Further Increase In Mn Content Research Articles

Structural, optical and magnetic characterization of nanorod-shaped polycrystalline Zn1−xMnxO films synthesized using sol–gel technique

The structural, optical and magnetic properties of nanorod structured polycrystalline Zn1−xMnxO3 films $$\left( {0 \le x \le 0.1} \right)$$ grown on glass substrate using Sol–Gel technique have been investigated. X-ray diffraction (XRD) analysis reveals average grain sizes from 15 to 25 nm. There was gradual increase in both the crystallite size and lattice constant with increase in Mn content up to 0.2%, and then decrease of them with further increase in Mn content. The same result has been confirmed by SEM experiments. It has been revealed that the band gap value of Zn1−xMnxO film decreases from 3.34 to 2.97 eV with an increase in Mn concentration from x = 0.0 to 0.1, which is in agreement with the previously reported results. The studies of the magnetization and magnetic resonance of Zn1−xMnxO films revealed the presence of the paramagnetic state without any magnetic ordering.

Waste plastics recycling for producing high-value carbon nanotubes: Investigation of the influence of Manganese content in Fe-based catalysts

Thermo-chemical conversion is a promising technology for the recycle of waste plastics, as it can produce high-value products such as carbon nanotubes (CNTs) and hydrogen. However, the low yield of CNTs is one of the challenges. In this work, the addition of Mn (0 wt.%, 1 wt.%, 5 wt.%, and 10 wt.%) to Fe-based catalyst to improve the production of CNTs has been investigated. Results show that the increase of Mn content from 0 wt.% to 10 wt.% significantly promotes CNTs yield formed on the catalyst from 23.4 wt.% to 32.9 wt.%. The results show that Fe-particles in the fresh catalysts are between 10−25 nm. And the addition of Mn in the Fe-based catalyst enhanced the metal-support interactions and the dispersion of metal particles, thus leading to the improved catalytic performance in relation to filamentous carbon growth. In addition, the graphitization of CNTs is promoted with the increase of Mn content. Overall, in terms of the quantity and quality of the produced CNTs, 5 wt.% of Mn in Fe-based catalyst shows the best catalytic performance, due to the further increase of Mn content from 5 wt.% to 10 wt.% led to a dramatic decrease of purity by 10 wt.%.

Effects of Mn addition and related Mn-containing dispersoids on the hot deformation behavior of 6082 aluminum alloys

The hot deformation behaviors of 6082 aluminum alloys containing different Mn contents (0.05–1.0 wt%) were systematically investigated by uniaxial compression tests in a temperature range of 400–550 °C and strain rate range of 0.001–1 s-1. Prior to the hot deformation, a low-temperature homogenization (450 °C for 6 h) was carried out on direct-chill cast billets to promote the precipitation of Mn-containing dispersoids. The large numbers of dispersoids in the Mn-containing alloys yielded significantly increased high-temperature flow stresses, compared to that of the base alloy without dispersoids. The material constants and activation energies for hot deformation were determined using the hyperbolic-sine constitutive equation and experimental peak flow stress data. The activation energy increased from 191 kJ/mol for the base alloy to 286 kJ/mol for the alloy with 0.5% of Mn. With further increase in Mn content, the activation energy increased only moderately to 315 kJ/mol for the alloy with 1.0% of Mn. The influences of the Mn content and deformation conditions on the dynamic recovery and recrystallization were quantitatively analyzed. The precipitation of dispersoids in the Mn-containing alloys promoted the retardation of the dynamic recovery and inhibition of the recrystallization owing to their strong pinning effect on the dislocation movement and subgrain migration.

Role of magnetic dopants in the phase diagram of Sm 1111 pnictides: The case of Mn

The deliberate insertion of magnetic Mn dopants in the Fe sites of the optimally-doped SmFeAsO0.88-F0.12 iron-based superconductor can modify in a controlled way its electronic properties. The resulting phase diagram was investigated across a wide range of manganese contents (x) by means of muon-spin spectroscopy (muSR), both in zero- and in transverse fields, respectively, to probe the magnetic and the superconducting order. The pure superconducting phase (at x < 0.03) is replaced by a crossover region at intermediate Mn values (0.03 =< x < 0.08), where superconductivity coexists with static magnetic order. After completely suppressing superconductivity for x = 0.08, a further increase in Mn content reinforces the natural tendency towards antiferromagnetic correlations among the magnetic Mn ions. The sharp drop of Tc and the induced magnetic order in the presence of magnetic disorder/dopants, such as Mn, are both consistent with a recent theoretical model of unconventional superconductors [M. Gastiasoro et al., ArXiv 1606.09495], which includes correlation-enhanced RKKY-couplings between the impurity moments.

Effects of Mn Additions on the Structure, Mechanical Properties, and Corrosion Behavior of Cu-Al-Ni Shape Memory Alloys

The influences of different amount (0.4, 0.7, and 1 wt.%) of Mn addition on the structure, mechanical properties, and corrosion behavior of Cu-Al-Ni shape memory alloys have been studied using differential scanning calorimetry, field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, tensile test, shape memory effect test, hardness test, and electrochemical test. It was observed that the transformation temperatures, microstructural characteristics, and mechanical properties are highly sensitive to the composition variations. The obtained results show that the transformation temperatures and mechanical properties of Cu-Al-Ni SMAs exhibited the best results with 0.7 wt.% of Mn addition. These kinds of enhancements are mainly due to the type, amount, and morphology of the martensite phase, including the grain refinement. The result of electrochemical test showed that an increment in Mn content up to 0.7 wt.% improved the corrosion resistance of Cu-Al-Ni SMA. However, further increase of Mn content decreases the corrosion resistance of the alloy.

Effects of Manganese Doping on the Dielectric Properties of Titanium Dioxide Ceramics

Dielectric properties of undoped and manganese (Mn)-doped titanium dioxide (TiO2) ceramics were measured by various test methods including impedance spectroscopy techniques. It was found that direct current conductivity and dielectric loss were effectively suppressed by small amount (∼0.05 mol%) of Mn doping due to generation of possible electron traps. Further increase of Mn content led to formation of oxygen vacancies and increase of dielectric loss. Increased grain-boundary resistivity was observed as Mn-doping concentration increases, presumably due to segregation of Mn solutes at the grain boundaries. Larger difference between the grain and grain-boundary conductivity gave rise to space charge polarization. It was shown that TiO2 ceramics with optimum amount of Mn-doping concentration possess good dielectric properties that are suitable for energy storage applications.

Effect of Mn substitution on the thermo-power of the superconductor Mg1−xMnxB2

In this communication a systematic study has been made on the effect of Mn substitution on the thermo-power of MgB2 superconducting compounds involving 0%, 0.5%, 1.0%, 1.5% and 2% Mn content. The superconducting transition has been found to be very sharp for the pure compound of MgB2 and it is observed that the transition width increases with Mn content. For small values of Mn content, the thermo-power S(T) increases with Mn content which suggests that the hole density increases. However, with further increase in Mn content, a small decrease in S(T) is observed. For all the compounds, we have observed the expected linear region at low temperatures. There is no systematic trend in the slopes dS/dT with Mn content.

Magnetic properties of Ho2Fe17−xMnx – influence of Mn substitution

The structural and magnetic properties of Ho2Fe17−xMnx (x=0−5) have been investigated by x-ray diffraction, Mössbauer spectroscopy and DC magnetization measurements (0-5 T) over the temperature range 4.5–350 K. Similar to other ferrimagnetic R2Fe17−xMnx systems, the unit cell volume generally increases with Mn content other than for low Mn values where a slight maximum is detected around x ~ 0.5. The nature of the magnetic phase transitions around TC is shown by Arrot plot analysis to be second order for all samples. The Curie temperature remains essentially unchanged for Mn contents up to x=1.0 (TC = 336 K for x=0.0, TC = 338 K for x=1.0) before decreasing steadily with further increase in Mn content (TC = 209 K for x=5). The 57Fe hyperfine interaction parameters have been determined from variable temperature Mössbauer spectra.

The effect of manganese on the microstructure and mechanical properties of zinc–aluminium based ZA-8 alloy

In this investigation, the effect of manganese as an alloying element in the range 0.01%–0.53 wt.%, on the hardness, 0.2% yield, tensile and impact strength, and creep properties of a gravity cast Zn–Al based ZA-8 alloy has been investigated. It was found that addition of Mn over the entire range of concentrations has a useful effect on the hardness of the alloy. Also, the 0.2% yield and ultimate tensile strength (UTS) of the samples did not change significantly with Mn additions up to 0.045 wt.% but decreased with a further increase in Mn content. Furthermore, the impact strength of the alloy improved with increasing Mn up to 0.045 wt.% and then decreased gradually with a further increase in Mn content. On the other hand, the creep resistance of the alloy increased continuously with increasing Mn content up to 0.53 wt.% Mn. Metallographic studies showed that addition of Mn resulted in microstructural modifications of the alloy involving the formation of complex intermetallic compound identified as MnAl6. The increase in creep resistance and decrease in tensile and impact strength were thought to have been caused by the changing morphology and amount of the intermetallic.

Effect of manganese on a potassium-promoted iron-based Fischer-Tropsch synthesis catalyst

The effects of manganese promoter on the reduction–carburization behavior, surface basicity, bulk phase structure and their correlation with Fischer-Tropsch synthesis (FTS) performances have been emphatically studied over a series of spray-dried Fe–Mn–K catalysts with a wide range of Mn incorporation amount. The catalysts were characterized by means of H2 and CO temperature-programmed reduction (TPR), CO2 temperature-programmed desorption (TPD), Mossbauer spectroscopy etc.. The results indicated that small amount of Mn promoter can promote the reduction of the catalyst in H2. However, FeO phase formed during reduction is stabilized by MnO phase with the further increase of Mn content, making FeO phase difficult to be reduced in H2. The addition of Mn promoter can stabilize the Fe2+ and Fe3+ ions, and suppresses the reduction and carburization of the catalyst in syngas and CO. Mn promoter can also enhance the amount of the basic sites and weaken the strength of the basic sites, which possibly come from the reason that the Mn–K interaction is strengthened with the addition of Mn promoter. The change of surface basicity can modify the selectivity of hydrocarbons and olefins, and the change of bulk structure phase derived from the addition of Mn promoter will affect the catalyst activity and run stability. The synergetic effects of the two main factors result in an optimized amount of Mn promoter for the highest catalyst activity and heavy hydrocarbon selectivity in slurry FTS reaction of Fe–Mn–K catalysts.

The influence of Mn dopant on the electromagnetic properties of NiCuZn ferrite

In this paper, a citrate precursor method was used to prepare nano-sized NiCuZn ferrite powders with a composition of (Ni 0.15Cu 0.2Zn 0.65O)(Fe 2− x Mn x O 3+0.5 x ) 0.99, ( x = 0–0.04). Because of excellent sintering activity, the nanocrystals can be sintered below 900 °C without the addition of sintering aids. The effect of Mn dopant on the microstructures and the initial permeability was investigated. The results show that the introduction of Mn into NiCuZn ferrite has a great influence on its electromagnetic properties. The initial permeability of NiCuZn ferrite increases greatly with a small amount of Mn addition firstly, and then further increase of Mn content leads to a decrease in the initial permeability. By changing the content of Mn addition, the useful frequency dependence of initial permeability could be adjusted in a range of frequency from several hundreds of kilohertzs to several megahertzs.

Metal–insulator transition and magnetotransport in III–V compound diluted magnetic semiconductors

Structural, magnetic and transport properties of diluted magnetic semiconductors, (Ga, Mn)As and (In, Mn)As, have been investigated. Manganese can be substitutionally doped into the group III site of the zincblend structure up to several percent. With Mn content of a few percent, these systems exhibit ferromagnetism at low temperatures. The highest Curie temperature so far achieved is ∼100 K for (Ga, Mn)As. The saturated magnetization values are consistent with S=5/2 local moment, suggesting divalent Mn which acts as an acceptor. The system becomes metallic with increasing Mn content, but a further increase of Mn content tends to decrease the hole density and increase disorder so that the system becomes nonmetallic again at higher Mn concentrations. Large negative magnetoresistance and highly anisotropic transport are observed in the semiconducting samples at low temperatures. The magnetic anisotropy in ultrathin films is found to be strongly affected by the lattice-mismatch-induced strain.

Nonmetal-metal-nonmetal transition and large negative magnetoresistance in (Ga, Mn)As/GaAs

We have studied magnetic and transport properties of a series of Ga 1−x Mn x As GaAs samples with different Mn concentrations ( x = 0.015−0.071. For Mn content higher than about 0.02, carrier(hole)-induced ferromagnetism is observed. Samples with x = 0.035 and 0.043 behave as ferromagnetic dirty metals. With further increase of Mn content above x ∼ 0.05, the zero-field resistivity turns a semiconducting temperature dependence. Very large negative magnetoresistance is observed in non-metallic samples near the metal-nonmetal transitions both in the low and the high Mn content regimes.

The influence of soil steaming on some properties of the soil and on the growth and heading of winter glasshouse lettuce. II. The reaction of the crop.

Soil steaming increased fresh and dry weights and N and Mn contents of the plants. Leaching the steamed soil caused a further increase in Mn content but decreased yields and N content. The addition of straw to the steamed soil did not affect growth or N content but it reduced the Mn content. Plants grown on steamed soil had darker coloured leaves and a greater incidence of leaf margin necrosis and bad heading than plants grown on unsteamed soil. See also Sous Fertil. 33 [1230]. (Abstract retrieved from CAB Abstracts by CABI’s permission)