The majority of work in graphene nanocomposites has focused on polymer matrices. Here we report for the first time use to enhance toughness bulk silicon nitride ceramics. Ceramics are ideally suited high-temperature applications but suffer from poor toughness. Our approach uses platelets (GPL) that homogeneously dispersed with particles and densified, at ∼1650 °C, using spark plasma sintering. sintering parameters selected enable GPL survive harsh processing environment, as confirmed by...

Carbon–carbon (C–C) composites are attractive materials for hypersonic flight vehicles but they oxidize in air at temperatures >500°C and need thermal protection systems to survive aerothermal heating. We investigated using multilayers of high‐temperature ceramics such as ZrB 2 SiC protect C–C against oxidation. Our approach combines pretreatment processing steps create continuous adherent ceramic coatings from infiltrated preceramic polymers. tested our protective above 2600°C the...

The oxyacetylene torch facility is used to measure the ablation rates of graphite and surface temperatures different aerospace materials. free‐stream flame environment characterized as a function chemistry for heat flux, pO 2 , flow velocity. Measured increase increasing flux which are validated by applying an oxygen diffusion based model. model uses experimentally measured values temperature, gas velocity in order confirm testing results reliable reproducible. Surface ultra‐high temperature...

Colloidal processing was used to make highly dispersed aqueous composite suspensions containing single‐wall carbon nanotubes (SWNTs) and Si 3 N 4 particles. The SWNTs particles were stabilized into using a cationic surfactant at low pH values. Bulk nanocomposites 1.0, 2.0, 6.0 vol% successfully fabricated rapid prototyping. survival of detected, Raman spectroscopy, after high‐temperature sintering, up 1800°C. have densities 97% the theoretical density. engineered nanostructures reveal an...

Investigating the powder processing effects on a ZrB 2 –25 vol% SiC ceramic composite densified using spark plasma sintering ( SPS ) allows for identification of densification mechanisms and enables reduction in temperature to minimum 1650°C. Attrition milling AM ball BM were investigated as methods produce fine coarse with or without tube furnace preheat treatment. Ceramics formed from powders contain 1.66 wt% oxygen contamination, primarily ZrO SiO , 0.35 contamination respectively. Heat...

Spark plasma joining is used to join ZrB 2 –SiC composites with seamless microstructures at the joint that results in retention of high‐temperature mechanical and oxidation properties after joining. Our approach uses a spark sintering furnace Zr–B powder filler layers parts together. The processing parameters optimize microstructure were composition, target temperature, hold time, volume filler. A 1 mm 3 conditions 1800°C for 300 s resulted formation region was indistinguishable from bulk...

Carbon–carbon (C–C) composites are ideal for use as aerospace vehicle structural materials; however, they lack high‐temperature oxidation resistance requiring environmental barrier coatings application. Ultra ceramics ( UHTC s) form oxides that inhibit oxygen diffusion at high temperature candidate thermal protection system materials temperatures >1600°C. Oxidation C–C can be achieved by duplicating the self‐generating oxide chemistry of bulk s formed a “composite effect” upon ZrB 2 – SiC...

Sol–gel precursors to HfB 2 and ZrB are processed by high‐energy ultrasonication of Hf , Zr oxychloride hydrates, triethyl borate, phenolic resin form precipitate‐free sols that turn into stable gels with no catalyst addition. Both precursor concentration structure (a sol or a gel) found influence the synthesis diboride phase at high temperature. Decreasing increases powder surface area from 3.6 6.8 m /g, whereas heat‐treating gel leads residual oxides carbides. Particles either fine...

The chemical compatibility between sealing glasses and interconnect materials for solid oxide fuel cells (SOFCs) has been studied in SOFC environments. Two borate‐based glass compositions were sealed to materials, 441 stainless‐steel (441SS) Mn 1.5 Co O 4 ‐coated 441SS. 441SS coupons analyzed as‐received using X‐ray diffraction (XRD) electron probe microanalysis (EPMA) obtain structural information concentration profiles, respectively. profiles the lack of Fe‐containing phases present XRD...

Ceramic honeycombs based on homogeneous composites of zirconia and iron oxide are formed using polymer-based coextrusion for testing in thermochemical reactors to generate CO renewable fuels. The honeycomb substrates possess controlled surface areas processed with 3 8 mol % yttria additions investigate the influence area oxygen conductivity substrate generation properties. was tested a gas chromatography mass spectrometer laboratory scale reactor capable precisely controlling temperature...

Using an organic solvent‐based formulation, flexible and homogeneous ZrB 2 tapes were cast for potential use as advanced aerospace exploration vehicles. Dispersant concentrations optimized attrition‐milled powder using gravitational sedimentation viscosity measurements. Tape slurry formulations with varying amounts of binder (6–8 vol%), plasticizer (7–11 solids loading (20–23 vol%) used to optimize the casting slurry. An optimal formulation was determined based on tape uniform particle...

Perovskite La0.9Sr0.1Ga0.9Mg0.1O3-δ (LSGM) is one of the fastest known oxide ion conductors, with reported enhanced p-type electronic transference numbers at grain boundaries, attributed to space charge effects. As this material applied as a solid fuel/electrolysis cell electrolyte, it interest learn how its mixed conductivity may be tailored. Field assisted sintering technique/spark plasma (FAST/SPS) and conventional without field or pressure were employed prepare pellets various sizes, in...

Oxidation of ZrB 2 + SiC composites is investigated using isothermal measurements to study the effects temperature, time, and gas flow on oxidation behavior microstructural evolution. A test method called dynamic nonequilibrium thermal gravimetric analysis (DNE‐TGA), which eliminates during heating ramp, has been developed monitor mass change from onset an hold period (15 min) as a function temperature (1000°C–1600°C) (50 200 mL/min). In comparing nonisothermal TGA measurements, scale...

Silicon carbide nanofiber dispersion within a silicon oxycarbide glassy ceramic was achieved through combination of fast sol–gel procedure for in situ matrix synthesis and conversion from sacrificial multiwalled carbon nanotube templates. Nanotubes were dispersed using both surfactant adsorption covalent sidewall modification scheme with gel‐grafting capabilities. The high temperature processing monoxide precursor concentrations allowed substantial carbothermal reduction the templates,...

A phase diagram‐assisted powder processing approach is shown to produce low‐oxygen (0.06 wt%O) ZrB 2 ceramics using minimal B 4 C additions (0.25 wt%) and spark plasma sintering. Scanning electron microscopy scanning transmission with elemental spectroscopy are used identify “trash collector” oxides. These oxides composed of manufacturer metal impurities that form discreet oxide particles due the absence standard Zr–B found in high oxygen samples. preliminary Zr–B–C–O quaternary...

Multiwalled carbon nanotubes were dispersed in a silicon carbide matrix to examine nanotube influence on mechanical properties of the resulting composite. The ceramic was generated through high temperature conversion poly(methylsilyne), preceramic polymeric precursor. Nanotube alkylation explored using two functionalization schemes: organic peroxide workup and alkyllithium displacement fluorinated nanotubes, which promoted extensive mixing within precursor solutions, thereby ensuring...

Abstract Carbon was used to reduce oxides in spark plasma sintered ZrB 2 ultra‐high temperature ceramics. A thermodynamic model evaluate the reducing reactions remove B O 3 and ZrO from powder. Powder oxygen content measured carbon additions of 0.5 0.75 wt% were used. C–ZrO pseudo binary diagram, –B –C ternaries, Zr–C–O potential phase diagrams generated show how can be related an open system experiment tube furnace. Scanning transmission electron microscopy identified impurity phases...

Abstract Ultra‐high temperature ceramics (UHTCs) are a group of advanced ceramic materials that possess excellent high capabilities, which make them especially suitable for extreme environment engineering applications. As an effective assembling method, joining is frequently required fabricating sophisticated structures such applications due to the excessive challenges and costs in producing near‐net shapes. Here, we introduce promising new technique effectively join UHTCs called...

Abstract Thermodynamic modeling of Zr–B–C–O quaternary system is conducted within the CALPHAD framework by employing data obtained from first‐principle calculations and literature. The lower order binary B–O assessed in this work estimating thermodynamic properties stable solid phases B 2 O 3 6 gas liquid phases. First‐principle calculations, conjunction with special quasirandom structure were used to predict enthalpies mixing for ternary solid‐solution phase FCC‐Zr(C, O). calculated results...