MCVD of fluorosilicate glass

Preforms with a fluorosilicate glass core produced by the modified chemical vapor deposition process with SiF₄ as the fluorination agent were used to study the effect of initial vapor mixture composition on the refractive-index difference Δn between the fluorosilicate and silica glasses and the glass deposition rate. The results indicate that Δn can reach about −0.01. The marked reduction in the deposition rate of fluorosilicate glass with increasing SiF₄ concentration seems to be due to chemical reactions that lead to the formation of stable gaseous chlorofluorosilanes.     

CVD of fluorosilicate glass for ULSI applications

Interlayer dielectrics are key materials for size reduction and speed enhancement of ultra large scale integrated devices. As intralevel metal spacing is reduced and lower capacitance is required, the choices for inorganic dielectrics are limited, Fluorosilicate glass is a material that is being considered to meet these requirements because it has shown the ability to extend SiO₂ chemical vapor deposition processing. Fluorine addition in a conventional glass improves gap fill while simultaneously lowering the dielectric constant. This paper will review the progress of fluorosilicate glass processing, examine the reliability of these materials, and discuss the role of fluorine in increasing gap fill and lowering the dielectric constant of standard SiO₂ films.     

Fluorine incorporation in silica glass by MCVD process – a critical study

The chemistry of fluorine incorporation in silica glass preparatory to preform fabrication by MCVD process was critically analysed on the basis of the thermodynamic properties of the constituent reagents. The theoretical findings were compared with the experimental results, pointing out the anomalies observed by different workers. The addition of phosphorus is found to have an insignificant role in modifying the fluorine incorporation level. The accepted model of dependence of fluorine content in the glass on the partial pressure of SiF4 to the power of 0.25 finds poor agreement with the experimental data at low fluorine dopant concentration.     

Properties of self-compacting concrete prepared with recycled glass aggregate

The effects of recycled glass (RG) cullet on fresh and hardened properties of self-compacting concrete (SCC) were investigated. RG was used to replace river sand (in proportions of 10%, 20% and 30%), and 10 mm granite (5%, 10% and 15%) in making the SCC concrete mixes. Fly ash was used in the concrete mixes to suppress the potential alkali-silica reaction. The experimental results showed that the slump flow, blocking ratio, air content of the RG–SCC mixes increased with increasing recycled glass content. The compressive strength, tensile splitting strength and static modulus of elasticity of the RG–SCC mixes were decreased with an increase in recycled glass aggregate content. Moreover, the resistance to chloride ion penetration increased and the drying shrinkage of the RG–SCC mixes decreased when the recycled glass content increased. The results showed that it is feasible to produce SCC with recycled glass cullet.     

Microstructure and luminescence of Yb3+-doped fluorosilicate glass ceramics

Yb³⁺-doped transparent glass ceramics containing cubic SrF₂ nanocrystals were prepared by heat treating the precursor fluorosilicate glass. The precipitated crystals increase in size and the crystallinity decreases with increasing Yb³⁺ doping level. With high-resolution transmission electron microscopy and electron diffraction, the nano-sized nature of SrF₂ was clearly observed. Owing to a significant change in the crystal-field effects with Yb³⁺ enriching in the SrF₂ phase, the glass ceramics present near infrared emission with large bandwidths and long lifetimes, simultaneously. This indicates the glass ceramics have potential application in the efficient IR lasers pumping by InGaAs diodes. The glass ceramics can also emit blue upconversion luminescence, deriving from Yb³⁺ pairs’ cooperative luminescence. It suggested that Yb³⁺ can be an efficient upconversion sensitizer for other rare earth ions.     

Preparation and photoluminescence properties of fluorosilicate glass ceramics containing CeOF: Dy nanocrystals

The Ce³⁺ and Dy³⁺ co-doped oxyfluoride glasses and glass ceramics containing CeOF or CeF₃ nanocrystals have been prepared in the reducing atmosphere. The crystallinity increased significantly with the Ce³⁺ concentration, while the crystal size of nanocrystals is mainly influenced by the annealing temperatures. The glasses and glass ceramics emitted white light, deriving from a combination of the Ce³⁺ blue and the Dy³⁺ yellow light. The emission intensity and CIE chromaticity coordinates of the Ce³⁺ and Dy³⁺ co-doped glasses can be tuned by adjusting the ratio of Ce³⁺/Dy³⁺ concentration or the annealing temperature.     

Properties of architectural mortar prepared with recycled glass with different particle sizes

The recycling of glass waste as a source of aggregate for the production of concrete products has attracted increasing interest from the construction industry. However, the use of recycled glass in architectural mortar is still limited. This study attempts to develop a self-compacting based architectural mortar using white cement and 100% recycled blue glass as key ingredients. To improve the aesthetic qualities, a certain minimum quantity of glass cullets of larger particle size must be present. The influence of particle size of the recycled glass on the engineering properties of fresh and hardened architectural mortar is investigated. The experimental results demonstrate that it is feasible to utilize 100% recycled glass as the aggregate for the production of self-compacting based architectural mortar. These products have an average compressive strength of 40 MPa and flexural strength of 6 MPa at 28 days which are appropriate for some architectural and building applications. Also, the overall performances of all the architectural mortars prepared with different particle sizes of glass aggregates are comparable to those of control mortar mix prepared with river sand.     

Large-mode-area leaky optical fiber fabricated by MCVD

A large-mode-area single-mode optical fiber based on leaky-mode filtering was prepared by a modified chemical vapor deposition (MCVD) technique. The fiber has a leaky cladding that discriminates the fundamental mode from higher-order modes. A preliminary version has a 25 μm core diameter and 0.11 numerical aperture. A Gaussian-like mode with 22 μm mode field diameter was observed after 3 m propagation, in agreement with modeling.     

Antibacterial silver-containing silica glass prepared by ion implantation

Recently, there is much interest in nanocomposites consisting of metal nanoparticles dispersed in dielectric matrix. Silver is the first candidate used in antibacterial research. In the present study, sliver-containing silica glass is prepared by ion implantation. The bactericidal properties of Ag-implanted samples are investigated using E. coli. The implanted samples are characterized by optical absorption spectroscopy, atomic force microscopy and transmission electron microscopy. The size and position of the silver nanoparticles formed by ion implantation can be optimized by adjusting the implanted process parameters. All the implanted samples show antibacterial properties. But the samples with silver nanoparticle-enriched surfaces possess excellent antibacterial properties in comparison with other implanted samples. This indicates that ion implantation is a potential method for synthesizing antibacterial biomaterials.     

Magnetic properties of multicore magnetite nanoparticles prepared by glass crystallisation

A glass with the composition 13K₂O*13Al₂O₃*16B₂O₃*43SiO₂*15Fe₂O_3?x was melted and rapidly quenched in water. This leads to the formation of phase-separated droplets with diameters from 100 to 150 nm. Magnetite crystals with a size of 10–20 nm precipitate within these droplets. The magnetite containing phase-separated regions can be separated from the glass by dissolving the SiO₂-rich amorphous glass matrix through boiling the pulverized glass in a concentrated aqueous sodium hydroxide solution. The residual, magnetite containing phase-separated droplets match multicore magnetite nanoparticles (McNP). The magnetite nanoparticles show superparamagnetic behaviour and as McNP, lead to a higher effective magnetic radius than single crystals. Magnetisation measurements of the McNP indicate that the particles show a narrow hysteresis, but the ratio of remanent to saturation magnetisation is not high enough for uniaxial anisotropy. The additionally performed temperature-dependent magnetorelaxometry (TMRX) measurements show peaks at 13 and 39 K in the distribution of the magnetic moment relaxation. The obtained inter-particle distance of the magnetite within the McNP is smaller than 5 d _C (core diameter), leading to strong magnetic interactions.     

Silver-coated glass fibers prepared by a simple electroless plating technique

Silver-coated glass fibers have been successfully fabricated using a simple electroless silver plating. The structures of the silver/glass fiber composites were characterized by X-ray diffraction, high-resolution transmission electron microscopy, and scanning electron microscopy, respectively. The morphology investigation showed that the silver coatings were compact and continuous. The minimum volume resistivity could reach 4.53 × 10^?4 Ω cm, suggesting excellent electric conductivity. It was found that the quality of silver deposition was influenced by dosage of ammonia solution and plating temperature. Ammonia solution served as complexing reagent and supplied an alkaline media, and higher temperature easily led to metallic oxidation. The current method is simple-handle, inexpensive, large production, and the obtained silver/glass fibers can be used as fillers to fabricate electromagnetic wave shielding materials.     

Nanostructure analysis of graded oxidation coated glass prepared by APCVD on-line

A solar-control coated glass was prepared using chemical vapor deposition in the A0 zone of an annealing furnace of a float glass manufacturing line. The surface morphology and microstructure of the coated composite film were analyzed by scanning electron microscopy (SEM) and secondary-ion mass spectrometry (SIMS). This shows that the surface of amorphous silicon is smooth, the size of the nodules is about 100-200 nm, the surface roughness is 9.66 nm and the thickness of the layer is 70-78 nm. An oxidization gradient along the thickness of the silicon layer was observed.     

Properties of Pd nanocrystals prepared by PVD method

Pd nanocrystals obtained by the physical vacuum deposition (PVD) method were studied by X-ray diffraction, transmission electron microsocpy (TEM), atomic force microsocpy (AFM) and optical absorption methods. These Pd fcc nanocrystals are embedded in carbonaceous matrix. The object of study was the structure of Pd nanocrystals and interaction between Pd and carbon matrix interface. In the research a metal-organic crystalline structure was found.The structural model of Pd fcc type nanocrystals with different sizes (adopting the full-shell model) was also proposed.     

Properties of porous magnesium prepared by powder metallurgy

Porous magnesium-based materials are biodegradable and promising for use in orthopaedic applications, but their applications are hampered by their difficult fabrication. This work reports the preparation of porous magnesium materials by a powder metallurgy technique using ammonium bicarbonate as spacer particles. The porosity of the materials depended on the amount of ammonium bicarbonate and was found to have strong negative effects on flexural strength and corrosion behaviour. However, the flexural strength of materials with porosities of up to 28 vol.% was higher than the flexural strength of non-metallic biomaterials and comparable with that of natural bone.     

Effect of fluorine doping on the optical loss in MCVD fibers based on heavily doped germanosilicate glass

We have studied the size distribution of silica glass particles in the fabrication of heavily doped germanosilicate glass fiber preforms by modified chemical vapor deposition (MCVD) at different Freon 113 concentrations in the gas mixture. The addition of Freon 113 to the gas mixture is shown to reduce the particle size in the deposited core glass layer and the optical loss in the fiber. A mechanism is proposed which accounts for the effect of the initial particle size in the core glass layer on the anomalous scattering and total optical loss in heavily doped step- and graded-index fibers.     

光纤预制棒制造设备控制系统

本文以MVCD制造设备控制系统为研究对象，采用单片机为处理芯片的控制系统设计方案。介绍了制造设备控制系统整体设计，具体说明了硬件设计的基本原理和方法，包括微处理器模块、过程通道模块以及人机接口模块设计等。设计了控制系统的应用程序，应用了模糊控制理论对模管进气端和出气端的压力差进行控制，减少了控制系统振荡，获得了较好的效果。     

Properties of μm-thick CdSe prepared by vacuum deposition

We have fabricated vacuum-evaporated CdSe films with thickness, of the order of micrometers. The films show hexagonal structure with c-axes perpendicular to the glass substrates. At higher temperatures, the sample exhibits grain-boundary scattering and Se the vacancy acts as a donor impurity; while at lower temperatures, shallow donor levels overlap into the conduction band and thus metallic impurity conduction occurs.