Tungsten Copper Powder Injection Molding Research (2/2)

Many parameters of injection molding should be perfectly controlled, such as the temperature, the pressure, the speed and so on. Theoretically, in the process of injection molding, the temperature and pressure are the largest influencing factors of molding properties. In order to press tungsten copper powder mixture into the mold cavity, the temperature inside the injection machine must be high enough so that moderate viscosity mixing, the two-phase does not separate. For injection pressure (to overcome the flow mixing cavity flow resistance, provide filling speed and compaction of the melt) and speed in the experiment demonstrated that there is an optimal match range, pressure and speed should not be too large or too small. The following is the impact of temperature and injection table corresponding to the formation of body performance and injection molding pressure and injection speed of the blank:

weight of the injection molded ball as a funtion of compact pressure and injection speed

From the figure above, we can also find the optimum temperature range for injection, injection pressure and speed. Since the injection process to fill the cavity is more complex, many parameters must be well controlled, once appear unreasonable control can cause a variety of defects. We introduce some common defects and the corresponding solutions: 1. Under-injection, it refers to the injection process feed can not fill the mold cavity, the corresponding solution is three-pronged approach from the injection temperature, feeding quantity and viscosity of the feed itself causes analyzed; 2. The pores, it is the most common type of defect, the corresponding method is to pay attention to whether the injection and mixing of air entrainment and make adjustments, check the injection speed, the injection pressure, etc; 3. Unstable quality, it should be considered that whether the powder is uniform and the segregation with the binder.

 

Tungsten Copper Powder Injection Molding Research (1/2)

Based on conventional molding process and combines plastic molding industry technology, PIM (Powder Injection Molding) has excellent applicability in some tungsten copper products with small size and complex shape or structure. So we study from mixing, injection, degreasing, sintering and several key process of tungsten copper powder injection molding, and analyze and summarize the advantages of the process and the defects.

The first is the selection of the binder and the preparation of mixture. Binders can reduce caking of the powder, which has good flowability, and plays the role of maintaining the shape of the body until degreasing sintering. Thus the choice of the binder is injection molded in a key ring, it should meet the deformation and cracking does not occur before the product sintering defect, and easy to be removed. Now more use thermoplastic or some polymers as binders, such as paraffin, stearic acid, HDPE, EVA and so on. In the process of mixing, paraffin and stearic acid are liquid phase, which does not destroy the nature of the binder. In addition, wherein the order of addition of powder and a binder is the final state of the blank has a certain influence. The next is granulating, and select particles about 2-3mm for injection molding.

AMT Structure Study

Several techniques have been used to study the structure of the Keggin-type polyoxometalate salt ammonium metatungstate (AMT)—(NH4)6[H2W12O40]*nH2O, a potential fuel cell catalyst. The dehydrated salt is comprised of a mixture of crystallites of different unit cells in a centered eutactic cubic configuration, with an average unit cell of a≅12.295. Varied orientations of the Keggin ions in the cubic arrangement create the differences, and orientational variation within each unit cell size represents an energy well. Progressive hydration of each crystallite leads to expansion of the lattice, with the degree of expansion depending on the locations of the water added in relation to the Keggin ion, which is influenced by cation location and hydrogen bonding. The structural hypothesis is supported by electron diffraction of single and multicrystal samples, by powder density measurements, X-ray powder diffraction studies, synchrotron powder X-ray diffraction, and a priori structural modeling studies. Based on the structure, projected active site densities are compared with nanostructured platinum catalysts for fuel cell application.
 
Graphical abstract
The structure of ammonium metatungstate powders are highly dependent on hydration and POM molecule rotation, with cation and hydrogen bonding forces directing a mixture of structures that have been studied with bulk and single-crystal methods. The illustration shows Monte Carlo simulated anion structural disorder for the fully dehydrated form of the title compound.


structure of ammonium metatungstate powders

AMT Neutralization–Nanofiltration–Crystallization Process

Neutralization is a chemical reaction in which an acid and a base react quantitatively with each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in solution. The pH of the neutralized solution depends on the acid strength of the reactants. Neutralization is used in many applications.
 
Nanofiltration is a membrane filtration-based method that uses nanometer sized cylindrical through-pores that pass through the membrane at 90°. Nanofiltration membranes have pore sizes from 1-10 nanometers, smaller than that used in microfiltration and ultrafiltration, but just larger than that in reverse osmosis. Membranes used are predominantly created from polymer thin films. Materials that are commonly use include polyethylene terephthalate or metals such as aluminum. Pore dimensions are controlled by pH, temperature and time during development with pore densities ranging from 1 to 106 pores per cm2. Membranes made from polyethylene terephthalate and other similar materials, are referred to as “track-etch” membranes, named after the way the pores on the membranes are made. “Tracking” involves bombarding the polymer thin film with high energy particles. This results in making tracks that are chemically developed into the membrane, or “etched” into the membrane, which are the pores. Membranes created from metal such as alumina membranes, are made by electrochemically growing a thin layer of aluminum oxide from aluminum metal in an acidic medium.
 
Using a coupling process of neutralization–nanofiltration–crystallization, pure ammonium metatungstate (AMT) was prepared. The effects of chemical neutralization of ammonium paratungstate (APT) by nitric acid, operating pressure, AMT concentration, the volume of washing water on the coupling process were systematically discussed. It was found that the better conditions of AMT preparation were as follows: the neutralization temperature was 80–95 °C, pH value was 2.0–3.5; the operating pressure of HDS-12-2 nanofiltration was 1.5–2.0 MPa, the density of AMT crystallization solution was 2.39 kg/L, and then cooling. APT conversion efficiency (δ) to AMT was more than 97.62%. The removal ratio of nitrate ion (NO3−) was more than 99% while AMT rejection (RAMT) was 99.9%. Besides, small-grained, even-proportioned, white-colored and high-purified AMT crystal was be obtained and analyzed. This method has several advantages such as simple technological process, short production cycle, lower environmental pollution and high quality.

AMT

Tungsten Gold-Plated Coins for Birthday Party

The concept of birthday celebration for modern people is no longer as indifference as the ancient people. Nowadays, people will use a variety of ways to celebrate their birthday, such as celebrating birthday outdoors with friends and relatives, or going to hotels to have a table of delicious bites, or going to KTV and singing together. Of course, there is another way to celebrate, is to invite your classmates, colleagues, relatives etc. to your home and hold a spectacular birthday party. Westerners prefer to hold a birthday party at home, because this will make a more meaningful birthday, and create more memorable memory. So, in addition to the video and photos, what can be permanently in memory of this memorable birthday party?
 
Tungsten gold-plated coins have golden color and beautiful appearance, which have been used to commemorate various special days, occasions or collections by many people. For the birthday party, its holding meaning is to commemorate, which coincides with the using nature of tungsten gold-plated coins.Therefore, tungsten gold-plated coins can be used as commemorative coins according to the different needs of different carving patterns or texts. Not only can commemorate the birthday but also the celebration of this unforgettable birthday party at the same time.
tungsten gold-plated coins for birthday party

 

 

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