Iridium

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Dean L. Jacobson - One of the best experts on this subject based on the ideXlab platform.

  • Sub-surface Iridium depletion in dilute solution tungsten-Iridium alloys due to high temperature work function testing
    International Journal of Refractory Metals & Hard Materials, 1992
    Co-Authors: L.a.d. Cruz, Dean L. Jacobson
    Abstract:

    Abstract Dilute solution tungsten-Iridium alloys with less than 2 wt % Ir have been found to exhibit the highest work functions among candidate alloys for thermionic emitters. Recent studies have investigated the effect of Iridium on the work function of tungsten-Iridium alloys fabricated either by arc-melting or sintering. In the present paper, an attempt has been made to understand the interrelationship between work function, composition and microstructure in these alloys. The ultimate aim was to ascertain the role of Iridium in the modification of the work function. The effective work function was determined using a vacuum emission vehicle (VEV) employing the thermionic method. Electron probe microanalysis was used to characterize the sub-surface Iridium depletion caused by elevated temperature testing. Theoretical estimates of the equilibrium segregation of Iridium in tungsten could not adequately account for the magnitude of Iridium depletion found at the electrode surfaces. An alternative explanation for the sub-surface Iridium depletion has been proposed and involves the creation of Iridium-rich surface layers during the pre-test heat treatment of the alloys.

  • ultrahigh temperature tensile properties of arc melted tungsten and tungsten Iridium alloys
    Scripta Metallurgica Et Materialia, 1991
    Co-Authors: Anhua Luo, Kwang S. Shin, Dean L. Jacobson
    Abstract:

    Tungsten is one of the most important metals for high temperature applications. The major deterrents to the use of tungsten are poor fabricability at room temperature and rapid decrease in strength at temperatures above 1600 K. Previous investigations have shown that the addition of rhenium to tungsten improves both room- temperature fabricability and high-temperature strength. Based on its similarity to rhenium's electron structure, Iridium as another potential alloying element in tungsten. It was recently confirmed that tungsten-Iridium alloys with less than 1.0w/o Iridium exhibit better fabricability than tungsten-rhenium alloys at room temperature. The strength properties of tungsten-Iridium alloys at ultrahigh temperatures have not yet been researched. The present paper reports the tensile properties of dilute tungsten-Iridium alloys in the temperature range 1600 to 2600 K. The focus of the present paper is to examine the effects of Iridium concentration and test temperature on the strength and fracture behavior of tungsten-Iridium alloys at ultrahigh temperatures.

Sugeng Triwahyono - One of the best experts on this subject based on the ideXlab platform.

  • ir pt hzsm5 for n pentane isomerization effect of Iridium loading on the properties and catalytic activity
    Journal of Catalysis, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono
    Abstract:

    Abstract The effects of Iridium loading on the properties of Ir/Pt-HZSM5 and n-pentane isomerization were studied. XRD, IR, and NMR results indicated that increasing Iridium loading did not much change the properties of catalysts, but eliminated the perturbed silanol groups at 3700 and 3520 cm−1, whereas IR and ESR spectroscopy confirmed that increasing Iridium loading continuously decreased the permanent Lewis and Bronsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. At low Iridium loading (0–0.3 wt%), cracking process proceed through dimerization-cracking step, whereas high Iridium loading (0.5–2.0 wt%) reduces the contribution of dimerization-cracking step and promotes the contribution of hydrogenolysis. The excessive amount of Iridium loading, with the presence of a low amount of active protonic acid sites and hydrogen gas, accelerated the hydrogenolysis process. The activity of Ir/Pt-HZSM5 was marginal in the absence of hydrogen, showing the dependence of activity on promotive effect of hydrogen.

  • ir study of Iridium bonded to perturbed silanol groups of pt hzsm5 for n pentane isomerization
    Applied Catalysis A-general, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono, Nur Hidayatul Nazirah Kamarudin, Rino R Mukti
    Abstract:

    Abstract The Ir/Pt-HZSM5 catalyst was prepared by impregnation of Iridium on Pt-HZSM5. The activity of Ir/Pt-HZSM5 was tested for n-pentane isomerization under hydrogen stream. The introduction of Iridium did not change the bands observed at 3740, 3665 and 3610 cm−1 indicating that neither non-acidic terminal silanol groups nor acidic bridging hydroxyl groups interacted with the Iridium. Additionally, the peaks corresponding to the perturbed silanol groups at 3700 and 3520 cm−1 decreased significantly. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Iridium is in the form of IrO2. 27Al MAS NMR confirmed the elimination of distorted tetrahedral aluminum. The presence of Iridium slightly increased the acidity of Pt-HZSM5 and its selectivity for iso-pentane. Hydrogen adsorption FTIR indicated that Iridium enhanced the formation of protonic acid sites which may participate in the isomerization, and inhibited the formation of hydroxyl groups at 3380, 3600 and 3680 cm−1 which may participate in the enhancement of the cracking reaction.

H D Setiabudi - One of the best experts on this subject based on the ideXlab platform.

  • ir pt hzsm5 for n pentane isomerization effect of Iridium loading on the properties and catalytic activity
    Journal of Catalysis, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono
    Abstract:

    Abstract The effects of Iridium loading on the properties of Ir/Pt-HZSM5 and n-pentane isomerization were studied. XRD, IR, and NMR results indicated that increasing Iridium loading did not much change the properties of catalysts, but eliminated the perturbed silanol groups at 3700 and 3520 cm−1, whereas IR and ESR spectroscopy confirmed that increasing Iridium loading continuously decreased the permanent Lewis and Bronsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. At low Iridium loading (0–0.3 wt%), cracking process proceed through dimerization-cracking step, whereas high Iridium loading (0.5–2.0 wt%) reduces the contribution of dimerization-cracking step and promotes the contribution of hydrogenolysis. The excessive amount of Iridium loading, with the presence of a low amount of active protonic acid sites and hydrogen gas, accelerated the hydrogenolysis process. The activity of Ir/Pt-HZSM5 was marginal in the absence of hydrogen, showing the dependence of activity on promotive effect of hydrogen.

  • ir study of Iridium bonded to perturbed silanol groups of pt hzsm5 for n pentane isomerization
    Applied Catalysis A-general, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono, Nur Hidayatul Nazirah Kamarudin, Rino R Mukti
    Abstract:

    Abstract The Ir/Pt-HZSM5 catalyst was prepared by impregnation of Iridium on Pt-HZSM5. The activity of Ir/Pt-HZSM5 was tested for n-pentane isomerization under hydrogen stream. The introduction of Iridium did not change the bands observed at 3740, 3665 and 3610 cm−1 indicating that neither non-acidic terminal silanol groups nor acidic bridging hydroxyl groups interacted with the Iridium. Additionally, the peaks corresponding to the perturbed silanol groups at 3700 and 3520 cm−1 decreased significantly. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Iridium is in the form of IrO2. 27Al MAS NMR confirmed the elimination of distorted tetrahedral aluminum. The presence of Iridium slightly increased the acidity of Pt-HZSM5 and its selectivity for iso-pentane. Hydrogen adsorption FTIR indicated that Iridium enhanced the formation of protonic acid sites which may participate in the isomerization, and inhibited the formation of hydroxyl groups at 3380, 3600 and 3680 cm−1 which may participate in the enhancement of the cracking reaction.

Aishah Abdul Jalil - One of the best experts on this subject based on the ideXlab platform.

  • ir pt hzsm5 for n pentane isomerization effect of Iridium loading on the properties and catalytic activity
    Journal of Catalysis, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono
    Abstract:

    Abstract The effects of Iridium loading on the properties of Ir/Pt-HZSM5 and n-pentane isomerization were studied. XRD, IR, and NMR results indicated that increasing Iridium loading did not much change the properties of catalysts, but eliminated the perturbed silanol groups at 3700 and 3520 cm−1, whereas IR and ESR spectroscopy confirmed that increasing Iridium loading continuously decreased the permanent Lewis and Bronsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. At low Iridium loading (0–0.3 wt%), cracking process proceed through dimerization-cracking step, whereas high Iridium loading (0.5–2.0 wt%) reduces the contribution of dimerization-cracking step and promotes the contribution of hydrogenolysis. The excessive amount of Iridium loading, with the presence of a low amount of active protonic acid sites and hydrogen gas, accelerated the hydrogenolysis process. The activity of Ir/Pt-HZSM5 was marginal in the absence of hydrogen, showing the dependence of activity on promotive effect of hydrogen.

  • ir study of Iridium bonded to perturbed silanol groups of pt hzsm5 for n pentane isomerization
    Applied Catalysis A-general, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono, Nur Hidayatul Nazirah Kamarudin, Rino R Mukti
    Abstract:

    Abstract The Ir/Pt-HZSM5 catalyst was prepared by impregnation of Iridium on Pt-HZSM5. The activity of Ir/Pt-HZSM5 was tested for n-pentane isomerization under hydrogen stream. The introduction of Iridium did not change the bands observed at 3740, 3665 and 3610 cm−1 indicating that neither non-acidic terminal silanol groups nor acidic bridging hydroxyl groups interacted with the Iridium. Additionally, the peaks corresponding to the perturbed silanol groups at 3700 and 3520 cm−1 decreased significantly. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Iridium is in the form of IrO2. 27Al MAS NMR confirmed the elimination of distorted tetrahedral aluminum. The presence of Iridium slightly increased the acidity of Pt-HZSM5 and its selectivity for iso-pentane. Hydrogen adsorption FTIR indicated that Iridium enhanced the formation of protonic acid sites which may participate in the isomerization, and inhibited the formation of hydroxyl groups at 3380, 3600 and 3680 cm−1 which may participate in the enhancement of the cracking reaction.

Rino R Mukti - One of the best experts on this subject based on the ideXlab platform.

  • ir study of Iridium bonded to perturbed silanol groups of pt hzsm5 for n pentane isomerization
    Applied Catalysis A-general, 2012
    Co-Authors: H D Setiabudi, Aishah Abdul Jalil, Sugeng Triwahyono, Nur Hidayatul Nazirah Kamarudin, Rino R Mukti
    Abstract:

    Abstract The Ir/Pt-HZSM5 catalyst was prepared by impregnation of Iridium on Pt-HZSM5. The activity of Ir/Pt-HZSM5 was tested for n-pentane isomerization under hydrogen stream. The introduction of Iridium did not change the bands observed at 3740, 3665 and 3610 cm−1 indicating that neither non-acidic terminal silanol groups nor acidic bridging hydroxyl groups interacted with the Iridium. Additionally, the peaks corresponding to the perturbed silanol groups at 3700 and 3520 cm−1 decreased significantly. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Iridium is in the form of IrO2. 27Al MAS NMR confirmed the elimination of distorted tetrahedral aluminum. The presence of Iridium slightly increased the acidity of Pt-HZSM5 and its selectivity for iso-pentane. Hydrogen adsorption FTIR indicated that Iridium enhanced the formation of protonic acid sites which may participate in the isomerization, and inhibited the formation of hydroxyl groups at 3380, 3600 and 3680 cm−1 which may participate in the enhancement of the cracking reaction.