An ultralight silica-modified ZrO2–SiO2 aerogel composite with ultra-low thermal conductivity and enhanced mechanical strength

2018 ◽  
Vol 143 ◽  
pp. 113-116 ◽  
Author(s):  
Xianbo Hou ◽  
Rubing Zhang ◽  
Daining Fang
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Low Thermal Conductivity ◽  
Aerogel Composite ◽  
Sio2 Aerogel

scholarly journals Study of the Turning Nickel Base Alloy Pyromet® 31V (SAE HEV8)

2011 ◽  
Vol 278 ◽  
pp. 312-320 ◽  
Author(s):  
Marcos Valério Ribeiro ◽  
André Luís Habib Bahia
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
High Temperatures ◽  
Base Alloy ◽  
Production Costs ◽  
Machining Parameters ◽  
Nickel Base Alloy ◽  
Low Thermal Conductivity ◽  
Nickel Base ◽  
Coated Carbide

Considering the constant technological developments in the aeronautical, space, automotive, shipbuilding, nuclear and petrochemical fields, among others, the use of materials with high strength mechanical capabilities at high temperatures has been increasingly used. Among the materials that meet the mechanical strength and corrosion properties at temperatures around 815 °C one can find the nickel base alloy Pyromet® 31V (SAE HEV8). This alloy is commonly applied in the manufacturing of high power diesel engines exhaust valves where it is required high resistance to sulphide, corrosion and good resistance to creep. However, due to its high mechanical strength and low thermal conductivity its machinability is made difficult, creating major challenges in the analysis of the best combinations among machining parameters and cutting tools to be used. Its low thermal conductivity results in a concentration of heat at high temperatures in the interfaces of workpiece-tool and tool-chip, consequently accelerating the tools wearing and increasing production costs. This work aimed to study the machinability, using the carbide coated and uncoated tools, of the hot-rolled Pyromet® 31V alloy with hardness between 41.5 and 42.5 HRC. The nickel base alloy used consists essentially of the following components: 56.5% Ni, 22.5% Cr, 2,2% Ti, 0,04% C, 1,2% Al, 0.85% Nb and the rest of iron. Through the turning of this alloy we able to analyze the working mechanisms of wear on tools and evaluate the roughness provided on the cutting parameters used. The tests were performed on a CNC lathe machine using the coated carbide tool TNMG 160408-23 Class 1005 (ISO S15) and uncoated tools TNMG 160408-23 Class H13A (ISO S15). Cutting fluid was used so abundantly and cutting speeds were fixed in 75 and 90 m/min. to feed rates that ranged from 0.12, 0.15, 0.18 and 0.21 mm/rev. and cutting depth of 0.8mm. The results of the comparison between uncoated tools and coated ones presented a machined length of just 30% to the first in relation to the performance of the second. The coated tools has obtained its best result for both 75 and 90 m/min. with feed rate of 0.15 mm/rev. unlike the uncoated tool which obtained its better results to 0.12 mm/rev.

Novel Al2O3–SiO2 aerogel/porous zirconia composite with ultra-low thermal conductivity

2017 ◽  
Vol 25 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Rubing Zhang ◽  
Changshou Ye ◽  
Baolin Wang
Keyword(s):  
Thermal Conductivity ◽  
Low Thermal Conductivity ◽  
Sio2 Aerogel ◽  
Porous Zirconia

Robust aerogels based on conjugated microporous polymer nanotubes with exceptional mechanical strength for efficient solar steam generation

2018 ◽  
Vol 6 (37) ◽  
pp. 18183-18190 ◽  
Author(s):  
Peng Mu ◽  
Wei Bai ◽  
Zheng Zhang ◽  
Jingxian He ◽  
Hanxue Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Steam Generation ◽  
Low Thermal Conductivity ◽  
Conjugated Microporous Polymer ◽  
Microporous Polymer ◽  
Solar Steam Generation ◽  
Polymer Nanotubes

We report the synthesis of elastomeric conjugated microporous polymer nanotube aerogels with exceptional mechanical strength, excellent porous features and low thermal conductivity, which show great potential for solar steam generation.

Carbon-fiber felt reinforced carbon/alumina aerogel composite fabricated with high strength and low thermal conductivity

2017 ◽  
Vol 84 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Ya Zhong ◽  
Junjun Zhang ◽  
Xiaodong Wu ◽  
Xiaodong Shen ◽  
Sheng Cui ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Fiber ◽  
High Strength ◽  
Low Thermal Conductivity ◽  
Alumina Aerogel ◽  
Carbon Fiber Felt ◽  
Aerogel Composite

Low-density graphene/carbon composite aerogels prepared at ambient pressure with high mechanical strength and low thermal conductivity

RSC Advances ◽  
2015 ◽  
Vol 5 (7) ◽  
pp. 5197-5204 ◽  
Author(s):  
Kang Guo ◽  
Zijun Hu ◽  
Huaihe Song ◽  
Xian Du ◽  
Liang Zhong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Compression Strength ◽  
Ambient Pressure ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Low Density ◽  
High Mechanical Strength ◽  
Low Thermal Conductivity ◽  
Composite Aerogels

SEM and TEM pictures show that GNSs can be well-dispersed in a carbon matrix. The resultant composite CAs exhibited high compression strength and extremely low thermal conductivity of 0.028 W m−1 K−1.

scholarly journals Synthesis of fibre reinforced Al2O3−SiO2 aerogel composite with high density uniformity via a facile high-pressure impregnation approach

2017 ◽  
Vol 11 (3) ◽  
pp. 185-190 ◽  
Author(s):  
Gang Yang ◽  
Yonggang Jiang ◽  
Junzong Feng ◽  
Sizhao Zhang ◽  
Jian Feng
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Aerogel Composite ◽  
Sio2 Aerogel ◽  
The Mean

Alumina-silica (Al2O3?SiO2) aerogel composite, with low density, low thermal conductivity and hightemperature stability, is attracting increased interest in the field of thermal insulation application. In this paper, a novel way to fabricate fibre reinforced Al2O3?SiO2 aerogel composite via a facile high-pressure impregnation approach was reported. Two Al2O3?SiO2 aerogel composites, HPe and LPe, were synthesized via high-pressure and low-pressure impregnation approach, respectively. The effects of the impregnation approach on the aerogel composites performance were studied, and the impregnation model was established. The results showed that the as-prepared HPe exhibited higher density uniformity, better high-temperature stability, higher specific surface area and lower thermal conductivity. It was also shown that the effect of impregnation approach on the mean density and morphology of the aerogel composites is negligible. However, the standard deviation of density (0.00857) and mean thickness shrinkage (9.98%) of HPe were 37.8% and 15.4% lower than that of LPe, respectively. The specific surface area (884.1m2/g) of HPe was 43.5% higher than that of LPe. The thermal conductivity of HPe at 1100?C was 2.74% lower than that of LPe. The impregnation model of the aerogel composites presented that the density uniformity and thermal conductivity of HPe were improved obviously, because there were less large pores in HPe than in the LPe.

scholarly journals Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2198 ◽  
Author(s):  
Hu Zhang ◽  
Chao Zhang ◽  
Wentao Ji ◽  
Xian Wang ◽  
Yueming Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Silica Aerogel ◽  
Volume Fraction ◽  
Nitrogen Atmosphere ◽  
Nanoporous Structure ◽  
High Porosity ◽  
Low Thermal Conductivity ◽  
Pure Silica ◽  
Aerogel Composite

Due to their high-porosity, nanoporous structure and pores, aerogel materials possess extremely low thermal conductivity and have broad potential in the thermal insulation field. Silica aerogel materials are widely used because of their low thermal conductivity and high temperature resistance. Pure silica aerogel is very fragile and nearly transparent to the infrared spectrum within 3–8 μm. Doping fibers and opacifiers can overcome these drawbacks. In this paper, the influences of opacifier type and content on the thermal conductivity of silica fiber mat-aerogel composite are experimentally studied using the transient plane source method. The thermal insulation performances are compared from 100 to 750 °C at constant pressure in nitrogen atmosphere among pure fiber mat, fiber mat-aerogel, 20% SiC-fiber mat-aerogel, 30% ZrO2-fiber mat-aerogel and 20% SiC + 30% ZrO2-fiber mat-aerogel. Fiber mat-aerogel doped with 20% SiC has the lowest thermal conductivity, 0.0792 W/m·K at 750 °C, which proves that the proper type and moderate content of opacifier dominates the low thermal conductivity. The pore size distribution indicates that the volume fraction of the micropore and mesopore is also the key factor for reducing the thermal conductivity of porous materials.

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