Photoflash

Rhenium is also used as an electrical contact material because it has good wear resistance and withstands arc corrosion. Thermocouples made of Re-W are used for measuring temperatures up to 2200C, and rhenium wire is used in photoflash lamps for photography. 

Zirconate compounds exhibit several interesting properties. Lead zirconate—titanate [12626-81 -2] compositions display piezoelectric properties which are utilized in the production of EM-coupled mode filters, resonators in microprocessor clocks, photoflash actuators, phonograph cartridges, gas... 

When Mg is alloyed with Al, for use in some incendiary, tracer and photoflash compns, the requirements of the US Armed Forces are given in the Mil Spec entitled, Magnesium-Aluminum Alloy, Powdered (Ref 1). It covers two types of Mg-Al alloy, Type A (50/50), and Type B (65/35)... 

Photo flash Compositions. Workers at PicArsn have investigated a series of mixts of K perchlorate with powd metals for use as photoflash compns. Info on candlepower, time to peak luminosity, and duration of flash, as well as performance at sea level and 1 x 10s feet, are given for each compn (Ref 23). A standard mil photo flash compn is given as 40% atomized Al, 30% Ba nitrate, and 30% K perchlorate (Ref 22, P 274)... 

S. Lopatin, Sea-Level and High-Altitude Performance of Experimental Photoflash Compo-... 

Flares. A flare compn is described in Refs 15 16 contg powd Mg, Na perchlorate, and a binder which can be cast and cured, and which has a luminous intensity of 50,500 candle-secs/g Incendiaries. A mixt of 1 OOg of Na perchlorate and 58.7g of powd Al has a Qr of 2751cal/g and can be used as a filler for incendiary bombs (Ref 6). A proc is described in Ref 14 for coating Na perchlorate with Al, and the use of the coated material in incendiaries Photo flash Compositions. Mixts of 80% Ca metal and 20% Na perchlorate and 80% Ca, 10% Na perchlorate, and 10% Na nitrate have been examined as expl photoflash compns for both sea level and high altitude use (Ref 13) Refs 1) Gmelin, System No 21 (1928), 408 Supp Part 1 (1964), 180 2) H.H. Willard ... 

Photoflash Compositions. See under Pyrotechnics, Military in this Vol... 

Photo flash powders are loose mixts of powdered oxidizers such as Ba nitrate and K perchlorates with metallic fuels, principally Mg, A1 and Zr. These ingredients have such small particle sizes that they bum with expl violence for durations of less than 0.1 sec. At present photoflash powders are used exclusively in military aerial photography, whereas civilian applications are served by electrically ignited Zr or Hf wire containing flashbulbs. Since 1970. non-electric, pyrotechnically functioned, flash cubes have appeared on the market (USPs 3535063,3540813 3674411)... 

Photo flash bombs and cartridges are pyro technic items which are classified with bombs (Vol 2, B229) because of their explosive effect. The various devices are similar, differing principally in size and the amount of delay. When fired, each photo flash cartridge, after 1, 2, or 4 seconds, produces a flash having a peak intensity of approx 50 million cd with a total output of 5 million cd sec, whereas photoflash bombs generate above 5 x 109 cd... 

Photoflash compns containing Hf and K perchlorate possess greater luminous efficiency on a volume basis than do other formulations (Ref 128). Zr, for example, when burned in oxygen has an average color temp of 4883°K compared with 5235°K for Hf when measured at peak intensity (Ref 65). In pyrotechnic flash units, substitution of Al with Hf and Ti produced comparable peak output, but inferior output... 

Typical photoflash compns as well as some of their performance data and device specifications are given in Ref 134, Tables 6-16 to 6-25... 

An intimate mixture of the finely divided components, once widely used as a photoflash composition, is readily ignitable and extremely sensitive to friction or impact. 

CIO radicals during the first few milliseconds after the photoflash. A delay in the appearance of C102 is perhaps associated with a shift to the left in the equilibrium... 

In this case I didn t use an inverter as a low-voltage source, but a flash circuitry out of a disposable camera. It consists of a 120uF Photoflash capacitor that is charged to about 300V DC in about 5 seconds from a 1.5V AAA battery. 

I soldered two wires to the Photoflash cap terminals and connected it to the diode-spark plug circuit. As a trigger I used just an ignition coil connected to 12V battery through a switch. Ignition is manual by closing and opening the switch. 

Because of its higher melting point and less-exothermic decomposition, potassium perchlorate produces mixtures that are less sensitive to heat, friction, and impact than those made withKClO] [2]. Potassium perchlorate can be used to produce colored flames (such as red when combined with strontium nitrate), noise (with aluminum, in "flash and sound" mixtures), and light (in photoflash mixtures with magnesium). 

Barium nitrate is a white, crystalline, non-hygroscopic material with a melting point of approximately 592°C. It is commonly used as the principal oxidizer in green flame compositions, gold sparklers, and in photoflash mixtures in combination with potassium pert hlorate. ... 

Therefore, the initial choice for an oxidizer is one with an exothermic heat of decomposition such as potassium chlorate (KCIO 3). However, mixtures of both chlorate and perchlorate salts with active metal fuels are too ignition-sensitive for commercial use, and the less-reactive - but safer - nitrate compormds are usually selected. Potassium perchlorate is used with aluminum and magnesium in some "photoflash" mixtures these are extremely reactive compositions, with velocities in the explosive range. 

Photoflash" mixtures, 145-148 Photon, energy of, 46 Potassium chlorate acid with, 57 discovery of, 4 hazards of, 59, 109, 134 in colored flame mixtures, 156, 161... 

To produce a burst of light of short duration, a composition is required that will react very rapidly. Fine particle sizes are used for the oxidizer and fuel to increase reactivity, but sensitivity is also enhanced at the same time. Therefore, these mixtures are quite hazardous to prepare, and mixing operations should always be carried out remotely. Several representative photoflash mixtures are given in Table 7.3. 

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