Effect Of Cr2O3 Research Articles

Effect of Cr2O3 on the break temperature and crystallization behavior of Cr-containing molten titanium slag

In the current study, the effect of Cr2O3 on the break temperature and crystallization behavior of Cr-containing molten titanium slag was investigated. The type, composition, and morphology of crystallized phase were analyzed by FactSage, X-ray diffraction (XRD), and scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). It was found that the break temperature (TBr) of Cr-containing molten titanium slag tended to increase with the increase of Cr2O3 content. When the Cr2O3 content was 4 wt%, the TBr was 1470 °C. With the increase of Cr2O3 content, the Ti-containing phase began to appear at the temperature above the TBr. Moreover, the main crystallized phase that existed at the temperature below the TBr transformed from only anosovite to both anosovite and spinel, indicating that Cr2O3 promoted the precipitation of spinel. The rapid increase in viscosity was mainly determined by the precipitation of anosovite in the slag without Cr2O3. When the Cr2O3 content was 2 wt%, the increased precipitation amount of Ti-containing phase caused the abrupt change in viscosity. As the Cr2O3 content further increased to 4 wt%, the precipitation amounts of anosovite and spinel significant increased, which resulted in the sudden increase in viscosity. This study could provide theoretical support for the comprehensive utilization of Cr-containing molten titanium slag and sustainable development of titanium and chromium resources.

Effect of Cr2O3 on the clinkerization and carbonation properties of γ-C2S

Dicalcium silicate (C2S) has strong CO2 reactivity and is a possible low-carbon binder. In order to facilitate its industrial production, it is important to evaluate the potential influence of minor elements in the raw material on the performance of γ-C2S. In this work, the effect of Cr2O3, a common impurity in solid wastes, on the structure and carbonation properties of C2S was investigated. The results show that doping Cr2O3 can stabilize the β-C2S crystalline form at low temperatures, inhibit the transition from β-C2S to γ-C2S due to the substitution of Si by Cr to change the silica-oxygen tetrahedra, thereby reduce the degree of carbonation of clinkers. During calcination at 1350 °C, Cr2O3 was partially evaporated. The leaching rate of Cr from carbonized clinker decreased significantly and the solidification rate of Cr in carbonized clinker was greater than 89.9 %. This work lays a solid foundation for the low-temperature preparation of β-C2S from industrial solid wastes.

Effects of Cr2O3 on Metallurgical Properties of High Chromium Vanadium-Titanium Magnetite Flux Pellets

Effects of Cr2O3 on Metallurgical Properties of High Chromium Vanadium-Titanium Magnetite Flux Pellets

Effect of Cr2O3 on properties of CaO–SiO2–FetO–MgO system and dissolution behavior of lime

Effect of Cr2O3 on properties of CaO–SiO2–FetO–MgO system and dissolution behavior of lime

Effect of Cr2O3 Content on the Viscosity and Crystallization Properties of Continuous Casting Mold Slag

Herein, the effect of Cr2O3 on the crystallization and flow behavior of CaO–SiO2–Al2O3–Na2O–CaF2 continuous casting mold slags is investigated. The viscosity in the slag at 1200–1500 °C is measured by the rotating cylinder method and a quantitative relationship between the viscosity and the Raman structure Q3/Q2 is constructed. The time–temperature–transformation and continuous cooling transformation diagrams for various slags are obtained using a single hot‐thermocouple technique. The results show that with the crystallization temperature decreases, it can be observed that the crystal growth mode gradually changes from 3D spherical and 2D massive to 1D needle‐like. The study finds the transition from network modifier to network forming agent in the slag for Cr2O3 content from 0 to 3 wt%. The Cr2O3 added to 1–2 wt% decreases the viscosity and promotes crystallization. The viscosity increases and the crystallization is inhibited when the content of Cr2O3 increases to 3 wt%. Meanwhile, when Cr2O3 is added to 3 wt%, the Cr2O3 crystalline phase precipitates except for the main crystalline phase 2CaO·SiO2.

Effect of Cr2O3 on the viscosity and structure of slag (or glass) of CaO-MgO-Al2O3-SiO2 system

Effect of Cr2O3 on the viscosity and structure of slag (or glass) of CaO-MgO-Al2O3-SiO2 system

Effect of Cr2O3 on the microstructure and wear resistance of coatings prepared from Cr2O3-SiC-Al composite powders

Introducing the in-situ reaction synthesis into the thermal spraying process, the content of each phase in the raw material will directly affect the phase and microstructure of the coating obtained by spraying. Therefore, composite powders with different Cr2O3–SiC–Al mass ratios were used as coating materials, and composite coatings were prepared using an atmospheric plasma spraying process. By analyzing the coatings' phase composition, microstructure, wear resistance, and other properties, the effect of the variation of Cr2O3 content in the composite powders on the performance of the coating was investigated. The results showed that with the decrease of Cr2O3 content in the composite powder, the coatings’ compactness, microstructure uniformity, and wear resistance decreased. The coating prepared by Cr2O3–SiC–Al composite powder with a mass ratio of 65:12:23 had good compactness and microstructure uniformity, the microhardness and toughness were also the best among the three groups of coatings, and it presented higher wear resistance.

Retraction of: An experimental investigation into the effects of Cr2O3 and ZnO2 nanoparticles on the mechanical properties and durability of self-compacting mortar

Article Retraction of: An experimental investigation into the effects of Cr2O3 and ZnO2 nanoparticles on the mechanical properties and durability of self-compacting mortar was published on March 7, 2023 in the journal International Journal of Materials Research (volume 0, issue 0).

Effect of Cr2O3 on Crystallization of Diopside Glass–Ceramics

CaO–MgO–Al2O3–SiO2–Cr2O3 diopside glass–ceramics were prepared from blast furnace slag, low-carbon ferrochromium alloy slag, and quartz sand by the melting method. The prepared glass–ceramics were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD),scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The effect of Cr2O3, a nucleating agent, in the crystallization process of diopside glass–ceramics was studied. The results show that chromium is present in glass–ceramics as Cr3+ and Cr6+, and Cr3+ accounts for more than 80% of the chromium contents. When the mass percentage of Cr2O3 in glass–ceramics is less than 1.60%, a small amount of diopside phase is precipitated during heat treatment, and Cr3+ is dispersed in the diopside phase. When the mass percentage of Cr2O3 reaches or exceeds 1.60%, Cr3+ preferentially forms the magnesia chrome spinel phase, which further induces the in situ growth of diopside. The leaching concentration of chromium meets the Chinese national standard, indicating that diopside glass–ceramics can effectively solidify the heavy metal chromium, and this fact makes the application of glass–ceramics feasible.

Effect of Cr2O3 on Physicochemical Properties of CaO-SiO2-FetO Slags during BOF Smelting Process of Chromium-Bearing Iron

The productivity of basic-oxygen-furnace (BOF) smelting process is directly affected by the slag-forming speed during the initial stage of converter. Therefore, it is essential to study the effect of different Cr2O3 content on the physicochemical properties of the primary slag in the smelting process of chromium-bearing semi-steel. In this work, Factsage8.1 software, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and a high-temperature melting point tester were used to study the effects of different Cr2O3 content on the melting temperature, solidification behavior, mineral composition, and other physicochemical properties of the CaO-SiO2-FetO system. The results showed that the melting temperature of slag samples increased from 1223 °C to 1354 °C as Cr2O3 increased from 0 wt% to 9.09 wt%. With the increase of Cr2O3, the content of CaFeSi2O6 decreased. Moreover, due to the addition of Cr2O3, the chromium-bearing spinel solid solution (Fe(Fe,Cr)2O4) began to form in the slag. Furthermore, Cr2O3 promoted the increase in the volume of free solid particles in the slag, resulting in an increase in slag viscosity. All in all, the increase of Cr2O3 content in the CaO-SiO2-FetO system will adversely affect the semi-steel steelmaking process.

Synthesis of WC-0.67wt.%Cr3C2 nanopowders by a one-step reduction-carbonization method and their characterization

Nano WC powders containing uniformly dispersed grain growth inhibitors are high-quality raw materials suitable for the fabrication of ultrafine grade WC-Co alloys. In this study, nano WC and WC-0.67wt.%Cr3C2 powders were prepared by a one-step reduction-carbonization method from WO3 and WO3-0.72wt.%Cr2O3 powders prepared via a spray drying-calcination process. The effect of Cr2O3 on the phase composition and microstructural evolution during the one-step reduction-carbonization of WO3 was investigated through X-ray diffraction, transmission electron microscopy, and scanning electron microscopy studies. When the reaction temperature was lower than 800 °C, WO2 and nano W phases were formed because Cr2O3 dispersed uniformly around the WO3 particles effectively hindered their reduction and inhibited the growth of W. With a further increase in the temperature to greater than 800 °C, Cr2O3 was gradually converted into Cr3C2 distributed on the surface of WC, leading to the formation of smaller WC grains. Additionally, Cr2O3 promoted the carbonation reaction due to the existent of smaller W with higher activity. Finally, the nano WC-0.67wt.%Cr3C2 powder with a narrow grain size distribution and high specific surface area of 4.58 m2/g−1 was obtained under a hydrogen gas flow rate of 50 L/min at 1100 °C in 0.5 h.

A new insight into the restriction of Cr(VI) removal performance of activated carbon under neutral pH condition

Abstract Activated carbon has been widely used to remove hazardous Cr(VI); however, the impact of Cr2O3 precipitate on gradually declining removal ability as pH increases has received little attention. Herein, to investigate the effect of Cr2O3, SEM-EDX (scanning electron microscope-energy dispersive X-ray analysis) coupling elements mapping of chromium-loaded powdered activated carbon (PAC) revealed that a chromium layer was formed on the PAC exterior after being treated with Cr(VI) at pH 7. XPS (X-ray photoelectron spectroscopy) study confirmed that 69.93% and 39.91% Cr2O3 precipitated on the PAC surface at pH 7 and pH 3, respectively, corresponding to 17.77 mg/g and 20 mg/g removal capacity. Exhausted PAC had a removal efficiency of 92.43% after Cr2O3 being washed by H2SO4 solution, which was much higher than the removal efficiency of 51.27 % after NaOH washing. This further verified that the intrinsically developed Cr2O3 precipitate on PAC under neutral conditions limited the durability of PAC as an adsorbent. Consecutive elution assessments confirmed that adsorption and reduction ability both declined as pH increased. Raman spectroscopy and C 1s spectra of materials demonstrated two distinct Cr(VI) removal mechanisms under pH 3 and pH 7. In conclusion, the exhausted AC after Cr(VI) adsorption can be rejuvenated after the surface coated Cr2O3 is washed by the acid solution, which can expand the longevity of AC and recover Cr(III).

Effect of Cr2O3 on structural and magnetic properties of SiO2–B2O3–Fe2O3–Al2O3–Na2O glass–ceramics

SiO2–B2O3–Fe2O3 magnetic glass–ceramics were prepared by conventional melt quench using a heat treatment method. The effects of Cr2O3 on the phase structure and magnetic properties of the ferrimagnetic glass–ceramics were examined by differential scanning calorimetry, photothermal measurement system, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The magnetic phase of the obtained glass–ceramics was Fe3O4, and the magnetic crystal size and amount of second phase (hematite, Fe2O3) increased with increasing amount of Cr2O3 added. More importantly, the coercivity and saturation magnetization of the sample without Cr2O3 were higher than the samples containing 1–4 wt.% Cr2O3, indicating the spontaneous crystallization capacity of magnetite.

Effect of Cr2O3 on the crystallization, structure, and properties of Ti-bearing blast furnace slag-based glass ceramics

ABSTRACT The effects of Cr2O3 on the crystallization, structure, and properties of Ti-bearing blast furnace slag-based glass ceramics were investigated. The results show that the transition temperature and crystallization temperature decreased with introduction of Cr2O3 as a while. Specifically, the crystallization temperature first decreased, then increased with the increase Cr2O3 concentration from 0.2 wt% to 0.8 wt%, and finally decreased with further increased in Cr2O3 concentration. The crystal phases were identified as anorthite, diopside, and akermanite. As the content of Cr2O3 increased to 0.8 wt%, the dendrites gradually decreased and the granular crystals gradually increased. When the Cr2O3 concentration further increased, the number of granular crystals gradually decreased and the dendrites gradually accumulated. With the increase of Cr2O3 from 0.2 wt% to 0.8 wt%, the structure of the investigated glass gradually depolymerized, while the opposite trend was presented with further increased in Cr2O3 content. With increasing Cr2O3 content from 0.2 wt% to 2 wt%, the flexural strength values and Vickers hardness values of the glass ceramics first increased and then decreased, and the maximum values of flexural strength and Vickers hardness were obtained as 94.371MPa and 974.43MPa, respectively. The prepared Ti-bearing blast furnace slag-based glass ceramics showed good acid and alkali resistance.

Effects of addition of chromium and/or nickel oxides on the electrical characteristics of yttrium oxide-doped high-voltage zinc oxide varistors

The effects of Cr2O3 and/or NiO addition to Y2O3-doped Bi-based high-voltage ZnO varistors were investigated, including crystal structure and interface states analysis. Incorporating 0.35 mol% Cr2O3 in Y-doped varistors increased the single-grain varistor voltage VNNGB from 2.6 to 3.3 V and decreased the leakage current density by a factor of 40, from 2 × 10−5 to 5 × 10-7 A/cm2. The nonlinearity index α before and after degradation increased from 21 to 35. 1.2 mol% NiO increased VNNGB to 4 V. Highest varistor voltage was 1500 V for 0.3 mol% NiO. Resistance to electrical degradation improved with optimal amounts of Cr or Ni by reduction of grain boundary oxygen vacancies. Though the donor density was changed prominently by addition of Cr and/or Ni, changes in the barrier height were suppressed by the change in interface state density. As a result, the change in VNNGB was related mainly to the empty interface state under no bias.

The Effect of Cr2O3+Al Addition on the Microstructure of Combustion Electrode Joint

During manual self propagating welding, there are segregation phenomena of iron rich phase and copper rich phase. Cr element can restrain the segregation phenomenon of iron rich phase and copper rich phase. Cr is a strong ferrite element. When the amount of Cr2O3 + Al in the flux is less than 3wt%, with the increase of &2O3 + Al content, the microstructure of the weld alloy tends to be homogenized and the mechanical properties of the welded joint improve; when the amount of Cr2O3 + Al in the flux is more than 4wt%, Cr and C form Carbides are easy to produce microcracks in the fusion zone and reduce the mechanical properties of the joint. The best addition of Cr2O3 + Al in the flux is 3wt% ~ 4wt%.

Effect of Cr2O3 on the Microstructure and Oxidation Resistance of Enamel Coating with TC4 Titanium Alloy

By adding 0 % to 50 % Cr2O3 ceramic particles, the enamel composite coating is produced on the surface of TC4 titanium alloys. The detection analysis indicates that with the increase of the amount of Cr2O3 particles added, the density of enamel coating increases as well, and the amount of the pore holes decreases at the same time, but the enamel coating becomes porous with more than 30 % of the amount of Cr2O3 particles added. The main crystalline phases of enamel coating are NaAlSi3O8 and Ca2SiO4, whereas the Cr2O3 ceramic particles added are mainly presented as an independent phase, and part of the particles are in the form of Ca5Cr3O12 phase after the reaction. The enamel coating with 30 % Cr2O3 ceramic particles added has the best high-temperature oxidation resistance, mainly because the main crystalline phase of NaAlSi3O8 is changed into Na2Si2O5 during the high-temperature oxidation, which is beneficial to the self-healing of the coating.

Effects of Cr2O3 on the Superconducting Properties of DyBa2Cu3-xCrxO7-δ (x = 0 to 0.70)

The effects of Cr2O3 substitution on DyBa2Cu3-xCrxO7-δ (x = 0 to 0.70) superconductor were investigated. The samples were characterized by using dc electrical resistance measurements, powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) observations. XRD patterns showed impurity peaks for x ≥ 0.2 samples SEM micrographs showed no change in the grain size for x ≤ 0.4. However, partial melting and increase in grain size was observed for higher Cr content (x > 0.4). The orthorhombicity, e $$ =\frac{b-a}{b+a} $$ of the unit cell initially increased with Cr substitution. The resistance-temperature curves showed metallic normal state behavior for x = 0 and semiconductor-like behavior for all Cr-added samples. A pronounced suppression of the transition temperature was observed as soon as Cr was substituted for 0 < x ≤ 0.2 followed by a lower suppression for 0.2 < x ≤ 0.7. Two distinct regions of superconductivity suppression were observed, and the different suppression mechanisms acting in those regions are discussed in this paper.

Effect of Cr2O3 on the microstructure and tribological performance of sprayed Fe-based coating on cylinder liner

Improving the vehicle efficiency by weight reduction and friction loss has become the severe challenge to machinery manufacturers. Generally, replacing heavy cast iron engine component by aluminum alloys played a key role in reducing fuel consumption and pollutants emission, but the durability in poor mechanical properties of aluminum alloys restricted its application in severe conditions of engine cylinder. In order to improve the tribological properties of aluminum cylinder liner, Cr2O3-added Fe-based coating was prepared by plasma spraying technology, and the effect of Cr2O3 on the microstructure and tribological performance of sprayed coating was investigated in this study. All the Cr2O3-added coatings improved mechanical properties significantly, such as hardness and wear resistance compared to that of Fe-based alloy. However, appropriate content of Cr2O3 was beneficial to wear resistant but the excessive Cr2O3 deteriorated the wear resistance under dry sliding condition. The degradation was likely generated by the embrittlement of the Cr2O3 reinforcements, weaker interface of Cr2O3/matrix, and the inherent lamellar structure of sprayed coating. As a result, Fe-based coating with 30 wt.% Cr2O3 provided excellent mechanical properties and can be substitute for the application in aluminum alloy cylinder liner.

Effect of Cr2O3 on the structural, optical and dielectric studies of LiF-SrO-B2O3 glasses

The melt quench technique was involved in synthesizing the glass system LiF-SrO-B2O3 alloyed with Cr2O3 in the range of 0 to 0.25 mol%. The aperoidic nature of these glasses was affirmed by the X-ray diffraction (XRD). These glasses were analyzed by contemplating the dielectric characteristics (a.c. conductivity, σac, dielectric constant, ε’, and dielectric loss, tanδ etc.,), spectroscopic properties such as electron spin resonance (ESR) optical absorption and Fourier transform infrared (FTIR) analysis. The optical absorption spectra evinced two bands which are features of Cr3+ ions in the octahedral domain. Using absorption edges, Urbach energies and optical band gap of these samples were estimated. The hike in the Cr3+ ions in the glass C5 (0.05 mol% of Cr2O3) is confirmed by the proliferation in the ESR signal intensity and optical absorption peak. The maximum a.c. conductivity of glass C5 was due to the dominant presence of Cr3+ ions. FTIR bands revealed that at 0.05 mol% of Cr2O3, BO4 units were converted into BO3 units. It is perceived that the semiconducting nature of glass C5 was the highest among all the prepared glasses.