J. Lamovec

Influence of pastes containing casein phosphopeptide-amorphous calcium phosphate on surface of demineralized enamel.

Purpose The purpose of the study was to evaluate the surface characteristics of demineralized enamel after treatment with pastes containing casein phosphopeptide–amorphous calcium phosphate (CPP-ACP) or casein phosphopeptide–amorphous calcium fluoride phosphate (CPP-ACFP) and to compare their efficacy with that of 0.05% NaF. Methods Following formation of the artificial carious lesion, enamel slabs were divided into 4 groups (CPP-ACP, CPP-ACFP, 0.05% NaF and control) and submitted to a chemical caries model. Remineralization potential was examined using scanning electron microscope, energy-dispersive spectroscopy (EDS) and microhardness test. Scanning electron microphotographs were analyzed for area, minimal, maximal and mean diameter, perimeter, roundness and number of enamel defects and percentage of tooth surface affected by defects. Results Treatment with 0.05% NaF partly reduced the appearance of enamel defects when compared with irregular demineralized enamel. Treatment with CPP-ACP or CPP-ACFP resulted in occlusion of defects which produced more flattened enamel surface. Image analysis revealed reduction of the dimensions of the defects in the 3 experimental groups. Treatment with CPP-ACFP decreased the number of enamel defects when compared with demineralized enamel. The EDS analysis did not show differences in Ca/O, P/O and Ca/P ratios between the groups (P>0.05). Microhardness test revealed significant effects of CPP-ACP and CPP-ACFP (P<0.05). Conclusions Pastes containing CPP-ACP or CPP-ACFP showed potential to remineralize enamel surface lesions.

Micromachining by maskless wet anisotropic etching {hkl} structures on {100} oriented silicon

The paper presents investigation of micromechanical technique using 3D anisotropically etched Si structures. Ridge-like structure oriented along (110) direction is first etched with mask following maskless etching in 25 wt. % TMAH solution in water at 80°C. The ridge structures investigated by maskless etching are convex prismatic edges included by {100} and {111} planes. Experimental results verify that the cutting planes developed at the ridge corners are {733} planes. From analytical relations applied to experiments, the ratio between the etching rates for the {733} (the fastest etching plane at the edge step) and {100} planes is found.

Investigation of silicon anisotropic etching in alkaline solutions with propanol addition

Different propanol isomers additives to 26 wt. % KOH water solution have been studied. It was stated that addition of both isomers result in changing etching anisotropy of (110) oriented corners on Si (100). For the same etching depth, IPA addition causes higher corner undercutting than 1-propanol addition. Surface topography is better in IPA containing solutions.

Assessment of the composite behavior of different Ni/Cu multilayer composite systems

Nickel and copper thin films were alternately electrodeposited from sulphamate and sulphate-based electrolytes respectively, on different substrates: polycrystalline cold rolled copper, single crystal (111)-oriented Si and 100 μm-thick electrodeposited nickel films. Electrodeposition of layers at a very narrow spacing contribute to high strength of the composites. The influence of the substrate and plating conditions on the mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Composite hardness models were applied to the experimental data in order to obtaine absolute film hardness.

Microfabrication by mask-maskless wet anisotropic etching for realization of multilevel structures in {100} oriented Si

Step-like structures oriented along 〈110〉 or 〈100〉 directions on {100} oriented Si substrates are first etched with mask following maskless etching in 30 wt. % KOH solution in water at 80°C. The step structures investigated by maskless etching are convex prismatic edges bounded by {100} and {111} planes for 〈110〉 oriented steps or only {100} planes for 〈100〉 oriented steps. Experimental results are used to verify the nature of {hkl} cutting planes that are developed at the convex corners of the steps during maskless anisotropic etching. From analytical relations and experimental results, the ratio between the etching rates for the {hkl} (fast-etching plane at the edge step) and {100} planes is found for both step orientations.

Structural and microhardness characterization of thin electrodeposited Ni/Cu multilayers on copper substrates

Multilayered composite systems of alternately electrodeposited nanocrystalline Cu and Ni films on cold-rolled microcrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The mechanical properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Composite hardness model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The highest value of all the composite film hardness values was obtained when the ratio of Ni : Cu layer thickness was 4:1.

Synergetic effect of additives on the hardness and adhesion of thin electrodeposited copper films

Thin copper films were electrodeposited on a polycrystalline coldrolled copper substrate. The composition of the laboratory-made copper sulphate electrolyte was changed by the addition of various additives. The influence of chloride ion (Cl), polyethylene glycol (PEG) and 3-mercapto-1-propane sulfonic acid (MPSA) on mechanical and adhesion properties of the electrodeposited copper films was investigated using Vickers microindentation technique. Calculations of the film hardness and adhesion were carried out using composite hardness models of Korsunsky and Chen-Gao. The hardness of the composite system is influenced by the adhesion of the copper film to the substrate. Increasing adhesion corresponds to increasing values of the calculated adhesion parameter b, named the critical reduced depth. When additives are added to a plating solution, the copper deposition mechanism is changed and fine-grained microstructure without the formation of microscopic nodules is obtained.

Prevention of convex corner undercutting in fabrication of silicon microcantilevers by wet anisotropic etching

This paper presents microcantilever fabrication on {100} oriented Si substrate using bulk micromachining technique. Detailed characteristics of convex corner compensation design for 〈100〉 oriented beam for two etching solutions: 25 wt. % TMAH and 30 wt. % KOH water solutions at 80 °C are given.

Comparative microhardness analysis of various thin metallic multilayer composite films

Different composite systems of electrodeposited monolayered and multilayered thin metal films of Ni and Cu on cold-rolled copper substrates were made. Thin metal layers were deposited at narrow spacing of 300 nm and 150 nm and high strength of composites was obtained. Microhardness analysis was performed on the systems of ED Ni film (sulphate “Slotonik 20” electrolyte) / ED Cu film (sulphate electrolyte), ED Ni film (sulphamate electrolyte) / ED Cu film (sulphate electrolyte) and ED Ni film (sulphamate electrolyte) / ED Ni film (“Slotonik 20” electrolyte). Characterization of mechanical properties of the composite systems was done using Vickers microhardness testing with loads ranging from 0.049 N to 1.96 N. Dependence of microhardness for different composite systems on microstructure and Ni/Cu and Ni/Ni layer thickness ratio was investigated. Composite hardness model of Korsunsky was applied to the experimental data in order to determine the absolute composite film hardness. The highest value of all the composite film hardness values was obtained for the system of multilayered Ni films from two different electrolytes, and ”Slotonik 20” and sulphamate and with sublayer thickness ratio 1:2, respectively.