A study on crystallization of amorphous nano silica particles by mechanical activation at the presence of pure aluminum

Borouni, Mansour; Niroumand, Behzad; Maleki, Ali

doi:10.1016/j.jssc.2018.04.014

Cited by 27 publications

(4 citation statements)

References 19 publications

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“…The XRD for each sample revealed a similar pattern and broad diffused peaks with maximum intensity at a 2θ angle of 22°, indicating that the amorphous nature of the silica was observed. This peak position angle is mainly due to the occurrence of disordered cristobalite [ 31 ]. At 600 °C incineration temperature, unleached and leached samples were proved to be in amorphous form, which indicated that HCl treatment on RH did not modify the silica structure transformation from amorphous to crystalline.…”

Section: Resultsmentioning

confidence: 99%

Effect of Different Pre-Treatment on the Microstructure and Intumescent Properties of Rice Husk Ash-Based Geopolymer Hybrid Coating

et al. 2022

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Despite the growing popularity of rice husk ash (RHA) in various applications, limited research has been devoted to identify the influence of silica content in RHA on the intumescent properties. The present work aims to introduce a novel and economical geopolymer hybrid fire retardant coating by utilizing the use of RHA. The silica from Rice husk (RH) was extracted using distilled water and hydrochloric acid as leaching agents and subjected to pyrolysis treatment. X-ray fluorescence (XRF) analysis indicated that RH that underwent HCl pre-treatment at 600 °C for one hour produced a high purity amorphous silica content of 93.92%. XRD measurements revealed that HCl pretreatment increased the crystallization temperature of RHA to 1000 °C and retained the amorphous state of silica for 2 h. In a fire resistance test, temperature at the equilibrium and time taken to reach 200 °C for sample S3 (93.92% wt. silica) showed 5.83% and 3.48% improvement compared to sample S1 (87.49% wt. silica). The microstructure analysis showed that sample S1 possessed bigger pores on the coating surface while an increment in silica content in sample S3 produced a dense foam structure. Results from a fire resistance test were supported by the Energy dispersive X-ray (EDX) analysis of the sample. The oxygen-to-carbon ratio of S1 and S3 coating samples were 1.695 and 1.622 respectively, which indicated that lower oxygen–to-carbon ratio in sample S3 coating resulted in better anti-oxidant properties. Interestingly, the increment of SiO2 content in RHA efficiently improved the compactness of the char layer, which resulted in a relatively higher fire-retardant efficiency. RHA proved to be a promising environmentally friendly strategy to replace halogenated fire retardant materials.

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Section: Resultsmentioning

confidence: 99%

Effect of Different Pre-Treatment on the Microstructure and Intumescent Properties of Rice Husk Ash-Based Geopolymer Hybrid Coating

et al. 2022

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“…2c shows around 17.5% mass loss between 50 and 400 °C, which might be associated with the adsorbed water release in the colloidal silica particles. In the DTA curve, an endothermic peak is observed at around 150 °C because of the adsorbed water elimination, and an exothermic peak is seen at around 850 °C, associated with the amorphous silica crystallization since this transformation needs thermal energy to break the amorphous silica bonds, reorder them and form a crystalline network [29]. Nakata et al [30] reported the appearance of an exothermic peak at around 990 °C that corresponded to the crystallization of the amorphous silica from rice hulls into cristobalite.…”

Section: Resultsmentioning

confidence: 99%

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

Olcoski

Chinelatto

2021

Cerâmica

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Mullite is a refractory material with singular properties, although high temperatures and long sintering times are required to obtain this material with good densification. In this study, aluminum hydroxide and colloidal silica were used to produce mullite through reactive sintering and MgO was employed as a sintering additive. The compositions were prepared with different amounts of MgO and sintered at 1350, 1450, and 1550 °C, and then analyzed using X-ray diffraction, scanning electron microscopy, and measurements of apparent porosity (AP) and flexural strength. The results showed that the raw materials used allowed the mullite formation at relatively low temperatures (1350 °C), regardless of the amount of MgO added but with the increase in MgO content, a spinel phase appeared, resulting in a fraction of residual α-alumina. The MgO addition lowered the densification temperature at around 50 °C. Furthermore, the higher the sintering temperature and the MgO content, the larger and more anisotropic the mullite grains were. At sintering temperatures above 1450 °C, AP was reduced to approximately 10%. The MgO addition and increase in sintering temperature improved the flexural strength of mullite materials.

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“…It should be noted that amorphous silica could be etched, in contrast to crystalline silica (cristobalite), which resisted any etching procedure. This may be due to the random arrangement of atoms in the amorphous structure, which does not require as much energy to react with acids [25].…”

Section: Discussionmentioning

confidence: 99%

The Effect of Surface Treatments of Presintered Zirconia on Sintered Surfaces

Abdelraouf,

Tsujimoto,

Hamdy

et al. 2023

J. Compos. Sci.

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Zirconia is a high-strength ceramic material that expands the design and application possibilities for all-ceramic restorations and dental implants. To enhance the bonding of zirconia restorations to tooth substrates and the osseointegration of implants with the surrounding bone, the surface should be modified by surface treatment. Unfortunately, the effective treatment of sintered zirconia is difficult. Surface treatment for presintered zirconia may be less difficult; thus, the effectiveness of surface treatments of presintered zirconia was investigated herein. The zirconia specimens were randomly divided into eight groups: (1) control (untreated) and seven treated groups subjected to surface treatment (s.ttt.) in the presintered stage, followed by sintering: (2) s.ttt. 1: hydrofluoric acid (HF) gel left during sintering; (3) s.ttt. 2: HF gel washed before sintering; (4) s.ttt. 3: coated with nanosilica; (5) s.ttt. 4: coated with microsilica; (6) s.ttt. 5: coat followed by airborne-particle abrasion; (7) s.ttt. 6: coat followed by partial etching; and (8) s.ttt. 7: coat followed by total etching. The surface microstructure was examined using scanning electron microscopy (SEM) and the crystalline phase was identified using X-ray diffraction (XRD). Biaxial flexural strength was also tested. The results of SEM for s.ttt. 1 and 2 displayed irregular surfaces. S.ttt. 3 showed deeper penetration of the nanosilica into zirconia (27 µm) compared to the microsilica used in s.ttt. 4. S.ttt. 5 and 6 showed irregular coats. S.ttt. 7 showed intergranular pores. The XRD of s.ttt. 1, 2, and 3 revealed tetragonal zirconia as the control group. S.ttt. 4 and 5 showed cristobalite silica and tetragonal zirconia. S.ttt. 6 and 7 contained amorphous silica and tetragonal zirconia, while s.ttt. 7 also showed monoclinic zirconia. The highest flexural strength was for s.ttt. 4 (982.4 MPa), while the lowest was for s.ttt. 7 (386.6 MPa). There was no significant difference in the flexural strength between the control, s.ttt. 1, and 2 (846.3 MPa, 830.0 MPa, and 835 MPa, respectively). Compared to the control group, s.ttt. 3 had a lower flexural strength (634.1 MPa), while s.ttt. 5 and 6 had higher flexural strengths (863.1 MPa and 872.2 MPa, respectively). It can be concluded that the surface modification of presintered zirconia is a promising method as long as no phase transformation or deep subsurface penetration occurs.

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A study on crystallization of amorphous nano silica particles by mechanical activation at the presence of pure aluminum

Cited by 27 publications

References 19 publications

Effect of Different Pre-Treatment on the Microstructure and Intumescent Properties of Rice Husk Ash-Based Geopolymer Hybrid Coating

Effect of Different Pre-Treatment on the Microstructure and Intumescent Properties of Rice Husk Ash-Based Geopolymer Hybrid Coating

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

The Effect of Surface Treatments of Presintered Zirconia on Sintered Surfaces

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