A Study of Gettering Efficiency and Stability in Czochralski Silicon

1995 ◽  
Vol 378 ◽  
Author(s):  
Scott A. McHugo ◽  
E. R. Weber ◽  
M. Mizuno ◽  
F. G. Kirscht
Keyword(s):  
Carbon Material ◽  
Strain Field ◽  
Annealing Treatment ◽  
Site Formation ◽  
Low Carbon ◽  
High Carbon ◽  
Carbon Doped ◽  
Annealing Conditions ◽  
Oxygen Precipitation ◽  
Induced Defects

AbstractGettering efficiencies and stabilities of internal gettering sites for metallic impurities in high and low carbon doped silicon have been compared with ramped and standard two-step pre-annealing conditions. This study was intended to compare two proposed techniques to shorten the long low temperature nucleation step in the standard Hi-Lo-Hi internal gettering site formation treatment. Specifically, we compare the affect of carbon and a ramped annealing sequence on oxygen precipitate formation and gettering effectiveness. Our results show both techniques accelerate oxygen precipitation, however, only the low carbon ramped materials produced efficient and stable gettering sites. The high carbon materials did not with either annealing treatment. This disparity in performance is due to a difference in the oxygen precipitate’s strain field. The precipitates in the low carbon material possessed a high strain field with strain-induced defects while in the high carbon material they were strain-free with no defects. These results indicate the strain stabilizes the gettered impurity such that the gettering rate is increased and stability is enhanced.

The Effect of Carbon on the Precipitation of Oxygen in Czochralski Silicon

1980 ◽  
Vol 2 ◽  
Author(s):  
R. F. Pinizzotto ◽  
H. F. SCHAAKE
Keyword(s):  
Interfacial Energy ◽  
Carbon Material ◽  
Single Step ◽  
Low Carbon ◽  
High Carbon ◽  
X Ray ◽  
Czochralski Silicon ◽  
Oxygen Precipitation ◽  
Carbon Impurities ◽  
Light Precipitation

ABSTRACTResearchers in both the U. S. and Japan have reported that carbon impurities can significantly alter the precipitation of oxygen in CZ silicon. We have employed FTIR, x-ray topography and TEM to study this phenomenon in silicon containing < 2 × 1016 C cm−3 or 1.3 × 1017 C cm−3. A single step anneal of 16 hours at 1000°C will cause oxygen precipitation to occur in the high carbon material, while a 32 hour pre-anneal at 600°C is necessary for precipitation in the low carbon material. If a single anneal of 120 hours at 750°C is used, light precipitation occurs in both types of material. A pre-anneal of 15 minutes at 1000°C followed by 120 hours at 750°C reduces precipitation in the high carbon material only slightly, but completely eliminates precipitation in the low carbon material. It can be concluded that carbon causes heterogeneous nucleation of oxygen precipitation in CZ silicon and it is proposed that it does so by lowering the interfacial energy of the precipitates.

The microstructure change of low-carbon electrical steels by residual aluminum

1989 ◽  
Vol 47 ◽  
pp. 286-287
Author(s):  
C.K. Hou ◽  
C.T. Hu ◽  
Sanboh Lee
Keyword(s):  
Annealing Treatment ◽  
Low Carbon ◽  
Electrical Steels ◽  
Vacuum Degassing ◽  
Spherical Inclusions ◽  
Residual Aluminum ◽  
Average Grain Size ◽  
The Matrix ◽  
Fine Size ◽  
To Come

The fully processed low-carbon electrical steels are generally fabricated through vacuum degassing to reduce the carbon level and to avoid the need for any further decarburization annealing treatment. This investigation was conducted on eighteen heats of such steels with aluminum content ranging from 0.001% to 0.011% which was believed to come from the addition of ferroalloys.The sizes of all the observed grains are less than 24 μm, and gradually decrease as the content of aluminum is increased from 0.001% to 0.007%. For steels with residual aluminum greater than 0. 007%, the average grain size becomes constant and is about 8.8 μm as shown in Fig. 1. When the aluminum is increased, the observed grains are changed from the uniformly coarse and equiaxial shape to the fine size in the region near surfaces and the elongated shape in the central region. SEM and EDAX analysis of large spherical inclusions in the matrix indicate that silicate is the majority compound when the aluminum propotion is less than 0.003%, then the content of aluminum in compound inclusion increases with that in steel.

Precipitation at the transformation interface of pearlite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 912-913
Author(s):  
F. A. Khalid ◽  
D. V. Edmonds
Keyword(s):  
Thin Foil ◽  
Carbon Steels ◽  
Model Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Growth Interface ◽  
Medium Carbon ◽  
Interphase Precipitation ◽  
Solution Treated ◽  
Wide Range

The austenite/pearlite growth interface in a model alloy steel (Fe-1lMn-0.8C-0.5V nominal wt%) is being studied in an attempt to characterise the morphology and mechanism of VC precipitation at the growth interface. In this alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the precipitation of VC at the austenite/ferrite interface, which reaction, termed interphase precipitation, occurs in a number of low- carbon HSLA and microalloyed medium- and high- carbon steels. Some observations of interphase precipitation in microalloyed low- and medium- carbon commercial steels are also reported for comparison as this reaction can be responsible for a significant increase in strength in a wide range of commercial steels.The experimental alloy was made as 50 g argon arc melts using high purity materials and homogenised. Samples were solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised at 1300 °C for 15 min. and isothermally transformed at 620 °C for 10-18hrs. and WQ. Specimens of microalloyed commercial steels were studied in either as-rolled or as- forged conditions. Detailed procedures of thin foil preparation for TEM are given elsewhere.

scholarly journals Interfacial Phenomena and Inclusion Formation Behavior at Early Melting Stages of HCFeCr and LCFeCr Alloys in Liquid Iron

2021 ◽  
Author(s):  
Yong Wang ◽  
Andrey Karasev ◽  
Joo Hyun Park ◽  
Wangzhong Mu ◽  
Pär G. Jönsson
Keyword(s):  
Liquid Iron ◽  
Diffusion Zone ◽  
Early Stage ◽  
Interfacial Phenomena ◽  
Solid Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Free Zone ◽  
Formation Behavior ◽  
Predetermined Time

AbstractChromium is normally added to liquid alloy in the form of different grades of ferrochromium (FeCr) alloys for the requirement of different alloy grades, such as stainless steels, high Cr cast iron, etc.. In this work, inclusions in two commercially produced alloys, i.e., high-carbon ferrochromium (HCFeCr) and low-carbon ferrochromium (LCFeCr) alloys, were investigated. The FeCr alloy/liquid iron interactions at an early stage were investigated by inserting solid alloy piece into contact with the liquid iron for a predetermined time using the liquid-metal-suction method. After quenching these samples, a diffusion zone between the alloys and the liquid Fe was studied based on the microstructural characterizations. It was observed that Cr-O-(Fe) inclusions were formed in the diffusion zone, FeOx inclusions were formed in the bulk Fe, and an “inclusion-free” zone was detected between them. Moreover, it was found that the HCFeCr was slowly dissolved, but LCFeCr alloy was rapidly melted during the experiment. The dissolution and melting behaviors of these two FeCr alloys were compared and the mechanism of the early-stage dissolution process of FeCr alloys in the liquid Fe was proposed.

scholarly journals Carbon Emission Governance Zones at the County Level to Promote Sustainable Development

Land ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 197
Author(s):  
He Zhang ◽  
Jingyi Peng ◽  
Dahlia Yu ◽  
Lie You ◽  
Rui Wang
Keyword(s):  
Sustainable Development ◽  
Carbon Emission ◽  
Total Carbon ◽  
Small Scale ◽  
County Level ◽  
Low Carbon ◽  
High Carbon ◽  
Governance System ◽  
Medium Carbon ◽  
Indicator Evaluation

Low-carbon governance at the county level has been an important issue for sustainable development due to the large contributions to carbon emission. However, the experiences of carbon emission governance at the county level are lacking. This paper discusses 5 carbon emission governance zones for 1753 counties. The zoning is formed according to a differentiated zoning method based on a multi-indicator evaluation to judge if the governance had better focus and had formulated a differentiated carbon emission governance system. According to zoning results, there is 1 high-carbon governance zone, 2 medium-carbon governance zones, and 2 low-carbon zones. The extensive high-carbon governance zone and medium-carbon zones are key governance areas, in which the counties are mainly located in the northern plain areas and southeast coastal areas and have contributed 51.88% of total carbon emissions. This paper proposes differentiated governance standards for each indicator of the 5 zones. The differentiated zoning method mentioned in this paper can be applied to other governance issues of small-scale regions.

Ultra Grain Refinement of Low C Steels by Accumulative Roll Bonding

2006 ◽  
Vol 503-504 ◽  
pp. 311-316 ◽  
Author(s):  
I. Salvatori
Keyword(s):  
Accumulative Roll Bonding ◽  
Orientation Imaging Microscopy ◽  
Low Carbon Steel ◽  
Small Samples ◽  
Low Carbon ◽  
High Angle ◽  
Misorientation Distribution ◽  
Roll Bonding ◽  
Orientation Imaging ◽  
Annealing Conditions

Refinement of grain size is one of the biggest challenges to produce steels with improved combination of strength and toughness. Ultrafine structures are being produced world-wide on various materials, including low carbon steel, using different types of processes. However, the majority of these processes also exhibit severe limitations because they are generally restricted to small samples and are difficult to be implemented on an industrial scale. A promising technique for industrial implementation is the Accumulative Roll Bonding (ARB), a process able to supply large samples, even in the laboratory scale. In this paper, warm intense straining (ε = 4) by ARB was applied to a plain low-C steel in order to develop ultrafine grains, aiming at sizes around 1-2 μm, suitable to maintain an adequate combination of strength and ductility. The effect of annealing conditions on the evolution of the work-hardened microstructure and the bonding behaviour after each pass were investigated. Orientation Imaging Microscopy was used to investigate the microstructure and give a quantitative assessment of high angle and low angle boundaries. It is showed that the frequency of high angle grain boundaries increases with the strain but the misorientation distribution remained far from that typical of a recrystallised material.

Effects of annealing conditions on heavily carbon‐doped InGaAs

1993 ◽  
Vol 62 (20) ◽  
pp. 2578-2580
Author(s):  
W. Y. Han ◽  
L. Calderon ◽  
Y. Lu ◽  
S. N. Schauer ◽  
R. P. Moerkirk ◽  
...  
Keyword(s):  
Carbon Doped ◽  
Annealing Conditions

Effects of Carbon Concentration Upon Oxygen Precipitation in Cz Si

1987 ◽  
Vol 104 ◽  
Author(s):  
S. Hahn ◽  
M. Arst ◽  
K. N. Ritz ◽  
S. Shatas ◽  
H. J. Stein ◽  
...  
Keyword(s):  
Carbon Content ◽  
Carbon Concentration ◽  
High Carbon ◽  
High Carbon Content ◽  
Oxygen Precipitation ◽  
Oxygen Precipitate ◽  
High Carbon Concentration ◽  
Precipitation Characteristics ◽  
C Complex ◽  
Oxide Precipitate

ABSTRACTEffects of high carbon concentration upon oxygen precipitate formation in Cz silicon have been investigated by combining various furnace and rapid thermal annneals. Even though oxide precipitate density increases with increasing carbon levels, Cs, synchrotron radiation section topographs of processed high carbon content wafers (Cs ∼ 4ppma) exhibit Pendellosung fringes, indicating a strain free bulk state. Our optical microscopic data have also shown very few defect etch features inside the bulk. A model based upon a direct coupling of both SiO2 and Si-C complex formation reactions is used to explain rather unique oxygen precipitation characteristics in the high carbon content Cz Si materials.

scholarly journals A Novel Decarburizing-Nitriding Treatment of Carburized/through-Hardened Bearing Steel towards Enhanced Nitriding Kinetics and Microstructure Refinement

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 112
Author(s):  
Fuyao Yan ◽  
Jiawei Yao ◽  
Baofeng Chen ◽  
Ying Yang ◽  
Yueming Xu ◽  
...  
Keyword(s):  
Surface Engineering ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Metallographic Analysis ◽  
Material Surface ◽  
Low Carbon ◽  
High Carbon ◽  
Softening Effect ◽  
Microstructure Refinement ◽  
Bearing Steels

Decarburization is generally avoided as it is reckoned to be a process detrimental to material surface properties. Based on the idea of duplex surface engineering, i.e., nitriding the case-hardened or through-hardened bearing steels for enhanced surface performance, this work deliberately applied decarburization prior to plasma nitriding to cancel the softening effect of decarburizing with nitriding and at the same time to significantly promote the nitriding kinetics. To manifest the applicability of this innovative duplex process, low-carbon M50NiL and high-carbon M50 bearing steels were adopted in this work. The influence of decarburization on microstructures and growth kinetics of the nitrided layer over the decarburized layer is investigated. The metallographic analysis of the nitrided layer thickness indicates that high carbon content can hinder the growth of the nitrided layer, but if a short decarburization is applied prior to nitriding, the thickness of the nitrided layer can be significantly promoted. The analysis of nitriding kinetics shows that decarburization reduces the activation energy for nitrogen diffusion and enhances nitrogen diffusivity. Moreover, the effect of decarburization in air can promote surface microstructure refinement via spinodal decomposition during plasma nitriding.

scholarly journals Laser Welding Dissimilar High-Strength Steel Alloys with Complex Geometries

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 792 ◽  
Author(s):  
Panos Efthymiadis ◽  
Khalid Nor
Keyword(s):  
Carbon Steel ◽  
Laser Welding ◽  
Cross Sections ◽  
High Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
High Carbon ◽  
Material Chemistry ◽  
Metallurgical Defects

Laser welding of dissimilar high-strength steels was performed in this study for two different geometries, flat and circular samples with material thicknesses of 5 and 8 mm. The material combinations were a low carbon to a medium or high carbon steel. Three different welding systems were employed: a Nd:YAG, a CO2 and a fiber laser. The process stability was evaluated for all the experiments. The resulting full penetration welds were inspected for their surface quality at the top and bottom of the specimens. Cross sections were taken to investigate the resulting microstructures and the metallurgical defects of the welds, such as cracks and pores. Significant hardening occurred in the weld region and the highest hardness values occurred in the Heat Affected Zone (HAZ) of the high carbon steel. The occurrence of weld defects depends strongly on the component geometry. The resulting microstructures within the weld were also predicted using neural network-simulated Continuous Cooling Transformation (CCT) diagrams and predicted the occurrence of a mixture of microstructures, such as bainite, martensite and pearlite, depending on the material chemistry. The thermal fields were measured with thermocouples and revealed the strong influence of component geometry on the cooling rate which in term defines the microstructures forming in the weld and the occurring hardness.

Sign in / Sign up

Export Citation Format

Share Document