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Articles 1 - 11 of 11
Full-Text Articles in Ceramic Materials
Thermal And Electrical Properties Of (Cr,Mo,Ta,V,W)C High-Entropy Carbide Ceramics, Ali Sarikhani, Steven M. Smith, Suzana Filipovic, William G. Fahrenholtz, Gregory E. Hilmas
Thermal And Electrical Properties Of (Cr,Mo,Ta,V,W)C High-Entropy Carbide Ceramics, Ali Sarikhani, Steven M. Smith, Suzana Filipovic, William G. Fahrenholtz, Gregory E. Hilmas
Materials Science and Engineering Faculty Research & Creative Works
The synthesis and characterization along with the resulting properties of fully dense (Cr,Mo,Ta,V,W)C high entropy carbide ceramics were studied. The ceramics were synthesized from metal oxide and carbon powders by carbothermal reduction, followed by spark plasma sintering at various temperatures for densification. Increasing the densification temperature resulted in grain growth and an increase in the lattice parameter. Thermal diffusivity increased linearly with testing temperature, resulting in thermal conductivity values ranging from ∼7 W/m•K at room temperature to ∼12 W/m•K at 200 °C. Measured heat capacity values matched theoretical estimates calculated using the Neumann-Kopp rule. Room temperature electrical resistivity decreased from …
Thermally Stable Sic Particulate-Reinforced Sic Composites Up To 2000 ℃ Fabricated By Precursor Impregnation And Pyrolysis Method, Jian Gu, Vu Viet Hung, Lun Feng, William G. Fahrenholtz, Daejong Kim, Seyoung Kim, Sea Hoon Lee
Thermally Stable Sic Particulate-Reinforced Sic Composites Up To 2000 ℃ Fabricated By Precursor Impregnation And Pyrolysis Method, Jian Gu, Vu Viet Hung, Lun Feng, William G. Fahrenholtz, Daejong Kim, Seyoung Kim, Sea Hoon Lee
Materials Science and Engineering Faculty Research & Creative Works
The thermo-mechanical properties of SiC particulate-reinforced SiC composites (SiC-PRCs), fabricated using precursor impregnation & pyrolysis (PIP) process, were analyzed up to 2000 ℃. The relative density of the SiC-PRCs after 4 PIP cycles was 88.6 %. The number of PIP cycles required decreased to nearly half compared with the conventional PIP method by using ultra-high concentration slurries up to 70 vol%. In addition, room-temperature bending strength (215 MPa) and Young's modulus (269 GPa) improved as the solid loading of the slurry increased. The bending strength increased to 232 MPa at 2000 ℃ in Ar. Despite the thermal deterioration of the …
Effects Of Wc Additions On The Phase Formation Of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 High Entropy Dual Phase Ceramics, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas
Effects Of Wc Additions On The Phase Formation Of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 High Entropy Dual Phase Ceramics, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas
Materials Science and Engineering Faculty Research & Creative Works
High entropy dual phase (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramics were produced from powders synthesized by boro-carbothermal reduction. Systematic additions of 2.5 wt%, 5 wt%, and 10 wt% WC were incorporated after powder synthesis. Additions of 2.5 wt% and 5 wt% WC dissolved into the host ceramics, resulting in complete solid solution formation and nearly full densification. In contrast, a secondary monoboride phase evolved for the composition with 10 wt% WC, in addition to the main high entropy carbide and diboride phases. Thermodynamic analysis revealed that WB formation was favorable for WC additions in the presence of metal diborides at the sintering …
Spark Plasma Sintering Of (Zr,Nb)C Ceramics, Jacob Stacy, Greg Hilmas, Jeremy Watts, Brian Taylor, Jhonathan Rosales
Spark Plasma Sintering Of (Zr,Nb)C Ceramics, Jacob Stacy, Greg Hilmas, Jeremy Watts, Brian Taylor, Jhonathan Rosales
Materials Science and Engineering Faculty Research & Creative Works
A range of (Zr,Nb)C ceramics containing 20–50 vol% NbC were spark plasma sintered at 2000°C. The ceramics had relative densities greater than 97 %, and all compositions formed a complete solid solution. The average grain size was ∼7.1 µm over all compositions. Elastic moduli values ranged from 436 to 445 GPa, and the fracture toughness ranged from 0.8 to 2.8 MPa·m1/2 over the compositional range, both increasing with increasing NbC content. The hardnesses of the (Zr,Nb)C ceramics ranged from 19.1 to 20.2 GPa at a load of 9.81 N. The flexural strength increased from 352 to 395 MPa as the …
Synthesis And Properties Of (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C Dual Phase Ceramics, S. Filipović, S. M. Smith, G. Hilmas, W. Fahrenholtz, N. Obradović, S. Curtarolo
Synthesis And Properties Of (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C Dual Phase Ceramics, S. Filipović, S. M. Smith, G. Hilmas, W. Fahrenholtz, N. Obradović, S. Curtarolo
Materials Science and Engineering Faculty Research & Creative Works
Dense, dual phase (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C ceramics were synthesized with varying contents of Mo and W. The final (Hf0.317Mo0.025Ti0.317W0.025Zr0.317)C–(Hf0.317Mo0.025Ti0.317W0.025Zr0.317)B2 was a nominally pure, dual phase ceramic, while compositions with higher amounts of Mo and W contained multiple phases. The final microstructures had submicron grains due to pinning effects. Vickers hardness values were up to 48.6 ± 2.2 GPa for an applied load of 0.49 N for the ceramic with optimized composition and densification. The solubility limits for Mo and …
A Super-Hard High Entropy Boride Containing Hf, Mo, Ti, V, And W, Suzana Filipovic, Nina Obradovic, Greg E. Hilmas, William G. Fahrenholtz, Donald W. Brenner, Jon Paul Maria, Douglas E. Wolfe, Eva Zurek, Xiomara Campilongo, Stefano Curtarolo
A Super-Hard High Entropy Boride Containing Hf, Mo, Ti, V, And W, Suzana Filipovic, Nina Obradovic, Greg E. Hilmas, William G. Fahrenholtz, Donald W. Brenner, Jon Paul Maria, Douglas E. Wolfe, Eva Zurek, Xiomara Campilongo, Stefano Curtarolo
Materials Science and Engineering Faculty Research & Creative Works
Super-Hard (Hf,Mo,Ti,V,W)B2 Was Synthesized by Boro-Carbothermal Reduction and Densified by Spark Plasma Sintering. This Composition Was Produced for the First Time as a Single-Phase Ceramic in the Present Research. the Optimized Ceramic Had a Single Hexagonal AlB2-Type Crystalline Phase with a Grain Size of 3.8 µm and Homogeneous Distribution of the Constituent Metals. the Vickers Hardness Exhibited the Indentation Size Effect, Increasing from 27 GPa at a Load of 9.8 N to as High as 66 GPa at a Load of 0.49 N. This is the Highest Hardness Reported to Date for High Entropy Boride Ceramics.
Synergistic Hardening In A Dual Phase High-Entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas, Stefano Curtarolo
Synergistic Hardening In A Dual Phase High-Entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas, Stefano Curtarolo
Materials Science and Engineering Faculty Research & Creative Works
A dual phase high-entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramic was synthesized using a single step boro-carbothermal reduction route. The synthesized powder was densified by spark plasma sintering at 2000°C, resulting in complete solid solution formation and a relative density of ≈99%. The dual phase ceramic was 43 vol% high-entropy carbide and 57 vol% high-entropy boride. The grain sizes were 0.85 ± 0.34 µm for the carbide and 0.87 ± 0.33 µm for the boride with minimal residual oxide (0.2 vol%) detected in the microstructure. The resulting composition had a higher microhardness than the individual boride and carbide ceramics across the range …
Sic Addition To A Dual Phase High Entropy Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Kantesh Balani, Gregory E. Hilmas, Jeremy Watts
Sic Addition To A Dual Phase High Entropy Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Kantesh Balani, Gregory E. Hilmas, Jeremy Watts
Materials Science and Engineering Faculty Research & Creative Works
Dual phase (Hf,Ta,Ti,W,Zr)B2-(Hf,Ta,Ti,W,Zr)C high entropy ultra-high temperature ceramics were processed from commercial diboride and carbide powders with and without SiC additions. A 30-min hold at a maximum temperature of 1850 °C in spark plasma sintering resulted in a relative density of ∼95 %, which increased to ∼100 % with the addition of 7.5 wt.% SiC. The compositions did not reach chemical equilibrium under the given sintering conditions resulting in an inhomogeneous distribution of transition metals in both the boride and carbide phases. The addition of SiC improved densification by inhibiting grain growth, which reduced the grain size from 9.0 ± …
Creep Behavior And Deformation Mechanisms Of Spark Plasma Sintered Oxide Ceramics For Aerospace Systems At 1300˚C - 1400˚C, David D. Swanson
Creep Behavior And Deformation Mechanisms Of Spark Plasma Sintered Oxide Ceramics For Aerospace Systems At 1300˚C - 1400˚C, David D. Swanson
Theses and Dissertations
The mechanical behavior of YAG and LuAG was investigated at elevated temperatures. The specific materials investigated in this work include high-purity, polycrystalline YAG, high-purity, polycrystalline LuAG, and two doped variants of YAG: 2at% Yb-doped, polycrystalline YAG and 2at% Er-doped, polycrystalline YAG. Several billets of each material were prepared and processed by means of spark plasma sintering (SPS). Many different sintering parameters were utilized in order to obtain materials with various physical properties and to identify the effects of sintering parameters on the average grain size of the resulting materials. The compressive creep behavior of these materials was investigated at 1300°C …
Fracture Toughness Improvement Of ����� Ceramics By Grain Size Control And Ductile Phase Reinforcement, Kesong Wang
Fracture Toughness Improvement Of ����� Ceramics By Grain Size Control And Ductile Phase Reinforcement, Kesong Wang
McKelvey School of Engineering Graduate Student Theses & Dissertations
This study used grain size control and ductile phase reinforcement to improve fracture toughness of ����� ceramics. Alpha alumina particles of 100 nm, 0.5-1 micrometers, and 10 micrometers were coated with 1-5 nm nickel by electroless nickel plating (ENP). The coated powders were consolidated at 1200℃-1500℃ by spark plasma sintering (SPS). The sintered samples were annealed at 1100 oC for 1.5 hours and 10 hours to determine the effect of post sintering annealing on hardness and fracture toughness. Density of the samples were measured by the standard Archimedes method using a 5 mL pycnometer. Hardness values were determined by Vickers …
Electroless Nickel Plating And Spark Plasma Sintering Of Nano Zro2 For Mechanical Property Enhancement, Kunlong Jia
Electroless Nickel Plating And Spark Plasma Sintering Of Nano Zro2 For Mechanical Property Enhancement, Kunlong Jia
McKelvey School of Engineering Graduate Student Theses & Dissertations
A new approach of combined electroless nickel plating (ENP) and spark plasma sintering (SPS) was used to determine the feasibility of fracture toughness improvement of ZrO2. Nano-grained yttria stabilized zirconia (YSZ) particles of 100nm average diameter were coated with about 1-5 nm of nickel coating by ENP. To reduce nano particle agglomeration throughout the ENP process; vigorous agitation with an ultrasonic horn was used. The coated powder was characterized using Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Transmission electron microscopy (TEM) to study the microstructure and coating characteristics. The coating was identified to be predominantly nickel and of …