Research Design

RESEARCH DESIGN AND METHODS The goal of this project is to develop a novel method of plating titanium and titanium-zirconium on ABS and ABS/PC polymers. First we will provide description of the plating process, which involves two main steps. The first step is to activate the surface of a polymer and the second is to electrodeposit metal on its surface. Thus, the entire project is defined by the following two aims: Aim 1. Implement and evaluate a new process of surface activation for the ABS and ABS/PC surface that promote adherence of the metal. Aim 2. Implement and evaluate a novel plating recipes for electrodeposition of turbo titanium/zirconium coating on plastic. The Process of Nano-Titanium-Zirconium layer deposition. As mentioned before a commercial titanium coating method is not available so far. The coating of titaniumzirconium alloy, as proposed here, can be obtained by an electrochemical process in which a nano- titaniumzirconium layer is electroplated on a plastic. In this setup a cathode is an electroplated plastic (ABS/PC) coated with nickel and anode is a platinum/titanium metal immersed into the salts solution. The entire process of plating is divided into two main steps described in more details below and summarized altogether in Table 2. Each step corresponds exactly to the appropriate aim stated above. Step 1 (Aim 1): The first step involves activation of the surface of the plastic and deposition a thin (100 microinches) layer of nickel metal. This step is performed in a series of 11 tanks in which consecutive etching, rinsing, activating, conditioning and nickel depositing is executed. Table 1. provides detailed description and comparison of the conventional electroless plating of nickel on plastic with new direct plating process, where palladium activation is eliminated (20). The main advantages of this new process, which will be used in our implementation, is much smaller number of elementary steps (e.g. used tanks), savings in electric energy, significantly reduced water consumption, elimination of chelates and improvement in overall productivity. Process Steps

Conventional Electroless Process

New Direct –Plate Process

Advantages and Disadvantages

ETCH

Time =12 MIN , Temp=68C, Makeup= 400g/l H2SO4, 400G/L CrO3,Withouth Catalyst

Time=5MIN, Temp=63C, Makeup= 400g/l H2SO4, 320G/L CrO3

Less Production of Cr3+, Less Cr drag out, Catalyst Cost

RINSE

4 Rinses

4 Rinses

Reduced waste water costs due to lower drag out

REDUCTION

Time =2 MIN TEMP=30-50C

NONE

No Cost, No Space Required

RINSE

3 Rinses

NONE

No Cost, No Space Required

ACID ACTIVATION

Pre-Immersion Dip in HCL

NONE

No Cost of the Chemicals

PALLADIUM ACTIVATION

Pd-Activator 5min, 30C

Activator Time=4 min, Temp=20C

Make Up= Complex Metal, Ammonium, Palladium Free, Possible need of cooling in summer

RINSE

3 Rinses

Conditioner Time=0.5min

Less Effluent

ACCELERATION

Accelerator Time=2-3 min, Temp= 50C

Conducting Solution Time=1 min, Room temp

Less Energy, No complexing and reducing agent, Unlimited Operational life

RINSE

3 Rinses

Conditioner Time=0.5min

Less Effluent

ELECTROLESS NICKEL

Time=10 min, Temp+30C

NONE

No HNO3 No Tank Stripping Reduce Energy Cost No Complexing Agent No Expensive Reduction Agent

RINSE

3 Rinses

NONE

No Waste Water Less Space

NONE

NONE

Electrolytic Nickel

Electroplate to Spec.

Table 1. Comparison of the conventional, electroless plating on plastic with the new, palladium-free method. The technology that will be used in our project does not use precious metals to activate plastic or electroless chemistries to produce the first conductive metallic layer. Instead, the process allows electrolytic nickel to plate directly onto the plastic substrate. A direct metallization process eliminates the need to use electroless chemistries and shortens the pretreatment time by reducing the number of processing steps. This direct-plate technology employs a mild etching process that ensures a high degree of adhesion. It has been used in production in several pilot plants since 2001. To summarize the benefits of direct-plate systems, certain processing considerations must be well understood. The etching process is an important factor and is responsible for the degree of adhesion on both ABS and ABS/PC resins. The etching process is also responsible for the actual ability to metallize such plastics. The best possible degree of adhesion and "metallization" for the direct-plate process is achieved by using a mild etch. Etching parameters directly influence surface chemistry. The mild etch enhances the formation of polar functional groups (-OH, -C=O, -COOH) on the plastic surface, where the percentage of hydroxyl groups (-OH) are found to be particularly high. These make a chemical link with the positively charged activator molecules possible. In the following conducting solution, the active metal is "wetted" to the plastic substrate via a bridge of sulfur as a result of a kind of vulcanization. These two reactions achieve an additional chemical adhesion. Activation is carried out following a mild etch and subsequent rinsing in a complex metal amine solution. With the direct-plate process there is no need for chromium reduction. The quality of the activator, i.e., its operational life and its "activity," depend on the conditions applicable during production. Drag-out and work volume, reduce the quality of the activator, but this is easily managed by replenishment. After activation, parts are given an alkaline rinse. Hydrolysis washes off loosely adherent complex metals as metallic hydroxides from the rack insulation. Immersion in the conditioner should be less than two minutes, since complex metals would be chemically removed from the surface of the production parts as a result of hydrolysis. The final sulfide conducting solution produces a grey, firmly adhering film that consists of metal and polysulfides. During the reaction that occurs between the complex metal and the sulfurous solution, further reactions take place on the highly active plastic surface. Here again, the immersion time has no effect on the metallization; one minute is sufficient (Fig.2). For the first electroplating bath, only electrolytes with potential lower than the reduction potential of the sulfide activator Figure 2: Area growth in sulphamate deposit are used. Typically, nickel is used since the potential from acid nickel at two volts, one min. with a copper electrolytes is too electropositive. Tests show that the pointed contact, depending on the sulfamate-nickel has excellent metallizing characteristics. The voltage concentration of the etch catalyst, on must start at two to three volts and increased step-by-step. The ABS and ABS/PC sample panels. prescribed voltage should be reached after four minutes. In this manner, burning is avoided and a constantly high area growth of about 0.5 to 1.0 dm²/min is ensured. Immersion time depends on part size, rectifier capacity and the number of contact points. The nickel plating time should be 5-12 minutes, depending on the size and complexity of the parts. Further metal deposits then may be applied as required. The advantages of the direct-plate process in comparison to conventional

processes for plating on plastics quite clearly outweigh the disadvantages. The reduction of the number of processing steps and rinsing baths shortens the pretreatment time from 50 to 20 minutes. The parameters of plastic plating are fairly well tested (20), but will be optimized and fine tuned in our own setup. Step 2 (Aim.2): Second step (beginning from step labeled green in Table 2) involves electroplating of titanium or titanium/zirconium alloys on activated plastic surface. This step is conducted in a series of 5 electrolytic tanks in which electroplating of Ti or Ti/Zr alloys and then rinsing and drying is performed. We propose the following composition of the salts solution to perform initial tests on small scale: 100g potassium titanate (K2Ti03), 26.1 g zirconium hydroxide (Zr(OH)4), 50g sodium sulfate (Na2S04), sodium carbonate (Na2C03) in the amount to adjust pH to the value of 5-5.2, 1g/l of sodium saccharin which are dissolved in 9.5 mol sulfuric acid (H2S04) (all quantities are per 1 liter of electrolyte.) The initial conditions for electroplating are as follows: temperature of bath will be maintained at 80 deg. C, the platinum/titanium anode will be used and the current density of 120-150Amps/sqf with Pulse Plating Power Supplier will be applied. All condition will be subjected to optimization in order to achieve the maximum efficiency of electrodeposition process. In our experimental setup both electrodes are connected through an external circuit. The process involves: a) the dissolution of the anode made of the platinum-titanium alloy, where platinum is a catalyst to speed up the oxidation process of titanium and b) the deposition of metallic titanium-zirconium on the other electrode (the cathode). Additional source of titanium ions is potassium titanate dissolved in the sulphuric acid solution. The Pulse Plating current from Pulse Plating Power Supply is applied between the anode (positive) and the cathode (negative). Conductivity between the electrodes is provided by an acidic solution of titanium and zirconium salts. Pulse plating technology is a recognized technology in the plating industry (21). In our setup it will be used to obtain an amorphous structure (nano-structure) of titanium/zirconium layer. During the pulse “ON” time, the ions are plated out of solution near the cathode interface. The cathode diffusion layer begins to build, until the current is turned OFF. During the pulse “OFF” time the solution near the cathode interface becomes replenished with metal ions. The diffusion layer is maintained to achieve evenly distributed thickness of deposited metal. Such procedure yields improvements in current density across the cathode surface and guarantying more uniform deposit thickness. With pulse plating, re-nucleation can occur with each pulse, greatly increasing the number of grains resulting in the grain reinforcement and nano structure buildup. Typically the pulse “ON”-time may be from 0.1-2.0 milliseconds long and the pulse “OFF”-time from 0.5 to 10.0 milliseconds long. In our setup we will test the efficiency of plating with the following parameters: “ON”time: between 0.2-2.0 milliseconds; “OFF”-time between 0.5-2.0 milliseconds and DUTY CYCLE 10%-50%. The average current is related to the rectifier output current or peak pulse current. Here, this current will be set to 120-150Amps/SqF. When titanium zirconium salts are dissolved in the sulfuric acid, the titanium and zirconium are present in the solution as positively charge ions: Ti2+ and Zr4+, respectively. When current flows (“ON” time) the titanium ions react with two electrons (2e-) and zirconium ions react with four (4e-) electrons and are converted to metallic titanium, zirconium at the cathode (e.g. activated ABS or ABS/PC plastic). The reverse occurs at the anode where metallic titanium dissolves to form divalent ions. Platinum of the anode is a catalyst to speed up the oxidation process of titanium. Since the titanium and zirconium ions discharged at the cathode are replenished by the titanium ions formed at the anode during an oxidation process and zirconium ions from the electrolyte solution, this process can be conducted for a long period of time without interruption. This process is relatively inexpensive and very efficient. The recommended nano-titanium/zirconium coating thickness is from 400-800 microinches with plating time of 90 minutes and a 14-15% of zirconium content (by wt.) in titanium-zirconium alloy layer. The thickness of Ti and the percentage content of Zr metal are the parameters responsible for superior mechanical properties (hardness, yield strength, tensile strength and elongation), greater corrosion resistance than steel, excellent resistance to wear, especially with the zirconium content of 14-15% by wt in the final layer (22). The presence of Zr in Ti-Zr alloys significantly improves resistance to wear of the deposit compared to pure titanium. All those

parameters will be subject to experimental verification and tuning. We will test how the resistance to wear depends on the zirconium content. As mentioned above, all parameters of the plating process will be subject of testing and fine-tuning. In particular we will focus on optimization of the following conditions: -

-

temperature of the bath for Ti and Ti/Zr plating parameters of the pulse plating, cycle Time (Duty Cycle), current density applied to electrodes, total time of plating composition of the salt solution to achieve 14-15% of Zr content in plated alloy percent of Zirconium (from 14% to 16% in the alloy) percent of sodium saccharin (from 1% to 3% in the electrolyte)

Standard tests for wear resistance, strength, tensile strength, yield strength, hardness, elongation will be performed for all test materials produced under various conditions. Our long-term goal is to design materials with potential application in dentistry and medicine such as implants, screws, plates and pins. However at this stage of a project we intend to create a prototype of such materials that have appropriate mechanical properties. Important parameters are yielding point, elongation at break and modulus of elasticity. Stainless steel and unalloyed titanium have low strength and are therefore cold worked. Addition of zirconium to titanium alloys increases the tensile strength from approximately 500MPa (value for pure titanium) to 700 MPa (22), and as such it would be more appropriate for dental applications. Mechanical properties of the material will be tested in specialized laboratory (Detroit Testing Club, Michigan), which include tests for: stress strength test, tensile test, elongation test, hardness etc. Description of the entire plating process is collected in Table 2. It contains short description of each individual elementary step, including time required for performing the step, number of tanks involved in the process, their properties such as dimensions, drainage, filters, temperature required and other parameters. Step-1 – activation of the ABS or ABS/PC plastic - involves all elementary steps beginning from LOAD to RINSE (before green block) in Table 2. Step-2 – electroplating of Ti-Zr alloy - begins from green block in Table 2 (denoted as TurboT3Z1) and ends at UNLOAD elementary step. Insert at the bottom – from START to END – represents schematic summary of the entire process. TIME DESCRIPTION

# OF STAT/ Tanks

(MIN)

TANK LENGTH

TANK WIDTH

TANK

TANK VOL

MAT.

OVER

DOT

DIS-

HEAT/

D.O.T.

DEPTH

GALLONS

OF

FLOW

DRAIN

CHARGE

CHILLER

4” S/L

CONS

70

PP

AGIFILTER

LOAD

1

1

ETCH –ACID

1

5

24”

18”

36”

CF RINSE

1(3)

1

36

18”

36”

Activator –Pd-Free

1

4

24”

18”

36”

70

PP

Conditioner

1

0.5

24”

18”

36”

70

PP

Conducting Solution

1

24”

18”

36”

70

CF RINSE

1(3)

1

36

18”

36”

Electrolytic Ni Plate

1

10

24”

18”

36”

CF RINSE

1(3)

1

36

18”

36”

ACID HCL

1

0.5

24”

18”

36”

70

PP

RINSE

1

0.5

24”

18”

36”

70

PP

PP

RECTIFIER TATION

TO

X

X

PP 70

VENT

X

WT

X

WT

X

WT

X

WT

X

WT

PP

X

X

WT

PP

X

X

WT

X

WT

140ºF

X

X X

18-22C

X X

X 12V 1500A

180ºF

X

X X

X

X

TURBO T3Z1

1

60-90

24”

18”

36”

CF RINSE

1(3)

1

36"

18”

36”

HOT DI RINSE

1

1

24”

18”

36”

70

PP

DRY

1

1

24”

18”

36”

70

PP

UNLOAD

1

1

24”

18”

36”

70

PP

TOTAL

70

PP

X

WT

X

X

PP

X

WT

X

X

X

X

WT

X

X

WT

Pulse Plate

X X

180ºF

X

X

16 Tanks

RECTIFIER

12V 1500A

END START

DEFINITIONS

CF

UNLOAD DRY

LOAD COUNT ERFLO W

ETCH -ACID

HOT DI RINSE

CF RINSE

ULTRASONIC Rinse

CF RINSE

ULTRASONIC Rinse

Ech= 400g/l H2S04

300g/Cr03 Pd –Activator -Complexed metal ,Ammonium ,Pd-free. Possible need for cooling in summer

Activator Conditioner -–Pd-Free

X

Conducti Electrolitic ng CF RINSE CF RINSE ACID HCL Ni Plate Solution

RINSE

TURBO T3Z1

Table 2. Description and requirements for each step of the titanium or titanium-zirconium electrodeposition process. Insert at the bottom – from START to END – represents schematic summary of the entire process. Alternative Step 2: Alternatively to the Ti or Ti/Zr plating from sulphuric acid solution described above (Step 2, green process in Table 2) we intend to test another method of plating from ionic liquid solution. This will be done only if the formula for Step-2 described above would not work properly or efficiently. This is a prototypical method implemented only in the academic laboratory and small scale by Mukhopadhyay et al. (1-2). They proposed the method of electrodeposition of Ti on Au from TiCl4 dissolved in ionic liquid: 1-methyl-3-butyl-imidazolium bis (trifluoro methyl sulfone) imide ([BMIm]BTA) (Fig.3). We will test whether this method could be applied to electrodeposition of Ti on Ni surface. The advantage of this method is that the electrodeposition can be done at room temperature and for the low cost. The disadvantage is that the reaction needs to be performed in anhydrous environment in an argon closed box, due to high hygroscopic property of ionic liquids.

Fig 3. Chemical formula of ionic liquid component and their molar masses. The electroplating from ionic liquid will be conducted using the following recipe: 1. Mixture of liquid ionic liquid [BMIm]BTA (98% pure) and TiCl4 , concentration: 0.24M TiCl4. 2. Ionic liquid [BMIm]BTA can be obtained from Solvent Innovation, Germany. It needs to be dried under vacuum at 120C. It is highly hydrophobic.

3. TiCl4 (99.999%) can be obtained from Alfa Aceser, Germany. It is well soluble in ionic liquid. It is highly hygroscopic.

4. Experiments need to be done in closed, argon filled glove box (with O2 and H2O less than 2ppm). 5. A teflon electrochemical cell needs to be used (with three electrodes configuration). All parts of the cell needs to be cleaned in a 50/50 vol% concentration H2SO4 and 30% H2O2 mixture at ambient temperature, followed by thorough cleaning in a stream of mili-Q (Milipore) water. 6. Electrodeposition will be done in room temperature using potential -1.8- -1.7V (calibrated against the ferricenium/ferrocene ([Fc]+/[Fc]) redox couple), 7. The current density and time of deposition needs to be determined experimentally. Based on work of Mukhopadhyay et al. (1-2) it is estimated that up to 1 hour is needed to deposit 1nm thick 3D growth of titanium.

SUMMARY We propose a novel method(s) of electroplating titanium or titanium/zirconium alloys on ABS or ABS/PC plastics with potential wide application in dentistry, medicine and other fields. The main elements characterizing the novelty of our approach are summarized below: 1) The titanium plating is performed not from aqueous but from sulphuric acid salt solution, which shifts reduction potentials of Ti and Zr in such direction that they are reduced before the hydrogen on a cathode. 2) One of the preparatory steps involves plating thin layer of nickel on activated plastic. The plastic is activated by the process that does not use palladium. 3) New method of plastic activation allows elimination of approximately 11 steps in the Step 1 of the process (see Table 1.). 4) The cost of the final product – Ti or Ti/Zr plated plastic will be much lower than analogous product made entirely of the Ti metal. 5) The process of Ti or Ti/Zr plating belongs to a nanotechnology category, because pulse plating method and application of sodium saccharin, which controls the grain size, leads to the formation of amorphous grains of the deposited alloys on the plated surface yielding extraordinary strength. Milestones 3 Months • Built complete setup for performing plastic activation (Step-1) and Ti/Zr electroplating (Step-2) • Complete refinement and testing of Step-1 • Initiate analysis of properties of activated ABS or ABS/PC plastics 6 Months • Complete refinement and testing of Step-2 – Ti/Zr electroplating setup • Perform testing of the first Ti/Zr electroplated ABS or ABS/PC plastics Detailed management plan Margaret Parker will be responsible for the overall management of the grant and for the coordination of collaborations with laboratories conducting stress tests of the electroplated products. Parker and Cieplak will be responsible for implementation of the plating process. Gorecka will be responsible for chemical formulation of the electrolytes and results’ data management.

BIBLIOGRAPHY