-band.

PubMed

Xing, P; Chen, G F R; Zhao, X; Ng, D K T; Tan, M C; Tan, D T H

2017-08-22

Ring resonators on silicon rich nitride for potential use as rare-earth doped amplifiers pumped at 1310 nm with amplification at telecommunications-band are designed and characterized. The ring resonators are fabricated on 300 nm and 400 nm silicon rich nitride films and characterized at both 1310 nm and 1550 nm. We demonstrate ring resonators exhibiting similar quality factors exceeding 10,000 simultaneously at 1310 nm and 1550 nm. A Dysprosium-Erbium material system exhibiting photoluminescence at 1510 nm when pumped at 1310 nm is experimentally demonstrated. When used together with Dy-Er co-doped particles, these resonators with similar quality factors at 1310 nm and 1550 nm may be used for O-band pumped amplifiers for the telecommunications-band.

Ferrocene-functionalized graphitic carbon nitride as an enhanced heterogeneous catalyst of Fenton reaction for degradation of Rhodamine B under visible light irradiation.

PubMed

Lin, Kun-Yi Andrew; Lin, Jyun-Ting

2017-09-01

To enhance degradation of Rhodamine B (RhB), a toxic xanthene dye, an iron-doped graphitic carbon nitride (CN) is prepared by establishing a covalent bond (-CN-) bridging ferrocene (Fc) and CN via a Schiff base reaction. The π-conjugation between the aromatic Fc and CN can be much enhanced by the covalent bond, thereby facilitating the bulk-to-surface charge transfer and separation as well as reversible photo-redox reactions during photocatalytic reactions. Thus, the resulting Fc-CN exhibits a much higher catalytic activity than CN to activate hydrogen peroxide (HP) for RhB degradation, because the photocatalytically generated electrons from CN can activate HP and effectively maintain the bivalence state of Fe in Fc, which also induces the activation of HP. The RhB degradation by the Fc-CN activated HP process (Fc-CN-HP) is validated to involve OH • by examining the effect of radical probe agent as well as electron paramagnetic resonance (EPR) spectroscopic analysis. Fc-CN is also proven to activate HP for RhB degradation over multiple times without loss of catalytic activity. Through determining the degradation intermediates, RhB is indeed fully decomposed by Fc-CN-HP into much lower-molecular-weight organic compounds. These features indicate that Fc-functionalization can be an advantageous technique to enhance the catalytic activity of CN for activating HP. The results obtained in this study are essential to further design and utilize Fc-functionalized CN for Fenton-like reactions. The findings shown here, especially the degradation mechanism and pathway, are also quite important for treating xanthene dyes in wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of x-ray mask in Taiwan

NASA Astrophysics Data System (ADS)

Sheu, Jeng Tzong; Su, Shyang

1996-05-01

This paper presents results of using silicon carbide (SiC) and silicon-rich silicon nitride (SiNx) as membrane for X-ray masks in technology of X-ray lithography. Microcrystalline silicon carbide film was deposited on silicon substrate by electron synchrotron resonance plasma-enhanced chemical vapor deposition at 300 degrees C utilizing a SiH4/CH4/H2/Ar gas mixture. Low tensile stress film which is suitable as X-ray membrane can be achieved by annealing after silicon carbide film deposition. The microwave power over 800 watts and the gas ratio (Methane:Silane) larger than 1.5 are needed for the stoichiometry of SiC film. On the other hand, we deposited silicon-rich silicon nitride film on silicon substrate by low pressure chemical vapor deposition at 850 degrees C to 900 degrees C. In order to get low tensile stress film, different gas flow ratios (Dichlorosilane:Ammonia) were tested. The increased gas flow ratio (Dichlorosilane:Ammonia) and the increased deposition temperature are related to the decrease of tensile stress of film. Roughness, uniformity, optical transmittance and soft X-ray transmission of both films are reported. The absorption bands of both films were measured by FTIR spectroscopy. The surface morphology was monitored by AFM. The photon transmission of both films was measured in the range of 400 to 800 nm for visible light and 800 to 1600 ev photon energy for SR soft X-ray transmission was conducted at the Synchrotron Radiation Research Center, Hsinchu, Taiwan. The deposition rate of both films are 13 nm/min and 40 nm/min for silicon nitride and silicon carbide, respectively.

Stepwise mechanism and H2O-assisted hydrolysis in atomic layer deposition of SiO2 without a catalyst.

PubMed

Fang, Guo-Yong; Xu, Li-Na; Wang, Lai-Guo; Cao, Yan-Qiang; Wu, Di; Li, Ai-Dong

2015-01-01

Atomic layer deposition (ALD) is a powerful deposition technique for constructing uniform, conformal, and ultrathin films in microelectronics, photovoltaics, catalysis, energy storage, and conversion. The possible pathways for silicon dioxide (SiO2) ALD using silicon tetrachloride (SiCl4) and water (H2O) without a catalyst have been investigated by means of density functional theory calculations. The results show that the SiCl4 half-reaction is a rate-determining step of SiO2 ALD. It may proceed through a stepwise pathway, first forming a Si-O bond and then breaking Si-Cl/O-H bonds and forming a H-Cl bond. The H2O half-reaction may undergo hydrolysis and condensation processes, which are similar to conventional SiO2 chemical vapor deposition (CVD). In the H2O half-reaction, there are massive H2O molecules adsorbed on the surface, which can result in H2O-assisted hydrolysis of the Cl-terminated surface and accelerate the H2O half-reaction. These findings may be used to improve methods for the preparation of SiO2 ALD and H2O-based ALD of other oxides, such as Al2O3, TiO2, ZrO2, and HfO2.

Stepwise mechanism and H2O-assisted hydrolysis in atomic layer deposition of SiO2 without a catalyst

NASA Astrophysics Data System (ADS)

Fang, Guo-Yong; Xu, Li-Na; Wang, Lai-Guo; Cao, Yan-Qiang; Wu, Di; Li, Ai-Dong

2015-02-01

Atomic layer deposition (ALD) is a powerful deposition technique for constructing uniform, conformal, and ultrathin films in microelectronics, photovoltaics, catalysis, energy storage, and conversion. The possible pathways for silicon dioxide (SiO2) ALD using silicon tetrachloride (SiCl4) and water (H2O) without a catalyst have been investigated by means of density functional theory calculations. The results show that the SiCl4 half-reaction is a rate-determining step of SiO2 ALD. It may proceed through a stepwise pathway, first forming a Si-O bond and then breaking Si-Cl/O-H bonds and forming a H-Cl bond. The H2O half-reaction may undergo hydrolysis and condensation processes, which are similar to conventional SiO2 chemical vapor deposition (CVD). In the H2O half-reaction, there are massive H2O molecules adsorbed on the surface, which can result in H2O-assisted hydrolysis of the Cl-terminated surface and accelerate the H2O half-reaction. These findings may be used to improve methods for the preparation of SiO2 ALD and H2O-based ALD of other oxides, such as Al2O3, TiO2, ZrO2, and HfO2.

Selected fretting-wear-resistant coatings for titanium - 6-percent-aluminum - 4-percent-vanadium alloy

NASA Technical Reports Server (NTRS)

Bill, R. C.

1976-01-01

A titanium - 6-percent-aluminum - 4-percent-vanadium alloy (Ti-6Al-4V) was subjected to fretting-wear exposures against uncoated Ti-6Al-4V as a baseline and against various coatings and surface treatments applied to Ti-6Al-4V. The coatings evaluated included plasma-sprayed tungsten carbide with 12 percent cobalt, aluminum oxide with 13 percent titanium oxide, chromium oxide, and aluminum bronze with 10 percent aromatic polyester; polymer-bonded polyimide, polyimide with graphite fluoride, polyimide with molybdenum disulfide (MoS2), and methyl phenyl silicone bonded MoS2, preoxidation surface treatment, a nitride surface treatment, and a sputtered MoS2 coating. Results of wear measurements on both the coated and uncoated surfaces after 300,000 fretting cycles indicated that the polyimide coating was the most wear resistant and caused the least wear to the uncoated mating surface.

Dispersion engineering of thick high-Q silicon nitride ring-resonators via atomic layer deposition.

PubMed

Riemensberger, Johann; Hartinger, Klaus; Herr, Tobias; Brasch, Victor; Holzwarth, Ronald; Kippenberg, Tobias J

2012-12-03

We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition. Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. The results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.

Reliability analysis of structural ceramic components using a three-parameter Weibull distribution

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois

1992-01-01

Described here are nonlinear regression estimators for the three-Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.

Foreign Object Damage of Two Gas-Turbine Grade Silicon Nitrides in a Thin Disk Configuration

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Pereira, J. Michael; Janosik, Lesley A.; Bhatt, Ramakrishna T.

2003-01-01

Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (K(sub IC)). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was V(sub c) approx. 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both silicon nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.

Superconducting bolometers for millimeter and sub-millimeter wavelengths

NASA Astrophysics Data System (ADS)

Jethava, N.; Kreysa, E.; Siringo, G.; Esch, W.; Gemünd, H.-P.; Menten, K. M.; May, T.; Anders, S.; Fritzsch, L.; Boucher, R.; Zakosarenko, V.; Meyer, H.-G.

2008-07-01

We present the experimental results and a bolometer model of the voltage-biased superconducting bolometer on the low stress silicon nitride (Si3N4) membrane, developed in collaboration between the Max-Planck-Institut fur Radioastronomie (MPIfR), Bonn and the Institute for Photonic Technology (IPHT), Jena, Germany. The superconducting thermistor, deposited on the low stress silicon nitride membrane, is a bilayer of gold-palladium and molybdenum and is designed for a transition temperature of 450 mK. Bolometers for the 1.2 mm atmospheric window were designed, built and tested. The thermal conductance of the bolometer is tuned by structuring the silicon nitride membrane into spider-like geometries. The incident radiation is absorbed by crossed dipoles made from gold-palladium alloy with a surface resistance of 10 Ω/. Using the COSMOS finite element analysis package, the thermal conductance is obtained for the bolometers of different geometries. FEA simulations showed that the deposition of a gold ring around the absorbing area could increase the sensitivity of the bolometer. Therefore, a gold ring is deposited around the center absorbing patch of the silicon nitride membrane. For the bolometer with a gold ring, the measured NEP is 1.7 × 10-16W/√ Hz and the time constant is in the range between 1.4 and 2 ms.

Quantitative Mapping of Pore Fraction Variations in Silicon Nitride Using an Ultrasonic Contact Scan Technique

NASA Technical Reports Server (NTRS)

Roth, Don J.; Kiser, James D.; Swickard, Suzanne M.; Szatmary, Steven A.; Kerwin, David P.

1993-01-01

An ultrasonic scan procedure using the pulse-echo contact configuration was employed to obtain maps of pore fraction variations in sintered silicon nitride samples in terms of ultrasonic material properties. Ultrasonic velocity, attenuation coefficient, and reflection coefficient images were obtained simultaneously over a broad band of frequencies (e.g., 30 to 110 MHz) by using spectroscopic analysis. Liquid and membrane (dry) coupling techniques and longitudinal and shear-wave energies were used. The major results include the following: Ultrasonic velocity (longitudinal and shear wave) images revealed and correlated with the extent of average through-thickness pore fraction variations in the silicon nitride disks. Attenuation coefficient images revealed pore fraction nonuniformity due to the scattering that occurred at boundaries between regions of high and low pore fraction. Velocity and attenuation coefficient images were each nearly identical for machined and polished disks, making the method readily applicable to machined materials. Velocity images were similar for wet and membrane coupling. Maps of apparent Poisson's ratio constructed from longitudinal and shear-wave velocities quantified Poisson's ratio variations across a silicon nitride disk. Thermal wave images of a disk indicated transient thermal behavior variations that correlated with observed variations in pore fraction and velocity and attenuation coefficients.

Chemical Interaction-Guided, Metal-Free Growth of Large-Area Hexagonal Boron Nitride on Silicon-Based Substrates.

PubMed

Behura, Sanjay; Nguyen, Phong; Debbarma, Rousan; Che, Songwei; Seacrist, Michael R; Berry, Vikas

2017-05-23

Hexagonal boron nitride (h-BN) is an ideal platform for interfacing with two-dimensional (2D) nanomaterials to reduce carrier scattering for high-quality 2D electronics. However, scalable, transfer-free growth of hexagonal boron nitride (h-BN) remains a challenge. Currently, h-BN-based 2D heterostructures require exfoliation or chemical transfer of h-BN grown on metals resulting in small areas or significant interfacial impurities. Here, we demonstrate a surface-chemistry-influenced transfer-free growth of large-area, uniform, and smooth h-BN directly on silicon (Si)-based substrates, including Si, silicon nitride (Si 3 N 4 ), and silicon dioxide (SiO 2 ), via low-pressure chemical vapor deposition. The growth rates increase with substrate electronegativity, Si < Si 3 N 4 < SiO 2 , consistent with the adsorption rates calculated for the precursor molecules via atomistic molecular dynamics simulations. Under graphene with high grain density, this h-BN film acts as a polymer-free, planar-dielectric interface increasing carrier mobility by 3.5-fold attributed to reduced surface roughness and charged impurities. This single-step, chemical interaction guided, metal-free growth mechanism of h-BN for graphene heterostructures establishes a potential pathway for the design of complex and integrated 2D-heterostructured circuitry.

Investigation of nickel-silicon metallization process

NASA Technical Reports Server (NTRS)

Macha, M.

1983-01-01

The metallization of silicon solar cells passivated with silicon nitride coating was investigated by using commercial Ni pastes #5517 from Thick Film Systems, #7028-5 from Cermalloy, experimental formulation # X-A by Sollos, Inc. and evaporated Ti-Ni film. Comparative and reference tests were done with the Dupont Ag paste #7095 and with a mixture of Ni paste #5517 with Ag paste #7095 in the respective ratio of 9 to 1 by weight. The evaluation criteria for the metallization was the mechanical bond strength of the contact, solderability, copper plating ability and electrical characteristics in terms of Voc, Isc values and shape of the V-I curve. The results revealed that the Dupont Ag paste #7095 mt all required criteria, while the quality of the cells metalized with the commercial Ni paste #5517 from Thick Film Systems, #7028-5 from Cermalloy as well as the experimental paste # X-A from Sollos, Inc. was below the acceptable standards. A significant improvement was obtained with the mixture of Ni paste #5517 from Thick Film Systems with 10% addition of Dupont paste # 7095.

Optimization of amino group density on surfaces of titanium dioxide nanoparticles covalently bonded to a silicone substrate for antibacterial and cell adhesion activities.

PubMed

Okada, Masahiro; Yasuda, Shoji; Kimura, Tsuyoshi; Iwasaki, Mitsunobu; Ito, Seishiro; Kishida, Akio; Furuzono, Tsutomu

2006-01-01

A composite consisting of titanium dioxide (TiO2) particle, the surface of which was modified with amino groups, and a silicone substrate through covalent bonding at their interface was developed, and antibacterial and cell adhesion activities of the composite were evaluated. The density of the amino groups on the TiO2 particle surface was controlled by the reaction time of the modification reaction. The degradation rate of CH3CHO in the presence of the TiO2 particles under UV irradiation decreased with an increase in the amino group density on the TiO2 surface. On the other hand, the number of L929 cells adhering on the TiO2/silicone composite increased with an increase in the amino group density. From the above two results, the optimum density of amino groups for both photoreactivity and cell adhesiveness was estimated to be 2.0-4.0 molecules/nm2. The optimum amino group-modified TiO2/silicone composite sheet (amino group density, 3.0 molecules/nm2) showed an effective antibacterial activity for Escherichia coli bacteria under UV irradiation. (c) 2005 Wiley Periodicals, Inc

Nano-Welding of Multi-Walled Carbon Nanotubes on Silicon and Silica Surface by Laser Irradiation

PubMed Central

Yuan, Yanping; Chen, Jimin

2016-01-01

In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm2) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on silica, after 3 s irradiation, nanoscale welding with good quality can be achieved due to breaking C–C bonds and formation of new graphene layers. While welding junctions can be formed until 10 s for the MWCNTs on silicon, the difference of irradiation time to achieve welding is attributed to the difference of thermal conductivity for silica and silicon. As the irradiation time is prolonged up to 12.5 s, most of the MWCNTs are welded to a silicon substrate, which leads to their frameworks of tube walls on the silicon surface. This is because the accumulation of absorbed energy makes the temperature rise. Then chemical reactions among silicon, carbon and nitrogen occur. New chemical bonds of Si–N and Si–C achieve the welding between the MWCNTs and silicon. Vibration modes of Si3N4 appear at peaks of 363 cm−1 and 663 cm−1. There are vibration modes of SiC at peaks of 618 cm−1, 779 cm−1 and 973 cm−1. The experimental observation proves chemical reactions and the formation of Si3N4 and SiC by laser irradiation. PMID:28344293

Silicon nitride Micromesh Bolometer Array for Submillimeter Astrophysics.

PubMed

Turner, A D; Bock, J J; Beeman, J W; Glenn, J; Hargrave, P C; Hristov, V V; Nguyen, H T; Rahman, F; Sethuraman, S; Woodcraft, A L

2001-10-01

We present the design and performance of a feedhorn-coupled bolometer array intended for a sensitive 350-mum photometer camera. Silicon nitride micromesh absorbers minimize the suspended mass and heat capacity of the bolometers. The temperature transducers, neutron-transmutation-doped Ge thermistors, are attached to the absorber with In bump bonds. Vapor-deposited electrical leads address the thermistors and determine the thermal conductance of the bolometers. The bolometer array demonstrates a dark noise-equivalent power of 2.9 x 10(-17) W/ radicalHz and a mean heat capacity of 1.3 pJ/K at 390 mK. We measure the optical efficiency of the bolometer and feedhorn to be 0.45-0.65 by comparing the response to blackbody calibration sources. The bolometer array demonstrates theoretical noise performance arising from the photon and the phonon and Johnson noise, with photon noise dominant under the design background conditions. We measure the ratio of total noise to photon noise to be 1.21 under an absorbed optical power of 2.4 pW. Excess noise is negligible for audio frequencies as low as 30 mHz. We summarize the trade-offs between bare and feedhorn-coupled detectors and discuss the estimated performance limits of micromesh bolometers. The bolometer array demonstrates the sensitivity required for photon noise-limited performance from a spaceborne, passively cooled telescope.

Substitution of ceramics for high temperature alloys. [advantages of using silicon carbides and silicon nitrides in gas turbine engines

NASA Technical Reports Server (NTRS)

Probst, H. B.

1978-01-01

The high temperature capability of ceramics such as silicon nitride and silicon carbide can result in turbine engines of improved efficiency. Other advantages when compared to the nickel and cobalt alloys in current use are raw material availability, lower weight, erosion/corrosion resistance, and potentially lower cost. The use of ceramics in three different sizes of gas turbine is considered; these are the large utility turbines, advanced aircraft turbines, and small automotive turbines. Special consideration, unique to each of these applications, arise when one considers substituting ceramics for high temperature alloys. The effects of material substitutions are reviewed in terms of engine performance, operating economy, and secondary effects.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

NASA Technical Reports Server (NTRS)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

Manufacture of sintered silicon nitrides

NASA Technical Reports Server (NTRS)

Iwai, T.

1985-01-01

Sintered silicon nitrides are manufactured by sintering Si3N powder containing 2 to 15% in wt of a powder mixture composed of nitride powder of lanthanide or Y 100 parts and AIN powder less than 100 parts at 1500 to 1900 deg. temperature under a pressure of less than 200 Kg/sq. cm. The sintered Si3N has high mechanical strength in high temperature. Thus, Si3N4 93.0, Y 5.0 and AlN 2.0% in weight were wet mixed in acetone in N atom, molded and sintered at 1750 deg. and 1000 Kg/sq. cm. to give a sintered body having high hardness.

Sandblasting nozzle

NASA Technical Reports Server (NTRS)

Perkins, G. S.; Pawlik, E. V.; Phillips, W. M. (Inventor)

1981-01-01

A nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al2O3, Y2O3 and Cr2O3, or mixtures of those compounds. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing.

[Synthesis of porous spherical silicon oxynitride material and evaluation of its properties in reversed-phase chromatographic separation].

PubMed

Zhong, Hongmin; Zhang, Hua; Wan, Huihui

2013-04-01

Silica has been widely used as HPLC column packing material. However, the fact that base can attack the silanol and dissolve the silica embarrasses the utilization of silica stationary phase in high pH mobile phases (pH >8). In our previous research, the use of porous spherical silicon oxynitride (sph-SiON) material from high temperature nitridation of silica microspheres as stationary phase for HPLC has been explored, and the sph-SiON is stable to alkaline mobile phases and demonstrates excellent separation of a variety of polar compounds in hydrophilic interaction liquid chromatography (HILIC) mode. Herein, the degree of nitridation was studied as a function of temperature of nitridation at 750-1 050 degrees C, yielding the silicon oxynitride with 0.40%-12.0% (mass fraction) nitrogen from elemental analysis. At the temperature of 1 050 degrees C, the nitrogen content increased from 12.0% to 24.5% with the nitridation time increasing from 20 h to 120 h. The sph-SiON is stable when disposed in different pH aqueous solutions for one week. The sph-SiON material can be modified to give hydrophobic surface through the reaction of surface Si-NHx with dimethyloctadecylchlorosilane. Elemental analysis and 13C cross-polarization magic-angle spinning (CP/MAS) NMR spectrum of C18-sph-SiON prove the integration of C18 alkyl groups attached onto the sph-SiON surface. The chromatographic evaluation of C18-sph-SiON in reversed-phase separation mode was performed with alkylbenzenes as hydrophobic probes. Three alkylbenzene compounds can be separated and retained well on C18-sph-SiON even in the mobile phase of methanol/H2O (70/30, v/v) with 78 507 plates/m, and an excellent tailing factor (0.95) can be obtained for ethylbenzene. In comparison with C18-SiO2, C18-sph-SiON shows distinct differences with respect to different classes of analytes, i. e. neutral analyte naphthalene, acidic analyte ibuprofen, and basic analyte amitriptyline.

Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

NASA Astrophysics Data System (ADS)

Yao, Guisheng; Li, Yong; Jiang, Peng; Jin, Xiuming; Long, Menglong; Qin, Haixia; Kumar, R. Vasant

2017-04-01

Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si3N4 and Si2N2O are formed as the nitridation products in the samples. Fibroid and short columnar Si3N4 are detected in the samples. The formation mechanisms of Si3N4 and Si2N2O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O2 in N2 atmosphere, forming a thin film of SiO2 on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO2 film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO2 film will crack, and N2 is infiltrated into the central section of the sample through cracks, generating Si2N2O and short columnar Si3N4 in situ. At the same time, metastable SiO(g) reacts with N2 and form fibroid Si3N4. In the regions where the oxygen partial pressure is high, Si3N4 is oxidized into Si2N2O.

Scaling Relations for Adsorption Energies on Doped Molybdenum Phosphide Surfaces

DOE PAGES

Fields, Meredith; Tsai, Charlie; Chen, Leanne D.; ...

2017-03-10

Molybdenum phosphide (MoP), a well-documented catalyst for applications ranging from hydrotreating reactions to electrochemical hydrogen evolution, has yet to be mapped from a more fundamental perspective, particularly in the context of transition-metal scaling relations. In this work, we use periodic density functional theory to extend linear scaling arguments to doped MoP surfaces and understand the behavior of the phosphorus active site. The derived linear relationships for hydrogenated C, N, and O species on a variety of doped surfaces suggest that phosphorus experiences a shift in preferred bond order depending on the degree of hydrogen substitution on the adsorbate molecule. Thismore » shift in phosphorus hybridization, dependent on the bond order of the adsorbate to the surface, can result in selective bond weakening or strengthening of chemically similar species. As a result, we discuss how this behavior deviates from transition-metal, sulfide, carbide, and nitride scaling relations, and we discuss potential applications in the context of electrochemical reduction reactions.« less

Q factor limitation at short wavelength (around 300 nm) in III-nitride-on-silicon photonic crystal cavities

NASA Astrophysics Data System (ADS)

Tabataba-Vakili, Farsane; Roland, Iannis; Tran, Thi-Mo; Checoury, Xavier; El Kurdi, Moustafa; Sauvage, Sébastien; Brimont, Christelle; Guillet, Thierry; Rennesson, Stéphanie; Duboz, Jean-Yves; Semond, Fabrice; Gayral, Bruno; Boucaud, Philippe

2017-09-01

III-nitride-on-silicon L3 photonic crystal cavities with resonances down to 315 nm and quality factors (Q) up to 1085 at 337 nm have been demonstrated. The reduction of the quality factor with decreasing wavelength is investigated. Besides the quantum well absorption below 340 nm, a noteworthy contribution is attributed to the residual absorption present in thin AlN layers grown on silicon, as measured by spectroscopic ellipsometry. This residual absorption ultimately limits the Q factor to around 2000 at 300 nm when no active layer is present.

Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

PubMed

Wang, Zhigao; Zhang, Xinghai; Wang, Fangqiang; Lan, Xinsheng; Zhou, Yiqian

2016-01-01

In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field.

Nitridation of silicon. M.S. Thesis Case Western Reserve Univ.

NASA Technical Reports Server (NTRS)

Shaw, N. J.

1981-01-01

Silicon powders with three levels of impurities, principally Fe, were sintered in He or H2. Non-densifying mechanisms of material transport were dominant in all cases. High purity Si showed coarsening in He while particle growth was suppressed in H2. Lower purity powder coarsened in both He and H2. The same three Si powders and Si /111/ single crystal wafers were nitrided in both N2 and N2/H2 atmospheres. Hydrogen increased the degree of nitridation of all three powders and the alpha/beta ratio of the lower purity powder. Some Si3N4 whiskers and open channels through the surface nitride layer were observed in the presence of Fe, correlating with the nitridation-enhancing effects of Fe. Thermodynamic calculations showed that when SiO2 is present on the Si, addition of H2 to the nitriding atmosphere decreases the amount of SiO2 and increases the partial pressure of Si-containing vapor species, that is, Si and SiO. Large amounts of NH3 and SiH4 were also predicted to form.

Combustion Synthesis Technology Applied to In-situ Resource Utilization

DTIC Science & Technology

2006-06-15

or bond energies. When both the precursor salts and the fuel are water soluble, a good homogenization can be achieved in the solution. In the...metallic compounds, e.g. Ni-Al. Steel processing additives, e.g. ferro-nitrides. Electrodes for electrolysis of corrosive media, e.g. TiN, TiB2...reactants; 4. Spreading of a molten phase; 5. Gasification of volatile impurities and reactants; 6. Chemical reaction with initial product formation; 7

Evaluation and ranking of candidate ceramic wafer engine seal materials

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

1991-01-01

Modern engineered ceramics offer high temperature capabilities not found in even the best superalloy metals. The high temperature properties of several selected ceramics including aluminum oxide, silicon carbide, and silicon nitride are reviewed as they apply to hypersonic engine seal design. A ranking procedure is employed to objectively differentiate among four different monolithic ceramic materials considered, including: a cold-pressed and sintered aluminum oxide; a sintered alpha-phase silicon carbide; a hot-isostatically pressed silicon nitride; and a cold-pressed and sintered silicon nitride. This procedure is used to narrow the wide range of potential ceramics considered to an acceptable number for future detailed and costly analyses and tests. The materials are numerically scored according to their high temperature flexural strength; high temperature thermal conductivity; resistance to crack growth; resistance to high heating rates; fracture toughness; Weibull modulus; and finally according to their resistance to leakage flow, where materials having coefficients of thermal expansion closely matching the engine panel material resist leakage flow best. The cold-pressed and sintered material (Kyocera SN-251) ranked the highest in the overall ranking especially when implemented in engine panels made of low expansion rate materials being considered for the engine, including Incoloy and titanium alloys.

Molecular transport through nanoporous silicon nitride membranes produced from self-assembling block copolymers.

PubMed

Montagne, Franck; Blondiaux, Nicolas; Bojko, Alexandre; Pugin, Raphaël

2012-09-28

To achieve fast and selective molecular filtration, membrane materials must ideally exhibit a thin porous skin and a high density of pores with a narrow size distribution. Here, we report the fabrication of nanoporous silicon nitride membranes (NSiMs) at the full wafer scale using a versatile process combining block copolymer (BCP) self-assembly and conventional photolithography/etching techniques. In our method, self-assembled BCP micelles are used as templates for creating sub-100 nm nanopores in a thin low-stress silicon nitride layer, which is then released from the underlying silicon wafer by etching. The process yields 100 nm thick free-standing NSiMs of various lateral dimensions (up to a few mm(2)). We show that the membranes exhibit a high pore density, while still retaining excellent mechanical strength. Permeation experiments reveal that the molecular transport rate across NSiMs is up to 16-fold faster than that of commercial polymeric membranes. Moreover, using dextran molecules of various molecular weights, we also demonstrate that size-based separation can be achieved with a very good selectivity. These new silicon nanosieves offer a relevant technological alternative to commercially available ultra- and microfiltration membranes for conducting high resolution biomolecular separations at small scales.

Design and fabrication of absorber coupled TES microbolometers on continuous silicon-nitride windows.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, C. L.; Carlstrom, J. E.; Datesman, A.

2008-04-01

The implementation of TES based microbolometer arrays will achieve unprecedented sensitivities for mm and sub-mm astronomy through fabrication of large format arrays and improved linearity and stability arising from strong electro-thermal feedback. We report on progress in developing TES microbolometers using Mo/Au thin films and Au absorbing structures. We present measurements of suppressing the thermal conductance through the etching of features on a continuous Silicon-Nitride window.

Storage Reliability of Missile Materiel Program, Monolithic Bipolar SSI/ MSI Digital and Linear Integrated Circuit Analysis

DTIC Science & Technology

1978-01-01

Beam Lead Sealed Junction (ELSJ) devices, the silicon nitride seals the devices from sodium and since the platinum silicide and titanium metals also...improve the surface stability of bipolar devices. These materials act as gettering agents for sodium ions, thus making the contamination far less...electric field, can cause appreciable device parameter instability. Silicon nitride has been shown to be an effective barrier to sodium migration. In

Mechanistic analysis of time-dependent failure of oxynitride glass-joined silicon nitride below 1000 degree C

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Brien, M.H.; Coon, D.M.

Time-dependent failure at elevated temperatures currently governs the service life of oxynitride glass-joined silicon nitride. Creep, devitrification, stress- aided oxidation-controlled slow crack growth, and viscous cabitation-controlled failure are examined as possible controlling mechanisms. Creep deformation failure is observed above 1000{degrees}C. Fractographic evidence indicates cavity formation and growth below 1000{degrees}C. Auger electron spectroscopy verified that the oxidation rate of the joining glass is governed by the oxygen supply rate. Time-to-failure data and those predicted using the Tsai and Raj, and Raj and Dang viscous cavitation models. It is concluded that viscous relaxation and isolated cavity growth control the rate of failuremore » in oxynitride glass-filled silicon nitride joints below 1000{degrees}C. Several possible methods are also proposed for increasing the service lives of these joints.« less

Quantum electromechanics on silicon nitride nanomembranes

PubMed Central

Fink, J. M.; Kalaee, M.; Pitanti, A.; Norte, R.; Heinzle, L.; Davanço, M.; Srinivasan, K.; Painter, O.

2016-01-01

Radiation pressure has recently been used to effectively couple the quantum motion of mechanical elements to the fields of optical or microwave light. Integration of all three degrees of freedom—mechanical, optical and microwave—would enable a quantum interconnect between microwave and optical quantum systems. We present a platform based on silicon nitride nanomembranes for integrating superconducting microwave circuits with planar acoustic and optical devices such as phononic and photonic crystals. Using planar capacitors with vacuum gaps of 60 nm and spiral inductor coils of micron pitch we realize microwave resonant circuits with large electromechanical coupling to planar acoustic structures of nanoscale dimensions and femtoFarad motional capacitance. Using this enhanced coupling, we demonstrate microwave backaction cooling of the 4.48 MHz mechanical resonance of a nanobeam to an occupancy as low as 0.32. These results indicate the viability of silicon nitride nanomembranes as an all-in-one substrate for quantum electro-opto-mechanical experiments. PMID:27484751

The Influence of Nano-Scale Silicon Nitride Additions on the Physical and Magnetic Properties of Iron Sheathed Magnesium Boride Wires

NASA Astrophysics Data System (ADS)

Zhu, W.; Cave, J.

2006-03-01

The enhancement of flux line pinning in magnesium boride wires is a critical issue for their future applications in devices and machines. It is well known that small size dopants can significantly influence the current densities of these materials. Here, the influence of nanometric (<30nm) silicon nitride on physical properties and current density is presented. The iron-sheathed powder in tube wires were prepared using pure magnesium and boron powders with silicon nitride additions. The wires were rolled flat and treated at up to 900 degrees C in flowing argon. SEM and XRD were used to identify phases and microstructures. Magnetization critical currents, up to several 100 of thousands A/cm2, at various temperatures and fields (5K - 20K and up to 3 tesla) show that there are competing mechanisms from chemical and flux pinning effects.

Ultra-thin alumina and silicon nitride MEMS fabricated membranes for the electron multiplication

NASA Astrophysics Data System (ADS)

Prodanović, V.; Chan, H. W.; Graaf, H. V. D.; Sarro, P. M.

2018-04-01

In this paper we demonstrate the fabrication of large arrays of ultrathin freestanding membranes (tynodes) for application in a timed photon counter (TiPC), a novel photomultiplier for single electron detection. Low pressure chemical vapour deposited silicon nitride (Si x N y ) and atomic layer deposited alumina (Al2O3) with thicknesses down to only 5 nm are employed for the membrane fabrication. Detailed characterization of structural, mechanical and chemical properties of the utilized films is carried out for different process conditions and thicknesses. Furthermore, the performance of the tynodes is investigated in terms of secondary electron emission, a fundamental attribute that determines their applicability in TiPC. Studied features and presented fabrication methods may be of interest for other MEMS application of alumina and silicon nitride as well, in particular where strong ultra-thin membranes are required.

Quantum electromechanics on silicon nitride nanomembranes.

PubMed

Fink, J M; Kalaee, M; Pitanti, A; Norte, R; Heinzle, L; Davanço, M; Srinivasan, K; Painter, O

2016-08-03

Radiation pressure has recently been used to effectively couple the quantum motion of mechanical elements to the fields of optical or microwave light. Integration of all three degrees of freedom-mechanical, optical and microwave-would enable a quantum interconnect between microwave and optical quantum systems. We present a platform based on silicon nitride nanomembranes for integrating superconducting microwave circuits with planar acoustic and optical devices such as phononic and photonic crystals. Using planar capacitors with vacuum gaps of 60 nm and spiral inductor coils of micron pitch we realize microwave resonant circuits with large electromechanical coupling to planar acoustic structures of nanoscale dimensions and femtoFarad motional capacitance. Using this enhanced coupling, we demonstrate microwave backaction cooling of the 4.48 MHz mechanical resonance of a nanobeam to an occupancy as low as 0.32. These results indicate the viability of silicon nitride nanomembranes as an all-in-one substrate for quantum electro-opto-mechanical experiments.

Synthesis of Silicon Nitride and Silicon Carbide Nanocomposites through High Energy Milling of Waste Silica Fume for Structural Applications

NASA Astrophysics Data System (ADS)

Suri, Jyothi

Nanocomposites have been widely used in a multitude of applications in electronics and structural components because of their improved mechanical, electrical, and magnetic properties. Silicon nitride/Silicon carbide (Si 3N4/SiC) nanocomposites have been studied intensively for low and high temperature structural applications, such as turbine and automobile engine components, ball bearings, turbochargers, as well as energy applications due to their superior wear resistance, high temperature strength, high oxidation resistance and good creep resistance. Silica fume is the waste material produced during the manufacture of silicon and ferro-silicon alloys, and contains 94 to 97 wt.% SiO2. In the present dissertation, the feasibility of using waste silica fume as the raw material was investigated to synthesize (I) advanced nanocomposites of Si3N4/SiC, and (2) porous silicon carbide (SiC) for membrane applications. The processing approach used to convert the waste material to advanced ceramic materials was based on a novel process called, integrated mechanical and thermal activation process (IMTA) process. In the first part of the dissertation, the effect of parameters such as carbothermic nitridation and reduction temperature and the graphite concentration in the starting silica fume plus graphite mixture, were explored to synthesize nanocomposite powders with tailored amounts of Si3N4 and SiC phases. An effective way to synthesize carbon-free Si3N 4/SiC composite powders was studied to provide a clear pathway and fundamental understanding of the reaction mechanisms. Si3N4/SiC nanocomposite powders were then sintered using two different approaches, based on liquid phase sintering and spark plasma sintering processes, with Al 2O3 and Y2O3 as the sintering aids. The nanocomposites were investigated for their densification behavior, microstructure, and mechanical properties. Si3N4/SiC nanocomposites thus obtained were found to possess superior mechanical properties at much lower costs. The second part of the work has comprised of the successful fabrication of bilayered SiC membranes with a graded porosity, consisting of porous nano-SiC layer on the surface of a porous coarse-grained SiC support layer. The effect of different particle sizes of SiC in the support layers was systematically studied. Also, the effects of sintering temperature were investigated to control the pore size, particle size and overall density of the bi-layered SiC membrane.

Mode-converting coupler for silicon-on-sapphire devices

NASA Astrophysics Data System (ADS)

Zlatanovic, S.; Offord, B. W.; Owen, M.; Shimabukuro, R.; Jacobs, E. W.

2015-02-01

Silicon-on-sapphire devices are attractive for the mid-infrared optical applications up to 5 microns due to the low loss of both silicon and sapphire in this wavelength band. Designing efficient couplers for silicon-on-sapphire devices presents a challenge due to a highly confined mode in silicon and large values of refractive index of both silicon and sapphire. Here, we present design, fabrication, and measurements of a mode-converting coupler for silicon-on-sapphire waveguides. We utilize a mode converter layout that consists of a large waveguide that is overlays a silicon inverse tapered waveguide. While this geometry was previously utilized for silicon-on-oxide devices, the novelty is in using materials that are compatible with the silicon-on-sapphire platform. In the current coupler the overlaying waveguide is made of silicon nitride. Silicon nitride is the material of choice because of the large index of refraction and low absorption from near-infrared to mid-infrared. The couplers were fabricated using a 0.25 micron silicon-on-sapphire process. The measured coupling loss from tapered lensed silica fibers to the silicon was 4.8dB/coupler. We will describe some challenges in fabrication process and discuss ways to overcome them.

Experimentally determined sulfur isotope fractionation between metal and silicate and implications for planetary differentiation

NASA Astrophysics Data System (ADS)

Labidi, J.; Shahar, A.; Le Losq, C.; Hillgren, V. J.; Mysen, B. O.; Farquhar, J.

2016-02-01

The Earth's mantle displays a subchondritic 34S/32S ratio. Sulfur is a moderately siderophile element (i.e. iron-loving), and its partitioning into the Earth's core may have left such a distinctive isotope composition on the terrestrial mantle. In order to constrain the sulfur isotope fractionation occurring during core-mantle differentiation, high-pressure and temperature experiments were conducted with synthetic mixtures of metal and silicate melts. With the purpose to identify the mechanism(s) responsible for the S isotope fractionations, we performed our experiments in different capsules - namely, graphite and boron nitride capsules - and thus at different fO2, with varying major element chemistry of the silicate and metal fractions. The S isotope fractionations Δ34Smetal-silicate of equilibrated metal alloys versus silicate melts is +0.2 ± 0.1‰ in a boron-free and aluminum-poor system quenched at 1-1.5 GPa and 1650 °C. The isotope fractionation increases linearly with increasing boron and aluminum content, up to +1.4 ± 0.2‰, and is observed to be independent of the silicon abundance as well as of the fO2 over ∼3.5 log units of variations explored here. The isotope fractionations are also independent of the graphite or nitride saturation of the metal. Only the melt structural changes associated with aluminum and boron concentration in silicate melts have been observed to affect the strength of sulfur bonding. These results establish that the structure of silicate melts has a direct influence on the S2- average bonding strengths. These results can be interpreted in the context of planetary differentiation. Indeed, the structural environments of silicate evolve strongly with pressure. For example, the aluminum, iron or silicon coordination numbers increase under the effect of pressure. Consequently, based on our observations, the sulfur-bonding environment is likely to be affected. In this scheme, we tentatively hypothesize that S isotope fractionations between the silicate mantle and metallic core of terrestrial planetary bodies would depend on the average pressure at which their core-mantle differentiation occurred.

The Hardest Superconducting Metal Nitride

DOE PAGES

Wang, Shanmin; Antonio, Daniel; Yu, Xiaohui; ...

2015-09-03

Transition–metal (TM) nitrides are a class of compounds with a wide range of properties and applications. Hard superconducting nitrides are of particular interest for electronic applications under working conditions such as coating and high stress (e.g., electromechanical systems). However, most of the known TM nitrides crystallize in the rock–salt structure, a structure that is unfavorable to resist shear strain, and they exhibit relatively low indentation hardness, typically in the range of 10–20 GPa. Here, we report high–pressure synthesis of hexagonal δ–MoN and cubic γ–MoN through an ion–exchange reaction at 3.5 GPa. The final products are in the bulk form withmore » crystallite sizes of 50 – 80 μm. Based on indentation testing on single crystals, hexagonal δ–MoN exhibits excellent hardness of ~30 GPa, which is 30% higher than cubic γ–MoN (~23 GPa) and is so far the hardest among the known metal nitrides. The hardness enhancement in hexagonal phase is attributed to extended covalently bonded Mo–N network than that in cubic phase. The measured superconducting transition temperatures for δ–MoN and cubic γ–MoN are 13.8 and 5.5 K, respectively, in good agreement with previous measurements.« less

The Hardest Superconducting Metal Nitride

NASA Astrophysics Data System (ADS)

Wang, Shanmin; Antonio, Daniel; Yu, Xiaohui; Zhang, Jianzhong; Cornelius, Andrew L.; He, Duanwei; Zhao, Yusheng

2015-09-01

Transition-metal (TM) nitrides are a class of compounds with a wide range of properties and applications. Hard superconducting nitrides are of particular interest for electronic applications under working conditions such as coating and high stress (e.g., electromechanical systems). However, most of the known TM nitrides crystallize in the rock-salt structure, a structure that is unfavorable to resist shear strain, and they exhibit relatively low indentation hardness, typically in the range of 10-20 GPa. Here, we report high-pressure synthesis of hexagonal δ-MoN and cubic γ-MoN through an ion-exchange reaction at 3.5 GPa. The final products are in the bulk form with crystallite sizes of 50 - 80 μm. Based on indentation testing on single crystals, hexagonal δ-MoN exhibits excellent hardness of ~30 GPa, which is 30% higher than cubic γ-MoN (~23 GPa) and is so far the hardest among the known metal nitrides. The hardness enhancement in hexagonal phase is attributed to extended covalently bonded Mo-N network than that in cubic phase. The measured superconducting transition temperatures for δ-MoN and cubic γ-MoN are 13.8 and 5.5 K, respectively, in good agreement with previous measurements.

A repeatable and scalable fabrication method for sharp, hollow silicon microneedles

NASA Astrophysics Data System (ADS)

Kim, H.; Theogarajan, L. S.; Pennathur, S.

2018-03-01

Scalability and manufacturability are impeding the mass commercialization of microneedles in the medical field. Specifically, microneedle geometries need to be sharp, beveled, and completely controllable, difficult to achieve with microelectromechanical fabrication techniques. In this work, we performed a parametric study using silicon etch chemistries to optimize the fabrication of scalable and manufacturable beveled silicon hollow microneedles. We theoretically verified our parametric results with diffusion reaction equations and created a design guideline for a various set of miconeedles (80-160 µm needle base width, 100-1000 µm pitch, 40-50 µm inner bore diameter, and 150-350 µm height) to show the repeatability, scalability, and manufacturability of our process. As a result, hollow silicon microneedles with any dimensions can be fabricated with less than 2% non-uniformity across a wafer and 5% deviation between different processes. The key to achieving such high uniformity and consistency is a non-agitated HF-HNO3 bath, silicon nitride masks, and surrounding silicon filler materials with well-defined dimensions. Our proposed method is non-labor intensive, well defined by theory, and straightforward for wafer scale mass production, opening doors to a plethora of potential medical and biosensing applications.

Fabrication of highly dense SiN4 ceramics without additives by high pressure sintering

NASA Technical Reports Server (NTRS)

Takatori, K.; Shimade, M.; Koizumi, M.

1984-01-01

Silicon nitride (Si3N4) is one of candidate materials for the engineering ceramics which is used at high temperatures. The mechanical strengths of hot pressed or sintered Si2N4 ceramics containing some amount of additives, however, are deteriorated at elevated temperatures. To improve the high temperature strength of Si3N4 ceramics, an attempt to consolidate Si3N4 without additives was made by high pressure sintering technique. Scanning electron micrographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully self-bonded sintered bodies were 310N sq m at room temperature and 174N/sq m at 1200 C.

Realization of an ultra-compact polarization beam splitter using asymmetric MMI based on silicon nitride / silicon-on-insulator platform.

PubMed

Sun, Xiao; Aitchison, J Stewart; Mojahedi, Mo

2017-04-03

We have experimentally demonstrated a compact polarization beam splitter (PBS) based on the silicon nitride/silicon-on-insulator platform using the recently proposed augmented-low-index-guiding (ALIG) waveguide structure. The two orthogonal polarizations are split in an asymmetric multimode interference (MMI) section, which was 1.6 μm wide and 4.8 μm long. The device works well over the entire C-band wavelength range and has a measured low insertion loss of less than 1 dB. The polarization extinction ratio at the Bar Port is approximately 17 dB and at the Cross Port is approximately 25 dB. The design of the device is robust and has a good fabrication tolerance.

Pushing the limits of CMOS optical parametric amplifiers with USRN:Si7N3 above the two-photon absorption edge

PubMed Central

Ooi, K. J. A.; Ng, D. K. T.; Wang, T.; Chee, A. K. L.; Ng, S. K.; Wang, Q.; Ang, L. K.; Agarwal, A. M.; Kimerling, L. C.; Tan, D. T. H.

2017-01-01

CMOS platforms operating at the telecommunications wavelength either reside within the highly dissipative two-photon regime in silicon-based optical devices, or possess small nonlinearities. Bandgap engineering of non-stoichiometric silicon nitride using state-of-the-art fabrication techniques has led to our development of USRN (ultra-silicon-rich nitride) in the form of Si7N3, that possesses a high Kerr nonlinearity (2.8 × 10−13 cm2 W−1), an order of magnitude larger than that in stoichiometric silicon nitride. Here we experimentally demonstrate high-gain optical parametric amplification using USRN, which is compositionally tailored such that the 1,550 nm wavelength resides above the two-photon absorption edge, while still possessing large nonlinearities. Optical parametric gain of 42.5 dB, as well as cascaded four-wave mixing with gain down to the third idler is observed and attributed to the high photon efficiency achieved through operating above the two-photon absorption edge, representing one of the largest optical parametric gains to date on a CMOS platform. PMID:28051064

Nondestructive evaluation of structural ceramics by photoacoustic microscopy

NASA Technical Reports Server (NTRS)

Khandelwal, Pramod K.

1987-01-01

A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failure initiating defects in substantially more specimens than microradiography and ultrasonic techniques. Photoacoustic microscopy detected 10 to 100 micron size surface and subsurface pores and inclusions, respectively, up to 80 microns below the interrogating surface in machined sintered silicon nitride. Microradiography detected 50 micron diameter fracture controlling pores and inclusions. Subsurface holes were detected up to a depth of 570 microns and 1.00 mm in sintered silicon nitride and silicon carbide, respectively. Seeded voids of 20 to 30 micron diameters at the surface and 50 microns below the interrogating surface were detected by photoacoustic microscopy and microradiography with 1 percent X-ray thickness sensitivity. Tight surface cracks of 96 micron length x 48 micron depth were detected by photoacoustic microscopy. PAM volatilized and removed material in the green state which resulted in linear shallow microcracks after sintering. This significantly limits the use of PAM as an in-process NDE technique.

Fabrication of close-packed TES microcalorimeter arrays using superconducting molybdenum/gold transition-edge sensors

NASA Astrophysics Data System (ADS)

Finkbeiner, F. M.; Brekosky, R. P.; Chervenak, J. A.; Figueroa-Feliciano, E.; Li, M. J.; Lindeman, M. A.; Stahle, C. K.; Stahle, C. M.; Tralshawala, N.

2002-02-01

We present an overview of our efforts in fabricating Transition-Edge Sensor (TES) microcalorimeter arrays for use in astronomical x-ray spectroscopy. Two distinct types of array schemes are currently pursued: 5×5 single pixel TES array where each pixel is a TES microcalorimeter, and Position-Sensing TES (PoST) array. In the latter, a row of 7 or 15 thermally-linked absorber pixels is read out by two TES at its ends. Both schemes employ superconducting Mo/Au bilayers as the TES. The TES are placed on silicon nitride membranes for thermal isolation from the structural frame. The silicon nitride membranes are prepared by a Deep Reactive Ion Etch (DRIE) process into a silicon wafer. In order to achieve the concept of closely packed arrays without decreasing its structural and functional integrity, we have already developed the technology to fabricate arrays of cantilevered pixel-sized absorbers and slit membranes in silicon nitride films. Furthermore, we have started to investigate ultra-low resistance through-wafer micro-vias to bring the electrical contact out to the back of a wafer. .

Joining of Silicon Carbide Through the Diffusion Bonding Approach

NASA Technical Reports Server (NTRS)

Halbig, Michael .; Singh, Mrityunjay

2009-01-01

In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Counter-rotating cavity solitons in a silicon nitride microresonator

NASA Astrophysics Data System (ADS)

Joshi, Chaitanya; Klenner, Alexander; Okawachi, Yoshitomo; Yu, Mengjie; Luke, Kevin; Ji, Xingchen; Lipson, Michal; Gaeta, Alexander L.

2018-02-01

We demonstrate the generation of counter-rotating cavity solitons in a silicon nitride microresonator using a fixed, single-frequency laser. We demonstrate a dual 3-soliton state with a difference in the repetition rates of the soliton trains that can be tuned by varying the ratio of pump powers in the two directions. Such a system enables a highly compact, tunable dual comb source that can be used for applications such as spectroscopy and distance ranging.

Crystallization of the glassy phase of grain boundaries in silicon nitride

NASA Technical Reports Server (NTRS)

Jefferson, D. A.; Thomas, J. M.; Wen, S.

1984-01-01

Three types of hot-pressed silicon nitride specimens (containing 5wt% Y2O3 and 2wt% Al2O3 additives) which were subjected to different temperature heat treatments were studied by X-ray diffraction, X-ray microanalysis and high resolution electron microscopy. The results indicated that there were phase changes in the grain boundaries after heat treatment and the glassy phase at the grain boundaries was crystallized by heat treatment.

Foreign Object Damage in Disks of Two Gas-turbine-grade Silicon Nitrides by Steel Ball Projectiles at Ambient Temperature

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Pereira, J. Michael; Janosik, Lesley A.; Bhatt, Ramakrishna T.

2003-01-01

Foreign object damage (FOD) behavior of two commercial gas-turbine-grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through postimpact strength testing of disks impacted by steel ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (k(sub Ic)). The critical impact velocity V(sub c) for which the corresponding postimpact strength was the lowest was V(sub c) approximately equal to 440 and 300 m/s AS800 and SN282, respectively. A unique lower strength regime was typified for both silicon nitrides depending on impact velocity and was attributed to significant radial cracking. The damage generated by projectile impact was typically in the form of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike the thick (4 millimeters) flexure bar specimens used in our previous studies, the thin (2 millimeter) disk target specimen exhibited a unique back-side radial cracking on the reverse side just beneath the impact sites at and above impact velocities of 160 meters per second for SN282 and 220 meters per second AS800.

Hydrothermal corrosion of silicon carbide joints without radiation

DOE PAGES

Koyanagi, Takaaki; Katoh, Yutai; Terrani, Kurt A.; ...

2016-09-28

In this paper, hydrothermal corrosion of four types of the silicon carbide (SiC) to SiC plate joints were investigated under pressurized water reactor and boiling water reactor relevant chemical conditions without irradiation. The joints were formed by metal diffusion bonding using molybdenum or titanium interlayer, reaction sintering using Ti—Si—C system, and SiC nanopowder sintering. Most of the joints withstood the corrosion tests for five weeks. The recession of the SiC substrates was limited. Based on the recession of the bonding layers, it was concluded that all the joints except for the molybdenum diffusion bond are promising under the reducing environmentsmore » without radiation. Finally, the SiC nanopowder sintered joint was the most corrosion tolerant under the oxidizing environment among the four joints.« less

Electron-beam induced damage in thin insulating films on compound semiconductors. M.S. Thesis, 1988

NASA Technical Reports Server (NTRS)

Pantic, Dragan M.

1989-01-01

Phosphorus rich plasma enhanced chemical vapor deposition (PECVD) of silicon nitride and silicon dioxide films on n-type indium phosphide (InP) substrates were exposed to electron-beam irradiation in the 5 to 40 keV range for the purpose of characterizing the damage induced in the dielectric. The electron-beam exposure was on the range of 10(exp -7) to 10(exp -3) C/sq cm. The damage to the devices was characterized by capacitance-voltage (C-V) measurements of the metal insulator semiconductor (MIS) capacitors. These results were compared to results obtained for radiation damage of thermal silicon dioxide on silicon (Si) MOS capacitors with similar exposures. The radiation induced damage in the PECVD silicon nitride films on InP was successfully annealed out in an hydrogen/nitrogen (H2/N2) ambient at 400 C for 15 min. The PECVD silicon dioxide films on InP had the least radiation damage, while the thermal silicon dioxide films on Si had the most radiation damage.

Dynamic Nuclear Polarization NMR Spectroscopy of Polymeric Carbon Nitride Photocatalysts: Insights into Structural Defects and Reactivity.

PubMed

Li, Xiaobo; Sergeyev, Ivan V; Aussenac, Fabien; Masters, Anthony F; Maschmeyer, Thomas; Hook, James M

2018-06-04

Metal-free polymeric carbon nitrides (PCNs) are promising photocatalysts for solar hydrogen production, but their structure-photoactivity relationship remains elusive. Two PCNs were characterized by dynamic-nuclear-polarization-enhanced solid-state NMR spectroscopy, which circumvented the need for specific labeling with either 13 C- or 15 N-enriched precursors. Rapid 1D and 2D data acquisition was possible, providing insights into the structural contrasts between the PCNs. Compared to PCN_B with lower performance, PCN_P is a more porous and more active photocatalyst that is richer in terminal N-H bonds not associated with interpolymer chains. It is proposed that terminal N-H groups act as efficient carrier traps and reaction sites. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Micro-machined thermo-conductivity detector

DOEpatents

Yu, Conrad

2003-01-01

A micro-machined thermal conductivity detector for a portable gas chromatograph. The detector is highly sensitive and has fast response time to enable detection of the small size gas samples in a portable gas chromatograph which are in the order of nanoliters. The high sensitivity and fast response time are achieved through micro-machined devices composed of a nickel wire, for example, on a silicon nitride window formed in a silicon member and about a millimeter square in size. In addition to operating as a thermal conductivity detector, the silicon nitride window with a micro-machined wire therein of the device can be utilized for a fast response heater for PCR applications.

Synthesis and Characterization of an f-Block Terminal Parent Imido [U=NH] Complex: A Masked Uranium(IV) Nitride

PubMed Central

2014-01-01

Deprotonation of [U(TrenTIPS)(NH2)] (1) [TrenTIPS = N(CH2CH2NSiPri3)3] with organoalkali metal reagents MR (M = Li, R = But; M = Na–Cs, R = CH2C6H5) afforded the imido-bridged dimers [{U(TrenTIPS)(μ-N[H]M)}2] [M = Li–Cs (2a–e)]. Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(TrenTIPS)(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride. The uranium–imido linkage was found to be essentially linear, and theoretical calculations suggested σ2π4 polarized U–N multiple bonding. Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(TrenTIPS)(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium–nitride complex [U(TrenTIPS)(N)] (5); this reaction is a new way to prepare the terminal uranium–nitride linkage and was calculated to be exothermic by −3.25 kcal mol–1. PMID:24697157

Boron nitride nanotube as a delivery system for platinum drugs: Drug encapsulation and diffusion coefficient prediction.

PubMed

Khatti, Zahra; Hashemianzadeh, Seyed Majid

2016-06-10

Molecular dynamics (MD) simulation has been applied to investigate a drug delivery system based on boron nitride nanotubes, particularly the delivery of platinum-based anticancer drugs. For this propose, the behavior of carboplatin drugs inserted in boron nitride nanotubes (BNNT) as a carrier was studied. The diffusion rate of water molecules and carboplatin was investigated inside functionalized and pristine boron nitride nanotubes. The penetration rate of water and drug in functionalized BNNT was higher than that in pristine BNNT due to favorable water-mediated hydrogen bonding in hydroxyl edge-functionalized BNNT. Additionally, the encapsulation of multiple carboplatin drugs inside functionalized boron nitride nanotubes with one to five drug molecules confined inside the nanotube cavity was examined. At high drug loading, the hydrogen bond formation between adjacent drugs and the non-bonded van der Waals interaction between carboplatin and functionalized BNNT inner surface were found to be influential in drug displacement within the functionalized BNNT cavity for higher drug-loading capacity. Copyright © 2016 Elsevier B.V. All rights reserved.

Silicon nitride sintered body

NASA Technical Reports Server (NTRS)

Suzuki, K.; Shinohara, N.

1984-01-01

The sintering of silicon carbide and it production are described. The method of production is by calcination in which molding is followed by sintering without compression. The invention improves the composition of the silicon carbide ceramic. Six examples of the invention are illustrated and discussed.

Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates

DTIC Science & Technology

2013-02-01

Nord, J.; Albe, K.; Erhart, P.; Nordlund, K. Modelling of Compound Semiconductors: Analytical Bond-order Potential for Gallium , Nitrogen and Gallium ...Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates by Iskander G. Batyrev, Chi-Chin Wu...Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates Iskander G. Batyrev and N. Scott Weingarten Weapons and

Nonlinear Silicon Photonics: Extending Platforms, Control, and Applications

NASA Astrophysics Data System (ADS)

Miller, Steven Andrew

Silicon photonics is a revolutionary technology that enables the control of light inside a silicon chip and holds promise to impact many applications from data center optical interconnects to optical sensing and even quantum optics. The tight confinement of light inside these chips greatly enhances light-matter interactions, making this an ideal platform for nonlinear photonics. Recently, microresonator-based Kerr frequency comb generation has become a prevalent emerging field, enabling the generation of a broadband optical pulse train by inputting a low-power continuous-wave laser into a low-loss chip-scale micro-cavity. These chip-scale combs have a wide variety of applications, including optical clocks, optical spectroscopy, and data communications. Several important applications in biological, chemical and atmospheric areas require combs generated in the visible and mid-infrared wavelength ranges, where there has been far less research and development compared with the near-infrared. Additionally, most platforms widely for combs are passive, limiting the ability to control and optimize the frequency combs. In this dissertation, we set out to address these shortcomings and introduce new tunability as well as wavelength flexibility in order to enable new applications for microresonator frequency combs. The silicon nitride platform for near-infrared combs is generally a passive platform with limited tuning capabilities. We overcome dispersion limitations in the visible range by leveraging the second-order nonlinearity of silicon nitride and demonstrate visible comb lines. We then further investigate the second-order nonlinearity of silicon nitride by measuring the linear electro-optic effect, a potential tuning mechanism. Finally, we introduce thermal tuning onto the silicon nitride platform and demonstrate tuning of the resonance extinction and dispersion of a micro-cavity using a coupled cavity design. We also address the silicon mid-infrared frequency comb platform. The transparency range of the traditional silicon platform prohibits operation beyond 4 mum wavelength. Here we show that a silicon photonics platform can be leveraged for broadband mid-infrared operation without introducing complexity in fabrication. Both an air-clad and fully suspended silicon platform can enable broadband, low-loss propagation and comb generation as high as 6 mum. We demonstrate a high quality factor resonator near 4 mum wavelength, more than an order of magnitude higher than the traditional platform. Finally, we discuss future avenues of research building on the work presented here.

Stochastic-Strength-Based Damage Simulation of Ceramic Matrix Composite Laminates

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Mital, Subodh K.; Murthy, Pappu L. N.; Bednarcyk, Brett A.; Pineda, Evan J.; Bhatt, Ramakrishna T.; Arnold, Steven M.

2016-01-01

The Finite Element Analysis-Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to characterize and predict the progressive damage response of silicon-carbide-fiber-reinforced reaction-bonded silicon nitride matrix (SiC/RBSN) composite laminate tensile specimens. Studied were unidirectional laminates [0] (sub 8), [10] (sub 8), [45] (sub 8), and [90] (sub 8); cross-ply laminates [0 (sub 2) divided by 90 (sub 2),]s; angled-ply laminates [plus 45 (sub 2) divided by -45 (sub 2), ]s; doubled-edge-notched [0] (sub 8), laminates; and central-hole laminates. Results correlated well with the experimental data. This work was performed as a validation and benchmarking exercise of the FEAMAC/CARES program. FEAMAC/CARES simulates stochastic-based discrete-event progressive damage of ceramic matrix composite and polymer matrix composite material structures. It couples three software programs: (1) the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC), (2) the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program (CARES/Life), and (3) the Abaqus finite element analysis program. MAC/GMC contributes multiscale modeling capabilities and micromechanics relations to determine stresses and deformations at the microscale of the composite material repeating-unit-cell (RUC). CARES/Life contributes statistical multiaxial failure criteria that can be applied to the individual brittle-material constituents of the RUC, and Abaqus is used to model the overall composite structure. For each FEAMAC/CARES simulation trial, the stochastic nature of brittle material strength results in random, discrete damage events that incrementally progress until ultimate structural failure.

Mechanical behavior and failure phenomenon of an in situ-toughened silicon nitride

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Choi, Sung R.; Freedman, Marc R.; Jenkins, Michael G.

1990-01-01

The Weibull modulus, fracture toughness and crack growth resistance of an in-situ toughened, silicon nitride material used to manufacture a turbine combustor were determined from room temperature to 1371 C. The material exhibited an elongated grain structure that resulted in improved fracture toughness, nonlinear crack growth resistance, and good elevated temperature strength. However, low temperature strength was limited by grains of excessive length (30 to 100 microns). These excessively long grains were surrounded by regions rich in sintering additives.

Realizing topological edge states in a silicon nitride microring-based photonic integrated circuit.

PubMed

Yin, Chenxuan; Chen, Yujie; Jiang, Xiaohui; Zhang, Yanfeng; Shao, Zengkai; Xu, Pengfei; Yu, Siyuan

2016-10-15

Topological edge states in a photonic integrated circuit based on the platform of silicon nitride are demonstrated with a two-dimensional coupled resonator optical waveguide array involving the synthetic magnetic field for photons at near-infrared wavelengths. Measurements indicate that the topological edge states can be observed at certain wavelengths, with light travelling around the boundary of the array. Combined with the induced disorders in fabrication near the edge, the system shows the defect immunity under the topological protection of edge states.

Processing and testing of high toughness silicon nitride ceramics

NASA Technical Reports Server (NTRS)

Tikare, Veena; Sanders, William A.; Choi, Sung R.

1993-01-01

High toughness silicon nitride ceramics were processed with the addition of small quantities of beta-Si3N4 whiskers in a commercially available alpha-Si3N4 powder. These whiskers grew preferentially during sintering resulting in large, elongated beta-grains, which acted to toughen the matrix by crack deflection and grain pullout. The fracture toughness of these samples seeded with beta-Si3N4 whiskers ranged from 8.7 to 9.5 MPa m(exp 0.5) depending on the sintering additives.

Storage Reliability of Missile Materiel Program. Storage Reliability Analysis Summary Report. Volume 1. Electrical and Electronic Devices

DTIC Science & Technology

1978-01-01

silicon nitride seals the devices from sodium and since the platinum silicide and titanium metals also offer very low mobility to the alkaline ions, the...of bipolar devices. These materials act as gettering agents for sodium ions, thus making the contamination far less mobile. The stability of the...parameter instability. Silicon nitride has been shown to be an effective barrier to sodium migration. In Beam Lead Sealed Junction (BLSJ) devices, the

Structural Analysis of a Magnetically Actuated Silicon Nitride Micro-Shutter for Space Applications

NASA Technical Reports Server (NTRS)

Loughlin, James P.; Fettig, Rainer K.; Moseley, S. Harvey; Kutyrev, Alexander S.; Mott, D. Brent; Obenschain, Arthur F. (Technical Monitor)

2002-01-01

Finite element models have been created to simulate the electrostatic and electromagnetic actuation of a 0.5 micrometers silicon nitride micro-shutter for use in a spacebased Multi-object Spectrometer (MOS). The microshutter uses a torsion hinge to go from the closed, 0 degree, position, to the open, 90 degree position. Stresses in the torsion hinge are determined with a large deformation nonlinear finite element model. The simulation results are compared to experimental measurements of fabricated micro-shutter devices.

Silicon Nitride Ceramic Fibers from Preceramic Polymers.

DTIC Science & Technology

1987-06-01

the preceramic fibers into high strength Si3 N and silicon carbide nitride (SiCN) fibers. In the past year, we have learned to prepare polysilazanes...INTHELOY, Given the Empirical Formula for a Material, It Should be Possible to Prepare a Chemical Analog CERAMC CHMIAL MONOMERIC UNIT MONOMERIC UNIT SI3 N4...e a d e nf u ible B y. POLYSILAZANE PRECURSORS TO Si3 Nj IN PRACTICE: It Is Difficult to Synthesize Even Simple, High Molecular Weight Preceramic

The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2012-01-01

Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These Include radiation, extreme temperatures, thermal cycling, to name a few. Preliminary data obtained on new Gallium Nitride and Silicon Carbide power devices under exposure to radiation followed by long term thermal cycling are presented. This work was done in collaboration with GSFC and JPL in support of the NASA Electronic Parts and Packaging (NEPP) Program

Enhanced saturation of sputtered amorphous SiN film frameworks using He- and Ne-Penning effects

NASA Astrophysics Data System (ADS)

Sugimoto, Iwao; Nakano, Satoko; Kuwano, Hiroki

1994-06-01

Optical emission spectroscopy reveals that helium and neon gases enhance the nitridation reactivity of the nitrogen plasma by Penning effects during magnetron sputtering of the silicon target. These excited nitrogen plasmas promote the saturation of frameworks of the resultant silicon nitride films. X-ray photoelectron spectroscopy, electron spin resonance, and x-ray diffraction analyses provide insight into the structure of these films, and thermal desorption mass spectroscopy reveals the behavior of volatile species in these films.

Strength evaluation test of pressureless-sintered silicon nitride at room temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Takahara, K.; Hashimoto, R.

1984-01-01

In order to study strength characteristics at room temperature and the strength evaluating method of ceramic materials, the following tests were conducted on pressureless sintered silicon nitride specimens: bending tests, the three tensile tests of rectangular plates, holed plates, and notched plates, and spin tests of centrally holed disks. The relationship between the mean strength of specimens and the effective volume of specimens are examined using Weibull's theory. The effect of surface grinding on the strength of specimens is discussed.

Low temperature production of large-grain polycrystalline semiconductors

DOEpatents

Naseem, Hameed A [Fayetteville, AR; Albarghouti, Marwan [Loudonville, NY

2007-04-10

An oxide or nitride layer is provided on an amorphous semiconductor layer prior to performing metal-induced crystallization of the semiconductor layer. The oxide or nitride layer facilitates conversion of the amorphous material into large grain polycrystalline material. Hence, a native silicon dioxide layer provided on hydrogenated amorphous silicon (a-Si:H), followed by deposited Al permits induced crystallization at temperatures far below the solid phase crystallization temperature of a-Si. Solar cells and thin film transistors can be prepared using this method.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Averichkin, P. A., E-mail: P-Yugov@mail.ru; Donskov, A. A.; Dukhnovsky, M. P.

The results of using carbidsiliconoxide (a-C:SiO1{sub .5}) films with a thickness of 30–60 nm, produced by the pyrolysis annealing of oligomethylsilseskvioksana (CH{sub 3}–SiO{sub 1.5}){sub n} with cyclolinear (staircased) molecular structure, as intermediate films in the hydride vapor phase epitaxy of gallium nitride on polycrystalline CVD-diamond substrates are presented. In the pyrolysis annealing of (CH{sub 3}–SiO{sub 1.5}){sub n} films in an atmosphere of nitrogen at a temperature of 1060°C, methyl radicals are carbonized to yield carbon atoms chemically bound to silicon. In turn, these atoms form a SiC monolayer on the surface of a-C:SiO{sub 1.5} films via covalent bonding with silicon.more » It is shown that GaN islands grow on such an intermediate layer on CVD-polydiamond substrates in the process of hydride vapor phase epitaxy in a vertical reactor from the GaCl–NH{sub 3}–N{sub 2} gas mixture.« less

Solar cell with a gallium nitride electrode

DOEpatents

Pankove, Jacques I.

1979-01-01

A solar cell which comprises a body of silicon having a P-N junction therein with a transparent conducting N-type gallium nitride layer as an ohmic contact on the N-type side of the semiconductor exposed to solar radiation.

Porous body infiltrating method

DOEpatents

Corman, Gregory Scot

2002-01-01

A mixture is formed that comprises at least some to about 10 wt % boron nitride and silicon. A body comprising a component that is wetted by or reacts with silicon is contacted with the mixture and the contacted body is infiltrated with silicon from the mixture.

Waveguide silicon nitride grating coupler

NASA Astrophysics Data System (ADS)

Litvik, Jan; Dolnak, Ivan; Dado, Milan

2016-12-01

Grating couplers are one of the most used elements for coupling of light between optical fibers and photonic integrated components. Silicon-on-insulator platform provides strong confinement of light and allows high integration. In this work, using simulations we have designed a broadband silicon nitride surface grating coupler. The Fourier-eigenmode expansion and finite difference time domain methods are utilized in design optimization of grating coupler structure. The fully, single etch step grating coupler is based on a standard silicon-on-insulator wafer with 0.55 μm waveguide Si3N4 layer. The optimized structure at 1550 nm wavelength yields a peak coupling efficiency -2.6635 dB (54.16%) with a 1-dB bandwidth up to 80 nm. It is promising way for low-cost fabrication using complementary metal-oxide- semiconductor fabrication process.

Hexagonal Ag nanoarrays induced enhancement of blue light emission from amorphous oxidized silicon nitride via localized surface plasmon coupling.

PubMed

Ma, Zhongyuan; Ni, Xiaodong; Zhang, Wenping; Jiang, Xiaofan; Yang, Huafeng; Yu, Jie; Wang, Wen; Xu, Ling; Xu, Jun; Chen, Kunji; Feng, Duan

2014-11-17

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays.

Are Nonadiabatic Reaction Dynamics the Key to Novel Organosilicon Molecules? The Silicon (Si(3P))-Dimethylacetylene (C4H6(X1A1g)) System as a Case Study.

PubMed

Thomas, Aaron M; Dangi, Beni B; Yang, Tao; Kaiser, Ralf I; Lin, Lin; Chou, Tzu-Jung; Chang, Agnes H H

2018-06-06

The bimolecular gas phase reaction of ground-state silicon (Si; 3 P) with dimethylacetylene (C 4 H 6 ; X 1 A 1g ) was investigated under single collision conditions in a crossed molecular beams machine. Merged with electronic structure calculations, the data propose nonadiabatic reaction dynamics leading to the formation of singlet SiC 4 H 4 isomer(s) and molecular hydrogen (H 2 ) via indirect scattering dynamics along with intersystem crossing (ISC) from the triplet to the singlet surface. The reaction may lead to distinct energetically accessible singlet SiC 4 H 4 isomers ( 1 p8- 1 p24) in overall exoergic reaction(s) (-107 -20 +12 kJ mol -1 ). All feasible reaction products are either cyclic, carry carbene analogous silylene moieties, or carry C-Si-H or C-Si-C bonds that would require extensive isomerization from the initial collision complex(es) to the fragmenting singlet intermediate(s). The present study demonstrates the first successful crossed beams study of an exoergic reaction channel arising from bimolecular collisions of silicon, Si( 3 P), with a hydrocarbon molecule.

Antifuse with a single silicon-rich silicon nitride insulating layer

DOEpatents

Habermehl, Scott D.; Apodaca, Roger T.

2013-01-22

An antifuse is disclosed which has an electrically-insulating region sandwiched between two electrodes. The electrically-insulating region has a single layer of a non-hydrogenated silicon-rich (i.e. non-stoichiometric) silicon nitride SiN.sub.X with a nitrogen content X which is generally in the range of 0

Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Y.; Roland, I.; Checoury, X.

We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities χ{sub zxx}{sup (2)}, χ{sub zyy}{sup (2)} and the electric fields of the fundamentalmore » cavity mode.« less

Synthesis of TiN/a-Si3N4 thin film by using a Mather type dense plasma focus system

NASA Astrophysics Data System (ADS)

Hussain, T.; R., Ahmad; Khalid, N.; A. Umar, Z.; Hussnain, A.

2013-05-01

A 2.3 kJ Mather type pulsed plasma focus device was used for the synthesis of a TiN/a-Si3N4 thin film at room temperature. The film was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD pattern confirms the growth of polycrystalline TiN thin film. The XPS results indicate that the synthesized film is non-stoichiometric and contains titanium nitride, silicon nitride, and a phase of silicon oxy-nitride. The SEM and AFM results reveal that the surface of the synthesized film is quite smooth with 0.59 nm roughness (root-mean-square).

Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

NASA Astrophysics Data System (ADS)

Wananuruksawong, R.; Jinawath, S.; Padipatvuthikul, P.; Wasanapiarnpong, T.

2011-10-01

Silicon nitride (Si3N4) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si3N4 ceramic as a dental core material. The white Si3N4 was prepared by pressureless sintering at relative low sintering temperature of 1650 °C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si3N4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si3N4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 wt% of zirconia powder (3 wt% Y2O3 - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si3N4 specimens, the firing was performed in electric tube furnace between 1000-1200°C. The veneered specimens fired at 1100°C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98×10-6 °C-1, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

Reaction pathways in remote plasma nitridation of ultrathin SiO2 films

NASA Astrophysics Data System (ADS)

Niimi, Hiro; Khandelwal, Amit; Lamb, H. Henry; Lucovsky, Gerald

2002-01-01

Low-temperature nitridation of 3 nm SiO2 films using He/N2 and N2 remote radio frequency (rf) plasmas was investigated. On-line Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy (ARXPS) were employed to determine the concentration, spatial distribution, and local chemical bonding of nitrogen in the resultant films. Experiments were performed using a substrate temperature of 300 °C and 30 W rf power. Nitridation using an upstream He/N2 remote plasma at 0.1 Torr incorporates nitrogen at the top surface of the SiO2 film. In contrast, a lower concentration of nitrogen distributed throughout the film is obtained when the process pressure is increased to 0.3 Torr. ARXPS indicates a N-Si3 local bonding configuration, irrespective of the spatial distribution of N atoms. Slightly more nitrogen is incorporated using a downstream He/N2 plasma at each process pressure. By comparison, nitridation of SiO2 films using a N2 remote plasma at 0.1 Torr is very slow. Optical emission spectroscopy indicates that He dilution enhances the generation of N2+(B 2Σu+) species by altering the plasma electron energy distribution and by providing an additional kinetic pathway (Penning ionization). Changing the He/N2 remote plasma configuration from upstream to downstream (at 0.1 and 0.3 Torr) also enhances N2+(B 2Σu+) generation. For upstream He/N2 remote plasmas, the intensity of N2 first positive emission from N2(B 3Πg) states increases with pressure, whereas the N2+ first negative emission from N2+(B 2Σu+) states decreases. We infer from these observations that N2+ species are primarily responsible for top surface nitridation at 0.1 Torr, and that neutral species [N2(A 3Σu+) metastables and N atoms] are associated with sub-surface nitrogen incorporation.

New frontiers of atomic layer etching

NASA Astrophysics Data System (ADS)

Sherpa, Sonam D.; Ranjan, Alok

2018-03-01

Interest in atomic layer etching (ALE) has surged recently because it offers several advantages over continuous or quasicontinuous plasma etching. These benefits include (1) independent control of ion energy, ion flux, and radical flux, (2) flux-independent etch rate that mitigates the iso-dense loading effects, and (3) ability to control the etch rate with atomic or nanoscale precision. In addition to these benefits, we demonstrate an area-selective etching for maskless lithography as a new frontier of ALE. In this paper, area-selective etching refers to the confinement of etching into the specific areas of the substrate. The concept of area-selective etching originated during our studies on quasi-ALE of silicon nitride which consists of sequential exposure of silicon nitride to hydrogen and fluorinated plasma. The findings of our studies reported in this paper suggest that it may be possible to confine the etching into specific areas of silicon nitride without using any mask by replacing conventional hydrogen plasma with a localized source of hydrogen ions.

Hydrogenated amorphous silicon nitride photonic crystals for improved-performance surface electromagnetic wave biosensors.

PubMed

Sinibaldi, Alberto; Descrovi, Emiliano; Giorgis, Fabrizio; Dominici, Lorenzo; Ballarini, Mirko; Mandracci, Pietro; Danz, Norbert; Michelotti, Francesco

2012-10-01

We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

Redeposition in plasma-assisted atomic layer deposition: Silicon nitride film quality ruled by the gas residence time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knoops, Harm C. M., E-mail: h.c.m.knoops@tue.nl, E-mail: w.m.m.kessels@tue.nl; Oxford Instruments Plasma Technology, North End, Bristol BS49 4AP; Peuter, K. de

2015-07-06

The requirements on the material properties and growth control of silicon nitride (SiN{sub x}) spacer films in transistors are becoming ever more stringent as scaling of transistor structures continues. One method to deposit high-quality films with excellent control is atomic layer deposition (ALD). However, depositing SiN{sub x} by ALD has turned out to be very challenging. In this work, it is shown that the plasma gas residence time τ is a key parameter for the deposition of SiN{sub x} by plasma-assisted ALD and that this parameter can be linked to a so-called “redeposition effect”. This previously ignored effect, which takesmore » place during the plasma step, is the dissociation of reaction products in the plasma and the subsequent redeposition of reaction-product fragments on the surface. For SiN{sub x} ALD using SiH{sub 2}(NH{sup t}Bu){sub 2} as precursor and N{sub 2} plasma as reactant, the gas residence time τ was found to determine both SiN{sub x} film quality and the resulting growth per cycle. It is shown that redeposition can be minimized by using a short residence time resulting in high-quality films with a high wet-etch resistance (i.e., a wet-etch rate of 0.5 nm/min in buffered HF solution). Due to the fundamental nature of the redeposition effect, it is expected to play a role in many more plasma-assisted ALD processes.« less

Silicon-on-Insulator Pin Diodes.

DTIC Science & Technology

1987-12-01

Thin (0.5 Micron) Silicon-on-Oxidized Silicon Fig. 2.8 SEM Photographs of CVD Silicon Dioxide on Aluminum 28 After 1500 0 C Anneal in Oxygen...silicon nitride over the silicon dioxide encapsu- -9- lation layer and by depositing the silicon dioxide with a plasma CVD process which uses N20 as...relief via thermal expansion matching varies lin- -27- A B Figure 2.8: SEM Photographs of CVD Silicon Dioxide on Aluminum after 15000 C Anneal in Oxygen

Joining and Integration of Silicon Nitride Ceramics for Aerospace and Energy Systems

NASA Technical Reports Server (NTRS)

Singh, M.; Asthana, R.

2009-01-01

Light-weight, creep-resistant silicon nitride ceramics possess excellent high-temperature strength and are projected to significantly raise engine efficiency and performance when used as turbine components in the next-generation turbo-shaft engines without the extensive cooling that is needed for metallic parts. One key aspect of Si3N4 utilization in such applications is its joining response to diverse materials. In an ongoing research program, the joining and integration of Si3N4 ceramics with metallic, ceramic, and composite materials using braze interlayers with the liquidus temperature in the range 750-1240C is being explored. In this paper, the self-joining behavior of Kyocera Si3N4 and St. Gobain Si3N4 using a ductile Cu-based active braze (Cu-ABA) containing Ti will be presented. Joint microstructure, composition, hardness, and strength as revealed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Knoop microhardness test, and offset compression shear test will be presented. Additionally, microstructure, composition, and joint strength of Si3N4/Inconel 625 joints made using Cu-ABA, will be presented. The results will be discussed with reference to the role of chemical reactions, wetting behavior, and residual stresses in joints.

Parallel fabrication of sub-50-nm uniformly sized nanoparticles by deposition through a patterned silicon nitride nanostencil.

PubMed

Yan, X-M; Contreras, A M; Koebel, M M; Liddle, J A; Somorjai, G A

2005-06-01

Using low-pressure chemical vapor deposition of silicon dioxide, we have reduced the size of 56-nm features in a silicon nitride membrane, called a stencil, down to 36 nm. Sub-50-nm uniformly sized nanoparticles are fabricated by electron-beam deposition of Pt through the stencil mask. A self-assembled monolayer (SAM) of tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane was used to reduce Pt clogging of the nanosize holes during deposition as well as to protect the stencil during the postdeposition Pt removal. X-ray photoelectron spectroscopy shows that the SAM protects the stencil efficiently during this postdeposition removal of Pt.

Degradation of GaAs/AlGaAs Quantized Hall Resistors With Alloyed AuGe/Ni Contacts.

PubMed

Lee, Kevin C

1998-01-01

Careful testing over a period of 6 years of a number of GaAs/AlGaAs quantized Hall resistors (QHR) made with alloyed AuGe/Ni contacts, both with and without passivating silicon nitride coatings, has resulted in the identification of important mechanisms responsible for degradation in the performance of the devices as resistance standards. Covering the contacts with a film, such as a low-temperature silicon nitride, that is impervious to humidity and other contaminants in the atmosphere prevents the contacts from degrading. The devices coated with silicon nitride used in this study, however, showed the effects of a conducting path in parallel with the 2-dimensional electron gas (2-DEG) at temperatures above 1.1 K which interferes with their use as resistance standards. Several possible causes of this parallel conduction are evaluated. On the basis of this work, two methods are proposed for protecting QHR devices with alloyed AuGe/Ni contacts from degradation: the heterostructure can be left unpassivated, but the alloyed contacts can be completely covered with a very thick (> 3 μm) coating of gold; or the GaAs cap layer can be carefully etched away after alloying the contacts and prior to depositing a passivating silicon nitride coating over the entire sample. Of the two, the latter is more challenging to effect, but preferable because both the contacts and the heterostructure are protected from corrosion and oxidation.

Type-II Superlattice Avalanche Photodiodes

NASA Astrophysics Data System (ADS)

Huang, Jun

Type-II superlattice avalanche photodiodes have shown advantages compared to conventional mercury cadmium telluride photodiodes for infrared wavelength detection. However, surface or interface leakage current has been a major issue for superlattice avalanche photodiodes, especially in infrared wavelength region. First, passivation of the superlattice device with ammonium sulfide and thioacetamide was carried out, and its surface quality was studied by X-ray Photoelectron Spectroscopy. The study showed that both ammonium sulfide and thiacetamide passivation can actively remove the native oxide at the surface. Thiacetamide passivation combine more sulfur bonds with III-V elements than that of ammonium sulfide. Another X-ray photoelectron spectra of thiacetamide-treated atomic layer deposited zinc sulfide capped InAs/GaSb superlattice was performed to investigate the interface sulfur bond conditions. Sb--S and As--S bonds disappear while In-S bond gets enhanced, indicating that Indium Sulfide should be the major components at the interface after ZnS deposition. Second, the simulation of electrical characteristics for zinc sulfide, silicon nitride and silicon dioxide passivated superlattice devices was performed by SILVACO software to fit the experimental results and to discover the surface current mechanism. Different surface current mechanism strengths were found. Third, several novel dual-carrier avalanche photodiode structures were designed and simulated. The structures had alternate carrier multiplication regions, placed next to a wider electron multiplication region, creating dual-carrier multiplication feedback systems. Gain and excess noise factor of these structures were simulated and compared based on the dead space multiplication theory under uniform electric field. From the simulation, the applied bias can be greatly lowered or the thickness can be shrunk to achieve the same gain from the conventional device. The width of the thin region was the most critical parameter determining the device performance.

Bond Sensitivity to Silicone Contamination

NASA Technical Reports Server (NTRS)

Caldwell, G. A.; Hudson, W. D.; Hudson, W. D.; Cash, Stephen F. (Technical Monitor)

2003-01-01

Currently during fabrication of the Space Shuttle booster rocket motors, the use of silicone and silicone-containing products is prohibited in most applications. Many shop aids and other materials containing silicone have the potential, if they make contact with a bond surface, to transfer some of the silicone to the substrates being bonded. Such transfer could result in a reduction of the bond strength or even failure of the subsequent bonds. This concern is driving the need to understand the effect of silicones and the concentration needed to affect a given bond-line strength. Additionally, as silicone detection methods used for materials acceptance improve what may have gone unnoticed earlier is now being detected. Thus, realistic silicone limits for process materials (below which bond performance is satisfactory) are needed rather than having an absolute no silicone permitted policy.

Improving optical properties of silicon nitride films to be applied in the middle infrared optics by a combined high-power impulse/unbalanced magnetron sputtering deposition technique.

PubMed

Liao, Bo-Huei; Hsiao, Chien-Nan

2014-02-01

Silicon nitride films are prepared by a combined high-power impulse/unbalanced magnetron sputtering (HIPIMS/UBMS) deposition technique. Different unbalance coefficients and pulse on/off ratios are applied to improve the optical properties of the silicon nitride films. The refractive indices of the Si3N4 films vary from 2.17 to 2.02 in the wavelength ranges of 400-700 nm, and all the extinction coefficients are smaller than 1×10(-4). The Fourier transform infrared spectroscopy and x-ray diffractometry measurements reveal the amorphous structure of the Si3N4 films with extremely low hydrogen content and very low absorption between the near IR and middle IR ranges. Compared to other deposition techniques, Si3N4 films deposited by the combined HIPIMS/UBMS deposition technique possess the highest refractive index, the lowest extinction coefficient, and excellent structural properties. Finally a four-layer coating is deposited on both sides of a silicon substrate. The average transmittance from 3200 to 4800 nm is 99.0%, and the highest transmittance is 99.97% around 4200 nm.

Novel Bonding Technology for Hermetically Sealed Silicon Micropackage

NASA Astrophysics Data System (ADS)

Lee, Duck-Jung; Ju, Byeong-Kwon; Choi, Woo-Beom; Jeong, Jee-Won; Lee, Yun-Hi; Jang, Jin; Lee, Kwang-Bae; Oh, Myung-Hwan

1999-01-01

We performed glass-to-silicon bonding and fabricated a hermetically sealed silicon wafer using silicon direct bonding followed by anodic bonding (SDAB). The hydrophilized glass and silicon wafers in solution were dried and initially bonded in atmosphere as in the silicon direct bonding (SDB) process, but annealing at high temperature was not performed. Anodic bonding was subsequently carried out for the initially bonded specimens. Then the wafer pairs bonded by the SDAB method were different from those bonded by the anodic bonding process only. The effects of the bonding process on the bonded area and tensile strength were investigated as functions of bonding temperature and voltage. Using scanning electron microscopy (SEM), the cross-sectional view of the bonded interface region was observed. In order to investigate the migration of the sodium ions in the bonding process, the concentration of the bonded glass was compared with that of standard glass. The specimen bonded using the SDAB process had higher efficiency than that using the anodic bonding process only.

Experimental and Computational Exploration of para-Selective Silylation with a Hydrogen-Bonded Template.

PubMed

Maji, Arun; Guin, Srimanta; Feng, Sheng; Dahiya, Amit; Singh, Vikas Kumar; Liu, Peng; Maiti, Debabrata

2017-11-20

The regioselective conversion of C-H bonds into C-Si bonds is extremely important owing to the natural abundance and non-toxicity of silicon. Classical silylation reactions often suffer from poor functional group compatibility, low atom economy, and insufficient regioselectivity. Herein, we disclose a template-assisted method for the regioselective para silylation of toluene derivatives. A new template was designed, and the origin of selectivity was analyzed experimentally and computationally. An interesting substrate-solvent hydrogen-bonding interaction was observed. Kinetic, spectroscopic, and computational studies shed light on the reaction mechanism. The synthetic significance of this strategy was highlighted by the generation of a precursor of a potential lipophilic bioisostere of γ-aminobutyric acid (GABA), various late-stage diversifications, and by mimicking enzymatic transformations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

B-H Bond Activation by an Amidinate-Stabilized Amidosilylene: Non-Innocent Amidinate Ligand.

PubMed

Khoo, Sabrina; Shan, Yu-Liang; Yang, Ming-Chung; Li, Yongxin; Su, Ming-Der; So, Cheuk-Wai

2018-05-21

The activation of B-H and B-Cl bonds in boranes by base-stabilized low-valent silicon compounds is described. The reaction of the amidinato amidosilylene-borane adduct [L{Ar(Me 3 Si)N}SiBH 3 ] [1; L = PhC(N tBu) 2 , and Ar = 2,6- iPr 2 C 6 H 3 ] with MeOTf in toluene at room temperature formed [L{Ar(Me 3 Si)N}SiBH 2 OTf] (2). [LSiN(SiMe 3 )Ar] in compound 2 then underwent a B-H bond activation with BH 2 OTf in refluxing toluene to afford the B-H bond activation product [LB(H)Si(H)(OTf){N(SiMe 3 )Ar}] (3). On the other hand, when compound 2 was reacted with 4-dimethylaminopyridine in refluxing toluene, another B-H bond activation product [(μ-κ1:κ1-L)B(H)(DMAP)Si(H){N(Ar)SiMe 3 }]OTf (4) was afforded. Mechanistic studies show that "(μ-κ1:κ1-L)B(H)(OTf)Si(H){N(Ar)SiMe 3 }" (2A) is the key intermediate in the reactions mentioned above. The formation of 2A is further evidenced by the activation of the B-Cl bond in PhBCl 2 by the amidinato silicon(I) dimer [LSi:] 2 to form the B-Cl bond activation product [(μ-κ1:κ1-L)B(Cl)(Ph)Si(Cl)] 2 (6). Compounds 2-4 and 6 were characterized by nuclear magnetic resonance spectroscopy and X-ray crystallography.

Sialons as high temperature insulators

NASA Technical Reports Server (NTRS)

Phillips, W. M.; Kuo, Y. S.

1978-01-01

Sialons were evaluated for application as high temperature electrical insulators in contact with molybdenum and tungsten components in hard vacuum applications. Both D.C. and variable frequency A.C. resistivity data indicate the sialons to have electrical resistivity similar to common oxide in the 1000 C or higher range. Metallographic evaluations indicate good bonding of the type 15R ALN polytype to molybdenum and tungsten. The beta prime or modified silicon nitride phase was unacceptable in terms of vacuum stability. Additives effect on electrical resistivity. Similar resistivity decreases were produced by additions of molybdenum or tungsten to form cermets. The use of hot pressing at 1800 C with ALN, Al2 O3 and Si3N4 starting powders produced a better product than did a combination of SiO2 and AIN staring powders. It was indicated that sialons will be suitable insulators in the 1600K range in contact with molybdenum or tungsten if they are produced as a pure ceramic and subsequently bonded to the metal components at temperatures in the 1600K range.

Electron beam induced damage in PECVD Si3N4 and SiO2 films on InP

NASA Technical Reports Server (NTRS)

Pantic, Dragan M.; Kapoor, Vik J.; Young, Paul G.; Williams, Wallace D.; Dickman, John E.

1990-01-01

Phosphorus rich plasma enhanced chemical vapor deposition (PECVD) of silicon nitride and silicon dioxide films on n-type indium phosphide (InP) substrates were exposed to electron beam irradiation in the 5 to 40 keV range for the purpose of characterizing the damage induced in the dielectic. The electron beam exposure was on the range of 10(exp -7) to 10(exp -3) C/sq cm. The damage to the devices was characterized by capacitance-voltage (C-V) measurements of the metal insulator semiconductor (MIS) capacitors. These results were compared to results obtained for radiation damage of thermal silicon dioxide on silicon (Si) MOS capacitors with similar exposures. The radiation induced damage in the PECVD silicon nitride films on InP was successfully annealed out in an hydrogen/nitrogen (H2/N2) ambient at 400 C for 15 min. The PECVD silicon dioxide films on InP had the least radiation damage, while the thermal silicon dioxide films on Si had the most radiation damage.

Closed-cycle hydrogen-fueled engine

NASA Technical Reports Server (NTRS)

Laumann, E. A.; Reynolds, R. K.

1977-01-01

Innovation avoids pollution by retaining combustion products. Potential uses include applicability to pollution-free powerplant using intermittent solar energy. Engine parts are fabricated from silicon carbide, silicon nitride, stainless steel, and other high-tensile strength materials.

Multisite silicon neural probes with integrated silicon nitride waveguides and gratings for optogenetic applications.

PubMed

Shim, Euijae; Chen, Yu; Masmanidis, Sotiris; Li, Mo

2016-03-04

Optimal optogenetic perturbation of brain circuit activity often requires light delivery in a precise spatial pattern that cannot be achieved with conventional optical fibers. We demonstrate an implantable silicon-based probe with a compact light delivery system, consisting of silicon nitride waveguides and grating couplers for out-of-plane light emission with high spatial resolution. 473 nm light is coupled into and guided in cm-long waveguide and emitted at the output grating coupler. Using the direct cut-back and out-scattering measurement techniques, the propagation optical loss of the waveguide is measured to be below 3 dB/cm. The grating couplers provide collimated light emission with sufficient irradiance for neural stimulation. Finally, a probe with multisite light delivery with three output grating emitters from a single laser input is demonstrated.

Recent Advances in Photoelectrochemical Applications of Silicon Materials for Solar-to-Chemicals Conversion.

PubMed

Zhang, Doudou; Shi, Jingying; Zi, Wei; Wang, Pengpeng; Liu, Shengzhong Frank

2017-11-23

Photoelectrochemical (PEC) technology for the conversion of solar energy into chemicals requires cost-effective photoelectrodes to efficiently and stably drive anodic and/or cathodic half-reactions to complete the overall reactions for storing solar energy in chemical bonds. The shared properties among semiconducting photoelectrodes and photovoltaic (PV) materials are light absorption, charge separation, and charge transfer. Earth-abundant silicon materials have been widely applied in the PV industry, and have demonstrated their efficiency as alternative photoabsorbers for photoelectrodes. Many efforts have been made to fabricate silicon photoelectrodes with enhanced performance, and significant progress has been achieved in recent years. Herein, recent developments in crystalline and thin-film silicon-based photoelectrodes (including amorphous, microcrystalline, and nanocrystalline silicon) immersed in aqueous solution for PEC hydrogen production from water splitting are summarized, as well as applications in PEC CO 2 reduction and PEC regeneration of discharged species in redox flow batteries. Silicon is an ideal material for the cost-effective production of solar chemicals through PEC methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of unexpected silicon- and disiloxane-bridged multiferrocenyl derivatives bearing Si-O-CH[double bond, length as m-dash]CH2 and Si-(CH2)2C(CH3)3 substituents via cleavage of tetrahydrofuran and trapping of its ring fragments.

PubMed

Bruña, Sonia; González-Vadillo, Ana Mª; Ferrández, Marta; Perles, Josefina; Montero-Campillo, M Merced; Mó, Otilia; Cuadrado, Isabel

2017-09-12

The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc 2 (CH 3 ) 3 C(CH 2 ) 2 SiCH[double bond, length as m-dash]CH 2 (5), Fc 2 (CH 2 [double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH 2 (6), Fc 2 (OH)SiCH[double bond, length as m-dash]CH 2 (7), Fc 2 (CH 2 [double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH 2 )Fc 2 (8) and Fc 2 (CH 2 [double bond, length as m-dash]CH-O)Si-O-SiFc 3 (9) is described. Silyl vinyl ether molecules 6, 8 and 9 and the heteroleptic vinylsilane 5 resulted from the competing metathesis reaction of lithioferrocene (FcLi), CH 2 [double bond, length as m-dash]CH-OLi or (CH 3 ) 3 C(CH 2 ) 2 Li with the corresponding multifunctional chlorosilane, Cl 3 SiCH[double bond, length as m-dash]CH 2 or Cl 3 Si-O-SiCl 3 . The last two organolithium species have been likely formed in situ by fragmentation of the tetrahydrofuran solvent. Diferrocenylvinyloxyvinylsilane 6 is noteworthy since it represents a rare example of a redox-active silyl mononomer in which two different C[double bond, length as m-dash]C polymerisable groups are directly connected to silicon. The molecular structures of the silicon-containing multiferrocenyl species 5, 6, 8 and 9 have been investigated by single-crystal X-ray diffraction studies, demonstrating the capture and storage processes of two ring fragments resulting from the cleavage of cyclic THF in redox-active and stable crystalline organometallic compounds. From electrochemical studies we found that by changing the anion of the supporting electrolyte from [PF 6 ] - to [B(C 6 F 5 ) 4 ] - , the redox behaviour of tetrametallic disiloxane 8 can be switched from a poorly resolved multistep redox process to four consecutive well-separated one-electron oxidations, corresponding to the sequential oxidation of the four ferrocenyl moieties.

Measurement and Control of In-plane Surface Chemistry at the Silicon/Silicon Dioxide Interface

NASA Astrophysics Data System (ADS)

Gokce, Bilal

In-plane directional control of surface chemistry during interface formation can lead to new opportunities regarding device structures and applications. Control of this type requires techniques that can probe and hence provide feedback on the chemical reactivity of bonds not only in specific directions but also in real time. In this thesis work, I demonstrate both control and measurement of the oxidation of H-terminated Si(111). The nonlinear optical tool of Second-Harmonic-Generation (SHG) is used to show that Si oxidation in air is a two-stage process where the H of the "up" bonds of the outermost Si layer is replaced by OH, followed by O insertion into the "back" bonds. Detailed information about both stages is revealed by investigating the effect of uniaxial strain and carrier concentration on this chemical reaction. It is shown that even small amounts of strain manipulate the reaction kinetics of surface bonds significantly, with tensile strain enhancing oxidation and compressive strain retarding it. This dramatic change suggests a strain-driven charge transfer mechanism between Si--H up bonds and Si--Si back bonds in the outer layer of Si atoms. Data on differently doped samples reveal that high concentrations of electrons increase the chemical reactivity of the outer-layer Si--Si back bonds relative to the Si--H up bonds while high concentrations of holes cause a greater increase in the reactivity of the Si--H up bonds than that of the Si--Si back bonds. However, the thicknesses of the natural oxides of all samples follow the same path and stabilize near 1 nm at room temperature, regardless of the chemical kinetics of the different bonds, as determined by spectroscopic ellipsometry. Real-time measurement during SHG experiments is achieved by analyzing SHG anisotropy data with the anisotropic bond-charge model of nonlinear optics where peaks in the SHG spectrum are correlated with the near alignment of bonds to the direction of the excitation field.

Compositional analysis of dilute nitride doped indium antimonide bulk crystal by VDS technique

NASA Astrophysics Data System (ADS)

Deshpande, Manisha; Maske, Dilip; Choudhari, Rashmi; Arora, Brij Mohan; Gadkari, Dattatray

2016-05-01

Dilute nitrides are suitable materials for fabrication of devices in detection of long wavelength infrared region. Dilute nitride doped Indium antimonide bulk crystals were grown using vertical directional solidification technique. The compositional characteristics of the crystals were carried out using EDS. The analysis was simulated and compared with observations using DTSA II software for accuracy. The ingots have uniform composition of Indium and Antimony. The actual nitrogen composition measured using EDS was 0.136% for doped nitrogen composition 0.1% except near conical end where it was 0.1%. The study of bonding between nitrogen, Indium and antimony was carried out using SIMS. The analysis shows strong presence of In-N bonding along with In-Sb bonds which indicates nitrogen has replaced antimony atoms in crystal lattice.

Development of a templated approach to fabricate diamond patterns on various substrates.

PubMed

Shimoni, Olga; Cervenka, Jiri; Karle, Timothy J; Fox, Kate; Gibson, Brant C; Tomljenovic-Hanic, Snjezana; Greentree, Andrew D; Prawer, Steven

2014-06-11

We demonstrate a robust templated approach to pattern thin films of chemical vapor deposited nanocrystalline diamond grown from monodispersed nanodiamond (mdND) seeds. The method works on a range of substrates, and we herein demonstrate the method using silicon, aluminum nitride (AlN), and sapphire substrates. Patterns are defined using photo- and e-beam lithography, which are seeded with mdND colloids and subsequently introduced into microwave assisted chemical vapor deposition reactor to grow patterned nanocrystalline diamond films. In this study, we investigate various factors that affect the selective seeding of different substrates to create high quality diamond thin films, including mdND surface termination, zeta potential, surface treatment, and plasma cleaning. Although the electrostatic interaction between mdND colloids and substrates is the main process driving adherence, we found that chemical reaction (esterification) or hydrogen bonding can potentially dominate the seeding process. Leveraging the knowledge on these different interactions, we optimize fabrication protocols to eliminate unwanted diamond nucleation outside the patterned areas. Furthermore, we have achieved the deposition of patterned diamond films and arrays over a range of feature sizes. This study contributes to a comprehensive understanding of the mdND-substrate interaction that will enable the fabrication of integrated nanocrystalline diamond thin films for microelectronics, sensors, and tissue culturing applications.

Anisotropic Nanomechanics of Boron Nitride Nanotubes: Nanostructured "Skin" Effect

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Menon, Madhu; Cho, KyeongJae

2000-01-01

The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab-initio total energy methods. Due to boron-nitride BN bond buckling effects, compressed zigzag BN nanotubes are found to undergo novel anisotropic strain release followed by anisotropic plastic buckling. The strain is preferentially released towards N atoms in the rotated BN bonds. The tubes buckle anisotropically towards only one end when uniaxially compressed from both. A "skin-effect" model of smart nanocomposite materials is proposed which will localize the structural damage towards the 'skin' or surface side of the material.

Ceramic Transactions. Volume 21. Proceedings of the Symposium on Microwave Theory and Application in Materials Processing Annual Meeting of the American Ceramic Society (23rd) Held in Cincinnati, Ohio on April 29-May 3 1991

DTIC Science & Technology

1992-04-27

spectrum analysis . 4. CONCLUSIONS * The nonthermal synthesis of crystalline nanoparticles of aluminum nitride, silicon carbide and silicon nitride is...51 R.E. Newnham, S.J. Jang, M. Xu, and F. Jones Theory of Microwave Interactions with Ceramic Mz terials .... 69 V.M. Kenkre An Analysis of the...the Performance of Microwave Process Systems Which Utilize High Q Cavities ............ 667 J.F. Gerling and G. Fournier Microwave Thermogravimetric

Dynamic and static fatigue behavior of sintered silicon nitrides

NASA Technical Reports Server (NTRS)

Chang, J.; Khandelwal, P.; Heitman, P. W.

1987-01-01

The dynamic and static fatigue behavior of Kyocera SN220M sintered silicon nitride at 1000 C was studied. Fractographic analysis of the material failing in dynamic fatigue revealed the presence of slow crack growth (SCG) at stressing rates below 41 MPa/min. Under conditions of static fatigue this material also displayed SCG at stresses below 345 MPa. SCG appears to be controlled by microcracking of the grain boundaries. The crack velocity exponent (n) determined from both dynamic and static fatigue tests ranged from 11 to 16.

Selective layer disordering in intersubband Al 0.028Ga 0.972 N/AlN superlattices with silicon nitride capping layer

DOE PAGES

Wierer, Jonathan J.; Allerman, Andrew A.; Skogen, Erik J.; ...

2015-06-01

We demonstrate the selective layer disordering in intersubband Al 0.028Ga 0.972 N/AlN superlattices using a silicon nitride (SiN x) capping layer. The (SiN x) capped superlattice exhibits suppressed layer disordering under high-temperature annealing. In addition, the rate of layer disordering is reduced with increased SiN x thickness. The layer disordering is caused by Si diffusion, and the SiN x layer inhibits vacancy formation at the crystal surface and ultimately, the movement of Al and Ga atoms across the heterointerfaces. In conclusion, patterning of the SiN x layer results in selective layer disordering, an attractive method to integrate active and passivemore » III–nitride-based intersubband devices.« less

Integrated Microreactor for Chemical and Biochemical Applications

NASA Technical Reports Server (NTRS)

Schwesinger, N.; Dressler, L.; Frank, Th.; Wurmus, H.

1995-01-01

A completely integrated microreactor was developed that allows for the processing of very small amounts of chemical solutions. The entire system comprises several pumps and valves arranged in different branches as well as a mixing unit and a reaction chamber. The streaming path of each branch contains two valves and one pump each. The pumps are driven by piezoelectric elements mounted on thin glass membranes. Each pump is about 3.5 mm x 3.5 mm x 0.7 mm. A pumping rate up to 25 microliters per hour can be achieved. The operational voltage ranges between 40 and 200 V. A volume stroke up to 1.5 millimeter is achievable from the membrane structures. The valves are designed as passive valves. Sealing is by thin metal films. The dimension of a valve unit is 0.8 x 0.8. 07 mm. The ends of the separate streaming branches are arranged to meet in one point. This point acts as the beginning of a mixer unit which contains several fork-shaped channels. The arrangement of these channels allows for the division of the whole liquid stream into partial streams and their reuniting. A homogeneous mixing of solutions and/or gases can be observed after having passed about 10 of the fork elements. A reaction chamber is arranged behind the mixing unit to support the chemical reaction of special fluids. This unit contains heating elements placed outside of the chamber. The complete system is arranged in a modular structure and is built up of silicon. It comprises three silicon wafers bonded together by applying the silicon direct bonding technology. The silicon structures are made only by wet chemical etching processes. The fluid connections to the outside are realized using standard injection needles glued into v-shaped structures on the silicon wafers. It is possible to integrate other components, like sensors or electronic circuits using silicon as the basic material.

Development and design of nanomaterial reagents in conjunction with new methods for their synthetic applications

NASA Astrophysics Data System (ADS)

Kwaramba, Farai Brian

This Ph.D. deals with the integration of nanotechnology with organometallic/ organic synthetic technologies. The first part of this research sought to develop a library of novel molecular gears programmed to exploit photo-switching and electrostatic repulsion to control the molecular rotation of covalently linked triptypyrazines. Incorporation of these two modes allows for control of triptycene based gear systems using unexplored external methods. The triptypyrazine was an attractive scaffold because of its intrinsic pH and electrochemical activity, thus providing a novel construct for controlling molecular motion. This design finds relevance in the fabrication of nano-electromechanical devices and understanding controlled molecular motion. This Ph.D. also sought to address the need to generate and recycle low cost hydrosilylation catalysts. Metal nanoparticle catalysts can potentially meet this need due to their high surface area and reactivity. Their morphology and surface texture provide avenues for selectivity in reactions. Metal-nanoparticles on a silicon matrix can be formed by reducing metal salts with silicon hydrides. Investigations towards iron-nanoparticle catalyzed hydrosilylation of unsaturated bonds were conducted. Furthermore, this research sought to develop highly functionalized silanes, as guiding scaffolds for generating chiral silicon hydrides. Fabrication of metal-nanoparticle catalysts with the same, could install surface definition on these heterogeneous green catalysts, thus allowing selectivity in their catalysis. A bottom up approach to nanofabrication, started with the generation of a library of highly functionalized alkynyl-silane building blocks using the hydrosilylation reaction. Hydrosilylation of carbon-carbon and carbon-heteroatom unsaturated bonds has proven to be an important reaction in organic syntheses. Additionally, silicon tethers have been utilized in complex organic syntheses as a way to increase reaction rates, and selectivity. The most commonly employed silicon tethers have been disiloxanes followed by siloxanes, then silanes. Of these methods the synthesis and utilization of tethered silyl-alkynes was limited. To address this gap, this work developed methodology to prepare tethered silyl alkynes through a hydrosilylation reaction. It was established that [IrCl(COD)]2 in the presence of excess COD can selectively catalyze the hydrosilylation of alkenes with alkynyl-silanes. This approach overrides traditional hydrosilylation catalysts' reactivity trends.

Materials Analysis of Transient Plasma-Wall Interactions

DTIC Science & Technology

2014-05-13

such as copper, aluminum, zirconium, titanium, and tungsten) and ceramics (beryllia, aluminum nitride, silicon carbide , etc.). These materials were...formation of silicon carbide . Therefore, a flat Macor disk was polished, and prepared for deuterium exposure by sonicating the sample in both methanol...of silicon constituents whereas the exposed sample clearly shows the addition of carbide and silicon segregation on the surface. 10 AFOSR

Dislocation-free strained silicon-on-silicon by in-place bonding

NASA Astrophysics Data System (ADS)

Cohen, G. M.; Mooney, P. M.; Paruchuri, V. K.; Hovel, H. J.

2005-06-01

In-place bonding is a technique where silicon-on-insulator (SOI) slabs are bonded by hydrophobic attraction to the underlying silicon substrate when the buried oxide is undercut in dilute HF. The bonding between the exposed surfaces of the SOI slab and the substrate propagates simultaneously with the buried oxide etching. As a result, the slabs maintain their registration and are referred to as "bonded in-place". We report the fabrication of dislocation-free strained silicon slabs from pseudomorphic trilayer Si/SiGe/SOI by in-place bonding. Removal of the buried oxide allows the compressively strained SiGe film to relax elastically and induce tensile strain in the top and bottom silicon films. The slabs remain bonded to the substrate by van der Waals forces when the wafer is dried. Subsequent annealing forms a covalent bond such that when the upper Si and the SiGe layer are removed, the bonded silicon slab remains strained.