Silica Glass Windows Research Articles

Multilayer aberration correction for depth-independent three-dimensional crystal growth in glass by femtosecond laser heating

Focused femtosecond lasers are known for their ability to modify transparent materials well below the surface with 3D selectivity, but spherical aberration causes degraded focal intensity and undesirable absorption conditions as focal depth increases. To eliminate such effects we have implemented an aberration correction procedure that accounts for multiple refracting layers in order to crystallize LaBGeO5 glass inside a temperature-controlled microscope stage via irradiation through a silica glass window. The correction, applied by a spatial light modulator, was effective at removing the focal depth-dependent degradation and achieving consistent heating conditions at different depths, an important consideration for patterning single-crystal architecture in 3D. Additional effects are noted, which produce a range of crystal cross-section shapes and varying degrees of partial crystallization of the melt.

English

This paper discussed the design and development of the Moderate and Intense Low oxygen Dilution (MILD) combustion burner using Computational Fluid Dynamics (CFD) simulations. The CFD commercial package was used to simulate preliminary designs for the burner before the final design was sent to workshop for the fabrication. The burner is required to be a non-premixed and open burner. To capture and use the exhaust gas, the burner was enclosed within a large circular shaped wall with an opening at the top. An external EGR pipe was used to transport the exhaust gas which was mixed with the fresh oxidant. To control the EGR and exhaust flow, butterfly valves were installed at the top opening as a damper to close the exhaust gas flow at the certain ratio for EGR and exhaust out to atmosphere. High temperature fused silica glass windows were installed to view and capture images of the flame and analyse the flame propagation. The burner simulation shows that MILD combustion was achieved for the oxygen mole fraction between 3-13%. The final design of the burner was fabricated and ready for the experimental validation.

Molybdic acid ionisation under hydrothermal conditions to 300 °C

This UV spectrophotometric study was aimed at providing precise, experimentally derived thermodynamic data for the ionisation of molybdic acid (H 2MoO 4) from 30 to 300 °C and at equilibrium saturated vapour pressures. The determination of the equilibrium constants and associated thermodynamic parameters were facilitated by spectrophotometric measurements using a specially designed high temperature optical Ti–Pd flow-through cell with silica glass windows. The following van’t Hoff isochore equations describe the temperature dependence of the first and second ionisation constants of molybdic acid up to 300 °C: log 10 K 1 = - 96.125 - 0.02875 · T + 17.660 · ln ( T ) log 10 K 2 = - 30.082 - 0.02690 · T + 5.9366 · ln ( T ) The resulting ionisation constants of molybdic acid demonstrate that in low sulphur containing hydrothermal fluids in the Earth’s crust, the transport of molybdenum is favoured by the HMoO 4 - / MoO 4 2 - species while the role of the associated H 2MoO 4 is of negligible importance at elevated temperatures above 200 °C.

Vacuum-Ultraviolet Light Sources and Their Applications for Processings. UV Photon-induced Surface Modification of Plastics by Using Excimer Laser/Excimer Lamp.

Surface modification of a selective area of plastics was accomplished by using an ArF excimer laser or an excimer lamp. The chemical stability of the plastics is attributed to the presence of C-H, C-F, C-Cl or C=O bonds. Plastic sheets were photochemically modified to be hydrophilic or metallic properties with ultra violet photons and chemical solutions. The chemical solution was sandwiched between the sample surface and a silica glass window. With UV photons, the solutions and sample surfaces were excited. In the case of the hydrophilic modification, the surfaces were dehydrogenated or difluorinated by the H or B atoms which were photodissociated from H2O or B(OH)3 aqueous solution, and replaced the photodissociated OH radicals. In the case of the metal deposition on the plastic surfaces, the copper sulfate aqueous solution was used. As a result conductive circuit patterns Cu thin films were deposited on the sample surfaces.

Excimer Laser-Induced Photochemical Surface Modification of Plastics.

Photo-induced surface modification of plastics was accomplished with an ArF excimer laser in the presence ofchemical solutions. The chemical stability of the plastics is attributed to the presence of C-H, C-F or C=Obonds. Mechanism of this surface modification is to pull the terminal atoms from C-H or C-F bond in theplastic surface and to substitute the functional group for the dangling bond of C. In this treatment, the chemicalsolution was sandwiched between the sample surface and silica glass window by capillary phenomenon. Then, the solution and sample surface were excited with UV photons. In addition, the sample surface was dehydrogenatedor defluorinated by the H or B atoms which were photodissociated from H2O or B (OH) 3 in an aqueous solution, and the photodissociated OH radicals were substituted for unbonding chain of C. As a result, the plasticssurface were photochemically modified to have hydrophilic, oleophilic or metallic properties.

Improvement of the aging characteristics of deuterium lamp

For an improvement of the aging characteristic of deuterium lamp, it was tried to exchange its regular window glass material(Type III silica glass) for other glass material(fluorine-doped silica glass). By using fluorine-doped silica glass as a new window material. The spectral irradiance of deuterium lamp was improved maximum 20% in comparison to those with TypeIII silica glass window after 402hours operation. This phenomenon is explained by difference of window material degradation. A cause of degradation is photoabsorption produced by defects which were made by photochemical reaction in the glass.

A high-temperature focusing X-ray powder camera with new features

A film-type X-ray high-temperature (up to about 2250 K) powder camera using the Guinier focusing principle in transmission is described. Use is made of a germanium monochromator. The powder specimen is spread without adhesive on a horizontal supporting film of refractory material, and rotates about a vertical axis. The support is surrounded by a cylindrical furnace of thin tantalum sheet enclosed in a chamber which can be evacuated or filled with an inert gas. The X-radiation enters and leaves the chamber through beryllium windows. The film holder is situated outside the chamber. The sample temperature is measured by thermocouples and optical pyrometry. Problems due to the coating by evaporated material of the silica glass window used to observe the specimen are obviated by the use of a transparent shield which can be rotated to give fresh surfaces when needed.

Enhanced Emission of Iron Nuclei in Solar Flares

A silica glass window from Apollo 12 CM and a piece of flint glass from the Surveyor 3 camera filter were examined for Fe nuclei tracks. A large difference between observed and predicted track densitites was found. At low rigidity (or energy), the solar particle Fe/He ratio is much higher than the photospheric abundance ratio, but decreases with increasing rigidity until it approaches the photospheric value at a rigidity of about 500 MV. It is felt that the low-energy Fe tracks are of solar origin. The implications that heavy nuclei can be preferentially emitted from a source of energetic particles are discussed. Other conclusions are the following: Rocks exposed on the lunar surface for 10 million yr would accumulate about 6 x 10 to the 12th power tracks/sq cm, and the rate of radiation-induced erosion is about 10 to the -9 cm/yr. The lunar soil should contain heavily irradiated small grains, some with track densities of about 10 to the 12th power/sq cm that have flaked from radiation-damaged rock surfaces and some that were irradiated while at the top of the soil layer.

Marine applications of glasses and ceramics

INTRODUCTION INOR6ANIC, non-metallic materials have found applications in marine structures for many years. Some of these materials have outstanding resistance to deterioration in the sea and are transparent. Silica-glass windows are standard items in the periscopes of submarines. Some of these materials are extremely resistant to compression stresses and are sufficiently rigid to offer high resistance to elastic buckling in thin shells under external pressure. Light-bulbs are surprisingly resistant to external pressure. Also some have low specific gravities. Hollow glass spheres are furnishing buoyancy in deep oceanography at modest cost. A number of improvements are being made in glasses and ceramics, and in their processes that improve their tensile strength, bending strength, resistance to impact and resistance to stress--corrosion cracking. Also, in the last five years, there has been a great increase in efforts to use these materials in sophisticated marine applications, such as in capsules for manned vehicles and for moored habitats, for deep submergence. The incentive is to exploit the favourable trade-offs of structures made of these materials with regard to allowable depths, buoyancy, durability and cost. These efforts on the development of materials and on their deep submergence uses are intimately conected. It has become evident that the latter goal can be attained more effectively by accelerating and exploiting the former. The purpose of this paper is to summarize advances being made in these related fields.