Hydroxyapatite (HA) has been wildly used in clinical practice for artificial implants. However, due to its inherent properties and preparation process, it is limited by low strength in practical applications. Therefore, highly porous hydroxyapatite scaffolds reinforced with 0 to 30 wt% doped wollastonite (WS) (HA/WS) were prepared by freeze-drying in combination with pressureless sintering method. The results demonstrated that WS could consistently improve the compressive properties of HA/WS scaffolds. The HA/WS scaffolds have optimal total porosity with good open pores and internal interconnections when the WS doping is 10%. In vitro osteoclast attachment experiments indicated that the HA/WS scaffolds had good biocompatibility. The findings of this study provide theoretical guidance for the application of HA in the field of artificial implants.

The occurrence of fractures has emerged as one of the most prevalent injuries in the human body. In bone reconstruction surgery, after the implantation of porous hydroxyapatite materials, there is an initial infiltration of body fluids into the porous implant, followed by biomineralization-mediated apatite crystal formation and the subsequent ingrowth of bone cells. Despite extensive research efforts in this field, previous investigations have primarily focused on the formation of apatite crystals on exposed surfaces, with limited literature available regarding the formation of apatite crystals within the internal microstructures of bone implants. Herein, we demonstrate the occurrence of dynamic biomineralization within a three-dimensional porous hydroxyapatite/wollastonite (HA/WS) skeleton, leading to the abundant formation of nano-sized apatite crystals across diverse internal environments. Our findings reveal that these apatite nanocrystals demonstrate distinct rates of nucleation, packing densities, and crystal forms in comparison to those formed on the surface. Therefore, the objective of this study was to elucidate the temporal evolution of biomineralization processes by investigating the microstructures of nanocrystals on the internal surfaces of HA/WS three-dimensional porous materials at distinct stages of biomineralization and subsequently explore the biological activity exhibited by HA/WS when combined with cell investigation into apatite crystal biomineralization mechanisms at the nanoscale, aiming to comprehend natural bone formation processes and develop efficacious biomimetic implants for tissue engineering applications. The simultaneous examination of bone cell attachment and its interaction with ongoing internal nanocrystal formation will provide valuable insights for designing optimal scaffolds conducive to bone cell growth, which is imperative in tissue engineering endeavors.

A thin bioglass (BG) layer or diffusion zone has been used to enhance interfacial bonding between co-sintered scaffold-like micro-porous hydroxyapatite (HA) coating over dense zirconia substrate. However, there still have problems such as low fracture toughness and low wear resistance. Therefore, while meeting the basic requirements of degradability and biocompatibility, how to improve the mechanical properties of the scaffold, endow it with osteoinductivity and build a low-density porous structure has become the focus of bone scaffold research. The tri-layer bio-ceramic composites, consisting of porous HA, BG diffusion zone, and strong zirconia substrate, are designed with superior loading-bearing capability to the scaffold. Surface handling properties of the scaffold-like HA coating are further enhanced by incorporating wollastonite. The gradient in material compositions across the coating and substrate interface is further minimized by adding HA into the zirconia substrate. Benefiting from these special design and the thin BG diffusion zone, the tri-layer bio-ceramics present excellent interfacial strength, which ensures good structural strength and machinability. The results could provide the feasible options for bio-ceramic scaffolds design and manufacturing process, thus advance the practical clinical applications of HA-based scaffolds for bone repair and regeneration.

A simple method of applying and distributing multi-walled carbon nanotubes (MWCNTs) onto grit-blasted steel substrates has been investigated in this study to overcome the difficulty of mixing MWCNTs in epoxy adhesives forming the MWCNT-reinforced adhesive joints. MWCNTs were dispersed in an acetone and resin (no hardener) solution with the weight ratio of 1:3:100 for MWCNT/resin/acetone, which was then applied onto the grit-blasted steel substrates. After evaporation of acetone, an ultra-thin layer of resin pre-coating kept well-distributed MWCNTs within the micro-cavities created by grit blasting. Epoxy adhesives (with hardener) were then applied to bond the steel substrates to create MWCNTs-reinforced adhesive joints. The results show that the MWCNT pre-coating (PC) method is beneficial to strong adhesive bonding. Most importantly, the MWCNT-PC method can be easily applied for structural applications on site. In the current study, MWCNTs were simply dispersed in the acetone and resin (no hardener) solution by simple rod stirring for around 1 minute, which can be adopted for large-scale applications. Scanning electron microscopy (SEM) observations on fracture surfaces and cross sections of the MWCNT-reinforced adhesive joints showed MWCNT micro-bundles were well dispersed within the epoxy adhesive joints taking the contour of microscopically uneven substrate surfaces.

Inherent weak interfaces exist in large plate and shell composites made from carbon fibre pre-pregs and in any laminar structures bonded by epoxy adhesives due to absence of Z-directional toughening. In-situ Z-directional movements of short and flexible fibres from ultra-thin un-bonded non-woven Aramid veils can potentially compensate for the inherent structural weakness. Incorporations of nano-fillers, carbon nano-tubes (CNT) and graphene can enhance the toughness of epoxy matrix, but cannot alter the interfacial structures of adhesive joints or provide effective Z-directional toughening. This study shows quasi-Z-directional fibre-bridging across carbon fibre plies can be created in-situ during composite processing from ultra-thin un-bonded non-woven Aramid veils between carbon fibre plies. CNT can also be incorporated into the un-bonded veils, and the hierarchical CNT and Aramid veil interfacial toughening is more effective as the hybrid fibre system can reinforce the epoxy matrix and alter the 3D interfacial structures between carbon fibre plies from movements of the free fibre ends. Un-bonded non-woven Aramid veils can be introduced during the pre-preging process. As a result, the common concept of interleaving will be changed, as the extra composite layup step is no longer required. The carbon fibre pre-pregs incorporated with ultra-thin non-woven veils can be used just as normal pre-pregs. Experiments on edge delamination in carbon fibre composites due to drilling and on adhesive bonding between aluminium plates are used to demonstrate the effectiveness of quasi-Z-directional toughening from un-bonded veils due to the out-of-plane movements of short flexible Aramid fibres.

This study presents a new bio-ceramic processing technique, which can be used to deposit thick porous hydroxyapatite(HA) coatings on strong three-dimensional (3D) zirconia substrates with a strong coating-substrate interface bonded by bio-glass infiltration during the sintering process. A thin bio-glass coating was first painted on the micro-porous zirconia substrates, pre-sintered at 900°C, then followed by thick HAslip coating with gelatin and ceramic and polymer additives. Freeze-drying was used to create porous scaffold structures within the thick HA coating. The green tri-layer ceramic composites were then co-sintered at 1300°C, resulting in thick scaffold-like HA-coating bonded strongly on load-bearing zirconia substrate or implant core. Such bio-ceramic composites with suitable strength and bio-active and bio-resorbable surface coating can provide useful implant options, bridging the gap between weak and fragile HA scaffolds and strong titanium implants.

Samarium magnesium hexaaluminate (SmMgAl11O19) powders with a magnetoplumbite type structure were synthesized directly by solid-state reaction at 1550 degrees C for 5 h. The SEM images show that the prepared powders present hexagonal plates. And then SmMgAl11O19 ceramic was prepared by a two step sintering method at 1700 degrees C for 0.5 h and a relatively low sintering temperature of 1650 degrees C for 10 h. The bulk density and flexural strength of SmMgAl11O19 ceramic are 4.31 g/cm(3) and 189.2 +/- 30.6 MPa, respectively. Results also show that the thermal properties of the as-prepared SmMgAl11O19 ceramic prepared by two-step sintering are better than that of LaMgAl11O19 ceramics. The thermal conductivity and thermal diffusivity decrease with increasing temperature. At 1073 K, the thermal conductivity and thermal diffusivity of SmMgAl11O19 ceramic are 2.43 W/mK and 0.532 m(2)/s, respectively. And the linear thermal expansion coefficient from 200 to 1200 degrees C is 9.5x10(-6) K-1.

This study presents the design, processing, properties and potential applications of a novel layered bio-ceramic composites consisting of three different micro-porous calcium phosphate coatings on strong zirconia cores manufactured using a recently developed slip coating-deposition and coating-substrate co-sintering technique. Detailed microstructures of the three graded micro-porous calcium phosphate coatings, and the coating/substrate interface have been investigated. Also, the flexural strength of the bio-ceramic composite and the bonding state between the coatings and zirconia substrate have been characterized. A preliminary and limited in vitro cell test indicates that the new scaffold composite has no cytotoxicity to the fibroblasts which can attach, proliferate and grow on the coating surfaces. Because of the combination of bio-function and strength, such layered load-bearing bio-ceramic composites are a potential candidate for large-scale head bone repairs.

In this paper,the erosion resistance of the magnesia-alumina spinel(MAS) in the synthesis process of lithium cobaltoxide and the related mechanism were studied.After ten cycles of the synthesis process,the erosion depth in the MAS ceramic is only about 100 μm.The MAS material shows good properties.Further researches on the erosion mechanism suggest that the Li-containing compound firstly react with the MAS ceramic,with LixMyOz(M=Al/Mg) compound as by-product;then the LixM'yOz(M'=Al/Mg/Co) compound forms due to the further permeation of Co-containing compound and separates out from the LixMyOz(M=Al/Mg) compound.

FeMo-Al2O3 composite ceramics were prepared at 1600 ℃ holding for 2 h by pressureless sintered in reducing atmosphere,using FeMo70 alloy and α-Al2O3 as starting materials.The effect of addition of FeMo70 alloy on phase composition and the mechanical properties of FeMo-Al2O3 composite ceramics were studied.Results showed that phases of samples were mainly α-Al2O3,Fe2Mo and Fe6Mo7N2.The average grain size of Al2O3 matrix increased from 4 μm to about 15 μm when adding FeMo70 alloy.Rockwell hardness and fracture toughness of increased first and then decreased with the increasing amount of FeMo70 alloy.When 13wt% FeMo-Al2O3 composite ceramics of FeMo70 alloy were added,Rockwell hardness(HRA)and fracture toughness(KIC)of composite ceramics reached a maximum value of 88.3 and 3.7 MPa·m1/2,respectively.

以Al(OH)3,La2O3,Gd2O3 和4MgCO3·Mg(OH)2·5H2O为原料,采用固相反应法在1500℃保温4h合成了镁基六铝酸镧钆(La1-xGdxMgAl11O19,x=0～1,LGMA)粉体.结果表明:合成的LGMA粉体具有畸变的磁铅石型晶体结构,形成一种镧钝共掺镁基六铝酸盐固溶体,LGMA晶粒发育良好,呈板片状,晶粒平均厚度约为350nm.采用无压烧结法在1 700℃保温6h后LGMA陶瓷仍能保持其稳定的磁铅石结构.在LaMgAl11O19晶格中掺入钆离子能显著降低LGMA陶瓷的高温热导率,在800℃,GdMgAl11O19陶瓷的最低热导率为1.78 W/(m·K),200～1 200℃范围的平均线性热膨胀系数为9.39×10-6/K.GMA陶瓷具有较低热导率的主要原因是:在LaMgAl11O19晶格中原子质量较重的Gd3+取代La3+能够增强声子散射作用,Gd3+掺入后引起的晶格畸变对声子散射也具有重要作用.

Si3N4-SiC-C refractory composites were prepared under the condition of 1450°C × 3h with electrofoging anthracite, Si3N4, SiC as the raw material and the modification emulsified bitumen as the binder. The effects of the silicon and silica fine powder additives on the compressive strength of Si3N4- SiC-C refractory composites were studied. The results indicated that adding an appropriate ratio range of silicon or silica fine powder in the composites both can improve the compressive strength of the material.

Lanthanum-gadolinium magnesium hexaluminate (La1-xGdxMgAl11O19, x=0-1, LGMA) powders were synthesized at 1500°C for 4 h using Al(OH)3, La2O3, Gd2O3 and 4MgCO3 · Mg(OH)2 · 5H2O as raw materials via a solid state reaction method. The results show that the LGMA powders exhibit a distorted magnetoplumbite-type (MP) crystal structure and forms a solid solution of co-doped lanthanum-gadolinium magnesium hexaluminate, and the morphology of LaMgAl11O19 particles appears plate-like with a clear edge and well-developed faces, and the average crystalline grain size of the LGMA powders is about 350 nm. The LGMA ceramic pressureless sintered at 1700°C for 6 h could maintain the stable MP crystal structure. The incorporation of Gd3+ into the lattice could reduce the high-temperature thermal conductivities of the LGMA ceramic. The thermal conductivity at 800°C of GdMgAl11O19 ceramic is 1.78 W/(m · K), and its linear thermal expansion coefficient from 200 to 1200°C is 9.39 × 10-6/K. The main reason of low thermal conductivity of LGMA ceramics is due to the enhanced phonon scattering effects caused by the heavy rare-earth Gd3+ replacing La3+ in the lattice of LaMgAl11O19. The lattice distortion induced by the dopping Gd3+ also plays an important role on phonon scattering.

The effects of temperature on the phase characteristics and sintering properties of fly ash and red mud between 1050 ℃ to 1200 ℃ had been studied. The results showed that the main mineral phase of fly ash was quartz (SiO2) and mullite(3Al2O3·2SiO2),the major mineral phases of red mud were gehlenite (Ca2Al2SiO7),quartz (SiO2),andradite(Ca3Fe2+3(SiO4)3) and morimotoite (Ca3TiFeSi3O12). Different ratio of fly ash and red mud samples got the relatively lower porosity,the higher bulk density and compressive strength at 1200 ℃. The 5# sample sintered at 1200 ℃ got the porosity of 1.67%,bulk density of 2.10 g·cm-3,compressive strength of 123.23 MPa,achieving sintering dense state,and the dominant phase was (anorthite,sodian) and mullite. The formation of mullite and addition of glass phase in the samples contributed to dense sintering at high temperature.

To provide a basic foundation for the ceramic application of red mud,and take the red mud from a Hejin Aluminum Plant as a case,effects of sintering temperature on the phase transformation and physical properties are studied.The results showed that the main crystalline phases of red mud samples are Gehlenite,Quartz,and a small amount of Albite,Morimotoite and Andradite.When the temperature higher than 1 000 ℃,Quartz,Albite and Morimotoite in sintered samples are gradually reduced,but Gehlenite and Andradite increased with the sintering temperature increased.The proper sintering temperature of red mud was at 1 150 ℃,with the bulk density of red mud samples of 1.82 g/cm3,water absorption of 19.9%,porosity of 36.0% and compressive strength of 58.8 MPa.The increase of Gehlenite and Andradite in red mud at a high temperature and the glass phase played an important role in developing the strength of red mud samples and promoting the ceramic mechanism of red mud.

Single phase YIG powders were synthesized successfully using Fe2O3 and Y2O3 as starting materials by solid state reaction, and YIG ceramics were prepared by pressureless sintering. The influence of synthesizing temperature and Fe2O3 content on the final production were studied The effect of Fe2O3 content on volume density and microstructure of the sintered YIG was also investigated. The results showed that single phase YIG powders were synthesized by solid state reaction at 1400°C for 3h. When Fe2O3 content was excessive 3 wt%, YIG ceramics with a density of 5.294g·cm-3 was fabricated by sintering at 1480°C for 2.5h.

Al2O3/LiTaO3 composite ceramics were fabricated by adding Al2O3 particles into LiTaO3 ceramics. The influence of Al2O3 particles on sintering properties of LiTaO3 ceramics was studied. Also, the microstructure of Al2O3/LiTaO3 composite ceramics and domain configurations in LiTaO3 grains were investigated. The results showed that the addition of Al2O3 particles was contributed to the sintering of LiTaO3 ceramics as aid. With the increase of Al2O3 content, the relative density of Al2O3/LiTaO3 composite ceramics enhanced. The relative density of 9vol% AL(2)O(3)/LiTaO3 composite ceramic prepared by pressureless sintering at 1300 degrees C was the highest in the experiment. 90 degrees domains were also observed in LiTaO3 grains in the prepared AL(2)O(3)/LiTaO3 composite ceramics.

Al2O3 structural ceramic has many advantages such as high strength, high hardness and good wear resistance. But the application of Al2O3 is limited due to its high brittleness. Several toughening mechanisms have been proposed, especially toughening by introducing second phase in Al2O3. In this paper, Research progress and toughening mechanisms in Al2O3 composite ceramic are summarized.