scholarly journals An investigative study on neutron emissions from titanium- deuterium system under thermal shock

2017 ◽  
Author(s):  
◽  
Modeste Tchakoua Tchouaso
Keyword(s):  
Thermal Shock ◽  
Room Temperature ◽  
Neutron Emission ◽  
High Vacuum ◽  
Exothermic Reaction ◽  
Experimental System ◽  
Fast Neutrons ◽  
Large Temperature ◽  
Neutron Burst ◽  
Deuterium Gas

The purpose of this study is to investigate the titanium-deuterium system under thermal shock, as a potential neutron source. The expected neutron emission is unique, i.e. it is monoenergetic with energy of 2.45 MeV, which is valuable for calibrating neutron detectors. In our study, titanium was loaded with deuterium gas at room temperature in an experimental system, and the system was subjected to rapid thermal cycling by repeated cooling with liquid nitrogen, followed by rapid warm up phases to create a non-equilibrium condition in titanium lattice. Neutron bursts were monitored using a [superscript 3]He detector, which responds to slow neutrons, a moderated [superscript 3]He detector, which responds to slow and fast neutrons, and a proton recoil detector, which responds to fast neutrons. The pressure and temperature of the system was monitored throughout the experiments. The result of this work shows that: 1) loading of titanium with deuterium gas should be done under high vacuum conditions (less than1 X 10[superscript 6] torr) to remove environmental contaminants, which was found to inhibit the titanium-deuterium reaction, 2) cracks observed in titanium samples from lattice stress varied in size and location in titanium lattice and dependent on the level of deuterium loading. The presence of cracks in some locations indicates that the titanium-deuterium reaction is a local effect, 3) low level neutron burst were observed in less than 23% of all experiments and involved the detection of a single neutron burst, suggesting that neutron emission is a statistical process occurring at low probability. The neutron burst was observed from partially deuterated titanium samples. The level of neutrons detected is consistent with what has been reported in literature. 4). A large temperature increased from room temperature to 450 [degree sign]C during phase transition from [delta]-titanium to [delta]-titanium occurred, but no neutrons were observed. The temperature increased is likely associated with the exothermic reaction that occurs during hydride formation, which does not lead to neutron emission. 5) No evidence of tritium or nuclear transmutation was observed in our experimental system.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

scholarly journals Annealing Condition Effects on the Structural Properties of FePt Nanoparticles Embedded in MgO via Pulsed Laser Deposition

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131
Author(s):  
Tingting Xiao ◽  
Qi Yang ◽  
Jian Yu ◽  
Zhengwei Xiong ◽  
Weidong Wu
Keyword(s):  
Pulsed Laser Deposition ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Annealing Process ◽  
Ultra High Vacuum ◽  
Laser Deposition ◽  
Fept Nanoparticles ◽  
Annealing Conditions ◽  
Vacuum Atmosphere

FePt nanoparticles (NPs) were embedded into a single-crystal MgO host by pulsed laser deposition (PLD). It was found that its phase, microstructures and physical properties were strongly dependent on annealing conditions. Annealing induced a remarkable morphology variation in order to decrease its total free energy. H2/Ar (95% Ar + 5% H2) significantly improved the L10 ordering of FePt NPs, making magnetic coercivity reach 37 KOe at room temperature. However, the samples annealing at H2/Ar, O2, and vacuum all showed the presence of iron oxide even with the coverage of MgO. MgO matrix could restrain the particles’ coalescence effectively but can hardly avoid the oxidation of Fe since it is extremely sensitive to oxygen under the high-temperature annealing process. This study demonstrated that it is essential to anneal FePt in a high-purity reducing or ultra-high vacuum atmosphere in order to eliminate the influence of oxygen.

Influence of Silicon Nitride on Properties of Corundum Based Castable

2013 ◽  
Vol 634-638 ◽  
pp. 2358-2361
Author(s):  
Jun Cong Wei ◽  
Li Rong Yang
Keyword(s):  
Electron Microscopy ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Cold Strength ◽  
X Ray ◽  
Refractory Castables ◽  
Shock Resistance ◽  
Scanning Electron

The effects of Si3N4 addition on the room temperature physical properties and thermal shock resistance properties of corundum based refractory castables were investigated using brown corundum, white corundum and alumina micropowder as the starting materials and pure calcium aluminate as a binder. The phase composition, microstructure, mechanical properties of corundum based castables were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that as the increase in Si3N4 addition, the bulk density decreased and apparent porosity increased, the cold strength deduced. However, the residual strength rate increased. That is, the thermal shock resistance was improved. This is because even though the introduction of Si3N4 inhibited the sintering of material and deduced the compactness, microcracks were produced in the materials due to a difference in thermal expansion coefficient. So the thermal shock resistance of corundum based castable was improved.

scholarly journals Temperature Dependence of Hall Mobility AndCarrier Concentration of pb0.55S0.45 Films

2009 ◽  
Vol 6 (1) ◽  
pp. 129-134
Author(s):  
Baghdad Science Journal
Keyword(s):  
Hall Mobility ◽  
Room Temperature ◽  
Annealing Temperature ◽  
High Vacuum ◽  
Life Time ◽  
Mean Free Path ◽  
Charge Carriers ◽  
Evaporation Technique ◽  
Carrier Life Time ◽  
Type Conduction

Measurements of Hall effect properties at different of annealing temperature have been made on polycrystalline Pb0.55S0.45 films were prepared at room temperature by thermal evaporation technique under high vacuum 4*10-5 torr . The thickness of the film was 2?m .The carrier concentration (n) was observed to decrease with increasing the annealing temperature. The Hall measurements showed that the charge carriers are electrons (i.e n-type conduction). From the observed dependence on the temperature, it is found that the Hall mobility (µH), drift velocity ( d) carrier life time ( ), mean free path (?) were increased with increasing annealing temperature

scholarly journals The Effect Of Thickness on The Optical Properties Of ZnS

2007 ◽  
Vol 4 (4) ◽  
pp. 647-652
Author(s):  
Baghdad Science Journal
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Near Infrared ◽  
High Vacuum ◽  
Ultra Violet ◽  
Infrared Region ◽  
Complex Dielectric Constant ◽  
Film Properties ◽  
Corning Glass ◽  
Different Thickness

Zinc sulfide(ZnS) thin films of different thickness were deposited on corning glass with the substrate kept at room temperature and high vacuum using thermal evaporation technique.the film properties investigated include their absorbance/transmittance/reflectance spectra,band gap,refractive index,extinction coefficient,complex dielectric constant and thickness.The films were found to exhibt high transmittance(59-98%) ,low absorbance and low reflectance in the visible/near infrared region up to 900 nm..However, the absorbance of the films were found to be high in the ultra violet region with peak around 360 nm.The thickness(using optical interference fringes method) of various films thichness(100,200,300,and 400) nm.The band gap measured was found to be in the range (3.52 -3.78 )eV.

scholarly journals Forming pressure effect on microstructure and mechanical properties of nanocrystalline aluminum synthesized by inert gas condensation

2019 ◽  
Vol 79 ◽  
pp. 02002
Author(s):  
Shangshu Wu ◽  
Zhou Yu ◽  
Junjie Wang ◽  
Hanxin Zhang ◽  
Chaoqun Pei ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Vacuum ◽  
Inert Gas ◽  
Helium Atmosphere ◽  
Gas Condensation ◽  
Inert Gas Condensation ◽  
In Situ Forming ◽  
Nanocrystalline Aluminum ◽  
Al Powder

The preparation of nanocrystalline aluminum (NC Al) was conducted in two steps. After the NC Al powder was synthesized by an Inert gas condensation (IGC) method in a helium atmosphere of 500 Pa, the NC Al powder was in-situ compacted into a pellet with a 10 mm diameter and 250 μm-300 μm thickness in a high vacuum (10-6 Pa-10-7 Pa) at room temperature. The NC Al samples were not exposed to air during the entire process. After the pressure reached 6 GPa, the relative density could reach 99.83%. The results showed that the grain size decreased with the increased of in-situ forming pressure. The NC Al samples present obvious ductile fracture, and the tensile properties were greatly changed with the increase of forming pressure.

Engineering and design of fast reactors

1990 ◽  
Vol 331 (1619) ◽  
pp. 301-312 ◽  
Keyword(s):  
Fast Neutrons ◽  
Large Temperature ◽  
Steam Generators ◽  
The Core ◽  
Mode Of Operation ◽  
Protection Systems ◽  
Core Components ◽  
Main Components ◽  
System Layout ◽  
Coolant System

The paper deals with the basic engineering aspects specific to a fast breeder reactor. The characteristic design features are mainly determined by the coolant being sodium and the fast neutrons in the core. Some particular properties of sodium, the high temperature and the large temperature differences impose severe requirements on materials and structures. Also the mode of operation, the protection systems and the auxiliary systems are strongly influenced by these conditions. The resulting engineering implications will be illustrated by describing, firstly, the core layout and the core components, secondly, the main coolant system layout and its auxiliaries and, thirdly, the design aspects of main components such as pumps, heat exchangers and steam generators.

Significantly enhanced room temperature electrocaloric response with superior thermal stability in sodium niobate-based bulk ceramics

2019 ◽  
Vol 7 (19) ◽  
pp. 11665-11672 ◽  
Author(s):  
Ying Yu ◽  
Feng Gao ◽  
Florian Weyland ◽  
Hongliang Du ◽  
Li Jin ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Temperature Change ◽  
Room Temperature ◽  
Large Temperature ◽  
Sodium Niobate ◽  
Bulk Ceramic

This work simultaneously achieved a large temperature change (ΔT, ∼0.70 K) at room temperature and ultra-stable ΔT(±1.4% variation between 300 K with 380 K) in 0.78NaNbO3–0.22BaTiO3bulk ceramic.

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