Implant Strength Contributes to the Osseointegration Strength of Porous Metallic Materials.

Creating the optimal environment for effective and long term osseointegration is a heavily researched and sought-after design criteria for orthopedic implants. A validated multimaterial finite element (FE) model was developed to replicate and understand the results of an experimental in vivo push-out osseointegration model. The FE model results closely predicted global force (at 0.5 mm) and stiffness for the 50-90% porous implants with an r2 of 0.97 and 0.98, respectively. In addition, the FE global force at 0.5 mm showed a correlation to the maximum experimental forces with an r2 of 0.90. The highest porosity implants (80-90%) showed lower stiffnesses and more equitable load sharing but also failed at lower a global force level than the low porosity implants (50-70%). The lower strength of the high porosity implants caused premature plastic deformation of the implant itself during loading as well as significant deformations in the ingrown and surrounding bone, resulting in lower overall osseointegration strength, consistent with experimental measurements. The lower porosity implants showed a balance of sufficient bony ingrowth to support osseointegration strength coupled with implant mechanical properties to circumvent significant implant plasticity and collapse under the loading conditions. Together, the experimental and finite element modeling results support an optimal porosity in the range of 60-70% for maximizing osseointegration with current structure and loading.

First-principles study of two-dimensional half-metallic ferromagnetism in CrSiSe4monolayer.

Two-dimensional (2D) ferromagnetic (FM) half-metallic materials have attracted intensive attention due to their unique electronic and magnetic properties and potential applications in spintronic devices. In this study, we predicted a stable 2D half-metallic material monolayer CrSiSe4using first-principles density functional theory. The structure, electronic and magnetic properties were systematically studied. The calculations show that the monolayer CrSiSe4is a dynamically stable FM half-metallic material. The spin-dependent transport properties and the Curie temperature up to 239 K are demonstrated. The spin band gap of monolayer CrSiSe4was about 0.83 eV by the the Heyd-Scuseria-Ernzerhof function calculation. The magnetic anisotropy energy of each Cr atom in the monolayer of CrSiSe4is-552.3µeV. When the applied biaxial tensile strain is greater than 2%, monolayer CrSiSe4spin-up conduction band and valence band will show a band gap at the Fermi level, and the electronic properties change from a half-metal to a semiconductor. Thus, the monolayer CrSiSe4can provide an ideal candidate material for exploring 2D magnetic and spintronics experiments.

Testing technology for tensile properties of metal materials based on deep learning model.

The properties of metallic materials have been extensively studied, and nowadays the tensile properties testing techniques of metallic materials still have not found a suitable research method. In this paper, the neural Turing machine model is first applied to explore the tensile properties of metallic materials and its usability is demonstrated. Then the neural Turing machine model was improved. The model is then improved so that the required results can be obtained faster and more explicitly. Based on the improved Neural Turing Machine model in the exploration of tensile properties of metal materials, it was found that both H-NTM and AH-NTM have less training time than NTM. A-NTM takes more training time than AH-NTM. The improvement reduces the training time of the model. In replication, addition, and multiplication, the training time is reduced by 6.0, 8.8, and 7.3%, respectively. When the indentation interval is 0.5-0.7 mm, the error of the initial indentation data is large. The error of the tensile properties of the material obtained after removing the data at this time is significantly reduced. When the indentation interval is 0.8-1.5 mm, the stress is closer to the real value of tensile test yield strength 219.9 Mpa and tensile test tensile strength 258.8 Mpa. this paper will improve the neural Turing machine model in the exploration of metal material tensile properties testing technology has some application value.

The Effect of Cylindrical Liner Material on the Jet Formation and Penetration Capability of Cylinder-Cone-Shaped Charge.

The jet formation and penetration capacity of cylinder-cone-shaped charges against steel targets were studied using the method of numerical simulation. Cylinder-cone-shaped charge models with five cylindrical liner materials, including nickel, tungsten, tantalum, steel 4340 and copper, were established to investigate the penetration capability and were compared with the classical conical-shaped charge. Moreover, the influence of the connection method of the cylindrical liner and the truncated liner on the jet performance was examined. The results show that the head velocity of the projectile formed by the cylinder-cone-shaped charge with a cylindrical nickel liner was larger than that with other cylindrical liner materials; in addition, it was larger by 50.2% compared with that formed by the classical conical-shaped charge. The penetration depth of the steel target by the cylinder-cone-shaped charge with a cylindrical copper liner was the largest, which could be 51.7% higher than that of a classical conical-shaped charge at a standoff of 2.5 D. For 2.0 D and 2.5 D standoff distances, the penetration depths were increased by 18.4% and 29.5%, respectively, by using the connection method of putting the cylindrical nickel liner on the neck of the truncated liner compared with that of the previous cylinder-cone-shaped charge with a cylindrical nickel liner.

Nano-Gradient Materials Prepared by Rotary Swaging.

Gradient nanostructured metallic materials with a nanostructured surface layer show immense potential for various industrial applications because of their outstanding mechanical, fatigue, corrosion, tribological properties, etc. In the past several decades, various methods for fabricating gradient nanostructure have been developed. Nevertheless, the thickness of gradient microstructure is still in the micrometer scale due to the limitation of preparation techniques. As a traditional but potential technology, rotary swaging (RS) allows gradient stress and strain to be distributed across the radial direction of a bulk cylindrical workpiece. Therefore, in this review paper, we have systematically summarized gradient and even nano-gradient materials prepared by RS. We found that metals processed by RS usually possess inverse nano-gradient, i.e., nano-grains appear in the sample center, texture-gradient and dislocation density-gradient along the radial direction. Moreover, a broad gradient structure is distributed from center to edge of the whole processed rods. In addition, properties including micro-hardness, conductivity, corrosion, etc., of RS processed metals are also reviewed and discussed. Finally, we look forward to the future prospects and further research work for the RS processed materials.

Polarization Selectivity of the Thin-Metal-Film Plasmon-Assisted Fiber-Optic Polarizer.

The interaction between light and metallic nanostructures leads to many impressive achievements and has a wide range of applications. The thin-metal-film plasmon-assisted fiber-optic polarizer is one of the essential applications. However, the polarization mechanism and the transmitted polarization of the plasmon-assisted polarizer have given rise to controversy over the past decade. Which of the polarizations is preferentially transmitted through the polarizer? The transverse electric polarization or the transverse magnetic polarization? Here, special emphasis is placed upon the polarization mechanism and the transmitted polarization of thin-metal-film plasmon-assisted fiber polarizers. We first investigate the polarization mechanism of the polarizers theoretically and numerically. Furthermore, a novel approach is proposed to demonstrate the transmitted polarization in the plasmon-assisted fiber polarizers experimentally. We demonstrate that the polarization mechanism is based on the polarization selective absorption of the metallic material, and the transverse electric polarization is the only transmitted polarization of the metallic plasmon-assisted polarizer. Moreover, the plasmon-assisted polarizer can offer a high polarization extinction ratio (33.1 dB) and a low insertion loss (1.1 dB) at room temperature and have excellent temperature stability in the range of -48 to 82 °C. Experimental results agree well with our theoretical and numerical analyses. The findings clarify the confusion about the polarization mechanism and the transmitted polarization of metallic plasmon-assisted fiber polarizers over the past decade, providing new ground for the exploration of polarization-sensitive optical systems, with good potential applications in the fields of optical sensors, plasmonic lasers, coherent optical communications, and biosensor systems.

Effects of palm biodiesel and blends of biodiesel with organic acids on metals.

This paper presents the corrosion behavior studies of five metallic materials used in auto part manufacturing exposed to pure palm biodiesel (B100) and palm biodiesel mixed with acidic species commonly found in biodiesel. Samples of AISI-SAE 1005 carbon steel, AISI-SAE 304 stainless steel, tin, aluminum and copper were exposed to a temperature of 45 °C for 12 months. The highest corrosion rates were present in totally immersed copper (B100-acetic acid blend) and in carbon steel (B100-oleic acid blend). The most corrosive blends for the metallic materials were B100-linoleic acid, B100-oleic acid and B100-acetic acid. The efficacy of two corrosion inhibitors, ethylenediamine (EDA) and tert-butylamine (TBA) increased as a function of exposure time. The characterization tests allowed the detection of different species, in the products of steel corrosion, associated with, lepidocrocite, ferrihydrite, magnetite, and some iron carbonates. In turn, cuprite, malachite, azurite, and some copper carbonates were found on the copper samples. Such corrosion products formed protective layers on the surface of the metals, which is reflected in a decrease in corrosion rates over time.

Different material factors affect the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells / 中国组织工程研究

BACKGROUND: In the treatment of bone defect or bone injury by tissue engineering, biomaterials affect the survival rate, proliferation and differentiation of bone marrow mesenchymal stem cells. OBJECTIVE: To review the research progress regarding how biomaterials affect the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells, and to guide the rational application of biomaterials. METHODS: A computer-based online search of CNKI, PubMed, Web of Science, and Wanfang database with the search terms “Bone marrow mesenchymal stem cells, Osteogenic differentiation, Biological materials, The microstructure”. The eligible literatures regarding the effects of different biomaterials on the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells were included. RESULTS AND CONCLUSION: (1) Metallic materials have the advantages of good biocompatibility, bone conductivity, and mechanical performance. Non-metallic materials exhibit good biocompatibility, bone conductivity, reabsorption, and three-dimensional shaping. (2) There are many factors that affect the surface microstructure of the biomaterial. As for the same biomaterial, greater surface energy/ wettability leads to better proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells; greater roughness better promotes the proliferation, adhesion, and differentiation of bone marrow mesenchymal stem cells; larger pore diameter and lower pore diameter rate are more prone to promote the osteogenic differentiation of bone marrow mesenchymal stem cells; greater substrate rigidity and elastic modulus better facilitate the osteogenic differentiation of bone marrow mesenchymal stem cells. The abovementioned factors of the biomaterials affect the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. These findings help promote the application of biomaterials seeded with bone marrow mesenchymal stem cells in the clinic.

Degradation behavior of Ca-Mg-Zn intermetallic compounds for use as biodegradable implant materials.

With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca-Mg-Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15-x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250 h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions.

The method of removing hardly soluble organic material from metallic specimen used in fracture surface analysis by scanning electron microscope.

Epoxy resin attached to a fatigue fracture surface of Ti-Al-Nb alloy was removed using a removal method for hardly soluble organic material attached to metallic material, which has been developed by the author. In the removal method process, the epoxy resin attached to the fracture surface was treated with an organic solvent, `tetrahydrofuran', and cold concentrated sulfuric acid of nearly 100% purity. After the epoxy resin was removed from the fracture surface with the removal method, damage of the microscopic feature of the fracture surface was investigated using a scanning electron microscope (SEM). For the first time, the degree of the removal of the epoxy resin with the method was investigated by energy dispersive X-ray spectroscopy (EDS) in this research. After the removal, no damage of the fracture surface was found with SEM observation. In addition, C Kα derived from the epoxy resin was not detected with the EDS after removal. The result of the EDS analysis clarified that the epoxy resin was completely removed with the removal method.

Parallel glide: flow of dislocations with internal stress source/sink distribution.

The unexpected glide of dislocations on a plane parallel to the film/substrate interface in ultrathin copper films, which has been called parallel glide (Balk et al 2003 Acta Metall. 51 447), is described using an analytical model. The phenomenon is observed as a problem involving inlet/outlet flow from different positions of a grain boundary into the grain channel. In this sense, parallel glide is presented as the flow of dislocations with an internal stress source/sink distribution.