Characterization of the thermal properties by scanning thermal microscopy in ultrafine-grained iron surface layer produced by ultrasonic shot peening

New micro- and nanoscale devices require electrically isolating materials with specific thermal properties. One option to characterize these thermal properties is the atomic force microscopy (AFM)-based scanning thermal microscopy (SThM) technique. It enables qualitative mapping of local thermal conductivities of ultrathin films. To fully understand and correctly interpret the results of practical SThM measurements, it is essential to have detailed knowledge about the heat transfer process between the probe and the sample. However, little can be found in the literature so far. Therefore, this work focuses on theoretical SThM studies of ultrathin films with anisotropic thermal properties such as hexagonal boron nitride (h-BN) and compares the results with a bulk silicon (Si) sample. Energy fluxes from the probe to the sample between 0.6 µW and 126.8 µW are found for different cases with a tip radius of approximately 300 nm. A present thermal interface resistance (TIR) between bulk Si and ultrathin h-BN on top can fully suppress a further heat penetration. The time until heat propagation within the sample is stationary is found to be below 1 µs, which may justify higher tip velocities in practical SThM investigations of up to 20 µms−1. It is also demonstrated that there is almost no influence of convection and radiation, whereas a possible TIR between probe and sample must be considered.

Download Full-text

Adhesive penetration of wood cell walls investigated by scanning thermal microscopy (SThM)

Holzforschung ◽

10.1515/hf.2008.014 ◽

2008 ◽

Vol 62 (1) ◽

pp. 91-98 ◽

Cited By ~ 57

Author(s):

Johannes Konnerth ◽

David Harper ◽

Seung-Hwan Lee ◽

Timothy G. Rials ◽

Wolfgang Gindl

Keyword(s):

Thermal Conductivity ◽

Thermal Properties ◽

Surface Temperature ◽

Cell Walls ◽

Adhesive Contact ◽

Wood Adhesive ◽

Bond Line ◽

Scanning Thermal Microscopy ◽

Thermal Probe ◽

Thermal Microscopy

Abstract Cross sections of wood adhesive bonds were studied by scanning thermal microscopy (SThM) with the aim of scrutinizing the distribution of adhesive in the bond line region. The distribution of thermal conductivity, as well as temperature in the bond line area, was measured on the surface by means of a nanofabricated thermal probe offering high spatial and thermal resolution. Both the thermal conductivity and the surface temperature measurements were found suitable to differentiate between materials in the bond region, i.e., adhesive, cell walls and embedding epoxy. Of the two SThM modes available, the surface temperature mode provided images with superior optical contrast. The results clearly demonstrate that the polyurethane adhesive did not cause changes of thermal properties in wood cell walls with adhesive contact. By contrast, cell walls adjacent to a phenol-resorcinol-formaldehyde adhesive showed distinctly changed thermal properties, which is attributed to the presence of adhesive in the wood cell wall.

Download Full-text

Characterization of nanocrystalline surface layer induced by shot peening and effect on their fatigue strength.

MRS Proceedings ◽

10.1557/proc-843-t3.7 ◽

2004 ◽

Vol 843 ◽

Author(s):

Hideo Mano ◽

Kondo Satoru ◽

Akihito Matsumuro ◽

Toru Imura

Keyword(s):

Residual Stress ◽

Surface Layer ◽

Fatigue Strength ◽

Vickers Hardness ◽

Shot Peening ◽

White Layer ◽

The Other ◽

Fatigue Properties ◽

Nanocrystalline Layer

ABSTRACTThe shot peening process is known to produce a hard layer, known as the white layer” on the surface of coil springs. However, little is known about the fatigue properties of this white-layer.In this study, coil springs with a white-layer were manufactured. The surface of these springs was then examined using micro Vickers hardness, FE-SEM etc. to test fatigue strength of the springs.From the results obtained, a microstructure of the white-layer with grain size of 50–100 nm was observed, with a Vickers hardness rating of 8–10 GPa.Tow category springs were manufactured utilizing a double-peening process. These springs had the same residual stress destruction and surface roughness. Only one difference was observed: one spring had a nanocrystalline layer on the surface, while the other did not. The results of the fatigue test realized an increase in the fatigue life of the nanocrystalline surface layer by 9%.

Download Full-text