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The influence of the ratio of the initial components on the combustion parameters and modes of mixtures of aluminum with copper oxide has been studied. It has been shown that under normal conditions, such mixtures can burn stably when they contain not less than 30% copper oxide. Moreover, with an increase in the content of copper oxide to the stoichiometric ratio, there is a regular change in combustion mode: self-oscillatory, spin, combined convective and multi-hotspot, flame, and fireball combustion modes. In addition, the effect of the ratio of the components on the combustion of copper oxide–aluminum–titanium ternary mixtures was studied, and concentration regions were determined for four main modes of their combustion: the self-oscillatory, hotspot, flame, and fireball modes. It has been shown that the hotspot combustion of such mixtures can proceed in five different modes: a spin mode, a multi-hotspot mode, a combined convective and multi-hotspot mode, a multi-hotspot mode with the formation of a counter front, and a multi-hotspot mode with periodic ejection of combustion products. Depending on the ratio of the initial components, the condensed combustion products of mixtures of copper oxide with aluminum and titanium were found to contain copper, Al3Ti, Ti3Al, and CuAl5Ti2 intermetallic compounds, and Al2O3, TiO2, TiO, Cu2O, Al2TiO5, and Cu3Ti3O oxides.

The effect of the ratio of the components of mixtures of nickel (II) oxide with titanium on the combustion modes and burning rate of compositions based on them is studied. It is found that under normal conditions, a change in the mass content of nickel oxide from 75 to 30% leads to a regular change in combustion mode: a flame, a multi-hotspot mode, and a self-oscillating mode with a periodic separation of combustion products from the burning surface. It is shown that the maximum burning rate of such mixtures (82 mm/s) is achieved at equal mass proportions of nickel oxide and titanium. In the condensed combustion products of a mixture of nickel oxide with titanium, Ti2Ni intermetallic and Ni2Ti4O $$_{x}$$ binary oxide were identified.

The conditions of occurrence, nature, size, and shape of combustion hotspots of energetic condensed systems and the spatial dynamics of the hotspot combustion wave are discussed. A model for the propagation of hotspot combustion waves in condensed systems is briefly described based on the cellular automata method. A possible explanation for the occurrence of unsteady effects in the combustion of solid rocket propellants is proposed.

The nitration of hyperbranched polyglycidols was studied. It was confirmed that there is no destruction of the polymeric chain when the nitration reaction is performed. The influence exerted by the molecular mass of polyglycidols on the degree of substitution of hydroxy groups in polyglycidol by nitrate groups was determined. The dependences of the degree of substitution of hydroxy groups on the reaction conditions and duration were found. It was shown that the fundamental aspects found in the study can be used to synthesize polyglycidyl nitrates with controllable degree of substitution from polyglycidols with various molecular masses.

Nitration of α-, β-, and γ-cyclodextrins with nitric acid of various concentrations was studied. The nitration occurs similarly for all the three cyclodextrins studied. The influence of the reaction conditions on the degree of substitution of hydroxy groups in cyclodextrin by nitrate groups was examined. The composition and degree of substitution of the nitration products depend not only on the nitric acid concentration, but also on the molar ratio of HNO3 to OH groups. The results obtained allow optimization of the procedure for preparing cyclodextrin nitrates with definite topology of substitution of cyclodextrin hydroxy groups.

Microcrystalline metallic bismuth powders of varied morphology were obtained by reduction of bismuth precursors, basic bismuth formate and bismuth(III) formate in benzyl alcohol, hydrazine hydrate, and sodium borohydride. The methods of X-ray diffraction analysis, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry were used to examine the phase composition and the morphology of the resulting metallic bismuth powders. A dispersion analysis of bismuth samples was made by the method of small-angle scattering of light for a proximate monitoring of the particle size in powders of different fractions. The specific surface area of the metallic bismuth sample was determined by the thermal desorption of argon.

This paper describes the study of the effect of physical and chemical properties of powder titanium and the equivalence ratio on the burning parameters of its mixtures with copper oxide. It is shown that the linear burning rate of such mixtures is significantly dependent on the brand of used titanium. Under normal conditions, the mixtures can stably burn with the content of copper oxide of not smaller than 13%. With an increase in the content of copper oxide to a stoichiometric ratio, there is a change of combustion regimes: multifocal, multifocal with detachment of solid residue, combination of convective and multifocal, multifocal with melt formation, flaming combustion, and fireball. It is determined that, in this system, there may be convective burning under atmospheric pressure in the absence of outer reinforcement.

The thermal decomposition of the energetic component and chemical reactions occurring at elevated temperatures in a flameless combustion wave of systems based on hexogen (filled with iron(II) formate and polyisocyanurate binding agent) afford a mixture of iron oxides and iron nitride as nanosized particles. The purposeful change in the ratio of the indicated basis components can provide individual Fe2O3, Fe3O4, or FeO in the conversion products. Additives of anthracene and hydroquinone to the initial composition can result in the formation of predominantly iron carbide in the products, whereas mainly iron nitrides are formed upon the addition of guanidine nitrate or 5-aminotetrazole. The addition of aluminum hydride components to the initial mixture results in the reduction of iron to the zero-valence state in the form of iron—aluminum intermetallic compounds.

The dependence of the combustion parameters of cellulose nitrate (nitrocellulose, NC) mixtures with magnesium oxide on the content of the energetic component was studied to reveal peculiarities of the combustion of NC in ballasted systems. It is experimentally shown that the combustion occurs in the flameless low-temperature region at the NC content in a mixture with magnesium oxide lower than 60%, and the reactive smoke reaction products can be ignited by a secondary thermal igniter heated to the temperature higher than 770 K. For the NC content in the initial mixture higher than 60%, a critical increase in the combustion temperature and velocity is observed due to the ignition of the reactive smoke products of NC decomposition inside the sample. The combustion of NC in the flame and flameless regimes is characterized by an intermediate isothermal stage at the temperature about 440 K corresponding to the temperature of onset of the fast NC decomposition. Thus, ballasting of a power material with an inert filler makes it possible to reveal and characterize the spatial and time stage character of its thermal decomposition under the combustion conditions.

The impact sensitivity of the energy systems based on nanoporous silicon, obtained by electrochemical etching of monocrystalline silicon wafers in an HF-containing electrolyte, and calcium perchlorate was studied using a modified Weller—Ventselberg technique (estimation of the impact sensitivity of initiating explosives). The impact sensitivity of these systems is shown to be determined by both the presence of hydrogen, which is stored on the porous silicon surface during the preparation of the latter, and also the influence of other factors, including the specific surface of porous silicon. The composition, amount of the generated gas, and gas evolution rate during nonisothermal and isothermal calcination of porous silicon in a temperature range of 60—120 °С were determined using methods of thermal gravimetry (TG), measurement of the gas volume, and mass spectrometry. The generated gas almost completely consists of hydrogen, and its content in the studied samples of porous silicon achieved ~3.8 wt.%. The calculated activation energy of the hydrogen evolution process in vacuo was 103.7±3.3 kJ mol–1. The dependences of the impact sensitivity of the energy composition based on porous silicon and heat of combustion of porous silicon on oxygen on the hydrogen content were established. The impact sensitivity of the energy system decreases with a decrease in the hydrogen content in porous silicon and its specific surface.

Cyclodextrin nitrates with different degrees of substitution of hydroxy groups by nitrate groups were synthesized. A procedure based on analysis of 1H NMR spectra was developed for determining the degree of nitration and the composition of the product mixtures obtained.

A new compound of dioxomolybdenum(VI)—[MoO2(L)(H2O)] · H2O, where L 2− = 2-[N-(hydroxynaphtylidene)amino]propan-1,2,3-triol)—is synthesized. Its structure is determined by X-ray diffraction. The Mo atom has an octahedral coordination formed by two oxo ligands located cis with respect to one another, two O atoms and the N atom of the tridentate bis(chelate) L 2− ligand, and the O atom of a water molecule. The crystallization water molecule is connected with two complex molecules by O-H…O hydrogen bonds.

Ten new dioxomolybdenum(VI) compounds with o-oxyazomethines, derivatives of substituted salicylaldehydes (I–X) and tris(hydroxymethyl)aminomethane, are synthesized. The structures of two of them, [MoO2(L)] · CH3OH; L = Z-substituted salicylalimines, Z = 3-NO2 (IV) and 3-OCH3 (V), are determined by X-ray diffraction analysis. Compounds IV and V have similar structures and geometric parameters. The Mo atoms are coordinated through the octahedral mode by two oxo ligands in the cis positions to each other, two O atoms, one N atom of the tridentate bis(chelating) ligand L, and the O atom of the MeOH molecule.

A method for the preparation of new representatives of polynitrogen hyperbranched polymers of heterocyclic series was developed involving polymerization of monomeric 2,4-diazido-6-propynyloxy-1,3,5-triazine by 1,3-dipolar cycloaddition. Kinetics of polymerization of diazidoacetylene monomer was compared with the kinetic data of polymerization of its closest analog, 2-azido-4,6-bis(propynyloxy)-1,3,5-triazine monomer. Properties of hyperbranched poly(1,2,3-triazole-1,3,5-triazine)s with terminal azide groups and terminal triple bonds were compared, as well.

The features of flameless low-temperature wave conversion (LWC) of some energetic materials in filled systems were studied experimentally and analyzed theoretically. The results attest to an relay-race mechanism of process propagation in the initial composition. An important role of the filling material in stabilization of the LWC wave of the energetic component is revealed. In the presence of mono- or oligomeric binders, flameless LWC of the energetic component affords strong highly porous composite materials. The possibility of using this method for preparing new high-performance grinding materials and catalysts containing nanosized particles of transition metals and their derivatives is demonstrated.

The synthesis of polyurethane block based on oligoesterdiols 4,4′-methylene-bis(phenylisocyanate), and various chain elongating agents was studied. The properties of these copolymers were compared (using literature data) with selected properties of polyurethanes obtained by the reactions of oligoetherdiols, viz., oligo-3,3′-bis(azidomethyl)oxetanediol and oligo-3-azidomethyl-3′-methyloxetanediol with diisocyanates. The complex of rheological and physicomechanical properties of the initial and plasticized polyurethane block copolymers was studied. Regularities of their deformation behavior were established. The process of mutual solubility was studied by the microinterference method for a wide range of systems block copolymers—plasticizers. On the basis of the data obtained, the phase diagrams were constructed for limitedly compatible systems.

The hydrogenation of 1,3-pentadiene into pentenes over the commercial 0.5% Pd/Al2O3 catalyst and over a new catalyst containing 1.0% Pd and 3.7% Ag (μ-catalyst) has been investigated. The new catalyst has been prepared via the flameless wave conversion of cyclotrimethylenetrinitramine in a porous composite. The catalytic properties of the new composite in the hydrogenation reaction depend on the hydrogen/1,3-pentadiene ratio and on the catalyst activation temperature. The reaction conditions for selective 1,3-pentadiene hydrogenation have been optimized. The pentenes yield as a function of temperature passes through a maximum at any H2/C5H8 ratio between 1 and 2. The 2-pentene/1-pentene ratio in the reaction products increases as the temperature is raised.

A method of synthesis of 2,6-diazido-3,5-dicyanopyridine, 2,4,6-triazido-3,5-dicyanopyridine, and 2,3,4,5-tetraazido-6-cyanopyridine was developed. The heats of formation and explosive properties of compounds obtained were determined; kinetics and the composition of the gaseous thermolysis products were studied. The replacement of endocyclic nitrogen atoms by C-CN fragments in the aromatic ring of polyazides strongly reduces the explosive risk of these compounds with retention of the energetic properties of the molecules.

It is established that the combustion of mixtures of sodium azide with aluminum oxide and potassium dichromate at the lower limit for the dichromate content occurs in a chaotic self-oscillatory regime. Modification of the structure of the starting mixture by increasing the dichromate particle sizes from 40–60 K to 250–500 µm lead to significant stabilization of its combustion parameters. The amount impurities and aerosols in generated nitrogen is considerably decreased by reducing the energy content of sodium azide based composition. Using the relay-race model of combustion of heterogeneous systems, it is shown that, under the given conditions, the burning rate of such compositions is determined by the time of heating of potassium dichromate particles to the ignition temperature by neighboring burning particles.

The effect of the content of combustible particles on the spatial forms of the combustion wave in a gasless thermite-inert material model system is studied. It is shown that the lower flammability concentration limit for this mixture is related to the formation of a three-dimensional binding percolation cluster or to a percolation phase transition. Near the lower concentration limit, the combustion of model mixtures enters a smoldering regime in which separate combustion sources move randomly in the volume of the unburned material. If the initial composition contains more than 47% thermite particles, a motionless heated surface forms, along which separate incandescent combustion sources move. The motion of this surface in the unburned material occurs only locally as a result of motion of the combustion sources on it. The formation of this unified heated surface corresponds to the occurrence of a second percolation phase transition. When the volumetric content of thermite particles in the initial mixture is higher than 70%, separate combustion sources merge into a unified surface of layer-by-layer combustion due to the occurrence of a third percolation phase transition.

The complexes [UO2(C6H4NO2)2(C6H5NO2) (I) and [UO2SO4(C6H5NO2)(H2O)] · H2O (II) were synthesized and studied by X-ray diffraction analysis. Crystals I are monoclinic: a = 7.0081(3), b = 14.9624(7), c = 9.1837(5) A, β = 96.594(2)°, Z = 2, space group P21/m. Crystals II are triclinic: a = 6.8097(6), b = 9.3837(8), c = 10.4556(10) A, α = 85.279(3), β = 75.434(3), γ = 69.180(3)°, Z = 2, space group $$P\bar 1$$ . The main structural unit of crystal I is a mononuclear fragment, which belongs to the crystal chemical group AB 2 01 M1 (A = UO 2 2+ , B01 are ions of pyridine-2-carboxylic (picolinic) acid, M1 are molecules of picolinic acid) of the uranyl complexes. The main structural unit of crystal II is a chain, which belongs to the crystal chemical group AT3M 2 1 (where T3-SO 4 2− , M1 are water and picolinic acid molecules) of the uranyl complexes. Picolinic acid in complexes I, II was found to have a zwitterion structure.

In systems filled by inert additives, combustion of cellulose nitrate (CN) proceeds in a flameless low-temperature regime with a low linear burning rate. At a standard temperature, the exponent in the low of CN combustion in ballasted mixtures with inert additives in the pressure range of 0.1 to 10 MPa is several times lower than that of pure cellulose nitrate and amounts to 0.23. The qualitative and quantitative composition of gaseous products of flameless CN conversion is found. It is noted that this composition approximately corresponds to data available in the literature for the products of thermal decomposition of cellulose nitrate at comparatively low temperatures. Based on this fact and on a weak dependence of the CN burning rate on pressure in ballasted systems, the process under these conditions is assumed to be controlled by conversion of the energetic component predominantly in the condensed phase. In the case of a composite consisting of cellulose nitrate, silicon carbide, and polymer binder, for samples 10–25 mm in diameter, armoring exerts practically no effect on combustion parameters. Combustion of the same mixture with smaller diameters of non-armored samples is unstable. The presence of a liner establishes a clearly expressed critical combustion diameter in the examined systems.

Rubidium hexanitratothorate was synthesized, and its crystal structure was determined by X-ray diffraction analysis: space group P21/n; a = 8.347(1) A, b = 6.890(1) A, c = 13.069(1) A, β = 91.88(1)°, Z = 2; 1812 independent reflections, R = 0.0165.

Thermodynamic analysis of the sodium azide-aluminum oxide system shows that aluminum in such mixtures can be reduced by a chain of successive conjugate reactions. It is shown experimentally that in the presence of small amounts of silicon dioxide, aluminum oxide reacts exothermically with sodium azide in a combustion regime to release nitrogen and form the corresponding nitrides and alumosilicates. In the three-component system containing sodium azide, aluminum oxide, and silicon oxide, the upper flammability limit (for the sodium azide content) under normal conditions is established.

A procedure for the synthesis of uranyltricarbonatetetrarubidium Rb4UO2(CO3)3 was developed. Its crystal structure was determined by X-ray diffraction analysis: space group C2/c; a=10.778(5) A, b=9.381(2) A, c=12.509(3) A. β=94.42(3)°, Z=4; 1178 independent reflections, R=0.0662.

The formation of highly porous materials in the combustion wave of mixtures of 5-aminotetrazole with potassium perchlorate is studied. Under normal conditions with an oxidizer deficiency, the combustion of such mixtures proceeds in an unsteady oscillatory regime with formation of condensed products of incomplete oxidation of 5-aminotetrazole. It is shown that in the presence of metallic iron or its oxide, the completeness of interaction of the mixture components increases sharply and combustion becomes steady-state. In the presence of silicon dioxide, a highly porous solid residue forms which retains the shape of the initial block. At a certain ratio of iron and silicon dioxide in the initial composition, the solid combustion products have the form of interwoven thin fibers about 1 µm in diameter and 10–30 µm long.

The crystal structures of complex antimony(III) fluorides RbSbF4 (I) and (C2N4H5)SbF4 (II) were determined. The crystals of I and II are monoclinic; for I: a = 4.628(1) A, b = 6.167(1) A, c = 7.922(1) A, β = 100.582(3)°, V = 222.24(7) A3, Z = 2, ρ(calcd.) = 4.23 g/cm3, ρ(exp.) = 4.25 g/cm3, F(000) = 248, space group P21/m, R = 0.0395; for II: a = 4.678(1) A, b = 7.339(4) A, c = 10.185(1) A, β = 90.88(2)°, V = 349.6(2) A3, Z = 2, ρ(calcd.) = 2.69 g/cm3, ρ(exp.) = 2.70 g/cm3, F(000) = 264, space group P21. The structure of I is formed by Rb+ cations and [SbF4]n−n anionic chains composed of SbF5E octahedra with two bridging fluorine atoms. The structure of IIis formed by (C2N4H5)+ cations and isolated [SbF4]− anions in which the antimony polyhedra are SbF4E trigonal bipyramids. The relationship between the crystal structures and electrophysical and biological properties of single-charged cation tetrafluoroantimonates(III) was studied.

The (C10H10N2)0.5[SnF(SO4)] compound was synthesized via reaction of SnF2 with 4,4"-bipyridine (C10H8N2) in a diluted sulfuric acid solution (pH 3) and its X-ray diffraction analysis was carried out. The Sn2+ atoms coordinate one fluorine atom (Sn–F 2.062(2) A) and two oxygen atoms of two sulfate groups (Sn–O 2.149(2) and 2.313(3) A) thus forming the coordination polyhedron as a trigonal bipyramid with a stereochemically active unshared electron pair in its vertex. The sulfate groups act as bidentate bridges and join the neighboring Sn2+ complexes into infinite chains of [SnF(SO4)] n– n anions combined in pairs through the Sn–F contacts (2.450(2) A) to form ribbons whose voids contain two-charge 4,4"-bipyridinium cations.

Combustion of composites based on granulated cellulose nitrates and containing, as fillers, aluminum oxide, silicon carbide, carbon, boron nitride, sodium chloride, zinc oxide, and tungsten particles, is studied. Burning rates under atmospheric pressure, combustion-front temperatures, and mass losses after complete combustion of the composites are measured. The dependence of the burning rate on the size of silicon-carbide particles is obtained. Models of solid and laminar combustion are used to predict combustion characteristics, which are in good agreement with experimental data. Some specific features of combustion of composites with particular fillers are explained.

The reaction of tungsten hexachloride with excess ethyl isocyanate in dichloroethane leads to the insertion of three ligand molecules at one of the tungsten–chlorine bonds. The data of elemental analysis and IR spectroscopy confirm that the thermolysis of the reaction mixture affords the WCl4(L3Cl) complex (I), where L = –N(Et)C(O)–. The structure of the chain of inserted molecules in I is established on the basis of IR and NMR data, and the results of X-ray diffraction analysis of crystals of an organic product (II) of the hydrolysis of I. According to the latter, compound (II) is a derivative of s-triazine—1,3,5-triethyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione.

Antimony(III) fluoride complexes with compositions (NH4)3Sb4F15(I) and Cs3Sb4F15(II) are structurally characterized. Crystals Iare triclinic: a= 8.317(3) A, b= 10.419(6) A, c= 10.826(3) A, α = 63.71(4)°, β = 73.24(3)°, γ = 77.42(5)°, Z= 2, ρcalcd= 3.42 g/cm3, ρexp= 3.45 g/cm3, space group P\(\overline {\text{1}} \), R= 0.051; crystals IIare monoclinic: a= 8.079(2) A, b= 29.116(8) A, c= 8.162(2) A, β = 117.08(2)°, Z= 4, ρcalcd= 4.549 g/cm3, ρexp= 4.50 g/cm3, space group P21/c, R= 0.036. Structure Iis composed of SbF4E and SbF5E polyhedra combined into tetranuclear chains; crystals IIconsist of SbF4E polyhedra, two of which form a dimer Sb2F7E2, while the other two are isolated (E is the antimony lone electron pair).

The NH4[SnF2(NCS)] compound was obtained and its structure was determined. The tin atom is surrounded by two fluorine atoms (Sn–F 2.060 A) and one nitrogen atom of the NCS group (Sn–N 2.351 A). The coordination polyhedron of tin(II) is a distorted trigonal pyramid with a stereochemically active lone electron pair at the vertex.

The influence of the composition of statistical copolymers of nonyl acrylate with acrylic acid on the rate of mass transfer and phase equilibrium in solutions with diglycidyl ether of bisphenol A was studied. For these systems, the data on concentration dependencies of mutual diffusion coefficients and phase diagrams were obtained. The results were interpreted on the basis of the assumption about the effect of the effective concentration of nodes of the network of hydrogen bonds on the mutual diffusion and phase equilibrium. The dependencies of the mutual diffusion coefficients on the content of acrylic acid in the copolymers are described in terms of the free volume theory. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2353–2356, 1999

Intermolecular hydrogen bonds in the systems based on cellulose nitrate and a number of low-molecular solvents were studied by IR spectroscopy. The majority of the systems under study are characterized only by redistribution of intensities of the spectral bands corresponding to the pure polymer accompanied by their minor shift. In this case, acceptors of cellulose nitrate become sterically accessible for the redistribution of hydrogen bonds, and only an insignificant portion of them forms hydrogen bonds with a solvent. New spectral bands in the IR spectra were observed only for solutions containing diethyldiphenyl carbamide, suggesting the formation of a molecular complex.

The phase equilibrium in the binary systems based on hydroxyl-terminated butadienes and diglycidyl ether of bisphenol A has been studied in wide ranges of temperature and compositions of the solution. The analysis of the obtained experimental and calculated data shows that the molecular weight, content of hydroxyl groups, functionality of the oligomer, and the presence of bromine in the oligomer affect the level of the thermodynamic compatibility. An increase in the content of hydroxyl groups and bromine results in an increase in the compatibility of the components. The results obtained are interpreted in terms of the Flory-Huggins theory. The correlation between the phase boundary concentrations and an upper critical solution temperature and solubility parameters of the oligobutadienes has been established.

Kinetics of thermal decomposition of ammonium persulfate was studied by calorimetry and Raman spectroscopy. The values of activation energies of the overall reaction and its individual stages were estimated.

The crystal structure of a novel antimony(III) fluoride complex, ammonium undecafluorotriantimonate(III) (NH4)2Sb3F11, was determined. The crystals are triclinic: a = 7.780(2) A, b = 8.370(2) A, c = 10.620(1) A, α = 71.06(1)°, β = 89.03(1)°, γ = 63.58(1)°, V = 579.1(2) A3, Z = 2, ρ(calcd) = 3.500 g/cm3, ρ(exp) = 3.51 g/cm3, F(000) = 548.0, space group P\(\overline 1\). The structure consists of anionic [Sb3F11]2– chains and ammonium cations combined into a framework by the N–H···F hydrogen bonds.

The density and viscosity of sodium phosphate solutions with a concentration of 30–41.6 wt % at 70–100°C were determined.

The crystal structure of thallium fluoroantimonate(III) complex TlSb4F13 (I), which is isostructural to KSb4F13 (II), is determined. Crystals I are tetragonal: a = 9.634(2) A, c = 6.590(2) A, V = 611.7(2) A3, Z = 2, ρ(calcd) = 5.094 g/cm3, F(000) = 804.0, space group I4¯. The structure consists of tetrameric [Sb4F13]– anions formed by SbF3 groups connected by the fluoride ion and the Тl+ cations.

In the reaction of o-aminothiophenol and N-methyl-o-aminothiophenol with tetraalkyldiamidophosphites and phosphonites, 2-substituted 4,5-benzo-1,3,2-thiazaphospholanes were obtained in high yields. On heating, 2-alkyl-4,5-benzo-1,3,2-thiazaphospholanes can transform into spirophosphoranes with a P-C bond.

In the present investigation the structure of Li/sub 2/U/sub 3/O/sub 10/ was studied with the aid of single crystals and also the structure of the synthetic zippeite Zn(UO/sub 2/)SO/sub 4/-(OH)/sub 4/.1.5H/sub 2/0, which is interesting from the point of view of analyzing the role of bridging hydroxo groups. In the three-dimensional U/sub 3/O/sub 10/ framework two basic structural elements have been isolated: infinite chains of (UO/sub 2/)O/sub 4/ octahedra and infinite strips of (UO/sub 2/)O/sub 5/ pentagonal bipyramids. The similarity and difference between this structure and the structures of H/sub 2/U/sub 3/O/sub 10/ and D/sub 2/U/sub 3/O/sub 10/ are discussed. The crystal structure of Zn(UO/sub 2/)/sub 2/SO/sub 4/(OH)/sub 4/.1.5H/sub 2/O--the first representative of uranyl hydroxosulfates - has been determined. In this structure there are hydroxouranylsulfate layers linked by bivalent cations. The hydroxo groups coordinated by UO/sub 2//sup 2 +/ groups make the maximum use of their coordination possibilities, being tridentate-bridging ligands.