Evaluation of Feasibility on Dental Zirconia-Accelerated Aging Test by Chemical Immersion Method.

The aim of this study was to investigate the low-temperature degradation (LTD) kinetics of tetragonal zirconia with 3 mol% yttria (3Y-TZP) dental ceramic using two degradation methods: hydrothermal degradation and immersed degradation. To study transformation kinetics, we prepared 3Y-TZP powders. We pressed these powders uniaxially into a stainless mold at 100 MPa. We then sintered the compacted bodies at intervals of 50 °C between 1300 °C and 1550 °C and immersed the specimens at various temperatures from 60 °C to 80 °C in 4% acetic acid or from 110 °C to 140 °C for the hydrothermal method. We used a scanning electron microscope (SEM) to confirm crystalline grain size and used X-ray diffraction to analyze the zirconia phase. As the sintering temperature increased, the calculated crystalline grain size also increased. We confirmed this change with the SEM image. The higher sintering temperatures were associated with more phase transformation. According to the Mehl-Avrami-Johnson equation, the activation energies achieved using the hydrothermal method were 101 kJ/mol, 95 kJ/mol, and 86 kJ/mol at sintering temperatures of 1450 °C, 1500 °C, and 1550 °C, respectively. In addition, the activation energies of the specimens immersed in 4% acetic acid were 60 kJ/mol, 55 kJ/mol, 48 kJ/mol, and 35 kJ/mol, with sintered temperatures of 1400 °C, 1450 °C, 1500 °C, and 1550 °C, respectively. The results showed that a lower sintering temperature would restrain the phase transformation of zirconia because of the smaller crystalline grain size. As a result, the rate of LTD decreased.

3D cell culture based on artificial cells and hydrogel under microgravity for bottom-up microtissue constructs.

The use of hydrogel as a filling medium to recombine dispersed microencapsulated cells to form an embedded gel-cell microcapsule complex is a new idea based on bottom-up tissue construction, which is benefit for cell distribution and of great significance for tissue construction research in vitro. In this experiment, sodium alginate and chitosan were used as the main materials, rat normal liver cell BRL-3A was used as the model cell to prepare "artificial cells". Silkworm pupa was used as raw material to extract silk fibroin solution, which was prepared by ultrasound to be the silk fibroin gel; silk fibroin hydrogel-microencapsulated hepatocyte embedded complex was then prepared by using silk fibroin gel as filling medium; the complex was cultured under three modes (static, shaking, and 3D microgravity), and the tissue forming ability of rat hepatocytes was investigated. The results showed that the microgravity culture condition can enhance the cell proliferation and promote the formation of cell colonies in the microcapsules; silk fibroin can form an embedded gel-cell microcapsule complex with microencapsulated cells, which provided mechanical support for the structure of the composite. We hope that this bottom-up construction system will have potential applications in the fields of cell culture and tissue construction.

Online Monitoring Technology of Metal Powder Bed Fusion Processes: A Review.

Metal powder bed fusion (PBF) is an advanced metal additive manufacturing (AM) technology. Compared with traditional manufacturing techniques, PBF has a higher degree of design freedom. Currently, although PBF has received extensive attention in fields with high-quality standards such as aerospace and automotive, there are some disadvantages, namely poor process quality and insufficient stability, which make it difficult to apply the technology to the manufacture of critical components. In order to surmount these limitations, it is necessary to monitor the process. Online monitoring technology can detect defects in time and provide certain feedback control, so it can greatly enhance the stability of the process, thereby ensuring its quality of the process. This paper presents the current status of online monitoring technology of the metal PBF process from the aspects of powder recoating monitoring, powder bed inspection, building process monitoring, and melt layer detection. Some of the current limitations and future trends are then highlighted. The combination of these four-part monitoring methods can make the quality of PBF parts highly assured. We unanimously believe that this article can be helpful for future research on PBF process monitoring.

Selective Conversion of Glycerol to Methanol over CaO-Modified HZSM-5 Zeolite.

Biodiesel is generally produced from vegetable oils and methanol, which also generates glycerol as byproduct. To improve the overall economic performance of the process, the selective formation of methanol from glycerol is important in biodiesel production. In the present study, a CaO modified HZSM-5 zeolite was prepared by an impregnation method and used for the conversion of glycerol to methanol. We found that the 10%CaO/HZSM-5 with Si/Al ratio of 38 exhibited highest selectivity to methanol of 70%, with a glycerol conversion of 100% under 340 ℃ and atmospheric pressure. The characterization results showed that the introduction of a small amount of CaO into the HZSM-5 did not affect the structure of zeolite. The incorporation of HZSM-5 as an acidic catalyst and CaO as a basic catalyst in a synergistic catalysis system led to higher conversion of glycerol and selectivity of methanol.

Biofunctionalization of Microgroove Surfaces with Antibacterial Nanocoatings.

OBJECTIVES: To investigate the physical properties of the modified microgroove (MG) and antibacterial nanocoated surfaces. In addition, the biological interactions of the modified surfaces with human gingival fibroblasts (HGFs) and the antibacterial activity of the surfaces against Porphyromonas gingivalis were studied. METHODS: The titanium nitride (TiN) and silver (Ag) coatings were deposited onto the smooth and MG surfaces using magnetron sputtering. A smooth titanium surface (Ti-S) was used as the control. The physicochemical properties including surface morphology, roughness, and hydrophilicity were characterized using scanning electron microscopy, atomic force microscopy, and an optical contact angle analyzer. The "contact guidance" morphology was assessed using confocal laser scanning microscopy. Cell proliferation was analyzed using the Cell Counting Kit-8 assay. The expression level of the main focal adhesion-related structural protein vinculin was compared using quantitative reverse transcription PCR and Western blotting. The antibacterial activity against P. gingivalis was evaluated using the LIVE/DEAD BacLight™ Bacterial Viability Kit. RESULTS: The Ag and TiN antibacterial nanocoatings were successfully deposited onto the smooth and MG surfaces using magnetron sputtering technology. TiN coating on a grooved surface (TiN-MG) resulted in less nanoroughness and greater surface hydrophilicity than Ag coating on a smooth surface (Ag-S), which was more hydrophobic. Cell proliferation and expression of vinculin were higher on the TiN-MG surface than on the Ag-coated surfaces. Ag-coated surfaces showed the strongest antibacterial activity, followed by TiN-coated surfaces. CONCLUSION: Nano-Ag coating resulted in good antimicrobial activity; however, the biocompatibility was questionable. TiN nanocoating on an MG surface showed antibacterial properties with an optimal biocompatibility and maintained the "contact guidance" effects for HGFs.

Exploration of the slow relaxation behavior in the manganese phosphate network.

Our endeavors are devoted to the explanation of the nature of the magnetic relaxation phenomena in the herein prepared [Mn(II)5(HPO4)2(PO4)2(H2O)4]n (1). The behavior investigation indicates the prominence of the half-occupied magnetic centers and the competence of the antiferromagnetic interactions and non-zero magnetic moments. The investigation suggests that the design and synthesis of unusual magnetic center materials with innate unquenched magnetic moments could provide a new route for the production of molecular magnets with magnetic relaxation.

Three novel 1D lanthanide-carboxylate polymeric complexes: syntheses, crystal structures and magnetic analyses.

Three novel one-dimensional (1D) lanthanide coordination complexes involving the 4-methyl-3-nitrobenzoic acid (HL) ligand, with the general formulae [Gd(L)3(H2O)(CH3OH)] (1), [Gd(L)3(H2O)2]·(4,4'-bpy)·CH3OH (2), [Dy(L)3(H2O)(CH3OH)] (3), have been synthesized by solvothermal reactions. These complexes have been structurally characterized by single-crystal X-ray diffraction, IR, PXRD, TGA, and elemental analysis. Complexes 1 and 3 are isostructural except for the distinction of the metal ion. Magnetic measurements indicate that complexes 1-3 show antiferromagnetic behaviors. Complex 3 behaves with slow relaxation of the magnetization, where the frequency-dependent out-of-phase signals are noticed. However, the characteristic maxima were not reached above 2 K under zero direct current (DC) fields. When a DC field of 5000 Oe was employed, the frequency dependent peaks of alternating current (AC) signals were obtained.

Decametallic Co(II)-cluster-based microporous magnetic framework with a semirigid multicoordinating ligand.

We have synthesized a microporous magnetic framework that contained supertetrahedral decametallic cobalt clusters as nodes and 4-(tris(hydroxymethyl)methyl)pyridine ligands as linkers in a NaCl-like network. This complex shows canted antiferromagnetism with spin-glass behavior. After the removal of the guest molecules, the spin-canting and spin-glass behaviors are maintained. The permanent porosity was evaluated by N2-adsorption measurements. This complex mainly shows a hydrophobic nature, as validated by MeOH- and water-adsorption measurements, which is consistent with the grand canonical Monte Carlo (GCMC) theoretical simulation.

Tuning the interactions from antiferro- to ferro-magnetic by molecular tailoring and manipulating.

Four novel Cu(II) complexes {Na[Cu(4)(hmp)(4)(CHOO)(3)](ClO(4))(2)·H(2)O}(n) (1), [Cu(8)(hmp)(8)(CH(3)COO)(6)](ClO(4))(2) (2), [Cu(4)(hmp)(4)(CH(3)CN)(2)(ClO(4))(2)(H(2)O)(2)](ClO(4))(2) (3), and [Cu(4)(hmp)(4)(CH(3)COO)(2)(H(2)O)(4)](ClO(4))(2)·2H(2)O (4) with Hhmp = 2-(hydroxymethyl)pyridine were prepared by structural modulation at room temperature. Taking advantage of the steric hindrance of the ancillary ligands, the 1D copper chain (1) is successfully cut down into the octa-nuclear copper cluster (2) with the unchanged antiferromagnetic [Cu(4)O(4)] open-cubane that is further separated into weak antiferromagnetic [Cu(4)O(4)] (3) and then modulated to be the ferromagnetic tetra-nuclear [Cu(4)O(4)] cluster (4). The obtained four complexes allow us to systematically investigate their magnetic properties and find the rules for further magnetic investigations. The results showed that there exist antiferromagnetic interactions between Cu(ii) ions in 1-3, while 4 displays ferromagnetic behaviour. The best fitting results to the experimental magnetic susceptibilities gave J(1) = J(2) = J(3) = -2.26 cm(-1), g = 2.11 for 3 and J(1) = 37.05 cm(-1), J(2) = -0.62 cm(-1), J(3) = -0.62 cm(-1), g = 2.13 for 4.

Two-step relaxation in the 3D spin-canted manganese phosphate with high P-O-Mn connectivity.

The manganese phosphate with high P-O-Mn connectivity shows a two-step relaxation process in two distinct spin glass states.