Banded structures in unstable combustion synthesis

1995 ◽  
Vol 10 (6) ◽  
pp. 1379-1386 ◽  
Author(s):  
H.P. Li
Keyword(s):  
Combustion Synthesis ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Processing Parameters ◽  
Processing Conditions ◽  
Oscillatory Frequency ◽  
Unstable Combustion ◽  
Band Spacing ◽  
Initial Processing ◽  
Oscillatory Combustion

Banded structures in combustion-synthesized products have been observed during unstable combustion synthesis. The formation of the banded structures is discussed in this article. It is noted that the band spacing was changed when several initial processing conditions were varied. Any change in the processing parameters that correspondingly caused more unstable combustion was observed to decrease the propagation velocity of the combustion front and increase the band spacing. The correlation of the band spacing and oscillatory frequency of the unstable oscillatory combustion with the propagation velocity was also discussed. From the results studied in this work, it is noted that the change of the band spacing can be used to infer the degree of the instability of the combustion front.

Investigation of propagation modes and temperature/velocity variation on unstable combustion synthesis

2002 ◽  
Vol 17 (12) ◽  
pp. 3213-3221 ◽  
Author(s):  
H. P. Li
Keyword(s):  
Activation Energy ◽  
Combustion Synthesis ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Combustion Reaction ◽  
Velocity Variation ◽  
Material Synthesis ◽  
Unstable Combustion

Combustion synthesis/micropyretic synthesis is a technique in which material synthesis is accomplished by the propagation of a combustion front across the sample. In some cases, the combustion front may propagate in an unstable mode where the propagation velocity and combustion temperature of the combustion front are altered periodically. In this study, the processing conditions leading to unstable combustion reaction were first studied theoretically. The boundary temperatures separating stable and unstable reactions were then determined. The numerical analysis showed that the combustion temperature and the propagation velocity changed periodically during unstable combustion. As the combustion reaction became unstable, the average propagation velocity and the oscillatory frequency of front propagation decreased. The products of unstable combustion synthesis possessed the banded structures, implying the occurrence of the unstable oscillatory propagation, as demonstrated experimentally. In this study, high activation energy combustion (Ti + 2B reaction) and low activation energy combustion (Ni + Al reaction) were both chosen to illustrate the effect of unstable combustion. It is the first time the experimental and numerical results were combined to investigate the temperature and propagation velocity variations during unstable combustion.

scholarly journals Binary Self-Assembly of Nanocolloidal Arrays using Concurrent and Sequential Spin Coating Techniques

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 274
Author(s):  
Shih-Jyun Shen ◽  
Demei Lee ◽  
Yu-Chen Wu ◽  
Shih-Jung Liu
Keyword(s):  
Silicon Substrate ◽  
Self Assembly ◽  
Spin Coating ◽  
Processing Parameters ◽  
The Self ◽  
Silicon Substrates ◽  
Processing Conditions ◽  
Polystyrene Spheres ◽  
Optimal Processing ◽  
Spin Coater

This paper reports the binary colloid assembly of nanospheres using spin coating techniques. Polystyrene spheres with sizes of 900 and 100 nm were assembled on top of silicon substrates utilizing a spin coater. Two different spin coating processes, namely concurrent and sequential coatings, were employed. For the concurrent spin coating, 900 and 100 nm colloidal nanospheres of latex were first mixed and then simultaneously spin coated onto the silicon substrate. On the other hand, the sequential coating process first created a monolayer of a 900 nm nanosphere array on the silicon substrate, followed by the spin coating of another layer of a 100 nm colloidal array on top of the 900 nm array. The influence of the processing parameters, including the type of surfactant, spin speed, and spin time, on the self-assembly of the binary colloidal array were explored. The empirical outcomes show that by employing the optimal processing conditions, binary colloidal arrays can be achieved by both the concurrent and sequential spin coating processes.

scholarly journals Combustion Synthesis and Characterization of Porous NiTi Intermetallic for Structural Application

2012 ◽  
Author(s):  
J. Vanterpool ◽  
O. J. Ilegbusi ◽  
N. Khatami
Keyword(s):  
Combustion Synthesis ◽  
Biomedical Application ◽  
Processing Conditions ◽  
Analysis Software ◽  
Porosity Distribution ◽  
Image Analysis Software ◽  
Input Processing ◽  
Diamond Saw ◽  
Cylindrical Samples

This paper describes experimental investigation of thermal and combustion phenomena as well as structure for self-propagating combustion synthesis of porous Ni–Ti intermetallic aimed for structural biomedical application. The objective is to correlate processing conditions with structure for the porous material. Ni–Ti mixture is prepared from elemental powders of Ni and Ti. The mixture is pressed into solid cylindrical samples of 1.1 cm diameter and 2–3 cm length, with initial porosity ranging from 30% to 42%. The samples are preheated to various initial temperatures and ignited from the top surface such that the flame propagates axially downwards. The flame images are recorded with a motion camera as well as the temperature profile. The samples were then cut using a diamond saw in both longitudinal and latitudinal directions. Image analysis software was then used to analyze the porosity distribution in each sample. The porosity distribution was then systematically correlated with the input processing conditions.

Microscale Thermoplastic Forming of Bulk Metallic Glasses: Numerical Simulations and Experiments

2008 ◽  
Author(s):  
David L. Henann ◽  
Lallit Anand
Keyword(s):  
Numerical Simulation ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Processing Parameters ◽  
Hot Embossing ◽  
Simulation Tool ◽  
Processing Conditions ◽  
Trial And Error ◽  
Physical Experiments ◽  
Thermoplastic Forming

An extremely promising microscale processing method for bulk metallic glasses called thermoplastic forming has emerged in recent years. However, most of the recent experimental thermoplastic forming studies have been conducted by trial-and-error. In this paper, the large-deformation constitutive theory of Henann and Anand [1] is used as a numerical simulation tool for the design of micro-hot-embossing processes. This numerical simulation capability is used to determine appropriate processing parameters in order to carry out several successful micron-scale hot-embossing operation on the metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1). By carrying out the corresponding physical experiments, it is demonstrated that microscale features in Vitreloy-1 may be accurately replicated under the processing conditions determined by use of the numerical simulation capability.

scholarly journals Effects of Ball Milling Processing Conditions and Alloy Components on the Synthesis of Cu-Nb and Cu-Mo Alloys

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1224 ◽  
Author(s):  
Xuekun Shang ◽  
Xitao Wang ◽  
Silian Chen
Keyword(s):  
Size Distribution ◽  
Ball Milling ◽  
Oxidation Process ◽  
Processing Parameters ◽  
Processing Conditions ◽  
Cold Welding ◽  
Immiscible Alloys ◽  
Ball Size ◽  
Milling Method

The effects of processing parameters in ball milling and the different behaviors of Cu-Nb and Cu-Mo alloys during milling were investigated. High powder yields can be obtained by changing the BPR value and ball size distribution and no clear dependence of BPR value on powder yield can be found from the experiment results. The addition of oxygen can largely reduce the effect of excessive cold welding during ball milling. A “two-step” ball milling method was introduced to evaluate the different evolution processes and morphologies in different alloys. With 8 h pre-milling, this method considerably benefits the oxidation process of Mo and shows its promising potential in the synthesis of immiscible alloys. Based on the experiment results and analysis, we suggest that the different behaviors of Cu-Nb and Cu-Mo alloys are related to the shear modules and different tendencies to be oxidized.

Influence of Deposition Processing Conditions on Polycrystalline Silicon Thin Film for Solar Cells on Ceramic Substrates

2005 ◽  
Vol 475-479 ◽  
pp. 1231-1234 ◽  
Author(s):  
Hai Feng Li ◽  
Yong Huang ◽  
Zhi Jian Wan ◽  
Hou Xing Zhang ◽  
Y. Xu
Keyword(s):  
Thin Film ◽  
Polycrystalline Silicon ◽  
Silicon Solar Cell ◽  
Processing Parameters ◽  
Processing Conditions ◽  
Silicon Thin Film ◽  
Ceramic Substrates ◽  
Al2o3 Ceramic ◽  
Silicon Thin Films ◽  
Deposition Conditions

Various polycrystalline silicon thin films were deposited on Al2O3 ceramic substrates by RTCVD processing under different deposition conditions. The influence of deposition conditions on thin film quality was studied and a set of typical processing parameters were obtained, which would direct the RTCVD processing of thin film silicon solar cell technique.

Influence of Processing Parameters on Surface Roughness in Micro Mill-Grinding Aluminium Alloy 6061

2014 ◽  
Vol 1017 ◽  
pp. 495-499
Author(s):  
Ya Dong Gong ◽  
Chao Wang ◽  
Jun Cheng ◽  
Xue Long Wen ◽  
Guo Qiang Yin
Keyword(s):  
Surface Roughness ◽  
Aluminium Alloy ◽  
Feed Rate ◽  
Processing Parameters ◽  
Micro Milling ◽  
Processing Conditions ◽  
Cutting Depth ◽  
Orthogonal Experiments ◽  
Alloy 6061 ◽  
Better Than

Orthogonal experiments of micro mill-grinding were conducted on aluminium alloy 6061. Electroplated CBN compound tools were used in machining. Surface topography and roughness of the machined workpieces were measured and analyzed. Influence rules of radial cutting depth,feed rate and spindle speed on surface roughness in micro mill-grinding were studied. The results were compared with those in micro milling. It shows that the influence rules of processing parameters on surface roughness in micro mill-grinding are approximately same with those in micro milling. And in the same processing conditions, the surface roughness of micro mill-grinding is better than that of micro milling. The minimum value of surface roughness Ra of micro mill-grinding is 0.609μm in the experiments.

Rapid solidification by unstable combustion synthesis

1993 ◽  
Vol 8 (10) ◽  
pp. 2515-2523 ◽  
Author(s):  
H.P. Li ◽  
J.A. Sekhar
Keyword(s):  
Combustion Synthesis ◽  
Rapid Solidification ◽  
Synthesis Conditions ◽  
Unstable Combustion ◽  
Rapidly Solidified ◽  
First Time

During combustion/micropyretic synthesis, conditions that give rise to rapid solidification and rapidly solidified microstructures may be encountered. In this article, many such conditions are identified for the first time in a Ni–Al system. In addition, the banded structures and aligned dendrites that are encountered in this system are also examined. The various techniques of rapid solidification that may be initiated with combustion synthesis are examined and discussed.

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