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Process Window (process + window)

Distribution by Scientific Domains
Polymers and Materials Science62%

Selected Abstracts

Novel Process Windows , Gate to Maximizing Process Intensification via Flow Chemistry

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009
V. Hessel
Abstract Driven by the economics of scale, the size of reaction vessels as the major processing apparatus of the chemical industry has became bigger and bigger [1, 2]. Consequently, the efforts for ensuring mixing and heat transfer have also increased, as these are scale dependent. This has brought vessel operation to (partly severe) technical limits, especially when controlling harsh conditions, e.g., due to large heat releases. Accordingly, processing at a very large scale has resulted in taming of the chemistry involved in order to slow it down to a technically controllable level. Therefore, reaction paths that already turned out too aggressive at the laboratory scale are automatically excluded for later scale-up, which constitutes a common everyday confinement in exploiting chemical transformations. Organic chemists are barely conscious that even the small-scale laboratory protocols in their textbooks contain many slow, disciplined chemical reactions. Operations such as adding a reactant drop by drop in a large diluted solvent volume have become second nature, but are not intrinsic to the good engineering of chemical reactions. These are intrinsic to the chemical apparatus used in the past. In contrast, today's process intensification [3,12] and the new flow-chemistry reactors on the micro- and milli-scale [13,39] allow such limitations to be overcome, and thus, enable a complete, ab-initio type rethinking of the processes themselves. In this way, space-time yields and the productivity of the reactor can be increased by orders of magnitude and other dramatic performance step changes can be achieved. A hand-in-hand design of the reactors and process re-thinking is required to enable chemistry rather than subduing chemistry around the reactor [40]. This often leads to making use of process conditions far from conventional practice, under harsh environments, a procedure named here as Novel Process Windows. [source]

High-Q Microwave Dielectrics in the (Mg1,xCox)2TiO4 Ceramics

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009
Cheng-Liang Huang
The microwave dielectric properties and the microstructures of (Mg1,xCox)2TiO4 ceramics prepared by the conventional solid-state route were investigated. Lattice parameters were also measured for specimens with different x. The formation of solid solution (Mg1,xCox)2TiO4 (x=0.02,0.1) was confirmed by the X-ray diffraction patterns, energy dispersive X-ray analysis, and the lattice parameters measured. By increasing x from 0 to 0.05, the Q×f of the specimen can be tremendously boosted from 150 000 GHz to a maximum of 286 000 GHz. A fine combination of microwave dielectric properties (,r,15.7, Q×f,286 000 GHz at 10.4 GHz, ,f,,52.5 ppm/°C) was achieved for (Mg0.95Co0.05)2TiO4 ceramics sintered at 1390°C for 4 h. Ilmenite-structured (Mg0.95Co0.05)TiO3 was detected as a second phase. The presence of the second phase would cause no significant variation in the dielectric properties of the specimen because it possesses compatible properties compared with that of the main phase. In addition, only a small deviation in the dielectric properties was monitored for specimens with x=0.04,0.05 at 1360°,1420°C. It not only provides a wide process window but also ensures an extremely reliable material proposed as a very promising dielectric for low-loss microwave and millimeter wave applications. [source]

Differences between chloro-carbon and hydro-carbon precursors in low-temperature epitaxial growth of 4H-SiC

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
Siva Kotamraju
Abstract The advantages of using the chlorinated carbon precursor chloromethane instead of the hydrocarbon precursor propane in low-temperature (1300 °C) epitaxial growth of 4H-SiC were investigated. Chloromethane was found to provide a much wider process window for variation of the C/Si ratio between the lower boundary corresponding to the formation of condensed silicon face and the upper boundary corresponding to polytype inclusions and polycrystalline degradation, which is critical for achieving high growth rates without epilayer quality degradation. Use of a high Cl/Si ratio provided by HCl addition in the propane-based epitaxial growth did not eliminate the critical differences between chloro-carbon and hydro-carbon precursors. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Pulsed Nanocomposite TiAlN Coatings on Complex Shaped Tools for High Performance Cutting Operations

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Kirsten Bobzin
Abstract The demand on high profitability in cutting operations has led to a variety of requirements for high performance tool coatings. Nanostructured coatings have shown most promising results in this connection. High oxidation resistance, hot hardness, and loW friction are just a few benefits that these coatings offer. The deposition of nanostructured coatings is only possible within a small deposition process window. Most cutting tool surfaces are complex shaped and include, for instance, small corner radii at the cutting edge or chip breakers. The local process window and the deposition parameters must be adapted to the actual shape of the cutting tools in order to obtain a hard nanocomposite coating with adequate adhesion properties. Finally, the performance of these coatings has been studied in machining tests. [source]

Effects of an Added Iodine Source (C2H5I) on Ru Metal,Organic Chemical Vapor Deposition,

CHEMICAL VAPOR DEPOSITION, Issue 2 2003
J.J. Kim
Abstract The effects of an iodine source (C2H5I) on ruthenium (Ru) films grown on TiN/Ti/Si wafers by metal,organic (MO)CVD using Ru(EtCp)2 as a precursor were investigated. When an additional step of adsorbing iodine source was inserted during the Ru MOCVD process, the films became smoother and the root mean square (rms) surface roughness of the 30,nm thick Ru film became less than 10,% of the film thickness, as low as 1.71,nm. Moreover, the surface reaction-limited regime was extended to 400,°C, causing a wide process window. [source]

Challenges in Measuring of Physical Properties of Liquid Phases for Material and Process Optimisation,

ADVANCED ENGINEERING MATERIALS, Issue 4 2007
S. Akbari
The exact knowledge of thermo-physical properties of molten phases is crucial to modern metallurgy. It leads to optimized process windows including better metal/slag separation, suitable slag selection or reduced slag/refractory wetting. The most important properties are melting and boiling point, electrical- and thermal conductivity, melting and transition enthalpies, wetting angle, density, viscosity and surface tension. The aim of this paper is to present opportunities, methods and uncertainties of characterization of this kind of materials. This will be examplified by measuring three physical properties (density, viscosity and surface tension). [source]

Helianthos: Roll-to-Roll Deposition of Flexible Solar Cell Modules

PLASMA PROCESSES AND POLYMERS, Issue 3 2007
Edward A. G. Hamers
Abstract In the development of the roll-to-roll deposition of amorphous silicon by means of plasma enhanced chemical vapor deposition, a number of different plasma aspects have been of importance. First, the understanding of process windows in terms of a dust free plasma has led to the formulation of an empirical scaling law for the dust free to dust forming transition in terms of the crucial process parameters such as, e.g., power and gas flows. Second, the homogeneity of deposition on an effective width of 30 cm has been demonstrated to be better than 5%. Increasing the deposition rate might be achieved by increasing the power density, but it scales only as (power density)0.77. A last important issue in roll-to-roll processing of long runs is process stability and on-line quality control. The accurate measurement of self bias voltage and optical thickness of the deposited stacks have proven to be very useful in this context. [source]