scholarly journals Mechanical behavior and phase change of alkali-silica reaction products under hydrostatic compression

2020 ◽  
Vol 76 (4) ◽  
pp. 674-682 ◽  
Author(s):  
Guoqing Geng ◽  
Zhenguo Shi ◽  
Andreas Leemann ◽  
Konstantin Glazyrin ◽  
Annette Kleppe ◽  
...  
Keyword(s):  
Mechanical Property ◽  
High Pressure ◽  
Phase Change ◽  
Alkali Silica Reaction ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Main Layer ◽  
Field Samples ◽  
Interlayer Region

Alkali-silica reaction (ASR) causes severe degradation of concrete. The mechanical property of the ASR product is fundamental to the multiscale modeling of concrete behavior over the long term. Despite years of study, there is a lack of consensus regarding the structure and elastic modulus of the ASR product. Here, ASR products from both degraded field infrastructures and laboratory synthesis were investigated using high-pressure X-ray diffraction. The results unveiled the multiphase and metastable nature of ASR products from the field. The dominant phase undergoes permanent phase change via collapsing of the interlayer region and in-planar glide of the main layer, under pressure >2 GPa. The bulk moduli of the low- and high-pressure polymorphs are 27±3 and 46±3 GPa, respectively. The laboratory-synthesized sample and the minor phase in the field samples undergo no changes of phase during compression. Their bulk moduli are 35±2 and 76±4 GPa, respectively. The results provide the first atomistic-scale measurement of the mechanical property of crystalline ASR products.

Study of high-pressure sintering behavior of cBN composites starting with cBN–Al mixtures

2008 ◽  
Vol 23 (9) ◽  
pp. 2366-2372 ◽  
Author(s):  
Yongjun Li ◽  
Sicheng Li ◽  
Ran Lv ◽  
Jiaqian Qin ◽  
Jian Zhang ◽  
...  
Keyword(s):  
High Pressure ◽  
Sintering Temperature ◽  
Cubic Boron Nitride ◽  
Sintering Behavior ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Al Content ◽  
High Pressure Sintering

Cubic boron nitride (cBN) composites starting with cBN–Al mixtures were sintered on WC-16 wt% Co substrates under static high pressure of 5.0 GPa and at temperatures of 800–1400 °C for 30 min. Vickers hardness of the sintered samples increased with increasing cBN content, and the highest hardness of 32.7 GPa was achieved for the cBN–5 wt% Al specimens sintered at 1400 °C. The reactions between cBN and Al started to occur at about 900 °C, and the reaction products strongly depended on the Al content, sintering temperature, and Co diffusion from the substrates according to the x-ray diffraction (XRD) observations. The high pressure and high temperature in situ resistance measurement indicated that the reactions between cBN and Al could be completed in about 90 s when the temperature was higher than ∼1200 °C at high pressure. The cBN composite sintered at 1200 °C from a cBN–15 wt% Al mixture showed the best cutting performance.

scholarly journals Atomistic structure of alkali-silica reaction products refined from X-ray diffraction and micro X-ray absorption data

2020 ◽  
Vol 129 ◽  
pp. 105958 ◽  
Author(s):  
Guoqing Geng ◽  
Zhenguo Shi ◽  
Andreas Leemann ◽  
Camelia Borca ◽  
Thomas Huthwelker ◽  
...  
Keyword(s):  
Alkali Silica Reaction ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Absorption Data ◽  
X Ray ◽  
X Ray Absorption ◽  
Atomistic Structure

High pressure X-ray diffraction and Raman spectroscopic studies of the phase change of D2O ice VII at approximately 11 GPa

2014 ◽  
Vol 34 (3) ◽  
pp. 289-296 ◽  
Author(s):  
Hisako Hirai ◽  
Hirokazu Kadobayashi ◽  
Takahiro Matsuoka ◽  
Yasuo Ohishi ◽  
Yoshitaka Yamamoto
Keyword(s):  
High Pressure ◽  
Phase Change ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic

Performance of a Fly Ash Stabilized Pavement

1989 ◽  
Vol 178 ◽  
Author(s):  
Joakim G. Laguros ◽  
Curt Hayes
Keyword(s):  
Fly Ash ◽  
Concrete Surface ◽  
Asphaltic Concrete ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Calcium ◽  
Field Samples ◽  
High Calcium Fly Ash ◽  
Term Basis

AbstractAn expansive shale roadbase, stabilized with a Class C (high-calcium) fly ash received an 11–inch full–depth asphaltic concrete surface layer and the highway was opened to traffic six years ago. Periodic sampling and visual observations indicate that the performance of the pavement test sections are above average.Analyses of field samples showed that fly ash was effective in ameliorating the texture and plasticity of the shale and imparting strength to it on a long term basis. Pavement deflections and the extent of cracking have not increased beyond acceptable levels during the six year period.X-ray diffraction studies show a reduction of the areas under the peaks and the SEM observations reveal a dense degree of packing and reduction of the void areas. These modifications occur during the first two years of service and any changes beyond that period appear to be minor.

Polyamide as a Matrix for the Creation of Form-Stable Phase Change Materials

2009 ◽  
Vol 610-613 ◽  
pp. 414-418 ◽  
Author(s):  
Jing Guo ◽  
Nan Li
Keyword(s):  
Block Copolymer ◽  
Phase Change ◽  
Phase Change Materials ◽  
Polyamide 6 ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
Thermal Reliability ◽  
Scanning Calorimetry ◽  
X Ray

Phase change materials (PCMs) with storing and releasing energy properties have been widely used in lots of fields such as solar energy storing, smart housing, thermo-regulated fibers, and agricultural greenhouse. Here, PCMs based on polyamide 6 (PA6) blended with Polyethylene glycol (PEG) was studied. In order to improve the compatibility between PA6 and PEG, a PA6-PEG block copolymer was synthesized and added to the blends. The structure and properties of the block copolymer were determined by Fourier Transform Infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and optics microscope (OM). The results of DSC analysis showed that tThe copolymer block is phase separated. DSC results also showed that the phase transition temperature of the blend is different from that of pure PEG, indicating the interaction occurrence between PEG and PA6 by using PA6-PEG block copolymer, the latent heat of PEG/PA6 blend increased with the mass percent of PEG. The results of tThermal cycling tests showed that the blend as a PCM has good long-term thermal reliability.

Leaching Behavior of Fixed-Bed Gasification Ash Derived from North Dakota Lignite

1985 ◽  
Vol 65 ◽  
Author(s):  
D. J. Hassett ◽  
K. R. Henke ◽  
G. J. McCarthy
Keyword(s):  
North Dakota ◽  
Fixed Bed ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Leaching Behavior ◽  
Solution Ph ◽  
X Ray ◽  
Leaching Experiments ◽  
Ash Disposal

ABSTRACTthree different fixed-bed gasifiers have been leached using: (1) the EPA-EP leaching test; (2) a similar test that starts with a synthetic North Dakota groundwater; (3) the ASTM D3987–81 method; (4) a long-term (120 day) leaching experiment. The gasification ashes were highly alkaline and produced pH's in the range 10–13 during tests 2 through 4. Compositions of major, minor and trace elements were determined by AAS and ICAP analyses of leachates. None of the EPA-EP test leachates from any of the ashes exceeded the EP Trigger values that define a hazardous waste according to the RCRA criteria. The long-term leaching experiments provided insights into the rates of extraction of elements from ash and could be useful in modeling selected failure scenarios in an ash disposal pit. At various times during the long-term leaching experiments, substantial fractions of the Na, K, Al, S, As, Mo, Se and V in the ash were extracted. Liquid to solid (l:s) ratios were important in determining the quantities of elements extracted and in controlling solution pH; during most of the 120 day experiments, pH's were near 13 in a 2:1 ratio experiment and just below 10 in a 20:1 ratio experiment. X-ray diffraction analysis of the leaching residue indicated that only a portion of the ash reacted with the leaching solutions. The reaction products were largely noncrystalline, but minor amounts of zeolites, calcite and gibbsite were identified. The formation of such secondary solid phases appears to be important in controlling leachant concentrations.

Effects of high pressure on the crystallization of carbon fiber reinforced polyetheretherketone (CF/PEEK) laminate composites

1990 ◽  
Vol 48 (4) ◽  
pp. 876-877
Author(s):  
Hong-Ming Lin ◽  
C. H. Liu ◽  
R. F. Lee
Keyword(s):  
High Pressure ◽  
Carbon Fiber ◽  
Sample Surface ◽  
High Yield ◽  
Fiber Reinforced ◽  
Laminate Composites ◽  
Peek Composite ◽  
Continuous Carbon Fiber ◽  
Carbon Fiber Reinforced

Polyetheretherketone (PEEK) is a crystallizable thermoplastic used as composite matrix materials in application which requires high yield stress, high toughness, long term high temperature service, and resistance to solvent and radiation. There have been several reports on the crystallization behavior of neat PEEK and of CF/PEEK composite. Other reports discussed the effects of crystallization on the mechanical properties of PEEK and CF/PEEK composites. However, these reports were all concerned with the crystallization or melting processes at or close to atmospheric pressure. Thus, the effects of high pressure on the crystallization of CF/PEEK will be examined in this study.The continuous carbon fiber reinforced PEEK (CF/PEEK) laminate composite with 68 wt.% of fibers was obtained from Imperial Chemical Industry (ICI). For the high pressure experiments, HIP was used to keep these samples under 1000, 1500 or 2000 atm. Then the samples were slowly cooled from 420 °C to 60 °C in the cooling rate about 1 - 2 degree per minute to induce high pressure crystallization. After the high pressure treatment, the samples were scanned in regular DSC to study the crystallinity and the melting temperature. Following the regular polishing, etching, and gold coating of the sample surface, the scanning electron microscope (SEM) was used to image the microstructure of the crystals. Also the samples about 25mmx5mmx3mm were prepared for the 3-point bending tests.

Effect of high pressure-temperature on silicon layered structures as determined by X-ray diffraction and electron microscopy

2004 ◽  
Vol 27 (1-3) ◽  
pp. 415-418
Author(s):  
J. Bak-Misiuk ◽  
A. Misiuk ◽  
J. Ratajczak ◽  
A. Shalimov ◽  
I. Antonova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Layered Structures ◽  
X Ray Diffraction ◽  
X Ray
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