First composition

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Seventy years ago, nearly all resources for the production of commodities and many technical products were materials derived from natural textiles. Textiles, ropes, canvas, and paper were made of local natural fibers, such as flax and hemp. Some of them are still used today. In 1908, the first composite materials were applied for the fabrication of big quantities of sheets, tubes, and pipes in electrotechnical usage (paper or cotton as reinforcement in sheets made of phenol- or melamine-formaldehyde resins). In 1896, for example, airplane seats and fuel tanks were made of natural fibers with a small content of polymeric binders [1]. 

Composites are combinations of two or more materials with the properties shown by individual components. They are made to perform as a single material. Nature made the first composite in living things. Wood is a composite of cellulose fibers held together with a matrix of lignin. Most sedimentary rocks are composites of particles bonded together by... 

Materials called composites are also in widespread use. A composite consists of small fibers of one substance embedded in a matrix of another substance. The fibers reinforce the matrix, adding stiffness. One of the first composites was fiberglass, in which thin fibers of glass reinforce a plastic material. Fiberglass is strong yet light in weight. 

What makes the fabrication of composite materials so complex is that it involves simultaneous heat, mass, and momentum transfer, along with chemical reactions in a multiphase system with time-dependent material properties and boundary conditions. Composite manufacturing requires knowledge of chemistry, polymer and material science, rheology, kinetics, transport phenomena, mechanics, and control systems. Therefore, at first, composite manufacturing was somewhat of a mystery because very diverse knowledge was required of its practitioners. We now better understand the different fundamental aspects of composite processing so that this book could be written with contributions from many composite practitioners. 

The special needs of the space program motivated the search for composite materials for other reasons also. For example, during tests of the first Atlas ICBM (intercontinental ballistic missile), engineers were concerned that the rocket s metallic components would not survive the missile s reentry into the atmosphere they feared it would melt down because of the intense heat to which it was exposed. By the late 1950s, therefore, aerospace researchers had begun to look for satisfactory substitutes for metal alloys for such applications. With that research, the modern held of composite design was horn. One of the first composites tested consisted of pieces of glass embedded in melamine, purported to be the first composite material developed for aerospace applications. 

Early on, people learned how to combine natural materials in a variety of ways to make them more useful. They found that the combination of mud and straw (bricks) was a stronger and more permanent building material than either material by itself. And, thus, one of the first composite materials was born. The importance of societies ability to manipulate natural materials is evident in the fact that the earliest human civilizations have actually been named for the primary substances with which they worked stone, iron, copper, and bronze. 

The first composite system is a barium osumilite composition reinforced with 30 wt% (25 vol%) No. 1 whiskers. The second composite system evaluated is a barium-stuffed cordierite matrix 30 wt% No. 1 whisker composite. The room-temperature properties of these two composites are given in Table 3.16. 

Minimum charge diameter of the first formula should be around 8 inches. Whereas the 2nd formulation can be used in bore holes 6 inches or greater in diameter. Water and wet blasting condition should be avoided with the first composition due to the lack of water tolerance. The 2nd explosive has a slightly greater tolerance, but with all AN explosives, unless they are designed for wet applications, water and wet conditions should be avoided. 

The first composition will not have a long storage life due to the break down of the gel matrix. The second formula is crossed linked with potassium chromate which will give a storage stable explosive. The density, as mentioned earlier, is critical if cap sensitivity is needed. The manufacturer would have to control this density in a batch by batch process. 

The AN is mixed with the water first and heated to effect solution. With solution the Paraformaldehyde is added and the solution heated as in the first composition and boiled for one hour as above and vacuum dehydrated as above. 

The term containing Jp in the first composite brackets on the right side of Eq. (5.2) can be removed by changing the volume element dp to Ipp dp. The terms in the second composite brackets represent the effective potential function for each vibrational—rotational state. 

Quinol (hydroquinone) crystal was the first composite to be called a clathrate. Nowadays, this term has been adopted for many complexes which consist of a host molecule (forming the basic frame) and a guest molecule (set in the host molecule by interaction). The clathrate that is of interest to this study is the clathrate hydrate, also referred to as gas hydrate. Clathrate hydrates were discovered in 1810 by Sir Humphrey Davy. In his lecture to the Royal Society in 1810, he said that he had found, by several experiments, that the solution of chlorine gas in water freezes more readily than pure water [9]. 

In many cases special ignition compositions are pasted or pressed on the surface of a composition in order to firstly ignite the ignition composition and secondly the main composition. We call the former the "first composition" and the latter the "second composition". The ignition of the second composition takes place mainly by the heat of conduction from the first composition. 

We must first clear up the character of the first composition. Paste the first composition on the outside of a small tin, which is filled with water. Ignite it. The water absorbs the heat of combustion of the first... 

Black powder, which is very often used as the first composition, has a force of only one half of the white potassium perchlorate composition. 

The next problem is how to ignite the second composition. For the first composition the author used black powder, which after experimentation has been found to have the smallest force of ignition, and red thermit the largest. 

Using red thermit as the first composition Ignition by mechanical action... 

Mixed Uranium-Plutonium Dioxide in Equimolar Sodium-Potassium Nitrate. The behavior of two compositions of mixed uranium-plutonium dioxide has been investigated thus far at PNL. The first composition, designated material A, consists of 5.44% Pu02/94.56% UO2. The second composition, designated material B, consists of 27.56% Pu02/72.44% UO2. Both materials were acquired as pellets that had been sintered at 1700°C. The behavior of both mixed-oxide materials was studied under the same conditions used in the previous experiments. 

---