Effect of gamma-irradiation on surface and catalytic properties of nanocrystalline CuO,NiO and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> supported on alumina

The effect of γ-irradiation on surface and catalytic properties of CuO/Al₂O₃, NiO/Al₂O₃ and Fe₂O₃/Al₂O₃ was investigated. The techniques employed were XRD, nitrogen adsorption at −196 °C and catalytic conversion of ethanol and isopropanol at 250–400 °C using micropulse technique. The results showed that the supported solids being calcined at 400 °C consisted of well crystallized CuO, NiO, Fe₂O₃ and AlOOH phases. The AlOOH crystallized into a poorly crystalline γ-Al₂O₃ upon heating at 600 °C. All phases present in different solids calcined at 400 and 600 °C showed that these solids are of nanocrystalline nature measuring an average crystallite size between 6 and 85 nm. The crystallite size of crystalline phases present was found to be much affected by the dose of γ-rays and the nature of the metal oxide. This treatment resulted in a progressive increase in the specific surface area reaching to a maximum limit at a dose of 0.8 MGy. The dose of 1.6 MGy exerted a measurable decrease in the S _BET. A radiation dose of 0.2 to 0.8 MGy brought about a progressive significant decrease in the catalytic activity of all the catalytic systems investigated. All the catalytic systems retained their high activity upon exposure to a dose of 1.6 MGy. The rise in precalcination temperature of the systems investigated from 400 to 600 °C brought about a measurable increase in their catalytic activity in the conversion of alcohols.     

Effect of gamma-irradiation on surface and catalytic properties of Co3O4 and NiO catalysts

The effects of g-irradiation (0.2-1.6 MGy) on the particle size, specific surface area and catalytic activity of Co₃O₄ and NiO solids were investigated. The investigated solids were prepared by heat treatment of cobalt carbonate at 500 and 700 °C and basic nickel carbonate at 400 °C. The techniques employed were XRD, nitrogen adsorption at -196 °C and decomposition of H₂O₂ at 30-50 °C. The results showed that g-irradiation resulted in a small decrease in the particle size of the investigated solids and effected a progressive increase in their specific surface areas. On the other hand, the exposure of Co₃O₄ and NiO catalysts to a dose of 0.2 MGy resulted in a significant decrease in their catalytic activities, which suffered further progressive decrease upon increasing the doses up to 1.6 MGy. Gamma-irradiation did not modify the activation energy of the catalyzed reaction but decreased the concentration of catalytically active sites without changing their energetic nature. These results were discussed in terms of splitting of the particles of the treated solids and removal of chemisorbed species present in nonstoichiometric cobalt and nickel oxides.     

Activity and selectivity of manganese oxides in alcohols Conversion as influenced by gamma-irradiation

Manganese oxide samples obtained from thermal decomposition of manganese carbonate at 400 and 600 °C were subjected to different doses of g-irradiation within the range 0.2 to 1.6 MGy. The surface and catalytic properties of the above samples were studied using nitrogen adsorption isotherms measured at -196 °C and catalytic conversion of ethanol and isopropanol at 300-400 °C using micropulse technique. The results obtained revealed that manganese oxides obtained at 400 °C consisted of a mixture of Mn₂O₃ and MnO₂ while the samples calcined at 600 °C composed entirely of Mn₂O₃. Gamma-irradiation resulted in a decrease in the particle size of manganese oxide phases with subsequent increase in their specific surface areas. Gamma-irradiation with 0.2 and 0.8 MGy effected a measurable progressive decrease in the catalytic activity in dehydration and dehydrogenation of both alcohols. However, the treated catalyst retained their initial activity upon exposure to a dose of 1.6 MGy. Also, g-irradiation increased the selectivities of the investigated solids towards dehydrogenation of both alcohols. The catalyst samples precalcined at 600 °C exhibited higher catalytic activities than those precalcined at 400 °C.     

Thermal and X-ray diffraction studies of the solid–solid interactions in CuO–MoO3/MgO system

The solid–solid interactions in pure and MoO₃-doped CuO/MgO system were investigated using TG, DTA and XRD. The composition of pure mixed solids were 0.1CuO/MgO, 0.2CuO/MgO and 0.3CuO/MgO and the concentrations of MoO₃ were 2.5 and 5 mol%. These solids were prepared by wet impregnation of finely powdered basic magnesium carbonate with solutions containing calculated amounts of copper nitrate and ammonium molybdate followed by heating at 400–1000°C. The results revealed that ammonium molybdate doping of the system investigated enhanced the thermal decomposition of copper nitrate and magnesium hydroxide which decomposed at temperatures lower than those observed in case of the undoped mixed solids by 70 and 100°C, respectively. A portion of CuO present dissolved in the lattice of MgO forming CuO–MgO solid solution with subsequent limited increase in its lattice parameter. The other portion interacted readily with a portion of MoO₃ at temperatures starting from 400°C yielding CuMoO₄ which remained stable up to 1000°C. The other portion of MoO₃ interacted with MgO producing MgMoO₄ at temperatures starting from 400°C and remained also stable at 1000°C. The diffraction peaks of Cu₂MgO₃ phase were detected in the diffractograms of pure and MoO₃-doped 0.3CuO/MgO precalcined at 1000°C. The formation of this phase was accompanied by an endothermic peak at 930°C.     

Thermodynamic relations among olivine,spinel, and phenacite structures in silicates and germanates: I. Volume relations and the systems NiOMgOGeO2 and CoOMgOGeO2

An experimental approach is outlined to systematically obtain free energy differences among olivine, spinel, and phenacite forms of silicates and germanates from the thermodynamics of terminal solid solutions in ternary systems. This is applied to the ternary systems NiOMgOGeO₂ and CoOMgOGeO₂ at 1200°C in air and to the system NiOMgOGeO₂ at 800°C and 0.57 kbar water pressure. From the location of conjugation lines, activity-composition relations along each orthogermanate join are calculated. The free energies of transformation from the olivine to the spinel structure at 1200°C are estimated to be +1.6, ?3.5, and ?8.2 kcal/mole for Mg₂GeO₄, Co₂GeO₄, and Ni₂GeO₄, respectively.Volume changes for the spinel-olivine and olivine-phenacite transitions are estimated for the silicates and germanates of Mg, Mn, Fe, Co, Ni, and Zn.     

Effects of doping with CeO2 and calcination temperature on physicochemical properties of the NiO/Al2O3 system

The effects of doping with CeO₂ and calcination temperature on the physicochemical properties of the NiO/Al₂O₃ system have been investigated using DTA, XRD, nitrogen adsorption measurements at −196°C and decomposition of H₂O₂ at 30–50°C. The pure and variously doped solids were subjected to heat treatment at 300, 400, 700, 900 and 1000°C. The results revealed that the specific surface areas increased with increasing calcination temperature from 300 to 400°C and with doping of the system with CeO₂. The pure and variously doped solids calcined at 300 and 400°C consisted of poorly crystalline NiO dispersed on γ-Al₂O₃. Heating at 700°C resulted in formation of well crystalline NiO and γ-Al₂O₃ phases beside CeO₂ for the doped solids. Crystalline NiAl₂O₄ phase was formed starting from 900°C. The degree of crystallinity of NiAl₂O₄ increased with increasing the calcination temperature from 900 to 1000°C. An opposite effect was observed upon doping with CeO₂. The NiO/Al₂O₃ system calcined at 300 and 400°C has catalytic activity higher than individual NiO obtained at the same calcination temperatures. The catalytic activity of NiO/Al₂O₃ system increased, progressively, with increasing the amount of CeO₂ dopant and decreased with increasing the calcination temperature.     

Effect of gamma-irradiation on surface and catalytic properties of Co3O4 doped with NiO

NiO-doped Co₃O₄ samples precalcined at 500 °C were subjected to various doses of -rays within the range 0.2-1.6 MGy. The particle size and BET-surface areas of different samples were determined using XRD and nitrogen adsorption at -196 °C. The catalytic reactions studied were conversion of ethanol and isopropanol at 250-400 °C using a micropulse technique and H₂O₂ decomposition in aqueous solution at 30-50 °C. The results revealed that the -irradiation brought a significant decrease in the particle size of Co₃O₄ phase with subsequent increase in the S_BET surface areas. The treatment brought also a progressive decrease in the total conversion of both alcohol (dehydration and dehydrogenation) falling to a minimum value (about 20% of its initial activity) at a dose of 0.8 MGy. The catalysts retain their initial activity upon exposure to a dose of 1.6 MGy. On the other hand, the catalytic activity in H₂O₂ decomposition of the investigated system decreased progressively by increasing the dose of -rays and the catalysts lost more than 90% of their initial activity upon exposure to a dose of 1.6 MGy.     

Hydrocracking of cumene over Ni/Al2O3 as influenced by CeO2 doping and γ-irradiation

Cumene hydrocracking was carried out over pure and doped Ni/Al₂O₃ solids and also, on these solids after exposure to different doses of γ-rays between 0.4 and 1.6 MGy. The dopant concentration was varied between 1 and 4 mol% CeO₂. Pure and doped samples were subjected to heat treatment at 400°C and cumene hydrocracking reaction was carried out using various solids at temperatures between 250°C and 400°C by means of micropulse technique. The results showed that both CeO₂ doping and γ-irradiation of the investigated system brought about an increase in its specific surface area. γ-irradiation of pure samples increased their catalytic activities effectively. However, the doping caused a decrease in the catalytic activity. γ-irradiation of the doped samples brought about a net decrease in the catalytic activity.The catalytic reaction products over different investigated solids were ethylbenzene as a major product together with different amounts of toluene, benzene and C₁–C₃ gaseous hydrocarbons. The selectivity towards the formation of various reaction products varies with the reaction temperature, doping and γ-irradiation.     

Physicochemical and catalytic investigations of grafted poly(tetrafluoroethylene) complexed with some transition metal nitrates

Radiation-induced graft polymerization of methacrylic acid into poly(tetrafluoroethylene) by the mutual irradiation technique has been studied. The obtained hydrophilic solids were treated with solutions containing calculated amounts of iron, cobalt, nickel, or copper nitrates. The amounts of these transition metal nitrates were fixed at 16 wt%, expressed as metal oxide. IR, XRD, TG, and catalysis of CO oxidation reaction by O₂ have been carried out on the various prepared solids. The results obtained revealed that most of iron and copper species were contributed in complex formation of the polymeric material via carboxylic groups while some of the cobalt and nickel were involved in the complex formation and the rest remained as separate phases. The thermal treatment either in air at 400°C or in vacuo at 240°C led to degradation of the treated grafted polymeric material with subsequent formation of poly(methacrylic acid) together with Co₃O₄ (poorly crystalline phase) and NiO (having moderate crystallinity) and minute amounts of Fe₂O₃ and CuO (undetected by XRD). The PTFE-g-PMAAc treated with the different transition metal nitrates and subjected to heating under vacuum at 240°C exhibited different catalytic activities that vary in the order: Co > Ni > Cu ? Fe. The catalytic activity was mainly dependent on the produced amount of free oxide and their degree of division. © 1993 John Wiley & Sons, Inc.     

Effect of γ-irradiation and doping with MoO3 and V2O5 on surface and catalytic properties of manganese oxides

The effects of γ-irradiation (0.2–1.6 MGy), thermal treatment and doping with MoO₃ and V₂O₅ (0.25–4 mol%) on the surface and catalytic properties of manganese oxides prepared by thermal decomposition of manganese carbonate at 400°C and 600°C have been investigated. The techniques employed were X-ray diffraction, nitrogen adsorption at −196°C, oxidation of CO by O₂ at 120–220°C and decomposition of H₂O₂ at 20–50°C. The results revealed that γ-irradiation decreased the particle size of manganese oxides, increased their specific surface areas, decreased the amount of surface excess oxygen and decreased their catalytic activities. The doping with MoO₃ and V₂O₅ conducted at 600°C brought about a measurable decrease in the BET-surface area and catalytic activities of the treated solids. These results were discussed in terms of splitting of manganese oxide particles and removal of chemisorbed oxygen by treating with γ-irradiation and formation of manganese molybdate and vanadates by treating with the used dopant oxides.     

Phase Equilibria in the System CuO‐NiO‐P4O10 and Synthesis,Crystal Structure,and Characterization of the New Copper Nickel Oxide Phosphate Cu3NiO(PO4)2

The system CuO‐NiO‐P₄O₁₀ was investigated using a solid state reaction between CuO, NiO, and (NH₄)₂HPO₄ in quartz crucibles at 900 °C. The powder samples were characterized by X‐ray diffraction, TG/DTA, electrochemical measurements, IR, and UV/Vis spectroscopy. Single crystals of a new quaternary phase Cu₃NiO(PO₄)₂ were achieved by cooling the melted compound in a sealed, evacuated quartz ampoule. Cu₃NiO(PO₄)₂ crystallizes in the monoclinic space group P2₁/n (no 14) with a = 8.2288(2) Å, b = 9.8773(2) Å, c = 8.2777(3) Å, β = 107.82(2)°, Z = 4. The three‐dimensional framework consists of distorted tetragonal pyramides [Cu1O₅], distorted planar squares [Cu2O₄], octahedra [Cu3O₆], and [NiO₆] and [PO₄] tetrahedra. The TG‐DTA of the new phase showed an incongruent melting at 1055 °C. The open circuit voltage of this material was measured to determine the electrochemical properties. The measurement revealed an initial capacity of 236 Ah · g^–1 and a voltage plateau at 2.05 V. Furthermore, it was possible to identify the phase equilibria and to obtain the phase diagram at 900 °C.     

Effect of gamma-irradiation on surface and catalytic properties of CuO−ZnO/Al2O3 system

A copper, zinc and aluminium mixed oxides sample having the nominal composition 0.25 CuO/0.03 ZnO/Al₂O₃ was prepared by impregnating Al(OH)₃ with copper and zinc nitrate solutions, drying at 100 °C then heating in air at 600 °C. The obtained solid was exposed to different doses of -rays (20–160 Mrad). The surface characteristics namelyS _BETV_P andr of different treated adsorbents were determined from N₂ adsorption isothems measured at –196 °C. The catalytic activity of various irradiated solids was determined by following up the kinetics of CO-oxidation by O₂ at 150–200 °C. The results showed that the doses up to 80 Mrad resulted in no significant change in theS _BET but increased slightly theV _P (20%) of the treated adsorbents. The irradiation at 160 Mrad caused an increase of 20% in theS _BET of the irradiated solid sample. The catalytic activity increased progressively by increasing the dose, a dose of 160 Mrad brought about an increase of 140% in the catalyst's activity. The apparent activation energy of the catalytic reaction decreased monotonically by increasing the absorbed dose of -rays which was attributed to a parallel induced decrease in the value of pre-exponential term of the Arrhenius equation. The observed increase in the catalytic activity due to -irradiation has been interpreted as a result of increasing the concentration of catalytically-active sites contributing in chemisorption and catalysis of CO-oxidation via a possible fragmentation of CuO crystallites.     

Thermal decomposition of nickel aluminium mixed hydroxides and formation of nickel aluminate spinel

Various nickel aluminium mixed hydroxide samples of different compositions were prepared by co-precipitation from their nitrate solutions using dilute NH₄OH. Additional samples were prepared by impregnation of hydrated Al₂O₃, preheated at 600 and 900°C, with nickel nitrate solution in an equimolar ratio. The thermal decomposition of different mixed solids was studied using DTA. The X-ray investigation of thermal products of the mixed solids was also studied.The results obtained revealed that the presence of NiO up to 33.3 mole % with aluminium oxide much enhanced the degree of crystallinity of the γ-Al₂O₃ phase. In contrast, the presence of Al₂O₃ much retarded the crystallization process of the NiO phase. With the exception of samples containing 20 mole% NiO, all the mixed hydroxide samples, when heated in air at 900°C, led to the formation of well-crystalline Ni Al₂O₄ spinel, alone, or together with either NiO or γ-Al₂O₃, depending on the composition of the mixed oxide samples. The solid containing 20% NiO and heated at 900°C was constituted of amorphous NiO dispersed in γ-Al₂O₃. Heating the nickel nitrate-impregnated Al₂O₃ in air at 800–1000°C led to the formation of Ni Al₂O₄ together with non-reacted NiO and γ-Al₂O₃. The degree of crystallinity of the spinel was found to increase by increasing the calcination temperature of the impregnated solids from 800 to 1000°C and by increasing the preheating temperature of the hydrated Al₂O₃ employed from 600 to 900°C.     

Effects of gamma-irradiation and Li2O-doping on surface and catalytic properties of unloaded Co3O4 solid

The effects of -irradiation (20–160 Mrad) and lithium oxide doping (0.75–6 mol%) on the surface and catalytic properties of unloaded Co₃O₄ solid have been investigated. The surface characteristics of various solids were determined from nitrogen adsorption isothems taken at –196 °C and their catalytic activities were measured by following the kinetics of CO-oxidation by O₂ at 100–150 °C using a static method. The results showed that -rays brough about a decrease of 21% inS _BET of Co₃O₄ due to widening of its pores and led also to a considerable increase in its catalytic activity. A maximum increase of 91% was observed upon exposure to a dose of 80 Mrad. Lithium oxide-doping at at 500 °C resulted in an increase of 150% inS _BET of treated solid without changing its mean pore radius. This treatment was also accompanied by an increase of about 50% in its catalytic activity measured at 150 °C. Gamma-irradiation and Li₂O-doping of unloaded Co₃O₄ did not change the magnitude of apparent activation energy of catalysis of CO-oxidation by O₂ but increased the concentration of catalytically active sites contributing in the catalytic process. In other words, -rays and lithium oxide doping did not alter the mechanism of catalytic oxidation of CO by O₂ over unloaded cobaltic oxide solid.     

Enhanced Thermal Decomposition Properties and Catalytic Mechanism of Ammonium Perchlorate over CuO/MoS2 Composite

In this report, CuO/MoS₂ composites were successfully prepared by the hydrothermal method where nano‐sized CuO was uniformly distributed on the surface of hierarchical MoS₂ substrates (CuO/MoS₂ composites). Their physicochemical properties and catalytic performance in ammonium perchlorate (AP) decomposition were investigated and characterized by XRD, SEM, TEM, BET, XPS, TG/DSC and combustion measurement. The results showed that it could decrease AP decomposition temperature at high decomposition stage from 416.5 °C to 323.5 °C and increase the heat release from 378 J/g (pure AP) to 1340 J/g (AP with catalysts), which was better than pure CuO nanoparticles (345.5 °C and 1046 J/g). Meanwhile, it showed excellent performance in combustion reaction either in N₂ or air atmosphere. The results obtained by photocurrent spectra, photoluminescence spectra and time‐resolved fluorescence emission spectra indicated that loading CuO mediated the generation rate and combination rate of electrons and holes, thus tuning the catalytic performance on AP decomposition. This study proved that employing the supports that can synergistically interact with CuO is an efficient strategy to enhance the catalytic performance of CuO.     

Effective ultrasound-assisted removal of heavy metal ions As(III), Hg(II), and Pb(II) from aqueous solution by new MgO/CuO and MgO/MnO<Subscript>2</Subscript> nanocomposites

A series of new (MgO) _x CuO and (MgO) _x MnO₂ nanocomposites were prepared and used as adsorbent for removal of As³⁺, Hg²⁺, and Pb²⁺ ions from aqueous solution with high capacity and detection limit. These nanocomposites were synthesized with different molar ratios by sonochemical method in alkaline solution using polyvinylpyrrolidone as a capping agent and were characterized by FTIR, AAS, UV–Vis spectroscopy, and TEM and SEM imaging. The maximum heavy metal ions adsorption was achieved for (MgO)_0.32CuO and (MgO)_2.9MnO₂ nanocomposites assisted by 3-min sonication using ultrasound. Adsorbent capacity of (MgO)_0.32CuO reached 500.0 mg/g and detection limit was 0.1 ppb for As³⁺. Also (MgO)_2.9MnO₂ nanocomposite adsorbed 457.1 mg/g of Hg²⁺ and 461.2 mg/g of Pb²⁺. Extremely low detection limits of 1.5 and 2.0 ppb were obtained for Hg(II) and Pb(II) ions, respectively, which are much lower than the WHO allowable limits. So, these nanocomposites should be excellent candidate for heavy metal removal with advantage of high capacity, high sensitivity, cost effectiveness and easy preparation.     

无氯 Cu/AC 催化剂的制备及其催化气相甲醇氧化羰基化反应性能

 以 Cu2(NO3)(OH)3/AC (活性碳) 为催化剂前驱体, 在惰性气氛中于不同温度热处理分别制得无氯的 CuO/AC, Cu2O/AC 和 Cu0/AC 催化剂, 并用于甲醇直接气相氧化羰基化合成碳酸二甲酯 (DMC) 反应. 结果表明, 200 °C 处理制得的催化剂中, Cu 物种以 CuO 为主. 随着处理温度的升高, 催化剂中 CuO 含量逐渐降低, 而 Cu2O 含量增加; 400 °C 制备的催化剂中, Cu 物种仅以 Cu2O 形式存在; 而 450 °C 以上处理时则以 Cu0 形式存在. 随着热处理温度的提高, 相应催化剂活性逐渐增加, 表明 CuO, Cu2O 和 Cu0 均具有催化活性, 其活性大小的顺序为 CuO < Cu2O < Cu0. 在 140 °C, CO:MeOH:O2 = 4:10:1, SV = 5 600 h1 条件下, 450 °C 处理制备的 Cu0/AC 催化剂表现出较高的催化甲醇氧化羰基化活性, 其中甲醇转化率达 11.5%, DMC 的时空收率和选择性分别为 261.9 mg/(g•h) 和 76.0%.     

Oxidation of carbon monoxide in the presence of hydrogen on the CuO, CoO, and Fe2O3 oxides supported on ZrO2

The catalytic activity of the CuO/ZrO₂, CoO/ZrO₂, Fe₂O₃/ZrO₂, and CuO/(CoO, Fe₂O₃)/ZrO₂ systems in the reaction of selective CO oxidation in the presence of hydrogen was studied at 20–450°C over the oxide concentration range of 2.5–10 wt % on the surface of ZrO₂. The conversion of CO on the CoO/ZrO₂ systems was almost independent of the concentration of CoO: 88 or 90% for 2.5 or 10% CoO, respectively. TPR data allowed us to relate the catalytic activity of CoO/ZrO₂ to Co-O-Zr clusters, the amount of which was almost constant over the test range of CoO concentrations. The conversion of CO on 2.5% CuO/ZrO₂ was 32% (190°C) or 62–66% on 5–10% CuO/ZrO₂ (170°C). According to TPR data, clusters like Cu-O-Zr occurred on the surface of ZrO₂, and the amount of these clusters reached a maximum upon supporting 5% CuO. The catalytic properties of 5% CuO/5% CoO/ZrO₂ and 5% CoO/5% CuO/ZrO₂ samples were identical to those of 5% CuO/ZrO₂ samples. It is likely that the formation of active reaction sites upon consecutively supporting the oxides occurred on the same surface sites of ZrO₂. In this case, Co and Cu oxides competed for cluster formation, and the copper cation can displace the cobalt cation from the formed clusters. The Fe₂O₃ samples were inactive; a maximum conversion of 34% (290°C) was observed on 10% Fe₂O₃/ZrO₂. The catalytic properties of CuO/Fe₂O₃/ZrO₂ were also identical to those of CuO/ZrO₂, and they depended on the presence of Cu-O-Zr clusters on the surface.     

Co oxidation with oxygen in the presence of hydrogen on CoO/CeO<Subscript>2</Subscript> and CuO/CoO/CeO<Subscript>2</Subscript> catalysts

The catalytic activity of the CoO/CeO₂ and CuO/CoO/CeO₂ systems in selective CO oxidation in the presence of hydrogen at 20–450°C ([CuO] = 1.0–2.5%, [CoO] = 1.0–7.0%) is reported. The maximum CO conversion (X) decreases in the following order: CuO/CoO/CeO₂ (X = 98–99%, T = 140–170°C) > CoO/CeO₂ (X = 67–84%, T = 230–240°C) > CeO₂ (X = 34%, T = 350°C). TPD, TPR, and EPR experiments have demonstrated that the high activity of CuO/CoO/CeO₂ is due to the strong interaction of the supported copper and cobalt oxides with cerium dioxide, which yields Cu-Co-Ce-O clusters on the surface. The carbonyl group in the complexes Co^δ+-CO and Cu⁺-CO is oxidized by oxygen of the Cu-Co-Ce-O clusters at 140–160°C and by oxygen of the Co-Ce-O clusters at 240°C. The decrease in the activity of the catalysts at high temperatures is due to the fact that hydrogen reduces the clusters on which CO oxidation takes place, yielding Co⁰ and Cu⁰ particles, which are inactive in CO oxidation. The hydrogenation of CO into methane at high temperatures is due to the appearance of Co⁰ particles in the catalysts.     

ZnO/MgO nanocomposites generated from alcoholic solutions

A process was proposed for the synthesis of ZnO/MgO nanocomposites from alcoholic solutions by means or the consecutive precipitation of coprecipitation of alcoholic solutions of zinc acetate and magnesium with an alkali solution followed by annealing in the range 400–500°C. X-ray powder diffraction showed crystalline ZnO and MgO phases in the resulting composite. Zinc oxide particle sizes in the composite with magnesium oxide were determined by transmission electron microscopy and from X-ray diffraction peak broadening. The zinc oxide nanoparticle size was weakly affected by the molar ratio of zinc to magnesium and the concentration of the precipitated component. The ZnO exciton peak in cathodoluminescence spectra for nanocomposites synthesized at low temperatures (400 and 500°C) shifted toward the UV. At ≥600°C or higher, Mg_{1 ? x} Zn _x O solid solution was generated, as evidenced by X-ray diffraction and cathodoluminescence data.