Influence Of Co Addition Research Articles

Influence of Co addition on constituent phases and performance of a NiCrAlYRe alloy system

MCrAlY alloys can serve as stand-alone overlay coatings or bond coats in thermal barrier coating systems, and their phase constituents play a vital role in determining their performance. In the present investigation, the influence of Co addition on the constituent phases of a NiCrAlY alloy system containing 3 wt.% Re in the temperature range of 800 °C–1200 °C was predicted through thermodynamic modeling. Based on the modeling results, four NiCrAlY alloy systems with different levels of Co (0, 10 wt.%, 20 wt.% and 30 wt.%) were prepared and evaluated experimentally. Scanning electron microscopy and transmission electron microscopy results show that the additions of Co increase the fractions of γ-Ni and β-NiAl at the expense of γ′-Ni 3Al and α-Cr, and thus change the depletion scheme from β → γ′ → γ to β → γ during 1100 °C oxidation.

Influence of cobalt doping on the crystalline structure, optical and mechanical properties of ZnO thin films

Uniform and transparent thin films of Zn 1 − x Co x O (0 ≤ x ≤ 0.10) were fabricated by sol–gel spin coating technique. Co addition up to x = 0.075, led to refinement in structure and improvement in film quality together with average grain size reduction from 17 nm in undoped ZnO to 15 nm with x = 0.05 and 12 nm with x = 0.10 Co additions. For x ≥ 0.035, CoO (cubic) was detected as the secondary phase. Influence of Co addition on the volume fraction of grain boundaries has been interpreted. Increase in Co content in the range 0 ≤ x ≤ 0.10 led to quenching of near-band edge and blue emissions, decrease in band gap energy ( E g) from 3.36 eV to 3.26 eV, decrease in film thickness and refractive index and an increase in extinction coefficient of Zn 1 − x Co x O thin films. The change in nature of stress from compressive to tensile with lower to higher doping of Co is corroborative with the angular peak shift of (002) plane of ZnO lattice. An overall increase in microhardness of Zn 1 − x Co x O thin films up to x = 0.05 is attributed to change in microstructure and evolution of secondary phase and as the secondary phase separates out the overall stress is released leading to lowering of hardness after this concentration. Hall–Petch behavior is also studied and found to obey until x = 0.05, however, considerable deviation after this dopant concentration is attributed to the increase in the volume fraction of grain boundaries, which results from the secondary phase separation from this dopant concentration.

Influence of Co addition on the magnetic properties and magnetocaloric effect of Nanoperm (Fe 1− XCo X) 75Nb 10B 15 type alloys prepared by mechanical alloying

Magnetic properties and magnetocaloric response of mechanically alloyed (Fe 1− X Co X ) 75Nb 10B 15 ( X = 0.15 and 0.30) powders have been studied as a function of crystalline fraction. From X-ray diffraction, it was observed that the amorphization process is delayed with the Co addition in the alloy. Crystallization temperature of the amorphous phase developed during milling decreases as Co content increases. Temperature dependence of magnetization curves shows that the Curie temperature of the amorphous phase increases as the Co content increases. The peak magnetic entropy change slowly increases with Co addition for low crystalline fractions and the refrigerant capacity decreases as Co increases in the alloy.

The Influence of Co Addition on Phase Transformation Behavior and Mechanical Properties of TiNi Alloys

The influences of Co-addition on phase transformation behavior and mechanical properties of TiNi alloys were investigated. Results indicate that, as a substitute for Ni, Co added to TiNi alloys can dramatically decrease the martensite transformation temperature, and R phase transformation and martensite transformation are accordingly separated. When Co-content reach 10 at.%, the martensite transformation temperature is lower than that of liquid nitrogen. During deformation at room temperature, Ti50Ni48Co2 alloy exhibits good ductility with a lower stress plateau caused by stress-induced martensite and martensite reorientation.

Influence of Co Addition on Magnetic Properties and Glass Formation of Fe-based Amorphous Alloys

AbstractIn the present work, the influence of Co addition on the glass forming ability (GFA) and magnetic properties of the ((Fe1−xCox)75B20Si5)93Nb4Y3 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) alloy is evaluated. Ribbons and 1 mm diameter ingots were prepared by melt-spinning technique and Cu-mold injection casting technique, respectively. The presence of the amorphous phase was confirmed through X-ray diffraction and high temperature differential scanning calorimetry (HT-DSC). Rapid solidification leads to fully amorphous ribbons for all compositions. Conversely, ingots with Co content with x > 0.5 present boride crystalline phases.Magnetization measurements were performed by means of vibration sample magnetometer in a temperature range from room temperature to 850 °C in order to determine the Curie temperature (TC) of the amorphous phase and to follow the formation of magnetic phases at high temperatures. In addition, hysteresis loops measurements were carried out to study the magnetic response of the samples. Co substitution until x = 0.5 is seen to simultaneously induce in the as cast ingots a decrease of coercive field from 52 to around 10 A/m and an increase of the Curie temperature of the amorphous phase from 480 to 700 K. A maximum saturation magnetization value of 123 emu/g was observed in the sample having x = 0.2. The role of Co substitution on glass formation is discussed on the basis of crystallization and melting behaviors, analyzed by HT-DSC. Magnetic properties are correlated with the presence of crystalline phases and their microstructures.

The influence of Co addition on the magnetocaloric effect of Nanoperm-type amorphous alloys

The effect of Co addition on the magnetocaloric effect of amorphous alloys with Nanoperm-type composition has been studied for temperatures above room temperature. Co addition produces an increase in the maximum magnetic entropy change and a shift of its associated temperature to higher temperatures. The maximum refrigerant capacity (RC) value obtained in this study is 82Jkg−1 for a maximum applied field H=15kOe. This value is ∼30% larger than that of a Mo-containing Finemet-type alloy measured under the same experimental conditions. However, the RC of the alloys, when calculated from temperatures corresponding to the half-maximum entropy change value, deteriorates with the presence of Co in the alloy. The field dependence of the magnetic entropy change has also been analyzed, showing a power dependence for all the magnetic regimes of the samples. This field dependence at the Curie temperature deviates from mean field predictions.

Influence of Co addition on the magnetocaloric effect of FeCoSiAlGaPCB amorphous alloys

The FeCoSiAlGaPCB alloys can be prepared as bulk amorphous materials, with outstanding mechanical properties and increased electrical resistivity. These features can be beneficial for their application as a magnetic refrigerant. The influence of Co addition on the magnetic entropy change of the alloy has been studied. This compositional modification displaces the temperature of the peak entropy change closer to room temperature, but reduces the refrigerant capacity of the material. For the Co-free alloy, the peak entropy change is increased with respect to a Finemet alloy containing Mo, but its refrigerant capacity is not enhanced.

Characterisation of oxidation products of modified Nd–Fe–B type magnets

In order to study the influence of Co addition on oxidation behaviour, magnets with the compositions Nd 16Fe 76B 8, Nd 16Co 3Fe 73.3B 7.7, Nd 16Co 5Fe 71.5B 7.5, Nd 16Co 7Fe 69.6B 7.4, Nd 16Co 10Fe 66.9B 7.1, Nd 14Dy 3Co 9.7Fe 66.4B 6.9, Nd 13.9Dy 3Co 9.7Fe 66.2B 6.9Zr 0.3 and Nd 13.9Dy 3Co 9.7Fe 66.2B 6.9V 0.3 in powder and solid pellet forms were oxidised at 400 °C for 96 h. The resultant phases were identified using X-ray diffraction (XRD) and Mössbauer spectroscopy. α-Fe 2O 3 is the main final oxidation product of the iron content of these magnets, while Fe 3O 4 is the intermediate phase of this oxidation procedure. In addition the presence of several Nd oxides, as well as Dy oxides in the compositions with Dy additions was confirmed in all samples. B seems to prefer to react with Nd with the formation of oxide phases, while a minority Fe 2B phase is also detected in the powder samples. A delay of the oxidation process is found for the case of compact pelletised samples, and this is extended for those samples containing Dy in their structure.

Influence of Co Addition on Martensitic and Magnetic Transitions in Ni-Fe-Ga β Based Shape Memory Alloys

The effect of Co addition on the martensitic transition and magnetic properties of the Ni-Fe-Ga β alloys is investigated. The values of both the Curie temperature T c and martenaitic transition starting temperature M s increase, while the saturation magnetization I s decreases with increasing Co content in the series of Ni 5 1 Fe 2 2 - X Co X Ga 2 7 alloys. On the other hand, the values of both T c and I s increase and M s decrease with increasing Co content in the series of Ni 5 4 - X Fe 1 9 Co X Ga 2 7 alloys. T c and I s show a strong dependence on the average magnetic valence number Zm. Consequently, Co is an effective element to control both the martensitic and the magnetic transition temperatures.

Tb–Fe–Co giant magnetostrictive thin film and its application to force sensor

A giant magnetostrictive material (GMM) has large magnetostriction. Therefore, GMM is successfully applied to many actuators and sensors. Recently, practical micro-actuators and micro-sensors have been anticipated in the industry. In this study, the influence of Co addition to a Tb–Fe GMM thin film and the influence of heat treatment were examined. Then the GMM thin film was applied to a force sensor. This paper describes the following: (1) The thin film which made the ratio of cobalt for the sum of iron and cobalt to be 25.5%, and annealing at 300 °C, showed the magnetostriction of 1200 ppm at 80 kA/m. (2) The characteristic of the force sensor that used the GMM thin film with a relative permeability of 210 is examined.

Study of structural and magnetic properties of (Fe 100–x Co x ) 73.5 Si 13.5 B 9 Nb 3 Cu 1 alloys

The influence of Co addition on structural and magnetic properties of nanocrystalline (Fe100–xCox)73.5 Si13.5B9Nb3Cu1 (x = 10, 20, 30, 40, 50, 80) alloys has been studied using DSC, Mossbauer spectrometry, XRD and magnetic measurements. Results show that a Fe70Co30-like nano-phase containing a small amount of Si precipitate in Co-rich alloys (x ≥ 30), whereas other alloys exhibits the characteristics of DO3 FeSi nanoparticles containing a small amount of Co. Exception is found for equi-atomic alloy (x=50), which decomposes into two phases having different Si content. This drastic change of microstructure for x ≥ 30 directly affects the magnetic properties because of the precipitation of a harder magnetic phase compared with alloys having a low Co content. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of Co addition on the magnetic and thermal stability behavior of Fe77−Co Al2.14P8.4C5B4Ga0.86Si2.6 amorphous alloys

The effect of Co additions on the magnetic properties , thermal stability of the super cooled liquid before crystallization and glass forming ability of amorphous ribbons with composition Fe 77−x Co x Al 2.14 Ga 0.86 P 8.4 Si 4 C 5 B 4 (x=0,2,4) is studied. As cast alloys exhibit low values of the coercive field in addition with high magnetization saturation values. Co addition shifts the Curie temperature to higher values.

Influence of Coadditives on Physical and Mechanical Properties of Jute Fabrics Improved by UV-Cured Coating with Urethane Acrylate

Twelve different formulations were developed with aliphatic backbone-based urethane acrylate oligomer (Ebecry-264) in combination with a number of monomers like N-vinyl pyrrolidone (NVP), tripropylene glycol diacrylate (TPGDA), plasticizer, diallyl phthalate (DP), and antibubling agent methyl ethyl ketone (MEK), along with a photoinitiator Irgacure 184. Some additives and coadditives, such as calcium carbonate, urea, copper, and acrylamide, were incorporated into these formulations to study their effects on the physical and mechanical properties of pendulum hardness, gel content, and tensile strength and elongation at break of the films produced under UV radiation with these formulated solutions. These formulations were applied on jute fabrics (Hessian cloth) and cured under UV radiation. The improvement of various physicomechanical properties, such as tensile strength, elongation at break, and water resistivity of the treated jute fabrics was determined. The best formulation was evaluated.

Glass-forming Ability and Magnetic Properties of Nd70−xFe20Al10Cox Alloys

The influence of Co addition on the glass-forming ability of slowly cooled Nd70-xFe20Al10Cox alloys (0 ≤ x ≤ 10) was studied by x-ray diffraction, constant-rate heating calorimetry, and magnetic measurements. Without addition of Co, the as-cast Nd70Fe20Al10 cylinders of 3-mm diameter show a mixture of amorphous and crystalline phases after copper mold casting. Increasing the Co content promotes amorphization, and bulk amorphous specimens can be obtained for Nd60Fe20Al10Co10. No glass transition or supercooled liquid region before crystallization was observed for the bulk Nd60Fe20Al10Co10 alloy. The bulk amorphous alloy exhibits hard magnetic behavior with a remanence (Jr) of 0.09 T, a magnetization (J1500) of 0.13 T, and a coercivity (Hc) of 298 kAm−1. The Curie temperature for the as-cast Nd70-xFe20Al10Cox cylinders increases from 480 K for x =0 to 487 K for x = 10. The enhanced glass-forming ability for the Nd–Fe–Al-based alloys upon Co addition will be critically discussed with respect to classical nucleation theory and the formation of metastable ordered clusters upon solidification.

Influence of Co addition on the structure of the precipitated phase in superalloys

Influence of Co addition on the structure of the precipitated phase in superalloys

Coercivity of metastable (Nd,Pr)-Fe-Co-B alloys

The beneficial influence of Co additions on the magnetic properties of rapidly quenched Nd-Fe-B, previously found for Nd15Fe77B8, also exists for a wide variety of other Nd-Fe-B compositions. High coercivities, Hci, result from a quenched-in metastable microstructure characterized by a non-equilibrium Nd(Fe,Co)2-type Laves phase. Annealing of either amorphous or optimally quenched Nd- and Co-rich samples leads to significantly lower Hci.

Sintering of cobalt-doped nickel oxide

The influence of Co additions on the sintering of nickel oxide was studied. On the basis of the density, specific surface area and Me3+ ion concentration changes, in the Co y Ni1−yO samples, having 0, 1, 5 and 10 cation % of Co, a positive effect of Co ions on the densification was assumed, during sintering at 500 to 900° C in an argon atmosphere. Using special heat-treatment, the differences in specific surface area of the investigated powders were eliminated. The differences in green densities were excluded as well and from the results, it was possible to show that dissolved Co ions enhance nickel oxide densification process.

Influence of Co Addition on the Properties of Doped Tungsten (Part II)

Effects of Co addition on some properties, particularly low-temperature ductility of doped tungsten wire have been studied.In particular, wires produced by additions of 0.01-0.06 weight % of Co together with common doping agents, Al2O3, SiO2 and K20 have shown a remarkably improved ductility before recrystallization. Increasing amounts of Co were effective in significantly increasing the maximum elongation. These wires at 0.39 mm diameter have shown the maximum elongation of 12-26% at room temperature after annealing, and the content of gaseous impurities in these wires have been effectively lowered.These wires containing 0.01-0.03% Co are not only remarkably ductile before recrystallization but have also superior in qualities to those of ordinary doped products after recrystallization, for example excellent in high temperature sag resistances essential to lamps and tubes as well as in ductility.

Influence of Co Addition on the Properties of Doped Tungsten (Part I)

Influence of Co Addition on the Properties of Doped Tungsten (Part I)