Quartz glass is the purest form of glass. It consists only of Silicon and Oxygen. Due to this unique chemical composition (single component glass) and the high purity – at Heraeus Conamic min. 99,999% SiO2 purity – quartz glass has excellent technical properties. In particular, the wide transmission spectrum from the ultraviolet, visible to infrared range (depending on grade between 160nm up to 4500nm) makes quartz glass an irreplaceable material for many technical lamps.
Fusion Processes for Technical Lamp Tubes
Heraeus is using different fusion methods for the manufacture of technical lamp tubes. In the following you find a short introduction to the methods:
Electric Fusion Process
Electric fusion is the most commonly used melting process for manufacturing quartz glass. Electric fusion is accomplished either by an electric gas discharge (arc melting) or by applying heat generated by electric resistance.
A further differentiation is made by selecting a continues or batch process. Single step electrically fused tubing is fabricated by pouring sand into the top of a vertical smelter that consists of a refractory metal crucible. At temperatures exceeding 1800°C the ordered micro- structure of the raw material changes into the irregular glass network, glass is formed. Through an outlet in the bottom of the crucible the glass is pulled directly in the shape of tubes or as a solid, a so-called ingot.
Electric fused quartz has the highest temperature resistance and highest viscosity of the vitreous silica types.
Flame Fusion Process
Flame fusion is the most traditional form to fuse quartz. A H2/O2-flame is used to fuse crystalline particles to fused quartz. Heraeus chemist Dr. Richard Küch was the first to use this method on an industrial scale over 100 years ago. For a continues process small grains of the raw material are constantly trickled into a flame and fused onto a glass rod, that is slowly removed as it grows. Flame fused quartz has better homogeneity and solarization resistance compared to electric fused quartz.
Synthetic Fusion Process
Heraeus is using two different Synthetic Fusion Processes. More common (trough use for manufacturing pre-forms for Telecommunication Fiber) is the CVD-process or Soot process. In this process chemical precursors (e.g. OMCTS or SiCl4) are oxidized (burned) in a H2/O2 flame. The forming SiO2 is deposited on a rotating bait tube like smoke off a candle deposits on a stick above the flame. The soot body is then vitrified into a transparent glass body in a second process step.
Second Fusion process is to manufacture solids in an OVD or DQ-process (direct quartz process). The process is comparable to the Flame Fusion process and differs in that a liquid chemical precursor (e.g. OMCTS) to be fused in the gas flame.
Because the precursors are made in an industrial chemical process, the raw materials have exceptionally high purity. Glass made of these precursors has an alkali- and metal ion content in the parts per billion (ppb) range. Synthetic fused silica has the best transmission, the highest purity and the best solarization resistance of all vitreous silica types.
Production Methods for Lamp Tubes
Heraeus is using different production methods for tubes manufacturing. In the following you find the differences methods:
- Single Step Tubing
The pulling of tubing directly from the melt is the most cost efficient production process. It is available only for electric fused quartz. The outlet of the crucible is ring shaped and the size of the forming tool determines the available dimensions of tubing (outer diameter, wall thickness). Because a change of the forming tool is not possible once the process started, the range of tube sizes per run is limited. A large amount of tubes must be drawn in order to justify using this process. Tubes produced in the single step process have tight tolerances and are most economic. - Multi Step Tubing:
In this process a pre-form (usually a cylinder) is locally heated and redrawn into tubing. The cylinder is either formed directly or an ingot is reshaped into a cylinder. Because the reforming of glass is independent on the actual production route of the quartz glass, multistep tubing is available in electric and flame fused quartz as well as synthetic fused silica. Furthermore, the additional process-steps homogenize the material usually resulting in a lower bubble content. The available finished sizes depend solely on the size of the starting cylinder. The advantage of the multistep process is the high flexibility regarding starting material and finished sizes, as well as a relatively small batch size.
Material Selection Guide for Technical Lamp Applications
Heraeus offers many different quartz grades under various trademarks. The following table details these material grades and can offer guidance on which grades are suitable for specific applications.
Material Grades for Technical Lamps
Material Grade | Production Type | Application | Feature | Lamp Type |
HLQ® 200 | Electric | Infra red processing, UV curing, UV disinfection, projection lamps for SC and LCD stepper | Clear fused, low OH < 1 ppm available | Infra red lamps, low and medium pressure UV lamps, sleeves, metal halide lamps |
HLQ® 210 | Electric | Laser excitation, beauty and medical | Clear fused, low OH < 1 ppm available, low bubble content, high homogeneity | Long arc cw and pulsed lamps, demanding short arc lamps |
HLQ® 270 | Electric | Lamps for digital projection, stage and studio, cinema | Clear fused, low OH < 1 ppm available, high homogeneity, low alkaline content, high recrystallisation resistance | High and ultra-high pressure short arc lamps, demanding metal halide lamps, demanding cw and pulsed long arc lamps |
HLQ® 235 | Electric | UV disinfection, projection lamps for SC and LCD stepper | Doped, ozone-free*, low OH < 1 ppm available | Ozone-free low and medium pressure UV lamps, short arc lamps |
HLQ® 250 | Electric | UV tanning | Doped, ozone-free*, low OH < 1 ppm available | FDA conform ozone-free lamps |
HLQ® 382 | Electric | Excitation lamps e.g. for laser fusion | doped, uv-free** | Long arc lamps |
Heralux® plus / vuv | Flame | UV curing, UV applications, laser excitation | Clear fused, almost free of bubbles, good UV transmission, high resitance to UV radiation | Medium pressure UV lamps, long arc lamps |
M215 / M235 | Flame | Projection lamps for SC and LCD stepper | Doped, ozone-free*, free of striae | Ozone-free short arc lamps |
M 235 plus | Flame | Projection lamps for SC and LCD stepper, laser exication, medical | Doped, ozone-free*, high homogeneity, free of striae | High intense ozone-free short arc lamps, ozone-free long arc lamps |
M 382 plus | Flame | Laser excitation, beauty and medical | Doped, uv-free**, high homogeneity, free of striae | Long arc cw and pulsed lamps, intense pulsed lamps |
Suprasil® 030 | Synthetic | Disinfection and purification | High purity, high UV transmission | Medium pressure lamps for deep UV, long life-sleeves for deep UV |
Suprasil® 130 | Synthetic | Ozone generation, grease destruction, disinfection and purification, production of ultra pure water | High purity, high UV transmission, high resistance to short-wave UV radiation | 185 nm low pressure lamps, medium pressure lamps for deep UV |
Suprasil® 300 | Synthetic | Spectroscopy, broad band optical applications | Highest purity, OH < 1 ppm, free of bubbles, highest transmission from UV to IR spectral range | Deuterium lamps, high intense mircro-wave lamps |
Suprasil® 310 | Synthetic | Surface cleaning in SC and LCD processing, photochemical vapour deposition, surface activation, photochemistry | Highest purity, free of bubbles, highest UV transmission, resistant to short- wave UV radiation | 172 nm Xe-excimer lamps, very demanding long arc lamps |
Spectrosil® 2000 | Synthetic | Highest intense VUV lamps | Highest purity, free of bubbles, highest UV transmission, resistant to short- wave UV radiation | Highest intense UV-C short arc lamps |
Purasil® | Synthetic | Disinfection and purification | High purity, high UV transmission | Long life-sleeves for deep UV |
Purasil® XP | Synthetic | Disinfection and purification | High purity, high UV transmission, high resistance to short-wave UV radiation | Longest life-sleeves for deep UV |
* (Wavelengths, where ozone forms are absorbed) | ||||
** (UV wavelengths are absorbed) | ||||
Tools and Services
In the selection process for the most suitable fused silica grade the transmission performance is among the first criteria. Please check our transmission calculator. As an additional service, we offer the possibility to search our portfolio for existing part numbers.
