bamboo metallization for aesthetic finishing of … · 2019. 4. 4. · drying at a temperature set...

BAMBOO METALLIZATION FOR AESTHETIC FINISHING OFFURNITURE AND WOOD DECORATIVE OBJECTS BY AN

ELECTROLESS/ELECTROLYTIC PROCESS

Jose de Jesus Perez Bueno*†Researcher/Dr.

E-mail: [email protected]

Maria de Lourdes Montoya GarcıaResearcher/M.C.

Centro de Investigacion y Desarrollo Tecnologico en Electroquımica, S.C.Parque Tecnologico Queretaro Sanfandila

Pedro Escobedo 76703, MexicoE-mail: [email protected]

Maria Luisa Mendoza LopezResearcher/Dra.

Tecnologico Nacional de MexicoInstituto Tecnologico de Queretaro

Av. Tecnologico s/n Esq. Mariano Escobedo, Col. CentroQueretaro 76000, Mexico


Gabriela Montoya GarcıaIndustrial/Ms.

Mueblerıa MontoyaAguascalientes, Mexico


(Received September 2018)

Abstract. This work aims to propose and describe bamboo metallizing, in part or totally, for furniture oraesthetical decorations. Bamboo provides a diverse metallic appearance; however, its use with real metal,already conferred to plastics, may increase the chance of use of this green material. The furniture industryrequires sustainable options for both the base material for manufacturing of many pieces of furniture with auseful purpose, and surfaces finished with high quality and variety in their aesthetic appearance. Thisincludes bamboo ornaments, which are useful to complement interior decoration. The coatings obtainedinclude copper, silver, nickel, brass, and tin, each of which had some variants in luster. The main changeincorporated into the process for metallizing nonconducting surfaces was the introduction of a common basefor all surfaces, regardless of its roughness, shape, size, or other surface conditions. Then, this base was takenthrough an electroless process followed by electrolytic stages. Modification of the current process preventsthe need for an initial stage of etching to increase chemical conditioning and roughness. The obtainedmetallic luster was that intended for decorative applications.

Keywords: Bamboo, furniture, sustainability, finishing, coatings, veneer.

INTRODUCTION

The furniture industry requires both the basematerial for the manufacturing of furniture with

useful purpose and surface finishing with highquality and variety in their aesthetic properties.Bamboo has been in use for centuries, but now itis considered one of the few sustainable materialsused in construction and other traditional uses ofwood (Obataya et al 2007). Bamboo is considered

* Corresponding author† SWST member

Wood and Fiber Science, 51(1), 2019, pp. 1-16© 2019 by the Society of Wood Science and Technology

mailto:[email protected]




an outstanding material for its mechanical prop-erties but mainly as a sustainable material, which isgaining popularity in applications usually devotedto diverse woods or even to metals (Eichhorn et al2010). Also, its use in interior decoration is risingin importance, which includes wood-made ob-jects and even some bamboo ornaments thatcould be used to complement indoor designs.Surface finishing of bamboo has progressedfrom simply dried surfaces to using countlessvarieties of paints and lacquers with dyes orabrasion-resistant particles adjusted for the manyapplications.

Surface modification of materials confers anexternal finishing that fulfills the required char-acteristics for their intended use. Currently,metallization of plastics such as Acrylonitrile-Butadiene-Styrene ABS has been applied tohave, at the same time, lightweight and lowproduction cost, as well as an aesthetic metallicappearance. The most frequent plating finishesare with nickel, chrome, copper, silver, gold, andbrass. Metallization of nonconducting surfaces isachieved mainly by using chemical procedures(Sun et al 2012). The electroless technique growsa homogeneous conducting thin film in the ab-sence of an external electrical current (Sittisartet al 2014; Zhao et al 2014). Among the manystages of the electroless process, pretreatment andactivation are of major concern because of thehazardous chemical composition and cost ofpalladium, respectively. Preconditioning of thesurface is crucial for the quality of the finalmetallic deposit. The surface condition affects theallocation of sites during activation and de-termines the feasibility for plating. After thecreation of an autocatalytic conductive metallicthin film, one or more layers are electrolyticallydeposited, thereby increasing the thickness,which confers mechanical resistance and themetallic appearance.

Metallization of nonconducting surfaces such aswood, paper, plastics, and fabrics has beenachieved by using a chitosan layer on the sub-strates and then activating by implantation ofmetallic ions, which is favorable because of theiraffinity to chitosan amine groups (Wang et al

2011; Shi et al 2017; Zhao et al 2018). Elec-tromagnetic interference shielding is of impor-tantance in metallizing wood (Sun et al 2012; Huiet al 2014), which is frequently accompanied byseeking to obtain self-cleaning performance (Xinget al 2018). Nonetheless, using a layer before ac-tivation with metallic ions of palladium, palladium/tin, tin, or other possible alternatives is an opensubject. The difficulty lies in the porosity andadsorption capacity, which prevents the use ofconventional methods that imply dipping into achemical bath that changes the wood and leavesresidues inside.

The aim of this work was to propose metallizing,in part or totally, of bamboo for furniture oraesthetic decorations, and the procedure to do so.Bamboo provides diverse metallic appearances;however, its use with real metal, already con-ferred to plastics, may increase the chance of useof this green material. The furniture industryrequires sustainable options for both the basematerial for manufacturing of many pieces offurniture with useful purposes and surfacesfinished with high quality and variety in theiraesthetic appearance. This includes bambooornaments useful for complementing interiordecoration.

MATERIALS AND METHODS

The culms of bamboo Guadua angustifolia ofabout 6-8 yr old were used. The top and lowestbottom zones of the culms were not used. Thevascular bundles, epidermis, phloem, protoxy-lem, metaxylem vessels, fiber, and cortical pa-renchyma did not vary significantly among thesamples (Xing-yan et al 2015).

The process steps include 1) natural bambooconditioning (cutting, cleaning, and dehydration),2) preserving bamboo, 3) bamboo dehydration, 4)applying lacquer, 5) drying, 6) application ofcolloidal copper, 7) drying, 8) surface activation,9) rinsing, 10) electroless process for metalliccoverage, 11) rinsing, 12) electrolytic process(nickel, chrome, brass, etc.), 13) rinsing, 14)draining and drying, and 15) placement on thedesign of a furniture or decorative object. Table 1

WOOD AND FIBER SCIENCE, JANUARY 2019, V. 51(1)2

presents a scheme including details of each stepof this process.

The following is the description of each of thesteps, which can be applied to bamboo, wood,natural fibers, or any material made of cellulose.

1. Natural bamboo conditioning (cutting, clean-ing, and dehydration). The bamboo was cut forpreparing parquet, which in turn was cut inthe shape and dimensions to be used inspecific furniture or ornamental object. Thebamboo should be cut from plants with anoptimum age (above 7 yr) and dried to ahumidity content less than 12%. The bam-boo poles are obtained with lower water andcarbohydrate levels by cutting them at dawnon a waning moon.

2. Preserving bamboo. The preserving meth-ods prevent wood deterioration by fungi,termites, woodworm, and other xylophagousinsects. The most common treatments in-clude immersion for 5-8 h in a saline solution

prepared with boric acid/borax/water (H3BO3/Na2B4O7$10H2O/H2O) at a ratio of 1:1:50.Another commonly used chemical treatmentis mercerization, which consists of treatingthe natural fibers with a solution containingaround 4% NaOH for 1 d, but the concen-tration is inversely proportional to the treat-ment time. Some chemical treatments usebiodegradable pesticides with the specificfunction of preserving and protecting thebamboo against woodborers or xylophagousinsects.

3. Bamboo dehydration. The humidity contentin bamboo not only increases the risk of at-tack by fungi or insects, but also affects thelayer deposition and its adherence. So, thewood pieces were introduced into an oven fordrying at a temperature set in the range from80 to 100°C. The drying time was from aminimum of 5 h to a maximum of 1 d.

4. Appling a lacquer. A lacquer was applied toprotect or seal the bamboo and as a basis of

Table 1. Process used for metallizing nonconducting surfaces of bamboo.

Stage Vol. (L) Material Immersion time Temperature Comments

Bamboopreparation

— Bamboo and wire — — —

Bamboopreserving

— H3BO3/Na2B4O7$10H2O/H2O)1:1:50

24 h — —

Bamboodehydration

— — Min. 5 h, max. 24 h 80-90°CFurnace

—

Lacquer — Varnish and thinner Three layers Airbrushpainting or immersion(min. 3 s)

— —

Drying — — Max. 30 min RT or max.40°C

—

Cu plating — Cu paint Three layers Airbrushpainting or immersion(min. 3 s)

— —

Drying — — Max. 30 min RT or max.40°C

—

Surface activation 4.5 (SnCl2)/HCl/deionized water Max. 5 min RT Mechanical stirringRinsing 4.5 Deionized water 3-10 s RT Mechanical stirringAg plating 0.5 Ag solution Max. 10 min RT Mechanical stirringRinsing 4.5 Deionized water 3-10 s RT Mechanical stirringNickel 22.5 Ni solution Max. 20 min 50-55°C Magnetic stirring,

1-2 A (rectifieror DC), 2 anodes

Rinsing 4.5 Deionized water 3-10 s RT Mechanical stirringDraining or drying 4.5 — 10 min RT —

RT, room temperature; Max., maximum; Min., minimum.

de Jesus Perez Bueno et al—BAMBOO METALLIZATION FOR AESTHETIC FINISHING 3

union between the bamboo and the next layer.The proportion of nitrocellulose lacquer tothinner was 1:1. The solution was appliedwith airbrushes, which provide uniform andthin covertures. The solution was appliedthree times with 5 min between each coatingfor air-drying. This stage can be carried out aswell by deep-coating with immersion for aminimum of 3 s. Nevertheless, handling ofpieces, solvent adsorption, and layer thick-nesses were difficult to control.

5. Drying. The lacquer applied to the bamboowas dried at room temperature for 2-3 h. Al-ternatively, an oven preheated to 40°C can beused for half an hour. Amoderate increment oftemperature can reduce treatment times.

6. Application of colloidal copper paint. Asimilar procedure used for the lacquer wasapplied for the copper-containing solution.

7. Drying. The difference from the previous caseis that it takes longer to dry.

8. Surface activation. The bamboo pieceswere immersed in a solution of stannouschloride (SnCl2)/HCl/de-ionized water for5 min, with a back-and-forth motion. Theywere removed from the solution and drainedfor 5 s.

9. Rinse. The pieces were immersed in deion-ized water for 3-10 s with gentle agitation,then removed and drained for 3-5 s.

10. Electroless process for metallic silver. Dif-ferent solutions were prepared to generate theplating, and the process consisted of thefollowing: 1) silver nitrate saturated solution;2) silver nitrate solution previously dissolvedwith ammonium hydroxide and potassiumhydroxide. The solution exhibits an exothermicreaction before it was allowed to cool. 3)Ammonium hydroxide was added dropwiseand under magnetic stirring until achieving thedissolution of the precipitates rich in silver. 4)To avoid an excess of ammonium hydroxide, a

Figure 1. The sequence followed in the process for plating the nonconducting substrates. Two examples of finishing areshown: brass-coated bamboo and silver-coated rose.


saturated solution of silver was added until itobtained a pale yellow color. Moreover, asilver reducing solution was prepared, whichcontained sucrose (9%) and concentratednitric acid (4 mL) in distilled water. Thesolution was boiled and cooled before use,with 20°C as the optimal working temper-ature. Later, the silver nitrate–ammoniumhydroxide solution was mixed with the re-ducing solution at a 4:1 proportion. Thebamboo pieces were completely covered bythe solution. The pieces were maintained inthe state for a maximum period of 10 min,after which the pieces were removed andallowed to drain. Thickness of the pieces wascontrolled by the immersion time or bycontrolling the silver nitrate concentration.

11. Rinse. The silvery bamboo pieces were im-mersed in deionizedwater for 3-10 s with gentleagitation, removed, and drained for 3-5 s.

12. Nickeling by an electrolytic process. Elec-trolytic nickeling was attained by using anickel sulfamate, boric acid, and deionizedwater preparation. The silvery bamboo pieceswere placed in an electrolytic cell in thecathode position. The setup consisted of twonickel anodes. The solution was heatedmaintaining a temperature in the range of 50-55°C under stirring. A current in the range of1-2 A was applied with a Direct Current (DC)rectifier for a maximum time of 20 min.

13. Rinse. The nickel-plated bamboo pieces wereimmersed in deionized water for 3-10 s withgentle agitation, removed, and drained for 3-5 s.

Figure 2. Optical micrographs showing evidence of wear as diagonal lines by Tabber tests (a) and (b). Different sites ofabrasive rubber wheel path on the nickel-plated bamboo sample (c) and (d).


14. Drain and dry. The pieces were allowed todrain. Subsequently, hot air was applied witha dryer machine for 10 min.

15. Finally, the plated bamboo pieces wereplaced within different furniture designs.

The processes were exemplified above with thenickel-plating finishing, but many others have beenapplied and even more are viable by electroless andelectrolytic procedures. Some examples of metalfinishing surfaces are bright copper, antique orrustic copper, bright nickel, opaque nickel, blacknickel, black silver, bright silver, gray zinc, brightyellow brass, dull yellow brass, bright tin, polishedchrome, and other variations in appearance thereof.

Taber Abraser Model 5150 (TABER® Industries,North Tonawanda, NY) was used to conductabrasion resistance tests on the coated pieces. Thetest was carried out using the CS10 abrasive rubberwheel (TABER® Industries) having a value of 88in Shore A hardness, with a weight of 1000 g anda rotation speed of 70 rpm.

The Taber tests for abrasion resistance of thecoatings were conducted according to the norm

ASTM G195-08 (2013) and the norm ASTMD4060-10 (2013). A circular sample of parquetwas prepared with a diameter of 10.8 cm and acentered hole of 0.6 cm, using 2-cm wide indi-vidual pieces. The circular piece of the parquetwas treated for final nickel metallization. The testwas stopped after 500 cycles and the sample wasweighed. Thereafter, the test was resumed untilcompleting 1000 cycles. The original weight was39.7018 g, which reduced to 39.6839 g andsubsequently to 39.6752 g, resulting in a finalTaber wear index of 0.0266 by applying Eq 1.

I¼ ðA�BÞð1000ÞC

; (1)

where I is the Taber wear index, A is the weight(mass) of the specimen before abrasion, B is theweight (mass) of the specimen after abrasion, andC is the number of test cycles.

I1 ¼ 39:7018� 39:6839� 1000=500 ¼ 0:0358;

I2 ¼ 39:6839 � 39:6752� 100=500

¼ 0:0174; and

Figure 3. A profilometry graph of a segment between the nickel layer and copper sublayer obtained by making a triangularcut (dark area). The inset shows the micrograph of the segment used for measurement.


I3 ¼ 39:7018� 39:6752� 1000=1000¼ 0:0266:

Scanning Electronic Microscope (SEM) JEOLmodel 5400-LV (JEOL, Tokyo, Japan) was used

to analyze the surface morphology of the platedbamboo pieces.

The reflectance spectra were measured using anUSB2000þ Fiber Optic gated Ocean Optics

Figure 4. (a) X-ray diffractograms corresponding to three nonmetallized samples: polish bamboo, pressed bamboo, andlacquered bamboo. (b) Diffractograms corresponding to three metallic stages: Cu lacquer, Ag, and Ni. The two insets representcellulose in its monoclinic and triclinic structures.


Table

2.Com

puteddata

from

diffractog

ramsof

differentanalyzed

samples

correspo

ndingto

cellu

lose

peaksandthoseformostintensepeaksof

Ni,Ag,

andCu.

Sam

plename

Observed

max

(2θ°)

Interplanar

distance

(nm)

Planes

Maxim

umintensity

(Cps)

L(nm)

Fullwidth

athigh

maxim

um(2θ°)

Raw

area

(Cps

�2θ°)

Net

area

(Cps

�2θ°)

Niplated

Ni

44.50

0.20

34(1

11)

3035

10.22(10.0)

0.84

4349

.432

83Bam

boo

22.28

0.39

87(2

00)

248

4.26

1.9

984.6

312.6

Agplated

Ag

38.12

0.23

59(1

11)

867

17.88(28.0)

0.47

2857

.260

2.2

Bam

boo

22.32

0.39

80(2

00)

3672

3.58

2.26

12,760

7585

.3Cupainted

Cu

43.2

0.20

92(1

11)

522

21.91(36.3)

0.39

477.2

59.36

Bam

boo

22.2

0.40

01(2

00)

3417

3.42

2.37

12,933

.763

46.2

Natural

bambo

o15

.65

0.56

58ð1

� 10Þ

2681

—2.76

11,382

4185

.322

.24

0.39

94(2

00)

5760

3.46

2.34

19,354

.711

,881

34.80

0.25

76(0

04)

498

—2.44

2724

.529

9.9

Com

pacted

commercial

bambo

o’

axialaxis

16.76

0.52

85(1

10)

892

—a

5011

.513

47.3

21.82

0.40

70(2

00)

1336

2.34

3.46

6746

.824

59.7

34.60

0.25

90(0

04)

606

—0.10

704.5

8.92

2Com

pacted

commercial

bambo

oka

xial

axis

17.22

0.51

45(1

10)

1072

—0.26

921.3

53.54

21.88

0.40

59(2

00)

1538

2.71

2.99

7135

.828

48.6

34.69

0.25

84(0

04)

1523

—0.41

1144

.244

9.3

Cps,countspersecond.

aUncom

puteddata.


spectrometer (Ocean Optics, FL). The whitereferences were Teflon� and an aluminum thinfilm. The black reference was a cavity, self-constructed in the laboratory.

A Bruker AXS diffractometer (Bruker AXS,Karlsruhe, Germany) with CuKα1 (λ¼ 1.5406 A)radiation was used to conduct the crystallinecharacterization. The overall measurement con-ditions were as follows: scan speed 3 s/step,increment 0.04°2θ, 40 kV, 40 mA, soller slit,0.6 mm slit, one scan. The TOPAS 4.2 software,and the AbsorbDX V. 1.1 and EVA V. 9.0software of Bruker were used to analyze thediffractograms (Bruker AXS).

Roughness measurement was carried out using aVeeco Dektak 6M stylus profilometer (VeecoInstruments Inc., NY), with a pathway length of5000 µm with a measurement time of 100 s usinga diamond tip of 5 µm.

The proposed form for determining averageroughness, quantifying the detected photons orcounts of the (200) cellulose peak and consid-ering the absorption of radiation, was

x ¼ � lnð1� pÞ�µ ðλÞ ρ

�1

sin γþ 1

sin ð2θ� γÞ�� 1

;

(2)

where x is the estimated depth, p is the % ofcontribution of the diffracted beam (µm), µ is themass attenuation coefficient (cm2$g�1), ρ is the

density of the material (g$cm3), γ is the anglebetween the incident beam and the surface, and2θ is the deviation of the beam.

The diffractograms were collected by fixing thetheta angle at 10° (X-ray source) and varying thedetector position (2-theta).

The apparent value of the cross-sectional di-mension L was calculated from the Scherrerequation (Newman 2008):

τ¼ K λβ cosθ

: (3)

Here, K is the dimensionless shape factor with atypical value of around 0.9; λ is the X-raywavelength (λ ¼ 1.5406 A for CuKα1); β is thefull width at half maximum, expressed in radiansof the peak corresponding to planes; and τ is themean size of the ordered (crystalline) domains,which is limited to nanometric scale. The cal-culated crystallite size may be smaller than thegrain size depending on crystalline defects, in-homogeneous strain, and instrumental effects,which contribute by broadening the peaks andreducing the value.

RESULTS AND DISCUSSION

Figure 1 describes the sequence followed forplating nonconducting substrates, specificallybamboo. The variation in the electroless processapplied to plastics lies in applying lacquer to sealthe porosity, obtruding the possible absorption ofthe plating solutions, which at the same time

Table 3. Thickness computed using ABSORB© and the quantified % of contribution to the diffractogram using TOPAS©.

Lacquer/Cu/Ag Lacquer/Cu/Ag/Ni

Lacquer/Cu Cu Ag Cu Ag Ni

% (TOPAS©) a 65.8 34.2 1.62 1.58 96.8Weighted profile R-factor — 13.79 — — 12.187direction a (1 1 1) (1 1 1) (1 1 1) (1 1 1) (1 1 1)2θ° 43.298 38.116 43.298 38.116 44.5E (keV) CuKα1 a 8048 8048 8048 8048 8048µ 50.92 212.1 50.92 212.1 46.13µL 456.2 2227 456.2 2227 410.6ρ (g/cm3) 8.96 10.5 8.96 10.5 8.9X (nm) a 3103 278 47.23 9.1 11.140

a Uncomputed data (non-available signal).


would contaminate the wood, decreasing thechemical reagent concentration and increasingthe cost. The sealing lacquer (organic solvent orwater based) and the copper conducting lacquerwere applied by spraying the surface with threelayers each, which provides a thin homogeneousfinishing. The next steps were the electroless/electrolytic process using stannous chloride (SnCl2)as an activating agent for posterior metallizationwith silver and nickel, or other metals. Figure 1shows two examples of finishing following theprocedure described earlier: brass-coated bambooand silver-coated rose.

The prepared nickel finishing using nickel sul-famate (Ni(SO3N2)2) had a typical wear re-sistance, similar to a Watts solution (Saito et al2007), which is around 26 mg loss/1000 cycles(Kanta et al 2009, 2010; Sahoo et al 2011;Brooman et al 2004). This result shows that thewear resistances achieved on bamboo were thosealready known for the finishing coatings accordingto their chemical composition and processconditions.

Figure 2(a) shows the darkened image of theabrasive rubber wheel path on the nickel-plated bamboo sample. The optical micrographin Fig 2(b) presents an enlarged image of the

area with the wear evident as diagonal lines.Figure 2(c) and (d) shows different sites on theworn path.

Figure 3 shows the profilometry graph of asegment between the nickel layer and coppersublayer obtained by a triangular cut (darkarea). The inset shows the micrograph of thesegment used for the measurement. The av-erage roughnesses were 1.27 mm for the Culayer and 1.17 mm for the Ni layer. The cutcaused a bend in the nickel layer because of theinternal stress, which had a thickness ofaround 12 nm (Fig 3). The nickel deposits hada highly uniform thickness and similar sub-strate roughness even at thick deposits. So, thefinal roughness greatly depended on the cop-per layer.

Because of the rough surface of the bamboo cuts,the thickness of each layer was difficult tomeasure. To analyze the metallic layers andobtain an average of their thicknesses in theilluminated area, X-ray diffraction was con-ducted in samples of each finishing: polishbamboo, pressed bamboo, lacquered bamboo,and Cu, Ag, and Ni layers. Figure 4(a) showsthree of the diffractograms corresponding tononmetallized samples. The peaks correspond to

Table 4. Thickness computed using ABSORB© and the quantified % of contribution to the diffractogram from the ratio of(element intensity)/(intensity of another element of the top layer, X1) and of (element intensity)/(element intensity of anothersample, X2).


cellulose in its monoclinic and triclinic struc-tures with the family of planes identified. Thetwo insets in Fig 4(a) represent structures with asize equal to three times the unitary cell in eachaxis. The unit cells are represented as the cen-tered shadow areas.

The pressed bamboo shows an intensification ofthe peak corresponding to the 004 planes. Thisincrease in crystallinity was identified perpen-dicular to the axial direction of the bamboo fibers.The tested samples showed a higher (004) peakaround 10 ton/cm2.

Figure 4(b) shows the other three diffractogramscorresponding to metallized samples. The graphscorrespond to a copper-lacquered sample, asucceeding silver-plated sample, and a samplewith the final top nickel finishing. The cellulosesignal decreased proportionally to the density andthickness of the layers.

Table 2 shows the different parameters associatedwith the diffractograms of each sample. The rawarea of natural bamboo (200) planes was taken asreference. Comparatively, the Cu, Ag, and Nisubsequent layers reduce their raw area to

Figure 5. (a) Computer-Aided Design (CAD) image with a design for a bamboo parquet table. (b) A real model made withlacquered parquet.


66.82%, 65.93%, and 5.01%, respectively. So,the attenuations caused by successive layers werearound 33.18% with copper paint, 0.897% withsilver plating (1.343%, attenuation relative to the

previous layer), and 28.986% with nickel plating(7.72%, attenuation relative to the previouslayer), relative to the raw area of bamboo (200)planes.

Figure 6. SEM images of bamboo parquet surfaces: (a) and (b) natural bamboo; (c) and (d) lacquer primer layer; (e) and (f)copper lacquer layer.


The intrinsic roughness of wood samples makesdetermining the average thickness of each metalliclayer difficult. Tables 3-5 present the thicknessmeasurement for each successive layer consider-ing the peaks of the corresponding diffractogramsfor bamboo, Cu, Ag, and Ni. Table 3 shows thethickness of each layer computed using the soft-ware ABSORB© (Bruker AXS) and the quanti-fied % of contribution to the diffractogram usingTOPAS© (Bruker AXS). So, the computed thick-ness valueswereXCu¼ 3.1mmandXAg¼ 0.28mm,and XCu ¼ 0.047 mm, XAg ¼ 0.009 mm, andXNi ¼ 11.14 mm.

Table 4 presents the percentage of attenuationsbetween one layer and the subsequent layers shownbelow the diagonal line. In Table 4, the maximumintensity (counts per second) of the mean peak

corresponding to each layer is shown above thediagonal line.

Figure 5 shows a folding table constructed withbamboo parquet. Figure 5(a) shows some designviews, one main image and some from differ-ent perspectives. The main image presents thesize and intercalation of metallized and var-nished wood with an aesthetic finishing purpose.Figure 5(b) shows the table made of bambooparquet. Metallized bamboo may be used inmany different design concepts for furniture forboth domestic and office use. Also, the bambooflooring can include metallized finishing withvarnish protection.

Figure 6 shows SEM micrographs correspondingto natural bamboo, Ag electroless, and Cu paint.

Figure 7. SEM images of bamboo parquet surfaces: (a) and (b) silver layer; (c) and (d) nickel finishing.


The images in the left column were taken at 100�with a scalebar corresponding to 250 mm. Theimages in the right columnwere taken at 1000�witha scalebar corresponding to 25 mm. The naturalbamboo images show a fibrous structure (Fig 6(a)and (b)). Figure 6(c) and (d) shows the cover-ture of most of these fibers with the Ag elec-troless layer, but the micrometric hole remainedopen. Also, there were some residues, fiber-likeagglomerates on the surface but not stronglyattached. Figure 6(e) and (f) shows the bamboocovered with a Cu paint, which contains Cuparticles in an organic lacquer. This paint wasincluded to compare with the electroless metal-lization. These micrographs show two types of

zones, some lamellar plates surrounded by a ma-trix of lacquer. The paint, because of applicationwith a paintbrush and the drying process, com-pletely covers the wood surface. Nevertheless, thelayer was not electrically conductive despite thehigh copper content.

Figure 7 shows the SEM micrographs corre-sponding to the primer lacquer layer and the Nielectroless top layer. The images in the leftcolumn were taken at 100� with a scalebarcorresponding to 250mm. The images in the rightcolumn were taken at 1000� with a scalebarcorresponding to 25 mm. The applied lacquerlayer resembles the surface finishing of the Cu

Figure 8. Reflectance spectra of different surface finishings: tin (Sn), nickel (Ni), chrome (Cr), silver (Ag), copper (Cuelectroless), copper paint (Cu paint), natural bamboo (bamboo parquet), and varnished bamboo (B-lacquer).

Table 5. Color parameters corresponding to different surfaces of bamboo samples.

Layer x y L* a* b* Purity λdominant

Sn 0.450 0.409 102.7 0.865 5.179 0.0780 547.3Ni 0.467 0.413 101.6 4.9 13.4 0.175 587.7Cr 0.442 0.408 101.0 �2.304 �2.000 0.0125 498.4Ag 0.4671 0.4163 116.8 4 17.6 0.197 589.7Cu electroless 0.442 0.408 98.7 �2.382 �2.310 0.0138 496.1Cu paint 0.5305 0.4029 96.9 30.3 43.9 0.543 590.5Bamboo parquet 0.4981 0.4191 86.6 11.8 31.5 0.431 586.7B-lacquer 0.5081 0.419 80.3 13.9 35.3 0.5 586.1


lacquer, but homogenous and without the copperlamellar plates. Meanwhile, the electroless nickeltop layer shows a continuous layer with somemetallized holes. In a closer view within theholes, the Ni layer had some nodules attributed tothe nucleation process of nickel or other previousmetallic layers.

Figure 8 shows the reflectance spectra of the topof each studied layer. The graphs correspond to tin(Sn), nickel (Ni), chrome (Cr), silver (Ag), copper(Cu electroless), copper paint (Cu paint), naturalbamboo (bamboo parquet), and varnished bamboo(B-lacquer). Some of these spectra are shown onlyfor comparative purposes. Reflectance values above100% are because of the difference between themetallic luster and the white reference, which cor-responds to Teflon� in the case of the graphs.

Table 5 presents the chromaticity diagram co-ordinates (a, y), CIE L*a*b* coordinates, colorpurity, and dominant wavelength. This charac-terization was carried out with the purpose ofshowing the quantitative values for the color ofeach surface. The values were obtained using analuminum thin film as the white reference insteadof Teflon�, which was used in the Fig 8 spectra.The differences in luster or luminosity, among themetallic surfaces and others, were observed. Thesesurfaces were far from a mirror finishing becauseof the initial surface roughness and the lacquerused as a primer layer, but the metallic luster wasthat intended for decorative applications.

CONCLUSIONS

This work describes how bamboo was success-fully plated with different metals and finishing. Thecoatings obtained include copper, silver, nickel,brass, and tin, each of which had some lustervariations. The main change incorporated in theprocess for metallizing nonconducting surfaceswas the introduction of a common base for allsurfaces, regardless of its roughness, shape, size, orother surface conditions. Then, this base was takenthrough the electroless process, followed by elec-trolytic stages. Modification of the current processprevents the need for an initial etching stage forchemical conditioning and increasing roughness.

The intrinsic roughness of wood samples makesdetermining the average thickness of each me-tallic layer difficult. This work proposes amethodology using X-ray diffraction and somequalitative and quantitative software to determinethe thickness of irregular metallic layers such asthose prepared in this study.

Differences in luster among the metallic surfacesand others were observed. These surfaces werefar from a mirror finishing because of the initialsurface roughness and the lacquer proposed as aprimer layer, but the metallic luster was thatintended for decorative applications.

ACKNOWLEDGMENTS

This work was carried out under the auspices ofthe Mexican Council for Science and TechnologyCONACYT, through the project CEMIE-SolNo. 207450 P18, P62, and P96; GraphenicMaterials National Laboratory No. 293371. Theauthors thank the World Bank and the EnergySecretariat for the grant of the PRODETES Price,No. 002/2017/PRODETES-PLATA. Also, thefirst author acknowledges CONACYT for hisgraduate fellowship.

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