New-generation biomaterials for bone regenerations should be highly bioactive, resorbable and mechanically strong. Mesoporous bioactive glass (MBG), as a novel bioactive material, has been used for the study of bone regeneration due to its excellent bioactivity, degradation and drug-delivery ability; however, how to construct a 3D MBG scaffold (including other bioactive inorganic scaffolds) for bone regeneration still maintains a significant challenge due to its/their inherit brittleness and low strength. In this brief communication, we reported a new facile method to prepare hierarchical and multifunctional MBG scaffolds with controllable pore architecture, excellent mechanical strength and mineralization ability for bone regeneration application by a modified 3D-printing technique using polyvinylalcohol (PVA), as a binder. The method provides a new way to solve the commonly existing issues for inorganic scaffold materials, for example, uncontrollable pore architecture, low strength, high brittleness and the requirement for the second sintering at high temperature. The obtained 3D-printing MBG scaffolds possess a high mechanical strength which is about 200 times for that of traditional polyurethane foam template-resulted MBG scaffolds. They have highly controllable pore architecture, excellent apatite-mineralization ability and sustained drug-delivery property. Our study indicates that the 3D-printed MBG scaffolds may be an excellent candidate for bone regeneration.

Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability

Zirconia-toughened alumina (ZTA) ceramic has potential dental restoration and repair applications due to its high mechanical strength, toughness, wear resistance, chemical durability, and biocompatibility. Nevertheless, there is a great deal of crack initiation caused by stress accumulation and also material wastage after computer-aided design/computer-aided manufacturing of ZTA ceramics in conventional clinical processing. In this study, we prepared a ZTA green compact using Stereolithography (SLA) technology followed by sintering at high temperatures ranging between 1450 °C and 1650 °C. The microstructures, mechanical properties, friction and wear performance, and cytotoxicity of the ZTA ceramic were investigated. The results indicate that all ZTA samples were composed of α-Al2O3, m-ZrO2, and t-ZrO2 phases before and after sintering. With increasing sintering temperatures from 1450 °C to 1650 °C, the density, mechanical properties, hardness, and wear performance of the ZTA samples were gradually improved. The ZTA sample sintered at 1650 °C with a relative density of 96.65% showed the best mechanical performance, with a flexural strength of 572.0 MPa, a Vickers hardness of 16.2 GPa, and a fracture toughness of 7.4 MPa m1/2. The sintered ZTA sample exhibited a good cell viability toward MC3T3-E1 cells. 

Microstructure, mechanical properties, friction and wear performance, and cytotoxicity of additively manufactured zirconia-toughened alumina for dental applications

Additive manufacturing and 3D printing methods based on the extrusion of material have become very popular in recent years. There are many methods of printing ceramics, but the direct extrusion method gives the largest range of sizes of printed objects and enables scaling of processes also in large-scale applications. Additionally, the application of this method to ceramic materials is of particular importance due to its low cost, ease of use, and high material utilization. The paper presents the most important literature reports on ceramics printed by direct extrusion. The review includes articles written in English and published between 2017 and 2022. The aim of this literature review was to present the main groups of ceramic materials produced by extrusion-based 3D printing.

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3D Printing Ceramics—Materials for Direct Extrusion Process

Laser butt joining of Al2O3 ceramic plates metallized by friction stir welding

Thermal-shock stable Al2O3 crucible for superalloy smelting through slip casting with particle gradation

Direct ink writing of aluminum-phosphate-bonded Al2O3 ceramic with ultra-low dimensional shrinkage

Catalytic semi-hydrogenation of alkynes to alkenes plays an important role in the polymer, fragrance, medicine, and other chemical industrial fields. However, increasing the selectivity of alkenes during the semi-hydrogenation process is a huge challenge. Herein, N-doped porous carbon support (NC) was fabricated from zinc-based zeolite imidazole frameworks (ZIF-8). Ultrafine PdNi bimetallic nanoparticles (NPs) were uniformly dispersed, stably anchored on the NC support, and used as an efficient alkynes semi-hydrogenation catalyst. The synthesized Pd2Ni2/NC catalyst had a selectivity of 95.1% toward styrene and high catalytic activity (TOF=977.7 h−1) for the semi-hydrogenation of phenylacetylene under mild reaction conditions. The catalyst was mainly through metal-support interaction and electron transfer between Pd and Ni metal, modulating the electronic structure of the active sites, thus improving the selectivity of styrene. Selective hydrogenation of various substituted alkynes on Pd2Ni2/NC catalyst has also proved excellent applicability, and the obtained catalyst can be reused with favorable stability. This study adjusted the catalytic performance by adding a secondary metal, which provided a useful strategy for designing highly efficient catalysts for the semi-hydrogenation of alkynes. 

ZIF-8 derived N-doped porous carbon confined ultrafine PdNi bimetallic nanoparticles for semi-hydrogenation of alkynes

Selective hydrogenation of alkynes to obtain alkenes is a key reaction in petrochemical and fine chemical industries. However, the development of stable and highly selective catalysts with uniformly dispersed active sites is still immensely challenging for the semi-hydrogenation of alkynes. In this study, N-doped porous carbon nanospheres (NPCNs) were synthesized by the nanoemulsion self-assembly and subsequently carbonization method. Ultrafine PdCu bimetallic nanoparticles (NPs) were uniformly dispersed and immobilized on NPCNs. The obtained PdCu/NPCNs catalyst exhibited an open framework and abundant active sites originating from ultrafine PdCu NPs. In the semi-hydrogenation of alkynes, the PdCu/NPCNs catalyst exhibited a remarkable performance and stability, outperforming most of the classical catalysts. The excellent performance was related to the introduction of a secondary metal Cu, which can regulate the electronic state of Pd active sites to further enhance the hydrogenation activity and selectivity. Hence, the facile approach reported herein may be useful for constructing highly dispersed bimetallic NP-based catalysts for selective hydrogenation of alkynes in the petrochemical industry.

Junyi Zhang

Papers

Direct ink writing of aluminum-phosphate-bonded Al2O3 ceramic with ultra-low dimensional shrinkage

ZIF-8 derived N-doped porous carbon confined ultrafine PdNi bimetallic nanoparticles for semi-hydrogenation of alkynes

Acceleration of the semi-hydrogenation of alkynes over an N-doped porous carbon sphere-confined ultrafine PdCu bimetallic nanoparticle catalyst.

Zeolite-encaged Ultrasmall Pt-Zn Species with Trace Amount of Pt for Efficient Propane Dehydrogenation