Ar Gas Atmosphere Research Articles

Characterisation of FR-4 substrate with various plasma treatment conditions

The effects of plasma treatment on the surface of the flame resistant-4 (FR-4) substrate with underfills under various treatment conditions (operating gas, operating time, operating power) are investigated by using contact angle measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The plasma treatment on substrate surfaces increased the oxygen containing functional groups or the polar component of the surface free energy, improving the wetting characteristics of the underfills/FR-4 substrates. The plasma treatment conditions which minimised the contact angle between the underfills and FR-4 substrates were an operating power of 300 W and operating time of 180 s under Ar gas atmosphere.

Effect of Ambient Ar Gas on the Composition Control and Crystalline Properties of TiNi Thin Films Fabricated by Using Pulsed Laser Deposition

Effect of Ambient Ar Gas on the Composition Control and Crystalline Properties of TiNi Thin Films Fabricated by Using Pulsed Laser Deposition

Superconducting Properties and Structure of In-Situ MgB$_{2}$ Tapes With SiC and TiC Addition Prepared by Hot Pressing

In-situ powder-in-tube MgB2 tapes have been prepared through a hot pressing process. Magnesium hydride MgH2 and amorphous B powders were mixed to synthesize MgB2 superconductor. The mixed powder was encased in a steel tube and rolled into a monocore tape of about 4 mm in width and 0.5 mm in thickness. Nano-sized SiC and TiC powders were added to the MgB2 core. The tapes were hot-pressed under 100 MPa during the heat treatment in Ar gas atmosphere. The Ic for the hot-pressed tapes with 5 mass% SiC addition exceeds 300 A at 4.2 K and 5 T, which corresponds to a core Jc of nearly 1,000 A/mm2. The core Jc is enhanced by more than a factor of two compared to that of tapes without pressing during the heat treatment. The higher Jc in hot pressed tapes results from the improvement of the denser MgB2 structures with less voids and better linkage among MgB2 grains.

Formation of single-wall carbon nanotubes in Ar and nitrogen gas atmosphere by using laser furnace technique

The formation of single-wall carbon nanotubes (SWNTs) by using laser vaporization technique in different ambient gas atmosphere was investigated. SWNTs were prepared with Rh/Pd (1.2/1.2 atom%)-carbon composite rod in Ar and nitrogen gas atmosphere, respectively. Raman spectra of raw carbon materials including SWNTs and photoluminescence mapping of dispersed SWNTs in a surfactant solution demonstrate that the diameter distribution of SWNTs prepared in Ar atmosphere is narrower than those obtained by using CVD technique (e.g. HiPco nanotube), even when the ambient temperature is as high as 1150 ○C. It was also found that nitrogen atmosphere gives wider diameter distribution of SWNTs than that obtained with Ar atmosphere. Furthermore, the relative yield of fullerenes (obtained as byproducts) is investigated by using HPLC (high-performance liquid chromatography) technique. It was found that the relative yield of higher fullerenes becomes lower, when nitrogen is used as an ambient gas atmosphere. Based on these experimental findings, a plausible formation mechanism of SWNTs is discussed.

Effect of annealing on dielectric behavior and electrical conduction of W6+ doped Bi3TiNbO9 ceramics

Bi 3 Ti 1 − x W x Nb O 9 + δ (x=0.15) (WBTN-15) ceramics were prepared using the solid state reaction method, and the behaviors of oxygen vacancies were confirmed and investigated by annealing the ceramic samples in O2 and Ar gas atmospheres. Dielectric measurements showed that oxygen vacancies had great contributions to the dielectric loss and constant of Ar-annealed sample, compared with those of as-sintered and O2-annealed samples. dc conductivity measurements indicate that oxygen vacancies played an important role mainly at lower temperature. The WBTN-15 ceramics exhibit intrinsic conduction mechanism at high temperature range and electronic and oxygen-vacancy ionic mixed conduction mechanism at low temperature range.

Polaron variable range hopping in [formula omitted] thin films

The mechanisms of electrical conduction in TiO 2 - δ ( - 0.04 ⩽ δ ⩽ 0.2 ) thin films have been investigated. The samples were rf-diode reactive sputtered films deposited in O 2 + Ar gas atmospheres where changes in δ and film structure had been achieved by varying the O 2 flow rate and the substrate temperature. The electrical transport properties of these samples were investigated by measuring the conductivity as a function of temperature between 17 K and room temperature. At the temperature range between 200 and 290 K the best fit to the experimental data was obtained assuming a dependence characteristic of adiabatic variable range hopping. At lower temperature the activation energy for the conductivity tends to zero. The results suggest that the conduction mechanism is adiabatic small polaron hopping, which switches to conduction in a polaron band at low temperatures.

Ar가스 분위기에서 PLD방법으로 제작된 TiNi박막의 조성 및 결정성에 관한 연구

TiNi shape memory alloy(SMA) was fabricated by PLD(plused laser deposition) using equiatomic TiNi target. Composition and crystallization of TiNi thin films which were fabricated in ambient Ar gas(200m Torr)and vacuum() were investigated. Composition of TiNi thin films was characterized by energy-dispersive X-ray spectrometry (EDXS) and crystallization was confirmed by X-ray diffraction (XRD). The composition of films depends on the distance between target and substrate but does not sensitively depend on the substrate temperature. It is found that the composition of films can be easily controlled when substrate is placed inside plume in ambient Ar gas. It is also found that the in situ crystallization temperature () in ambient Ar gas is lowered in comparison with that of TiNi film prepared under vacuum. The low crystallization temperature in ambient Ar gas makes it possible to prepare the crystalline TiNi thin film without contamination.

Brazing of CP-Titanium / CP-Titanium and Titanium Alloy / Stainless Steel with Laminated Ti-Based Filler Metal

Joining technology of CP-Titanium and Titanium alloy is very important for manufacturing field. In that case of titanium brazing, chemical compositions of brazing filler metal and brazing atmosphere are very important. In this study, CP-Ti/CP-Ti and Ti alloy/Stainless Steel were brazed with Ti-based laminated brazing filler metal by using continuous type furnace under Ar gas atmosphere containing extremely low oxygen. Laminated filler was fabricated by roll bonding technology. Chemical compositions of laminated filler metal used in this study were Ti-15Cu-15Ni and Ti-20Zr-20Cu-20Ni. Brazing temperature employed in this study was 850, 900, 950, and 1000 C. These brazing temperatures were based on thermal analysis results and alpha-beta transformation temperature of the base metal used in this study. Firstly melting properties of laminated brazing filler metal was investigated with DTA and DSC. Secondary joint characteristics were estimated by micro-structural observation at the joint and mechanical properties measurement. Sound joint was obtained in this study according to outside appearance of the specimen. Ti-20Zr-20Cu-20Ni filler had low melting point as compared with Ti-15Cu-15Ni according to thermal analysis results and fillet form-ability. Ni and Cu were diffused from molten brazing filler to base metal during brazing and Ti-Cu-Ni eutectoid reaction was took placed at the based metal during cooling after brazing.

Coating of Ti-6Al-4V alloy substrates with TiN/Ti multi-layered films by magnetron sputtering

Coating of Ti-6Al-4V alloy substrates with TiN/Ti multi-layered films by magnetron sputtering in Ar gas atmosphere was examined, aiming at the application of the alloy to artificial heart valves, in order to improve not only the adhesion between the deposited film and the alloy but also the surface smoothness of titanium nitride coatings and thereby to improve the blood compatibility as well as the biocompatibility of the alloy coated with the titanium nitride film. The effects of the thickness of the TiN (titanium nitride) layer on the surface morphology of the film were investigated, in order to develop TiN coatings with higher blood compatibility. The multi-layered films were deposited by sputtering in sequence pure titanium and titanium nitride targets. The thickness of titanium nitride layer was varied from 300 nm to 800 nm, while that of pure titanium was constantly 200 nm. Under visual observation, the obtained multi-layered films looked yellow gold and appeared to be uniform and adhesive, while TiN monolithic films deposited directly onto the alloy substrate under the same sputtering conditions peeled off partly. Therefore it was found that the multi-layered thin films were more adhesive to the alloy than the monolithic films. According to AFM (Atomic Force Microscope) images for both of the films, the surface morphology of each TiN layer observed under the scope of nanometer-scaled area was rough with pits and bumps, while that under the scope of micrometer-scaled area was smooth without such pits and bumps. Furthermore based on the AFM, the surface roughness measured under the area of nanometer scale was found to increase with the increase of the thickness of the TiN layer in the multi-layered film, although that measured under the area of micrometer scale was assumed to be independent of the thickness of the TiN layer.

Size and structure of nanoparticles formed via ultraviolet photolysis of ferrocene

Iron nanoparticles enclosed in carbon shells were formed by laser-assisted chemical vapor decomposition of ferrocene (Fe(C5H5)2) vapor in Ar gas atmosphere. The particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser was examined and, e.g., an effective size decrease of the iron core was observed at elevated laser fluences. Characterizations of the iron and carbon microstructures were performed by x-ray diffraction and transmission electron microscopy, while relative iron deposition rates were measured by x-ray fluorescence spectroscopy. Both α-Fe and γ-Fe phases were found for the single crystalline iron cores, surrounded by graphitic (inner) and amorphous (outer) carbon layers. The temperature rise of the laser-excited particles was also determined by optical spectroscopy of the emitted thermal radiation, which allowed an estimation of the iron loss of the nanoparticles due to evaporation. The estimated and measured iron losses are in good agreement.

Raman spectroscopy of SWNTs produced by a XeCl excimer laser ablation at high temperatures

Synthesis of single-wall carbon nanotubes (SWNTs) was carried out by an ablation method using a XeCl excimer laser. It was irradiated onto a graphite target containing Co and Ni at the temperatures of 1073, 1173, 1273, 1373, 1473, 1523 and 1623 K under the atmosphere (0.1 MPa) of Ar gas with the flow rate of 12 ml/min. The measurement by a scanning/transmission electron microscope and Raman spectroscopy found the formation of SWNTs with the diameter of about 1.3 nm and the length of about 2 μm in ablated carbonaceous soot. The ratio of peak intensity of 1590 cm −1 (G band) to that of 1335 cm −1 (D band) in the high frequency Raman spectra increased with increasing the ambient temperature. The radial breathing mode (RBM) in the low frequency Raman spectra shows that the mean diameter of SWNTs increased with increasing the ambient temperature.

Synthesis of high quality single-walled carbon nanotubes by arc discharge method in large scale

Single-walled carbon nanotubes (SWNTs) were synthesized by a novel method. The dc arc discharge in H 2–Ar gas atmosphere with Fe 3O 4 as catalyst was used. The morphology and structures of the as-prepared SWNTs were characterized by SEM, HRTEM and Raman spectroscopy techniques. The results indicated that this new catalyst could be used to produce SWNTs with high purity and yield in large scale. The purity and yield of the SWNTs synthesized from these new catalysts were affected by the mixture buffer gas. Based on the overall ease and low-cost advantages of these new catalysts, these results suggest a potential opportunity for cost-effective and commercial production of SWNTs.

Mg-C 複合材料の創製とその水素吸蔵特性

Mg-based alloys possess light-weight and high hydrogen absorption capacity, so they have been investigated extensively for several decades. Also, attention has recently been paid to graphite as a hydrogen absorber. In this study Mg-C composites were prepared by ball milling and their hydrogenation properties were investigated. Powders were first mixed with a 1:1 molar ratio of Mg (99.9% purity) to graphite (99.9% purity), and then milled using ZrO2 balls in a ZrO2 pot for 60 hours. This process was performed in a vibration ball mill at the speed of 345 rpm under an Ar gas atmosphere. The powders prepared in this way were handled in a glove box filled with an Ar gas. From the XRD patterns, it was found that the peak corresponding to the Mg phase shifted slightly to lower diffraction angles, indicating that the lattice spacing of the Mg phase was expanded by alloying partially with C in the powders. On the other hand, graphite peaks were rather broadened. An affinity for the powders with hydrogen was confirmed from the absorption experiment at the temperature of 453 K and the hydrogen pressure of 1.8 MPa. The total amount of absorbed hydrogen was estimated to be 3.5 mass% from the TDS measurement.

Behavior of Alumina Inclusions Just after Deoxidation

Many efforts have been made to remove nonmetallic inclusions from molten steel, however, the required level of steel cleanness from steel users has become stricter year by year. Not only the way of removing the inclusions but also the way of keeping the inclusion size small are considered effective countermeasures for meeting the users' demand. Hence, it is important to investigate control factors governing the size distribution of inclusions in steel. From the viewpoint described above, the initial size distribution of alumina inclusions just after deoxidation reaction in steel has been studied by using a new sampling method with varying aluminum and oxygen contents in laboratory scale experiment. Two kilograms of steel was melted in a Tammann furnace at 1 873 K under an Ar gas atmosphere, then the carbon and oxygen concentrations were adjusted. The sampling method that enables to take a steel sample just after the addition of aluminum was used. The size distribution of alumina inclusions in steel samples was measured by using an electron probe micro analyzer with LaB6 filament of an electron beam gun and with newly developed software for particle analysis. The result showed that the size distribution of alumina inclusions was affected by oxygen content in the steel, and that the growth of the inclusions during 1 s after the deoxidation was considered to be controlled by the oxygen diffusion.

プラズマ溶射 TBC システムの高温酸化特性に及ぼす溶射後熱処理条件の影響

In order to improve the high-temperature durability of the plasma sprayed thermal barrier coating (TBC) systems, high-temperature oxidation test was conducted under the isothermal condition at 1100°C for 100 h for several kinds of TBC systems in connection with their coating characteristics such as the coating microstructures and interfacial natures depending on the coating process conditions. Specimens with different coating characteristics were prepared by controlling the coating parameters such as the top-coat spraying conditions and the reheat-treatment (RHT) conditions after spraying. Especially, the RHT was applied to the TBC specimen with different temperature, heating rate, holding time at maximum temperature and so on in inert argon (Ar) gas atmosphere. High-temperature oxidation behavior was found to differ depending strongly on the RHT conditions. The RHT at lower temperature could not inhibit the heterogeneous development of thermally grown oxides (TGO) layer and the wart-like oxides at the top-coat/bond-coat interface. On the contrary, the RHT with either the slow rate heating or the long time holding at the maximum temperature was found to be effective for an improvement of the oxidation resistance, since such a RHT process is able to develop dominantly the continuous α-Al2O3 layer at the interface so as to reduce sufficiently the growth rate of TGO to maintain the suitable environmental barrier function during high-temperature oxidation. The influence of the RHT conditions on the high-temperature oxidation property was discussed in connection with both the morphology of bond-coat powders and the surface morphology of bond-coat sprayed.

Effect of Repeated Quenching Heat Treatment on Microstructure and Dry Sliding Wear Behavior of Low Carbon PM Steel

The effect of repeated quenching heat treatment on microstructure and dry sliding wear behavior of low carbon PM steel was investigated. For this purpose, atomized iron powder was mixed with 0.3 % graphite and 1 % Ni powders. The mixed powders were cold pressed and sintered at 1200°C for 30 min under pure Ar gas atmosphere. Some of the sintered specimens were intercritically annealed at 760°C and quenched in water (single quenching). The other sintered specimens were first fully austenized at 890°C and water quenched. These specimens were then intercritically annealed at 760°C and re-quenched in water. The martensite volume fraction in the double quenched specimens was higher than that of the single quenched specimen. Wear tests were carried out on the single and double quenched specimens under dry sliding wear condition using a pin-on-disk type machine at constant load and speed. The experimental results showed that the wear coefficient effectively decreased in the double quenched specimen.

Synthesis of tungsten sub-carbide W2C from graphite/tungsten powder mixtures by eruptive heating in a solar furnace

Abstract Synthesis of single-phase tungsten sub-carbide phase W 2 C was attempted in inert Ar gas atmosphere started from compacted powder mixtures of graphite (G) and tungsten (W) with controlled mole ratios between 0.35 and 0.50 under solar radiation heating for 30 min at two target temperatures T , 1600 °C and 1900 °C, followed by initial eruptive heating from the ambient temperature to the target temperature. Under most of the examined conditions excluding the G/W = 0.50 specimens at both T = 1600 °C and 1900 °C, there was discernible proportion of non-reacted metallic W co-existed with the formed W 2 C. For the reference test specimen possessing the G/W mole ratio exactly at 1.0, W 2 C phase emerged as the trace second phase co-exiting with the principal mono-carbide phase WC. Vickers microhardness Hv was measured using a load of 25 g to be 2785 ± 335 and 2645 ± 210, respectively, for the WC phase in the G/W = 1.0 specimen and for the W 2 C phase in the G/W = 0.50 specimen processed at T = 1900 °C. Discrete growth of nano-meter scale WC whiskers over the top surface of the specimens heated to 1900 °C was detected by scanning electron microscope inspection.

Fast coloration in sputtered gasochromic tungsten oxide films

AbstractThin films of WO3 were deposited with different thickness in a mixed atmosphere of O2 and Ar gas from a high purity target of 99.99% tungsten using reactive DC‐sputtering technique. Same amount of the Pt catalyst was sputtered from a high purity target of 99.99% platinum in Ar atmosphere onto the top of the WO3 films with different thickness. Coloration takes place in hydrogen and bleaching in oxygen gases. During the coloration/bleaching process several optical parameters were determined. The velocity of coloration process increases with increasing the thickness of the films. The change of the transmission in the visible and near infrared regions was measured during coloration and bleaching process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Rheological Properties of Molten Al-Cu Alloys for Manufacturing Metallic Foam

The surface tension and the viscosity characteristics of molten metal are the most important factors in casting process and metallic foam manufacturing especially. The surface tension (by the modified ring method) and the viscosity (by the rotational method) of molten Al-Cu alloys have been measured under high purity Ar gas atmosphere. The surface tension and the viscosity of Al-Cu alloys were investigated in the temperature range of 660-800oC, and the effects of the additional elements were investigated at the 660~680. The result show that the surface tension and viscosity of these alloys decrease with increasing temperature together. The viscosity of Al-Cu alloys near the melting point is about 4.7 to 5.7 [mPa.s]. The effect of additional thickening elements has the tendency that is the surface tension decreased and the viscosity increased. This anomalous behavior has the relation of the preferential adsorption of high activity elements on the surface.

Dry sliding wear behaviour of heat treated iron based powder metallurgy steels with 0.3% Graphite + 2% Ni additions

To determine the effect of various heat treatments on the microstructure and dry sliding wear behaviour of iron based powder metallurgy (PM) steels, atomized iron powder was mixed with 0.3% graphite + 2% Ni. The mixed powders were cold pressed at 700 MPa and sintered at 1200 °C for 30 min under pure Ar gas atmosphere. One of the sintered specimens was quenched from 890 °C and then tempered at 200 °C for 1 h. The other sintered specimens were annealed at different intercritical heat treatment temperatures of 728 and 790 °C and water quenched. Through this intercritical annealing heat treatment, the specimens with various ferrite + martensite volume fractions were produced. Wear tests were carried out on the quenched + tempered and intercritically annealed specimens under dry sliding conditions using a pin-on-disk type machine at constant load and speed and the results were compared in terms of microstructure, hardness and wear strength. It was seen that hardness and wear strength in intercritically annealed specimens were higher than that of quenched + tempered specimen.