The decomposition of supersaturated sodium aluminate solution in the process of alumina production was reviewed. Some fundamental problems, such as the structure of supersaturated sodium aluminate solution and the growth unit of gibbsite precipitation as well as the decomposition mechanism of sodium aluminate solution, were investigated by model analytic technique and theoretical calculation. It is found that the main Al-contained species is S₄ symmetric Al(OH)₄(H₂O)₄］^-. Na↑+
(H₂O)₄·Al(OH)^-₄］is found to form in intermediate concentrated solution while［Na⁺(H₂O)₂·Al(OH)^-₄］in highly concentrated solution. Meanwhile, it is proved that
［(H₂O)₂Al(OH)₄］^- is the basic growth unit of gibbsite and［Al₆(OH)₁₈(H₂O)₆］is a favorable growth unit. Based on above results and ab initio quantum mechanical calculation and transition state theory, a reaction pathway of the decomposition of supersaturated sodium aluminate solution was put forward, in which the transformation of pentacoordinate aluminates ion to hexacoordinate basic growth unit as well as the formation of circled growth unit ［Al₆(OH)₂₂(H₂O)₂］^4- are the controlling steps.

Flotation de-silica from the diasporic-bauxite is one of the key basic research projects. It aimed to reveal the scientific mechanism between the crystal structure and surface properties, structure-properties of effective flotation reagent as well as the solution chemistry of flotation and interfacial interactions in the flotation system of diaspore and aluminosilicate minerals. It will underlay the new technology of reverse-flotation de-silica. The technology is important to enhance the mass ratio of Al₂O₃ to SiO₂, decreasing the silica content and energy consumption in producing aluminum oxide and economically utilizing the diasporic-bauxite in China.

Recent development of inert anodes for the primary aluminium industry was reviewed. The preparation method of functionally gradient material was introduced into inert anode research area, and a research flow sheet of functionally gradient cermet inert anode was set down. In order to carry out the preparation and optimization of composite oxides as the ceramic matrix of cermet inert anode, the following problems: solid state reaction synthesis of complex oxides, corrosion mechanism of complex oxides in Na₃AlF₆-Al₂O₃ melts, effects of NiO content on the corrosion rate and resistivity at high temperature of NiFe₂O₄-NiO ceramics were studied. The preparation and sintering mechanism of NiFe₂O₄ based cermets were deeply studied to properly control the sintering atmosphere and temperature system. By efficaciously controlling the sintering atmosphere, the oxidization of metallic phase and the decomposition or deoxidization of ceramic phase are avoided effectively during the sintering process of cermets at various temperatures. By optimizing the composition recipe and sintering temperature system, cermets of relatively high density are prepared without the spillage or asymmetric distribution of metallic phase.

It was found that there lies a linear relationship among the thermodynamic data of complicate inorganic compounds with similar components. A method for estimating the thermodynamic data of complicate compound and a thermodynamic database involving alumina production were developed. It was found that the alumina digestion rate of activated diasporic bauxite by means of heat field increased much due to the structure aberration, i.e, from perfect structure to unstable corundum. The results from thermodynamic calculation and experiments showed that it was feasible for desilication at atmospheric pressure, and the effects on equilibrium concentration of SiO₂ included temperature, mole ratio of Na₂O/Al₂O₃ (α_k), caustic and Na⁺ concentration. The technology of desilication of green liquor at atmosphere and separation of alumina and silica in aluminate solution with high concentration were established. The reaction activity of compounds containing silica and the converting law among compounds were studied, and the prototype technology of desilication products by hydrotreatment was also developed.

The electrokinetic and flotation of kaolinite in solution of hexadecylammonium bromide were studied. The point of zero charge (PZC) of kaolinite was determined by measuring zeta potential (streaming potential method) as a function of pH. Hexadecylammonium bromide ion seems to be strongly adsorbed on the interface because it makes the zeta potential more positive as the concentration increases. The PZC of kaolinite is at pH 4.3. Floatability of kaolinite was studied and shown to be influenced by both collector and hydrogen ion concentration. The optimal flotation conditions (mainly pH value and concentrations) observed experimentally agree well with that of predicted from solution chemistry, and the floatability of kaolinite is poor if the pH value of flotation system is higher than 9 or lower than 2.

There is quite abundant resource of ludwigite ore in Liaoning Province of China. Content of MgO in the slag of pyrometallurgical separation of boron from iron is much higher than that in the ordinary slags. Through the equilibrium partition ratio of sulfur L_S between the metal and the slag in an atmosphere of CO-N₂, the acidic coefficients for B₂O₃ and the basic coefficients for MgO were estimated. The basic formulae were given for the blast furnace-type slag containing B₂O₃ and high MgO.

Aiming at reducing energy and carbon consumption and enhancing current efficiency of aluminum electrolysis, a batch of property-modified prebaked carbon anodes prepared in industrial production were applied to 160kA prebaked anode aluminum electrolysis cells in a domestic aluminum company. The industrial statistical data show that, the property-modified anodes can averagely reduce carbon consumption 11.6kg per ton aluminum and energy consumption 106.1kW·h, further more, enhance current efficiency 0.72%. The industrial testing results prove that this kind of new type of prebaked anodes has remarkable effect of saving energy, reducing carbon consumption and enhancing current efficiency of aluminum electrolysis.

Acid leaching solution was obtained after mixing pyrite cinders with H₂SO₄, then heating the mixture of pyrite cinders and H₂SO₄ at 200-300℃, leaching the heated mixture with water and filtrating. Polyferric sulfate (PFS) solution was produced by adding suitable amounts of FeSO₄·7H₂O and NaClO₃ into acid leaching solution. By concentrating and drying PFS solution, solid PFS with alkali degree of 6.40%-22.4% was prepared. Fe_4.67(SO₄)₆(OH)₂·20H₂O in the solid PFS was discovered by XRD analysis. FT-IR spectroscopy shows that the absorption peaks at 3400cm^-1 and 1635cm^-1 arise from OH and absorption peaks at 998cm^-1 and 669cm^-1 come from Fe—OH in the solid PFS.

The electrochemical kinetics equation of the oxidation of gold in thiourea solution in the presence of sulfur dioxide was given out. The kinetic parameters are determined as: the transmission coefficient β=0.477; when the reaction time is zero, the initial over potential of the oxidation of gold in acid thiourea solution is 0.267V. The dynamics of anodic process of gold electrode was studied by using Tafel plots. In the solution containing 5×10^-6mol/L sulfur dioxide the activated energy is 46.11kJ/mol. When the electrode potential is higher than 270mV, the gold is oxidized by thiourea. The addition of H₂SO₃ can obviously improve the corrosion speed of gold.

Experimental technique has been inadequate to anodic overvoltage measurements in aluminum electrolysis. To determine its ohmic/voltage drop precisely, a current interruption technique was modified with a high frequency digital oscilloscope, current interrupters with fast switching time, an improved cell configuration and a simulation applied to the oscillating potential decay curve. The results show that the technique can give good reproducibility for overvoltage studies. A substantial increase of anodic overvoltage is observed with graphite powder addition, metallic aluminum addition and CO bubbling in the melts.

The concept of ambient temperature curable TiB₂ cathode coating was put forward, and the ambient temperature curable TiB₂ cathode coating was prepared successfully. Differing from the previous TiB₂ cathode coating solidified approximately at 200℃，the ambient temperature curable TiB₂ cathode coating can be solidified at room temperature, so the heating equipment is not necessary, which simplifies the preparation process and facilitates the industrial application of TiB₂ cathode coating. Many kinds of resin and curing agent were investigated. On the above-mentioned basis, the ambient temperature curable TiB₂ cathode coating was prepared with furan resin 5500 mixed with complex resins B as carbon binder and DXG1 as curing agent in 24h. The results show that the properties of prepared coating are excellent, the electrical resistivity is 29.8μΩ·m, the compressive strength is 33.6MPa, which are all better than the relevant properties of partially graphitized cathode carbon block for aluminum electrolysis prescribed by the GB 8744-88. SEM morphologies show that the section morphology of the TiB₂ coating is unaltered during the electrolysis test, the TiB₂ coating can be used in aluminum electrolysis industry to save energy and prolong the life of aluminum electrolysis cell.

The microstructure of gibbsite precipitated with seeds from sodium aluminate solution was studied using SEM. The results show that there are a lot of fine secondary nuclei with diameter less than 1μm and the surfaces of seeds precipitated by low frequency ultrasound are very irregular. The new nuclei are pseudohexagonal slices with nanometer grade in thickness. At higher precipitation temperature, such as 75℃, SEM micrographs show that there exist something like colloid on joints of different small granules which have agglomerated to a large particle. It is suggested that the formation of such hexagonal crystalline units is promoted by low frequency ultrasound, while the colloids on the surface may be produced by imcompletely crystallization of the growth units.

The zeta potential measurements show that the flotation separation of diaspore from kaolinite, illite and pyrophyllite could be achieved in the range of pH 4-6.5 with cationic collectors. A special quaternary ammonium salts(DTAL) shows better selectivity than that the dodecyl amine(DDA) does for the flotation of three silicates. The closed-circuit flotation results show that the reverse flotation de-silicate can be achieved with DTAL as collector, a new inorganic reagent(SFL) as depressant and MIBC as frother to obtain a bauxite concentrate m(Al₂O₃)/m(SiO₂)＞10, Al₂O₃ recovery＞86%).

Data coming from different sources have different types and temporal states. Relations between one type of data and another ones, or between data and unknown parameters are almost nonlinear. It is not accurate and reliable to process the data in building the digital earth with the classical least squares method or the method of the common nonlinear least squares. So a generalized nonlinear dynamic least squares method was put forward to process data in building the digital earth. A separating solution model and the iterative calculation method were used to solve the generalized nonlinear dynamic least squares problem. In fact, a complex problem can be separated and then solved by converting to two sub-problems, each of which has a single variable. Therefore the dimension of unknown parameters can be reduced to its half, which simplifies the original high dimensional equations.

The method of condition number is commonly used to diagnose a normal matrix N  whether it is ill-conditioned state or not. For its shortcoming, a method to measure multi-collinearity of a matrix was put forward. The method is that implement Gram-Schmidt orthogonalizing process to column vectors of a design matrix A(α_l)， then calculate the norms of every vector before and after orthogonalization process and their corresponding ratio， and use the minimum ratio among the group of ratios to measure the multi-collinearity of A. According to the corresponding relationship between the multi-collinearity and the ill-conditioned state of a matrix, the method also studies and offers reference indexes weighing the ill-conditioned state of a matrix based on the relative norm. The remarkable characteristics of the method are that the measure of multi-collinearity has idiographic geometry meaning and clear lower and upper limit, the size of the measure reflects the multi-collinearity of column vectors objectively. It is convenient to study the reason that results in the matrix being multi-collinearity and to put forward solving plan according to the method which is summarized as the method of minimum norm and abbreviated as F method.

Under minimum squared error (MSE) rule, discrete K-L transform (DKLT) was given. The 2nd information function, the 2nd information entropy and geometry entropy under DKLT were proposed, by which information characteristics of DKLT were metricized. Two new concepts of information rate (IR) and accumulated information rate (AIR) were proposed by which the degree of information feature compression of DKLT was illustrated.

In order to process different kinds of observing data with different precisions, a new solution model of nonlinear dynamic integral least squares adjustment was put forward, which is not dependent on their derivatives. The partial derivative of each component in the target function is not computed while iteratively solving the problem. Especially when the nonlinear target function is more complex and very difficult to solve the problem, the method can greatly reduce the computing load.

A new edge detector based on the nonlinear intensity of curved surface was proposed. The edge detector describes the largest curvature and the smallest curvature of curved surface, therefore it can reflect the real largest direction of image edge jump. By the new edge detector, it is convenient to calculate the curvature in any direction of the curved surface and the curvature can be used in the identification of edge direction and the feature extraction of objects on remote sensing image.