A simple customized surgical guide for orthodontic miniplates with tube.

PubMed

Paek, Janghyun; Su, Ming-Jeaun; Kwon, Soon-Yong; Kim, Seong-Hun; Chung, Kyu-Rhim; Nelson, Gerald

2012-09-01

This article reports the use of a customized surgical guide for simple and precise C-tube plate placement with minimized incision. Patients who were planning to have orthodontic miniplate treatment because of narrow interradicular space were recruited for this study. A combined silicone and stainless steel wire surgical guide for the C-tube was fabricated on the cast model. The taller wire of the positioning guide is used to accurately start the incision. The incision guide-wire position is verified by placing the miniplate on the coronal horizontal wire to confirm that the incision will coordinate with the screw holes. Because the miniplate is firmly held in place, there is no risk of the miniplate anchoring screws (diameter, 1.5 mm; length, 4 mm) sliding on the bone surface during placement with a manual hand driver. The surgical guide was placed on the clinical site, and it allowed precise placement of the miniplate with minimum incision and preventing from slippage or path-of-insertion angulation errors that might interfere with accurate placement. Customized surgical guide enables precise planning for miniplate positions in anatomically complex sites.

Application of the DART Code for the Assessment of Advanced Fuel Behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rest, J.; Totev, T.

2007-07-01

The Dispersion Analysis Research Tool (DART) code is a dispersion fuel analysis code that contains mechanistically-based fuel and reaction-product swelling models, a one dimensional heat transfer analysis, and mechanical deformation models. DART has been used to simulate the irradiation behavior of uranium oxide, uranium silicide, and uranium molybdenum aluminum dispersion fuels, as well as their monolithic counterparts. The thermal-mechanical DART code has been validated against RERTR tests performed in the ATR for irradiation data on interaction thickness, fuel, matrix, and reaction product volume fractions, and plate thickness changes. The DART fission gas behavior model has been validated against UO{sub 2}more » fission gas release data as well as measured fission gas-bubble size distributions. Here DART is utilized to analyze various aspects of the observed bubble growth in U-Mo/Al interaction product. (authors)« less

Release of metal in vivo from stressed and nonstressed maxillofacial fracture plates and screws.

PubMed

Matthew, I R; Frame, J W

2000-07-01

To analyze the release of metal into the adjacent tissues from stressed and nonstressed titanium and stainless steel miniplates and screws. Two miniplates were inserted into the cranial vaults of 12 beagle dogs while they were under general endotracheal anesthesia. One miniplate was shaped to fit the curvature of the skull (control). Another miniplate, made of the same material, was bent in a curve until the midpoint was raised 3 mm above the ends. Screws were inserted and tightened until the plate conformed to the skull curvature, creating stresses in the system. Four animals (2 each, having titanium or stainless steel plates and screws) were killed after 4, 12, and 24 weeks. Metallosis of adjacent soft tissues was assessed qualitatively. Miniplates and screws were removed, and adjacent soft tissue and bone was excised. Titanium, iron, chromium, nickel, and aluminum levels were assayed by ultraviolet/visible light and atomic absorption spectrophotometry. Nonparametric statistical methods were used for data analysis. There was no clear relationship between pigmentation of soft tissue adjacent to the miniplates and screws and the concentrations of metal present. The data did not demonstrate any consistent differences in the concentrations of metallic elements next to stressed and nonstressed (control) miniplates and screws of either material. Stresses arising through poor contouring of miniplates do not appear to influence the extent of release of metal into the adjacent tissues.

Strength of titanium intramedullary implant versus miniplate fixation of mandibular condyle fractures.

PubMed

Frake, Paul C; Howell, Rebecca J; Joshi, Arjun S

2012-07-01

To test the strength of internal fixation of mandibular condyle fractures repaired with titanium miniplates versus titanium intramedullary implants. Prospective laboratory experimentation in urethane mandible models and human cadaveric mandibles. Materials testing laboratory at an academic medical center. Osteotomies of the mandibular condyle were created in 40 urethane hemimandible models and 24 human cadaveric specimens. Half of the samples in each group were repaired with traditional miniplates, and the other half were repaired with intramedullary titanium implants. Anteroposterior and mediolateral loads were applied to the samples, and the displacement was measured with reference to the applied force. Titanium intramedullary implants demonstrated statistically significant improved strength and stiffness versus miniplates in the urethane model experimental groups. Despite frequent plastic deformation and mechanical failures of the miniplates, a 1.6-mm-diameter titanium intramedullary pin did not mechanically fail in any of the cases. Intramedullary implantation failures were due to secondary fracture of the adjacent cortical bone or experimental design limitations including rotation of the smooth pin implant. Mechanical implant failures that were encountered with miniplate fixation were not seen with titanium intramedullary implants. These intramedullary implants provide stronger and more rigid fixation of mandibular condyle fractures than miniplates in this in vitro model.

Miniplate With a Bendable C-Tube Head Allows the Clinician to Alter Biomechanical Advantage in Extremely Complicated Anatomic Structure.

PubMed

Seo, Kyung Won; Iskenderoglu, Nur Serife; Hwang, Eui Hwan; Chung, Kyu-Rhim; Kim, Seong-Hun

2017-05-01

This article reports C-tube miniplates as a practical temporary anchorage device choice to treat open bite patients with maxillary sinus pneumatization. The C-tube components are titanium anchor plates and monocortical screws that are basically similar to any other miniplate systems, but it has the unique characteristic of the tube head to be malleable. The manipulation of the head part is easy due to the composition of pure titanium. The I-shaped C-tube with 3 holes and T-shaped C-tube miniplates were placed above the apices of maxillary molars as an absolute anchorage system to intrude the posterior maxilla. The bending of the tube heads assisted in reduction of severe open bite patient with maxillary sinus pneumatization. Sinus perforation during placement of skeletal anchorage system weakens stability of the anchorage and further cause complications. Placement of titanium C-tube miniplates allowed reliable skeletal anchorage and avoided maxillary sinus perforation in patients with extreme pneumatizations. Simple bending of C-tube miniplates ensured increased orthodontic intrusion force without having to replace them, and eliminated consequences such as perforation of maxillary sinus, sinusitis, soft tissue irritation, or infection. Anatomic difficulties in the placement of temporary anchorage device can be easily managed by using the bendable C-tube miniplate. It can serve as a great alternative over miniscrews or regular miniplates with reduced risk of sinus perforation and ability to bend the head portion to control orthodontic vectors and forces.

Ultrastructural analysis of metal particles released from stainless steel and titanium miniplate components in an animal model.

PubMed

Matthew, I R; Frame, J W

1998-01-01

Low-vacuum scanning electron microscopy (Ivac SEM) was used to characterize the appearance of metal particles released from stressed and unstressed Champy miniplates placed in dogs and to study the relationship of the debris to the surrounding tissues. Under general endotracheal anesthesia, two Champy miniplates (titanium or stainless steel) were placed on the frontal bone in an animal model. One miniplate was bent to fit the curvature of the frontal bone (unstressed) and another miniplate of the same material was bent in a curve until the midpoint was raised 3 mm above the ends. The latter miniplate adapted to the skull curvature under tension during screw insertion (stressed). The miniplates and surrounding tissues were retrieved after intervals of 4, 12, and 24 weeks. Decalcified sections were prepared and examined by light microscopy and Ivac SEM. Under Ivac SEM examination, the titanium particles had a smooth, polygonal outline. Stainless steel particles were typically spherical, with numerous small projections on the surface. Most particles were 1 to 10 microns in diameter. The tissue response to the particles was variable; some particles were covered by fibrous connective tissue or enclosed by bone, and others were intracellular. The metal particles released from stressed or unstressed Champy miniplates were similar, and this was related to their source of origin and duration within the tissues. The tissue response to the particles appeared to depend on their location.

Development of molecular dynamics potential for uranium silicide fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Jianguo; Zhang, Yongfeng; Hales, Jason D.

2016-09-01

Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimentalmore » evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possible to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.« less

Development of molecular dynamics potential for uranium silicide fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Jianguo; Zhang, Yongfeng; Hales, Jason D.

Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimentalmore » evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possible to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.« less

SAFARI-1: Achieving conversion to LEU - A local challenge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piani, C.S.B.

2008-07-15

Two years have passed since the South African Department of Minerals and Energy authorised the conversion from High Enriched Uranium (HEU) to Low Enriched Uranium (LEU) of the South African Research Reactor (SAFARI-1) and the associated fuel manufacturing at Pelindaba. The scheduling, as originally proposed, allowed approximately three years for the full conversion of the reactor, anticipating simultaneous manufacturing ability from the fuel production plant. Due to technical difficulties experienced in the conversion of the local manufacturing plant from HEU (UAl alloy) to LEU (U Silicide) and the uncertainty as to costing and scheduling of such an achievement, the conversionmore » of SAFARI-1 based on local supply has been allocated a lower priority. The acquisition in mid-2006 of 2 LEU silicide elements of SA design, manufactured by AREVA- CERCA and irradiated as test elements in SAFARI-1 to burn-ups of {approx}65% each; was successfully accomplished within 9 cycles of irradiation each. Furthermore, four 'Hybrid' elements (AREVA-CERCA plates assembled locally at Pelindaba) are ready for irradiation and have received regulatory authorisation to load. This will enable the SAFARI-1 conversion program to continue systematically according to an agreed schedule. This paper will trace the developments of the above and reflect the current status and the rescheduled conversion phases of the reactor according to latest expectations. (author)« less

Modified Miniplates for Temporary Skeletal Anchorage in Orthodontics: Placement and Removal Surgeries

PubMed Central

Cornelis, Marie A.; Scheffler, Nicole R.; Mahy, Pierre; Siciliano, Sergio; De Clerck, Hugo J.; Tulloch, J.F. Camilla

2009-01-01

Purpose Skeletal anchorage systems are increasingly used in orthodontics. This article describes the techniques of placement and removal of modified surgical miniplates used for temporary orthodontic anchorage and reports surgeons’ perceptions of their use. Patients and Methods We enrolled 97 consecutive orthodontic patients having miniplates placed as an adjunct to treatment. A total of 200 miniplates were placed by 9 oral surgeons. Patients and surgeons completed questionnaires after placement and removal surgeries. Results Fifteen miniplates needed to be removed prematurely. Antibiotics and anti-inflammatories were generally prescribed after placement but not after removal surgery. Most surgeries were performed with the patient under local anesthesia. Placement surgery lasted on average between 15 and 30 minutes per plate and was considered by the surgeons to be very easy to moderately easy. The surgery to remove the miniplates was considered easier and took less time. The patients’ chief complaint was swelling, lasting on average 5.3 ± 2.8 days after placement and 4.5 ± 2.6 days after removal. Conclusions Although miniplate placement/removal surgery requires the elevation of a flap, this was considered an easy and relatively short surgical procedure that can typically be performed with the patient under local anesthesia without complications, and it may be considered a safe and effective adjunct for orthodontic treatment. PMID:18571028

The experiment of magnesium ECAP miniplate as alternative biodegradable material (on male white New Zealand rabbits)

NASA Astrophysics Data System (ADS)

Wiwanto, Siska; Sulistyani, Lilies Dwi; Latief, Fourier Dzar Eljabbar; Supriadi, Sugeng; Priosoeryanto, Bambang Pontjo; Latief, Benny Syariefsyah

2018-02-01

Study of biodegradations of Magnesium ECAP (Equal Channel Angular Pressing) miniplate in the osteosynthesis system has been used as a new material for plate and screw in oral and maxillofacial surgery. This miniplate and screw that were made of Magnesium ECAP were implanted in the femurs of New Zealand rabbits. The degradation process was detected through pocket gas that appeared in hard and soft tissues surrounding in the implanted miniplates and screws. From the changes on the tissues, we can assess the biodegradation process by measuring the gas pocket through micro-CT Scan. Upon the first month of study we euthanized the rabbits and made a micro-CT Scan to see how far the effect of the gas pocket was. Histological analyses were performed to investigate the local tissue response adjacent to the Magnesium ECAP miniplates. We analyzed the femur of a rabbit a month, three months, and five months after implantation. The result showed a degradation rate in the implanted Magnesium ECAP miniplate of 0.61±0.39 mm/year. Unlike the screws, miniplates have higher water content and blood flow than bone, therefore they degrade faster. This study shows promising results for further development of Magnesium ECAP and in the production of osteosynthesis material for rigid fixation in Oral and Maxillofacial skeleton.

Maxillary Protraction With Intermaxillary Elastics to Miniplates Versus Bone-Anchored Face-Mask Therapy in Cleft Lip and Palate Patients.

PubMed

Jahanbin, Arezoo; Kazemian, Mozhgan; Eslami, Neda; Pouya, Iman Saeedi

2016-07-01

Cleft lip and palate patients usually have deficient maxilla due to postsurgical scars. The aim this study was to compare the effectiveness of miniplates-anchored face-mask therapy versus intermaxillary elastics to miniplates for maxillary traction in cleft lip and palate patients. This clinical trial included 11 prepubertal patients with cleft lip and palate. Initially, a w-arch expander was cemented and activated 3 mm per month to overcorrect the crossbite. Then, the patients were divided into 2 groups: mini-plate-anchored face-mask (n = 5): 2 miniplates were placed in the maxilla and the patients were instructed to wear a face-mask for 12 to 14 hours/per day. Intermaxillary elastics to miniplates (n = 6): 2 miniplates were inserted in the maxilla; 1 on each side and 2 miniplates were placed in the anterior mandible on both sides. Intermaxillary elastics with a force of 250 g per side were attached to the hooks. Cephalometric parameters before treatment (T1) and after achieving positive overjet (T2) were compared between the 2 groups. Fisher exact, paired, and independent t tests were used for statistical comparison. At T1 or T2 there was not a significant difference between the 2 groups in the skeletal, dental, and soft tissue variables. According to results of our preliminary study, intermaxillary elastics to miniplates might have a promising effect as an alternative for face mask therapy in maxillary protraction of cleft lip and palate patients.

Metallic fragments on the surface of miniplates and screws before insertion.

PubMed

Ray, M S; Matthew, I R; Frame, J W

1999-02-01

Particulate metal fragments have been identified histologically within the tissues adjacent to miniplates and screws after they have been removed. These were thought to have been caused by corrosion and degradation of the metal. However, the particles may have originated from rough edges or from protuberances left on the metal surface after cutting and machining during manufacture, and subsequently become detached. This study was undertaken to analyse the incidence and distribution of metal fragments on the surface of miniplates and screws before use. Fifteen miniplates and 60 screws were examined by stereomicroscopy and scanning electron microscopy. Rough metal edges or protuberances were identified on over half the samples, mostly in the countersink area of screw holes on the mini-plates. Fragments were detected within some of the cruciform screw heads and on some screw threads. We conclude that metal protuberances are present on the surface of mini-plate components when they are received from the manufacturer. There is a risk that the fragments might be detached and deposited into the tissues during insertion.

Custom-made prefabricated titanium miniplates in Le Fort I osteotomies: principles, procedure and clinical insights.

PubMed

Philippe, B

2013-08-01

This paper describes a new type of miniplate system that is designed and custom made during virtual surgery planning based on an individual patient's osteotomy. These miniplates are prefabricated with commercially pure porous titanium using direct metal laser sintering. The principles that guide the conception and production of this new miniplate are presented. The surgical procedure from the stage of virtual surgery planning until the final Le Fort I osteotomy and bone fixation are described using a case example. Copyright © 2013 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Development of the neurocranium after transsutural fixing by new, resorbable poly-L-lactide miniplates. A comparison to fixing with the common titanium miniplates.

PubMed

Antikainen, T; Pernu, H; Törmälä, P; Kallioinen, M; Waris, T; Serlo, W

1994-01-01

The right coronal sutures of twelve (12) newborn rabbits were fixed with commercially available, self-reinforced poly-L-lactide miniplates, with eight (8) rabbits sham treated with titanium miniplate fixation as reference experiments, in order to demonstrate the possible effects on skull growth. After six (6) months follow-up, both types of plate were detected to have caused a similar asymmetry in the neurocranium. Therefore, in our opinion, fixing across growing sutures, even with the new biodegradable devices, should be avoided.

Mechanical Properties of Uranium Silicides by Nanoindentation and Finite Elements Modeling

NASA Astrophysics Data System (ADS)

Carvajal-Nunez, U.; Elbakhshwan, M. S.; Mara, N. A.; White, J. T.; Nelson, A. T.

2018-02-01

Three methods were used to measure the mechanical properties of {U}3{Si}, {U}_3{Si}2, and USi. Quasi-static and continuous stiffness measurement nanoindentation were used to determine hardness and Young's modulus, and microindentation was used to evaluate the bulk hardness. Hardness and Young's modulus of the three U-Si compounds were both observed to increase with Si content. Finally, finite elements modelling was used to validate the nanoindentation data calculated for {U}3{Si}2 and estimate its yield strength.

Efficacy of 3-Dimensional plates over Champys miniplates in mandibular anterior fractures

PubMed Central

Barde, Dhananjay H; Mudhol, Anupama; Ali, Fareedi Mukram; Madan, R S; Kar, Sanjay; Ustaad, Farheen

2014-01-01

Background: Mandibular fractures are treated surgically by either rigid or semi-rigid fixation, two techniques that reflect almost opposite concept of craniomaxillofacial osteosynthesis. The shortcomings of these fixations led to the development of 3 dimensional (3D) miniplates. This study was designed with the aim of evaluating the efficiency of 3D miniplate over Champys miniplate in anterior mandibular fractures. Materials & Methods: This study was done in 40 patients with anterior mandibular fractures. Group I consisting of 20 patients in whom 3D plates were used for fixation while in Group II consisting of other 20 patients, 4 holes straight plates were used. The efficacy of 3D miniplate over Champy’s miniplate was evaluated in terms of operating time, average pain, post operative infection, occlusion, wound dehiscence, post operative mobility and neurological deficit. Results: The mean operation time for Group II was more compared to Group I (statistically significant).There was significantly greater pain on day of surgery and at 2nd week for Group II patients but there was no significant difference between the two groups at 4th week. The post operative infection, occlusal disturbance, wound dehiscence, post operative mobility at facture site, neurological deficit was statistically insignificant (chi square test). Conclusion: The results of this study suggest that fixation of anterior mandibular fractures with 3D plates provides three dimensional stability and carries low morbidity and infection rates. The only probable limitation of these 3D plates may be excessive implant material, but they seem to be easy alternative to champys miniplate. How to cite the article: Barde DH, Mudhol A, Ali FM, Madan RS, Kar S, Ustaad F. Efficacy of 3-Dimensional plates over Champys miniplates in mandibular anterior fractures. J Int Oral Health 2014;6(1):20-6. PMID:24653598

Treatment of a skeletal Class II malocclusion using fixed functional appliance with miniplate anchorage

PubMed Central

Celikoglu, Mevlut; Unal, Tuba; Bayram, Mehmet; Candirli, Celal

2014-01-01

Based on our literature search, we found that the use of miniplate anchorage with Forsus fatigue-resistance device (FRD) has not yet been reported. Therefore, the aim of the present case report was to present the treatment of a patient with skeletal Class II malocclusion with mandibular retrusion using Forsus FRD with miniplate anchorage. Fixed appliances with 0.022-inch slots were attached to the maxillary teeth and after 8 months of the leveling and alignment of the upper arch, 0.019 × 0.025-inch stainless steel archwire was inserted and cinched back. Two weeks after the placement of the miniplates bilaterally at the symphysis of the mandible, Forsus FRD was adjusted to the miniplates with a 35-mm length of rod chosen. Nine months after the skeletal anchored Forsus worn, Class I canine and molar relations were achieved and overjet was eliminated. PMID:24966783

Fully customized placement of orthodontic miniplates: a novel clinical technique

PubMed Central

2014-01-01

Introduction The initial stability and survival rate of orthodontic mini-implants are highly dependent on the amount of cortical bone at their insertion site. In areas with limited bone availability, mini-plates are preferred to provide effective skeletal anchorage. The purpose of this paper was to present a new clinical technique for the insertion of mini-plates. Methods In order to apply this new technique, a cone-beam image of the insertion area is required. A software (Galaxy Sirona, Bensheim, Germany) is used to construct a three-dimensional image of the scanned area and to virtually determine the exact location of the mini-plate as well as the position of the fixation screws. A stereolithographic model (STL) is then created by means of a three-dimensional scanner. Prior to its surgical insertion, the bone plate is adapted to the stereo-lithographic model. Finally, a custom transfer jig is fabricated in order to assist with accurate placement of the mini-plate intra-operatively. Results The presented technique minimizes intra-operative decision making, because the final position of the bone plate is determined pre-surgically. This significantly reduces the duration of the surgical procedure and improves its outcome. Conclusions A novel method for surgical placement of orthodontic mini-plates is presented. The technique facilitates accurate adaptation of mini-plates and insertion of retaining surgical screws; thereby enabling clinicians to more confidently increase the use of bone plates, especially in anatomical areas where the success of non-osseointegrated mini-screws is less favorable. PMID:24886597

Peculiarities of Employment of Polymeric Miniplates for Mandibular Osteosynthesis: A Preliminary Study

PubMed Central

Vares, Yan

2013-01-01

Searching for new materials for bone substitution, fixation, and reconstruction is a challenging task that attracts scientists and researchers of different fields of medicine. During the last few decades, much interest has been paid to polymeric materials, polyethylene in particular. The aim of this study is to present generalizations about our own experience in the employment of polyethylene miniplates for the surgical treatment of mandibular fractures. Ninety patients with 139 uni- and bilateral mandibular fractures in different locations were involved. Treatment modalities included open reduction and internal fixation with self-made polyethylene miniplates of straight, T-shaped, Y-shaped, and X-shaped configurations and titanium screws. In 88 (97.8%) cases of surgical treatment of mandibular fractures using polymer miniplates, good anatomical and functional results were achieved. Regardless of the necessity for improvement of some mechanical properties of polyethylene, the results obtained in our clinical investigation allow us to recommend polyethylene miniplates for routine practice. PMID:24436731

Stability of maxillary position after Le Fort I osteotomy using self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws.

PubMed

Kim, Bong Chul; Padwa, Bonnie L; Park, Hyung-Sik; Jung, Young-Soo

2011-05-01

The purpose of this study was to evaluate the stability of Le Fort I osteotomy using self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws. Nineteen patients who had Le Fort I osteotomy and internal fixation using self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws were evaluated both radiographically and clinically. Changes in maxillary position after operation were documented 1 week, 1, 3, 6 mo, and/or 1-yr postoperatively with lateral cephalometric tracings. Complications of the self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws were evaluated by follow-up roentgenograms and clinical observation. A mixed model analysis for repeated measures was used for statistical analysis. Maxillary position was stable after operation with no change between time points (P > .05). There were no complications with the self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws. Internal fixation of the maxilla after Le Fort I osteotomy with self-reinforced biodegradable poly-70L/30DL-lactide miniplates and screws is a reliable method for maintaining the postoperative maxillary position after Le Fort I osteotomy. Copyright © 2011 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Nuclear Energy Advanced Modeling and Simulation (NEAMS) Accident Tolerant Fuels High Impact Problem: Coordinate Multiscale U 3Si 2 Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamble, K. A.; Hales, J. D.; Miao, Y.

Since the events at the Fukushima-Daiichi nuclear power plant in March 2011 significant research has unfolded at national laboratories, universities and other institutions into alternative materials that have potential enhanced accident tolerance when compared to traditional \\uo~fuel zircaloy clad fuel rods. One of the potential replacement fuels is uranium silicide (\\usi) for its higher thermal conductivity and uranium density. The lower melting temperature is of potential concern during postulated accident conditions. Another disadvantage for \\usi~ is the lack of experimental data under power reactor conditions. Due to the aggressive development schedule for inserting some of the potential materials into leadmore » test assemblies or rods by 2022~\\cite{bragg-sitton_2014} multiscale multiphysics modeling approaches have been used to provide insight into these materials. \\\\ \

Mechanical Properties of Uranium Silicides by Nanoindentation and Finite Elements Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvajal-Nunez, U.; Elbakhshwan, M. S.; Mara, N. A.

Three methods were used to measure the mechanical properties of U 3Si, U 3Si 2, and USi. Quasi-static and continuous stiffness measurement nanoindentation were used to determine hardness and Young’s modulus, and microindentation was used to evaluate the bulk hardness. Hardness and Young’s modulus of the three U-Si compounds were both observed to increase with Si content. In conclusion, finite elements modelling was used to validate the nanoindentation data calculated for U 3Si 2 and estimate its yield strength.

Mechanical Properties of Uranium Silicides by Nanoindentation and Finite Elements Modeling

DOE PAGES

Carvajal-Nunez, U.; Elbakhshwan, M. S.; Mara, N. A.; ...

2017-12-04

Three methods were used to measure the mechanical properties of U 3Si, U 3Si 2, and USi. Quasi-static and continuous stiffness measurement nanoindentation were used to determine hardness and Young’s modulus, and microindentation was used to evaluate the bulk hardness. Hardness and Young’s modulus of the three U-Si compounds were both observed to increase with Si content. In conclusion, finite elements modelling was used to validate the nanoindentation data calculated for U 3Si 2 and estimate its yield strength.

Use of monocortical miniplates for the intraoral treatment of mandibular fractures.

PubMed

Chiodo, Thomas A; Milles, Maano

2009-03-01

Fixation of mandibular fractures using rigid hardware has gained wide acceptance over the past 3 decades. The goal of rigid internal fixation is to allow for fracture healing with limited, or no, time in maxillo-mandibular fixation. There has been significant evolution in plate and screw materials and design over the past 30 years. The term miniplate is used to describe a fracture plate with a screw diameter of 2.0 mm or less. With correct diagnosis and understanding of the forces affecting mandible fractures, miniplates can be applied transorally in various situations, allowing for less invasive treatment with open reduction of mandible fractures. This article describes the use of monocortical miniplates for the intraoral treatment of mandibular fractures.

[Guided maxillofacial surgery: Simulation and surgery aided by stereolithographic guides and custom-made miniplates.

PubMed

Philippe, B

2013-08-05

We present a new model of guided surgery, exclusively using computer assistance, from the preoperative planning of osteotomies to the actual surgery with the aid of stereolithographic cutting guides and osteosynthetic miniplates designed and made preoperatively, using custom-made titanium miniplates thanks to direct metal laser sintering. We describe the principles that guide the designing and industrial manufacturing of this new type of osteosynthesis miniplates. The surgical procedure is described step-by-step using several representative cases of dento-maxillofacial dysmorphosis. The encouraging short-term results demonstrate the wide range of application of this new technology for cranio-maxillofacial surgery, whatever the type of osteotomy performed, and for plastic reconstructive surgery. Copyright © 2013. Published by Elsevier Masson SAS.

Functional and radiologic outcome of open reduction and internal fixation of condylar head and neck fractures using miniplate or microplate system.

PubMed

Xie, Si-Tian; Singhal, Dhruv; Chen, Chien-Tzung; Chen, Yu-Ray

2013-12-01

Although the appropriate management of condylar process fractures after miniplate or microplate fixation has been described, there has been no comparative analysis of these plating systems. A retrospective review of patients who underwent open reduction and internal fixation (ORIF) of condylar head or neck fractures at our institution from January 2000 through August 2010 identified 70 patients. Of these, 38 were treated with microplates and 32 with miniplates. The primary functional and radiographic results were the maximal mouth opening and condylar bone resorption, respectively. The rates of complications, including malocclusion, chin deviation, temporomandibular joint complaints, and facial nerve palsy, were recorded. The maximal mouth opening was larger in the microplate group than in the miniplate group throughout the follow-up period; this difference was statistically significant 12 (P = 0.020), 18 (P = 0.026), and 24 (P = 0.032) months after ORIF. Similarly, the radiographic scores for bone resorption and condyle morphology were significantly better in the microplate group than in the miniplate group throughout the follow-up period [6 (P = 0.011), 12 (P = 0.035), 24 (P = 0.026), and 48 (P = 0.040) months after ORIF]. Moreover, patients who underwent miniplate fixation experienced a significantly higher incidence of temporomandibular joint click than those who underwent microplate fixation (P = 0.014). Microplates limit dissection, providing excellent fixation for intracapsular condylar head fractures, and also provide adequate rigidity for fixation of condylar neck fractures. Microplate fixation of condylar head and neck fractures yielded excellent functional and radiographic results. The rates of complications after microplate fixation were equal to or less than those in the miniplate group. Prospective studies are needed to confirm these findings.

A Comparative Study of 3-Dimensional Titanium Versus 2-Dimensional Titanium Miniplates for Open Reduction and Fixation of Mandibular Parasymphysis Fracture.

PubMed

Mittal, Yogesh; Varghese, K George; Mohan, S; Jayakumar, N; Chhag, Somil

2016-03-01

Three dimensional titanium plating system was developed by Farmand in 1995 to meet the requirements of semi rigid fixation with lesser complication. The purpose of this in vivo prospective study was to evaluate and compare the clinical effectiveness of three dimensional and two dimensional Titanium miniplates for open reduction and fixation of mandibular parasymphysis fracture. Thirty patients with non-comminuted mandibular parasymphysis fractures were divided randomly into two equal groups and were treated with 2 mm 3D and 2D miniplate system respectively. All patients were systematically monitored at 1st, 2nd, 3rd, 6th week, 3rd and 6th month postoperatively. The outcome parameters recorded were severity of pain, infection, mobility, occlusion derangement, paresthesia and implant failure. The data so collected was analyzed using independent t test and Chi square test (α = .05). The results showed that one patient in each group had post-operative infection, occlusion derangement and mobility (p > .05). In Group A, one patient had paresthesia while in Group B, two patients had paresthesia (p > .05). None of the patients in both the groups had implant failure. There was no statistically significant difference between 3D and 2D miniplate system in all the recorded parameters at all the follow-ups (p > .05). 3D miniplates were found to be better than 2D miniplates in terms of cost, ease of surgery and operative time. However, 3D miniplates were unfavorable for cases where fracture line was oblique and in close proximity to mental foramen, where they were difficult to adapt and more chances for tooth-root damage and inadvertent injury to the mental nerve due to traction.

Chemical reactivity of CVC and CVD SiC with UO2 at high temperatures

NASA Astrophysics Data System (ADS)

Silva, Chinthaka M.; Katoh, Yutai; Voit, Stewart L.; Snead, Lance L.

2015-05-01

Two types of silicon carbide (SiC) synthesized using two different vapor deposition processes were embedded in UO2 pellets and evaluated for their potential chemical reaction with UO2. While minor reactivity between chemical-vapor-composited (CVC) SiC and UO2 was observed at comparatively low temperatures of 1100 and 1300 °C, chemical-vapor-deposited (CVD) SiC did not show any such reactivity. However, both CVD and CVC SiCs showed some reaction with UO2 at a higher temperature (1500 °C). Elemental maps supported by phase maps obtained using electron backscatter diffraction indicated that CVC SiC was more reactive than CVD SiC at 1500 °C. Furthermore, this investigation indicated the formation of uranium carbides and uranium silicide chemical phases such as UC, USi2, and U3Si2 as a result of SiC reaction with UO2.

Three-dimensional finite element analysis of a newly designed onplant miniplate anchorage system.

PubMed

Liu, Lin; Qu, Yin-Ying; Jiang, Li-Jun; Zhou, Qian; Tang, Tian-Qi

2016-06-01

The purpose of this research was to evaluate the structural stress and deformation of a newly designed onplant miniplate anchorage system compared to a standard anchorage system. A bone block integrated with a novel miniplate and fixation screw system was simulated in a three-dimensional model and subjected to force at different directions. The stress distribution and deformation of the miniplate system and cortical bone were evaluated using the three-dimensional finite element method. The results showed that the stress on the plate system and bone was linearly proportional to the force magnitude and was higher when the force was in a vertical direction (Y-axis). Stress and deformation values of the two screws (screw 1 and 2) were asymmetric when the force was added along Y-axis and was greater in screw 1. The highest deformation value of the screws was 7.5148 μm, much smaller than the limit value. The load was decreased for each single miniscrew, and the ability of the new anchorage system to bear the load was also enhanced to some degree. It was suggested that the newly designed onplant miniplate anchorage system is effective, easily implanted and minimally invasive.

Comparison of titanium and biodegradable miniplates for fixation of mandibular fractures.

PubMed

Lee, Hyo-Bin; Oh, Ji-Su; Kim, Su-Gwan; Kim, Hak-Kyun; Moon, Seong-Yong; Kim, Young-Kyun; Yun, Pil-Young; Son, Jun-Sik

2010-09-01

The purpose of the present study was to compare the use of biodegradable miniplates and titanium miniplates for the fixation of mandibular fractures. BioSorb FX biodegradable plates and screws and titanium miniplates were used in 91 patients (65 males and 26 females; age range 11 to 69 years) for the treatment of mandibular fractures. The clinical and radiographic findings were recorded at 1, 3, 6, and 12 months after surgery. The overall complication rate was 4.41%. In the biodegradable plate group, infection occurred in 2 cases (4.26%) and was resolved by incision and drainage and antibiotics. In the titanium plate group, infection occurred in 1 case and plate fracture in 1 case (4.56%). The fractured plate was removed, and a new titanium miniplate was applied using a trocar. The infection was resolved with antibiotics. No adverse tissue reactions, malocclusions, or malunions occurred during the observation period. Our results have shown that the rate of morbidity is very low with the use of biodegradable plates and titanium plates, suggesting that biodegradable and titanium plates have the potential for successful use in the fixation of mandibular fractures. Crown Copyright 2010. Published by Elsevier Inc. All rights reserved.

Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study.

PubMed

Mansuri, Samir; Abdulkhayum, Abdul Mujeeb; Gazal, Giath; Hussain, Mohammed Abid Zahir

2013-12-01

Surgical treatment of fracture mandible using an internal fixation has changed in the last decades to achieve the required rigidity, stability and immediate restoration of function. The aim of the study was to do a Prospective study of 10 patients to determine the efficacy of rectangular grid compression miniplates in mandibular fractures. This study was carried out using 2.0 rectangular grid compression miniplates and 8 mm multidirectional screws as a rigid internal fixation in 10 patients without post operative intermaxillary fixation (IMF). Follow up was done for period of 6 months. All fractures were healed with an absolute stability in post operative period. None of the patient complained of post operative difficulty in occlusion. Within the limits of this study, it can be concluded that rectangular grid compression miniplates was rigid, reliable and thus can be recommended for the treatment of mandibular angle fractures. How to cite this article: Mansuri S, Abdulkhayum AM, Gazal G, Hussain MA. Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study. J Int Oral Health 2013;5(6):93-100 .

Use of miniplates as a method for orthodontic anchorage: a case report.

PubMed

Peres, Fernando Gianzanti; Padovan, Luis Eduardo Marques; Kluppel, Leandro Eduardo; Albuquerque, Gustavo Calvalcanti; Souza, Paulo Cesar Ulson de; Claudino, Marcela

2016-01-01

Temporary anchorage devices (TADs) have been developed to be used as direct adjuncts in orthodontic treatment and have facilitated treatment of more complex orthodontic cases, including patients with dental impaction. This clinical case reports the applicability of TADs in the orthodontic treatment of a patient with impacted mandibular second molars. Surgical and orthodontic procedures related to the use of miniplates were also discussed in this study. The use of temporary anchorage devices, such as miniplates, can be suggested as an alternative to treat patients with impacted mandibular second molars.

A Comparison of Implants Used in Open-Door Laminoplasty: Structural Rib Allografts Versus Metallic Miniplates.

PubMed

Tabaraee, Ehsan; Mummaneni, Praveen; Abdul-Jabbar, Amir; Shearer, David; Roy, Esha; Amin, Beejal; Ames, Christopher; Burch, Shane; Deviren, Vedat; Berven, Sigurd; Hu, Serena; Chou, Dean; Tay, Bobby K

2017-06-01

A retrospective case-controlled study. Open-door laminoplasty has been successfully used to address cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament. Two common implants include rib allograft struts and metallic miniplates. The goals of this study were to compare outcomes, complications, and costs associated with these 2 implants. A retrospective review was done on 51 patients with allograft struts and 55 patients with miniplates. Primary outcomes were neck visual analog scale (VAS) pain scores and Nurick scores. Secondary outcomes included length of the procedure, estimated blood loss, rates of complications, and the direct costs associated with the surgery and inpatient hospitalization. There were no differences in demographic characteristics, diagnoses, comorbidities, and preoperative outcome scores between the 2 treatment groups. Mean follow-up was 27 months. The postoperative neck VAS scores and Nurick scores improved significantly from baseline to final follow-up for both groups, but there was no difference between the 2 groups. The average length of operation (161 vs. 136 min) and number of foraminotomies (2.7 vs. 1.3) were higher for the allograft group (P=0.007 and 0.0001, respectively). Among the miniplate group, there was no difference in complications but a trend for less neck pain for patients treated without hard collar at final follow-up (1.8 vs. 2.3, P=0.52). The mean direct costs of hospitalization for the miniplate group were 15% higher. Structural rib allograft struts and metallic miniplates result in similar improvements in pain and functional outcome scores with no difference in the rate of complications in short-term follow-up. Potential benefits of using a plate include shorter procedure length and less need for postoperative immobilization. When costs of bracing and operative time are included, the difference in cost between miniplates and allograft struts is negligible.

Evaluation of the effects of skeletal anchoraged Forsus FRD using miniplates inserted on mandibular symphysis: A new approach for the treatment of Class II malocclusion.

PubMed

Unal, Tuba; Celikoglu, Mevlut; Candirli, Celal

2015-05-01

To evaluate the skeletal, dentoalveolar, and soft tissue effects of the Forsus Fatigue Resistant Device (FRD) appliance with miniplate anchorage for the treatment of skeletal Class II malocclusion. The prospective clinical study group included 17 patients (11 girls and 6 boys; mean age 12.96 ± 1.23 years) with Class II malocclusion due to mandibular retrusion and treated with skeletal anchoraged Forsus FRD. After 0.019 × 0.025-inch stainless steel archwire was inserted and cinched back in the maxillary arch, two miniplates were placed bilaterally on the mandibular symphysis. Then, the Forsus FRD EZ2 appliance was adjusted to the miniplates without leveling the mandibular arch. The changes in the leveling and skeletal anchoraged Forsus FRD phases were evaluated by means of the Paired and Student's t-tests using the cephalometric lateral films. The success rate of the miniplates was found to be 91.5% (38 of 42 miniplates). The mandible significantly moved forward (P < .001) and caused a significant restraint in the sagittal position of the maxilla (P < .001). The overjet correction (-5.11 mm) was found to be mainly by skeletal changes (A-VRL, -1.16 mm and Pog-VRL, 2.62 mm; approximately 74%); the remaining changes were due to the dentoalveolar contributions. The maxillary and mandibular incisors were significantly retruded (P < .001). This new approach was an effective method for treating skeletal Class II malocclusion due to the mandibular retrusion via a combination of skeletal and dentoalveolar changes.

Virtually fabricated guide for placement of the C-tube miniplate.

PubMed

Paek, Janghyun; Jeong, Do-Min; Kim, Yong; Kim, Seong-Hun; Chung, Kyu-Rhim; Nelson, Gerald

2014-05-01

This paper introduces a virtually planned and stereolithographically fabricated guiding system that will allow the clinician to plan carefully for the best location of the device and to achieve an accurate position without complications. The scanned data from preoperative dental casts were edited to obtain preoperative 3-dimensional (3D) virtual models of the dentition. After the 3D virtual models were repositioned, the 3D virtual surgical guide was fabricated. A surgical guide was created onscreen, and then these virtual guides were materialized into real ones using the stereolithographic technique. Whereas the previously described guide required laboratory work to be performed by the orthodontist, our technique is more convenient because the laboratory work is done remotely by computer-aided design/computer-aided manufacturing technology. Because the miniplate is firmly held in place as the patient holds his or her mandibular teeth against the occlusal pad of the surgical guide, there is no risk that the miniscrews can slide on the bone surface during placement. The software program (2.5-dimensional software) in this study combines 2-dimensional cephalograms with 3D virtual dental models. This software is an effective and efficient alternative to 3D software when 3D computed tomography data are not available. To confidently and safely place a miniplate with screw fixation, a simple customized guide for an orthodontic miniplate was introduced. The use of a custom-made, rigid guide when placing miniplates will minimize complications such as vertical mislocation or slippage of the miniplate during placement. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Use of miniplates as a method for orthodontic anchorage: a case report

PubMed Central

Peres, Fernando Gianzanti; Padovan, Luis Eduardo Marques; Kluppel, Leandro Eduardo; Albuquerque, Gustavo Calvalcanti; de Souza, Paulo Cesar Ulson; Claudino, Marcela

2016-01-01

ABSTRACT Introduction: Temporary anchorage devices (TADs) have been developed to be used as direct adjuncts in orthodontic treatment and have facilitated treatment of more complex orthodontic cases, including patients with dental impaction. Objectives: This clinical case reports the applicability of TADs in the orthodontic treatment of a patient with impacted mandibular second molars. Surgical and orthodontic procedures related to the use of miniplates were also discussed in this study. Conclusions: The use of temporary anchorage devices, such as miniplates, can be suggested as an alternative to treat patients with impacted mandibular second molars. PMID:27901235

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burkes, Douglas E.; Senor, David J.; Casella, Andrew M.

Numerous global programs are focused on the continued development of existing and new research and test reactor fuels to achieve maximum attainable uranium loadings to support the conversion of a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Some of these programs are focused on development and qualification of a fuel design that consists of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix as one option for reactor conversion. The current paper extends a failure model originally developed for UO2-stainless steel dispersion fuels and used currently available thermal-mechanical property information for the materials ofmore » interest in the current proposed design. A number of fabrication and irradiation parameters were investigated to understand the conditions at which failure of the matrix, classified as pore formation in the matrix, might occur. The results compared well with experimental observations published as part of the Reduced Enrichment for Research and Test Reactors (RERTR)-6 and -7 mini-plate experiments. Fission rate, a function of the 235U enrichment, appeared to be the most influential parameter in premature failure, mainly as a result of increased interaction layer formation and operational temperature, which coincidentally decreased the yield strength of the matrix and caused more rapid fission gas production and recoil into the surrounding matrix material. Addition of silicon to the matrix appeared effective at reducing the rate of interaction layer formation and can extend the performance of a fuel plate under a certain set of irradiation conditions, primarily moderate heat flux and burnup. Increasing the dispersed fuel particle diameter may also be effective, but only when combined with other parameters, e.g., lower enrichment and increased Si concentration. The model may serve as a valuable tool in initial experimental design.« less

A novel approach for treatment of skeletal Class II malocclusion: Miniplates-based skeletal anchorage.

PubMed

Al-Dumaini, Abdullsalam Abdulqawi; Halboub, Esam; Alhammadi, Maged Sultan; Ishaq, Ramy Abdul Rahman; Youssef, Mohamed

2018-02-01

The objective of this study was to evaluate the effect of a new approach-bimaxillary miniplates-based skeletal anchorage-in the treatment of skeletal Class II malocclusion compared with untreated subjects. The study (miniplates) group comprised 28 patients (14 boys, 14 girls) with skeletal Class II malocclusion due to mandibular retrusion, with a mean age of 11.83 years. After 0.017 × 0.025-in stainless steel archwires were placed in both arches, 4 miniplates were fixed bilaterally, 2 in the maxillary anterior areas and 2 in the mandibular posterior areas, and used for skeletal treatment with elastics. Twenty-four Class II untreated subjects (11 boys, 13 girls), with a mean age of 11.75 years, were included as controls. Skeletal and dental changes were evaluated using pretreatment and posttreatment or observational lateral cephalometric radiographs. The treatment changes were compared with the growth changes observed in the control group using independent t tests. Compared with the minimal changes induced by growth in the control group, the skeletal changes induced by miniplates were more obvious. The mandibular length increased significantly (3 mm), and the mandible moved forward, with a significant restraint in the sagittal position of the maxilla (P <0.001). The overjet correction (-4.26 mm) was found to be a net result of skeletal changes (A-Y-axis = -1.18 mm and B-Y-axis = 3.83 mm). The mandibular plane was significantly decreased by 2.75° (P <0.001). This new technique, bimaxillary miniplates-based skeletal anchorage, is an effective method for treating patients with skeletal Class II malocclusions through obvious skeletal, but minimal dentoalveolar, changes. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Replacing a failed mini-implant with a miniplate to prevent interruption during orthodontic treatment.

PubMed

Lee, Jin-Hwa; Choo, Hyeran; Kim, Seong-Hun; Chung, Kyu-Rhim; Giannuzzi, Lucille A; Ngan, Peter

2011-06-01

When mini-implants fail during orthodontic treatment, there is a need to have a backup plan to either replace the failed implant in the adjacent interradicular area or wait for the bone to heal before replacing the mini-implant. We propose a novel way to overcome this problem by replacement with a miniplate so as not to interrupt treatment or prolong treatment time. The indications, advantages, efficacy, and procedures for switching from a mini-implant to a miniplate are discussed. Two patients who required replacement of failed mini-implants are presented. In the first patient, because of the proximity of the buccal vestibule to the mini-implant, it was decided to replace the failed mini-implant by an I-shaped C-tube miniplate. In the second patient, radiolucencies were found around the failed mini-implants, making the adjacent alveolar bone unavailable for immediate placement of another mini-implant. In addition, the maxillary sinus pneumatization was expanded deeply into the interradicular spaces; this further mandated an alternative placement site. One failed mini-implant was examined under a scanning electron microscope for bone attachment. Treatment was completed in both patients after replacement with miniplates without interrupting the treatment mechanics or prolonging the treatments. Examination under the scanning electron microscope showed partial bone growth into the coating pores and titanium substrate interface even after thorough cleaning and sterilization. Replacement with a miniplate is a viable solution for failed mini-implants during orthodontic treatment. The results from microscopic evaluation of the failed mini-implant suggest that stringent guidelines are needed for recycling used mini-implants. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Phase formation during the carbothermic reduction of eudialyte concentrate

NASA Astrophysics Data System (ADS)

Krasikov, S. A.; Upolovnikova, A. G.; Sitnikova, O. A.; Ponomarenko, A. A.; Agafonov, S. N.; Zhidovinova, S. V.; Maiorov, D. V.

2013-07-01

The phase transformations of eudialyte concentrate during the carbothermic reduction in the temperature range 25-2000°C are studied by thermodynamic simulation, differential thermal analysis, and X-ray diffraction. As the temperature increases to 1500°C, the following phases are found to form sequentially: iron and manganese carbides, free iron, niobium carbide, iron silicides, silicon and titanium carbides, and free silicon. Strontium, yttrium, and uranium in the temperature range under study are not reduced and are retained in an oxide form, and insignificant reduction of zirconium oxides with the formation of carbide ZrC is possible only at temperatures above 1500°C.

Effect of High Si Content on U3Si2 Fuel Microstructure

NASA Astrophysics Data System (ADS)

Rosales, Jhonathan; van Rooyen, Isabella J.; Meher, Subhashish; Hoggan, Rita; Parga, Clemente; Harp, Jason

2018-02-01

The development of U3Si2 as an accident-tolerant nuclear fuel has gained research interest because of its promising high uranium density and improved thermal properties. In the present study, three samples of U3Si2 fuel with varying silicon content have been fabricated by a conventional powder metallurgical route. Microstructural characterization via scanning and transmission electron microscopy reveals the presence of other stoichiometry of uranium silicide such as USi and UO2 in both samples. The detailed phase analysis by x-ray diffraction shows the presence of secondary phases, such as USi, U3Si, and UO2. The samples with higher concentrations of silicon content of 7.5 wt.% display additional elemental Si. These samples also possess an increased amount of the USi phase as compared to that in the conventional sample with 7.3 wt.% silicon. The optimization of U3Si2 fuel performance through the understanding of the role of Si content on its microstructure has been discussed.

Chemical reactivity of CVC and CVD SiC with UO 2 at high temperatures

DOE PAGES

Silva, Chinthaka M.; Katoh, Yutai; Voit, Stewart L.; ...

2015-02-11

Two types of silicon carbide (SiC) synthesized using two different vapor deposition processes were embedded in UO 2 pellets and evaluated for their potential chemical reaction with UO 2. While minor reactivity between chemical-vapor-composited (CVC) SiC and UO 2 was observed at comparatively low temperatures of 1100 and 1300 C, chemical-vapor-deposited (CVD) SiC did not show any such reactivity, according to microstructural investigations. But, both CVD and CVC SiCs showed some reaction with UO 2 at a higher temperature (1500 C). Elemental maps supported by phase maps obtained using electron backscatter diffraction indicated that CVC SiC was more reactive thanmore » CVD SiC at 1500 C. Moreover, this investigation indicated the formation of uranium carbides and uranium silicide chemical phases such as UC, USi 2, and U 3Si 2 as a result of SiC reaction with UO 2.« less

Current status of U{sub 3}Si{sub 2} fuel element fabrication in Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durazzo, M.; Carvalho, E.F. Urano de; Saliba-Silva, A.M.

2008-07-15

IPEN has been working for increasing radioisotope production in order to supply the expanding demand for radiopharmaceutical medicines requested by the Brazilian welfare. To reach this objective, the IEA-R1 research reactor power capacity was recently increased from 2 MW to 4 MW. Since 1988 IPEN has been manufacturing its own fuel element, initially based on U{sub 3}O{sub 8}-Al dispersion fuel plates with 2.3 gU/cm{sup 3}. To support the reactor power increase, higher uranium density in the fuel plate meat had to be achieved for better irradiation flux and also to minimize the irradiated fuel elements to be stored. Uranium silicidemore » was the chosen option and the fuel fabrication development started with the support of the IAEA BRA/4/047 Technical Cooperation Project. This paper describes the results of this program and the current status of silicide fuel fabrication and its qualification. (author)« less

Temperature-dependent structure and phase variation of nickel silicide nanowire arrays prepared by in situ silicidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Hailong; She, Guangwei, E-mail: shegw@mail.ipc.ac.cn; Mu, Lixuan

Graphical abstract: Display Omitted Highlight: ► Nickel silicides nanowire arrays prepared by a simple in situ silicidation method. ► Phases of nickel silicides could be varied by tuning the reaction temperature. ► A growth model was proposed for the nickel silicides nanowires. ► Diffusion rates of Ni and Si play a critical role for the phase variation. -- Abstract: In this paper, we report an in situ silicidizing method to prepare nickel silicide nanowire arrays with varied structures and phases. The in situ reaction (silicidation) between Si and NiCl{sub 2} led to conversion of Si nanowires to nickel silicide nanowires.more » Structures and phases of the obtained nickel silicides could be varied by changing the reaction temperature. At a relatively lower temperature of 700 °C, the products are Si/NiSi core/shell nanowires or NiSi nanowires, depending on the concentration of NiCl{sub 2} solution. At a higher temperature (800 °C and 900 °C), other phases of the nickel silicides, including Ni{sub 2}Si, Ni{sub 31}Si{sub 12}, and NiSi{sub 2}, were obtained. It is proposed that the different diffusion rates of Ni and Si atoms at different temperatures played a critical role in the formation of nickel silicide nanowires with different phases.« less

Fabrication and Gas-Sensing Properties of Ni-Silicide/Si Nanowires.

PubMed

Hsu, Hsun-Feng; Chen, Chun-An; Liu, Shang-Wu; Tang, Chun-Kai

2017-12-01

Ni-silicide/Si nanowires were fabricated by atomic force microscope nano-oxidation on silicon-on-insulator substrates, selective wet etching, and reactive deposition epitaxy. Ni-silicide nanocrystal-modified Si nanowire and Ni-silicide/Si heterostructure multi-stacked nanowire were formed by low- and high-coverage depositions of Ni, respectively. The Ni-silicide/Si Schottky junction and Ni-silicide region were attributed high- and low-resistance parts of nanowire, respectively, causing the resistance of the Ni-silicide nanocrystal-modified Si nanowire and the Ni-silicide/Si heterostructure multi-stacked nanowire to be a little higher and much lower than that of Si nanowire. An O 2 sensing device was formed from a nanowire that was mounted on Pt electrodes. When the nanowires exposed to O 2 , the increase in current in the Ni-silicide/Si heterostructure multi-stacked nanowire was much larger than that in the other nanowires. The Ni-silicide nanocrystal-modified Si nanowire device had the highest sensitivity. The phenomenon can be explained by the formation of a Schottky junction at the Ni-silicide/Si interface in these two types of Ni-Silicide/Si nanowire and the formation of a hole channel at the silicon nanowire/native oxide interface after exposing the nanowires to O 2 .

Status and progress of the RERTR program in the year 2003.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Travelli, A.; Nuclear Engineering Division

2003-01-01

One of the most important events affecting the RERTR program during the past year was the decision by the U.S. Department of Energy to request the U.S. Congress to significantly increase RERTR program funding. This decision was prompted, at least in part, by the terrible events of September 11, 2001, and by a high-level U.S./Russian Joint Expert Group recommendation to immediately accelerate RERTR program activities in both countries, with the goal of converting all the world's research reactors to low-enriched fuel at the earliest possible time, and including both Soviet-designed and United States-designed research reactors. The U.S. Congress is expectedmore » to approve this request very soon, and the RERTR program has prepared itself well for the intense activities that the 'Accelerated RERTR Program' will require. Promising results have been obtained in the development of a fabrication process for monolithic LEU U-Mo fuel. Most existing and future research reactors could be converted to LEU with this fuel, which has a uranium density between 15.4 and 16.4 g/cm{sup 3} and yielded promising irradiation results in 2002. The most promising method hinges on producing the monolithic meat by cold-rolling a thin ingot produced by casting. The aluminum clad and the meat are bonded by friction stir welding and the cladding surface is finished by a light cold roll. This method can be applied to the production of miniplates and appears to be extendable to the production of full-size plates, possibly with intermediate anneals. Other methods planned for investigation include high temperature bonding and hot isostatic pressing. The progress achieved within the Russian RERTR program, both for the traditional tube-type elements and for the new 'universal' LEU U-Mo pin-type elements, promises to enable soon the conversion of many Russian-designed research and test reactors. Irradiation testing of both fuel types with LEU U-Mo dispersion fuels has begun. Detailed studies are in progress to define the feasibility of converting each Russian-designed research and test reactor to either fuel type. The plan for the Accelerated RERTR Program is structured to achieve LEU conversion of all HEU research reactors supplied by the United States and Russia during the next nine years. This effort will address, in addition to the fuel development and qualification, the analyses and performance/economic/safety evaluations needed to implement the conversions. In combination with this over-arching goal, the RERTR program plans to achieve at the earliest possible date qualification of LEU U-Mo dispersion fuels with uranium densities of 6 g/cm{sup 3} and 7 g/cm{sup 3}. Reactors currently using or planning to use LEU silicide fuel will rely on this fuel after termination of the FRRSNFA program, because it is acceptable to COGEMA for reprocessing. Qualification of LEU U-Mo dispersion fuels has suffered some unavoidable delays but, to accelerate it as much as possible, the RERTR program, the French CEA, and the Australian ANSTO have agreed to jointly pursue a two-element qualification test of LEU U-Mo dispersion fuel with uranium density of 7.0 g/cm{sup 3} to be performed in the Osiris reactor during 2004. The RERTR program also intends to eliminate all obstacles to the utilization of LEU in targets for isotope production, so that this important function can be performed without the need for weapons-grade materials. All of us, working together as we have for many years, can ensure that all these goals will be achieved. By promoting the efficiency and safety of research reactors while eliminating the traffic in weapons-grade uranium, we can prevent the possibility that some of this material might fall in the wrong hands. Few causes can be more deserving of our joint efforts.« less

Ni-silicide growth kinetics in Si and Si/SiO2 core/shell nanowires.

PubMed

Ogata, K; Sutter, E; Zhu, X; Hofmann, S

2011-09-07

A systematic study of the kinetics of axial Ni silicidation of as-grown and oxidized Si nanowires (SiNWs) with different crystallographic orientations and core diameters ranging from ∼ 10 to 100 nm is presented. For temperatures between 300 and 440 °C the length of the total axial silicide intrusion varies with the square root of time, which provides clear evidence that the rate limiting step is diffusion of Ni through the growing silicide phase(s). A retardation of Ni-silicide formation for oxidized SiNWs is found, indicative of a stress induced lowering of the diffusion coefficients. Extrapolated growth constants indicate that the Ni flux through the silicided NW is dominated by surface diffusion, which is consistent with an inverse square root dependence of the silicide length on the NW diameter as observed for (111) orientated SiNWs. In situ TEM silicidation experiments show that NiSi(2) is the first forming phase for as-grown and oxidized SiNWs. The silicide-SiNW interface is thereby atomically abrupt and typically planar. Ni-rich silicide phases subsequently nucleate close to the Ni reservoir, which for as-grown SiNWs can lead to a complete channel break-off for prolonged silicidation due to significant volume expansion and morphological changes.

Ni-Silicide Growth Kinetics in Si and Si/SiO2 Core/Shell Nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hofmann, S.; Sutter, E.; Ogata, K.

A systematic study of the kinetics of axial Ni silicidation of as-grown and oxidized Si nanowires (SiNWs) with different crystallographic orientations and core diameters ranging from {approx} 10 to 100 nm is presented. For temperatures between 300 and 440 C the length of the total axial silicide intrusion varies with the square root of time, which provides clear evidence that the rate limiting step is diffusion of Ni through the growing silicide phase(s). A retardation of Ni-silicide formation for oxidized SiNWs is found, indicative of a stress induced lowering of the diffusion coefficients. Extrapolated growth constants indicate that the Nimore » flux through the silicided NW is dominated by surface diffusion, which is consistent with an inverse square root dependence of the silicide length on the NW diameter as observed for <111> orientated SiNWs. In situ TEM silicidation experiments show that NiSi{sub 2} is the first forming phase for as-grown and oxidized SiNWs. The silicide-SiNW interface is thereby atomically abrupt and typically planar. Ni-rich silicide phases subsequently nucleate close to the Ni reservoir, which for as-grown SiNWs can lead to a complete channel break-off for prolonged silicidation due to significant volume expansion and morphological changes.« less

METHOD OF MAKING FUEL BODIES

DOEpatents

Goeddel, W.V.; Simnad, M.T.

1963-04-30

This patent relates to a method of making a fuel compact having a matrix of carbon or graphite which carries the carbides of fissile material. A nuclear fuel material selected from the group including uranium and thorium carbides, silicides, and oxides is first mixed both with sufficient finely divided carbon to constitute a matrix in the final product and with a diffusional bonding material selected from the class consisting of zirconium, niobium, molybdenum, titanium, nickel, chromium, and silicon. The mixture is then heated at a temperature of 1500 to 1800 nif- C while maintaining it under a pressure of over about 2,000 pounds per square inch. Preferably, heating is accomplished by the electrical resistance of the compact itself. (AEC)

Defect-free erbium silicide formation using an ultrathin Ni interlayer.

PubMed

Choi, Juyun; Choi, Seongheum; Kang, Yu-Seon; Na, Sekwon; Lee, Hoo-Jeong; Cho, Mann-Ho; Kim, Hyoungsub

2014-08-27

An ultrathin Ni interlayer (∼1 nm) was introduced between a TaN-capped Er film and a Si substrate to prevent the formation of surface defects during thermal Er silicidation. A nickel silicide interfacial layer formed at low temperatures and incurred uniform nucleation and the growth of a subsequently formed erbium silicide film, effectively inhibiting the generation of recessed-type surface defects and improving the surface roughness. As a side effect, the complete transformation of Er to erbium silicide was somewhat delayed, and the electrical contact property at low annealing temperatures was dominated by the nickel silicide phase with a high Schottky barrier height. After high-temperature annealing, the early-formed interfacial layer interacted with the growing erbium silicide, presumably forming an erbium silicide-rich Er-Si-Ni mixture. As a result, the electrical contact property reverted to that of the low-resistive erbium silicide/Si contact case, which warrants a promising source/drain contact application for future high-performance metal-oxide-semiconductor field-effect transistors.

The influence of alloying on the phase formation sequence of ultra-thin nickel silicide films and on the inheritance of texture

NASA Astrophysics Data System (ADS)

Geenen, F. A.; Solano, E.; Jordan-Sweet, J.; Lavoie, C.; Mocuta, C.; Detavernier, C.

2018-05-01

The controlled formation of silicide materials is an ongoing challenge to facilitate the electrical contact of Si-based transistors. Due to the ongoing miniaturisation of the transistor, the silicide is trending to ever-thinner thickness's. The corresponding increase in surface-to-volume ratio emphasises the importance of low-energetic interfaces. Intriguingly, the thickness reduction of nickel silicides results in an abrupt change in phase sequence. This paper investigates the sequence of the silicides phases and their preferential orientation with respect to the Si(001) substrate, for both "thin" (i.e., 9 nm) and "ultra-thin" (i.e., 3 nm) Ni films. Furthermore, as the addition of ternary elements is often considered in order to tailor the silicides' properties, additives of Al, Co, and Pt are also included in this study. Our results show that the first silicide formed is epitaxial θ-Ni2Si, regardless of initial thickness or alloyed composition. The transformations towards subsequent silicides are changed through the additive elements, which can be understood through solubility arguments and classical nucleation theory. The crystalline alignment of the formed silicides with the substrate significantly differs through alloying. The observed textures of sequential silicides could be linked through texture inheritance. Our study illustrates the nucleation of a new phase drive to reduce the interfacial energy at the silicide-substrate interface as well as at the interface with the silicide which is being consumed for these sub-10 nm thin films.

Experimental studies of thermal and chemical interactions between oxide and silicide nuclear fuels with water

DOE Office of Scientific and Technical Information (OSTI.GOV)

farahani, A.A.; Corradini, M.L.

Given some transient power/cooling mismatch is a nuclear reactor and its inability to establish the necessary core cooling, energetic fuel-coolant interactions (FCI`s commonly called `vapor explosions`) could occur as a result of the core melting and coolant contact. Although a large number of studies have been done on energetic FCI`s, very few experiments have been performed with the actual fuel materials postulated to be produced in severe accidents. Because of the scarcity of well-characterized FCI data for uranium allows in noncommercial reactors (cermet and silicide fuels), we have conducted a series of experiments to provide a data base for themore » foregoing materials. An existing 1-D shock-tube facility was modified to handle depleted radioactive materials (U{sub 3}O{sub 8}-Al, and U{sub 3}Si{sub 2}-Al). Our objectives have been to determine the effects of the initial fuel composition and temperature and the driving pressure (triggering) on the explosion work output, dynamic pressures, transient temperatures, and the hydrogen production. Experimental results indicate limited energetics, mainly thermal interactions, for these fuel materials as compared to aluminum where more chemical reactions occur between the molten aluminum and water.« less

Simulated Fission Gas Behavior in Silicide Fuel at LWR Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yinbin; Mo, Kun; Yacout, Abdellatif

As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U 3Si 2) at LWR conditions needs to be well-understood. However, existing experimental post-irradiation examination (PIE) data are limited to the research reactor conditions, which involve lower fuel temperature compared to LWR conditions. This lack of appropriate experimental data significantly affects the development of fuel performance codes that can precisely predict the microstructure evolution and property degradation at LWR conditions, and therefore evaluate the qualification of U 3Si 2 as an AFT for LWRs. Considering the high cost,more » long timescale, and restrictive access of the in-pile irradiation experiments, this study aims to utilize ion irradiation to simulate the inpile behavior of the U 3Si 2 fuel. Both in situ TEM ion irradiation and ex situ high-energy ATLAS ion irradiation experiments were employed to simulate different types of microstructure modifications in U 3Si 2. Multiple PIE techniques were used or will be used to quantitatively analyze the microstructure evolution induced by ion irradiation so as to provide valuable reference for the development of fuel performance code prior to the availability of the in-pile irradiation data.« less

Bone repair in mandibular body osteotomy after using 2.0 miniplate system – histological and histometric analysis in dogs

PubMed Central

Sverzut, Cássio Edvard; Lucas, Marina Amaral; Sverzut, Alexander Tadeu; Trivellato, Alexandre Elias; Beloti, Marcio Mateus; Rosa, Adalberto Luiz; de Oliveira, Paulo Tambasco

2008-01-01

The objective of this study was to evaluate the bone repair along a mandibular body osteotomy after using a 2.0 miniplate system. Nine adult mongrel dogs were subjected to unilateral continuous defect through an osteotomy between the mandibular 3rd and 4th premolars. Two four-hole miniplates were placed in accordance with the Arbeitgeimeinschaft für Osteosynthesefragen Manual. Miniplates adapted to the alveolar processes were fixed monocortically with 6.0-mm-length titanium alloy self-tapping screws, whereas miniplates placed near the mandible bases were fixed bicortically. At 2, 6 and 12 weeks, three dogs were sacrificed per period, and the osteotomy sites were removed, divided into three thirds (Tension Third, TT; Intermediary Third, IT; Compression Third, CT) and prepared for conventional and polarized light microscopy. At 6 weeks, while the CT repaired faster and showed bone union by woven bone formation, the TT and IT exhibited a ligament-like fibrous connective tissue inserted in, and connecting, newly formed woven bone overlying the parent lamellar bone edges. At 12 weeks, bone repair took place at all thirds. Histometrically, proportions of newly formed bone did not alter at TT, IT and CT, whereas significantly enhanced bone formation was observed for the 12-week group, irrespective of the third. The results demonstrated that although the method used to stabilize the mandibular osteotomy allowed bone repair to occur, differences in the dynamics of bone healing may take place along the osteotomy site, depending on the action of tension and compression forces generated by masticatory muscles. PMID:18336526

Orthodontic miniplate with tube as an efficient tool for borderline cases.

PubMed

Chung, Kyu-Rhim; Kim, Seong-Hun; Kang, Yoon-Goo; Nelson, Gerald

2011-04-01

An orthodontic miniplate tube device, the C-tube, was designed for use in patients for whom a conventional miniscrew is not suitable, such as those with narrow interradicular spaces, extended maxillary sinuses, dilacerated roots, or severe alveolar bone loss. After local anesthesia, 2 parallel horizontal incisions are made in the area of placement, and the periosteum is elevated. The C-tube is slipped under the mucosal flap and fixed with self-drilling miniscrews (diameter, 1.5 mm; length, 4 mm). Because the screws are short, there is adequate retention in the alveolar plate, and the clinician can avoid the increased morbidity of anchoring to the zygomatic buttress. This makes placement possible with superficial anesthesia. A small rolled tube at the head part can act as an orthodontic tube and accommodate archwires or as a hook to attach orthodontic elastics. However, in some patients with pneumatization or systemic diseases, such as diabetes mellitus, or in heavy smokers, cross-type C-tubes with longer miniscrews are recommend for better stability. This new type of orthodontic miniplate can be an effective alternative to conventional 1-component screws or miniplates in complex situations. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

METHOD OF FORMING TANTALUM SILICIDE ON TANTALUM SURFACES

DOEpatents

Bowman, M.G.; Krikorian, N.H.

1961-10-01

A method is described for forming a non-corrosive silicide coating on tantalum. The coating is made through the heating of trirhenium silicides in contact with the tantalum object to approximately 1400 deg C at which temperature trirhenium silicide decomposes into rhenium and gaseous silicons. The silicon vapor reacts with the tantalum surface to form a tantalum silicide layer approximately 10 microns thick. (AEC)

Synthesis of metal silicide at metal/silicon oxide interface by electronic excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.-G., E-mail: jglee36@kims.re.kr; Nagase, T.; Yasuda, H.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, α-Pt{sub 2}Si, was successfully formed at the platinum/silicon oxide interface under 25–200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation.more » It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation.« less

Ultra Thin Poly-Si Nanosheet Junctionless Field-Effect Transistor with Nickel Silicide Contact

PubMed Central

Lin, Yu-Ru; Tsai, Wan-Ting; Wu, Yung-Chun; Lin, Yu-Hsien

2017-01-01

This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet resistance (Rs). The JL NS-FET with nickel silicide contact exhibited favorable electrical properties, including a high driving current (>107A), subthreshold slope (186 mV/dec.), and low parasitic resistance. In addition, this study compared the electrical characteristics of JL NS-FETs with and without nickel silicide contact. PMID:29112139

Ultra Thin Poly-Si Nanosheet Junctionless Field-Effect Transistor with Nickel Silicide Contact.

PubMed

Lin, Yu-Ru; Tsai, Wan-Ting; Wu, Yung-Chun; Lin, Yu-Hsien

2017-11-07

This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet resistance (Rs). The JL NS-FET with nickel silicide contact exhibited favorable electrical properties, including a high driving current (>10⁷A), subthreshold slope (186 mV/dec.), and low parasitic resistance. In addition, this study compared the electrical characteristics of JL NS-FETs with and without nickel silicide contact.

Radiation Re-solution Calculation in Uranium-Silicide Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, Christopher; Andersson, Anders David Ragnar; Unal, Cetin

The release of fission gas from nuclear fuels is of primary concern for safe operation of nuclear power plants. Although the production of fission gas atoms can be easily calculated from the fission rate in the fuel and the average yield of fission gas, the actual diffusion, behavior, and ultimate escape of fission gas from nuclear fuel depends on many other variables. As fission gas diffuses through the fuel grain, it tends to collect into intra-granular bubbles, as portrayed in Figure 1.1. These bubbles continue to grow due to absorption of single gas atoms. Simultaneously, passing fission fragments can causemore » collisions in the bubble that result in gas atoms being knocked back into the grain. This so called “re-solution” event results in a transient equilibrium of single gas atoms within the grain. As single gas atoms progress through the grain, they will eventually collect along grain boundaries, creating inter-granular bubbles. As the inter-granular bubbles grow over time, they will interconnect with other grain-face bubbles until a pathway is created to the outside of the fuel surface, at which point the highly pressurized inter-granular bubbles will expel their contents into the fuel plenum. This last process is the primary cause of fission gas release. From the simple description above, it is clear there are several parameters that ultimately affect fission gas release, including the diffusivity of single gas atoms, the absorption and knockout rate of single gas atoms in intra-granular bubbles, and the growth and interlinkage of intergranular bubbles. Of these, the knockout, or re-solution rate has an particularly important role in determining the transient concentration of single gas atoms in the grain. The re-solution rate will be explored in the following sections with regards to uranium-silicide fuels in order to support future models of fission gas bubble behavior.« less

Dynamic observation on the growth behaviors in manganese silicide/silicon nanowire heterostructures.

PubMed

Hsieh, Yu-Hsun; Chiu, Chung-Hua; Huang, Chun-Wei; Chen, Jui-Yuan; Lin, Wan-Jhen; Wu, Wen-Wei

2015-02-07

Metal silicide nanowires (NWs) are very interesting materials with diverse physical properties. Among the silicides, manganese silicide nanostructures have attracted wide attention due to their several potential applications, including in microelectronics, optoelectronics, spintronics and thermoelectric devices. In this work, we exhibited the formation of pure manganese silicide and manganese silicide/silicon nanowire heterostructures through solid state reaction with line contacts between manganese pads and silicon NWs. Dynamical process and phase characterization were investigated by in situ transmission electron microscopy (in situ TEM) and spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), respectively. The growth dynamics of the manganese silicide phase under thermal effects were systematically studied. Additionally, Al2O3, serving as the surface oxide, altered the growth behavior of the MnSi nanowire, enhancing the silicide/Si epitaxial growth and effecting the diffusion process in the silicon nanowire as well. In addition to fundamental science, this significant study has great potential in advancing future processing techniques in nanotechnology and related applications.

Prototype of a silicon nitride ceramic-based miniplate osteofixation system for the midface.

PubMed

Neumann, Andreas; Unkel, Claus; Werry, Christoph; Herborn, Christoh U; Maier, Horst R; Ragoss, Christian; Jahnke, Klaus

2006-06-01

The favorable properties of silicon nitride (Si3N4) ceramics, such as high mean strength level and fracture toughness, suggest biomedical use as an implant material. Minor reservations about the biocompatibility of Si3N4 ceramics were cleared up by previous in vitro and in vivo investigations. A Si3N4 prototype minifixation system was manufactured and implanted for osteosynthesis of artificial frontal bone defects in 3 minipigs. After 3 months, histological sections, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans were obtained. Finite element modeling (FEM) was used to simulate stresses and strains on Si3N4 miniplates and screws to calculate survival probabilities. Si3N4 miniplates and screws showed satisfying intraoperative workability. There was no implant loss, displacement, or fracture. Bone healing was complete in all animals. The formation of new bone was observed in direct contact to the implants. The implants showed no artifacts on CT and MRI scanning. FEM simulation confirmed the mechanical reliability of the screws, whereas simulated plate geometries regarding pullout forces at maximum load showed limited safety in a bending situation. Si3N4 ceramics show a good biocompatibility outcome both in vitro and in vivo. In ENT surgery, this ceramic may serve as a biomaterial for osteosynthesis (eg, of the midface including reconstruction the floor of the orbit and the skull base). To our knowledge, this is the first introduction of a ceramic-based miniplate-osteofixation system. Advantages compared with titanium are no risk of implantation to bone with mucosal attachment, no need for explantation, and no interference with radiologic imaging. Disadvantages include the impossibility of individual bending of the miniplates.

Microwave absorption properties of Ni/(C, silicides) nanocapsules

PubMed Central

2012-01-01

The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the ‘core/shell’ interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon. PMID:22548846

Shutdown-induced tensile stress in monolithic miniplates as a possible cause of plate pillowing at very high burnup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medvedev, Pavel G; Ozaltun, Hakan; Robinson, Adam Brady

2014-04-01

Post-irradiation examination of Reduced Enrichment for Research and Test Reactors (RERTR)-12 miniplates showed that in-reactor pillowing occurred in at least 4 plates, rendering performance of these plates unacceptable. To address in-reactor failures, efforts are underway to define the mechanisms responsible for in-reactor pillowing, and to suggest improvements to the fuel plate design and operational conditions. To achieve these objectives, the mechanical response of monolithic fuel to fission and thermally-induced stresses was modeled using a commercial finite element analysis code. Calculations of stresses and deformations in monolithic miniplates during irradiation and after the shutdown revealed that the tensile stress generated inmore » the fuel increased from 2 MPa to 100 MPa at shutdown. The increase in tensile stress at shutdown possibly explains in-reactor pillowing of several RERTR-12 miniplates irradiated to the peak local burnup of up to 1.11x1022 fissions/cm3 . This paper presents the modeling approach and calculation results, and compares results with post-irradiation examinations and mechanical testing of irradiated fuel. The implications for the safe use of the monolithic fuel in research reactors are discussed, including the influence of fuel burnup and power on the magnitude of the shutdown-induced tensile stress.« less

Finite element analysis of three patterns of internal fixation of fractures of the mandibular condyle.

PubMed

Aquilina, Peter; Chamoli, Uphar; Parr, William C H; Clausen, Philip D; Wroe, Stephen

2013-06-01

The most stable pattern of internal fixation for fractures of the mandibular condyle is a matter for ongoing discussion. In this study we investigated the stability of three commonly used patterns of plate fixation, and constructed finite element models of a simulated mandibular condylar fracture. The completed models were heterogeneous in the distribution of bony material properties, contained about 1.2 million elements, and incorporated simulated jaw-adducting musculature. Models were run assuming linear elasticity and isotropic material properties for bone. This model was considerably larger and more complex than previous finite element models that have been used to analyse the biomechanical behaviour of differing plating techniques. The use of two parallel 2.0 titanium miniplates gave a more stable configuration with lower mean element stresses and displacements over the use of a single miniplate. In addition, a parallel orientation of two miniplates resulted in lower stresses and displacements than did the use of two miniplates in an offset pattern. The use of two parallel titanium plates resulted in a superior biomechanical result as defined by mean element stresses and relative movement between the fractured fragments in these finite element models. Copyright © 2012 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Experimental analysis of internal rigid fixation osteosynthesis performed with titanium bone screw and plate systems.

PubMed

Righi, E; Carta, M; Bruzzone, A A; Lonardo, P M; Marinaro, E; Pastorino, A

1996-02-01

The authors report the results of an experimental analysis performed on titanium miniplates and screws in order to gain a better understanding of dynamic forces in internal rigid fixation. Ten segments of bovine scapula were prepared. Osteotomies were carried out along the minor axis, following which five were fixed with four hole straight miniplates and the other five with six hole double-Y miniplates. Each sample was fastened in a special clamp adapted to a tension test machine and shearing force was applied. Force versus time was recorded and the 50 bone fragments were examined by a pathologist. On the basis of the test results, two simple computer models were developed. No significant difference was evident between the mechanical and computed tests. The most critical sections were located near the hole proximal to the osteotomy and the microscopic findings confirmed this. On the basis of the experimental results, the authors propose a new plate design in which the area subject to most stress, proximal to the bone section, would be of miniplate thickness, the distal aspect being thinner as in a microplate. It is suggested that this design would provide sufficient stability and a high degree of anatomical adjustment of the system.

Interactive planning of miniplates

NASA Astrophysics Data System (ADS)

Gall, Markus; Reinbacher, Knut; Wallner, Jürgen; Stanzel, Jan; Chen, Xiaojun; Schwenzer-Zimmerer, Katja; Schmalstieg, Dieter; Egger, Jan

2017-03-01

In this contribution, a novel method for computer aided surgery planning of facial defects by using models of purchasable MedArtis Modus 2.0 miniplates is proposed. Implants of this kind, which belong to the osteosynthetic material, are commonly used for treating defects in the facial area. By placing them perpendicular on the defect, the miniplates are fixed on the healthy bone, bent with respect to the surface, to stabilize the defective area. Our software is able to fit a selection of the most common implant models to the surgeon's desired position in a 3D computer model. The fitting respects the local surface curvature and adjusts direction and position in any desired way. Conventional methods use Computed Tomography (CT) scans to generate STereoLithic (STL) models serving as bending template for the implants or use a bending tool during the surgery for readjusting the implant several times. Both approaches lead to undesirable expenses in time. With our visual planning tool, surgeons are able to pre-plan the final implant within just a few minutes. The resulting model can be stored in STL format, which is the commonly used format for 3D printing. With this technology, surgeons are able to print the implant just in time or use it for generating a bending tool, both leading to an exactly bent miniplate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, Anders David Ragnar; Stanek, Christopher Richard; Noordhoek, Mark

Uranium silicides, in particular U 3Si 2, are being explored as an advanced nuclear fuel with increased accident tolerance as well as competitive economics compared to the baseline UO 2 fuel. They benefit from high thermal conductivity (metallic) compared to UO 2 fuel (insulator or semi-conductor) used in current Light Water Reactors (LWRs). The U-Si fuels also have higher fissile density. In order to perform meaningful engineering scale nuclear fuel performance simulations, the material properties of the fuel, including the response to irradiation environments, must be known. Unfortunately, the data available for USi fuels are rather limited, in particular formore » the temperature range where LWRs would operate. The ATF HIP is using multi-scale modeling and simulations to address this knowledge gap.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, Anders David Ragnar; Stanek, Christopher Richard; Noordhoek, Mark J.

Uranium silicides, in particular U 3Si 2, are being explored as an advanced nuclear fuel with increased accident tolerance as well as competitive economics compared to the baseline UO2 fuel. They benefit from high thermal conductivity (metallic) compared to UO 2 fuel (insulator or semi-conductor) used in current Light Water Reactors (LWRs). The U-Si fuels also have higher fissile density. In order to perform meaningful engineering scale nuclear fuel performance simulations, the material properties of the fuel, including the response to irradiation environments, must be known. Unfortunately, the data available for USi fuels are rather limited, in particular for themore » temperature range where LWRs would operate. The ATF HIP is using multi-scale modeling and simulations to address this knowledge gap.« less

Theoretical investigation of silicide Schottky barrier detector integrated in horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguide.

PubMed

Zhu, Shiyang; Lo, G Q; Kwong, D L

2011-08-15

An ultracompact integrated silicide Schottky barrier detector (SBD) is designed and theoretically investigated to electrically detect the surface plasmon polariton (SPP) propagating along horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguides at the telecommunication wavelength of 1550 nm. An ultrathin silicide layer inserted between the silicon core and the insulator, which can be fabricated precisely using the well-developed self-aligned silicide process, absorbs the SPP power effectively if a suitable silicide is chosen. Moreover, the Schottky barrier height in the silicide-silicon-silicide configuration can be tuned substantially by the external voltage through the Schottky effect owing to the very narrow silicon core. For a TaSi(2) detector with optimized dimensions, numerical simulation predicts responsivity of ~0.07 A/W, speed of ~60 GHz, dark current of ~66 nA at room temperature, and minimum detectable power of ~-29 dBm. The design also suggests that the device's size can be reduced and the overall performances will be further improved if a silicide with smaller permittivity is used. © 2011 Optical Society of America

Exploitation of a Self-limiting Process for Reproducible Formation of Ultrathin Ni(1-x)Pt(x) Silicide Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Z Zhang; B Yang; Y Zhu

This letter reports on a process scheme to obtain highly reproducible Ni{sub 1-x}Pt{sub x} silicide films of 3-6 nm thickness formed on a Si(100) substrate. Such ultrathin silicide films are readily attained by sputter deposition of metal films, metal stripping in wet chemicals, and final silicidation by rapid thermal processing. This process sequence warrants an invariant amount of metal intermixed with Si in the substrate surface region independent of the initial metal thickness, thereby leading to a self-limiting formation of ultrathin silicide films. The crystallographic structure, thickness, uniformity, and morphological stability of the final silicide films depend sensitively on themore » initial Pt fraction.« less

Surface morphology of erbium silicide

NASA Technical Reports Server (NTRS)

Lau, S. S.; Pai, C. S.; Wu, C. S.; Kuech, T. F.; Liu, B. X.

1982-01-01

The surface of rare-earth silicides (Er, Tb, etc.), formed by the reaction of thin-film metal layers with a silicon substrate, is typically dominated by deep penetrating, regularly shaped pits. These pits may have a detrimental effect on the electronic performance of low Schottky barrier height diodes utilizing such silicides on n-type Si. This study suggests that contamination at the metal-Si or silicide-Si interface is the primary cause of surface pitting. Surface pits may be reduced in density or eliminated entirely through either the use of Si substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition and silicide formation or by means of ion irradiation techniques. Silicide layers formed by these techniques possess an almost planar morphology.

Miniplates and mini-implants: bone remodeling as their biological foundation1

PubMed Central

Consolaro, Alberto

2015-01-01

Abstract The tridimensional network formed by osteocytes controls bone design by coordinating cell activity on trabecular and cortical bone surfaces, especially osteoblasts and clasts. Miniplates and mini-implants provide anchorage, allowing all other orthodontic and orthopedic components, albeit afar, to deform and stimulate the network of osteocytes to command bone design remodeling upon "functional demand" established by force and its vectors. By means of transmission of forces, whether near or distant, based on anchorage provided by miniplates, it is possible to change the position, shape and size as well as the relationship established between the bones of the jaws. Understanding bone biology and the continuous remodeling of the skeleton allows the clinician to perform safe and accurate rehabilitation treatment of patients, thus increasing the possibilities and types of intervention procedures to be applied in order to restore patient's esthetics and function. PMID:26691966

Orthodontic camouflage of skeletal Class III malocclusion with miniplate: a case report

PubMed Central

Farret, Marcel Marchiori; Farret, Milton M. Benitez; Farret, Alessandro Marchiori

2016-01-01

ABSTRACT Introduction: Skeletal Class III malocclusion is often referred for orthodontic treatment combined with orthognathic surgery. However, with the aid of miniplates, some moderate discrepancies become feasible to be treated without surgery. Objective: To report the case of a 24-year-old man with severe skeletal Angle Class III malocclusion with anterior crossbite and a consequent concave facial profile. Methods: The patient refused to undergo orthognathic surgery; therefore, orthodontic camouflage treatment with the aid of miniplates placed on the mandibular arch was proposed. Results: After 18 months of treatment, a Class I molar and canine relationship was achieved, while anterior crossbite was corrected by retraction of mandibular teeth. The consequent decrease in lower lip fullness and increased exposure of maxillary incisors at smiling resulted in a remarkable improvement of patient's facial profile, in addition to an esthetically pleasing smile, respectively. One year later, follow-up revealed good stability of results. PMID:27653269

Orthodontic camouflage of skeletal Class III malocclusion with miniplate: a case report.

PubMed

Farret, Marcel Marchiori; Farret, Milton M Benitez; Farret, Alessandro Marchiori

2016-01-01

Skeletal Class III malocclusion is often referred for orthodontic treatment combined with orthognathic surgery. However, with the aid of miniplates, some moderate discrepancies become feasible to be treated without surgery. To report the case of a 24-year-old man with severe skeletal Angle Class III malocclusion with anterior crossbite and a consequent concave facial profile. The patient refused to undergo orthognathic surgery; therefore, orthodontic camouflage treatment with the aid of miniplates placed on the mandibular arch was proposed. After 18 months of treatment, a Class I molar and canine relationship was achieved, while anterior crossbite was corrected by retraction of mandibular teeth. The consequent decrease in lower lip fullness and increased exposure of maxillary incisors at smiling resulted in a remarkable improvement of patient's facial profile, in addition to an esthetically pleasing smile, respectively. One year later, follow-up revealed good stability of results.

Rate Theory Modeling and Simulation of Silicide Fuel at LWR Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yinbin; Ye, Bei; Hofman, Gerard

As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U 3Si 2) at LWR conditions needs to be well understood. In this report, rate theory model was developed based on existing experimental data and density functional theory (DFT) calculations so as to predict the fission gas behavior in U 3Si 2 at LWR conditions. The fission gas behavior of U 3Si 2 can be divided into three temperature regimes. During steady-state operation, the majority of the fission gas stays in intragranular bubbles, whereas the dominance of intergranularmore » bubbles and fission gas release only occurs beyond 1000 K. The steady-state rate theory model was also used as reference to establish a gaseous swelling correlation of U 3Si 2 for the BISON code. Meanwhile, the overpressurized bubble model was also developed so that the fission gas behavior at LOCA can be simulated. LOCA simulation showed that intragranular bubbles are still dominant after a 70 second LOCA, resulting in a controllable gaseous swelling. The fission gas behavior of U 3Si 2 at LWR conditions is benign according to the rate theory prediction at both steady-state and LOCA conditions, which provides important references to the qualification of U 3Si 2 as a LWR fuel material with excellent fuel performance and enhanced accident tolerance.« less

Columnar and subsurface silicide growth with novel molecular beam epitaxy techniques

NASA Technical Reports Server (NTRS)

Fathauer, R. W.; George, T.; Pike, W. T.

1992-01-01

We have found novel growth modes for epitaxial CoSi2 at high temperatures coupled with Si-rich flux ratios or low deposition rates. In the first of these modes, codeposition of metal and Si at 600-800 C with excess Si leads to the formation of epitaxial silicide columns surrounded by single-crystal Si. During the initial stages of the deposition, the excess Si grows homoepitaxially in between the silicide, which forms islands, so that the lateral growth of the islands is confined. Once a template layer is established by this process, columns of silicide form as a result of selective epitaxy of silicide on silicide and Si on Si. This growth process allows nanometer control over silicide particles in three dimensions. In the second of these modes, a columnar silicide seed layer is used as a template to nucleate subsurface growth of CoSi2. With a 100 nm Si layer covering CoSi2 seeds, Co deposited at 800C and 0.01 nm/s diffuses down to grow on the buried seeds rather than nucleating surface silicide islands. For thicker Si caps or higher deposition rates, the surface concentration of Co exceeds the critical concentration for nucleation of islands, preventing this subsurface growth mode from occurring. Using this technique, single-crystal layers of CoSi2 buried under single-crystal Si caps have been grown.

[Miniplate internal fixation and autogenous iliac bone graft in surgical treatment of old metatarsal fractures].

PubMed

Pan, Hao; Yu, Guangrong; Xiong, Wen; Zhao, Zhiming; Ding, Fan; Zheng, Qiong; Kan, Wushen

2011-07-01

To summarize the experience of treating old metatarsal fractures with surgery methods of miniplate internal fixation and autogenous iliac bone. Between May 2009 and July 2010, 7 patients with old metatarsal fractures were treated surgically, including 5 multi-metatarsal fractures and 2 single metatarsal fractures. There were 5 males and 2 females aged from 25 to 43 years (mean, 33 years). The time from fracture to operation was 4-12 weeks. The X-ray films showed that a small amount of callus formed at both broken ends with shortening, angulation, or rotation displacement. The surgical treatments included open reduction, internal fixation by miniplate, and autogenous iliac bone graft (1.5-2.5 cm(3)). The external plaster fixation was used in all patients for 4 to 6 weeks postoperatively (mean, 5 weeks). All incisions healed by first intention. The 7 patients were followed up 8-18 months (mean, 13.5 months). The clinical fracture healing time was 6 to 12 weeks postoperatively (mean, 8.4 weeks). No pain of planta pedis occurred while standing and walking. The American Orthopaedic Foot and Ankle Society (AOFAS) mesopedes and propodium score was 75-96 (mean, 86.4). It has the advantages of reliable internal fixation, high fracture healing rate, less complications to treat old metatarsal fractures with surgery methods of miniplate internal fixation and autogenous iliac bone graft, so it is an effective treatment method.

Microstructure evolution of the Ir-inserted Ni silicides with additional annealing

NASA Astrophysics Data System (ADS)

Yoon, Kijeong; Song, Ohsung

2009-02-01

Thermally-evaporated 10 nm-Ni/1 nm-Ir/(poly)Si structures were fabricated in order to investigate the thermal stability of Ir-inserted nickel silicide after additional annealing. The silicide samples underwent rapid thermal annealing at 300 ° C to 1200 ° C for 40 s, followed by 30 min annealing at the given RTA temperatures. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates, mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution x-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope were used to determine the cross-section structure and surface roughness. The silicide, which formed on single crystal silicon substrate with surface agglomeration after additional annealing, could defer the transformation of Ni(Ir)Si to Ni(Ir)Si2 and was stable at temperatures up to 1200 °C. Moreover, the silicide thickness doubled. There were no outstanding changes in the silicide thickness on polycrystalline silicon. However, after additional annealing, the silicon-silicide mixing became serious and showed high resistance at temperatures >700 °C. Auger depth profiling confirmed the increased thickness of the silicide layers after additional annealing without a change in composition. For a single crystal silicon substrate, the sheet resistance increased slightly due to the significant increases in surface roughness caused by surface agglomeration after additional annealing. Otherwise, there were almost no changes in surface roughness on the polycrystalline silicon substrate. The Ir-inserted nickel monosilicide was able to maintain a low resistance in a wide temperature range and is considered suitable for the nano-thick silicide process.

On the size-dependent magnetism and all-optical magnetization switching of transition-metal silicide nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glushkov, G. I.; Tuchin, A. V.; Popov, S. V.

Theoretical investigations of the electronic structure, synthesis, and all-optical magnetization switching of transition-metal silicide nanostructures are reported. The magnetic moment of the nanostructures is studied as a function of the silicide cluster size and configuration. The experimentally demonstrated magnetization switching of nanostructured nickel silicide by circularly polarized light makes it possible to create high-speed storage devices with high density data recording.

Effects of cleft type, facemask anchorage method, and alveolar bone graft on maxillary protraction: a three-dimensional finite element analysis.

PubMed

Yang, Il-Hyung; Chang, Young-Il; Kim, Tae-Woo; Ahn, Sug-Joon; Lim, Won-Hee; Lee, Nam-Ki; Baek, Seung-Hak

2012-03-01

To investigate biomechanical effects of cleft type (unilateral/bilateral cleft lip and palate), facemask anchorage method (tooth-borne and miniplate anchorage), and alveolar bone graft on maxillary protraction. Three-dimensional finite element analysis with application of orthopedic force (30° downward and forward to the occlusal plane, 500 g per side). Computed tomography data from a 13.5-year-old girl with maxillary hypoplasia. Eight three-dimensional finite element models were fabricated according to cleft type, facemask anchorage method, and alveolar bone graft. Initial stress distribution and displacement after force application were analyzed. Unilateral cleft lip and palate showed an asymmetric pattern in stress distribution and displacement before alveolar bone graft and demonstrated a symmetric pattern after alveolar bone graft. However, bilateral cleft lip and palate showed symmetric patterns in stress distribution and displacement before and after alveolar bone graft. In both cleft types, the graft extended the stress distribution area laterally beyond the infraorbital foramen. For both unilateral and bilateral cleft lip and palate, a facemask with a tooth-borne anchorage showed a dentoalveolar effect with prominent stress distribution and displacement on the upper canine point. In contrast, a facemask with miniplate anchorage exhibited an orthopedic effect with more favorable stress distribution and displacement on the middle maxilla point. In addition, the facemask with a miniplate anchorage showed a larger stress distribution area and sutural stress values than did the facemask with a tooth-borne anchorage. The pterygopalatine and zygomatico-maxillary sutures showed the largest sutural stress values with a facemask with a miniplate anchorage and after alveolar bone grafting, respectively. In this three-dimensional finite element analysis, it would be more advantageous to perform maxillary protraction using a facemask with a miniplate anchorage than a facemask with a tooth-borne anchorage and after alveolar bone graft rather than before alveolar bone graft, regardless of cleft type.

Gas cluster ion beam assisted NiPt germano-silicide formation on SiGe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozcan, Ahmet S., E-mail: asozcan@us.ibm.com; Lavoie, Christian; Jordan-Sweet, Jean

We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultra-shallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces.

Silicide surface phases on gold

NASA Technical Reports Server (NTRS)

Green, A. K.; Bauer, E.

1981-01-01

The crystalline silicide layers formed on (111) and (100) surfaces of Au films on various Si single-crystal substrates are studied by LEED and AES in conjunction with sputter-depth profiling as a function of annealing temperature. On the (111) surface, three basic silicide structures are obtained corresponding to layers of various thicknesses as obtained by different preparation conditions. The (100) surface shows only two different structures. None of the structures is compatible with the various bulk silicide structures deduced from X-ray diffraction. Using LEED as a criterion for the presence or absence of silicide on the surface, smaller layer thicknesses are obtained than reported previously on the basis of AES studies.

FastDart : a fast, accurate and friendly version of DART code.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rest, J.; Taboada, H.

2000-11-08

A new enhanced, visual version of DART code is presented. DART is a mechanistic model based code, developed for the performance calculation and assessment of aluminum dispersion fuel. Major issues of this new version are the development of a new, time saving calculation routine, able to be run on PC, a friendly visual input interface and a plotting facility. This version, available for silicide and U-Mo fuels,adds to the classical accuracy of DART models for fuel performance prediction, a faster execution and visual interfaces. It is part of a collaboration agreement between ANL and CNEA in the area of Lowmore » Enriched Uranium Advanced Fuels, held by the Implementation Arrangement for Technical Exchange and Cooperation in the Area of Peaceful Uses of Nuclear Energy.« less

First principles investigations of the electronic structure and chemical bonding of U3Si2C2 - A uranium silicide-carbide with the rare [SiC] unit

NASA Astrophysics Data System (ADS)

Matar, S. F.; Pöttgen, R.

2012-10-01

The electronic structure of U3Si2C2, with the rare [SiC] unit is examined from ab initio with an assessment of the properties of chemical bonding. We show that plain GGA fails describing the experimental lattice parameters and the electronic structure. A better agreement with experiment (crystal determination and magnetic properties) is obtained with the GGA + U method and U = 4 eV. The energy-volume equation of state and the set of elastic constants are obtained showing incompressibility along the c-axis with U-C-Si alignment and a brittle material. Bonding of U1 and U2 selectively with Si and C and Si-C bonds are remarkable

Microstructural investigation of nickel silicide thin films and the silicide-silicon interface using transmission electron microscopy.

PubMed

Bhaskaran, M; Sriram, S; Mitchell, D R G; Short, K T; Holland, A S; Mitchell, A

2009-01-01

This article discusses the results of transmission electron microscopy (TEM)-based investigation of nickel silicide (NiSi) thin films grown on silicon. Nickel silicide is currently used as the CMOS technology standard for local interconnects and in electrical contacts. Films were characterized with a range of TEM-based techniques along with glancing angle X-ray diffraction. The nickel silicide thin films were formed by vacuum annealing thin films of nickel (50 nm) deposited on (100) silicon. The cross-sectional samples indicated a final silicide thickness of about 110 nm. This investigation studied and reports on three aspects of the thermally formed thin films: the uniformity in composition of the film using jump ratio maps; the nature of the interface using high resolution imaging; and the crystalline orientation of the thin films using selected-area electron diffraction (SAED). The analysis highlighted uniform composition in the thin films, which was also substantiated by spectroscopy techniques; an interface exhibiting the desired abrupt transition from silicide to silicon; and desired and preferential crystalline orientation corresponding to stoichiometric NiSi, supported by glancing angle X-ray diffraction results.

High-Temperature Ceramic Matrix Composite with High Corrosion Resistance

DTIC Science & Technology

2010-06-02

ceramics with silicide additives may be explained in the following ways: 1) metal oxide, for example Ta2O5, formed at oxidation of TaSi2, in the...practically monophase ones, possibly, the additives of corresponding metals in silicide powders were present in insignificant amounts. For...boride with zirconium silicide we prepared the mixtures with 20 vol. % of silicide , the latter being hot pressed in the temperature range of 1600

Cosine (Cobalt Silicide Growth Through Nitrogen-Induced Epitaxy) Process For Epitaxial Cobalt Silicide Formation For High Performance Sha

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Chong Wee; Shin, Chan Soo; Gall, Daniel

A method for forming an epitaxial cobalt silicide layer on a MOS device includes sputter depositing cobalt in an ambient to form a first layer of cobalt suicide on a gate and source/drain regions of the MOS device. Subsequently, cobalt is sputter deposited again in an ambient of argon to increase the thickness of the cobalt silicide layer to a second thickness.

Formation of low resistivity titanium silicide gates in semiconductor integrated circuits

DOEpatents

Ishida, Emi [Sunnyvale, CA

1999-08-10

A method of forming a titanium silicide (69) includes the steps of forming a transistor having a source region (58), a drain region (60) and a gate structure (56) and forming a titanium layer (66) over the transistor. A first anneal is performed with a laser anneal at an energy level that causes the titanium layer (66) to react with the gate structure (56) to form a high resistivity titanium silicide phase (68) having substantially small grain sizes. The unreacted portions of the titanium layer (66) are removed and a second anneal is performed, thereby causing the high resistivity titanium silicide phase (68) to convert to a low resistivity titanium silicide phase (69). The small grain sizes obtained by the first anneal allow low resistivity titanium silicide phase (69) to be achieved at device geometries less than about 0.25 micron.

A physical description of fission product behavior fuels for advanced power reactors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaganas, G.; Rest, J.; Nuclear Engineering Division

2007-10-18

The Global Nuclear Energy Partnership (GNEP) is considering a list of reactors and nuclear fuels as part of its chartered initiative. Because many of the candidate materials have not been explored experimentally under the conditions of interest, and in order to economize on program costs, analytical support in the form of combined first principle and mechanistic modeling is highly desirable. The present work is a compilation of mechanistic models developed in order to describe the fission product behavior of irradiated nuclear fuel. The mechanistic nature of the model development allows for the possibility of describing a range of nuclear fuelsmore » under varying operating conditions. Key sources include the FASTGRASS code with an application to UO{sub 2} power reactor fuel and the Dispersion Analysis Research Tool (DART ) with an application to uranium-silicide and uranium-molybdenum research reactor fuel. Described behavior mechanisms are divided into subdivisions treating fundamental materials processes under normal operation as well as the effect of transient heating conditions on these processes. Model topics discussed include intra- and intergranular gas-atom and bubble diffusion, bubble nucleation and growth, gas-atom re-solution, fuel swelling and ?scion gas release. In addition, the effect of an evolving microstructure on these processes (e.g., irradiation-induced recrystallization) is considered. The uranium-alloy fuel, U-xPu-Zr, is investigated and behavior mechanisms are proposed for swelling in the {alpha}-, intermediate- and {gamma}-uranium zones of this fuel. The work reviews the FASTGRASS kinetic/mechanistic description of volatile ?scion products and, separately, the basis for the DART calculation of bubble behavior in amorphous fuels. Development areas and applications for physical nuclear fuel models are identified.« less

Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements.

PubMed

Polley, Craig M; Clarke, Warrick R; Simmons, Michelle Y

2011-10-03

We examine nickel silicide as a viable ohmic contact metallization for low-temperature, low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular, we compare a nickel silicide metallization with aluminium, a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures (<400°C) required for maintaining atomic precision placement in donor-based devices, and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly, we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field.

Long-term stability of soft tissue changes in anterior open bite adults treated with zygomatic miniplate-anchored maxillary posterior intrusion.

PubMed

Marzouk, Eiman S; Kassem, Hassan E

2018-03-01

To evaluate soft tissue changes and their long-term stability in skeletal anterior open bite adults treated by maxillary posterior teeth intrusion using zygomatic miniplates and premolar extractions. Lateral cephalograms of 26 patients were taken at pretreatment (T1), posttreatment (T2), 1 year posttreatment (T3), and 4 years posttreatment (T4). At the end of treatment, the soft tissue facial height and profile convexity were reduced. The lips increased in length and thickness, with backward movement of the upper lip and forward movement of the lower lip. The total relapse rate ranged from 20.2% to 31.1%. At 4 years posttreatment, 68.9% to 79.8% of the soft tissue treatment effects were stable. The changes in the first year posttreatment accounted for approximately 70% of the total relapse. Soft tissue changes following maxillary posterior teeth intrusion with zygomatic miniplates and premolar extractions appear to be stable 4 years after treatment.

CAD-CAM plates versus conventional fixation plates for primary mandibular reconstruction: A biomechanical in vitro analysis.

PubMed

Rendenbach, Carsten; Sellenschloh, Kay; Gerbig, Lucca; Morlock, Michael M; Beck-Broichsitter, Benedicta; Smeets, Ralf; Heiland, Max; Huber, Gerd; Hanken, Henning

2017-11-01

CAD/CAM reconstruction plates have become a viable option for mandible reconstruction. The aim of this study was to determine whether CAD/CAM plates provide higher fatigue strength compared with conventional fixation systems. 1.0 mm miniplates, 2.0 mm conventional locking plates (DePuy Synthes, Umkirch, Germany), and 2.0 mm CAD/CAM plates (Materialise, Leuven, Belgium/DePuy Synthes) were used to reconstruct a polyurethane mandible model (Synbone, Malans, CH) with cortical and cancellous bone equivalents. Mastication was simulated via cyclic dynamic testing using a universal testing machine (MTS, Bionix, Eden Prairie, MN, USA) until material failure reached a rate of 1 Hz with increasing loads on the left side. No significant difference was found between the groups until a load of 300 N. At higher loads, vertical displacement differed increasingly, with a poorer performance of miniplates (p = 0.04). Plate breakage occurred in miniplates and conventional locking plates. Screw breakage was recorded as the primary failure mechanism in CAD/CAM plates. Stiffness was significantly higher with the CAD/CAM plates (p = 0.04). CAD/CAM plates and reconstruction plates provide higher fatigue strength than miniplates, and stiffness is highest in CAD/CAM systems. All tested fixation methods seem sufficiently stable for mandible reconstruction. Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Evaluation of long-term stability of skeletal anterior open bite correction in adults treated with maxillary posterior segment intrusion using zygomatic miniplates.

PubMed

Marzouk, Eiman S; Kassem, Hassan E

2016-07-01

This study evaluated the long-term stability of maxillary molar intrusion and anterior open-bite correction in adults treated by maxillary posterior teeth intrusion with zygomatic miniplates. The sample included 26 skeletal anterior open-bite patients, who had maxillary posterior segment intrusion with zygomatic miniplates. Lateral cephalograms were taken at pretreatment, posttreatment, 1 year posttreatment, and 4 years posttreatment. The mean maxillary molar intrusion was 3.04 mm (P ≤0.01), and the mean bite closure was 6.93 mm (P ≤0.01). The intruded maxillary molars relapsed by 10.20% in the first year after treatment and by 13.37% by 4 years after treatment. Overbite relapsed by 8.19% and 11.18% after 1 year and 4 years posttreatment, respectively. The first year after treatment accounted for 76.29% and 73.2% of the total relapses of molar intrusion and overbite, respectively. The 4-year posttreatment relapse amounts of maxillary molar intrusion and overbite were positively correlated with the amount of pretreatment maxillary molar height and the initial open-bite severity, respectively, but negatively correlated with the amounts of maxillary molar intrusion and open-bite correction gained by treatment. Molar intrusion with zygomatic miniplates appears to be stable 4 years after treatment. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Improvement of heavy dopant doped Ni-silicide using ytterbium interlayer for nano-scale MOSFETS with an ultra shallow junction.

PubMed

Shin, Hong-Sik; Oh, Se-Kyung; Kang, Min-Ho; Li, Shi-Guang; Lee, Ga-Won; Lee, Hi-Deok

2011-07-01

In this paper, a novel Ni silicide with Yb interlayer (Yb/Ni/TiN) on a boron cluster (B18H22) implanted source/drain junction is proposed for the first time, and its thermal stability characteristics are analyzed in depth. The proposed Ni-silicide exhibits a wider RTP temperature window for uniform sheet resistance, surface roughness and better thermal stability than the conventional structure (Ni/TiN). In addition, the cross-sectional profile of the proposed Ni-silicide showed less agglomeration despite the high temperature post-silicidation annealing, and it can be said that the proposed structure was little dependence on the temperature post-silicidation annealing. The improvement of Ni silicide properties is analyzed and found to be due to the formation of the rare earth metal--NiSi (YbNi2Si2), whose peaks were confirmed by XRD. The junction leakage current of the p + -n junction with Yb/Ni/TiN and B18H22 implantation is smaller than that with Ni/TiN by almost one order of magnitude as well as improving the thermal stability of ultra shallow junction.

Characterisation of nickel silicide thin films by spectroscopy and microscopy techniques.

PubMed

Bhaskaran, M; Sriram, S; Holland, A S; Evans, P J

2009-01-01

This article discusses the formation and detailed materials characterisation of nickel silicide thin films. Nickel silicide thin films have been formed by thermally reacting electron beam evaporated thin films of nickel with silicon. The nickel silicide thin films have been analysed using Auger electron spectroscopy (AES) depth profiles, secondary ion mass spectrometry (SIMS), and Rutherford backscattering spectroscopy (RBS). The AES depth profile shows a uniform NiSi film, with a composition of 49-50% nickel and 51-50% silicon. No oxygen contamination either on the surface or at the silicide-silicon interface was observed. The SIMS depth profile confirms the existence of a uniform film, with no traces of oxygen contamination. RBS results indicate a nickel silicide layer of 114 nm, with the simulated spectra in close agreement with the experimental data. Atomic force microscopy and transmission electron microscopy have been used to study the morphology of the nickel silicide thin films. The average grain size and average surface roughness of these films was found to be 30-50 and 0.67 nm, respectively. The film surface has also been studied using Kikuchi patterns obtained by electron backscatter detection.

A customized fixation plate with novel structure designed by topological optimization for mandibular angle fracture based on finite element analysis.

PubMed

Liu, Yun-Feng; Fan, Ying-Ying; Jiang, Xian-Feng; Baur, Dale A

2017-11-15

The purpose of this study was to design a customized fixation plate for mandibular angle fracture using topological optimization based on the biomechanical properties of the two conventional fixation systems, and compare the results of stress, strain and displacement distributions calculated by finite element analysis (FEA). A three-dimensional (3D) virtual mandible was reconstructed from CT images with a mimic angle fracture and a 1 mm gap between two bone segments, and then a FEA model, including volume mesh with inhomogeneous bone material properties, three loading conditions and constraints (muscles and condyles), was created to design a customized plate using topological optimization method, then the shape of the plate was referenced from the stress concentrated area on an initial part created from thickened bone surface for optimal calculation, and then the plate was formulated as "V" pattern according to dimensions of standard mini-plate finally. To compare the biomechanical behavior of the "V" plate and other conventional mini-plates for angle fracture fixation, two conventional fixation systems were used: type A, one standard mini-plate, and type B, two standard mini-plates, and the stress, strain and displacement distributions within the three fixation systems were compared and discussed. The stress, strain and displacement distributions to the angle fractured mandible with three different fixation modalities were collected, respectively, and the maximum stress for each model emerged at the mandibular ramus or screw holes. Under the same loading conditions, the maximum stress on the customized fixation system decreased 74.3, 75.6 and 70.6% compared to type A, and 34.9, 34.1, and 39.6% compared to type B. All maximum von Mises stresses of mandible were well below the allowable stress of human bone, as well as maximum principal strain. And the displacement diagram of bony segments indicated the effect of treatment with different fixation systems. The customized fixation system with topological optimized structure has good biomechanical behavior for mandibular angle fracture because the stress, strain and displacement within the plate could be reduced significantly comparing to conventional "one mini-plate" or "two mini-plates" systems. The design methodology for customized fixation system could be used for other fractures in mandible or other bones to acquire better mechanical behavior of the system and improve stable environment for bone healing. And together with SLM, the customized plate with optimal structure could be designed and fabricated rapidly to satisfy the urgent time requirements for treatment.

Dentofacial effects of skeletal anchored treatment modalities for the correction of maxillary retrognathia.

PubMed

Sar, Cağla; Sahinoğlu, Zahire; Özçirpici, Ayça Arman; Uçkan, Sina

2014-01-01

The aim of this clinical study was to investigate the skeletal, dentoalveolar, and soft-tissue effects of 2 skeletal anchorage rationales for Class III treatment compared with an untreated Class III control group. Fifty-one subjects who were in the prepubertal or pubertal growth period were included in the study. In group 1 (n = 17), facemasks were applied from miniplates placed in the lateral nasal walls of the maxilla, and intermaxillary Class III elastics were applied from symphyseal miniplates to a bonded appliance on the maxilla in group 2 (n = 17). These skeletal anchored groups were compared with an untreated control group (n = 17). Lateral cephalometric radiographs were obtained at the beginning and the end of the observation periods in all groups and analyzed according to the structural superimposition method. Differences between the groups were assessed with the Wilcoxon signed rank test or the paired-samples t test. The treatment periods were 7.4 and 7.6 months in groups 1 and 2, respectively, and the untreated control group was observed for 7.5 months. The maxilla moved forward by 3.11 mm in group 1 and by 3.82 mm in group 2. The counterclockwise rotation of the maxilla was significantly less in group 1 compared with group 2 (P <0.01). The mandible showed clockwise rotation and was positioned downward and backward in the treatment groups, and it was significantly greater in group 2 compared with group 1 (P <0.01). Changes in the maxillary incisor measurements were negligible in group 1 compared with group 2. A significant amount of mandibular incisor retroclination was seen in group 1, and a significant proclination was seen in group 2. The maxillomandibular relationships and the soft-tissue profiles were improved remarkably in both treatment groups. The protocols of miniplates with facemasks and miniplates with Class III elastics offer valid alternatives to conventional methods in severe skeletal Class III patients. However, the 2 maxillary protraction protocols demonstrated significant skeletal and dentoalveolar effects. The miniplate with facemask protocol is preferred for patients with severe maxillary retrusion and a high-angle vertical pattern, whereas in patients with a decreased or normal vertical pattern and retroclined mandibular incisors, miniplates with Class III elastics can be the intraoral treatment option. Therefore, the exact indication of the procedure should be considered carefully. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Effect of Chemistry and Particle Size on the Performance of Calcium Disilicide Primers. Part 1 - Synthesis of Calcium Silicide (CaSi2) by Rotary Atomization

DTIC Science & Technology

2010-02-01

Metallurgist. 45, 267, 2001. 10. Dodero, M. "Electrolytic Preparation of Calcium Silicide ," Compt. Rend.. 198, 1593, 1934. 11. Dodero, M...Allqem. Chem.. 242, 117, 1939. 13. Yamaguchi, Y. and Hayakawa, Y., "The Preparation of Calcium Silicide by Reacting Solid Silicon Carbide and...SYNTHESIS OF CALCIUM SILICIDE (CaSi2) BY ROTARY ATOMIZATION Paul E. Anderson Kin Yee Eugene Homentowski Gartung Cheng Neha Mehta Gary Chen U.S

Effects of temperature dependent pre-amorphization implantation on NiPt silicide formation and thermal stability on Si(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozcan, Ahmet S.; Wall, Donald; Jordan-Sweet, Jean

Using temperature controlled Si and C ion implantation, we studied the effects of pre-amorphization implantation on NiPt alloy silicide phase formation. In situ synchrotron x-ray diffraction and resistance measurements were used to monitor phase and morphology evolution in silicide films. Results show that substrate amorphization strongly modulate the nucleation of silicide phases, regardless of implant species. However, morphological stability of the thin films is mainly enhanced by C addition, independently of the amorphization depth.

Monolithic porous magnesium silicide.

PubMed

Hayati-Roodbari, N; Berger, R J F; Bernardi, J; Kinge, S; Hüsing, N; Elsaesser, M S

2017-07-11

Macroporous magnesium silicide monoliths were successfully prepared by a two-step synthesis procedure. The reaction of gaseous magnesium vapor with macro-/mesoporous silicon, which was generated from hierarchically organized meso-/macroporous silica by a magnesiothermic reduction reaction, resulted in monolithic magnesium silicide with a cellular, open macroporous structure. By adjusting the reaction conditions, such as experimental set-up, temperature and time, challenges namely loss of porosity or phase purity of Mg 2 Si were addressed and monolithic magnesium silicide with a cellular network builtup was obtained.

Transmission electron microscopy study of erbium silicide formation from Ti/Er stack for Schottky contact applications.

PubMed

Ratajczak, J; Łaszcz, A; Czerwinski, A; Katcki, J; Phillipp, F; Van Aken, P A; Reckinger, N; Dubois, E

2010-03-01

In this paper, we present results of transmission electron microscopy studies on erbium silicide structures fabricated under various thermal conditions. A titanium cap has been used as a protective layer against oxidation during rapid thermal annealing of an erbium layer in a temperature range of 300-700 degrees C. Both layers (200 nm Ti and 25 nm Er) were deposited by electron-beam sputtering. The investigations have shown that the transformation of the 25-nm-thick erbium into erbium silicide is completed after annealing at 500 degrees C. At higher temperatures, the formation of a titanium silicide layer above erbium silicide is observed. The lowest Schottky barrier has been measured in the sample annealed at 700 degrees C.

Controlling the growth and field emission properties of silicide nanowire arrays by direct silicification of Ni foil.

PubMed

Liu, Zhihong; Zhang, Hui; Wang, Lei; Yang, Deren

2008-09-17

Nickel silicide nanowire arrays have been achieved by the decomposition of SiH(4) on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm(-1), and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters.

Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements

PubMed Central

2011-01-01

We examine nickel silicide as a viable ohmic contact metallization for low-temperature, low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular, we compare a nickel silicide metallization with aluminium, a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures (<400°C) required for maintaining atomic precision placement in donor-based devices, and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly, we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field. PMID:21968083

Plasmonic-Electronic Transduction

DTIC Science & Technology

2012-01-31

including metal silicides (Pt-, Pd-, Ni-, W- silicides ), semimetals (Sb, Bi, graphite), doped-semiconductors (Si, CuInSe), and conducting polymers... silicides and doped silicon,” J. W. Cleary, R. E. Peale, D. J. Shelton, G. D. Boreman, C. W. Smith, M. Ishigami, R. Soref, A. Drehman, W.R. Buchwald

Valence Band Control of Metal Silicide Films via Stoichiometry.

PubMed

Streller, Frank; Qi, Yubo; Yang, Jing; Mangolini, Filippo; Rappe, Andrew M; Carpick, Robert W

2016-07-07

The unique electronic and mechanical properties of metal silicide films render them interesting for advanced materials in plasmonic devices, batteries, field-emitters, thermoelectric devices, transistors, and nanoelectromechanical switches. However, enabling their use requires precisely controlling their electronic structure. Using platinum silicide (PtxSi) as a model silicide, we demonstrate that the electronic structure of PtxSi thin films (1 ≤ x ≤ 3) can be tuned between metallic and semimetallic by changing the stoichiometry. Increasing the silicon content in PtxSi decreases the carrier density according to valence band X-ray photoelectron spectroscopy and theoretical density of states (DOS) calculations. Among all PtxSi phases, Pt3Si offers the highest DOS due to the modest shift of the Pt5d manifold away from the Fermi edge by only 0.5 eV compared to Pt, rendering it promising for applications. These results, demonstrating tunability of the electronic structure of thin metal silicide films, suggest that metal silicides can be designed to achieve application-specific electronic properties.

Improved high-temperature silicide coatings

NASA Technical Reports Server (NTRS)

Klopp, W. D.; Stephens, J. R.; Stetson, A. R.; Wimber, R. T.

1969-01-01

Special technique for applying silicide coatings to refractory metal alloys improves their high-temperature protective capability. Refractory metal powders mixed with a baked-out organic binder and sintered in a vacuum produces a porous alloy layer on the surface. Exposing the layer to hot silicon converts it to a silicide.

Formation, structure, and orientation of gold silicide on gold surfaces

NASA Technical Reports Server (NTRS)

Green, A. K.; Bauer, E.

1976-01-01

The formation of gold silicide on Au films evaporated onto Si(111) surfaces is studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). Surface condition, film thickness, deposition temperature, annealing temperature, and heating rate during annealing are varied. Several oriented crystalline silicide layers are observed.

Low-loss silicide/silicon plasmonic ribbon waveguides for mid- and far-infrared applications.

PubMed

Cho, Sang-Yeon; Soref, Richard A

2009-06-15

We report low-loss silicide/silicon plasmonic ribbon waveguides for mid- and far-IR applications. The composite modes in silicide ribbon waveguides offer a low-loss and highly confined mode profile, giving excellent plasmon waveguiding for long-wavelength applications. The calculated propagation loss of the composite long-range surface-plasmon polariton mode at a wavelength of 100 microm is 2.18 dB/cm with a mode height of less than 30 microm. The results presented provide important design guidelines for silicide/Si plasmon waveguides.

ITEP MEVVA ion beam for rhenium silicide production.

PubMed

Kulevoy, T; Gerasimenko, N; Seleznev, D; Kropachev, G; Kozlov, A; Kuibeda, R; Yakushin, P; Petrenko, S; Medetov, N; Zaporozhan, O

2010-02-01

The rhenium silicides are very attractive materials for semiconductor industry. In the Institute for Theoretical and Experimental Physics (ITEP) at the ion source test bench the research program of rhenium silicide production by ion beam implantation are going on. The investigation of silicon wafer after implantation of rhenium ion beam with different energy and with different total dose were carried out by secondary ions mass spectrometry, energy-dispersive x-ray microanalysis, and x-ray diffraction analysis. The first promising results of rhenium silicide film production by high intensity ion beam implantation are presented.

Manganese silicide nanowires on Si(001).

PubMed

Liu, H J; Owen, J H G; Miki, K; Renner, Ch

2011-05-04

A method for promoting the growth of manganese silicide nanowires on Si(001) at 450 °C is described. The anisotropic surface stress generated by bismuth nanolines blocks the formation of embedded structures and stabilizes the nucleation of manganese silicide islands which grow in a preferred direction, forming nanowires with a band gap of approximately 0.6 eV, matching the reported band gap of MnSi(1.7). This method may also provide a means to form silicide nanowires of other metals where they do not otherwise form. © 2011 IOP Publishing Ltd

Nickel/Platinum Dual Silicide Axial Nanowire Heterostructures with Excellent Photosensor Applications.

PubMed

Wu, Yen-Ting; Huang, Chun-Wei; Chiu, Chung-Hua; Chang, Chia-Fu; Chen, Jui-Yuan; Lin, Ting-Yi; Huang, Yu-Ting; Lu, Kuo-Chang; Yeh, Ping-Hung; Wu, Wen-Wei

2016-02-10

Transition metal silicide nanowires (NWs) have attracted increasing attention as they possess advantages of both silicon NWs and transition metals. Over the past years, there have been reported with efforts on one silicide in a single silicon NW. However, the research on multicomponent silicides in a single silicon NW is still rare, leading to limited functionalities. In this work, we successfully fabricated β-Pt2Si/Si/θ-Ni2Si, β-Pt2Si/θ-Ni2Si, and Pt, Ni, and Si ternary phase axial NW heterostructures through solid state reactions at 650 °C. Using in situ transmission electron microscope (in situ TEM), the growth mechanism of silicide NW heterostructures and the diffusion behaviors of transition metals were systematically studied. Spherical aberration corrected scanning transmission electron microscope (Cs-corrected STEM) equipped with energy dispersive spectroscopy (EDS) was used to analyze the phase structure and composition of silicide NW heterostructures. Moreover, electrical and photon sensing properties for the silicide nanowire heterostructures demonstrated promising applications in nano-optoeletronic devices. We found that Ni, Pt, and Si ternary phase nanowire heterostructures have an excellent infrared light sensing property which is absent in bulk Ni2Si or Pt2Si. The above results would benefit the further understanding of heterostructured nano materials.

Use of rectangular grid miniplates for fracture fixation at the mandibular angle.

PubMed

Hochuli-Vieira, Eduardo; Ha, Thi Khanh Linh; Pereira-Filho, Valfrido Antonio; Landes, Constantin Alexander

2011-05-01

The aim of this study was to evaluate the clinical outcome of patients with mandibular angle fractures treated by intraoral access and a rectangular grid miniplate with 4 holes and stabilized with monocortical screws. This study included 45 patients with mandibular angle fractures from the Department of Oral and Maxillofacial Surgery São Paulo State University, Araraquara, Brazil, and from the Clinic of Oral and Maxillofacial Surgery at the University of Frankfurt, Germany. The 45 fractures of the mandibular angle were treated with a rectangular grid miniplate of a 2.0-mm system by an intraoral approach with monocortical screws. Clinical evaluations were postoperatively performed at 15 and 30 days and 3 and 6 months, and the complications encountered were recorded and treated. The infection rate was 4.44% (2 patients), and in 1 patient it was necessary to replace hardware. This patient also had a fracture of the left mandibular body; 3 patients (6.66%) had minor occlusal changes that have been resolved with small occlusal adjustments. Before surgery, 15 patients (33.33%) presented with hypoesthesia of the inferior alveolar nerve; 4 (8.88%) had this change until the last clinical control, at 6 months. The rectangular grid miniplate used in this study was stable for the treatment of simple mandibular angle fractures through intraoral access, with low complication rates, easy handling, and easy adjustment, with a low cost. Concomitant mandibular fracture may increase the rate of complications. This plate should be indicated in fractures with sufficient interfragmentary contact. Copyright © 2011 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Raman scattering from rapid thermally annealed tungsten silicide

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Dasgupta, Samhita; Jackson, Howard E.; Boyd, Joseph T.

1987-01-01

Raman scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films have been formed by rapid thermal annealing of thin tungsten films sputter deposited on silicon substrates. The Raman data are interpreted by using data from resistivity measurements, Auger and Rutherford backscattering measurements, and scanning electron microscopy.

Ion-beam mixed ultra-thin cobalt suicide (CoSi2) films by cobalt sputtering and rapid thermal annealing

NASA Astrophysics Data System (ADS)

Kal, S.; Kasko, I.; Ryssel, H.

1995-10-01

The influence of ion-beam mixing on ultra-thin cobalt silicide (CoSi2) formation was investigated by characterizing the ion-beam mixed and unmixed CoSi2 films. A Ge+ ion-implantation through the Co film prior to silicidation causes an interface mixing of the cobalt film with the silicon substrate and results in improved silicide-to-silicon interface roughness. Rapid thermal annealing was used to form Ge+ ion mixed and unmixed thin CoSi2 layer from 10 nm sputter deposited Co film. The silicide films were characterized by secondary neutral mass spectroscopy, x-ray diffraction, tunneling electron microscopy (TEM), Rutherford backscattering, and sheet resistance measurements. The experi-mental results indicate that the final rapid thermal annealing temperature should not exceed 800°C for thin (<50 nm) CoSi2 preparation. A comparison of the plan-view and cross-section TEM micrographs of the ion-beam mixed and unmixed CoSi2 films reveals that Ge+ ion mixing (45 keV, 1 × 1015 cm-2) produces homogeneous silicide with smooth silicide-to-silicon interface.

Effect of silicide/silicon hetero-junction structure on thermal conductivity and Seebeck coefficient.

PubMed

Choi, Wonchul; Park, Young-Sam; Hyun, Younghoon; Zyung, Taehyoung; Kim, Jaehyeon; Kim, Soojung; Jeon, Hyojin; Shin, Mincheol; Jang, Moongyu

2013-12-01

We fabricated a thermoelectric device with a silicide/silicon laminated hetero-structure by using RF sputtering and rapid thermal annealing. The device was observed to have Ohmic characteristics by I-V measurement. The temperature differences and Seebeck coefficients of the proposed silicide/silicon laminated and bulk structure were measured. The laminated thermoelectric device shows suppression of heat flow from the hot to cold side. This is supported by the theory that the atomic mass difference between silicide and silicon creates a scattering center for phonons. The major impact of our work is that phonon transmission is suppressed at the interface between silicide and silicon without degrading electrical conductivity. The estimated thermal conductivity of the 3-layer laminated device is 126.2 +/- 3.7 W/m. K. Thus, by using the 3-layer laminated structure, thermal conductivity is reduced by around 16% compared to bulk silicon. However, the Seebeck coefficient of the thermoelectric device is degraded compared to that of bulk silicon. It is understood that electrical conductivity is improved by using silicide as a scattering center.

Epitaxial insertion of gold silicide nanodisks during the growth of silicon nanowires.

PubMed

Um, Han-Don; Jee, Sang-Won; Park, Kwang-Tae; Jung, Jin-Young; Guo, Zhongyi; Lee, Jung-Ho

2011-07-01

Nanodisk-shaped, single-crystal gold silicide heterojunctions were inserted into silicon nanowires during vapor-liquid-solid growth using Au as a catalyst within a specific range of chlorine-to-hydrogen atomic ratio. The mechanism of nanodisk formation has been investigated by changing the source gas ratio of SiCl4 to H2. We report that an over-supply of silicon into the Au-Si liquid alloy leads to highly supersaturated solution and enhances the precipitation of Au in the silicon nanowires due to the formation of unstable phases within the liquid alloy. It is shown that the gold precipitates embedded in the silicon nanowires consisted of a metastable gold silicide. Interestingly, faceting of gold silicide was observed at the Au/Si interfaces, and silicon nanowires were epitaxially grown on the top of the nanodisk by vapor-liquid-solid growth. High resolution transmission electron microscopy confirmed that gold silicide nanodisks are epitaxially connected to the silicon nanowires in the direction of growth direction. These gold silicide nanodisks would be useful as nanosized electrical junctions for future applications in nanowire interconnections.

Silicide/Silicon Hetero-Junction Structure for Thermoelectric Applications.

PubMed

Jun, Dongsuk; Kim, Soojung; Choi, Wonchul; Kim, Junsoo; Zyung, Taehyoung; Jang, Moongyu

2015-10-01

We fabricated silicide/silicon hetero-junction structured thermoelectric device by CMOS process for the reduction of thermal conductivity with the scatterings of phonons at silicide/silicon interfaces. Electrical conductivities, Seebeck coefficients, power factors, and temperature differences are evaluated using the steady state analysis method. Platinum silicide/silicon multilayered structure showed an enhanced Seebeck coefficient and power factor characteristics, which was considered for p-leg element. Also, erbium silicide/silicon structure showed an enhanced Seebeck coefficient, which was considered for an n-leg element. Silicide/silicon multilayered structure is promising for thermoelectric applications by reducing thermal conductivity with an enhanced Seebeck coefficient. However, because of the high thermal conductivity of the silicon packing during thermal gradient is not a problem any temperature difference. Therefore, requires more testing and analysis in order to overcome this problem. Thermoelectric generators are devices that based on the Seebeck effect, convert temperature differences into electrical energy. Although thermoelectric phenomena have been used for heating and cooling applications quite extensively, it is only in recent years that interest has increased in energy generation.

Success rates of a skeletal anchorage system in orthodontics: A retrospective analysis.

PubMed

Lam, Raymond; Goonewardene, Mithran S; Allan, Brent P; Sugawara, Junji

2018-01-01

To evaluate the premise that skeletal anchorage with SAS miniplates are highly successful and predictable for a range of complex orthodontic movements. This retrospective cross-sectional analysis consisted of 421 bone plates placed by one clinician in 163 patients (95 female, 68 male, mean age 29.4 years ± 12.02). Simple descriptive statistics were performed for a wide range of malocclusions and desired movements to obtain success, complication, and failure rates. The success rate of skeletal anchorage system miniplates was 98.6%, where approximately 40% of cases experienced mild complications. The most common complication was soft tissue inflammation, which was amenable to focused oral hygiene and antiseptic rinses. Infection occurred in approximately 15% of patients where there was a statistically significant correlation with poor oral hygiene. The most common movements were distalization and intrusion of teeth. More than a third of the cases involved complex movements in more than one plane of space. The success rate of skeletal anchorage system miniplates is high and predictable for a wide range of complex orthodontic movements.

Influence of phototherapies on the outcome of complete tibial fractures grafted or not with MTA: Raman spectroscopic study on rabbits

NASA Astrophysics Data System (ADS)

Pinheiro, Antônio L. B.; Soares, Luiz G. P.; da Silva, Aline C. P.; Santos, Nicole R. S.; da Silva, Anna Paula L. T.; Neves, Bruno Luiz R. C.; Soares, Amanda P.; Silveira, Landulfo

2018-02-01

The aim of the present study was to assess, by means of Raman spectroscopy, the repair of complete surgical tibial fractures fixed with wire osteosynthesis or miniplates treated or not with infrared laser (λ780 nm) or infrared LED (λ850 +/- 10 nm) lights, 142.8 J/cm2 per treatment, associated or not to the use of mineral trioxide aggregate (MTA) cement. Surgical fractures were created on 36 rabbits and fixed with WO or miniplates and some groups were grafted with MTA. Irradiated groups received lights at every other day for 15 days and sacrifice occurred after 30 days. The results showed that only irradiation with either laser or LED influenced the peaks of phosphate ( 960 cm-1) and carbonated ( 1,070 cm-1) hydroxyapatite. Collagen peak (1,450 cm-1) was influenced by both the use of MTA and irradiation with either laser or LED. It is concluded that the use of either laser or LED phototherapy associated to MTA cement was efficacious on improving the repair of complete tibial fractures treated with wire osteosynthesis or miniplates.

Class II malocclusion with accentuated occlusal plane inclination corrected with miniplate: a case report

PubMed Central

Farret, Marcel Marchiori; Farret, Milton M. Benitez

2016-01-01

ABSTRACT Introduction: A canted occlusal plane presents an unesthetic element of the smile. The correction of this asymmetry has been typically considered difficult by orthodontists, as it requires complex mechanics and may sometimes even require orthognathic surgery. Objective: This paper outlines the case of a 29-year-old woman with Class II malocclusion, pronounced midline deviation and accentuated occlusal plane inclination caused by mandibular deciduous molar ankylosis. Methods: The patient was treated with a miniplate used to provide anchorage in order to intrude maxillary teeth and extrude mandibular teeth on one side, thus eliminating asymmetry. Class II was corrected on the left side by means of distalization, anchored in the miniplate as well. On the right side, maxillary first premolar was extracted and molar relationship was kept in Class II, while canines were moved to Class I relationship. The patient received implant-prosthetic rehabilitation for maxillary left lateral incisor and mandibular left second premolar. Results: At the end of treatment, Class II was corrected, midlines were matched and the canted occlusal plane was totally corrected, thereby improving smile function and esthetics. PMID:27409658

Miniplate for osteosynthesis in a 9-year-old with symphysis fracture: clinical report.

PubMed

Srinivasan, Ila; Kumar, Naveen; Jaganathan, Udhya; Bhandari, Arihant

2013-09-01

Osteosynthesis using minimum material in pediatric mandibular fractures is the key, due to the limited space available in the mandible, especially in the mental foramen and apical region. There is an important role of open reduction and rigid internal fixation in re-establishing facial height, width and projection. During the early years of growth and development, there is a high osteogenic potential of the bones. The thick periosteum allows for rapid consolidation and remodeling at the site of fracture. Primary teeth have short, bulbous crowns which compromise stable maxillomandibular fixation during fracture reduction and stabilization using traditional methods. Further, stability of the fractured segments may be hampered because of the displaced or mobile permanent anterior teeth in the mixed dentition along the line of fracture. This clinical report outlines the use of miniplate with monocortical screws in a 9-year-old boy with symphysis fracture. How to cite this article: Srinivasan I, Kumar N, Jaganathan U, Bhandari A. Miniplate for Osteosynthesis in a 9-Year-Old with Symphysis Fracture: Clinical Report. Int J Clin Pediatr Dent 2013;6(3):213-216.

NMOS contact resistance reduction with selenium implant into NiPt silicide

NASA Astrophysics Data System (ADS)

Rao, K. V.; Khaja, F. A.; Ni, C. N.; Muthukrishnan, S.; Darlark, A.; Lei, J.; Peidous, I.; Brand, A.; Henry, T.; Variam, N.; Erokhin, Y.

2012-11-01

A 25% reduction in NMOS contact resistance (Rc) was achieved by Selenium implantation into NiPt silicide film in VIISta Trident high-current single-wafer implanter. The Trident implanter is designed for shallow high-dose implants with high beam currents to maintain high throughput (for low CoO), with improved micro-uniformity and no energy contamination. The integration of Se implant was realized using a test chip dedicated to investigating silicide/junction related electrical properties and testable after silicidation. The silicide module processes were optimized, including the pre-clean (prior to RF PVD NiPt dep) and pre- and post-implant anneals. A 270°C soak anneal was used for RTP1, whereas a msec laser anneal was employed for RTP2 with sufficient process window (800-850°C), while maintaining excellent junction characteristics without Rs degradation.

Chemical compatibility between UO2 fuel and SiC cladding for LWRs. Application to ATF (Accident-Tolerant Fuels)

NASA Astrophysics Data System (ADS)

Braun, James; Guéneau, Christine; Alpettaz, Thierry; Sauder, Cédric; Brackx, Emmanuelle; Domenger, Renaud; Gossé, Stéphane; Balbaud-Célérier, Fanny

2017-04-01

Silicon carbide-silicon carbide (SiC/SiC) composites are considered to replace the current zirconium-based cladding materials thanks to their good behavior under irradiation and their resistance under oxidative environments at high temperature. In the present work, a thermodynamic analysis of the UO2±x/SiC system is performed. Moreover, using two different experimental methods, the chemical compatibility of SiC towards uranium dioxide, with various oxygen contents (UO2±x) is investigated in the 1500-1970 K temperature range. The reaction leads to the formation of mainly uranium silicides and carbides phases along with CO and SiO gas release. Knudsen Cell Mass Spectrometry is used to measure the gas release occurring during the reaction between UO2+x and SiC powders as function of time and temperature. These experimental conditions are representative of an open system. Diffusion couple experiments with pellets are also performed to study the reaction kinetics in closed system conditions. In both cases, a limited chemical reaction is observed below 1700 K, whereas the reaction is enhanced at higher temperature due to the decomposition of SiC leading to Si vaporization. The temperature of formation of the liquid phase is found to lie between 1850 < T < 1950 K.

Structural and electrochemical properties of nanostructured nickel silicides by reduction and silicification of high-surface-area nickel oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xiao; Zhang, Bingsen; Li, Chuang

Graphical abstract: Nanostructured nickel silicides have been synthesized by reduction and silification of high-surface-area nickel oxide, and exhibited remarkably like-noble metal property, lower electric resistivity, and ferromagnetism at room temperature. Highlights: Black-Right-Pointing-Pointer NiSi{sub x} have been prepared by reduction and silification of high-surface-area NiO. Black-Right-Pointing-Pointer The structure of nickel silicides changed with increasing reaction temperature. Black-Right-Pointing-Pointer Si doping into nickel changed the magnetic properties of metallic nickel. Black-Right-Pointing-Pointer NiSi{sub x} have remarkably lower electric resistivity and like-noble metal property. -- Abstract: Nanostructured nickel silicides have been prepared by reduction and silicification of high-surface-area nickel oxide (145 m{sup 2} g{sup -1})more » produced via precipitation. The prepared materials were characterized by nitrogen adsorption, X-ray diffraction, thermal analysis, FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, magnetic and electrochemical measurements. The nickel silicide formation involves the following sequence: NiO (cubic) {yields} Ni (cubic) {yields} Ni{sub 2}Si (orthorhombic) {yields} NiSi (orthorhombic) {yields} NiSi{sub 2} (cubic), with particles growing from 13.7 to 21.3 nm. The nickel silicides are ferromagnetic at room temperature, and their saturation magnetization values change drastically with the increase of Si content. Nickel silicides have remarkably low electrical resistivity and noble metal-like properties because of a constriction of the Ni d band and an increase of the electronic density of states. The results suggest that such silicides are promising candidates as inexpensive yet functional materials for applications in electrochemistry as well as catalysis.« less

Investigation of silicide-induced-dopant-activation for steep tunnel junction in tunnel field effect transistor (TFET)

NASA Astrophysics Data System (ADS)

Kim, Sihyun; Kwon, Dae Woong; Park, Euyhwan; Lee, Junil; Lee, Roongbin; Lee, Jong-Ho; Park, Byung-Gook

2018-02-01

Numerous researches for making steep tunnel junction within tunnel field-effect transistor (TFET) have been conducted. One of the ways to make an abrupt junction is source/drain silicidation, which uses the phenomenon often called silicide-induced-dopant-segregation. It is revealed that the silicide process not only helps dopants to pile up adjacent to the metal-silicon alloy, also induces the dopant activation, thereby making it possible to avoid additional high temperature process. In this report, the availability of dopant activation induced by metal silicide process was thoroughly investigated by diode measurement and device simulation. Metal-silicon (MS) diodes having p+ and n+ silicon formed on the p- substrate exhibit the characteristics of ohmic and pn diodes respectively, for both the samples with and without high temperature annealing. The device simulation for TFETs with dopant-segregated source was also conducted, which verified enhanced DC performance.

Controlled assembly of graphene-capped nickel, cobalt and iron silicides

PubMed Central

Vilkov, O.; Fedorov, A.; Usachov, D.; Yashina, L. V.; Generalov, A. V.; Borygina, K.; Verbitskiy, N. I.; Grüneis, A.; Vyalikh, D. V.

2013-01-01

The unique properties of graphene have raised high expectations regarding its application in carbon-based nanoscale devices that could complement or replace traditional silicon technology. This gave rise to the vast amount of researches on how to fabricate high-quality graphene and graphene nanocomposites that is currently going on. Here we show that graphene can be successfully integrated with the established metal-silicide technology. Starting from thin monocrystalline films of nickel, cobalt and iron, we were able to form metal silicides of high quality with a variety of stoichiometries under a Chemical Vapor Deposition grown graphene layer. These graphene-capped silicides are reliably protected against oxidation and can cover a wide range of electronic materials/device applications. Most importantly, the coupling between the graphene layer and the silicides is rather weak and the properties of quasi-freestanding graphene are widely preserved. PMID:23835625

Highly efficient phosphorescent organic light-emitting diode with a nanometer-thick Ni silicide/polycrystalline p-Si composite anode.

PubMed

Li, Y Z; Wang, Z L; Luo, H; Wang, Y Z; Xu, W J; Ran, G Z; Qin, G G; Zhao, W Q; Liu, H

2010-07-19

A phosphorescent organic light-emitting diode (PhOLED) with a nanometer-thick (approximately 10 nm) Ni silicide/ polycrystalline p-Si composite anode is reported. The structure of the PhOLED is Al mirror/ glass substrate / Si isolation layer / Ni silicide / polycrystalline p-Si/ V(2)O(5)/ NPB/ CBP: (ppy)(2)Ir(acac)/ Bphen/ Bphen: Cs(2)CO(3)/ Sm/ Au/ BCP. In the composite anode, the Ni-induced polycrystalline p-Si layer injects holes into the V(2)O(5)/ NPB, and the Ni silicide layer reduces the sheet resistance of the composite anode and thus the series resistance of the PhOLED. By adopting various measures for specially optimizing the thickness of the Ni layer, which induces Si crystallization and forms a Ni silicide layer of appropriate thickness, the highest external quantum efficiency and power conversion efficiency have been raised to 26% and 11%, respectively.

Metallic rare-earth silicide nanowires on silicon surfaces.

PubMed

Dähne, Mario; Wanke, Martina

2013-01-09

The formation, atomic structure, and electronic properties of self-assembled rare-earth silicide nanowires on silicon surfaces were studied by scanning tunneling microscopy and angle-resolved photoelectron spectroscopy. Metallic dysprosium and erbium silicide nanowires were observed on both the Si(001) and Si(557) surfaces. It was found that they consist of hexagonal rare-earth disilicides for both surface orientations. On Si(001), the nanowires are characterized by a one-dimensional band structure, while the electronic dispersion is two-dimensional for the nanowires formed on Si(557). This behavior is explained by the different orientations of the hexagonal c axis of the silicide leading to different conditions for the carrier confinement. By considering this carrier confinement it is demonstrated how the one-dimensional band structure of the nanowires on Si(001) can be derived from the two-dimensional one of the silicide monolayer on Si(111).

Magnetic Binary Silicide Nanostructures.

PubMed

Goldfarb, Ilan; Cesura, Federico; Dascalu, Matan

2018-05-02

In spite of numerous advantageous properties of silicides, magnetic properties are not among them. Here, the magnetic properties of epitaxial binary silicide nanostructures are discussed. The vast majority of binary transition-metal silicides lack ferromagnetic order in their bulk-size crystals. Silicides based on rare-earth metals are usually weak ferromagnets or antiferromagnets, yet both groups tend to exhibit increased magnetic ordering in low-dimensional nanostructures, in particular at low temperatures. The origin of this surprising phenomenon lies in undercoordinated atoms at the nanostructure extremities, such as 2D (surfaces/interfaces), 1D (edges), and 0D (corners) boundaries. Uncompensated superspins of edge atoms increase the nanostructure magnetic shape anisotropy to the extent where it prevails over its magnetocrystalline counterpart, thus providing a plausible route toward the design of a magnetic response from nanostructure arrays in Si-based devices, such as bit-patterned magnetic recording media and spin injectors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Core-shell chromium silicide-silicon nanopillars: a contact material for future nanosystems.

PubMed

Chang, Mu-Tung; Chen, Chih-Yen; Chou, Li-Jen; Chen, Lih-Juann

2009-11-24

Chromium silicide nanostructures are fabricated inside silicon nanopillars grown by the vapor-liquid-solid mechanism. The remarkable field-emission behavior of these nanostructures results from extensive improvement of carrier transport due to the reduced energy barrier between the metal and semiconductor layers. The results warrant consideration of chromium silicide as a potentially important contact material in future nanosystems.

The deposition of aluminide and silicide coatings on γ-TiAl using the halide-activated pack cementation method

NASA Astrophysics Data System (ADS)

Munro, T. C.; Gleeson, B.

1996-12-01

The halide-activated pack cementation method (HAPC) was utilized to deposit aluminide and silicide coatings on nominally stoichiometric γ-TiAl. The deposition temperature was 1000°C and deposition times ranged from 2 to 12 hours. The growth rates of the coatings were diffusion controlled, with the rate of aluminide growth being about a factor of 2 greater than that of silicide growth. The aluminide coating was inward growing and consisted of a thick, uniform outer layer of TiAl3 and a thin inner layer of TiAl2, with the rate-controlling step being the diffusion of aluminum from the pack into the substrate. Annealing experiments at 1100 °C showed that the interdiffusion between the aluminide coating and the γ-TiAl substrate was rapid. In contrast to the aluminide coating, the silicide coating was nonuniform and porous, consisting primarily of TiSi2, TiSi, and Ti5Si4, with the rate-controlling step for the coating growth believed to be the diffusion of aluminum into the γ-TiAl ahead of the silicide/γ-TiAl interface. The microstructural evolution of the aluminide and silicide coating structures is discussed qualitatively.

Metal silicide/poly-Si Schottky diodes for uncooled microbolometers.

PubMed

Chizh, Kirill V; Chapnin, Valery A; Kalinushkin, Victor P; Resnik, Vladimir Y; Storozhevykh, Mikhail S; Yuryev, Vladimir A

2013-04-17

: Nickel silicide Schottky diodes formed on polycrystalline Si 〈P〉 films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22â"ƒ to 70â"ƒ; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%â"ƒ to 0.6%/â"ƒ for forward bias and around 2.5%/â"ƒ for reverse bias of the diodes.

Silicide Nanowires for Low-Resistance CMOS Transistor Contacts.

NASA Astrophysics Data System (ADS)

Zollner, Stefan

2007-03-01

Transition metal (TM) silicide nanowires are used as contacts for modern CMOS transistors. (Our smallest wires are ˜20 nm thick and ˜50 nm wide.) While much research on thick TM silicides was conducted long ago, materials perform differently at the nanoscale. For example, the usual phase transformation sequences (e.g., Ni, Ni2Si, NiSi, NiSi2) for the reaction of thick metal films on Si no longer apply to nanostructures, because the surface and interface energies compete with the bulk energy of a given crystal structure. Therefore, a NiSi film will agglomerate into hemispherical droplets of NiSi by annealing before it reaches the lowest-energy (NiSi2) crystalline structure. These dynamics can be tuned by addition of impurities (such as Pt in Ni). The Si surface preparation is also a more important factor for nanowires than for silicidation of thick TM films. Ni nanowires formed on Si surfaces that were cleaned and amorphized by sputtering with Ar ions have a tendency to form NiSi2 pyramids (``spikes'') even at moderate temperatures (˜400^oC), while similar Ni films formed on atomically clean or hydrogen-terminated Si form uniform NiSi nanowires. Another issue affecting TM silicides is the barrier height between the silicide contact and the silicon transistor. For most TM silicides, the Fermi level of the silicide is aligned with the center of the Si band gap. Therefore, silicide contacts experience Schottky barrier heights of around 0.5 eV for both n-type and p-type Si. The resulting contact resistance becomes a significant term for the overall resistance of modern CMOS transistors. Lowering this contact resistance is an important goal in CMOS research. New materials are under investigation (for example PtSi, which has a barrier height of only 0.3 eV to p-type Si). This talk will describe recent results, with special emphasis on characterization techniques and electrical testing useful for the development of silicide nanowires for CMOS contacts. In collaboration with: P. Grudowski, D. Jawarani, R. Garcia, M.L. Kottke, R.B. Gregory, X.-D. Wang, D. Theodore, P. Fejes, W.J. Taylor, B.Y. Nguyen, C. Capasso, M. Raymond, D. Denning, K. Chang, R. Noble, M. Jahanbani, S. Bolton, P. Crabtree, D. Goedeke, M. Rossow, M. Chowdhury, H. Desjardins, A.Thean.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces.

PubMed

Hong, Ie-Hong; Liao, Yung-Cheng; Tsai, Yung-Feng

2013-11-05

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces

PubMed Central

2013-01-01

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process. PMID:24188092

Non-stoichiometry in U 3Si 2

DOE PAGES

Middleburgh, Simon C.; Grimes, Robin W.; Lahoda, Ed J.; ...

2016-10-08

Uranium silicides, in particular U 3Si 2, are being explored as an advanced nuclear fuel with increased accident tolerance as well as competitive economics compared to the baseline UO 2 fuel. Here we use density functional theory calculations and thermochemical analysis to assess the stability of U 3Si 2 with respect to non-stoichiometry reactions in both the hypo- and hyper-stoichiometric regimes. We find that the degree of non-stoichiometry in U 3Si 2 is much smaller than in UO 2 and at most reaches a few percent at high temperature. Non-stoichiometry impacts fuel performance by determining whether the loss of uraniummore » due to fission leads to a non-stoichiometric U 3Si 2±x phase or precipitation of a second U-Si phase. Lastly, we also investigate the U 5Si 4 phase as a candidate for the equilibrium phase diagram.« less

Dual fuel gradients in uranium silicide plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, B.W.

1997-08-01

Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final coremore » gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.« less

Metallic impurities-silicon carbide interaction in HTGR fuel particles

NASA Astrophysics Data System (ADS)

Minato, Kazuo; Ogawa, Toru; Kashimura, Satoru; Fukuda, Kousaku; Shimizu, Michio; Tayama, Yoshinobu; Takahashi, Ishio

1990-12-01

Corrosion of the coating layers of silicon carbide (SiC) by metallic impurities was observed in irradiated Triso-coated uranium dioxide particles for high temperature gas-cooled reactors with an optical microscope and an electron probe micro-analyzer. The SiC layers were attacked from the outside of the particles. The main element observed in the corroded areas was iron, but sometimes iron and nickel were found. These elements must have been contained as impurities in the graphite matrix in which the coated particles were dispersed. Since these elements are more stable thermodynamically in the presence of SiC than in the presence of graphite at irradiation temperatures, they were transferred to the SiC layer to form more stable silicides. During fuel manufacturing processes, intensive care should be taken to prevent the fuel from being contaminated with those elements which react with SiC.

Fundamental Studies and Isolation Strategies for Metal Compound Nanoclusters

DTIC Science & Technology

2009-02-28

probe nanocluster structure, bonding and stability, metal oxide, carbide and silicide clusters with up to 50 atoms were investigated with mass...transition metal compounds (carbides, oxides, silicides ) that are expected to have high stability, an essential property for their isolation...Metal carbide, oxide and silicide nanoclusters are studied in the size range from a few up to about 300 atoms. New infrared laser spectroscopy

The Longwave Silicon Chip - Integrated Plasma-Photonics in Group IV And III-V Semiconductors

DTIC Science & Technology

2013-10-01

infrared applications; SiGeSn heterostructure photonics; group IV plasmonics with silicides , germanicides, doped Si, Ge or GeSn; Franz-Keldysh...SPP waveguide in which localized silicide or germanicide “conductors” are introduced to give local plasmonic confinement. Therefore, guided-wave...reconfigurable integrated optoelectronics, electro-optical logic in silicon, silicides for group IV plasmonics, reviews of third-order nonlinear optical

Kinetic manipulation of silicide phase formation in Si nanowire templates.

PubMed

Chen, Yu; Lin, Yung-Chen; Zhong, Xing; Cheng, Hung-Chieh; Duan, Xiangfeng; Huang, Yu

2013-08-14

The phase formation sequence of silicides in two-dimensional (2-D) structures has been well-investigated due to their significance in microelectronics. Applying high-quality silicides as contacts in nanoscale silicon (Si) devices has caught considerable attention recently for their potential in improving and introducing new functions in nanodevices. However, nucleation and diffusion mechanisms are found to be very different in one-dimensional (1-D) nanostructures, and thus the phase manipulation of silicides is yet to be achieved there. In this work, we report kinetic phase modulations to selectively enhance or hinder the growth rates of targeted nickel (Ni) silicides in a Si nanowire (NW) and demonstrate that Ni31Si12, δ-Ni2Si, θ-Ni2Si, NiSi, and NiSi2 can emerge as the first contacting phase at the silicide/Si interface through these modulations. First, the growth rates of silicides are selectively tuned through template structure modifications. It is demonstrated that the growth rate of diffusion limited phases can be enhanced in a porous Si NW due to a short diffusion path, which suppresses the formation of interface limited NiSi2. In addition, we show that a confining thick shell can be applied around the Si NW to hinder the growth of the silicides with large volume expansion during silicidation, including Ni31Si12, δ-Ni2Si, and θ-Ni2Si. Second, a platinum (Pt) interlayer between the Ni source and the Si NW is shown to effectively suppress the formation of the phases with low Pt solubility, including the dominating NiSi2. Lastly, we show that with the combined applications of the above-mentioned approaches, the lowest resistive NiSi phase can form as the first phase in a solid NW with a Pt interlayer to suppress NiSi2 and a thick shell to hinder Ni31Si12, δ-Ni2Si, and θ-Ni2Si simultaneously. The resistivity and maximum current density of NiSi agree reasonably to reported values.

NUCLEAR FUEL MATERIAL

DOEpatents

Goeddel, W.V.

1962-06-26

An improved method is given for making the carbides of nuclear fuel material. The metal of the fuel material, which may be a fissile and/or fertile material, is transformed into a silicide, after which the silicide is comminuted to the desired particle size. This silicide is then carburized at an elevated temperature, either above or below the melting point of the silicide, to produce an intimate mixture of the carbide of the fuel material and the carbide of silicon. This mixture of the fuel material carbide and the silicon carbide is relatively stable in the presence of moisture and does not exhibit the highly reactive surface condition which is observed with fuel material carbides made by most other known methods. (AEC)

Si-Ge Nano-Structured with Tungsten Silicide Inclusions

NASA Technical Reports Server (NTRS)

Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

2014-01-01

Traditional silicon germanium high temperature thermoelectrics have potential for improvements in figure of merit via nano-structuring with a silicide phase. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples are prepared using powder metallurgy techniques; including mechanochemical alloying via ball milling and spark plasma sintering for densification. In addition to microstructural development, thermal stability of thermoelectric transport properties are reported, as well as couple and device level characterization.

Superconductivity of ternary silicide with the AlB(2)-type structure Sr(Ga(0.37),Si(0.63))(2).

PubMed

Imai, M; Abe, E; Ye, J; Nishida, K; Kimura, T; Honma, K; Abe, H; Kitazawa, H

2001-08-13

A ternary silicide Sr(Ga(0.37),Si(0.63))(2) was synthesized by a floating zone method. Electron diffraction and powder x-ray diffraction measurements indicate that the silicide has the AlB(2)-type structure with the lattice constants of a = 4.1427(6) A and c = 4.7998(9) A, where Si and Ga atoms are arranged in a chemically disordered honeycomb lattice and Sr atoms are inercalated between them. The silicide is isostructural with the high-temperature superconductor MgB(2) reported recently. Electrical resistivity and dc magnetization measurements revealed that it is a type-II superconductor with onset temperature of 3.5 K.

IRRADIATION TESTING OF THE RERTR FUEL MINIPLATES WITH BURNABLE ABSORBERS IN THE ADVANCED TEST REACTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

I. Glagolenko; D. Wachs; N. Woolstenhulme

2010-10-01

Based on the results of the reactor physics assessment, conversion of the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL) can be potentially accomplished in two ways, by either using U-10Mo monolithic or U-7Mo dispersion type plates in the ATR fuel element. Both designs, however, would require incorporation of the burnable absorber in several plates of the fuel element to compensate for the excess reactivity and to flatten the radial power profile. Several different types of burnable absorbers were considered initially, but only borated compounds, such as B4C, ZrB2 and Al-B alloys, were selected for testing primarily duemore » to the length of the ATR fuel cycle and fuel manufacturing constraints. To assess and compare irradiation performance of the U-Mo fuels with different burnable absorbers we have designed and manufactured 28 RERTR miniplates (20 fueled and 8 non-fueled) containing fore-mentioned borated compounds. These miniplates will be tested in the ATR as part of the RERTR-13 experiment, which is described in this paper. Detailed plate design, compositions and irradiations conditions are discussed.« less

Process spectroscopy in microemulsions—Raman spectroscopy for online monitoring of a homogeneous hydroformylation process

NASA Astrophysics Data System (ADS)

Paul, Andrea; Meyer, Klas; Ruiken, Jan-Paul; Illner, Markus; Müller, David-Nicolas; Esche, Erik; Wozny, Günther; Westad, Frank; Maiwald, Michael

2017-03-01

A major industrial reaction based on homogeneous catalysis is hydroformylation for the production of aldehydes from alkenes and syngas. Hydroformylation in microemulsions, which is currently under investigation at Technische Universität Berlin on a mini-plant scale, was identified as a cost efficient approach which also enhances product selectivity. Herein, we present the application of online Raman spectroscopy on the reaction of 1-dodecene to 1-tridecanal within a microemulsion. To achieve a good representation of the operation range in the mini-plant with regard to concentrations of the reactants a design of experiments was used. Based on initial Raman spectra partial least squares regression (PLSR) models were calibrated for the prediction of 1-dodecene and 1-tridecanal. Limits of predictions arise from nonlinear correlations between Raman intensity and mass fractions of compounds in the microemulsion system. Furthermore, the prediction power of PLSR models becomes limited due to unexpected by-product formation. Application of the lab-scale derived calibration spectra and PLSR models on online spectra from a mini-plant operation yielded promising estimations of 1-tridecanal and acceptable predictions of 1-dodecene mass fractions suggesting Raman spectroscopy as a suitable technique for process analytics in microemulsions.

Update on mandibular condylar fracture management.

PubMed

Weiss, Joshua P; Sawhney, Raja

2016-08-01

Fractures of the mandibular condyle have provided a lasting source of controversy in the field of facial trauma. Concerns regarding facial nerve injury as well as reasonable functional outcomes with closed management led to a reluctance to treat with an open operative intervention. This article reviews how incorporating new technologies and surgical methods have changed the treatment paradigm. Multiple large studies and meta-analyses continue to demonstrate superior outcomes for condylar fractures when managed surgically. Innovations, including endoscopic techniques, three-dimensional miniplates, and angled drills provide increased options in the treatment of condylar fractures. The literature on pediatric condylar fractures is limited and continues to favor a more conservative approach. There continues to be mounting evidence in radiographic, quality of life, and functional outcome studies to support open reduction with internal fixation for the treatment of condylar fractures in patients with malocclusion, significant displacement, or dislocation of the temporomandibular joint. The utilization of three-dimensional trapezoidal miniplates has shown improved outcomes and theoretically enhanced biomechanical properties when compared with traditional fixation with single or double miniplates. Endoscopic-assisted techniques can decrease surgical morbidity, but are technically challenging, require skilled assistants, and utilize specialized equipment.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction.

PubMed

Hsu, Hsun-Feng; Huang, Wan-Ru; Chen, Ting-Hsuan; Wu, Hwang-Yuan; Chen, Chun-An

2013-05-10

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction

PubMed Central

2013-01-01

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation. PMID:23663726

Methodology, Technical Approach and Measurement Techniques for Testing of TPM Thermal Protection Materials in IPM Plasmatrons

DTIC Science & Technology

2000-04-01

system, 8 - experiments on a study of boundary layer spectrum infrared window). before boiling of glass- silicide coating. This simple 3. SAMPLES AND...dependencies of surface temperature of tested materials and make conclusions concerned joint gllass- silicide coating and anode power of generator...obtained using test stagnation point configuration. glass- silicide coating vs anode power of HF-generator. Temperature peak at constant power

Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

PubMed Central

2013-01-01

Nickel silicide Schottky diodes formed on polycrystalline Si 〈P〉 films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22℃ to 70℃; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%℃ to 0.6%/℃ for forward bias and around 2.5%/℃ for reverse bias of the diodes. PMID:23594606

Nanopatterning of metal-coated silicon surfaces via ion beam irradiation: Real time x-ray studies reveal the effect of silicide bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Atwani, Osman; Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907; Gonderman, Sean

We investigated the effect of silicide formation on ion-induced nanopatterning of silicon with various ultrathin metal coatings. Silicon substrates coated with 10 nm Ni, Fe, and Cu were irradiated with 200 eV argon ions at normal incidence. Real time grazing incidence small angle x-ray scattering (GISAXS) and x-ray fluorescence (XRF) were performed during the irradiation process and real time measurements revealed threshold conditions for nanopatterning of silicon at normal incidence irradiation. Three main stages of the nanopatterning process were identified. The real time GISAXS intensity of the correlated peaks in conjunction with XRF revealed that the nanostructures remain for amore » time period after the removal of the all the metal atoms from the sample depending on the binding energy of the metal silicides formed. Ex-situ XPS confirmed the removal of all metal impurities. In-situ XPS during the irradiation of Ni, Fe, and Cu coated silicon substrates at normal incidence demonstrated phase separation and the formation of different silicide phases that occur upon metal-silicon mixing. Silicide formation leads to nanostructure formation due the preferential erosion of the non-silicide regions and the weakening of the ion induced mass redistribution.« less

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sridharan, Kumar; Mariani, Robert; Bai, Xianming

Zirconium-alloy fuel claddings have been used successfully in Light Water Reactors (LWR) for over four decades. However, under high temperature accident conditions, zirconium-alloys fuel claddings exhibit profuse exothermic oxidation accompanied by release of hydrogen gas due to the reaction with water/steam. Additionally, the ZrO 2 layer can undergo monoclinic to tetragonal to cubic phase transformations at high temperatures which can induce stresses and cracking. These events were unfortunately borne out in the Fukushima-Daiichi accident in in Japan in 2011. In reaction to such accident, protective oxidation-resistant coatings for zirconium-alloy fuel claddings has been extensively investigated to enhance safety margins inmore » accidents as well as fuel performance under normal operation conditions. Such surface modification could also beneficially affect fuel rod heat transfer characteristics. Zirconium-silicide, a candidate coating material, is particularly attractive because zirconium-silicide coating is expected to bond strongly to zirconium-alloy substrate. Intermetallic compound phases of zirconium-silicide have high melting points and oxidation of zirconium silicide produces highly corrosion resistant glassy zircon (ZrSiO 4) and silica (SiO 2) which possessing self-healing qualities. Given the long-term goal of developing such coatings for use with nuclear reactor fuel cladding, this work describes results of oxidation and corrosion behavior of bulk zirconium-silicide and fabrication of zirconium-silicide coatings on zirconium-alloy test flats, tube configurations, and SiC test flats. In addition, boiling heat transfer of these modified surfaces (including ZrSi 2 coating) during clad quenching experiments is discussed in detail.« less

Oxygen chemisorption and oxide formation on Ni silicide surfaces at room temperature

NASA Astrophysics Data System (ADS)

Valeri, S.; Del Pennino, U.; Lomellini, P.; Sassaroli, P.

1984-10-01

Auger spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) have been used in a comparative study of the room temperature oxidation of Ni silicides of increasing silicon content, from Ni3Si to NiSi2. The results were compared with those for the oxidation of pure Si and Ni. All suicide surfaces in the exposure range between 0.2 and 104 L follow two-step oxidation kinetics: the first step is characterized by an oxygen uptake rate higher than in the second one. Attention was focused on the oxygen induced modifications of metal and silicon AES and XPS spectra in silicides, which are indicative of changes in the local electronic structure and in the chemical bonding. In general oxygen bonds with silicon leaving the metal unaffected; however, at high exposures, characteristic feature of the Ni-oxygen bonds appear in the Ni(MVV) Auger line of the Ni-rich silicides. The presence of Ni atoms enhances considerably the Si oxidation process in silicides with respect to pure Si, in terms both of a higher Si oxidation state and a higher oxygen uptake; this enhancement is stronger in Ni-rich silicides than in Si-rich silicides. The oxygen induced contributions in the Si(LVV) Auger line show structures at 76 and 83 eV, and those in the Si 2p photoemission spectra show binding energy shifts between -1 and -3.8 eV; we conclude that the oxidation products are mainly silicon suboxides, like Si2O3 and SiO; only on Ni3 Si at 104 L, a significant contribution of SiO2 was found. The Ni catalytic effect on Si oxidation has been discussed in terms of the suicide heat of formation, of the breaking of the silicon sp3 configuration in silicides and of the metal atom dissociative effect on the O2 molecule.

Solidification Based Grain Refinement in Steels

DTIC Science & Technology

2010-07-20

methods which worked in the SVSU foundry. However, additions of NbO powder, FeTi, misch metal , and rare earth silicide were successful. Misch metal ...and rare earth silicide additions at the ladle are the most promising from an industrial stand point. The project group has begun preparing for the... metal and rare earth silicide additions have also reduced grain size and improved hardness. Instructions: You may use this MS Word file to submit the

Self-organized patterns along sidewalls of iron silicide nanowires on Si(110) and their origin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Debolina; Mahato, J. C.; Bisi, Bhaskar

Iron silicide (cubic FeSi{sub 2}) nanowires have been grown on Si(110) by reactive deposition epitaxy and investigated by scanning tunneling microscopy and scanning/transmission electron microscopy. On an otherwise uniform nanowire, a semi-periodic pattern along the edges of FeSi{sub 2} nanowires has been discovered. The origin of such growth patterns has been traced to initial growth of silicide nanodots with a pyramidal Si base at the chevron-like atomic arrangement of a clean reconstructed Si(110) surface. The pyramidal base evolves into a comb-like structure along the edges of the nanowires. This causes the semi-periodic structure of the iron silicide nanowires along theirmore » edges.« less

Controlled Formation of Radial Core-Shell Si/Metal Silicide Crystalline Heterostructures.

PubMed

Kosloff, Alon; Granot, Eran; Barkay, Zahava; Patolsky, Fernando

2018-01-10

The highly controlled formation of "radial" silicon/NiSi  core-shell nanowire heterostructures has been demonstrated for the first time. Here, we investigated the "radial" diffusion of nickel atoms into crystalline nanoscale silicon pillar 11 cores, followed by nickel silicide phase formation and the creation of a well-defined shell structure. The described approach is based on a two-step thermal process, which involves metal diffusion at low temperatures in the range of 200-400 °C, followed by a thermal curing step at a higher temperature of 400 °C. In-depth crystallographic analysis was performed by nanosectioning the resulting silicide-shelled silicon nanopillar heterostructures, giving us the ability to study in detail the newly formed silicide shells. Remarkably, it was observed that the resulting silicide shell thickness has a self-limiting behavior, and can be tightly controlled by the modulation of the initial diffusion-step temperature. In addition, electrical measurements of the core-shell structures revealed that the resulting shells can serve as an embedded conductive layer in future optoelectronic applications. This research provides a broad insight into the Ni silicide "radial" diffusion process at the nanoscale regime, and offers a simple approach to form thickness-controlled metal silicide shells in the range of 5-100 nm around semiconductor nanowire core structures, regardless the diameter of the nanowire cores. These high quality Si/NiSi core-shell nanowire structures will be applied in the near future as building blocks for the creation of utrathin highly conductive optically transparent top electrodes, over vertical nanopillars-based solar cell devices, which may subsequently lead to significant performance improvements of these devices in terms of charge collection and reduced recombination.

Impurity effects in transition metal silicides

NASA Technical Reports Server (NTRS)

Lien, C.-D.; Nicolet, M.-A.

1984-01-01

Impurities can affect the properties of silicides directly by virtue of their presence. Impurities can also influence the processes by which silicides are formed. The effect of impurities on the reaction of transition metal films with a silicon substrate induced by thermal annealing are well documented. The interpretation of these results is discussed. It is shown that impurity redistribution is a major factor in determining how significant the effect of an impurity is. Redistribution observed for dopant impurities is also discussed.

Transmission electron microscopy characterization of the erbium silicide formation process using a Pt/Er stack on a silicon-on-insulator substrate.

PubMed

Łaszcz, A; Katcki, J; Ratajczak, J; Tang, Xiaohui; Dubois, E

2006-10-01

Very thin erbium silicide layers have been used as source and drain contacts to n-type Si in low Schottky barrier MOSFETs on silicon-on-insulator substrates. Erbium silicide is formed by a solid-state reaction between the metal and silicon during annealing. The influence of annealing temperature (450 degrees C, 525 degrees C and 600 degrees C) on the formation of an erbium silicide layer in the Pt/Er/Si/SiO(2)/Si structure was analysed by means of cross-sectional transmission electron microscopy. The Si grains/interlayer formed at the interface and the presence of Si grains within the Er-related layer constitute proof that Si reacts with Er in the presence of a Pt top layer in the temperature range 450-600 degrees C. The process of silicide formation in the Pt/Er/Si structure differs from that in the Er/Si structure. At 600 degrees C, the Pt top layer vanishes and a (Pt-Er)Si(x) system is formed.

Probing Transition-Metal Silicides as PGM-Free Catalysts for Hydrogen Oxidation and Evolution in Acidic Medium

PubMed Central

Mittermeier, Thomas; Madkikar, Pankaj; Wang, Xiaodong; Gasteiger, Hubert A.; Piana, Michele

2017-01-01

In this experimental study, we investigate various transition-metal silicides as platinum-group-metal-(PGM)-free electrocatalysts for the hydrogen oxidation reaction (HOR), and for the hydrogen evolution reaction (HER) in acidic environment for the first time. Using cyclic voltammetry in 0.1 M HClO4, we first demonstrate that the tested materials exhibit sufficient stability against dissolution in the relevant potential window. Further, we determine the HOR and HER activities for Mo, W, Ta, Ni and Mo-Ni silicides in rotating disk electrode experiments. In conclusion, for the HOR only Ni2Si shows limited activity, and the HER activity of the investigated silicides is considerably lower compared to other PGM-free HER catalysts reported in the literature. PMID:28773022

Phase transformations in ion-irradiated silicides

NASA Technical Reports Server (NTRS)

Hewett, C. A.; Lau, S. S.; Suni, I.; Hung, L. S.

1985-01-01

The present investigation has three objectives. The first is concerned with the phase transformation of CoSi2 under ion implantation and the subsequent crystallization characteristics during annealing, taking into account epitaxial and nonepitaxial recrystallization behavior. The second objective is related to a study of the general trend of implantation-induced damage and crystallization behavior for a number of commonly used silicides. The last objective involves a comparison of the recrystallization behavior of cosputtered refractory silicides with that of the ion-implanted silicides. It was found that epitaxial regrowth of ion-irradiated CoSi2 occurred for samples with an epitaxial seed left at the Si/CoSi2 interface. A structural investigation of CoSi2 involving transmission electron microscopy (TEM) showed that after high-dose implantation CoSi2 is amorphous.

Interdiffusion behavior of U3Si2 with FeCrAl via diffusion couple studies

NASA Astrophysics Data System (ADS)

Hoggan, Rita E.; He, Lingfeng; Harp, Jason M.

2018-04-01

Uranium silicide (U3Si2) is a candidate to replace uranium oxide (UO2) as light water reactor (LWR) fuel because of its higher thermal conductivity and higher fissile density relative to the current standard, UO2. A class of Fe, Cr, Al alloys collectively known as FeCrAl alloys that have superior mechanical and oxidation resistance are being considered as an alternative to the standard Zirconium based LWR cladding. The interdiffusion behavior between FeCrAl and U3Si2 is investigated in this study. Commercially available FeCrAl, along with U3Si2 pellets were placed in diffusion couples. Individual tests were ran at temperatures ranging from 500 °C to 1000 °C for 30 h and 100 h. The interdiffusion was analyzed with an optical microscope, scanning electron microscope, and transmission electron microscope. Uniform and planar interdiffusion layers along the material interface were illustrated with backscatter electron micrographs and energy-dispersive X-ray spectroscopy. Electron diffraction was used to validate phases present in the system, including distinct U2Fe3Si/UFe2 and UFeSi layers at the material interface. U and Fe diffused far into the FeCrAl and U3Si2 matrix, respectively, in the higher temperature tests. No interaction was observed at 500 °C for 30 h.

CNEA/ANL collaboration program to develop an optimized version of DART validation and assessment by means of U{sub 3}Si{sub x} and U{sub 3}O{sub 8-}Al dispersed CNEA miniplate irradiation behavior.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solis, D.

1998-10-16

The DART code is based upon a thermomechanical model that can predict swelling, recrystallization, fuel-meat interdiffusion and other issues related with MTR dispersed FE behavior under irradiation. As a part of a common effort to develop an optimized version of DART, a comparison between DART predictions and CNEA miniplates irradiation experimental data was made. The irradiation took place during 1981-82 for U3O8 miniplates and 1985-86 for U{sub 3}Si{sub x} at Oak Ridge Research Reactor (ORR). The microphotographs were studied by means of IMAWIN 3.0 Image Analysis Code and different fission gas bubbles distributions were obtained. Also it was possible tomore » find and identify different morphologic zones. In both kinds of fuels, different phases were recognized, like particle peripheral zones with evidence of Al-U reaction, internal recrystallized zones and bubbles. A very good agreement between code prediction and irradiation results was found. The few discrepancies are due to local, fabrication and irradiation uncertainties, as the presence of U{sub 3}Si phase in U{sub 3}Si{sub 2} particles and effective burnup.« less

Bone condition of the maxillary zygomatic process prior to orthodontic anchorage plate fixation.

PubMed

Präger, T M; Brochhagen, H G; Mischkowski, R; Jost-Brinkmann, P G; Müller-Hartwich, R

2015-01-01

The clinical success of orthodontic miniplates depends on the stability of the miniscrews used for fixation. For good stability, it is essential that the application site provides enough bone of good quality. This study was performed to analyze the amount of bone available for orthodontic miniplates in the zygomatic process of the maxilla. We examined 51 dental CT scans (Somatom Plus 4; Siemens, Erlangen, Germany) obtained from 51 fully dentate adult patients (mean age 24.0 ± 8.1 years; 27 male and 24 female) prior to third molar surgery. The amount of bone in the zygomatic process region at the level of the first molar root tips and at several other cranial levels as far as 15 mm from the root tips was measured Bone thickness at the root tip level averaged 4.1 ± 1.0 mm; the lowest value measured at this level in any of the patients was 2.7 mm. Bone thickness averaged 8.3 ± 1.0 mm at 15 mm cranial to the root tips; 6.9 mm was the lowest value. The zygomatic process appears to provide sufficient bone to accommodate screws for miniplate fixation. While some patients may possess a borderline amount of bone at more caudal levels, lack of volume is not a problem near the zygomatic bone.

A new palatal distractor device for bodily movement of maxillary bones by rigid self-locking miniplates and screws system.

PubMed

Cortese, Antonio; Savastano, Mauro; Cantone, Antonio; Claudio, Pier Paolo

2013-07-01

A new palatal distractor device for bodily movement of the maxillary bones after complete segmented Le Fort I osteotomy for 1-stage transversal distraction and tridimensional repositioning on 1 patient is presented. The new distractor has an intrinsic tridimensional rigidity also in the fixation system by self-locking miniplates and screws for better control of the 2 maxillary fragments during distraction. Le Fort I distraction and repositioning procedure in association with a bilateral sagittal split osteotomy were performed on 1 patient with complete solution of the cross-bite and class III malocclusion. Results of dental and cephalometric analysis performed before surgery (T1), after surgery and distraction time (T2), and 18 months after surgery and orthodontic appliance removal (T3) are reported. No complications were encountered using the new distractor device. Advantages of this device and technique are presented including improved rigidity of both distraction (jackscrew) and fixation (4 self-locking miniplates and screws) systems resulting in complete control of the position of the 2 maxillary fragments during distraction and surgery. In addition, this new device allows resuming palatal distraction in the event of cross-bite relapse without causing dental-related problems or the risks of screw slackening.

Determination of the Tribological Fundamentals of Solid Lubricated Ceramics. Volume 3. Appendices P through II

DTIC Science & Technology

1991-09-01

9H and tungsten silicides may also be present in the microstructure. The non-SiC eiemental concentrations for NC-203 would not be expected to exceed...lesser amounts of yttrium silicate and tungsten silicide . Trace amounts of a-Si 3N4 , silicon oxynitride, tungsten-iron- silicide , and yttrium silicon...SiC ESK On this sample, we detect Silicon, Carbon, and also Oxygen and Nitrogen, as well as Calcium and Sodium traces. After ionic etching up to about

Titanium disilicide formation by sputtering of titanium on heated silicon substrate

NASA Astrophysics Data System (ADS)

Tanielian, M.; Blackstone, S.

1984-09-01

We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated

Solidification Based Grain Refinement in Steels

DTIC Science & Technology

2011-09-27

project (Tasks 7-9). An industrial trial on an investment casting was done using rare earth silicide additions in a furnace prior to pouring (Task 7...an investment casting was done using rare earth silicide additions in a furnace prior to pounng (la.sk 7). Some of the test parts had a finer...poured at the end of a six casting batch. One test tree with no RE addition was poured. Before the second test tree was poured, sufficient RE silicide was

Surface morphology of molybdenum silicide films upon low-energy ion beam sputtering.

PubMed

Gago, R; Jaafar, M; Palomares, F J

2018-07-04

The surface morphology of molybdenum silicide (Mo x Si 1-x ) films has been studied after low-energy Ar + ion beam sputtering (IBS) to explore eventual pattern formation on compound targets and, simultaneously, gather information about the mechanisms behind silicide-assisted nanopatterning of silicon surfaces by IBS. For this purpose, Mo x Si 1-x films with compositions below, equal and above the MoSi 2 stoichiometry (x  =  0.33) have been produced by magnetron sputtering, as assessed by Rutherford backscattering spectrometry (RBS). The surface morphology of silicon and silicide films before and after IBS has been imaged by atomic force microscopy (AFM), comprising conditions where typical nanodot or ripple patterns emerge on the former. In the case of irradiated Mo x Si 1-x surfaces, AFM shows a marked surface smoothing at normal incidence with and without additional Mo incorporation (the former results in nanodot patterns on Si). The morphological analysis also provides no evidence of ion-induced phase separation in irradiated Mo x Si 1-x . Contrary to silicon, Mo x Si 1-x surfaces also do not display ripple formation for (impurity free) oblique irradiations, except at grazing incidence conditions where parallel ripples emerge in a more evident fashion than in the Si counterpart. By means of RBS, irradiated Mo x Si 1-x films with 1 keV Ar + at normal incidence have also been used to measure experimentally the (absolute) sputtering yield and rate of Si and Mo x Si 1-x materials. The analysis reveals that, under the present working conditions, the erosion rate of silicides is larger than for silicon, supporting simulations from the TRIDYN code. This finding questions the shielding effect from silicide regions as roughening mechanism in metal-assisted nanopatterning of silicon. On the contrary, the results highlight the relevance of in situ silicide formation. Ripple formation on Mo x Si 1-x under grazing incidence is also attributed to the dominance of sputtering effects under this geometry. In conclusion, our work provides some insights into the complex morphological evolution of compound surfaces and solid experimental evidences regarding the mechanisms behind silicide-assisted nanopatterning.

Silicide/Silicon Heterointerfaces, Reaction Kinetics and Ultra-short Channel Devices

NASA Astrophysics Data System (ADS)

Tang, Wei

Nickel silicide is one of the electrical contact materials widely used on very large scale integration (VLSI) of Si devices in microelectronic industry. This is because the silicide/silicon interface can be formed in a highly controlled manner to ensure reproducibility of optimal structural and electrical properties of the metal-Si contacts. These advantages can be inherited to Si nanowire (NW) field-effect transistors (FET) device. Due to the technological importance of nickel silicides, fundamental materials science of nickel silicides formation (Ni-Si reaction), especially in nanoscale, has raised wide interest and stimulate new insights and understandings. In this dissertation, in-situ transmission electron microscopy (TEM) in combination with FET device characterization will be demonstrated as useful tools in nano-device fabrication as well as in gaining insights into the process of nickel silicide formation. The shortest transistor channel length (17 nm) fabricated on a vapor-liquid-solid (VLS) grown silicon nanowire (NW) has been demonstrated by controlled reaction with Ni leads on an in-situ transmission electron microscope (TEM) heating stage at a moderate temperature of 400 ºC. NiSi2 is the leading phase, and the silicide-silicon interface is an atomically sharp type-A interface. At such channel lengths, high maximum on-currents of 890 (microA/microm) and a maximum transconductance of 430 (microS/microm) were obtained, which pushes forward the performance of bottom-up Si NW Schottky barrier field-effect transistors (SB-FETs). Through accurate control over the silicidation reaction, we provide a systematic study of channel length dependent carrier transport in a large number of SB-FETs with channel lengths in the range of (17 nm -- 3.6 microm). Our device results corroborate with our transport simulations and reveal a characteristic type of short channel effects in SB-FETs, both in on- and off-state, which is different from that in conventional MOSFETs, and that limits transport parameter extraction from SB-FETs using the conventional field-effect transconductance measurements. In addition to application of silicide in Si NW devices, the fundamental materials science of Ni-Si reaction is also of interest, and in-situ TEM has been shown to be a useful tool in obtaining dynamical phase transformation information and therefore providing insights into the new phase formation process. By using in-situ TEM techniques, a new gold catalyzed solid-liquid-solid (SLS) silicide phase growth mechanism in Si NWs is observed for the first time, which shows the liquid mediating growth can be also used in synthesis of metallic silicide nanowires. SLS is analogous to the VLS in both being liquid-mediated, but is fundamentally different in terms of nucleation and mass transport. In our SLS growth at 700 ºC, the Ni atoms are supplied from remote Ni particles by interstitial diffusion through Si NW into the pre-existing Au particle at the tip. Upon supersaturation of both Ni and Si in Au, octahedral shape of Ni disilicide phase nucleates in the middle of the Au liquid alloy, which thereafter sweeps through the Si NW and transform Si into NiSi2. Dissolution of Si by Au(Si,Ni) liquid mediating layer and growth of NiSi2 are shown to proceed in different manners. Using in-situ TEM technique, we also have the chance to present direct evidence that Si (111) twin boundaries and Si grain boundaries on Si NW surface can be efficient heterogeneous nucleation site for the silicide growth. By analyzing the nucleation site favorability, unlike other typical FCC materials like Cu or Si, we infer (111) twin defects in NiSi2 may have high interfacial energy. These results may provide valuable insights into the MOSFET source/drain (S/D) contact silicide formation process when defects are either unintentionally formed during the process or intentionally introduced to engineering the strain along the channel.

Comparison of strains produced by titanium and poly D, L-lactide Acid plating systems to in vitro forces.

PubMed

Chacon, Guillermo E; Dillard, Frederick Matt; Clelland, Nancy; Rashid, Robert

2005-07-01

To determine if a specific resorbable plating system provides similar fixation, in terms of strain distribution under load, to a titanium system when the Champy technique is applied for the treatment of a mandibular angle fracture. A formalin-fixed cadaver mandible was harvested just before the study. A bicortical osteotomy was then made using a diamond disc extending in an oblique direction in the area of the angle. It was then passively fixated with a 4-hole 2.0-mm miniplate. Two stacked rosette strain gauges were bonded to the mandible on either side of the fracture. Each rosette had 3 strain gauges arranged in specific degrees relative to each other. The mandible was then placed on a dynanometer and 30 lb loads were delivered on the ipsilateral molar. Static resistance was placed in the condylar neck region to simulate the glenoid fossa. Loading was repeated 10 times with a period of 3 minutes between loads. Measurements were recorded for each strain gauge after loads were in place for 30 seconds. The same process was repeated using a 4-hole 2.1-mm resorbable miniplate. The strains were then used to calculate the maximum and minimum strains for each rosette. Hooke's law was used to calculate the principal stresses. Differences were observed between the strain gauges for each individual plating system. There was variability within the resorbable plate measurements as shown by the standard deviation. Using the REML ANOVA test, a significant difference was found between the 2 materials. In this in vitro study, there were significant biomechanical differences observed between a 2.0-mm titanium miniplate and a 2.1-mm resorbable miniplate when used to treat a mandibular angle fracture following Champy's principles. Based on our finding, both systems cannot be used interchangeably for the treatment of mandibular angle fractures under the same clinical conditions.

Fundamentals of Intrinsic Stress during Silicide Formation

NASA Astrophysics Data System (ADS)

Özçelik, A.; van Bockstael, C.; Detavernier, C.; Vanmeirhaeghe, R.

2007-04-01

Silicides are a very useful group of materials which can be used to make electrical contacts to circuits in electronic devices with an extremely high performance. The stress in thin films is an increasingly important technological issue from the standpoint of reliability and performance in IC processing. Manufacturers of micro electronic devices have to control the stress levels in the contact films to avoid device failures. Phase transitions such as silicidation or even a simple rearrangement of atoms like relaxation in the metal film cause a difference in the volume of the film from its starting value. This volume change produces stress inside the film. In this work we analyzed the stress evolution during the silicidation reaction of some metals such as W and Mo by using a home built in situ stress system at the University of Ghent.

Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Escobedo-Cousin, Enrique; Vassilevski, Konstantin; Hopf, Toby

Patterned few-layer graphene (FLG) films were obtained by local solid phase growth from nickel silicide supersaturated with carbon, following a fabrication scheme, which allows the formation of self-aligned ohmic contacts on FLG and is compatible with conventional SiC device processing methods. The process was realised by the deposition and patterning of thin Ni films on semi-insulating 6H-SiC wafers followed by annealing and the selective removal of the resulting nickel silicide by wet chemistry. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to confirm both the formation and subsequent removal of nickel silicide. The impact of process parameters such asmore » the thickness of the initial Ni layer, annealing temperature, and cooling rates on the FLG films was assessed by Raman spectroscopy, XPS, and atomic force microscopy. The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 4 monolayers for initial Ni layers between 3 and 20 nm thick. Self-aligned contacts were formed on these patterned films by contact photolithography and wet etching of nickel silicide, which enabled the fabrication of test structures to measure the carrier concentration and mobility in the FLG films. A simple model of diffusion-driven solid phase chemical reaction was used to explain formation of the FLG film at the interface between nickel silicide and silicon carbide.« less

Study of Silicidation Process of Tungsten Catalyzer during Silicon Film Deposition in Catalytic Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Honda, Kazuhiro; Ohdaira, Keisuke; Matsumura, Hideki

2008-05-01

In catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD, source gases are decomposed by catalytic cracking reactions with heated catalyzing metal wires. In the case of silicon (Si) film deposition, such metal wires are often converted to silicide, which shortens the lifetime of catalyzing wires. As a catalyzer, tungsten (W) is widely used. Thus, the process of silicidation of a W catalyzer at temperatures over 1650 °C, which is the temperature used in Cat-CVD for Si film deposition, was studied extensively in various experiments. It is found that two phases of tungsten-silicide, WSi2 and W5Si3, are formed at this temperature, and that the radiation emissivity of WSi2 is 1.2 to 1.7 times higher than that of W5Si3 and pure W. The increase of surface emissivity due to the formation of WSi2 decreases the catalyzer surface temperature which induces further growth of the tungsten-silicide layer. It is also found that the suppression of WSi2 formation by elevating catalyzer temperatures over 1750 °C is a key to extending the lifetime of the W catalyzer in Cat-CVD.

Cobalt silicide nanocables grown on Co films: synthesis and physical properties.

PubMed

Hsin, Cheng-Lun; Yu, Shih-Ying; Wu, Wen-Wei

2010-12-03

Single-crystalline cobalt silicide/SiO(x) nanocables have been grown on Co thin films on an SiO(2) layer by a self-catalysis process via vapor-liquid-solid mechanism. The nanocables consist of a core of CoSi nanowires and a silicon oxide shell with a length of several tens of micrometers. In the confined space in the oxide shell, the CoSi phase is stable and free from agglomeration in samples annealed in air ambient at 900 °C for 1 h. The nanocable structure came to a clear conclusion that the thermal stability of the silicide nanowires can be resolved by the shell encapsulation. Cobalt silicide nanowires were obtained from the nanocable structure. The electrical properties of the CoSi nanowires have been found to be compatible with their thin film counterpart and a high maximum current density of the nanowires has been measured. One way to obtain silicate nanowires has been demonstrated. The silicate compound, which is composed of cobalt, silicon and oxygen, was achieved. The Co silicide/oxide nanocables are potentially useful as a key component of silicate nanowires, interconnects and magnetic units in nanoelectronics.

Two-dimensional self-organization of an ordered Au silicide nanowire network on a Si(110)-16 x 2 surface.

PubMed

Hong, Ie-Hong; Yen, Shang-Chieh; Lin, Fu-Shiang

2009-08-17

A well-ordered two-dimensional (2D) network consisting of two crossed Au silicide nanowire (NW) arrays is self-organized on a Si(110)-16 x 2 surface by the direct-current heating of approximately 1.5 monolayers of Au on the surface at 1100 K. Such a highly regular crossbar nanomesh exhibits both a perfect long-range spatial order and a high integration density over a mesoscopic area, and these two self-ordering crossed arrays of parallel-aligned NWs have distinctly different sizes and conductivities. NWs are fabricated with widths and pitches as small as approximately 2 and approximately 5 nm, respectively. The difference in the conductivities of two crossed-NW arrays opens up the possibility for their utilization in nanodevices of crossbar architecture. Scanning tunneling microscopy/spectroscopy studies show that the 2D self-organization of this perfect Au silicide nanomesh can be achieved through two different directional electromigrations of Au silicide NWs along different orientations of two nonorthogonal 16 x 2 domains, which are driven by the electrical field of direct-current heating. Prospects for this Au silicide nanomesh are also discussed.

Chromium silicide formation by ion mixing

NASA Technical Reports Server (NTRS)

Shreter, U.; So, F. C. T.; Nicolet, M.-A.

1984-01-01

The formation of CrSi2 by ion mixing was studied as a function of temperature, silicide thickness and irradiated interface. Samples were prepared by annealing evaporated couples of Cr on Si and Si on Cr at 450 C for short times to form Si/CrSi2/Cr sandwiches. Xenon beams with energies up to 300 keV and fluences up to 8 x 10 to the 15th per sq cm were used for mixing at temperatures between 20 and 300 C. Penetrating only the Cr/CrSi2 interface at temperatures above 150 C induces further growth of the silicide as a uniform stoichiometric layer. The growth rate does not depend on the thickness of the initially formed silicide at least up to a thickness of 150 nm. The amount of growth depends linearly on the density of energy deposited at the interface. The growth is temperature dependent with an apparent activation energy of 0.2 eV. Irradiating only through the Si/CrSi2 interface does not induce silicide growth. It is concluded that the formation of CrSi2 by ion beam mixing is an interface-limited process and that the limiting reaction occurs at the Cr/CrSi2 interface.

Unsuccessful Treatment of Atrophic Mandible Fracture by Use of Improper Materials.

PubMed

de Moraes Ferreira, Ana Carulina Rezende; Garcia Junior, Idelmo Rangel; Silva, Adalberto Novaes; de Carvalho Reis, Erik Neiva Ribeiro; Pires, Willian Ricardo; Bonardi, João Paulo; Borba, Alexandre Meireles

2016-06-01

Fractures of atrophic mandibles are present on the day by day of buccomaxillofacial surgeons. Mandible atrophy occurs due to tooth loss, which over time induces bone resorption leading to a fragile and susceptible to fracture structure. This paper reports the case of a patient victim of face trauma resulting in atrophic mandible fracture with treatment failure through the use of shared load miniplate. Therefore, a new treatment was performed with miniplate of system 2.4 along with bone graft. After 6 months, the patient was rehabilitated with implant-supported prosthesis installation. It is concluded that for successful treatment of atrophic mandible fractures, the use of rigid plates is necessary, allowing an excellent rehabilitation of the stomatognathic system.

Energetic Materials Laboratory

DTIC Science & Technology

2015-04-30

regolith simulants mixed with magnesium, supported by NASA. It has also been used for studies on combustion synthesis of magnesium silicide , a...ammonium dinitramide based monopropellant.  The laser flash apparatus has been used for thermal diffusivities measurements for magnesium silicide and

Ensuring the Consistency of Silicide Coatings

NASA Technical Reports Server (NTRS)

Ramani, V.; Lampson, F. K.

1982-01-01

Diagram specifies optimum fusing time for given thicknesses of refractory metal-silicide coatings on columbium C-103 substrates. Adherence to indicated fusion times ensures consistent coatings and avoids underdiffusion and overdiffusion. Accuracy of diagram has been confirmed by tests.

Room temperature ferromagnetic gadolinium silicide nanoparticles

DOEpatents

Hadimani, Magundappa Ravi L.; Gupta, Shalabh; Harstad, Shane; Pecharsky, Vitalij; Jiles, David C.

2018-03-06

A particle usable as T₁ and T₂ contrast agents is provided. The particle is a gadolinium silicide (Gd₅Si₄) particle that is ferromagnetic at temperatures up to 290 K and is less than 2 .mu.m in diameter. An MRI contrast agent that includes a plurality of gadolinium silicide (Gd.sub.5Si.sub.4) particles that are less than 1 .mu.m in diameter is also provided. A method for creating gadolinium silicide (Gd₅Si₄) particles is also provided. The method includes the steps of providing a Gd₅Si₄ bulk alloy; grinding the Gd₅Si₄ bulk alloy into a powder; and milling the Gd₅Si₄ bulk alloy powder for a time of approximately 20 minutes or less.

Silicide formation process of Er films with Ta and TaN capping layers.

PubMed

Choi, Juyun; Choi, Seongheum; Kim, Jungwoo; Na, Sekwon; Lee, Hoo-Jeong; Lee, Seok-Hee; Kim, Hyoungsub

2013-12-11

The phase development and defect formation during the silicidation reaction of sputter-deposited Er films on Si with ∼20-nm-thick Ta and TaN capping layers were examined. TaN capping effectively prevented the oxygen incorporation from the annealing atmosphere, which resulted in complete conversion to the ErSi2-x phase. However, significant oxygen penetration through the Ta capping layer inhibited the ErSi2-x formation, and incurred the growth of several Er-Si-O phases, even consuming the ErSi2-x layer formed earlier. Both samples produced a number of small recessed defects at an early silicidation stage. However, large rectangular or square-shaped surface defects, which were either pitlike or pyramidal depending on the capping layer identity, were developed as the annealing temperature increased. The origin of different defect generation mechanisms was suggested based on the capping layer-dependent silicidation kinetics.

Surface morphology of molybdenum silicide films upon low-energy ion beam sputtering

NASA Astrophysics Data System (ADS)

Gago, R.; Jaafar, M.; Palomares, F. J.

2018-07-01

The surface morphology of molybdenum silicide (Mo x Si1‑x ) films has been studied after low-energy Ar+ ion beam sputtering (IBS) to explore eventual pattern formation on compound targets and, simultaneously, gather information about the mechanisms behind silicide-assisted nanopatterning of silicon surfaces by IBS. For this purpose, Mo x Si1‑x films with compositions below, equal and above the MoSi2 stoichiometry (x  =  0.33) have been produced by magnetron sputtering, as assessed by Rutherford backscattering spectrometry (RBS). The surface morphology of silicon and silicide films before and after IBS has been imaged by atomic force microscopy (AFM), comprising conditions where typical nanodot or ripple patterns emerge on the former. In the case of irradiated Mo x Si1‑x surfaces, AFM shows a marked surface smoothing at normal incidence with and without additional Mo incorporation (the former results in nanodot patterns on Si). The morphological analysis also provides no evidence of ion-induced phase separation in irradiated Mo x Si1‑x . Contrary to silicon, Mo x Si1‑x surfaces also do not display ripple formation for (impurity free) oblique irradiations, except at grazing incidence conditions where parallel ripples emerge in a more evident fashion than in the Si counterpart. By means of RBS, irradiated Mo x Si1‑x films with 1 keV Ar+ at normal incidence have also been used to measure experimentally the (absolute) sputtering yield and rate of Si and Mo x Si1‑x materials. The analysis reveals that, under the present working conditions, the erosion rate of silicides is larger than for silicon, supporting simulations from the TRIDYN code. This finding questions the shielding effect from silicide regions as roughening mechanism in metal-assisted nanopatterning of silicon. On the contrary, the results highlight the relevance of in situ silicide formation. Ripple formation on Mo x Si1‑x under grazing incidence is also attributed to the dominance of sputtering effects under this geometry. In conclusion, our work provides some insights into the complex morphological evolution of compound surfaces and solid experimental evidences regarding the mechanisms behind silicide-assisted nanopatterning.

Screw-Wire Osteo-Traction: An Adjunctive or Alternative Method of Anatomical Reduction of Multisegment Midfacial Fractures? A Description of Technique and Prospective Study of 40 Patients

PubMed Central

O'Regan, Barry; Devine, Maria; Bhopal, Sats

2013-01-01

Stable anatomical fracture reduction and segment control before miniplate fixation can be difficult to achieve in comminuted midfacial fractures. Fracture mobilization and reduction methods include Gillies elevation, malar hook, and Dingman elevators. No single method is used universally. Disadvantages include imprecise segment alignment and poor segment stability/control. We have employed screw-wire osteo-traction (SWOT) to address this problem. A literature review revealed two published reports. The aims were to evaluate the SWOT technique effectiveness as a fracture reduction method and to examine rates of revision fixation and plate removal. We recruited 40 consecutive patients requiring open reduction and internal fixation of multisegment midfacial fractures (2009–2012) and employed miniplate osteosynthesis in all patients. SWOT was used as a default reduction method in all patients. The rates of successful fracture reduction achieved by SWOT alone or in combination and of revision fixation and plate removal, were used as outcome indices of the reduction method effectiveness. The SWOT technique achieved satisfactory anatomical reduction in 27/40 patients when used alone. Other reduction methods were also used in 13/40 patients. No patient required revision fixation and three patients required late plate removal. SWOT can be used across the midface fracture pattern in conjunction with other methods or as a sole reduction method before miniplate fixation. PMID:24436763

Maxillary distraction osteogenesis in cleft lip and palate patients with skeletal anchorage.

PubMed

Minami, Katsuhiro; Mori, Yoshihide; Tae-Geon, Kwon; Shimizu, Hidetaka; Ohtani, Miyuki; Yura, Yoshiaki

2007-03-01

Maxillary distraction osteogenesis with the rigid external distraction (RED) system has been used to treat cleft lip and palate (CLP) patients with severe maxillary hypoplasia. We introduce maxillary distraction osteogenesis for CLP patients with skeletal anchorage adapted on a stereolithographic model. Six maxillary deficiency CLP patients treated according to our CLP treatment protocol had undergone maxillary distraction osteogenesis. In all patients, computed tomography (CT) images were recorded preoperatively, and the data were transferred to a workstation. Three-dimensional skeletal structures were reconstructed with CT data sets, and a stereolithographic model was produced. On the stereolithographic model, miniplates were adapted to the surface of maxilla beside aperture piriforms. The operation performed involved a high Le Fort I osteotomy with pterygomaxillary disjunction. Miniplates were fixed to the maxillary segment with three or four screws and used for anchorage of the RED system. Retraction of the maxillary segment was initiated after 1 week. The accuracy of the stereolithographic models was enough to adapt the miniplates so that there was no need to readjust the plates during surgery. Postoperative cephalometric analysis showed that the direction of the retraction was almost parallel to the palatal plane, and dental compensation did not occur. We performed maxillary distraction osteogenesis with skeletal anchorage adapted on the stereolithographic models. Excellent esthetic outcome and skeletal advancement were achieved without dentoalveolar compensations.

Stacked silicide/silicon mid- to long-wavelength infrared detector

NASA Technical Reports Server (NTRS)

Maserjian, Joseph (Inventor)

1990-01-01

The use of stacked Schottky barriers (16) with epitaxially grown thin silicides (10) combined with selective doping (22) of the barriers provides high quantum efficiency infrared detectors (30) at longer wavelengths that is compatible with existing silicon VLSI technology.

Stacked silicide/silicon mid- to long-wavelength infrared detector

DOEpatents

Maserjian, Joseph

1990-03-13

The use of stacked Schottky barriers (16) with epitaxially grown thin silicides (10) combined with selective doping (22) of the barriers provides high quantum efficiency infrared detectors (30) at longer wavelengths that is compatible with existing silicon VLSI technology.

An inert marker study for palladium silicide formation - Si moves in polycrystalline Pd2Si

NASA Technical Reports Server (NTRS)

Ho, K. T.; Lien, C.-D.; Shreter, U.; Nicolet, M.-A.

1985-01-01

A novel use of Ti marker is introduced to investigate the moving species during Pd2Si formation on 111 and 100 line-type Si substrates. Silicide formed from amorphous Si is also studied using a W marker. Although these markers are observed to alter the silicide formation in the initial stage, the moving species can be identified once a normal growth rate is resumed. It is found that Si is the dominant moving species for all three types of Si crystallinity. However, Pd will participate in mass transport when Si motion becomes obstructed.

Method for forming metallic silicide films on silicon substrates by ion beam deposition

DOEpatents

Zuhr, Raymond A.; Holland, Orin W.

1990-01-01

Metallic silicide films are formed on silicon substrates by contacting the substrates with a low-energy ion beam of metal ions while moderately heating the substrate. The heating of the substrate provides for the diffusion of silicon atoms through the film as it is being formed to the surface of the film for interaction with the metal ions as they contact the diffused silicon. The metallic silicide films provided by the present invention are contaminant free, of uniform stoichiometry, large grain size, and exhibit low resistivity values which are of particular usefulness for integrated circuit production.

Organometallic Routes into the Nanorealms of Binary Fe-Si Phases

PubMed Central

Kolel-Veetil, Manoj K.; Keller, Teddy M.

2010-01-01

The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, α-FeSi2 and β-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR). The silicon-rich β-FeSi2 is a direct band gap material usable in light emitting diode (LED) applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM) of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe)-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions.

Impact of laser anneal on NiPt silicide texture and chemical composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feautrier, C.; Ozcan, A. S.; Lavoie, C.

We have combined synchrotron X-ray pole figure measurements and transmission electron microscopy (TEM) nano-beam diffraction to study the impact of millisecond laser anneal on the texture and microstructure of NiPt silicide thin films. The powerful use of nano-beam diffraction in plan-view geometry allows here for both a mapping of grain orientation and intra-grain measurements even if these crystalline grains become very small. With this unique combination of local and large-scale probes, we find that silicide formation on n and p doped substrates using laser annealing results in smaller grains compared with the films processed using standard rapid thermal annealing. Themore » laser annealed samples also result in grains that are more epitaxially oriented with respect to the Si substrate. For n-type substrate, the film is dominated by (020) and (013) oriented fibers with significant levels of intra-grain bending (transrotation) observed in both types of grains. For p-type substrates, mostly epitaxially aligned grains are detected. TEM coupled with energy-dispersive X-ray analysis was also used to study the elemental distribution in the silicide samples. Here, we confirm that laser anneal leads to a larger accumulation of platinum at the silicide-substrate interface and modifies the distribution of dopants throughout the film.« less

In situ micro-Raman analysis and X-ray diffraction of nickel silicide thin films on silicon.

PubMed

Bhaskaran, M; Sriram, S; Perova, T S; Ermakov, V; Thorogood, G J; Short, K T; Holland, A S

2009-01-01

This article reports on the in situ analysis of nickel silicide (NiSi) thin films formed by thermal processing of nickel thin films deposited on silicon substrates. The in situ techniques employed for this study include micro-Raman spectroscopy (microRS) and X-ray diffraction (XRD); in both cases the variations for temperatures up to 350 degrees C has been studied. Nickel silicide thin films formed by vacuum annealing of nickel on silicon were used as a reference for these measurements. In situ analysis was carried out on nickel thin films on silicon, while the samples were heated from room temperature to 350 degrees C. Data was gathered at regular temperature intervals and other specific points of interest (such as 250 degrees C, where the reaction between nickel and silicon to form Ni(2)Si is expected). The transformations from the metallic state, through the intermediate reaction states, until the desired metal-silicon reaction product is attained, are discussed. The evolution of nickel silicide from the nickel film can be observed from both the microRS and XRD in situ studies. Variations in the evolution of silicide from metal for different silicon substrates are discussed, and these include (100) n-type, (100) p-type, and (110) p-type silicon substrates.

Synthesis and design of silicide intermetallic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrovic, J.J.; Castro, R.G.; Butt, D.P.

1997-04-01

The overall objective of this program is to develop structural silicide-based materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation and corrosion resistance for applications of importance to the U.S. processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature materials and important applications in major energy-intensive U.S. processing industries. The program presently has amore » number of developing industrial connections, including a CRADA with Schuller International Inc. targeted at the area of MoSi{sub 2}-based high temperature materials and components for fiberglass melting and processing applications. The authors are also developing an interaction with the Institute of Gas Technology (IGT) to develop silicides for high temperature radiant gas burner applications, for the glass and other industries. Current experimental emphasis is on the development and characterization of MoSi{sub 2}-Si{sub 3}N{sub 4} and MoSi{sub 2}-SiC composites, the plasma spraying of MoSi{sub 2}-based materials, and the joining of MoSi{sub 2} materials to metals.« less

Impact of laser anneal on NiPt silicide texture and chemical composition

NASA Astrophysics Data System (ADS)

Feautrier, C.; Ozcan, A. S.; Lavoie, C.; Valery, A.; Beneyton, R.; Borowiak, C.; Clément, L.; Pofelski, A.; Salem, B.

2017-06-01

We have combined synchrotron X-ray pole figure measurements and transmission electron microscopy (TEM) nano-beam diffraction to study the impact of millisecond laser anneal on the texture and microstructure of NiPt silicide thin films. The powerful use of nano-beam diffraction in plan-view geometry allows here for both a mapping of grain orientation and intra-grain measurements even if these crystalline grains become very small. With this unique combination of local and large-scale probes, we find that silicide formation on n and p doped substrates using laser annealing results in smaller grains compared with the films processed using standard rapid thermal annealing. The laser annealed samples also result in grains that are more epitaxially oriented with respect to the Si substrate. For n-type substrate, the film is dominated by (020) and (013) oriented fibers with significant levels of intra-grain bending (transrotation) observed in both types of grains. For p-type substrates, mostly epitaxially aligned grains are detected. TEM coupled with energy-dispersive X-ray analysis was also used to study the elemental distribution in the silicide samples. Here, we confirm that laser anneal leads to a larger accumulation of platinum at the silicide-substrate interface and modifies the distribution of dopants throughout the film.

Texture in thin film silicides and germanides: A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Schutter, B., E-mail: bob.deschutter@ugent.be; De Keyser, K.; Detavernier, C.

Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi{sub 2}, C54-TiSi{sub 2}, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si{sub 1−x}Ge{sub x} in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is ofmore » utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.« less

Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khanbabaee, B., E-mail: khanbabaee@physik.uni-siegen.de; Pietsch, U.; Lützenkirchen-Hecht, D.

We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe{sup +} ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 10{sup 17} and 5 × 10{sup 17} ions cm{sup −2} exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-raymore » photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe{sub 3}Si) close to the surface into a Si-rich silicide (FeSi{sub 2}) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr{sup +} ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.« less

Texture in thin film silicides and germanides: A review

NASA Astrophysics Data System (ADS)

De Schutter, B.; De Keyser, K.; Lavoie, C.; Detavernier, C.

2016-09-01

Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi2, C54-TiSi2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si1-xGex in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuryev, V. A., E-mail: vyuryev@kapella.gpi.ru; Chizh, K. V.; Chapnin, V. A.

Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si{sub 3}N{sub 4}/SiO{sub 2}/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy.more » Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about −2%/ °C in the temperature interval from 25 to 50 °C.« less

Surface-interface exploration of Mg deposited on Si(100) and oxidation effect on interfacial layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarpi, B.; Daineche, R.; Girardeaux, C.

Using scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, and low energy electron diffraction, we have studied the growth of Mg deposited on Si(100)-(2 × 1). Coverage from 0.05 monolayer (ML) to 3 ML was investigated at room temperature. The growth mode of the magnesium is a two steps process. At very low coverage, there is formation of an amorphous ultrathin silicide layer with a band gap of 0.74 eV, followed by a layer-by-layer growth of Mg on top of this silicide layer. Topographic images reveal that each metallic Mg layer is formed by 2D islands coalescence process on top of the silicidemore » interfacial layer. During oxidation of the Mg monolayer, the interfacial silicide layer acts as diffusion barrier for the oxygen atoms with a decomposition of the silicide film to a magnesium oxide as function of O{sub 2} exposure.« less

Palladium silicide formation under the influence of nitrogen and oxygen impurities

NASA Technical Reports Server (NTRS)

Ho, K. T.; Lien, C.-D.; Nicolet, M.-A.

1985-01-01

The effect of impurities on the growth of the Pd2Si layer upon thermal annealing of a Pd film on 100 line-type and amorphous Si substrates is investigated. Nitrogen and oxygen impurities are introduced into either Pd or Si which are subsequently annealed to form Pd2Si. The complementary techniques of Rutherford backscattering spectrometry, and N-15(p, alpha)C-12 or O-18(p, alpha)N-15 nuclear reaction, are used to investigate the behavior of nitrogen or oxygen and the alterations each creates during silicide formation. Both nitrogen and oxygen retard the silicide growth rate if initially present in Si. When they are initially in Pd, there is no significant retardation; instead, an interesting snow-plowing effect of N or O by the reaction interface of Pd2Si is observed. By using N implanted into Si as a marker, Pd and Si appear to trade roles as the moving species when the silicide front reaches the nitrogen-rich region.

A high-strength silicide phase in a stainless steel alloy designed for wear-resistant applications.

PubMed

Bowden, D; Krysiak, Y; Palatinus, L; Tsivoulas, D; Plana-Ruiz, S; Sarakinou, E; Kolb, U; Stewart, D; Preuss, M

2018-04-10

Hardfacing alloys provide strong, wear-resistant and corrosion-resistant coatings for extreme environments such as those within nuclear reactors. Here, we report an ultra-high-strength Fe-Cr-Ni silicide phase, named π-ferrosilicide, within a hardfacing Fe-based alloy. Electron diffraction tomography has allowed the determination of the atomic structure of this phase. Nanohardness testing indicates that the π-ferrosilicide phase is up to 2.5 times harder than the surrounding austenite and ferrite phases. The compressive strength of the π-ferrosilicide phase is exceptionally high and does not yield despite loading in excess of 1.6 GPa. Such a high-strength silicide phase could not only provide a new type of strong, wear-resistant and corrosion-resistant Fe-based coating, replacing more costly and hazardous Co-based alloys for nuclear applications, but also lead to the development of a new class of high-performance silicide-strengthened stainless steels, no longer reliant on carbon for strengthening.

Miniplate with a bendable C-tube head allows the clinician to alter biomechanical advantage without physically moving the skeletal anchorage device.

PubMed

Seo, Kyung-Won; Ahn, Hyo-Won; Kim, Seong-Hun; Chung, Kyu-Rhim; Nelson, Gerald

2014-01-01

This article introduces a binary function of a miniplate with a bendable C-tube head used in corticotomy-assisted segment intrusion. The advantage of the device is that the point of force application can be altered without having to move the miniplate or place an additional anchorage device. Cases for this study were selected from patients who received perisegmental corticotomy with compression osteogenesis (Speedy Surgical Orthodontics) for segmental intrusion. For the skeletal anchorage on patients who received Speedy Surgical Orthodontics for posterior segment intrusion to improve on severe open bite correction, the C-tube was placed on the buccal wall of the maxilla for traction of orthopedic force as a temporary skeletal anchorage. The C-tube head portion is made with titanium grade II, which makes bending easy with a Weingart plier. This adjustment regains distance and range needed to continue intrusion of posterior segment. As an alternative to orthognathic surgery to correct a severe open bite, perisegmental corticotomy combined with orthopedic force application from a temporary skeletal anchorage device can be used. The corticotomy-assisted segment intrusion is a 2-stage procedure: first, the corticotomy is performed in the palate and 2 weeks later in the buccal alveolus. A C-plate was placed in the midpalatal area, and a C-tube was placed apical to the buccal corticotomy site. Elastics were used with orthopedic forces to induce compression osteogenesis. As the intrusion took place, the elastic stretched, and resultant force and range in the buccal segment decreased. The C-tube head was adjusted by bending to gain more distance, reviving the elastic force on the posterior segment until desired intrusion was accomplished. The miniplate with a bendable C-tube head serves for temporary skeletal anchorage of orthopedic traction force to achieve segmental intrusion and has the advantage that the bendable head can be adjusted to improve the force application for intrusion without having to move or place another temporary skeletal anchorage device.

An in vitro evaluation of rigid internal fixation techniques for sagittal split ramus osteotomies: setback surgery.

PubMed

Brasileiro, Bernardo Ferreira; Grotta-Grempel, Rafael; Ambrosano, Glaucia Maria Bovi; Passeri, Luis Augusto

2012-04-01

The aim of this study was to evaluate the biomechanical features of 3 different methods of rigid internal fixation for sagittal split ramus osteotomy for mandibular setback in vitro. Sixty polyurethane replicas of human hemimandibles were used as substrates, simulating a 5-mm setback surgery by sagittal split ramus osteotomy. These replicas served to reproduce 3 different techniques of fixation, including 1) a 4-hole plate and 4 monocortical screws (miniplate group), 2) a 4-hole plate and 4 monocortical screws with 1 additional bicortical positional screw (hybrid group), and 3) 3 bicortical positional screws in a traditional inverted-L pattern (inverted-L group). After fixation, hemimandibles were adapted to a test support and subjected to lateral torsional forces on the buccal molar surface and vertical cantilever loading on the incisal edge with an Instron 4411 mechanical testing unit. Peak loadings at 1, 3, 5, and 10 mm of displacement were recorded. Means and standard deviation were analyzed using analysis of variance and Tukey test with a 5% level of significance, and failures during tests were recorded. Regardless of the amount of displacement and direction of force, the miniplate group always showed the lowest load peak scores (P < .01) compared with the other fixation techniques. The hybrid group demonstrated behavior similar to the inverted-L group in lateral and vertical forces at any loading displacement (P > .05). Molar load tests required more force than incisal load tests to promote the same displacement in the mandibular setback model (P < .05). For mandibular setback surgery of 5 mm, this study concluded that the fixation technique based on the miniplate group was significantly less rigid than the fixation observed in the hybrid and inverted-L groups. Mechanically, adding 1 bicortical positional screw in the retromolar region in the miniplate technique may achieve the same stabilization offered by inverted-L fixation for mandibular sagittal split ramus osteotomy setback surgery in vitro. Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

[Effectiveness of arthroscopic treatment of anterior cruciate ligament tibial eminence avulsion fracture with non-absorbable suture fixation combined with mini-plate].

PubMed

Wang, Suiyuan; Xiao, Yang; Tong, Zuoming; Li, Guiqiu; Jiang, Juhua; Yao, Jinghui; Wu, Zhiyong; Li, Tengfei; Wu, Qun

2013-09-01

To evaluate the surgical techniques and effectiveness of arthroscopic treatment of anterior cruciate ligament (ACL) tibial eminence avulsion fracture with non-absorbable suture fixation combined with the miniplate. Between January 2009 and March 2012, 32 patients with ACL tibial eminence avulsion fractures were treated. There were 18 males and 14 females, aged 12-40 years (mean, 17.5 years). The injury causes included traffic accident injury in 15 cases, sport injury in 6 cases, and falling injury in 11 cases. The time from injury to operation ranged 7-18 days with an average of 9.5 days. Before operation, the results of Lachman test were all positive; the Lysholm score was 52.13 +/- 4.22 and the International Knee Documentation Committee (IKDC) score was 44.82 +/- 2.44. According to Meyers-McKeever classification criteria, there were 12 cases of type II and 20 cases of type III. After arthroscopic poking reduction of fracture, tibial eminence avulsion fractures were fixed with the Ethibond non-absorbable sutures bypass figure-of-eight tibial tunnel combined with the metacarpal and phalangeal mini-plate. Primary healing was obtained in all incisions; no joint infection or skin necrosis occurred after operation. All patients were followed up with an average time of 22.4 months (range, 12-50 months). The patients showed negative Lachman test at 12 weeks after operation. Except 3 patients having knee extension limitation at last follow-up, the knee extension range of motion (ROM) was normal in the other patients; the knee flexion ROM was normal in all patients. The Lysholm score and IKDC score were significantly improved to 94.19 +/- 0.93 and 94.35 +/- 1.22 at last follow-up, showing significant differences when compared with preoperative values (t = 55.080, P = 0.000; t = 101.715, P = 0.000). The arthroscopic treatment of ACL tibial eminence avulsion fracture with Ethibond non-absorbable suture fixation combined with mini-plate is an effective procedure with the advantages of minimal trauma, reliable fixation, and satisfactory recovery of the knee joint function.

Solution synthesis of metal silicide nanoparticles.

PubMed

McEnaney, Joshua M; Schaak, Raymond E

2015-02-02

Transition-metal silicides are part of an important family of intermetallic compounds, but the high-temperature reactions that are generally required to synthesize them preclude the formation of colloidal nanoparticles. Here, we show that palladium, copper, and nickel nanoparticles react with monophenylsilane in trioctylamine and squalane at 375 °C to form colloidal Pd(2)Si, Cu(3)Si, and Ni(2)Si nanoparticles, respectively. These metal silicide nanoparticles were screened as electrocatalysts for the hydrogen evolution reaction, and Pd(2)Si and Ni(2)Si were identified as active catalysts that require overpotentials of -192 and -243 mV, respectively, to produce cathodic current densities of -10 mA cm(-2).

Accelerated Exploration of Multi-principal Element Alloys for Structural Applications (Postprint)

DTIC Science & Technology

2015-04-27

SS phases (BCC, HCP and FCC), three silicide phases (M5Si3, M5Si4 and M3Si3), an ordered B2 phase, and two Laves phases (C14 and C15). In total, 453...alloys containing silicide phases (M5Si3, M5Si4, and M3Si2) is probably due to very negative, often below 50 kJ/mol [51 53] enthalpies of formation of...The majority of equiatomic alloys containing two or more phases are (SSþ IM) alloys.5. BCC, HCP and FCC SS phases, three silicide phases (M5Si3, M5Si4

Silicide phases formation in Co/c-Si and Co/a-Si systems during thermal annealing

NASA Astrophysics Data System (ADS)

Novaković, M.; Popović, M.; Zhang, K.; Lieb, K. P.; Bibić, N.

2014-03-01

The effect of the interface in cobalt-silicon bilayers on the silicide phase formation and microstructure has been investigated. Thin cobalt films were deposited by electron beam evaporation to a thickness of 50 nm on crystalline silicon (c-Si) or silicon with pre-amorphized surface (a-Si). After deposition one set of samples was annealed for 2 h at 200, 300, 400, 500, 600 and 700 °C. Another set of samples was irradiated with 400 keV Xe+ ions and then annealed at the same temperatures. Phase transitions were investigated with Rutherford backscattering spectroscopy, X-ray diffraction and cross-sectional transmission electron microscopy. No silicide formation was observed up to 400 °C, for both non-irradiated and ion-irradiated samples. When increasing the annealing temperature, the non-irradiated and irradiated Co/c-Si samples showed a similar behaviour: at 500 °C, CoSi appeared as the dominant silicide, followed by the formation of CoSi2 at 600 and 700 °C. In the case of non-irradiated Co/a-Si samples, no silicide formation occurred up to 700 °C, while irradiated samples with pre-amorphized substrate (Co/a-Si) showed a phase sequence similar to that in the Co/c-Si system. The observed phase transitions are found to be consistent with predictions of the effective heat of formation model.

Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology.

PubMed

Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

2015-12-03

This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm(2), and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p(+-)n homojunction through the formation of re-grown crystalline silicon layer (~5-10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method.

Challenges of nickel silicidation in CMOS technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breil, Nicolas; Lavoie, Christian; Ozcan, Ahmet

2015-04-01

In our paper, we review some of the key challenges associated with the Ni silicidation process in the most recent CMOS technologies. The introduction of new materials (e.g.SiGe), and of non-planar architectures bring some important changes that require fundamental investigation from a material engineering perspective. Following a discussion of the device architecture and silicide evolution through the last CMOS generations, we focus our study on a very peculiar defect, termed NiSi-Fangs. We describe a mechanism for the defect formation, and present a detailed material analysis that supports this mechanism. We highlight some of the possible metal enrichment processes of themore » nickel monosilicide such as oxidation or various RIE (Reactive Ion Etching) plasma process, leading to a metal source available for defect formation. Furthermore, we investigate the NiSi formation and re-formation silicidation differences between Si and SiGe materials, and between (1 0 0) and (1 1 1) orientations. Finally, we show that the thermal budgets post silicidation can lead to the formation of NiSi-Fangs if the structure and the processes are not optimized. Beyond the understanding of the defect and the discussion on the engineering solutions used to prevent its formation, the interest of this investigation also lies in the fundamental learning within the Ni–Pt–Si–Ge system and some additional perspective on Ni-based contacts to advanced microelectronic devices.« less

Mini-Implants in the Anchorage Armamentarium: New Paradigms in the Orthodontics

PubMed Central

Yamaguchi, Masaru; Inami, Toshihiro; Ito, Ko; Kasai, Kazutaka; Tanimoto, Yasuhiro

2012-01-01

Paradigms have started to shift in the orthodontic world since the introduction of mini-implants in the anchorage armamentarium. Various forms of skeletal anchorage, including miniscrews and miniplates, have been reported in the literature. Recently, great emphasis has been placed on the miniscrew type of temporary anchorage device (TAD). These devices are small, are implanted with a relatively simple surgical procedure, and increase the potential for better orthodontic results. Therefore, miniscrews not only free orthodontists from anchorage-demanding cases, but they also enable clinicians to have good control over tooth movement in 3 dimensions. The miniplate type also produces significant improvements in treatment outcomes and has widened the spectrum of orthodontics. The purpose of this paper is to update clinicians on the current concepts and versatile uses and clinical applications of skeletal anchorage in orthodontics. PMID:22719763

Chin plate with a detachable C-tube head serves for both osteotomy fixation and orthodontic anchorage.

PubMed

Seo, Kyung-Won; Nahm, Kyung-Yen; Kim, Seong-Hun; Chung, Kyu-Rhim; Nelson, Gerald

2013-07-01

This article reports the dual function of a double-Y miniplate with a detachable C-tube head (C-chin plate; Jin Biomed Co., Bucheon, Korea) used to fixate an anterior segmental osteotomy and provide skeletal anchorage during orthodontic tooth movement. Cases were selected for this study from patients who underwent anterior segmental osteotomy under local anesthesia. A detachable C-tube head portion was combined with a double-Y chin plate. The double-Y chin plates were fixated between the osteotomy segments and the mandibular base with screws in a conventional way. The C-tube head portion exited the tissue near the mucogingival junction. Biocreative Chin Plates were placed on the anterior segmental osteotomy sites. The device allowed 3 points of fixation: 1, minor postosteotomy vertical adjustment of the segment during healing; 2, minor shift of the midline during healing; and 3, to serve as temporary skeletal anchorage device during the post-anterior segmental osteotomy orthodontic treatment. When tooth movement goals are accomplished, the C-tube head of the chin plate can be easily detached from the fixation miniplate by twisting the head using a Weingart plier under local anesthesia. This dual-purpose device spares the patient from the need for 2 separate installations for stabilization of osteotomy segments. The dual-purpose double-Y miniplate combined with a C-tube head (Biocreative Chin Plate) provided versatile application of 3 points of post-osteotomy fixation and of temporary skeletal anchorage for orthodontic tooth movement.

Skeletal Class lll severe openbite treatment using implant anchorage.

PubMed

Sakai, Yuichi; Kuroda, Shingo; Murshid, Sakhr A; Takano-Yamamoto, Teruko

2008-01-01

A female patient with a skeletal Class III severe anterior openbite was treated using miniplates as the anchorage. The patient was 15 years and 10 months of age when she reported to our university hospital with a chief complaint of anterior openbite and reversed occlusion. The patient had an anterior openbite with an overjet of -3.0 mm and overbite of -5.0 mm and a Class III molar relationship. The cephalometric analysis showed a skeletal Class III relationship (ANB 0 degrees ). After the extraction of the bilateral mandibular third molars, miniplates were placed in the mandibular external oblique line. The mandibular dentition was retracted using elastic chain and miniplates. After treatment, an Angle Class I molar relationship was achieved and overjet and overbite had become 2.0 mm and 1.5 mm. A good facial appearance and occlusal relationship were obtained. The total active orthodontic treatment period was 23 months. Wrap-around type retainers were placed on both jaws and a lingual bonded retainer was also attached in the mandibular incisors. After 1 year of retention, the occlusion was stable, and a good facial profile was also retained. The mandibular deviation to the left was improved and the strain in the circumoral musculature during lip closure disappeared. An appropriate interincisal relationship was achieved by the uprighting of mandibular dentition without changing the vertical intermaxillary relationship. A panoramic radiograph showed no marked root resorption. Our results suggest that implant anchorage is useful for correction of skeletal Class III severe anterior openbite cases.

Fused slurry silicide coatings for columbium alloy reentry heat shields. Volume 2: Experimental and coating process details

NASA Technical Reports Server (NTRS)

Fitzgerald, B.

1973-01-01

The experimental and coating process details are presented. The process specifications which were developed for the formulation and application of the R-512E fused slurry silicide coating using either an acrylic or nitrocellulose base slurry system is also discussed.

Development of fused slurry silicide coatings for tantalum reentry heat shields

NASA Technical Reports Server (NTRS)

Warnock, R. V.; Stetson, A. R.

1972-01-01

A fused slurry silicide coating was developed to provide atmospheric reentry protection for the 90Ta-lOW alloy. Overlaying the silicide with a highly refractory glass greatly improved total lifetime and reliability of the coating system. Low pressure, slow cycle lifetimes in excess of 100 cycles were consistently recorded for 1700 K - 13 and 1300 N/sq m test conditions. A minimum of 25 cycles was obtained for 1810 K - 1300 N/sq m conditions. About 50 simulated reentry cycles (variable temperature, pressure, and stress) were endured by coated 1-inch miniature heat shield panels when exposed to a maximum of 1700 K and either internal or external pressure conditions.

WSi2 in Si(1-x)Ge(x) Composites: Processing and Thermoelectric Properties

NASA Technical Reports Server (NTRS)

Mackey, Jonathan A.; Sehirlioglu, Alp; Dynys, Fred

2015-01-01

Traditional SiGe thermoelectrics have potential for enhanced figure of merit (ZT) via nano-structuring with a silicide phase, such as WSi2. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples were prepared using powder metallurgy techniques; including mechano-chemical alloying, via ball milling, and spark plasma sintering for densification. Processing, micro-structural development, and thermoelectric properties will be discussed. Additionally, couple and device level characterization will be introduced.

Synthesis of silicon nanotubes with cobalt silicide ends using anodized aluminum oxide template.

PubMed

Zhang, Zhang; Liu, Lifeng; Shimizu, Tomohiro; Senz, Stephan; Gösele, Ulrich

2010-02-05

Silicon nanotubes (SiNTs) are compatible with Si-based semiconductor technology. In particular, the small diameters and controllable structure of such nanotubes are remaining challenges. Here we describe a method to fabricate SiNTs intrinsically connected with cobalt silicide ends based on highly ordered anodic aluminum oxide (AAO) templates. Size and growth direction of the SiNTs can be well controlled via the templates. The growth of SiNTs is catalyzed by the Co nanoparticles reduced on the pore walls of the AAO after annealing, with a controllable thickness at a given growth temperature and time. Simultaneously, cobalt silicide forms on the bottom side of the SiNTs.

Phase formation and morphological stability of ultrathin Ni-Co-Pt silicide films formed on Si(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Peng; Wu, Dongping, E-mail: dongpingwu@fudan.edu.cn; Kubart, Tomas

Ultrathin Ni, Co, and Pt films, each no more than 4 nm in thickness, as well as their various combinations are employed to investigate the competing growth of epitaxial Co{sub 1-y}Ni{sub y}Si{sub 2} films against polycrystalline Pt{sub 1-z}Ni{sub z}Si. The phase formation critically affects the morphological stability of the resulting silicide films, with the epitaxial films being superior to the polycrystalline ones. Any combination of those metals improves the morphological stability with reference to their parent individual metal silicide films. When Ni, Co, and Pt are all included, the precise initial location of Pt does little to affect the final phasemore » formation in the silicide films and the epitaxial growth of Co{sub 1-x}Ni{sub x}Si{sub 2} films is always perturbed, in accordance to thermodynamics that shows a preferential formation of Pt{sub 1-z}Ni{sub z}Si over that of Co{sub 1-y}Ni{sub y}Si{sub 2}.« less

{sup 45}Sc Solid State NMR studies of the silicides ScTSi (T=Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harmening, Thomas; Eckert, Hellmut, E-mail: eckerth@uni-muenster.de; Fehse, Constanze M.

The silicides ScTSi (T=Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt) were synthesized by arc-melting and characterized by X-ray powder diffraction. The structures of ScCoSi, ScRuSi, ScPdSi, and ScIrSi were refined from single crystal diffractometer data. These silicides crystallize with the TiNiSi type, space group Pnma. No systematic influences of the {sup 45}Sc isotropic magnetic shift and nuclear electric quadrupolar coupling parameters on various structural distortion parameters calculated from the crystal structure data can be detected. {sup 45}Sc MAS-NMR data suggest systematic trends in the local electronic structure probed by the scandium atoms: both the electric field gradients andmore » the isotropic magnetic shifts relative to a 0.2 M aqueous Sc(NO{sub 3}){sub 3} solution decrease with increasing valence electron concentration and within each T group the isotropic magnetic shift decreases monotonically with increasing atomic number. The {sup 45}Sc nuclear electric quadrupolar coupling constants are generally well reproduced by quantum mechanical electric field gradient calculations using the WIEN2k code. Highlights: Black-Right-Pointing-Pointer Arc-melting synthesis of silicides ScTSi. Black-Right-Pointing-Pointer Single crystal X-ray data of ScCoSi, ScRuSi, ScPdSi, and ScIrSi. Black-Right-Pointing-Pointer {sup 45}Sc solid state NMR of silicides ScTSi.« less

Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology

PubMed Central

Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

2015-01-01

This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm2, and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p+−n homojunction through the formation of re-grown crystalline silicon layer (~5–10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method. PMID:26632759

Silicide Coating Fabricated by HAPC/SAPS Combination to Protect Niobium Alloy from Oxidation.

PubMed

Sun, Jia; Fu, Qian-Gang; Guo, Li-Ping; Wang, Lu

2016-06-22

A combined silicide coating, including inner NbSi2 layer and outer MoSi2 layer, was fabricated through a two-step method. The NbSi2 was deposited on niobium alloy by halide activated pack cementation (HAPC) in the first step. Then, supersonic atmospheric plasma spray (SAPS) was applied to obtain the outer MoSi2 layer, forming a combined silicide coating. Results show that the combined coating possessed a compact structure. The phase constitution of the combined coating prepared by HAPC and SAPS was NbSi2 and MoSi2, respectively. The adhesion strength of the combined coating increased nearly two times than that for single sprayed coating, attributing to the rougher surface of the HAPC-bond layer whose roughness increased about three times than that of the grit-blast substrate. After exposure at 1200 °C in air, the mass increasing rate for single HAPC-silicide coating was 3.5 mg/cm(2) because of the pest oxidation of niobium alloy, whereas the combined coating displayed better oxidation resistance with a mass gain of only 1.2 mg/cm(2). Even more, the combined coating could significantly improve the antioxidation ability of niobium based alloy at 1500 °C. The good oxidation resistance of the combined silicide coating was attributed to the integrity of the combined coating and the continuous SiO2 protective scale provided by the oxidation of MoSi2.

Study of nickel silicide formation by physical vapor deposition techniques

NASA Astrophysics Data System (ADS)

Pancharatnam, Shanti

Metal silicides are used as contacts to the highly n-doped emitter in photovoltaic devices. Thin films of nickel silicide (NiSi) are of particular interest for Si-based solar cells, as they form at lower temperature and consume less silicon. However, interfacial oxide limits the reduction in sheet resistance. Hence, different diffusion barriers were investigated with regard to optimizing the conductivity and thermal stability. The formation of NiSi, and if it can be doped to have good contact with the n-side of a p-n junction were studied. Reduction of the interfacial oxide by the interfacial Ti layer to allow the formation of NiSi was observed. Silicon was treated in dilute hydrofluoric acid for removing the surface oxide layer. Ni and a Ti diffusion barrier were deposited on Si by physical vapor deposition (PVD) methods - electron beam evaporation and sputtering. The annealing temperature and time were varied to observe the stability of the deposited film. The films were then etched to observe the retention of the silicide. Characterization was done using scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and Rutherford back scattering (RBS). Sheet resistance was measured using the four-point probe technique. Annealing temperatures from 300°C showed films began to agglomerate indicating some diffusion between Ni and Si in the Ti layer, also supported by the compositional analysis in the Auger spectra. Films obtained by evaporation and sputtering were of high quality in terms of coverage over substrate area and uniformity. Thicknesses of Ni and Ti were optimized to 20 nm and 10 nm respectively. Resistivity was low at these thicknesses, and reduced by about half post annealing at 300°C for 8 hours. Thus a low resistivity contact was obtained at optimized thicknesses of the metal layers. It was also shown that some silicide formation occurs at temperatures starting from 300°C and can thus be used to make good silicide contacts.

Orthodontic retreatment using anchorage with miniplate to camouflage a Class III skeletal pattern.

PubMed

Farret, Marcel Marchiori

2016-06-01

This manuscript describes the treatment of a 27-year-old patient who was previously treated with two maxillary first premolar extractions. The patient had skeletal Class III malocclusion, Class III canine relationship, anterior crossbite, and a concave profile. As the patient refused orthognathic surgery, a miniplate was used on the right side of the lower arch as an anchorage unit after the extraction of mandibular first premolars, aiding the retraction of anterior teeth. At the end of treatment, anterior crossbite was corrected, in which first molars and canines were in a Class I relationship, and an excellent intercuspation was reached. Furthermore, patient's profile remarkably improved as a result of mandibular incisor retraction. A 30-month follow-up showed good stability of the results obtained. This case was presented to the Brazilian Board of Orthodontics and Dentofacial Orthopedics (BBO) as one of the requirements to become diplomate by the BBO.

Orthodontic retreatment using anchorage with miniplate to camouflage a Class III skeletal pattern

PubMed Central

Farret, Marcel Marchiori

2016-01-01

ABSTRACT This manuscript describes the treatment of a 27-year-old patient who was previously treated with two maxillary first premolar extractions. The patient had skeletal Class III malocclusion, Class III canine relationship, anterior crossbite, and a concave profile. As the patient refused orthognathic surgery, a miniplate was used on the right side of the lower arch as an anchorage unit after the extraction of mandibular first premolars, aiding the retraction of anterior teeth. At the end of treatment, anterior crossbite was corrected, in which first molars and canines were in a Class I relationship, and an excellent intercuspation was reached. Furthermore, patient's profile remarkably improved as a result of mandibular incisor retraction. A 30-month follow-up showed good stability of the results obtained. This case was presented to the Brazilian Board of Orthodontics and Dentofacial Orthopedics (BBO) as one of the requirements to become diplomate by the BBO. PMID:27409659

Comparative biomechanical evaluation of mono-cortical osteosynthesis systems for condylar fractures using photoelastic stress analysis.

PubMed

Christopoulos, Panos; Stathopoulos, Panagiotis; Alexandridis, Constantinos; Shetty, Vivek; Caputo, Angelo

2012-10-01

Fractures of the condyle account for 20-30% of all mandibular fractures, and are therefore one of the most common facial injuries. Precise evaluation of the mechanical stresses that develop in a fractured mandible is essential, particularly for the testing of systems currently used for stabilisation of the condylar fragment. Photoelastic stress analysis can be used to visualise alterations in the strain that is induced in the mandible by a fracture, and in the osteosynthesis materials used to stabilise it. This method, used on currently used osteosynthesis materials, showed that stabilisation of a subcondylar fracture with a single miniplate does not provide enough stability, whereas the use of two miniplates - properly positioned - offers sufficient stability in all loading conditions. A microplate may be used as a tension-resisting plate with equally good results. Copyright © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

[3-D finite element modeling of internal fixation of mandibular mental fracture and the design of boundary constraints].

PubMed

Luo, Xiaohui; Wang, Hang; Fan, Yubo

2007-04-01

This study was aimed to develop a 3-D finite element (3-D FE) model of the mental fractured mandible and design the boundary constrains. The CT images from a health volunteer were used as the original information and put into ANSYS program to build a 3-D FE model. The model of the miniplate and screw which were used for the internal fixation was established by Pro/E. The boundary constrains of different muscle loadings were used to simulate the 3 functional conditions of the mandible. A 3-D FE model of mental fractured mandible under the miniplate-screw internal fixation system was constructed. And by the boundary constraints, the 3 biting conditions were simulated and the model could serve as a foundation on which to analyze the biomechanical behavior of the fractured mandible.

Status and progress of the RERTR program in the year 2000.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Travelli, A.

2000-09-28

This paper describes the progress achieved by the Reduced Enrichment for Research and Test Reactors (RERTR) Program in collaboration with its many international partners during the year 2000 and discusses the main activities planned for the year 2001. The past year was characterized by important accomplishments and events for the RERTR program. Four additional shipments containing 503 spent fuel assemblies from foreign research reactors were accepted by the U.S. Altogether, 3,740 spent fuel assemblies from foreign research reactors have been received by the U.S. under the acceptance policy. Postirradiation examinations of three batches of microplates have continued to reveal excellentmore » irradiation behavior of U-MO dispersion fuels in a variety of compositions and irradiating conditions. h-radiation of two new batches of miniplates of greater sizes is in progress in the ATR to investigate me swelling behavior of these fuels under prototypic conditions. These materials hold the promise of achieving the program goal of developing LEU research reactor fuels with uranium densities in the 8-9 g /cm{sup 3} range. Qualification of the U-MO dispersion fuels is proceeding on schedule. Test fuel elements with 6 gU/cm{sup 3} are being fabricated by BWXT and are scheduled to begin undergoing irradiation in the HFR-Petten in the spring of 2001, with a goal of qualifying this fuel by the end of 2003. U-Mo with 8-9 gU/cm{sup 3} is planned to be qualified by the end of 2005. Joint LEU conversion feasibility studies were completed for HFR-Petten and for SAFARI-1. Significant improvements were made in the design of LEU metal-foil annular targets that would allow efficient production of fission {sup 99}Mo. Irradiations in the RAS-GAS reactor showed that these targets can formed from aluminum tubes, and that the yield and purity of their product from the acidic process were at least as good as those from the HEU Cintichem targets. Progress was made on irradiation testing of LEU UO{sub 2} dispersion fuel and on LEU conversion feasibility studies in the Russian RERTR program. Conversion of the BER-11reactor in Berlin, Germany, was completed and conversion of the La Reins reactor in Santiago, Chile, began. These are exciting times for the program. In the fuel development area, the RERTR program is aggressively pursuing qualification of high-density LEU U-Mo dispersion fuels, with the dual goal of enabling fi.uther conversions and of developing a substitute for LEU silicide fuels that can be more easily disposed of after expiration of the FRR SNF Acceptance Program. The {sup 99}Mo effort has reached the point where it appears feasible for all the {sup 99}Mo producers of the world to agree jointly to a common course of action leading to the elimination of HEU use in their processes. As in the past, the success of the RERTR program will depend on the international friendship and cooperation that has always been its trademark.« less

Preparation and Characterization of Single Crystals and Epitaxial Layers of Silicon Carbide by Molten Salt Electrolysis.

DTIC Science & Technology

1980-10-01

requires the simultaneous cathodic deposi- tion of silicon and carbon under conditions where reaction to form SiC will occur. In this study sodium or...reactivity with the melt. Nickel suffers from the disadvantage that it reacts with silicon to form nickel silicides , but the concentration of silicides in

Charge retention characteristics of silicide-induced crystallized polycrystalline silicon floating gate thin-film transistors for active matrix organic light-emitting diode.

PubMed

Park, Jae Hyo; Son, Se Wan; Byun, Chang Woo; Kim, Hyung Yoon; Joo, So Na; Lee, Yong Woo; Yun, Seung Jae; Joo, Seung Ki

2013-10-01

In this work, non-volatile memory thin-film transistor (NVM-TFT) was fabricated by nickel silicide-induced laterally crystallized (SILC) polycrystalline silicon (poly-Si) as the active layer. The nickel seed silicide-induced crystallized (SIC) poly-Si was used as storage layer which is embedded in the gate insulator. The novel unit pixel of active matrix organic light-emitting diode (AMOLED) using NVM-TFT is proposed and investigated the electrical and optical performance. The threshold voltage shift showed 17.2 V and the high reliability of retention characteristic was demonstrated until 10 years. The retention time can modulate the recharge refresh time of the unit pixel of AMOLED up to 5000 sec.

The efficacy of the use of IR laser phototherapy associated to biphasic ceramic graft and guided bone regeneration on surgical fractures treated with miniplates: a histological and histomorphometric study on rabbits.

PubMed

Pinheiro, Antonio L B; Aciole, Gilberth Tadeu Santos; Ramos, Thais Andrade; Gonzalez, Tayná Assunção; da Silva, Laís Nogueira; Soares, Luiz G Pinheiro; Aciole, Jouber Mateus Santos; dos Santos, Jean Nunes

2014-01-01

The aim of the present study was to assess, by light microscopy and histomorphometry, the repair of surgical fractures fixed with internal rigid fixation (IRF) treated or not with IR laser (λ780 nm, 50 mW, 4 × 4 J/cm(2) = 16 J/cm(2), ϕ = 0.5 cm(2), CW) associated or not to the use of hydroxyapatite and guided bone regeneration. Surgical tibial fractures were created under general anesthesia on 15 rabbits that were divided into 5 groups, maintained on individual cages, at day/night cycle, fed with solid laboratory pelted diet, and had water ad libidum. The fractures in groups II, III, IV, and V were fixed with miniplates. Animals in groups III and V were grafted with hydroxyapatite and GBR technique used. Animals in groups IV and V were irradiated at every other day during two weeks (4 × 4 J/cm(2), 16 J/cm(2) = 112 J/cm(2)). Observation time was that of 30 days. After animal death, specimens were taken, routinely processed to wax, cut and stained with HA and Sirius red, and used for histological assessment. The results of both analyses showed a better bone repair on all irradiated subjects especially when the biomaterial and GBR were used. In conclusion, the results of the present investigation are important clinically as they are suggestive that the association of hydroxyapatite, and laser light resulted in a positive and significant repair of complete tibial fractures treated with miniplates.

Effects of miniplate anchored and conventional Forsus Fatigue Resistant Devices in the treatment of Class II malocclusion.

PubMed

Turkkahraman, Hakan; Eliacik, Sule Kocabas; Findik, Yavuz

2016-11-01

To compare the skeletal, dentoalveolar, and soft tissue effects of the miniplate anchored Forsus Fatigue Resistant Device (FRD) and the conventional Forsus FRD in the treatment of Class II malocclusion. The study was carried out with 30 patients (10 girls, 20 boys). In the MA-Forsus group, 15 patients (2 girls, 13 boys) were treated with a miniplate anchored Forsus FRD for 9.40 ± 2.25 months. In the C-Forsus group, 15 patients (8 girls, 7 boys) were treated with a conventional Forsus FRD for 9.46 ± 0.81 months. A total of 16 measurements were calculated and statistically analyzed to find intragroup and intergroup differences. Statistically significant differences were found between the groups in IMPA, SN/Occ, SN/GoGn, overjet, overbite, and Li-S measurements (P < .05). In the C-Forsus group, a substantial amount of lower incisor protrusion was observed, whereas retrusion was found in the MA-Forsus group (P < .001). The mandible rotated backward in the MA-Forsus group, whereas it remained unchanged in the C-Forsus group (P < .05). Reductions in overjet (P < .001) and overbite were greater in the C-Forsus group (P < .05). Stimulation of mandibular growth and inhibition of maxillary growth were achieved in both treatment groups. In the C-Forsus group, a substantial amount of lower incisor protrusion was observed, whereas retrusion of lower incisors was found in the MA-Forsus group. The MA-Forsus group was found to be more advantageous as it had no dentoalveolar side effects on mandibular dentition.

The Redox Balance in Erythrocytes, Plasma, and Periosteum of Patients with Titanium Fixation of the Jaw

PubMed Central

Borys, Jan; Maciejczyk, Mateusz; Krȩtowski, Adam J.; Antonowicz, Bozena; Ratajczak-Wrona, Wioletta; Jabłońska, Ewa; Załęski, Piotr; Waszkiel, Danuta; Ładny, Jerzy R.; Żukowski, Piotr; Zalewska, Anna

2017-01-01

Titanium miniplates and screws are commonly used for fixation of jaw fractured or osteotomies. Despite the opinion of their biocompatibility, in clinical practice symptoms of chronic inflammation around the fixation develop in some patients, even many years after the application of miniplates and screws. The cause of these complications is still an unanswered question. Taking into account that oxidative stress is one of the toxic action of titanium, we have evaluated the antioxidant barrier as well as oxidative stress in the erythrocytes, plasma and periosteum covering the titanium fixation of the jaw. The study group was composed of 32 patients aged 20–30 with inserted miniplates and screws. The antioxidant defense: catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase-1 (SOD1), uric acid (UA), total antioxidant capacity (TAC), as well as oxidative damage products: advanced oxidation protein products (AOPP), advanced glycation end products (AGE), dityrosine, kynurenine, N-formylkynurenine, tryptophan, malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), total oxidant status (TOS), and oxidative status index (OSI) were evaluated. SOD1 activity (↓37%), and tryptophan levels (↓34%) showed a significant decrease while AOPP (↑25%), TOS (↑80%) and OSI (↑101%) were significantly elevated in maxillary periosteum of patients who underwent bimaxillary osteotomies as compared to the control group. SOD-1 (↓55%), TAC (↓58.6%), AGE (↓60%) and N-formylkynurenine (↓34%) was statistically reduced while AOPP (↑38%), MDA (↑29%), 4-HNE (↑114%), TOS (↑99%), and OSI (↑381%) were significantly higher in the mandibular periosteum covering miniplates/screw compared with the control tissues. There were no correlations between antioxidants and oxidative stress markers in the periosteum of all patients and the blood. As exposure to the Ti6Al4V titanium alloy leads to disturbances of redox balance in the periosteum surrounding titanium implants of the maxilla and the mandible so antioxidant supplementation should be recommended to the patients undergoing treatment of dentofacial deformities with the use of titanium implants. The results we obtained may also indicate a need to improve the quality of titanium jaw fixations through increase of TiO2 passivation layer thickness or to develop new, the most highly biodegradable materials for their production. PMID:28638348

ESD protection design for advanced CMOS

NASA Astrophysics Data System (ADS)

Huang, Jin B.; Wang, Gewen

2001-10-01

ESD effects in integrated circuits have become a major concern as today's technologies shrink to sub-micron/deep- sub-micron dimensions. The thinner gate oxide and shallower junction depth used in the advanced technologies make them very vulnerable to ESD damages. The advanced techniques like silicidation and STI (shallow trench insulation) used for improving other device performances make ESD design even more challenging. For non-silicided technologies, a certain DCGS (drain contact to gate edge spacing) is needed to achieve ESD hardness for nMOS output drivers and nMOS protection transistors. The typical DCGS values are 4-5um and 2-3um for 0.5um and 0.25um CMOS, respectively. The silicidation reduces the ballast resistance provided by DCGS with at least a factor of 10. As a result, scaling of the ESD performance with device width is lost and even zero ESD performance is reported for standard silicided devices. The device level ESD design is focused in this paper, which includes GGNMOS (gate grounded NMOS) and GCNMOS (gate coupled NMOS). The device level ESD testing including TLP (transmission line pulse) is given. Several ESD issues caused by advanced technologies have been pointed out. The possible solutions have been developed and summarized including silicide blocking, process optimization, back-end ballasting, and new protection scheme, dummy gate/n-well resistor ballsting, etc. Some of them require process cost increase, and others provide novel, compact, and simple design but involving royalty/IP (intellectual property) issue. Circuit level ESD design and layout design considerations are covered. The top-level ESD protection strategies are also given.

Sputtered Thin Film Research

DTIC Science & Technology

1974-11-01

yield (100) oriented wafers, which were lapped and chemi-mechanically polished in sulf uric-peroxide or sodium hypochlorite etches. Prior to mounting...This material will viot oxidize, melt, or diffuse during the subsequent high temperature processing. Platinum silicide contacts are used because...formation of the platinum silicide contacts, the gate region was opened and the wafer was placed in the sput- tering chamber. The same deposition

Electronic and chemical structure of metal-silicon interfaces

NASA Technical Reports Server (NTRS)

Grunthaner, P. J.; Grunthaner, F. J.

1984-01-01

This paper reviews our current understanding of the near-noble metal silicides and the interfaces formed with Si(100). Using X-ray photoemission spectroscopy, we compare the chemical composition and electronic structure of the room temperature metal-silicon and reacted silicide-silicon interfaces. The relationship between the interfacial chemistry and the Schottky barrier heights for this class of metals on silicon is explored.

A Study on Characterization of Light-Induced Electroless Plated Ni Seed Layer and Silicide Formation for Solar Cell Application

NASA Astrophysics Data System (ADS)

Takaloo, Ashkan Vakilipour; Joo, Seung Ki; Es, Firat; Turan, Rasit; Lee, Doo Won

2018-03-01

Light-induced electroless plating (LIEP) is an easy and inexpensive method that has been widely used for seed layer deposition of Nickel/Copper (Ni/Cu)-based metallization in the solar cell. In this study, material characterization aspects of the Ni seed layer and Ni silicide formation at different bath conditions and annealing temperatures on the n-side of a silicon diode structure have been examined to achieve the optimum cell contacts. The effects of morphology and chemical composition of Ni film on its electrical conductivity were evaluated and described by a quantum mechanical model. It has been found that correlation exists between the theoretical and experimental conductivity of Ni film. Residual stress and phase transformation of Ni silicide as a function of annealing temperature were evaluated using Raman and XRD techniques. Finally, transmission line measurement (TLM) technique was employed to determine the contact resistance of Ni/Si stack after thermal treatment and to understand its correlation with the chemical-structural properties. Results indicated that low electrical resistive mono-silicide (NiSi) phase as low as 5 mΩ.cm2 was obtained.

Large-area Co-silicide nanodot arrays produced by colloidal nanosphere lithography and thermal annealing.

PubMed

Cheng, S L; Wong, S L; Lu, S W; Chen, H

2008-09-01

We report here the successful fabrication of large-area size-tunable periodic arrays of cobalt and Co-silicide nanodots on silicon substrates by employing the colloidal nanosphere lithography (NSL) technique and heat treatments. The growth of low-resistivity epitaxial CoSi(2) was found to be more favorable for the samples with smaller Co nanodot sizes. The sizes of the epitaxial CoSi(2) nanodots can be tuned from 50 to 100 nm by varying the diameter of the colloidal spheres and annealing temperatures. The epitaxial CoSi(2) nanodots were found to grow with an epitaxial orientation with respect to the (001)Si substrates: [001]CoSi(2)//[001]Si and (200)CoSi(2)//(400)Si. From the results of planview HRTEM, XTEM, and SAED analysis, the epitaxial CoSi(2) nanodots were identified to be inverse pyramids in shape, and the average sizes of the faceted silicide nanodots were measured to decrease with annealing temperature. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to facilitate the growth of a variety of well-ordered silicide nanodots with selected shape, size, and periodicity.

Electrical characterization of n/p-type nickel silicide/silicon junctions by Sb segregation.

PubMed

Jun, Myungsim; Park, Youngsam; Hyun, Younghoon; Choi, Sung-Jin; Zyung, Taehyung; Jang, Moongyu

2011-08-01

In this paper, n/p-type nickel-silicided Schottky diodes were fabricated by incorporating antimony atoms near the nickel silicide/Si junction interface and the electrical characteristics were studied through measurements and simulations. The effective Schottky barrier height (SBH) for electron, extracted from the thermionic emission model, drastically decreased from 0.68 to less than 0.1 eV while that for hole slightly increased from 0.43 to 0.53 eV. In order to identify the current conduction mechanisms, the experimental current-temperature-voltage characteristics for the n-type diode were fitted based on various models for transport of charge carrier in Schottky diodes. As the result, the large change in effective SBH for electron is ascribed to trap-assisted tunneling rather than barrier height inhomogeneity.

The formation of magnetic silicide Fe3Si clusters during ion implantation

NASA Astrophysics Data System (ADS)

Balakirev, N.; Zhikharev, V.; Gumarov, G.

2014-05-01

A simple two-dimensional model of the formation of magnetic silicide Fe3Si clusters during high-dose Fe ion implantation into silicon has been proposed and the cluster growth process has been computer simulated. The model takes into account the interaction between the cluster magnetization and magnetic moments of Fe atoms random walking in the implanted layer. If the clusters are formed in the presence of the external magnetic field parallel to the implanted layer, the model predicts the elongation of the growing cluster in the field direction. It has been proposed that the cluster elongation results in the uniaxial magnetic anisotropy in the plane of the implanted layer, which is observed in iron silicide films ion-beam synthesized in the external magnetic field.

Thermoelectric silicides: A review

NASA Astrophysics Data System (ADS)

Nozariasbmarz, Amin; Agarwal, Aditi; Coutant, Zachary A.; Hall, Michael J.; Liu, Jie; Liu, Runze; Malhotra, Abhishek; Norouzzadeh, Payam; Öztürk, Mehmet C.; Ramesh, Viswanath P.; Sargolzaeiaval, Yasaman; Suarez, Francisco; Vashaee, Daryoosh

2017-05-01

Traditional research on thermoelectric materials focused on improving the figure-of-merit z T to enhance the energy conversion efficiency. With further growth and commercialization of thermoelectric technology beyond niche applications, other factors such as materials availability, toxicity, cost, recyclability, thermal stability, chemical and mechanical properties, and ease of fabrication become important for making viable technologies. Several silicide alloys were identified that have the potential to fulfill these requirements. These materials are of interest due to their abundancy in earth’s crust (e.g., silicon), non-toxicity, and good physical and chemical properties. In this paper, an overview of the silicide thermoelectrics from traditional alloys to advanced material structures is presented. In addition, some of the most effective approaches as well as fundamental physical concepts for designing and developing efficient thermoelectric materials are presented and future perspectives are discussed.

Enhanced light absorption in waveguide Schottky photodetector integrated with ultrathin metal/silicide stripe.

PubMed

Guo, Jingshu; Wu, Zhiwei; Zhao, Yanli

2017-05-01

We investigate the light absorption enhancement in waveguide Schottky photodetector integrated with ultrathin metal/silicide stripe, which can provide high internal quantum efficiency. By using aab0-quasi-TE hybrid modes for the first time, a high absorptance of 95.6% is achieved in 5 nm thick Au stripe with area of only 0.14 μm², without using resonance structure. In theory, the responsivity, dark current, and 3dB bandwidth of the corresponding device are 0.146 A/W, 8.03 nA, and 88 GHz, respectively. For most silicides, the quasi-TM mode should be used in this device, and an optimized PtSi device has a responsivity of 0.71 A/W and a dark current of 35.9 μA.

Titanium-based silicide quantum dot superlattices for thermoelectrics applications.

PubMed

Savelli, Guillaume; Stein, Sergio Silveira; Bernard-Granger, Guillaume; Faucherand, Pascal; Montès, Laurent; Dilhaire, Stefan; Pernot, Gilles

2015-07-10

Ti-based silicide quantum dot superlattices (QDSLs) are grown by reduced-pressure chemical vapor deposition. They are made of titanium-based silicide nanodots scattered in an n-doped SiGe matrix. This is the first time that such nanostructured materials have been grown in both monocrystalline and polycrystalline QDSLs. We studied their crystallographic structures and chemical properties, as well as the size and the density of the quantum dots. The thermoelectric properties of the QDSLs are measured and compared to equivalent SiGe thin films to evaluate the influence of the nanodots. Our studies revealed an increase in their thermoelectric properties-specifically, up to a trifold increase in the power factor, with a decrease in the thermal conductivity-making them very good candidates for further thermoelectric applications in cooling or energy-harvesting fields.

Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pizzocchero, Filippo; Bøggild, Peter; Booth, Timothy J.

We show that surface arc-discharge deposited carbon plays a critical intermediary role in the breakdown of thermally grown oxide diffusion barriers of 90 nm on a silicon wafer at 1035 °C in an Ar/H{sub 2} atmosphere, resulting in the formation of epitaxial copper silicide particles in ≈ 10 μm wide channels, which are aligned with the intersections of the (100) surface of the wafer and the (110) planes on an oxidized silicon wafer, as well as endotaxial copper silicide nanoparticles within the wafer bulk. We apply energy dispersive x-ray spectroscopy, in combination with scanning and transmission electron microscopy of focusedmore » ion beam fabricated lammelas and trenches in the structure to elucidate the process of their formation.« less

Characteristics of a promising new thermoelectric material - Ruthenium silicide

NASA Technical Reports Server (NTRS)

Ohta, Toshitaka; Vining, Cronin B.; Allevato, Camillo E.

1991-01-01

A preliminary study on arc-melted samples has indicated that ruthenium silicide has the potential to obtain figure-of-merit values four times higher than that of conventional silicon-germanium material. In order to realize the high figure-of-merit values, high-quality crystal from the melt is needed. A Bridgman-like method has been employed and has realized much better crystals than arc-melted ones.

Stacked Metal Silicide/Silicon Far-Infrared Detectors

NASA Technical Reports Server (NTRS)

Maserjian, Joseph

1988-01-01

Selective doping of silicon in proposed metal silicide/silicon Schottky-barrier infrared photodetector increases maximum detectable wavelength. Stacking layers to form multiple Schottky barriers increases quantum efficiency of detector. Detectors of new type enhance capabilities of far-infrared imaging arrays. Grows by molecular-beam epitaxy on silicon waferscontaining very-large-scale integrated circuits. Imaging arrays of detectors made in monolithic units with image-preprocessing circuitry.

On the Alloying and Properties of Tetragonal Nb₅Si₃ in Nb-Silicide Based Alloys.

PubMed

Tsakiropoulos, Panos

2018-01-04

The alloying of Nb₅Si₃ modifies its properties. Actual compositions of (Nb,TM)₅X₃ silicides in developmental alloys, where X = Al + B + Ge + Si + Sn and TM is a transition and/or refractory metal, were used to calculate the composition weighted differences in electronegativity (Δχ) and an average valence electron concentration (VEC) and the solubility range of X to study the alloying and properties of the silicide. The calculations gave 4.11 < VEC < 4.45, 0.103 < Δχ < 0.415 and 33.6 < X < 41.6 at.%. In the silicide in Nb-24Ti-18Si-5Al-5Cr alloys with single addition of 5 at.% B, Ge, Hf, Mo, Sn and Ta, the solubility range of X decreased compared with the unalloyed Nb₅Si₃ or exceeded 40.5 at.% when B was with Hf or Mo or Sn and the Δχ decreased with increasing X. The Ge concentration increased with increasing Ti and the Hf concentration increased and decreased with increasing Ti or Nb respectively. The B and Sn concentrations respectively decreased and increased with increasing Ti and also depended on other additions in the silicide. The concentration of Sn was related to VEC and the concentrations of B and Ge were related to Δχ. The alloying of Nb₅Si₃ was demonstrated in Δχ versus VEC maps. Effects of alloying on the coefficient of thermal expansion (CTE) anisotropy, Young's modulus, hardness and creep data were discussed. Compared with the hardness of binary Nb₅Si₃ (1360 HV), the hardness increased in silicides with Ge and dropped below 1360 HV when Al, B and Sn were present without Ge. The Al effect on hardness depended on other elements substituting Si. Sn reduced the hardness. Ti or Hf reduced the hardness more than Cr in Nb₅Si₃ without Ge. The (Nb,Hf)₅(Si,Al)₃ had the lowest hardness. VEC differentiated the effects of additions on the hardness of Nb₅Si₃ alloyed with Ge. Deterioration of the creep of alloyed Nb₅Si₃ was accompanied by decrease of VEC and increase or decrease of Δχ depending on alloying addition(s).

Moissanite (SiC) with metal-silicide and silicon inclusions from tuff of Israel: Raman spectroscopy and electron microscope studies

NASA Astrophysics Data System (ADS)

Dobrzhinetskaya, Larissa; Mukhin, Pavel; Wang, Qin; Wirth, Richard; O'Bannon, Earl; Zhao, Wenxia; Eppelbaum, Lev; Sokhonchuk, Tatiana

2018-06-01

Here, we present studies of natural SiC that occurs in situ in tuff related to the Miocene alkaline basalt formation deposited in northern part of Israel. Raman spectroscopy, SEM and FIB-assisted TEM studies revealed that SiC is primarily hexagonal polytypes 4H-SiC and 6H-SiC, and that the 4H-SiC polytype is the predominant phase. Both SiC polytypes contain crystalline inclusions of silicon (Sio) and inclusions of metal-silicide with varying compositions (e.g. Si58V25Ti12Cr3Fe2, Si41Fe24Ti20Ni7V5Zr3, and Si43Fe40Ni17). The silicides crystal structure parameters match Si2TiV5 (Pm-3m space group, cubic), FeSi2Ti (Pbam space group, orthorhombic), and FeSi2 (Cmca space group, orthorhombic) respectively. We hypothesize that SiC was formed in a local ultra-reduced environment at respectively shallow depths (60-100 km), through a reaction of SiO2 with highly reducing fluids (H2O-CH4-H2-C2H6) arisen from the mantle "hot spot" and passing through alkaline basalt magma reservoir. SiO2 interacting with the fluids may originate from the walls of the crustal rocks surrounding this magmatic reservoir. This process led to the formation of SiC and accompanied by the reducing of metal-oxides to native metals, alloys, and silicides. The latter were trapped by SiC during its growth. Hence, interplate "hot spot" alkali basalt volcanism can now be included as a geological environment where SiC, silicon, and silicides can be found.

Combined effect of Pt and W alloying elements on Ni-silicide formation

NASA Astrophysics Data System (ADS)

Luo, T.; Mangelinck, D.; Descoins, M.; Bertoglio, M.; Mouaici, N.; Hallén, A.; Girardeaux, C.

2018-03-01

A combinatorial study of the combined effect of Pt and W on Ni silicide formation is performed. Ni(Pt, W) films with thickness and composition gradients were prepared by a co-deposition composition spread technique using sputtering deposition from Pt, W, and Ni targets. The deposited Ni(Pt,W) films were characterized by X-ray diffraction, X-ray reflectivity, Rutherford backscattering, and atom probe tomography. The maximum content of alloying elements is close to 27 at. %. Simulations of the thickness and composition were carried out and compared with experimental results. In situ X-ray diffraction and atom probe tomography were used to study the phase formation. Both additive alloying elements (Pt + W) slow down the Ni consumption and the effect of W is more pronounced than the one of Pt. Regarding the effect of alloying elements on Ni silicides formation, three regions could be distinguished in the Ni(Pt,W)/Si wafer. For the region close to the Ni target, the low contents of alloying elements (Pt + W) have little impact on the phase sequence (δ-Ni2Si is the first silicide and NiSi forms when Ni is entirely consumed) but the kinetics of silicide formation slows down. The region close to the Pt target has high contents of (Pt + W) and is rich in Pt and a simultaneous phase formation of δ-Ni2Si and NiSi is observed. For the high (Pt + W) contents and W-rich region, NiSi forms unexpectedly before δ-Ni2Si and the subsequent growth of δ-Ni2Si is accompanied by the NiSi consumption. When Ni is entirely consumed, NiSi regrows at the expense of δ-Ni2Si.

Evaluation of Two Miniplate Systems and Figure-of-eight Bandages for Stabilization of Experimentally Induced Ulnar and Radial Fractures in Pigeons ( Columba livia ).

PubMed

Bennert, Beatrice M; Kircher, Patrick R; Gutbrod, Andreas; Riechert, Juliane; Hatt, Jean-Michel

2016-06-01

Although plate fixation has advantages over other fixation methods for certain indications, it is rarely used in avian surgery, especially in birds that weigh less than 1000 g. Exceptionally small plating systems for these birds are required, which are relatively expensive and difficult to insert. To study avian fracture healing after repair using miniplates, we evaluated 2 steel miniplate systems in 27 pigeons ( Columba livia ) divided into 4 groups. In each pigeon, the left ulna and radius were transected and the ulna was repaired with a bone plate. In groups A and B, a 1.3-mm adaption plate was applied without and with a figure-of-eight bandage; in groups C and D, a 1.0-mm compression plate was applied without and with a bandage, respectively. Healing was evaluated with radiographs after 3, 14, and 28 days; flight tests were conducted after 14, 21, and 28 days; and the wing was macroscopically examined after euthanasia of birds on day 28. Fractures healed without bending or distortion of the plate in all 27 birds, and no significant differences in healing were found between treatment groups. At the end of the study, 23 pigeons (85.2%) showed good or very good flight ability. Results show the 1.3-mm adaption plate and the 1.0-mm compression plate meet the requirements for avian osteosynthesis and can be recommended for fracture repair of the ulna or other long bones in birds weighing less than 500 g. The application of a figure-of-eight bandage might be beneficial in fracture healing.

Revisiting the stability of mini-implants used for orthodontic anchorage.

PubMed

Yao, Chung-Chen Jane; Chang, Hao-Hueng; Chang, Jenny Zwei-Chieng; Lai, Hsiang-Hua; Lu, Shao-Chun; Chen, Yi-Jane

2015-11-01

The aim of this study is to comprehensively analyze the potential factors affecting the failure rates of three types of mini-implants used for orthodontic anchorage. Data were collected on 727 mini-implants (miniplates, predrilled titanium miniscrews, and self-drilling stainless steel miniscrews) in 220 patients. The factors related to mini-implant failure were investigated using a Chi-square test for univariate analysis and a generalized estimating equation model for multivariate analysis. The failure rate for miniplates was significantly lower than for miniscrews. All types of mini-implants, especially the self-drilling stainless steel miniscrews, showed decreased stability if the previous implantation had failed. The stability of predrilled titanium miniscrews and self-drilling stainless steel miniscrews were comparable at the first implantation. However, the failure rate of stainless steel miniscrews increased at the second implantation. The univariate analysis showed that the following variables had a significant influence on the failure rates of mini-implants: age of patient, type of mini-implant, site of implantation, and characteristics of the soft tissue around the mini-implants. The generalized estimating equation analysis revealed that mini-implants with miniscrews used in patients younger than 35 years, subjected to orthodontic loading after 30 days and implanted on the alveolar bone ridge, have a significantly higher risk of failure. This study revealed that once the dental surgeon becomes familiar with the procedure, the stability of orthodontic mini-implants depends on the type of mini-implant, age of the patient, implantation site, and the healing time of the mini-implant. Miniplates are a more feasible anchorage system when miniscrews fail repeatedly. Copyright © 2014. Published by Elsevier B.V.

Angular Stable Miniplate Fixation of Chronic Unstable Scaphoid Nonunion.

PubMed

Schormans, Philip M J; Brink, Peter R G; Poeze, Martijn; Hannemann, Pascal F W

2018-02-01

Background  Around 5 to 15% of all scaphoid fractures result in nonunion. Treatment of long-lasting scaphoid nonunion remains a challenge for the treating surgeon. Healing of scaphoid nonunion is essential for prevention of scaphoid nonunion advanced collapse and the subsequent predictable pattern of radiocarpal osteoarthritis. Purpose  The purpose of this study was to investigate the feasibility of fixation of the scaphoid nonunion with a volar angular stable miniplate and cancellous bone grafting. We hypothesized that this technique could be successful, even in patients with previous surgery for nonunion and in patients with a long duration of nonunion. Patients and Methods  A total of 21 patients enrolled in a single-center prospective cohort study. Healing of nonunion was assessed on multiplanar computed tomography scan of the wrist at a 3-month interval. Functional outcome was assessed by measuring grip strength, range of motion, and by means of the patient-rated wrist and hand evaluation (PRWHE) questionnaire. Results  During follow-up, 19 out of 21 patients (90%) showed radiological healing of the nonunion. The range of motion did not improve significantly. Postoperative PRWHE scores decreased by 34 points. Healing occurred regardless of the length of time of the nonunion (range: 6-183 months) and regardless of previous surgery (38% of patients). Conclusion  Volar angular stable miniplate fixation with autologous cancellous bone grafting is a successful technique for the treatment of chronic unstable scaphoid nonunion, even in patients with long-lasting nonunion and in patients who underwent previous surgery for a scaphoid fracture. Rotational interfragmentary stability might be an important determining factor for the successful treatment of unstable scaphoid nonunion. Level of Evidence  Level IV.

Growth of single-crystalline cobalt silicide nanowires and their field emission property.

PubMed

Lu, Chi-Ming; Hsu, Han-Fu; Lu, Kuo-Chang

2013-07-03

In this work, cobalt silicide nanowires were synthesized by chemical vapor deposition processes on Si (100) substrates with anhydrous cobalt chloride (CoCl2) as precursors. Processing parameters, including the temperature of Si (100) substrates, the gas flow rate, and the pressure of reactions were varied and studied; additionally, the physical properties of the cobalt silicide nanowires were measured. It was found that single-crystal CoSi nanowires were grown at 850°C ~ 880°C and at a lower gas flow rate, while single-crystal Co2Si nanowires were grown at 880°C ~ 900°C. The crystal structure and growth direction were identified, and the growth mechanism was proposed as well. This study with field emission measurements demonstrates that CoSi nanowires are attractive choices for future applications in field emitters.

Contacts to Semiconductor Nanowires

DTIC Science & Technology

2009-10-03

SiNW diameters and the amount of metal deposited, or alternatively, the atomic ratio between Pt and Si. The uniformity of the silicided NWs was...program. The Schottky contact is a metal silicide formed by rapid thermal annealing of the deposited contact metal . The θ- Ni2Si/n-Si NW Schottky...decision. unless so designated by other documentation. 14. ABSTRACT Metal contacts to semiconductor nanowires share similarities with their thin-film

SeaFrame: Building an Affordable Future Fleet. Volume 6, Issue 1, 2010

DTIC Science & Technology

2010-01-01

metal alloy combinations, but are up against a long design cycle in getting to know how the complex interplay between new...the heat treatment process. Magnesium silicide nanoparticles come out during heat treatment to strengthen the alloy, and engineers found it...already had valid data we could work with.” To help accurately model the magnesium silicide particles, called a precipitate, in the AA6082

Oxidation Resistance of Alloys from Nb-Si-Cr System for High Temperature Applications

DTIC Science & Technology

2013-01-02

higher education for undergraduate students while prepare the graduate students for professional careers in research (at one of the ONR facilities...generate interest in students to pursue higher education for undergraduate students while prepare the graduate students for professional careers in...reduces the amount of primary a significantly but still contains a rather coarser eutectic like microconstituent. A NbßSi (3-1 silicide ) silicide phase

Copper-Silicon Bronzes

DTIC Science & Technology

1933-05-11

copper alloys which have good static properties are disa:cinting in their endurance properties. The silicide allo~rs that are given high tensile strength...works satisfactorily, but the best welds 4 have been obtained by using a flux cdmposed of 905 fused borax and i0. sodium fluoride., The flux is...properties re- main almost the same. Grain size increases with sil- icon. III A study of hardening copper by heat treating its alloys with silicides

Plasma-Enhanced Deposition and Processing of Transition Metals and Transition Metal Silicides for VLSI.

DTIC Science & Technology

1986-05-20

molybdenum trifluoride in the deposited material. Titanium silicide films formed from a discharge of titanium tetrachlotide, silane, and hydrogen...displayed resistivities of -150 /4-cm, due to small amounts of oxygen and chlorine incorporated during deposition. Plasma etching studies of tungsten films...material, thereby reducing speed, and aluminum is a low melting material, thereby limiting processing latitude. As a result, mmition metals and

Long-Wavelength Infrared Surface Plasmons on Ga-Doped ZnO Films Excited via 2D Hole Arrays for Extraordinary Optical Transmission (Preprint)

DTIC Science & Technology

2013-10-01

Express 1, 1090-1099 (2011). [16] Soref, R., Peale, R. E., and Buchwald, W., “Longwave plasmonics on doped silicon and silicides ,” Opt. Express 16, 6507...Soref, R., Drehman, A., and Buchwald, W.R., “IR permittivities for silicides and doped silicon,” J. Opt. Soc. Am. B 27, 730-734 (2010). [19] Ginn

Electrical and optical properties of sub-10 nm nickel silicide films for silicon solar cells

NASA Astrophysics Data System (ADS)

Brahmi, Hatem; Ravipati, Srikanth; Yarali, Milad; Shervin, Shahab; Wang, Weijie; Ryou, Jae-Hyun; Mavrokefalos, Anastassios

2017-01-01

Highly conductive and transparent films of ultra-thin p-type nickel silicide films have been prepared by RF magnetron sputtering of nickel on silicon substrates followed by rapid thermal annealing in an inert environment in the temperature range 400-600 °C. The films are uniform throughout the wafer with thicknesses in the range of 3-6 nm. The electrical and optical properties are presented for nickel silicide films with varying thickness. The Drude-Lorentz model and Fresnel equations were used to calculate the dielectric properties, sheet resistance, absorption and transmission of the films. These ultrathin nickel silicide films have excellent optoelectronic properties for p-type contacts with optical transparencies up to 80% and sheet resistance as low as ~0.15 µΩ cm. Furthermore, it was shown that the use of a simple anti-reflection (AR) coating can recover most of the reflected light approaching the values of a standard Si solar cell with the same AR coating. Overall, the combination of ultra-low thickness, high transmittance, low sheet resistance and ability to recover the reflected light by utilizing standard AR coating makes them ideal for utilization in silicon based photovoltaic technologies as a p-type transparent conductor.

Low-Temperature Wet Conformal Nickel Silicide Deposition for Transistor Technology through an Organometallic Approach.

PubMed

Lin, Tsung-Han; Margossian, Tigran; De Marchi, Michele; Thammasack, Maxime; Zemlyanov, Dmitry; Kumar, Sudhir; Jagielski, Jakub; Zheng, Li-Qing; Shih, Chih-Jen; Zenobi, Renato; De Micheli, Giovanni; Baudouin, David; Gaillardon, Pierre-Emmanuel; Copéret, Christophe

2017-02-08

The race for performance of integrated circuits is nowadays facing a downscale limitation. To overpass this nanoscale limit, modern transistors with complex geometries have flourished, allowing higher performance and energy efficiency. Accompanying this breakthrough, challenges toward high-performance devices have emerged on each significant step, such as the inhomogeneous coverage issue and thermal-induced short circuit issue of metal silicide formation. In this respect, we developed a two-step organometallic approach for nickel silicide formation under near-ambient temperature. Transmission electron and atomic force microscopy show the formation of a homogeneous and conformal layer of NiSi x on pristine silicon surface. Post-treatment decreases the carbon content to a level similar to what is found for the original wafer (∼6%). X-ray photoelectron spectroscopy also reveals an increasing ratio of Si content in the layer after annealing, which is shown to be NiSi 2 according to X-ray absorption spectroscopy investigation on a Si nanoparticle model. I-V characteristic fitting reveals that this NiSi 2 layer exhibits a competitive Schottky barrier height of 0.41 eV and series resistance of 8.5 Ω, thus opening an alternative low-temperature route for metal silicide formation on advanced devices.

The effect of thermomechanical processing on second phase particle redistribution in U-10 wt%Mo

NASA Astrophysics Data System (ADS)

Hu, Xiaohua; Wang, Xiaowo; Joshi, Vineet V.; Lavender, Curt A.

2018-03-01

The multi-pass hot-rolling process of an annealed uranium-10 wt% molybdenum (U10Mo) coupon was studied by plane-strain compression finite element modeling. As-cast U10Mo typically contains second phase particles such as uranium carbides (UC) and silicides along the grain boundaries. The volume fraction of UC is typically large, while the other phases can be redissolved in the matrix by certain heat treatments. The UC particle distribution is important due to its influence on the recrystallization processes (particle stimulated nucleation) that occur during annealing between rolling passes. Unfavorable particle distribution and fracture after rolling can affect the grain size and also influence the fuel performance in the reactor. A statistical method, i.e., the two-point correlation function (2PCF), was used to analyze the carbide particle distribution after each rolling reduction. The hot rolling simulation results show that the alignment of UC particles along grain boundaries will rotate during rolling until it is parallel to the rolling direction, to form stringer-like distributions which are typically observed in rolled products that contain inclusions. 2PCF analysis shows that the interparticle spacing shrinks along the normal direction (ND) and increases along the rolling direction (RD). The simulated particle distribution is very similar to that measured experimentally for similar rolling reductions. The magnitudes of major peaks of 2PCF along the ND decrease after large reduction. The locations of major peaks indicate the inter-stringer distances. Many more small peaks appear for the 2PCF along the RD, and this is related to the neighboring particles within stringers, which are along the RD.

Development and fabrication of improved Schottky power diodes, phases I and II

NASA Technical Reports Server (NTRS)

Cordes, L. F.; Garfinkle, M.; Taft, E. A.

1974-01-01

Reproducible methods for the fabrication of silicon Schottky diodes were developed for the metals tungsten, aluminum, conventional platinum silicide and low temperature platinum silicide. Barrier heights and barrier lowering were measured permitting the accurate prediction of ideal forward and reverse diode performance. Processing procedures were developed which permit the fabrication of large area (approximately 1 sqcm) mesa-geometry power Schottky diodes with forward and reverse characteristics that approach theoretical values.

Single-Crystal Material on Non-Single-Crystalline Substrate

DTIC Science & Technology

1999-02-01

point frit or solder glass can be deposited on a surface and bonded to a second surface using pressure and temperature. A sodium silicate material...interface. A metal or silicide at the bonding interface may be advantageous fQr electrical current conduction across the interface. 10 Applications...substrate, or a silicide or metal to aid bonding and vertical electrical current conduction. In some cases, it is difficult to polish the non- single

Band-to-Band Tunnel Transistor Design and Modeling for Low Power Applications

DTIC Science & Technology

2012-05-10

suggestions for reducing this burden, to Washington Headquarters Services , Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway...Fabrication 4.3 Analysis of the Silicided Source TFET 4.4 Subthreshold Swing Data Quality Analysis 4.5 Selective Silicide Using Germanium 4.6... International Electron Devices Meeting (IEDM) Short Course, 2007 [1.3] W. Y. Choi, B.-K. Park, J. D. Lee, and T.-J. King Liu, “Tunneling Field-Effect

Effect of Saturation Pressure Difference on Metal–Silicide Nanopowder Formation in Thermal Plasma Fabrication

PubMed Central

Shigeta, Masaya; Watanabe, Takayuki

2016-01-01

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size–composition distribution for a metal–silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal–silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder. PMID:28344300

In-pile test results of U-silicide or U-nitride coated U-7Mo particle dispersion fuel in Al

NASA Astrophysics Data System (ADS)

Kim, Yeon Soo; Park, J. M.; Lee, K. H.; Yoo, B. O.; Ryu, H. J.; Ye, B.

2014-11-01

U-silicide or U-nitride coated U-Mo particle dispersion fuel in Al (U-Mo/Al) was in-pile tested to examine the effectiveness of the coating as a diffusion barrier between the U-7Mo fuel kernels and Al matrix. This paper reports the PIE data and analyses focusing on the effectiveness of the coating in terms of interaction layer (IL) growth and general fuel performance. The U-silicide coating showed considerable success, but it also provided evidence for additional improvement for coating process. The U-nitride coated specimen showed largely inefficient results in reducing IL growth. From the test, important observations were also made that can be utilized to improve U-Mo/Al fuel performance. The heating process for coating turned out to be beneficial to suppress fuel swelling. The use of larger fuel particles confirmed favorable effects on fuel performance.

Vertically grown multiwalled carbon nanotube anode and nickel silicide integrated high performance microsized (1.25 μL) microbial fuel cell.

PubMed

Mink, Justine E; Rojas, Jhonathan P; Logan, Bruce E; Hussain, Muhammad M

2012-02-08

Microbial fuel cells (MFCs) are an environmentally friendly method for water purification and self-sustained electricity generation using microorganisms. Microsized MFCs can also be a useful power source for lab-on-a-chip and similar integrated devices. We fabricated a 1.25 μL microsized MFC containing an anode of vertically aligned, forest type multiwalled carbon nanotubes (MWCNTs) with a nickel silicide (NiSi) contact area that produced 197 mA/m(2) of current density and 392 mW/m(3) of power density. The MWCNTs increased the anode surface-to-volume ratio, which improved the ability of the microorganisms to couple and transfer electrons to the anode. The use of nickel silicide also helped to boost the output current by providing a low resistance contact area to more efficiently shuttle electrons from the anode out of the device. © 2012 American Chemical Society

On the diffraction pattern of bundled rare-earth silicide nanowires on Si(0 0 1).

PubMed

Timmer, F; Bahlmann, J; Wollschläger, J

2017-11-01

Motivated by the complex diffraction pattern observed for bundled rare-earth silicide nanowires on the Si(0 0 1) surface, we investigate the influence of the width and the spacing distribution of the nanowires on the diffraction pattern. The diffraction pattern of the bundled rare-earth silicide nanowires is analyzed by the binary surface technique applying a kinematic approach to diffraction. Assuming a categorical distribution for the (individual) nanowire size and a Poisson distribution for the size of the spacing between adjacent nanowire-bundles, we are able to determine the parameters of these distributions and derive an expression for the distribution of the nanowire-bundle size. Additionally, the comparison of our simulations to the experimental diffraction pattern reveal that a (1  ×  1)-periodicity on top of the nanowires has to be assumed for a good match.

Development of a fused slurry silicide coating for the protection of tantalum alloys

NASA Technical Reports Server (NTRS)

Packer, C. M.; Perkins, R. A.

1974-01-01

Results are reported of a research program to develop a reliable high-performance, fused slurry silicide protective coating for a tantalum-10 tungsten alloy for use at 1427 to 1538 C at 0.1 to 10 torr air pressure under cyclic temperature conditions. A review of silicide coating performance under these conditions indicated that the primary wear-out mode is associated with widening of hairline fissures in the coating. Consideration has been given to modifying the oxidation products that form on the coating surface to provide a seal for these fissures and to minimize their widening. On the basis of an analysis of the phase relationships between silica and various other oxides, a coating having the slurry composition 2.5Mn-33Ti-64.5Si was developed that is effective in the pressure range from 1 to 10 torr.

Versatile Titanium Silicide Monolayers with Prominent Ferromagnetic, Catalytic, and Superconducting Properties: Theoretical Prediction.

PubMed

Wu, Qisheng; Zhang, Jun-Jie; Hao, Peipei; Ji, Zhongyang; Dong, Shuai; Ling, Chongyi; Chen, Qian; Wang, Jinlan

2016-10-06

On the basis of global structure search and density functional theory calculations, we predict a new class of two-dimensional (2D) materials, titanium silicide (Ti 2 Si, TiSi 2 , and TiSi 4 ) monolayers. They are proved to be energetically, dynamically, and thermally stable and own excellent mechanical properties. Among them, Ti 2 Si is a ferromagnetic metal with a magnetic moment of 1.37 μ B /cell, while TiSi 2 is an ideal catalyst for the hydrogen evolution reaction with a nearly zero free energy of hydrogen adsorption. More importantly, electron-phonon coupling calculations suggest that TiSi 4 is a robust 2D phonon-mediated superconductor with a transition temperature of 5.8 K, and the transition temperature can be enhanced up to 11.7 K under a suitable external strain. The versatility makes titanium silicide monolayers promising candidates for spintronic materials, hydrogen evolution catalysts, and 2D superconductors.

Effect of Saturation Pressure Difference on Metal-Silicide Nanopowder Formation in Thermal Plasma Fabrication.

PubMed

Shigeta, Masaya; Watanabe, Takayuki

2016-03-07

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size-composition distribution for a metal-silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal-silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder.

Growth of single-crystalline cobalt silicide nanowires and their field emission property

PubMed Central

2013-01-01

In this work, cobalt silicide nanowires were synthesized by chemical vapor deposition processes on Si (100) substrates with anhydrous cobalt chloride (CoCl2) as precursors. Processing parameters, including the temperature of Si (100) substrates, the gas flow rate, and the pressure of reactions were varied and studied; additionally, the physical properties of the cobalt silicide nanowires were measured. It was found that single-crystal CoSi nanowires were grown at 850°C ~ 880°C and at a lower gas flow rate, while single-crystal Co2Si nanowires were grown at 880°C ~ 900°C. The crystal structure and growth direction were identified, and the growth mechanism was proposed as well. This study with field emission measurements demonstrates that CoSi nanowires are attractive choices for future applications in field emitters. PMID:23819795

Study of optical and luminescence properties of silicon — semiconducting silicide — silicon multilayer nanostructures

NASA Astrophysics Data System (ADS)

Galkin, N. G.; Galkin, K. N.; Dotsenko, , S. A.; Goroshko, D. L.; Shevlyagin, A. V.; Chusovitin, E. A.; Chernev, I. M.

2017-01-01

By method of in situ differential spectroscopy it was established that at the formation of monolayer Fe, Cr, Ca, Mg silicide and Mg stannide islands on the atomically clean silicon surface an appearance of loss peaks characteristic for these materials in the energy range of 1.1-2.6 eV is observed. An optimization of growth processes permit to grow monolithic double nanoheterostructures (DNHS) with embedded Fe, Cr and Ca nanocrystals, and also polycrystalline DNHS with NC of Mg silicide and Mg stannide and Ca disilicide. By methods of optical spectroscopy and Raman spectroscopy it was shown that embedded NC form intensive peaks in the reflectance spectra at energies up to 2.5 eV and Raman peaks. In DNS with β-FeSi2 NC a photoluminescence and electroluminescence at room temperature were firstly observed.

A long-term ultrahigh temperature application of layered silicide coated Nb alloy in air

NASA Astrophysics Data System (ADS)

Sun, Jia; Fu, Qian-Gang; Li, Tao; Wang, Chen; Huo, Cai-Xia; Zhou, Hong; Yang, Guan-Jun; Sun, Le

2018-05-01

Nb-based alloy possessed limited application service life at ultrahigh temperature (>1400 °C) in air even taking the effective protective coating strategy into consideration for last decades. In this work a long duration of above 128 h at 1500 °C in air was successfully achieved on Nb-based alloy thanked to multi-layered silicide coating. Through optimizing interfaces, the MoSi2/NbSi2 silicide coating with Al2O3-adsorbed-particles layer exhibited three-times higher of oxidation resistance capacity than the one without it. In MoSi2-Al2O3-NbSi2 multilayer coating, the Al2O3-adsorbed-particles layer playing as an element-diffusion barrier role, as well as the formed porous Nb5Si3 layer as a stress transition zone, contributed to the significant improvement.

Thermal transport across metal silicide-silicon interfaces: An experimental comparison between epitaxial and nonepitaxial interfaces

NASA Astrophysics Data System (ADS)

Ye, Ning; Feser, Joseph P.; Sadasivam, Sridhar; Fisher, Timothy S.; Wang, Tianshi; Ni, Chaoying; Janotti, Anderson

2017-02-01

Silicides are used extensively in nano- and microdevices due to their low electrical resistivity, low contact resistance to silicon, and their process compatibility. In this work, the thermal interface conductance of TiSi2, CoSi2, NiSi, and PtSi are studied using time-domain thermoreflectance. Exploiting the fact that most silicides formed on Si(111) substrates grow epitaxially, while most silicides on Si(100) do not, we study the effect of epitaxy, and show that for a wide variety of interfaces there is no dependence of interface conductance on the detailed structure of the interface. In particular, there is no difference in the thermal interface conductance between epitaxial and nonepitaxial silicide/silicon interfaces, nor between epitaxial interfaces with different interface orientations. While these silicide-based interfaces yield the highest reported interface conductances of any known interface with silicon, none of the interfaces studied are found to operate close to the phonon radiation limit, indicating that phonon transmission coefficients are nonunity in all cases and yet remain insensitive to interfacial structure. In the case of CoSi2, a comparison is made with detailed computational models using (1) full-dispersion diffuse mismatch modeling (DMM) including the effect of near-interfacial strain, and (2) an atomistic Green' function (AGF) approach that integrates near-interface changes in the interatomic force constants obtained through density functional perturbation theory. Above 100 K, the AGF approach significantly underpredicts interface conductance suggesting that energy transport does not occur purely by coherent transmission of phonons, even for epitaxial interfaces. The full-dispersion DMM closely predicts the experimentally observed interface conductances for CoSi2, NiSi, and TiSi2 interfaces, while it remains an open question whether inelastic scattering, cross-interfacial electron-phonon coupling, or other mechanisms could also account for the high-temperature behavior. The effect of degenerate semiconductor dopant concentration on metal-semiconductor thermal interface conductance was also investigated with the result that we have found no dependencies of the thermal interface conductances up to (n or p type) ≈1 ×1019 cm-3, indicating that there is no significant direct electronic transport and no transport effects that depend on long-range metal-semiconductor band alignment.

On the Alloying and Properties of Tetragonal Nb5Si3 in Nb-Silicide Based Alloys

PubMed Central

Tsakiropoulos, Panos

2018-01-01

The alloying of Nb5Si3 modifies its properties. Actual compositions of (Nb,TM)5X3 silicides in developmental alloys, where X = Al + B + Ge + Si + Sn and TM is a transition and/or refractory metal, were used to calculate the composition weighted differences in electronegativity (Δχ) and an average valence electron concentration (VEC) and the solubility range of X to study the alloying and properties of the silicide. The calculations gave 4.11 < VEC < 4.45, 0.103 < Δχ < 0.415 and 33.6 < X < 41.6 at.%. In the silicide in Nb-24Ti-18Si-5Al-5Cr alloys with single addition of 5 at.% B, Ge, Hf, Mo, Sn and Ta, the solubility range of X decreased compared with the unalloyed Nb5Si3 or exceeded 40.5 at.% when B was with Hf or Mo or Sn and the Δχ decreased with increasing X. The Ge concentration increased with increasing Ti and the Hf concentration increased and decreased with increasing Ti or Nb respectively. The B and Sn concentrations respectively decreased and increased with increasing Ti and also depended on other additions in the silicide. The concentration of Sn was related to VEC and the concentrations of B and Ge were related to Δχ. The alloying of Nb5Si3 was demonstrated in Δχ versus VEC maps. Effects of alloying on the coefficient of thermal expansion (CTE) anisotropy, Young’s modulus, hardness and creep data were discussed. Compared with the hardness of binary Nb5Si3 (1360 HV), the hardness increased in silicides with Ge and dropped below 1360 HV when Al, B and Sn were present without Ge. The Al effect on hardness depended on other elements substituting Si. Sn reduced the hardness. Ti or Hf reduced the hardness more than Cr in Nb5Si3 without Ge. The (Nb,Hf)5(Si,Al)3 had the lowest hardness. VEC differentiated the effects of additions on the hardness of Nb5Si3 alloyed with Ge. Deterioration of the creep of alloyed Nb5Si3 was accompanied by decrease of VEC and increase or decrease of Δχ depending on alloying addition(s). PMID:29300327

The impact of Ti and temperature on the stability of Nb5Si3 phases: a first-principles study

PubMed Central

Papadimitriou, Ioannis; Utton, Claire; Tsakiropoulos, Panos

2017-01-01

Abstract Nb-silicide based alloys could be used at T > 1423 K in future aero-engines. Titanium is an important additive to these new alloys where it improves oxidation, fracture toughness and reduces density. The microstructures of the new alloys consist of an Nb solid solution, and silicides and other intermetallics can be present. Three Nb5Si3 polymorphs are known, namely αNb5Si3 (tI32 Cr5B3-type, D8l), βNb5Si3 (tI32 W5Si3-type, D8m) and γNb5Si3 (hP16 Mn5Si3-type, D88). In these 5–3 silicides Nb atoms can be substituted by Ti atoms. The type of stable Nb5Si3 depends on temperature and concentration of Ti addition and is important for the stability and properties of the alloys. The effect of increasing concentration of Ti on the transition temperature between the polymorphs has not been studied. In this work first-principles calculations were used to predict the stability and physical properties of the various Nb5Si3 silicides alloyed with Ti. Temperature-dependent enthalpies of formation were computed, and the transition temperature between the low (α) and high (β) temperature polymorphs of Nb5Si3 was found to decrease significantly with increasing Ti content. The γNb5Si3 was found to be stable only at high Ti concentrations, above approximately 50 at. % Ti. Calculation of physical properties and the Cauchy pressures, Pugh’s index of ductility and Poisson ratio showed that as the Ti content increased, the bulk moduli of all silicides decreased, while the shear and elastic moduli and the Debye temperature increased for the αNb5Si3 and γNb5Si3 and decreased for βNb5Si3. With the addition of Ti the αNb5Si3 and γNb5Si3 became less ductile, whereas the βNb5Si3 became more ductile. When Ti was added in the αNb5Si3 and βNb5Si3 the linear thermal expansion coefficients of the silicides decreased, but the anisotropy of coefficient of thermal expansion did not change significantly. PMID:28740563

Anterior management of C2 fractures using miniplate fixation: outcome, function and quality of life in a case series of 15 patients.

PubMed

Franke, Axel; Bieler, Dan; Wern, Rebecca; Trotzke, Tim; Hentsch, Sebastian; Kollig, Erwin

2018-06-01

The classification systems by Anderson and D'Alonzo, Effendi, Benzel and others have limitations when it comes to morphologically categorising fractures of the second cervical vertebral body (C2) that present with or without an additional fracture of the dens or with or without an extension of the fracture line into the vertebral arch and displacement. Currently, there are no definitive recommendations for the treatment of fractures at the junction of the dens with the vertebral body of C2 on the basis of outcome and stability data. Depending on patient anatomy, either anterior or posterior approaches can be used to fuse C1 and C2 and to achieve definitive surgical stabilisation. The anterior management of C2 fractures without C1-C2 fusion has the theoretical advantage that it preserves rotational motion at this motion segment and that the anterior approach is associated with lower morbidity. In the study presented here, we followed up a group of our patients who underwent anterior miniplate fixation for C2 fractures. Fifteen patients underwent fixation of C2 fractures with titanium miniplates (Medartis Hand fixation system, 2.0 or 2.3 mm) that were placed using a submental approach. To our knowledge, this construct has not yet been described in the literature. Where necessary, this procedure was combined with screw fixation of the dens as described by Böhler. We retrospectively analysed operative reports and medical records, evaluated the patients' health status using the Short Form (36) Health Survey (SF-36), and performed clinical follow-up examinations. From January 2009 to June 2015, 226 traumatic lesions of the cervical spine were managed at our institution in the inpatient setting. Ninety-two patients underwent conservative treatment. Of the 134 cases that required surgery for fractures and instability, 67 involved the C0-C3 motion segments. In 15 patients, stability was achieved using an anterior miniplate or miniscrews alone (n = 4) or in addition to other techniques (n = 11). Anderson and D'Alonzo type II and III dens fractures with involvement of the body or lateral mass of C2 accounted for eight cases. Effendi type II body fractures with or without instability were seen in four cases. There was no perioperative mortality and morbidity in this patient group. All fractures healed and stability was achieved in all cases. No patient had neurological deficits or required revision surgery. An assessment of postoperative quality of life showed that 11 patients (7 men, 4 women) with a mean age of 57 (± 5.3) years reached an SF-36 score that was normal for their age group after a mean period of 33 (± 6.3) months following their injury. Compared to a group of healthy subjects, the patients had a range of motion that was limited only at the extremes. In patients with appropriate indications, anterior fixation with miniplates alone or additionally is a further useful treatment option in the management of fractures at the junction of the dens with the vertebral body of C2. Since this type of treatment preserves motion at the C1-C2 motion segment after fracture healing and since an anterior approach is associated with less surgical trauma than posterior instrumentation, the technique presented here should be included in a discussion on (surgical) treatment options. These slides can be retrieved under Electronic Supplementary Material.

New Possible Structure of Silicide Mg2Si under Pressure

NASA Astrophysics Data System (ADS)

Luniakov, Yu. V.

2018-05-01

As a result of an evolutionary search based on the density functional theory, a new low-symmetry structure of silicide Mg2Si under pressure was discovered. This structure can exist along with the known structures of the symmetry Pnma and P63/mmc and is stable at a pressure of about 20 GPa. The lattice parameters of the discovered structure are in better agreement with the experimental values than the lattice parameters of the known structures.

Biopropellant Engine Plume Contamination Program. Volume 1. Chamber Measurements. Phase 1

DTIC Science & Technology

1979-12-01

motor-actuated/linked bipropellant valve manufactured by Moog, Inc. The thrust chambers mechanically attached to the injector were silicide -coated...was NaCI ( sodium chloride); IR camera data were recorded from the side viewport of the lOY chamber. The flowfield viewed with the 8-deg fov lens...100, Contoured Six-Element Splash Plate (0 and 45 deg) 0.0167 (Pc = 150 psia) 100 to 300 100 to 300 0.0006 Silicide -Coated, Columbium Alloy

Symposium Q: Magnetic Thin Films, Heterostructures, and Device Materials

DTIC Science & Technology

2007-05-22

results in the formation of sodium carboxylate groups, that electronics, also known as magnetoelectronics or spintronics. Mn promoted the adsorption of...Q8.29 Magnetic Properties of Microcrystalline Si Thin films and Nickel Silicide Nanowires. Joondong Kim’, Seongjin Jang 2 , Bi-Ching Shih 2 , Hao...Buffalo, New York. The silicides , such as NiSi 2 and CoSi2 , have been attractive materials to crystallize Si and grow an epitaxial Si film with a small

Thermal Diagrams of Thermo-Electrical Devices (Selected Chapters)

DTIC Science & Technology

1974-10-09

for example silicides ) the electric-spark treatment is a long process; thus, this method is unsuitable for obtaining a large number of holes...converters for marine use were developed with useful electric power of 500- 2000 W. Sodium -potassium eutectic was used both for supplying the heat from...oxidizing mdiu•r. In view of this fact it is advisable at present to examine onlýy the silicides of certain metals that are stable under the ettnr, con

Fusion silicide coatings for tantalum alloys.

NASA Technical Reports Server (NTRS)

Warnock, R. V.; Stetson, A. R.

1972-01-01

Calculation of the performance of fusion silicide coatings under simulated atmospheric reentry conditions to a maximum temperature of 1810 K (2800 F). Both recently developed and commercially available coatings are included. Data are presented on oxidation rate with and without intentional defecting, the influence of the coatings on the ductile-brittle bend transition temperature, and the mechanical properties. Coatings appear capable of affording protection for at least 100 simulated cycles to 2600 F and 63 cycles to 2800 F.

Silicide Schottky Barrier For Back-Surface-Illuminated CCD

NASA Technical Reports Server (NTRS)

Hecht, Michael H.

1990-01-01

Quantum efficiency of back-surface-illuminated charge-coupled device (CCD) increased by coating back surface with thin layer of PtSi or IrSi on thin layer of SiO2. In its interaction with positively-doped bulk Si of CCD, silicide/oxide layer forms Schottky barrier that repels electrons, promoting accumulation of photogenerated charge carriers in front-side CCD potential wells. Physical principle responsible for improvement explained in "Metal Film Increases CCD Output" (NPO-16815).

Metallization of Large Silicon Wafers

NASA Technical Reports Server (NTRS)

Pryor, R. A.

1978-01-01

A metallization scheme was developed which allows selective plating of silicon solar cell surfaces. The system is comprised of three layers. Palladium, through the formation of palladium silicide at 300 C in nitrogen, makes ohmic contact to the silicon surface. Nickel, plated on top of the palladium silicide layer, forms a solderable interface. Lead-tin solder on the nickel provides conductivity and allows a convenient means for interconnection of cells. To apply this metallization, three chemical plating baths are employed.

Controlling the formation and stability of ultra-thin nickel silicides - An alloying strategy for preventing agglomeration

NASA Astrophysics Data System (ADS)

Geenen, F. A.; van Stiphout, K.; Nanakoudis, A.; Bals, S.; Vantomme, A.; Jordan-Sweet, J.; Lavoie, C.; Detavernier, C.

2018-02-01

The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of tc = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 ° C , thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of "thickness gradients," which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness tc. The results are discussed in the framework of classical nucleation theory.

System analysis with improved thermo-mechanical fuel rod models for modeling current and advanced LWR materials in accident scenarios

NASA Astrophysics Data System (ADS)

Porter, Ian Edward

A nuclear reactor systems code has the ability to model the system response in an accident scenario based on known initial conditions at the onset of the transient. However, there has been a tendency for these codes to lack the detailed thermo-mechanical fuel rod response models needed for accurate prediction of fuel rod failure. This proposed work will couple today's most widely used steady-state (FRAPCON) and transient (FRAPTRAN) fuel rod models with a systems code TRACE for best-estimate modeling of system response in accident scenarios such as a loss of coolant accident (LOCA). In doing so, code modifications will be made to model gamma heating in LWRs during steady-state and accident conditions and to improve fuel rod thermal/mechanical analysis by allowing axial nodalization of burnup-dependent phenomena such as swelling, cladding creep and oxidation. With the ability to model both burnup-dependent parameters and transient fuel rod response, a fuel dispersal study will be conducted using a hypothetical accident scenario under both PWR and BWR conditions to determine the amount of fuel dispersed under varying conditions. Due to the fuel fragmentation size and internal rod pressure both being dependent on burnup, this analysis will be conducted at beginning, middle and end of cycle to examine the effects that cycle time can play on fuel rod failure and dispersal. Current fuel rod and system codes used by the Nuclear Regulatory Commission (NRC) are compilations of legacy codes with only commonly used light water reactor materials, Uranium Dioxide (UO2), Mixed Oxide (U/PuO 2) and zirconium alloys. However, the events at Fukushima Daiichi and Three Mile Island accident have shown the need for exploration into advanced materials possessing improved accident tolerance. This work looks to further modify the NRC codes to include silicon carbide (SiC), an advanced cladding material proposed by current DOE funded research on accident tolerant fuels (ATF). Several additional fuels will also be analyzed, including uranium nitride (UN), uranium carbide (UC) and uranium silicide (U3Si2). Focusing on the system response in an accident scenario, an emphasis is placed on the fracture mechanics of the ceramic cladding by design the fuel rods to eliminate pellet cladding mechanical interaction (PCMI). The time to failure and how much of the fuel in the reactor fails with an advanced fuel design will be analyzed and compared to the current UO2/Zircaloy design using a full scale reactor model.

Processing of a Mullite Matrix, Molybdenum Disilicide Reinforced Composite

DTIC Science & Technology

1991-01-01

at high temperatures (best of the silicides and almost as good as SiC) is due to the formation of protective SiO2 layers on the surface of the MoSi 2...of the precipitation preparation process) consisted largely of sodium . Previous work 52 showed that the particle size was 160 A (TEM analysis) not...M.K. Brun, L.E. Szala, "Kinetics of Oxidation of Carbide and Silicide Dispersed Phases in Oxide Matrices," Adv. Ceram. Mat., 3 [5] 491-497 (1988). 5

Optical response at 10.6 microns in tungsten silicide Schottky barrier diodes

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Boyd, Joseph T.; Jackson, Howard E.

1987-01-01

Optical response to radiation at a wavelength of 10.6 microns in tungsten silicide-silicon Schottky barrier diodes has been observed. Incident photons excite electrons by means of junction plasmon assisted inelastic electron tunneling. At 78 K, a peak in the second derivative of current versus junction bias voltage was observed at a voltage corresponding to the energy of photons having a wavelength of 10.6 microns. This peak increased with increasing incident laser power, saturating at the highest laser powers investigated.

Method of Forming Three-Dimensional Semiconductors Structures

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor)

2002-01-01

Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow columns of metal silicide embedded in a matrix of single crystal, epitaxially grown silicon. Higher substrate temperatures and lower deposition rates yield larger columns that are farther apart while more silicon produces smaller columns. Column shapes and locations are selected by seeding the substrate with metal silicide starting regions. A variety of 3-dimensional, exemplary electronic devices are disclosed.

Practical field repair of fused slurry silicide coating for space shuttle t.p.s.

NASA Technical Reports Server (NTRS)

Reznik, B. D.

1971-01-01

Study of short-time high-temperature diffusion treatments as part of a program of development of methods of reapplying fused slurry silicide coating in the field. The metallographic structure and oxidation behavior of R512E applied to Cb-752 coated under simulated field repair conditions was determined. Oxidation testing in reduced pressure environment has shown that performance equivalent to furnace-processed specimens can be obtained in a two-minute diffusion at 2700 F.

Large magnetoresistance of nickel-silicide nanowires: non-equilibrium heating of magnetically-coupled dangling bonds.

PubMed

Kim, T; Chamberlin, R V; Bird, J P

2013-03-13

We demonstrate large (>100%) time-dependent magnetoresistance in nickel-silicide nanowires and develop a thermodynamic model for this behavior. The model describes nonequilibrium heating of localized spins in an increasing magnetic field. We find a strong interaction between spins but no long-range magnetic order. The spins likely come from unpaired dangling bonds in the interfacial layers of the nanowires. The model indicates that although these bonds couple weakly to a thermal bath, they dominate the nanowire resistance.

Quantitative EPMA of Nano-Phase Iron-Silicides in Apollo 16 Lunar Regolith

NASA Astrophysics Data System (ADS)

Gopon, P.; Fournelle, J.; Valley, J. W.; Pinard, P. T.; Sobol, P.; Horn, W.; Spicuzza, M.; Llovet, X.; Richter, S.

2013-12-01

Until recently, quantitative EPMA of phases under a few microns in size has been extremely difficult. In order to achieve analytical volumes to analyze sub-micron features, accelerating voltages between 5 and 8 keV need to be used. At these voltages the normally used K X-ray transitions (of higher Z elements) are no longer excited, and we must rely of outer shell transitions (L and M). These outer shell transitions are difficult to use for quantitative EPMA because they are strongly affected by different bonding environments, the error associated with their mass attenuation coefficients (MAC), and their proximity to absorption edges. These problems are especially prevalent for the transition metals, because of the unfilled M5 electron shell where the Lα transition originates. Previous studies have tried to overcome these limitations by using standards that almost exactly matched their unknowns. This, however, is cumbersome and requires accurate knowledge of the composition of your sample beforehand, as well as an exorbitant number of well characterized standards. Using a 5 keV electron beam and utilizing non-standard X-ray transitions (Ll) for the transition metals, we are able to conduct accurate quantitative analyses of phases down to ~300nm. The Ll transition in the transition metals behaves more like a core-state transition, and unlike the Lα/β lines, is unaffected by bonding effects and does not lie near an absorption edge. This allows for quantitative analysis using standards do not have to exactly match the unknown. In our case pure metal standards were used for all elements except phosphorus. We present here data on iron-silicides in two Apollo 16 regolith grains. These plagioclase grains (A6-7 and A6-8) were collected between North and South Ray Craters, in the lunar highlands, and thus are associated with one or more large impact events. We report the presence of carbon, nickel, and phosphorus (in order of abundance) in these iron-silicide phases. Although carbon is an especially difficult measurement, (with contamination from the lab environment, sample, and vacuum system being a large problem) we found that the iron-silicide phases contain a few weight percent carbon. X-ray mapping shows carbon to be concentrated within the silicide blebs. We conducted sample reference (i.e. baseline) carbon measurements in standards mounted in the same block as the sample, to establish a contamination baseline then any carbon measured above this baseline was assumed to be real. This finding seems to indicate that while the iron-silicide phases formed in the reducing conditions of the lunar surface, these conditions were not low enough to form the phases on their own and needed the presence of carbon to reduce them down to the much lower reducing conditions were native silicon is stable. The source of the carbon and nickel found in the iron-silicides is most likely form an impactor, rather than from the lunar surface.

Wear Resistance Enhancement of Ti-6Al-4 V Alloy by Applying Zr-Modified Silicide Coatings

NASA Astrophysics Data System (ADS)

Li, Xuan; Hu, Guangzhong; Tian, Jin; Tian, Wei; Xie, Wenling; Li, Xiulan

2018-03-01

Zr-modified silicide coatings were prepared on Ti-6Al-4 V alloy by pack cementation process to enhance its wear resistance. The microstructure and wear properties of the substrate and the coatings were comparatively investigated using GCr15 and Al2O3 as the counterparts under different sliding loads. The obtained Zr-modified silicide coating had a multilayer structure, consisting of a thick (Ti, X)Si2 (X represents Al, Zr and V elements) outer layer, a TiSi middle layer and a Ti5Si4 + Ti5Si3 inner layer. The micro-hardness of the coating was much higher than the substrate and displayed a decrease tendency from the coating surface to the interior. Sliding against either GCr15 or Al2O3 balls, the coatings showed superior anti-friction property to the Ti-6Al-4 V alloy, as confirmed by its much lower wear rate under each employed sliding condition.

Plasma-enhanced deposition and processing of transition metals and transition metal silicides for VLSI

NASA Astrophysics Data System (ADS)

Hess, D. W.

1986-05-01

Radiofrequency (rf) discharges have been used to deposit films of tungsten, molybdenum and titanium silicide. As-deposited tungsten films, from tungsten hexafluoride and hydrogen source gases, were metastable (beta W), with significant (>1 atomic percent) fluorine incorporation. Film resistivities were 40-55 micro ohm - cm due to the beta W, but dropped to about 8 micro ohm cm after a short heat treatment at 700 C which resulted in a phase transition to alpha W (bcc form). The high resistivity (>10,000 micro ohm) associated with molybdenum films deposited from molybdenum hexafluoride and hydrogen appeared to be a result of the formation of molybdenum trifluoride in the deposited material. Titanium silicide films formed from a discharge of titanium tetrachloride, silane, and hydrogen, displayed resistivities of about 150 micro ohm cm, due to small amounts of oxygen and chlorine incorporated during deposition. Plasma etching studies of tungsten films with fluorine containing gases suggest that the etchant species for tungsten in these discharges are fluorine atoms.

Polycrystalline silicon on tungsten substrates

NASA Technical Reports Server (NTRS)

Bevolo, A. J.; Schmidt, F. A.; Shanks, H. R.; Campisi, G. J.

1979-01-01

Thin films of electron-beam-vaporized silicon were deposited on fine-grained tungsten substrates under a pressure of about 1 x 10 to the -10th torr. Mass spectra from a quadrupole residual-gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. During separate silicon depositions, the atomically clean substrates were maintained at various temperatures between 400 and 780 C, and deposition rates were between 20 and 630 A min. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry before and after cleaning, deposition, and annealing. Auger depth profiling, X-ray analysis, and SEM in the topographic and channeling modes were utilized to characterize the samples with respect to silicon-metal interface, interdiffusion, silicide formation, and grain size of silicon. The onset of silicide formation was found to occur at approximately 625 C. Above this temperature tungsten silicides were formed at a rate faster than the silicon deposition. Fine-grain silicon films were obtained at lower temperatures.

Interfacial reactions in borsic/Ti-3Al-2-1/2V composite

NASA Technical Reports Server (NTRS)

Rao, V. B.; Houska, C. R.; Unnam, J.; Brewer, W. D.; Tenney, D. R.

1979-01-01

The paper provides a detailed X-ray characterization of a borsic/Ti-3Al-2-1/2V composite, and to correlate the relative intensities of the reaction products with the mechanical properties. Based on X-ray integrated intensity data two stages of interface reactions were identified: during the first stage there is a simultaneous interdiffusion of Si, C, and Ti atoms at the filament/matrix interface resulting in the formation of Ti5Si3, TiSi and small amounts of TiSi2 and TiC. The second stage is associated with considerable TiSi2 and boride formation. It appears that the alpha-phase of Ti is more reactive in forming silicides and borides than the beta-phase. The silicide intensities and the reaction zone thicknesses are shown to be directly related to the reduction of the ultimate tensile strength by thermal degradation, and the results indicate that silicide reaction products are as detrimental to strength as the borides.

Interfacial structure of two-dimensional epitaxial Er silicide on Si(111)

NASA Astrophysics Data System (ADS)

Tuilier, M. H.; Wetzel, P.; Pirri, C.; Bolmont, D.; Gewinner, G.

1994-07-01

Auger-electron diffraction (AED) and surface-extended x-ray-absorption fine structure (SEXAFS) have been used to obtain a complete description of the atomic structure of a two-dimensional epitaxial Er silicide layer on Si(111). AED reveals that a monolayer of Er is located underneath a buckled Si double layer. The relevant Er-Si interlayer spacings are determined by means of single scattering cluster simulations and a R-factor analysis to be 1.92+/-0.05 Å to the first and 2.70+/-0.05 Å to the second Si top layer. Er near-neighbor bond lengths and coordination numbers are obtained independently from polarization-dependent SEXAFS. The SEXAFS data, when combined with the Si top-layer geometry inferred from AED, permit the determination of the atomic positions at the silicide/Si(111) interface. The Er is found to reside in relaxed T4 sites of Si(111) with a single Er-Si distance of 3.09+/-0.04 Å to the first- and second-layer Si atoms of the substrate.

Structure, growth kinetics, and ledge flow during vapor-solid-solid growth of copper-catalyzed silicon nanowires.

PubMed

Wen, C-Y; Reuter, M C; Tersoff, J; Stach, E A; Ross, F M

2010-02-10

We use real-time observations of the growth of copper-catalyzed silicon nanowires to determine the nanowire growth mechanism directly and to quantify the growth kinetics of individual wires. Nanowires were grown in a transmission electron microscope using chemical vapor deposition on a copper-coated Si substrate. We show that the initial reaction is the formation of a silicide, eta'-Cu(3)Si, and that this solid silicide remains on the wire tips during growth so that growth is by the vapor-solid-solid mechanism. Individual wire directions and growth rates are related to the details of orientation relation and catalyst shape, leading to a rich morphology compared to vapor-liquid-solid grown nanowires. Furthermore, growth occurs by ledge propagation at the silicide/silicon interface, and the ledge propagation kinetics suggest that the solubility of precursor atoms in the catalyst is small, which is relevant to the fabrication of abrupt heterojunctions in nanowires.

Kinetic analysis of the combustion synthesis of molybdenum and titanium silicides

NASA Astrophysics Data System (ADS)

Wang, Lily L.; Munir, Z. A.

1995-05-01

The temperature profiles associated with the passage of self-propagating combustion waves during the synthesis of MoSi2 and Ti5Si3 were determined. From these profiles, kinetic analyses of the combustion synthesis process for these two silicides were made. The synthesis is associated with high heating rates: 1.3 × 104 and 4.9 × 104 K·s-1 for MoSi2 and Ti5Si3, respectively. The width of the combustion zone was determined as 1.3 and 1.8 mm for the silicides of Mo and Ti, respectively. The degree of conversion, η, and its spatial distribution and the conversion rate, ∂η/∂t, were determined. However, because of the inherent characteristics of wave propagation in MoSi2, only in the case of Ti5Si3 could the activation energy be calculated. An average value of 190 kJ µ mol-1 was determined for titanium suicide.

Boron modified molybdenum silicide and products

DOEpatents

Meyer, M.K.; Akinc, M.

1999-02-02

A boron-modified molybdenum silicide material is disclosed having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo{sub 5}Si{sub 3} phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi{sub 2} heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo{sub 5}Si{sub 3} for structural integrity. 7 figs.

Boron modified molybdenum silicide and products

DOEpatents

Meyer, Mitchell K.; Akinc, Mufit

1999-02-02

A boron-modified molybdenum silicide material having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo.sub.5 Si.sub.3 phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi.sub.2 heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo.sub.5 Si.sub.3 for structural integrity.

Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy.

PubMed

Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

2015-12-01

In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment in less than 3 min. The improved potential resolution in the SKPM measurement was verified. Moreover, the resolution of the topography is comparable to that of a bare silicon tip. In addition, the negative charges found on the PSM tips suggest the possibility of exploring the use of current PSM tips to sense electric fields more precisely. The ultra-fast and cost-effective preparation of the PSM tips provides a new direction for the preparation of functional tips for scanning probe microscopy.

Copper silicide/silicon nanowire heterostructures: in situ TEM observation of growth behaviors and electron transport properties.

PubMed

Chiu, Chung-Hua; Huang, Chun-Wei; Chen, Jui-Yuan; Huang, Yu-Ting; Hu, Jung-Chih; Chen, Lien-Tai; Hsin, Cheng-Lun; Wu, Wen-Wei

2013-06-07

Copper silicide has been studied in the applications of electronic devices and catalysts. In this study, Cu3Si/Si nanowire heterostructures were fabricated through solid state reaction in an in situ transmission electron microscope (TEM). The dynamic diffusion of the copper atoms in the growth process and the formation mechanism are characterized. We found that two dimensional stacking faults (SF) may retard the growth of Cu3Si. Due to the evidence of the block of edge-nucleation (heterogeneous) by the surface oxide, center-nucleation (homogeneous) is suggested to dominate the silicidation. Furthermore, the electrical transport properties of various silicon channel length with Cu3Si/Si heterostructure interfaces and metallic Cu3Si NWs have been investigated. The observations not only provided an alternative pathway to explore the formation mechanisms and interface properties of Cu3Si/Si, but also suggested the potential application of Cu3Si at nanoscale for future processing in nanotechnology.

Revealing lithium-silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy.

PubMed

Ogata, K; Salager, E; Kerr, C J; Fraser, A E; Ducati, C; Morris, A J; Hofmann, S; Grey, C P

2014-01-01

Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.

Role of atomic bonding for compound and glass formation in Ni-Si, Pd-Si, and Ni-B systems

NASA Astrophysics Data System (ADS)

Tanaka, K.; Saito, T.; Suzuki, K.; Hasegawa, R.

1985-11-01

Valence electronic structures of crystalline compounds and glassy alloys of Ni silicides, Pd silicides, and Ni borides are studied by soft-x-ray spectroscopy over wide ranges of Si and B concentrations. The samples prepared include bulk compounds, glassy ribbons, and amorphous sputtered films. Silicon Kβ emissions of Ni and Pd silicides generally consist of a prominent peak fixed at ~=4.5 and ~=5.8 eV below the Fermi level EF, respectively, with a shoulder near EF which grows and shifts toward lower energy with increasing Si concentration. The former is identified as due to Si p-like states forming Si 3p-Ni 3d or Si 3p-Pd 4d bonding states while the latter as due to the corresponding antibonding states. Ni L3 and Pd L3 emissions of these silicides indicate that Ni 3d and Pd 4d states lie between the above two states. These local electronic configurations are consistent with partial-density-of-states (PDOS) calculations performed by Bisi and Calandra. Similar electronic configurations are suggested for Ni borides from B Kα and Ni L3 emissions. Differences of emission spectra between compounds and glasses of similar compositions are rather small, but some enhancement of the contribution of antibonding states to the PDOS near EF is suggested for certain glasses over that of the corresponding compounds. These features are discussed in connection with the compound stability and glass formability.

On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

NASA Astrophysics Data System (ADS)

Chaia, N.; Portebois, L.; Mathieu, S.; David, N.; Vilasi, M.

2017-02-01

To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF2 as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V3Si, V5Si3, V6Si5 and VSi2) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10-9 to 10-13 cm2 s-1. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi2 layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum.

Short circuit in deep brain stimulation.

PubMed

Samura, Kazuhiro; Miyagi, Yasushi; Okamoto, Tsuyoshi; Hayami, Takehito; Kishimoto, Junji; Katano, Mitsuo; Kamikaseda, Kazufumi

2012-11-01

The authors undertook this study to investigate the incidence, cause, and clinical influence of short circuits in patients treated with deep brain stimulation (DBS). After the incidental identification of a short circuit during routine follow-up, the authors initiated a policy at their institution of routinely evaluating both therapeutic impedance and system impendence at every outpatient DBS follow-up visit, irrespective of the presence of symptoms suggesting possible system malfunction. This study represents a report of their findings after 1 year of this policy. Implanted DBS leads exhibiting short circuits were identified in 7 patients (8.9% of the patients seen for outpatient follow-up examinations during the 12-month study period). The mean duration from DBS lead implantation to the discovery of the short circuit was 64.7 months. The symptoms revealing short circuits included the wearing off of therapeutic effect, apraxia of eyelid opening, or dysarthria in 6 patients with Parkinson disease (PD), and dystonia deterioration in 1 patient with generalized dystonia. All DBS leads with short circuits had been anchored to the cranium using titanium miniplates. Altering electrode settings resulted in clinical improvement in the 2 PD cases in which patients had specific symptoms of short circuits (2.5%) but not in the other 4 cases. The patient with dystonia underwent repositioning and replacement of a lead because the previous lead was located too anteriorly, but did not experience symptom improvement. In contrast to the sudden loss of clinical efficacy of DBS caused by an open circuit, short circuits may arise due to a gradual decrease in impedance, causing the insidious development of neurological symptoms via limited or extended potential fields as well as shortened battery longevity. The incidence of short circuits in DBS may be higher than previously thought, especially in cases in which DBS leads are anchored with miniplates. The circuit impedance of DBS should be routinely checked, even after a long history of DBS therapy, especially in cases of miniplate anchoring.

Characterization of Ultra High Temperature Ceramics via Transmission Electron Microscopy. Part 2: UHTCs sintered with addition of TaSi2

DTIC Science & Technology

2010-01-21

substituted by Hf in the TaSi2 phase, indicating that this silicide has a great solubility for the group IV metals . At the triple point junctions Ta5Si3...Mathis Müller for his precious help in TEM specimens’ preparations . FA8655-09-M-4002 40 References 1. L. E. Toth: Transition Metal Carbides and...Transition Metal Disilicides,’ Acta Mater., 44, 3035 (1996). 21. H. Pastor and R. Meyer: An Investigation of the Effect of Additions of Metal Silicides

Basic factors controlling pest in high temperature systems

NASA Technical Reports Server (NTRS)

Berkowitz-Mattuck, J.; Rossetti, M.

1971-01-01

The catastrophic disintegration in air at intermediate temperatures of refractory materials which are very resistant to oxidation at high temperatures is known as pest. A study was undertaken to determine whether the mechanism proposed for pest failure in silicides might also be responsible for pest failure in NbAl3. The aim was to correlate oxidation kinetics in the range where disintegration of NbAl3 is observed with delayed failure data obtained under similar conditions. Studies were also undertaken to develop some understanding of deformation mechanisms in both silicides and aluminides.

Electron and Phonon Engineered Nano- and Heterostructures for Increased Speed and Performance Enhancement of the Electronic and Optoelectronic Devices

DTIC Science & Technology

2011-01-01

doped source and drain form ohmic contact to metal silicide [2]-[6] due to their immunity to short channel effect [7]-[10]. In this project, we...investigated the hole mobility of SB Si NW. II. Device Fabrication Technology We prepared SiNWs by Au-catalyzed vapor-transport as described in Ref. [11...overlapping Ti/Au (70/50 nm) top gate is defined. Devices are characterized at this stage and also after annealing. III. Silicide Formation Our devices

Fine structure of the K X-ray absorption spectra of titanium in some hydrides, borides, and silicides (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vainshtein, �. E.; Zhurakovskii, E. A.

1959-08-01

X-ray spectral analyses confirmed the hypothesis on the metal-like state of hydrogen in tithnium hydrides. Experiments with titunium borides and silicides indicate the special character and degree of the 3d--level participation in the metallic'' bond between the atoms of various complexes. The structure of metalloid elements becomes more complicated with an increase in the specific number of boron and silicon atoms and the bond between the atoms tends to become covalent. (R.V.J.)

On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fatima,; Hossain, Sehtab; Mohottige, Rasika

Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77 K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires.

Progress in doping of ruthenium silicide (Ru2Si3)

NASA Technical Reports Server (NTRS)

Vining, C. B.; Allevato, C. E.

1992-01-01

Ruthenium silicide is currently under development as a promising thermoelectric material suitable for space power applications. Key to realizing the potentially high figure of merit values of this material is the development of appropriate doping techniques. In this study, manganese and iridium have been identified as useful p- and n-type dopants, respectively. Resistivity values have been reduced by more than 3 orders of magnitude. Anomalous Hall effect results, however, complicate interpretation of some of the results and further effort is required to achieve optimum doping levels.

Redistribution of phosphorus during Ni0.9Pt0.1-based silicide formation on phosphorus implanted Si substrates

NASA Astrophysics Data System (ADS)

Lemang, M.; Rodriguez, Ph.; Nemouchi, F.; Juhel, M.; Grégoire, M.; Mangelinck, D.

2018-02-01

Phosphorus diffusion and its distribution during the solid-state reactions between Ni0.9Pt0.1 and implanted Si substrates are studied. Silicidation is achieved through a first rapid thermal annealing followed by a selective etching and a direct surface annealing. The redistribution of phosphorus in silicide layers is investigated after the first annealing for different temperatures and after the second annealing. Phosphorus concentration profiles obtained thanks to time of flight secondary ion mass spectrometry and atom probe tomography characterizations for partial and total reactions of the deposited 7 nm thick Ni0.9Pt0.1 film are presented. Phosphorus segregation is observed at the Ni0.9Pt0.1 surface and at Ni2Si interfaces during Ni2Si formation and at the NiSi surface and the NiSi/Si interface after NiSi formation. The phosphorus is evidenced in low concentrations in the Ni2Si and NiSi layers. Once NiSi is formed, a bump in the phosphorus concentration is highlighted in the NiSi layer before the NiSi/Si interface. Based on these profiles, a model for the phosphorus redistribution is proposed to match this bump to the former Ni2Si/Si interface. It also aims to bind the phosphorus segregation and its low concentration in different silicides to a low solubility of phosphorus in Ni2Si and in NiSi and a fast diffusion of phosphorus at their grain boundaries. This model is also substantiated by a simulation using a finite difference method in one dimension.

On Nb Silicide Based Alloys: Alloy Design and Selection.

PubMed

Tsakiropoulos, Panos

2018-05-18

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb₅Si₃ (Materials 11 (2018) 69), and hexagonal C14-NbCr₂ and cubic A15-Nb₃X phases (Materials 11 (2018) 395) and eutectics with Nb ss and Nb₅Si₃ (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys.

Interaction transfer of silicon atoms forming Co silicide for Co/√(3)×√(3)R30°-Ag/Si(111) and related magnetic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Cheng-Hsun-Tony; Fu, Tsu-Yi; Tsay, Jyh-Shen, E-mail: jstsay@phy.ntnu.edu.tw

Combined scanning tunneling microscopy, Auger electron spectroscopy, and surface magneto-optic Kerr effect studies were employed to study the microscopic structures and magnetic properties for ultrathin Co/√(3)×√(3)R30°-Ag/Si(111). As the annealing temperature increases, the upward diffusion of Si atoms and formation of Co silicides occurs at temperature above 400 K. Below 600 K, the √(3)×√(3)R30°-Ag/Si(111) surface structure persists. We propose an interaction transferring mechanism of Si atoms across the √(3)×√(3)R30°-Ag layer. The upward transferred Si atoms react with Co atoms to form Co silicide. The step height across the edge of the island, a separation of 0.75 nm from the analysis of the 2 × 2 structure,more » and the calculations of the normalized Auger signal serve as strong evidences for the formation of CoSi{sub 2} at the interface. The interaction transferring mechanism for Si atoms enhances the possibility of interactions between Co and Si atoms. The smoothness of the surface is advantage for that the easy axis of magnetization for Co/√(3)×√(3)R30°-Ag/Si(111) is in the surface plane. This provides a possible way of growing flat magnetic layers on silicon substrate with controllable silicide formation and shows potential applications in spintronics devices.« less

On Nb Silicide Based Alloys: Alloy Design and Selection

PubMed Central

Tsakiropoulos, Panos.

2018-01-01

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb5Si3 (Materials 11 (2018) 69), and hexagonal C14-NbCr2 and cubic A15-Nb3X phases (Materials 11 (2018) 395) and eutectics with Nbss and Nb5Si3 (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys. PMID:29783707

Nanopatterning dynamics on Si(100) during oblique 40-keV Ar+ erosion with metal codeposition: Morphological and compositional correlation

NASA Astrophysics Data System (ADS)

Redondo-Cubero, A.; Gago, R.; Palomares, F. J.; Mücklich, A.; Vinnichenko, M.; Vázquez, L.

2012-08-01

The formation and dynamics of nanopatterns produced on Si(100) surfaces by 40-keV Ar+ oblique (α = 60°) bombardment with concurrent Fe codeposition have been studied. Morphological and chemical analysis has been performed by ex situ atomic force microscopy, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and scanning and transmission electron microscopies. During irradiation, Fe atoms incorporated into the target surface react with Si to form silicides, a process enhanced at this medium-ion energy range. The silicides segregate at the nanoscale from the early irradiation stages. As the irradiation proceeds, a ripple pattern is formed without any correlation with silicide segregation. From the comparison with the pattern dynamics reported previously for metal-free conditions, it is demonstrated that the metal incorporation alters both the pattern dynamics and the morphology. Although the pattern formation and dynamics are delayed for decreasing metal content, once ripples emerge, the same qualitative pattern of morphological evolution is observed for different metal content, resulting in an asymptotic saw-tooth-like facetted surface pattern. Despite the medium ion energy employed, the nanopatterning process with concurrent Fe deposition can be explained by those mechanisms proposed for low-ion energy irradiations such as shadowing, height fluctuations, silicide formation and segregation, ensuing composition dependent sputter rate, and ion sculpting effects. In particular, the interplay between the ion irradiation and metal flux geometries, differences in sputtering rates, and the surface pattern morphology produces a dynamic compositional patterning correlated with the evolving morphological one.

Twisting phonons in complex crystals with quasi-one-dimensional substructures [Twisting Phonons in Higher Manganese Silicides with a Complex Nowotny Chimney Ladder Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abernathy, Douglas L.; Ma, Jie; Yan, Jiaqiang

A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain themore » low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.« less

Iron silicides at pressures of the Earth's inner core

NASA Astrophysics Data System (ADS)

Zhang, Feiwu; Oganov, Artem R.

2010-01-01

The Earth's core is expected to contain around 10 wt % light elements (S, Si, O, possibly C, H, etc.) alloyed with Fe and Ni. Very little is known about these alloys at pressures and temperatures of the core. Here, using the evolutionary crystal structure prediction methodology, we investigate Fe-Si compounds at pressures of up to 400 GPa, i.e. covering the pressure range of the Earth's core. Evolutionary simulations correctly find that at atmospheric pressure the known non-trivial structure with P213 symmetry is stable, while at pressures above 20 GPa the CsCl-type structure is stable. We show that among the possible Fe silicides (Fe3Si, Fe2Si, Fe5Si3, FeSi, FeSi2 and FeSi3) only FeSi with CsCl-type structure is thermodynamically stable at core pressures, while the other silicides are unstable to decomposition into Fe + FeSi or FeSi + Si. This is consistent with previous works and suggests that Si impurities contribute to stabilization of the body-centered cubic phase of Fe in the inner core.

Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy

NASA Astrophysics Data System (ADS)

Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

2014-09-01

Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

Development of Coatings for Tantalum Alloy Nozzle Vanes

NASA Technical Reports Server (NTRS)

Stetson, A. R.; Wimber, R. T.

1967-01-01

A group of silicide coatings developed for the T222 tantalum-base alloy have afforded over 600 hours of protection at 1600 and 2400 F during cyclic exposure in air. These coatings were applied in two steps. A modifier alloy was applied by slurry techniques and was sintered in vacuum prior to siliciding by pack cementation in argon. Application of the modifier alloy by pack cementation was found to be much less effective. The addition of titanium and vanadium to molybdenum and tungsten yielded beneficial modifier alloys, whereas the addition of chromium showed no improvement. After siliciding, the 15Ti- 35W-15V-35Mo modifier alloy exhibited the best performance; one sample survived 1064 hours of oxidation at 2400 F. This same coating was the only coating to reproducibly provide 600 hours of protection at both 1600 and 2400 F; in the second and third of three experiments, involving oxidation of three to five specimens at each temperature in each experiment, no failures were observed in 600 hours of testing. The slurry coatings were also shown to protect the Cb752 and D43 columbium-base alloys.

Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates.

PubMed

Bhatta, Umananda M; Rath, Ashutosh; Dash, Jatis K; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P V

2009-11-18

Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio ( approximately 15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

Twisting phonons in complex crystals with quasi-one-dimensional substructures [Twisting Phonons in Higher Manganese Silicides with a Complex Nowotny Chimney Ladder Structure

DOE PAGES

Abernathy, Douglas L.; Ma, Jie; Yan, Jiaqiang; ...

2015-04-15

A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain themore » low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.« less

Carrier-transport mechanism of Er-silicide Schottky contacts to strained-silicon-on-insulator and silicon-on-insulator.

PubMed

Jyothi, I; Janardhanam, V; Kang, Min-Sung; Yun, Hyung-Joong; Lee, Jouhahn; Choi, Chel-Jong

2014-11-01

The current-voltage characteristics and the carrier-transport mechanism of the Er-silicide (ErSi1.7) Schottky contacts to strained-silicon-on-insulator (sSOI) and silicon-on-insulator (SOI) were investigated. Barrier heights of 0.74 eV and 0.82 eV were obtained for the sSOI and SOI structures, respectively. The barrier height of the sSOI structure was observed to be lower than that of the SoI structure despite the formation of a Schottky contact using the same metal silicide. The sSOI structure exhibited better rectification and higher current level than the SOI structure, which could be associated with a reduction in the band gap of Si caused by strain. The generation-recombination mechanism was found to be dominant in the forward bias for both structures. Carrier generation along with the Poole-Frenkel mechanism dominated the reverse-biased current in the SOI structure. The saturation tendency of the reverse leakage current in the sSOI structure could be attributed to strain-induced defects at the interface in non-lattice-matched structures.

Nucleation and atomic layer reaction in nickel silicide for defect-engineered Si nanochannels.

PubMed

Tang, Wei; Picraux, S Tom; Huang, Jian Yu; Gusak, Andriy M; Tu, King-Ning; Dayeh, Shadi A

2013-06-12

At the nanoscale, defects can significantly impact phase transformation processes and change materials properties. The material nickel silicide has been the industry standard electrical contact of silicon microelectronics for decades and is a rich platform for scientific innovation at the conjunction of materials and electronics. Its formation in nanoscale silicon devices that employ high levels of strain, intentional, and unintentional twins or grain boundaries can be dramatically different from the commonly conceived bulk processes. Here, using in situ high-resolution transmission electron microscopy (HRTEM), we capture single events during heterogeneous nucleation and atomic layer reaction of nickel silicide at various crystalline boundaries in Si nanochannels for the first time. We show through systematic experiments and analytical modeling that unlike other typical face-centered cubic materials such as copper or silicon the twin defects in NiSi2 have high interfacial energies. We observe that these twin defects dramatically change the behavior of new phase nucleation and can have direct implications for ultrascaled devices that are prone to defects or may utilize them to improve device performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Nicholas; Burns, Joseph R.

The aftermath of the Tōhoku earthquake and the Fukushima accident has led to a global push to improve the safety of existing light water reactors. A key component of this initiative is the development of nuclear fuel and cladding materials with potentially enhanced accident tolerance, also known as accident-tolerant fuels (ATF). These materials are intended to improve core fuel and cladding integrity under beyond design basis accident conditions while maintaining or enhancing reactor performance and safety characteristics during normal operation. To complement research that has already been carried out to characterize ATF neutronics, the present study provides an initial investigationmore » of the sensitivity and uncertainty of ATF systems responses to nuclear cross section data. ATF concepts incorporate novel materials, including SiC and FeCrAl cladding and high density uranium silicide composite fuels, in turn introducing new cross section sensitivities and uncertainties which may behave differently from traditional fuel and cladding materials. In this paper, we conducted sensitivity and uncertainty analysis using the TSUNAMI-2D sequence of SCALE with infinite lattice models of ATF assemblies. Of all the ATF materials considered, it is found that radiative capture in 56Fe in FeCrAl cladding is the most significant contributor to eigenvalue uncertainty. 56Fe yields significant potential eigenvalue uncertainty associated with its radiative capture cross section; this is by far the largest ATF-specific uncertainty found in these cases, exceeding even those of uranium. We found that while significant new sensitivities indeed arise, the general sensitivity behavior of ATF assemblies does not markedly differ from traditional UO2/zirconium-based fuel/cladding systems, especially with regard to uncertainties associated with uranium. We assessed the similarity of the IPEN/MB-01 reactor benchmark model to application models with FeCrAl cladding. We used TSUNAMI-IP to calculate similarity indices of the application model and IPEN/MB-01 reactor benchmark model. This benchmark was selected for its use of SS304 as a cladding and structural material, with significant 56Fe content. The similarity indices suggest that while many differences in reactor physics arise from differences in design, sensitivity to and behavior of 56Fe absorption is comparable between systems, thus indicating the potential for this benchmark to reduce uncertainties in 56Fe radiative capture cross sections.« less

Swelling of U-7Mo/Al-Si dispersion fuel plates under irradiation - Non-destructive analysis of the AFIP-1 fuel plates

NASA Astrophysics Data System (ADS)

Wachs, D. M.; Robinson, A. B.; Rice, F. J.; Kraft, N. C.; Taylor, S. C.; Lillo, M.; Woolstenhulme, N.; Roth, G. A.

2016-08-01

Extensive fuel-matrix interactions leading to plate pillowing have proven to be a significant impediment to the development of a suitable high density low-enriched uranium molybdenum alloy (U-Mo) based dispersion fuel for high power applications in research reactors. The addition of silicon to the aluminum matrix was previously demonstrated to reduce interaction layer growth in mini-plate experiments. The AFIP-1 project involved the irradiation, in-canal examination, and post-irradiation examination of two fuel plates. The irradiation of two distinct full size, flat fuel plates (one using an Al-2wt%Si matrix and the other an Al-4043 (∼4.8 wt% Si) matrix) was performed in the INL ATR reactor in 2008-2009. The irradiation conditions were: ∼250 W/cm2 peak Beginning Of Life (BOL) power, with a ∼3.5e21 f/cm3 peak burnup. The plates were successfully irradiated and did not show any pillowing at the end of the irradiation. This paper reports the results and interpretation of the in-canal and post-irradiation non-destructive examinations that were performed on these fuel plates. It further compares additional PIE results obtained on fuel plates irradiated in contemporary campaigns in order to allow a complete comparison with all results obtained under similar conditions. Except for a brief indication of accelerated swelling early in the irradiation of the Al-2Si plate, the fuel swelling is shown to evolve linearly with the fission density through the maximum burnup.

Status of reduced enrichment programs for research reactors in Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanda, Keiji; Nishihara, Hedeaki; Shirai, Eiji

1997-08-01

The reduced enrichment programs for the JRR-2, JRR-3, JRR-4 and JMTR of Japan Atomic Energy Research Institute (JAERI), and the KUR of Kyoto University Research Reactor Institute (KURRI) have been partially completed and are mostly still in progress under the Joint Study Programs with Argonne National Laboratory (ANL). The JMTR and JRR-2 have been already converted to use MEU aluminide fuels in 1986 and 1987, respectively. The operation of the upgraded JRR-3(JRR-3M) has started in March 1990 with the LEU aluminide fuels. Since May 1992, the two elements have been inserted in the KUR. The safety review application for themore » full core conversion to use LEU silicide in the JMTR was approved in February 1992 and the conversion has been done in January 1994. The Japanese Government approved a cancellation of the KUHFR Project in February 1991, and in April 1994 the U.S. Government gave an approval to utilize HEU in the KUR instead of the KUHFR. Therefore, the KUR will be operated with HEU fuel until 2001. Since March 1994, Kyoto University is continuing negotiation with UKAEA Dounreay on spent fuel reprocessing and blending down of recovered uranium, in addition to that with USDOE.« less

Interdiffusion in U 3Si-Al, U 3Si 2-Al, and USi-Al dispersion fuels during irradiation

NASA Astrophysics Data System (ADS)

Kim, Yeon Soo; Hofman, Gerard L.

2011-03-01

Uranium-silicide compound fuel dispersion in an Al matrix is used in research and test reactors worldwide. Interaction layer (IL) growth between fuel particles and the matrix is one of performance issues. The interaction layer growth data for U 3Si, U 3Si 2 and USi dispersions in Al were obtained from both out-of-pile and in-pile tests. The IL is dominantly U(AlSi) 3 from out-of-pile tests, but its (Al + Si)/U ratio from in-pile tests is higher than the out-of-pile data, because of amorphous behavior of the ILs. IL growth correlations were developed for U 3Si-Al and U 3Si 2-Al. The IL growth rates were dependent on the U/Si ratio of the fuel compounds. During irradiation, however, the IL growth rates did not decrease with the decreasing U/Si ratio by fission. It is reasoned that transition metal fission products in the IL compensate the loss of U atoms by providing chemical potential for Al diffusion and volume expansion by solid swelling and gas bubble swelling. The addition of Mo in U 3Si 2 reduces the IL growth rate, which is similar to that of UMo alloy dispersion in a silicon-added Al matrix.

Convective cooling in a pool-type research reactor

NASA Astrophysics Data System (ADS)

Sipaun, Susan; Usman, Shoaib

2016-01-01

A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U3Si2Al) in the form of rectangular plates. Gaps between the plates allow coolant to pass through and carry away heat. A study was carried out to map out heat flow as well as to predict the system's performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm-3. An MSTR model consisting of 20% of MSTR's nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s-1 from the 4" pipe, and predicted pool surface temperature not exceeding 30°C.

[The use of titanium nickelide devices in treating fractures of the zygomatico-orbital complex].

PubMed

Medvedev, Iu A; Sivolapov, K A

1993-01-01

The authors analyze the results of surgical treatment of 78 patients with zygomatico-orbital injuries. Mini-cramps and mini-plates of titanium nickelide with thermomechanical memory were employed for fracture fixation. Surgical strategy based on osteosynthesis with the use of such devices provides a reliable fixation of bone fragments and makes the operation less traumatic.

Computer-aided position planning of miniplates to treat facial bone defects

PubMed Central

Wallner, Jürgen; Gall, Markus; Chen, Xiaojun; Schwenzer-Zimmerer, Katja; Reinbacher, Knut; Schmalstieg, Dieter

2017-01-01

In this contribution, a software system for computer-aided position planning of miniplates to treat facial bone defects is proposed. The intra-operatively used bone plates have to be passively adapted on the underlying bone contours for adequate bone fragment stabilization. However, this procedure can lead to frequent intra-operatively performed material readjustments especially in complex surgical cases. Our approach is able to fit a selection of common implant models on the surgeon’s desired position in a 3D computer model. This happens with respect to the surrounding anatomical structures, always including the possibility of adjusting both the direction and the position of the used osteosynthesis material. By using the proposed software, surgeons are able to pre-plan the out coming implant in its form and morphology with the aid of a computer-visualized model within a few minutes. Further, the resulting model can be stored in STL file format, the commonly used format for 3D printing. Using this technology, surgeons are able to print the virtual generated implant, or create an individually designed bending tool. This method leads to adapted osteosynthesis materials according to the surrounding anatomy and requires further a minimum amount of money and time. PMID:28817607

[Osteosynthesis in facial bones: silicon nitride ceramic as material].

PubMed

Neumann, A; Unkel, C; Werry, C; Herborn, C U; Maier, H R; Ragoss, C; Jahnke, K

2006-12-01

The favorable properties of silicon nitride (Si3N4) ceramic, such as high stability and biocompatibility suggest its biomedical use as an implant material. The aim of this study was to test its suitability for osteosynthesis. A Si3N4 prototype minifixation system was manufactured and implanted for osteosynthesis of artificial frontal bone defects in three minipigs. After 3 months, histological sections, CT and MRI scans were obtained. Finite element modeling (FEM) was used to simulate stresses and strains on Si3N4 miniplates and screws to calculate survival probabilities. Si3N4 miniplates and screws showed satisfactory intraoperative workability. There was no implant loss, displacement or fracture. Bone healing was complete in all animals and formation of new bone was observed in direct contact to the implants. Si3N4 ceramic showed a good biocompatibility outcome both in vitro and in vivo. This ceramic may serve as biomaterial for osteosynthesis, e.g. of the midface including reconstruction of the floor of the orbit and the skull base. Advantages compared to titanium are no risk of implantation to bone with mucosal attachment, no need for explantation, no interference with radiological imaging.

Computer-aided position planning of miniplates to treat facial bone defects.

PubMed

Egger, Jan; Wallner, Jürgen; Gall, Markus; Chen, Xiaojun; Schwenzer-Zimmerer, Katja; Reinbacher, Knut; Schmalstieg, Dieter

2017-01-01

In this contribution, a software system for computer-aided position planning of miniplates to treat facial bone defects is proposed. The intra-operatively used bone plates have to be passively adapted on the underlying bone contours for adequate bone fragment stabilization. However, this procedure can lead to frequent intra-operatively performed material readjustments especially in complex surgical cases. Our approach is able to fit a selection of common implant models on the surgeon's desired position in a 3D computer model. This happens with respect to the surrounding anatomical structures, always including the possibility of adjusting both the direction and the position of the used osteosynthesis material. By using the proposed software, surgeons are able to pre-plan the out coming implant in its form and morphology with the aid of a computer-visualized model within a few minutes. Further, the resulting model can be stored in STL file format, the commonly used format for 3D printing. Using this technology, surgeons are able to print the virtual generated implant, or create an individually designed bending tool. This method leads to adapted osteosynthesis materials according to the surrounding anatomy and requires further a minimum amount of money and time.

Prediction of changes due to mandibular autorotation following miniplate-anchored intrusion of maxillary posterior teeth in open bite cases.

PubMed

Kassem, Hassan E; Marzouk, Eiman S

2018-05-14

Prediction of the treatment outcome of various orthodontic procedures is an essential part of treatment planning. Using skeletal anchorage for intrusion of posterior teeth is a relatively novel procedure for the treatment of anterior open bite in long-faced subjects. Data were analyzed from lateral cephalometric radiographs of a cohort of 28 open bite adult subjects treated with intrusion of the maxillary posterior segment with zygomatic miniplate anchorage. Mean ratios and regression equations were calculated for selected variables before and after intrusion. Relative to molar intrusion, there was approximately 100% vertical change of the hard and soft tissue mention and 80% horizontal change of the hard and soft tissue pogonion. The overbite deepened two folds with 60% increase in overjet. The lower lip moved forward about 80% of the molar intrusion. Hard tissue pogonion and mention showed the strongest correlations with molar intrusion. There was a general agreement between regression equations and mean ratios at 3 mm molar intrusion. This study attempted to provide the clinician with a tool to predict the changes in key treatment variables following skeletally anchored maxillary molar intrusion and autorotation of the mandible.

Method of preparing high-temperature-stable thin-film resistors

DOEpatents

Raymond, L.S.

1980-11-12

A chemical vapor deposition method for manufacturing tungsten-silicide thin-film resistors of predetermined bulk resistivity and temperature coefficient of resistance (TCR) is disclosed. Gaseous compounds of tungsten and silicon are decomposed on a hot substrate to deposit a thin-film of tungsten-silicide. The TCR of the film is determined by the crystallinity of the grain structure, which is controlled by the temperature of deposition and the tungsten to silicon ratio. The bulk resistivity is determined by the tungsten to silicon ratio. Manipulation of the fabrication parameters allows for sensitive control of the properties of the resistor.

Ferromagnetic nickel silicide nanowires for isolating primary CD4+ T lymphocytes

NASA Astrophysics Data System (ADS)

Kim, Dong-Joo; Seol, Jin-Kyeong; Lee, Mi-Ri; Hyung, Jung-Hwan; Kim, Gil-Sung; Ohgai, Takeshi; Lee, Sang-Kwon

2012-04-01

Direct CD4+ T lymphocytes were separated from whole mouse splenocytes using 1-dimensional ferromagnetic nickel silicide nanowires (NiSi NWs). NiSi NWs were prepared by silver-assisted wet chemical etching of silicon and subsequent deposition and annealing of Ni. This method exhibits a separation efficiency of ˜93.5%, which is comparable to that of the state-of-the-art superparamagnetic bead-based cell capture (˜96.8%). Furthermore, this research shows potential for separation of other lymphocytes, B, natural killer and natural killer T cells, and even rare tumor cells simply by changing the biotin-conjugated antibodies.

Method of preparing high-temperature-stable thin-film resistors

DOEpatents

Raymond, Leonard S.

1983-01-01

A chemical vapor deposition method for manufacturing tungsten-silicide thin-film resistors of predetermined bulk resistivity and temperature coefficient of resistance (TCR). Gaseous compounds of tungsten and silicon are decomposed on a hot substrate to deposit a thin-film of tungsten-silicide. The TCR of the film is determined by the crystallinity of the grain structure, which is controlled by the temperature of deposition and the tungsten to silicon ratio. The bulk resistivity is determined by the tungsten to silicon ratio. Manipulation of the fabrication parameters allows for sensitive control of the properties of the resistor.

Carbon or boron modified titanium silicide

DOEpatents

Thom, A.J.; Akinc, M.

1998-07-14

A titanium silicide material based on Ti{sub 5}Si{sub 3} intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000 C. Boron is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end. 3 figs.

Carbon or boron modified titanium silicide

DOEpatents

Thom, A.J.; Akinc, M.

1997-12-02

A titanium silicide material based on Ti{sub 5}Si{sub 3} intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000 C. Boron is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end. 3 figs.

Carbon or boron modified titanium silicide

DOEpatents

Thom, Andrew J.; Akinc, Mufit

1996-12-03

A titanium silicide material based on Ti.sub.5 Si.sub.3 intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000.degree. C. Boron is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end.

Controlling the width of self-assembled dysprosium silicide nanowires on the Si(001) surface.

PubMed

Cui, Y; Chung, J; Nogami, J

2012-02-01

We present STM data that show that it is possible to use a metal induced 2 × 7 reconstruction of Si(001) to narrow the width distribution of Dy silicide nanowires. This behavior is distinct from the effect of the 7 × 7 reconstruction on the Si(111) surface, where the 7 × 7 serves as a static template and the deposited metal avoids the unit cell boundaries on the substrate. In this case, the 2 × 7 is a dynamic template, and the nanowires nucleate at anti-phase boundaries between 2 × 7 reconstruction domains.

Carbon or boron modified titanium silicide

DOEpatents

Thom, Andrew J.; Akinc, Mufit

1997-12-02

A titanium silicide material based on Ti.sub.5 Si.sub.3 intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000.degree. C. Boron is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end.

Carbon or boron modified titanium silicide

DOEpatents

Thom, A.J.; Akinc, M.

1996-12-03

A titanium silicide material based on Ti{sub 5}Si{sub 3} intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000 C. Boron is added to a Ti{sub 5}Si{sub 3} base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end. 3 figs.

Infrared photodetectors with tailorable response due to resonant plasmon absorption in epitaxial silicide particles embedded in silicon

NASA Technical Reports Server (NTRS)

Fathauer, R. W.; Dejewski, S. M.; George, T.; Jones, E. W.; Krabach, T. N.; Ksendzov, A.

1993-01-01

Tailorable infrared photoresponse in the 1-2 micron range are demonstrated in a device incorporating electrically floating metal silicide particles. Photons absorbed by excitation of the metallic-particle surface plasmon are shown to contribute to the photoresponse. Quantum efficiencies of roughly 0.2 percent are measured at 77 K, with dark currents of less than 2 nA/sq cm at a reverse bias of 1 V and detectivities of 4 x 10 exp 9 - 8 x 10 exp 9 cm sq rt Hz/W are obtained.

Carbon or boron modified titanium silicide

DOEpatents

Thom, Andrew J.; Akinc, Mufit

1998-07-14

A titanium silicide material based on Ti.sub.5 Si.sub.3 intermetallic compound exhibits substantially improved oxidative stability at elevated temperatures. In particular, carbon is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.6 weight % C) effective to impart substantially improved oxidative stability at elevated temperatures, such as about 1000.degree. C. Boron is added to a Ti.sub.5 Si.sub.3 base material in an amount (e.g. about 0.3 to about 3.3 weight % B) to this same end.

X-ray photoemission spectromicroscopy of titanium silicide formation in patterned microstructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, S.; Solak, H.; Cerrina, F.

1997-04-01

Titanium silicide has the lowest resistivity of all the refractory metal silicides and has good thermal stability as well as excellent compatibility with Al metallization. It is used as an intermediate buffer layer between W vias and the Si substrate to provide good electrical contact in ULSI technology, whose submicron patterned features form the basis of the integrated circuits of today and tomorrow, in the self aligned silicide (salicide) formation process. TiSi{sub 2} exists in two phases: a metastable C49 base-centered orthorhombic phase with specific resistivity of 60-90 {mu}{Omega}-cm that is formed at a lower temperature (formation anneal) and themore » stable 12-15 {mu}{Omega}-cm resistivity face-centered orthorhombic C54 phase into which C49 is transformed with a higher temperature (conversion anneal) step. C54 is clearly the target for low resistivity VLSI interconnects. However, it has been observed that when dimensions shrink below 1/mic (or when the Ti thickness drops below several hundred angstroms), the transformation of C49 into C54 is inhibited and agglomeration often occurs in fine lines at high temperatures. This results in a rise in resistivity due to incomplete transformation to C54 and because of discontinuities in the interconnect line resulting from agglomeration. Spectromicroscopy is an appropriate tool to study the evolution of the TiSi2 formation process because of its high resolution chemical imaging ability which can detect bonding changes even in the absence of changes in the relative amounts of species and because of the capability of studying thick {open_quotes}as is{close_quotes} industrial samples.« less

Silicon-germanium and platinum silicide nanostructures for silicon based photonics

NASA Astrophysics Data System (ADS)

Storozhevykh, M. S.; Dubkov, V. P.; Arapkina, L. V.; Chizh, K. V.; Mironov, S. A.; Chapnin, V. A.; Yuryev, V. A.

2017-05-01

This paper reports a study of two types of silicon based nanostructures prospective for applications in photonics. The first ones are Ge/Si(001) structures forming at room temperature and reconstructing after annealing at 600°C. Germanium, being deposited from a molecular beam at room temperature on the Si(001) surface, forms a thin granular film composed of Ge particles with sizes of a few nanometers. A characteristic feature of these films is that they demonstrate signs of the 2 x 1 structure in their RHEED patterns. After short-term annealing at 600°C under the closed system conditions, the granular films reconstruct to heterostructures consisting of a Ge wetting layer and oval clusters of Ge. A mixed type c(4x2) + p(2x2) reconstruction typical to the low-temperature MBE (Tgr < 600°C) forms on the wetting layer. Long-term annealing of granular films at the same conditions results in formation of c(4x2)-reconstructed wetting layer typical to high-temperature MBE (Tgr < 600°C) and huge clusters of Ge. The other type of the studied nanostructures is based on Pt silicides. This class of materials is one of the friendliest to silicon technology. But as silicide film thickness reaches a few nanometers, low resistivity becomes of primary importance. Pt3Si has the lowest sheet resistance among the Pt silicides. However, the development of a process of thin Pt3Si films formation is a challenging task. This paper describes formation of a thin Pt3Si/Pt2Si structures at room temperature on poly-Si films. Special attention is paid upon formation of poly-Si and amorphous Si films on Si3N4 substrates at low temperatures.

Study of ion beam sputtered Fe/Si interfaces as a function of Si layer thickness

NASA Astrophysics Data System (ADS)

Kumar, Anil; Brajpuriya, Ranjeet; Singh, Priti

2018-01-01

The exchange interaction in metal/semiconductor interfaces is far from being completely understood. Therefore, in this paper, we have investigated the nature of silicon on the Fe interface in the ion beam deposited Fe/Si/Fe trilayers keeping the thickness of the Fe layers fixed at 3 nm and varying the thickness of the silicon sandwich layer from 1.5 nm to 4 nm. Grazing incidence x-ray diffraction and atomic force microscopy techniques were used, respectively, to study the structural and morphological changes in the deposited films as a function of layer thickness. The structural studies show silicide formation at the interfaces during deposition and better crystalline structure of Fe layers at a lower spacer layer thickness. The magnetization behavior was investigated using magneto-optical Kerr effect, which clearly shows that coupling between the ferromagnetic layers is highly influenced by the semiconductor spacer layer thickness. A strong antiferromagnetic coupling was observed for a value of tSi = 2.5 nm but above this value an unexpected behavior of hysteresis loop (step like) with two coercivity values is recorded. For spacer layer thickness greater than 2.5 nm, an elemental amorphous Si layer starts to appear in the spacer layer in addition to the silicide layer at the interfaces. It is observed that in the trilayer structure, Fe layers consist of various stacks, viz., Si doped Fe layers, ferromagnetic silicide layer, and nonmagnetic silicide layer at the interfaces. The two phase hysteresis loop is explained on the basis of magnetization reversal of two ferromagnetic layers, independent of each other, with different coercivities. X-ray photo electron spectroscopy technique was also used to study interfaces characteristics as a function of tSi.

Custom-Machined Miniplates and Bone-Supported Guides for Orthognathic Surgery: A New Surgical Procedure.

PubMed

Brunso, Joan; Franco, Maria; Constantinescu, Thomas; Barbier, Luis; Santamaría, Joseba Andoni; Alvarez, Julio

2016-05-01

Several surgical strategies exist to improve accuracy in orthognathic surgery, but ideal planning and treatment have yet to be described. The purpose of this study was to present and assess the accuracy of a virtual orthognathic positioning system (OPS), based on the use of bone-supported guides for placement of custom, highly rigid, machined titanium miniplates produced using computer-aided design and computer-aided manufacturing technology. An institutional review board-approved prospective observational study was designed to evaluate our early experience with the OPS. The inclusion criteria were as follows: adult patients who were classified as skeletal Class II or III patients and as candidates for orthognathic surgery or who were candidates for maxillomandibular advancement as a treatment for obstructive sleep apnea. Reverse planning with computed tomography and modeling software was performed. Our OPS was designed to avoid the use of intermaxillary fixation and occlusal splints. The minimum follow-up period was 1 year. Six patients were enrolled in the study. The custom OPS miniplates fit perfectly with the anterior buttress of the maxilla and the mandible body surface intraoperatively. To evaluate accuracy, the postoperative 3-dimensional reconstructed computed tomography image and the presurgical plan were compared. In the maxillary fragments that underwent less than 6 mm of advancement, the OPS enabled an SD of 0.14 mm (92% within 1 mm) at the upper maxilla and 0.34 mm (86% within 1 mm) at the mandible. In the case of great advancements of more than 10 mm, the SD was 1.33 mm (66% within 1 mm) at the upper maxilla and 0.67 mm (73% within 1 mm) at the mandibular level. Our novel OPS was safe and well tolerated, providing positional control with considerable surgical accuracy. The OPS simplified surgery by being independent of support from the opposite maxilla and obviating the need for classic intermaxillary occlusal splints. Copyright © 2016 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Work function characterization of solution-processed cobalt silicide

DOE PAGES

Ullah, Syed Shihab; Robinson, Matt; Hoey, Justin; ...

2012-05-08

Cobalt silicide thin films were prepared by spin-coating Si6H12-based inks onto various substrates followed by a thermal treatment. The work function of the solution processed Co-Si was determined by both capacitance-voltage (C-V) measurements of metal-oxide-semiconductor (MOS) structures as well as by ultraviolet photoelectron spectroscopy (UPS). The UPS-derived work function was 4.80 eV for a Co-Si film on Si (100) while C-V of MOS structures yielded a work function of 4.36 eV where the metal was solution-processed Co-Si, the oxide was SiO2 and the semiconductor was a B-doped Si wafer.

Polarization-independent dual-band terahertz metamaterial absorbers based on gold/parylene-C/silicide structure.

PubMed

Wen, Yongzheng; Ma, Wei; Bailey, Joe; Matmon, Guy; Yu, Xiaomei; Aeppli, Gabriel

2013-07-01

We design, fabricate, and characterize dual-band terahertz (THz) metamaterial absorbers with high absorption based on structures consisting of a cobalt silicide (Co-Si) ground plane, a parylene-C dielectric spacer, and a metal top layer. By combining two periodic metal resonators that couple separately within a single unit cell, a polarization-independent absorber with two distinct absorption peaks was obtained. By varying the thickness of the dielectric layer, we obtain absorptivity of 0.76 at 0.76 THz and 0.97 at 2.30 THz, which indicates the Co-Si ground plane absorbers present good performance.

Microalloying of transition metal silicides by mechanical activation and field-activated reaction

DOEpatents

Munir, Zuhair A [Davis, CA; Woolman, Joseph N [Davis, CA; Petrovic, John J [Los Alamos, NM

2003-09-02

Alloys of transition metal suicides that contain one or more alloying elements are fabricated by a two-stage process involving mechanical activation as the first stage and densification and field-activated reaction as the second stage. Mechanical activation, preferably performed by high-energy planetary milling, results in the incorporation of atoms of the alloying element(s) into the crystal lattice of the transition metal, while the densification and field-activated reaction, preferably performed by spark plasma sintering, result in the formation of the alloyed transition metal silicide. Among the many advantages of the process are its ability to accommodate materials that are incompatible in other alloying methods.

Photocatalytic hydrogen evolution over β-iron silicide under infrared-light irradiation.

PubMed

Yoshimizu, Masaharu; Kobayashi, Ryoya; Saegusa, Makoto; Takashima, Toshihiro; Funakubo, Hiroshi; Akiyama, Kensuke; Matsumoto, Yoshihisa; Irie, Hiroshi

2015-02-18

We investigated the ability of β-iron silicide (β-FeSi2) to serve as a hydrogen (H2)-evolution photocatalyst due to the potential of its conduction band bottom, which may allow thermodynamically favorable H2 evolution in spite of its small band-gap of 0.80 eV. β-FeSi2 had an apparent quantum efficiency for H2 evolution of ∼24% up to 950 nm (near infrared light), in the presence of the dithionic acid ion (S2O6(2-)) as a sacrificial agent. It was also sensitive to infrared light (>1300 nm) for H2 evolution.

Degradation and reuse of radiative thermal protection system materials for the space shuttle

NASA Technical Reports Server (NTRS)

Bartlett, E. S.; Maykuth, D. J.; Grinberg, I. M.; Luce, R. G.

1971-01-01

Three silicide coated columbium alloys and two cobalt alloys were subjected to identical simulated reentry profiling exposures in both static (controlled vacuum leak) and dynamic (hypersonic plasma shear) environments. Primary emphasis in the columbium alloy evaluation was on the Cb752 and C129Y alloys with a lesser amount on FS85. Commercial silicide coatings of the R512E and VH109 formulations were used. The coated specimens were intentionally defected to provide the types of coating flaws that are expected in service. Temperatures were profiled up to peak temperatures of either 2350 F or 2500 F for 15 minutes in each cycle.

Rapid Solid-State Metathesis Routes to Nanostructured Silicon-Germainum

NASA Technical Reports Server (NTRS)

Rodriguez, Marc (Inventor); Kaner, Richard B. (Inventor); Bux, Sabah K. (Inventor); Fleurial, Jean-Pierre (Inventor)

2014-01-01

Methods for producing nanostructured silicon and silicon-germanium via solid state metathesis (SSM). The method of forming nanostructured silicon comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and an alkaline earth metal silicide into a homogeneous powder, and initating the reaction between the silicon tetraiodide (SiI4) with the alkaline earth metal silicide. The method of forming nanostructured silicon-germanium comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and a germanium based precursor into a homogeneous powder, and initiating the reaction between the silicon tetraiodide (SiI4) with the germanium based precursors.

Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

NASA Astrophysics Data System (ADS)

Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

2018-03-01

In this work, the Nb-rich ternary eutectic in the Nb-Si-Cr system has been experimentally determined to be Nb-10.9Si-28.4Cr (in at. pct). The eutectic is composed of three main phases: Nb solid solution (Nbss), β-Cr2Nb, and Nb9(Si,Cr)5. The ternary eutectic microstructure remains stable for several hundred hours at a temperature up to 1473 K (1200 °C). At 1573 K (1300 °C) and above, the silicide phase Nb9(Si,Cr)5 decomposes into α-Nb5Si3, Nbss, and β-Cr2Nb. Under creep conditions at 1473 K (1200 °C), the alloy deforms by dislocation creep while the major creep resistance is provided by the silicide matrix. If the silicide phase is fragmented and, thus, its matrix character is destroyed by prior heat treatment [ e.g., at 1773 K (1500 °C) for 100 hours], creep is mainly controlled by the Laves phase β-Cr2Nb, resulting in increased minimum strain rates. Compared to state of the art Ni-based superalloys, the creep resistance of this three-phase eutectic alloy is significantly higher.

Growth, stability and decomposition of Mg2Si ultra-thin films on Si (100)

NASA Astrophysics Data System (ADS)

Sarpi, B.; Zirmi, R.; Putero, M.; Bouslama, M.; Hemeryck, A.; Vizzini, S.

2018-01-01

Using Auger Electron Spectroscopy (AES), Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Low Energy Electron Diffraction (LEED), we report an in-situ study of amorphous magnesium silicide (Mg2Si) ultra-thin films grown by thermally enhanced solid-phase reaction of few Mg monolayers deposited at room temperature (RT) on a Si(100) surface. Silicidation of magnesium films can be achieved in the nanometric thickness range with high chemical purity and a high thermal stability after annealing at 150 °C, before reaching a regime of magnesium desorption for temperatures higher than 350 °C. The thermally enhanced reaction of one Mg monolayer (ML) results in the appearance of Mg2Si nanometric crystallites leaving the silicon surface partially uncovered. For thicker Mg deposition nevertheless, continuous 2D silicide films are formed with a volcano shape surface topography characteristic up to 4 Mg MLs. Due to high reactivity between magnesium and oxygen species, the thermal oxidation process in which a thin Mg2Si film is fully decomposed (0.75 eV band gap) into a magnesium oxide layer (6-8 eV band gap) is also reported.

Electrical characterization of strained and unstrained silicon nanowires with nickel silicide contacts.

PubMed

Habicht, S; Zhao, Q T; Feste, S F; Knoll, L; Trellenkamp, S; Ghyselen, B; Mantl, S

2010-03-12

We present electrical characterization of nickel monosilicide (NiSi) contacts formed on strained and unstrained silicon nanowires (NWs), which were fabricated by top-down processing of initially As(+) implanted and activated strained and unstrained silicon-on-insulator (SOI) substrates. The resistivity of doped Si NWs and the contact resistivity of the NiSi to Si NW contacts are studied as functions of the As(+) ion implantation dose and the cross-sectional area of the wires. Strained silicon NWs show lower resistivity for all doping concentrations due to their enhanced electron mobility compared to the unstrained case. An increase in resistivity with decreasing cross section of the NWs was observed for all implantation doses. This is ascribed to the occurrence of dopant deactivation. Comparing the silicidation of uniaxially tensile strained and unstrained Si NWs shows no difference in silicidation speed and in contact resistivity between NiSi/Si NW. Contact resistivities as low as 1.2 x 10(-8) Omega cm(-2) were obtained for NiSi contacts to both strained and unstrained Si NWs. Compared to planar contacts, the NiSi/Si NW contact resistivity is two orders of magnitude lower.

Ultrashort channel silicon nanowire transistors with nickel silicide source/drain contacts.

PubMed

Tang, Wei; Dayeh, Shadi A; Picraux, S Tom; Huang, Jian Yu; Tu, King-Ning

2012-08-08

We demonstrate the shortest transistor channel length (17 nm) fabricated on a vapor-liquid-solid (VLS) grown silicon nanowire (NW) by a controlled reaction with Ni leads on an in situ transmission electron microscope (TEM) heating stage at a moderate temperature of 400 °C. NiSi(2) is the leading phase, and the silicide-silicon interface is an atomically sharp type-A interface. At such channel lengths, high maximum on-currents of 890 (μA/μm) and a maximum transconductance of 430 (μS/μm) were obtained, which pushes forward the performance of bottom-up Si NW Schottky barrier field-effect transistors (SB-FETs). Through accurate control over the silicidation reaction, we provide a systematic study of channel length dependent carrier transport in a large number of SB-FETs with channel lengths in the range of 17 nm to 3.6 μm. Our device results corroborate with our transport simulations and reveal a characteristic type of short channel effects in SB-FETs, both in on- and off-state, which is different from that in conventional MOSFETs, and that limits transport parameter extraction from SB-FETs using conventional field-effect transconductance measurements.

High temperature chlorosilane corrosion of iron and AISI 316L stainless steel

NASA Astrophysics Data System (ADS)

Aller, Joshua Loren

Chlorosilane gas streams are used at high temperatures (>500°C) throughout the semiconductor, polycrystalline silicon, and fumed silica industries, primarily as a way to refine, deposit, and produce silicon and silicon containing materials. The presence of both chlorine and silicon in chlorosilane species creates unique corrosion environments due to the ability of many metals to form both metal-chlorides and metal-silicides, and it is further complicated by the fact that many metal-chlorides are volatile at high-temperatures while metal-silicides are generally stable. To withstand the uniquely corrosive environments, expensive alloys are often utilized, which increases the cost of final products. This work focuses on the corrosion behavior of iron, the primary component of low-cost alloys, and AISI 316L, a common low-cost stainless steel, in environments representative of industrial processes. The experiments were conducted using a customized high temperature chlorosilane corrosion system that exposed samples to an atmospheric pressure, high temperature, chlorosilane environment with variable input amounts of hydrogen, silicon tetrachloride, and hydrogen chloride plus the option of embedding samples in silicon during the exposure. Pre and post exposure sample analysis including scanning electron microscopy, x-ray diffraction, energy dispersive x-ray spectroscopy, and gravimetric analysis showed the surface corrosion products varied depending on the time, temperature, and environment that the samples were exposed to. Most commonly, a volatile chloride product formed first, followed by a stratified metal silicide layer. The chlorine and silicon activities in the corrosion environment were changed independently and were found to significantly alter the corrosion behavior; a phenomenon supported by computational thermodynamic equilibrium simulations. It was found that in comparable environments, the stainless steel corroded significantly less than the pure iron. This is likely due to the alloying elements present in stainless steel that promote formation of other stable silicides. Mechanistic models were developed to describe the formation and evolution of metal silicide and/or metal chloride surface corrosion products in chlorosilane environments. These models will help inform materials selection and/or support process development for next-generation chlorosilane-based production and deposition systems. The implementation of low cost materials of construction in these systems could lower the cost of final products in these industries.

Domestic Aluminum Resources: Dilemmas of Development. Volume II. Appendixes II-VII. Detailed Agency Comments and GAO Response.

DTIC Science & Technology

1980-07-17

31 Clay/hydrochloric acid, gas - induced crystallization 32 Clay/nitric acid evaporative crystallization 32 Clay/hydrochloric acid, evapora- tive...ALUMINA AND ALUMINUM TECHNOLOGIES 53 Evaluation of nonbauxitic alumina production processes 54 Clay/carbo-chlorination 54 Clay/hydrochloric acid, gas ...reports that the miniplant program is centered on a single process-- clay/hydrochloric acid- gas precipitation. The Bureau of Mines has not retreated

Treatment of traumatic infra orbital nerve paresthesia

PubMed Central

Lone, Parveen Akhter; Singh, R. K.; Pal, U. S.

2012-01-01

This study was done to find out the role of topiramate therapy in infraorbital nerve paresthesia after miniplate fixation in zygomatic complxex fractures. A total 2 cases of unilateral zygomatic complex fracture, 2-3 weeks old with infra orbital nerve paresthesia were slected. Open reduction and plating was done in frontozygomaticregion. Antiepileptic drug tab topiramate was given in therapeutic doses and dose was increased slowly until functional recovery was noticed. PMID:23833503

Development of a Scale-up Tool for Pervaporation Processes

PubMed Central

Thiess, Holger; Strube, Jochen

2018-01-01

In this study, an engineering tool for the design and optimization of pervaporation processes is developed based on physico-chemical modelling coupled with laboratory/mini-plant experiments. The model incorporates the solution-diffusion-mechanism, polarization effects (concentration and temperature), axial dispersion, pressure drop and the temperature drop in the feed channel due to vaporization of the permeating components. The permeance, being the key model parameter, was determined via dehydration experiments on a mini-plant scale for the binary mixtures ethanol/water and ethyl acetate/water. A second set of experimental data was utilized for the validation of the model for two chemical systems. The industrially relevant ternary mixture, ethanol/ethyl acetate/water, was investigated close to its azeotropic point and compared to a simulation conducted with the determined binary permeance data. Experimental and simulation data proved to agree very well for the investigated process conditions. In order to test the scalability of the developed engineering tool, large-scale data from an industrial pervaporation plant used for the dehydration of ethanol was compared to a process simulation conducted with the validated physico-chemical model. Since the membranes employed in both mini-plant and industrial scale were of the same type, the permeance data could be transferred. The comparison of the measured and simulated data proved the scalability of the derived model. PMID:29342956

Congenital cervical kyphosis in an infant with Ehlers-Danlos syndrome.

PubMed

Kobets, Andrew J; Komlos, Daniel; Houten, John K

2018-07-01

Ehler-Danlos syndome (EDS) refers to a group of heritable connective tissue disorders; rare manifestations of which are cervical kyphosis and clinical myelopathy. Surgical treatment is described for the deformity in the thoracolumbar spine in adolescents but not for infantile cervical spine. Internal fixation for deformity correction in the infantile cervical spine is challenging due to the diminutive size of the bony anatomy and the lack of spinal instrumentation specifically designed for young children. We describe the first case of successful surgical treatment in an infant with a high cervical kyphotic deformity in EDS. A 15-month-old female with EDS presented with several months of regression in gross motor skills in all four extremities. Imaging demonstrated 45° of kyphosis from the C2-4 levels with spinal cord compression. Corrective surgery consisted of a C3 corpectomy and C2-4 anterior fusion with allograft block and anterior fixation with dual 2 × 2 hole craniofacial miniplates, supplemented by C2-4 posterior fusion using four craniofacial miniplates fixated to the lamina. Radiographs at 20 months post-surgery demonstrated solid fusion both anteriorly and posteriorly with maintenance of correction. Ehlers-Danlos syndrome may present in the pediatric population with congenital kyphosis from cervical deformity in addition to the more commonly seen thoracolumbar deformities.

Development and fabrication of improved Schottky power diodes

NASA Technical Reports Server (NTRS)

Cordes, L. F.; Garfinkel, M.; Taft, E. A.

1975-01-01

Reproducible methods for the fabrication of silicon Schottky diodes have been developed for tungsten, aluminum, conventional platinum silicide, and low temperature platinum silicide. Barrier heights and barrier lowering under reverse bias have been measured, permitting the accurate prediction of forward and reverse diode characteristics. Processing procedures have been developed that permit the fabrication of large area (about 1 sq cm) mesageometry power Schottky diodes with forward and reverse characteristics that approach theoretical values. A theoretical analysis of the operation of bridge rectifier circuits has been performed, which indicates the ranges of frequency and voltage for which Schottky rectifiers are preferred to p-n junctions. Power Schottky rectifiers have been fabricated and tested for voltage ratings up to 140 volts.

Diamond Composite Films for Protective Coatings on Metals and Method of Formation

NASA Technical Reports Server (NTRS)

Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

1997-01-01

Composite films consisting of diamond crystallites and hard amorphous films such as diamond-like carbon, titanium nitride, and titanium oxide are provided as protective coatings for metal substrates against extremely harsh environments. A composite layer having diamond crystallites and a hard amorphous film is affixed to a metal substrate via an interlayer including a bottom metal silicide film and a top silicon carbide film. The interlayer is formed either by depositing metal silicide and silicon carbide directly onto the metal substrate, or by first depositing an amorphous silicon film, then allowing top and bottom portions of the amorphous silicon to react during deposition of the diamond crystallites, to yield the desired interlayer structure.

Nickel-silicide colloid prepared under mild conditions as a versatile Ni precursor for more efficient CO2 reforming of CH4 catalysts.

PubMed

Baudouin, David; Szeto, Kaï Chung; Laurent, Pierre; De Mallmann, Aimery; Fenet, Bernard; Veyre, Laurent; Rodemerck, Uwe; Copéret, Christophe; Thieuleux, Chloé

2012-12-26

Preparing highly active and stable non-noble-metal-based dry reforming catalysts remains a challenge today. In this context, supported nickel nanoparticles with sizes of 1.3 ± 0.2 and 2.1 ± 0.2 nm were synthesized on silica and ceria, respectively, via a two-step colloidal approach. First, 2-nm nickel-silicide colloids were synthesized from Ni(COD)(2) and octylsilane at low temperature; they were subsequently dispersed onto supports prior to reduction under H(2). The resulting catalysts display high activity in dry reforming compared to their analogues prepared using conventional approaches, ceria providing greatly improved catalyst stability.

Thermoelectric properties of higher manganese silicide/multi-walled carbon nanotube composites.

PubMed

Truong, D Y Nhi; Kleinke, Holger; Gascoin, Franck

2014-10-28

Composites made of Higher Manganese Silicide (HMS)-based compound MnSi1.75Ge0.02 and multi-walled carbon nanotubes (MWCNTs) were prepared by an easy and effective method including mechanical milling under mild conditions and reactive spark plasma sintering. SEM compositional mappings show a homogeneous dispersion of MWCNTs in the HMS matrix. Electronic and thermal transport properties were measured from room temperature to 875 K. While power factors are virtually unchanged by the addition of MWCNTs, the lattice thermal conductivity is significantly reduced by about 30%. As a consequence, the maximum figure of merit for the composites with 1 wt% MWCNTs is improved by about 20% compared to the MWCNT free HMS-based sample.

High-Temperature Syntheses of New, Thermally-Stable Chemical Compounds.

DTIC Science & Technology

SYNTHESIS(CHEMISTRY), HEAT RESISTANT PLASTICS, NITRILES, FLUORINE COMPOUNDS, COMPLEX COMPOUNDS, NITROGEN, SULFIDES, ORGANOMETALLIC COMPOUNDS, ORGANOBORANES, BORIDES, SPINEL, CARBIDES, NITRIDES, SILICIDES .

Convective cooling in a pool-type research reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sipaun, Susan, E-mail: susan@nm.gov.my; Usman, Shoaib, E-mail: usmans@mst.edu

2016-01-22

A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U{sub 3}Si{sub 2}Al) in the form of rectangular plates. Gaps between the plates allow coolant to passmore » through and carry away heat. A study was carried out to map out heat flow as well as to predict the system’s performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm{sup −3}. An MSTR model consisting of 20% of MSTR’s nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s{sup −1} from the 4” pipe, and predicted pool surface temperature not exceeding 30°C.« less

Study of iridium silicide monolayers using density functional theory

NASA Astrophysics Data System (ADS)

Popis, Minh D.; Popis, Sylvester V.; Oncel, Nuri; Hoffmann, Mark R.; ćakır, Deniz

2018-02-01

In this study, we investigated physical and electronic properties of possible two-dimensional structures formed by Si (silicon) and Ir (iridium). To this end, different plausible structures were modeled by using density functional theory and the cohesive energies calculated for the geometry of optimized structures, with the lowest equilibrium lattice constants. Among several candidate structures, we identified three mechanically (via elastic constants and Young's modulus), dynamically (via phonon calculations), and thermodynamically stable iridium silicide monolayer structures. The lowest energy structure has a chemical formula of Ir2Si4 (called r-IrSi2), with a rectangular lattice (Pmmn space group). Its cohesive energy was calculated to be -0.248 eV (per IrSi2 unit) with respect to bulk Ir and bulk Si. The band structure indicates that the Ir2Si4 monolayer exhibits metallic properties. Other stable structures have hexagonal (P-3m1) and tetragonal (P4/nmm) cell structures with 0.12 and 0.20 eV/f.u. higher cohesive energies, respectively. Our calculations showed that Ir-Si monolayers are reactive. Although O2 molecules exothermically dissociate on the surface of the free-standing iridium silicide monolayers with large binding energies, H2O molecules bind to the monolayers with a rather weak interaction.

Microstructure of the irradiated U 3Si 2/Al silicide dispersion fuel

NASA Astrophysics Data System (ADS)

Gan, J.; Keiser, D. D.; Miller, B. D.; Jue, J.-F.; Robinson, A. B.; Madden, J. W.; Medvedev, P. G.; Wachs, D. M.

2011-12-01

The silicide dispersion fuel of U 3Si 2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm 3 fuel loading. An irradiated U 3Si 2/Al dispersion fuel ( 235U ˜ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U 3Si 2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 10 27 f/m 3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel-matrix-interaction layer are approximately 1.1 and 4-10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (<1 μm) in the fuel particle are ˜94 nm, 1.05 × 10 20 m -3 and ˜11%, respectively. The results and their implication on the performance of the U 3Si 2/Al silicide dispersion fuel are discussed.

Structural diversity and electronic properties in potassium silicides

NASA Astrophysics Data System (ADS)

Hao, Chun-Mei; Li, Yunguo; Huang, Hong-Mei; Li, Yan-Ling

2018-05-01

Stable potassium silicides in the complete compositional landscape were systematically explored up to 30 GPa using the variable-composition evolutionary structure prediction method. The results show that K4Si, K3Si, K5Si2, K2Si, K3Si2, KSi, KSi2, KSi3, and K8Si46 have their stability fields in the phase diagram. The spatial dimensional diversity of polymerized silicon atoms (0D "isolated" anion, dimer, Si4 group, 1D zigzag chain, 2D layer, and 3D network) under the potassium sublattice was uncovered as silicon content increases. Especially, the 2D layered silicon presents interestingly a variety of shapes, such as the "4 + 6" ring, "4 + 8"ring, and 8-membered ring. K-Si bonding exhibits a mixed covalency and ionicity, while Si-Si bonding is always of covalent character. Semiconductivity or metallicity mainly depends on the form of sublattices and K:Si ratio, which allows us to find more semiconductors in the Si-rich side when closed-shell K cations are encompassed by polymerized Si. The semiconducting silicides present strong absorption in the infrared and visible light range. These findings open up the avenue for experimental synthesis of alkali metal-IVA compounds and potential applications as battery electrode materials or photoelectric materials.

Crystal structure of the ternary silicide Gd2Re3Si5.

PubMed

Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

2014-12-01

A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta-silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo-octa-hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti-prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re-Re distance of 2.78163 (5) Å and isolated squares with an Re-Re distance of 2.9683 (6) Å.

Crystal structure of the ternary silicide Gd2Re3Si5

PubMed Central

Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

2014-01-01

A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta­silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo­octa­hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti­prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5) Å and isolated squares with an Re—Re distance of 2.9683 (6) Å. PMID:25552967

Rare-earth metal gallium silicides via the gallium self-flux method. Synthesis, crystal structures, and magnetic properties of RE(Ga 1–xSi x)₂ (RE=Y, La–Nd, Sm, Gd–Yb, Lu)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darone, Gregory M.; Hmiel, Benjamin; Zhang, Jiliang

Fifteen ternary rare-earth metal gallium silicides have been synthesized using molten Ga as a molten flux. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with three different structures—the early to mid-late rare-earth metals RE=La–Nd, Sm, Gd–Ho, Yb and Y form compounds with empirical formulae RE(Ga xSi 1–x)₂ (0.38≤x≤0.63), which crystallize with the tetragonal α-ThSi₂ structure type (space group I4₁/amd, No. 141; Pearson symbol tI12). The compounds of the late rare-earth crystallize with the orthorhombic α-GdSi₂ structure type (space group Imma, No. 74; Pearson symbol oI12), with refined empirical formula REGa xSi 2–x–y (RE=Ho, Er, Tm;more » 0.33≤x≤0.40, 0.10≤y≤0.18). LuGa₀.₃₂₍₁₎Si₁.₄₃₍₁₎ crystallizes with the orthorhombic YbMn₀.₁₇Si₁.₈₃ structure type (space group Cmcm, No. 63; Pearson symbol oC24). Structural trends are reviewed and analyzed; the magnetic susceptibilities of the grown single-crystals are presented. - Graphical abstract: This article details the exploration of the RE–Ga–Si ternary system with the aim to systematically investigate the structural “boundaries” between the α-ThSi₂ and α-GdSi₂-type structures, and studies of the magnetic properties of the newly synthesized single-crystalline materials. Highlights: • Light rare-earth gallium silicides crystallize in α-ThSi₂ structure type. • Heavy rare-earth gallium silicides crystallize in α-GdSi₂ structure type. • LuGaSi crystallizes in a defect variant of the YbMn₀.₁₇Si₁.₈₃ structure type.« less

Formation, optical properties, and electronic structure of thin Yb silicide films on Si(111)

NASA Astrophysics Data System (ADS)

Galkin, N. G.; Maslov, A. M.; Polyarnyi, V. O.

2005-06-01

Continuous very thin (2.5-3.0 nm) and thin (16-18 nm) ytterbium suicide films with some pinhole density (3×107- 1×108 cm-2) have been formed on Si(111) by solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE) growth methods on templates. The stoichiometric ytterbium suicide (YbSi2) formation has shown in SPE grown films by AES and EELS data. Very thin Yb suicide films grown by RDE method had the silicon enrichment in YbSi2 suicide composition. The analysis of LEED data and AFM imaging has shown that ytterbium suicide films had non-oriented blocks with the polycrystalline structure. The analysis of scanning region length dependencies of the root mean square roughness deviation (σR(L)) for grown suicide films has shown that the formation of ytterbium suicide in SPE and RDE growth methods is determined by the surface diffusion of Yb atoms during the three-dimensional growth process. Optical functions (n, k, α, ɛ1, ɛ2, Im ɛ1-1, neff, ɛeff) of ytterbium silicide films grown on Si(1 1 1) have been calculated from transmittance and reflectance spectra in the energy range of 0.1-6.2 eV. Two nearly discrete absorption bands have been observed in the electronic structure of Yb silicide films with different composition, which connected with interband transitions on divalent and trivalent Yb states. It was established that the reflection coefficient minimum in R-spectra at energies higher 4.2 eV corresponds to the state density minimum in Yb suicide between divalent and trivalent Yb states. It was shown from optical data that Yb silicide films have the semi-metallic properties with low state densities at energies less 0.4 eV and high state densities at 0.5-2.5 eV.

Irradiation behavior of U 6Mn-Al dispersion fuel elements

NASA Astrophysics Data System (ADS)

Meyer, M. K.; Wiencek, T. C.; Hayes, S. L.; Hofman, G. L.

2000-02-01

Irradiation testing of U 6Mn-Al dispersion fuel miniplates was conducted in the Oak Ridge Research Reactor (ORR). Post-irradiation examination showed that U 6Mn in an unrestrained plate configuration performs similarly to U 6Fe under irradiation, forming extensive and interlinked fission gas bubbles at a fission density of approximately 3×10 27 m-3. Fuel plate failure occurs by fission gas pressure driven `pillowing' on continued irradiation.

Isothermal and cyclic oxidation resistance of pack siliconized Mo-Si-B alloy

NASA Astrophysics Data System (ADS)

Majumdar, Sanjib

2017-08-01

Oxidation behaviour of MoSi2 coated Mo-9Si-8B-0.75Y (at.%) alloy has been investigated at three critical temperatures including 750, 900 and 1400 °C in static air. Thermogravimetric analysis (TGA) data indicates a remarkable improvement in the oxidation resistance of the silicide coated alloy in both isothermal and cyclic oxidation tests. The cross-sectional scanning electron microscopy and energy dispersive spectroscopic analysis reveal the occurrence of internal oxidation particularly at the crack fronts formed in the outer MoSi2 layer during thermal cycling. The dominant oxidation mechanisms at 750-900 °C and 1400 °C are identified. Development of MoB inner layer further improves the oxidation resistance of the silicide coated alloy.

Capping of rare earth silicide nanowires on Si(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appelfeller, Stephan; Franz, Martin; Kubicki, Milan

The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along (111) lattice planes. This behavior is related to strain duemore » to the lattice mismatch between the Si overlayer and the nanowires.« less

A promising new thermoelectric material - Ruthenium silicide

NASA Technical Reports Server (NTRS)

Vining, Cronin B.; Mccormack, Joseph A.; Zoltan, Andrew; Zoltan, Leslie D.

1991-01-01

Experimental and theoretical efforts directed toward increasing thermoelectric figure of merit values by a factor of 2 or 3 have been encouraging in several respects. An accurate and detailed theoretical model developed for n-type silicon-germanium (SiGe) indicates that ZT values several times higher than currently available are expected under certain conditions. These new, high ZT materials are expected to be significantly different from SiGe, but not unreasonably so. Several promising candidate materials have been identified which may meet the conditions required by theory. One such candidate, ruthenium silicide, currently under development at JPL, has been estimated to have the potential to exhibit figure of merit values 4 times higher than conventional SiGe materials. Recent results are summarized.

Comparative study of metallic silicide-germanide orthorhombic MnP systems.

PubMed

Connétable, Damien; Thomas, Olivier

2013-09-04

We present a comparative study of the structural, energetic, electronic and elastic properties of MX type MnP systems (where X=Si or Ge, and M=Pt, Pd or Ni) using first-principles calculations. The optimized ground state properties of these systems are in excellent agreement with the experimental values. A detailed comparative study of the elastic properties of polycrystalline structures is also presented. We analyze the relationship between the composition and the properties of the systems. Finally, we present the properties of NiSi1-xGex alloys. We show that these properties depend linearly on the Ge content of the alloy. This work has important consequences for semiconductor devices in which silicides, germanides and alloys thereof are used as contact materials.

Europium Silicide – a Prospective Material for Contacts with Silicon

PubMed Central

Averyanov, Dmitry V.; Tokmachev, Andrey M.; Karateeva, Christina G.; Karateev, Igor A.; Lobanovich, Eduard F.; Prutskov, Grigory V.; Parfenov, Oleg E.; Taldenkov, Alexander N.; Vasiliev, Alexander L.; Storchak, Vyacheslav G.

2016-01-01

Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi2/Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n-Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics. PMID:27211700

Europium Silicide - a Prospective Material for Contacts with Silicon.

PubMed

Averyanov, Dmitry V; Tokmachev, Andrey M; Karateeva, Christina G; Karateev, Igor A; Lobanovich, Eduard F; Prutskov, Grigory V; Parfenov, Oleg E; Taldenkov, Alexander N; Vasiliev, Alexander L; Storchak, Vyacheslav G

2016-05-23

Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi2/Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n-Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics.

Optimized capping layers for EUV multilayers

DOEpatents

Bajt, Sasa [Livermore, CA; Folta, James A [Livermore, CA; Spiller, Eberhard A [Livermore, CA

2004-08-24

A new capping multilayer structure for EUV-reflective Mo/Si multilayers consists of two layers: A top layer that protects the multilayer structure from the environment and a bottom layer that acts as a diffusion barrier between the top layer and the structure beneath. One embodiment combines a first layer of Ru with a second layer of B.sub.4 C. Another embodiment combines a first layer of Ru with a second layer of Mo. These embodiments have the additional advantage that the reflectivity is also enhanced. Ru has the best oxidation resistance of all materials investigated so far. B.sub.4 C is an excellent barrier against silicide formation while the silicide layer formed at the Si boundary is well controlled.

CATALYTIC PROPERTIES OF SEMICONDUCTORS.

DTIC Science & Technology

SEMICONDUCTORS, CATALYSTS), (*CATALYSIS, REACTION KINETICS), (* SODIUM COMPOUNDS, TUNGSTATES), (*GALLIUM ALLOYS, ARSENIC ALLOYS), (*YTTERBIUM...COMPOUNDS, SILICIDES ), (*GERMANIUM, CATALYSIS), INTERNAL CONVERSION, EXCHANGE REACTIONS, HEAT OF ACTIVATION, THERMODYNAMICS, DEUTERIUM, POWDERS, SURFACES, HYDROGEN

The Metacarpal Locked Intramedullary Nail: Comparative Biomechanical Evaluation of New Implant Design for Metacarpal Fractures.

PubMed

Boonyasirikool, Chinnakart; Tanakeatsakul, Sakkarin; Niempoog, Sunyarn

2015-04-01

The optimal fixation of metacarpal fracture should provide sufficient stability to permit early functionfor all types of fracture. However; it must preserve surrounding soft tissue during application and not require secondary removal due to its prominence. The prototype of metacarpal locked intramedullary nail (MCLN) was designed by our institute aiming to achieve those allfeatures. To biomechanically test our newly designed, locked metacarpal nail and compare with common current available fixation methods. Thirty chicken humeri were devided into 3 groups (n = 1 per group) according tofixation techniques: MCLN, 1.5 mm miniplate (Synthes), and Kirschner wire. After complete fixation, all specimens were osteotomized at mid-shaft creating transverse fractures. Five specimens from each group were tested by load of failure under axial compression, and another five under bending force. In axial compression model, the loads tofailure in MCLN group was greatest (460 ± 17 N), which was significant higher than the Kirschner wire group. The MCLN group also showed the highest load to failure in bending test (341 ± 10 N). This value reaches statistical significance when compared with plate and Kirschner wire groups. The MCLN construct provided higher stability than miniplate and Kirschner wire fixation both in axial and bending mode. Together with the minimally invasive and soft tissue-friendly design concept, this study suggests that MCLN is promising fixation option for metacarpal fracture.

Assessing bone volume for orthodontic miniplate fixation below the maxillary frontal process.

PubMed

Präger, T M; Brochhagen, H G; Mischkowski, R; Jost-Brinkmann, P-G; Müller-Hartwich, R

2014-09-01

The maxillary bone below the frontal process is used for orthodontic anchorage; indications have included skeletally anchored protraction of the maxilla for treating Class III malocclusions or the intrusion of teeth in patients with a deep bite. This study was conducted to assess the condition of bone before cortically implanting miniplates in that area of the maxilla. A total of 51 thin-sliced computed tomography scans of 51 fully-dentate adult patients (mean age 24.0 ± 8.1 years; 27 men and 24 women) obtained prior to third-molar osteotomy were evaluated. Study parameters included total bone thickness, thickness of the facial cortical plate, and width of the nasal maxillary buttress. All these parameters were measured at different vertical levels. The bone volume adjacent to the piriform aperture was most pronounced at the basal level and decreased progressively toward more cranial levels. The basal bone structure had a mean total thickness of 7.8 mm, facial cortical plate thickness of 1.9 mm, and nasal maxillary buttress width of 9.2 mm. At 16 mm cranial to the aperture base, these values fell to 5.6 mm, 1.3 mm, and 5.8 mm, respectively. These bone measurements suggest that screws 7 mm in length can be inserted at the base level of the piriform aperture and screws 5 mm long at the cranial end of the bone.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, S. K.; Mohan, S.; Bysakh, S.

The formation of surface oxide layer as well as compositional changes along the thickness for NiTi shape memory alloy thin films deposited by direct current magnetron sputtering at substrate temperature of 300 °C in the as-deposited condition as well as in the postannealed (at 600 °C) condition have been thoroughly studied by using secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, and scanning transmission electron microscopy-energy dispersive x-ray spectroscopy techniques. Formation of titanium oxide (predominantly titanium dioxide) layer was observed in both as-deposited and postannealed NiTi films, although the oxide layer was much thinner (8 nm) in as-deposited condition. The depletionmore » of Ti and enrichment of Ni below the oxide layer in postannealed films also resulted in the formation of a graded microstructure consisting of titanium oxide, Ni{sub 3}Ti, and B2 NiTi. A uniform composition of B2 NiTi was obtained in the postannealed film only below a depth of 200–250 nm from the surface. Postannealed film also exhibited formation of a ternary silicide (Ni{sub x}Ti{sub y}Si) at the film–substrate interface, whereas no silicide was seen in the as-deposited film. The formation of silicide also caused a depletion of Ni in the film in a region ∼250–300 nm just above the film substrate interface.« less

Magnetic and magnetothermal studies of pure and doped gadolinium silicide nanoparticles for self-controlled hyperthermia applications

NASA Astrophysics Data System (ADS)

Alnasir, M. Hisham; Awan, M. S.; Manzoor, Sadia

2018-03-01

We report on magnetic and magnetothermal properties of undoped and doped gadolinium silicide (Gd5Si4) nanoparticles with the objective of simultaneously attaining high specific absorption rate (SAR) and low Curie temperature (TC) suitable for self-controlled hyperthermia applications for which TC ∼ 315-320 K. Pellets of doped gadolinium silicide Gd5(Si1-xGex)4 and (Gd1-xRx)5Si4 with R = Ho, Nd and Er and 0 ≤ x ≤ 0.35 were made by arc melting and reduced to nanoparticulate form by surfactant assisted ball milling. Structural and morphological studies were done using X-ray diffraction and scanning electron microscopy respectively. All samples show soft magnetic properties. At low fields there is a ferromagnetic to paramagnetic transition that reduces remanance and coercivity to zero making these materials very attractive for biomedical applications. Zero-field-cooled thermal demagnetization measurements showed that TC of these nanoparticles can be lowered to lie within the limits required for self-controlled hyperthermia by varying the dopant concentration. Specific absorption rates (SAR's) were obtained from magnetothermia measurements made in an ac magnetic field of amplitude 10 Oe and frequency 300 kHz. We have identified samples that have SAR values larger or comparable to those of magnetite and several ferrite nanoparticles, while having Curie temperatures that are low enough for self controlled hyperthermia applications.

Magnesium and Manganese Silicides For Efficient And Low Cost Thermo-Electric Power Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trivedi, Sudhir B.; Kutcher, Susan W.; Rosemeier, Cory A.

2013-12-02

Thermoelectric Power Generation (TEPG) is the most efficient and commercially deployable power generation technology for harvesting wasted heat from such things as automobile exhausts, industrial furnaces, and incinerators, and converting it into usable electrical power. We investigated the materials magnesium silicide (Mg2Si) and manganese silicide (MnSi) for TEG. MgSi2 and MnSi are environmentally friendly, have constituent elements that are abundant in the earth's crust, non-toxic, lighter and cheaper. In Phase I, we successfully produced Mg2Si and MnSi material with good TE properties. We developed a novel technique to synthesize Mg2Si with good crystalline quality, which is normally very difficult duemore » to high Mg vapor pressure and its corrosive nature. We produced n-type Mg2Si and p-type MnSi nanocomposite pellets using FAST. Measurements of resistivity and voltage under a temperature gradient indicated a Seebeck coefficient of roughly 120 V/K on average per leg, which is quite respectable. Results indicated however, that issues related to bonding resulted in high resistivity contacts. Determining a bonding process and bonding material that can provide ohmic contact from room temperature to the operating temperature is an essential part of successful device fabrication. Work continues in the development of a process for reproducibly obtaining low resistance electrical contacts.« less

Interfacial stability of CoSi2/Si structures grown by molecular beam epitaxy

NASA Technical Reports Server (NTRS)

George, T.; Fathauer, R. W.

1992-01-01

The stability of CoSi2/Si interfaces was examined in this study using columnar silicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were codeposited using MBE at 800 C and the resulting columnar silicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800 C results in the growth of the buried silicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The column sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer. In the second set of experiments, annealing of a 250 nm-thick buried columnar layer at 1000 C under a 100 nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.

Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content.

PubMed

Redondo-Cubero, A; Galiana, B; Lorenz, K; Palomares, F J; Bahena, D; Ballesteros, C; Hernandez-Calderón, I; Vázquez, L

2016-11-04

We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe(+) ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.

Advanced Materials and Manufacturing for Low-Cost, High-Performance Liquid Rocket Combustion Chambers

NASA Technical Reports Server (NTRS)

Williams, Brian E.; Arrieta, Victor M.

2013-01-01

A document describes the low-cost manufacturing of C103 niobium alloy combustion chambers, and the use of a high-temperature, oxidation-resistant coating that is superior to the standard silicide coating. The manufacturing process involved low-temperature spray deposition of C103 on removable plastic mandrels produced by rapid prototyping. Thin, vapor-deposited platinum-indium coatings were shown to substantially improve oxidation resistance relative to the standard silicide coating. Development of different low-cost plastic thrust chamber mandrel materials and prototyping processes (selective laser sintering and stereolithography) yielded mandrels with good dimensional accuracy (within a couple of mils) for this stage of development. The feasibility of using the kinetic metallization cold-spray process for fabrication of free-standing C1O3 thrusters on removable plastic mandrels was also demonstrated. The ambient and elevated temperature mechanical properties of the material were shown to be reasonably good relative to conventionally processed C103, but the greatest potential benefit is that coldsprayed chambers require minimal post-process machining, resulting in substantially lower machining and material costs. The platinum-iridium coating was shown to provide greatly increased oxidation resistance over the silicide when evaluated through oxyacetylene torch testing to as high as 300 F (= 150 C). The iridium component minimizes reaction with the niobium alloy chamber at high temperatures, and provides the high-temperature oxidation resistance needed at the throat.

Kinetics of silicide formation over a wide range of heating rates spanning six orders of magnitude

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molina-Ruiz, Manel; Lopeandía, Aitor F.; Gonzalez-Silveira, Marta

Kinetic processes involving intermediate phase formation are often assumed to follow an Arrhenius temperature dependence. This behavior is usually inferred from limited data over narrow temperature intervals, where the exponential dependence is generally fully satisfied. However, direct evidence over wide temperature intervals is experimentally challenging and data are scarce. Here, we report a study of silicide formation between a 12 nm film of palladium and 15 nm of amorphous silicon in a wide range of heating rates, spanning six orders of magnitude, from 0.1 to 10{sup 5 }K/s, or equivalently more than 300 K of variation in reaction temperature. The calorimetric traces exhibit severalmore » distinct exothermic events related to interdiffusion, nucleation of Pd{sub 2}Si, crystallization of amorphous silicon, and vertical growth of Pd{sub 2}Si. Interestingly, the thickness of the initial nucleation layer depends on the heating rate revealing enhanced mass diffusion at the fastest heating rates during the initial stages of the reaction. In spite of this, the formation of the silicide strictly follows an Arrhenius temperature dependence over the whole temperature interval explored. A kinetic model is used to fit the calorimetric data over the complete heating rate range. Calorimetry is complemented by structural analysis through transmission electron microscopy and both standard and in-situ synchrotron X-ray diffraction.« less

Modified fused silicide coatings for tantalum (Ta-10W) reentry heat shields

NASA Technical Reports Server (NTRS)

Packer, C. M.; Perkins, R. A.

1973-01-01

Results are presented of a program of research to develop a reliable, high performance, fused slurry silicide coating for the Ta-10W alloy. The effort was directed toward developing new and improved formulations for use at 2600 to 2800 F (1700 to 1811 K) in an atmospheric reentry thermal protection system with a 100-mission capability. Based on a thorough characterization of isothermal and cyclic oxidation behavior, bend transition temperatures, room- and elevated-temperature tensile properties, and creep behavior, a 2.5 Mn-33Ti-64.5Si coating (designated MTS) provides excellent protection for the Ta-10W alloy in simulated reentry environments. An extensive analysis of the oxidation behavior and characteristics of the MTS coating in terms of fundamental mechanisms also is presented.

Friction and wear of radiofrequency-sputtered borides, silicides, and carbides

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1978-01-01

The friction and wear properties of several refractory compound coatings were examined. These compounds were applied to 440 C bearing steel surfaces by radiofrequency (RF) sputtering. The refractory compounds were the titanium and molybdenum borides, the titanium and molybdenum silicides, and the titanium, molybdenum, and boron carbides. Friction testing was done with a pin-on-disk wear apparatus at loads from 0.1 to 5.0 newtons. Generally, the best wear properties were obtained when the coatings were bias sputtered onto 440 C disks that had been preoxidized. Adherence was improved because of the better bonding of the coatings to the iron oxide formed during preoxidation. As a class the carbides provided wear protection to the highest loads. Titanium boride coatings provided low friction and good wear properties to moderate loads.

Electronic structure of semiconducting alkali-metal silicides and germanides

NASA Astrophysics Data System (ADS)

Tegze, M.; Hafner, J.

1989-11-01

We present self-consistent linearized-muffin-tin-orbital calculations of the electronic structure of three alkali-metal germanides and silicides (KGe, NaGe, and NaSi). Like the alkali-metal-lead compounds investigated in our earlier work [M. Tegze and J. Hafner, Phys. Rev. B 39, 8263 (1989)] the Ge and Si compounds of the alkali metals form complex structures based on the packing of tetrahedral Ge4 and Si4 clusters. Our calculations show that all three compounds are narrow-gap semiconductors. The width of the energy gap depends on two main factors: the ratio of the intracluster to the intercluster interactions between the group-IV elements (which increases from Pb to Si) and the strength of the interactions between the alkali-metal atoms (which varies with the size ratio).

Thermoelectric Properties of the Quasi-Binary MnSi1.73-FeSi2 System

NASA Astrophysics Data System (ADS)

Sadia, Yatir; Madar, Naor; Kaler, Ilan; Gelbstein, Yaniv

2015-06-01

The higher manganese silicides (HMS) are regarded as very attractive p-type thermoelectric materials for direct conversion of heat to electricity. To compete with other thermodynamic engines (e.g. the Stirling and Rankine cycles), however, the thermoelectric figure of merit of such silicides must be improved. HMS follow a complicated solidification reaction on cooling from the melt, which leads to formation of undesired secondary phases. Furthermore, the electronic carrier concentration of HMS is much higher than the optimum for thermoelectric applications and should be compensated by introduction of doping agents. In this research, the electronic donor action associated with substitution of HMS by FeSi2 was investigated. The effects of excess Si on phase distribution and thermoelectric properties are also discussed in detail.

Electronic structure of nickel silicide in subhalf-micron lines and blanket films: An x-ray absorption fine structures study at the Ni and Si L3,2 edge

NASA Astrophysics Data System (ADS)

Naftel, S. J.; Coulthard, I.; Sham, T. K.; Xu, D.-X.; Erickson, L.; Das, S. R.

1999-05-01

We report a Ni and Si L3,2-edge x-ray absorption near edge structures (XANES) study of nickel-silicon interaction in submicron (0.15 and 0.2 μm) lines on a n-Si(100) wafer as well as a series of well characterized Ni-Si blanket films. XANES measurements recorded in both total electron yield and soft x-ray fluorescence yield indicate that under the selected silicidation conditions, the more desirable low resistivity phase, NiSi, is indeed the dominant phase in the subhalf-micron lines although the formation of this phase is less complete as the line becomes narrower and this is accompanied by a Ni rich surface.

Structure determination of the ordered (2 × 1) phase of NiSi surface alloy on Ni(111) using low-energy electron diffraction

NASA Astrophysics Data System (ADS)

Sazzadur Rahman, Md.; Amirul Islam, Md.; Saha, Bidyut Baran; Nakagawa, Takeshi; Mizuno, Seigi

2015-12-01

The (2 × 1) structure of the two-dimensional nickel silicide surface alloy on Ni(111) was investigated using quantitative low-energy electron diffraction analysis. The unit cell of the determined silicide structure contains one Si and one Ni atom, corresponding to a chemical formula of NiSi. The Si atoms adopt substitutional face-centered cubic hollow sites on the Ni(111) substrate. The Ni-Si bond lengths were determined to be 2.37 and 2.34 Å. Both the alloy surface and the underlying first layers of Ni atoms exhibit slight corrugation. The Ni-Si interlayer distance is smaller than the Ni-Ni interlayer distance, which indicates that Si atoms and underlying Ni atoms strongly interact.

Oxidation at through-hole defects in fused slurry silicide coated columbium alloys FS-85 and Cb-752

NASA Technical Reports Server (NTRS)

Levine, S. R.

1973-01-01

Metal recession and interstitial contamination at 0.08-centimeter-diameter through-hole intentional defects in fused slurry silicide coated FS-85 and Cb-752 columbium alloys were studied to determine the tolerance of these materials to coating defects. Five external pressure reentry simulation exposures to 1320 C and 4.7 x 1,000 N/sq m (maximum pressure) resulted in a consumed metal zone having about twice the initial defect diameter for both alloys with an interstitial contamination zone extending about three to four initial defect diameters. Self-healing occurred in the 1.33 x 10 N/sq m, 1320 C exposures and to a lesser extent in internal pressure reentry cycles to 1320 C and 1.33 x 100 N/sq m (maximum pressure).

Development of Ambient Temperature Lithium-Ion Cells

NASA Technical Reports Server (NTRS)

Huang, C. K.; Ratnakumar, B. V.; Surampudi, S.; Halpert, G.

1994-01-01

Four types of materials have been evaluated as anodes for Li-ion cell fabrication. Among the materials evaluated, graphite and magnasium silicide were identified to be suitable candidate anode materials.

Subsurface Growth Of Silicide Structures In Silicon

NASA Technical Reports Server (NTRS)

Fathauer, Robert W.; George, Thomas; Pike, William T.; Schowalter, Leo

1993-01-01

Technique shows promise for fabrication of novel electronic, optoelectronic, and electro-optical devices. Experiments demonstrated feasibility of growing microscopic single-crystal CoSi2 structures beneath surfaces of Si substrates.

Miniplate-Aided Mandibular Dentition Distalization as a Camouflage Treatment of a Class III Malocclusion in an Adult.

PubMed

Hakami, Zaki; Chen, Po Jung; Ahmida, Ahmad; Janakiraman, Nandakumar; Uribe, Flavio

2018-01-01

This case report describes orthodontic camouflage treatment for a 32-year-old African American male patient with Class III malocclusion. The treatment included nonextraction, nonsurgical orthodontic camouflage by en masse distalization of the mandibular teeth using skeletal anchorage devices. The total treatment time was 23 months. Normal overjet and overbite with Class I occlusion were obtained despite the compensated dentition to the skeletal malocclusion. His smile esthetics was significantly improved at the completion of his treatment.

Miniplate-Aided Mandibular Dentition Distalization as a Camouflage Treatment of a Class III Malocclusion in an Adult

PubMed Central

Chen, Po Jung; Ahmida, Ahmad; Janakiraman, Nandakumar; Uribe, Flavio

2018-01-01

This case report describes orthodontic camouflage treatment for a 32-year-old African American male patient with Class III malocclusion. The treatment included nonextraction, nonsurgical orthodontic camouflage by en masse distalization of the mandibular teeth using skeletal anchorage devices. The total treatment time was 23 months. Normal overjet and overbite with Class I occlusion were obtained despite the compensated dentition to the skeletal malocclusion. His smile esthetics was significantly improved at the completion of his treatment. PMID:29721340

TUNGSTEN BRONZE RELATED NON-NOBLE ELECTROCATALYSTS.

DTIC Science & Technology

FUEL CELLS, *CATALYSTS), (*OXYGEN, *ELECTRODES), (* SILICIDES , ELECTRODES), (*CARBIDES, ELECTRODES), (*TUNGSTEN COMPOUNDS, *ELECTROCHEMISTRY...CATALYSTS, TITANIUM COMPOUNDS, ZIRCONIUM COMPOUNDS, VANADIUM COMPOUNDS, NIOBIUM COMPOUNDS, TUNGSTEN COMPOUNDS, TANTALUM COMPOUNDS, MOLYBDENUM COMPOUNDS, SULFURIC ACID, CRYSTAL GROWTH, SODIUM COMPOUNDS

Growth and characterization of Pt-Si droplets for silicon nanowires synthesis

NASA Astrophysics Data System (ADS)

Khumalo, Z. M.; Topić, M.; Mtshali, C. B.; Blumenthal, M.

2018-02-01

The formation of platinum silicide phases as a function of the annealing temperature was investigated using in-situ real-time Rutherford backscattering spectrometry. The in-situ real-time RBS revealed the reaction of platinum and silicon to start at about 220 °C to form platinum silicide phases, Pt2Si and PtSi in sequence. Scanning electron microscope revealed the morphological change in the platinum layer (formation of droplets) at 800 °C. The particle induced X-ray emission analysis showed the variation of platinum intensity, in the droplets areas, between 1600 and 2000 counts. The surrounding areas are left almost uncovered due to platinum film dewetting. In-plane as well as out-of-plane silicon nanowires were observed to form at 800 °C and 1000 °C using pulsed laser ablation and thermal annealing techniques, respectively.

Interaction of metal layers with polycrystalline Si

NASA Technical Reports Server (NTRS)

Nakamura, K.; Olowolafe, J. O.; Lau, S. S.; Nicolet, M.-A.; Mayer, J. W.; Shima, R.

1976-01-01

Solid-phase reactions of metal films deposited on 0.5-micron-thick polycrystalline layers of Si grown by chemical vapor deposition at 640 C were investigated by MeV He-4 backscattering spectrometry, glancing angle X-ray diffraction, and SEM observations. For the metals Al, Ag, and Au, which form simple eutectics, heat treatment at temperatures below the eutectic results in erosion of the poly-Si layer and growth of Si crystallites in the metal film. Crystallite formation is observed at temperatures exceeding 550 C for Ag, at those exceeding 400 C for Al, and at those exceeding 200 C for Au films. For Pd, Ni, and Cr, heat treatment results in silicide formation. The same initial silicides (Pd2Si, Ni2Si, and CrSi2), are formed at similar temperatures on single-crystal substrates.

Accident-tolerant oxide fuel and cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mariani, Robert D.

Systems and methods for accident tolerant oxide fuel. One or more disks can be placed between fuel pellets comprising UO.sub.2, wherein such disks possess a higher thermal conductivity material than that of the UO.sub.2 to provide enhanced heat rejection thereof. Additionally, a cladding coating comprising zircaloy coated with a material that provides stability and high melting capability can be provided. The pellets can be configured as annular pellets having an annulus filled with the higher thermal conductivity material. The material coating the zircaloy can be, for example, Zr.sub.5Si.sub.4 or another silicide such as, for example, a Zr-Silicide that limits corrosion.more » The aforementioned higher thermal conductivity material can be, for example, Si, Zr.sub.xSi.sub.y, Zr, or Al.sub.2O.sub.3.« less

A general lithography-free method of microscale/nanoscale fabrication and patterning on Si and Ge surfaces

PubMed Central

2012-01-01

Here, we introduce and give an overview of a general lithography-free method to fabricate silicide and germanide micro-/nanostructures on Si and Ge surfaces through metal-vapor-initiated endoepitaxial growth. Excellent controls on shape and orientation are achieved by adjusting the substrate orientation and growth parameters. Furthermore, micro-/nanoscale pits with controlled morphologies can also be successfully fabricated on Si and Ge surfaces by taking advantage of the sublimation of silicides/germanides. The aim of this brief report is to illustrate the concept of lithography-free synthesis and patterning on surfaces of elemental semiconductors, and the differences and the challenges associated with the Si and the Ge surfaces will be discussed. Our results suggest that this low-cost bottom-up approach is promising for applications in functional nanodevices. PMID:22315969

A novel nanoscaled Schottky barrier based transmission gate and its digital circuit applications

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Loan, Sajad A.; Alamoud, Abdulrahman M.

2017-04-01

In this work we propose and simulate a compact nanoscaled transmission gate (TG) employing a single Schottky barrier based transistor in the transmission path and a single transistor based Sajad-Sunil-Schottky (SSS) device as an inverter. Therefore, just two transistors are employed to realize a complete transmission gate which normally consumes four transistors in the conventional technology. The transistors used to realize the transmission path and the SSS inverter in the proposed TG are the double gate Schottky barrier devices, employing stacks of two metal silicides, platinum silicide (PtSi) and erbium silicide (ErSi). It has been observed that the realization of the TG gate by the proposed technology has resulted into a compact structure, with reduced component count, junctions, interconnections and regions in comparison to the conventional technology. The further focus of this work is on the application part of the proposed technology. So for the first time, the proposed technology has been used to realize various combinational circuits, like a two input AND gate, a 2:1 multiplexer and a two input XOR circuits. It has been observed that the transistor count has got reduced by half in a TG, two input AND gate, 2:1 multiplexer and in a two input XOR gate. Therefore, a significant reduction in transistor count and area requirement can be achieved by using the proposed technology. The proposed technology can be also used to perform the compact realization of other combinational and sequential circuitry in future.

Diagenetically altered fossil micrometeorites suggest cosmic dust is common in the geological record

NASA Astrophysics Data System (ADS)

Suttle, Martin D.; Genge, Matthew J.

2017-10-01

We report the discovery of fossil micrometeorites from Late Cretaceous chalk. Seventy-six cosmic spherules were recovered from Coniacian (87 ± 1 Ma) sediments of the White Chalk Supergroup. Particles vary from pristine silicate and iron-type spherules to pseudomorphic spherules consisting of either single-phase recrystallized magnetite or Fe-silicide. Pristine spherules are readily identified as micrometeorites on the basis of their characteristic mineralogies, textures and compositions. Both magnetite and silicide spherules contain dendritic crystals and spherical morphologies, testifying to rapid crystallisation of high temperature iron-rich metallic and oxide liquids. These particles also contain spherical cavities, representing weathering and removal of metal beads and irregular cavities, representing vesicles formed by trapped gas during crystallization; both features commonly found among modern Antarctic Iron-type (I-type) cosmic spherules. On the basis of textural analysis, the magnetite and Fe-silicide spherules are shown to be I-type cosmic spherules that have experienced complete secondary replacement during diagenesis (fossilization). Our results demonstrate that micrometeorites, preserved in sedimentary rocks, are affected by a suite of complex diagenetic processes, which can result in disparate replacement minerals, even within the same sequence of sedimentary beds. As a result, the identification of fossil micrometeorites requires careful observation of particle textures and comparisons with modern Antarctic collections. Replaced micrometeorites imply that geochemical signatures the extraterrestrial dust are subject to diagenetic remobilisation that limits their stratigraphic resolution. However, this study demonstrates that fossil, pseudomorphic micrometeorites can be recognised and are likely common within the geological record.

Buckling reversal of the Si(111) bilayer termination of 2-dimensional ErSi2 upon H dosing

NASA Astrophysics Data System (ADS)

Wetzel, P.; Pirri, C.; Gewinner, G.

1997-05-01

Hydrogen-induced reconstruction of 2-dimensional (2D) ErSi2 epitaxially grown on Si(111) is studied by Auger-electron diffraction (AED) and low-energy electron diffraction (LEED). The intensity of the Er MNN Auger line is measured vs. polar angle along the [1 - 2 1] and [- 1 2 - 1] azimuths for clean and H-saturated (1 × 1) ErSi2 silicides. The atomic structure of clean 2D silicide, previously established by AED as well as other techniques, consists of a hexagonal monolayer of Er located underneath a buckled Si layer comparable to the Si(111) substrate double layers. Moreover, for clean 2D ErSi2 only the B-type orientation is observed, i.e. the buckled Si top layer is always rotated by 180° around the surface normal relative to the relevant double layers of the substrate. After atomic H saturation, AED reveals drastic changes in the silicide structure involving a major most remarkable reconstruction of the Si bilayer termination. The latter is found to switch from B-type to A-type orientation upon H dosing, i.e. H-saturated 2D ErSi2 exhibits a buckled Si top layer oriented in the same way as the substrate double layers. A comparison with single scattering cluster simulations demonstrates that the latter phenomenon is accompanied by a large expansion of the Er-Si interlayer spacing close to 0.3 Å.

A high-resolution core-level photoemission study of the Au/4H-SiC(0001)-([Formula: see text]) interface.

PubMed

Stoltz, D; Stoltz, S E; Johansson, L S O

2007-07-04

We present a systematic study of different reconstructions obtained after deposition of Au on the [Formula: see text]-4H-SiC(0001) surface. For 1-2 monolayers (ML) Au and annealing temperature T(anneal)∼675 °C, a 3 × 3 reconstruction was observed. For 4 ML Au and T(anneal)∼650 °C, a [Formula: see text] reconstruction appeared, while 5 ML Au annealed at 700 °C reconstructed to give a [Formula: see text] pattern. From the Si 2p and Au 4f core-level components, we propose interface models, depending on the amount of Au on the surface and the annealing temperature. For 1-4 ML Au annealed at 650-675 °C, gold diffuses under the topmost Si into the SiC and forms a silicide. An additional Si component in our Si 2p spectra is related to the interface between the silicide and SiC. For 5 ML Au annealed at 700 °C, silicide is also formed at the surface, covering unreacted Au on top of the SiC substrate. The interface Si component is also observed in the Si 2p spectra of this surface. The key role in [Formula: see text]-4H-SiC(0001) interface formation is played by diffusion and the silicon-richness of the surface.

Formation of silicides in annealed periodic multilayers

NASA Astrophysics Data System (ADS)

Maury, H.; Jonnard, P.; Le Guen, K.; André, J.-M.

2009-05-01

Periodic multilayers of nanometric period are widely used as optical components for the X-ray and extreme UV (EUV) ranges, in X-ray space telescopes, X-ray microscopes, EUV photolithography or synchrotron beamlines for example. Their optical performances depend on the quality of the interfaces between the various layers: chemical interdiffusion or mechanical roughness shifts the application wavelength and can drastically decrease the reflectance. Since under high thermal charge interdiffusion is known to get enhanced, the study of the thermal stability of such structures is essential to understand how interfacial compounds develop. We have characterized X-ray and EUV siliconcontaining multilayers (Mo/Si, Sc/Si and Mg/SiC) as a function of the annealing temperature (up to 600°C) using two non-destructive methods. X-ray emission from the silicon atoms, describing the Si valence states, is used to determine the chemical nature of the compounds present in the interphases while X-ray reflectivity in the hard and soft X-ray ranges can be related to the optical properties. In the three cases, interfacial metallic (Mo, Sc, Mg) silicides are evidenced and the thickness of the interphase increases with the annealing temperature. For Mo/Si and Sc/Si multilayers, silicides are even present in the as-prepared multilayers. Characteristic parameters of the stacks are determined: composition of the interphases, thickness and roughness of the layers and interphases if any. Finally, we have evidenced the maximum temperature of application of these multilayers to minimize interdiffusion.

[Latest trends in the surgical management of mandibular condyle fractures in France, 2005-2012].

PubMed

Trost, O; Péron, J-M

2013-12-01

The surgical treatment of mandibular condylar fractures is commonly performed. We had for aim to present the latest trends in the surgical management of condylar fractures in France, between 2005 and 2012. A survey was performed among the 49 members of the French college of oral and maxillofacial surgeons between January and September 2012, with a questionnaire sent by email. We analyzed the therapeutic management, the surgical indications; the techniques used according to the fracture, and the postoperative treatment protocols. The data was compared to that of a similar study performed in 2005. The overall reply rate was 86%. Low subcondylar fractures were operated on in all institutions (100%), compared to 76% in 2005. The most popular technique was the high submandibular approach with intraoral miniplate fixation osteosynthesis. High subcondylar and diacapitular fractures were operated on in respectively 82% and 35% of the cases compared to 29% and 10% in 2005 with various surgical techniques and postoperative management. French maxillofacial surgeons operated on more mandibular condylar fractures in 2012 than in 2005. As observed in 2005, the lower and the more dislocated the fractures were, the more they were operated on. The high submandibular approach has become the most popular approach. The use of miniplates for bone fixation has become common. Diacapitular fractures were usually treated functionally. The postoperative management varied greatly from one team to the other. Copyright © 2013. Published by Elsevier Masson SAS.

Treatment effects of skeletally anchored Forsus FRD EZ and Herbst appliances: A retrospective clinical study.

PubMed

Celikoglu, Mevlut; Buyuk, Suleyman Kutalmis; Ekizer, Abdullah; Unal, Tuba

2016-03-01

To evaluate the skeletal, dentoalveolar, and soft tissue effects of the Forsus FRD appliance with miniplate anchorage inserted in the mandibular symphyses and to compare the findings with a well-matched control group treated with a Herbst appliance for the correction of a skeletal Class II malocclusion due to mandibular retrusion. The sample consisted of 32 Class II subjects divided into two groups. Group I consisted of 16 patients (10 females and 6 males; mean age, 13.20 ± 1.33 years) treated using the Forsus FRD EZ appliance with miniplate anchorage inserted in the mandibular symphyses. Group II consisted of 16 patients (9 females and 7 males; mean age, 13.56 ± 1.27 years) treated using the Herbst appliance. Seventeen linear and 10 angular measurements were performed to evaluate and compare the skeletal, dentoalveolar, and soft tissue effects of the appliances using paired and Student's t-tests. Both appliances were effective in correcting skeletal class II malocclusion and showed similar skeletal and soft tissue changes. The maxillary incisor was statistically significantly more retruded in the skeletally anchored Forsus FRD group (P < .01). The mandibular incisor was retruded in the skeletally anchored Forsus FRD group (-4.09° ± 5.12°), while it was protruded in the Herbst group (7.50° ± 3.98°) (P < .001). Although both appliances were successful in correcting the skeletal Class II malocclusion, the skeletally anchored Forsus FRD EZ appliance did so without protruding the mandibular incisors.

Evaluating the Effect of Minimizing Screws on Stabilization of Symphysis Mandibular Fracture by 3D Finite Element Analysis.

PubMed

Kharmanda, Ghias; Kharma, Mohamed-Yaser

2017-06-01

The objective of this work is to integrate structural optimization and reliability concepts into mini-plate fixation strategy used in symphysis mandibular fractures. The structural reliability levels are next estimated when considering a single failure mode and multiple failure modes. A 3-dimensional finite element model is developed in order to evaluate the ability of reducing the negative effect due to the stabilization of the fracture. Topology optimization process is considered in the conceptual design stage to predict possible fixation layouts. In the detailed design stage, suitable mini-plates are selected taking into account the resulting topology and different anatomical considerations. Several muscle forces are considered in order to obtain realistic predictions. Since some muscles can be cut or harmed during the surgery and cannot operate at its maximum capacity, there is a strong motivation to introduce the loading uncertainties in order to obtain reliable designs. The structural reliability is carried out for a single failure mode and multiple failure modes. The different results are validated with a clinical case of a male patient with symphysis fracture. In this case while use of the upper plate fixation with four holes, only two screws were applied to protect adjacent vital structure. This behavior does not affect the stability of the fracture. The proposed strategy to optimize bone plates leads to fewer complications and second surgeries, less patient discomfort, and shorter time of healing.

The change of amyloplasts structure and composition of storage starch in potato minitubers during imitated microgravity

NASA Astrophysics Data System (ADS)

Nedukha, O. M.; Kordyum, E. L.; Martyn, G. M.; Schnyukova, E. I.

Potato was designated for food production in the controlled ecological life-support system CELSS because its tubers as it is known contain starch and significant protein content and are edible food after the long-term storage We used the cultivation of potato miniplants under influence of long-term horizontal clinorotation 2 rev min which imitated microgravity as a model for the technology of potato food production in the CELSS The aim of our work was to determine content and composition storage starch as well as amyloplast ultrastructure of storage parenchyma cells in potato minitubers formed under long-term to 6 weeks slow horizontal clinorotation 2 rpm Minitubers developed from axillary buds of potato miniplants growing in the aseptic stationary conditions and under clinorotation Methods of scanning and transmission electron microscopy were used for the study of surface and ultrastructure of amyloplasts the biochemical method by Hovenkamp-Hermelink et al 1988 - for study of starch composition Some differences were observed in amyloplast structure under clinorotation namely increased volume of starch grains in plastid decreased stroma volume changed structure of envelope membranes in comparison with the stationary control Besides an appearance of fraction of gigantic amyloplasts in central layers of parenchyma was observed under clinorotation after 4 weeks of growth The total starch content increased and reached to 219 5 - 4 1 mg g FW at 6 weeks of clinorotation it was 167 5 - 5 6 mg g FW in the control minitubers A ratio of

Surgical repositioning of the premaxilla with bone graft in 50 bilateral cleft lip and palate patients.

PubMed

Carlini, João L; Biron, Cassia; Gomes, Kelston Ulbricht; Da Silva, Rafael M

2009-04-01

The aim of this study was to evaluate a modified surgical technique for premaxilla repositioning with concomitant autogenous bone grafting in bilateral trans-foramen cleft lip and palate patients. The study included 50 bilateral trans-foramen cleft lip and palate patients. Bone graft was harvested from the mandibular symphysis in 24 patients. Whenever more grafting was necessary, the iliac crest bone was used as the donor site (26 patients). The premaxilla was displaced by rupturing the bone and the palatine mucosa, and repositioned in a more adequate position using a surgical guide. The premaxilla and the grafts were fixed with miniplates and screws or screws only. The surgical guide was kept in place for 2 months, whereas the miniplates and screws were removed after 6 months, together with the complete bilateral lip and nose repair. Follow-up examinations were performed at 3, 6, and 12 months by means of periapical and occlusal radiographs, and by clinical examination. Thereafter, the patients were referred for completion of the orthodontic treatment. Overall, in 48 cases (96%) the treatment achieved total graft integration, with complete closure of the bucconasal and palatal fistulas, and premaxilla stability (either at first surgery or after reoperation). In the remaining 2 patients (4%), the treatment failed, due to necrosis of the premaxilla. The procedure is complex and involves risk. However, the patient's social inclusion, especially at the addressed age group, is the best benefit achieved.

Evaluation of surgical treatment in mandibular condyle fractures.

PubMed

Vesnaver, Aleš; Ahčan, Uroš; Rozman, Janez

2012-12-01

In the past, fractures of the mandibular condylar process were, as a rule, treated conservatively. At the Department of Maxillofacial and Oral Surgery of the University Medical Centre Ljubljana, Slovenia, our doctrine was changed in 2002 on the basis of preliminary results and reports in the literature, and these fractures were started to be treated surgically by open reduction and internal fixation with miniplates and screws, which led to good results and a shorter rehabilitation period. The goal of this study was to determine the safety and efficiency of surgical treatment, as well as to compare long-term results of surgical and conservative treatment, as objectively as possible. Two groups of patients, which had all sustained a unilateral, extra-articular mandibular condyle fracture, were compared. In the test group, there were 42 surgically treated patients, and in the control group, 20 conservatively treated patients. Clinical parameters and X-ray images were assessed in both groups and compared by the two tailed Student t test, and in case of attributive variables by the χ(2) test. Within the surgically treated group, postoperative and intraoperative complications were noted: temporary facial nerve palsy, development of a parotid salivary fistula, disturbance of auricle sensibility due to injury of the greater auricular nerve, miniplate fracture, as well as intraoperative bleeding, postoperative haematoma formation, infection, reoperation due to fragment malposition and other complications. Postoperative scars were also assessed. Statistically significant differences between the surgically and conservatively treated patients were found when comparing clinical parameters as well as X-ray images, the results being better in the surgically treated group. Complications of surgical treatment were also noted, the most important among them temporary paresis of facial nerve branches, which occurred in 10 patients (24%). Plate fractures occurred in five patients (12%), in four of them miniplates of sizes less than 2.0mm were used. There were no cases of significant intraoperative bleeding, two cases (5%) required drainage of postoperative haematomas, and one patient (2%) experienced a mild postoperative infection, which was easily controlled with amoxicillin with clavulanic acid. The scar was hidden best if a facelift incision was used, and a hypertrophic scar developed in only one patient (2%). Results of surgical treatment of condylar process fractures are superior to the results of conservative treatment, and the procedure is safe with the transparotid surgical approach and adequate surgical technique. Copyright © 2011 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Interface Engineering to Create a Strong Spin Filter Contact to Silicon

NASA Astrophysics Data System (ADS)

Caspers, C.; Gloskovskii, A.; Gorgoi, M.; Besson, C.; Luysberg, M.; Rushchanskii, K. Z.; Ležaić, M.; Fadley, C. S.; Drube, W.; Müller, M.

2016-03-01

Integrating epitaxial and ferromagnetic Europium Oxide (EuO) directly on silicon is a perfect route to enrich silicon nanotechnology with spin filter functionality. To date, the inherent chemical reactivity between EuO and Si has prevented a heteroepitaxial integration without significant contaminations of the interface with Eu silicides and Si oxides. We present a solution to this long-standing problem by applying two complementary passivation techniques for the reactive EuO/Si interface: (i) an in situ hydrogen-Si (001) passivation and (ii) the application of oxygen-protective Eu monolayers-without using any additional buffer layers. By careful chemical depth profiling of the oxide-semiconductor interface via hard x-ray photoemission spectroscopy, we show how to systematically minimize both Eu silicide and Si oxide formation to the sub-monolayer regime-and how to ultimately interface-engineer chemically clean, heteroepitaxial and ferromagnetic EuO/Si (001) in order to create a strong spin filter contact to silicon.

Multiple Types of Topological Fermions in Transition Metal Silicides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Peizhe; Zhou, Quan; Zhang, Shou -Cheng

Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of crystalline symmetries, such as spin-1 excitations with threefold degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using the ab initio density functional theory, we show that these unconventional quasiparticles coexist with type-I and type-II Weyl fermions in a family of transition metal silicides, including CoSi, RhSi, RhGe, and CoGe, when spin-orbit coupling is considered. Their nontrivial topology results in a series of extensive Fermi arcs connecting projections of these bulk excitations on the side surface, whichmore » is confirmed by (001) surface electronic spectra of CoSi. Additionally, these stable arc states exist within a wide energy window around the Fermi level, which makes them readily accessible in angle-resolved photoemission spectroscopy measurements.« less

Outer skin protection of columbium Thermal Protection System (TPS) panels

NASA Technical Reports Server (NTRS)

Culp, J. D.

1973-01-01

A coated columbium alloy material system 0.04 centimeter thick was developed which provides for increased reliability to the load bearing character of the system in the event of physical damage to and loss of the exterior protective coating. The increased reliability to the load bearing columbium alloy (FS-85) was achieved by interposing an oxidation resistant columbium alloy (B-1) between the FS-85 alloy and a fused slurry silicide coating. The B-1 alloy was applied as a cladding to the FS-85 and the composite was fused slurry silicide coated. Results of material evaluation testing included cyclic oxidation testing of specimens with intentional coating defects, tensile testing of several material combinations exposed to reentry profile conditions, and emittance testing after cycling of up to 100 simulated reentries. The clad material, which was shown to provide greater reliability than unclad materials, holds significant promise for use in the thermal protection system of hypersonic reentry vehicles.

Fused slurry silicide coatings for columbium alloys reentry heat shields. Volume 1: Evaluation analysis

NASA Technical Reports Server (NTRS)

Fitzgerald, B.

1973-01-01

The R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20in x 20in) single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission space shuttle heat shield applications. Structural life under simulated space shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels. Demonstrated coating damage tolerance showed no immediate structural failure on exposure. The FS-85 columbium alloy was selected from five candidate alloys (Cb-752, C-129Y, WC-3015, B-66 and FS-85) based on the evaluation tests which have designed to determine: (1) change in material properties due to coating and reuse; (2) alloy tolerance to coating damage; (3) coating emittance characteristics under reuse conditions; and (4) new coating chemistries for improved coating life.

Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactantmore » fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.« less

Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One systemmore » operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.« less

Silicon dendritic web material

NASA Technical Reports Server (NTRS)

Meier, D. L.; Campbell, R. B.; Sienkiewicz, L. J.; Rai-Choudhury, P.

1982-01-01

The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined.

Silicon dendritic web material

NASA Astrophysics Data System (ADS)

Meier, D. L.; Campbell, R. B.; Sienkiewicz, L. J.; Rai-Choudhury, P.

1982-03-01

The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined.

Nanoamorphous carbon-based photonic crystal infrared emitters

DOEpatents

Norwood, Robert A [Tucson, AZ; Skotheim, Terje [Tucson, AZ

2011-12-13

Provided is a tunable radiation emitting structure comprising: a nanoamorphous carbon structure having a plurality of relief features provided in a periodic spatial configuration, wherein the relief features are separated from each other by adjacent recessed features, and wherein the nanoamorphous carbon comprises a total of from 0 to 60 atomic percent of one or more dopants of the dopant group consisting of: transition metals, lanthanoids, electro-conductive carbides, silicides and nitrides. In one embodiment, a dopant is selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La and other lanthanides, Hf, Ta, W, Rh, Os, Ir, Pt, Au, and Hg. In one embodiment, a dopant is selected from the group consisting of: electro-conductive carbides (like Mo.sub.2C), silicides (like MoSi.sub.2) and nitrides (like TiN).

Solid-state reaction of iron on β-SiC

NASA Astrophysics Data System (ADS)

Kaplan, R.; Klein, P. H.; Addamiano, A.

1985-07-01

The solid-state reaction between Fe and β-SiC has been studied using Auger-electron and electron-energy-loss spectroscopies and ion sputter profiling. Fe films from submonolayer coverage to 1000 Å thickness were grown in ultrahigh vacuum, and annealed at temperatures up to 550 °C. Auger line-shape changes occurred even for initial Fe coverage at 190 °C, indicating substantial bond alteration in the SiC substrate. A 1000-Å film was largely consumed by reaction with Si and C diffused from the substrate during a 500 °C anneal, and exhibited both Fe silicide and carbide throughout most of its original volume and free C present as graphite primarily at the surface. As an aid in identifying the reaction products studied in this work, Auger line shapes were first determined for the SiLVV peak in Fe silicide and for the CKLL transition in Fe carbide.

Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

DOEpatents

Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

2015-08-11

Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactant fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.

Fabrication and RF characterization of a single nickel silicide nanowire for an interconnect.

PubMed

Lee, Dongjin; Kang, Myunggil; Hong, Suheon; Hwang, Donghoon; Heo, Keun; Joo, Won-Jae; Kim, Sangsig; Whang, Dongmok; Hwang, Sung Woo

2013-09-01

We fabricated a nickel silicide nanowire (NiSi NW) device with a low thermal budget and characterized it by measuring the S-parameters in the radio-frequency (RF) regime. A single silicon nanowire (Si NW) was assembled on a substrate with a two-port coplanar waveguide structure using the dielectrophoresis method. Then, the Si NW on the device was perfectly transformed into a NiSi NW. The NiSi NW device was characterized by performing measurements in the DC and RF regimes. The transformation into the NiSi NW resulted in reducing about three-order more the resistance than before the transformation. Hence, the transmission of the NiSi NW device was 25 dB higher than that of the Si NW device up to gigahertz. We also discussed extracting the intrinsic properties of the NiSi NW by using de-embedding, circuit modeling, and simulation.

Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

DOEpatents

Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

2015-07-14

Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

Multiple Types of Topological Fermions in Transition Metal Silicides

DOE PAGES

Tang, Peizhe; Zhou, Quan; Zhang, Shou -Cheng

2017-11-17

Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of crystalline symmetries, such as spin-1 excitations with threefold degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using the ab initio density functional theory, we show that these unconventional quasiparticles coexist with type-I and type-II Weyl fermions in a family of transition metal silicides, including CoSi, RhSi, RhGe, and CoGe, when spin-orbit coupling is considered. Their nontrivial topology results in a series of extensive Fermi arcs connecting projections of these bulk excitations on the side surface, whichmore » is confirmed by (001) surface electronic spectra of CoSi. Additionally, these stable arc states exist within a wide energy window around the Fermi level, which makes them readily accessible in angle-resolved photoemission spectroscopy measurements.« less

Intermetallic nickel silicide nanocatalyst—A non-noble metal–based general hydrogenation catalyst

PubMed Central

Pohl, Marga-Martina; Agapova, Anastasiya

2018-01-01

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO2 as the silicon atom source. The process involves thermal reduction of Si–O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon–carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal–based catalysts. PMID:29888329

Intermetallic nickel silicide nanocatalyst-A non-noble metal-based general hydrogenation catalyst.

PubMed

Ryabchuk, Pavel; Agostini, Giovanni; Pohl, Marga-Martina; Lund, Henrik; Agapova, Anastasiya; Junge, Henrik; Junge, Kathrin; Beller, Matthias

2018-06-01

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO 2 as the silicon atom source. The process involves thermal reduction of Si-O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon-carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H 2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal-based catalysts.

The Diagenesis and Replacement of Cosmic Dust in the Geological Record

NASA Astrophysics Data System (ADS)

Suttle, M. D.; Genge, M. J.

2017-07-01

We report the discovery of abundant pseudomorphic fossil cosmic spherules, preserved in 87Ma old Cretaceous chalk. These replaced micrometeorites are composed of hematite or iron silicides and identified on the basis of characteristic textures.

A new technique for cranioplasty with L-shaped titanium plates and combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite).

PubMed

Miyake, H; Ohta, T; Tanaka, H

2000-02-01

The use of hydroxyapatite-based ceramics for cranioplasties has recently increased in Japan, because of the good cosmetic outcomes, biocompatibility, strength, osteoconductive properties, and lack of risk of disease transmission associated with these materials. However, miniplate fixation has not been possible for ceramic implants. We describe a new technique for miniplate fixation of ceramic implants. Combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite; NGK Spark Plug Co., Aichi, Japan) were used for cranioplasties. A slot and a pair of holes were cut in each Ceratite implant, for use as a fixation unit. We have also developed a new L-shaped titanium plate (HOMS Engineering Inc., Nagano, Japan) that fits into the fixation unit. We first insert an L-shaped titanium plate through the slot from the back surface of the Ceratite implant. We then bend the plate outward at the front surface of the Ceratite implant and fix it to the cranium of the patient with titanium screws. The Ceratite implant is usually firmly fixed to the cranium of the patient with three L-shaped titanium plates. Using L-shaped titanium plates and Ceratite implants, we successfully performed cranioplasties for seven patients with cranial defects resulting from external decompression craniotomies. The Ceratite implant exactly fit the bone window for each patient. Surgical maneuvers were simple and easy for all patients, permitting shorter operating times. All Ceratite implants were firmly fixed, and no postoperative infections have occurred. Our new technique for cranioplasty is simple and allows rigid fixation of Ceratite implants.

Impairment of wound healing after operative treatment of mandibular fractures, and the influence of dexamethasone.

PubMed

Snäll, Johanna; Kormi, Eeva; Lindqvist, Christian; Suominen, Anna Liisa; Mesimäki, Karri; Törnwall, Jyrki; Thorén, Hanna

2013-12-01

Our aim was to clarify the incidence of impaired wound healing after open reduction and ostheosynthesis of mandibular fractures, and to find out whether the use of dexamethasone during the operation increased the risk. Patients were drawn from a larger group of healthy adult dentate patients who had participated in a single-blind, randomised study, the aim of which was to clarify the benefits of operative dexamethasone after treatment of facial fractures. The present analysis comprised 41 patients who had had open reduction and fixation of mandibular fractures with titanium miniplates and monocortical screws through one or 2 intraoral approaches. The outcome variable was impaired healing of the wound. The primary predictive variable was the perioperative use of dexamethasone; other potential predictive variables were age, sex, smoking habit, type of fracture, delay in treatment, and duration of operation. Wound healing was impaired in 13/41 patients (32%) (13/53 of all fractures). The incidence among patients who were given dexamethasone and those who were not did not differ significantly. Only age over 25 was significantly associated with delayed healing (p=0.02). The use of dexamethasone 30 mg perioperatively did not significantly increase the risk of impaired wound healing in healthy patients with clinically uninfected mandibular fractures fixed with titanium miniplates through an intraoral approach. Older age is a significant predictor of impaired healing, which emphasises the importance of thorough anti-infective care in these patients during and after the operation. Copyright © 2013 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Interdiffusion behaviors in doped molybdenum uranium and aluminum or aluminum silicon dispersion fuels: Effects of the microstructure

NASA Astrophysics Data System (ADS)

Allenou, J.; Tougait, O.; Pasturel, M.; Iltis, X.; Charollais, F.; Anselmet, M. C.; Lemoine, P.

2011-09-01

Si addition to Al is considered as a promising route to reduce (U,Mo)-Al interaction kinetics, due to its accumulation in the interaction layer, yielding the formation of silicide phases. The (U,Mo) alloy microstructure, and especially its homogenization state, could play a role on this accumulation process. The addition of a third element in γ(U,Mo) could also influence diffusion mechanisms of Al and Si. These two parameters were studied by means of diffusion couple experiments by joining γU based alloys with Al and (Al,Si) alloy. Chemical elements X added into γ(U,Mo) were thoroughly chosen on the following criteria: (i) the potential solubility of the alloying element into the γ(U,Mo) matrix, (ii) its capability to form the ternary aluminides based on the CeCr 2Al 20 and Ho 6Mo 4Al 43 - types, and (iii) the feasibility to control the microstructure of the alloys. On this basis, a test matrix is defined. It concerns γ(U80,Mo15,X5) alloys (in at.%) with X = Y, Cu, Zr, Ti or Cr. These alloys were homogenized and coupled with Al or (Al,Si) alloy. Results evidenced, first, the importance of the state of homogenization of the γ(U,Mo) binary alloy on interaction processes with (Al,Si) alloy, and the benefit on the diffusion of Si through the interaction layer, as observed on the elementary concentration profiles, when the third element X has some solubility into γ(U,Mo) alloy.

Warthog: Coupling Status Update

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, Shane W. D.; Reardon, Bradley T.

The Warthog code was developed to couple codes that are developed in both the Multi-Physics Object-Oriented Simulation Environment (MOOSE) from Idaho National Laboratory (INL) and SHARP from Argonne National Laboratory (ANL). The initial phase of this work, focused on coupling the neutronics code PROTEUS with the fuel performance code BISON. The main technical challenge involves mapping the power density solution determined by PROTEUS to the fuel in BISON. This presents a challenge since PROTEUS uses the MOAB mesh format, but BISON, like all other MOOSE codes, uses the libMesh format. When coupling the different codes, one must consider that Warthogmore » is a light-weight MOOSE-based program that uses the Data Transfer Kit (DTK) to transfer data between the various mesh types. Users set up inputs for the codes they want to run, and then Warthog transfers the data between them. Currently Warthog supports XSProc from SCALE or the Sub-Group Application Programming Interface (SGAPI) in PROTEUS for generating cross sections. It supports arbitrary geometries using PROTEUS and BISON. DTK will transfer power densities and temperatures between the codes where the domains overlap. In the past fiscal year (FY), much work has gone into demonstrating two-way coupling for simple pin cells of various materials. XSProc was used to calculate the cross sections, which were then passed to PROTEUS in an external file. PROTEUS calculates the fission/power density, and Warthog uses DTK to pass this information to BISON, where it is used as the heat source. BISON then calculates the temperature profile of the pin cell and sends it back to XSProc to obtain the temperature corrected cross sections. This process is repeated until the convergence criteria (tolerance on BISON solve, or number of time steps) is reached. Models have been constructed and run for both uranium oxide and uranium silicide fuels. These models demonstrate a clear difference in power shape that is not accounted for in a stand-alone BISON run. Future work involves improving the user interface (UI), likely through integration with the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Workbench. Furthermore, automating the input creation would ease the user experience. The next priority is to continue coupling the work with other codes in the SHARP package. Efforts on other projects include work to couple the Nek5000 thermo-hydraulics code to MOOSE, but this is in the preliminary stages.« less

A Unique Supernova Graphite: Contemporaneous Condensation of All Things Carbonaceous

NASA Astrophysics Data System (ADS)

Croat, T. K.; Jadhav, M.; Lebsack, E.; Bernatowicz, T. J.

2011-03-01

We report a supernova graphite that contains internal subgrains of TiC, SiC, Fe and Ni silicides, and iron metal. These phases comprise a complete list of the phases predicted by equilibrium calculations to condense from C-rich supernova zones.

Corrosion of Cellular Metals in Marine Environments

DTIC Science & Technology

2006-09-30

phosphides and silicides during the brazing process. Phosphorus, particularly, which is very proficient at depressing the filler alloy melting point...theories of corrosion were constructed for isolated AL-6XN in neutral sodium chloride solutions. This also demonstrated the intrinsic resistance of AL

Iridium-Coated Rhenium Combustion Chamber

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

1994-01-01

Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

Discovery of Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Nakamura-Messenger, Keiko; Clemett, Simon J.; Messenger, Scott; Jones, John H.; Palma, Russell L.; Pepin, Robert O.; Klock, Wolfgang; Zolensky, Michael E.; Tatsuoka, Hirokazu

2011-01-01

The Earth accretes approximately 40,000 tons of cosmic dust annually, originating mainly from the disintegration of comets and collisions among asteroids. This cosmic dust, also known as interplanetary dust particles (IDPs), is a subject of intense interest since it is made of the original building blocks of our Solar System. Although the specific parent bodies of IDPs are unknown, the anhydrous chondritic-porous IDPs (CP-IDPs) subset has been potentially linked to a cometary source. The CP-IDPs are extremely primitive materials based on their unequilibrated mineralogy, C-rich chemistry, and anomalous isotopic signatures. In particular, some CP-IDPs escaped the thermal, aqueous and impact shock processing that has modified or destroyed the original mineralogy of meteorites. Thus, the CP-IDPs represent some of the most primitive solar system materials available for laboratory study. Most CP-IDPs are comprised of minerals that are common on Earth. However, in the course of an examination of one of the CP-IDPs, we encountered three sub-micrometer sized grains of manganese silicide (MnSi), a phase that has heretofore not been found in nature. In the seminar, we would like to focus on IDP studies and this manganese silicide phase that has been approved as the first new mineral identified from a comet by the International Mineralogical Association (IMA) in 2008. The mineral is named in honour of Donald E. Brownlee, an American astronomer and a founder of the field of cosmic dust research who is the principal investigator of the NASA Stardust Mission that collected dust samples from Comet 81P/Wild-2 and returned them to Earth. Much of our current view and understanding of the early solar system would not exist without the pioneering work of professor Don Brownlee in the study of IDPs.

Two-Dimensional Mapping of the Calculated Fission Power for the Full-Size Fuel Plate Experiment Irradiated in the Advanced Test Reactor

NASA Astrophysics Data System (ADS)

Chang, G. S.; Lillo, M. A.

2009-08-01

The National Nuclear Security Administrations (NNSA) Reduced Enrichment for Research and Test Reactors (RERTR) program assigned to the Idaho National Laboratory (INL) the responsibility of developing and demonstrating high uranium density research reactor fuel forms to enable the use of low enriched uranium (LEU) in research and test reactors around the world. A series of full-size fuel plate experiments have been proposed for irradiation testing in the center flux trap (CFT) position of the Advanced Test Reactor (ATR). These full-size fuel plate tests are designated as the AFIP tests. The AFIP nominal fuel zone is rectangular in shape having a designed length of 21.5-in (54.61-cm), width of 1.6-in (4.064-cm), and uniform thickness of 0.014-in (0.03556-cm). This gives a nominal fuel zone volume of 0.482 in3 (7.89 cm3) per fuel plate. The AFIP test assembly has two test positions. Each test position is designed to hold 2 full-size plates, for a total of 4 full-size plates per test assembly. The AFIP test plates will be irradiated at a peak surface heat flux of about 350 W/cm2 and discharged at a peak U-235 burn-up of about 70 at.%. Based on limited irradiation testing of the monolithic (U-10Mo) fuel form, it is desirable to keep the peak fuel temperature below 250°C to achieve this, it will be necessary to keep plate heat fluxes below 500 W/cm2. Due to the heavy U-235 loading and a plate width of 1.6-in (4.064-cm), the neutron self-shielding will increase the local-to-average-ratio (L2AR) fission power near the sides of the fuel plates. To demonstrate that the AFIP experiment will meet the ATR safety requirements, a very detailed 2-dimensional (2D) Y-Z fission power profile was evaluated in order to best predict the fuel plate temperature distribution. The ability to accurately predict fuel plate power and burnup are essential to both the design of the AFIP tests as well as evaluation of the irradiated fuel performance. To support this need, a detailed MCNP Y-Z mini-plate fuel model was developed. The Y-Z model divides each fuel plate into 30 equal intervals in both the Y and Z directions. The MCNP-calculated results and the detailed Y-Z fission power mapping were used to help design the AFIP fuel test assembly to demonstrate that the AFIP test assembly thermal-hydraulic limits will not exceed the ATR safety limits.

Oxidation-resistant silicide coating applied to columbium alloy screen

NASA Technical Reports Server (NTRS)

Torgerson, R. T.

1971-01-01

Coated screens withstand temperature cycling in special transpiration-cooling systems and provide porous surface that is effective at temperatures well above those limiting superalloy screen efficiency. Thickness of coating depends on time, temperature and activator concentration. Coatings are uniform and resistant to thermal cycling.

Interface Engineering to Create a Strong Spin Filter Contact to Silicon

PubMed Central

Caspers, C.; Gloskovskii, A.; Gorgoi, M.; Besson, C.; Luysberg, M.; Rushchanskii, K. Z.; Ležaić, M.; Fadley, C. S.; Drube, W.; Müller, M.

2016-01-01

Integrating epitaxial and ferromagnetic Europium Oxide (EuO) directly on silicon is a perfect route to enrich silicon nanotechnology with spin filter functionality. To date, the inherent chemical reactivity between EuO and Si has prevented a heteroepitaxial integration without significant contaminations of the interface with Eu silicides and Si oxides. We present a solution to this long-standing problem by applying two complementary passivation techniques for the reactive EuO/Si interface: (i) an in situ hydrogen-Si (001) passivation and (ii) the application of oxygen-protective Eu monolayers–without using any additional buffer layers. By careful chemical depth profiling of the oxide-semiconductor interface via hard x-ray photoemission spectroscopy, we show how to systematically minimize both Eu silicide and Si oxide formation to the sub-monolayer regime–and how to ultimately interface-engineer chemically clean, heteroepitaxial and ferromagnetic EuO/Si (001) in order to create a strong spin filter contact to silicon. PMID:26975515

Rapid epitaxy-free graphene synthesis on silicidated polycrystalline platinum

PubMed Central

Babenko, Vitaliy; Murdock, Adrian T.; Koós, Antal A.; Britton, Jude; Crossley, Alison; Holdway, Philip; Moffat, Jonathan; Huang, Jian; Alexander-Webber, Jack A.; Nicholas, Robin J.; Grobert, Nicole

2015-01-01

Large-area synthesis of high-quality graphene by chemical vapour deposition on metallic substrates requires polishing or substrate grain enlargement followed by a lengthy growth period. Here we demonstrate a novel substrate processing method for facile synthesis of mm-sized, single-crystal graphene by coating polycrystalline platinum foils with a silicon-containing film. The film reacts with platinum on heating, resulting in the formation of a liquid platinum silicide layer that screens the platinum lattice and fills topographic defects. This reduces the dependence on the surface properties of the catalytic substrate, improving the crystallinity, uniformity and size of graphene domains. At elevated temperatures growth rates of more than an order of magnitude higher (120 μm min−1) than typically reported are achieved, allowing savings in costs for consumable materials, energy and time. This generic technique paves the way for using a whole new range of eutectic substrates for the large-area synthesis of 2D materials. PMID:26175062

Analysis of optical and magnetooptical spectra of Fe{sub 5}Si{sub 3} and Fe{sub 3}Si magnetic silicides using spectral magnetoellipsometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyashchenko, S. A., E-mail: lsa@iph.krasn.ru; Popov, Z. I.; Varnakov, S. N.

The optical, magnetooptical, and magnetic properties of polycrystalline (Fe{sub 5}Si{sub 3}/SiO{sub 2}/Si(100)) and epitaxial Fe{sub 3}Si/Si(111) films are investigated by spectral magnetoellipsometry. The dispersion of the complex refractive index of Fe{sub 5}Si{sub 3} is measured using multiangle spectral ellipsometry in the range of 250–1000 nm. The dispersion of complex Voigt magnetooptical parameters Q is determined for Fe{sub 5}Si{sub 3} and Fe{sub 3}Si in the range of 1.6–4.9 eV. The spectral dependence of magnetic circular dichroism for both silicides has revealed a series of resonance peaks. The energies of the detected peaks correspond to interband electron transitions for spin-polarized densities ofmore » electron states (DOS) calculated from first principles for bulk Fe{sub 5}Si{sub 3} and Fe{sub 3}Si crystals.« less

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE PAGES

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; ...

2018-01-11

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Progress of p-channel bottom-gate poly-Si thin-film transistor by nickel silicide seed-induced lateral crystallization

NASA Astrophysics Data System (ADS)

Lee, Sol Kyu; Seok, Ki Hwan; Park, Jae Hyo; Kim, Hyung Yoon; Chae, Hee Jae; Jang, Gil Su; Lee, Yong Hee; Han, Ji Su; Joo, Seung Ki

2016-06-01

Excimer laser annealing (ELA) is known to be the most common crystallization technology for the fabrication of low-temperature polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) in the mass production industry. This technology, however, cannot be applied to bottom-gate (BG) TFTs, which are well developed for the liquid-crystal display (LCD) back-planes, because strong laser energy of ELA can seriously damage the other layers. Here, we propose a novel high-performance BG poly-Si TFT using Ni silicide seed-induced lateral crystallization (SILC). The SILC technology renders it possible to ensure low damage in the layers, smooth surface, and longitudinal large grains in the channel. It was observed that the electrical properties exhibited a steep subthreshold slope of 110 mV/dec, high field-effect mobility of 304 cm2/Vsec, high I on/ I off ratio of 5.9 × 107, and a low threshold voltage of -3.9 V.

Microwave plasma synthesis of Si/Ge and Si/WSi2 nanoparticles for thermoelectric applications

NASA Astrophysics Data System (ADS)

Petermann, Nils; Schneider, Tom; Stötzel, Julia; Stein, Niklas; Weise, Claudia; Wlokas, Irenäus; Schierning, Gabi; Wiggers, Hartmut

2015-08-01

The utilization of microwave-based plasma systems enables a contamination-free synthesis of highly specific nanoparticles in the gas phase. A reactor setup allowing stable, long-term operation was developed with the support of computational fluid dynamics. This paper highlights the prospects of gas-phase plasma synthesis to produce specific materials for bulk thermoelectrics. Taking advantage of specific plasma reactor properties such as Coulomb repulsion in combination with gas temperatures considerably higher than 1000 K, spherical and non-aggregated nanoparticles of multiple compositions are accessible. Different strategies towards various nanostructured composites and alloys are discussed. It is shown that, based on doped silicon/germanium alloys and composites, thermoelectric materials with zT values up to almost unity can be synthesized in one step. First experimental results concerning silicon/tungsten silicide thermoelectrics applying the nanoparticle-in-alloy idea are presented indicating that this concept might work. However, it is found that tungsten silicides show a surprising sinter activity more than 1000 K below their melting temperature.

Friction and wear properties of three hard refractory coatings applied by radiofrequency sputtering

NASA Technical Reports Server (NTRS)

Brainard, W. A.

1977-01-01

The adherence, friction, and wear properties of thin hard refractory compound coatings applied to 440C bearing steel by radiofrequency sputtering were investigated. Friction and wear tests were done with nonconforming pin on disk specimens. The compounds examined were chromium carbide, molybdenum silicide, and titanium carbide. The adherence, friction, and wear were markedly improved by the application of a bias voltage to the bearing steel substrate during coating deposition. Analysis by X-ray photoelectron spectroscopy indicated that the improvement may be due to a reduction in impurities in bias deposited coatings. A fivefold reduction in oxygen concentration in MoSi2 coating by biasing was noted. Chromium carbide was not effective as an antiwear coating. Molybdenum silicide provided some reduction in both friction and wear. Titanium carbide exhibited excellent friction and antiwear properties at light loads. Plastic flow and transfer of the coating material onto the pin specimen appears to be important in achieving low friction and wear.

High-performance silicon nanowire field-effect transistor with silicided contacts

NASA Astrophysics Data System (ADS)

Rosaz, G.; Salem, B.; Pauc, N.; Gentile, P.; Potié, A.; Solanki, A.; Baron, T.

2011-08-01

Undoped silicon nanowire (Si NW) field-effect transistors (FETs) with a back-gate configuration have been fabricated and characterized. A thick (200 nm) Si3N4 layer was used as a gate insulator and a p++ silicon substrate as a back gate. Si NWs have been grown by the chemical vapour deposition method using the vapour-liquid-solid mechanism and gold as a catalyst. Metallic contacts have been deposited using Ni/Al (80 nm/120 nm) and characterized before and after an optimized annealing step at 400 °C, which resulted in a great decrease in the contact resistance due to the newly formed nickel silicide/Si interface at source and drain. These optimized devices show a good hole mobility of around 200 cm2 V-1 s-1, in the same range as the bulk material, with a good ON current density of about 28 kA cm-2. Finally, hysteretic behaviour of NW channel conductance is discussed to explain the importance of NW surface passivation.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.; Gupta, Shalabh; Pecharsky, Vitalij K.; Hadimani, Ravi L.

2018-05-01

Gadolinium silicide (Gd5Si4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd5Si4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd5Si4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd5Si3 impurity. As the particle sizes decrease, the volume fraction of Gd5Si3 phase increases at the expense of the Gd5Si4 phase, and the ferromagnetic transition temperature of Gd5Si4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.

X-ray spectroscopy study of electronic structure of laser-irradiated Au nanoparticles in a silica film

NASA Astrophysics Data System (ADS)

Jonnard, P.; Bercegol, H.; Lamaignère, L.; Morreeuw, J.-P.; Rullier, J.-L.; Cottancin, E.; Pellarin, M.

2005-03-01

The electronic structure of gold nanoparticles embedded in a silica film is studied, both before and after irradiation at 355nm by a laser. The Au 5d occupied valence states are observed by x-ray emission spectroscopy. They show that before irradiation the gold atoms are in metallic states within the nanoparticles. After irradiation with a fluence of 0.5J/cm2, it is found that gold valence states are close to those of a metal-poor gold silicide; thanks to a comparison of the experimental Au 5d states with the calculated ones for gold silicides using the density-functional theory. The formation of such a compound is driven by the diffusion of the gold atoms into the silica film upon the laser irradiation. At higher fluence, 1J/cm2, we find a higher percentage of metallic gold that could be attributed to annealing in the silica matrix.

Magnesium silicide nanoparticles as a deoxygenation agent for cancer starvation therapy

NASA Astrophysics Data System (ADS)

Zhang, Chen; Ni, Dalong; Liu, Yanyan; Yao, Heliang; Bu, Wenbo; Shi, Jianlin

2017-05-01

A material that rapidly absorbs molecular oxygen (known as an oxygen scavenger or deoxygenation agent (DOA)) has various industrial applications, such as in food preservation, anticorrosion of metal and coal deoxidation. Given that oxygen is vital to cancer growth, to starve tumours through the consumption of intratumoral oxygen is a potentially useful strategy in fighting cancer. Here we show that an injectable polymer-modified magnesium silicide (Mg2Si) nanoparticle can act as a DOA by scavenging oxygen in tumours and form by-products that block tumour capillaries from being reoxygenated. The nanoparticles are prepared by a self-propagating high-temperature synthesis strategy. In the acidic tumour microenvironment, the Mg2Si releases silane, which efficiently reacts with both tissue-dissolved and haemoglobin-bound oxygen to form silicon oxide (SiO2) aggregates. This in situ formation of SiO2 blocks the tumour blood capillaries and prevents tumours from receiving new supplies of oxygen and nutrients.

Oxidation resistant Mo-Mo2B-silica and Mo-Mo2B-silicate composites for high temperature applications

NASA Astrophysics Data System (ADS)

Cochran, J. K.; Daloz, W. L.; Marshall, P. E.

2011-12-01

Development of Mo composites based on the Mo-Si-B system has been demonstrated as a possible new route to achieving a high temperature Mobased material. In this new system, the silicide phases are replaced directly with silica or other silicate materials. These composites avoid the high ductile to brittle transition temperature observed for Mo-Si-B alloys by removing the Si that exists in solid solution in Mo at equilibrium with its silicides. A variety of compositions is tested for room temperature ductility and oxidation resistance. A system based upon Mo, Mo2B, and SrO·Al2O3·(SiO2)2 is shown to possess both ductility at 80 vol.% Mo and oxidation resistance at 60 vol.%. These composites can be produced using a powder processing approach and fired to greater than 95% theoretical density with a desirable microstructure of isolated boride and silicate phases within a ductile Mo matrix.

Synthesis, Characterization, and Mechanism of Formation of Janus-Like Nanoparticles of Tantalum Silicide-Silicon (TaSi2/Si)

PubMed Central

Nomoev, Andrey V.; Bardakhanov, Sergey P.; Schreiber, Makoto; Bazarova, Dashima Zh.; Baldanov, Boris B.; Romanov, Nikolai A.

2014-01-01

Metal-semiconductor Janus-like nanoparticles with the composition tantalum silicide-silicon (TaSi2/Si) were synthesized for the first time by means of an evaporation method utilizing a high-power electron beam. The composition of the synthesized particles were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), selective area electron diffraction (SAED), and energy dispersive X-ray fluorescence (EDX) analysis. The system is compared to previously synthesized core-shell type particles in order to show possible differences responsible for the Janus-like structure forming instead of a core-shell architecture. It is proposed that the production of Janus-like as opposed to core-shell or monophase particles occurs due to the ability of Ta and Si to form compounds and the relative content of Ta and Si atoms in the produced vapour. Based on the results, a potential mechanism of formation for the TaSi2/Si nanoparticles is discussed. PMID:28346996

Oxygen impurity effects at metal/silicide interfaces - Formation of silicon oxide and suboxides in the Ni/Si system

NASA Technical Reports Server (NTRS)

Grunthaner, P. J.; Grunthaner, F. J.; Scott, D. M.; Nicolet, M.-A.; Mayer, J. W.

1981-01-01

The effect of implanted oxygen impurities on the Ni/Ni2Si interface is investigated using X-ray photoelectron spectroscopy, He-4(+) backscattering and O(d, alpha)-16 N-14 nuclear reactions. Oxygen dosages corresponding to concentrations of 1, 2, and 3 atomic percent were implanted into Ni films evaporated on Si substrates. The oxygen, nickel, and silicon core lines were monitored as a function of time during in situ growth of the Ni silicide to determine the chemical nature of the diffusion barrier which forms in the presence of oxygen impurities. Analysis of the Ni, Si, and O core levels demonstrates that the formation of SiO2 is responsible for the Ni diffusion barrier rather than Ni oxide or mixed oxides, such as Ni2SiO4. It is determined that 2.2 x 10 to the 16th O/qu cm is sufficient to prevent Ni diffusion under UHV annealing conditions.

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion

PubMed Central

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems. PMID:24994964

Synthesis, Characterization, and Mechanism of Formation of Janus-Like Nanoparticles of Tantalum Silicide-Silicon (TaSi₂/Si).

PubMed

Nomoev, Andrey V; Bardakhanov, Sergey P; Schreiber, Makoto; Bazarova, Dashima Zh; Baldanov, Boris B; Romanov, Nikolai A

2014-12-25

Metal-semiconductor Janus-like nanoparticles with the composition tantalum silicide-silicon (TaSi₂/Si) were synthesized for the first time by means of an evaporation method utilizing a high-power electron beam. The composition of the synthesized particles were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), selective area electron diffraction (SAED), and energy dispersive X-ray fluorescence (EDX) analysis. The system is compared to previously synthesized core-shell type particles in order to show possible differences responsible for the Janus-like structure forming instead of a core-shell architecture. It is proposed that the production of Janus-like as opposed to core-shell or monophase particles occurs due to the ability of Ta and Si to form compounds and the relative content of Ta and Si atoms in the produced vapour. Based on the results, a potential mechanism of formation for the TaSi₂/Si nanoparticles is discussed.

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion.

PubMed

Noh, Jin-Seo

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems.

Magnesium silicide nanoparticles as a deoxygenation agent for cancer starvation therapy.

PubMed

Zhang, Chen; Ni, Dalong; Liu, Yanyan; Yao, Heliang; Bu, Wenbo; Shi, Jianlin

2017-05-01

A material that rapidly absorbs molecular oxygen (known as an oxygen scavenger or deoxygenation agent (DOA)) has various industrial applications, such as in food preservation, anticorrosion of metal and coal deoxidation. Given that oxygen is vital to cancer growth, to starve tumours through the consumption of intratumoral oxygen is a potentially useful strategy in fighting cancer. Here we show that an injectable polymer-modified magnesium silicide (Mg 2 Si) nanoparticle can act as a DOA by scavenging oxygen in tumours and form by-products that block tumour capillaries from being reoxygenated. The nanoparticles are prepared by a self-propagating high-temperature synthesis strategy. In the acidic tumour microenvironment, the Mg 2 Si releases silane, which efficiently reacts with both tissue-dissolved and haemoglobin-bound oxygen to form silicon oxide (SiO 2 ) aggregates. This in situ formation of SiO 2 blocks the tumour blood capillaries and prevents tumours from receiving new supplies of oxygen and nutrients.

Low Temperature Ohmic Contact Formation of Ni2Si on N-type 4H-SiC and 6H-SiC

NASA Technical Reports Server (NTRS)

Elsamadicy, A. M.; Ila, D.; Zimmerman, R.; Muntele, C.; Evelyn, L.; Muntele, I.; Poker, D. B.; Hensley, D.; Hirvonen, J. K.; Demaree, J. D.;

Coaxial metal-silicide Ni2Si/C54-TiSi2 nanowires.

PubMed

Chen, Chih-Yen; Lin, Yu-Kai; Hsu, Chia-Wei; Wang, Chiu-Yen; Chueh, Yu-Lun; Chen, Lih-Juann; Lo, Shen-Chuan; Chou, Li-Jen

2012-05-09

One-dimensional metal silicide nanowires are excellent candidates for interconnect and contact materials in future integrated circuits devices. Novel core-shell Ni(2)Si/C54-TiSi(2) nanowires, 2 μm in length, were grown controllably via a solid-liquid-solid growth mechanism. Their interesting ferromagnetic behaviors and excellent electrical properties have been studied in detail. The coercivities (Hcs) of the core-shell Ni(2)Si/C54-TiSi(2) nanowires was determined to be 200 and 50 Oe at 4 and 300 K, respectively, and the resistivity was measured to be as low as 31 μΩ-cm. The shift of the hysteresis loop with the temperature in zero field cooled (ZFC) and field cooled (FC) studies was found. ZFC and FC curves converge near room temperature at 314 K. The favorable ferromagnetic and electrical properties indicate that the unique core-shell nanowires can be used in penetrative ferromagnetic devices at room temperature simultaneously as a future interconnection in integrated circuits.

Investigating phase transition temperatures of size separated gadolinium silicide magnetic nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunagund, Shivakumar G.; Harstad, Shane M.; El-Gendy, Ahmed A.

Gadolinium silicide (Gd 5Si 4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd 5Si 4 ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd 5Si 4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd 5Si 3 impurity. Here as the particle sizes decrease, the volumemore » fraction of Gd 5Si 3 phase increases at the expense of the Gd 5Si 4 phase, and the ferromagnetic transition temperature of Gd 5Si 4 is reduced from 316 K to 310 K, while the ordering of the minor phase is independent of the particle size, remaining at 110 K.« less

Impurity gettering in silicon using cavities formed by helium implantation and annealing

DOEpatents

Myers, Jr., Samuel M.; Bishop, Dawn M.; Follstaedt, David M.

1998-01-01

Impurity gettering in silicon wafers is achieved by a new process consisting of helium ion implantation followed by annealing. This treatment creates cavities whose internal surfaces are highly chemically reactive due to the presence of numerous silicon dangling bonds. For two representative transition-metal impurities, copper and nickel, the binding energies at cavities were demonstrated to be larger than the binding energies in precipitates of metal silicide, which constitutes the basis of most current impurity gettering. As a result the residual concentration of such impurities after cavity gettering is smaller by several orders of magnitude than after precipitation gettering. Additionally, cavity gettering is effective regardless of the starting impurity concentration in the wafer, whereas precipitation gettering ceases when the impurity concentration reaches a characteristic solubility determined by the equilibrium phase diagram of the silicon-metal system. The strong cavity gettering was shown to induce dissolution of metal-silicide particles from the opposite side of a wafer.

Oxidation/vaporization of silicide coated columbium base alloys

NASA Technical Reports Server (NTRS)

Kohl, F. J.; Stearns, C. A.

1971-01-01

Mass spectrometric and target collection experiments were made at 1600 K to elucidate the mode of oxidative vaporization of two columbium alloys, fused-slurry-coated with a complex silicide former (Si-20Cr-Fe). At oxygen pressures up to 0.0005 torr the major vapor component detected by mass spectrometry for oxidized samples was gaseous silicon monoxide. Analysis of condensates collected at oxygen pressures of 0.1, 1.0 and 10 torr revealed that chromium-, silicon-, iron- and tungsten- containing species were the major products of vaporization. Equilibrium thermochemical diagrams were constructed for the metal-oxygen system corresponding to each constituent metal in both the coating and base alloy. The major vaporizing species are expected to be the gaseous oxides of chromium, silicon, iron and tungsten. Plots of vapor phase composition and maximum vaporization rate versus oxygen pressure were calculated for each coating constituent. The major contribution to weight loss by vaporization at oxygen pressures above 1 torr was shown to be the chromium-containing species.

Impurity gettering in silicon using cavities formed by helium implantation and annealing

DOEpatents

Myers, S.M. Jr.; Bishop, D.M.; Follstaedt, D.M.

1998-11-24

Impurity gettering in silicon wafers is achieved by a new process consisting of helium ion implantation followed by annealing. This treatment creates cavities whose internal surfaces are highly chemically reactive due to the presence of numerous silicon dangling bonds. For two representative transition-metal impurities, copper and nickel, the binding energies at cavities were demonstrated to be larger than the binding energies in precipitates of metal silicide, which constitutes the basis of most current impurity gettering. As a result the residual concentration of such impurities after cavity gettering is smaller by several orders of magnitude than after precipitation gettering. Additionally, cavity gettering is effective regardless of the starting impurity concentration in the wafer, whereas precipitation gettering ceases when the impurity concentration reaches a characteristic solubility determined by the equilibrium phase diagram of the silicon-metal system. The strong cavity gettering was shown to induce dissolution of metal-silicide particles from the opposite side of a wafer. 4 figs.

Efficient and Stable Silicon Microwire Photocathodes with a Nickel Silicide Interlayer for Operation in Strongly Alkaline Solutions.

PubMed

Vijselaar, Wouter; Tiggelaar, Roald M; Gardeniers, Han; Huskens, Jurriaan

2018-05-11

Most photoanodes commonly applied in solar fuel research (e.g., of Fe 2 O 3 , BiVO 4 , TiO 2 , or WO 3 ) are only active and stable in alkaline electrolytes. Silicon (Si)-based photocathodes on the other hand are mainly studied under acidic conditions due to their instability in alkaline electrolytes. Here, we show that the in-diffusion of nickel into a 3D Si structure, upon thermal annealing, yields a thin (sub-100 nm), defect-free nickel silicide (NiSi) layer. This has allowed us to design and fabricate a Si microwire photocathode with a NiSi interlayer between the catalyst and the Si microwires. Upon electrodeposition of the catalyst (here, nickel molybdenum) on top of the NiSi layer, an efficient, Si-based photocathode was obtained that is stable in strongly alkaline solutions (1 M KOH). The best-performing, all-earth-abundant microwire array devices exhibited, under AM 1.5G simulated solar illumination, an ideal regenerative cell efficiency of 10.1%.

Alloying and Hardness of Eutectics with Nbss and Nb5Si3 in Nb-silicide Based Alloys

PubMed Central

Tsakiropoulos, Panos

2018-01-01

In Nb-silicide based alloys, eutectics can form that contain the Nbss and Nb5Si3 phases. The Nb5Si3 can be rich or poor in Ti, the Nb can be substituted with other transition and refractory metals, and the Si can be substituted with simple metal and metalloid elements. For the production of directionally solidified in situ composites of multi-element Nb-silicide based alloys, data about eutectics with Nbss and Nb5Si3 is essential. In this paper, the alloying behaviour of eutectics observed in Nb-silicide based alloys was studied using the parameters ΔHmix, ΔSmix, VEC (valence electron concentration), δ (related to atomic size), Δχ (related to electronegativity), and Ω (= Tm ΔSmix/|ΔHmix|). The values of these parameters were in the ranges −41.9 < ΔHmix <−25.5 kJ/mol, 4.7 < ΔSmix < 15 J/molK, 4.33 < VEC < 4.89, 6.23 < δ < 9.44, 0.38 < Ω < 1.35, and 0.118 < Δχ < 0.248, with a gap in Δχ values between 0.164 and 0.181. Correlations between ΔSmix, Ω, ΔSmix, and VEC were found for all of the eutectics. The correlation between ΔHmix and δ for the eutectics was the same as that of the Nbss, with more negative ΔHmix for the former. The δ versus Δχ map separated the Ti-rich eutectics from the Ti-poor eutectics, with a gap in Δχ values between 0.164 and 0.181, which is within the Δχ gap of the Nbss. Eutectics were separated according to alloying additions in the Δχ versus VEC, Δχ versus , δ versus , and VEC versus maps, where = Al + Ge + Si + Sn. Convergence of data in maps occurred at δ ≈ 9.25, VEC ≈ 4.35, Δχ in the range ≈ 0.155 to 0.162, and in the range ≈ 21.6 at.% to ≈ 24.3 at.%. The convergence of data also indicated that the minimum concentration of Ti and maximum concentrations of Al and Si in the eutectic were about 8.7 at.% Ti, 6.3 at.% Al, and 21.6 at.% Si, respectively, and that the minimum concentration of Si in the eutectic was in the range 8 < Si < 10 at.%. PMID:29641503

Alloying and Hardness of Eutectics with Nbss and Nb₅Si₃ in Nb-silicide Based Alloys.

PubMed

Tsakiropoulos, Panos

2018-04-11

In Nb-silicide based alloys, eutectics can form that contain the Nb ss and Nb₅Si₃ phases. The Nb₅Si₃ can be rich or poor in Ti, the Nb can be substituted with other transition and refractory metals, and the Si can be substituted with simple metal and metalloid elements. For the production of directionally solidified in situ composites of multi-element Nb-silicide based alloys, data about eutectics with Nb ss and Nb₅Si₃ is essential. In this paper, the alloying behaviour of eutectics observed in Nb-silicide based alloys was studied using the parameters ΔH mix , ΔS mix , VEC (valence electron concentration), δ (related to atomic size), Δχ (related to electronegativity), and Ω (= T m ΔS mix /|ΔH mix |). The values of these parameters were in the ranges -41.9 < ΔH mix <-25.5 kJ/mol, 4.7 < ΔS mix < 15 J/molK, 4.33 < VEC < 4.89, 6.23 < δ < 9.44, 0.38 < Ω < 1.35, and 0.118 < Δχ < 0.248, with a gap in Δχ values between 0.164 and 0.181. Correlations between ΔS mix , Ω, ΔS mix , and VEC were found for all of the eutectics. The correlation between ΔH mix and δ for the eutectics was the same as that of the Nb ss , with more negative ΔH mix for the former. The δ versus Δχ map separated the Ti-rich eutectics from the Ti-poor eutectics, with a gap in Δχ values between 0.164 and 0.181, which is within the Δχ gap of the Nb ss . Eutectics were separated according to alloying additions in the Δχ versus VEC, Δχ versus , δ versus , and VEC versus maps, where = Al + Ge + Si + Sn. Convergence of data in maps occurred at δ ≈ 9.25, VEC ≈ 4.35, Δχ in the range ≈ 0.155 to 0.162, and in the range ≈ 21.6 at.% to ≈ 24.3 at.%. The convergence of data also indicated that the minimum concentration of Ti and maximum concentrations of Al and Si in the eutectic were about 8.7 at.% Ti, 6.3 at.% Al, and 21.6 at.% Si, respectively, and that the minimum concentration of Si in the eutectic was in the range 8 < Si < 10 at.%.