Addition Of HO Research Articles

The Influence of Holmium on the Microstructure and Hardness of Mg-Nd-Gd-Zn-Zr Alloys

The influence of holmium on the microstructure and hardness of Mg-Nd-Gd-Zn-Zr alloys were investigated. Conventional casting methods are used to produce the alloys. All the results were characterized by optical microscopy, scanning electron microscope (SEM) and the Vickers hardness test to highlight the influence of holmium addition. The addition of 2.0 wt.% holmium leads to the combination of rare earth elements which formed Mg-Zn-Nd-Ho phase. The results have shown the addition of Ho improved the microstructure and hardness of Mg-Nd-Gd-Zn-Zr alloys. By adding grain size of 2.0 wt.% holmium had reduced by 18.43%, while the volume fraction increased by 7.34%. The Vickers hardness value improved 6.18% due to the grain refine and volume fraction precipitates. The 2.0 wt.% holmium addition showed a positive result in microstructure and hardness value.

Investigation of structural, dielectric and magnetic properties of Ho substituted nanostructured lithium ferrites synthesized via auto-citric combustion route

Abstract A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho3+) lithium ferrites; Li1.2Co0.4HoxFe2−xO4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO3) were appeared for x ≥ 0.06 indicating the solubility limit of Ho3+ ions. The lattice constant ′a′ increased from 8.351 to 8.360 A upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 A. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral (v1) and octahedral (v2) intrinsic vibrational bands at 627 cm−1 and 479 cm−1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants (Ko and Kt) were calculated and discussed with the tetrahedral (rA) and octahedral (rB) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 103 to 5.56 × 104 (Ω-cm)−1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li1.2Co0.4Ho0.12Fe1.88O4. The improved coercivity may suggest their utilization in perpendicular recording media applications.

Photocatalytic degradation of clofibric acid by g-C3N4/P25 composites under simulated sunlight irradiation: The significant effects of reactive species

Pharmaceutically emerging micropollutants have become an environmental concern in recent years. In the present paper, the reactive species (RSs)-induced degradation mechanism of clofibric acid (CA) was investigated using a newly sunlight-driven g-C3N4/P25 photocatalyst. A very low g-C3N4 content of 8.0 weight percent resulted in a 3.36 and a 2.29 times faster reaction rate for CA photodegradation than for pristine g-C3N4 and P25, respectively. Electron spin resonance and quenching experiments demonstrated the participation of HO, h+, e−, 1O2 and O2·- in the photocatalytic system, and the contribution rates were calculated to 73.3%, 15.3%, 5.1%, 6.7% and 33.1%, respectively. According to the pulse radiolysis measurements and the competitive kinetics approaches, the bimolecular reaction rate constants for HO, e−, and 1O2 with CA were (8.47 ± 0.33) × 109 M−1s−1, (6.41 ± 0.48) × 109 M−1s−1 and (6.6 ± 0.37) × 106 M−1s−1, respectively. RSs were found to significantly influence the degradation of CA, and the degradation pathways occurred primarily via e− reduction, HO addition and 1O2 attack reactions on the basis of mass spectrometry and theoretical calculations.

Novel holmium-modified Fe-Mn/TiO2 catalysts with a broad temperature window and high sulfur dioxide tolerance for low-temperature SCR

Novel highly-efficient low-temperature SCR catalysts were developed through modifying Fe-Mn/TiO2 catalyst with holmium (Ho). It was found that Ho/Ti=0.1 was the optimal molar ratio for the amount of Ho addition. With this ratio, 85% NOx conversion was obtained at 60°C and the catalytic performance enhanced to 90% at 120°C. The optimal catalyst presented a broad operating temperature window in the range of 60–200°C and exhibited superior sulfur-poisoning resistance, while the further increase of the doped Ho did not have a positive effect on the catalytic performance and structural properties.

Mechanical properties, in vitro corrosion and biocompatibility of newly developed biodegradable Mg-Zr-Sr-Ho alloys for biomedical applications.

Our previous studies have demonstrated that Mg-Zr-Sr alloys can be anticipated as excellent biodegradable implant materials for load-bearing applications. In general, rare earth elements (REEs) are widely used in magnesium (Mg) alloys with the aim of enhancing the mechanical properties of Mg-based alloys. In this study, the REE holmium (Ho) was added to an Mg-1Zr-2Sr alloy at different concentrations of Mg1Zr2SrxHo alloys (x = 0, 1, 3, 5 wt. %) and the microstructure, mechanical properties, degradation behaviour and biocompatibility of the alloys were systematically investigated. The results indicate that the addition of Ho to Mg1Zr2Sr led to the formation of the intermetallic phases MgHo3, Mg2Ho and Mg17Sr2 which resulted in enhanced mechanical strength and decreased degradation rates of the Mg-Zr-Sr-Ho alloys. Furthermore, Ho addition (≤5 wt. %) to Mg-Zr-Sr alloys led to enhancement of cell adhesion and proliferation of osteoblast cells on the Mg-Zr-Sr-Ho alloys. The in vitro biodegradation and the biocompatibility of the Mg-Zr-Sr-Ho alloys were both influenced by the Ho concentration in the Mg alloys; Mg1Zr2Sr3Ho exhibited lower degradation rates than Mg1Zr2Sr and displayed the best biocompatibility compared with the other alloys.

Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure.

Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5–2.3 eV for GO, which is an insulator, to 3.9–1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO• is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique.

Phase Relationship and Magnetostriction of Tb–Dy–Ho–Fe Alloys

The phase relationship of $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ $(1.6\le x\le 2.4)$ alloys in the Tb–Dy–Ho–Fe system was determined by using optical microscopy, X-ray diffraction, and differential thermal analysis. The vertical section of $\mbox{Tb}_{{\kern-.5pt}0{\kern-.25pt}.{\kern-.25pt}26}\mbox{Dy}_{{\kern-.25pt}0{\kern-.25pt}.{\kern-.25pt}49}\mbox{Ho}_{{\kern-.5pt}0{\kern-.25pt}.{\kern-.25pt}25}\mbox{Fe}_{{\kern-.5pt}x}$ alloys consists of two single-phase regions, namely, L (liquid) and (Tb, Dy, Ho)Fe 2, and four two-phase regions, namely, L + (Tb, Dy, Ho)Fe 3, L + (Tb, Dy, Ho)Fe 2, (Tb, Dy, Ho)Fe 2 + (Tb, Dy, Ho)Fe 3, and (Tb, Dy, Ho)Fe 2 + (Tb, Dy, Ho). The range between the liquidus and peritectic temperatures for $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ alloys becomes narrow with addition of Ho, which is beneficial to decrease the properitectic (Tb, Dy, Ho)Fe 3 phase. The magnetic field dependence of magnetostriction $(\lambda_{//},\lambda_{\perp})$ for $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ alloys has been determined. The magnetostriction quickly increases with increasing magnetic field value when it is less than 240 kA/m. Among the present studied alloys, the sample with $x=1.9$ possesses the largest magnetostriction. It has been found that magnetic annealing improves the magnetostriction $\lambda_{//}$ of Tb 0.26Dy 0.49Ho 0.25Fe 1.9 alloy.

Holmium acetylacetonate, a compatibilizer between ZnO quantum dots and epoxy resin

: Ho(AcAc)3 modified ZnO quantum dots (QDs) were successfully prepared via a conventional method. The FTIR spectra were taken to explore the combination of Ho(AcAc)3 and ZnO QDs. The addition of Ho(AcAc)3 could lower the emission intensity of ZnO QDs by modifying the defects of ZnO QDs. Three types of ZnO QDs with different optical defects were used to composite with Ho(AcAc)3. The effect of Ho(AcAc)3 on different optical defects in ZnO QDs was distinctive. Ho(AcAc)3 modified ZnO QDs were successfully composited with the epoxy resin. With the addition of ZnO QDs, the emission intensity and UV absorption increased. Samples with Ho(AcAc)3 had higher visible light transmittance than those without Ho(AcAc)3. As such, Ho(AcAc)3 could improve the dispersity of ZnO QDs in epoxy. Thus, Ho(AcAc)3 could act as a compatibilizer between ZnO QDs and epoxy resin.

The mechanism study of efficient degradation of hydrophobic nonylphenol in solution by a chemical-free technology of sonophotolysis

Nonylphenol is a hydrophobic endocrine disrupting compound, which can inhibit the growth of sewage bacteria in biological processes. This study investigated the degradation of 4-n-nonylphenol (NP) in water by a chemical-free technology of sonophotolysis with emphasis on the impacts of several important parameters, including light intensity, solution pH, two commonly seen inorganic ions (i.e. NO3− and HCO3−), and principally on the examination of degradation mechanisms. It was found that, solution pH could significantly influence both NP degradation efficiency and the synergistic effect of sonophotolytic process, where higher synergistic effect was obtained at more acidic condition. In addition, the presence of NO3− accelerated NP degradation by both acting as a photosensitizer and providing NO2 radicals, while HCO3− had little effect on NP degradation. Identification of intermediates of NP degradation indicated that NP sonophotolysis was mainly initiated by the formation of hydroxy-NP, and a new intermediate di-hydroxy-NP was identified for the first time ever in this study. Through thermodynamic analysis, results indicated that both ortho- and meta-hydroxy-NP species can coexist in the solution but the ortho-4-NBZQ (4-nonyl-benzoquinone) is dominant. In addition, the mechanism of ortho-hydroxy-NP formation was suggested by the addition of HO and H radicals.

Combustive, Postcombustive, and Tropospheric Butadiyne Oxidation by O2, Following Initial HO Attack. Theoretical Study.

Butadiyne (diacetylene, HC(4)H) is produced during combustions, and has been quantified in different flames as well as a biomass burning emission. Its reaction with the hydroxyl radical, HO((2)Π(3/2)), under combustion conditions, was investigated in a thorough RRKM study by J. P. Senosiain, S. J. Klippenstein, and J. A.Miller (Proc. Combust. Inst. 2007, 31, 185−192). The present densityfunctional theory (DFT) study focuses on the mechanism of further oxidation by O(2)(3Σ(g)(−)). The DFT(M06-2X)/cc-pVTZ reaction energy hypersurface for the system C(4)H(2)/HO•/O(2) is studied to define a variety of reaction pathways, and the relevant thermochemistry for temperatures ranging from 200 to 2500 K is assessed, thus encompassing combustive, postcombustive, and tropospheric conditions.Energies are then recomputed at the coupled cluster level[CCSD(T)/cc-pVTZ], and combined with the DFT thermochemistry.Finally, the role of the different reaction channels is assessed by RRKM-ME simulations in the same temperature range for P = 1 atm,to comprise the situation of emission in the troposphere and those pertaining to different flames. This shows that, when considering HO addition to the triple bond, dioxygen takes part in C(4)H(2) oxidation with higher efficiency at lower temperatures, whereas, as T rises, the O(2) adducts are inclined to redissociate: for instance, a 50% redissociation is estimated at T = 1800 K. For 200 < T < 1100 K, two polycarbonyl products (CHO.CO.CCH and CHO.CO.CHCO) and two fragmentation products (HCOOH plus OC(•)−CCH) are the main species predicted as products from the addition channel (fragmentation is entropy-favored by higher T values). However, at higher temperatures, aninitial H abstraction by HO can give the but adiynyl radical (HC(4)(•)) as the starting point for subsequent dioxygen intervention.Then, new pathways opened by O(2) addition become accessible and bring about fragmentations mainly to HC(3)(•) + CO(2) and also to HC(3)(•)O + CO.

Experimental and theoretical studies on aqueous-phase reactivity of hydroxyl radicals with multiple carboxylated and hydroxylated benzene compounds.

In this study, we shed light on the initial addition of hydroxyl radicals (HO˙) to multiple carboxylated and hydroxylated benzene compounds in aqueous-phase advanced oxidation processes (AOPs). We analyze the experimentally measured transient spectra near neutral pH using quantum mechanical-based time-dependent density functional theory (TD-DFT). The ab initio DFT method was first used to find and optimize aqueous-phase transition state structures, then the TD-DFT was used to analyze molecular orbitals (MOs) of the optimized transition state structures to reveal the functional groups that are responsible for the individual absorption peaks. The initial addition of HO˙ to the benzene ring produced hydroxycyclohexadienyl radicals. Then, HO-adducts are generated from dimerization or disproportionation of hydroxycyclohexadienyl radicals and represent their transient spectral peaks at approximately 350 nm and 250 nm. As reaction proceeds, the HO-adducts are decreased depending on the subsequent reactions. These investigations into the experimental transient spectra coupled with the theoretical analysis using the TD-DFT enable us to visualize an initial transformation of organic compounds induced by the aqueous phase HO˙ oxidation. Moreover, the experimental reaction rate constants and the theoretically calculated aqueous phase free energies of activation provide quantitative insights into the addition of HO˙ to multiple carboxylated and hydroxylated benzene compounds.

The Influences of Holmium on Microstructure and Properties of &lt;i&gt;In Situ&lt;/i&gt; Mg&lt;sub&gt;2&lt;/sub&gt;Si/Al Composites

In this study, Mg2Si in in-situ Mg2Si/Al composites were subjected to modification treatment using rare earth element Holmium (Ho). The phase composition and microstructure before and after modification of Mg2Si were also analyzed using X-ray diffraction (XRD) and optical microscope (OM); in addition, its mechanical properties were detected as well. The results showed that moderate addition of rare earth element Ho in in-situ Mg2Si/Al composites presents good modification effects on Mg2Si, the morphology of primary Mg2Si was changed from cross shape before modification to dispersed irregular mass; optimal modification effect was obtained when 0.4% rare earth element Ho was added. Under this condition, the average size of primary Mg2Si was decreased from 74 μm before modification to 16 μm; its mechanical properties were promoted significantly; and its tensile strength increased from 134 MPa before modification to 174.6 MPa, its brinell hardness elevated from 76 HB to 90 HB.

Preparation of Nano BaTiO&lt;sub&gt;3&lt;/sub&gt;-Based Dielectric Ceramics by Different Sintering Methods

Microstructure control in thin-layer multilayer ceramic capacitors (MLCCs) is one of the nowaday challenges for increasing capacitive volumetric efficiency and high voltage dielectric properties. In this paper, the ultrafine-grained BaTiO3 dielectric ceramics with uniform grain size distribution were prepared by chemical coating approach. The doping effects of rare-earth element (Ho) on the microstructures and dielectric properties of the ceramics were investigated. The addition of Ho in nano BaTiO3-based ceramics was found to improve the temperature coefficient of capacitance (TCC) performance, which could be attributed to a significant reduction in the grain size. Moreover, the effects of two-step sintering (TSS) method on the microstructures and dielectric properties, compared with conventional sintering (CS) method, were also discussed. The dielectric constant of ceramics sintered by the TSS method was higher than that of ceramics prepared by CS method. The results reveal that the adoption of TSS method could control the grain size and suppress the abnormal grain growth more effectively, which improves the TCC characteristics.

Favorable Effect of Ho Addition on the Microstructure and Magnetostriction of Textured Tb&lt;sub&gt;0.3&lt;/sub&gt;Dy&lt;sub&gt;0.7&lt;/sub&gt;Fe&lt;sub&gt;1.95&lt;/sub&gt;

This paper reports the effect of Ho on the microstructure, texture and magnetostrictive properties of Tb0.3Dy0.7-xHoxFe1.95 (with x = 0, 0.05, 0.1, 0.15 and 0.2) alloys. The alloys were vacuum induction melted and directionally solidified by modified Bridgman technique. Ho addition has been found to improve the magnetostriction at lower concentration due to absence of deleterious pro-peritectic (Tb,Dy)Fe3 phase. The static strain co-efficient is found to be better in Ho added alloys and the prevalence of strong and texture is attributed to be the reason.

Microstructure, precipitates and compressive properties of various holmium doped NiAl/Cr(Mo, Hf) eutectic alloys

The microstructure and mechanical properties of NiAl–28Cr–6Mo–0.2Hf eutectic alloys with various holmium additions have been investigated by using of SEM, TEM and compression test. The results reveal that minor Ho addition could optimize the microstructure by refining the lamella inside of eutectic cell and controlling the coarsening of intercellular region. However the minor Ho addition results in the Ni 2Al 3Ho phase, which has hexagonal crystal structure and an orientation relationship with NiAl phase of [ 1 2 0 ] Ni 2 Al 3 Ho / / [ 1 1 1 ] NiAl and ( 0 0 2 ¯ ) Ni 2 Al 3 Ho / / ( 1 1 ¯ 0 ) NiAl . Moreover the Ni 17Ho 2 phase is found in the Ni 2Al 3Ho phase, which has twin crystal inside and an orientation relationship with Ni 2Al 3Ho phase of [ 1 2 3 ] Al 17 Ho 2 / / [ 1 2 4 ] Ni 2 Al 3 Ho and ( 1 1 1 ¯ ) Al 17 Ho 2 / / ( 2 ¯ 1 0 ) Ni 2 Al 3 Ho . In addition, the Ho addition promotes the precipitation of Ni 2AlHf phase. More Ho addition coarsens the Cr(Mo) phases along the intercellular and results in more strengthening precipitates inside eutectic cell. When the Ho addition comes to 0.5 at.%, the alloy almost loses the cellular eutectic characteristic and exhibits a microstructure with coarse NiAl, massive Cr(Mo) and Ni 2Al 3Ho phases. The microstructure optimizations improve the mechanical properties of the alloy significantly, especially the alloy with 0.1 at.% Ho content.

Effects of Ho on the microstructure and mechanical properties of Mg-Zn-Ho-Zr magnesium alloys

The microstructure and mechanical properties of Mg-Zn-Ho-Zr alloys have been investigated in detail. The grain size of the as-cast Mg-Zn-Ho-Zr alloy was greatly decreased by the addition of Ho, and the grain growth during solution treatment was suppressed by Mg-Zn-Ho phases formed at grain boundaries. These thermally stable Mg-Zn-Ho phases could not completely dissolve into the matrix during solution treatment, and the strengthening effect of solution-plus-ageing treatment weakened. The addition of Ho can greatly enhance the high-temperature elongation of the Mg-Zn-Ho-Zr alloy, but the increase of high-temperature tensile strength was just a little.

Linear Free Energy Relationships between Aqueous phase Hydroxyl Radical Reaction Rate Constants and Free Energy of Activation

The hydroxyl radical (HO(•)) is a strong oxidant that reacts with electron-rich sites on organic compounds and initiates complex radical chain reactions in aqueous phase advanced oxidation processes (AOPs). Computer based kinetic modeling requires a reaction pathway generator and predictions of associated reaction rate constants. Previously, we reported a reaction pathway generator that can enumerate the most important elementary reactions for aliphatic compounds. For the reaction rate constant predictor, we develop linear free energy relationships (LFERs) between aqueous phase literature-reported HO(•) reaction rate constants and theoretically calculated free energies of activation for H-atom abstraction from a C-H bond and HO(•) addition to alkenes. The theoretical method uses ab initio quantum mechanical calculations, Gaussian 1-3, for gas phase reactions and a solvation method, COSMO-RS theory, to estimate the impact of water. Theoretically calculated free energies of activation are found to be within approximately ±3 kcal/mol of experimental values. Considering errors that arise from quantum mechanical calculations and experiments, this should be within the acceptable errors. The established LFERs are used to predict the HO(•) reaction rate constants within a factor of 5 from the experimental values. This approach may be applied to other reaction mechanisms to establish a library of rate constant predictions for kinetic modeling of AOPs.

Oxidative Stress Induces the Formation of D‐Aspartyl Residues in the Elastin Mimic Peptides

Racemization of aspartyl (Asp) residues in peptides and proteins has been considered to be a nonenzymatic chemical reaction which occurs via succinimide formation. However, it has not been known yet what conditions in living body accelerate the inversion of the L- to the D-form. Here, we examined the effect of ultraviolet (UV) exposure or oxidative stress on the formation of D-Asp residues in the elastin mimic peptides with or without heat treatment. As a result, UV exposure did not affect the D-Asp formation in peptides. On the other hand, the amount of D-Asp in heat-treated peptide solution at the same time as addition of HO(.) radical, H(2)O(2), and lipid peroxide was significantly increased. These results indicate that the inversion rate to D-form of Asp residues in skin elastin is accelerated by generation of reactive oxygen species (ROS), and that oxidative stress might be closely related to D-Asp formation in aging proteins.

HO • radicals induce an unexpected high proportion of tandem base lesions refractory to repair by DNA glycosylases

Reaction of HO(*) radicals with double-stranded calf thymus DNA produces high levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and, to a minor extent, 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxodAdo). Formation of the hydroxylated purine lesions is explained by addition of HO(*) to the C8 position of the purine moiety. It has been reported that tandem lesions containing a formylamine residue neighboring 8-oxodGuo could be produced through addition of a transiently generated pyrimidine peroxyl radical onto the C8 of an adjacent purine base. Formation of such tandem lesions accounted for approximately 10% of the total 8-oxodGuo. In the present work we show that addition of HO(*) onto the C8 of purine accounts for only approximately 5% of the generated 8-oxodGuo. About 50% of the 8-hydroxylated purine lesions, including 8-oxodGuo and 8-oxodAdo, are involved in tandem damage and are produced by peroxyl addition onto the C8 of a vicinal purine base. In addition, the remaining 45% of the 8-oxodGuo are produced by an electron transfer reaction, providing an explanation for the higher yield of formation of 8-oxodGuo compared to 8-oxodAdo. Interestingly, we show that >40% of the 8-oxodGuo involved in tandem lesions is refractory to excision by DNA glycosylases. Altogether our results demonstrate that, subsequently to a single oxidation event, peroxidation reactions significantly increase the yield of formation of hydroxylated purine modifications, generating a high proportion of tandem lesions partly refractory to base excision repair.

Microstructure and mechanical properties of NiAl–Cr(Mo)–Hf/Ho near-eutectic alloy prepared by suction casting

Abstract The microstructure and mechanical properties of 0.15 at.% Hf and 0.2 at.% Ho doped Ni-33Al-28Cr-6Mo near-eutectic alloys prepared by conventional casting and suction casting were investigated. The results reveal that the addition of Hf and Ho results in the formation of Ni2AlHf and Ni2Al3Ho phases, respectively, along the NiAl and Cr(Mo) phase interface in intercellular regions. Compared with the conventional-cast alloy, the microstructure of suction-cast alloy is well optimized, characterized by the thin interlamellar spacing, high proportion of eutectic cell area and fine homogeneously distributed Ni2AlHf and Ni2Al3Ho phases. Furthermore, the room temperature mechanical properties of the suction-cast alloy improve significantly, which can be attributed to fine microstructure, uniform distribution of the Ni2AlHf and Ni2Al3Ho phases and solid solubility extension.