Monolithic Materials Research Articles

A highly carboxylated sponge-like material: preparation, characterization and protein adsorption

Producing of high-purity protein products using separation materials is critical to the biopharmaceutical industry. Efforts to achieve protein adsorption materials with large adsorption capacity and high processing efficiency have been challenging. Herein, a highly carboxylated sponge-like monolithic adsorbent material was prepared by using SiO2 nanofibers as a rigid support framework, and esterification crosslinking reactants with polyvinyl alcohol (PVA)/polymeric carboxylic acid (polyacrylic acid, PAA) as a functional organic binder, which were modified in situ on the nanofiber framework. The obtained PVA/PAA sponge-like monolithic adsorbent material (PVA/PAA SMAM) exhibits a porous structure and possesses mechanical stability and recoverability of underwater compression. The high porosity provides more sites for carboxyl groups, making PVA/PAA SMAM rich in carboxyl groups. Experiments showed that PVA/PAA SMAM selectively adsorbes proteins with high isoelectric points. Using Cytochrome C (Cyt-C) as the main model protein with a high isoelectric point, the maximum adsorption of Cyt-C by the PVA/PAA SMAM at pH = 9 was 3079.3 mg/g with a rapid equilibration time (40 min), which is clearly superior to the currently reported Metal-organic frame structure (MOF) composites for Cyt-C adsorption. The isothermal adsorption model for the Cyt-C adsorption of the PVA/PAA SMAM material agrees well with the Freundlich adsorption model and the quasi-first kinetic model. Excellent mechanical and chemical structural stability endow the PVA/PAA SMAM material with protein elution capacity and good reusability, and secondary structure of the protein after elution was unchanged. Subsequently, selective adsorption and separation of Cyt-C from porcine heart supernatant was successfully achieved with PVA/PAASMAM material. This work provides new materials with excellent performance for various bio-separation applications.

Novel efficient capture of hexavalent chromium by polyethyleneimine/amyloid fibrils/polyvinyl alcohol aerogel beads: Functional design, applicability, and mechanisms

The harmful effects of hexavalent chromium (Cr(VI)) on the environment and human health have aroused wide public concern. In this study, bulk spherical aerogel beads (PAP) were synthesized from polyethyleneimine (PEI), protein amyloid fibrils (AFL), and polyvinyl alcohol (PVA) through green technology and its removal of Cr(VI) from wastewater was comprehensively studied. The results showed that although the bulk PAP beads (∼ 5 mm) only had an average pore size of 16.88 nm and a BET surface area of 12 m2/g, its maximum adsorption capacity for Cr(VI) reached 121.44 mg/g (at 298 K). Cr(VI) adsorption onto PAP conformed to pseudo-second-order adsorption kinetics and was endothermic. The adsorption of Cr(VI) decreased stepwise with the increase of solution alkalinity (pH = 2: 91.97%; pH = 10: 0.04%). Importantly, PAP showed high selectivity towards Cr(VI) in mixed heavy metal solutions (Cr(VI) > Pb(II) > Ni(II) > Cu(II) > Cd(II)) and good reusability (removal efficiency > 88% after 5 cycles). PAP had excellent anti-interference ability against FA and HCO3- with the overall removal rate exceeding 87% in the presence of 5 – 25 mg/L of these ions. Cations such as Na+, Mg2+, and other heavy metal ions at high concentrations could promote the removal efficiency of Cr(VI). The removal rates of Cr(VI) and Cr(III) by PAP in a tannery wastewater were 34.4% and 59.3%, respectively. Meanwhile, the removal rates of Cr(VI) in a electroplating wastewater and a contaminated soil leachate reached 84.4∼89.7%, showing high practicability. Mechanism studies revealed that electrostatic attraction, hydrogen bonding, reduction, and complexation were the main reactions for Cr(VI) removal by PAP. In general, the study of PAP provides a new insight into using bulk monolith materials for treating Cr(VI) contaminated wastewater.

Effect of Simulated Annual At-home Bleaching on Susceptibility to Staining, Translucency, and Whiteness Variations of Computer-aided Design and Computer-aided Manufacturing Monolithic Materials.

The effect of annual at-home bleaching on the color, translucency, and whiteness properties of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials requires investigation. The aim of the present in vitro study was to evaluate the effect of simulated annual at-home bleaching (consisting of daily applications for 10 hours a day for 14 days), for up to 3 years, on susceptibility to staining (ΔE00), translucency (ΔTP00), and whiteness (ΔWID) variations and on topography of CAD-CAM monolithic materials. Disks from the Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), and IPS e.max CAD (EMAX) were allocated as follows: 1) nonbleached or 2) bleached with 10% carbamide peroxide. After reading the CIE L*a*b* coordinates at baseline (R0), specimens were bleached or not and subsequently immersed for a 1-year simulated period in coffee before the next reading (R1). This process was repeated two more times, resulting in R2 and R3. The ΔE00, ΔTP00, and ΔWID between R1, R2, and R3 in relation to R0 were calculated. The surface topography was analyzed by scanning electron microscopy. In general, bleaching increased the staining susceptibility of all materials when compared to the nonbleached groups and that of the LU, VE, and EMAX over the years. Bleaching decreased the translucency of the VE in all years and over the years. When compared to the nonbleached groups, bleaching decreased the whiteness of the LU and EMAX and increased the whiteness of the EMP, while the VE was not affected. In the LU, the whiteness decreased over the years in both treatments, whereas the other materials were not affected with time. All materials showed progressive topographic changes over the years. The simulated annual at-home bleaching with 10% carbamide peroxide adversely affected the topography and the optical and/or colorimetric properties of the evaluated materials.

Strength Assessment of PET Composite Prosthetic Sockets.

A prosthesis is loaded by forces and torques exerted by its wearer, the amputee, and should withstand instances of peak loads without failure. Traditionally, strong prosthetic sockets were made using a composite with a variety of reinforcing fibres, such as glass, carbon, and Kevlar. Amputees in less-resourced nations can lack access to composite prosthetic sockets due to their unavailability or prohibitive cost. Therefore, this study investigates the feasibility of polyethylene terephthalate (PET) fibre-reinforced composites as a low-cost sustainable composite for producing functional lower-limb prosthetic sockets. Two types of these composites were manufactured using woven and knitted fabric with a vacuum-assisted resin transfer moulding (VARTM) process. For direct comparison purposes, traditional prosthetic-socket materials were also manufactured from laminated composite (glass-fibre-reinforced (GFRP)), monolithic thermoplastic (polypropylene (PP) and high-density polyethylene (HDPE)) were also manufactured. Dog-bone-shaped specimens were cut from flat laminates and monolithic thermoplastic to evaluate their mechanical properties following ASTM standards. The mechanical properties of PET-woven and PET-knitted composites were found to have demonstrated to be considerably superior to those of traditional socket materials, such as PP and HDPE. All the materials were also tested in the socket form using a bespoke test rig reproducing forefoot loading according to the ISO standard 10328. The static structural test of sockets revealed that all met the target load-bearing capacity of 125 kg. Like GFRP, the PETW and PETK sockets demonstrated higher deformation and stiffness resistance than their monolithic counterparts made from PP and HDPE. As a result, it was concluded that the PET-based composite could replace monolithic socket materials in producing durable and affordable prostheses.

Biomimetic porphyrin-modified 3D porous composite material adsorption enhances photocatalytic CO2 reduction and tetracycline oxidative degradation

Facing energy waste caused by carbon emissions and environmental pollution brought by the overuse of antibiotics, this work successfully synthesized a series of biomimetic porphyrin-modified three-dimensional (3D) porous composites as catalysts and used photocatalysis to recycle CO2 greenhouse gas and degrade tetracycline (TC) into harmless small molecules. The integration of adsorption and catalysis is an important way to achieve efficient photocatalysis. A prepared composite material (x-TA/C-ZCF) featured a porous structure, high content of pyridine nitrogen, and modified surface amino groups with strong adsorption capacity for CO2, as well as excellent light absorption performance derived from the incorporation of the TCPP porphyrin component. This material showed outstanding pollutant adsorption and degradation capacity for the photocatalytic reduction of CO2 and degradation of TC. Notably, 1-TA/C-ZCF catalyst achieved high yields of CO (392.23 μmol g−1) and CH4 (34.55 μmol g−1) and excellent TC adsorption degradation effect. In terms of practical application, the sponge monolithic material is designed to facilitate recycling and reuse, and showed excellent reusability and stability. This work, combined with the design of dual degradation functional monolithic catalysts with the advantages of adsorption and catalysis, will provide valuable reference for the preparation of efficient photocatalysts for resource and environmental applications.

Development of biomimetic hexapeptide functionalized monolithic material for capillary microextraction of microcystins in environmental waters

In this work, a histidine-tagged hexapeptide functionalized monolithic material is described for the efficient capillary microextraction (CME) of microcystins (MCs) from environment waters. 1-Vinylimidazole (VIM) monomer was utilized to synthesize the matrix polymer monolith by the copolymerization with divinylbenzene (DVB) crosslinker in the presence of radical initiator azobisisobutyronitrile (AIBN). The affinity sorbent was then prepared by a metal ion chelation-based multi-step approach, in which the histidine tag peptide Trp-His-Trp-Leu-Gln-Trp (WHWLQW) was functionalized on a Cu2+ modified polymer monolith via a chelation reaction between the imidazole group of histidine and Cu2+. The resultant WHWLQW functionalized monolithic material had high affinity, hierarchical porosity and good mechanical stability. Especially, it exhibited favorable enrichment capacity for MCs compared to other affinity materials as previously reported. With the optimized CME protocol, MCs at ultra-trace level can be analyzed by CME coupled to high performance liquid chromatography-mass spectrometry (HPLC-MS) in different aqueous environmental matrices. The average recoveries were ranged from 89.3% to 104.5% with relative standard deviations (RSD%) of 2.1–8.4, demonstrating high extraction efficiency and repeatability. The limits of detection (LODs) of MCs were determined to be 0.28–0.45 ng L-1. This novel biomimetic sorbent shows promising potential for the enrichment of ultra-trace pollutants in environment waters.

High velocity ballistic performance of ZrSiO4 reinforced aluminum alloy matrix composites

Multi-layered composite structures are a suitable strategy for achieving superior ballistic performance as compared to the monolithic materials. Typically, in the multi-layered structures, high hardness and strength material is configured as a front face and highly deformable material in the back layers. In the present study, ceramic particles ZrSiO4 reinforced Al-Si12Cu (LM13) aluminum alloy composites are investigated for ballistic performance. The 15 wt% ZrSiO4 particles of different sizes 20, 60 and 120 µm are incorporated in the aluminum alloy matrix via stir casting technique. Ballistic impact tests were performed by firing 0.308 calibers bullets with AK-47 rifle from a distance of 10 m. The deformations of the composite plates are predicted by correlating the decrease in the final velocity of the bullet after impact. It was found that composite reinforced with finer size particles offered higher resistance to bullet penetration as compared to the coarse size reinforced particles. The residual velocity as compared to the striking velocity was reduced to ∼34%, ∼29% and ∼22% for composite reinforced with ZrSiO4 particles of 20, 60 and 120 µm, respectively. At exit face the spall diameter is 34, 30 and 17 mm for composite of particle size 20, 60 and 120 µm, respectively. Microstructural analysis of the affected zones is also performed to explore the behavior of composite under the high impact loading.

Corrosion characteristics of monolithic SiC materials in beryllium-bearing molten fluoride salt

Chemical vapor deposited SiC single crystal and polycrystals were exposed to a static beryllium-bearing molten fluoride salt, 2LiF–BeF2 for 500 and 1000 h at 750 °C. Overall, the single crystal and polycrystalline SiC materials experienced slight weight loss and nominal surface etching regardless of the material type. Localized pitting and nonuniform Si removal from surface regions were associated with trace metal impurities and oxygen. Cross-sectional observation revealed minimal subsurface changes in the microstructure. The corrosion damage processes were similar to those reported for molten LiF–KF–NaF salt with trace impurities, indicating that the impurities significantly affect SiC corrosion.

Selective adsorption and photocatalytic degradation of antibiotics by LaFeO3 modified Ag3PO4 @sepiolite composite

This paper used a simple hydrothermal method to modify silver phosphate grown on top of fibrous sepiolite with lanthanum ferrite. The Z-scheme heterojunction constructed on the basis of sepiolite effectively improved a variety of deficiencies of the monolithic material. The performance of the catalysts was examined in terms of adsorption of sulfamethoxazole (SMX) and photocatalytic degradation of various antibiotics, mainly ciprofloxacin (CIP). For the adsorption of CIP (30 min), the composite LAE11 (51%) was much more efficient than LaFeO3 (26%), Ag3PO4 (9%) and AE (23%). After 1 h of lighting, the composite LAE11 removed up to 92% of CIP with kinetic constants 7.05, 1.92 and 2.02 times higher than those of LaFeO3, Ag3PO4 and AE, respectively. And after six cycles, the degradation efficiency of CIP still remained at 79%, which obviously improved the defect of Ag3PO4 instability. The composite LAE showed highly efficient adsorption and degradation of a wide range of antibiotics, with LAE11 showing strong selective adsorption of sulfamethoxazole (SMX), up to 93% within 30 min, and 58% for tetracycline hydrochloride (TC). The adsorption process of antibiotics fitted to the pseudo-second-order kinetic model. Under one hour of visible light irradiation, the composite LAE11 achieved degradation efficiencies of 92%, 89% and 94% for CIP, TC and SMX respectively. The experiments show that the construction of LaFeO3/Ag3PO4 Z-scheme heterojunction photocatalysts based on sepiolite not only facilitates improved adsorption performance but also provides more reaction sites and effectively enhances photocatalytic activity. The composite LAE11 has shown excellent synergy in the adsorption and photocatalytic degradation of pollutants.

Principle of virtual power and drilling degrees of freedom for dynamic modeling of the behavior of liquid crystal elastomer films

In this work, we aim to model the reorientation process of mesogens in nematic liquid crystal elastomers within the context of dynamics. We consider a continuum model with separate mappings for the deformation of the monolithic material and the orientation of the nematic director, where the latter describes the inclination of the mesogens. We achieve the inextensibility of the nematic director through the introduction of drilling degrees of freedom. We combine this approach with the application of the principle of virtual power and a mixed finite element formulation, in order to formulate distinct momentum and angular momentum balance laws for the two separate mappings. Furthermore, we include in our continuum model a volume load and a surface load associated only with the orientation mapping. We show in the presented three numerical examples that our formulation enables the fulfillment of all momentum and angular momentum balance laws.

Biofilm Formation on the Surfaces of CAD/CAM Dental Polymers.

Dental polymers are now available as monolithic materials which can be readily used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems. Despite possessing numerous advantages over conventionally produced polymers, the polymers produced by either of these systems fail to exhibit immunity to surface microbial adhesion when introduced into the oral environment, leading to the development of oral diseases. The aim of this study was to analyze the biofilm formation of six microorganisms from the oral cavity and its correlation to the surface characteristics of CAD/CAM dental polymers. A total of ninety specimens were divided into three groups: resin-based composite, polymethyl methacrylate, and polyether ether ketone. The experimental procedure included surface roughness and water contact angle measurements, colony forming unit counting, and scanning electron microscopy analysis of biofilm formed on the surface of the tested materials. The data were analyzed using the Kruskal-Wallis test, with a Dunn's post hoc analysis, and one way analysis of variance, with a Tukey's post hoc test; the correlation between the measurements was tested using Spearman's correlation coefficient, and descriptive statistics were used to present the data. Despite using the same manufacturing procedure, as well as the identical manufacturer's finishing and polishing protocols, CAD/CAM dental polymers revealed significant differences in surface roughness and water contact angle, and the increased values of both parameters led to an increase in biofilm formation on the surface of the materials. The CAD/CAM resin-based composite showed the lowest number of adhered microorganisms compared to CAD/CAM polymethyl methacrylate and CAD/CAM polyether ether ketone.

Monolithic Zirconium-based Metal-Organic Frameworks for Energy-Efficient Water Adsorption Applications.

Space cooling and heating, ventilation and air conditioning (HVAC) accounts for roughly 10% of global electricity use and is responsible for ca. 1.13 gigatonnes of CO2 emissions annually. Adsorbent-based HVAC technologies have long been touted as an energy-efficient alternative to traditional refrigeration systems. However, thus far, no suitable adsorbents have been developed which overcome the drawbacks associated with traditional sorbent materials such as silica gels and zeolites. Metal-organic frameworks (MOFs) offer order of magnitude improvements in water adsorption and regeneration energy requirements. However, the deployment of MOFs in HVAC applications has been hampered by issues related to MOF powder processing. Herein, we develop three high-density, shaped, monolithic MOFs (UiO-66, UiO-66-NH2 and Zr-Fumarate) with exceptional volumetric gas/vapor uptake - solving previous issues in MOF-HVAC deployment. We visualized the monolithic structures across the mesoporous range using SAXS and lattice-gas models, giving accurate predictions of adsorption characteristics of the monolithic materials. We also demonstrate that a fragile MOF such as Zr-fumarate can be synthesized in monolithic form with a bulk density of 0.76 gcm-3 without losing any adsorption performance, having a coefficient of performance (COP) of 0.71 with a low regeneration temperature (≤ 100 ᵒC). This article is protected by copyright. All rights reserved.

Sustainable and Practical Superhydrophobic Surfaces via Mechanochemical Grafting

AbstractThe broad adoption of superhydrophobic surfaces in practical applications is hindered by limitations of existing methods in terms of excessive usage of solvents, the need for tedious and lengthy chemical processes, insufficient biocompatibility, and the high cost of materials. Herein, a mechanochemical approach for practical and solvent‐free manufacturing of superhydrophobic surfaces is reported. This approach enables solvent‐free and ultra‐rapid preparation of superhydrophobic surfaces in a single‐step without the need for any washing, separation, and drying steps. The hydrolytic rupture of siloxane bonds and generation of free radicals induced by mechanochemical pathways play a key role in covalent grafting of silicone to the surface of nanoparticles that leads to superhydrophobic surfaces with a water contact angle of >165° and a sliding angle of <2°. The direct use of industrially available and non‐functional silicone materials together with demonstrated applicability to inorganic nanoparticles of varied composition greatly contribute to the scalability of the presented approach. The resulting superhydrophobic surfaces are highly biocompatible as demonstrated by fibroblast cells using two different assays. Monolith materials fabricated from silicone‐grafted nanoparticles exhibit bulk and durable superhydrophobicity. The presented approach offers tremendous potential with sustainability, scalability, cost‐effectiveness, simplicity, biocompatibility, and universality.

Porogen Concentration Effect on the Pore Structure and Properties Evolution of Polymer Monolith Based on Oligocarbonate Dimethacrylate OCM-2.

Porous polymer monolith materials of 2-mm thickness were obtained by visible light-induced radical polymerization of oligocarbonate dimethacrylate (OCM-2) in the presence of 1-butanol (10 to 70 wt %) as a porogenic additive. The pore characteristics and morphology of polymers were studied by mercury intrusion porosimetry and scanning electron microscopy. Monolithic polymers with both open and closed pores up to 100 nm in size are formed when the alcohol content in the initial composition is up to 20 wt %. The pore structure in such materials is a system of holes in the bulk of the polymer (hole-type pores). Open interconnected pores with a specific volume up to 2.22 cm3/g and modal pore size up to 10 microns are formed in the volume of the polymer with 1-butanol content of more than 30 wt %. Such porous monoliths are a structure of covalently bonded polymer globules (interparticle-type pores). The free space between the globules represents a system of open interconnected pores. In the transition region of 1-butanol concentrations (from 20 to 30 wt %), areas with both structures and intermediate frameworks, as well as honeycomb structures of polymer globules connected by bridges, are fixed on the polymer surface. It was found that the transition from one type of pore system to another is accompanied by a sharp change in the strength characteristics of the polymer. Approximation of experimental data using the sigmoid function made it possible to determine the concentration of the porogenic agent in the vicinity of which the percolation threshold is observed.

Preparation and Fracture Analysis of Advanced Layered Composite with Graphene-Coated Alumina Nanofibers

The present work aims at the preparation and characterization of ceramic layered composite prepared from fine submicron-sized Al2O3 with the addition of electrospun graphene-coated Al2O3 fibers (Al2O3/G-Fs) by Spark Plasma Sintering with double pressure sintering process. A layered composite containing 2.5 wt. % of Al2O3/G fibers in three homogeneous layers was prepared and compared with the pure monolithic Al2O3 material obtained under the same conditions. The microstructures of the samples were studied by optical microscopy, scanning, and transmission electron microscopy. The presence of graphene after the sintering in the final composite was proved by Raman spectroscopy. The effect of the graphene-coated fibers on the composite`s microstructure and mechanical properties was described along with the fractographic analysis. Graphene on the surface of the electrospun Al2O3 fibers suppressed the grain growth which dominantly takes place during the sintering of the composite, which significantly influenced the character of the fracture. While predominantly intergranular fracture occurs in the monolithic fracture surface, the fracture character becomes transgranular with the addition of layers of Al2O3/G-Fs. Fracture toughness improvement took place because of the presence of small pores, in order of a few nanometers, which showed high energy absorption and provided self-induced crack propagation inhibition.

Fracture strength and energy-dispersive spectroscopy analysis of 3-unit fixed partial dentures fabricated from different monolithic zirconia materials

Statement of problemMastication forces in different regions affect the survival of multiunit posterior restorations. The fracture strength of 3-unit posterior monolithic zirconia fixed partial dentures (FPDs) and their fracture patterns require investigation. PurposeThe purpose of this in vitro study was to evaluate and compare the fracture strength and fracture pattern of 3-unit posterior FPDs fabricated from different monolithic zirconia materials. Material and methodsThirty 3-unit FPDs were fabricated from BruxZir, FireZr, and Upcera (n=10 per group). Energy-dispersive spectroscopy analysis was performed on 2 selected specimens from each group. All specimens were exposed to a mastication simulator for 1.2×106 cycles and then monotonically loaded to fracture at a crosshead speed of 1 mm/min. The surfaces of a selected fractured specimen were examined at magnifications of ×25 and ×500 with scanning electron microscopy. Conformity to normal distribution was evaluated with the Shapiro-Wilk test. One-way analysis of variance was used to compare the normally distributed initial crack formation load F initial (Fi) and catastrophic failure strength F maximum (Fm) means by group. Weibull statistics were calculated by using the maximum likelihood estimation method. The chi-square test was used to compare shape and scale parameters (α=.05). ResultsThe mean Fm values were fail1878.9 N for Upcera, 2177.8 N for BruxZir, and 2229.4 N for FireZr. Upcera and BruxZir showed statistically significant differences for the Fm mean values (P=.039). The differences between the fracture type distributions according to the groups were statistically similar (P>.05). For Fi, Upcera presented the highest Weibull modulus value (2.199), FireZr had the lowest (1.594), while for Fm, BruxZir had the highest Weibull modulus value (9.267) and FireZr the lowest (6.572). ConclusionsUsing the zirconia materials BruxZir, FireZr, and Upcera resulted in high Fm values after aging procedures. With all materials, the fractures were most commonly found in the connector areas in the tested FPDs.

A novel method to chemically convert waste PET plastic into high–value monolithic materials with excellent flame retardancy, mechanical strength and hydrophobicity

A novel method to chemically convert waste PET plastic into high–value monolithic materials with excellent flame retardancy, mechanical strength and hydrophobicity

Monolithic Covalent Organic Frameworks with Hierarchical Architecture: Attractive Platform for Contaminant Remediation

The insolubility in solvents and poor processability of powder covalent organic frameworks (COFs) considerably impede their practical application. To address these issues and bridge the gap between powder COFs and their practical application, the construction of monolithic COFs has emerged as a feasible and effective solution. Monolithic COFs (i.e., macroscopic three-dimensional architectures) with hierarchical structures have attracted tremendous interest for environmental remediation and exhibited good contaminant removal performances owing to their wide distribution of pore sizes ranging from micropores to macropores, large specific surface area, tailored chemical components, and excellent chemical stability. Monolithic COFs can be either pure COFs with self-supporting structures or composites of COFs with other materials. The resulting COF-based monoliths inherit the merits of the parent powder COFs (such as tunable pore size, tailored structure, and super chemical/thermal stability) and the intriguing features of monolithic materials, such as hierarchical structure, high porosity, and easy handling, endowing them with fast mass transfer and high adsorption capacity. This review provides a comprehensive summary of the recent advances in the synthesis of monolithic COF materials. Additionally, the recent progress of their application in environmental remediation is summarized, including metal-ion removal, organic-pollutant capture, and oil–water separation. Furthermore, this review discusses the current challenges and provides future perspectives. We sincerely hope that it will contribute to the further development of COF-based materials in other fields, especially environmental remediation.

The Fracture Load as a Function of the Material Thickness: The Key to Computing the Strength of Monolithic All-Ceramic Materials?

The thickness of a material has a significant impact on its fracture load. The aim of the study was to find and describe a mathematical relationship between the material thickness and the fracture load for dental all-ceramics. In total, 180 specimens were prepared from a leucite silicate ceramic (ESS), a lithium disilicate ceramic (EMX), and a 3Y-TZP zirconia ceramic (LP) in five thicknesses (0.4, 0.7, 1.0, 1.3, and 1.6 mm; n = 12). The fracture load of all specimens was determined using the biaxial bending test according to the DIN EN ISO 6872. The regression analyses for the linear, quadratic, and cubic curve characteristics of the materials were conducted, and the cubic regression curves showed the best correlation (coefficients of determination (R2): ESS R2 = 0.974, EMX R2 = 0.947, LP R2 = 0.969) for the fracture load values as a function of the material thickness. A cubic relationship could be described for the materials investigated. Applying the cubic function and material-specific fracture-load coefficients, the respective fracture load values can be calculated for the individual material thicknesses. These results help to improve and objectify the estimation of the fracture loads of restorations, to enable a more patient- and indication-centered situation-dependent material choice.

Tough monolithic TiO2 materials fabricated by the sol-gel process accompanied with phase separation in solutions of SiC nanofibers and preceramic polymers

In recent decades, the sol-gel process accompanied with phase separation has been employed to fabricate porous monolithic ceramic materials. However, it is challenging to obtain crack-free samples by using this method, due to the fragile nature of porous ceramic materials and the large internal stress generated from drying and calcination process. In this work, tough monolithic titania (TiO2) materials were fabricated by the sol-gel process accompanied with phase separation in solutions of silicon carbide (SiC) nanofibers and preceramic polymers. It was found that polyethylene oxide (PEO) and ethylenediamine (EDA) can promote phase separation and sol-gel process respectively, and the micro-morphology of porous monolithic TiO2 materials can be flexibly tuned by adjusting the contents of PEO and EDA. The addition of SiC nanofibers effectively enhanced the mechanical performance and photocatalytic activity of porous TiO2 materials without altering their bicontinuous micro-morphology. Taking TiO2 materials as an example, this work demonstrates a novel methodology to fabricate ceramic nanofibers reinforced porous monolithic ceramic materials.