A novel real-time confocal imaging technique for examining host–implant interfacial shear failure patterns

In clinical practice, implant failure usually occurs at the biomaterial–host tissue interface, typically involving both biomechanical and biochemical mechanisms. By definition, any new ‘bioactive’ material will bond to living bone but, prior to clinical use, interface formation, performance, longevity and failure pattern characterizations are necessary. The common missing link in many biomaterial interface investigations is imaging at the point of presumed loaded failure. The novel real‐time confocal technique described here allows bond strength, formation rate, longevity and bone–material interface failure pattern characterization for a wide range of biomaterials capable of forming tissue interfaces, in one real‐time imaged microshear stress process, conducted using imaging frame matched load/displacement data acquisition under relatively normal near in vivo environmental conditions. The technique, validated by post‐failure scanning electron microscopy imaging, revealed that more slowly reacting melt‐derived 45S5 glass materials produced stronger and more stable long‐term interfaces than faster reacting microporous bioactive sol‐gel glasses.     

Ion microprobe studies of reactions in squeeze-cast aluminium alloy matrix composites

An ion microprobe with high lateral resolution has been used to study the chemical reactions at the fibre/matrix interface of metal–matrix composites. During the squeeze-casting process, the Al–Si–Mg matrix reacts with the preform made of Saffil fibres (96% Al₂O₃, 4% SiO₂). The reaction occurs mainly between the silica binder and Mg from the matrix according to SiO₂ + 2Mg = 2MgO + Si. A continuous layer of MgO was formed around the fibres, even on surfaces that were not covered by the silica binder. Possible reasons are discussed for the formation of MgO in areas where binder coating was missing. In such areas, Mg reduces SiO₂ that is contained in the fibre. However, the fibres (A1₂O₃) are not attacked by Mg. In the isolated case of fibres that were completely uncoated, no reaction products were observed at the interface. The presence of silica binder seems to be an essential requirement for this reaction to occur. When squeeze-casting is performed with sufficiently high melt temperature, Al from the matrix also reduces silica.     

The formation of micro-blisters on Al–Mg alloy surfaces during hot rolling

Micro-blisters occurring on the surfaces of Al–Mg alloys after the first hot rolling pass were studied. The micro-blisters had a nanocrystyalline structure and comprised of an outer MgO shell and an inner Al/Al₂O₃ lining. It is proposed that the micro-blisters are linked to the presence of carbide particles protruding from the work roll surface and the evolution of hydrogen from the reaction of water vapor, permeated through the porous oxide-rich surface layer, with the bulk aluminum.     

The degradation of EBSD-patterns as a tool to investigate surface crystallized glasses and to identify glassy surface layers

Surface crystallized samples of glass-ceramics containing cordierite, rhombohedral BaAl₂B₂O₇ and fresnoite were analyzed using electron backscatter diffraction (EBSD). The first two materials were chosen because surface crystallized samples of these materials have previously been shown to contain crystals covered by a very thin layer of glass. In all materials, EBSD pattern degradation occurs if the step size of a scan is chosen to be small. It is shown that the minimum step size enabling an evaluable EBSD-scan increases notably, if the crystals are covered by a thin layer of glass. It is also shown that pattern degradation may be utilized to prove the existence of such a thin glass or otherwise thermally sensitive layer. This provides significant information concerning the nucleation process of glasses also with respect to nucleation theory of glass-ceramics. It is also possible to describe the quantity of crystalline surface covered by the thermally sensitive layer.     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

XPS研究吖啶橙掺杂玻璃

采用低温熔融法制备了磷酸盐基质玻璃及掺杂有机染料吖啶橙的有机/无机玻璃复合材料。用x-射线光电子能谱(XPS)测试研究了两类玻璃的结构特性。F_Is的XPS谱为双峰,说明玻璃中的F以两种键合状态存在。高能峰在687.0～687.2ev,属于P-F键；低能峰位于684.6～684.7ev,属于M-F键(M=Sn²⁺和或Pb²⁺).O_is谱给出了桥氧(BO)和非桥氧(NBO)的相对含量。有机染料吖啶橙掺杂到基质玻璃中后,F_Is谱中P-F键的相对含量增加。     

Cryo-X-ray analysis-A novel tool to better understand the physicochemical reactions at the bioglass/biological fluid interface

The present study deals with the short-term physicochemical reactions at the interface between bioactive glass particles [55SiO(2)-20CaO-9P(2)O(5)-12Na(2)O-4MgO. mol%] and biological fluid (Dulbecco Modified Eagle's Medium (DMEM)). The physicochemical reactions within the interface are characterized by scanning transmission electron microscopy (TEM) (STEM) associated with Energy-dispersive X-ray spectroscopy (EDXS). Microanalysis of diffusible ions such as sodium, potassium, or oxygen requires a special care. In the present investigation the cryo-technique was adopted as a suitable tool for the specimen preparation and characterization. Cryosectioning is essential for preserving the native distribution of ions so that meaningful information about the local concentrations can be obtained by elemental microanalysis. The bioglass particles immersed in biological fluid for 24 h revealed five reaction stages: (i) dealkalization of the surface by cationic exchange (Na(+), Ca(2+) with H(+) or H(3)O(+)); (ii) loss of soluble silica in the form of Si(OH)(4) to the solution resulting from the breakdown of Si--O--Si bonds (iii); repolymerization of Si(OH)(4) leading to condensation of SiO(2)); (iv) migration of Ca(2+) and PO(4) (3-) to the surface through the SiO(2)-rich layer to form CaO-P(2)O(5) film; (v) crystallization of the amorphous CaO-P(2)O(5) by incorporating OH-- or CO(3) (2-) anions with the formation of three different surface layers on the bioactive glass periphery. The thickness of each layer is approximately 300 nm and from the inner part to the periphery they consist of Si--OH, which permits the diffusion of Ca(2+) and PO(4) (3-) ions and the formation of the middle Ca--P layer, and finally the outer layer composed of Na--O, which acts as an ion exchange layer between Na(+) ions and H(+) or H(3)O(+) from the solution.     

Amorphous calcium phosphate (ACP) in tissue repair process

Synthetic biomaterials submitted to new structural technologies have become ideal for the recovery of traumatized bone tissues and some bone substitutes such as bioactive glass, β‐Tricalcium phosphate (β‐TCP) and amorphous calcium phosphate (ACP) are being used in areas of tissue defects. For this study, ACP was produced in the form of fibers and then submitted to cytotoxicity testing. A sample of ACP was inserted into the mandibular region of a patient with a lost implant so after removal and curettage, the remaining bone site was filled with the ACP biomaterial. Preliminary cytotoxicity test was negative. After 15 weeks of healing, a titanium implant was inserted at the site. Clinical and radiographic follow‐up was conducted for 12 months and sequential radiographic analyses revealed tissue formation resembling spongy bone. Images under immunohistochemistry demonstrated efficient deposition and osteoconduction of the newly deposited tissue. Residual portion of the CaO:P₂O₅ outer layers served as a substrate for osteoid matrix deposition, aiding growth, and the results of fiber absorption favored maturation of the new bone tissue.     

Transmission electron microscopy studies of plasma-etched silicon nitride/silicon carbide composites

Transmission electron microscopy has been used to isolate and examine the intergranular glass phase in hot-pressed silicon nitride/silicon carbide composites. Previously there have been difficulties in locating a suitable region for studies of this nature because the interfering nitride and carbide grains inhibit isolation of the glass for examination. Radiofrequency plasma etching of thinned sections of 6 wt% Y₂O₃, 2 wt% A1₂O₃ in Si₃N₄ containing 30 vol% of SiC proved to be fruitful in isolating the glass phase. A mixture of CF₄ and O₂ quantitatively remove the acicular nitride phase without any evidence of attack on either the glass or carbide. Composites containing ceria and magnesia as substitutes for yttria behave similarly. This indicates that glasses containing minor to major concentrations of elements forming stable fluorides inhibit the attack of fluoride ions on silica glasses containing these elements.     

The application of high resolution electron microscopy to the study of oxidation

High resolution electron microscopy has been used to examine both the similarities and differences in the growth morphologies of Fe₂O₃, Cr₂O₃ as formed on iron alloys, and MgO as formed by burning Mg in moist air. A general discussion is also given of the relative advantages and disadvantages of a variety of TEM techniques as applicable to the study of oxidation phenomena.     

Oxidation and ignition behavior of a magnesium alloy containing rare earth elements

The oxidation and ignition behavior of Mg–8 wt.%Al alloy added with rare earth (RE) was investigated. When 0.1 wt.%RE was added, the ignition-proof effect was optimum and the ignition temperature of the alloy increased from 654°C to 823°C. The oxide scales and substrates of the alloy with 0.1 wt.%RE were characterized by scanning electronic microscope, X-ray diffraction, and energy dispersive spectrometer. The results show that a layer of tightly coherent oxidation film formed on the alloy surface under high temperature mainly consists of MgO, RE₂O₃, and Al₂O₃, which is about 2.5–3.5 µm thick. The oxidation kinetics curve of Mg–8 wt.%Al–0.1 wt.%RE follows the parabola rule at 400°C and 700°C and cubic rule at 600°C, which proves that the oxidation at these temperatures is controlled by diffusion obstruction so that the oxidation film can effectively restrain the alloy from further oxidation.     

TEM and AES investigations of the natural surface nano‐oxide layer of an AISI 316L stainless steel microfibre

The chemical composition, nanostructure and electronic structure of nanosized oxide scales naturally formed on the surface of AISI 316L stainless steel microfibres used for strengthening of composite materials have been characterised using a combination of scanning and transmission electron microscopy with energy‐dispersive X‐ray, electron energy loss and Auger spectroscopy. The analysis reveals the presence of three sublayers within the total surface oxide scale of 5.0–6.7 nm thick: an outer oxide layer rich in a mixture of FeO.Fe₂O₃, an intermediate layer rich in Cr₂O₃ with a mixture of FeO.Fe₂O₃ and an inner oxide layer rich in nickel.     

Processing of hollow micro- and nanostructures using the hydrophilic nature of MgO

We show that covering the water-saturated MgO surface with an Al₂O₃ film using atomic layer deposition and then annealing it at 400 °C leads to plastic deformation of alumina by trapped water vapor with consequent development of hollow structures. This phenomenon is applied to thin films, nanopatterned surfaces and isolated 3D nanostructures.     

Influence of Mg doping on the morphology and optical properties of ZnO films for enhanced H2 sensing

Highly oriented ZnO and Mg doped ZnO thin films were fabricated on Al₂O₃ substrate by sputtering at room temperature. The effect of Mg doping on the structural, optical, and morphological properties of ZnO film was investigated. The intensity of (002) peak in X‐ray diffraction measurements revealed the influence of Mg doping on the crystallinity and orientation of ZnO film. Photoluminescence (PL) results show that the Ultraviolet (UV) emission peak was shifted to lower wavelength side for Mg:ZnO film indicating the possibility for quantum confinement. UV–vis–NIR optical absorption revealed an improvement in optical transmittance from 70 to 85%, and corresponding optical band gap from 3.25 to 3.54 eV. Atomic force microscope (AFM) images revealed the nano‐size particulate microstructure of the films. The surface topography of Mg doped ZnO film confirmed decreased grain size with large surface roughness and increased surface area, favorable for sensing. Pure ZnO and Mg doped ZnO film were used as active layer and tested for its sensing performance to hydrogen. Compared to undoped ZnO, 22 at.% Mg doped ZnO film showed much higher sensor response to H₂ at a concentration as low as 200 ppm and at a lower operating temperature of 180°C. A linear sensor response was observed for H₂ concentration in the range of 100–500 ppm. Microsc. Res. Tech. 76:1118–1124, 2013. © 2013 Wiley Periodicals, Inc.     

The chemistry,mechanism and function of tricresyl phosphate (TCP) as an anti‐wear lubricant additive

The detailed understanding of the physical and reaction chemistry of engineering lubricants is key to new developments in the future. Here, we draw together the main chemical/engineering literature in the first systematic review of the standard anti‐wear additive used as an aviation lubricant, tricresyl phosphate (TCP), focusing on understanding the links between the surface chemistry, tribology and decomposition of TCP. While there is still debate concerning the mechanism of TCP, it is clear that it is activated by moisture, oxygen or oxidised metal surfaces. Its anti‐wear properties arise from the resulting formation of iron phosphate or polyphosphate on the contact surfaces. Evidence stresses the importance of chemistry at the boundary layer and a mechanism involving pre‐coordination of TCP at the surface, resulting in activation at the P‐centre and subsequent attack by residual H₂O or surface O²⁻. This perspective provides a potential baseline for the development of future phosphorus‐based high‐performance additives. Copyright © 2015 John Wiley & Sons, Ltd.     

Multiferroic behavior of the functionalized surface of a flexible substrate by deposition of Bi2O3 and Fe2O3

Thin films of bismuth and iron oxides were obtained by atomic layer deposition (ALD) on the surface of a flexible substrate poly(4,4′-oxydiphenylene-pyromellitimide) (Kapton) at a temperature of 250°C. The layer thickness was 50 nm. The samples were examined by secondary-ion mass spectrometry, and uniform distribution of elements in the film layer was observed. Surface morphology, electrical polarization, and mechanical properties were investigated by atomic force microscope, piezoelectric force microscopy, and force modulation microscopy. The values of current in the near-surface layer varied in the range of ±80 pA when a potential of 5 V was applied. Chemical analysis was performed by X-ray photoelectron spectroscopy, where the formation of Bi₂O₃ and Fe₂O₃ phases, as well as intermediate phases in the Bi–Fe–O system, was observed. Magnetic measurements were carried out by a vibrating sample magnetometer that showed a ferromagnetic response. The low-temperature method of functionalization of the Kapton surface with bismuth and iron oxides will make it possible to adapt the Bi–Fe–O system to flexible electronics.     

Fragility, DSC and elastic moduli studies on tellurite–vanadate glasses containing molybdenum

Ternary xMoO₃–40TeO₂–(60 − x)V₂O₅ glasses with 0 ? x ? 60 (in mol%) have been prepared by normal melt quenching method. DSC curves of these glasses have been investigated. The glass transition properties that have been measured and reported in this paper, include the glass transition temperature (T_g), glass transition width (ΔT_g), heat capacity change at glass transition (ΔC_P) and calculated fragility (F). Thermal stability, Poisson’s ratio, fragility and glass forming tendency of these glasses have been evaluated, to determine relationship between chemical composition and the thermal stability or to interpret the structure of glass. In addition, Makishima and Makenzie’s theory was applied for calculation of Young’s modulus, bulk modulus and shear modulus, indicating a strong relation between elastic properties and structure of glass. Generally, results of this work show that glass with x = 60 has the highest shear, bulk and Young’s moduli which make it as suitable candidate for the manufacture of strong glass fibers in technological applications; but it should be mentioned that glass with x = 20 has higher handling temperature and super resistance against thermal attack.     

Friction and wear behaviour of Sialon/ (Ca,Mg)‐Sialon with lubrication by coated PbS nanoparticles as oil additives

The friction and wear behaviour of Sialon/(Ca,Mg)‐Sialon with lubrication by liquid paraffin containing PbS nano‐particles coated with dialkyldithiophosphate or oleic acid as additives was investigated using an SRV ball‐on‐disc test rig. It was found that the addition of such nanoparticles reduced the friction coefficient of the friction couple irrespective of the concentration of the additive and the wear volume of (Ca,Mg)‐Sialon, especially under relatively high loads such as 150 N or more. X‐ray photoelectron spectroscopy and electron probe microanalysis revealed that a tribochemical film composed of PbSO₄, PbS₂O₃, PbSO₃, etc., was formed on the worn surface, and contributed to the lubricity of the PbS nanoparticles.     

Facile green synthesis approach for the production of chromium oxide nanoparticles and their different in vitro biological activities

Green synthesis of nanoparticles using plants has become a promising substitute for the conventional chemical synthesis methods. In the present study, our aim was to synthesize chromium oxide nanoparticles (Cr₂O₃NPs) through a facile, low‐cost, eco‐friendly route using leaf extract of Rhamnus virgata (RV). The formation of Cr₂O₃NPs was confirmed and characterized by spectroscopic profile of UV–Vis, EDX, FTIR, and XRD analyses. The UV‐visible spectroscopy has confirmed the formation of Cr₂O₃NPs by the change of color owing to surface plasmon resonance. The bioactive functional groups present in the leaf extract of RV involved in reduction and stabilization of Cr₂O₃NPs were determined by FTIR analysis. Based on XRD analysis, crystalline nature of Cr₂O₃NPs was determined. The morphological shape and elemental composition of Cr₂O₃NPs were investigated using SEM and EDX analyses, respectively. With growing applications of Cr₂O₃NPs in biological perspectives, Cr₂O₃NPs were evaluated for diverse biopotentials. Cr₂O₃NPs were further investigated for its cytotoxicity potentials against HepG2 and HUH‐7 cancer cell lines (IC₅₀: 39.66 and 45.87 μg/ml), respectively. Cytotoxicity potential of Cr₂O₃NPs was confirmed against promastigotes (IC₅₀: 33.24 μg/ml) and amastigotes (IC₅₀: 44.31 μg/ml) using Leishmania tropica (KMH₂₃). The Cr₂O₃NPs were further evaluated for antioxidants, biostatic, alpha‐amylase, and protein kinase inhibition properties. Biocompatibility assay was investigated against human macrophages which confirmed the nontoxic nature of Cr₂O₃NPs. Overall, the synthesized Cr₂O₃NPs are biocompatible and nontoxic and proved to possess significant biopotentials. In future, different in vivo studies are needed to fully investigate the cytotoxicity and mechanism of action associated with these Cr₂O₃NPs.     

Mg(PO3)2-BaF2-AlF3系统玻璃的振动谱研究

应用红外及拉曼光谱研究了Mg(PO₃)₂-BaF₂-AlF₃系统氟磷玻璃的结构特征.证实了双键氧(P=O)及由Al(O.F)₄四面体和P(O.F)₄四面体所混合构成的网络结构存在于玻璃之中.在拉曼光谱中,V_Ba-F、V_Mg-F和V_Al-F振动吸收峰分别出现在480-510cm^-1、530-550cm^-1和580cm^-1处.根据红外及拉曼光谱的结果得出:随系统中氟化物含量的增加,玻璃结构逐渐由聚磷酸盐转变为焦磷酸盐和一氟正磷酸盐混合物,同时双键氧(P=O)消失.