Physicochemical Degradation of Titania-Stabilized Soluble Phosphate Glasses for Medical Applications

Four different formulations of phosphate glasses in the system P₂O₅–CaO–Na₂O–TiO₂ were developed. Their physicochemical, morphologic, and structural evolution was analyzed during in vitro degradation in SBF (simulated body fluid) at 37°C up to 16 weeks. The results showed that the addition of TiO₂ into the glass system enhanced both the elastic modulus and the chemical durability of the glasses. Indeed, the elastic modulus increased from 66.6 to 75.95 GPa and the weight loss percentage diminished from 1.6% to 0.3% with the addition of 8 mol% TiO₂. A uniform and superficial degradation mechanism could be observed throughout the dissolution time by means of environmental scanning electron microscopy (ESEM), inductively coupled plasma mass spectroscopy (ICP-MS), and Raman spectroscopy. The degradation process undergone by these glasses allows them to maintain their mechanical properties during the degradation process. Therefore, these materials offer an interesting choice for slowly resorbable materials in biomedical applications.     

高可靠性的轴位监控仪

介绍了一种新研制的轴位监控仪的工作原理及几个主要电路的设计方案（如警告、报警、危险报警、监视电路）．列出了该仪器警告报警与危险报警的实测数据。     

化工装置反应能量系统的(火用)传递描述

对反应(能量)系统的描述,焓分析法单讲能的量的利用,火用分析法只作静态描述,只有火用传递法可作动态描述。运用火用传递理论分析,反应系统具有化学火用转换元在系统中起主导作用,各输火用元皆以反应高温火用源为公共火用源,呈放射型并联结构的特点。据此建立的反应系统通用火用传递模型——化学火用转换元与输火用元并联群相串联的串-并联复合结构模型,清楚地显示了模型的结构特点和基本特征。基于反应系统化学平衡、火用平衡方程和传递学原理建立的系统火用传递方程,揭示了系统中计量和过量反应物、生成物,以及杂质等各项火用流变化率的性质及其相互转换或传递的数量关系,由此可获得对反应系统火用传递机理的清晰描述,进而可以作反应系统的火用传递计算和火用传递分析。     

Physical,chemical, and biological investigations of composites for biomedical applications

In this article, the interplay between structural, electrical, and surface properties in determining the collective behavior of (hydroxyapatite, HAP) and (strontium titanate, ST) composites was reported. The monoliths HAP and ST were synthesized using sol-gel and solid-state reaction, respectively, and were mixed in different atomic concentrations (20, 40, 60, and 80 at.%) to prepare a series of composites. The prepared composites were then subjected to x-ray diffraction (XRD) and Raman analysis for probing the microstructural aspects. The analysis revealed no evidence of a phase that the reaction between the two monoliths might form. The crystallite sizes were in the range of 27.2–37.3 nm, and it increased with the content of ST in the composites. The Raman analysis revealed the presence of rutile that was later found to be the link in the display of bone-like apatite nucleation ability in the monolith ST and its composites. The FESEM analysis revealed that the grain sizes were 64–144 nm between the monoliths and were found to follow a similar trend to the crystallite size. The dielectric constant varied with temperature ranging from 5 to 35 (1 MHz) at 310 K for all the specimens. The dependence of on the grain size of the composites followed a nearly exponential relation. The bone-like apatite forming ability of the composites was studied by incubating the specimens in simulated body fluid (SBF). Additionally, the cytocompatibility (MG63 cell lines) and protein adsorption (bovine serum albumin [BSA]) of the selected specimens were also studied to comprehensively understand the delicate relationship between the electrical and biological properties. The protein adsorption was primarily related to the surface charge, and its dependence was found to be linear. Additionally, the of the composites was ≤35, which compliments the protein adsorption behavior of the specimens. The amount of adsorbed protein for all the specimens considered in this study was in the range of 3–32 μ g/ml. Furthermore, the specimens exhibited excellent cell viability of more than 90%. Based on the physical and biological investigations, 20H-80S was established as the best specimen that blends the characteristic feature of both the monoliths. Finally, the TEM and STEM mapping of the best specimen, projecting the suitability of 20H-80S in the design of electrically active scaffolds and possibly bioelectrets for biomedical applications, was also studied.     

A Layered Alumina Composite Tested at High Temperature in Air

An oxidation-resistant interphase for layered alumina composites was prepared by aerosol spray deposition of submicrometer alumina powder. A model composite specimen was made by placing the interphase between thin layers of monolithic alumina. The composite sandwich was hot-pressed to control the interphase fracture resistance for successful crack deflection. Specimens were tested under four-point bending in air at two crosshead speeds at ambient temperature, 1000°C, and 1200°C. The fracture behavior was temperature dependent, with a higher work of fracture at higher temperatures. Interphase delamination and composite toughening behavior were very pronounced at all temperatures. At the highest temperature, the transition to multiple widely distributed cracks and increased crack deflection may be related to inelastic deformation in the alumina.     

Analytical Modeling of Chemical Vapor Infiltration in Fabrication of Ceramic Composites

A model for chemical vapor infiltration is applied to the study of the growth of alumina from the chemical reaction among AlCl₃, H₂, and CO₂ within a SiC-fiber bundle which is situated in an isothermal hot-wall reactor. The pore space between the fibers is simulated by cylindrical capillary tubes. The model considers binary diffusion of CO₂ and H₂, chemical reaction on the inner surface of the tube, and deposition film growth. Furthermore, diffusion-controiled and chemical-reaction-controlled processes are taken into account to determine the dominating process in chemical vapor infiltration. Both molecular diffusion and Knudsen diffusion are considered sequentially in this model during the infiltration process. Based upon this model, the optimum processing conditions required for chemical vapor infiltration to form a SiC/Al₂O₃ composite can be predicted for different fiber preform systems.     

Oxidation protective multilayer coatings for carbon-carbon composites

An oxidation protective double layered coating was deposited on a carbon-carbon composite (C/C) using a simple and low cost method. A surface modification of the C/C was obtained by direct reaction of liquid silicon with the C/C, promoting the formation of a 5-10 μm β-SiC layer on the composite surface. The inner layer, in contact with the C/C, is a composite made with a barium borosilicate glass matrix (SABB) and boron carbide particles; the outer layer is another composite layer formed by a SABB glass matrix and yttrium oxide particles. The layers are deposited by a slurry technique. Oxidation tests were carried out in a furnace in air, in order to verify the coating stability and its effectiveness. No mass loss of the C/C composite was observed after 100 h at 1200°C, while after 150 h at 1300°C the C/C mass loss did not exceed 1%.     

Recent advances in flexible sensors for wearable and implantable devices

Flexible devices are emerging as important applications for future display, robotics, in vitro diagnostics, advanced therapies, and energy harvesting. In this review, we provide an overview of recent achievements in flexible mechanical and electrical sensing devices, focusing on the properties and functions of polymeric layers. In the order of historical development, sensing platforms are classified into four types: electronic skins for robotics and medical applications, wearable devices for in vitro diagnostics, implantable devices for human organs or tissues for surgical applications, and advanced sensing devices with additional features such as transparency, self‐power, and self‐healing. In all of these examples, a polymer layer is used as a versatile component including a flexible structural support and a functional material to generate, transmit, and process mechanical and electrical inputs in various ways. We briefly discuss some outlooks and future challenges toward the next steps for flexible devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1429–1441, 2013     

Atomic layer deposition onto carbon fiber fabrics

Carbon fiber fabrics, consisting of interwoven bundles of 3000 single fibers, were coated with Al₂O₃ using the atomic layer deposition (ALD) process, exposing the fabrics to alternating pulses of trimethyl aluminium and water vapors. The thickness and uniformity of the coatings were investigated using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The obtained coatings were conformal, 84 ALD cycles gave rise to approximately 20‐nm‐thick coatings and 168 ALD cycles to approximately 40‐nm‐thick coatings. It was found, that a uniform coating can be obtained at a purge time of 40 seconds. Reducing purge times below 20 seconds gives rise to increased particle growth and thus the coating becomes inhomogeneous. Initially, the samples that were coated had a size of 2×10 cm (thickness 0.3 mm). The size of the fabric was subsequently increased up to 8×20 cm and a uniform coating of the same quality was obtained. By oxidizing the coated fabrics, fabrics composed of interwoven alumina microtubes were obtained. Infiltration of the microtubes with solutions of two distinguishable fluorescent dyes showed that interchange of the dyes between warp and weft microtubes occurs, but is absent at approximately 20% of the crossovers. Taking all our findings into account, we conclude that the majority of the fibers were separated from each other by the coating prior to the oxidation. This work demonstrates that ALD is a suitable method to produce thin, conformal coatings on the surface of carbon fiber fabrics.     

Preparation of core–shell structured alumina–polyaniline particles and their application for corrosion protection

Polyaniline (PANI) was synthesized by chemical oxidative polymerization of aniline (ANI) in the presence of alumina (Al₂O₃) particles. The polymerization of ANI occurred preferentially on the surfaces of the particles, resulting core–shell structured alumina–polyaniline (Al₂O₃‐PANI) particles. Morphology examination showed that with decreasing of the weight ratio of Al₂O₃/ANI in the reactants, the thickness of the PANI layer increased and changed from an even surface morphology to a particulate morphology. UV–vis and Fourier transformed infrared (FTIR) spectra indicated that there is no chemical interaction between the PANI layer and the Al₂O₃ surfaces. The PANI layer adhered well to the particles and can be used as anticorrosive fillers for polymer coatings. Enhanced corrosion protection performance was achieved for the emeraldine base (EB) form of PANI deposited Al₂O₃ particles (Al₂O₃‐EB) filled epoxy coating on carbon steel in 3.0 wt % aqueous NaCl solution. The particles demonstrate both excellent corrosion protection performance and lower cost, which will be of great importance in practical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4372–4377, 2006     

塑木复合材料助剂进展

综述了塑木复合材料（WPC）的优点、市场情况及前景,主要塑木助剂的作用和发展趋势以及为了改善WPC制品的户外耐用性和外观开发的与WPC助剂（包括润滑剂、相容剂、发泡剂、抗菌剂和着色剂）相关的新技术。     

Mixed matrix membranes as potential transdermal devices for gemfibrozil release

Aim of this work was the development of mixed matrix membranes as potential devices for transdermal controlled release of gemfibrozil (2,2‐dimethyl‐5‐(2,5‐dimethylphenoxy) pentanoic acid). The effect of the hydrophilic NaX zeolite and of drug loading on the release kinetics of the drug was investigated. The material used as membrane matrix was polydimethylsiloxane. Scanning electron microscopy analysis showed as zeolite crystals were well embedded into the polymeric matrix. Membrane characterizations by means of swelling ratio, moisture uptake, and erosion degree determination indicated low swelling degree and moisture uptake, and the absence of erosion. This results confirmed as these membranes did not promote bacterial growth and skin irritation. The performance of the membranes was evaluated by performing in vitro release studies and percutaneous tests through the stratum corneum taken from the skin of rabbit ear. In vitro experiments indicated as the best system was the membrane containing 12 wt % of zeolite and 2.6 wt % of gemfibrozil (PDMS‐2.6GEM‐12NaX) and so it was used in the percutaneous tests. In this case, the permeation rate was lower owing to the presence of an additional resistance applied by rabbit skin. An interesting result was the linear behavior indicating that the permeation of the drug thorough the device occurred with zero‐order kinetic which is the feature of the transdermal controlled delivery systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41698.     

Isopropyl myristate modified silicone as a potential new encapsulating material for implantable devices

A new modified silicone was obtained by the physical entrapment of a hydrophobic lipid, isopropyl myristate (IPM), to improve the encapsulation properties and corrosion resistance of medical electronic implants. Differences between the water transport for films in contact with water vapor versus those in contact with liquid water were identified; they showed increased permeability to water vapor, which was possibly the result of differences in the water organization at the hydrophobic film interface. Improvements, including enhanced scratch resistance and adhesion, in the mechanical properties of the modified material was also achieved. The incorporation of IPM further resulted in a significant improvement in the cell biocompatibility compared with the unmodified polymer; this suggested that the IPM combination could be a viable basis for implant device packaging. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A New Vapor Deposition Method to Form Composite Anodes for Solid Oxide Fuel Cells

A solid oxide fuel cell (SOFC) is a complete solid-state energy conversion device with the potential advantages of high efficiency, silent operation, and low emissions. However, the current performance of SOFCs is still limited by a number of problems. Investigations in this field have indicated that it is imperative to fabricate efficient and compatible anodes for SOFCs to minimize polarization loss and to concurrently achieve long-term stability. In this paper, a critical review of previous studies is given and several criteria for the theoretically ideal anode are summarized. Accordingly, a newly developed vapor deposition technique, polarized electrochemical vapor deposition (PEVD), is applied to fabricate composite anodes to meet these criteria. The initial experimental results in the present study show that PEVD is capable of depositing a thin layer of yttria-stabilized zirconia on a porous metallic electrode to form a composite anode. This will not only provide continuous ionic and electronic conducting paths in the anode to reduce the overpotential loss and resistance, but also protect the metallic electrode from further sintering, vapor loss, and poisoning in the harsh SOFC operating conditions.     

Gradient HfB2-SiC multilayer oxidation resistant coating for C/C composites

The gradient HfB₂ modified SiC coating was prepared on the surface of SiC-coated C/C composites by in-situ synthesis. Anti-oxidation behaviors of the coated C/C samples at 1773, 1873 and 1973?K were investigated. The results show that the gradient HfB₂ modified SiC coatings possess excellent oxidation resistance, which can protect C/C substrates from oxidation for 800, 305 and 100?h at 1773, 1873 and 1973?K, respectively. In addition, with the oxidation temperature increasing, the evaporation of the Hf-Si-O glass layer and the active oxidation of SiC were accelerated, which is the reason for the worst oxidation resistance of the sample at 1973?K among the three temperatures.     

Whisker Toughening: A Comparison Between Aluminum Oxide and Silicon Nitride Toughened with Silicon Carbide

Two whisker-toughened materials have been studied, with the objective of identifying the mechanisms that provide the major contribution to toughness. It is concluded that, for composites with randomly oriented whiskers, bending failure of the whiskers obviates pullout, whereupon the major toughening mechanisms are the fracture energy consumed in creating the debonded interface and the stored strain energy in the whiskers, at failure, which is dissipated as acoustic waves. The toughening potential is thus limited. High toughness requires extensive pullout and, hence, aligned whiskers with low fracture energy interfaces.     

A critical review of bioceramics for magnetic hyperthermia

Magnetic hyperthermia (HT) using biocompatible ceramics is a ground-breaking, competent, and safe thermo-therapeutic strategy for cancer treatment. The magnetic properties of bioceramics, along with their structure and synthesis parameters, are responsible for the controlled heating of malignant tumors and are the key to clinical success. After providing a brief overview of magnetism and its significance in biomedicine, this review deals with materials selection and synthesis methods of bioceramics/glasses used for HT. Relevant research carried out on promising bioceramics for magnetic HT, with a focus on their size, shape, surface functionalization, magnetic field parameters, and in vitro/in vivo properties to optimize cancer therapy, is also discussed. Recent progress in magnetic HT combined with chemotherapy and phototherapy is especially highlighted, with the aim to provide interdisciplinary knowledge to advance further the applications of bioceramics in this field.     

A novel strategy for fabricating zirconia implants with a trabecular biomimetic porous surface

For successful osseointegration of load-bearing implants, an improved bone–implant contact area through a trabecular porous surface resulting in minimized stress shielding effect is highly desirable. We propose a novel strategy of green net shaping a ceramic dough, combined with a reticular foam replica method and gradient coating, to fabricate biomimetic porosity in a customizable ceramic dental implant for the first time. About 85 vol% porosity and 300–600-μm pore size were evident in microCT and electron microscopy of the sintered samples, suitable for bone ingrowth. Excellent integrity at the interface along with homogeneous distribution of secondary alumina phase in zirconia matrix was achieved, despite the difference in the green state powder loading between the dough and the slurry.     

热压法制备Al2O3/TiB2/AlN/TiN复合陶瓷

将金属Al,Al3Ti和TiB2以AlTiB中间合金的形式引入Al2O3基体材料中,利用热压法制备Al2O3/TiB2/AlN/TiN复合陶瓷.探讨了复合陶瓷致密化程度与AlTiB体积含量之间的关系.复合陶瓷在烧结过程中属过渡液相烧结.烧结过程中Al,Ti和N2(保护气氛)通过化学反应生成新相AIN和TiN.对热压烧结后材料的硬度、断裂韧性和抗弯强度进行了测试和分析.分析了复合陶瓷的力学性能随AlTiB体积含量变化的规律.比较了复合陶瓷1500℃和1600℃的相对密度及力学性能.探讨了复合陶瓷断面断裂方式的变化对其力学性能的影响,并分析了AlTiB中间合金的细化特性.