Defect Characterization in a CVD α-Si3N4

1991 ◽  
Vol 49 ◽  
pp. 936-937
Author(s):  
Karren L. More
Keyword(s):  
Hot Isostatic Pressing ◽  
Chemical Vapor ◽  
Processing Method ◽  
Defect Characterization ◽  
Structural Ceramic ◽  
Alternative Processing ◽  
Torr Pressure ◽  
Strong Candidate ◽  
Hot Pressing Sintering ◽  
Processing Techniques

Silicon nitride possesses an attractive combination of thermo-mechanical properties which makes it a strong candidate material for many structural ceramic applications. Unfortunately, many of the conventional processing techniques used to produce Si3N4, such as hot-pressing, sintering, and hot-isostatic pressing, utilize significant amounts of densification aids (Y2O3, Al2O3, MgO, etc.) which can ultimately lower the utilization temperatures to well below that of pure Si3N4. Chemical vapor deposition (CVD) is an alternative processing method for producing pure Si3N4. The CVD Si3N4 material examined in this study was supplied by Union Carbide. Deposition was performed at 1450°C and 1 Torr pressure using SiCl4 and NH3 as the reacting gases. The CVD methods used were similar to those described by Niihara and Hirai.

Low-temperature Mo-catalyzed growth of crystalline Si3N4 by CVD

1993 ◽  
Vol 51 ◽  
pp. 918-919
Author(s):  
K.L. More ◽  
R.A. Lowden ◽  
T.M. Besmann
Keyword(s):  
Vapor Deposition ◽  
Hot Isostatic Pressing ◽  
Chemical Vapor ◽  
Processing Method ◽  
Crystalline Material ◽  
Structural Ceramic ◽  
Alternative Processing ◽  
Strong Candidate ◽  
Hot Pressing Sintering ◽  
Processing Techniques

Silicon nitride possesses an attractive combination of thermo-mechanical properties which makes it a strong candidate material for many structural ceramic applications. Unfortunately, many of the conventional processing techniques used to produce Si3N4, such as hot-pressing, sintering, and hot-isostatic pressing, utilize significant amounts of densification aids (Y2O3, Al2O3, MgO, etc.) which ultimately lowers the utilization temperature to well below that of pure Si3N4 and also decreases the oxidation resistance. Chemical vapor deposition (CVD) is an alternative processing method for producing pure Si3N4. However, deposits made at temperatures less than ~1200°C are usually amorphous and at slightly higher temperatures, the deposition of crystalline material requires extremely low deposition rates (~5 μm/h). Niihara and Hirai deposited crystalline α-Si3N4 at 1400°C at a deposition rate of ~730 μm/h. Hirai and Hayashi successfully lowered the CVD temperature for the growth of crystalline Si3N4 by adding TiCl4 vapor to the SiCl4, NH3, and H2 reactants. This resulted in the growth of α-Si3N4 with small amounts of TiN at temperatures as low as 1250°C.

Sintering of HA/Zirconia Composite for Biomedical and Dental Applications: A Review

2013 ◽  
Vol 686 ◽  
pp. 290-295
Author(s):  
Kok Fong Lim ◽  
Muchtar Andanastuti ◽  
Rusnah Mustaffa ◽  
Chou Yong Tan
Keyword(s):  
Mechanical Properties ◽  
Microwave Sintering ◽  
Hot Isostatic Pressing ◽  
Medical Application ◽  
Processing Method ◽  
Isostatic Pressing ◽  
Alternative Processing ◽  
Conventional Sintering ◽  
Phosphate Product ◽  
Dental Applications

Hydroxyapatite is a calcium phosphate product that being widely use in medical application due to its excellence biocompatibility. However its application has being limited due to the inferior mechanical properties, many researcher attempted to improve its mechanical properties. HA-ZrO2 composites have great potential because of their advantages from both constituent materials, such as the excellent biocompatibility of HA and the considerable mechanical strength and toughness of ZrO2. The synergy of the two materials provides a new possibility for developing a composite material with better properties than monolithic ZrO2 and HA. In this work, the stages of development, as well as the different sintering and processing methods of HA and ZrO2 such as conventional sintering, solid-state reaction, microwave sintering and hot isostatic pressing were discussed. It can be concluded that hot isostatic pressing processing yield the most satisfying result amount above method, however the use of nano structured material maybe able to provide alternative processing method and yield better result.

Robustness versus Performance Assessment for Different Gamma-TiAl Processing Routes

2011 ◽  
Vol 1295 ◽  
Author(s):  
Marc Thomas
Keyword(s):  
High Performance ◽  
Cost Effective ◽  
Processing Route ◽  
Transportation Industry ◽  
Tial Alloys ◽  
Alternative Processing ◽  
Aerospace Applications ◽  
Robust Processing ◽  
Processing Techniques ◽  
Robust Process

ABSTRACTOne of the main driving force for the development of advanced structural materials is weight saving especially in the transportation industry in order to reduce CO2 emission. The utilization of gamma aluminides, as good candidates for aerospace applications, is strongly related to the development of a cost-effective and robust processing route, as far as possible. It is well established that the processing route, i.e. cast, wrought or PM, has a dramatic effect on the microstructure and texture of gamma-TiAl alloys. Therefore, significant microstructural variations through post-heat treatments coupled with compositional modifications can only guarantee a proper balance of desired properties. However, a number of metallurgical factors during the processing steps can contribute to some scattering in properties. This review will highlight several critical process variables in terms of the resulting g-TiAl microstructures. Of primary importance is the as-cast texture which is difficult to control and may contribute to prefer some alternative processing routes to ensure a better repeatability in mechanical results. Some innovative processing techniques for controlling the structure will then be presented. The main point which will be discussed in this paper is whether an approach leading to a robust process would not be at the expense of the high performance of the structural material.

Fracture behavior of 3-d Braided Nicalon/Silicon Carbide Composite

1988 ◽  
Vol 120 ◽  
Author(s):  
J.-M. Yang ◽  
J.-C. Chou ◽  
C. V. Burkland
Keyword(s):  
Fracture Toughness ◽  
Silicon Carbide ◽  
Thermal Shock Resistance ◽  
Fracture Behavior ◽  
Ceramic Composite ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Fiber Architecture ◽  
Structural Ceramic ◽  
Shock Resistance

AbstractThe fracture behavior of a 3-D braided Nicalon fiber-reinforced SiC matrix composite processed by chemical vapor infiltration (CVI) has been investigated. The fracture toughness and thermal shock resistance under various thermomechanical loadings have been characterized. The results obtained indicate that a tough and durable structural ceramic composite can be achieved through the combination of 3-D fiber architecture and the low temperature CVI processing.

scholarly journals Recognition of Pashto Handwritten Characters Based on Deep Learning

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5884
Author(s):  
Muhammad Sadiq Amin ◽  
Siddiqui Muhammad Yasir ◽  
Hyunsik Ahn
Keyword(s):  
Character Recognition ◽  
Test Accuracy ◽  
Forensic Evidence ◽  
Handwritten Character Recognition ◽  
Data Set ◽  
Research Attention ◽  
Handwritten Character ◽  
Proposed Model ◽  
Strong Candidate ◽  
Processing Techniques

Handwritten character recognition is increasingly important in a variety of automation fields, for example, authentication of bank signatures, identification of ZIP codes on letter addresses, and forensic evidence. Despite improved object recognition technologies, Pashto’s hand-written character recognition (PHCR) remains largely unsolved due to the presence of many enigmatic hand-written characters, enormously cursive Pashto characters, and lack of research attention. We propose a convolutional neural network (CNN) model for recognition of Pashto hand-written characters for the first time in an unrestricted environment. Firstly, a novel Pashto handwritten character data set, “Poha”, for 44 characters is constructed. For preprocessing, deep fusion image processing techniques and noise reduction for text optimization are applied. A CNN model optimized in the number of convolutional layers and their parameters outperformed common deep models in terms of accuracy. Moreover, a set of benchmark popular CNN models applied to Poha is evaluated and compared with the proposed model. The obtained experimental results show that the proposed model is superior to other models with test accuracy of 99.64 percent for PHCR. The results indicate that our model may be a strong candidate for handwritten character recognition and automated PHCR applications.

scholarly journals Plasma-Assisted Chemical Vapor Deposition of TiBN Coatings on Nanostructured Cemented WC-Co

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1680
Author(s):  
Matija Sakoman ◽  
Danko Ćorić ◽  
Mateja Šnajdar Musa
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Hot Isostatic Pressing ◽  
Base Material ◽  
Surface Preparation ◽  
Chemical Vapor ◽  
Hard Coatings ◽  
Cemented Carbides ◽  
Wear Properties ◽  
Coating Adhesion

The plasma-assisted chemical vapor deposition (PACVD) technique has shown many advantages in applications, where thin coatings with superior wear properties are demanded, especially for geometrically complex parts. In this study, multilayered gradient TiBN coatings that were deposited on nanostructured cemented carbides by the PACVD method were investigated. Nanostructured samples of cemented carbides with the addition of 5 and 15 wt.% Co were sintered by the hot isostatic pressing, sinter-HIP technique. Surface preparation was conducted on samples in order to enable maximum coating adhesion. Tests that were conducted on produced samples aimed to investigate the mechanical and physical properties of coated samples. These tests included nanoindentation, surface layer characterization, and coating adhesion evaluation while using the Rockwell and scratch test. The obtained results confirmed that the PACVD process can be utilized for applying thin hard coatings to nanostructured cemented carbides that are produced by the sinter HIP process, resulting in a base material/ coating system that exhibits excellent physical and mechanical properties. The results presented in this paper give a valuable contribution to the research of TiBN coating systems and their potential for application under heavy wear conditions.

Preparation of monolithic ZnSxSe1−x layers via chemical vapor deposition followed by hot isostatic pressing

2006 ◽  
Vol 42 (8) ◽  
pp. 839-844 ◽  
Author(s):  
E. M. Gavrishchuk ◽  
D. V. Savin ◽  
V. B. Ikonnikov ◽  
S. M. Mazavin ◽  
A. I. Suchkov ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Hot Isostatic Pressing ◽  
Chemical Vapor ◽  
Isostatic Pressing

Treatment of Thermophoretic Deposition in Tube Flow for Materials Processing Applications

2003 ◽  
Author(s):  
Patrick A. Tebbe
Keyword(s):  
Stokes Equations ◽  
Chemical Vapor ◽  
Nano Particles ◽  
Navier Stokes ◽  
Large Temperature ◽  
Tube Flow ◽  
Navier Stokes Equations ◽  
Complex Solutions ◽  
Processing Techniques ◽  
Compare And Contrast

Material processing techniques based on vapor or particle transport involve a number of interrelated hydrodynamic and thermal effects. For cases with large temperature gradients or small (nano) particles, thermal gradients can induce motion referred to as thermophoresis. Thermophoresis directly impacts material quality and production rates for chemical vapor deposition (CVD) and related processes. A simple yet useful geometry for the study of thermophoretic deposition is axial tube flow. This geometry is particularly useful as it closely represents one process used to produce fiber optic preforms. While considerable research has been conducted on thermophoretic deposition, a global description and understanding of the phenomena is still difficult. This paper will first review the analytical study of thermophoretic deposition. Starting with the simple Graetz problem the development of more complex solutions to the governing Navier-Stokes equations will be detailed from the literature. Next, the creation of a coupled, two code Eulerian approach to solve this problem will be presented. Finally, the results of numerical case studies performed by the author will be discussed. These results will be used to compare and contrast the influence of different factors.

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