Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity. Inlet concentration of silver nitrate or silver acetate, applied as metal precursors, varied between 10 and 50 mM, and flow rates ranged from 0.635 to 2.5 dm³/h, to give 3–24 s reaction time. Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10–20 nm) spherical silver nanoparticles within a few seconds. Its restricted solubility in ethylene glycol, applied as the solvent and reducing agent, appeared to be vital for effective separation of the stage of particle growth from its nucleation to enable rapid synthesis of small particles in a highly loaded system. This was not possible to obtain using silver nitrate. All the observations could perfectly be explained by a classical LaMer–Dinegar model of NPs’ formation, but taking into account also nonisothermal character of the continuous-flow process and acetate dissolution in the reaction system. The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method.

Elbrusite-(Zr) Ca₃(U⁶⁺Zr)(Fe³⁺₂Fe²⁺)O₁₂, a new uranian garnet (Ia3d, a ≈ 12.55 Å, V ≈ 1977 ų, Z = 8), within the complex solid solution elbrusite-kimzeyite-toturite Ca₃(U,Zr,Sn,Ti,Sb,Sc,Nb...)₂(Fe,Al,Si,Ti)₃O₁₂ was discovered in spurrite zones in skarn xenoliths of the Upper Chegem caldera. The empirical formula of holotype elbrusite-(Zr) with 25.14 wt% UO₃ is (Ca_3.040Th_0.018Y_0.001) _∑3.059(U⁶⁺_0.658Zr_1.040Sn_0.230 Hf_0.009Mg_0.004) _∑1.941 (Fe³⁺_1.575Fe²⁺_0.559Al_0.539 Ti⁴⁺_0.199Si_0.099Sn_0.025V⁵⁺_0.004) _∑3O₁₂. Associated minerals are spurrite, rondorfite, wadalite, kimzeyite, perovskite, lakargiite, ellestadite-(OH), hillebrandite, afwillite, hydrocalumite, ettringite group minerals, and hydrogrossular. Elbrusite-(Zr) forms grains up to 10–15 μm in size with dominant {110} and minor {211} forms. It often occurs as zones and spots within Fe³⁺-dominant kimzeyite crystals up to 20–30 μm in size. The mineral is dark-brown to black with a brown streak. The density calculated on the basis of the empirical formula is 4.801 g/cm³ The following broad bands are observed in the Raman spectra of elbrusite-(Zr): 730, 478, 273, 222, and 135 cm⁻¹. Elbrusite-(Zr) is radioactive and nearly completely metamict. The calculated cumulative dose (α-decay events/mg) of the studied garnets varies from 2.50 × 10¹⁴ [is equivalent to 0.04 displacement per atom (dpa)] for uranian kimzeyite (3.36 wt% UO₃), up to 2.05 × 10¹⁵ (0.40 dpa) for elbrusite-(Zr) with 27.09 wt% UO₃.

Two new barium-bearing minerals: gurimite, Ba₃(VO₄)₂ (IMA2013-032) and hexacelsian, BaAl₂Si₂O₈ (IMA2015-045) were discovered in veins of paralava cutting gehlenite-flamite hornfels located in the Gurim Anticline in the Negev Desert, Israel. Gurimite and hexacelsian occur in oval polymineralic inclusions in paralava and are associated with gehlenite, pseudowollastonite or wollastonite, rankinite, flamite, larnite, schorlomite, andradite, fluorapatite, fluorellestadite, kalsilite, cuspidine, aradite, zadovite and khesinite. Gurimite and hexacelsian form elongate crystals <10 μm thick. The minerals are colourless and transparent with a white streak and vitreous lustre, and have (0001) cleavage, respectively good in gurimite and very good in hexacelsian. Fracture is irregular. Density calculated using empirical formulas gave 5.044 g cm^–3 for gurimite and 3.305 g cm^–3 for hexacelsian. Mean refractive indexes, 1.945 and 1.561, respectively, were also calculated using the empirical formulas and the Gladstone-Dale relationship. The minerals are uniaxial and nonpleochroic. The following empirical crystal chemical formulae were assigned to holotype gurimite: (Ba_2.794K_0.092Ca_0.084Na_0.033Sr_0.017)_∑3.020(V_1.827⁵⁺S_0.091⁶⁺P_0.051⁵⁺Al_0.040Si_0.005Fe_0.005³⁺)_∑2.017O₈,and holotype hexacelsian: (Ba_0.911K_0.059Ca_0.042Na_0.010)_∑1.022Al_1.891Fe_0.072³⁺Si_2.034O₈. The Raman spectrum of hexacelsian is similar to the one of the synthetic disordered β-BaAl₂Si₂O₈. The Raman spectrum of gurimite is identical to that of synthetic Ba₃(VO₄)₂. The electron back-scattered diffraction (EBSD) pattern of gurimite was fitted to the structure of its synthetic analogue with the cell parameters of R3m, a = 5.784(1),c = 21.132(1) Å, V = 612.2(2) ų, Z = 3, giving a mean angular deviation = 0.43° (good fit). The Raman spectra of hexacelsian and its EBSD pattern suggest that natural hexacelsian corresponds to disordered synthetic β-hexacelsian P6₃/mcm, a = 5.2920(4) Å, c = 15.557(2) Å, α = β = 90°, γ = 120°. We suggest that after relatively fast crystallization of the main constituents of the paralava, gurimite, hexacelsian and also other Ba-bearing phases crystallized from residual melt enriched in incompatible elements that filled interstices between crystals of the main constituents.