Key Engineering Materials Vol. 508

Abstract: The Present Work Investigated the Effects of Adsorbed Moisture in Substrates on the Growth of a Self-Forming Barrier Layer between Mn and SiO₂. In Order to Control the Adsorbed Moisture, the Substrates of TEOS-SiO₂/Si Were Pre-Annealed in Vacuum at Various Temperatures. Then, Mn Thin Films Were Deposited on the Substrate with or without Pre-Annealing. The Results of Interface Reaction after Additional Post-Annealing Indicated that an Interface Reaction Layer Becomes Thinner with Decreasing the Adsorbed Moisture in the SiO₂ Substrates.

Abstract: hBN-TiN Binary Composite Was Fabricated Using Spark Plasma Sintering (SPS) at Temperatures between 1973 and 2273 K. With Increasing TiN Content from 10 to 90 Vol%, the Relative Density Increased from 75.7 to 96.4%. The Maximum Relative Density of 96.4% Was Achieved in the hBN-TiN Containing 90 Vol%TiN Sintered at 2273 K. hBN and TiN Was Stably Coexisted at 1973 K without TiB₂ Formation.

Abstract: The Powder Mixture of Thermally Exfoliated Graphite (TEG) and Amorphous Molybdenum (VI) Sulfide MoS₃ Has Been Annealed in Vacuum at 723, 1073, and 1273 K. The Obtained Samples Were Examined Using Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), and Raman Spectroscopy. XRD and Raman Spectroscopy Detected that the Main Product of MoS₃ Annealing Is MoS₂ Nanoparticles. TEM Images Showed the Formation of a Continuous Coating on the Surface of TEG Platelets at 1273 K and Fourier Analysis of the High Resolution TEM Image Revealed that this Coating Corresponds to the Mo₂S₃ Layers.

Abstract: The CNTs/PMMA Nanocomposite Foams Are a Kind of Novel Multifunctional Foams which Have a Potential Application for Lightweight Conductive and EMI Shielding Materials. In this Work, the CNTs/PMMA Nanocomposite Foams with Different CNTs Contents from 1wt.% to 10wt.% Were Prepared at a Temperature Range of 50-140 °C with Supercritical Carbon Dioxide as Blowing Agent. The Results Suggest that the Fully Heterogeneous Nucleation Is Achieved due to the Contribution of Well-Dispersed CNTs in PMMA. The CNTs/PMMA Nanocomposite Foams Exhibit a Uniform Cell Distribution, and the Cell Density Is Two Orders of Magnitude Higher than that of PMMA Foams. The Cell Size and Cell Density of CNTs/PMMA Nanocomposite Foams Could Be Controlled by Adjusting the Foaming Process and CNTs Contents. It Is Also Suggested that the Foaming Process Plays an Important Role on the Cell Structure Rather than that of CNTs Content when it Is Higher than 1wt.%.

Abstract: Silicon Carbide (SiC) Layers Were Prepared on Diamond Powders by Rotary Chemical Vapor Deposition (RCVD) Using C₆H₁₈Si₂ as a Precursor. Diamond Particles with Cleavable and Sharp Configurations Were Covered with Smooth Layers by RCVD. Infrared Absorption Bands at around 800 and 1000 cm^-1 Attributed to Si-C Bonding Were Observed in FTIR Spectrum on the Diamond Powders. The Pellet Sample Sintered by Spark Plasma Sintering Using the Diamond Powders Suggested that β-SiC Was Deposited on the Diamond Particles.

Abstract: In this Paper, Silicon Nitride Porous Ceramics with Hierarchical Porosity Were Prepared Using Pressureless Sintering and their Mechanical Properties as a Function of Porosity and Pore Size Were Analyzed. In these Porous Ceramics, Macro-Pores with the Pore Size of 0.1 µm Were Formed by the Continuous Reaction of ZrP₂O₇ at ~250 °C and Macro-Cellular Pores with the Pore Size of 10~30μm Were Formed by the Burnout of Starch at ~550 °C or the Sublimation of Naphthalene at 80 °C. The Flexural Strength Decreased from 105 MPa to 6 MPa with the Porosity Increased from 35% to 65%. The Obtained Results Showed that the Flexural Strength Was Fit for the Equation of σ=σ₀exp(-bP), where σ₀ Is the Bending Strength of Nonporous Body of the same Material, P Is the Porosity and b Is the Factor Determines by Pore Structure. The Difference of Pore Size Was Determined by the Different Value of b and the Value of b Increased with the Increasing of Pore Size. Macro-Pores with the Pore Size of 0.1 µm Referred to a b Value of 4.3 and Macro-Cellular Pores with the Pore Size of 10 μm and 30 μm Referred to a b Value of 5.1 and 6.0 Respectively.

Abstract: Carbon Nanotubes (CNTs) and Graphene Have Attracted Tremendous Attention as the Most Promising Carbon Nanomaterials in the 21st Century for a Variety of Applications such as Electronics, Biomedical Engineering, Tissue Engineering, Neuroengineering, Gene Therapy and Biosensor Technology. For the Biomedical Applications, Cnts Have Been Utilized over Existing Drug Delivery Vectors due to their Ability to Cross Cell Membranes Easily and their High Aspect Ratio as Well as High Surface Area, which Provides Multiple Attachment Sites for Drug Targeting. Besides, it Has Also Been Proved that the Functionalization of CNTs May Remarkably Reduce their Cytotoxic Effects and at the Same Time Increase their Biocompatibility. So, the Functionalized CNTs Are Safer than Pristine or Purified CNTs, Thus Offering the Potential Exploitation of Nanotubes for Drug Administration. On the other Hand, More Recently Graphene and its Derivatives Have Been Enormously Investigated in the Biological Applications because of their Biocompatibility, Unique Conjugated Structure, Relatively Low Cost and Availability on both Sides of a Single Sheet for Drug Binding. In Our Study, we Have Covalently Functionalized Multiwalled Carbon Nanotubes (MWCNTs) and Graphene Oxide (GO) with Highly Hydrophilic and Biocompatible Excipients in Order to Increase their Aqueous Solubility and Biocompatibility. Various Excipients Used Were Polyvinyl Alcohol, Pluronic F38, Tween 80 and Maltodextrin. The Poorly Water-Soluble Anticancer Drugs such as, Camptothecin and Ellagic Acid, Were Loaded onto the Functionalized MWCNTs and GO via Non-Covalent Interactions. Furthermore, Drug Loading and Cytotoxic Activity of Drugs Incorporated with the Functionalized MWCNTs and GO as Nanocarriers Were Also Investigated. Drugs Loaded on both Carbon Nanocarriers Exhibited a Higher Cytotoxic Activity than Free Drug. On the other Hand, No Significant Toxicity Was Found even at Higher Concentrations when the Cells Were Incubated with the Functionalized Mwcnts and GO. Therefore, both these Functionalized Carbon Nanomaterials Are Ideal Carriers for Drug Delivery.

Abstract: HfO₂ Has High Effective Atomic Number and No Radioactive-Isotope as the Background Source, and it Can Be the Candidate for the High-Stopping Scintillator Instead of Lu₂SiO₅:Ce Scintillator Used in Medical Imaging, Astronomy and etc. However, HfO₂ Has an Extremely High Melting Point of 2774 °C, and it Is Difficult to Grow the Crystal from the Melt Using Crucible, as there Is No Suitable Metals, which Can Survive around that Temperature. Thus, Czochralski, Bridgman, and Micro-Pulling down Method Cannot Be Applied. Therefore we Investigated Optical Properties of a 17-mol% b-Doped (Stabilized) HfO2 Crystal Grown by the Skull Melting Method, and this Crystal Had a High Refractive Index of 2.5 at 550 nm, and the Maximum Emission Peak at ~550 nm from ⁵D₄ Excited States of Tb³⁺. In Addition, we Found the Radiation Reaction of the Crystal Irradiated with Alpha and Gamma Rays Measuring with a Photomultiplier.

Abstract: Polymeric Micro-Fabricated Filters Have Excellent Sieving Properties. Their Identical Properties such as High Surface Porosity and Perfectly Patterned Pore Structure, which Is Combined with Mechanical Strength Make them Ideal for many Applications such as Microorganism Removal, Blood Filtration and Protein Purification. To Improve the Performance of the Micro-Fabricated Filters, we Employed Oxygen Plasma Treatment to Increase the Surface Hydrophilicity and Reduce the Membrane Fouling during Microfiltration. Hydrophilization and Integrity of the Surfaces Were Analyzed by Contact Angle Measurements and Topographic Imaging with an Atomic Force Microscope (AFM). Treatment of Polymeric Membranes with Oxygen Plasma Led to a Stable Hydrophilization and an Increased Surface Roughness. The Filtration Properties of the Modified and Unmodified Membranes Were Examined Using Clay Particles. A Significant Increase in Total Collected Volume of Filtrate Was Observed for the Treated Membranes during Filtration of Simulated Drinking Water Samples Using Clay Suspension.

Abstract: Fe-Si-B Amorphous Alloys with Less than 80 at% Fe Are now in Practical Use due to their Excellent Magnetic Softness (Low Coercivity H_c) Combined with Rather High Saturation Magnetic Polarization (J_s) which Basically Owing to the Lack of Intrinsic Magnetic Anisotropy and the High Fe Content, Respectively. In Order to Obtain High J_s, High Fe Content Is Required. However, Alloys with High Fe Content Exceeding the Limit Usually Have the as-Quenched Structure Consisting of Coarse α-Fe Grains in the Amorphous Matrix, which Results in Inferior Magnetic Softness. We Have Developed a New Fe_85.2B₁₀P₄Cu_0.8 Nanocrystalline Soft Magnetic Alloy Ribbon (with 5 mm in Width and about 20 µm in Thickness) Made from Industrial Raw Materials in Air Atmosphere. The as-Quenched Structure of Fe_85.2B₁₀P₄Cu_0.8 Alloy Has Heterogeneous Amorphous Structure (a Large Amount of Extremely Small α-Fe Clusters in Addition to Amorphous Phase). Homogeneous Nanocrystalline Structure Composed of α-Fe Grains with a Size ~19 nm Was Realized by Crystallizing the Hetero-Amorphous Alloy. The Nanocrystalline Alloy Exhibit High J_s ~ 1.83 T (Comparable to the Commercial Fe-3.5 Mass% Si Steel) and Extremely Low H_c ~ 6.0 A/m. Additionally the Alloy Has a Large Economical and Industrial Advantage of Lower Material Cost and Good Reproductivity, which Has a High Potential for the Power Applications.