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An electrolytic process was utilised to fabricate NiCoCrAlY coatings, involving deposition of a composite coating consisting of the (Ni,Co) matrix and CrAlY particles, followed by a diffusion heat treatment to convert the composite coating to the desired NiCoCrAlY microstructure. This study focused on the effects of the post-deposition heat-treating conditions (temperature and atmosphere) on the final coating microstructure and composition. The (Ni,Co)–CrAlY composite coatings were heat-treated for 2 h at 1000, 1100 and 1200°C in vacuum and Ar, respectively. Phase constituents and concentrations of the major elements in the coating after heat treatment were examined. Vacuum heat treatment at temperatures ≥1100°C resulted in a significant decrease in Cr content at the coating surface due to Cr evaporation. Heat treatment at 1200°C also caused outward diffusion of Ti from the substrate alloy to the coating layer.

An electrolytic sediment codeposition process was employed to fabricate composite coatings containing CrAlY particles embedded in an Ni matrix. The effects of three main deposition parameters and their interactions on the amount of CrAlY particles incorporated in the composite coating were investigated using a design of experiments (DoEs) method. Current density, agitation rate and concentration of CrAlY particles in the solution were the parameters considered in the 23 full factorial design. With different combinations of the deposition parameters, the amount of CrAlY particles in the composite coatings ranged from 20 to 49 vol.-%. The DoE results show that the agitation rate exhibited the greatest influence on the amount of CrAlY particles incorporated in the composite coating, followed by the interaction between agitation and particle loading and then the particle loading itself. Current density did not appear to affect the particle incorporation for the present set-up.

The fatigue crack growth behaviour of a nickel based superalloy at elevated temperatures 550, 650 and 710°C was studied. The direct current potential drop (DCPD) technique was used to measure the crack length during the test. It was found that the crack growth rates slightly increased with increasing temperatures, but the temperature effect on crack growth rates was less pronounced at higher ΔK ranges. At the same temperature the crack growth rates increased with increasing load ratios. The oxidation induced crack closure is considered to be a reason of the observed crack growth behaviour in this study.

The structure of a new nonlinear optical crystal, Ca9Y0·5La0·5(VO4)7, was solved, for first time to our knowledge. It belongs to trigonal system with space group R3c, its unit-cell parameters are: a = 10·8717(2) A, c = 38·0753(14) A, V = 3897·34(18) A3, Z = 6, dc = 6·3279 g cm−3. The thermal expansion, the special heat capacity and the thermal conductivity of the crystal were investigated in detail. The crystal’s relative intensity for second harmonic generation is about 1·8 times as large as that of KH2PO4. Its transmittance exceeds 70% in the range of 400–2700 nm. From the measured principal refractive indices, the Sellmeier equations were derived. The results show that Ca9Y0·5La0·5(VO4)7 is expected to be a promising new frequency-doubling laser crystal.

Subsolidus phase relations in the ternary system TiO2–BaO–B2O3 were analysed with X-ray diffraction. According to the constructed phase relations, 15 ternary phase regions were identified in the subsolid phase, in which 11 binary compounds and 2 ternary compounds were investigated in detail. Additionally, the crystallisation region of rutile was identified, and it was found that rutile crystal with dimension of 10×4×2 mm was grown through spontaneous nucleation from a new flux BaO–B2O3.

This paper reports on the growth and spectral properties of NaNd(MoO4)2 crystal. NaNd(MoO4)2 crystal with dimensions of 23×15×15 mm was grown from a flux of Na2Mo2O7 by top seed solution growth method. The absorption and emission spectra of NaNd(MoO4)2 crystal were investigated. The results show that NaNd(MoO4)2 crystal has large absorption cross-section of 3·74×10–20 cm2 with broad full width at half maximum of 15 nm at 806 nm for π-polarisation and 2·49×10–20 cm2 with full width at half maximum of 16 nm at 807 nm for σ-polarisation respectively. The emission cross-sections are 6·0×10–19 cm2 at 1058 nm for π-polarisation and 3·93×10–19 cm2 at 1065 nm for σ-polarisation respectively. The above results indicated that NaNd(MoO4)2 crystal may be regarded as potential self-active laser materials.

The Cr3+/RbAl(MoO4)2 crystal was grown by top seeding solution growth method, and its thermal and spectral properties were investigated. Based on the absorption and photoluminescence spectra, the crystal field strength Dq, the Racah parameters B and C, the effective phonon energy ħω and the Huang–Rhys factor S were calculated. The results of spectroscopic characterisation show that the Cr3+ ions occupy medium crystal field sites in Cr3+/RbAl(MoO4)2 and Cr3+/RbAl(MoO4)2 crystals may be a potential candidate for tunable laser applications.

An Nd3+ :Li3Ba2Y3(WO4)8 crystal with dimensions up to 32 × 20 × 14 mm has been grown by the top seed solution growth method. The spectral characterisation of Nd3+ :Li3Ba2Y3(WO4)8 crystal was investigated. The investigated results show that Nd3+ :Li3Ba2Y3(WO4)8 crystal has a broad absorption band with full width at half maximum (FWHM) of ∼9 nm at 805 nm. The absorption cross-sections are 10·12 × 10–20 cm2 for E//Y, 2·33 × 10–20 cm2 for E//X and 3·69 × 10–20 cm2 for E//Z respectively. The emission cross sections are 4·45 × 10–20 cm2 at 1065 nm for E//X, 15·51 × 10–20 cm2 at 1061 nm for E//Y and 6·67 × 10–20 cm2 at 1061 nm for E//Z respectively. The quantum efficiency η is 93·7%. These results suggest that Nd3+ :Li3Ba2Y3(WO4)8 crystal may be regarded as a new high efficiency laser crystal material.

This paper reports growth and spectroscopic properties of Yb3+/Er3+:CaMoO4 crystal. Yb3+/Er3+:CaMoO4 crystal with dimensions of 20 × 40 mm has been grown by Czochralski method from a flux of Na2MoO4. The spectroscopic properties were investigated. Yb3+/Er3+:CaMoO4 crystal has a strong and broad absorption band with full width at half maximum of 66 nm, which is suitable for diode laser pumping. Two strong up-conversion emission bands at 510–570 nm and 640–690 nm were observed. Based on the rate equation method, the proportion η of the up-conversion emission intensity of 533, 553 and 671 nm was determined to be 57·83%, which indicates the high effective energy transfer and up-conversion process from Yb3+ to Er3+ ion in Yb3+/Er3+:CaMoO4 crystal.

The present paper reports the growth and spectroscopic properties of KYb(WO4)2 crystal. The KYb(WO4)2 crystal with dimensions of 32 × 29 × 12 mm was grown from a mixed flux of K2WO4 and KF by the TSSG method. The spectroscopic properties of KYb(WO4)2 crystals were investigated. The absorption and emission cross-sections of KYb(WO4)2 crystal are 4˙32 × 10–20 cm2 at 981 nm and 3˙69 × 10–20 cm2 at 1024 nm for E//X polarisation respectively. The laser parameters of KYb(WO4)2 crystal were evaluated. These results suggest KYb(WO4)2 crystal as a potential candidate for microchip laser medium.

The Yb3+/Na+:CaMoO4 crystal with dimensions of o20 × 30 mm3 has been grown by Czochralski method from a flux of Na2MoO4. The absorption and emission spectra of Yb3+/Na+:CaMoO4 crystals were investigated. The absorption bands at 934 nm have a FWHM of 59 nm for π polarisation and 65 nm for σ polarisation respectively. The absorption cross-sections σ a are 1˙73 × 10–20 cm2 for π polarisation and 1˙44 × 10–20 cm2 for σ polarisation at 934 nm respectively. The emission bands have a FWHM of 68 nm at 1022 nm for π polarisation and 65 nm at 1023 nm for σ polarisation respectively. The emission cross-sections σ e are 1˙14 × 10–20 cm2 at 1022 nm for π polarisation and 1˙27 × 10–20 cm2 at 1023 nm for σ polarisation respectively. The Yb3+/Na+:CaMoO4 crystal may be considered as a potential laser gain material.

The spectroscopic characteristics of Er3+/Yb3+:LiLa(WO4)2 crystal were investigated. Based on the Judd–Ofelt theory, the following intensity parameters Ωλ were obtained: Ω2=9˙03 × 10–20 cm2, Ω4=2˙02 × 10–20 cm2 and Ω6=0˙59 × 10–20 cm2. The upconversion emission of Er3+/Yb3+:LiLa(WO4)2 crystal was investigated under excitation with the 976 nm diode laser. The Er3+/Yb3+:LiLa(WO4)2 crystal has the intensity parameters Ωλ and a strong emission of 562 nm wavelength. Er3+/Yb3+:LiLa(WO4)2 crystal may be regarded as an upconversion laser material for the green light.

The Tm3+/Yb3+:LiGd(MoO4)2 crystal with dimensions of Φ21 × 45 mm was grown by the Czochralski method. The spectroscopic properties of Tm3+/Yb3+:LiGd(MoO4)2 crystals were investigated. Based on the Judd–Ofelt theory, the oscillator strength parameters Ωt are: Ω2=16·468 × 10−20 cm2, Ω4=3·376 × 10−20 cm2, Ω6=2·613 × 10−20 cm2 for π-polarisation and Ω2=19·3 × 10−20 cm2, Ω4=1·582 × 10−20 cm2, Ω6=2·397 × 10−20 cm2 for σ-polarisation. The absorption cross-section σab are 4·17 × 10−20 cm2 at 796 nm and 5·31 × 10−20 cm2 at 797 nm for π- and σ-polarisation respectively. The emission cross-section σem are 1·72 × 10−20 cm2 at 1606 nm for π-polarisation and 2·00 × 10−20 cm2 at 1609 nm for σ-polarisation respectively. The Tm3+/Yb3+:LiGd(MoO4)2 crystals may be regarded as a potential infrared laser crystal.

Aγ–Yb3+ : LaSc3(BO3)4 with a dimension of 30 × 20 × 10 mm has been grown from a mixed flux of Li6B4O9 and LiF by the top seeded solution growth method. The spectral properties have been investigated. The absorption and emission cross-sections of γ–Yb3+ : LaSc3(BO3)4 crystals are 1˙74 × 10−20 cm2 at 972˙3 nm and 8˙03 × 10−21 cm2 at 1026 nm respectively. The radiative lifetime and fluorescence lifetime of γ–Yb3+ : LaSc3(BO3)4 crystals are 0˙8 and 1˙658 ms respectively. The β min, l sat and l min are 9˙8%, 0˙7 kW cm−2 and 7˙1 kW cm−2 respectively. To sum up the spectral properties of γ–Yb3+ : LaSc3(BO3)4 crystal, it was suggested as a potential laser gain material.

A Yb3+:Y0·8La0·2Ca4O(BO3)3 crystal with the dimensions of o16 × 20 mm has been grown by the Czochralski method. The absorption and emission cross-sections of the Yb3+:Y0·8La0·2Ca4O(BO3)3 crystals are 1·37 × 10−20 cm2 at 977 nm and 0·64 × 10−20 cm2 at 1033 nm respectively, which are larger than that of Yb3+:YCa4O(BO3)4 and Yb3+:GdCa4O(BO3)4 crystals. It shows that the spectroscopic properties of Yb3+:Y0·8La0·2Ca4O(BO3)4 crystal can be improved by substituting the part La3+ ions for the Y3+ ions in YCa4O(BO3)4 to form mixed YxLa1−xCa4O(BO3)3.

This paper reports on the spectral parameters of Er3+ in Er3+/ Yb3+: Ca3Y2(BO3)(4), Er3+/ Yb3+: Ca3Gd2(BO3)(4) and Er3+/ Yb3+: Ca3La2(BO3)(4) crystals. The results show that the oscillator strength parameters Omega(t), fluorescence quantum efficiency and emission cross-sections of Er3+/ Yb3+: Ca(3)Ln(2)(BO3)(4) ( Ln=Y, Gd, La) crystals are larger than those of Er3+: Ca(3)Ln(2)(BO3)(4) (Ln=Y, Gd, La) crystals, and the codoped Er3+/ Yb3+ can enhance the optical transition probability of Er 3z in the crystals and improve the fluorescence quantum efficiency and emission cross section of the (4)/(13/2) -> (4)/(15/2) transition of Er3+ in Er3+/ Yb3+: Ca(3)Ln(2)(BO3)(4) ( Ln=Y, Gd, La) crystals.

A Nd3+/Yb3+ : Sr3Gd2(BO3)(4) crystal 40 mm in diameter and 15 mm in height was grown by the Czochralski method. The spectroscopic characterization of Nd3+/Yb3+:Sr3Gd2(BO3)(4) crystal was investigated. The emission crosssection of Yb3+ in the Nd3+/Yb3(+):Sr3Gd2(BO3)(4) crystal is 1.57 x 10(-20) cm(2) at 1014 nm, and the radiation lifetime tau(rad) of F-2(5/2) of Yb3+ is 881.6 mu s. The result shows that the energy transfer occurs from F-4(3/2) of Nd3+ to F-2(5/2) of Yb3+ in the Nd3+/Yb3+:Sr3Gd2(BO3)(4) crystal, which should enhance the laser efficiency of Yb3+ in the Nd3+/Yb3+:Sr3Gd2(BO3)(4) crystal.

The characteristics of fast electrons (e-) and heavy particles (N2+, N+, N2f, Nf) in the cathode dark space (CDS) of nitrogen dc glow discharge are simultaneously studied by Monte Carlo simulation. The calculated energy and angular distributions of these particles at different positions from the cathode provide a clear picture of their transport behaviours within the CDS. The density and mean energy of these particles indicate that the electrons and the atomic ions (N+) are the main high-energy species and the molecular ions (N2+) are the major ions in the CDS. It can be seen from the energy distributions of the bombarding particles at the cathode surface that the molecular ions and the fast atoms (Nf) are the main active species participating in the cathode nitride material synthesis process. The influence of the backscattering of the electrons from the negative glow to the CDS is also investigated. All the calculated results provide good information on the spatial characteristics of the particles considered in this paper and also their internal connections in the CDS of nitrogen dc glow discharge.

This paper reports the thermal properties and 1·064 m m lasing characteristics of Nd3+:LaVO4 crystal pumped with a Ti:sapphire laser. The maximum laser output power is 107 mW at the pumping power of 461 mW. The slope and light conversion efficiency are 52·8 and 22·9% respectively, and the laser threshold is 45 mW. These results indicate that Nd3+:LaVO4 crystal can be regarded as a new laser crystal.

A Yb3+ :Sr2La0·667(VO4)2 crystal with dimensions 18 × 15 × 30 mm3 has been grown by the Czochralski method. The absorption cross-section is 1·45×10−20 cm2 at 976 nm wavelength. The fluorescence spectrum exhibits a broad emission band from 925 nm up to 1125 nm and the emission cross-section is 0·64 × 10−20 cm2 at 1029 nm. The radiative and fluorescence lifetimes are 0·66 and 1·13 ms, respectively. In comparison with other Yb3+-doped materials, the value of I min of the Yb3+ :Sr2La0·667(VO4)2 crystal is lower, which implies that the Yb3+ :Sr2La0·667(VO4)2 crystal may possess a lower laser threshold.

Lower hybrid wave (LHW)-plasma coupling experiments in HT-7 [J. K. Xie and HT-7 Group, Proceedings of the 16th International Conference on Fusion Energy, Montreal, 1996 (IAEA, Trieste, 1997), Vol. 1, p. 685] were carried out by means of puffing gas (CD4 and D2) just around the antenna. Both experiments show that wave-plasma coupling is improved by the gas puffing. The maximum distance between the plasma and the antenna is limited to about 8 cm due to the plasma disruption. The variation in the lined averaged density in the different channels gives a possible evidence of the mechanism of the ionization of neutral gas. The effect of the gas flow rate on the wave-plasma coupling shows that an optimized gas flow rate is necessary for good coupling, being consistent with simulation through Brambilla theory qualitatively. Experiments with puffing D2 show that the improved coupling results from the global density increase and the local gas puffing. Langmuir probe measurements indicate that the gas puffing effect...