In general, the normal gap value of tungsten points of the distributor is between 0.35mm and 0.45mm. If the gap is large than normal gap value of 0.1mm, the petrol consumption of car engine will more than 3% of normal petrol consumption; if smaller than 0.1mm of normal gap value, then the consumption will add 5％of fuel.

The influence factors of the automotive ignition system performance are ignition advance angle, ignition energy and the maximum secondary voltage. If the ignition advance angle is too large or small, the mixture gases would not burn normally after igniting. If the ignition energy is not sufficient, the mixture gases would not properly ignite. If the maximum secondary voltage is low, the spark plugs would not normally flash over. The factors described above will decline the power of engine, rise fuel consumption and dysfunction and other aspects. Therefore, if the gap of tungsten points of distributor is proper, the influence of car ignition advance angle, ignition energy and the maximum secondary voltage to car ignition system will be reduced.


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Silver tungsten points’ preparation can adopt infiltration or powder metallurgy method.

Silver material properties:
Low wear resistance;
Low melting point;
Low hardness;
Volatile;
Good thermal conductivity;

The silver point is easier to form arcs and weld when its load is large;
Under the influence of DC, silver film form electrical erosion spikes because of silver’s low hardness and volatile characteristics;
Silver will form silver sulfide film in the surface of sulfur or sulfur compounds at the condition of high temperature and humidity,.

The content of tungsten of silver tungsten points is usually around 20% -80%. Silver tungsten points’ merits: arc erosion resistance, excellent electrical wear resistance, good electrical and thermal conductivity, good oxidation resistance and good anti-welding capability. Silver tungsten points’ defects: unstable contact resistance. Tungsten will produce mixed oxide when the silver tungsten points operating frequently and the splash degree of contact resistance of the film surface will improved.

Silver tungsten points’ application: widely applied in micro-switches, circuit breakers, thermostats, etc., and can also be used as a part in high current heavy equipment and electrical points.


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Tungsten points, also known as tungsten electrical points or tungsten contacts, which are used in equipment, instruments and switching equipment as a contact part. They are playing a role in turning on and turning off the current. Thus, tungsten points will influence the properties of the switching devices directly when they are in running state. People began to use contact materials about a hundred years ago, which started with pure silver, pure gold and pure platinum and other contact materials. People began to use alloy materials until the 1940s, such as, gold silver, platinum indium and silver copper materials. People gradually found composite materials of precious metal after the 1960s. People gradually turn their attention to tungsten materials since tungsten was found in 1781.

Tungsten contact materials possess high purity, high melting point (up to 3422 ° C), high density, high hardness, nice wear resistance, good corrosion resistance, low conductivity and other properties.

Properties of silver material are: silver owns excellent processing performance, the best thermal conductivity and high antioxidant capacity and other properties in all metals.


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Tunable dye laser spectroscopy has been used to study energy transfer processes in CaWO₃:Sm³⁺ crystals. Fluorescence and excitation transitions for samarium ions in different crystal-field sites have been identified and their changes in width and position with temperature studied. This information is used to characterize energy migration among samarium ions as a function of temperature, samarium concentration, time after the laser pulse, and pressure. The interaction mechanism causing energy migration is identified as electric quadrupole-quadrupole. At low temperatures it was found that only single-step transfer between nearby ions takes place, while at high temperatures multi-step diffusion of energy occurs. These results are interpreted in terms of the Anderson (1958) localization concepts for systems with inhomogeneously broadened transitions, and quantitative estimates of the transfer rates and diffusion parameters are obtained.

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If the gap of tungsten contacts of distributor is reduced, then: the closing time of tungsten contacts will be prolonged; ignition coil ignition energy will store more; before the tungsten contacts opening, current formed in the primary coil will be relatively large; when the tungsten contacts are opened, the maximum secondary voltage is relatively high.

If the gap of tungsten contacts of distributor is increased, then: the closing time of tungsten contacts will be shortened, which resulting in ignition energy reduction and the maximum secondary voltage drop. And because the opening time of tungsten contacts open ahead, it will cause that ignition advance angle increases.

However, the gap of tungsten contacts of distributor is not too small. If the gap is too small, when tungsten contacts are closed, it will form a strong contact spark and lost the primary ignition energy, resulting in tungsten contact ablation. And because the cutoff of primary current circuit is not complete, so the maximum secondary voltage will be reduced.




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The normal value of tungsten contacts gap of the distributor is generally around 0.35mm-0.45mm. If the gap is large than normal value of 0.1mm, the engine will use more petrol than 3% of fuel; if small  than 0.1mm, then 5％of fuel.

Ignition energy, ignition advance angle and the maximum secondary voltage will affect the automotive ignition system performance. If the ignition energy is insufficient, it will cause the mixture gases do not ignite properly. If the ignition advance angle is too small or too large, so the mixture gases will not normally burn after ignition. If the maximum secondary voltage is low, then the spark plugs do not flash over normally. These factors will make the power of engine decline, fuel consumption rise and dysfunction and so on. So, appropriate tungsten contacts gap of the distributor can mitigate the impact of car ignition energy, ignition advance angle and the maximum secondary voltage to car ignition system.




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The preparation of silver tungsten contacts can be powder metallurgy or infiltration method.

Silver material characteristics:
Low melting point, low hardness, volatile, low wear resistance, good thermal conductivity characteristics;
When the load is large, the silver contacts material is easier to form an arc and welding;
Because silver has low hardness and volatile characteristics, so under the effect of DC, silver film will form electrical erosion and spikes;
At high temperature and humid environment, silver will form silver sulfide film in the surface of sulfur or sulfur compounds.

Tungsten content of silver tungsten contacts material is usually around 20% -80%, silver tungsten contacts advantages: they own good oxidation resistance, good electrical and thermal conductivity, arc erosion resistance, excellent electrical wear resistance ability and good anti-welding capability. Silver tungsten contact shortcoming: contact resistance is unstable. When the silver tungsten contacts frequently running because the contact surface of silver and tungsten will produce a mixed oxide, the splash degree of contact resistance of the film surface will increase.

Silver tungsten contacts application: it is widely used in thermostats, circuit breakers, micro-switches, etc., and can also be used for electrical contacts, high current heavy equipment.




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For trivalent praseodymium (Pr³⁺) and quadrivalent praseodymium (Pr⁴⁺) codoped CaMO₄ (M = W, Mo) powders, the luminescence propriety of matrix is obviously influenced by carrier concentration. The light emission intensity of CaWO₄ matrix decreases exponentially with increasing of Pr concentration because oxygen-deficient obtains an electron supplied by Pr³⁺ (5d). However, the light emission intensity of CaMoO₄ is enhanced by Pr codoping because the quasi-free electrons increase the probability of radiative combination. The difference of photoluminescence properties in the two materials are attributed to the bonding character of M and O in the CaMO₄ structure.

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Tungsten contacts, also known as tungsten points or tungsten electrical contacts, which are used to act as a contact part, used in instruments, equipment and switching equipment, etc. Their roles are: turn on and interrupt the current. Therefore, tungsten contacts will directly affect the performance of the switching devices that is running state. About a hundred years ago, people started using contact materials, which began with pure gold, pure silver and pure platinum and other contact materials, until about the 1940s, people began using alloy materials, such as, silver copper, gold silver and platinum indium materials. After the 1960s, people gradually found more composite materials of precious metal. Tungsten was found in 1781, since then, people gradually shift their attention to tungsten materials.

Tungsten contact materials have wear-resistance, high density (19.25g / cm3), high melting point (up to 3422 ° C), high purity, high hardness, corrosion resistance, low conductivity and other characteristics.

Characteristics of silver material: in all metals, silver has the best thermal conductivity, excellent processing performance and high antioxidant capacity and so on.




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In the studies on phonons in CaWO₄, Kanamori et al. investigated the phonon dispersion of translational modes alone, ignoring the finite moment of inertia of tungstate ions and Coulomb interactions. In our present investigations, based on external mode formalism (Venkataraman and Sahni), we consider the coupling of the translational and librational modes and include the long range interactions. The effective ionic charges of the Coulomb interactions and the effective ionic radii of Born–Mayer short range potential arc determined so that the dynamical equilibrium conditions are satisfied and lattice energy is of the right order in comparison with other complex ionic crystals (Rao et al.). The phonon dispersion relations in CaWO₄ along [001] and [110] directions arc calculated and found to be in reasonable agreement with available neutron data (Steinman et al.). The generalized LST relations (Venkataraman et al.) computed with our model agree with the IR data of Barker. In the long wavelength limit, the acoustic branches fit well with experimental data, indicating that this model can explain the acoustic properties as well. Zone centre phonons in CaMoO₄, SrWO₄, SrMoO₄, BaWO₄, BaMoO₄, PbWO₄, and PbMoO₄ are also investigated and compared with experimental data to study the influence of polarizability and a possible breakdown of external mode formalism.

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