Effects of added kaolinite on the strength and porosity of freeze-cast kaolinite–silica nanocomposites

Abstract

This paper examines the effects of kaolinite on the mechanical strength and porosity of freeze-cast kaolinite-silica composites. Measurement of the equibiaxial flexural strength shows that, after sintering at 1250°C for 1 h, a ceramic containing 10 vol% kaolinite and 8 vol% silica has a strength that is 52 times greater than a ceramic containing only 18 vol% silica and 2.5 times greater than one containing only 18 vol% kaolinite, yet while also being 69 % porous (i.e., the porosity after sintering). It is proposed that this greater strength arises from three mechanisms. First, the kaolinite and silica particles bond together to form a connected network in which the much larger kaolinite platelets distribute the applied stress over a larger region of the sample (this increased strength is even seen in the freeze-cast green bodies before sintering). Second, X-ray diffraction measurements indicate that upon sintering at 1250°C, new phases are formed when both silica and kaolinite are present, which we postulate contribute greatly to the strength of the composite. Third, the pore walls in samples containing both kaolinite and silica are much more continuous and unbroken than in samples containing only kaolinite.

Active nano/microbilayer hemostatic agents for diabetic rat bleeding model

“…Furthermore, Li et al examined the effects of kaolinite on the mechanical strength and porosity of freeze‐cast kaolinite‐silica composites. As a result, it was observed that the samples containing kaolinite and silica are stronger compared to the individual performances . Additionally, Chen et al prepared a new polymer/kaolinite nanocomposite based on polyurethane‐imide foams in their study, and the results showed that the addition of kaolinite to the structure significantly improved the mechanical properties …”

“…As a result, it was observed that the samples containing kaolinite and silica are stronger compared to the individual performances. 28 Additionally, Chen et al prepared a new polymer/kaolinite nanocomposite based on polyurethane-imide foams in their study, and the results showed that the addition of kaolinite to the structure significantly improved the mechanical properties. 29 The compressive strength and deformation percent of bilayer hemostatic dressings in wet form are presented in Figure 4 25 According to the compression test results, the compression modulus of BC/CTS was found as 25 6 0.37 kPa, whereas the compression modulus of wet BC/CTS scaffolds material (50:50 wt%) lyophilizated at 808C was 5.49 6 0.8 kPa in the aforementioned study.…”

Effects of Rod‐like Particles on the Microstructure and Strength of Porous Silica Nanoparticle Composites

“…(2) Increased Strength from Rods In previous work, it was found that adding relatively large kaolinite platelets to a silica nanoparticle suspension led to a significant increase in the mechanical strength of both the freeze-cast and sintered composites created from the suspension. 24,36,37 The suggested reason for this increase was that the platelets were capable of distributing any applied stress over a larger portion of the sample, which would reduce the likelihood of stress being concentrated at any one point.…”

Positioning growth of scalable silica nanorods on the interior and exterior surfaces of porous composites

“…1. 34 Since the pores replicated the morphologies of ice crystals that formed during the freezing process, three-dimensional porous structures were produced with typical pore dimensions of tens of microns. 31,32 In this present study, the kaolinite-to-silica ratio in the composite was maintained at 5 : 4 by volume, and the porosity of the resulting scaffold was previously determined to be $70%.…”