The dazzling appearance and hard heart seem to associate diamonds with the word “expensive” from the start. As early as the fourth century BC, India began trading diamonds. At the time, diamonds were used as gems or amulets, and limited diamond production was only sufficient to meet the limited market of India’s affluent class. In 1947, De Beers created the classic slogan “Diamonds are long-lasting, a lasting pass”, and diamonds became a symbol of eternal commitment to the international market.
A: “Diamonds have no other drawbacks, they are too expensive”
B: “Isn’t expensive your fault?” “
C: “Try to tear up the gorgeous marketing packaging of the diamond and you’ll find that you’re not the only drawback of it!” “
How hard is not a “fear of light”
Diamond is commonly known as “diamond”, that is, the original diamond, it is the nature of the most natural existence of the hardest substance. Because of its highest hardness, diamond processing must be done by rubbing against each other with diamond powder with the same hardness.
It is odd that if a diamond is observed in the sun with a magnifying glass, the diamond may slowly disappear (thermodynamic carbon oxidizes in the air; dynamically carbon accelerates reaction at the high temperature of the spotlight). This is because when the sun focuses on a point on the diamond and the temperature reaches the diamond’s point of ignition, the diamond burns into carbon dioxide gas. Scientists have found that diamonds burn 720 to 800 degrees C in pure oxygen and 850 to 1000 degrees Celsius in the air, that is to say, diamonds are not only afraid of light, but also afraid of heat… So don’t let your diamond get close to the heat, let alone be too curious to test it with a big fire.
Diamond is hard, but it’s still afraid of impact? Yes, diamonds are their own, but often the harder the material, the less resilient it is. Although diamonds can cut anything, not afraid of wear and tear, but afraid of impact, so please do not take “precious” diamonds to do drastic activities, such as: with stone, ceramics and other hard objects colliding or falling to the marble floor.
Diamonds and carbon are twins.
Like other well-known gemstones, diamonds are common chemicals. Just as sapphire is aluminum trioxide, jade is silica, mossam is silicon carbide, and diamonds are just carbon (C) isomorphic.
Just as H2O takes on different forms under different conditions – liquid water, solid ice and gaseous water vapor – the C element has different forms of expression at different temperatures and pressures: black carbon or graphite, which is common at room temperature and pressure, becomes a shiny diamond at high temperature and high pressure, and under certain conditions it may also be liquid or gaseous C.
The morphology of water and carbon under different temperature and pressure conditions
Diamonds and graphite are the same chemical element C of the same isomorphic, but the atomic structure is different, the diamond is a stable tetrahexon structure, and graphite is a layerstructure, between the two layers can slide arbitrarily. Different atomic structures lead to completely different physical and chemical properties: diamonds are the hardest-to-use substanceon on Earth, and their hardness is defined as Mohs’ hardness of 10; It’s like a little bit of saccharined water as a child, a little bit of it will be very sweet, and a little more words will become very bitter, in the two extremes of the transformation.
Atomic structure diagrams of diamonds and graphite
Since diamonds and graphite are both C-elements of the opposite sex, is there any way to make them the same structure?
The answer is yes.
Just as water can turn into ice, it’s all about rearranging the C atoms. According to the phase map C we can get as long as the temperature and pressure control under certain conditions, for example, we control the pressure at 4.5 to 6.0GPa, the temperature at 1100 degrees C to 1500 degrees C, graphite will become a diamond.
Under the action of the catalyst, the rate of chemical reaction of graphite into diamond is accelerated, and the required temperature and pressure conditions are reduced. The chemical reaction is like crossing a mountain, originally need to climb to the top of the mountain before going down to pass, but after joining the catalyst, it is like opening the tunnel at the bottom of the mountain, making the reaction easier. At present, the most common catalysts are metal catalysts, mainly pure iron, pure copper and pure magnesium, alloy catalysts have nickel-based catalysts (such as nickel manganese, nickel-manganese copper, nickel-cobalt manganese, etc.) and iron-based catalysts (e.g. iron nickel, ferro-cobalt, ferromanganese, iron-nickel cobalt, ferro-cobalt manganese nickel, etc.;
Straw can also be “gold”.
Diamonds are mainly found in craters, natural diamonds originate more than 160 kilometers below the surface, the earth’s internal high temperature and high pressure environment gave it the conditions to form, 300 to 400 million years ago, volcanic eruptions, pushing them to the earth’s surface, when even dinosaurs did not appear. But because the caldera’s diamonds are still scarce, they are unusually expensive. But as the pursuit and love of diamonds continues to grow, intelligent humans have finally found simple ways to make synthetic diamonds. Since the main component of straw burning is carbon, and the diamond composition is the same, people joke: straw variable “gold”.
Current methods for synthetic diamonds are chemical vapor deposit and high temperature and high pressure HPHT. The former is chemical vapor deposition diamonds, the latter is synthetic diamonds by high temperature and high pressure, CVD mainly produces large-particle diamonds, HPHT mainly produces small shredding diamonds.
CVD method: low-molecular hydrocarbons (CH4, C2H2, C6H6, etc.) as raw materials for the gas and hydrogen mixture (some also add edgy oxygen), under certain conditions to remove hydrocarbons. In plasma, hydrogen, which binds hydrogen to each other, is pumped away by a vacuum-pumping device, and the remaining carbon ions are positively charged. In the diamond or non-diamond (Si, SiO2, Al2O3, SiC, Cu, etc.) on the substrate negative electricity, under the guidance of the electric field, the positively charged carbon ions will move to the negative power substrate, and finally settled on the substrate, and in accordance with the diamond lattice growth law on the substrate to grow the diamond. The CVD method of growing diamonds on the back of diamonds is also known as the extension growth method, which is constantly accumulated and grown according to the crystal surface parameters of the diamond seed crystal, so the growth of single crystal diamonds must be grown by CVD extension growth method.
At present, the quality of diamonds synthesized by CVD method is almost identical to that of natural diamonds, which is difficult to discern with the naked eye, and can only be distinguished from natural diamonds by observing the phosphorus performance under short-wave ultraviolet light.
HPHT method: simulates the high temperature and high pressure environment under the earth’s crust, at high temperature and high pressure, the graphite melts into the melted metal catalyst. The graphite and liquid metal pressure to a certain pressure and to a certain temperature, for example: 55,000 atmospheric pressure, 1400 degrees C to 2500 degrees C, all graphite will be dissolved into the molten metal catalyst, and transformed into a natural diamond composition and structure almost identical to the diamond.
It is some professional identification laboratories that cannot distinguish between HPHT diamonds and natural diamonds. The simplest way is for consumers to buy diamonds must ask for the world’s authoritative certificate, IGI certification will be on the certificate and diamond waist indicated that the diamond color after HPHT treatment, so consumers should pay attention to the word when reading the certificate.
CVD method synthetic diamond equipment and growth schematics
HPHT method preparation diamond equipment and internal schematics
Synthetic diamonds have become mainstream?
China’s synthetic diamonds have flourished since the 1990s, and since the beginning of the 21st century, they have dominated the world’s synthetic diamond field, with production approaching 20 billion carats in 2016: 11.33 million couples were registered in the same year, and if the average distribution of synthetic diamonds produced in the country for that year, each couple could be divided into 1,800 carats.
China’s current synthetic diamond prices are about 50% to 70% of natural diamonds, with technological progress and large-scale production of the marginal cost of decline, the future cost of synthetic diamonds may even fall to 10% to 30% of natural diamonds. According to Morgan Stanley research, by 2020, the market price of small-grain synthetic diamonds will reach 50 per cent of natural diamonds of the same class, while the price of large-grain synthetic diamonds is likely to fall to 30 per cent of natural diamonds of the same class. Morgan Stanley also predicts that, while synthetic diamond sales now account for only 1 per cent of the global market, synthetic diamonds could account for about 15 per cent of the gem market by 2020 as process quality and diamond size improve rapidly.
Take off the cloak of faithful symbolism, the future diamond may be nothing more than a flat little stone.