Emission after fracture

Significant neutral emission is also observed during and after fracture. When analyzing the time dependence of the observed NE, one must take into account both the time dependence of the emission itself and the time-of-flight of the neutral species (associated with Boltzmann velocity distributions) from the source to the mass spectrometer. We expect NE intensities to be much higher than the PIE intensities of the same molecular species due to the high probability of reneutralization as ions leave the surface. NE will be discussed more fully in the following section. 

Ibis is definitely so in the case of olivine from San Carlos, Arizona, USA. This olivine is believed to be derived from magmatic material. Figure 9 shows the NE detected by a QMS scanning the mass range from 0 to 110 AMU once every 80 ms Q4). The time of fracture is indicated by an arrow. A wide variety of emissions are observed and persist for 100 s of ms after fracture. Many of these emissions are due to hydrocarbons. We believe that many of these hydrocarbons originate from internal mineral surfaces exposed at fracture. Finally, we mention that the fracture of alkali containing glasses and minerals (e.g., obsidian, feldspar, and rock salt) yield intense alkali atom emission. In the case of alkali halides, we also see emission of... 

Electron emission during and after fracture of a) E-glass/epoxy and b) S-glass/epoxy strands. Note the different time scales (15). 

FE may serve as a way to measure the surface temperature at the crack tip by careful modeling of the emission curves at short times after fracture. Our modeling to date has required an elevated temperature of fracture that decays quickly away. 

The fractured surfaces for specimens before healing and after healing were characterized using a scanning electron microscope (SEM) (Quanta 3D PEG field-emission electron microscope). This was used to investigate the crack interface, where an adhesive layer was formed by molten thermoplastic particles for bonding the two fractured surfaces. 

Fig. 1. Idealized emission curve for FE accompanying fracture of a material. The time intervals shown are before, during, and after crack growth.

Figure 9.1 Field emission scanning electron microscopy (FE-SEM) image of the fracture section of HCP-DVB-VBC with an increase in DVB content, with 0%, 0.5%, 1%, 2%, 5% and 10% DVB before (a, scale 200 nm) and after (b, scale 100 nm) the hyper-crosslinking reaction.

Figure 5-54. Extensions of the Rice-Thompson model suggest a) how modes II and HI components can translate the mixed mode line down the dislocation emission surface until it intersects with the cleavage surface giving fracture, and b) how hydrogen might translate the cleavage surface until it intersects the load line, producing embrittlement after substantial emission (Gerberich et al., 1992).

To observe the GO dispersion in epoxy matrices, the fracture surfaces of cured samples were examined using a field emission scanning electron microscope. As seen from Figure 9.4, the fracture surface of neat epoxy is characterized by a smooth surface after... 

We illustrate CNT-polymer interface morphology using a CNT/PS and a CNT/ epoxy system." Rod specimen of CNT/PS composite with 1 mm diameter was fabricated using an extrusion process, with a CNT content of about 1 wt.%. Tensile failure surfaces of the CNT/PS composite rod were examined under a field emission seanning electronic microscope (FESEM) and transmission electron microscope (TEM). CNT/epoxy (EPON SU-8 photo resist) thin film with 0.1 wt.% CNT and 5.8/xm in thickness was fabricated by spin-coating mixture of CNT and epoxy on to a silicon wafer. The fracture surface of CNT/ epoxy specimens was examined under FESEM and TEM after shaft-loaded test (inset of Fig. 13.7). 

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