The Effect of Different Colloidal Silica Binders on Strengths of Corundum-Mullite Castables

2015 ◽  
Vol 1094 ◽  
pp. 127-130
Author(s):  
Wen Jie Yuan ◽  
Qing You Zhu ◽  
Cheng Ji Deng ◽  
Hong Xi Zhu
Keyword(s):  
Electron Microscope ◽  
Fracture Surface ◽  
Scanning Electron Microscope ◽  
Size Distribution ◽  
Colloidal Silica ◽  
Modulus Of Rupture ◽  
Fracture Surfaces ◽  
The Difference ◽  
Slit Island Method ◽  
Scanning Electron

Three kinds of colloidal silica (GS-30, AM and HS-30) were applied as binders to corundum-mullite castables. The apparent porosity and cold modulus of rupture for samples fired at 800 oC and 1000 oC were compared. The fractography of colloidal silica bonded corundum-mullite castables was carried out by slit island method. The microstructure of fracture surface was characterized by scanning electron microscope. The results showed that castables by using imported colloidal silica (AM and HS-30) presented higher strength than those with domestic (GS-30), which was determined by the activity of silica and modified ion. The difference of the size distribution of the salient on the fracture surfaces indicated that the strength of castables was dependent on the bonding among the components.

scholarly journals Fractal Dimension of Fracture Surface in Rock Material after High Temperature

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Z. Z. Zhang
Keyword(s):  
Fractal Dimension ◽  
Electron Microscope ◽  
High Temperature ◽  
Fracture Surface ◽  
Scanning Electron Microscope ◽  
Fractal Dimensions ◽  
Threshold Value ◽  
Fracture Surfaces ◽  
Increasing Temperature ◽  
Scanning Electron

Experiments on granite specimens after different high temperature under uniaxial compression were conducted and the fracture surfaces were observed by scanning electron microscope (SEM). The fractal dimensions of the fracture surfaces with increasing temperature were calculated, respectively. The fractal dimension of fracture surface is between 1.44 and 1.63. Its value approximately goes up exponentially with the increase of temperature. There is a quadratic polynomial relationship between the rockburst tendency and fractal dimension of fracture surface; namely, a fractal dimension threshold can be obtained. Below the threshold value, a positive correlativity shows between rockburst tendency and fractal dimension; when the fractal dimension is greater than the threshold value, it shows an inverse correlativity.

A Comparison of TEM and SEM Fractography

1970 ◽  
Vol 28 ◽  
pp. 398-399
Author(s):  
James L. Hubbard
Keyword(s):  
Electron Microscope ◽  
Fracture Surface ◽  
Scanning Electron Microscope ◽  
Stress Corrosion ◽  
Surface Features ◽  
Fracture Surfaces ◽  
Mental Picture ◽  
Scanning Electron

For many years now, metallurgists have been using replica techniques for electron micrographic studies of the fracture surfaces of metals. The general features which are indicative of a certain mode of fracture, such as fatigue, overstress, or stress corrosion, have become quite familar in a wide variety of alloys. Although replicas are subject to many artifacts these features are usually recognized as such and disregarded in the analysis of the surface. Also since negative replicas are generally used one must reverse his perspective in order to obtain a true mental picture of the fracture surface.With the scanning electron microscope, micrographs of such samples can now be taken directly with no surface replication or preparation involved. The scanning micrographs, while limited in resolution, present a picture not only true to the surface but with a stereo perspective with which one can relate the surface features to reality.

The different influence of magnesite emissions on the surface waxes of Norway spruce and silver fir

1988 ◽  
Vol 66 (1) ◽  
pp. 125-129 ◽  
Author(s):  
E. Bermadinger ◽  
D. Grill ◽  
P. Golob
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Marked Effect ◽  
Abies Alba ◽  
Silver Fir ◽  
Fine Dust ◽  
Surface Waxes ◽  
The Difference ◽  
Dust Load ◽  
Scanning Electron

The difference in vigour between Picea abies (L.) Karst. and Abies alba Mill, in an area exposed to fine dust containing MgO is reflected in scanning electron microscope studies of the needle surfaces. The greater vitality of the silver fir is correlated with intact wax structures and a somewhat lower dust load. In contrast, the spruce reveals a marked effect on the epicuticular wax by a heavy fine-dust load. Possible causes and physiological consequences are discussed.

A Scanning Electron Microscope With Two Secondary Electron Detectors and Its Application to the Surface Topography Measurements of Magnetic Media

1992 ◽  
Vol 114 (2) ◽  
pp. 274-279 ◽  
Author(s):  
K. Tanaka ◽  
K. Nishimori ◽  
K. Maeda ◽  
J. Matsuda ◽  
M. Hotta
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Topography ◽  
Secondary Electron ◽  
Wear Testing ◽  
Magnetic Media ◽  
Wear Process ◽  
Surface Gradient ◽  
The Difference ◽  
Scanning Electron

A scanning electron microscope (SEM) with two secondary electron detectors is applied for the surface topography measurement of magnetic media. The principle of gradient determination of the SEM is based on a relation that the difference in the square signals between the two detectors is linearly proportional to surface gradient. The great advantage of the instrument is the capability of relocation for profiling. It is extremely useful for the examination of wear process at a fixed position in a sequential manner during wear testing. This is demonstrated by two sample data of measurement on thin film rigid disks.

Considerations in Making Stereo Micrographs with the Scanning Electron Microscope - Positioning the Stereo Window

1976 ◽  
Vol 34 ◽  
pp. 508-509
Author(s):  
Earl R. Walter
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Tilt Angle ◽  
Field Of View ◽  
Stereo Pair ◽  
The Difference ◽  
Scanning Electron

A variety of factors must be controlled in order to obtain stereo micrograph pairs with the SEM which provide maximum effectiveness along with ease of viewing. These include the following:1. Where possible, micrographs should be sharp from edge to edge. This may require the use of an Autofocus attachment although somewhat the same effect can be obtained by maintaining the point of sharpest focus near opposite edges of the two micrographs forming the stereo pair.2. The difference in tilt angle between the two micrographs of the pair should be kept in the 4to 6° range to provide a normal perspective.3. Micrographs forming a stereo pair should be made at relatively low tilt angles to prevent large differences in the field of view of the two micrographs and to minimize the left to right magnification variations.

Stress Corrosion Cracking in Steam Turbine: Two Case Studies

2017 ◽  
Author(s):  
Vamadevan Gowreesan ◽  
Kirill Grebinnyk
Keyword(s):  
Electron Microscope ◽  
Fracture Surface ◽  
Scanning Electron Microscope ◽  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Steam Turbines ◽  
Root Section ◽  
Scanning Electron

Stress corrosion cracking in steam turbines had been an old problem though some modern steam turbines have almost eliminated this problem by several methods. The methods include design modification to reduce the stress levels below the threshold stress level for stress corrosion cracking, inducing compressive stress by different means and using pure steam [1, 2]. Some of the older steam turbine discs are prone to stress corrosion cracking. Two cases where such machines experienced stress corrosion cracking in their discs are discussed here. The row 6 disc of an integral steam turbine rotor developed cracks in the root sections. Some of the cracks were mechanically opened for the evaluation. Evaluation of the fracture surfaces with a scanning electron microscope showed evidence of intergranular mode of cracking. Optical microscopy of a cracked root confirmed intergranular mode of cracking. In addition, it showed branching of cracks. Based on these findings, it was concluded that stress corrosion cracking was the reason for the cracks. In addition, finite element analysis was used to calculate the stress distribution in the blade root of the disc. The location of the maximum equivalent stress coincided perfectly with that of the actual crack location in the disc root section. Unfortunately, redesign of the root geometry to minimize the local stress concentration is very difficult due to the size limitation of the blade roots. Small amount of chlorine was identified on the fracture surface and the chlorine could have come from the steam used. The customer was advised to analyze their steam quality and to improve the quality of the steam if needed. The cracked portion was removed from the disc and weld-build up to machine new root sections with the same type of roots. Root section of the row 6 disc of another steam turbine developed failure. This disc had radial entry type blades. Portion of the disc root and some blades were liberated from the disc due to the cracking. The fracture surface had heavy oxide layer on it. Evaluation of the fracture surface with a scanning electron microscope revealed intergranular mode of failure. Energy dispersive spectroscopy analysis of the fracture surface found oxides on the fracture surface. Optical microscopy showed secondary cracking and branched cracking. All these evidences confirmed that the failure occurred due to stress corrosion cracking. In addition, it was suspected that forging was not heat treated properly due to measured lower toughness and different microstructure. The lower toughness was believed to be a result of improper heat treatment rather than that of embrittlement. Methods to mitigate the risk of stress corrosion cracking were proposed.

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