NFT Wing Protection on HAMR Head Using a Window Underlayer Structure

Ensuring the mechanical reliability of the NFT is critical due to contact with the disk during touchdown and the presence of high thermal asperities (TAs) at low clearance. Here, we tune the thermomechanical design of the HAMR head to ensure the NFT is protected from direct contact with the disk. We propose embedding the NFT in a localized window of underlayer material chosen for its small thermal expansion in comparison to a standard material such as alumina. By optimizing the size and material properties of the window structure, simulation predicts that the NFT is well protected under recording conditions.

Study on Fabrication and Properties of In Situ Si and Al2O3 Particulate Reinforced Composites

The properties of in-situ (Si+Al2O3)/Al composites fabricated from Al-SiO2 reaction system are investigated by X-Ray Diffraction, Scanning Electron Microscope and Differential Scanning Calorimetry technologies. The results indicate that the Si phase is plate shaped and the Al2O3 phase is mainly round and ellipsoidal. The composite prepared by this method have performances of low density, high conductivity and small thermal expansion coefficient (<10×10-6/K) which meets the performance requirements of electronic packaging materials.

Chemical, Mechanical and Electrical Properties of Glassy Polymeric Carbon

ABSTRACTGlassy Polymeric Carbon (GPC) is obtained by a molding technique, in various shapes, from a phenolic resin precursor. The heat treatment of the precursor is achieved in three stages up to 1000 °C. Similar GPC materials produced in our laboratory displayed large strain to failure ratio, small thermal expansion coefficient and low density. Like all carbon forms, is attacked by oxygen, especially atomic oxygen. Nevertheless the kinetics for reaction with atmospheric oxygen is very slow. We investigated the composition and structural changes of the phenolic precursor as a function of temperature and evaluated materials stability when exposed to high temperatures in presence of hydrogen or oxygen.

Properties of Crucible Materials for Bulk Growth of AlN

A variety of different crucible materials have been suggested and/or employed for the sublimation-recondensation growth of AlN single crystals above 2000 C. Representative materials all have melting points well above 2300 C, a reasonable degree of chemical compatibility with AlN, relatively low vapor pressures, and relatively small thermal expansion coefficients. We analyze the current state of knowledge on crucible materials such as C, W, Re, W-Re alloys, BN, HfN, HfC, NbC, TaC, Ta2C, TaN, ZrC and ZrN with respect to published bulk AlN growth conditions. Crucible materials pyrolytic graphite, pyrolytic BN, and W have integrated thermal contraction values (upon cooling from growth temperatures) that are less than that of AlN; the other materials have larger values. The lowest vapor pressure materials in a nitrogen atmosphere are W, TaC, and Re; thus they are expected to yield higher purity crystals than the other candidates. The materials C, BN, Hf, and ZrN are expected to contribute to higher impurity levels in the AlN crystals.

AEM of Bi-Processed Mg2Al4Si5O18: Cation Chemistry of Hexagonal and Orthorhombic Cordierites

Cordierite, Mg2Al4Si5O18, is a refractory aluminosilicate whose low dielectric constant, good strength, and small thermal expansion coefficient are valued in applications of ceramic technology. A significant impediment to its widespread use in ceramic packaging of electronic circuits has been difficulties inherent in standard fabrication techniques. Recently, a new process has been developed for the preparation of cordierite below 1000°C using a bismuth oxide flux. This process produces dense cordierite bodies containing residual amounts of bismuth oxide flux at grain boundaries and triple points.

Planar defects in AIN

Aluminum nitride has recently become the subject of much interest as a technologically useful ceramic. The mechanical strength, high thermal conductivity and large electrical resistivity and a relatively small thermal expansion coefficient, make this material extremely well suited as a semiconductor substrate material. AlN has the hexagonal, wurtzite structure rather than the cubic structure of the more common semiconductors. It is also a polar material. The characterization of microstructural defects in this material is obviously necessary to the understanding of the materials properties.In sintered AlN material, several different planar defects have previously been examined. Anti-phase boundaries (which produce the same configuration as basal twins in this structure) and stacking-faults have been identified in this material. A defect described as a “dome-like defect” has also been reported. The association of oxygen impurities with these extended defects has also been proposed. In this paper we report the observation of a defect (which may be the same as the “dome-like defect”) consisting of a flat, planar, basal fault and a curved, planar fault (rather than a spherical one) which join together to enclose a region of AlN, and separate it from the rest of the grain.