Studies on high‐density nickel zinc ferrite and its magnetic properties using novel hydrazine precursors

Nickel zinc ferrites have been very widely used in the high‐frequency applications. In our present study we have prepared Ni1−x Znx Fe2O4 (0≤x≤1) using novel hydrazinium metal hydrazinecarboxylate precursors. High densities (∼99%) have been obtained for all the ferrites sintered at relatively low temperatures, 1100 °C, in comparison with the conventional method (≥1200 °C). The variation of magnetic properties like magnetic moment, Curie temperature, and permeability with zinc concentration have been studied.

Reactive hot pressing of ZrB2-ZrCx ultra-high temperature ceramic composites with the addition of SiC particulate

Starting with non-stoichiometric Zr-B4C powder mixture ZrB2-ZrC matrix composites with SiC particulate addition have been made. It was found that variable amounts (5-25 vol%) of SiC could be incorporated and reactively hot pressed (RHPed) to relative densities of 97-99% at 1400-1500 degrees C. This technique has the potential to fabricate ZrB2-based matrices at low temperatures with a variety of reinforcements whose composition and volume fraction are not limited by stoichiometric considerations. The hardness of the composites is in the range of 17-22 GPa. (C) 2010 Elsevier Ltd. All rights reserved.

Enhancement of Surface Flashover Performance of High Voltage Ceramic Disc Insulators

In this paper, an effort is made to study accurately the field distribution for various types of ceramic insulators used for high-voltage transmission. The surface charge simulation method (SCSM) is employed for the field computation. With the help of SCSM program, a Novel field reduction electrode is designed and developed to reduce the maximum field around the pin region. In order to experimentally analyze the performance of discs with field reduction electrode, special artificial pollution test facility was built and utilized. The experimental results show better surface flashover performance of ceramic insulators used in high-voltage transmission and distribution systems.

Electron-Beam-Induced Modifications in High-Density Polyethylene

Post-irradiation studies have been carried out to elucidate the effects of electron beam irradiation on the structural, optical, dielectric, and thermal properties of high-density polyethylene (HDPE) films. The experimental results showed that both the optical band gap and activation energy of HDPE films decreases with an increase in the doses of electron radiation. The electrical measurements showed that dielectric constant and the ac conductivity of HDPE increases with an increase in the dose of electron radiation. The thermal analysis carried out using DSC and TGA revealed that the melting temperature, degree of crystallinity, and thermal stability of the HDPE films increased, obviously, due to the predominant cross-linking reaction following high doses of electron irradiation.

Recent Advances in Low CTE and High Density System-on-a-Package (SOP) Substrate with Thin Film Component Integration

The Packaging Research Center has been developing next generation system-on-a-package (SOP) technology with digital, RF, optical, and sensor functions integrated in a single package/module. The goal of this effort is to develop a platform substrate technology providing very high wiring density and embedded thin film passive and active components using PWB compatible materials and processes. The latest SOP baseline process test vehicle has been fabricated on novel Si-matched CTE, high modulus C-SiC composite core substrates using 10mum thick BCB dielectric films with loss tangent of 0.0008 and dielectric constant of 2.65. A semi-additive plating process has been developed for multilayer microvia build-up using BCB without the use of any vacuum deposition or polishing/CMP processes. PWB and package substrate compatible processes such as plasma surface treatment/desmear and electroless/electrolytic pulse reverse plating was used. The smallest line width and space demonstrated in this paper is 6mum with microvia diameters in the 15-30mum range. This build-up process has also been developed on medium CTE organic laminates including MCL-E-679F from Hitachi Chemical and PTFE laminates with Cu-Invar-Cu core. Embedded decoupling capacitors with capacitance density of >500nF/cm2 have been integrated into the build-up layers using sol-gel synthesized BaTiO3 thin films (200-300nm film thickness) deposited on copper foils and integrated using vacuum lamination and subtractive etch processes. Thin metal alloy resistor films have been integrated into the SOP substrate using two methods: (a) NiCrAlSi thin films (25ohms per square) deposited on copper foils (Gould Electronics) laminated on the build-up layers and two step etch process for resistor definition, and (b) electroless plated Ni-W-P thin films (70 ohms to few Kohms per square) on the BCB dielectric by plasma surface treatment and activation. The electrical design and build-up layer structure along- - with key materials and processes used in the fabrication of the SOP4 test vehicle were presented in this paper. Initial results from the high density wiring and embedded thin film components were also presented. The focus of this paper is on integration of materials, processes and structures in a single package substrate for system-on-a-package (SOP) implementation

Coding for High-Density Recording on a 1-D Granular Magnetic Medium

In terabit-density magnetic recording, several bits of data can be replaced by the values of their neighbors in the storage medium. As a result, errors in the medium are dependent on each other and also on the data written. We consider a simple 1-D combinatorial model of this medium. In our model, we assume a setting where binary data is sequentially written on the medium and a bit can erroneously change to the immediately preceding value. We derive several properties of codes that correct this type of errors, focusing on bounds on their cardinality. We also define a probabilistic finite-state channel model of the storage medium, and derive lower and upper estimates of its capacity. A lower bound is derived by evaluating the symmetric capacity of the channel, i.e., the maximum transmission rate under the assumption of the uniform input distribution of the channel. An upper bound is found by showing that the original channel is a stochastic degradation of another, related channel model whose capacity we can compute explicitly.

Photoresist functionalisation method for high-density protein microarrays using photolithography

Since the last decade, there is a growing need for patterned biomolecules for various applications ranging from diagnostic devices to enabling fundamental biological studies with high throughput. Protein arrays facilitate the study of protein-protein, protein-drug or protein-DNA interactions as well as highly multiplexed immunosensors based on antibody-antigen recognition. Protein microarrays are typically fabricated using piezoelectric inkjet printing with resolution limit of similar to 70-100 mu m limiting the array density. A considerable amount of research has been done on patterning biomolecules using customised biocompatible photoresists. Here, a simple photolithographic process for fabricating protein microarrays on a commercially available diazo-naphthoquinone-novolac-positive tone photoresist functionalised with 3-aminopropyltriethoxysilane is presented. The authors demonstrate that proteins immobilised using this procedure retain their activity and therefore form functional microarrays with the array density limited only by the resolution of lithography, which is more than an order of magnitude compared with inkjet printing. The process described here may be useful in the integration of conventional semiconductor manufacturing processes with biomaterials relevant for the creation of next-generation bio-chips.

Non-covalent functionalization using lithographically patterned polyelectrolyte multilayers for high-density microarrays

We describe a method to fabricate high-density biological microarrays using lithographic patterning of polyelectrolyte multi layers formed by spin assisted electrostatic layer-by-layer assembly. Proteins or DNA can be immobilized on the polyelectrolyte patterns via electrostatic attachment leading to functional microarrays. As the immobilization is done using electrostatically assembled polyelectrolyte anchor, this process is substrate independent and is fully compatible with a standard semiconductor fabrication process flow. Moreover, the electrostatic assembly of the anchor layer is a fast process with reaction saturation times of the order of a few minutes unlike covalent schemes that typically require hours to reach saturation. The substrate independent nature of this technique is demonstrated by functionalizing glass slides as well as regular transparency sheets using the same procedure. Using a model protein assay, we demonstrate that the non-covalent immobilization scheme described here has competitive performance compared to conventional covalent immobilization schemes described in literature. (C) 2012 Elsevier B.V. All rights reserved.

In vitro osteogenic cell proliferation, mineralization, and in vivo osseointegration of injection molded high-density polyethylene-based hybrid composites in rabbit animal model

The present work reports the biocompatibility property of injection molded HDPE-HA-Al2O3 hybrid composites. In vitro cytocompatibility results reveal that osteogenic cell viability and bone mineralization are favorably supported in a statistically significant manner on HDPE-20% HA-20% Al2O3 composite, in comparison to HDPE-40 wt.% HA or HDPE-40 wt.% Al2O3. The difference in cytocompatibility property is explained in terms of difference in substrate wettability/surface energy and importantly, both the cell proliferation at 7 days or bone mineralization at 21 days on HDPE-20% HA-20% Al2O3 composite are either comparable or better than sintered HA. The progressive healing of cylindrical femoral bone defects in rabbit animal model was assessed by implantation experiments over 1, 4 and 12 weeks. Based on the histological analysis as well as histomorphometrical evaluation, a better efficacy of HDPE-20% HA-20% Al2O3 over high-density polyethylene (HDPE) for bone regeneration and neobone formation at host bone-implant interface was established. Taken together, the present study unequivocally establishes that despite the presence of 20% Al2O3, HDPE-based hybrid composites are as biocompatible as HA in vitro or better than HDPE in vivo.

Ultra-high density carbon nanotubes on Al-Cu for advanced vias

An integration scheme for carbon nanotube via interconnects is described to produce nanotube densities of 2.5 1012 tubes/cm2 or 8 1012 walls/cm2 on metallic Al-Cu lines, an order of magnitude beyond the previous state of art, and, for first time, close to that needed for implementation. ©2010 Crown.

Behavior of ar plasma formed in a high-density plasma source - an ecr reactor

In order to develop the ultra-large scale integration(ULSI), low pressure and high density plasma apparatus are required for etching and deposit of thin films. To understand critical parameters such as the pressure, temperature, electrostatic potential and energy distribution of ions impacting on the wafer, it is necessary to understand how these parameters are influenced by the power input and neutral gas pressure. In the present work, a 2-D hybrid electron fluid-particle ion model has been developed to simulate one of the high density plasma sources-an Electron Cyclotron Resonance (ECR) plasma system with various pressures and power inputs in a non-uniform magnetic field. By means of numerical simulation, the energy distributions of argon ion impacting on the wafer are obtained and the plasma density, electron temperature and plasma electrostatic potential are plotted in 3-D. It is concluded that the plasma density depends mainly on both the power input and neutral gas pressure. However, the plasma potential and electron temperature can hardly be affected by the power input, they seem to be primarily dependent on the neutral gas pressure. The comparison shows that the simulation results are qualitatively in good agreement with the experiment measurements.

Mechanisms of thermal shock failure for ultra-high temperature ceramic

The materials considered in our analysis were ZrB2 ceramic matrix composites. Effect of two different additives (graphite and AlN) on thermal shock stability for the materials was measured by water quench test. It showed that it may provide more stable thermal shock properties with additives of graphite. It was explained by different thermal properties and crack resistance of the two materials in detail. Surface oxidation was one of main reasons for strength degradation of ceramic with additives of graphite after quenched in water, and surface crack was one of main reasons for strength degradation of ceramic with additives of AlN after quenched in water. It was presented that it was a potential method for improving thermal shock stability of ZrB2 ceramic matrix composites by introducing proper quantities of graphite.

Influence of target thickness on the generation of high-density ion bunches by ultrashort circularly polarized laser pulses

Ion acceleration by ultrashort circularly polarized laser pulse in a solid-density target is investigated using two-dimensional particle-in-cell simulation. The ions are accelerated and compressed by the continuously extending space-charge field created by the evacuation and compression of the target electrons by the laser light pressure. For a sufficiently thin target, the accelerated and compressed ions can reach and exit from the rear surface as a high-density high-energy ion bunch. The peak ion energy depends on the target thickness and reaches maximum when the compressed ion layer can just reach the rear target surface. The compressed ion layer exhibits lateral striation which can be suppressed by using a sharp-rising laser pulse. (c) 2008 American Institute of Physics.