Today, APT is the most important and almost exclusively used precursor for tungsten products. Only in tungsten melting metallurgy and for producing WC directly from ore concentrates are other starting materials used. Intermediates, such as tungsten trioxide, tungsten blue oxide, tungstic acid, and ammonium metatungstate can be derived from APT as shown in Fig. 5.15, either by partial or complete thermal decomposition or by chemical attack.
Although a hexahydrate and a decahydrate exist, only the tetrahydrate (NH4)10[H2W12O42]•4H2O forms under industrial conditions, since the hexahydrate is unstable at temperatures exceeding 96℃, while the decahydrate crystallizes only from solutions at room temperature.
Characterization
PR: Its preparation will be treated in detail in chapter5.
PR: D: 4.61g•cm-1(X-ray); CR: monoclinic, p21/n; besides the technically important tetrahydrate, depending on drystallization conditions, a triclinic hexahydrate and an orthorhombic decahydrate can be formed.
A: It is today the most common, highly pure imtermediate for most tungsten products.
Ion associate complexes of isopolytungstates with secondary and tertiary alkyl amines play an important role in the technical solvent extraction process.
APT is a white, crystallized powder. The average crystal size of commercial products ranges between 30 and 100 µm. The SEM image in Fig. 5.16 reveals mainly faceted crystals and only few intergrown or agglomerates. A typical grain size distribution of a crystallized APT is shown in Fig. 5.17. For special purposes, classified APT is also available. Specification of some physical properties and impurity concentrations as common today are given in Table 5.7. They reflect the high standard of the technical APT production.
Specially purified APT (by multiple-step liquid extraction of selected, very pure batches under clean-room conditions) for the production of 4N and 6N tungsten sputter targets shows a much lower impurity content.
Solubility.
The solubility in water is low: 20g wo3/l at 20℃; 60g wo3/l at 90℃.
Although a hexahydrate and a decahydrate exist, only the tetrahydrate (NH4)10[H2W12O42]•4H2O forms under industrial conditions, since the hexahydrate is unstable at temperatures exceeding 96℃, while the decahydrate crystallizes only from solutions at room temperature.
Characterization
PR: Its preparation will be treated in detail in chapter5.
PR: D: 4.61g•cm-1(X-ray); CR: monoclinic, p21/n; besides the technically important tetrahydrate, depending on drystallization conditions, a triclinic hexahydrate and an orthorhombic decahydrate can be formed.
A: It is today the most common, highly pure imtermediate for most tungsten products.
Ion associate complexes of isopolytungstates with secondary and tertiary alkyl amines play an important role in the technical solvent extraction process.
APT is a white, crystallized powder. The average crystal size of commercial products ranges between 30 and 100 µm. The SEM image in Fig. 5.16 reveals mainly faceted crystals and only few intergrown or agglomerates. A typical grain size distribution of a crystallized APT is shown in Fig. 5.17. For special purposes, classified APT is also available. Specification of some physical properties and impurity concentrations as common today are given in Table 5.7. They reflect the high standard of the technical APT production.
Specially purified APT (by multiple-step liquid extraction of selected, very pure batches under clean-room conditions) for the production of 4N and 6N tungsten sputter targets shows a much lower impurity content.
Solubility.
The solubility in water is low: 20g wo3/l at 20℃; 60g wo3/l at 90℃.
Please visit our site www.tungsten-powder.com in order to get more information about tungsten powder.
没有评论:
发表评论