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  1. #1
    Mustafa Umut Sarac's Avatar
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    DIY Fluoride UV Lens, Platinum in camera

    I had been opened an thread on laser salt windows making technology transferred in to camera lens building. Final conclusion Sodium Chloride Rock Salt Transparent medium was very sensitive to moisture and self cracking nature.

    After few years passed , Now I found fluoride salts have 95 abbe number and 1.45 refractive index number and have ultra wide transmission range.

    I found fluoride is used in toothpastes and sold as in capsules , cheap and it can be soluble in water.

    I thought if we can evaporate the water , may be we can make an transparent fluoride lens in the mold.

    How would it be possible ?

    Umut
    Last edited by Mustafa Umut Sarac; 10-27-2013 at 01:19 AM. Click to view previous post history.

  2. #2

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    If the vapor pressure of the flouride salt is below that of water, you might be able to freeze dry it using high vacuum. You may be able to control the crystal growth by regulating the temperature.

  3. #3
    Mustafa Umut Sarac's Avatar
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    Hi Winterclock,

    What is the temperature range to control the crystal growth , low or high , I need an approximation for concept and do it at home.
    What is the high vacuum , is it nasa grade high vacuum or diy at home.

    Umut

  4. #4

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    This will all depend on the vapor pressure of the salt. It is not very difficult to acheive quite high levels of vacuum DIY, but as the water is drawn off, the salt will cool down. it would probably take some experimentation to determine a suitable salt and temperature range to grow an optical crystal in a mold.

  5. #5
    Mustafa Umut Sarac's Avatar
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    Hello again Winterclock ,

    Thank you replying my pm in thread. What kind of temperature range are we talking about , few hundreds celcius or 500 , 800 or higher.

    I have no idea about that temperature problem. Do I need to find a phase diagram of fluoride ?

    Thanks again ,
    Umut

  6. #6
    Mustafa Umut Sarac's Avatar
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    I found below list when looking for vapor pressure data. Does it tell something ?

    lgP (YF3) = 1,7259 + 1,1103.lgP(CaF2);
    lgP (ScF3) = 2,2163 + 0,9641.lgP(CaF2);
    lgP (PrF3) = 0,8570 + 0,9577.lgP(CaF2);
    lgP (LaBr3) = 1,6662 + 0,5617.lgP(CaF2);
    lgP (CeBr3) = 1,6852 + 0,5381.lgP(CaF2);
    lgP (PrBr3) = 1,6978 + 0,5273.lgP(CaF2);
    lgP (NdBr3) = 1,8257 + 0,5275.lgP(CaF2);
    lgP (YBr3) = 2,2958 + 0,5003.lgP(CaF2);
    lgP (HoBr3) = 2,1859 + 0,5017.lgP(CaF2);
    lgP (LuBr3) = 2,4073 + 0,4691.lgP(CaF2);
    lgP (TbBr3) = 1,9795 + 0,4946.lgP(CaF2);
    lgP (GdBr3) = 1,9423 + 0,5057.lgP(CaF2).

  7. #7

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    You need to know what salt you want to use see: http://www.google.com/url?sa=t&rct=j...O4%2520KTH.pdf
    Toothpaste contains calcium fluoride. It does not appear to be very soluable in water.

  8. #8

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    From the pdf I posted, potassium flouride would be a better choice for a water based process. It precipitates from a super saturated solution above 45C at concentrations near 60%. 3:30 AM here, going to bed now good morning!

  9. #9
    Mustafa Umut Sarac's Avatar
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    Thank you Winterclock for very useful information. Yes You are right , it is the best of all , others traveling around %3.
    What would be needed to extract all water and where I can find the information after 45 degree to 100 degree % 60 alembic process.
    And I found some papers suggesting 1500 celcius degrees for some crystals but I found some papers writing about 260 celcius degrees.
    I will attach these papers but APUG is slow. I am going to internet explorer to attach them. I will try . I am here.

    The Potassium Fluoride – water system
    The solubility of potassium fluoride, KF has strong temperature dependence. The salt is much
    more soluble than sodium fluoride and it forms two hydrates. The tetrahydrate, KF·4H2O is the stable
    form in equilibrium with a binary solution at temperatures below 17.7 °C. Between 17.7 and
    approximately 45 °C, the dihydrate, KF·2H2O is the stable form. Above 45 °C, the anhydrous form of
    KF will precipitate from supersaturated solutions.
    The eutectic point of KF-H2O solutions is
    between -21.8 °C and -21.5 °C due to the high solubility of KF.

  10. #10
    Mustafa Umut Sarac's Avatar
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    The Goal
    The goal in growing crystals for a single crystal X-ray diffraction experiment is to grow single crystals (obviously) of suitable size. The optimum size for a crystal is one which has dimensions of 0.2 - 0.4 mm in at least two of the three dimensions. Most potential structure determinations are thwarted by a lack of suitable crystals.
    General Considerations
    The factors during crystal growth which affect the size of the crystals are, solubility of compound in the solvent chosen for recrystallization, the number of nucleation sites, mechanical agitation to the system, and time.
    Solvent. Choose a solvent in which your compound is moderately soluble. If the solute is too soluble, this will result in small crystal size.

    Avoid solvents in which your compound forms supersaturated solutions. supersatuated solutions tend to give crystals which are too small in size


    PS. This is contradictory to above finding.


    Nucleation. The fewer sites at which crystals begin to grow will result in fewer crystals each of larger size. This is desirable. Conversely, many nucleation sites results in a smaller average crystal size, and is not desirable. In many recrystallizations ambient dust in the laboratory provide sites of nucleation. It is important to minimize dust or other extraneous particulate matter in the crystal growing vessel.
    Mechanics. Mechanical disturbance of the crystal growing vessel results in smaller crystals. Let the crystals grow with a minimum of disturbance. This means: Don't try to grow crystals next to your vacuum pump, and don't pick up the vessel everyday to check on how your crystals are growing. Set up the crystal growing attempt, in a quiet, out of the way place and forget about it (if possible!) for a week.
    Time. This is related to mechanics. Crystals fully recognize that patience is a virtue and will reward those who practice it.
    Techniques
    Crystal growing is an art, and there are as many variations to the basic crystal growing recipes as there are crystallographers. The recipes given below are ones which I have either tried or I have read about and sound reasonable. The techniques chosen will largely depend on the chemical properties of the compound of interest: Is the compound air sensitive, moisture sensitive? Is it hygroscopic? etc. etc.
    Slow Evaporation. This is the simplest way to grow crystals and works best for compounds which are not sensitive to ambient conditions in the laboratory. Prepare a solution of the compound in a suitable solvent. The solution should be saturated or nearly saturated. Transfer the solution to a CLEAN crystal growing dish and cover. The covering for the container should not be air tight. Aluminium foil with some holes poked in it works well, or a flat piece of glass with microscope slides used as a spacer also will do the trick. Place the container in a quiet out of the way place and let it evaporate. This method works best where there is enough material to saturate at least a few milliliters of solvent.
    Slow Cooling. This is good for solute-solvent systems which are less than moderately soluble and the solvent's boiling point is less than 100 deg C. Prepare a saturated solution of the compound where is the solvent is heated to just it's boiling point or a just below it. Transfer the solution to a CLEAN large test tube and stopper. Transfer the test tube to a Dewar flask in which hot water (heated to a temperature of a couple of degrees below the solvent boiling point). The water level should exceed the solvent level in the test tube, but should not exceed the height of the test tube. Stopper the Dewar flask with a cork stopper and let the vessel sit for a week. A more elaborate version of this involves a thermostated oven rather than a Dewar flask.
    Variations on Slow Evaporation and Slow Cooling. If the above two techniques do yield suitable crystals from single solvent systems, one may expand these techniques to binary or tertiary solvent systems. The basic rationale for this is by varying the solvent composition one may inhibit growth of certain crystal faces and promote the growth of other faces, yielding crystals of suitable morphology and size. If you choose this route for growing crystals, it absolutely necessary to record the solvent composition you use! If crystal growing is an art, growing crystals from binary or tertiary solvent mixtures is that much more imprecise. Remember reproducibility is paramount in science.
    Vapor Diffusion. (excerpted and paraphrased from Stout and Jensen p. 65). This method is good for milligram amounts of material. A solution of the substance is prepared using solvent S1 and placed in test tube T. A second solvent, S2, is placed in a closed beaker, B. S2 is chosen such that when mixed with S1 the solute will become less soluble. The test tube containing S1 is then placed in the beaker and the beaker is sealed. Slow diffusion of S2 into T and S1 out of T will cause crystals to form. If S2 is more volatile than S1 the solvent level will increase and prevent microcrystalline crusts from forming on the sides of T.
    problem.
    Last edited by Mustafa Umut Sarac; 10-27-2013 at 03:09 AM. Click to view previous post history.

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