Low-Cost Magnesium-Based Thermoelectric Materials: Progress, Challenges, and Enhancements.

Magnesium-based thermoelectric (TE) materials have attracted considerable interest due to their high ZT values, coupled with their low cost, widespread availability, nontoxicity, and low density. In this review, we provide a succinct overview of the advances and strategies pertaining to the development of Mg-based materials aimed at enhancing their performance. Following this, we delve into the major challenges posed by the severe working conditions, such as high temperature and thermal cycling, which adversely impact the behavior and long-term stability of the TE modules. Challenges include issues like the lack of mechanical strength, chemical instability, and unreliable contact. Subsequently, we focus on the key methodologies aimed at addressing these challenges to facilitate the broader application of the TE modules. These include boosting the mechanical strength, especially the toughness, through grain refining and additions of second phases. Furthermore, strategies targeted at enhancing the chemical stability through coatings and modifying the microstructure, as well as improving the contact design and materials, are discussed. In the end, we highlight the perspectives for boosting the practical applications of Mg-based TE materials in the future.

Ceramic conversion treated titanium implant abutments with gold for enhanced antimicrobial activity.

INTRODUCTION: Peri-implantitis is an inflammatory process around dental implants that is characterised by bone loss that may jeopardize the long-term survival of osseo integrated dental implants. The aim of this study was to create a surface coating on titanium abutments that possesses cellular adhesion and anti-microbial properties as a post-implant placement strategy for patients at risk of peri-implantitis. MATERIALS AND METHODSMETHODS: Titanium alloy Grade V stubs were coated with gold particles and then subjected to ceramic conversion treatment (CCT) at 620 °C for 3, 8 and 80 h. The surface characteristics and chemistry were assessed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. The leaching profile was investigated by inductively coupled plasma mass spectroscopy (ICP-MS) for all groups after 7, 14 and 28 days in contact with distilled water. A scratch test was conducted to assess the adhesion of the gold coating to the underlying titanium discs. Two bacterial species (Staphylococcus aureus (SA) & Fusobacterium nucleatum (FN)) were used to assess the antibacterial behaviour of the coated discs using a direct attachment assay test. The potential changes in surface chemistry by the bacterial species were investigated by grazing angle XRD. RESULTS: The gold pre-coated titanium discs exhibited good stability of the coating especially after immersion in distilled water and after bacterial colonisation as evident by XRD analysis. Good surface adhesion of the coating was demonstrated for gold treated discs after scratch test analysis, especially titanium, following a 3-hour (3 H) ceramic conversion treatment. All coated discs exhibited significantly improved antimicrobial properties against both tested bacterial species compared to untreated titanium discs. CONCLUSIONS: Ceramic conversion treated titanium with a pre-deposited gold layer showed improved antimicrobial properties against both SA and FN species than untreated Ti-C discs. Scratch test analysis showed good adherence properties of the coated discs the oxide layer formed is firmly adherent to the underlying titanium substrate, suggesting that this approach may have clinical efficacy for coating implant abutments.

Silver-promoted ceramic conversion treatment of Ti6Al4V alloy and its mechanical performance.

In this paper, the Ti6Al4V alloy surface was modified via ceramic conversion treatment (CCT) with or without a pre-deposited silver layer. After characterizing the surface morphologies, microstructure and phase constituents of the ceramic oxide layer formed at 620 °C, we investigated the surface hardness and the cross-sectional nano-hardness profile under the oxide layer. The static load-bearing capacity of the oxide layers was examined by applying discrete loads via a Vickers indenter and observing the indentations. A scratch test was used to evaluate the load-bearing capacity and the adhesion/cohesion of the oxide layers. The wettability of the surface changed due to the incorporation of silver and the change of surface morphology. Reciprocating friction and wear test was used to assess the tribological properties. Small and dispersed silver nanoparticles and clusters were found in the oxide layer of the Ag pre-deposited Ti6Al4V samples, and they had much better tribological properties in terms of reduced coefficient of friction and wear volume. With the assistance of silver, the efficiency of the CCT was significantly improved.

A Novel Treatment to Selectively Harden Ti6Al4V Surfaces.

Various surface treatments have been developed on titanium and its alloy to improve their tribological properties. However, for some components, only specific surfaces need to be hardened rather than the whole surfaces. This study develops a duplex heat treatment including selective surface hardening by prepainting TiO2 powders and thermal oxidation. It is found that the TiO2 powder layer can be used as an oxygen reservoir for boosting diffusion treatment at temperatures of 800-900 °C. The abundance of oxygen provides high potential and accelerates the diffusion process, deeply hardening the surface case. Moreover, the duplex treatment is optimal for selectively hardened surfaces with high load-bearing capacity and much improved tribological properties. Prepainting the surfaces that need to be hardened is easy to operate and has good potential to be applied in industry.

High-Temperature Oxidation Behaviour of CrSi Coatings on 316 Austenitic Stainless Steel.

In this study, a closed-field unbalanced magnetron sputtering system, which is environmentally friendly and has high deposition efficiency, was used to deposit CrSi coatings on 316 austenitic stainless steel. This system utilised separate Cr and Si targets, and the appropriate content of Cr and Si of the coatings was adjusted by changing the currents applied to the targets. A series of CrSi coatings with different Si/Cr ratios were produced, and their oxidation behaviour at elevated temperatures was investigated. By analysing the weight gain, surface morphology and microstructure, composition and phase constituents, the oxidation behaviour at 600 °C, 700 °C and 800 °C was investigated and the optimized coating to protect the stainless steel has been identified. The outcome of the research indicated that a small amount of Si (between 4-7 at.%) in Cr coatings is effective in protecting the austenitic stainless steel against oxidation at high temperatures, while a high Si content (around 10 at.% or more) makes the coating more brittle and prone to cracking or delamination during oxidation at 800 °C.

A Novel Catalytic Ceramic Conversion Treatment of Zr702 to Combat Wear.

Zr and its alloys are widely used in multiple areas, including the nuclear and medical fields. Previous studies indicate that a ceramic conversion treatment (C2T) of Zr-based alloys can address the issues of low hardness, high friction, and poor wear resistance of Zr based alloys. This paper introduced a novel catalytic ceramic conversion treatment (C3T) to Zr702 by pre-depositing a catalytic film (such as silver, gold, platinum, etc.) before the ceramic conversion treatment, which efficiently promoted the C2T process, in terms of reduced treatment times, with a thick, good quality, surface ceramic layer. The formed ceramic layer significantly improved the surface hardness and tribological properties of Zr702 alloy. Compared with conventional C2T, the C3T technique provided two orders of magnitude reduction of wear factor and reduced the coefficient of friction from 0.65 to <0.25. Among the C3T samples, the C3TAg and the C3TAu samples have the highest wear resistance and lowest CoF, mainly due to the self-lubricant formation during the wear processes.

Characterization of Magnetron Sputtered BiTe-Based Thermoelectric Thin Films.

Thermoelectric (TE) technology attracts much attention due to the fact it can convert thermal energy into electricity and vice versa. Thin-film TE materials can be synthesized on different kinds of substrates, which offer the possibility of the control of microstructure and composition to higher TE power, as well as the development of novel TE devices meeting flexible and miniature requirements. In this work, we use magnetron sputtering to deposit N-type and P-type BiTe-based thin films on silicon, glass, and Kapton HN polyimide foil. Their morphology, microstructure, and phase constituents are studied by SEM/EDX, XRD, and TEM. The electrical conductivity, thermal conductivity, and Seebeck coefficient of the thin film are measured by a special in-plane advanced test system. The output of electrical power (open-circuit voltage and electric current) of the thin film is measured by an in-house apparatus at different temperature gradient. The impact of deposition parameters and the thickness, width, and length of the thin film on the power output are also investigated for optimizing the thin-film flexible TE device to harvest thermal energy.

Nanoindentation of Multifunctional Smart Composites.

Three multifunctional smart composites for next-generation applications have been studied differently through versatile nanoindentation investigation techniques. They are used in order to determine peculiarities and specific properties for the different composites and to study the charge/matrix, charge/surface, or smart functions interactions. At first, a mapping indentation test was used to check the distribution of hardness and modulus across a large region to examine any non-uniformity due to structural anomalies or changes in properties for a carbon nanotubes (CNTs)-reinforced polypropylene (PP V-2) nanocomposite. This smart composite is suitable to be used in axial impeller fans and the results can be used to improve the process of the composite produced by injection moulding. Secondly, the interfacial properties of the carbon fibre (CF) and the resin were evaluated by a push-out method utilizing the smaller indentation tip to target the individual CF and apply load to measure its displacement under loads. This is useful to evaluate the effectiveness of the surface modification on the CFs, such as sizing. Finally, nanoindentation at different temperatures was used for the probing of the in situ response of smart shape memory polymer composite (SMPC) usable in grabbing devices for aerospace applications. Furthermore, the triggering temperature of the shape memory polymer response can be determined by observing the change of indentations after the heating and cooling cycles.

3D Printing Processability of a Thermally Conductive Compound Based on Carbon Nanofiller-Modified Thermoplastic Polyamide 12.

A polyamide (PA) 12-based thermoplastic composite was modified with carbon nanotubes (CNTs), CNTs grafted onto chopped carbon fibers (CFs), and graphene nanoplatelets (GNPs) with CNTs to improve its thermal conductivity for application as a heat sink in electronic components. The carbon-based nanofillers were examined by SEM and Raman. The laser flash method was used to measure the thermal diffusivity in order to calculate the thermal conductivity. Electrical conductivity measurements were made using a Keithley 6517B electrometer in the 2-point mode. The composite structure was examined by SEM and micro-CT. PA12 with 15 wt% of GNPs and 1 wt% CNTs demonstrated the highest thermal conductivity, and its processability was investigated, utilizing sequential interdependence tests to evaluate the composite material behavior during fused filament fabrication (FFF) 3D printing processing. Through this assessment, selected printing parameters were investigated to determine the optimum parametric combination and processability window for the composite material, revealing that the selected composition meets the necessary criteria to be processable with FFF.

Novel Catalytic Ceramic Conversion Treatment of Ti6Al4V for Improved Tribological and Antibacterial Properties for Biomedical Applications.

Titanium oxide layers were produced via a novel catalytic ceramic conversion treatment (CCCT, C3T) on Ti-6Al-4V. This CCCT process is carried out by applying thin catalytic films of silver and palladium onto the substrate before an already established traditional ceramic conversion treatment (CCT, C2T) is carried out. The layers were characterised using scanning electron microscopy, X-ray diffraction, transmission electron microscopy; surface micro-hardness and reciprocating tribological performance was assessed; antibacterial performance was also assessed with S. aureus. This CCCT has been shown to increase the oxide thickness from ~5 to ~100 µm, with the production of an aluminium rich layer and agglomerates of silver and palladium oxide surrounded by vanadium oxide at the surface. The wear factor was significantly reduced from ~393 to ~5 m3/N·m, and a significant reduction in the number of colony-forming units per ml of Staphylococcus aureus on the CCCT surfaces was observed. The potential of the novel C3T treatment has been demonstrated by comparing the performance of C3T treated and untreated Ti6Al4V fixation pins through inserting into simulated bone materials.

The Impact of Carbon Nanofibres on the Interfacial Properties of CFRPs Produced with Sized Carbon Fibres.

In this work, different amounts of CNFs were added into a complex formulation to coat the CFs surfaces via sizing in order to enhance the bonding between the fibre and the resin in the CF-reinforced polymer composites. The sized CFs bundles were characterised by SEM and Raman. The nanomechanical properties of the composite materials produced were assessed by the nanoindentation test. The interfacial properties of the fibre and resin were evaluated by a push-out method developed on nanoindentation. The average interfacial shear strength of the fibre/matrix interface could be calculated by the critical load, sheet thickness and fibre diameter. The contact angle measurements and resin spreadability were performed prior to nanoindentation to investigate the wetting properties of the fibre. After the push-out tests, the characterisation via optical microscopy/SEM was carried out to ratify the results. It was found the CFs sizing with CNFs (1 to 10 wt%) could generally increase the interfacial shear strength but it was more cost-effective with a small amount of evenly distributed CNFs on CFs.

Curcumin Inhibits ERK/c-Jun Expressions and Phosphorylation against Endometrial Carcinoma.

Curcumin has been shown to have anticancer effects in a variety of tumors. However, there are fewer studies on the role of curcumin in endometrial carcinoma (EC). The purpose of this experiment was to examine the inhibitory effect of curcumin on endometrial carcinoma cells and ERK/c-Jun signaling pathway. We first predicted the mechanism of action of curcumin on endometrial carcinoma by network pharmacology. Then, we found that curcumin can decrease the cell viability of Ishikawa cells, inhibit the migration of cancer cells, induce apoptosis, and cause cell cycle arrest in the S phase. For molecular mechanism, curcumin reduced the mRNA expression levels of ERK2 and JUN genes and inhibited the phosphorylation of ERK and c-Jun. This suggests that curcumin inhibits the proliferation of endometrial carcinoma cells by downregulating ERK/c-Jun signaling pathway activity.

Effects of a single transient transfection of Ten-eleven translocation 1 catalytic domain on hepatocellular carcinoma.

Tumor suppressor genes (TSGs), including Ten-eleven translocation 1 (TET1), are hypermethylated in hepatocellular carcinoma (HCC). TET1 catalytic domain (TET1-CD) induces genome-wide DNA demethylation to activate TSGs, but so far, anticancer effects of TET1-CD are unclear. Here we showed that after HCC cells were transiently transfected with TET1-CD, the methylation levels of TSGs, namely APC, p16, RASSF1A, SOCS1 and TET1, were distinctly reduced, and their mRNA levels were significantly increased and HCC cells proliferation, migration and invasion were suppressed, but the methylation and mRNA levels of oncogenes, namely C-myc, Bmi1, EMS1, Kpna2 and c-fos, were not significantly change. Strikingly, HCC subcutaneous xenografts in nude mice remained to be significantly repressed even 54 days after transient transfection of TET1-CD. So, transient transfection of TET1-CD may be a great advance in HCC treatment due to its activation of multiple TSGs and persistent anticancer effects.

Plasma Surface Functionalization of Carbon Nanofibres with Silver, Palladium and Platinum Nanoparticles for Cost-Effective and High-Performance Supercapacitors.

Due to their relatively low cost, large surface area and good chemical and physical properties, carbon nanofibers (CNFs) are attractive for the fabrication of electrodes for supercapacitors (SCs). However, their relatively low electrical conductivity has impeded their practical application. To this end, a novel active-screen plasma activation and deposition technology has been developed to deposit silver, platinum and palladium nanoparticles on activated CNFs surfaces to increase their specific surface area and electrical conductivity, thus improving the specific capacitance. The functionalised CNFs were fully characterised using scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) and their electrochemical properties were evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results showed a significant improvement in specific capacitance, as well as electrochemical impedance over the untreated CNFs. The functionalisation of CNFs via environmental-friendly active-screen plasma technology provides a promising future for cost-effective supercapacitors with high power and energy density.

Cytotoxic Constituents and Mechanism from Peganum harmala.

Peganum harmala L. is a traditional Chinese and Uygur medicine used to treat cancer. Bioactivity-guided fractionation was applied to determine the cytotoxic constituents from P. harmala. A novel triterpenoid and a phenolic glycoside were isolated and identified, as well as seven known compounds. The novel metabolites were elucidated to be 3α-acetoxy-27-hydroxyolean-12-en-28-oic acid methyl ester (1, OA) and N-acetyl-9-syringinoside (9). Some compounds exhibited potent cytotoxicity against human tumor cells. Among them, OA showed the highest cytotoxicity against human lung cancer cells A549 with an IC50 value of 8.03 ± 0.81 µm. OA had a potent anti-NSCLC cell activity by interfering with the epidermal growth factor receptor (EGFR) activation and its downstream signaling, and could exert an antiproliferative effect by inactivation of EGFR-driven antiapoptotic pathway followed by the release of mitochondrial cytochrome c, which might prove to be a promising leading compound for the development of an anti-lung cancer drug.

[Compound amino acid combined with vitamin E for idiopathic asthenospermia].

Objective: To study the therapeutic efficacy of compound amino acid combined with vitamin E in the treatment of idiopathic asthenospermia. Methods: This study included 120 cases of idiopathic asthenospermia treated in the Outpatient Department of our hospital between February 2014 and January 2015. We randomized the patients into a treatment group( n = 70,aged23- 43 [mean 32. 5] years) and a control group( n = 50,aged 23- 44 [mean 31. 7] years),the former treated with compound amino acid plus vitamin E while the latter with vitamin E only. After 90 days of medication, we evaluated the therapeutic effects by comparing the total sperm motility( progressive motility + non-progressive motility, PR + NP),the percentage of progressively motile sperm( PR),and the pregnancy rate between the two groups. Results: Before treatment, PR + NP and PR were(26. 24 ± 6. 56) %and(24. 65 ± 6. 43) % in the treatment group and(15. 13 ± 5. 68) % and(14. 73 ± 6. 16) in the control, with no statistically significant differences between the two groups( P > 0. 05). After 90 days of medication, PR + NP and PR were( 49. 63 ± 9. 78) % and(33. 33 ± 5. 64)% in the former and(37. 67 ± 7. 98)% and(27. 23 ± 6. 46)% in the latter, remarkably increased in both groups as compared with the baseline( P < 0. 05),but significantly more in the treatment than in the control group( P < 0. 05). Four pregnancies(5. 71%) were achieved in the former group but only 1(2. 00%) in the latter. The total rate of effectiveness was markedly higher in the treatment group than in the control(74. 28% vs 44. 00%,P < 0. 05). No adverse reactions were observed in either group. Conclusion: Compound amino acid combined with vitamin E can safely and effectively improve sperm motility in idiopathic asthenospermia patients.

Cytotoxic indole alkaloids against human leukemia cell lines from the toxic plant Peganum harmala.

Bioactivity-guided fractionation was used to determine the cytotoxic alkaloids from the toxic plant Peganum harmala. Two novel indole alkaloids, together with ten known ones, were isolated and identified. The novel alkaloids were elucidated to be 2-(indol-3-yl)ethyl-α-L-rhamnopyranosyl-(1 → 6)-ß-D-glucopyranoside (2) and 3-hydroxy-3-(N-acetyl-2-aminoethyl)-6-methoxyindol-2-one (3). The cytotoxicity against human leukemia cells was assayed for the alkaloids and some of them showed potent activity. Harmalacidine (compound 8, HMC) exhibited the highest cytotoxicity against U-937 cells with IC50 value of 3.1 ± 0.2 µmol/L. The cytotoxic mechanism of HMC was targeting the mitochondrial and protein tyrosine kinase signaling pathways (PTKs-Ras/Raf/ERK). The results strongly demonstrated that the alkaloids from Peganum harmala could be a promising candidate for the therapy of leukemia.

Triterpenoids of sour jujube show pronounced inhibitory effect on human tumor cells and antioxidant activity.

Sour jujube is a common fruit and traditional medicine in China. Bioactivity-guided fractionation of sour jujube was used to determine the chemical identity of potent antiproliferative and antioxidant constituents. Four novel ursane-type triterpenoids, together with 8 known were isolated and identified. The new triterpenoids were elucidated to be 2α,3ß,13ß,23-tetrahydroxy-urs-11-en-28-oic acid (3), 2α,3ß-dihydroxy-urs-20(30)-en-28-oic acid (9), 2α,3ß,28-trihydroxy-urs-20(30)-ene (10), and 3ß,12ß,13ß-trihydroxy-ursan-28-oic acid (11). Among the triterpenoids isolated, 2α,3ß,19α-trihydroxy-urs-12-en-28-oic acid (7), 9 and 10 showed high potent inhibitory activity toward the proliferation of HepG2 cells, which the IC50 values were lower than 5 µM. Compounds 9 and 10 also exhibited pronounced activity against MCF-7 cells, with IC50 value of 0.8 ± 0.03 and 1.5 ± 0.1 µM, respectively. Compound 10 showed high antioxidant activity with an EC50 of 0.8 ± 0.02 µM, which was 18.9 times higher than ascorbic acid in antioxidant capacity.

In vitro and in vivo antimammary tumor activities and mechanisms of the apple total triterpenoids.

Consumption of apples has been linked to the prevention of various chronic diseases, including tumors and cardiovascular diseases. The apple total triterpenoid content (ATT) was extracted and concentrated from apple peels. The in vitro and in vivo antitumor activities, related antitumor mechanisms, were investigated. In vitro, ATT showed potent antiproliferative activities against human breast cancer (MCF-7, MDA-MB-231), human colon cancer (Caco-2), and human liver cancer (HepG2) cell lines. In vivo antitumor experiments showed that ATT could substantially reduce the occurrence and growth of mammary tumor with a good dose-dependent manner in a rat model. During the apoptosis in MDA-MB-231 cells induced by ATT, the caspase-independent pathway was involved in the process of apoptosis, and the mitochondrial transmembrane potential was markedly reduced. Also the PI3K/Akt/NF-κB pathway was activated. These results indicated that ATT-induced apoptosis of MDA-MB-231 cells may involve a mitochondrial-related pathway.

Cytotoxic ceramides and glycerides from the roots of Livistona chinensis.

A 70% ethanol extract of the roots of Livistona chinensis has been investigated, led to the isolation of 13 compounds, including a new ceramide, (2S,3S,4R,9Z)-2-[(2R)-2-hydroxytricosanoylamino]-9-octadecene-1,3,4-triol (2), a new glycosyl ceramide, 1-O-ß-D-glucopyranosyl-(2S,3S,4R,9Z)-2-[(2R)-2-hydroxydocosanoylamino]-9-octadecene-1,3,4-triol (3), three new monoacylglycerols, 1-(34-hydroxytetratriacontanoyl)-sn-glycerol (9), 1-[nonadeca-(9Z,12Z)-dienoyl]-sn-glycerol (10), and 1-[12-hydroxypentatriaconta-(13E,15Z)-dienoyl]-sn-glycerol (11), a new diacylglycerol, 1-(heptadeca-6Z,9Z-dienoyl)-3-(octadeca-6Z,9Z,12Z-trienoyl)-sn-glycerol (12), as well as a new diacylglycerol aminoglycoside, 1-octadecanoyl-2-nonadecanoyl-3-O-(6-amino-6-deoxy)-ß-D-glucopyranosyl-sn-glycerol (13). The structures of new compounds were elucidated, based on spectroscopic, zymologic and chemical methods. Among the compounds tested, compounds 3, 4 and 13 showed significantly antiproliferative effects against the human tumor cell lines (K562, HL-60, HepG2, and CNE-1) with the IC50 of 10-65 µM. To our knowledge, this is first report of the occurrence of ceramides and acylglycerols in the genus Livistona.